IS-95A Rev Ch Walsh Modulation and Spreading (CDMA Reference Blockset)

IS-95A Rev Ch Walsh Modulation and Spreading

Perform Walsh code modulation, spreading with the long code, and power group randomization

Library

IS-95A Mobile Station Transmitter

Description

This block first performs an M-ary Walsh modulation, where M = 2^W and W is the Walsh order parameter. For every W input bits, the block generates one of the Walsh symbols from a set of 2^W Walsh sequences. Then the block internally generates the long code with which it spreads the Walsh symbols by a factor of 4.

The reverse channel transmission is gated in such a manner that the transmission in the nonfull-rate cases is only performed for a fraction of the time: half the time for half-rate channel, quarter for quarter-rate and an eighth of the time for the eighth-rate. This gating is done in terms of 1.25-ms intervals known as power groups. Using the long code, the internal data burst randomizer generates a power group rate-gating switch to gate off the redundant power groups after long code spreading.

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)	Input Value
Access (always Half rate)	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

Binary vector of size 576 representing the input data frame to be modulated.

Outputs

Data Out: Real vector of bipolar data (scaled by 2^-1/2) of size 2^W representing the modulated, spread, and randomized data sequence. The output is provided once per sample period, which results in four outputs for each Walsh symbol. The default size, 64, corresponds to one-fourth of each Walsh symbol interval.
Gating Sig: Binary vector representing the masking signal that indicates whether the data symbol is masked or if it is to be transmitted. The default size is 1 and it is generated once per Walsh symbol.

Dialog Box

Parameters

Channel type: The channel type, either Access or Traffic.
Long code mask: Integer scalar that specifies the mask applied to the long code generator. It must be between 0 and 2⁴² - 1.
Walsh order: Integer scalar that specifies the order of the Walsh code used for modulation.
Sample time: Real scalar that specifies the block sample time.

Specification References

IS-95A 6.1.3.1.6, 6.1.3.1.7, 6.1.3.1.8
J-STD-008 2.1.3.1.6, 2.1.3.1.7, 2.1.3.1.8

IS-95A Rev Ch Walsh Demodulator IS-95A Rev Ch Walsh Modulator