Massive MIMO uses large antenna arrays at base stations to serve many users simultaneously. It is a promising technique for 5G networks to boost capacity while reducing transmission power. However, pilot contamination from neighboring cells reusing the same pilot sequences limits performance. Small cell networks can help mitigate this issue by reducing cell sizes and the distance between co-pilot cells. Overall, massive MIMO has the potential to increase capacity over 10 times and improve energy efficiency for 5G communication systems.

1. Massive MIMO in 5G Communication
Presenters:
Fawad Masood
Usman Arshad
Advance Digital Communication
INSTITUTE OF SPACE TECHNOLOGY, ISLAMABAD
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2. An Overview
• Introduction
• Massive MIMO
• What is 5G?
• 5G technology Requirements
• Wireless comparisons
• 5G Features
• Millimeter wave Frequency
• Beam Forming
• Why Massive MIMO
• Overview of Massive MIMO
• Massive Antenna Based Multi-User MIMO systems
• Massive MIMO Features
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3. An Overview
• Massive MIMO system Architecture and Modeling
• Architecture
• Co-pilot cells
• Modeling
• Pilot contamination
• Techniques to remove pilot contamination
• Best solution for mitigating Pilot Contamination
• SCN
• Conclusions for Massive MIMO in 5G.
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4. Introduction
• Massive MIMO
• What is 5G?
• 5G technology Requirements
• Wireless comparisons
• 5G Features
• Millimeter wave Frequency
• Beam Forming
• Why Massive MIMO
• Overview of Massive MIMO
• Massive Antenna Based Multi-User MIMO systems
• Massive MIMO Features
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5. Massive MIMO(A hot research topic)
• Very large antenna array at each base station
• A large numbers of users are served simultaneously
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6. What is 5G?
• 5th Generation of Mobile Network.
• An idea of connecting every device to internet.
• Cloud of all devices.
• More Capacity like 100 times Faster then 4G LTE.
• Improved Coverage.
• Latency should be reduced significantly compared to LTE.
• Signaling efficiency should be enhanced.
• Idea of utilizing millimeter-wave frequencies.
• Using of up to 500MHz BW Which is Higher ,and are scarcely used by
other Broadcast Technologies , So more speed & More capacity.
• Millimeter-wave frequencies don't pass through solid objects very
well and are not used in Previous Technologies Here we are Going to
make more Base stations
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7. What is 5G?
• Increase in Spectrum means Sharing of Data in between base stations
as well as every one phones
• Self-driving car where to go and how to react to situations that
require a split-second reaction
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8. What is 5G?
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9. What is 5G?
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10. What is 5G?
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11. 5G Technology Requirements
• 1-10Gbps connections to end points in the field (i.e. not theoretical
maximum).
• 1 millisecond end-to-end round trip delay (latency).
• 1000x bandwidth per unit area.
• 10-100x number of connected devices.
• (Perception of) 99.999% availability.
• (Perception of) 100% coverage.
• 90% reduction in network energy usage.
• Up to ten year battery life for low power, machine-type devices.
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12. Wireless Comparison
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13. 5G Key Features
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14. 5G Key Features
• Small (Pico) cells
• Device to device ( D2D) communication
• Multi-hop networks
• Mm-wave technology
• Massive MIMO
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15. Millimeter Wave Frequency
• Huge amount of spectrum available using millimeter frequencies.
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16. Beam Forming
• Higher frequencies, however, also offer significant opportunities:
• As the carrier frequency gets higher, the antenna elements get
smaller.
• With this, it becomes possible to pack more elements into a smaller
antenna.
• For example, a state-of-the-art antenna for 2.6GHz is roughly one
meter tall, and contains 20 elements.
• At 15GHz, it is possible to design an antenna with 200 elements that
is only 5 cm wide and 20 cm tall.
• With more antenna elements, it becomes possible to steer the
transmission towards the intended receiver.
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17. Beam Forming
• Since we are concentrating the transmission in a certain direction,
coverage is significantly improved.
• With more antenna elements, the beams get narrower. It then
becomes vital to transmit the signal in the appropriate direction, to
maximize the received signal energy at the mobile.
• Such a scheme is called user-specific beam forming.
• We can steer the transmissions in both the vertical and horizontal
dimension, specifically to each individual user. Since one cell may
serve hundreds of users, the beam direction may change several
times per millisecond.
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18. Why Massive MIMO
• I think the main reason for Massive MIMO for 5G is 'there is no other
choice'.
• It is highly likely that we will use very high frequency (mm Wave)
signal in 5G.
• High frequency mean that the size of single antenna will be very
small and the aperture (the area for receiving energy) will be very
small.
• To overcome this small aperture on receiver side at high frequency,
we need to use a large number of transmission antenna.
• This would be the main reason, but once we adopt the Massive
MIMO technology, we can enjoy some other advantages coming from
using a large array antenna that will be described later.
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19. Why Massive MIMO
• In mm Wave, wavelength is very short, meaning the value of lambda
get very small
• Leads to decrease received power i.e. Rx
• This is big problem. How it can be solved
• Increase in Tx power or Increase in number of Tx/ Rx antenna
• This is Massive MIMO
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20. Overview of Massive MIMO
• As the name implies, Massive MIMO is an antenna array system using
Massive Amount of Antenna. It is also called Large Scale MIMO.
• Then you may ask "How many Antenna is required to be called
'Massive (Large Scale) MIMO' ?".
• The answer may be different depending on how you design the
receiver algorithm (equalizer design).
• We may need over 300 antenna. If you think this is too big number,
you may decrease the number by applying a little bit smarter receiver
(equalizer) algorithm.
• In conventional LTE using a normal MIMO, the maximum number of
antenna in MIMO as of now (Mar 2015) is 8 x 2 or 4 x 4.
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21. Massive Antenna Based Multi- User MIMO
system
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22. Massive MIMO Features
• Massive ( Very Large)
• Large Transmitters/Receivers ( 10 or 100 Antenna’s)
• More Signal Paths
• High Data Rate
• Link Reliability
• Complexity increased
• Equipment Price Increased
• Number of RF Amplifier
• More Energy Consumption
• Boost Capacity
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23. Massive MIMO Features
• Massive MIMO technique is approach to increase the system capacity
• In multi-cell massive MIMO networks, each BS is equipped with a
large number of antennas
• Provides high multiplexing and diversity gains in both uplink and
downlink directions.
• As a result, massive MIMO technique promises to increase the
capacity of the network while reducing the transmission power.
• It can be seen that in massive MIMO systems, the effect of AWGN
and small scale fading are eliminated.
• Furthermore, in such systems the simplest linear pre-coding and
detectors (such as Zero-Forcing) perform optimally.
• Therefore, the only limiting factor on the performance of massive
MIMO systems is Pilot Contamination.
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24. An Overview
• Massive MIMO system Architecture and Modeling
• Architecture
• Co-pilot cells
• Modeling
• Pilot contamination
• Techniques to remove pilot contamination
• Best solution for mitigating Pilot Contamination
• SCN
• Conclusions for Massive MIMO in 5G.
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25. Architecture
• Consists of the BTS and user equipment (UE)
• Allocating a large number of BTS antennas to communicate with
multiple UEs simultaneously.
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26. Co-Pilot Cells
• We define the co-pilot cells as the cells which use the same set of
pilot sequences.
• Also, we take co-pilot distance to be smallest distance between the
centres of two co-pilot cells.
• Here, it is worth mentioning that while they might look similar, co-
pilot distance is a completely different concept from frequency reuse
distance.
• There might be situations in which they are not equal to each other.
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27. Modelling
• We consider a cellular network with hexagonal cells of radius R
where each cell contains a base station with M (very large number)
antennas serving K single antenna users. We also assume that the
number of users per unit area is fixed,
• i.e.,
:CellularnetworkwithcellradiusRandcopilotdistanceD.
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28. Modelling
• This coefficient reflects the path loss and shadowing effect and is the
same for all antennas on a BS. More specifically, βjkl can be
represented as:
• rjkl is the distance between kth user in lth cell and the jth BS.
• Also, α is the path loss exponent.
• zjkl represents the shadowing
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29. Modelling
• During the channel estimation phase in TDD systems, every user in
each cell transmits its assigned pilot sequence.
• We assume synchronized transmission and reception in every cells,
provides the worst-case situation from the pilot contamination point
of view.
• Since the same set of pilots is used in all the cells, the estimated
channel in BS of cell 1 would be as:
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30. Modelling
• Where nj is M noise matrix.
• Also here, ρp is a factor representing the transmission SNR during
channel estimation.
• As it represents, the estimation of the channel suffers from the
interference of the surrounding co-pilot cells.
• Which introduces the following SIR for this user:
• This SIR results in the following capacity for kth user in cell 1:
Ck = B log2(1 + SIRk)
• Where B is the transmission bandwidth associated to each user.
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31. Pilot Contamination
• Is the interference between the pilot sequences.
• Transmitted by the users during the channel estimation.
• This phenomenon introduces a finite Signal to Interference Ratio(SIR)
to the network, which in turn, imposes an upper-bound on the
capacity of the system
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32. Techniques to remove Pilot contamination
• Several techniques has been proposed to remove the effect of pilot
contamination.
• Since pilot contamination is essentially a consequence of linear pre-
coding and detection schemes in massive MIMO systems (which are
the most computationally efficient methods).
• These proposed techniques introduce non-linear channel estimation
methods which are very complicated compared to the linear
techniques.
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33. Best Solution For mitigating Pilot
Contamination
• The concept of cell-size reduction provides an effective and simple
solution to this problem.
• Small-Cell Networks (SCNs) are one of the promising architectures
based on this idea.
• Generally, a SCN is a cellular network where the size of the cells are
very small (compared to the conventional microcell networks), with
self-organizing, low-power, low-cost Base Stations (BS) employed in
each cell.
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34. SCN (Small Cell Networks)
• Since the users are randomly distributed inside different cells, it
might be interesting to investigate the effect of cell size on pilot
contamination.
• It has can proved that pilot contamination is being eliminated as cell
size reduces.
• Therefore, massive MIMO technique can be extensively used in SCNs
to increase the capacity of network
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35. SCN
• In addition to their benefits in the green system design point of view,
SCNs are considered as the simplest and most effective way to
increase the system capacity.
• Furthermore, It is also clear that area spectral efficiency increases
with reduction of the cell-size in cellular networks.
• Consequently, cell-size reduction designs has been attracted many
interests in the literature and will play an important rule in the next
generations of cellular networks.
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36. Conclusion for Massive MIMO in 5G
• Massive MIMO can increase the capacity 10 times or more and
simultaneously, improve the radiated energy-efficiency in the order
of 100 times.
• Massive MIMO increases the robustness both to unintended man-
made interference and to intentional jamming.
• We had addressed pilot contamination problem in massive MIMO
systems and investigated the effect of cell size reduction on this
phenomenon.
• Hence Massive MIMO technique can extensively be used in 5G
communication,
• It will open door to a new world of internet like world is in your
hands!!!
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