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Dropping GSM or UMTS for LTE

Recently, UK regulator OFCOM announced that operators can utilise 900, 1800 and 2100MHz for LTE.  Such decision goes well with the longer term evolution for mobile networks: single radio access standard working across all frequencies.

The 3GPP world is not new to squeezing multiple technologies into one frequency band: UMTS was introduced into 900MHz to share with GSM to provide better depth of coverage than 2100MHz, and eventually LTE was introduced into 1800MHz – simply because for many operators that is the only band that has sufficiently wide spectrum to let LTE flex its maximum bandwidth muscles.

Some mature networks have up to six technology-band combinations (G9, G18, U9, U21, L18, L26), add in multiple UMTS carriers and small cells to the mix: creating a traffic steering strategy and managing all the layers in the live network is a pain for radio planning departments for many operators.

I foresee that we will soon begin to see technology simplifications in mobile networks. “Technology simplification” here means elimination of some the abovementioned technology-band combinations – to be replaced by LTE in each respective band. Simplification will reduce network management and planning hassles, and also reduce/eliminate a number of network operational cost items.

Two key decisions are needed for a technology simplification roadmap:

  1. Establish an order for simplification: which technology-band combinations to turn off first
  2. Establish when (or under what conditions) each can be turned off.

Every network is different, and so the answer is different for every operator. GSM switch-off in 2017 has been announced last year by AT&T (note AT&T 2G operates on 850 and 1900MHz); and UMTS switch-off was recently announced by Altel (mobile subsidiary of Kazakhtelecom).

GSM, being the older of the two technologies, is commonly perceived to be the technology to hang on to. This may be due to GSM being the common-denominator for roaming/M2M and GSM is likely to be the cheapest to run. However, UMTS is the newer and more capable technology, and some networks may prefer to hang on to UMTS instead.UMTS

The actual technology simplification roadmap depends on a number of factors, some of which are outside the operator’s control. Many of these factors also affect traffic management and level of preparations required for each step in the roadmap. A few examples:

  • Amount of spectrum holding in each band, including any likely changes in the medium/long term due to license expiry
  • Liberalisation of spectrum policies to allow LTE to be deployed on an old band
  • Terminal mix within the network (current mix, and projected mix which can be influenced by both the Marketing department, and the overall terminal market including any M2M terminals)
  • Base station technology mix, including range of coverage and capacity
  • LTE Voice (maturity of network, handset, to take over the bread and butter voice traffic)
  • Roaming (importance of roaming, terminal mix of inbound roamers)

If there will be a looming technology switch-off and migration-to-LTE soon, it makes sense to start preparing for it as soon as possible (eg. minimise capacity additions in the chosen switch-off technologies, carefully selecting what handsets to distribute…)