Wideband measurements were perfonned using a directsequence spread-spectrum measurement system in the airto-ground radio environment to characterize propagation between an airborne transmitter and a ground-based receiving antenna array at a center frequency of 2.05 GHz. The transmitter was flown along constant-radius arcs at low altitudes around the receiver location to obtain measurement resul...

This paper uses a bi-partite network model to calculate the coverage achieved by a delay-tolerant information dissemination algorithm in a specialized setting. The specialized Delay Tolerant Network (DTN) system comprises static message buffers or throwboxes kept in popular places besides the mobile agents hopping from one place to another. We identify that an information dissemination techniqu...

In this outdoor propagation study, low antenna heights of 1. 7 m are used at both the transmitter and the receiver to measure wideband (100 MHz baseband) power-delay profiles (PDPs) of the channel for a peer-to-peer communications system operating at 1.8 GHz. Rural and urban areas are studied in 22 different transmitter-receiver links, and the path loss and delay spread characteristics are pres...

This paper addresses cyclic delay diversity (CDD) in an ultra-wideband communication system based on orthogonal frequency division multiplexing (OFDM) technique. Symbol error rate and outage probability have been derived. It is shown that with only two transmit antennas, CDD effectively improves SER performance and reduces outage probability significantly especially when the channel delay sprea...

This paper investigates the use of frequency domain equalization techniques to suppress narrowband interference and combine multiple paths in both direct sequence spread spectrum (DS-SS) and orthogonal frequency division multiplexing (OFDM) spread spectrum (OFDM-SS) systems. The similarities between the two signaling formats are highlighted and it is shown that the same receiver structures can ...

This paper investigates the use of frequency domain equalization techniques to suppress narrowband interference and combine multiple paths in both direct sequence spread spectrum (DS-SS) and orthogonal frequency division multiplexing (OFDM) spread spectrum (OFDM-SS) systems. The similarities between the two signaling formats are highlighted and it is shown that the same receiver structures can ...

Abstrac -This paper presents comprehensive experimental results obtained from narrowband and wideband radio channel measurements in an underground mine with narrow veins at 2.4 GHz. From CW measurement data, large-scale distance-power curves and path-loss exponents of the environment are determined. Other relevant parameters such as, mean excess delay, maximum excess delay and rms delay spread ...

In this paper, estimation of both global (long term) and local (instantaneous) frequency selectivity and rms delay spread of wireless communication channel are investigated. A practical algorithm for averaged channel frequency correlation estimation, which is used for measuring frequency selectivity, is given. Average rms delay spread of the channel is calculated from the channel frequency corr...

This research was funded in part by Semiconductor Research Corporation under contract (#98-HJ-638) and in part by DARPA. Abstract The increase in power consumption due to interconnects and the variation in delays (delay spread) among long interconnects are becoming important issues for design of high performance and low power circuits in scaled technologies. In this paper we propose an adaptive...

A real-time simulation tool called BERSIM is developed and used to study bit-by-bit errors, average bit error rate and block outage probabilities for Tt/4 DQPSK at megabit rates with raised-cosine pulse shaping. Simulation results show that when the ratio of nns delay spread to bit duration is greater than about 0.02, the irreducible average BER is not only a function of rms delay spread, but i...