Partial Processing Satellite Relays for Frequency-Hop Antijam Communications

Military satellite communications systems may be implemented with varying levels of satellite on-board processing. For frequency-hop (FH) spread-spectrum signals two options are the dehop-rehop transponder (DRT) and the symbol regenerative processor (SRP). This paper considers FH, -ary FSK modulation in the presence of full band and worst case partial-band noise jamming. The relationships among end-to-end signal-to-noise ratio (SNR) performance or probability of bit errors and the uplink and downlink SNR are derived. For a DRT, an additional parameter is the satellite filter bandwidth Wssince this may differ from the despread modulation bandwidth Wrfor a particular user access under TDMA variable-data-rate operation. The SNR performance in this case depends upon the ratio a well as the uplink and downlink SNR. The resulting penalty in the link budget of the weaker of the uplink or downlink is much less than the mismatched ratio and diminishes as the links become unbalanced. The SRP slightly outperforms the DRT but it is more complex and does not as easily accommodate variable data rates.