Wireless Local Loop

The traditional wired local loop used to connect each telephone subscriber to the nearest exchange is expensive and unreliable. Wireless Local Loop (WLL) systems largely eliminate these copper wires using wireless technologies and could provide a cost effective solution. corDECT is one such WLL system, based on the DECT (Digital Enhanced Cordless Telecommunications) standard, that provides toll-quality voice and data capability at a cost below that of a wired local loop. Using micro-cells and Dynamic Channel Selection (DCS), it can handle high subscriber densities without frequency planning. corDECT is gaining commercial acceptance in India and a number of other countries. Using a simple Queueing Network Model (QNM), we find that the 1,000-line corDECT system could achieve a Busy Hour Call Attempt (BHCA) of 36,000 calls/hour, which is far greater than its requirement of 20,000 calls/hour. We show how the system could be expanded to a 10,000-line exchange with a BHCA of over 2,10,000 calls/hour. We also investigate the feasibility of implementing 64 kbps data service along with voice. It is shown that this requires modest hardware improvements.

Broadband satellite will play an important role to provide universal broadband access for the users. In order to lower the cost, the next-generation satellite systems should support IPv6 and seamlessly integrate with terrestrial networks, including wireless local loops. Based on the studies on the requirements and design constraints, in this paper, a novel network architecture has been proposed as a potential solution to the above problems. The proposed network architecture supports both transparent and regenerative topologies and can seamlessly interworking with WLL. It also integrates QoS, multicast, security, and mobility functions to support a range of transport requirements. How to apply this network architecture to support three different scenarios, namely corporate application scenario, residential application scenario and collective access terminal scenario, are also described.

The multipath characteristics of the wireless local loop (WLL) channel were studied over both short and long time periods in urban and sub-urban high-rise and small-house environments. Wideband measurements were performed at a centre frequency of 1.3 GHz with a sliding correlation measurement system using a chip rate of 15 MHz. The receiver was situated at regular cellular base stations,

Wireless Local Loop (WLL) licenses have been issued to increase the tele-density in the country. Almost all WLLoperators have chosen Code Division Multiple Access (CDMA) based technologies to implement their networks. Government policy allows limited mobility, which, if implemented literally, can severely degrade the performance of these networks. On the other hand, if

In this paper, the capacity of the Code Division Multiple Access Wireless Local Loop (CDMA WLL) system is analytically derived, and the capacity gain achieved in a CDMA WLL over a cellular mobile environment is calculated. The results show that the CDMA WLL system can support up to 36 % more users than CDMA cellular mobile system. The paper also

Abstmct-The growth of Internet and related multimedia applications has been exponential. Until mently most of the multimedia applications have been stand-alone or delivered through wired Intemet using fast connections. The multimedia support through wireless local loops or cellular networks has been very limited. In the future growing need for multimedia services will also lead towards wireless multimedia systems. Local Multipoint Distribution Systems (LMDS) are finally getting some momentum also in Europe. This is driven by the need to provide broadband dig. ital services, espedally data-services such as Intemet, to homes and small omces. LMDS together with 3 6 and 46 mobile communication standards will provide possibility to distribute fast multimedia (over 2 Mbps per user) through wireless conneetion. We report the early development and tests done with two-layer wireless LMDS systems operating at 40 GIIZ hquency. The demanding R&D task is to develop cost-effective architec tures and devices, because services are not only broadcast oriented, but also interactive. The architecture situation has been studied in several projects, and in this paper we will show our early results especially B.om the EWACTS-project CABSINET. The main driver in future broadband networks will undoubtedly be Internet and multimedia servlces, instead of video on demand.

The traditional wired local loop used to connect each telephone subscriber to the nearest exchange is expensive and unreliable. Wireless Local Loop (WLL) systems largely eliminate these copper wires using wireless technologies and could provide a cost effective solution. corDECT is one such WLL system, based on the DECT (Digital Enhanced Cordless Telecommunications) standard, that provides toll-quality voice and data capability at a cost well below that of a wired local loop. A closed Queueing Network Model (QNM) is proposed for the corDECT system. The model is validated against actual measurements. Our model predicts that the 1,000-line corDECT system would meet a Busy Hour Call Attempt (BHCA) of 36,000 calls/hr, which is far greater than its requirement of 20,000 calls/hr. The bottlenecks that limit the BHCA to 36,000 calls/hr were identified by the model. We show how the system could be expanded to a 10,000-line exchange with a BHCA of over 2,10,000 calls/hr. We also investigate the feasibility of implementing 64 kbps data service along with voice. It is shown that this requires modest hardware improvements.

This paper presents a costing model for estimating costs of interconnection services in the fixed public switched telephone networks with wireless local loop system based access network. The costing model estimates unit component costs of the fixed public switched telephone networks and aggregates them into costs of different interconnection services. The cost based interconnection service provision promotes effective service-based competition in the telecommunications sector

The multipath characteristics of the wireless local loop (WLL) channel were studied over both short and long time periods in urban and sub-urban high-rise and small-house environments. Wideband measurements were performed at a centre frequency of 1.3 GHz with a sliding correlation measurement system using a chip rate of 15 MHz. The receiver was situated at regular cellular base stations, and the transmitter with an omnidirectional antenna was moved to several rooms in different buildings around the base station sites. During the recordings the movement of people in the measurement rooms was restricted. The short-term results show a high degree of similarity in the multipath characteristics of the WLL channel in urban and sub-urban high-rise environments. The maximum measured values of delay spreads for the urban and suburban high-rise environments were 410 ns and 360 ns, respectively. For the sub-urban small-house environment the data indicate lower values of delay spread. The channel was shown to be very slowly fading, being in most situations essentially static over short time periods of the order of several tens of seconds. The variation of the channel characteristics over long time periods was shown to be significant

This paper considers the problem of mitigating fading and interference in wireless orthogonal frequency division multiplexing (OFDM) multiple access communication systems. Applications include cellular mobile radio, wireless local loop, and wireless local area networks. The effect of interchannel interference (ICI) arising from time-selective fading and frequency offsets and co-channel interference (CCI) is analyzed. A loop-timing method that enables a synchronous uplink between multiple mobile transceivers and a base-station is described. Adaptive antenna arrays are utilized at the base for uplink reception, and optimum array combining based on the maximum SINR criterion is used for each subchannel over slowly timevarying channels. For operation over fast time-varying channels, a novel two-stage adaptive array architecture that incorporates combined spatial diversity and constraint-based beamforming is presented. While ICI alone is most effectively overcome by spatial diversity, combined beamforming and diversity are most effective to combat CCI in the presence of fading. The overall method is suitable for real-time implementation and can be used in conjunction with traditional coding schemes to increase the link-margin.

The aim of the work presented in this paper was to produce measurement-based wideband channel models for wireless local loops (WLL). The paper describes the ® eld measurements, the resulting channel characteristics, and the channel models based on the results. The impulse response measurements were performed at 1.28 GHz in three different environments, namely urban, suburban high-rise, and suburban small house. At each site several rooms were selected, and in each room a burst of impulse responses was recorded at several transmitter antenna positions. A long-term recording was also performed in one location at each site. The multipath characteristics of the urban and suburban high-rise environments are very similar, with rms delay spreads of below 280 ns at 90% of positions. The suburban small-house environm ent can be expected to show less severe multipath propagation. In general the multipath characteristics can vary signi® cantly even within a single room. Also, the long-term variation of the channel characteristics is signi® cant. The results were combined into six channel models, each with a different delay power spectrum. The amplitude fading for all these is characterized by a Rician distribution with the Rician factor varying between 3 and 18 dB, the level-crossing rate between 0.1 and 0.51 / s, and the fade durations between 0.25 and 20 s.

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 ...

This paper is intended to provide an overview of wireless local loop (wll) today, ie the access to final customers through radio systems; this domain covers a wide range of applications, from telephony in rural areas or in developing countries to broadband ...

The universal mobile telecommunications system (UMTS) will deliver a convergent network incorporating cellular, cordless, wireless local loop, and satellite technologies. In this paper, a signaling protocol for intersegment handover (ISHO) in an integrated space/terrestrial-UMTS environment is presented. After discussing a number of possible ISHO scenarios, backward mobile-assisted handover (HO) incorporating signaling diversity is chosen as the most appropriate ISHO scheme.

In this communication we deal with the use of direct sequence spread spectrum tecllniques for radio transmission in the local loop. We present a direct sequence spread-spectrum system that is being developed to transmit signals from ISDN-U [I] interfaces between subscriber premises and the local station. Some attention is' devoted to tlie IF and RF blocks.

Abstract In this article we propose a new simulation module for NS-2 able to reproduce the performance of fixed terminals operating in a wireless network with one or more antennas at the receive end, based on empirical models validated on the literature. This is relevant to ...

The aim of the work presented in this paper wasto produce measurement-based wideband channel models forwireless local loops (WLL). The paper describes thefield measurements, the resulting channelcharacteristics, and the channel models based on the results.The impulse response measurements were performed at 1.28GHz in three different environments, namely urban,suburban high-rise, and suburban small house. At each site several rooms were selected, and ineach room a burst of impulse responses was recorded atseveral transmitter antenna positions. A long-termrecording was also performed in one location at each site. The multipath characteristics of theurban and suburban high-rise environments are verysimilar, with rms delay spreads of below 280 ns at 90%of positions. The suburban small-house environment can be expected to show less severe multipathpropagation. In general the multipath characteristicscan vary significantly even within a single room. Also,the long-term variation of the channel characteristics is significant. The results were combined intosix channel models, each with a different delay powerspectrum. The amplitude fading for all these ischaracterized by a Rician distribution with the Rician factor varying between 3 and 18 dB, thelevel-crossing rate between 0.1 and 0.51/s, and the fadedurations between 0.25 and 20 s.

This paper is concerned with the application of pre-rake processing in the up link of a DS-CDMA system for a Wireless Local Loop (WLL) scenario with Time Division Duplex (TDD) access. It is well known that rake processing allows optimum time diversity gain in a multipath channel. And alternative approach, known as pre-rake processing, exploits the channel reciprocity in TDD systems in the up and down links to perform the optimum combination at the transmitter with the consequent receiver simplification. Typically, the prerake works at the base station, transmitting all users information with their particular pre-distortion. In this paper we explore other possibility, that is, each user performs its own pre-distortion, in order to simplify the synchronization and multiuser detection at the base station. Several simulations show its feasibility in comparison with standard multiuser detection techniques.

We propose and demonstrate a multipurpose fiber-optic access network (MFAN). This network uses the same fiber infrastructure for a variety of services including baseband, cable television (CATV), personal communication service (PCS), wireless local loop (WLL), and local multipoint communication service (LMCS). The experimental results show that the proposed network could support the independent operation of these services.

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.

The universal mobile telecommunications system (UMTS) will deliver a convergent network incorporating cellular, cordless, wireless local loop, and satellite technologies. In this paper, a signaling protocol for intersegment handover (ISHO) in an integrated space/terrestrial-UMTS environment is presented. After discussing a number of possible ISHO scenarios, backward mobile-assisted handover (HO) incorporating signaling diversity is chosen as the most appropriate ISHO scheme.