Channel Capacity Of Communication Systems Research Articles

Analysis on improving channel capacity of MPPM

Nowadays, optical wireless communication has been widely applied and various techniques are used to achieve signals with higher quality and higher efficiency. Pulse position modulation (PPM) is a commonly used modulation scheme. However, PPM suffers from its low bandwidth efficiency and Multiple pulse position modulation (MPPM) is generated to improve the performance of signals. Further research can be carried out to figure out ways to further improve channel capacity of communication systems by combining modulation techniques together. In this paper, three different schemes are introduced, including LDPC-coded MPPM UWOC system, MIMO-MPPM WOC system, and PSM-MPPM system. Fundamental principles of these three techniques are mentioned before going through the methods used to carrying out experiments. Both simulations derived from numerical analysis and experiment results are obtained to support the results. In LDPC-coded and MIMO research, turbulence effects are considered by adopting different statistical distributions. The aim of the paper is to compare properties of three recent research and discuss how they can be applied in different scenarios to improve the communication systems.

Terahertz Dual-Band Dual-Polarization 3-Bit Coding Metasurface for Multiple Vortex Beams Generation

Terahertz technology and vortex beams have demonstrated powerful capabilities in enhancing the channel capacity of communication systems. This work proposes a design strategy of dual-band and dual-function 3-bit coding metasurface based on beam polarization characteristics. The unit cell of the metasurface is composed of two pattern structures, which has the ability to flexibly and independently control the reflection phases of incident plane wave at two frequency bands. The metasurface designed in this work is a combination of two patterns according to the addition operation and the convolution operation. The 3-bit coding metasurface generates two orbital angular momentum (OAM) beams with a deflection of 12.1° with modes l1=+1 and l2=−1 under the y-polarized incidence at 0.6 THz. Similarly, the designed metasurface produces two OAM beams with a deflection of 16.5° under the incidence of x-polarized wave at 0.9 THz, and the modes are l3=+1 and l4=−2. The full-wave simulation results agree well with the theoretical predictions, which could prove the correctness and effectiveness of the proposed method. The metasurface designed according to this method has potential applications in multiple-input multiple-output (MIMO) communication systems.

High-efficiency ultra-broadband orbital angular momentum beam generators enabled by arrow-based fractal metasurface

Vortex beams carrying orbital angular momentum (OAM) are of great importance owing to the capacity to expand channel capacity of communication systems from microwave to optical regimes. In this work, a single-layer ultra-broadband meta-atom is designed by using the method of fractal. The reflected co-polarization amplitude of the arrow-based fractal meta-atom can exceed 0.9 in a frequency range from 6 to 19.7 GHz and the complete 2π phase control can be achieved by rotating the structure. Based on the proposed meta-atom, metasurface-based vortex beam generators are designed. As an illustrative example, a metasurface-based OAM beam generator with a mode of +1 is designed, fabricated, and measured. Both the experimental and simulated results match well with each other, proving the practicability of the proposed high-efficiency ultra-broadband metasurface.

The $\kappa$- $\mu$ Shadowed Fading Model With Integer Fading Parameters

We show that the popular and general {\kappa}-{\mu} shad- owed fading model with integer fading parameters {\mu} and m can be represented as a mixture of squared Nakagami (or Gamma) distributions. Thus, its PDF and CDF can be expressed in closed-form in terms of a finite number of elementary functions (powers and exponentials). The main implications arising from such connection are then discussed, which can be summarized as: (1) the performance evaluation of communication systems operating in {\kappa}-{\mu} shadowed fading becomes as simple as if a Nakagami fading channel was assumed; (2) the {\kappa}-{\mu} shadowed distribution can be used to approximate the {\kappa}-{\mu} distribution us- ing a closed-form representation in terms of elementary functions, by choosing a sufficiently large value of m; and (3) restricting the parameters {\mu} and m to take integer values has limited impact in practice when fitting the {\kappa}-{\mu} shadowed fading model to field measurements. As an application example, the average channel capacity of communication systems operating under {\kappa}-{\mu} shadowed fading is obtained in closed-form.

Introducing Information Capacity as a Figure of Merit for Instrument Systems Using the Concepts of Energy Bandwidth

Relationships between signalling rate and channel capacity of communication systems are generalised to the case of all information machines. A maximum rate of measuring and controlling, which is related to the physical elements of the system, is defined. It is also shown that essential noise may be related to these physical elements. Hence, the Shannon-Hartley theorem of information theory is seen to be applicable to all information machines.