A COMMUNICATION SYSTEM AND A METHOD OF OPERATING IT CAPABLE OF INTERRUPTION TALK DURING DATA TRANSMISSION

Abstract: A system for performing talk and data transmission by polling process between a plurality of terminal units (1) and a central station (3), which system is capable of interruption talk during data transmission. The central station (3) is provided with slots for use in interruption given at appropri­ ate time intervals in the polling process. Thus the central station (3) is given, as one of its functions, the function of until the predetermined polling is finished, repeating steps of (i) generating interruption acceptance signals at appropriate intervals in the polling mode, (ii) giving thereafter a plurality of time slots for receiving the interruption signals from the terminal units, and (iii) when interruption signals from the terminal units are received in the plurality of time slots, returning to the talk mode by generating a polling finish signal and terminating the polling or simply terminating the polling, and when not received, continuing the polling. Thus the talk and the data transmission by polling process are realized in the same channel.

Description: The present invention relates to a communication system and to a method of operating it capable of interruption talk during data transmission, and, more particularly, to a radio communication system and to a method of operating it capable of interruption talk during data transmission by polling between a fixed central station and a plurality of mobile terminal units. Description of the Prior Art A conventional radio communication system of this kind comprises a central station and a plurality of terminal units such as mobile units. The central station sends digital polling signals to the terminal units and receives response data signals from the terminal units, respectively. During the time when data transmission is performed by polling operation, etc., it has been inhibited to make a free talk from terminal units in order to avoid any data destruction by collision. This has caused inconveniences, such as impossibility of talk even in an emergency or the like. A further example of a communication system known from the prior art is given in the Patent Abstract of Japan, vol. 4, no. 189 (E-39)[671], 25th December 1980. SUMMARY OF THE INVENTION The purpose of the present invention is, therefore, to provide a new communication system and a new method of operating it that is capable of realizing an interruption talk even during polling operation. As described above, the present invention provides a communication system comprising a central station, and a plurality of terminal units linked thereto, (1) said central station comprising: means for generating a sequence of digital signals comprising a plurality of polling signals and at least one interruption acceptance signal, said interruption signal being inserted into said polling signals at a time interval and being followed by a plurality of empty time slots; means for sending said digital signals to said terminal units, (2) said terminal units each comprising: means for receiving said digital signals; means for sending to said control station a response signal corresponding to each of said polling signals; means responsive to a control signal for sending an interruption signal after the reception of said interruption acceptance signal, (3) said central station further comprising means for sending a polling completion signal in response to the reception of said interruption signal within said empty time slots, to said terminal units, (4) each of said terminal units further comprising means for receiving said polling completion signal, whereby the terminal unit sending said interruption signal talks with said central station. DESCRIPTION OF THE DRAWINGS The present invention will hereinafter be explained with reference to the accompanying drawings: Fig. 1 illustrates a block diagram of a radio communication system including a central station and a plurality of terminal units or stations, to which the present invention is applicable; Fig. 2 is a block diagram of any of the terminal units and the central station of the present invention; Fig. 3 illustrates a state transition diagram of the terminal units according to the present invention; Fig. 4 illustrates a state transition diagram of the central station according to the present invention; Figs. 5 and 6 show respectively examples of a timing chart of the central station and that of the system; and Fig. 7 shows an example of a signal format. In Fig. 1 showing a radio communication system to which the present invention is applicable, the terminal units 1₁, 1₂, 1₃, . . . 1 N are linked to the central station 3 by a pair of radio carrier waves 2. The radio carrier waves 2 in this case may be replaced by a single carrier wave. Further, the communication system in this case may be either full or half duplex one. Moreover, the terminal units may be either fixed or mobile ones. The terminal units may be linked to the central station by transmission wires, respectively. Fig. 2 shows a block diagram of the equipments of the terminal units and of the central station shown, in Fig. 1, in the style common to the terminal units and the central station. The information data generated from an information generator 11 comprising keys, sensors, etc. are processed by a controller 12, converted to baseband signals, for example, FSK signals, PSK signals by a modulator/demodulator 13 and supplied to a data/voice switching section 14. The controller 12 controls the data/voice switching section 14 to control the transmission and reception of the data and/or voice, as described hereinafter. On the other hand, a tranceiver 15 also is connected to the data/voice switching section 14. In the case of half duplex communication system or the like, a transmission start signal may be sent from the tranceiver 15 to the controller 12. The signal selected by the data/voice switching section 14 is converted to radio modulated carrier wave in a radio section 16 and transmitted to a remote unit or station through an antenna 17. On the other hand, the signal from a remote unit or station is received by the antenna 17, demodulated into the baseband signal by the radio section 16 and supplied to the data/voice switching section 14. The data signals are always demodulated in the modulator/demodulator 13 and sent to the controller 12. The controller 12 then controls the data/voice switching section 14 under the conditions also explained hereinafter so that in the case of voice, connection is made to the tranceiver 15, and in the case of data, decoding is made by the controller 12 to send its outputs to an information output means 18 comprising a display, a printer, etc. In this connection, it is to be noted that although Fig. 2 shows an embodiment employing a subcarrier modulation system, similar result can be obtained by employing a direct modulation system to effect the modulation into the radio carrier waves direct by the data. Fig. 3 illustrates state transition diagram at the terminal units. First, "power on" operation permits start of a talk mode. In this talk mode, it is so arranged that the transmission of either of voice or data can freely be made. Usually the operation is made in this talk mode and upon receipt of a polling signal from the central station, the state moves to a polling mode. The meaning of the term "polling signal" used herein is not limited only to the polling signal addressed to one specific terminal unit, but covers all of the polling signals carried by the same channel, say in the example of the below mentioned signal format, all the signals having a polling command as their commands. In the polling mode, it is so arranged that any free transmission of voice and data is inhibited, but only during the polling addressed to one specific terminal unit, its own data can be transmitted. This is to avoid any destruction of data by collision. The release of the polling mode usually is effected in either of two manners, one is the reception of a polling completion signal from the central station and the other is the time over, that is, the absence of the polling signal within a predetermined period of time. According to the present invention, however, another function, that is, a compulsory release function of the polling mode is specifically provided for any interruption talk. Namely, by pushing an interruption button or by generating a control signal, the state goes to the wait of interruption acceptance signal. It is so arranged that even in this state, usual polling function is maintained. Upon receipt of an interruption acceptance signal from the central station, an interruption signal is transmitted and the state returns to the talk mode. Fig. 4 illustrates a state transition diagram at the central station. Similarly to the terminal units, "power on" operation permits start of a talk mode and usually the operation proceeds in this mode. In the talk mode, free talking is possible and when the data from terminal units are received, a response signal will be sent back. The transition to a polling mode is manually started or automatically started by means of a timer, etc. In the polling mode, the polling of the terminal units is carried out sequentially and, during such polling operation, interruption acceptance signals are transmitted to the terminal units at fixed or unfixed time intervals and the state moves to the wait of interruption signals from the terminal units. In the "wait of interruption signals" state, any reception of interruption signals within a predetermined period of time causes transmission of a polling completion signal or the like to return to the talk mode, but if no interruption signals are received within the period, the state returns to the polling mode and the polling continues. Upon completion of the polling of the necessary number of the terminal units, the state returns to the talk mode. At such time, a polling completion signal may either be generated or not. Fig. 5 shows an example of a timing chart of the central station. As soon as the polling is started, the terminal units are sequentially polled. In this example, five terminal units are polled and, at the time of completing the polling of them, an interruption acceptance signal X is transmitted and subsequently interruption signal reception time slots (or empty time slots) Y are given. A plurality of these time slots are given for reducing any collision of signals when two or more terminal units request interrupts at the same time. By random selection of these time slots, such reduction can be made. Upon finish of the interruption time slots, the polling of the following units is started. Thus, after completion of polling all the units, the state returns to the talk mode. Fig. 6 shows an example of a timing chart of the system, wherein an interruption is made. As mentioned hereinbefore, usually the state stands in a talk mode. Referring also to Fig. 2, upon start of the polling, polling signals are transmitted from the central station 3 as shown by A to C. In response thereto, the necessary data are transmitted from the terminal units 1₁ and 1₂ as response signals a to c . Now it is assumed that an interruption button is pushed in the terminal unit 1₂. Then the state goes to the wait of an interruption acceptance signal from the central station 3. The central station 3 discontinues the polling after an appropriate time interval and transmits an interruption acceptance signal X and further continuously gives an appropriate number of interruption signal reception time slots Y. The terminal unit 1₂, after receiving the interruption acceptance signal X, selects at random one of the interruption signal reception time slots Y and transmits an interruption signal x. The central station 3, upon receipt of the interruption signal x in the time slots Y, transmits a polling completion signal z and returns to the talk mode. Then the terminal unit returns to the talk mode by this polling completion signal. In this connection, it is also possible to employ means for returning to the talk mode by the termination of the polling in the central station, and the timeout in the terminal unit without generating the polling completion signal. In the case wherein an urgent operation is required, however, this example is more suitable. Fig. 7 shows an example of a signal format. In this Fig. 7, bit synchronization signal is a preamble for stabilizing the system. The frame synchronization signal indicates a head of the frame and means that the data will follow thereafter. The data portion is constituted by various informations. Its command portion discriminates polling signals, response signals, interruption acceptance signals, interruption signals, polling completion signals, etc. The individual numbers to follow are the identification numbers to be alloted to the terminal units and the central station. The data portion is constituted also by other various informations. As described above, the present invention also provides a method of operating a communication system capable of interruption talk during data transmission by polling process between terminal units and a central station. The central station has the functions of (a) usually in a talk mode, talking with the terminal units, (b) when manually or automatically changed to a polling mode, effecting data collection by polling against at least a part of the terminal units sequentially and continuously, and, when finished, returning to the talk mode by generating a polling completion signal or simply terminating the polling, and (c) until the predetermined polling is finished, repeating steps of (i) generating interruption acceptance signals at appropriate intervals in the polling mode, (ii) giving thereafter a plurality of time slots for receiving the interruption signals from the terminal units, and (iii) when interruption signals from the terminal units are received in the plurality of time slots, returning to the talk mode by generating a polling finish signal and terminating the polling or simply terminating the polling, and when not received, continuing the polling. The plural terminal units have the functions of (a) usually in a talk mode, talking with the central station or other terminal units by simplex or duplex operation, (b) changing to a polling mode upon receipt of a polling start signal or a polling signal from the central station, inhibiting the talking in the polling mode and, when the polling signal to themselves is received, sending their own messages, (c) when occasion demands to do talk in the polling mode, either manually or automatically, assuming a plurality of slots timed with the central station independently after receiving the interruption acceptance signal from the central station, electing at random one of the slots and sending an interruption signal through such slots, and (d) releasing the polling mode to the talk mode either when a polling finish signal is received or a polling signal is not received for a predetermined time interval; Thus the talk and the data transmission by polling process are realized in the same channel. As it is understood from the above explanation, the interruption talk system of the present invention enables interruption talk even during the polling. Namely, it enables to realize the data transmission by the polling process in the same channel as that of the talking.

Claims: A communication system comprising a central station (3), and a plurality of terminal units (1₁ - 1 N ) linked thereto, (a) said central station (3) comprising: means (12) for generating a sequence of digital signals comprising a plurality of polling signals (A - D) and at least one interruption acceptance signal (X), said interruption acceptance signal (X) being inserted into said polling signals (A -D) at a time interval and being followed by a plurality of empty time slots (Y); and means (13, 16, 17) for sending said digital signals to said terminal units; (b) each of said terminal units (1₁ - 1 N ) comprising: means (13, 16, 17) for receiving said digital signals; means (12, 13, 16, 17) for sending to said central station (3) a response signal (a - d) corresponding to each of said polling signals; and means (12, 13, 16, 17) responsive to a control signal for sending an interruption signal (x) after the reception of said interruption acceptance signal (X); (c) said central station (3) further comprising means (12, 13, 16, 17) for sending to said terminal units (1₁ - 1 N ) a polling completion signal in response to the reception of said interruption signal (x) within said empty time slots (Y); and (d) each of said terminal units (1₁ - 1 N ) further comprising means (12, 13, 16, 17) for receiving said polling completion signal (Z), whereby the terminal unit (1₁ - 1 N ) sending said interruption signal (x) talks with said central station (3). A method of operating a communication control system which is capable of interrupting talk during data transmission in response to a polling process between terminal units (1₁ - 1 N ) and a central station (3), wherein said central station (3) operates in the following steps: (a) talking with the terminal units (1₁ - 1 N ) by simplex or duplex operation while said system is in a talk mode; (b) changing said system to a polling mode, collecting data by sequentially and continuously polling against at least some of the terminal units (1₁ - 1 N ), and returning to the talk mode when said polling is finished responsive to a termination of the polling; and (c) repeating until the predetermined polling is finished the steps of (i) generating interruption acceptance signals (X) at appropriate intervals in the polling mode, (ii) thereafter giving a plurality of interruption slots (Y) for receiving interruption signals (x) from the terminal units (1₁ - 1 N ), and (iii) responding to interruption signals (x) from the terminal units (1₁ - 1 N ) which are received in the plurality of interruption slots (Y), said central station (3) returning to the talk mode by generating a polling finish signal (Z) and terminating the polling or by simply terminating the polling; whereby the talk and the data transmission by polling process are realized in the same channel. A method of operating a communication control system which is capable of interrupting talk during data transmission in response to a polling process between terminal units (1₁ - 1 N ) and a central station (3), wherein said plurality of terminal units (1₁ - 1 N ) operates in the following steps: (a) talking with the central station (3) or other terminal units (1₁ - 1 N ) by simplex or duplex operation when operating in a talk mode; (b) changing to a polling mode in response to a receipt of a polling signal (A - D) from the central station (3), inhibiting talking while said system is in the polling mode, and responding from a terminal unit (1₁ - 1 N ) in response to its receiving its own polling signal; (c) responding to a demand for talking while the system is in the polling mode by assuming a plurality of slots (Y) which are independently timed with the central station (3) after a receipt of an interruption acceptance signal (X) from the central station (3), selecting at random one of the slots (Y) and sending an interruption signal (x); and (d) releasing the polling mode to the talk mode in response to the receipt of either a polling finish signal (Z) or a failure to receive a polling signal (A - D) within a predetermined time interval; whereby the talk and the data transmission by polling process are realized in the same channel. A method of operating a communication control system which is capable of interrupting talk during data transmission in response to a polling process between terminal units (1₁ - 1 N ) and a central station (3), wherein: (1) said central station (3) operates in the following steps: (a) talking with the terminal units (1₁ - 1 N ) by simplex or duplex operation while said system is in a talk mode; (b) changing said system to a polling mode, collecting data by sequentially and continuously polling against at least some of the terminal units (1₁ - 1 N ), and returning to the talk mode when said polling is finished responsive to a termination of the polling; and (c) repeating until the predetermined polling is finished the steps of (i) generating interruption acceptance signals (X) at appropriate intervals in the polling mode, (ii) thereafter giving a plurality of interruption slots (Y) for receiving interruption signals (x) from the terminal units (1₁ - 1 N ), and (iii) responding to interruption signals (x) from the terminal units (1₁ - 1 N ) which are received in the plurality of interruption slots (Y), said central station (3) returning to the talk mode by generating a polling finish signal (Z) and terminating the polling or by simply terminating the polling; and (2) said plurality of terminal units (1₁ - 1 N ) operates in the following steps: (a) talking with the central station (3) or other terminal units (1₁ - 1 N ) by simplex or duplex operation when operating in a talk mode; (b) changing to a polling mode in response to a receipt of a polling signal (A - D) from the central station (3), inhibiting talking while said system is in the polling mode, and responding from a terminal unit (1₁ - 1 N ) in response to its receiving its own polling signal; (c) responding to a demand for talking while the system is in the polling mode by assuming a plurality of slots (Y) which are independently timed with the central station (3) after a receipt of an interruption acceptance signal (X) from the central station (3), selecting at random one of the slots (Y) and sending an interruption signal (x); and (d) releasing the polling mode to the talk mode in response to the receipt of either a polling finish signal (Z) or a failure to receive a polling signal (A - D) within a predetermined time interval; whereby the talk and the data transmission by polling process are realized in the same channel.

Inventors: KASUGAI, TERUAKI C/O NEC CORPORATION
Applicants: NEC CORPORATION
Application year: 1986
Main classification: H04Q7
IPC codes: H04B7, H04W74