Helal Chowdhury

Data downloading on the sparse coverage-based wireless networks

Infostation, hotspot, and drive-thru internet are examples of sparse coverage-based wireless networks. These wireless communication networks provide low-cost, delay insensitive high data rate services intermittently with discontinuous coverage. Radio propagation parameters, velocity of the user, distance between the user, and access point are the key factors that affect the throughput and the amount of information downloaded from such sparse coverage-based wireless networks. To evaluate the performance of such wireless communication networks analytically the impact of above mentioned factors can be modeled with simplified relationship model such as received signal strength versus distance or signal to noise ratio versus throughput. In the paper, we exploit the relationship between throughput and distance and develop two throughput distance relationship models to evaluate the performance of multirate wireless networks. These two throughput distance relationship models are used in calculation of average throughput as well as downloaded file size. Numerical values are presented for the IEEE 802.11n standard. The numerical results verify that the new proposed technique can be used as an alternative to the simulations to evaluate the performance of sparse coverage-based wireless networks.

Cooperative data download on the move in indoor hybrid radio-optical WLAN-VLC hotspot coverage

In this work, we study the performance of hybrid radio-optical wireless local area network WLAN-visible light communication VLC hotspot and compare its performance with stand-alone VLC-only or WLAN-only hotspot cases. We consider data download on move scenario in an indoor environment for single-user and for multi-user cases. Short-range spotlighting cell so-called VLC hotspot is considered for high data rate region. On the other hand, WLAN hotspot is used for providing reliable connectivity and moderate data rate support. Throughput-distance relationships are developed both for WLAN and VLC to evaluate the performance of indoor environment by taking into account the radio and optical channel characteristics. The impact of the velocity of mobile users and the number of VLC hotspots present in the considered service area are also considered on the performance of hybrid WLAN-VLC hotspot. Simulations have been performed to evaluate the performance of such network for data downloading on move scenario by taking into account performance metrics such as file size, average connectivity and system throughput. Simulation results reveal that the considered hybrid WLAN-VLC performs always better than stand-alone VLC-only or WLAN-only hotspots both for single and multi-user cases. Copyright

Cooperative multihop connectivity performance in visible light communications

In this work, we have studied the cooperative multi-hop communication using relays to increase the connectivity in visible light communications (VLC). Short transmission range, narrow field of view and occlusion/obstruction by object are limiting the user connectivity to the access point in VLC. The connectivity performance of such cooperative communications is characterized by taking into account optical line-of-sight (LOS) channel model, relay selection algorithm, velocity of user, semi-angle at half power of the light emitting diode (LED) and the field of view (FOV) of the photo detector. Simulations have been performed to evaluate the connectivity performance of such networks with and without relays. In user connectivity performance several simulation parameters are considered: user density, coverage range ratio of multi-hop region (MR), relay probabilities. Simulation results reveal that in case of all considered simulation parameters user connectivity increases using relays in comparison to without relays.

Data Download on Move in Indoor Hybrid (Radio-Optical) WLAN-VLC Hotspot Coverages

In this work, we will study the performance of combined wireless local area network (WLAN) and visible light communication (VLC) in indoor environment by taking into account the data download on move scenario. In this combined networks both WLAN, and VLC are characterized by their data rates and communication range. In VLC, short range spotlighting cell is considered for high data rate region acts as VLC hotspot. WLAN is used for continuous connectivity and increasing coverage range of hybrid WLAN-VLC hotspot. Moreover, mobility issues of mobile users have also been considered in the performance of hybrid WLAN-VLC hotspot. Simulations have been performed to evaluate the performance of such network for data downloading on move scenario by taking into account performance metric such as file size. Simulation results reveal that there is impact of mobile user velocity and number of VLC hotspots present in the considered service area of hybrid WLAN-VLC hotspot.

Traffic Statistics on the Coverage of WLAN-BASED Music Shower

WLAN-based music shower is music delivery system. In WLAN-based music shower high speed WLAN technologies will be used as underlying technologies to deliver music to the mobile user quickly and cheaply. The size of music file downloaded from the WLAN-based music shower depends on many factors such as distance between user and WLAN-based music shower, channel characteristics, as well as the underlying technologies used in the WLAN-based music shower. The impact of these factors can be characterized with throughput-distance relationship model. This paper provides a mathematical framework for calculating the received average throughput and total file size while randomly crossing the coverage area of an WLAN-based music shower. Two throughput-distance relationship models are presented to analyze the music file transfer during random crossing of the coverage area of an WLAN-based music shower. Utilizing the results of this analysis, the performance of WLAN-based music shower using IEEE 802.11b and IEEE 802.11g WLAN technologies are also compared

On the Random Crossing of an Infostation Coverage

Infostations system provides low-cost, delay insensitive high data rate services intermittently with its discontinuous coverage. Key factors that affects to maximize the amount of information downloaded from the infostation include channel characteristics, velocity of the user, distance between user and the infostation as well as the underlying technologies used in the infostation. In general, throughput increases as the distance between infostation and the user decreases. This phenomenon can be characterized with throughput-distance relationship model. This paper provides a mathematical framework for calculating the received average throughput and total file size while randomly crossing the coverage area of an infostation. Two throughput-distance relationship models are presented to analyze the information transfer during random crossing of the coverage area of an infostation. Utilizing the results of this analysis, the performance of infostation using IEEE802.11b and g WLAN technologies is also compared.

Data downloading in relay assisted mobile vehicles

Traditionally, every mobile station (MS) riding in the mobile vehicle uses conventional connection to the base station (BS). However, in 802.16j mobile multihop relay (MMR) networks, one of the studied usage model is “coverage on mobile vehicle”. Therein, a relay station (RS) is mounted on a vehicle. The RS provides service to MSs riding on the vehicle by relaying their data to the mobile multihop relay base station (MMR-BS). This brings several benefits compared to the situation where every MS would individually connect to the MMR-BS, including power savings and better channel condition. In this work, we consider a scenario where user is considered sitting in the vehicle and downloading data via relay station which is mounted on top the vehicle. The downloading typically uses the RS mounted on the vehicle but direct communication to the MMR-BS is also allowed. We characterize both the access links (MS-RS, MS-BS) and the relay link (RS-BS) by throughput-distance relationship models. The decision whether to use RS or to communicate directly with the MMR-BS is decided based on comparing the combined throughput distance model. (MS-RS-BS) with the throughput obtained using direct access link. Numerical results are provided using a two-turn mobility model. The results show that mobility and velocity of mobile vehicle have a great impact on the performance of mobile vehicle relay assisted network.

Interference Analysis Due to Spot Beams Drift in Integrated Satellite-Terrestrial Networks

Integrated satellite-terrestrial networks can improve both the service coverage and spectral efficiency in spot-beam-based mobile satellite service system (MSS). In an integrated satellite-terrestrial network, MSS frequency is reused in both satellite spot beams and complementary ground component (CGC). Due to reuse of frequency, co-channel interference is present in both intra-component (between CGCs) and inter-component (between satellite spot beam and CGC). Without spot beams drift, these interferences have tolerable levels for acceptable performance in voice and/or data communication. However, in practice, especially the inter component interference will start to grow if the spot beams drift from their nominal positions due to pointing error of spot beams. In this paper, we study the interference from the satellite component to the ground component when the drifted spot beams start to interfere with CGCs reusing the same frequency. The interference levels depend on the drift magnitude, drift angle, and also the protection ring size utilized by the ground component. Simulation results are provided for different values of these parameters and giving new insight into the effects of spot beam drifting in an integrated satellite-terrestrial network.

Broadband Services on Move in the Coverage of Relay-Based Network

This paper provides a mathematical framework for calculating the received average throughput and total aggregated throughput while a user traverses the coverage area of relay enhanced cell. In multi-hop communication, the performance of relay-based network depends on the link budget evaluation for access link as well as relay link. In this work, both the access link and relay link has been characterized by throughput-distance relationship model. These two throughput-distance relationship models have been utilized to develop combined throughput-distance model. Finally utilizing the combined throughput- distance model, the performance of relay-based network has been carried out. In performance evaluation of relay based network, both average throughput and aggregated throughput have been presented as performance metrics and numerical results are compared in case of single-hop, multi-hop and combined coverage scenario. Finally, we have shown how to select the coverage range and where to position the relay to meet the certain service demand while a mobile user is traversing the coverage of relay based network at different velocities.

Heterogeneous Software-Defined Networks: Implementation of a Hybrid Radio-Optical Wireless Network

Visible light communication (VLC) is an emerging optical wireless technology which has the potential to complement existing radio frequency (RF) communication systems aiming at exploiting the advantages of both networks. The concept of such complementing as hybrid VLC#x002F;RF systems is well understood theoretically but not much has been done on practical realization. In this paper, we report implementation details of a hybrid VLC#x002F;RF point-to-point system, where two nodes are connected with each other via VLC and RF links. In this implementation, we consider VLC link as primary link therefore it will always be an active link whenever it is available. Nodes are capable of vertical handover between two types of communication links in case of primary (VLC) link failure and restoration. The VLC link state plays important role so we describe a continuous link monitoring protocol and criteria for switching between VLC and RF links. To switch between two links a Linux kernel bonding driver has been used. A simple link monitoring protocol has been implemented for VLC link state and it is passed continuously to bonding driver for decision. Performance of this system has been evaluated for user datagram protocol (UDP) content distribution while handover. Hence, a simple hybrid system capable of handover between VLC and RF links has been achieved.