Collision arbitration method and apparatus for reading multiple radio frequency identification tags

• US 6,377,203 B1
• Filed: 02/01/2000
• Issued: 04/23/2002
• Est. Priority Date: 02/01/2000
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Doany, Ziyad Hanna
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US09/496,227
• Time in Patent Office: 812 Days
• Field of Search: 342/42-51, 340/870-1-8, 340/505, 340/10-- 1
• US Class Current: 342/44
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10039 interrogator driven, i.e. synchronous
• CPC Class Codes: G06K 7/10059 transponder driven

Abstract

A method for simultaneously reading a serial number and/or other information from multiple colliding RF signals from RF identification tags requires minimal additional logic in the tag'"'"'s processor and provides for a powerful and rapid sorting and identification scheme. This technique employs a primary communication channel and multiple secondary channels. A locator or reader unit interrogates the tags, which respond with an RF signal. Upon receiving multiple signals, the locator or reader unit commands the RFID tags and requires them to transmit another response, which is transmitted in one of the secondary channels based on a portion of their unique serial identification number, thereby forcing the tags to sort in the secondary channels. These secondary channels are assigned using a portion of the unique serial identification numbers for the tags. The reader then detects an acknowledgment in the occupied secondary channels and commands a tag in a particular channel to move to the primary channel. Once the signal is transmitted in the primary channel, the reader reads the identification number. If there is further collision, the collided tags are returned to the secondary channel and sorted again using a different portion of their ID number. This process continues until all the tags are sorted and identified. Once the tags are all sorted, the tags are assigned yet another channel distinct from the secondary channels that are used for sorting.

Claims

1. A method for communicating with a plurality of buried transmitters, comprising the steps of:

a) transmitting an interrogation signal requesting all buried transmitters receiving the interrogation signal to respond in a primary channel;

b) assigning each buried transmitter whose reply signal is successfully received a unique dedicated channel in a first group of channels;

c) assigning all buried transmitters whose reply signal is not successfully received to a first channel in a second group of channels;

d) commanding all buried transmitters currently assigned to the first channel in the second group of channels to move to one of the channels in the second group of channels based on a portion of a number available to each of the buried transmitters;

e) detecting an acknowledgment from each buried transmitter indicating which channels among the first and second groups of channels are occupied;

f) commanding, one by one, those buried transmitters assigned to each of the channels in the second group of channels in step d) to transmit a signal in the primary channel;

g) commanding those buried transmitters whose signals are successfully received in step f) to move to a unique dedicated channel in the first group of channels; and

h) repeating steps c) through g) until all buried transmitters are assigned a unique dedicated channel in the first group of channels.

2. The method according to claim 1, wherein the portion of the number available to each of the plurality of buried transmitter includes a portion of a number formed from one or more of the following:

a unique serial number, marker type, sub-type, utility, frequency, owner, and time-of-day.

3. The method according to claim 1, further comprising the step of polling each of the plurality of buried transmitters assigned to a dedicated channel using a single command and sequentially receiving, in response to the polling request, data from each of the plurality of buried transmitters in a dedicated channel.

4. The method according to claim 1, wherein each of the plurality of first and second groups of channels is delayed from the primary channel by a predetermined amount of time.

5. The method according to claim 1, wherein each of the channels in the first and second groups of channels is assigned a unique time-frequency space relative to the primary communications channel and all other channels in the first and second groups of channels.

6. The method according to claim 1, wherein each of the channels in the first and second groups of channels is assigned a unique time-frequency-codeword space relative to the primary communications channel and all other channels in the first and second groups of channels.

7. A method for communicating between a single transmitter and a reader unit attempting to communicate with a plurality of other transmitters, comprising the steps of:

a) receiving an interrogation signal requesting any transmitter receiving the interrogation signal to respond in a primary channel;

b) transmitting a reply signal to in response to the interrogation signal received in step a);

c) moving, in response to a second signal from the reader indicating that the transmitted reply signal in step b) was successfully received, to a unique dedicated channel in a first group of channels;

d) moving upon lack of receipt of a second signal from the reader indicating that the transmitted reply signal in step b) was successfully received, to a first channel in a second group of channels;

e) moving, upon receipt of a command to all transmitters currently assigned to the first channel in the second group of channels, to one of the channels in the second group of channels based on a portion of a number available to the single transmitter;

f) transmitting, upon receipt of a command from the reader unit to any transmitter assigned to said one of the channels in the second group of channels, a signal in the primary channel;

g) moving, upon receipt of a signal from the reader that the signal transmitted in step f) in the primary channel was successfully received, to a unique dedicated channel in the first group of channels; and

h) repeating steps d) through f) using a different portion of the number available to the single transmitter in step e) until receiving a signal from the reader indicating that the signal transmitted in step f) was successfully received.

8. The method according to claim 7, wherein the portion of the number available to the single transmitter includes a portion of a number formed from one or more of the following:

a unique serial number, marker type, sub-type, utility, frequency, owner, and time-of-day.

9. A method for communicating between a reader unit and a plurality of transmitters, comprising the steps of:

a) transmitting an interrogation signal requesting all transmitters receiving the interrogation signal to respond in a primary channel;

b) commanding each responding transmitter whose reply signal is successfully received to transmit further transmissions in a unique dedicated channel in a first group of channels;

c) commanding all other transmitters to transmit further transmissions in one channel in a second group of channels based on a portion of a number available to each of said all other transmitters;

d) commanding all transmitters assigned in step c) to each channel in the second group of channels, one channel at a time, to transmit an identification signal in the primary channel;

e) commanding those transmitters whose identification signal is successfully received in step d) to transmit further transmissions in a unique dedicated channel in the first group of channels; and

f) repeating steps c) through e) until all transmitters are assigned a unique dedicated channel in the first group of channels.

10. A method for communicating between a single transmitter and a reader unit attempting to communicate with a plurality of other transmitters, comprising the steps of:

a) receiving an interrogation signal requesting any transmitter receiving the interrogation signal to respond in a primary channel;

b) transmitting a reply signal to in response to the interrogation signal received in step a);

c) moving, in response to a second signal from the reader indicating that the transmitted reply signal in step b) was successfully received, to a unique dedicated channel in a first group of channels;

d) moving upon lack of receipt of a second signal from the reader indicating that the transmitted reply signal in step b) was successfully received, to one of the channels in the second group of channels based on a portion of a number available to the single transmitter;

e) transmitting, upon receipt of a command from the reader unit to any transmitter assigned to said one of the channels in the second group of channels, an identification signal in the primary channel;

f) moving, upon receipt of another signal from the reader that the identification signal transmitted in step e) was successfully received, to a unique dedicated channel in the first group of channels; and

g) repeating steps d) through e) using a different portion of the number available to the single transmitter in step d) until receiving a signal from the reader indicating that the signal transmitted in step e) was successfully received.

11. An apparatus for marking a utility line and for communicating with a reader unit attempting to communicate with a plurality of other similar apparatuses comprising:

an inductor-capacitor network modulating an interrogation signal received from the reader unit and reflecting a modulated reply signal;

a memory storing a number assigned to the apparatus as an identification number;

a processor coupled to the inductor-capacitor network and memory, wherein said processor is programmed to;

a) move, in response to a second signal from the reader indicating that the reply signal was successfully received, to a unique dedicated channel in a first group of channels;

b) move, upon lack of receipt of a second signal from the reader indicating that the reply signal was successfully received, to a first channel in a second group of channels;

c) move, upon receipt of a command to all apparatuses currently assigned to the first channel in the second group of channels, to one of the channels in the second group of channels based on a portion of a number stored in the memory;

d) transmit, upon receipt of a command from the reader unit to any transmitter assigned to said one of the channels in the second group of channels, a signal in the primary channel;

e) move, upon receipt of a signal from the reader that the signal transmitted in step d) in the primary channel was successfully received, to a unique dedicated channel in the first group of channels; and

f) repeat steps b) through e) using a different portion of the number stored in memory in step c) until receiving a signal from the reader indicating that the signal transmitted in step d) was successfully received.