
The desired MSE is application dependent, so there can be no general
rule. If the approximation doesn't satisfy your needs you can
increase the filter length to obtain a better match.
There is no straightforward way to change the FIR Wiener filter solution to an IIR solution because the IIR formulation results in a set of nonlinear equations which have no closed-form solution. The IIR solution might also be unstable, so FIR filters are a much more practical choice when computing a Wiener filter.


Using a Wiener Filter to Estimate a Transfer Function
In June I will have to travel from Oslo Gardermoen airport to Oslo Central Station to catch the train to Finse. I already booked a ticket from Oslo central station to Finse (with NSB), but didn't want to be tied to a certain time for the ticket from Oslo airport to Oslo Central Station. 

As soon as I pick up my luggage I want to go to the train so that I have some time to spare in Oslo.

I was wondering how easy it is to buy a ticket at the airport, are there any vending machines around where you just can buy a ticket?
