The document contains my MSc viva slides on Downlink Performance of Base station Cellular Systems using Beamforming Techniques

1. Downlink Performance of
Cooperative Base Station
Cellular Systems using
Beamforming Techniques
An Msc Dissertation Presentation by
Chinaemerem Nwankwo
Downlink Performance of Base station
Cellular Systems using Beamforming
Techniques
31/12/2011 1

2. Introduction/ Objectives of the
Dissertation
• To investigate the downlink performance of cellular systems under
combined Cooperative Multipoint with Beamforming Strategy.
• To investigate and evaluate the energy and spectral efficiency
trade-off of cellular systems under Coordinated MultiPoint
(CoMP).
• To identify the trade-off between the performance improvement
and the extra energy needed due to CoMP.
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3. Conventional Cellular System
• This is otherwise known as Figure 1: A Convention Cellular Network showing the
desired signals in bold lines and the interfering
the Single Cell beamforming signals in dotted lines
system
• A conventional system is
designed such that that
each BS serves associated
mobile terminals
independently and
experiences interference
from neighbouring cells
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4. Base Station Cooperation and
Coordination
Figure 2: Cells showing Coordinated Multipoint
technology where all signals from the different
• Inter-site CoMP cells are useful signals
• Intra-site CoMP
• CoMP-BF
• CoMP-JP
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5. Coordinated MultiPoint Technology
Figure 3: Downlink CoMP transmission showing the
• CoMP-BF forms of joint processing : a) Joint transmission; b)
Dynamic cell selection; c) Coordinated beamforming
o Data only available at the
serving cell
• CoMP-JP
o Data is available in the
cooperating set
-Joint transmission
-Dynamic cell selection
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6. Why Cooperation and Coordination
• Improved capabilities of • Improved network
mobile devices performance, especially to
edge users
• Improved capacity of the
cellular network • Energy
efficiency/conservation
• Spectral efficiency
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7. System Model and Problem
Formulation
• Downlink system model
• This is formulated as:
Minimise total transmitted power of the base station antenna
array
Subject to :the received signal power at the i-th mobile
received interference + noise at i-th mobile
is greater than a given threshold, ϒi
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8. Algorithm based on Semidefinite
Optimisation
• Downlink convex problems o Semidefinite
can be solved either by: optimisation- here our
constraint is SINR and we
exploit the Uplink-
o Power control based
Downlink Duality in TDD
algorithm – most suited for systems to obtain the
beamforming problems on convex equation:
the uplink where the
Subject to:
constraint is power
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9. Single cell Beamforming Implementation
• The diagram shows a cell • Recall
having 6 adjacent base
stations
Subject to
For the single cell case, we
translate the above
equations to:
s.t
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Cellular Systems using Beamforming
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10. CBF Implementation
S.T:
1.
2.
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Cellular Systems using Beamforming
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11. CoMP-JP Implementation
The convex equation is given as:
Subject to
Notice that the system is now reduced to a ‘Network MIMO.’ For
our case, we have:
Subject to:
1.
2.
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12. Performance Evaluation and Results
Performance Evaluation and Results
• We shall evaluate
Cellular Layout 10 cells
Number of cooperating cells 2
the performance of
Reuse factor
Mobile Noise Figure
1
7dB
the cellular system
Number of antenna elements per site 2 using the
SINR requirements Voice= -30.5 dB, Video= -26.5dB, Data= -27dB parameters in the
Data rates Voice = 13kbps, video=32kbps, data= 28.8kbps table under the
Bandwidth 10MHz following scenarios
Inter-site Distance 500m -the single cell case
Active User Equipment per site 1 (except for the conventional case that has 2)
-the CoMP-BF
UE-Base station distance >= 50m
-the CoMP-JP
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13. Conventional System
An illustration of a conventional The plot of Pmin vs mobile distance and azimuth
angle of orientation
beamforming system showing the
active cell surrounded by 6 adjacent
cells servicing 2 mobile users with one
stationary and the other moving
around the cell area.
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14. Cooperating Systems
• In CBF, the transmission to a • For JP/JT, the
single User is done from the transmission to a single
serving cell. Scheduling is UE is simultaneously
dynamically coordinated transmitted from
between the cells in order to multiple transmission
reduce the interference points, across cell sites.
The multi-point
between different
transmissions will be
transmissions. coordinated as a single
transmitter with
• See diagrams and graphs in antennas that are
the next slide geographically separated
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15. Cooperating Systems
• The coordinated base station cellular system with 2
cooperating sets, each having 6 adjacent cells
30
60
90 0
Cell 4
120
Cell 5 Cell 3
Cell 6 Cell2
150
Cell 10
Cell 1
Cell 9
Cell 7
180 Cell 8
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16. Non-cooperating and the Cooperating
Schemes
• The graph below shows the system performance as the mobile
distance from the base station changes for the three schemes
under consideration at constant SINR
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17. Non-cooperating and the Cooperating
Schemes
• The graph below shows the system performance as the mobile azimuth
angle of orientation from the base station changes for the three schemes
under consideration at constant SINR.
• Notice the behaviour of CBF and CJP
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18. Non-cooperating Vs the Cooperating
Schemes
• As the quality of service requirement increases, CoMP triumphs more.
• Notice from the next graph, that the difference in power requirements
narrows as higher QoS is desired and CoMP-JP power requirement rises
sharply
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19. Cellular System Capacity
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20. Evaluation of the System Capacity
• The graph below shows the performance of the three schemes
when several mobile applications of different throughput are
considered.
• The best performance is realised using CoMP-JP, which narrows
with respect to CBF as the throughput increases
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21. CONCLUSION
• CBF Vs CoMP-JP
• Performance of coordinated systems
-At low SINR – CoMP-JP
-At higher SINR – Similar performance
-CBF mitigates interference
-CoMP-JP can eliminate interference
-both increases LTE transmission rates
• Challenges of Coordinated Systems
-extra equipment cost
-extra overhead in terms of processing and backhaul for
CoMP-JP
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22. FUTURE WORK
• Investigating the viability of
implementing CoMP-JP be
evaluating the extra energy
cost required
• Assuming a scenario where
more base station in the
cellular architecture are
cooperating
• Seek out and implementing a
different path loss model.
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23. Thank you
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