 corresponding data rate values are summarized in Table 6.3. It can be observed that 8 PSK does not contribute to the link adaptation curve. Table 6.3 Peak Data Rate for 10-MHz System Data Rate BPSK 1/6 1.2 Mb/s BPSK 1/3 2.4 Mb/s QPSK 1/2 8 PSK 1/3 7.2 Mb/s QPSK 2/3 9.6 Mb/s QPSK 3/4, 8 PSK 1/2 10.8 Mb/s 16QAM 1/2, 8 PSK 2/3 14.4 Mb/s 8 PSK 3/4 16.2 Mb/s 16 QAM 2/3 19.2 Mb/s 16 QAM 3/4 21.6 Mb/s 16 QAM 4/5 23 Mb/s C 2009 by Taylor & Francis Group, LLC Single-Carrier Transmission for UTRA LTE Uplink 6.7 Impact of Fast HARQ A fast level-1 (L1) HARQ retransmission concept is used with the aim of facili- tating more aggressive and spectrally efficient packet scheduling [12]. Two soft- combining HARQ retransmission mechanisms are considered: chase combining and incremental redundancy. Both retransmission mechanisms ensure that the past retransmission is fully utilized. The major difference between these two retrans- mission mechanisms is that chase combining requires the same transmitted signal in each retransmission, whereas incremental redundancy transmits different parity bits in each retransmission. The HARQ within the medium access control (MAC) sublayer has the follow- ing characteristics: N-process stop-and-wait (SAW) HARQ is used. The HARQ processes are transmitted over N parallel time channels in order to ensure the continuous transmission to the UE. The HARQ is based on acknowledges/negative acknowledges (ACKs/ NACKs). The received data packets are acknowledged after each trans- mission. NACK implies a retransmission request for either an additional redundancy for HARQ incremental redundancy or an identical packet for the HARQ chase combining case. For the uplink, the HARQ is based on synchronous retransmissions. In the following simulations, we have assumed no error in the transmission of ACK/NACK from the BS to the UE, six SAW parallel channels, and a maxi- mum of four retransmissions. In practice, four to six SAW parallel channels are used [13]. Figure 6.13 shows the performance results of 16 QAM for lowe