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

[Vikas Jain]

Thanks Xavier and Joe for your inputs.

We were able to bring up the end-to-end LTE call with ZeroMQ based RF
driver over TCP when running the UE and ENB applications in the same Linux
host (i.e. using IP loopback address 127.0.0.1). We were looking to
replicate the same with UDP i.e. achieve connectivity between these
applications running in the same Linux host. So, were looking to get
feedback on whether other folks had done similar experiments and how they
achieved it over UDP.

Thanks.



On Wed, Feb 5, 2020 at 6:28 AM J Giovatto <jgiovatto at adjacentlink.com>
wrote:

> 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> 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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>> srslte-users at lists.softwareradiosystems.com
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>>
>
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