Spectrum Considerations for Emergency Mobile Radio Backhaul

John Yaldwyn – CTO

Australia is a big place

It is common in land mobile radio systems to

concentrate on the radio spectrum requirements of the

air interface between users terminals and base

stations.

Often an implicit assumption that there is some form of

invisible backhaul ‘cloud’ connecting base station sites.

In the past fixed line circuits leased from Telstra and

analog UHF duplex links were used to backhaul radio

systems.

Today, as the world moves towards a total IP form of

implementation, new technology backhaul solutions

are required.

However there is one constant – the need for backhaul

spectrum.

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LMR networking today

Legacy 4-wire analog and TDM E1/T1 interfaces have

rapidly given way to IP over Ethernet interconnection.

Mid-tier digital LMR such as Motorola Mototrbo™ and the

Icom/Kenwood NEXEDGE™ systems feature IP based

network interconnection.

High end public safety Project 25 digital LMR systems

from most vendors now support the P25 Inter RF

Subsystem Interface (ISSI) enabling agencies to be

interconnected. Same systems connections are

transitioning from typically 9K6 serial to IP.

IP and the Ethernet interface have become unifying

standards for interconnection of LMR networks.

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IP backhaul for public safety

IP interconnections provide the basis for

information sharing and interworking of

decision support tools at control and incident

management centres. With care digital LMR

systems can also be linked over the same

network infrastructure.

IP networking will increasingly allow shared

network use supporting new response tools

such as video and PDA type applications.

Effective IP backhaul needs to be available

for remote and rural Australia.

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Backhaul network topology and ownership

Both point to point and point to multipoint microwave

backhaul options exist. These two complementary

topologies offer a range of network architectural choices:

• P-P established approach with distance - capacity

trade-off and wide range of vendors.

• P-MP to date proprietary but great promise from

WiMAX and other standards based solutions. More

limited range for given constraints.

Intuitively would always opt for P-MP flexibility but real

world issues mean a blend of approaches is often best.

Mesh systems appear attractive but capacity and QoS

need careful evaluation.

Who will own your backhaul and what are their day to

day priorities?

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Backhaul frequency choices

Backhaul networking technology need to be

appropriate to the problem being solved.

City and metro areas have a large range of

implementation options available including

short haul microwave (7+ GHz) radio, fibre, or

leased line.

In remote areas long haul digital microwave

radio is the method of choice. Such systems

operate in lower microwave spectrum below

3 GHz and offer impressive NLOS capabilities,

but spectrum is scarce. Suitable spectrum is

limited and must be carefully maintained.

Unlicensed radio frequencies are not

appropriate for safety of life systems.

Backhaul network issues

Capacity

Range

Site acquisition

Spectrum availability

Physical infrastructure

Reliability and security

Installation and maintenance

Interference

Cost

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Flexibility and ease of use

Free standing tower

Wooden pole

Simple grid type and Yagi antennas can be used in the sub

3GHz bands instead of the solid parabolic antennas used at

higher bands, with significant cost and time benefits:• Expensive self supporting towers can be replaced by

cheaper pole mounts or guyed masts• With minimal support needed, site acquisition can be

simpler and done more quickly

Grid type and Yagi antennas are significantly less affected by

wind forces than solid types reducing the need for supporting

structure stiffness. Costs are greatly reduced.

FST

FAT

MT

FST

MT

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400 MHz band SCTF

Single channel two frequency (SCTF) fixed links ACMA

FX17:

•High/Medium Spectrum Density requires antenna with good F/B

ratio (Yagi)

•Outside these areas a low cost Yagi will be adequate

•25 kHz channels

•112 kbps @ 64 QAM

•Ideal for analog LMR and digital P25 backhaul

•Lowest cost backhaul radio system

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900 MHz band SCTF and LCTF

Single channel two frequency (SCTF) fixed links

ACMA FX17:

•High/Medium Spectrum Density requires antenna with good

F/B ratio (small grid or two stacked Yagi)

•Outside these areas a low cost Yagi will be adequate

•25 kHz channels

•112 kbps @ 64 QAM

•Ideal for analog LMR and digital P25 backhaul

Low Capacity Two Frequency (LCTF) fixed links

ACMA SPP 6/93:

•2M notional antenna

•50, 100, and 200 kHz channels

•256, 400, and 1,024 kbps @ 64QAM

•Ideal for P25 and Tetra backhaul

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1.5 GHz band

World’s most popular low capacity link band

1427 -1535 MHz:

• 20 km minimum path length

• 1.8M grid style dish minimum

• 4 MHz channels

• 17 Mbps @ 64QAM

• 240 km links in use for public safety

• Superb combination of capacity vs cost

Restrictions:

• Telstra DRCS use - obsolete

• Digital satellite broadcasting – it will never happen

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2.1 and 2.2 GHz bands

Excellent band for medium capacity

links in remote area.

ITU proposals for IMT upset use and

caused a decade of uncertainty - now

resolved.

2.1 GHz overlaps IMT / LTE allocation

so not recommended for new uses.

2.2 GHz band Embargoed from 1994,

from 2005 remote density area use OK:

•20 km minimum path

•3M notional antenna

•14 MHz channels

•65 Mbps @ 64QAM

New threat - ENG IFC01/10

  Sub

band

(MHz)

LTE E-UTRA band Description

  1900 –

1920

Band 33 TDD / top band

39 TDD

TDD Region 1 & 3

PCS extension Region 2

(TDD 1900)

 

1910 –

1930

Band 37 TDD TDD Region 1 & 3, PCS

centre Region 2

1920 –

1980

Band 1 uplink 3G UMTS uplink Region

1, 2 & 3

(IMT core)

1930 –

1990

Band 2 downlink / band

36 TDD

3G UMTS uplink Region

1, 2 & 3

(PCS / TDD 1900)

1980 –

2010

NOT USED Mobile satellite phone

services uplink

(subject to WRC-11)

2010 –

2025

Band 34 TDD 3G UMTS TDD Region 1

& 2 (TDD 2000)

2025 –

2110

NOT USED Space services –

operations and earth

exploration

Fixed service links

(ITU-R F.1098 & T/R 13-

01 E Annex C)

2110 –

2155

Band 4 downlink 3G UMTS downlink

Region 1, 2 & 3

(AWS USA downlink)

2110 –

2170

Band 1 down / band 10

down

3G UMTS downlink

Region 1, 2 & 3

(IMT core)

2170 –

2200

NOT USED Mobile satellite phone

services downlink

(subject to WRC-11)

2200 –

2290

NOT USED Space services –

operations and earth

exploration

Fixed service links

(ITU-R F.1098 & T/R 13-

01 E Annex C)

2300 –

2400

Band 40 TDD 3G UMTS 2.3 TDD

 

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Existing long haul 2 GHz link

Remote Area LMR Base Urban Area HQ

ACMA IFC01/10: … fixed links operating over long distancesmay require replacement by two links in the alternativebands to achieve the same distance.

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New sites and new radios

Urban Area HQRemote Area LMR Base

Higher bands = short links and more sitesMore sites = higher backhaul costs

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ACMA

Section 3b of the object of the Radiocommunications Act 1992 requires the ACMA to make adequate provision of spectrum for use by public safety.

The Act does not define how ACMA should determine how much spectrum is ‘adequate’.

ACMA “does not consider it possible or appropriate to provide a general definition of adequate provision”.

•From ACMA March 2009 Response to submission on the draft spectrum management principles

There are many complex ways to attempt to measure adequacy:

•ACMA chooses the total welfare standard to assess public interest …

•Total welfare is a competition policy theory, one of them at least

•Some argue the true consumer welfare standard gives better outcomes

The key is whose welfare is to be measured?

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ACMA engagement

Public safety is the public’s safety

There is one simple way to draw attention to public safety needs …

Public safety spectrum requirements must be clearly

articulated to ACMA.

Public safety agencies must ensure that all

opportunities to engage with ACMA are addressed

and exploited.

There are 4,000 licences issued to 260 users of 900

MHz and 1.5 GHz but feedback from ACMA

indicates these users are not talking.

Make sure you do!

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Talk to the ACMA about spectrum for backhaul!

Rural and remote Australia

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WELLINGTON 6035

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