multiple-input and multiple-output, mimo (mee-moh or my-moh)

Multiple-Input and Multiple-Input and Multiple-OutputMultiple-Output, , MIMOMIMO((mee-mohmee-moh or or my-mohmy-moh))

Understanding of SISO, SIMO, Understanding of SISO, SIMO, MISO MISO and MIMOand MIMO

TopicsTopics IntroductionIntroduction What is MIMO?What is MIMO? History of MIMOHistory of MIMO Functions of MIMOFunctions of MIMO Forms of MIMOForms of MIMO Applications of MIMOApplications of MIMO Mathematical DescriptionMathematical Description

IntroductionIntroduction

In radio, In radio, multiple-input and multiple-multiple-input and multiple-outputoutput, or , or MIMOMIMO is the use of multiple is the use of multiple antennas at both the transmitter and antennas at both the transmitter and receiver to improve communication receiver to improve communication performance. performance.

It is one of several forms of It is one of several forms of smart smart antenna (SA),antenna (SA), and the state of the art and the state of the art of SA technology.of SA technology.


MIMO technology has attracted MIMO technology has attracted attention in attention in wireless communicationswireless communications, , since it offers significant increases in since it offers significant increases in data throughput and link range without data throughput and link range without additional bandwidth or transmit power.additional bandwidth or transmit power.

It achieves this by higher spectral It achieves this by higher spectral efficiency (more bits per second per efficiency (more bits per second per Hertz of bandwidth) and link reliability Hertz of bandwidth) and link reliability or diversity (reduced fading).or diversity (reduced fading).


MIMO is a current theme of international MIMO is a current theme of international wireless research. wireless research.

The major limitation encountered when The major limitation encountered when developing wireless technologies is that as developing wireless technologies is that as capacity increases so too must the capacity increases so too must the spectrum and/or transmitting power. To spectrum and/or transmitting power. To combat this problem, the use of multiple combat this problem, the use of multiple antennas at both ends has been proposed antennas at both ends has been proposed – popularly known as a multiple-input-– popularly known as a multiple-input-multiple-output (MIMO). multiple-output (MIMO).

What is MIMO?What is MIMO?

A technique for boosting wireless A technique for boosting wireless bandwidth and range by taking bandwidth and range by taking advantage of multiplexing. advantage of multiplexing.

What is MIMO?What is MIMO? MIMO wireless uses different waveforms on MIMO wireless uses different waveforms on

typically two, but sometimes three or more typically two, but sometimes three or more transmitting antennas inputting to the transmitting antennas inputting to the channel carrying radio waves from Point A to channel carrying radio waves from Point A to Point B. Multiple antennas and radios Point B. Multiple antennas and radios (typically, two or three) also are applied to (typically, two or three) also are applied to the output of the radio channel at the the output of the radio channel at the receiver, along with a lot of signal receiver, along with a lot of signal processing, which ideally improves range processing, which ideally improves range and throughput compared with simpler or and throughput compared with simpler or traditional radio designs operating under traditional radio designs operating under similar conditions. similar conditions.

What is MIMO?What is MIMO?

MIMO is at the heart of the MIMO is at the heart of the 802.11n802.11n draft specification for 100Mbps draft specification for 100Mbps wireless. wireless.

MIMO is sometimes referred to as MIMO is sometimes referred to as spatial multiplexing, because it uses a spatial multiplexing, because it uses a third, spatial dimension - beyond third, spatial dimension - beyond frequency and time - as a carrier for frequency and time - as a carrier for information.information.

History of MIMOHistory of MIMO

Background TechnologiesBackground Technologies

The earliest ideas in this field go back The earliest ideas in this field go back to work by A.R. Kaye and D.A. George to work by A.R. Kaye and D.A. George (1970) and W. van Etten (1975, 1976).(1970) and W. van Etten (1975, 1976).

Jack Winters and Jack Salz at Bell Jack Winters and Jack Salz at Bell Laboratories published several papers Laboratories published several papers on beamforming related applications in on beamforming related applications in 1984 and 1986.1984 and 1986.


Principal TechnologiesPrincipal Technologies

Arogyaswami PaulrajArogyaswami Paulraj and and Thomas Thomas KailathKailath proposed the concept of proposed the concept of Spatial Multiplexing using MIMO in Spatial Multiplexing using MIMO in 1993. Their US Patent No. 5,345,599 1993. Their US Patent No. 5,345,599 issued 1994 on Spatial Multiplexing issued 1994 on Spatial Multiplexing emphasized applications to wireless emphasized applications to wireless broadcast. broadcast.



In 1996, In 1996, Greg RaleighGreg Raleigh and and Gerard J. Gerard J. FoschiniFoschini refine new approaches to refine new approaches to MIMO technology, which considers a MIMO technology, which considers a configuration where multiple transmit configuration where multiple transmit antennas are co-located at one antennas are co-located at one transmitter to improve the link transmitter to improve the link throughput effectively.throughput effectively.



Bell Labs was the first to demonstrate Bell Labs was the first to demonstrate a laboratory prototype of a laboratory prototype of spatial spatial multiplexing (SM)multiplexing (SM) in 1998, where in 1998, where spatial multiplexing is a principal spatial multiplexing is a principal technology to improve the technology to improve the performance of MIMO communication performance of MIMO communication systems.systems.


Wireless StandardsWireless Standards

Iospan Wireless Inc.Iospan Wireless Inc. developed the developed the first commercial system in 2001 that first commercial system in 2001 that used MIMO-OFDMA technology. Iospan used MIMO-OFDMA technology. Iospan technology supported both diversity technology supported both diversity coding and spatial multiplexing.coding and spatial multiplexing.

In 2005, In 2005, Airgo NetworksAirgo Networks had had developed a pre-11n version based on developed a pre-11n version based on their patents on MIMO. their patents on MIMO.


Wireless StandardsWireless Standards Several companies (Beceem Communications, Several companies (Beceem Communications,

Samsung, Runcom Technologies, etc.) have Samsung, Runcom Technologies, etc.) have developed MIMO-OFDMA based solutions for developed MIMO-OFDMA based solutions for IEEE 802.16e WIMAX broadband mobile IEEE 802.16e WIMAX broadband mobile standard. All upcoming 4G systems will also standard. All upcoming 4G systems will also employ MIMO technology. Several research employ MIMO technology. Several research groups have demonstrated over 1 Gbit/s groups have demonstrated over 1 Gbit/s prototypes.prototypes.

Functions of MIMOFunctions of MIMO

MIMO can be sub-divided into three MIMO can be sub-divided into three main categories, main categories, precodingprecoding, , spatial multiplexingspatial multiplexing, or SM, and , or SM, and diversity codingdiversity coding..


PrecodingPrecoding - is multi-layer beamforming in a narrow sense or - is multi-layer beamforming in a narrow sense or all spatial processing at the transmitter in a wide-all spatial processing at the transmitter in a wide-sense.sense.- In (single-layer) beamforming, the same signal is - In (single-layer) beamforming, the same signal is emitted from each of the transmit antennas with emitted from each of the transmit antennas with appropriate phase (and sometimes gain) weighting appropriate phase (and sometimes gain) weighting such that the signal power is maximized at the such that the signal power is maximized at the receiver input. receiver input.


PrecodingPrecoding - when the receiver has multiple antennas, - when the receiver has multiple antennas, the transmit beamforming cannot the transmit beamforming cannot simultaneously maximize the signal level at simultaneously maximize the signal level at all of the receive antenna and precoding is all of the receive antenna and precoding is used. Note that precoding requires used. Note that precoding requires knowledge of the channel state information knowledge of the channel state information (CSI) at the transmitter. (CSI) at the transmitter.


Spatial multiplexingSpatial multiplexing - requires MIMO antenna - requires MIMO antenna configuration. configuration. - In spatial multiplexing, a high rate - In spatial multiplexing, a high rate signal is split into multiple lower rate signal is split into multiple lower rate streams and each stream is streams and each stream is transmitted from a different transmit transmitted from a different transmit antenna in the same frequency antenna in the same frequency channel. channel.


Spatial multiplexingSpatial multiplexing

- If these signals arrive at the receiver - If these signals arrive at the receiver antenna array with sufficiently different antenna array with sufficiently different spatial signatures, the receiver can spatial signatures, the receiver can separate these streams, creating parallel separate these streams, creating parallel channels for free. Spatial multiplexing is a channels for free. Spatial multiplexing is a very powerful technique for increasing very powerful technique for increasing channel capacity at higher channel capacity at higher Signal to Signal to Noise Ratio (SNR)Noise Ratio (SNR). .


Spatial multiplexingSpatial multiplexing

- The maximum number of spatial - The maximum number of spatial streams is limited by the lesser in the streams is limited by the lesser in the number of antennas at the transmitter number of antennas at the transmitter or receiver. Spatial multiplexing can or receiver. Spatial multiplexing can be used with or without transmit be used with or without transmit channel knowledge. channel knowledge.


Diversity codingDiversity coding

- used when there is no channel - used when there is no channel knowledge at the transmitter. In knowledge at the transmitter. In diversity methods a single stream diversity methods a single stream (unlike multiple streams in spatial (unlike multiple streams in spatial multiplexing) is transmitted, but the multiplexing) is transmitted, but the signal is coded using techniques signal is coded using techniques called called space-time codingspace-time coding. .


Diversity codingDiversity coding

- Diversity exploits the independent - Diversity exploits the independent fading in the multiple antenna links to fading in the multiple antenna links to enhance signal diversity. Because enhance signal diversity. Because there is no channel knowledge, there there is no channel knowledge, there is no beamforming or array gain from is no beamforming or array gain from diversity coding.diversity coding.

Forms of MIMOForms of MIMO

MIMO Communications

- Up to now, multi-antenna MIMO (or - Up to now, multi-antenna MIMO (or Single user MIMO) technology has Single user MIMO) technology has been mainly developed and is been mainly developed and is implemented in some standards, e.g. implemented in some standards, e.g. 802.11n (draft) products. 802.11n (draft) products.

Multi-antenna types

SISO/SIMO/MISO are degenerate cases of MIMO

• Multiple-input and single-output (MISO) is a degenerate case when the receiver has a single antenna.• Single-input and multiple-output (SIMO) is a degenerate case when the transmitter has a single antenna.• Single-input single-output (SISO) is a radio system where neither the transmitter nor receiver have multiple antenna.

Multi-antenna types

Multi-user types

-Recently, the research on multi-user MIMO technology is emerging. While full multi-user MIMO (or network MIMO) can have higher potentials, from its practicality the research on (partial) multi-user MIMO (or multi-user and multi-antenna MIMO) technology is more active.

• Multi-user MIMO (MU-MIMO) - Employ advanced decoding techniques.

• Cooperative MIMO (CO-MIMO)- Utilizes distributed antennas which belong to other users.

• MIMO Routing - Routing a cluster by a cluster in each hop, where the number of nodes in each cluster is larger or equal to one. MIMO routing is different from conventional (SISO) routing since conventional routing protocols route a node by a node in each hop.

Multi-user types

Applications of MIMOApplications of MIMO

MIMO is planned to be used in Mobile MIMO is planned to be used in Mobile radio telephone standards such as radio telephone standards such as recent 3GPP and 3GPP2 standards. recent 3GPP and 3GPP2 standards. In 3GPP, High-Speed Packet Access In 3GPP, High-Speed Packet Access plus (HSPA+) and Long Term plus (HSPA+) and Long Term Evolution (LTE) standards take MIMO Evolution (LTE) standards take MIMO into account. into account.

Mathematical DescriptionMathematical Description

MIMO channel model

Mathematical DescriptionMathematical Description• A transmitter sends multiple streams by multiple

transmit antennas. • The transmit streams go through a matrix channel which consists of multiple paths between multiple transmit antennas at the transmitter and multiple receive antennas at the receiver. • Then, the receiver gets the received signal vectors by the multiple receive antennas and decodes the received signal vectors into the original information.

Mathematical DescriptionMathematical Description•MIMO system model

y = Hx + n

where y and x are the receive and transmit

vectors, respectively. In addition, H and n are the channel matrix and the noise vector, respectively.

• The average capacity of a MIMO system is as follows:

which is min(N_t, N_r) times larger than that of a SISO system.

Mathematical DescriptionMathematical Description

Given the nature of MIMO, it is not limited to wireless communication. It can be used to wire line communication as well. For example, a new type of DSL technology (Gigabit DSL) has been proposed based on Binder MIMO Channels.

multiple-input and multiple-output, mimo (mee-moh or my-moh)

Documents

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mimo wireless

multipleoutput mimo

introduction mimo technology

mimo meemoh

moh slide

multiple output

wireless technologies