Channel characterization for indoor wireless communication
by Kwok Wai Cheung
THESIS
1997
Ph.D. Electrical and Electronic Engineering
vii, 119 leaves : ill. ; 30 cm
Abstract
Indoor wireless communications have created enormous interest among subscribers and operator companies since the successful introduction of cellular telephone systems about a decade ago. The development of indoor wireless communication systems is a crucial step towards the ambitious goal of communication anywhere-anytime and promises to become a major part of the telecommunication infrastructure in the future. However, a problem with the indoor wireless communications is that indoor wireless channels are difficult to communicate through due to the occurrence of various propagation phenomena such as fading and multipath. To minimize these adverse propagation phenomena and to enhance the wireless network performance, system designers are required to understand the radio channel characteri...[ Read more ]
Indoor wireless communications have created enormous interest among subscribers and operator companies since the successful introduction of cellular telephone systems about a decade ago. The development of indoor wireless communication systems is a crucial step towards the ambitious goal of communication anywhere-anytime and promises to become a major part of the telecommunication infrastructure in the future. However, a problem with the indoor wireless communications is that indoor wireless channels are difficult to communicate through due to the occurrence of various propagation phenomena such as fading and multipath. To minimize these adverse propagation phenomena and to enhance the wireless network performance, system designers are required to understand the radio channel characteristics thoroughly and to design a system which closely matches the wireless channel. Therefore, indoor radio channel characterization is a major requirement for the successful design of indoor communication systems.
In this thesis, extensive channel measurements, detailed studies and analysis of the indoor radio channel are presented. Five new contributions are described and these include a computationally efficient narrowband indoor propagation prediction model, a method for optimizing the locations of basestations, investigations into the performance of distributed antennas, analysis of wideband channel measurements and finally superresolution techniques for channel measurements.
The new narrowband indoor propagation prediction model is based on a computationally efficient empirical method, but also incorporates essential features from full ray-tracing approaches. The resultant model is not only computationally efficient but also accurate for a variety of building types. Comparisons of the new model predicted results to the actual propagation measurements indicate that accuracy of ±5 dB is achieved.
A method for automatically optimizing the locations of basestations is also described. Here, the objective function for the optimization is a quality of service criteria which can handle both coverage and interference limited environments. Results are provided which are based on an accurate propagation prediction model to estimate the mean path loss. These results demonstrate that significant improvements in quality of service can be obtained by optimizing the locations of basestations.
Investigations into the performance of a distributed-antenna system is also provided. Measurement and simulation results are carried out to examine the increased channel fading caused by interference between individual antennas in the distributed-antenna system. Its influence and significance on coverage and system design for indoor environments are also determined.
Extensive measurements of the indoor wideband channel response in the 1.75-1.85 GHz frequency band with antenna separation from 5 to 30 meters in a modem building are presented. From the channel measurements, some of the channel parameters, including mean excess delay, root mean square (RMS) delay spread and path loss, are investigated and their possible relations are also studied.
Finally, the wireless channel parameters including the multipath amplitudes, arrival times, and phases are estimated using super-resolution techniques based on array signal processing. Measurements inside an anechoic chamber are taken to verify the accuracy and usefulness of the super-resolution techniques. Furthermore, actual indoor channel measurements in Hong Kong University of Science and Technology are taken and super-resolved.
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