Agilent Technologies 8935 series e6380a manual Interpreting IS-2000 Channel Ordering

CDMA Measurements - Screens and Control Fields

CDMA Measurements

•Improved Convolutional Encoding for 14.4 Kbps Voice Channels – Improved spectral efficiency and higher spreading rates allow voice channels using the 14.4 Kbps vocoder now have robust convolutional encoding.

•Fast Closed Loop Power Control on Forward Link traffic.

•Auxiliary Pilot support for Beam Forming

•Forward Link Transmit Diversity - OTD, Multi-Antenna

Interpreting IS-2000 Channel Ordering

The IS-95 standard includes only 64 Walsh codes which map directly into channels, numbered consecutively from 0 to 63 (Hadamard ordering). This provided a uniform channel size regardless of purpose.

The IS-2000 standard allows up to 128 Walsh codes. In addition, to handle the wide range of data rates available in IS-2000 (9.6 kbps for voice up to 307.2 kbps for low mobility data), variable length Walsh code spreading is used. The code tree representation, shown in Figure 5-9, of the variable length Walsh codes is useful in understanding how these codes are generated and how they can be selected to maintain orthogonality.

Figure 5-9 Building a tree using the Bit Reverse method

0

0

1

	000	(0)
00	100	(4)
10	010	(2)
	110	(6)
	0 01	(1)
01	1 01	(5)
11	011	(3)
	111	(7)

To generate a Walsh code tree, take the initial code, first add a place (bit) in the most significant number’s (MSN) place. Then, for the upper branch, give this bit the value “0”. Finally, for the lower branch give this number the value “1”. This process proceeds to generate more and more branches until you have reached the desired Walsh code length. The code sets are denoted by their length in bits which corresponds to the vertical columns (all codes that have the same Spread Factor) in the tree.

The Walsh order (number of bits that comprises the specified code) (see Figure 5-10) indicates the bit number to use to spread the data. Before being spread, data is assigned to the Walsh codes encompassed by the spread. After encoding and interleaving, the data is spread according to the Walsh order.

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