In his wireless blog, Mark Heath of Unwired Insight discusses the latest LTE speeds reported by mobile network operators.
Am I the only one that gets frustrated by all the hype surrounding LTE speeds and LTE performance?
Many in the industry are seeing LTE as the means of avoiding the looming 3G capacity crisis, as mobile network traffic levels continue to rise. Ericsson has just announced that global mobile data traffic has nearly tripled within 12 months and there’s little sign of this trend abating.
In their desire to encourage mobile network operators to upgrade to LTE networks, equipment vendors have been keen to promote LTE as delivering a huge step-change in performance. With theoretical peak LTE speeds of between 173Mbps and 326Mbps on the downlink, it’s not surprising that many in the industry believe that LTE will deliver more than an order of magnitude improvement in average throughputs and capacities compared with HSPA networks. No wonder, then, that so many believe that LTE will be the saviour to the looming 3G capacity crisis and, once LTE arrives, everything will be fine.
As we continue to see increased LTE deployment, I’m hoping that people will begin to see the reality of the situation. There are two issues, which mean that LTE capacity won’t be quite as high as some are assuming.
Firstly, substantial increases in peak LTE speeds do not equate to similar increases in network capacity. LTE maximises the data rate available to end users that experience excellent radio conditions (for example close to a base station). However, mobile users that experience poor signal conditions will continue to achieve relatively poor data rates. Hence, it is only a lucky few within a base station coverage area that will experience data rates approaching the peak rates possible. It is true that these users will increase the average throughput delivered by the base station, but by nowhere near the magnitude suggested by the peak data rates.
Secondly, the highest LTE speeds are only achieved through the use of large spectrum allocations – ideally 2x20MHz – which is four times the 2x5MHz spectrum used by W-CDMA and HSPA.
When considering network capacity, it is vital to make a true like-for-like comparison, and compare the spectrum efficiencies – that is the actual average throughput achieved per MHz of spectrum - as shown in the table below (taken from our report “Will 3G Networks Cope?”). As this shows, LTE will roughly triple the capacity achieved by a given amount of spectrum compared with HSPA. Certainly not an order of magnitude improvement.
As LTE networks come into operation, we’re now getting a better view of the average throughputs that can realistically be achieved. Verizon Wireless has reported average downlink LTE speeds of between 5 and 12Mbps. While it has been reported that Verizon’s network team had been “shocked” (in a positive way) by these results, they are actually lower than the numbers in the table, since Verizon is using 2x10MHz of spectrum. 5-12Mbps in 2x10MHz of spectrum is really equivalent to 2.5-6Mbps in 2x5MHz (used by HSPA), which is perhaps more “adequate” that “shocking”.
TeliaSonera has just reported faster LTE speeds than Verizon Wireless. However, closer inspection reveals that TeliaSonera is using twice the amount of spectrum (2x20MHz).
Over the coming months I’m expecting to see a string of operators claiming the fastest LTE speeds in the world and demonstrating very high throughputs. However, we need to be cautious about these. You know the scenario – a well-engineered base station, excellent coverage, the maximum amount of spectrum and no other traffic or interference in the cell – not exactly representative of the mobile broadband dongle user at home, relying on a distant base station that has to support a large number of competing users.
The fact remains that LTE will provide a useful, albeit not massive, capacity uplift, so mobile network operators won’t be able to escape from careful management of future network traffic.