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27 June 2016

Proximus trials DSL/LTE hybrid to boost broadband for remote users  

Belgian operator Proximus is working with local start-up Tessares on a trial of an LTE/DSL hybrid technology which could lower the cost of connecting the underserved user base by combining wireless and wireline resources.

The trial uses Multipath TCP, an emerging IETF standard which enables TCP sessions to spread out across multiple paths for increased redundancy, and also to increase bit rate over networks where bandwidth is constrained, such as cellular. Despite not being finally ratified, it has been deployed, most famously by Apple for its Siri voice recognition app on iPhones and iPads, where it improves QoS by minimizing impact of intermittent throughput over individual paths.

Proximus is testing it for a purpose which is increasingly popular among owners of fixed and mobile assets, and one of the ways they can secure competitive edge against single-network rivals. This is to bolster fixed line DSL with an extra LTE connection in the home, a practice which could be further enhanced by 5G, reducing the need to invest in fiber-to-the-home everywhere.

Long subscriber loops, which usually cannot provide sufficient speed for IPTV services, can be bolstered by adding the two elements together, and LTE can be used as a fallback if broadband fails or slows or has latency issues.

The approach was pioneered by Deutsche Telekom in Germany, Swisscom in Switzerland and Vodafone in Spain and now Belgacom unit Proximus has joined the party with a trial of a hybrid DSL/LTE modem, based on technology from Tessares., initially in Frasnes-Lez-Anvaing where only 60% of homes can receive 100Mbps over VDSL, but there is good 4G coverage. The tests will start in July and run for few months, and if successful, will lead to a wider roll-out.

Proximus says it has 92.4% of Belgium households in reach of its upgraded network, VDSL, and it plans to upgrade another 1,000 street cabinets this year. But anyone who is further than 1.6 km from the cabinet will not get full VDSL speeds, hence the LTE augmentation.

Tessares has implemented a form of Multipath TCP, which means that either one of the two networks can send or resend packets. Responsibility for counting packets is devolved to the end points, so that if one network drops during a send, there is no extra work carried out by the network layer in link handovers.

Back in January Swisscom offered DSL/LTE bonding, combining the bandwidths of both fixed and mobile networks. That technology allowed for speeds of up to 20 Mbps with higher bandwidths to be tested in later phases. Swisscom was aiming for reaching 85% of all homes with ultra-fast broadband by the end of 2020 using a mix of technologies including vectoring, Fiber to the Street, Fiber to the Building and Fiber to the Home.

Vodafone is trying something similar in Spain, using Huawei equipment to help VDSL when apps burst above their upper limits, citing a top line rate of 200Mbps, but this was for businesses only.

Finally, Deutsche Telekom held trials with this technology last year to expand its subscriber base in hard-to-reach and rural areas on the back of strong cellular deployments. Slowly we expect the rest of Europe to use this as and when each network is ready.