You can't easily use SAW filtering because it's hard to support a large array of RF bands from one IF frequency.
When we think of WiMAX, we have to think about filtering.
Filtering for adjacent and alternate channels is needed and beside the receive-side filtering, designers have to filter the transmit side too.
In other applications, SAW filters were the choice because channel bandwidth was limited. WiMAX is different. You can't easily use SAW filtering because it's hard to support a large array of RF bands from one IF frequency.
Filtering on the die is possible and probably likely but it will require a lot of real estate if it is done efficiently. Using digital filtering in the baseband includes innovative filtering technologies with large Q are being used.
The larger the Q, the better filter shape. So let's have at it, designers.