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BANC – Broadband Access Network Coordination

A practical solution to the critical problem of interference in the unlicensed spectrum bands

Graham Barnes, CEONextWeb, Inc.

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Overview

• Critical Problem of Interference in Unlicensed Bands with a Multi-Operator Environment

• There are Successful Interference Countermeasures

• Unlicensed does NOT mean Uncoordinated• Unlicensed does NOT mean Unreliable• Unlicensed does NOT mean Uninvolved

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Why is Interference Getting

Worse – Not Better?

• Weren’t technology improvements supposed to eliminate interference?– Spread spectrum– Adaptive modulation– Multi-carrier techniques– New frequency bands

• More payload• More users / operators• Lower cost equipment• Unrealistic expectations?

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It’s a “JUNGLE” out there!

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Why is a Frequency Management

Program Important?

• Even if you don’t have interference problems today – you will!

• Private parties deploying campus systems• School districts and cities deploying

unlicensed WANs• New wireless ISPs entering the market• Investor confidence

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Frequency Management

Program Tools

• Terrain Map-based Engineering Plans• Open Disclosure of NextWeb Network• Interference Countermeasures• Knowledge of Channel Plans from Major

Vendors• Spectrum Analyzer Surveys to Monitor and

Identify Use• Active Participation in Coordination• Joint, Controlled Interference Resolution

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Terrain Map-Based Engineering

• Anticipated coverage expectations

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Terrain Map-Based Engineering

• Not all problems are due to interference

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Open Disclosure of Network (to those who need to know :-)

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Interference Countermeasures

• Directional antennas

• Narrow Channels• Short paths• Max C/I• Vendor

technology• Good contracts

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What does not work?

• More transmitter power– Adjacent channels– Complaints from other operators– Self interference

• Uncontrolled rooftops– Interference protection language in contracts

• Seeing other WISPs as “the competition” instead of partners– Telco/cable monopolies are “the competition”

• Blind faith in the claims of the vendors’ marketing departments

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Sample Channel

Plans from Major

Vendors

• 5.8 GHz• ISM• UNII

Frequency Axxcelera YDI (EX-1) Canopy (4) Trango Quick-Bridge Tsunami-45572557265727572857295730573157325733573457355736 C (12) Ch1 C (22) Ch1

573757385739574057415742 C (20) 3A/5A

574357445745 C (16) Ch10 C (25)

5746 C (12) Ch2

5747574857495750 C (48) A1

575157525753575457555756 C (12) Ch3 C (22) Ch2

5757575857595760 C (16) Ch11

57615762576357645765 C (25)

5766 C (12) Ch4

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Sample 5.8 GHz Spectrum

Axxcelera NearbyAxxcelera

Axxcelera Trango w/Unknown

Trango

NearbyTrango

Unknown

Unknown

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Active Participation in Coordination

Cellular

Cellular

Cellular

5.8 GHz PTP

5.8 GHz PMP

5.8 GHz PMP

5.8 GHzPMP

One corner of shared base station

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Opposite Corner of Same Building

18 GHz

18 GHz11 GHz

23 GHz

Cellular

Axxcelera5.8 GHzPMP

5.3/5.8 GHz PTP

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Initial Status:

Three different fixed wireless providers (red, green and blue), built out their unlicensed networks in the same area, over time.

By careful selection of frequency channels, all three operators are able to provide reliable interference-free connections from their access points (APs) to their customers’ subscriber units (SUs).

Joint, Controlled Interference Resolution

SU

AP

AP

SU

SU

SU

SU

AP

SU

SU

SU

SU

SU

SU

SU

SU

SU

SU

AP

AP

SUSU

SU

SU

SU

SU

SU

SU

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Enter a rogue interferer:

A new unlicensed link (yellow) is turned on, causing interference to one of the green operator’s subscribers resulting in significant bit or frame losses.

The areas of influence of the new link’s transmitters are shown as yellow circles.

SU

AP

AP

SU

SU

SU

SU

AP

SU

SU

SU

SU

SU

SU

SU

SU

SU

SU

AP

AP

SUSU

SU

SU

SU

SU

SU

SU

Joint, Controlled Interference Resolution

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Typical scenario:

The green operator sees interference, but the red and blue operator does not. However, the green operator attempts to switch his AP to a new channel to avoid the interference.

The new channel now causes interference to red and blue operators who must also change channels, if possible.

SU

AP

AP

SU

SU

SU

SU

AP

SU

SU

SU

SU

SU

SU

SU

SU

SU

SU

AP

AP

SUSU

SU

SU

SU

SU

SU

SU

Joint, Controlled Interference Resolution

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With BANC pre-coordination:The green operator sends out a group message to make sure no BANC member has made a change.

As no member made an uncoordinated change, the green operator concludes that a new private link is causing interference.

The green operator lets the BANC group know of the proposed channel change of his AP.

BANC group helps coordinate to find a good channel solution so no NEW interference problem occurs.SU

AP

AP

SU

SU

SU

SU

AP

SU

SU

SU

SU

SU

SU

SU

SU

SU

SU

AP

AP

SUSU

SU

SU

SU

SU

SU

SU

Joint, Controlled Interference Resolution

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www.wbanc.com

• Why should I join?– Protect revenues and predictable performance– High cost of interference– Cannot afford a glitch: churn; time– Hard to identify and resolve a case of interference

on your own

• What are the rules?– No fees– New members welcomed– Neutral exchange of information by web and e-mail

(yahoo groups)– Survey first before turning on transmitter– Pre-coordinate prior to installing or changing freq

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BANC policies

• Declaration– Subsequent operators must use due dilligence to

determine and avoid existing spectrum in use– Those who disrupt existing operations are offered

the opportunity to correct before civil legal action

• Protocols– Scan spectrum first before operating– Advise other operators of tests by e-mail in

advance– Send out warning and seek consultation when

attempting to correct cases of interference

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Growth of BANC

• Reach out to encourage participation– Other WISPs– Other users of outdoor unlicensed equipment– Vendors– FCC / DoD

• Multiple regional BANC groups– All linked to central web site– Find out if there is a BANC group in your region– Seek participation nationally– Learn from best practices

• Occasional meetings hosted by participants, rotating basis

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Future of Unlicensed Broadband

• Regulators love unlicensed– Responsive to the needs of industry– Deregulation aids tight budgets– We must push for more spectrum and more

flexibility

• Technology to the rescue!– Cognitive radio – when?– The “list”: always-on, non-LOS, increased range,

blg penetration, high throughput, VoIP quality, $300 CPE

• Potential Explosive Growth– Economy rebounds– NextGen equipment ships– Financial markets wake up to potential