# how to make a "fading"?

Started by August 9, 2002
 Hi I'm getting into radio channel simulations and I've come across the following r = t * c + n r (received) t (transmitted) c fading n (noise) where, books say, c is a complex gaussian variable with mean 0 and variance 0.5 per real dimension. My question is, given that c is complex, what's the mean and variance of the imaginary dimension? Cheers Bruno
 I believe you are trying to synthesize Rayleigh fading (as opposed to Rician), since you are taking the mean value of the real part of the fading coefficient to be zero. This corresponds to a fading scenario where you do not have line of sight (LOS) and all you receive is the reflections from the environment. In a rayleigh fading scenario, the complex multiplicative coeficient is referred to as: c(t) = c_r(t) + j.c_i(t), where j=sqrt(-1). c_r(t) and c_i(t) are real valued random processes, with zero mean, and 0.5 variance. To achieve this you need to produce two independenty generated zero mean, unity variance random processes, scale them by 1/sqrt(2), then combine them as written above to achieve c(t). The magnitude of random process c(t), which is equal to sqrt(c_r (t).^2 + c_i(t).^2) is rayleigh distributed. If you need a rician fading, you should simply have non-zero mean. Tansu --- In matlab@y..., "brunomaggi2002" wrote: > Hi > I'm getting into radio channel simulations and I've come across the > following > r = t * c + n > r (received) > t (transmitted) > c fading > n (noise) > where, books say, c is a complex gaussian variable with mean 0 and > variance 0.5 per real dimension. My question is, given that c is > complex, what's the mean and variance of the imaginary dimension? > Cheers > Bruno
 Hi, Assuming that the signal 't' is real (for BPSK modulation), r = t * c + n where 'c' is complex gaussian variable with mean 0 and var 0.5 per real dimension. 'c' can be written as |c| (magnitude which is rayleigh random variable) and angle(c) (this is uniformly distributed r.v.) c can also be represented as x + j*y, x = N(0,0.5) and y = N(0,0.5) where N(a,b) is gaussian r.v. with mean a and variance b. hope this helps. if u have further doubts, you can check out my homepage (in my signature below). i have put up some reports on rayleigh fading, rician fading, etc ... logesh. On Fri, 9 Aug 2002, brunomaggi2002 wrote: > Hi > I'm getting into radio channel simulations and I've come across the > following > r = t * c + n > r (received) > t (transmitted) > c fading > n (noise) > where, books say, c is a complex gaussian variable with mean 0 and > variance 0.5 per real dimension. My question is, given that c is > complex, what's the mean and variance of the imaginary dimension? > Cheers > Bruno > > > _____________________________________ > Note: If you do a simple "reply" with your email client, only the author of this message will receive your answer. You need to do a "reply all" if you want your answer to be distributed to the entire group. > > _____________________________________ > About this discussion group: > > To Join: > > To Post: > > To Leave: > > Archives: http://www.yahoogroups.com/group/matlab > > More DSP-Related Groups: http://www.dsprelated.com/groups.php3 > > ">http://docs.yahoo.com/info/terms/ -- ------------------------ Logeshwaran Vijayan Graduate Student/Research Assistant EECS Department-The University of Kansas Lawrence, Kansas. Office : Room 339, Raymond Nichols Hall Information and TeleCommunication Technology Center Phone No. (785)-864-7799 E-Mail : URL : www.ittc.ku.edu/~logesh Residence : 1301 W 24th Street, #o-06, Lawrence, KS 66046 Phone No. (785)-749-4398 ____________________________________________________________ Create a vision of who you want to be and live into that picture as if it were already true - Arnold Schwarzenegger ------------------------
 Hi, Thanks iceman and Logeshwaran. did not have problems thanks to your indication - now I'm trying to have parallel channels and i want to know if it possible to choose the correlation between them. I mean, something like function[ch1fading, ch2fading] = makefading(correlation_index) or I have generate one and repeat the generation of the second until I obtain the desired correlation Cheers!! bruno --- In matlab@y..., Logeshwaran Vijayan wrote: > Hi, > > Assuming that the signal 't' is real (for BPSK modulation), > > r = t * c + n > > where 'c' is complex gaussian variable with mean 0 and var 0.5 per real > dimension. > > 'c' can be written as |c| (magnitude which is rayleigh random variable) > and angle(c) (this is uniformly distributed r.v.) > > c can also be represented as x + j*y, x = N(0,0.5) and y = N(0,0.5) > where N(a,b) is gaussian r.v. with mean a and variance b. > > hope this helps. if u have further doubts, you can check out my homepage > (in my signature below). i have put up some reports on rayleigh fading, > rician fading, etc ... > > logesh. > > On Fri, 9 Aug 2002, brunomaggi2002 wrote: > > > Hi > > I'm getting into radio channel simulations and I've come across the > > following > > r = t * c + n > > r (received) > > t (transmitted) > > c fading > > n (noise) > > where, books say, c is a complex gaussian variable with mean 0 and > > variance 0.5 per real dimension. My question is, given that c is > > complex, what's the mean and variance of the imaginary dimension? > > Cheers > > Bruno > > > > > > > > > > _____________________________________ > > Note: If you do a simple "reply" with your email client, only the author of this message will receive your answer. You need to do a "reply all" if you want your answer to be distributed to the entire group. > > > > _____________________________________ > > About this discussion group: > > > > To Join: matlab-subscribe@y... > > > > To Post: matlab@y... > > > > To Leave: matlab-unsubscribe@y... > > > > Archives: http://www.yahoogroups.com/group/matlab > > > > More DSP-Related Groups: http://www.dsprelated.com/groups.php3 > > > > ">http://docs.yahoo.com/info/terms/ > > > > > > -- > ------------------------ > Logeshwaran Vijayan > Graduate Student/Research Assistant > EECS Department-The University of Kansas > Lawrence, Kansas. > > Office : > Room 339, Raymond Nichols Hall > Information and TeleCommunication Technology Center > Phone No. (785)-864-7799 > E-Mail : logesh@i... > URL : www.ittc.ku.edu/~logesh > > Residence : > 1301 W 24th Street, #o-06, > Lawrence, KS 66046 > Phone No. (785)-749-4398 > ____________________________________________________________ > Create a vision of who you want to be and live into that > picture as if it were already true - Arnold Schwarzenegger > ------------------------