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The packet erasure channel is a communication channel model where sequential packets are either received or lost (at a known location). This channel model is closely related to the binary erasure channel .
In coding theory and information theory, a binary erasure channel (BEC) is a communications channel model. A transmitter sends a bit (a zero or a one), and the receiver either receives the bit correctly, or with some probability P e {\displaystyle P_{e}} receives a message that the bit was not received ("erased") .
A binary erasure channel (BEC) with erasure probability p is a binary input, ternary output channel. The possible channel outputs are 0, 1, and a third symbol 'e' called an erasure. The erasure represents complete loss of information about an input bit. The capacity of the BEC is 1 − p bits per channel use.
If the channel characteristics cannot be determined, or are highly variable, an error-detection scheme may be combined with a system for retransmissions of erroneous data. This is known as automatic repeat request (ARQ), and is most notably used in the Internet.
Linear Network Coding, a type of erasure correcting code across networks instead of point-to-point links; Long code; Low-density parity-check code, also known as Gallager code, as the archetype for sparse graph codes; LT code, which is a near-optimal rateless erasure correcting code (Fountain code) m of n codes
Thus, the message can be decoded iteratively. For other channel models, the messages passed between the variable nodes and check nodes are real numbers, which express probabilities and likelihoods of belief. This result can be validated by multiplying the corrected codeword r by the parity-check matrix H:
A broadcast channel is a channel that provides a broadcasting service, i.e. that sends data addressed to all users in the network. Cellular network examples are the paging service as well as the Multimedia Broadcast Multicast Service. A multicast channel is a channel where data is addressed to a group of subscribing users. LTE examples are the ...
Voltage-gated ion channel. When the membrane is polarized, the voltage sensing domain of the channel shifts, opening the channel to ion flow (ions represented by yellow circles). Voltage-gated ion channels open and close in response to the electrical potential across the cell membrane. Portions of the channel domain act as voltage sensors.