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We examine a new problem called the Zone Selection Problem (ZSP) in wireless Orthogonal Frequency‐Division Multiple Access (OFDMA)‐based systems. We consider the case where the mobile station (MS) informs the base station of its preferences regarding possible working modes supported by the system. In Worldwide Interoperability for Microwave Access (WiMAX) systems, which are used as a practical reference system for constraints and specific modes of operations, each working mode must be assigned at a different time interval called a Zone. Such zone may, in the downlink subframe, define a specific transmission scheme, which can be either single‐input single‐output or one of the multiple‐in multiple‐out (MIMO) modes supported by the system. We define ZSP as a problem where the base station assigns MSs to zones in a way that optimizes the system utilization (in terms of resource usage) while trying to satisfy the preferences of the users as much as possible. This makes ZSP a bi‐objective optimization problem. We derive assignment costs from physical channel models that integrate specific MIMO schemes and channel conditions. We provide an exact solution to ZSP by using a combinatorial optimization abstraction. We propose a simplified and practical mode ranking approach that enables the MS to define its preferences regarding operation in the optional MIMO modes in the system. We prove that ZSP is NP‐hard and describe two heuristic solutions: a greedy approach and a local search approach. Simulation results show the performance of the exact algorithms on a realistic WiMAX system assumptions and present the trade‐off between the user preferences and system preferences. Copyright © 2016 John Wiley & Sons, Ltd.

This paper addresses the problem of efficient mapping and allocation of voice over IP (VoIP) traffic with multiple VoIP vocoders in WiMAX systems. We show that by taking advantage of the periodicity of VoIP frames, generated by multiple vocoder types, and by applying semi‐fixed allocations in the existing resource allocation process, the mapping overhead can be reduced substantially. We present a system model that allows the evaluation of the proposed solutions for the problem at hand. Using this model, we show that the problem is NP hard and present a set of observations on the resource allocation process leading to good mapping decisions from the perspective of mapping overhead. We present a new mapping algorithm that implement the decisions and show by extensive simulations that the proposed mapping algorithm can reduce the overhead down to 25% of the overhead experienced in orthogonal frequency division multiple access (OFDMA)‐based systems such as WiMAX and IEEE802.16, while retaining a low computational complexity. Copyright © 2009 John Wiley & Sons, Ltd.

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