Co-channel interference in high capacity fixed wireless loops (FWL)

The importance of the incident power density pattern (IPDP) for future fixed wireless loop (FWL) systems is discussed. Also an investigation into some of the important S/I implications of the IPDP for proper system capacity simulations is presented     

On the scalability of fixed broadband wireless access network deployment

Fixed broadband wireless access systems, such as the local multipoint distribution service, use an open system architecture that supports a scalable solution for the Internet services over IEEE 802.16 wireless networks. This article presents an overview of various features of BWA systems toward realizing a high level of scalability to support a potentially fast expanding network. This is achieved by optimizing various network resources, which include utilizing the available bandwidth efficiency, making a minor enhancement to an existing system that minimizes the disruption to network services during the network expansion process, and combining the benefits of different features to increase network capacity.     

Engineering wireless broadband access to IPTV

IPTV is now extending to wireless broadband access. If broadband video streaming is to achieve competitive quality the video stream itself must be carefully engineered to cope with challenging wireless channel conditions. This paper presents a scheme for doing this for H.264/AVC codec streaming across a WiMAX link. Packetization is an effective tool to govern error rates and, in the paper, source-coded data-partitioning serves to allocate smaller packets to more important data. A packetization strategy is insufficient in itself, as temporal error propagation should also be addressed by insertion of intra-coded data. It may be necessary to include redundant packets when channel conditions worsen. The whole should be protected by application-layer rateless coding. Therefore, the contribution of the paper is a complete scheme comprised of various protection measures aimed at robust IPTV streaming. Due to computational overheads, the scheme is aimed at the new generation of smartphones with GHz CPUs.     

多信道多点分配系统-一种新的宽带固定无线接人技术

多信道多点分配系统（Multichannel Multipoint Distribution System MMDS）是近几年刚刚兴起和获得商业应用的宽带固定无线接入技术，它具有中宽带、中等数据传输速率以及应用灵活、设备安装速度快、投资少，收益大等特点，可以为中小企业提供各种宽带交互式数据，话音和视频传输业务，成为宽带接入技术中不可忽视的重要组成部分。     

Near capacity multiple access scheme for interference channel usingcomplex-valued signals

A multiuser detection scheme is proposed for channels using non-spread signals. Trellis encoders and different random interleavers are employed for each user to remove the ambiguity in decoding each user's data from the composite received signal. With symbol-by-symbol soft decision, near channel capacity performance is obtained     

An overview of the standardisation in the area of the broadband fixed wireless access

The broadband fixed wireless access systems will be subject to an increasing development during the next years; these systems will allow to offer the subscriber a full set of services, from the conventional narrow band applications up to the emergent broadband services like Internet access, or leased lines. This rapid growth has carried several initiatives in the telecommunications standardisation bodies, like ETSI in Europe, IEEE in North America, or ITU at international level. These initiatives resulted in the creation of ad hoc groups, for instance the BRAN/Hiperaccess project of ETSI, the IEEE 802.16, or the jrg 8A-9B in ITU standards resulting from this activity are expected in 2000/2001. In parallel to this standardisation activity it appeared necessary to designate, or at least to recommend, dedicated frequency bands for fixed wireless access (fwa) or multimedia wireless systems (mws) applications. In order to satisfy this need the regulation authorities, especially the CEPT in Europe, are preparing decisions and recommendations which are expected to favour a certain level of harmonisation in the use of the spectrum by fwa or mws systems.     

Optimal DLC protocol configuration for realistic broadband fixed wireless access networks based on ATM

DLC protocols, scheduling, and multiplexing issues for broadband fixed wireless access networks based on ATM are discussed. The established DSA++ mac protocol has been developed at ComNets and has been widely applied within the German project ATMmobil. It has been a fundamental contribution to the etsi bran standardisation of HIPERLAN /2. The DSA++ is here modified to perform optimal within the fixed wireless access network environment. Therefore, realistic traffic as well as radio channel models for the respective scenarios are introduced. Simulation results are presented, showing the feasibility of the respective protocol stack for offering broadband multimedia services with reasonable quality of service. In addition to this advanced protocol approach, two systems are discussed which are currently under standardisation process. The IEEE 802.16 as well as the European hiperaccess systems are both proposed for fixed wireless access networks. Expected scenarios and applications are presented and basic requirements the standards have to fulfil are derived. As another aspect of access networks, their impact on the global information society is discussed.     

脉冲干扰下的宽带接入网上行信道MER研究

脉冲干扰严重影响实际通信过程中宽带接入网上行信道的系统性能。基于特征函数理论,推导脉冲干扰的数学模型,并模拟实现脉冲干扰对宽带接入网上行信道的干扰特性。设计和构造宽带接入网上行信道的通信系统平台。得出脉冲干扰下的宽带接入网上行信道16QAM系统的调制误码率(MER)与载噪比(C/N)关系的仿真曲线。仿真结果验证了设计的正确性,同时表明脉冲噪声对系统的影响受到脉冲个数和幅度的制约。     

窄带连续波干扰下的宽带接入网上行信道误码率研究

利用窄带连续波噪声特征函数模型建立了宽带接入网上行信道系统仿真模型,得到了窄带连续波噪声干扰下的宽带接入网上行信道QPSK系统误码率(BER)与载噪比(C/N)的关系曲线,并分析了系统模型的误码率仿真曲线.这些结果对分析宽带接入网上行信道系统的性能提供了有效的参考依据,并且为进一步设计实际应用系统提供了理论基础.     

宽带无线通信射频收发前端设计

介绍了一种宽带无线通信系统(BWCS)。提出了一种应用于该系统TDD模式射频(RF)子系统设计方案,并对RF子系统进行了分析。研制出射频子系统电路,给出了测试结果。测试结果表明研制的RF子系统各项指标都满足宽带通信系统的设计要求。     

Training sequence design and channel estimation of OFDM-CDMA broadband wireless access networks with diversity techniques

In this paper, an OFDM-CDMA system employing various diversity schemes is considered for a possible candidate of broadband wireless access networks and broadcasting applications. With an emphasis on a preamble design for multi-channel separation, we address a channel estimation based on the time-domain windowing and its imperfectness in OFDM-based multiple-antenna transmission systems. By properly designing each preamble for multiple antennas to be orthogonal in the time domain, the channel estimation can be applied to the HIPERLAN/2 and IEEE 802.11a standards in the case of more than two transmit antennas. Also, the effect of diversity techniques on the performance of OFDM-CDMA based broadband wireless access networks is investigated and the maximum achievable diversity gain for a two-path Rayleigh fading environment is evaluated. Simulation results show that the OFDM-CDMA system applying a space-time-frequency diversity with a full-rate full diversity code can give the diversity of D=4 and D=8 for both multi-user cases of maximum user and half user capacities, respectively.     

A road to future broadband wireless access: MIMO-OFDM-Based air interface

Orthogonal frequency-division multiplexing is a popular method for high-data-rate wireless transmission. OFDM may be combined with multiple antennas at both the access point and mobile terminal to increase diversity gain and/or enhance system capacity on a time-varying multipath fading channel, resulting in a multiple-input multiple-output OFDM system. In this article we give a brief technical overview of MIMO-OFDM system design. We focus on various research topics for the MIMO-OFDM-based air interface, including spatial channel modeling, MIMO-OFDM transceiver design, MIMO-OFDM channel estimation, space-time techniques for MIMO-OFDM, and error correction code. The corresponding link-level simulation results are encouraging, and show that MIMO-OFDM is a promising road to future broadband wireless access.     

Turbo space-time processing to improve wireless channel capacity

By deriving a generalized Shannon capacity formula for multiple-input, multiple-output Rayleigh fading channels, and by suggesting a layered space-time architecture concept that attains a tight lower bound on the capacity achievable. Foschini (see Wireless Pers. Commun., vol.6, no.3, p.311-35, 1998) has shown a potential enormous increase in the information capacity of a wireless system employing multiple-element antenna arrays at both the transmitter and receiver. The layered space-time architecture allows signal processing complexity to grow linearly, rather than exponentially, with the promised capacity increase. This paper includes two important contributions. First, we show that Foschini's lower bound is, in fact, the Shannon bound when the output signal-to-noise ratio (SNR) of the space-time processing in each layer is represented by the corresponding "matched filter" bound. This proves the optimality of the layered space-time concept. Second, we present an embodiment of this concept for a coded system operating at a low average SNR and in the presence of possible intersymbol interference. This embodiment utilizes the already advanced space-time filtering, coding and turbo processing techniques to provide yet a practical solution to the processing needed. Performance results are provided for quasi-static Rayleigh fading channels with no channel estimation errors. We see for the first time that the Shannon capacity for wireless communications can be both increased by N times (where N is the number of the antenna elements at the transmitter and receiver) and achieved within about 3 dB in average SNR about 2 dB of which is a loss due to the practical coding scheme we assume-the layered space-time processing itself is nearly information-lossless.     

3.5GHz固定无线接入业务应用及干扰特性分析

1 3.5GHz无线接入频率资源情况 2000年4月,信息产业部无线电管理局发布<关于3.5 GHz频段无线接入使用频率的通知>,规划了3.5 GHz无线接入系统业务的工作频率,具体为上行频段3399.50～3431.00MHz,下行频段3499.     

Broadband fixed wireless access as a key component of the futureintegrated communications environment

It is an exciting time for broadband fixed wireless with key developments in frequency bands from 1 to 60 GHz and a range of new technologies being developed. While working on these new technologies, it is easy to forget that fixed wireless access will form part of an integrated communications environment of the future where users will have one communications device working in the home, at the office, and outdoors. This article predicts the communications environment of the next 20 years and looks at the role of fixed access within that environment. This involves assessing how fixed access systems will interface and integrate with in-home wireless networks, how their architecture will enable multiservice operators to utilize the same core network across a range of different access technologies, and how they will act as a channel to carry mobile traffic originating within the building. Based on the requirements this vision and architecture implies, this article critically assesses the different fixed wireless technologies available to date and compares their capabilities to provide future-proof broadband fixed wireless platforms     

A multiple access scheme for wireless access to a broadband ATM LANbased on polling and sectored antennas

An adaptive polling scheme for multiple access in a broadband wireless local area networks (LANs) is proposed. It is designed to accommodate asynchronous transfer mode (ATM) traffic with a large and variable range of bit rates. The radio architecture is microcellular, with switched sectored-beam antennas and a small frequency reuse factor. Features of the multiple access scheme include polling rate depending on a terminal's average bit rate, fixed-length frames divided into segments corresponding to base antenna sectors, and automatic-repeat-request (ARQ) for error control, combined with randomized sector segment ordering. The steady-state performance (cell loss, call blocking and dropping probabilities, waiting time, and buffer occupancy) are evaluated by simulation for an open indoor environment, and for handoff, ARQ, and simple power control enhancements; focusing mainly on the effects of the propagation and interference conditions     

Investigation of wind and rain effects in a foliated tropical region for fixed wireless access

This paper investigates the effects of trees on fixed wireless access operating at 5.8 GHz frequency of the Unlicensed National Information Infrastructure (UNII) band. Measurements are focused on the temporal scale of the received signal strength for a three different links (one line of sight (LOS) link and two non-line of sight (NLOS) link). The statistical characterisation of the combined effects of typical weather phenomena often experienced in a tropical region is presented. As expected, the LOS link is not affected even during heavy rain condition. However, the presence of trees in the vicinity of the transmission path can cause relevant signal deterioration in the case of NLOS link, where the fading of the received signal varies from 2 to 16 dB as the strength of wind and rain increases. Rician distribution can be used to characterise the temporal variation of these weather effects. The work reported in this paper enables the effects of wind, rain and humidity to be properly taken into consideration in the deployment of fixed wireless links in a foliated channel, allowing an optimisation of planning for the end users.     

Investigations on radio propagation channel measurements at 2.2 GHz and 3.5 GHz for the fixed wireless access in an urban area

Within a competitive context the wireless local loop is emerging as an alternative to the traditional wireline network. This solution is attractive because of its low capital cost and its flexible deployment. Nevertheless a propagation channel study has to be performed so as to develop specific engineering tools and propagation models. This paper presents wideband propagation measurement results carried out in Mulhouse in a small cell environment at 2.2 GHz and 3.5 GHz. Under different propagation scenarios, the propagation channel is characterised in terms of path loss and wideband selectivity parameters. Because of the experimental setting, the influence of the receiving height, the frequency and the receiving antenna pattern on the deviations of the path loss and the selectivity parameters have been investigated.