Medium Access Control (MAC) and Physical Layer (PHY) - CISE

4-June-07 P1901_PRO_016_r0
Burst
header
symbol M data symbols
HEADER
HEADER
HEADER
First
INTER-
PACKET
HEADER
Completed
PACKET
CRC
WORD
N-
INTER-
PACKET
HEADER
Completed
PACKET
Submission page 154 UPA-OPERA
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CRC
WORD
64 bits 32 bits 64 bits 32 bits
First
INTER-
PACKET
HEADER
Fragmented
PACKET
PADDING
CRC
WORD
64 bits 32 bits
First
INTER-
PACKET
HEADER
Fragmented
or Completed
PACKET
CRC
WORD
Second
INTER-
PACKET
HEADER
Completed
PACKET
CRC
WORD
N-
INTER-
PACKET
HEADER
Fragmented
or Completed
PACKET
CRC
WORD
64 bits 32 bits 64 bits
32 bits
64 bits 32 bits
For more information about the Burst Header see 5.2.
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Figure 57 Unencrypted Burst examples
Each burst can contain more than one CLPDU. For more information about the CLPDU format see 6.2.
The length of a burst is equal to a number of data symbols. The maximum length of a burst is 30 OFDM symbols,
excluding the burst header. The maximum capacity of the burst in 32-bit words depends on the bit-loading table and
the number of data symbols.
When one packet has to be divided into fragments, each fragment length must be multiple of 256 bytes, except the
last fragment. No 32-bit words are added as padding in the last fragment to obtain 256 bytes. If one packet has
length equal to X with X = Y * 256 + Z bytes, the packet could be sent in up to (Y+1) different bursts using
fragmentation. If one packet has length equal to X bytes with X less than 256 bytes, this packet is sent with X bytes
plus the needed padding to align it to 32-bit words. In any case, the only added padding is to be aligned to 32-bit
words.
The inter-packet header is used for disassembling bursts in reception. An inter-packet header shall always precede
each packet or fragment of a packet.
At the end of each fragment or packet, a 32-bits CRC of the preceding fragment or packet (excluding inter-packet
header) shall be sent.
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