A Joint Bandwidth Allocation and Routing Scheme for the IEEE 802 A Joint Bandwidth Allocation and Routing Scheme for the IEEE 802.16j 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

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

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

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

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

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.

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

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

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

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

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.

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

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

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)

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

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

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

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

Conclusion Future work The paper proposes a joint resource allocation and routing scheme for the downlink of IEEE 802.16j 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.

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