Rate Allocation Scheme for Machine-to-Machine Service Based on 3GPP in Heterogeneous Wireless Networks

In this study,an explicit adaptive traffic allocation scheme for Machine-to-Machine(M2M)service is proposed to achieve optimum distribution in heterogeneous networks.Based on the characteristics of M2M services,the presented scheme is formulated as a convex optimization problem that maximises the utility of the M2M service,and then determines how to allocate the total rate among the multiple access networks.The analysis and numerical simulations indicate that the proposed scheme makes a significant improvement in performance compared with the traditional schemes.

The Full-Duplex Artificial Noise Scheme for Security of a Cellular System

This paper focuses on the problem of secure transmission in a cellular system. A full-duplex base station using artificial noise is adopted to improve both the uplink and downlink secrecy rate via pairing terminals which reverses the downlink and uplink of each other. We give the designs of artificial noise and the user's desired signal, and derive the pairing prin-ciple between terminals. Moreover, the influence of self-interference cancellation on secrecy rate is ex-plored. Simulation results show that the secrecy rate can get much better performance by adopting full-duplex artificial noise scheme and proposed pair-ing method. The downlink secrecy rate decreases with the distance between terminals. Besides the uplink secrecy rate is sensitive to the ability of self-interference cancellation.

Spot beam handover trigger and channel allocation scheme in GEO mobile satellite communication

An effective spot beam handover trigger and channel allocation scheme is proposed for GEO mobile satellite communication based on its characteristic and application. By using both signal strength and terminal location information, necessary handover is triggered promptly and accurately to reduce the negative effect of long signaling delay. Then handover decision is made with the handover queuing and channel allocation strategy. An adaptive channel resource allocation scheme is considered to optimize resource utilization with guarantee of emergency communication, which is significant for emergency rescue and disaster relief. Simulation results show that the proposed scheme prevents unnecessary handover effectively and has favorable adaptability to emergent requirement of satellite communication.

Spectrum Allocation and Performance Analysis for Backhauling of UAV Assisted Cellular Network

To reinforce the coverage and QoS(quality of service) of on-ground cellular communication system, unmanned aerial vehicles which are carrying small cells are deployed in some emergency and disaster areas. Although ASCs(aerial small cells) can provide a higher probability of LoS(line-of-sight) transmission, the wireless backhaul link will bring extra interference to the whole system if not well designed. Therefore, in this paper, we study the backhaul scheme for UAV-assist cellular network. We first analyze the interference environments of UAV-assist cellular network considering the IBOG(In-Band to On-Ground), OBOG(Out-of-Band to On-Ground) and IBTU(In-Band to Tethered-UAV) backhauling mode, and give the descriptions of the performance metrics for each mode. Then, the considered problem is formulated as an optimization of achievable rate. We derive the optimal solutions for the involved three backhauling modes for ASCs respectively, and closed-form optimal value for each mode is acquired with proof. We also give a pseudo-code form of our proposed optimal access/backhaul spectrum allocation algorithm. The simulation results indicate that the proposed scheme can deliver a significant gain, while IBTU performs best among proposed backhauling modes.

Propagation characteristics of wideband high-speed railway channel in viaduct scenario at 2.35 GHz

In order to obtain accurate characteristics of wireless channels in the viaduct area of China, a channel meas- urement was taken in a railway viaduct scenario of the Zhengzhou-Xi＇an passenger dedicated line with a bandwidth of 50 MHz at 2.35 GHz. The single-slope log-distance model is used to analyze the path-loss （PL）, and the distribution of shadow fading （SF） is obtained by statistical methods, which shows that the normal distribution fits the samples well. Ricean K-factor is analyzed by the method of moments, and the variation of K-factor is given along the measured route. Small scale such as delay spread and Doppler behavior are parameterized. Based on empirical channel measurement, this paper provides parameters for the evaluation and simulation work on viaduct scenarios of high-speed railway.

A Virtual TDOA Localization Scheme of Chinese DTMB Signal in Radio Monitoring Networks

As the radio communications technology widely used,wireless location technology plays a more important role in maintaining the order of the air waves.However concretely effective symbol calibration method with regard to Chinese DTMB signal of different frame mode is quite under research due to the multiple structure of DTMB signal.In this paper,we propose a Time Difference of Arrival(TDOA)-based passive location scheme using least square principle.Utilizing the large number of anchor nodes in wireless monitoring network,a novel algorithm is formulated to solve the None-LineOf-Sight problem.The derived Cramer Rao Lower Bound of the localization method guides to the accuracy of the position outcome with regards to the calibration precision.In contrast with traditional multi-terminal location schemes,our location scheme can reduce calculation complexity and location costs abruptly.A twostep NLOS identification algorithm is proposed.Computer simulation is employed to verify the well performance of the calibration method of3-4 dB superiority than normal method and also the whole localization scheme for less than 50 meters through channel of SNR lower than dB.Simulation also shows that our algorithm can effectively identify NLOS path and improve positioning accuracy.

Space-Time Correlation Based Fast Regional Spectrum Sensing in Cognitive Radio

In this paper,a space-time correlation based fast regional spectrum sensing(RSS)scheme is proposed to reduce the time and energy consumption of traditional spatial spectrum sensing. The target region is divided into small meshes,and all meshes are clustered into highly related groups using the spatial correlation among them. In each group,some representative meshes are selected as detecting meshes(DMs)using a multi-center mesh(MCM)clustering algorithm,while other meshes(EMs)are estimated according to their correlations with DMs and the Markov modeled dependence on history by MAP principle. Thus,detecting fewer meshes saves the sensing consumption. Since two independent estimation processes may provide contradictory results,minimum entropy principle is adopted to merge the results. Tested with data acquired by radio environment mapping measurement conducted in the downtown Beijing,our scheme is capable to reduce the consumption of traditional sensing method with acceptable sensing performance.

Resource Allocation for Two-Way Amplify and Forward OFDM Relay Networks

Physical-layer network coding(PNC) promises substantial theoretical gain to achieve the maximum system throughput in cooperative relay transmission. However, with the increasing global warming, how to reduce power consumption while satisfy system throughput requirement is becoming a vital issue. In this paper, we investigate energy-efficiency resource allocation(RA) based on PNC with amplify-and-forward(AF) protocol in orthogonal frequency division multiple(OFDM) bidirectional transmission. To minimize the overall transmit power consumption with required system throughput requirement, we consider joint subcarriers and power allocation and formulate the objective task into a constrained optimization problem where the best relay node is selected to minimize total transmit power. The closed form optimization power allocation solutions are acquired by analytical derivation. Based on derivation, we propose a novel optimal energy-efficient power allocation(OE-PA). Numerical results are given to evaluate the performance of the derived scheme as compared to other schemes and show that our scheme has signifi cant improvement to energy saving.

On Measuring the Privacy of Anonymized Data in Multiparty Network Data Sharing

This paper aims to find a practical way of quantitatively representing the privacy of network data. A method of quantifying the privacy of network data anonymization based on similarity distance and entropy in the scenario involving multiparty network data sharing with Trusted Third Party (TTP) is proposed. Simulations are then conducted using network data from different sources, and show that the measurement indicators defined in this paper can adequately quantify the privacy of the network. In particular, it can indicate the effect of the auxiliary information of the adversary on privacy.

Power Ramping Schemes for M2M and H2H Co-existing Scenario

To analyze and reduce the impact of Machine-to-Machine (M2M) Devices (MDs) on the traditional Human-to-Human (H2H) users for the blending scenario, where both M2M and H2H services coexist in the current Universal Mobile Telecommunication System (UMTS) and perform the Random Access (RA) procedure simultaneously, a comprehensive RA analysis model of RA is proposed in this paper. Further, a power ramping strategy based on the logarithm for M2M is proposed. The efficiency of both the existing and proposed scheme is assessed through a simulation across several metrics, including average target power, throughput, blocking probability, and delay statistics. Numerical results show that the proposed algorithm can ensure a minimal impact on H2H communication while maintaining the throughput of the M2M communication. Meanwhile, because of its low energy consumption, this algorithm has a significant guide value for real-world applications.

Dynamic Random Access Channel Allocation Scheme Based on the Pseudo-Bayesian Algorithm in OFDMA System

Random Access Channel （RACH） is an uplink contention-based transport channel usually used for initial channel access, bandwidth request, etc. How to use RACH resources effectively is very important in wireless corrnunication systel In this paper, a dynamical RACH allocation scheme is proposed for Orthogonal Frequency-Division Multiple Access （OFDMA） systen. Based on the PseudoBayesian algorithm, this mechanism predicts the number of RACHs for the next frame according to the current load. A new dynamic RACH assignment algorithm and an adaptive access probability method are adopted by the proposed scheme to irrprove the utilization ratio of RACH resources and increase the successful access rate. Numerical simulation shows that the proposed strategy achieves both improvement in the utilization ratio of RACHs and reduction in the access delay compared with other RACH allocation schemes.

Ergodic Capacity Analysis and Adaptive Transsmion Scheme in Multi-user Distributed Antenna Systems

This paper focuses on analyzing the ergodic capacity performance of limited feedback (LFB) beamforming in multi-user distributed antenna system (DAS). In such a system, multi-user interference (MUI) is inevitably due to the channel uncertainties caused by quantization error. Considering this, we propose a parameter named effective ergodic capacity rate (EECR), which denotes the capacity offset between finite rate feedback and perfect channel state information (CSI). The simulation results show that the derived approximated EECR is very tight to actual EECR. Based on the approximated EECR, an adaptive minimum bit feedback scheme is proposed, which can effectively reduce the overhead of feedback channel and the complexity of the system. The simulation results verify the effectiveness of the proposed scheme.

Spatial channel characteristics in the outdoor hotspot environment based on wideband MIMO measurements

Wideband multiple-input multiple-output (MIMO) channel measurements were performed at5.25GHz in the hotspot environment in Beijing.The propagation mechanism was line-of-sight and ob-structed-line-of-sight (LOS/OLOS) in the outdoor scenario.Using a large amount of estimated angle ofdeparture (AoD) and angle of arrival (AoA) results,the cumulative distribution functions (CDFs) of di-rectional spread (DS) are extracted,which illustrate that the spatial dispersion is quite significant at bothends due to the low antenna height of base station and rich scatterers.The average power azimuth spec-trum (PAS) is found to be well fitted with a Laplacian function.In addition,the non-isotropic property ofspatial correlation is investigated,and the average envelop correlation over arbitrary antenna spacing pro-vides the correlation distance to facilitate the MIMO optimization and deployment in the outdoor hotspotenvironment.

Capacity evaluation of the backhaul link in the outdoor relay system at 2.35GHz

A measurement campaign has been conducted at 2.35 GHz with a bandwidth of 50 MHz to ob- tain the statistics and evaluate the capacity of the backhaul link. Based on the measured channel im- pulse response, the channel gain, the eigenvalue statistics and the capacity are investigated. The distribution and corresponding parameters for describing the eigenvalue dispersion, the maximum and minimum eigenvalues are given. It is found that the backhaul link is relatively stable, which shows small variance of the channel gain. In spite of the fact that there are not many scatterers in the backhaul link, the channel rank can be enhanced by using dual-polarized antennas. Thus, the backhaul link can provide enough capacity.

Handover Mechanism in Coordinated Multi-Point Transmission/Reception System

Coordinated Multi-Point （CoMP） transmission/reception technology has been the focus of much attention recently and has becom a key research interest in 3GPP LTE-Advanced due to its ability to improve both cell-edge and average system performance. However, CoMP technology requires brand-new handover mechanism, or else its real performance will be limited. This paper proposes a novel handover mechanism supporting CoMP based on the handover scenario in CoMP communication system architecture, including information sharing and signaling transmission procedure of CoMP cooperating sets handover and CoMP transmission points selection/update. The proposed scheme could not only support CoMP well, but also reduce the overhead of information exchange and signaling transmission.

Intelligent and efficient development of wireless networks:A review of cognitive radio networks

Facing the challenges on how to improve spectrum efficiency and how to realize heterogeneous network convergence in future wireless networks,a cognitive radio network(CRN) is proposed as one of the solutions.This has become a major research topic in recent years and it is timely to give an overview of the development of CRN and to summarize key issues and technologies.The fundamental concepts of CRN,including the cognitive cycle model,the network architecture,and the cognitive ability and intelligent decision functions,are introduced in detail based on recent advances.Key issues for each topic,followed with recent research on theory and method,are then classified and the industrialization developments of CRN testbeds based on TD-LTE cellular system and standards are briefly presented.Finally,conclusions are reached on the perspectives and directions of future development.

Reconfiguration decision making in cognitive wireless network

Facing the challenges of dynamic adaptation capabilities in the time-varying environment of cognitive wireless networks(CWNs),we introduce reconfiguration capabilities that flexibly and dynamically adapt to changing wireless environments and service requirements.As an essential characteristic of CWNs,the cognitive reconfiguration can meet user requirements,realize interoperability between heterogeneous networks,make full use of radio resources and adapt to time-varying environments to achieve end-to-end requirements.However,the reconfiguration implementation is still challenging due to the need for complex environment cognition,multi-objective optimization,autonomic decision-making and end-to-end requirement extraction.As an intelligent technology for solving complex issues,we apply adaptive neuro-fuzzy inference system(ANFIS) techniques in this paper to address these challenges in cognitive reconfiguration for self-learning and optimal decision making based on multi-domain cognition results.Moreover,this paper designs a generic ANFIS cognitive reconfiguration system including three functional entities,which are the context management module,multi-domain database and ANFIS optimization module.Finally,numerous results prove the effective performance improvements of the ANFIS based reconfiguration solution in CWN for global end-to-end goals.

Robust multi-path routing for dynamic topology in wireless sensor networks

Wirreless sensor networks are being widely researched and are expected to be used in several scenarios. On the leading edge of treads, on-demand, high-reliability, and low-latency routing protocol is desirable for indoor environment applications. This article proposes a routing scheme called robust multi-path routing that establishes and uses multiple node-disjoint routes. Providing multiple routes helps to reduce the route recovery process and control the message overhead. The performance comparison of this protocol with dynamic source routing （DSR） by OPNET simulations shows that this protocol is able to achieve a remarkable improvement in the packet delivery ratio and average end-to-end delay.

Cognitive information metrics for cognitive wireless networks

Considering the dynamic changes and uncertainty features of the radio environment in cognitive wireless networks(CWNs),the environment cognition ability is critical for the performance evaluation of CWNs design and optimization.However,there are no effective metrics to evaluate the ability and gain of information cognition in CWNs from an information theory perspective.Therefore,the novel cognitive information concept is proposed and defined as a metric to evaluate the uncertainty of both the internal and external environments of one system that can be removed by other systems or nodes using cognitive radio techniques.As an intelligent wireless communication system that is aware of its surrounding radio,network,and user multi-domains environment,the more cognitive information it achieves,the higher level cognitive capability it is.In this paper,we define and analyze the mathematical features of cognitive information.Results reveal that the increase of cognitive information can improve the spectrum efficiency and reduce the interference probability simultaneously in CWNs.Thus cognitive information can be regarded as a metric for CWNs optimization.Finally,we apply the theory of cognitive information in the parameters optimization in energy detection and cooperative spectrum sensing.

Design of coordinator to eliminate redundant local retransmission in wireless networks

Owing to limited bandwidth, high bit error rate, and bursty error in the wireless environment, the performance of the transmission control protocol （TCP） degrades greatly in wireless networks. Up to now, many researchers have contributed greatly to the wireless TCP field. However, in most of their works, the wireless TCP module usually works in the TCP layer and has no idea of the actual time of the packet transmission, which is determined by the Scheduler in the media access control （MAC） layer, and this will bring the inaccuracy to the local retransmission fimeout and induce the redundant local retransmission. In this article, a coordinator is introduced into the base-station （BS）, which can provide efficient cooperation between the TCP module and the scheduler module. On the bais of the performance analysis and simulation results, the proposed method is shown to eliminate redundant local retransmission, increase throughput, and improve TCP-level fairness in wireless networks. Moreover, this scheme is orthogonal to those existing wireless TCP schemes, thus it can give great compatibility to the current networks, and further enhance the performance of TCP under the condition that the performance improvement benefiting from the existing approaches will not be affected.