GMSK调制解调系统英文03Word文件下载.docx

1、Based on GSM technology developed by the European Telecommunications Standards Institute （ETSI） specification developed by Global Communications （GSM） digital cellular mobile systems; Formulated by the European Post and Telecommunications Association （CEPT）, European Telecommunications Standards the

2、 ETS1300 a 175 Cordless Telecommunications standard （DECT）; The United Kingdom and Hong Kong-based communication standard for cordless phones （Cordless Phones） and telecommunications points （Telepoint） system, CT-2 and CT-3 system; Based on Ericssons Mobitex protocol, Mobitex system （Europe）, and RA

3、M Mobile Data System （U.S.）; Establishment of wireless data services in the North American Advanced Mobile Phone System （AMPS） Cellular Digital Packet Data （CDPD） system; Third-generation personal communications systems （PCs）, the the PCS1900 of the United States based on the GSM standard; and Europ

4、e by ETIS development and establishment of personal communications network （PCN） standard DCSI 800; As the system of the European wireless LAN （WLAN） standard HiperLAN / 1 and many now discussed as a wireless personal area network （WPAN） standard Bluetooth （Bluetooth）; According to the International

5、 Civil dirty Organization （ICAO） to develop satellite communications, navigation, search / air traffic management of CNS / ATM） system and other proprietary systems; General Packet Radio Service （GPRS） as well as improved data rates for GSM （EDGE） as communication standard by the second generation t

6、o third generation communication standard transition program is GMSK as a modulation scheme;In 1999, the ITU begin to build third-generation wireless communication standard for IMT2000 system. Divided into five categories according to different applications and technologies: （1） IMT-DS: Direct Seque

7、nce Spread Spectrum CDMA scheme based on the ETSI W-CDMA technology,; （2） IMT-MC: North America-based cdma-One （tm） multi-carrier CDMA technology; （3） IMT-TC: ETSI TD-CDMA technology, the time division duplex （TDD） and TDMA / CDMA multiple access methods; （4） IMT-SC: based on the UWC-136 / EDGE netw

8、ork; （5） IMT-FT:, using FDM.4-DECT technology. Which the latter three types of wireless interface modulation GMSK technology or compatible .As noted above, GMSK has a wide range of applications. Therefore, since the technology from the 1980s, the majority of researchers carried out a lot of research

9、 for its modem program.GMSK Signal Modulation SchemeMinimum Shift Keying （MSK）MSK is continuous phase frequency shift keying （CPFSK） in a special form. Modulation index h = 0.5, for the quadrature signal, MSK within a symbol time T, the minimum frequency offset （assuming coherent demodulation）. MSK

10、signal can also be regarded as the sine pulse formation of staggered quadrature phase shift keying （of OQPSK）.In order to meet the requirements of the wireless communication, a modulation scheme requires the following features: Compact the output power spectrum; Meet the Class C non-linear amplifier

11、; Has a strong immunity to noise and interference; Easy to implement.MSK Many properties are satisfactory. This makes it very suitable as a wireless communication modulation schemes. It also has its own shortcomings, its power spectral density of the side lobe. In order to make its output power spec

12、trum is more compact, we introduce the concept of pre-modulation low-pass filter.Gaussian minimum shift keying（GMSK）In order to make the output power spectrum of the MSK signal is more compact, the prefabricated low-pass filter should meet the following conditions: Bandwidth, and high frequency comp

13、onents of sharp cut-off; Corresponding lower pulse is used to prevent excessive instantaneous frequency deviation; Able to maintain the output impulse response area under the curve corresponds to the / 2 phase.As a pulse forming filter, GMSK meet the above conditions, the Gaussian filter. Data flow

14、through a Gaussian low-pass filter, and then the MSK modulation. The filter bandwidth is determined by the time-bandwidth constant BT. No carrier drift and adjacent-channel-band radiated power relative to the total power less than-60dB, BT = 0.28 is more suitable for conventional （IEEE-defined band

15、of 300 1,000 MHz） mobile wireless communication systems. The introduction of the pre-modulation filter the signal spectrum is more compact, but he also in the time domain broadening of the signal pulse, the introduction of inter-symbol interference （ISI）. Specifically, the modulation filter makes th

16、e pulse broadening, making the waveform in the time domain is greater than the symbol time T, so we sometimes GMSK signal in the part of the response signal.Gaussian low-pass filter impulse response h （t） can be expressed as： （2-1）Gaussian low-pass filter square wave pulse response g （t）： （2-2）Recta

17、ngular function rect is （x） is defined as： （2-3）Calculation, the impulse response g （t） can be expressed as： （2-4）Among them, the Q （t） for the Q function： （2-5）Modulated signal phase is written： （2-6）Where is the modulation of non-zero code （NRZ）. Modulation index h = 0.5. This ensures that the gre

18、atest change in volume of the phase within a symbol. Therefore, the ultimate expression of the GMSK signal is： （2-7）Among them, the signal energy per bit is, the random initial phase is. In order to facilitate the analysis, under normal circumstances, we can assume that = 0.GMSK modulation signal ph

19、ase pathBy the formula 2-5, we can easily see that the phase of the GMSK signal path impulse response waveform shape of the decision. In other words, the value of a symbol of the modulated wave phase change depends on the pulse of the area the meantime. Due to the introduction of the Gaussian low-pa

20、ss filter, the broadening of the pulse waveform in the time domain, making the overlap between adjacent pulses, in determining a symbol pulse area is the need to consider the impact of the adjacent code. In this way, different stream patterns, the area of the pulse within a symbol corresponding to t

21、he phase path is also different.The rules for determining the phase path is:Code within one yards for the change to increase or decrease, depending on the area of positive and negative polarity pulse waveform superimposed code. If the area is positive, this phase increase, and vice versa reduced. A

22、code phase change depends on the pulse area the size of this code within the overlay. （Pulse width for the 3T, for example） when the adjacent three yards of +1, +1, +1, a code phase by / 2; adjacent 3 yards to -1, phase to reduce the symbol / 2; other stream map, superimposed upon the pulse area is

23、smaller than the above two cases, due to the polarity offset is less than / 2 phase changes. Digital signal power spectral densityMake a digital phase modulation signals as follows： （2-8）Among them, is a random process contains information, which is the phase path. is the initial phase （the analysis

24、 can be set to 0）. The power spectrum analysis method more and have their own characteristics and uses. The main method is probably the following: The direct Fourier transform method. Through direct Deriving Z （t） the Fourier transform of the truncated signal for its amplitude spectrum. And then use

25、 the statistical characteristics of symbols as well as the basic principle of stationary random process to be translated into the power spectrum. This is the way to determine the direct classical methods of signal spectral analysis of the transition to the random signal.Correlation function method .

26、 Wiener - Xin Xin Theorem Fourier transform to obtain the power spectrum using the autocorrelation function is estimated worth.The transition probability method （signal flow graph method） . Listed first symbol of the transfer of state and calculate the corresponding transition probability matrix, an

27、d then use that contains the transition probability of the power spectral density analysis type directly to calculate the power spectral distribution.Other modern spectrum estimation . Maximum entropy method, like the natural spectrum estimation, autoregressive spectral estimation .Described above, the direct method. The method uses a truncated form of bandpass signal Z （t） obtained directly bilateral power spectrum of the degree of Z （t）. GMSK signal power spectral density is the same, with the decrease of BT co