Compatibility with PHS System Compatibility with Existing PHS XGP takes the symmetrical constitution of 2.5 ms (add up to 5 ms) TDMA slot for download and upload respectively. This represents the same constitution with existing PHS. The followings are considered as two ways to co-exist XGP and existing PHS in the same bandwidth in future.          Setting guard band in between the existing PHS and XGP, synchronizing the system and operating them together.          Dividing existing PHS and XGP in each TDMA slot. Using the 1st and the 2nd TDMA slots for existing PHS and saving the 3rd and the 4th TDMA slots for XGP for example. Top of page