Pioneering development of intelligent wireless transmission control techniques using adaptive modulation

Concept of Intelligent Radio Transmission Control and its Enabling Techniques

Fig.1 Concept of Intelligent Radio Transmission Control and its Enabling Techniques

Concept of Adaptive Modulation

Fig.2 Concept of Adaptive Modulation

    Wireless mobile communications including cellular phones are no longer a voice communication tool, rather one of our most important infrastructures in our life due to the revolution development of information and communication technology (ICT). The most crucial issue for further spreading of mobile communication networks is the efficient utilization of limited spectrum to avoid congestion of wireless networks. For this purpose, in late 1990, many engineers had developed various adaptive signal processing techniques in the receiver to overcome this issue, such as diversity, adaptive equalizer, forward error correction, interference canceller. However, commonsense in those days was to fixedly use a modulation scheme in a system.

    What Norihiko Morinaga and Seiichi Sampei developed was the adaptive modulation technique in which modulation and coding scheme was adaptively controlled in the transmitter side according to the expected channel conditions for the signal to be transmitted, and they showed its effects through theoretical and experimental analysis. Moreover, they established a new technical field named intelligent radio transmission control in which the adaptive modulation was a core technique.

    The adaptive modulation has changed the methodology for wireless communication system design: Conventionally, the wireless communication system was designed to guarantee a certain quality even under severe fading conditions, i.e., a worst case guarantee-type system design. However, the ratio of the bad channel condition is not so high, which means the channel condition for rest of time period is not so bad, in which case, we have sufficient received signal level for a modulation scheme with higher modulation level.

    The adaptive modulation they developed employs a modulation scheme with higher modulation level when the received signal level is relatively high; thereby data throughput is enhanced without transmission performance degradation. In addition to quadrature amplitude modulation (QAM), they have shown applicability and effectiveness of the adaptive modulation to orthogonal frequency division multiplexing (OFDM) and/or code division multiple access (CDMA) employed systems. In addition to the theoretical analysis, they have also developed channel state information (CSI) feedback and some other techniques, and developed an experimental adaptive modulation models to verify the effects and feasibility of the adaptive modulation.

    The adaptive modulation also has a good compatibility with the software radio techniques, and would also be effective in migration of wireless access systems from the practical point of views. Actually, adaptive modulation is already introduced in many systems in the world, which shows they were pioneers in this field based on their deep insight in the field of wireless transmission techniques.

    This evidence stated above shows that the development of adaptive modulation techniques was based on their deep insight for the necessary wireless transmission techniques. This evidence shows that their development is extraordinary scientific contribution to the efficient utilization of spectrum, and has a big social impact.

    The Institute of Electronics, Information and Communication Engineers awarded the Achievement Award to Norihiko Morinaga and Seiichi Sampei in 2001 for the technique



Publications

[1] Seiichi Sampei, Shozo Komaki, and Norihiko Morinaga、Adaptive Modulation/TDMA scheme for large capacity personal multi-media communication systems、1994、IEICE Transactions on Communications, vol.E77-B, no.9
[2] Toyoki Ue, Seiichi Sampei, Norihiko Morinaga, and Kiyoshi Hamaguchi、Symbol Rate and Modulation Level-Controlled Adaptive Modulation/TDMA/TDD System for High-Bit-Rate Wireless Data Transmission、1998、IEEE Transactions on Vehicular Technology, vol.47, no.4.
[3] Seiichi Sampei and Norihiko Morinaga、Adaptive Modulation Techniques for High-Speed Wireless Data Transmission、2002、Journal of the IEICE, vol.85, no.4.

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