How do USB wireless N adapters get by with one antenna connector?

On 21 Nov 2010 08:22:53 +1000, in <4ce83c2d$(E-Mail Removed)>, "me
here" <(E-Mail Removed)> wrote:

>
>After reading a current post, and looking at a wireless N PCI card with
>the usual 2 or 3 antennas, and then looking at a USB N adapter, I have
>to ask how the USB adapter gets by with one antenna.
>
>To go directional antenna with N obviously you don't want multiple
>yagi's etc to deal with, so the USB adapter appears to have a distinct
>advantage in this aspect.
>
>So how does the USB adapter do it?

<http://www.wi-fi.org/files/kc/WFA_802_11n_Industry_June07.pdf>

Even single-antenna mobile devices, such as Wi-Fi phones, will enjoy
the benefits of increased range and throughput of Wi-Fi CERTIFIED
802.11n by virtue of the transmit diversity capabilities, such as
Space Time Block Coding (STBC), Cyclic Shift Diversity (CSD) and
Transmit Beamforming.

802.11n is well-equipped to improve the operating range even for
single-antenna handheld devices used in such outdoors networks.
Increased range of handheld devices is achieved through AP transmit
and receive diversity mechanisms. Transmit diversity of APs,
including STBC and transmit Beamforming, improves the downlink range
performance. Receive diversity of APs, including MRC, reciprocate the
transmit diversity and thus maintain the range for both the uplink
and the downlink directions.

--
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FAQ for Wi-Fi: <http://wireless.navas.us/wiki/Wi-Fi>
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Fixes to Wi-Fi Problems: <http://wireless.navas.us/wiki/Wi-Fi_Fixes>

After reading a current post, and looking at a wireless N PCI card with
the usual 2 or 3 antennas, and then looking at a USB N adapter, I have
to ask how the USB adapter gets by with one antenna.

To go directional antenna with N obviously you don't want multiple
yagi's etc to deal with, so the USB adapter appears to have a distinct
advantage in this aspect.

So how does the USB adapter do it?

--

John Navas wrote:

> On 21 Nov 2010 08:22:53 +1000, in <4ce83c2d$(E-Mail Removed)>, "me
> here" <(E-Mail Removed)> wrote:
>
> >
> > After reading a current post, and looking at a wireless N PCI card
> > with the usual 2 or 3 antennas, and then looking at a USB N
> > adapter, I have to ask how the USB adapter gets by with one antenna.
> >
> > To go directional antenna with N obviously you don't want multiple
> > yagi's etc to deal with, so the USB adapter appears to have a
> > distinct advantage in this aspect.
> >
> > So how does the USB adapter do it?
>
> <http://www.wi-fi.org/files/kc/WFA_802_11n_Industry_June07.pdf>
>
> Even single-antenna mobile devices, such as Wi-Fi phones, will
> enjoy the benefits of increased range and throughput of Wi-Fi
> CERTIFIED 802.11n by virtue of the transmit diversity
> capabilities, such as Space Time Block Coding (STBC), Cyclic Shift
> Diversity (CSD) and Transmit Beamforming.
>
> 802.11n is well-equipped to improve the operating range even for
> single-antenna handheld devices used in such outdoors networks.
> Increased range of handheld devices is achieved through AP transmit
> and receive diversity mechanisms. Transmit diversity of APs,
> including STBC and transmit Beamforming, improves the downlink
> range performance. Receive diversity of APs, including MRC,
> reciprocate the transmit diversity and thus maintain the range for
> both the uplink and the downlink directions.

OK thanks for that.

So a PCI card could theoretically still get by with just one antenna?

--

me here wrote:

> John Navas wrote:
>
> > On 21 Nov 2010 08:22:53 +1000, in <4ce83c2d$(E-Mail Removed)>,
> > "me here" <(E-Mail Removed)> wrote:
> >
> > >
> > > After reading a current post, and looking at a wireless N PCI card
> > > with the usual 2 or 3 antennas, and then looking at a USB N
> > > adapter, I have to ask how the USB adapter gets by with one
> > > antenna.
> > >
> > > To go directional antenna with N obviously you don't want multiple
> > > yagi's etc to deal with, so the USB adapter appears to have a
> > > distinct advantage in this aspect.
> > >
> > > So how does the USB adapter do it?
> >
> > <http://www.wi-fi.org/files/kc/WFA_802_11n_Industry_June07.pdf>
> >
> > Even single-antenna mobile devices, such as Wi-Fi phones, will
> > enjoy the benefits of increased range and throughput of Wi-Fi
> > CERTIFIED 802.11n by virtue of the transmit diversity
> > capabilities, such as Space Time Block Coding (STBC), Cyclic
> > Shift Diversity (CSD) and Transmit Beamforming.
> >
> > 802.11n is well-equipped to improve the operating range even for
> > single-antenna handheld devices used in such outdoors networks.
> > Increased range of handheld devices is achieved through AP
> > transmit and receive diversity mechanisms. Transmit diversity of
> > APs, including STBC and transmit Beamforming, improves the
> > downlink range performance. Receive diversity of APs, including
> > MRC, reciprocate the transmit diversity and thus maintain the
> > range for both the uplink and the downlink directions.
>
> OK thanks for that.
>
> So a PCI card could theoretically still get by with just one antenna?


Actually I can answer my own question on this as after doing a bit of
browsing I see that the TP-Link TL-WN781N PCI card only has one antenna.

So you can get them.

If going directional with PCI, this would make much more sense than
having to deal with multiple antenna.

But USB is the better option as stated.

--

me here <(E-Mail Removed)> wrote:

> After reading a current post, and looking at a wireless N PCI card with
> the usual 2 or 3 antennas, and then looking at a USB N adapter, I have
> to ask how the USB adapter gets by with one antenna.

They could use Metamaterials and cram several antennas in the adapter:

http://www.smallnetbuilder.com/content/view/30274/100/

Axel Hammerschmidt wrote:

> me here <(E-Mail Removed)> wrote:
>
> > After reading a current post, and looking at a wireless N PCI card
> > with the usual 2 or 3 antennas, and then looking at a USB N
> > adapter, I have to ask how the USB adapter gets by with one antenna.
>
> They could use Metamaterials and cram several antennas in the adapter:
>
> http://www.smallnetbuilder.com/content/view/30274/100/

Interesting article.

I suppose they could do as you say with USB adapters, but I doubt that
is the case in instances where a single antenna connector is used.

More likely to be as JN posted.

I notice that the megamaterial antennas have reasonable separation in
the board shown, and to put multiple very small antennas in close
proximity in the end of a USB adapter may be asking a bit much.

--

me here wrote:
>
> After reading a current post, and looking at a wireless N PCI card with
> the usual 2 or 3 antennas, and then looking at a USB N adapter, I have
> to ask how the USB adapter gets by with one antenna.
>
> To go directional antenna with N obviously you don't want multiple
> yagi's etc to deal with, so the USB adapter appears to have a distinct
> advantage in this aspect.
>
> So how does the USB adapter do it?

I don't know about N, but all A, B and G connectors with multiple
attennas internally pick the one antenna with the best signal strength.
They do not actually use all their antennas.

Jeff Liebermann wrote:

> On Mon, 22 Nov 2010 10:10:47 -0800, Philip <(E-Mail Removed)> wrote:
>
> > I don't know about N, but all A, B and G connectors with multiple
> > attennas internally pick the one antenna with the best signal
> > strength. They do not actually use all their antennas.
>
> 802.11a,b, and g radios use two antennas for "receive diversity". The
> purpose of diversity is to reduce frequency selective fading:
> <http://www.cisco.com/en/US/tech/tk72...s_tech_note091
> 86a008019f646.shtml>
> <http://www.eetimes.com/design/other/4008994/Dual-Rx-boosts-WLAN-OFDM>
> <http://www.eetimes.com/design/commun...8941/Antenna-D
> iversity-Strengthens-Wireless-LANs>
>
> 802.11n uses multiple antennas for "MIMO spatial diversity", "beam
> forming", or both.
> <http://hubpages.com/hub/spatial-multiplexing-spatial-diversity>
> <http://www.radio-electronics.com/inf...enna-beamformi
> ng.php>
> <http://www.ruckuswireless.com/whitep...tifying_beamfo
> rming>
>
> Single antenna 802.11n is somewhat of a mystery to me. As near as I
> can decode the various papers, it requires an access point with 2 or
> more antennas, that provides "transmit diversity" to the MIMO
> supported single antenna client radio. If it did exist, the access
> point would be labeled 2T1R, which Google can't seem to find. I've
> also never played with these devices, and therefore cannot comment
> much on them.
>
> Misusing MIMO
> <http://www.smallnetbuilder.com/blog/30133-misusing-mimo>
> In my never humble opinion, single antenna or single stream MIMO is
> not really MIMO, but I can easily be convinced otherwise with a
> demonstration of such a system going faster than what could
> theoretically be achieved with a non-MIMO equivalent. Google for
> "1T2R".

I did a bit of research and reading some of the available paperwork and
it appears that more antennas equals more speed with N,

I at first went along with the notion that access points need at least
two antennas, and then I found this product:

http://www.kenable.co.uk/product_inf...oducts_id=3799

So it looks like that's also variable.

I've stuck with G because it's easy to set up directional antennas, but
looking at N if products as above are capable of better comparative
performance, and a single directional antenna can be fitted (yes
upgradable in this case), maybe they are worth considering - 4X better
???.





--

Well fro what i have been told because i 2 am thinking about buying a wireless usb adapter some people have been telling me that all that needs to be done is just to buy the adapter install the cd that comes with it first and then u can use it as a wireless receiver to help you to receive a wireless signal but you don't need a router and it don't matter if you have dial up or whatever.

Meanwhile, at the alt.internet.wireless Job Justification Hearings, Jeff
Liebermann chose the tried and tested strategy of:

> Here's another example:
> <http://www.ubnt.com/bulletm>
> They claim the Bullet 2M will do 100+ mbits/sec "real TCP throughput".
> Well, their own data sheet on the product quits at 54 Mbits/sec
> association (thruput is about half of this speed). No 100+ Mbits/sec
> in sight.
> <http://www.ubnt.com/downloads/bm2hp_datasheet.pdf>

A quick google for 'mcs0 data rate' turns up this:

http://www.ubnt.com/forum/showthread.php?t=23941

which isn't quite 100Mbps TCP, but more than you'd get if the wireless rate
topped out at 54Mbps.

> Looking at the feature list at:
> <http://www.ubnt.com/downloads/wiki/UBNT-AOS_prod-specs-rf_5.pdf>
> shows that it doesn't support MIMO. So, where did the 100+ MBits/sec
> thruput come from? Probably from the advertising agency or marketing
> department.

From looking at Ubiquiti's marketing material, I would be surprised if their
advertising 'agency' was anything other than Adwords ;-)

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