We propose an efficient uplink media access control (MAC) protocol for a variable spreading gain interference-limited wideband CDMA system. It can, with high spectral efficiency, support both real-time traffic like speech and video and also nonreal-time data traffic based on packet transmission. The schemes for power allocation, joint scheduling, and transmission rate adaptation for nonreal time data traffic are designed as integrated parts of the MAC, working together to improve the system performance in terms of capacity and delay. With these associated resource management mechanisms, the performances of the MAC protocol with two different channel-allocation methods for real-time traffic are numerically compared. One is demanding channel allocation, and the other is reserve channel allocation, in which a certain bandwidth is reserved for concurrent real-time traffic.

An analytical model is developed to investigate integrated packet-switching/circuit-switching service CDMA cellular systems. Due to the defer-first-transmission mode, link-level congestion control is essential for packet-data transmission. With congestion control, the intra-cell and inter-cell interference interact each other. To reflect this interaction closely, a recursive model is used to derive the inter-cell interference in this paper. With this model, the performances of a CDMA system are numerically evaluated in terms of voice capacity, data delay, and data blocking probability.

Fitzpatrick's algorithm for solving the classical Reed-Solomon key equation is shown to be related to an algorithm for solving the Welch-Berlekamp key equation. It can be made more efficient when decoding binary BCH codes. Its efficiency is about the same as for the Berlekamp-Massey algorithm.

The paper describes analysis carried on frequency-selective channels to establish and quantify the performance improvements offered by broadband channels. The work focuses on the two types of diversity, frequency and path, which are offered only by wideband communications systems. For this reason a geometric propagation channel model is developed enabling the performance study of frequency-selective channels to be carried out at their operating frequencies; i.e. at bandpass. The channel model provides the transfer function and parameters such as coherence bandwidth and multipath spread of broadband channels. Based on these transfer functions the time responses of communication channels, separated by one or more signalling bandwidths, are compared and statistically quantified. The results indicate that, depending on the channel bandwidth, there is considerable correlation between broadband communications which are centred at different carrier frequencies. The high correlation between the different broadband channels can be used for propagation path-loss estimation for transmission power control applications in DS and hybrid CDMA systems.

Key-stream generators are discussed in which shift registers are clocked in a quasi-random manner under the control of other shift registers. They are a promising practical alternative to those using nonlinear combining functions on the outputs from regularly stepped shift registers and are now almost as well understood. Some World War II ciphers using stuttered rotors are briefly described as natural predecessors, including one cryptanalyzed on the Colossus machines. The algebraic theory is discussed, from which it is shown how large periods and linear equivalences can readily be obtained. The work of a number of authors on cascades is reviewed; these are linear hierarchies in which each register except the first is clock controlled by its predecessor. Other schemes are considered. Results on statistical properties and autocorrelation functions are quoted.>