This paper demonstrates that no ultra narrow band modulation method, which includes VMSK and VPSK, can have substantially greater efficiency than conventional methods, such as QAM, in transmission in the same frequency band. Keywords– VMSK, VPSK, Ultra Narow Band Modulation, QAM

<p>Adaptive quadrature amplitude modulation (QAM) is a crucial scheme that enables the modern communication systems to overcome adverse effects of channel fluctuations and maintain an acceptable spectral efficiency. In order enhance adaptive even further, adoption odd-bit QAM constellations alongside had been suggested improve transmission efficiency modulation. Hence, extensively studied...

A customized IQ modulator driven by equal-amplitude binary signals for generating offset-free 16-quadrature amplitude modulation (QAM) is proposed and validated through simulations. The incorporation of tunable splitters demonstrates the feasibility of the transmitter and enables more efficient constellations such as hexagonal 16-QAM.

Orthogonal Frequency Division Multiplexing (OFDM) has been adopted as the modulation technique for many of the next generation wireless broadband multimedia communications systems, for example, Digital Audio Broadcasting (DAB), terrestrial Digital Video Broadcasting (DVB), and the wireless local area network (LAN) standards HIPERLAN/2, and IEEE 802.11a. One problem inherent in plain vanilla OFD...

In this letter, performance of a multiantenna multiuser unmanned aerial vehicle (UAV)-assisted terrestrial-satellite communication system over mixed free space optics (FSO)/radiofrequency (RF) channels is analyzed. Downlink transmission from the satellite to UAV completed through FSO link which follows gamma–gamma distribution with pointing error impairments. Both heterodyne detection an...

In this paper, we propose a novel on-line blind demodulation algorithm for Quadrature Amplitude Modulation (QAM). The proposed approach can demodulate QAM signal without constellation knowledge, and reach the theoretical optimal performance under the constraint of sequential detection. Numerical simulations are provided to validate the analytical results. Results show that when iterations are l...

Optical quadrature amplitude modulation (QAM) is experimentally demonstrated with a low-complexity modulator based on a semiconductor optical amplifier and electroabsorption modulator. Flexible amplitude/phase format transmission is achieved. The applicability of octary QAM for coherent optical access networks with sustainable 3 Gb/s per-user bandwidth is investigated for a long reach of 100 km...

For quadrature amplitude modulation (QAM) systems, the joint blind equalization (JBE) algorithm, concatenation of two di erent equalization modes, has been widely used. After the eye is opened by the blind equalization mode, the decision-directed (DD) mode follows to improve the equalization performance with fast convergence. This paper proposes a shell partition-based CMA (SPCMA) which acts as...

This paper proposes hardware architectures of adaptive equalizers applicable to both the quadrature amplitude modulation (QAM) and vestigial sideband modulation (VSB) systems. This paper presents digitization methods for QAM and VSB systems requiring a low hardware cost with the performance comparable to that of the algorithm employing oating-point operations. To reduce the hardware cost of the...