A device to device, D2D, synchronization method that is applicable to a user equipment (103a∼103k, 212∼214, 312∼314, 322∼324, 401, 402, 501, 502, 601), the method comprising: receiving detected signals from a receiver of the user equipment (103a∼103k, 212∼214, 312∼314, 322∼324, 401, 402, 501, 502, 601); and obtaining from the detected signals a first synchronization signal having a first timing information and a second synchronization signal having a second timing information; the method being characterized in further comprising: determining whether to forward one of the first timing information, the second timing information, and none of the first timing information and the second timing information based on an upper bound power restriction of a power level of the first synchronization signal and a power level of the second synchronization signal, a power difference between the power level of the first synchronization signal and the power level of the second synchronization signal, and a priority between the first synchronization signal and the second synchronization signal; and determining whether to transmit a third timing information that is inherent of the user equipment, UE, (103a∼103k, 212∼214, 312∼314, 322∼324, 401, 402, 501, 502, 601) based on whether the power level of the first synchronization signal and the power level of the second synchronization signal are below power thresholds, wherein the upper bound power restriction comprises a first edge power threshold. receiving detected signals from a receiver of the user equipment (103a∼103k, 212∼214, 312∼314, 322∼324, 401, 402, 501, 502, 601); and obtaining from the detected signals a first synchronization signal having a first timing information and a second synchronization signal having a second timing information; the method being characterized in further comprising: determining whether to forward one of the first timing information, the second timing information, and none of the first timing information and the second timing information based on an upper bound power restriction of a power level of the first synchronization signal and a power level of the second synchronization signal, a power difference between the power level of the first synchronization signal and the power level of the second synchronization signal, and a priority between the first synchronization signal and the second synchronization signal; and determining whether to transmit a third timing information that is inherent of the user equipment, UE, (103a∼103k, 212∼214, 312∼314, 322∼324, 401, 402, 501, 502, 601) based on whether the power level of the first synchronization signal and the power level of the second synchronization signal are below power thresholds, determining whether to forward one of the first timing information, the second timing information, and none of the first timing information and the second timing information based on an upper bound power restriction of a power level of the first synchronization signal and a power level of the second synchronization signal, a power difference between the power level of the first synchronization signal and the power level of the second synchronization signal, and a priority between the first synchronization signal and the second synchronization signal; and determining whether to transmit a third timing information that is inherent of the user equipment, UE, (103a∼103k, 212∼214, 312∼314, 322∼324, 401, 402, 501, 502, 601) based on whether the power level of the first synchronization signal and the power level of the second synchronization signal are below power thresholds, wherein the upper bound power restriction comprises a first edge power threshold.