Are signaling bottlenecks making LTE a victim of its own success?

5 May

LTE networks are being overwhelmed by data traffic and with signaling in the core taking the brunt of unprecedented demand, it looks as though Diameter, the ETSI and 3GPP standard, may not, on its own, be up to the task of managing a more complex and burgeoning network. So what’s the alternative? Is there a newer and better solution out there?

Welcome to Part 2 of this extended TelecomTV article. Yesterday, in Part 1, we reported that subscribers, sometimes a few, frequently a lot, are complaining that they are not getting what they were led to expect they would get from signing-up to expensive and lengthy ‘4G’ service contracts. They say they are paying premium prices for what can be less-than-robust, underperforming network services as well as apps that fall over and drop-out and data (and even voice) calls that are often actually better over much cheaper 3G networks.

Robin Kent, Director of European Operations at UK-headquartered Adax, the packet processing, security, and network infrastructure for the all-IP network company says the problem can be laid directly at the feet of the Diameter signaling standard and protocol.

He told me, “While LTE is delivering on its promise of providing users with a quicker, more data-centric mobile broadband service, the backbone of the network is not being properly supported. Diameter signaling is now the bottleneck in LTE performance, because the transport that Diameter runs over is insufficient”. Trenchant stuff.

Long Term Evolution, which is if course what the acronym LTE stands for, is exactly that – a standard, based on GSM/EDGE and UMTS/HSPA network technologies and using a different radio interface in concert with core network improvements, to permit evolutionary progression towards true 4G.

Thus network operators do not have to scrap their expensively constructed old networks and take another huge capex hit but instead can keep them and tweak them to provide 4G-like services and apps. That is one of the reasons LTE is increasingly popular and why the network signaling that manages data sessions and polices traffic policies is having to accommodate volumes and complexities that are drastically degrading performance and limiting growth. It’s an untenable situation.

Some in the industry compare the complexities of Diameter signaling to the problems exhibited by Signaling System 7 (SS7) when the first mobile networks were introduced. SS7 was the source of many difficulties when it was first introduced but matured to become robust and reliable. The question is whether or not Diameter signaling can do the same?

For SS7’s early problems pale into comparative insignificance when measured against the 77 different and unique Diameter signaling interfaces that are assigned to specific IMS and LTE network elements.
And then there’s SCTP, (the Stream Control Transmission Protocol) that focuses on the transport and session layers rather than the network layer and operates on top of IP. It is important and is supported in the Linux kernel, but, Robin Kent contends, SCTP “just can’t cope with the specific signaling needs that the LTE network demands.

Larger volumes of data transfer and consumption mean that the strain on the network is being felt at various levels, and critical, evolved signaling and transport solutions are needed to match the demands that are being placed on the network”.

He adds, “The emergence of new technology usually breeds other new technologies, largely by way of support, but with recent network developments and the uptake of LTE, current signaling transport technology is no longer sufficient because of the data pressures that are being placed on the network. Transport protocols such as SCTP, in its existing form, are insufficient and operators have to address the problem that this will pose on LTE performance”.

What is needed then is a strong, high-performing transport layer and Robin Kent is, understandably, quick to point out that his company’s product, Adax SCTP for Telecom (Or SCTP/T) was designed specifically to meet the demands of LTE and IMS wireless networks for thousands of simultaneous connections. That said, and of course, Adax is not alone in seeking to provide answers to the overwhelmed Diameter signaling problem and there are other products by other manufacturers out there on the market.

And, regardless of the manufacturer, the solution to be applied must be able to do much the same things: to perform vigilant and almost instant in-service quality monitoring of the signaling link and be able to detect degradation of link quality at very, very short, programmable intervals.

That’s because the flat all-IP architecture of the LTE network requires a very large number of signaling connections as well as signaling concentration for efficient routing. Diameter signaling is the choke-point in LTE signaling performance and while a convenient and apparently economical solution, the Linux-supplied SCTP for Diameter, is freely available, it is simply is not up to a task that it was not designed to perform.

For LTE subscribers the technology is all about the perceived quality of experience they receive and, for the network operators it is the maximisation of that experience is based on a pro-active, immediate and flexible management of network capacity including the capability to conduct near-instantaneous data analysis, packet processing, DPI and the freeing-up of host CPU resources to remove bottlenecks.

Diameter signaling cannot do this unaided and LTE congestion, service attenuation and loss and consumer frustration will only inevitably increase unless something is done to address the matter now.

The philosopher and trancendentalist Henry David Thoreau, musing in his cabin on Walden Pond in Massachusetts in the mid-19th century wrote, “We must heap up a great pile of doing, for a small diameter of being”. Now, that’s what I call foresight.


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