Adaptive Bit-Interleaved Coded OFDM With Reduced Feedback Information

Power Allocation for Multiband Coded OFDM Systems with Limited Feedback

“…For the MCS candidates with code rates higher than half, the channel codes are obtained by puncturing from the mother code, where the puncturing patterns, the minimum Hamming distances, and the total input weights of error events for each Hamming distance are given in [12]. For BER estimation, i.e., P b (E; m, h), we use the derivation in [7].…”

“…For comparison purposes, we include in our simulations the symbol-level adaptive modulation and coding system with equal power control as proposed in [7]. We assume that the channel estimation and prediction are perfect.…”

“…Excessive feedback loads may lead to a difficulty in practical implementation. In order to reduce the amount of feedback information, a more realistic system called OFDM with symbol-level adaptive modulation and coding (symbol-level AMC) was proposed in [7]. In this symbollevel scheme, the signals transmitted by all the subcarriers of an OFDM symbol (which is a codeword) are encoded and modulated by a single pair of encoder and modulation scheme, which is adaptively decided by the receiver based on a prediction of channel state information (CSI).…”

“…Furthermore, the whole bandwidth consisting of multiple OFDM bands can share a fixed amount of power budget. Motivated by these conditions and inspired by the approach in [7], [8], we propose a new and efficient power allocation method over OFDM bands based on the greedy and dynamic programming principles. In this method, the receiver predicts the CSI of all OFDM bands and then accordingly allocates suitable transmission power levels and corresponding modulation and coding schemes 1 .…”

“…In this method, the receiver predicts the CSI of all OFDM bands and then accordingly allocates suitable transmission power levels and corresponding modulation and coding schemes 1 . The advantages of the proposed method are as follows: i) Since the receiver only needs to feedback a transmission power level and a pair of modulation format and coding for each OFDM band, the total amount of feedback information can be kept significantly lower than that of a conventional system which provides feedback for all subcarriers; ii) Rather than allocating power for all OFDM symbols equally in the conventional symbol level AMC approach in [7], [8], the proposed method allows us to enjoy more freedom in allocating transmission power over multiple OFDM symbols. Therefore, the average throughput is improved because an OFDM band in a better condition will be assigned with a higher power level and can transmit in a higher data rate effectively.…”