TechInfoDepot:MIMO

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MIMO[edit]

Multiple-input Multiple-Output (MIMO) is a communication method for wireless transmission where both

transmitter and receiver use multiple antennas.

The use of multiple antennas at both sides of the link creates a multi-path propagation environment

between transmitter and receiver that can be used to significantly improve the system throughput.

The origin of the improvement can be intuitively understood by thinking of the multi-path propagation

MIMO environment as the equivalent of several separate paths between transmitter and receiver.

Every one of these paths (or “streams”) can be independently used for data transmission with each

employing the full bandwidth available to the system. This is referred to as spatial multiplexing.

The higher the number of antennas, the higher the multiplexing gain.

In addition, MIMO enables other advanced techniques like beamforming and MU-MIMO.

The higher the number of antennas, the more efficient these techniques become.

MU-MIMO[edit]

Multi-User MIMO (MU-MIMO) provides an alternative use of the spatial multiplexing that is provided by MIMO.

MIMO enables the transmission of multiple independent streams between a transmitter and a receiver with
multiple antennas. However, without MU-MIMO, the spatial multiplexing gain is limited by the number
of antennas at the client devices (typically one or two), leaving a lot of spatial diversity unused.

MU-MIMO extends the MIMO concept to the case with one transmitter and multiple receivers (Downlink MU-MIMO)

or to the case with one receiver and multiple transmitters (Uplink MU-MIMO), allowing the full use of the spatial
diversity provided by the channel. Instead of being able to transmit to a single client, an MU-MIMO capable
system can transmit to several clients simultaneously, using the full bandwidth of each link.

802.11a/g[edit]

Proprietary MIMO technology can be found in some Wireless-G devices.

However, both the access point and the adapter must support the same technology.

These proprietary MIMO modes are not standardized between vendors..

Most high throughput modes (including some branded as MIMO) do not use MIMO tech.

Proprietary vendor specific MIMO modes, by manufacturer[edit]

Airgo True MIMO (Gen1, AGN100) - max. PHY rate of 108Mbps (2x2/2x3),

two spatial streams
7 client adapters using AGN1xx, 6Empty strings are not accepted. embedded systems using AGN1xx

Airgo True MIMO (Gen3, AGN300) - max. PHY rate of 240Mbps (2x2/2x3) • PCWordl,

two spatial streams, channel bonding
14 client adapters using AGN3xx, 6Empty strings are not accepted. embedded systems using AGN3xx

Atheros VLocity (AR5513) - 108Mbps (two Tx/Rx chains, single spatial stream

[not really 'True' MIMO], channel bonding [Super G / Super AG])
11 client adapters using AR5513, 4Empty strings are not accepted. embedded systems using AR5513

Additional (non-MIMO) proprietary vendor specific modes, by manufacturer[edit]

Atheros Super G / Super AG - 108Mbps max. signalling rate (w/ channel bonding)

Super G (wireless networking) on Wikipedia

Broadcom Afterburner (125HSM) - 125Mbps theoretical max. signalling rate

125 High Speed Mode on Wikipedia
  • Linksys SpeedBooster

Ralink MIMO XR - 108Mbps (while branded MIMO, RT2661 only supports multiple receive chains..)

  • Linksys RangeBooster
  • Belkin Wireless G Plus MIMO
35 client adapters using RT2661, 17Empty strings are not accepted. embedded systems using RT2661

Intersil Nitro - claimed ~140Mbps throughput (per Wikipedia)

Nitro (wireless networking) on Wikipedia

802.11n[edit]

MIMO is a part of the 802.11n specification. Different notations may be used

to describe the MIMO capabilities of a given device.

TxR:S

  • T: Number of transmit radio chains
  • R: Number of receive radio chains
  • S: Number of spatial data streams
1x1:1 - 150Mbps transmitting and receiving
1x2:2 - 150Mbps transmitting, 300Mbps receiving
2x2:2 - 300Mbps transmitting and receiving
2x3:2 - 300Mbps transmitting and receiving
3x3:2 - 300Mbps transmitting and receiving
3x3:3 - 450Mbps transmitting and receiving

May also be described as xTyR where x is the number of transmit radio chains and y is the number

of receive radio chains. This notation neglects the number of spatial data streams.
  • 1T1R SISO - 150Mbps transmitting and receiving (single input single output)
  • 1T2R MISO - 150Mbps transmitting, 300Mbps receiving (multiple input single output)
  • 2T2R MIMO - 300Mbps transmitting and receiving (multiple input multiple output)
  • 2T3R MIMO - Usually 300Mbps transmitting and receiving (multiple input multiple output)
  • 3T3R MIMO - 300Mbps or 450Mbps transmitting and receiving depending on the number
of spatial streams (multiple input multiple output)

What is a "Stream" anyway? (how 802.11n works)

Modulations[edit]

Modulations 802.11.png

See also[edit]

Tables[edit]

No QAM[edit]

  802.11a 802.11b 802.11g 802.11n 802.11ac 802.11ad 802.11ax 802.11ay 802.11??
1x1:1 54 11 54 150 433 4620 N/A?    
2x2:2   N/A   300 867        
3x3:3   N/A   450 1300        
4x4:4   N/A   600 1733        
5x5:5   N/A     2165        
6x6:6   N/A     2598        
7x7:7   N/A     3031        
8x8:8   N/A     3464        
9x9:9   N/A              
10x10:10   N/A              

64-QAM[edit]

  802.11a 802.11b 802.11g 802.11n 802.11ac 802.11ad 802.11ax 802.11ay 802.11??
1x1:1   N/A              
2x2:2   N/A              
3x3:3   N/A              
4x4:4   N/A              
5x5:5   N/A              
6x6:6   N/A              
7x7:7   N/A              
8x8:8   N/A              
9x9:9   N/A              
10x10:10   N/A              

256-QAM[edit]

  802.11a 802.11b 802.11g 802.11n 802.11ac 802.11ad 802.11ax 802.11ay 802.11??
1x1:1   N/A         961    
2x2:2   N/A         1922    
3x3:3   N/A              
4x4:4   N/A   800 1733   3844    
5x5:5   N/A              
6x6:6   N/A              
7x7:7   N/A              
8x8:8   N/A         7688    
9x9:9   N/A              
10x10:10   N/A              

1024-QAM[edit]

  802.11a 802.11b 802.11g 802.11n 802.11ac 802.11ad 802.11ax
2.4/5
802.11ay 802.11??
1x1:1   N/A         574/1201    
2x2:2   N/A         1148/2402    
3x3:3   N/A              
4x4:4   N/A   1000 2167   2296/4804    
5x5:5   N/A              
6x6:6   N/A              
7x7:7   N/A              
8x8:8   N/A         4592/9608    
9x9:9   N/A              
10x10:10   N/A