CN108934043B - Beam tracking method, user equipment and base station using same - Google Patents

Abstract

The invention discloses a beam tracking method and user equipment and a base station using the same, wherein the method comprises the following steps: receiving a first plurality of reference signal sequences including a first reference signal sequence associated with a first cell beam and a second reference signal sequence associated with a second cell beam over a first time period; measuring a beam quality comprising a first measurement of a first cell beam and a second measurement of a second cell beam; generating a measurement reward based on the beam quality; and transmitting the measurement report.

Description

Beam tracking method, user equipment and base station using same

Technical Field

The present disclosure relates to a beam tracking method in a multi-cell group of a millimeter wave communication system, and a user equipment and a base station using the same.

Background

Since the next generation wireless communication systems require better performance, certain aspects of the next generation communication systems will be fully tailored. Specifically, since the next-generation communication system will transmit at a higher carrier frequency, electromagnetic waves at higher frequencies will experience greater path loss for their propagation. For example, electromagnetic waves around the millimeter wave (mmWave) frequency range will have significantly higher attenuation than around the microwave frequency range, so beamforming will be required for transmission in the millimeter wave frequency range.

Fig. 1 illustrates an example of radiation patterns for different transmission wavelengths. Generally, communication systems for operation in the microwave band with wavelengths in the centimeter range (i.e., cmWave) tend to use a small number of antennas. The radiation pattern of a single microwave frequency antenna 101 intended for long distance transmission has a wide-field-of-view (FoV) coverage and a single microwave frequency antenna 101 intended for long distance transmission is typical for 3G/4G communication systems using microwave bands with a smaller number of Base Station (BS) antennas to achieve higher received SNR quality. However, lower data rates due to smaller Bandwidth (BW) exist in such systems. In order to increase the data rate by using a larger BW, a millimeter wave band is considered for use in future communication systems (e.g., 5G systems). The radiation pattern of the single millimeter wave single frequency antenna 102 will cover a shorter distance; however, by using the millimeter wave antenna array for beamforming at the same transmission power, the millimeter wave radiation pattern with the narrower FoV coverage 103 in the millimeter wave beamforming result can be extended to a farther place. To achieve wide FoV coverage as in 3G/4G communication systems, multiple beams 104 may be used at the BS, and the beam sweeping mechanism for the BS beams is taken into account. In particular, each BS beam 104 may have a different beam sequence ID for beam sweeping (i.e., the qth beam has a beam sequence ID q). In general, millimeter wave communication systems using smaller sized antenna arrays tend to have shorter distances and wider coverage; whereas millimeter-wave communication systems using larger sized antenna arrays tend to have longer distances and narrower coverage.

The transmission framework of the millimeter wave wireless communication system may be classified into two categories based on the radio access interface. The first category is multiple radio access technology (multi-RAT), and the second category is single radio access technology (single RAT). Fig. 2 illustrates an example of a first category of 5G multi-RAT communication system and a second category of 5G single-RAT communication system. The multi-RAT system has at least two RATs, for example, an LTE system and a millimeter wave system, which have been described as LTE + millimeter wave integrated systems that will coexist simultaneously for communication. For example, control signaling may be transmitted via use of a conventional LTE communication frequency, while user data may be transmitted via use of a millimeter wave communication frequency. In this case, a Carrier Aggregation (CA) scheme may be used. User data may be transmitted on a millimeter wave frequency band via using, for example, a Secondary Component Carrier (SCC), but control signals may be transmitted on a microwave (i.e., cmWave) frequency via using a Primary Component Carrier (PCC). Network entry may be performed via cmWave using PCC, since the successful detection rate of control signaling may operate in larger coverage, higher mobility, and lower SNR scenarios. On the other hand, the second category of single RAT communication systems will use only one radio access technology for communication applications by using the millimetre wave frequency band for transmitting both user data and control signals. Network entry will be performed via a carrier in the millimeter wave band. As such, the successful detection rate of control signaling may need to operate in smaller coverage, lower mobility, and higher SNR scenarios. Thus, beamforming techniques may be used. It is noted that for the exemplary embodiments of the present disclosure, only the second category of single millimeter wave RATs is considered.

As with the standalone next generation (i.e., 5G) communication systems described in the second category of fig. 2, several design challenges may exist. For example, referring to fig. 3A, a User Equipment (UE) supporting the next generation 5G standard of the second category is configured to receive a directional beam 301 from a Base Station (BS) supporting the next generation 5G standard of the second category. However, under some circumstances, the directional beam 302 may be blocked by an obstacle such as a concrete building. In addition, referring to fig. 3B, since the 5G BS has a coverage 303 of a specific area, a handover mechanism from one cell beam to another cell beam will need to be determined when the 5G UE is at the boundary 304 between the areas of coverage.

To solve the problems related to mobility, for example, a UE-centric non-cell (UE-centric non-cell) system may be proposed. Fig. 4 shows a comparison between a cell-centric cellular (cell-centric cellular) system and a UE-centric non-cell system. A method of satisfying the demand for ultra-high traffic density in the 5G communication system may use an ultra-dense network (UDN) based design. In legacy systems, such as 3G and LTE networks, the cellular communication is a cell centric cellular system. However, for 5G communication systems, deployment will be based on non-cell radio access systems centred around the User Equipment (UE). The abstraction of UE radio access along with the concept of virtualized cells enables the segmentation of Radio Access Networks (RANs) by separating physical cells from UEs to cope with mobility related issues, and by separating physical topologies and services, and by simplifying heterogeneous node deployments to cope with blocking related issues.

In a 5G communication system, the cell size will likely be smaller due to the higher carrier frequency. Handover due to UE mobility can be efficiently addressed via UDN. However, the ultra-high traffic load and high density experienced by 5G networks may force fronthaul networks (fronthaul networks) to be separated from entities and cause splits (C/U splits) between the control plane and the data plane in the future. Fig. 5 illustrates the split between the control plane and the user plane in a 5G communication system via using the virtual layer concept. This means that the control plane (C-plane) will be deployed only on the virtual layer, and thus the data plane (U-plane) will be deployed on the physical layer. Thus, physical layer data may be decoded in the physical layer and forwarded to the virtual layer via the fronthaul network. The decoded data is then converted into MAC messages for communication with the core network. This approach eliminates the need for cell reselection or handover for the UE within the same virtual layer. This concept would coincide with an embodiment of a UE-centric virtual cell that may correspond to the virtual layer of fig. 5.

Disclosure of Invention

Accordingly, the present disclosure relates to a beam tracking method for multi-cell groups in a millimeter wave communication system, and a user equipment and a base station using the same.

In one of the exemplary embodiments, the present disclosure relates to a beam tracking method used by a user equipment of a multi-cell group in a millimeter wave communication system, and the method will include but is not limited to: receiving a first plurality of reference signal sequences including a first reference signal sequence associated with a first cell beam and a second reference signal sequence associated with a second cell beam over a first time period; measuring a beam quality comprising a first measurement of a first cell beam and a second measurement of a second cell beam; generating a measurement reward based on the beam quality; and transmitting the measurement report.

In one of the exemplary embodiments, the present disclosure relates to a beam tracking method used by a base station of a multi-cell group in a millimeter wave communication system, and the method would include: transmitting a first reference signal sequence generated according to a first time-division multiplexing (TDM) configuration of a plurality of TDM configurations over a first time period, wherein the first TDM configuration is unique to each cell within a multi-cell group over the time period; receiving a measurement report from a preferred cell beam in response to transmitting the first reference signal sequence; performing cell quality measurements based on the received UL signals from the preferred cell beam in response to the received measurement reports; and transmitting the cell quality measurements to the controller.

In one of the exemplary embodiments, the present disclosure relates to a user equipment that will include, but is not limited to: a transmitter; a receiver; and a processor coupled to the transmitter and the receiver and configured to: receiving, via a receiver, a first plurality of reference signal sequences including a first reference signal sequence associated with a first cell beam and a second reference signal sequence associated with a second cell beam over a first time period; measuring a beam quality comprising a first measurement of a first cell beam and a second measurement of a second cell beam; generating a measurement reward based on the beam quality; and transmitting the measurement report via the transmitter.

In one of the exemplary embodiments, the present disclosure relates to a base station that will include, but is not limited to: a transmitter; a receiver; and a processor coupled to the transmitter and the receiver and configured to: transmitting, via a transmitter, a first reference signal sequence generated according to a first Time Division Multiplexing (TDM) configuration of a plurality of TDM configurations over a first time period, wherein the first TDM configuration is unique to each cell within a multi-cell group over the time period; receiving, via the receiver, a measurement report from the preferred cell beam in response to transmitting the first reference signal sequence; performing cell quality measurements based on the received UL signals from the preferred cell beam in response to the received measurement reports; and transmitting the cell quality measurements to the controller via the transmitter.

In order to facilitate an understanding of the foregoing features and advantages of the disclosure, exemplary embodiments are described below in detail with reference to the accompanying drawings. It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the disclosure as claimed.

It should be understood, however, that the present disclosure may not encompass all aspects and embodiments of the disclosure, and is therefore not intended to be limiting or restrictive in any way. In addition, the present disclosure will encompass improvements and modifications readily apparent to those skilled in the art.

In order to make the aforementioned and other features and advantages of the disclosure more comprehensible, embodiments accompanied with figures are described in detail below.

Drawings

The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the disclosure and, together with the embodiments, serve to explain the principles of the disclosure.

Fig. 1 is a schematic diagram of the features of a millimeter wave communication system.

Fig. 2 is a schematic diagram of a 5G New Radio (NR) transmission framework.

Fig. 3A is a schematic diagram of a 5G NR standalone communication system.

Fig. 3B is a schematic diagram of a 5G NR standalone communication system.

Fig. 4 is a diagram comparing a cell-centric cellular system with a UE-centric non-cell system.

Fig. 5 illustrates the split between the control plane and the user plane in a 5G communication system via using the concept of virtual layers.

FIG. 6 is a schematic diagram of comparing concepts between joint tracking and individual tracking in an exemplary embodiment according to the present disclosure.

Fig. 7 is a schematic illustration of a decision of a preferred beam in an exemplary embodiment according to the present disclosure.

Fig. 8 is a diagram illustrating a concept between comparing a non-reusable beam sequence and a reusable sequence in an exemplary embodiment according to the present disclosure.

Fig. 9A illustrates the concept of beam sequence ambiguity for a sequence reuse system in an exemplary embodiment according to the present disclosure.

Fig. 9B illustrates an example of beam sequence ambiguity with J-Q-8 in an exemplary embodiment according to the present disclosure.

Fig. 10 illustrates an example of interleaved swept beams in an exemplary embodiment according to the present disclosure.

Fig. 11 illustrates another example of interleaved swept beams in an exemplary embodiment according to the present disclosure.

Fig. 12 illustrates a configuration of a TDM-based beam sequence ID map in an exemplary embodiment according to the present disclosure.

Fig. 13 illustrates an example of a beam sequence for inter-BS boresight alignment and J-Q-8 in an exemplary embodiment according to the present disclosure.

Fig. 14 illustrates an example of a beam sequence for inter-BS boresight misalignment and J-Q-8 in an exemplary embodiment according to the present disclosure.

Fig. 15 illustrates an example of a beam sequence for inter-BS boresight alignment but with different beam sweep order directions and J-Q-8 in an exemplary embodiment according to the present disclosure.

Fig. 16 illustrates another example of a sequence of beams for inter-BS boresight misalignment but different beam sweep order directions and J-Q-8 in an exemplary embodiment according to the present disclosure.

Fig. 17 illustrates an example of a beam sequence for J24 ≧ Q8 and primary boresight alignment between BSs in an exemplary embodiment in accordance with the present disclosure.

Fig. 18 illustrates an example of transmitting multiple BQM-RSs from a cell in an exemplary embodiment according to the present disclosure.

Fig. 19 illustrates BTS-based BQM-RS allocation in an exemplary embodiment according to the present disclosure.

Fig. 20 illustrates an example of BSS-based BQM-RS allocation in an exemplary embodiment according to the present disclosure.

Fig. 21 illustrates an example of distributed BTS based BQM-RS allocation in an exemplary embodiment according to the present disclosure.

Fig. 22 illustrates an example of beam tracking in an exemplary embodiment according to the present disclosure.

Fig. 23 illustrates an SNR table in an exemplary embodiment according to the present disclosure.

Fig. 24 illustrates SNR measurement reporting in an exemplary embodiment according to the present disclosure.

Fig. 25 illustrates SNR reporting from a UE to a BS in an exemplary embodiment according to the present disclosure.

Fig. 26 illustrates RAP transmission via a UE in an exemplary embodiment according to the present disclosure.

Fig. 27A and 27B illustrate non-contention RAP-based diversity in an exemplary embodiment according to the present disclosure.

Fig. 28 illustrates the application of an SNR table in an exemplary embodiment according to the present disclosure.

Fig. 29A is a functional block diagram of a UE in an exemplary embodiment according to the present disclosure.

Fig. 29B is a functional block diagram of a BS in an exemplary embodiment according to the present disclosure.

Fig. 30A illustrates the steps of a beam tracking method used in a multi-cell group of a millimeter wave communication system from the perspective of a UE in an exemplary embodiment according to the present disclosure.

Fig. 30B illustrates the steps of a beam tracking method used in a multi-cell group of a millimeter wave communication system from the perspective of a BS in an exemplary embodiment according to the present disclosure.

[ notation ] to show

101: microwave frequency antenna

102: single millimeter wave single frequency antenna

103: fov coverage

104: wave beam

301. 302: directional beam

303: coverage rate

304: boundary of

1301: overlapping area

1401. 1402, 1503, 1504, 1603, 1701: zone(s)

1501: clockwise direction

1502: in the counter-clockwise direction

1601: clockwise direction

1602: in the counter-clockwise direction

1901: distributed distribution

1902: localized distribution

2001. 2101: beam quality measurement reference signal

2002. 2102: cell 0

2003. 2103: cell 1

2004: UE beam 1

2104: best UE beam

2105: all four UE beams

2301: preferred cell beam index

2302: preferred DL cell sweep beam period index

2311: periodic indexing of DL cell swept beams

2312: beam index of cell

2313: beam index of UE

2401: DL cell sweeping beam period 1

2402: UL cell sweep Beam period 1

2901. 2911, 2916: processor with a memory having a plurality of memory cells

2902. 2912: millimeter wave transceiver

2903. 2913: antenna array

2904: unlicensed band transceiver

2905. 2915: storage medium

2914: centimeter wave transceiver

BF: beamforming

BS: base station

CCH: control channel

DL: downlink link

ID: identifier

UL: uplink link

FoV: visual field

PUCCH: physical uplink control channel

PUSCH: physical uplink shared channel

PRACH: physical random access channel

RACH: random access channel

RAP: random access preamble

RAT (RAT): radio access technology

RAN: radio access network

SCH: shared channel

SNR: signal to noise ratio

TDM: time division multiplexing

UE: user equipment

mmWave: millimeter wave

S301 to S304, S311 to S314: step (ii) of

Detailed Description

Reference will now be made in detail to the present exemplary embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

The present disclosure relates to a beam tracking method and related apparatus for multi-cell groups in millimeter wave communication systems, and in particular provides a multi-beam and multi-cell tracking (MBMCT) method for an apparatus in a millimeter (millimeter wave) communication system. In the present disclosure, each UE may measure or detect the quality of cell-swept beams based on Downlink (DL) signals; and the BS may measure or detect the quality of a cell from a preferred cell sweep beam based on an Uplink (UL) signal reported by the UE. Thus, cell sweep beam quality and cell quality may be measured or tracked separately. Individual cell-swept beams of the base station may carry (reference signal) sequences and each sequence will correspond to an Identifier (ID). Since the same set of sequences generated by a base station may also be used by other base stations within the same millimeter wave system, the same set of single or multiple beam sequence IDs (or sequences) may be reused by another cell or cells within the millimeter wave system.

In addition, the base station may (repeatedly) transmit a set of beam quality measurement reference signals (BQM-RSs), where each BQM-RS has a different beam sequence ID than the remaining BQM-RSs transmitted via the base station. The beam sequence IDs derived from BQM-RS may be carried by the swept beams of the cell and are staggered. With one BQM-RS per cell per transmission, BQM-RSs carried by cell-swept beams can be transmitted simultaneously from different cells. And each BQM-RS would be associated with a different beam sequence ID. For example, the first reference signal sequence may be derived from BQM-RS received in the first cell beam, and the second reference signal sequence may be derived from the second BQM-RS received in the second cell beam. The first beam sequence ID may be derived from a first reference signal sequence and the second beam sequence ID may be derived from a second reference signal sequence.

Beam quality measurement statistics, not limited to signal-to-noise ratio (SNR), may be measured by the UE based on BQM-RS for tracking beams of the cell and beams of the UE. The beam quality measurements and/or preferred beam sequence IDs associated with a particular cell swept beam may be reported by the UE via a control/shared channel (CCH/SCH) within an Uplink (UL) Beamforming (BF) header at a preferred reporting time corresponding to the reporting time used for the received swept beam in the Downlink (DL) transmission having the largest measured SNR. The Random Access Preamble (RAP) with the unique sequence ID used by the UE should be known to some BSs (and/or networks) in the vicinity of the UE and can be transmitted on the Random Access (RA) channel (RACH) of the UL BF header at the above preferred UL time. The SNR-like quality of a cell on CCH RS/SCH RS/RACH can be measured at the BS, and the best cell can be decided via the controller based on the SNR measurement of the cell.

The comparison between joint tracking and individual tracking is first described. The comparison shown in fig. 6 describes that the tracking of multiple beams and multiple cells may be based on a joint tracking mechanism or an individual tracking mechanism. For joint tracking, the quality of the beam and the quality of the cell will be measured via the UE based on the DL signal provided by the BS in step S611, or the quality of the beam and the quality of the cell will also be measured via the BS based on the UL signal provided by the UE in step S612. This means that the quality of the beam and the quality of the cell will be measured or tracked jointly via the UE and/or the BS. For individual tracking, on the other hand, in step S601, the cell-swept beam quality transmitted from the BS may be measured or tracked via the UE by using DL signals provided by the BS, and in step S602, the quality of the cell may be measured or tracked via UL signals provided by the UE. It is noted that the present disclosure relates primarily, but not exclusively, to the individual tracking mechanisms described above. The advantages of individual tracking over joint tracking would include less computational complexity, shorter measurement periods, and less RS/signaling overhead. And it is noted that the present disclosure is not limited to the necessity of possessing all of the aforementioned advantages.

Under an individual tracking mechanism, as shown in fig. 7, beam decisions for a preferred UE may be decided via the UE itself, and such decisions may be transparent to the BS or controller. The decision on the preferred cell beam may be decided via the UE or via the controller. The preferred cell may be determined via the controller. The term "controller" in this disclosure refers to a concept similar to a Radio Network Controller (RNC) that is typically connected to and controls a plurality of base stations.

Fig. 8 illustrates a comparison between a non-reusable beam sequence and a reusable sequence. The beam sequence Identifier (ID) for beam positioning may be non-reused or reused for multiple cells as shown in fig. 8. It should be noted that the beam sequence ID as described in this disclosure is not a beam ID or beam index that is typically used to index each individual beam of a base station. For a system where the sequence is not reusable, multiple or different sets of Q beam sequence IDs or sequences will be used for multiple cells. Assuming there are Nd sets (i.e., Nd cells), QNd measurements and detections would be needed. This may achieve the best performance, but will induce slower measurements/reporting and higher RS/signaling overhead. For a sequence-reusable system, a single (same) set of J (Q ≦ J ≦ QNd) beam sequence IDs may be reused for multiple cells. By using J measurements and detections, the measurement and reporting can be faster and the need for RS/signaling overhead can be reduced by sacrificing some (very small amount) of performance degradation.

Fig. 9A illustrates the concept of beam sequence ambiguity for a sequence reuse system, according to one of the exemplary embodiments of the present disclosure. One potential problem associated with sequence reuse systems is that beam sequence ID ambiguity may exist if two or more beam sequences from different cells but having the same beam sequence ID are received simultaneously via the UE, as shown in fig. 9A. The beam sequence ID ambiguity is caused by non-coherent combinations in the received signals rp, q (n) from the two cells (i.e., (h1,2, i + h1,2, j) s2(n)), where hp, q, i are the channel gains from the q-th beam to the p-th UE beam of the i-th cell, and sq (n) is a Zadoff-chu (zc) sequence with the beam sequence ID (i.e., root) q. Beam sequence ID ambiguity will then cause inaccurate measurements on the beam sequence ID.

Fig. 9B illustrates an example of beam sequence ambiguity with J-Q-8 in an exemplary embodiment according to the present disclosure. It can be seen from fig. 9B that both BS0 and BS1 have the same beam sequence configuration, for example, configuration 0 with 8 beam sequence IDs. Any UE located within the area 901 may experience beam sequence ID ambiguity due to the reception of a first cell-swept beam with a beam sequence ID of 2 from BS0 and a second cell-swept beam also with a beam sequence ID of 2 from BS 1.

To avoid beam sequence ID ambiguity, an interleaved beam transmission structure may be used. Fig. 10 illustrates an example of interleaved swept beams in an exemplary embodiment according to the present disclosure. In order to effectively measure the beam quality of a cell, a set of beam quality measurement reference signals (BQM-RSs) will be used in the DL Beamforming (BF) header. Via BQM-RS within the DL signal received from the BS, the UE may perform beam quality measurements based on BQM-RS. Therefore, to avoid beam sequence ID ambiguity problems, the beam sequence IDs for the BQM-RSs carried by the beams of the cell should be staggered to avoid beam sequence ID ambiguity problems. For this exemplary embodiment, it may be contemplated that multiple BQM-RSs are transmitted from multiple cells. From the example of fig. 10, it can be seen that BQM-RSs were transmitted simultaneously from at least two different cells. The first BQM-RS with the first beam sequence ID (with a specific ZC sequence sq (n) per cell transmitted) and carried via the first cell-swept beam of cell i will be received by the UE for beam selection or beam tracking. A second BQM-RS with a second beam sequence ID (which has another ZC sequence) and carried via a second cell-swept beam of cell j may also be received by the UE for beam selection or beam tracking. In this way, it can be seen from fig. 10 that, for example, at time index t ═ 1, the beam sequence ID of the cell-swept beam from cell i is 1, and the beam sequence ID of the cell-swept beam from cell j is 0. Similarly, as shown in fig. 11, at time index t ═ 2, the beam sequence ID of the cell-swept beam from cell i is 2, and the beam sequence ID of the cell-swept beam from cell j is 1. Thus, beam sequence ID ambiguity problems can be avoided.

In response to receiving BQM-RS, the UE may perform multiple beam quality measurements. For example, in response to acquiring the first BQM-RS, the UE may perform a first beam quality measurement of the first cell sweeping beam. Similarly, in response to acquiring the second BQM-RS, the UE may perform a second beam quality measurement for a second cell sweeping beam. The UE may also receive a third BQM-RS, a fourth BQM-RS, and so on, and perform beam quality measurements accordingly. The UE may determine a preferred beam sequence ID from the multiple beam quality measurements for a consideration angle with the highest signal to noise ratio (SNR) and then select a preferred UE beam to transmit (all of) the multiple beam quality measurements and/or the preferred beam sequence ID to the preferred cell sweep beam at a time of the cell sweep beam corresponding to the cell having the highest beam quality (e.g., the highest SNR as measured via the UE) in the cell beam measurements. In response to receiving the reward of the UE from the preferred cell sweep beam, the cell may perform a cell quality measurement based on the reward of the UE and transmit a result of the cell quality measurement to the controller. Similarly, another cell may also perform cell quality measurements based on the reward of the UE and transmit the results of the cell quality measurements to the controller. The controller may then determine at least one preferred cell to serve the UE based on the received cell quality measurements.

By configuring each cell to generate a reference signal sequence based on a time index and one of a plurality of configurations and then transmit the reference signal sequence, beam sequence ID ambiguity problems can be avoided. Fig. 12 illustrates a configuration of a TDM-based beam sequence ID map according to one of the exemplary embodiments of the present disclosure. The information of fig. 12 may be stored as a look-up table within any BS or UE, and such a table may be referred to as a TDM-based beam sequence ID configuration table. In the example of fig. 12, the identification capacity is assumed to be eight and the number of beams of a cell is assumed to be four, so J is 8 and Q is 4; however, the present disclosure is not limited to these specific numbers. The configuration within the time period per cell is unique to the base stations within the multi-cell group. For example, at time index t-21201, there will be up to eight different configurations, so eight different sequences are detected by the UE and distinguished among eight cells. Thus, within a multi-cell group, no UE will receive two BS swept beams with the same beam sequence ID from two different cells, since the TDM based beam sequence ID configuration is unique for each cell. The beam sequence ID configuration for a particular TDM-based in each cell may be determined via the controller.

In general, the beam sequence is per cell

Can haveA specific mapping to a time index t (0 ≦ t ≦ Q-1) is referred to as TDM-based beam sequence ID mapping. For example, if Q beams are used at each cell of a system with identifying capacity J, then

Can be generated as follows:

where nConfig is a configuration index for the image, which may be semi-persistently scheduled, dynamically scheduled, or configured via the controller. A maximum of J BQM-RSs will be transmitted from multiple cells within the multi-cell group because each cell will use a different beam sequence ID for each time index, and multiple unique beam sequence IDs can be received simultaneously via the UE to perform MBMCT. Accordingly, BQM-RS transmitted via the swept beams of cells may be reused among multiple cells within a multi-cell group. Fig. 13-17 provide various examples for avoiding beam sequence ID ambiguity.

Fig. 13 illustrates an example of a sequence of beams for inter-BS boresight alignment with J-Q-8, while each configuration would have 8 time periods per (beam) cycle, and each time period in a cycle corresponds to a certain time index l-0-7. In this example, BS0 has been configured with configuration 0 configured based on the TDM beam sequence ID, BS1 has been configured with configuration 1, so UEs within the overlap region 1301 at l 2 may receive a first swept beam from BS0 with a beam sequence ID of 2 and a second swept beam from BS1 with a beam sequence ID of 3. In this way, there is no beam sequence ID ambiguity within the overlap region 1301.

Fig. 14 illustrates an example of a beam sequence for inter-BS boresight misalignment and J-Q-8. In this example, BS0 has been configured with configuration 0 configured based on the TDM beam sequence ID, and BS1 has been configured with configuration 1. At l 2, a UE within region 1401 may receive a first swept beam from BS0 and beam sequence ID 2 and a second swept beam from BS1 and beam sequence ID 3. In this way, there is no beam sequence ID ambiguity within region 1401. For region 1402, the UE will receive a first swept beam from BS0 with a beam sequence ID of 2 and a second swept beam from BS1 with a beam sequence ID of 2. However, the beam sequence ID 2 from BS0 is received at time index l 2, and the beam sequence ID 2 from BS1 is received at time index l 1, so there is no beam sequence ID ambiguity in region 1402.

Fig. 15 illustrates an example of a beam sequence with inter-BS boresight alignment but different beam sweep order directions and J-Q-8. In this example, BS0 has been configured with configuration 0 of the TDM based beam sequence ID configuration, and BS1 has been configured with configuration 1. BS0 may sweep up to 8 swept beams in a clockwise direction 1501 and BS1 may sweep up to 8 swept beams in a counterclockwise direction 1502. In region 1503, the UE will receive the first swept beam from BS0 and beam sequence ID 2 at time l-2, and the UE will receive the second swept beam from BS1 and beam sequence ID 6 at time l-5, so there is no beam sequence ID ambiguity in region 1503. There is no ambiguity in the beam sequence ID when the UE receives the swept beam coverage 1504 corresponding to the beam sequence ID 3 transmitted from BS1 at time index l 2. This is because at time index l-2 there is no sweeping beam from BS0 and corresponding to beam sequence ID 3. And the beam sequence ID 3 is identical to the beam sequence ID of the swept beam also transmitted from BS1 at time index l-2.

Fig. 16 illustrates another example of a beam sequence for inter-BS boresight misalignment but different beam sweep order directions and J-Q-8. In this example, BS0 has been configured with configuration 0 configured based on the TDM beam sequence ID and transmits swept beams in a clockwise direction 1601. BS1 has been configured with configuration 1 and transmits swept beams in a counterclockwise direction 1602. When the time index l is 2, the UE within region 1603 may receive a first swept beam from BS0 and beam sequence ID is 2 and a second swept beam from BS1 and beam sequence ID is 3. In this way, there is no beam sequence ID ambiguity within region 1603.

The beam identifiable capacity J may be greater than the maximum number of swept beams transmitted by each cell. Fig. 17 illustrates an example of a beam sequence for J24 ≧ Q8 and alignment of the primary boresight between BSs. In this example, each BS (BS0, BS1) has 3 cells, each cell uses Q-8 unique different beam sequence IDs, and these 3 cells also use different beam sequence IDs from each other. In this case, each BS would therefore have 24 different beam sequence IDs in total. It is noted that the set of beam sequence IDs used in BS0 will be the same (i.e., reusable) as the set of beam sequence IDs used in BS 1. Since the UE will not receive two cell-swept beams with the same beam sequence ID from two different BSs, there will also be no beam sequence ID ambiguity for this example. For example, in region 1701, at time index l of 2, the UE scans a first cell scan beam with a receive beam sequence ID of 18 and a second cell scan beam with a beam sequence ID of 2. Since the beam sequence IDs of two cell-swept beams from two different BSs are different, there will be no beam sequence ID ambiguity. This particular embodiment of fig. 17 may achieve slightly better performance but at the cost of relatively high RS/signaling overhead and measurement complexity.

The maximum number of cells in a multi-cell group will be determined by the beam identifiable capacity J. Fig. 18 illustrates an example of transmitting multiple BQM-RSs from cells in a multi-cell group. Since J-8 in the example of fig. 18, there will be a maximum of J BQM-RSs transmitted via multiple cells, where each cell transmits a different beam sequence ID at each time index. All of these BQM-RSs may be received simultaneously via a UE that performs an MBMCT mechanism.

To implement beam detection or tracking as described above, a frame structure containing BQM-RSs is shown in FIG. 19, FIG. 19 illustrating BQM-RS assignment based on Beam Tracking Signals (BTSs). Instead of the BTS, a Beam Search Signal (BSS) may also be used as a substitute for the BQM-RS. The use of a BSS may have lower RS overhead but require longer measurement periods/times and may exhibit insufficient slow beam tracking capability for rapidly changing channels. The BTS-based BQM-RS resource allocation may be within a Beam Quality Measurement Resource (BQMR) within the DL BF header. BQM-RS may be distributed 1901 or localized 1902. It can be seen from fig. 19 that the BQMR comprising BQM-RSs of distributed allocation 1901 type are alternately placed in the DL BF header in a distributed manner and form the same group with other signals. While the BQMRs of BQM-RS, which comprise localized allocation 1902 type, are placed together in a DL BF header in a sequential manner. In other words, the BQMRs of the distributed allocation 1901 type are not contiguous with each other; while BQMRs of localized allocation 1902 type are contiguous with each other.

For the embodiment of fig. 19, there will be Q swept beams transmitted from the base station at the cell. Q swept beams may be deterministically defined and transmitted sequentially over M mmwave radio frames, and each BF header of a radio frame will be assigned N swept beams, where N is Q/M. The allocation of Q beams may be repeated every M millimeter wave radio frames, so N ═ Q/M beams with indices mN — (M +1) N-1 may be used in the mth millimeter wave time unit. For this exemplary embodiment, the UE side will use P swept beams. In each BQMR of the DL BF headers of cell-swept beams, the index of the best UE beam is kopt, or L (1 ≦ L ≦ P) swept UE beams indexed kL ≦(K +1) L-1 may be used to receive BQI-RS in the kth millimeter wave time unit, 0 ≦ K ≦ K-1, where K ≦ MP/L is the UE swept beam period. The UE may measure the signal quality of cell-swept beams based on the received BQM-RS, and the UE may then self-select a preferred UE-swept beam to transmit the measured signal quality to the BS corresponding to the cell-swept beam via the appropriate cell-swept beam and time period according to the TDM-based beam sequence ID configuration table as previously described.

An example of a BSS-based BQM-RS for Nd 2, J4 and P4 is shown in fig. 20 to further describe the principles of operation of BQM-RS. Where Nd is the number of cells within the multi-cell group, J is the identification capacity or maximum number of beam sequence IDs used by the BS beam group, Q is the beam number of cells, and P is the beam number of UEs. The DL BF header of the frame shown in fig. 20 will contain at least four DL sweep beam periods, namely DL sweep beam period 0, DL sweep beam period 1, DL sweep beam period 2, DL sweep beam period 3. Each of the four BQM-RS 2001 will be associated with a different beam sequence ID that can be derived from each of the BQM-RS 2001. For example, IDs 0-ID 3 are transmitted via four swept beams steered to four different directions for cell 02002 and cell 12003, but each cell (0, 1) will transmit a different ID at any given time period. In response to receiving BQM-RS 2001, the UE will perform beam quality measurements and transmit the results of the beam quality measurements with the UE beam that has been determined by the UE to be the best UE beam for UE beam 12004 in this example.

An BQM-RS example for Nd-2, J-Q-4 and P-4 and based on a distributed BTS is shown in fig. 21. The frame structure of this example would include at least, but is not limited to, one DL BF header and one UL BF header. The DL BF header will contain, without limitation, four DL sweep beam periods, DL sweep beam period 0, DL sweep beam period 1, DL sweep beam period 2, and DL sweep beam period 3. Each of the four BQM-RSs 2101 will be associated with a different beam sequence ID. For example, ID 0-ID 3 are transmitted via four different swept beams steered into four different directions for both cell 02102 and cell 12103. However, in this example, the UE may perform reception of Beam Search Signals (BSS), Broadcast signals (BCS) and Cell Search Signals (CSS) via the best UE Beam 2104 and reception of the BTS via a full sweep using all four UE beams 2105 during each DL sweep Beam period. From the examples of fig. 20 and 21, it can be seen that the time for measuring all combinations of swept beams of cells and swept beams of UEs is 4 mm wave time units for BSS based BQM-RS and 1 mm wave time unit for BTS based BQM-RS.

An example of how beam tracking is performed is shown in fig. 22. In response to a UE receiving multiple BQM-RSs, e.g., BQM-RSs corresponding to the cell beam from ID 2 of cell i and the cell beam corresponding to ID1 from cell j, the UE will measure the signal-to-noise ratio (SNR) of the beams and record such information in an SNR list or table, which may be stored and updated in a storage medium of the UE. Based on the BQM-RS measurements, the UE can determine its preferred beam and the preferred beam of the cell.

The SNR table described above is shown in fig. 23. Although beam tracking may be via SNR measurements of beams performed at the UE on BQM-RSs, other measurement criteria may also be used, such as signal-to-interference ratio (SIR), signal-to-interference-and-noise ratio (SINR), Received Signal Strength Indicator (RSSI), Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), and so forth. The SNR table for each of the combinations of beams of the cell and beams of the UE may be calculated based on a time-domain matched-filter (MF) output SNR. The SNR table may contain a period index 2311 for each DL cell sweeping a beam, a beam index 2312 for the cell, and a beam index 2313 for the UE. The contents of the SNR table may be transmitted in part or in whole from the UE to the BS as a measurement reward, which may include a preferred cell beam index and at least two beam quality measurements. Since the UE has received cell-swept beams from various cells, the UE will perform measurements to populate or update a table and determine a preferred UE beam index based on the maximum SNR value (e.g., 2304) or other measured metric. From the SNR table, the UE may report back to one or more BSs, including without limitation one or more of the following: a preferred cell beam index (e.g., 2301) and a preferred DL cell sweep beam period index (e.g., 2302), or a smaller subset of the entire row for which the preferred UE beam index corresponds. It is noted that only information on the beam quality, not on the cell quality, can be obtained in beam tracking here. A total (fixed number) of J2P SNR values in the SNR table may need to be calculated as shown in fig. 23. It may be of higher computational complexity, but the network may not require additional signaling or contain configuration.

An exemplary embodiment of the timing points for SNR measurement reporting back is shown in fig. 24. For this exemplary embodiment, the BS or controller would simply receive the measurement reports returned by the UEs from the cell-swept beams without knowing which UE-swept beams are preferred or optimal, since the preferred or optimal UE-swept beams are up to the UE's discretion, which does not need to be known to the BS or controller. The measurement report including SNR (or other signal quality measurement indicator) may be determined by the UE at the preferred reporting time and reported in the UL. The measurement reward may be transmitted via the preferred UE beam or via the current UE beam and the measurement reward may be received from the preferred cell beam or the current cell beam. For example, assuming that it is determined that the DL cell sweep beam used during DL cell sweep beam period 12401 (corresponding to ID 1) has the largest DL SNR measurement, the UE will need to transmit measurement reports during the uplink transmission period at the corresponding UL cell sweep beam period 12402 (i.e., the so-called preferred reporting time) in turn upon reception with the cell sweep beam having the largest DL SNR measurement (corresponding to ID 1). Such a relationship may be defined by the TDM-based beam sequence ID mapping table of fig. 12. At a preferred reporting time, information from the SNR table and a preferred beam sequence ID corresponding to a cell sweep beam may be reported to one or more BSs via the UE. The SNR or preferred beam sequence ID corresponding to the cell swept beam may be reported back via a physical uplink control channel/physical uplink shared channel (PUCCH/PUSCH) at the BF header using the swept beam of the preferred UE. The preferred reporting time may be the current usage reporting time or the UL time corresponding to the reception of the swept beam by the cell with the DL maximum measured SNR, as shown in fig. 24.

Fig. 25 illustrates such an example of SNR reporting from a UE to a BS within a multi-cell group with a mm wave communication network. The preferred time or predetermined time period may be decided via the UE. At a preferred or predetermined time period, the SNR measurement reports for the cell beams will be transmitted via the UE to the serving BS and/or to the neighbor BSs via use of the preferred UE swept beam decided by the UE and the swept beam of the cell. The preferred UE swept beam may be the UE beam currently in use or the UE beam with the largest measured SNR in the SNR table. The preferred cell may then be decided via the controller based on the quality measurements received in return by the UE in PUCCH/PUSCH.

The random access preamble used by the UE may be known via some BSs or controllers in the vicinity of the UE. Fig. 26 shows an example of transmitting RAP by the UE. The UE may transmit a RAP via a Random Access Channel (RACH) (e.g., S2601). RAP can be transmitted over the RACH of the BF header via using a preferred UE swept beam, which may be the currently used UE swept beam or may be the UE swept beam with the largest SNR in the SNR table. The RAP may be received via a cell sweep beam of the plurality of cells with a preferred or predetermined time period.

When the cell has received PUCCH RS/PUSCH RS and/or RACH from the UL signal of the UE, the cell may perform SNR measurement based on the received PUCCH RS/PUSCH RS and/or RAP. The SNR measurement for each received PUCCH RS/PUSCH RS and/or RAP in a cell within a preferred time period defined by the mapping table above in the Uplink (UL) part of the Beamforming (BF) header may be performed by multiple BSs. The cell SNR results measured at the BS may be transmitted to a controller, which may then determine one or more preferred cells to serve the UE by comparing the cell SNR results measured at the BS. The BS may also continually update the SNR table for the cell to make such comparisons.

The above-mentioned RAP may be a non-competitive RAP based. To facilitate diversity of non-contention based RAPs, subband-based allocations in the frequency domain are shown in fig. 27A, and periodic-based transmissions in the time domain can be considered as shown in fig. 27B. According to an exemplary embodiment, the RAP of the shorter transmission period may be used for higher mobility UEs, and the RAP of the longer transmission period may be used for lower mobility UEs.

Fig. 28 illustrates a cell SNR table in an exemplary embodiment according to the present disclosure. According to an exemplary embodiment, a fixed number of SNRs with Nd total may need to be calculated. The SNR of the cell may be the cell SNR measured over PUCCH RS/PUSCH RS and/or RAP, such SNR being only known to the BS and controller. For example, as shown in 2801 of fig. 28, during a DL cell scan with a beam period index of 1, for each of the cells corresponding to indices 0, 1,2 and 3, the SNR corresponding to the PUCCH RS, RUSCHs RS or RAP of the cell needs to be calculated and input into the table for recording and comparison.

Fig. 29A is a functional block diagram of a UE in an exemplary embodiment according to the present disclosure. The UE may include, but is not limited to, a processor 2901 coupled to a storage medium 2905, a millimeter wave 2902 transceiver, an unlicensed band transceiver 2904, and an antenna array 2903. The storage medium 2905 provides temporary storage or permanent storage, such as the SNR table of fig. 23, the TDM map table of fig. 12, and other related data. The millimeter wave 2902 transceiver includes one or more transmitters and receivers connected to the antenna array 2903 to transmit beamformed signals. Unlicensed band transceiver 2904 may contain one or more transceivers for communicating in unlicensed spectrum, e.g., Wi-Fi, bluetooth NFC, etc. The processor 2901 may include one or more hardware processing units, such as a processor, controller, or discrete integrated circuit, to control the millimeter wave 2902 transceiver to transmit and receive beamformed signals and to perform functions related to the beam tracking methods described above and related exemplary embodiments and examples thereof.

The term "user equipment" (UE) in this disclosure may be, for example, a mobile station, Advanced Mobile Station (AMS), server, client, desktop computer, laptop computer, network computer, workstation, Personal Digital Assistant (PDA), tablet Personal Computer (PC), scanner, telephone device, pager, camera, television, palmtop video game device, music device, wireless sensor, and the like. In some applications, the UE may be a stationary computer device operating in a mobile environment, such as a bus, train, airplane, ship, automobile, and so forth.

Fig. 29B is a functional block diagram of a BS in an exemplary embodiment according to the present disclosure. The BS may include, but is not limited to, a processor 2911 coupled to a storage medium 2915, a millimeter wave 2912 transceiver, a centimeter wave transceiver 2914, and an antenna array 2913. The storage medium 2915 provides temporary or permanent storage, such as the SNR table of fig. 23, the TDM map table of fig. 12, and other related data. The millimeter wave 2912 transceiver includes one or more transmitters and receivers connected to the antenna array 2913 to transmit beamformed signals. The processor 2911 may contain one or more hardware processing units, such as a processor, controller, or discrete integrated circuit, that controls the millimeter wave 2912 transceiver to transmit and receive beamformed signals and performs the functions associated with the beam tracking methods described above and the associated exemplary embodiments and examples thereof.

The term BS in this disclosure may be a variant or advanced version of a macrocell BS, microcell BS, picocell BS, femtocell BS, "eNodeB" (eNB), Node-B, Advanced BS (ABS), Base Transceiver System (BTS), access point, home BS, relay station, scatterer (scatterer), repeater, intermediate Node, intermediary (intermediate), satellite-based communication BS, etc.

Fig. 30A illustrates the steps of a beam tracking method used by a multi-cell group in a mm wave communication system from a UE-based perspective in an exemplary embodiment according to the present disclosure. In step S301, the UE will receive a first plurality of reference signal sequences including a first reference signal sequence associated with a first cell beam and a second reference signal sequence associated with a second cell beam over a first time period. In step S302, the UE will measure a beam quality comprising a first measurement of the first cell beam and a second measurement of the second cell beam. In step S303, the UE will generate a measurement report based on the beam quality. In step S304, the UE will transmit a measurement report.

Fig. 30B illustrates the steps of a beam tracking method used by multiple cell groups in a mm wave communication system from a BS-based angle in an exemplary embodiment according to the present disclosure. In step S311, the BS transmits a first reference signal sequence generated according to a first time-division multiplexing (TDM) configuration of a plurality of TDM configurations during a first time period, wherein the first TDM configuration is unique for each cell within the multi-cell group during the time period. In step S312, the BS will receive a measurement reward from the preferred cell beam or the current cell beam in response to transmitting the first reference signal sequence. In step S313, the BS will perform cell quality measurements based on the measurement reports. In step S314, the BS transmits the cell quality measurement to the controller. Thus, a change from the first TDM configuration to the second TDM configuration may be determined via the controller.

In view of the above, the present disclosure is suitable for use in a wireless communication system and is capable of tracking beam quality received via a UE and cell quality measured via a BS in a manner that may reduce computational complexity, reduce signaling overhead, and reduce required measurement periods.

No element, act, or instruction used in the detailed description of the disclosed embodiments of the present application should be construed as critical or essential to the disclosure unless explicitly described as such. Also, as used herein, the indefinite articles "a" and "an" can each comprise more than one item. If it is intended to mean there is only one item, then the term "single" or similar language may be used. Further, as used herein, the term "any of" preceding a list of a plurality of items and/or a plurality of categories of items is intended to encompass any of the items and/or categories of items "any of", "any combination of", "any plurality of" and/or "any combination of a plurality of" either individually or in combination with other items and/or other categories of items. Additionally, as used herein, the term "set" is intended to encompass any quantity of items, including zero. In addition, as used herein, the term "number" is intended to encompass any number, including zero.

It will be apparent to those skilled in the art that various modifications and variations can be made in the structure of the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure cover modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents.

Claims (27)

1. A beam tracking method for user equipment in a multi-cell group of a millimeter wave communication system, the method comprising:

receiving, from a base station, a first plurality of reference signal sequences including a first reference signal sequence associated with a first cell beam and a second reference signal sequence associated with a second cell beam during a first time period, the first reference signal sequence being generated by the base station according to a first time-division multiplexing (TDM) configuration during the first time period, wherein the first TDM configuration of the base station during a time period is unique to each cell in a multi-cell group to which the UE belongs;

measuring a beam quality comprising a first measurement of the first cell beam and a second measurement of the second cell beam;

generating a measurement report based on the beam quality; and

transmitting the measurement report to the base station;

the first reference signal sequence is derived from a first beam quality measurement reference signal received by the first cell beam, and the second reference signal sequence is derived from a second beam quality measurement reference signal received by the second cell beam.

2. The method of claim 1, wherein the measurement report includes an index of a preferred cell beam and at least two beam quality measurements.

3. The method of claim 2, wherein the index of the preferred cell beam corresponds to the first cell beam in response to having determined that the first cell beam has a highest beam quality of cell beams among the beam quality measurements.

4. The method of claim 3, wherein transmitting the measurement reward comprises:

transmitting the measurement report via using a preferred user equipment beam.

5. The method of claim 4, wherein the preferred user equipment beam corresponds to a currently in use user equipment beam or the highest beam quality of a cell beam among the beam quality measurements.

6. The method of claim 3, wherein determining the highest beam quality among the beam quality measurements comprises:

recording or updating each of the beam quality measurements; and

determining the highest beam quality of a cell beam based on one of the beam quality measurements having a highest signal-to-noise ratio value.

7. The method of claim 6, further comprising:

the beam quality measurements are maintained in a table, wherein each of the beam quality measurements corresponds to a cell beam index and a user equipment beam index.

8. The method of claim 6, wherein transmitting the measurement reward comprises:

transmitting the measurement report in a physical uplink control channel or a physical uplink shared channel in an uplink portion of a beamforming header during the preferred time period.

9. The method of claim 8, further comprising:

transmitting a random access preamble in a physical random access channel during the preferred time period.

10. The method of claim 9, wherein the preferred time period corresponds to an uplink time period currently in use or an uplink time period associated with the cell beam having the highest beam quality among the beam quality measurements of cell beams in a downlink.

11. The method of claim 9, wherein the random access preamble is frequency subband based or periodic based.

12. A method of beam tracking, the method comprising:

transmitting, via a base station, a first reference signal sequence generated according to a first time division multiplexing configuration of a plurality of time division multiplexing configurations to a user equipment during a first time period, wherein the first time division multiplexing configuration during a time period is unique for each cell within a multi-cell group;

receiving a measurement report from a preferred cell beam in response to transmitting the first reference signal sequence;

performing a cell quality measurement based on the uplink signal received from the preferred cell beam in response to receiving the measurement report; and

transmitting the cell quality measurements to a network controller connected to the base station.

13. The method of claim 12, wherein transmitting the first reference signal sequence comprises:

transmitting a first reference signal sequence corresponding to a first beam sequence identifier of a plurality of beam sequence identifiers based on the first time division multiplexing configuration of the plurality of time division multiplexing configurations.

14. The method of claim 13, further comprising:

transmitting a second reference signal sequence corresponding to a second one of the beam sequence identifiers during the first time period, wherein the beam sequence identifiers are shared by other base stations of the multi-cell group.

15. The method of claim 12, wherein the measurement report includes an index of a preferred cell beam and at least a portion of the cell quality measurement.

16. The method according to claim 15, wherein the preferred cell beam corresponds to a currently in use cell beam or a cell beam that has been determined to have a highest beam quality among the cell quality measurements.

17. The method of claim 14, wherein the first beam sequence identifier corresponds to a first beam quality measurement reference signal located in a first cell beam transmitted by the base station and the second beam sequence identifier corresponds to a second beam quality measurement reference signal located in a second cell beam transmitted by the base station.

18. The method of claim 17, wherein receiving the uplink signal from the preferred cell beam comprises:

receiving a signal quality measurement of the first beam quality measurement reference signal in the measurement report, wherein the measurement report is in a physical uplink control channel or a physical uplink shared channel in an uplink portion of a beamforming header during a preferred time period.

19. The method of claim 18, wherein receiving the uplink signal from the preferred cell beam comprises:

receiving a random access preamble, wherein the random access preamble is located in a physical random access channel in an uplink portion of a beamforming header during a preferred time period.

20. The method according to claim 19, wherein the preferred time period corresponds to an uplink time period currently in use or an uplink time period associated with the cell beam having the highest beam quality of cell beams among the beam quality measurements in downlink.

21. The method of claim 12, wherein performing the cell quality measurement based on the received uplink signal comprises:

performing the cell quality measurements on a physical uplink control channel or a physical uplink shared channel or a physical random access channel or reference signals associated with the physical uplink control channel or physical uplink shared channel of the preferred cell beam during a preferred time period.

22. The method of claim 21, wherein the random access preamble is frequency subband based or periodic based.

23. The method of claim 12, wherein the first one of the plurality of time-division multiplexing configurations is configured via the network controller or semi-persistently scheduled or dynamically scheduled, and a change from the first time-division multiplexing configuration to a second time-division multiplexing configuration is determined via the network controller.

24. The method according to claim 12, wherein the preferred cell beam is determined based on the measurement report received from a user equipment on the cell beam.

25. The method of claim 12, further comprising:

receiving a decision of a preferred cell from the controller based on the cell quality measurement on the uplink signal received from the preferred cell beam.

26. A user equipment, comprising:

a transmitter;

a receiver; and

a processor coupled to the transmitter and the receiver and configured to:

receiving, from a base station via the receiver, a first plurality of reference signal sequences including a first reference signal sequence associated with a first cell beam and a second reference signal sequence associated with a second cell beam during a first time period, the first reference signal sequence being generated by the base station according to a first time-division multiplexing (TDM) configuration of time-division multiplexing (TDM) configurations during the first time period, wherein the first TDM configuration of the base station during a time period is unique for each cell in a multi-cell group to which the UE belongs;

measuring a beam quality comprising a first measurement of the first cell beam and a second measurement of the second cell beam;

generating a measurement report based on the beam quality; and

transmitting the measurement report to the base station via the transmitter;

the first reference signal sequence is derived from a first beam quality measurement reference signal received by the first cell beam, and the second reference signal sequence is derived from a second beam quality measurement reference signal received by the second cell beam.

27. A base station, comprising:

a transmitter;

a receiver; and

a processor coupled to the transmitter and the receiver and configured to:

transmitting, via the transmitter, a first reference signal sequence generated according to a first time division multiplexing configuration of a plurality of time division multiplexing configurations to a user equipment during a first time period, wherein the first time division multiplexing configuration is unique for each cell within a multi-cell group during a time period;

receiving a measurement report from the preferred cell beam via the receiver in response to transmitting the first reference signal sequence;

performing a cell quality measurement based on an uplink signal received from the preferred cell beam in response to receiving the measurement report; and

transmitting, via the transmitter, the cell quality measurements to a network controller connected to the base station.

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