Next-generation networks deliver a new generation of technology and infrastructure to serve current customer needs more efficiently and effectively. However, customer and application requirements cannot evolve overnight - they take time to develop and mature. As such, next-generation networks need to support future capabilities.  As networks are being built upon, however, service providers will still need to serve existing customers while maintaining their business. In mobile networking, a generation cycle is typically around 20 years. This means that a service provider will be supporting old networks and adapting to new ones for a long period of time.

A true next-generation network will be adaptable over time. In fact, in both metro and backbone transport networks, service providers are deploying Packet-Optical Transport Systems (P-OTS) for their next-generation networks for exactly the same reason. For the mobile backhaul network, it is even more critical to be able to evolve while serving not one or two, but multiple generations of the radio network while riding over more than one generation of transport access networks over time. More importantly, the explosion of mobile broadband services puts exponential and - more importantly - unpredictable bandwidth demands on service providers' networks.

This begs the question: what are the adaptability requirements and how can a mobile backhaul network address them effectively without creating a generation gap?

The Evolving Mobile Network
Today, mobile networks run on 2G and 3G speeds, and the debut of 4G LTE is anticipated this year. This means that there will be three generations of mobile networks coexisting in the foreseeable future.

First, let's explore a little background. 2G networks are primarily used to support voice services such as TDM voice with T1/E1 interfaces and sometimes low-speed data services. 3G networks are evolving - and early version of 3G GSM supports both voice and data via ATM over T1/E1 interfaces, and the later version supports Ethernet interfaces for mobile broadband data. 3G CDMA follows a similar step from early data traffic over T1/E1 interfaces to over Ethernet interfaces. For 3G networks, voice stays as TDM voice that requires T1/E1 interfaces. But for 4G LTE and WiMAX, all voice, data, and video traffic are pure packets and require Ethernet interfaces.

TDM traffic stays on the TDM network while backhaul data traffic is carried over a packet network. Today, service providers often choose a hybrid approach for mobile backhaul. As they evolve their transport infrastructure from a TDM network to a packet network, TDM traffic will be needed to backhaul over the packet network with circuit emulation. The mobile backhaul network will be required to support both TDM traffic and packet traffic while adapting various services accordingly for transport. In approximately five years, 2G networks are predicted to begin retiring, which means that 2G mobile backhaul requirements will be phased out along with the T1/E1 interfaces. On the other hand, 4G LTE network deployments will likely be in full swing at this time. 4G mobile backhaul requirements will be primarily packet transport, as will the Ethernet interfaces.

Furthermore, in some parts of the world, including the U.S., a significant number of cell sites are co-located with multiple mobile service providers who have multiple mobile technologies such as GSM, CDMA, and WiMAX. This adds a scalability requirement, as they are serving multiple customers from one cell site.

The Evolving Transport Access Network
There are many access network infrastructures that a service provider employs, ranging from T1/E1, SONET/SDH, to Ethernet over dark fiber, DSL, and PON. Each varies based on availability, quality of service (QoS) requirements, and bandwidth requirements. As service providers upgrade their access infrastructure, they push the fiber reach to the premise or nodes in the neighborhood. Cable operators are also pushing fiber into the neighborhood. As bandwidth demands increase over the next several years, more fiber will be deployed to the cell site from nearby fiber nodes. A flexible mobile backhaul network that supports different kinds of access networks and evolution over time is required.

The Evolving Mobile Broadband Services
Mobile broadband services have been growing significantly over the last couple of years. As the smartphone and its associated applications are growing exponentially, so too is the mobile broadband bandwidth fueled by ever increasing speed, with 3G networks' stepping up their speed every couple of years. When it's deployed, 4G LTE will continue to push the speed into the 100Mbps and higher range. In fact, some mobile backhaul service providers have already signed contracts requiring 20Mbps initially and up to 400Mbps in the future - a wide range indeed.

To use a real-world example, iPhone users and others on the same network have started to experience dropped calls, are unable to make calls, and are experiencing call quality degradation. This phenomenon has been further compounded by the bursty traffic that can come and go very quickly, rending capacity planning useless. Therefore, a real-time monitoring and adaptation of the traffic demand is an absolute must. The ability first to recognize each service and adapt accordingly is a must. More importantly, as applications and networks evolve, so must the requirements. Consequently, a real-time recognition and adaptation solution will need to evolve over time as well.

Service Providers Business Imperatives
Minimizing CAPEX and OPEX, while growing revenue with an improving margin, is a primary objective for all businesses. To achieve a lower total cost of ownership (TCO), goals must be measured over time. While lower TCO is necessary for businesses success, it is not a sufficient standalone goal, as competitors do not stand still. Enterprises are continuously innovating to stay ahead of their competitors - that will always be the case. A mobile backhaul network should be able to support continuous innovation in order to address the revenue and margin equation both today and well into the future.

Summary of Requirements
By outlining the different characteristics of 2G, 3G and 4G networks and their associated requirements above, we have established that the only constant is change - not only now, but throughout the network's life cycle, and even over multiple life cycles. Change is a multi-faceted problem - evolving mobile networks, evolving transport access networks, and evolving mobile broadband services under the context of service providers' business imperatives.

What does a next generation mobile backhaul network look like?

As human beings grow into different stages of life, we often change our clothing choices for a variety of reasons and needs from changing physical size, professions, styles, and tastes. Department stores and tailors continuously provide new clothing as we see fit. Unfortunately, network changes and upgrades are not as flexible - we cannot easily and quickly change them or switch them out with newer forms. However, what we can do is prepare for these changes and upgrades by creating a mobile backhaul solution that allows service provider's to adjust based on current speeds and demands. Furthermore, a mobile backhaul solution should be able to independently recognize the requirements of the network and adjust accordingly.

To lower CAPEX and OPEX, the solution must have:

• A modular hardware platform with slots to accommodate for the evolution of mobile and transport networks, and their bandwidth growths over multiple generations

• Upgradable hardware using FPGA (Programmable Hardware) and a software platform

• Growing revenue and improving margin

Growing revenue can be accomplished by:

• Service differentiation such as offering real-time, non-intrusive service level agreements (SLAs) to ensure superior TDM-like performance
• Service expansion and acceleration such as capturing customer traffic profiles, which services providers can use to up-sell higher premium and bandwidth services
• Service satisfaction such as with preventative and proactive measure in real-time

Improving margin can be accomplished by:

• Reducing truck rolls using real-time, non-intrusive performance monitoring and testing tools remotely
• Reducing network-outage times and resolving problems quickly using real-time non-intrusive performance monitoring and testing tools for preventative and proactive action as it happens
• Providing a high quality of experience (QoE) under busty and unpredictable traffic patterns