D2D Synchronisation Signal Symmetry Reducing LTE PSS Cross-Correlation
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Solution Overview
Problem
Current D2D communication systems face interference issues due to high cross-correlation between D2D synchronisation signals and LTE PSS signals, leading to increased detection thresholds and decreased detection probability, especially in scenarios without cellular infrastructure.
Innovation Solution
The generation of a D2D synchronisation signal using a SC-FDMA waveform with centrally symmetric or anti-symmetric Fourier coefficients, allowing for reduced cross-correlation with LTE PSS signals, thereby minimizing interference and maintaining detection performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If D2D synchronisation signals use the same waveform as LTE PSS signals, then device compatibility is improved, but cross-correlation interference increases leading to decreased detection probability
Solution Approach 1:
The patent applies asymmetry by designing the D2D synchronisation signal with centrally symmetric or anti-symmetric Fourier coefficients, while LTE PSS signals have different symmetry properties. This asymmetry in signal structure reduces cross-correlation between D2D and LTE signals, allowing both to coexist without interfering with detection probability
Solution Approach 2:
The patent changes the spectral parameters of the D2D synchronisation signal by imposing symmetry constraints on Fourier coefficients. This parameter modification alters the signal's frequency domain characteristics, reducing overlap and correlation with LTE PSS signals while maintaining SC-FDMA waveform compatibility
2Measurement precision
If detection threshold is increased to reduce false alarms from interference, then false alarm rate is improved, but detection probability decreases
Solution Approach 1:
The patent converts the harmful interference from LTE signals into a beneficial situation by designing D2D synchronisation signals with specific symmetry properties that are inherently less susceptible to LTE interference. This allows the receiver to maintain lower detection thresholds without suffering from high false alarm rates, thereby preserving detection probability
3Device complexity
If simple matched filter detection is used for D2D synchronisation signals, then receiver complexity is reduced, but detection performance may be affected by high cross-correlation with LTE signals
Solution Approach 1:
The patent enables simple matched filter detection to work effectively by introducing asymmetry in the form of symmetry constraints on the D2D synchronisation signal's Fourier coefficients. This signal design reduces cross-correlation with LTE signals, allowing the simple matched filter to achieve good detection performance without requiring complex interference cancellation algorithms
Data Source
Figure 1a~1b
Figure 1c
Figure 2a~2c
AI summary
A transmitter (110) and a method therein, configured for generating a synchronisation signal for Device-to-Device (D2D) communication utilising a Single Carrier-Frequency Division Multiplexing Access (SC-FDMA) waveform, wherein a synchronisation sequence is modulating a set of subcarriers. The transmitter (1 10) comprises: a processor (520), configured for determining a synchronisation sequence d u [l], where \d u [l] \ = \d u [L - 1 - l] \, l = 0,1,..., L - 1, and \d u [l] \ = K, for a positive constant K wherein u is a root index and L is the length of the synchronisation sequence d u [l]; and also configured for selecting the root index u from a set of root indices; and in addition configured for generating the synchronisation signal, based on the determined synchronisation sequence d u [l] and the selected root index u. Also, a receiver (120) configured for detecting a received synchronisation signal for D2D communications utilising an SC-FDMA waveform is disclosed.