Heterogeneous Mobile Network

Heterogeneous Mobile Network

Dr. Jin Yang Verizon Communications Inc. IEEE ComSoc SCV April 2012

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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

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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

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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


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



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



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



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


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

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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

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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)


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

Heterogeneous Mobile Network

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