WJCE6353SL9G5882170 INTEL [Intel Corporation], WJCE6353SL9G5882170 Datasheet - Page 14

• Manufacturer Part Number: WJCE6353SL9G5882170
• Description: Nordig Unified DVB-T COFDM Terrestrial Demodulator for PC-TV and Hand-held Digital TV (DTV)
• Manufacturer: INTEL [Intel Corporation]

2.15
The Viterbi decoder accepts the soft decision data from the OFDM demodulator and outputs a decoded bit-stream.
The decoder does the de-puncturing of the input data for all code rates other than 1/2. It then evaluates the branch
metrics and passes these to a 64-state path-metric updating unit, which in turn outputs a 64-bit word to the survivor
memory. The Viterbi decoded bits are obtained by tracing back the survivor paths in this memory.
depth of 128 is used to minimize any loss in performance, especially at high code rates.
The decoder re-encodes the decoded bits and compares these with received data (delayed) to compute bit errors
at its input, on the assumption that the Viterbi output BER is significantly lower than its input BER.
2.16
The Viterbi decoded bit stream is aligned into 204-byte frames. A robust synchronization algorithm is used to
ensure correct lock and to prevent loss of lock due to noise impulses.
2.17
Errors at the Viterbi output occur in bursts and the function of the de-interleaver is to spread these errors over a
number of 204-byte frames to give the Reed-Solomon decoder a better chance of correcting these. The de-
interleaver is a memory unit which implements the inverse of the convolutional interleaving function introduced by
the transmitter.
2.18
Every 188-byte transport packet is encoded by the transmitter into a 204-byte frame, using a truncated version of a
systematic (255,239) Reed-Solomon code. The corresponding (204,188) Reed-Solomon decoder is capable of
correcting up to eight byte errors in a 204-byte frame. It may also detect frames with more than eight byte errors.
In addition to efficiently performing this decoding function, the Reed-Solomon decoder in CE6353 keeps a count of
the number of bit errors corrected over a programmable period and the number of uncorrectable blocks.
information can be used to compute the post-Viterbi BER.
2.19
The de-scrambler de-randomizes the Reed-Solomon decoded data by generating the exclusive-OR of this with a
pseudo-random bit sequence (PRBS). This outputs 188-byte MPEG transport packets. The TEI bit of the packet
header may be set if required to indicate uncorrectable packets.
2.20
MPEG data can be output in parallel or serial mode. The output clock frequency is automatically chosen to present
the MPEG data as uniformly spaced as possible to the transport processor. This frequency depends on the guard
ratio, constellation, hierarchy and code rate. There is also an option for the data to be extracted from the CE6353
with a clock provided by the user.
Viterbi Decoder
MPEG Frame Aligner
De-interleaver
Reed-Solomon Decoder
De-scrambler
MPEG Transport Interface
Intel Corporation
CE6353
14
Data Sheet
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