Radio Propagation and Adaptive Antennas for Wireless Communication Networks by unknow

Author:unknow
Language: eng
Format: epub
ISBN: 9781118659540
Publisher: Wiley
Published: 2014-04-01T16:02:40+00:00

8.5. Predicting Models for Indoor Communication Channels

The increasing use of adaptive antennas in radio indoor communications demands an intensive study of the indoor propagation environments, including offices, buildings, warehouses, factories, hospitals, apartments, and so on. In References 21 and 22, the temporal data on indoor propagation have been collected and analyzed, from which a new statistical time-domain model for indoor propagation was created [21].

However, most measurements carried out until very recently dealt with time domain data and did not include any data on the AOA distribution in indoor communication links. As was mentioned in the previous chapter, knowledge of the AOA associated with a multipath arrival is important because of increasing use of multiple antenna systems with different kinds of antenna diversity, namely, the use of phased array beamforming [25], diversity combining or adaptive array processing (see the corresponding references in Chapter 7) to mitigate the effects of multipath fading and multiple user servicing. In a latter case, for multiple access communications, the adaptive antenna systems have the potential to allow multiple subscribers to simultaneously use the same frequency band, making efficient utilization of the system bandwidth.

In order to predict the performance of such access, knowledge of both time and angle of each arrival in a multipath and multiple interference channel is needed. Some works have begun recently to address the AOA signal distribution in indoor communication channels, and the first of them, using the statistical approach proposed in References 23 and 24, have found that the AOA distribution of the multipath components of the total signal arriving at the receiver can be accurately described by the Laplacian law [18, 22]. In Reference 25, it was found that multipath arrivals tend to occur at various angles indoors. In Reference 26, a data acquisition system was used (which is similar with that of References 18 and 22) to collect narrowband AOA data and wideband TOA data, but this was done separately without accounting for their joint distribution by measuring simultaneously signal features in the angle and time domains. In Reference 27, the authors used a rectangular antenna array to estimate both elevation and azimuth (or AOA) for major multipaths, but without accounting for the corresponding TOA of each multipath component of the total signal. Authors in Reference 28 used a rectangular adaptive array to make simultaneous measurements of angle and TOA, similar to what was done in References 18 and 22. However, as was mentioned in References 30 and 31, the experiment carried out in Reference 28 was not extensive enough to make any conclusions about the propagation channel.

To satisfy the recent increasing demand on communication speed and ubiquity for the wireless local area networks (WLANs), wireless private branch exchangers (WPBXs), home phone line network alliance (HomePNA), as well for Internet and data network applications, a new theoretical approaches and more precise experiments were carried out [32–41]. We will discuss only a few of them, which in our opinion give a realistic physical description of the channel. First of all, this is a continuation of the research, started in References 18, 22, and 23, made in Reference 36.

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