P Hafezi

Propagation measurements at 5.2 GHz in commercial and domestic environments

This paper presents the results of an investigation into the wideband propagation characteristics of four different indoor operational environments within the 5.2 GHz band using a swept time-delay cross-correlator (STDCC) channel sounder. For each environment the cumulative distribution of delay spread for both omni-directional and a 20 dB horn antenna are presented. It is shown that a suitably aligned narrowbeam antenna makes possible to achieve delay spread reduction through spatial filtering. The effects of moving people and different room transmission situations are also presented.

An experimental investigation of the impact of human shadowing on temporal variation of broadband indoor radio channel characteristics and system performance

This paper reports the results of extensive measurements and analysis of the temporal variations of the indoor radio propagation channel as a result of human traffic. The broadband measurements presented were taken at 5.2 GHz and were carried out in a large laboratory environment. Four antenna configurations were considered: for three sets of measurement the receiver used an omni-directional antenna while at the transmitter omni, 60/spl deg/ and 90/spl deg/ antennas were employed. The fourth arrangement used a pair of 90/spl deg/ antennas at the transmitter and receiver. The measurements also considered the performance of a multi-rate QPSK modem in terms of bit errors measured in the presence of human shadowing. The statistics of the received signal power, RMS delay spread and Rician K-factor are compared for the shadowing and static channel conditions.

Indoor channel characterisation measurements with directional antennas for future high frequency ATM wireless access systems

This paper presents a selection of wideband channel sounding measurements performed as part of the ACTS AWACS (ATM Wireless Access Communications System) project. The results were obtained for two different indoor operating environments (mainly in line-of-sight conditions) at a carrier frequency of 19.37 GHz. The paper discusses the configuration of the wideband channel sounder and its connection to the prototype ATM transmission system. Measurements concentrate on average power, RMS delay spread and K-factor for a number of different antenna configurations and beamwidths. Mixed antenna configurations are also analysed with a directive antenna at the base station and an omni antenna at the mobile station. In particular, the results demonstrate the improvement in K-factor and the reduction in RMS delay spread that can be achieved with correctly oriented high gain antennas.

AWACS: ATM wireless access system—potential candidate for European HIPERLINK standard

Wireless ATM is receiving a significant attention as a solution for wireless access. The integration of wireless access and ATM is an essential requirement for the future of telecommunications so that emerging wideband services which embody multimedia applications can be made transparently available to mobile terminals. There are many ongoing activities within the European ACTS program (Advanced Communications Technologies and Services) which are related to evolving ATM oriented wireless networks at various frequencies such as 5, 17, 40 and 60 GHz. AWACS (ATM Wireless Access Communication System) is one of these projects and addresses the feasibility of low cost, high-data-rate radio LAN systems based on ATM (both indoor and outdoor) at 19 GHz. This article overviews the AWACS project which has contributed to the definition of emerging European radio LAN standards such as ETSI BRAN HIPERLINK.

European Smart antenna test-beds

The European Commission, through RACE, ACTS and now the IST programs, has funded numerous consortium based research projects addressing capacity enhancement by means of Smart or Adaptive Antenna Technology. In addition to capacity enhancement, these projects have also considered the additional operational benefits, such as multipath mitigation and range extension, that this technology can offer to wireless network deployments. This paper provides an overview of the key results obtained from the test-beds and field trials conducted under the RACE and ACTS TSUNAMI projects as well as ACTS AWACS project. Further, new research activities, which embody Smart Antenna Technology, now supported under IST funding are also introduced.

Performance evaluation of a high frequency ATM wireless access system using directional antennas

This paper presents the results of a series of evaluation trials undertaken in the scope of the ACTS project AWACS in order to investigate the feasibility of the use of directional antennas to support high bit rate transmissions using a single carrier unequalised modem. The relationship between the antenna directivity, propagation statistics and modem performance are reported here. The results illustrate the effectiveness of correctly aligned, high gain antennas in reducing the undesired effects of multipath propagation. Further, the transceiver trials indicate the need for balancing antenna directivity at both ends of the link.