what is window size? i am working on simulation of an article "A Real-time ECG Data Compression Algorithm for a Digital Holter System". This algorithm has five steps "Difference=> ECG Signal=>Classification=> DCT=> Window Filter => Huffman" . it described window filter as "In order to implement a high compression ratio, the DCT window size, which is chosen to be proportional to the DCT result, is adjusted from 15% to 100%.". i do not understand this step and how can i do it? how can i change window size? 
please help me
thanx
That paper is very poorly written. It's no wonder you have a hard time understanding it; I certainly did!

What I think is happening is that several of the DCT coefficients are being thrown out (windowed). So if the window is 100%, then all the DCT coefficients are kept; if the window is 30% then 70% of the coefficients are thrown out (zeroed).

See Figure 11 of that paper:



The left hand signal are the DCT coefficients. The right-hand graph is the applied window. The two are multiplied together.