Achievement Award 2013

Achievement Award

Pioneering Work on Signal Processing Antennas for Mobile Communications

Yasutaka Ogawa

　It is remarkable the degree to which cellular phones are now in widespread use around the world and the extremely high transmission speeds that have been achieved. Also, it is projected that we will need to accommodate a much greater volume of traffic in the near future. The award winner has contributed to the development of signal processing antennas for mobile communications.
　A signal processing antenna, also called an adaptive antenna or a smart antenna, consists of multiple antenna elements and optimizes its transmitting and receiving characteristics, such as radiation patterns, by adjusting the amplitude and phase of each antenna element under given radio environments. Studies on such antennas for military use were initiated in the 1960s because a signal processing antenna can reduce intentional and hostile interference on the battlefield.
　In the early 1980s, the award winner was the first researcher in the world to propose application of signal processing antennas to commercial digital mobile communications [1], and to clarify their behavior [2]-[4]. At that time, digital modulation schemes were being considered for introduction into mobile communications. However, waveform distortion caused by multipath signals with long delay differences that could not be ignored compared with symbol duration was a critical issue. The effect is serious in a higher-speed transmission system because the symbol duration is shorter. He proposed reducing multipath signals by controlling the radiation pattern of the signal processing antenna, as shown in Fig. 1. The signal processing antenna has the advantage that it can strongly reduce multipath signals with long delay differences. In Europe, a research project called TSUNAMI (Technology in Smart antennas for the UNiversal Advanced Mobile Infrastructure), which included multipath reduction was conducted in 1994-1995. The award winner’s work was so ahead of its time that it predated the TSUNAMI project by about 10 years.

Fig. 1 Concept of multipath reduction with a signal processing antenna

　We can improve channel efficiency by simultaneously accommodating multiple users in the same frequency band with a multi-beam signal processing antenna, as shown in Fig. 2. This technique is called SDMA (Space Division Multiple Access). In uplink transmission, the multi-beam signal processing antenna at the base station separately receives multiple signals transmitted from user terminals. And, in downlink transmission, the antenna at the base station separately sends multiple signals to the user terminals in a manner such that the signals do not interfere with each other, by controlling the transmission patterns. The award winner proposed a radiation pattern control scheme for downlink transmission with channel prediction. This scheme improves SDMA performance in time-varying environments [5]. He also served as a project general manager in the study group for the SDMA technique in the Personal Handy-phone System (PHS) for the Association of Radio Industries and Businesses, Japan (ARIB) from December 1999 through March 2001. The study group concluded that the SDMA technique can be used in actual environments, a finding that led to the first-ever realization of SDMA.

Fig. 2 Concept of space division multiple access (SDMA)

　A MIMO (Multiple-Input Multiple-Output) system with multiple antennas at both the transmitter and receiver is considered to be an advanced signal processing antenna system that can achieve higher-speed transmission. An SDMA system that also has multiple antenna elements at user terminals is called a multi-user MIMO system, which is included in the 4th Generation mobile communication standard, LTE-Advanced. It can be said that the award winner’s study on SDMA contributed to formulation of the basic platform for the multi-user MIMO system. He also put forth a performance improvement to the multi-user MIMO system with channel prediction in time-varying environments [7]-[10].
　These achievements by the award winner have been highly rated among the antenna and wireless communications research communities. He received the IEICE Best Paper Award in 2007 and the Telecom System Technology Award from the Telecommunications Advancement Foundation of Japan in 2008, and was elevated to the ranks of Fellow of the IEICE in 2008 and Fellow of the IEEE in 2011. As stated above, his achievements are outstanding and he fully deserves to be recognized with an IEICE Achievement Award.

References

(１)　Y. Ogawa, M. Ohmiya, and K. Itoh, “Behaviors of an LMS adaptive array for multipath fading reduction,” Trans. IECE of Japan, vol. E67, no. 7, pp.395-396, July 1984.
(２)　Y. Ogawa, M. Ohmiya, and K. Itoh, “An LMS adaptive array for multipath fading reduction,” IEEE Trans. Aerospace and Electronic Systems, vol. AES-23, no. 1, pp.17-23, Jan. 1987.
(３)　Y. Ogawa, M. Ohmiya, and K. Itoh, “Fading equalization using an adaptive antenna for high-speed digital mobile communications,” Proc. ISAP'89, vol. 4, 4A2-3, pp. 857-860, Aug. 1989.
(４)　Y. Ogawa, Y. Tanabe, T. Nishimura, and T. Ohgane, “Basestation adaptive antennas for a high-speed FDD/TDMA system,” 2001 IEEE International Conference on Communications (ICC2001), Conference Record, vol. 8, pp. 2558-2562, June 2001.
(５)　Y. Kishiyama, T. Nishimura, T. Ohgane, Y. Ogawa, and Y. Doi, “Weight estimation for downlink null steering in a TDD/SDMA system,” Proc. IEEE VTC2000-Spring, vol.1, pp.346-350, May 2000.
(６)　Y. Doi, J. Kitakado, T. Ito, T. Miyata, S. Nakao, T. Ohgane, Y. Ogawa, “Development and evaluation of the SDMA test bed for PHS in the field,” IEICE Trans. Commun., vol. E86-B, no. 12, pp. 3433-3440, Dec. 2003.
(７)　H. P. Bui, Y. Ogawa, T. Nishimura, and T. Ohgane, “Performance evaluation of multiuser MIMO E-SDM systems in time-varying fading environments,” IEICE Trans. Commun., vol. E92-B, no. 7, pp. 2374-2388, July 2009.
(８)　H. P. Bui, Y. Ogawa, T. Nishimura, and T. Ohgane, “Performance evaluation of a multi-user MIMO system with prediction of time-varying indoor channels,” IEEE Trans. Antennas and Propagation, vol. 61, no. 1, pp. 371-379, Jan. 2013.
(９)　K. Yamaguchi, H. P. Bui, Y. Ogawa, and T. Nishimura, T. Ohgane, “Considerations on a Multi-User MIMO System Using Channel Prediction Based on an AR Model,” Proc. 2013 IEEE AP-S International Symposium, pp, 550-551, July 2013.
(１０)　Y. Ogawa, K. Yamaguchi, H. P. Bui, T. Nishimura, and T. Ohgane, “Behavior of a multi-user MIMO system in time-varying environments,” IEICE Trans. Commun., vol. E96-B, no. 10, pp. 2364-2371, Oct. 2013.