Decode and Forward Based Cooperative Receiving ARS Group for UL Channel Enhancement (AWD-relay)

Document Number: IEEE C802.16m-09_1820Date Submitted: 2009-08-29Source:

Kanchei(Ken) Loa, Tsung-Yu Tsai, Jiun-Je Jian, Yi-Ting Lin, Chun-Yen Hsu, Youn-Tai Lee, Chiu-Wen Chen E-mail: loa@iii.org.tw Institute for Information Industry (III)

Venue: Base Contribution: N/A

Re : P802.16m/D1 Relay Purpose: Discussion and approval of the proposal into the IEEE 802.16m AWDNotice:

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Introduction• In IEEE802.16j system, the deposition of relay group is used to

enhance DL channel via macro diversity.• However, the mechanism of using relay group to enhance the

UL channel is not considered in IEEE 802.16j• Since AMS are generally power-limited devices, the signal quality of

UL channel is more difficult to be maintained than that in the DL channel

• Re-transmission introduces more packet delay and additional re-transmission resource and overhead. The negative effect may even larger in the relay network.

Introduction

• In this contribution, a decoded and forward based (DF-based) cooperative receiving mechanism by using ARS groups is proposed to enhance the UL channel– Improves the overall system efficiency by enhancing the channel

robustness– QoS is guaranteed better due to lower packet latency and error rate– The coverage of the relay station could be extended which reduces

the rate of inter-RS handover– Beneficial for the power saving of AMS devices by improving the

equivalent signal quality and reducing the re-transmission

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Basic Procedure of DF-based UL ARS Group

• More than one ARSs are allocated as a ARS relay group to assist AMS’s UL transmission

• AMS transmits a burst P1 to the ARS group• Each ARS in the ARS group decodes the received burst and

check the burst CRC. Then report the decoding status (i.e. ACK or NAK) to their super-ordinate station (ABS or scheduling ARS) via the forward ACK Channel– The forward ACK Channel is a 6*6 distributed resource and can be

multiplexed by up to three ARS groups– If there are at least one ARS in the ARS group successfully decodes the

AMS’s burst, the super-ordinate station of the ARS group will allocate the resource to let the ARSs to relay it

• The effective burst error probability in the UL access link can be decreased significantly via the cooperative receiving of the ARS group (Approximately decrease exponentially to the number of ARS in the ARS group)

Cooperating the AMS Scheduling Information in the ARS group

• In the distributed scheduling mode, the conveying of the scheduling information of AMS’s transmission to the ARS group members could be achieved in two approaches– Primary ARS– Persistent allocation in UL (for UGS or ertPS)

Primary ARS

• An scheduling ARS is allocated in an ARS group as primary RS to schedule the AMS’s transmission– The primary ARS sends a MAC management message AAI_SCH-INFO

carrying the scheduling information of one or more AMSs’ transmission to the super-ordinate station of the ARS group

– The super-ordinate station forwards the scheduling information send by the primary ARS to the ARS group via broadcast messages (e.g. A-MAP)

– By receiving the scheduling information, the ARSs in the ARS group knows the resource location and the subframe in which the AMS will transmit

– The procedure of cooperating the scheduling information could be done within one frame

Conveying of Scheduling Information

• The scheduling information send from the primary ARS to the super-ordinate station shall contain the following information– STID of scheduled AMSs– Subframe offset (the offset from the current subframe)– Resource Indicator– MCS used by the transmitting AMSs

• The super-ordinate station then forwards the scheduling information to the ARS group via IEs in the A-MAP– The scheduling information may divide into more than one A-MAP IEs

Persistent Allocation in UL

• Suitable for the case of UGS and ertPS flow• Pre-defined location UL resource could be allocated to an UGS

flow or ertPS flow in a periodic manner• The ARSs in the ARS group could know the location of

predefined resource allocated for AMS and

Forward ACK Channel

• Forward ACK channel can be allocated to one or more UL ARS group to transmit the decoding status to their super-ordinate station

• Forward ACK channel consists of three 2*6 distributed forward ACK tiles (FAT)– Each FAT is allocated to a RS group for sending decoding report of a

UL cooperative receiving burst to their super-ordinate station.

Forward ACK Channel

• A FAT is further divided into three 2*2 FAT mini-tiles– Each location of the FAT mini-tile in a FAT can be dedicated to two

ARS in the ARS group to transmit 1-bit ACK/NAK orthogonal sequence• A 4-bit orthogonal sequence pair is allocated to an ARS• The orthogonal sequence used and the mapping to the physical resource is the

same as that of HMT in the HARQ feedback channel

– Dedicated mini-FAT can assist the ABS to know the individual receiving status of each ARS in an ARS group

Sequence Index

Orthogonal Sequence 1-bit ARS report

0 [+1 +1 +1 +1] Even number ARS ACK

1 [+1 -1 +1 -1] Even number ARS NACK

2 [+1 +1 -1 -1] Odd number ARS ACK

3 [+1 -1 -1 +1] Odd number ARS NACK

Burst Relaying

• Base on the decoding report of a ARS group in the forward ACK channel, the super-ordinate station of the ARS group sends relevant scheduling information of relaying the AMSs’ burst in CR-IND IE in the A-MAP– CR-IND IE contains the preferred ARS for relaying the specific burst– CR-IND IE can bring unsolicited resource grant to the ARS for relaying

Proposed Text[Insert the following section in 15]

15.x ARS group

15.x.x UL cooperative receiving of ARS group

The performance of UL transmission can be improved with the help of ARS group.

15.x.x.1 Decode and forward based UL cooperative receiving

15.x.x.1.1 Mechanism of decoded and forward based UL cooperative receiving

When an AMS transmits in the UL resource, multiple ARSs can form the AMS’s super-ordinate ARS group and decode the transmitted burst individually. Then they report the decoding status to super-ordinate ABS or ARS via the forward ACK channel as described in 15.x.x.1.1.2 . The location of the forward ACK channel is indicated by the super-ordinate station of the ARS group using FAC IE in the A-MAP.

Based on the decoding status of each ARS in the ARS group from the forward ACK channel, the super-ordinate station sends the relevant scheduling information to the ARS group for relaying burst using CR-IND IE in the A-MAP. The CR-IND IE contains the preferred ARS for relaying the specific burst. The CR-IND IE may also contain unsolicited resource grant to the ARSs for relaying the specific burst.

.

For coordinating the scheduling information of AMS’s transmission among the ARS group in the distributed scheduling mode, a scheduling ARS is assigned as a primary ARS in an ARS group. The primary ARS schedules one or more AMSs’ transmission for cooperative relaying, then it sends the scheduling information by the AAI_SCH-INFO message to its super-ordinate station, then the super-ordinate station broadcast the information carried in the AAI_SCH-INFO to the ARSs in the ARS group via CR-SCH-INFO IE in the A-MAP

15.x.x.1.1.2 Forward ACK channel

Forward ACK channel consists of three 2*6 distributed forward ACK tiles (FAT). Each FAT is allocated for ARSs in a group for sending decoding status of a received burst to their super-ordinate station. A FAT is further divided into three 2*2 FAT mini-tile, which are indexed as 1 to 3, as shown in Fig. xxx. A FAT mini-tile can be dedicatedly assigned to two ARSs in an ARS group. A pair of orthogonal sequences are allocated to an ARS in an ARS group. The mapping of ARS and the orthogonal sequence pair is shown in table xxx. The procedure of dedicating mini-tile index and orthogonal sequence pair to an ARS in an ARS group is TBD. The mapping between the 4-bit orthogonal sequences and the FAT mini-tiles is same as in 15.3.9.2.2.

Fig. xxx Forward ACK channel structure

Sequence Index

Orthogonal Sequence 1-bit ARS report

0 [+1 +1 +1 +1] Even number ARS ACK

1 [+1 -1 +1 -1] Even number ARS NACK

2 [+1 +1 -1 -1] Odd number ARS ACK

3 [+1 -1 -1 +1] Odd number ARS NACK

Table xxx- Orthogonal sequence for forward ACK channel