1. A Joint Bandwidth Allocation and Routing Scheme for the IEEE 802
A Joint Bandwidth Allocation and Routing Scheme for the IEEE j Multi-hop Relay Networks
Kyungjoo Lee, Hyukjoon Lee, Yong-Hoon Choi, Younguk Chung
Kwangwoon University , Seoul , Korea
Young-il Kim
Electronics and Telecommunications Research Institute , Daejon , Korea
光雲大學
電子通訊研究所
IEEE ICOIN 2009

2. Outline Introduction Motivation and Goal
Joint Bandwidth Allocation and Routing Scheme
Simulation
Conclusion

3. Introduction IEEE 802.16j multi-hop relay system
Transparent Relay Mode – Enhance link throughput
Non-Transparent Relay Mode – Extend service coverage
MR-BS
MR-BS
High rate RS
Low rate RS MS MS
Transparent Relay Mode
Non-Transparent Relay Mode

4. Introduction IEEE 802.16j Transparent Relay Mode Frame structure MR-BS
RS1
RS1
RS1
RS1
MS2
MS2
MS2
MS2
MS1
MS1
MS1
MS1

5. Motivation IEEE 802.16j Transparent Relay Mode Limited radio resource
Routing path selection
Allocation of corresponding resource MS RS
MR-BS RS MS
Transparent Relay Mode

6. Goal Base on the IEEE 802.16j transparent relay mode.
In order to maximizing the total downlink system throughput in a single cell.
The proposed scheme is on the selection of routes and the allocation of corresponding resources.

7. Joint Bandwidth Allocation and Routing Scheme
Problem description
The lengths of DL access zone and transparent zone should be determined according to the total amount of data transported to the MSs directly from the MR-BS and via the RSs.
Therefore, the two problems of routing and resource allocation must be solved jointly. RS MS
DL-Subframe MS MS RS MS RS
MR-BS MS MS MS
DL-Access
DL-Transparent RS MS
DL-Subframe MS MS RS MS RS
MR-BS MS MS MS
DL-Access
DL-Transparent

8. Joint Bandwidth Allocation and Routing Scheme
Problem description
Assume
MS receive all of its downlink traffic from the MR-BS either directly or through one RS.
No two MSs communicate without going through the MR-BS.
At each OFDMA slot, only one station can transmit data to a receiver.
One BS, M-1 RSs , N MSs are placed randomly.
Objective function:
(RjTw/B1j )B1j = RjTw ,
Bij : The maximum amount of data that can be transported by transmitter i for receiver j in a single OFDMA slot.
Rj : The required average data rate for receiver j.
Tw : The frame duration
N : Number of MSs
M : Number of BS and RSs

9. Joint Bandwidth Allocation and Routing Scheme
Constraint(1) for the problem
DL-access zone and DL-transparent zone
(RjTw/B1j )
(RjTw/B2j )B2j / B12= RjTw / B12
MR-BS1
MSj
RjTw
B1j
RjTw/Bij
MR-BS1
MSj
RS2
RjTw
B12
MSj
RSi
RjTw
Bij
ωACCESS : Total length of DL-Access Zone
ωRELAY : Total length of DL-Access Zone
Bij : The maximum amount of data that can be transported by transmitter i for receiver j in a single OFDMA slot.
Rj : The required average data rate for receiver j.
Tw : The frame duration
N : Number of MSs
M : Number of BS and RSs

10. Joint Bandwidth Allocation and Routing Scheme
Constraint(2) for the problem
Maximal transmission data
MR-BS1
MSM+1
MSM+N …
RM+1Tw
RM+NTw
RS2
RSM
RMTw
R2Tw
RjTw
RjTw
MR-BS1
MSM+1
RS2
RM+1Tw
MSM+N
RM+NTw …
ki: The number of slots allocated for the transmitters in the DL access zone
Bij : The maximum amount of data that can be transported by transmitter i for receiver j in a single OFDMA slot.
N : The number of MSs
M : The number of BS and RSs

11. Joint Bandwidth Allocation and Routing Scheme
Multi-Dimensional Multi-choice Knapsack Problem (MMKP)
The goal of MMKP is to select exactly one item from each of N groups of items for the maximum total value of the selected items, subject to the M volume constraints.
M items (M-dimensional)
MR-BS1 …
RSM
RS2 …
RSi … …
MSM+1
MSj
MSM+N
N groups
Each MS is mapped to a group with nj = M+1 items.
The (M+1)th item means the amount of the data needed to be transmitted per frame by an MS should remain.

12. Joint Bandwidth Allocation and Routing Scheme
Multi-Dimensional Multi-choice Knapsack Problem (MMKP)
Maximal transmission data
MR-BS1
MSM+1
RS2
MSM+8
MSM+3
C2=
a2M+1
a2M+3
a2M+8
Ci : The total allowable volume of ith dimension
N : The number of MSs
M : The number of BS and RSs

13. Joint Bandwidth Allocation and Routing Scheme
Multi-Dimensional Multi-choice Knapsack Problem (MMKP)
The (M+1)th item means the amount of the data needed to be transmitted per frame by an MS should remain.
Rj : The amount of data which is receiving from j
Ci : The total allowable volume of ith dimension
N : The number of MSs
M : The number of BS and RSs

14. Joint Bandwidth Allocation and Routing Scheme
[9] M. Moser, D. P. Jokanovic, and N. Shiratori,
"An algorithm for the multidimensional multiple-choice knapsack problem,“IEICE Transaction Fundamentals,1997
Multi-Dimensional Multi-choice Knapsack Problem (MMKP)
Since the MMKP is a NP-hard problem, polynomial time sub-optimal heuristic algorithms such as proposed in [9] are used in general.
Based on Lagrange multipliers
Let λ1 ,λ2 ,… , λM be the M non-negative Lagrange multipliers.
constraints(1)
constraints(2)

15. Heuristic algorithm based on Lagrange multipliers
Remain some MSs
Update
Check constraints(2),(1)
Find anther BS or RS
MR-BS1
Update
RS2
RS3
RS4
MS1
MS2
MS3
MS4

16. Heuristic algorithm based on Lagrange multipliers
MR-BS1
Check anther BS or RS
RS2
RS3
RS4
RS5
MS1
MS2
MS3
MS4

17. Simulations Simulation parameter DL-access zone 7 ms
RS1
145 m
145 m
RS2
MR-BS
DL-access zone
7 ms
DL-transparent zone
3 ms
Constant bit rate application traffic
512 (bytes /packet)
Packet interval
2 ms to 6 ms

18. Simulations Simulation result The LQB scheme computes for each MSj,
and selects the route with the highest value of Qj.
The number of slots allocated for the MR-BS, RS1 and RS2 in the DL access zone

19. Conclusion Future work
The paper proposes a joint resource allocation and routing scheme for the downlink of IEEE j MR system.
And transform the optimization problem to a MMKP and then derived a sub-optimal polynomial-time heuristic algorithm based on Lagrange multipliers.
Through simulation we showed our scheme performed better than a link quality-based scheme but did not reach the optimal solution as expected.
Future work
An adaptive scheme to adjust the boundary of DL access zone and transparent zone needs to be added in order to make scheme more complete. Our pursuit for this scheme along with more extensive simulation study is left for future works.

20. Thank you very much