Adaptive time-division multiplexing communications protocol method and system

• US 5,687,175 A
• Filed: 11/17/1994
• Issued: 11/11/1997
• Est. Priority Date: 08/13/1992
• Status: Expired due to Fees

• Current Assignee: UTICS Corporation
• Original Assignee: UTICS Corporation
• Inventors: Jonson, Charles Stephen, Hunt, Ariel Mark, Rochester, Virgil Maurice Jr., Weaver, John D.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Patel, Ajit
• Application Number:
  US08/341,015
• Time in Patent Office: 1,090 Days
• Field of Search: 370/85.7, 370/85.8, 370/95.1, 370/95.2, 370/95.3, 370/449, 370/457, 370/503, 370/508, 370/509-512, 370/461, 370/462, 340/825.08, 340/825.07, 375/354, 375/355, 375/556
• US Class Current: 370/449
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom
• CPC Class Codes: H04W 56/00 Synchronisation arrangements
• CPC Class Codes: H04W 74/06 using polling
• CPC Class Codes: H04W 92/18 between terminal devices

Abstract

A system and method for an adaptive time-division multiplexing communications protocol for collecting data from remote sensors equipped with RF transceivers using an RF transceiver equipped mobile data collection unit. RF transceivers interfaced to remote sensors actively monitor a predetermined RF transmission frequency to ascertain the presence of a signal transmitted by the mobile unit. All remote units detecting the RF signal listen for a message from the mobile unit requesting transmission of their unique identifier, i.e., their ID. This message contains the Time Division Base (TDB) specifying the number of time slots allocated for transmission of remote sensor IDs to the mobile unit. Using the TDB, each remote sensor randomly selects a time slot and transmits its ID to the mobile unit. Unique IDs of remote sensors received by the mobile unit are used to individually poll each sensor for data packet transmission. Upon receipt of a data packet from a remote sensor, the mobile unit sends an acknowledgment packet indicating its data has been received. Upon receipt of the acknowledgment packet, the sensor is set to a state whereby it will not respond to a request for identifier for a specified period of time.

Claims

1. A communication protocol method for communicating data between a mobile unit and a plurality of remote units, the method comprising the steps of:

transmitting a poll signal from the mobile unit to the remote units, the poll signal specifying a predetermined number of time slots;

associating a respective time slot with each remote unit;

transmitting a poll response signal from each remote unit to the mobile unit in the time slot associated with the remote unit, in response to the receipt of the poll signal by the remote unit, the poll response signal from each remote unit including identification data identifying the remote unit;

transmitting a data signal to the mobile unit from at least one of the remote units; and

transmitting an acknowledgment signal from the mobile unit to said at least one remote unit which transmitted the data signal;

wherein said step of transmitting said poll response signal comprises the steps of;

synchronizing a clock with respect to said poll signal;

determining a wait time period between the poll signal and the time slot associated with the remote unit;

timing the period of time lapsing from the receipt of the poll signal with the clock, in response to the poll signal; and

transmitting said poll response signal upon the time period timed with the clock reaching the wait time period.

2. A method as recited in claim 1, further comprising the steps of:

selecting a time slot; and

transmitting a send data signal from the mobile unit to the remote unit which sent a poll response signal in the selected time slot, the send data signal including identification data for addressing the remote unit which sent a poll response signal in the selected time slot.

3. A method as recited in claim 2, wherein the step of transmitting said data signal to the mobile unit from said at least one remote unit comprises the step of transmitting a data signal to the mobile unit from the remote unit which sent a poll response signal in the selected time slot, in response to the send data signal transmitted by the mobile unit.

4. A method recited in claim 3, wherein the step of transmitting an acknowledgement signal comprises the step of transmitting an acknowledgement signal in response to said data signal, said acknowledgement signal being transmitted from the mobile unit to the remote unit which sent said data signal.

5. A communication protocol method for communicating data between a central unit and a plurality of remote units, the method comprising the steps of:

transmitting a first signal from said central unit within a transmission range;

receiving the first signal by remote units within the transmission range of the first signal;

transmitting first response signals from remote units which received the first signal, in response to the receipt of the first signal;

receiving first response signals by the central unit;

transmitting a second signal from said central unit to each remote unit from which a first response signal was received;

receiving the second signal by remote units to which the second signal was sent;

transmitting a data signal from each remote unit which received the second signal to said central unit, in response to the receipt of the second signal;

receiving data signals by said central unit;

transmitting an acknowledge signal from said central unit to each remote unit from which a data signal was received;

receiving the acknowledge signal by remote units to which the acknowledge signal was sent; and

inhibiting the transmission of a response signal by each remote unit which received the acknowledge signal.

6. A method as recited in claim 5, wherein the first response signal sent by each remote unit includes identification data for identifying the remote unit which sent the first response signal.

7. A method as recited in claim 5, wherein the first signal contains data specifying a predetermined number of time slots and wherein the step of transmitting first response signals comprises the steps of:

assigning a respective time slot to each remote unit which received the first signal; and

transmitting first response signal from each remote unit to the central unit in the time slot assigned to the remote unit.

8. A method as recited in claim 7, wherein the number of time slots is dependent on the number of remote units within the transmission range of the first signal.

9. A method as recited in claim 5, wherein the signal frequency of each of the first and second signals is substantially the same.

10. A method as recited in claim 5, wherein the signal frequency of each of the first response signals sent by the remote units is substantially the same and constant.

11. A method as recited in claim 5, wherein the central unit comprises a mobile unit operable to travel along a route and the remote units comprise stationary units located along the route of the mobile unit.

12. A method as recited in claim 5, wherein the acknowledge signal includes device wait time information and wherein said step of inhibiting the transmission of a response signal by each remote unit comprises inhibiting response signal transmissions for a time period dependant on the device wait time information.

13. A communication protocol method for communicating data between a central unit and a plurality of remote units, the method comprising the steps of:

transmitting a first signal from said central unit within a transmission range;

receiving the first signal by remote units within the transmission range of the first signal;

transmitting a first response signal from each remote unit which received the first signal, in response to the receipt of the first signal, wherein the first response signal sent by each remote unit includes identification data for identifying the remote unit which sent the first response signal;

receiving first response signals by the central unit;

transmitting a second signal from said central unit to each remote unit from which a first response signal was received;

receiving the second signal by remote units to which the second signal was sent;

transmitting a data signal from each remote unit which received the second signal to said central unit, in response to the receipt of the second signal;

receiving data signals by said central unit;

storing identification data for each remote unit from which a first response signal and a data signal were received by the central unit;

transmitting a third signal from said central unit within a transmission range, following the step of receiving data signals;

receiving the third signal by remote units within the transmission range of the third signal;

transmitting second response signals from remote units which received the third signal, in response to the receipt of the third signal, wherein each second response signal includes identification data for identifying the remote unit which sent the second response signal;

receiving second response signals by said central unit;

comparing identification data included in each second response signal received by said central unit with stored identification data to determine if a second response signal was received from any remote unit from which a first response signal and a data signal were received;

transmitting a fourth signal from said central unit to each remote unit from which a second response signal was received but from which both a first response signal and a data signal were not received and inhibiting the transmission of the fourth signal to any remote unit from which both a first response signal and a data signal were received;

receiving the fourth signal by remote units to which the fourth signal was sent; and

transmitting a data signal from remote units which received the fourth signal to said central unit, in response to the receipt of the fourth signal.

14. A communication protocol method for communicating data between a central unit and a plurality of remote units, the method comprising the steps of:

transmitting a first signal from said central unit within a transmission range;

receiving the first signal by remote units within the transmission single of the first signal;

transmitting first response signals from remote units which received the first signal, in response to the receipt of the first signal;

receiving first response signals by the central unit;

transmitting a second signal from said central unit to each remote unit from which a first response signal was received;

receiving the second signal by remote units to which the second signal was sent;

transmitting a data signal from each remote unit which received the second signal to said central unit, in response to the receipt of the second signal;

receiving data signals by said central unit;

wherein the step of transmitting said first response signal in the time slot assigned to a remote unit comprises the steps of;

synchronizing a clock with respect to the first signal;

determining a wait time period between the first signal and the time slot assigned to the remote unit;

timing the period of time lapsing from the receipt of the first signal with the clock, in response to the first signal; and

transmitting said first response signal upon the period time with the clock reaching the wait time period.