# 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