Re: [Discuss-gnuradio] Smart Antenna
In gnuradio-examples/python/multi-antenna or multi_usrp Lin 2007/1/22, Roberto Mastrodonato <[EMAIL PROTECTED]>: Hi where cai I find MIMO USRP codes? 10x R 2007/1/19, Lin HUANG <[EMAIL PROTECTED]>: > > Hi Roberto, > > I don't think there is code related to Smart Antenna, but many people > are working on MIMO-USRP. The difference between them is the correlation > between antennas. If you have antenna array for smart antenna, I think you > may utilize some code of MIMO. > > Lin > > > 2007/1/18, Roberto Mastrodonato <[EMAIL PROTECTED]>: > > > > Hi all > > > > is there anybody that experienced USRP projects with SMART Antenna > > technology? If yes, where can I find codes or something else related to > > USRP-SMART Antenna? > > Thanks a lot > > > > Roberto > > > > ___ > > Discuss-gnuradio mailing list > > Discuss-gnuradio@gnu.org > > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > > > > > ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] Re: more gmsk issues
Brett Trotter wrote: I switched to NFS for my testing and I can transfer about 600 KiB before it stalls for a while, but NFS seems to be good enough at re-trying over cruddy networks Hello Brett! You should be aware that you are using quite high level protocols when using SSH or NFS. You are moving in OSI Layer 5 (Session). Layer 1 would be PHY, the radio part. Layer 2 would be MAC, physical addressing, media access (timing, concurrent access). Layer 3 would be IP, "logical" addressing, first error detection. Layer 4 would be TCP/UDP, with subaddressing for both, retransmistion and congestion control with TCP. Layer 5 finally is your SSH/NFS. You see an error in layer 5, which leaves lots of possibilities for underlying errors or misconfigurations. In general TCP is quite capable of recovering from lots of errors, but it's busy with itself for this purpose, which leaves less capacity for its payload. IP does not correct errors, only detects (checksums). This leaves possible error correction to layer 2 and 1. In layer 2 we have a mixture of Ethernet and a back off algorithm, pretty like ethernet, but in Python code: the framing and thus addressing is done by the operating system, media access is handled by Python, using an exponential backoff when a carrier is sensed. Note: AFAICS check for successful transmission is done. On Ethernet you have Collision Detection, which leads to backoffs and retransmits. The current tunnel implementation seems to just listen for traffic that could jam the transmission before sending. As there is no reliable way to detect concurrent transmissions while sending (in contrast to wire bound Ethernet)[1] some kind of reservation like in WLAN or at least acknowledge would be desirable. Layer 1 finally uses whatever modulation you have available, without channel coding, like forward error correction (FEC) with convolution codes or Reed-Solomon code. This is quite a stack of systems with lots of places for errors. I'd suggest to get some levels lower and analyse at MAC (L2) and network layer (L3, IP). IP has checksums, so errors are very likely to be reported by the IP stack in the kernel. Take a look at 'iptraf'. As presumingly 'ifconfig' and and 'netstat -i' show interface statistics, that is of the MAC, you probably want to take a look at the packets directly. As pointed out before, tcpdump get you the packets. I like wireshark, formerly ethereal, for analysing data, but it needs X, something that is not always accessible at test machines (especially remote machines). nevertheless tcpdump saves data in a format that is fine readable for wireshark. Take a look at the IP checksum under heavy load. You may want to check some timing statistics too see if collision has probably happened. TCP retransmits are a sign for connections that have gone haywire. > Anyone have any thoughts on improving the stability? FEC would be necessary, media reservation or at least acknowledging would be fine. Perhaps CRC at data link layer (L2) would bring some light in. Emulab should have the right setup to test these things. Patrick [1] ALOHA as predecessor of Ethernet and being a radio system used acknowledge messages and retransmits. See code at http://typo3.cs.uni-paderborn.de/en/research-group/research-group-computer-networks/projects/gsr.html -- Engineers motto: cheap, good, fast: choose any two Patrick Strasser Student of Telematik, Techn. University Graz, Austria ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Smart Antenna
Roberto Mastrodonato wrote: > Hi all > > is there anybody that experienced USRP projects with SMART Antenna > technology? If yes, where can I find codes or something else related to > USRP-SMART Antenna? > Thanks a lot I have been experimenting with direction finding and passive radar using gnuradio and multiple antenna's. These experiments are on hold for now, due to lack of time, but I hope to continue with them sometime in the future. What exactly would you like to do and with how much array-elements. The simplest smart antenna using usrp/gnuradio I can think of is a smart transmitter using two antenna's. The phase-difference you introduce between the two signals, combined with the positioning of your two antenna's determines the maximum and minimum gain direction(s) of the whole system. Introducing a fixed phase difference is just multiplying with a const complex number. Phi=wanted phase difference in radians signal=original signal to transmit sink1=sink where the first output should go sink2=sink where the second output should go phasediff=gr.multiply_const_cc(gr_complex(cos(Phi),sin(Phi)) fg.connect(signal,sink1) fg.connect(signal,phasediff,sink2) The same goes for reception: Phi=expected phase difference in radians input1=signal from first antenna input2=signal from second antenna receiver=reception chain phasediff=gr.multiply_const_cc(gr_complex(cos(Phi),sin(Phi)) adder=gr.add_cc() fg.connect(signal1,(adder,0)) fg.connect(signal2,phasediff,(adder,1)) fg.connect(adder,receiver) If you want to automatically determine the phase-differences and amplitudes things get much more complicated but can still be done. I even tested with a very slow correlator and agc which automatically determined the phase difference of the strongest signal received and tuned the two antenna array for maximum sensitivity for this signal. Greetings, Martin > > Roberto > > > > > ___ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Smart Antenna
Hi where cai I find MIMO USRP codes? 10x R 2007/1/19, Lin HUANG <[EMAIL PROTECTED]>: Hi Roberto, I don't think there is code related to Smart Antenna, but many people are working on MIMO-USRP. The difference between them is the correlation between antennas. If you have antenna array for smart antenna, I think you may utilize some code of MIMO. Lin 2007/1/18, Roberto Mastrodonato <[EMAIL PROTECTED]>: > > Hi all > > is there anybody that experienced USRP projects with SMART Antenna > technology? If yes, where can I find codes or something else related to > USRP-SMART Antenna? > Thanks a lot > > Roberto > > ___ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
