Definition of Spread spectrum rate(SR) and RC

1.1 Definition of SR and RC

1.1.1 Spread Spectrum Rate, SR

“Spread spectrum rate (SR)” refers to the PN chip rate in the forward or reverse CDMA channel. SR1 and SR3 are introduced below.

In the CDMA 1X system that provides SR1, both the forward and reverse CDMA channels employ DS with a chip rate 1.2288Mchip/s for the single carrier. Basically, SR1 serves to comply with IS-95 and to upgrade smoothly to 3G.

The other spread spectrum rate is SR3, i.e., 3X. The 3X system has 3 carriers in the forward CDMA channel, each of which employs DS with a chip rate of 1.2288Mchip/s. The three carriers, together, are called the multi-carrier, MC. The reverse CDMA channel has one single carrier with a bandwidth of 3*1.2288MHZ, which employs DS with a chip rate of 3.6864Mchip/s.

Band configuration of SR1 and SR3 are very flexible. There are altogether three patterns of configuration: independent configuration, mixed configuration, and overlapped configuration.

The mixed configuration pattern, that is, the forward channel is configured with SR3 and the reverse channel has SR1, is very suitable for asymmetric data service. Besides, the modulation pattern of SR3 and SR1 ensures SR3 and SR1 to be orthogonal (or quasi-orthogonal) and makes it possible for SR3 and SR1 to be overlapped in configuration. In case of mixed configuration, SR1 and SR3 can share the same forward channel, such as the synchronous channel etc. The system then can support simultaneously the MSes working at SR1 and SR3, i.e., two MSes can demodulate the same synchronous channel, then configure in accordance with the system basic parameters carried in the synchronous channel and work in their specific mode. Apart from this, the MS compliant with IS-95 can access the BS that supports SR1 (1X); and for the 3G MS that supports 1X, as long as it supports the compatible IS-95 RC, it can access the compatible IS-95 BS. Even if it may not support the compatible IS-95 RC, it can demodulate the public channel of the IS-95 BS and find other CDMA 2000 frequencies and channels by way of the system configuration parameters carried in the public channel. Thus in the existing 2G system, IS-95 can be smoothly upgraded to CDMA 2000.

1.1.2 Radio Configuration, RC

“Radio configuration (RC)” refers to the working mode of a series of forward or reverse service channels. Each RC supports a set of data rates. Their difference lies in the various parameters of the physical channels, such as modulation characteristics and spread spectrum rate etc.

The relationship between RC and SR is shown in the following table:

Table 2-2 Characteristics of the Reverse Service Channel RC