JP2012195920A - Direct communication between mobile stations in cellular wireless network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protocol used for direct communication between mobile stations (MS) in a cellular wireless network including a cellular wireless relay network.SOLUTION: For priority transmission of an MS-to-MS direct communication data packet, an MS-to-MS direct communication zone is specified for the frame structure of a cellular wireless network or a cellular wireless relay network. Based on a characteristics definition of MS-to-MS direct communication, concentrated scheduling and distributed scheduling for MS-to-MS direct communication within the same cell and in different cells are defined. A resource request message and an allocation signaling system are defined. Examination is made with regard to MS-to-MS direct communication when infrastructure station support is available and when not available. Further, explanation is made about selection of a new BS or a concentrated scheduler (CS) when the infrastructure station has gone wrong.

Description

  The present invention relates to wireless communications, and in particular, to a protocol for direct communication between mobile stations in a cellular wireless network.

  As you can see, cellular wireless communications are now part of people's lives around the world. Recently, cellular wireless relay communication has appeared. For example, both IEEE 80.16j-2009 and IEEE 802.16m adopt the relay communication mode.

  Current cellular wireless networks, including cellular wireless relay networks, do not support direct communication between mobile stations (MS). As shown in FIG. 1 (a), in a conventional cellular wireless network, when MS-A needs to send a data packet to MS-B within a cell, the data packet passes through the cell's base station (BS). There is a need. Similarly, in the cellular wireless relay network shown in FIG. 1B, when the MS-B needs to send a data packet to the MS-C, the data packet needs to pass through the upper stations RS-A and BS. Further, as shown in FIG. 1 (c), when two MSs in communication belong to two cells, the data packet needs to pass through all related higher-level stations including BS and RS (if applicable). . When two such MSs that are within communication distance of each other are involved, it will obviously introduce extra delay and use more bandwidth resources. Cellular wireless networks and cellular wireless relay networks with high traffic cannot afford to waste bandwidth resources.

  The above problems occur due to the fact that many current cellular wireless networks and cellular wireless relay networks do not support direct communication between two MSs. This is because these frame structure designs support only uplink and downlink communications. A typical time division duplex (TDD) frame structure for a cellular wireless network is shown in FIG. A frame consists of downlink (DL) and uplink (UL) subframes. FIG. 2 (b) shows a TDD frame structure for a cellular wireless relay network. A frame consists of a DL access zone, a DL relay zone, a UL access zone, and a UL relay zone. All subframes / zones are communication between an infrastructure station and a mobile station, or between two infrastructure stations (such as RS). It is for. Direct communication between mobile stations is not supported in the frame structure design of conventional cellular wireless networks, even in newer cellular wireless relay networks such as IEEE 802.16j-2009 and IEEE 802.16m.

  The present invention is directed to a direct communication protocol between MSs that substantially eliminates one or more of the problems due to limitations and disadvantages of the related art.

  It is an object of the present invention to improve network performance by conserving bandwidth resources and reducing packet transmission delay, and to provide a solution for direct communication between MSs in cellular wireless networks and cellular wireless relay networks.

  The present invention includes direct communication zones (DCZ), direct communication MAP messages, centralized and distributed scheduling of direct communication between MSs in small cells, and direct communication between MSs in different cells.

  The direct communication zone is designated for priority transmission of direct communication between MSs and aims to guarantee quality of service (QoS). Direct communication between MSs is not limited to DCZ, and DCZ is not limited to direct communication between MSs. Both DCZ size and application can be made flexible. The direct communication MAP message conveys resource allocation and signaling information. With the two scheduling mechanisms, transmission scheduling using an infrastructure station and transmission scheduling without infrastructure support are possible, and direct communication between MSs can be both one-hop and two-hop.

  Another object of the present invention is to enable direct communication between MSs when the data source and the destination MS are different cells. Invent a handover scheme and a frame sharing scheme supported by self-coexistence to support this type of direct communication between MSs.

FIG. 1A is an example of communication between MSs in a cell of a conventional cellular wireless network. FIG. 1 (b) is an example of inter-MS communication within a cell of a cellular wireless relay network such as IEEE 802.16j-2009 or IEEE 802.16m. FIG. 1 (c) is an example of communication between two MSs in different cells of a conventional cellular wireless network. FIG. 2A shows a TDD frame structure of a conventional cellular wireless network. FIG. 2B shows a TDD frame structure of a conventional cellular wireless relay network. FIG. 3A shows a direct communication zone in the TDD frame structure and DL and UL subframes independent of the direct communication zone. FIG. 3 (b) shows a direct communication zone that partially occupies UL subframes in the TDD frame structure (OFDMA PHY). FIG. 3 (c) shows a direct communication zone that partially occupies a DL subframe in the TDD frame structure (OFDMA PHY). FIG. 3D shows a direct communication zone that occupies a part of a relay zone or access zone in a TDD frame structure that supports wireless relay communication (OFDMA PHY). FIG. 3 (e) shows a direct communication zone in the FDD frame structure and a DL or UL subframe independent of the direct communication zone. FIG. 3 (f) shows a direct communication zone that occupies a part of the DL or UL subframe in the FDD frame structure (OFDMA PHY). FIG. 3G shows a direct communication zone operated by a frequency channel different from the DL and UL frequency channels of the FDD frame structure. FIG. 3 (h) shows a direct communication zone that occupies a part of the access zone or relay zone of the DL or UL subframe of the FDD frame structure for wireless relay communication (OFDMA PHY). FIG. 3 (i) shows a direct communication zone that uses another frequency channel other than DL and UL subframes of a TDD frame structure for wireless communication. FIG. 4A is an example of direct communication between one-hop MSs of a cellular wireless network. FIG. 4B is an example of direct communication between one-hop MSs of a cellular wireless relay network. FIG. 4C is an example of direct communication between two-hop MSs of a cellular wireless network. FIG. 4D is an example of direct communication between two-hop MSs of a cellular wireless relay network. FIG. 5 shows a three-way handshake procedure for distributed scheduling in a wireless network. FIG. 6 shows a frame shared between adjacent cells of a cellular wireless network.

  Direct communication between MSs involves a protocol for scheduling direct transmission between MSs in a frame. Here, the details of space, scheduling mechanism, and related messages for direct communication between MSs are introduced.

  1 Direct communication zone

  The direct communication zone (DCZ) is a space of consecutive symbols according to frequency and continuous symbols according to time in a frame allocated for direct communication between MSs.

  The DCZ is in one frame and does not span a plurality of consecutive frames.

  As shown in FIGS. 3A and 3E, the DCZ can be independent of the DL and UL subframes, and as shown in FIGS. 3B, 3C, 3D, 3F, and 5H. In addition, when OFDMA PHY is used, a part of DL or UL subframe can be occupied.

  As shown in FIGS. 3G and 3I, the DCZ can use another frequency channel other than the DL and UL frequency channels.

  The DCZ can be in a TDD frame or an FDD frame.

  As shown in FIGS. 3D and 3H, the DCZ can be part of the access zone or relay zone of the DL or UL subframe when OFDMA PHY is used.

  The DCZ does not span DL and UL subframes. The DCZ does not span the relay zone and access zone.

  The priority of the schedule for direct communication between MSs is DCZ. If there is no schedule for direct communication between MSs, downlink and uplink burst transmissions can be scheduled in the DCZ.

  The size of the DCZ can be expanded. The number of subchannels according to frequency and the number of symbols according to time can be updated periodically by the BS.

  One frame may consist of one or more DCZs as required.

  Since DCZ has a priority in scheduling direct communication between MSs, one advantage of DCZ is that it can provide quality of service (QoS) for direct communication between MSs.

  2 Direct communication between MSs (DC)

  As shown in FIGS. 4A, 4B, 4C, and 4D, direct communication between MSs is classified into one-hop MS DC and two-hop MS DC.

  In direct communication between one-hop MSs, the MS directly transmits / receives data packets to / from another MS (one or more) and does not relay or pass through other stations.

  In the two-hop MS DC, the MS communicates with another MS (one or more) by transferring the user data or control signal system by the intermediate MS.

  The priority of the schedule for direct communication between MSs is DCZ.

  When direct communication between MSs requires a capacity larger than DCZ, it may request to expand DCZ.

  MS direct communication can be scheduled in two ways. Centralized scheduling and distributed scheduling. In the case of centralized scheduling, the BS or centralized scheduler schedules transmission. In the case of distributed scheduling, MSs and adjacent stations involved in direct communication distribute and schedule transmission.

  Direct communication between MSs may occur between MSs in a cell, or may be performed between MSs in different cells.

  3 Direct communication MAP message

  The direct communication MAP (DC-MAP) message is a signal for resource allocation and other control information for direct communication between MSs. Since direct communication between MSs is not limited to being scheduled in the direct communication zone, resource allocation is not limited to the direct communication zone.

  4 Centralized scheduler

  When the BS fails, the MS or RS can function as a centralized scheduler (CS) for centralized scheduling of direct communication between MSs.

  The MS or RS has a one-hop neighbor and can become a centralized scheduler if the BS of the cell fails.

  Traffic to the CS is the uplink and traffic from the CS is the downlink.

  5 Centralized scheduling of direct communication between MSs in the same cell

  Centralized scheduling of direct communication between MSs is performed by the BS or by the CS if the BS is not available.

  In order to request resources for direct communication in centralized scheduling, polling may be used for the MS.

  A DCCS (Direct Communication Centralized Scheduling) message can be used to request a resource. DCCS: Request is sent to the BS or CS by the requester MS. In the case of a tree topology cellular wireless relay network, DCCS: Request is sent along the path to the BS or CS.

  The BS or CS collects the bandwidth request of the MS in the cell and provides resources accordingly. Send authorized resources for direct communication between MSs using DC-MAP messages. The DC-MAP message is sent to the MS involved in the relevant direct communication. Resource permissions are approved as needed.

  Transmission of DCCS messages is scheduled in the UL subframe by the BS or CS.

  6 Distributed scheduling for direct communication between MSs in the same cell

  In distributed scheduling, direct communication between MSs is scheduled by a data source MS, data destination MS, and MS (RS if applicable) within a one-hop communication range.

  Distributed scheduling is only used to schedule direct communication between one-hop MSs in the direct communication zone.

  Distributed scheduling can be used when a cell has a BS or CS. If there is no BS or CS, it is necessary to select MS as BS or CS. If the system does not support the MS functioning as a BS or CS, it can also support distributed scheduling without a BS or CS. If the MS is selected and functioning as a BS or CS, communication with other MSs follows the protocol for uplink or downlink transmission.

  In the absence of a BS or CS, the DCZ may occupy all uplink and downlink subframes.

  In distributed scheduling, a three-way handshake procedure (apply, grant, grant approval) is used.

  A three-way handshake procedure is shown in FIG. DCDS (Direct Communication Distributed Scheduling) messages are used for the three-way handshake procedure of distributed scheduling.

  As shown in FIG. 5, the DCDS: Request (request) is transmitted by the requester MS. The DCDS: Grant is sent by the grantor MS and responds to requests with a proposed subset of resources, if possible. DCDS: Grant ACK (granting approval) is sent by the first requester MS and includes the permitted resources and confirms the schedule. The requester and grantor one-hop neighbors (neighboring stations) are informed of the schedule by either DCDS: Grant or DCDS: Grant ACK.

  If there is a BS or CS in the cell, transmission of the DCDS message is centrally scheduled by the BS or CS. If there is no BS or CS in the cell, the transmission of the DCDS message is distributed by the MS (and RS if applicable).

  If there is a BS or CS in the cell, the resource allocation is reported to the BS or CS by DCDS: Report. Upon receipt of the DCDS: Report, the BS or CS knows the resource allocation and will not allocate the same resource to other stations unless an appropriate mechanism is employed to solve the co-channel interference problem.

  7 Direct communication between MSs in different cells

  It is possible for MSs in different cells one hop away to communicate directly.

  If the MS needs to communicate with another cell's MS, the direct method is MS handover and associate with another cell's BS. After the handover, direct communication with the MS of the cell can be started by using the protocol for direct communication between the MS of the cell. When the direct communication ends, the MS handover is canceled and the original cell is returned.

  When multiple neighboring cells are operated on the same frequency channel and the self-coexistence mechanism of frame sharing is applied, direct communication between MSs in different cells becomes easier.

  The frame sharing self-coexistence mechanism is one in which a plurality of adjacent cells are operated in different frames in the time domain on the same frequency channel, as shown in FIG. In general, a self-coexistence beacon is transmitted between cells in a specified self-coexistence window. Transmission of self-coexistence beacons between different cells is scheduled by a self-coexistence mechanism. Neighboring cells can exchange control information by exchanging self-existing beacons.

  In this case (when sharing different frames on the same frequency channel), if the MS needs to communicate with another cell's MS, it may be synchronized to that cell's frame by tracking the frame preamble. After synchronization, a resource request is transmitted to the destination MS of another cell by transmitting a self-coexistence beacon. Upon receipt of a resource request message carried by a self-coexisting beacon from another cell's one-hop neighbor, the MS reports this request to the BS or CS and allocates resources by centralized scheduling, or distributed scheduling as shown in FIG. Start the procedure. In this case, the DCDS message is transmitted as part of the self-existing beacon.

Claims (17)

  A mechanism that enables direct communication between mobile stations in cellular wireless networks and cellular wireless relay networks. In a mechanism for specifying a subchannel according to the frequency domain and a space for symbols according to the time domain in the frame structure,
a. DCZ can be independent of DL and UL subframes on the same frequency channel in both TDD and FDD frames,
b. DCZ can operate on different frequency channels other than DL and UL operating frequency channels in both TDD and FDD frames,
c. If OFDMA PHY is used in both TDD and FDD frames, DCZ can be part of DL subframe, UL subframe, access zone, relay zone,
d. The mechanism of claim 1, wherein the DCZ does not span frames, subframes, or different zones. In the use of DCZ,
a. DCZ is for priority transmission of direct communication between MSs,
b. DL and UL data packets can be transmitted using DCZ;
c. The mechanism of claim 1, wherein the DCZ includes being able to be resized to accommodate DL and UL traffic and inter-MS communication traffic. Direct communication between MSs has the feature,
a. MS-to-MS direct communication is scheduled in DCZ and has priority compared to DL and UL communication,
b. The direct communication between MSs is not limited to being scheduled to DCZ,
c. Direct communication between MSs is one-hop and two-hop,
d. Direct communication between MSs is in one cell or between MSs in different cells,
e. MS direct communication can be scheduled with or without infrastructure support,
f. The mechanism according to claim 1, wherein the direct communication between MSs can be scheduled by using centralized scheduling or distributed scheduling.   The mechanism according to claim 1, characterized in that a direct communication MAP (DC-MAP) is used to signal resource allocation and other control information for direct communication between MSs.   Centralized source allocation is scheduled using centralized scheduling of direct communication between MSs. For this purpose, a DCCS (Direct Communication Centralized Scheduling) message is sent from the requester MS to the BS or centralized scheduler (CS), and the BS or CS The mechanism of claim 1, wherein the allocation is based on a current resource allocation.   The mechanism according to claim 6, wherein a DCCS message is used, including a sub-field of DCCS: Request including resource request, origin station, and destination station information.   The mechanism of claim 6, wherein DCCS message scheduling is scheduled in a UL subframe by a BS or CS.   If there is no BS or CS in the cell, when the MS can function as a BS or CS, the MS (RS if applicable) is selected as the new BS or CS, the BS (or RS) has a one-hop neighbor, and the BS Alternatively, the mechanism is selected as CS.   The mechanism according to claim 1, characterized in that the resources can be distributed and scheduled using distributed scheduling of direct communication between MSs, and for this purpose a DCDS (Direct Communication Distributed Scheduling) message is transmitted.   The mechanism of claim 10, wherein the mechanism is a three-way handshake procedure for distributing and scheduling transmissions between MSs.   The mechanism of claim 10, wherein DCDS message transmission is scheduled by a BS or CS.   The mechanism of claim 10, wherein resource allocation is reported to a BS or CS, and the BS or CS knows the resource allocation.   10. The mechanism according to claim 9, wherein the DCDS message is a mechanism including DCDS: Request, DCDS: Grant, and DCDS: Grant ACK subfields.   If the MS needs to communicate directly with another cell's MS, hand over to another cell, associate with the cell's BS, use the direct inter-MS communication mechanism for direct communication, and terminate the direct communication The mechanism according to claim 1, wherein the handover is returned to the original cell even if the handover is canceled.   When using the frame-sharing self-coexistence mechanism on the same frequency channel, when the MS needs to communicate directly with another cell's MS, it synchronizes with the frame of that cell, and the request contained in the self-coexistence beacon The mechanism according to claim 1, wherein a resource is requested by transmitting, and when the requested resource is granted, direct communication is started in a frame of the target cell.   Upon receipt of a resource request contained in a self-coexistence beacon from another cell's MS, the request is reported to the BS or CS for resource allocation, and when the resource is granted, grant is sent to the requester MS. The mechanism according to claim 16.

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