We obtain the Shannon capacity of a fading channel with channel side information at the transmitter and receiver, and at the receiver alone. The optimal power adaptation in the former case is "water-pouring" in time, analogous to water-pouring in frequency for time-invariant frequency-selective fading channels. Inverting the channel results in a large capacity penalty in severe fading.

Addressed are the uplink access control problems for cellular CDMA systems that service heterogeneous traffic with various types of Quality-of-Service (QoS) and use Multi-Code CDMA to support variable bit rates. Considering its distinct QoS requirements, class-I real-time traffic (e.g., voice and video) is differentiated from class-II nonreal -time traffic (e.g., data). Connection-oriented transmission is achieved by assigning mobile-oriented code channels for class-I traffic where each corresponding mobile needs to pass an admission test. Class-II traffic is transmitted in a best-effort manner through a transmission-rate request access scheme which utilizes the bandwidth left unused by class-I traffic: whenever a mobile has class-II messages to transmit, the mobile requests code channels via a base station (BS)-oriented transmission-request code channel, then, according to the base station scheduling, the transmission is scheduled and permitted. Addressed are the admission test for cl...

 In this paper, prediction of signal power in Code Division Multiple Access (CDMA) systems in urban radio channels is investigated. We focus on the processing of the measured input signal for power control purposes in a mobile station receiver. Predictive filtering based on a polynomial signal model is proposed, and a class of FIR-type polynomial filters is investigated with simulations. Two alternative schemes are examined; direct prediction of the squared power signal, and prediction of the in-phase and quadrature signal components separately. The simulations show that FIR polynomial predictors can provide smoothed signal power samples with the signal-to-noise ratio (SNR) improved by ca. 5 dB, without any delaying of the signal. The results show that polynomial prediction is a highly potential tool for delayless filtering of additive noise and smoothing of fast fading of the signal. I. INTRODUCTION As the CDMA systems are inherently interference limited, it is of paramount impo...

. The paper presents a new cellular architecture for radio access, CDPA, that can be applied to present and future cellular systems, independently of the cell size. It poses as an appealing alternative to systems based on classical bandwidthsubdivision methods, namely TDMA, FDMA or CDMA. In these systems, parallelism of communications is achieved by subdividing the bandwidth "a priori" among cells. In CDPA no bandwidth subdivision is operated. All cells and terminals use a single frequency channel and transmit packets on a slotted channel. Parallel transmission in different cells is achieved through the "capture" capability. A dynamic polling mechanism, C-PRMA, managed by the base station, guarantees almost immediate retransmission of packets that are not captured, thus assuring that packets are eventually correctly received . Analytical evaluations show that CDPA has the potential to provide larger capacity than the other cited systems in the case of continuous traffic sources. Furthe...

Recently, a new method for achieving spectrum reuse in cellular systems, called Capture-Division Packetized Access (CDPA), has been introduced. The method is based on packet switching and uses a single frequency in all cells, allowing each transmitter to access the full bandwidth. Practically, the CDPA's way of operation can be seen as an S-ALOHA scheme among different cells in which the Mobile Stations belonging to the same cell transmit using a collision-free mechanism, which is easily obtained due to the very short intra-cell propagation delay. Parallel transmission in different cells is achieved through the "capture" capability. Packets that are not captured are almost immediately retransmitted, thus assuring that packets are eventually correctly received. In this paper we analyze the capacity of the system in which two frequencies are used for the communications to and from the base stations. Analytical evaluations show that, although uplink and downlink channels behave differentl...

The paper discusses the features and compares the performance of two packet oriented channel-access schemes that appear particularly suitable for the PCN cellular environment. These schemes exploit the packet capture and can deal with inter-cell interference without any a priori bandwidth-consuming techniques such as those used in FDMA and CDMA. The first scheme is the well knownS-ALOHA, whereas the secondone is the Capture Division Packetized Access, recently proposed. The analytical model accounts for several features of real-world systems, e.g., the exact traffic pattern that must be offered in order to achievethroughput fairness, the exact interference caused by the traffic in the same cell and in other cells, the fading, the slow shadowing attenuation and some means to counteract it, such as best base station selection and power control. We also discuss the effects of outage, i.e., a mechanism which prevents a user from attempting more than a predetermined number of transmissions ...

Addressed is the uplink access control problems for cellular CDMA systems that service heterogeneous traffic with various types of quality-of-service (QoS) and use Multi-Code CDMA (MC-CDMA) to support variable bit rates. Considering its distinct QoS requirements, class-I real-time traffic (e.g., voice and video) is differentiated from class-II nonreal -time traffic (e.g., data). Connection-oriented transmission is achieved by assigning transmitter-oriented code channels for class-I traffic where each corresponding mobile client needs to pass an admission test. Class-II traffic is transmitted in a best-effort manner using the bandwidth left unused by class-I traffic and a transmission-rate request access scheme: whenever a mobile has class-II messages to transmit, the mobile requests code channels via a receiveroriented transmission-request code channel, then, according to the base station scheduling, the transmission is scheduled and permitted. Addressed are the admission test for clas...

In this paper we study the system capacity of cellular systems with time-division multiple access and slow time-frequency hopping (F-TDMA). System capacity is defined as the number of users/cell\Theta bit/s/Hz, for a given maximum outage probability. Outage is defined as the event that the mutual information of the interference channel falls below the actual code rate. We develop a general framework and a numerical example based on a typical urban mobile environment. Keywords --- Cellular system capacity, block-fading channels, outage probability. I. Introduction Cellular systems may be viewed as multiterminal communication networks where a number of transmitters and receivers communicate by sharing a common radio channel. A key concept in cellular system is channel reuse. Many users can share the same time-frequency interval (channel) provided that they are sufficiently separated in space and/or that their messages can be separated in the signal space by some coordinate decoding al...

A limiting factor for the performance of the conventional CDMA receiver is the near-far effect. Practical CDMA systems use power control to overcome this problem, which requires additional circuitry at the mobile. On the other hand, optimal and suboptimal multiuser detectors have been proposed which are shown to be near-far resistant, and thus increase the capacity of the system significantly. The major drawback of these detectors is their computational complexity which makes them less attractive for implementation. This paper describes a simple detector which is a spatio-temporal interference canceller. The receiver employs an array of M antennas, which allows it to discriminate between the users based on their spatial diversity. The received signal goes through a bank of K beamformers, each matched to one user, followed by a bank of matched filters. The K outputs are compared to rank the users in the order of their strength. Multiple access interference from each user is cancelled su...

Successive interference cancellation, in conjunction with very low rate convolutional codes, has been shown to approach the Shannon capacity of a Gaussian channel [1]. This approach to CDMA is very well suited to asynchronous (uplink) wireless channels. However, accurate phase and amplitude estimation is required for effective operation. In this paper, we develop a power control algorithm specifically designed to relax the requirements on estimation accuracy. Using this power control algorithm in conjunction with superorthogonal codes and successive interference cancellation, it is shown that even with average estimation error up to 30%, the capacity over an IS-95 CDMA system can be increased by an order of magnitude. I.