BITS Faculty Publications
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Item Exploiting multiple antenna cognitive radio system for cooperative spectrum sharing(IEEE, 2015) Vashistha, AnkushThis paper proposes a cooperative spectrum sharing scheme in which multiple antennas of a secondary (aka cognitive) system is exploited to nullify the interference from the primary (aka licensed) to secondary system and vice versa. The secondary system also acts as a "decode-and-forward" relay for the primary system thus boosting its performance. The performance of primary and secondary system is analyzed by obtaining the closed form expressions for outage probability. The simulation results are also shown to validate the theoretical expressions obtained in this paper.Item Outage analysis of a multiple-antenna cognitive radio system with cooperative decode-and-forward relaying(IEEE, 2014-12) Vashistha, AnkushIn this paper, we analyze a two-phase hierarchical spectrum sharing protocol based on cooperative decode and forward relay transmission wherein it is assumed that the cognitive (i.e secondary) system is equipped with multiple antennas. The performance of the licensed (i.e. primary) as well as cognitive system is quantified by deriving the closed form expressions for outage probability. The theoretical and simulation results show that by exploiting multiple antennas at secondary transmitter (ST), we can drastically improve the performance of both primary and secondary systems as compared to conventional spectrum sharing schemes.Item Cooperative spectrum sharing using transmit antenna selection for cognitive radio systems(Springer, 2015-10) Vashistha, AnkushIn this paper, a spectrum sharing scheme that utilizes the two-phase cooperative decode-and-forward relaying protocol is proposed. The cooperation between primary (i.e. licensed) and secondary (i.e. unlicensed) system helps in achieving the desired target rate for the primary system and spectrum access for cognitive (i.e. secondary) system. In the proposed scheme, secondary transmitter which is equipped with multiple antennas uses transmit antenna selection to improve the primary’s performance by reducing the interference level of secondary signal at primary receiver, while keeping the performance of secondary system unaffected. Closed form expressions for outage probability have been derived for both systems by varying transmit power level at secondary transmitter. The theoretical results have been compared with simulation results to validate the analysis done in this paper.Item Interference-Constrained Power Adaptive Decode-and-Forward Relaying Policy: Design and Performance Analysis(IEEE, 2020) Bitragunta, SainathPower adaptation is a feasible and promising solution to avoid interference at the primary, caused by transmissions of secondary underlay cooperative spectrum sharing systems. For it, we propose a novel interference-constrained power adaptive decode-and-forward (IC-PADnF) relaying policy jointly with a simple probabilistic relay selection (PRS) policy. The proposed IC-PADnF relaying policy, apart from acting as a regenerative relay, adaptively sets its transmit power and gain to optimize the underlay cooperative spectrum sharing system's performance. Further, the relay selection policy is easy to implement due to less channel state information (CSI) requirements. To evaluate the proposed IC-PADnF policy's performance, we derive analytical expressions for optimal fading averaged spectral efficiency and optimal fading averaged energy efficiency. We also obtain upperbound to these essential performance measures. We perform Monte-Carlo simulations to validate the derived analytical results. Furthermore, we compared the proposed policy with benchmark policies to explicitly show the performance improvements and its applicability for cooperative spectrum sharing systems and networks. Lastly, we find that IC-PADnF relaying policy jointly with PRS policy outperforms the benchmark policies.