subject: Uwb Wireless Communication Technologies And Their Applications - Uwb, Mb-ofdm, Ds-cdma-communication [print this page] System framework, then describes the main technical features and standardization, the last of the UWB Technology prospect.
Keyword: UWB, MB-OFDM, DS-CDMA, IEEE802.15.3a, wireless USB, Bluetooth
An overview of Ultra-Wideband UWB (UltraWideband) is a non-carrier technology, originated in the late 60s, in the past only used in military radar and positioning devices. With the rapid development of wireless communications technology, people have a higher high-speed wireless communications requirements, UWB technologies have been reintroduced. UWB use nanosecond to picosecond-level data transmission of non-sine wave pulse, the bandwidth occupied by these pulses and even up to several GHz, so the maximum data transfer rate can reach several hundred Mbps. While in high speed communications, UWB devices transmit power is very small, only one per cent of the existing equipment a few. Therefore, UWB is a high-speed but low power data communication.
UWB integrity of the system architecture shown in Figure 1. The lower part was the physical layer and MAC layer for the convergence in the layer above the convergence layer is the application layer of the wireless USB, wireless 1394 and other applications. The article mentioned below the MB-OFDM and DS-CDMA belong to the physical layer and MAC layer technology solutions.
Figure 1 UWB system architecture II, UWB technical standards for the two
2003, the Working Group in collecting IEEE802.15.3a proposal, Intel, TI and XtremeSpectrum proposed the multi-band (Multiband), orthogonal frequency division multiplexing (OFDM) and direct sequence code division multiple access (DS-CDMA) three options, then programs and multi-band orthogonal frequency division multiplexing program integration, thus forming a multi-band OFDM (MB-OFDM) and DS-CDMA are two options. The following describes each of these two programs.
1. MB-OFDM and DS-CDMA technical characteristics of the program
MB-OFDM is the core of the 528MHz frequency band into multiple sub-bands, each sub-band with TFI-OFDM (time - frequency interleaved orthogonal frequency multiplexing) method, data transmission in each subband. Traditional sense of the UWB system using less than 1ns pulse cycle, while the MB-OFDM caused by multiple sub-dynamic bandwidth allocation to achieve an increase of symbols of the time. The benefits of a long symbol time is anti-ISI (ISI) ability. But this performance increase is the complexity of sending and receiving equipment for the price, and because of weak signal with OFDM technology enables near perfect energy capture, so it will be far away from communication.
DS-CDMA was first used by XtremeSpectrum firms. It uses low frequency (3.1 ~ 5.15GHz), high frequency (5.825 ~ 10.6GHz) and dual-band (3.1 ~ 5.15GHz and 5.825 ~ 10.6GHz) three modes of operations. Provide low-frequency 28.5 ~ 400Mbit / s transfer rate, high frequency provide 57 ~ 800Mbit / s transfer rate. DS-CDMA over 1GHz, each band of data with very short pulses, with 24 yds pieces of DS-SS (Direct Sequence Spread Spectrum) to achieve coding gain, Correction Method using R-S code and convolution code.
Table 1 shows the MB-OFDM and DS-CDMA are two main technical parameters of the program.
Table 1 MB-OFDM and DS-CDMA are two main technical parameters of the program
2. Standardization Status of UWB Program from the above two techniques proposed date, IEEE802.15.3a Working Group has been unable to reach agreement. Technically speaking, MB-OFDM and DS-CDMA can not compromise with each other, DS-UWB has proposed a general Signaling And hope to compatible with the MB-OFDM, but was rejected MB-OFDM. After three years of fruitless debate competition, IEEE802.15.3a working group to renounce the development of the UWB standard, the Working Group dissolved.
IEEE802.15.3a Working Group dissolved, MB-OFDM WiMedia forum supporters turn via ECMA / ISO standards you want to activate. December 2005, WiMedia with ECMAInternational (International Europe Computer Manufacturers Association) co-formulated and approved the establishment of ECMA 368/369. ECMA368/369 based MB-OFDM technology, support for more than the rate of up to 480Mbps. ECMA has submitted to the ISO standard, the group said the fourth quarter of this year is expected to become ISO standard.
3, UWB technology prospects IEEE802.15.3a Working Group disbanded as the two sides will continue to compete in the technology, perhaps the market will decide which technology to win. Figure 2 shows the application field of UWB, UWB applications can be seen throughout the personal computer, consumer electronics and Mobile Communications.
Figure 2 UWB applications (1) PC and peripherals UWB technology can replace the cable for the PC users with wireless USB, so as to PC and printer, scanner, keyboard, monitor and other peripherals to provide wireless connectivity.
(2) mobile electronic devices and communication equipment
Once PC using UWB as an alternative to short-range cable, digital cameras, digital cameras and mobile consumer electronics products will change. UWB technology can not only capture all the video equipment and personal computers connected, and can be connected directly to display devices, printers and P2P Equipment; the UWB technology makes the mobile phone into a personal Server Can be directly with personal computers, printers, large-screen monitor, speakers and car electrical interconnect.
(3) home consumer electronics products UWB technology will eliminate between home entertainment devices Cable And will provide personal computers, home entertainment equipment and consumer electronics devices wireless connectivity.
Related applications in the UWB, MB-OFDM has been adopted as the wireless USB-IF USB technology; the same time, this year in March, Bluetooth SIG (Bluetooth Special InterestGroup, the Bluetooth Special Interest Group) that will combine the existing MB-OFDM technology and Bluetooth technology, enabling new high-speed applications. In contrast, DS-CDMA, the development of slightly inferior, to seize a large USB market, this year in January, UWBForum established Cable -Free USB Initiative, to develop its own wireless USB specification.
