Performance improvement of decision-directed channel estimation for DPC-OF/TDMA in a fast fading environment

A new beyond-3G system, named dynamic parameter controlled orthogonal frequency and time division multiple access (DPC/OF-TDMA) is being developed in Japan. In this system, a decision-directed channel estimation (DDCE) technique can be employed for increased channel estimation accuracy in a fast fading environment. This technique, however, has a structurally unavoidable processing delay due to the decision for the generation of new reference data. In the fast fading environment, propagation characteristics vary during this delay, resulting in channel estimation error or considerable output delay. The paper proposes a novel DDCE method to reduce such estimation error. The proposed channel estimation method is performed by introducing circuits that are independent of the system output process. These independent circuits enable considerable output delay to be avoided. In addition, the paper proposes a method of detecting inaccurate channel estimates obtained for errors of decoded data to increase channel estimation accuracy.