Backhaul is not a capacity issue

Lance Hiley, VP marketing strategy for Cambridge Broadband Networks, tells Annie Turner how mobile operators can reduce backhaul CAPEX by up to 44%  and improve OPEX by as much as 81% using point to multipoint microwave.

AT: How critical is the mobile backhaul situation becoming‾

LH: The fact is that backhaul problems are not primarily about a lack of capacity so much as a lack of planning: if the available capacity were used properly, it would work well enough.

The big issue is that mobile will become the primary means of accessing the Internet - and not just in developing economies, where there is already more mobile broadband than fixed. Dongles and flat rate data plans, it's driving packet data traffic, but not revenue. It's a diverging graph - traffic up, revenue flat or down.

AT: What can the operators do‾

LH: Network architecture has to change, as does the approach operators take to designing networks and allocating resources within them. Right now there is an issue with quality of service via dongles, which has echoes of  the late 1980's and early 90's when mobile operators regularly reported how many subscribers were churning due to dropped calls.

AT: How must the architecture and prioritisation change‾

LH: Point to point (PTP) microwave links have been used extensively since the 1940's. Most PTP backhaul networks are deployed in a tree and branch topology, meaning that 3.5 PTP radio (or 1.75 PTP links) are used per cell site. This is hugely inefficient.

AT: What technologies are available to improve things‾

LH: VectaStar deploys point-to-multipoint (PTM) architecture, which is structured so that a single access point can reach several packet microwave terminals. This decreases the number of radios required to build a network. Customers typically deploy five to 11 microwave bases to achieve the same coverage with PTP would require 20.

PTM groups access point into hubs: each access point has an antenna that divides the transition paths into sectors of 90º, so four access points provide 360º coverage, each with a radius of six to 10km.

They share the spectrum and bandwidth among all the terminals in that sector, meaning operators get far more efficient use from their assets. In radio networks, contention is extremely low. HSPA traffic is very bursty and there are very rarely maximum peaks from all five or ten cell sites at once. This means that a customer covered 20 cell sites with a hub, they would only need 24 radios overall using VectaStar versus a minimum of 40 if they were using PTP technology.

AT: How big are the efficiency gains‾

LH: They need less spectrum, less space on a tower and fewer radios. This can reduce CAPEX by up to 44% and OPEX by as much as 81%, compared with other backhaul technologies.

You can instantly share resources across radios. As capacity and density rise, the spectrum requirement grows the total sum of the mean bandwidths of each sector in a busy hour for all sites. PTM offers a natural trunking gain.

In addition, data is optimised at the cell site, before it is even starts its journey towards core network: for example, we remove empty frame headers in Ethernet or by removing IMA overhead in 3G.

 

We convert whatever we take from Node B and optimise it by a factor of between 20% and 80%, depending on the nature of the traffic and the format using our propriety, over the air (OTA) protocol.

AT: You mention prioritisation"&brkbar;

LH: Well, for instance, giving VoIP precedence over browser traffic - that at the edge of the network so that all the traffic passing OTA to the access/aggregation point to use spectrum at maximum efficiency and to get the same maximum efficiency from the stat mux as you do in a PTP microwave network.

This means that although we provide a 150Mbps link in total across  between all the radios, optimisation and stat mux gain means that in effect, the operator has four to five times that amount of bandwidth. In theory, this means each cell can have a working capacity of 60Mbps.

Also, you can add terminals as necessary to accommodate new base stations, which hugely accelerates the deployment of cell sites, down to half a day from weeks and spectrum planning isn't needed

AT: Surely propriety protocols is exactly what operators are moving away from‾

LH: It doesn't matter in this instance because the VectaStar access point only talk to other VectaStar terminals. The only thing that matters is that there are standard interfaces between the aggregating unit and Node B. We accommodate base stations from Nokia, Ericsson and Motorola in our customers' deployments.

AT: What about the implications for future technologies‾

LH: We buy into LTE, WiMAX and HSPA because of their great headline data transmission figures, but to get the performance advertised, users would have to be right next to the base station, which is not practical. For operators to deliver a performance that is good enough to avoid churn, the networks would have to be very dense, with a lot of base stations. Relying on the economics and practicalities of PTP is impossible - fibre would be the favourite option.

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