Effect of Outdated Channel Estimates on Multiple Antennas Multiple Relaying Networks

( Lei Wang ),( Yueming Cai ),( Weiwei Yang ),( Wei Yan ),( Jialei Song ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.5

In this paper, we propose an intergraded unified imperfect CSI model and investigate the joined effects of feedback delay and channel estimation errors (CEE) for two-hop relaying systems with transmit beamforming and relay selection. We derived closed-form expressions for important performance measures including the exact analysis and lower bounds of outage probability as well as error performance. The ergodic capacity is also included with closed-form results. Furthermore, diversity and coding gains based on the asymptotic analysis at high SNRs are also presented, which are simple and concise and provide new analytical insights into the corresponding power allocation scheme. The analysis indicates that delay effect results in the coding gain loss and the diversity order loss, while CEE will merely cause the coding gain loss. Numerical results verify the theoretical analysis and illustrate the system is more sensitive to transmit beamforming delay compared with relay selection delay and also verify the superiority of optimum power allocation. We further investigate the outage loss due to the CEE and feedback delays, which indicates that the effect of the CEE is more influential at low-to-medium SNR, and then it will hand over the dominate role to the feedback delay.

On the Performance of the Block-Based Selective OFDM Decode-and-Forward Relaying Scheme for 4G Mobile Communication Systems

Yang, Wendong,Cai, Yueming The Korea Institute of Information and Commucation 2011 Journal of communications and networks Vol.13 No.1

In this paper, we propose a block-based selective orthogonal frequency division multiplexing (OFDM) decode-and-forward relaying scheme for 4G mobile communication systems. In the scheme, an OFDM symbol is divided into blocks and one relay is selected for each block. Theoretical outage performance and error performance are analyzed and evaluated. A unified outage expression is given for our scheme and the other two schemes and the lower bound of the bit error rate of the three schemes is also obtained. The effect of the coherence bandwidth on the proposed scheme is also investigated. Monte Carlo simulations are carried out to validate our analysis. The scheme can obtain a good tradeoff between complexity and performance and can be used in future 4G mobile communication systems.

Increasing Secrecy Capacity via Joint Design of Cooperative Beamforming and Jamming

( Xinrong Guan ),( Yueming Cai ),( Weiwei Yang ),( Yunpeng Cheng ),( Junquan Hu ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.4

In this paper, we propose a hybrid cooperative scheme to improve the secrecy rate for a cooperative network in presence of multiple relays. Each relay node transmits the mixed signal consisting of weighted source signal and intentional noise. The problem of power allocation, the joint design of beamforming and jamming weights are investigated, and an iterative scheme is proposed. It is demonstrated by the numerical results that the proposed hybrid scheme further improves secrecy rate, as compared to traditional cooperative schemes.

On the Performance of the Block-Based Selective OFDM Decode-and-Forward Relaying Scheme for 4G Mobile Communication Systems

Wendong Yang,Yueming Cai 한국통신학회 2011 Journal of communications and networks Vol.13 No.1

In this paper, we propose a block-based selective orthogonal frequency divisionmultiplexing (OFDM) decode-and-forward relaying scheme for 4G mobile communication systems. In the scheme, an OFDM symbol is divided into blocks and one relay is selected for each block. Theoretical outage performance and error performance are analyzed and evaluated. A unified outage expression is given for our scheme and the other two schemes and the lower bound of the bit error rate of the three schemes is also obtained. The effect of the coherence bandwidth on the proposed scheme is also investigated. Monte Carlo simulations are carried out to validate our analysis. The scheme can obtain a good tradeoff between complexity and performance and can be used in future 4G mobile communication systems.

Joint Spectrum and Power Allocation for Green D2D Communication with Physical Layer Security Consideration

( Hualiang Chen ),( Yueming Cai ),( Dan Wu ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.3

In this paper, we consider cooperative D2D communications in cellular networks. More precisely, a cellular user leases part of its spectrum to facilitate the D2D communication with a goal of improving the energy efficiency of a D2D pair. However the D2D pair is untrusted to the cellular user, such resource sharing may result in the information of this cellular user unsecured. In order to motivate the cellular user`s generosity, this D2D pair needs to help the cellular user maintain a target secrecy rate. To address this issue, we formulate a joint spectrum and power allocation problem to maximize the energy efficiency of the D2D communication while guaranteeing the physical layer security of the cellular user. Then, a theorem is proved to indicate the best resource allocation strategy, and accordingly, an algorithm is proposed to find the best solution to this resource allocation problem. Numerical results are finally presented to verify the validity and effectiveness of the proposed algorithm.

Joint Mode Selection, Link Allocation and Power Control in Underlaying D2D Communication

( Wei Zhang ),( Wanbing He ),( Dan Wu ),( Yueming Cai ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.11

Device-to-device (D2D) communication underlaying cellular networks can bring significate benefits for improving the performance of mobile services. However, it hinges on elaborate resource sharing scheme to coordinate interference between cellular users and D2D pairs. We formulate a joint mode selection, link allocation and power control optimization problem for D2D communication sharing uplink resources in a multi-user cellular network and consider the efficiency and the fairness simultaneously. Due to the non-convex difficulty, we propose a three-step scheme: firstly, we conduct mode selection for D2D pairs based on a minimum distance metric after an admission control and obtain some cellular candidates for them. And then, a cellular candidate will be paired to each D2D pair based on fairness. Finally, we use Lagrangian Algorithm to formulate a joint power control strategy for D2D pairs and their reused cellular users and a closed-form of solution is derived. Simulation results demonstrate that our proposed algorithms converge in a short time. Moreover, both the sum rate of D2D pairs and the energy efficiency of cellular users are improved.

Energy-Efficient Secure Multiuser Scheduling in Energy Harvesting Untrusted Relay Networks

Dechuan Chen,Yunpeng Cheng,Xiangdong Wang,Weiwei Yang,Jianwei Hu,Yueming Cai 한국통신학회 2019 Journal of communications and networks Vol.21 No.4

In this paper, we investigate opportunistic secure multiuserscheduling in energy harvesting untrusted relay networks,where an energy-constrained amplify-and-forward (AF) relay harvestsenergy from the received radio frequency signal via usingthe power splitting protocol. To exploit the potential advantages(e.g., multiuser diversity and direct links) for secrecy improvement,we examine three opportunistic user scheduling schemes,i.e., optimal scheduling scheme, maximum scheduling scheme, andminimum scheduling scheme. Specifically, the optimal schedulingscheme performs user selection by maximizing the ratio betweenthe signal-to-noise-ratio (SNR) at the destination and the correspondingSNR at the untrusted relay. The maximum schedulingscheme is conventional user selection that maximizes the channelgain of the direct links. For the minimum scheduling scheme, wetry to reduce the overheard information at the untrusted relay byselecting the user with the lowest channel gain of the relay links. For these three schemes, we comprehensively examine the achievablesecrecy performance including probability of positive secrecyrate, secrecy outage probability (SOP), asymptotic SOP, secrecythroughput (ST), as well as secure energy efficiency (SEE) to helpfacilitate an energy-efficient secure transmission design. Simulationresults demonstrate that the maximum scheduling scheme outperformsthe minimum scheduling scheme in terms of SOP at relativelylow SNRs and target secrecy rates.

Social-Aware Collaborative Caching Based on User Preferences for D2D Content Sharing

( Can Zhang ),( Dan Wu ),( Liang Ao ),( Meng Wang ),( Yueming Cai ) 한국인터넷정보학회 2020 KSII Transactions on Internet and Information Syst Vol.14 No.3

With rapid growth of content demands, device-to-device (D2D) content sharing is exploited to effectively improve the service quality of users. Considering the limited storage space and various content demands of users, caching schemes are significant. However, most of them ignore the influence of the asynchronous content reuse and the selfishness of users. In this work, the user preferences are defined by exploiting the user-oriented content popularity and the current caching situation, and further, we propose the social-aware rate, which compre-hensively reflects the achievable contents download rate affected by the social ties, the caching indicators, and the user preferences. Guided by this, we model the collaborative caching problem by making a trade-off between the redundancy of caching contents and the cache hit ratio, with the goal of maximizing the sum of social-aware rate over the constraint of limited storage space. Due to its intractability, it is computationally reduced to the maximi-zation of a monotone submodular function, subject to a matroid constraint. Subsequently, two social-aware collaborative caching algorithms are designed by leveraging the standard and continuous greedy algorithms respectively, which are proved to achieve different approxima-tion ratios in unequal polynomial-time. We present the simulation results to illustratethe performance of our schemes.