OFDMA_Part27 - 4.1.2.1 Survey Of Margin Adaptive Resource...

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27 The following optimization problem, constrained by E15 and E19, illustrates the basic idea of the MA approach for the multi-user system being considered: min c k , n , p n c k , n p n n k …(E20) where c k , n × F ( SNR k , n , P e ) n R k , k …(E21) and SNR k , n = p n × h k , n 2 σ 2 …(E22) In the above equations, the function F provides the achievable data rate per subcarrier for a given signal-to-noise-ratio ( SNR ), modulation scheme, and probability of bit-error ( P e ). R k is the minimum data rate requirement for user k . Now that I have defined the MA problem for the single-user and multi-user scenarios, let us consider some real-world MA algorithms to better understand margin-adaptive resource allocation in OFDMA systems. Please note that the single-user problem was posed only for illustration purposes and its solution is trivial. However, the multi-user problem that was posed in reference to Figure 11 is a very interesting problem. All the real-world algorithms surveyed in the following subsection try to solve this problem by using different flavors of the MA approach.
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Unformatted text preview: 4.1.2.1 Survey Of Margin Adaptive Resource Allocation Algorithms In [28], Wong and Cheng consider an adaptive multi-user subcarrier allocation scheme. Their scheme tries to exploit all the subcarriers (except maybe those that are in deep fade for all the users at a given time). In this scheme, the authors assume perfect channel information and ignore the overhead created by the transmission of the subcarrier allocation information. [28] considers the multi-user problem that was discussed in section 4.1.2. The problem is reformulated as a convex optimization problem over a convex set as follows [28]: min c k , n , r k , n c k , n h k , n 2 n = 1 N ∑ f k r k , n ( ) k = 1 K ∑ …(E23) with the constraints on r k,n and c k,n such that R k ≤ c k , n r k , n n = 1 N ∑ and c k , n k = 1 K ∑ = 1 …(E24)...
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This note was uploaded on 09/27/2009 for the course ECE 399 taught by Professor Prof during the Spring '09 term at University of Texas at Austin.

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