higher order modulation in lmds networks bbwwf - san francisco, february 2001
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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?. - PowerPoint PPT PresentationTRANSCRIPT
All rights reserved © 2001, Alcatel — 2Higher Order Modulation in LMDS Networks
Higher Order Modulation in LMDS NetworksBBWWF - San Francisco, February 2001
Joe Fournier
All rights reserved © 2001, Alcatel — 3Higher Order Modulation in LMDS Networks
Agenda
Why the consideration of modulation?
Frequency Planning
Interference Prone Zones
Cell Radius
Dynamic or Static Multi Modulation Networks
Summary
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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
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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.
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Frequency Planning
14 dB
19 dB
22 dB
Victim (blue) is interfered with by many interferers along radials
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Frequency Planning
14 dB
19 dB
22 dB
14 dB C/I achieved
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Frequency Planning
14 dB
19 dB
22 dB
Analogous for the remaining 3 types of sectors:14 dB C/I achieved (specific freq. used in yellow sectors)
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Frequency Planning
14 dB
19 dB
22 dB
4 frequencies to cover all cells:14 dB C/I achieved
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Frequency Planning
14 dB
19 dB
22 dB
16 frequencies to cover all cells:19 dB C/I achieved
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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%
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...So the solution is a combination of both
Modulation Co-existence
~100% radio coverage<100% frequency reuse i.e. 90% QPSK only 50% 16QAM only
Interferenceprone zone
Non ccinterferenceprone zone
~100% radio coverage (80%16QAM & 20%QPSK *)... But QPSK frequency reuse
QAM16
QPSKonly
* multi-cell network
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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
VictimInterferer
InterfererInterferer
Interference sliver
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Interference Prone Zones
16-QAM sliver
4-QAM sliver
Interference prone slivers contours are larger for 16-QAM than for 4-QAM
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Cell Radius
Typical cell radii for single modulation networks1:
QPSK : 3000m
16-QAM: 2100m1Rain region K, ITU-R rain model, multi-carrier
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Multi Modulation Static Networks
16QAM
Static multi modulation network (single cell shown)
QPSK
Clear Sky RainQPSK
QAM16
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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
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Multi Modulation Dynamic Networks
16-QAM
Dynamic multi modulation network (single cell shown)
4-QAM
Clear Sky RainQPSK
QAM16
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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
All rights reserved © 2001, Alcatel — 20Higher Order Modulation in LMDS Networks
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