SR and RC

CDMA2000 defines two spreading rates, referred to as spreading rate 1
(SR1) and spreading rate 3 (SR3). The SR1 spreading rate is utilized for IS-
95A/B and CDMA2000 phase 1, 1xRTT implementations, whereas SR3 is
destined for CDMA2000 Phase 2, 3xRTT.
For CDMA2000, the SR1 has a chip rate of 1.2288 Mbps and occupies the
same bandwidth as CDMAOne signals. The SR1 is a direct spread method
and follows the same concept as that used for IS-95 systems. However, for
3xRTT, a SR3 signal is introduced and has a rate of 3.6864 Mbps (3

1.2288 Mcps) and therefore occupies three times the bandwidth of a
cdmaOne or 1xRTT channel. The SR3 system incorporates all the new coding
implemented in a SR1 system while supporting even higher data rates.
The 3xRTT channel scheme utilizes a multicarrier forward link and direct
spread reverse link.
The IS-2000 specification also defines for both 1xRTT and 3xRTT radio
access methods a total of nine forward and six reverse link radio configurations,
as well as two different spreading rates. The radio configurations
involve different modulations, coding, and vocoders, while the spreading
rates address the usage amount of two different chip rates. The radio configurations
are referred to as RC1 for radio configuration 1.
RC1 is backward-compatible with cdmaOne for 9.6-Kbps voice traffic
and it supports circuit-switched data rates of 1.2 Kbps to 9.6 Kbps. RC3 is
based on the 9.6-Kbps rate and supports variable voice rates from 1.2k to
9.6 Kbps, while also supporting packet data rates of 19.2, 38.4, 76.8, and
153.6 Kbps, but it operates using a SR1.
Tables 7-8 and 7-9 are meant to help illustrate the perturbations that
exist with the different radio configurations and spreading rates. Table 7-8
is associated with the forward link, whereas Table 7-9 is associated with the
reverse link.