A simple idealized linear (and planar) uplink, cellular, multiple-access communication model, where only adjacent cell interference is present and all signals may experience fading is considered. Shannon theoretic arguments are invoked to gain insight into the implications on performance of the main system parameters and multiple-access techniques. The model treated in Part I [1] is extended here to account for cell-site receivers that may process also the received signal at an adjacent cell site, compromising thus between the advantage of incorporating additional information from other cell sites on one hand and the associated excess processing complexity on the other. Various settings which include fading, time-division multiple access (TDMA), wideband (WB), and (optimized) fractional inter-cell time sharing (ICTS) protocols are investigated and compared. In this case and for the WB approach and a large number of users per cell it is found, surprisingly, that fading may enhance performance in terms of Shannon theoretic achievable rates. The linear model is extended to account for general linear and planar configurations. The effect of a random number of users per cell is investigated and it is demonstrated that randomization is beneficial. Certain aspects of diversity as well as some features of TDMA and orthogonal code-division multiple access (CDMA) techniques in the presence of fading are studied in an isolated cell scenario.

The effect of using randomly selected sequence multisets for the uplink of a synchronous code-division multiple-access channel is considered. A tight lower bound on the expected value of the sum capacity over the ensemble of randomly selected sequence multisets is given. For large systems, the sum rate penalty for using randomly selected multisets is shown to be at most 1 nat and to vanish as the number of users becomes large, compared to the sequence length.

We consider the effect of using randomly selected sequence multisets for the uplink of a code-division multiple-access channel. In particular, we calculate a tight lower bound on the expected value of the sum capacity, over the ensemble of randomly selected sequence multisets. We show that for large systems, the sum rate penalty for using randomly selected multisets is at most 1 nat, and vanishes, as the number of users becomes large, compared to the sequence length. Keywords -- Code-Division Multiple-Access channels, sum capacity, random sequences, multiaccess I. Introduction The study of code-division multiple-access (CDMA) systems with error control coding has been limited to a few publications e.g. [1, 2, 3, 4]. In general the approach has been to use a multiuser device to supply metrics to soft input single user Viterbi decoders. Optimal coded CDMA systems require in addition to the design of good spreading sequences, joint encoding /decoding strategies. The selection of optima...

this document: Lars Rasmussen, John Asenstorfer, Michael Miller, Christian Schlegel, Phil Whiting and Steven Pietrobon. Finally, I thank Robyn for her support and understanding through the last three years. Chapter 1 Introduction Imagine a situation, in which at a lively party, you wish to carry on a conversation with some friends. Each friend has something interesting to say to you, but all insist on speaking simultaneously. You may try to listen to just one person, and ignore all others, but you find this difficult, due to the overwhelming amount of noise made by the other speakers. In addition, they have to shout over the loud music and other conversations in the background. Obviously, unless you impose some sort of structure on the conversation, for example, allow only one person to speak at a time, confusion will prevail, and you will understand no-one. You wish to gather as much information as possible from each of your friends. What should you do? It is an analogous situation that confronts the designer of many types of communications networks, in which many transmitters desire simultaneous communication with a common receiver. This scenario, known as a multiple access channel, can be found in cellular mobile networks, and in satellite communications systems. We shall be particularly interested in mobile communications networks. Figure 1.1 shows a simplified schematic representation of the uplink (mobile (M) -- base (B) channel) of one cell in a mobile network. Demand for mobile and personal communication services is increasing rapidly, whereas the available frequency spectrum is a precious, finite resource. In order to support increasing numbers of users, and increasing data rates, more efficient use must be 1. Introduction M