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Carrier Frequency / Symbol Clock Offset Proposal for TGn FRCC

Carrier Frequency / Symbol Clock Offset Proposal for TGn FRCC. Colin Lanzl Aware, Inc. 40 Middlesex Turnpike, Bedford, MA 01730-1432 781-687-0578 clanzl@aware.com John Ketchum Qualcomm, Inc. 9 Damonmill Square, Suite 2A, Concord, MA 01742 781-276-0915 johnk@qualcomm.com.

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Carrier Frequency / Symbol Clock Offset Proposal for TGn FRCC

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  1. Carrier Frequency / Symbol Clock Offset Proposal for TGn FRCC Colin Lanzl Aware, Inc. 40 Middlesex Turnpike, Bedford, MA 01730-1432 781-687-0578 clanzl@aware.com John Ketchum Qualcomm, Inc. 9 Damonmill Square, Suite 2A, Concord, MA 01742 781-276-0915 johnk@qualcomm.com Lanzl, Aware; Ketchum, Qualcomm

  2. Carrier Frequency / Symbol Clock Offset • Originally specified as an impairment, common to all PHY simulations: random choice of +/-40ppm offset of Rx relative to Tx, different for each simulation run • Large simulation burden • Consensus in SMSC to shift to a comparison criterion for this effect Lanzl, Aware; Ketchum, Qualcomm

  3. Offset Effects • Carrier frequency / symbol clock offsets are estimated in acquisition • Offsets may be tracked / compensated during symbol decoding • Effect of poor offset compensation is poor packet error rate performance relative to no offset Lanzl, Aware; Ketchum, Qualcomm

  4. Stress parameters • Generally, worst system performance for poor offset compensation will occur for largest offset • Generally, offset compensation is affected by SNR: lower SNR stresses acquisition estimates • However, highest constellations (operating in highest SNR conditions) need best jitter performance Lanzl, Aware; Ketchum, Qualcomm

  5. Basic Concept • To reduce simulation load, ask proposers to quantify impact of carrier frequency / symbol clock offset in “standalone” simulation • Stress offset estimation: use lowest useable average SNR • Use worst-case multipath environment • Compare performance to no offset Lanzl, Aware; Ketchum, Qualcomm

  6. Details • To reduce simulation load, need a way to measure impact of offset compensation • If offset compensation is done well, there should be no difference in system performance between zero offset and any other offset • To stress proposals, ask for impact at lowest average SNR in channel E (worst reasonable multipath inside guard interval) that the proposal can sustain (longest range) • Use PER at xx% (1%?) as the performance criterion • Also, need to ask for impact at highest SNR in channel E to judge impact of compensation on biggest constellations Lanzl, Aware; Ketchum, Qualcomm

  7. Proposed Language for a CC: Offset Compensation • Provide the impact on PER of carrier frequency offset and symbol clock offset by comparing to the PER achieved at the lowest average SNR that achieves a 1% PER in channel E with no carrier and symbol clock offset. • Also, provide that same impact on PER using the highest average SNR possible for the proposed system in channel E. • The carrier offset and symbol clock differences at the receiver relative to the transmitter shall range from -40ppm to +40ppm. The results shall be presented in such a manner that it is clear whether there are specific values of offset for which the proposed system has better or worse performance relative to no offset. Lanzl, Aware; Ketchum, Qualcomm

  8. Assumptions • Average SNR defined as follows: The average SNR is the ratio of the received power at a single receive antenna, to the input-referred receiver noise power. The received signal power is as measured in -10dB signal bandwidth at a single receive antenna, is summed over all transmit antennas and averaged over time and receive antennas. • The PER threshold needs to be decided, 1% is a suggested value to stimulate discussion. • The PER must be computed from at least (xx%/100)-1 packet errors (for example, 100 packet errors for 1% PER). Lanzl, Aware; Ketchum, Qualcomm

  9. Keeping us Honest • A comparison criterion that measures proposals robustness to the complete range of carrier offsets and symbol clock offsets is useful, but… • In the comparison of other aspects of proposals, simulations need some nominal carrier offset to ensure that offset compensation is enabled • Specify some nominal carrier offset in the impairments section: -13.7ppm?? Lanzl, Aware; Ketchum, Qualcomm

  10. Proposed Replacement Language for IM2: Nominal Carrier Frequency Offset • Simulations for all comparisons except Offset Compensation shall be run using a fixed carrier frequency offset of –13.7 ppm at the receiver, relative to the transmitter. The symbol clock shall have the same relative frequency offset as the carrier frequency offset. Lanzl, Aware; Ketchum, Qualcomm

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