zeroes using Walsh code zero, so its only coding is the short PN code. A synchronization channel of 1200 bits per sec- ond is sent using Walsh code 32. The paging channel is sent on another Walsh code tween one and seven, inclusive) and has its own long PN code. 10.1.5 cdmaOne reverse channel coding The reverse cdmaOne channel takes the RS1 voice signal, 0.8 to 8.55 kbps, and adds frame, quality, and overhead information to bring it to 1.2, 2.4, 4.8, or 9.6 kbps. This is Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Worldwide CDMA Standards Worldwide CDMA Standards tripled by convolutional forward error correction to 28.8 kbps or less. When the speech coder is running at lower rates, we use the data burst randomizer below rather than repeating the bits at this stage. The reason why the forward direction repeats the bits and the reverse direction sends them in bursts is discussed in Sec. 8.6. As in the forward direction, RS2 uses a less aggressive forward error correction scheme, 2 to 1 instead of 3 to 1, so its full 13-kbps rate still comes out to 28.8 kbps. Each 6 bits is spread using the Walsh functions to 64 bits for a rate of 307.2 kbps. These Walsh codes are not orthogonal in the reverse direction, but they do present a good noncoherent spreading scheme with a ratio of 64 to 6. When the speech coder is not operating at full rate, there is a data burst randomizer that sends rate one-half, rate one-quarter, and rate one-eighth data at full rate one-half, one-quarter, or one- eighth of the time. The bursts are not genuinely random, of course, since the receiver has to know when to detect them, but they are well distributed over time. The 307.2-kbps stream is spread by another factor of 4 using the long PN code to get a 1.2288-Mbps data stream. This goes through an offset quadrature phase shift keying (OQPSK) noncoherent modulator before 