Signal transmission process

• US 4,862,481 A
• Filed: 05/20/1988
• Issued: 08/29/1989
• Est. Priority Date: 05/25/1987
• 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): Griffin, Robert L.
• Assistant Examiner(s): Chin, Stephen
• Application Number:
  US07/196,494
• Time in Patent Office: 466 Days
• Field of Search: 375/17, 375/37, 375/39, 375/53, 375/57, 375/58, 375/67, 371/43, 371/44, 371/45, 340/347 DD
• US Class Current: 375/284
• CPC Class Codes: H04L 2025/03407 Continuous phase
• CPC Class Codes: H04L 25/03178 Arrangements involving sequence estimation techniques

Abstract

During a signal transmission process, digital data are reproduced in a transmitter in accordance with a given process for the continuous phase modulation of a carrier wave (CPM) in a time-dependent envelope curve, the envelope curve is transmitted by the carrier wave via a channel with a given unit pulse response, an additive, white Gaussian noise being superimposed, the digital data are sent through a channel-specific filter and sampled in a receiver, and a sequence of estimated symbols is determined with an optimization algorithm.

Claims

1. A signal transmission process transmitting digital data from a transmitter to a receiver according to a continuous phase modulation method, comprising the steps of:

(a) converting digital data which are present as a sequence of symbols α

_k, which symbols have a given time interval T and may assume M values, into a symbol vector c_k or M^L components;

(b) converting said symbol vector c_k into a time-dependent scalar envelope signal v(t) using a baseband filter having a characteristic r(t) of M^L components, where ##EQU18## (c) phase modulating a carrier wave according to the envelope signal v(t) and transmitting said modulated carrier wave to a receiver via a channel with a given unit pulse response h_c (t), an additive, white Gaussian noise w(t) being superimposed, so that at a receiver the envelop signal v(t) is transformed into a signal y(t) of the form

space="preserve" listing-type="equation">y(t)=h.sub.c *v(t)+w(t) ,

where "*" denotes a convolution product;

(d) demodulating said carrier wave into said signal y(t);

(e) filtering said signal y(t) by a channel specific filter of the form h_c *(-t) for getting sufficient statistics in a subsequent sampling step;

(f) filtering said filtered signal y(t) by an adjoined baseband filter of M^L components of the form

space="preserve" listing-type="equation">r.sup.30 (-t),

wherein "⁺ " denotes conjugate complex;

(g) sampling the filtered signal produced by step (f) after the adjoined baseband filter at points of time kT, where k denotes an integer; and

(h) determining, based on the sampled filtered signal produced by step (g), a sequence of estimated symbols α

_k by an optimization algorithm.

2. A signal transmission process transmitting digital data from a transmitter to a receiver according to a continuous phase modulation method, comprising the steps of:

converting digital data which are present as a sequence of symbols α

_k, which symbols have a given time interval T and may assume M values, into a symbol vector c_k of M^L components;

converting said symbol vector c_k into a time-dependent scalar envelop signal v(t) using a baseband filter r(t) of M^L components, where ##EQU19## phase modulating a carrier wave according to the envelope signal v(t) and transmitting said modulated carrier wave to a receiver via a channel with a given unit pulse response h_c (t), an additive, white Gaussian noise w(t) being superimposed, so that at a receiver the envelope signal v(t) is transformed into a signal y(t) of the form

space="preserve" listing-type="equation">y(t)=hc*v(t)+w(t),

where "*" denotes a convolution product;

demodulating said carrier wave into said signal y(t);

first filtering said signal y(t) by a channel specific filter of the form h_c *(-t) to produce a first filtered signal for getting sufficient statistics in a subsequent sampling step;

second filtering said first filtered signal y(t) by an adjoined baseband filter of M^L components of the form

space="preserve" listing-type="equation">r.sup.+ (-t)

where "⁺ " denotes conjugate complex, thereby producing a second filtered signal;

sampling the second filtered signal after the adjoined baseband filter at points at time kT, where k denotes an integer; and

determining, based on the sampled second filtered signal, a sequence of estimated symbols α

_k by a Viterbi algorithm extended by a compensation element maximizing an increment Z_n of the form, ##EQU20## where c_n =symbol vector,

y_n =signal vector,

X_i =channel operator, and

L_c =channel interference length.

3. A signal transmission process transmitting digital data from a transmitter to a receiver according to a continuous phase modulation method, comprising the steps of:

converting digital data which are present as a sequence of symbols α

_k, which symbols have a given time interval T and may assume M values, into a symbol vector c_k of M^L components;

converting said symbol vector c_k into a time-dependent scalar envelop signal v(t) using a baseband filter r(t) of M^L components, where ##EQU21## phase modulating a carrier wave according to the envelope signal v(t) and transmitting said modulated carrier wave to a receiver via a channel with a given unit pulse response j_c (t), an additive, white Gaussian noise w(t) being superimposed, so that at the receiver the envelope signal v(t) is transformed into a signal y(t) of the form

space="preserve" listing-type="equation">y(t)=h.sub.c *v(t)+w(t),

where "*" denotes a convolution product;

demodulating said carrier wave into said signal y(t);

first filtering said signal y(t) by a channel specific filter of the form h_c *(-t) to produce a first filtered signal for getting sufficient statistics in a subsequent sampling step;

second filtering said first filtered signal y(t) by an adjoined baseband filter of M^L components of the form

space="preserve" listing-type="equation">r.sup.+ (-t)

where "⁺ " denotes conjugate complex, thereby to generate a signal vector y(t) of M^L components;

sampling the signal vector y(t) at points of time kT, where k denotes an integer, thereby generating a digital signal vector y_k ; and

transforming said digital signal vector y_k into a de-emphasized signal vector γ

_k using a pre-emphasis filter which functions according to the principle of lease error squares in the sense that the expectation value

space="preserve" listing-type="equation">D({A.sub.i })=E[(γ

.sub.k -X.sub.r-k.sup.c).sup.+ X.sub.r.sup.-1 (γ

.sub.k -X.sub.r-k.sup.c)],

where ##EQU22## γ

_k =de-emphasized signal vector X_r =channel operator of the white channel

c_k =symbol vector is minimized; and

determining, based on the de-emphsized signal vector γ

_k, a sequence of estimated symbols α

_k by an optimization algorithm.

4. A signal transmission process as claimed in claim 3, wherein the sequence of estimated symbols are determined using a Viterbi algorithm.