Wireless Communication

K. M. Rajasekaran ¹, S. Tamilselvan ²

Affiliations
1 Department of ECE, Adhiyamaan College of Engineering, Hosur, IN
2 Department of ECE, Pondicherry Engineering College, Pondicherry, IN

Abstract

The emerging broadband wireless access technology based on IEEE 802.16 is one of the most promising solutions to provide ubiquitous wireless access to the broadband service at low cost and is being actively promoted by the Worldwide Interoperability for Microwave Access (WiMAX) Forum: an industry-led consortium. Based on the IEEE 802.16, WiMAX can support a very high capacity, wide area mobility, and multimedia services with different traffic characteristics and various quality-of-service (QoS) requirements. This paper proposes an efficient uplink bandwidth request allocation algorithm for real-time services in Mobile WiMAX networks based on IEEE 802.16e. In order to minimize bandwidth wastage without degrading quality of service, the algorithm introduces a notion of target delay and dual feedback approach. The proposed algorithm calculates the amount of bandwidth request such that the delay is regulated around the desired level to minimize delay violation and delay jitter for extended real-time services. Also, it can increase utilization of wireless channel by making use of dual feedback, where the bandwidth request is adjusted based on the information about the backlogged amount of traffic in the queue and the rate mismatch between packet arrival and service rates. Due to the target delay and dual feedback, the proposed scheme can control delay and allocate bandwidth efficiently while satisfying QoS requirement. The performance is evaluated in terms of queue regulation, rate adaptation, delay controllability, and robustness to traffic characteristics. Finally, the performance of optimal bandwidth allocation is compared for extended real-time services and real-time services in mobile WiMAX networks.

Keywords

Mobile WiMAX Networks, IEEE 802.16, Uplink Scheduling, Bandwidth Request, Quality of Service, Real-Time Service.

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S. Tamilselvan ¹, R. Madhivanan ², K. M. Rajasekaran ³

Affiliations
1 Department of ECE, Pondicherry Engineering College, Pondicherry, IN
2 Department of ECE, Christ College of Engineering and Technology, Pondicherry, IN
3 Department of ECE, Adhiyamaan College of Engineering, Hosur, IN

Abstract

Wireless network refers to any type of computer network that is wireless, and is commonly associated with a telecommunications network whose interconnections between nodes are implemented without the use of wires. To accommodate various features of wireless networks, the 2D uplink and downlink wireless CAC problems are decomposed into two independent 1D CAC. To formulate the 1D CAC optimizations, the demands of service providers and subscribers are jointly taken into consideration. To solve the optimization problem, a utility and fairness-constrained optimal revenue policy and corresponding approximation algorithm is developed. Optimal utility and optimal revenue were obtained by using fairness constrained greedy algorithm. The average revenue and the blocking probability were determined. In order to compare the performance of different traffic arrival rate the utility and fairness constrained optimal revenue algorithm has been implemented. Simulation results are presented to demonstrate the effectiveness of the proposed wireless approach.

Keywords

Call Admission Control (CAC), Optimization, Orthogonal Frequency-Division Multiple Access (OFDMA), Time-Division Duplex (TDD).

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S. Tamilselvan ¹, C. Tamizhselvan ²

Affiliations
1 Department of ECE, Pondicherry Engineering College, Pondicherry, IN
2 Electronics and Communication Engineering, Pondicherry Engineering College, IN

Abstract

Nowadays the demand for various multimedia services requiring high capacity increases, shortage of wireless resources becomes a serious problem in cellular networks. It is difficult to suddenly increase the capacity of current wireless communication networks because of high cost and complexity. In order to increase the capacity of wireless communication networkswith minor changes and low cost, internetworking is needed.

Keywords

Media Independent Handover (MIH), HNE, HTCE, Vertical Handover.

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S. Vasanthakumar ¹, S. Tamilselvan ², G. Annalakshmi ²

Affiliations
1 Department of Electronics and Communication Engineering, Pondicherry Engineering College Pondicherry University, Pondicherry-605014
2 Department of Electronics and Communication Engineering, Pondicherry University, Pondicherry, IN

Abstract

The main feature of the next-generation wireless systems will be the convergence of multi-media services such as speech, audio, video, image, and data. This implies that a future wireless terminal, by guaranteeing high speed data, will be able to connect to   different networks in order to support various services: switched traffic, IP data packets, and broadband streaming services such as video. Multicarrier code-division multiple-access (MC-CDMA) scheme is the promising candidate for future broadband wireless systems, as it provides higher flexibility, transmission rates and spectral efficiency. It combines an orthogonal frequency division multiplexing (OFDM) modulation with a code-division multiple-access (CDMA) scheme and hence exploits the advantages of   OFDM as well as CDMA.

A well-known, major drawback of conventional orthogonal frequency-division multiplexing (OFDM) transmission schemes is their strong envelope fluctuation and high peak-to-mean envelope power ratio (PMEPR), leading to power amplification difficulties. That is the OFDM signal which is the superposition of large number of modulated subcarriers, usually exhibits a high instantaneous peak value with respect to average value leading to envelope fluctuations. This is cited as a major drawback in OFDM scheme. This drawback is found in MC-CDMA too.  As MC-CDMA signals have high envelope fluctuations and a high peak-to-mean envelope power ratio (PMEPR), which leads to amplification difficulties.

In order to avoid the out-of-band  radiation levels which are inherent to nonlinear distortion, power amplifiers for OFDM transmission are required to have linear characteristics and/or a significant input back off  has to be adopted. Therefore, reduced power efficiency is the price to pay for a high bandwidth efficiency. A class of low-complexity signal-processing schemes for reduced PMEPR, spectrally efficient MC-CDMA transmission was proposed.

Keywords

Clipping, Envelope Fluctuations, PAPR, PMEPR.

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S. Tamilselvan ¹, K. Manivannan ¹

Affiliations
1 Pondicherry Engineering College, Pillaichavadyt, Pondicherry, IN

Abstract

Code Division Multiple Access (CDMA) cellular system that provides seamless connectivity is featured by soft handoff, which is accompanied by power control, selection diversity and rake receiver. In IS-95/CDMA-2000 based handoff schemes or systems some handoff calls unnecessarily occupy multiple channels with little contribution to the performance of handoffs. It is noted that new calls are blocked due to the channel resource shortage. In order to efficiently utilize the channel resource those extra channels occupied by handoff calls are grouped into a set called channel convertible set (CCS) by considering the relative mobility of the call. A new scheme called Channel-Conversion with Dynamic Guard channel reservation (CCDG) that reallocates those extra channels in the CCS to new handoff calls when there is no available channel in the system is proposed. According to the variation of the CCS the scheme dynamically adjusts the number of guard channels reserved exclusively for handoff, which still enhances the system performance. It is noted that the proposed scheme can significantly decrease both the number of dropped handoff calls and the number of blocked calls without degrading the quality of communication service.

Keywords

CDMA, Power Control, Handoff, Guard Channel.

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S. Tamilselvan ¹, S. Kalaiselvan ¹, K. Manivannan ¹

Affiliations
1 Pondicherry Engineering College, Pillaichavady, Pondicherry, IN

Abstract

The unbalanced traffic load in the cellular Code Division Multiple Access (CDMA) system occurs frequently, and it may lead to system performance deterioration. In this paper, new soft handover (SHO) algorithm with adaptive handover thresholds is proposed to resolve this problem. The basic objective of the adaptive algorithm is to modify the coverage among the serving cells based on the load distribution, and consequently attain the traffic load balancing in the service regions. According to the simulation results, the proposed algorithm can balance the traffic load and has better overall performance compared with the Universal Mobile Telecommunication System (UMTS) SHO algorithm with fixed handover thresholds. In particular, the new adaptive algorithm can be implemented in the UMTS system without any alteration.

Keywords

CDMA, UMTS, Soft Handoff, Load Distribution, Threshold, Coverage.

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