The pilot channel occurs as two distinct bursts in each timeslot of the 1xEV-DO forward link frame. It cannot be de-activated and does not appear as a configurable parameter in the software. The PN offset of the pilot channel indicates the cell or sector of the transmitting access network (AT).
The medium access control (MAC) channel coding is not implemented for factory test mode (Test Mode Signal) frames. Instead, all zero I/Q symbols are time division multiplexed into the MAC portion of each frame timeslot.
The number of physical layer packets to be transmitted over the traffic channel is a user-defined parameter. The preambles and physical layer packets are constructed based on the data rate control (DRC) value selected for the traffic data rate set. The preamble of each physical layer packet is coded with a 32-symbol bi-orthogonal cover derived from the MAC index that uniquely identifies the access terminal for which the physical layer packet is intended. The data transmitted during the MAC layer packet portion of the physical layer packet is set with the Payload parameter in the forward channel configuration table.
The payload is a raw data sequence, not a formatted MAC layer packet. This level of signal coding is sufficient to verify physical layer receiver performance. When PN sequences are selected as the payload, a continuous PN sequence is distributed across the MAC layer packet portions of the total number of packets specified. After the last packet has been filled with data, the PN sequence is truncated. All zero data is transmitted during the pad portions of packet and a frame check sequence (FCS) and tail bits are appended to the end of each packet. The Traffic Data Rate parameter allows you to select from 12 traffic channel DRC values to set the data rate, encoding rate, and modulation type for the packet transmission. The table below lists the modulation characteristics and packet structures associated with specific DRC values.
|
DRC value |
Data rate (kbps) |
Encoding rate |
Modulation type |
Number of bits per packet |
Number of slots per packet |
Number of 32-chip preamble repetitions |
Number of slots per preamble |
|---|---|---|---|---|---|---|---|
|
0x1 |
38.4 |
1/5 |
QPSK |
1024 |
16 |
32 |
16 |
|
0x2 |
76.8 |
1/5 |
QPSK |
1024 |
8 |
16 |
8 |
|
0x3 |
153.6 |
1/5 |
QPSK |
1024 |
4 |
8 |
4 |
|
0x4 |
307.2 |
1/5 |
QPSK |
1024 |
2 |
4 |
2 |
|
0x5 |
614.4 |
1/3 |
QPSK |
1024 |
1 |
2 |
1 |
|
0x6 |
307.2 |
1/3 |
QPSK |
2048 |
4 |
4 |
4 |
|
0x7 |
614.4 |
1/3 |
QPSK |
2048 |
2 |
2 |
2 |
|
0x8 |
1228.8 |
1/3 |
QPSK |
2048 |
1 |
2 |
1 |
|
0x9 |
921.6 |
1/3 |
8-PSK |
3072 |
2 |
2 |
2 |
|
0x10 |
1843.2 |
1/3 |
8-PSK |
3072 |
1 |
2 |
1 |
|
0x11 |
1228.8 |
1/3 |
16-QAM |
4096 |
2 |
2 |
2 |
|
0x12 |
2457.6 |
1/3 |
16-QAM |
4096 |
1 |
2 |
1 |
Packets that occupy multiple frame slots are transmitted using four-slot interlacing. For example, as indicated in the table above, a single packet transmitted at 153.6 kbps occupies four frame timeslots. If only one packet is selected for transmission, frame slots 1, 5, 9, and 13 are active while slots 2, 3, 4, 6, 7, 8, 10, 11, 12, 14, 15, and 16 are idle. On the other hand, if four packets are transmitted at 153.6 kbps, the first packet occupies frame slots 1, 5, 9, and 13, the second packet occupies slots 2, 6, 10, and 14, the third packet occupies slots 3, 7, 11, and 15, and the fourth packet occupies slots 4, 8, 12, and 16. If more than four packets are selected for transmission, additional frames are filled in a similar manner to accommodate the additional packets.
The control channel sends synchronization information to the access terminal. This channel allows the AT to acquire system time and the pilot channel PN offset. The modulation characteristics and physical layer packet structure for control channel transmissions are either DRC values 0x1 or 0x2. The control channel data rate, 38.4 or 76.8 kbps, is selected in the Test Mode Signal Control window.