Gaussian Filtered Minimum Shift Keying Research Articles

GMSK Modulator and Demodulator Techniques on Hardware and Software Platform with Research Gaps and Trends

The modulation system of Gaussian filtered Minimum Shift Keying (GMSK) is a narrow band and constant envelope format that is acceptable for bandwidth, power restricted environment of radio communication. The modulation technique encounters extensive approval from the cellular network market. Nonetheless, the present GMSK modulation scheme is majorly held back due to its two critical shortcomings, the necessity at the receiver section to shape the GMSK's symbol pulses for ISI and the absence of amended GMSK model including the bandwidth efficiency to improvise the link quality. At the moment, rare progressive research studies are being conducted in favor of hardware implementation of GMSK that can satisfactorily be applied to any GSM or AIS application. A standardized algorithm or framework that can guarantee high resiliency is yet to be introduced. Therefore, the paper gives a comprehensive outlook in the direction of understanding the drawbacks that are posed for the implementation of GMSK.

GMSK iterative carrier recovery for AIS burst-mode

In this paper, an iterative carrier recovery algorithm of Gaussian filtered minimum shift keying (GMSK) in burst-mode was designed. The data utilization rate and precision of the traditional demodulation method for recovering carrier signal in burst data packet with limited-length is poor. In order to solve this problem, this paper proposed an iterative carrier recovery algorithm. This algorithm can improve the estimated precision of carrier recovery and data utilization rate of burst data packet in a large extent by performing multiple forward and backward iterations. And the algorithm can be implemented in Simulink environment. As the communication mode of automatic identification system (AIS) is abrupt, the algorithm is especially suitable for satellite-based AIS.

Positioning Error Analysis of Ranging-Mode Using AIS Signals in China

In order to provide resilient position, navigation, and time (PNT) information forE-Navigation, the ranging-mode (R-Mode) positioning using automatic identification system (AIS) signals is encouraged. As the accuracy is the key for the positioning system, this paper investigates the position error of the R-Mode positioning based on AIS shore-based station in China. The measurement errors of Gaussian filtered minimum shift keying (GMSK) demodulation based on carrier phase locking loop are investigated in theory. The dilution of precision (DOP) for time of arrival (TOA) and time difference of arrival (TDOA) used in R-Mode positioning of AIS is discussed in two measurement mechanisms. The positioning error distributions in the North, East, and South Sea regions of China based on the existing AIS shore-based stations are evaluated. The positioning accuracy is at the meter level in the most traffic dense areas to meet the requirements for vessel navigation.

Jamming 환경에서 SFH 변조 방식에 따른 위성 통신 시스템의 BER 성능 분석

FHSS(Frequency Hopping Spread Spectrum) 방식은 군 통신 시스템에서 재밍(Jamming)에 의한 간섭을 줄이기 위해 사용된다. 하지만 사용되는 변조 방식의 종류, 재밍 신호의 특성에 따른 위성 통신 시스템의 BER 성능이 무선 채널 상태에 따라 어떤 성능 차이를 보이는지 분석되지 않았다. 따라서 본 논문에서는 PBNJ(Partial-Band Noise Jamming)와 WPBJ(Worst case Partial-Band noise Jamming)의 두 가지 재밍 환경에서 NC-MFSK(Non-Coherent M-ary Frequeency-Shift Keying), SDPSK(Symmetric Differential Phase-Shift Keying), GMSK (Gaussian filtered Minimum-Shift Keying)의 세 가지 변조 방식에 따른 위성 통신 시스템의 BER 성능 변화를 분석한다. 또한, 분석된 결과를 이용하여 전송 환경에 따른 최적의 전송 방식을 제안하도록 한다. The FHSS(Frequency Hopping Spread Spectrum), in which a transmitter changes its carrier frequency according to a certain hopping pattern, is widely used in the military communication system, since it is highly resistant to deliberate Jamming. However, the difference of BER performance of satellite communication system which using the different modulation scheme and Jamming model was not studied. Thus, in this paper, we consider PBNJ(Partial-Band Noise Jamming) and WPBJ(Worst case Partial-Band noise Jamming) as Jamming models, and evaluate BER(Bit Error Rate) performances of NC-MFSK(Non-Coherent M-ary Frequency-Shift Keying), SDPSK(Symmetric Differential Phase-Shift Keying), and GMSK(Gaussian filtered Minimum-Shift Keying) modulation schemes. Based on the results, we suggest the best transmission method for each condition.

Preserving Radio Astronomy in Developing Nations

Due to the very weak nature of signals from cosmic radio sources, the sensitivity of a radio telescope and receiver is about 40–60 dB higher than those of communications receivers. Hence, radio telescopes are generally located in relatively radio-quiet locations and operate in frequency bands that are protected against radio interference through frequency planning by national governments. Taking advantage of the much lower degree of radio interference in developing countries and the relatively labour-intensive nature of metre-wave radio telescopes, several such radio telescopes have been built and are planned in Argentina, Brazil, China, India, Mauritius and South Africa. Radio telescopes operating at cm-wavelengths are also planned in Egypt and Mexico.A particularly severe problem arises for the radio astronomy service and other passive services below 2 GHz from the possibility of unacceptable emissions from satellites in unwanted bands (out-of-band and spurious emissions), due to the specific modulation schemes used in satellite transmitters. It is noted that this can be circumvented within the existing technologies if the satellite transmitters employ suitable bit-shaping or filtering techniques or use modulation schemes like Gaussian-filtered Minimum-Shift Keying (GMSK) which produce very little out-of-band emission. Although radio astronomy started in the western world at low frequencies, much low frequency radio astronomy is now planned or operational in developing countries. In order to protect the interests of these and other passive services within developing nations, it is important that suitable regulations be recommended to UNISPACE-III to provide appropriate protection.

A GMSK Compatible Modulation with Improved Spectral Properties

For the controlled spectral shaping of modulation methods similar to Minimum Shift Keying (MSK), Gaussian filtered Minimum Shift Keying (GMSK) and Tamed Frequency Modulation (TFM), three optimization approaches with different degrees of intersymbol interference and envelope fluctuations are discussed. For a frequency division multiplex transmission with a bitwise correlating receiver, a weighting function for the transmitter's power spectral density which is a good measure for the Bit Error Rate (BER) caused by Adjacent Channel Interference (ACI) is proposed. Its application to a separate or also joint optimization of the transmitter and the receiving filter reducing ACI power by roughly 20 dB is presented. For a given receiving filter, a compatible modulation that outperforms GMSK in both bandwidth and power efficiency can be designed.

Continuous‐phase modulations for CDMA radio communications: Modem architecture and performance

AbstractIn this paper we analyze the structure and the performance of a digital modem for band‐limited spread‐spectrum signals to be employed in a radio communication network with asynchronous code‐division multiple access and constant‐envelope continuous‐phase modulation. After a description of the modem structure and the evaluation of its bit error rate in the presence of co‐channel interference, we tackle the key point of code synchronization. In particular, we present a detailed analysis of the code acquisition strategy, assessing its performance in terms of false alarm probability, missed detection probability and mean acquisition time. Furthermore, we address the problem of code chip timing recovery, describing the performance of three different code tracking loops in terms of the steady‐state RMS chip timing error jitter. The analytical approach we present can be applied to any Continuous Phase Modulation (CPM) format that can be approximated by an Offset‐QAM signal, such as Gaussian‐filtered Minimum‐Shift Keying (GMSK).

Error performance of two decision schemes for frequency‐detector gaussian minimum shift keying (gmsk) on a frequency‐selective fading channel

AbstractIn high‐speed digital mobile communication systems, one of the most spectrally efficient modulation methods is Gaussian‐filtered minimum shift keying (GMSK). In this paper, two decision schemes of frequency‐detected GMSK under frequency‐selective fading are compared theoretically from the viewpoint of bit error rate (BER) performances.The GMSK signal which is encoded differentially has an eye pattern with three levels; and, by using the characteristic, the offset decision is made. The BER performances of the offset decision method are compared with those of the conventional one which is based on the eye pattern with two levels.Under the frequency‐selective fading, which is characterized by a two‐ray model, the BER performances for BbT = 0.20 with the offset‐type decision are superior to those with the conventional one when normalized rms delay spread (τ/2T for two‐ray model, τ: delay spread) is less than 0.10.By using the post‐detection selection diversity with two diversity branches, we can reduce the degradation of signal energy per bit to noise power spectral density ratio with the offset decision greater than that with the conventional one for τ/2T < 0.20.

BER performance of CMA adaptive array for high-speed GMSK mobile communication-a description of measurements in central Tokyo

This paper describes the performance of an adaptive array as a countermeasure to multipath fading for a 256 kbps Gaussian-filtered minimum shift keying (GMSK) mobile communication system operating in the 1.5 GHz band. An adaptive array having four antenna elements is implemented using the digital beam forming concept. The constant modulus algorithm (CMA) is employed for the adaptation process to ease the implementation. Measurements in central Tokyo of the bit error rate (BER) performance and an array pattern arising in the multipath environment are presented. Analysis of the array pattern confirms that the array succeeds in directing nulls to the delayed signals. BER performance shows an improvement in E/sub b//N/sub 0/, compared with that of a single antenna system, of 17.5 to 22 dB at a BER of 1.0*10/sup -2/ in a frequency-selective fading channel. >

An implementation of a CMA adaptive array for high speed GMSK transmission in mobile communications

The hardware implementation of an adaptive array as a technique for compensating multipath fading in mobile communications is described. The number of the antenna elements is four. The target communication system is modulated by 256 kbps Gaussian-filtered minimum shift keying (MSK) and has a time-division multiplexing (TDM) architecture with 24 time slots. Based on the digital beamforming concept, all of the signals and the array weights are digital-signal processed. The constant modulus algorithm (CMA) is employed for weight optimizing. In an additive white Gaussian noise channel, this system has 5.6-dB gain in an energy-per-bit-to-noise-density ratio at a bit error rate (BER) of 1.0*10/sup -3/, compared with a single antenna system. The result of the basic field test shows that the gain at a BER of 1.0*10/sup -3/ reaches 22.3 dB in a nonselective, slow Rayleigh fading channel given a 5 Hz maximum Doppler shift. >

Predetection filtering effect on the probability of error of GMSK with discriminator detection in mobile radio channels

Simple closed-form expressions for the probability of error of Gaussian filtered minimum-shift keying (GMSK) with discriminator detection in a fast-Rayleigh-fading channel were previously derived by the author (see ibid., vol.VT-35, p.71-6, May 1986) by assuming that the intermediate frequency filter does not distort the received signal. The effect of this filter on the probability of error is now investigated. The optimum bandwidth of the filter is calculated for cases of practical interest. The equations used for the computation of the probability of error are derived and the results are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

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.

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.

Spectrum efficiency of GMSK land mobile radio

Gaussian-filtered minimum-shift keying (GMSK) is a constant envelope and narrow-band modulation suitable for power- and band-limited digital radio communication. From the viewpoint of efficient spectrum use by land mobile radio, geographical reuse of cochannels as well as power spectrum compactness are desired. The output power spectrum of GMSK modulation can be made compact, at a sacrifice of co-channel interference protection. Parameters for optimizing GMSK are determined maintaining a compromise between co-channel reuse and power spectrum compactness.

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.

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.

Improved Coherent Detection of GMSK

It is pointed out that the degradation effect due to premodulation filtering in GMSK (Gaussian-filtered minimum shift keying) is largest at the edges of time slots, which instant has been adopted as the sample timing in the conventional coherent detector of GMSK. Then a new coherent detector employing signals sampled at a different timing in a deviated-frequency-locking scheme is presented to achieve a better bit-error-rate performance versus carrier-to-noise ratio.

Differential detection of manipulated MSK signals with decision feedback

AbstractThe types of manipulated MSK (Minimum Shift Keying) signals obtained by narrowing MSK band which are currently attracting attention include TFM (Tamed Frequency Modulation) and GMSK (Gaussian filtered MSK) signals. A new 2‐bit delay differential detection technique for these manipulated signals is proposed and its performance is compared with the conventional technology. In the proposed technique, a decision feedback circuit which controls the phase references of the delayed signals is used to reduce the intersymbol interference caused by the transmit and receive filters. the proposed technique is especially effective for manipulated MSK signals. Computer simulation results show that the proposed technique requires a smaller receive filter bandwidth and the bit error performance results in an improvement of 3 to 8 dB in the SN ratio compared with the conventional technique.

High-speed digital transmission experiments in 920 MHz urban and suburban mobile radio channels

Field experiments have been conducted to clarify the feasibility of introducing a newly developed Gaussian filtered minimum shift keying (GMSK) modulation method into 920 MHz mobile radio systems, and have been performed in the Tokyo urban, and the Yokosuka suburban areas.