Fractional Multi‐bit Differential Detection Technique for Continuous Phase Modulation

A new low‐complexity differential detection technique, fractional multi‐bit differential detection (FMDD), is proposed in order to improve the performance of continuous phase modulation (CPM) signals such as Gaussian minimum shift keying (GMSK) and Gaussian frequency shift keying (GFSK). In comparison to conventional one‐bit differential detected (1DD) GFSK, the FMDD‐employed GFSK provides a signal‐to‐noise ratio advantage of up to 1.8 dB in an AWGN channel. Thus, the bit‐error rate performance of the proposed FMDD is brought close to that of an ideal coherent detection while avoiding the implementation complexity associated with the carrier recovery. In the adjacent channel interference environment, FMDD achieves an even larger SNR advantage compared to 1DD.     

Simulation of digital transmission over mobile channels at 300 kb/s

Studies of digital transmission over typical urban and suburban mobile channels using simulations that employ a local area model for the time varying mobile channel impulse response are discussed. The digital transmission techniques of coherently detected and differentially coherent detected versions of quadrature phase-shift keying (QPSK), Gaussian minimum shift keying (GMSK), and coherently detected binary phase-shift keying (BPSK) over example mobile channels are presented. Two measures of performance are considered; the mean bit error ratio (and irreducible bit error ratio), which is used to compare the robustness of the various modulation methods to delay spread, and the outage probability, which provides a measure of the overall transmission quality as would be perceived by a user. Emphasis is placed on results obtained for GMSK, which is the modulation scheme to be employed in the Pan-European digital cellular mobile system. The effects of RMS delay spread on the mean bit error ratio, mean irreducible bit error ratio, and probability of outage are considered for different channel types     

Evaluation of 16 kbit/s digital voice transmission for mobile radio

In this paper 16 kbit/s digital voice transmission with conventional channel spacing of 25 kHz, employing a 16 kbit/s adaptive delta modulation (ADM) coder-decoder (CODEC) is evaluated. The main characteristics of narrow-band digital FM modulation schemes, such as tamed FM, Gaussian filtered minimum shift keying (GMSK), four-level FM and phase locked loop-quaternary phase shift keying (PLL-QPSK), are compared by laboratory tests. Digitized voice quality in a digital channel incorporating a 16 kbit/s ADM CODEC and GMSK coherent detection was compared with voice quality of a conventional analog FM channel. Bit error ratio (BER) performance is shown to depend primarily on demodulation schemes. Digital voice quality is inferior to that of analog voice with an opinion score difference of about 0.5 in fading environments. This kind of digital voice transmission will be applicable for those systems that require high security at an expense of speech quality.     

水下复合信道对GMSK无线光通信系统性能的影响

The absorption and scattering of light in seawater channel cause signal attenuation, and the turbulence of seawater causes signal amplitude fluctuation, both of which will reduce the bit error rate (BER) performance of underwater wireless optical communication (UWOC) system. The effects of the two channel characteristics on the signal performance were considered comprehensively, and a method was proposed to equate the transmission distance and turbulence probability density function to the system signal-to-noise ratio (SNR) and turbulence noise, and then the signal attenuation and turbulence noise were combined into the signal waveform to establish the underwater composite channel signal transmission model. According to the experimental system parameters, the signal transmission waveforms of Gaussian minimum frequency shift keying (GMSK) modulation under composite channel were simulated, and the one-bit difference demodulation algorithm was used to compare the demodulated waveforms with the original waveform, and the influence relationships of composite channel on the system BER performance was analyzed. The simulation experiment results show that, compared with on-off keying modulation (OOK), pulse position modulation (PPM), GMSK system can obtain the SNR gain of 3.3 dB, 4.8 dB respectively only in the attenuation channel with seawater attenuation coefficient of 0.151 m?1. Under the composite channel, GMSK modulation performance is superior to OOK modulation and PPM modulation. When the water attenuation coefficient is 0.151 m?1, and turbulence intensity variance is smaller than 0.16, GMSK modulation system has no error rate limit, the system BER is decided by signal attenuation and turbulence noise and Gaussian noise together, GMSK modulation achieves SNR gain of 4.35 dB compared with PPM modulation. Furthermore, turbulence intensity variance is greater than 0.16, system BER arrives limit, which value is determined by the turbulence intensity, and the limit value of BER increases nonlinearly with the increase of turbulence intensity.     

GMSK信号的多普勒频移快捕和跟踪

GMSK信号具有良好的频谱和功率特性,特别适用于功率受限和信道存在非线性、衰落以及多普勒频移的数字卫星移动突发通信系统。本文提出了一种GMSK信号的多普勒频移快捕和跟踪方法。该方法根据突发通信时帧结构的特点,采用独特码和FFT并行处理信号能量检测、帧同步检测和多普勒频移快捕,并采用判决反馈PLL环跟踪多普勒频移的变化。仿真结果表明,多普勒频移在-Rb／2～Rb/2范围内变化时,与理论值相比,采用该方法的准相干解调器误比特率Pb 性能恶化仅为0．3dB。在信息速率Rb=9．6kbps时,多普勒频移速率可达4000Hz／s。     

GMSK with differential phase detection in the satellite mobilechannel

A formula is derived for the error probability of partial-response continuous-phase modulation (which contains Gaussian minimum shift keying (GMSK) as a special case) with N-b (N=1, 2) differential phase detection (DPD) for the satellite mobile channel, which contains as special cases the Gaussian and Rayleigh channels. In the satellite mobile channel, the input signal is the sum of a direct component, a diffuse component, and white Gaussian noise. The receiver is either with or without decision feedback, and the decision region is optimized for 2-b DPD to minimize the error probability. The error probability for GMSK is computed as a function of signal-to-noise ratio and other system or channel parameters (Doppler frequency, Gaussian filter bandwidth, ratio of powers in the direct and diffuse signal components, etc.). It is shown that decision feedback is more effective for GMSK with narrow bandwidth. The 2-b DPD is superior to the 1-b DPD for low Doppler frequencies and signal-to-noise ratios. For practical vehicle velocities and bit rates, a 2-b DPD with decision feedback outperforms all other analyzed schemes when the signal-to-noise ratio is low     

Performance of 16 kbit/s GMSK transmission with postdetection selection diversity in land mobile radio

Through laboratory simulation tests and field experiments in the Tokyo metropolitan area, 16 kbit/s Gaussian filtered minimum shift keying (GMSK) transmission performance has been experimentally clarified in the 920 MHz land mobile radio environment. The experimental results agree closely with theory, and they show that fast multipath fading severely degrades average bit error rate (BER) performance in GMSK transmission. However, a space diversity reception technique using a postdetection selection combining scheme is able to efficiently mitigate the fast multipath fading.     

Performance of 16 kbit/s GMSK Transmission with Postdetection Selection Diversity in Land Mobile Radio

Through laboratory simulation tests and field experiments in the Tokyo metropolitan area, 16 kbit/s Gaussian filtered minimum shift keying (GMSK) transmission performance has been experimentally clarified in the 920 MHz land mobile radio environment. The experimental results agree closely with theory, and they show that fast multipath fading severely degrades average bit error rate (BER) performance in GMSK transmission. However, a space diversity reception technique using a postdetection selection combining scheme is able to efficiently mitigate the fast multipath fading.     

Combined frequency and differential phase shift keying withnon-coherent detection in a satellite mobile channel

We analyze the performance of combined binary frequency and M-ary differential phase shift keying (2FSK/MDPSK) in the satellite mobile channel (SMC). We use two detectors in which the frequency symbol is detected by a limiter discriminator detector (LDD) and the phase symbol by a differential phase detector (DPD). It is shown that this system is power and bandwidth efficient when compared with other systems with constant envelope (or nearly constant envelope) and noncoherent detection like L-ary DPSK (LDPSK), Gaussian minimum shift keying (GMSK) and MSK     

Blind detection of CPM signals transmitted over frequency-flatfading channels

We propose a novel detection scheme for continuous-phase modulation (CPM) signals transmitted over frequency-flat fading channels. Its most significant feature is that it operates without statistical information on the fading channel, and for this reason it is nicknamed “blind detector.” Its error-rate performance is assessed with minimum shift keying (MSK) and Gaussian MSK (GMSK) schemes and compared with the performance of other decoders     

一种GMSK调制解调器的实现

GMSK信号具有很好的频谱和功率特性,特别适用于功率受限和信道存在非线性、衰落以及多普勒频移的移动突发通信系统。论文提出了基于CMX909B调制芯片和8051控制芯片的GMSK无线调制解调器的软、硬件设计方案,接收/发送速率可达38.4kbps,并对GMSK调制进行了性能仿真。该设计成本低,操作灵活,具有应用意义。     

F-QPSK-a superior modulation technique for mobile and personalcommunications

A brief review of the principles and properties of F-QPSK (quadrature phase shift keying) modulation is given. Its spectral efficiency is compared with that of Gaussian minimum-shift keying (GMSK) using adjacent channel interference (ACI) as a parameter. It is established that in a noncellular environment, hardlimited F-QPSK has a spectral efficiency of 1.42 b/s/Hz, which is up to 51% more spectrally efficient than GMSK BT=0.5 for ACI=20 dB. F-QPSK's BER performance in AWGN and Rayleigh fading channels is shown to be superior to that of GMSK. The spectral efficiency of the modulations in cellular/microcellular environments where frequency is reused in geographically separate cells to achieve higher capacity is compared. It is shown that the application of F-QPSK in such environment would leads to a 95% increase of system capacity compared to GMSK. It is concluded that the power and spectrally efficient F-QPSK make it an excellent candidate for future high-capacity personal communication system (PCS) networks     

A fully digital noncoherent and coherent GMSK receiver architecturewith joint symbol timing error and frequency offset estimation

We propose a fully digital noncoherent and coherent Gaussian minimum shift keying (GMSK) receiver architecture with joint frequency offset compensation and symbol timing recovery. Carrier phase offset can be estimated if the coherent demodulation mode is adopted. The converted base-band complex signal is first frequency discriminated and then passed through a digital filter which performs a fast Fourier transform (FFT). The frequency offset can be estimated from the DC component of the FFT, and the symbol timing error can be estimated from the phase angle of the FFT at a specified frequency which is equal to an integral multiple of half the bit rate. These two estimated parameters are then used for frequency offset compensation and symbol timing recovery during a preamble period. Coarse carrier phase can be estimated by averaging sampled in-phase and quadrature-phase signals and finding its phase angle within the preamble period after carrier frequency offset is estimated and compensated. The bit error rate (BER) performance of this GMSK receiver architecture is assessed for an additive white Gaussian noise (AWGN) channel by computer simulation     

Differential detection of Gaussian MSK in a mobile radio environment

Minimum shift keying with Gaussian shaped transmit pulses is a strong candidate for a modulation technique that satisfies the stringent out-of-band radiated power requirements of the mobil radio application. Numerous studies and field experiments have been conducted by the Japanese on urban and suburban mobile radio channels with systems employing Gaussian minimum-shift keying (GMSK) transmission and differentially coherent reception. A comprehensive analytical treatment is presented of the performance of such systems emphasizing the important trade-offs among the various system design parameters such as transmit and receiver filter bandwidths and detection threshold level. It is shown that two-bit differential detection of GMSK is capable of offering far superior performance to the more conventional one-bit detection method both in the presence of an additive Gaussian noise background and Rician fading.     

Analysis of GMSK with Two-Bit Differential Detection in Land Mobile Radio Channels

The effect of intersymbol interference (ISI) of Gaussian filtered minimum shift keying (GMSK) on the probability of error of twobit differential detection is analyzed theoretically in fast Rayleigh fading characterizing land mobile radio channels. A closed form expression is derived for the probability of error. Numerical results are presented for cases of practical interest to researchers and designers of cellular land mobile radio systems.     

Performance Enhancement of Gaussian Minimum Shift Keying Using Optimum Phase Sampling Technique for Turbulent Free-Space Optical Communication

In this paper, analytical performances of Gaussian minimum shift keying (GMSK) are studied for free space optical communication system. Authors propose an innovative sampling technique called, optimum phase sampling technique to investigate the bit error performance of GMSK modulation. Subsequently, performances of GMSK like, bit error rate (BER), power spectral density, and adjacent carrier interference (ACI) have also been investigated and compared with other modulation techniques. Furthermore, return to zero (RZ) coding input bit stream prior to GMSK technique improves the ACI performance of GMSK. To end with, we present the improvement of degradation parameter (γ) in a tabular form through phase sampling technique. Moreover, both optimum phase sampling and narrow pulse shaping of RZ-GMSK obtains near optimal result of BER. The numerical results show, that the proposed phase sampled RZ-GMSK of 70% duty cycle at BT?=?0.6 has a degradation value of 0.979, which is comparable to GMSK at BT?=?∞. Moreover, the proposed RZ-GMSK achieves lower ACI value and has an error rate of 7?×?10^?7, which is lower than the GMSK of 1?×?10^?6 BER value.

     

Analysis of GMSK with differential detection in land mobile radio channels

The effect of intersymbol interference (ISI) of Gaussian filtered minimum shift keying (GMSK) on the probability of error of one bit differential detection is analyzed theoretically in fast Rayleigh fading characterizing land mobile radio channels. A closed-form expression is derived for the probability of error as a function of the fading rate, IF filter bandwidth, signal-to-noise ratio (SNR) and ISI. Numerical results are presented for cases of practical interest to researchers and designers of cellular land mobile radio systems.     

GMSK调制及其在软件无线电上的应用

GMSK（高斯最小移频键控）是一种典型的连续相位调制方式,具有包络恒定、频谱紧凑、抗干扰能力强等特点。本文阐述了GMSK调制的原理与特点,提出了其在软件无线电发射机系统中的应用,通过MATLAB软件,利用Simulink建模仿真,详细分析了各模块作用及设置,最后给出了GMSK信号调制的信号仿真图。仿真结果表明,GMSK基带信号具有良好的功率谱,同时能够有效避免I/Q两条支路信号幅度及正交载波相位失衡,可有效降低邻道干扰,在通信中有广阔的应用前景。     

Error probability of binary phase shift keying in Nakagami-m fadingchannel with phase noise

The error performance of coherent detection of binary phase shift keying (BPSK) signals with noisy phase reference is analysed for a flat Nakagami-m fading channel and in the presence of additive white Gaussian noise (AWGN). By assuming Gaussian and Tikhonov probability density functions (PDFs) for the phase error, closed-form expressions for the average bit error rate (BER) are derived