Introduction of Wireless Channel and Random Matrices 5
Introduction of Wireless Channel and Random Matrices 5
1.1 Wireless Channels The performance of wireless communication is mainly governed by the wireless channel environment As opposed to the static and predictable characteristics of a wired channel,the wireless channel is rather random and unpredictable. A unique characteristic in a wireless channel is a phenomenon called fading',the variation of the signal amplitude over time and frequency. 6
6 The performance of wireless communication is mainly governed by the wireless channel environment. As opposed to the static and predictable characteristics of a wired channel, the wireless channel is rather random and unpredictable. A unique characteristic in a wireless channel is a phenomenon called ‘fading’ , the variation of the signal amplitude over time and frequency. 1.1 Wireless Channels
1.1.2 Channel Fading The fading phenomenon can be classified into two different types: large-scale fading and small-scale fading Fading channel Large-scale fading Small-scale fading Path loss Shadowing Multi-path fading Time variance Frequency-selective fading Flat fading Fast fading Slow fading 7
7 1.1.2 Channel Fading The fading phenomenon can be classified into two different types: large-scale fading and small-scale fading
1.1.2 Channel Fading:Large-scale Fading Definition:Large-scale fading is the result of signal loss due to propagation over large distances and diffraction around large objects in the propagation path. Large-scale fading is caused by path loss of signal .shadowing by large objects such as buildings 8
8 1.1.2 Channel Fading: Large-scale Fading Definition: Large-scale fading is the result of signal loss due to propagation over large distances and diffraction around large objects in the propagation path. Large-scale fading is caused by : •path loss of signal •shadowing by large objects such as buildings
1.1.2 Channel Fading:Small-scale Fading Definition:Small-scale fading is the rapid variation of signal level in the short term Small-scale fading is caused by .Multi-path propagation .High-speed move of mobile terminal .Move of surrounding objects 9
9 1.1.2 Channel Fading: Small-scale Fading Definition: Small-scale fading is the rapid variation of signal level in the short term Small-scale fading is caused by : •Multi-path propagation •High-speed move of mobile terminal •Move of surrounding objects