The rapid growth of traffic on today’s mobile networks is forcing mobile operators to push for the early roll out of LTE, but with the added capacity and performance enabled by the high speed mobile platform, backhaul will need massive upgrades to keep up.
Paul Steinberg, chief architect for Motorola’s wireless infrastructure products, told CommsDay that LTE is a necessary migration path for operators facing escalating traffic loads on their 3G and HSPA networks.
According to Steinberg, most operators are reporting 6 to 14x increases in data usage in 2007, while the revenue from data traffic is only growing at 10%-30% annually. “3.5G networks will struggle with mass market mobile data adoption,” he said.
Citing research by ComScore, Steinberg says that reasonable traffic profiles for mobile users by 2011 will range from 2.7GB of data for typical users with only a mobile phone to 11.1GB of data a month for heavy users accessing the mobile network with both a laptop and handset.
Without LTE, operators will have to implement costly cell splitting of their existing infrastructure because they will be running out of spectrum, he said. At the same time, they will also have to ramp up their backhaul and core networks to support the increased load.
According to Steinberg, an increasing number of operators are looking to roll out LTE as early as end-2009 in order to mitigate these issues on their existing 3G networks. So far, six operators are planning to deploy LTE in 2009 while another 10 operators have plans to roll out LTE in 2010, according to Motorola. Combined, these operators represent some 1.8 billion of the world’s 3.5 billion total mobile subscriber base.
BIG BACKHAULS: One of the key advantages of LTE over today’s HSPA networks is performance. “HSDPA is shared, so with a 7.2Mbps system, the effective throughput is probably around 1.9Mbps,” Motorola said.
“With LTE, in the same 5MHz spectrum, the effective throughput is probably around 7.85Mbps. So it’s a three-to-four fold improvement for LTE in 5MHz, but most LTE will be deployed with 10MHz, 20MHz, you’ll be looking at about 30 times improvement per sector.”
So while HSDPA and its variants will offer multi-megabit speeds only at the optimal coverage conditions, LTE will offer such high speed access regardless of where the user is on the network. This obviously reduces the cost per megabit for operators on the radio access network, but they will have to upgrade their backhaul to support a significant increase in traffic.
According to Motorola, each LTE base station will require 200Mbps-300Mbps of backhaul capacity, which out-paces most fixed or wireless access technologies out on the market today except fibre or Gigabit Ethernet.
Operators are now exploring a host of solutions, including high-capacity point-to-point microwave links, and relay – “basically taking some of the air interface capacity, and put in some underlay cells to actually relay traffic within bands from one site to another site,” Steinberg said. “Links and capacity to link up an LTE carrier is not ubiquitous, so having a fibre hook up to every base stations is not a given. To the extent that there’s access to the IP cloud, then the problem is solved, but if not then it’s a challenge.”
As such, the success and performance of LTE will rely heavily on the existing broadband infrastructure. Steinberg points out that in the UK, the mobile operators have already signed wholesale agreements with BT’s fixed network to ensure they have the capacity to link up their mobile base stations. Four out of the UK’s five operators have signed wholesale deals with BT.
Tony Chan
