Original URL: http://www.theregister.co.uk/2010/05/07/lte_tdd/
China Mobile sees time-sliced evolution
Speedy 4G at Shanghai Expo
Huawei and Motorola have been working with China Mobile to get a time-duplexed LTE network deployed at the Shanghai Expo, offering 20Mb/sec over cheap and cheerful spectrum.
The deployment is experimental and will only last as long as the Expo, but the companies involved have been demonstrating peak speeds of 80Mb/sec, with 24 simultaneous video streams for those who really, really, like mobile TV.
Long Term Evolution (LTE) is the preferred 4G wireless technology for GSM operators around the world, but the planned deployments (and the single existing one) all use Frequency Division Duplexing (FDD); one frequency for the uplink and a separate one for the downlink. That requires "paired" spectrum, and regulators around the world have been happy to parcel up frequencies that way, rather to the annoyance of the WiMAX crowd who'd like spectrum in big chunks instead.
Current WiMAX deployments use Time Division Duplexing - one frequency is used and the connection flips between sending and receiving.
There are advantages to TDD: devices only need one radio and asynchronous connections can be arranged, but the big difference is that unpaired spectrum is generally cheaper. In Sweden, for example, 100MHz of FDD spectrum at 2.6GHz sold for more than €200m, while 50MHz of unpaired spectrum suitable for TDD only raised €16.5m.
Motorola has been demonstrating that its solutions can roam between LTE networks using FDD and TDD, even managing a live handoff, and is supplying TDD-LTE dongles for the World Expo in Shanghai which kicked off yesterday.
Those dongles will be operating on an LTE network run by China Mobile, with Huawei providing the network infrastructure, and it's only a proof of concept that disappears with the Expo at the end of October.
But assuming the technology works it will demonstrate how LTE can push into the spectrum previously thought of as the exclusive preserve of WiMAX - as though more nails were needed for that particular coffin. ®