Ultra Wideband Signals And Systems In Communication Engineering: An Overview
Ultra wideband (UWB) signals and systems are emerging as a promising technology for various applications in communication engineering, such as wireless personal area networks (WPANs), positioning and location, radar and imaging, and biomedical sensing. UWB signals have some distinctive features that make them attractive for these applications, such as high data rate, low power consumption, high resolution, robustness to multipath fading, and coexistence with other wireless systems.
This article provides an overview of UWB signals and systems in communication engineering, covering the basic properties, generation methods, signal-processing techniques, channel modeling, communication schemes, antenna design, positioning algorithms, and applications of UWB technology. It also reviews the current standards and regulations for UWB communication systems, as well as some advanced topics and challenges in UWB research.
Basic Properties of UWB Signals and Systems
UWB signals are defined as signals whose fractional bandwidth is greater than 20% or whose absolute bandwidth is larger than 500 MHz [^1^]. Fractional bandwidth is the ratio of the bandwidth to the center frequency of the signal. Absolute bandwidth is the difference between the highest and lowest frequencies of the signal. UWB signals can be classified into two types: impulse radio (IR) UWB and multicarrier (MC) UWB. IR UWB signals consist of short pulses with durations in the order of nanoseconds or picoseconds. MC UWB signals use multiple subcarriers with narrow bandwidths to form a wideband signal.
UWB systems are systems that use UWB signals for transmitting and receiving information. UWB systems have several advantages over conventional narrowband systems, such as:
High data rate: UWB systems can achieve data rates up to several gigabits per second (Gbps) by exploiting the large bandwidth available.
Low power consumption: UWB systems can operate at very low power levels (less than 1 mW) due to the short duration and low duty cycle of the pulses.
High resolution: UWB systems can resolve multipath components and targets with high accuracy due to the fine time resolution of the pulses.
Robustness to multipath fading: UWB systems can cope with severe multipath fading by using rake receivers or diversity techniques.
Coexistence with other wireless systems: UWB systems can coexist with other wireless systems by using spread spectrum techniques or frequency hopping schemes.
Generation of UWB Waveforms
There are various methods for generating UWB waveforms, depending on the type of UWB signal. For IR UWB signals, some common methods are:
Gaussian monocycle pulse: This is a pulse whose shape is proportional to the first derivative of a Gaussian function. It has a zero DC component and a single zero-crossing point.
Gaussian doublet pulse: This is a pulse whose shape is proportional to the second derivative of a Gaussian function. It has a zero DC component and two zero-crossing points.
Hermite pulse: This is a pulse whose shape is proportional to a Hermite polynomial. It has a zero DC component and multiple zero-crossing points.
Pulse position modulation (PPM): This is a modulation scheme that varies the position of a fixed pulse within a symbol interval to convey information.
Pulse amplitude modulation (PAM): This is a modulation scheme that varies the amplitude of a fixed pulse within a symbol interval to convey information.
Pulse shape modulation (PSM): This is a modulation scheme that varies the shape of a fixed pulse within a symbol interval to convey information.
For MC UWB signals, some common methods are:
Multiband orthogonal frequency division multiplexing (MB-OFDM): This is a modulation scheme that divides the available bandwidth into several subbands, each containing multiple orthogonal subcarriers. The subcarriers are modulated by different data streams using quadrature amplitude modulation (QAM) or phase shift keying (PSK).
Multicode direct sequence spread spectrum (MC-DS-SS): This is a modulation scheme that uses multiple spreading codes to ec8f644aee