Time filter

Source Type

Mandal P.,Center for Development of Telematics
Journal of Network and Computer Applications | Year: 2017

In a network with long and random propagation delay, where sensor nodes communicate to a single receiver, there can be two variants of time division multiple access (TDMA), viz., receiver synchronized TDMA and transmitter synchronized TDMA. In receiver synchronized TDMA (RS-TDMA), the transmitter transmits according to the receiver's time slot and in transmitter synchronized TDMA (TS-TDMA), the transmitter transmits according to the transmitter's time slot.In this paper, we study RS-TDMA and TS-TDMA in the presence of distance dependent propagation delay deviation, which is one of the most important parameters for underwater wireless ad hoc networks. First we analyze RS-TDMA and TS-TDMA using discrete time Markov chain in the presence of distance dependent propagation delay deviation. Further we find the optimum parameters to get the maximum frame utilization and compare RS-TDMA and TS-TDMA with respect to arrival rate, transmission range, distance dependent propagation delay variability constant and slot size. In addition to the frame utilization we also parameterize the delay and blocking probability. Our numerical results are verified by discrete event based simulation results. © 2017 Elsevier Ltd.

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 | Year: 2010

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.

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

De S.,Indian Institute of Technology Delhi | Mandal P.,Center for Development of Telematics | Chakraborty S.S.,University of Ulster
Mathematical and Computer Modelling | Year: 2011

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.

Nitin Babu K.M.,Center for Development of Telematics | Vinaymurthi K.K.,Center for Development of Telematics
ICCSP 2011 - 2011 International Conference on Communications and Signal Processing | Year: 2011

This paper demonstrates an economical implementation of Gaussian Minimum shift keying (GMSK) modulator for Global System for Mobile communication (GSM) system using the basics of direct waveform synthesis. This method makes use of pre-calculated filter response of Gaussian filter for pulse shaping and Phase concatenation circuit for accumulation. Baseband in-phase and quadrature-phase component generation using quarter Sine or Cosine waveform LUT. (Further these signals are given for up-conversion.) Hardware realization is done using VHDL; circuits are synthesized. Prototyped our design in Altera Cyclone-3 FPGA (Field Programmable Gate Array), verified using R&S (Rhode and Schwarz) Vector signal analyzer. The design and hardware implementation of this modulator was done for indigenous GSM BTS (Base transceiver station) project. © 2011 IEEE.

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 | Year: 2013

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.

Mandal P.,Center for Development of Telematics | De S.,Indian Institute of Technology Delhi
IEEE Journal of Oceanic Engineering | Year: 2015

In a wireless network, where propagation delay is high and communications are sporadic, some kind of reservation protocol is generally used. Reservation access protocols were proposed earlier in earth stations-to-satellite communication with known propagation delay. However, optimality of the number of access slots with respect to the system performance parameters, such as system utilization, blocking probability, and delay, were not thoroughly studied. Besides, the effect of propagation delay uncertainty, which predominantly happens in underwater communications, are yet to be addressed. In this paper, we first analyze the system performance in many-to-one multiaccess data transfer scenario in underwater wireless ad hoc sensor networks with a fixed number of access slots and with the assumption of perfect propagation delay information. We propose two system state aware dynamic approaches to suitably adjust the number of access slots, and investigate the optimum slotting strategy to maximize the system utilization. Next, by accounting the propagation delay uncertainty, we relook into the optimality criteria on the number of access slots, where we apply a modified receiver-synchronized slotted Aloha principle to maximize the access performance. Via mathematical analysis, supported by discrete event simulations, we show that the system utilization and blocking probability performances with our proposed dynamic reservation protocols are consistently better compared to the competitive reservation protocols with fixed as well as variable access slots. Further, we conduct NS3 simulations to study the protocol performances under more realistic channel and traffic conditions, which also demonstrate that the proposed optimized dynamic slotting offers a much better system utilization performance compared to a similar underwater reservation multiaccess protocol. © 1976-2012 IEEE.

Mandal P.,Center for Development of Telematics | De S.,Indian Institute of Technology Delhi | Chakraborty S.S.,Technology and Education Consultant
Ad Hoc Networks | Year: 2013

In a wireless network, where propagation delay is high but known, slotted Aloha (S-Aloha) is synchronized with respect to the receiver's time slots. Since the transmitter knows the propagation delay to its receiver, after a frame is generated, the transmitter introduces a suitable delay before its transmission, such that the frame arrives exactly in a slot at the receiver. However, in an underwater wireless network, due to significantly less signal propagation speed, the channel dynamics has a significant effect on the time dispersion of propagation speed. Due to this uncertainty in propagation speed, even if the transmitter-receiver distance is exactly known, it is likely that a perfect synchronization at the receiver is not possible. In this paper, we first show that, even a little-less-than-perfect synchronization at the receiver reduces the throughput of receiver synchronized S-Aloha (RSS-Aloha) to that of pure Aloha. We modify the RSS-Aloha for underwater by accommodating the error in delay estimate while deciding the receiver-end slot size. Via probabilistic analysis, supported by simulations, we show that our proposed modified protocol offers a gradual increase in throughput as the propagation delay uncertainty decreases. We also show that the throughput of our proposed modified protocol is consistently higher compared to the transmitter synchronized S-Aloha when operating under the same propagation delay uncertainty. However, when the uncertainty is high, delay performance of the modified RSS-Aloha remains poorer than that of the transmitter synchronized S-Aloha in a system with smaller nodal communication range. © 2011 Elsevier B.V. All rights reserved.

Anand M.,Center for Development of Telematics | Kumar N.,Amrita University
IEEE Vehicular Technology Conference | Year: 2014

Dimming control function in light emitting diodes (LED) based visible light communication (VLC) is not only important but challenging too. Many interesting techniques are being investigated for different application scenarios. In this paper, an attempt is made to design a new and effective dimming control mechanism which is adaptive as per environmental condition to address successful data communication in case of infrastructure to vehicular (I2V) or vehicle to vehicle (V2V) or vehicle to infrastructure (V2I) mode of communication in intelligent transportation systems (ITS). We developed pulse dual slope amplitude modulation (PDSAM) to address both flickering and dimming in VLC system and combines the properties of slope and amplitude variation resulting in improved bit error rate (BER) performance. © 2014 IEEE.

Center For Development Of Telematics | Date: 2010-04-13

The concept of profiling the STB (01) through the Smart Cards (02) as per the service provider specific requirements makes towards interoperability. Smart cards (02) are embedded with greater operator specific intelligence. The scheme used in the present invention mainly focuses on downloading of profiling data from smart card (02) to the STB (01) and pushing CAS implementation fully from STB to Smart card (02).

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