Abstract-With the proliferation of wireless local area network (WLAN) technologies, wireless Internet access via public hotspots will become a necessity in the near future. In outdoor areas where the installation of a large number of wired access points is practically or economically infeasible, mobile users located at the edge of the network communicate with the access point at a very low rate and in turn waste network resources. In this work, we promote the use of tetherless relay points (TRPs) to improve the throughput of a WLAN in such environments. We first provide a high level description on how to integrate TRPs in a multi-rate WLAN architecture. We then propose an integer-programming optimization formulation and an iterative approach to compute the best placement of a fixed number of TRPs. Finally, we show in numerical analysis, through a case study based on relay-enabled rate adaptation and IEEE 802.11-like multi-rate physical model with Rayleigh fading, that for a wide range of system parameters, significant performance gain can be achieved when TRPs are strategically installed in the network.Index Terms-Wireless local area network, tetherless relay point, placement optimization, capacity improvement, mathematical programming/optimization.

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Abstract. Fixed broadband wireless access is a promising technology allowing Internet service providers to expend their customer base in sparsely populated rural areas. Because the size of the target service area is humongous, relay infrastructure is essential. Installing and maintaining this relay infrastructure is the main cost associated with such networks. Thus, we develop an optimization framework which computes the minimum number of relay stations and their corresponding channel configurations such that a pre-specified subscribers' traffic demand can be satisfied. Since the problem is a mixed-integer program, we propose an efficient optimization algorithm to compute the optimal solution in a reasonable amount of time. Our numerical results show that by using a few relay stations in a rural community, broadband Internet access can be established in a cost effective manner.

Abstract. The throughput capacity of WLANs can be improved by a carefully designed relay infrastructure. In this work, we propose an optimization formulation based on Lagrangian relaxation and a subgradient algorithm to compute the best placement of a fixed number of relay nodes (RNs) in a WLAN. We apply this optimization framework to a multi-rate WLAN based on the IEEE 802.11g standard under Rayleigh fading. We then study the expected throughput capacity of a WLAN with relay infrastructure and investigate how the optimal placement of RNs is affected by the number of RNs, path-loss characteristics, and the traffic pattern. Our numerical results show that, in some network scenarios, more than 120% performance gain can be achieved when RNs are strategically installed in the network. Furthermore, we also show that for a wide range of system parameters, optimally placed RNs can significantly increase the network throughput capacity over random placement.

Fixed Broadband Wireless Access (FBWA) technology is designed to serve as a wireless DSL replacement technology to provide broadband access in underserved areas where no other access technology exists. Due to the enormousness of the target service area, relay equipment play an important role in such networks, and the installation and maintenance cost of the network is directly proportional to the cost of the relay equipment. To minimize the network operational cost, we develop an optimization framework which computes the minimum number of relay stations and their placement in the network such that the demands from the end users are met.