Pixelation issues

What you are calling PIXELATION, is actually known as digital tiling. Each channel you watch is on a different frequency, and a single channel exhibiting digital tiling is an indication of either a low signel level or some kind of interference on that frequency. 

If you have accessible splitters, replace them, as well as replacing any cable wires you can, cable box to wall modem to wall, etc etc. Doing so may help in reducing interference, as well as strengthening signal levels. 

If that doesn't help, it may require a technician to come out, If you have Cox Complete Care, (10$ a month i think), then it will not cost you anything. If you don't have CCC, then if the problem is inside the home wiring, there may be a 75$ service charge, if the problem is with the delivery of service up to the audit box on the back/side of home, then Cox won't charge you to fix their equipment.