Wanbin Tang

Joint optimal sensing and power allocation for cooperative relay in cognitive radio networks

In this paper, we investigate the joint optimization of sensing and power allocation for cooperative relay in cognitive radio networks (CRNs). Specifically, in the sensing time slot, the source secondary user (SU) and the relay SUs individually sense the channel, and then the relay SUs send their sensing results to the source SU, in which a fusion rule is employed to determine whether the primary user (PU) is idle or not on the channel. In the data transmission slot, the selective amplify-and-forward (S-AF) cooperative relay scheme is considered to assist the source SU for data transmission. By jointly considering the two slots, the optimization problems are respectively formulated to maximize the CRNs average throughput and minimize the outage probability of secondary transmission under the average transmit power constraint of SUs and the average interference power constraint of PU. The optimal algorithms are developed to acquire the optimal sensing time and power allocation. Moreover, in the S-AF scheme, a relay selection scheme is also considered in the optimization problem. Finally, we provide simulation results to validate our proposed algorithms.

Outage Probability and SER of Amplify-and-Forward Cognitive Relay Networks

This letter considers amplify-and-forward (AF) cognitive relay networks with interference power constraint and transmit power constraint in a spectrum-sharing context. In particular, we impose the interference power constraint on secondary source node, and impose the interference power constraint and the transmit power constraint on secondary relay node. We derive the exact outage probability and the lower bound on symbol error rate (SER) of cognitive transmission over Rayleigh fading channels. Our results show that the outage probability and SER saturation phenomenons occur when the interference power constraint or the transmit power constraint reaches a specified value. Monte Carlo simulations are shown to validate the accuracy of the analytical results.

Joint optimal sensing time and power allocation for multi-channel cognitive radio networks considering sensing-channel selection

In this paper, we consider a multi-channel cognitive radio network (CRN) where each secondary user (SU) can only choose to sense a subset of channels. We formulate a joint optimization problem of sensing-channel selection, sensing time and power allocation under the constraints of average transmit power budget and average interference power budget, which maximizes the CRN’s total throughput. We propose a greedy algorithm to solve the joint optimization problem, which has much less computational complexity. Moreover, it is shown that the search space of the greedy algorithm can be further pruned. Finally, numerical results demonstrate that the greedy algorithm has comparable performance to the exhaustive search algorithm.

Bandwidth and power allocation for cooperative relay in cognitive radio networks

In this article, we consider a cognitive radio (CR) relay network where one source secondary user (SU) communicates with its corresponding destination SU with the help of relay SUs. Conventionally, equal bandwidth and/or power are allocated to each relay SU, which may not be efficient for the CR with limited bandwidth and power. Therefore, this article presents bandwidth and power allocation with amplify-and-forward (AF) or decode-and-forward (DF) relaying protocol to (1) maximize the sum network throughput; (2) minimize the total transmit power of the CR network with considering the fairness of power drain of relay SUs; (3) maximize the energy efficiency of the CR network. It is shown that DF relaying protocol can achieve better performance when the decoding rate constraint is not considered. In contrast, when considering the decoding rate constraint in DF relaying protocol, we propose the hybrid relaying protocol that combines AF and DF relaying protocols. We formulate the joint bandwidth and power allocation problem with hybrid relaying protocol to maximize the sum network throughput. A greedy algorithm is developed to solve the joint optimization problem, which has much less computational complexity. It is shown that the greedy algorithm has comparable performance to the exhaustive search algorithm. Finally, numerical results are provided to endorse our proposed algorithms.

An analytical performance model considering access strategy of an opportunistic spectrum sharing system

In an opportunistic spectrum sharing system, secondary users (SUs) opportunistically access the white space spectrum that is not occupied by the primary user (PU). Some analytical performance models have been available based on Markov chain modeling. In these models, SUs and PUs access the spectrum by randomly selecting the available channels with equal probability. However, how SUs and PUs use the spectrum are controlled by the access strategy designed in their MAC layer in an ad‐hoc network or centralized radio resource management layer in an infrastructure‐based network. To analyze the grade of service (GoS) of the secondary system under consideration for the access strategy, we propose an access rule transition matrix to model the access behavior of radio resource management, and apply it into the continuous‐time Markov chain model. It was proved that the proposed model is equivalent to the original models assuming the random access strategy by simulation. Moreover, we analyzed the GoS performance of the secondary system by assuming an ordered hunt access strategy. The results showed that the GoS performance of secondary systems can be improved greatly if it knows the spectrum access strategy of the primary system. Copyright

Positioning noncooperative receiver using full-duplex relay technique

Since it is challenging to position the noncooperative receiver (Rx), especially when the backward frequency band of the Rx cannot be obtained by the anchors. In this paper, we propose a novel noncooperative Rx positioning method using full-duplex relay technique, where the anchors act as full-duplex relays for the Rx. It can trigger the close-loop-power-control (CLPC) between the transmitter (Tx) and the Rx, which contains the information of the Rxs location. By measuring the received signal from the Tx, the anchors can estimate the location of the Rx. Simulation results demonstrate the performance of the proposed Rx positioning method, and the root-mean-square-error (RMSE) can reach about 30%, which is similar to the conventional Tx positioning using received-signal-strength (RSS).