RFRDS vs RDS-2: Understanding the Key Differences
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This page compares RDS vs RDS-2 and mentions the difference between RDS and RDS-2.
Introduction:
RDS (Radio Data System) signals are transmitted by FM radio stations along with other signals such as mono audio, stereo audio, tone, and direct band. The European standard specifications are published under document CENELEC EN 50067.
Most FM stations use RDS, mostly in car radio receivers in Europe. RDS carries information such as station identification, time, and program information along with audio.
RDS occupies about 4 KHz bandwidth and it is transmitted on a 57 KHz center frequency using BPSK modulation. BPSK modulated RDS information is frequency shifted to 57 KHz and mixed with other components of the FM signal before FM transmission. BPSK symbols are transmitted at a rate of about 1187.5 symbols/sec. Hence, the RDS raw data rate is about 1.2 Kbps including overhead information.
RDS uses CRC (Cyclic Redundancy Check) for error detection. RDS has been in use since 1984 and standardized in 1990. In 2016, the RDS forum proposed modifications to existing RDS. The RDS-2 specifications were published in Oct. 2018 under IEC 62106:2018 document.
The RDS forum has developed a new protocol known as RDS2 file transfer which can be used to transfer all kinds of file types up to the size of 163 KB. RDS-2 is backward compatible with the RDS version.
RDS is used with FM and digital radio whereas RDS-2 is used by FM/digital radio and internet radio.
Following table summarizes the difference between RDS and RDS2 versions.
| Specifications/Features | RDS | RDS-2 |
|---|---|---|
| AFs (Alternative Frequencies) | 87.5 to 108 MHz | 64 to 108 MHz |
| PS (Programme Service) | 8 characters (Max.) | Upto 32 bytes, UTF-8 coded |
| Programme Logo | Not available | Various formats up to 12 Kbyte size can be used |
| Enhanced radio text | Up to 64 characters (Latin/UTF-8 coded) | Up to 128 byte (UTF-8 coded) |
| Traffic Message Channel | Carries few messages viz. 50 messages/minute (max.) | Carries many more messages viz. 250 messages/minute using second subcarrier |
| Number of subcarriers (SCs) | 1 | Up to 4 |
| Number of parallel active open data applications | 20 (8 in Type-A, 12 in Type-B) | As supported in RDS plus additional 64 (Type-C) |
| Cost of implementation | Low | High |
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