Interference suppression using CPP adaptive notch filters for UWB synchronization in stochastic non-linear channels

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Ultra wideband (UWB) is a promising technology in delivering high data rate for short range wireless communication systems. Because of their large bandwidth, UWB signals may encounter some problems especially with high sampling rate requirements. Moreover, coherence existence with other narrowband systems is a major concern which needs to be addressed through proper mechanisms. The problem becomes so complex if multiple users exist. Since narrowband interference (NBI) signals have sparse representation in the discrete cosine transform (DCT) domain, they can be estimated and suppressed using Compressive Sensing (CS). CS also has the ability to reduce the high sampling rate requirements. For training based NBI mitigation with CS, three groups of pilot symbols are used to estimate the NBI signal subspace, the UWB signal subspace, and to provide information about the channel. In this paper, the distribution of pilot symbols among the three groups is investigated in the presence of strong NBI. The investigation is based on the bit error rate performance and throughput. The influence of each pilot symbols group is studied. The performance is also evaluated in the presence of multiuser interference in addition to the NBI. Simulation results show that the size of the third group of pilot symbols which is used to estimate the channel is the most dominant one.

Narrow-band interference (NBI) from the coexisting narrow-band services affects the performance of ultra wideband (UWB) systems considerably due to the high power of these narrow-band signals with respect to the UWB signals. Specifically, IEEE 802.11a systems which operate around 5 GHz and overlap the band of UWB signals may interfere with UWB systems significantly. In this paper, we suggest a novel NBI suppression technique based on singular value decomposition (SVD) algorithm in time hopping UWB (TH-UWB) systems. SVD is used to approximate the interference which then is subtracted from the received signals. The algorithm precision and closed-form bit error rate (BER) expression are derived in the wireless multipath channel. Comparing with the conventional suppression methods such as a notch filter and a RAKE receiver, the proposed method is simple and robust and especially suitable for UWB systems.

Ultra wideband (UWB) is a reliable candidate for supporting a physical layer in Body Area Networks (BAN) and because of their wideband, UWB systems can have their performance degraded due to the interference from narrowband transmission. Methods must be developed to protect UWB systems that are exposed to this negative impact of the narrowband interference (NBI). Most proposed solutions have been developed for coherent and transmitted-reference receivers but a very few of these principles are eligible with the noncoherent energy detector (ED) receiver. The work presented thereafter aims at proposing a novel method to identify and mitigate the narrowband interference in ultra wideband transmissions. We use an efficient algorithm with a modified but still simple energy detector, and the performance of the method is evaluated by means of computer simulations.

<p>Wireless communication applications with large signal bandwidth are developed tremendously in recent times. Due to large bandwidth the wide band communication causes huge power consumption and signal deterioration after addition of narrow band interference (NBI). The ultra wide band (UWB) energy detector, which is highly robust against NBI signal is presented. Compressed sensing is implemented to reduce the power consumption at the analog to digital converter with approximated message passing reconstruction. In addition to this, digital notch is employed to eliminate the NBI affected measurements from compressed version of the received signal before applying it to the energy detector. To analyze the efficiency of the detector, the energy detection and bit error probability of the detector in the absence of NBI and after mitigating NBI is compared. The simulation results are the evidence of effectiveness of the presented energy detector.</p><p> </p>

To solve the coexistence of ultra wideband (UWB) system with other existed narrowband systems operating within the UWB bandwidth, we propose an adaptive non-linear chirp UWB waveform based on the atan function in this paper. With the utilization of cognitive radio (CR) technology and the good time-frequency relationship of the chirp function, the flexible multiple narrowband interferences (NBIs) suppression can be achieved. Simulation results demonstrate the superior multiple NBIs suppression ability of the proposed scheme in direct sequence bipolar pulse amplitude modulation (DS-BPAM) UWB system, which is also compared with the linear chirp pulse based UWB system.

The interference of ultra wideband (UWB) signals on conventional radio systems, called victims, is still an open issue. In this paper we show that not only the interference power but also the amplitude statistics have significant influence on the bit error rate (BER) of the victim. The amplitude probability distribution (APD) of UWB signals at the channel and inside the victim's receiver is studied analytically and verified by simulation. It is shown under which boundary conditions the UWB signal looses its pulsed behavior inside the victim's receiver. From this an interference model for the additional BER caused by UWB is proposed. The theoretical model is evaluated by simulations with a WLAN and a UMTS victim

Received ultra wideband (UWB) signals in most indoor environments are stochastic in nature, typically composed of abundant multi-path components with random attenuation and arrival time. A commonly adopted detection strategy is to use a chosen deterministic template to correlate the received signal segment by segment, and only those segments having significant cross-correlation with the template are selected, temporally synchronized and co-phased in their projections for coherent combining. Correlating a deterministic template with a random signal usually results in only partial energy captured by the receiver since a random signal is of multidimensions. In this paper, we construct a receiver with multiple orthogonal branches to fully capture the signal energy, in much the same way as a quadrature receiver does in conventional digital communications. The local reference signals are derived from the orthogonal expansion of UWB signals. The random projections of a UWB signal onto different orthogonal basis functions are non-coherently combined, leading to the concept of dimension diversity. Dimension diversity can be either used alone, or alongside a Rake receiver to further exploit path diversity. The error performance of proposed receivers is analyzed, and their superiority over the conventional ones is examined by numerical results based on real UWB data.

Ultrawideband (UWB) signals are extremely power limited due to the severe power spectral density constraints obligated by the Federal Communications Committee. Therefore, the design of radiation efficient antennas for UWB signaling is a challenging step in the design and development of impulse radio UWB (IR-UWB) communication systems, especially when these signals coexist with previously standardized narrowband (NB) wireless services. In this paper, a dual-band-notched quad-element UWB multiple-input multiple-output (MIMO) antenna design is presented. The proposed design is capable of suppressing NB interference (NBI). The NBI suppression capability of the proposed design is tested both experimentally and through simulations. Moreover, the experimentally measured spectral characteristics of the proposed design are employed in simulating the bit error rate (BER) performance of IR-UWB systems, considering the biphase modulation (BPM) scheme. Both experimental and simulation results show that the proposed design is capable of improving the BER performance of BPM-modulated IR-UWB systems in an NBI environment by suppressing the NBI signals located at six different frequencies within the bandwidth of the two band notches of the proposed design, while introducing a negligible distortion to the IR-UWB signaling waveforms.

Ultra-wideband (UWB) signals are widely used in radar, navigation and satellite communications. It is rather difficult to process UWB signals. In this paper we adopt dechirp pulse compression method to process the received UWB linear frequency modulated (LFM) signals. UWB signals are converted into signals with frequency components that are proportional to the relative range between the target and the reference target. It means to select low-speed analog-to-digital converters (ADC) for sampling UWB signals. The simulation results show that LFM signal with 600MHz center frequency, 200MHz bandwidth and 30usec pulse width can be processed under 70MHz sampling frequency by means of the method.

A novel scheme to generate ultra-wideband (UWB) signals based on cross-gain modulation (XGM) effect in a DFB laser is proposed. In this scheme, a gain-switched laser (GSL) is used as master laser (ML), the optical pulses are optically injected into a DFB laser, which is used as slave laser (SL). By proper system configuration, UWB monocycle, doublet or triplet UWB signals can be generated after detection by a balanced photodiode. Besides, other modulation formats can also be realized, such as on-off keying (OOK) and pulse amplitude modulation (PAM) by properly modulating the ML optical pulses. Finally, fiber transmission of the modulated UWB signals is experimentally investigated.

Ultra-wideband signal generator based on cross gain modulation effect in a distributed feedback laser

The performance of ultra wideband (UWB) signals transmission using radio-over-fiber (ROF) technology is analyzed. UWB signals are directly modulated onto the optical carrier of wavelength 1550 nm for single mode fiber (SMF) system and 850 nm for multimode fiber (MMF) system. Bit error rates (BER) as a function of SMF and MMF lengths are presented. The ranges of SMF length are 0 to 5.5 km and 25.2 km to 31 km and 0 to 700 m for MMF. By varying the attenuation between the UWB transmitter and ROF modulator and between the photo-detector and UWB receiver, BER of less than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> is achieved for SMF system. Reliable transmission of UWB signals using ROF technology is thus demonstrated. MMF system achieves a BER of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> for lengths less than 450 m

The IEEE 802.15.4a standard for wireless sensor networks is designed for highly accurate ranging with impulse radio Ultra Wideband (UWB) signals. The standard is designed for coherent and non-coherent (energy detector) receivers, thus the choice of complexity is left to the implementer. In this paper, the maximal operating distance is analyzed for ranging, using a coherent receiver and an energy detector under FCC/EC regulations. The analysis is based on the working points of the receivers and a link budget calculation. The preamble of the standard is defined by several parameters, which influence the allowed FCC transmit power, the free space losses and thus the maximal operating distance. It is shown which code and channel combinations achieve the largest operating distance. The best performance is achieved by using long spreaded codes, where coherent receivers can achieve a maximal operating distance up to several thousand meters and energy detectors up to several hundred meters.

Ultra wide band (UWB) is an extremely promising wireless technology for researchers and industrials. One of the most interesting is its high data rate and fading robustness due to selective frequency fading. However, beside such advantages, UWB system performance is highly affected by existing narrowband interference (NBI), undesired UWB signals and tone/multi-tone noises. For this reason, research about NBI cancellation is still a challenge to improve the system performance vs. receiver complexity, power consumption, linearity, etc. In this work, the two major receiver sections, i.e., analog (radiofrequency or RF) and digital (digital signal processing or DSP), were considered and new techniques proposed to reduce circuit complexity and power consumption, while improving signal parameters. In the RF section, different multiband UWB low-noise amplifier key design parameters were investigated like circuit configuration, input matching and desired/undesired frequency band filtering, highlighting the most suitable filtering package for efficient UWB NBI cancellation. In the DSP section, due to pulse transmitter signals, different issues like modulation type and level, pulse variety, shape and color noise/tone noise assumptions, were addressed for efficient NBI cancelation. A comparison was performed in terms of bit-error rate, signal-to-interference ratio, signal-to-noise ratio, and channel capacity to highlight the most suitable parameters for efficient DSP design. The optimum number of filters that allows the filter bandwidth to be reduced by following the required low sampling rate and thus improving the system bit error rate was also investigated.