AT&T SVP of access architecture Hank Kafka revealed implementation of a centralised RAN architecture is a key element in the operator’s ambitious push toward 5G.
In a recent interview, Kafka told Mobile World Live (MWL) AT&T’s 5G Evolution approach includes not only small cell densification but also centralised RAN (C-RAN) capabilities. As the name suggests, the latter centralises processing to enable improved coordination among all of the small cells. But Kafka noted the upgraded topology also sets the stage for virtualisation of the RAN architecture as well.
Kafka told MWL the number of centralised sites needed in a given area varies from situation to situation, but said processing delays play a key role in determining how many are needed. Kafka added AT&T is also eyeing future 5G and edge computing requirements as it puts the centralised topology into place.
In a pure C-RAN architecture, engineers shift base station processing functions from multiple sites to a single centralised location, the SVP explained. But such a strict architecture doesn’t necessarily work well with technologies including FD-MIMO and other 5G capabilities since they require a large number of signals to be rapidly backhauled and processed. Kafka said this is where RAN virtualisation comes in.
“You can actually start to split the functions a little differently and instead of saying that the split is at the radio versus the base station…you move some of the processing capability to the antenna and co-locate it with the antenna and then you have other processing capabilities located at the central point.”
While this preserves the topology of needing equipment at both the site and centralised location, the virtual functional split offers important impacts on latency, cost and ability to share capabilities, he said.
Kafka said implementation of conventional C-RAN functions is already underway and AT&T is currently working on proofs-of-concept and trials to virtualise radio access functions. Over the next few years, Kafka said onlookers can expect an incremental increase in the percentage of functions which are virtualised.
Earlier this week AT&T announced plans to be the first US operator to offer 5G for mobile customers via launch of the technology in a dozen markets later this year, in a move which steals a march on rivals Verizon and T-Mobile US.