Joint Access Point Placement and Channel Assignment for Wireless LANs Xiang Ling School of Communication and Information Engineering University of Electronic Science and Technology of China Chengdu, China Kwan Lawrence Yeung Dept of Electrical and Electronic Engineering University of Hong Kong Hong 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 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  AP Placement  Maximizing 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,  Load balancing  Minimizing the load carried by the heaviest- loaded AP

Introduction (cont.) Goal  Consider the co-channel interference between cells AP placement Channel assignment  Throughput & Fairness

Throughput estimation [8] G.Bianchi, “Performance analysis of IEEE 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 MT 1 ’s radiating range (b). Mobile terminals located in AP 1 ’s interference range

Restrain criteria (cont.) (c). If MT 1 is in AP 2 ’s interference range, mobile terminals associated to AP 2 will restrain MT 1. (b). If AP 1 and AP 2 are so close that they can interfere with each other directly, mobile terminals associated to AP 2 are MT 1 ’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 b 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