IS-95A Fwd Ch Convolutional Encoder (CDMA Reference Blockset)

Convolutionally encode the input data frame

Library

IS-95 Base Station Transmitter

Description

This block convolutionally encodes the input data frame. For the Sync and Paging channels, the data frame consists only of the information bits. For the Traffic channel, the data frame includes the information data, the CRC bits and the tail bits in accordance with the IS-95A specification. Note that as a result, the last 8 bits of each Traffic channel input frame must be 0.

The convolutional encoder is a rate 1/2 encoder having a constraint length of nine. The generator functions are 753 (octal) and 561 (octal). The state of the convolutional encoder, upon initialization, is the all-zeros state. For this block, the Frame In port size is equal to the maximum possible size of 288 (Rate Set II, Traffic Full Rate). Similarly, the output port size is equal to the maximum possible size of 576 (Rate Set II, Traffic Full Rate). The following table shows the number of relevant bits in the input and output, which depends on the channel type and the data rate. The block ignores input bits beyond the relevant bits, and sets output bits beyond the relevant bits to zero.

Channel Type
Number of Relevant Input Bits
Number of Relevant Output Bits

Sync, Eighth Rate
32
64

Paging, Full Rate
192
384

Paging, Half Rate
96
192

Traffic, Rate Set I, Full Rate
192
384

Traffic, Rate Set I, Half Rate
96
192

Traffic, Rate Set I, Quarter Rate
48
96

Traffic, Rate Set I, Eighth Rate
24
48

Traffic, Rate Set II, Full Rate
288
576

Traffic, Rate Set II, Half Rate
144
288

Traffic, Rate Set II, Quarter Rate
72
144

Traffic, Rate Set II, Eighth Rate
36
72

Channel Type	Number of Relevant Input Bits	Number of Relevant Output Bits
Sync, Eighth Rate	32	64
Paging, Full Rate	192	384
Paging, Half Rate	96	192
Traffic, Rate Set I, Full Rate	192	384
Traffic, Rate Set I, Half Rate	96	192
Traffic, Rate Set I, Quarter Rate	48	96
Traffic, Rate Set I, Eighth Rate	24	48
Traffic, Rate Set II, Full Rate	288	576
Traffic, Rate Set II, Half Rate	144	288
Traffic, Rate Set II, Quarter Rate	72	144
Traffic, Rate Set II, Eighth Rate	36	72

Inputs

Rate

Integer scalar that specifies the data rate for the input signal. To indicate a rate fraction of Full, Half, Quarter, or Eighth, use an input value of 0, 1, 2, or 3, respectively. The table below shows all valid channel types and rate fractions, along with their associated data rates and Rate input values.


Channel Type	Data Rate (bps)	Rate Input Value
Sync (always Eighth rate)	1200	3
Paging, Full	9600	0
Paging, Half	4800	1
Traffic, Rate Set I, Full	9600	0
Traffic, Rate Set I, Half	4800	1
Traffic, Rate Set I, Quarter	2400	2
Traffic, Rate Set I, Eighth	1200	3
Traffic, Rate Set II, Full	14400	0
Traffic, Rate Set II, Half	7200	1
Traffic, Rate Set II, Quarter	3600	2
Traffic, Rate Set II, Eighth	1800	3

Frame In

Real binary vector of size 288 containing the input frame, which consists of information bits, CRC, tail bits, and zeros.

Outputs

Binary vector of size 576 containing the convolutionally encoded output frame.

Dialog Box

Parameters

Rate set: The rate set, either Rate Set I or Rate Set II.
Channel type: The channel type, either Sync, Paging, or Traffic.
Initial encoder state: Integer scalar that specifies the convolutional encoder's initial state. The default value is between 0 and 511. Empty brackets indicate the default value of 0.

Specification References

IS-95A 7.1.3.1.3
J-STD-008 3.1.3.1.3

IS-95A Fwd Ch Base Station Transmitter Interface IS-95A Fwd Ch Descrambler