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High Rate Uplink Requirements and Limitations for Communication Systems

This document outlines the high rate uplink requirements for operational commanding and emergency commanding, detailing various data rates categorized from very low (bits/s) to very high (1-25 Mbits/s). It highlights key features including coding limitations, frame structure, RF modulation (BPSK/QPSK), and acquisition methods. Special attention is given to landmarks like COP-1 limitations, randomiser effects on BER performance, and CCSDS recommendations for PCM/PSK/PM systems. Ultimately, it summarizes the conditions under which different data rates can be achieved and the necessary modifications for improved reliability.

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High Rate Uplink Requirements and Limitations for Communication Systems

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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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