認知MIMO系統(tǒng)中差分空時編碼技術

1、認知mimo系統(tǒng)中差分空時編碼技術abstract: the cognitive mimo system utilizes the difference space-time coding technique the cognitive link and the authorization link in the mimo system both transmit antennas and a receiving antenna. in the cognitive system, cognitive users can have the opportunity to use authorize

2、d spectrum, which can use idle authorization in band, so the whole spectrum efficiency is raised. multiple transmitting antenna receiving anterrna of space-time coding technique can minimize the influence of multipath fading and improve performance, improve the wireless digital transmission capacity

3、 of the channel, but you need to assume that the receiver has optimal charmel state information estimation and using the correlation detection. in some cases, however, such as fast moving environment or channel attenuation rapidly and accurately estimate the channel state of cognitive mimo system is

4、 very difficult or the price is too high. to solve this problem, we proposed a difference space-time coding technique for the cognitive mimo system1 the introductionwith the development of wireless technology in recent years, public wireless spectrum resources have become increasingly scarce most wi

5、reless innovation is done in unlicensed frequencies, so unauthorised frequencies become crowded. however, most authorized frequencies are not used in certain periods and places cognitive radio (cr) is an important technology to solve this problem, it allows unauthorized (cognitive) users can have th

6、e opportunity to use are the authorization of idle spectrum, the spectrum efficiency can be greatly improved.increasing the complexity and dynamic environment of wireless networks is a current trend. cognitive networks are developed in this direction. the cable network also has this tendency to be e

7、xcluded from a promising network of cognitive networks, but in complex web environments, wireless networks are the focus of research previous studies have produced a series of problems with the combination of wireless and cognition, and the cognitive wireless network presents a new approach to solvi

8、ng these problemsas we all know, the more transmitting antenna receiving antenna of space-time coding technique can minimize the influence of multipath fading and improve performance, increase the wireless digital transmission capacity of the channe 1. however, under this condition, it is usually as

9、sumed that the receiving end has the optimal channel status information and uses the relevant tests when the channel status changes less than the symbol rate, the transmitter sends the pilot sequence, and the receiver can accurately estimate the channel status informat io n. however, in some cases,

10、such as high-speed mobile environment or channel attenuation change quickly, accurately estimate the channel state information is very difficult, sometimes the price is too high in this case, it is efficient to use the difference space encoding, because the difference space-time coding technique doe

11、s not require the transmitter and receiver to estimate the channel status information. for single emission antennas, difference schemes, such as differential phase shift keying (dpsk), do not require channel estimation in demodulation. the difference scheme is widely used in the actual cellular mobi

12、le communication systemnext we consider applying the difference empty time encoding scheme to the mi mo system we propose the difference space time encoding scheme because the receiving end of the decoding is not required for the channel status informat io n. in this paper, we will discuss the appli

13、cation of coding scheme in the difference space time2 cognitive mimo system2.1 mimo technologymimo (multiple - out, multi-input) technology is a major breakthrough in the technology of intelligent antenna in wireless mobile communications mimo technology can increase the capacity of the communicatio

14、n system and the frequency of the spectrum without increasing the bandwidth with the continuous research and development of the technology in the world, there is reason to believe that mimo technology will be the key technology that the new generation of mobile communication systems must adoptmimo t

15、echnology is the result of wireless communications antenna diversity and smart anten na tech no logy, it is the more into the list (miso) with single into more (simo) technology, the combination of have both advantages and characteristics mimo system in the transmitter and the receiver adopts multip

16、le antenna unit, using the advanced antenna transmission and signal processing technology, the use of wireless channel multipath propagation, the development of space resources,establish spatial parallel transmission channel, without any increase in bandwidth and transmission power, exponentially im

17、prove the quality of the wireless communication and data rate, an important breakthrough in the field of modern communication.mimo technology is no ionger the traditional wireless communication smart antenna, with its advantages over conventional smart antennas. the intelligent antenna uses a weight

18、ed selection algorithm to drive the beam directi on, which increases the signal-to-noise ratio by aggregating the energy to the desired direction, rather than using the multipath propagation. for mimo system, if the deputy vice receiving antenna transmitting antenna and n m form of wireless link m *

19、 n channel matrix element is completely independent of the capacity of the system with the minimum number of antenna linear growth in theory, if the space and cost of antenna and radio frequency (rf) channel is not restricted, mimo systems can provide infinite capacity, which is a combination of spa

20、ce dimension of the time dimension of the results, namely using space-time coding data flow by using the matrix channel is not vector data transmission channel of the smart antenna systemmimo technology takes advantage of the inherent characteristics of wireless channel multipath propagation. if the

21、 sender and the receiver using multiple antenna systems at the same time, as long as each antenna element spacing is large enough, the spread of the scattering wireless channel multipath component is rich enough, each to send/receive antenna unit between the multipath fading is tend to be more indep

22、endent, namely each of equivalent to send/receive antenna wireless transmission channel between tend to be independent, that is the same frequency, at the same time, same channel signature of sub channels tend to be orthogonal to each other2. 2 mimo technical research processthe three most important

23、 elements of the wireless communication system are signal decline, intercode interference (isi) and common channel interference (cci) the signal decline and intercode interference are generated by the multi-diameter propagation of the wireless channel, which is usually generated by the unknown sourc

24、e of the disturbance source in the common channel user or system in order to combat the decline of the signal, the single-user mi mo system is handled by the diversity technique, such as the spatial diversity, time diversity, polarization diversity, and frequency diversity spatial diversity and pola

25、rization are obtained by using array antennas: frequency diversity can be obtained by using multidiameter physical channel; time sets can be obtained through specific (coded modulation) emission technologies to eliminate or exploit the isi in the wireless communication system, channel balancing tech

26、niques include adaptive equalization or rake reception, which can be used to balance multichannel channels in order to eliminate the interference of the common channel, the adaptive beam formation is the technique which is used to interfere with the unknown information. multi-user detection is a bet

27、ter option when the interference information is known in the receiver. the combination of adaptive beam forming technology and multi-user detection technology can further improve the performance of the system, but it is conditional on the increasing complexity of the system. using array antenna tech

28、nology, the mimo system can make full use of all emptytime-frequency domain characteristics of the signal:(1) use or remove multiple diameter declines mimo technology can be used to improve the performance of the wireless communication system by using various kinds ofemission/synthesis technologies(

29、2) eliminate the common channel interference the mimo system can be used to prevent or eliminate the interference of the common channel by using adaptive beam forming technique or multi-user detection technology.(3) increase the efficiency of the spectrum, increase the efficiency of emission, reduce

30、 the emission power, reduce the space electromagnetic interference and increase the capacity of the system because the array antenna can reduce the influence of the common channel interference and multipath fading, and so on under the condition of certain snr (signal-to-noise ratio) can reduce the b

31、it error rate, or under a certain ber can reduce the testing required by the signal-to-noise ratio. mimo system can restrain or eliminate the common channel interference and intersymbol interference, at the same time use diversity to improve the signal-to-noise ratio of the received signal, so the t

32、ransmission power of base station and mobile terminal can be a certain degree of lower, at the same time reducing the effects of space electromagnetic interference, prolong the life time of the mobile terminal battery, minimize the impact on the ecological environment, reduce the system requirements

33、 for power and control precision devicethis paper introduces the research status of several key technologies in mimo space reuse system(1) the study of precoding techniquesin linear precoding svd precoding techniques, it will through the mimo channel into parallel sub channels, and can be sent throu

34、gh the water injection technology (water pouring) in order to achieve the maximum capacity of the system but, after the decomposition of different channel, each channel signal interference to noise ratio (sinr) is not the same, so it needs strict bit allocation (bit allocation) technology to match e

35、ach child channe1. but the bit-allocation technique not only increases the complexity of sending and receiving both ends, but also because the granularity of the signal constellations causes the loss of capacity(2) the study of detecting technologydetection generally refers to the process of process

36、ing the base band signal on the receiving end to restore the launch symbo1. detection algorithm based on maximum likelihood criterion is optimal in the performance, but its computational complexity of modulation order of antenna number and increase exponentially, so how to obtain good compromise bet

37、ween computational complexity and detection performance has always been a hot topic of such research from the detection mechanism of the detection algorithm can be divided into two categories: one is the approximate maximum likelihood detection, the detection method from reduced maximum likelihood d

38、etection in the end the number of search, try to approximate maximum likelihood function at the same time: another kind is from the perspective of matrix inversion, such as forced zero detection, mmse detection, and based on the introduction of some other criteria of detection algorithm, such as sor

39、ting offset, parallel multistage serial interference detection, some of these relative to the maximum likelihood test method has the characteristics of low complexity but performance loss is high(3) the research of opportunity beam forming techniquein multi-user mimo system, if a frequency resource

40、block just good user scheduling for a channel conditions, are often cannot make full use of the mimo system spatial degrees of freedom transmitted every time scheduling randomly generated multiple beam first, then put each beam matching of multiple users assigned to the channel conditions, so that y

41、ou can get at the same time the multi-user diversity gain and spatial multiplexing gain. in random orthogonal beam in air separation multiple access technology, produce carry multiple user data for each beam when multiple beam between orthogonal to each other, with the increasing of users, it can gr

42、adually achieve multiple antenna systems radio channel capacity growth but when the number of users is limited, the performance of the solution drops dramatical1y. these problems need to be solved further.(4) the study of antenna selection techniquesalthough mimo system can improve the spectrum effi

43、ciency, but its weakness is that both send and receive using multiple antennas, compared with the siso system, mimo systems will increase the complexity and cost, especially the radio frequency link (ineluding low noise amplifier, frequency converter, a/d and d/a converters, etc) are expensive there

44、fore, consider among multiple antenna selection a root or a better quality of some root channel antenna for data transmission, and poor quality of the other channel antenna to be used to give up, so i can stay under the condition of overall system performance, in basic significantly reduces the comp

45、lexity of the system and the hardware cost common antenna selection criteria include maximising minimum euclidean distance, maximum processing of the signal-to-noise ratio, maximizing the minimum singular value and maximizing system capacitythree cognitive systemthe expansion of the users of wireles

46、s services and equipment, such as mobile communications, public security, wifi and tv service is how modern society dependence on wireless spectrum is the least controversial example it is important to note that unauthorized frequency band (such as the ism and uni i) in the wireless ecosystem plays

47、a very important role, because the band was not timely regulation and control, the use of too much this will lead to new applications, including on one kilometer broadband wireless access, wireless pans/lans, mans, and wireless phone without authorization operation success and breakthrough technolog

48、y made great progress, and the spectrum of measurement show that authorized spectrum band such as tv, serious lack of use, the supervision institution (such as fcc) considering opening up more bands for unauthorized userswireless cog nition (cr) can be see n as a solution to the current low frequenc

49、y of radio spectrum utilization. it uses the characteristics of wireless operation for practical environmental conditions, enabling the spectrum to be flexible, efficient and reliable wireless cognition has the potential of large-scale intelligent use of undeveloped spectrum without affecting the no

50、rmal use of band authorized devices wireless cognition is a kind of wireless technology, the rapid devel opine nt of important (for example, the software defined radio, frequency agility, power control, etc)，is characterized by use of disruptive technologies such as broadband spectrum perception, re

51、al - time spectrum allocation and access to, and real - time rfcs, transmission scheme for potential and problem have a good understanding of cognitive radiocognitive radio technology (cr) is the evolution of software radio technology, a new intelligent wireless communication technology. the main ch

52、aracteristic of cognitive radio technology is to improve the communication quality by adapting parameters to meet the requirements of communication. currently, the broadband wireless communication system has orthogonal frequency division multiplexing (ofdm), and the multi-input multiple output (mimo

53、) and other key technologies introducing cr in mi mo system, the use of special ante nna design, perception of broadband transmission characteristics, from the space, time, frequency, modulation mode, such as multidimensional spectrum sharing, can improve the flexibility of spectrum utilization, the

54、 suppression of narrowband interferenee effectively. lte is the next mobile broadband network standard defined by 3gpp, based on key technologies such as ofdm and mi mo, and discusses the process of implementing cr. the concept of cognitive radio (cr) is put forward by dr joseph mitola, is on the ba

55、sis of software radio, increase the ability to function as testing requirements and take the initiative to change, make the wireless device can automatically adjust to changes in the external environment and their own needs the three common types of frequency resource management are: centralized, di

56、stributed, and centralized + distributedcr system is intelligent communication system can sense the external communication environment, by studying constantly feel the change of the outside world, and adaptively adjust their internal communication mechanism to adapt to the environment changes, which

57、 have detection, analysis, adjustment, such as reasoning, learning process, the cycle of a series of process of cognition. this adaptive adjustment process improves the stability of the system while improving the utilization of spectral resourcesit is known that cr has the following characteristics:

58、(1) the ability to perceive the environment(2) the ability to learn from the environment(3) adaptability to environmental change(4) high reliability of communication quality(5) the utilization of spectral resourcesthe refactorability of the system function modulecognitive radio network has dynamic,

59、flexible and intelligent use of spectrum resources, improve the utilization ratio of frequency spectrum characteristics of the network structure and protocol architecture design is the key to realize the network function. network architecture based on cognitive radio technology are mainly corvus system in america, based on the ieee 802 22 wireless local area network (wran) and supports multiple channel interface wireless mesh network; the protocol system h