KR950001260B1 - Base station emulator - Google Patents

Abstract

None.

Description

Duplex communication system using base station imitator, communication method and wireless digital communication system using same

1 is a block diagram showing an overall system using the present invention.

2 is a schematic diagram of an RCC waveform used in a standard base station.

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

4 is a schematic diagram showing the positive edge of the received signal amplitude used in coarse synchronization.

5 is a block diagram of a circuit for obtaining coarse synchronization of the present invention.

6 is a block diagram of a received AGC circuit used in the present invention.

7 is a block diagram showing a frequency acquisition circuit used in the present invention.

8 is a schematic diagram of a structure of a wireless communication system using the present invention.

FIG. 9 is a schematic diagram similar to FIG. 8 showing a dual subscriber system. FIG.

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

11 is a schematic diagram of multiple dual subscriber system frame formats.

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

13 is a schematic representation of a repeater system using the present invention.

14 is a schematic diagram of an implementation system of the present invention using multiple repeaters.

Figure 15 is a schematic diagram of an implementation system of the present invention in which a single repeater is used to drive not only a subscriber unit but also multiple other repeaters.

* Explanation of symbols for main parts of the drawings

12: telephone 14: local telephone connector

16: codec 18: speech processor

20: change demodulator (modem) 24: two-way switch

26: radio (wireless phone) 30: antenna

38: computer 44: gain control signal

50: calculating device 52: comparator

54: edge detector 56: amplitude calculator

58: comparator 66: delay means

64, 72: adder 74: multiplier (mixer)

78: filter 80: amplifier

84: delay means 90: subscriber unit

92, 94: antenna 96: base station

100: connector 102: double subscriber unit

108, 110: subscriber 112, 114: antenna

124, 126, 128: subscriber unit 122: base station

130: telephone 132: data terminal

148: imitated base station 150: standard base station

158, 164: repeater 160, 162: auxiliary repeater

In general, today's telephone systems tend to use wireless technology for long distance calls, and in some cases digital technologies. However, the use of any of these systems today cannot provide effective and efficient wireless digital technology for local calls to individual subscribers. Such techniques are routinely owned by the assignee of the present applicant, for example in several recent patents, such as in U.S. Patent No. 4,644,561 on February 17, 1987, and U.S. Patent No. 4,675,863 on June 23, 1987. Was released. The techniques disclosed in these patents provide a base station that uses digital radio time division circuits to communicate with both central offices and multiple subscriber stations. In such digital radio time division circuits, repetitive and sequential slot positions within a transmission channel bit stream are provided. Is determined.

The base station used in the time division system is relatively complex and expensive, but can be economically used in large systems that serve a large number of subscribers. However, in a relatively small system that serves a relatively small number of subscribers, such a base station is economically infeasible. Such a system also uses a pair of frequencies, transmit and receive frequencies, which, in view of the limited channel size available in the spectrum, would be highly desirable if a frequency could be effectively used as a transmit and receive frequency.

It is therefore an object of the present invention to provide what can be called a simulated or mimic base station that can be effectively replaced in place of an actual base station in certain circumstances.

It is a further object of the present invention to provide a system which can be used for several subscribers but which can be operated on only one frequency.

Basically, the system of the present invention uses what is actually a modified subscriber station to act as a simulation or imitation base station, thereby greatly reducing the total cost and complexity of the system. This mimic base station differs from the subscriber station in that it can basically only initiate synchronization processing, while the subscriber unit scans the RF signal transmitted by the mimic base station until it finds an assigned frequency and slot. It just works. The base station imitated in the interval between RF signal transmissions is adapted to receive RF signals from the subscriber unit. In this way, the subscriber unit is connected to another subscriber unit which is synchronized with the subscriber unit by the imitated base station or by the imitated base station acting as another subscriber unit.

According to one aspect of the invention, synchronization information comprising allocating timeslots of at least two transmission slots for transmission from a base station (station) and at least two reception slots for reception by the base station to a selected frequency; A control unit for providing a; One signal for the first duplex communication is transmitted by the radio (radiotelephone) over the selected frequency in the first assigned transmission slot, and one signal for the second duplex communication is sent in the second assigned transmission slot. A modulator for converting the digital information signal into an analog information signal to be transmitted on a selected frequency; And receiving one signal for first duplex communication and one signal for second duplex communication for demodulation by the demodulator, wherein the signals are selected frequencies in a first allocated reception slot and a second assigned reception slot, respectively. A radio being transmitted from the subscriber unit (station) via the control unit, which provides modulation information to the modulator and provides a selected frequency to the radio, thereby providing the selected unit to the radio via a frequency to which synchronization information is assigned. The base station to be sent to; Receiving synchronization information transmitted from the base station, confirming, by the control unit, the frequency selected for the duplex communication signal with the base station and the assigned transmission and reception slots, and receiving the duplex communication signal for demodulation by a modulator; Radio at which the signals at this time are transmitted from the base station via the selected frequency in the assigned base station transmission slot; And a subscriber unit including a demodulator for converting the digital information signal into an analog information signal such that a signal for duplex communication is transmitted to the base station through a selected frequency in the base station receiving slot to which the signal is transmitted by the rider. A duplex communication system using a base station imitator for communication between a base station and a plurality of subscriber units via one of a plurality of available frequencies is provided.

According to another aspect of the present invention, a base station is assigned, including assigning timeslots of at least two transmission slots for transmissions from the simulated base station and at least two reception slots for reception by the base station to one selected frequency. Send synchronization information from the station to the subscriber unit; Transmit one signal from the base station for the first and second duplex communication, respectively, on the selected frequency in the first and second assigned transmission slots; And receiving one of a plurality of available frequencies, including receiving, by the base station, one signal for the first and second duplex communication, respectively, transmitted from the subscriber unit through the selected frequencies in the first and second allocated receiving slots. Also provided is a duplex communication method for communication between multiple subscriber units with a base station.

According to another feature of the invention, it comprises at least two stations (base station and subscriber unit) in RF communication with each other, where one station initiates the timing of the RF signal and the other station initiates the timing according to the initiated timing. A computing device for synchronizing, wherein said synchronizing means in said other station comprises a course frequency learning circuit, said circuit separating said signal received from said one station into high and low band energy frequencies; An adder for subtracting the high band energy output from the low band energy output to obtain a result signal; Stripping means for stripping the sine of the resulting signal to determine only its amplitude; Amplifiers for filtering out noise and emphasizing stripped signals; And a low pass filter for supplying a stripped signal including an adder, delay means, and a feedback loop to a voltage controlled crystal oscillator providing timing at the other station. .

According to another aspect of the invention, at least two stations comprising a first station and a second station communicating with each other by means of an RF frequency signal, wherein the RF frequency signal comprises a plurality of frames each frame consisting of one single time slot. Consists of a waveform divided into timeslots; Control unit at each station; Controlled by the control unit to monitor the signal amplitude from another station and determine the position of the positive edge (figure 4) in the waveform of that signal by comparing each signal amplitude from the other station with a predetermined limit signal. An amplitude calculator in each station, the first station having frame synchronization initiation means and the second station having frequency acquisition means (FIG. 7) to direct the timing of the signal received from the first station to the first station. To synchronize with the timing initiated by; The inclusion of synchronization initiation means within the first station makes the first station different from the second station; An amplitude calculation device, further comprising a slow rising, fast attenuation automatic gain control (AGC) circuit (FIG. 6) in which the system avoids tracking in the absence of a signal, wherein the circuit is supplied with a received signal and outputs an amplitude signal; A comparator for receiving the amplitude signal and subtracting the received signal from a predetermined threshold value to form a difference signal; A scaling multiplier for determining the positive or negative sine of the difference signal to selectively effect slow attenuation or fast rise in an AGC signal; And a low pass filter for supplying a signal implemented to the control unit, including an adder, a delay means, and a feedback loop.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The overall internal operation of the system designated by (10) is shown in block diagram form in FIG. In this system, a caller speaks into the telephone 12 during a telephone conversation and a voice signal is sent to the local telephone connector 14. At this time, the signal is counted by the codec 16, and the resulting digital data system is sent to the voice processor 18 which compresses the voice data at a low data rate. The compressed data is then fed to the demodulator via line 22 and double-throw switch 24, where the demodulator acts to convert the data stream into a highly efficient analog signal. This analog signal is supplied to the radio (wireless telephone) 26 via line 28. At this time, the radio (radiotelephone) upconverts the signal into a radio frequency (RF) signal and transmits the RF signal via the antenna 30.

In the interval between RF signal transmissions, this unit is adapted to receive RF signals from one subscriber unit. The radio 26 downconverts each of these RF signals to an IF signal, and supplies the IF signal to the demodulator 20 via line 32. The demodulator 20 demodulates the IF signal to form a digital signal, which is then supplied to the voice processor via switches 24 and 36. Upon receiving a digital signal, the speech processor acts to expand the signal into a digitized speech signal, which codec 16 outputs the next analog speech signal to the telephone 12 via the telephone connector 14. Are fed into.

The data transfer mode is similar to that described above except that the telephone is replaced by the data terminal or computer 38, and the telephone, codec and voice processor are connected to terminal 38 by lines 40 and 42. Bypassed by the selected position of the switch 24 to be made.

The demodulator 20 and the radio 26 are both coupled to the control unit 44. This control unit 44 is initially set to a predetermined slot, modulation and training mode for the demodulator and to a predetermined RF frequency and output level for the radio. However, these parameters may be manufactured by the subscriber unit if they are not suitable for providing satisfactory reception to the subscriber station.

For example, in a system using an actual base station such as the system described in patent 4,675,863 described above, the waveform transmitted is divided into multiplicity, or 45 msec frames. Each frame is then divided into four 11.25msec slots. The base station continues to transmit all four slots, generating a 100% modulus of shock modulated waveform, with the exception being the Radio Control Channel (RCC). The RCC slot is somewhat shorter than 11.25 msec, which causes a small gap in modulation where all the frames start. Such a gap is known as an AM hole. A diagram of the RCC channel waveform in the actual base station format is shown in FIG. However, there is no 100% impact coefficient waveform transmission in the system of the present invention. Instead there is only one slot transmission per frame (25% impact coefficient waveform) as shown in FIG. This modified frame format requires changes in coarse synchronization, automatic gain control (AGC), and frequency acquisition. These changes can be seen in the following description.

[Coarse Synchronization]

Since the system of the present invention uses only a 25% impact coefficient waveform, the system of the present invention monitors the amplitude of the received signal and finds a positive edge in the amplitude signal. These positive edges are described in FIG. The subscriber unit adjusts the frame timing to align with the occurrence of these positive edges.

The circuit for acquiring the type of coarse synchronization is shown in the form of a block diagram in FIG. 5 wherein the signal received in the circuit is supplied and generated into an amplitude calculation device 50 that generates a computer amplitude signal. The amplitude signal is then sent to comparator 52 where it is compared with a predetermined limit signal to form a digital signal (1 = signal present, 0 = signal absent). Such a digital signal may be strobe to indicate the detection of a positive edge. It is fed into an edge detector 54 which outputs a strobe.

[AGC]

25% shock coefficient modulation requires a clear form of receiving AGC circuit that avoids tracking in the absence of a signal. Thus, a slow rising fast attenuation AGC is provided. This is shown in FIG. 6 where the received signal is fed to an amplitude calculator 56 of a pre-programmed ROM, from which the resulting amplitude signal is subtracted from a predetermined limit magnitude to form a difference signal. Supplied to comparator 58. The difference signal at this time is fed into a low pass filter comprising an adder 64 and a delay means 66 connected via a loop 68 via one of the two scaling multipliers shown at 60 and 62. One or the other of the two multipliers is used depending on the sine of the difference signal. If the difference signal is positive, the low speed attenuation is performed in the AGC control signal. If the difference signal is negative, the high speed rise is performed in the AGC control signal. The output of the filter is a gain signal which is supplied to the control unit 44 shown in FIG.

[Rough frequency acquisition]

In the 25% impact coefficient cycle frame format, the frequency acquisition circuit is not required to perform frequency acquisition during off time (75% information null time) and because frame timing is not known when frequency acquisition is performed. A modified form was provided as shown in FIG. The signal received in such a circuit calculates a discrete Fourier transform (DFT) that outputs high band energy (energy in the frequency band above the center frequency) and low band energy (energy in the frequency band below the center frequency). Supplied into the device 70. The high band energy output is subtracted from the low band energy output in adder 72 and the output is fed to mixer or multiplier 74. The received RF signal is also sent to strip means 76 which strips the sine of the signal (negative or positive), thereby determining only the amplitude of the signal. The stripped signal is then fed to a filter 78 where it is averaged to smooth the signal. The output of filter 78 is sent to multiplier 74 via amplifier 80.

The primary purpose of the circuits through (76) (78) is to emphasize the output signal itself and to prevent noise in the output signal. In this regard, since noise generally has a small amplitude, the noise is effectively filtered out during smoothing. On the other hand, since the actual signal usually has a large amplitude, it becomes prominent by passing the smoothed or filtered signal to the mixer 74.

The scaled signal leaving the mixer 74 is balanced between high and low energy frequencies and this balanced signal proportional to the short term average amplitude of the received signal is added to the adder 82 and a feedback loop ( 86 is fed to a regional pass filter comprising looped delay means 84. Delay means 84 causes the output signal 88 to VCXO control to represent the output immediately before the output fed into the actual lowpass filter. VCXO control is used to adjust the frequency of the master oscillator in the system.

After initial or rough synchronization has started, the system is in idle voice mode but is completely locked for voice operation only. If the phone on one side is off-hook, the phone on the other side will ring until the call is answered or the caller is on-hook.

This call is made by the voice code word (VCW) at the beginning of the main slot, where the code word indicates an off-hook condition at the initiating station. When this happens, the station acting as an imitated base station is off-hook to the central office (CO) and thus connected to the central office. The originating subscriber station then makes a call by dialing the desired number. The mocked base station receives such information by the VCW when the calling originating subscriber unit is on-hook and presents the appearance of an on-hook to the central office.

The simulated base station detects a value from the central office and the subscriber unit is ringed by the corresponding VCW from the simulated base station. The next time the subscriber unit is off-hook the imitated base station receives such information through the corresponding VCW and informs the central office of the appearance of the off-hook.

A wireless telephone system configuration of this kind is illustrated in FIG. 8 where subscriber unit 90 is shown in wireless communication with a base station 96 that has been imitated via antennas 92 and 94. The base station 96 is in wired communication with the central office via the line 98 and the connector 100.

Dual Subscriber System

The system described above can be used with dual subscriber deployment as shown in FIG. In such a system, each channel can support two complete conversations without using duplex. In this regard, the dual subscriber unit 102 is connected in pairs to the subscriber telephone set 108, 110 by leads 104, 106. The subscriber unit 102 is in wireless communication via the simulated dual base station 116 and the antennas 112 and 114. Unit 116 is connected to the central office by wires 118 and 120. The two separate subscribers 108 and 110 use a type slot arrangement, as disclosed above, in particular in No. 4,675,863, wherein each subscriber is assigned a separate slot. The frame format for this arrangement is shown in FIG. 10, where the four slots are numbered 1,2,3 and 4. The first two slots are used for the simulated base station and the last two slots are used for two subscribers.

Multiple dual subscriber systems can operate over different channels without a duplexer by synchronizing all of the simulated base station transmissions. This is illustrated by the frame format shown in FIG. 11 where channel 1 is shown above and channel n (which represents some preferred channel number) is shown below. The first slot in each channel is for transmission and the last two are for reception.

[Paged Remote Service]

One mimicked base station can be used with multiple different subscribers, one at a time. In such a case, for reception, the subscriber shall not transmit the radio control channel as described more fully in the above-mentioned application No. 4,675,863, until paged by the base station imitated by the subscriber's ID number (SID). Continue to monitor. After receiving a page, the subscriber starts transmitting back to the simulated base station using the synchronization process described above. To initiate the call, the subscriber transmits over the RCC using the synchronization process described above.

[Monitor function]

The system of the present invention can be used to monitor one or more functions. In this regard, using a computer as a control / data listing device, a number of subscribers periodically review several functions, such as temperature, weather conditions, safety and flood warnings, fuel depletion warnings, remote gas, electricity or mole meter readings. To report. This is illustrated in FIG. 12, where the simulated base station 122 is in wireless communication with a plurality of subscriber units, designated 124, 126 and 128, respectively. The base station 122 is wired to both the telephone 130 for voice communication and the computer or data terminal 132 for data input. Similarly, each subscriber unit is all connected to the same data device as each of the telephones 134, 136 or 138 and 140, 142 or 144 for voice communication.

Repeater System

An important use of the present system is that it is used as an iterator to expand the scope of the system. In this arrangement, the simulated base station can be used to overcome interference disturbances such as mountain climbing. 13 illustrates this function and shows that the subscriber unit 146 is in wireless communication with the base station 148, which is imitated at the top of the mountain. Unit 148 is also wirelessly connected to the standard base station 150 which is connected to the central office.

The relatively simple and inexpensive imitation of the base station makes it very advantageous in terms of price as a repeater unit. It can also be used as an iterator to extend the long-range range of a system with or without obstacles. The repeater unit uses time slot arrays, which are clearly connected to both standard base stations and subscribers without the use of any duplexers, making them suitable for building a complete system. Of course, this may be mediated between the subscriber and another imitated base station instead of the standard base station. Such arbitration may be provided at various stages from one imitated base station to another to significantly increase the scope of the system in a relatively less expensive way. Such a description is shown in FIG. 14, where a series of repeater units 152 is arbitrated between subscriber 154 and base station 156.

In addition to extending the scope of the system, the repeater unit allows the actual base station signal to be cleared through equalization prior to retransmission to the subscriber.

One repeater may be used to be called a repeater star system to drive multiple repeaters and / or subscribers. This is illustrated in FIG. 15, where a single repeater unit 158 is in wireless communication with auxiliary repeaters 160 and 162 as well as with one or more subscribers as in 164. Any of the auxiliary repeaters, such as repeater 162, may be used as the final repeater 162 in direct communication with the base station, indicated at 178.

Multiple iterators can be placed in different locations on different channels and synchronized so that their transmission and reception occur simultaneously, thus avoiding the use of duplexers. In such a configuration, the master repeater can be used to monitor the base station's RCC channel and relay the monitored information to multiple subscribers via the simulated base station's RCC. In this configuration, each subscriber is assigned one repeater channel through a setup.

Claims (4)

At least two stations (base station and subscriber unit) in RF communication with each other, one station 122 initiates the timing of the RF signal, the other station 124 synchronizes the timing in accordance with the initiated timing, A synchronization device in the other station 124 includes a coarse frequency acquisition circuit (FIG. 7), wherein the circuit separates the signal received from the station into a high band and a low band energy frequency ( 70), an adder 72 for obtaining a resultant signal by subtracting the highband energy output from the lowband energy output, stripping means 76 for stripping the sine of the resultant signal and determining only its amplitude; A stripped signal including an amplifier 80 for filtering noise 78 and emphasizing the stripped signal, and an adder 82, delay means 84, and a feedback loop 86 Base station emulators using a wireless digital communication system characterized in that it comprises a low pass filter for supplying a voltage controlled crystal oscillator that provides the timing from the other station. At least two stations comprising a first station 122 and a second station 124 communicating with each other by an RF frequency signal, wherein the RF frequency signal comprises a plurality of timeframes in which each frame consists of one single timeslot ( 10, which is composed of waveforms divided by the control unit 44 at each station 122 and 124, and the signal amplitudes from the other stations, and by comparing the signal amplitudes from the other stations with the predetermined limit signals ( 52. Amplitude calculation device 50, frame at each station 122, 124 controlled by control unit 44 to determine the position of positive edges in the waveform of such a signal (FIG. 4). Frame adjustment means in each station 122, 124 controlled by the control unit 44 to adjust the frame timing to match the occurrence of the positive edge. The first station 122 has frame synchronization initiation means and the second station 124 has frequency acquisition means (FIG. 7) to determine the timing of the signal received from the first station 122. By synchronizing to the timing initiated by 122 and including the synchronization count in the first station so that the first station 122 is different from the second station 124, and the system 10 An amplitude calculation device 56 further comprising a slow rising, fast attenuation automatic gain control (AGC) circuit (FIG. 6) to avoid tracking in the absence, wherein the circuit is supplied with a received signal and outputs an amplitude signal; Comparator 58 for receiving a signal and subtracting the received signal from a predetermined threshold value to form a difference signal, optionally a slow attenuation or a rapid rise in the AGC signal. The control unit includes scaling multipliers 60 and 62 for determining the positive or negative sine of the difference signal, and an adder 64, a delay means 66, and a feedback loop 68. 44. A wireless digital communication system using a base station imitator, characterized in that it comprises a low pass filter for supplying a signal carried out in step 44). i) time slots of at least two transmission slots (FIG. 10) for transmission from base station (station) 122 and at least two receiving slots (FIG. 10) for reception by base station 122 A control unit 44 for providing synchronization information including allocating at a selected frequency, ii) a transmission slot in which one signal for first duplex communication is first assigned for transmission by a radio (radiotelephone) 26 A modulator 20 for converting the digital information signal into an analog information signal to be transmitted through a selected frequency within the second signal and transmitting one signal for a second duplex communication through a selected frequency in a second allocated transmission slot. And iii) receiving one signal for the first duplex communication and one signal for the second duplex communication for demodulation by the modulator 20. The control unit 44 comprises a radio 26 as the signals are transmitted from subscriber units (stations) 124, 126 and 128 on the frequencies selected in the first assigned receive slot and the second assigned receive slot, respectively. Base station 122, which provides modulation information to modulator 20 and provides a selected frequency to radio 26 to be sent to subscriber units 124, 126 and 128 by radio 26 via a frequency to which synchronization information is assigned. And i) receive the synchronization information transmitted from the base station 122, and confirm by the control unit 44 the selected frequency and the assigned transmission and reception slots for the duplex communication signal with the base station 122 ( 10), receiving a duplex communication signal for demodulation by the demodulator 20, in which signals are transmitted from a base station over a frequency selected in the assigned base station transmission slot. The digital information signal is transmitted such that one signal for duplex communication for transmission by the radio 26, ii) radio 26 of the losing bar is transmitted to the base station 122 via the selected frequency in the base station receiving slot assigned to it. Between base station 122 and a plurality of subscriber units 124, 126, 128 via one of a plurality of available frequencies, characterized in that it consists of subscriber units 124, 126, 128 comprising a modulator 20 for converting an analog information signal. A duplex communication system using a base station imitator for communication of 10. i) assigning a base station at one selected frequency, the time slots of at least two transmission slots for transmission from the simulated base station 122 and at least two reception slots for reception by the base station 122 Transmits the synchronization information from the 122 to the subscriber units 124, 126, 128, and ii) transmits one signal for the first and second duplex communication through the selected frequency in the first and second assigned transmission slots, respectively, to the base station 122. And iii) send one signal to the base station 122 for the first and second duplex communication, respectively, transmitted from the subscriber unit 124, 126, 128 over the selected frequency in the first and second assigned receive slots. A duplex communication method for communication between a base station (122) and a plurality of subscriber units (124, 126, 128) over one of a plurality of available frequencies, including receiving.

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