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Higher Order Modulation in LMDS Networks BBWWF - San Francisco, February 2001

Higher Order Modulation in LMDS Networks BBWWF - San Francisco, February 2001. Joe Fournier. Agenda. Why the consideration of modulation? Frequency Planning Interference Prone Zones Cell Radius Dynamic or Static Multi Modulation Networks Summary. Why The Consideration of Modulation?.

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Higher Order Modulation in LMDS Networks BBWWF - San Francisco, February 2001

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  1. Higher Order Modulation in LMDS NetworksBBWWF - San Francisco, February 2001 Joe Fournier

  2. Agenda • Why the consideration of modulation? • Frequency Planning • Interference Prone Zones • Cell Radius • Dynamic or Static Multi Modulation Networks • Summary

  3. Why The Consideration of Modulation? • An Operator may require greater channel capacity which can be achieved by larger carriers and/or higher order modulation than QPSK or both • ... and have the need for greater network capacity • Many ways of achieving this including larger spectral license, cell splitting, micro-cell insertion, increased #sectors/cell, • .... And higher order modulation (16-QAM, 64-QAM) • The key is to limit the impact on the network when using higher order modulation due to • reduced frequency reuse • non serviceable areas due to interference • smaller cell radius

  4. Impact of Modulation on...Frequency Planning • Frequency re-use determines C/I levels in network • 16 and 64 QAM require better noise performance (C/N) than QPSK. (12dB for QPSK vs. 19dB for 16 QAM and 25dB for 64 QAM) • This makes 16 and 64 QAM more sensitive to interference. • In a real world LMDS multi-cell network, this greatly impacts frequency reuse and therefore overall spectral efficiency.

  5. Frequency Planning 22 dB 19 dB 14 dB Victim (blue) is interfered with by many interferers along radials

  6. Frequency Planning 22 dB 19 dB 14 dB 14 dB C/I achieved

  7. Frequency Planning 22 dB 19 dB 14 dB Analogous for the remaining 3 types of sectors: 14 dB C/I achieved (specific freq. used in yellow sectors)

  8. Frequency Planning 22 dB 19 dB 14 dB 4 frequencies to cover all cells: 14 dB C/I achieved

  9. Frequency Planning 22 dB 19 dB 14 dB 16 frequencies to cover all cells: 19 dB C/I achieved

  10. Single Modulation Networks • Minimum of 4 and 16 frequencies for 4 and 16-QAM respectively (no cross-polarization assumed) • If more frequencies are available, these can be used in every sector resulting in the following re-uses: • 4-QAM re-use = (N-3)/N *100% (where N=total # of freq’s) • 16-QAM re-use = (N-15)/N *100% • Example (Total spectrum of 30 frequencies) • 4-QAM re-use = (30-3)/30 *100% = 90% • 16-QAM re-use = (30-15)/30 *100% = 50%

  11. Interference prone zone Non cc interference prone zone ...So the solution is a combination of both • Modulation Co-existence QPSK only QAM16 ~100% radio coverage <100% frequency reuse i.e. 90% QPSK only 50% 16QAM only ~100% radio coverage (80%16QAM & 20%QPSK *) ... But QPSK frequency reuse * multi-cell network

  12. Interference Prone Zones • Interference prone slivers contours depend on requires C/I and re-use and TS antenna pattern • The frequencies in the slivers must follow the re-use scheme shown earlier. Outside slivers, any frequency can be used Interferer Interferer Victim Interferer Interference sliver

  13. Interference Prone Zones • Interference prone slivers contours are larger for 16-QAM than for 4-QAM 16-QAM sliver 4-QAM sliver

  14. Cell Radius • Typical cell radii for single modulation networks1: • QPSK : 3000m • 16-QAM: 2100m 1Rain region K, ITU-R rain model, multi-carrier

  15. QPSK QAM16 Multi Modulation Static Networks • Static multi modulation network (single cell shown) 16QAM QPSK Clear Sky Rain

  16. Static or Dynamic Modulation • Multi Modulation Static or Dynamic Networks • Several levels of modulations used in every sector • Can be assigned to each user either statically or dynamically based upon channel conditions • Cell radius determined by lowest order modulation used and additional back-off if required

  17. QPSK QAM16 Multi Modulation Dynamic Networks • Dynamic multi modulation network (single cell shown) 16-QAM 4-QAM Clear Sky Rain

  18. Multi Modulation Static or Dynamic Networks • Design networks for 4-QAM • Static networks: pre-assign modulation to users. Use same modulation for clear sky and rain conditions • Typical ratios of users allocated to 4-QAM and 16-QAM1: • Clear or Rain: 4-QAM ~ 15-20%, 16-QAM ~ 80-85% • Dynamic networks: dynamically assign modulation to users based upon channel conditions...gain due to cell radius • Typical ratios of users allocated to 4-QAM and 16-QAM1: • Clear sky: 4-QAM ~ 5-10%, 16-QAM ~ 90-95% • Rain: 4-QAM ~ 15-20%, 16-QAM ~ 80-85% 1Numbers based upon certain assumptions and are not guaranteed

  19. Summary • Higher order modulation increases channel efficiency and can increase network capacity • Design networks for QPSK and use modulation co-existence • Consider larger interference prone zones where higher order modulation coexistence is present • Consider a smaller cell radius for the static higher order modulation users • With dynamic modulation, negate the impact on cell radius during clear sky conditions • Whatever the case, every method is strictly a template used as the starting point for actual detailed planning using RNP tools

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