| 摘要 |
<p>A modulation scheme is proposed for use in TETRA mobile communications systems that can provide an enhanced data transmission rate. The modulation scheme uses 3π/8 differential phase shift keying, which encodes 3 bits per symbol and uses a Gray code mapping in which each consecutive set of 3 bits is used to represent a phase change of +/- π/8, +/- 3π/8, +/- 5π/8, and +/- 7π/8. The modulation scheme can be represented by: S(k) = S(k-l) exp [jDΖ (k)] S(O) = 1 where: S(k) is the kth symbol in the burst, k=l, 2, ..., n, and n is the total number of symbols in the burst. The modulation scheme is used in standard TETRA channels (e.g. spacing, slot and frame structure) and at the standard TETRA symbol rate. The modulation scheme therefore provides an enhanced raw bit rate of 54000 bits/s (3 bits per symbol).</p> |
