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High Rate Uplink Requirements

19/01/2007. High Rate Uplink Requirements. Emergency Commanding Very Low (bits/s) Operational Commanding Low (kbits/s) Software Loads and Audio High (10-100kbits/s) Video Very High (1-25Mbits/s). 19/01/2007. High Rate Uplink. Start with current TC Standard at S-band TC Limitations

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High Rate Uplink Requirements

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  1. 19/01/2007 High Rate Uplink Requirements • Emergency Commanding • Very Low (bits/s) • Operational Commanding • Low (kbits/s) • Software Loads and Audio • High (10-100kbits/s) • Video • Very High (1-25Mbits/s)

  2. 19/01/2007 High Rate Uplink • Start with current TC Standard at S-band • TC Limitations • BCH Coding • Frame Structure • RF • Sub-carrier • Modulation (BPSK or QPSK) direct on the Carrier • Acquisition methods • COP-1 • Randomisation

  3. 19/01/2007 High Rate Uplink • Areas with no limitations • BCH Coding • Frame Structure (Digital) • Acquisition Methods (RF / PLOP) • Areas with limitations • RF • Sub-carrier • Modulation direct on the Carrier • COP-1 • Randomisation

  4. 19/01/2007 RF Limitation • CCSDS recommendation PCM/PSK/PM (Sub carrier) limitation R = 4000*2n bps (nmax=6) 2.2.7, Radio Frequency And Modulation Systems, CCSDS 401.0-b • 256 kbit/s (coded bits) • CCSDS recommendation BPSK limitation R = 1000*2n bps (nmax=10), 2.2.8, Radio Frequency And Modulation Systems, CCSDS 401.0-b • 1024 kbits/s (coded bits) • Limited by bandwidth allocation for category A missions • 5 to 6 Mbits/s

  5. 19/01/2007 COP-1 Limitation • COP-1 is limited by; • 8bit Frame Sequence Number • User Frame Size • Window size • Maximum data rate is defined by the following formula; • For the lunar example (6x105km Round trip); • 15kbits/s for minimum frame size • 0.5Mbits/s for maximum frame size

  6. 19/01/2007 Randomiser Limitation • 255 bit randomiser is not a technical BER performance limitation it just creates an “Ugly Spectrum”. This itself is not a technical issue, it will still work, it is a regulatory limit • The regulatory limitation for BPSK is 1 Mbit/s (QPSK is 2 Mbits/s) assuming you are at the limit of the following conditions • EIRP • Periodic Data Content (“0000”, “1111”, “1010”…)

  7. 19/01/2007 Summary • TC Standard, as it stands, will work for data rates up to 1 Mbit/s • Higher data rates 1 to 32 Mbits/s would require the following modifications; • RF • Higher band (Ka) • COP-1 • Switch it off • Higher level reliability (CFDP) • Video uplink is not required • Randomisation • Longer sequence, matching the longest available TC Frame available (213 bits)

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