面对第四代移动通信的思考

第三代移动通信发展之际,世界已开始关注第四代移动通信。本文回顾了移动通信的发展历程,探讨了第四代移动通信及其性能和系统网络结构及其关键技术,分析了4G面临的问题,介绍了世界及我国对4G的关注。

Physical layer design of wireless sensor network nodes

Major consideration dimensions for the physical layer design of wireless sensor network （WSN） nodes is analyzed by comparing different wireless communication approaches, diverse mature standards, important radio frequency （RF） parameters and various microcontroller unit （MCU） solutions. An implementation of the WSN node is presented with experimental results and a novel ＂one processor working at two frequencies＂ energy saving strategy. The lifetime estimation issue is analyzed with consideration to the periodical listen required by common WSN media access control （MAC） algorithms. It can be concluded that the startup time of the RF which determines the best sleep time ratio and the shortest backoff slot time of MAC, the RF frequency and modulation methods which determinate the RX and TX current, and the overall energy consumption of the dual frequency MCU SOC （ system on chip） are the most essential factors for the WSN node physical layer design.

Medium Access Control： A Physical Layer Network- Coded Approach

This paper investigates the medium access control （MAC） stratifies for communication systems. Since the signals are naturally superposed in public medium, we introduce physical layer network coding into MAC system and propose the physical layer network coded MAC （PNC-MAC） to utilize the collisions occurring in the MAC process. The implicit expressions of the throughput and average delay of the system operated with the new algorithm are derived in an iterative way. To show the performance of the algorithm, we compare the throughput and average delay induced by the new algorithm with current schemes via simulations. The results show that when operated with our proposed PNC-MAC, MAC system can achieve a larger throughput while the frames bear shorter average delay. Moreover, in many users case, the throughput increases slightly while the average delay ascends drastically.

Physical-layer security enhancement method for wireless HetNets via transmission pair scheduling

In order to enhance the physical-layer security of wireless transmission in a wireless heterogeneous network (HetNet), a two-stage-based cooperative framework is advocated. To be specific, a source-destination (SD) pair is opportunistically chosen at the beginning of the transmission slot, which can be used to assist the transmissions of other SD pairs. Under this framework, a transmit antenna selection assisted opportunistic SD pair scheduling (TAS-OSDS) scheme is proposed, and the intercept probability (IP) of the proposed TAS-OSDS, the conventional round-robin source-destination pair scheduling (RSDS) and the conventional non-cooperation (non-coop) schemes is also analyzed, where the RSDS and non-coop schemes are used for comparison with the proposed TAS-OSDS. Numerical results show that increasing the number of the SD pairs can effectively reduce the IP of the TAS-OSDS scheme, whereas the IP of the RSDS and the non-coop remain unchanged with an increasing number of the SD pairs. Furthermore, the TAS-OSDS scheme achieves a lower IP than that of the RSDS and the non-coop schemes, showing the superiority of the proposed TAS-OSDS.

Performance of Physical-Layer Network Coding in Asymmetric Two-Way Relay Channels

In this paper, we study the performance of physical-layer network coding in asymmetric two-way relay channels using four different cases having different poor channels:phase asymmetry, downlink asymmetry, uplink asymmetry and node asymmetry. The decision and mapping rule for symmetric and asymmetric cases are studied. The performance in terms of bit error rate for each case will be studied and analysed by computer simulation. Analytical and simulation results show that uplink asymmetry is the worst case;intra-phase asymmetry and unreliable uplink channels will more severely affect the performance degradation, which is caused by channel asymmetry.

Generalized Physical Layer Channel Model for RelayBased Super Dense Networks

The κ-μ fading model is an advanced channel model in super dense wireless networks.In this paper,we evaluate the performance of the system over κ-μ fading channel in super dense relay networks with consideration of multiple independent but not necessarily identically distributed(i.n.i.d.) cochannel interference(CCI) under interferencelimited environment.More specifically,we derive a useful and accurate cumulative distribution function(CDF) expression of the end-to-end signal-to-interference plus noise(SINR) ratio.Moreover,we derive novel analytical expressions of the outage probability(OP),average bit error probability(ABEP) and average capacity for binary modulation types and arbitrary positive values of κ-and μ of such system.Furthermore,we propose asymptotic analysis for both the OP and ABEP to give physical insights.A simplified analytical form for the ABEP at high-SNR regimes is provided as well.Finally,the accuracy of the derived expressions is well validated by Monte Carlo simulations.

Physical layer impairments tolerance based lightpath provision in software defined optical network

As all-optical networks grow with ever increasing ultra-high speed,the communication quality suffers seriously from physical layer impairments( PLIs). The same problem still exists in software defined optical network( SDON) controlled by OpenFlow. Aimed to solve this problem,a PLIs tolerance based lightpath provision scheme is proposed for OpenFlow controlled optical networks. This proposed approach not only takes the OSNR model to represent those linear PLIs factors,but also introduces those nonlinear factors into the OSNR model. Thus,the proposed scheme is able to cover most PLIs factors of each optical link and conduct optical lightpath provison with better communication quality. Moreover,PLIs tolerance model is also set up and considered in this work with some necessary extension to OpenFlow protocols to achieve better compatibility between physical layer impairments factors and various services connections. Simulation results show that the proposed scheme is able to get better performance in terms of packet loss rate and connection setup time.