ARIB Grants Radiowave Meritorious Award to Kyocera for Development of PHS Adaptive Array Antenna


ARIB granted the Radiowave Meritorious Award to Kyocera Corporation in May 1999 for its successful world-first development of an adaptive array antenna for PHS. ARIB, a “Center for the Promotion of Effective Use of Radiowaves” designated by the Minister of Posts and Telecommunications, has been awarding those making significant achievements for the promotion of effective and proper use of radiowaves.

Adaptive.gif - 7495 Bytes


Kyocera acknowledged the superiority of adaptive array antenna technology long ago and has been conducting research thereon, aiming to develop PHS cell stations (CSs) utilizing this technology.

An outline of adaptive array antenna technology as well as the benefits of introducing PHS CSs utilizing this technology follows.
Adaptive array antenna technology in principle consists of two functions:
1) Adaptive Beam Forming
2) Adaptive Null Steering

“Adaptive Beam Forming” function enables transmission of signals to a target personal station (PS) at maximum transmission power and “Adaptive Null Steering” function enables “null transmission” to an interfering PS. “Null transmission” refers to transmission of signals at minimum power to an interfering PS. Fig. 1 is a communication model illustrating 1) and 2).
PHS, a TDD system that uses the same frequency for both transmission and reception, thus conducts both transmission and reception at the same level of radiowave intensity. It is therefore possible to subdue interference being caused by incoming signals of a PS by minimizing the responding antenna’s receiving power and then responding to the interfering PS with a null transmission.
Kyocera’s adaptive array CS houses four antennas. By sending null transmissions to the interfering PSs, this CS protects itself from interference. As a result, the CS can offer much improved PHS speech quality, by sending signals to a target PS at maximum transmission power and suppressing interference from an interfering PS N in other words, by increasing the C/I (Carrier/Interference) ratio.

Benefits of introducing PHS CSs that have employed adaptive array antenna technology include:
i) Improved speech quality
ii) More efficient use of frequency resources
iii) More traffic capacity

Concerning i), this type of CS can improve the target PSs’ speech quality dramatically. There is a close connection between ii) and iii): more efficient use of frequencies leads to an increase in traffic capacity.

In principle, traffic can be increased by building more CSs. However, this results in a higher possibility of multiple PSs and CSs coming to use the same slot or frequency, leading to more frequent interferences and subsequent deterioration of speech quality. In other words, traffic can be increased by this method only up to a certain volume, or a saturation point where no more traffic can be secured despite construction of more CSs.

Adaptive array CSs, on the other hand, enable much more effective use of frequencies and much more increased traffic capacity through their interference suppression functionality.