PDCP PDUs. This includes:
- Modifying the byte_buffer_t to include PDCP SN meta-data. This way,
the RLC can keep track of the ack'ed bytes for a specific PDCP PDU.
- Added in the RLC an `undelivered_sdu_info queue`, to keep track of the
amount of ack'ed bytes and the total size of the PDCP PDU,
so the RLC can know when delivery is finished.
- Added an interface between the PDCP and the RLC so that the RLC can
notify the PDCP when it receives an ack from the status PDUs. The RLC
passes to the PDCP a vector of all the ack'ed pdus in a rx'ed status PDU.
- Added some tests to the notify functionality. This includes some tests
where the PDUs are acked imediatly, and one test where the PDU is
retx'ed.
this patch adds support for measuring the:
* SDU rx latency (Average time in ms from first RLC segment to full SDU)
* amount of buffered bytes (sum of payload of PDUs buffered in rx_window)
the implementation is using std::chrono
when retrieving the RLC metrics, the number of TTIs since the last
call are passed. This allows to calculate the actual rate
based on the LTE timing rather than only the system timing.
* rlc_am: add TC for pollRetx timer handling
* rlc_am: fix stopping of pollRetx timer
stopping the pollRetx timer when receiving a status PDU
without checking the acknowledged PDUs is wrong.
if an ACK for another PDU, for which the polling bit has been set,
is still pending, it won't be rescheduled until another
PDU is transmitted that again starts the pollRetx timer.
this fixes the issue with missing RLC AM segment retx in #1992,
and #2003
this patch refactors the SDU queuing and dropping policy of the RLC and PDCP layer.
the previous design had issues when packets have been generated at a higher
rate above the PDCP than they could be consumed below the RLC.
When the RLC SDU queues were full, we allowed two policies, one to block on the write
and the other to drop the SDU. Both options are not ideal because they either
lead to a blocking stack thread or to lost PDCP PDUs.
To avoid this, this patch makes the following changes:
* PDCP monitors RLC's SDU queue and drops packets on its north-bound SAP if queues are full
* a new method sdu_queue_is_full() has been added to the RLC interface for PDCP
* remove blocking write from pdcp and rlc write_sdu() interface
* all writes into queues need to be non-blocking
* if Tx queues are overflowing, SDUs are dropped above PDCP, not RLC
* log warning if RLC still needs to drop SDUs
* this case should be avoided with the monitoring mechanism
Here is the test output with the fix disabled:
13:47:42.679774 [RLC_UM_1] [D] MAC opportunity - 14 bytes
13:47:42.679784 [RLC_UM_1] [D] pdu_space=14, head_len=2
13:47:42.679790 [RLC_UM_1] [D] adding new SDU segment - 10 bytes of 10 remaining
13:47:42.679834 [RLC_UM_1] [D] Complete SDU scheduled for tx. Stack latency: 0 us
13:47:42.679909 [RLC_UM_1] [D] pdu_space=4, head_len=2
13:47:42.679922 [RLC_UM_1] [D] adding new SDU segment - 0 bytes of 10 remaining
13:47:42.679928 [RLC_UM_1] [I] Tx PDU SN=0 (14 B)
13:47:42.679974 [RLC_UM_1] [D] vt_us = 1
The test checks the correct packing and of the two PDUs at the end.
previously PDCP security (integrity and ciphering) could only
be enabled for both Rx and Tx at the same time.
this, however, caused an issue during the conformance testing in which,
in TC_8_2_1_1() for example, the eNB sends a SecModeCommand and a
RRC Reconfiguration in the same MAC TB. In this case, the eNB
needs to be able to enable DL security right after sending the SecModeCmd
in order to send the RRCReconfig encrypted. However, enabling UL security needs
to be postponed until after the SecModeComplete is received.
This patch allows to enable PDCP security for rx/tx independently if
that is needed. The default way is like before, enabling it for tx/rx at
the same time.
Pedro Alvarez
David Rupprecht
Andre Puschmann
faluco
faluco
Francisco Paisana
Francisco Paisana
Xavier Arteaga