JP2001057533A - Radio digital telephone system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve radio frequency use efficiency by designating 1st and 2nd time slots for the transmission of a transmission signal and also 3rd and 4th time slots for the reception of a received signal and performing transmission and reception by using time slots whose single frequencies are shifted from each other. SOLUTION: A transmitting and receiving part 26 can receives RF signals from the subscriber station of the opposite communication side during a period between the transmission and reception of the RF signals. The part 26 performs frequency conversion of each of the received RF signals into an IF signal and supplies the IF signal to a modem 20 via a line 32. Then, both the modem 20 and the RF transmitting and receiving part 26 are connected to a control circuit 44, and the circuit 44 transmits a signal only in a time slot designated as a transmission slot by a transmitting means and controls a time slot so as not to transmit the signal in a time slot designated as a receiving slot.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless digital telephone system, and more particularly to a wireless digital telephone system with improved radio frequency utilization efficiency.

[0002]

Although current telephone systems often use wireless technology for long-distance calls, and in some instances have begun to use digital technology, there is a need for individual subscribers. It has yet to provide effective and efficient wireless digital technology for local calls. This type of technology is disclosed in U.S. Pat. Nos. 4,644,561 and Feb. 12, 1987.
No. 4,675,863, issued June 23, 2011, to a recent patent owned by the assignee of the present applicant. The technology disclosed in these patents uses both a telephone office and a plurality of subscriber offices, and a digital radio time division circuit.
That is, it provides a base station in communication with the use of a time-sharing circuit that has repetitive sequential slot locations within the transmission channel bit stream and associates each of those slots with a particular subscriber station.

[0003] The base stations used in such time division systems are relatively complex and expensive, but are economically feasible for large systems accommodating a large number of subscribers.
However, a relatively small system accommodating a relatively small number of subscribers is not economically feasible. Also,
The above system uses one frequency for transmission and one frequency for reception, that is, a pair of frequencies for transmission and reception, and performs transmission and reception at a single frequency due to the limited number of available frequency channels. It is strongly desired.

Accordingly, it is an object of the present invention to provide a wireless digital telephone system in which transmission and reception are performed using mutually offset time slots of a single frequency.

It is another object of the present invention to provide a simulated or emulated base station that can function as a substitute for an actual base station under certain circumstances.

[0006] Other objects will become apparent from the following description and the appended claims.

[0007]

SUMMARY OF THE INVENTION The system of the present invention uses a modified subscriber station to function as a simulated or emulated base station, thereby significantly reducing the cost and complexity of the overall system. The only difference between the emulated base station and the above-mentioned subscriber station is that the former can set the standard of synchronous operation, and the subscriber station uses a radio frequency (RF) signal from the emulated base station.
It only functions to scan the signal until the frequency and slot assigned to it are found. The emulated base station receives an RF signal from a subscriber station during a period between transmissions of the RF signal. In this way, the subscriber station can talk to the emulated base station already functioning as another regular subscriber station, and has reached synchronization with the emulated base station. You can talk to other subscriber stations.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The overall internal structure of the system of the present invention, indicated generally at 10, is shown in the block diagram of FIG. The subscriber sends voice to the telephone 12 during a call, and the resulting voice signal is sent to the local telephone interface unit 14. The audio signal is digitized by a codec 16 and the resulting digital data stream is provided to an audio processor 18 which compresses the data to a lower data rate. The compressed data is supplied to the modem 20 via the line 22 and the double throw switch 24, and is converted into an analog signal having high frequency spectrum utilization efficiency by the modem 20. This analog signal is supplied to the RF transmitting / receiving unit 26 via the line 28. The RF transmitting / receiving unit 26 converts the frequency of the analog signal into an RF signal (up-converts), and transmits the RF signal through the antenna 30.

The transmission / reception section 26 can receive an RF signal from a subscriber station of a communication partner during a period between transmissions of the RF signal. The transmission / reception unit 26 frequency-converts (down-converts) each of these received RF signals into IF signals.
Then, the IF signal is supplied to the modem 20 via the line 32. The modem 20 demodulates the IF signal to generate a digital signal, which is supplied to the audio processor 18 via the double throw switch 24 and the line 36. At this stage, the audio processor
Reference numeral 18 functions to decompress the input digital signal into a digitized audio signal, and the output digitized audio signal is supplied to the codec 16, and the output analog audio signal of the codec 16 is transmitted to the telephone via the local telephone interface unit 14. Supplied to 12.

The data transmission mode is exactly the same as the telephone call mode, except that the telephone 12 is replaced by a data terminal or a computer 38, and the path from the telephone 12 to the interface unit 14, the codec 16 and the voice processing unit 18 is connected by a line 40. And double throw switch 24, bypassed by 42
Is different only in that it is connected to another pair of fixed contacts.

The modem 20 and the RF transceiver 26 are both connected to a control circuit 44. The control circuit 44 initially modulates and modulates the predetermined time slot, ie, the modem.
The mode is set, and the transmission / reception unit 26 is set to a predetermined time slot for setting a predetermined RF frequency and an output power level. These parameters can be adjusted at the subscriber station if the reception by the subscriber station is not satisfactory.

The system described in the aforementioned US Patent No. 4,675,863 is described.
Systems that use actual base stations like systems
For example, the transmitted waveform consists of multiple frames, each 45 milliseconds in length.
Is divided into Each frame, on the other hand, has four lengths of 11.25 mm.
Divided into re-slots. The base station uses these four
Sent in all lots, duty cycle 100
% Modulation waveform. However, the radio control channel (R
CC) is the only exception. RCC slot from 11.25 ms
Slightly shorter, which allows for a slight modulation at the start of each frame.
Creates a small gap. This gap is between AM Hall
It is known as In the format of the actual base station
FIG. 2 shows the waveform of the RCC channel. The cis of the present invention
System, the transmission of a 100% duty cycle waveform
No communication, one per frame as shown in Figure 3.
Transmit only in the slots of the
Cycle 25%). This modified frame format
Realization of coarse synchronization, automatic gain control (AGC) and frequency acquisition
The trap needs to be changed. The following describes these changes:
You.Coarse synchronization  The system of the present invention utilizes a 25% duty cycle waveform.
Monitor the amplitude of the received signal,
Need to search for positive edges. These positive edges
It is shown in FIG. The subscriber station sets its own frame timing.
Adjustments are made to fit these positive edges.

A circuit for achieving the above coarse synchronization is shown in FIG.
Shown in the lock diagram. In this figure, the received signal is amplitude calculated.
Circuit 50, which generates the calculated amplitude signal
I do. This calculated value is compared with a predetermined threshold signal in the comparator 52.
Are compared, thereby forming a digital signal (1
= Signal present, 0 = no signal). This digital signal
Is supplied to the local detector 54, which detects the positive edge.
Outputs the indicated strobe.AGC  Modulation with 25% duty cycle follows when there is no signal
Requires a special receiving AGC circuit that can be avoided. for that reason
A low-speed rising high-speed falling AGC is provided. This point
Is shown in FIG. That is, in FIG.
Signals can be calculated with pre-programmed ROM amplitude calculations
The calculated amplitude signal at the output of the comparator 56 is supplied to a comparator 56.
58 and subtracted from a predetermined threshold to produce a difference signal.
You. This difference signal is applied to one of two scaling multipliers 60 and 62.
Through adder 64, delay device 66 and loop 68
Supplied to the low-pass filter. The above two multipliers 60 and
And 62 are selectively selected according to the sign of the difference signal.
Is driven. Slow AGC control signal if difference signal is positive
Use a falling signal. AGC control when the difference signal is negative
Make the signal a fast rising signal. The output of the low-pass filter is
This is a gain control signal, which is supplied to the control circuit 44 in FIG.
Supplied.Coarse frequency acquisition  25% duty cycle frame format
Frequency acquisition during the no-signal period (75% no-signal period)
It is not necessary to perform
Since the timing is unknown, the deformation as shown in FIG.
A frequency acquisition circuit is used. In this circuit, the received signal
Is supplied to a discrete Fourier transform (DFT) device 70,
The device 70 outputs high frequency band components (frequency below the center frequency).
Band energy). High frequency band component output
The adder 72 subtracts from the low frequency band component output,
The difference output is provided to a mixer or multiplier 74. On the other hand,
The signal has its sign (positive or negative) removed and the absolute value of the amplitude
Is supplied to a code removal circuit 76 that outputs only the signal. Sign removal
The subsequent signal is supplied to a filter 78, where the signal
Signal is smoothed by time averaging. Output of filter 78
Is supplied to the multiplier 74 via the amplifier 80.

The code removing circuit 76, the filter 78 and the amplifier 80
The main purpose of the circuit consisting of is to prevent the adverse effects of noise on the output signal and to emphasize the signal itself. That is, since noise generally has a small amplitude, it is substantially removed in the process of smoothing. On the other hand, the actual signal is generally of relatively large amplitude and is enhanced by adding the smoothed or filtered output to a multiplier 74.

The output signal of the scaling multiplier 74 is balanced between the high and low frequencies and the balanced signal
That is, this balanced signal, which is proportional to the short-term average amplitude of the received signal, is supplied to a low-pass filter, that is, a low-pass filter comprising an adder 82, a delay means 84, and a loop 86 connecting them. The delay means 84 outputs the output signal 88 to the VCXO control circuit.
Represents its output just before the actual output supply to the low-pass filter. The VCXO control circuit is used to adjust the frequency of the main oscillator in the system.

After the initial synchronization, ie, the coarse synchronization is achieved, the system is in idle voice mode, but is ready to respond completely to voice activity. That is, when one telephone goes off-hook, the other called telephone generates a ringing tone that continues until the called party answers or the calling telephone goes on-hook.

The call is ready with a voice codeword (VCR) at the beginning of each voice slot, a codeword indicating the off-hook state of the calling station. In this state, the station functioning as the emulated base station goes off-hook from the point of view of the local exchange (CO), thereby forming a connection with the central office. The calling subscriber station then completes the call by dialing the desired number. When the subscriber unit of the calling subscriber enters the on-hook state, the emulated base station receives the information by the VCW and indicates the on-hook state to the telephone station.

When the emulated base station detects a ring signal from the central office, the called subscriber unit generates a ringing tone with a corresponding VCW from the emulated base station. When the called subscriber unit goes off-hook in response, the emulated base station receives the information via the corresponding VCW and indicates the off-hook state to the central office.

A radio telephone system of the type described above is shown in FIG.
Is illustrated in FIG. That is, in this figure, the subscriber unit
The knit 90 has an emulated base station 96, antenna 92 and
And 94 as being in wireless communication.
The emulated base station 96 is connected to the line 98 and the interface.
In radio communication with the central office via base 100.Dual subscriber system  The above system is a dual subscriber unit as shown in FIG.
Can be used with In this system
Means that each channel has two channels without using a duplexer.
Can support full calls. That is, the dual subscriber unit
Knit 102 is a pair of subscriber telephones with conductors 104 and 106
Machines 108 and 110, respectively. Subscriber unit
102 is an emulated dual base station 116 and antenna 112 and
And 114 are in wireless communication. Emulated
Dual base station 116 connects to central office via lines 118 and 120
Have been.

The two separate subscriber telephones 108 and 110 utilize the time slot arrangement described in the aforementioned US Pat. No. 4,675,863, ie, a time slot arrangement in which each subscriber telephone is assigned a separate slot. The frame format for this arrangement has four slots 1, 2, 3, and 4, as shown in FIG. The first two slots are used for emulated base stations and the last two slots are used for two subscriber telephones.

Transmission from a plurality of emulated base stations
Synchronization between all uses a duplexer
Multiple dual subscriber systems without different
Can be operated in the channel. Frame in that state
The system format is illustrated in FIG. That is,
In the figure, channel 1 is shown at the top and channel 1
n is shown at the bottom (a desired number of channels
Are indicated by dotted lines). In each channel,
The other two slots are for transmission and the other two slots
The unit is used for reception.Wireless selective call remote service  A single emulated base station can be
The subscriber can use one subscriber at a time. In such an array
For reception, the subscriber station operates the radio frequency control channel.
(RCC), i.e., U.S. Pat.
The transmission of the RCC, which is more clearly described by a particular subscriber,
The station sends the subscriber station ID number (S
(ID) to continue monitoring until a selective radio call is made.
You. Upon receiving a radio selective call, the subscriber station will receive the synchronization
Return to the emulated base station using the process
Start sending. To initiate a call, the subscriber station must
Via the RCC using the synchronization process.Monitor function  Use the system of the present invention for the purpose of monitoring one or more functions
You can also. That is, a control / data automatic recording device
And use a computer to control multiple subscriber stations.
Degree, weather conditions, security, water / flood warning, fuel exhaustion warning, distant
Many such as reading gas meters, wattmeters or water meters in remote areas
Polling periodically to get a number of functional reports
It can be configured as follows. FIG. 12 shows an embodiment thereof.
Illustrated in In this figure, the emulated base
The local office 122 has no subscriber units 124, 126 and 128.
Line communication is in progress. Emulated base station 122 has voice
Telephone 130 for communication and computer for data entry
Or both the data terminal 132 and the
You. Similarly, subscriber units 124, 126, and 128
Telephones 134, 136 and 138 for voice communication and data terminals
Terminals 140, 142 and 144, respectively.Relay system  Another application of the system of the present invention is the communication range of the system.
This is a use as a relay device for expanding the surroundings. That is,
Eliminate the effects of obstacles such as mountains on emulated base stations
It is used for the purpose of. Figure 13 illustrates this function.
The emulated base station 14 at the top of the mountain
8 and the subscriber station 146 in radio communication. Emulation
The base station 148 that was turned on is also a normal base station 1 connected to the central office.
In radio communication with 50.

The above emulated base station is relatively simple and inexpensive, so that it is very cost effective as a repeater. This emulated base station can be used as a repeater to extend the communicable range regardless of the presence or absence of obstacles. In other words, by utilizing the time slot arrangement, the repeater can be adapted to a wireless communication system without using a duplexer, while maintaining transparency for both ordinary base stations and subscriber stations. . Of course, this repeater could be inserted between the subscriber station and another emulated base station, rather than between the subscriber station and a normal base station. The repeaters are arranged in multiple stages between one emulated base station and another emulated base station, thereby greatly expanding the coverage of the system at relatively low cost. This is illustrated in FIG. That is, in the figure, a series of relay stations 152 are arranged between the subscriber station 154 and the base station 156.

In addition to extending the coverage of the system,
This relay station has a function of removing the noise component of the actual base station signal through equalization before retransmission to the subscriber station.

A single repeater can be used in a star connection repeater system to drive a large number of repeaters and subscriber stations. This embodiment is illustrated in FIG. In this figure, one relay station 158 is in wireless communication with one or more subscriber stations, such as subscriber station 164, and auxiliary repeaters 160 and 162. These auxiliary repeaters 160 and 162 are connected to subscriber stations 166, 168, 170, 172 and 174, and other repeaters 176.
And is in wireless communication. Any one of the auxiliary repeaters such as the auxiliary repeater 162 can be used as the last repeater in direct communication with the base station 178.

[0025] A number of repeaters operating on different channels can be installed at one location and synchronized with each other so that transmission and reception by those repeaters occur simultaneously, thereby avoiding the use of duplexers. . In such a configuration, a main repeater is used to monitor the RCC channel of the base station, and the main repeater relays monitoring information to various subscriber stations via the emulated base station RCC. In such a configuration, a relay station channel is assigned to each of the subscriber stations when setting up a call.

As described above, according to the present invention, the use of radio frequencies in a wireless digital telephone system can be made much more efficient.
It can be applied to wireless digital relay system for multiple remote monitoring and expansion of communication range.

[Brief description of the drawings]

FIG. 1 is a block diagram of an entire system embodying the present invention,

FIG. 2 is a schematic diagram of an RCC waveform used in a normal base station,

FIG. 3 is a schematic diagram of an RCC waveform used in the present invention;

FIG. 4 is a schematic diagram of a positive edge of the amplitude of a received signal used for coarse synchronization according to the present invention;

FIG. 5 is a block diagram of a circuit for achieving coarse synchronization according to the present invention;

FIG. 6 is a block diagram of a reception AGC circuit used in the present invention,

FIG. 7 is a block diagram of a frequency acquisition circuit used in the present invention;

FIG. 8 is a schematic diagram of a wireless telephone system configuration embodying the present invention;

FIG. 9 is a schematic diagram of a system that is the same as the system of FIG. 8 except for a dual subscriber system;

FIG. 10 is a schematic diagram of a frame format of the dual subscriber system of FIG. 9;

FIG. 11 is a schematic diagram of a frame format of a multiple duplex subscriber system;

FIG. 12 is a schematic diagram of a system embodying the present invention used to monitor one or more functions;

FIG. 13 is a schematic diagram of a relay system embodying the present invention;

FIG. 14 is a schematic diagram of a system implementing the present invention using a number of repeaters;

FIG. 15 is a schematic diagram of a system embodying the present invention using one repeater to drive a plurality of other repeaters and subscriber stations.

[Explanation of symbols]

 10 System 12 Telephone 14 Telephone interface unit 16 Codec 18 Audio processor 20 Modem 24 Double throw switch 26 Radio frequency (RF) transceiver 30 Antenna 38 Data terminal or computer 44 Control circuit 50,56 Amplitude calculation circuit 52 Comparator 54 Edge Part detector 70 Discrete Fourier transformer 76 Code removal circuit 78 Filter 96 Emulated base station 90 Subscriber unit 100 Interface unit 102 Dual subscriber unit 116 Emulated dual base station 122,148 Emulated base station 124,126,128 subscriber unit 132,140,142,144 data terminal 146,154,164,166,168,170,172,174 subscriber station 150 normal base station 152,158,176 relay station 160,162 auxiliary relay station 156,178 base station

Continuing the front page (72) Inventor Scott David Kurtz 08054 New Jersey USA Mount Laurel, West Bluebell Lane 104

Claims (6)

[Claims] 1. A transmitting / receiving station for performing a plurality of simultaneous and parallel dual telephone communications, each including transmission of a transmission (TX) signal from a local station and reception of a reception (RX) signal to the local station, Means for simultaneously transmitting a plurality of duplex telephone communications over a single identical radio frequency (RF) carrier frequency based on a selected frame format (FIG. 10) divided into at least four first to fourth time slots. And means for receiving, wherein at least the first and second time slots are designated for transmission of the transmit (TX) signal and at least the third and fourth time slots are received for the receive (RX) signal. The transmitting means transmits a signal only in a time slot designated as a transmission slot, and does not transmit a signal in a time slot designated as a reception slot (FIG. 11). A first duplex transmission (TX) signal is transmitted in the first time slot, and a first duplex reception (RX) signal is received in the third time slot. 2 by transmitting a duplex transmission (TX) signal in the second time slot and receiving a second duplex reception (RX) signal in the fourth time slot (FIG. 10). A transmitting and receiving station that can do. 2. The transmitting / receiving station according to claim 1, wherein said frame format has four time slots consisting of a time slot for transmission and two time slots for reception. 3. The transmission / reception station has a plurality of transmission / reception means operable at a plurality of different frequencies, each of the plurality of transmission / reception means via a single identical radio (RF) carrier frequency in a selected frame format. The transmission and reception of the dual telephone communication of the present invention are performed in parallel so that each of the frame formats designates at least two time slots therein for transmission and the other at least two time slots for reception. 2. The transmitting / receiving station according to claim 1, wherein each of the transmitting / receiving means does not transmit any communication signal in the time slot designated for the reception (FIG. 11). 4. A transmission / reception method for performing a plurality of simultaneous and parallel dual telephone communications, each including a transmission (TX) signal transmitted by a transmission / reception station and a reception (RX) signal received by the transmission / reception station, Simultaneous transmission and reception of multiple duplex telephone communications over a single identical radio frequency (RF) carrier frequency based on a selected frame format (FIG. 10) divided into four first through fourth time slots. Designating at least first and second time slots for transmission of the transmit (TX) signal, and at least third and fourth time slots for reception of the receive (RX) signal; And transmitting a signal only in the time slot designated as the reception time slot and not transmitting a signal in the time slot designated as the reception time slot (FIG. 11). Transmitting the first duplex transmission (TX) signal in the first time slot and transmitting the first duplex reception (RX) signal in the third time slot. The second duplex transmission (TX) signal is received and transmitted in the second time slot, and the second duplex reception (RX) signal is received in the fourth time slot (FIG. 10). A transmitting and receiving method comprising the steps of: 5. Designation of selected frame formats via a single identical radio frequency (RF) carrier frequency, i.e. at least two time slots in each of which are designated for transmission and at least two other time slots designated for reception. Performing a plurality of duplex communications over a plurality of frequency channels, each transmitting and receiving a plurality of duplex telephone communications simultaneously and in a selected format, each of which is divided into a plurality of time slots, and 5. The transmission / reception method according to claim 4, further comprising transmitting the transmission (TX) signal in a time slot designated for transmission and not transmitting any communication signal in a time slot designated for reception (FIG. 11). 6. Transmission using wireless transmission between one primary subscriber unit and one or more secondary subscriber units over the same one of a plurality of available radio (RF) carrier frequencies. A transmitting and receiving system for performing a plurality of simultaneous and parallel dual telephone communications comprising (TX) voice information and received (RX) voice information, wherein the primary subscriber unit sets the timing of the voice information and performs the secondary subscription. A transmitting and receiving system in which the subscriber unit synchronizes its own timing with its timing, the primary subscriber unit comprising: (i) means for transmitting synchronization information including an assignment of a time slot on the one RF carrier frequency; (ii) means for simultaneously transmitting and receiving the plurality of simultaneous dual telephone communications through the one RF carrier frequency, and (a) a first dual telephone communication using the one RF carrier frequency. (B) means for transmitting a signal carrying the TX voice information of the second duplex telephone communication using the one RF carrier frequency; Receiving means for receiving a signal carrying the RX voice information of the first dual telephone communication from a secondary subscriber unit over the one RF carrier frequency; and (iii) the RF carrier Means for receiving a signal carrying said TX voice information of said second dual telephone communication in a frequency assigned time slot; and (iv) a second time slot in said RF carrier frequency assigned time slot. Means for transmitting said signal carrying RX voice information corresponding to dual telephone communication.