ETSI
TSI TS 102 361-1 V1.2.1 (2006
1)
0
NOTE 2: A SYNC pattern is always required in the data header and voice burst A, therefore the outbound
transmission has to be delayed by a burst where either a data header or voice burst A would otherwise
coincide with the embedded outbound Reverse Channel position.
For data and control messages, the embedded field shall be a data SYNC pattern except for special cases such as
Reverse Channel signalling. For voice calls, the voice SYNC pattern occurs in the first burst of every voice superframe.
In addition to marking the superframe boundaries, periodically inserting these periodic syncs allow late entry receivers
to pick up voice messages after the transmission has started. See clause 5.1.2.1 for details on the superframe structure.
Figure 4.6 illustrates the best case and worst-case synchronization period for an inbound (MS to BS) TDMA channel.
Since data and control messages contain a frame synchronization field in each burst, SYNC opportunities can occur as
frequently as every 60 ms. During a voice call, SYNC opportunities occur every 360 ms, the length of a voice
superframe. The first burst of every inbound transmission shall contain a SYNC pattern in order to allow the target to
detect and synchronize to the transmission.
Data Data
Time
Voice Voice Voice Voice Voice Voice Voice
60 ms 360 ms
Data
SYNC
Voice
SYNC
Data
SYNC
Voice
SYNC
DataData DataData
TimeTime
VoiceVoice Voice Voice Voice Voice Voice VoiceVoice
60 ms 360 ms
Data
SYNC
Data
SYNC
Voice
SYNC
Voice
SYNC
Data
SYNC
Data
SYNC
Voice
SYNC
Voice
SYNC
Figure 4.6: Inbound synchronization timing
Figure 4.7 illustrates the best case and worst-case synchronization period for an outbound (BS to MS) TDMA channel.
Because an outbound channel is continuously keyed, both TDMA channels always contain some type of signalling. In
addition, since the target MS can receive both TDMA slots, the target MS can detect SYNC in either slot. Because data
and control messages will typically contain a frame synchronization field in each burst, SYNC opportunities can occur
as frequently as every 30 ms. During a voice call, SYNC opportunities occur every 360 ms, the length of a voice
superframe, on each channel.
The figure 4.7 illustrates the worst-case SYNC timing for voice, 330 ms, which occurs when two voice calls are active
and their superframes (for details of superframes see clause 5.1.2.1) are offset by 30 ms.
Based on these assumptions, the time between SYNC opportunities can be as short as 30 ms and as long as 330 ms.
Data Data
Voice
SYNC
Voice
SYNC
Time
Data
SYNC
Data
SYNC
Voice
SYNC
Voice
SYNC
Data Voice Voice Voice Voice Voice Voice VoiceVoice Voice Voice Voice Voice Voice Voice
30 ms 30 ms330 ms
Data DataData
Voice
SYNC
Voice
SYNC
Voice
SYNC
Voice
SYNC
TimeTime
Data
SYNC
Data
SYNC
Voice
SYNC
Voice
SYNC
Voice
SYNC
Data Voice Voice Voice Voice Voice Voice VoiceVoiceVoice Voice Voice Voice Voice Voice VoiceVoice
30 ms 30 ms330 ms30 ms 30 ms330 ms
Figure 4.7: Outbound synchronization timing