V. Nithya

Finite-state Markov channel modelling under jointly varying amplitude and phase in time-varying flat fading channels

In this study, the authors investigate the first-order finite-state Markov chain modelling of time-varying flat fading channels. The scope of this work is to consider the joint effects of unknown channel phase and amplitude on the received signal. Performance measures such as level crossing rate, steady-state probability, state transition probability and state time duration of the fading models are derived, plotted and analysed. Comparison of the performance measures are made for Rician, Lognormal and Weibull fading distributions.

Curbing of TCP Incast in data center networks

Data centre networks widely uses TCP for communication between the servers as it provides reliability and congestion control. However, TCP does not work well for certain type of communication patterns. One such a pattern is barrier synchronized many to one communication. During this type of data transmissions, multiple servers simultaneously transmits data to a single client and also the client cannot issues its next request until it receives all the data from current transmission. This will leads to severe throughput collapse in the networks which is called as TCP Incast. The major causes of TCP Incast are the basic TCP which is used as a transport protocol and the congestion that happens at switch. In this paper, we use TCP Lite as transport protocol instead of basic TCP and also an active queue management scheme called Random early detection Input/Output with Coupled average queue (RIO-C) is incorporated to the incast scenario. This controls the congestion that occurs due to barrier synchronized transmission. The performance analysis of RIO-C mechanism is done on the basis of metrics such as bytes received, throughput, packet loss and number of retransmissions.

Physical scenario perusal of eta-mu fading channels

In this paper, we present a physical scenario analysis for two formats of eta-mu fading distribution i.e. Format 1 and Format 2, respectively. Generally the performance of wireless communication system depends on the characteristics of the fading channel. Hence it is necessary to study the behaviour of the fading phenomena. The small - scale variation of the faded signal is better represented by eta-mu fading distribution under Non-Line-Of-Sight (NLOS) conditions. The physical scenario analysis is carried out by plotting the Probability Density Function (PDF) and Cumulative Distribution Function (CDF) for two formats of eta-mu fading distribution with various eta and mu values. The results indicate that the Format 1 prevails in suburban and rural areas whereas Format 2 prevails in urban areas.

Performance analysis of TCP incast with TCP Lite and Abstract TCP

Data center networks widely uses TCP for communication between the servers as it provides reliability and congestion control. However, TCP does not work well for certain type of communication patterns. One such a pattern is barrier synchronized many to one communication. During this type of data transmissions, multiple servers simultaneously transmits data to a single client and also the client cannot issues its next request until it receives all the data from current transmission. This will leads to severe throughput collapse in the networks which is called as TCP Incast. There are numerous other variants of TCP which will provides better congestion avoidance than TCP In this paper, we analyze the performance of TCP Incast using QualNet simulator with different TCP variants namely TCP Lite and Abstract TCP The performance analysis is based on the metrics such as bytes received, throughput, packet loss and number of retransmission.

Analysis of BER and energy efficiency of raptor codes under BEC for wireless sensor network

This paper has explored the energy efficiency of Raptor codes; a first known class of fountain codes in an energy constrained network. Transmission power is adjusted dynamically to overcome unreliability over lossy links in wireless sensor network. One of the most felicitous key for this reliability issue is using Forward Error Correction (FEC) codes. This paper investigates the energy bagged by one such FEC code called Raptor codes in the Binary Erasure Channel (BEC) scenario. The performance analysis of Raptor codes in terms of energy by varying its precoder is carried out. The network parameters such as Bit Error Rate (BER), Throughput and Energy Spent per Bit are considered for the study. The simulation results show that Raptor code with BCH code as a precoder improves the network lifetime over Raptor code alongside LDPC (Low Density Parity Check) code as a precoder by 88.24%.

Energy Conservation in IEEE 802. 15. 4 Compliant Wireless Sensor Network using LT codes

In this paper, we investigate the energy efficiency of a IEEE 802. 15. 4 based RF transceiver using Direct Sequence Spread SpectrumOffset Quadrature Phase Shift Keying (DSSSOQPSK) modulation under 2.4 GHz frequency band in a WSN. Multi path propagation in a wireless environment affects the reliability of the network and therefore the sensor nodes wastes the battery power to ensure successful delivery of data by adopting Automatic Repeat reQuest (ARQ) schemes. Error control coding is one of the most suitable solutions to this reliability issue. In this paper, the use of one such Forward Error Correction (FEC) codes such as Luby Transform (LT) codes to reduce energy expenditure by the network nodes is analyzed under Rayleigh fading channel environment. The performance metrics considered for our study are Bit Error Rate (BER) and Energy spent per bit. Simulation results show that LT codes show improved performance under severe fading channel conditions, i. e., for low SNR values (-5 to 2 dB) and ARQ scheme provides better performance under high SNR values (above 2 dB).