Last Post: September 30, 2006:
IEEE 802.11 clause 15 defines DSSS PHY with 1 and 2 Mbps modulations and defines channels to be non-overlapping if center to center channel separation is at least 30 MHz.
IEEE 802.11 clause 18 defines HR/DSSS PHY with 1, 2, 5.5, and 11 Mbps modulations and defines channels to be non-overlapping if center to center channel separation is at least 25 MHz, regardless of modulation.
I wish I could explain why 25 MHz is good for HR/DSSS PHY while 30 MHz is good for DSSS PHY, but I can't.
I can say that HR/DSSS and ERP PHYs interoperate fairly well even when their channels overlap a bit. And there aren't many DSSS PHYs in service in 2006 (I hope).
I hope this helps. Can you put your location in your forum profile? Thanks. /criss