Coexistence and competition in unlicensed spectrum

Abstract: Spectrum regulation is tricky and until recently the methods used for almost a century has sufficed. But as wireless communication has increased the demands on spectrum has increased. The regulators have responded by relaxing the current regulatory framework as well as opening up more bands for license exempt or unlicensed operation.In unlicensed spectrum users can be expected to act greedily and possibly also break etiquette rules. Using game theory we find that in most cases a user benefits form acting greedily and this decrease total system capacity. It is possible to deter a user from cheating by applying punishment to the user. This function should preferably be incorporated in the access network.We also study the case of networks competing in unlicensed spectrum and find that the most successful network is the one with lowest quality guarantees and with the most dense access network. In the case studied here the greedy behavior of the networks increases the spectrum utilization. We also evaluate a number of cases where two networks that cooperate in unlicensed spectrum. Isolation between the networks is the key factor to achieve better performance than splitting the spectrum.The evaluations are carried out using numerical experiments and game theory. Game theory ia a powerful tool for modelling coexistence problems in unlicensed spectrum, but the systems are too complex to allow a fully analytical treatment.