The present invention allows two different block codes to be encoded by one-type of encoding section. Each pixel region includes a first photodiode having a first area and a second photodiode having a second area equal to or smaller than the first area. Therefore, a method is disclosed for determining the number of time slots to assign to a user as a function of the user’s current data rate requirement and the actual current cumulative data rate of the time slots currently assigned to the user. The time delays are used to generate the schedule.