10.2.1. TDD Frame Format
The TDD frame is 2mS in length, and is composed of two symmetrical 960 S TX and RX
subframes. Each subframe contains 96 bits of 10 S duration, with 40 S guard times between
both TX and RX subframes.
Each subframe consists of the following five fields:
- A 12-bit Preamble field
- An 8-bit Data Channel field
- An 8-bit Sync Word
- A 64-bit ADPCM Payload
- A 4-bit Post-amble
Both the 8-bit sync word and 8-bit data channel are programmable
via the DSP interface. In addition, the 64-bit payload can be filled
either with ADPCM voice data, or can be used by the host DSP as a
fast data channel between base and handset.
10.3. Spread Spectrum
Transmission and reception are operated using the spread spectrum method.
DSS (Digital Spread Spectrum)
Mixing the original signal with the pseudo random noise code (PN code) works the spread
spectrum. In this system PN code is 15 chip. Although the band width is spread fifteen times, the
power level per channel becomes lower.
Fig. 8
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