How can I improve RF timing performance

[janakfun]

Hi All,

I am using a RF communication system. Currently I'm getting a round trip time around 30mS and I want to reduce it having distance between the two nodes fixed.
I have following options:

1. Using BPSK @40kbps data rate
2. Using O-QPSK @ 250, 100 or 1Mbps data rate.
3. Using Directional antenna instead of omni directional antenna.
4. Increasing the power

Let me know which factor will have the impact on time.
Using IEEE 802.15.4 MAC with 1Ghz radio.


Thanks,
JANAKFUN