Performance of Voice/Data Integration on a TDM System

Data queueing is of primary concern in a voice/data integrated TDM system. The data queueing model is represented in the discrete-time domain with multiple servers and voice is given a higher priority than data. The data arrival process is assumed to be Poisson and the voice arrival process is characterized by a Markov chain. The correlation coefficient of the number of on voice calls between consecutive frames is used to measure the correlation behavior of the voice process. While the generating function approach may be used to analyze the queueing process, it involves the evaluation of a large number of boundary terms. On the assumption that the voice traffic consists ofNi.i.d. two-state Markov chains, we derive a simple expression for the mean queue size as a function of two variables in the form of the traffic departure processes. The results clearly reveal a significant influence of the correlation coefficient on the data queueing process. Then, an approximate analysis based on the departure processes is introduced. The numerical and simulation results indicate that this approximate approach yields reasonably accurate results.     

Inmarsat-M系统数据信道性能分析

Inmarsat是著名的卫星移动通信系统,提供全球范围的卫星移动通信。介绍了InmarsatM系统,分析了其组成和工作原理,并通过针对性试验获得InmarsatM数据业务信道的有关性能,分析了影响其信道特性的有关因素。最后说明了对其他Inmarsat系统统计实验工作的现实意义。     

Performance Analysis of Fair Channel Sharing Policies in an Integrated Cellular Voice/Data Network

We study channel sharing in an integrated cellular voice/data network with a finite queue for data call requests that cannot be served immediately upon arrival. Using analytical techniques, a comparison of different fair channel sharing policies is made. As a main result, a closed-form expression is derived for the expected sojourn time (waiting time plus transfer time) of a data call, conditional on its size, indicating that the sojourn time is proportional to the call size. This attractive proportionality result establishes an additional fairness property for the channel sharing policies proposed in the paper. Additionally, as a valuable intermediate result, the conditional expected sojourn time of an admitted data call is obtained, given the system state at arrival, which may serve as an appreciated feedback information service to the data source. An extensive numerical study is included to compare the proposed policies and to obtain insight in the performance effects of the various system and policy parameters.     

On Handoff Performance for an Integrated Voice/Data Cellular System

One of the key challenges in the design of bandwidth allocation policies for a multi-services mobile cellular network is to guarantee the potentially different Quality of Service (QoS) requirement from diverse applications, while at the same to ensure that the scarce bandwidth be utilized efficiently. Complete Sharing (CS) and Dynamic Partition (DP) schemes have been shown as viable techniques for managing the bandwidth. However, there has been no study that compares their respective performance, which is the focus of this paper. Specifically, in this paper, through both analysis and simulation, we demonstrate that both schemes can achieve comparable performance by proper manipulation of control parameters. The tradeoff is that DP scheme can more easily achieve the target QoS requirement, at the expense of some over-provisioning, thus can potentially lead to less channel efficiency when comparing to a CS based scheme.     

Performance Analysis of Privacy Protection System During Data Transfer in MANETs

The openness of a Mobile Adhoc network (MANET) makes it vulnerable to various attacks that can breach privacy, and this demands a privacy protection system. In this paper, we propose a privacy protection system with flexible and adaptable policies to protect privacy during data transfer based on application and context attributes. We also provide the performance analysis model to test the suitability of policies for maintaining privacy, which is essential for the real-time implementation of this system in a resource-limited MANET. Finally, the proposed privacy protection system is compared with previous works using simulations, and the results obtained show the effectiveness of the proposed privacy protection system.     

改进的传输参考型超宽带系统抗NBI性能

为研究带有有限长脉冲响应陷波滤波器(NF)的传输参考型超宽带系统(TR-UWB)的抗窄带干扰性能,在IEEE 802.15.3a建议的标准超宽带信道下,分析比较了在不同参数设置下,该系统自相关接收机的误比特性能。仿真结果表明,带有陷波滤波器的传输参考型超宽带系统能够有效降低窄带干扰,并且系统接收机结构简单,无需信道估计,大大降低了计算量和系统复杂度。     

Performance of a Multi-hop UWB Transmitted Reference System using Decode-and-Forward Relays

In this paper, end-to-end average bit error rate (ABER) of a multi-hop decode-and-forward relay system is evaluated using ultra-wideband transmitted reference (TR) receiver over a multi-path fading channel. Distribution of individual hop signal to noise ratio (SNR) is approximated by a log-normal distribution and corresponding ABER is evaluated by Gauss-Hermite Quadrature rule. These individual hop ABERs are then used to find the end-to-end ABER performance analytically which is faster than the simulation method available in the literatures. Performances of three variants of non-coherent TR receivers: simple transmitted reference, average transmitted reference and differential transmitted reference (DTR) receivers are compared assuming same total transmit power for a fixed end-to-end distance in line-of-sight (LOS) and non line-of-sight (NLOS) channel model. It is observed that the end-to-end ABER performance using DTR receivers is the best and multi-hop relaying is also most effective using these receivers to improve the performance. It is also found that the laws of diminishing returns hold for performance gain in average transmit SNR per bit at a particular ABER in LOS channel i.e. performance improvement in terms of transmit SNR is not equal as the number of hop increases. It decreases with increase in hop number but the reverse trend can be found in NLOS channel.     

Voice/Data Integrated Wireless Channel Access in Third Generation Digital Cellular Networks: The Performance of Bursty Data Generated by Interactive Applications

Mobile wireless communications, which includecellular telephones, land mobile radio, and personalcommunications systems, have experienced enormous growthover the last decade. Data services represent a critical component of future wirelesscommunications, but have received little attention sofar. While some attention has been given to specializedmobile data networks, less has been directed at the ongoing design of data services in evolvingthird generation digital cellular wireless networks. Inthis work we present the results of a simulation studythat explores the performance of a Reservation Random Access (RRA) scheme for transmittingdata packets over a common radio broadcast channel in acellular radio environment. In addition to voicetraffic, we consider data packet traffic generated by interactive applications. It is expected thatsuch applications will be very important in thirdgeneration wireless access mobile communication systems.Through an extensive simulation study of the data message delay distribution, we show that theproposed RRA scheme, originally designed under thePoisson data message arrival process assumption, canalso efficiently operate and be optimized under theextremely bursty data message arrival processcharacterized by independent, identically distributed,Pareto message interarrival times.     

Data Performance in Burst Switching When the Voice Silence Periods Have a Hyperexponential Distribution

The performance of data in burst switching has been analyzed in previous work with a fluid approximation of the data traffic. This study extends the previous model to the case where the silence interval between talkspurts has a hyperexponential, rather than an exponential, distribution. It is shown that data performance is extremely sensitive to the variance of the silence interval, and that, for empirical talkspurt and silence distributions, this model provides a vast improvement on models which assume that both types of intervals are exponentially distributed.     

cdma 1x话音和数据用户并发条件下的无线信道容量的计算

本文对cdma 1x系统前反向容量的计算进行了研究，着重对前向功率对信道容量的影响进行了剖析，希望能给引入数据业务后对无线网络容量的影响机制有一个清楚地认识，以便能为cdma 1x无线网络的规划和设计更适应当前话音和数据混合并用的cdma 1x Re1．0的无线网络现状提供有益的帮助。     

多径衰落信道下MC-CDMA系统性能分析

该文提出了一种改进的MC-CDMA方案,该方案取发射的符号周期为切普周期的整数倍,允许各子载波经历多径衰落信道,消除了原方案对切普周期和符号周期的限制,并在接收端可对多径信号进行分离。推导出了在多径衰落信道下改进方案的误码率(BER)表达式,并通过计算机仿真进行了验证。与典型的MC-CDMA方案相比,改进的方案不但又获得了多径分集增益,还使系统的性能得到了显著的改善。     

双正交多码CDMA系统在衰落信道的性能分析

在直接序列扩频通信（ＤＳ／ＣＤＭＡ）系统中,为了有效地实现用户高数据率的传输,以适应宽带ＣＤＭＡ技术发展的要求,本文提出了一种双正交多码ＣＤＭＡ系统（称为ＢＭＣ－ＣＤＭＡ）。相似于多载波调制,传输的高数据泫首先进行串－并转换,然后对变换后的低数据流用双正交码进行扩频调制。不同于多载波调制,各支路扩频信号用同一载波进行调制。并对此系统在衰落信道性能进行了计算,还对数值结果进行了分析。     

Power Control Using Two-Level Channel Inversion for Data Traffic in a Cellular CDMA System: Performance and Optimal Design

In this paper, we propose and analyze a simple adaptive uplink power control scheme, called two-level channel inversion, for data traffic in a cellular CDMA system. The basic idea is to reduce out-cell interference by reducing the rate of, or even suspending, transmission when the wireless channel is in a bad condition. We first describe the scheme in detail, and then present a probabilistic analysis model for evaluating the system performance. With this model, we determine the queueing delay and system throughput. Numerical results show that in comparison with the traditional channel inversion scheme, the two-level channel inversion scheme can substantially improve system throughput at a moderate cost of extra queueing delay. Finally, we present a design algorithm to optimize the overall performance while maintaining each user's quality of service (QoS).     

QUACS: Routing Data Packets in Ad Hoc Networks on Buffer-Constrained Load Balancing Conditions During Emergency Rescue Crisis

Mobile wireless networks have been gaining popularity since the turn of the new millennium as they enable communication to take place without fixed communication infrastructure. This form of communication, which has been made possible by radio links proved its usefulness during emergency medical rescues such as an Ebola pandemic, battlefield communications or other emergency situations, where quick communication is of paramount importance. Nature-inspired algorithms such as AntHocNet, AntSense, among other ant inspired techniques, have been mimicked in solving the communication challenges in wireless networks, but they focus mostly on the ‘next-hop’ in determining routing of data packets from the source to the destination, which tends to suffer from congestion-related problems. Ant routing methods focus more on next-hop neighbours when choosing the shortest path which might have many data packets and are prone to congestion. Focusing on the next-hop neighbours poses a challenge of having other nodes that end up being congested. This problem of routes being heavily used, often decreases throughput rates, leading to the proposed Queuing Ant Colony System (QUACS) which is a bio-inspired, complementing the queuing optimisation approach in routing of data packets across the network. The results of simulations show that QUACS performs better in throughput, packet delivery ratio, end-to-end delay and communication overhead than other ant routing algorithms. This study is particularly beneficial in the ad hoc networks where the QUACS routing method can greatly assist in faster communication and evacuation in emergency for treatment of patients during emergency medical rescue operations.     

The Capacity Performance of ASTC-MIMO-OFDM System in a Correlated Rayleigh Frequency-Selective Channel

Algebraic Space-Time Codes (ASTC) for Multiple Input Multiple Output (MIMO) systems are based on quaternion algebras. Thanks to their algebraic construction, the ASTC codes are full-rank, full-rate and have the non-vanishing determinant property. These codes have been proposed for MIMO flat fading channels in order to increase the spectral efficiency and to maximize the coding gain. The purpose of this work is to analyze the performance of the ASTC in a frequency selective Rayleigh channel. To deal with the frequency selectivity, we use the OFDM modulation. The capacity performances of an ASTC-MIMO-OFDM system, under correlated Rayleigh frequency-selective channel, have been evaluated.     

一种并行数据传输系统的性能分析

并行正交调幅数据传输系统利用很多相互重叠的子信道,能够使得总的信号速率非常接近给定频带的奈奎斯特速率。文中首先对并行数据传输系统进行了描述,然后,在存在相位偏移和延迟失真的情况下,对系统的性能进行了分析。结果表明总失真与子信道数目的平方成反比,从而说明了并行传输系统具有抵抗延迟失真的作用。此外,通过改变解调相位,还可大大改善并行系统的性能。     

Voice Communication System Performance in the Presence of Automotive Ignition Noise

This paper reports on recent measurements of voice system performance in a controlled automotive ignition noise environment. At a quiet measurement site in the vicinity of Tucson, AZ, various combinations of from 1 to 12 vehicles of various ages, types, and manufacture were used to provide impulsive interference to four-voice communication system types. These systems were SSB at 23 MHz, with a 10-kHz bandwidth, FM at 75 MHz with a 30-kHz bandwidth, AM at 300 MHz with a 30-kHz bandwidth, and a FM/ PCM system at 900 MHz with a 300-kHz bandwidth. The statistical characterisitcs ( amplitude probability distribution of the received noise envelope and the average crossing-rate characteristics) of the interference were measured simultaneously with the system performance. Two methods were used to measure system performance. An objective measurement using instrumentation termed voice intelligibility analysis system ( VIAS) was used which produces an intelligibility measure called articulation index ( Al). In addition, a subjective method was used employing phonetically balanced word lists and a highly trained listener panel to obtain the articulation score ( AS). One object of the measurements was to ascertain if a relationship exits between Al and AS for impulsive noise, and, indeed, quite good correlation was obtained for all four systems. The results of the system performance measurements and associated results are presented and discussed in detail in this paper.     

无线城域网接入系统信道估计方法性能分析

从无线城域网IEEE802.16d协议和OFDM技术出发,首先分析IEEE802.16d协议规定的两种导频结构,并从理论上对这两种导频结构在不同城域网信道模型中的适用性进行研究,然后分别在两种导频结构的辅助下仿真分析相关信道估计方法的性能,最后根据仿真结果为IEEE802.16d系统在不同信道环境下选择适当的导频结构和信道估计方法给出建议。     

频率选择性衰落信道下STBC—DFDM系统的性能

本文将基于平衰落信道提出的空时块编码（STBC）方案应用到OFDM系统中,理论分析和仿真证明在理想信道估计下这种STBC-OFDM系统在频率选择性信道下能够获得对应的STBC在平衰落信道下的性能。     

A Generic Quantitative Approach to the Scheduling of Synchronous Packets in a Shared Uplink Wireless Channel

The scheduling logic at the base station of a shared wireless medium supports time-dependent (synchronous) applications by allocating timely transmission grants. To this end, it must take into account not only the deadlines of the pending packets, but also the channel conditions for each potential sender, the requirements of nonsynchronous applications, and the packet retransmission strategy. With respect to these factors, we identify three scheduling scenarios and show that the scheduler logic faces a different challenge in addressing each of them. We then present a generic scheduling algorithm that translates all the factors relevant to each scenario into a common profit parameter, and selects the most profitable transmission instances.