Scarce Bandwidth Research Articles

Robust Repetitive Current Control of Two-Level Utility-Connected Converter using LCL Filter

This paper investigates the implementation and performance limits of conventional and odd-harmonic repetitive controllers used for current control of two-level grid-connected inverter. This research is motivated by the relatively poor performance of classical (PI) controller when utility voltage has high harmonic distortion. Repetitive controllers (RCs) have the ability to track or reject periodic signals. However, their effectiveness is limited severely by the scarce bandwidth of the plant. To address this issue, the relationship between plant bandwidth and the converter’s LCL filter is also investigated. In addition, the effects of variation in parameters of low-pass filter used in RC loop on the performance of the system are studied. Odd-harmonic repetitive controller (ORC) is used to overcome the excessive memory requirement in RC implementation. The performance of RC and ORC is tested for different total harmonic distortion (THD) values of utility voltage. The results show that RC improves steady state error and THD of the output current. Also, RC is found to be robust under variations in output-side inductance.

A Destination and Mobility Path Prediction Scheme for Mobile Networks

Mobile multimedia services are gaining great momentum among subscribers of mobile networks (MNs). An understanding of the network traffic behavior is essential in the evolution of today's MNs and, thus, leads to more efficient planning and management of the network's scarce bandwidth resources. The communication efficiency can be largely improved (i.e., optimizing the allocation of the network's limited resources and sustaining a desirable quality of service) if the network anticipates the needs of its users on the move and, thus, performs reservation of radio resources at cells along the path to the destination. In this vein, we propose a mobility prediction scheme for MNs; more specifically, we first apply probability and Dempster–Shafer processes for predicting the likelihood of the next destination, for an arbitrary user in an MN, based on the user's habits (e.g., frequently visited locations). Then, at each road junction, we apply the second-order Markov chain process for predicting the likelihood of the next road segment transition, given the path from the trip origin to that specific road junction and the direction to the destination. We evaluate our proposed scheme using real-life mobility traces; the simulation results show that the proposed scheme outperforms traditional schemes.

A dual mode self-adaption handoff for multimedia services in mobile cloud computing environment

Since mobile devices are becoming the primary platforms for many users who always roam around and access the cloud computing applications, the two concepts of mobile computing and cloud computing have emerged as a new widely accepted paradigm, mobile cloud computing. More and more users use cloud computing service and offload their local applications to the cloud. Unfortunately, developing mobile multimedia cloud services over heterogeneous wireless networks poses a challenge for service continuity. The degraded link quality and connection losses are likely to happen and these may affect service availability and service usage times in mobile cloud computing scenarios. To improve handoff quality and minimize utilized bandwidth, we propose a dual mode self-adaption handoff mechanism for multimedia services in mobile cloud computing environment. The new mechanism uses multipath transmission for media flows based on "make before break" technology, and consists of the duplicate mode and the effective mode, which are changed according to the network condition. Analytic model and simulation are developed to investigate our new mechanism. The results demonstrate that the self-adaption handoff mechanism can realize seamless handoff for multimedia services in cloud, reduce the packet loss rate, as well as obtain a more efficient use of the scarce wireless bandwidth and the power of mobile devices.

Reliable Adaptive Video Streaming Driven by Perceptual Semantics for Situational Awareness.

A novel cross-layer optimized video adaptation driven by perceptual semantics is presented. The design target is streamed live video to enhance situational awareness in challenging communications conditions. Conventional solutions for recreational applications are inadequate and novel quality of experience (QoE) framework is proposed which allows fully controlled adaptation and enables perceptual semantic feedback. The framework relies on temporal/spatial abstraction for video applications serving beyond recreational purposes. An underlying cross-layer optimization technique takes into account feedback on network congestion (time) and erasures (space) to best distribute available (scarce) bandwidth. Systematic random linear network coding (SRNC) adds reliability while preserving perceptual semantics. Objective metrics of the perceptual features in QoE show homogeneous high performance when using the proposed scheme. Finally, the proposed scheme is in line with content-aware trends, by complying with information-centric-networking philosophy and architecture.

Energy-Efficient Topology Control With Selective Diversity in Cooperative Wireless Ad Hoc Networks: A Game-Theoretic Approach

Due to the scarce bandwidth and limited power supply in mobile terminals, performance and energy consumption in wireless communications must be continually focused upon. Cooperative transmissions improve the capacity performance of wireless ad hoc networks (WANETs). However, when energy efficiency is considered, the advantage of user cooperation over non-cooperation does not always exist since it involves multiple nodes with more energy consumption in transmissions. To exploit the benefits of user cooperation in cooperative WANETs, we propose a distributed energy-efficient selective diversity (EESD) topology control to improve energy efficiency, which jointly considers network capacity and energy consumption in terms of bits per Joule . EESD forms transmission coalitions via cooperative manner (i.e, diversity) selection, by taking into account the cost of channel information exchange. We then formulate EESD as a coalition game and propose an adaptive coalition formation algorithm for EESD with proved convergence property and stable coalition structures. Simulation results show the performance improvement of EESD in energy efficiency and network lifetime compared to the existing topology control schemes.

Neighborhood-Aware and Overhead-Free Congestion Control for IEEE 802.11 Wireless Mesh Networks

It has been reported that the IEEE 802.11 MAC protocol and the TCP congestion control are highly problematic in terms of flow starvation in wireless mesh networks (WMNs). However, the economic features of IEEE 802.11 make it the commonly-used MAC protocol in WMNs. Therefore, solving starvation at the transport layer seems to be more appropriate. Indeed, the main starvation cause in TCP is that congestion is managed as a link-based problem. However, since bandwidth is a spatially-shared resource in WMNs, congestion is a neighborhood phenomenon that should be handled using mutual cooperation within a congested neighborhood. Such cooperation considerably consumes the already scarce bandwidth of WMNs causing more congestion. In this paper, we propose a neighborhood-aware and overhead-free congestion control scheme (NICC) that solves the starvation problem without impacting the scarce bandwidth of WMNs. NICC makes use of some underexploited fields in the IEEE 802.11 frame header, without modifying the standard frame size, to provide an overhead-free multi-bit congestion feedback; being overhead-free, this feedback allows performing neighborhood cooperation without generating control overhead. Furthermore, being multi-bit, it yields source nodes a fine-grained indication of the congestion degree, providing accurate rate control. The NICC performance in terms of starvation avoidance and bandwidth efficiency is proven through extensive simulations.

VQ-encoded images in reversible data hiding of high bit-compression-ratio

Bandwidth scarcity and data confidentiality are big constraints for internet application development. In order to transmit an image along with secret data over the internet efficiently, a compression-based, reversible information hiding scheme can be used to achieve data concealment as well as data compression. Therefore, using this kind of scheme is advantageous when bandwidth and confidentiality are major concerns of the users. In this study, we propose a novel, reversible information hiding scheme for vector quantisation (VQ)-encoded images. The proposed encoding scheme uses a given value to decide the embedding capacity of secret data in an image, and produces either a VQ-encoded image or a compressed codestream as the output. The embedded secret data and the original VQ-encoded image can be extracted from the output when needed. The proposed scheme utilises the fact that two adjacent blocks in a VQ-encoded image are usually similar: First, it uses codebook re-ordering based on the similarity to the codeword of the first block in an image. Second, it calculates the difference of the new indices of two adjacent image blocks. Finally, it encodes the secret bits along with the difference value as the compressed output for each block. We conducted several experiments and then used several representative images as the input to compare the proposed scheme with other related works. The results showed that the proposed scheme is very efficient in terms of bit rate, particularly when the input image has many similar neighbouring blocks in it.

Network pricing: can both ISP and P2P benefit?

SummaryInternet service providers are facing increasing back pressure from rising access demand by users, especially peer‐to‐peer (P2P)‐based applications that greatly enhance the large‐scale distribution of content into and out of their networks. With the ever increasing consumption pressure on scarce bandwidth resources, ISPs have been forced to reconsider their business model of overselling ‘all‐you‐can‐eat’ broadband at flat rates. Technical solutions such as traffic differentiation or blocking violate the principle of network neutrality; traffic shaping and deep packet analysis fall short in the presence of encryption; and P4P (localized P2P)‐based solutions are difficult to achieve in a heterogeneous environment. Economically, various usage‐based pricing schemes have been proposed and discussed. While they can improve efficiency in bandwidth consumption, they tend to face strong customer resistance as users have strong preference in favour of simple flat rates. We argue that any feasible pricing reforms cannot deviate much from the current flat rates while providing financial incentives for bandwidth hogs to limit their bandwidth access. In contrast to normal usage‐based pricing models that charge by volume, we propose a temporal‐based pricing model that may generate a mutually beneficial solution that can not only increase the profitability of ISPs but also accommodate P2P, rather than killing it, without changing the software, protocols or hardware that clients or ISPs use on the network.Copyright © 2014 John Wiley & Sons, Ltd

Spectrum Sensing using Energy Detection Technique for Cognitive Radio Networks using PCA Technique

With the growth of subscribers in wireless and data communication there is a scarcity of additional bandwidth to meet the demand. For the efficient usage of the spectrum bandwidth we go for a technology which is Cognitive Radio technique. The spectrum holes in the unutilized spectrum are to be used efficiently for the communication for the secondary user. The Cognitive Radio uses spectrum sensing techniques for determining the spectrum holes in the network. In order to improve the efficiency of the energy detection technique it is combined and used with the statistical Principal Component Analysis (PCA) technique. In conventional PCA technique the signal space power to the noise space power does not match with the actual SNR so a PCA correction technique is followed. The correction factor is applied to the noise space power and signal space power to equate it to the actual SNR. The threshold energy required is determined from the modified energy detection technique and the probability of false alarm value. The proposed method is the combination of PCA and energy detection spectrum sensing. The correction factor is applied to the PCA and it clearly defines the process for threshold Energy computation.

Comparative Performance Analysis of AODV and AODV-MIMC Routing Protocols for Mobile Ad hoc Networks

Bandwidth Scarcity is a major drawback in multi-hop ad hoc networks. When a single-interface single-channel (SISC) approach is used for both incoming and outgoing traffic the bandwidth contention between nodes along the path has occurred as well as throughput is degraded. This drawback is overwhelmed by using MIMC approach as well as some of the Quality of Service (QoS) requirements has been enhanced. In this paper we applied multi-interface muti-channel approach to AODV routing protocol, called AODV-MIMC routing protocol and its performance is compared with AODV routing protocol. The simulation results show the Network Life Time, Throughput, and Packet Delivery Ratio of AODV-MIMC routing protocol has been tremendously improved than the AODV routing protocol.

Surrogate Object Based Mobile Transaction

The advancement in wireless technology and rapid growth in the use of mobile devices in mobile paradigm have the potential to revolutionize computing by the illusion of a virtually infinite computing infrastructure. This new mobile paradigm enabled mobile devices to support data and transaction management in addition to the static nodes. A mobile device from anywhere in the wireless environment could utilize seamlessly a large computing power or any other resources in order to provide effective data and transaction process. In addition, advancement in wireless network together with ubiquity of devices has resulted in storing and retrieving incredible volumes of knowledge provided by data in the mobile devices. Knowledge provided by data from mobile system has become very essential in many day-to-day applications. However, transaction management and knowledge discovery in mobile environment faces several challenges such as scarce bandwidth, limited battery resources, asymmetry in wired and wireless connectivity, asymmetry in mobile and fixed hosts, and mobility of host and their limitations. In addition to the traditional mobile system challenges, it also faces many challenges such as dependency on continuous network connections, data sharing applications and federation with multiple service providers. Due to these challenges, data loss, frequent disconnection, unpredicted number of wireless and wired access and high transaction aborts has occurred in data and transaction management over distributed mobile paradigm. To realize data management in mobile cloud, Surrogate Object based Mobile Transaction is proposed to deal with the fundamental issues of asymmetry problems, latency problems, low abort rate and disconnection. The proposed strategy caches the data in the surrogate object which helps in reducing the average transaction time. The required reliability is provided by sending the transaction request to surrogate object and network lifetime is maximized by migrating the surrogate objects in a way to avoid improper load balancing. The performance of proposed models have been evaluated and compared with existing models by simulation.

A Survey of Bandwidth Utilization: Case Study of Federal University of Technology Minna

The effective utilization of the limited scarce bandwidth resources allocated by a spectrum regulator usually the Nigerian Communications Commissions (NCC) in Nigeria universities is paramount in maximizing the usage of the expensive scarce bandwidth resources. A significant bandwidth allocation is needed in order to meet up with the challenges of the day and the task of networking, communicating and reaching the word in our universities. Therefore, bandwidth management becomes necessary and essential. This paper contributes in that direction by surveying the bandwidth utilization at Federal University of Technology Minna campus with the hope of proffering a general solution that can be adopted in Nigerian universities for effective bandwidth management. Also, factors that hindered the development of most Nigeria universities are also examined. The federal university of technology minna which is structured like all other universities in the country in terms of the bandwidth requirement was choosing as a case study for this research work. Furthermore, some policies which can be adopted in order to effectively manage the scarce bandwidth resources in Nigerian universities are also proposed.

Modeling and Simulation Analysis of an Efficient MASNET Routeless Routing Protocol

The deployment of wireless ad-hoc mobile sensor network (MASNET) technology proves critical in many civilian and military applications. Routing over MASNET faces many challenges, such as scarce bandwidth, dynamic change of topology, limited computational capabilities, and power budgets of sensor nodes. Hence, we introduced a new routeless routing model that efficiently copes with such challenges, as asserted by initial simulation-obtained results. In this paper we validate our routing protocol via both mathematical modeling and simulation.

From the far side of the Moon: Delay/disruption-tolerant networking communications via lunar satellites

Delay/Disruption-Tolerant Networking (DTN) originated from research on Interplanetary Internet and still today space applications are the most important application field and research stimulus. This paper investigates DTN communications between the Earth and the far side of the Moon, by means of a lunar orbiter acting as relay. After an introductory part, the paper presents a comprehensive analysis of the DTN performance that can be achieved on the identified communication scenario. The focus is on the evaluation of the state-of-the-art ability of Interplanetary Overlay Network (ION), the NASA DTN implementation of Bundle Protocol (BP) and Contact Graph Routing (CGR), to meet the many challenges of the space communication scenario investigated (and more generally of a future interplay-netary Internet): intermittent links, network partitioning, scarce bandwidth, long delays, dynamic routing, handling of high priority and emergency traffic, interoperability issues. A study of security threats and Bundle Security Protocol (BSP) countermeasures complete the work. The many results provided, confirm the essential role of DTN in future space communications.

Network and Economic Trade-Off Performance Regions of Cognitive Radio Systems with Power Control

Cognitive radio will enable terminals with access to licensed and unlicensed portions of the spectrum. This feature is expected to solve bandwidth scarcity problems in future wireless networks. However, different parts of the spectrum will be subject not only to different propagation conditions, but also to different licensing a nd billing agreements. Therefore, in order to obtain the major profit and spectrum efficiency, resource allocation algorithms must no w target both network and economic performance metrics. This problem can be conveniently expressed as a multi-objective portfolio optimization problem, which has been studied in detail in the field of economics. This paper addresses the study of network and eco nomic Pareto optimal trade-off performance regions of cognitive radio systems under average transmit power control policies. Each packet transmission in primary and secondary mode is regarded as a financial asset whose average transmit power is optimized so as to simu ltaneously maximize return and minimize risk, where risk is the variance of the return. This paper studies three types of Pareto optima l trade-off regions: primary vs. secondary throughput, return vs. risk, and sum-throughput vs. fairness, where fairness is evalu ated by means of the Gini index. The boundaries of these trade-off regions are derived in parametric closed-form expressions. A power control policy is further proposed that maximizes return while simultaneously controlling risk and ensuring a level of quality of service fo r primary and secondary users. This means that operators can maximize revenue and network efficiency, while simultaneously minimiz ing risk and also ensuring fairness between primary and secondary users.

Resolving Unordered Issues for CMT-SCTP in Heterogeneous Wireless Network

Concurrent Multi-path Transfer extension of the Stream Control Transport Protocol (CMT-SCTP) has great potential to improve the utilization of scarce network bandwidth resource. Traditional CMT-SCTP adopts Round Robin (RR) algorithms to carry out packet scheduling that could affect the performance of SCTP traffic as unordered issues. In this paper, we discuss the unordered issues and propose a novel packet scheduling algorithm to improve the performance in heterogeneous wireless network. Our main idea is predicting the packet arriving time and then provides a path selection strategy. Through measuring round-trip time (RTT) and available bandwidth, we achieve an algorithm to predict the arriving time of data packets on one path, then give a reasonable path selection strategy to make sure that data arrives in the right order. By using proposed algorithm, the unordered packets and receive buffer blocking are reduced. We evaluate the performance of our algorithm by comparing it with the RR algorithm and show that it can resolve several performance issues.

Designing Two-Dimensional Spectrum Auctions for Mobile Secondary Users

Dynamic spectrum access by non-licensed users has emerged as a promising solution to address the bandwidth scarcity challenge. In a secondary spectrum market, primary users lease chunks of unused spectrum to secondary users. Auctions perform as one of the natural mechanisms for allocating the spectrum, generating an economic incentive for the licensed user to relinquish channels. Existing spectrum auction designs, while taking externality introduced by interference into account, fail to consider the potential mobility of secondary users, which leads to another dimension of externality: mobile communication motivates a secondary user to exclusively occupy a channel, i.e., forbidding channel reuse in its mobility region. In this work, we design two expressive auctions for mobility support, by introducing two-dimensional bids that reject a secondary user's willingness to pay for exclusive and non-exclusive channel usage, for the single-channel and multiple-channel scenarios, respectively. In the outcome of our 2D auctions, a channel is either monopolized or simultaneously reused without interference, whereas a secondary user can be mobile or is regulated to be static. We prove the existence of desirable equilibria in both auctions, where 1/10 and c/7(1+c) of optimal social welfare are guaranteed to be recoverable, respectively (c is the number of channels).

An Analysis on Decentralized Adaptive MAC Protocols for Cognitive Radio Networks

The scarcity of bandwidth in the radio spectrum has become more vital since the demand for more and more wireless applications has increased. Most of the spectrum bands have been allocated although many studies have shown that these bands are significantly underutilized most of the time. The problem of unavailability of spectrum and inefficiency in its utilization has been smartly addressed by the cognitive radio (CR) technology which is an opportunistic network that senses the environment, observes the network changes, and then uses knowledge gained from the prior interaction with the network to make intelligent decisions by dynamically adapting their transmission characteristics. In this paper, some of the decentralized adaptive medium access control (MAC) protocols for CR networks have been critically analyzed, and a novel adaptive MAC protocol for CR networks, decentralized non-global MAC (DNG-MAC), has been proposed. The results show the DNG-MAC outperforms other CR-MAC protocols in terms of time and energy efficiency.

Energy Efficient Random Transmission Control for Cognitive Radio Systems

Cognitive radio technology will allow terminals to access licensed and unlicensed portions of the spectrum. This feature will improve end-user satisfaction and will partially solve bandwidth scarcity problems. However, this opportunistic access implies more transmission attempts and thus higher power consumption. This goes against the energy/power efficient design that underpins modern wireless communication systems. This paper partially addresses this issue by proposing a random transmission policy that is energy-efficient and that provides high throughput gains. To facilitate analysis, a reception model for Rayleigh channels is here proposed that allows the calculation of correct packet reception statistics in the presence/absence of interference between primary/secondary users. The analysis initially focuses on the derivation of the boundaries of two types of trade-off regions: primary vs. secondary throughput, and sum-throughput vs. power consumption. It is observed that secondary transmissions always increase power consumption, and in the case of low interference they always lead to higher sum-throughput at the expense of reduced primary performance. By contrast, in the case of high interference, secondary transmissions can reduce both sum-throughput and primary user performance, thus requiring more complex control. It is shown that the minimum sum-throughput solution is also the boundary of the region where primary/secondary contributions to sum-throughput start to become dominant. An optimum transmission policy is further derived that maximizes sum-throughput while keeping primary/secondary throughput and power consumption under control. Sketches of the trade-off regions show the benefits of the proposed transmission policy.

Unravelling the Economic and Political Drivers of Deep Packet Inspection

The use of Deep Packet Inspection technology has been the focus of a growing amount of scholarly work due to its impact on sensitive policy issues. In this paper we look at the use of DPI for throttling or blocking peer to peer protocols by 288 broadband operators over three years, and correlate this with economic and political variables. Our empirical data shows that as of 2011, half of the studied ISPs are actively using DPI in their networks, although to varying degrees. We examine the role of seven economic and political drivers of DPI technology based on typical use-cases: bandwidth scarcity, network security, competition, surveillance, privacy protections, censorship and the strength of copyright industries. Performing bivariate analysis, we find that a few of these drivers are significantly correlated with the use of DPI.