M. Ruiz-Garcia

Effects of multipath fading on BER statistics in cellular CDMA networks with fast power control

An analytical approach for the calculation of the bit error rate statistics in a cellular code-division multiple access system with imperfect fast power control is presented. Usually, imperfections in power control after despreading are modeled as a lognormal random variable. It has been shown that, in a fading channel, the standard deviation of this variable is a function of whether or not the mobile is communicating with the base station where the power is measured. We show that when this fact is not taken into account the results obtained are too optimistic.

Interference statistics of cellular DS/CDMA systems with base station diversity under multipath fading

A theoretical characterization of intracell and intercell interference statistics in cellular direct-sequence code-division multiple-access systems in a multipath environment is presented considering both fast and slow power control. Unlike many of the previous papers, mobiles are assumed to connect to a base station according to a minimum attenuation criterion, also known as base station diversity. Interference statistics are used to estimate system capacity and results have been validated by Monte Carlo simulations. Our results confirm that much greater capacity can be achieved when multipath fading is compensated by power control, while the relative benefits of perfect compensation of multipath fading decreases as the number of resolvable paths at the receiver increases.

Average block error probability of multicell CDMA packet networks with fast power control under multipath fading

We derive the average block error probability of multicell code-division multiple access (CDMA) packet networks with fast power control under multipath fading. Unlike many previous works, we consider that users are connected to a base station on a minimum attenuation basis. An analytical approach for the calculation of the intracell and intercell statistics is presented. By making use of these expressions, the mean block error probability is analyzed as a function of the number of resolvable paths and the number of base stations to which mobiles can connect.

Forward link capacity analysis of CDMA systems

We show the results of the evaluation of the downlink capacity of CDMA systems by using simulation. The proposed simulator analyses the system performance with time by measuring the power received by each mobile terminal from its own cell site and the total energy from all the cell site transmitters. Both measurements depend on path losses and on the traffic model. The introduction of the behavioural models of a wide range of services, which are expected to be supported by third generation (3G) wireless networks, is the most important benefit of the proposed simulation technique. A 3G system based on WCDMA, such as UMTS (Universal Mobile Telecommunication System) is evaluated considering voice traffic and a complex data traffic such as Web browsing.

Capacity analysis of UTRA/TDD systems

Next generation wireless communication systems has to be able to provide a variety of new services with different requirements of quality and different traffic conditions. These systems have their basis in the CDMA technique, therefore, their capacity is very limited by the interference level. For this reason the initial interference structure is crucial in the research of this capacity and has to be transferred to the characteristics of the traffic system. The goal of this paper is to estimate the capacity of UTRA/TDD systems. In this system, it is necessary to take into account that the capacity can be limited by the intercell interference level or by the number of available codes within a time slot. Thus, it is necessary to give shape to the intercell interference according to the parameters having to do with the traffic cell. The results we obtained allow us to make the dimensioning of an UTRA/TDD system according to the type of traffic that it has to bear.

Multiaccess strategies in an integrated UTRA system

This paper deals with the study of the uplink mechanisms of medium access within an UTRA system which offers the possibility of holding on to voice and data services. The voice service is beamed off through a dedicated channel whereas a common channel is used for a very widespread service nowadays like the Web traffic. The first investigations on homogeneous systems reveal that the access channel is longer occupied in the data system than in the voice system. The simulations related to the integrated voice and data system show that, in spite of the fact that the voice experiences a greater delay than in the homogeneous system, the QoS parameters for voice and data are guaranteed with no need to use all the available system resources. Following this, the integrated system allows for certain losses in the common RACH (random access channel).

Outage Probability of EGC Under Co-Channel Interferers with Arbitrary Powers in Rayleigh Fading

Two tight closed-form approximated expressions for the outage probability of equal-gain combining (EGC) are presented for the case of co-channel interferers with arbitrary powers in Rayleigh fading. A recent exact expression for the outage probability is extended to account for arbitrary power interferers for the sake of comparison. Comparisons between this new approach and the exact solution for EGC show excellent agreement. Contrary to most previous works in the subject, our analysis is suitable for performance evaluation of power controlled multi-cell networks, in which in-cell users are received with equal average powers and other cell-users are received with different average powers. In addition, we provide a comparison of outage probability for EGC, maximal ratio combining (MRC) and selection combining (SC) for arbitrary power interferers.

Cellular multicode CDMA capacity with SIR-based power control in a multipath fading environment

In this paper, the reverse link capacity is analysed for a multicode direct sequence-code division multiple access (multicode DS/CDMA) system with SIR-based power-control in a multiple-cell environment. Mean and variance statistics of total interference power are derived in order to investigate the effect of two important factors on capacity: (1) the required signal to interference ratio (SIR) and (2) the required number of codes, for each type of user. Unlike most previous works related to SIR-based power control, the effect of multipath fading is explicitly accounted for and mobiles are assumed to connect to the base station whose pilot signal is received with the highest power.