Interference Mitigation between Ultra-Wideband Sensor Network and Other Legal Systems

Abstract

Ultra-wideband impulse radio (UWB-IR) sensor network has intensive military and commercial applications. However, the interference between UWB and other existed networks should be casually investigated. In this paper, we consider interference mitigation in UWB sensors in the context of cognitive radio (CR). Firstly, we suggest a general state transition model to characterize the working states evolution of legal networks, also referred to as primary users (PU). Spectrum sensing, used to identify the state of PU, is formulated as detection of a corresponding state sequence. Maximum posterior probability (MAP) criterion is adopted to perform spectrum sensing. By exploring potential gain of state transitions, detection probability for nearby networks is improved significantly. Subsequently, based on the radius basis function neural network (RBF), we present a novel spectrum sculptor to design UWB waveforms. Attributed to the excellent reconfiguration of RBF, our scheme can produce UWB waveforms tracing available spectrums. The designed waveforms can entirely utilize multiple unoccupied bands to maintain uninterrupted communications. Also, sufficient spectral attenuation can be generated in specific bands to mitigate mutual interference between UWB sensors and other networks. Besides, orthogonal waveforms can be easily derived, which either improves transmission performance or provides a flexible accessing strategy for UWB sensors.

Adaptive narrowband interference mitigation by designing UWB waveforms based on radial basis function neural networks

“…More importantly, with no change of hardware structure, the implementation algorithm can adaptively adjust the frequency spectrum to dynamically avoid authorized frequency working bands in a short time [11][12][13]. Figure 1 shows the network theoretical model for UWB pulse generation [9], which according to the external environment such as authorized users' working states, determine the expected optimal spectrum UWB signal t, then set t as the target signal, adaptively update the parameters of the networks including network weight w, position and waveform of base function to get the minimum error between the network output a and target signal t [14]. The detailed description of all components of the network model is presented in the following sections.…”

A novel adaptive spectrum forming filter: Application in cognitive ultra-wideband

“…By adjusting its network parameters adaptively, the frequency domain output of RBF network can avoid the authorized bands flexibly according to the working state of the authorized users [15,28]. Moveover, RBF network can approximate any function at any precision by altering its basis functions [25].…”

“…So, t mainly depends on the state of authorized users obtained by spectrum sensing [15]. One can refer to the popular spectrum sensing algorithms in [29].…”

“…2) If the active authorized users are found working around, UWB devices should change their emission spectrum at once to perform effective spectrum avoidance and eliminate interference to those sensitive wireless systems [15]. Meanwhile, UWB signals should also make full use of the regulatory spectral power of the remaining frequency bands.…”

“…Considering the communication priority of these authorized users, UWB devices should dynamically adjust its emission spectrum according to the working state of authorized bands in order to avoid interfering these primary users [15]. By closing specific subcarriers, orthogonal frequency division multiplexing based UWB multiband signal (MB-OFDM) can flexibly generate the spectrum nulling (or the spectrum notch) to avoid specific legal systems.…”