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In this paper we present results of real-life localization experiments performed in an unprecedented cooperative and heterogeneous wireless context. The experiments covered measurements of different radio devices packed together on a trolley, emulating a multi-standard Mobile Terminal (MT) along representative trajectories in a crowded office environment. Among all the radio access technologies involved...
The reliability of bidirectional communication link can be guaranteed with Automatic Repeat Request Procedures (ARQ). The standard STANAG 5066 describes the ARQ procedure for HF communications that can either be applied to existing HF physical layers modems or adapted to future physical layer designs. In this contribution the physical layer parameters of an HF modem (HFDVL), developed by the authors...
This contribution results from the implementation of the physical layer of the STANAG 4444. Two operation modes are available in the STANAG 4444, namely the EEWF and DSWF. The performance of each mode has been evaluated making special emphasis in the DSWF one which uses Direct-sequence Spread-spectrum for symbol modulation. In order to accomplish with the specifications dictated by the norm in terms...
The principal parameters of a multipath channel are the delay and the gain coefficient of each path, and the number of significant paths. We develop a methodology for estimating path-delays and path-coefficients and applied it to the ionospheric channel estimation. Also, if path coefficients are stationary random processes, the power spectral density of the coefficients can be estimated from measured...
This paper describes a broadband (1MHz) digital HF transceiver for the HF band (3-30MHz) specifically designed for the transmission and reception of multicarrier and multichannel modulations. The wide modem bandwidth (1MHz) is not meant for the transmission of a single 1MHz wide signal, since the goal is to achieve flexible transmission and reception using several channels with a common standard bandwidth.
Multi-carrier modulations are widely employed in HF communications, and particularly OFDM, mainly because their ease of generation by means of DFT and also their appealing properties that can turn a selective fading channel into a set of flat channels. In order to cope with deep nulls in the channel traditional approach has been the use of channel coding and interleaving, thus causing an increase...
The present needs for more accurate modelling and simulation of the wideband HF channel motivate the development and implementation of wideband channel simulators. It has been showed that many HF communication systems may properly mitigate the ISI distortion of the HF channel, but it may perform badly under the HF noise and interference. In this paper, a software simulation of a wideband noise and...
This paper presents the results of several real link tests performed with a low-latency HF modem. Three different configurations are presented, tested and compared with simulated results. The delay introduced by the system is below 100 ms, making the system capable to transport digital voice in interactive applications.
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