Sequential Optimization for Subcarrier Pairing and Power Allocation in CP-SC Cognitive Relay Systems

( Hongwu Liu ),( Jaijin Jung ),( Kyung Sup Kwak ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.5

A sequential optimization algorithm (SOA) for resource allocation in a cyclic-prefixed single-carrier cognitive relay system is proposed in this study. Both subcarrier pairing (SP) and power allocation are performed subject to a primary user interference constraint to minimize the mean squared error of frequency-domain equalization at the secondary destination receiver. Under uniform power allocation at the secondary source and optimal power allocation at the secondary relay, the ordered SP is proven to be asymptotically optimal in maximizing the matched filter bound on the signal-to-interference-plus-noise ratio. SOA implements the ordered SP before power allocation optimization by decoupling the ordered SP from the power allocation. Simulation results show that SOA can optimize resource allocation efficiently by significantly reducing complexity.

Joint Subcarrier Matching, Power Allocation and Bit Loading in OFDM Dual-Hop Systems

Hyung-Yun Kong,Jin-Hee Lee 한국전자파학회JEES 2010 Journal of Electromagnetic Engineering and Science Vol.10 No.2

Orthogonal Frequency Division Multiplexing(OFDM) dual-hop systems can take full advantages of the techniques of both multi-hop communication and OFDM. To achievethis end, we propose a joint subcarrier matching, power allocation and bit loading algorithm operating under a total power constraint and the same Bit Error Rate(BER) threshold over all subcarriers. Simulation results demonstrated system throughput improvement compared to single-hop systems and dual-hop systems with different bit loading algorithms for each relay position, power constraint, and required BER.

Adaptive OFDMA with Partial CSI for Downlink Underwater Acoustic Communications

Yuzhi Zhang,Yi Huang,Lei Wan,Shengli Zhou,Xiaohong Shen,Haiyan Wang 한국통신학회 2016 Journal of communications and networks Vol.18 No.3

Multiuser communication has been an important researcharea of underwater acoustic communications and networking. This paper studies the use of adaptive orthogonal frequencydivisionmultiple access (OFDMA) in a downlink scenario, wherea central node sends data to multiple distributed nodes simultaneously. In practical implementations, the instantaneous channelstate information (CSI) cannot be perfectly known by the centralnode in time-varying underwater acoustic (UWA) channels, due tothe long propagation delays resulting from the low sound speed. In this paper, we explore the CSI feedback for resource allocation. An adaptive power-bit loading algorithm is presented, which assignssubcarriers to different users and allocates power and bits toeach subcarrier, aiming to minimize the bit error rate (BER) underpower and throughput constraints. Simulation results show considerableperformance gains due to adaptive subcarrier allocationand further improvement through power and bit loading, as comparedto the non-adaptive interleave subcarrier allocation scheme. In a lake experiment, channel feedback reduction is implementedthrough subcarrier clustering and uniform quantization. Althoughthe performance gains are not as large as expected, experiment resultsconfirm that adaptive subcarrier allocation schemes based ondelayed channel feedback or long term statistics outperform theinterleave subcarrier allocation scheme.

An Efficient Adaptive Modulation Scheme for Wireless OFDM Systems

Changwook Lee,전기준 한국전자통신연구원 2007 ETRI Journal Vol.29 No.4

An adaptive modulation scheme is presented for multiuser orthogonal frequency-division multiplexing systems. The aim of the scheme is to minimize the total transmit power with a constraint on the transmission rate for users, assuming knowledge of the instantaneous channel gains for all users using a combined bit-loading and subcarrier allocation algorithm. The subcarrier allocation algorithm identifies the appropriate assignment of subcarriers to the users, while the bit-loading algorithm determines the number of bits given to each subcarrier. The proposed bit-loading algorithm is derived from the geometric progression of the additional transmission power required by the subcarriers and the arithmeticgeometric means inequality. This algorithm has a simple procedure and low computational complexity. A heuristic approach is also used for the subcarrier allocation algorithm, providing a trade-off between complexity and performance. Numerical results demonstrate that the proposed algorithms provide comparable performance with existing algorithms with low computational cost.

Subcarrier and Power Allocation for Multiuser MIMO-OFDM Systems with Various Detectors

( Jing Mao ),( Chen Chen ),( Lin Bai ),( Haige Xiang ),( Jinho Choi ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.10

Resource allocation plays a crucial role in multiuser multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM) systems to improve overall system performance. While previously proposed resource allocation algorithms are mainly designed from the point of view of the information-theoretic, we formulate the resource allocation problem as an average bit error rate (BER) minimization problem subject to a total power constraint when considering employing realistic MIMO detection techniques. Subsequently, we derive the optimal subcarrier and power allocation algorithms for three types of well-known MIMO detectors, including the maximum likelihood (ML) detector, linear detectors, and successive interference cancellation (SIC) detectors. To reduce the complexity, we also propose a two-step suboptimal algorithm that separates subcarrier and power allocation for each detector. We also analyze the diversity gain of the proposed suboptimal algorithms for various MIMO detectors. Simulation results confirm that the proposed suboptimal algorithm for each detector can achieve a comparable performance with the optimal allocation with a much lower complexity. Moreover, it is shown that the suboptimal algorithms perform better than the conventional algorithms that are known in the literature.

Improved Power Allocation to Enhance the Capacity in OFDMA System for Proportional Resource Allocation

와풋닛,로빈,김재명,Var, Puthnith,Shrestha, Robin,Kim, JaeMoung The Korean Institute of Communications and Informa 2013 韓國通信學會論文誌 Vol.38 No.7A

Orthogonal Frequency Division Multiple Access(OFDMA)는 4세대 무선 통신을 위해 고려되는 변조와 다중 접속 기술이다. 본 논문에서는, OFDMA 시스템에서 더 나은 proportional rate의 자원할당 기법을 위해 전체 전력, 비트 오류율, 유저 간의 rate proportionality에 대한 제한 조건을 만족시키면서, 유저의 전송률을 최대화 시키는 전략 할당 알고리즘에 대해 기술하였다. 그리고 subcarrier 할당의 비율과 유저의 정규화된 proportionality 조건에 기반을 둔 전력 할당 방식을 제안하였다. 유저에게 subcarrier 할당을 위한 방법으로는 greedy 알고리즘과 waterfilling 기술이 적용되었다. 제안된 알고리즘에 대한 평가는 시뮬레이션을 통해서 이루어졌으며, 시뮬레이션을 통해서 제안된 알고리즘이 유저 간의 rate proportionality를 유지하면서 더 높은 시스템 채널 용량과 적은 소요 시간을 보인다는 것을 확인할 수 있었다. The Orthogonal Frequency Division Multiple Access (OFDMA) is considered as a novel modulation and multiple access technique for 4th generation wireless systems. In this paper, we formulate a base station's power allocation algorithm for each user to maximize the user's sum rate, subject to constraints on total power, bit error rate, and rate proportionality among the users for a better proportional rate adaptive (RA) resource allocation method for OFDMA based system. We propose a novel power allocation method based on the proportion of subcarrier allocation and the user's normalized proportionality constant. We adapt a greedy algorithm and waterfilling technique for allocating the subcarriers among the users. In an end-to-end simulation, we validate that the proposed technique has higher system capacity and lower CPU execution times, while maintaining the acceptable rate proportionality among users.

Joint Resource Allocation and Artificial Noise Design for Multiuser Wiretap OFDM Channels

Xiang Chen,Haohao Qin,Limin Xiao 한국통신학회 2017 Journal of communications and networks Vol.19 No.5

PHY-layer security is one of promising techniques forenhanced security and privacy protection in 5G communications. In this paper, the joint resource allocation and artificial noise (AN)design problem of multiuser wiretap orthogonal frequency-divisionmultiplexing (OFDM) systems is investigated to improve the systemsecrecy rate and power efficiency, which can help to provide waveformdesign references for secure 5G communications. In such amultiuser wiretap OFDM system, one legitimate transmitter (Alice),multiple legitimate receivers (Bobs), and one eavesdropper(Eve) are simultaneously considered. The time-domain artificialnoise is firstly involved to guarantee the target secrecy rates of multipleBobs. Then a sum secrecy rate maximization problem withnonconvex integer nonlinear programming is formulated to jointlyoptimize the power, subcarrier allocation and AN design. To solvethis tough problem with low computational complexity, a heuristicalsub-optimal subcarrier allocation method is proposed, followedby the Lagrange dual method based joint power allocation and ANdesign scheme. Moreover, considering that sum secrecy rate maximizationmay result in unfairness for Bobs with bad channel gains,the transmit power minimization problem that ensures a target secrecyrate for each individual Bob is further addressed. An iterativealgorithm is proposed to solve this power minimization problemby updating the subcarrier, power allocation and AN design alternatively. Numerical results demonstrate the effectiveness of theproposed algorithms.

Intelligent Water Drops Based Joint Subcarrier Pairing and Power Allocation with Fairness in Cooperative Relay Networks

Guiyan Liu,Song-Tao Guo,Huan Zhao,Fei Wang 한국통신학회 2017 Journal of communications and networks Vol.19 No.1

In this paper, we propose a joint subcarrier pairing andpower allocation (JS2PA) scheme with fairness based on the intelligentwater drop (IWD) optimization method for orthogonal frequencydivision multiple access cooperative relay networks. Theproposed scheme consists of a subcarrier pairing and selection al-gorithm and a power allocation algorithm. We first formulate theJS2PA problem as a mixed integer programming problem aimingto maximize the total network utility under the constraints of in-dividual power, subcarrier fairness requirement and pairing. Tosolve the non-convex JS2PA problem, firstly, we propose a subcar-rier pairing and selection algorithm based on Hungarian methodso as to select the appropriate subcarrier pairs for relaying. Sec-ondly, we provide a power allocation algorithm based on the IWDmethod in which water drops act as the agents to find the optimalpower allocation for each node. In particular, to improve the opti-mality of power allocation, we integrate network utility and powerrequirement into heuristic function to measure the desirability ofthe IWD selecting the next visiting node. Finally, we conduct sim-ulations to validate the proposed algorithms and the results showthat the proposed JS2PA scheme outperforms the existing methodsin terms of convergence, total network utility and fairness.

Resource Allocation Algorithm for Multi-cell Cognitive Radio Networks with Imperfect Spectrum Sensing and Proportional Fairness

Jianyao Zhu,Jianyi Liu,Zhaorong Zhou,Li Li 한국전자통신연구원 2016 ETRI Journal Vol.38 No.6

This paper addresses the resource allocation (RA) problem in multi-cell cognitive radio networks. Besides the interference power threshold to limit the interference on primary users PUs caused by cognitive users CUs, a proportional fairness constraint is used to guarantee fairness among multiple cognitive cells and the impact of imperfect spectrum sensing is taken into account. Additional constraints in typical real communication scenarios are also considered—such as a transmission power constraint of the cognitive base stations, unique subcarrier allocation to at most one CU, and others. The resulting RA problem belongs to the class of NP-hard problems. A computationally efficient optimal algorithm cannot therefore be found. Consequently, we propose a suboptimal RA algorithm composed of two modules: a subcarrier allocation module implemented by the immune algorithm, and a power control module using an improved sub-gradient method. To further enhance algorithm performance, these two modules are executed successively, and the sequence is repeated twice. We conduct extensive simulation experiments, which demonstrate that our proposed algorithm outperforms existing algorithms.

Joint Subcarrier and Bit Allocation for Secondary User with Primary Users` Cooperation

( Xiaorong Xu ),( Yu-dong Yao ),( Sanqing Hu ),( Yingbiao Yao ) 한국인터넷정보학회 2013 KSII Transactions on Internet and Information Syst Vol.7 No.12

Interference between primary user (PU) and secondary user (SU) transceivers should be mitigated in order to implement underlay spectrum sharing in cognitive radio networks (CRN). Considering this scenario, an improved joint subcarrier and bit allocation scheme for cognitive user with primary users` cooperation (PU Coop) in CRN is proposed. In this scheme, the optimization problem is formulated to minimize the average interference power level at the PU receiver via PU Coop, which guarantees a higher primary signal to interference plus noise ratio (SINR) while maintaining the secondary user total rate constraint. The joint optimal scheme is separated into subcarrier allocation and bit assignment in each subcarrier via arith-metric geo-metric (AM-GM) inequality with asymptotical optimization solution. Moreover, the joint subcarrier and bit optimization scheme, which is evaluated by the available SU subcarriers and the allocated bits, is analyzed in the proposed PU Coop model. The performance of cognitive spectral efficiency and the average interference power level are investigated. Numerical analysis indicates that the SU`s spectral efficiency increases significantly compared with the PU non-cooperation scenario. Moreover, the interference power level decreases dramatically for the proposed scheme compared with the traditional Hughes-Hartogs bit allocation scheme.