SoftBank has already soft-launched its TD-LTE mobile broadband network, using a dense network of microcells, with a commercial launch planned before the end of February.

In a little over a year’s time 99% of Japan’s 127 million people will be within range of what is being hailed as the world’s largest commercial TD-LTE network, a mobile broadband network that uses a dense network of tiny base stations.

The company behind the project is SoftBank, one of Japan’s biggest telecommunications operators, and it believes that the architecture — with 150 base stations per square kilometre — will help it overcome the capacity problems that are threatening the viability of mobile broadband operators everywhere.

By using so many base stations so close together the available spectrum can be used again and again. The suitcase-sized base stations are linked in groups to create a super-base station, controlled centrally.

"We have already launched our system — on November 1 last year," says Yoshioki Chika, the chief technology officer of the project. So far it is for "friendly customers only", he adds, speaking to Global Telecoms Business in mid-January 2012. Initial deployment covered the three cities of Tokyo, Osaka and Fukuoka. “We are going to launch a commercial project next month.”

Huawei, which is delivering the network backbone of the project to SoftBank, has nominated the project for a GSMA award and is awaiting the decision of the judges at this year’s Mobile World Congress in Barcelona at the end of February.

TD-LTE is the TDD — time-division duplex — variant of LTE that is held by many to be more efficient at using spectrum than the more traditional FDD, frequency-division duplex.

LTE — long-term evolution — is already being adopted globally at a unified standard for mobile broadband services by operators from the GSM camp and others, such as Verizon Wireless, from the CDMA camp. But in a world where operators are trying to squeeze every bit of potential out of the limited spectrum that is available, many engineers see the TDD variety as more efficient.

Put simply, FDD uses different frequencies for uplink and downlink, with a guard band of completely unused spectrum in between to avoid interference. TDD uses the same frequency for both uplink and downlink, with a tiny time interval between the two transmissions. Control needs to be tighter, but if that can be achieved the wastage of time is less than the wastage of spectrum with FDD.

Source: Global Telecoms Business