evolution in mobile radio networks - iaria.org
TRANSCRIPT
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1 © Nokia Siemens Networks 2013
Evolution in Mobile Radio Networks Multiple Antenna Systems & Flexible Networks
InfoWare 2013, July 24, 2013
Wolfgang Aichmann / 2013-07-24
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2 © Nokia Siemens Networks 2013
The thirst for mobile data will continue to grow exponentially
Video integrated everywhere
Billions of connected objects
Digital universe continues to grow exponentially
3D, high- and ultra-high definition screens
Everything from and on the cloud
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3 © Nokia Siemens Networks 2013
Content
Wolfgang Aichmann / 2013-07-24
• Multiple antennas
• Network architecture
• Liquid Net for mass events
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4 © Nokia Siemens Networks 2013
Multiple Antennas
• Antenna configurations
• Antenna vs. antenna port
• Multiple receiving antennas
• MIMO & multiuser MIMO
• Beam forming
• Hybrid beam forming
Wolfgang Aichmann / 2013-07-24
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Antenna Configurations
Wolfgang Aichmann / 2013-07-24
Base station antennas
• Omni-directional
• Directional (≈λ/2)
• vertical : tilt, adaptive
• horizontal : sector, beam forming
• Diversity
• Orthogonal polarization
• Spacing segments (>>λ)
Terminal antennas
• Single omni-directional antenna
• Two cross-polarized antennas
2 TX pipes
2x2 MIMO
4 TX Pipes
4x2 MIMO /
4x4 MIMO
8 TX Pipes
Beamforming
λ/2 >>λ
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E
Antenna vs. Antenna Port
Wolfgang Aichmann / 2013-07-24
Measure 1st pilot
Measure 2nd pilot
Antenna port
• Each port bears its own pilot
• Data are mapped to port according pre-coding rules
Port 1
1st pilot
+ data
Antenna 1
Antenna 3
Port 2
2nd pilot
+ data
Antenna 2
Antenna 4
Terminal ‚sees‘ logical antenna ports, not physical antennas
Example
Antenna
• HF signal of TX pipes is transmitted on air
TX pipe
• Several antenna segments can be connected by a common TX pipe
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Multiple Receiving Antennas CIR & SINR as Measure for Radio Quality
Carrier to Interference Ratio : Measured at RX antenna
Wolfgang Aichmann / 2013-07-24
Signal to Noise and Interference Ratio : Measured at equalizer output
antenna RXat power ceinterferen
antenna RXat power carrier CIR
outputequalizer at power noise ceinterferen
outputequalizer at power signalSINR
equalizer
equalizer
• No mutual dependency of RX antennas
• Impact from TX diversity
• RX combining gain
• Impact from TX diversity
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Multiple Receiving Antennas
Power of received signal (coherent) : PS = |w1∙r1 + w2∙r2|2 ≈ |s + s|2 = 4|s|2
Power of noise & interference (incoherent) : PI = |w1∙i1 + w2∙i2|2 ≈ |i1|
2 + |i2|2 ≈ 2 |i1|
2
TX signal : s
UE channel : h1
channel : h2
BS
combined
signal :
w1∙r1 + w2∙r2
equalizer : w2
equalizer : w1
RX signal : r1=s∙h1 + i1
RX signal : r2
interference : i1
interference : i2
Wolfgang Aichmann / 2013-07-24
typically 2, 4 or 8 antennas
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Multiple Receiving Antennas Equalizing at Single Receiving Antenna
OFDM : Operation per PRB
• Narrow band signal
• Operation in frequency domain
→ Weight is complex scalar
TX symbol Equalized symbol
h w
Restoring TX symbol
• Phase alignment: w ~ h*
• Unbiasing: |w|=1/|h|
RX symbol
Wolfgang Aichmann / 2013-07-24
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combining & unbiasing
IRC : Pcarrier
IRC : Pinterference
MRC : Pcarrier
MRC : Pintreference
Maximum Ratio Combining
• Equalizing ‚per antenna‘ : hi*/(ii∙ii*)
• Adding of equalized signals
Multiple Receiving Antennas Combined Equalizing
Interference Rejection Combining
• Combined equalizing
• Constraint : maximize SINR
h1
h2
i1
i2
w1
w2
TX symbol
Wolfgang Aichmann / 2013-07-24
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Multiple Receiving Antennas IRC LTE FDD 4RX – Post Equalizer Powers
• MRC shows higher carrier power than IRC
• MRC shows much higher interference power than IRC
Power [mdB]
Cu
mu
lative
De
nsity F
un
ctio
n
IRC post-equalizer interference power
MRC post-equalizer interference power
IRC post-equalizer signal power
MRC post-equalizer signal power
Wolfgang Aichmann / 2013-07-24
Interference
power Signal
power
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Multiple Receiving Antennas IRC LTE FDD 4RX – CIR and SINR
• CIR of MRC and IRC aligned (measured at antenna, i.e., before equalizer)
• SINR much better for IRC compared to MRC (measured at equalizer output)
Power [mdB]
IRC SINR [post-equalizer]
MRC SINR [post-equalizer]
IRC CIR [antenna]
MRC CIR [antenna]
Wolfgang Aichmann / 2013-07-24
Cu
mu
lative
y D
en
sity F
un
ctio
n
IRC gain
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MIMO & Multiuser MIMO
Singleuser MIMO (e.g. DL)
• Diversity by spatial antenna separation or polarization
• Maximum number of data streams limited by number of TX and RX antennas
• Multiple streams differ in RX signal strength which limits the maximum achievable data rate
• Closed loop : Antenna phase factor information is signalled by UE
Wolfgang Aichmann / 2013-07-24
Multiuser MIMO (e.g. UL)
• Transmission of single streams to different UEs
• UE selection such as to assign the strongest stream to each of them
• High data rates possible on both streams
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-5
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Beam Forming
Multiple TX antennas
• RX signal strength depends on phase differences of incoming signals
• Optimization of phase difference for single terminal already on TX side
• Requires good channel knowledge for each TX to RX antenna path
• Applied only for TDD systems (same physical channel for UL and DL)
• Multiple terminals can be served in parallel with different beams
Wolfgang Aichmann / 2013-07-24
Uniform linear array, 6 elements, 0.5λ spacing, antenna pattern in dB
Beam direction 0º Beam direction 30º
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Long term weights u for
beam forming.
Hybrid Beam Forming
Wolfgang Aichmann / 2013-07-24
u1 u2 u3 u4
w11
w12
w21
w22
2
3
4
6
7
8
1 5
2/
u1 u2 u3 u4
Short term weights w for
mapping code words to
data layers.
CW1
CW2
Example
• 4 X-Pol segments, i.e., 8 antennas at all
• Polarization MIMO
• Spatial diversity beam forming
• Effective weights: (short term weights) x (long term weights)
MIMO & BF : hybrid
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Network Architecture
• Co-ordinated Multipoint (CoMP)
• Distributed Antennas
• Supercell
• Heterogeneous Networks (HetNet)
• Carrier Aggregation
Wolfgang Aichmann / 2013-07-24
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Co-ordinated Multipoint (CoMP) Step 1: Co-Sited
eNodeB w/o CoMP
Wolfgang Aichmann / 2013-07-24
Cell 0 Cell 1
Cell 2
AP 0
AP 1
AP 2
AP
0 Ant 0
Ant 1
AP
1 Ant 0
Ant 1
AP
2 Ant 0
Ant 1
Cell 0 RX 0
RX 1
RX 2
RX 3
Cell 1 RX 0
RX 1
RX 2
RX 3
Cell 2 RX 0
RX 1
RX 2
RX 3
eNodeB with CoMP
AP
0 Ant 0
Ant 1
AP
1 Ant 0
Ant 1
AP
2 Ant 0
Ant 1
Cell 0 RX 0
RX 1
Cell 1 RX 0
RX 1
Cell 2 RX 0
RX 1
Logical separation of antenna point from cell
• More cell antennas w/o new antenna locations
• Low technical effort, at least in uplink (MRC / IRC)
Requirement:
• Remote radio head (RRH)
• Fast data connection to all Antenna Points (AP)
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CoMP Simulation Results for UL Inter-Site CoMP
• Each cell has 2 own antennas
• Each cell has access to antenna points of the 2 co-located cells
• At maximum 4 antennas are used for combining (MRC)
Wolfgang Aichmann / 2013-07-24
eNodeB site with 3 cells
Intra-site cell edge
Inter-site cell edge
CoMP Gain
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Co-ordinated Multipoint (CoMP) Step 2: Inter-Site CoMP
Wolfgang Aichmann / 2013-07-24
Intra-site CoMP
• eNodeB located at antenna points
• Sharing antenna points of cells hosted in same eNodeB
• Interface within eNodeB
source: 3GPP TR 36.819 V11.1.0 (2011-12)
eNB
Coordination area
High Tx
power RRH
Assume high Tx power RRH
as same as eNB
Optical fiber
intra-site CoMP
inter-site CoMP
Inter-site CoMP
• Many remote antenna points
• All accessible in each cell
• Fast data connection to all Antenna Points (AP)
• Interface within eNodeB
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Distributed Antenna Systems (DAS)
• Hosting multiple wireless operators and technologies
• DAS infrastructure provided by venue
• Operators attach their RF Head antenna ports to the DAS node
Wolfgang Aichmann / 2013-07-24
source: High Capacity Mobile Broadband for Mass Events, White Paper, Nokia Siemens Networks, 2013
Example: Stadium with 12 cells each with six antennas
High Carrier to Interference Ratio (CIR) indicates antenna locations
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Supercell
• Installation of additional cells
• Coverage holes
• Insertion of additional cells
• Increase capacity
• Decrease cell size
• Cell fragmentation
• High number of hand-overs
• High inter-cell interference
• Combining different cells to one logical supercell
Wolfgang Aichmann / 2013-07-24
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Heterogeneous Networks (HetNet)
• Challenge: Traffic hot spot within an existing network
• Solution: Placing small cells inside the network
• Applicable: Office buildings, railway stations, parking aerea, shopping centre
Wolfgang Aichmann / 2013-07-24
• High interference because of overlapping cells within the same frequency band
• Interference management
• Interference Rejection Combining (IRC)
• Enhanced Inter-Cell Interference Co-ordination (eICIC)
• …
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Heterogenious Networks Simulation Results
Wolfgang Aichmann / 2013-07-24
Downlink
• Average cell throughput decreases (no simple scaling with # of cells)
• Total cell throughput increases (more cells)
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Carrier Aggregation
Aggregation of multiple carriers
• Diversity gain from scheduling on best carrier(s)
• Pooling & load balancing
• Increased througput
• Decreased delay
Wolfgang Aichmann / 2013-07-24
source: Efficient resource Utilization Improves the Customer Experience, White Paper, Nokia Siemens Networks, 2013
Smart phones cause bursty traffic:
• Big variation of required radio resources
• Over time
• Between cells
• Between frequency layers
At any time significant unused resources while other parts are in overload.
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Liquid Net for Mass Events
• Traffic Profiles at Mass Events
• Liquid Net Measures
Wolfgang Aichmann / 2013-07-24
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Traffic Profiles at Mass Events
Typical challenges at mass events:
• Large number of people using smart phones to share pictures
• This creates traffic profiles that differ from typical ones:
• Higher uplink traffic
• More frequent packet transmission
Wolfgang Aichmann / 2013-07-24
Examples:
• Huge sports event in UK: >25GB of data per hour
• Korean fireworks festival: >150GB of data per hour
• 6-day Hajj pilgrimage: >100TB
source: High Capacity Mobile Broadband for Mass Events, White Paper, Nokia Siemens Networks, 2013
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Liquid Net Measures
• Appropriate parameterization
• Cell parameters
• Control channels
• Signalling
• Increasing number of cells
• Overlapping of cells increases interference
• Careful cell planning recommended
• Usage of active antennas for flexible beam steering, e.g., vertical sectorization
• Distributed Antenna Systems
• Smart Wi-Fi Capacity
Wolfgang Aichmann / 2013-07-24
source: High Capacity Mobile Broadband for Mass Events, White Paper, Nokia Siemens Networks, 2013
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Conclusion
• High smart phone penetration
• Completely new user bahviour
• High data traffic with small packages
• High upload traffic at mass events
• There is not a single technical solution.
• A bundle of technical possibilities available
Wolfgang Aichmann / 2013-07-24
Intelligent & flexible application of all these solutions makes the radio network running.
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