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Wireless Common Sense

Shifting the Collection of Prejudices

Robert J. Berger Internet Bandwidth Development Consulting

[email protected]

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Common senseis the collection of

prejudices acquired by age eighteen- Albert Einstein

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Tech You Grew Up with Shapes your Prejudices of Wireless Tech Capabilities

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Claude Shannon’s Communications

Theory Shows us the Reality beyond our prejudices

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C=W log (1+S/N)

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Shannon’s Theory

where; C=channel capacity (bits/second)

C=W log (1+S/N)

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Shannon’s Theory

where; C=channel capacity (bits/second)W=Bandwidth (How much Spectrum we are using)

C=W log (1+S/N)

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Shannon’s Theory

where; C=channel capacity (bits/second)W=Bandwidth (How much Spectrum we are using)

S=signal power, and N=noise power

C=W log (1+S/N)

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Propagation Characteristics & Path Loss

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• Determines how much of the signal power gets to the receiver

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• The higher the frequency- the less easily the signal propagates

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• The higher the frequency- the less easily the signal propagates- The more buildings, trees, hills the

more attenuation

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• The higher the frequency- the less easily the signal propagates- The more buildings, trees, hills the

more attenuation

• Physical Reality is such a Drag!!

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Radio & TV: Broadcast HIGH POWER & low frequency

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Radio & TV: Broadcast HIGH POWER & low frequencyMEGA WATTS of Power!!!

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Spectrum in the 80 - 800 MHz range

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50Khz - 6Mhz Channel Bandwidth

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50Khz - 6Mhz Channel Bandwidth

Gets Large Channel Capacity via Power and Significant Spectrum

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Tech from the 1930’s

Very simple analog modulationUses spectrum inefficiently

Receiver has difficulty rejecting noise

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Cell Phones: Tiny Channel Capacity

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Low Signal Power & Advanced Modulation

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800 - 1900Mhz a bit more difficult propagation, but still good

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But only requires 4kbps Channel Capacity

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But only requires 4kbps Channel Capacity

High speed data phones will have less coverage or need more basestations

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Past Experience Does Not Apply to WiFi

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Uses Unlicensed Spectrum2.4Ghz & 5 - 6Ghz, Very Low Power

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Rapid comidification & evolution -Very low cost & advanced modulation

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Rapid comidification & evolution -Very low cost & advanced modulation

Developed “Bottoms Up” like the Internet, not from Carriers or

Broadcasters

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Unlicensed Wireless Constraints

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Original Spectrum considered “Junk Spectrum”2.4Ghz is absorption frequency of water5 - 6 Ghz propagates about 1/2 as well

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Can’t interfere, but must accept interference

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Very low power, but lots of spectrumVery low power, but lots of spectrum

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Very low power, but lots of spectrum

Very short distance with high bandwidth

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Average WiFi Link Budget

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AP to Client limited by weakest linkAvg clients’ Signal Power: 15dBmAvg AP Sensitivity 1Mbps: -94dBm

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AP to Client limited by weakest linkAvg clients’ Signal Power: 15dBmAvg AP Sensitivity 1Mbps: -94dBmLink Budget avg client to AP:

signal power + xmit antenna gain - free space path loss + receiv antenna gain - receive

sensitivity = Margin

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AP to Client limited by weakest linkAvg clients’ Signal Power: 15dBmAvg AP Sensitivity 1Mbps: -94dBmLink Budget avg client to AP:

signal power + xmit antenna gain - free space path loss + receiv antenna gain - receive

sensitivity = Margin15dBm + 2dB - (-84) + 7dB - (-94dBM) =

34 dBm Margin at 150 Meters

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Link Margin

150

125

100 75 50 25

24 2628

3134

40

35 3739

4245

51

1 Mbps 11 Mbps

Meters

Link

Mar

gin

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Link MarginThe Free Space Loss calculations are optimistic

150

125

100 75 50 25

24 2628

3134

40

35 3739

4245

51

1 Mbps 11 Mbps

Meters

Link

Mar

gin

13


Realistic distance of a laptop to an AP is ~30m in the open

150

125

100 75 50 25

24 2628

3134

40

35 3739

4245

51

1 Mbps 11 Mbps

Meters

Link

Mar

gin

13


Realistic distance of a laptop to an AP is ~30m in the open

At 150 Meters, One good tree will knock out your link 15

012

510

0 75 50 25

24 2628

3134

40

35 3739

4245

51

1 Mbps 11 Mbps

Meters

Link

Mar

gin

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Real World Constraints

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Real World ConstraintsWiFi originally designed for indoor LAN

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WiFi CSMA does not handle large numbers of clients accessing an AP

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Nearby clients and APs not associated to an SSID can cause contention

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Asymmetrical Power causes client misbehavior

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Asymmetrical Power causes client misbehavior

Obstructions: One Tree: 20dB One Wall: 10dB

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WiFi has to Evolve Around Limitations

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802.11 Phy has already evolved from 1Mbps to 802.11n with 125Mpbs

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Distance not really improved (but more bandwidth for same short distance)

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Distance not really improved (but more bandwidth for same short distance)

Contention by nearby nodes not addressed yet (802.11s may, Proprietary extensions today)

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WiFi Recapitulates Ethernet Evolution

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Originally Considered a “Toy”

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Started out as LAN evolved to MAN

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“Good Enough” and much less expensive

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Designed by NetHeads, not BellHeads

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Designed by NetHeads, not BellHeads

Continually pushed beyond original limitations, first by proprietary extensions,

that migrate to standards

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Still at the Hub & Bridge

Stage Compared toEthernet Evolution

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Mesh: Ideal Architecture for Unlicensed Bands

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• Take advantage of

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• Take advantage of- Limited range

150

125

100 75 50 25

24 26 2831

34

4035 37 39

4245

51

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• Take advantage of- Limited range- Low Cost

components

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components- Good amount of

Spectrum

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components- Good amount of

Spectrum- Millions of Nodes

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Not Yet Near the Ideal

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Not Yet Near the IdealSome use 2.4Ghz for backhaul & access!

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Uses standard 802.11 CSMA protocol

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Gives great demo: Works great unloaded

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Gives great demo: Works great unloaded

As usage grows, contention is multiplied & becomes unusable

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Today’s Best Practices for Mesh

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Use different bands for Mesh & Access

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Coordinate transmissions & directional antennas

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Multiple Mesh Radios pluses and minuses

Features

Wireless! High-performance, multi-node and

multi-radio mesh architecture.! Low latency and high throughput

across multiple wireless hops.! Up to six radios per node

(upgradeable).! Full duplex mesh.

System! All nodes auto-discover and self-

configure.! Self-tuning and self-healing mesh

for network optimization.! User definable QoS with voice,

video and data prioritization.! Up to 16 BSSIDs per radio.! Multiple SSIDs (per network and

per node) and VLAN tagging, withconfigurable security parameterson a per-SSID basis.

! Session persistence for roaming,path optimization or failover.

! Manager/One® Web interfaceprovides a full suite of intuitivemanagement tools at the network,node, and radio levels.

! Additional remote managementoptions include SNMP, CLI overTelnet or SSH, HTTP/HTTPS,DHCP, and BOOTP.

! Seamless interoperability with theStrix Access/One® Indoor WirelessSystem (IWS) and Edge WirelessSystem (EWS).

Security! Supports all industry standard

security protocols.! RADIUS, WPA, EAP-MD5, EAP-

TLS, PEAP-TTLS authentication.! 802.11i with AES, WEP and TKIP

encryption.! MAC address Access Control Lists

on a per SSID basis.! Full VPN support.

OWS 3600 SERIES

DELIVERS INDUSTRYÊÂS HIGHEST THROUGHPUT,LOWEST LATENCY ACROSS MULTIPLE HOPS

The award winning Access/One® Outdoor Wireless System (OWS) 3600 is theindustry’s highest highest throughput, lowest latency modular multi-radio meshnetworking system. Utilizing Strix DMATM, the Access/One OWS delivers multi-radio, multi-RF and multi-channel capabilities usingadvanced algorithms to deliver high throughput overmultiple hops from the core to the edge of the network.The OWS intelligently self-tunes, self-configures andself-heals to optimize the overall performance andavailability. The OWS architecture makes 802.11 a fullduplex technology, moving traffic more efficientlythrough the network and utilizing different RFfrequencies and channels for network connectivity andclient access. RF Channels are selected dynamically,making the network more resilient to interference thanstandard mesh networks. Working closely together,these features deliver higher throughput and lowerlatency across multiple hops, supporting real timevoice, video, and data applications. The OWS scales

efficientlyand econ-omicallyminimizing the number of wiredtermination points required in thenetwork, greatly reduces deploymentand operating costs and the Total Costof Ownership (TCO). Extendedoperating temperature ranges andflexible mounting options make theOWS suitable for all types of

deployment scenarios. All OWS nodes can be centrally managed managed usingthe Manager/One® secure Web interface, or the carrier grade SNMP basedmanagement tools. Enhanced features including Virtual/Strix, Priority/One andRogue/One support deployments of mixed use networks where varying securityschemes are implemented based on user type and different levels of priority canbe assigned to the various network traffic. Access/One Network OWS is an idealsolution for carriers, service providers, municipalities, public safety, federalgovernment applications and more.

OWS is the most secure meshnetworking systemavailable, with

the tools to authenticate users,encrypt wireless traffic, andmonitor network activity all

provided as standard features.Secure private networks canoperate in tandem with open

public access networks—with dataintegrity guaranteed.

Strix Systems, Inc.26610 Agoura Road,Calabasas, CA 91302 USA

1-877-STRIXSYS (787-4979) Toll FreeWeb Site: www.strixsystems.com

www.strixsystems.com

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Multiple tiers of Wireless backhaul

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Multiple tiers of Wireless backhaul

Expect < 1Mbps delivered19

State of Muni-Wireless(US Centric View)

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First phase build-outs

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Significant Learning Curve

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First Generation Equipment

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Be prepared for negative Hype CyclePeople’s expectations too high

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Be prepared for negative Hype CyclePeople’s expectations too high

Its still very early

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WiMax?

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WiMax?If WiFi recapitulates

the evolution of Ethernet;WiMax recapitulates the

evolution of all of Ethernet’s competitors

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WiMax?

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WiMax?No real advantage when comparing unlicensed

WiMax & WiFi

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WiMax & WiFi

Licensed WiMax can be useful(ATM was useful for some things too)

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WiMax & WiFi


Getting a License can be difficult & Expensive

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WiMax & WiFi


Getting a License can be difficult & Expensive

Very good for feeding WiFi Mesh

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WiMax?

Beware of Hype

Very few deployments of “real” WiMax

No deployments of Mobile WiMax

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Wireless Tech of the Future

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• Ultrawideband- Ultra Short Range- 2 to 3 x bandwidth

over 802.11n

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over 802.11n

• 60 - 70 Ghz- Extreme Bandwidth &

Directionality

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over 802.11n

• 60 - 70 Ghz- Extreme Bandwidth &

Directionality

• Super Mesh- 802.11s evolution?- Short Range is good- More Bandwidth!

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No Silver Bullets on the Horizon

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Wireless Common Sense

Shifting the Collection of Prejudices

Robert J. Berger Internet Bandwidth Development Consulting

[email protected]

26

Download - Wireless commonsense fontsfixed

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