3.4.2. Step Sequence

The step method refers to uniformly selecting pixels in an original sequence with interval *k*. To do this, we uniformly segmen<sup>t</sup> pixel set [**<sup>r</sup>**1**r**2 ...**r***N*] into *k* groups. For each transmission, one pixel is selected from each group in turn. If *k=5*, the resulting transmission pixel sequence would be {**<sup>r</sup>**1,**r**6,**r**11, ...**r**2,**r**7,**r**12...}, as shown in Figure 3b. As a result, the transmitted pixels are the samples uniformly picked from the pixel set. Theoretically, using such sequence would make the PSP-BS converge more quickly, because in this case fewer received pixels can represent the image better.
