Coin cell batteries have been used in low current application in the past. Due to their low cost and small size, they are an attractive option for use in wireless sensor networks. The rated capacity of a coin cell batter is not achievable. In fact, the achievable life time could be significantly shorter mainly due to characteristics of the draw currents in wireless applications. Measurements have revealed the dependence of coin cell battery capacity on characteristics of the current draw. Here we model lithium CR2032 coin cell battery capacity. It is shown that significant battery life time overestimation could result, if the capacity dependencies are ignored. Parallel coin cell battery configuration is proposed as a simple alternative to single battery case. It is demonstrated that parallel coin cell battery configuration results in longer battery life compared to the single battery case. The battery life improvement factor is shown to be a function of both the current draw and the functional end point voltage. The number of batteries in the parallel configurations influences the results and performance saturation occurs when the number of parallel batteries exceeds three. Based on our estimates, battery improvement factors of up to 600% are obtained.

The construction of spectral gaps via tone nulling in OFDM signaling for interference mitigation is investigated. Design formulas for the nominal gap bandwidth and gap depth are derived and shown to be in good agreement with simulation results. It is shown that the resulting gap spectrum is U-shaped with a maximum rejection depth approaching 20 dB even under ideal tone nulling; selectivity and bandwidth control are poor. In addition, to increase the rejection depth by even a modest amount, a significant number of tones must be nulled. When considering demanding spectral gap requirements, tone nulling requires significant margins and is of limited effectiveness in replacing conventional filtering for interference mitigation. I. INTRODUCTION

Ultra-wideband (UWB) emissions are analyzed in relation to the recent FCC waiver. The FCC waiver allows average and peak power measurements to be made in normal operating mode which can include hopped or gated signals. It is shown that signals with low peak-to-average power benefit most from gating to increase peak power and improve system performance in some fashion. Multi-band OFDM (MB-OFDM) and direct sequence UWB (DS-UWB) modulations for the IEEE 802.15 task group 3a alternative physical layer in wireless per- sonal area network (WPAN) standard are compared. It is shown that DS-UWB has significantly more peak power headroom than MB-OFDM which can be used to extend range or battery life.

Ultra-wideband (UWB) outdoor coverage prediction using ray tracing techniques is presented. The scenario consists of a farm area with clusters of scatterers over moderately varying terrain. A multiple frequency step approach, with weighted power levels is developed and shown to he useful in coverage and reliability prediction equivalent to a two-ray path loss model. Based on the simulation results, it is shown that UWB provides up. to 100 m range under different environmental conditions. The technique presented here can be generalized to UWB channel sounding using frequency scanning.

An ultra-wideband (UWB) channel modeling approach using ray tracing techniques is presented. The scenario consists of a farm area with clusters of scatterers over moderately varying terrain. The channel sounding consists of power-scaled distinct frequencies whereby all relevant ray signal descriptors are captured. From this we develop a two-ray and three-ray path loss model with associated parameters. The technique is suitable for UWB channel characterisation using narrowband channel sounding in outdoor environments with small number of scatterers over moderately varying terrain.

This paper describes a comprehensive statistical model for UWB propagation channels that is valid for a frequency range from 3-10 GHz. It is based on measurements and simulations in the following environments: residential indoor, office indoor, built-up outdoor, industrial indoor, farm environments, and body area networks. The model is independent of the used antennas. It includes the frequency dependence of the pathloss, as well as several generalizations of the Saleh-Valenzuela model, like mixed Poisson times of arrival and delay dependent cluster decay constants. The model can thus be used for realistic performance assessment of UWB systems. It was accepted by the IEEE 802.15.4a working group (WG) as standard model for evaluation of UWB system proposals

A model for multi-band orthogonal frequency division multiplex (MB-OFDM) interference on in-band broadband uncoded QPSK receivers is provided. Multi-band OFDM results in periodic gated noise with power scaled to equal the total power of AWGN over the entire hop time. Since MB-OFDM can have high peak-to-average power (PAP), its impulsive characteristics are captured by the model as a function of the hop depth. Based on the proposed model, it is shown that MB-OFDM is a more harmful interference than ungated AWGN for the same effective isotropic radiated power (EIRP).

The method introduced in this article is a new approach to text compression that shows merit in a higher compression ratio, its ability to be integrated with existing utilities to augment their performance, and its resiliency to error introduced through bit corruption by limiting the error effect to only that word where the error occurred. The results introduced, based on a comprehensive evaluation of the proposed method with respect to existing utilities, demonstrate such merits and are provided in support of these assertions.

An efficient and versatile wavelet based picture compression standard, known as JPEG 2000, is under development. Since wireless multimedia is among the intended applications of this standard, JPEG 2000 has to be robust to channel errors. Our results indicate that the quality of received imagery using JPEG 2000 even with error resilient provisions could be very poor. Worst case PSNR serves as an important bench mark for comparing image transmission schemes and a larger worst case peak signal-to-noise ratio (PSNR) is preferred. We present a scheme for increasing worst case PSNR, known as transmission diversity for JPEG 2000. In TD-JPEG 2000, instead of transmitting an image at full rate, the image is transmitted twice at half rate. The image encoder and decoder structures are given and a detailed operation of the decoder based on a set of rules is provided. It is observed that the worst case PSNR improves significantly compared to conventional JPEG 2000 when our method is applied to the transmission of images over noisy channels. Additionally, subjective evaluations of the received images verify the improvements in picture quality.

The 802.11a standard has been considered and applied to DSRC (dedicated short-range communication) in the 5.9 GHz band. Among the parameters of the DSRC are support for data transfers during high-mobility applications. Given that the 802.11a standard was designed for relatively low speed (3 MPH) wireless LAN applications, it is necessary to analyze the suitability of the standard in outdoor high-speed mobility applications. We present an analysis of the error rate of 802.11a in high-speed mobile applications. It is shown that 802.11a/RA communication exhibits high packet error rates and consequently lower channel capacity. An example is submitted and discussed.

There are some applications where the information source is nonsymmetric. Here, it is shown that differential pulse code modulation (DPCM) of video signals results in a nonsymmetric source. Previous works on 2-D signal design have been focused around equally likely sources. In this paper, an iterative algorithm for minimum error signal design subject to average power (or peak power) constraint is presented. Then, design of minimum cost signal sets is addressed, and application to a DPCM system for picture transmission is developed. Comparisons are made between the nonsymmetric and symmetric signal design in one case and between minimum error signal design and minimum cost signal selection in the other case, for the transmission of DPCM-coded signals. It is seen that nonsymmetric signal design gains significant improvements over the equally likely signal selection when the channel is noisy. Minimum cost signal design also demonstrated some improvement relative to minimum error signal selection over noisy channels.

The problem of DPCM picture transmission over noisy channels is considered. It is well known that DPCM systems are very sensitive to channel errors. The goal in this work is to build robustness against channel errors. Three methods are proposed in this paper and are obtained by modeling the encoded signal as a Markov sequence. First, an optimum method for decoding correlated sequences is derived, and it is shown to require Viterbi decoding. Then, a modified MAP method (MMAP) for Markov sequences is described. A maximal signal-to-noise (MSNR) receiver for DPCM systems is also developed that minimizes the distortion power due to channel errors. The appropriate cost matrix for this receiver is computed. These methods are applied to DPCM picture transmission over noisy channels and are compared with a another method. The SNR graphs, as well as subjective examination of the received pictures, demonstrate that the proposed procedures are quite effective and superior to that method. Among the proposed methods, the MSNR receiver was found to be more effective than the others for a given order of the Markov model. It is observed that the proposed methods are most beneficial for low detail pictures.