PHICH (LTE)
PHICH Physical Hybrid ARQ Indicator Channel is the Physical Hybrid ARQ Automatic Repeat Request 1) A distinct unit of data that is carried on an ARQ-enabled connection. Such a unit is assigned a sequence number, and is managed as a distinct entity by the ARQ state machines. Block size is a parameter negotiated during connection establishment. 2) automatic retransmission request - A signal used in digital communications systems used to signal the transmitting device to retransmit a block of data. Indicator Channel and carries the hybrid-ARQ ACK Acknowledgement/NACK Negative Acknowledgement.
The modulation type is BPSK Binary phase shift keying - A type of phase modulation using 2 distinct carrier phases to signal ones and zeros. (CDM). CDM stands for Code Domain Modulation. Multiple users have the same PHICH allocation, but their data is separated by orthogonal codes, similar to CDMA Code Division Multiple Access: One of several digital wireless transmission methods in which signals are encoded using a specific pseudo-random sequence, or code, to define a communication channel. A receiver, knowing the code, can use it to decode the received signal in the presence of other signals in the channel. This is one of several "spread spectrum" techniques, which allows multiple users to share the same radio frequency spectrum by assigning each active user an unique code. CDMA offers improved spectral efficiency over analog transmission in that it allows for greater frequency reuse. Other characteristics of CDMA systems reduce dropped calls, increase battery life and offer more secure transmission. See also IS-95..
See Downlink Control Channel Properties for more information on PHICH.
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