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VOLUME 5 N° 1 FEBRUARY/MARCH2006

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For wirelesscomms professionals in northern equatorial Africa

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POINT TO POINT

Sharpening the poin',,

Laying fibre optic cables isprohibitive when networktraffic is low density," saysJoseph Joseph, Harris

Microwave Communications Director EMEA.

"The physical act of digging-up roads takestime, as does gaining planning permission.This all increases the time to market for an

operator and makes it longer for them torecoup costs," he adds. In most areas, the onlyway to provide telephone and internetconnections, without a large-scale subsidy, isby reducing the infrastructure cost.

Joseph's comments summaries the appealof using point-to-point (p2p) technologies forincreasing the range of wireless networks.Their use in providing expanded bandwidthcapacity is rising with the demand forcombined voice, data and video connections.

Grant Grafton, Sales Director for Europeand North Africa at Orthogon Systems, amicrowave communications provider, says:"The general thirst for communication is theengine driving the demand for consumergoods and services in many areas ofthe continent."

Mike Moyes, a Director of Engineering atRedline Telecommunications, an African FSOprovider, cites specific examples: "A GSMbase station could run out of capacity andrequires a micro-cell extender to be installedin the shortest time possible. There is no timeto wait for copper cables to be installed, or ifa GSM network operator has a fibre ringwithin the city and needs short distanceconnectivity to its base stations."

The necessity of linking 3G masts is alsocreating opportunities for p2p, according toJim Kernahan, worldwide Sales andMarketing Director at SunflowerTechnologies, a provider of wireless opticalsolutions. 3G masts have higher bandwidthrequirements than 2/2.5G ones, he says,especially where operators are aggregatingbandwidth for a number of closely proximatemasts via a central point.

However, providing a p2p solution,specifically to rural areas, has been expensive

FSO enables

transmission fromone building...

in the past. "The traditional backhaul solutionhas been to engineer longer-distance links inthe 7-15GHz bands, although they frequentlyhave far more capacity than is actually neededfor a remote or rural application," saysAmanda Ingalls of Skyworks Solutions, aprovider of radio solutions and precisionanalogue semiconductors for mobilecommunications. She says that, togetherwith the capital cost of radio equipment,these bands require much larger, moreexpensive solid dish antennas and robustmechanical mounting.

"Dual antenna configurations are also oftenessential to deliver the required level ofavailability, further increasing equipment andinfrastructure costs," says Ingalls.

WiMAX is on the list of potentialbroadband access solutions for ruralcommunities (see WiMAX: The last word inlast mile? NA we December 2005/January2006). Equipment certified by the WiMAXForum conforming to the IEEE802.16dstandard is expected to make highperformance links available to the networkproviders cheaply. But even though somedeployments have taken place, a like-for-likefinancial comparison with other options hasyet to be conducted. Furthermore, with theIEEE802.16e standard having yet to proveitself, the extent to which WiMAX canoperate as a fully-fledged mobile solutionremains to be seen.

Defining p2pp2p technologies enhance a network in twoways. Firstly, there is access, which supportssite-to-site access, such as base stationconnectivity. Secondly, there is transport,which could connect switches between towns.

But beyond all 'that, what exactly constitutes ap2p solution? Precise definitions are sketchy.Andy Singer, President of microwave antennamanufacturer, Radio Waves, says that a truep2p solution is one which simply transportsinformation from point A to point B."Although from a network operator'sstandpoint," he adds, "a P2P solution is awireless system that has the required

18 NORTHERN AFRICAN WIRELESS COMMUNICATIONS February/March 2006

Demand for GSM is d. . '" ~

to increase coverage \.. :, 0on base stations. Ca ~ .0

speeds are also rising. .) 5 "11is one way of ach:~. "

not the only solution. C ~ ertechnologies, such as free-s; a =:1

can complement existir; secomplete solutions'" 1

John-Paul Kamath exa -- - eoptions for enhanc: ~; :.

POINT TO POINT

ht on point-to-pointA microwave p2p solutioncould prove ideal in lowerspeed applicatiolls over longerdistances.

driving African operatorswithout increasing spend

:altfOr broadband data. sing a WiMAX solutionhi ing this - but it's

. Other point-to-point (p2p)

.e-space optics and microwave,iting set-ups and even offeriPns in their own right.!xamines the available p2p~cing wireless networks.

capacity to transport their infonnationreliably from point A to point B:'

The idea of a client's requirementsdetermining th~ appropriateness of a givensolution fOnDSthe basis for other definitions.

"A true point-lo-point solution should offerthe highest possible bandwidth and with asignificantly cheaper outlay than a leasedline/dark fibre connection," says StuanWilliams, General Manager of MRV, aprovider of optical transport solutions.

Meanwhile. u.igh McBain, a ProjectManagement Director at free space opticsvendor Fsona. says that a p2p solution is onewhich meets the speed-over-distance need~ ofthe end user - not what industry punditsclaim is the 'next big thing'. Choosing atechnology platfonn to implement a p2psolution is easier than one would think. Each

method serves a specific niche and. in somecases, can be used jointly to strengthen asingle offering.

More than microwavesFree space optics (FSQ) uses infrared totransmit data across point.;;, "An internationalvideo production house in Africa recentlyneeded connectivity with its clients whoprovide broadcast video editing servkes.Radio systems could not provide thebandwidth required without resorting toexpensive solutions. A series of lOOMbps fullduplex FSO links does Ibe job with plenty ofbandwidth to spare," says Redline's Moyes.

FSO p2p technology can also work as anetwork traffic backhaul solurion. In scenarios

where a multiple antenna sector approach isused by the operator to deliver broadbandservices. the required amount of backhaulaggregation traffic could be carried over ahigh capacity optical wireless link.

Peter Schoon. President of System SupponSolutions. supports this type of application.He says that FSO fits better when nltra highbandwidth (FatE and GigE) is needed atrelatively shorter distances of up to about twokilometres. Some microwave providersquestion the usefulness of this offering."Although. FSO throughput is often greaterthan microwave access, we still find that

300Mbps is generally enough for mostapplications:' says Grafton.

"Realistically, FSO has a maximum rangeof three to five kilometres," he adds. In

comparison to RF though, the use of FSOwould not require the operator to use parts ofthe relatively nan-ow band WiMAX spectrumfor traffic backhaul.

While fibre still offe" the highesttransmission rates over media, FSO provideshigher transmission than microwave.Commercially available FSO systems offercapacities in the range of l00Mbps to2.5Gbps over several kilometres, saysSkyworks' Ingalls, adding that licensedmicrowave communications support data ratesof 2Mbps to 622Mbps over distances of 100metres to 100 kilometres.

"While traffic capacity in free space opticssystems is quite scalable from E I(2.048Mbps) levels all the way up to GigabitEthernet (1.25Gbps) and beyond, microwavesystems operate at lower capacity levels:'says Heinz Willebrand, CTO and founder ofUghtpointe, a vendor of FSO products.

Ross Lunan of Harris Communications

outlines the cost-distance relationship. Hesays that the cost, not necessarily the price,for a FSO system is virtually the same forcapacities from 10m to 155m. Microwavesystems are the opposite. The distance isn'tthe critical costing factor - bandwidth is.

'There is therefore a breakpoint in price.Very high capacity short links commerciallyfavour FSO while long distance smallercapacity links commercially favourmicrowave. The longer lhe FSO link, thehigher the cost," says Lunan.

However, depending on the country, theavailability of spectrum can be an issue withmicrowave, as frequency shortages in built-upareas become apparent. Willebrand says thatwhile the freqnency spectrum of FSO is freefor use worldwide, higher capacitymicrowaves need large amounts for operation- and this can be expensive.

The spectrum used for FSO systemoperation does not require a license becauseof the lack of cross platform interference;provided line-of-sight is established betweenthe two locations in question. "An FSO linkcan also be established, without concerns,

over crossed beam paths or self-inflicted

interference due to less than necessary fresnel ~zone allowances," says McBain. There is no

...but a clear

Une-of -sight isessenJialfor

the signalsto get through.

February/March 2006 NORTHERN AFRICANWIRELESSCOMMUNICATIONS19

...cmIng requirement because. unlike RF, an~ ttansmission does nol emit anyoo:uomagnetic inlerference (EMI).

'ntrusion threat"" .. id1any communications technology. the

~ of security ranks high on the list of. -It..:emswhen evaluating a suitable solution...,.. degree of FSO security depends on the" .er and frequency of the radio, the width of-~ !am and the type of infonnation being

_nee!." says Ingalls. With a very nanow-.c.m far overhead. the outskins of the beam-' seminales infinitesimally low power.T~ into that energy would be extremely.~ Even then. tapping inlo the signal

'"Trafficcapacity infree space opticssystems is quitescalable from E1

levels all the way upto Gigabit Ethernet

and beyond"Htinz Willebrand.CTO andfoutldtr.

Lightpoinl.

- «quire convertingtheRF radiosignalftZ . Y1Dat that you're sending. whether. "". LANdata.videoor allthree.

S ct"DttaSt. lower frequency radios. sayftZ ~ to six gigahertz bands, can transmit;'t -a levels of hundreds of Walts (versus

~,.m -shesays.1besecancoversingle-~ ... .---es of 30-40 miles producing a.r -..II.can fan out hundreds of feet wide

r~ Zone). and with more detectable

energy in the side lobes. Such factors raise thechances of surreptitious interception.

"Jusl as an examp1e."says Willebrand. "thebeam divergence angle of an FSO-basedtransmission system is on the order of 0.1 100.3 degrees. The transmission angle of amicrowave antenna is in the order of 10degrees or more."

In other words. while the FSO transmissionbeam has a di~eler of only one to threemetres after travelling one kiJometre,themicrowave signal will already be spread outover an area of 170mor more after the samedistance. making it relalively easy 10tap into.

Beware the fogWhile the nanow spread of its beam maymake FSO technkally more secure. overlonger distances, environmental obstacles canprove problematic for it. For FSO solutions.environmental attenuation increases with link

distance and so canier-c1ass systems muslbe designed to accommodate heavyabnOspheric attenuation.

''The effect of fog on FSO radialion isentirely analogous 10 the attenuation sufferedby RF wireless systems due 10 rainfall.Similar to the case of rain attenuation with RFwireless, fog attenualion is not a 'show-stopper' for FSO:' says fsona's'McBain.

Sunflower's Kernahan advises thai to

mitigate against Ihe effects of fog. the FSOlink should be no longer than ~ 700 melres.If it is a crilicallink. it should have a licence-

exempt radio back-up solution installedalongside. with spanning tree installed on thecommon swilch.

"With radio complementing FSO,availabilities to 99.999 per cent could beattained because radios operate through thefog that disables FSO links, wbereas FSOlinks are far less vulnerable to rain cell

passages that cause millimetre wave radio linkoutage." says Ross Lunan.

In this respect, FSO and microwave can beviewed as being complementary technologies.adds MRV's Williams.

In spite of this hybrid-installation.Orthogon still believes that over longerdistances. it is microwave thai makes bettersense. "With FSO, you can improve yourrange and data rate. but at a cost that will beprohibitive for the majorily of customers.thereby making an apples. to-applescomparison between FSO and other

Howto choosea p2psolution:. .M:~ent circumstances will favour" ,echnology over another. Herein ;.orneof the key considerations-.iI-a Communications recommends

~ -~ evaluating your requirements:~ and right...

~e anger the link, the more-i :Jable a microwave solutiont, :'_.0 be.

u d, .dth- : oandwidths over shorto'-,"",es tend to favour FSO,

Overall system cost(acquisition and recurring)FSOhas the system acquisition costadvantage for short links. It hasadvantages where there is a highre<:urringcost of licensing fees. Fibreoptic cabling solutions are almostalways more expensive, especiallyover greater distances or whereextensive civilworks are required.Time to deployIf this is the driver, then both FSOand microwave solutions would bebetter choices over fibre optic cable.

-POINT TO PCt

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MRVengineersinstaUan FSOtransmitter.

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microwave technologies." says Grafton. Headds that microwave, in the 5.8I5.4GHz areasof operation. is still able to deliver data ratesat up to 300Mbps over non line-of-sight paths.which equals FSO.

UpgradesNevertheless, both these p2p tecbnologies areexpanding their capabililies. Carriersevaluating FSO technology from thePDHlSDH tnmspon standpoint are askingmanufactures 10 find methods to avoid short

tenn intenuPlions of network lraffic."One of the features cuslomers are asking

for is active IraCking, which actively keepsthe beam right onlO the larget position,"says Willebrand.

Calls for proven standards.basedredundancy are also increasing says McBain,who adds: "A good example is our fullyredundant Ethernet solution. It has been

designed to provide access to backupsolutions at whalever data rate the consumer

may require. as well as 10address a fulJcomplement of RF frequencies and evenwireline carrier services:'

Out-of.band management is beingdemanded by more and more customers.according to Redline. "Tbe traditional in.bandmanagement fails when the link fails therebylimiting the amounl of crucial infonnaLionrequired in situations such as these. Rcdlinehas implemented an 'SMS-GSM modem'-based system which provides oUI-of-handmonitoring from virtually any location in Iheworld," says Mike Moyes.

In microwave. fealures that makeinstallation and maintenance easier are a

common request. Orthogon. for example, hasintroduced a feature allowing its links 10 bealigned using a 'goodness' meter displayed ona PDA which enables remme monitoring.

Using either a microwave or FSO-basedtechnology for a p2p solution is governed bythe speed-over-distance requirements. If theavailabilily of spectrum and related licensingcosts aren't prohibitive. lower speed andlonger distance applications are potenliallybetter served by using a microwave link. Ifhigh througbput (such as 1000IOOOMbpsEthernet) is needed. and the distance invoh"edis shorter (less than two kilometres. forexample), an FSO based solution wooldappear to be a better lit.

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.FebruarylMarch 2006 NORTHERN AFRICAN WIRELESS COfJ'" - <.,;1.--