1. Proposed Correction of LDPC Tone Mapping Equation
Month Year
doc.: IEEE yy/xxxxr0
Proposed Correction of LDPC Tone Mapping Equation
Date:
Authors:
Slide 1
Hossein Taghavi et al.
John Doe, Some Company

2. Summary
We propose a correction to equation (page 126, line 51) of D0.1 [1], involving LDPC tone mapping
Hossein Taghavi et al.

3. Review of LDPC Tone Mapping
LDPC tone mapping (D0.1, Subclause [1]) was proposed in IEEE /1300r0 [2] and approved by the TG
In higher rates of 11ac, the length of the LDPC codeword (LCW) can be significantly smaller than the number of bits in an OFDM symbol (NCBPS)
Without the LDPC tone mapping, the coded bits from each LDPC codeword are transmitted only through a fraction of the tones, thus not achieving the full frequency diversity
LDPC tone mapping provides full frequency diversity without the extra delay of interleaving
For LDPC-coded streams, maps consecutive QAM symbols to data tones which are separated by at least DTM -1 other data tones
With LDPC
tone mapping
Here DTM=3
Hossein Taghavi et al.

4. Proposed Correction In Subclause 22.3.11.8.2, the equation
LDPC Tone Mapper
In Subclause , the equation
defines the mapping of the k’th QAM symbol of an LDPC-coded stream in each OFDM symbol to data tone t(k)
For example, at 20MHz (DTM = 4), QAM symbols with indices k = 0, 1, 2, 3, … are mapped to data tones t(k) = 0, 4, 8, 12,...
In other words, the input QAM symbol should become to the output QAM symbol , which is transmitted on data tone t(k)
The first paragraph of page 127 explains this process accurately
However, there is an error in Eq since it does the reverse: It maps QAM symbol t(k) to data tone k.
Eq should be corrected to
Hossein Taghavi et al.

5. Premotion
Do you agree with changing equation (page 126, line 51) of D0.1 [1], involving LDPC tone mapping, from to
Approved with no objection.
Hossein Taghavi et al.

6. Reference [1] IEEE P802.11ac/D0.1
[2] “ ac-ldpc-for-11ac”, Jun Zheng et al.
Hossein Taghavi et al.