There has been a vast increase in data growth in most markets over the last few years, with rising mobile penetration in the rural regions of emerging markets often cited as a key driver for competitiveness.
This has lead to many discussions on how best to develop and promote mobile penetration in rural areas, with the most notable issues being those of infrastructure deployment and backhauling. Handling the boom in data-hungry services requires reliable networks that can offer increased capacity, but delivering such coverage to rural areas presents many challenges.
Someone who knows a lot about the advantages and disadvantages of different backhauling solutions is Jose Quintero, Director of Technology for Mobile at network operator Cable & Wireless in Panama. The Central American country’s urban centres are very spread out due to a high amount of rural reservations. Quintero is adamant that reliable backhauling is essential for providing coverage in these more remote areas. While there are satellites with a good footprint over Panama, the amount of bandwidth they have available is limited. Satellite is suitable for GSM, but technologies such as HSPA and LTE would create a bottleneck.
“Backhaul is like blood vessels in the body – you can have all the heart you want, but if it gets blocked you’re going to have a stroke. If you don’t have capillaries reaching out to the extremities, they will die. You can change the heart but you can’t change the outside plan overnight – that’s why [backhaul is] the most critical part of the network going forward”, says Quintero.
The most reliable means of backhauling, he claims, is fibre. However, in rural areas, this can be prohibitively expensive, particularly in countries such as Panama where much of the available infrastructure is owned by electricity companies and must be leased. The alternative for these areas is to use microwave backhauling – in order to increase fidelity, the lowest frequencies possible are used.
While microwave backhaul is resilient, Quintero believes that without deploying more fibre, it will become increasingly difficult to backhaul both mobile and fixed broadband as data usage increases. “Everything that happened in fixed years ago is happening in mobile data now – for example, 5% of users consuming 50% of throughput”, he says. “Deploying more fibre means expanding the capacity available for backhaul.”
Data growth has leapt up as smartphones and tablets become more widespread – these devices are responsible for 80% of the data throughput in mobile. Quintero notes that traffic has essentially doubled on a year-on-year basis, with virtually all growth driven by Android & iOS devices.
Devices can now connect via HSPA+, WiFi, and - eventually - LTE, and the radio access networks that they are connected through will require the same backhaul to stay connected to operation points, backbone points and then into the internet.
“It’s a technology of access, but the modulation and multiplexing are only part of the equation – the other is rollout”, adds Quintero. “This involves support, backhaul, traffic management – you need to look at the architecture as a whole. If you look at a building, you don’t just focus on the furniture – you have to look at the structure.”
So how best to build a rural network that delivers the necessary bandwidth? Traditional macro base stations are increasingly being shunned in favour of small cells - the next generation of high-bandwidth delivery architecture. Like macro cells, they have high synchronisation requirements. There are four protocols that can deliver the requisite level: PTP (precision time protocol), NTP (network time protocol), GPS/GNSS, and Synchronised Ethernet.
Small cells are intended for use in many different environments, and the types of backhaul used will vary, says Manish Gupta of precise time solutions provider Symmetricom. “For PTP, it’s a layer 2 or 3 physical implementation so you can run anything at a physical layer and run PTP on top of it. It’s the same for GNSS; it’s a local environment, so if you can get a signal with a GPS antenna it doesn’t matter what the backhaul looks like”, he notes.
Small cells were created to provide better coverage to residential areas – with around 50% of all traffic generated by homes, the benefits of offloading traffic to the cell tower become clear. However, says Gupta, despite their origins in densely populated residential areas, small cells are equally well-suited to rural – and a number of backhaul methods can be used to achieve the required synchronisation, including microwave, millimetre wave and satellite.
A metro small cell can be installed for roughly a third of the price of installing a macro base station. Macro architecture consists of three separate pieces - a base band, an RF and an antenna - whereas a small cell, by definition, is ‘all-in-one’, providing an automatic cost advantage. The OPEX is also lower than cabling, and auto-discovery makes it a lot easier to deploy, position and manage a small cell compared to a typical macro or distributor antenna architecture.
“The solutions are evolving to the point where the backhaul is integrated into the base band, allowing a small cell to serve the access side”, says Gupta. “This could also support the backhaul, allowing for an integrated environment where backhaul and access are provided by the same package.”
Macro cells will continue to have a role in rural backhaul, particularly where topographical, access and power supply considerations mean that larger cell areas are more efficient at providing coverage. But as the efficiency and power of small cells improves and the demand for data increases, all-in-one small cell solutions are looking increasingly attractive to network operators for rural as well as metro locations.
