1 introduction
The ultra-wide band (UWB) communication has the high speed, the high performance, the low power loss, the low cost, the anti-multi-diameters to decline, the easy digitization and so on many merits. In the Internet, multimedia and wireless communication technology fusion today, it is realizes in the small scope the seamless cover wireless multimedia transmission demand popular technological means that regards as the new generation wireless territory net physics level standard technology.
At present UWB has two big standards: First, take Intel Corporation as the first submission multi-belt Orthogonal Frequency Division Multiplexing (MB-OFDM) plan; Another is as the first submission expands the code division multiple access (DS-CDMA) plan straight take Freescale Corporation. But the MB-OFDM plan has become MBOA alliance standard in fact. Based on this proposed the time-frequency interweaves the MB-OFDM way, has many similarities with traditional OFDM, also conforms to FCC about the UWB definition, has the UWB characteristic, is one kind of new UWB correspondence realizes the way, enabled the MB-OFDM chip to have more and more many manufacturer supports and the application.
2 key technologies
1) multi-frequency band division
FCC announces the UWB signal the definition is: The relative bandwidth of (ratio of signal band width and the center frequency) is bigger than 0.2 or the absolute bandwidth is bigger than 500 MHz the radio signals. The UWB system may, in the emissive power spectral density is smaller than in the - 41.3 dBm/MHz situations, the use does not need 3.1~10.6 CHz frequency bands which is authorized. Here has not limited the UWB signal to realize the way, so long as the absolute bandwidth is bigger than 500 MHz, must use the pulse by no means to be radio. Therefore, the MB-OFDM-UWB technology has broken the traditional viewpoint. May divide into this frequency band 14 band widths is 528 MHz innertubes, 5 frequency band group: 1 group: 3 168~4 752 MHz; 2 groups: 4 752~6 336 MHz; 3 groups: 6 336~7 920 MHz; 4 groups: 7 920~9 504 MHz; 5 groups: 9 504~1 056 MHz. Because UWB effective bandwidth in 3.1~5 GHz, therefore, has 1 group of 3 innertubes available, other retentions spare.
2) the time-frequency interweaves the (TFI) technology
The time-frequency interweaves technical schematic drawing as shown in Figure 1.
The OFDM mark sub-takes to bring with in 3 carries on the time domain frequency range to interlock the transmission, namely in OFDM mark time, has an innertube in the work. Through interlocked various innertubes signal, the UWB system likely has used the entire band width, like this might in be smaller in much band widths the process information, not only reduced the design the order of complexity, the power loss and the cost, moreover could also raise the frequency spectrum use factor and the flexibility, was helpful in globally conforms to the related standard.
3) circulates the prefix and the protection gap design
In each innertube uses the OFDM modulation, completes with 128 IFFT, each sub-carrier realizes the constellation mapping with QPSK. The OFDM mark space is 312.5 ns,3 mark is one cyclical 937.5 ns, the sub-intercarrier distance is 4. Uses 60.6 ns circulation prefix to resist the multi-diameters, 9.5 ns protection gap provides the sufficient frequency band switching time, the IFFT cycle is 242.4 ns, the parameter see Table 1. Interweaves through the frequency-hopping the information bit to the sub-carrier, has the good frequency diversity effect and the anti-frequency selectivity decline performance.
4) extendibility design
The MB-TFI-OFDM technology has the good extendibility, can give dual attention to the present technology in the realizability and may the promotion. The channel coding uses the convolution code, the code rate has 1/3,11/32,1/2,5/8 and 3/4, the system support’s data rate has 55,80,110,160,200,320,480 Mbit/s. The use frequency band may expand from 3 frequency band groups to 7 frequency band groups.
3 system performances and characteristic
3.1 performance analyses
System carries on the simulation using the MATLAB software to MB-TFI-OFDM the UWB, shown in Figure 2 after frequency-hopping’s OFDM mark the power spectral density simulation profile which sub-takes to bring with in 3, obviously, each innertube band width approximately is 528 MHz, uses the time-frequency to interweave the technology to be able to realize in the same time uses the different frequency band work, but will not cause between the mark to disturb. Therefore, in the different frequency band’s 3 OFDM signal may the parallel transmission, the system capacity be big, the channel use factor is high, the frequency spectrum is more flexible.
The reliability is a system performance important target, expressed by mistake in this with the wrapping rate curve. As shown in Figure 3, harms Bao Lv is increases along with the signal-to-noise ratio reduces, and under same wrapping rate, the high speed corresponds the high signal-to-noise ratio by mistake, therefore, uses the high speed the MB-TFI-OFDM ultra-wide band system, the anti-noise and disturbance ability are very strong, have the very big flexibility, may facilitate adapts the different local frequency spectrum standard. But the high speed can only obtain on certain distance, namely the transmitting range and the speed are restrict mutually, therefore the UWB system has high characteristics and so on speed, short distance. Obviously, this kind of MB-TFI-OFDM the UWB technology satisfies WPAN the data rate and the error rate and the transmitting range request.
3.2 technical merits
1) the anti-multi-diameters, catch multi-diameter signal ability. Overcomes the latency expansion which with the aid of the circulation prefix the multi-diameter channel said that with the structure simple receiver, can catch in the highly many diameter environment to more signals, the electric circuit is simple, the cost is low, the power loss is low, the battery may support the mobile equipment long time long-term usage.
2) the frequency spectrum flexibility is strong, the coexistence is good. The UWB use does not need to be authorized the frequency band, guaranteed that to will not be authorized the frequency band equipment to have the disturbance. The MB-OFDM-UWB signal is by a/D switch production, the available software dynamic opens or closes certain specific frequency bands, causes it to tally local stipulated that this is helpful in uses the MB-OFDM system in the different country.
3) designs the order of complexity to be low, goes on the market quickly. The traditional OFDM system is complex, the MB-TFI-OFDM system passes through designs specially, only uses the QPSK modulation, reduced IFFT and FFT realizes the order of complexity as well as to ADC and the DAC resolution request. Front end the simulation the electric circuit even gross structure’s design, easy realized with 90 nm CMOS, reduces the product to put in the market the time.
4) the safety mechanism establishment is convenient. May establish one embedded, to be at “the clear” throughout the condition security construction, provides the security and the privacy mechanism in agreement stack’s some levels, guaranteed the wireless technology needs strong and to user’s transparency.
4 technical applications and forecast
4.1 MBOA UWB general platforms
Because the IEEE802.15.3a standard presents the deadlock, MBOA has formed the special hobby club at the beginning of 2004, begins to draw up and to promote own physical level and the MAC level standard, argues vigorously into the global fact standard. in May, 2004, the WiMedia alliance and 1394 alliances and MBOA united, cause MBOA the physical level and the MAC level standard may widely support each kind of application layer service, became the UWB standard general platform, as shown in Figure 4, it might support wireless USB, wireless 1394, general namely to insert namely uses (UPNP), IP and so on many kinds of applications. The physical level standard has had 480 Mbit/s airborne decoding abilities, may further promote, supports wireless digital demonstration connection (DVI) and high clear media connection (HDMI) as well as the Gbit/s speed data transmission.
4.2 Wisair-UWB chip sets
The MBOA chip already tends to be mature, has the representative product is the UWB chip set which Wi-sair Corporation develops, has obtained the American FCC authentication. This chip set includes: Based on MB-OFDM way radio frequency receiving and dispatching chip (Wi-sair 502 PHY RF chip) and baseband processing chip (Wisair 531MAC \ Baseband chip). And, may substitute the field first batch with 0.18μm the silicon germanium biCMOS craft production’s 502 transceivers to conform to WiMedia and the MBOA standard 501 transceivers. It reduced the UWB wireless solution power loss, the size and the total cost, but also supports multi-frequency band OFDM TFI and the FFI pattern. The hold frequency spectrum between 3.1 GHz and 4.8 GHz, is mainly 3 528 MHz wide child frequency band. It may provide reaches as high as 480 Mbit/s in the short distance the data transfer rates. In addition, it including a piece on the bandpass filter, has the very wide programmable dynamirange wide band receiver, as well as has on the piece the pressure to control oscillator’s super speed frequency-hopping wide band mixer. Its programmable power amplifier may guarantee the biggest permission output. Moreover also supports with 2 antennas realizes the antenna diversity, does not need the external coupling not balanced transformer. The Wisair531UWB baseband chip mainly aims at the expense electronic installation to grow unceasingly to the supervelocity video frequency and the data transfer demand. They are also suitable for realize the PC peripheral device, motion and the automobile product fast, as well as the request realize high speed transmission other applications in the short distance.
4.3 various manufacturers application situation
2006 is one year which UWB activates, at the global ultra-wide band summit, some 12 manufacturers has demonstrated the UWB product and the solution. in January, 2007 unfolds on (CES) in the American expense electron, also had many manufacturers to display based on the UWB technology commercial product. If American DC REDNA Research institute, in plum side Si - runs quickly on R500 to use the wide band technology to realize the high clear video frequency broadcast, has used the Intel UWB solution; The Tristar SC-D365 wireless digit camera, is global first uses the ultra-wide band technology, had demonstrated by the seamless way through the wireless USB link transmission’s video frequency editing, it no longer needs to take out the memory or through the electric wire connection, but is can transmit the home movie fragment by the wireless way to PC carries on the memory or the demonstration; A Chinese Large Company’s section of wireless HDMI product, uses UWB to support the S-Video port, the HDMI signal as well as A-DI ADV202 the JPEG2000 image decoding chip, may use in the high speed movie picture transmission, music downloading, the printing, as well as PC peripheral device and expense electronic products data synchronization. in May, 2007, Hong Kong should the branch courtyard and Shenzhen elegant chart science and technology demonstrates them to research and develop “in together the world the first wireless ultra-wide band video frequency class technology ultra large screen projection television”.
4.4 existence questions and prospect forecast
The UWB application promotion has 3 very important questions: First, the standard question, the field manufacturer must pool brains and brawn the formulation standard, can bring the widespread intercommunication and the application; Second, industrial chain’s keeping up, including chip, system manufacturer technology and product research and development and promotion; Third, interconnection intercommunication network architecture and agreement.
The WPAN technology main goal is replaces electronic installation’s between segment the wireless connection, causes in the family or between the office each kind of equipment’s exchange of information is more convenient, nimble and quickly. The MB-OFDM-UWB technology also realizes one of WPAN best choices, therefore, in the digitized wireless family network, the digitized office, individual mobile equipment and the military and so on many domains has the broad development and the application prospect.
5 subtotals
The MB-TFI-OFDM technology is in the UWB correspondence one kind new realizes the way, by its unique superiority, will promote the MB-OFDM chip commercialization and the production advancement, enabled the MB-OFDM plan to have more and more many manufacturer supports and the application, thus became the WPAN physics level hopefully the standard technology. This technology was still at the start stage, the market potential is huge, the prospects for development are broad. Our country should hold internationally the UWB research and development upsurge, participates in international standardization positively, according to having the proprietary intellectual property rights technology to formulate our country’s related standard, develops the UWB technology positively the industrial production path.
