Apparatus and method is disclosed for storing and subsequently transmitting later messages for system pagers with acknowledge back capability that nevertheless fail to acknowledge back in the first instance. Addresses are retransmitted for pagers initially failing to acknowledge back on a continuous periodic basis until such acknowledge back is received, at which time the message intended therefor is sent, or a predetermined time period expires.
A method and apparatus in a radio communication system that employs frequency reuse is used for optimizing transmission of messages to a selective call transceiver (116). The radio communication system transmits a first message (202) to the selective call transceiver (116) instructing it to listen to a second message destined for another selective call transceiver (116), to measure a signal quality level of the second message, and to transmit a response signal representative of measured signal quality. After transmitting the second message (204) to the other selective call transceiver (116), the radio communication system receives the response signal (206) from the selective call transceiver (116). In response, the radio communication system transmits a third message (212) to the selective call transceiver (116) utilizing a frequency reuse plan in accordance with the signal quality level.
A packet data transmission system is used to link a number of remote hand-held data-gathering units such as bar code readers to a central computer. Data packets are sent from the remote units by an RF link to intermediate base stations, then sent by the base stations to the central computer by a serial link. Direct sequence spread spectrum modulation is used for the RF link. The remote hand-held units initiate an exchange using RF transmission to and from the base stations, receiving only during a rigid time window following a transmission from the remote unit. The base stations cannot initiate an exchange with the remote units, but instead send data to the remote units only as part of the exchange. To alert a remote unit when a message is waiting at a base station to be sent to a particular unit, some of the acknowledge (base-to-remote) packets sent by the base station may contain an identification such as a list of all remote units (identified by ID number) which have messages waiting. Alternatively, a bit map can be used to identify these remotes. These base-to-remote packets with the identification of remotes with messages waiting are called "announcements." Each remote unit (if not engaged in regular exchanges for a time interval) periodically listens (activates its receiver) to receive an announcement packet containing such a list or bit map and decodes this announcement to see if it has a message waiting. If so, this remote unit then sends a transmit packet so the base can send the waiting message in an acknowledge packet.
A system for generating and substituting tokens for frequently used phrases within the information portion of messages comprises a central control terminal (140) and a selective call receiver (160). The central control terminal (140) includes a dynamic token generator for generating a set of most frequently used phrases having uniquely associated tokens therewith, the token generator accumulating and analyzing a number of the information portion of messages received at the central control terminal (140) intended for transmission to one or more selective call receivers to derive the set of most frequently used phrases, a most frequently used phrase storage memory for storing within the central control terminal the generated set of most frequently used phrases and associated tokens, and a most frequently used phrase downloading device for transmitting via a radio frequency transmitted message the generated set of most frequently used phrases and associated tokens to the one or more selective call receivers.
A method (200) and apparatus (100, 402) are shown for determining whether first and second data messages in a communication system are duplicates. The method comprises forming (304) from the first and second data messages a corresponding pair of first and second message identifiers (120, 126). The identifiers (120, 126) comprise bits generated from first and second message characteristic values calculated (206) from portions (118, 124) of the first and second data messages. The method further comprises comparing 316 the first and second message identifiers (120, 126) to determine whether the first and second message identifiers (120, 126) are substantially equivalent to each other, substantially equivalent identifiers (120, 126) being indicative that the first and second data messages are duplicates.
A facility is provided for use in a packet switch to control unnecessary multiple retransmissions of a data packet. In an exemplary embodiment of the invention, such control is achieved by tracking in a list the sequence numbers of transmitted data packets and retransmitting a data packet only if its sequence number appears in the list prior to the sequence number of the last data packet that is received correctly by a receiver. The sequence number associated with a retransmitted data packet is deleted from the list and then appended to the list to place the number in proper relationship with the sequence numbers of data packets transmitted after the initial transmission of the retransmitted data packet.
