Showing papers by "Devendra Jalihal published in 2012"

A rapidly deployable disaster communications system for developing countries

Abstract: We address the problem of designing a communication system for deploying under disaster situations where the pre-disaster communication infrastructure has been uprooted. The disaster communication system is required to aid in rescue effort by providing text, voice, and video communication links between the field worker and the operation center. It is also required to provide some communication services to the affected citizens so that the overwhelming demands made on the communication infrastructure during the times of disaster are mitigated to some extent. The other highlights of the design are its low-cost nature by exploiting the economies of scale and the fact that basic mobile phones with text-only features are widely available in developing countries.

Almost exact threshold calculations for covariance absolute value detection algorithm

Abstract: Design of robust test statistics which mitigate the channel and noise uncertainties are the essential requirement of detection applications. Covariance absolute value (CAV) detection is one of the non-parametric detection methods which claims robustness [1]. Achieving the theoretical probability of detection performance depends on the accuracy in calculating the thresholding parameter, which in turn depends on the distribution of the test statistic under the null hypothesis. Since the exact analysis of distribution is cumbersome, approximation techniques are used. We present approximation techniques which achieve performance very close to the one obtained from exact distribution of the test statistic (using Monte-Carlo simulation). Further, an equivalent test statistic compared to CAV is proposed which uses the Bartlett decomposition of the sample covariance matrix and its performance is compared with CAV. The robustness of the proposed test statistic is verified for the noise uncertainty model assumed [2].

WiMAX Mesh Based Back-Haul For Tactical Military And Disaster Area Networks

Abstract: Tactical Military and Disaster Area Communications require the establishment of on-the-fly wireless ad-hoc networks in diverse terrains with minimal set up time and reasonable Quality-of-Service (QoS) guarantees. In this paper, we study the architecture of a WiMAX mesh based back-haul network to replace the typical TDM based wire-line backhaul of a WiMAX Area Service Network (ASN). In particular, the paper presents the detailed design of a MAC layer frame structure based on Scalable OFDMA, the associated cluster-head election algorithm, and a distributed scheduling algorithm required for the back-haul mesh solution. The performance of the system has been studied using a custom-built discrete event simulator and performance results presented for varying traffic types including voice and video.

Joint precoding for two way AF MIMO relays in frequency selective OFDM channels

Abstract: This paper considers the joint design of source-relay precoders in OFDM systems where power constraint is specified for a contiguous block of subcarriers The design criteria considered are the popular Arithmetic sum of average Bit Error Rate(ABER) and Arithmetic sum of average Mean Square Error(AMSE) criteria The proposed algorithm optimizes the precoders for a block of subcarriers For the ABER criterion, it gives a performance improvement of about 3 dB at an ABER of 10−3 when compared to a system with equal power allocation on all subcarriers However, the same approach for the AMSE criterion does not give any significant improvement in performance This behavior is reasoned by plotting the performance surface of ABER and AMSE criteria