IBOC System Networking

IBOC SystemNetworking

© Nautel Limited 2006This presentation has been produced for Nautel customers and agents and is not for distribution without the expressed written consent of Nautel.

April, 2006Rev. 1.x.x Draft

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IBOC System Networking

• Topics– Overview - System Architecture

– Network Basics

– Real Systems

– Managing the Traffic

– Glossary of Terms and Acronyms

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TRANSMITTER

STUDIO

LANSTL

IMPORTER

AUTOMATIONSYSTEMS

GPS

LAN

AUDIOSTL

TRANSMITTER SITE(Low Level Combine)

LANSTL

M50EXCITER

AUDIOSTL

NE IBOC

• Overview - System Architecture– Importer/NE IBOC (G2 IBOC Exciter)

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4

STUDIO

LANSTL

IMPORTER

GPS

EXPORTER

AUTOMATIONSYSTEMS

LAN

AUDIOSTL

TRANSMITTER SITE(Low Level Combine)

LANSTL M50

EXCITER

TRANSMITTER

AUDIOSTL

• Overview - System Architecture

– Importer/Exporter (G3 IBOC Exciter)

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Overview - System Architecture

– G2 to G3 Conversion

• Install Nautel supplied replacement M50

• Send M50 to Nautel for upgrade.

• Exgine is added, Remote I/F is replaced

• Upgrade software

• Install LAN STL

• Install upgraded M50. Upgrade V transmitter software.

• Move NEIBOC to studio and reconfigure to Exporter with software upgrade.

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Mode Digital Carriers(per sb)

DataCapacity

(kb/s)

E2XB/W

(kb/s)

LogicalChannels

(kb/s)

Combined Power (Ratio)

Low Level High Level

MP1 190 98.4 110 P1 (98.4) 1 1

MP2 209 110.8 120 P1 (98.4)P2 (12.4)

1 1.1

MP3 228 123.2 140 P1 (98.4)P3 (24.8)

1 1.2

MP11 266 148 160 P1 (98.4)P3 (49.6)

1 1.4


– Service Modes/Logical Channels

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Multicast is mono if < 32 kb/s

Minimum bit rate for MPS is 48 kb/s

Minimum bit rate for SPS is 12 kb/s

When assigning allocation in MP2 mode and higher, audio channel must stay within a logical channel

OOPS!

If you use MP3, you must leave 1 kb/s unassigned to prevent dropout problems with some radios.

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0 129361 198402-129361-198402

MP1


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0 122457 198402-122457-198402

MP2


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0 115553 198402-115553-198402

MP3


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0 101744 198402-101744-198402

MP11


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NETWORKEQUIPMENT

NETWORKEQUIPMENT

SWITCHor HUB

ROUTER

10.10.10.11 10.10.10.10

Gateway10.10.10.12

External24.24.24.24

OTHERNETWORK(S)

• Network Basics

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Network Basics

Network equipment is normally connected to a hub, switch or router with CAT5 cable (RJ45 connectors).

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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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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Network Basics

– What if the network needs to be extended to a remote facility such as a transmitter site?

Option 1:

PC

PC

SWITCH ROUTER

INTERNET

ROUTER SWITCH

PC

PC

LOCAL OFFICE REMOTE OFFICE

Requires connection to ISP at remote site

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Network Basics (What if the network needs to be extended…?)

SWITCH

PC

PC

ROUTER

INTERNET

BRIDGE SWITCH

PC

PC

More control over reliability, security and latency

Option 2:

LOCAL OFFICE REMOTE OFFICE

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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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SWITCHSWITCH

PC

PC

ROUTER

T1MODEM

T1MODEM

T1 1.5 Mbs

PC

PC

100 Mbs

100 Mbs

100 Mbs

100 Mbs 100 Mbs

100 Mbs

100 Mbs

Network Basics (What can go wrong?)

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.

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• Real Systems– Typical G2 Installation (audio paths not shown)

IMPORTER MPS SAE

SPS1 SAE SPS2 SAE

STL

Other Studio

Devices

STLE1, T1

Licensed RFUnlicensed RF

TCP orBidirectional UDP

I2E

LANSwitch

NE IBOC(EXPORTER)

GPS

TRANSMITTERwithM50

Not a LANConnection!

LANSwitch

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Real Systems

– Typical G3 Installation (audio paths not shown)

IMPORTER EXPORTER

SPS1 SAE SPS2 SAE

STL

Other Studio

Devices

STLE1, T1

Licensed RFUnlicensed RF

Satellite

TCP or UDPE2X

LANSwitch

TRANSMITTERwithM50

GPS

MPS SAE

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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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Real Systems (I2E: Importer to Exporter)

1.48 Second Frame

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Req60

Req#

Req#

Req#

Req#

Req#

Req#

Req#

ChnlData9,463

ChnlData

*

ChnlData

*

ChnlData

*

ChnlData

*

ChnlData

*

ChnlData

*

ChnlData

*Req

# # - Packet size is 60, but only issued in MP2 and MP3 modes* - For MP1, channel data = 0; for MP2, channel data = 440; for MP3, channel data = 728Chnl

Data*

Mode Data Through (bps)Forward Back

MP1 51,151 324

MP2 70,178 2,918

MP3 82,632 2,918

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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 M50 master clock.

- M50 can be programmed to use CLOCK packets, local 10MHz or local

1PPS as a timing reference.

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Real Systems (E2X – Exporter to Exgine)

1.48 Second Frame

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Clock60

Clock60

Clock60

Clock60

Clock60

Clock60

Clock60

Clock60

Clock60

Clock60

Clock60

Clock60

Clock60

Clock60

Clock60

Clock60

ChnlData

*

ChnlData108

ChnlData

#

ChnlData108

ChnlData

#

ChnlData108

ChnlData

#

ChnlData108

ChnlData

#

ChnlData108

ChnlData

#

ChnlData108

ChnlData

#

ChnlData108

ChnlData

#

ChnlData108

Mode Data Through (kbps)Forward Back

MP1 115.50 if UDP

<11.4 if TCPMP2 128

MP3 140.2

* - For MP1, channel data = 18,788; for MP2, channel data = 19,076; for MP3, channel data = 19,330# - For MP1, channel data = 108; for MP2, channel data = 346; for MP3, channel data = 684<> If TCP then all packets have additional 24 bytes overhead. Acknowledge packets are 66 bytes.

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Real Systems

– E2X: Reliable UDP

Many installations use main/standby exciters. TCP cannot be used because the Exporter only supports TCP connection to a single destination and you cannot use the same IP address in two or more pieces of equipment on the LAN. Even if the Exporter supported two or more exciters, STL traffic would double.

UDP can be used because it uses a broadcast IP address. Therefore, all equipment on the same subnet receives the Exporter data. This is not a robust protocol, however, unless the STL bridge BER is 0.

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Real Systems

– E2X: Reliable UDP (continued)

Nautel has implemented a bidirectional UDP protocol with programmable buffer depth.

- It supports main/standby exciters

- Each exciter tracks packet sequence number and requests a resend if

a packet is lost.

- Exciters can be programmed to buffer data up to 15 seconds so that

short periods of STL interruption can be tolerated. (This increases the

required diversity delay).

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• 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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Managing the Traffic

– Importer History

Problems with V1.2 resulted in one broadcast group reverting to V1.1.2 in a split configuration. It required two Importers, one at the studio and one at the transmitter site.

The next major release for Importer/Exporter is scheduled for June. The I2E and E2X interfaces should be more robust over ‘real’ LANs and STLs.

V1.1.1 May 25, 2005 First production releaseBidirectional UDP

V1.1.2 Sept 09, 2005 Split configuration and buffer

V1.2 Oct 27, 2005 TCP

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– 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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– How Do You Check Your LAN?

Use “PING” to check network latency.

Run from PC command prompt. Specify destination, number of

packets and packet size. Measures time for response from destination.

“NAUTEL” ping can be run as a scheduled task. Creates a log.

Use “Ethereal” to capture packet moving over any part of the LAN.

- Insert a hub to see all packets

- Use Analysis>Filter on IP packets to view specific packets

- Use Statistics>Summary to view average throughput

- Large packets can be fragmented to meet ethernet MTU

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– M50 Web Server

The Exgine can do more than connect to an Exporter. It includes a web server with two pages to monitor network statistics and operational status.

It is also possible to use TFTP to change configuration and upgrade software from a PC anywhere on the network.

Future releases of Exgine software will provide more elaborate web pages that provide convenient controls.

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Managing the Traffic (M50 Web Server)

Statistics Page Running count of packets

received

Running count of missing (discarded) packets

Running count of packets with CRC error

Running count of out-of-sequence packets.

Running count of packets requested (reliable UDP)

Running count of duplicate packets.

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Managing the Traffic (M50 Web Server)

Status Page Indicates Exgine state

(Reset, Init, Sync, Run)

Indicates buffer depth (1 count = 92.5mS)

Indicates timing reference (10MHz, 1PPS, 0.673Hz)

Indicates 10MHz VCXO lock (in/out sync).

Indicates std dev on clock packets (< 15mS).

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Glossary of Terms and AcronymsBER 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.

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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

SPS Secondary Program Service

STL Studio-Transmitter Link

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Glossary of Terms and Acronyms

TCP 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.

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IBOC System Networking