digital communications Data transmission and data reception or, more broadly, data communication or digital communications is the transfer and reception of data in the form of a digital bitstream or a digitized analog signal transmitted over a point-to-point or ...

, a chip is a pulse of a

direct-sequence spread spectrum In telecommunications, direct-sequence spread spectrum (DSSS) is a spread-spectrum modulation technique primarily used to reduce overall signal interference. The direct-sequence modulation makes the transmitted signal wider in bandwidth than ...

(DSSS) code, such as a pseudo-random noise (PN) code sequence used in direct-sequence

code-division multiple access Code-division multiple access (CDMA) is a channel access method used by various radio communication technologies. CDMA is an example of multiple access, where several transmitters can send information simultaneously over a single communicatio ...

(CDMA)

channel access In telecommunications and computer networks, a channel access method or multiple access method allows more than two terminals connected to the same transmission medium to transmit over it and to share its capacity. Examples of shared physical med ...

techniques. In a binary direct-sequence system, each chip is typically a rectangular pulse of +1 or −1 amplitude, which is multiplied by a data sequence (similarly +1 or −1 representing the message

bit The bit is the most basic unit of information in computing and digital communications. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represente ...

s) and by a carrier waveform to make the transmitted signal. The chips are therefore just the bit sequence out of the code generator; they are called chips to avoid confusing them with message bits. The chip rate of a code is the number of pulses per second (chips per second) at which the code is transmitted (or received). The chip rate is larger than the symbol rate, meaning that one symbol is represented by multiple chips. The ratio is known as the spreading factor (SF) or processing gain: :

\mbox = \frac

Orthogonal variable spreading factor

Orthogonal variable spreading factor (OVSF) is an implementation of

(CDMA) where before each signal is transmitted, the signal is spread over a wide spectrum range through the use of a user's code. Users' codes are carefully chosen to be mutually orthogonal to each other. These codes are derived from an OVSF code tree, and each user is given a different code. An OVSF code tree is a complete binary tree that reflects the construction of

Hadamard matrices In mathematics, a Hadamard matrix, named after the French mathematician Jacques Hadamard, is a square matrix whose entries are either +1 or −1 and whose rows are mutually orthogonal. In geometric terms, this means that each pair of rows in ...

References

External links

CDMA basics
{{Wireless-stub

Orthogonal variable spreading factor

See also

References

External links