Summary
Although the benefits of Ethernet backhaul were readily apparent to most mobile operators, technical and business obstacles often stood in the way. TDM has held tremendous sway with operators because all of their voice traffic depends on the legacy transmission framework for call quality and channel integrity. Sending that TDM voice traffic over Ethernet wasn’t an option until synchronization issues were worked out.
Analysis
While Ethernet-over-copper technologies are on the market, most Ethernet transport is dependent on fiber, which only goes to a small, but growing, percentage of U.S. base stations. There are 1.8 million cell sites in the world and it might take a long time to deploy an Ethernet-based network to all of them. Meanwhile mobile operators are still firmly grounded in a world of TDM. Until recently most base stations simply didn’t have Ethernet ports.
Part of the problem with popularizing carrier Ethernet to mobile operators has been the issue of cross communications. Ethernet emerged from the enterprise as a LAN technology, and when it migratedinto the metro network it became an access and transport technology that, again, primarily served theenterprise. Enterprises have different requirements for reliability and redundancy than mobile operators; they have different service expectations and different capacity demands. But most of all they talk about Ethernet coming from an IT background — a language that operators serving those enterprises have adopted.
But in the last year operators have experienced huge upticks in mobile data growth. In many cases data has surpassed voice in overall volume of network traffic, making TDM an increasingly more inefficient means of transport. That volume will only increase with 4G technologies such as LTE, and carriers are starting to turn to Ethernet sooner rather than later.
The most significant requirement that must be applied to Ethernet to make it suitable as a mobile backhaul technology is synchronization, which is imperative for wireless networks to maintain channel integrity and voice quality. TDM inherently supports precise timing, but Ethernet does not, meaning either GPS or master clocks must be spread throughout the network.
