An Efficient Simulation Model for Wireless LANs Applied to the IEEE 802.11 Standard

In this research report, we propose a simple simulation model for wireless LANs. In wireless LANs, contrary to LANs different transmission results can be observed by network nodes. This phenomenon is the result of radio propagation laws where the signal decay is by far more important than on cables. This leads to new and interesting modelization and simulation problems. In this article we propose a simple but general physical model to take into account radio propagation. We then apply this model to the study of the IEEE 802.11 standard. We show how IEEE 802.11 can be efficiently modeled and simulated. This allows us to offer a detailed study of the standard. We will give performance evaluations of the IEEE 802.11 DS standard with transmisson rate 1, 2, 5.5 or 11 Mbit/s which take into account the exact protocol overhead. We also study special behaviour as broadcast transmission, performance with hidden nodes, spatial reuse

Throughput in multihop CSMA mobile adhoc network

A lot of research has been done in routing protocols for ad-hoc network especially at the IETF in the working group MANET. These studies have mostly focused on the conception of routing protocols for mobile radio networks where the radio channel capacity is generally limited. The present article does not target the study of these routing protocols but investigate how carrier sense multiple access (CSMA) protocols can be tuned to optimize the network throughput. We buid two models of interference of simultaneous transmissions and conduct simple computations to guide our optimizations. The first interference model only considers the strongest interferer as the second one takes into account all the contributions. We use simulations to test our optimizations results. The result of this paper is a guide to optimize CSMA multihop networks; the obtained results show that a good tuning of CSMA protocols in term of carrier sense threshold and transmission range allows one to gain a lot of network throughput (up to 9

Available Bandwidth and RSRP Based Handover Algorithm for LTE/LTE-Advanced Networks Tested in LTE-Sim Simulator

In this paper, we propose a new algorithm that improves the performance of the operation of Handover (HO) in LTE-Advanced (LTE-A) networks. As recognized, Mobility Management (MM) is an important pillar in LTE/LTE-A systems to provide high quality of service to users on the move. The handover algorithms define the method and the steps to follow to ensure a reliable transfer of the UEs from one cell to another without interruption or degradation of the services offered by the network. In this paper, the authors proposed a new handover algorithm for LTE/LTE-A networks based on the measurement and calculation of two important parameters, namely the available bandwidth and the Received Power (RSRP) at the level of eNodeBs. The proposed scheme named LTE Available Bandwidth and RSRP Based Handover Algorithm (LABRBHA) was tested in comparison with well-known algorithms in the literature as the LHHA, LHHAARC and the INTEGRATOR scheme using the open source simulator LTE-Sim. Finally, the network performances were investigated via three indicators: the number of lost packets during the handover operation, the latency as well as the maximum system throughput. The results reported that our algorithm shows remarkable improvements over other transfer schemes

A low-loss dual-band bandpass filter using open-loop stepped-impedance resonators and spur-lines for sub-6 GHz 5G mobile communications

This article presents the design of a low-loss microstrip dual-band bandpass filter with improved inter-band isolation and selectivity for 5G sub-6 GHz mobile communications. The proposed filter utilizes the two first resonance mode frequencies provided by the stepped-impedance resonator to generate its two passbands at 3.6 GHz and 3.5 GHz, and spur-lines located before the input/output ports to improve the isolation and selectivity between passbands. The filter is designed using an RT/Duroid 5870 substrate with a relative permittivity of 2.33 and a thickness of 0.79 mm, manufactured and tested to validate the proposed design. The experimental results show that the filter operates at 3.61 GHz and 5.51 GHz with a 3-dB fractional bandwidth of 12.74% and 16.7%, respectively. Insertion losses at the two passbands center frequencies are 0.6 dB and 0.9 dB. In addition, the proposed filter has the advantage of covering the licensed and unlicensed 5G bands and provides a simple structure without using vias or DGS structures

Dual Port Antenna Combining Sensing and Communication Tasks for Cognitive Radio

Dynamic spectrum access has been proposed asthe effective solution to overcome the spectrum scarcity issue,supported by cognitive radio technology. Sensing and communicationfunctions are both the most important tasks in cognitiveradio systems. In this paper, an antenna system combiningsensing and communication tasks is proposed to be integratedinto cognitive radio front-ends. Sensing task is performed bythe means of an ultra-wideband quasi-omnidirectional antenna.Whilst the communication task is ensured by using a narrowbandantenna. Both antennas have been designed on the same layer ofa FR4 substrate, for manufacturing cost constraint. Therefore,the isolation between them must take into consideration. Themeasured mutual coupling of less than -18dB is achieved overthe whole impedance bandwidth. The proposed sensing antennacovers a wide range frequency bands ranging from 2 to 5.5GHz.While the communication antenna operates at 2.8GHz, and byadding inductors to the antenna, the resonant frequency canbe tuned from 2.6 to 2.7GHz. The whole antenna system wasdesigned, fabricated, and tested. Measurement and simulationresults prove the feasibility of the proposed structure for cognitiveradio applications

Exponential MLWDF (EXP-MLWDF) Downlink Scheduling Algorithm Evaluated in LTE for High Mobility and Dense Area Scenario

Nowadays, with the advent of smartphones, most of people started to make voice and video conference calls continuously even in a high mobility scenario, the bandwidth requirements have increased considerably, which can cause network congestion phenomena. To avoid network congestion problems and to support high mobility scenario, 3GPP has developed a new cellular standard based packet switching, termed LTE (Long Term Evolution). The purpose of this paper is to evaluate the performance of the new proposed algorithm, named Exponential Modified Largest Weighted Delay First ‘EXP-MLWDF’, for high mobility scenario and with the presence of a large number of active users, in comparison with the well-known algorithms such as a proportional fair algorithm (PF), Exponential Proportional Fairness (EXP/PF), Logarithm Rule (LOG-Rule), Exponential Rule (EXP-Rule) and Modified Largest Weighted Delay First (MLWDF). The performance evaluation is conducted in terms of system throughput, delay and PLR. Finally, it will be concluded that the proposed scheduler satisfies the quality of service (QoS) requirements of the real-time traffic in terms of packet loss ratio (PLR), average throughput and packet delay. Because of the traffic evolution, some key issues related to scheduling strategies that will be considered in the future requirements are discussed in this article

Performance Optimization of WiMAX Mobile Networks with a Predictive Handover Process

Worldwide Interoperability for Microwave Access (WiMAX) is one of the most promising technologies for the next generation networks as it provides high data rates at medium and long range with full support of mobility. The technology is based on IEEE 802.16 standards and amendments specifying the MAC and PHY layers for fixed, nomadic, portable and mobile access. High speed mobility scenarios require low delay handover so as not to degrade end-to-end QoS indicators, such as delay time or data loss, that are significantly more affected. The WiMAX Forum Network Working Group aims to provide methods for controlled transition of the MS between BSs without significant loss of data or decreased QoS. It has been observed that prediction-based methods reduce handover latency and by the way the packets loss rate. In this paper we use the linear regression model to build a predictive hard handover algorithm that predict the Received Signal Strength Indicator (RSSI) value and advertize the MS to trigger the scanning procedure and the handover process operations reducing so the total handover latency and packets loss rate. The numerical analysis and simulation results show that the proposed method significantly reduces the handover latency and the packets loss rate

CPW and microstrip line-fed compact fractal antenna for UWB-RFID applications

In this study, we present an implementation of Ultra Wide Band (UWB) Koch Snowflake antenna for Radio Frequency Identification (RFID) applications. The compact antenna, based on the Koch Snowflake shape, is fed by coplanar waveguide (CPW) and by microstrip line with an overall size of 31 × 27 × 1.6mm3. The simulation analysis is performed by CST Microwave Studio and compared with HFSS software. The antenna design exhibits a very wide operating bandwidth of 13GHz (3.4- 16.4GHz) and 11 GHz (3.5-14.577 GHz) with return loss better than 10 dB for microstrip line antenna and CPW antenna respectively. A prototype of CPW and microstrip antenna was fabricated on an FR4 substrate and measured. Simulated and measured results are in close agreement. The small size of the antenna and the obtained results show that the proposed antenna is an excellent candidate for UWB-RFID localization system applications