CDMA2000 1xEVDO has a chip rate of 1.2288 MHz, the same as cdmaOne and CDMA2000 1xRTT. Each chip lasts for a duration of 0.8138 microseconds. In downlink, an EVDO signal can be time-divided into “half slots.” Each half slot has 1024 chips.
The 1024 chips in a half slot can be further time-divided into three different channels: Pilot, MAC, and Data. The Pilot Channel provides synchronization for the EVDO Access Terminals (for example, cell phones, laptops, and so forth.). The MAC (Medium Access Control) Channel controls the overall EVDO traffic. The Data Channel transmits data to various users.
The Pilot and MAC Channels are always active in an EVDO signal, but the Data Channel may sometimes transmit no data. When no data is transmitted, the half slot is considered idle. Otherwise, it is called an active slot.
