Micro- and macrodiversity MDPSK on shadowed frequency-selectivechannels

The performance of M-ary differential phase shift keying (MDPSK) on frequency-selective slow Rayleigh fading, lognormal shadowed channels with diversity combining is analyzed for mobile and portable applications. The use of L-branch equal gain postdetection microdiversity combining to mitigate the effects of fading and P-port macrodiversity to alleviate the effects of shadowing are investigated. Four performance criteria are considered for a frequency-selective multipath fading, intersymbol interference channel. These are, the short term bit error rate (BER), the irreducible BER, the complementary distribution over the lognormal shadowing of the average BER, and the probability that the instantaneous BER exceeds a threshold value, averaged over a spatial environment. Closed-form expressions for the four performance criteria are obtained. The BER and outage performance results show that diversity combining is an effective method for improving the system performance (and hence system reliability), when the normalized delay spread is not large. It is also seen that, in most cases, 4DPSK gives the best performance followed by 8DPSK and 2DPSK, respectively, for a given information throughput     

Optimal Detection of Hard-Limited Data Signals in Different Noise Environments

A number of digital techniques for detecting binary antipodal signals are based on examining the polarities of the received signal samples and ignoring their amplitudes. The structure of the optimum detector for the hard-limited samples is derived, and its performance is compared to those of some commonly used schemes in impulsive as well as Gaussian noise environments. The optimum receiver forM-ary signaling based on received signal samples quantized to an arbitrary number of levels is obtained and compared to other detectors.     

A pulse design paradigm for ultra-wideband communication systems

A novel paradigm is proposed to design time-limited pulse shapes for ultra-wideband communication systems. Pulses can be designed using the new paradigm that not only conform to spectral emission constraints, but also achieve good bit error rate performance in multiple access interference environments. Compared with previously proposed pulses, the novel pulses provide the same multiple access performance as the Gaussian monocycles yet have advantages over them in terms of power spectrum and spectral emission constraints. Our pulse design paradigm provides a flexible and effective method for designing suitable pulses for ultra-wideband communication applications that comply with frequency emission constraints.     

Linking active living and nutrition counselling: dietitians' perceptions.

Healthy eating and active living have become key concepts in health promotion, and, increasingly, the two messages are being combined. Dietitians are in an ideal position to promote physical activity as an adjunct to nutrition counselling. Focus group interviews were used to identify dietitians' perceptions and needs related to incorporating active living messages into their practices. Six focus groups, involving 42 participants (40 registered dietitians and two dietetic interns), were conducted in cities throughout Alberta. Issues explored during the interviews included the dietitian's role in promoting active living, barriers to promoting physical activity, opportunities for collaboration between dietitians and exercise professionals, and dietitians' perceived needs for integrating active living messages into their practices effectively. Findings indicate strong support for incorporating active living messages into nutrition counselling. However, lack of knowledge was identified as a barrier to dietitians' proactive role, and concerns were raised about public and professional perceptions if dietitians counselled on this issue. Participants felt that they required additional knowledge and training in physical activity in order to promote it effectively. Development and implementation of programs designed to meet these needs would help dietitians integrate active living messages into their practices.     

Bandwidth efficient QPSK in cochannel interference and fading

The performances of QPSK in the presence of cochannel interference in both nonfading and fading environments are analyzed. Three approaches for representing the cochannel interference are investigated. These are a precise error probability method, a sum of sinusoids (sinusoidal) model, and a Gaussian interference model. In addition to determining precise results for the performance of QPSK in cochannel interference, we examine the validity of these two interference models in both additive white Gaussian noise (AWGN) environments and in different flat fading environments; Rayleigh, Ricean, and Nakagami. Nyquist pulse shaping is considered and the effects of cross channel ISI produced by the cochannel interference are accounted for in the precise interference model. Also accounted for are the random symbol and carrier timing offsets of the interfering signals. Two performance criteria are considered. These are the average bit error rate and the interference penalty. The latter is defined as the increase in signal-to-noise power ratio (SNR) required by a system with cochannel interference in order to maintain the same BER as a system without interference. Attention is given, in particular, to the outdoor microcellular fading environment. In this environment, the fading experienced by the interfering signals may be represented by a Rayleigh-fading model while the fading experienced by the desired signal may be represented by a Ricean or a Nakagami-fading model     

SER of threshold-based hybrid selection/maximal-ratio combining in equicorrelated Nakagami fading

The average symbol error rate (SER) of threshold-based hybrid selection/maximal-ratio combining (T-HS/MRC) in equicorrelated Nakagami-m fading is obtained for positive integer values of fading parameter, m. The derivation allows different M-ary linear modulation schemes. We illustrate our methodology using M-ary phase-shift keying as an example.     

Accurate evaluation of multiple-access performance in TH-PPM and TH-BPSK UWB systems

A characteristic function method is proposed for precisely calculating the bit-error probability of time-hopping (TH) ultra-wideband (UWB) systems with multiple-access interference in an additive white Gaussian noise environment. The analytical expressions are validated by simulation and used to assess the accuracy of the Gaussian approximation. The Gaussian approximation is shown to be inaccurate for predicting bit-error rates (BERs) for medium and large signal-to-noise ratio (SNR) values. The performances of TH pulse position modulation (PPM) and binary phase-shift keying (BPSK) modulation schemes are accurately compared in terms of the BER. It is shown that the BPSK system outperforms the binary PPM system for all values of SNR. The sensitivity of the performance of the modulation schemes to the system parameters is also addressed through numerical examples.     

Segmentation of textured polarimetric SAR scenes by likelihood approximation

A hierarchical stepwise optimization process is developed for polarimetric synthetic aperture radar image segmentation. We show that image segmentation can be viewed as a likelihood approximation problem. The likelihood segment merging criteria are derived using the multivariate complex Gaussian, the Wishart distribution, and the K-distribution. In the presence of spatial texture, the Gaussian-Wishart segmentation is not appropriate. The K-distribution segmentation is more effective in textured forested areas. The validity of the product model is also assessed, and a field-adaptable segmentation strategy combining different criteria is examined.     

An optimal lognormal approximation to lognormal sum distributions

Sums of lognormal random variables occur in many problems in wireless communications because signal shadowing is well modeled by the lognormal distribution. The lognormal sum distribution is not known in the closed form and is difficult to compute numerically. Several approximations to the distribution have been proposed and employed in applications. Some widely used approximations are based on the assumption that a lognormal sum is well approximated by a lognormal random variable. Here, a new paradigm for approximating lognormal sum distributions is presented. A linearizing transform is used with a linear minimax approximation to determine an optimal lognormal approximation to a lognormal sum distribution. The accuracies of the new method are quantitatively compared to the accuracies of some well-known approximations. In some practical cases, the optimal lognormal approximation is several orders of magnitude more accurate than previous approximations. Efficient numerical computation of the lognormal characteristic function is also considered.