1. Sharp Laboratories USA
March 2001
Frame FEC Formats for e
John M. Kowalski
Sharp Laboratories USA
Camas, Washington
(360)
John M. Kowalski,

2. Outline Requirements Frame format
March 2001
Outline
Requirements
Frame format
Description of frame format & performance
John M. Kowalski,

3. Requirements for MAC Level FEC
March 2001
Requirements for MAC Level FEC
Applicable to all known PHYs
Provide a reduction in BER
Be optional yet allow non-FEC capable stations to interpret FEC coded data.
FEC enabled MACS shall not send up frames to higher layers
The MAX MPDU size of is maintained. Payload delivered to higher layers (if not fragmented) is octets maximum.
Delayed ACK or unacknowledged must be used to accomodate Rx/Txturnaround time for a
John M. Kowalski,

4. Requirements for MAC Level FEC (cont.)
March 2001
Requirements for MAC Level FEC (cont.)
Any encryption performed is done prior to FEC encoding
MAC FEC is performed on a TC. The MAC MLME, based on requests for parameterized QoS, instantiates MAC-Level FEC. ESTAs announce their FEC capability via bit 11 of the Capability Information Field .
Legacy STAs cannot read the FEC fields, therefore FEC encoded MPDUs shall not be sent to them
FCS is included so that legacy ESTAs can compute FCS errors in a consistent way. Another FCS (on non-parity check octets) is included to prevent errored frames from being passed to higher layers.
John M. Kowalski,

5. Frame Format MAC Header Header FEC 32 16 Frame Body FEC FEC FEC ... 16
March 2001
Frame Format
MAC Header
Header FEC 32 16
Frame Body
Security IV+
MSDU1
FEC
FEC
MSDU2
MSDUN+ICV+
FEC FCS
FEC
... 16 16
208
208
up to 208 16
FCS
Includes 4 octet FCS field
only over
uncoded octets 4
Over all octets
John M. Kowalski,

6. Description of Fields & Performance
March 2001
Description of Fields & Performance
ALL coded fields use (224,208) Reed-Solomon Code.
Header uses truncated code w/ header taking up the first 32 octets of an (untransmitted) 208 octet field.
Assuming 10% PER, for a 1000 byte packet, uncoded, P(Header Failure) < 10-17
John M. Kowalski,

7. Description of Fields & Performance (Cont.)
March 2001
Description of Fields & Performance (Cont.)
If security field is present, it’s coded in the first block of the frame body.
The FCS is done as in IEEE section
GF(256) polynomial is:
f(x) = x8 + x4 + x3 + x2 + 1 f(x) = x8 + x4 + x3 + x (used in DVB)
P(Frame body error) < 7.01X (1000 octets)
John M. Kowalski,