无线本地环路（WLL）技术及发展趋势

本文介绍无线本地环路（ＷＬＬ）系统的基本结构及其相关技术，指出无线本地环路ＷＬＬ的优势和关键技术，并就ＷＬＬ的现状和发展趋势作出分析。     

数字无线本地环路系统

本文对数字无线本地环路（ＤＷＬＬ）进行系统的介绍，着重研究和讨论了ＤＷＬＬ的体系结构及关键技术，为开发和利用数字无线本地环路提供一种借鉴和参考。     

照亮大街小巷的“空中之星”

无线本地环路ＷＬＬ以其经济，有效，方便等特点，被迅速引入到通信网中。本文陈述了ＷＬＬ的技术发展过程，接着介绍了美国ＵＴ期达康公司的ＡｉｒＳｔａｒ＾ＴＭＷＬＬ系统，最后分析了中国市场上ＷＬＬ的应用前景。     

无线本地环路系统

无线本地环路系统（ＷＬＬ）是近年来发展起来的新技术，它向用户提供具有市话有线用户环路同等功能的电话业务，是一种低成本的无线传输系统。本文将介绍无线本地环路技术 发展背景、特点，并介绍无线本地坏路系统概况，最后介绍Ｍｏｔｏｒｏｌａ公司的ＰＡＣＳ（Ｐｅｒｓｏｎａｌ Ａｃｃｅｓｓ Ｃｏｍｍｕｎｉｃａｔｉｏｎｓ Ｓｙｓｔｅｍ）系统及我国发展无线本地环路技术的策略。     

PHS-WLL无线接入系统简介

和有线本地环路相比，无线本地环路（ＷＬＬ－ＷｉｒｅｌｅｓｓＬｏｃａｌＬｏｏｐ）由于具有安装容易，维护方便等优点而应用得越来越多。ＷＬＬ有多种技术解决方案，其中ＰＨＳＷＬＬ是造价较低，性能较好的方案之一。１ＰＨＳ与ＰＨＳＷＬＬ的技术特点ＰＨＳ（Ｐｅ...     

数字无线本地环路和系统

本文对数字无线本地环路进行系统的介绍，着重研究和讲话了ＤＷＬＬ的体系结构及关键技术，为开发和利用数字无线本地环路提供一种借鉴和参考。     

采用CDMA及V5接口技术的WLL系统

文章分析了无线本地环路（ ＷＬＬ） 的优势及所采用的技术，介绍了采用ＣＤＭＡ 及Ｖ５ 接口技术的ＷＬＬ 系统。     

无线本地环路的研究与应用

无线本地环路（ＷＬＬ）技术发展迅猛。本文在介绍ＷＬＬ系统结构的基础上，着重对其技术类型和业务应用进行了探讨，并就我国发展ＷＬＬ技术的有关问题提出了建议。     

方兴未艾的无线本地环路

本文主要对无线本地环路的概念，结构组成，基本功能与特点进行了介绍，并对ＷＬＬ的发展状况及应用前景作了一定概述。     

无线用户环路技术

本文概念了国际上接入网发展的趋势，分析了无线用户环路（ＷＬＬ）的定义，讨论了ＷＬＬ的适用范围，介绍了国外电信公司ＷＬＬ的各种产品。最后，对我国ＷＬＬ的发展提出了一些建议。     

Reverse link performance of wireless local loop CDMA networks

We study the effect of directional subscriber antennas on the reverse link performance of a power-controlled code-division multiple access (CDMA) network in wireless local loop deployments. We investigate the capacity gain that is attained in wireless local loop (WLL) CDMA over mobile cellular systems and its variation as a function of the channel statistics. We also determine the overhead that soft handoff and directional subscriber antennas impose on the WLL system capacity     

Digital wireless local loop system

The digital access technologies for the wireless local loop (WLL) or fixed wireless system are discussed. WLL is an important means of providing telephone services more cheaply and quickly in the developing countries than through a wireline system. Capacities of a WLL system based on the IS-54 (now IS-136) TDMA, IS-95A CDMA, and ETSI GSM technologies are developed and compared     

宽带CDMAWLL系统的数字接收机的实现

无线本地环(WLL)是一种无线接入系统,它用无线的方式代替了传统的铜线连接用户到本地交换机。介绍了一种用于宽带CDMAWLL系统的数字接收机。叙述了WLL的系统组成、网络结构、反向链路信道结构和反向中继接收机设计规范,并论述了代码捕获和代码跟踪模块的功能。接收机的运行时钟频率可达65.536MHz。     

韩国LG公司的CDMA—WLL系统

以韩国LG公司CDMA无线本地环路（CDMA-WLL）为例,介绍CDMA技术特点及WLL的原理及技术指标。     

A comparison of wireless local loop with competing accesstechnologies

It is important to remember that wireless local loop (WLL) is in competition with other fixed access technologies. There are a number of different access techniques which are emerging, including techniques which enhance basic copper cables, such as ISDN and xDSL, new forms of cable, such as coax and fibre, video distribution systems and alternative means of delivering voice and data, such as mobile radio and digital television broadcasting. All these are competing with wireless local loop to provide a convergent service whereby voice, data and television are provided through the same access medium. This paper provides some details about each of the different access technologies, makes predictions about their future success, and examines the likely future of WLL in tomorrow's access technology market-place     

A single-chip 2.4-GHz direct-conversion CMOS receiver for wirelesslocal loop using multiphase reduced frequency conversion technique

A single-chip direct-conversion CMOS receiver for 2.4-GHz wide-band code-division multiple-access wireless local loop (WLL) is described. The chip includes a low noise amplifier, a 12-phase downconverter, a variable gain amplifier, a g_m-C channel selection filter, a programmable phase-locked loop for seven channel frequencies, and a 4-bit flash analog-to-digital converter. The proposed multiphase reduced frequency conversion scheme combined with a multiphase sampling fractional-N prescaler, a cascaded dc-offset canceler and distributed automatic gain control loops offers solutions to problems of a direct-conversion receiver. Experimental results show -115-dBm sensitivity, 4.4-dB noise figure, and 95-dB dynamic range, which sufficiently meet commercial WLL specification     

A wireless local loop system based on wideband CDMA technology

This article describes a wireless local loop system based on wideband CDMA technology. The unique features of CDMA technology make it a formidable alternative for fixed wireless telephone applications. The W-CDMA technology used by this WLL system is selected to provide primarily ISDN-like services and data rates to subscribers. This technology also provides a smooth transition into the third generation wireless technology. The air interface used in this WLL system is an interim TTA standard, which specifies a CDMA-based protocol operating in the 2.30-2.40 GHz band. The standard allows two types of bandwidth (5 and 10 MHz). The WLL system described in this article includes the WLL gateway switch, the radio port controller and the radio interface unit. The gateway switch connects the radio system to the PSTN and ISDN. The RPC provides concentration and control functions to a number of base stations called RPs. The RIU is comprised of the fixed units attached to the residential or commercial buildings. Also included are the radio port operation and maintenance (RPOM) unit, which is responsible for maintaining and managing the radio network elements, and the interworking function unit, which is used as a gateway to data services such as the Internet and PSPDN     

The effect of narrowbeam antenna and multiple tiers on systemcapacity in CDMA wireless local loop

The wireless local loop (WLL) system is a local telephone system without wireline connection. It is believed to be a fast and cost-effective means to provide local phone service in rural areas and third world countries. WLL is a fixed radio communication system; narrowbeam antennas can be employed at both the base station and subscriber's side at high spots so that the propagation between base station and house is very close to free space propagation. This gives the WLL system many inherent advantages over the traditional cellular system, such as bigger coverage area, low power, reduced interference, higher capacity, no fast fading, and no handoff. In this article ideal multiple-tier hexagonal cells are used to derive the capacity of a CDMA WLL system. First, the reverse link interference from each tier to the center cell is calculated separately. Then, the interference ratio of reverse links in a WLL system is analytically derived as a function of total tier number. The result shows that interference from other cells is proportional to the beam width of the house antenna. The authors also found that tier number plays a vital role in system capacity in a free-space propagation (20 dB/dec) environment. At the extreme, the system capacity will drop to zero for an infinite-tier cell structure. A WLL simulator is also built to verify the authors' analytical solution     

IP QoS delivery in a broadband wireless local loop: MAC protocoldefinition and performance evaluation

The wireless approach to the last mile access (wireless local loop, known as WLL) is becoming increasingly attractive to network operators and service providers since it offers a flexible and cost-effective solution to enable delivery of even broadband services to end customers. In this paper, a full-blown broadband WLL network is presented. The proposal is based on the OFDM-CDMA technique, to which an added dynamic reservation/request MAC protocol is proposed, fully exploiting the OFDM-CDMA platform. Central to our proposal is the support of different QoS profiles, in the context of QoS aware networks. As a case study, the explicit presentation of the IETF integrated services support over our WLL system is addressed. An extensive performance evaluation focused on the MAC layer is then reported. We prove that our scheme achieves high utilization efficiency, as well as a fair share of the available radio capacity, even in the presence of highly heterogeneous traffic mix. Delay performance is provided for both reference traffic models, as well as for measured IP and MPEG traffic traces offered to the system     

Repacking on demand for two-tier wireless local loop

This paper proposes a radio channel assignment scheme called repacking on demand (RoD) for two-tier wireless local loop (WLL) networks. A two-tier WLL overlays a macrocell with several microcells. When a new call arrives at a two-tier WLL with RoD, if no idle channel is available in both the microcell and the macrocell, repacking is performed (i.e., a call in the macrocell is moved to its corresponding microcell), and then the reclaimed macrocell channel is used to serve the new call. An analytic model is proposed to compute the call blocking probability of the two-tier WLL with repacking. This analytic model is validated against simulation experiments. We prove that the blocking probability is not affected by the call holding time distributions, but is only dependent on the mean of the call holding times. Compared with some previous proposed schemes, RoD has low blocking probability and significantly reduces repacking rate.