Signal transmission method

• US 4,882,737 A
• Filed: 07/15/1988
• Issued: 11/21/1989
• Est. Priority Date: 07/31/1987
• Status: Expired due to Term

• Current Assignee: Brown Boveri & CIE AG (ABB Limited)
• Original Assignee: Brown Boveri & CIE AG (ABB Limited)
• Inventors: Dzung, Dacfey
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US07/219,343
• Time in Patent Office: 494 Days
• Field of Search: 375/12, 375/13, 375/14, 375/15, 375/39, 375/102, 375/96, 364/724.2, 333/18, 370/20
• US Class Current: 375/235
• CPC Class Codes: H04L 25/03834 using pulse shaping
• CPC Class Codes: H04L 27/3494 using non - square modulating pulses, e.g. using raised cosine pulses; Partial response QAM, i.e. with partial response pulse shaping QAM over partial response channels H04L25/497

Abstract

A signal transmission method according to the principle of quadrature/amplitude modulation, in which digital data occurring at a time interval T are formed into a transmit signal with the aid of pulse shapers (3a, 3b) having a given unit pulse response r(t) in a transmitter (4), the transmit signal is transmitted by means of a carrier oscillation via a channel (5) having a channel unit pulse response h(t), when an additive white noise w(t) is superimposed on it, so that a receive signal y(t) is present in a receiver (10), and in which the receive signal y(t) is preprocessed by channel-matched filters (7 a, 7b) in the receiver (10), has channel-matched filters (7a, 7b) which are matched to a filter cascade H(t) formed by pulse shapers (3a, 3b) and channel (5) as a whole. The channel-matched filters f(7a, 7b) are preferably transverse filters the data points of which are at a time interval ΔT which is small in relation to the time interval T of the digital data. An estimation of the channel unit pulse response h(t) is determined in that the unit pulse response of the filter cascade H(t) is convoluted with a filter r^-1 (t) which is inverse to the pulse shaper.

Claims

1. Signal transmission method according to the principle of quadrature amplitude modulation, comprising the steps of:

in a transmitter

(a) sampling digital data in predetermined time intervals T;

(b) forming a transmit signal by feeding the digital data to a pulse shaper, said pulse shaper having a given unit pulse response r(t);

(c) amplitude-modulating a carrier oscillation by the transmit signal;

(d) transmitting said amplitude-modulated carrier oscillation via a channel, said channel having a unit pulse response h(t) and superimposing an additive white noise w(t);

in a receiver

(e) demodulating the transmitted carrier oscillation into a receive signal y(t);

(f) sampling said receive signal in time intervals Δ

T which are small in relation to the time interval T;

(g) preprocessing said sampled receive signal in a transverse channel-matched filter, said channel-matched filter being matched to a filter cascade H(t) formed by said pulse shaper and said channel as a whole,

space="preserve" listing-type="equation">H(t)=h*r(t),

where "*" stands for the convolution product; and

(h) determining original digital data from the preprocessed sampled receive signal in an analysis circuit.

2. Signal transmission method according to the principle of quadrature amplitude modulation, comprising the steps of:

in a transmitter

(a) sampling digital data in predetermined time intervals T, and based thereon generating by that data coefficients c_k ;

(b) forming a transmit signal by feeding the data coefficients to a pulse shaper, said pulse shaper having a given unit pulse response r(t);

(c) amplitude-modulating a carrier oscillation by the transmit signal;

(d) transmitting said amplitude-modulated carrier oscillation via a channel, said channel having a unit pulse response h(t) and superimposing an additive white noise w(t);

in a receiver

(e) demodulating the transmitted carrier oscillation into a receive signal y(t);

(f) sampling said receive signal in time intervals Δ

T which are small in relation to the time interval T, and based thereon generating a sampled transmit signal y_k ;

(g) preprocessing said sampled receive signal y_k in a transverse channel-matched filter, said channel-matched filter being matched to a filter cascade H(t) formed by said pulse shaper and said channel as a whole, H(t)=h*r(t), where * stands for the convolution product, having coefficients H(i), i=0, . . . , L_c, which are determined in accordance with the principle of least error squares between the transmit signal and the receive signal, fulfilling the equations ##EQU6## where c_k =data coefficient,

y_k =sampled transmit signal,

y_k =complex conjugate of y_k, and

c_k-i =complex conjugate of c_k-i ; and

(h) determining original data coefficients c_k from the preprocessed sampled receive signal in an analysis circuit.

3. Signal transmission method as claimed in claim 2, using data coefficients for forming the transmit signal and for preprocessing the sampled receive signal, which coefficients correspond to a predetermined sequence of digital data known to the transmitter and the receiver.

4. Signal transmission method as claimed in claim 2, wherein the filter cascade used for preprocessing is periodically estimated.

5. Signal transmission method according to the principle of quadrature amplitude modulation, comprising the steps of:

in a transmitter

(a) sampling digital data in predetermined time intervals T, and based thereon generating data coefficients c_k ;

(b) forming a transmit signal by feeding the data coefficients to a pulse shaper, said pulse shaper having a given unit pulse response r(t);

(c) amplitude-modulating a carrier oscillation by the transmit signal;

(d) transmitting said amplitude-modulated carrier oscillation via a channel, said channel having a unit pulse response h(t) and superimposing an additive white noise w(t);

in a receiver

(e) demodulating the transmitted carrier oscillation into a receive signal y(t);

(f) sampling said receive signal in time intervals Δ

T which are small in relation to the time interval T, generating by that a sampled transmit signal y_k ;

(g) feeding said sampled receive signal into a channel estimating circuit controlling a transverse channel-matched filter by calculating coefficients H(i), i=0, . . . , Lc, which are determined in accordance with the principle of least error squarres between the transmit signal and the receive signal, said coefficients H(i) fulfilling the equations, ##EQU7## where c_k =data coefficient,

y_k =sampled transmit signal,

y_k =complex conjugate of y_k, and

c_k-i =complex conjugate of c_k-i ;

(h) preprocessing said sampled receive signal in the transverse channel-matched filter, said channel-matched filter being matched to a filter cascade H(t) formed by said pulse shaper and said channel as a whole,

H(t)=h*r(t), where * stands for the convolution product,

and using said coefficients H(i), i=0, . . . , Lc;

(i) determining original data coefficients c_k from the preprocessed sampled receive signal in an analysis circuit; and

(k) feeding back the determined data coefficients c_k to the channel estimating circuit.

6. Signal transmission method as claimed in claim 5, comprising the step of determining the channel unit pulse response h(t) by convoluting an estimation of the filter cascade H(t) with a unit pulse response r^-1 (t) which is inverse to the unit pulse response r(t) of the pulse shaper.