Cm Simmonds

Downlink calibration requirements for the TSUNAMI (II) adaptive antenna testbed

The TSUNAMI (II) project is an investigation into the use of adaptive antenna technology. The field trial system has been developed for the purposes of investigating the feasibility of implementing such a system using a GSM-1800 base station system. The field trial system uses a digital baseband beamforming technique (DBF) which, like all DBF systems, relies on the accurate transfer of weighted signals to and from the antenna array elements. As such, an accurate and reliable calibration system is required to combat effects arch as temperature and humidity on the individual antenna array paths. In this paper, results are presented of studies made on the field trial system, with regard to the operational temperature variations over an extended period of time. Investigations are presented of the TSUNAMI (II) downlink calibration technique and the implications for future adaptive antenna array calibration systems.

Network planning aspects of DS-CDMA with particular emphasis on soft handoff

A study into the application of soft handoff in wideband direct sequence code division multiple access (DS-CDMA) communications systems is described. Soft handoff is explained in terms of macroscopic diversity, a form of diversity combining in which signals transmitted via independently fading paths can be combined in order to enhance the overall performance. Results from a series of outdoor propagation studies, specifically designed to investigate the propagation aspects of soft handoff, are presented, and the future work activities of the project are outlined.

An investigation of RAKE receiver operation in an urban environment for various spreading bandwidth allocations

The renewed interest in the application of the spread-spectrum techniques such as CDMA to cellular mobile radio systems, in both the US, and within Europe through the RACE II and UK DTI/SERC LINK programs continues to gather momentum. To this end, an analytical performance model has been developed in order to provide a greater insight into the operation of this technique, in particular the sensitivity of the bandwidth efficiency of the network to the form of diversity signal processing used in the mobile transceiver. This theme is continued with an investigation of the wideband channel characteristics of an urban service area. Results are presented relating the statistics of the RAKE receiver branches to the spreading bandwidth used.<<ETX>>

Propagation aspects of mobile spread spectrum networks

Publisher Summary In this chapter, the propagation aspects of frequency hopping and direct-sequence spread spectrum are characterized in terms of providing a high-quality, high-capacity wireless communication network. In particular, the impact of the mobile channel on service provision is examined. It is indicated that both DS and FH-SS can be employed to mitigate the deleterious effects of the mobile environment, resulting in improved quality of service for a wireless multimedia network. Comparison of direct sequence and frequency hopping CDMA indicates similar voice-channel-capacity performance. In addition, FH-CDMA displays a greater soft capacity facility than DS-CDMA, which is important in the provision of a flexible cellular system. Furthermore, the nature of FH-CDMA eases the frequency planning requirements in a cellular network, as the interference pattern is randomized at each hop and consequently, no one interferer can dominate. In contrast, DS-CDMA requires complex closed-loop power control to mitigate the effects of the near-far effect. However, it is easier to exploit soft handover in a DS-CDMA network to provide an enhancement in the quality of service. The application of FH-CDMA is limited to medium data-rate services in high-time dispersion, such as urban macrocellular environments.

An evaluation of the range extension achieved by the TSUNAMI (II) adaptive antenna testbed

The TSUNAMI (II) project has been an investigation into the application of adaptive antenna technology for use in future generation mobile communications systems. The key aims of the project were to investigate the increase in system capacity and coverage that can be realised above existing, non-adaptive networks. To this end, extensive field trials with a modified GSM1800 basestation equipped with an 8-element adaptive antenna system were conducted at a test site operated by Orange PCS in Bristol, UK. This paper presents a subset of the results obtained from the field trial which demonstrate that a practical increase in usable cell radius (range extension) of the order of 54% was achieved.

Performance of the TSUNAMI (II) macrocellular field trial system using a dynamic interference source

The TSUNAMI (II) project has been an investigation into the application of adaptive antenna technology for use in future generation mobile communications systems. The key aims of the project were to investigate the complexity versus increase in system capacity and coverage extension that can be achieved over the existing, non-adaptive networks. May 1998 saw the completion of an 8 month field trial, covering both macrocellular and microcellular trials. These investigations were performed at the Orange Testbed in Bristol, U.K., using a modified DCS-1800 base station. In this paper are presented a subset of the macrocellular field trial results, obtained using spatial and temporal reference beamforming (TRB and SRB) in the presence of a moving, deliberate interference source. The results presented show the comparative performance of several selected adaptive antenna algorithms used by the TSUNAMI (II) testbed. The results of these trials demonstrate how the interference source and chosen algorithms ability to track wanted to unwanted users influences the overall performance of the adaptive antenna base station (AA-BSS).

Calibration architectures for use in UTRA adaptive antenna basestations

The ACTS Smart Universal BEAMforming (SUNBEAM) project intends to develop innovative base station array processing architectures and algorithms for the Universal Mobile Telecommunication System (UMTS) that are sufficiently flexible to support a range of different second and third generation air interface standards. This paper describes the candidate calibration architectures to be studied under the project for use with adaptive antenna base station systems (AA-BSSs), with particular reference to the UTRA air interface standards of wideband-code division multiple access (W-CDMA) and time division-CDMA (TD-CDMA). This paper introduces a semi-transparent calibration scheme for use with the uplink of either a FDD or TDD adaptive antenna base station.