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In this paper, we propose a Markov chain based analysis to model the unslotted CSMA/CA medium access control protocol used in non-beacon enabled IEEE 802.15.4 networks that operate under unsaturated traffic conditions. The proposed analysis is then used to evaluate the performance of the protocol in terms of the aggregate network throughput. Based on our(More)
In this paper, we apply a discrete-time Markov Chain model to analyse the performance of IEEE 802.15.4 MAC Protocol with acknowledgement (ACK) frame transmission under unsaturated traffic conditions. We evaluate the system performance in terms of aggregate throughput and average power consumption of a node. Analytical results are substantiated through ns2(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, 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)
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delay, the available channel state information (CSI) between the secondary and primary users is considered as an outdated but correlated version of the actual(More)
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)
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)