a 5g paradigm based on two-tier physical network architecture€¦ · voice plus variable data, 4...

UofT Wireless Lab

A 5G Paradigm Based on Two-Tier

Physical Network Architecture

Elvino S. Sousa

Jeffrey Skoll Professor in

Computer Networks and Innovation

University of Toronto

Wireless Lab

IEEE Toronto 5G Summit 2015 (Nov 14/2015) 1

UofT Wireless Lab

Cellular System Evolution

• 1G, 2G, 3G, 4G, clear. 1 – Analog, 2 - digital voice, 3 -

voice plus variable data, 4 LTE-Advanced (Internet

access). 1978 – 2012, or about 8 years/generation

• Computing: Similar approach to classification of

generations (1G-4G, 1953 – 1982).

• 5th generation? ... Not clear and we could also loose

interest in calling it a generation (at least from

technology standpoint).

• One difference: Terminology here driven by industry

group and standards.

• Currently we see the search is on for 5G, and it seems

simultaneously for beyond 5G.


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Classification by Generations

• Going forward it will be more like looking

to the past, as opposed to 1-3G.

• 4G to some extent was coined after the

fact.

• 4G defining features: OFDM on wider

bandwidths, MIMO

• But MIMO not widely implemented

because of terminal constraint


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Key to Network Capacity

• Goal of wireless systems is to provide not

only sufficient user capacity (in terms of

capability of modulation scheme) but also

network capacity

• Ultimately network capacity depends on

More efficient physical layer, interference

control

Quantity of Spectrum

Cell size (Small Cells)


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My Take on Recent History

• My view of 4G (evolution to higher

capacities beyond 3G)

• 2003 white paper – “Autonomous

infrastructure wireless networks – 4G is

Here”.

• 2007? – Femto cells

• Later – “small cells”.

• Reality: Data offloading - WiFi integrated

into all smart phones


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Future Goal

• Current data usage (typical plans)

• In home Internet access: Typical plan 90

GB/month

• Cellular typical plan: 3 GB/month

• Ratio: 30:1, or one month to one day.

• Goal: Make wireless access (“as

accessible” as wired access, i.e. 1:1.


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1000x Capacity

• Common goal, referred to currently, is

1000x capacity

• Not achievable with improvements in

modulation and even spectrum allocation.

• Solution: small cells

• Problem: Infrastructure to deploy small

cells may be costly.


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Some Architectural Approaches

• Femtocells

Use existing network connection points

Business issues (private, public femtocell)

Third party traffic on network connection point?

• Small Cells

• Larger than Femtocells

• Infrastructure Cost

• Cloud RAN

Best for Intercell-Interference control

Rigidity in expansion

Organic growth at physical layer?

Back-haul/Front-Haul Approaches


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Alternative to Small Cells

• Increase the efficiency of existing cells

sites.

• Achieve large capacities by use of “large

antennas” at the “terminal”.

• Space division multiplexing at the

“Terminal”.


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Two-Tier Networks

• Primary Nodes (P node): Classical Base station

with Large Antenna and Power Capability.

• Secondary Nodes (S node): “Transceiver” with

“large” capability for spatial processing. D1 –

Distance to P node.

• User Equipment (UE). Small, with usual antenna

and power limitations. D2 – Distance to S node.

• D1 >> D2.

• Tier 1 spectrum more precious depending on

ratio D1/D2.


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Two-Tier Network Architecture


Tier 1

Tier 2

P node

S node

http://findicons.com/icon/93307/phone?id=407635















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Spectrum

• Tier 1 – Licensed

• Tier 2 – Licensed or Unlicensed?


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Physical Layers

• Tier 1 – Cellular Technologies, e.g. 4G,

5G, evolution. Key: Interference

Management

• Tier 2 – Cellular Technologies, WiFi and

evolutions, LTE-U, Bluetooth, other

technologies


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S Node Sharing Options

• Dedicated to a user terminal.

– Active vs. Passive

• Shared among a user account.

• Shared among public users.


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S Node Design – Use Cases

• Generic Nodes based on “Antenna Size”,

and or configurations, i.e. antenna design

• Fixed nodes for home?

• Fixed nodes for commercial applications?

• Nodes for vehicle (generic or specific to

vehicle model).

• Notes for buses, street cars, trains?

• Portable organically deployed nodes, e.g.

construction site.


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Role for Millimeter Wave

Spectrum

• Use mmWave in Tier 1 for Line-of-sight

scenarios (use cases).

• S Node: Capability for both microWave

and mmWave on Tier 1 interface, self-

configurable (mmWave, microWave) to

handle blocked propagation cases.


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Public/Private Networks

• Tier 1 P nodes

– Public

– Slower to deploy

• Tier 2 S nodes

– Private or Public?

– Organic deployment


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Physical Layer Design

• Tier 1 – S node

– S node fixed

• Easy channel estimation (reference signals)

• Easier Power Control

• Easier resource allocation and antenna adaptation

– S node mobile (e.g. vehicle, or bus)

• Predicable motion

• Advantages in channel estimation, power control,

antenna adaptation, resource allocation

• Tier 2 - UE

– Current approaches in smartphones (cellular & WiFi),

other technologies


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S Node Antenna Design

• Massive Beam-forming

• Massive MIMO

• Other spatially efficient technologies – e.g.

for mmWave.


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Tier 1 Signal Design

• New Strategy for pilot signal design

• LTE pilot approach does not scale for

large MIMO. When one antenna transmits,

all the others are off!

• Signal design based on class of use

cases.

• Different modes depending on use case

and S node class.


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Optimum Ratio of D2 to D1

• UE has two options

– Connect directly to P node

– Connect through S node

• Strategy for selection of P node or S node

– Distance/power consideration

– Spectral efficiency (need D2 not too large)

– Traffic Load at P node.

– Latency issues?


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Network Optimization: Self-

Organizing S Node

• First time when the S node is turned on, it goes

into initialization mode and self-configuration.

• Network environment learning

• Optimization of Tier 1: P node to S node link.

• In the initialization mode the S node senses the

spectrum and chooses a band with minimum

interference and if necessary it communicates

with nearby co-channel S nodes to perform self-

configuration.


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Indoor Use Case?

• Indoor cells vs. Coverage from the

outside.

• Two systems (macro/femto) or continuum?

• Do we isolate indoors?

• Could even modify construction

• Advantage of isolating indoors vs.

Flexibility of capturing external signals


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Vehicular Use Case?

• Vehicular movement is regular.

• Room for better smart antennas.

• Many possibilities here for a new system

architecture. Antenna custom design to model.

• Initial benefits: (hot spot at night?, one wireless

account?). Other better benefits.


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Vehicular Scenarios

• Vehicle in the city – high level MIMO link to P

node or other highly directional antenna

• Vehicle at home – user at home, evening and

night

• Vehicle in the country side – link range

extension

• Vehicle in the highway (remote area) – reduce

density of base stations required to cover

highways.


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Summary

• Two approaches for large cellular network

capacities

– Small Cells

• Need the associated infrastructure

• Ultimately achieves the highest capacities

– Two-Tiering

• Organic deployment of S nodes

• Antenna offloading

• Public/private

• S node public sharing vs. private

• Tier 2 technologies?


a 5g paradigm based on two-tier physical network architecture€¦ · voice plus variable data, 4...

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