D2D Synchronization Signal Root Index Design for LTE Interference
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Solution Overview
Problem
Existing D2D communication systems face challenges in achieving efficient synchronization between devices while minimizing interference with cellular networks and ensuring compatibility with legacy systems.
Innovation Solution
The use of a D2D synchronization signal (D2DSS) based on a ZC sequence with a unique length and root index, designed to avoid detection by legacy UEs and reduce detection complexity, while supporting fine time and frequency synchronization within D2D groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If a D2D synchronization signal is transmitted using traditional sequences, then legacy UEs can detect the signal, but detection complexity increases and false detection may occur
Solution Approach 1:
The patent applies local quality by using different ZC sequence root indices for different D2D synchronization purposes. Specifically, root indices that are multiples of 6 are used for D2DSS to ensure legacy UEs cannot detect them, while other root indices may be used for other synchronization signals. This localized differentiation in sequence properties resolves the contradiction by making the signal inherently undetectable to legacy UEs while maintaining full functionality for D2D UEs.
Solution Approach 2:
The patent changes the parameter of ZC sequence root index to resolve the detection complexity and reliability contradiction. By constraining root indices to be multiples of 6 for D2DSS, the patent ensures that legacy UEs (which use root indices 25, 29, 33) cannot detect the signal, thereby eliminating false detections and reducing detection complexity for D2D UEs while maintaining synchronization accuracy.
2Adaptability or versatility
If D2D UEs use the same ZC sequence parameters as LTE PSS, then compatibility is maintained, but interference with cellular networks increases
Solution Approach 1:
The patent applies local quality by assigning specific ZC sequence root indices (multiples of 6) exclusively to D2DSS transmissions. This creates a localized quality distinction where D2D synchronization signals have different sequence properties than LTE PSS signals, ensuring that D2D UEs can distinguish D2DSS from cellular signals and preventing interference while maintaining overall system compatibility.
Solution Approach 2:
The patent converts the potential harm of signal interference into a benefit by using the collision between D2DSS and LTE PSS detection as a useful distinction mechanism. Legacy UEs attempting to detect D2DSS will fail (which is beneficial), and D2D UEs can use this detection failure pattern to identify and filter out cellular synchronization signals, thereby converting the interference problem into a useful signal identification mechanism.
3Reliability
If D2D synchronization signals are transmitted periodically, then synchronization is maintained, but detection complexity increases for UEs
Solution Approach 1:
The patent changes the parameter of ZC sequence root index to a specific pattern (multiples of 6) for D2DSS, which provides unique correlation properties that simplify UE detection. This parameter change enables UEs to efficiently identify and synchronize with D2D signals while maintaining periodic transmission for reliable synchronization, thereby reducing detection complexity without sacrificing synchronization maintenance.
Data Source
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AI summary
A method for device-to-device (D2D) communications includes generating, by a synchronization source, a primary device-to-device synchronization signal that is different from a primary synchronization signal (PSS) sent by an Evolved NodeB (eNodeB) and an existing uplink (UL) signal sent by device-to-device communications devices (block 305), and transmitting, by the synchronization source, the primary device-to-device synchronization signal in a single carrier frequency division multiple access (SC-FDMA) waveform (block 315).