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

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.
Reply to
John Navas
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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?

Reply to
me here

OK thanks for that.

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

Reply to
me here

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.

Reply to
me here

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

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Reply to
Axel Hammerschmidt

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.

Reply to
me here

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.

Reply to
Philip

I don't know about N either, but I do know that it can use multiple antennas simultaneously. (Beamforming?).

Have a look at "phased array antennas" if no N docs are enlightening enough.

Reply to
bod43

802.11a,b, and g radios use two antennas for "receive diversity". The purpose of diversity is to reduce frequency selective fading: 802.11n uses multiple antennas for "MIMO spatial diversity", "beam forming", or both.

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

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".

Reply to
Jeff Liebermann

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:

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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 ???.

Reply to
me here

Yep.

It looks to me more like creative advertising. When I see benchmarks and reproduceable tests, I might believe it.

Here's another example:

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.

Looking at the feature list at:

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.

What are you trying to accomplish that would require more speed?

Reply to
Jeff Liebermann

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

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

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

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

Reply to
alexd

Which is pretty stupid when you think about it. Wireless is for mobile use. So what do you think happens to the signal in the first case, spatial diversity when you wriggle a bit on the chair with a laptop - on your lap?

Reply to
Axel Hammerschmidt

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