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Comparison Of Radio Systems
Many of the world's radio stations broadcast in a variety of analog and digital formats. This page will list and compare them in chart form. CONTENTS * 1 Table * 2 References TABLE WORLD RADIO SYSTEMS (TERRESTRIAL) SYSTEM TYPE MODULATION DATA RATE SIDEBANDS? CH
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Single Channel Simulcast
SINGLE/MULTI CHANNEL SIMULCAST is the simultaneous transmission of an amplitude modulated and Digital Radio Mondiale
Digital Radio Mondiale
(DRM) in the same (SingleChannel Simulcast - SCS) or a neighbouring channel (MultiChannel Simulcast - MCS). To produce this SCS multiplex signal, the initial carrier is modulated by the DRM signal using quadrature phase modulation. This FM signal is then modulated as if it were a normal AM carrier, thus producing two modes on the single signal. Clearly the advantage of this is that both DRM and analogue radios can receive a signal they can discriminate and demodulate, with little disadvantage to either mode. It can, however, decrease DRM range, and the phase changes in the carrier can induce local oscillator interference in the AM receiver, which will show as white noise
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Orthogonal Frequency-division Multiplexing
ORTHOGONAL FREQUENCY-DIVISION MULTIPLEXING (OFDM) is a method of encoding digital data on multiple carrier frequencies. OFDM has developed into a popular scheme for wideband digital communication , used in applications such as digital television and audio broadcasting, DSL internet access , wireless networks , power line networks , and 4G mobile communications. In COFDM CODED ORTHOGONAL FREQUENCY-DIVISION MULTIPLEXING forward error correction (convolutional coding) and time/frequency interleaving are applied to the signal being transmitted. This is done to overcome errors in mobile communication channels affected by multipath propagation and Doppler effects . COFDM was introduced by Alard in 1986 for Digital Audio Broadcasting
Digital Audio Broadcasting
for Eureka Project 147. In practice, OFDM has become used in combination with such coding and interleaving, so that the terms COFDM and OFDM co-apply to common applications
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DQPSK
PHASE-SHIFT KEYING (PSK) is a digital modulation process which conveys data by changing (modulating) the phase of a reference signal (the carrier wave ). The modulation occurs by varying the sine and cosine inputs at a precise time. It is widely used for wireless LANs , RFID
RFID
and Bluetooth
Bluetooth
communication. Any digital modulation scheme uses a finite number of distinct signals to represent digital data. PSK uses a finite number of phases, each assigned a unique pattern of binary digits . Usually, each phase encodes an equal number of bits. Each pattern of bits forms the symbol that is represented by the particular phase. The demodulator , which is designed specifically for the symbol-set used by the modulator, determines the phase of the received signal and maps it back to the symbol it represents, thus recovering the original data
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HD Radio
HD RADIO is a trademarked term for iBiquity 's in-band on-channel (IBOC) digital radio technology used by AM and FM radio stations to transmit audio and data by using a digital signal embedded "on-frequency" immediately above and below a station's standard analog signal , providing the means to listen to the same program in either HD (digital radio with less noise) or as a standard broadcast (analog radio with standard sound quality). The HD format also provides the means for a single radio station to simultaneously broadcast one or more different programs in addition to the program being transmitted on the radio station's analog channel. It was selected by the U.S. Federal Communications Commission (FCC) in 2002 as a digital audio broadcasting method for the United States, and is the only digital system approved by the FCC for digital AM/FM broadcasts in the United States. It is officially known as NRSC-5, with the latest version being NRSC-5-C
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Channel (communications)
A COMMUNICATION CHANNEL or simply CHANNEL refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking . A channel is used to convey an information signal, for example a digital bit stream , from one or several senders (or transmitters) to one or several receivers . A channel has a certain capacity for transmitting information, often measured by its bandwidth in Hz or its data rate in bits per second . Communicating data from one location to another requires some form of pathway or medium. These pathways, called communication channels, use two types of media: cable (twisted-pair wire, cable, and fiber-optic cable) and broadcast (microwave, satellite, radio, and infrared). Cable or wire line media use physical wires of cables to transmit data and information. Twisted-pair wire and coaxial cables are made of copper, and fiber-optic cable is made of glass
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MPEG-4
MPEG-4 is a method of defining compression of audio and visual (AV) digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO /IEC Moving Picture Experts Group
Moving Picture Experts Group
(MPEG) ( ISO/IEC JTC1 /SC29/WG11) under the formal standard ISO/IEC 14496 – Coding of audio-visual objects. Uses of MPEG-4 include compression of AV data for web (streaming media ) and CD distribution, voice (telephone , videophone ) and broadcast television applications
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Spectral Band Replication
SPECTRAL BAND REPLICATION (SBR) is a technology to enhance audio or speech codecs , especially at low bit rates and is based on harmonic redundancy in the frequency domain. It can be combined with any audio compression codec: the codec itself transmits the lower and midfrequencies of the spectrum, while SBR replicates higher frequency content by transposing up harmonics from the lower and midfrequencies at the decoder. Some guidance information for reconstruction of the high-frequency spectral envelope is transmitted as side information. When needed, it also reconstructs or adaptively mixes in noise-like information in selected frequency bands in order to faithfully replicate signals that originally contained no or fewer tonal components
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In-band On-channel
IN-BAND ON-CHANNEL (IBOC) is a hybrid method of transmitting digital radio and analog radio broadcast signals simultaneously on the same frequency . By utilizing additional digital subcarriers or sidebands , digital information is "multiplexed " on an AM or FM analog signal, thus avoiding re-allocation of the broadcast bands. However, by putting RF energy outside of the normally-defined channel , interference to adjacent channel stations is increased when using digital sidebands. IBOC does allow for multiple program channels, though this can entail taking some existing subcarriers off the air to make additional bandwidth available in the modulation baseband . On FM, this could eventually mean removing stereo . On AM, IBOC is incompatible with analog stereo, and any additional channels are limited to highly compressed voice, such as traffic and weather
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HVXC
HARMONIC VECTOR EXCITATION CODING, abbreviated as HVXC is a speech coding algorithm specified in MPEG-4 Part 3 ( MPEG-4 Audio) standard for very low bit rate speech coding. HVXC supports bit rates of 2 and 4 kbit/s in the fixed and variable bit rate mode and sampling frequency 8 kHz. It also operates at lower bitrates, such as 1.2 - 1.7 kbit/s, using a variable bit rate technique. The total algorithmic delay for the encoder and decoder is 36 ms. It was published as subpart 2 of ISO /IEC 14496-3:1999 ( MPEG-4 Audio) in 1999. An extended version of HVXC was published in MPEG-4 Audio Version 2 (ISO/IEC 14496-3:1999/Amd 1:2000). MPEG-4 Natural Speech Coding Tool Set uses two algorithms: HVXC and CELP ( Code Excited Linear Prediction ). HVXC is used at a low bit rate of 2 or 4 kbit/s. Higher bitrates than 4 kbit/s in addition to 3.85 kbit/s are covered by CELP
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CELP
CODE-EXCITED LINEAR PREDICTION (CELP) is a speech coding algorithm originally proposed by M. R. Schroeder and B. S. Atal in 1985. At the time, it provided significantly better quality than existing low bit-rate algorithms, such as residual-excited linear prediction and linear predictive coding vocoders (e.g., FS-1015 ). Along with its variants, such as algebraic CELP , relaxed CELP , low-delay CELP and vector sum excited linear prediction , it is currently the most widely used speech coding algorithm. It is also used in MPEG-4 Audio speech coding. CELP is commonly used as a generic term for a class of algorithms and not for a particular codec
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QAM
QUADRATURE AMPLITUDE MODULATION (QAM) is both an analog and a digital modulation scheme. It conveys two analog message signals, or two digital bit streams , by changing (modulating) the amplitudes of two carrier waves , using the amplitude-shift keying (ASK) digital modulation scheme or amplitude modulation (AM) analog modulation scheme. The two carrier waves of the same frequency, usually sinusoids , are out of phase with each other by 90° and are thus called quadrature carriers or quadrature components — hence the name of the scheme. The modulated waves are summed, and the final waveform is a combination of both phase-shift keying (PSK) and amplitude-shift keying (ASK), or, in the analog case, of phase modulation (PM) and amplitude modulation. In the digital QAM case, a finite number of at least two phases and at least two amplitudes are used
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Frequency Allocation
FREQUENCY ALLOCATION (or SPECTRUM ALLOCATION) is the division of the electromagnetic spectrum into radio frequency bands . This spectrum management is regulated by governments in most countries. Radio propagation does not stop at national boundaries. Giving technical and economic reasons, governments have sought to harmonise the allocation of RF bands and their standardization. CONTENTS * 1 ITU definition * 2 Bodies * 3 Example * 4 See also * 5 References * 6 External links ITU DEFINITIONThe International Telecommunication Union – defines frequency allocation as being of "a given frequency band for the purpose of its use by one or more terrestrial or space radiocommunication services or the radio astronomy service under specified conditions". Frequency allocation
Frequency allocation
is also a special term, used in national frequency administration
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Single-frequency Network
A SINGLE-FREQUENCY NETWORK or SFN is a broadcast network where several transmitters simultaneously send the same signal over the same frequency channel. SINGLE FREQUENCY NETWORK MODEL Top:Multi Frequency
Frequency
Network Bottom:Single Frequency
Frequency
Network Analog AM and FM radio broadcast networks as well as digital broadcast networks can operate in this manner. SFNs are not generally compatible with analog television transmission, since the SFN results in ghosting due to echoes of the same signal. A simplified form of SFN can be achieved by a low power co-channel repeater , booster or broadcast translator , which is utilized as gap filler transmitter. The aim of SFNs is efficient utilization of the radio spectrum , allowing a higher number of radio and TV programs in comparison to traditional multi-frequency network (MFN) transmission
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Metadata
METADATA is "data that provides information about other data". Three distinct types of metadata exist: DESCRIPTIVE METADATA, STRUCTURAL METADATA, and ADMINISTRATIVE METADATA. * Descriptive metadata describes a resource for purposes such as discovery and identification. It can include elements such as title, abstract, author, and keywords. * Structural metadata is metadata about containers of data and indicates how compound objects are put together, for example, how pages are ordered to form chapters. It describes the types, versions, relationships and other characteristics of digital materials. * Administrative metadata provides information to help manage a resource, such as when and how it was created, file type and other technical information, and who can access it
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Digital Subchannel
In broadcasting, DIGITAL SUBCHANNELS are a method of transmitting more than one independent program stream simultaneously from the same digital radio or television station on the same radio frequency channel. This is done by using data compression techniques to reduce the size of each individual program stream, and multiplexing to combine them into a single signal. The practice is sometimes called "multicasting "
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