Is Backhaul the Bottleneck?

Last month I attended the 4GWE conference as part of ITEXPO West in Austin, TX.  At this small but well-organized conference, the recurring theme of the surge in mobile data traffic was the basis for many of the presentations and panel discussions on backhaul for 4G networks. In many sessions, the popular theme of network congestion was discussed with the commonly asked question, “Is backhaul the bottleneck?"

In the last couple of years that that we’ve been following and participating in these discussions at conferences and with mobile operators, I’ve noticed a pattern in how this question gets answered:

1. Absolutely yes — Vendors of backhaul equipment and backhaul service providers
   
   It’s without doubt that backhaul remains one of the strongest growth areas of capital investment. It’s also the case that the economics of transport technologies mean that the transition from TDM-based backhaul to Ethernet is inevitable and well underway. This means that even without immediate capacity additions, vendors in this space are benefiting from the technology updates underway at most operators.
   
   
2. Sometimes — Operators that own their backhaul or have constrained lease options
   
   Before or during transition to the higher capacity, more flexible backhaul technologies, an operator may find itself in a position where in some markets or areas, backhaul is the bottleneck. We’ve even come across examples where data-capacity bottlenecks are due to capacity limitations in packet core connectivity. While these are often operationally complex problems to resolve, once the transition has been made, the backhaul bottleneck mostly goes away. Another set of operators in this area are those who have limited leasing options or constrained contractual choices for their backhaul provision. Resolution here is through the arrival of new backhaul service provider options, the operator choosing to build and operate some part of its backhaul or contractual renegotiation. Once one of these routes has been taken, backhaul is no longer the issue.
   
   
3. No — Most mobile operators – those that lease backhaul and those with real data traffic
   
   A few months ago I was speaking to an engineering executive at a North American mobile operator that leases most of its backhaul capacity. When I asked him if he thought that backhaul was the bottleneck he answered “No!" without hesitation. With a number of backhaul capacity suppliers to choose from in most markets, he can get additional capacity from a cell site with almost zero notice. As such, they put very little effort into even anticipating the needs of backhaul planning. This is enabled by the flexibility brought by Ethernet.

If backhaul isn’t the bottleneck, then what is?

The answer depends on the operator and it ranges from the RF RAN, fixed-net RAN to the packet core. The rapid growth of data traffic has meant that the aggregation nodes in the RAN and all parts of the packet core become the bottleneck and point of congestion at some point in time at most operators. Modeling, anticipating and proactively avoiding these shortages is the only robust means of mitigating these issues.  

Having said all of this, the ultimate bottleneck is the availability of spectrum. Small cells can reduce this to the theoretical limit where every device is served by its own cell and then the MHz available determine the maximum throughput.

In summary, is backhaul the bottleneck? For some yes, but most instances resolve to bottlenecks elsewhere in the network – RAN and Packet Core. But ultimately, the available spectrum is the bottleneck, the only truly finite resource.

Russ Green is SVP, Product Management & Marketing, VPIsystems.  He has 15 years of enterprise software experience in large-scale, high availability systems, working with globally-distributed development groups and customers. Before joining VPIsystems, Russ was the vice president of Development for 724 Solutions, based in Switzerland.