CDMA Cellular Systems Research Articles

INVESTIGATING THE PATH LOSS OF CELLULAR MOBILE NETWORK IN SUBURBAN AREAS OF BENIN METROPOLIS OF NIGERIA AT 910MHZ

This paper focuses on investigating path loss of mobile cellular network in suburban areas of Benin metropolis at a propagation frequency of 910MHz. The network Cell Info Lite application installed in GIONEE M5 CDMA was used to measure the received signal strength of the transmitted signal. The relative parameters were obtained from 100meters from the Glo base station from August, 2021 to October, 2021 within an average temperature of 270C. The results showed that Hata models are extensively used for the analysis of path loss evident in mobile cellular networks, GSM and CDMA system as depicted by the terrain of sub-urban areas of Benin City Metropolis. It was observed that the more the mobile stations move away from the base station, the higher the signal loss. This paper therefore guides cellular network service provider on accurate method of designing, deploying, and managing network to enhance good network coverage.

Proposed Model for Interference Estimation in Code Division Multiple Access

Cellular CDMA systems are usually affected by interference experienced by users in adjacent cells that decrease the Quality of Services in wireless communication network. Hence, interference is the limiting factor of capacity in CDMA cellular and it is one of the problems fighting against the high efficiency of any mobile network. In this paper, a mathematical model to estimate the average number of users contributing in inter-cell interference at the busy hours of CDMA network is proposed. As the power exponent value has significant affect on interferer signal attenuation and hence other-cells interference, measurements were carried through a drive test to determine the received power level at various distance from CDMA base stations at Baghdad. The results obtained show that the power exponent was 2.71. This value was applied in dual-slop path loss model to determine the expected interference factor, and the number of users that can be hold at each cell. Simulations showed that users at a boundary cell generate more interference than those close to the base station. Furthermore, it was denoted that greater number of users caused to increase the interference factor, and greater power exponent value result in interference factor reduction.

A Comparative study on Handoff Algorithms for GSM and CDMA Cellular Networks

The GSM, CDMA cellular systems are most trendy 2G and 3G digital cellular telecommunications systems, which is widely used throughout the world. These systems have many advantages such as high security, higher quality of call transmission over the long distances, low transmitted power, and enhanced capacity with more efficient utilization of the frequency spectrum. With these advantages these cellular systems have attracted more subscribers with more attention in the field of mobile communications. One of the most attractive features of cellular system is handoff which is a continuation of an active call when the mobile is moving from one cell to another without disconnecting the call. Usually, continuous service is achieved by efficiently designed handoff algorithms. So, efficient handoff algorithms are necessary for enhancing the capacity and QoS of cellular system. In this paper, the handoff analysis for GSM, CDMA cellular networks are done under various propagation models. Various handoff algorithms of GSM are described and also a novel received signal strength (R<sub>SS</sub>) based GSM handoff algorithm with adaptive hysteresis is analyzed. CDMA Soft handoff algorithm is analyzed and effective soft handoff parameters are estimated for better performance. The Comparison of handoff algorithms is studied based on results.

A Survey of Public Key Infrastructure-Based Security for Mobile Communication Systems

Mobile communication security techniques are employed to guard the communication between the network entities. Mobile communication cellular systems have become one of the most important communication systems in recent times and are used by millions of people around the world. Since the 1990s, considerable efforts have been taken to improve both the communication and security features of the mobile communications systems. However, these improvements divide the mobile communications field into different generations according to the communication and security techniques such as A3, A5 and A8 algorithms for 2G-GSM cellular system, 3G-authentication and key agreement (AKA), evolved packet system-authentication and key agreement (EPS-AKA), and long term evolution-authentication and key agreement (LTE-AKA) algorithms for 3rd generation partnership project (3GPP) systems. Furthermore, these generations have many vulnerabilities, and huge security work is involved to solve such problems. Some of them are in the field of the public key cryptography (PKC) which requires a high computational cost and more network flexibility to be achieved. As such, the public key infrastructure (PKI) is more compatible with the modern generations due to the superior communications features. This paper surveys the latest proposed works on the security of GSM, CDMA, and LTE cellular systems using PKI. Firstly, we present the security issues for each generation of mobile communication systems, then we study and analyze the latest proposed schemes and give some comparisons. Finally, we introduce some new directions for the future scope. This paper classifies the mobile communication security schemes according to the techniques used for each cellular system and covers some of the PKI-based security techniques such as authentication, key agreement, and privacy preserving.

Uplink Blocking Probabilities in Priority-Based Cellular CDMA Networks with Finite Source Population

Fast proliferation of mobile Internet and high-demand mobile applications necessitates the introduction of different priority classes in next-generation cellular networks. This is especially crucial for efficient use of radio resources in the heterogeneous and virtualized network environments. Despite the fact that many analytical tools have been proposed for capacity and radio resource modelling in cellular networks, only a few of them explicitly incorporate priorities among services. We propose a novel analytical model to analyse the performance of a priority-based cellular CDMA system with finite source population. When the cell load is above a certain level, low-priority calls may be blocked to preserve the quality of service of high-priority calls. The proposed model leads to an efficient closed-form solution that enables fast and very accurate calculation of resource occupancy of the CDMA system and call blocking probabilities, for different services and many priority classes. To achieve them, the system is modelled as a continuous-time Markov chain. We evaluate the accuracy of the proposed analytical model by means of computer simulations and find that the introduced approximation errors are negligible.

Game Theoretic Distributed Power Control Algorithms for Uplink Wireless Data in Flat Fading Channels

<p>In this paper we present a game-theoretic power control algorithms for wireless data in CDMA cellular systems under two realistic channels: (a1) Fast flat fading channel and (a2) Slow flat fading channel. The fading coefficients under both (a1) and (a2) are studied for three appropriate small scale channel models that are used in the CDMA cellular systems: Rayleigh channel, Rician channel and Nakagami channel. This work is inspired by the results presented by [1] under nonfading channels. In other words, we study the impact of the realistic channel models on the findings in [1] through the followings: we evaluate the average utility function, the average number of bits received correctly at the receiver per one Joule expended, for each channel model. Then, using the average utility function we study the existence, uniqueness of Nash equilibrium (NE) if it exists, and the social desirability of NE in the Pareto sense. Results show that in a non-cooperative game (NPG) the best policy for all users in the cell is to target a fixed signal-to-interference and noise ratio (SINR) similar to what was shown in [1] for non-fading channel. The difference however is that the target SINR in fading channels is much higher than that in a non-fading channel. Also, for spreading gain less than or equal to 100, both NPG and non-cooperative power control game with pricing (NPGP) perform poorly, where all the terminals except the nearest one were not able to attain their corresponding minimum SINR even if sending at the maximum powers in their strategy spaces.</p>

Performance Analysis of Channel-barrowing Hand-off Scheme in CDMA Cellular Systems

For cellular communication systems, mobility and limited radio coverage of a cell require calls to be handed over from one Base Station System (BSS) to another. Due to the limited band width available in various cells, there is a finite probability that an ongoing call, while being handed off, may get dropped. Minimizing the dropping of ongoing calls during hand off is an important design criterion. Some digital cellular systems, e.g., the Global System for Mobile Communications and the IS-136, use Mobile-Assisted Hand off (MAHO), in which a Mobile Terminal (MT) assists, it's BSS and a mobiles witching center in making hand off decisions. MAHO requires an MT to regularly report, back to its serving BSS, its current radio-link state (defined in terms of the Received Signal Strength Indicator (RSSI) and the Bit Error Rate (BER)) of transmissions received from neighboring BSSs. In the proposed technique, the MT reports back not only the RSSI and the BER but the number of free channels that are available for the hand off traffic as well. This will ensure that a handed-off call has acceptable signal quality as well as a free available channel. The performance of this hand off technique is analyzed using an analytical model whose solution gives the desired performance measures in terms of blocking and dropping probabilities.

Call Admission Control for Soft Handoff Coverage in CDMA Cellular System

In code division multiple access mobile cellular networks, the transmission quality can be improved by using the soft handoff techniques. The present investigation is concerned with the admission control policies by exploiting the soft handoff coverage area of the cellular radio network. We suggest finite Markov models for the admission control based on reserve channel and sub-rating policies. In reserve channel policy, a fixed number of channels are reserved exclusively to serve the handoff calls whereas according to sub-rating policy, the occupied channels can be split into two half rate channels to accommodate more handoff voice calls. It is also considered that the new call generation rate per unit area is uniformly distributed over the service area. Various performance indices are derived in terms of steady state probabilities. For some special situations, we validate and compare the models developed with previous existing models by setting the system descriptors. To examine the effect of various parameters on the performance measures, the sensitivity analysis is carried out by taking illustrations.

Performance Analysis of Handoff in CDMA Cellular System

Handoff mechanism is extremely important in cellular network because of the cellular architecture employed to maximize spectrum utilization. This unique feature has driven the rapid growth in the mobile network industry, changing it from a new technology into a massive industry within less than two decades. Handoff is the essential functionality for dealing with the mobility of the mobile users. This paper shows the soft handoff effects on the uplink direction of IS-95 CDMA networks is carried out, leading to optimize soft handoff for capacity under perfect power control approach. In practical systems, there is a nonzero handoff completion delay and soft handoff provides the required robustness to delays, although it comes at the expense of additional network resources. Thus, there is a tradeoff between the extent of soft handoff required and the handoff execution delay. This paper presents an analytical framework to study this tradeoff and also discuss simulation results simulated with the help of Matlab. For this, handoff dropping probability is minimized up to 0.1%.

A Soft Computing Based Adaptive Call Admission Control Scheme for Bi-Class Traffic in CDMA Cellular Network

Soft handoff in CDMA cellular system increases system capacity as compared to hard handoff as interference is reduced by transmitting signals as lower power level. A CDMA cellular system involving voice and data calls is considered in this paper. The model proposed in this paper is for data and voice services (Bi-class). It is based on reservation for handoff voice and data calls along with call queuing scheme for handoff data calls. Preemptive priority scheme is used for handoff voice calls over ongoing data calls. Upper channel limits are set for new voice as well as data calls to give priority to handoff calls. For better resource management and efficient call admission to originating and handoff calls, Neuro-fuzzy call admission controller is designed. This controller uses the adaptable feature of soft handoff threshold parameters to accommodate important voice and data calls. The proposed ASNFC controller is compared with the two variants of Bi-class CAC scheme. General Terms Call Admission Control, Soft Computing

Effects of Nakagami-Fading Parameters and Power Control Error on Performance of DS-CDMA Cellular Systems with Adaptive Beamforming

It is well known that power control error (PCE) is a critical issue in CDMA cellular systems. In this paper, the bit error rate (BER) of a direct sequence-code division multiple access (DS-CDMA) re...

A Comparative Analysis of Queuing and Fuzzy Logic based Admission Control Schemes in CDMA Cellular Network

In CDMA cellular system, the coverage area of the cell is greatly influenced by soft handoff process. The variation in soft handoff coverage area can be taken as the parameter influencing the performance parameters of the CDMA cellular system. This paper is concerned with a comparative analysis of two queuing based call admission control schemes with a fuzzy based CAC (call admission controller) model. The analytical models developed are based on channel reservation scheme for handoff calls. Finite queuing scheme for handoff call is used in first model whereas finite queuing for both handoff as well as new call is considered in the second model. The fuzzy call admission controller is implemented on Mamdani inference scheme taking relative mobility of user and number of reserved channels for handoff calls as input parameters. The output parameter is taken as handoff queue capacity. The fuzzy CAC searches for optimum handoff queue capacity to meet the QoS requirements.

On the optimum processing gain for a hybrid DS/FFH‐CDMA cellular system over Rayleigh fading channels

AbstractThe optimization between the processing gain and the theoretically achievable average channel capacity per user (in the Shannon sense) of a constant total system's allocated bandwidth hybrid direct sequence/fast frequency hopping code‐division multiple‐access (DS/FFH‐CDMA) cellular system, when operating in a Rayleigh fading environment, is presented. Then, the spectral efficiency, expressed in (bits/s/Hz), is estimated in terms of the achievable average channel capacity per user, during the operation over a broadcast cellular time‐varying link, and leads to a simple theoretical novel‐closed‐form expression for the optimal processing gain value based on the maximization of the achieved spectral efficiency. The final expression derived can be useful for the practical design of a DS/FFH‐CDMA cellular system and for an initial quantitative analysis since it relates to the optimal processing gain applied and all system's parameters. Finally, numerical results are presented to illustrate and prove the validity of the presented analysis. Copyright © 2011 John Wiley & Sons, Ltd.

Analysis of Interference in Air-to-Ground CDMA Cellular Systems Under Idealized Assumptions

In this paper, we study the air-to-ground cellular systems with no frequency reuse. We provide an analysis of the inter-cell interference under idealized assumptions: 3D hexagonal cell planning, a line of sight channel model with no shadowing and idealized antenna patterns. Based on this model, we derive approximate bounds for the inter to intra-cell interference ratio for the air-to-ground link. In addition, we provide upper bounds on the interference and the outage probability for the ground-to-air link. Simulation results are provided to validate the accuracy of the analytical results.

Combined fuzzy-based power control with window-based transmission rate management in multimedia CDMA cellular systems

Power control and transmission rate management play vital roles in multimedia CDMA cellular systems. To support multimedia services in CDMA cellular systems, different quality of service (QoS) requirements, such as minimum transmission rate or bit energy to interference spectral density ratio, should be set for different services. In this paper, we propose a novel scheme which combines fuzzy-based power control with window-based transmission rate management for use in multimedia CDMA cellular systems. We use window-based measurements to adjust transmission power by using fuzzy logic control (FLC) so that each service can maintain its signal-to-interference ratio ( SIR). Simulation results show that the new proposed method outperforms the original SPC (selective power control) and LRPC (Lagrangian relaxation technique and power control) methods in various measurements, such as outage probability, average transmission rate, probability of unsuccessful transmission, and probability of changes in transmission rates.

A novel subspace tracking algorithm and its application to blind multiuser detection in cellular CDMA systems

In this paper, we propose and develop a new algorithm for the principle subspace tracking by orthonormalizing the eigenvectors using an approximation of Gram-Schmidt procedure. We carry out a novel mathematical derivation to show that when this approximated version of Gram-Schmidt procedure is added to a modified form of projection approximation subspace tracking deflation (PASTd) algorithm, the eigenvectors can be orthonormalized within a linear computational complexity. While the PASTd algorithm tries to extracts orthonormalized eigenvectors, the new scheme orthonormalizes the eigenvectors after their extraction, yielding much more tacking efficiency. We apply the new tracking scheme for blind adaptive multiuser detection for non-stationary cellular CDMA environment and use extensive simulation results to demonstrate the performance improvement of the proposed scheme.

Adaptive channel reservation for call admission control to support prioritized soft handoff calls in a cellular CDMA system

This paper proposes a prioritized call admission control (CAC) model to support soft handoff calls with quality of service (QoS) assurances for both the uplink and downlink connections in a CDMA system. CAC is formulated as a combinatorial optimization problem in which the problem objective is to minimize the handoff forced termination rate. The model, which is based on the adaptive channel reservation (ACR) scheme for prioritized calls, adapts to changes in handoff traffic where the associated parameters (reserved channels, and new and handoff call arrival rates) can be varied. To solve the optimization model, iteration-based Lagrangean relaxation is applied by allocating a time budget. We express our achievements in terms of the problem formulation and performance improvement. Computational experiments demonstrate that the proposed ACR scheme outperforms other approaches when there are fewer rather than more channels, and it reduces the handoff call blocking rate more efficiently when the handoff traffic is heavily loaded. Moreover, the model can be adapted to any kind of reservation service.

Robust power control of CDMA cellular radio systems with time-varying delays

Power control is an important factor to increase communication link quality and system capacity in the direct-sequence code-division multiple access (DS-CDMA) cellular radio systems. The Smith prediction filter can achieve the unbiased asymptotic tracking about a desired target signal to interference noise ratio (SINR) under the fixed round-trip delay. However, it is sensitive to the variation of round-trip delay. In order to track the desired SINR with the time-varying round-trip delay, a multiple-mode Smith prediction filter, which combines the multiple Smith predictors with a likelihood function, is proposed for the power control of CDMA systems. The proposed scheme can compensate for the unknown time-varying round-trip delay. Simulation results show that the performance of the proposed multiple-mode power control method is robust to time-varying round-trip delay in the CDMA cellular radio systems.

Recursive analysis for soft handoff schemes in CDMA cellular systems

In this paper, we study the performance of the call admission control for a CDMA based cellular system. We describe the soft handoff procedure and the cellular geometry in CDMA system under certain assumptions and present analytical model for this scheme based on continuous time Markov chain. We obtain the close form solution for the performance indices, such as blocking probability and handoff dropping probability. In order to reduce the huge computational overhead of the original solution, we derive four methods to compute the performance metrics of interest, and provide extensive analysis on the computational complexity which indicates that the fourth method with two correlated recursions yields the lowest computational overhead.

An efficient receiver scheme for downlink ZP-CDMA

A signal transmitted through a wireless channel may be severely distorted by intersymbol interference (ISI) and multiple access interference (MAI). In this paper, we propose an efficient CDMA receiver based on frequency domain equalization (FDE) with a regularized zero forcing (RZF) equalizer and parallel interference cancellation with a unit clipper decision function (CPIC) to combat both the ISI and the MAI. We call this receiver the FDE-RZF-CPIC receiver. This receiver is suitable for downlink zero padding CDMA cellular systems. The effects of the decision function, the channel estimation, the number of cancelled users, and the user loading on the performance of the proposed receiver are discussed in the paper. The bit error rate (BER) of the data received by the proposed receiver is evaluated by computer simula- tions. The experimental results show that the proposed receiver provides a good performance, even with a large number of interfering users. At a BER of 10 −3 ,t he performance gain of the proposed receiver is about 2 dB over the RAKE receiver with a clipper decision function and PIC in the half-loaded case (eight users) and is much larger in the full-loaded case (16 users).