Optimal Power Allocation for Relay Assisted Cognitive Radio Networks.
ABSTRACT In this paper, we study the optimal power allocation of wireless relay nodes which are used in the secondary user (SU) communication of a cognitive radio (CR) network. We consider the behavior of transmitting powers of SUs where those powers are limited to the tolerable interference as seen by the primary user (PU) communication. To improve the performance of the secondary communication based on minimizing the outage probability, we re-formulate the power allocation problem with a new set of constraints. These are obtained by considering the co-channel interference generated by the SU communication to the PU communication. The power allocation problem is solved for both regenerative and non regenerative relay models under Rayleigh fading conditions. SU communication with N number of relays is discussed and compared. The outage probability of SU communication is limited by the interference power threshold (IPT) constraints of PUs and is affected significantly by the IPT levels of PUs.
Conference Proceeding: Power allocation for regenerative relay channel with Rayleigh fading[show abstract] [hide abstract]
ABSTRACT: Cooperative relaying is considered as an effective way to combat Rayleigh fading, to offer better quality of communication link or channel capacity. From the perspective of information theory, channel capacity depends on the SNR of the received signal, therefore, how to allocate transmit power between transmitter and relay to achieve maximum SNR at the receiver or maximum channel capacity is an important issue. In general, there are two types of relaying system, i.e. non-regenerative and regenerative systems. This paper puts emphasis on the power allocation (PA) of regenerative systems. Based on a 2-hop relaying channel suffering from Rayleigh fading, with and without diversity, an adaptive PA scheme is proposed, under transmit power constraints, to keep the system running at the optimum level. Numerical results indicate that with the proposed PA scheme, the system performance not only outperforms that of the direct transmission system, but also obtains the maximum channel capacity or SNR of the relaying system.Vehicular Technology Conference, 2004. VTC 2004-Spring. 2004 IEEE 59th; 06/2004
Conference Proceeding: Performance analysis of two-hop relayed transmissions over Rayleigh fading channels[show abstract] [hide abstract]
ABSTRACT: Closed form expressions for the statistics of the harmonic mean of two independent exponential variates are presented. These statistical results are then applied to study the performance of wireless communication systems with non-regenerative relays over flat Rayleigh fading channels. It is shown that these results can either be exact or tight lower bounds on the performance of these systems depending on the choice of the relay gain. More specifically, outage probability formulas for noise limited systems are obtained. Furthermore, outage capacity and bit error rate (BER) expressions for binary differential phase shift keying are derived. Finally, comparisons between regenerative and non-regenerative systems are presented. Numerical results show that the former systems clearly outperform the latter ones for low average signal-to-noise-ratio (SNR). They also show that the two systems have similar performance at high average SNR.Vehicular Technology Conference, 2002. Proceedings. VTC 2002-Fall. 2002 IEEE 56th; 02/2002
Conference Proceeding: A Cooperative Relay Scheme for Secondary Communication in Cognitive Radio Networks.[show abstract] [hide abstract]
ABSTRACT: In cognitive radio networks, secondary users (SUs) opportunistically exploit the spectrum unutilized by primary users (PUs). In this paper, we study the secondary communication where secondary transmitters and receivers have different available spectrum. Considering the spectrum diversity and the space distance between different PUs, we introduce cognitive relay node into the secondary communication and propose a novel Cooperative Relay Scheme (CRS) to increase the SINR at secondary receivers. A novel Opportunistic Sharing Scheme (OSS) is also proposed for the secondary transmitters to share the spectrum of relay nodes. We model it with a non-cooperative game, and study the performance of competition of SUs. The Nash equilibrium and Pareto efficiency of this game is presented. Simulations show that CRS can increase SINR at secondary receivers under proper configurations.Proceedings of the Global Communications Conference, 2008. GLOBECOM 2008, New Orleans, LA, USA, 30 November - 4 December 2008; 01/2008