4GEE bandwidth @ 10MHz

Back in October 2012 Everything Everywhere a.k.a. EE launched 4G LTE services in the UK. As EE is the merger of T-Mobile UK and Orange UK, it "re-farmed" part of the 1800MHz spectrum these two companies had and used that for it's 4G LTE network.

At the time I wondered how much spectrum they had managed to re-farm for launch and few days back I had some empirical confirmation of how much that is. The log extract below is taken from a WCDMA SIB19 message which is used by the UE for reselection purposes from 3G to 4G.

Part of the information broadcasted in SIB19 is the IE "measurementBandwidth". As LTE allows for flexible bandwidth allocation (1.4, 3, 5, 10, 15 & 20MHz), the UE has to be informed how much bandwidth is used in order to average the RSRP measurements as explained here.

Rather than specifying the bandwidth in MHz, 3GPP uses Resource Blocks (RB) instead. A RB is 180KHz wide, so 50 RBs give us 9MHz. Taking into account the guard bands on each side of the allocated bandwidth we get a total bandwidth of 10MHz.

This means that at least until EE manage to re-farm some additional spectrum they can only offer 50% of the potential maximum LTE throughput. The good thing about EE is that they have quite a lot of 1800MHz spectrum so I imagine they will continuously monitor their 2G traffic (the 1800MHz was originally awarded to T-Mobile and Orange for GSM services) and as soon as possible another 5MHz block can be re-farmed taking the allocated bandwidth to 15MHz and finally 20MHz. As all LTE devices have to support the maximum of 20MHz, this can happen transparently to the end user.

Looking at the additional information in the log extract, we can also see the exact frequency EE are using which is broadcasted as EARFCN 1617. This translates to a centre DL frequency of 1846.7MHz as shown below.

This in turn can be mapped on EEs 1800MHz spectrum holdings (source: OFCOM) as shown below in red.

Taking into account that EE currently use 10MHz for LTE we can also see what is the top theoretical speed their network could achieve. This is shown in the table below.

In the DL using 2x2 MIMO a maximum throughput of 73Mbps is possible. As 4x4 MIMO is not currently implemented by neither operators or UE manufacturers that column is a bit academical. In the UL a maximum throughput of 36Mbps is possible. As a rule of thumb we can say in the best "real life" situation about 2/3 of those speeds is achievable that would make it as DL approx. 50Mbps and UL approx. 24Mbps. Obviously as more users are added to the system the throughput will decrease accordingly.

The final point to note about the log extract is the priority assigned to the LTE layer. This is configured as 6. As the highest priority is 7, EE have left some room for configuring a higher priority layer. This could be a "small cell" layer or if they are feeling confident of obtaining some 800MHz in the upcoming auction they could use that as a "coverage" layer forcing UEs to camp there by assigning it priority 7 and use the current 1800MHz layer as a "capacity" layer.