WO1990008447A1 - Equipement de communications mobile - Google Patents

Equipement de communications mobile Download PDF

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Publication number
WO1990008447A1
WO1990008447A1 PCT/AU1990/000020 AU9000020W WO9008447A1 WO 1990008447 A1 WO1990008447 A1 WO 1990008447A1 AU 9000020 W AU9000020 W AU 9000020W WO 9008447 A1 WO9008447 A1 WO 9008447A1
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WO
WIPO (PCT)
Prior art keywords
unit
link
communications equipment
equipment according
mobile
Prior art date
Application number
PCT/AU1990/000020
Other languages
English (en)
Inventor
Anatol Zygmunt Tirkel
Original Assignee
Superior Electronic Developments Pty. Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Superior Electronic Developments Pty. Ltd. filed Critical Superior Electronic Developments Pty. Ltd.
Publication of WO1990008447A1 publication Critical patent/WO1990008447A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/02—Terminal devices
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M1/00—Substation equipment, e.g. for use by subscribers
    • H04M1/72—Mobile telephones; Cordless telephones, i.e. devices for establishing wireless links to base stations without route selection
    • H04M1/725—Cordless telephones
    • H04M1/72502—Cordless telephones with one base station connected to a single line
    • H04M1/72505—Radio link set-up procedures

Definitions

  • the present invention relates to mobile communications equipment and finds particular application in systems incorporating mobile or portable radio telephone units.
  • Mobile communications equipment which comprises a telephone switching system or network, for instance the public switched telephone network, by means of which mobile or portable radio telephone .units can communicate.
  • Each unit can usually communicate, via the switching system or network, either with another mobile unit or with a fixed conventional telephone unit such as a wired subscriber's telephone.
  • a radio or similar link is generally provided between each mobile unit and the switching system or network.
  • an area served by a telephone network is divided into cells and a fixed network transceiver is allotted to each cell.
  • Mobile units within a cell access the network by communicating with the fixed transceiver by means of allotted frequency channels. Allotment of the channels is centrally controlled by the network.
  • each cell will be relatively small and, if possible, will have a high number of channels allocated to it. Conversely, in a sparsely populated area, each cell will generally be substantially larger.
  • communications equipment may be required to operate in a communication environment which can be rendered hostile by any of the following: i) initial interference between neighbouring RF links; ii) interference from external sources; iii) interference due to multipath transmission (which can occur for instance due to reflections in the path of the RF link); iv) signal fading (which can occur for instance due to obstructions moving into the path of the RF link).
  • a further constraint on equipment employing mobile or portable units is that they may have to conform to stringent size, weight, power consumption and cost constraints, as well as offering the user a degree of communications privacy.
  • An object of the present invention is to provide mobile communications equipment in which the above problems are ameliorated, and which can be designed to meet the above constraint.
  • mobile communications equipment comprising a first, mobile unit incorporating transceiving means, and a second unit incorporating transceiving means and connection means for connecting the second unit to a telephone switching system or network, the transceiving .T. ⁇ ans of the first and second units being adapted for establishing a communication link between them, wherein either the first, mobile unit or the second unit further incorporates a sensor for sensing characteristics of the communication link, and the equipment further comprises feedback and control means for controlling aspects of said link in
  • the link is adaptive in accordance with its communications environment.
  • the link may comprise a radio communications link.
  • the characteristics sensed by the sensor include characteristics of the link after it has been established, such that the link is dynamically adaptive in accordance with its communications environment.
  • the characteristics sensed by the sensor may advantageously include the level of interference associated with the link and/or the signal power being received over the link.
  • Such communications equipment can be used in a variety of environments and in particular it can be used where the environment relevant to the communication link is likely to vary.
  • the second unit may be connected to any of a variety of points in a geographically dispersed telephone switching system or network, such as the public switched telephone network, since the equipment can automatically and immediately provide an acceptable quality of communication link, within reasonable limits, regardless of the local conditions under which the link must be established.
  • the number and mobile nature of the units in a mobile communications arrangement means that the number of communication links established in a small area can vary substantially. For instance, in any area which attracts a crowd it is possible that a large number of mobile units will be brought together
  • equipment according to embodiments of the present invention csn detect the effect of a change in loca l occupancy and adapt i ts manner of operation to avoid interference between competing communication links .
  • the communication link established between the transceiving means of the first and second units is coded according to a spread spectrum technique (SST) wherein transmission is based on a broadband f requency regime .
  • SST spread spectrum technique
  • narrow frequency band carriers to provide separate channels for neighbouring communication links
  • each channel is differentiated by modulation of the carrier f requency according to a predetermined code .
  • the modulation might comprise f requency hopping between two or more specified frequencies .
  • Such techniques have an inherent advantage in that low signal power at any single frequency may be used, which signi f icant ly reduces interference wi th or by other equipment .
  • Addi tiona l ly the number of channels avai lable, defined by unique and distinguishable codes , is considerably greater than when channels are def ined by narrow frequency bands .
  • embodiments of the invention may include arrangements wherein the first and second units are both mobile and indeed the adaptive quality
  • TE SHEET of such embodiments is then of enhanced importance .
  • Both the f i rst and second units may include a sensor for sensing characteristics of the communication link established between them, linked to the feedback and control means .
  • a particular aspect of an SST communication link which may be controlled by the control means is the SST code assigned to it .
  • the control means may instigate a "back-off " procedure whereby the allocated codes are changed so as to eradicate the interference .
  • Figure 1 shows a schematic diagram of communications equipment according to an embodiment of the present invention, for use with a cellular telephone system
  • Figure 2 shows a block diagram of elements of a transceiving unit for use in the equipment of Figure 1;
  • Figure 3 shows in " more detail selected elements of the unit shown in Figure 2 , including transmitting , receiving and correlating means ;
  • Figure 4 shows a block diagram of steps performed under the control of a microprocessor in converting an audio voice signal for supply to the transmitting means of Figure 3 ;
  • Figure 5 shows in greater detail a switch shown in block form in Figure 3;
  • Figure 6 shows in greater detail a single side band up- converter shown in block form in Figure 3;
  • Figure 7 shows in greater detail an oscillator and audio input shown in Figure 3;
  • Figure 8 shows schematically the control process of a microprocessor shown in block form in Figure 2;
  • Figure 9 shows frequency responses of components of the oscillator and audio input shown in Figure 7;
  • Figure 10 shows a modified system of the invention;
  • Figure 11 illustrates in more detail some of the receiver components of Figure 10;
  • Figure 12 shows still further detail of some of the carrier detection and AGC components of Figure 11.
  • a particular form of the communications equipment may comprise two mobile transceiving. units, one of which is a base unit 1 having coupling means 3 for direct or indirect connection to a telephone switching system or network, and the other of which is a remote unit 2 carried by a user.
  • the coupling means 3 may for instance comprise an audio port for communication via a cellular telephone with a fixed base station of a cellular telephone network, or a plug for direct connection into a PSTN.
  • Radio frequency (RF) communication link 4 established under the control of either mobile unit 1, 2 and monitored by both units 1, 2.
  • the RF link 4 exploits SST signalling and data is sent in packet format, time division multiplexed, with identifying address information to alert the remote unit 2.
  • the overall manner in which the communications equipment may be used is as a "pocket radio" link for application as a
  • the base unit 1 receives the audio output of the cellular telephone and converts it for retransmission by means of the RF link 4 to the remote unit 2 which may be a selected one of a plurality of remote units 2.
  • the RF link 4 can be described as a half duplex, spread spectrum link which relies on code diversity and time division multiplexing to permit communication between two mobile units 1, 2 regardless, within reason, of the proximity of other mobile units sharing the same spectrum.
  • the base unit 1 is usually attached to a vehicle while the remote unit 2 is carried by a user. Both mobile units 1, 2 comprise substantially the same components and monitor the communications environment before and after an RF link 4 has been established.
  • An RF link 4 is established using time slot and SST code assignment performed by consensus between the mobile units 1, 2 on a predetermined "protocol" or "supervisory" channel.
  • each mobile unit 1, 2 can be considered to comprise a transmitter 5 and a receiver 6 which both operate under the control of a microprocessor 8 with input/output control elements.
  • a digitiser 9 and a digital/analogue conversion unit 95 interface the microprocessor 8 with a microphone (audio input) 10 and a loudspeaker (audio output) 11 respectively.
  • each unit 1, 2 is operated in transmit or receive mode under the control of a transmitter/receiver (T/R) switch 7 which in turn is controlled by the microprocessor 8 associated with that unit.
  • T/R transmitter/receiver
  • the switch 7 is shown in
  • SUBSTITUTE SHEET further detail in Figure 5. It is a standard component, based on a pair of PIN diodes 20, 21, with a control voltage input 100 from the microprocessor 8 which is high when transmit mode is selected and low when receive mode is selected.
  • the transmitter 5 is provided with a pair of frequency modulated sources (oscillators) 12 operating 1 MHz apart.
  • Each oscillator comprises a known surface acoustic wave (SAW) device designed to oscillate at a frequency of the order of 900 MHz.
  • SAW surface acoustic wave
  • the outputs of the two oscillators 12 are alternately connected to a transmitting antenna 15, via suitable amplifiers 16, 17, according to a predetermined pseudo-random sequence which can be reconstructed by the receiver 6.
  • the selection process effectively impresses a high frequency, frequency modulation (FSK)on the signal FM carrier and spreads the transmitted spectrum in accordance with the speed and characteristics of the chosen pseudo-random sequence.
  • FSK frequency modulation
  • audio modulation is applied to each oscillator 12 via the summing input of an operational amplifier 84 in an oscillator arrangement 85 which also maintains the centre frequency of the oscillator.
  • the arrangement provides a voltage controlled oscillator (VCO) and a phase detector which together provide a phase locked loop (PLL) .
  • VCO voltage controlled oscillator
  • PLL phase locked loop
  • the VCO comprises a transistor 71, delay lines 72 and a varacter diode 73.
  • the phase detector comprises a prescaler 74, which operates on the frequency of a crystal oscillator 75 to multiply it
  • the phase detector detects the difference in phase between the VCO output and the crystal oscillator 75 and a resultant error voltage drives the loop via the low pass filter 77.
  • the low pass filter 77 of the loop is designed to have a cut-off frequency 78 of 100 Hz, whilst the audio modulation has a bandwidth 79 in the range from 5 KHz to 50 KHz.
  • This provides mutually exclusive filtering such that the loop response is not fast enough to affect the audio input, and the audio modulation applied to the summing input of the operational amplifier 84 does not interfere with the basic loop operation. This allows the centre frequency of the oscillatorto be maintained during the application of the modulation.
  • the same pair of oscillators 12 are used as local oscillators for the receiver 6, but offset in frequency by means of a single side band (SSB) up-converter 18 to permit the use of a moderately high first intermediate frequency (IF).
  • SSB single side band
  • the receiver 6 otherwise comprises the elements of a standard heterodyne receiver, supplemented by components 6A for use in synchronisation, and connections to the microprocessor 8 for use in monitoring the communications environment.
  • the SSB up-converter 18 comprises a standard component based on a 35 MHz crystal oscillator 22 and configured to eradicate all but a single sideband.
  • Two buffers 23, 24 prevent unwanted reflections of the up-converter output, for instance into the transmitter 5.
  • the crystal oscillator 22 is gated to operate when the unit 1 or
  • SUBSTITUTE SHEET 2 is in receive mode only, by means of a control input 25 from the microprocessor 8.
  • the digitiser 9, microprocessor and input/output control elements 8 convert a speech signal input to the microphone 10 to the signal FM carrier on which the oscillators 12 impress the SST pseudo-random sequence.
  • the conversion is performed in a series of steps (80 to 83) under the control of the microprocessor 8. These steps comprise:
  • a mobile base unit 1 When a mobile base unit 1 is operated by a user to establish a communication link 4 with a mobile remote unit 2, it alerts the remote unit 2 by transmitting on a fixed supervisory channel. Both units 1, 2 select by consensus a free channel for voice transmission and subsequent transmission takes
  • Channels, including the supervisory channel, are distinguished by the SST pseudo-random sequence associated with them.
  • a speech signal at the microphone 10 is operated on according to steps i ) to iv) described above.
  • it is acquired in real time, digitised and stored in a "frame" in a buffer allocated to the transmitter 5, with added framing and synchronisation bits.
  • the prepared packet of data is read out of the buffer at approximately 16 times the aquisition rate, converted back to an 8 bit (256 level) "analogue- form and output to frequency modulate the two RF oscillators 12 at rates in the range of 5 KHz to 50 KHz, with a maximum deviation of approximately 50 KHz.
  • the 256 level "analogue" form used to modulate the oscillator is a known signalling technique in which the signal value is allowed to take one of 256 levels during a sampling interval.
  • Typical packet length may be selected to be 10 m sec, corresponding to 160 m sec of acquired audio, so as to -aintai ⁇ conversation continuity without allowing synchronisation and propagation delay overheads ( up to 10 micro sec.) to become significant.
  • the frequency modulated RF output from the oscillators 12 would be capable of being transmitted through a channel 300 KHz wide. However, this spectral occupancy is spread by the imposing of the
  • the frequency hopping can occur at clocking rates of up to approximately 6 MHz in Australia and 12 MHz in the United States. It has the effect of spreading the transmission spectrum in two ways, firstly because two frequencies are applied but more significantly because the frequency hopping itself generates a series of sidebands representing harmonics.
  • the receiver on receiving such a signal and being synchronised thereto will then reconstruct the original ' audio RF modulation but will further spread any interference effects or noise which is not frequency hopped according to the selected sequence.
  • code sets for use as pseudo-random sequences in signalling which offer a range of codes sufficiently orthogonal to be clearly distinguished.
  • One such set of codes are known as Gold codes and it is proposed to use Gold code sequences of 127 clock periods in communications equipment according to the present invention. There are 129 such distinguishable Gold code sequences and one of these is reserved for the supervisory channel, leaving 128 channel codes.
  • the code repetition period (127 clock periods at 6 MHz or 12 MHz clocking rate) is thus 21 micro sec. in Australia and 10.56 micro sec. in the United States.
  • the synchronisation time of the receiver 6 is less than the time taken to transmit a single data packet.
  • the SST coded packet is amplified and applied to the antenna 15 for transmission as an RF signal.
  • Output power is controlled by the microprocessor 8 to provide an adequate signal to noise ratio at the receiver 6, so as to use the minimum power commensurate with an acceptable standard of communication.
  • the local oscillation is frequency hopped using the same Gold code as that impressed on the RF signal by the base unit 1.
  • the local oscillation is provided by the oscillators 12 of the remote unit transmitter 5, up-converted by 35 MHz to give a first IF of 35 MHz.
  • the RF signal received at the antenna 15 is applied to a preamplifier 30 through the T/R switch 7 and mixed at a DBM 142 Vari L mixer 31 with the frequency hopped local oscillation which is hopped in synchronisation with the oscillators at the base unit 1 which has
  • BSTITUTE SHEET generated the RF signal.
  • the output of the mixer 31 is thus a despread IF signal at 35 MHz and can be demodulated by a standard IF discriminator 32.
  • the power output of the IF filter/amplifier 33, 34 is indicative of the signal to noise ratio of the incoming RF signal, and of the degree of synchronisation between the two units 1, 2, and can therefore be used for diagnostic purposes. Additionally, if the modulating sequence is deliberately dithered in the time domain (shifted repeatedly to and fro in time), synchronisation can be maintained by monitoring the effect of the dither.
  • synchronisation from a cold start is achieved by the known technique of sweeping the receiver code sequence and looking for a match with the code sequence of the RF signal. More specifically, the receiver code sequence is time shifted by 1/2 clock period increments, under the control of the microprocessor 8, and the received power observed. Synchronisation is indicated by maximum power as shown by the output of a correlation score registered in the microprocessor in accordance with the received RF signal power. In general, such a process is also known as "aquisition from a cold start".
  • the code sequence applied at either the transmitting unit 1 or the receiving unit 2 is periodically advanced and retarded (dithered). It is. then possible to monitor received power and detect when the two sequences are moving out of synchronisation since when they are synchronised, two power peaks will be observed evenly spaced during
  • the communications equipment uses the supervisory channel in a series of different ways. This embodies a controlling protocol for call initiation, duration and termination.
  • the use of the supervisory channel is as follows.
  • This mode is reserved for the period when no calls have been or are about to be initiated and involves monitoring of the electromagnetic environment by each receiver, with analysis of traffic and/or interference on each channel. This results in a prioritization of favourable channels in readiness for call initialization.
  • synchronization pulses can be sent and received at periodic intervals on the supervisory channel and status of the link and operational hardware verified in anticipation of call requests.
  • SUBSTITUTE SHEET This mode is used to establish call initiation by use of the supervisory channel.
  • the first objective is to prepare both units 1, 2 for an orderly data transfer. This includes the decision on a mutually agreeable code, verification of hardware operation and synchronization, advance information regarding imminent data transfer and the decision as to which unit 1, 2 will go first into transmit mode.
  • Diagnostics relating to the quality of the link can be gathered e.g. fades and multipath and corrective action taken as required.
  • STITUTE SHEET equipment is under the overall control of the microprocessor 8. This control is implemented as follows.
  • Signals to be output from the transmitter 5 require application of a code sequence whether relevant to a supervisory channel or to a data transfer channel.
  • the microprocessor S determines the code sequence to be applied and controls an electrically programmable logic device ( ⁇ PLD) 41 to supply the selected code sequence to tie oscillator pair 12.
  • ⁇ PLD electrically programmable logic device
  • the digitised signal is formatted and stored in a transmitter (TX) buffer 42, from which it is read out at 16 times the aquisition rate under a clock control input 43 from the microprocessor 8.
  • the 8 bit (256 level) "analogue” conversion is then performed on the high speed read out from the buffer 42 and the signal is supplied to the "Aadio Modulation Data In" terminal 44 of the transmitter 5.
  • the microprocessor 8 also controls the output power of the transmitter 5, via t e power amplifier 17 between the transmitter 5 and the T/R switch 7. It does so by means of a charge pump 90, that is, a gated integrator, as known fzt instance for use in remote control of television loudness or brightness.
  • a charge pump 90 that is, a gated integrator, as known fzt instance for use in remote control of television loudness or brightness.
  • the microprocessor 8 receives the output of the IF discri ins cr 32, again via a digitiser 46. It also receives pcwer information from the RF signal at correlation and dither inputs 47, 48 for use in establishing and monitoring synchronisation.
  • the code sequence to be applied for despreading the signal is again determined by the microprocessor 8 and applied to the oscillator pair 12, and thus to the local oscillation for the receiver 6, by means of the EP D 41.
  • the received signal packets are then transferred to a receiver (RX) buffer 49 and read out at low speed (divided by 16) to provide a re-expanded output signal for analogue conversion, filtering, and playback at the audio output 11.
  • RX receiver
  • the microprocessor 8 controls the receiver gain at the IF amplifier 34, again by use of a charge pump 91, and determines whether the associated unit 1, 2 is in transmit or receive mode by two further dedicated control outputs 92, 93.
  • embodiments of the present invention provide a secure, adaptive form of communication which can be used in a wide range of environments.
  • a range between mobile units 1, 2 of from 2.5 km to 10 km in free space can be achieved, with the ability to offer more than 1000 independent channels.
  • the mutually orthogonal Gold codes selected lend themselves to unscannable communication far superior for security purposes to narrow frequency band communication.
  • the modulator 202 receives input from the
  • the bi-phase modulator 204 corresponds generally
  • 35 modulator 204 reverses the phase of the signal from the FM
  • the signal is analogous to a DSB suppressed carrier signal.
  • the receiver 6 is again similar to the receiver arrangement illustrated in Figure 3 except that the receiver has its own oscillator 210 having a frequency equal to the sum of the carrier and intermediate frequencies i.e. 956.5 MHz. Its output is coupled to a bi-phase modulator 212 connected to the despreading mixer 31.
  • the modulator 212 and intermediate frequency amplifier 34 are controlled by a code tracking loop 214 which is functionally equivalent to the up-converter 18 of Figure 3.
  • the code tracking loop 214 includes a clock generation and control circuit 216 the output of which is coupled to a PN code generator 218 the output of which is, in turn, connected to a dither generator 220.
  • the circuit 216 includes a dither clock output 219 which is also connected to the generator 220. Output from the generator 220 is inputted to the bi-phase modulator 212 as shown in Figure 10.
  • the loop 214 also includes a carrier detection and AGC circuit 224 which corresponds generally to the component 6A of Figure 3.
  • FIG 11 illustrates in more detail the code tracking loop 214.
  • This circuit could be implemented in a variety of ways and the circuit illustrated is by way of example only.
  • Figure 12 shows one circuit realisation for the circuit 224.
  • the circuit includes an integration control logic circuit 230 the truth table of which is set out below.
  • the information signal (voice or data) from D/A converter 45 frequency modulates a carrier at 921.5 MHz from oscillator 200.
  • the resulting signal is bi ⁇ phase modulated in . modulator 204 by a PN code sequence generated by the PN code generator 206 at a rate of 6.5 MHz.
  • the resulting spread spectrum signal is amplified by amplifier 17 and transmitted via the antenna 15 to the receiving unit. Transmission power is controlled by means of manual adjustment of the transmitter power amplifier gain.
  • the received spread spectrum signal received by the antenna 15 is filtered and amplified before being despread by the receiver's local reference code sequence in mixer 31, which is synchronized to the transmitted modulating code.
  • the resulting despread signal is filtered and amplified before being despread by the receiver's local reference code sequence in mixer 31, which is synchronized to the transmitted modulating code.
  • SUBSTITUTE SHEET is FM demodulated by discriminator 32 to recover the original information signal at output 19.
  • carrier detection circuitry During signal reception, carrier detection circuitry provides signal diagnostics to the microprocessor 8, which uses the information to take adaptive measures, thereby maintaining overall system performance.
  • the microprocessor 8 issues control signals to t h e clock generation and control circuitry 216, to control t h e phase and frequency of the receiver's code generator f or code synchronization.
  • Th e co d e tracking loop 214 performs t h ree b asic functions: !• Initial Synchronization 2. Tracking 3. Automatic Gain Control
  • the receive 6 is receiving a maximal length code modulated carrier, sent by the transmitter.
  • the receiver performs a phase search of its local reference co d e sequence until the point of maximum correlation is found.
  • T h e phase searching process is controlled by the microprocessor 8, with code phase shifts initiated by means of "retard" and "advance" control signals.
  • Phase search process consists of acquiring the level of correlation for each 0.5 bit phase shift of the local reference code sequenc over the entire lengt h of the code sequence.
  • the carrier level provides an in d ication of the level of correlation and is made available to the microprocessor 8, using a square law detection circuit 232 and low pass filter 234, as an analog signal to be sample d and digitized.
  • the carrier detection circuity comprising the square law detector circuit 232 and low pass filter 234 is also shown in circuit realisation of Figure 12.
  • the remote unit is generally the same as that described previously and the base unit 1 would be adapted to directly connect to the public switched telephone network.
  • any relatively slow data input could be transmitted on an RF link according to the above arrangement.

Abstract

L'invention concerne un équipement de communications mobile comprenant une unité de base mobile (2) montée dans un véhicule, ainsi qu'un certain nombre d'unités portatives (1) pouvant comprendre des postes téléphoniques portatifs. Les première et seconde unités (2) sont reliées par une liaison de communication (4), et comprennent un microprocesseur (8) détectant les caractéristiques de la liaison de communications (4), l'équipement comprenant en outre des moyens de retour et de commande (5, 8) permettant la commande adaptative de la liaison en fonction de l'environnement des communications.
PCT/AU1990/000020 1989-01-23 1990-01-23 Equipement de communications mobile WO1990008447A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPJ2381 1989-01-23
AUPJ238189 1989-01-23

Publications (1)

Publication Number Publication Date
WO1990008447A1 true WO1990008447A1 (fr) 1990-07-26

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PCT/AU1990/000020 WO1990008447A1 (fr) 1989-01-23 1990-01-23 Equipement de communications mobile

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU678051B2 (en) * 1993-10-26 1997-05-15 Kabushiki Kaisha Toshiba Radio telecommunication apparatus
WO1998057444A1 (fr) * 1997-06-13 1998-12-17 Ericsson Inc. Architecture de telephone satellitaire/cellulaire a modes physiquement separables
EP1005241A1 (fr) * 1998-11-26 2000-05-31 Alcatel Procédé de communication entre un terminal mobile et un accessoire
WO2007104957A1 (fr) * 2006-03-13 2007-09-20 Matsushita Electric Industrial Co., Ltd. Schéma pour atténuer la dégradation d'un signal due à des boucles de régulation numérique de gain

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EP0112108A2 (fr) * 1982-12-08 1984-06-27 Racal-Ses Limited Systèmes radio
JPS60226232A (ja) * 1984-04-24 1985-11-11 Nec Corp 干渉波検出方式
US4613990A (en) * 1984-06-25 1986-09-23 At&T Bell Laboratories Radiotelephone transmission power control
US4639914A (en) * 1984-12-06 1987-01-27 At&T Bell Laboratories Wireless PBX/LAN system with optimum combining
EP0219085A2 (fr) * 1985-10-16 1987-04-22 AT&T Corp. Central téléphonique privé par ondes radio à spectre étalé
EP0244872A2 (fr) * 1986-05-09 1987-11-11 Nec Corporation Station de base capable de surveiller l'occurrence d'interférences sur chaque transmission
US4751725A (en) * 1987-01-30 1988-06-14 Motorola, Inc. VOX remote unit control in a cellular system

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Publication number Priority date Publication date Assignee Title
EP0112108A2 (fr) * 1982-12-08 1984-06-27 Racal-Ses Limited Systèmes radio
JPS60226232A (ja) * 1984-04-24 1985-11-11 Nec Corp 干渉波検出方式
US4613990A (en) * 1984-06-25 1986-09-23 At&T Bell Laboratories Radiotelephone transmission power control
US4639914A (en) * 1984-12-06 1987-01-27 At&T Bell Laboratories Wireless PBX/LAN system with optimum combining
EP0219085A2 (fr) * 1985-10-16 1987-04-22 AT&T Corp. Central téléphonique privé par ondes radio à spectre étalé
EP0244872A2 (fr) * 1986-05-09 1987-11-11 Nec Corporation Station de base capable de surveiller l'occurrence d'interférences sur chaque transmission
US4751725A (en) * 1987-01-30 1988-06-14 Motorola, Inc. VOX remote unit control in a cellular system

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PATENT ABSTRACTS OF JAPAN, E-392, page 18; & JP,A,60 226 232 (NIPPON DENKI K.K.), 11 November 1985 (11.11.85). *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU678051B2 (en) * 1993-10-26 1997-05-15 Kabushiki Kaisha Toshiba Radio telecommunication apparatus
WO1998057444A1 (fr) * 1997-06-13 1998-12-17 Ericsson Inc. Architecture de telephone satellitaire/cellulaire a modes physiquement separables
US6134437A (en) * 1997-06-13 2000-10-17 Ericsson Inc. Dual-mode satellite/cellular phone architecture with physically separable mode
AU746057B2 (en) * 1997-06-13 2002-04-11 Ericsson Inc. Dual-mode satellite/cellular phone architecture with physically separable modes
EP1005241A1 (fr) * 1998-11-26 2000-05-31 Alcatel Procédé de communication entre un terminal mobile et un accessoire
FR2786650A1 (fr) * 1998-11-26 2000-06-02 Cit Alcatel Procede de communication entre un telephone mobile et un accessoire
WO2007104957A1 (fr) * 2006-03-13 2007-09-20 Matsushita Electric Industrial Co., Ltd. Schéma pour atténuer la dégradation d'un signal due à des boucles de régulation numérique de gain

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