Decode and Forward Based Cooperative Receiving ARS Group for UL Channel Enhancement
(AWD-relay)
Document Number: IEEE C802.16m-09_1820
Date Submitted: 2009-08-29
Source:
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 AWD
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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 retransmission 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
1
3
2
4
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. AMAP)
– 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
Table xxx- Orthogonal sequence for forward ACK channel
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