A method in a first base station for determining a spectrum allocation to be used by the first base station in a wireless network and for informing other second base stations about said spectrum allocation, which wireless network is dedicated a spectrum S, and which first base station is associated with a first operator, the method comprising: detecting a number N of second signals, wherein each second signal is transmitted by a respective second base station to announce its intended use of said spectrum at a time t, each second base station being associated with a respective second operator or the first operator, wherein the number N of second signals is one or more than one, determining the spectrum allocation to be used by the first base station at the time t as a subset of the spectrum S, wherein a bandwidth of the subset of the spectrum S allocated to the first base station is a function of N, and the method further comprising: sending a first signal to each second base station to announce that the first base station intends to use said subset of the spectrum S at the time t, wherein the first signal comprises a first identity Id x associated with an order x, wherein each one or more second signals comprise a respective second identity associated with a respective order, wherein the first identity and the one or more second identities make up a set of identities {Id n}, and wherein an allocated position of said subset of the spectrum S is given by the order x of the first identity Id x in the set of identities {Id n}. detecting a number N of second signals, wherein each second signal is transmitted by a respective second base station to announce its intended use of said spectrum at a time t, each second base station being associated with a respective second operator or the first operator, wherein the number N of second signals is one or more than one, determining the spectrum allocation to be used by the first base station at the time t as a subset of the spectrum S, wherein a bandwidth of the subset of the spectrum S allocated to the first base station is a function of N, and the method further comprising: sending a first signal to each second base station to announce that the first base station intends to use said subset of the spectrum S at the time t, wherein the first signal comprises a first identity Id x associated with an order x, wherein each one or more second signals comprise a respective second identity associated with a respective order, wherein the first identity and the one or more second identities make up a set of identities {Id n}, and wherein an allocated position of said subset of the spectrum S is given by the order x of the first identity Id x in the set of identities {Id n}. sending a first signal to each second base station to announce that the first base station intends to use said subset of the spectrum S at the time t, wherein the first signal comprises a first identity Id x associated with an order x, wherein each one or more second signals comprise a respective second identity associated with a respective order, wherein the first identity and the one or more second identities make up a set of identities {Id n}, and wherein an allocated position of said subset of the spectrum S is given by the order x of the first identity Id x in the set of identities {Id n}.