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31 January 2012

Development of Millimeter Wave Band Wireless System Which Enables Transmission of 4 km at 1 Gbps
- An optical fiber network and a wireless network are connected seamlessly -

Japan Radio Co., Ltd. (Main office: Suginami-ku, Tokyo, Japan; Representative Director and President: Takayoshi Tsuchida; hereafter JRC) has developed a "38 GHz millimeter wave band fixed wireless access (FWA) system" of 1 Gbps seamlessly connectable with an optical fiber network in collaboration with Professor Makoto Ando, Professor Akira Matsuzawa, et al. of the Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology. Many component technologies, such as a highly efficient small size antenna and a high-performance analog / digital (A/D) converter which can use a 64 Quadrature Amplitude Modulation (64QAM), were concentrated, transmission speed was raised to 1 Gbps, and 4 km long-distance transmission has been attained.

Since transmission speed was as slow as a 100 - 200 Mbps until now, the seamless connection with an optical fiber network was difficult for FWA system which bears trunk connection on wireless. Development of this system explored the radio frequency resources of a millimeter wave band with realization of seamless connection. By adopting it as the trunk wireless network of a cell-phone base station (i.e. mobile back-haul), etc., the insufficient situation of the radio frequency resources by increase of electric wave use needs in recent years can be reduced, and since installation is easy, a quick construction of an ultra high-speed wireless network is possible.

< The Background of Research and Development >

Expansion of network capacity is demanded from diversification of the global scale expansion of the IP network in recent years by the explosive increase in a smart phone, etc., and the application service incidental to this. Not only an optical fiber network but construction is easy for this, and it is the same also about the early wireless network of restoration at the time of a disaster. On the other hand, since the public radio services of mobile communications, wireless LAN, etc. including a mobile phone spread, radio frequency resources of 10 GHz or less have been tight. Therefore, as long as the existing radio frequency band is used, it is in a difficult situation to make further broadband and larger capacity.

< The Result and Significance of Research and Development >

Then, JRC and Tokyo Institute of Technology, et al. performed development of equipment and various devices which can be used for a millimeter wave band, paying attention to the millimeter wave band which can secure a wide band. The main development technology is as follows. (1) The small antenna with the high spatial isolation which employed the special feature of the millimeter wave band efficiently which has a separate body between the antenna and transmission/reception, (2) Baseband signal processing system LSI which incorporated ultra high-speed and high resolution A/D, D/A converter, and the M-QAM modulation and demodulation circuit, (3) Gallium nitride monolithic microwave integrated circuit (GaN-MMIC) for high efficiency transmission power amplification, (4) Indium phosphorus (InP) MMIC for the super low noise amplification, (5) Gallium arsenic (GaAs) MMIC for broadband frequency conversion, (6) Silicon germanium (SiGe) MMIC for the I/Q quadrature modulation and demodulation.

The 38 GHz millimeter wave band FWA system which unifies these devices and operates by symbol transmission speed 200 M symbol/sec, a single-carrier TDD (Time Division Duplex) system, and maximum modulation method of 64QAM was realized. This system can operate with the effective transmission speed (transmission speed which united the up-and-down band) of 1 Gbps, and the maximum communication distance is 4 km. Twelve wireless-lines were installed in the Tokyo Institute of Technology Ookayama campus, the wireless network was built, the outdoor transmission experiment was conducted, and the performance was checked. Now, the wireless network which has arranged the wireless-line in communication distance from 100 m to 4000 m is built, the influence of rainfall and the long-term stability in a millimeter wave band are checked, and the actual proof of the validity of a millimeter wave band wireless system is performed continuously. The research and development will be promoted which aimed at utilization of the system and the spread of millimeter wave band communications in future. In addition, this work was partly supported by "The research and development project for expansion of radio spectrum resources" of The Ministry of Internal Affairs and Communications, Japan.

< System Outline >

The wireless system developed this time by making seamless connection to wired networks, such as an optical fiber network, in the area where the cable system infrastructure is not fixed, the place where construction of a fiber optic cable is difficult, or infrastructure restoration at the time of a disaster, a quick and easy construction of high-speed line is enabled.

In order to prove a system, the radio frequency bands adopted experimentally are 38 GHz bands, and it is the band assigned to FWA systems in Japan. A communication method support a single-carrier TDD system, a modulation method support QPSK, 16QAM, and 64QAM, and the maximum effective transmission speed becomes 1 Gbps on 64QAM. Moreover, this system can raise radio frequency use efficiency effectually by controlling a ratio of up-and-down band adaptively with a TDD system, and even when the ratio (CNR) of a received carrier to noise not easily obtained by rain attenuation etc., it is possible to maintain wireless communication up to several kilometers also at the time of rainfall by shifting a modulation method from 64QAM to 16QAM or QPSK adaptively.

The appearance of the equipment made as an experiment this time is shown in Fig. 1, and the main specifications of a system are shown in Table 1, respectively.

photo:Trial production equipment.

Fig. 1 Trial production equipment.

Table 1 System main specifications.

System configuration

Point to Point communication / FWA system

Radio frequency

38 GHz bands

Communication mode

Single-carrier TDD

Modulation method

QPSK, 16QAM, and 64QAM (adaptive modulation function)

Transmission power

Maximum 250 mW (+24 dBm)

Radio clock frequency

200 MHz

Maximum effective transmission speed *

1 Gbps (adaptive radio resouce control function)

QoS control

Bandwidth control and priority control

Network interface

10 / 100 / 1000 Base-T (RJ-45) Ethernet

(*Maximum transmission speed is the sum total of an up-and-down band.)

For further information: please contact

Japan Radio Co.,Ltd.

Resarch & Development Center