A new adaptive frequency hopping technique

Abstract

The paper presents a new concept for adaptive frequency hopping wireless networks. In order to reduce the effect of multiple access interference and increase spectral efficiency, we propose to adapt the spacing between the hopping carriers according to the load and channel conditions. Indeed, for a given overall bandwidth and data bit-rate, reducing the separation between adjacent hopping channels has the positive effect of increasing the number of available hopping channels. This can definitely lead to decreasing the collision rate (i.e., reduces the probability of two signals interfering by hopping to the same channel at the same time). On the other hand, decreasing the space between adjacent hopping frequencies makes the system more vulnerable to transmissions in adjacent channels. It is shown that, in addition to the type of transmitter and receiver filters, the optimum carrier spacing depends on the number of users and the type of fading. Our numerical results reveal that an improvement of more than 30% in the overall spectral efficiency can be achieved by using this concept.