Wireless Channel Error Model

[Nimrod Mesika <nimrodm@ibm.net>]

Karunaharan Ratnam wrote:
> In other words, when the ErrorModel uses Expo or TwoStateMarkov,
> forward link can be in
> burst error state (fading) but the reverse link may not be experiencing
> any fading, and transmitting error free.
> 
> Is it a correct model for wireless channel.
> 
> The links cannot be totally independant because,
> * Fadding affects on both links are almost same (even if different
> bands were used they are in similar spectrum).
> 
> The links may not be totally dependant because,
> * Radio at the hub (base station) may control power differently
>   to handle the fading than the customer radio.
> 
> I'd like to see response on this (especially from radio engineers).
> 
> Karu.

What type of network are you referring to? In the cellular environment
the separation between the forward (downlink) and reverse (uplink)
channels is 45 MHz (70 MHz in the PCS band). This is more than enough to
assume fading on these channels is independent (at least regarding
outdoor environment and bandwidths < 1~2 MHz). This refers to multipath
fading (aka small-scale fading).

Shadowing, however, does make the forward and reverse links correlated
as it has similar influence on both. This effect is normally much slower
(and much more dependent on the environment) and can be simulated
separately - by reading a path-loss matrix from a file periodically, for
example.

-- Nimrod.