Radar Signal Timing in TDD Mobile Devices
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Solution Overview
Problem
Mobile communication devices equipped with radar functionality face interference challenges when operating in mobile communication systems due to the wide frequency bandwidth of radar signals, which can disrupt RF communications with base stations and other devices.
Innovation Solution
The solution involves timing the radar operation window within the cyclic prefix period of OFDM symbols in a Time Division Duplex (TDD) wireless communication system, allowing radar signals to be transmitted during redundant or marginally available periods to avoid interference with communication signals, and adjusting transmission power based on path delay and multi-path delay spread uncertainties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If radar signals are transmitted in a mobile communication device, then radar sensing capability is achieved, but RF interference towards base station or neighboring UEs occurs
Solution Approach 1:
The patent segments the transmission timeline into distinct communication slots and radar operation windows. Radar signals are transmitted only during designated radar windows that are separated from communication transmission periods, thereby dividing the operational timeline to prevent interference between radar and communication functions
Solution Approach 2:
The patent utilizes the time dimension by scheduling radar operations during cyclic prefix periods and guard periods when communication signals are not being transmitted. This temporal dimensioning allows both radar and communication to coexist by operating in different time segments of the same frequency spectrum
2Object-affected harmful factors
If radar signal transmission time is advanced to arrive during cyclic prefix reception window, then interference with communication is reduced, but timing precision and path delay information accuracy become critical
Solution Approach 1:
The patent performs preliminary timing calculations based on path delay information before transmitting radar signals. The device pre-determines the optimal transmission time within the cyclic prefix window by calculating the round-trip delay to target objects, ensuring the radar signal arrives and returns within the guard period without interfering with subsequent communication symbols
Solution Approach 2:
The system uses feedback from path delay measurements and timing advance information to adjust radar transmission timing. By continuously monitoring the actual arrival times and comparing with expected times, the system refines its timing precision to ensure radar operations remain synchronized with communication slots
3Reliability
If radar operation window duration is extended to improve sensing coverage, then radar sensing performance is improved, but interference risk to communication increases
Solution Approach 1:
The patent implements partial radar operation within the cyclic prefix window, transmitting radar signals only for the duration necessary to complete essential sensing functions. By using a shortened radar operation window that fits within the guard period, the system achieves adequate sensing performance without extending into communication slots, thus preventing interference
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient radar sensing with minimal interference to uplink and downlink communications, effectively utilizing available radio spectrum and reducing the risk of intersymbol interference, thereby improving coexistence between radar operations and communication systems.
Implementation Method 1
a radar operation window 215 during which to transmit a radar signal 509 and receive a backscatter signal of the radar signal 509... determined timing of the radar operation window is configured to cause the radar signal, when transmitted from the mobile communication device at the determined radar signal transmission time, to arrive at the receiver during a portion of the cyclic prefix reception window
Data Source
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AI summary
A radar sensing function is performed in a mobile communication device that operates in a Time Division Duplex (TDD) wireless communication system having an air interface that comprises a plurality of uplink symbol times associated with symbols transmitted in an uplink direction and a plurality of downlink symbol times associated with symbols transmitted in a downlink direction, and in which each transmitted symbol from a plurality of transmitted symbols has a corresponding cyclic prefix that is transmitted immediately before the corresponding transmitted symbol, and that is a repetition of an end part of the corresponding transmitted symbol. Information about a path delay between the mobile communication device and a receiver is used as one of one or more bases to determine a timing of a radar operation window having a duration that is shorter than a duration of a cyclic reception window of the receiver and comprising a radar signal transmission time and a radar backscatter reception period. The determined timing of the radar operation window is configured to cause the radar signal, when transmitted from the mobile communication device at the determined radar signal transmission time, to arrive at the receiver during a portion of the cyclic prefix reception window of the receiver. The radar signal is transmitted at the determined time.