Microwave, Fibre or Satellite - which is best as Africa moves to IP Networks?

Details: James Barton; Category: Optical & Fixed Networks; 24 May 2013; 9639 views

Across Africa, fibre has long been seen as a panacea for providing high-reliability, high-bandwidth connectivity, especially at a time when microwave was considered to be relatively unreliable due to the power required. Africa is an extremely dynamic environment and there are massive changes taking place across many countries, in terms of construction of infrastructure in both metropolitan and rural areas, but fibre is still a long-term sustainable solution for Africa...

While it has relatively high CAPEX the OPEX is very low and it is sustainable in terms of bandwidth growth. It requires mostly reconfiguration or terminal equipment changes rather than an overhaul of the entire length of cable; it’s therefore very easy for the operator to project their costs, both in terms of operation and reinvestment to support growth.

There are of course disadvantages to fibre deployment within Africa – most obviously, the inherent unreliability that comes with attempting to build out infrastructure in countries that are very much beginning to develop economically, with major construction and rebuilding programs underway in a lot of markets. Fibre networks are typically built alongside highways – indeed, to minimise the initial investment a lot of operators build them on the shoulder of the highway, instructing subcontractors not to lay the cable more than a metre or two away from the road.

If the local government decides to improve the road by widening it, miles of fibre can be ripped up – and the operator is often left unable to redeploy for some time while construction is ongoing. Permitting is often disregarded, with the result that even if construction workers are contractually obliged to protect the infrastructure, they are often unaware of its exact location and therefore highly likely to damage it by accident or through negligence.

“If you were to dig deep enough into the regulation then governments are probably obliged to compensate operators for damaging their infrastructure, but in reality it’s very difficult to ascribe accountability – and even operators succeed in doing so, getting anything officially processed is even harder”, says John Earley, president of the Africa region at Ceragon.

For long distance transmission there are only three alternatives: fibre, microwave and satellite. Satellite is prohibitively expensive for any high-bandwidth applications, although it is typically much more reliable than fibre or microwave. Microwave meanwhile cannot truly replace fibre - it has applications that can do so for relatively short distances, but ultimately it works better as a resilience route for fibre.

“The technology driving microwave backhaul has really shifted gear in terms of both capacity and operational cost. Previously, capacity limits were pretty tough – pre-IP, everything was based on channelised SDH, so regardless of innovations in microwave video you were limited to n x 155Mb, where n was controlled by the amount of available spectrum. This was typically limited, particularly on long-haul backbone routes”, adds Earley.

With more IP-centric backbones there is a lot more capacity in the network, and with advances in IP compression it’s possible to increase the available bandwidth by two or three times per MHz of radio spectrum. Microwave now offers multi-gigabit capacity, so transmission for long-haul is becoming more attractive.

If microwave is properly planned and engineered, it can give extremely high reliability. However, the bandwidth is relatively limited - operators must ensure that they plan the network so that critical traffic can be switched from fibre to microwave automatically, allowing for continuity of service. Less critical traffic such as web browsing can be placed onto lower priority or, if absolutely necessary, disabled.

Microwave can offer enough bandwidth to provide serious backup capabilities to fibre; it essentially acts as a safety net. Operators are building more and more rings of fibre and backing up the most critical rings with high-capacity microwave; they are investing heavily in building up capacity and making the switch to all-IP.

In the days of TDM, switching traffic between multiple routes was a complex process – in some cases it was even a manual process that involved unplugging a cable and plugging it back into a different location. IP is dynamic, almost on a second-by-second basis – as long as it has the right planning for quality of service, the whole process of balancing between transmission media is automatic.

Even in developing areas there has been a rapid increase in demand for capacity in networks, driven by mobile operators pushing data services into even the most remote areas. Until recently traffic was almost exclusively voice, but there is now a significant increase in data-based applications for rural services such as moving around farming information, providing weather data or local market pricing.

Users in very remote areas are beginning to expect high quality services to be made available to them. Using satellite to deliver this would eat up vast amounts of bandwidth and cost; microwave is therefore a viable alternative. Remote build-outs are made feasible (and cost-effective) by solar power, which can be used in areas which previously would have been impossible to service with fuel or power lines.

“If you deploy fibre, you can only be sure of one thing – it will fail. Whether it’s within days, weeks or months, you will be digging it up to repair it”, notes Earley. While many would debate this assertion, few would disagree that while fibre remains sustainable in the long-term, microwave now presents an excellent means of bolstering its reliability by providing additional bandwidth.