Support of RoHC Piggyback Feedback in LTE standard

KarthikBalaguru · 4G Newbie Joined: 01 May 2009 Posts: 3

Hi,

LTE standrad clearly states that PDCP Control Packet (Feedback) shall not be ciphered and PDCP data packets shall be ciphered by configured algorithm. In case of Piggyback feedback packet, DataPacket will be attached at the end of feedback packet.
But, if the Data Packets are ciphered for these piggyback packets, then how will the Peer entity generate COUNT input
for cipher algorithm as PDCP-SN will not be available ?

Any ideas ?

Thx in advans,
Karthik Balaguru

KarthikBalaguru · 4G Newbie Joined: 01 May 2009 Posts: 3

Hi,

The LTE PDCP standard states that , the PDCP Control PDU carries only interspersed ROHC feedback
packets (Refer - section 5.5.4 and 6.2.5 of TS36.323v850 3GPP).
But, The LTE PDCP standard does not explicitly talk about piggyback feedback.

The query/dilemma is due to the 2 statements from Section 5.5.4 from
TS36.323v850. I have mentioned it below :-
" The header compression protocol generates two types of output packets:
- compressed packets, each associated with one PDCP SDU
- standalone packets not associated with a PDCP SDU, i.e. interspersed
ROHC feedback packets "

Kindly clarify regarding the term 'Compressed packet' in the section 5.5.4
TS36.323v850 .
Does it refer to 'Rohc Feedback Packet and Rohc Compressed header
(Piggybacked) ' or only 'Rohc Compressed header ' alone ?

The LTE PDCP standard does not explicitly talk about piggyback feedback.
The PDCP Standard does not explicitly state that PDCP Data PDUs can
carry the entire ROHC packet (i.e. piggybacked feedback, if any, and the
ROHC header and payload) in the data part of the PDCP PDU .
The clarification of the term 'Compressed packet' in the section 5.5.4 will
solve this problem.
So, does that term 'Compressed packet' refer to 'Rohc Feedback Packet
and Rohc Compressed header (Piggybacked) ' or
only 'Rohc Compressed header ' alone ? Any ideas ?

Thx in advans,
Karthik Balaguru