IBOC Basics | In Band On Channel Digital Radio | Modes

This page covers IBOC basics and mentions IBOC features. IBOC is the short form of In Band On Channel digital radio. It mentions IBOC modes viz. hybrid mode, extended hybrid mode and all digital mode. The difference between these modes can be derived.

The technology has been developed to support CD quality sound on existing FM channel along with data transmission for various applications. The typical data services broadcasted using IBOC technology include weather, stock quotes, sports news, emergency and regulatory messages from government establishments etc.

It allows transmissions in both analog and digital format on existing FM channel. The digital signal uses OFDM as transmission modulation. OFDM stands for Orthogonal Frequency Division Multiplexing. Following table mentions features/specifications of IBOC technology.

Specifications or Features IBOC Support
Full Form In Band On Channel
Frequency of Operation 88 to 108 MHz as per country wise allocations of the FM band
Data Rate • As per IBOC mode of operation
• Hybrid: 97 Kbps, Extended Hybrid: 147 kbps, All digital: 277 kbps
It carries both audio and data together at different rates.
As per one example, 96kbps is used as audio and rest is utilized for data.
For example for 147kbps, 96kbps used for audio and 51kbps used for data.
Support Audio/Data
Modes Hybrid, Extended Hybrid and All digital modes

IBOC Modes | hybrid mode, extended hybrid mode, all digital mode

Following are the three IBOC Modes of Operation.
• Hybrid Mode
• Extended Hybrid Mode
• All Digital Mode

IBOC Hybrid Mode

Hybrid IBOC Mode

The figure-1 depicts IBOC hybrid mode type. In this mode, digital information is placed on bandwidth of 69.041 KHz as shown on either side of analog FM signal. They are placed at 129.361KHz away from the FM carrier signal. Both the side bands are 23 dB down compare to total power of FM signal.

IBOC Extended Hybrid Mode

Extended Hybrid IBOC Mode

The figure-2 depicts IBOC extended hybrid mode type. This mode includes hybrid mode and adds additional digital signals which are placed close to the analog signal. It uses 27.617 KHz bandwidth to insert this additional digital information. The insertion of information is done at 101.744 KHz on both the sides of the analog FM signal.

The extra digital sidebands are used in order to increase the data capacity. Hence the mode is known as extended hybrid mode. The total power of digital sidebands is about 20 dB lower compare to nominal power of FM carrier.

IBOC All Digital Mode

All Digital IBOC Mode

The figure-3 depicts IBOC all digital mode type. This mode uses all the digital informations which are transmitted on FM carrier. The middle analog part is being removed here and the same has been replaced using low power digital sidebands. The power of these sidebands is 10dB lower compare to FM analog carrier.

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