Time filter

Source Type

Acharya D.P.,National Institute of Technology Rourkela | Panda G.,National Institute of Technology Rourkela | Lakshmi Y.V.S.,Center for Development of Telematics
Digital Signal Processing: A Review Journal

Independent component analysis (ICA) technique separates mixed signals blindly without any information of the mixing system. Fast ICA is the most popular gradient based ICA algorithm. Bacterial foraging optimization based ICA (BFOICA) and constrained genetic algorithm based ICA (CGAICA) are two recently developed derivative free evolutionary computational ICA techniques. In BFOICA the foraging behavior of E. coli bacteria present in our intestine is mimicked for evaluation of independent components (IC) where as in CGAICA genetic algorithm is used for IC estimation in a constrained manner. The present work evaluates the error performance of fast ICA, BFOICA and CGAICA algorithms when they are implemented with finite length register. Simulation study is carried on both fixed and floating point ICA algorithms. It is observed that the word length greatly influences the separation performance. A comparison of fixed-point error performance of the three algorithms is also carried out in this work. © 2009 Elsevier Inc. All rights reserved. Source

Prasad M.V.S.N.,National Physical Laboratory India | Ratnamala K.,National Geophysical Research Institute | Dalela P.K.,Center for Development of Telematics | Misra C.S.,AIRCOM International Pvt Ltd.
International Journal of Wireless and Mobile Computing

The present study reports the field strength measurements of some GSM transmitters in the 900 MHz band located in the urban and suburban regions of Delhi in India. The measured signal levels converted into path loss values have been compared with the losses predicted from models such as Hata, Lee and COST 231 Walfisch and Ikegami. The prediction errors and standard deviations of the prediction errors have been deduced. Based on these results, Lee prediction method has been tuned and new model parameters have been derived. The model comparison is done in terms of statistical parameters such as root mean square error, coefficient of determination and average hit rate error. © 2011 Inderscience Enterprises Ltd. Source

Mandal P.,Center for Development of Telematics
2014 IEEE International Conference on Advanced Networks and Telecommunication Systems, ANTS 2014

In this paper, I study the receiver synchronized time division multiple access (TDMA) in the presence of propagation delay deviation, which is one of the major parameter to consider for underwater wireless sensor networks. First I describe how the receiver synchronized TDMA protocol can be used in a network without propagation delay deviation. Then I modify the receiver synchronized TDMA to get higher utilization in the presence of propagation delay deviation. I analyse this modified TDMA protocol using discrete time markov chain. Further I find the optimum parameters to get the maximum frame utilization. All analytical results are verified by simulation based results. © 2014 IEEE. Source

De S.,Indian Institute of Technology Delhi | Mandal P.,Center for Development of Telematics | Chakraborty S.S.,University of Ulster
Mathematical and Computer Modelling

Standard analyses of wireless random access protocols that are available in the literature assume negligible propagation delay between any two nodes. This assumption holds good in reasonably short-range terrestrial RF (radio frequency) wireless networks. On the contrary, in wireless communications involving acoustic wave propagation, as in underwater wireless networks, even short distance propagation has appreciably large propagation delay. This observation has led to several recent simulation and experimental studies on underwater Aloha and slotted-Aloha (S-Aloha) protocols and also a few new proposals on random access protocols for underwater wireless ad hoc networks (UWN). To study the efficiency of more advanced multiaccess communication protocols for UWN, it is important to benchmark their performances with respect to the two basic random access protocols, Aloha and S-Aloha. This paper provides an analytic framework to capture the performance of Aloha and S-Aloha protocols in an underwater environment with high and random internodal signal propagation delay. The performance of underwater Aloha and S-Aloha are contrasted with those in short-range terrestrial RF wireless networks. The analysis shows that random internodal propagation delay has no effect on the underwater Aloha performance. It also sheds light on the throughput degradation of underwater S-Aloha with a slotting concept that achieves RF S-Aloha equivalent one-slot vulnerability. Additionally, a modified slotting concept is introduced where the slot size is judiciously reduced such that even by allowing some collisions the overall system throughput can be increased. Our calculations show that, with the modified slotting approach up to 17% throughput performance gain can be achieved over the naive (RF S-Aloha equivalent) slotting approach in UWN. Our analytic results are supported by discrete event simulations. © 2010 Elsevier Ltd. Source

Stephen R.G.,Center for Development of Telematics | Stephen R.G.,Indian Institute of Science | Murthy C.R.,Indian Institute of Science | Coupechoux M.,Indian Institute of Science | Coupechoux M.,Telecom ParisTech
IEEE Transactions on Wireless Communications

This paper considers antenna selection (AS) at a receiver equipped with multiple antenna elements but only a single radio frequency chain for packet reception. As information about the channel state is acquired using training symbols (pilots), the receiver makes its AS decisions based on noisy channel estimates. Additional information that can be exploited for AS includes the time-correlation of the wireless channel and the results of the link-layer error checks upon receiving the data packets. In this scenario, the task of the receiver is to sequentially select (a) the pilot symbol allocation, i.e., how to distribute the available pilot symbols among the antenna elements, for channel estimation on each of the receive antennas; and (b) the antenna to be used for data packet reception. The goal is to maximize the expected throughput, based on the past history of allocation and selection decisions, and the corresponding noisy channel estimates and error check results. Since the channel state is only partially observed through the noisy pilots and the error checks, the joint problem of pilot allocation and AS is modeled as a partially observed Markov decision process (POMDP). The solution to the POMDP yields the policy that maximizes the long-term expected throughput. Using the Finite State Markov Chain (FSMC) model for the wireless channel, the performance of the POMDP solution is compared with that of other existing schemes, and it is illustrated through numerical evaluation that the POMDP solution significantly outperforms them. © 2013 IEEE. Source

Discover hidden collaborations