The RTT for GEO satellites is more than 500 ms.
And as the TA update interval must be greater than the RTT, we increase it to 1 second instead of 100 ms.
Should also do no harm for terrestrial networks.
According to the RRC specification, cellSpecificKoffset is:
Scheduling offset used for the timing relationships that are modified for NTN (see TS 38.213 [13]).
The unit of the field K_offset is number of slots for a given subcarrier spacing of 15 kHz.
If the field is absent UE assumes value 0
This parameter `cellSpecificKoffset_r17` can be set in the gNB conf file, in the section `servingCellConfigCommon`
A particular GCC version (v13?) used by CI machines potentially has a
bug that issues a mismatch bound warning on function array arguments.
This commit should prevent it from happening.
There is already a command line option called 'ue-scan-carrier' which
seemed to blindly look for SSB by changing the center frequency by
+/-100Hz if the previous attempt failed. This is probably copied from
LTE and is not suitable for NR. This commit uses this option to either
1. Perform initial sync on one GSCN if the SSB position if known
2. Or scan the all GSCN (if the SSB postion is unknown)
Also, the following is done for re-synchronization
1. Scan all GSCN when UE comes back from IDLE state
2. Scan one GSCN when UE does re-estabishment
Removed dependency of lte-softmodem.h in nr-softmodem.c.
CONFIG_HLP_UESCAN is declared also in lte-softmodem.h.
Changed Info to Debug because the logs are too much if large number of
GSCN scans run concurrently. Print PSS correlation peak and average
power of detected cells.
Till this commit, the UE gets the position of SSB in frequency from
command line and does the syncronization by locating the SSB in time. It
does this by generating a PSS time signal during initialization with the
SSB offset given via command line. Then PSS detection is done by
correlation.
In this commit, the UE computes a list of GSCN in the current NR band
that falls within the current bandwidth for the set center frequency.
For each GSCN in the list, the UE starts a thread and performs the
following:
1. Generate PSS time signal with SSB offset for current GSCN.
2. Detect PSS, SSS and decode PBCH (this step remains the same).
After all threads finishes, the results are collected.
For now, only the first detected PBCH is used to proceed further. So
this PBCH is indicated to MAC and UE exits initial sync.
Future work: The cell search can be standalone feature where the UE
could scan for SSB in the entire NR band. This would require changing
radio's frequency on the fly as the UE's bandwidth would not cover an
entire NR band. The cell detection can futher be imporved by looking
for SIB1 for each decoded PBCH.
Integration: `2024.w22` (Part 1)
See merge request oai/openairinterface5g!2773
* !2698 Handle division by 0 gracefully in average channel level calculation
* !2743 Demystifying 10log10(2^30) in signal energy calculations.
* !2767 NR UE imeisv fix
* !2768 Over-estimate short and long BSR for better latency and TCP throughput
* !2769 maxMIMOLayers parameter in configuration file
38.321 6.1.3.1 says: "The size of the RLC headers and MAC subheaders are
not considered in the buffer size computation" [for BSR]. However, prior
to this commit, we take the size signaled of the BSR and schedule the UE
with that amount of data, making it impossible for the UE to transmit
all its data at once (because it is the size signaled + headers).
In this commit, over-estimate the buffer status size. As we cannot know
the exact number and size of headers, we simply use "BSR size + n", as
done in function overestim_bsr_index().
* nb_re_pdsch is directly linked to nb_rb_pdsch, if the latter is 0 the
former is also 0
* compute average channel level only when number of RE for PDSCH is not 0
the average channel level will be set to 0 otherwise
* Added a log message to handle this special case, which is consequence
of other issues in the RX chain
* with this commit, the inconsistency in the RX chain will be handled
in later in nr_ue_pdsch_procedures with a demodulation failure
other minor changes:
* Improved clarity by using NR_NB_SC_PER_RB instead of hard-coded value 12 in nb of RBs calculation
* cleaned up unused variable and outdated comments
Compiling the nrUE with -fsanitize=undefined leads to a crash
because the function nas_stream_encrypt_eia1() accesses the data
as uint32_t but the data is not aligned.
Actually this function wants 64 bits (big-endian) of data, so let's
introduce a simple function to read a big-endian 64 bits value.
It may seem bad (unoptimized), but looking at the output of gcc
without -fsanitize=undefined this will be translated as just one
movbeq instruction (on the machine where I did the test), which is
actually less instructions than the previous version which was doing
too movbel plus orq.
Moreover, after the main loop we need to process the last remaining
bytes (so less than 8). The code was wrong, reading past the input
data (and also not caring about alignment). It may work, it may fail,
it depends on many things. But it's plain wrong. So this was replaced
for something better, simpler. No need for mask32bit() anymore, only
one call to U64() is needed.
And now -fsanitize=undefined is happy, so all is good.
We also restrict the input length to be multiple of 8 bits. I don't
think it's a problem. To be refined if I'm wrong. (I think RRC and
NAS messages are 8-bits aligned, so it shouldn't be a problem.)
It should not be > 0xffffff.
Normally the core network would prevent this case from happening.
Plus to reach this value means to send a lot of NAS messages, which
is very doubtful in practice.
Anyway, it's better to deal with the case.
We exit if that happens. To be refined if needed (very doubtful).
This function was very wrong, now it's just wrong.
(It does not sanitize the input properly. Some bad input may have
unexpected effects on the nrUE.)
It needs a serious rewrite.
I just wanted to "fix" it so that it processes correctly some
correct input data.
OAI core network is sending Deregistation Accept in clear, even
after security context activation.
The standards is not clear to me, so let's accept it.
To be removed if incorrect with respect to the standards.
(The core network will need to be fixed then.)
The version before this commit is wrong, taking wrong byte for msg_type
in some cases.
I don't have much time to implement a proper NAS PDU parser, so let's go
with hardcoded values.
Some later work will be done to have a cleaner solution. As of now, it's
too much work.
Get the security algorithms from SecurityModeCommand.
Restructure the code a bit: add the function handle_security_mode_command()
and adapt the code to use it.
Derive also knas_enc (not used yet).
Do the derivation for knas_enc and knas_int only after reception
of SecurityModeCommand. We need the algorithms configured by core
network to derive those keys.
Thomas Schlichter