Radio Resource Management for WLAN Networks through Power Control

Cross-layer radio resource management in integrated WWAN and WLAN networks

Interconnection of different access network technologies is an important research topic in mobile telecommunications systems. In this paper, we propose an ns-3 architecture for simulating the interconnection of wireless local area network (WLAN) and Universal Mobile Telecommunications System (UMTS). This architecture is based on the architecture proposed by the Third Generation Partnership Project, being the use of virtual interfaces as its main innovation. In order to demonstrate the value of the proposed simulation framework, we implemented the UMTS and WLAN interconnection considering three joint radio resource management strategies for distributing arriving calls. From the simulations results, we can conclude that the proposed simulation architecture is suitable to test and evaluate performance aspects related to the interconnection and joint management of UMTS and WLAN technologies. Copyright © 2012 John Wiley & Sons, Ltd.

Wireless local area networks (WLANs) provide mobility and convenience to users, the efficiency of todaypsilas WLANs are still far from satisfactory. In this paper discusses the performance of WLANs and wireless ad-hoc networks, our main contribution is analyze several methods to compare the throughput performance on simulation and experimental results. We describe NS-2 (network simulation) implementations for fine-tuning WLAN and wireless Ad-Hoc network parameters such as the physical layer (IEEE802.11) datalink layer (MAC) and network layer (routing protocol) related parameters. Customizing these parameters oppose to using the values specified in the standards will increase throughput and channel utilization under fixed load conditions.

Teleoperated systems are used in multiple fields since they allow the user to remotely work in locations where it would otherwise be infeasible due to cost, safety, or accessibility. However, due to the vast distances involved, teleoperated systems suffer from degraded communication between the operator and end device. This often takes the form of either delay or loss in the control signal. Understanding this degradation is necessary to advance the development of teleoperated systems. The objective of this research is to identify how normal operation of a teleoperated device is altered by delay in the communication signal and how system performance can be improved. A 4-degrees-of-freedom (4-DOF) teleultrasound robot was used to measure the time delay between a command and its response as well as the position error resulting from the time delay. The delay was measured by both a video recording and a network analysis software. The position error was measured by comparing physical coordinates of the actual robot with position of a simulated robot. These tests were then moved from a Wireless Local Area Network (WLAN) to a Virtual Local Area Network (VLAN) to see if there is a noticeable change from the different network topology. This study verified that the communication channel between the operator and robot is a significant source of delay. In the experimental WLAN setup, the system experienced an average of about 300 milliseconds of delay. It was verified that signal degradation affects operation of the system. The error in displacement was found to have a quadratic relation with signal delay. It was found that a VLAN network performed better than a WLAN network, with about 40% reduction in average delay time and 70% reduction in maximum displacement error. Contribution of this work was on quantifying effects of delay in position of a 4-DOF end-effector in a teleultrasound robot.

In certain study programs, especially electrical engineering, informatic engineering, information system and the like there are courses in computer program design. In this case, lecturer provides the learning how to design a computer program with a specific programming language systematically and sequentially, step by step. To increase the role of lecturer of the computer program design in a college, requires the implementation of a multimedia technology that can guarantee the systematic and sequential learning, step by step, especially when in a certain condition, the student is unable to attend the computer program design course given lecturer in the class. Although it may be found the equivalent tutorial on the internet, but the student still need the learning from lecturer. On the other hand, the lecturer of the computer program design is hard to repeat the explanation of the course given at the previous meeting to the absent student in the class, as it can spend the time already allocated for the next course explanation. In this paper provided a solution to overcome these problems by creating a streaming video provider server of computer program design courses that have been given lecturers at previous meeting in class. Access to streaming video is limited, accessible only to students who follow the course of computer program design through WLAN network on the college where the student is in college and when the end of the semester, the database server containing that streaming video is deleted by the system automatically so it can be filled with video streaming of next semester lectures, so as to save bandwidth and server memory. The explanation in this paper is limited to how to access streaming video in Wireless Local Area Network (WLAN). The methodology used is to simulate WLAN network with one computer as Learning Server and two laptops as client terminal. Keywords: Learning Server, Wireless LAN (WLAN), program

To solve the problem that the efficiency decreases with the increase of terminal nodes in wireless local area network(WLAN) distributed parallel simulation, a WLAN-oriented distributed hierarchical parallel simulation method is proposed. Firstly, considering the WLAN star network topology, the process of the simulated access point (AP) is denoted as the main process, which is responsible for time synchronization with the other processes of the simulated station (STA) nodes in the WLAN network. Secondly, the processes of all simulated STAs are then evenly divided into groups, and the group leader is responsible for the synchronization of processes within the group. Then, after the main process broadcasts the simulation start event, the group leader process firstly collects the end message of the group member's terminal node, and then reports to the main process. A three-layer hierarchical structure is constructed, consisting of the main process layer, the group leader process layer and the group member process layer. Finally, the time gain factor of the hierarchical simulation method is analyzed and obtained in closed-form expression, under the different computational loads. Simulation results show that comparing to the existing non-hierarchical simulation method, when the average computational load is 1.2x time unit and the nodes number is 100, the gain of the proposed method can reach 50%.

A signal-to-interference-noise ratio (SINR) constrained power control for code division multiple access (CDMA) and minimum mean square error (MMSE) multiuser detection is investigated. Two scenarios of a CDMA wireless local area network (WLAN) with MMSE multiuser detection are considered, i.e., the centralized power control for the uplink of a cellular WLAN, and the decentralized power control for an ad- hoc WLAN. It is proved that in both scenarios the interference between terminals is standard, so that the convergence of the proposed iterative power control (IPC) algorithm is guaranteed. Assuming asymptotically large number of communicating terminals and asymptotically large processing gain, it is shown that the power control becomes independent of particular spreading sequences, and thus, the random spreading sequences can be assumed. Furthermore, the transmitting powers can be readily adapted while the terminals join or leave the network. Numerical examples confirm that the simple IPC algorithm presented in this paper is very effective for cellular as well as ad-hoc CDMA WLAN's with MMSE multiuser detection for small to medium traffic loads and various SINR's requirements.

The opportunistic beamforming (OB) technique in multicellular OFDMA networks is investigated in this paper. For this reason, three cross-layer radio resource management (RRM) algorithms for OFDMA operational scenarios that are based on typical resource allocation targets such as minimization of transmit power, maximization of throughput and interference averaging are considered. The OB concept is combined with the considered RRM algorithms and a comparative performance analysis between the two types of resulted networks (omni and OB) is performed in terms of throughput, blocking probability and fairness. The simulation results suggest that OB is preferred for OFDMA systems with opportunistic rate adaptation rather than power controlled systems which offer QoS provision. According to the presented results, OB provides to OFDMA systems with opportunistic rate adaptation a ~13% throughput gain and ~75% gain in terms of blocking probability. In addition, it is shown that the combination of OB with interference averaging RRM algorithms has a minor beneficial impact only on the system fairness.

Wireless local area network (WLAN) has changed the paradigm of communication and become ubiquitous. As the number of devices connected to wireless is increasing, it is therefore, essential to find vulnerabilities in the security of wireless networks. In this research WLAN security vulnerabilities are exposed in real time. WLAN security techniques (MAC filtering, Hidden SSID and WPA2) available to residential users were practically exploited. Tenda WiFi wireless access point was set up with MAC filtering, hidden SSID and WPA2 security mechanisms in different combinations in such a way as to add an additional layer of security to previous configuration. Kali Linux version 2017.1 was used as a platform to exploit WLAN networks in real time. In this research, the sensitive information broadcasted by WLAN was utilized to carry out attacks on wireless networks. A practical demonstration of exposing vulnerabilities in MAC filtering, Hidden SSID with MAC filtering and WPA2-PSK with hidden SSID and MAC filtering security mechanisms of AP was carried out in real time. It was observed that the existing security mechanisms were vulnerable. Researchers have exploited many security mechanisms of WLAN focusing upon a single parameter of WLAN security at a time. However, in this work, the three available security mechanisms were cascaded to produce a three layer security mechanism i.e. WPA2 with hidden SSID and MAC filtering. This cascaded model was exploited in real time.

Network quality of experience (QoE) metrics are proposed in order to capture the overall performance of radio resource management (RRM) algorithms in terms of video quality perceived by the end users. Metrics corresponding to average, geometric mean, and minimum QoE in the network are measured when Max C/I, proportional fair, and Max-Min RRM algorithms are implemented in the network. The objective is to ensure a fair QoE for all users in the network. In our study, we investigate both the uplink (UL) and downlink (DL) directions, and we consider the use of distributed antenna systems (DASs) to enhance the performance. The performance of the various RRM methods in terms of the proposed network QoE metrics is studied in scenarios with and without DAS deployments. Results show that a combination of DAS and fair RRM algorithms can lead to significant and fair QoE enhancements for all the users in the network.

An approach for seamless handoff among mobile WLAN/GPRS integrated networks

This paper considers optimizing the utilization of radio resources in a heterogeneous integrated system consisting of two different networks: a wireless local area network (WLAN) and a wideband cod...

Nowadays, the development of new wireless protocols and standards are an engineering challenge due to the increased demand of Internet services via wireless access networks. Incoming standards, such as the IEEE 802.11ax, aim to improve the availability and performance of the wireless local area networks (WLAN). Recent works related to the development of the IEEE 802.11ax standard are focused on the description and initial performance evaluations of the expected technical improvements; however, there is no evaluation available regarding the QoS improvements that can be achieved with the new features included in the standard. In this work, we present a qualitative evaluation, as well as a set of laboratory and emulation tests aiming to compare current WLAN networks (IEEE 802.11g/n/ac) with the future IEEE 802.11ax networks. Datasets from real wireless scenarios are collected to evaluate QoS metrics in current IEEE 802.11g networks, and the IEEE 802.11ax standard is evaluated via emulation in NS3 with the injection of the same datasets, considering there are no deployments available with the new standard to date. Results show a significant improvement in terms of effective transfer rate (throughput) and round-trip-time (RTT) for the future WLAN networks, which is in line with the huge potential expected with the introduction of the upcoming high efficiency IEEE 802.11ax standard.

Over the past few years, mobile networks have emerged as a promising approach for future mobile IP applications. With limited frequency resources, designing an effective MAC (Medium Access Control) protocol is a hot challenge. IEEE 802.11b/g/a/n networks are currently the most popular wireless LAN products on the market [1]. The conventional IEEE 802.11b and 802.11g/a specification provide up to 11 and 54 Mbps data rates, respectively. However, the MAC protocol that they are based upon is the same and employs a CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) protocol with binary exponential back-off. IEEE 802.11 DCF (Distributed Coordination Function) is the de facto MAC protocol for wireless LAN because of its simplicity and robustness [2,3]. Therefore, considerable research efforts have been put on the investigation of the DCF performance over wireless LAN [2]. With the successful deployment of IEEE 802.11a/b/g wireless LAN and the increasing demand for real-time applications over wireless, the IEEE 802.11n Working Group standardized a new MAC and PHY (Physical) layer specification to increase the bit rate to be up to 600 Mbps [3]. The throughput performance at the MAC layer can be improved by aggregating several frames before transmission [3]. Frame aggregation not only reduces the transmission time for preamble and frame headers, but also reduces the waiting time during CSMA/CA random backoff period for successive frame transmissions. The frame aggregation can be performed within different sub-layers. In 802.11n, frame aggregation can be performed either by A-MPDU (MAC Protocol Data Unit Aggregation) or A-MSDU (MAC Service Data Unit Aggregation). Although frame aggregation can increase the throughput at the MAC layer under ideal channel conditions, a larger aggregated frame will cause each station to wait longer before its next chance for channel access. Under errorprone channels, corrupting a large aggregated frame may waste a long period of channel time and lead to a lower MAC efficiency [4]. On the other hand, wireless LAN mobile stations that are defined as the stations that access the LAN while in motion are considered in this chapter. The previous paper analyzed the IEEE 802.11b/g/n MAC performance for wireless LAN with fixed stations, not for wireless LAN with mobile stations [5, 6, 7, 8, 9, 10]. On the contrary, Xi Yong [11] and Ha Cheol Lee [12] analyzed the MAC performance for IEEE 802.11 wireless LAN with mobile stations, but considered only IEEE 802.11 and 802.11g/a wireless LAN specification. So, this chapter summarizes all the reference papers and analyzes the IEEE 802.11b/g/a/n MAC performance for wireless LAN with fixed and mobile stations. In other words, we will present the analytical evaluation of saturation

With the explosively increasing demand of multimedia applications in wireless local area networks (WLAN), Quality of Service (QoS) provisioning has become an important issue. IEEE 802.11 WLAN is the most popular WLAN technology today. In this paper, we propose an adaptive p-persistent based IEEE 802.11 medium access control (MAC) scheme in WLAN. The proposed scheme can maximize the total channel throughput and also can provide the service differentiation to multiple traffic classes. This is achieved by updating the transmission probability for each station in a timely manner based on the network measurements. The simulation results show the scheme can quickly adapt the station transmission probabilities to the desirable values to achieve maximum throughput and QoS provisioning in a dynamic WLAN environment. The simulation results also match well with the theoretical analysis.