Your options are:
- Use uGPS (there's a way to fan out one uGPS for multiple 450i AP's AUX port).
- You can use PacketFlux.
- You can use a CMM4 with a modified pin-out... as per Matt Mangriotis @ Cambium: "450i does support timing using the AUX port (it's now an RJ-45 vs. RJ-11 connection to the radio though). The other current option is using the CMM4 (with a slight tweak to the pin out). This is documented in the User Guide on page 6-40."