What is HARQ and explain cell breathing.

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Hybrid automatic repeat-request(HARQ):Data and voice blocks are transmitted in 10 ms time-intervals called frames. At each frame and for each transmission the SIR is evaluated and used to derive the Block Error Rate (BLER).  Each block is then considered correct or erroneous
according to a random experiment based on the BLER. For the packet switched traffic only, an ideal ARQ procedure is adopted, i.e., the transmitted block is kept in the transmitting queue in
case of error and is cancelled otherwise

Cell breathing is the constant change of the range of the geographical area covered by a cellular telephone transmitter based on the amount of traffic currently using that transmitter. When a cell becomes heavily loaded, it shrinks.

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