The arrival of 3G cellular - and, with it, bandwidth-intensive apps like music downloads, media streams and even video sharing, to name a few - has forced mobile operators to revisit their suddenly insufficient backhaul infrastructure.
Existing TDM-based cellular backhaul was designed for 2G voice, not 3G data, and even ATM overlays for packet traffic face clunky (and expensive) scalability challenges once traffic loads start ramping up.
Much has been made of new wireless technologies like WiMAX as a quick and relatively inexpensive backhaul upgrade for 3G networks, but the technology currently leading the charge in the cellular backhaul network is that old workhorse: microwave.
Microwave has been around so long - and to this day can be found in cellular networks where leased-line capacity is insufficient or non-existent - that it's virtually a commodity in terms of pricing. On the other hand, that's what makes it an attractive option for cellcos, says John Lipp, director of advanced solutions business development for the mobile communications group at Alcatel.
'The prices have gone down, but that's also driven volumes up so we're certainly seeing an upswing in sales,' he says.
According to a 3G backhaul report from analyst outfit Heavy Reading, microwave has emerged as the most cost-effective option for 3G operators to build their own access transmission networks. The report cites Vodafone as an example - the mobile giant expects to save up to 20% on opex in its European operations over the next two years via microwave deployments.
The old reliable
Of course, the attraction of microwave in the backhaul network isn't just the price tag, says Lipp - it's also the mileage.
'Microwave is attractive because it's a mature technology, it's stable and secure, and many operators already use it, so they're comfortable with it,' he says.
Michael Lee, systems solutions GM for Ericsson Hong Kong & Macau, notes that microwave is also more than capable of supporting the performance parameters that cellcos expect, from latency and redundancy to spectral efficiency.
'Spectrum reuse is very high, so you can have dense capacity and use the same carriers for many transmission channels,' Lee says. 'That way, you can keep the number of carriers in use quite low.'
Another appealing factor for microwave, says Lee, is that it's also an opportunity for cellcos to shake their dependency on fixed leased lines - not just in terms of the cost of scaling E1s, but also in terms of competition. 'With convergence, mobile operators may find themselves competing with the carriers they are leasing backhaul from.'
Ironically, owning their own microwave backhaul infrastructure could also help cellcos to get into the leased-capacity game, Lee says. 'The operator can also consider leasing excess microwave capacity to other service providers.'