| 1pps | One pulse per second. An output of a GPS receiver. The 1pps epoc is synchronised to UTC. |
Band III digital radio
allocation in the UK | 217.5 - 230 MHz. |
| BER | Bit Error Rate – the number of bit errors in the data stream. An example is 1 in 104. This means 1 errored bit in 10,000. |
| CIF | Common Interleaved Frame. Common interleaved frames (CIFs) exist in the COFDM modulator. After convolutional coding and time interleaving have been applied to each audio and data stream, these streams are multiplexed together to form CIFs. The number of CIFs per transmission frame is dependent on the mode. |
| COFDM | Coded Orthogonal FrequencyDivision Multiplexing. |
| Converlutional Coding | A form of forward error correction can also be called viterbi error correction. |
| CRC | Cyclic Redundancy Check sum. |
| Crest factor | A way of defining the peak to mean of the signal. |
| DAB | Digital Audio Broadcasting, also known as digital radio. |
| DQPSK | Differential Quadrative Phase Shift Keying. DQPSK is the modulation applied to each carrier in a digital radio ensemble. |
| DR | Digital radio. |
| Ensemble | A 1.536MHz block of carriers. |
| ETSI | European Telecom Standardisation Institute. |
| Eureka 147 | The DAB project in the European Research Commission Agency. |
| FEC | Forward Error Correction. |
| FFT | Fast Fourier Transform. |
| FIBs | Fast Information Block(s). FIBs are carried in the FIC. |
| FIC | Fast Information Channel. The FIC is used for overhead and control information. In particular it is used to send the Multiplex Configuration Information (MCI). |
| GPS | Global Positioning System. |
| Guard Band | The amount of spectrum between digital radio ensembles. |
| Guard Interval | The length of time the symbol is repeated. In mode 1 this is 250µs. |
| I/Q Signals | Inphase and Quadrature Signals. |
| IFFT | Inverse Fast Fourier Transform. |
| Impulse Response | This is an output of a digital radio receiver which allows the time and voltage component of two or more transmissions working in a SFN to be compared. |
L Band digital radio
allocation | 1452 to 1492 MHz. |
| MCI | Multiplex Configuration Information. |
| Mode | There are four modes defined in digital radio modes I-IV they are defined in the table below. (See Transmission modes). |
| MSC | Main Service Channel. Used to carry audio and data service components. |
| Multiplex | The name given to a collection of audio and data services which are to be transmitted on an ensemble. |
| Multiplexer | The unit which takes the audio and data services and combines then into a single serial data stream. |
| Musicam | Musicam is a method for audio base band coding. The bit rate of the coding process is reduced by using a psychoucoustic model. Masking pattern, Universal Sub band, Integrated Coding And Multiplexing. |
| NA | Network Adaptive. A 2 Mbit/s data stream which contains the same data as the NI data stream but now conforms to the G704 framing structure and contains a time stamp and Reed Solomon coding. |
| NI | Network Independent. A 2 Mbit data stream which is the output of a multiplexer. The data stream is a multiplex of Musicam audio data streams so has a 24ms frame structure. |
| PAD | Programme Associated Data. |
| SFN | Single Frequency Network. |
| T DAB | Terrestrial Digital Audio Broadcasting. |
| TFPC | Time Frequency and Phase Control. |
| Transmission Frame | A transmission frame comprises of three elements: the synchronisation channel, the fast information channel and the main service channel (MSC). |
Transmission modes |
| Transmission mode I:
intended for SFN in
Bands I, II and III | Duration of transmission frame: 96 ms
No. of FIBs per transmission frame: 12
No. of CIFs per transmission frame: 4 | no. of carriers: 1536
carrier spacing: 1 kHz
symbol duration: 1,246 µs
guard interval: 246 µs |
| Transmission mode II:
intended for local services
in Bands I, II, III, IV, V
and L-band | Duration of transmission frame: 24 ms
No. of FIBs per transmission frame: 3
No. of CIFs per transmission frame: 1 | no. of carriers: 384
carrier spacing: 4 kHz
symbol duration: 312 µs
guard interval: 62 µs |
| Transmission mode III:
intended for frequencies
below 3 GHz and cable | Duration of transmission frame: 24 ms
No. of FIBs per transmission frame: 4
No. of CIFs per transmission frame: 1 | no. of carriers: 192
carrier spacing: 8 kHz
symbol duration: 156 µs
guard interval: 31 µs |
| Transmission mode IV:
intended for local services
in Bands I, II, III, IV, V and
L-band (for optimum SFN
operation in L-band) | Duration of transmission frame: 48 ms
No. of FIBs per transmission frame: 6
No. of CIFs per transmission frame: 2 | no. of carriers: 768
carrier spacing: 2 kHz
symbol duration: 623 µs
guard interval: 123 µs |
|
|
| UEP | Unequal Error Protection. |
| UTC | Co-ordinated Universal Time. |
| XPAD | Extended Programme Associated Data. |
References |
| Ref. 1: European Telecommunication Standard: | 1. ETS 300 401 - Radio Broadcasting Systems; Digital Audio Broadcasting (DAB) to mobile, portable and fixed receivers. 2. ETS 300 799 - Digital Audio Broadcasting (DAB); Distribution Interfaces; Ensemble Transport Interface (ETI). 3. Eureka Project 147 - Digital Audio Broadcasting system guidelines for implementation and operation, volumes 1, 2 and 3. |
Ref. 2: Digital Broadcasting by
P. Dambacher, 1996: | The Institution of Electrical Engineers. |
| Ref. 3: Radio Authority documents: | 1. Notes for guidance to local radio multiplex licence applications. 2. National digital radio multiplex service licence, notes of guidance for applicants. |
