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A unified approach to adaptive antenna array design and transceiver signal processing architectures is proposed for the user segment of the land mobile satellite communication service. This technique is described in its conceptual form, and compared with steered antenna array configurations currently favored for this class communication system. The proposed system uses established diversity combining techniques previously developed for mobile terrestrial radio. It is suggested that a diversity-based receiver architecture would allow the coherent recombination of the multipath signal energy present at the mobile terminal site, and thereby enhance system performance for a given link budget. The cophasing of the multipath signals can be implemented using a FFSR (feedforward signal regeneration) signal-processing architecture, which uses the presence of a pilot-tone within the communications channel. On transmit, a retrodirective beam is formed towards the active satellite. The economic viability of such a transceiver is also considered.

In this paper the proposal for a Diversity Combining Antenna Array for a land mobile satellite (LMS) terminal is further examined by the authors. This novel approach employs established diversity combining techniques previously developed for mobile terrestrial radio. Here it is suggested that a diversity based receiver architecture would allow the coherent recombination of the multipath signal energy present at the mobile terminal site, thereby enhancing system performance for a given link budget. In order to justify this new approach to terminal design it has been necessary to obtain additional propagation measurements of the land mobile satellite channel and these results are presented here. Finally, the implementation of such a transceiver is briefly addressed.

In a given number of wireless systems, and ultrawideband (UWB) in particular, a way to communicate between transceivers is by correlating received pulses with one or several reference-pulse templates. The reference template(s) aim to give a good representation of the transmitted signal. However, even for unscattered signals, resulting from line-of-sight (LOS) transmissions, radiated pulses may differ as a function of the antennas’ angle of departure/capture or may "look different" due to limited spatial resolution at the receiver. As these inaccuracies are often neglected and may have an impact on the robustness of a communication’s link, unscattered LOS UWB measurements, from 3.5 GHz to 10.5 GHz, are used in this paper to explore: (i) the effects of correlating received signals with different pulse templates as a result of distance changes between antennas (shorter than the spatial resolution of the system) and different angles of antenna radiation/capture; and (ii) the error in distance prediction from a system relaying on peak detection and limited by its spatial resolution. As a result, pulse correlation values were found to fluctuate from one and up to a value of 0.4 in some cases. Also, errors in distance estimation were characterised against different interpolation factors, from which modelling parameters are presented.

A new and simple Power Amplifier (PA) linearization method is proposed and demonstrated using a very high efficiency yet inherently nonlinear inverse class-F PA. This was conducted in the presence of a generic variable envelope RF signal in order to extract its AM-AM and AM-PM characteristics. Deducing the polynomial pre-distortion parameters from the AM-AM and AM-PM characteristic has resulted in the successful linearization of the PA in the presence of 3GPP Long Term Evolution (LTE) signals. The results obtained for the PA - a 12W GaN HEMT inverse Class-F structure designed to operate at 900MHz - demonstrate the proof of concept and the efficiency of the proposed linearization technique with significant advantageous reduction in base-band resources for 3GPP LTE applications. A new and simple power amplifier (PA) linearization method is proposed and demonstrated using a very high efficiency yet inherently nonlinear inverse class-F PA. This was conducted in the presence of a generic variable envelope RF signal in order to extract its AM-AM and AM-PM characteristics. Deducing the polynomial pre-distortion parameters from the AM-AM and AM-PM characteristic has resulted in the successful linearization of the PA in the presence of 3GPP long term evolution (LTE) signals. The results obtained for the PA - a 12 W GaN HEMT inverse class-F structure designed to operate at 900 MHz - demonstrate the proof of concept and the efficiency of the proposed linearization technique with significant advantageous reduction in base-band resources for 3GPP LTE applications.

This paper presents early results of an investigation into the fabrication of a textile E-shaped patch antenna suitable for broadband communications in the ISM band (2.4 GHz - 2.5 GHz). The design was inspired from literature and further tuned using in-house FDTD software. The textile antenna compares reasonably well with the same antenna in conventional technology featuring 17% bandwidth with a centre frequency of 2.4 GHz and good radiation patterns

The likelihood of line-of-sight (LoS) is an essential component in any radio channel model. It is particularly useful for radio network planning and urban coverage prediction. Empirical LoS models are hard to derive due to a strong dependency on local topology and the need for large measurement datasets. Since buildings are the major obstructions in a dense urban environment, we propose a new theoretical model to determine the LoS probability for air-to-ground channels based on local building geometry and knife-edge diffraction theory. The model takes into account key statistical parameters such as building height, building size, building coverage, street width and street angle distribution. The theoretical model is shown to agree well with ray tracing simulation results. The statistical parameters, such as mean building height, percentage of area covered by buildings (building coverage) and building density, can all be easily obtained for a specific location. We also derive equations for the likelihood of LoS for a direct slant path. These equations can be used in the analysis of air-to-ground channels.

The lecture discusses how the past 40 years or so have witnessed a tremendous growth in the use and application of mobile communications. The UK has played a major role in the research and development of the technologies, systems and networks that are in use today. Professor McGeehan discusses how wireless and mobile communications have changed over this period, highlighting some of the key, but perhaps little known, innovations that have shaped the way we communicate today. In particular, consideration will be given to pioneering academic research in areas including propagation, multi-level modulation, ‘linearised’ power amplifiers, SMART antennas, CDMA and Wireless LANs. Several disruptive technologies and their impact on the future are also discussed.

Upper bounds for symbol-error probability are developed for multichannel reception of M-ary phase-shift keying (M-PSK) over frequency-flat Rayleigh-fading channels. Differential coherent demodulation of differentially encoded M-PSK (M-DPSK), pilot-tone aided coherent demodulation of M-PSK (PTA M-CPSK) and pilot-symbol aided coherent demodulation of M-PSK (PSA M-CPSK) are considered in the formulation. The bounds enable the investigation of the effects of fading correlation and unequal average power level between channels using postdetection diversity reception with maximal-ratio combining. Error-performance degradation due to imperfect demodulation effects, such as Doppler spread in M-DPSK schemes, noisy reference signals in PTA M-CPSK, and PSA M-CPSK schemes can be taken into account in the formulation. Exact bit-error probabilities for both binary and quaternary phase-shift keying are also derived. Upper bounds for symbol-error probability are developed for multichannel reception of M-ary phase-shift keying (M-PSK) over frequency-flat Rayleigh-fading channels. Differential coherent demodulation of differentially encoded M-PSK (M-DPSK), pilot-tone aided coherent demodulation of M-PSK (PTA M-CPSK) and pilot-symbol aided coherent demodulation of M-PSK (PSA M-CPSK) are considered in the formulation. The bounds enable the investigation of the effects of fading correlation and unequal average power level between channels using postdetection diversity reception with maximal-ratio combining. Error-performance degradation due to imperfect demodulation effects, such as Doppler spread in M-DPSK schemes, noisy reference signals in PTA M-CPSK, and PSA M-CPSK schemes can be taken into account in the formulation. Exact bit-error probabilities for both binary and quaternary phase-shift keying are also derived.

This paper focuses on the performance of equalisation strategies for a downlink MC-CDMA (Multi Carrier-Code Division Multiple Access) based system. MC-CDMA is a leading candidate modulation/multiple access scheme for so called 4th Generation communications. Simulation results utilising Maximum Ratio Combining (MRC), Equal Gain Combining (EGC), Orthogonal Restoring Combining (ORC), and Minimum Mean-Squared Error Combining (MMSEC) for multi-user scenarios are presented. Performance is characterised by bit error rate (BER) for the downlink. A time domain least square channel estimator was implemented along with a frequency based pilot estimation scheme and comparisons made with perfect channel estimation. A complexity analysis of each equalisation scheme is also undertaken. Performance results show that MMSEC provides the best performance for the multi-user scenario as MRC and ultimately EGC both enter error floors as the number of users increase in a wideband channel thereby reducing their usefulness as multi user equalisation schemes

The European Commission, through RACE, ACTS and now the IST programmes, 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 additional operational benefits, such as multipath mitigation and range extension, that this technology can offer wireless network deployments. This paper1 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.

In this paper a number of techniques are investigated for predicting the performance of a digital system in fading channels. A method is presented which combines both bit error rate simulation and site-specific channel characterisation using ray tracing techniques. Probability density functions are developed for the resulting signal variations which show instantaneous bit error rate versus fade depth. Using this approach, the irreducible error rate for both random FM and RMS delay spread have been determined for π/4DQPSK. It is shown that RMS delay spread alone cannot fully represent the distorting effect of the wideband channel. However, if combined with narrowband fading statistics, it becomes possible to estimate the average bit error rate for a given propagation environment. To increase the speed of our fading simulations, an importance sampling approach has also been developed which yields results that are comparable to those generated from full simulations

Present mobile radio services offer primarily voice communication to customers roaming within large cell topographies. Typically these systems do not require large bandwidths and offer little or nothing in the way of data based services with the result that they operate with bit error rates as high as one in one thousand. However, in recent years there has been a trend towards more spectrally efficient, small cell, high data rate systems and a growing demandfor a new type of service offering very high data rates for indoor wireless LAN applications. In this paper we present a model which predicts propagation characteristics for given small cell environments and subsequently uses the propagation data to analyse the radio link performance for a variety of system designs. In order to achieve very accurate high data rate transmission the benefits of linear modulation combined with techniques such as diversity, frequency hopping and pulse shaping are investigated

In this contribution, a software multipath fading simulation package (previously applied to the statistical analysis of the fading statistics of single transmitter schemes for three very different mobile radio environments) is used to analyze the performance of a quasi-synchronous, multitransmitter, amplitude modulated sideband diversity area coverage system. By conducting field trials in an area known to obey Rayleigh fading statistics, it has been possible to compare the simulated statistical results to those obtained theoretically and experimentally, and to show that good agreement exists. The fading simulator is capable of being extended to other types of multitransmitter radio scheme employing different forms of modulation.

The paper briefly reviews a new pilot tone SSB configuration, transparent tone-in-band (TTIB), which may be used in mobile radio systems from low-band VHF to microwave frequencies. Results are presented for the system performance when it is used to transmit coherent PSK, noncoherent FSK and DPSK data formats under white noise and Rayleigh fading conditions