Spectrum Sharing in Wireless Networks

Stephen Hanly

CSIRO-Macquarie University Chair in Wireless Communications

stephen.hanly@mq.edu.au

The CSIRO-Macquarie University Chair in Wireless Communications has been established with funding

provided by the Science and Industry Endowment Fund.

Spectrum Sharing Continuum

Exclusive license

Open Access

Carriers Sharing

Licensed shared access

Private Parks

What is the optimal point on this continuum for any particular frequency?

We lose more energy at high frequency:

Inverse square law:

Received power depends on antenna aperture:

(power per unit area)

Small CellsIt is envisaged that small cells

will help meet the wireless

data crunch.

The infrastructure is very

expensive

Traffic is much less

predictable on small

space-scales.

Do we need sharing?

micro cell

macro cell

pico cell

However:

Small Cells

The “red”

service provider

has deployed a

network

Small cells cover traffic hotspots.

It is allocated some “red” spectrum

It can manage its own interference

Small Cells The “blue” service

provider has deployed a

network

It is allocated some

“blue” spectrum

frequency

The blue spectrum may

consist of low, medium,

and high frequencies

Low in the macros, medium in the micros,

high in the picos

Spectrum sharing? The pico blue

channels could

be used in the

pink picocell

The pico pink

channels could

be used in the

blue picocell

frequency

How do we define a spectrum asset?

Spectrum assets

A service provider may prefer to have both assets:

These are complementarities

The first case (A & B) also shows that interference is an

externality

frequency

Asset A Asset B

frequency

Asset C

Asset D

Here are two different spectrum assets, A & B.

A service provider may prefer to have both assets:

Here are two different spectrum assets, C & D.

o Same frequency, but different spatial

location

o Different frequencies, for different ranges

Wireless Engineering

With N antennas, base station can send up to N

non-interfering beams

If the base stations are connected by backhaul

then they can coordinate their beams to

mitigate interference

Multiple antennas and/or sophisticated signal

processing can allow multiple links to co-exist

in the same band

Interference can be cancelled

Can more spectrum be “open-access”?

Economics

Economics is required to work out how to incentivize sharing, how to make

contracts, and how to monitor behaviour to ensure compliance

There are interesting open problems in the

design of two-sided markets (eg for secondary

spectrum markets) even without considering

all the complexities of spectrum

The challenge is to incentive the revelation of

truthful values without sacrificing too much

efficiency

Conclusions

Many open questions in the area of spectrum sharing

Wireless Communications Engineering establishes the

technological constraints and potential gains from sharing

Economics considers the way regulatory frameworks,

pricing structures and market mechanisms provide the

right incentives to realize these gains

Joint work between engineering and economics is

required, and this area is in its infancy.