Ranjith Liyanapathirana

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The IEEE 802.15.4 medium access control (MAC) protocol, widely used in current wireless sensor networks (WSNs), shows poor data transmission reliability in delay sensitive synchronised periodic monitoring applications due to synchronicity in data transmission procedures and short backoff window length of the protocol. In this paper, we propose a new(More)
In this paper, the outage probability analysis of two-hop amplify-and-forward (AF) multiple-input multiple-output (MIMO) relay networks is presented. The source and the destination are equipped with multiple antennas and communicate with each other, with the help of a single antenna relay which is subject to interference. Two systems are considered;(More)
We investigate the relay selection, sub-carrier pairing and power allocation problems in a two-hop, multi-relay-assisted cooperative OFDM system with amplify-and-forward (AF) relays. We propose a sub optimal but more feasible approach to solve the power allocation problem with relay selection and sub-carrier pairing. The proposed method is based on(More)
In this paper, we study power allocation in OFDM based cognitive radio (CR) relay networks when the fading statistics between cognitive and primary users are known at the CR transmitters. The objective of power allocation is to maximize the instantaneous capacity of the CR network. Optimal power allocation schemes are developed for both decode-and-forward(More)
In this paper, we investigate optimal and suboptimal power allocation schemes for amplify-and-forward (AF) relay assisted OFDM-based cognitive radio (CR) transmission. Due to channel feedback delay, the available channel state information (CSI) between the secondary and primary users is considered as an outdated but correlated version of the actual(More)
The IEEE 802.15.4 medium access control (MAC) protocol, which is widely used in current WSN deployments, does not provide any hidden node avoidance mechanisms. This leads to severe performance degradation in IEEE 802.15.4 MAC protocol in the presence of hidden nodes. In this paper, we apply a discrete-time Markov Chain model to analyse the throughput of(More)
We present an importance sampling (IS) based approach for efficient simulation of Orthogonal Frequency Division Multiplexing Systems (OFDM) operating over multipath fading channels. We derive the optimal biasing parameters for Rayleigh fading multipath channels considering an OFDM system and an OFDM system with Orthogonal Space-Time Block Coded (OSTBC)(More)
A three-dimensional discrete-time Markov Chain model is applied to analyse the performance of the IEEE 802.15.4 MAC protocol under burst channel errors. Real world wireless sensor network conditions including unsaturated traffic, frame retransmission and acknowledgement (ACK) frame transmission are considered for the analysis. The system performance is(More)
This paper presents an improved wireless MAC protocol that enables IEEE 802.15.4 based WSNs to provide an energy-efficient, reliable, and delay-limited data transmission for hybrid monitoring applications. The proposed protocol is implemented in ns-2, and its performance is evaluated in terms of energy consumption, delay, and reliability in data(More)