Download Packet Backhaul Solution Sheet

Interview with Dave Lee - VP of Business Development for North America

Q. What is driving the need for packet backhaul of mobile services? A. The mobile access network, also known as the radio access network (RAN), was initially architected to support voice services via legacy T1/E1 TDM transport service. The proliferation of data services through the introduction of data-heavy mobile devices such as iPhone, Blackberry, Android, 3G air cards, and iPAD, and the increasing development of applications for them, has caused demand for bandwidth to rise exponentially.

From a scalability perspective, copper leased lines have a capacity limit of 100Mbps and are dependent on distance, available pairs, etc.  The coverage and reliability is limited and variable.  Most importantly, a copper infrastructure lacks scalability and involves significant operational expense to maintain.

Fiber scales to support a much greater capacity - in excess of 1 Gbps - and is highly reliable.  While distances of 50 miles/ 80km can be supported without amplifiers, the cost to build out fiber is most economical if available fiber plant is within 1000 feet of the cell site. For areas where it is not cost justifiable to build out fiber, microwave systems make sense to deploy.

Q. What are the challenges that wireless service providers face when trying to migrate their networks to advanced 3G and/or 4G technologies?

A. Well, not all subscribers will opt for new service and/or devices, so in addition to supporting the propagation of new data rich services, providers will still need to support their existing legacy 2G/3G TDM-based customers

Although Ethernet is recognized as the best transport technology to address high bandwidth data requirements, it was not optimized for real time applications like TDM-voice and video or call handoff between base stations, all of which require precise synchronization.

In addition to synchronization, there is also a need for reliable and strict CoS mechanisms, end-to-end service assurance and monitoring and provider operational challenges to overcome.

Q. Does this mean that the wireless provider will need two networks?

A. This really depends on a number of factors. In some cases, a provider may decide to maintain two networks because current revenues do not support build-out for future demand at the expense of revenues for existing voice services. Additionally, in the US the cost of T1 lines is decreasing and many providers are locked into long-term T1 leases. Where fiber is available, some providers’ may initially opt to overlay the packet-based network over their existing TDM-based services using WDM or SONET.  There is some reluctance to place voice services over packet due to concerns of maintaining voice reliability and quality. 

Q. What synchronization technologies are available for packet backhaul?

A. Unlike TDM, which is connection oriented and has inherent synchronization capability, packet-based technologies are connectionless and asynchronous by design. That said, there are several technologies, such as Pseudowire/Circuit Emulation using adaptive clock recovery, IEEE-1588v2 (PTP/NTP) and Synchronous Ethernet (SyncE).

The two methods that have received the most attention relative to mobile backhaul are 1588v2 and SyncE. While IEEE-1588v2 is software based and can be relatively easily implemented, it travels in-band with customer data so it could be impacted by network congestion unless managed under strict CoS control. SyncE on the other hand is hardware-based and would not be affected by network congestion, but it requires that all devices in the path be capable of supporting a hardware upgrade to support.

Due to the issues related to deployment of 1588v2 and SyncE, and the reality of network architectures being a mix of old and new hardware, the ideal solution would include the ability to interwork between both technologies and the primary reference source (PRS), while maintaining frequency, phase and time of day accuracy required by mobile networks.

Q. You mentioned operational challenges.  What kind of operational challenges will providers face?

A. Packet-based connectionless networks like Ethernet are new to the RAN and therefore represent big obstacles relative to training of staff, updating operational procedures, new management tools, etc. It is important for vendors to provide solutions that will help alleviate this burden by reducing the complexity of deploying these new services.

Q. Telco Systems recently announced a strategy to address some of these issues.  Can you elaborate on what the company is doing?

A. Telco Systems has purpose built solutions specifically designed to address these issues with features such as:

• Proven Pseudowire/Circuit Emulation Services which allow seamless integration of new high-bandwidth services and legacy TDM services over a single cost effective network infrastructure.
• Multiple synchronization options including IEEE 1588v2, SyncE and Any-to-Any Sync interworking allowing providers to maximize their current investment by upgrading the network slice-by-slice.
• Advanced QoS and OAM mechanisms that provide per-service per-customer CoS granularity and service management.
• Service Management System that offers service template development, end-to-end service monitoring and provisioning with “point-and-click” simplicity and engineering planning tools.
• Multiple transport protocol options like Provider Bridged Q-in-Q, MPLS/H-VPLS, LAG & LACP to provide deployment flexibility.