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 energyto-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.BACKGROUND ON MUOS SA-WCDMA CAI
The DoD's next generation UHF SATCOM system, the Mobile User Objective System (MUOS), utilizes a 3G cellular WCDMA waveform in which satellites function as the cell towers. The system's large 5MHz channel bandwidth makes it necessary to be able to "lock out" frequencies with existing legitimate RF network traffic to avoid causing interference to these other users, a process called "notching." To evaluate the method of terminalbased scanning followed by notching for detected user nets, we first reduce RF spectrum analyzer collection campaign data then develop a model to test the effectiveness and efficiency of a WCDMA scan-thennotch spectral etiquette algorithm. Real-world analyzer data is first filtered for half duplex network activity and its hold and interarrival time statistics. The statistics help define the persistence, or dwell, of dynamic WCDMA spectral notches at net frequencies. Using simulated trial runs against the reduced analyzer data, the algorithm is evaluated for its effectiveness in protecting the nets and in preserving the WCDMA link. The relative costs and benefits of the scan-then-notch algorithm are considered in a summary analysis.
Statistical propagation models for the combined efect of ionospheric scintillation and terrestrial multipath are derived. These models are used to determine the satellite link performance of the Mobile User Objective System ( W O S ) under various operational conditions. The models are described byJirst order statistics in the form of probability density functions (PDFs) and cumulative distribution ficnctions (CDFs). The PDFs include combinations of Rayleigh, Rician and lognornial distribution functions. The corresponding CDFs are used to assess satellite link performance and establish link margins. The degrading effect of combined ionospheric scintillation and terrestrial multipath fading on link availability is illustrated with a number of examples.
Next generation mobile tactical narrowband systems, embodied in the Mobile User Objective System (MUOS), must plan internetworking operations expected to serve 12 years starting in 2007. MUOS may deploy its own satellite Common Air Intet$ace (CAI) waveform to serve low rate, high mobility handhelds as well as larger terminals with higher capacity than predecessor UFO. The CAI media access control (MAC) is likely to be specialized to handle fading, interference and ef$cient multiple access. Above the MAC, use of commercial off-the-shelf (COTS) standards and "middleware '' for network management, connections and transport can mitigate development and O M cost and risk on one hand, while exploiting protocol and technology innovations on the other to achieve a "sustainable" internetwork strategy. This paper considers three COTS-based internetworking constructs: I ) a transparent, client-server-based "Access Registry'', 2) negotiated connections using Mobile IP for network security, and 3) variable Layer 3-to-MAC CAI data modes using IP or ATM cells with a closer look at an ATMMAC. The three constructs are proposed to be widely applicable across varying CAI MAC and multiple access approaches.
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