A 3‐D Propagation Model Considering Building Transmission Loss for Indoor Wireless Communications

In the development of a new wireless communications system, a versatile and accurate radio channel for indoor communications is needed. In particular, the investigation of radio transmission into buildings is very important. In this letter, we present an improved three‐dimensional electromagnetic wave propagation prediction model for indoor wireless communications that takes into consideration building penetration loss. A ray tracing technique based on an image method is also employed in this study. Three‐dimensional models can predict any complex indoor environment composed of arbitrarily shaped walls. A speed‐up algorithm, which is a modified deterministic ray tube method, is also introduced for efficient prediction and computation.     

Performance of an OFDM Based Downlink Multiple Access System for Indoor Wireless Communications

We have analyzed the downlink performance of a multiuser Orthogonal Frequency Division Multiplexing based multiple access system for indoor wireless communications. The optimization problem for minimizing the total transmit power from a base station while satisfying the bit-rate and bit-error rate criterion of the various portable users in the system has been outlined. The analytical solution obtained cannot be realized in a simple manner and we present a realizable method for the combined allocation of subcarriers, modulation mode, and power to the signals transmitted to the different users. Simulation results are used to compare the performance of the analytical solution with that using the new method under various channel conditions. Performance comparisons between the new method and an OFDM-TDMA system clearly indicate the advantages of the new algorithm under most conditions. The correlation of the frequency-domain channel strengths among the various users is shown to have an influence on the performance of the new algorithm.     

预测室内电波传播的混合方法

射线跟踪(RT)算法与时域有限差分(FDTD)法是对室内无线电波传播进行研究的有力工具。大多文献对此作有详细的探讨,而对于两者结合而形成的混合法则很少提及。本文对基于混合法的室内传播预测进行了详细的讨论,计算结果表明了该方法的有效性和准确性。     

用修正的UTD模型预测室内电波传播

分析了现有预测室内电波传播的2-D/3-D混合算法模型的不足,提出一种修正模型,该模型建立在环境的二维对地平面图基础上。在建立可见性树时,结合实际三维环境的特点引入分别相对于发射机和接收机的两个对地投影平面图和一个矢量标准判据来决定可见的元素。计算结果与测量结果符合较好,表明该模型的准确性和高效性。     

An Efficient Hybrid Parabolic Equation – Integral Equation Method for the Analysis of Wave Propagation in Highly Complex Indoor Communication Environments

An efficient, full-wave computational technique to investigate the electromagnetic wave propagation within a complex building environment, resulting from contemporary indoor communication systems, is proposed. Unlike a standard ray-tracing technique, this new methodology is based on the parabolic wave equation (PE), appropriately modified to deal with the extremely wide-angle propagation cases, encountered in a typical wireless system of this kind. It is also successfully applied to model the field in the presence of walls, doors or other penetrable structures, taking into account the exact geometric configuration of the environment under consideration. Next, the PE technique is significantly enhanced by an integral equation formulation, in which the computed field in the interior of the walls and other obstacles is used as a secondary equivalent current source and a corrected version of the electromagnetic field is recalculated in the whole indoor environment. This combined approach has all the advantages of a full wave method, does not call for a highly dense mesh, and it also has moderate requirements of computational resources.     

电力系统无线通信中的低复杂度Rake接收机

针对电力系统中高速无线通信,提出了一种分级式Rake接收机架构,有效节约了硬件资源,避免了布线拥塞。基于该推荐架构,实现了一种8路并行8指Rake接收机。在SMIC.18 CMOS工艺下,该Rake接收机相对于传统方案获得了13.1%芯片面积和37.2%布线网络的节约。     

一种对室外到室内的电波传播进行预测的混和方法

射线跟踪(RT)法和时域有限差分(FDTD)法是研究无线电波传播的重要的方法,本文对基于混和法的室外到室内的电波传播预测进行了详细的介绍和讨论,同时通过计算结果来验证了此方法的有效性和准确性.     

未来无线通信的研究动态

主要介绍未来无线通信的一些概念以及各国的研究进展,澄清其中的部分错误观念,并总结了目前有关未来无线通信的发展趋势,指出我国应当及早开展这方面的研究。     

Modeling of 3D In—Building Propagation by Ray Tracing Technique

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Polarization Behaviours at 2, 5 and 60 GHz for Indoor Mobile Communications

The behaviours of linear polarizations at 2.15, 5.3 and 61.7 GHz in corridors are studied in this paper. It shows that there is no significant difference between the received powers for vertical and horizontal polarizations. Depolarization is obvious at 2.15 GHz due to different antenna type is applied at the receiver, and it is more serious in non-line-of-sight (NLOS) cases.     

Adaptive Modulation/TDMA/TDD with Convolutionally Coded Type-II Hybrid ARQ for Wireless Communication Systems

This paper proposes a time divisionmultiple access/time division duplex (TDMA/TDD)-basedadaptive modulation system (AMS) with aconvolutionally coded Type-II Hybrid automatic repeatrequest (ARQ) protocol to achieve high throughput datatransmission in wireless communication systems. First,this paper discusses the cause of throughputlimitation of the conventional fixed-rate quaternaryphase shift keying (QPSK) with ARQ protocol andsuggests that the effective means to improvethroughput performance are the reduction ofre-transmission probability under bad channelcondition and the increase of transmission bit rate perTDMA/TDD slot under good channel condition. Based onthese strategies, this paper discusses an AMS with aconvolutionally coded type-II hybrid ARQ protocol(type-II hybrid ARQ/AMS) and evaluates itsperformance by computer simulation. The resultsconfirm that the proposed type-II hybrid ARQ/AMS candrastically improve throughput performances comparedto the conventional fixed-rate QPSK with selectiverepeat ARQ protocol (SR-ARQ/QPSK) or a simplecombination of SR-ARQ and AMS (SR-ARQ/AMS) under anychannel conditions, especially under severe channelconditions.     

In-Cell Frequency Reuse for Broadband Indoor Wireless Systems Using Sectored Antennas

This paper proposes a hybrid Space-Time Division Multiple Access (S-TDMA) for broadband indoor wireless systems using sectored antennas. It is shown that portables which are located in different sectors of the indoor microcell may be able to reuse the same frequency and the same time slot. However this requires careful scheduling of packet transmissions in order to avoid transmitting packets that would jam each other during the same time slot. It is proposed that the scheduling be performed by the base station, i.e., a central control architecture. If the number of channels (simultaneous transmissions) is larger than two, the optimum scheduling algorithm, the one that maximizes the number of packets transmitted per frame, is in the NP-Complete class of problems and so can not be solved in real time. Therefore a sub-optimum algorithm named the First Fit Algorithm (FFA) is proposed for frame scheduling and its performance is investigated through measurement results obtained in some typical indoor environments. Computer simulations based on the measured data showed that the FFA can provide a large capacity gain. For example, for a minimum acceptable signal-to- interference ratio of 10 dB and for a sectorization level ten (using ten sectors in the base station) the FFA can multiply the capacity by 3.6 in a typical open indoor location. This means that on average, 3.6 packets can be transmitted per time slot while using the same radio frequency.     

Wideband Propagation Measurements and Channel Implications for Indoor Broadband Wireless Local Area Networks at the 60 GHz Band

This paper addresses some wideband propagation characteristics for Indoor Broadband Wireless LANs at the 60 GHz band. Important system design characteristics from measured results obtained from two wideband 60 GHz LOS radio links are presented. Measurements had been undertaken using the swept frequency channel sounding method. Analysis from the complex frequency responses in a worst-case scenario have yielded to a lower coherence bandwidth value of 5 MHz. Minimum and maximum B_0.9coherence bandwidths obtained with a directional horn transmit and an omnidirectional receive antenna is 1.10 MHz and 105.33 MHz respectively. It has been observed that the coherence bandwidth fluctuates significantly with the location of the receiver with respect to the base station. These results can be used for modelling and design of future Indoor BWLANs.     

混合DS－SFH扩频多址室内无线数字通信性能分析

本文讨论了ＤＳ－ＳＦＨ扩频多址室内无线通信系统在瑞利多径衰落信道中的平均差错概率和多址容量。基于多径干扰、多址干扰和信道噪声的机理分析，推导了计算平均差错概率的有效近似公式。理论分析和数值模拟指出：混合系统的ＤＳ部分具有良好的多址容量并提供抗来自指定用户的多径干扰能力，混合系统的ＦＨ部分则具有抗来自非指定用户的多址和多径干扰能力。     

Capacity Analysis for Connection Admission Control in Indoor Multimedia CDMA Wireless Communications

In this paper, the capacity analysis for connection admission control is presented for the reverse-link transmission of a packetized indoor multimedia wireless communication system using direct sequence code division multiple access (DS/CDMA). Since CDMA is interference limited, the signal-to-interference-plus-noise ratio criterion is used to check if there is enough system resources (i.e., the CDMA channels and received signal power) for each new connection request. Taking into account the stochastical nature of multimedia traffic, the effective bit rate is used to characterize the resources required by each mobile user and a linear approximation is then used to find the total resources required by all the mobile users already admitted to the system and the new connection request. Transmission errors due to both base station buffer overflow and wireless channel impairments are considered. The capacity of multimedia traffic is determined in such a way that the utilization of the system resources is maximized and, at the same time, the required transmission bit error rate and transmission delay of all users admitted to the system are guaranteed. Computer simulation results are given to demonstrate the performance of the proposed method for capacity analysis.     

《无线通信》课程的教学方案研究

通信技术的飞速发展对《无线通信》课程的教学提出了新的挑战。该文在分析《无线通信》课程教学内容的基础上,从教学方法、教学实践等方面,具体阐述该课程的教学改革方案,并对下一步的课程建设进行展望。     

Design Template and Measurements for Antenna Planning in an Indoor Radio Environment at 1800 MHz

Recently, the demand for an accurate design on the distribution of the antennas in shopping malls is growing rapidly. To provide a guaranteed coverage inside the shopping malls, mobile operators may have installed a lot more antennas than that is really needed. This over-engineering design has increased the installation and operation cost. Therefore, the need to have a relatively more accurate indoor design is the most requesting goal in the telecommunication industry. The purpose of this paper is to derive an indoor design template, which can facilitate mobile operators to evaluate efficiently the optimized number of antennas and their locations within a premises. A tunnel propagation model is used to represent the propagation loss in an indoor environment. Measurements are also taken to derive the losses of various media. Field tests are finally performed to verify the accuracy of the distribution of RF signal strength predicted by the design template.     

Measurements and Statistical Modeling of 900 MHz Radio Propagation Channels for Microcellular and Personal Communications in Tunnels

This paper reports the results of measurements of 900 MHz narrow-band radio wave propagation in four tunnels with pedestrians and vehicles. Analysis of the measured data files shows that the power distance factor ranges from 1.87 to 4.44. The power attenation rate with distance is insensitive to the location of the transmit antenna in the cross section of a tunnel, but the transmit antenna insertion loss is. The log-normal distribution fits slow variation of the received signals. The Racian distribution closely describes fast fading in the straight sections of tunnels. However, the Rayleigh distribution does not fit the fast fading in the curved sections of tunnels, as expected.     

Performance of a Multiple-Antenna Multiple-Equalizer System for a CDMA Indoor Wireless System

A multiple-antenna multiple-equalizer (MAME) system for interferencesuppression in some code-division multiple-access (CDMA) indoor wirelesssystems is investigated. The MAME system offers enhanced interferencesuppression capabilities over existing approaches under certain conditions andcan thus increase system capacity. The details of the MAME system arediscussed and the unique features of this work as compared with many otherstudies on space-time processing are explained using spectral correlation anddiversity domain concepts. The effects of the number of antennas, tap spacingof the equalizers, spectral correlation, and diversity domains are discussedusing simulation results. Adaptation performance results are also presentedand a recently proposed quasi-Newton algorithm is recommended for use in theMAME system. Decision-directed equalization results are also studied undervarious conditions and bit-error rate results are presented. Simulationresults illustrate that the MAME system can offer enhanced interferencesuppression capabilities in CDMA indoor wireless systems.