Adaptive Sub-carrier Block Modulation with Differentially Modulated Pilot Symbol Assistance for Down-link OFDM Using Up-link Delay Spread

摘要

In an AMS/OFDM system, base station is in control of the modulation level of each sub-carrier, and then, adaptive modulated packet is transmitted from the base station to the mobile station. In this case, the mobile station is required the modulation level information (MLI) to demodulate the received packet. The ML1 is generally transmitted as a data symbol, therefore, the throughput is degraded. In an OFDM, the channel response at a particular sub-carrier frequency is not supposed to be totally different from its neighboring frequencies, and hence, they must have correlation that depends on the coherence bandwidth of the channel 5c. If we could assign the same modulation level for coherently faded sub-carrier block, MLI is required only one time for each sub-carrier block. Moreover, we can assign the data on the empty space of pilot signals for increasing the total transmission. In this paper, we propose an adaptive sub-carrier block modulation with differentially modulated pilot symbol assistance for downlink OFDM using up-link delay spread.