HD Radio Update Nautel Users Group

Single Frequency Networks and HD Multiplex

April 17, 2016

Presentation Overview

• IBOC Single Frequency Networks for HD Radio

– HD Multiplex Update

– Planning IBOC SFN Networks

• John Kean, Kean Consultants LLC

– Nautel IBOC SFN implementation

• Philipp Schmid, Research Engineer at Nautel

HD Multiplex Update

IBOC Signal HD Multiplex: Update

• Over 27 million HD Radio

receivers

• Some markets are approaching

20% of cars on the road

equipped with HD Radio

receivers

– New York, 18.6% Dec 2015

• Now is the time to plan for an all-

digital future

• HD Multiplex works with existing

receivers

96.5 MHz 96.7 MHz

IBOC Signal HD Multiplex: Interleaving IBOC Signals

-200 kHz -100 kHz 100 kHz 200 kHz -300 kHz 300 kHz

96.6 MHz

600 kHz wide

1512 carriers

369.9 kbps

15 audio services

Compatible with

todays receivers (European tuning)

FM

Up to 300 audio services

in the FM band

HD Multiplex Applications

• Unleash content cost effectively in rural areas

– 95% lower energy bill compared to FM

• Multi-cultural programming in urban centers

• More sports play-by-play for home and away

• Add “on demand” news and traffic on HD2

• On stage concert experience

– Surround sound for HD Radio

– Dedicated binaural headphone channel

• More data services …

Application:

Coupon Radio

• Transmit store discount coupons via QR codes

– Added station revenue, retain listeners

– Capture with audio tagging button, easy transfer to smartphone app

• Embed market information: call sign, timestamp

• 15 looping audio streams • Audio clips processed thanks to Omnia

• Running on VS and GV transmitters

• A variety of receivers

• Watch the video at: http://www.nautel.com/solutions/advanced-solutions/hd-multiplex/

HD Multiplex: NABShow Demonstration

Why IBOC SFNs?

• Fill gaps due to terrain shielding

– Few translator frequencies available

• Extend station coverage

– Super powered FM stations with limited IBOC injection

– Cover the length of a highway

• Enhance station frequency branding

• Seamless “hand-off” between transmitters for IBOC

– Requires proper RF coverage planning

SFN Planning

Planning a Synchronous Network for FM Broadcast

A “Booster” sounds simple, but most of us know there have been difficulties... Stronger signals, but with distorted audio

Interference to the original signal coverage (here's an example of stereo FM with an 8 dB ratio between direct and delayed signal)

Multipath Always the cause of booster troubles It can be predicted at the engineering design stage

Advanced tools are needed to calculate and map it

In a perfect world…

• There would be no terrain effects, and multipath would be easier to predict

• The blue circles show how the signal-to-interference zones between two identical transmitters would look if signals propagated uniformly in all directions – The S/I ratio at any location is indicated by the circle

– In the real world, terrain and clutter effects have a huge effect on the S/I

• At least the time-of-arrival differences, shown as green iso-contour lines, is relatively stable around each transmitter

• We know that multipath reception is worse in areas – Where the S/I is low or ΔTOA is high, and

• Multipath is better – Where the S/I is high or ΔTOA is low

S/I

low

S/I medium

S/I high

HD Radio is susceptible to multipath effects

• Tests by author – Two car receivers

– Independent Rayleigh fading

– Two RF signal levels (strong, medium-strong)

– Criteria >95% HD Radio reception availability

• OFDM Guard Interval indicates fixed-signal break point at approx. 70µS – Break occurred at 30µS (receivers accepted

S/I of 0dB below this time)

– Required S/I rises quickly

– Inflection at 40-60µS, but higher S/I still required as TOA difference increases

• Combined version of data used in following studies

Signal coverage

Comparison: KUSC-FM

• Main transmitter, 39 kw DA on Mt.

Wilson (no booster)

• Yellow: portable

• Green: in-home

• Red: in-car

• Signal coverage from booster, 200w

DA on Oak Mountain, Porter Ranch,

toward Santa Clarita

• Same color coding

• Hi signal levels in Santa Clarita

• Terrain causes signal

fragmentation

• Side and back radiation on

antenna causes signal in San

Fernando Valley

KUSC multipath effects for

HD Radio

• Unsynchronized HD Radio

Predicted digital reception

difficulties for present -20 dBc

injection on both Main and

booster

• Synchronized HD Radio

Flight time to booster 176µs,

booster is delayed by 176µs -

40µs

• Time of Arrival Contours

Equal delay is 20µs from

booster

SFN Implementation

Time Tagging: Input→Output

exporter

GPS

FM + Delay

Exgine

FM + Delay + Δ

Exgine Δdelay

FM HD

Mod Monitor

GPS

processor

+

GPS

FM HD

Mod Monitor

studio

Main TX

Booster TX

Variable

STL delay

Variable

STL delay

FM accurate within 20 us

good for mono FM or

with terrain shielding

!! check audio polarity !!

+

input output

IBOC

FM

IBOC

FM

IBOC SFN Pipeline

Audio capture

44.1kHz

ASRC Exporter

process

PPS+ SYNC

E2X IP Packet

TX

PPS+ SYNC

Exgine Modu-lator

PPS+ SYNC

Digital upconver-

sion

PPS+ SYNC

RF out DAC clock

10 MHz

XO PLL

GPS

module GPS

module

10 MHz

XO PLL

exporter exgine / exciter STL

Sample count

0-44099

PLL maintains

true sample

rate

4096 audio

Samples

SYNC <= first

sample count

after last PPS

Clock packet

(SYNC)

Data packet

Variable STL

latency (< 1s)

1 E2X packet

32 Symbols

Optional added

stages

Start RF at

PPS+SYNC

PLL maintains

sync after start

Exciter Synchronization

Exgine modulator

(digital PAR1)

E2X Clock

Packet Receive

E2X Data Packet

Receive

sync

0’s

IBOC

IQ

wait for PPS

convert SYNC PPS

pulse

gate

syn

c

+ digital

upconversion

DAC

FM input and

modulation

output buffer

RF

Required: fixed FM analog delay

744kHz IQ sample rate

makes it easy to added

to FM IQ

Better resolution with

higher sample rate.

Startup Delay: better than ± 2μs (0 samples)

Improved Digital Diversity Delay Stability

(unsync’ed typical ±400 μs to 3 ms)

guard interval

Lab Results: Digital Startup

33us

time

offset

KUSC Installation Nautel

NV15

main processor MPX Delay

Pilot Sync

FM Generator

Exgine

+

Nautel ExporterPlus

Nautel

VS300

HD-1 AES FM AES

or MPX

PPS exporter

Reliable HD TX

GPS

MPX Delay

Pilot Sync+Δ

FM Generator

Exgine

+

Δdelay

E2X IP

External GPS

PPS

STL

Studio

STL

E2X IP

E2X IP

FM AES

FM AES FM HD

Mod

Monitor

FM HD

Mod

Monitor

match delay

& audio phase

to HD reference

KUSC Drive Test Results

Thursday Apr 14, 2016

• Tested both -20 dBc and -14 dBc on Booster

• Solid IBOC coverage of Santa Clarita valley

• Good coverage along route 14 in Canyon

Country. HD is locked even with severe FM

impairment. Intermittent drops only with

expected terrain shielding in canyons.

• Only short intermittent drops in Sylmar region

only with clear obstruction like underpasses

with little signal from either transmitter.

• Proves IBOC is synchronized

• Significantly Impressed with coverage from

2W IBOC transmission at 3000’

• Test was successful: HD Boosters are an

effective option to extend coverage

Thank you Ron Thompson and

Tom King of KUSC

Thank You