all redundant bits are transmitted and the information bit rate drops. In very bad link conditions retransmissions occur due to HARQ which ensures correct reception of the sent information but further decreases the bit rate. Thus HSDPA adapts to achieve very high bit rates, of the order of 14 megabit/sec, on clear channels using 16-QAM and close to 1/1 coding rate. On noisy channels HSDPA adapts to provide reliable communications using QPSK and 1/3 coding rate but the information bit rate drops to about 2.4 megabit/sec. This adaptation is performed up to 500 times per second. See also Cliff effect Hierarchical modulation Radio resource management References Quantized radio modulation modes Radio resource management