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

1.1 Impulse Radio (IR) Ultra Wideband (UWB) Communications Ultra wideband (UWB) communication is a fast emerging technology that offers new opportunities such as high data rates, low equipment cost, low power, precise positioning capability and extremely low interference Ghawami (2005). A wide range of possible UWB communication system applications includes radars due to UWB ultra high precision ranging at the centimeter level, wireless personal area networks (WPAN), sensor networks, imaging systems, UWB positioning systems, etc. Yang (2004), Kshetrimayum (2009). From a commercial point of view, the high data rates are the most attractive feature of UWB systems for which speeds of over 100Mb/s have been demonstrated Ghawami (2005). There exist three main types of UWB technologies: impulse radio (IR UWB), direct sequence (DS UWB), and multi-band orthogonal frequency division multiplexing (MB OFDM) Ran (2009). IR UWB communication technique is essentially different from all other communication techniques because it is carrier free and uses for communication between transmitters and receivers very narrow radio frequency (RF) pulses generated from the UWB pulse generator, while traditional transmission systems transmit information by varying the power, frequency, and/or phase of a sinusoidal wave in a modulation process Kshetrimayum (2009), Yao (2007). Consequently, complicated frequency mixers and local oscillators for carrier frequency up and down conversion are not necessary Yao (2007). IR UWB modulation techniques are especially important because the UWB spectrum has been made available by the Federal Communication Commission (FCC) and it can be used with IRs developed to date Lin (2005). Waveforms for IR UWB are designed to obtain a flat frequency response over the bandwidth of the pulse and to avoid a DC component. The large spectrum of a UWB signal may interfere with existing users. In order to keep this interference to the minimum, FCC specifies spectral masks for different applications, i.e. the allowed power output for specific frequencies Ghawami (2005). A contiguous bandwidth of 7.5GHz is available in the frequency interval of (3.1− 10.6)GHz at a maximum power output of −41.3dBm/MHz which is considered as extremely low Ghawami (2005). The power spectral density (PSD) of UWB systems defined as a ratio of the transmitted power P in watts and a signal bandwidth B in hertz is extremely low as compared to other communication systems due to the very wide bandwidth B of short pulses that are typically of nanosecond or picosecond order Ghawami (2005). The selection of the impulse signal type for IR UWB communication system is essential since it determines

The 5G prospect of seamlessly connected global devices with delay-tolerant communication, millisecond latency and gigabits per second data rate suggests the need for location-aware devices, systems and networks. This requires new methods for high resolution positioning services. It is however believed that Impulse Radio (IR) Ultrawideband (UWB) promises better positioning methods for accuracy-critical situations expected in 5G setting. This paper discusses the IR UWB D2D-based localization for ultra-dense networks. It proposes an IR-UWB D2D WWAN along with its cluster formation scheme. This is followed with performance evaluation of the cluster lifetime and system throughput. Also proposed is an IR UWB D2D-propagation-based combined localization and communication scheme (UD-CLOCS). Results of related UD-CLOCS performance assessment experiments have been impressive while some highlights are presented in this paper. It is believed that the proposed solutions have potential for robust and cost efficient localization in 5G setting as well as prospect to decongest licensed spectrums in 5G wireless environment.

Ultra Wideband (UWB) communications are steadily gaining acceptance worldwide, as theregulatory bodies of several countries define its frequency bands and rules of operation. OutofthemanytechnologiesavailabletogenerateanUWBsignal,twoofthemhavebeenfavored,in recent standardization activities, namely Orthogonal Frequency Division Multiplexing(OFDM) and Impulse Radio (IR). On one hand the IEEE 802.15.3a standard defines an UWBsignal based on OFDM, which consists of a large number of digitally-generated narrow sub-carriers. On the other hand, the IEEE 802.15.4a standard defines an UWB signal based onpulses of short duration, technology known as IR. In addition to these technologies includedin standards, other modulation schemes have been proposed for UWB, such as frequency-modulated UWB, or IR transmitting even shorter, sub-nanosecond pulses. The latter has theadvantage of providing very accurate ranging and localization estimates based on the time ofarrival, which can be measured with high precision thanks to the large signal bandwidth.In this chapter we will address the challenges encountered in the transmission and detec-tion of an Impulse Radio Ultra Wideband (IR–UWB) signal in environments with multipathpropagation. The main problem in such systems is that multipath produces time dispersionresulting in a very large number of resolvable paths at the receiver. We will argue that it isconsiderably difficult to design receivers that have both high efficiency in capturing the re-ceived signal energy and low complexity. The traditional approaches, such as correlating thereceived signal with a local template, or the RAKE Receiver, suffer from poor performancesince they have to lock to a single propagation path, or a small subset of them, respectively.Non-coherent receivers also fail to deliver the full potential of UWB; in particular, they do notprovide sufficient ranging accuracy.Motivated by this challenge, in this chapter we develop a receiver architecture based on afrequency domain filter bank. The receiver consists mainly of a stage of bandpass filters fol-

In-car wireless data communications systems require a short-range unlicensed radio communications technology that causes a very low level of interference in the other, already deployed radio links and networks, offers low and medium data rate, can reuse the already occupied radio-frequency (RF) bands, and assures low probability of message collisions. Ultrawide band (UWB) impulse radio employs RF pulses with very short duration to carry the information; consequently, it is an optimal candidate for the in-car wireless communications and intravehicular wireless sensor networks. Data rate and shape of RF carrier pulse determine the performance of a UWB radio link. To limit the interference caused, the maximum power radiated by an UWB device is restricted by the Federal Communications Commission (FCC) in the U.S. Introducing a new mathematical model and starting from the FCC regulations, analytical expressions for the calculation of FCC power limits are derived here. It is shown that the low- and high-rate UWB impulse radio systems are peak and average power limited, respectively. The relationship between the mathematical model and the parameters of an UWB carrier pulse used in a built UWB radio is established. The performances of RF carrier pulses known from the literature are evaluated and compared. All expressions derived are verified by measurements.

An adaptive beamforming method based on radial-basis function (RBF) neural network is examined for ultra-wideband (UWB) array illuminated by nearfield source in this paper. An analysis of the principle of space-time processing employing Gaussian monocycle model as UWB signal is conducted. The nearfield regionally constrain of UWB beamformer is reflected by a set of samples exerted on neural network training sample space. The recursive least square algorithm has been used for network weights updating. It improves the robustness against large errors in distance and directions of arrival. The efficiency and feasibility of presented approach is proved through the experimental results.KeywordsRadial Basis Function Neural NetworkUniform Linear ArrayNeural Network SystemRadical Basis FunctionCompensate Time DelayThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

In this paper, a novel detection algorithm based on variance detection (VD) is proposed for non-coherent impulse radio (IR) ultra-wideband (UWB) receivers. In the VD-based detection algorithm, after the received IR UWB signals are squared, their variance instead of their mean is measure to recover information bits. Computer simulations show that as compared to the conventional energy detection (ED) based receiver, the newly proposed VD-based receiver can achieve a much better bit-error-rate performance under both AWGN and multipath channels. Furthermore, unlike the conventional ED-based receiver, which is vulnerable to narrowband interference (NBI), the VD-based receiver has an inherent ability to mitigate the destructive effects caused by strong NBI.

An indoor positioning system (IPS) is a technology employed to locate objects and people within a building scenario using signal processing or other sensory information. Ultra Wide Band (UWB) is a versatile wireless technology that can be employed as an IPS and has shown very good performances. UWB can be used in many scenarios and its effectiveness in through wall detection along with its excellent resolution for person localization is one of the best applications of Impulse Radio (IR) UWB. The main objective of this work is to propose a concept for intelligent radar systems employing UWB augmented by machine learning approaches to not only localize but understand the location of a person or target within a building. Although suitably developed UWB is excellent for obtaining localizing data it does not automatically understand what that location effectively means or where it is thus further methods are required to create meaningful data for end user appreciation. Learning from the huge amount of UWB signal data through Multi Class Support Vector Machine (MC-SVM) architecture enables a truly evolving scheme to both localize targets and identify them in a useful way. Statistical analysis of the experimental results supports the proposed algorithm.

We investigate timing tolerances of ultra-wideband (UWB) impulse radios. We quantify the bit-error rate (BER) sensitivity to epoch timing offset under different operating conditions, including frequency-flat fading channels, dense multipath fading channels, multiple access with time hopping, and various receiver types including sliding correlators and RAKE combiners. For a general correlation-based detector, we derived in Part I unifying expressions for the decision statistics as well as BER formulas under mistiming, given fixed channel realizations. In Part II, we provide a systematic approach to BER analysis under mistiming for fading channels. The BER is expressed in terms of the receiver's energy capture capability, which we quantify under various radio operating conditions. We also develop the optimal demodulator in the presence of timing offset and show a proper design of the correlation-template that is robust to mistiming. Through analyses and simulations, we illustrate that the reception quality of a UWB impulse radio is highly sensitive to both timing acquisition and tracking errors. © 2005 IEEE.

The recently allocated 71-76 GHz and 81-86 GHz bands provide an opportunity for realising Line Of Sight (LOS) links for directional point-to-point "last mile" applications. An efficient use of this spectrum may allow wireless to finally "catch up" with wires, leading to systems such as "multi-Gigabit wireless Ethernet," and "wireless fiber." However, the transmission at such a frequency range shows some additional challenges compared to lower frequency bands, from both technological and propagation point of view, which makes difficult to use them efficiently. In this scenario, IR (Impulse Radio) UWB (Ultra Wide Band) technology might offer some more degrees of freedom for the design of a highly integrated and low cost transceiver. This work has at its core the comparison of two main IR-UWB architecture transceivers operating in E band, focusing their performance.

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.

Power efficient ultra-wideband based wireless communication for wireless body area network applications

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.

This paper describes the efforts required for the precursor mission Wireless Compose (WICO), a sensing and positioning experiment, which is operated in the Columbus module of the International Space Station (ISS). Moreover, a Ground Reference Model is deployed in the Evolution & Design of Environmentally closed Nutrion-Sources (EDEN) laboratory in Antarctica by German Aerospace Centre (DLR). It evaluates also agriculture/vertical farming concepts in human spaceflight. WICOs main objective is the deployment of a wireless sensor network for sensor data acquisition and the demonstration of positioning capabilities on the ISS. The wireless sensor network (WSN) is based on impulse radio - ultra wideband (IR-UWB) in the physical layer, which also allows time-of-flight measurements between two special locations. The utilization of wireless technologies in space habitats provides a great potential for several kinds of applications, decreasing the harness complexity and providing easier access for installation as well as maintenance tasks. For this reason, WICO also uses energy harvesting from internal light sources to drive the sensor modules thus allowing maintenance-free operation. The paper describes the hardware design, the operational concept and aspects of applied quality and safety requirements for Human Spaceflight. Finally, the status is presented with a focus on the analysis of different applications on Earth and in space for the implementation of wireless sensor networks in order to help and to identify new applications for future space missions.

The demand for high data rate applications is on the rise in the recent years which is due to the rapid growth in wireless communication. The existing technologies like Wireless Fidelity (Wi-Fi) and Bluetooth cannot support such high data rates because of their narrowband and also they drain the battery at rapid pace. Ultra Wide Band (UWB) system differs from conventional narrow band system by transmitting short duration pulses occupying a large bandwidth with power levels almost comparable to that of the noise floor. Any communication technology which uses more than 500 MHz of bandwidth in the range of 3.1 to 10.6 GHz is defined as UWB. The transmitter side of impulse radio consists of pulse generator and modulator. The pulse generator is used to generate the required short pulse in the desired range of frequency. The proposed pulse generator is of pulse combination type impulse generator which is fully digital constructed with MOS Current Mode Logic (MCML) as Fine Delay Elements without using passive components thus reducing circuit complexity. The proposed pulse generator is designed using 90 nm technology with 1 V supply voltage. The maximum power consumption is 330 μW. The output voltage shape complies with FCC regulation.

Measurements on ultra-wideband (UWB) pulse propagation over the ground show the presence of three distinct propagation regimes: (1) in the first regime, the signal power decreases as ~ d <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> , where d is the separation distance between the transmitter and the receiver; (2) in the second regime, the signal power decreases on the average as ~ d <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> with distance, but exhibits interference maxima and minima; (3) in the third regime, the signal power decreases as ~ d <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> . Theoretical analysis indicates two characteristic length scales d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> and d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , called first and second breakpoint distances, determine the sizes of the three propagation regimes. These characteristic lengths depend both on the geometrical parameters such as the heights of the transmitter (h <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> ) and the receiver (h <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) over the ground as well as on UWB pulse properties such as pulse duration (t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> ) and cycle time (t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ). Simple expressions for break points exist when h <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> , h <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> >> ct <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> and d >> h <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> : d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> ≈ 4h <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> h <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /cT <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> ≈ 4h <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> h <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> B/c, and d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ≈ 4h <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> h <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /cT <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ≈ 4h <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> h <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> /c, where B ~ 1/t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> is the bandwidth and f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ~ 1/t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> is the center frequency of the UWB pulse. For a given transmitter height h <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> , the loci of first and second breakpoints in the (d, h <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) plane are hyperbolas with the transmitter and its image as the foci. Based on the propagation results presented here, we suggest that waveform diversity can effectively be used to improve the performance of a UWB based adaptive communication or navigation system.