Subband Based Adaptive Bit and Power Allocation for OFDM Systems

In this paper, by contrast with "subcarrier-to-subcarrier" allocation method, subband based bit and power allocation methods are discussed to decrease the computational complexity for OFDM systems. Hughes Hartogs algorithm (HHA) is modified for subband based allocation. Bit and power is adaptively allocated into subbands by two means: constant bit rate (CBR) adaptation and variable bit rate (VBR) adaptation. The simulations are carried out on a 1024-subcarrier OFDM platform and the results show that in the range of low average bit SNR (under 15 dB) over vehicular A channel the computational complexity overhead can be reduced by 80% or 90% at the cost of performance loss less than 1 dB or 3 dB respectively

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