herein floor(a) represents a rounding down operation; mod(a,b) represents a modulo operation; n1 and k1 identify time positions and frequency positions of the discovery resource elements in the preceding discovery resource period of the current discovery resource period, respectively; n2 and k2 identify time positions and frequency positions of the discovery resource element in the current discovery resource period, respectively; N represents the number of the discovery resource elements in a time direction; K represents the number of the discovery resource elements in a frequency direction; and values of A, B, M and L are all integers.

The central processing unit 74 is further arranged to interleave positions of the discovery resource elements in the preceding discovery resource period of the current discovery resource period using the interleaver and establish a mapping relationship between the positions of the discovery resource elements in the preceding discovery resource period of the current discovery resource period and positions of the discovery resource element in the current discovery resource period according to the result of the interleaving.

The central processing unit 74 is further arranged to randomly select the time positions of the discovery resource elements for sending the device discovery signals in the time direction of discovery resources in the current discovery resource period and establish the following mapping relationship between the frequency position of the discovery resource element in the preceding discovery resource period of the current discovery resource period and the frequency positions of the discovery resource elements in the current discovery resource period: k2=mod(k1+M,K);