It’s not all about small cells ‘ while LTE-Advanced’s menu of techniques will be an important catalyst for higher volumes of metrocell deployment (see separate item), they will also extend the capacity and efficiency of traditional macrocells. While several operators are preparing to support a key LTE-A feature, carrier aggregation, from this year, T-Mobile USA claims it will be in the best position to support LTE-A, because its network is brand new. That may sound like making a virtue out of necessity (it has rolled out 4G well behind the big two operators), but the firm is innovating hard, and some of its changes do not even require LTE-A. For instance, it is focusing on new MIMO advances already supported in LTE Release 9, as it races to narrow the gap between its fledgling 4G network and the major roll-outs of Verizon and AT&T.
According to GigaOM, citing information from TMo’s main LTE suppliers, Ericsson and Nokia Siemens, the carrier ‘ recently merged with MetroPCS to expand its spectrum and reach for LTE ‘ is to use 4×2 MIMO antennas in its network, to double the number of transmission paths compared to standard 2×2 LTE designs.
That will improve performance at the cell edge since their devices will be receiving more signals ‘ NSN’s head of technology in north America, Petri Hautakangas, told GigaOM that lab tests had delivered speed gains of up to 100% on the uplink at the cell edge, and between 50% and 60% on the downlink. He said: ‘Simple geometry means overall network gains would be big (the further the distance from the tower the more space is covered). The end result is a big boost in the real world capacity of the cell ‘ it can support more simultaneous connections while making more of those connections faster and more resilient.’
Mark McDiarmid, the cellco’s VP of radio network engineering, told the report that 4×2 MIMO is just one new LTE technique which TMo is considering, saying: “We have a very good handle on what 4×2 MIMO can do for us. And we’re one of the few that are in a position to use it.” Since 4×2 is included in the current LTE release, most devices will support it unchanged.
The company is under pressure to be innovative in its network, to make the best use of its spectrum ‘ which, despite MetroPCS, is less plentiful in many markets than its major rivals’ ‘ and to try to lure users with superior performance. The change to 4×2 will require a software upgrade at the base station as well as the installation of the additional antennas.
TMo will also be able to support carrier aggregation when needed, using its existing LTE kit, though this hardly qualifies it to make its claims that its network is ‘LTE-A ready’, as many other features of the diverse, mix-and-match base that is Release 10/11 will require upgrades to infrastructure and/or devices.