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Re: [STDS-802-16] turbo-codes and subchannelization

According to the answers received so far, it seems that everybody's interpretation is that you should code over several OFDM symbols in case of subchannelization with a small number of subchannels. I think this might be in contradiction with sentence p.439 L16 : "The data block size (in bytes per OFDM symbol) may be calculated as N/4." that clearly implies that coding is performed over 1 symbol only.
 
Then there is a second issue related to BTC only, that code rates described in Table 217 do not map to the code rates and modulations defined in Table 216. For instance 96 bits with 1/2 rate seems to map to QPSK 1/2, but what about 192 bits 3/8?
This means that it is impossible to describe use of these rates using the burst profiles as described in Table 354.
 
Ambroise

De : owner-stds-802-16@listserv.ieee.org [mailto:owner-stds-802-16@listserv.ieee.org] De la part de Ofer Kelman
Envoyé : mercredi 13 octobre 2004 21:36
À : STDS-802-16@listserv.ieee.org
Objet : Re: [STDS-802-16] turbo-codes and subchannelization

Ambroise,
 
Your second interpretation is the appropriate one. And if you think IP, your scheduling mechanism will anyway allocate time and capacity to forward data blocks larger then the minimum code block.
 
Regards

===============================

Ofer Kelman

Airspan Networks (Israel) Ltd.

E-mail:        okelman@airspan.com

Tel:            +972-3-977-7550

Mobile:       +972-54-4248359

-----Original Message-----
From: owner-stds-802-16@listserv.ieee.org [mailto:owner-stds-802-16@listserv.ieee.org]On Behalf Of Ambroise Popper
Sent: 13 October, 2004 4:51 PM
To: STDS-802-16@listserv.ieee.org
Subject: [STDS-802-16] turbo-codes and subchannelization

In the 802.16-2004 OFDM PHY, turbo-codes have been extended to support uplink subchannelization. A minimum block size is defined both in BTC (96 bits) and CTC (48 bits).
How do you accomodate this with the use of a small number of subchannels?
A first interpretation would be that you cannot use turbo-codes with a small number of subchannels (for instance in BTC QPSK 1/2, you can only support 4 or 8 subchannels to reach the minimum block size of 96 bits).
A second interpretation is that you must code over several OFDM symbols to reach desired block size (for instance in BTC QPSK 1/2 with one used subchannel, a coded block is necessarily a multiple of 4 symbols).
 
Best regards,
 
Ambroise Popper
tel   : +33 1 44 89 48 11
cell : +33 6 60 63 57 20
 
SEQUANS Communications
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