NTT DOCOMO takes another step closer to LTE
Develops low-power LSI with MIMO signal detection and decoding
NTT DOCOMO has announced that it has successfully developed a trial large-scale-integration (LSI) chip that consumes less than 0.04 W of power yet supports multiple-input multiple-output (MIMO) signal detection and decoding for downlink transmissions at 100 Mbps, the speed required for the forthcoming mobile system known as Super 3G, or Long Term Evolution (LTE), approved by the 3rd Generation Partnership Project (3GPP).
Compared with chips currently used in handsets compatible with DOCOMO's High Speed Downlink Packet Access (HSDPA) service, which have a maximum downlink rate of 7.2 Mbps, the new chip will enable downlinks that are more than 10 times as fast.
Back in Sept. 2007, DOCOMO developed a trial LSI chip that demodulates orthogonal frequency division multiplexing (OFDM) signals and detects MIMO signals transmitted from four antennas at a rate of 200 Mbps and also consumes no more than 0.1 W of power.
The chip being announced this time demodulates OFDM signals transmitted in the 20 MHz bandwidth from two antennas and detects MIMO signals based on Maximum Likelihood Detection (MLD) technology, which ensures relatively high-quality communication even in bad environments for signal reception. The MLD method detects MIMO-multiplexed signals by comparing the received signals and all possible signals to be transmitted to assess maximum likelihood.
The chip also includes error correction decoding, which requires almost the same level of complexity as MIMO signal detection.
In the new chip, which is made with 65-nanometer processing, the circuits have been further optimized, particularly by eliminating redundant circuits for computationally complex processes such as MIMO-signal detection and error-correction decoding.
DOCOMO says it will incorporate its new LSI chip technology in ongoing research and development of LTE and International Mobile Telecommunications-Advanced (IMT-Advanced) systems, as well as in its active support of the establishment of related international standards.