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The paper studies an efficient ICI cancellation method termed segment equalization scheme. According to the time-variant nature of the mobile channel, the received OFDM signal and channel impulse response (CIR) are divided into many segments before FFT, then all the segments are equalized in the frequency-domain, the results are summed to demodulate the OFDM signal. Simulations and performance analysis show that an OFDM system using the proposed segment equalization can effectively reduce the ICI caused by the frequency offset and large Doppler frequencies in mobile radio channels.

To satisfy the request for high data rate and high frequency efficiency for new generation communication systems, an adaptive modulation method, subcarrier and power allocation is proposed for multicarrier DS/CDMA systems. With the downlink channel parameter acquired from the uplink channel feedback, an optimization algorithm is utilized to maximize frequency efficiency and minimize the required transmitting power for a given QoS and data throughput. Compared with non-adaptive OFDM system, the required transmitting power is greatly decreased and the convergence rate of this algorithm is very high which makes it very appropriate for engineering applications.

A novel trellis coded modulation scheme for a multicarrier DS-CDMA system is studied in this paper. Based on the concept of transmission diversity in the time-frequency domain, we propose a code design criterion that includes diversity gain and coding gain. In terms of the proposed criterion, we can search for codes that have larger coding gain while keeping the maximum diversity. Results show that the bit error rate performance of the system with the novel trellis coded modulation is much better than that of the traditional system while not occupying additional spectral bandwidth.

Considering a Multiple Input Multiple Output (MIMO) interference channel with K-user pairs, an iterative algorithm based on projection is proposed. In this algorithm, the objective function is the weighted sum of leakage of interference and desired signal out of their corresponding subspace. This algorithm can increase distance between interference subspace and desired signal subspace. Simulation results show that sum rate of the adjustable weight iteration algorithm is superior to other schemes.