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Orthogonal frequency division multiplexing (OFDM) is one of the promising techniques in the next generation high-speed data rate wireless networks for its ability to combat the intersymbol interference(ISI), and fair scheduling algorithms are used to utilize the independence of the fading statistics of different user to improve the spectral efficiency. In this paper, we try to analysed the performance of fair scheduling algorithms in the OFDM systems and choose the appropriate subband size to tradeoff between the throughput and the channel feedback. We show that asymptotic scheduling gain of fair scheduling algorithms in the OFDM system increases as the number of user increases and decreases with the average received SNR. We also present the distribution of the averaged received signal-to-noise-ratio (SNR) in a subband, give a formula to evaluate the scheduling gain approximately, and point out that the maximal eigenvalue is a good indicator to choose the appropriate subband size. It is shown that the appropriate subband number is 16 for channel A or 32 for channel B.

An optimum combining algorithm applied in space diversity diffuse channel is presented. Theoretically, this algorithm gives the space diversity channel's performance threshold and achieves the best performance compared to others, such as the equal weight combining algorithm and the selectable combining algorithm. Since the channel bandwidth in a general diffuse channel is relatively narrow, we can only consider the relationship between flat fading and the bit error rate, ignoring the influence of frequency selection fading.

Each wireless technology now used is optimized just for some particular applications and environments. However, the next generation wireless networks coexisting with fiber-optic based broadband communication networks will be required to operate over a wide range of cell size (from picocell to massive satellite cell) and offer multimedia services where each service may have a unique rate. A new architecture of wireless network, wireless ATM, is proposed in this paper, which consolidates various radio environments and applications under a single protocol. The wireless ATM architecture embedded into B-ISDN protocol stack can adapt a wide range of physical channels. In the last section, flow control, the key technique of multiplex and multiple access in wireless ATM, is described.

This paper presents a performance analysis of WCDMA synchronization channel (SCH) and gives the optimal transfer power allocation scheme of SCH and common pilot channel (CPICH) to achieve best cell search performance. The AWGN channel, noncoherent detection and multi-slot, multi-frame accumulation are employed in performance simulation. One considerable scheme is P/sub SSCH/:P/sub PSCH/=0.25:0.75 and P/sub CPICH/:P/sub SCH/=0.35:0.65, under which the UE can finish cell search in 160 ms with satisfactory performance.

In this text, we consider the problem of fair scheduling in the downlink of orthogonal frequency division (OFDM) systems. Based on the proportional fair scheduling algorithm proposed in the CDMA/HDR, we present three schemes to manage the parallel subscribers in the OFDM system to utilize the time selectivity and frequency selectivity. Subcarriers in a slot are divided into several nonoverlapped subbands, which are the scheduling objects. The first scheme is that every subband is placed with a scheduler and the average rates are updated independently; the second scheme transfers the two-dimensional channel resource into one-dimension equivalent channel, and then schedule the resource like in HDR systems; for the third scheme, the users contend every subband in a same slot using one scheduler without updating the average rates, after finishing the slot, the average rates are updated together. Compared to the first scheme, the third one has the least complexity and its performance degrades a bit. It is shown that system throughput is improved by 40%/spl sim/100%, the appropriate number of subbands is 16/spl sim/32 and scheme 3 is an appropriate choice for practice systems.