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4G using MIMO

Presented by:Joel AbrahamAnoop PrabhaBinaya Parhy

Why MIMODifferent Arrangements of AntennasWorkingMIMO vs SIMO/MISOTypes of MIMODiversitySpatial MultiplexingUplink Collaborative MIMO LinkActual WorkingChannel MatrixSystem ModelAdvantages and Application

AgendaMIMO is an acronym that stands for Multiple Input Multiple Output. Motivation: current wireless systems Capacity constrained networks Signal Fading, Multi-path, increasing interference, limited spectrum. MIMO exploits the space dimension to improve wireless systems capacity, range and reliability MIMO-OFDM the corner stone of future broadband wireless access WiFi 802.11n WiMAX 802.16e (a.k.a 802.16-2005) 3G / 4G

Why MIMO ?In 2005, Airgo Networks had developed a pre-11n version based on their patents on MIMO. Following that in 2006, several companies (including at least Broadcom, Intel, and Marvell) have fielded a MIMO-OFDM solution based on a pre-standard for IEEE 802.11n WiFi standard. Also in 2006, several companies (Beceem Communications, Samsung, Runcom Technologies, etc.) have developed MIMO-OFDMA based solutions for IEEE 802.16e WIMAX broadband mobile standard. All upcoming 4G systems will also employ MIMO technology.

In wireless communications, fading is deviation or the attenuation that a carrier-modulated telecommunication signal experiences over certain propagation media. The fading may vary with time, geographical position and/or radio frequency, and is often modelled as a random process. A fading channel is a communication channel that experiences fading. In wireless systems, fading may either be due to multipath propagation, referred to as multipath induced fading, or due to shadowing from obstacles affecting the wave propagation, sometimes referred to as shadow fading.

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Different types4MIMO DefinedIn short - Two or more data signals transmitted in the same radio channel at the same timeIt is an antenna technology that is used both in transmission and receiver equipment for wireless radio communication. MIMO uses multiple antennas to send multiple parallel signals (from transmitter).

MIMO is a revolutionary multi-dimensional approach that transmits and receives two or more unique data streams through a single radio channel whereby the system delivers two or more times the data rate per channel. As shown in Figure 1, more than one coherent radio up-converter and antenna are used to transmit the multiple signals, and more than one coherent radio down-converter and antenna are used to receive the multiple signals. With MIMO, the maximum data rate per channel grows linearly with the number of different data streams that are transmitted in the same channel.

5MIMO takes advantage of multi-path. MIMO uses multiple antennas to send multiple parallel signals (from transmitter). In an urban environment, these signals will bounce off trees, buildings, etc. and continue on their way to their destination (the receiver) but in different directions. Multi-path occurs when the different signals arrive at the receiver at various times.

How does MIMO work?

MIMO systems divide a data stream into multiple unique streams, each of which is modulated and transmitted through a different radio-antenna chain at the same time in the same frequency channel. A revolutionary technique that reverses 100 years of thinking about how radio signals are transmitted, MIMO leverages environmental structures and takes advantage of multipath signal reflections to actually improve radio transmission performance. Through the use of multipath, each MIMO receive antenna-radio chain is a linear combination of the multiple transmitted data streams. The data streams are separated at the receiver using MIMO algorithms that rely on estimates of all channels between each transmitter and each receiver. Each multipath route can then be treated as a separate channel creating multiple virtual wires over which to transmit signals. MIMO employs multiple, spatially separated antennas to take advantage of these virtual wires and transfer more data. In addition to multiplying throughput, range is increased because of an antenna diversity advantage, since each receive antenna has a measurement of each transmitted data stream. With MIMO, the maximum data rate per channel grows linearly with the number of different data streams that are transmitted in the same channel

6With MIMO, the receiving end uses an algorithm or special signal processing to sort out the multiple signals to produce one signal that has the originally transmitted data.They are called multi-dimensional signalsThere can be various MIMO configurations. For example, a 4x4 MIMO configuration is 4 antennas to transmit signals (from base station) and 4 antennas to receive signals (mobile terminal).

How does MIMO work(cont..)Because there are multiple signals each being transmitted from a different radio and antenna, MIMO signals are sometimes called "multi-dimensional" signals. Conventional radio signals are referred to as "one-dimensional signals" because they only transmit one data stream over the radio channel even if multiple antennas are used.74 x 4 MIMO ConfigurationThe total number of channel = NTx x NTr

MIMO vs SIMO/MISOLinear vs Logarithmic Improvement9

Forms of MIMOMIMO involves Space Time Transmit Diversity (STTD), Spatial Multiplexing (SM) and Uplink Collaborative MIMO. Space Time Transmit Diversity (STTD) - The same data is coded and transmitted through different antennas, which effectively doubles the power in the channel. This improves Signal Noise Ratio (SNR) for cell edge performance. Spatial Multiplexing (SM) - the Secret Sauce of MIMO. SM delivers parallel streams of data to CPE by exploiting multi-path. It can double (2x2 MIMO) or quadruple (4x4) capacity and throughput. SM gives higher capacity when RF conditions are favorable and users are closer to the BTS. Uplink Collaborative MIMO Link - Leverages conventional single Power Amplifier (PA) at device. Two devices can collaboratively transmit on the same sub-channel which can also double uplink capacity.Types of MIMOMIMO diversity refers to a family of techniques that attempts to spread information across transmit antennas to enable robust transmission in the presence of fading. Spatial multiplexing, refers to a scheme which divide data into multiple substreams - transmitting each substream on a different antenna to achieve higher capacity.

Diversity offers higher reliability and multiplexing offers high rate.11

Mimo Increases Throughput(Spatial Multiplexing)Wireless throughput scales as more radio transmissions are addedOnly baseband complexity, die size/cost and power consumption limits the number of simultaneous transmission

MIMO Increases RangeEach multipath route is treated as a separate channel, creating many virtual wires over which to transmit signalsTraditional radios are confused by this multipath, while MIMO takes advantage of these echoes to increase range and throughputConsider a simple BPSK bit sequence 1,-1,1,1,-1We code 1 as C1 and -1 as C2C1 = c2 =

1 -1Dimension of C is determined by the Number of Tx and Rx

The Working

MIMO channel Matrix

Y = Hx + n H = Channel Matrix n = Noise

Rx1 = h11Tx1 + h21Tx2 + h31Tx3 + n1MIMO system model

Single Radio vs MIMO PerformanceUsing the space dimension (MIMO) to boost data rates up to 600 Mbps through multiple antennas and signal processing.Target applications include: large files backup, HD streams, online interactive gaming, home entertainment, etc.Backwards compatible with 802.11a/b/gApplicationWLAN WiFi 802.11n Mesh Networks (e.g., MuniWireless) WMAN WiMAX 802.16e 4G RFID Digital HomeGeneral Info & Applicationhttp://en.wikipedia.org/wiki/4Ghttp://en.wikipedia.org/wiki/MIMO#MIMO_literaturehttp://www.wirelessnetdesignline.com/howto/wlan/185300393;jsessionid=3R20PO41AV3Y1QE1GHRSKHWATMY32JVN?pgno=1www.ieeeexplore.comhttp://www.ece.ualberta.ca/~HCDC/mimohistory.htmlhttp://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.13.4732&rep=rep1&type=pdf

ReferencesThank youPresented ByAnoop Madhusoodhanan Prabha36576876Rayleigh Model Statistical Modeling of wireless channels. Magnitude of signal varies randomly as it propagates in the medium. Best fit for tropospheric and ionospheric signal propagation.Fits fine for Urban environments too.Highlight No dominant light of sight communication between transmitter and receiver.Rate of channel fade Studied by Doppler shift. 10Hz to 100 Hz is the shift considered in GSM phones modeling for an operating frequency of 1800 MHz and speed between 6km/h to 60 km/h Distribution of Fading channel Racian FadingComes into picture when there is a dominant component present (especially line of sight way)v(t) =Ccoswct+Nn=1rncos (wct+fn) ExamplesVehicle to vehicle communication Satellite channelsIndoor communication

Distribution of Fading channel (Contd.) Nakagami fading Reason for modeling Empirical results matched with short wave ionospheric propagation. If amplitude Nakagami distributed, power gamma distributed and m is the shape factor in this distribution. For m=1, its Rayleigh fading (amplitude distribution) and corresponding power distribution is exponential. These days many recent papers recommend this model as an approx. to Rician model.Distribution of Fading Channel (Contd.) The fading and shadowing effects are overcome by spatial diversity i.e. my installing multiple antennas.Antennas separated by 4 10 times the wavelength to ensure unique propagation paths. As a part 4G, one of important emphasis is on throughput improvement. This stressed on better modulation techniques and coding practices.Evolution of MIMOMIMO Architecture

Spatial Diversity at Receiver

SNR (Receiver Diversity)

Transmitter Diversity

SNR (Transmitter Diversity)

Transmit/Receive Diversity For transmit/receive beamforming we have a diversity order ofMN, referred to asfull diversity. M Number of transmitting antennas N Number of receiving antennas v beamforming vector for receiver u beamforming vector for transmitter

SNR(Transmitter/Receiver Diversity)

The design goal of 802.11n was HT, High throughput.Speed 600 Mbps unlike the 802.11g (54Mbps)The achievement of this speed is as follows: More Subcarriers (OFDM) from 48 (802.11g) to 52 thus speed increased to 58.5MbpsFEC squeezing to a coding rate of 5/6 instead of boosted the link rate to 65Mbps.Guard interval of 800ns in 802.11g was reduced to 400ns thus increasing the throughput to 72.2Mbps. MIMO with a max of 4X4 architecture which means 72.2X4 = 288.9Mbps Channel width of 802.11g was 20Mhz each which was increased to 40MHz which eventually resulted in 600MHz throughput.Application on 802.11n http://www.wirelesscommunication.nl/Wikipediahttp://www.intel.com/technology/itj/2006/volume10issue02/art07_mimo_architecture/p04_mimo_systems_reliability.htmhttp://www.wirevolution.comReferencesPresented ByBinaya ParhyMIMO Wireless Communication System

AgendaMIMO Wireless CommunicationsCapacity of MIMOWell known STBC codesCriteria to be a good ST BC code.Cyclic and Unitary STBCOrthogonal STBCDiagonal algebricBLAST(V-BLAST & D-BLAST)Differential STBC(Non coherent detection)SummarizeSISO CapacityCapacity of any communication system is given by the most famous equation

:SNR, h: Channel gainNote: Since channel is assumed to be N(0,1), this reduces to just MIMO Capacity EquationIt is similar but when it is MIMO we have MtxMr channel coefficients.

MIMO Wireless Communication System

38Here are a few key ideas behind this release. While a lot of what weve done is infrastructural, its important to understand that these enhancements were to: (1) make it possible to leverage the EME more and more going forward, (2) make it possible to develop things with Ab Initio software at ever higher levels, and (3) extend the Ab Initio processing model to new uses, including so-called service-oriented architectures.Block Diagram Of a MIMO communication system

21Mt12MrH1,1h1,2H1,MrH2,1h2,2H2,MrhMt,1hMt,2hMt,Mr

Channel Matrix H=MIMO Capacity cont

39The third major thrust of this release supports existing and emergent services architectures. This support consists of a combination of standards-compliant facilities and new models of processing with Ab Initio software.MIMO Capacity contMIMO Capacity

Four CasesMt=Mr=1 Reduces to SISO Mr=1, Mt>1Mt=1, Mr>1Mr>1, Mt>1

MIMO Capacity contCase:2(Mr=1, Mt>1)

MrCapacity =10 dB =5 dB =1 dBMIMO Capacity contCase:3(Mt=1, Mr>1)

MtCapacity =10 dB =5 dB =1 dBMIMO Capacity contCase:4(Mt>1, Mr>1)

MtCapacity =10 dB =5 dB =1 dBMIMO Capacity contConclusion:

M=min(Mt,Mr)The capacity of the MIMO system increases linearly with the minimum of transmitter and receiver antenna.To achieve the potential huge capacity, new coding and modulation called Space Time coding or ST-modulation is developed since 1998.

ST code design criteriaThe maximum probability of error (also called PEP- Piece wise error probability) of a MIMO system is given by

r-> rank of and is are the eigen valus of

Based on the PEP code design criteria were proposed by Tarokh in 1998.

Rank criterion or Diversity criterionThe minimum rank of difference of any 2 code word over all possible pairs should be should be as large as possible. If there are L signals then there are L(L-1)/2 pairs.Product criterion or Coding gain criterionThe minimum value of the product over all pairs of distinct code word difference should be as large as possible.

ST code design criteria cont.Q: Among these two criteria which one is more important?A: Diversity is the more important one.Accordingly lets define two terms that define the wellness of a ST codeDiversity order = rxMrNormalized coding gain

Where T=Mt and 0