|Issue:||North America 2011|
|Topic:||Backhaul for a mobile revolution|
Dave Stehlin is the President of Overture Network; he has more than two decades of telecommunications industry experience. Mr Stehlin has been CEO of three venture-backed start-ups, most recently Ceterus Networks, which was acquired by Overture. Additionally, he was President of the Keptel and Network Transport divisions of Antec. Early in his career he held leadership positions with Keptel, Laser Precision and Siecor. He holds one U.S. patent. Dave Stehlin served as an officer in the US Marine Corps following his graduation from the US Naval Academy. He earned his MBA from National University.
To enable next generation data and video applications, wireless carriers are building 4G networks. Carriers will use backhaul providers to connect their cell sites to mobile switching centres with high speed, flexible, native Ethernet fibre optic links. By 2015, single carrier cell sites will need between 30 Mb and 300 Mb. Multi-carrier locations, about half of all cell towers, will require up to 500 Mb, depending on location. Radio-hub sites will have to scale to 1GigE or more.
Backhaul for a mobile revolution by Dave Stehlin, President, Overture Networks There is no doubt that mobility will drive much of what we in the telecommunications industry think about and act on for years to come. Why? Because mobile communications is now a basic component of our lives whether at work or at play. For many, it’s almost like breathing. Behind this simple reality is a complex fabric of issues that mobile operators deal with on a daily basis and with increasing velocity. Issues such as service requirements, bandwidth, network architecture, customer segments, markets, partnerships, mobile devices, applications, service differentiation … the list goes on and on and keeps a large and growing set of people very busy because the fact is simple, mobility is the new king of the hill. Driving this change is, of course, the Internet and the possibility it unlocks and creates. While basic voice service remains a requirement and texting continues to grow, the explosion is caused by data applications and, increasingly, with video services. Looking forward, tremendous data growth will be driven by a series of factors including a shift to smart phones, growing tablet usage, strong growth in the emerging markets such as Africa, the Middle East, Latin America and Eastern Europe, new mobile applications and a significant increase in mobile video traffic. In fact, some sources believe that mobile video will be responsible for two thirds of all global data traffic in 2015. There are many aspects that go into building a mobile network that scales effectively as new services are created and assures the operational efficiency required to run a sustainable business. For this article we’ll focus on the backhaul segment of the network. Even though we hold an un-tethered device in our hands, the network depends on landline connectivity back into the core. In North America, starting at the cell tower, backhaul is typically via a fibre or copper cable. Backhaul is, historically, the single most expense component of the network, and it will remain so as carriers move to 4G technologies. To enable next generation data and video applications, wireless carriers are building 4G networks and are relying on backhaul providers to connect their growing number of cell sites to mobile switching centres with high speed, flexible native Ethernet fibre optic links. To some, cell tower backhaul is mundane when compared to the latest smart mobile device or the clarity of video downloads, but without scalable Carrier Ethernet connectivity the new networks simply won’t work. Capacity needed at the tower The amount of capacity at the tower is determined by the population’s demographic profile and density within the tower’s footprint. A tower that serves a rural or suburban edge is going to have a different bandwidth profile than a tower in the urban centre. With growth, profiles will change over time and add to the need for a flexible network design. A recent Infonetics study of the global network indicates that the average cell site currently consumes 15Mb-30Mb, but will grow to 20Mb-60Mb by 2014. This data indicates that the typical tower needs broadband backhaul. It is clear from this data that Carrier Ethernet is needed at all towers, and that the bandwidth need continues to grow at a rapid pace. It is also important to note that the carriers and backhaul providers indicated that cell sites that require scaling of bandwidth would leverage Carrier-Ethernet. Because the global data is an average, it does not show the wide variation in density by market. For that detail, a model based on different market types is used. A breakdown by population density shows that not all cell sites in the network are alike. In North America, by the end of 2011, an average site in the urban centre will require 50Mb, a rural area cell tower will require 10Mb and suburban and urban edge locations will fall somewhere in the middle. The average U.S. cell site houses more than two wireless carriers, so backhaul providers serving more than one carrier can expect to double or triple the bandwidth requirements per site. The newest LTE equipment can pump up to 100Mb to each of the three sectors at each cell site and could enable a theoretical throughput of 300Mb per cell site. These values are for a single carrier cell site. Urban cell tower locations, with multiple carriers, could have bandwidth requirements in the 300Mb range. Carriers are constantly looking for ways to describe their network as being faster than the competitors’ – usually by pointing to the maximum possible capacity of the technology they are using instead of the actual capacity they are deploying. Wireless carrier requests-for-proposals (RFP) to backhaul providers typically ask for a standard initial capacity and maximum scale potential capacity at every cell site. Usually there is not a breakdown by site or commitment to a growth rate by year. One of the largest wireless carriers, for example, states that their requirement is 50Mb on day one, growing to 300Mb, with some towers requiring a full 1GigE (Ethernet transmission at 1 Gbps). The conclusion for backhaul providers is that backhaul to all towers needs to be Carrier Ethernet. The math shows that by 2015, single carrier cell sites will need between 30 Mb and 300 Mb depending on whether it is in a rural or urban site. Multi-carrier locations, about 50 per cent of all cell towers, will require between 75Mb and 500 Mb, again depending on location. Radio-hub sites will need 1GigE or more. Not all cell towers are the same, so optimal backhaul architectures should be flexible and scalable to address the specifics of the tower profiles in each market. 10GigE mobile backhaul With the increasing reliance on mobile communications and the projected massive increase in bandwidth needs, wireless carriers and backhaul providers are now analyzing where in the architecture to deploy10GigE. To determine where to use 10GigE, you must look into the mobile backhaul network architecture and the provider’s fibre assets. Depending on the size and scale of a backhaul provider network, there are either two or three layers of transport-aggregation-switching. Let’s look at the three-layer scenario. A medium-large backhaul provider network will typically take advantage of a three-layer architecture, with an access, collector and a core as shown in the example. In this larger network, the core is already 10GigE, scaling to nx10GigE (n times 10GigE fibres) or even 40-100GigE in the future. A collector layer sits between access and the core. Because of the number of towers and their geographic distribution, it is more efficient to aggregate these with a local collector ring and backhaul high-utilization 10GigE to the core instead of backhauling all the access rings directly to the core Access should be a combination of 1GigE linear/rings and 10GigE G.8032 rings depending on the capacity needs at the tower and the number of towers per ring. While 10GigE for the core and collector rings should be the solution for virtually all networks, the decision of when to deploy 1GigE or 10GigE in access requires some analysis. Most networks should use a rational mix of 1GigE and 10GigE rings depending on the specifics of each group of towers being served. _____________________________________ The importance of mobile networks will continue to increase around the globe providing essential communications needs, enhanced business capabilities and exploding consumer applications. We’ve seen that there is an ever-growing set of interesting and potentially profitable applications that requires the support of reliable and flexible networks capable of efficient growth. Backhaul from the cell site to the switching centre will remain one of the most critical aspects of the mobile network. Backhaul providers have the dual challenge of delivering a scalable Carrier Ethernet service to the most towers possible while maximizing their CAPEX efficiency. A review of the data paints a clear picture that Carrier Ethernet is required at all cell sites to address this scalability. Backhaul providers must develop a plan that supports scaling these networks over the next three to five years. Projected bandwidth profiles indicate a clear requirement for 10GigE in core and collector rings, and a rational mix of 1GigE and 10GigE G.8032 access rings. We know that service providers focused on delivering maximum scalability are already architecting 10GigE solutions for mobile backhaul. They maximize their 10GigE footprint and at the same time optimize CAPEX efficiency by incorporating the three to five-year bandwidth growth projections, equipment CAPEX and fibre costs into their design models. Smart usage of 10GigE in network deployments ensures cost effective and seamless scaling to handle the 300Mb-500Mb or more of demand at the cell tower. Market leading providers differentiate themselves by selecting 10GigE solutions that deliver on all areas: features, performance, operational flexibility and CAPEX efficiency.