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Digital Communication via Multipath Fading Channel
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Digital Communication via Multipath Fading ChannelDigital Communication via Multipath Fading ChannelDigital Communication via Multipath Fading Channel
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Digital Communication via Multipath Fading Channel Zhiwei Zeng November 2000
I
Cpre537x Final Project
Digital Communication
Via Multipath Fading Channel
Zhiwei Zeng
Instructor: Dr. Russell
November 2000
Digital Communication via Multipath Fading Channel Zhiwei Zeng November 2000
I
Abstract
Multipath fading is a common phenomenon in wireless signal transmission. When a
signal is transmitted over a radio channel, it is subject to reflection, refraction and
diffraction. The communication environment changes quickly and thus introduces more
complexities and uncertainties to the channel response. This simulator offers a better
understanding of this phenomenon. In order to observe the effects of multipath fading
channel on the transmitted signal, a whole digital communication system simulator was
developed. Three kinds of digital communication systems: baseband transmission via
additive white Gaussian noise (AWGN) channel, passband transmission via single
AWGN channel, and passband transmission via multipath fading channel, are simulated.
Digital Communication via Multipath Fading Channel Zhiwei Zeng November 2000
II
Contents
Introduction
Baseband transmission via AWGN channel
Signal source
Sampling
Waveform encoding and decoding
Pulse Code Modulation (PCM)
Simple DPCM
General DPCM
Delta Modulation
Error control coding
Block codes
Convolutional codes
Line coding
Baseband filtering
Eye pattern
Optimum receiver in AWGN channel
Lowpass filtering
Passband transmission via single AWGN channel
M-ASK
QASK
M-FSK
M-PSK
Passband transmission via multipath fading channel
Time variant multipath fading channel
Characterization of multipath fading channel
Channel model for multipath fading channel
Signal design for multipath fading channel
RAKE demodulator
Simulation results
Reference
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1
2
2.1
2.2
2.3
2.3.1
2.3.2
2.3.3
2.3.4
2.4
2.4.1
2.4.2
2.5
2.6
2.7
2.8
2.9
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3.1
3.2
3.3
3.4
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4.1
4.2
4.3
4.4
4.5
4.6
Digital Communication via Multipath Fading Channel Zhiwei Zeng November 2000
1
1. Introduction
This report describes a simulator for digital communication systems. Three kinds of
digital communication systems: baseband transmission via additive white Gaussian noise
(AWGN) channel, passband transmission via single AWGN channel, and passband
transmission via multipath fading channel, are simulated, as shown in Figure 1. Passband
transmission via multipath fading channel is emphasized.
Multipath fading is a common phenomenon in wireless signal transmission. When a
signal is transmitted over a radio channel, it is subject to reflection, refraction and
diffraction. Especially in the urban and suburban areas where cellular phones are most
often used, the communication environment changes quickly and thus introduces more
complexities and uncertainties to the channel response. This simulator offers a better
understanding of this phenomenon.
In order to observe the effects of multipath fading channel on the transmitted signal, a
whole digital communication system simulator was developed. For simplicity, complex
techniques, such as multiplexing and spread spectrum communication, were not
simulated. Analyses of the performances of the systems are not given. Section 2 briefly
describes baseband transmission via AWGN channel. Section 3 briefly presents passband
transmission via single AWGN channel. Passband transmission via multipath fading
channel is described in detail in Section 4.
2. Baseband transmission via AWGN channel
Baseband transmission is usually used in wired communication system, such as wired
telephone and wired local area network (LAN). Figure 2 shows the structure of a digital
Fig 1 Contents of the simulator
Digital Communication via Multipath Fading Channel Zhiwei Zeng November 2000
2
communication system with baseband transmission, which consists of signal source,
sampler, waveform encoder, error control encoder, code transformer, baseband filter,
AWGN channel, optimum receiver, inverse code transformer, error control decoder, and
lowpass filter. The following subsections describe the above blocks. Users can display
the required figures at different steps in Figure 2 by clicking the small rectangles, whose
color stands for a display format specified in the legend at the bottom of Figure 2.
2.1 Signal source
A signal source is used to transform information such as voice into electric signal. In
this simulator, a sine waveform is generated with the amplitude, frequency, and initial
phase specified by the user. Figure 3 shows the pre-filtered signal to be transmitted with
amplitude 3V, frequency 1000Hz, and initial phase 45°. After some processing, this
signal will be transmitted through an AWGN channel, and be recovered by the receiver.
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x 10
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Original signal
0 0. 2 0. 4 0. 6 0. 8 1 1. 2 1. 4 1. 6 1. 8 2
x 10
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Sa mpled sig nal
Fig 2 Baseband transmission via AWGN channel
Fig 3 Original signal Fig 4 Sampled signal
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资源评论
- ljfxst2013-08-20当时只做参考用
- daodao20082014-07-05可以作为参考使用
epiphone23
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