Peak-to-Average Power Ratio Characteristics of WCDMA over Satellite Communication Links

It is well known that WCDMA signals exhibit a higher peak to average power ratio (PAPR) than TDMA signals. When WCDMA is implemented in a satellite link, the relatively high PAPR presents a number of problems related to power levels on the spacecraft. First, in order to maintain linearity it may be necessary to operate the satellite amplifiers at backoffs greater than those used for TDMA systems. Second, the high peak power levels can affect the survivability of the satellite - instantaneously high peak power levels can damage spacecraft electronic components. The purpose of this paper is to determine the PAPR characteristics of WCDMA over satellite. We evaluate the PAPR statistics of the satellite downlink signal as a function of satellite loading, traffic characteristics, and other relevant parameters. We show that the PAPR can be significantly reduced by introducing relative time delays between each WCDMA carrier. The results of the paper are directly applicable to the MUOS system currently being developed by DoD.