Method and system for transmitting messages in an answer-back paging system

Abstract

The invention relates to a message transmission system, a method for operating the system, and primary and secondary stations used in the system. During the method, the primary station transmits a control signal in the receiving direction, with which it calls secondary stations that wish to establish transmission in the transmitting direction to do so. Secondary stations that wish to respond to the call perform their transmissions. The primary station receives at least some transmissions, analyzes the understandable ones from among the received transmissions, and in the case of the analyzed, understandable transmissions, determines which ones contain responses to messages previously transmitted in the receiving direction, acknowledges at least the responses, and repeats the transmission of the control signal in the receiving direction. The system includes at least one primary station and several secondary stations.The primary station includes means for compiling messages in the receiving direction to be transmitted to the secondary station; means for transmitting a signal in the receiving direction, which signal calls on the secondary stations to transmit responses to the messages in the transmitting direction; means for receiving and analyzing the responses; means for acknowledging receipt of successfully analyzed responses, and means for determining which messages have been answered and for repeating the call to those secondary stations whose responses have not been acknowledged to transmit or retransmit their responses.Each secondary station includes means for receiving transmissions in the receiving direction; means for determining whether a message is addressed to it; means for receiving an invitation from the receiving direction; means for transmitting a response to a message addressed to the secondary station in the transmitting direction; and means for responding if no acknowledgement is received for its response and for repeating the transmission of the response when prompted to do so. à.

Description

The invention relates to a message transmission system, a method for operating the system, and primary and secondary stations used in the system. The system is, for example, a voice response paging system, and for convenience, we will deal with such a paging system, but it is obvious that the invention can be applied to other two-way message transmission systems as well. Voice response paging systems are described, for example, in PCT patent specification WO 96 / 14716. In its basic form, such a system requires a paging network controller (PNC) to arrange a message for transmission to a predetermined recipient. When the recipient receives a call, a simple response can be transmitted by a low-power transmitter incorporated in the paging device. The above-mentioned specification and the corresponding patent EP0738452 B1 describe a system in which a series of messages are transmitted to the appropriate recipients, and the paging network controller (PNC) transmits calls to the recipients to transmit their responses substantially simultaneously as spread spectrum signals, which the paging network controller (PNC) combines (de-spreads the spectrum) and forwards the responses to the appropriate party requesting the response.In order to avoid the need for power control methods in pagers to ensure that responses are received at comparable power levels by the PNC, the PNC transmits its calls at incrementally increasing (or decreasing) power levels, and only those pagers that can receive the call sent at that power level transmit their responses. One disadvantage of this known method is that it requires strict control of the power level to be transmitted in the receive direction at the primary station. The aim of our invention is to make the operation of message relay systems more flexible. To this end, instead of measuring the reception level according to the known method, we examine the interpretability following code division message recovery, and based on this, we give an acknowledgement or a targeted call for repetition. This problem is solved according to the invention with respect to a method for operating a message transmission system consisting of at least one primary station performing downlink transmissions and several secondary stations performing uplink transmissions in that the primary station transmits a control signal in the receive direction and calls the secondary stations that wish to transmit to do so; the secondary stations that wish to respond to the call perform their transmission; the primary station receives at least some transmissions, analyzes the intelligible ones from the received transmissions, and in the case of the analyzed intelligible transmissions, determines which of them contain responses to the responses previously transmitted in the receive direction, acknowledges at least the responses, and repeats the transmission of the control signal in the receive direction. The directional designations of downlink and uplink are used in the context of the operation of the terminal equipment, i.e. secondary stations. Transmissions in the downlink direction may include responses to messages and / or service requests transmitted in the downlink direction. These transmissions may be in the form of code division multiplex (CDMA) signals transmitted essentially simultaneously. In another preferred embodiment of the method according to the invention, which is used to operate a message transmission system comprising a primary station transmitting messages in the receiving direction to a plurality of secondary stations, the primary station calls the secondary stations to transmit their responses in the transmitting direction, the primary station analyzes the responses received in the transmitting direction and acknowledges the receipt of the successfully analyzed responses, the primary station determines which messages have been answered and repeats the call to those secondary stations whose responses have not been acknowledged to transmit their responses or to repeat their transmission in the transmitting direction. The problem is solved according to the invention with respect to the message transmission system in that the system comprises at least one primary station and several secondary stations, the primary station comprising - a device for compiling messages to be sent to the secondary station in the receiving direction, - a means for transmitting a signal in the receiving direction, which signal calls on the secondary stations to transmit responses to the messages in the transmitting direction, - a tool for receiving and analyzing responses, - a tool for acknowledging receipt of successfully analyzed responses, - means for determining which messages have been answered and for repeating the call to those secondary stations whose replies have not been acknowledged to transmit their replies or to repeat their transmission, each secondary station comprising - a device for receiving transmissions in the receive direction, - a means of determining whether a message is addressed to him, - a device for receiving the call from the receiving direction, - means for transmitting a response to a message addressed to the secondary station in the transmit direction, and - a device that reacts if its response is not acknowledged and that repeats the transmission of the response when prompted to do so. In connection with the message transmission method and system according to the invention, it has been found that the cycle of analyzing the responses, acknowledgment and repeatedly calling on the secondary stations that have not received an acknowledgment to transmit or retransmit their responses or other transmissions increases the speed of processing the responses compared to known systems. This means that the capacity of the system is increased without the need to increase the amount of infrastructure equipment. Secondary stations transmit their replies or other forward transmissions essentially simultaneously as code division multiple access (CDMA) signals. HU 222 334 B1 can be transmitted, and in this case the stronger response signals mask the weaker signals. This is known as the near-far problem. In the method according to the invention, the stronger signals are first detected and acknowledged in the transmission direction, and then the secondary stations whose responses or other transmissions have been masked are called to transmit their responses or other transmissions or to repeat their transmissions. After repeating the cycle of analyzing the responses or other transmissions, acknowledging successful responses or other transmissions and issuing another call or control signal several times, it was found that the percentage of processing of the responses or other transmissions was very high. Those that are not processed are typically too weak to be processed and / or the secondary station is either turned off or out of range. The time spent on the above-mentioned cycle may vary, as a shorter time is required to process a relatively small number of strong responses or other transmissions, and a longer time is required to process a relatively large number of weak responses or other transmissions. If desired, the allocated time can be adapted to the number of responses or other transmissions. This saves processing time compared to the variant in which fixed intervals of time are allocated to process each series of responses or other transmissions. The acknowledgement signal and the solicitation signal may be transmitted simultaneously. One method for this purpose is for the primary station to transmit messages in an ordered sequence and for the next solicitation message to include a field having elements in the ordered sequence corresponding to the message sequence, the elements being configured to distinguish successfully parsed responses from unsuccessfully parsed responses, for example by changing a binary '0' to 'Γ' in the case of successful parsing. To increase message throughput, the population of secondary stations is divided into at least two groups, and while responses or other transmissions from one group are being analyzed, the otherwise inactive transmitter can transmit messages to the other group and vice versa. The population can be divided based on odd and even addresses or signal strengths (RSSI). The problem is solved according to the invention with respect to the primary station, which is comprised of a message transmission system that transmits messages in the receiving direction to a plurality of secondary stations capable of transmitting responses in the transmitting direction, in that the primary station comprises: - a device for compiling messages to be sent to the secondary station in the receiving direction, - a means for transmitting a signal in the receiving direction, which signal calls on the secondary stations to transmit responses to the messages in the transmitting direction, - a tool for receiving and analyzing responses, - a tool for acknowledging receipt of successfully analyzed responses, - a means for determining which messages have been answered and for repeating the call to those secondary stations whose replies have not been acknowledged to transmit their replies or to repeat their transmission. The problem with respect to the secondary station, which is comprised of a message transmission system that transmits messages in the receiving direction to a plurality of secondary stations capable of transmitting responses in the transmitting direction, is solved according to the invention in that the secondary station comprises: - a device for receiving transmissions in the receive direction, - a means of determining whether a message is addressed to him, - a device for receiving the call from the receiving direction, - means for transmitting a response to a message addressed to the secondary station in the transmit direction, and - a device that reacts if its response is not acknowledged and that repeats the transmission of the response when prompted to do so. Our invention is described in more detail with reference to its exemplary embodiments with the help of our drawings, of which the Figure 1 is a block diagram of the message transmission system, Figure 2 is a diagram showing the transmission of messages by a primary station and the receipt of acknowledgements and time division multiple access (TDMA) responses by the primary station, Figure 3 is a diagram showing the transmission of call signals, Receiving CDMA responses and analyzing the responses is shown, the Figure 4 is a diagram showing the interconnected operation of a CDMA response type system, Figures 5a and 5b show how the acknowledgements are combined with the paging signal transmitted in the receive direction, Figure 6 is a block diagram of the paging network controller (PNC), the Figure 7 is a flowchart showing the sequence of operations, Figure 8 is a block diagram of a pager. In the figures, the same reference numerals are used to denote the same elements. 1 shows a paging network controller (PNC) 10 having 12 message input ports. The paging network controller (PNC) 10 receives call addresses and associated messages from an operator with a personal computer (PC) or directly from a subscriber with a PC and a modem. The paging network controller (PNC) 10, which contains tables of contents containing information such as paging receiver identification codes (RICs), areas to be called, frequencies, paging types, prevailing protocols such as POCSAG (or CCIR Radiopaging Code No 1) and RING, and pager status, processes the messages and their associated receiver identification codes, as well as other relevant information. HU 222 334 B1 data packets and forwards them to the paging area controller (PAC) 14. The paging area controller (PAC) 14 converts the paging receiver identification codes (RICs) and their associated messages into a format that the base station transmitters 16 (or the transceiver part of a base station) can transmit via the receive direction to the one-way pagers 18 and the two-way pagers 20. When a two-way pager 20 identifies that a message with the pager's receiver identification code (RIC) has been transmitted, it receives and decodes the message. If the user wishes to transmit a short response, he selects a pre-stored response using an integrated hand-held keypad and, when called by the pager area controller (PAC) 14, transmits his response via a transmission path. The response signals may be transmitted simultaneously, as CDMA signals, or in a time slot frame. In this case, one time slot is used per response. One or more receivers 22 (or transceiver receivers) are used to receive the responses and transmit them to the paging area controller (PAC) 14, which decodes or demultiplexes them in the case of CDMA signals and transmits them as data packets to the paging network controller (PNC) 10. The paging network controller (PNC) 10 includes means for analyzing the signals and matching the responses with the messages transmitted in the receive direction. The responses that have been matched are transmitted to the appropriate user in any suitable form, such as by e-mail or by transmission as a one-way paging message. Alternatively, the responses are submitted to a message answering service operated by the paging network. In both cases, an acknowledgement is submitted to the appropriate two-way pager 20. However, not all responses are matched, since, for example, in a time division multiplex arrangement, two or more responses collide and are incomprehensible, and in a CDMA system, strong responses cancel out weak responses due to near-far effects. If the paging network controller (PNC) 10 determines that only a small proportion of the messages transmitted in the receive direction have been answered, it issues a general call to those pagers that have not responded to the messages or received no acknowledgement to transmit their responses in the transmit direction or to repeat their transmission.The newly received responses are analyzed, matched where possible, and acknowledgements are transmitted. If the paging network controller (PNC) 10 determines that the total number of successful responses is still below a statistically determined threshold level, the cycle is repeated by transmitting another paging signal in the receive direction. The process is repeated until a predetermined number of cycles have occurred or the threshold level has been exceeded and it is apparent that no more meaningful responses can be recovered for the message stack. In the case of CDMA reply signals transmitted essentially simultaneously, when a reply burst is received, the successfully analyzed replies will generally always have the highest power level at the receiver antenna 22. Thus, since they are excluded from the total number of replies, they are decoded and matched when the next paging signal responds to signals from weaker sources, i.e., more distant pagers. In a TDMA type response system, one way of operating the system is described in connection with Figure 2. Here, it is assumed that the protocol has a burst structure in which a signal channel is divided into consecutive bursts B in the time domain. Each burst begins with a synchronization code word S and contains several concatenated frames F. One burst, the burst B(Tx), is used to transmit the M1.. .M8 paging messages in the receive direction, according to a known paging protocol, such as POCSAG. The last word in the burst is an invitation to the addressed pagers to transmit their responses in the appropriate frames of the next burst B(Rx). The responses are analyzed upon arrival and matched to the outgoing messages where possible. If matching is performed, an ACK acknowledgement is sent to the pager in the receive direction.When the analysis is complete, the paging network controller (PNC) 10 determines whether it has received all the responses to the messages, and if not, it issues another call in the receive direction, and the cycle of operations is repeated one or more times. Figure 3 shows an example of a system in which the responses comprise CDMA signals transmitted simultaneously in response to a pager signal in the receive direction. In Figure 3, the messages not shown have already been transmitted in the receive direction. A first pager, INV1, is transmitted in the receive direction. The pagers that detect a message addressed to them respond to the INV1 pager by transmitting a code sequence within a specified RES1 time slot. After the time slot has expired, an SCH search routine is initiated. The search routine sequentially compares the codes stored in the paging network controller (PNC) 10 (Figure 1) with the response code sequences and identifies the responses to the messages in question one by one.However, due to the short range problem, only the strongest response signals are detected and these are eliminated from the next search by the acknowledgement signals transmitted in a receive direction to those pagers that were successful in not responding to the consecutive INV2 and INV3 call signals in the sequence. It is assumed that in a practical system, most of the two-way pagers 20 (FIG. 1) will be some distance from the antenna of the receiver(s) 22, which means that the power at the antenna will be low. Therefore, although the RES1, RES2 and RES3 time slots may be equal in duration, as shown in the figure, it is advantageous to allocate different time slots according to the expected number of responses, for example, a small number of relatively high power responses and a large number of relatively low power responses. The short time slots are initially allocated so that the few high powers can be effectively suppressed while the relatively low noise and interference can be effectively eliminated. The longer time slots are then allocated so that the low received powers are included, HU 222 334 Bl which compete with significant noise levels and interference. If desired, the transmitters of the two-way pagers 20 may have power control to vary the strength of their response signals, thereby reducing the number of call-response cycles. As a refinement of the embodiment described in connection with Figure 3, according to Figure 4, the population of pagers is divided into two groups, and the transmission of messages and calls in the receive direction for one group, Gp1, is combined with the analysis of the responses received in the transmit direction from the other group, Gp2. One method of dividing the pager population is to assign odd-numbered calls to one group, say Gpl, and even-numbered calls to the other, say Gp2. Alternatively, the pagers measure the received signal strength (RSSI) and determine which of the two groups they belong to based on a preset threshold. One method of issuing a paging message and at the same time informing the pagers whose responses have been successfully analyzed consists in transmitting the messages M1.. .M14 in an ordered sequence as shown in Figure 5a and in the paging signal (Figure 5b) and forming an FD field in which there is a corresponding number of time slots on a one-to-one basis, i.e. time slot 3 corresponds to the M3 message. When the first paging signal, INV1, is transmitted, then in the FD field, say, all bits are zero. This indicates that no response has been received. However, after the first round of analysis, acknowledgements are transmitted, say, to the pagers to whom the messages M1, M3, M4, M9, MII and M13 were addressed by changing the bit value from '0' to 'Γ' in time slots 1, 3, 4, 9, 11 and 13 of the FD field. Additional bits change when additional messages are acknowledged. The number of cycles in which we transmit calls can be fixed. However, if we determine that the number of successfully decoded responses exceeds a statistically defined threshold, we stop further iteration. Figure 6 shows a block diagram of a paging network controller (PNC) 10 connected to a paging area controller (PAC) 14, a base station transmitter 16, and a receiver 22. The message input port 12 is connected to a microcontroller 24. The table of contents 26-36 is connected to the microcontroller 24. These tables of contents are for paging receiver identification codes (RICs), areas to be called, frequencies, paging types, prevailing protocols, and pager status. A message store 38 is connected to the microcontroller 24 and stores messages received at the message input port 12. The message store 38 has a field 40 for storing indications that a response to a corresponding message has been received and acknowledged. The output 42 of the microcontroller 24 is connected to the paging area controller (PAC) 14 to provide data packets to be formalized before transmission by the base station transmitter 16. The responses received by the receiver 22 are forwarded by the paging area controller (PAC) 14 to the signal analyzer 44. If each response is successfully analyzed, these are passed to the microcontroller 24 for matching with the messages in the message store 38. After matching, the microcontroller 24 arranges for an acknowledgement to be transmitted when the next page signal is transmitted in the receiving direction. The recipients of the responses are informed at a convenient time, for example by e-mail or a one-way paging message, or the responses are stored with the appropriate paging number so that the subscriber can query the store at will. When the microcontroller 24 has determined that the responses have been received for all practical purposes, it deletes the messages in the message store 38 and can receive further messages via the message input port 12. It is more convenient for the message store 38 to consist of two halves. One storage side handles the acknowledgements of messages already delivered in the receiving direction, while the other storage side stores the messages to be delivered. Figure 7 is a flow chart showing the sequence of operations involved in transmitting a message, receiving responses, and receiving acknowledgements. Block 50 is the start. Block 52 is the transmission of a message sequence, followed by block 54, the transmission of a paging signal. Block 56 is the reception of CDMA responses, which are analyzed in block 58 and matched with the corresponding messages. Block 60 is the transmission of acknowledgements. Block 62 is a check to see if the number of successful responses exceeds a threshold, indicating that the possible number of responses has been received. If the response is NO (N), the process proceeds to block 64, which is a check to see if a predetermined number of pagings has been exceeded. If the response is NO (N), the process returns to block 54. If the answer is YES (Y) in blocks 62 and 64, the process returns to block 52 and the cycle repeats. 8, the two-way pager 20 includes a receiver 68 connected to a decoder 70. The decoder 70 is connected to a control processor 72. The processor 72 operates according to a program stored in a ROM 74. The processor also includes a directory (not shown) containing the pager's own addresses. When the pager receives a message, it is stored in a RAM 76. The messages can then be displayed on a liquid crystal display 80, which is connected to a drive unit 78 connected to the control processor 72. Signaling devices are connected to the control processor 72. Such signaling devices include an acoustic transducer 82, a light emitting transducer 84, and a vibrator 86. The hand-held keyboard 88 provides a human-machine interface by which the user can instruct the processor to perform various functions, such as displaying a stored message on the liquid crystal display 80.A transmitter 90 is connected to the output of the processor 72 and to an antenna 92. A receiver power control stage 94 is connected between the processor 72 and the receiver 68 to maintain the battery in accordance with the requirements of the calling protocol to be followed. If the pager transmits the response signals as spread spectrum signals, the control processor 72 stores a certain number of pseudorandom codes. These are all 5. One of the codes corresponds to the specific response selected by the user by operating the hand-held keypad 88. The selected code is then transmitted to the transmitter 90 for forward transmission. If optional power control is to be transmitted to the transmitter 90, a power control signal is provided by the processor 72 via control line 96. Although our invention has been described in connection with a digital paging system, the invention can also be used in a cellular or mobile telephone system in which two-way transmission is possible. The signals transmitted in the transmit direction may also include requests for services, such as registration, and accordingly the present invention can be applied to processing such service requests in the same way as processing a response, except that there will be no matching with an outgoing message. Other modifications will be apparent to those skilled in the art based on the description. These modifications may include features that are different from those already known in the design, manufacture, and use of message transmission systems and their components, and features that may be used in place of or in addition to the features described herein. The invention can be used in any low-power responsive messaging system.

Claims

PATENT CLAIMS 1. Method for operating a message transmission system consisting of at least one primary station performing transmissions in the receiving direction and several secondary stations performing transmissions in the transmitting direction, during which a control signal is transmitted in the receiving direction at the primary stations, with which the secondary stations wishing to establish transmission in the transmitting direction are called to transmit, the transmissions are carried out with the secondary stations wishing to respond to the call, at least some transmissions are received with the primary stations, and the understandable ones are analyzed from the received transmissions, characterized in that in the case of the analyzed, understandable transmissions, it is determined which ones contain responses to the messages previously transmitted in the receiving direction, at least the responses are acknowledged, and the transmission of the control signal is repeated in the receiving direction.

2. The method of claim 1, wherein at least one transmission in the forward direction comprises a response to the message transmitted in the receive direction.

3. The method of claim 1, wherein at least one of the forward transmissions comprises a service request.

4. The method of claim 1, wherein the forward transmissions are substantially simultaneously transmitted code division multiple access (CDMA) signals.

5. A method for operating a message transmission system comprising a primary station transmitting messages in the receive direction to a plurality of secondary stations, in which the primary station calls the secondary stations to transmit their responses in the transmit direction, characterized in that the primary station analyzes the responses received in the transmit direction and acknowledges the receipt of the successfully analyzed responses, and the primary station determines which messages have been answered and repeats the call to those secondary stations whose responses have not been acknowledged to transmit their responses or to repeat their transmission in the transmit direction.

6. The method according to claim 5, characterized in that the cycle consisting of calling, analyzing and acknowledgment is repeated a predetermined number of times.

7. The method of claim 5, characterized in that the cycle of calling, analyzing and acknowledging is repeated until it appears that all responses that can be analyzed have been analyzed.

8. The method of claim 5, wherein the responses are code division multiple access (CDMA) signals transmitted simultaneously in the transmission direction.

9. The method according to claim 5, characterized in that a shorter time is allocated for analyzing stronger response signals than for analyzing weaker response signals.

10. The method according to claim 5, characterized in that a variable time is allocated for analyzing the response signals depending on the number of secondary stations responding to a call.

11. The method according to claim 1 or 5, characterized in that a call is repeated simultaneously with the primary station and the successfully analyzed responses are acknowledged.

12. The method according to claim 1, characterized in that the messages are transmitted in an ordered sequence with the primary station, the repeated call signal includes a field in which the elements are designated in an ordered sequence corresponding to the message sequence, and the elements in that field can be used to distinguish successfully analyzed response signals from unsuccessfully analyzed ones.

13. The method of claim 1 or 5, characterized in that the population of secondary stations is divided into at least two groups and the transmission of messages in one group is combined with the analysis of response signals of the other group of the at least two groups and the transmission of acknowledgements therefor.

14. A message transmission system comprising at least one primary station and a plurality of secondary stations, the primary station comprising - means for compiling messages to be delivered to the secondary station in the receiving direction, - means for transmitting a signal in the receiving direction, which signal calls on the secondary stations to transmit responses to the messages in the transmitting direction, HU 222 334 Β1 - means for receiving and analyzing the responses, and each secondary station comprising - means for receiving transmissions in the receiving direction, - means for determining whether a message is addressed to it, - means for receiving the call from the receiving direction, - means for transmitting a response to a message addressed to the secondary station in the transmitting direction, characterized in that the primary station further comprises - means for acknowledging receipt of successfully analyzed responses, - means for determining which messages have been answered, and to repeat the call to the number of secondary stations thatwhose replies are not acknowledged to transmit or retransmit their replies, and the secondary stations further comprise - means for responding if no acknowledgement is received for its reply and for repeating the transmission of the reply when called upon to do so., 15. The system of claim 14, wherein each secondary station includes means for transmitting responses as code division multiple access (CDMA) signals, and the primary station includes means for decoding code division multiple access (CDMA) responses.

16. The system of claim 15, wherein the primary station includes means for varying the time allocated for analyzing the responses depending on the number of secondary stations responding to the call.

17. The system of claim 14, wherein the population of secondary stations is divided into at least two groups, and the primary station comprises means for combining analysis of responses received in the transmit direction from one group with transmission of messages to the other group in the receive direction.

18. A primary station for a message transmission system in which there are a plurality of secondary stations capable of transmitting responses in the transmission direction, the primary station comprising - means for compiling messages to be delivered to the secondary station in the reception direction, - means for transmitting a signal in the reception direction, which signal calls on the secondary stations to transmit responses to the messages in the transmission direction, - means for receiving and analyzing the responses, characterized in that it further comprises - means for acknowledging the receipt of successfully analyzed responses, - means for determining which messages have been answered and for repeating the call to those secondary stations whose responses have not been acknowledged, to transmit their responses, or to repeat their transmission.

19. A secondary station for a message transmission system comprising a primary station transmitting signals in the receiving direction and a plurality of secondary stations capable of transmitting responses in the transmitting direction, the secondary station comprising - means for receiving transmissions in the receiving direction, - means for determining whether a message is addressed to it, - means for receiving an invitation from the receiving direction, - means for transmitting a response to a message addressed to the secondary station in the transmitting direction, characterised in that it further comprises - means for responding if no acknowledgement has been received for its response and for repeating the transmission of the response if it is so requested.

20. A secondary station according to claim 19, characterized in that it includes means for transmitting responses as code division multiplex (CDMA) signals.