Abstract

With the unique features of spatial multiplexing and interference suppression, Multiple Input Multiple Output (MIMO) techniques have great potential in the improvement of network capacity over conventional antenna technologies. In order to exploit the benefit of simultaneous transmissions provided by MIMO, researchers have proposed a number of cross-layer optimizations and MAC layer designs to increase the throughput of wireless mesh or ad hoc networks, where the number of elements in the antenna arrays are pre-allocated or evenly assigned to the routers. In this paper, we argue that using the same number of elements in each antenna array in all routers is not a necessary condition for the improvement of system performance. This is because the requirement for the number of elements is quite different for each router. Especially at those critical routers that have huge aggregate traffic toward the gateway, more elements are needed not only for the traffic relay but also for the interference suppression. Based on this observation, we define the joint problem of bandwidth allocation, element assignment and scheduling to characterize the throughput benefits of cross-layer optimizations. We propose a Cost-Aware Element Assignment (CAEA) technique to minimize the total number of the antenna elements when still achieving the optimal bandwidth allocation. In addition, to verify the efficiency of the CAEA assignment, a heuristic Traffic-aware Stream-controlled Link Scheduling (TSLS) algorithm is proposed to provide a schedulable bandwidth allocation. We demonstrate through extensive simulations that our solutions (CAEA, TSLS) not only effectively save the total cost on antenna elements but also perform close to optimal on the average.

Keywords: Wireless mesh networks; MIMO; Bandwidth allocation; Element assignment; Scheduling

Article Outline

1. Introduction

2. System model

2.1. Network architecture

2.2. Wireless transmission and interference model

2.3. Abstraction of MIMO links

3. Constraints and problem definitions

3.1. Constraints

3.2. Problem definitions

4. Bandwidth allocation

4.1. Max–min fair allocation

4.2. Proportional fair allocation

5. Antenna element assignment

5.1. An optimal solution of element assignment problem

5.1.1. The DOF requirement for transmission

5.1.2. The DOF requirement for reception

5.1.3. The DOF requirement for both transmission and reception

5.2. Algorithm of Cost-Aware Element Assignment

6. Scheduling

7. Discussion

8. Simulations

9. Related work

10. Conclusion and future work

Acknowledgements

References