determine at most one discovery resource element for sending the device discovery signals in the current discovery resource period according to the positions of the discovery resource elements which send the device discovery signals in the preceding discovery resource period of the current discovery resource period and the mapping relationship.

The central processing unit 74 is further arranged to establish mapping relationships k2=mod(floor((n1*K+k1+A)/N),K) and n2=mod(n1*K+k1+A,N), or

establish mapping relationships n2=mod(floor((k1*N+n1+B)/K),N) and k2=mod(k1*N+n1+B,K); or

establish mapping relationships k2=mod(k1+M,K) and n2=mod(n1+k1+L,N); or

interleave frequency positions of the discovery resource elements in the preceding discovery resource period of the current discovery resource period using an interleaver, establish a mapping relationship between the frequency positions of the discovery resource elements in the preceding discovery resource period of the current discovery resource period and frequency positions of the discovery resource elements in the current discovery resource period according to the result of the interleaving, and then establish a mapping relationship of n2=mod(n1+k1+L,N);