DE1815962A1 - Synchronization method for address-coded telephone systems - Google Patents

Description

Me / ub

"Patelhold" Patentverwertungs- & Elektro-Holaing AG., Glarus (Switzerland)

Synchronous isie r verfa lead for ad resscodierte Fernsp_rec_hsyst_eine

The invention relates to a synchronization method for operating an address-coded telephone system by means of analog or digital pulse modulation, where each information pulse is divided into a group of shorter pulses and encoded in the time-frequency level (= matrix) can carry the full address of the partner and to ensure the high station density due to the many external impulses, difficult address recognition by the partner through suitable processing the information - for example modified delta "modulation - is provided for a low pulse frequency.

Such systems (which are often used in the English-language literature are summarized under the designation "RADA" = "Random Access Discrete Address *") are based essentially on the fact that a broadband channel is potentially available to a large number of participants at the same time, but in each of them

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Moment is only actually used by a small number. The relatively low channel load from the individual participant is not only achieved by actually speaking a small fraction of the time, but especially advantageous because it is also active in the active state, i.e. during the send-ivorganrros - the channel as a percentage in terms of time only briefly occupied.

The conversion of the language into a binary impulse feed must therefore take place in such a way that the mean frequency of the resulting pulses remains small. This can be done e.g. with a modified Achieve delta modulation:

The reproduction of steep positive planks occurs with the usual Delta modulation through the pulse train (... 1111 ...), the negative edge through (... 0000 ...), while constant input signals through the rapid changes (... 0101 ...) their clock frequency is far above the pass band of the receiving low-pass filter, reproduced v / ground.

The addition modulo-2 of an alternating signal (... 010101 ...) The following pulse groups arise for the delta signal:

... 101010 ... ascending

... 010101 ... descending )

... 111111 ... j} Input signal

... 000000 ...) constant)

Constant signal levels can thus either be achieved through the O sequence

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ORIGINAL

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or i'i'rsli the! "Sequence to be characterized" 181SS6 !!

Vierti-sai it is always advantageous on the transmission side through the O sequence shown, so arise on the receiving side after a the same üiodulo-2 ~ ümsetzunf; probably small mistakes here and there the size of a quantization level which was to be sent out However, impulses are greatly reduced: with a clock frequency of the delta modulator of ^ i0 kite, the mean impulse frequency drops of the modified delta signal to values of 2 ... 3'kIIs. In addition, it has a modified delta modulation the advantage that there are never two 1-impulses in a row can occur: they are always separated by at least one zero. This fact allows on the sending side the use of the double interval for pulse broadening, increasing the number of addresses or reducing the peak power.

Faults appearing in clusters, one behind the other fake impulses following the following clock intervals are converted into a (... 010101 ...) alternating signal and strongly suppressed in the receiving low-pass filter.

The modulation system just outlined in its main features for the message still needs to have the ability to transfer addresses can be added. The principle of the time-frequency matrix is a simple solution, especially above all This is because the nature of the resulting intrinsic interference does little to reduce speech transmission with this modulation system

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1615962

impaired .. With this conception, the whole becomes Available bandwidth B divided into U channels ("channel grid"); Each channel comprises η discrete frequencies ("frequency raster"), of which h frequencies are used to identify the address. Any original message impulse is replaced by a group of h pulses, each of which is emitted at one of k possible time slots within the 50 μs interval will. The receiver monitors the frequencies assigned to it and feeds the incoming pulses into delay lines of the correct length, so that all pulses are one for the group determined for him occur simultaneously at the output of all delay lines and so the original message impulse to mark.

The allocation of different addresses to a single device as well as the receipt of the priority call is possible without difficulty.

When the transmission medium is heavily loaded by many active devices and / or due to multipath propagation, there is a certain probability that each recipient will create false ones Address pulses, whereas the probability of suppressing a correct pulse is much smaller and practically neglected (the phase and amplitude of an interferer should have exactly the right values).

The increased probability of incorrect addresses has two effects which, without countermeasures, make such a transmission system unusable;
1. If the receiver demodulation channel is constantly open, all false pulses caused by the coincidence of the h outputs of the

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BAD OWGJNAl

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Delay lines arise, demodulate and lead to strong noise.

2. At the same time, it is no longer possible to synchronize a narrow tent gate, which scans the coincidence circuit to be provided for this at a rate of kO kHz only for a few, us and thus eliminates most of all interference, to the desired transmitter.

With a satisfactory solution to the synchronization problem for the time gate, the effect of the high station density increased Palschadress-V / a likely reduced considerably will; even assuming a fault of approx. 14 - 205 » of all sampling moments due to incorrect impulses, the word intelligibility would still be over 85S with exact synchronization simultaneous (unlikely) failure of 13? of all useful impulses (Range limit) one would still have a word intelligibility of over 60S »(corresponding to a signal-to-noise ratio of ft * 16 dB or »8 dB).

The invention is based on the task of getting the shortcomings up to now * systems of the type described above, which are practically not subject to a high system load due to numerous active interferers was calculated, in the case of the presence of a high station density and to eliminate the effect of a high Reduce the probability of disturbed addresses through additional synchronization. According to the invention, this is thereby achieved achieves that in order to increase the

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preparation of reduced frequency of address read-out by the calling subscriber station and thus to improve the synchronization of the station called with this address with the calling station each calling station periodically and in larger time intervals before longer, dense pulse train (e.g. 20 pulses in the shortest permissible time -Rasterabstand) sends that pulse sequence is encoded in the time-frequency plane with the address of the called station, and that the relative duration of the pulse train is chosen short, significantly increases that neither the overall system load, nor the corresponding loss of information is virtually perceived .

In a practically conveniently realizable embodiment of the invention, the procedure is as follows: triggered by pressing the transmit button and from this point in time every 3 seconds the transmitter automatically emits the appropriately addressed pulse sequence 1010 ... 10, consisting of 20 "one" and 20 "zeros " consists. Such a "binary word" takes up a time interval of 20 times 50 ^ us s 1 ms. It is inserted into the language on the sending side every 3 seconds and replaced by a corresponding gap on the receiving side after recognition. In the receiver, a binary pass-through memory (shift register with taps) with a resolution of 5 / Us (approx. 200 cells) records the received signal.

As soon as there are 15 or more ones at the correct distance of 50, us are in the pass-through memory (shift register), it regards the signal as intended for it, deletes the memory contents and

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BATH ORIGINAL

is synchronized at the same time. If one demands that i'iixöi Hxtifes between the one, for example, there are at least 5 envelopes, in this way, incorrect synchronization caused by constant disturbances is excluded «,

For the purpose of further drastic reduction of the temporal and frequency-wise system load, the actual information pulses can be completely freed from the address, so that the address recognition and associated synchronization is carried out exclusively by means of the nested address-coded, dense m pulse trains (binary words).

Also, it may be expedient in many cases, in the receiver of the called station means for detecting a plurality of different addresses _s automatically provided so that the receiver upon detection of one of these addresses to the recognized address is synchronized.

Finally you can - to the recipient of the calling station to be able to receive and check a kind of "acknowledgment" for correct reception on the other side - together with the synchronization of the recipient of the called Statinn also whose transmitter can be automatically set to the received address, so that when sending from this station the received address is reproduced.

The probability of the due recognition P of by the address coded, dense pulse train given word is in essential determined by the expression:

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Where P is the probability of detecting a hight News enlnpu'lses. Assuming a vrortverstandlichke.lt of $ 80 for monosyllabic words, P = 0.135 (range limit). Kit of this fourth you get:

P _c 2 0 35 "" ^{= 20
c} * "■ - 0.135

f ..

This means that in over 95 % of all extreme cases the synchronization takes place with the first binary word.

conversely, such a word can also be faked by wrong addresses. If one calculates with an average value of P " _{Ä of} the false Ädress probability (systemic disturbances and real world limit) of 17 JS, the result for the probability ρ of the pretense is:

(S)

tit _ TZ:

k a O

_q fm - 20

* - ■ "'Fit"" ^s; *

In relation to the resolution capacity of the memory, this means that a false start of the synchronization occurs anyway in the event of a heavy system load per address Int Middle about every 4 minutes. After such a start, the recipient is for 3

0058087t042

6AD OWGJNAL

Blocks seconds, but opens again immediately if the next package is missing.

About a possible loss of synchronization during the conversation To make it unlikely, the requirements could be reduced in the synchronized state and, for example, only nor require the receipt of 10 or less ones.

With such a synchronization device it is possible Establish and maintain connections even with heavy system loads. At the same time it can be used for synchronization Encryption devices are used.

In special cases it is even possible to let the sender »in agreement with the receiver - after synchronization to the complete addressing of all message impulses and instead of three or four only zv; ei © ö @ p in extreme cases only © to use inen pulse * the "Falseh address WahrsshelnlieJhkeit ⁹⁸ siisnmt this niohfc much to _see since the Ssfstembe las tang <$ nt spre © HEM is smaller _(Ρ ΡΑ ^ 20ο» ° 25% at glelefsei? Spreciisr- 'nu ^ a pulse) = the main advantage of a corres-EedlMktioe is to name the average transmit power. "

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Claims (1)

- 30 - P W D Patent claims : 1. Ancestors of operating an address-coded Fernsproehsyatero by means of analoper or dipital pulse modulation, v; obei, leder Information impulses by dividing them into a group of shorter ones Pulses and coding in the time-frequency level (= r * .atrix) the full address of the partner can and for the purpose of Guaranteed at high station density due to the many external impulses made address recognition more difficult by the partner due to clean processing. the information - for example modified delta modulation - for pearly Iirrrulsh-iufl-lieit resorp; t is characterized by the fact that for the purpose of Erh'Shur-f the as a result of the information atlons preparation with degraded H.tufirkelt the address sentunf by the calling subscriber tatlon and thus for the purpose of improving the synchronization of the r.it this Address of the called station with the calling station Each calling station periodically and at regular intervals longer, dense pulse sequence (e.g. 20 pulses in the shortest to ~ permissible time grid spacing) sends out which Imoulsfolpe In the time-frequency level is encoded with the address of the called station, and that the relative duration of this pulse train is so it is chosen briefly that neither the entire system load is noteworthy increased, nor is the corresponding loss of information practically more true. 2. Method n «! Ch claim 1, characterized in that 009808/1043 ■■ '■ - ■ - ii - ρ ² ig3 π send the Trnulsfolre (Bir.'lrwort) touching the Mresseccie Later, in certain cases, the duration of the pulse sequence ^ rossen ^ time intervals (e.g. every 3 sec) in the Sprachsi elnprefCErt and er-pfanrsseltlr after recognition by a corresponding gap is replaced. 3 "Ve FfaMreEt according to claim; 1 vein 2 ', thereby: K.elceniiireichp «et that Kvieelcs Kelterer ^. drastic ^ erinderunc- dler temporal \ mM freciusetizn'issipere S'vsten & elastunr · d ^r fe © f ^ eimtllcitera In fornatJOMSimpulse completely .flndliFr van the address are freed; ,, so · that <you Aöresserfcen.EiuTir and d '? nf; t rerfounivene- S.Tmehroni'-unp: exclusively by means of which a switched acTressrtert dense Ir ^ xtlsfcrlceEi CBlwlrvi-urter): will prevail · » A * YerFaliren according to claims 1 or 2 and 3, characterized by, that in Enpfilnger the station called a binary Burial memory in the form of an R-It Anz-anfunp-en: \ reFsehenen Shift register is voiFf-eseheri; which is the enipfancerie Siptnal takes up and at Yorhandenseln, a rampant Ansah! In the r-ichtlpen. Distance atif each other flashing blues; nalen is automatically preMscht, - wontit rlelchzeltlp- die SynchronIslerunr this receiver of the called station on the address 5 «Method according to claim 1 or 2, 3 and h _s characterized in that in the receiver of the called station means for 009808/1043 - 12 - ? 1 * 9% Ό Recognition of several different addresses are available and that the recipient is automatically synchronized to the recognized address when one of these addresses is recognized. 6. The method according to claim 1 or 2, 3 and H as well as according to claim 5, characterized in that together with the synchronization of the receiver of the called station, its transmitter is automatically set to the received address so that when sending from this station the received Address is reproduced. Patelhold Patent exploitation and electrical holdinp; AG. Authorization Central Dept. Ill No. φ / AQ Gon. VoltlH. 009808/10 A3