We present a feasibility analysis of the controlled delivery power grid (CDG) that uses aggregated power request by users to reduce communications overhead. The CDG, as an approach to the power grid, uses a data network to communicate requests and grants of power in the distribution of electrical power. These requests and grants allow the energy supplier know the power demand in advance and to designate the loads and the time when power is supplied to them. Each load is assigned a power-network address that is used for communication of requests and grants with the energy supplier. With addressed loads, power is only delivered to selected loads. However, issuing a request for power before delivery takes place requires knowing the demand of power the load consumes during the operation interval. However, it is a general concern that having issuing requests in a time-slot basis may risk request losses and therefore, generate intermittent supply. Therefore, we propose request aggregation to minimize the number of requests issued. We show by simulation that the CDG with request aggregation attains high performance, in terms of satisfaction ratio and waiting time for power supply.

Ultra-wideband indoor line-of-sight frequency-domain channel measurements have been performed in the 2-6 GHz frequency band using three different transmit/receive antenna combination pairs. The effects of antenna directivity on path loss and multipath propagation in the channel are analyzed extensively for various omnidirectional and directional antenna combinations. A statistical model of the path loss in the channel is presented, in which all path loss exponents result in better than free space loss. The shadow fading experienced in the channel is shown to highly agree with the normal probability assumption. There is a significant reduction in root mean square delay spread when directional antennas are used at the transmitter and receiver or solely at the receiver with respect to an omnidirectional/omnidirectional antenna pair. Finally, a distance-dependent statistical impulse response model of the channel is presented along with simulation results that significantly concur with the measured data.

In this paper we analyze the performance of ultra-wideband (UWB) communications in the presence interference. The interference is modeled as a zero mean random process with constant power spectral density over a certain bandwidth. Closed-form expressions are developed for the processing gain of a pulse position modulation UWB utilizing rectangular pulses. Simple approximations are obtained for special cases (narrowband and wideband interference). We compare the interference suppression properties of UWB and direct-sequence spread spectrum (DS-SS) under certain assumptions. It is shown that in case of narrowband interference (with respect to the spread spectrum bandwidth), UWB provides more effective interference suppression than DS-SS.

A design procedure has been developed to determine the required operating conditions for a pulse-frequency modulation (PFM) system (modulation index, required system bandwidth, and receiver carrier-to-noise ratio (CNR) for a specified receiver SNR (signal-to-noise ratio) and number of clicks per second. The PFM processing gain (=SNR/CNR) was measured to be 40 dB for a modulation index of beta =2.5, which agrees closely with the theory. The theoretical processing gain advantage of PFM over FM is 15.9 dB for a modulation index of beta =2.5 with receiver bandwidth B/sub rx/=50 MHz.>