Performance analysis of channel-borrowing handoff scheme based on user mobility in CDMA cellular systems

Soft handoff is an essential component of code-division multiple-access (CDMA) digital mobile communication systems. While soft handoff has some advantages of system capacity and communication quality, it also has some disadvantages arising from the excessive use of channel resources. In this study, we propose a new control policy to alleviate effectively this excessive use of channel resources. For CDMA cellular mobile systems consisting of homogeneous cells, a variety of traffic parameters are estimated by the detailed traffic analysis, based on which a Markovian queueing model is developed to analyze the performance of the proposed call control policy. With a well-known performance objective, a mathematical problem of finding optimal call control parameters is proposed, along with its solution method.

Call admission control for reducing dropped calls in CDMA cellular systems

In this paper, the performance of a code-division multiple-access (CDMA) cellular system with various traffic types is examined. Traffic integration and resource management are two major issues in the design of the next generation of wireless networks with integrated services. To provide design guidelines for traffic integration, the impact of the line rate (actual transmission bit rate in the radio channel) selection on the system capacity is examined. Since in a CDMA system the signal from one specific user is spread over the entire available bandwidth, the actual bandwidth resource occupied by a user depends on the amount of the transmission power of the user. In this paper, we also address how to assign suitable power levels to the different traffic types. A method for optimizing the power assignment for multiple traffic types is developed.

In this paper the analysis a new base station receiver is proposed and analyzed for a code-division multiple-access (CDMA) cellular system. The proposed receiver can achieve remarkable diversity gain by increasing diversity order with reasonable cost and complexity. From the numerical results, it is confirmed that the proposed receiver structure can be a practical solution for enhancing reverse-link capacity and improving performance in CDMA cellular system operations. The result in the letter can find its applications to legacy IS-95/cdma 2000 1xbase stations with simple modifications.

Some operational advantages of AT&T's code-division multiple access (CDMA) cellular system are discussed from a service provider's perspective. Improvements in radio-frequency allocation and administrative simplifications are included, as well as inherent advantages of CDMA technology. Also discussed are advantages of CDMA technology in accommodating new subscriber services, such as data and facsimile, that are expected to drive the cellular market needs. Service providers will be able to take these factors into consideration in choosing between TDMA and CDMA when migrating from analog to digital services. >

It is shown that the capacities of both the reverse link and the forward link of a code division multiple access (CDMA) cellular system are increased significantly by using a steerable directional antenna on a mobile station. The additional cost for a directional antenna must be taken into consideration for implementation. It is shown that the interference from signals originating beyond the first two cell rings is not negligible for both the reverse link and the forward link. >

The demand for wireless communication has forced researchers to exploit digital technology to satisfy the increasing demand for service. This demand has led to severe capacity limitations in many areas and spread spectrum techniques are being considered as one means to support these services. Characteristics of spread spectrum Code Division Multiple Access (CDMA) make it ideal for application in cellular mobile radio network. In this paper the design methodology of a cellular CDMA system using non-coherent FH/FSK is presented. The CDMA capacity equation and the interference model for cellular environment are also presented. The FH-CDMA system is simulated and its performance is compared with the theoretical results.

This paper carries comprehensive comparison of Interleave Division Multiple Access (IDMA) and Code Division Multiple Access (CDMA) systems in terms of performance (BER) and behavior to different number of users. Performance analysis of two systems whose transmitter and receiver structures are almost same are studied under Additive White Gaussian Noise (AWGN) and performance differences are illustrated by simulation results. Although Multiple Access Interference (MAI) and Intersymbol Interference (ISI) can affect the performance of the CDMA system, simulation results illustrates that IDMA system model achieves this type of problem using their interleavers. Results also show that large number of users can easily be adapted by the IDMA scheme much easier than CDMA scheme.

When operated in the asynchronous mode, code-division multiple access (CDMA) allows the remote users to transmit at any arbitrary time instant, therefore simplifying the design of the remote terminals. The cost of this flexibility is paid by the tolerance of the interferences from other users in the same cell. A CDMA cellular system that utilizes the M-ary signaling technique to reduce the effects of the interferences is presented. The performance of this system is investigated in terms of the bit error rate achievable by the system. >

The 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 potential tool for delayless filtering of additive noise and smoothing of fast fading of the signal.

The capacity of CDMA (code-division multiple access) systems is limited by its other-user interference because all users in a cell share the same frequency band. To achieve maximum capacity, the 'near-far' problem needs to be dealt with. In practice, this is done through appropriate power control. Due to the interaction between the power control process, CDMA systems may become unstable if the desired SNR is not set appropriately. When CDMA systems are stable, the received power at the base station converges to the optimal power with a desired SNR (signal-to-noise ratio) setting. We analyze the associated power and the interference estimation in the discrete time domain and find the stability SNR upper bounds that can guarantee the system stability.

Code-division multiple access (CDMA) has been proven to be one of the promising mainstream multiaccessing techniques in future cellular mobile communication systems. A quality-based birth-and-death queueing model is developed for the purpose of evaluating the performance of a CDMA cellular that supports two-rate transmissions. Performance measures obtained include channel utilization and call blocking probability. Based on these results, three call admission schemes are compared.

A unique feature of code division multiple access (CDMA) systems is the use of soft handoff between cells. Soft handoff, in general, increases the system capacity because while the link between a mobile and one base station is poor, it might be better between the same mobile and some other base station. Hence, the user may transmit at a lower power in a soft handoff situation. Teletraffic analysis of soft handoff is complex because one cannot separate transmission issues from traffic issues. Many papers in the literature have independently analyzed the effect of soft capacity and soft handoff on network performance. Some papers have analyzed the effect of soft handoff on soft capacity but there has been no proper teletraffic analysis that includes both soft capacity and soft handoff. This paper proposes a traffic model for a DS-CDMA cellular network that includes both soft capacity and soft handoff. Network performance is then computed in terms of call blocking.

In code division multiple access (CDMA) cellular phone systems, such as those using the IS-95 standard, multiple users produce cochannel multiple access interference (MAI). In this paper adaptive time-domain interference mitigation techniques are developed and applied to the angle of arrival (AOA) estimation problem. This interference mitigation approach is motivated by a maximum likelihood formulation of multiuser space-time channel estimation. This approach is exercised using experimental data approximating that which might be experienced by an emergency response vehicle attempting to locate the source of an emergency 911 call using a vehicle-mounted antenna array. In this multiuser environment the users span a large range of received powers.

Improvement of the capacity of the CDMA (code division multiple access) system is a major objective. The capacity of the system is mainly limited by the signal to noise ratio, where the noise comes from the channel background and from MAI (multiple access interference). Usually, the way to improve the capacity is to decrease the MAI; this is why orthogonal codes are adopted by the IS-95 standard. One problem is that the number of orthogonal codes is constrained by the dimensionality of the signal space. So in IS-95, there are only 64 orthogonal codes available when the number chips for each sequence is 64. To solve this problem, a non-orthogonal code called WBE (Welch bound equality) sequences (Massey and Mittelholzer 1991) is used in this paper The criterion to construct the code is to minimize the MAI. Two methods are used to construct the WBE sequences: from a linear cyclic code or from a Hadamard matrix. In order to improve the performance of the WBE sequence set, an iteration receiver (Sari et al. 1999) is applied. The conclusion obtained is that when the number of users is slightly greater than the signal space dimensionality, after the first iteration, the performance is only marginally worse than the orthogonal CDMA system.