scholarly journals Throughput Maximization of Cognitive Radio Multi Relay Network with Interference Management

2018 ◽  
Vol 8 (4) ◽  
pp. 2230
Author(s):  
Pradip Varade ◽  
Akanksha Wabale ◽  
Ravinder Yerram ◽  
Rupesh Jaiswal
Keyword(s):  
Cognitive Radio ◽  
Orthogonal Frequency Division Multiplexing ◽  
Optimization Problem ◽  
Transmission Rate ◽  
Interference Management ◽  
Threshold Level ◽  
Throughput Maximization ◽  
Relay Network ◽  
Frequency Division ◽  
Subcarrier Pairing

<span>In this paper, an Orthogonal Frequency Division Multiplexing (OFDM) based cognitive multi relay network is investigated to maximize the transmission rate of the cognitive radio (CR) with enhanced  fairness among CR users  with interference to the primary users (PUs) being managed below a certain threshold level. In order to improve the transmission rate of the CR, optimization of the subcarrier pairing and power allocation is to be carried out simultaneously. Firstly joint optimization problem is formulated and Composite Genetic and Ordered Subcarrier Pairing (CGOSP) algorithm is proposed to solve the problem. The motivation behind merging genetic and OSP algorithm is to reduce the complexity of Genetic Algorithm (GA). Further, to have a fair allocation of resources among CR users, the Round Robin allocation method is adopted so as to allocate subcarrier pairs to relays efficiently. The degree of fairness of the system is calculated using Jain’s Fairness Index (JFI). Simulation results demonstrate the significant improvement in transmission rate of the CR, low computational complexity and enhanced fairness.</span>

scholarly journals Mobile Fog Computing-Assisted Resource Allocation for Two-Hop SWIPT OFDM Networks

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Xiaofei Di ◽  
Yu Zhang ◽  
Tong Liu ◽  
Shaoli Kang ◽  
Yue Zhao
Keyword(s):  
Resource Allocation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Fog Computing ◽  
Achievable Rate ◽  
Fast Time ◽  
Power Splitting ◽  
Frequency Division ◽  
Decode And Forward ◽  
Subcarrier Pairing ◽  
Receiver Architecture

The mobile fog computing-assisted resource allocation (RA) is studied for simultaneous wireless information and power transfer (SWIPT) two-hop orthogonal frequency division multiplexing (OFDM) networks, where a decode-and-forward (DF) relay first harvests energy from signals emitted by a source and then helps the source to forward information to its destination by using the harvested energy. Power splitting (PS) strategy is adopted at the relay and a different PS (DPS) receiver architecture is proposed, where the PS factors of all subcarriers are different. A RA problem is formulated to maximize the system’s achievable rate by jointly optimizing subcarrier pairing, power allocation, and PS factors. Since the RA problem is a nonconvex problem and is difficult to solve, an efficient RA algorithm is designed. As the wireless channels are fast time-varying, the computation is performed in mobile fog node close to end nodes, instead of remote clouds. Results demonstrate that the achievable rate is significantly increased by using the proposed RA algorithm. It is also found that the computation complexity of RA algorithm of DPS receiver architecture is much lower than the existing identical PS (IPS) receiver architecture, and thus the proposed DPS architecture is more suitable for computation-constrained fog system.

QoS-Constrained Resource Allocation Scheduling for LTE Network

2015 ◽  
Vol 4 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Hung-Chin Jang ◽  
Yun-Jun Lee
Keyword(s):  
Resource Allocation ◽  
Data Transmission ◽  
Orthogonal Frequency Division Multiplexing ◽  
Transmission Rate ◽  
High Mobility ◽  
System Throughput ◽  
Frequency Division ◽  
High Data ◽  
Single Carrier ◽  
Allocation Method

The goal of LTE (Long Term Evolution) is to provide high data transmission rate, scalable bandwidth, low latency, high-mobility, etc. LTE employs OFDM (Orthogonal Frequency Division Multiplexing) and SC-FDMA (Single Carrier - Frequency Division Multiple Access) for downlink and uplink data transmission, respectively. As to SC-FDMA, there are two constraints in doing resource allocation. First, the allocated resource blocks (RBs) should be contiguous. Second, those of the allocated RBs are forced to use the same modulation technique. The aim of this research is to propose a QoS-constraint resource allocation scheduling to enhance data transmission for uplink SC-FDMA. The proposed scheduling is a three-stage approach. In the first stage, it uses a time domain scheduler to differentiate user equipment (UE) services according to their distinct QoS service requirements. In the second stage, it uses a frequency domain scheduler to prioritize UE services based on channel quality. In the third stage, it limits the number of times of modulation downgrade of RBs allocation in order to enhance system throughput. In the simulations, the proposed method is compared to fixed sub-carrier dynamic resource allocation method and adaptive dynamic sub-carrier resource allocation method. Simulation results show that the proposed method outperforms the other two methods in terms of throughput, transmission delay, packet loss ratio, and RB utilization.

scholarly journals ECCM Schemes against Deception Jamming Using OFDM Radar with Low Global PAPR

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 2071
Author(s):  
Xinhai Wang ◽  
Gong Zhang ◽  
Xiangmin Wang ◽  
Qingqing Song ◽  
Fangqing Wen
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Optimization Problem ◽  
Average Power ◽  
Doppler Spectrum ◽  
Frequency Division ◽  
Ofdm Symbol ◽  
Alternating Direction ◽  
Parseval’S Theorem ◽  
Joint Range ◽  
Huge Challenge

In this paper, a type of effective electronic counter-countermeasures (ECCM) technique for suppressing the high-power deception jamming using an orthogonal frequency division multiplexing (OFDM) radar is proposed. Concerning the velocity deception jamming, the initial phases of the pulses transmitted in a coherent processing interval (CPI) are designed to minimize the jamming power within a specific range, forming a notch around the jamming in the Doppler spectrum. For the purpose of suppressing the range deception jamming and the joint range-velocity deception jamming, the phase codes of the subcarriers belonging to the OFDM pulses are optimized to minimize the jamming power, distributing some specific bands in the range and the range-velocity domain, respectively. According to Parseval’s theorem, the phase encoding, acting as the coding manner of the OFDM subcarriers can ensure that the energy of each OFDM symbol stays the same. It is worth noticing that the phase codes of the OFDM subcarriers can influence the peak-to-average power ratio (PAPR). Thus, an optimization problem is formulated to optimize the phase codes of the subcarriers under the constraint of global PAPR, which can regulate the PAPRs of multiple OFDM symbols at the same time. The proposed problem is non-convex; therefore, it is a huge challenge to tackle. Then we present a method named by the phase-only alternating direction method multipliers (POADMM) to solve the aforementioned optimization problem. Some necessary simulation results are provided to demonstrate the effectiveness of the proposed radar signaling strategy

scholarly journals Spectrum sensing in cognitive radio wireless networks for orthogonal freqnency division multiplexing in additive white Gaussian noise channel

2017 ◽  
Vol 1 (T4) ◽  
pp. 180-186
Author(s):  
Tri Minh Nguyen ◽  
Tu Thanh Nguyen ◽  
Phuong Huu Nguyen
Keyword(s):  
Cognitive Radio ◽  
Gaussian Noise ◽  
Orthogonal Frequency Division Multiplexing ◽  
Additive White Gaussian Noise ◽  
Sliding Window ◽  
White Gaussian Noise ◽  
Frequency Division ◽  
Low Snr ◽  
Primary Users ◽  
Ofdm Signals

Cognitive radio (CR) systems are one of the most interesting topics in recent years. They would enable more efficient use of the spectrum. The main problem of CR is how to dectect exactly the spectrum usage of primary users. There are many ways to do this, such as energy detector (ED), Axell’s detector, the sliding window detector, etc. Among them, cyclostationarity (CS) based dection methods attracted much attention because of their better results in low-SNR regimes. This paper will propose a method based on the autocorrelation property of orthogonal frequency division multiplexing (OFDM) signals in additive white Gaussian noise (AWGN).

A Novel Proportional Fairness Scheduling for Subcarrier Allocation in OFDM Based Relaying Systems

2013 ◽  
Vol 765-767 ◽  
pp. 436-439
Author(s):  
Ya Ru Fu ◽  
Qi Zhu
Keyword(s):  
Communication Networks ◽  
Orthogonal Frequency Division Multiplexing ◽  
Transmission Rate ◽  
Scheduling Algorithm ◽  
Proportional Fairness ◽  
Wireless Communication Networks ◽  
Subcarrier Allocation ◽  
Frequency Division ◽  
Channel Condition ◽  
Relaying Systems

Different data rate services are expected to support for heterogeneous users in OFDM based relaying networks. And fairness of users is an important factor that cannot be neglected in the process of resource allocation, particularly for users at the cell edge. The traditional proportional fairness (PF) scheduling algorithm provides a trade-off between average throughout and fairness in wireless communication networks. This paper investigates subcarrier allocation problem of Orthogonal Frequency Division Multiplexing (OFDM) aided relaying systems with PF constraint and proposes an efficient PF scheduling priority by using the users channel condition of past scheduling time and current scheduling time more comprehensively and uniformly which can both maximize the system transmission rate and enhance the system fairness no less than traditional ones. The simulation results show the validity.

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