Systems and methods for asymmetric backscatter communications
First Claim
1. A method for decoding concurrent signals, comprising:
- transmitting a carrier signal to a plurality of backscatter tags;
receiving a combined signal comprising respective backscattered signals transmitted by the plurality of backscatter tags, wherein the backscattered signals are transmitted at least partially concurrently by the plurality of backscatter tags, and wherein the plurality of backscatter tags transmit the backscatter signals starting at respective offsets and transmission rates;
detecting edges in the received combined signal based on a signal vector formed by in-phase (I) and quadrature (Q) signals corresponding to the received combined signal;
assigning each of the detected edges to streams corresponding to the plurality of backscatter tags, based on one or more of the offsets and transmission rates of the plurality of backscatter tags; and
decoding the streams of detected edges by assigning one of a plurality of values to each of the detected edges of the streams corresponding to the plurality of backscatter tags, wherein the plurality of values correspond to possible edge states of the detected edges.
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Accused Products
Abstract
Systems and methods for backscatter communications are provided that employ a backscatter reader to transmit a carrier signal to multiple backscatter tags having heterogeneous hardware and specifications. In response to receiving the carrier, the tags encode data into the received signal and, concurrently, transmit their respective backscattered signal to the reader. The concurrent signals are received by the reader as a combined signal. The reader detects edges in the received signal, based on the corresponding in-phase (I) and quadrature (Q) signals. The edges are then assigned to streams based on the offset or transmission rate of the tags. In some cases, the reader can detect edge collisions. These collisions can be resolved by causing the colliding signals to be retransmitted or by separating the colliding signals. The individual streams corresponding to each of the tags can then be decoded to identify the originally transmitted data from each tag.
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Citations
29 Claims
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1. A method for decoding concurrent signals, comprising:
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transmitting a carrier signal to a plurality of backscatter tags; receiving a combined signal comprising respective backscattered signals transmitted by the plurality of backscatter tags, wherein the backscattered signals are transmitted at least partially concurrently by the plurality of backscatter tags, and wherein the plurality of backscatter tags transmit the backscatter signals starting at respective offsets and transmission rates; detecting edges in the received combined signal based on a signal vector formed by in-phase (I) and quadrature (Q) signals corresponding to the received combined signal; assigning each of the detected edges to streams corresponding to the plurality of backscatter tags, based on one or more of the offsets and transmission rates of the plurality of backscatter tags; and decoding the streams of detected edges by assigning one of a plurality of values to each of the detected edges of the streams corresponding to the plurality of backscatter tags, wherein the plurality of values correspond to possible edge states of the detected edges. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for decoding concurrent signals, comprising:
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transmitting a carrier signal to a plurality of backscatter tags; receiving a combined signal comprising respective backscattered signals transmitted by the plurality of backscatter tags, wherein the backscattered signals are transmitted at least partially concurrently by the plurality of backscatter tags, and wherein the plurality of backscatter tags transmit the backscatter signals starting at respective offsets and transmission rates; detecting edges in the received combined signal based on in-phase (I) and quadrature (Q) signals corresponding to the received combined signal; detecting a presence of colliding edges among the detected edges, the colliding edges indicating that two or more of the streams have overlapping edges caused by respective backscatter tags transitioning between edge states at a same time; resolving the colliding edges by (1) causing the backscattered signals corresponding to the colliding edges to be retransmitted, or (2) separating the colliding edges; assigning each of the detected edges to streams corresponding to the plurality of backscatter tags, based on one or more of the offsets and transmission rates of the plurality of backscatter tags; and decoding the streams of detected edges by assigning one of a plurality of values to each of the detected edges of the streams corresponding to the plurality of backscatter tags, wherein the plurality of values correspond to possible edge states of the detected edges, wherein detecting the presence of colliding edges includes; plotting the I and/or Q signals corresponding to the received combined signal on respective IQ plots; and identifying a number of clusters in each of the IQ plots, with each cluster in the IQ plots representing a possible edge state, wherein the colliding edges are deemed to be present among the detected edges if the number of identified clusters in any of the IQ plots exceeds a number of possible edge states, and wherein the separating the colliding edges includes; identifying an origin cluster in the IQ plots, the origin cluster representing a constant edge state; identifying midpoint clusters by; locating groups of the clusters that are co-linear; and locating the midpoint clusters among each of the groups of co-linear clusters; and identifying edge differentials based on the located midpoint clusters, the edge differentials indicating signal changes relative to a signal at the origin cluster. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A backscatter reader, comprising:
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one or more antennas configured to communicate with a plurality of backscatter tags by;
(1) transmitting a carrier signal, and (2) receiving a combined signal that includes backscattered signals transmitted by the plurality of backscatter tags at least partly concurrently, wherein the backscattered signals are transmitted by the plurality of backscatter tags at respective offsets and transmission rates; anda microcontroller operable to process transmission logic configured to decode the received combined signal by; detecting edges in the received combined signal based on a signal vector formed by in-phase (I) and quadrature (Q) signals corresponding to the received combined signal; assigning each of the detected edges to streams corresponding to the plurality of backscatter tags, based on one or more of the offsets and transmission rates of the plurality of backscatter tags; and decoding the streams of detected edges by assigning one of a plurality of values to each of the detected edges of the streams corresponding to the plurality of backscatter tags, wherein the plurality of values correspond to possible edge states of the detected edges. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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24. A backscatter reader, comprising:
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one or more antennas configured to communicate with a plurality of backscatter tags by;
(1) transmitting a carrier signal, and (2) receiving a combined signal that includes backscattered signals transmitted by the plurality of backscatter tags at least partly concurrently, wherein the backscattered signals are transmitted by the plurality of backscatter tags at respective offsets and transmission rates; anda microcontroller operable to process transmission logic configured to decode the received combined signal by; detecting edges in the received combined signal based on in-phase (I) and quadrature (Q) signals corresponding to the received combined signal; detecting a presence of colliding edges among the detected edges, the colliding edges indicating that two or more of the streams have overlapping edges caused by respective backscatter tags transitioning between edge states at a same time; resolving the colliding edges by (1) causing the backscattered signals corresponding to the colliding edges to be retransmitted, or (2) separating the colliding edges, assigning each of the detected edges to streams corresponding to the plurality of backscatter tags, based on one or more of the offsets and transmission rates of the plurality of backscatter tags; and decoding the streams of detected edges by assigning one of a plurality of values to each of the detected edges of the streams corresponding to the plurality of backscatter tags, wherein the plurality of values correspond to possible edge states of the detected edges, wherein the detecting the presence of colliding edges includes; plotting the I and/or Q signals corresponding to the received combined signal on respective IQ plots; and identifying a number of clusters in each of the IQ plots, with each cluster in the IQ plots representing a possible edge state, wherein the colliding edges are deemed to be present among the detected edges if the number of identified clusters in any of the IQ plots exceeds a number of possible edge states, and wherein the separating of the colliding edges includes; identifying an origin cluster in the IQ plots, the origin cluster representing a constant edge state; identifying midpoint clusters by; locating groups of the clusters that are co-linear; and locating the midpoint clusters among each of the groups of co-linear clusters; and identifying edge differentials based on the located midpoint clusters, the edge differentials indicating signal changes relative to a signal at the origin cluster. - View Dependent Claims (25, 26, 27, 28, 29)
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Specification