Resource allocation in wireless ad hoc networks is usually modelled in a non-cooperative game theoretic framework with the objective of maximising individual utility. However, the selfishness of autonomous users under such framework may lead to throughput unfairness which only benefits certain users. To alleviate this unfairness problem, the authors propose a payment-based power control scheme using game theory where each user announces a set of price coefficients that reflects different compensations paid by other users for the interference they produce. Users who generate higher interference are required to pay more by transmitting at a lower power to give other users a fairer chance of sharing the throughput. Without any incentive to play fairly, users could misbehave by broadcasting high price coefficients to force other users to transmit at a lower power. The authors treat this problem casting it into a price game which resembles a Prisoner's Dilemma game. Users who play this game iteratively will behave cooperatively and broadcast the price coefficients truthfully. Together with analytical proof, the proposed approach is shown to converge to Nash equilibrium where at this point it is able to provide a fairer throughput share among users at the expense of a slight loss in total throughput.

In wireless ad hoc networks, co-channel interference can be suppressed effectively through proper integration of channel assignment (CA) and power control (PC) techniques. Unlike centralised cellular networks where CA and PC can be coordinated by base stations, the integration of CA and PC into infrastructureless wireless ad hoc networks where no global information is available is more technically challenging. The authors model the CA and PC problems as a non-cooperative game, in which all wireless users jointly pick an optimal channel and power level to minimise a joint cost function. To prove the existence and uniqueness of Nash equilibrium (NE) in the proposed non-cooperative CA and PC game (NCPG), the authors break the NCPG into a CA subgame and a PC subgame. It is shown that if NE exists in these two subgames, the existence of NE in the NCPG is ensured. Nonetheless, due to unpredictable network topology and diverse system conditions in wireless ad hoc networks, the NCPG may encounter the ‘ping-pong’ effect that renders NE unattainable. By incorporating a call-dropping strategy and no-internal-regret learning into the NCPG, an iterative and distributed algorithm that ensures convergence to NE is proposed. It is shown through simulation results that the proposed approach leads to convergence and results in significant improvements in power preservation and system capacity as compared with the popular distributed dynamic CA technique incorporated with PC.

Precise measurement and modelling of the Direction of Arrival (DoA) and Direction of Departure (DoD) in the Multiple-Input Multiple-Output (MIMO) channel based on their correlation properties and joint distributions have not been investigated properly. Our main contribution in this paper is two fold. Firstly, based on a modified Gumbel's bivariate exponential approach, we propose a generic indoor MIMO channel modelling framework particularly for the double-directional 'general trend'' that has been observed in these dual-spatial domains. Secondly, we propose a transformation technique to generate the pair wise DoA and DoD components incorporating the correlation properties of the variates around the full azimuth range. Results show that the newly proposed modelling approaches provide a good match to the real data, offering an alternative hassle-free method to generate realistic directional-based stochastic MIMO channel responses in different indoor environments.

The increasing demand for wireless network services have resulted a plethora of studies on the efficient management of radio resources to improve network capacity. As radio spectrum is a scarce resource, sharing of radio frequency has to be considered among wireless network nodes and by doing so introduces interference among users, which in turn limit the network capacity. Our study addresses the problem of dynamically assigning channels in ad-hoc wireless networks via power control in order to satisfy their minimum QoS requirements. The objective then is to maximize the number of co-channel links subject to some stability conditions. In order to assign the optimal number of co-channel nodes that can co-exist over a wide range of operating SINR values, we propose two novel ways to find the optimal combination of co-channel links so that a feasible power vector can be found within its power limits.

In wireless communication systems, a call admission control mechanism is usually deployed to determine whether a new communication node can be admitted into the network system. In wireless systems that implement power control, the maximum achievable signal-to-interference plus noise ratio (SINR) for a new node depends on the link gains amongst all the co-channel interfering nodes involved and the white noise strength. Thus, one of the challenges in call admission control (CAC) in a wireless system with power control is the estimation of maximum achievable SINR when information about global link gains is not available. In this paper, by ignoring the white noise factor we present a predictor for the maximum achievable signal-to-interference ratio (SIR) of a new node trying to get admission into a wireless system. Using the SIR predictor we then calculate an optimal active link protection margin, which together with the SINR or SIR threshold would constitute an enhanced threshold value for the new node to attain. By doing so current active links would be protected from performance degradation should the maximum achievable SIR value common to all the nodes be lower than the SIR threshold. For each nodal topology ranging from low density to high density values, the accuracy of the predictor is evaluated by means of simulation in terms of mean error and root mean square error.

Precise modelling of the direction of arrival (DoA) and direction of departure (DoD) of multipath components (MFCs) in a multiple-input multiple-output (MIMO) channel based on correlation properties and joint distributions have not been investigated properly. This paper examines the correlation between DoAs and DoDs, and presents a modelling approach particularly for the "general trend" of these dual-spatial domains, based on statistical results obtained from several indoor MIMO measurement campaigns. We show that the Laplacian distribution provides better fits for the directional parameters than the normal and Von Mises distributions. The "general trend" of DoA/DoD joint distribution and power density are modelled using a modified Gumbel's bivariate exponential approach. Results show that the proposed bivariate distribution provides a good match to the real data, and offers an alternative approach to generate realistic directional-based stochastic MIMO channel responses in different environments

This paper proposes several linear estimators for the long code CDMA problem. These proposed receivers will be compliant with the specifications issued by the 3rd Generation Partnership Project (3GPP). Using channel estimates derived from a simple cross-correlation scheme on the known pilot bits, various linear estimators are developed. Simulations are carried out over a fast-fading mobile channel model, and results are conclusive to indicate that the linear minimum mean-square error (LMMSE) estimator is the best overall linear estimator in terms of the bit-error rate (BER) performance.

The statistics of received signal power at the receiver in a cellular direct-sequence code-division multiple-access (DS-CDMA) system with flat Rayleigh fading and fast closed-loop power control mechanism are studied. A simple model for the fast closed-loop power control mechanism is proposed to ease the analysis. The probability density function (pdf) of the received signal power is derived by taking into consideration the updating frequency of power control mechanism, maximum allowable transmitted power, and Doppler frequency of the fading channel. The pdf derived can be used to study the performance of a reverse-link DS-CDMA system with noncoherent M-ary orthogonal modulation. The result shows that when optimum maximum allowable transmitted power is used, system capacity can be substantially increased for typical normalized Doppler frequency in cellular communication.

A performance analysis of an RF transceiver for UTRA/FDD WCDMA user equipment through simulation is presented. The main building blocks of this transceiver are power amplifier (PA), low noise amplifier (LNA), automatic gain control amplifiers (AGCs), mixers, modulator, demodulator, frequency synthesizers (oscillators and phase lock loop) and variable gain power amplifier driver. All these components are commercially available. Critical RF characteristics of the transceiver, such as adjacent channel leakage power ratio (ACLR), maximum output power, noise figure (NF), gain, 3/sup rd/ order input intercept point (IIP3) and selectivity, were analysed based on commercial standard dual conversion transmitter and heterodyne receiver architectures. Results obtained from this simulation could be used as a design methodology for future RF transceiver implementation.

Transmitter power control is an effective scheme to improve the performance of cellular DS/CDMA systems. In the reverse link, time-multiplexed pilot symbols are used to assist the estimation of received signal power in order to improve the performance of power control. In this paper, two different approaches for received power estimation in power controlled CDMA systems are proposed and compared in terms of bit error rate (BER) by means of analytical and simulation studies. The first power estimator uses a simple sample average and the second power estimator uses a minimum mean square error (MMSE) filter approach. The MMSE approach requires knowledge of the Doppler spread and the signal-to-interference ratio (SIR). Comparison of the performance of the two power estimators is done with respect to deviations in the SIR and Doppler spread as used for the design of the MMSE filter, from their nominal values. Analysis results show that when the MMSE filter approach is used, BER can be further improved as compared to the simple sample average power estimator.