Press Release

February 24, 2012
Advanced Telecommunications Research Institute International(ATR)

ATR Develops an 8×8 Non-Linear Multi-User MIMO Experimental Radio System
- Field Experiments Start Toward Future Mobile Communication System -

Kyoto, Japan February 24, 2012 --- Advanced Telecommunication Research Institute International (ATR) today announced that it has developed an 8×8 non-linear multi-user multiple-input-multiple-output (MIMO) experimental radio system, and has been licensed by the Ministry of Internal Affairs and Communications for field experiments. ATR utilized block-decomposition vector-perturbation (BD-VP), a non-linear transmission signal processing technology, in the experimental system consisting of an 8-antenna base station (BS) and four of 2-antenna user equipments (UEs). This is the world's first 8×8 multi-user MIMO experimental radio system utilizing the BD-VP technology in downlink (BS to UEs). ATR will begin field experiments in the areas of Kansai Science City in Kyoto, Tokyo, Osaka and Kawasaki, and will evaluate and improve the performance of the system. This work is supported by the Ministry of Internal Affairs and Communications under a grant entitled “Research and development on nonlinear multi-user MIMO technologies.”

This achievement is related to a technology enhancing the performance of multi-user MIMO system which is expected to be widely used for fourth-generation (4G) mobile communication systems. The achievement has three technical features (Fig. 1).
  1. A non-linear signal processing technology BD-VP makes it possible to enhance data transmission performance even when there are adjacent user terminals in the line-of-sight propagation channel. In such a situation, conventional linear transmission signal processing technologies cannot discriminate plural user signals with sufficiently small interference.
  2. The non-linear technology has been realized in downlink (BS to UEs), in which higher data rate are required than in uplink (UEs to BS).
  3. The system has been implemented in an 8×8 multi-user MIMO configuration with which simultaneous signal processing of 4 UEs can be achieved.
Both BS and UEs consist of a baseband signal processing unit with field programmable gate arrays (FPGAs) and digital signal processors (DSPs), a radio frequency (RF) unit, antennas and a control terminal (Fig.2). The carrier frequencies are chosen as 3.36 GHz and 3.26 GHz in downlink and uplink, respectively, based on the technology trend in the fourth generation mobile communication system.

The experimental radio system using the BD-VP technology is designed by following the signal format specified by the third generation partnership project (3GPP) Release 10. ATR reduced the computational complexity by optimizing the search range of perturbation signals for performance improvement, and eliminating a part of processes in the frequency domain without any performance degradation. These techniques have made it possible to achieve the world’s first real-time operated BD-VP multi-user MIMO experimental radio system. For the performance evaluations under realistic environments, ATR constructed 1 BS and 4 UEs for the 8×8 MIMO system configuration, and additional BS and UE as surrounding interference stations.

Fig.1 The architecture of the experimental radio system

Fig. 2 Photos of the experimental system (left: base station, right: experimental system consisting of a base station and four user equipments)