Joint Access Point Placement and Channel Assignment for 802.11 Wireless LANs

Xiang LingSchool of Communication and Information EngineeringUniversity of Electronic Science and Technology of ChinaChengdu, China

Kwan Lawrence YeungDept of Electrical and Electronic EngineeringUniversity of Hong KongHong Kong, China

IEEE Wireless Communications and Networking Conference (WCNC) 2005

Outline

Introduction Throughput estimation

Restrainers Objective Function (OF) Patching algorithm Simulations Conclusions

Introduction

More and more multi-cell 802.11 WLANs are being deployed to provide seamless coverage

Deciding AP placement and channel assignment become increasingly important

Introduction (cont.)

[1] R.C.Rodrigues, G.R.Mateus, and A.A.F.Loureiro, “On the design and capacity planning of a wireless local area network,” IEEE/IFIP Network Operations and Management Symposium 2000.

AP PlacementMaximizing the total receiving signal strength

Introduction (cont.)

[2] Y.Lee, K.Kim, and Y.Choi, “Optimization of AP placement and channel assignment in wireless LANs,” Proceedings of the 27th Annual IEEE Conference on Local Computer Networks, 2002.

Load balancingMinimizing the load carried by the heaviest-lo

aded AP

Introduction (cont.)

GoalConsider the co-channel interference

between cells AP placement Channel assignment

Throughput & Fairness

Throughput estimation

[8] G.Bianchi, “Performance analysis of IEEE 802.11 distributed coordination function,” IEEE Journal on Selected Areas in Communications, vol. 18, no. 3, pp. 535~547, March 2000.

Throughput estimation (cont.)

Restrain criteria

(a). Mobile terminals in MT1’s radiating range

(b). Mobile terminals located in AP1’s interference range

Restrain criteria (cont.)

(c). If MT1 is in AP2’s interference range, mobile terminals associated to AP2 will restrain MT1.

(b). If AP1 and AP2 are so close that they can interfere with each other directly, mobile terminals associated to AP2 are MT1’s restrainers.

Throughput estimation (cont.)

Objective Function (OF)

β approaches 1

when all THRs are the same

β converges to 1/N when throughputs are heavily unbalanced

Patching algorithm

Example

Simulations

NS-2 2 APs (Cells) MTs are uniformly distributed UDP / CBR / 1500-byte

System throughput

Fairness index

System throughput

Fairness index

OF values got by patching algorithm and exhaustive searching

Computation complexity

Conclusion

This paper proposed an method to estimate the throughput of a multi-cell 802.11b WLAN system

Co-channel overlapping between cells is considered in the estimation

Patching algorithm reduce the computational complexity

Simulation results show that better throughput and fairness are provided