[srslte-users] Using UDP sockets for ZeroMQ based RF driver

[J Giovatto]

FYI,

I initially tried to use UDP sockets but this was in vain since the
sheer size and rate of a packetized frame was more that the the socket
buffers could handle w/o too much loss. I spent most of my effort on
trying to catch up, stay in sync and discard old frames. I tried IP-UDP
and UNIX sockets. I finally fell back to using LXC containers and Posix
shared memory on the same platform/server, this proved to be robust
enough to keep up and stay in perfect time sync.

You can look at https://github.com/jgiovatto/srsLTE.git faux_rf for
ideas if you like.

Best
Joe

On 2/5/20 9:04 AM, Xavier Arteaga wrote:
> Hi Vikas,
> Many thanks for your email and interest.
>
> I understand your needs but our ZeroMQ module was not designed for
> running real-time streaming.
>
> I am afraid that the protocols you mentioned are NOT supported by our
> ZeroMQ module and I do not know any out-of-the-box alternative way
> that satisfies your requirements.
>
> Kind regards,
> Xavier
>
> On Wed, 5 Feb 2020 at 10:23, Vikas Jain <vjain0974 at gmail.com
> <mailto:vjain0974 at gmail.com>> wrote:
>
>     Hi,
>
>     We are trying to bring up the LTE call between UE and ENB using 
>     ZeroMQ UDP sockets (instead of the ZeroMQ REQ/REPLY sockets which
>     are TCP based).  
>
>     ZeroMQ suggests to use RADIO and DISH type sockets to achieve UDP
>     communication as per http://api.zeromq.org/master:zmq-udp
>
>     We made the following change to the lib/src/phy/rf/rf_zmq_imp.c file:
>
>     int rf_zmq_open_multi(char* args, void** h, uint32_t nof_channels)
>     {
>          ....
>          //rx_opts.socket_type   = ZMQ_REQ;
>          //tx_opts.socket_type   = ZMQ_REP;
>          rx_opts.socket_type   = ZMQ_RADIO;
>          tx_opts.socket_type   = ZMQ_DISH;
>          ....
>     }
>
>     After making the above change, we see that the sockets get
>     instantiated, but the zmq_recv and zmq_send operation are failing
>     with zmq_errno = 95 (ENOTSUP Not supported). 
>     We had the following questions:
>     (1) Does srsLTE support operation with ZeroMQ UDP sockets e.g.
>     using RADIO/DISH socket types as suggested by ZeroMQ?
>     (2) If the ZeroMQ based UDP operation is supported, please guide
>     us on if there are any steps that we are missing or need to do
>     differently for UDP operation.
>     (3) if ZeroMQ based UDP is not supported, are there any other
>     alternate ways in which we can achieve UDP based fake RF driver
>     for UE and eNB connectivity?
>
>     Any help on this topic will be greatly appreciated.
>     Thanks.
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