MUOS Spectrum Notching Effect on Handheld Terminal Uplink Performance

The Mobile User Objective System (MUOS) adapts a commercial third generation (3G) WCDMA cellular architecture to military UHF geostationary satellites to serve several terminal types including handhelds (HHT). The satellites also serve Legacy narrowband (NB) nets. The WCDMA uplink (terminal-to-base) waveform, or Common Air Interface (CAI), is a secondary user of its 5 MHz channel, sharing the bandwidth with other services. Uplink CAI spectrum modifications to 3G WCDMA use spectrally adapted (SA) "notching" designed to prevent interference with primary NB users. The new SA-WCDMA signal has increased amplitude modulation quantified here as peak-to-average power ratio (PAPR). To preserve the SA capabilities, as well as low bit energy-to-noise density capability, adequate fidelity is needed from a terminal power amplifier (PA). The HHT has an additional regulatory radiated power limit imposed for users\´ safety. Despite these constraints, the HHT must provide a minimum uplink availability under channel fading and interference, as well as acceptable battery life and thermal behavior. We present simulations of SA-WCDMA PAPR and its effect on PA operation. Pre-PA processing, PA backoff and efficiency, and other RF issues are considered with the goal of improving the terminal designer\´s understanding of practical MUOS HHT implementation.