The Future Challenges Faced By The Mobile Backhaul Network

The rise of the smart phone is creating a mobile enterprise user who works anywhere, with anybody, anytime. This creates an end-to-end content ecosystem with a content producer, infrastructure provider, content supplier and consumer, following the natural flow of information across related platforms and vendors.

In turn, this is driving consumer demand for more bandwidth to accommodate the requirements of the content ecosystem and the mobile enterprise. In the UK for example, mobile broadband traffic doubled when the BBC made their iPlayer available for the iPhone.

As a consequence of this demand operators are looking to reduce the cost per bit in order to increase revenue. To do this they need to create high leverage and sophisticated networks with load balancing and high availability capabilities, so that the traffic can be taken off the core network as quickly as possible.

The estimate is for 300 million LTE subscribers globally by 2015. Along with this is the need for mobility and service availability which will bring demand for more bandwidth capacity at the core and access networks, with IP being the solution to making more bandwidth available in the network.

Legacy networks are still there and will remain for the foreseeable future, creating a technical challenge in integrating LTE with existing core infrastructure. This heterogeneous network will call for compatibility and interoperability with support for multiple deployment scenarios.

With this rapid increase in data traffic mobile operators have seen their costs increase substantially, and according to the Yankee Group those costs associated with mobile backhaul account for up to 30 per cent of overall OPEX.

These costs can be expected to rise further with broadband connectivity such as LTE, HSPA and WiMAX requiring a dramatic increase in capacity for cell sites of up to 1 Gbps, which is three or four times the capacity available at a typical NodeB today. With pressure mounting on the transport network and with the revenue per bit decreasing rapidly the operators must evaluate all options for their backhaul migration strategies to cost-effectively optimize their transport networks.

Higher capacities and lower latencies are a must for LTE backhaul as is the ability to support IP traffic and all-IP architectures. However, today’s backhaul networks are still dominated by TDM, be it T1/E1 lines or high-capacity SDH/SONET, and one of the main consideration for operators is how to migrate their networks to IP.

A transition to an all-packet backhaul has to be done in a cost-effective manner and an ecosystem is required that is capable of being applied to all of the backhaul architectures.

To do this it must accommodate TDM, ATM, and other packet traffic, such as Ethernet, MPLS, and IP simultaneously and support a wide range of the services from 2G/3G to WiMAX, LTE and beyond, behaving as a TDM platform, a TDM/packet interworking platform, and an all-packet platform. Consequently the platform is required to support both TDM and packet switching functionality with both TDM and packet interfaces.

The mobile backhaul network provides connectivity between the radio base station (RBS) site and the switch site at the edge of a transport network, and the Radio Access Network (RAN) typically aggregates traffic from 10 to 100 RBS sites, feeding it to the switch site.

With a large number of cell base station sites in the RAN and the dynamic changes in the network, the RAN must be cost-effective, simple, upgradeable, flexible, and able to provide peak capacity. Around the globe, depending on the operator, RANs use multiple physical link technologies including microwave, copper, and fibre. Whist microwave usually provides the lowest total cost of ownership, both fibre and copper serve as common first-mile backhaul solutions in many parts of the world.

As stated mobile broadband has been a huge success and has triggered a sharp rise in demand for mobile data services. This trend will continue with the rollout of HSPA and LTE, and historically the transition to new mobile technologies has resulted in the need for a four or fivefold increase in backhaul capacity. This will ultimately increase the capacity requirement to gigabits per second all the way to the cell site.

Fibre access is the obvious first choice for any high-speed link and the capacities of point-to-point or gigabit passive optical network (GPON) links exceed any LTE backhaul requirement so far, but microwave and copper can also reach Gbps capacity. A successful migration will require low-cost, high-capacity backhaul solutions. Where fibre is available, the recommended choice is optical access, and where there is no fibre infrastructure, microwave and copper can be used.

How will those mobile backhaul networks evolve as traffic loads increase and become more packet-based? As previously discussed, today’s 2G networks support TDM traffic and 3G networks support ATM backhaul such as Inverse Multiplexing for ATM (IMA) and pseudowire emulation (PWE). However, with demand for data services increasing the strain on the existing mobile backhaul infrastructure it is possible that new services cannot be deployed without a network upgrade.

Migrating directly to an All-IP network is not possible for many operators as they need to make the most of their existing TDM and ATM based assets but they need to add low cost Ethernet access as this can enable high-bandwidth data applications to be offloaded at the cell sites while voice traffic continues to be carried over the existing TDM or ATM lines.

This helps to ease the strain from the data demand, and multiple backhaul transport options are available to operators, with Carrier Ethernet (MPLS-TP) providing one of the best alternatives to realise all of the economic and scalability opportunities of IP.

For example, with pseudowire at the cell site allowing ATM and TDM access to existing 2G/3G base stations over a packet-based network, Carrier Ethernet provides a complete backhaul for all voice and data traffic over a common infrastructure.

The network is then ready for the increased bandwidth required, enabling the operator to meet the demand for carrier-grade services. According to a Gartner estimate, Carrier Ethernet has the potential to offer the lowest cost backhaul solution, providing the potential for savings of 50 per cent or more over equivalent SONET/SDH based approaches.

Robin Kent joined Adax in 1994 to establish the Adax business unit in Europe and he has successfully overseen its transition from an OEM technology supplier to a customer focused provider of high quality, high performance telecommunications products and services to network equipment providers and integrators throughout Europe, the Middle-East, Africa and India. Robin has over 25 years experience in providing superior signaling solutions to premier telecoms companies worldwide.