WO2018062927A1

WO2018062927A1 - Method and apparatus for supporting non-anchor prb in wireless communication system

Info

Publication number: WO2018062927A1
Application number: PCT/KR2017/010906
Authority: WO
Inventors: Sangwook Han; Youngdae Lee; Gwanmo KU; Sangwon Kim; Jaewook Lee
Original assignee: Lg Electronics Inc.
Priority date: 2016-09-30
Filing date: 2017-09-29
Publication date: 2018-04-05

Abstract

Disclosed herein is a method of processing a signal at a user equipment (UE) in a wireless communication system. The method includes receiving system information from a base station; determining whether a field indicating that a plurality of non-anchor physical resource blocks (PRBs) are supported by the base station is present or not in the system information; selecting one PRB of the plurality of non-anchor PRBs and an anchor PRB based on a result of determining; and receiving a paging message via the selected one PRB.

Description

METHOD AND APPARATUS FOR SUPPORTING NON-ANCHOR PRB IN WIRELESS COMMUNICATION SYSTEM

The present disclosure relates to a wireless communication system, and more particularly, to a method and apparatus for supporting non-anchor PRB (physical resource block) in a wireless communication system.

As an example of a mobile communication system to which the present invention is applicable, a 3rd Generation Partnership Project Long Term Evolution (hereinafter, referred to as LTE) communication system is described in brief.

FIG. 1 is a view schematically illustrating a network structure of an E-UMTS as an exemplary radio communication system. An Evolved Universal Mobile Telecommunications System (E-UMTS) is an advanced version of a conventional Universal Mobile Telecommunications System (UMTS) and basic standardization thereof is currently underway in the 3GPP. E-UMTS may be generally referred to as a Long Term Evolution (LTE) system. For details of the technical specifications of the UMTS and E-UMTS, reference can be made to Release 7 and Release 8 of “3rd Generation Partnership Project; Technical Specification Group Radio Access Network”.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE), eNode Bs (eNBs), and an Access Gateway (AG) which is located at an end of the network (E-UTRAN) and connected to an external network. The eNBs may simultaneously transmit multiple data streams for a broadcast service, a multicast service, and/or a unicast service.

One or more cells are present per eNB. A cell is configured to use one of bandwidths of 1.44, 3, 5, 10, 15, and 20MHz to provide a downlink or uplink transport service to several UEs. Different cells may be set to provide different bandwidths. The eNB controls data transmission and reception for a plurality of UEs. The eNB transmits downlink scheduling information with respect to downlink data to notify a corresponding UE of a time/frequency domain in which data is to be transmitted, coding, data size, and Hybrid Automatic Repeat and reQuest (HARQ)-related information. In addition, the eNB transmits uplink scheduling information with respect to uplink data to a corresponding UE to inform the UE of an available time/frequency domain, coding, data size, and HARQ-related information. An interface may be used to transmit user traffic or control traffic between eNBs. A Core Network (CN) may include the AG, a network node for user registration of the UE, and the like. The AG manages mobility of a UE on a Tracking Area (TA) basis, each TA including a plurality of cells.

Although radio communication technology has been developed up to LTE based on Wideband Code Division Multiple Access (WCDMA), demands and expectations of users and providers continue to increase. In addition, since other radio access technologies continue to be developed, new advances in technology are required to secure future competitiveness. For example, decrease of cost per bit, increase of service availability, flexible use of a frequency band, simple structure, open interface, and suitable power consumption by a UE are required.

An object of the present disclosure is to provide a method and apparatus for supporting non-anchor PRB (physical resource block) in a wireless communication system.

To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method of processing a signal at a user equipment (UE) in a wireless communication system is suggested. Especially, the method comprises receiving system information from a base station; determining whether a field indicating that a plurality of non-anchor physical resource blocks (PRBs) are supported by the base station is present or not in the system information; selecting one PRB of the plurality of non-anchor PRBs and an anchor PRB based on a result of determining; and receiving a paging message via the selected one PRB/

In another aspect of the present invention, a user equipment (UE) in a wireless communication system includes a wireless communication module and a processor connected to the wireless communication module. The processor is configured to receive system information from a base station, determine whether a field indicating that a plurality of non-anchor physical resource blocks (PRBs) are supported by the base station is present or not in the system information, select one PRB of the plurality of non-anchor PRBs and an anchor PRB based on a result of determining, and receive a paging message via the selected one PRB.

Preferably, a random access procedure is also performed via the selected PRB.

More preferably, when the field is not present in the system information, for receiving paging message and performing the random access procedure, the anchor PRB is selected.

While, when the field is present in the system information, for receiving paging message and performing the random access procedure, the one PRB of the plurality of non-anchor PRBs is selected by using an identity of the UE. Or, when the field is present in the system information, for receiving paging message and performing the random access procedure, the one PRB of the plurality of non-anchor PRBs and the anchor PRB is selected by using the identity of the UE.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

According to embodiments of the present disclosure, it is possible to more efficiently support non-anchor PRB in a wireless communication system.

It will be appreciated by persons skilled in the art that that the effects that can be achieved through the present invention are not limited to what has been particularly described hereinabove and other advantages of the present invention will be more clearly understood from the following detailed description.

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention.

In the drawings:

FIG. 1 is a diagram showing a network structure of an Evolved Universal Mobile Telecommunications System (E-UMTS) as an example of a wireless communication system.

FIG. 2 is a diagram conceptually showing a network structure of an evolved universal terrestrial radio access network (E-UTRAN).

FIG. 3 is a diagram showing a control plane and a user plane of a radio interface protocol between a UE and an E-UTRAN based on a 3rd generation partnership project (3GPP) radio access network standard.

FIG. 4 is a diagram showing physical channels used in a 3GPP system and a general signal transmission method using the same.

FIG. 5 is a diagram showing the structure of a radio frame used in a Long Term Evolution (LTE) system.

FIG. 6 is a diagram showing a general transmission and reception method using a paging message.

FIG. 7 is a diagram showing a process of operating a UE and an eNB in a contention based random access procedure provided by an LTE system.

FIG. 8 is an example of a system bandwidth including a plurality of narrow bands.

FIG. 9 is a flow chart showing a method of processing signals by a NB-IoT UE supporting non-anchor PRB according to an embodiment of the present application.

FIG. 10 is a block diagram illustrating a communication device according to embodiments of the present invention.

Hereinafter, structures, operations, and other features of the present invention will be readily understood from the embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Embodiments described later are examples in which technical features of the present invention are applied to a 3GPP system.

Although the embodiments of the present invention are described using a long term evolution (LTE) system and a LTE-advanced (LTE-A) system in the present specification, they are purely exemplary. Therefore, the embodiments of the present invention are applicable to any other communication system corresponding to the above definition. In addition, although the embodiments of the present invention are described based on a frequency division duplex (FDD) scheme in the present specification, the embodiments of the present invention may be easily modified and applied to a half-duplex FDD (H-FDD) scheme or a time division duplex (TDD) scheme.

FIG. 2 is a diagram conceptually showing a network structure of an evolved universal terrestrial radio access network (E-UTRAN). An E-UTRAN system is an evolved form of a legacy UTRAN system. The E-UTRAN includes cells (eNB) which are connected to each other via an X2 interface. A cell is connected to a user equipment (UE) via a radio interface and to an evolved packet core (EPC) via an S1 interface.

The EPC includes a mobility management entity (MME), a serving-gateway (S-GW), and a packet data network-gateway (PDN-GW). The MME has information about connections and capabilities of UEs, mainly for use in managing the mobility of the UEs. The S-GW is a gateway having the E-UTRAN as an end point, and the PDN-GW is a gateway having a packet data network (PDN) as an end point.

FIG. 3 is a diagram showing a control plane and a user plane of a radio interface protocol between a UE and an E-UTRAN based on a 3GPP radio access network standard. The control plane refers to a path used for transmitting control messages used for managing a call between the UE and the E-UTRAN. The user plane refers to a path used for transmitting data generated in an application layer, e.g., voice data or Internet packet data.

A physical (PHY) layer of a first layer provides an information transfer service to a higher layer using a physical channel. The PHY layer is connected to a medium access control (MAC) layer located on the higher layer via a transport channel. Data is transported between the MAC layer and the PHY layer via the transport channel. Data is transported between a physical layer of a transmitting side and a physical layer of a receiving side via physical channels. The physical channels use time and frequency as radio resources. In detail, the physical channel is modulated using an orthogonal frequency division multiple access (OFDMA) scheme in downlink and is modulated using a single carrier frequency division multiple access (SC-FDMA) scheme in uplink.

The MAC layer of a second layer provides a service to a radio link control (RLC) layer of a higher layer via a logical channel. The RLC layer of the second layer supports reliable data transmission. A function of the RLC layer may be implemented by a functional block of the MAC layer. A packet data convergence protocol (PDCP) layer of the second layer performs a header compression function to reduce unnecessary control information for efficient transmission of an Internet protocol (IP) packet such as an IP version 4 (IPv4) packet or an IP version 6 (IPv6) packet in a radio interface having a relatively small bandwidth.

A radio resource control (RRC) layer located at the bottom of a third layer is defined only in the control plane. The RRC layer controls logical channels, transport channels, and physical channels in relation to configuration, re-configuration, and release of radio bearers (RBs). An RB refers to a service that the second layer provides for data transmission between the UE and the E-UTRAN. To this end, the RRC layer of the UE and the RRC layer of the E-UTRAN exchange RRC messages with each other.

One cell of the eNB is set to operate in one of bandwidths such as 1.25, 2.5, 5, 10, 15, and 20 MHz and provides a downlink or uplink transmission service to a plurality of UEs in the bandwidth. Different cells may be set to provide different bandwidths.

Downlink transport channels for transmission of data from the E-UTRAN to the UE include a broadcast channel (BCH) for transmission of system information, a paging channel (PCH) for transmission of paging messages, and a downlink shared channel (SCH) for transmission of user traffic or control messages. Traffic or control messages of a downlink multicast or broadcast service may be transmitted through the downlink SCH and may also be transmitted through a separate downlink multicast channel (MCH).

Uplink transport channels for transmission of data from the UE to the E-UTRAN include a random access channel (RACH) for transmission of initial control messages and an uplink SCH for transmission of user traffic or control messages. Logical channels that are defined above the transport channels and mapped to the transport channels include a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), and a multicast traffic channel (MTCH).

When a UE is powered on or enters a new cell, the UE performs an initial cell search operation such as synchronization with an eNB (S401). To this end, the UE may receive a primary synchronization channel (P-SCH) and a secondary synchronization channel (S-SCH) from the eNB to perform synchronization with the eNB and acquire information such as a cell ID. Then, the UE may receive a physical broadcast channel from the eNB to acquire broadcast information in the cell. During the initial cell search operation, the UE may receive a downlink reference signal (DL RS) so as to confirm a downlink channel state.

After the initial cell search operation, the UE may receive a physical downlink control channel (PDCCH) and a physical downlink control channel (PDSCH) based on information included in the PDCCH to acquire more detailed system information (S402).

When the UE initially accesses the eNB or has no radio resources for signal transmission, the UE may perform a random access procedure (RACH) with respect to the eNB (steps S403 to S406). To this end, the UE may transmit a specific sequence as a preamble through a physical random access channel (PRACH) (S403) and receive a response message to the preamble through the PDCCH and the PDSCH corresponding thereto (S404). In the case of contention-based RACH, the UE may further perform a contention resolution procedure.

After the above procedure, the UE may receive PDCCH/PDSCH from the eNB (S407) and may transmit a physical uplink shared channel (PUSCH)/physical uplink control channel (PUCCH) to the eNB (S408), which is a general uplink/downlink signal transmission procedure. Particularly, the UE receives downlink control information (DCI) through the PDCCH. Here, the DCI includes control information such as resource allocation information for the UE. Different DCI formats are defined according to different usages of DCI.

Control information transmitted from the UE to the eNB in uplink or transmitted from the eNB to the UE in downlink includes a downlink/uplink acknowledge/negative acknowledge (ACK/NACK) signal, a channel quality indicator (CQI), a precoding matrix index (PMI), a rank indicator (RI), and the like. In the case of the 3GPP LTE system, the UE may transmit the control information such as CQI/PMI/RI through the PUSCH and/or the PUCCH.

FIG. 5 is a diagram showing the structure of a radio frame used in an LTE system.

Referring to FIG. 5, the radio frame has a length of 10 ms (327200×T_s) and is divided into 10 subframes having the same size. Each of the subframes has a length of 1 ms and includes two slots. Each of the slots has a length of 0.5 ms (15360×T_s). T_s denotes a sampling time, and is represented by T_s=1/(15 kHz×2048)=3.2552×10^-8 (about 33 ns). Each of the slots includes a plurality of OFDM symbols in a time domain and a plurality of Resource Blocks (RBs) in a frequency domain. In the LTE system, one RB includes 12 subcarriers×7 (or 6) OFDM symbols. A transmission time interval (TTI) that is a unit time for transmission of data may be determined in units of one or more subframes. The structure of the radio frame is purely exemplary and thus the number of subframes included in the radio frame, the number of slots included in a subframe, or the number of OFDM symbols included in a slot may be changed in various ways.

Hereinafter, an RRC state of a UE and an RRC connection method will be described.

The RRC state indicates whether the RRC layer of the UE is logically connected to the RRC layer of the E-UTRAN. When the RRC connection is established, the UE is in a RRC_CONNECTED state. Otherwise, the UE is in a RRC_IDLE state.

The E-UTRAN can effectively control UEs because it can check the presence of RRC_CONNECTED UEs on a cell basis. On the other hand, the E-UTRAN cannot check the presence of RRC_IDLE UEs on a cell basis and thus a CN manages RRC_IDLE UEs on a TA basis. A TA is an area unit larger than a cell. That is, in order to receive a service such as a voice service or a data service from a cell, the UE needs to transition to the RRC_CONNECTED state.

In particular, when a user initially turns a UE on, the UE first searches for an appropriate cell and camps on the cell in the RRC_IDLE state. The RRC_IDLE UE transitions to the RRC_CONNECTED state by performing an RRC connection establishment procedure only when the RRC_IDLE UE needs to establish an RRC connection. For example, when uplink data transmission is necessary due to call connection attempt of a user or when a response message is transmitted in response to a paging message received from the E-UTRAN, the RRC_IDLE UE needs to be RRC connected to the E-UTRAN.

Referring to FIG. 6, the paging message includes a paging record having paging cause and UE identity. Upon receiving the paging message, the UE may perform a discontinuous reception (DRX) operation in order to reduce power consumption.

In detail, a network configures a plurality of paging occasions (POs) in every time cycle called a paging DRC cycle and a specific UE receives only a specific paging occasion and acquires a paging message. The UE does not receive a paging channel in paging occasions other than the specific paging occasion and may be in a sleep state in order to reduce power consumption One PO is a subframe where there may be P-RNTI transmitted on PDCCH addressing the paging message. One Paging Frame (PF) is one Radio Frame, which may contain one or multiple Paging Occasion(s). When DRX is used the UE needs only to monitor one PO per DRX cycle.

The eNB and the UE use a paging indicator (PI) as a specific value indicating transmission of a paging message. The eNB may define a specific identity (e.g., paging - radio network temporary identity (P-RNTI)) as the PI and inform the UE of paging information transmission. For example, the UE wakes up in every DRX cycle and receives a subframe to determine the presence of a paging message directed thereto. In the presence of the P-RNTI on an L1/L2 control channel (a PDCCH) in the received subframe, the UE is aware that a paging message exists on a PDSCH of the subframe. When the paging message includes an ID of the UE (e.g., an international mobile subscriber identity (IMSI)), the UE receives a service by responding to the eNB (e.g., establishing an RRC connection or receiving system information).

More specifically, PF and PO is determined by following formulae using the DRX parameters provided in System Information:

PF is given by following equation:

- SFN mod T= (T div N)*(UE_ID mod N)

Index i_s pointing to PO from subframe pattern defined in following tables 1 (for FDD) and table 2 (for TDD) will be derived from following calculation:

- i_s = floor(UE_ID/N) mod Ns

System Information DRX parameters stored in the UE shall be updated locally in the UE whenever the DRX parameter values are changed in SI. If the UE has no IMSI, for instance when making an emergency call without USIM, the UE shall use as default identity UE_ID = 0 in the PF and i_s formulas above.

The following Parameters are used for the calculation of the PF and i_s:

- T: DRX cycle of the UE. T is determined by the shortest of the UE specific DRX value, if allocated by upper layers, and a default DRX value broadcast in system information. If UE specific DRX is not configured by upper layers, the default value is applied.

- nB: 4T, 2T, T, T/2, T/4, T/8, T/16, T/32.

- N: min(T,nB)

- Ns: max(1,nB/T)

- UE_ID: IMSI mod 1024.

IMSI is given as sequence of digits of type Integer (0..9), IMSI shall in the formulae above be interpreted as a decimal integer number, where the first digit given in the sequence represents the highest order digit.

For example, IMSI = 12 (digit1=1, digit2=2)

In the calculations, this shall be interpreted as the decimal integer "12", not "1x16+2 = 18".

In the following description, system information is explained. First of all, the system information should contain necessary information a user equipment should be aware of to access a base station. Therefore, the user equipment should receive all system information before accessing the base station and should have latest system information all the time. Since all user equipments in a cell should be aware of the system information, the base station periodically transmits the system information.

System information can be divided into MIB (Master Information Block), SB (Scheduling Block) and SIB (System Information Block). The MIB enables a user equipment to recognize such a physical configuration of a corresponding cell as a bandwidth and the like. The SB indicates such transmission information of SIBs as a transmission cycle and the like. In this case, the SIB is an aggregate of system informations related to each other. For instance, a specific SIB contains information of a neighbor cell only and another SIB just contains information of a UL radio channel used by a user equipment.

Next, a Random Access (RA) procedure provided by the LTE system will be described. The RA procedure provided by the LTE system is divided into a contention based RA access procedure and a non-contention based RA procedure. The contention based RA procedure and the non-contention based RA procedure are determined depending on whether the UE or the eNB directly selects a random access preamble used in the RA procedure.

In the non-contention based RA procedure, the UE uses a random access preamble directly allocated by the eNB. Accordingly, if the eNB allocates a specific random access preamble only to the UE, only the UE uses the random access preamble and the other UEs do not use the random access preamble. Accordingly, a one-to-one relationship between the random access preamble and the UE which uses the random access preamble is satisfied and collision does not occur. In this case, since the eNB may become aware of the UE as soon as the random access preamble is received, efficiency increases.

In contrast, in the contention based RA procedure, since the UE arbitrarily selects one available random access preamble and transmits the selected random access preamble, there is a possibility that a plurality of UEs uses the same random access preamble. Accordingly, even when the eNB receives a specific random access preamble, the eNB is not aware of the UE which transmits the random access preamble.

First, a UE performs the RA procedure when the UE performs initial access because there is no RRC Connection with an eNB, when the UE initially accesses a target cell during a handover procedure, when the RA procedure is requested by a command of an eNB, when there is uplink data transmission in a situation where uplink time synchronization is not aligned or where a specific radio resource used for requesting radio resources is not allocated, and when a recovery procedure is performed in case of radio link failure or handover failure.

FIG. 7 is a diagram showing a process of operating a UE and an eNB in a contention based RA procedure provided by an LTE system.

Referring to FIG. 7, the UE receives and stores information about RA from the eNB through system information. If the RA procedure is necessary, the UE transmits a random access preamble (also referred to as Message 1) to the eNB (S710). When the eNB receives the random access preamble from the UE, the eNB transmits a random access response (also referred to as Message 2) to the UE (S720). More specifically, downlink scheduling information of the random access response message may be CRC-masked with an RA-RNTI so as to be transmitted on an L1/L2 control channel (PDCCH). The UE which receives the downlink scheduling signal masked with the RA-RNTI may receive and decode the random access response message through a PDSCH.

Thereafter, the UE determines whether the random access response information allocated to the UE is present in the random access response message. The determination as to whether the random access response information allocated to the UE is present may be made depending on whether a Random Access Preamble ID (RAID) for the preamble transmitted by the UE is present. The random access response information includes timing advance (TA) indicating timing offset information for synchronization, radio resource allocation information used for uplink (uplink grant information), a temporary identifier (e.g., T-CRNTI) for identifying the UE, etc.

When the UE receives the random access response information, the UE transmits an uplink message (also referred to as Message 3) via an uplink shared channel (SCH) according to the radio resource allocation information (uplink grant) included in the response information (S730). The eNB transmits a contention resolution message (also referred to as Message 4) to the UE (S740) after receiving the uplink message from the UE.

Recently, machine type communication (MTC) has come to the fore as a significant communication standard issue. MTC refers to exchange of information between a machine and an eNB without involving persons or with minimal human intervention. For example, MTC may be used for data communication for measurement/sensing/reporting such as meter reading, water level measurement, use of a surveillance camera, inventory reporting of a vending machine, etc. and may also be used for automatic application or firmware update processes for a plurality of UEs. In MTC, the amount of transmission data is small and UL/DL data transmission or reception (hereinafter, transmission/reception) occurs occasionally. In consideration of such properties of MTC, it would be better in terms of efficiency to reduce production cost and battery consumption of UEs for MTC (hereinafter, MTC UEs) according to data transmission rate. Since the MTC UE has low mobility, the channel environment thereof remains substantially the same. If an MTC UE is used for metering, reading of a meter, surveillance, and the like, the MTC UE is very likely to be located in a place such as a basement, a warehouse, and mountain regions which the coverage of a typical eNB does not reach. In consideration of the purposes of the MTC UE, it is better for a signal for the MTC UE to have wider coverage than the signal for the conventional UE (hereinafter, a legacy UE).

Such a communication technology as MTC is specialized from 3GPP to transmit and receive IoT-based information and the MTC has a difference according to each release of the technology. Release 10 and Release 11 are focusing on a method of controlling loads of IoT (M2M) products and a method of making the loads have least influence on a network when the IoT products make a request for accessing an eNB at the same time. Release 12 and Release 13 are focusing on a low-cost technology enabling a battery to be simply implemented and very little used by reducing complicated functions mounted on a legacy smartphone as many as possible.

Low complexity UEs are targeted to low-end (e.g. low average revenue per user, low data rate, delay tolerant) applications, e.g. some Machine-Type Communications.

A low complexity UE has reduced Tx and Rx capabilities compared to other UE of different categories. In particular, a low complexity UE does not require such a function of high performance as a function of a smartphone and an amount of data used by the low complexity UE is not that big in general. Hence, there is no reason for a complicated and high-price communication module to come to the market for such a UE as the low complexity UE.

In order to manufacture a low-cost IoT (M2M) device, a concept such as UE Category 0 has been introduced. A UE category corresponds to a general figure used in 3GPP to indicate the amount of data capable of being processed by a UE in a communication modem. In general, as the amount of data to be processed is getting bigger, a price of a modem is also increasing due to a memory or performance enhancement. In case of a currently commercialized smartphone, performance of the smartphone is continuously increasing from 100Mbps to 150Mbps and 300Mbps on the basis of download.

Table 3 shows UE categories used in 3GPP.

A Category 0 low complexity UE may access a cell only if SIB1 indicates that access of Category 0 UEs is supported. If the cell does not support access of Category 0 UEs, the UE considers the cell as barred.

The eNB determines that a UE is a Category 0 UE based on the LCID for CCCH and the UE capability.

The S1 signaling has been extended to include the UE Radio Capability for paging. This paging specific capability information is provided by the eNB to the MME, and the MME uses this information to indicate to the eNB that the paging request from the MME concerns a low complexity UE.

And, since it is able to perform transmission and reception on specific time only without performing transmission and reception at the same time like FIG. 6, it may be able to perform an operation of TDD in FDD (since transmission and reception are not performed at the same time). Additionally, unlike legacy TDD, since it is able to provide sufficient switching time as much as 1ms to a section at which switching is performed between transmission and reception, it is able to expect a revolutionary cost reduction effect in terms of overall hardware part especially a modem and an RF. On the contrary, according to a regulation of a legacy LTE UE, it is mandatory to use at least 2 or more reception antennas.

NB-IoT (Narrow Band Internet of Things) provides access to network services using physical layer optimized for very low power consumption (e.g. full carrier bandwidth is 180 kHz, subcarrier spacing can be 3.75 kHz or 15 kHz).

Further, a number of E-UTRA protocol functions supported by all Rel-8 UEs are not used for NB-IoT and need not be supported by eNBs and UEs only using NB-IoT. For NB-IoT, the narrowband physical downlink control channel (NPDCCH) is located in available symbols of configured subframes. Within a PRB pair, two control channel elements are defined, with each control channel element composed of resources within a subframe. NPDCCH supports aggregations of 1 and 2 control channel elements and repetition. NPDCCH supports C-RNTI, Temporary C-RNTI, P-RNTI, and RA-RNTI.

The contention-based random access is supported for NB-IoT. Configuration of RACH parameters may be different per coverage level. RACH attempts/reattempts should follow the assumptions listed below: i) Multiple RACH attempts are supported, ii) RACH reattempts may be done on the same or different coverage level, iii) Triggering too many attempts needs to be avoided. There will be one or more thresholds that limit the number of attempts, MAX NUMBER OF ATTEMPTS or similar per coverage level, and iv) MAC indicates random access problem to the RRC layer, when MAC has exhausted all attempts for a RACH procedure.

RAN node can determine the UE’s coverage level from the random access procedure. How this is done depends on the physical layer RACH design. The original eMTC design, e.g. by using S1 Context Release message to indicate coverage level, can be used as the baseline, at least for the UP solution. The CN may include coverage enhancement (CE) level information, Global Cell Id and Paging Attempt Count IE in the Paging message to indicate related information to the RAN node. In idle mode, UEs in general do not make specific access only to report coverage level change.

For NB-IoT, Asynchronous adaptive HARQ is supported, a single HARQ process is supported for dedicated transmissions (1 for UL and 1 for DL), and An NB-IoT UE only needs to support half duplex operations.

For NB-IoT, the RLC layer supports the following functions: i) Transfer of upper layer PDUs, ii) Concatenation, segmentation and reassembly of RLC SDUs. But the following RLC layer functions are assumed not supported: i) Reordering of RLC data PDUs (dependent on HARQ mechanism), ii) Duplicate detection (dependent on HARQ mechanism), and iii) the RLC UM is not supported.

The PDCP layer supports the following functions: i) PDCP SN size is 7 bits (or less), ii) Transfer of data (user plane or control plane), iii) Header compression and decompression of IP data flows using the ROHC protocol, iv) Ciphering and Integrity Protection, and v) Ciphering and deciphering. But the following PDCP layer functions are assumed not supported: i) In-sequence delivery of upper layer PDUs at PDCP re-establishment procedure for RLC AM (dependent on support of RRC reestablishment and RLC-AM), ii) Duplicate detection and duplicate discarding of lower layer SDUs at PDCP re-establishment procedure for RLC AM (dependent on support of RRC reestablishment and RLC-AM), iii) Duplicate detection and duplicate discarding of lower layer SDUs at PDCP re-establishment procedure for RLC AM (dependent on support of RRC reestablishment and RLC-AM, iv) For split bearers, routing and reordering, and v) PDCP status report.

Recently, in the 3GPP standard, it is agreed that NB-IOT UE can receive a paging message or perform a random access via non-anchor narrowband or carrier (i.e., non-anchor PRB). When the UE which can support non-anchor narrowband in idle moves into a Cell which cannot support non-anchor narrowband, the UE cannot receive paging message or perform random access via non-anchor narrowband. In a cell, the UE needs to check the system information whether the UE can receive paging message or perform random access via non-anchor narrowband.

Therefore, according to a first embodiment of the present application, it is suggested that the cell should broadcast the system information including a field indicating whether a cell can support non-anchor narrowband. Hereafter, the field refers to NonanchorPRB-Allowed.

More specifically, the presence of this field “NonanchorPRB-Allowed” indicates whether receiving paging message or performing random access via non-anchor PRB is allowed or not in the cell. If the NonanchorPRB-Allowed field is present, the UE may select a PRB among the anchor PRB and the non-anchor PRB(s) for receiving the paging message and/or performing the random access procedure according to configuration from a cell. Or, if the NonanchorPRB-Allowed field is present, the UE may select the non-anchor PRB(s) for receiving the paging message and/or performing the random access procedure.

Further, if the NonanchorPRB-Allowed field is not present, the UE may select only the anchor PRB for paging reception and/or random access procedure according to configuration from a cell. Or, when the UE had received the paging message or performed the random access via the non-anchor PRB in a first cell, if the NonanchorPRB-Allowed field is not present in the system information received from a second cell, the UE should stop receiving the paging message or performing the random access via the non-anchor PRB, and then should receive the paging message or perform the random access via the anchor PRB from the second cell.

Hereinafter, the present invention will be described in detail with reference to the drawing. FIG. 7 is an example of a system bandwidth including a plurality of narrow bands. Referring to FIG. 7, it is shown that the plurality of PRBs are included in the system bandwidth for supporting the NB-IoT. Further, Nb indicates the total number of PBRs (Narrowbands).

When an idle UE which can support non-anchor narrowband moves into a new cell, the idle UE checks the system information. If Non-anchorPRB-Allowed is present in the system information, the UE can receive paging message or perform random access via anchor and non-anchor PRB.

More specifically, when receiving the paging message, for selecting PRB equally between the anchor PRBs and the non-anchor PRBs, if P-RNTI is monitored on NPDCCH, the PRB for receiving the paging message is determined by the following equation:

[Equation 1]

PRB = floor(UE_ID) mod Nb.

Here, UE_ID is derived from IMSI.

The UE should monitor the P-RNTI for receiving the paging message in the PRB determined according to the above Equation 1.

When performing the random access procedure, the PRBs on which the random access procedure is performed are distributed by generating random number.

For example, when there are PRBs having indexes numbered from 1 to Nb, the UE may generate the random number from 1 to Nb, and perform the random access procedure on a PRB having the generated random number. If the UE wishes to perform the random access procedure a specific PRB, the UE may generate the random number by weighting that particular number corresponding the specific PRB.

While, if the Non-anchorPRB-Allowed field is not present in the system information, the UE should receive paging message or perform random access via only anchor PRB.

Referring to FIG. 9, in S901, the UE in idle state receives system information from a base station. Further, in S903, the UE determines whether a field “Non-anchorPRB-Allowed” indicating that a plurality of non-anchor PRBs are supported by the base station is present or not in the system information.

If the field “Non-anchorPRB-Allowed” is not present in the system information, the base station does not support the plurality of non-anchor PRBs for the paging and random access procedure. Thus, in S905, the UE may select the anchor PRB for the paging and the random access procedure.

While, the field “Non-anchorPRB-Allowed” is present in the system information, the base station can support the plurality of non-anchor PRBs for the paging and random access procedure. Therefore, in S907, the UE may select one PRB of the plurality of non-anchor PRBs by using an identity of the UE. Preferably, the UE may select one PRB of the plurality of non-anchor PRBs and the anchor PRB by using the identity of the UE for the paging and random access procedure.

According to a second embodiment of the present application, via random access resource configuration, the UE might guess whether the cell supports non-anchor PRB operation. In other words, non-anchor PRB resources are configured as random access resources, the UE could expect that paging reception in non-anchor PRBs is also supported. Otherwise, the UE thinks that paging reception in anchor PRB is only supported in the cell.

More specifically, the cell broadcasts random access resource configuration. The configuration includes non-anchor PRB resources as random access resources. And, the UE acquires the required system information (e.g. SIB2).

Next, the UE checks whether the cell supports transmission of paging message in the non-anchor PRBs by the acquired random access resource configuration. If the non-anchor PRB resources are configured as the random access resources, the UE determines and tries to receive the paging message via the non-anchor PRBs in its paging occasion. Otherwise, the UE tries to receive paging message via the anchor PRBs.

Additionally, the UE considers only the non-anchor PRBs used for random access as available PRBs for reception of paging message. Alternatively, the UE considers all available non-anchor PRBs (which is broadcasted by cell) as available PRBs for paging reception.

FIG. 10 is a block diagram of a communication apparatus according to an embodiment of the present invention.

Referring to FIG. 10, a communication device 1000 includes a processor 1010, a memory 1020, a radio frequency (RF) module 1030, a display module 1040, and a user interface (UI) module 1050.

The communication device 1000 is illustrated for convenience of description and some modules may be omitted. The communication device 1000 may further include necessary modules. Some modules of the communication device 1000 may be further divided into sub-modules. The processor 1000 is configured to perform operations according to the embodiments of the present invention exemplarily described with reference to the drawings. Specifically, for a detailed description of operations of the processor 1000, reference may be made to the description described with reference to FIGs. 1 to 9.

The memory 1020 is connected to the processor 1010 and stores operating systems, applications, program code, data, and the like. The RF module 1030 is connected to the processor 1010 and performs a function of converting a baseband signal into a radio signal or converting a radio signal into a baseband signal. For this, the RF module 1030 performs analog conversion, amplification, filtering, and frequency upconversion or performs inverse processes thereof. The display module 1040 is connected to the processor 1010 and displays various types of information. The display module 1040 may include, but is not limited to, a well-known element such as a liquid crystal display (LCD), a light emitting diode (LED), or an organic light emitting diode (OLED). The UI module 1050 is connected to the processor 1010 and may include a combination of well-known UIs such as a keypad and a touchscreen.

The above-described embodiments are combinations of elements and features of the present invention in a predetermined manner. Each of the elements or features may be considered selective unless otherwise mentioned. Each element or feature may be practiced without being combined with other elements or features. Further, an embodiment of the present invention may be constructed by combining parts of the elements and/or features. Operation orders described in embodiments of the present invention may be rearranged. Some constructions of any one embodiment may be included in another embodiment and may be replaced with corresponding constructions of another embodiment. In the appended claims, it will be apparent that claims that are not explicitly dependent on each other can be combined to provide an embodiment or new claims can be added through amendment after the application is filed.

The embodiments according to the present invention can be implemented by various means, for example, hardware, firmware, software, or combinations thereof. In the case of a hardware configuration, the embodiments of the present invention may be implemented by one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, etc.

In the case of a firmware or software configuration, the method according to the embodiments of the present invention may be implemented by a type of a module, a procedure, or a function, which performs functions or operations described above. For example, software code may be stored in a memory unit and then may be executed by a processor. The memory unit may be located inside or outside the processor to transmit and receive data to and from the processor through various well-known means.

The present invention may be carried out in other specific ways than those set forth herein without departing from the spirit and essential characteristics of the present invention. The above embodiments are therefore to be construed in all aspects as illustrative and not restrictive. The scope of the invention should be determined by the appended claims and their legal equivalents and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

Claims

A method of processing a signal at a user equipment (UE) in a wireless communication system, the method comprising:

receiving system information from a base station;

determining whether a field indicating that a plurality of non-anchor physical resource blocks (PRBs) are supported by the base station is present or not in the system information;

selecting one PRB of the plurality of non-anchor PRBs and an anchor PRB based on a result of determining; and

receiving a paging message via the selected one PRB.
The method according to claim 1, further comprising:

performing a random access procedure via the selected PRB.
The method according to claim 2, wherein selecting the one PRB comprises:

when the field is not present in the system information, selecting the anchor PRB for receiving paging message and performing the random access procedure.
The method according to claim 2, wherein selecting the one PRB comprises:

when the field is present in the system information, selecting the one PRB of the plurality of non-anchor PRBs for receiving paging message and performing the random access procedure by using an identity of the UE.
The method according to claim 2, wherein selecting the one PRB comprises:

when the field is present in the system information, selecting the one PRB of the plurality of non-anchor PRBs and the anchor PRB for receiving paging message and performing the random access procedure by using an identity of the UE.
A user equipment (UE) in a wireless communication system, the UE including:

a wireless communication module; and

a processor connected to the wireless communication module,

wherein the processor is configured to receive system information from a base station, determine whether a field indicating that a plurality of non-anchor physical resource blocks (PRBs) are supported by the base station is present or not in the system information, select one PRB of the plurality of non-anchor PRBs and an anchor PRB based on a result of determining, and receive a paging message via the selected one PRB.
The UE according to claim 6, wherein the processor is further configured to perform a random access procedure via the selected PRB.
The UE according to claim 7, wherein the processor is configured to select the anchor PRB for receiving paging message and perform the random access procedure when the field is not present in the system information.
The UE according to claim 7, wherein the processor is configured to select the one PRB of the plurality of non-anchor PRBs for receiving paging message and perform the random access procedure by using an identity of the UE, when the field is present in the system information.
The UE according to claim 7, wherein the processor is configured to select the one PRB of the plurality of non-anchor PRBs and the anchor PRB for receiving paging message and perform the random access procedure by using an identity of the UE, when the field is present in the system information.