Vol 6 No 4 North Americathinkinghighways.com52

COMMUNICATIONS & NETWORKS

David E. Pickeral on preserving the 5.9 GHz band for ITS

White space

 Having been closely

involved with the

allocation of 75MHz,

the 5.9 GHz band for

dedicated short range

communications systems (DSRC) more

than a decade ago and the subsequent

development of regulations, standards,

technologies and best practices for its use,

for much of the time since then I have

been following with some trepidation the

recent dialogue about the potential for

using this same band for the deployment

of unlicensed applications.

I am not known for mincing my words

and in this case I fear that the ITS

community and the US transport

ecosystems could face signi"cant

diminishment of national ITS capabilities if

such proposals are acted upon. As I will

detail further into the article, the technical

and operational parameters here all point

to DSRC Band Diversi"cation as a

lose-lose-lose scenario as pertains to the

ITS community, would-be deployers of

unlicensed applications, and above all the

public who will ultimately rely on such

services as an integral part of their travel

experience.

A NOTABLE MILESTONEAs with other e#orts around the world to

secure the 5.8/5.9 bands for DSRC, the

allocation of 75 MHz of clear spectrum by

the US Federal Communications

Commission (FCC) 12 years ago1 was a

major victory for the then largely $edgling

ITS community. In a very forward thinking

move for the Commission in an era where

the order of the day was focused on

auctioning o# large blocks of previously

government-held spectrum for commercial

use to augment the treasury, the DSRC

band (5.850–5.925 GHz) was designated

from the outset to encourage innovation

from the ground up rather than raise

revenue from a maturing wireless ICT

market. %rough deployment of

standardized, compatible technologies, the

5.9 would be a true ‘white space’ platform

to support new ITS technology for critical

next-generation transportation systems

including, but not limited to, road user

charging, traveler information systems and

above all critical safety and emergency

response and eventually crash avoidance

through vehicle-to-vehicle (V2V) and

vehicle-to-infrastructure (V2I)

applications. During the "rst decade of the

century the US Department of

Transportation (USDOT) ITS Joint

Program O&ce worked with multiple

USDOT modal agencies and state and local

concerns worked through the Connected

Vehicle Initiative (nee VII, nee IntelliDrive)

to facilitate public and private interest in

and development of the 5.9 band with

positive results accruing as the 10-year

anniversary of the allocation passed.

GOOD NEIGHBORS%e regulatory regime for the use of

radiofrequency (RF) Spectrum was devised

a century ago – in no small part due to

transportation needs of the time and the

tragic sinking of the RMS Titanic 100 years

ago this coming spring, but that is a story

for another time. %e legal and legislative

authorities of the time, realizing the

signi"cant potential of new wireless

equipment as well as the risks and con$icts

of not properly regulating its use around

the world, used what were, by then, very

well established concepts for the

management of physical space. For that

reason spectrum management was

conceived and indeed operates to this day

very much like the land use management,

North America Vol 6 No 4 thinkinghighways.com 53

DSRC

with spectrum remaining the valuable and

sometimes highly contended real estate of

the airwaves.

Allocations for certain types of uses are

equivalent to zoning, while assignment of

users to frequencies through primary

licensing is analogous to the issuance of titles,

and secondary licensure akin to leases, with

type acceptance operating as the ‘building

codes’ to ensure appropriate end use. %e

type of use now contemplated on the 5.9

band, however, e#ectively falls outside of

all of these well-managed and clearly

de"ned categories. Under Part 15 of the

Title 47 of the US Code of Regulations,

unlicensed devices can operate on fully

unlicensed bands – analogous perhaps to

public lands such as national forests that

support both citizen and commercial use.

Such “Part 15” devices can in certain

cases operate on certain other bands

licensed to other uses – akin to public right

of access (easements) to shorelines or

roadways. Again the old real estate legacy

comes through. A key element of

unlicensed operation under FCC – and

indeed worldwide under International

Telecommunication Union

Radiocommunication section (ITU-R)

standards – is that such unlicensed

operations must not, must never, interfere

in any way with the operations of their

licensed neighbors or, like unwelcome

visitors, the law provides they must

immediately cease operations and vacate

the band in favor of licensees.

In the context of the DSRC band this

presents something of a challenge. As

envisaged much of the operations of both

the licensed and unlicensed users of 5.9

would by de"nition be mobile, meaning

that the interference scenarios discussed

above would be hard to isolate in terms of

both the cause and recipient of the

interference. %is in turn would create any

number of problems especially

regarding safety-related operations >>>

“�e allocation of 75 MHz of clear spectrum by the US Federal Communications Commission (FCC) 12 years ago was a major victory for the then largely �edgling ITS community”

5.9 would be a true ‘white space’ platform to support new ITS technology for emergency response

Vol 6 No 4 North Americathinkinghighways.com54

COMMUNICATIONS & NETWORKS

Vol 6 No 3 North Americathinkinghighways.com54

where interference-free operation is critical

at all times. In such cases the only

permissible outcome under the FCC

Regulations may well be to require the

shut-down of all unlicensed operations on

the 5.9 band to ensure licensed operators

with the interference-free operation to

which they are entitled.

%e end result may be that concerns

spend a great deal of resources developing

unlicensed applications for the 5.9 band

only to discover that their e#orts are wasted

because operation proves technically

unworkable. %is is particularly of concern

given that licensed DSRC operations are

still – and will be continually – evolving

such that each new application may react

di#erently to the presence of adjacent

unlicensed emitters. Once again, the only

remedy may well be to clear the band, with

no possible recovery or recourse for the

unlicensed users regardless of their

investment.

%e above also makes an assumption that

will not likely be so easy in operational

practice – that of the FCC’s ability to

actually "nd and close down unlicensed

devices causing interference to licensed 5.9

users. While ITS technology has advanced

by an order of magnitude in recent years,

the ability to detect and intercept harmful

RF emitters remains a comparatively less

exact science – especially the kind of

real-time tracking that mobile activity

would require. Not really a case of

searching for a needle in a haystack so

much as looking for a very tiny, very fast

mouse.

HIGHEST AND BEST USEEvery band of RF spectrum has its own

so-called propagation characteristics

driven by its particular frequency, broadly

described as a balance of penetration (the

ability to go through objects versus being

scattered, absorbed or re$ected), range,

throughput (capacity to carry data streams)

and latency (delay of the data stream

compared to real time). When originally

allocated, the 5.9 band was considered to

be largely unusable for most applications

due to its low range and high power

requirements compared to lower, more

attractive bands, with most of the prime

real estate being in the ‘low numbers’ from

say 500 MHz to 3 GHz – far below the 5.9

band to say the least.

Sparing the technical jargon, even

“�rough deployment of standardized, compatible technologies, the 5.9 would be a true ‘white space’ platform to support new ITS technology”

A key element of unlicensed operation- is that such unlicensed operations must never interfere in any way with the operations of their licensed neighbors

North America Vol 6 No 4 thinkinghighways.com 55

DSRC

though advancing technology has vastly

improved the range of usable frequencies,

the 5.9 band remains highly, and perhaps

uniquely suited for DSRC since it (only)

allows reliable high speed broadband data

bursts over short distances (typically up to

2000 meters). %is is of course quite

amenable to roadside equipment (RSE)

based applications and far less so for other

personal and/or commercial applications

which may be dispersed over a wide area.

%is is especially true when it must be

considered that Part 15 devices are

invariably restricted to far lower power

outputs (e#ective isotropic radiated power

or EIRP) than adjacent licensed operations,

making the viability of successful

unlicensed applications even more

speculative. Simply put, exclusive use of the

5.9 band for DSRC represents, to borrow

once more from the doctrines of property

regulation, was in 1999 and remains today

the highest and best use of those

frequencies.

KEEPING UP GLOBALLYAt this point thanks to the e#orts of ITS

advocates working with the allocation of

DSRC spectrum on either the 5.8 or 5.9

bands by national regulatory authorities is

a reality across much of the world thanks to

the e#orts of national/regional ITS

organizations including ITS America and

ERTICO, ITU-R, the ISO 204 committee

for ITS standards and other entities

working tirelessly to ensure interoperability

and compatibility from the start. Such

standardized selections of band, known as

harmonization, will do a lot to facilitate

truly global technology development and

deployment in keeping with the ITS

community’s e#orts around the world to

ensure global interoperability and

compatibility from the start.

%e current divergence in terms of US

spectrum to say the very least presents

something of an anomaly in this global

coordination e#ort, if not ultimately a

unilateral departure from it. I won’t

speculate as yet on the global implications

of a decision to allow unlicensed 5.8 usage,

but at the outset it certainly pulls against,

rather than with, the worldwide e#ort at

standardization and has the potential to set

US development back as overseas

technology development continues with

the assurance of dedicated, exclusive DSRC

band use as originally envisaged.

CONCLUSIONAs laid out here, from both a technical and

socio-economic perspective the

deployment of unlicensed services on the

5.9 band o#ers little in terms of return on

investment for any involved in the band.

Correspondingly it could delay or

compromise over a decade of US

innovation in DSRC.

%e fact that no other nation seems to be

following America’s lead in considering

this scenario for the 5.8/5.9 band should be

a wake up call for us – and a caution for any

other nation in going down this uncertain

and potentially challenging route.

David Pickeral is Global Development Executive for Smarter Transportation at IBM, based in Washington, DC, USA

depicker@us.ibm.com

www.linkedin.com/in/pickeral

For previous articles by this author, enter PICKERAL into the search box on our home page

fyi

“When originally allocated, the 5.9 band was considered to be largely unusable for most applications due to its low range and high power requirements compared to lower, more attractive bands”