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Summary form only given. Nowadays, diversity is widely applied for receiving at base stations for mobile cellular systems. However there is no experimental or simulated analysis have been conducted for diversity on on-body systems. This motivation has lead to the experimental of diversity measurement in the on body environment using two different types of diversity antennas. All the measurements were carried out at 2.45 GHz. Its necessity is suggested by the need for higher performance when large quantity of data has to be transferred with higher speed. The antennas used for the measurements were a monopole antenna and a disk-loaded monopole antenna integrated with PIN diode switches as a transmitter and receiver, respectively. The beams of a pattern diversity antenna were switched very quickly and controlled by PIC microcontroller. In this analysis, postures with different levels of mobility have been studied and roughly classified as sitting and standing positions. During the measurements, in both sitting and standing postures, free movements are allowed for each part of the body like leaning down, turning the trunk, walking, kneeling, and moving arms pretending to handle objects like in a real environment. Five potential channels have been investigated: belt-to-chest, belt-to-wrist, belt-to-ankle, belt-to-head and belt- to-back. Transmitter antenna was always be placed on the belt on the left side of the body while other positions are for receiver which in the opposite side. The diversity performance is generally measured as a diversity gain. This gain can be obtained by implementing one of the diversity combining methods, namely Switched Diversity Combining. The results show improvement in the signal reliability that proves the applicability of a diversity scheme to on-body communication systems.

UWB impulse radio communications can provide multi-path diversity when a rake receiver is used. The narrow time domain pulse can effectively combat the fading. Perfect pulse synchronisation is, however, required to obtain optimum performance. For a correlation receiver, small timing jitter between the reference pulse and the received pulse causes performance degradation. Analytical results for the performance degradation caused by timing jitter can be combined with a suitable channel fading probability distribution function to form a combined probability distribution for the received signal power at the output of the correlator. This paper analyses the statistical distribution of the received power at the output of a correlation receiver for a single pulse with timing jitter. By treating the power degradation due to timing jitter as a mathematical equivalence, it is shown that path diversity combining can be a potential technique to mitigate the timing jitter as well as the multi-path fading.

The achievable performance of various diversity combining schemes used in fast frequency hopping (FFH) aided M-ary frequency shift keying (MFSK) systems operating in a multiple access scenario subjected to Nakagami-m fading is investigated. Specifically, linear, self-normalization, hard limiting majority vote, soft limiting, product combining and order statistics-normalized envelope detection based diversity combining schemes are considered. The comparison of various diversity combining schemes is based on the achievable bit error rate versus the number of simultaneous users supported. It is shown using simulation results that although some of the combining schemes considered result in an inferior performance compared to the optimum soft limiting combiner, they offer the advantage of achieving an acceptable interference suppression performance without requiring side information.

This paper examines the performance improvement to be achieved by precoding the message vector by the Walsh Hadamard transform (WHT) in a MB-OFDM system, co-existing with a narrowband communication system, to both the MB-OFDM system and the narrowband communication system. The complexity added to the system is considered, and a simplified maximal ratio combining (MRC) receiver is proposed for the precoded system.

In current 3GPP R6 MBMS specifications, multimedia services are expected to be multicast/broadcast to all users or groups of users within the cell range. MBMS counting mechanism intends to analyse whether is more economic to transmit the multimedia services in a point to point (PtP) or point to multipoint (PtM) mode, evaluating in terms of radio resources management if it is preferable to use a single common channel reaching down the cell edge or single dedicated channels allocated to each user which conveys identical MBMS content. Macro diversity combining (MDC) is proposed as an enhancement for the MBMS standards, this method is proposed as a way to improve the received signal quality and at the same time increase the network coverage with considerable gains at radio resources availability.

Partial parallel interference cancellation (PPIC) and its adaptive implementation are investigated in this paper. The concept and methodology of the adaptive PPIC implementation is borrowed from the DS-CDMA context. A modification for the adaptive version is also proposed which leads to less complexity and better performance. Different scenarios have been considered to fully investigate the performances in a range of system loading with different combinations of convolutional coding, turbo coding and constellation. The performances are provided in terms of BER, FER, number of active users and in presence of multipath fading channel. They are also compared with the performances of the Equal Gain Combining (EGC) detector. In the low to moderate loadings the PPIC achieves a good performance. High order modulations, on the other hand, deteriorate its performance.

In this paper, we present the results of an investigation into the performance of an antenna architecture that simultaneously utilises the spatial and polarization dimensions to offer diversity and provide three orthogonal and independent subchannels respectively. Experimental results indicate that such a system would provide a 10% outage capacity gain of 8.5 b/s/Hz or 42.5 Mb/s in a 5 MHz UMTS channel over the traditional Single-Input Single-Output (SISO) system. At the same time, an Equal Gain Combining (EGC) diversity gain of up to 6 dB is obtained. It is demonstrated that correlation values in both the spatial and polarization dimensions are substantially low, i.e. below the threshold of 0.7. We also illustrate how the combined gain is reduced when the mode of operation is changed so that diversity is implemented in the spatial dimension and MEMO in the polarisation dimension. This system can adaptively operate in three modes, including a 6x6 MEMO operational mode in situations that do not need any diversity but offer a very high-data rate. Since the polarized antenna elements are co-located, the resulting compact system would be a good candidate for beyond 3G designs of robust high-performance small handsets.

Packet combining techniques are used to improve the performance of the hybrid ARQ mechanisms. This paper assesses the impact of several variations of packet combining, in its two basic forms (diversity combining and code combining), on a selective-repeat ARQ mechanism in an EGPRS wireless system. These variations range from the application of no packet combining at all, to the application of both diversity combining and code combining on all possible combinations of available packets. A link-level simulator for the EGPRS downlink in a typical urban mobile radio propagation environment is implemented. Mobile speeds of 5 km/h and 50 km/h are considered. It is shown that packet combining can significantly improve performance and has a greater impact at the higher speed. Furthermore, a packet combining strategy of moderate complexity is shown to be optimal in terms of the trade-off between performance, on the one hand, and the associated decoding-related processing load at the receiver, on the other.

The improvement in network performance due to the use of smart antennas in UTRA FDD handsets is investigated. A statistical model was derived, from published results, for the performance of a handset having a smart antenna. This model was used in simulations of a UTRA FDD network, and results gathered to identify the benefits of using a smart antenna in a handset compared to using a conventional antenna. It was found that handsets using smart antennas in UTRA FDD networks offer significant performance improvements that can be translated into substantial economic benefits.

This paper compares the effectiveness of three selection diversity reception schemes on the bit-error-rate (BER) performance of a PSA-16QAM system over frequency-selective Rayleigh fading channels. The first selection scheme is based on the fading distortion information on the received pilot symbols, the second scheme is based on the signal strength of the received pilot symbol and data symbols, and the third scheme is based on the energy of the received pilot symbol and data symbols. Computer simulation results have shown that the three selection schemes have very similar BER performance in most of the tested conditions.

The multi-carrier code-division multiple access (MC-CDMA) system is characterized by implementing the spectral spreading operation in the frequency domain, however, it can be also viewed as a special form of DS-CDMA in the time domain. In this paper, a time-domain adaptive centralized decision-feedback multiuser detector (MUD) is proposed for a synchronous MC-CDMA system in a frequency-selective multipath-fading channel. The suggested receiver employs a nonlinear centralized decision-feedback equalizer to suppress both intersymbol interference (ISI) and multi-access interference (MAI). The recursive least-squares (RLS) algorithm is employed to optimize the receiver parameters by minimizing the time-average weighted squared error. The performance of the proposed receiver architecture is evaluated in a multipath-fading channel exhibiting four propagation paths. Uniform and exponential multipath intensity profiles (MIP) are investigated. Computer simulation results demonstrate that the overall performance of the considered system which uses the proposed MUD outperforms both the conventional equal gain and maximum ratio combiner (EGC, MRC), as well as the single-user detector (SUD).

This paper shows analytically and through bit error rate (BER) simulations that both the G/sub 2/ space-time block (STB) and the maximal ratio receive combining (MRRC) systems suffer a BER performance degradation as a consequence of channel estimation errors, suffering the G/sub 2/ STB system the greatest degradation. Also, it is shown that both systems suffer equal performance degradation due to fading correlation.

Satellite and high altitude platforms (HAPs) are an important concept for next generation fixed and mobile communications. To predict indoor field strength levels from such distant transmitters, modifications to the standard indoor ray-tracing concept are proposed. These modifications require an array of virtual transmitters to be placed around the building under test. A range of diversity generation and combining techniques are considered to improve the performance of a 17 GHz indoor to indoor system. Diversity gains are computed and typical generation and combining strategies compared and ranked based on cost, complexity and performance. Investigation of a HAP to indoor environment shows the weakness of illumination from directly overhead.

Linearly polarised radio signals propagated through the ionosphere are received as a combination of elliptically polarised components. The high frequency signals received by two orthogonal antennas will consist of different blends of these components. If the combinations are sufficiently distinct, then the resulting diversity may be used to improve the quality of signal at the input to a modem using some kind of diversity combining. This paper presents a preliminary analysis of the channel characteristics of an HF polarisation diversity system.

There has been considerable effort devoted to increasing data rates over 3 kHz HF channels. The two most commonly employed serial-tone waveform standards, Mil-Std 188-110A and STANAG 4285, provide user data rates of 2400 bps after coding. Both permit data rates greater than this, but without forward error correction they have only limited utility in the difficult HF environment. Data rates approaching 9600 bps may be feasible on HF channels with good signal-to-noise ratios (SNR). However, in order to support these data rates on long-haul circuits, some means more effective than those currently employed must be found for dealing with the fading which is experienced on these circuits. In Serinken et al. (1996), the advantages of using polarization diversity on a sky-wave link between St. John's, Newfoundland and Ottawa, Ontario were demonstrated not only for diversity reception, but also for the case where diversity is employed in the transmission. Receive diversity was accomplished by introducing a combiner prior to the modem, a less-than-ideal approach for a fading frequency-dispersive channel. This paper represents a continuation of the work in Serinken et al. using a modem developed at the Communications Research Centre (CRC) which treats diversity combining and equalization as a joint optimization problem. In this work, the emphasis has been placed on using polarization diversity to achieve high data rates over a long-haul HF link.

All pass filters are increasingly important as components in digital communications systems, and, although digital baseband realizations are increasingly important, passive analogue filters remain the lowest cost implementations and those with the lowest power consumption for many radio applications. Conventional approaches are based an two port networks with bridged T and lattice structures. These require accurate matching of components to maintain the all-pass characteristics. This paper describes theoretical work and the results of simulation and experiment on the implementation of all pass networks and the related problem of voltage controlled phase shifting networks (for such applications as diversity combining) based on the reflection coefficient of lossless networks. (3 pages)

This paper is concerned with a number of techniques for improving the performance of the ETSI HIPERLAN physical layer. After a brief review of the HIPERLAN standard, a description of pre-coded GMSK is presented. The methods used to model the HIPERLAN radio channel are introduced and the performance impact of combined diversity and Decision Feedback Equalisation (DFE) presented. Important issues for an adhoc radio LAN such as frame synchronisation and frequency offset correction are addressed from a practical standpoint. Finally, incorporating the standard's BCH(31, 26) block code and interleaving strategy, the bit error rate (BER) and frame error rate (FER) performance is simulated both for standard and enhanced receiver designs. (7 pages)