Page 94 - Electrical Engineering Dictionary

tary switch is not turned on until the desig- information will always result in the same ci-
nated blanking time has elapsed. phertext whena particularblockcipher is em-
ployed for encryption. See also encryption,
blind deconvolution the recovery of a sig- stream cipher.
nal x[n] from y[n] — the convolution of the
signal with an unknown system h[n]: block code a mapping of k input binary
symbols into n output symbols.
y[n]= h[n]∗ x[n].
block coding (1) an error control coding
Occasionally, some knowledge of h[n] is technique in which a number of information
available (e.g., that it is a high-pass or low- symbols, and blocks, are protected against
pass filter). Frequently, detailed knowledge transmission errors by adding additional re-
is available about the structure of x. See also dundant symbols. The additional symbols
convolution. are usually calculated according to a mathe-
matical transformation based on the so-called
blind via a via connected to either the generator polynomial of the code. A block
preliminary side or secondary side and one code is typically characterized by the param-
or more internal layers of a multilayer pack- eters (n, k), where k is the number of infor-
aging and interconnecting structure. mation symbols per data word, and n the fi-
nal number of symbols in the code word after
blink incomputerdisplaysystems, atech- the addition of parity symbols or redundant
nique in which a pixel is alternatively turned symbols. The rate of a block code is given
on and off. by k/n.
Typically, the lower the rate of a code
Bloch vector a set of linear combinations the greater the number of errors detectable
of density matrix elements, written in vector and correctable by the code. Block codes
form, that can often be related to specific ob- in which the block of information symbols
servables in a quantum mechanical system. and parity symbols are readily discernable,
For example, in two-level systems the Bloch are known as systematic block codes. The
vector components are 2Re(ρ 12 ),2Im(ρ 12 ), receiver uses the parity symbols to deter-
and ρ 11 − ρ 22 , which are related to nonlin- mine whether any of the symbols were re-
ear refractive index, absorption, and popula- ceived in error and either attempts to cor-
tion differences, respectively. The time evo- rect errors or requests a retransmission of
lution of two-level systems can be described the information. See also automatic repeat
in terms of rotations of the Bloch vector. request, binary code, convolutional coding,
error control coding.
block a group of sequential locations held (2) refers to (channel) coding schemes
as one unit in a cache and selected as whole. in which the input stream of information
Also called a line. See also memory block. symbols is split into nonoverlapping blocks
which then are mapped into blocks of en-
block cipher an encryption system in coded symbols (codewords). The mapping
which a successive number of fundamen- only depends on the current message block.
tal plaintext information symbols, usually Compare with trellis coding.
termed a block of plaintext information, are
encrypted according to the encryption key. block diagram a diagrammatic represen-
All information blocks are encrypted in the tation of system components and their inter-
same manner according to the transforma- connections. In elementary linear systems,
tion determined by the encryption key. This the blocks are often defined by transfer func-
implies that two identical blocks of plaintext tions or state space equations while the inter-

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