February 7, 2011

DOCOMO Begins Field Experiments of 4G LTE-Advanced System

Tokyo, Feb 7, 2011 - (JCN Newswire) - NTT DOCOMO, INC. announced today that on January 27 it was pre-licensed by the Kanto Bureau of Telecommunications of the Ministry of Internal Affairs and Communications for field experiments of LTE-Advanced, a true fourth-generation (4G) mobile communication technology that provides data rates much faster than currently possible with LTE.

Once the license is issued, DOCOMO will begin field experiments of LTE-Advanced in real radio environments in the cities of Yokosuka and Sagamihara in Kanagawa Prefecture, Japan.

In the field experiments, the performance of key technologies for LTE-Advanced implemented in the experimental equipment will be evaluated in indoor and outdoor environments.

DOCOMO has already confirmed the performance of LTE-Advanced technologies using radio environment simulators in its R&D center, achieving transmission data rates of approximately 1 Gbps in the downlink and 200 Mbps in the uplink.

LTE-Advanced, as the name suggests, is an evolved version of LTE, which DOCOMO currently offers on a commercial basis under the Xi(TM) ("Crossy") brand in Japan. LTE-Advanced is backward compatible with LTE, which will enable a smooth migration from DOCOMO's existing LTE network.

Standardization of LTE-Advanced is currently being finalized by the 3rd Generation Partnership Project (3GPP). In October 2010, LTE-Advanced was accepted by the International Telecommunication Union Radiocommunication Sector (ITU-R) as a technology compliant with the requirements of IMT-Advanced.

LTE-Advanced Key Technologies Implemented in DOCOMO's Experimental Equipment

1. Bandwidth extension based on carrier aggregation

Carrier aggregation achieves extra-wide frequency bandwidth transmission by bundling multiple 20 MHz-wide bands, i.e., component carriers, for the uplink and downlink. By using link adaptation and channel coding, as well as hybrid automatic repeat-request, for each component carrier, the transmission data rate can be increased efficiently. The experimental equipment allows up to five component carriers to be aggregated to extend the transmission frequency bandwidth to 100 MHz for the downlink, and two can be aggregated to achieve a 40 MHz bandwidth for the uplink.

2. Uplink MIMO transmission

Uplink MIMO in LTE-Advanced is categorized into multiple-input and multiple-output (MIMO) multiplexing and closed loop transmit diversity. Under good radio conditions, MIMO multiplexing increases spectral efficiency and the transmission data rate. Under bad radio conditions, closed loop transmit diversity improves the received signal quality. In the field experiment, DOCOMO aims to achieve a data rate of approximately 200 Mbps in the uplink using two transmit and two receive antennas, combined with carrier aggregation.

3. Downlink multiuser MIMO transmission

Spectral efficiency is improved by simultaneously transmitting signals from one base station to multiple mobile stations via MIMO multiplexing. The experimental equipment supports four transmit antennas in the base station and two antennas in each of the two mobile stations. Using multiuser MIMO and carrier aggregation, DOCOMO hopes to achieve a 1 Gbps data rate in the downlink.

4. Downlink coordinated multi-point (CoMP) transmission

CoMP improves the transmission data rate between a base station and mobile stations that are located near cell edges. The base station's centralized control of multiple remote radio equipment (RRE) units in different locations helps to reduce interference between radio cells, resulting in transmission at a higher data rate.


NTT DOCOMO is the world's leading mobile operator and provider of advanced mobile services. The company serves over 56 million customers in Japan, including 49 million using i-mode(TM), the world's most popular mobile e-mail/Internet platform, and 54 million using FOMA(TM), the world's original 3G mobile service based on W-CDMA. As a leader in the development of cutting-edge mobile technologies, DOCOMO is continually expanding the role of mobile phones as versatile and highly personalized "lifestyle tools" for everyday life, including with a wide range of innovative services for mobile payments, GPS, mobile TV, multimedia content and much more. NTT DOCOMO is listed on the Tokyo (9437), London (NDCM) and New York (DCM) stock exchanges. For more information, visit www.nttdocomo.com.



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