Showing papers on "Minimum-shift keying published in 2020"

Blind Modulation Classification for Asynchronous OFDM Systems Over Unknown Signal Parameters and Channel Statistics

Abstract: Blind modulation classification (MC) is an integral part of designing an adaptive or intelligent transceiver for future wireless communications. However, till date, only a few works have been reported in the literature for blind MC of orthogonal frequency division multiplexing (OFDM) system over frequency-selective fading environment. In this paper, a blind MC algorithm has been proposed and implemented over National Instruments (NI) testbed setup for linearly modulated signals of OFDM system by using discrete Fourier transform (DFT) and normalized fourth-order cumulant. The proposed MC algorithm works in the presence of synchronization errors, i.e., frequency, timing, and phase offsets and without the prior information about the signal parameters and channel statistics. To nullify the effect of timing offset in the feature extraction process, a statistical average has been taken over OFDM symbols after introducing uniformly distributed random timing offsets in each of the OFDM symbols. In this work, we have classified a more extensive pool of modulation formats for OFDM signal, i.e., binary phase-shift keying (BPSK), quadrature PSK (QPSK), offset QPSK (OQPSK), minimum shift keying (MSK), and 16 quadrature amplitude modulation (16-QAM). Classification is performed in two stages. At the first stage, a normalized fourth-order cumulant is used on the DFT of the received OFDM signal to classify OQPSK, MSK, and 16-QAM modulation formats. At the second stage, first we compute the DFT of the square of the received OFDM signal and then a normalized fourth-order cumulant is used to classify BPSK and QPSK modulation formats. The success rate of the proposed MC algorithm is evaluated through analytical and Monte Carlo simulations and compared with existing methods. Finally, the work is validated by providing an experimental setup on NI hardware over an indoor propagation environment.

Error performance analysis of PPM-and FSK-based hybrid modulation scheme for FSO satellite downlink

Abstract: To enhance the error performance of satellite downlink optical wireless communication system, a hybrid modulation scheme called PPM-FSK-SIM is proposed in this study. It is based on the concept of pulse position modulation (PPM), M-ary frequency shift keying (MFSK) and subcarrier intensity modulation (SIM). The analytical bit error rate (BER) of the proposed hybrid scheme is derived, in the presence of atmospheric turbulence with avalanche photodiode (APD) detection by using Meijer-G, which stands out as a reliable and efficient analytical tool that replaces the time-consuming Monte-Carlo simulation method to target a desirable BER. It is analysed over additive white gaussian noise (AWGN), log-normal and gamma–gamma channel models for geostationary satellite to Earth (downlink) communication. As compared to PPM and minimum shift keying (MSK), PPM-MFSK-SIM gives better error rate performance. The scheme is power efficient making it a favourable modulation technique for satellite downlink communication.

PAPR Reduction of OFDM Signal Through DFT Precoding and GMSK Pulse Shaping in Indoor VLC

Abstract: Optical orthogonal-frequency-division-multiplexing (O-OFDM) has been widely explored for visible light communication (VLC) to achieve high data rates. However, O-OFDM suffers from high peak-to-average power ratio (PAPR), which causes clipping distortion, reduces illumination to communication conversion efficiency and affects the lifetime of the light-emitting diode (LED). This paper proposes a novel modulation technique, an amalgamation of discrete Fourier transform (DFT) precoding and Gaussian minimum shift keying (GMSK) pulse shaping to reduce the PAPR of OFDM based VLC system. Furthermore, the concept of group precoding is also introduced to deal with the increased complexity of the DFT precoding system. The results show that different variants of the proposed scheme provide improved PAPR, symbol-error-rate (SER), and power-saving performance as compared to the corresponding DFT precoded O-OFDM and O-OFDM counterpart. Moreover, the analytical study of PAPR, computational complexity and spectral efficiency for the proposed system have also been investigated and reported in this paper.

Rényi Entropy-Based Spectrum Sensing in Mobile Cognitive Radio Networks Using Software Defined Radio

Abstract: A very important task in Mobile Cognitive Radio Networks (MCRN) is to ensure that the system releases a given frequency when a Primary User (PU) is present, by maintaining the principle to not interfere with its activity within a cognitive radio system. Afterwards, a cognitive protocol must be set in order to change to another frequency channel that is available or shut down the service if there are no free channels to be found. The system must sense the frequency spectrum constantly through the energy detection method which is the most commonly used. However, this analysis takes place in the time domain and signals cannot be easily identified due to changes in modulation, power and distance from mobile users. The proposed system works with Gaussian Minimum Shift Keying (GMSK) and Orthogonal Frequency Division Multiplexing (OFDM) for systems from Global System for Mobile Communication (GSM) to 5G systems, the signals are analyzed in the frequency domain and the Renyi-Entropy method is used as a tool to distinguish the noise and the PU signal without prior knowledge of its features. The main contribution of this research is that uses a Software Defined Radio (SDR) system to implement a MCRN in order to measure the behavior of Primary and Secondary signals in both time and frequency using GNURadio and OpenBTS as software tools to allow a phone call service between two Secondary Users (SU). This allows to extract experimental results that are compared with simulations and theory using Renyi-entropy to detect signals from SU in GMSK and OFDM systems. It is concluded that the Renyi-Entropy detector has a higher performance than the conventional energy detector in the Additive White Gaussian Noise (AWGN) and Rayleigh channels. The system increases the detection probability (PD) to over 96% with a Signal to Noise Ratio (SNR) of 10dB and starting 5 dB below energy sensing levels.

Performance enhancement of hybrid-SIM for optical wireless downlink communication with aperture averaging and receiver diversity

Abstract: Error performance of hybrid subcarrier intensity modulation (hybrid-SIM) in optical free-space satellite downlink has been studied in this work. Bit error rate (BER) is improved by aperture averaging and spatial receiver diversity and it is found out be effective in strong turbulence regime. Subsequently, the reduction in scintillation index has been investigated by implementing a single large receiver and an array of point receivers of length n R with the same effective aperture area. Moreover, the BER at different turbulence conditions is compared with minimum shift keying and multiple levels of pulse position modulation pertaining to aperture averaging. Upon analysing the single input multiple outputs (SIMO) system, the desired response is obtained above a certain threshold in average received irradiance. At different zenith angles and turbulence strengths for n R = 4 , the threshold is 4.59 and 3.35 dB, respectively, and it rises by 13.6 and 26.43 dB when n R is increased to 9. This constraint can be exploited to optimise the number of receivers concerning system requirement and availability. Further, the pointing error effects are also investigated for SISO and SIMO systems, which takes into account both atmospheric turbulence and misalignment induced fading.

Detection of Malicious Primary User Emulation Based on a Support Vector Machine for a Mobile Cognitive Radio Network Using Software-Defined Radio

Abstract: Mobile cognitive radio networks provide a new platform to implement and adapt wireless cellular communications, increasing the use of the electromagnetic spectrum by using it when the primary user is not using it and providing cellular service to secondary users. In these networks, there exist vulnerabilities that can be exploited, such as the malicious primary user emulation (PUE), which tries to imitate the primary user signal to make the cognitive network release the used channel, causing a denial of service to secondary users. We propose a support vector machine (SVM) technique, which classifies if the received signal is a primary user or a malicious primary user emulation signal by using the signal-to-noise ratio (SNR) and Renyi entropy of the energy signal as an input to the SVM. This model improves the detection of the malicious attacker presence in low SNR without the need for a threshold calculation, which can lead to false detection results, especially in orthogonal frequency division multiplexing (OFDM) where the threshold is more difficult to estimate because the signal limit values are very close in low SNR. It is implemented on a software-defined radio (SDR) testbed to emulate the environment of mobile system modulations, such as Gaussian minimum shift keying (GMSK) and OFDM. The SVM made a previous learning process to allow the SVM system to recognize the signal behavior of a primary user in modulations such as GMSK and OFDM and the SNR value, and then the received test signal is analyzed in real-time to decide if a malicious PUE is present. The results show that our solution increases the detection probability compared to traditional techniques such as energy or cyclostationary detection in low SNR values, and it detects malicious PUE signal in MCRN.

Proposal of spread spectrum MSK for BDS RDSS signal modulation

Abstract: BPSK is the basis of current GNSS (Global Navigation Satellite System) signals. BDS (Beidou navigation satellite system) RDSS (Radio Determination Satellite Service) system also adopts BPSK to realize communication and ranging simultaneously. To realize higher system capacity, RDSS signals overlap in time and frequency domain. The signal performance is heavily determined by the MAI (Multiple Access Interference) between overlapping signals. In this paper, SSMSK (spread spectrum MSK) is proposed. The signal performance is investigated under four conditions considering the main lobe bandwidth and the receiver bandwidth. The maximum number of overlapping signals for SSMSK is 11.7% higher than BPSK when the receiver bandwidth is for the side subcarrier. And the value is 10.6% when the receiver bandwidth is. SSMSK can be received utilizing BPSK local signal. When the receiving bandwidth is 2 R c , the correlation peak of SSMSK_BPSK is identical to BPSK. The tracking accuracy of SSMSK is higher than BPSK when the correlation interval is between 0.2-1 chips. The accuracy of SSMSK_BPSK is higher than BPSK when the correlation interval is 0.5 chips. The disadvantage of SSMSK is larger quantization word length. SSMSK is a better modulation for RDSS based on the comprehensive performance.

CubeSat Communication System for Maritime Needs

Abstract: This paper proposes a design of CubeSat communication system between ships and ground station for Automatic Identification System (AIS) using Software Defined Radio (SDR). The CubeSat operates as a relay point to increase the ground station’s detection range. The communication system design is divided into three subsystems; AIS, data communication, and Telemetry, Tracking & Control (TT&C). Each subsystem utilizes Very High Frequency (VHF), S-band and Ultra High Frequency (UHF) respectively. Data communication uses Differential Phase Shift Keying (DPSK), while AIS and TT&C use Gaussian Minimum Shift Keying (GMSK). The simulation takes into account Doppler shift in space communication. Based on the result from link budget analysis, the communication system satisfies the design specifications. This indicates that the proposed CubeSat communication system is applicable for AIS.

315-GHz Self-Synchronizing Minimum Shift Keying Receiver in 65-nm CMOS

Abstract: A self-synchronizing minimum shift keying (MSK) receiver operating at 315-GHz RF is demonstrated in 65-nm CMOS. The receiver outputs digital bits and utilizes a PLL based architecture that includes a frequency doubler in the loop to achieve the 315-GHz operation. The receiver is used to form a 10-Gbps link with BER < 10−11 at an RF input power of −21-dBm without using separate frequency synchronization between the transmitter and receiver, and data equalization. The 315-GHz RF is the highest for self-synchronizing receivers and for MSK receivers.

Effects of atmospheric weather and turbulence in MSK based FSO communication system for last mile users

Abstract: In this paper, a minimum shift keying (MSK) based free space optical (FSO) communication system for the terrestrial user is modeled. In our setup 10 Gbps downlink MSK modulated signal is transmitted first over 100 km dispersion shifted fiber and then the area where deployment of fiber is not possible due to some constraints, FSO link is used to transmit the data to the last mile users. FSO link suffers from various weather conditions and atmospheric turbulence i.e. scintillation effect. Hence, both the cases are considered to transmit the data through FSO link to the end users and Gamma–Gamma fading model is used to study the scintillation effect. FSO link range is optimized to analyze the behaviour of the proposed system for six different weather conditions over weak, moderate and strong turbulence using BER curves and eye diagrams. Also, from the base station uplink data is modulated by MSK and is transmitted back to central station via same fiber and detected successfully.

Algorithm Design Simulation Performance Analysis of MIMO GMSK System for Radio Communication on AWGN Channel

Abstract: GMSK (Gaussian Minimum Shift Keying) has become the system whose importance increases as the world getting the age of electronics and associating with cellular technologies. GMSK is the most preferred Modulation format for Mobile communication such as GSM, CDPD, DECT and Digital communications system in the 900Hz to 1800 MHz band. GMSK used for GSM because of its spectral efficiency and for radio power amplifiers it delegates’ high efficiency. Power consumption or using the low battery is the crucial factor in cellular technology which can be attained by using a nonlinear amplifier to give a better response. Modulation Scheme becomes an essential factor for better performance of cellular technology. As, ISI degrades the performance of the GMSK system with various types of MIMO. Here in the research article we proposed an approach for reducing the ISI for different m values i.e. 4, 8, 16, 32 and 64 along with the different power i.e. 10dB, 20dB 30dB. As well as GMSK performance is improved by using optimum filter as cost and noise is the major factor we must reduce in our system or different modulation scheme so that we can have better cellular technology. Also we made a comparison for PSK and QAM by computing the probability of BER for different modulating techniques

A New Receiver Design: Simultaneous Wireless Power Transfer With Modulation Classification

Abstract: This work proposes a new simultaneous wireless power transfer and modulation classification (SWPTMC) scheme, appropriate for internet of things (IoT) and military applications. The problem of SWPTMC is investigated for various modulation formats, i.e, quadrature phase-shift-keying (QPSK), 16-pulse amplitude modulation (16-PAM), π/4-QPSK, minimum shift keying (MSK), offset QPSK (OQPSK), and 16-quadrature amplitude modulation (16-QAM). We propose a new receiver architecture that incorporates conventional power splitting under a linear model with a certain level of sensitivity. The blind modulation classification algorithm is based on the higher-order cumulants and cyclic cumulants of the received signal. The cyclic cumulants use the non-zero cycle frequency position, while the higher-order cumulants use threshold values for classifying modulation formats. Monte Carlo simulations are carried out to validate the accuracy of the proposed SWPTMC scheme.

Performance vs. Spectral Properties For Single-Sideband Continuous Phase Modulation

Abstract: This study reports on a single side band spectrum directly generated by a continuous phase modulation (CPM) signal. This signal is analyzed in terms of modulation indices, pulse lengths, and pulse widths, all of which affect error probabilities, bandwidths, and SSB property. The error probability performance is based on an approximation of the minimum Euclidean distance. A numerical power spectral density calculation for this particular SSB modulation in terms of modulation index is presented. Reasonable tradeoffs in designing modulation schemes have been defined using multi-objective optimization to ensure sizable improvements in bit error rate (BER) and spectral efficiencies, without losing the property of being a SSB signal. Performance comparisons are made with known CPM schemes, e.g., Gaussian Minimum Shift Keying (GMSK) and Raised Cosine based CPM (RC).

Design and analysis of optimized CORDIC based GMSK system on FPGA platform

Abstract: The Gaussian minimum shift keying (GMSK) is one of the best suited digital modulation schemes in the global system for mobile communication (GSM) because of its constant envelop and spectral efficiency characteristics. Most of the conventional GMSK approaches failed to balance the digital modulation with efficient usage of spectrum. In this article, the hardware architecture of the optimized CORDIC-based GMSK system is designed, which includes GMSK Modulation with the channel and GMSK Demodulation. The modulation consists of non-return zero (NRZ) encoder, an integrator followed by Gaussian filtering and frequency modulation (FM). The GMSK demodulation consists of FM demodulator, followed by differentiation and NRZ decoder. The FM Modulation and demodulation use the optimized CORDIC model for an In-phase (I) and quadrature (Q) phase generation. The optimized CORDIC is designed by using quadrant mapping and pipelined structure to improve the hardware and computational complexity in GMSK systems. The GMSK system is designed on the Xilinx platform and implemented on Artix-7 and Spartan-3EFPGA. The hardware constraints like area, power, and timing utilization are summarized. The comparison of the optimized CORDIC model with similar CORDIC approaches is tabulated with improvements.

Performance Analysis of GMSK and Chirp-Binary Orthogonal Keying in AWGN and Multipath Fading Channels

Abstract: Gaussian Minimum Shift Keying (GMSK) is a special form of minimum shift keying, which is one of the most prominent modulation techniques, and has long been used in all the standards of Global System for Mobile Communication (GSM) in the world, since its inception. Later, it has been identified that Chirp signals offer inherent protection against fading in multipath channels. In this work, an investigation has been carried out into the performance of Chirp-Binary Orthogonal Keying (C-BOK) scheme in AWGN and multipath fading channels. Its performance has also been compared with the GMSK scheme under the same channel conditions. It has been found that C-BOK scheme offers better performance in both the AWGN and Multipath fading channels compared to the GMSK scheme. Therefore C-BOK may be a good candidate to be used as a modulation technique for wireless and other communication systems with multipath channel environment.

Simulation and evaluation of the influence of electromagnetic environment on UHF communication

Abstract: Based on the analysis of the complex electromagnetic environment, this paper starts from the signal layer, aiming at six kinds of communication signals with different modulation styles, such as CPFSK, GMSK, BPSK, QPSK, 16QAM, 32QAM, and so on. By means of mathematical simulation, using Matlab/Simulink simulation tool, the simulation model is established and the anti-interference performance of six kinds of signals is analyzed. Using the actual communication equipment and wireless channel simulator, through the simulation test of six kinds of signals, the influence of different electromagnetic environment factors such as Co-Channel Interference, adjacent frequency interference, IF interference, mirror frequency interference, intermodulation interference on different modulation modes of voice communication and data communication in electromagnetic environment is studied, and the adaptability of electromagnetic environment is analyzed and compared.

One-Step Backtracking Algorithm Based on Viterbi Algorithm in GMSK Demodulation

Abstract: Viterbi algorithm is a commonly used algorithm for Gaussian filtered minimum frequency shift keying (GMSK) demodulation, but there exist some problems such as large delay, high overhead, and data overflow in the hardware implementation. Aiming at the problems of delay and overhead, we propose a novel update rule to optimize the stored transfer-state information table and realize one-step backtracking in this paper. It also ensures the realization of pipeline operation, reduces demodulation delay, and saves hardware resources. Furthermore, we adopt combinational logic to perform pre-decision, which not only satisfies the timing requirements, but also achieves the anti-overflow. The hardware implementation results demonstrate the feasibility and correctness of the design.

Onboard and Ground Station Telemetry Architecture Design for a LEO Nanosatellite

Abstract: This paper details the communication system architecture for a 3U hyperspectral imaging cubesat. The paper begins with discussions on objectives of and requirements from the communication system. Based on these, an architecture has been proposed. The architecture has been designed to ensure that the system works even in the case of emergencies, including, but not limited to antenna deployment failure or other component failures. This has been done by introducing multiple redundancy provisions. The architecture is broadly classified into three sections - Uplink, Downlink and Beacon transmission. The satellite implements a full-duplex UHF-VHF architecture using Gaussian Minimum Shift Keying (GMSK) modulation scheme for data downlink and uplink, while a Morse coded, simplex, On-Off Keying (OOK) scheme is used for beacon transmission. Onboard the satellite, a single monopole antenna is used for receiving uplink, while the other antenna doubles as a turnstile and dipole for downlink and beacon transmissions respectively. All the components to be used in the system, both onboard the satellite and at the Ground Station (GS) have been discussed. The reasons for selecting and details regarding interfacing of these components have been elucidated. The paper also describes the flight plan for TTC and how the microcontroller switches between the modes of operations. Entry and exit conditions for each mode are defined. Discussions on terrestrial testing of individual modules and architecture of the system have been included. All of the conducted tests were satisfactorily passed and the proposed architecture was proven to be a viable option for use in the satellite.

Single carrier equalization method for GMSK signal

Abstract: The invention relates to the technical field of wireless communication, in particular to a single carrier equalization method for GMSK signals. The method comprises the following steps: receiving a GMSK signal and carrying out synchronization head processing on a carrier to determine the starting position and the ending position of each subsequent hop; carrying out sliding correlation on the GMSKsignal near the training sequence and carrying out matched filtering; coherent demodulation and frequency domain equalization are carried out on the GMSK signal; and finally, carrying out soft information dispreading and LDPC decoding on the GMSK signal. According to the GMSK/QPSK/BPSK cyclic channel estimation algorithm device, the GMSK coherent demodulation algorithm and the single carrier frequency domain equalization algorithm, the theoretical limit of the algorithms can be approached, Meanwhile, the multipath amplitude information, the phase information and the time delay information of each path can be accurately estimated under a complex multipath channel. Meanwhile, noise is effectively suppressed, an MMSE algorithm is adopted for balancing, so that the performance is optimal, andthe method can adapt to various high-speed moving environments such as suburb channels, urban channels and open zones. The effect of resisting complex terrain multipath is achieved, and high creativity is achieved.

Hardware Realization of GMSK System Using Pipelined CORDIC Module on FPGA

Abstract: GMSK system is used in many diverse communication systems and which provides compact spectral Bandwidth and high spectral efficiency for next-generation communication systems. In this manuscript, the cost-effective GMSK system is designed using a Pipelined CORDIC model and realized on the FPGA hardware system. The GMSK system mainly has NRZ Encoder-Decoder, Integrator, and differentiator, Gaussian filter, FM modulator and demodulator along with Channel. The FM modulator and demodulator is designed Using a pipelined CORDIC model and Digital Frequency Synthesizer (DFS). The 8-bit Pipelined CORDIC model is used for In-phase and Quadrature-Phase (IQ) generation along with DFS for arbitrary waveform generation for the formation of IQ modulation. The complete GMSK system is designed using Verilog-HDL on Xilinx ISE 14.7 environment and prototyped on FPGA. The GMSK system implementation results are compared with existing approaches with better improvement in hardware constraints like chip area (Slices) and operating frequency.

GMSK signal demodulation method

Abstract: The invention discloses a GMSK signal demodulation method The invention belongs to the technical field of electronic measuring instrument signal modulation characteristic testing The invention designs a demodulation test method for a modulation characteristic test of a GMSK signal By adopting a forward demodulation scheme, the problem of contradiction between short data and high-precision demodulation caused by a loop locking process in an existing feedback demodulation scheme is solved, and the method can adapt to a short data demodulation test, and is wide in test scene application rangeand high in test scene applicability; by improving a carrier synchronization link in a forward demodulation scheme and adding frequency offset fine estimation, the frequency offset estimation range isensured, the estimation precision is improved, high-precision demodulation is realized, and the problem of low demodulation precision of an existing forward demodulation scheme is solved

Joint Viterbi detection and decoding algorithm for bluetooth low energy systems

Abstract: An efficient joint Viterbi detection and decoding (JVDD) algorithm for a bluetooth low energy (BLE) system is proposed. Since the convolutional coded Gaussian minimum-shift keying (GMSK) signal is specified in the BLE 5.0 standard, two Viterbi processors are needed for detection and decoding. However, the proposed JVDD scheme uses only one Viterbi processor by modifying the branch metric with inter-symbol interference information from GMSK modulation; therefore, the hardware complexity can be significantly reduced without performance degradation.

SDR Based Implementation of MSK and GMSK Receiver in Rich Multipath Environment

Abstract: This paper presents software defined radio based implementation of Minimum Shift Keying (MSK) and Gaussian Minimum Shift Keying (GMSK) digital receiver. The performance of MSK receiver and GMSK receiver is assessed under practical multipath fading scenario in mode-stirred metal enclosure. Metal enclosure when stirred with pedal creates rich isotropic multipath fading environment. The isotropic field and the severity of fading can be reduced by placing radiation-absorbent material (RAM) in the metal enclosure. The effect of addition of number of absorbers is to reduce the number of scattered waves hence reduce isotropic field distribution in the enclosure. This effect has direct implication of increased Rician K-factor. The performance of MSK and GMSK receiver is analyzed when the metal enclosure was loaded with few pieces of RAM.

LDPC Coded Non-Recursive GMSK System with Quasi-Coherent Demodulation

Abstract: A novel low-density parity-check (LDPC) coded Gaussian minimum shift keying (GMSK) scheme is proposed for wireless communications subject to low SNRs, limited power and spectrum resources. We first design a non-recursive GMSK modulator to alleviate the impact of error propagation. Then, a pilot-aided quasi-coherent demodulation algorithm (PA-QCDA) is derived, where a modified BCJR-based detection is used to produce the soft-output with initial and ending trellis-states being determined using the overhead-limited pilot. We choose proper parameters for the non-recursive GMSK signaling according to the trade-off of the power and spectral efficiency. Simulation results show that the proposed non-recursive GMSK system with the PA-QCDA can achieve performance similar to the LDPC coded BPSK system and can also work well in the presence of large frequency and phase offsets or burst errors.

Modulation recognition based on spectral correlation function

Abstract: As a very important inherent characteristic of modulated signals, Cyclostationarity can be exploited for various signal processing tasks such as detection, classification, especially for signal buried in noise or masked interference. In this paper, cyclostationarity of some typical digitally modulated signals are analyzed and Spectral correlation functions (SCF) of these signals are simulated. Based on two features extracted from cycle frequency profile of SCF, three common digitally modulated signals (BPSK, QPSK, MSK) are recognized with a decision tree classifier. The proposed scheme for modulation recognition is easy for implementation and doesn't require any prior knowledge such as carrier frequency or symbol rate. Simulations prove that the proposed scheme is able to achieve 90% recognition rate when signal to noise ratio (SNR) higher than -3dB.

A Novel Hybrid MSK Modulation Scheme for Additional Data Transmission

Abstract: In the paper, a novel hybrid modulation scheme is proposed to embed a phase-modulated signal into the minimum shift keying (MSK) signal, where the additional signal could be used to transmit some additional important data In order to achieve the imperceptibility of the additional signal to the MSK signal, the orthogonal condition between the additional signal and the MSK signal is investigated The bit-error-rate (BER) performances of the hybrid modulation over addition white Gaussian noise (AWGN) channel are also investigated The theoretical analysis and simulation results show that the additional signal with the orthogonal frequency makes little effect on the BER performance of the original MSK receiver, and the information in the additional signal is also robust

Analysis of the Joint Functioning of the Timing and Phase Synchronization Algorithms of the GMSK-Signal

Abstract: The paper provides an analysis of phase and timing synchronization algorithms for a GMSK signal with a changing frequency shift without using known data in the signal, based on raising to a power. To eliminate the changing frequency shift, a feedback loop with first-order astatism is used. The possibility of the simultaneous operation of these algorithms is shown, a joint block diagram for their implementation is presented. The numerical dependences of the variances of the phase and timing estimates versus the signal-to-noise ratio are calculated with various values of the coefficient in the feedback loop and the filter length as parameters.

GMSK signal frequency offset estimation algorithm based on FFT

Abstract: The invention discloses a GMSK signal frequency offset estimation algorithm based on FFT, and the algorithm comprises the steps: removing the phase information of a GMSK modulation signal during demodulation, obtaining a maximum spectral line and a secondary spectral line through FFT operation, and calculating a frequency shift factor; setting a threshold value for judging whether the offset is inthe central area or not, and directly utilizing the obtained frequency shift factor to calculate the frequency offset when judging that the offset is in the central area according to the threshold value; otherwise, solving the amplitude of the center position frequency of the adjacent spectral lines on the left side and the right side of the maximum spectral line through frequency spectrum refinement to serve as the criterion of the correction direction, carrying out frequency spectrum shifting on the to-be-measured signal, correcting the frequency shift factor, and then calculating the frequency offset. According to the method, higher estimation precision is obtained, and unnecessary calculation amount is not increased, so that good estimation precision can be obtained in a low signal-to-noise ratio environment and under the condition that the to-be-estimated frequency offset is close to a quantized frequency point.