LTE: Cleaning up the cell site

Posted by GenD on Thursday, March 18, 2010 with No comments
I’ve winced every time I’ve heard the time “convergence” over the past several years. Convergence has always been a marketing word for “mess”, where multiple technologies co-exist and intermingle in ways that increase Tylenol consumption and slow down true telecom innovation.

Today’s wireless networks, including the current 3G deployments, still rely on this dirty word with “converged” cell site connections – duplicating provisioning of both TDM private lines for voice, timing and signaling and Ethernet for data.
There are many good reasons why. Until recently, Ethernet hasn’t proven as reliable as required to carry conversations, and T1s are already in place at cell sites where sync is required to keep radios locked on a common frequency and phase for roaming hand-offs. Necessary for now, but inefficient (and despised?) all the same.
LTE offers a chance to do some spring cleaning at the cell site, simplifying backhaul connectivity with a single, performance-assured Carrier Ethernet link. Simplicity looks like it’s making its way back into telecom, right?
Unfortunately, we may be gaining capacity and working with less equipment, but the clutter has simply moved from physical equipment to the way it’s configured. No one ever had their Mom tell them “clean up your virtual room”, but this is where the mess goes in LTE backhaul networks – into the provisioning, monitoring and performance assurance required to compensate for having all your data running through a single pipe.
Making a clean break to a fully packet-based architecture, voice calls will be VoIP, carried over the same all-IP infrastructure carrying the latest generation of multicast and on-demand web-based video, Internet, messaging and email traffic. With each vying for available bandwidth, maintaining per-application Quality of Service (QoS) is critical – the best-effort, limited-bandwidth backhaul connections serving legacy data services will not suffice.
4G services require ultra-low latency, jitter, and packet loss with assured throughput and availability. Latency can spell the end of conversations if signaling delays interrupt session continuity when roaming between cells. Jitter and packet loss can make audio inaudible and video unwatchable. Insufficient backhaul bandwidth leads to congestion, increasing latency, packet loss and packet retransmission resulting in degraded QoS. Availability is the most basic of all – if the network goes down, so do your customers – outages and lack of bandwidth are the primary drivers for customer churn.
So while Ethernet to the cell site is certainly the future (and looks clean from the perspective of slick, stylized network diagrams), it doesn’t come without its own baggage. Best to be prepared for the surprises that are popping up in field trials – keep an eye on QoS, monitor it proactively or you may just discover the monsters in the closet.
CTIA next week will be a good place to explore these trends – check out the backhaul pavilion, get trained and attend the talks going on to learn all about what we’re facing.