Like in UMTS, China is determined to go its own ways with LTE as well. Instead of adopting FDD (Frequency Division Duplex) LTE like the rest of the world, China Mobile wants to deploy TDD (Time Division Duplex) LTE. One of the reasons stated for this is to have an upgrade path from TDD UMTS (which, to the best of my knowledge, is not yet deployed on a broad scale in China). I am sure Chinese companies and joint ventures have put a lot of work into TDD UMTS over many years and yet, it hasn't made it anywhere. So why should TDD LTE be different?
In fact, I see the same problems with TDD LTE:
- Economy of scale: China is a big country but in order for the technology to be a success, other countries have to adopt TDD LTE as well. As with TDD UMTS, I think that this is unlikely to happen, I don't see an incentive.
- Devices: Same issue as above. For a limited market, only few vendors will be tempted to develop mobile devices. One way out of the dilemma could be dual mode TDD/FDD devices. But what is the chance of this happening?
So without a real need for an upgrade path, why TDD-LTE? Unlike with UMTS, Chinese companies like Huawei do not have to catch up to the rest of the pack, this time they start at the same time and with an advantage.
The center gap, a glimmer of hope? In many countries the center gap between the uplink and downlink channel of UMTS and LTE is unused. Some operators in Europe for example have even bought TDD spectrum in the 2.1 GHz band during the UMTS auctions back in 2000. So maybe those bands might trigger some operator interest for TDD LTE!?
As always, comments are welcome.