Reliable message delivery system - Patent Review 5396537

What is claimed is:

1. A method in a communication system for reliably delivering messages to at least one portable selective call receive from a communication controller the method comprising within the communication controller, the steps of:

(a) storing messages comprising address cyclical redundancy codes (CRCs), and message data;

(b) transmitting the messages over a first communication medium for reception by at least one portable selective call receiver, wherein the CRCs transmitted within the messages are unique according to corresponding message data and are used to identify the corresponding message data;

(c) receiving a message reconciliation request from one portable selective call receiver of the at least one portable selective call receiver over a second communication medium, different than the first communication medium, the message reconciliation request identifying a predetermined address for the one portable selective call receiver;

(d) reconciling stored messages with the one portable selective call receiver over the second communication medium using the CRCs to identify the transmitted messages to determine a reception status of the transmitted messages for the one portable selective call receiver; and

(e) transmitting to the one portable selective call receiver, over the second communication medium, at least the message data of the transmitted messages having a reception status indicating that the one portable selective call receiver failed to receive the transmitted messages for reliably delivering messages to the at least one portable selective call receiver in the communication system.

2. The method of claim 1 wherein the first communication medium is a radio frequency paging channel.

3. The method of claim 1 wherein the second communication medium is a dial-up telephone line interface using modem communication,

4. The method of claim 1 wherein the second communication medium is a radio frequency communication channel,

5. The method of claim 1 wherein step (d) comprises the steps of:

(f) handshaking the CRCs of the stored messages that include the address information matching the predetermined address to the one portable selective call receiver; and

(g) receiving acknowledgment from the one portable selective call receiver indicating the reception status of the messages identified by the handshaking of the CRCs.

6. The method of claim 5, wherein the one portable selective call receiver performs the, steps of:

(h) receiving the messages transmitted in step (b);

(i) searching the received messages that included address information matching the predetermined address identified in the message reconciliation request for matching the handshaking CRCs to the CRCs of the searched messages;

(j) after determining that there is no match between one of the CRCs handshaking in step (f) and the CRCs of the searched messages, transmitting the acknowledgment indicating a reception status that the one portable selective call receiver failed to receive a message corresponding to the one of the CRCs handshaking in step (f); add

(k) receiving at least the message data of the message indicated as having been failed to received in step (j) over the second communication medium for reliably delivering messages to the at least one portable selective call receiver in the communication system.

7. The method of claim 5, wherein the one portable selective call receiver performs the steps of:

(l) receiving the messages transmitted in step (b);

(m) determining from a corresponding CRC that there is an error in one of the received messages;

(n) identifying the predetermined address in the message reconciliation request matching the address information of the one of the received messages;

(o) matching one of the CRCs handshaking in step (f) with the corresponding CRC of the one of the received messages;

(p) transmitting an acknowledgment in step (g) indicating a reception status that the one portable selective call receiver failed to receive the one of the received messages; and

(q) receiving at least the message data of the one of the received messages indicated in step (p) over the second communication medium for reliably delivering messages to the at least one portable selective call receiver in the communication system.

8. The method of claim 7, wherein step (m) comprises the step of:

(r) determining error in one of the received messages by comparing the CRC of the one of the received messages to a computed value based on the content of the one of the received messages.

9. A method in a communication system for reliably delivering messages from a communication controller to at least one portable selective call receiver, the method comprising the steps of:

(a) storing messages at the communication controller, the messages comprising address information, cyclical redundancy codes (CRCs), and message data;

(b) transmitting the messages from the communication controller over a first communication medium for reception by at least one portable selective call receiver, wherein the CRCs transmitted within the messages are unique according to the corresponding message data and are used to identify the message data;

(c) receiving a message reconciliation request at the communication controller from the at least one portable selective call receiver over a second communication medium, different than the first communication medium, the message reconciliation request identifying a predetermined address for the portable selective call receiver;

(d) searching the messages stored at the communication controller for locating the messages that were transmitted which include address information matching the predetermined address identified in step (c);

(e) transmitting at least one of the CRCs of at least one of the messages found in step (d) from the communication controller to the at least one portable selective call receiver over the second communication medium;

(f) verifying at the at least one portable selective call receiver, in response to receiving the at least one of the CRCs at the portable selective call receiver, whether the portable selective call receiver failed to receive the at least one of the messages identified by the at least one of the CRCs, respectively;

(g) transmitting a reconciliation acknowledgment from the portable selective call receiver to the communication controller over the second communication medium to confirm a reception status of the at least one of the messages identified by the at least one of the CRCs verified in step (f) the reception status indicating that the portable selective call receiver failed to receive the at least one of the messages or that it correctly and completely received the at least one of the messages; and

(h) transmitting at least the message data of the at least one of the messages identified by the at least one of the CRCs being acknowledged in the reconciliation acknowledgment from the communication controller to the portable selective call receiver over the second communication medium, the reconciliation acknowledgment confirming that the portable selective call receiver failed to receive the at least one of the messages identified by the at least one of the CRCs.

10. A communication system for reliably delivering messages to at least one communication receiver, the communication system comprising:

first memory means for storing messages destined for transmission to at least one communication receiver, the messages comprising address information, message data, and cyclical redundancy codes (CRCs) which are unique according to corresponding message data and are used to identify the corresponding message data;

first message transmitting means coupled to the memory means for transmitting the messages over a first communication medium for reception by the at least one communication receiver;

second message transmitting means coupled to the memory means for transmitting at least the message data of the messages over a second communication medium for reception by the at least one communication receiver, the second communication medium being different than the first communication medium;

retrieving means for retrieving messages stored in the first memory means; and

message reconciliation request processing means coupled to the retrieving means and to the second message transmitting means for receiving a message reconciliation request from the at least one communication receiver over the second communication medium, and in response to the message reconciliation request:

determining that at least one message was not received by the at least one communication receiver over the first communication medium,

retrieving at least the message data of the at least one message from the first memory means, least the message data of the at least one message being identified by the CRC of the at least one message, and

transmitting the message data of the at least one message over the second communication medium for reception by the at least one communication receiver, for reliably delivering messages from the communication system to the at least one communication receiver over at least one of the first communication medium and the second communication medium; and

the at least one communication receiver for communicating with the communication system over the first communication medium and the second communication medium.

11. The communication system of claim 10 wherein the second communication medium is a dial-up telephone line interface using modem communication.

12. The communication system of claim 10 wherein the second communication medium is a radio frequency communication channel.

Description Submit all comments and votes

FIELD OF THE INVENTION

This invention relates generally to message delivery systems, such as for electronic mail systems, and more specifically to a method and apparatus for reliably delivering messages to one or more remote units from a central communication system utilizing a paging transmitter system.

BACKGROUND OF THE INVENTION

Communication systems, such as paging systems, typically communicate messages from an originating device to one or more destination devices. These messages can include numeric and alphanumeric information for a user of the destination device. The destination device, e.g., a selective call receiver or pager, typically presents the information received to the user by displaying the information on a display.

Contemporary paging systems offer a limited message length for communicating information. For example, an alphanumeric message may be typically 80 l characters or less. These typical message lengths have provided reasonably reliable delivery Of messages to the users of the communication system.

On the other hand, a distinct trend in the market is for customers desiring much longer messages, such as from ten to one hundred times longer messages or more. Transmission of these messages over a paging channel can encounter a number of obstacles to reliable delivery of the longer messages, such as different types of interference, fading, noise, and other phenomena detracting from error-free and reliable communication of the messages to the destination devices.

This difficulty in reliable transmission of the longer messages is especially frustrating to customers that are used to communicating long messages over a more reliable communication medium, such as direct wire line or dial-up telephone communication. This:is particularly the case for electronic mail system users which typically desire to send relatively long messages with a high degree of certainty that the messages are received error free. Typically, an originating device, such as a personal computer or workstation, can send long messages to one or more destination devices, such as other personal computers or workstations, over a direct wire line interface, or over a local area network (LAN), or over a dial-up telephone line connection using the public switched telephone network (PSTN).

Therefore, a need exists to enhance the reliability of transmitting messages, including long messages, in communication systems that utilize paging systems for delivering the messages.

SUMMARY OF THE INVENTION

According to an embodiment of the present invention, there is provided a method and apparatus for reliably delivering messages to a communication receiver in a communication system. The communication system transmits messages to the communication receiver and the communication receiver receives transmitted messages over a first communication medium. The communication receiver reconciles messages that it failed to receive, e.g., missed messages and erroneously received messages, over the first communication medium with the communication system over a second communication medium. The reconciliation process between the communication receiver and the communication system utilizes message identifiers transmitted with the messages to identify the messages being reconciled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a communication system in accordance with the preferred embodiment of the present invention.

FIG. 2 is a message block diagram illustrating a transmitted message according to the preferred embodiment of the present invention.

FIG. 3 is a message sequence diagram illustrating a first example of received messages being stored in the memory of a remote unit of the communication system according to the preferred embodiment of the present invention.

FIG. 4 is a message sequence diagram illustrating a second example of received messages being stored in the memory of a remote unit of the communication system according to the preferred embodiment of the present invention.

FIG. 5 is a block diagram illustrating messages stored in the memory of a central terminal of the communication system and messages stored in the memory of a remote unit before a reconciliation of messages between the central terminal and the remote unit, in accordance with the preferred embodiment of the present invention.

FIG. 6 is a flow diagram illustrating an operational sequence for a remote unit, according to the preferred embodiment of the present invention.

FIGS. 7 and 8 are message sequence diagrams illustrating a timing aspect of the second example of FIG. 4, in accordance with the preferred embodiment of the present invention.

FIGS. 9 and 10 are flow diagrams illustrating operational sequences for the central terminal of FIG. 1, according to the preferred embodiment of the present invention.

FIGS. 11 and 12 are flow diagrams illustrating operational sequences for the remote unit of FIG. 1, according to the preferred embodiment of the present invention.

FIG. 13 is a message block diagram illustrating a transmitted message according to an alternative embodiment 15 of the present invention.

FIG. 14 is a flow diagram illustrating an operational sequence for the central terminal of FIG. 1, according to the alternative embodiment of the present invention.

FIGS. 15 and 16 are flow diagrams illustrating an operational sequence for the remote unit of FIG. 1, according to the alternative embodiment of the present invention.

DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 shows a communication system 100 utilizing a paging transmitter system 120, 122, 124, 126, for delivering messages to at least one portable remote unit, e.g., a portable selective call receiver 130, in accordance with the preferred embodiment of the present invention. A central terminal 102 comprises input sections 110, 112 for receiving inputs from a number of different devices 104, 106, 108, including receiving page requests for initiating pages that are transmitted by the paging transmitter system 120, 122, 124, 126, to the at least one portable remote unit 130. The central terminal 102 has input sections 110 that interface with the telephone company equipment, such as the public switched telephone network (PSTN) 107. Personal computers or other computing devices 104 can access the input sections 110 through the PSTN using a dial-up telephone line and modem communication. Other calling devices, such as telephone input devices 106 can access the input sections 110 of the central terminal 102 through the PSTN 107. Typically, these input devices 104, 106, can remotely initiate page requests through the central terminal 102 by calling up the input sections 110 of the central terminal 102 over dial-up telephone lines of the PSTN 107.

Alternatively, other input sections 112 of the central terminal 102 can receive inputs, such as page requests, from local computing devices 108, such as a local personal computer or console or other terminal device. Typically, the one or more local input devices 108 interface with the input sections 112 of the central terminal 102 via direct wire line connections using standard RS-232 or RS-422 interface.

The input sections 110, 112, communicate page requests to a controller 114 through a communication bus 116. The controller 114 may comprise controller circuitry and associated memory such that an incoming page request may be accepted and stored into available memory for subsequent transmission to one or more selective call receivers 130. Additionally, a non-volatile memory device 118, such as battery backed up RAM, one or more disc drive units, or other non-volatile storage medium, is utilized by the controller 114 for longer term storage of messages destined for the one or more selective call receivers 103. The controller 114 typically couples the message information and other associated information to the memory device 118 via the bus 116. The message information, which can include numeric, alphanumeric, or binary information, and other associated information stored in the memory 118 can be used by the controller 114 for reliable delivery of the message to the destination or remote unit 130, as will be more fully discussed below.

The controller 114 couples messages to the paging encoder 120 over the bus 116 for encoding the messages for transmission over a paging channel. The paging encoder 120 then couples the encoded messages over a communication path 122' to one or more paging transmitter systems 124, 126, for transmission over a paging communication channel. The communication path 122, in this example, will be labeled path B which routes the messages from the central terminal 102 to a paging transmitter system 124, for transmission and over a paging communication channel for reception by the one or more selective call receivers 130. The general operation of a communication system including a paging system of the type shown in FIG. 1 is more fully described in U.S. Pat. No. 5,138,311, issued Aug. 11, 1992, entitled, "Communication System Having adaptable Message Information Formats", which is assigned to the same assignee as the present invention and is incorporated herein by reference.

The selective call receiver 130 preferably incorporates a paging receiver 134 that operates to receive messages transmitted over the paging communication channel through the antenna 132. The operation of a paging receiver 134 of the general type shown in FIG. 1 is well known and is more fully described in U.S. Pat. No. 4,518,961 issued May 21, 1985, entitled, "Universal Paging Device With Power Conservation", which is assigned to the same assignee as the present invention and is incorporated herein by reference.

The paging receiver 134 couples a received message to the controller 136 through the bus 138. The controller 136 address information in the received message and then match predetermined address in the selective call receiver 130. In this way, the controller 136 can determine whether the received message is intended for the particular selective call receiver 130. Further, a memory 140 is coupled to the paging receiver 134 and the controller 136 through the bus 138 for storing the received message in the memory 140. A user can access user input means 141, such as buttons or switches, at the remote unit 130 to cause the message data of a received message to be displayed on a display, e.g., a liquid crystal display (not shown). The user can then read the message that is visible on the display. User input at the remote unit 130 can also cause the remote unit 130 to perform other functions that are well known to users of selective call receivers and portable personal computing devices.

A real time clock 142 is also coupled through the bus 138 to the controller 136 for providing time information thereto. The remote unit 130 is then capable providing time information to the user by displaying the time information on the display (not shown). Additionally, the controller 136 can utilize the, time information provided by the real time clock 142 to keep track of the time when messages were received at the remote unit 130 and to perform and other useful operations that will be more fully discussed below.

Furthermore, the selective call receiver 130 includes a modem transmitting unit and a modem receiving unit 144 and the associated telephone interfacing circuitry or other suitable communications apparatus (e.g., packet radio modem) which allows the user of the selective call receiver 130 to connect the selective call receiver to a telephone interface 150, such as may be provided by an RJ11 plug 148 and associated wiring 146 at the selective call receiver 130 and the complimentary wall jack 150 and associated wiring 152 thereof. This telephone interface 144, 146, 148, 150, 152, allows the controller 136 of the selective call receiver 130 to remotely access the central terminal 102 through a dial-up telephone line and the PSTN 107. At the central terminal 102, a modem transmitting unit and a modem receiving unit 111 is capable of communicating with the modem 144 at the selective call receiver 130. In this way, the selective call receiver 130 can communicate with the central terminal 102 and receive message information therefrom through a separate communication path which, in this example, is labeled path A 152. Therefore, the selective call receiver 130 cab receive message information from the central terminal 102 via path A 152 and via path B 122. The path A 152 communication medium and the path B 122 communication medium can comprise any communication paths, such as direct wired line path, telephone line path, or wireless communication path including at least one radio communication channel preferably path A 152 is different than path B 122.

In the preferred embodiment, path A 152 is a dial-up telephone line using modem communication between the central terminal 102 and the remote unit 130. Also, preferably path B includes a paging communication channel for transmitting messages to the selective call receiver 130. Alternatively, path A may be a one-way or two-way radio frequency communication channel between the remote unit 130 and the central terminal 102, and path B can be a paging communication channel. Additionally, in another alternative, path A and path B can be one-way or two-way radio frequency communication channels. An advantage of delivering messages to the remote unit 130 through the paging communication channel Over the two-way radio frequency communication channel is that typically more messages can be delivered through the medium in the paging communication channel. This in turn enhances the commercial viability of the communication system. However, using two-way radio frequency communication channels for both path A and path B may be perfectly acceptable in some systems.

By using a dial up telephone line interface for path A 152, and utilizing modem communication between the remote unit 130 and the central terminal 102 in the preferred embodiment, the reliability of transferring messages between the central terminal 102 and the remote unit 130 is relatively high and approaches the reliability that users of conventional computing systems have previously experienced. Hence, it is advantageous to transfer messages over the dial-up telephone line interface 152 because it is a more reliable communication medium than transmission over the paging communication channel 122, e.g., over a radio paging channel. On the other hand, the dial-up telephone line interface 152 has several draw backs. First, dial-up telephone line interfacing typically interfaces between one originating and one receiving device which significantly reduces the number of remote units that can subscribe to any type of communication system. Second, the telephone line interface 152 normally requires that the remote unit 130 connect to a telephone line interface which may not always be available. Third, the remote unit is not as portable due to the requirement that it be interconnected with the telephone interface. In the case of a paging communication channel transmission, the remote unit 130 is portable and can receive messages transmitted over the paging communication channel while the remote unit 130 is being carried by a user. Hence, although the telephone line interface communication tends to be more reliable than the paging channel communication, it can significantly limit the number of subscribing remote units 130 in the communication system, and it tends to inconvenience users by requiring them to connect their remote units 130 to a telephone line interface 152 for communication with the central terminal 102. Therefore, the preferred embodiment of the present invention utilizes both path A and path B communication of messages in a manner that significantly increases the reliability of transmission of messages between the central terminal 102 and the remote units 130 while allowing large numbers of portable remote units 130 to be serviced in the communication system, as will be more fully discussed below.

The communication system 100 of the preferred embodiment of the present invention allows high throughput of messages between the central terminal 102 and the portable remote units 130 by transmitting messages over the path B 122, e.g., a radio frequency paging channel, for normal communication of new messages between the central terminal 102 and the remote units 130. Additionally, for a higher grade of service, the central terminal 102 can transmit messages multiple tinges over path B 122 to better guarantee that the remote unit 130 will receive at least one of the transmissions of the same message. For example, the central terminal 102 can transmit a message three separate times over the paging channel 122 where each subsequent transmission of the same message is delayed by a predetermined time interval from the previous transmission, e.g., three minutes. In this way, the remote unit 130 has a higher probability of receiving the message transmitted over the paging channel 122.

Nonetheless, there may be times when the message is not received by the remote unit 130. In such event the communication system 100 provides a means at the remote unit 130 for determining that a message was missed and further for reconciling with the central terminal 102 to receive at least the message information of a missed message over a more reliable communication medium, such as provided through path A 152. However, the required throughput of path A 152 can be much lower than the throughput of messages through path B 122 because the number of missed messages will be much lower than the number of new transmitted messages for the communication system 100. Hence, the bulk of communication transmission including the transmission of new messages can be handled through path B 122, e.g., the radio frequency paging channel. The reconciliation of missed messages between the remote units 130 and the central terminal 102 can be handled over the more reliable communication medium provided through path A 152. Further the portable remote units 130 can be carried by a user while receiving new message transmissions over the paging channel 122. The users of the remote units 130 will be minimally inconvenienced by requiring that the remote unit 130 be connected with the telephone line interface 152 to perform reconciliation of missed messages because messages typically will be missed relatively infrequently. Optionally, as mentioned earlier, path A 152 can be configured as a one-way or two-way radio frequency communication channel between the central terminal 102 and the remote units 130. In this case, the message reconciliation can be performed while the users carry the remote selective call receivers 130 such that. Hence, the users are minimally inconvenienced.

PIG. 2 is a message block diagram illustrating a transmitted message according to the preferred embodiment of the present invention. The transmitted message 200 typically includes identification and control information 202, as well as message data information 204. The message data 204 normally is the information that is communicated between an originating party and the destination remote unit 130. That is, the message data 204 is the message information communicated to the user of the selective call receiver 130. The message data 204 can include numeric information, alphanumeric information, and binary data. The identification and control information 202 included with the message 200 normally is required for delivering the message in the communication system 100. Such information 202 includes address information 206 which identifies one or more remote units 130 as the destination of that message data 204. Hence, when a remote unit 130 receives a message 200 that was transmitted from the central terminal 102, the remote unit 130 can determine whether that particular message 200 was intended for reception by the particular remote unit 130. Normally, the address information 206 included with the message 200 is decoded by the remote unit 130 and compared to a predetermined address in the remote unit 130. If the address information 206 in the message 200 matches the predetermined address in the remote unit 130 then the message 200 was intended for that particular remote unit 130. The remote unit 130 can then store the received message data 204 in a memory 140 in the remote unit 130, or optionally in a computer memory of a computing device associated with the remote unit 130 for later processing. A user of the remote unit 130 can subsequently review the message data 204 to communicate the message to the user. Typically, the user reviews the message on a display on the remote unit 130. That is, for example, the user can read the message on a display screen such as commonly available on portable personal computers and portable selective call display receivers.

Additionally, in the preferred embodiment of the present invention, the message 200 includes other identification information fox enhancing the reliability of delivering the message from the central terminal 102 to the portable selective call receiver 130. For example, each message 200 can include a message sequence number 208 which identifies the relative sequence of the message 200 in a transmission sequence for messages transmitted from the central terminal 102 to the remote unit 130 for a particular address information 206. That is, each message that includes the same address information 206, i.e., that is destined for reception by the same one or more remote units 130, can be tagged with a message sequence number 208 that identifies to the one or more remote units 130 when a transmitted message 200 is received out of sequence or when a transmitted message was not received by the remote unit 130.

When a transmitted message 200 is received by the remote unit 130 and the address information 206 in the message 200 matches a predetermined address for the remote unit 130, then, if the message sequence number 208 identifies the message 200 as being out of sequence with a transmission sequence established by previously received messages, the remote unit 130 may determine that one or more messages were transmitted by the central terminal 102 and not received by the remote unit 130. Those transmitted messages that intervened between the last received message in the transmission sequence and the received message being out of sequence may have been missed by the remote unit 130. However, the intervening messages may not always have been missed.

For example, the communication system 100, as discussed earlier, can transmit messages multiple times over the paging communication channel 122 to provide a higher grade of service for the destination remote units 130. In this case a message 200 can be received by the remote unit 130 and the message sequence number 208 may indicate that the received message 200 is out of sequence with a transmission sequence established by previously received messages at the remote unit 130. However, this may only indicate that one transmission of a message was missed by the remote unit 130 and that subsequent re-transmissions of that message may be received by the remote unit 130, thereby reestablishing the transmission sequence of received messages at the remote unit 130.

Preferably, a message repetition count 210 is included with each transmitted message 200 to identify to a receiving remote unit 130 the relative position of the received message 200 in a repetition sequence. For example if under a grade of service, messages are repeatedly transmitted three times for delivery to a receiving remote unit 130, where the repeatedly transmitted messages have the same destination address 206, a received message 200 including a message repetition count 210 of two may identify to the receiving remote unit 130 that the received message 200 was the second transmission of that message from the central terminal 102.

Other information can be transmitted with a transmitted message 200, such as error detecting and/or correcting code. For example, a cyclic redundancy code (CRC) 212 can be included with each transmitted message 200 to help identify at the receiving remote unit 130 when received message data 204 has been erroneously received, e.g., when the message data 204 has been received with errors included therein. In this cage, although the message 200 has been received by the remote unit 130, the message data 204 may not ba completely and correctly communicated to the user of the remote unit 130. Hence, the remote unit 130 has failed to receive the message 200 accurately enough to communicate the message information to the user of the remote unit 130. Hence, two possible conditions can identify when the remote unit 130 has failed to receive a transmitted mess