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Using microwave backhaul to deliver mobile broadband

Neeren Ramharakh, Vice-President, Sub-Saharan Africa at Cambridge Broadband Networks, discusses how African operators are delivering mobile broadband to regions where there is no fixed line infrastructure...

Neeren Ramharakh, Vice-President Sub-Saharan Africa at Cambridge Broadband Networks, discusses how African operators are delivering mobile broadband to regions where there is no fixed line infrastructure.

African operators have broken with tradition in their approach to delivering mobile broadband, and are among the best prepared for Next Generation Networks (NGN) as a result. As one of the fastest growing markets globally, networks are being rapidly rolled out and upgraded but, unlike western markets, there is no fixed line infrastructure to support this growth which creates a problem for backhauling the traffic generated by the expansion.

The majority of providers in established markets have made outsourcing arrangements with fixed line providers to cope with the explosion in backhaul traffic (and resulting cost) created by HSPA and the onset of mobile broadband. This generates a significant operating expenditure for the MNO which is largely out of their control, and limits the extent to which operators can make data "pay" and thereby expand their network capability.

In a bid to roll out their networks as fast as possible and retain control of their finances, African operators such as Vodacom Tanzania, MTN Nigeria and Wana in Morocco have adopted a point-to-multipoint microwave backhaul approach. It is a proven technology that has already demonstrated that it's "NGN" ready, and currently powers the backhaul networks of several WiMAX operators in the region, a situation which contrasts strongly with the delayed launch of Sprint's Xohm WiMAX network in the US last year because the backhaul network could not be built fast enough.

The growth of mobile and resulting challenges

Mobile connections are already out-stripping landline connections by a factor of eight across Africa. The mobile subscriber base has already grown to 282 million, and mobile broadband services in the region are on target to outstrip the fixed line alternatives. MTN Group reported 2008 results showing 48% subscriber growth and revenues up 40%: pretty heady stuff compared to what their mature market contemporaries are reporting!

ImageAfricaNext Investment Research has forecast that mobile broadband will account for over half of the African continent's broadband subscriber base by 2012, while Informa Telecoms and Media predict that African mobile data traffic will grow from 33.11 Petabytes (Pb) in 2008 to 94.21 Pb in 2012 - an astonishing compound annual growth rate of 23.3%.

These growth results and predictions pose significant challenges for operators in the region who need to dramatically expand their backhaul requirements if the network performance is to meet the service levels that will sustain this rate of growth. The performance of any cellular network is only as good as its ability to backhaul voice and data traffic from its base-stations and into the core network. If the backhaul capacity isn't available, regardless of the radio access network performance, end users will be saddled with a poor experience and disappointing data transfer rates.

The problem is that providing optimal backhaul capacity comes at a significant cost - estimated at around 30% of a typical operator's annual capital and operational expenditure. This expense becomes harder to justify when Average Revenues Per User (ARPU) are relatively low and need to be built up. In Africa this can vary from as much as US$11.25 in South Africa to US$5.31 in the Democratic Republic of Congo and US$2.61 in Mozambique. African operators have limited room for manoeuvre when it comes to costs, and simply cannot afford to overspend on the provision of backhaul.

A blessing in disguise

The lack of fixed line infrastructure might seem a severe restriction to the growth potential of mobile networks but in many ways it has benefited operators in Africa. By choosing microwave, and in particular point-to-multipoint microwave, operators have been spared the prohibitive cost of digging hundreds of kilometres of tunneling to lay fibre-optic cable, and in turn their customers have not been inconvenienced by associated road works as a result of the construction.

Even more importantly, carriers have been able to achieve fibre-like connectivity speeds while owning and controlling their own backhaul network - to the extent that some operators are able to operate their backhaul infrastructure with half the operating expenditure of their counterparts using more traditional options. Point-to-multipoint aids the process by supporting voice and data on a single platform and dramatically reducing the time it takes to build the network - up to 50% less than a comparable point-to-point architecture.

A case in point

Point-to-MultiPoint (PMP) microwave uses a dynamic architecture to address the backhaul issue. Rather than fixed links such as point-to-point or fixed line alternatives offer, PMP brings a number of cell-site links back to a single aggregation point or hub. Immediately, this reduces the number of radios and antennae making the network less expensive to build. The traffic is also optimised at the cell site, reducing traffic by up to 60% for one African operator, while the statistical multiplexing methods applied to each sector can reduce the backhaul demand by up to 80%. In addition, because the spectrum for the system is licensed across a number of radios, the resource is in effect shared, making the utilisation of the spectrum more efficient and more flexible. This automatically makes the network more energy efficient and reduces the running costs so funding can be redirected back into the network and enabling operators to bring the more advanced services to its customers, such as mobile broadband.

Working with a base raw data rate of over 150Mb/s gross throughput, PMP backhaul architectures then apply data optimisation and statistical multiplexing  to provide an "efficiency gain factor" of up to 5x. This effectively upgrades the capacity of a comparable PMP solution to backhaul 700 Mb/s or more per sector - sufficient for the onset of "NGN" technology such as WiMAX and LTE. Not only is PMP faster to deploy than other backhaul technologies, it also offers environmental benefits as well. PMP typically uses 50% fewer radios to deploy a backhaul network therefore the power consumption is significantly lower and the PMP hub "aggregation" sites only have four antennae - reducing the visual impact of microwave backhaul on the environment.

For a typical African operator the cost savings can amount to 50% compared with traditional microwave solutions. As a result of these capabilities, Cambridge Broadband Networks estimates that market for this technology will grow from US$115 million per annum in 2008 to US$442 million in 2012.

Operators need to invest in a backhaul solution that takes into account the realities of their current network infrastructure as well as the vision of their future network. With its inherently traffic-neutral, flexible, innovative architecture, PMP microwave will in most cases fit the bill. Achieving higher backhaul capacity is not just a matter of adding bandwidth; it also involves increasing the efficiency of traffic handling.

Clearly no "one-size-fits-all" model exists for every operator but when weighted against competing options, microwave, and in particular PMP microwave, offers a compelling argument based on the four main metrics which matter to operators - capacity, quality of service, capex and opex.

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