This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: UCSB Spring 2010 ECE 146B: Laboratory Assignment 4 Lab Objectives: Introduction to modeling and performance evaluation for signaling on wireless fading channels. Let us consider the following simple model of a wireless channel (obtained after filtering and sampling at the symbol rate, and assuming that there is no ISI). If { b [ n ] } is the transmitted symbol sequence, then the complexvalued received sequence is given by y [ n ] = h [ n ] b [ n ] + w [ n ] (1) where { w [ n ] = w c [ n ] + jw s [ n ] } is an iid complex Gaussian noise sequence with w c [ n ], w s [ n ] i.i.d. N (0 , 2 = N 2 ) random variables. We say that w [ n ] has variance 2 per dimension. The channel sequence { h [ n ] } is a timevarying sequence of complex gains. Rayleigh fading: The channel gain sequence { h [ n ] = h c [ n ] + jh s [ n ] } , where { h c [ n ] } and { h s [ n ] } are zero mean, independent and identically distributed colored Gaussian random processes. The reason this is called Rayleigh fading is that  h [ n ]  = radicalbig h 2 c [ n ] + h 2 s [ n ] is a Rayleigh random variable. Remark: The Gaussianity arises because the overall channel gain results from a superposition of gains from multiple reflections off scatterers. Simulation of Rayleigh fading: We will use a simple firstorder autoregressive (AR(1)) model, wherein the colored channel gain sequence { h [ n ] } is obtained by passing white Gaussian noise through a firstorder recursive filter, as follows: h c [ n ] = h c [ n 1] + u [ n ] h s [ n ] = h s [ n 1] + v [ n ] (2) where { u [ n ] } and { v [ n ] } are independent realvalued white Gaussian sequences, with i.i.d. N (0 , 2 ) elements. The parameter (0 < < 1) determines how rapidly the channel varies. Setting up fading simulator (a) Set up the AR(1) Rayleigh fading model in matlab, with and 2 as programmable parameters....
View
Full
Document
 Fall '08
 Staff

Click to edit the document details