Hi , I made a mistake. The unit of the throughput is wrong. It should be Kb/s. And I wrote a TCP client and server to run over the gr-ieee802-11. I set the sample rate to 5M so that no O errors and the packet lost rate is only 3%. Also I choose the BPSK1/2 encoding. The throughput is only 115K bits/s as shown by my TCP server. If I run my program over wifi cards, the result is around 15M bits/s. I mean my program works fine. Then how to explain the relationship between the 5M and the 115K bits/s throughput?
Best regards. Siyu 2017-06-08 21:41 GMT+08:00 Bastian Bloessl <m...@bastibl.net>: > Hi, > > On 06/07/2017 02:32 PM, zhan siyu wrote: > >> Thanks for your reply. Let me explain what I 'm doing. >> >> I have two B210s connected with two computers. I want to measure the >> throughput between the two computers over the usrp connection over >> gr-ieee802-11. But no matter how hard I try, like tuning the parameters and >> turning off my own wifi card and AP, I can only get 150K B/s, which should >> be around 300K B/s if my theoretical calculation is right. There are no >> underrun or overrun errors. The throughput measurement tool I'm using is >> iperf, which is an application to measure the end to end throughput. >> >> Could you give me some hints? >> > > I'm afraid I can't help a lot, since I have no idea what iperf is doing. I > guess it floods the network stack with UDP packets. The GNU Radio > transceiver, however, has no back pressure mechanism, so it will just drop > the frames when they are injected into the GNU Radio flow graph. > > Also, I don't understand what exact analytical number you are trying to > reproduce here. In fact, I have no idea what this experiment is supposed to > show/prove or what part of the transceiver you are trying to profile. If, > at all, this experiment will tell you how fast the TX-side can produce > frames. > > This was investigated in > > Gonzalo Arcos, Rodrigo Ferreri, Matías Richart, Pablo Ezzatti and Eduardo > Grampín, "Accelerating an IEEE 802.11 a/g/p Transceiver in GNU Radio," > Proceedings of 9th Latin America Networking Conference (LANC'16), > Valparaíso, Chile, October 2016, pp. 13-19. > > Turns out, you can improve the TX-side by improving the OFDM Carrier > Allocator. > > Best, > Bastian > > > >> Best regards. >> >> Siyu >> >> 2017-06-07 14:02 GMT+08:00 Bastian Bloessl <m...@bastibl.net <mailto: >> m...@bastibl.net>>: >> >> >> Hi, >> >> On 06/07/2017 03:04 AM, zhan siyu wrote: >> >> Thanks. I just wonder why. Because I meet some performance >> problem. I thought it maybe caused by my misconfiguration of the >> gr-ieee802-11 code. Now, it seems not. >> >> >> I'm a bit confused why the fact that the transceiver is not >> configured through iwconfig ruled out any configuration issues, but >> great that all seems to be set up now. >> >> >> However, theoretically, as my current sample rate is 10M and >> BPSK. So the coding rate should be 10M/2 = 5M b/s. The >> throughtput should be around 5M/8 = 625K B/s. Assuming the 12% >> head cost, so the data throughput should be 625 * 88 % = 550K >> B/s. But as my experiment shows, the throughput is only 150K B/s. >> >> I'm new to the communication. Is my calculation right ? >> >> >> BPSK 1/3 is 3Mbit/s gross at 10MHz. The overhead per packet has to >> be subtracted, i.e. the actual maximum rate depends on the frame size. >> >> >> If it were right, then what might cause the gap? >> >> >> Since you don't explain what you are doing, this is very hard to >> tell. You would reach this theoretical throughput only if you send >> frames back-to-back (which probably only works if you pregenerate >> the sample stream). But also a WiFi card will insert inter-frame >> space, so that the actual throughput will not match the theoretical >> maximum physical layer throughput. >> >> Best, >> Bastian >> >> >> >> One more question, I didn't run the volk_profile. Does it matter? >> >> Best regards. >> >> Siyu >> >> >> 2017-06-07 4:23 GMT+08:00 Bastian Bloessl <m...@bastibl.net >> <mailto:m...@bastibl.net> <mailto:m...@bastibl.net >> >> <mailto:m...@bastibl.net>>>: >> >> Hi, >> >> On 06/06/2017 03:55 PM, zhan siyu wrote: >> >> Hi all, >> >> I just found I can't use the iwconfig tap0 rate 20M to >> setup the >> bandwidth of the tap0. The error message is : >> >> Error for wireless request "Set Bit Rate" (8B20) : >> SET failed on device tap0 ; Operation not >> supported. >> >> But in their video , it can be set in this way. May I >> know how >> to solve it ? >> >> >> The WiFi transceiver is attached to the tun/tap interface, >> which is >> a virtual Ethernet device. This device doesn't support >> WiFi-specific >> configuration through iwconfig. >> >> If you wanted this level of integration, you would have to >> write a >> kernel module that attaches the transceiver to a virtual >> WiFi card. >> >> Some group already did that, but they didn't release the >> source code. >> >> Best, >> Bastian >> >>
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