1、Multiple-Input-Multiple-Output (MIMO) SystemsHehe GongDalian Maritime University, Dalian, ChinaE-mail:Abstract - MIMO, which is short of “Multiple-Input Multiple-Output “. Such technology can multiply the capacity of communication system and the spectrum efficiency, which is the key technology that
2、must be used in the new generation of mobile communication system. This paper mainly studies the principle of MIMO wireless communication technology, analyzes the main advantages of MIMO ,the application of MIMO technology and , finally the development tendency is introduced and analyzed ,such lay t
3、he foundation for deep understanding and research of MIMO communication technology.Index Terms - MIMO Multiple-Input Multiple-Output Wireless Mobile Communication. INTRODUCTIONultiple-Input Multiple-Output (MIMO) wireless systems, which use arrays of antennas instead of single transmit and receive a
4、ntennas, hold the promise of providing data rates far exceeding those of conventional wireless systems. Such MIMO systems operate by transmitting multiple signals in the same frequency band and at the same time over multiple transmit antennas. At the receiver, multiple antennas are also used, and th
5、e received correlated signals are processed to separate the different transmitted data streams. MIMO communications is made possible by the extension of receiver processing to include spatial dimensionality as well as time (spatial-temporal processing). Although the idea of using multiple antennas i
6、s not newit nds application in such techniques as diversity combining and beam formingonly MIMO systems approach the information-carrying-capacity potential of such channels. BASIC PRINCIPLE OF MIMOMIMO can be divided into several categories: space diversity, spatial multiplexing, beam forming, dive
7、rsity coding .Space diversity : multiple antennas are used at the receiver and transmitter, receiving multiple copies that carrying the same information through multiple channels. Because the transmission characteristics of multiple channels are different, the signal fading of multiple copies is not
8、 the same. Receivers can correctly recover the original signal with the information of multiple copies, improving the quality of the data transmission. As shown in Figure 1.Figure 1. Space diversitySpatial multiplexing: multiple antennas are used at the receiver and transmitter, making full use of t
9、he multipath component of space propagation , firstly , transmitted signal is converted to several parallel signal streams by serial-parallel conversion . And at the same time, transmitting multiple signals in the same frequency band by multiple transmit antennas. So as the number of antennas increa
10、ses, capacity will linearly increase. As shown in Figure2.Figure2. Spatial multiplexingBeam forming: utilizing the interference formed between the array emission wave, the energy is concentrated in a particular direction to form beam, so as to achieve greater coverage and interference suppression. A
11、s shown in Figure3. MFigure3. Beam forming. THE MAIN ADVANTAGES OF MIMOWith the increasing of the number of antennas the channel capacity increases linearly. In other words, we can double the capacity of wireless channel based on MIMO channel. Spectrum efficiency can be enhanced greatly without incr
12、easing the bandwidth and transmitting power.MIMO technology can improve the capacity of the channel, but also can improve the reliability of the channel, reducing the bit error rate. The former utilize the spatial multiplexing gain provided by MIMO channel, the latter utilize the spatial diversity g
13、ain provided by MIMO channel. At present, another research focus is the space-time coding in the field of MIMO technology. Common space-time codes include space-time block codes, space-time trellis codes. The main idea of space-time codes is to achieve spatial diversity and time diversity certain by
14、 the using of spatial and time coding, thereby reducing the bit error rate of the channel. . THE APPLICATION OF MIMOMIMO technology has became one of the key technologies in wireless communication field, applied in a variety of wireless communication systems. In the wireless broadband mobile communi
15、cation system, the third generation mobile communication (3GPP) cooperation plan has joined the content relevant to the MIMO technology in the standard, MIMO technology has also been applied in B3G and 4G system. In the wireless broadband access system, 802.16e, 802.11n and 802.20 standard are also
16、using MIMO technology. At present, reducing the complexity of the algorithm and the realization of the MIMO technology become the great challenge faced by the industry in performance based on how to guarantee the system performance. The application of MIMO multi antenna technology can effectively pr
17、omote the development of the WiMAX network. . DEVELOPMENT TREND OF MIMOWith the rapid development of wireless technology, data services are rapidly growing in wireless networks. The development tendency of MIMO technology will be a large scale MIMO, for the technique, the base station has a lot of a
18、ntennas, and the user terminal has a few. It can increase the transmission rate and spectrum efficiency, increasing the reliability of data transmission and the channel capacity. See Figure4.Figure4. Massive MIMOREFERENCES1 P.GoudJr, C.Schlegel, R.Hang, and V.Rajamani, “MIMO channel measurements for
19、 an indoor ofce environment,”in Proc.Wireless2003:Int.Conf.WirelessCommun,Calgary,Alta, July2003, pp.423427.2 D.Gesbert, and A.J.Paulraj , “Outdoor MIMO wireless channels : Models and performance prediction,” IEEE Trans. Commun, vol.50, pp.19261934,Dec.2002.3 D.Chizhik, J.Ling,P.W. Wolniansky, R.A.V
20、alenzuela, N.Costa and K.Huber, “Multiple-input-multiple-output measurements and model in gin Manhattan,” IEEEJ.Select.AreasCommun.,vol.23,pp.32133, Apr.2003.4 A.Goldsmith, Wireless Communications. Cambridge, U.K.: Cambridge Univ.Press, 2004,to be published.5 M.Martone, Multi antenna Digital RadioTransmission,1st ed, Norwood, Mass.:Artech House, 2002.
