Pre-Compensation for Rayleigh Fading Channels in Time Division Duplex OFDM Systems

Coherent demodulation results in good detection performance but requires channel estimation. Fading pre-compensation (precoding) at the transmitter can lead to low-complex receiver structures with good performance capabilities, without the need for channel estimation. Time division duplex systems based on orthogonal frequency division multiplex (OFDM) are particularly suited to this because intersymbol interference effects can be neglected, simplifying transmitter adjustments. Methods that involve amplitude and/or phase pre-compensation are compared in terms of resulting bit error rate and increase in peak-to-average power ratio. Dynamic channels degrade the performance as the block lengths get longer. For a certain block length the performance degrades below that of traditional differential decoding. A block length of up to 40 times that used in the Digital European Cordless Telephone system, DECT, is possible using channel estimation and ideal Wiener prediction.     

Immunoelectroosmophoresis for detection of reo-like virus: methodology and comparison with electron microscopy

In two separate studies, faecal samples were collected from children with acute gastroenteritis; the samples were tested both by electron microscopy and immunoelectroosmophoresis with a view to detect reo-like virus. In 94 per cent and 100 per cent of samples positive by electron microscopy in the first and second material, respectively, a precipitin line was found after electrophoresis, using a guinea pig antiserum against a purified bovine virus. No false positives were detected by this method.     

Outdoor-to-Indoor Office MIMO Measurements and Analysis at 5.2 GHz

The outdoor-to-indoor wireless propagation channel is of interest for cellular and wireless local area network applications. This paper presents the measurement results and analysis based on our multiple-input-multiple-output (MIMO) measurement campaign, which is one of the first to characterize the outdoor-to-indoor channel. The measurements were performed at 5.2 GHz; the receiver was placed indoors at 53 different locations in an office building, and the transmitter was placed at three "base station" positions on a nearby rooftop. We report on the root-mean-square (RMS) angular spread, building penetration, and other statistical parameters that characterize the channel. Our analysis is focused on three MIMO channel assumptions often used in stochastic models. 1) It is commonly assumed that the channel matrix can be represented as a sum of a line-of-sight (LOS) contribution and a zero-mean complex Gaussian distribution. Our investigation shows that this model does not adequately represent our measurement data. 2) It is often assumed that the Rician if-factor is equal to the power ratio of the LOS component and the other multipath components (MPCs). We show that this is not the case, and we highlight the difference between the Rician if-factor often associated with LOS channels and a similar power ratio for the estimated LOS MPC. 3) A widespread assumption is that the full correlation matrix of the channel can be decomposed into a Kronecker product of the correlation matrices at the transmit and receive array. Our investigations show that the direction-of-arrival (DOA) spectrum noticeably depends on the direction-of-departure (DOD); therefore, the Kronecker model is not applicable, and models with less-restrictive assumptions on the channel, e.g., the Weichselberger model or the full correlation model, should be used.     

Characterization of Vehicle-to-Vehicle Radio Channels from Measurements at 5.2 GHz

The development of efficient vehicle-to-vehicle (V2V) communications systems requires an understanding of the underlying propagation channels. In this paper, we present results on pathloss, power-delay profiles (PDPs), and delay-Doppler spectra from a high speed measurement campaign on a highway in Lund, Sweden. Measurements were performed at a carrier frequency of 5.2 GHz with the communicating vehicles traveling on the highway in opposite directions. A pathloss coefficient of 1.8 shows the best fit in the mean square sense with our measurement. The average root mean square (RMS) delay spread is between 263 ns and 376 ns, depending on the noise threshold. We investigate and describe selected paths in the delay-Doppler domain, where we observe Doppler shifts of more than 1,000 Hz.     

Measurement of keyhole effect in a wireless multiple-input multiple-output (MIMO) channel

It has been predicted theoretically that for some environments, the capacity of wireless multiple-input multiple-output systems can become very low even for uncorrelated signals; this effect has been termed "keyhole" or "pinhole." In this letter, we present the (to our knowledge) first measurement of this effect. The measurements are done in a controlled indoor environment, with transmitter and receiver in two adjacent rooms. One of the rooms is shielded, and propagation to the other room can occur only through a hole or a waveguide in the wall. We find that only the waveguide leads to an unambiguous keyhole, while a hole of the same size still allows multimodal propagation. Measurement of amplitude statistics also confirm theoretical predictions.     

Non-Coherent Fourth-Order Detector for Impulse Radio Ultra Wideband Systems: Empirical Evaluation Using Channel Measurements

Low-complex and low-power non-coherent energy detectors (EDs) are interesting for low data rate impulse radio (IR) ultra wideband (UWB) systems, but suffer from a loss in performance compared to coherent receivers. The performance of an ED also strongly depends on the integration interval (window size) of the integrator and the window position. This paper presents a non-coherent fourth-order detector (FD) which can discriminate between Gaussian noise signals and non-Gaussian IR-UWB signals by directly estimating the fourth-order moment of the received signal. The performance of the detectors is evaluated using realistic channels measured in a corridor, an office and a laboratory environment. The results show that bit-error-rate (BER) performance of the proposed FD receiver is slightly better than the ED in low signal-to-noise ratio (SNR) region and its performance improves as the SNR increases. In addition, BER of the FD receiver is less sensitive to overestimation of the integration interval making it relatively robust to variations of the channel delay spread. Finally, a criteria for the selection of integration time of the proposed detector is suggested.     

Characterisation of a time-variant wireless propagation channel for outdoor short-range sensor networks

This study presents sample measurements and analysis characterising the radio channel for outdoor short-range sensor networks. A number of transmit and receive antennas are placed on the ground in an open area. The measured propagation channel is time varying because of the controlled motion of a person walking in the vicinity of the nodes. The statistics of both the line-of-sight (LOS) path and the scattered component of the measured channel are observed to be non-stationary. The channel (power) gains are found to be significantly influenced by the pedestrian movement, only when the LOS path is momentarily blocked. The authors present a generic approach to model receive signal fluctuations because of body blockage of the LOS path. Our approach, which is similar to the referenced work of Pagani and Pajusco, additionally models the time-variant Doppler spectrum of the residue (scattered) component of the measured channel, that is the remainder of the measured channel after the LOS path has been extracted. The proposed modelling approach is parameterised and validated from the measurements.     

Physico- Chemical Characteristics and Functional Properties of Starch and Dietary Fibre in Grass Pea Seeds

Physico-chemical and functional properties of starch and fibre in raw and processed grass pea seeds were evaluated. Whole grass pea seeds were found to contain 41 % starch and 17% total dietary fibre (2% soluble and 15% insoluble) on dry matter basis. Examination by using scanning electron microscopy revealed oval shaped starch granules with an average width of 17 μm and length of 25 μm. Raw sample had a gelatinization onset temperature of 62°C and two endothermic transition peaks at about 73°C and 94°C, in addition the starch isolated from grass pea flour was shown to have a transition enthalpy (ΔH) of 10 Jg⁻¹. The viscosity of the raw sample (using a Brabender amylograph) reached peak maximum at 80–95°C, decreasing during the 30 min holding time (at 95°C) followed by an increase during cooling to 50°C. Raw whole seed flour was shown to have a water absorption and water solubility index (WSI) of 3 and 16%, respectively. Samples that had been cooked for 60 min had a lower WSI than those cooked for 30 min; this was further reduced in the samples cooked after soaking. The carbohydrate extracted from raw flour was found to be mainly high Mwt carbohydrate (55%), eluted at Kav < 0.2.     

The building process as a tool towards an all-inclusive school. A Swedish example focusing on children with defined concentration difficulties such as ADHD, autism and Down’s syndrome

Professionals who take part in the building process have long been concerned with the same environmental factors, e.g. spatial layout, capacity, and function, as well as user demography. Through the knowledge gained on the ways environmental factors affect users of buildings, the need to understand how to handle these factors has grown, due to their influence on the building process. It will be shown how research on the influence of environmental factors found in the school environment can be applied to the building process. The purpose is to increase the accessibility to education through prolonged concentration ability among extra-sensitive children who have defined concentration difficulties such as Autism Spectrum Disorders (autism), Attention Deficit Hyperactivity Disorder (ADHD), and Down’s syndrome. This is a direct attempt to implement Swedish legislation (The Swedish Education Act, SFS 1985, p. 1100) regarding children’s accessibility to education, including the aims of the Swedish National Action Plan for Disability Policy (“From Patient to Citizen”, Swedish Government Bill 1999/2000, p. 79), which is based on the United Nations’ Universal Declaration of Human Rights (1948), where it is stated that all children should have equal access to education. The Swedish Work Environment Authority also declares that the work environment, in this case the school, should be adjusted to the physical and psychological needs of the users of the building (The Work Environment Act, AFS 2000, p. 42).