CZ279415B6 - Method of transmitting communication signals and apparatus for making the same - Google Patents

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

A method of transmitting communication signals and apparatus for performing the method

Technical field

The invention relates to a method of transmitting communication signals and to a device for transmitting them.

BACKGROUND OF THE INVENTION

In general, telephone systems increasingly use wireless technologies for long-distance connections and in some cases have started to use digital technology. However, none of the systems generally used today is able to provide efficient and effective wireless digital technology for local calls to and from individual subscribers.

Such technology has been described in various recent patents jointly owned by the present Applicant's agent, such as US Patent No. 4,644,561 of February 17, 1987 and US Patent No. 4,675,863 of June 23, 1987. The technology described in these patents provides base stations in conjunction with both a control panel and a set of subscriber stations using digital time division digital circuitry, in which subsequent repetitive slot positions are created in the bitstream of the transmission channel, each slot being associated with one subscriber .

The base stations used in the aforementioned time division system are relatively complex and expensive, but economically acceptable for a large system serving a large number of subscribers. However, relatively small systems serving a relatively small number of participants may be economically disadvantageous. Moreover, such a system uses a pair of frequencies, one for transmission and one for reception, and given the limited number of channels available in the spectrum, it would be highly advantageous if only one frequency could be used effectively.

It is therefore an object of the present invention to provide what can be called a simulated or emulated base station that can effectively replace the actual base station in certain situations.

Another object of the invention is to provide a system that can be used for a set of subscribers but which operates on a single frequency only.

Other features of the invention will be apparent from the following description and claims.

SUMMARY OF THE INVENTION

The communication signal transmitting apparatus of the present invention employs a method of modifying a subscriber station that acts as a simulated or emulated base station, thereby greatly reducing the overall cost and complexity of the system. This emulated base station differs substantially from participation

The station only acts to sweep the high frequency signals transmitted by the emulated base station until it finds the frequency and the slot assigned to it. At intervals between transmissions of radio frequency signals, the emulated base station is adapted to receive radio frequency signals from subscriber stations or units. In this way, the subscriber unit may either talk to the emulated base station, which then acts as another subscriber station _t, or may talk to another subscriber station that has been synchronized by the emulated base station.

The essence of the method of transmitting communication signals in a wireless digital communication system with at least two stations is to first initiate in the first station a synchronization process including the assignment of several frames in one selected frequency channel, each frame being divided into at least two slots, further transmitting the first communication signal at the assigned slot of the selected frequency, then detecting the second communication signal from the remote station and receiving the second communication signal at another slot of the same selected frequency frame and repeating the steps of transmitting the next first communication signal until receiving the second communication signal until the communication is interrupted .

Preferably, each time frame is divided into more than two slots, further when the first communication signal is transmitted in the first slot and the second communication signal is transmitted in the second slot, and when each slot is of the same time period.

It is also preferred that, after initiating a synchronization signal based on the time division of a frame of one frequency at a first station, a second station is allocated with an assigned frequency, then a first communication signal containing a synchronization signal is transmitted at a specified frequency, followed by examination of a frequency spectrum containing the allocated frequency , by the second station to detect the communication at the allocated frequency, in response to the communication, the second station tunes to the allocated frequency to receive the signal, followed by sending a second communication signal at the allocated frequency from the second station received by the first station, and continuing the synchronization signal until communication is interrupted.

It is preferred that the time sliced frames use one slot for each transmission.

The device for transmitting a communication signal comprises at least one subscriber telephone station connected by a wireless telephone link to a base station connected by telephone lines to a control panel, the base station and each subscriber station comprising a telephone connected to a telephone interface connected to an analog-to-digital converter connected to a speech processor connected to a modem connected to a radio transmitter connected to an antenna, the modem and the radio transmitter also connected to a control unit comprising a time slot control circuit connected to the modem, the essence of the invention is that the base station control unit it comprises a main timing circuit connected to the modem while the attendance control unit

The station includes a synchronization circuit consisting of an amplitude calculation circuit connected by its input to the signaling input of the control unit, by its output to the first comparator input, the second input of which is connected to the threshold forming circuit and the output of which is connected to an edge detector. which is connected to the time slot control circuit of the control unit, the control unit being connected via a radio transducer to an automatic gain control circuit and via a primary frequency sensing circuit to a radio transducer.

Preferably, the primary frequency sensing circuit comprises a separating circuit for separating the low and high frequency bands, the input of which is connected to the input of the receiver of the radio transducer, and further to a limiting circuit for suppressing the polarity of the signal connected to the filter, the mixer input, the output of the separation circuit being connected via an adder to a first mixer input, the output of which is connected to a balancing circuit for balancing the high and low frequency bands, comprising an adder whose first input is connected to the mixer output and whose output is connected to the delay the circuit whose output is connected to the second input of the adder and to the oscillator (VCXO) connected to the control unit.

It is also preferred that the automatic gain control circuit comprises an amplitude calculation circuit whose input is connected to the receiving output of the radio transducer and whose output is connected to the first input of the comparator, whose second input is connected to the audio value generating circuit and whose output is connected in parallel. to two multipliers, with parity selection, the outputs of which are connected via a selector switch to an adder, which is connected to a delay circuit, the output of which is connected to the second adder input and to the control unit.

Advantageously, although the base station is a modified subscriber station distinct from the subscriber station in that the control unit comprises a main timing circuit connected to the modem, while the subscriber station includes a timing achievement circuit connected to the modem to detect and perform the subscriber station timing from the base station. wherein the timing achievement circuit comprises an amplitude calculation circuit connected to a comparator, the second input of which is coupled to a threshold forming circuit, and the output of which is connected to an edge detector coupled to the control slot of the control slot for single frequency communication at a single frequency time slot.

A preferred subscriber unit is when the apparatus of the invention comprises a plurality of stations and time slot control circuits controlling the creation of a time slot frame with a separate slot for each subscriber station.

Preferably, the base station is wirelessly connected to several of the same base stations, the last base station being wirelessly connected to the subscriber station.

It is preferred that the base station comprises a main timing circuit of communication on one frame frequency with at least two slots, one slot for transmission to the subscriber station and the other.

-3E 279415 B6 _in '&

a receiving slot from the subscriber station, while the subscriber station consists of a timing sensing circuit connected to a modem to detect and execute the timing of the subscriber station, the timing sensing circuit including an amplitude calculation circuit associated with a comparator whose second input is connected to an edge detector connected to a control slot of the control unit time slot.

Suitably, the device according to the invention comprises a plurality of subscriber stations and a control slot time slot control unit of the control unit to create a slot-separated time frame for each subscriber station.

Preferably, the base station is wirelessly connected to several of the same base stations, the last base station being wirelessly connected to the subscriber station.

It is also preferred that the subscriber station is connected to the base station by wireless transmission.

Overview of the drawings

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of the entire apparatus embodying the invention; FIG. 2 is a schematic representation of the control channel signal used in a standard base station; FIG. Figure 4 is a schematic diagram showing positive amplitude edges of the received signal used during synchronization in the device of the invention; Figure 5 is a block diagram of a circuit for obtaining run synchronization in the device of the invention; Fig. 6 is a block diagram of an automatic gain control circuit used in the device of the invention; Fig. 7 is a block diagram showing a frequency sensing circuit used in the device of the invention; Figure 8 is a schematic representation of the communication signal transmitting apparatus of the present invention; Figure 9 is a schematic representation of the circuit of Figure 8 but showing the dual subscriber system; Figure 10 is a schematic representation of the frame format of the dual subscriber apparatus of Figure 9; Fig. 11 is a schematic illustration of a frame format of a dual subscriber system; Fig. 12 is a schematic illustration of a device embodying the invention that is used to monitor one or more functions; Fig. 13 is a schematic illustration of a repeater device embodying the invention; Fig. 14 is a schematic illustration of a device embodying the present invention using multiple repeaters; and Fig. 15 is a diagram. A visual representation of a device embodying the present invention wherein a single repeater is used to control a set of additional repeaters as well as subscriber units.

DETAILED DESCRIPTION OF THE INVENTION

The overall internal operation of the device 10 is shown in the block diagram of FIG. 1. In this system, during a telephone conversation, the person speaks to the telephone 12 and the speech signal is sent to the unit. 14 of the local telephone interface, the signal is digitized by the encoder and decoder 16, and the resulting digital data stream is then received

This is said to the speech processor 18, which compresses the speech data to a lower data rate. The compressed data is then fed to the modem 20 via a line 22 and a switch 24 where the modem 20 acts to convert the data stream into a spectrally effective analog signal. This analog signal is supplied to the radio 26 via line 28. The radio 26 converts the signal into a high frequency signal and then transmits the radio frequency signal via the antenna 30.

At intervals between transmissions of the radio frequency signals, the unit is adapted to receive the radio frequency signals of the subscriber unit. The radio 26 converts each of these radio frequency signals to an intermediate signal and feeds the intermediate signal to modem 20 via line 32. Modem 20 demodulates the intermediate signal to produce a digital signal, which is then fed to the speech processor via switch 24 and line 36. The speech processor produces from this signal the digitized speech signal and the digitized signal are then fed to an encoder with a decoder 16, from which the analog speech signal is then output to the telephone 12 via the telephone interface 14.

The data transmission mode is similar to the one described above except that the telephone is replaced by a data terminal or computer 38 and the telephone, encoder and decoder and speech processor are bypassed via the alternate position of the switch 24, which is then connected to terminal 38 by lines 40 and 42.

Modem 20 and radio 26 are connected to control unit 44. Control unit 44 is initially set to a predetermined slot modulation and training mode for the modem and to a predetermined high frequency and power level for the radio. However, these parameters can be set by the subscriber unit and in this case are not suitable to provide satisfactory reception at the subscriber station.

In a device using a current base station, such as the system described in the aforementioned Patent No. 4,675 S63, the transmitted signal is split into a system of, for example, a frame of 45 ms duration. Each frame is again divided into four 11.25 msec slots. The base station broadcasts on everyone. four slots to create a 100% signal utilization factor, with the only exception being the radio control channel. The control channel slot is slightly shorter than 11.25 ms and this causes a small modulation gap at the beginning of each frame. This gap is known as the amplitude modulation aperture. The radio channel control signal pattern of the current base station format is shown in Figure 2. However, the device of the invention does not transmit a signal with 100% duty cycle as shown in Figure 3. This modified frame format enforces coarse synchronization changes in automatic gain control and reaching the frequency. These changes are outlined in the following description.

Since the device according to the invention uses only a 25% utilization factor, it monitors the amplitude of the received signal and looks for positive edges in the amplitude signal. These positive edges are shown in FIG. 4. The subscriber unit sets its frame timing to center with the appearance of these positive edges.

- 5A

The circuit for obtaining the above-described type of rough synchronization is shown in the form of a block diagram in Fig. 5 where an optional signal is shown as being applied to a circuit 50 which generates a computer amplitude signal which then comes to the comparator 52 where it is compared with a predetermined signal. , thereby producing a digital signal where the logical unit means that it is further present, while logical 0 means that the signal is not present. This digital signal is applied to an edge detector 54, at the output of which a withdrawal pulse appears to indicate a positive edge detection.

Modulation with a 25 percent duty cycle requires a special type of automatic gain control receiver circuit that is not monitored when no signal is present. Thus, automatic gain control with slow increase and rapid 'decrease' is provided. This is shown in Fig. 6, where the received signal is fed to an amplitude calculation circuit 56 that can be formed as a pre-programmed non-volatile memory from which the resulting amplitude signal is fed to a comparator 58 where it is subtracted from a predetermined threshold value. to create a differential signal. This differential signal is fed and via one or two scale multipliers 60 and 62, respectively, to a low-pass filter comprising an adder 64 and a delay circuit 66 connected through a loop 68. One or the other of the two multipliers is used in accordance with the difference signal sign. If the difference signal is positive, the automatic gain control signal fades slowly. If the difference signal is negative, there is a rapid increase in the automatic gain control control signal. The filter output is the gain signal that is thus fed to the gain control unit 44 shown in FIG. 1.

Because in a 25% frame format, frequency capture is not required during the disconnect time when 75% is zero time, and because frame timing is not known at the time the frequency scan is performed, a modified frequency capture circuit as shown in . In this circuit, the received signal is fed to a discrete Fourier transform calculation circuit 70, at the output of which the upper band energies, i.e., the frequency band above the center frequency and the lower band energy, i.e. the energy bandwidth below the center frequency, appear. . The output of the high band is subtracted from the low band power of the adder 72, the output of which is applied to a mixer or multiplier 74. The received RF signal is also applied to a limiting circuit 76 which cuts the signal sign, negative or positive, absolute value of signal amplitude. The cut signal is then fed to the filter 78 to smooth the signal by averaging it. The output of the filter 78 is fed through the amplifier 80 to the multiplier 74.

The primary purpose of the circuitry 76, 78, 80 is to prevent noise from outputting the signal while enhancing the signal itself. In this regard, since noise generally has a small amplitude, it is effectively filtered during the smoothing process. On the other hand, since the actual signal generally has a relatively large amplitude, it is in fact enhanced by adding a dedicated or filtered signal to the mixer 74.

-6GB 279415 B6

The scaling signal exiting the mixer 74 is balanced between the high and low energy frequencies, and this balanced signal, which is proportional to the short-term average amplitude of the received signal, is fed to a low-pass filter comprising an adder 82 and a delay circuit 84 which are connected by loop 86. causes the output signal 88 to control VCXO to be an output immediately before the output signal is actually applied to the low pass filter. The VCXO control is used to set the main oscillator frequency in the system.

After initial synchronization or runtime synchronization has been performed, the system is in unusable voice mode but is fully configured for voice activity. If the handset is picked up at either end of the phone, the phone will ring at the other end until the answering phone is answered or the first phone is hung up.

The calls are set by a voice code word at the beginning of each voice slot, where this code word indicates the condition of removing the handset at the initiation station. When this occurs, the station acting as the emulated base station then appears to itself as a pickup handset to the headquarters and a connection to the headquarters is made. The incoming subscriber station then proceeds to complete the call by dialing the desired number. When the initiating subscriber station hangs up, the emulated base station is then informed by a voice code word and the headquarters appears to be in a hang-up state. .

When the emulated base station detects a ring signal from the central office, it causes the subscriber unit to ring through the corresponding voice code word from the emulated base station. Then, when the subscriber unit hangs up, the emulated base station is thus informed by the corresponding voice code word and the central unit presents itself off-hook.

The aforementioned type of configuration of the cordless telephone system is shown in the exemplary embodiment of FIG. 8, wherein the subscriber unit 90 is shown in wireless connection over antennas 92 and 94 to the emulated base station 96. The station 96 is in wireless connection over line 98 and interface 100 s. headquarters.

The apparatus described above can be used with a dual subscriber arrangement as shown in FIG. 9. In this system, each channel is capable of bearing two complete talks without the need for a duplexer. In this regard, the dual subscriber unit 102 is connected by lines 104 and 106 to a pair of subscriber telephone receivers 108 and 110. The subscriber unit 102 is in wireless communication via antennas 112 and 114 with an emulated dual base station 116. The unit 116 is connected to the central by wired lines 118 and 120.

Two separate subscribers 108 and 110 use a time slot arrangement as described in the aforementioned Patent No. 4,675,863, wherein each subscriber is assigned a separate slot. The frame format for this arrangement is shown in Figure 10, showing four slots, namely No. 1, No. 2, No. 3 and No. 4, where the first two slots are used for the emulated base station and the last two slots. are used for two participants.

The dual subscriber system can be utilized on different channels without duplexers by synchronizing all transmissions of the emulated base stations. This is illustrated by the frame format shown in Fig. 11, wherein channel 1 is shown at the top and channel n indicating any desired number of channels in between is shown at the bottom. On each channel, the first two slots are for transmission and the last two are for reception.

One emulated base station can be used by a set of different subscribers simultaneously. In such a reception arrangement, the subscribers continuously monitor the transmission of the control radio channel, which is described in more detail in the aforementioned Patent No. 4,675,863, until the subscriber is paged by the emulated base station via the subscriber identification number. Upon receipt of the page, the subscriber indicates transmission back to the emulated base station using the synchronization process described above. To initiate a call, the subscriber transmits on the control channel using the synchronization process described above.

The device can be used to monitor one or more functions. In this view of using a computer as a data management or storage device, the subscriber system can be periodically examined to obtain a report on a function such as temperature, weather conditions, safety, water or flood warning, low fuel warning, remote gas, sensing electricity or water status, and the like. This is illustrated in Fig. 12, where the emulated base station 122 is in wireless connection to a plurality of subscriber units 124, 125, and 128, respectively. The unit 122 is in wired connection to a voice telephone 130 and a computer or data terminal 132 for data input. . Similarly, each subscriber unit is connected both to the respective telephone 13 6 or 13 8 for voice communication and to the data circuit 14 0, 14 _f and 144, respectively.

An important use of this equipment is to use it as a repeater to extend the range of equipment. In this arrangement, the emulated base station can be used to overcome disruptive obstacles such as mountains and the like. Giant. 13 illustrates this function and shows subscriber unit 146 in wireless connection with emulated base station 148 at the top of a mountain. The unit 148 is also in wireless communication with a standard base station 150 connected to the central office.

. The relative simplicity and cheapness of the emulated base station make it very cost effective as an amplification unit. It can also be used as amplifiers to extend the long range of the system regardless of the presence or absence of obstacles. Using the time slot arrangement, the amplification unit fits into the complex system without using any duplexer, while remaining transparent to both the standard base station and the subscriber. However, it may also be included between the subscriber and another emulated base station instead of a standard base station. This can be done in multiple stages from one emulated base station to another for a significant increase in system size in a relatively inexpensive manner. This is shown in Figure 14,

279415 B6 wherein the set of amplifier units 152 is included among the subscriber

154 and base station 156.

In addition, an amplification unit is used to expand the range of the device to clear the actual base station signal by aligning it before re-sending to the subscriber.

One amplifier can also be used in what can be called an amplification star system to control multiple amplifiers and / or subscribers. This is illustrated in Fig. 15, where the single amplifier unit 158 is in wireless communication with the subsidiary amplifiers 162, as well as one or more subscribers 164. The sub-amplifiers are themselves in wireless communication with the subscribers 166, 168, 170, 172 and 174 as well as Any other branch amplifiers, such as amplifier 162, may be used as a final amplifier in direct connection with base station 178.

Multiple amplifiers can be located in one place on different channels and synchronized so that their transmissions and receivers appear simultaneously, avoiding the use of duplexors. In such a configuration, an amplifier is mainly used for monitoring the base station control radio channel and transmitting the monitored information to different subscribers via the emulated base station control radio channel. In such a call setup configuration, each subscriber is assigned an amplifier channel.

Example of Industrial Use The invention is applicable to wireless communication between at least two stations.

Claims (13)

PATENT CLAIMS A method of transmitting communication signals between at least two stations, characterized in that a first synchronization process is initiated at the first station including allocating several frames in one selected frequency channel, each frame being divided into at least two slots, further transmitting the first communication signal at the allocated slot of the selected frequency, detecting the second communication signal from the remote station and receiving the second communication signal at another slot of the same selected frequency frame and repeating the steps of transmitting the next first communication signal until receiving the second second communication signal until the communication is interrupted. The transmission method of claim 1, wherein each time frame is divided into more than two slots. -9EN 279415 B6 5. Way by, and the other The way The method according to claim 1, wherein the first communication signal is. transmits in the first slot the communication signal is transmitted in the second slot. transmitting according to claim 1, characterized in that each slot is of the same time period. transmitting according to claim 1, characterized in that after initiating the synchronization signal based on the division of one frequency frame at the first station, a second assigned frequency station is formed, then a first communication signal containing the synchronization signal is transmitted at a designated frequency, followed by examining the frequency spectrum including the second station to tune to the allocated frequency to receive the signal, followed by sending a second communication signal at the allocated frequency from the second station received by the first station, and continuing the synchronization signal until communication is interrupted. 6. The transmission method of claim 5, wherein the time sliced frames use one slot for each transmission. A device for transmitting communication signals according to a method as in claim 1, comprising at least one subscriber telephone station connected by a wireless telephone link to a base station connected by telephone lines to a switchboard, the base station and each subscriber station comprising a telephone connected to a telephone interface connected to an analog-to-digital converter which is connected to a speech processor connected to a modem which is connected to a radio converter connected to an antenna, wherein the modem and the radio converter are also connected to a control unit comprising a time slot control circuit connected to the modem, you learn. characterized in that the control unit (44) of the base station (96) comprises a main timing circuit connected to the modem (20), while the control unit (44) of the subscriber station (90) comprises a synchronization circuit (49) consisting of a circuit (50) calculating the amplitude connected by its input to the signal input of the control unit (44), by its output to the first input of the comparator (52), the second input of which is connected to the threshold forming circuit and the output of which is connected to the edge detector (54) to the time slot control circuit of the control unit (44), the control unit (44) being coupled via the radio transducer (26) to the automatic gain control circuit (59) and via the primary frequency sensing circuit (69) to the radio transducer (26). Device according to claim 7, characterized in that the primary frequency sensing circuit (69) comprises a separating circuit (70) for separating the low energy frequency band and the high energy frequency band, the input of which is connected to the input of the receiver (32) of the radio transducer (26). and to a signal polarity suppression circuitry (76) connected to a filter (78) which is connected via an amplifier (80) to a second input of the mixer (74), the output being separated The circuit (70) is connected via an adder (72) to the first input of the mixer (74), the output of which is connected to a balancing circuit (79) for balancing the high and low frequency bands comprising an adder (82). the first input is connected to the output of the mixer (74) and whose output is connected to the delay circuit (84), the output of which is connected to the second input of the adder (82) and the oscillator (VCKO) connected to the control unit (44). The apparatus of claim 8, wherein the automatic gain control circuit (59) comprises an amplitude calculation circuit (56) whose input is connected to a receiving output of the radio transducer (26) and whose output is connected to a first comparator input. (58), the second input of which is connected to the audio value generating circuit (57) and whose output is connected in parallel to two parity selectors (60, 62), the outputs of which are connected via a selector switch to an adder (64), is connected to a delay circuit (66), the output of which is connected to the second input of the adder (64) and to the control unit (44). Device according to claim 7, characterized in that the base station (96) is a modified subscriber station different from the subscriber station (90) in that the control unit (44) comprises a main timing circuit connected to the modem (20). whereas the subscriber station (90) comprises a timing achievement circuit (50, 52, 54) connected to a modem (20) for detecting and executing the timing of the subscriber station (90) from the base station (96), the timing achievement circuit consisting of a circuit (50) calculating an amplitude coupled to the comparator (52), the second input of which is coupled to the threshold generating circuit, and the output of which is coupled to an edge detector (54) coupled to the control slot time slot control circuit (44) for single frequency communication at a single time slot. The apparatus of claim 7, characterized in that it comprises a plurality of subscriber stations and time slot control circuits of the controller (44) to form a time slot with a separate slot for each subscriber station. The apparatus of claim 7, wherein the base station (96) is wirelessly connected to a plurality of identical base stations (152), the last base station being wirelessly connected to the subscriber station (90). Apparatus according to claim 7, wherein the base station (96) on one and the other characterized in that the main timing circuit comprises a single frame frequency to be transmitted through a slot for receiving with at least two slots, at the subscriber station (90) from the subscriber station. (90), while the subscriber station (90) consists of a timing sensing circuit coupled to the modem (20) for detecting and performing the timing of the subscriber station (90) from the base station (96), the timing sensing circuit including an amplitude calculation circuit (50) coupled with a comparator (52), the second input of which is coupled to an edge detector (54) connected to the control slot time slot control unit (44). The apparatus of claim 1, comprising a plurality of subscriber stations and a time slot control circuit of the control unit (44) to form a slot-separated time frame for each subscriber station. The apparatus of claim 7, wherein the base station (96) is wirelessly coupled to several identical base stations (152), the last base station being wirelessly coupled to the subscriber station (90). 16. The apparatus of claim 7, wherein the subscriber station is connected to the base station (96) by wireless transmission (92, 94).