Sten Nordell: Networks are moving to ethernet-based backhaul
using synchronous ethernet or timing-over-packet schemes 
                           
                           
The explosion in mobile data traffic progresses unabated and wireless operators are continuing to roll out high-speed wireless backhaul in order to cope with the growing demands. This situation creates opportunities for wholesale wireline and cable operators with fibre assets in the right locations. Digging new fibre is expensive, so having the right fibre in the right place can be a key asset.
But they need to consider how best to build a transport network over this fibre. Each available solution will have varying levels of economics and scalability. Naturally each vendor will claim to provide the lowest cost solution on day one and throughout the life of the network — cost models that can be assessed by simple modelling exercises with a shortlist of vendors.
In addition to ensuring the best whole-life economics, there are some key technical features to be considered that can have a significant impact on the service quality offered and therefore the competitiveness in the mobile backhaul market.
Beyond the obvious features, such as ultra-low latency and jitter to support LTE backhaul, operators should also consider network synchronisation. Networks are moving to ethernet-based backhaul using synchronous ethernet (SyncE) or timing-over-packet schemes, such as 1588v2.
Adoption of these technologies varies between wireless operators and a wholesale backhaul provider needs to keep its options open by providing both.
If an operator chooses the right implementation of SyncE-enabled backhaul, where the synchronisation is created by clocking the ethernet network itself in a similar manner to SDH or Sonet networks, then it also has the opportunity to offer significantly better quality synchronisation than was achievable over SDH/Sonet based networks.
Yet SDH/Sonet networks were previously considered to be the gold-standard for synchronised networks.
At Transmode, we have wholesale customers which provide their wireless operator customers with synchronisation that is more than 10 times better than they previously had over E1/SDH-based synchronisation. This improvement has tangible benefits for network performance and ultimately for customer satisfaction.
A further angle to consider is multiple SyncE synchronisation domains. A backhaul network may be required to support multiple wireless technologies with differing clocks or even multiple wireless operators. Supporting transparent wholesale services with SyncE over a transport network isn’t always easy and not all optical systems can support them, let alone multiple SyncE signals over the same wavelength.
But some do and this capability can have a significant impact on the economics of supporting multiple wireless technologies or multiple customers over the same backhaul infrastructure.
Let’s now consider 1588v2 as the alternative to SyncE for synchronisation over an ethernet service. Here the timing information is encoded into sync data packets and sent over the network without the ethernet network being synchronised itself.
This is potentially easier for a wholesale operator to support as they don’t necessarily need to support the functionality in all nodes, just in the source and destination nodes that perform the ingress and egress functions where the synchronisation data is inserted or extracted from ethernet frames.
Often the wireless operators will perform this within their own equipment and they will simply need the ethernet backhaul network to provide a reliable and stable transport of these frames.
This makes things considerably easier for the wholesale operator — but certain factors determine how the 1588v2 mechanism can scale. These primarily relate to latency, jitter and packet loss in the ethernet network. The better the underlying performance of the wholesale ethernet backhaul service the better the performance and scalability of the 1588v2 synchronisation.
Wholesale operators should not have to dictate synchronisation mechanisms or the size of synchronisation domains to their wireless operator customers due to limitations within their network. If at all possible, they should provide the wireless operator with a solution that keeps their options open and allows them the flexibility to use any synchronisation mechanism in their network.
If wholesale operators do not do this, then they may find that a competitor does, suddenly leaving them completely exposed if the wireless operator wants the alternative mechanism or scale that they aren’t able to support.
In addition to checking out the usual factors of economics, scalability and low-latency, operators should ask vendors about the quality of their SyncE support, both in terms of Layer 2 performance and multiple domains at Layer 1. They should also ensure they dig deep in terms of Layer 2 ethernet performance and its impact on 1588v2 scalability.
If you don’t like the answers then give us a call and we’ll show you how the right approach to ethernet transport can have a major impact on how you can differentiate your services in this very competitive market. GTB

                           
Sten Nordell is CTO of Transmode 
                           
For more, please visit www.transmode.com/solutions/mobile-backhaul