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This paper presents and evaluates artificial neural network (ANN) models used for macrocell path-loss prediction. Measurement data obtained by utilizing the IS-95 pilot signal from a commercial code-division multiple-access (CDMA) mobile network in rural Australia are used to train and evaluate the models. A simple neuron model and feed-forward networks with different numbers of hidden layers and neurons are evaluated regarding their training time, prediction accuracy, and generalization properties. Furthermore, different backpropagation training algorithms, such as gradient descent and Levenberg--Marquardt, are evaluated. The artificial neural network inputs are chosen to be distance to base station, parameters easily obtained from terrain path profiles, land usage, and vegetation type and density near the receiving antenna. The path-loss prediction results obtained by using the ANN models are evaluated against different versions of the semi-terrain based propagation model Recommendation ITU-R P.1546 and the Okumura--Hata model. The statistical analysis shows that a non-complex ANN model performs very well compared with traditional propagation models with regard to prediction accuracy, complexity, and prediction time. The average ANN prediction results were 1) maximum error: 22 dB; 2) mean error: 0 dB; and 3) standard deviation: 7 dB. A multilayered feedforward network trained using the standard backpropagation algorithm was compared with a neuron model trained using the Levenberg--Marquardt algorithm. It was found that the training time decreases from 150 000 to 10 iterations, while the prediction accuracy is maintained. [ABSTRACT FROM AUTHOR]

This paper investigates the features of a cellular geometry in code-division multiple-access (CDMA) systems with soft handoff and distinguishes controlling area of a cell from coverage area of a cell. Some important characteristics of the cellular configuration in soft handoff systems are used to propose a new design of efficient call admission control (CAC) in CDMA systems. Then, the paper constructs a continuous-time Markov chain (CTMC) model for CAC in CDMA with a soft handoff queue, obtains closed-form solutions, and thus develops loss formulas as performance indices such as the new blocking probability and the handoff dropping probability. In order to determine handoff traffic arrival rate, a fixed-point strategy is developed. Algorithms are also provided to stably compute loss probabilities and to determine the optimal number of guard channels. A new soft handoff scheme—eliminating pseudo handoff calls (EPHC)—is proposed to improve channel utilization efficiency based on mobility information. As an application of the loss formulas, the proposed modeling techniques are used to evaluate and compare the performance of conventional and proposed EPHC soft handoff schemes. Numerical results show the effectiveness of the proposed Markov chain models and the benefits of the new soft handoff scheme. [ABSTRACT FROM AUTHOR]

This paper considers the optimal distributed assignment of rates to elastic users in a broadband multicell code-division multiple-access (CDMA) network with variable rate assignments, which is connected to a traditional wired Internet Protocol (IP) network. We show that by using an optimization framework, it is possible to construct a distributed rate assignment algorithm similar to current congestion control protocols that addresses both media access control and transport layer issues (i.e., addresses both interference and congestion control). Practical implementation of this algorithm, as well as its impact on convergence and performance, is also addressed. [ABSTRACT FROM AUTHOR]

Power control has been widely studied and shown to be crucial for the capacity and performance of direct-sequence code-division multiple-access (DS-CDMA) systems. Practical implementations typically employ fast closed-loop power control, where transmitters adjust their transmit powers according to commands received in a feedback channel. The loop delay resulting from the measurements, processing, and transmission of the power control commands can result in oscillations of the transmission powers and lead to degradation in the system performance. In this paper we present new adaptive closed-loop power control algorithms that are able to alleviate the effect of the loop delay. The algorithms are based on self-tuning controllers designed for a log-linear model of the power control process. We carried out computational experiments on a DS-CDMA network using the distributed constrained power control (DCPC) as a reference algorithm. Practical versions of the algorithms are also provided and they were compared with the fixedstep power control (FSPC) algorithm employed in the IS-95 and WCDMA systems. The numerical results indicate that our algorithms can significantly improve the radio network capacity without any increase in power control signaling. [ABSTRACT FROM AUTHOR]

Call admission control (CAC) strongly influences the performance of 3G/4G spread spectrum systems because it determines the number of active users that are admitted to the network, i.e., influences spectral efficiency. A novel air interface CAC algorithm is introduced in this paper. It optimizes the utilization of radio resources and provides real-time adaptation to the radio channel with generalized multiplicative fading. Users are handled as memory-less traffic sources. The suggested CAC method was evaluated for lognormal fading and ON/OFF traffic. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach for designing a call-admission control (CAC) algorithm for code-division multiple-access CDMA) networks with arbitrary call-arrival rates. The. design of the CAC algorithm uses global information; it incorporates e call-arrival rates and the user mobilities across the network and guarantees the users' quality of service (QoS) as well as prespecific blocking probabilities. On the other hand, its implementation in each cell uses local information; it only requires the number f calls currently active in that cell. We present several cases for a nontrivial network topology where our CAC algorithm guarantees QoS and blocking probabilities while achieving significantly higher throughput than that achieved by traditional techniques. We so calculate the network capacity, i.e., the maximum throughput f r the entire network, for prespecified blocking probabilities and QoS requirements. [ABSTRACT FROM AUTHOR]

Positioning algorithms in cellular networks has become increasingly important as a means of supporting emerging services that require a sufficiently precise estimation of the position of the mobile terminal (MT) associated with a given base station (BS). Currently, even the most sophisticated positioning algorithms require at least three BSs to achieve satisfactory precision. This paper presents a novel algorithm that makes use of a single-BS antenna array to locate MTs in cellular networks. A triangulation technique is utilized and supported by some minimal information about the environment in the BS neighborhood. This algorithm is shown to perform well when operating in a microcellular environment with perfect channel-parameter estimation. The effect of finite resolution of the input parameters is also investigated. The performance is analyzed for a universal mobile telecommunications system microcellular scenario through a three-dimensional deterministic channel model. Finally, the performance of the proposed positioning technique is compared to the well-known location method based on the time-of-arrival measurements at three different BSs. [ABSTRACT FROM AUTHOR]