Semi-analytic selection of sub-carrier allocation schemes in uplink orthogonal frequency division multiple access

The authors propose a generalised framework that analytically compares different sub-carrier allocation (SA) or sub-channelisation schemes (such as interleaved SA (ISA), localised SA (LSA) or hybrid schemes) in uplink (UL) orthogonal frequency division multiple access (OFDMA). The ultimate goal of the proposed framework is to systematically determine the best SA scheme among the considered candidates for a given condition of inter-user frequency offsets (IUFOs) and the target bit error rate (BER). As an illustration, two typical SA schemes are considered, that is, ISA and LSA for comparison. First, based on the well-known fact that multiple access interference by IUFO and frequency diversity gain are both dictated by the employed SA scheme, the authors propose a semi-analytic approach to derive coded BER curve formula as a function of frequency offset bound (FOB) for each scheme. Then, the signal-to-noise ratio gain of ISA over LSA for various target BERs and FOBs is derived. Finally, the cutoff FOB over which ISA obtains worse than LSA is obtained and its functional relationship with the target BER is investigated. By following the overall procedure in the proposed framework, the best SA scheme among the various SA candidates for the general UL OFDMA systems with arbitrary system parameters can be chosen.