An efficient anti jamming technique for Wireless Sensor Networks

In Wireless Sensor Networks security is of major concern as it is susceptible to various types of attacks. Jamming is one such Denial of Service attack that has been addressed at the physical layer that prevents the legitimate nodes from performing its basic function thereby decreasing the network performance. Hence anti jamming techniques has become essential for ensuring proper delivery of measured event. Direct Sequence Spread Spectrum (DSSS) used in the standard has few limitations in terms of security level as the number of 15 chip PN sequences used is limited to overcome the problems of storage overhead and energy consumption. The objective of this paper is to propose uncorrelated groups based DSSS technique, which is a slight modification of DSSS used in IEEE 802.15.4 standard, in which all possible 15 chip PN sequences are used to form groups of 5 sequences each. Here each group will be assigned an index and initially a group is randomly selected for spreading and its corresponding index is called as the initial index. In this technique each bit is spreaded with a PN sequence and once all the sequences from the selected group are used, next group will be selected which should be totally uncorrelated with the previous group. The initial index will be transmitted along with the spreaded message. This technique will be effective because the attacker will not be aware of the groups formed and hence it is difficult to find the PN sequence used for spreading. Performance of the technique is evaluated by calculating the probability of matching the groups in the presence of different numbers of jammer along with complexity analysis and by comparing the results with the traditional DSSS technique.