Indoor off-body wireless communication: static beamforming versus space-time coding

The performance of beamforming versus space-time coding using a body-worn textile antenna array is experimentally evaluated for an indoor environment, where a walking rescue worker transmits data in the 2.45 GHz ISM band, relying on a vertical textile four-antenna array integrated into his garment. The two transmission scenarios considered are static beamforming at low-elevation angles and space-time code based transmit diversity. Signals are received by a base station equipped with a horizontal array of four dipole antennas providing spatial receive diversity through maximum-ratio combining. Signal-to-noise ratios, bit error rate characteristics, and signal correlation properties are assessed for both off-body transmission scenarios. Without receiver diversity, the performance of space-time coding is generally better. In case of fourth-order receiver diversity, beamforming is superior in line-of-sight conditions. For non-line-of-sight propagation, the space-time codes perform better as soon as bit error rates are low enough for a reliable data link

Area spectral efficiency of soft-decision space–time–frequency shift-keying-aided slow-frequency-hopping multiple access

Slow-frequency-hopping multiple access (SFHMA) can provide inherent frequency diversity and beneficially randomize the effects of cochannel interference. It may also be advantageously combined with our novel space-time–frequency shift keying (STFSK) scheme. The proposed system’s area spectral efficiency is investigated in various cellular frequency reuse structures. Furthermore, it is compared to both classic Gaussian minimum shift keying (GMSK)-aided SFHMA and GMSK-assisted time- division/frequency-division multiple access (TD/FDMA). The more sophisticated third-generation wideband code-division multiple access (WCDMA) and the fourth-generation Long Term Evolution (LTE) systems were also included in our comparisons. We demonstrate that the area spectral efficiency of the STFSK-aided SFHMA system is higher than the GMSK-aided SFHMA and TD/FDMA systems, as well as WCDMA, but it is only 60% of the LTE system

Buffer-Aided Relaying with Adaptive Link Selection - Fixed and Mixed Rate Transmission

We consider a simple network consisting of a source, a half-duplex DF relay with a buffer, and a destination. We assume that the direct source-destination link is not available and all links undergo fading. We propose two new buffer-aided relaying schemes. In the first scheme, neither the source nor the relay have CSIT, and consequently, both nodes are forced to transmit with fixed rates. In contrast, in the second scheme, the source does not have CSIT and transmits with fixed rate but the relay has CSIT and adapts its transmission rate accordingly. In the absence of delay constraints, for both fixed rate and mixed rate transmission, we derive the throughput-optimal buffer-aided relaying protocols which select either the source or the relay for transmission based on the instantaneous SNRs of the source-relay and the relay-destination links. In addition, for the delay constrained case, we develop buffer-aided relaying protocols that achieve a predefined average delay. Compared to conventional relaying protocols, which select the transmitting node according to a predefined schedule independent of the link instantaneous SNRs, the proposed buffer-aided protocols with adaptive link selection achieve large performance gains. In particular, for fixed rate transmission, we show that the proposed protocol achieves a diversity gain of two as long as an average delay of more than three time slots can be afforded. Furthermore, for mixed rate transmission with an average delay of $E{T}$ time slots, a multiplexing gain of $r=1-1/(2E{T})$ is achieved. Hence, for mixed rate transmission, for sufficiently large average delays, buffer-aided half-duplex relaying with and without adaptive link selection does not suffer from a multiplexing gain loss compared to full-duplex relaying.Comment: IEEE Transactions on Information Theory. (Published

UTHM water quality classification based on sub index

River or stream at their source is unpolluted, but as water flow downstream, the river or lake is receiving point and non-point pollutant source. Ammoniacal nitrogen (NH3- N) and suspended solids (SS) strongly influences the dynamics of the dissolved oxygen in the water. Studies on monitoring this parameter were conducted for a river or lake but limited to the small man-made lake. This study is initiate to determine the changes in water quality of UTHM watershed as the water flows from upstream to downstream. The monitoring of NH3-N and TSS were monitored at two sampling schemes, 1) at the two-week interval and, 2) at a daily basis followed by the determination of the water quality sub-index particularly SIAN and SISS. The results showed that the two lakes in UTHM watershed were classified as polluted. In conclusion, the remedial action should be implemented to improve the water quality to meet the requirements at least to meet the recreational purpose

MGF Approach to the Analysis of Generalized Two-Ray Fading Models

We analyze a class of Generalized Two-Ray (GTR) fading channels that consist of two line of sight (LOS) components with random phase plus a diffuse component. We derive a closed form expression for the moment generating function (MGF) of the signal-to-noise ratio (SNR) for this model, which greatly simplifies its analysis. This expression arises from the observation that the GTR fading model can be expressed in terms of a conditional underlying Rician distribution. We illustrate the approach to derive simple expressions for statistics and performance metrics of interest such as the amount of fading, the level crossing rate, the symbol error rate, and the ergodic capacity in GTR fading channels. We also show that the effect of considering a more general distribution for the phase difference between the LOS components has an impact on the average SNR.Comment: 14 pages, 8 Figures and 2 Tables. This work has been accepted for publication at IEEE Transactions on Wireless Communications. Copyright (c) 2014 IEEE. Personal use of this material is permitted. However, permission to use this material for any other purposes must be obtained from the IEEE by sending a request to [email protected]

Blind multi-user combining at the base station for asynchronous CDMA systems

This paper studies the potential benefits of antenna arrays in cellular CDMA communications and proposes a powerful scheme to undertake the array processing at the base station in CDMA mobile systems. The proposed technique exploits the temporal structure of CDMA signals. The necessary information is extracted directly from the received signals, thus no training signal orPeer ReviewedPostprint (published version