Hi Felix, thank you for your explanation and being pation with me. I learn it by my self and keywords you gave help me to find needed information. So, i continue to digg in to google books and wikis now.
I see now, that my initial assumption that STBC some thing like "frequency diversity" is wrong. Well, it say by itself Space and Time, no freq :) Am 02.05.2013 20:01, schrieb Felix Fietkau: > On 2013-05-02 7:32 PM, Oleksij Rempel wrote: >> Am 02.05.2013 18:55, schrieb Adrian Chadd: >>> On 2 May 2013 01:11, Oleksij Rempel <li...@rempel-privat.de> wrote: >>> >>>> +#define WLAN_RC_TX_STBC_FLAG 0x20 /* TX STBC */ >>>> +#define WLAN_RC_RX_STBC_FLAG 0xC0 /* RX STBC ,2 bits */ >>> >>> I thought we covered this; why are you marking two bits here? >> >> becouse firmware checks for two bits (and then use it as bool ;)), so i >> pass what firmware can handle. >> >>> Atheros 11n hardware only supports 1-stream STBC RX. >> >> Did you got my email with lots of assumptions and questions? >> What do you mean by 1-stream STBC RX? After i did some home work on STBC >> i see that it encoded from at least two spatial streams. >> Is >> 1-stream STBC RX = 2 spatial streams with mirrored data? >> and >> 2-stream STBC RX = 4 spatial streams with mirrored data? >> >> or >> >> 1-stream STBC RX = compatibility mode for one stream hardware(so only of >> two streams received)? > When you're talking about 'streams', please specify where you're talking > about Spatial Streams (Nss, defined by the MCS), or Space-Time Streams > (Nsts). STBC is useful whenever the number of possible Space-Time > streams exceeds the number of Spatial streams, i.e. if the number of tx > chains is bigger than the number of spatial streams. > There's an asymmetry between Rx and Tx here. If a receiver has 1 chain > and the transmitter has 2 chains, tx can use 2 Space-Time streams to > encode 1 Spatial stream to improve the reliability of the signal. > The HT STBC capability field indicates the maximum number of Spatial > Streams, not Space-Time streams. Atheros hardware only supports STBC > with Nss = 1, so announcing 2-stream STBC is definitely wrong. Ok, i finally found it on ieee 802.11 specification. For STBC: Nsts=2 - Nss=1 Nsts=3 - Nss=2 Nsts=4 - Nss=2 Nsts=4 - Nss=3 >> That would make sense for 1x1:1 hardware, but if you say all atheros N >> hardware support only 1-stream STBC RX, will mean that STBC is useless >> on this hardware. > Only STBC With Nss=1, Nsts=2 is supported, but this does not make it > useless at all. It helps, even if the receiver only has one antenna. Found it too.. :) Thx! -- Regards, Oleksij _______________________________________________ ath9k-devel mailing list ath9k-devel@lists.ath9k.org https://lists.ath9k.org/mailman/listinfo/ath9k-devel
