higher order modulation in lmds networks bbwwf - san francisco, february 2001

All rights reserved © 2001, Alcatel — 2Higher Order Modulation in LMDS Networks

Higher Order Modulation in LMDS NetworksBBWWF - 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?

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


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.


Frequency Planning

14 dB

19 dB

22 dB

Victim (blue) is interfered with by many interferers along radials


Frequency Planning

14 dB

19 dB

22 dB

14 dB C/I achieved


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)


Frequency Planning

14 dB

19 dB

22 dB

4 frequencies to cover all cells:14 dB C/I achieved


Frequency Planning

14 dB

19 dB

22 dB

16 frequencies to cover all cells:19 dB C/I achieved


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%


...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



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



16-QAM sliver

4-QAM sliver

Interference prone slivers contours are larger for 16-QAM than for 4-QAM


Cell Radius

Typical cell radii for single modulation networks1:

QPSK : 3000m

16-QAM: 2100m1Rain region K, ITU-R rain model, multi-carrier


Multi Modulation Static Networks

16QAM

Static multi modulation network (single cell shown)

QPSK

Clear Sky RainQPSK

QAM16


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


Multi Modulation Dynamic Networks

16-QAM

Dynamic multi modulation network (single cell shown)

4-QAM

Clear Sky RainQPSK

QAM16


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


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

higher order modulation in lmds networks bbwwf - san francisco, february 2001

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