Re: [44net] OFDM Modem

Ron, Unfortunately, these details are outside my expertise. What I'm curious to know is how this can be used. Specifically, I'm curious to know if this can be used in a point-to-multi-point configuration as follows: -- Central site device accepts connections from multiple clients devices, much like a packet BBS or dial-up server or WiFi access point or VPN server or ... -- Primary application is multiple individuals/sites connecting to a central server, such as a POP/SMTP email server. Clients connect, up/download, disconnect, thereby vacating the channel for others to use. MAC capable of multiple simultaneous connections (albeit slower for each connection), much like packet or Ethernet or WiFi or ... -- Secondary application is clients connecting directly to each other, but also for a brief time (connect, transfer, disconnect) so channel can be shared by many. -- Capable of operating within the current 70 cm band FCC restrictions If so, I think I could find a local team of folks willing to work on and test a prototype. And, as I've mentioned, we've got plenty of folks waiting for such a device. Michael N6MEF > -----Original Message----- > From: 44Net [mailto:44net-bounces+n6mef=mefox.org@hamradio.ucsd.edu] On > Behalf Of Ron Economos > Sent: Saturday, September 2, 2017 4:59 PM > To: 44net(a)hamradio.ucsd.edu > Subject: Re: [44net] OFDM Modem > > Here's a little more background on the project. First, the DVB-T2 > transmitter is part of GNU Radio itself. I developed the original DVB-T2 > transmitter as an OOT (Out of Tree) module back in the winter of > 2014/2015. > > https://github.com/drmpeg/gr-dvbt2 > > Since then, the code has been integrated into the GNU Radio mainline > along with DVB-T, DVB-S, DVB-S2, DVB-S2X, ATSC and cable QAM > transmitters. There are also receivers for ATSC and DVB-T. The above OOT > module is now deprecated. > > Here's an example DVB-T2 flow graph. This one implements the exact same > parameters as used by the BBC for their television transmitters in the > UK. It has 40.2 Mbps of throughput in an 8 MHz channel. > > http://www.w6rz.net/dvbt2bbc.png > > The blocks in the lower right hand corner implement the interface to the > SDR hardware. The UHD: USRP SInk is for Ettus Research products and the > osmocom Sink is for other SDR's like bladeRF and hackRF. > > The flow graph for the OFDM modem looks like this. > > http://www.w6rz.net/dvbt2ule.png > > The IP over TS Packet Source block is implemented in the gr-ule OOT > module. > > https://github.com/drmpeg/gr-ule > > The other DVB-T2 blocks are just the regular DVB-T2 blocks merged > together to avoid buffering between blocks (to reduce latency). Those > blocks are implemented in the gr-dvbt2ll OOT module. > > https://github.com/drmpeg/gr-dvbt2ll > > The network interface is provided by a kernel driver. The driver > implements both the ULE protocol and the MPE protocol, but MPE is not > complete for some reason. > > https://github.com/torvalds/linux/blob/master/drivers/media/dvb- > core/dvb_net.c > > The dvb_net driver just exposes a regular Ethernet interface, so all the > routing tools of Linux are available. To connect to the Internet, all I > had to do was make the interface the default route on the "remote" node, > enable IP4 forwarding on the "local" node that's connected to the > Internet, and add the 44.4.15.8/29 route to my Asus RT-AC66U router. > > http://www.w6rz.net/dvb0_0.png > > Ron W6RZ > > On 09/01/2017 08:21 AM, Andrew Ragone wrote: > > Er, looks like I stand corrected ... I think this is the project > > implementing the GNU Radio functionality: https://github.com/drmpeg/gr- > ule > > > > On Fri, Sep 1, 2017 at 9:17 AM, Andrew Ragone <ajr9166(a)rit.edu> wrote: > > > >> Ron, this is great work! I know you mentioned there is room for > >> optimization on the buffering / GNU Radio side of things, but it > doesn't > >> look like any of the links provided were for the actual radio design > you > >> worked on. Were you planning on throwing that up on GitHub or your > website? > >> I have a Pervices Noctar SDR which I wouldn't mind playing with your > >> project on (and helping optimize). > >> > >> -Andrew > >> Kc2LTO > >> > >> On Fri, Sep 1, 2017 at 7:01 AM, Brian Kantor <Brian(a)ucsd.edu> wrote: > >> > >>> Sounds a lot like the ALOHA network from back in June 1971. > >>> - Brian > >>> > >>> On Fri, Sep 01, 2017 at 08:57:38AM -0400, Mark Phillips wrote: > >>>> This has been thought of before I'm sure. > >>> _________________________________________ > >>> 44Net mailing list > >>> 44Net(a)hamradio.ucsd.edu > >>> http://hamradio.ucsd.edu/mailman/listinfo/44net > >>> > >> > >