Simulation of Wireless Fading Channels

Document type: Researchreports
Peer reviewed: Yes
Full text:
Author(s): Ronnie Gustafsson, Abbas Mohammed
Title: Simulation of Wireless Fading Channels
Translated title: Simulering av Trådlösa Fädande Kanaler
Series: Research Report
Year: 2003
Issue: 2
ISSN: 1103-1581
Organization: Blekinge Institute of Technology
Department: Department of Telecommunications and Signal Processing (Institutionen för telekommunikation och signalbehandling)
Department of Telecommunications and Signal Processing S-372 25 Ronneby
+46 455 38 50 00
Authors e-mail: rgs@bth.se, amo@bth.se
Language: English
Abstract: Future services in wireless communications will increase the need for high bit rates in the system because of the use of ``wideband'' contents such as streaming video and audio. For example, there might be services where the users can download movies to the car theatre system, or where a user can react to the doorbell ringing even though he or she is miles away from home.
It will be possible to run business software remotely using mobile devices, removing the need for ``dumb down'' software in the terminal devices. Also, users might want to be able to seamlessly roam between different air interfaces or standards using the same device. Some basic services are already implemented in the existing 2G systems such as GSM or IS-136, more services are planned for the new 3G systems and other advanced features have to wait until 2011 when 4G is scheduled for release. The demands for higher bit rates combined with the ever-increasing number of users, however, introduces the need for clever and efficient usage of the limited resource of the wireless channel.

Two major impediments to high-performance wireless communication systems are intersymbol interference (ISI) and cochannel interference (CCI). ISI is caused by the frequency selectivity (time dispersion) of the channel due to
multipath propagation and CCI is due to cellular frequency reuse. Equalizers can be used to compensate for ISI and CCI can be reduced by the use of adaptive antenna arrays (also known as "smart antennas"). The smart antenna
utilizes an array of antenna elements that provide directional (spatial) information about the received signals. Since the desired signal and unwanted cochannel interferers generally arrive from different directions, an adaptive beamforming algorithm can adjust the spatial gain to enhance the desired signal and mitigate the cochannel interferers.

In this Report we discuss the basic propagation mechanisms affecting the performance of wireless communication systems. We also present the
implementation of a simulator which takes these mechanisms into account and verifies its performance for different channels. We also introduce basic equalization and beamforming concepts. Finally, we evaluate the recursive
least squares (RLS) equalizer and receiver structures and assess their performance in combating the destructive effects of the channel.
Summary in Swedish: simulering, fädning, fädande kanaler, mobiltelefonisystem, rayleigh, lobformning, lob
Subject: Telecommunications\General
Keywords: simulation, fading, fading channels, wireless communications, rayleigh, beamforming
Note: Published in Licentiate Thesis: R. Gustafsson, "Combating Intersymbol Interference and Cochannel Interference in Wireless Communication Systems", Blekinge Institute of Technology, May, 2003
URN: urn:nbn:se:bth-00222
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