|Ⅱ How UWB works?|
|Ⅲ UWB Characteristics|
|Ⅳ UWB applications|
UWB (Ultra-wideband) technology is a wireless carrier communication technology using a frequency bandwidth of over 1GHz. Although wireless communication is used, its data transmission rate can reach several hundred tog of bits per second. Using UWB technology, signals can transmitted at a very wide bandwidth. The US Federal Communications Commission (FCC) is specified in UWB technology: 500MHz or more bandwidth in 3.1 ~ 10.6GHz band.
The UWB technology began in a pulse communication technology initiated by the 1960s. UWB technology communicates with a ultra-wide band pulse, so it is also known as baseband communication technology and wireless carrier communication technology. UWB is mainly used in a communication system for military radar, positioning, and low-intercept. In February 2002, the US Federal Communications Commission issued a preliminary regulation of civil UWB devices using spectrum and power. In this provision, communication systems with respect to a relative bandwidth greater than 0.2 or any time bandwidth is greater than 500 MHz are called a UWB system, and the UWB technology is approved for civil goods. Subsequently, Japan opened the ultra-wideband band in August 2006. UWB technology becomes the preferred technology of wireless personal LAN communication technology (WPAN).
UWB is essentially an impact pulse with a low duty cycle as an inori-carrier expanded technique of the information carrier. A typical UWB transmits impact burst directly and no longer has a conventional intermediate frequency and radio concept. The signal transmitted can only be seen as a baseband signal, and also a radio frequency signal.
Impact pulses typically use single cycle Gaussian pulses. One information bit can be mapped to hundreds of such pulses. The width of the single cycle pulse is in the nanosecond, with a wide spectrum. UWB has developed a new wireless channel with Ghtz capacity and the highest spatial capacity. CDMA-based UWB pulse wireless transceiver generates a pulse sequence of a certain repetition cycle in the sending end clock generator. The information to be transmitted and the pseudo random code indicating the user address is composed, and the above periodic pulse sequence is modulated. The modulated pulse sequence drives the pulse generating circuit to form a certain pulse shape and the regular pulse sequence, then zoom in to the desired power, and then coupled to the UWB antenna emission. At the receiving end, the signal received by the UWB antenna is amplified by the low noise amplifier, and the input terminal of the correlator is sent. Another input of the correlator adds a pulse sequence that is generated by the user-pseudo-randing code modulated by the originator. The receiving end signal functions along the multiplication, integration and sampling of the locally synchronized pseudo-random code modulation, generating a signal that is separated from the user address information and the signal is then demodulated.
UWB technology solves major problems that plague traditional wireless communication technologies for many years. It has the advantages of low channel decline, low transmission signal power spectral density, low intercept ratios, and low system complexity.
The communication carrier used by the current wireless communication technology is a continuous radio wave. The frequency and power of the carrier varies within a certain range, and the information is transmitted by the state of the carrier. The UWB technology does not use carriers, which transmits data signals by sending nanosecond non-sinusoidal narrow pulses. The transmitter in the UWB system is directly used by pulse small excitation antennas, which does not require the upper frequency conversion required for traditional transceivers, so that the functional amplifier and mixer are required. The UWB system allows very low broadband transmitters. At the same time, the receiver of the UWB system is also different from the traditional receiver. It does not require intermediate frequency processing, so the implementation of the UWB system structure is relatively simple.
In civil goods, the UWB signal is generally required to be within 10m. According to the modified channel capacity formula, the transfer rate of civil commodities can reach 500 mbit / s. UWB technology is an ideal modulation technique for implementing personal communication and wireless local area network. The UWB technology exchanges high-speed data transmission at a very wide frequency bandwidth, and does not occupy the crowded frequency resources, but shared the frequency band used by other wireless technologies. In military applications, UWB technology can utilize huge spread spectrum gains to achieve long distance, low intercept ratio, low detection rate, high security, and high speed data transmission.
The UWB system uses an intermittent pulse to send data. The pulse duration is very short, typically between 0.20 to 1.5 ns. The system consumes low power, and the power consumption of the system is only a few hundred micro wool to dozens of millions when high-speed communication. The power of civil UWB devices is generally about 1/100 of the power required for traditional mobile phones, and is about 1/20 of the power required for Bluetooth devices. The military UWB radio is also very low. Therefore, the UWB device has great advantages compared to traditional wireless communication devices on battery life and electromagnetic radiation.
As the physical layer technology of the communication system, UWB technology has natural safety performance. Since the UWB signal generally disperse signal energy within a wide range of bands, the UWB signal corresponds to the white noise signal for the general communication system. In most cases, the power spectral density of the UWB signal is lower than the power spectral density of natural electronic noise. It is a very difficult thing to detect the pulse signal from the electronic noise. After encoding the pulse parameters, the pulse detection will be more difficult.
Since the radio frequency signal of conventional wireless communication is mostly a continuous signal or its duration is much larger than the multipath propagation time, the multipath propagation effect limits the communication quality and the data transmission rate. Ultra-wideband radio transmitted single-cycle pulse whose duration is extremely short and the duty cycle is extremely small, so the multipath signal is separable in time. If the multipath pulse is overlapped in time, the multipath transmission path length should be less than the product of the pulse width and the propagation speed. Since the pulse multipath signal does not overlap in time, the multipath component is easily separated to take advantage of the energy of the transmitted signal. A large number of experiments show that the multipath environment of the conventional radio signal multipath fading is from 10 to 30 dB, and the decline of the ultra-wideband radio signal is less than 5 dB.
The puncturing pulse has high positioning accuracy. Using UWB technology, it is easy to position the positioning and communication. UWB technology has strong penetration capabilities that can be accurately positioned indoors and underground. GPS can only work within the visual range of GPS positioning satellites. Unlike GPS, the ultra-wideband radio locator can give relative positions, and its positioning accuracy can reach the centimeters, in addition, the ultra-wideband radio locator is cheaper in price.
In project implementation, UWB technology is much simpler than other wireless technologies, and can be fully digitally implemented. It only needs to generate a pulse in a mathematical manner, and modulate the pulse. The circuit required to achieve the above process can be integrated into a chip, and the cost of the device is very low.
The UWB system transmits and receives the non-sinusoidal narrow pulse of the nanoseconds. It does not require the use of a sinusoidal carrier to be modulated, and the receiver can directly complete signal detection using the associated device. In this way, the transceiver does not require a complex carrier modem circuit and filter. Only one digital mode is required to generate a non-sinusoidal narrow pulse of the nanosecond. Therefore, UWB technology can greatly reduce the complexity of the system, reduce the volume of the transceiver, reduce the power consumption of the transceiver, easy to digitize, and adopt software radio technology.
UWB has a powerful data transmission rate advantage, but is limited by transmit power. Providing high-speed wireless data transfer within a short distance will be an important application field of UWB, such as the current WLAN and WPAN various applications. In general, UWB is mainly divided into two aspects of military and civilian use.
(1) Military communication
Military communication requirements present large capacity, low cut (LPI / D), high rate, UWB can meet these needs.
(2) Military radar and navigation
UWB technology can achieve three functions of radar, positioning, communication, particularly suitable for radar high detection resolution and miniaturization requirements for easy installation on small aircraft and mobile chariots. In addition, UWB technology has a wide range of application value in the fields of wearing wall/ground, high-precision positioning navigation systems, etc., and these technologies have been in the stage of actual equipments in the US military.
UWB is broad in wireless domain, high-speed data transmission, etc.. Its application development trend will focus mainly in the following aspects.
(1) Wireless Personal Space Network (WPAN)
It also known as a home network, is one of the main development directions of UWB. Today, home electronics consumption products have emerged, with the development of network technology, people want to connect home entertainment systems with Internet.
(2) Wireless Adhoc network
The advantages of the UWB itself can significantly improve the performance of the wireless Adhoc network. UWB anti-multipath interference robustness solves the difficulties that plague wireless Adhoc networks. UWB low-emission power makes UWB-based wireless ADHOC networks can coexist with existing networks, saving valuable spectrum resources, improves data rate, thus the application of large-scale sensor networks is possible.
(3) Wireless USB (WUSB)
WUSB technology is a new communication standard based on ultra-wideband wireless communication technology, which extends the connectivity between the devices via USB interface and the most advanced wireless communication technology. While inheriting the higher transmission rate advantage of the traditional wired USB 2.0 standard, the flexibility and extreme degree of freedom of UWB transmission technology can be fully utilized, and the equivalent bandwidth of 480 Mbit/s can be achieved within 3m distances. Features such as safety, reliability, and power consumption.
(4) Intelligent Wireless LAN
The basic requirements of the smart wireless LAN are to provide a low-cost, low-power intelligent transport network. The UWB system can be easily applied to wireless local area networks, such as intelligent transportation systems, providing high performance, low-cost solutions.
(5) Che-sheika system
The sensing system based on ultra-wideband technology improves the resolution of traditional close-range moving sensors, relying on high quality accuracy and distinction between ultra-wideband. Intelligent collision avoidance and cruise control system is not far away.
(6) Outside the network
This network is mainly used in the outdoor meeting of the handheld computer (PDA) data exchange, the rapid download of the digital kiosk newspaper, and the rental and sale of audio-visual products, these practical value constitute a huge potential market for UWB applications.
Of course, UWB has many applications in the fields of medical, services, and its ultimate goal is to seamlessly coexist with other heterogeneous networks and work together to achieve communication with anytime.