Introduction to Ultra Wideband (UWB) Wireless Communication Technology
UWB (Ultra Wide Band) is a wireless technology that transmits data at high speed over a short distance with very low power. This technology, which was originally used by the exclusive military, attracted the attention of the world with the official approval of the Federal Communications Commission (FCC) in February 2002. UWB has a series of excellent and unique technical features and is a competitive short-range wireless transmission technology.
1, the concept of UWB
UWB (Ultra Wideband) is a wireless carrier communication technology that uses a nanosonic non-sinusoidal narrow pulse to transmit data without using a sinusoidal carrier, so it occupies a wide spectrum. UWB is a technology that uses a nanosecond narrow pulse to transmit wireless signals, and is suitable for high-speed, close-range wireless personal communication. According to the FCC regulations, the 7.5 GHz bandwidth frequency from 3.1 GHz to 10.6 GHz is the frequency range used by UWB.
In terms of frequency domain, UWB is different from traditional narrowband and wideband, and its frequency band is wider. Narrowband means that the relative bandwidth (the ratio of signal bandwidth to center frequency) is less than 1%, the relative bandwidth is between 1% and 25%, which is called broadband, the relative bandwidth is greater than 25%, and the center frequency is greater than 500MHz. Broadband.
In the time domain, ultra-wideband systems are different from traditional communication systems. The general communication system modulates the signal by transmitting the RF carrier, while the UWB directly modulates the time domain pulse (tens of nanoseconds) using the starting and falling points. The ultra-wideband transmission places the modulation information process in a very wide frequency band. The above is performed, and the frequency range occupied by the bandwidth is determined by the duration of the process.
2. Main technical features of UWB
UWB is a "maverick" wireless communication technology that will bring low-power, high-bandwidth and relatively simple wireless communication technologies to the interface cards and access technologies of wireless LANs and personal area networks (PANs). UWB solves the major communication problems that have plagued traditional wireless technologies for many years. It has the advantages of insensitivity to channel fading, low power spectral density of transmitted signals, low probability of interception, low system complexity, and centimeter-level positioning accuracy.
UWB has the following characteristics:
2.1 Strong anti-interference performance
UWB adopts time-hopping spread spectrum signal, and the system has large processing gain. When transmitting, the weak radio pulse signal is dispersed in a wide frequency band, and the output power is even lower than that generated by ordinary equipment. The signal energy is restored during reception, and a spread gain is generated during the despreading process. Therefore, compared with IEEE 802.11a, IEEE 802.11b and Bluetooth, UWB has stronger anti-interference under the same code rate conditions.
2.2 High transmission rate
The data rate of UWB can reach tens of Mbit/s to several hundred Mbit/s, which is expected to be 100 times higher than that of Bluetooth, and higher than IEEE 802.11a and IEEE 802.11b.
2.3 Wide bandwidth
UWB uses bandwidths above 1 GHz and up to several GHz. The UWB system has a large capacity and can work simultaneously with the current narrowband communication system without interfering with each other. This has opened up a new kind of time domain radio resources in today's increasingly tense frequency resources.
2.4 Low power consumption
In general, a wireless communication system needs to continuously transmit a carrier when communicating, and therefore consumes a certain amount of power. UWB does not use a carrier wave, but sends a transient pulse wave, that is, it is sent directly by O and 1, and the pulse wave is sent when needed, so the power consumption is small.
2.5 Good confidentiality
UWB confidentiality is manifested in two aspects: on the one hand, it uses time-hopping spread spectrum, and the receiver can only solve the transmitted data when the transmitter-side spreading code is known; on the other hand, the transmission power density of the system is extremely low, using traditional The receiver cannot receive it.
2.6 The transmission power is very small
The UWB system has very low transmit power, and communication equipment can communicate with a transmit power of less than 1 mW. Low transmit power greatly extends system power supply operating time. Moreover, the transmission power is small, and the electromagnetic wave radiation has little influence on the human body. In this way, UWB has a wide range of applications.
3. Comparison of UWB and related technologies
UWB technology is very different from other existing wireless communication technologies, which will bring low power, high bandwidth and relatively simple solutions for wireless local area network (LAN) and personal area network (PAN) access. UWB technology solves major problems that have plagued traditional radio technologies for many years, such as channel fading, high system complexity, high cost, and high power consumption. However, UWB communication will not quickly replace other existing wireless communication technologies.
3.1 UWB and IEEE802.11a
IEEE802.11a is one of the wireless LAN standards originally developed by IEEE. It is mainly used to solve the wireless access of users and user terminals in office LAN and campus network. It works in the 5GHz U-NII band, the physical layer rate is 54Mbps, and the transmission layer rate. 25Mbps. It adopts Orthogonal Frequency Division Multiplexing (OFDM) spread spectrum technology; it can provide 25Mbps wireless ATM interface and 10Mbps Ethernet wireless frame structure interface, and TDD/TDMA air interface to support voice, data and image services. When IEEE802.11a is used as a wireless local area network, the communication distance can reach 100m, while UWB can only communicate within a range of 10m. According to Intel's FCC regulations, UWB can achieve transmission performance of up to several hundred Mbps for distances up to 10m, but it is better for IEEE802.11a/b wireless LAN devices at 20m. . Therefore, in the current limited UWB transmit power, UWB can only be used for high-speed data communication within 10m, and 10m to 100m wireless LAN communication needs to be completed by 802.11, of course, compared with UWB, 802.11 power consumption. Large, low transmission rate.
3.2 UWB and Bluetooth
Since the FCC approved UWB for civil wireless communication on February 14, 2002, UWB has been commented on as the killer of Bluetooth, because Bluetooth is the closest wireless communication method in terms of performance and price. UWB, but from the current situation, UWB will not replace Bluetooth. First of all, from the application field, Bluetooth works on the 2.4GHz ISM band, which is not required to be applied, and is mainly used to connect office equipment such as printers and notebook computers. Its communication rate is usually below 1Mbps, and the communication distance can reach more than 10m. UWB's communication rate is several hundred Mbps, and the communication distance is only a few meters, so the application fields of the two are not the same. Secondly, from a technical point of view, after years of development, Bluetooth has a relatively complete communication protocol. Bluetooth's core protocols include physical layer protocols and link access protocols, link management protocols and service development protocols, etc., while UWB's industrial utility protocols are still under development. In addition, Bluetooth is the name of a short-range wireless connection technology standard. The essence of Bluetooth is to establish a common standard for radio air interface and its control software. In this respect, UWB can be regarded as a special type. The way in which radio waves transmit data at high speeds, strictly speaking, does not constitute a complete communication protocol or standard. Considering the high-speed, low-power characteristics of UWB, perhaps in the next-generation Bluetooth standard, UWB may be used as the physical layer communication method. Finally, from a market perspective, Bluetooth products have matured and been promoted and used, and UWB research is still in its infancy. For the above reasons, in the next few years, UWB and Bluetooth are more likely to be both competitors and partners.
Combined with the above discussion, Table 1 can be used to make a simple comparison of three short-range wireless communications.
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