Viterbi Coprocessor (VCP2): performance and parameters

Vyacheslav Klimentyev

Other Parts Discussed in Thread: TMS320TCI6614

I read manuals KeyStone Architecture Viterbi Coprocessor (VCP2) and TMS320TCI6614 Communications Infrastructure KeyStone SoC but I didn't find information about max throughput and puncturing.

The TMS320TCI6614 device has four high-performance embedded Viterbi decoder coprocessors (VCP2) that significantly speed up channel-decoding operations on-chip. Each VCP2, operating at CPU clock divided-by-3, can decode more than 694 7.95-Kbps adaptive multi-rate (AMR) [K = 9, R = 1/3] voice channels. The VCP2 supports constraint lengths K = 5, 6, 7, 8, and 9, rates R = 3/4, 1/2, 1/3, 1/4, and 1/5, and flexible polynomials, while generating hard decisions or soft decisions.

Can I use the coprocessor for punctured code (e.g., r = 5/6)? And what is about max throughput for single channel? I wanna decode 54 Mbps. Is it possible?

over 6 years ago

0 Victor Kazmirenko over 6 years ago

Guru 13202 points

Hello!

Decoding of punctured convolutional codes requires extra step, namely de-puncturing. Logically, one should insert back punctured bits as unknown values, neither 1, not 0. Practically, you set erasures equally distant from certain 1 and 0. As VCP2 takes soft inputs in form of signed integers in range [-M; +M], zero value is right for this case. You use this value to calculate branch metrics for punctured positions. Once branch metrics computed, you submit them to VCP2 for decoding.

As to performance numbers, I think it's right to take values for mother code before puncturing.

Hope this helps.

0 Vyacheslav Klimentyev over 6 years ago in reply to Victor Kazmirenko

Prodigy 100 points

Thanks for your answer. Yes, I though about the decoding procedure.

Unfortunately, I don't know max throughput of VCP2 for non-punctured code.

0 Yordan Kovachev over 6 years ago

TI__Guru**** 161600 points

Hi,

Let me check this with the design team.

Best Regards,
Yordan

0 Vyacheslav Klimentyev over 6 years ago in reply to Yordan Kovachev

Prodigy 100 points

Hello,

Thank you! I will wait your reply.

0 dzhou over 6 years ago in reply to Vyacheslav Klimentyev

TI__Genius 9065 points

Hello Vyacheslav,

Please take a look at page 3 in the following document. This has some performance numbers.

http://www.ti.com/lit/ml/sprt610/sprt610.pdf

I am not a domain expert on this device and we have lost most experts so your best bet would be relying on published documents or run tests to confirm it.

best regards,

David Zhou

0 Vyacheslav Klimentyev over 6 years ago in reply to dzhou

Prodigy 100 points

Hello David,

Thank you. 38 Mbps for 4 Viterbi decoders -> 9.5 Mbps/decoder (40 bit blocks).

After reading your reply I found description for Keystone 2:

Eight Viterbi Decoders

– Supports up to 96 Mbps (Length9, Rate1/2, BlockSize 6000)

96/8 = 12 Mbps/decoder.

So, we have about 10 Mbps per Viterbi decoder.

0 dzhou over 6 years ago in reply to Vyacheslav Klimentyev

TI__Genius 9065 points

Glad you figured it out. Good luck!

best regards,

David Zhou

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Viterbi Coprocessor (VCP2): performance and parameters