RFIBOC Basics: In-Band On-Channel Digital Radio
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This page provides a basic overview of IBOC, which stands for In-Band On-Channel digital radio, and its various modes.
IBOC technology was developed to bring CD-quality sound and data transmission capabilities to existing FM channels. This allows for a richer listening experience and the delivery of useful information alongside traditional radio programming.
Typical data services broadcast using IBOC include:
- Weather updates
- Stock quotes
- Sports news
- Emergency alerts and regulatory messages from government agencies
IBOC enables both analog and digital signals to be transmitted on the same FM channel. The digital signal is modulated using Orthogonal Frequency Division Multiplexing (OFDM).
IBOC Features and Specifications
Here’s a table summarizing the key features and 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-specific FM band allocations |
| Data Rate | • As per IBOC mode of operation |
| • Hybrid: 97 Kbps, Extended Hybrid: 147 kbps, All digital: 277 kbps | |
| Audio/Data Handling | It carries both audio and data together at different rates. For example, 96kbps can be used for audio, and the rest for data. Using 147kbps, 96kbps is used for audio and 51kbps for data. |
| Audio/Data Modes | Hybrid, Extended Hybrid, and All-Digital modes |
IBOC Modes: Hybrid, Extended Hybrid, and All-Digital
IBOC offers three primary modes of operation:
- Hybrid Mode
- Extended Hybrid Mode
- All-Digital Mode
Let’s explore each of these modes in more detail.
IBOC Hybrid Mode
Figure 1: Hybrid IBOC Mode
As shown in Figure 1, Hybrid Mode places digital information within a 69.041 KHz bandwidth on either side of the analog FM signal. These digital signals are positioned 129.361 KHz away from the FM carrier signal. The sidebands are attenuated by 23 dB relative to the total power of the FM signal.
IBOC Extended Hybrid Mode
Figure 2: Extended Hybrid IBOC Mode
Figure 2 illustrates the Extended Hybrid Mode. This mode builds upon the Hybrid Mode by adding supplementary digital signals closer to the analog signal. It utilizes a 27.617 KHz bandwidth to insert this additional digital information, positioning it at 101.744 KHz on both sides of the analog FM signal. These extra digital sidebands increase data capacity, hence the name “extended hybrid mode.” The total power of the digital sidebands is approximately 20 dB lower than the nominal power of the FM carrier.
IBOC All Digital Mode
Figure 3: All-Digital IBOC Mode
Figure 3 shows the All-Digital Mode. In this mode, all information is transmitted digitally on the FM carrier. The center analog portion is removed and replaced with low-power digital sidebands. The power of these sidebands is 10 dB lower than the original FM analog carrier.
