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发表于 2012-9-4 00:42:09
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This book is about receivers for digital communications. The word digital carries a
double meaning. It refers to the fact that information is transported in digital form.
It also refers to the property of the receiver to retrieve the transmitted information,
apart from the analog front end, entirely by means of digital signal processing.
The ever-increasing demand for mobile and portable communication ultimately
calls for optimally utilizing the available bandwidth. This goal is only attainable by
digital communication systems capable of operating close to the information theo-
retic limits. The implementation of such systems has been made possible by the
enormous progress in semiconductor technology which allows the communication
engineer to economically implement “systems on silicon” which execute:
1. Advanced compression algorithms to drastically reduce the bit rate required to
represent a voice or video signal with high quality.
2. Sophisticated algorithms in the receiver for power control, channel estimation,
synchronization, equalization, and decoding.
3. Complex protocols to manage traffic in networks.
4. User-friendly graphical man-machine interfaces.
Seen from a different perspective we argue that the communication engineer to-
day can trade the familiar physical performance measures bandwidth and power
eficiency for signal processing complexity. As a consequence, the design process
is characterized by a close interaction of architecture and algorithm design, as
opposed to a separation between theory and implementation in the traditional
way.
This book differs substantially from other texts in communication engineering in
the selection and treatment of topics. We focus on channel estimation, synchroniza-
tion, and digital signal processing. In most books on digital communications, syn-
chronization and channel estimation are addressed only superficially, if at all. This
must give the reader the impression that these tasks are trivial and that the error per-
formance is always close to the limiting case of perfect channel knowledge and syn-
chronization. However, this is a most unfortunate misconception for the following
reasons:
1. Error performance: Synchronization and channel estimation are critical to error
performance;
2. Design effort: A large amount of design time is spent in solving these problems; |
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