US20150029989A1 - Wireless communication system, wireless base station, wireless terminal, and wireless communication method - Google Patents
Wireless communication system, wireless base station, wireless terminal, and wireless communication method Download PDFInfo
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- US20150029989A1 US20150029989A1 US14/487,664 US201414487664A US2015029989A1 US 20150029989 A1 US20150029989 A1 US 20150029989A1 US 201414487664 A US201414487664 A US 201414487664A US 2015029989 A1 US2015029989 A1 US 2015029989A1
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Definitions
- the present invention relates to a wireless communication system, a wireless terminal, a wireless base station, and a wireless communication method.
- LTE long term evolution
- LTE-A LTE-advanced
- LTE includes, in addition to LTE and LTE-A, other wireless communication systems that are made by enhancing LTE unless otherwise noted.
- CoMP coordinated multiple point
- UE user equipment
- eNB evolved node B
- UL uplink
- DL downlink
- a wireless terminal carries out communication with different wireless base stations for UL and DL.
- a wireless terminal carries out communication with an identical wireless base station for UL and DL. That is, it is common that a wireless terminal carries out communication with a connected wireless base station (serving cell).
- a wireless terminal receives UL scheduling information from a connected wireless base station on a DL and sends data to the connected wireless base station on a UL based on the received UL scheduling information.
- a wireless terminal receives data from a connected wireless base station on a DL and sends a response signal (ACK signal or NACK signal) to the received data to the connected wireless base station on a UL.
- ACK signal or NACK signal response signal
- Such problem easily occurs as well in a so-called heterogeneous network, for example, where macrocells, which are regular base stations, and picocells and the like (also microcells, femtocells, and the like), which are small base stations, are mixed.
- a picocell is desired to suppress the DL cell size (suppress the sending power) in order to inhibit interference in a macrocell. That is, a macrocell and a picocell greatly differ in DL cell size (sending power). Therefore, a situation may occur that, for a wireless terminal located at a cell edge of the connected macrocell, the DL quality is better with a macrocell while the UL quality is better with a picocell.
- a scenario is under review in which a wireless terminal carries out communication with different wireless base stations for UL and DL as described above.
- the wireless terminal when there is another wireless base station whose communication quality of UL for a wireless terminal is higher than the connected wireless base station, the wireless terminal carries out UL communication with the base station different from the connected wireless base station.
- the wireless terminal receives UL scheduling information from the connected wireless base station on a DL and sends data to a base station different from the connected wireless base station on a UL based on the received UL scheduling information.
- a wireless terminal receives data from the connected wireless base station on a DL and sends a response signal to the received data to a base station different from the connected wireless base station on a UL.
- a wireless terminal receives data from the connected wireless base station on a DL and sends a response signal to the received data to a base station different from the connected wireless base station on a UL.
- Non Patent Literatures 3GPP TS36.211 V10.4.0 (2011-12), 3GPP TS36.213 V10.4.0 (2011-12), 3GPP TR36.814 V9.0.0 (2010-03), 3GPP TR36.819 V11.0.0 (2011-09), 3GPP R1-114324 “On Reference Signal Enhancements for UL CoMP” (2011-11) are examples of the related art.
- a wireless communication system includes a wireless base station, and a wireless terminal configured to receive from the wireless base station a downlink frame including data and a downlink control signal for decoding the data, the downlink control signal being mapped to a first downlink control resource element of downlink control resource elements that are resource units used for transmissions of downlink control signals in the downlink frame, and to transmit an uplink frame including an uplink control signal for acknowledging a decoding result of the data, the uplink control signal being mapped to a first uplink control resource element of uplink control resource elements that are resource units used for transmissions of uplink control signals in the uplink frame, the first uplink control resource element being determined by shifting a second uplink control resource element of the uplink control resource elements by an offset number whose unit is one of the uplink control resource elements, the second uplink control resource element being determined based on a location of the first downlink control resource element in the downlink frame, the offset number being determined based on a first offset information included in the downlink control signal.
- FIG. 1 is a diagram illustrating problems in conventional techniques.
- FIG. 2 is a diagram illustrating one example of a network configuration of a wireless communication system in a first embodiment.
- FIG. 3 is one example of a process sequence diagram of the wireless communication system in the first embodiment.
- FIG. 4 is a diagram illustrating one example of a DCI format in the wireless communication system of the first embodiment.
- FIG. 5 is one example of a functional configuration diagram of a wireless base station in the wireless communication system of the first embodiment.
- FIG. 6 is one example of a functional configuration diagram of a wireless terminal in the wireless communication system of the first embodiment.
- FIG. 7 is one example of a hardware configuration diagram of the wireless base station in the wireless communication system of the first embodiment.
- FIG. 8 is one example of a hardware configuration diagram of the wireless terminal in the wireless communication system of the first embodiment.
- FIG. 9 is one example of a process sequence diagram of a wireless communication system in a second embodiment.
- FIG. 10 is a diagram illustrating one example of a DCI format in the wireless communication system of the second embodiment.
- FIG. 11 is one example of a process sequence diagram of a wireless communication system in a third embodiment.
- FIG. 12 is one example of a process sequence diagram of a wireless communication system in a fourth embodiment.
- FIG. 13 is one example of a process sequence diagram of a wireless communication system in a fifth embodiment.
- FIG. 14 is one example of a process sequence diagram of a wireless communication system in a sixth embodiment.
- FIGS. 15A-B are diagrams illustrating one example of a DCI format in a wireless communication system of a seventh embodiment.
- Scheduling of a wireless resource is to determine a wireless resource that is used for sending and receiving of a wireless signal (to assign a wireless resource or to determine allocation of a wireless resource is synonymous).
- a wireless resource is defined by a time component and a frequency component.
- Scheduling of a wireless resource is carried out by a connected wireless base station to a subordinate wireless terminal. The connected wireless base station notifies a connected wireless terminal of scheduling information related to the determined scheduling on a DL, and the connected wireless terminal and the wireless base station carry out sending and receiving of a wireless signal based on the scheduling information.
- the connected wireless base station sends UL scheduling information to the wireless terminal on a DL.
- the wireless terminal sends a wireless signal including UL data using a UL wireless resource that is specified by the received UL scheduling information.
- the connected wireless base station sends the UL scheduling information also to another wireless base station via a backhaul network (network that links between wireless base stations and a wireless base station with a core network).
- the other wireless base station receives a wireless signal including UL data from the wireless terminal using the wireless resource that is specified by the received UL scheduling information.
- a wireless terminal carries out communication with different wireless base stations for UL and DL
- scheduling is carried out without a problem and the other wireless base station is capable of receiving data from the wireless terminal.
- a phenomenon is confirmed in which another wireless base station different from the connected base station is sometimes not capable of receiving data from the wireless terminal.
- the disclosed technique has made in view of the above, and it is an object thereof to provide a wireless communication system, a wireless terminal, a wireless base station, and a wireless communication method that allow, when a wireless terminal carries out communication with different wireless base stations for UL and DL, another wireless base station different from the connected base station to receive data from the wireless terminal.
- a wireless terminal sends a wireless signal including UL data (called as a first wireless signal) using a wireless resource that is specified by UL scheduling information received from the connected wireless base station.
- another wireless base station receives a wireless signal including UL data from the wireless terminal based on scheduling information received from the connected wireless base station (that is, based on a wireless resource defined by the connected wireless base station).
- the other wireless base station has already sent the scheduling information specifying the wireless resource to another wireless terminal connected thereto. This is because it is not possible for the other wireless base station to predict a UL reception request from the connected wireless base station in advance.
- the other wireless terminal sends a wireless signal including data (called as a second wireless signal) to the other wireless base station using the wireless resource specified by the UL scheduling information received from the other wireless base station.
- the wireless terminal and the other wireless terminal turn out to carry out UL sending using same wireless resources (sending time, sending frequency).
- the first wireless signal and the second wireless signal are sent on same wireless resources.
- conflict occurs in a UL wireless resource. Since the first wireless signal and the second wireless signal include different data and interfere with each other, it becomes difficult for the other wireless base station to decode any data. Accordingly, in such a case, the other wireless base station turns out not to be capable of receiving data without an error from the wireless terminal.
- FIG. 1 illustrates an outline of this problem.
- conflict of a wireless resource may occur in UL sending. Then, when conflict of a wireless resource occurs in UL sending, it is not possible that another wireless base station different from the connected base station receives data without an error from the wireless terminal. Accordingly, in the scenario where a wireless terminal carries out communication with different wireless base stations for UL and DL, there is a problem that the other wireless base station is sometimes not capable of receiving data from the wireless terminal.
- the wireless terminal and the other wireless terminal turn out to carry out resending of data in response to reception of a NACK signal or a timeout of a response signal. Resending of data leads to a waste of wireless resources and thus is not preferred.
- FIG. 2 illustrates a network configuration of a wireless communication system in the first embodiment.
- the present embodiment is an embodiment of a wireless communication system compliant with LTE. Therefore, some of LTE specific terms and concepts appear. However, the present embodiment is merely one example and it is noted that it is applicable to a wireless communication system compliant with a communication standard other than LTE.
- the wireless communication system illustrated in FIG. 2 is provided with a plurality of wireless base stations (eNB: evolved node B) 1 a , 1 b , 1 c , wireless terminals (UE: user equipment) 2 a , 2 b , and the like.
- eNB evolved node B
- UE user equipment
- the plurality of wireless base stations 1 a , 1 b , 1 c may be represented collectively as wireless base stations 1 .
- the plurality of wireless terminals 2 a , 2 b may be represented collectively as wireless terminals 2 .
- Wireless networks between the wireless base stations and the wireless terminals are called as wireless access networks.
- the wireless base stations 1 are connected with a wired or wireless network (transmission network) called as a backhaul network.
- a backhaul network is a network that links between the wireless base stations 1 and the wireless base stations 1 with a core network.
- the wireless base stations 1 are capable of carrying out communication with a device connected to the core network via the backhaul network.
- an MME mobility management entity
- SAE-GW system architecture evolution gateway
- An LTE network may also be called as an EPS (evolved packet system).
- the EPS includes a eUTRAN (evolved universal terrestrial radio network), which is a wireless access network, and an EPC (evolved packet core), which is a core network.
- the core network may also be called as an SAE (system architecture evolution).
- the wireless base stations 1 (may also be called simply as base stations) in FIG. 2 is a device that carries out wireless communication with the wireless terminals 2 via the wireless access network and also is connected to the backhaul network.
- the wireless base station 1 a carries out sending and receiving of data with the subordinate wireless terminal 2 a (may be referred to as a connected wireless terminal) and also carries out a variety of control over the wireless terminal 2 a by exchanging various types of control information with the subordinate wireless terminal 2 a .
- the wireless base station 1 a carries out relay of data with the other wireless base stations 1 b , 1 c , each other, via the backhaul network and also is capable of cooperation by exchanging various types of control information with the other wireless base stations 1 b , 1 c.
- the wireless base stations 1 carries out exchange of a variety of control information with a control device, such as an MME connected to the core network beyond the backhaul network, via the backhaul network.
- a control device such as an MME connected to the core network beyond the backhaul network
- the wireless base station 1 a relays the data received from the subordinate wireless terminal 2 a to a relay device, such as an SAE-GW connected to the core network, and also relays the data received from the relay device, such as an SAE-GW, to the subordinate wireless terminal 2 a.
- the wireless base stations 1 may be connected with the backhaul network by wire and may also be connected wirelessly.
- the wireless base stations 1 may also have a communication function with the wireless access network as an extended RRH, which is a separate device, and connect by wire therewith.
- a “cell” is a range that the wireless base stations 1 covers in order that the wireless terminals 2 sends and receives a wireless signal (strictly, there are UL cells and DL cells), the wireless base stations 1 and the cell are almost corresponding concepts, so that it does not matter if the “cell” and the “wireless base station” are read interchangeably as appropriate in the descriptions below.
- the wireless terminals 2 may also be called simply as terminals; may also be called as user devices, subscriber stations, mobile stations, and the like) in FIG. 2 are devices that carry out wireless communication with the wireless base stations 1 via the wireless access network.
- the wireless terminal 2 a is connected to one wireless base station 1 a , and as a change occurs in a wireless state by transfer and the like, the wireless base station 1 to be connected is switched by handover.
- connection indicates that a wireless terminal is registered in (attached to) a wireless base station, it may also be interpreted to simply mean in communication.
- the wireless base station 1 a connected by the wireless terminal 2 a is called as a connected wireless base station or a serving cell.
- the wireless terminal 2 a carries out sending and receiving of data by wireless communication with the connected wireless base station 1 a and also is subject to a variety of control by exchanging various types of control information by wireless communication with the connected wireless base station 1 a.
- the wireless terminal 2 a in the present embodiment receives a DL wireless signal from the connected wireless base station 1 a .
- the wireless terminal 2 a in the present embodiment is capable of sending a UL wireless signal to the connected wireless terminal 1 a or the other wireless base stations 1 b , 1 c .
- the wireless terminal 2 a in the present embodiment is capable of carrying out communication with wireless base stations 1 different for DL and UL. Details are described later.
- the wireless communication system in the present embodiment uses an OFDMA (orthogonal frequency division multiple access) scheme as a DL wireless access scheme.
- OFDMA orthogonal frequency division multiple access
- SC-FDMA single carrier frequency division multiple access
- the wireless communication system in the present embodiment is configured with, as well as a DL wireless signal and a UL wireless signal, a wireless frame (may also be referred to simply as a frame) having a predetermined length (for example, 10 milliseconds). Further, one wireless frame is respectively configured with a predetermined number (for example, 10) of wireless subframes (may also be referred to simply as subframes) having a predetermined length (for example, 1 millisecond). Then, each subframe is further divided into each physical channel, which is a physical communication path. Since a “frame” and a “subframe” are merely terms that indicate processing units of a wireless signal, these terms may also be read interchangeably as appropriate in the following.
- a DL physical channel there are a downlink shared channel (PDSCH: physical downlink shared channel) that is used for transmission of a DL data signal and the like, a downlink control channel (PDCCH: physical downlink control channel) that is used for transmission of a DL control signal, and the like.
- PDSCH physical downlink shared channel
- PDCCH physical downlink control channel
- PUSCH physical uplink shared channel
- PUCCH physical uplink control channel
- FIG. 3 is a process sequence when sending data (UL data) to the connected wireless base station 1 a occurs in the wireless terminal 2 a .
- the wireless terminal 2 a in the present embodiment is capable of receiving a DL wireless signal from the connected wireless base station 1 a and also sending a UL wireless signal to the connected wireless base station 1 a or the other wireless base station 1 b , which is another wireless base station. That is, the wireless terminal 2 a is capable of carrying out communication with wireless base stations 1 different for DL and UL.
- FIG. 3 is one example of such asymmetric wireless communication.
- UL data occurs in the wireless terminal 2 a .
- UL data occurs when an audio signal, data, and the like are sent from the wireless terminal 2 a to the other wireless terminal 2 b , when an application on the wireless terminal 2 a sends data to a server on the Internet, and the like.
- the wireless terminal 2 a sends UL schedule requesting information, which is information to request a UL wireless resource in order to send the UL data, to the connected wireless base station 1 a on a UL wireless signal.
- UL schedule requesting information information indicating a UL wireless resource amount to be used (UL wireless resource amount information) is stored.
- the connected wireless base station 1 a As receiving the UL schedule requesting information, the connected wireless base station 1 a starts scheduling of a UL wireless resource to the wireless terminal 2 a .
- the connected wireless base station 1 a firstly obtains, for example, UL receiving quality from the wireless terminal 2 a . It is possible to obtain the UL receiving quality based on a sound reference signal (SRS) included in the UL wireless signal. Then, the connected wireless base station 1 a decides whether the obtained UL receiving quality satisfies a predetermined criterion. Based on this decision, in S 103 , the connected wireless base station 1 a determines whether or not to set a base station to receive UL data as a local station (connected wireless base station 1 a ).
- SRS sound reference signal
- the connected wireless base station 1 a determines the base station to receive UL data as the local station (connected wireless base station 1 a ). In contrast, when the receiving quality does not satisfy a predetermined criterion, the connected wireless base station 1 a determines the base station to receive UL data as any of the other wireless base stations 1 b , 1 c other than the local station (at this time point, the other wireless base stations 1 b , 1 c do not have to be determined into one).
- the connected wireless base station 1 a in this example carries out determination of whether or not to receive at a local station in S 103 based on the UL receiving quality, instead of or in addition to this, the determination may also be carried out based on another index. For example, when the UL wireless resource use amount or activity rate of the local station is not less than the predetermination (when there are less space in the UL wireless resource), it is possible that the connected wireless base station 1 a determines the base station to receive UL data as other than the local station.
- the connected wireless base station 1 a determines, in S 103 , the base station to receive UL data as other than the local station (connected wireless base station 1 a ).
- the connected wireless base station 1 a sends wireless resource requesting information, which is information to request a UL wireless resource to the other wireless base stations 1 b , 1 c via the transmission network.
- the connected wireless base station 1 a is capable of carrying out selection of a sending destination of the wireless resource requesting information based on, for example, DL receiving quality of each wireless base station stored in a measurement report, not illustrated, that is successively received from the wireless terminal 2 a .
- the other wireless base stations 1 b , 1 c to be the sending destination of wireless resource requesting information may be one or a plurality, and in the example of FIG. 3 , it is assumed that two other wireless base stations 1 b , 1 c are selected as the sending destination.
- an unused wireless resource in the other wireless base station 1 b is a UL wireless resource that the other wireless base station 1 b does not cause any subordinate wireless terminal 2 b to use for UL sending (not to be scheduled for UL sending).
- the wireless terminal 2 a subordinate to the connected wireless base station 1 a carries out UL sending using an unused wireless resource to the other wireless base station 1 b , resource conflict turns out not to occur.
- the other wireless base station 1 b controls and manages schedules of all subordinate wireless terminals 2 b , it is possible to obtain the unused wireless resources easily.
- the other wireless base stations 1 b , 1 c respectively send other station wireless resource information including unused wireless resources information that indicates the obtained unused wireless resources to the connected wireless base station 1 a via the transmission network.
- the connected wireless base station 1 a receives the other station wireless resource information including the unused wireless resources information respectively from the other wireless base stations 1 b , 1 c . Then, in S 107 , the connected wireless base station 1 a determines a UL wireless resource (referred to as a determined wireless resource) that is used for UL sending from the subordinate wireless terminal 2 a and the other wireless base station (referred to as a determined wireless base station) to be a sending destination of the UL sending based on the received unused wireless resources information.
- a UL wireless resource referred to as a determined wireless resource
- the other wireless base station referred to as a determined wireless base station
- the connected wireless base station 1 a is capable of determining the determined wireless resource and the determined wireless base station by an arbitrary criterion based on the unused wireless resources indicated by the unused wireless resources information. For example, it is possible that the connected wireless base station 1 a selects arbitrary one from the unused wireless resources capable of securing the requested UL wireless resource amount to determine the determined wireless resource therefrom. Then, the connected wireless base station 1 a is capable of setting the other wireless base station 1 b that has sent the selected unused wireless resource (information) as the determined wireless base station.
- the connected wireless base station 1 a determines the determined wireless resource from the unused wireless resources that the other wireless base station 1 b has sent and determines the other wireless base station 1 b as the determined wireless base station.
- the connected wireless base station 1 a sends information indicating the determined wireless resource determined in S 107 (referred to as determined wireless resource information) to the subordinate wireless terminal 2 a on a DL wireless signal.
- this DL wireless signal includes DCI (data control information), which is a DL control signal defined by LTE.
- DCI is a DL control signal including control information, such as information related to data scheduling, used by the wireless terminal 2 a for sending and receiving of data.
- There are several formats in DCI and a control object is different depending on the format. For example, format 0 in DCI is to control over the PUSCH, that is, UL data. Formats 1A, 1B, 1C, 1, 2 are respectively to control over the PDSCH, that is, DL data.
- FIG. 4 illustrates one example of a DCI format in the first embodiment.
- the DCI illustrated in FIG. 4 is defined by LTE, and it is used as is in the first embodiment.
- the DCI in FIG. 4 includes an RNTI (radio network temporary identifier), which is an identifier of a DCI destination (wireless terminal 2 a ), RB assignment (resource block assignment), which is information indicating the wireless resource having data allocated thereto (to which resource block (RB) on the wireless frame data is assigned), and MCS (modulation and coding scheme), which indicates modulation and coding scheme of data.
- RNTI radio network temporary identifier
- RB assignment resource block assignment
- MCS modulation and coding scheme
- DCI includes, as well as these, parameters, such as an RV (redundancy version), an NDI (new data indicator), a HARQ (hybrid automatic repeat request) processing number, and PUCCH power control, details are omitted.
- the determined wireless resource information corresponds to the RB assignment of DCI. That is, in S 108 , the connected wireless base station 1 a in the present embodiment sends the determined wireless resource information to the subordinate wireless terminal 2 a by sending the DCI on a DL wireless signal. In contrast, in S 108 , the wireless terminal 2 a receives the DL wireless signal including the DCI that includes the determined wireless resource information (RB assignment). At this time, the wireless terminal 2 a recognizes (detects) the DCI towards itself based on the RNTI included in the DCI. In addition, the wireless terminal 2 a recognizes (detects) that the DCI targets the UL data based on the DCI format.
- the connected wireless base station 1 a sends the determined wireless resource information to the other wireless base station 1 b , which is the determined wireless base station determined in S 107 via the transmission network.
- the connected wireless base station 1 a in the present embodiment sends the determined wireless resource information to the other wireless base station 1 b , which is the determined wireless base station, by sending the DCI in S 109 .
- S 108 and S 109 may also be simultaneous or opposite in order. This completes scheduling of UL wireless sending from the subordinate wireless terminal 2 a to the other wireless base station 1 b by the connected wireless base station 1 a .
- regular UL wireless resource scheduling may be carried out, so that the description is omitted.
- the wireless terminal 2 a sends a UL wireless signal including the UL data using the UL wireless resource indicated by the received determined wireless resource information (RB assignment of DCI). At this time, the wireless terminal 2 a carries out coding and modulation of the UL data based on an MCS included in the DCI received in S 108 .
- the other wireless base station 1 b receives the UL wireless signal sent by the wireless terminal 2 a using the UL wireless resource indicated by the received determined wireless resource information. At this time, the other wireless base station 1 b carries out demodulation and decoding of the UL data based on the MCS included in the DCI received in S 109 .
- the other wireless base station 1 b sends (transfers) the UL data included in the received UL wireless signal to the connected wireless base station 1 a via the transmission network. This completes reception of the UL data in S 112 .
- the connected wireless base station 1 a receives the other station wireless resource information including the unused wireless resources information, which is information indicating UL wireless resources not used by the other wireless base station 1 b , from the other wireless base station 1 b . Then, the connected wireless base station 1 a schedules the UL wireless resource used for UL sending from the subordinate wireless terminal 2 a to the other wireless base station 1 b based on the received unused wireless resources information.
- the wireless terminal 2 a when the wireless terminal 2 a carries out communication with different wireless base stations for UL and DL, it is possible that the other wireless base station different from the connected base station receives data from the wireless terminal. In addition, as a result, it is possible to achieve efficient utilization of wireless resources.
- FIG. 5 is a diagram illustrating one example of functional configuration of the wireless base station 1 in the first embodiment.
- the wireless base station 1 is provided with, for example, a UL wireless receiving unit 101 , a UL frame analysis unit 102 , a UL reference signal processing unit 103 , a UL control signal demodulation and decoding unit 104 , a UL data signal demodulation and decoding unit 105 , a scheduler unit 106 , a DL data signal generation unit 107 , a DL data signal coding and modulation unit 108 , a DL control signal generation unit 109 , a DL control signal coding and modulation unit 110 , a DL reference signal generation unit 111 , a DL frame generation unit 112 , a DL wireless sending unit 113 , a transmission network sending unit 114 , and a transmission network receiving unit 115 .
- the UL wireless receiving unit 101 receives a UL wireless signal, downconverts the received wireless signal by frequency conversion and the like for conversion to a baseband signal corresponding to a UL frame, and outputs it to the UL frame analysis unit 102 .
- the UL frame analysis unit 102 extracts a UL data signal, a UL control signal, and a UL reference signal from the baseband signal corresponding to the UL frame.
- the UL frame analysis unit 102 carries out extraction of each signal based on UL scheduling information (information equivalent to RB assignment of DCI) inputted from the scheduler unit 106 .
- the UL frame analysis unit 102 outputs the UL reference signal to the UL reference signal processing unit 103 , outputs the UL control signal to the UL control signal demodulation and decoding unit 104 , and outputs the UL data signal to the UL data signal demodulation and decoding unit 105 .
- the UL reference signal processing unit 103 obtains UL channel characteristics based on a demodulation reference signal (DM-RS) among the UL reference signal and inputs them to the UL control signal demodulation and decoding unit 104 and the UL data signal demodulation and decoding unit 105 .
- DM-RS demodulation reference signal
- the UL reference signal processing unit 103 obtains UL receiving quality based on a sounding reference signal (SRS), which is a reference signal for scheduling, among the UL reference signal and inputs it to the scheduler unit 106 .
- SRS sounding reference signal
- the UL control signal demodulation and decoding unit 104 demodulates the UL control signal to carry out error correction and decoding.
- the UL control signal demodulation and decoding unit 104 carries out demodulation and decoding of the UL control signal using the UL channel characteristics inputted from a UL reference signal generation unit 212 and predetermined modulation scheme and error correction and coding scheme.
- the UL control signal demodulation and decoding unit 104 inputs the demodulated and decoded UL control signal to the scheduler unit 106 .
- the UL control signal there are UL schedule requesting information, a UL response signal (ACK/NACK signal) to DL data, and the like.
- the UL data signal demodulation and decoding unit 105 demodulates the UL data signal to carry out error correction and decoding.
- the UL data signal demodulation and decoding unit 105 carries out demodulation and decoding of the UL data signal using the UL channel characteristics inputted from the UL reference signal generation unit 212 and the modulation scheme and the error correction and coding scheme inputted from the scheduler unit 106 .
- the UL data signal demodulation and decoding unit 105 inputs the demodulated and decoded UL data signal to the scheduler unit 106 .
- the scheduler unit 106 carries out scheduling of a wireless resource used for wireless communication and also carries out a variety of control associated with the scheduling of a wireless resource.
- the scheduler unit 106 schedules respective UL and DL wireless resources. As a first example, when UL schedule requesting information, which is one item of the UL control information sent by the wireless terminal 2 a , is inputted from the UL control signal demodulation and decoding unit 104 , the scheduler unit 106 schedules a UL wireless resource to the wireless terminal 2 a .
- the scheduler unit 106 schedules a DL wireless resource.
- the scheduler unit 106 in the present embodiment selectively determines the wireless base station 1 to be a UL sending destination.
- the scheduler unit 106 in the present embodiment is capable of selecting the other wireless base stations 1 b , 1 c other than the local station (wireless base station 1 a ) as the UL sending destination.
- the scheduler unit 106 may also select the local station (wireless base station 1 a ) as the UL sending destination.
- the scheduler unit 106 may employ a variety of methods in determination of the wireless base station 1 to be the UL sending destination of the wireless terminal 2 a and determination of the UL wireless resource to be assigned to the wireless terminal 2 a .
- the scheduler unit 106 may also carry out these determinations collectively and may also carry out them in order.
- the contents of the other station wireless resource information may be, as an example, information indicating a UL wireless resource not used by the other wireless base station 1 b (referred to as unused wireless resources information).
- the unused wireless resources information is, so to speak, information indicating a wireless resource where resource conflict does not occur even when being used by the wireless base station 1 a (even when being scheduled as the UL wireless resource used in UL sending from the wireless terminal 2 a subordinate to the wireless base station 1 a to the other wireless base station 1 b ).
- the scheduler unit 106 of the connected wireless base station 1 a selectively determines the UL wireless resource to be assigned to the subordinate wireless terminal 2 a from the unused wireless resources information received from the other wireless base station 1 b.
- the unused wireless resources information is merely one example of the other station wireless resource information.
- information indicating a UL wireless resource used by the other wireless base station 1 b (referred to as used wireless resource information) is also available.
- the used wireless resource information is, so to speak, information indicating a wireless resource where resource conflict occurs when being used by the wireless base station 1 a (when being scheduled as the UL wireless resource used in the UL sending from the wireless terminal 2 a subordinate to the wireless base station to the other wireless base station 1 b ).
- the scheduler unit 106 of the wireless base station 1 a selectively determines the UL wireless resource to be assigned to the subordinate wireless terminal 2 a from the UL wireless resource other than the used wireless resource information received from the other wireless base station 1 b.
- the scheduler unit 106 carries out, for example, sending of requesting information (referred to as wireless resource requesting information) that requests other station wireless resource information to the other wireless base stations 1 b , 1 c . Specifically, it goes as follows, for example. Firstly, when the UL receiving quality inputted from the UL reference signal unit is lower than a predetermined value, the scheduler unit 106 determines to send wireless resource requesting information.
- the scheduler unit 106 sends wireless resource requesting information to the other wireless base stations 1 b , 1 c (adjacent wireless base or peripheral wireless base station).
- the other wireless base stations 1 b , 1 c to be the sending destination may be one or may also be a plurality.
- the other wireless base stations 1 b , 1 c send other station information including the other station wireless resource information to the connected wireless base station 1 a in response to the wireless resource requesting information.
- the scheduler unit 106 of the wireless base station 1 a is capable of obtaining the other station wireless resource information from the other wireless base stations 1 b , 1 c .
- the procedure where the connected wireless base station 1 a obtains other station wireless resource information from the other wireless base stations 1 b , 1 c and they are described later (described in a fourth embodiment through a sixth embodiment).
- the scheduler unit 106 carries out UL scheduling to the subordinate wireless terminal 2 a based on the other station wireless resource information. Specifically, the scheduler unit 106 determines the determined wireless resource, which is the UL wireless resource used for the UL sending from the subordinate wireless terminal 2 a , and the determined wireless base station, which is the other wireless base station 1 b to be the sending destination of the UL sending, based on the unused wireless resources information included in the received other station wireless resource information.
- the magnitude of the determined wireless resources is not less than the UL wireless resource amount requested in the UL schedule requesting information from the wireless terminal 2 a .
- the scheduler unit 106 is capable of determining the determined wireless resource and the determined wireless base station by an arbitrary criterion based on the unused wireless resources indicated by the unused wireless resources information. For example, it is possible that the scheduler unit 106 selects arbitrary one from the unused wireless resources capable of securing the requested UL wireless resource amount to determine the determined wireless resource therefrom. Then, the scheduler unit 106 is capable of setting the other wireless base station 1 b that has sent the selected unused wireless resource (information) as the determined wireless base station.
- the scheduler unit 106 carries out scheduling of the UL wireless resource to the wireless base station 1 b from the wireless terminal 2 a when the other wireless base station 1 b is selected as the UL sending destination from the wireless terminal 2 a .
- the scheduler unit 106 inputs the UL scheduling result to the DL control signal generation unit 109 .
- the UL scheduling result is information including a wireless resource for UL sending (the above determined wireless resource), an identifier of the wireless terminals 1 a , a coding and modulation scheme of a signal, and the like.
- the scheduler unit 106 when selecting the other wireless base station 1 b , the scheduler unit 106 also inputs the UL scheduling result to the transmission network sending unit 114 . Further in this case, the scheduler unit 106 inputs base station identification information indicating the UL receiving other wireless base station 1 b (corresponding to the determined wireless base) to the transmission network sending unit 114 .
- the scheduler unit 106 when selecting the local station as the UL sending destination from the wireless terminal 2 a , the scheduler unit 106 carries out general UL scheduling (the description is omitted). Then, in order to generate a DCI, the scheduler unit 106 inputs the UL scheduling result to the DL control signal generation unit 109 . For the preparation of UL reception at the local station, the scheduler unit 106 inputs the UL scheduling result to the UL frame analysis unit 102 .
- the scheduler unit 106 schedules DL sending.
- the scheduler unit 106 carries out general DL scheduling (the description is omitted).
- the scheduler unit 106 inputs the DL scheduling result to the DL control signal generation unit 109 .
- the DL scheduling result is information including a wireless resource for DL sending, an identifier of the wireless terminal 1 a , a coding and modulation scheme of a signal, and the like.
- the scheduler unit 106 inputs DL data to the DL data signal generation unit 107 .
- the DL data signal generation unit 107 As the DL data is inputted from the scheduler unit 106 , the DL data signal generation unit 107 generates a DL data signal and inputs it to a DL data coding and modulation unit.
- the DL data coding and modulation unit codes and modulates the DL data signal based on the coding scheme and the modulation scheme inputted from the scheduler unit 106 and inputs it to the DL frame generation unit 112 .
- a DL control information generation unit generates DL control information based on the scheduling result inputted from the scheduler unit 106 and inputs it to the DL control signal coding and modulation unit 110 .
- the DL control signal generation unit 109 generates the DCI described before based on the inputted scheduling result.
- the DL control signal generation unit 109 sets an RB assignment value of the DCI based on the determined wireless resource included in the scheduling result inputted from the scheduler unit 106 .
- the DL control signal generation unit 109 sets the wireless terminal identifier inputted from the scheduler as an RNTI value and sets the modulation scheme and the coding scheme as an MCS value.
- the DL control signal generation unit 109 inputs the generated DL control signal to the DL control signal coding and modulation unit 110 .
- the DL control signal coding and modulation unit 110 codes and modulates the DL control signal based on the predetermined modulation scheme and coding scheme and inputs it to the DL frame generation unit 112 .
- the DL reference signal generation unit 111 generates the DL reference signal and inputs it to the DL frame generation unit 112 .
- the DL frame generation unit 112 places (also called as maps) the DL data signal, the DL control signal, and the DL reference signal after coding and modulation in a DL frame and generates a DL frame.
- the DL frame generation unit 112 carries out mapping of each DL signal using the DL scheduling result inputted from the scheduler unit 106 . That is, the DL frame generation unit 112 carries out mapping of each signal to the wireless resource (RB) defined in the DL scheduling result inputted from the scheduler unit 106 .
- the DL frame generation unit 112 inputs the baseband signal corresponding to the generated DL frame to the DL wireless sending unit 113 .
- the DL wireless sending unit 113 upconverts the baseband signal corresponding to the inputted DL frame to a wireless signal by frequency conversion and the like and wirelessly sends the wireless signal to the wireless terminal 2 a.
- the transmission network sending unit 114 sends a data signal and a control signal to the other wireless base stations 1 b , 1 c , other control devices, relay devices, and the like via the backhaul network.
- the transmission network sending unit 114 sends the wireless resource requesting information described above to the other wireless base stations 1 b , 1 c .
- the sending of the wireless resource requesting information is carried out by accepting an input of base station identifiers indicating the other wireless base stations 1 b , 1 c from the scheduler unit 106 .
- the transmission network sending unit 114 sends the determined wireless resource information described above to the other wireless base station 1 b .
- the sending of the determined wireless resource information is carried out by accepting an input of the UL scheduling result and the base station identifier from the scheduler unit 106 .
- the transmission network receiving unit 115 receives a data signal and a control signal from the other wireless base stations 1 b , 1 c , other control devices, relay devices, and the like via the backhaul network. For example, when the scheduler unit 106 selects other than the local station as the UL sending destination, the transmission network receiving unit 115 receives the other station wireless resource information described before from the other wireless base stations 1 b , 1 c . The transmission network receiving unit 115 inputs the received other station wireless resource information to the scheduler unit 106 .
- the other wireless base station 1 b also has a functional configuration same as FIG. 5 , different process is carried out in a part of the functions. It goes without saying that the respective wireless base stations 1 may be provided with both a function provided in the connected wireless base station 1 a and a function provided in the other wireless base station 1 b . In other words, the respective wireless base stations are capable of behaving as the connected wireless base station to a certain wireless terminal and behaving as another wireless base station to another wireless terminal.
- the transmission network receiving unit 115 of the other wireless base station 1 b receives a data signal and a control signal from the connected wireless base station 1 a , other control devices, relay devices, and the like connected to the backhaul network.
- the transmission network receiving unit 115 receives the wireless resource requesting information described before from the connected wireless base station 1 a .
- the transmission network receiving unit 115 inputs the received wireless resource requesting information to the scheduler unit 106 .
- the transmission network receiving unit 115 receives the determined wireless resource information described before from the connected wireless base station 1 a .
- the transmission network receiving unit 115 inputs the received determined wireless resource assignment information to the scheduler unit 106 .
- the scheduler unit 106 of the other wireless base station 1 b generates other station wireless resource information based on the inputted wireless resource requesting information.
- the other station wireless resource information includes the unused wireless resources information, which is information indicating UL resources not used by the other wireless base station 1 b .
- the scheduler unit 106 generates the unused wireless resources information as follows.
- the scheduler unit 106 of the other wireless base station 1 b subjectively and also fully determines scheduling of each wireless terminal 2 b subordinate to the other wireless base station 1 b . Therefore, the scheduler unit 106 recognizes fixed scheduling (wireless resource to be used) in the present and future of each subordinate wireless terminal 2 b . In addition, the scheduler unit 106 is also capable of controlling not to use a certain wireless resource in the future (not to use a certain frequency range in a certain period). Accordingly, the scheduler unit 106 of the other wireless base station 1 b is capable of recognizing a wireless resource not used by the local station (other wireless base station 1 b ), in other words, a wireless resource not to be scheduled for the subordinate wireless terminal 2 b by the local station.
- the scheduler unit 106 of the other wireless base station 1 b selects a part or all of the wireless resources not used by the local station to set information indicating the selected wireless resource as the unused wireless resources information. Then, the scheduler unit 106 generates other station wireless resource information including the unused wireless resources information. The scheduler unit 106 inputs the generated other station wireless resource information to the transmission network sending unit 114 .
- the scheduler unit 106 of the other wireless base station 1 b carries out scheduling to accept the UL sending from the wireless terminal 2 a subordinate to the connected wireless base station 1 a based on the determined wireless resource information received from the connected wireless base station 1 a .
- the determined wireless resource information is determined by the connected wireless base station 1 a based on the unused wireless resources information sent earlier, and is information indicating a part or all of the UL wireless resource indicated by the unused wireless resources information.
- the scheduler unit 106 inputs the UL scheduling result that reflects the received UL resource assignment information to the UL frame analysis unit 102 .
- the UL frame analysis unit 102 extracts respective information from the UL frame based on the UL scheduling result.
- the transmission network sending unit 114 of the other wireless base station 1 b in the present embodiment sends the other station wireless resource information including the unused wireless resources information to the connected wireless base station 1 a .
- the sending is carried out by accepting an input of the other station wireless resource information from the scheduler unit 106 .
- FIG. 6 is a diagram illustrating one example of a functional configuration of the wireless terminals 2 a in the first embodiment.
- the wireless terminal 2 a is provided with, for example, a DL wireless receiving unit 201 , a DL frame analysis unit 202 , a DL reference signal processing unit 203 , a DL control signal demodulation and decoding unit 204 , a DL data signal demodulation and decoding unit 205 , an upper layer unit 206 , a UL schedule management unit 207 , a UL data signal generation unit 208 , a UL data signal coding and modulation unit 209 , a UL control signal generation unit 210 , a UL control signal coding and modulation unit 211 , a UL reference signal generation unit 212 , a UL frame generation unit 213 , and a UL wireless sending unit 214 .
- the DL wireless receiving unit 201 receives a DL wireless signal, downconverts the received wireless signal by frequency conversion and the like to convert it to a baseband signal corresponding to the DL frame, and outputs it to the DL frame analysis unit 202 .
- the DL frame analysis unit 202 extracts a DL data signal, a DL control signal, and a DL reference signal from the baseband signal corresponding to the DL frame. Then, the DL frame analysis unit 202 outputs the DL reference signal to the DL reference signal processing unit 203 , outputs the DL control signal to the DL control signal demodulation and decoding unit 204 , and outputs the DL data signal to the DL data signal demodulation and decoding unit 205 .
- the DL reference signal processing unit 203 of the wireless terminal 2 a estimates DL channel characteristics based on the DL reference signal and outputs the DL channel characteristics respectively to the DL control signal demodulation and decoding unit 204 and the DL data signal demodulation and decoding unit 205 .
- the DL control signal demodulation and decoding unit 204 demodulates the DL control signal and extracts DL control information by carrying out error correction and decoding.
- the DL control signal demodulation and decoding unit 204 carries out demodulation and decoding of the DL control signal using the DL channel characteristics and predetermined demodulation scheme and error correction and decoding scheme.
- the DL control signal demodulation and decoding unit 204 recognizes (detects) a DCI towards itself based on the RNTI included therein.
- the DL control signal demodulation and decoding unit 204 recognizes (detects) whether the scope of DCI application is UL data (PUSCH) or DL data (PDSCH) based on the DCI format.
- the DL control signal demodulation and decoding unit 204 inputs the RB assignment and the MCS included in the DCI to the DL data signal demodulation and decoding unit 205 .
- the DL control signal demodulation and decoding unit 204 inputs the RB assignment and the MCS included in the DCI to the UL schedule management unit 207 .
- the DL data signal demodulation and decoding unit 205 demodulates the DL data signal and extracts DL data information by carrying out error correction and decoding.
- the DL data signal demodulation and decoding unit 205 carries out extraction of a DL data signal towards itself using the RB assignment inputted from the DL control signal demodulation and decoding unit 204 .
- the DL data signal demodulation and decoding unit 205 carries out demodulation and decoding of the DL data signal based on the DL channel characteristics and the MCS inputted from the DL control signal demodulation and decoding unit 204 .
- the DL data signal demodulation and decoding unit 205 inputs the obtained DL data to the upper layer unit 206 .
- the upper layer unit 206 processes the inputted DL data to provide various functions in the wireless terminal 2 a . Although there are, for example, a voice call, a web browser, a mailer, and the like as the functions provided by the upper layer unit 206 , there may also be other arbitrary functions.
- the upper layer unit 206 generates UL data (information) based on the functions to be provided and inputs them to the UL schedule management unit 207 .
- the UL schedule management unit 207 carries out management of the UL schedule when UL data occurs. This is carried out as follows. As UL data is inputted from the upper layer unit 206 , the UL schedule management unit 207 inputs an instruction signal that is to send UL wireless resource requesting information, which is one of the UL control signal, to the connected wireless base station 1 a to the UL control signal generation unit 210 for the purpose of securing the UL wireless resource in a resource amount to be used for the UL data. With respect to the UL wireless resource requesting information, the connected wireless base station 1 a notifies the wireless terminal 2 a of the UL wireless resource by the DCI, which is a DL control signal.
- the DL control signal demodulation and decoding unit 204 inputs the RB assignment and the MCS included in the DCI to the UL schedule management unit 207 .
- the UL schedule management unit 207 inputs the UL data inputted earlier to the UL data signal generation unit 208 for the purpose of carrying out UL data sending.
- the UL schedule management unit 207 inputs the inputted MCS to the data signal coding and modulation unit and also inputs the RB assignment to the UL frame generation unit 213 .
- the UL data signal generation unit 208 generates a UL data signal based on the inputted UL data information and inputs it to the UL data signal coding and modulation unit 209 .
- the UL data signal coding and modulation unit 209 makes error correction and coding and modulation of the inputted UL data signal based on the MCS inputted from the UL schedule management unit 207 and inputs it to the UL frame generation unit 213 .
- the UL control information generation unit generates UL control information based on the instruction signal inputted from the UL schedule management unit 207 and the like and inputs it to the UL control signal coding and modulation unit 211 .
- the UL control signal there are UL schedule requesting information to request a UL wireless resource to the connected wireless base station 1 a when UL data occurs, a response signal (ACK/NACK signal) to DL data, and the like.
- the UL control signal coding and modulation unit 211 makes error correction and coding and modulation of the UL control signal inputted from the UL control signal generation unit 210 based on a predetermined modulation scheme and a coding scheme and inputs it to the UL frame generation unit 213 .
- the UL reference information generation unit generates UL reference information based on the instruction from the UL schedule management unit 207 and inputs it to the UL frame generation unit 213 .
- UL reference signals include, as described before, a DM-RS (demodulation reference signal) and a SRS (surrounding reference signal).
- the UL frame generation unit 213 places (maps) the UL data signal, the UL control signal, and the UL reference signal in a UL frame and generates a UL frame.
- the UL frame generation unit 213 carries out mapping of each signal using the RB assignment inputted from the UL schedule management unit 207 .
- the UL frame generation unit 213 inputs a baseband signal corresponding to the generated UL frame to a wireless sending unit.
- the wireless sending unit upconverts the baseband signal corresponding to the inputted UL frame by frequency conversion and the like to a wireless signal for wireless sending of the wireless signal to the wireless base station 1 .
- FIG. 7 illustrates one example of a hardware configuration of the wireless base station 1 in the present embodiment.
- the wireless base station 1 in an embodiment is provided with a wireless IF (interface) 11 , an analog circuit 12 , a digital circuit 13 , a processor 14 , a memory 15 , a transmission network IF 16 , and the like.
- the wireless IF 11 is an interface device to carry out wireless communication with the wireless terminals 2 and is, for example, an antenna.
- the analog circuit 12 is a circuit to process an analog signal and may be roughly categorized into those carrying out receiving process, those carrying out sending process, and those carrying out other process.
- the analog circuit that carries out receiving process includes, for example, a low noise amplifier (LNA), a band pass filter (BPF), a mixer, a low pass filter (LPF), an automatic gain control amplifier (AGC: automatic gain controller), an analog-to-digital converter (ADC), a phase locked loop (PLL), and the like.
- LNA low noise amplifier
- BPF band pass filter
- LPF low pass filter
- LPF low pass filter
- ADC automatic gain control amplifier
- ADC analog-to-digital converter
- PLL phase locked loop
- the analog circuit that carries out sending process includes, for example, a power amplifier (PA), a BPF, a mixer, an LPF, a digital-to-analog converter (DAC), a PLL, and the like.
- the analog circuit that carries out other process includes a duplexer and the like.
- the digital circuit 13 is a circuit to process a digital signal and includes, for example, an LSI (large scale integration), an FPGA (field-programming gate array), an ASIC (application specific integrated circuit), and the like.
- the processor 14 is a device to process data and includes, for example, a CPU (central processing unit), a DSP (digital signal processor), and the like.
- the memory 15 is a device to memorize data and includes, for example, a ROM (read only memory), a RAM (random access memory), and the like.
- the transmission network IF 16 is an interface device to be connected to the backhaul network of the wireless communication system by a wired link or a wireless link and to carry out wired communication or wireless communication with a device on a transmission network side including another wireless base station 1 connected to the backhaul network or the core network.
- the UL wireless receiving unit 101 is achieved by, for example, the wireless IF 11 and the analog circuit 12 (those carrying out receiving process). That is, the wireless IF 11 receives a UL wireless signal from the wireless terminal 2 a , and the analog circuit 12 downconverts the received wireless signal by frequency conversion and the like to convert it to a baseband signal corresponding to a UL frame.
- the UL frame analysis unit 102 is achieved by, for example, the processor 14 , the memory 15 , and the digital circuit 13 . That is, the processor 14 controls the memory 15 as occasion calls, cooperates with the digital circuit 13 as occasion calls, and extracts a UL data signal, a UL control signal, and a UL reference signal from the baseband signal corresponding to the UL frame. In addition, the digital circuit 13 may also extract a UL data signal, a UL control signal, and a UL reference signal from the baseband signal corresponding to the UL frame.
- the UL reference signal processing unit 103 is achieved by, for example, the processor 14 , the memory 15 , and the digital circuit 13 . That is, the processor 14 controls the memory 15 as occasion calls, cooperates with the digital circuit 13 as occasion calls, obtains the UL channel characteristics based on the DM-RS, and obtains the UL receiving quality based on the SRS. In addition, the digital circuit 13 may also obtain the UL channel characteristics based on the DM-RS and obtain the UL receiving quality based on the SRS.
- the UL control signal demodulation and decoding unit 104 is achieved by, for example, the processor 14 , the memory 15 , and the digital circuit 13 . That is, the processor 14 controls the memory 15 as occasion calls, cooperates with the digital circuit 13 as occasion calls, demodulates a UL control signal, and carries out error correction and decoding. In addition, the digital circuit 13 may also demodulate a UL control signal and carry out error correction and decoding.
- the UL data signal demodulation and decoding unit 105 is achieved by, for example, the processor 14 , the memory 15 , and the digital circuit 13 .
- the processor 14 controls the memory 15 as occasion calls, cooperates with the digital circuit 13 as occasion calls, demodulates a UL data signal, and carries out error correction and decoding.
- the digital circuit 13 may also demodulate a UL data signal and carry out error correction and decoding.
- the scheduler unit 106 is achieved by, for example, the processor 14 , the memory 15 , and the digital circuit 13 . That is, the processor 14 controls the memory 15 as occasion calls, cooperates with the digital circuit 13 as occasion calls, and carries out scheduling of the wireless resource used for wireless communication, and also carries out a variety of control associated with the scheduling of the wireless resource. In addition, the digital circuit 13 may also carry out scheduling of the wireless resource used for wireless communication and also carry out a variety of control associated with the scheduling of the wireless resource.
- the DL data signal generation unit 107 is achieved by, for example, the processor 14 , the memory 15 , and the digital circuit 13 . That is, the processor 14 controls the memory 15 as occasion calls, cooperates with the digital circuit 13 as occasion calls, and generates a DL data signal. In addition, the digital circuit 13 may also generate a DL data signal.
- the DL data coding and modulation unit is achieved by, for example, the processor 14 , the memory 15 , and the digital circuit 13 . That is, the processor 14 controls the memory 15 as occasion calls, cooperates with the digital circuit 13 as occasion calls, and codes and modulates a DL data signal. In addition, the digital circuit 13 may also code and modulate a DL data signal.
- the DL control information generation unit is achieved by, for example, the processor 14 , the memory 15 , and the digital circuit 13 . That is, the processor 14 controls the memory 15 as occasion calls, cooperates with the digital circuit 13 as occasion calls, and generates DL control information. In addition, the digital circuit 13 may also generate DL control information.
- the DL data coding and modulation unit is achieved by, for example, the processor 14 , the memory 15 , and the digital circuit 13 . That is, the processor 14 controls the memory 15 as occasion calls, cooperates with the digital circuit 13 as occasion calls, and codes and modulates a DL control signal. In addition, the digital circuit 13 may also code and modulate a DL control signal.
- the DL reference signal generation unit 111 is achieved by, for example, the processor 14 , the memory 15 , and the digital circuit 13 . That is, the processor 14 controls the memory 15 as occasion calls, cooperates with the digital circuit 13 as occasion calls, and generates a DL reference signal. In addition, the digital circuit 13 may also generate a DL reference signal.
- the DL frame generation unit 112 is achieved by, for example, the processor 14 , the memory 15 , and the digital circuit 13 . That is, the processor 14 controls the memory 15 as occasion calls, cooperates with the digital circuit 13 as occasion calls, places the DL data signal, the DL control signal, and the DL reference signal after coding and modulation in a DL frame, and generates a DL frame. In addition, the digital circuit 13 may also place the DL data signal, the DL control signal, and the DL reference signal after coding and modulation in a DL frame and generate a DL frame.
- the DL wireless sending unit 113 is achieved by, for example, the wireless IF 11 and the analog circuit 12 (those carrying out sending process). That is, the analog circuit 12 upconverts a baseband signal corresponding to the inputted DL frame by frequency conversion and the like to a wireless signal, and the wireless IF 11 wirelessly sends the wireless signal to the wireless terminals 2 . While the DL wireless sending unit 113 and the UL wireless receiving unit 101 may be achieved by different wireless IFs 11 (antennas), they may also share one wireless IF 11 by using a duplexer, which is the analog circuit 12 .
- the transmission network sending unit 114 is achieved by, for example, the transmission network IF 16 , the analog circuit 12 , the processor 14 , the memory 15 , and the digital circuit 13 . That is, the processor 14 controls the memory 15 as occasion calls, cooperates with the digital circuit 13 as occasion calls, and converts a data signal and a control signal to be sent to a digital baseband signal.
- the analog circuit 12 converts the digital baseband signal to a wired signal or a wireless signal
- the transmission network IF 16 sends the wired signal or the wireless signal.
- the transmission network receiving unit 115 is achieved by, for example, the transmission network IF 16 , the analog circuit 12 , the processor 14 , the memory 15 , and the digital circuit 13 .
- the transmission network IF 16 receives the wired signal or the wireless signal, and the analog circuit 12 converts the wired signal or the wireless signal to a digital baseband signal.
- the processor 14 controls the memory 15 as occasion calls, cooperates with the digital circuit 13 as occasion calls, and converts a digital baseband signal to a data signal and a control signal.
- FIG. 8 illustrates one example of a hardware configuration of the wireless terminal 2 in the first embodiment.
- the wireless terminal 2 in the above embodiment is provided with a wireless IF 21 , an analog circuit 22 , a digital circuit 23 , a processor 24 , a memory 25 , an input IF 26 , an output IF 27 , and the like.
- the wireless IF 21 is an interface device to carry out wireless communication with the wireless base stations 1 and is, for example, an antenna.
- the analog circuit 22 is a circuit to process an analog signal and may be roughly categorized into those carrying out receiving process, those carrying out sending process, and those carrying out other process.
- the analog circuit that carries out receiving process includes, for example, an LNA, a BPF, a mixer, an LPF, an AGC, an ADC, a PLL, and the like.
- the analog circuit that carries out sending process includes, for example, a PA, a BPF, a mixer, an LPF, a DAC, a PLL, and the like.
- the analog circuit that carries out other process includes a duplexer and the like.
- the digital circuit 23 includes, for example, an LSI, an FPGA, an ASIC, and the like.
- the processor 24 is a device to process data and includes, for example, a CPU, a DSP, and the like.
- the memory 25 is a device to memorize data and includes, for example, a ROM, a RAM, and the like.
- the input IF 26 is a device to carry out an input and includes, for example, an operation button, a microphone, and the like.
- the output IF 27 is a device to carry out an output and includes, for example, a display, a speaker, and the like.
- the DL wireless receiving unit 201 is achieved by, for example, the wireless IF 21 and the analog circuit 22 (those carrying out receiving process). That is, the wireless IF 21 receives a DL wireless signal from the wireless base station 1 , and the analog circuit 22 downconverts the received wireless signal by frequency conversion and the like to convert it to a baseband signal corresponding to a DL frame.
- the DL frame analysis unit 202 is achieved by, for example, the processor 24 , the memory 25 , and the digital circuit 23 . That is, the processor 24 controls the memory 25 as occasion calls, cooperates with the digital circuit 23 as occasion calls, and extracts a DL data signal, a DL control signal, and a DL reference signal from the baseband signal corresponding to the DL frame.
- the digital circuit 23 may also extract a DL data signal, a DL control signal, and a DL reference signal from the baseband signal corresponding to the DL frame.
- the DL reference signal processing unit 203 is achieved by, for example, the processor 24 , the memory 25 , and the digital circuit 23 . That is, the processor 24 controls the memory 25 as occasion calls, cooperates with the digital circuit 23 as occasion calls, and obtains the DL channel characteristics based on the DL reference signal. In addition, the digital circuit 23 may also obtain the DL channel characteristics based on the DL reference signal.
- the DL control signal demodulation and decoding unit 204 is achieved by, for example, the processor 24 , the memory 25 , and the digital circuit 23 . That is, the processor 24 controls the memory 25 as occasion calls, cooperates with the digital circuit 23 as occasion calls, demodulates a DL control signal, and carries out error correction and decoding. In addition, the digital circuit 23 may also demodulate a DL control signal and carry out error correction and decoding.
- the DL data signal demodulation and decoding unit 205 is achieved by, for example, the processor 24 , the memory 25 , and the digital circuit 23 .
- the processor 24 controls the memory 25 as occasion calls, cooperates with the digital circuit 23 as occasion calls, demodulates a DL data signal, and carries out error correction and decoding.
- the digital circuit 23 may also demodulate a DL data signal and carry out error correction and decoding.
- the upper layer unit 206 is achieved by, for example, the processor 24 , the memory 25 , and the digital circuit 23 . That is, the processor 24 controls the memory 25 as occasion calls, cooperates with the digital circuit 23 as occasion calls, processes the inputted DL data, provides various functions in the wireless terminal 2 a , and also generates UL data (information) based on the provided functions. In addition, the digital circuit 23 may also process the inputted DL data, provide various functions in the wireless terminal 2 a , and also generate UL data (information) based on the provided functions.
- the UL schedule management unit 207 is achieved by, for example, the processor 24 , the memory 25 , and the digital circuit 23 .
- the processor 24 controls the memory 25 as occasion calls, cooperates with the digital circuit 23 as occasion calls, and carries out management of a UL schedule when UL data occurs.
- the digital circuit 23 may also carry out management of a UL schedule when UL data occurs.
- the UL data signal generation unit 208 is achieved by, for example, the processor 24 , the memory 25 , and the digital circuit 23 . That is, the processor 24 controls the memory 25 as occasion calls, cooperates with the digital circuit 23 as occasion calls, and generates a UL data signal. In addition, the digital circuit 23 may also generate a UL data signal.
- the UL data coding and modulation unit is achieved by, for example, the processor 24 , the memory 25 , and the digital circuit 23 . That is, the processor 24 controls the memory 25 as occasion calls, cooperates with the digital circuit 23 as occasion calls, and codes and modulates a UL data signal. In addition, the digital circuit 23 may also code and modulate a UL data signal.
- the UL control information generation unit is achieved by, for example, the processor 24 , the memory 25 , and the digital circuit 23 . That is, the processor 24 controls the memory 25 as occasion calls, cooperates with the digital circuit 23 as occasion calls, and generates UL control information. In addition, the digital circuit 23 may also generate UL control information.
- the UL data coding and modulation unit is achieved by, for example, the processor 24 , the memory 25 , and the digital circuit 23 . That is, the processor 24 controls the memory 25 as occasion calls, cooperates with the digital circuit 23 as occasion calls, and codes and modulates a UL control signal. In addition, the digital circuit 23 may also code and modulate a UL control signal.
- the UL reference signal generation unit 212 is achieved by, for example, the processor 24 , the memory 25 , and the digital circuit 23 . That is, the processor 24 controls the memory 25 as occasion calls, cooperates with the digital circuit 23 as occasion calls, and generates a UL reference signal. In addition, the digital circuit 23 may also generate a UL reference signal.
- the UL frame generation unit 213 is achieved by, for example, the processor 24 , the memory 25 , and the digital circuit 23 . That is, the processor 24 controls the memory 25 as occasion calls, cooperates with the digital circuit 23 as occasion calls, places the UL data signal, the UL control signal, and the UL reference signal after coding and modulation in a UL frame, and generates a UL frame. In addition, the digital circuit 23 may also place the UL data signal, the UL control signal, and the UL reference signal after coding and modulation in a UL frame and generate a UL frame.
- the UL wireless sending unit 214 is achieved by, for example, the wireless IF 21 and the analog circuit 22 (those carrying out sending process). That is, the analog circuit 22 upconverts a baseband signal corresponding to the inputted UL frame by frequency conversion and the like to a wireless signal, and the wireless IF 21 wirelessly sends the wireless signal to the wireless terminals 2 . While the UL wireless sending unit 214 and the DL wireless receiving unit 201 may be achieved by different wireless IFs 21 (antennas), they may also share one wireless IF 21 by using a duplexer, which is the analog circuit 22 .
- the connected wireless base station 1 a receives other station wireless resource information including unused wireless resources information, which is information indicating a UL wireless resource not used by the other wireless base station 1 b from the other wireless base station 1 b . Then, the connected wireless base station 1 a schedules a UL wireless resource used for UL sending from the subordinate wireless terminal 2 a to the other wireless base station 1 b based on the received unused wireless resources information.
- FIG. 9 corresponds to process, as described before, where sending data (DL data) to the subordinate wireless terminal 2 a occurs in the wireless base station 1 a.
- DL data occurs in the connected wireless base station 1 a .
- DL data occurs when an audio signal, data, and the like are sent from the other wireless terminal 2 b to the subordinate wireless terminal 2 a , a server on the Internet sends data to the wireless terminal 2 a , and the like.
- the connected wireless base station 1 a schedules a DL wireless resource to send the DL data to the wireless terminal 2 a .
- the scheduling of a DL wireless resource may use a general technique, so that the descriptions are omitted here.
- the connected wireless base station 1 a schedules a UL wireless resource to receive a response signal (ACK/NACK signal) from the wireless terminal 2 a that have received the DL data. This is carried out as below.
- the connected wireless base station 1 a obtains the UL receiving quality from the wireless terminal 2 a and determines whether or not to set a reception destination of the response signal as the local station based on the UL receiving quality in S 203 .
- the connected wireless base station 1 a sends wireless resource requesting information to the other wireless base stations 1 b , 1 c via the transmission network.
- the other wireless base stations 1 b , 1 c respectively obtain unused wireless resources in S 205 , and send other station wireless resource information including the unused wireless resources information to the connected wireless base station 1 a via the transmission network in S 206 .
- the connected wireless base station 1 a determines a UL wireless resource for the response signal and the other wireless base station 1 b to be the UL sending destination.
- S 203 through S 207 are similar to S 103 through S 107 , so that the details are omitted.
- the connected wireless base station 1 a sends determined wireless resource information, which is information indicating the selected UL wireless resource, to the subordinate wireless terminal 2 a on a DL wireless signal.
- the connected wireless base station 1 a in the second embodiment sends, in addition to the determined wireless resource information, DL data on a DL wireless signal as well.
- the connected wireless base station 1 a sends DL data in a conventional LTE system.
- the connected wireless base station 1 a places (maps) the DL data in the DL wireless resource (resource block) on the DL frame.
- the connected wireless base station 1 a places a DCI (refer to FIG. 4 ), which is DL control information, in a predetermined region of the DL frame same as the DL data.
- the DCI includes RB assignment, which is information indicating the DL wireless resource assigned to the DL data.
- the connected wireless base station 1 a sends a DL wireless signal including the DL frame to the wireless terminal 2 a.
- the wireless terminal 2 a receives a DL wireless signal including the DL frame.
- the wireless terminal 2 a recognizes (detects) the presence of DL data towards itself based on the RNTI included in the DCI in the DL frame, and recognizes (detects) that the scope of DCI application is the DL data (PDSCH) based on the DCI format.
- the wireless terminal 2 a extracts the DL data based on the RB assignment included in the DCI and carries out demodulation and decoding of the DL data based on the MCS included in the DCI.
- the wireless terminal 2 a sends a response signal (an ACK signal indicating decoding success or a NACK signal indicating decoding failure) to the connected wireless base station 1 a on a UL frame in accordance with the decoding result.
- the wireless terminal 2 a places the response signal in the UL frame corresponding to the placement of the DCI itself in the DL frame received earlier (note that it is not the placement indicated by the RB assignment in the DCI).
- the connected wireless base station 1 a is capable of easily linking the sent DL data with the received response signal.
- Resource specification in the PUCCH (logical channel for a UL control signal) is carried out by a CCE (control channel element) number of the PDCCH (logical channel for a DL control signal) represented by a formula (1).
- specification of the UL wireless resource for ACK/NACK is carried out by placement of the DCI resource represented by a formula (1).
- n PUCCH (1, ⁇ tilde over (p) ⁇ 0 ) n CCE +N PUCCH (1) (1)
- n CCE is a minimum CCE number used for sending of the corresponding DCI (for example, minimum CCE number upon configuring the PDCCH)
- N PUCCH (1) is a parameter notified by an upper layer.
- a CCE is a wireless resource unit that a RB is divided further, details are omitted.
- the DL control information (DCI) related to the DL data and the UL control information (ACK/NACK) are only capable of using a mutually corresponding wireless resource. Accordingly, regarding control information related to the DL data, when the other wireless base station 1 b uses a certain UL wireless resource R1, for example, the connected wireless base station 1 a is not only incapable of using the UL wireless resource R1 (to avoid resource conflict) but also incapable of using a DL wireless resource R1. Even in a situation where the DL resources do not interfere with each other, the connected wireless base station 1 a in this example has no option but to use a UL wireless resource R2 ( ⁇ R1) and a DL wireless resource R2. Accordingly, in the conventional LTE system, scheduling for control information related to the DL data may be considered to be poor in flexibility.
- the wireless terminal 2 a having received the DL data as well as the DCI places a response signal to the DL data in a wireless resource that is shifted by the resource offset stored in the DCI from the corresponding wireless resource of the DCI.
- FIG. 10 illustrates one example of a DCI format according to the second embodiment.
- the DCI format in FIG. 10 includes the resource offset.
- the resource specification using the resource offset may be represented as a formula (2).
- n PUCCH (1, ⁇ tilde over (p) ⁇ 0 ) n CCE +N PUCCH (1) +n PUCCH — offset (2)
- n PUCCH — offset is a resource offset of the PUCCH, and the unit is a CCE.
- the wireless communication system in the second embodiment it is possible to assign a non-corresponding wireless resource to the DL control information (DCI) related to the DL data and the UL control information (ACK/NACK).
- DCI DL control information
- ACK/NACK UL control information
- the other wireless base station 1 b uses a certain UL wireless resource R1 and a DL wireless resource R1
- the connected wireless base station 1 a sends the DCI, which is DL control information, and the DL frame including the DL data to the wireless terminal 2 a .
- the DCI includes, in addition to the resource offset described before, the RNTI, the RB assignment related to the DL data, the MCS, and the like.
- this resource offset corresponds to the determined wireless resource information (UL wireless resource for UL sending from the wireless terminal 2 a to other wireless base station 1 b ).
- the wireless terminal 2 a receives the DL frame sent by the connected wireless base station 1 a .
- the wireless terminal 2 a recognizes (detects) the presence of the DL data towards itself based on the RNTI included in the DCI in the DL frame, and recognizes (detects) that the scope of DCI application is the DL data (PDSCH) based on the DCI format.
- the wireless terminal 2 a extracts DL data based on RB assignment included in the DCI, and carries out demodulation and decoding of the DL data based on the MCS included in the DCI.
- the reception of DL data is completed.
- the resource offset included in the DCI is to be used when sending a UL control signal (ACK/NACK) and is not used here.
- the connected wireless base station 1 a sends determined wireless resource information to the other wireless base station 1 b , which is a sending source of the unused wireless resource to be the origin of the determined wireless resource via the transmission network.
- the determined wireless resource information sent by the connected wireless base station 1 a corresponds to information indicating placement of adding the resource offset included in the DCI to the placement of the DCI included in the DL frame sent by the connected wireless base station 1 a .
- S 208 and S 210 may be simultaneous or in the reverse order.
- the wireless terminal 2 a in response to the decoding result of S 208 , the wireless terminal 2 a sends a UL wireless signal including the UL frame where a response signal (ACK signal indicating decoding success or NACK signal indicating decoding failure), which is a UL control signal, is placed.
- the wireless terminal 2 a of the present embodiment places a response signal in a UL frame using the resource offset included in the DCI as described before.
- the wireless terminal 2 a has placement of the response signal in the UL frame as placement where the resource offset included in the DCI is added to the placement of the DCI itself in the DL frame received earlier.
- the other wireless base station 1 b receives a response signal, which is a UL control signal placed in the UL frame included in the UL wireless signal sent by the wireless terminal 2 a .
- the other wireless base station 1 b receives a response signal using the UL wireless resource indicated by the determined wireless resource information received from the connected wireless base station 1 a .
- the determined wireless resource information received from the connected wireless base station 1 a is the information indicating placement where the resource offset included in the DCI is added to the placement of the DCI included in the DL frame sent by the connected wireless base station 1 a.
- the other wireless base station 1 b sends (transfers) the response signal included in the received UL wireless signal to the connected wireless base station 1 a via the transmission network. This completes the reception of a response signal (ACK/NACK) in the connected wireless base station 1 a in S 213 .
- ACK/NACK response signal
- correspondence relationship related to the placement of the DL control information (DCI) related to the DL data and the UL control information (ACK/NACK) is separated and sends the information related to the placement of the corresponding UL control information in the DL control information.
- the wireless communication system in the second embodiment exhibits, in addition to the effect obtained in the wireless communication system in the first embodiment, an effect of allowing flexible scheduling to the control information related to the DL data.
- the third embodiment is a modification that is applicable to the first embodiment or the second embodiment, and the connected wireless base station 1 a selects the other wireless base station 1 b , which is a UL sending destination, based on the UL receiving quality notified in advance from the other wireless base stations 1 b.
- the connected wireless base station 1 a sends, in addition to wireless resource requesting information (similar to S 104 in FIG. 3 ), SRS resource information to the other wireless base stations 1 b , 1 c .
- the SRS resource information indicates resource information to be used for reception of an SRS, which is a UL reference signal for UL receiving quality measurement generated by the wireless terminal 2 a .
- the SRS resource information includes, for example, an RB to which an SRS is assigned, data series information of an SRS, and the like. Since the generated SRS is different for each wireless terminal 2 , only the connected wireless base station 1 a that regularly recognizes the SRS resource information is capable of receiving it. By obtaining the SRS resource information, the other wireless base stations 1 b , 1 c become capable of receiving an SRS.
- the other wireless base stations 1 b , 1 c confirm a used wireless resource (similar to S 105 in FIG. 3 ).
- the other wireless base stations 1 b , 1 c receive an SRS from the wireless terminal 2 a using the SRS resource information and measures the UL receiving quality.
- the other wireless base stations 1 b , 1 c send, in addition to the other station wireless resource information (similar to S 106 in FIG. 3 ), the UL receiving quality information measured in S 306 to the connected wireless base station 1 a.
- the connected wireless base station 1 a is capable of using the received UL receiving quality information in the determination of UL reception destination and UL resource.
- the connected wireless base station 1 a is capable of determining, among the other wireless base stations 1 b , 1 c capable of securing the UL wireless resource in the amount requested in the UL schedule requesting information (this is obtained by the other station wireless resource information), that having best receiving quality indicated by the received UL receiving quality information as the UL reception destination. Since S 309 through S 313 in FIG. 11 are similar to S 108 through S 112 in FIG. 3 , the description is omitted.
- the connected wireless base station 1 a selects the other wireless base station 1 b , which is the UL sending destination, based on the UL receiving quality notified in advance from the other wireless base stations 1 b , 1 c .
- the connected wireless base station 1 a sends the SRS resource information to the other wireless base stations 1 b , 1 c in advance.
- the wireless communication system in the third embodiment exhibits, in addition to an effect obtained by the wireless communication system in the first embodiment, an effect of allowing selection of the other wireless base stations 1 b , 1 c having good UL receiving quality as the UL sending destination.
- the fourth embodiment is a modification that is applicable to as any of the first embodiment through the third embodiment, and the connected wireless base station 1 a notifies the other wireless base stations 1 b , 1 c in advance of a wireless resource amount to be used for the UL sending of the wireless terminal 2 a.
- the connected wireless base station 1 a sends wireless resource requesting information, which is information to request a UL wireless resource, to the other wireless base stations 1 b , 1 c via the transmission network.
- the connected wireless base station 1 a in the present embodiment stores requested amount information of the UL wireless resource included in the UL schedule requesting information received in S 402 in the wireless resource requesting information for sending.
- the other wireless base stations 1 b , 1 c obtain unused wireless resources.
- the other wireless base stations 1 b , 1 c in the present embodiment obtain the unused wireless resources of the requested amount based on the UL wireless resource amount information included in the received wireless resource requesting information.
- the other wireless base stations 1 b , 1 c send other station wireless resource information including unused wireless resources information indicating the obtained unused wireless resources to the connected wireless base station 1 a via the transmission network, respectively.
- the other station wireless resource information sent in S 406 satisfies the requested amount (of the UL wireless resource) included in the wireless resource requesting information received in S 404 .
- the connected wireless base station 1 a receives other station wireless resource information including the unused wireless resources information respectively from the other wireless base stations 1 b , 1 c . Then, in S 407 , the connected wireless base station 1 a selects the UL wireless resource that is used for UL data sending from the wireless terminal 2 a based on the received unused wireless resources information.
- the connected wireless base station 1 a in the first embodiment arbitrarily selects unused wireless resources of the requested wireless resource amount based on the received unused wireless resources information in S 107 in FIG. 3 .
- the unused wireless resources information received by the connected wireless base station 1 a of the present embodiment indicates unused wireless resources of the requested wireless resource amount.
- the connected wireless base station 1 a in the present embodiment may select one item of the unused wireless resources information received respectively from the other wireless base stations 1 b , 1 c in S 407 . That is, in the connected wireless base station 1 a of the present embodiment, selection of the UL wireless resource based on the unused wireless resources and selection of the other wireless base station 1 b to be a sending destination of UL sending are equivalent. Here, it is assumed that the connected wireless base station 1 a selects the unused wireless resources of the other wireless base station 1 b as the UL wireless resource.
- the connected wireless base station 1 a sends the determined wireless resource information to the wireless terminal 2 a (similar to S 108 in FIG. 3 ).
- the connected wireless base station 1 a sends response information indicating to be selected as the other wireless base station 1 b to be a sending destination of UL sending to the other wireless base station 1 b to be the sending destination of the UL sending.
- the connected wireless base station 1 a in the present embodiment different from the connected wireless base station 1 a in the first embodiment, does not have to notify the other wireless base station 1 b of information indicating the selected unused wireless resources. This is because the other wireless base station 1 b recognizes the selected unused wireless resources. Since S 410 through S 412 in FIG. 12 are same as S 110 through S 112 in FIG. 3 , the description is omitted.
- the fourth embodiment compared with the first embodiment, although a size of wireless resource requesting information is slightly greater for including the UL wireless resource amount information, the other station wireless resource information (unused wireless resources information) may be same or smaller.
- the connected wireless base station 1 a may send, instead of the determined wireless resource information, the response information. Accordingly, according to the fourth embodiment, compared with the first embodiment, an effect of suppressing the information amount sent and received between the wireless base stations 1 is expected.
- the fifth embodiment is a modification that is applicable to any of the first embodiment through the third embodiment, and the connected wireless base station 1 a notifies of, without obtaining other station wireless resource information from the other wireless base stations 1 b , 1 c , a UL wireless resource used for the UL sending from the wireless terminal 2 a .
- the connected wireless base station 1 a notifies the other wireless base stations 1 b , 1 c one-sidedly of the UL wireless resource used for the UL sending from the wireless terminal 2 a.
- the connected wireless base station 1 a When the UL reception destination is determined as other than the local station in S 503 , the connected wireless base station 1 a further determines a UL wireless resource and a UL reception destination used for the UL reception in S 504 .
- the connected wireless base station 1 a is capable of determining the UL wireless resource and the UL reception destination used for the UL reception in an arbitrary method.
- the connected wireless base station 1 a sends the determined UL wireless resource to the wireless terminal 2 a (similar to S 108 in FIG. 3 ). Then, in S 506 , the connected wireless base station 1 a sends wireless resource requesting information, which is the information to request the determined UL wireless resource, to the other wireless base station 1 b , which is the determined UL sending destination, via the transmission network. Since S 507 through S 509 in FIG. 13 are similar to S 110 through S 112 in FIG. 3 , the description is omitted.
- the other station wireless resource information (unused wireless resources information) becomes not requested and the information sent from the connected wireless base station 1 a to the other wireless base station 1 b is also reduced. Accordingly, according to the fifth embodiment, compared with the first embodiment, an effect of suppressing the information amount sent and received between the wireless base stations 1 is expected.
- the sixth embodiment is a modification that is applicable to as any of the first embodiment through the third embodiment, and the other wireless base stations 1 b , 1 c sense an event to be an opportunity, thereby sending other station wireless resource information to the connected wireless base station 1 a .
- the other station wireless base stations 1 b , 1 c send other station wireless resource information to the connected wireless base station 1 a.
- the other wireless base stations 1 b , 1 c sense a predetermined event to be a trigger (opportunity) to send other station wireless resource information.
- This event may be an arbitrary event and may be, as an example, a lapse of predetermined time from the last sending of the other station wireless resource information. As another example, it may be the UL wireless used resource amount in the other wireless base stations 1 b , 1 c at a predetermined value or less.
- the other station wireless base stations 1 b , 1 c confirm the used wireless resource and send the other station wireless resource information (similar to S 105 and S 106 in FIG. 3 ).
- S 604 through S 606 in FIG. 14 UL data occurs in the wireless terminal 2 a , and the wireless terminal 2 a sends UL schedule requesting information and the connected wireless base station 1 a determines whether or not to set the UL reception destination as the local station (similar to S 101 through S 103 in FIG. 3 ). Then, when the UL reception destination is determined as other than the local station in S 606 , the connected wireless base station 1 a determines, in S 607 , a UL wireless resource and a UL reception destination based on the other station wireless resource information received in S 603 . Since S 607 through S 612 in FIG. 14 are similar to S 107 through S 112 in FIG. 3 , the description is omitted. Although S 601 through S 603 in FIG. 14 are carried out at a timing before S 605 , they do not have to be so and S 601 through S 603 may be at any timing as long as before S 607 .
- the wireless resource requesting information becomes not requested. Accordingly, according to the sixth embodiment, compared with the first embodiment, an effect of suppressing information amount sent and received between the wireless base stations 1 is expected.
- the wireless terminal 2 a generates and sends a DM-RS, which is one of the UL reference signals, in accordance with the other wireless base station 1 b , which is a UL sending destination. It is possible to combine the seventh embodiment with the first embodiment or the second embodiment, and there are many points in common with them. In the following descriptions, descriptions are given mainly to the points in the seventh embodiment different from the first embodiment in the following descriptions.
- the wireless terminal 2 a when sending a UL wireless frame, the wireless terminal 2 a generates a DM-RS, which is one of the UL reference signal, and maps it in a UL wireless frame for sending.
- the connected wireless base station 1 a that has received the UL wireless frame demodulates the UL control signal and the data signal using channel characteristics to estimate the channel characteristics based on the DM-RS.
- the DM-RS is information (pattern) different for each wireless base station 1 .
- the DM-RS is generated based on a base station identifier.
- the wireless terminal 2 a generates a DM-RS for the connected wireless base station 1 a using the identifier of the connected wireless base station 1 a and sends it in a UL wireless frame.
- the connected wireless base station 1 a carries out channel estimation by analyzing the DM-RS in the received UL wireless frame using the identifier of the connected wireless base station 1 a .
- the connected wireless base station 1 a is capable of appropriately receiving the DM-RS and capable of estimating the channel characteristics with high precision, so that decoding errors are suppressed.
- the other wireless base station 1 b receives the DM-RS and utilizes it for demodulation. Since the DM-RS towards the other wireless base station 1 b is generally different from the DM-RS towards the connected wireless base station 1 a , the other wireless base station 1 b is not capable of appropriately estimating the channel characteristics based on the DM-RS. In this case, it turns out to increase decoding errors and thus not preferred.
- the connected wireless base station 1 a stores an identifier of the other wireless base station 1 b in the DL control information (DCI) for sending. Then, the wireless terminal 2 a having received the DL wireless frame, when sending the UL wireless frame, generates the DM-RS using the identifier of the other wireless base station 1 b and maps the DM-RS in the UL wireless frame for sending.
- DCI DL control information
- FIG. 15 illustrates a DCI format in the seventh embodiment.
- FIG. 15(A) is a DCI format of a modification where the seventh embodiment is applied to the first embodiment.
- FIG. 15(B) is a DCI format of a modification where the seventh embodiment is applied to the second embodiment.
- the DCI formats in FIG. 15 both have a region to store a UL sending destination identifier, which is an identifier of the other wireless base station 1 b.
- the wireless terminal 2 a is capable of generating and sending the DM-RS towards the other wireless base station 1 b , so that an effect of suppressing decoding errors in the other wireless base station 1 b is obtained.
- the eighth embodiment is also to solve the problem same as the seventh embodiment, and it is possible to combine with the first embodiment or the second embodiment. Since the eighth embodiment has many points in common with the seventh embodiment, descriptions are given mainly to the points in the eighth embodiment different from the seventh embodiment in the following descriptions.
- the eighth embodiment it does not have to store an identifier of the other wireless base station 1 b in the DCI as in the seventh embodiment.
- the other wireless base station 1 b analyzes the DM-RS in the received UL wireless frame using the identifier of the connected wireless base station 1 a (not the identifier of itself) and carries out channel estimation.
- the other wireless base station 1 b is capable of learning the identifier of the connected wireless base station 1 a in a message sent and received with the connected wireless base station 1 a.
- the other wireless base station 1 b is capable of appropriately receiving the DM-RS towards the connected wireless base station 1 a and capable of estimating the channel characteristics with high precision, so that an effect of suppressing decoding errors is obtained.
- the former has to use a function compatible with both the wireless base stations 1 and the wireless terminals 2 , while the latter has to use a function compatible only with the wireless base stations 1 , so that the latter is considered to be easier for introduction.
- the ninth embodiment is also to solve the problem same as the seventh embodiment and the eighth embodiment, and it is possible to combine with the first embodiment or the second embodiment.
- the ninth embodiment is equivalent to an embodiment in which the seventh embodiment and the eighth embodiment are combined.
- the wireless terminal 2 a in the present embodiment When an identifier of the other wireless base station 1 b is stored in the DCI in the received DL wireless frame, the wireless terminal 2 a in the present embodiment generates the DM-RS using the identifier of the other wireless base station 1 b . At this time, the other wireless base station 1 b analyzes the DM-RS in the UL wireless frame received as regularly using the identifier of itself and carries out channel estimation.
- the wireless terminal 2 a when the identifier of the other wireless base station 1 b is not stored in the DCI, the wireless terminal 2 a generates the DM-RS using an identifier of the connected wireless base station 1 a .
- the other wireless base station 1 b analyzes the DM-RS in the received UL wireless frame using the identifier of the connected wireless terminal 2 a and carries out channel estimation.
- the other wireless base station 1 b is regularly not capable of learning whether or not an identifier of the other wireless base station 1 b is stored in the DCI. Therefore, the other wireless base station 1 b has to be notified of whether or not the identifier of the other wireless base station 1 b is stored in the DCI from the connected wireless base station 1 a in advance.
- the connected wireless base station 1 a carries out determination of the other wireless base station 2 b to be the destination (determined wireless base station) and the UL wireless resource to be used (determined wireless resource).
- the subject of such determination is not limited to the connected wireless base station 1 a.
- an upper station connected to the core network and the like may also determine the determined wireless base station and the determined wireless resource.
- the other wireless base station 1 b different from the connected wireless base station 1 a may also determine the determined wireless base station and the determined wireless resource.
- the wireless terminal 2 a may also determine the determined wireless base station and the determined wireless resource.
- an upper station (upper device), the other wireless base station 1 b , the wireless terminal 2 a , and the like may also receive other station wireless resource information from the other wireless base stations 2 b , 2 c in a procedure similar to that carried out by the connected wireless base station 1 a in the first through ninth embodiments described above. Then, the upper station (upper device), the other wireless base station 2 b , wireless terminal 2 a , and the like may also determine the determined wireless base station and the determined wireless resource based on the received other station wireless resource information.
- connection to is able to be replaced with “coupled to”.
- an element when an element is referred to as being “connected to” or “coupled to” another element, it can be not only directly but also indirectly connected or coupled to the other element (namely, intervening elements may be present). So do “connecting to”, “coupling to”, “connection to”, “coupling to” and so on.
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Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
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US15/015,702 US10708896B2 (en) | 2012-03-19 | 2016-02-04 | Wireless communication system, wireless base station, wireless terminal, and wireless communication method |
US16/863,264 US11265867B2 (en) | 2012-03-19 | 2020-04-30 | Wireless communication system, wireless base station, wireless terminal, and wireless communication method |
Applications Claiming Priority (1)
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- 2012-03-19 KR KR1020167025926A patent/KR20160114733A/ko not_active Application Discontinuation
- 2012-03-19 RU RU2014142024A patent/RU2619587C2/ru not_active IP Right Cessation
- 2012-03-19 CA CA 2867670 patent/CA2867670A1/en not_active Abandoned
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- 2012-03-19 CN CN201910874950.XA patent/CN110445598B/zh active Active
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Also Published As
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CN110445598A (zh) | 2019-11-12 |
KR101660037B1 (ko) | 2016-09-27 |
US20160157215A1 (en) | 2016-06-02 |
WO2013140436A1 (ja) | 2013-09-26 |
CN104170489B (zh) | 2019-10-15 |
US10708896B2 (en) | 2020-07-07 |
US20200260425A1 (en) | 2020-08-13 |
RU2619587C2 (ru) | 2017-05-17 |
JPWO2013140436A1 (ja) | 2015-08-03 |
CN104170489A (zh) | 2014-11-26 |
MX341404B (es) | 2016-08-18 |
US11265867B2 (en) | 2022-03-01 |
CA2867670A1 (en) | 2013-09-26 |
JP5971329B2 (ja) | 2016-08-17 |
EP2830371A4 (en) | 2015-03-11 |
EP2830371A1 (en) | 2015-01-28 |
MX2014011146A (es) | 2014-12-10 |
CN110445598B (zh) | 2022-07-08 |
KR20160114733A (ko) | 2016-10-05 |
RU2014142024A (ru) | 2016-05-10 |
KR20140135754A (ko) | 2014-11-26 |
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