Method and apparatus for recognizing digital information in digital information transmission, particularly in mobil radio communications systems

A method and apparatus are disclosed for recognizing digital information, particularly in an information transmission in mobile radio communications systems, in which a sampling pulse is derived from the received information at a whole multiple of the information clock frequency. A sampling pulse is placed into the respective area of an information element which has assumed its suspected, quasi-stationary state. A further, non-correlated sampling pulse is derived from the received information at a further whole multiple of the information clock frequency, the edges of which are placed at a corresponding number of sampling times within an extended sampling range of the pulse which represents the information element. Respective comparison of a first sampling result to one or more following sampling results is carried out for an information element and a majority decision is undertaken on the basis of the existing sampling results. All sampling modes are simultaneously effective and each information element gained is intermediately stored and respectively compared to each other information element during an intermediate storage phase. One of a plurality of information elements perceived as being error-free is relayed to an information sink at the end of the storage phase and the remaining stored information elements are erased.

CROSS REFERENCE TO RELATED APPLICATIONS 
This application is related to my co-pending applications Ser. No. 296,972 
and Ser. No. 296,867, both filed on Aug. 27, 1981. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a method and to an apparatus for 
recognizing digital information in a digital information transmission, 
particularly an information transmission in mobile radio communications 
systems. 
2. Description of the Prior Art 
Speech information, data information and image information are the forms of 
information which are to be transmitted in known, wire-bound 
communications systems and in a future mobile ratio communications 
systems. Given a transmission of information, particularly digitized 
information, in a mobile radio communications system, a problem arises in 
that, due to so-called multi-path propagation on the radio path, fading 
arises which can cause information bit errors during transmission. 
Techniques are known by which a sampling pulse is derived at the respective 
receiver from the received digital information and is employed for placing 
a sampling time into the respective area of an information element in 
which the pulse to be sampled, and which represents the information 
element, assumes its suspected, quasi-stationary state, cf., for example, 
see the German allowed and published application Ser. No. 1,804,719. These 
known methods, however, have the disadvantage that, in those cases in 
which pulses representing information elements are distorted in amplitude 
and/or in phase due to disruptive influence, a bit error can be simulated 
precisely in the respective area sampled, although the appertaining pulse, 
when viewed as a whole, can be free of error. 
In mobile communications systems previously designed, attempts are made to 
provide as favorable as possible a bit error rate by applying different 
encoding methods, for example, "forward error correcting". This 
philosophy, however, is opposed by the attempts to achieve a 
standardization of the operating modes. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide a method and an apparatus 
for recognizing digital information in a digital information transmission 
of the type mentioned above, by means of which favorable bit error rates 
can be achieved without having to accept one of the aforementioned 
disadvantages. 
The above object is achieved, in systems of the type mentioned above, in 
which a sampling pulse from the digital information received at a receiver 
is preferably derived with a whole multiple of the information clock 
frequency and in which a sampling time is placed in the respective area of 
an information element in which the pulse to be sampled and representing 
this information element assumes a suspected, quasi-stationary state, and 
which is characterized in that at least one further, non-correlated 
sampling pulse is derived from the received digital information, the 
further sampling pulse exhibiting a further, whole multiple of the 
information clock frequency. The edges of the sampling pulse are placed at 
a corresponding number of sampling times within a further, extended 
sampling area of the pulse representing the information element. A 
respective comparison of a first sampling result with one or more 
following sampling results is carried out for an individual information 
element. A majority decision is made on the basis of the existing sampling 
results and all sampling modes provided are simultaneously effective. Each 
gained information element is intermediately stored and each information 
element is respectively compared to each other information element during 
an intermediate storage phase. At the end of the intermediate storage 
phase, one of a possible plurality of information elements perceived as 
being error-free is relayed toward a data sink and the remaining 
information elements are erased. 
The present invention offers the advantage that a multiple sampling of the 
information elements can be executed in a simple manner and that pulses 
which are error-free overall per se, but which represent distorted 
information elements, can be accepted as error-free so that the 
information transmission experiences a higher utilization effect.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to FIG. 2, a receiver is illustrated as comprising a 
demodulator D, a carrier frequency generator TF, a plurality of 
non-correlated clock generating devices TE1, TE2 . . . TEn in a sampling 
device T, a plurality of comparators V1, V2 . . . Vn, a plurality of 
majority decision stages ME2 . . . MEn, an error rate evaluation device 
FA, a majority decision circuit MEF for judging the mean error rate 
including an input weighting stage G, a selector W (shown as a rotary 
switch), a selector control WS, a memory S, and an information sink IS. 
The transmitter is also illustrated with devices which are known per se 
and which are only shown for an understanding of the interrelationships 
involved. The transmitter is thus shown as comprising an information 
source IQ, a carrier frequency generator TF and a modulator M. 
Referring now to FIG. 1, a pulse I, representing the information element to 
be sampled, can be sampled in sampling areas having various widths by the 
various sampling pulses P1, P2 . . . Pn. To this end, a comparison of a 
first sampling result to one or more following sampling results is 
respectively carried out for an individual information element within a 
time range Z. On the basis of a majority decision concerning the existing 
sampling results, that respective sampling mode is employed which exhibits 
the smallest-perceived information error rate. 
To this end, individual comparators V1, V2 . . . Vn are respectively 
assigned and connected to the clock generating devices TE1, TE2 . . . TEn 
of the sampling device T. With the assistance of these comparators, the 
sampling results are derived from a single sampling or, respectively, from 
a respective multiple sampling of a single, individual information 
element. Individual majority decision stages ME2 . . . MEn are 
respectively connected to the comparators V2 . . . Vn, the majority 
decision stages selecting that sampling result as the "correct" sampling 
result in a manner known per se, for example, by means of so-called 
majority logic, which predominantly occurred in the multitude of the 
individual sampling results for a single information element. For that 
insrtance in which no majority occurs, the signal output of the 
appertaining majority decision stage is made high-resistant or, 
respectively, inactive for example, by means of a tristate logic device. 
All such final sampling results identified from the first comparator V1 and 
the indivudual majority decision stages ME2 . . . MEn are supplied to a 
majority decision circuit MEF for evaluating the mean error rate which is 
preceded by a weighting stage G and to the error rate evaluation device 
FA. In the error rate evaluation device, the comparison results and a 
majority decision signal from the majority decision circuit MEF are 
processed or, respectively, edited in a known manner with one another. The 
selector control WS is connected to the signal output of the error rate 
evaluation device FA and receives a signal on the basis of which it is 
operable to set the selector W to the sampling mode, namely to the 
sampling pulse, for example to the pulse P2, which exhibits the 
smallest-perceived information bit error rate. The information sink IS of 
the information receiver is connected to the signal output of the selector 
W. 
All sampling modes provided for the invention are simultaneously effective. 
Each information element obtained by sampling is intermediately stored in 
a memory S, which is designed as a flow memory--for example, with 
charge-coupled device (CCD) memories. At the end of the information 
storage phase, one of a possible plurality of information elements 
perceived as being error-free is tapped by the selector W which has been 
set for that purpose to the appertaining output of the memory S. 
A method for recognizing digital information which makes the recognition of 
the digital information less sensitive to disruptions has been provided by 
the present invention including both the method and circuit arrangement 
suitable for implementation of the method, the arrangement of FIG. 2 
representing a preferred exemplary embodiment. 
Although I have described my invention by reference to particular 
illustrative embodiments, many changes and modifications of the invention 
may become apparent to those skilled in the art without departing from the 
spirit and scope of the invention. I therefore intend to include within 
the patent warranted hereon all such changes and modifications as may 
reasonably and properly be included within the scope of my contribution to 
the art.