Telecommunication is the assisted Transmission of Signal over a distance for the purpose of communication. In earlier times, this may have involved the use of smoke signals, Drum , Semaphore line, flag signals or heliograph.... , Manchester code (also known as Phase Encoding, or PE) is a line code
Line code
In telecommunication, a line code is a code chosen for use within a communications system for transmission purposes. Line coding is often used for digital data transport.... in which the encoding of each data bit
Bit
A bit is a binary numeral system numerical digit, taking a value of either 0 or 1. Binary digits are a basic unit of information Computer data storage and transmission in digital computing and digital information theory.... has at least one transition and occupies the same time. It is, therefore, self-clocking
Self-clocking signal
In telecommunications and electronics, a self-clocking signal is one that can be decoded without the need for a separate clock signal or other source of synchronization.... , which means that a clock signal
Clock signal
In electronics and especially Synchronous logic digital circuits, a clock signal is a Signalling used to coordinate the actions of two or more Electronic circuit.... can be recovered from the encoded data.
Ethernet is a family of Data frame-based computer networking technologies for local area networks . The name comes from the physical concept of the Luminiferous aether.... . See also RFID). There are more complex codes e.g. 8B/10B encoding
8B/10B encoding
In telecommunications, 8b/10b is a line code that maps 8-bit Symbol s to 10-bit symbols to achieve DC-balance and bounded disparity, and yet provide enough state changes to allow reasonable clock recovery.... which use less bandwidth to achieve the same data rate (but which may be less tolerant of frequency errors and jitter
Jitter
Jitter is an unwanted variation of one or more characteristics of a periodic Signalling in electronics and telecommunications. Jitter may be seen in characteristics such as the interval between successive pulses, or the amplitude, frequency, or phase of successive cycles.... in the transmitter and receiver reference clocks).
hester code ensures frequent line voltage transitions, directly proportional to the clock rate.
Telecommunication is the assisted Transmission of Signal over a distance for the purpose of communication. In earlier times, this may have involved the use of smoke signals, Drum , Semaphore line, flag signals or heliograph.... , Manchester code (also known as Phase Encoding, or PE) is a line code
Line code
In telecommunication, a line code is a code chosen for use within a communications system for transmission purposes. Line coding is often used for digital data transport.... in which the encoding of each data bit
Bit
A bit is a binary numeral system numerical digit, taking a value of either 0 or 1. Binary digits are a basic unit of information Computer data storage and transmission in digital computing and digital information theory.... has at least one transition and occupies the same time. It is, therefore, self-clocking
Self-clocking signal
In telecommunications and electronics, a self-clocking signal is one that can be decoded without the need for a separate clock signal or other source of synchronization.... , which means that a clock signal
Clock signal
In electronics and especially Synchronous logic digital circuits, a clock signal is a Signalling used to coordinate the actions of two or more Electronic circuit.... can be recovered from the encoded data.
Ethernet is a family of Data frame-based computer networking technologies for local area networks . The name comes from the physical concept of the Luminiferous aether.... . See also RFID). There are more complex codes e.g. 8B/10B encoding
8B/10B encoding
In telecommunications, 8b/10b is a line code that maps 8-bit Symbol s to 10-bit symbols to achieve DC-balance and bounded disparity, and yet provide enough state changes to allow reasonable clock recovery.... which use less bandwidth to achieve the same data rate (but which may be less tolerant of frequency errors and jitter
Jitter
Jitter is an unwanted variation of one or more characteristics of a periodic Signalling in electronics and telecommunications. Jitter may be seen in characteristics such as the interval between successive pulses, or the amplitude, frequency, or phase of successive cycles.... in the transmitter and receiver reference clocks).
Features
Manchester code ensures frequent line voltage transitions, directly proportional to the clock rate. This helps clock recovery.
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as battery , thermocouples, solar cells, and commutator-type electric machines of the dynamo type.... component of the encoded signal is not dependent on the data and therefore carries no information, allowing the signal to be conveyed conveniently by media (e.g. Ethernet) which usually do not convey a DC component.
Description
Extracting the original data from the received encoded bit (from Manchester as per 802.3):
original data = clock XOR Manchester value
0 0 0
0 1 1
1 0 1
1 1 0
Summary:
Each bit is transmitted in a fixed time (the "period").
A 0 is expressed by a low-to-high transition, a 1 by high-to-low transition (according to G.E. Thomas' convention -- in the IEEE 802.3 convention, the reverse is true).
The transitions which signify 0 or 1 occur at the midpoint of a period.
Transitions at the start of a period are overhead and don't signify data.
Manchester code always has a transition at the middle of each bit period and may (depending on the information to be transmitted) have a transition at the start of the period also. The direction of the mid-bit transition indicates the data. Transitions at the period boundaries do not carry information. They exist only to place the signal in the correct state to allow the mid-bit transition. Although this allows the signal to be self-clocking, it doubles the bandwidth requirement compared to NRZ
Non-return-to-zero
In telecommunication, a non-return-to-zero line code is a Binary coding code in which "1s" are represented by one significant condition and "0s" are represented by some other significant condition , with no other neutral or rest condition.... coding schemes (or see also NRZI).
In the Thomas convention, the result is that the first half of a bit period matches the information bit and the second half is its complement.
Manchester encoding as phase-shift keying
Manchester encoding is a special case of binary phase-shift keying (BPSK), where the data controls the phase
Phase (waves)
The phase of an oscillation or wave is the fraction of a complete cycle corresponding to an offset in the displacement from a specified reference point at time t = 0.... of a square wave carrier
Carrier wave
In telecommunications, a carrier wave, or carrier is a waveform that is Modulation with an signal for the purpose of conveying information.... whose frequency is the data rate. Such a signal is easy to generate.
Electronic filters are electronic circuits which perform signal processing functions, specifically to remove unwanted frequency components from the signal and/or to enhance wanted ones.... can reduce the bandwidth to as low as 1Hz per bit/second without loss of information in transmission. In radio transmission, the encoded signal may also be modulated with a carrier wave
Carrier wave
In telecommunications, a carrier wave, or carrier is a waveform that is Modulation with an signal for the purpose of conveying information.... ; however, the property of 1Hz per bit/second is preserved.
Conventions for representation of data
There are two opposing conventions for the representations of data.
The first of these was first published by G. E. Thomas in 1949 and is followed by numerous authors (e.g., Tanenbaum
Andrew S. Tanenbaum
Andrew Stuart "Andy" Tanenbaum is a professor of computer science at the Vrije Universiteit, Amsterdam in the Netherlands. He is best known as the author of MINIX, a free Unix-like operating system for teaching purposes, and for his computer science textbooks, regarded as standard texts in the field.... ). It specifies that for a 0 bit the signal levels will be Low-High (assuming an amplitude physical encoding of the data) - with a low level in the first half of the bit period, and a high level in the second half. For a 1 bit the signal levels will be High-Low.
The second convention is also followed by numerous authors (e.g., Stallings) as well as by IEEE 802.4
IEEE 802.4
IEEE 802.4 defines the medium access control layer for bus networks that use a token-passing mechanism . This is an application of the concepts used in token ring networks.... (token bus) and lower speed versions of IEEE 802.3
IEEE 802.3
IEEE 802.3 is a collection of IEEE standards defining the physical layer, and the media access control of the data link layer, of wired Ethernet.... (Ethernet) standards. It states that a logic 0 is represented by a High-Low signal sequence and a logic 1 is represented by a Low-High signal sequence.
If a Manchester encoded signal is inverted in communication, it is transformed from one convention to the other. This ambiguity can be overcome by using differential Manchester encoding
Differential Manchester encoding
Differential Manchester encoding is a method of encoding data in which data and clock signals are combined to form a single self-synchronizing data stream.... .
In telecommunications, Asynchronous communication is transmission of data without the use of an external clock signal. Any timing required to recover data from the communication symbols is encoded within the symbols.... s, and the signal spectrum
Electromagnetic spectrum
The electromagnetic spectrum is the range of all possible electromagnetic radiation frequencies. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation from that particular object.... is much wider. Most high-speed communication now uses encoding schemes with better coding performance.
One consideration is synchronization of the receiver to the transmitter. It might appear that a half bit period error would give an inverted output at the receiver, but for typical data this leads to code violations. The receiver can detect these violations and use this information to synchronise accurately.
In telecommunication, coded mark inversion is a non-return-to-zero line code. It encodes zero bits as a half bit time of zero followed by a half bit time of one, and while one bits are encoded as a full bit time of a constant level....
Differential Manchester encoding is a method of encoding data in which data and clock signals are combined to form a single self-synchronizing data stream....
In telecommunications and electronics, a self-clocking signal is one that can be decoded without the need for a separate clock signal or other source of synchronization....
