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Lou S.,Nanjing University of Posts and Telecommunications | Lou S.,Wideband Wireless Communications and Sensor Networks Technology Laboratory | Yang L.,Nanjing University of Posts and Telecommunications | Yang L.,Wideband Wireless Communications and Sensor Networks Technology Laboratory
IET Conference Publications | Year: 2013

In this paper we consider a joint algorithm which combines relay selection with power allocation for two-way Decode- and-Forward (DF) relay channels. The selected relay use network coding to assist transceivers exchanging information. Power allocation at each node under the total transmit power constraint are proposed for better BER performance. A closed-form expression of the end-to-end BER is derived. Simulation results verify the theoretical analysis and show a performance improvement, in terms of bit error rate, of the optimal power allocation comparing to the equal power allocation scheme. Especially while one of the hops suffers deep fading, the joint algorithm can provide significant gain comparing to traditional relay selection scheme. Source


Lou S.,Nanjing University of Posts and Telecommunications | Lou S.,Wideband Wireless Communications and Sensor Networks Technology Laboratory | Yang L.,Nanjing University of Posts and Telecommunications | Yang L.,Wideband Wireless Communications and Sensor Networks Technology Laboratory
KSII Transactions on Internet and Information Systems | Year: 2013

This paper studies relay selection and power allocation for amplify-and-forward (AF) based two-way relay networks (TWRN) with asymmetric traffic requirements (ATR). A joint relay selection and power allocation algorithm is proposed to decrease the outage probability of TWRN with ATR. In this algorithm, two sources exchange information with the help of the relay during two time slots. We first calculate the optimal power allocation parameters based on instantaneous channel state information (CSI), and then derive a tight lower bound of outage probability. Furthermore, we propose a simplified relay selection criterion, which can be easily calculated as harmonic mean of instantaneous channel gains, according to the outage probability expressions. Simulation results verified the theoretical analyses we presented. It is shown that the outage probability of our algorithm improves 3-4dB comparing with that of other existing algorithms, and the lower bound is tight comparing with actual value for the entire signal-to-noise ratio (SNR) region. © 2013 KSII. Source


Lou S.,Nanjing University of Posts and Telecommunications | Lou S.,Wideband Wireless Communications and Sensor Networks Technology Laboratory | Yang L.,Nanjing University of Posts and Telecommunications | Yang L.,Wideband Wireless Communications and Sensor Networks Technology Laboratory
KSII Transactions on Internet and Information Systems | Year: 2014

Outdated Channel State Information (CSI) was proved to have negative effect on performance in two-way relay networks. The diversity order of widely used opportunistic relay selection (ORS) was degraded to unity in networks with outdated CSI. This paper proposed a multiple relay selection scheme for amplify-and-forward (AF) based two-way relay networks (TWRN) with outdated CSI. In this scheme, two sources exchange information through more than one relays. We firstly select N best relays out of all candidate relays with respect to signal-noise ratio (SNR). Then, the ratios of the SNRs on the rest of the candidate relays to that of the Nth highest SNR are tested against a normalized threshold μ∈[0, 1], and only those relays passing this test are selected in addition to the N best relays. Expressions of outage probability, average bit error rate (BER) and ergodic channel capacity were obtained in closed-form for the proposed scheme. Numerical results and Simulations verified our theoretical analyses, and showed that the proposed scheme had significant gains comparing with conventional ORS. © 2014 KSII. Source


Jian W.,Nanjing University of Posts and Telecommunications | Jian W.,Wideband Wireless Communications and Sensor Networks Technology Laboratory | Longxiang Y.,Nanjing University of Posts and Telecommunications | Longxiang Y.,Wideband Wireless Communications and Sensor Networks Technology Laboratory | And 2 more authors.
Proceedings - 4th International Conference on Intelligent Computation Technology and Automation, ICICTA 2011 | Year: 2011

Cognitive Radio (CR) which aims to improve the spectrum utilization by accessing opportunistically the spectrum originally licensed to a primary system is a promising concept. OFDM is regarded as a potential technology for CR systems and dynamic resource allocation is an important task in such systems. This paper focuses on the sub carrier and power allocation algorithms which are to maximize secondary users' transmitted data rate while adjusting the interference introduced to the PU band below a threshold and maintaining the total power under a limit. The issue of sub carrier allocation in multi-user CR networks is firstly discussed. Secondly, three sub optimal power allocation algorithms based on LWF (linear water-filling algorithm) which have less complexity than the optimal algorithm are proposed. Simulation results show that the power interference algorithm based on linear water-filling scheme (LWF-PI) offers the best performance among the sub optimal power allocation algorithms, which is the closest to the optimal scheme. © 2011 IEEE. Source


Wu J.,Nanjing University of Posts and Telecommunications | Wu J.,Wideband Wireless Communications and Sensor Networks Technology Laboratory | Yang L.,Nanjing University of Posts and Telecommunications | Yang L.,Wideband Wireless Communications and Sensor Networks Technology Laboratory | And 2 more authors.
7th International Conference on Wireless Communications, Networking and Mobile Computing, WiCOM 2011 | Year: 2011

Cognitive Radio (CR) is a promising concept for improving the utilization of scarce radio spectrum resource. OFDM is regarded as a potential technology for CR systems and resource allocation is a vital task in such systems. In this paper, a subcarrier and power allocation algorithm based on the linear waterfilling(LWF) scheme is proposed to maximize the downlink capacity of the CR systems while keeping both the total power budget and interference introduced to the primary user blow the pre-constraints. In the proposed algorithm, subcarrier allocation is first performed by assuming an equal power distribution. Secondly, the linear water-filling scheme under the interference constraint is proposed through searching for a rapid means for confirming the subcarriers which need not allocate power, then an iterative suboptimal power allocation algorithm based on LWF which have less complexity than the optimal algorithm is proposed. The proposed algorithm is shown to achieve a good performance which is close to the optimal algorithm. © 2011 IEEE. Source

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