Overcoming Technical Challenges

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Certification Training

Overcoming Technical Challenges


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Objectives of Module

• This module will enable you to:• Explain the specific techniques used by

Motorola Point to Point 400 and 600 series to overcome the five technical challenges in deploying a robust point-to-point link

• Explain the special features used by Motorola Point to Point 400 and 600 series links and how they assist in overcoming the technical challenges


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Overcoming Technical Challenges

Motorola Backhaul technology overcomes allFive major challenges:

• Attenuation:-•Distance•Obstructions

• Fading:-•Ducting•Scintillation•Multi-path•Polarization Shift

• Dispersion• Interference• Links Over Water


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Attenuation (Path Loss) - Distance

Distance

The further any radio wave travels the smaller it gets, until that radio signal becomes so small it cannot be distinguished against the ambient noise.


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Attenuation (Excess Path Loss) - Obstructions

The signal is significantly reduced by an obstructions, typically up to to 1/1000th of a normal LoS signal (30dB).


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Attenuation

• Overcome by maximizing system gain• Dual high-power transmitters

• +25dBm 400 Series 5.4GHz & 5.8GHz• +23dBm 400 Series 4.9GHz• +25dBm 600 Series

(subject to local regulations)

• Dual ultra-sensitive receivers:-• –96dBm 400 Series• –88dBm 600 Series

• Automatic power control optimizes signalstrength for any environment (400 Series Only)

• Connectorised version of radio enablesexternal high gain antennas


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Fading

Fading is caused by many different radio elements.They include:-

• Ducting

• Scintillation

• Multi-path

• Polarization Shift


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Ducting

Ducting overcome by spatial diversityMultiple antennas at one or both ends• Optimum spacing based on Link Estimator

results and available vertical real estateProvides redundant paths which arenot affected at the same time• Over water, long distances, very flat terrain,

desert environments, or mountain top links Straight line path between antennasActual radio path, trapped in hot air duct


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Fading – Ducting ITU-R P530-10 cont.

Ducting effects differ in every area, and information for this is in the ITU document P530-10

This information is included in the link estimator


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Fading – Ducting ITU-R P530-10 Flatness

One of the causes of ducting is flat area’s of land.This information is included in the link estimator


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Fading – Ducting - Other Factors

Height difference decreases the probabilityLonger the range increases probability


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Scintillation

Scintillation is an effect caused by hot area’s of air over a long links (over 35Km).These hot areas of air cause the radio wave’s to converge or disperse.This effect is only countered by increasing the fade margin.The effect of Scintillation is included in the link estimator calculation


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Multipath Fading

Caused by radio signals arriving multiple times out of phase: overcome by Multiple-input Multiple-output (MIMO).

• Innovative way of sending signals multiple times and recombining them, to negate effect of out-of-phase radio waves counteracting each other

• Motorola Point to Point 400 and 600 series radios can realize up to 3 dBadditional system gain in high multipathenvironments due to MIMO

• Receivers on both vertical and horizontal polarity are active at the same time to overcome the effects of polarization shift

• Reduced signal loss means a lower fade margin is required: Motorola Backhaul can make the link where other products cannot


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What Causes Fading?

• Best case: paths different by evennumber of half wavelengths

• Worst case: paths different by oddnumber of half wavelengths

• Typical case: paths different bysomething in between two extremes

Best case scenario

Worst case scenario


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Polarization Shift

• Overcome by both vertical andhorizontal polarization transmittersand receivers active at all times

Vertical

Horizontal

Vertical

Horizontal


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MIMO ( Single Payload )

MOTOROLA

M ¦ O ¦ T ¦ O ¦ R ¦ O ¦ L ¦ A ¦

M ¦ O ¦ T ¦ O ¦ R ¦ O ¦ L ¦ A ¦

MOTOROLA

M ¦ O ¦ T ¦ O ¦ R ¦ O ¦ L ¦ A ¦

M ¦ O ¦ T ¦ O ¦ R ¦ O ¦ L ¦ A ¦

V V

H HData is sent with two polarizations giving radio signal redundancyWith LOS the signal maintains its polarization


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Multiple-input Multiple-output (MIMO)

Motorola Point to Point 400 and 600 series needs smaller fade marginfor same availability as other products

•Single-carrier radio: Other radios need 40dB fade margin to cope with fading

•MIMO signal: Motorola Point to Point 400 and 600 series only needs 15dB margin for same signal availability

•Conventional Radio •Multiple-input Multiple-output

-40dB

-15dB

0dB


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Multiple-input Multiple-output (MIMO)

• Motorola Backhaul needs smaller fade marginfor same availability as other products


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Adaptive Modulation

Combats fading due to obstructionmovement or temporary signal fade• Allows for higher availability with lower fade

margins compared to conventional radios• Radios automatically up and down shift

modulation modes when needed withoutdropping packets

• 600 Series has 13 modulation modes• 400 Series has 8 modulation modes

600 Series5x300 SoftwareModulation Mode

RX Threshold

dBm

TX PowerdBm

Aggregate Throughput

Mbps256 QAM .81 Dual -59.1

-64.0-62.0-68.1-65.9-71.7-71.0-75.2-74.8-79.3-81.6-84.6-88.1

300.2256 QAM .81 Single

+18+18+18+18+18+18+20+22+20+22+23+24

150.164 QAM .92 Dual 252.964 QAM .75 Dual 206.764 QAM .92 Single 126.464 QAM .75 Single 103.316 QAM .87 Dual 160.816 QAM .63 Dual 115.616 QAM .87 Single 80.416 QAM .63 Single 57.8QPSK .87 Single 40.2QPSK .63 Single 28.9

+25BPSK .63 Single 14.4


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Dispersion

Intelligent-OFDM overcomes dispersion• Data is sent for longer period of time, so echoes

arrive while original data is still being heardSpectrum divided into multipleindependent sub-carriers• Each orthogonal by making peak of each

sub-carrier coincide with nulls of othersMotorola’s Intelligent-OFDMoutperforms other products

A B C D E


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Comparison of OFDM and I-OFDM

• Stabilizing against inter-symbol interference• Motorola Point to Point 400 and 600 series takes 1 microsecond out of

each 35• Compared to 1 out of each 9.5 in others• 3.7 times less loss

• Tones to equalize signal• Motorola Point to Point 400 and 600 series takes 30 out of each 1024• Compared to 30 out of each 256 in others• 4 times less loss

• Performance• Motorola Point to Point 400 and 600 series : 994 usable carriers per 35 μseconds

• Others: 226 usable carriers per 9.5 μseconds• 20% better performance overall


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Interference

Overcome by combination of techniques:• Advanced spectrum management: Intelligent

Dynamic Frequency Selection• ARQ Error Correction• Ethernet compression


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Intelligent-DFS

Intelligent-Dynamic FrequencySelection overcomes interference• In-service Spectrum Analyser built into

every radio• Automatically moves to the cleanest channel• Proactive channel adjustment• Continuously monitors all channels• TDD or FDD allowed with asymmetric

DFS enabled• Allows for co-existence at hub sites or with

other products


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ARQ and Ethernet Compression

Automatic Repeat reQuest• Ensures data integrity• Radio itself requests repeat transmission of lost

data rather than end user device• Faster correction of errors• Improves overall network availability• Reduces overall network latency, as don’t need to

wait for end user device to make request of dataEthernet Compression• Radio compresses data before sending over the

air when operating in the three lowest modulation modes

• Effectively doubles throughput when transmitting non-compressed data


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Solution for links over water

Wireless Signals across water or hard surfaces (desert) pose challenges for performance and reliability owing to:

Reflection (Multi-Path) - Water or hard desert surfaces are highly reflective. Also, links over the sea are subject to varying water heights due to tidal changes, creating further challenges.


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Spatial Diversity: Antenna Configurations


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Spatial Diversity: Configuration Example


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This Module Covered…

Five key problems and how they are overcome• Superior system gain to overcome attenuation• Multiple Input Multiple Output (MIMO) and Adaptive

Modulation to overcome fading• User of vertical and horizontal polarization

antennas to overcome polarisation shift• Intelligent-OFDM and powerful equalizers to

overcome dispersion• Spatial diversity options to overcome ducting• Intelligent-Dynamic Frequency Selection, ARQ

and Ethernet compression to overcomeinterference

• Links over Water

Documents

Overcoming Technical Challenges