Marine Radio - Marine Radio Decoder User Manual

Subblock : 1, 2 or 4 sliding windows
Frame or subframe (length < 5114)
First subblock
Middle subblock
Middle subblock
Middle subblock
Last subblock
Beta
Prolog
portion
Alpla
Prolog
portion
Reliability
portion
Prolog
Only used in SP mode.
in SA mode, start from
known state 0
Prolog
Only used in SP mode
Sliding Window
Sliding Window
Sliding Window
Sliding Window
subframes (not last).
in SA mode and SP
mode last subframe,
use tail symbols
8.2 Subframe Segmentation (SP mode only)
www.ti.com Architecture
Figure 96. Sliding Windows and Sub-blocks Segmentation (Example with 5 Sub-blocks, frame length
≤ 20730)
Figure 96 show diagrams for the sliding windows for both alpha and beta. Each sliding window consists of
a reliability section and a prolog section. The size of the reliability section can range from 40 to 128 and
the size of the prolog section can range from 4 to 48 in the TCP2. The alpha sliding window starts at the
left and goes right (forward order) and the beta sliding window starts at the right and goes left (reverse
order). See Table 40 for the number of sub-blocks and sliding windows.
Table 40. Examples for NUM_BLOCK, NUM_SUBBLOCK, NUM_SW, and WIN_REL
NUM_BLOCK NUM_SUBBLOCK NUM_SW WIN_REL
40 1 0 40
128 1 0 128
129 1 1 65
256 1 1 128
257 2 1 65
512 2 1 128
3840 15 1 128
16122 63 1 128
20730 81 1 128
A frame needs to be segmented into subframes when working in shared processing (SP) mode; therefore,
the minimum number of subframes is 2. The subframe length should be chosen so that it has a reliable
portion that is both less than 20480 and also a multiple of 256. Figure 97 shows the segmentation.
Each subframe is then further divided into sub-blocks and sliding windows as described in Section 8.1 . All
subframes except the last one must have the same length and be a multiple of 256.
SPRUGK1 – March 2009 TMS320C6457 Turbo-Decoder Coprocessor 2 61
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