Robert Akl, D.Sc.

Optimal access point placement and channel assignment in IEEE 802.11 networks:

Designing IEEE 802.11 wireless networks includes two major components: placement of access points in the demand areas and assignment of radio frequencies to each access point. Coverage and capacity are some key issues when placing access points. A major challenge in designing wireless networks is the frequency assignment problem. The 802.11 wireless LANs operate in the unlicensed ISM frequency, and all access points share the same frequency. As a result, as 802.11 access points become widely deployed, they start to interfere with each other and degrade network throughput. Efficient assignment of channels becomes necessary to avoid and minimize interference.

An overwhelming number of models in the literature use average inter-cell interference for the calculation of capacity of a Code Division Multiple Access (CDMA) network. The advantage gained in terms of simplicity by using such models comes at the cost of rendering the exact location of a user within a cell irrelevant. We calculate the actual per-user interference and analyze the effect of user-distribution within a cell on the capacity of a CDMA network. We show that even though the capacity obtained using average interference is a good approximation to the capacity calculated using actual interference for a uniform user distribution, the deviation can be tremendously large for non-uniform user distributions.

Global versus optimized local call admission control in CDMA networks:

Call admission control (CAC) algorithms are responsible for efficient management of a network’s resources while guaranteeing the quality of service and grade of service, i.e., accepting the maximum number of calls without affecting the quality of service of calls already present in the network. We design and implement global and local CAC algorithms, and through simulations compare their network throughput and blocking probabilities for varying mobility scenarios. We show that even though our global CAC is better at resource management, the lack of substantial gain in network throughput and exponential increase in complexity makes our optimized local CAC algorithm a much better choice for a given traffic distribution profile.