Probably a dumbest question to ask about MIMO & Single Stream routers

[zjohnr]

OK, what the heck.

I assume that since MIMO stands for Multiple-Input, Multiple-Output (correct?) that a Single Stream aka 150 Mbps router could never support MIMO. Right?

I am asking because while I think I understand some of the basic concepts at an overview level, I feel better getting a second opinion. And also because I frankly have never understood why Single Stream routers even exist, aside from creating an artificial (to me) marketing niche, of course.

The other thing(s) I really do not understand is what underlying component technologies have to all dance together in order to reach the theoretical link speeds the various router manufacturers claim.

For example, I have DIR-655 which I believe has a theoretical link speed of 300 Mbps. But I am not sure what technologies need to be enabled in both the client & the wireless access point (DIR-655) for this link rate to be displayed by an AP or client?

I understand variables such as signal strength can influence this, but I'm not asking how to improve my 802.11n speed. I'm just asking what needs to be working "under the covers" for 300 Mbps to be even a remote possibility?

MIMO? Channel bonding aka 40 MHz? Some other magic fairy dust or smoke?

Same question for 150 Mbps or 450 Mbps if anyone wants to take a stab at answering this?

-irrationally tedious john

 

[overdrive31]

http://www.overclock.net/networking-security/917186-wireless-information-troubleshooting.html

Wireless N @ 20MHz has 52 subcarriers per channel where 802.11g only has 48, the difference being 54Mbps for G and 65Mbps for N.

Wireless N has 1.25Mbps per subcarrier, subcarriers increase to 108 using 40MHz to produce speeds of 135-single, 270-2 stream, 405-3 stream, and 540-4 stream.

Single stream is just that, single. MIMO is more than one, so the answer is no.

Single stream 150 is the one stream of 65Mbps base N speed bonded using 40MHz mode effectively doubling to 135Mbps plus SGI to make it 150.

MIMO for example operates at 65 per stream @ 20MHz, 2 streams would be 130(150 w/ SGI), 3 streams 195(225 w/ SGI), 4 streams 260(300 w/ SGI).

MIMO channel bonded @ 40MHz doubles those figures, to 270/300(2 stream), 405/450(3 stream), 540/600(4 stream).

Channel bonding is not advised in 2.4GHz since it uses up 2/3 the spectrum, MIMO allows speed increases without channel bonding.

The highest common denominator will determine speed based on single or multiple streams used between a client and host ap.

 

[zjohnr]

Thank you. That helps a lot!

-irrational john

 

[thiggins]

Single stream N was created to allow less-expensive N-compliant devices to be created for mobile devices. It was never intended for use in access points and routers.

See also SmallNetBuilder's Wireless FAQ: The Essentials,
recently added Question 11

 

[zjohnr]

Thanks!

Single stream N was created to allow less-expensive N-compliant devices to be created for mobile devices. It was never intended for use in access points and routers.

Did anyone bother to tell the router manufacturers ... and their marketeering departments in particular ... about this?

See also SmallNetBuilder's Wireless FAQ: The Essentials, recently added Question 11

Thanks, Tim. Every extra bit of explaining "the obvious" helps in my case.

-irrational john