DK174255B1

DK174255B1 - Wireless digital telephone system base station emulator - initiates synchronisation for assigning time slots to subscriber station within frame pattern of signal using positive edges

Info

Publication number: DK174255B1
Application number: DK199000278A
Authority: DK
Inventors: Scott David Kurtz; David Kaewell John Jr
Original assignee: Interdigital Tech Corp
Priority date: 1990-02-02
Filing date: 1990-02-02
Publication date: 2002-10-21
Also published as: DK176714B1; DK27890D0; DK200101860A; DK27890A

Abstract

The system uses a modified subscriber station to act as a simulated or emulated base station. This emulated base station essentially differs from the subscriber station only in being able to initiate the synchronization process, whereas the subscriber unit only acts to scan the RF signals sent out by the emulated base station until it finds the frequency and slot assigned to it. The signal received from one station is separated into high band and low band energy frequencies. The high band energy output is substracted from the low band energy output to obtain a resultant signal, which is stripped of its sign determine only the amplitude. The stripped signal is accentuated while substantially filtering out noise, and fed to a voltage controlled crystal oscillator (VCXO) which provides the timing at the other station.

Description

DK 174255 B1 iDK 174255 B1 i

Den foreliggende opfindelse angår et trådløst digitalt telefonsystem omfattende en primær abonnentstation og i det mindste én sekundær abonnentstation, der kommunikerer med hinanden i tidsmultiplex på det samme højfrekvensbærersignal, hvor den primære abonn-5 entstation og enhver af de sekundære abonnentstationer er indrettet til såvel at sende som modtage på samme frekvens, og hvor den primære abonnentstation og den i det mindste ene sekundære abonnentstation er synkroniseret med hinanden ved hjælp af tidsrammer.The present invention relates to a wireless digital telephone system comprising a primary subscriber station and at least one secondary subscriber station communicating with each other in time multiplex on the same high frequency carrier signal, wherein the primary subscriber station and any of the secondary subscriber stations are adapted to transmit as well. receiving at the same frequency and wherein the primary subscriber station and the at least one secondary subscriber station are synchronized with each other by time frames.

10 Vore dages telefonsystemer benytter generelt i stigende grad trådløs teknologi til opkald over store afstande og i visse tilfælde er der påbegyndt brug af digital teknologi; imidlertid har intet system, der er i almindelig brug i dag, været i stand til at tilveje-15 bringe en effektiv og virksom trådløs digital teknologi til lokale opkald til og fra individuelle abonnenter.10 Today's telephone systems are generally increasingly using wireless technology for long distance calls and in some cases the use of digital technology has begun; however, no system in general use today has been able to provide effective and efficient wireless digital technology for local calls to and from individual subscribers.

En sådan teknologi er omtalt i forskellige nyere patenter, der indehaves af nærværende ansøgnings indehaver, såsom f.eks. i US patent nr. 4 644 561 af 17. februar 20 1987 og OS patent nr. 4 675 863 af 23. juni 1987. Den teknologi, der er omtalt i disse patenter, tilvejebringer basisstationer, der kommunikerer med såvel en central som adskillige abonnentstationer under brug af digitale trådløse tidsdelte kredsløb, hvori der er gen-25 tagne sekventielle vinduespositioner i en transmissionskanalbit strøm, idet hvert vindue er tilknyttet en bestemt abonnent. Endvidere kendes der fra DE-Al-34 23 780 et radiosystem, hvor alle de indgående radioenheder sender og modtager på en enkelt, fælles fre-30 kvens og fra DE-Ai-31 18 018 et radiosystem, hvor basisstation og abonnentstation er rammetidssynkronisere-de med hinanden.Such technology is disclosed in various recent patents held by the present application holder, such as e.g. in U.S. Patent No. 4,644,561 of February 17, 1987, and U.S. Patent No. 4,675,863 of June 23, 1987. The technology disclosed in these patents provides base stations which communicate with both a central and several subscriber stations using digital wireless time-shared circuits in which sequential window positions are repeated in a transmission channel bit stream, each window being associated with a particular subscriber. Furthermore, from DE-Al-34 23 780 a radio system is known, in which all the incoming radio units transmit and receive on a single common frequency and from DE-Ai-31 18 018 a radio system where base station and subscriber station are frame time synchronized. they with each other.

2 DK 174255 B1 (2 DK 174255 B1 (

Basisstationerne, der benyttes i ovennævnte tidsdelingssys tein, er relativt komplekse og dyre, men økonomisk egnede i et stort system, der betjener et stort antal abonnenter; for relativt små systemer, der 5 betjener et relativt lille antal abonnenter, kan det imidlertid være økonomisk uegnet. Yderligere benytter et sådant system et par frekvenser, en til transmission og en til modtagelse, og med henblik på den begrænsede mængde af kanaler, der er tilgængelige i spekteret, 10 ville det være særdeles fordelagtigt, hvis blot en enkelt frekvens kunne benyttes effektivt.The base stations used in the aforementioned time-sharing system are relatively complex and expensive, but economically useful in a large system serving a large number of subscribers; however, for relatively small systems serving a relatively small number of subscribers, it may be economically unsuitable. Furthermore, such a system uses a few frequencies, one for transmission and one for reception, and for the limited amount of channels available in the spectrum, it would be extremely advantageous if only a single frequency could be used effectively.

Det er derfor en hensigt med nærværende opfindelse, at tilvejebringe det, der kan kaldes en simuleret eller emuleret basisstation, som effektivt kan er-15 statte en faktisk basisstation i visse situationer.It is therefore an object of the present invention to provide what may be called a simulated or emulated base station which can effectively replace an actual base station in certain situations.

En anden hensigt er, at tilvejebringe et system, som kan benyttes af adskillige abonnenter, men som fungerer på blot en enkelt frekvens.Another object is to provide a system which can be used by several subscribers but which operates on just a single frequency.

Andre hensigter vil fremgå af den følgende be-20 skrivelse og kravene:Other intentions will become apparent from the following description and claims:

Essentielt benytter systemet ifølge nærværende opfindelse det, der faktisk er en modificeret abonnentstation, til at fungere som en simuleret eller emuleret basisstation, hvorved de totale omkostninger ved og 25kompleksiteten af systemet mindskes væsentligt. Denne emulerede basisstation_afviger i det væsentlige kun fra abonnentstationen ved at være i stand til at initiere synkroniseringsprocessen, medens abonnentenheden kun er indrettet til at skandere RF signalerne, der udsen-30des af den emulerede basisstation, indtil den finder den frekvens og det vindue, der er tildelt den. I intervallerne mellem transmissioner af RF signalerne er den emulerede basisstation indrettet til at modtage RFEssentially, the system of the present invention utilizes what is actually a modified subscriber station to act as a simulated or emulated base station, thereby substantially reducing the total cost and complexity of the system. This emulated base station essentially deviates from the subscriber station only in being able to initiate the synchronization process, while the subscriber unit is only designed to scan the RF signals emitted by the emulated base station until it finds the frequency and window that are present. assigned to it. In the intervals between transmissions of the RF signals, the emulated base station is arranged to receive RF

3 DK 174255 B1 signaler fra abonnentenhederne. På denne måde kan abonnentenheden enten tale med den emuleree basisstation, som så fungerer som en anden abonnentstation, eller den kan tale med en anden abonnentstation, som er synkroni-5 seret dermed af den emulerede basisstation.3 DK 174255 B1 signals from the subscriber units. In this way, the subscriber unit can either talk to the emulated base station which then functions as another subscriber station, or it can speak to another subscriber station which is synchronized therewith by the emulated base station.

Opfindelsen forklares nærmere i det følgende ved hjælp af udførelseseksempler under henvisning til tegningen hvor, fig. 1 viser et blokdiagram af et totalt system 10 ifølge opfindelsen, fig. 2 et skitse af RCC bølgeformen, der benyttes i standardbasisstationen, fig. 3 en skitse af RCC bølgeformen, der benyttes i forbindelse med nærværende opfindelse, 15 fig. 4 en skitse, der viser de positive flanker for amplituden af det modtagne signal, der benyttes ved grovsynkronisering ifølge opfindelsen, fig. 5 et blokdiagram af kredsløbet til opnåelse af grovsynkronisering ifølge opfindelsen, 20 fig. 6 et blokdiagram af modtager-AGC-kredslø- bet, der benyttes ifølge opfindelsen, fig. 7 et blokdiagram af frekvensregenereringskredsløbet, der benyttes ifølge opfindelsen, fig. 8 en skitse af en trådløs telefonsystemkon-25 figuration ifølge opfindelsen, fig. 9 en skitse svarende til fig. 8, men som viser et dobbeltabonnentsystem, fig. 10 en skitse af rammeformatet i dobbelta-bonnentsystemet i fig. 9, 30 fig. 11 en skitse af rammeformatet for adskilli ge dobbeltabonnentsystemer, fig. 12 en skitse af et system ifølge opfindelsen, som benyttes til overvågning af en eller flere funktioner, ! 4 DK 174255 B1 fig. 13 en skitse af et repeatersystem ifølge opfindelsen, fig. 14 en skitse af et system ifølge opfindelsen, der benytter sig af adskillige repeatere, 5 fig. 15 en skitse af et system ifølge opfindel sen, hvor en enkelt repeater benyttes til at drive adskillige andre repeatere såvel som abonnentenheder.BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail by way of example with reference to the accompanying drawings, in which: FIG. 1 is a block diagram of a total system 10 according to the invention; FIG. 2 is a sketch of the RCC waveform used in the standard base station; FIG. 3 shows a sketch of the RCC waveform used in connection with the present invention; FIG. 4 is a diagram showing the positive flanks of the amplitude of the received signal used in coarse synchronization according to the invention; FIG. 5 is a block diagram of the coarse synchronization circuit according to the invention; FIG. 6 is a block diagram of the receiver AGC circuit used in accordance with the invention; FIG. 7 is a block diagram of the frequency regeneration circuit used in accordance with the invention; FIG. Fig. 8 is a sketch of a wireless telephone system configuration according to the invention; 9 is a sketch similar to FIG. 8, but showing a dual subscriber system; FIG. 10 is a sketch of the frame format of the dual subscriber system of FIG. 9, 30 FIG. 11 is a sketch of the frame format for several dual subscriber systems; FIG. 12 is a sketch of a system according to the invention used for monitoring one or more functions; 4 DK 174255 B1 fig. Fig. 13 is a sketch of a repeater system according to the invention; 14 is a sketch of a system according to the invention using several repeaters; FIG. 15 is a sketch of a system according to the invention wherein a single repeater is used to operate several other repeaters as well as subscriber units.

Den totale interne funktion af systemet 10 er vist i blokdiagramform i fig. 1. I dette system taler 10 en person i telefonen 12 under en telefonsamtale og talesignalet sendes til den lokale telefonlnterfaceen-hed 14. Signalet digitaliseres af codec'en 16._og den resulterende digitale datastrøm føres til taleprocesso-ren 18, som komprimerer taledataene til en lavere da-15 tahas_tighed. De komprimerede data føres så til modemet 20 via linien 22 og den dobbelte omskifter 24, idet modemet er indrettet til at konvertere datastrømmen til et spektralt effektivt analogt signal. Dette analoge signal føres til radioen 26 via linien 28. Radioen 20 opkonverterer signalet til et radiofrekvenssignal (RF) og transmitterer dette RF-signal via antennen 30.The overall internal function of the system 10 is shown in block diagram form in FIG. 1. In this system, 10 a person in the telephone 12 speaks during a telephone conversation and the voice signal is sent to the local telephone interface 14. The signal is digitized by the codec 16. And the resulting digital data stream is fed to the speech processor 18 which compresses the voice data to a lower then-15 tahas_tige. The compressed data is then fed to modem 20 via line 22 and dual switch 24, the modem being adapted to convert the data stream into a spectrally efficient analog signal. This analog signal is fed to the radio 26 via line 28. The radio 20 converts the signal to a radio frequency signal (RF) and transmits this RF signal through the antenna 30.

I intervallerne mellem transmissioner af RF-sig-nalerne er enheden indrettet til at modtage RF-signaler fra en abonnentenhed. Radioen 26 nedkonverterer hvert 25 af disse RF-signaler til et IF-signal og afgiver dette IF-signal til modemet 20 via linien 32. Modemet____20 demodulerer IF-signalet for dannelse af et digitalt signal, som føres til taleprocessoren via omskifteren 24 og linien 36. Taleprocessoren er dernæst indrettet 30 til at ekspandere signalet til et digitaliseret talesignal og dette digitaliserede signal føres dernæst til codec'en 16, som afgiver et analogt talesignal til telefonen 12 via telefoninterfacen 14.In the intervals between transmissions of the RF signals, the device is arranged to receive RF signals from a subscriber unit. Radio 26 downconverts each 25 of these RF signals to an IF signal and outputs this IF signal to modem 20 via line 32. Modem____20 demodulates the IF signal to generate a digital signal which is fed to the speech processor via switch 24 and line 36 The speech processor is then arranged to expand the signal to a digitized voice signal and this digitized signal is then fed to the codec 16 which delivers an analog speech signal to the telephone 12 via the telephone interface 14.

5 DK 174255 B15 DK 174255 B1

Datatransmissionsmodusen svarer til det ovenfor beskrevne bortset fra, at telefonen erstattes af en dataterminal eller computer 38 og telefoncodec’en og taleprocessoren forbikobles ved hjælp af den anden po-5 sition af omskifteren 24, som så er koblet til terminalen 38 via linierne 40 og 42.The data transmission mode is similar to that described above except that the telephone is replaced by a data terminal or computer 38 and the telephone codec and speech processor are bypassed by the second position of switch 24, which is then connected to terminal 38 via lines 40 and 42 .

Modemet 20 og radioen 26 er begge forbundet med en styreenhed 44. Styreenheden 44 er fra starten sat til et forudbestemt vindue, en modulations- og træ-10 ningsmodus for modemet og til en forudbestemt RF-fre-kvens og effektniveau for radioen. Imidlertid kan disse parametre justeres af abonnentenheden i tilfælde af, at de ikke er tilstrækkelige til at give en tilfredsstillende modtagelse ved abonnentstationen.The modem 20 and the radio 26 are both connected to a controller 44. The controller 44 is initially set to a predetermined window, a modulation and training mode of the modem, and to a predetermined RF frequency and power level of the radio. However, these parameters can be adjusted by the subscriber unit in case they are not sufficient to provide a satisfactory reception at the subscriber station.

15 I et system, der benytter en faktisk basissta tion, såsom f.eks. systemet beskrevet i det førnævnte US-patent nr. 4 675 863, er den transmitterede bølgeform opdelt i mangfoldige (dvs. 45) ms rammer. Hver ramme er dernæst opdelt i fire 11,25 ms vinduer. Basis-20 stationen transmitterer i alle fire vinduer for at generere en 100% duty cycle modulationsbølgeform, idet den eneste undtagelse er radiostyrekanalen (RCC). RCC vinduet er lidt kortere end 11,25 ms og dette bevirker et lille gab i modulationen ved begyndelsen af hver 25 ramme. Dette gab er kendt som et AM hul. Et diagram af bølgeformen for RCC kanalen i den faktiske basisstations format er vist 1 fig. 2. I systemet ifølge nærværende opfindelse er der imidlertid ikke nogen transmission af en 100% duty cycle bølgeform. I steet transmit-30teres kun et vindue pr. ramme (en 25% duty cycle bølgeform), som vist i fig. 3. Dette modificerede rammeformat nødvendiggør ændringer i grovsynkronisering automatisk forstærkningsstyring (AGC) og frekvensregenere- 6 DK 174255 B1 ring. Disse ændringer er indikeret i den følgende beskrivelse:In a system using an actual base station such as e.g. In the system described in the aforementioned U.S. Patent No. 4,675,863, the transmitted waveform is divided into multiple (i.e., 45) ms frames. Each frame is then divided into four 11.25 ms windows. The base-20 station transmits in all four windows to generate a 100% duty cycle modulation waveform, the only exception being the radio control channel (RCC). The RCC window is slightly shorter than 11.25 ms and this causes a small gap in the modulation at the beginning of every 25 frames. This gap is known as an AM hole. A diagram of the waveform of the RCC channel in the actual base station format is shown in FIG. 2. However, in the system of the present invention there is no transmission of a 100% duty cycle waveform. Only one window per transmission is transmitted. frame (a 25% duty cycle waveform), as shown in FIG. 3. This modified frame format requires changes in coarse synchronization automatic gain control (AGC) and frequency regeneration 6 DK 174255 B1. These changes are indicated in the following description:

Eftersom systemet ifølge nærværende opfindelse kun benytter en 25% duty cycle bølgeform overvåger det 5 amplituden af det modtagne signal og søger efter positive flanker i amplitudesignalet. Disse positive flanker er vist i fig. 4. Abonnentenheden justerer sin rammetidsstyring til at stemme overens med forekomsten af disse positive flanker.Since the system of the present invention uses only a 25% duty cycle waveform, it monitors the amplitude of the received signal and searches for positive flanks in the amplitude signal. These positive flanks are shown in FIG. 4. The subscriber unit adjusts its frame time management to match the occurrence of these positive flanks.

10 Kredsløbet til opnåelse af den ovenfor nævnte type grovsynkronisering er vist i blokdiagramform i fig. 5, hvor det modtagne signal er vist tilført en amplitudeberegningsenhed 50, som genererer et computer-amplitudesignal, som dernæst afgives til en komparator 15 52, hvor det sammenlignes med et forudbestemt tærskelsignal, hvorved der dannes et digitalt signal {1 * signal tilstede, 0 = intet signal tilstede). Dette digitale signal føres til en flankedetektor 54, som afgiver en strobe, for at indikere detektioen af en 20 positiv flanke.10 The circuit for obtaining the above-mentioned type of coarse synchronization is shown in block diagram form in FIG. 5, where the received signal is shown applied to an amplitude calculator 50 which generates a computer amplitude signal, which is then output to a comparator 15 52, where it is compared to a predetermined threshold signal, thereby forming a digital signal {1 * signal present, 0 = no signal present). This digital signal is fed to a flank detector 54 which emits a strobe to indicate the detection of a positive flank.

25% duty cycle modulationen kræver en bestemt type modtage-AGC kredsløb, som undgår sporing, når der ikke er noget signal tilstede. En langsom stigende, hurtigt faldende AGC er derfor tilvejebragt. Denne er 25 vist i fig. 6, hvor det modtagne signal føres til en amplitudeberegningsenhed 56, som kan være en forprogrammeret ROM, hvorfra et resulterende amplitudesignal føres til en komparator 58, hvori det subtraheres fra en forudbestemt tærskelværdi for dannelse af et diffe-30 renssignal. Dette differenssignal føres, via en af to skallerende multiplikatorer 60 og 62, til et lavpasfilter, der omfatter en additionsenhed 64 og en forsinkelse 66, der er forbundet via en sløjfe 68. Den ene 7 DK 174255 B1 eller den anden af de to multiplikatorer benyttes i overensstemmelse med fortegnet for ·differenssignalet.The 25% duty cycle modulation requires a particular type of receive AGC circuit which avoids detection when no signal is present. A slow-rising, rapidly declining AGC is therefore provided. This is shown in FIG. 6, where the received signal is fed to an amplitude calculator 56, which may be a preprogrammed ROM, from which a resultant amplitude signal is fed to a comparator 58, where it is subtracted from a predetermined threshold value to generate a differential signal. This difference signal is passed, via one of two scaling multipliers 60 and 62, to a low-pass filter comprising an addition unit 64 and a delay 66 connected via a loop 68. One or the other of the two multipliers is used. in accordance with the sign of the difference signal.

Hvis differenssignalet er positivt implementeres det langsomme fald i AGC styresignalet. Hvis differenssig-5 nalet er negativ implementeres en hurtig stigning i AGC styresignalet. Udgangssignalet fra filteret er så det forstærkningssignal, som føres til forstærkningsstyreenheden 44, vist i fig. 1.If the difference signal is positive, the slow decrease in the AGC control signal is implemented. If the differential signal is negative, a rapid increase in the AGC control signal is implemented. The output of the filter is then the gain signal applied to the gain control unit 44 shown in FIG. First

På grund af 25% dury cycle rammeformatet er det 10 ikke nødvendigt at udføre frekvensregenerering under slukketiden (75% nul tid) og eftersom rammetidsstyringen ikke er kendt på det tidspunkt, hvor frekvensregenerering udføres, er der tilvejebragt en modificeret form for frekvensregenereringskredsløb, som vist i fig.Due to the 25% dury cycle frame format, it is not necessary to perform frequency regeneration during the off time (75% zero time) and since the frame time control is not known at the time of frequency regeneration, a modified form of frequency regeneration circuit is provided, as shown in FIG. FIG.

15 7. I dette kredsløb føres det modtagne signal til en beregningsenhed 70 til beregning af en diskret fourier transformeret (DFT), som afgiver højbåndsenergien (energien i frekvensbåndet over centerfrekvensen) og lavbåndsenergien (energien i frekvensbåndet under 20 centerfrekvensen). Højbåndsenergiudgangssignalet subtraheres fra lavbåndsenergiudgangssignalet i additionsenheden 72 og udgangssignalet derfra føres til en blander eller multiplikator 74. Det modtagne RF-signal afgives også til et amplitudedannende middel 76, som 25 fjerner fortegnet fra signalet (negativt eller positivt), hvorved det kun bestemmer amplituden af signalet. Amplitudesignalet føres dernæst til et filter 78, som udglatter signalet ved middelværdidannelse. Udgangssignalet fra filteret 78 føres via forstærke-30 ren 80 til multiplikatoren 74.7. In this circuit, the received signal is fed to a computing unit 70 for calculating a discrete fourier transform (DFT) which emits the high band energy (the energy in the frequency band above the center frequency) and the low band energy (the energy in the frequency band below the 20 center frequency). The high band energy output is subtracted from the low band energy output of the addition unit 72 and the output thereof is fed to a mixer or multiplier 74. The received RF signal is also output to an amplitude generating means 76 which removes the sign from the signal (negative or positive), thereby determining only the signal. . The amplitude signal is then fed to a filter 78 which smoothes the signal by averaging. The output of filter 78 is passed through amplifier 80 to multiplier 74.

Det primære formål med kredsløbet via 76, 78 og 80 er at forhindre støj i at indvirke på udgangssignalet, medens selve signalet fremhæves. Eftersom støj 8 DK 174255 B1 sædvanligvis har en lille amplitude, frafiltreres den i denne sammenhæng effektivt ved udglatningsprocessen.The primary purpose of the circuit via 76, 78 and 80 is to prevent noise from affecting the output signal while highlighting the signal itself. Since noise 8 usually has a small amplitude, in this context it is effectively filtered out by the smoothing process.

Eftersom det faktiske signal sædvanligvis har en relativt stor amplitude, bliver dette på den anden side 5 fremhævet, ved at tilføje det udglattede eller filtrerede signal til blanderen 74.On the other hand, since the actual signal has a relatively large amplitude, this is highlighted by adding the smoothed or filtered signal to the mixer 74.

Det skalerede signal, der forlader blanderen 74 er balanceret mellem høj- og lavenergifrekvenser, og dette balancerede signal, som er proportionalt med 10 korttidsmiddelamplituden af det modtagne signal føres til et lavpasfilter, der omfatter en additionsenhed 82 og en forsinkelse 84, som er sløjfet ved 86. Forsinkelsen 84 gør, at det afgivne signal 88 til VCXO styring repræsenterer udgangssignalet umiddelbart før 15 udgangssignalet faktisk føres til lavpasfilteret. VCXO-styringen benyttes til at justere frekvensen af hovedoscillatoren i systemet.The scaled signal exiting mixer 74 is balanced between high and low energy frequencies, and this balanced signal proportional to the short-term mean amplitude of the received signal is fed to a low pass filter comprising an addition unit 82 and a delay 84 which are looped at 86. The delay 84 causes the output signal 88 for VCXO control to represent the output signal immediately before the output signal is actually fed to the low pass filter. The VCXO control is used to adjust the frequency of the main oscillator in the system.

Efter at indledende eller grovsynkronisering er udført, er systemet i en tomgangstale modus men er helt 20 sat op til taledrift. Hvis telefonen i den ene ende tages af, vil telefonen i den anden ende ringe, indtil den ringende telefon besvares, eller den initierende telefon lægges på.After initial or coarse synchronization is performed, the system is in idle mode but is fully set to voice operation. If the phone is removed at one end, the phone at the other end will ring until the ringing telephone is answered or the initiating phone is hung up.

Opkaldene opsættes af et talekodeord (VCW) ved 25 begyndelsen af hvert talevindue, idet dette kodeord indikerer en "røret taget af tilstand" i den initierende station. Når dette forekommer, vil stationen, der fungerer som en emuleret basisstation, fra centralen (CO) synes selv at overgå til tilstanden "røret taget af", 30 hvorved den opretter en forbindelse med centralen. Den initierende abonnentstation fortsætter så med at færdiggøre opkaldet ved at dreje det ønskede nummer. Når den initierende abonnentenhed lægger røret på, infor- 9 DK 174255 B1 meres den emulerede basisstation herom ved vcw’en og ser fra centralen ud til at gå i en tilstand med røret på.The calls are set up by a voice code word (VCW) at the beginning of each voice window, this password indicating a "tube taken out of state" in the initiating station. When this occurs, the station which functions as an emulated base station, from the switchboard (CO), seems to itself switch to the "tube taken off" state, thereby establishing a connection with the switchboard. The initiating subscriber station then proceeds to complete the call by rotating the desired number. When the initiating subscriber unit puts the tube on, the emulated base station is informed thereof at the vcw and from the control panel appears to be in a state with the tube on.

Når den emulerede basisstation detekterer et 5 ringesignal fra centralen, bringes abonnentenheden til at ringe ved hjælp af den tilsvarende VCW fra den emulerede basisstation. Når abonnentenheden derefter tager røret af, informeres den emulerede basisstation herom via den tilsvarende VCW og ser fra centralen ud til at lOvære i tilstanden "røret taget af".When the emulated base station detects a 5 ring signal from the exchange, the subscriber unit is called by the corresponding VCW from the emulated base station. When the subscriber unit then takes the tube off, the emulated base station is informed thereof via the corresponding VCW and appears from the control panel to be in the "tube taken off" state.

Den omtalte type trådløs telefonsystemkonfiguration er eksemplificeret i fig. 8, hvor abonnentenheden 90 er vist i trådløs kommunikationt via antenner 92 og 94, med den emulerede basisstation 96. Sta-15 tionen 96 er i trådløs kommunikation, via linien 98 og interfacen 100, med centralen.The mentioned type of wireless telephone system configuration is exemplified in FIG. 8, where the subscriber unit 90 is shown in wireless communication via antennas 92 and 94, with the emulated base station 96. The station 96 is in wireless communication, via the line 98 and the interface 100, with the exchange.

Det ovenfor beskrevne system kan anvendes i forbindelse med et dobbeltabonnentarrangement, som vist i fig, 9. I dette sytem er hver kanal i stand til at be-20 tjene to komplette konversationer uden behovet for at benyttet en duplexer. Med henblik herpå er en dobbelt-abonnentenhed 102 med ledninger 104 og 106 forbundet med et par abonnenttelefoner 108 og 110. Abonnentenheden 102 kommunikerer trådløst, via antenner 25 112 og 114, med en emuleret dobbelt basisstation 116. Enheden 116 er forbundet med centralen, via ledningsforbindelser 118 og 120.The system described above can be used in conjunction with a dual subscriber arrangement, as shown in Fig. 9. In this system, each channel is capable of serving two complete conversations without the need to use a duplexer. To this end, a dual subscriber unit 102 with wires 104 and 106 is connected to a pair of subscriber telephones 108 and 110. The subscriber unit 102 communicates wirelessly, via antennas 25, 112 and 114, with an emulated dual base station 116. The unit 116 is connected to the central station via wire connections 118 and 120.

De to separate abonnenter 108 og 110 benytter et tidsvinduesarrangement, som omtalt i det førnævnte 30 US-patent nr. 4 675 863, hvori hver abonnent er tildelt et separat tidsvindue. Rammeformatet for dette arrangement er vist i fig. 10, hvor fire vinduer er vist nummererede 1, 2, 3 og 4, idet de første to vinduer benyt- 10 DK 174255 B1 tes af den emulerede basisstation og de sidste to benyttes af de to abonnenter.The two separate subscribers 108 and 110 utilize a time window arrangement, as disclosed in the aforementioned US Patent No. 4,675,863, wherein each subscriber is assigned a separate time window. The frame format for this arrangement is shown in FIG. 10, where four windows are shown numbered 1, 2, 3 and 4, the first two windows being used by the emulated base station and the last two being used by the two subscribers.

Adskillige dobbeltabonnentsystemer kan fungere på forskellige kanaler uden duplexere ved at synkroni-5 sere alle de emulerede basisstationstransmlssioner^Several dual subscriber systems can operate on different channels without duplexing by synchronizing all the emulated base station transmissions

Dette er illustreret ved rammeformatet, der er vist i fig. li, hvor kanal l er vist øverst og kanal n (hvilket indikerer et vilkårligt antal kanaler ind imellem) er vist forneden. På hver kanal er de første 10 to vinduer til transmission og de sidste to til modtagelse.This is illustrated by the frame format shown in FIG. 1, where channel 1 is shown at the top and channel n (indicating any number of channels in between) is shown below. On each channel, the first 10 are two windows for transmission and the last two for reception.

En emuleret basisstation kan benyttes i forbindelse med adskillige forskellige abonnenter en ad gangen. I et sådant arrangement overvåger abonnenterne 15 kontinuerligt transmissionerne i radiostyrekanalerne (RCC) for modtagelse, hvilket er mere udførligt beskrevet i det førnævnte US-patent nr. 4 675 863, indtil en bestemt abonnent søges af den emulerede basisstation ved hjælp af abonnentens ID nummer (SID). Efter modta-20 gelse af en søgning, initierer abonnenten en transmission tilbage til den emulerede basisstation under brug af den ovenfor beskrevne synkroniseringsproces. For initiering af et opkald transmitterer abonnentstationen på RCCen under brug af den tidligere beskrevne synkro-25 niseringsproces.An emulated base station can be used in conjunction with several different subscribers one at a time. In such an arrangement, subscribers 15 continuously monitor the transmissions in the radio control channels (RCC) for reception, which is more fully described in the aforementioned U.S. Patent No. 4,675,863 until a particular subscriber is searched by the emulated base station by the subscriber ID number ( SID). Upon receipt of a search, the subscriber initiates a transmission back to the emulated base station using the synchronization process described above. For initiating a call, the subscriber station on the RCC transmits using the previously described synchronization process.

Systemet kan benyttes til overvågning af en eller flere funktioner. Ved brug af en computer som en styrende/dataloggende enhed kan mangfoldige abonnenter i denne sammenhæng periodisk afspørges for at rapporte-30 re om en eller anden funktion, såsom temperatur vejrbetingelser, sikkerhed, vand/oversvømmelsesadvarsler, advarsler om lavt brændstofniveau, fjernaflæsning af gas-, el- eller vandmålere etc. Dette er vist i fig.The system can be used to monitor one or more functions. Using a computer as a control / data logging device, multiple subscribers in this context may be periodically interrogated to report on some function such as temperature weather conditions, safety, water / flood warnings, low fuel level warnings, remote reading of gas , electricity or water meters etc. This is shown in fig.

11 DK 174255 B1 12, hvor en emuleret basisstation 122 kommunikerer trådløst med adskillige abonnentenheder henholdsvis 124, 126 og 128. Enheden 122 er lednings forbundet med såvel en telefon 130, til talekommunikation, som 5 en computer eller dataterminal 132, for indgivelse af data. Tilsvarende er hver abonnentenhed forbundet såvel med en tilhørende telefon 134, 136 eller 138, til talekommunikation, og en dataenhed henholdsvis 140, 142 eller 144.The emulated base station 122 communicates wirelessly with several subscriber units 124, 126 and 128. The unit 122 is wired to both a telephone 130, for voice communication, and a computer or data terminal 132, for data entry. Similarly, each subscriber unit is connected as well to an associated telephone 134, 136 or 138 for voice communication and a data unit 140, 142 or 144 respectively.

10 En vigtig benyttelse af systemet er som repea ter, for at udvide rækkevidden for systemet. I dette arrangement kan den emulerede basisstation benyttes til at overvinde forstyrrende forhindringer, såsom bjerge og lignende. Fig. 13 viser denne funktion, idet den vi-15 ser en abonnentenhed 146, der kommunikerer trådløst med en emuleret basisstation 148 på toppen af en bjerg. Enheden 148 kommunikerer også trådløst med en standardbasisstation 150, der er forbundet med en central.10 An important use of the system is as repeats, to extend the reach of the system. In this arrangement, the emulated base station can be used to overcome disruptive obstacles such as mountains and the like. FIG. 13 shows this feature, showing a subscriber unit 146 communicating wirelessly with an emulated base station 148 at the top of a mountain. The unit 148 also communicates wirelessly with a standard base station 150 connected to a switchboard.

20 Den emulerede basisstations relative enkelthed og billighed gør den meget omkostningseffektiv som en repeaterenhed. Den kan også benyttes som en repeater til at udvide langdistancerækkevidden for systemet, uafhængigt af tilstedeværelsen eller fraværet af for-25 hindringer. Ved at benytte tidsvinduesarrangementet, passer repeaterenheden uden brug af nogen duplexer, i det komplette system, idet den forbliver transparent for såvel standardbasisstationen som abonnenten. Den kan naturligvis også anbringes mellem abonnenten og en 30 anden emuleret basisstation i stedet for en standardbasisstation. Dette kan tilvejebringes i adskillige trin fra en emuleret basissation til en anden, for at øge systemets rækkevidde meget på en billig måde. Dette er 12 DK 174255 B1 vist i fig. 14, hvor en række repeaterenheder 152 er anbragt mellem abonnenten 154 og basisstationen 156.20 The relative simplicity and cheapness of the emulated base station makes it very cost effective as a repeater unit. It can also be used as a repeater to extend the long-range range of the system, regardless of the presence or absence of obstacles. By using the time window arrangement, the repeater unit fits without the use of any duplexes in the complete system, remaining transparent to both the standard base station and the subscriber. Of course, it can also be placed between the subscriber and another emulated base station instead of a standard base station. This can be provided in several steps from one emulated base to another, to greatly increase the range of the system in a cheap way. This is shown in FIG. 14, where a number of repeater units 152 are arranged between the subscriber 154 and the base station 156.

Udover udvidelse af rækkevidden for systemet, tjener repeaterenheden også til at rense det faktiske 5 basisstationssignal ved udligning før retransmission til abonnenten.In addition to extending the range of the system, the repeater unit also serves to purify the actual 5 base station signal by equalizing before retransmission to the subscriber.

En repeater kan også benyttes, i det der kan betegnes som et repeaterstjernesystem, til at drive adskillige repeatere og/eller abonnenter. Dette er vist i 10 fig, is, hvor den enkelte repeaterenhed 158 kommunikerer trådløst med hjælperepeatere 160 og 162 såvel som med en eller flere abonnenter, såsom 164. Hjælpe-repeaterne kommunikerer hver især trådløst med abonnenter, såsom 166, 168, 170, 172 og 174, såvel som med 15 andre hjælperepeatere, såsom 176. En vilkårlig af ' hjælperepeaterne, såsom repeater 162, kan benyttes som den sidste repeater i direkte forbindelse med basisstationen 178.A repeater can also be used, in what may be termed a repeater star system, to operate several repeaters and / or subscribers. This is shown in Figure 10, where the individual repeater unit 158 communicates wirelessly with auxiliary repeaters 160 and 162 as well as with one or more subscribers, such as 164. The auxiliary repeaters each communicate wirelessly with subscribers such as 166, 168, 170, 172 and 174, as well as with 15 other auxiliary repeaters, such as 176. Any of the auxiliary repeaters, such as repeater 162, may be used as the last repeater in direct connection with the base station 178.

Adskillige repeatere kan placeres i én position 20 på forskellige kanaler og synkroniserede, således at deres transmission og modtagelse forekommer samtidigt, hvorved man undgår brugen af duplexere. I en sådan konfiguration benytes en masterrepeater til at overvåge RCC kanalen fra basisstationen og til at videregive den 25 overvågede information til de forskellige abonnenter via de emulerede basisstationers RCC. Ved en sådan konfiguration tildeles hver af abonnenterne en repeater-kanal ved opkaldsopstilling.Several repeaters can be placed in one position 20 on different channels and synchronized so that their transmission and reception occur simultaneously, thereby avoiding the use of duplexers. In such a configuration, a master repeater is used to monitor the RCC channel from the base station and to transmit the monitored information to the various subscribers via the RCC of the emulated base stations. In such a configuration, each of the subscribers is assigned a repeater channel on call setup.

Claims

A wireless digital telephone system comprising a primary subscriber station and at least one secondary subscriber station communicating with each other in 5 time multiplexes on the same high frequency carrier signal, wherein the primary subscriber station and any of the secondary subscriber stations are arranged to transmit as well as receive on the same frequency, and wherein the primary subscriber station and the at least one secondary subscriber station are synchronized with each other by time frames, characterized in that the primary subscriber station and the at least one secondary subscriber station correspond to each other except that the primary subscriber station provides synchronization signals while at least one subscriber stat ion has reestablishment means for adjusting its timeframes in accordance with the synchronization signals.

2. System according to claim 1, characterized in that the at least one primary subscriber station communicates with a central telephone station.

System according to claim 1 or 2, characterized by at least two secondary subscriber stations, the time frame having a separate time window for each secondary subscriber station.

System according to claim 1 or 2, characterized in that the primary subscriber station communicates wirelessly with a number of corresponding primary subscriber stations, the last corresponding primary subscriber station in the series communicating wirelessly with a secondary subscriber station.

A wireless digital communication system according to claim 1, characterized in that the synchronizing means comprise a coarse-frequency regenerative circuit which comprises computing means which separates the signal received from the primary subscriber station in high-band and low-band energy frequencies; Means for subtracting the high band energy output signal from the low band energy output signal to obtain a resultant signal; means for removing the sign from the resulting signal, to determine its amplitude only; Means for highlighting the amplitude signal, with its noise being substantially filtered out; and means for passing the amplitude signal to a voltage controlled crystal oscillator (VCXO) which provides the timing of the secondary subscriber station.

Wireless digital communication system according to claim 1, characterized in that the high frequency carrier signal comprises waveforms divided into multiple time frames, each frame comprising a single time window; a controller in each station; amplitude monitoring means at each station controlled by the control to monitor the amplitude of signals from another station and to determine the placement of positive flanks in the waveforms of such signals by comparing the amplitude of each signal from another station with a predetermined threshold signal; frame adjusting means in each station controlled by the controller to adjust the frame timing control therein to create the frames with the occurrence of the positive flanks; the primary subscriber station having frame synchronization initiating means and the secondary subscriber station having frequency recovery means for synchronizing the timing of signals received from the primary subscriber station with the timing initiated therefrom; the primary subscriber station essentially differs from the secondary subscriber station only in that it contains the synchronization initiating means; the system further comprises a slow-rising, rapidly decreasing automatic gain control circuit (AGC circuit) which avoids detection when there is no signal, which AGC circuit comprises, an amplitude calculator which supplies a received signal and outputs an amplitude signal. 15 a comparator for receiving the amplitude signal and subtracting it from a predetermined threshold value for generating a difference signal; and means for determining the positive or negative sign of the difference signal, to selectively implement a slow decrease or rapid increase of the AGC signal; and means for passing the implemented signal to the controller.