System and method for determining synchronization point in OFDM modems for accurate time of flight measurement
First Claim
1. A method for determining a synchronization point in an orthogonal frequency division multiplexing (OFDM) modem of a node in a wireless communication network, the synchronization point being used for time of flight (TOF) measurements, the method comprising:
- detecting receipt of a frame by the node;
cross-correlating the receipt of the received frame with a stored waveform in the node to determine the synchronization point; and
performing TOF measurements using the determined synchronization point by operating a counter in the node to count a period of time from receipt of the frame by the node, based on the determined synchronization point, to transmission of a response frame by the node.
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Accused Products
Abstract
A system and method including an algorithm that can use the linear time shift property of the subcarrier modulation to provide accurate frame synchronization for communications between nodes in a wireless network, where nodes employ orthogonal frequency division multiplexing (OFDM) modems. The subcarrier modulation is typically performed with a Fast Fourier Transform (FFT) that includes a time shift between Inverse Fast Fourier Transform (IFFT) and guard interval insertion at transmission, but due to the guard insertion, the system and method of the present invention corrects the time shifts allowing accurate TOF calculations.
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Citations
16 Claims
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1. A method for determining a synchronization point in an orthogonal frequency division multiplexing (OFDM) modem of a node in a wireless communication network, the synchronization point being used for time of flight (TOF) measurements, the method comprising:
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detecting receipt of a frame by the node; cross-correlating the receipt of the received frame with a stored waveform in the node to determine the synchronization point; and performing TOF measurements using the determined synchronization point by operating a counter in the node to count a period of time from receipt of the frame by the node, based on the determined synchronization point, to transmission of a response frame by the node. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A system for determining a synchronization point in an orthogonal frequency division multiplexing (OFDM) modem of a node in a wireless communication network, the synchronization point being used for time of flight (TOF) measurements, the system comprising:
a controller, adapted to detect receipt of a frame by the node, and further adapted to cross-correlate the receipt of the received frame with a stored waveform in the node to determine the synchronization point, and to control the node to perform TOF measurements using the determined synchronization point by operating a counter in the node to count a period of time from receipt of the frame by the node, based on the determined synchronization point, to transmission of a response frame by the node. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
Specification