Manik Raina

Analysis and improvement of contention access protocol in IEEE 802.15.4 star network

The wireless standard IEEE 802.15.4 is emerging as a key enabling technology for different wireless sensor network applications. IEEE802.15.4 supports a low data rate wireless sensor network with low power requirement. In this paper, we discuss the performance analysis of IEEE 802.15.4 MAC assuming star topology in the beacon enabled mode. We obtain analytical expressions for channel sensing probabilities and saturation throughput during the contention access period. We have included the packet discard analysis and validated the analytical expressions for these parameters using ns-2 simulation. Further, we also discuss the performance analysis of the MAC when the contention access mechanism of IEEE 802.15.4 is modified to have only one channel sensing. Finally, we discuss adaptation of the frame length for the case with one channel sensing.

Secure data aggregation using commitment schemes and quasi commutative functions

A scheme is proposed for secure data aggregation in wireless sensor networks. Commitment schemes and a class of functions called quasi commutative functions are used to achieve provably secure data aggregation. Efficient schemes to verify the data aggregation are provided.

Secure group communication in wireless sensor networks

In this paper we address the issues of forming secure multicast group within wireless sensor networks. We describe a protocol that establishes a secure multicast group, and distributes a group key by mutually authenticating a group of devices over an open insecure wireless channel. We choose a conference keying mechanism and extend it with symmetric authentication protocols and a key hierarchy on which group key could be distributed efficiently. We address two problems in this work. Firstly, the formation of secure groups in sensor network with a low communication complexity, secondly, provides an efficient solution to maintain such multicast group.

Simple Multiuser Detectors for DS-UWB Systems

UWB is an emerging technology inviting major advances in wireless communication, networking, radar and positioning systems. In this paper, we present novel algorithms for the multiuser detection based on minimum mean square error (MMSE) for a DS-UWB multiuser communication system. The algorithms exploit the inherent multipath diversity and also mitigate the effects of both inter symbol interference(ISI) and multiuser interference (MUI). Simulation results show that the given algorithms perform better than the other known detectors in literature. We also provide closed form expression for the BER results of the above scheme

Multiuser Detectors for Multiple Antenna UWB Systems

Ultra-wideband (UWB) transmissions have well-documented advantages for low-power, peer-to-peer, and multiple-access communications. In this paper, we present novel linear receiver algorithms for multiuser detection (MUD) based on minimum mean square error (MMSE) for UWB multiuser communication systems. We assume multiple antennae at the receiver. The algorithms exploit inherent multipath diversity and mitigate the effects of both inter symbol interference (ISI) and multiuser interference (MUI). Further, the receiver algorithms also optimally exploit receiver diversity. We provide performance evaluation of the detectors through detailed simulations. The simulations show that MUD based receivers perform well for multiuser UWB environment. An analytical framework for obtaining closed form expression for the bit error rate (BER) of the above schemes is also discussed.

An Estimator for Multi-Sensor Data Fusion

In this paper, we examine binary hypothesis testing and parameter estimation problem in a sensor network. We address the problem of detection and also the estimation of the underlying parameter at the fusion center by optimally combining the test statistics sent by different sensors. We make no assumptions on the noise statistics at the sensor nodes except that their first and second order statistics are known. We show that the proposed method is optimal as an estimator as well as a detector.