Narrowband Interference Avoidance Research Articles

Avoidance of narrowband interference in UWB wireless sensor device using square low technology

Impulse radio ultra-wideband system has been adopted in wireless sensor networks research due to its high performance in conditions of active influence of various noises and interferences, the presence of reflections, etc. In this paper, this system represents a transmitter based on the controller STM32 and a receiver implemented using blocks of analog and digital processing based on FPGA. This paper focuses on a realisation of an additional device that can provide the avoidance of narrowband interference in ultra-wideband wireless sensor network system to improve a value of bit error rate. For this purpose, a real device with using square low technique has been developed. According to the results of experiments this approach enables to improve a dependence of the bit error rate on the signal-to-noise ratio.

Generation of balanced quadrature phase shift keyed sequences through guided scrambling

Balanced codes (also called DC-free codes) are widely used in binary communication systems to increase the likelihood of accurate symbol recovery with practical demodulators. Guided scrambling (GS) is recognised as a viable approach to efficiently generate DC-free binary sequences. In this study the authors extend the use of GS to generate balanced sequences of quadrature phase shift keyed (QPSK) symbols by using arithmetic from the ring of polynomials defined over the Galois field of four elements. In addition to ensuring adequate timing information and consistent decision thresholds to improve the performance of practical demodulators, balanced encoding of QPSK symbol sequences creates a null at DC in the spectrum of the equivalent complex baseband signal. This corresponds to a null at the centre frequency of the bandpass QPSK signal that enables the insertion of a pilot tone and avoidance of narrowband interference without filtering or distortion of the signal. The authors outline sufficient conditions for the generation of balanced GS QPSK sequences, and based upon these conditions the authors recommend scrambling polynomials and quotient selection criteria. The authors then present analytical and simulation results that confirm the generation of balanced sequences using this approach.

Noise Resistant OFDM for Power-Line Communication Systems

In this paper, we present a new approach to noise suppression for power-line communications based on orthogonal frequency-division multiplexing (OFDM). Previous work for wireless systems has suggested that augmentation of OFDM using spreading codes prior to modulation offers some narrowband interference (NBI) resistant capabilities. We present a study of the performance of such a system for power-line networks-well known to be affected by such noise. Termed interference suppression OFDM (IS-OFDM) and its counterpart NBI avoidance (NBIA), we also present a further modification of these techniques in order to improve NBI suppression performance. The proposed algorithm, orthogonal narrowband interference avoidance (ONBIA), avoids narrowband interference on contaminated subcarriers while preserving the orthogonality of the spreading code. Both theoretical analysis and simulation results demonstrate the improvements of ONBIA over the standard IS-OFDM and NBIA methods across a wide range of interference-to-signal ratios (ISR).

Narrowband interference avoidance for ultra-wideband single-carrier block transmissions with frequency-domain equalization

In this article, a novel method of performing interference avoidance in next-generation single-carrier ultrawideband block transmission systems is presented. This method relies on the application of a time-domain window to each data block prior to transmission, where the window is optimized such that the required notch depth is achieved for each transmission. Furthermore, a modification of this technique is also detailed, whereby the complexity can be reduced from O(N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) to O(N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) where N is the number of symbols per block. It is shown that the proposed techniques overcome many of the drawbacks of current methods such as transmit power control, frequency notching, and active interference cancellation.

On the Capacity of Ultra Wideband Block Transmission Systems with Narrowband Interference Avoidance

In this letter, the theoretical capacities of single-carrier and multi-carrier block transmission systems that employ narrowband interference avoidance are derived. It is shown that the capacity of an OFDM system that implements active interference cancellation is degraded by approximately one bit per second per Hz at high SNR when 10% of the band is nulled. In contrast, the capacity of a single-carrier system that uses envelope scaling in the time domain to create deep frequency notches is not significantly affected by the nulling process.

Narrowband Interference Avoidance in OFDM-Based UWB Communication Systems

In this letter we present a new method for mitigating narrowband interference in orthogonal frequency-division multiplexing-based ultra-wideband communication systems. The proposed narrowband interference avoidance (NBIA) method performs spectral shaping of the transmitted signal using binary signature sequences with minimum total squared correlation (TSC) to avoid the narrowband interfering signal. We illustrate the proposed method with plots that show the spectrum of the transmitted signal with and without NBIA, and also present numerical results obtained from simulations showing improvement in the bit error rate (BER) performance of the system when NBIA is employed.

Designing optimal pulse-shapers for ultra-wideband radios

Ultra-wideband (UWB) technology is gaining increasing interest for its potential application to short-range indoor wireless communications. Utilizing ultra-short pulses, UWB baseband transmissions enable rich multipath diversity, and can be demodulated with low complexity receivers. Compliance with the FCC spectral mask, and interference avoidance to, and from, co-existing narrow-band services, calls for judicious design of UWB pulse shapers. This paper introduces pulse shaper designs for UWB radios, which optimally utilize the bandwidth and power allowed by the FCC spectral mask. The resulting baseband UWB systems can be either single-band, or, multi-band. More important, the novel pulse shapers can support dynamic avoidance of narrow-band interference, as well as efficient implementation of fast frequency hopping, without invoking analog carriers.