Conference Paper

Optimal Power Allocation for Relay Assisted Cognitive Radio Networks

DOI: 10.1109/VETECF.2010.5594529 Conference: Proceedings of the 72nd IEEE Vehicular Technology Conference, VTC Fall 2010, 6-9 September 2010, Ottawa, Canada
Source: DBLP


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.

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Available from: Nandana Rajatheva, Nov 18, 2015
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    • "Relay in various forms, like maximizing signal to noise ratio (SNR) on its path selection [5], using decode and forward (DF), amplify and forward (AF) in OFDM system with a sum-power constraint [6], power allocation incorporating dynamically changing environment [7], cooperative relay schemes (CRS) to increase signal-tointerference noise ratio (SINR) at secondary receiver [8] and many others have been explored in CR research. The selection of relay strategy depends upon the channel condition and the performance criterion. "
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    ABSTRACT: This paper proposes power allocation algorithm in orthogonal frequency division multiplexing (OFDM) based cognitive radio (CR) system using decode and forward (DF) relay. It is reported in the literature that both classical i.e. uniform power loading scheme and water filling methods that allocate power on OFDM subcarriers based on the channel gain are not effective for cognitive radio network (CRN) as the schemes introduce large interference to primary user (PU). To this aim, the present work proposes a simple, computationally efficient yet effective power loading scheme that maximizes the transmission capacity of CR while keeping the interference introduced to the PU below acceptable limits. To meet the objective, proposed power allocation to subcarriers not only considers channel gains but also the relative distances between CR subcarriers and PU band. This capacity performance is further improved significantly using DF relay, where our research direction focuses on optimal sharing of power between CR and relay using maximal ratio combiner (MRC) at destination receiver. Performance for the proposed power allocation schemes are compared with OFDM based hybrid power allocation as well as joint subcarrier and power adaptation methods reported in the literature. Numerical results show that the relative gain on CR's capacity are 3.7 times and 2.3 times, respectively compared to the optimal and hybrid OFDM power allocation schemes, while for interference introduced to PU is set at 3 times 10-6 (in watt). Finally, a few related research problems are also highlighted as future scope of works.
    Full-text · Article · Dec 2012 · Procedia Engineering
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    • "Hence, the transmitting secondary user now, upon sensing a spectrum hole, transmits to the relays as well as the destination. Power allocation for relayassisted cognitive radio networks has been discussed in [7] [8] [9] [10] [11] [12] [13] [14] [15]. These works proposed strategies to maximize the throughput for a cognitive relay network that is allowed to share the frequency band with the primary user. "
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    ABSTRACT: Optimal resource allocation for cooperative cognitive radio networks with opportunistic access to the licensed spectrum is studied. Resource allocation is based on minimizing the symbol error rate at the receiver. Both the cases of all-participate relaying and selective relaying are considered. The objective function is derived and the constraints are detailed for both scenarios. It is then shown that the objective functions and the constraints are nonlinear and nonconvex functions of the parameters of interest, that is, source and relay powers, symbol time, and sensing time. Therefore, it is difficult to obtain closed-form solutions for the optimal resource allocation. The optimization problem is then solved using numerical techniques. Numerical results show that the all-participate system provides better performance than its selection counterpart, at the cost of greater resources.
    Full-text · Article · May 2012 · Journal of Computer Networks and Communications
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    ABSTRACT: In this paper, we present two optimal resource allocation schemes that maximize throughput and symbol correct rate (SCR). The throughput and SCR are derived. The derived throughput and SCR are optimized with respect to the sensing time, the source transmission power and the relay transmission power. Numerical results show that the optimal sensing time is dependent on the primary user's signal-to-noise-ratio (SNR). They also show that SCR increases with increase in the number of relays.
    Full-text · Article · Jan 2012
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