Optimal Strategies for Cooperative Spectrum Sensing in Multiple Cross-over Cognitive Radio Networks

( Hang Hu ),( Youyun Xu ),( Zhiwen Liu ),( Ning Li ),( Hang Zhang ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.12

To improve the sensing performance, cooperation among secondary users can be utilized to collect space diversity. In this paper, we focus on the optimization of cooperative spectrum sensing in which multiple cognitive users efficiently cooperate to achieve superior detection accuracy with minimum sensing error probability in multiple cross-over cognitive radio networks. The analysis focuses on two fusion strategies: soft information fusion and hard information fusion. Under soft information fusion, the optimal threshold of the energy detector is derived in both noncooperative single-user and cooperative multiuser sensing scenarios. Under hard information fusion, the optimal randomized rule and the optimal decision threshold are derived according to the rule of minimum sensing error (MSE). MSE rule shows better performance on improving the final false alarm and detection probability simultaneously. By simulations, our proposed strategy optimizes the sensing performance for each cognitive user which is randomly distributed in the multiple cross-over cognitive radio networks.

Power Allocation in Heterogeneous Networks: Limited Spectrum-Sensing Ability and Combined Protection

Yuehuai Ma,Youyun Xu,Dongmei Zhang 한국통신학회 2011 Journal of communications and networks Vol.13 No.4

In this paper, we investigate the problemof power alloca-tion in a heterogeneous network that is composed of a pair of cog-nitive users (CUs) and an infrastructure-based primary network. Since CUs have only limited effective spectrum-sensing ability and primary users (PUs) are not active all the time in all locations and licensed bands, we set up a new multi-area model to charac-terize the heterogeneous network. A novel combined interference-avoidance policy corresponding to different PU-appearance situ-ations is introduced to protect the primary network from unac-ceptable disturbance and to increase the spectrum secondary-reuse efficiency. We use dual decomposition to transform the original power allocation problem into a two-layer optimization problem. We propose a low-complexity joint power-optimizing method to maximize the transmission rate between CUs, taking into account both the individual power-transmission constraints and the com-bined interference power constraint of the PUs. Numerical results show that for various values of the system parameters, the pro-posed joint optimization method with combined PU protection is significantly better than the opportunistic spectrum access mode and other heuristic approaches.

Power Allocation in Heterogeneous Networks: Limited Spectrum-Sensing Ability and Combined Protection

Ma, Yuehuai,Xu, Youyun,Zhang, Dongmei The Korea Institute of Information and Commucation 2011 Journal of communications and networks Vol.13 No.4

In this paper, we investigate the problem of power allocation in a heterogeneous network that is composed of a pair of cognitive users (CUs) and an infrastructure-based primary network. Since CUs have only limited effective spectrum-sensing ability and primary users (PUs) are not active all the time in all locations and licensed bands, we set up a new multi-area model to characterize the heterogeneous network. A novel combined interference-avoidance policy corresponding to different PU-appearance situations is introduced to protect the primary network from unacceptable disturbance and to increase the spectrum secondary-reuse efficiency. We use dual decomposition to transform the original power allocation problem into a two-layer optimization problem. We propose a low-complexity joint power-optimizing method to maximize the transmission rate between CUs, taking into account both the individual power-transmission constraints and the combined interference power constraint of the PUs. Numerical results show that for various values of the system parameters, the proposed joint optimization method with combined PU protection is significantly better than the opportunistic spectrum access mode and other heuristic approaches.

Massive MIMO Full-Duplex Relaying with Hardware Impairments

Wei Xie,Xiaochen Xia,Youyun Xu,Kui Xu,YurongWang 한국통신학회 2017 Journal of communications and networks Vol.19 No.4

Massive multiple-input-multiple-output full-duplex relaying(MM-FDR), which exploits both the benefits of large-scaleantenna arrays and full-duplex transmission, is considered as apromising technology to achieve very high spectral efficiency inthe future wireless network. Despite the inevitable presence oftransceiver impairments due to the use of low-cost hardware components,most of the prior works on MM-FDR assume perfecttransceiver hardware which is unrealistic in practice. This paperinvestigates the impact of hardware impairments on the MM-FDR. Based on the recent experimental results, the effect of hardware impairmentsis modeled using transmit and receive distortion noises. The end-to-end achievable rate is derived and the scaling behaviorsof echo interference due to the full-duplex operation, multi-userinterference and effective distortions caused by hardware impairmentsare obtained. The scaling results show that the achievablerate of MM-FDR is limited by the hardware impairments at thesources and destinations, instead of that at the relay or other interferences,as the number of relay antenna tends to infinity. Alow-complexity power control scheme is proposed to further improvethe energy efficiency of MM-FDR with hardware impairments. Simulation results show that the proposed scheme can improvethe spectral-energy efficiency tradeoff significantly.

A Flexible Network Access Scheme for M2M Communications in Heterogeneous Wireless Networks

( Hui Tian ),( Wei Xie ),( Youyun Xu ),( Kui Xu ),( Peng Han ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.10

In this paper, we deal with the problem of M2M gateways` network selection for different types of M2M traffic in heterogeneous wireless networks. Based on the difference in traffic`s quality of service (QoS) requirements, the M2M traffic produced by various applications is mainly classified as two categories: flexible traffic and rigid traffic. Then, game theory is adopted to solve the problem of network-channel selection with the coexistence of flexible and rigid traffic, named as flexible network access (FNA). We prove the formulated discrete game is a potential game. The existence and feasibility of the Nash equilibrium (NE) of the proposed game are also analyzed. Then, an iterative algorithm based on optimal reaction criterion and a distributed algorithm with limited feedback based on learning automata are presented to obtain the NE of the proposed game. In simulations, the proposed iterative algorithm can achieve a near optimal sum utility of whole network with low complexity compared to the exhaustive search. In addition, the simulation results show that our proposed algorithms outperform existing methods in terms of sum utility and load balance.

A Comparative Study on Interference-Limited Two-Way Transmission Protocols

Xiaochen Xia,Dongmei Zhang,Kui Xu,Youyun Xu 한국통신학회 2016 Journal of communications and networks Vol.18 No.3

This paper investigates the performance of interferencelimitedtwo-way transmission protocols in the Rayleigh fadingchannels. New lower bound of outage probability and approximateexpression of bit error rate (BER) for three-phase two-way relaying(3P-TWR) protocol are derived in closed-form. These expressionsare valid for arbitrary signal-to-noise ratio values, numbersof co-channel interferers and amajority ofmodulation formats employedin the practical system. Then a comparative study is developedfor the performance of three two-way transmission protocols,i.e., direct transmission (DT) protocol, two-phase two-way relaying(2P-TWR) protocol and 3P-TWR protocol based on the asymptoticexpressions of outage probability and BER. On the basis of the theoreticalresults, the thresholds on the strength (variance) of directchannel and target rate for the relative performance of differentprotocols are obtained and the effect of interferences at the terminaland relay on the relative performance is analyzed. The resultspresent key insights on how to choose proper two-way transmissionprotocol with the knowledge of fading channels, required daterate and modulation format to optimize the system performance inthe practical interference-limited scenarios. Simulation results arepresented to validate the theoretical analysis.

Hybrid S-ALOHA/TDMA Protocol for LTE/LTE-A Networks with Coexistence of H2H and M2M Traffic

( Nannan Sui ),( Cong Wang ),( Wei Xie ),( Youyun Xu ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.2

The machine-to-machine (M2M) communication is featured by tremendous number of devices, small data transmission, and large uplink to downlink traffic ratio. The massive access requests generated by M2M devices would result in the current medium access control (MAC) protocol in LTE/LTE-A networks suffering from physical random access channel (PRACH) overload, high signaling overhead, and resource underutilization. As such, fairness should be carefully considered when M2M traffic coexists with human-to-human (H2H) traffic. To tackle these problems, we propose an adaptive Slotted ALOHA (S-ALOHA) and time division multiple access (TDMA) hybrid protocol. In particular, the proposed hybrid protocol divides the reserved uplink resource blocks (RBs) in a transmission cycle into the S-ALOHA part for M2M traffic with small-size packets and the TDMA part for H2H traffic with large-size packets. Adaptive resource allocation and access class barring (ACB) are exploited and optimized to maximize the channel utility with fairness constraint. Moreover, an upper performance bound for the proposed hybrid protocol is provided by performing the system equilibrium analysis. Simulation results demonstrate that, compared with pure S-ALOHA and pure TDMA protocol under a target fairness constraint of 0.9, our proposed hybrid protocol can improve the capacity by at least 9.44% when λ₁:λ ₂=1:1 and by at least 20.53% when λ₁: λ₂=10:1, where λ₁:λ₂ are traffic arrival rates of M2M and H2H traffic, respectively.