Process for transmitting digital signals which combines advantages of OQPSK and π/4-QPSK

Claim 1

A process for transmitting digital signals comprising the following steps: coding data to be transmitted into inphase I and quadrature Q components; differentially encoding the inphase and quadrature components separately into symbols, each symbol having a symbol period T s ; staggering the encoded I and Q components with half a symbol period T s /2; filtering each of the I and Q components by SRRC pulse shaping; feeding the filtered I and Q components to a modulator generating a QPSK modulated transmission signal; receiving the transmission signal and mixing it down into the baseband; filtering I and Q components from the baseband in respective SRRC-type low pass filters; scanning the filtered I and Q components twice per symbol period T s ; preprocessing the scanned values I k , I k-2 , Q k , Q k-2 of the I and Q components according to the formulas, X.sub.k =I.sub.k I.sub.k-2 +Q.sub.k Q.sub.k-2 Y.sub.k =Q.sub.k I.sub.k-2 +I.sub.k Q.sub.k-2 decoding according to the 16 phases of the following table, in which Z A represents an initial phase, and Z E represents a final phase: ______________________________________ X.sub.2K = Y.sub.2K = Z.sub.A Z.sub.E X.sub.2K+1 -Y.sub.2K+1 ______________________________________ 1 1 1 1 1 1 1 1 2 0 1 1 1 1 1 1 1 -1 1 -1 1 1 1 -1 1 1 -1 1 0 2 1 1 1 -1 1 1 -1 -1 -1 1 1 1 -1 1 1 -1 1 1 1 0 1 1 -1 1 1 -1 1 -1 1 -1 1 1 -1 -1 1 -1 -1 1 -1 0 1 1 -1 -1 1 -1 -1 -1 -1 -1 1 -1 1 1 -1 1 1 1 0 -2 1 -1 1 1 -1 1 1 -1 -1 -1 1 -1 1 -1 -1 1 -1 1 2 0 1 -1 1 -1 -1 1 -1 -1 1 1 1 -1 -1 1 -1 -1 1 1 -1 0 1 -1 -1 1 1 -1 1 -1 -1 1 1 -1 -1 -1 -1 -1 -1 1 1 0 1 -1 -1 -1 -1 -1 -1 -1 1 1. ______________________________________

Claim 3

A device for transmitting digital signals from a transmitter to a receiver, comprising: in the transmitter: a coder for coding data into in-phase I and quadrature Q components; differential coders differentially encoding the respective in-phase and quadrature components separately into symbols, each symbol having a symbol period T s ; a time delay element for staggering the encoded I and Q components with half a symbol period T s /2; pulse shapers for filtering each of the I and Q components by an SRRC pulse shape; and a quadrature modulator for generating a QPSK modulated transmission signal in accordance with the pulse-shaped I and Q components: and in the receiver: mixers for mixing the received transmission signal down to baseband; SRRC-type low-pass filters for respectively filtering I and Q components of the received transmission signal at baseband; scampers for respectively scamping the I and Q components twice per symbol period; a predecoder for preprocessing the scanned values I k , I k-2 , Q k and Q k-2 of the I and Q components according to the formulas, X.sub.k =I.sub.k I.sub.k-2 +Q.sub.k Q.sub.k-2 Y.sub.k =Q.sub.k I.sub.k-2 -I.sub.k Q.sub.k-2 ; a decoder for decoding outputs of the predecoder according to the sixteen phases of the following table, in which Z A represents an initial phase and Z E represents a final phase: ______________________________________ X.sub.2K = Y.sub.2K = Z.sub.A Z.sub.E X.sub.2K+1 -Y.sub.2K+1 ______________________________________ 1 1 1 1 1 1 1 1 2 0 1 1 1 1 1 1 1 -1 1 -1 1 1 1 -1 1 1 -1 1 0 2 1 1 1 -1 1 1 -1 -1 -1 1 1 1 -1 1 1 -1 1 1 1 0 1 1 -1 1 1 -1 1 -1 1 -1 1 1 -1 -1 1 -1 -1 1 -1 0 1 1 -1 -1 1 -1 -1 -1 -1 -1 1 -1 1 1 -1 1 1 1 0 -2 1 -1 1 1 -1 1 1 -1 -1 -1 1 -1 1 -1 -1 1 -1 1 2 0 1 -1 1 -1 -1 1 -1 -1 1 1 1 -1 -1 1 -1 -1 1 1 -1 0 1 -1 -1 1 1 -1 1 -1 -1 1 1 -1 -1 -1 -1 -1 -1 1 1 0 1 -1 -1 -1 -1 -1 -1 -1 1 1 ______________________________________ and differential decoders for differentially decoding the results of the decoder.

Claim 4

A device for transmitting digital signals from a transmitter to a receiver, comprising: in the transmitter: a coder for coding data into in-phase I and quadrature Q components; differential coders differentially encoding the respective in-phase and quadrature components separately into symbols, each symbol having a symbol period T s ; a time delay element for staggering the encoded I and Q components with half a symbol period T s /2; pulse shapers for filtering each of the I and Q components by an SRRC pulse shape; and a quadrature modulator for generating a QPSK modulated transmission signal in accordance with the pulse-shaped I and Q components: and in the receiver: mixers for mixing the received transmission signal down to baseband; SRRC-type low-pass filters for respectively filtering I and Q components of the received transmission signal at baseband; scampers for respectively scamping the I and Q components twice per symbol period; a predecoder for preprocessing the scanned values I k , I k-2 , Q k and Q k-2 of the I and Q components according to the formulas, X.sub.k =I.sub.k I.sub.k-2 +Q.sub.k Q.sub.k-2 Y.sub.k =Q.sub.k I.sub.k-2 -I.sub.k Q.sub.k-2 ; a decoder for decoding outputs of the predecoder according to the sixteen phases of the following table, in which Z A represents an initial phase and Z E represents a final phase: ______________________________________ X.sub.2K = Y.sub.2K = Z.sub.A Z.sub.E X.sub.2K+1 -Y.sub.2K+1 ______________________________________ 1 1 1 1 1 1 1 1 2 0 1 1 1 1 1 1 1 -1 1 -1 1 1 1 -1 1 1 -1 1 0 2 1 1 1 -1 1 1 -1 -1 -1 1 1 1 -1 1 1 -1 1 1 1 0 1 1 -1 1 1 -1 1 -1 1 -1 1 1 -1 -1 1 -1 -1 1 -1 0 1 1 -1 -1 1 -1 -1 -1 -1 -1 1 -1 1 1 -1 1 1 1 0 -2 1 -1 1 1 -1 1 1 -1 -1 -1 1 -1 1 -1 -1 1 -1 1 2 0 1 -1 1 -1 -1 1 -1 -1 1 1 1 -1 -1 1 -1 -1 1 1 -1 0 1 -1 -1 1 1 -1 1 -1 -1 1 1 -1 -1 -1 -1 -1 -1 1 1 0 1 -1 -1 -1 -1 -1 -1 -1 1 1 ______________________________________ and differential decoders for differentially decoding the results of the decoder.