NOMA with Adaptive Transmit Power Using Intelligent Reflecting Surfaces

In this article,we use Intelligent Reflecting Surfaces(IRS)to improve the throughput of Non Orthogonal Multiple Access(NOMA)with Adaptive Transmit Power(ATP).The results are valid for Cognitive Radio Networks(CRN)where secondary source adapts its power to generate low interference at primary receiver.In all previous studies,IRS were implemented with fixed transmit power and previous results are not valid when the power of the secondary source is adaptive.In CRN,secondary nodes are allowed to transmit over the same band as primary users since they adapt their power to minimize the generated interference.Each NOMA user has a subset of dedicated reflectors.At any NOMA user,all IRS reflections have the same phase.CRN-NOMA using IRS offers 7,13,20 dB gain vs.CRN-NOMAwithout IRS for N=8,16,32 reflectors.We also evaluate the effects of primary interference.The results are valid for any number of NOMA users,Quadrature Amplitude Modulation(QAM)and Rayleigh channels.

Energy efficiency maximization for buffer-aided multi-UAV relaying communications

This paper studies a multiple unmanned aerial vehicle(UAV)relaying communication system,where multiple UAV re-lays assist the blocked communication between a group of ground users(GUs)and a base station(BS).Since the UAVs only have limited-energy in practice,our design aims to maximize the energy efficiency(EE)through jointly designing the communica-tion scheduling,the transmit power allocation,as well as UAV trajectory under the buffer constraint over a given flight period.Actually,the formulated fractional optimization problem is diffi-cult to be solved in general because of non-convexity.To re-solve this difficulty,an efficient iterative algorithm is proposed based on the block coordinate descent(BCD)and successive convex approximation(SCA)techniques,as well as the Dinkel-bach’s algorithm.Specifically,the optimization variables of the formulated problem are divided into three blocks and we alter-nately optimize each block of the variables over iteration.Numeri-cal results verify the convergence of the proposed iterative al-gorithm and show that the proposed designs achieve significant EE gain,which outperform other benchmark schemes.

A Proposed Calibration Method for Precise Wide Range Scatterometric Measurements

The co-effect of transmitted power fluctuation and system nonlinearity produce deviations in scatterometer measurement results . An internal calibration method to deal with this problem is proposed. The method can result in more precise scatterometric measurements in a wide range. The basic principle of the method is combining real-transmitted-power detection with the calibration of system nonlinearity. A practical scheme to implement the method is also presented, which is developed based on a special designed mechanism of a microwave radiometer-scatterometer combined system.

Reliable and Energy Efficient Protocol for Wireless Sensor Network

Low-power design is one of the most important issues in wireless sensor networks (WSNs) , while reliable information transmitting should be ensured as well. Transmitting power (TP) control is a simple method to make the power consumption down, but excessive interferences from potential adjacent operating links and communication reliability between nodes should be considered. In this paper, a reliable and energy efficient protocol is presented, which adopts adaptive rate control based on an optimal TP. A mathematical model considering average interference and network connectivity was used to predict the optimal TP. Then for the optimal TP, active nodes adaptively chose the data rate with the change of bit-error–rate(BER) performance. The efficiency of the new strategy was validated by mathematical analysis and simulations. Compared with 802.11 DCF which uses maximum unified TP and BASIC protocol, it is shown that the higher average throughput can achieve while the energy consumption per useful bit can be reduced according to the results.

On the energy efficiency of MIMO cooperative relaying networks

Cooperative relaying techniques can greatly improve the capacity of the multiple input and multiple output （MIMO） wireless system. The transmit power allocation （TPA） strategies for various relaying protocols have become very important for improving the energy efficiency. This article proposes novel TPA schemes in the MIMO cooperative relaying system. Two different scenarios are considered. One is the hybrid decode-and-forward （HDF） protocol in which the zero-forcing （ZF） process is operated on relays, and the other is the decode-and-forward （DF） protocol with relay node and antenna selection strategies. The simulation results indicate that the proposed schemes can bring about significant capacity gain by exploiting the nature of the relay link. Additionally, the proposed TPA scheme in the HDF system can achieve the same capacity as the equal TPA with fewer relay nodes used. Finally, the capacity gain with the proposed schemes increases when the distribution range of relay nodes expands.

Performance analysis of WCDMA wireless access standard

Based on the transmitting power of a mobile station and the maximum cell capacity,the analysis of a wide-band code-division multiple access(WCDMA)standard and the comparison of the corresponding parameters with CDMA2000 or evolution-data only(EV-DO)are given in this paper.The result proves that the mobile station of WCDMA cannot provide the required transmitting power on the specified frequency band and data rate,and the symmetrical capacity in an up-downlink cannot meet the requirement of a mobile Internet.It is questionable for the International Telecommunication Union(ITU)to select the frequency band of 2 GHz for vehicular mobile telecommunication and unreasonable to distribute it over the downlink and uplink channels symmetrically.Only CDMA20001X EV-DO or enhanced data rate for GSM evolution(EDGE),which adopts the Time Division Multiple Access(TDMA)mode,can provide the high-speed data rate for a wireless access.