* [ath9k-devel] Is there a way to connect pairs of wifi cards to achieve full duplex @ 2013-06-19 16:50 David Goodenough 2013-06-19 22:09 ` Ben Greear 0 siblings, 1 reply; 8+ messages in thread From: David Goodenough @ 2013-06-19 16:50 UTC (permalink / raw) To: ath9k-devel I would like to have a point to point full duplex link (outdoors). I realise that this can not be done with a single wifi card/antenna, I will need a pair. I only need a single point to point link, not a master/slave setup. I would want the low level protocol bits to work this way as well so that ACKS and management responses to work this way as well as data packets. Any ideas? David ^ permalink raw reply [flat|nested] 8+ messages in thread
* [ath9k-devel] Is there a way to connect pairs of wifi cards to achieve full duplex 2013-06-19 16:50 [ath9k-devel] Is there a way to connect pairs of wifi cards to achieve full duplex David Goodenough @ 2013-06-19 22:09 ` Ben Greear 2013-06-19 22:56 ` Adrian Chadd 0 siblings, 1 reply; 8+ messages in thread From: Ben Greear @ 2013-06-19 22:09 UTC (permalink / raw) To: ath9k-devel On 06/19/2013 09:50 AM, David Goodenough wrote: > I would like to have a point to point full duplex link (outdoors). I realise > that this can not be done with a single wifi card/antenna, I will need a pair. > > I only need a single point to point link, not a master/slave setup. > > I would want the low level protocol bits to work this way as well so that ACKS > and management responses to work this way as well as data packets. > > Any ideas? That sounds interesting. I wonder if some specialized type of bonding interface could do the trick. I'd guess you wouldn't need any specific driver support. The bond would just always TX on pair A (with peer TX pair B). I'd ask around on the bonding mailing list (assuming such thing exists) and see if they have any suggestions. Thanks, Ben > > David > _______________________________________________ > ath9k-devel mailing list > ath9k-devel at lists.ath9k.org > https://lists.ath9k.org/mailman/listinfo/ath9k-devel > -- Ben Greear <greearb@candelatech.com> Candela Technologies Inc http://www.candelatech.com ^ permalink raw reply [flat|nested] 8+ messages in thread
* [ath9k-devel] Is there a way to connect pairs of wifi cards to achieve full duplex 2013-06-19 22:09 ` Ben Greear @ 2013-06-19 22:56 ` Adrian Chadd 2013-06-19 22:58 ` Ben Greear 0 siblings, 1 reply; 8+ messages in thread From: Adrian Chadd @ 2013-06-19 22:56 UTC (permalink / raw) To: ath9k-devel .. just keep in mind that adjacent high power transmitters can actually leak enough RF to trigger ADC saturation and thus the device may actually not try to decode anything. Thus, whilst your TX is TXing, the RX side may be unhappy. :-) Adrian (This is why TDMA is awesome.) On 19 June 2013 15:09, Ben Greear <greearb@candelatech.com> wrote: > On 06/19/2013 09:50 AM, David Goodenough wrote: >> I would like to have a point to point full duplex link (outdoors). I realise >> that this can not be done with a single wifi card/antenna, I will need a pair. >> >> I only need a single point to point link, not a master/slave setup. >> >> I would want the low level protocol bits to work this way as well so that ACKS >> and management responses to work this way as well as data packets. >> >> Any ideas? > > That sounds interesting. > > I wonder if some specialized type of bonding interface could do > the trick. I'd guess you wouldn't need any specific driver > support. The bond would just always TX on pair A (with peer TX pair B). > > I'd ask around on the bonding mailing list (assuming such thing exists) > and see if they have any suggestions. > > Thanks, > Ben > >> >> David >> _______________________________________________ >> ath9k-devel mailing list >> ath9k-devel at lists.ath9k.org >> https://lists.ath9k.org/mailman/listinfo/ath9k-devel >> > > > -- > Ben Greear <greearb@candelatech.com> > Candela Technologies Inc http://www.candelatech.com > > _______________________________________________ > ath9k-devel mailing list > ath9k-devel at lists.ath9k.org > https://lists.ath9k.org/mailman/listinfo/ath9k-devel ^ permalink raw reply [flat|nested] 8+ messages in thread
* [ath9k-devel] Is there a way to connect pairs of wifi cards to achieve full duplex 2013-06-19 22:56 ` Adrian Chadd @ 2013-06-19 22:58 ` Ben Greear 2013-06-20 10:26 ` David Goodenough 0 siblings, 1 reply; 8+ messages in thread From: Ben Greear @ 2013-06-19 22:58 UTC (permalink / raw) To: ath9k-devel On 06/19/2013 03:56 PM, Adrian Chadd wrote: > .. just keep in mind that adjacent high power transmitters can > actually leak enough RF to trigger ADC saturation and thus the device > may actually not try to decode anything. > > Thus, whilst your TX is TXing, the RX side may be unhappy. :-) We've had decent multi-NIC throughput when there is a mostly-solid aluminium chassis plate between the NICs, and when one is on 2.4 and the other is on 5Ghz. Pretty much anything else is pushing your luck though :) Ben -- Ben Greear <greearb@candelatech.com> Candela Technologies Inc http://www.candelatech.com ^ permalink raw reply [flat|nested] 8+ messages in thread
* [ath9k-devel] Is there a way to connect pairs of wifi cards to achieve full duplex 2013-06-19 22:58 ` Ben Greear @ 2013-06-20 10:26 ` David Goodenough 2013-06-20 17:58 ` Felix Fietkau 0 siblings, 1 reply; 8+ messages in thread From: David Goodenough @ 2013-06-20 10:26 UTC (permalink / raw) To: ath9k-devel On Wednesday 19 Jun 2013, Ben Greear wrote: > On 06/19/2013 03:56 PM, Adrian Chadd wrote: > > .. just keep in mind that adjacent high power transmitters can > > actually leak enough RF to trigger ADC saturation and thus the device > > may actually not try to decode anything. > > > > Thus, whilst your TX is TXing, the RX side may be unhappy. :-) > > We've had decent multi-NIC throughput when there is a mostly-solid > aluminium chassis plate between the NICs, and when one is on 2.4 > and the other is on 5Ghz. > > Pretty much anything else is pushing your luck though :) > > Ben The only place I have noticed that do this with wifi kit is Microtik who say they can do setups like this - but as usual with them there is no indication of how it is done under the covers. David ^ permalink raw reply [flat|nested] 8+ messages in thread
* [ath9k-devel] Is there a way to connect pairs of wifi cards to achieve full duplex 2013-06-20 10:26 ` David Goodenough @ 2013-06-20 17:58 ` Felix Fietkau 2013-06-20 18:13 ` David Goodenough 0 siblings, 1 reply; 8+ messages in thread From: Felix Fietkau @ 2013-06-20 17:58 UTC (permalink / raw) To: ath9k-devel On 2013-06-20 12:26 PM, David Goodenough wrote: > On Wednesday 19 Jun 2013, Ben Greear wrote: >> On 06/19/2013 03:56 PM, Adrian Chadd wrote: >> > .. just keep in mind that adjacent high power transmitters can >> > actually leak enough RF to trigger ADC saturation and thus the device >> > may actually not try to decode anything. >> > >> > Thus, whilst your TX is TXing, the RX side may be unhappy. :-) >> >> We've had decent multi-NIC throughput when there is a mostly-solid >> aluminium chassis plate between the NICs, and when one is on 2.4 >> and the other is on 5Ghz. >> >> Pretty much anything else is pushing your luck though :) >> >> Ben > The only place I have noticed that do this with wifi kit is Microtik > who say they can do setups like this - but as usual with them there is > no indication of how it is done under the covers. They're doing it with hacked up proprietary protocol modifications. So I get why you would want to do combine two links to get full-duplex. But why would you want to mess around with things like ACKs? - Felix ^ permalink raw reply [flat|nested] 8+ messages in thread
* [ath9k-devel] Is there a way to connect pairs of wifi cards to achieve full duplex 2013-06-20 17:58 ` Felix Fietkau @ 2013-06-20 18:13 ` David Goodenough 2013-06-20 20:09 ` Felix Fietkau 0 siblings, 1 reply; 8+ messages in thread From: David Goodenough @ 2013-06-20 18:13 UTC (permalink / raw) To: ath9k-devel On Thursday 20 Jun 2013, Felix Fietkau wrote: > On 2013-06-20 12:26 PM, David Goodenough wrote: > > On Wednesday 19 Jun 2013, Ben Greear wrote: > >> On 06/19/2013 03:56 PM, Adrian Chadd wrote: > >> > .. just keep in mind that adjacent high power transmitters can > >> > actually leak enough RF to trigger ADC saturation and thus the device > >> > may actually not try to decode anything. > >> > > >> > Thus, whilst your TX is TXing, the RX side may be unhappy. :-) > >> > >> We've had decent multi-NIC throughput when there is a mostly-solid > >> aluminium chassis plate between the NICs, and when one is on 2.4 > >> and the other is on 5Ghz. > >> > >> Pretty much anything else is pushing your luck though :) > >> > >> Ben > > > > The only place I have noticed that do this with wifi kit is Microtik > > who say they can do setups like this - but as usual with them there is > > no indication of how it is done under the covers. > > They're doing it with hacked up proprietary protocol modifications. > > So I get why you would want to do combine two links to get full-duplex. > But why would you want to mess around with things like ACKs? > > - Felix Most of my links are quite long, so removing any turnaround had got to be a good thing (hasn't it?). I presume that every time the link turns around you have to turn off the receive path (or at least disconnect it) and then power up the transmitter, and allow time for the receiver at the other end to sync. Then at the receiving end if it was transmitting before (this is point to point) it has to shut down the transmit path in an orderly fashion so that it remains loaded while active. Surely that has to take a significant time? By quite long I am talking up to 7km. David ^ permalink raw reply [flat|nested] 8+ messages in thread
* [ath9k-devel] Is there a way to connect pairs of wifi cards to achieve full duplex 2013-06-20 18:13 ` David Goodenough @ 2013-06-20 20:09 ` Felix Fietkau 0 siblings, 0 replies; 8+ messages in thread From: Felix Fietkau @ 2013-06-20 20:09 UTC (permalink / raw) To: ath9k-devel On 2013-06-20 8:13 PM, David Goodenough wrote: > On Thursday 20 Jun 2013, Felix Fietkau wrote: >> On 2013-06-20 12:26 PM, David Goodenough wrote: >> > On Wednesday 19 Jun 2013, Ben Greear wrote: >> >> On 06/19/2013 03:56 PM, Adrian Chadd wrote: >> >> > .. just keep in mind that adjacent high power transmitters can >> >> > actually leak enough RF to trigger ADC saturation and thus the device >> >> > may actually not try to decode anything. >> >> > >> >> > Thus, whilst your TX is TXing, the RX side may be unhappy. :-) >> >> >> >> We've had decent multi-NIC throughput when there is a mostly-solid >> >> aluminium chassis plate between the NICs, and when one is on 2.4 >> >> and the other is on 5Ghz. >> >> >> >> Pretty much anything else is pushing your luck though :) >> >> >> >> Ben >> > >> > The only place I have noticed that do this with wifi kit is Microtik >> > who say they can do setups like this - but as usual with them there is >> > no indication of how it is done under the covers. >> >> They're doing it with hacked up proprietary protocol modifications. >> >> So I get why you would want to do combine two links to get full-duplex. >> But why would you want to mess around with things like ACKs? >> >> - Felix > Most of my links are quite long, so removing any turnaround had got to > be a good thing (hasn't it?). I presume that every time the link turns > around you have to turn off the receive path (or at least disconnect it) > and then power up the transmitter, and allow time for the receiver at > the other end to sync. Then at the receiving end if it was transmitting > before (this is point to point) it has to shut down the transmit path > in an orderly fashion so that it remains loaded while active. Surely that has > to take a significant time? The rx/tx switching time is very short, short enough to be insignificant. The inter-frame duration, slot time, etc. are significantly longer, but aggregation effectively cuts it down to a fraction relative to the number of packets. With a lot of changes to the software it would be possible to disable the on-chip ACK functionality, retransmission, etc. However, I think the disadvantages outweigh the advantages, mainly due to the extra latency of processing lots of things in software that are currently accelerated by the hardware. The increase in complexity is not particularly nice either. - Felix ^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2013-06-20 20:09 UTC | newest] Thread overview: 8+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2013-06-19 16:50 [ath9k-devel] Is there a way to connect pairs of wifi cards to achieve full duplex David Goodenough 2013-06-19 22:09 ` Ben Greear 2013-06-19 22:56 ` Adrian Chadd 2013-06-19 22:58 ` Ben Greear 2013-06-20 10:26 ` David Goodenough 2013-06-20 17:58 ` Felix Fietkau 2013-06-20 18:13 ` David Goodenough 2013-06-20 20:09 ` Felix Fietkau
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