How to create a search window for Block matching Motion estimation?

I have a set of images, which is divided into blocks of size 8 * 8. I resized each image into the size of 32. So, i totally have 16 blocks now. Now, i have to create a search window for Block matching concept. Is there any specific range to create that search window? Also, there is a concept called center pixel is being used. How to implement the center pixel concept? Thanks in advance..

[Neda]

To determine search window size you should consider some options. For example, if we assume the maximum motion estimation is 20, the size of search window shouldn't be less or larger than this number. If the search window is too small, large movements or displacement will be underestimated or misinterpreted, and if too large, the algorithm will be too time-consuming.