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MIMO in 4G Wireless

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  • Here’s the outline of various topics that we are going to cover. We’ll introduce ourselves to MIMO technology, understand how it works and how the benefits from MIMO, mainly higher throughput and reliability, are realized in wireless broadband infrastructure. We will examine how wireless throughput can be multiplied and how the wireless connection, I mean the Over The Air’ link can be made more robust and reliable by using Antenna Diversity, Beamforming and SDM. Then we will talk about how MIMO is used in various wireless broadband standards, that include, WiFi, WiMax and LTE. Finally we will have a glimpse of the future of MIMO, and see where this technology is going.
  • Multiple Input and Multiple Input, means multiple Tx and Rx Antennas and that implies multiple radio channels between the Transmitter and Receiver. The term input and output refers to the radio channel and not the devices themselves, that means we have multiple signal inputs into the radio channels at the Tx and multiple outputs taken out of the radio channels at the Rx.As you see in the figure, 1…M are the Tx antennas and 1..N are the Rx antennas. And there are multiple radio channels or we can say communication paths between the Tx & Rx.
  • This is how real life MIMO transmitters and receivers look like! Some of you may have seen them in the stores. As time goes by and MIMO is adopted everywhere, you will see more of them.
  • Before someone had even heard of MIMO and from the time wireless communication began, we had SISO technology, which is, a single input and single output, In other words, a single radio channel and a single communication path. All of us have used it and even using it now in second and third generation mobile phones. Infact, SISO is the most commonly used transmission mode.
  • Does this picture look familiar? You must have seen these microwave dish like antennas on cell towers. These provide communication link with the core network or with other cell towers and are point to point links. This is essentially a SISO system.
  • From SISO, we evolve to a SIMO system, single input, but multiple output. What makes this system work? By having multiple antennas at the Rx pointing in different directions, I could take advantage of the multipath propagation of radio waves, and therefore, add to my signal strength, increase my Signal to Noise Ratio, make it more reliable and so on.
  • You see in this picture, I have a radio signal received directly from the Tx, then I have another one from a tall office building, and a third copy of the signal reflected from the hilltop!, all signals arriving at my SIMO receiver with different signal strengths and phase response. A SIMO system can help me get the best out of a combination of 3 copies of the same signal. We will see how?
  • Now moving on to MISO, the multiple input and single output system, where the receiver such as my handset or cellphone has a single antenna, but I have the luxury of 3 radio channels transmitted from 3 different antennas on the transmitter. Does it sound like I have some redundancy or back up radio channels available? Well, that is true and this can help me make my signal transmission more robust.
  • <Describe the slide>
  • And finally we have MIMO, where I have even more luxury of having multiple antennas at the transmitter as well as receiver. I have multiple radio channels available that can help me add more capacity, in addition to making my communication link more robust.
  • Before we move on, I would like to pose an interactive question. <Read the question and the possible answers> Please take a moment and text me the right answer number. You can type the answer in the chat window. …..Now, ok the right answer is 1…why? As we discussed before, the terms input and output refer to the radio channels. Although you see multiple receivers in the picture, but each receiver has a single antenna input.
  • So, what do we get out of MIMO, by having multiple antennas at the transmitter and receiver, that adds more complexity to our wireless system design. Well, there are many benefits.Many of us are familiar with the effects of fading and multipath interference that we have to contend with, in a wireless communication link. Remember when you are trying to make a call from your mobile phone while driving and sometimes the signal will fade, your phone shows only a single bar of signal strength and the call drops. Also, even on a 3rd generation phone, a video download could be very frustrating. Well, with MIMO…<Read through the slide>
  • So, what are the different ways and techniques that we can use to realize the promises offered by MIMO…<Read through the slide>Now, we will discuss more about each of these techniques.
  • First, let us understand Multipath Propagation in a little more detail..In the picture you see a mobile receiver, that is receiving radio signal from 3 different paths. One is direct line of sight from the transmitter, and the other 2 are reflected from a tall building and a hilltop. These signals propagate along paths of different lengths, and may arrive at the receiver with different amplitudes and phases. If the signals are 180 deg out of phase, they will cancel out, and if they are in phase, they will add up. As the mobile station moves about, the phases of various paths vary in a random fashion. Since there are in reality several propagation paths, they rarely cancel out each other completely. Typically a drop in signal level of 20-30 dB is observed that causes fading.For digital signals, multipath propagation results in ISI (Inter Symbol Interference), that means the receiver sees the adjacent symbols super-imposed, which appears as useless or corrupted data bits. So, the challenge for a mobile wireless system design is to remove / avoid the ISI.
  • First, let us understand Multipath fading in a little more detail..In the picture you see a mobile receiver, that is receiving radio signal from 3 different paths. One is direct line of sight from the transmitter, and the other 2 are reflected from a tall building and a hilltop. These signals propagate along paths of different lengths, and may arrive at the receiver with different amplitudes and phases. If the signals are 180 deg out of phase, they will cancel out, and if they are in phase, they will add up. As the mobile station moves about, the phases of various paths vary in a random fashion. Since there are in reality several propagation paths, they rarely cancel out each other completely. Typically a drop in signal level of 20-30 dB is observed that causes fading.For digital signals, multipath propagation results in ISI (Inter Symbol Interference), that means the receiver sees the adjacent symbols super-imposed, which appears as useless or corrupted data bits. So, the challenge for a mobile wireless system design is to remove / avoid the ISI.
  • One solution offered by MIMO is – Receive Antenna Diversity, that means deploy multiple antennas on the receiver, spaced at least half wavelength apart, and combine the signals from these antennas in such a way so that SNR is enhanced at the receiver and the effects of multipath fading & ISI are mitigated. Well, keeping them half wavelength apart minimizes the correlation between the 3 received signals and creates relatively independent paths to and from the different antennas.Well, the antenna configuration you see here is essentially a SIMO configuration – which can be considered as a special case of MIMO.Now, there are different ways to combine the signals from multiple antennas.
  • One method is Selection Combining, which uses a switch to select the received signal with the maximum SNR. So, the circuitry in the receiver selects the antenna with the strongest signal level.
  • Second method is ‘Equal Gain Combining’, which uses an equally weighted combination of all received signals. <Describe from slide>
  • And the third method is Maximal Ratio Combining, which uses a weighted combination of the received signals based on SNR, that is, the strongest signal has more weight and the weakest has the least weight. <Describe from slide>
  • Now let us move on to the Transmit Diversity technique, where we deploy multiple antennas on the transmitter. The antenna configuration is MISO, which can be considered as a special case of MIMO. This technique can prove to be more practical in cases, where because of the form factor of mobile hand held wireless devices, it is often not possible to deploy multiple antennas on the receiver that are half wavelength apart.So, what do we get out of Transmit diversity. We have multiple transmitted radio beams, one from each antenna, that can be spatially distinguished. Each radio beam carries an identical copy of the signal. Space Time Block Codes are used to insert time delays in the transmission paths, so that individual signals can be separated. The time delays can typically range between 50 and 200 ns. The benefits here are , improved SNR and reduced effects of multipath propagation – namely faded signal and ISI.
  • Before we move on, I would like to pose an interactive question. <Read the question and the possible answers> Please take a moment and text me the right answer number. You can type the answer in the chat window. …..Now, ok the right answer is 3. …why? As we discussed before, Antenna Diversity provides Diversity Gain by improving SNR, and there are multiple copies of signal involved. However, there is no impact on BW.
  • Next we talk about Beamforming, which can be realised when we have multiple antennas, or an array of antennas. This technique is used to control the shape and direction of transmitted or received signals. It combines signals in antenna elements in such a way, that constructive interference happens in a certain direction and destructive interference happens in other directions. Beamforming can be used to extend the range of signals in a certain direction, such as towards a highway, where density of mobile users is more compared to other directions. In other words, the beam can be steered in the desired direction.
  • So, you see in this picture, that the radio beam is steered towards the receiver in a different direction. This is a valuable technique for commercial carriers and allows them to increase user coverage, by focusing radio beams on areas that have the desired user population.
  • Space Division Multiplexing is used to achieve higher data rates instead of signal quality. So, it works well when SNR of the channel is high. In other words, the data carrying capacity of the channel is high. Therefore, multiple data streams can be sent over spatially separate radio beams but over the same RF bandwidth. So, SDM doesn’t exhaust the frequency resource, but uses space as a resource by exploiting different directional beams that can be sent from an antenna array.<Describe the slide>
  • Let us find out a little more detail about how it works.<Describe the slide>
  • <Describe the slide>.Matrix H is estimated during training sequence. The singular values of H provide a measure of the strength and separation of the MIMO data streams.
  • Before we move on, I would like to pose an interactive question. <Read the question and the possible answers> Please take a moment and text me the right answer number. You can type the answer in the chat window. …..Now, ok the right answer is 2. …why? As we discussed before, Antenna Diversity provides Diversity Gain by improving SNR, and there are multiple copies of signal involved.
  • Higher the Multiplexing Rate, higher will be the throughput
  • <Describe the slide>
  • <Describe the slide>
  • <Describe the slide>
  • <Describe the slide>
  • <Describe the slide>
  • <Describe the slide>
  • <Describe the slide>Here Diversity Gain of 6 means that SNR is improved by a factor of 6.
  • Now, we have competing demands on a MIMO system. On one hand, we want to increase throughput by having a higher Multiplexing Rate. On the other hand, we also want to maximze signal strength and mitigate the effects of multipath propagation by having a higher Diversity Gain. However, tradeoff is possible. Multiplexing and Diversity Gain can be used in combination. Let us see how. <Describe the calculation>
  • <Describe the calculation>
  • <Read the slide>
  • Now, we will discuss how MIMO antennas are typically implemented in a WiFi Access Point. Here you see a narrowband monopole implementation where half wavelength separation is kept between antennas to reduce mutual coupling between radiating elements. This is the easiest implementation, however, it is narrowband, and has high profile. If the separation between elements is reduced, then mutual coupling between elements induces large impedance at the feed. This deteriorates impedance matching, radiation efficiency, radiation patterns and diversity performance. It is also difficult to ensure omni directional coverage in both azimuth and elevation planes.
  • Here you see a multiband compact Antenna Design. Each element has a inverted F shape and has two parts. The left part is the 5 GHz antenna element and right part is for 2.4 GHz. From the top view, you see there are 3 such slanted Antenna elements spaced at 120 deg each, to provide satisfactory omni directional and multiband coverage. The elements are fabricated on a PCB, that helps to make it compact and low profile.
  • For portableWiFi devices such as laptops, iPads, smartphones, there are additional challenges. Antennas are packed with several other peripherals which are conductive and lossy, and it reduces the efficiency of the antenna. Therefore there are tradeoffs to be made between design, performance and placement. The performance parameters such as operating bandwidth, impedance matching, peak and average gain, radiation patterns, efficiency, specific absorption rate, are important. Also, the human body effects on the antenna need to be considered.The picture shows Case1 where diversity is achieved by placing a second radiating element along the length of the ground plane.
  • Here in Case 2, the second antenna element is placed beside the first one, so there is limited spatial diversity. However, the antenna feed points are much closer compared to Case1.
  • Before we move on, I would like to pose an interactive question. <Read the question and the possible answers> Please take a moment and text me the right answer number. You can type the answer in the chat window. …..Now, ok the right answer is 3. …why? As we discussed before, to avoid mutual coupling between Antenna elements…
  • < Read from the slide>
  • <Read from the slide>
  • Let us consider Single User MIMO first. <Describe the slide>
  • <Describe the slide>
  • <Describe the slide>MU-MIMO allows single antenna devices (several handheld wireless devices) to share the same time-frequency resource to improve spectral efficiency and average user experience.
  • So, what does the future hold for us with respect to MIMO…Welcome massive MIMO which is finding application in a new standard called WiGig. 60 GHz means wavelength is only 5 mm. So, the spacing between antenna elements will be only 2.5 mm. This will allow fabrication of antenna elements within a small form factor, such as 1 cm square.<Describe the slide>
  • <Describe the slide> You could have smartphones with multiple antennas, and capable of multi Gigabit reliable throughput. You could also have base stations in smaller form factor, such as the size of a pizza box, that could pack 256 or more antenna elements.
  • To dig dipper into MIMO, please refer these publications.
  • Transcript

    • 1. MIMO in 4G Wireless  MIMO Introduction  Realizing Benefits from MIMO  Antenna Diversity, Beamforming and SDM Applications of MIMO in WiFi, WiMax and LTE  Future of MIMO Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 2. Introduction  Multiple Input Multiple Output o Multiple Tx & Rx Antennas - Multiple radio channels 1 1 2 2 Tx Rx M N Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 3. Introduction  Multiple Input Multiple Output o Multiple Tx & Rx Antennas - Multiple radio channels Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 4. What came before MIMO?  SISO o Single Input Single Output 1 Tx 1 Rx Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 5. What came before MIMO?  SISO o Single Input Single Output Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 6. What came before MIMO?  SIMO o Single Input Multiple Output 1 1 2 Tx Rx N Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 7. What came before MIMO?  SIMO o Single Input Multiple Output Rx Tx Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 8. What came before MIMO?  MISO o Multiple Input Single Output 1 1 2 Tx Rx M Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 9. What came before MIMO?  MISO o Multiple Input Single Output Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 10. Finally MIMO!  MIMO o Multiple Input Multiple Output Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 11. Interactive Question #1  Which Antenna configuration is depicted by the following figure? 1. 2. 3. 4. SISO SIMO MISO MIMO Rx Rx Rx Tx Rx Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 12. Promises of MIMO  Robust Radio Channel o Effects of fading and multipath interference mitigated o No breaks in voice calls or data  Higher Throughput o Faster downloads o More Mbps with existing spectrum and power  Enables 4G Wireless Broadband applications o WLAN (IEEE 802.11n/ad) o WiMAX (IEEE 802.16m) o LTE-A (3GPP Rel 10) Is this handset in I your future? Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 13. Realizing MIMO Promises  Antenna Diversity o Receive Diversity o Transmit Diversity  Beamforming  Space Division Multiplexing (SDM) Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 14. Multipath Propagation Path 1 20 -30 dB I Fading Path 2 Path 3 + = Tx Rx + = no signal Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 15. Multipath Propagation Inter Symbol I Interference (ISI) Path 1 Path 2 Path 3 s1 s2 Path 3 Tx Rx Path 2 Path 1 + s1, s2 + s1 s2 s2 time Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 16. Receive Diversity  Mitigates Effects of Multipath Propagation  Enhances Signal to Noise Ratio (SNR)  SIMO Configuration λ/2 Tx Signals combined I from multiple antennas λ/2 Rx Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 17. Receive Diversity  Mitigates Effects of Multipath Propagation  Enhances Signal to Noise Ratio (SNR)  SIMO Configuration Selection I Combining λ/2 λ/2 Rx Tx Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 18. Receive Diversity  Mitigates Effects of Multipath Propagation  Enhances Signal to Noise Ratio (SNR)  SIMO Configuration Equal Gain I Combining λ/2 λ/2 Rx Tx Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 19. Receive Diversity  Mitigates Effects of Multipath Propagation  Enhances Signal to Noise Ratio (SNR)  SIMO Configuration Maximal Ratio I Combining λ/2 λ/2 Rx Tx Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 20. Transmit Diversity Redundant copies of signal transmitted across space and time  Space Time Block Codes (STBC) used o 50 – 200 ns time delay inserted in transmission paths  Mitigates Effects of Multipath Propagation  Enhances Signal to Noise Ratio (SNR)  MISO Configuration Ant 3 Ant 2 Ant 1 time Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 21. Interactive Question #2  What is not a benefit of Antenna Diversity? 1. 2. 3. 4. Diversity Gain Enhanced Signal to Noise Ratio Increased Bandwidth Redundant Copies of Signal Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 22. Beamforming  Controls shape and direction of radio signals  Used on Transmit or Receive Antenna Arrays  Extends range of radio signals in a direction o Signals from multiple antennas add up constructively to maximize receiver gain  Mitigates Effects of Multipath Propagation Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 23. Beamforming  Controls shape and direction of radio signals  Used on Transmit or Receive Antenna Arrays  Extends range of radio signals in a direction o Signals from multiple antennas add up constructively to maximize receiver gain  Mitigates Effects of Multipath Propagation Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 24. Space Division Multiplexing (SDM)  Different signals transmitted and received simultaneously over same RF bandwidth  Exploits spatial separation provided by MIMO Configuration  Achieves Higher Throughput  Ideal for RF channels with High Signal to Noise Ratio (SNR) 1 λ / 2 1 M X N MIMO 2 2 Tx λ / 2 Rx M N Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 25. Space Division Multiplexing (SDM)  Signal Path Coefficients (h11….hMN) represent amplitude and phase response for each signal path o Determined during training sequence – Tx generates known training signal – Rx processes training signal to estimate path responses 1 h11 1 h21 h1N λ / 2 M X N MIMO 2 2 h22 Tx λ / 2 Rx hM2 M hMN N Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 26. Space Division Multiplexing (SDM)  MIMO channel represented as matrix of signal path coefficients, H  Receivers use H-1 to spatially demultiplex the original transmitted signals o T = H-1 R Rx1 h11 h21 • • hM1 Tx1 h21 h22 • • hM2 Tx2 • • • • • • • • • • • • • RxN hM1 hM2 • • Rx2 • R Received I Signals ₌ H I MIMO Channel hMN TxM T Transmitted I Signals Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 27. Interactive Question #3  Which technique will you recommend when the radio channel is very noisy (SNR is low)? 1. 2. 3. 4. Space Division Multiplexing (SDM) Transmit Antenna Diversity Space Time Block Codes (STBC) Time Division Multiplexing (TDM) Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 28. Multiplexing Rate in MIMO  Multiplexing Rate o Number of distinctive data streams that can be received correctly and simultaneously – For MxN MIMO, it is the min (M,N) 1 Base Station 2 3 1 2 Single User 3 X 2 MIMO Multiplexing Rate = 2 Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 29. Multiplexing Rate in MIMO  Multiplexing Rate o Number of distinctive data streams that can be received correctly and simultaneously – For MxN MIMO, it is the min (M,N) 1 Base Station 2 3 1 2 Single User 3 X 2 MIMO Multiplexing Rate = 2 Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 30. Multiplexing Rate in MIMO  Multiplexing Rate o Number of distinctive data streams that can be received correctly and simultaneously – For MxN MIMO, it is the min (M,N) 1 Base Station 2 3 1 2 Single User 3 X 2 MIMO Multiplexing Rate = 2 Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 31. Multiplexing Rate in MIMO  Multiplexing Rate o Number of distinctive data streams that can be received correctly and simultaneously – For MxN MIMO, it is the min (M,N) 1 Base Station 2 3 1 2 Single User 3 X 2 MIMO Multiplexing Rate = 2 Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 32. Multiplexing Rate in MIMO  Multiplexing Rate o Number of distinctive data streams that can be received correctly and simultaneously – For MxN MIMO, it is the min (M,N) 1 Base Station 2 3 1 2 Single User 3 X 2 MIMO Multiplexing Rate = 2 Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 33. Multiplexing Rate in MIMO  Multiplexing Rate o Number of distinctive data streams that can be received correctly and simultaneously – For MxN MIMO, it is the min (M,N) 1 Base Station 2 3 1 2 Single User 3 X 2 MIMO Multiplexing Rate = 2 Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 34. Multiplexing Rate in MIMO  Multiplexing Rate o Number of distinctive data streams that can be received correctly and simultaneously – For MxN MIMO, it is the min (M,N) 1 Base Station 2 3 1 2 Single User 3 X 2 MIMO Multiplexing Rate = 2 Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 35. Diversity Gain in MIMO  For narrow band system with slow fading o Product of M & N 1 Base Station 2 3 1 2 Single User 3 X 2 MIMO Diversity Gain = 6 Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 36. Multiplexing & Diversity Combo  Trade Off is Possible  For 5x4 MIMO oCase 1: Reliable Mode – Multiplexing Rate = 2 – Diversity Gain = 3x2 = 6 Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 37. Multiplexing & Diversity Combo  Trade Off is Possible  For 5x4 MIMO oCase 2: High Rate Mode – Multiplexing Rate = 3 – Diversity Gain = 2x1 = 2 Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 38. MIMO in WiFi  IEEE 802.11n standard has adopted MIMO o Antenna Diversity upto 4 x 4 o Tx Beamforming o Space Division Multiplexing (SDM)  2.4/5 GHz ISM band o 20/40 MHz Bandwidth  PHY Data rates upto 600 Mbps o Throughput > 200 Mbps  Extended Range o Indoor 70 m o Outdoor 250 m Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 39. MIMO in WiFi  Antennas for Access Point o Narrowband Monopole λ / 4 λ/2 λ/2 Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 40. MIMO in WiFi  Antennas for Access Point o Multiband Compact Multiband Antenna Element 5 GHz 2.4 GHz Antenna Element Top View Ground RF Cable Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 41. MIMO in WiFi  Antennas for Portable Devices o Tradeoffs between design, performance and placement Antenna Configuration: Case1 Ground Plane Antenna Feed Point Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 42. MIMO in WiFi  Antennas for Portable Devices o Tradeoffs between design, performance and placement Antenna Configuration: Case2 Ground Plane Antenna Feed Point Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 43. Interactive Question #4  What is the recommended physical separation between Antenna elements of a MIMO system? 1. 2. 3. 4. λ/4 Depends on the wireless standard Minimum λ/2 Does not matter Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 44. MIMO in WiMax  IEEE 802.16m has full featured MIMO o Antenna Diversity o Beamforming o Space Division Multiplexing (SDM)  2.3-2.4, 3.3-3.4 GHz (country specific) o 5-10 MHz Bandwidth  Enhanced Throughput o 1 Gbps for fixed stations o 100 Mbps for mobile stations  Single or Multi User MIMO o SU-MIMO o MU-MIMO Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 45. MIMO in LTE-A  3GPP Rel 10 (LTE-A) has full featured MIMO o Antenna Diversity o Beamforming o Space Division Multiplexing (SDM)  22 Freq. bands covering 698-3600 MHz o Scalable Bandwidth (20-100 MHz)  Enhanced Throughput o 1 Gbps Downlink o 500 Mbps Uplink  Single or Multi User MIMO o SU-MIMO o MU-MIMO Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 46. SU-MIMO  Single User gets the benefit of full Throughput 1 Base Station 2 1 2 Single User 3 X 2 MIMO 3 Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 47. SU-MIMO  Single User gets the benefit of full Throughput 1 3 X 2 MIMO Base Station 2 1 2 Single User 3 Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 48. MU-MIMO  Multiple Users share full Throughput 1 1 Base Station 2 2 Multiple Users 3 3 Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 49. A Glimpse of the Future  Massive MIMO & WiGig (IEEE 802.11ad) o 60 GHz unlicensed band – 4 channels of 2 GHz each o Upto 7 Gbps data rates o mm Wave MIMO Antenna Arrays – small λ ( 5 mm) means very small antenna Distance between elements λ /2 = 2.5 mm 1 cm Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 50. A Glimpse of the Future  Massive MIMO & WiGig (IEEE 802.11ad) o 60 GHz unlicensed band – 4 channels of 2 GHz each o Upto 7 Gbps data rates o mm Wave MIMO Antenna Arrays – small λ ( 5 mm) means very small antenna 256 elements 16 elements Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
    • 51. Bibliography “An Introduction to MU-MIMO Downlink” IEEE Communications Magazine, October 2004  “MIMO-OFDM based air interface” IEEE Communications Magazine, January 2005  “Downlink MIMO in LTE-A” IEEE Communications Magazine, February 2012  “Understanding IEEE 802.11n amendment” IEEE Circuits and Systems Magazine 1Q 2008  “Advancement of MIMO in WiMax” IEEE Communications Magazine June 2009  “MIMO in WiMax and LTE” IEEE Communications Magazine May 2010  “MIMO-OFDM Wireless Systems” IEEE Wireless Communications August 2006  “Antennas for WiFi Connectivity” Proceedings of the IEEE July 2012  “Overview of Mobile WiMax – Technology and Evolution” IEEE Communications Magazine October 2008  The ARRL Handbook for Radio Communications, 2010 Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com

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