US 4,940,974 AGranted

Multiterminal communication system and method

AssigneeNorand Corporation

InventorMarvin L. Sojka

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Abstract

In an exemplary communications system a multiplicity of mobile terminals are to share a communications link with a primary processor. The primary processor may transmit a multiterminal polling signal defining a series of successive response time slots which the terminals may randomly select. A terminal wishing to send a message transmits a brief response burst in the selected time slot giving its identification. The primary processor may then sequentially poll specific individual terminals having messages to send. The primary processor may maintain a record of currently active terminals and/or of collisions (where more than one terminal seeks to transmit in the same response time slot), and as needed may automatically send e.g. with its multiterminal poll, a time slot number change, creating a greater or lesser number of time slots for future use by the active terminals. The system is thus highly adaptable on a dynamic basis during operation so as to readily maintain optimum throughput under changing conditions. As a consequence additional terminals may become active simply by transmitting their respective identifications in randomly selected response time slots. The multiterminal poll may include a listing of one or more terminals for which the primary processor has a message so that the primary processor may be assured that such terminal is available (as indicated by its response in a random time slot) before a lengthy message is sent.

Claims9

Dependent claims

A method of effecting communication between a primary transceiver means and a group of mobile secondary transceiver means having respective distinctive identification means, with communication link means for affording communication therebetween, said method comprising:

(a) operating said primary transceiver means to transmit a group polling message via said communication link means, specifying a series of response time slots in which the secondary transceiver means may respond,
(b) operating the secondary transceiver means which receive said group polling message and which have a coded data message to transmit to said primary transceiver means
(b1) to randomly select one of the series of response time slots and
(b2) in the respective randomly selected response time slots, to send respective response messages which contain the respective identification means such that the primary transceiver means may identify respective secondary transceiver means of the group which have responded to the group polling message,
(c) operating the primary transceiver means to time the expiration of the series of response time slots defining a response time interval and after expiration of such response time interval, to initiate communication via said communication link means with a particular one of said secondary transceiver means which has responded to said group polling message for receiving a coded data message therefrom,
(d) performing steps (a) a multiplicity of times, and operating said primary transceiver means to change the number of response time slots which are specified in a group polling message according to step (a) in accordance with the number of times a collision occurs wherein plural secondary transceiver means send respective response messages according to step (b2) in the same response time slot, and
(e) operating said primary transceiver means subsequent to the issuance of a group polling message according to step (a) specifying a changed number of response time slots to observe a different response time interval corresponding to the expiration of the changed number of response time slots before initiating further communications according to step (c) via said communication link means.

4 more elements

In a data capture system,

(a) base station transceiver means,
(b) a multiplicity of mobile hand-held transceiver units operating at varying distances from the base station transceiver means and operable to switch from receive to transmit mode in not more than fifteen milliseconds and to transmit a minimum duration identifying response message in a brief time interval of not more than fifteen milliseconds.
(c) said mobile hand-held transceiver means collecting data for transmission as a coded data message to the base station transceiver means in a data transmission time interval which is of duration greatly exceeding said brief time interval,
(d) said base station transceiver means being operative to communicate with a multiplicity of mobile hand-held transceiver units via a radio frequency communication channel and automatically periodically switching to a multiterminal polling mode and sending a multiterminal polling message via said radio frequency communication channel so as to be received in common by a multiplicity of mobile hand-held transceiver units for the purpose of polling the mobile hand-held transceiver units for coded data messages, wherein said multiterminal polling message also specifies a series of common response time slots in which the mobile hand-held transceiver units may respond, the base station being operative to change the number of common response time slots which are specified in subsequent multiterminal polling messages in accordance with the number of times a collision occurs, wherein a multiplicity of mobile hand-held transceiver units transmit respective identifying responses in the same response time slot,
(e) respective mobile hand-held transceiver units when having a coded data message to transmit to said base station transceiver means being normally in receive mode so as to receive multiterminal polling messages from the base station transceiver means, the respective mobile hand-held transceiver units upon receiving a multiterminal polling message each beginning a slot timing cycle extending from the time of receipt of such multiterminal polling message and defining a series of common response time slots essentially common to the respective mobile hand-held transceiver units, each of the respective mobile hand-held transceiver units randomly selecting one of the series of common response time slots and switching to transmit mode and transmitting a respective minimum duration identifying response in the respective selected ones of said series of common response time slots,
(f) said base station transceiver means being operative to time the expiration of the series of common response time slots specified in a multiterminal polling message defining a response time interval and after expiration of such response time interval responding to received minimum duration identifying responses following a multiterminal polling message to conduct a sequential polling operation wherein the base station transceiver means transmits a coded individual polling message addressed to a respective one of the mobile hand-held transceiver units, such addressed mobile hand-held transceiver unit upon receipt of such coded individual polling message addressed thereto, automatically switching to transmit mode and transmitting its coded data message via said radio frequency communication channel for a data transmission time interval which is of duration greatly exceeding said brief time interval, whereby data messages are automatically collected from mobile hand-held transceiver means having data messages to send entirely on the basis of polling messages automatically initiated by the base station transceiver means.

3 more elements

Dependencies are inferred from the claim text.