comtech
aha
corporation
PRODUCT BRIEF
AHA4524
(4 Kbit Block Version)
TURBO PRODUCT CODE ENCODER/DECODER
The AHA4524 device is a single-chip Turbo
Product Code (TPC) Forward Error Correction
(FEC) Encoder/Decoder. This device integrates
independent TPC encoder and decoder functions,
and can be configured for full or half duplex
operation. In addition to TPC coding, the device
includes helical interleaving, CRC computation,
and data scrambling. Each of the functional blocks
can be independently bypassed. Figure 1 shows the
functional block diagram.
The encoder and decoder accept data and
configuration through a synchronous 3-wire or data
bus interface designed to connect directly to a DSP
or user logic.
Encoder and decoder configuration registers are
written and read through the same interface as the
data. Configuration registers may be accessed at the
start of every block transfer.
The encode datapath, with all functional blocks
enabled, computes and inserts CRC bits, scrambles
the data, inserts error correction code (ECC) bits,
and helically interleaves the data. The decoder
datapath is the reverse of the encoder datapath. With
all functional blocks enabled, the received data is
helically deinterleaved before decoding. The
decoder output is descrambled, and the CRC is
computed to verify data integrity. Decoded data is
then output in a serial bit stream.
The decoder input interface includes an option to
accept 4 bit parallel soft metric data symbols. The
parallel decoder input is used to support a symbol per
transfer for fast channel input rates. The AHA4524
also includes fast code changing feature which
allows the device to process multiple block types
simultaneously.
• Supports two dimensional (2D) and three
dimensional (3D) Turbo Product Codes
• Supports 2D enhanced Turbo Product Codes
• Correction count for channel SNR estimation
• Simultaneously processes multiple block types
FLEXIBILITY:
• Code Rates from 0.25 to 0.97
• Encoded block Sizes from 64 bits to 4 Kbits
• Programmable code shortening supports exact
block sizes
• Programmable decoder input quantization for up
to 4 bit wide soft metrics
• Programmable iterations up to 255 per block
• 4 programmable block configurations which are
selectable for fast code changing
• On chip PLL allows low frequency system clock
CHANNEL INTERFACE:
• Synchronous 3-wire input and output ports
designed to be compatible with DSP serial ports
• Bus mode input and output ports designed to be
compatible with a DSP bus
• Chip selects on encoder and decoder ports for full
or half-duplex operation
• Pin selectable interface control signal polarity
• Decoder supports 4 bit parallel soft metric input
data for fast decode operation
SYSTEM INTERFACE:
• Secondary input communication cycles are used
for accessing the AHA4524 configuration
registers through the data ports
• Block status is optionally output at the end of
every decoded block to provide correction and
CRC error information
ELECTRICAL:
FEATURES
PERFORMANCE:
• 60 Mbit/sec channel rate and 50 Mbit/sec payload
data rate for (64,57)x(64,57) code with 3
iterations
• Integrated 16 bit scrambler and descrambler
• Integrated 32 bit CRC computation and
verification
•
•
•
•
•
3.3V I/O, 1.8V core operation
5V tolerant inputs
TTL signal compatible
64 pin TQFP Package
Commercial or Industrial temperature rating
comtech
aha
corporation
ThIs product is covered under multiple patents held or licensed by Comtech AHA
Corporation.
This product is covered by a Turbo Code Patent License from France Telecom -
TDF - Groupe des ecoles des telecommunications.
comtech
aha
corporation
Figure 1:
AHA4524 Functional Block Diagram
ENCODER
U_DATA
E_DATA
I/O
Formatter
CRC
Computation
Scrambler
Configuration
Registers
Helical
Interleaver
eTPC
Encoder
DECODER
C_DATA
D_DATA
I/O
Formatter
Helical
Deinterleaver
eTPC
Decoder
Configuration
Registers
CRC
Verification
Descrambler
AHA4524
SYSTEM APPLICATION
Figure 2 is a block diagram of a wireless system
that shows AHA4524 being used as a TPC
encoder/decoder. During decoding, data is routed
between the Analog Front End (AFE) and
ASIC/DSP through a serial port. The data is then
processed in the ASIC/DSP to block and prepare the
data for the AHA4524 decoder. Data blocks are then
transferred to the AHA4524 for TPC decoding.
Data received from AHA4524 is then routed to
memory/peripheral functions. Encoding is done in a
similar manner where the ECC bits are added to the
block of data. The encoded data block is further
processed for modulation and frame
synchronization as required, then transmitted.
Figure 2:
System Block Diagram, Wireless Communication
Analog
Front End
(AFE)
Transmit
AHA4524
(Encoder)
ASIC / DSP
ASIC / DSP
AHA4524
(Decoder)
Memory /
Peripheral
Memory /
Peripheral
comtech
aha
corporation
CODE PERFORMANCE
Table 1 gives an abridged list of possible codes supported by AHA4524, along with the code rate and
coding gain of each code. This is a very small subset of supported codes. AHA can provide software to
assist the code selection process.
Table 1:
Partial Code List and Performance
CODE
(X)x(Y)x(Z)
BLOCK SIZE DATA SIZE
(bits)
(bits)
RATE
0.954
0.863
0.793
0.495
CODING GAIN*
(dB)
MAX CHANNEL RATE AT
3 ITERATIONS
(Mb/s)
(64,63)x(64,62)+
(64,57)x(64,62)+
(64,57)x(64,57)
(32,26)x(32,26)x(4,3)
*
+
4096
4096
4096
4096
3906
3534
3249
2028
4.4
5.8
6.7
7.3
39.2
39.2
60.0
40.8
Estimated Coding Gain is measured on a Binary Input Additive White Gaussian Noise (AWGN) channel at 10
-6
Bit Error Rate
(BER) and 3 iterations.
enhanced TPC (includes hyper axis). In enhanced codes, the Y axis is shortened by one. The shortening and addition of hyper
axis is included in the code description.
Figure 3:
Comparison of TPC Code Types
TPC @ 3 Iterations
1.E+00
1.E-01
1.E-02
1.E-03
Uncoded BPSK
RS(255,239) R=.937
TPC(64,63)x(64,62)+ R=.954
TPC(64,57)x(64,62)+ R=.863
TPC(64,57)^2 R=.793
TPC(32,26)x(32,26)x(4,3 ) R=.495
Bit Error Rate P(e)
1.E-04
1.E-05
1.E-06
1.E-07
1.E-08
1.E-09
1.E-10
0
1
2
3
4
5
6
7
8
9
10
Eb/No (dB)
comtech
aha
corporation
Figure 4:
TPC Performance with 3, 8 and 32 Iterations
TPC (64,57)^2, rate 0.793 @ 3, 8, and 32 Iterations
1.E+00
1.E-01
1.E-02
1.E-03
Bit Error Rate P(e)
1.E-04
1.E-05
1.E-06
1.E-07
1.E-08
1.E-09
1.E-10
0
1
2
3
4
5
6
Uncoded BPSK
TPC(64,57)^2, 3 iter
TPC (64,57)^2, 8 iter
TPC(64,57)^2, 32 iter
Eb/No (dB)
ABOUT AHA
Comtech AHA Corporation (AHA) develops
and markets superior integrated circuits, boards,
and intellectual property core technology for
communications systems architects worldwide.
AHA has been setting the standard in Forward Error
Correction and Lossless Data Compression
technology for many years and provides flexible,
cost-effective solutions for today’s growing
bandwidth and reliability challenges. Comtech
AHA Corporation is a wholly owned subsidiary of
Comtech Telecommuncations Corp. (NASDAQ:
CMTL). For more information, visit www.aha.com.
ORDERING INFORMATION
PART NUMBER
DESCRIPTION
AHA4524A-031 PTC 4 Kbit Block TPC Encoder/
Decoder - Commercial Temp
4 Kbit Block TPC Encoder/
AHA4524A-031 PTI Decoder - Industrial Temp
comtech
aha
corporation
A subsidiary of Comtech Telecommunications Corporation
1126 Alturas Drive
Moscow, ID 83843-8331
tel: 208.892.5600
fax: 208.892.5601
e-mail: sales@aha.com
www.aha.com
PB4524_0204
©
2005 Comtech AHA Corp.
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