System Aspects of Smart Antennas Technology in Cellular Wireless Communications RAWCON `99

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System Aspects of Smart Antennas Technology in
Cellular Wireless CommunicationsRAWCON 99

• Adrian Boukalov, Sven-Gustav Haggman
• Helsinki University of Technology
• Communications Laboratory
• Otakaari 5 A, FIN-02150 Espoo, Finland
• e-mail adrian.boukalov_at_hut.fi,sven-gustav.haggma
  n_at_hut.fi
• fax/ voice int. 358-9 - 4512359/17

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Smart Antenna TechnologyMotivation
Link level improvements System improvements
- Interference cancellation on the up and down
links - SNR improvement due to antenna gain
- Multipath mitigation
capacity coverage Quality of service (QoS), bit
rate, mobility rate
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Cellular Network Components Influencedby Smart
Antenna Technology
Network Planning - Capacity, coverage,
interference planning - Joint fixed and radio
network optimization, planning -
System upgrade, economical issues
1G- analog systems 2G- digital systems 2.5G-
digitalpacket .. (GPRS,..) 3G - W-CDMA 4G-
cellular gigabit WLAN
Radio Interface Receiver structure, Tx, Rx
algorithms - Spatial proc. - Time domain proc. -
Coding - Detection - Diversity - ..
Radio Network Management
DSP tech. SW Radio
Services -gt MS location
Network control - R.resource management - call
control
Cell control - admission control - broadcast
channel control - handover control -
macro-diversity control
1G
2G
Air Interface - Multiple access - Duplexing -
Modulation - Framing - Availability of pilots
Link level control - Power Control - Quality
Control - Tracking
2.5G
3G
4G
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Spatial Processing Approaches
- Sectorization - Macro-diversity with
Combining maximum ratio combining - MRC
optimum combining -OC,.. Prefiltering/Coding
Space -Time Coding V-BLAST - Beamforming
(BF) Switched-beam Smart Antenna Adaptive
beamforming - Smart Antennas at MS These
approaches can be/should be combined/mixed
together !
Sectorization
Macro-diversity
Switched-beam ant.
Adaptive BF
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BF/OC Techniques Classified by Reference Type
- Spatial reference based beamforming,
Direction of arrival based beamforming
(DoABF) - Reference signal based/time reference
beamforming (TRB) and/or optimum combining (OC)
- Signal structure (temporal /spectral) based
beamforming, SSBF/property restored beamforming
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Spatial Processing Integration with Air
Interface (Physical Layer)
Antennas elements geometry, numbers of elements -
M.
Radio Transmission Technologies
MS
Internetworking
Physical Channel Definition, Multi- plexing
Multiple Access Technology
Frame Structure
Duplexing Technology
RF- Channel parameters
Channel Coding
Modulation Technology
Source Coding
Availability of the training signal Frame length
- T
Mapping control, traffic channels
FDD TDD
Modulation type CM... Finite Alphabet Linearity
FDMA CDMA
Combination with Space Processing
Bandwidth-B Carrier frequency fo
UL-gtDL link
Wide/narrow band SA rec, BF, AoA est
Blind methods SSBF, ST

Ref. Signal based BF, S-T
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Smart Antennas Receiver System Integration
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Network Planning with SA
- Concepts of HSR, SFIR, SDMA.. in F/TDMA
networks - CDMA network planning with SA
(near-far problem mitigation). - Networks
upgrade with SA (different areas, strategies) -
Simulation tools
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Three Stages of Introduction Adaptive Antenna
Technology in Cell Planning Process
1. High Sensitivity Reception (HSR) 2. Spatial
Filtering for Interference Reduction (SFIR) 3.
Space Division Multiple Access (SDMA) 4.
SFIRSDMA ?
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HSR concept
- SA at the up-link only - Gain approximately
10logM - with 8 elements reduction of number
of BS by factor of 0.3 only by factor of 0.5
with diversity - revolving beam technique
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SFIR concept
- CCI cancellation SA at the down-link -
capacity improvements 2.5 require 6 dB CIR
improvement (already achieved by Ericsson with
simple SA algorithms) - the same range extension
as with HSR - simulations shows that
approximately the same capacity gain can be
achieved with SFIR and SDMA while SFIR require
considerable less network control upgrade
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SFIR concept
- it was found reasonable to combine in GSM
SFIR with random slow frequency hopping to
benefit from interference and frequency
diversity - reuse factor 1/3 seems reasonable
1/1 possible but to complex since dynamic RR
management based on CCI measurements is
required - frequency re-planning, but network
control (RR) less affected
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SDMA concept

- expected up to 8 times capacity improvement -
power classes concept (can be dynamic or
static) - with ref. signal BF MSs can be
separated even when they have the same angular
position to BS ! - for DoABF MSs angular
distribution is important (macrocell) -
network planning (frequency) i simpler, but
larger cell size can require new planning,
more smooth migration into existing network -
more network management upgrade required
PCH 1
PCH 1
PCH 1
PCH 1
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SFIRSDMA concept
- In theory it is possible to combine SFIR and
SDMA concepts - Intercell reuse distance and
intracell reuse distance of co-channels will
increase - Complexity is very high to be
implemented in the near future
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Network upgrade with SA
- smooth migration is possible and even several
BS with SA can provide considerable capacity
improvements - feasibility of sectorization
and SA (3-4 sectors with SA based on ULA) -
down-link considered as more problematic by
network planners in interference limited
network since dynamic control of
channelassignment to control CCI is difficult
- introduction BS with SA can increase amount
of channels level of CCI in the neighboring
cells. Balance can be achieved since
transmitted power by MSs will be reduced due to
the antenna gain. Another approach -
introduction SA at the neighboring BS
Nch,CCI
BS

BS with SA
BS
BS
BS
Ptrx_tot
SA
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CDMA network planning with SA
- reuse factor 1, only HSR and SFIR concept is
applicable - in multi- layer ( single
carrier ) CDMA network may (?)exist since SA
can reduce near-far effect - range will
increase - pilot pollution problem can be
solved - cells breathing effect can be
mitigated - capacity will increase since less
interference at the receiver - SA can be very
effective in interference suppression which is
coming from high bit rate users
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Impact of SA on network planning
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NetSim simulation tool for study network
control and planning with SA
Two Users LOS propagation scenario
Center of Helsinki
-75 dB
300
120
60
MS1
-80 dB
160
30
250
-85 dB
250
180
0
200
BS
330
150
210
240
300
270
100
MS2
- incoming impulses from the MS1 - amplitude and
AOA
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- incoming impulses from the MS2 - amplitude and
AOA, considered as interference for MS1 (and
vs)
0
250
300
150
0
50
100
200
basis X-coordinate
- Smart Antennas radiation pattern antenna main
lobe locked on the signals coming from MS1
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NetSim structure
Current version Version under
development Pedestrians on Models
domestic users predefined route and car
passengers Control and traffic Multi-services
model channels model packet and circuit
Voice service switched with
VAD Deterministic -Deterministic 3D
raytracing model raytracing models
- Model based on
measurements
- Statistical model Conventional
, 2D-RAKE, optimal
more complex beamformers SA models..
downlink model
SIR base Joint BS
assignment, distributed power
control and power control
beamforming Soft/hard HO,
Multi-carrier network optimum
simulation combining at the uplink
Visualization tools

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Network Control with SA.
- power control. Quality monitoring. Tracking. -
initial access, handover (HO), initial access,
- resource management - broadcast channels
control with SA - resource management -
services layer . Geolocation.
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Layer 1. Power control. Quality monitoring.
Tracking.
- power control at up and down links is
beneficial (60 more capacity ) (DL in SDMA
can be problematic due to furthest mobile) -
dynamic behavior of tracking, power control ? -
user identification problem to support SDMA
individual color codes needed to support each
SDMA traffic channel channel, also for
admission control .. - for rescue omni
directional channel for call recovery is
proposed - power classes concept (SDMA, others
..? )lt --gtRR management( tradeoff needed to
avoid trunking effects)
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Layer 2. Initial access. Handover.
- location aware HO or through
omni-directional channel ? - initial access with
omni directional channelgt gt narrow beam
or transition wide beam gt narrow beam - to
setup beamformer just before user dedicated
channel is allocated (access procedure
modification or increased access time ) -
delayed handover while new BS has not been
localized - how to make down-link BF when ch.
info at up-link is not available yet
(temporal omni-directional DL or longer
access) - allow different syncronisation
sequences - packet capturing by SA can packet
transmission via random access channel
(admission, data transfer-down-link problem)
t
Initial access
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Broadcast channels control with SA
- revolving beam concept in TDMA (more feasible
for coverage extension) neighboring cell
monitoring can be more problematic . Frame
structure... - control cell coverage by
reshaping transmitted antenna pattern
(sectorized and non-sectorized) - auxiliary
pilot is needed (IS-95) (since pilot and
traffic channels have propagate differently
) can be assigned for cluster of MS or
single MS - should be considered at network
planning - need careful split beamformed and
omni- directional channels ..
slot 1
slot 2
BS
slot 3
Pilot/BCH
sector2
BS
sector1
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Layer 3. Resource management.
- new functions physical ch. allocation based on
angular information and or link quality
monitoring - Dynamic channel allocation (DCA)
(localization with different precision... ??
needed) gt precise localization - centralized
DCA or gt no DCA with SFIR and interference
averaging approach or gt subdivision on sectors
and create list of forbidden sectors - joint
power control , beamforming and BS assignment -
centralized or distributed control (bunch
concept) ? - smoothing of spatial traffic
distribution - more benefit we expect to get
the more RR should be aware of spatial
characteristics
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Network Control with SA. Higher layers.
Geolocation.
New service (991, transport control)
Combined DOA measurements and time delay based
approach Raytheon proposed commercial
available geolocation system (SA option is
included)
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Impact SA on the network control
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Summary
- More benefits with SA- gt more Resource
management should be aware of - gt User
location (AoA,..)and/or - gt Power (power
classes ,...)and/or - gt Channel quality (and
spatial properties ?) Co-ordination
between BSs -gt at least loose form of
synchronization for time reference BF
(Layer 1) -gt exchange information about user
location and /or - gt channel quality (and
spatial properties ?) -gt exchange information
about cells traffic load
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Summary (contd)
- It is need to incorporate more user
dedicated information into channels (user
dedicated pilots, color codes, different
synchronization sequences) to separate/identify
users (implemented in new air interfaces cdma-
2000,UTRA) - Channels structure should be more
carefully divided between beamformed and
omnidierctional. Minimize blanket coverage in
terms of frequency/time - DTX(comfort
level?), HO, initial protocol perhaps should be
slightly modified, but it can increase signaling
overheadgt more interference in CDMA -
combination with link adaptation (since at the
beginning channel history is not available.
This combination will increase soft capacity
limit - some changes can be expected at the MS
(receiver, ant., protocols)
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With Smart Antennas where we go ?
1 -gt Integration into existing
systems (.) 1A -gt System modification (perhaps
locally in few BSs) to achieve better performance
with SA Equipment , frequency reuse , new
services (???) 2A -gt SA integration into
various WLL applications (.) 2 -gt SA
integration into standartized
WLL (..) Perhaps in future we should
combine 1 2A (or 1A ?)
Modified Systems ???
1A
AMPS,NMT GSM,IS-95
reuse
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Smart Antennas Tech.
Layer 1
2A
WLL standardized
WLL
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