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Heterogeneous Mobile Network
Dr. Jin Yang Verizon Communications Inc. IEEE ComSoc SCV April 2012
2
Outline
• Heterogeneous mobile wireless network (HetNet)
• Deployment scenarios for low-power nodes
• LTE performance
• Increase network capacity
• Improve network mobility
• UE’s role in HetNet
• HetNet: Benefits and Challenges
3 Copyright 2011 Verizon, all rights reserved. Contents provided AS IS and subject to change without notice.
Mobile Traffic Trend
• Mobile traffic is growing exponentially
– Various video applications
– Smartphone, tablet and laptop
– File sharing and gaming
– Social networking
– Machine-to-machine
4
Heterogeneous Mobile Wireless Network
MME
Microcell
OA&M
SGW
PDN GW
PCRF HSS
Enterprise Femto
HeNB
Radio
Access Network
SecGW ePDG
WiFi
HeNB GW
Microcell
Baseband Bank
5
Deployment Scenarios for Low-Power Nodes
6
LTE Network Performance
Baseline
• Commercial LTE network has achieved
a very high performance standard
– High average user throughputs
– High SINR and percentage of MIMO rank 2
• LTE-Adv is going to further improve the
network and user performance
– Carrier aggregation
– Interference mitigation
– Coordinated multipoint Tx/Rx and distributed
MIMO
SINR Distribution
0
10
20
30
40
50
60
70
80
90
100
-10 -5 0 5 10 15 20 25 30
SINR [dB]
CD
F [
%]
UL_SINR_Loaded
UL_SINR_UnLoaded
DL_SINR_Loaded
DL_SINR_UnLoaded
Note: SINR from a trial network
7 Copyright 2011 Verizon, all rights reserved. Contents provided AS IS and subject to change without notice.
Increase Network Capacity
Interference Mitigation
• Interference mitigation is crucial
– Small cell power 50 mW to 5 Watts
– Macro cell power 40 Watts per antenna
– Further RF unbalance due to site height, antenna gain
• Interference mitigation at base station
– Interference Aware Scheduler
– Sub-band scheduling in frequency domain
– Resource partitioning in time domain
• Advanced Receiver at terminal
Macro eNB
PeNB
P-UE
M - UE
Interference from MeNB
Desirable MeNB signal
Interference from PeNB
Desirable PeNB signal
P-UE
M - UE
M - UE
M - UE
M - UE
Macro eNB
PeNB
P-UE
M - UE
P-UEM - UE
8 Copyright 2011 Verizon, all rights reserved. Contents provided AS IS and subject to change without notice.
Increase Network Capacity
Cell Range Expansion (CRE)
• Cell range expansion improves network utilization of high and low-
power nodes and provides flexibility on low-power node site selection
• Field trials demonstrated almost linearly gain of sector capacity as the
number of small cell embedded increases
• Rel 8 UE cannot support larger than 6 dB bias. UE with advanced
receiver are needed Homogenous
Macro Setting
8, 6, 4, 2 dB
9 Copyright 2011 Verizon, all rights reserved. Contents provided AS IS and subject to change without notice.
Increase Network Capacity
Example: Interference Mitigation and CRE
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
0 1 2 3 4 5 6 7 8 9 0
Pico DL
Macro DL
Pico UL
Macro UL
2 6 0 1 2 3 4 5 6 7 8 92 6
0 1 2 3 4 5 6 7 8 9 02 6 0 1 2 3 4 5 6 7 8 92 6
Data not served
on subframe
Data served
on subframe
radio frame
Data possibly
served on subframe
0 4 8 2 6
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 90 4 8 2 6
Served throughput vs. Edge UE throughput
Edge (5%tile) UE throughput (Mbps)
Se
rve
d th
rou
gh
pu
t (M
bps)
• Simulations demonstrated capacity gain from resource partitioning and
interference cancellation
10 Copyright 2011 Verizon, all rights reserved. Contents provided AS IS and subject to change without notice.
Increase Network Capacity
CoMP and Distributed Radio Access Network
• Tight coordinated CoMP with distributed
MIMO in stadium and venue
– Centralized baseband bank with pooling gain
– Higher order spatial multiplexing and beam
forming gain with distributed MIMO
– Tight coordinated multipoint Tx/Rx and joint
processing
• Challenging: high throughput and low
latency backhaul between master BS
and other BSs or radiating points
Different
Cell IDs Same
Cell IDs
Advanced DRAN with joint processing
Baseband
Bank
11 Copyright 2011 Verizon, all rights reserved. Contents provided AS IS and subject to change without notice.
Improve Network Mobility
• Mobility among small cells and
macro cells are essential to
ensure seamless user experience
– Cell radius reduced from few miles to
few hundred feet
– Handover frequency increased as
more small cells deployed
• Optimized handover and power
control parameter/scheme to
improve reliability and utilization
– Macro cells to/from small cells
– Small cell to small cell
– Macro to macro
S
E
12
UE’s Role in Heterogeneous Network
• UE has played an important role in LTE network
– Provides channel state, precoding matrix and rank indications
– UE with poor antenna/RF design could have low MIMO, therefore, lower throughput
• UE is going to play even critical role in LTE-Adv
– Advanced receiver with interference canceller
– LTE-adv transmission mode to leverage spatial multiplexing: DL TM9, UL TM2
13
UE’s Role in Heterogeneous Network
Example: 700 MHz MIMO performance
Average rank two (MIMO) selection ratio Throughput normalized to reference antenna throughput Free space on roof (FSR), Hands in van (HV), Hands on roof (HR) in loaded (L) and unloaded (NL) network settings
Ref: 2 pol-antenna with no limitation; SP1/SP2: Smart phone 3”x6”, SP2 has high correlation. FP1: feature phone, 2.5”x4.5”
0
0.2
0.4
0.6
0.8
1
1.2
1.4 [FSR] [urban] [L]
[FSR] [urban] [NL]
[HV] [urban] [L]
[HV] [urban] [NL]
[HR] [urban] [L]
SP1
SP2
FP1 0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
1 [FSR] [urban] [L]
[FSR] [urban] [NL]
[HV] [urban] [L]
[HV] [urban] [NL]
[HR] [urban] [L]
[HR][urban] [NL]
Ref
SP1
SP2
FP1
• MIMO has provided a substantial performance improvement at 700 MHz
SINR (dB)
14 Copyright 2011 Verizon, all rights reserved. Contents provided AS IS and subject to change without notice.
Heterogeneous Network: Benefits and Challenges
• Hetnet will play an important role to address exponential traffic growth
– A high capacity, high scalability and cost effective solution
– Better throughput and consistent user experience
• Challenges
– High capacity backhaul
• Fiber availability and NLOS PTMP microwave solutions
– Engineering / site acquisition / zoning
• RF propagation and usage prediction tools for below the building clutter
– Network operation and management
• Macro and low-power nodes co-existence and optimization
– High performance devices