Turbo码在无线图像传输系统中的应用

通过Matlab仿真,信源编码采用矢量量化法,对静止图像通过无线瑞利(Rayleigh)衰落信道传输时,不采用信道编码和采用Turbo码作为信道编码两种情况进行了研究。依据失真度的主观评价,对两种情况下重构的图像进行了比较和分析。结果表明,Turbo码具有很强的抗衰落和抗多径效应能力,它不仅有效地提高了无线图像传输的可靠性,而且大大节省了系统发射功率。

FULL-DUPLEX WIRELESS COMMUNICATIONS

Just as Dickens wrote,it is the best of times,it is the worst of times.Ever increasing traffic demands will bring us into the era of 5G.Vast of unprecedented or even unanticipated fancy wireless applications will definitely change our life.Regarding the beautiful visions promised by 5G,meanwhile the wireless engineers are faced with unprecedented challenges and pressures for realizing much higher spectrum efficiency and

Semi-blind Adaptive Beamforming for High-throughput Quadrature Amplitude Modulation Systems

A semi-blind adaptive beamforming scheme is proposed for wireless systems that employ high-throughput quadrature amplitude modulation signalling. A minimum number of training symbols, equal to the number of receiver antenna arrayts elements, are first utilised to provide a rough initial least squares estimate of the beamformer＇s weight vector. A concurrent constant modulus algorithm and soft decision-directed scheme is then applied to adapt the beamformer. This semi-blind adaptive beamforming scheme is capable of converging fast to the minimum mean-square-error beamforming solution, as demonstrated in our simulation study.

Power Versus Bandwidth Efficiency in Wireless Communications:from Economic Sustainability to Green Radio

We carry out a comprehensive analysis of a range of wireless network efficiency considerations. Firstly, we explore the properties and the implications of the power-versus bandwidth-efficiency criteria. Secondly, we perform a detailed top-down analysis of a typical commercial wireless network, which emphasizes the inherent differences between the aforementioned two efficiency metrics, while demonstrating that the appropriate choice of the network optimization criterion can have a profound effect on the overall network performance. Finally, we address the issue of resource management and its impact on the definition of the overall system efficiency. Our results suggest that no substantial area spectral efficiency gains beyond those exhibited by the 2G cellular technol- ogy may be economically achieved, and hence, no significant economic gains may be realized by simply increasing the bps/Hz bandwidth efficiency. In contrast, manifold utility and throughput gains as well as substantial Quality of Service enhancements may be attained by the appropriate combination of improved power efficiency, bandwidth expansion as well as the appropriate evolution of the networking paradigm.

Petahertz communication:Harmonizing optical spectra for wireless communications

With the rapid deployment of Next-Generation Networks(NGN),the research community has initiated discussions on an entirely new suite of optical enabling techniques.To pave the way for the development of future wireless networks,this article aims to unify the existing infrared,visible light,and ultraviolet subbands while also exploring the potential of the Petahertz(PHz)band to support extremely bandwidth-thirsfy telepresence style applications.Our focus is on the emerging Petahertz Communication(PetaCom)framework,scenario-dependent propagation channels,modulation schemes,system performance,multiple access techniques,and networking.We conclude with a range of PetaCom challenges and open research issues.

Mobile Social Networking Aided Content Dissemination in Heterogeneous Networks

Since more and more mobile applications are based on the proliferation of social information, the study of Mobile Social Networks （MSNs） combines social sciences and wireless communications. Operating wireless networks more efficiently by exploiting social relationships between MSN users is an appealing but challenging option for network operators. An MSN-aided content dissemination technique is presented as a potential extension of conventional cellular wireless networks in order to satisfy growing data traffic. By allowing the MSN users to create a self-organized ad hoc network for spontaneously disseminating contents, the network operator may be able to reduce the operational costs and simultaneously achieve an improved network performance. In this paper, we first summarize the basic features of the MSN architecture, followed by a survey of the factors which may affect MSN-aided content dissemination. Using a case study, we demonstrate that one can save resources of the Base Station （BS） while substantially lowering content dissemination delay. Finally, other potential applications of MSN-aided content dissemination are introduced, and a range of lustre challenges are summarized.

Blind Joint Maximum Likelihood Channel Estimation and Data Detection for SIMO Systems

A blind adaptive scheme is proposed for joint maximum likelihood （ML） channel estimation and data detection of singleinput multiple-output （SIMO） systems. The joint ML optimisation over channel and data is decomposed into an iterative optimisation loop. An efficient global optimisation algorithm called the repeated weighted boosting search is employed at the upper level to optimally identify the unknown SIMO channel model, and the Viterbi algorithm is used at the lower level to produce the maximum likelihood sequence estimation of the unknown data sequence. A simulation example is used to demonstrate the effectiveness of this joint ML optimisation scheme for blind adaptive SIMO systems.

Measurement-device-independent quantum secure direct communication

Quantum secure direct communication(QSDC)is a unique technique,which supports the secure transmission of confidential information directly through a quantum channel without the need for a secret key and for ciphertext.Hence this secure communication protocol fundamentally differs from its conventional counterparts.In this article,we report the first measurement-deviceindependent(MDI)QSDC protocol relying on sequences of entangled photon pairs and single photons.Explicitly,it eliminates the security loopholes associated with the measurement device.Additionally,this MDI technique is capable of doubling the communication distance of its conventional counterpart operating without using our MDI technique.We also conceive a protocol associated with linear optical Bell-basis measurements,where only two of the four Bell-basis states could be measured.When the number of qubits in a sequence reduces to 1,the MDI-QSDC protocol degenerates to a deterministic MDI quantum key distribution protocol.

Power optimization for multiple QoS,delay,and BER classes relying on nite-delay information theory

Future communication systems will include di erent types of messages requiring di erent transmission rates,packet lengths,and service qualities.We address the power-optimization issues of communication systems conveying multiple message types based on nite-delay information theory.Given both the normalized transmission rate and the packet length of a system,the actual residual decoding error rate is a function of the transmission power.We propose a generalized power allocation framework for multiple message types.Two di erent optimization cost functions are adopted:the number of service-quality violations encountered and the sum log ratio of the residual decoding error rate.We provide the optimal analytical solution for the former cost function and a heuristic solution based on a genetic algorithm for the latter one.Finally,the performance of the proposed solutions are evaluated numerically.