Modeling a foreign exchange rate using moving average of Yen-Dollar   market data
  We introduce an autoregressive-type model with self-modulation effects for a foreign exchange rate by separating the foreign exchange rate into a moving average rate and an uncorrelated noise. From this model we indicate that traders are mainly using strategies with weighted feedbacks of the past rates in the exchange market. These feedbacks are responsible for a power law distribution and characteristic autocorrelations of rate changes. 
Takayuki Mizuno, Misako Takayasu, Hideki Takayasu