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HD Radio
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Content
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HD Radio Introduction
FM HD Radio Basic Technical Description
Methods of Broadcasting FM HD Radio
AM HD Radio Basic Technical Description
Methods of Broadcasting AM HD Radio
IBOC System Networking
Importer Plus Overview
Exporter Plus Overview
AM IBOC Exciter Overview
Station Configuration for Multicasting
Glossary of Terms and Acronyms
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HD Radio Introduction
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HD Radio Introduction
• HD Radio IBOC (In-Band On-Carrier) allows AM and FM radio
stations to simultaneously broadcast new digital services – audio
channels and wireless data – and their traditional analog signal in
their current spectrum.
• The analog and HD signals are separate signals at different power
levels.
• These new digital signals are broadcast as "sideband" transmissions
bracketing the top and bottom of the current "host" analog signal.
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RF Spectrum
• HD Radio transmission adds ~400 low
power carriers to the RF spectrum
–
200 in upper sideband and 200 in lower
sideband
• The HD Radio carriers range in frequency
from 129,361 Hz to 198,402 Hz above and
below the analog carrier
–
These carriers are modulated using QPSK and
OFDM
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How HD Radio Works
• It works the same way that traditional analog transmits, except that
the audio is digital formatted and transmitted as a continuous digital
data stream in addition to the analog waveform signal.
• On the broadcast end, audio is digitally compressed and broadcast
by a transmitter designed specifically for HD Radio broadcasting.
• The combined analog and digital signals are transmitted.
• Audio is transmitted in its analog form, as usual. The radio station
sends out the analog and digital signals on the same broadcast
frequency, along with the signals for the text data.
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How HD Radio Works
• On the listener end, the signals are received and decoded.
• An HD Radio tuner picks up the digital radio transmission with
its accompanying text. Older analog receivers continue to pick
up the analog broadcasters.
• Currently, stations broadcasting in HD Radio are operating in a
hybrid mode of both analog and digital in order to reach both
receivers.
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Power in the IBOC Carriers
• Each carrier power’s spectral density is -45.8 dBc or
.0025% of analog carrier power
• The total HD Radio power is:
– PTotal ~ 10LOG (400) + (-45.8 dBc)
– PTotal ~ -20 dBc
• The average HD Radio power is ~20 dB below, or 1%
of the analog carrier power
• New proposed injection levels at -10 dBc (10% of
analog).
8
Time Domain
• Unlike traditional FM transmission signals, the HD
Radio RF envelop has amplitude variations over
time
• The instantaneous voltage is the vector sum of
the ~400 carriers
• When these carriers align, the vector sum results
in a peak; when the vector sum nulls, a trough is
created
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Time Domain
• Power measurement of this signal must quantify both the
average power and the peak to average ratio (PAR)
• A good approximation for an HD Radio signal (carriers only) is
the peaks have 4 times the power as the average, or PAR= 6
dB (actual PAR=5.5 dB)
• When a signal is composed of both FM and HD Radio carriers,
PAR is reduced to approximately 1.5 dB due to the constant
amplitude of the analog carrier dominating the signal content
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Time Domain
Fig: Time Domain of HD Radio RF Signal
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RF Emissions Mask
• In order to minimize interference between adjacent stations,
Ibiquity has proposed an RF emissions mask which details the
permissible spectral output of the IBOC transmitter.
• To meet this mask, the transmitter must either have extreme
linearity or filtering capable of removing the intermodulation
products.
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FM HD Radio - Basic Technical Description
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FM HD Radio - Basic Technical Description
• FM HD Radio is an OFDM (Orthogonal Frequency Division
Multiplex) system which creates a set of digital sidebands
each side of the normal FM signal.
• The combined FM and HD Radio signal fits in the same
spectral mask as is specified for conventional FM.
• The system allows for growth towards eventual full utilization
of the spectrum by the digital signal.
•
Hybrid
•
Extended Hybrid
•
Full Digital
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RF Spectrum of Hybrid Waveform
Table: Hybrid Waveform Spectral Summary
Fig: Spectrum of hybrid waveforms
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FM HD Radio - Hybrid Mode
Lower Digital
Sideband
Upper Digital
Sideband
Primary
Primary
-20dBc
-20dBc
Analog Host
Signal
(Stereo or Mono)
10 partitions
199kHz
191
Subcarriers
•
•
•
•
•
130kHz
10 partitions
130kHz
0 Hz
199kHz
191
Subcarriers
109 kbps data throughput, 96 kbps for audio, and 1.411 kbps for PAD, balance is overhead.
Multicasting up to three channels is possible
Supports Stereo Analog and SCA / RDS
Digital sub-carriers are 20 dB (1/100th) below analog
The Upper and Lower Digital Sidebands are redundant
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FM HD Radio - Extended Hybrid Mode
Lower Digital
Sideband
Upper Digital
Sideband
Primary
Main
Primary
Extended
10 partitions
1, 2, or 4
partitions
Main
Extended
Analog Host
Signal
1, 2, or 4
partitions
10 partitions
(Stereo or Mono)
199kHz
191
Subcarriers
•
•
•
•
•
130kHz 100kHz
76
Subcarriers
100kHz 130kHz
0 Hz
76
Subcarriers
199kHz
191
Subcarriers
151 kbps data throughput, assignable by the station
There will be some impact to the host in extended hybrid mode
Supports Stereo Analog and SCA / RDS
Digital sub-carriers are 20 dB (1/100th) below analog
Multicasting up to 3 channels is possible
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FM HD Radio - Full Digital Mode
Lower Digital Sideband
Secondary
Primary
Main
Upper Digital Sideband
Secondary
Extended
Protected
10 partitions
4
partitions
Main
4
partitions
10 partitions
Protected
Extended
Extended
10 partitions
10 partitions
76 subcarriers
0
Hz
76 subcarriers
76 subcarriers
191 subcarriers
191 subcarriers
4
partitions
12 carriers
4
partitions
Extended
Main
Main
12 carriers
•
•
•
•
76 subcarriers
191 subcarriers
199kHz
Primary
191 subcarriers
199kHz
300 kbps data throughput, assignable by the station
Conventional FM signal is no longer present
Multicasting up to 8 channels may be possible
Not yet implemented in transmitter systems, or receivers.
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FM Spectrum
-200kHz 1st Adj.
+200kHz 1st Adj.
+400kHz 2nd Adj.
+400kHz 2nd Adj.
Noise Floor of
Instrument
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Methods of Broadcasting FM HD Radio
Separate Amplification
Using a high power analog transmitter and separate digital
transmitter
• Separate Antennas
• High Level Combining
Common Amplification
Using a hybrid FM + digital transmitter
• Low Level Combining
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Separate Amplification
Separate Antennas
Spatial Combining – Similar to
high level combining except each
transmitter has its own antenna.
The analog and digital antenna
patterns must be similar in order to
maintain the 20dB ratio in the
broadcast area.
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Separate Antennas – New Architecture
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Separate Antennas
Separate Antennas:
• Highest system efficiency
• Existing analog system unchanged
• At least 35 dB of isolation between antennas is
recommended
• Many variations of antenna configurations
• Digital transmitter may be used as analog backup
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Separate Amplification
High Level Combined
High Level Combining – One
transmitter amplifies the analog signal
while another transmitter amplifies the
IBOC signal. The transmitters are
combined before the antenna. PAR for
the IBOC transmitter is 5.5 dB.
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High Level Combined – New Architecture
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Separate Amplification
High Level Combined:
• Requires 7 dB to 10 dB more digital power
• Requires at least 10% more analog power
• Overall system efficiency may be comparable
to low level combined system
• Digital transmitter may be used as analog
backup
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Common Amplification
Low Level Combining – Both the
analog and the IBOC carriers are
amplified by a single transmitter.
PAR is approximately 1.5dB.
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Low Level Combined – New Architecture
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AM HD Radio - Basic Technical Description
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AM HD Radio - Basic Technical Description
• AM HD Radio is also a OFDM system which creates several
sets of sidebands each side and under the normal AM signal.
• The combined Mono AM, limited to 5 kHz, and HDRadio signal
fits in a +/-15 kHz spectral mask and meets FCC
requirements.
• The system can be converted to all digital at a future date for
improved audio performance and increased ancillary data
rate.
• Hybrid Mode
• Full Digital Mode
• Multicasting up to 2 channels may be possible.
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AM HD Radio - Hybrid Mode
Lower Digital
Sidebands
Lower Digital
Sidebands
Secondary
Primary
Tertiary
Tertiary
Secondary
Primary
-28 dBc
-28 dBc
Analog
Host
Signal
(Mono)
-40 dBc
C1
and
C3
C2
-40 dBc
C1
and
C3
C2
-50 dBc
C2
15kHz
10kHz
5kHz
0
Hz
5kHz
10kHz
15kHz
• The AM HDRadio Hybrid mode supports the current AM Mono signal as well as
the HD Radio signal
• 40 kbps data throughput, 36 kbps for Audio, 4 kbps for PAD
• Allocation adjustable
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AM IBOC System
• AM IBOC (hybrid) has subcarriers out to +/-15kHz
• 81 OFDM subcarriers in each sideband (QAM @ 181.7Hz spacing)
• Subcarriers 54, 55, and 56 are not transmitted to avoid interference
with a station 10kHz away.
• Subcarriers 27 and 53 carry IBOC Data Services (IDS). This
information includes station information. Capacity is 400bps.
• Subcarriers are organized into primary, secondary and tertiary groups.
Primary is 64QAM, secondary is 16-QAM and tertiary is QPSK. IDS
subcarriers are 16 QAM.
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AM IBOC System
• Secondary and tertiary regions are under the analog signal. They
are low power but they do pass through an AM detector.
• The upper and lower sideband secondary and tertiary subcarriers
can be combined such that they are additive and the analog signal is
subtractive. Receivers implement equalization to improve this
process. Similarly TX equalization is helpful.
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AM IBOC Hybrid Signal
analog
Primary subcarriers
(Fmax = +/- 14717Hz)
•
•
•
•
Secondary subcarriers
(Fmax = +/- 9629Hz)
Tertiary subcarriers
(Fmax = +/-4906Hz)
Primary subcarrier levels are fixed. Secondary and tertiary are
adjustable which is sometimes necessary to meet spectrum mask.
IBOC data is ogranized into logical channels. Logical channels are
signed to subcarrier groups based on service mode.
MA1- P1 assigned to both primary groups (20.2kbps), P3 is assigned
to secondary and tertiary groups (16.2kbps).
MA2- P1 assigned to lower primary group (20.2kbps), P2 assigned to
upper primary group (20.2kbps), P3 is assigned to secondary and
tertiary groups (16.2kbps). NOT USED.
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AM HD Radio - Full Digital Mode
Lower Digital
Sidebands
Tertiary
Upper Digital
Sidebands
Primary
-13 dBc
-28 dBc
Secondary
Primary
-13 dBc
C1 and C3
C1 and C3
C2
C2
9.6kHz
-28 dBc
5kHz
0
Hz
5kHz
9.6kHz
Allows for a data rate of up to 60kbps. Full Digital Mode provides
improved audio quality with song title/artist information.
Two channel multicasting is possible with the full digital mode.
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AM Spectrum
-20kHz 2nd Adj
+20kHz 2nd Adj
-20kHz 2nd Adj
+20kHz 2nd Adj
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IBOC System Networking
37
IBOC System Networking
Network Basics
10.10.10.10
10.10.10.11
NETWORK
EQUIPMENT
NETWORK
EQUIPMENT
SWITCH
or HUB
OTHER
NETWORK(S)
ROUTER
Gateway
10.10.10.12
External
24.24.24.24
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IBOC System Networking
Network Basics
 Network equipment is normally connected to a hub, switch or router.
 A hub is the simplest LAN component. All traffic on any port is
passed to all other ports.
 A switch includes a high-speed processor and memory. It examines
packet addresses and only forwards packets on the port that the
addressed equipment is connected.
 A router is used to separate networks. Separation protects networks
and can be used to control traffic flow.
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IBOC System Networking
Network Basics
•
Applications exchange data as IP packets which can be TCP (destination
acknowledges reception) or UDP (fire–and-forget).
•
TCP is a reliable transport since the source will resend data if an
acknowledgement is not received. Bidirectionality is a requirement.
•
UDP is useful for broadcasting data to many destinations and can be used on a
unidirectional channel, but the applications must be able to tolerate lost data.
•
Ethernet is a physical layer that encapsulates IP packets into Ethernet packets.
•
Ethernet protocol uses CSMA/CD (Carrier Sense Multiple Access with Collision
Detection). Delivery is not guaranteed.
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IBOC System Networking
Network Basics
– Network extended to a remote facility such as a transmitter site.
 Requires connection to
ISP at remote site
Option 1:
PC
PC
SWITCH
ROUTER
ROUTER
SWITCH
PC
PC
INTERNET
LOCAL OFFICE
REMOTE OFFICE
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IBOC System Networking
Network Basics
INTERNET
Option 2
 More control over reliability,
security and latency
ROUTER
PC
PC
SWITCH
BRIDGE
SWITCH
PC
PC
LOCAL OFFICE
REMOTE OFFICE
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IBOC System Networking
Network Basics
– What can go wrong?
 LAN throughput efficiency decreases as the number of devices
increases. If the LAN becomes too slow, Ethernet devices may not be
able to deliver packets. If the higher level protocol is TCP/IP, the
packets can be resent. If the higher level protocol is UDP, the packets
cannot be recovered.
 If the data being carried contains audio, lost packets means lost
audio. Even delayed packets are treated as lost if the audio they are
carrying is late reaching the destination.
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IBOC System Networking
Network Basics
A LAN can contain cascaded switches and/or bridges. If any segment
of the path between two device groups cannot support the throughput,
packets will be lost due to buffer overflow in the switches and/or
bridges.
ROUTER
PC
100 Mbs
SWITCH
PC
100 Mbs
100 Mbs
100 Mbs
T1
T1
MODEM
MODEM
100 Mbs
SWITCH
100 Mbs
100 Mbs
T1
PC
PC
1.5 Mbs
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IBOC System Networking
Real Systems - Typical G3 Installation (audio paths not shown)
GPS
IMPORTER
EXPORTER
STL
MPS SAE
SPS1 SAE
E1, T1
Licensed RF
Unlicensed RF
Satellite
TCP or UDP
E2X
SPS2 SAE
TRANSMITTER
with
M50
STL
LAN
Switch
Other
Studio
Devices
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45
IBOC System Networking
• System Architecture - Importer/Exporter (G3 IBOC Exciter)
AUTOMATION
SYSTEMS
TRANSMITTER
LAN
STL
IMPORTER
AUDIO
STL
GPS
LAN
STL
AUDIO
STL
M50
EXCITER
EXPORTER
LAN
STUDIO
TRANSMITTER SITE
(Low Level Combine)
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IBOC System Networking
Real Systems - I2E: Importer to Exporter
 Must be bidirectional STL
 Exporter requests channel data from Importer
 TCP or bidirectional UDP
 Latency from request to reply must be less than 140 ms
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IBOC System Networking
Real Systems - E2X: Exporter to Exgine
 TCP or UDP
 Unidirectional or bidirectional STL
 Includes CLOCK packets that can be used as a timing reference for
the exciter’s master clock.
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IBOC System Networking
• Managing the Traffic
– The IBOC system is sensitive to lost data between the
Importer, Exporter and Exgine.
 Importer to Exporter:
- Audio drop-out on SPS
- Lockup of Importer software (rare)
 Exporter to Exgine:
- Receiver loses lock, taking several seconds to recover.
- Exporter E2X interface can lock up requiring reboot (TCP only).
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IBOC System Networking
Managing the Traffic - General Recommendations
 I2E and E2X paths must be virtually error free
- Bidirectional with resend
- Unidirectional with very, very low BER (high SNR, FEC, etc)
 Prevent unnecessary traffic from passing through the STL
- Router to create a subnet. (some packet types go to all equipment on a subnet)
 Maintain adequate bandwidth capacity in the LAN STL.
- Understand the utilization by each application using the LAN STL.
- Rule-of-thumb for good ethernet performance is 35% utilization.
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Importer Plus Overview
51
Product Overview – Importer Plus
•
•
•
•
•
The Importer Plus is used in digital radio transmission systems with
Nautel's NE IBOC (In-Band-On-Channel) signal generator, Exporter or
Exporter Plus.
The Importer Plus allows multiple broadcasts within a single FM channel.
It consists of a PC with compatible audio cards to support the secondary
program.
The Importer Plus' application software enables partitioning of the available
transmitted HD (high definition) data bandwidth, between main program
service (MPS) audio and other audio and data services, collectively called
advanced application services (AAS).
Audio AAS are called secondary program services (SPS), and include and
program associated data (PAD).
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Importer Plus
• Broadcaster can implement two more digital program channels.
• The Importer contains the hardware and software necessary to
supply Multicast and Advanced Application Services (AAS)
• Inputs for Multicast include secondary channel audio (AES/EBU)
and associated Programmed Audio Data (PAD)
• Connects to IBOC Exciter via Ethernet using standard protocol
(Exporter Link)
• Plug-and-play compatible with Nautel HD system
• Can be placed at studio (requires bi-directional link to site) or
transmitter site (second AES/EBU STL channel required)
53
AAS Overview
•
This figure shows a block
diagram of the AAS
framework as part of the
broadcast infrastructure.
•
The 3 main elements are:
1) the clients (e.g. service
providers and
administrators)
2) the Importer
3) the Exporter.
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Importer Plus
• Inputs for Multicast include secondary channel audio (AES/EBU) and
associated Programmed Audio Data (PAD)
• Connects to NE IBOC via Ethernet using standard protocol (Exporter
Link)
• Plug-and-play compatible with Nautel HD system
• Can be placed at studio (requires bi-directional link to site) or transmitter
site (second AES/EBU STL channel required)
• Units shipped support two secondary audio channels.
55
Typical System
56
Typical System
57
Exporter Plus Overview
58
Exporter Plus Quick Specs
• The Exporter Plus encodes main program service audio and combines it with
audio and data services from the Importer.
• Dual ethernet interfaces support IP routing, which can be used to enhance the
robustness of streaming HD IP data.
• The Exporter Plus is fully compatible with Nautel’s award-winning Reliable HD
Transport protocol.
59
Exporter Plus Overview
•
The Exporter Plus represents the latest in HD Radio Exporter technology.
•
Operates under the Linux Operating System.
•
Accepts AES/EBU-format audio from an audio processor.
•
In FM systems the Exporter Plus will also accept program service data (PSD)
for the main program service (MPS) audio and Advanced Application Service
data from an Importer via the Ethernet port.
•
The MPS audio is coded and merged with PSD and Importer data to create a
single data stream that is delivered to the FM exciter, also over the Ethernet
port.
60
Exporter Plus Product Overview
•
The Exporter Plus may also be used to provide a delayed copy of the
MPS audio for the FM exciter.
•
The delayed MPS audio will become the analog component of the
hybrid broadcast. The delay is necessary for smooth blending between
the digital MPS audio and analog MPS audio in areas of poor
reception.
•
The Exporter Plus produces two MPS audio feeds, one of which is
simply delayed, and the other which is coded for eventual transmission
on the IBOC carriers.
•
In FM systems the delayed MPS audio output is 44.1 kHz AES/EBU.
•
In an AM system, the delayed MPS audio is part of the IP data stream.
61
AM IBOC Exciter
62
AM IBOC Exciter
The AM IBOC Exciter is a companion device for the Exporter Plus when
installed in Nautel AM broadcast transmitters.
63
AM IBOC Exciter Overview
The AM IBOC Exciter’s primary functions are:
•
Modulating IBOC data received over an Ethernet connection from
the Exporter Plus.
•
Generating Magnitude and Phase outputs on two sets of RJ45
connectors, one set for a daytime transmitter and one for a nighttime transmitter.
•
Producing an RF output for a linear transmitter (when properly
configured).
64
AM IBOC Exciter Overview
• Typical Configuration
Note:
The Exporter Plus and AM IBOC Exciter should be located at the same site.
65
Station Configuration for Multicasting
© Nautel Limited 2009
This presentation has been produced for Nautel customers and agents
and is not for distribution without the expressed written consent of Nautel.
66
Topics
– Importer to Exporter (I2E)
– Exporter to Exgine (E2X)
– Managing the HD Network
– Provisioning the STL/LAN Link
– Reference Timing
67
Configurations
• There are two distinct physical configurations that the station may
implement for deployment of AAS for multicasting on the HD Radio
system:
• Importer to exciter (I2E)
• Exporter to exgine (E2X)
68
Importer to Exciter (I2E) Configuration
• The I2E configuration connects an importer to an
exporter/exgine via a bidirectional Ethernet connection.
• Only the Advanced Applications Services (AAS), such as
multicast programming and data services, are transported by
this link, which is not concerned with the main program digital
service.
• A bidirectional link is required to accommodate the command
and response nature of the I2E configuration.
69
I2E Configuration
Studio importer connection over bi-directional (duplex) STL.
In this configuration, even with moderately bad network conditions
(up to one percent packet loss and 100 millisecond latency) the
system continues to perform well.
The key is to provide adequate bandwidth overhead to allow the
system to recover lost packets through TCP packet retransmission.
70
I2E Configuration
• For a station running MP1 mode with 48kb/s of AAS, the
average utilized bandwidth will be 54kb/s, requiring at
least 90kb/s to be available through the STL.
•
A 128kb/s LAN/WAN extender or two DS0s should
provide sufficient bandwidth for any MP1 configuration.
• For the maximum MP3 extended hybrid configuration of
one SPS at 48kb/s and a second SPS at 24kb/s, the
minimum bandwidth required of the STL/WAN link is
156kb/s, requiring three DS0s for 196kb/s.
71
Exporter to exgine (E2X) Configuration
• The importer-to-exporter-to-exgine (E2X) configuration
is the most bandwidth-efficient method of deploying an
HD Radio multicasting data network.
• With this implementation, a single data stream may be
conveyed to the transmitter site over the STL/WAN link,
which contains all of the MPS information as well as the
Advanced Applications Services from the importer, such
as SPS and associated data.
72
E2X Configuration
Importer to exporter to exgine configuration.
Studio-to-transmitter transport of the E2X data stream is currently supported
only as simplex (one-way) UDP and can operate over most unidirectional STL
systems of sufficient bandwidth and robustness.
With UDP transmission, the loss of a single packet results in the loss of the
entire audio frame of which it is a part. The resulting outage will last for the
duration of that single audio frame: 1.48 seconds.
73
E2X Configuration
• A 128kb/s LAN/WAN extender or two DS0s will provide sufficient
bandwidth for any MP1 configuration.
• For MP3, 256kb/s or four DS0s should be considered.
74
Managing the HD Network
Recommended network deployment of subnetting using VLANs.
Because the STL system is usually the tightest bandwidth bottleneck in the
HD Radio network, it is important that broadcast, multicast and other
extraneous traffic be kept off the network path to the transmitter site.
All HD Radio devices — importer, exporter and exciter — should use
statically assigned IP addresses within their own subnet.
75
Managing the HD Network
• The subnet must be separate from the rest of the facility through the
use of VLANs or physically separated networks.
• The only way to be sure that no extraneous traffic is traversing the
STL link is to place the entire HD Radio system on its own IP subnet
as shown in the previous slide.
• The exciter should always be on the WAN subnet, which it may
share with the exporter and importer, or the importer may be placed
on program automation subnet.
• Except for equipment that may be necessary to build the
infrastructure — that is, routers and switches — no other station
equipment should be on the WAN link subnet.
76
Provisioning the STL/WAN Link
• For TCP, the STL/WAN link must have a minimum of 40 percent
reserve bandwidth to accommodate the temporarily higher data rates
that occur when the stream recovers from packet loss.
•
If a TCP WAN link is provisioned such that the aggregate data
stream, including VNC, utilities and other extraneous traffic, occupies
no more than 60 percent of the WAN link's available bandwidth, the
installation should be successful under most network conditions.
• For UDP, the total traffic across the link should be no more than 75
percent of the provisioned bandwidth to allow for network contention.
77
Reference Timing Synchronization
• Reference timing between the importer, exporter and exgine are not
maintained across the network infrastructure.
• The use of GPS as a timing reference for the importer, exporter and
exgine to precisely lock their respective clocks in step eliminates the
phase and frequency issues and is highly recommended.
78
Glossary of Terms and Acronyms
79
IBOC System Networking
Glossary of Terms and Acronyms
BER
Bit Error Ratio. The ratio between the number of incorrect bits
transmitted to the total number of bits.
Exgine An IBOC component which resides in the exciter. The Exgine decodes
the exciter link data and provides the appropriate I/Q modulation.
E2X
Exporter to Exgine
FEC
Forward Error Correction. A system of error control for data
transmission.
GUI
Graphical user Interface
IBOC
Nautel In-Band-On-Channel technology provides high quality digital
audio over existing AM and FM radio channels.
80
IBOC System Networking
Glossary of Terms and Acronyms
IP
Internet Protocol. Specifies format of packets (or datagrams).
Maximum packet size is 64 K, but typically set according to limitations
of physical layer (1500 for Ethernet).
I2E
Importer to Exporter
LAN
Local Area Network
MPS
Main program Service
OFDM Orthogonal Frequency Division Multiplexing: an FDM modulation
technique for transmitting large amounts of digital data over a radio
wave.
QPSK Quadrature Phase-shift Keying: Phase-shift keying in which four
different phase angles are used.
81
IBOC System Networking
Glossary of Terms and Acronyms
SPS
STL
TCP
Secondary Program Service
Studio-Transmitter Link
Transfer Control Protocol. Allows two hosts to establish a connection
to exchange data and guarantees data delivery.
TCP/IP Guaranteed delivery; requires two-way communication for packet
acknowledgement.
UDP
User Datagram Protocol. This is a connection-less protocol. There are
few error recovery services. Typically used for broadcasting.
UDP/IP Delivery is “fire-and-forget”. Can transmit to multiple destinations. Can
be used on a one-way link.
82