CDMA Wireless Networks Research Articles

Performance analysis toward 880 m/4.255 Gbps underwater optical wireless communication CDMA network based on hybrid M-ary differential pulse position modulation and double length modified prime code

Performance analysis toward 880 m/4.255 Gbps underwater optical wireless communication CDMA network based on hybrid M-ary differential pulse position modulation and double length modified prime code

Increasing the Channel Capacity of a Wireless CDMA Network Using Radio Resource Allocation Scheme

Increasing the Channel Capacity of a Wireless CDMA Network Using Radio Resource Allocation Scheme

Top Down Code Search to Locate An Optimum Code and Reduction in Code Blocking for CDMA Networks

In this paper, a top down code search scheme is proposed that identify an optimum OVSF code for assignment at the base station of CDMA wireless networks. An optimum vacant code is the one whose usage produces least code blocking compared to other eligible codes. This scheme provides least code blocking compared to existing schemes without reassignments. In addition, the codes searched during locating the optimum code are significantly less than other existing schemes. The call establishment delay which is a significant factor for real time applications is directly proportional to the number of searches and should be low. The design is explained for single code, and extended to multi code assignment to improve code blocking. The multi code assignment is done using four ways. The first and second multi code schemes uses minimum and maximum rakes for a fixed rate system. The third scheme called scattered multi code scheme divide the incoming call into rate fractions equal to number of rakes available in the system, and each rate fraction is handled in a similar way in which the new call is handled in single code scheme. The rate fractions may be scattered or grouped in the code tree. The fourth multi code scheme, namely grouped multi code scheme allocates codes to all the fractions as close as possible. This maximizes future higher rate vacant codes availability by leaving a complete sub tree vacant when call using multi code ends.

Implementation of Vehicle Control System Based on IPV6-CAN Gateway

Vehicle will be connected to the Internet as both for ubiquitous remote controlling and as a means to meet Intelligent Transportation Systems (ITS) needs. At first, a gateway system between Controller Area Network (CAN) and IPV6 is required to connect vehicles to the Internet. Then this paper achieves the access of vehicle information and the control of vehicle using the CDMA wireless network based on the gateway. Finally, according to the result of the test, we have verified the correction and effectiveness of the control system.

QoS-aware game-theoretic rate & power control for CDMA wireless communication networks

This paper shows how to tailor a game-theoretic approach to the issue of distributed resource allocation in a CDMA multiple-access wireless network with different quality of service constraints. According to the nature of the terminals (either fixed/vehicular or mobile/battery-powered, in one respect, and either primary or secondary in another), each user pursues a different goal in the network. Game theory is used as an expedient tool to ensure optimum coexistence of users with highly conflicting interests. In the proposed game, after an initial centralized stage of admission control, each user is allowed to jointly set its transmit power and data rate according to a utility-maximizing criterion, where the utility is defined as the ratio of the throughput to the transmit power. The noncooperative Nash solution of the game is investigated and closed-form expressions for this equilibrium are derived and compared with numerical results for a decentralized resource control algorithm.

Analysis of Interference and Chanel Capacity in a CDMA Wireless Network Using Dynamic Channel Assignment (DCA) Strategy

Analysis of Interference and Chanel Capacity in a CDMA Wireless Network Using Dynamic Channel Assignment (DCA) Strategy

A Game-Theoretic Perspective on Code Synchronization for CDMA Wireless Systems

This paper introduces a game-theoretic formulation for the problem of resource allocation in an infrastructure CDMA wireless communication network, focusing on the issue of initial code synchronization. To capture the tradeoff between obtaining good synchronization performance and saving as much energy as possible, we propose a noncooperative game in which each transmitter-receiver pair seeks to maximize the ratio of the probability of code alignment detection to the transmitted energy per acquisition, under a constraint on the maximum probability of spurious code locks - this is achieved by properly setting the receiver threshold and the transmit power. Our framework also considers the coexistence between different types of synchronizers and different QoS requirements. The generalized Nash solution of the game is investigated and closed-form expressions are derived and compared with simulation results for an iterative decentralized algorithm.

EVALUATION OF SPECTRAL EFFICIENCY, SYSTEM CAPACITY AND INTERFERENCE EFFECTS ON CDMA COMMUNICATION SYSTEM

Wireless communication technology have been developed based on exploring new mobile communications frequency bands, reasonable use of frequency resources and minimization, portability and multifunction’s of mobile stations. The technology of wireless communications with duplex transmission is one of the fastest expanding in the world today. A very effective solution in achieving network performance in terms of system capacity and spectral efficiency with respect to the CDMA wireless network is presented in this paper. The effect of how interference grows as the number of users increases is analyzed. Equally, this paper presents the major problems in CDMA as the multiple access interference which arises due to the deviation of the spreading codes from orthogonality.

Distributed Uplink Power Control in Multiservice Wireless Networks via a Game Theoretic Approach with Convex Pricing

In this paper, the problem of efficient distributed power control via convex pricing of users' transmission power in the uplink of CDMA wireless networks supporting multiple services is addressed. Each user is associated with a nested utility function, which appropriately represents his degree of satisfaction in relation to the expected trade-off between his QoS-aware actual uplink throughput performance and the corresponding power consumption. Initially, a Multiservice Uplink Power Control game (MSUPC) is formulated, where each user aims selfishly at maximizing his utility-based performance under the imposed physical limitations and its unique Nash equilibrium point is determined. Then the inefficiency of MSUPC game's Nash equilibrium is proven and a usage-based convex pricing policy of the transmission power is introduced, which offers a more effective approach compared to the linear pricing schemes that have been adopted in the literature. Consequently, a Multiservice Uplink Power Control game with Convex Pricing (MSUPC-CP) is formulated and its unique Pareto optimal Nash equilibrium is determined. A distributed iterative algorithm for computing MSUPC-CP game's equilibrium is proposed, while the overall approach's efficiency is illustrated via modeling and simulation.

Performance Improvement in OVSF Based CDMA Networks Using Flexible Assignment of Data Calls

Orthogonal variable spreading factor (OVSF) codes are used to support multimedia calls in CDMA wireless networks. The inefficient use of OVSF code tree reduces the system throughput. The paper discusses a novel code assignment design to provide flexibility of rate variation in data calls maximizing channel utilization. The ongoing call uses different codes at different times depending on the code tree status and instantaneous traffic load. For low traffic loads, the high rate codes can be utilized. For medium to high instantaneous load conditions, the vacant codes with capacity less than the call rate can be utilized. For same call reassignments are done to assign different codes at different times. The utilization of the code tree can reach close to 100%. Simulation results are given to verify the superiority of the proposed design.

On the performance modeling of outage probability in CDMA wireless networks

Outage probability is a key performance measure for real time traffic in wireless networks and is often considered as more critical than drop call probability. In this paper, we study the outage probability in a wireless mobile environment, where the interferers are distributed on the ground. Taking into consideration the background noise and the cell radius, we formulate an outage probability model coupled with observed data from Airtel Nigeria formally Zain Communications Limited, a Telecommunication company operating in Nigeria and simulate the system’s performance using the Java programming language. We also present a geographical information system (GIS) solution showing the distribution of signal outages at various base stations in Akwa Ibom State (East region) of Nigeria for observed and simulated data. A performance evaluation of these data reveals that our model could greatly improve the system’s performance. The results obtained allow us to study the stability of the network and evaluate the network in a more efficient and accurate manner.

Performance modeling of QoS in a multicode multicarrier CDMA wireless network with fading

AbstractFor emerging wireless mesh networks, multicode multicarrier CDMA(MC‐CDMA) based technology is one of the most viable candidates. We perform stochastic modelling of the queues at the mobile station for uplink communication with multicode multicarrier CDMA system with two types of traffic, namely real‐time and non‐real‐time. Each traffic is assigned its own codes. However, the non‐real‐time traffic is allowed to use codes assigned to real‐time traffic, when real‐time traffic is not using its codes. Based on the probability of bit error for a multicode MC‐CDMA system, we first compute the probability of packet error. The packet in error will be inserted into the queue until it successfully gets through to the receiver. The packet arrival process at the input queue is modelled as Markov modulated Poisson processes (MMPP). The QoS performance in terms of packet loss for real‐time traffic and the occupancy distribution for non‐real‐time traffic is evaluated using matrix geometric techniques. We present numerical results for low and high load of real‐time traffic with varying loads of non‐real‐time traffic. We observe the binomial tweaking feature of occupancy distribution at higher loads due to batch departures. Copyright © 2009 John Wiley & Sons, Ltd.

A Game-Theoretic Approach to Energy-Efficient Power Control and Receiver Design in Cognitive CDMA Wireless Networks

The uplink of a multiuser cognitive radio network, wherein secondary users communicating with a secondary access point coexist with primary users communicating with a primary access point, is considered in this paper. Primary and secondary users' signals coexist in the same frequency band, and the transmit powers of the secondary users are constrained so that the interference from the whole secondary network to each primary user does not exceed a prescribed threshold. Given this constraint, a noncooperative power control game for maximum energy efficiency with a fairness constraint on the maximum received powers for the secondary users has been considered. The considered game is shown to admit a unique Nash equilibrium, also in the case in which energy efficiency is maximized with respect to both transmit power and choice of the linear uplink receiver. Based on large system analysis, a one-shot procedure for computing the users' transmit powers at the Nash equilibrium with no need for iteration among users is also derived. Numerical simulations confirm the theoretical results on the existence and uniqueness of the Nash equilibrium, confirm the effectiveness of the results obtained through the large system analysis, and show that secondary users have a beneficial impact on the whole network throughput, at the price of a moderate degradation in the performance of the primary users.

A Dynamic Utility Adaptation Framework for Efficient Multimedia Service Support in CDMA Wireless Networks

In this paper the problem of channel-aware opportunistic resource allocation for the downlink in CDMA wireless networks supporting simultaneously real-time multimedia and non-real-time data services is addressed. In order to treat different types of services with diverse QoS prerequisites through common optimization formulation a utility-based power and rate allocation framework is adopted. Emphasis is placed on real-time services' strict short-term QoS prerequisites, the fulfillment of which requires a significantly different treatment than the use of static utility functions, traditionally used to address long-term QoS or fairness prerequisites of delay-tolerant data services. To that end, we introduce a novel framework that enables the dynamic adaptation of real-time multimedia users' utilities as the system evolves, with respect to the corresponding short-term throughput service performance variations. The corresponding non-convex network utility maximization (NUM) problem is then formulated and solved, to obtain optimal power and rate allocation. Via simulation and analysis it is demonstrated that significant performance improvements are achieved in terms of real-time user's short-term throughput requirement satisfaction, without any considerable loss in total system throughput. Finally, essential tradeoffs between fulfilling real-time services' short-term QoS prerequisites and maximizing system performance, under an opportunistic scheduling wireless environment, are revealed and quantified.

Nonconvex Optimization for Power Control in Wireless CDMA Networks

In this paper, we propose an efficient power control algorithm for the downlink wireless CDMA systems. The goal of our paper is to achieve the optimum and fair resource utilization by maximizing a weighted sum utility with the power constraint. In fact, the objective function in the power optimization problem is always nonconcave, which makes the problem difficult to solve. We make progress in solving this type of optimization problem using PSO (particle swarm optimization). PSO is a new evolution algorithm based on the movement and intelligence of swarms looking for the most fertile feeding location, which can solve discontinuous, nonconvex and nonlinear problems efficiently. It's proved that the proposed algorithm converges to the global optimal solutions in this paper. Numerical examples show that our algorithm can guarantee the fast convergence and fairness within a few iterations. It also demonstrates that our algorithm can efficiently solve the nonconvex optimization problems when we study the different utility functions in more realistic settings.

Uplink Power Control in QoS-aware Multi-Service CDMA Wireless Networks

In this paper the problem of QoS-driven power control in the uplink of CDMA wireless networks supporting multiple services is considered. Due to the need for supporting simultaneously various services with diverse QoS requirements, each user is associated with a nested utility function which appropriately represents his degree of satisfaction in relation to the expected tradeoff between his QoS-aware actual uplink throughput performance and the corresponding power consumption. Based on this framework, the problem is formulated as a non-convex noncooperative Multi-Service Uplink Power Control (MSUPC) game where users aim selfishly at maximizing their utilitybased performance under the imposed physical limitations. We first prove the existence and uniqueness of a Nash equilibrium point of the MSUPC game, and then a decentralized iterative algorithm to obtain MSUPC game’s equilibrium point is introduced. Finally, through modeling and simulation, the operation and features of the proposed framework and the decentralized MSUPC algorithm are evaluated with respect to the fulfillment of assorted services’ QoS requirements, while numerical results and relevant discussions that demonstrate the tradeoffs among users’ channel conditions, corresponding power consumption and utility-based performance are presented.

Power and rate control with outage constraints in CDMA wireless networks

A radio power control strategy to achieve maximum throughput for the up-link of CDMA wireless systems with variable spreading factor is investigated. The system model includes slow and fast fading, rake receiver, and multi-access interference caused by users with heterogeneous data sources. The quality of the communication is expressed in terms of outage probability, while the throughput is defined as the sum of the users' transmit rates. The outage probability is accounted for by resorting to a lognormal approximation. A mixed integer-real optimization problem P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> , where the objective function is the throughput under outage probability constraints, is investigated. Problem P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> is solved in two steps: firstly, we propose a modified problem P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> to provide feasible solutions, and then the optimal solution is obtained with an efficient branch-and-bound search. Numerical results are presented and discussed to assess the validity of our approach.

Vertical handoff algorithm in heterogeneous networks for reducing interference

A vertical handoff decision algorithm in heterogeneous networks composed of CDMA Cell Networks (CN) and Wireless Local Area Network (WLAN) is proposed to minimize the total interference in CDMA. The scope of WLAN is determined by minimizing interference and each communicating node shall handoff to WLAN as soon as it enters the scope. We first propose a model for heterogeneous networks, and based on it we obtain the close-form expression of interference. In order to minimize interference, we use simulation annealing method to get the WLAN radius, which is called basic algorithm. In order to reduce the interference further, we improve the basic and get the enhanced algorithm. Through numerical computing, we analyze the interference in condition of different call arrive rates, and results show that the enhanced can reduce interference more greatly than the basic.

Game theoretic distributed uplink power control for CDMA networks with real-time services

In this paper, the issue of efficient power allocation in the uplink of CDMA wireless networks supporting real-time services with various QoS constraints, is addressed. Within the proposed framework, utility functions are adopted to reflect a user’s degree of satisfaction with respect to its actual throughput requirements satisfaction and respective power consumption. The corresponding problem is formulated as a non-cooperative game where users aim selfishly at maximizing their utility-based performance under the imposed limitations. The existence and uniqueness of a Nash equilibrium point of the proposed Uplink Power Control (UPC) game is proven, at which all users have attained a targeted SINR threshold value or transmit with their maximum power, leading essentially to an SINR-balanced system. Moreover, a distributed iterative algorithm for reaching UPC game’s equilibrium is provided. The properties of equilibrium in a pure optimization theoretical framework are studied, and the tradeoffs between users’ overall throughput performance and real-time services’ QoS requirements satisfaction, in channel aware resource allocation processes, are revealed and quantified. Through modeling and simulation the efficacy of the introduced framework and proposed UPC algorithm are demonstrated and evaluated.

Utility Based Short-term Throughput Driven Scheduling Approach for Efficient Resource Allocation in CDMA Wireless Networks

In this paper, we address the problem of efficient recourse allocation in CDMA wireless networks supporting multimedia services with various and often diverse QoS prerequisites, placing special emphasis on real-time services' essential requirements satisfaction. We first provide an analytical framework for studying real-time users' short-term delay and throughput properties under fundamental opportunistic scheduling policies. The corresponding results demonstrate that probabilistic delay constraints are insufficient indicators of real-time services' QoS prerequisites, while probabilistic short-term throughput requirements are more appropriate in asserting their performance expectations. Based on these observations and results, we propose and develop a scheduling policy for efficiently supporting heterogeneous services that include delay-tolerant non-real-time and delay-sensitive real-time services, over a wireless CDMA system under a common utility based framework. A user's utility characterizes his degree of satisfaction for the received service as well as QoS expectations fulfillment, in a normalized way. Aiming at the maximization of users' utilities, both non-real-time services' long-term and real-time services' short-term throughput QoS requirements are met, under the proposed opportunistic scheduler. Finally, via modeling and simulation it is demonstrated that significant performance improvements concerning both types of services' QoS requirements satisfaction are achieved through the proposed scheduling approach.