Scarce Bandwidth Research Articles

A cache invalidation strategy for mobile networks

The diversity of services delivered over wireless channels has increased people's desire in ubiquitously accessing these services from their mobile devices. However, a ubiquitous mobile computing environment faces several challenges such as scarce bandwidth, limited energy resources, and frequent disconnection of the server and mobile devices. Caching frequently accessed data is an effective technique to improve the network performance because it reduces the network congestion, the query delay, and the power consumption. When caching is used, maintaining cache consistency becomes a major challenge since data items that are updated on the server should be also updated in the cache of the mobile devices. In this paper we propose a new cache invalidation scheme called Selective Adaptive Sorted ( SAS) cache invalidation strategy that overcomes the false invalidation problem that exists in most of the invalidation strategies found in the literature. The performance of the proposed strategy is evaluated and compared with the selective cache invalidation strategy and the updated invalidation report startegy found in the literature. Results showed that a significant cost reduction can be obtained with the proposed strategy when measuring performance metrics such as delay, bandwidth, and energy.

An end‐to‐end approach to secure routing in MANETs

AbstractProviding secure routing in mobile ad hoc networks (MANETs) is far more difficult than establishing secure routing in wired networks or static wireless networks. Node mobility and the relative scarcity of bandwidth render prior solutions ineffective. Solutions based on securing link or path information do not work well in MANETs because the dynamic nature of links requires extensive use of flooding to establish effective countermeasures. On the other hand, solutions based on hop‐by‐hop exchanges of distance information are easily compromised. Instead of trying to secure the ordering of nodes, we argue that secure routing in MANETs must be based on the end‐to‐end verification of physical‐path characteristics aided by the exploitation of path diversity to increase the probability of finding secure paths. We apply this approach to the design of the Secure Routing through Diversity and Verification (SRDV) protocol, a secure routing protocol that we show to be as efficient as unsecured on‐demand or proactive routing approaches in the absence of attacks. We prove that the countermeasures used in SRDV can defend against a variety of known attacks to routing protocols, including attacks involving collusion, and the fabrication and modification of routing packets. We also show the effectiveness of the end‐to‐end mechanisms via simulations. Copyright © 2009 John Wiley & Sons, Ltd.

SIP Multicast-Based Mobile Quality-of-Service Support over Heterogeneous IP Multimedia Subsystems

The Universal Mobile Telecommunications System (UMTS) all-IP network supports IP multimedia services through the IP multimedia subsystem (IMS). This paper proposes a mobile quality-of-service (QoS) framework for heterogeneous IMS interworking. To reduce the handoff disruption time, this framework supports the IMS mobility based on the concept of session initiation protocol (SIP) multicast. In our approach, the mobility of a user equipment (UE) is modeled as a transition in the multicast group membership. With the concept of dynamic shifting of the multicast group's members, the flow of actual data packets can be switched to the new route as quickly as possible. To overcome mobility impact on service guarantees, UEs need to make QoS resource reservations in advance at neighboring IMS networks, where they may visit during the lifetime of the ongoing sessions. These locations become the leaves of the multicast tree in our approach. To obtain more efficient use of the scarce wireless bandwidth, our approach allows UEs to temporarily exploit the inactive bandwidths reserved by other UEs in the current IMS/access network. Analytic and simulation models are developed to investigate our resource reservation scheme. The results indicate that our scheme yields comparable performance to that of the previously proposed channel assignment schemes.

Comunicación inter-vehicular utilizando redes ad-hoc inalámbricas

This thesis proposes a new routing algorithm to allow communication in highly mobile, wireless ad-hoc networks, which in nature are wireless and infrastructureless. In motorway environments, the topology of the network changes frequently and unpredictable due to the mobility of the nodes. We investigate a new reactive routing algorithm based in location information in the context of inter-vehicular communication. In such a scenario, the originator of the communication does not know the position of its communication partner in advance. Rapid topology changes and scarce bandwidth prevent the nodes from exchanging positions regularly throughout the network. Therefore, we focus on reactive algorithms and explore several mechanisms limiting the flooding of discoveries location packets. The originator of a message uses scoped and controlled flooding to reach the destination. The receivers of the flooded message use their knowledge of the local environment to decide whether they can reach the intended destination of the message or retransmit the message to their neighbours. To evaluate our communication algorithm, we first validate it in a small scale network with the results o f a test bed. Then for large scale networks, our protocol is compared with the models of two prominent reactive routing algorithms: Ad-Hoc On-Demand Distance Vector (AODV) and Dynamic Source Routing (DSR) on a multi-lane rectangular and circular dual carriageway representative of city and motorway driving. Finally, our algorithm is analysed on a multi-lane circular carriageway representative of a six lane motorway driving with one location-based routing algorithm: Greedy Perimeter Stateless Routing (GPSR). The mobility of the vehicles on a Motorway using a Microscopic traffic model developed in OPNET has been used to evaluate the performance of each protocol in terms of: Route Discovery Time (RDT), End to End Delay (EED), Routing Overhead (RO), Overhead (O), Routing Load (RL) and Delivery Ratio (DR).

Efficient Resource Allocation for Wireless Multicast

In this paper, we propose a bandwidth-efficient multicast mechanism for heterogeneous wireless networks. We reduce the bandwidth cost of an Internet protocol (IP) multicast tree by adaptively selecting the cell and the wireless technology for each mobile host to join the multicast group. Our mechanism enables more mobile hosts to cluster together and leads to the use of fewer cells to save the scarce wireless bandwidth. Besides, the paths in the multicast tree connecting to the selected cells share more common links to save the wireline bandwidth. Our mechanism supports the dynamic group membership and offers mobility of group members. Moreover, our mechanism requires no modification to the current IP multicast routing protocols. We formulate the selection of the cell and the wireless technology for each mobile host in the heterogeneous wireless networks as an optimization problem. We use integer linear programming to model the problem and show that the problem is NP-hard. To solve the problem, we propose a distributed algorithm based on Lagrangean relaxation and a network protocol based on the algorithm. The simulation results show that our mechanism can effectively save the wireless and wireline bandwidth as compared to the traditional IP multicast.

Mobile Network Adaptation in the Ubidata Mobile File System

An important characteristic of mobile networks is the large variations of available bandwidth. Network conditions can vary from strong to weak to total disconnection. These variations may be masked from the users by a common technique called “data hoarding”. Limited mobile network bandwidth is an expensive resource today and in the foreseeable future. Efficiently utilizing scarce mobile bandwidth is a challenge for managing data in the mobile environment. In this paper, we introduced the network adaptation approaches used in the UbiData mobile file system. UbiData mobile file system is designed to automatically select a mobile user's active data set and automatically migrate that data when the user switches from device to device. Automation of data management, including data set selection, data replication, network adaptation, and data reintegration, is a goal in our system to tackle the problems incurred from data unavailability in weak and disconnection modes. We discuss the adaptation techniques in our UbiData system and present enhancements. To further reduce the network bandwidth requirement, two major approaches are introduced in our system. First, the communication requests are shortly delayed and optimized. Secondly, we employ content aware/transparent adaptation to reduce possible data transmission within acceptable weak connection bandwidth. The mobile network adaptation techniques can significantly reduce the potential communications between the mobile devices and the fixed host.

An efficient power saving MAC protocol for IEEE 802.11 ad hoc wireless networks

To support mobility, mobile devices must be powered by batteries with limited energy. Thus, energy-efficient management becomes one of the most important design issues in mobile wireless networks. A well-designed energy-efficient MAC protocol for mobile wireless networks should be developed for both minimum energy consumption as well as maximum data throughput. IEEE 802.11 MAC protocol is based on the carrier sense multiple access with collision avoidance (CSMA/CA) medium access procedure to transmit/receive both control and data frames. We know that CSMA/CA wastes the scarce energy and bandwidth due to frame collisions and lengthens the transmission delay due to waiting backoff time, especially in heavy traffic load. In addition, the IEEE 802.11 power management scheme does not specify how to determine the ATIM window size in a beacon interval. The fixed ATIM window size can not always accommodate the dynamically changing traffic conditions. To conquer these problems, we propose a novel power saving MAC protocol for IEEE 802.11 ad hoc networks. The proposed protocol possesses two properties: (1) based on overhearing ATIM frames in an ATIM window, power saving (PS) stations can be scheduled to transmit data frames in order after the ATIM window, and (2) depending on the fluctuant traffic conditions, PS stations adjust the ATIM window size dynamically to save energy and achieve the superior network throughput. Through extensive simulations, we demonstrate the advantages of our new MAC protocol.

Energy‐efficient capacity‐constrained routing in wireless sensor networks

A critical issue in the design of routing protocols for wireless sensor networks is the efficient utilization of resources such as scarce bandwidth and limited energy supply. Many routing schemes proposed in the literature try to minimize the energy consumed in routing or maximize the lifetime of the sensor network without taking into consideration limited capacities of nodes and wireless links. This can lead to congestion, increased delay, packet losses and ultimately to retransmission of packets, which will waste considerable amount of energy. This paper presents a Minimum‐cost Capacity‐constrained Routing (MCCR) protocol which minimize the total energy consumed in routing while guaranteeing that the total load on each sensor node and on each wireless link does not exceed its capacity. The protocol is derived from polynomial‐time minimum‐cost flow algorithms. Therefore protocol is simple and scalable. The paper improves the routing protocol in (1) to incorporate integrality, node capacity and link capacity constraints. This improved protocol is called Maximum Lifetime Capacity‐constrained Routing (MLCR). The objective of MLCR protocol is to maximize the time until the first battery drains its energy subject to the node capacity and link capacity constraints. A strongly polynomial time algorithm is proposed for a special case of MLCR problem when the energy consumed in transmission by a sensor node is constant. Simulations are performed to analyzed the performance of the proposed protocols.

On the Cross-Layer Impact of TCP ACK Thinning on IEEE 802.11 Wireless MAC Dynamics

ACK thinning refers to the technique to discard or reduce TCP acknowledgements (ACKs) for the purpose of diverting scarce bandwidth to TCP data traffic. It has been shown that under some circumstances the technique is effective to boost the TCP throughput on wireless links, in particular the IEEE 802.11 wireless LAN (WLAN). In this letter, however, we show that ACK thinning backfires under congestion due to its cross-layer impact on the 802.11 MAC dynamics. With the ACK filtering example, we demonstrate the phenomenon and analyze the cause. Based on the analysis. we show how the IEEE 802.11 contention window size control solves the problem.

Efficient Cache Placement in Multi-Hop Wireless Networks

In this paper, we address the problem of efficient cache placement in multi-hop wireless networks. We consider a network comprising a server with an interface to the wired network, and other nodes requiring access to the information stored at the server. In order to reduce access latency in such a communication environment, an effective strategy is caching the server information at some of the nodes distributed across the network. Caching, however, can imply a considerable overhead cost; for instance, disseminating information incurs additional energy as well as bandwidth burden. Since wireless systems are plagued by scarcity of available energy and bandwidth, we need to design caching strategies that optimally trade-off between overhead cost and access latency. We pose our problem as an integer linear program. We show that this problem is the same as a special case of the connected facility location problem, which is known to be NP-hard. We devise a polynomial time algorithm which provides a suboptimal solution. The proposed algorithm applies to any arbitrary network topology and can be implemented in a distributed and asynchronous manner. In the case of a tree topology, our algorithm gives the optimal solution. In the case of an arbitrary topology, it finds a feasible solution with an objective function value within a factor of 6 of the optimal value. This performance is very close to the best approximate solution known today, which is obtained in a centralized manner. We compare the performance of our algorithm against three candidate cache placement schemes, and show via extensive simulation that our algorithm consistently outperforms these alternative schemes.

Perceptive admission control for wireless network quality of service

As wireless networks become more widely used, there is a growing need to support advanced services, such as multimedia streaming and voice over IP. Traditional approaches to guarantee quality of service (QoS) work well only with predictable channel and network access. In wireless mobile networks, where conditions dynamically change as nodes move about the network, a stateless, high level approach is required. Since shared wireless resources are easily over-utilized, the load in the network must be controlled so that an acceptable QoS for real-time applications can be maintained. If minimum real-time requirements are not met, these unusable packets waste scarce bandwidth and hinder other traffic, compounding the problem. To enable high QoS for all admitted traffic, we propose the Perceptive Admission Control (PAC) protocol. PAC monitors the wireless channel and dynamically adapts admission control decisions to enable high network utilization while preventing congestion. Through discussion, simulations and testbed experiments, we demonstrate that PAC ensures low packet loss and delay for all admitted flows.

Dynamic rate-based borrowing scheme for QoS provisioning in high speed multimedia wireless cellular networks

The provisioning of QoS in wireless networks carrying multimedia traffic imposes a big challenge to network designers and traffic engineers. Guaranteeing QoS in wireless networks is a complicated task due to the unique characteristics of wireless networks such as user mobility, limited link capacity, frequent link failure, scarcity of bandwidth, channel fading, and inability to predict the availability of resources in the network. In this paper, we investigate multiple QoS schemes in multimedia wireless networks. A modification to an existing scheme, rate-based borrowing scheme, where the concept of borrowing bandwidth from existing connections to accept both new and handoffs connections is proposed. Unlike Rate-Based Borrowing Scheme (RBBS) and Statistical Scheme (SBS), Dynamic Rate-Based Borrowing Scheme (DRBBS) exploits the positive feature of fair borrowing bandwidth and avoids pre-allocation of resources. This is based on the concept of borrowing from existing connections. Extensive simulation experiments have been performed using a simulation package designed for the purpose of this research. Using the call dropping/blocking probabilities and bandwidth utilization as a performance metrics, the proposed scheme, DRBBS outperforms the previously known schemes in terms of the aforementioned performance metrics. Fair borrowing from ongoing connections shows a decrease in the rate of calls dropping probabilities and a decrease in the calls blocking probabilities, while avoiding pre-allocation of resources offers a significant improvement in the bandwidth utilization.

A Fast Multicast Handoff Based Hierarchical Mobile Multicast Architecture

Mobile communication is playing an increasing role in our lives. Mobile users expect similar kinds of applications to static ones. Multicast not only brings attractive applications, but also has the benefit of saving scarce bandwidth in wireless environment. It would be fruitful to combine these two technologies. This paper proposes a framework to provide multicast in mobile environment called Fast Multicast Handoff Based Hierarchical Mobile Multicast Architecture (FHMM). It uses a hierarchical mobile multicast architecture to isolate the local movement from outside, and improve the stability of the main multicast delivery tree. It introduces a fast multicast handoff mechanism which can reduce handoff latency and packet loss rate for inter-domain handoff and intra-domain handoff. Furthermore, FHMM is a universal solution because it can still work even if the access network does not support multicast. Simulation results show that FHMM is effective with low packet loss rate, high multicast packet

Efficient QoS Provisioning for Adaptive Multimedia in Mobile Communication Networks by Reinforcement Learning

The scarcity and large fluctuations of link bandwidth in wireless networks have motivated the development of adaptive multimedia services in mobile communication networks, where it is possible to increase or decrease the bandwidth of individual ongoing flows. This paper studies the issues of quality of service (QoS) provisioning in such systems. In particular, call admission control and bandwidth adaptation are formulated as a constrained Markov decision problem. The rapid growth in the number of states and the difficulty in estimating state transition probabilities in practical systems make it very difficult to employ classical methods to find the optimal policy. We present a novel approach that uses a form of discounted reward reinforcement learning known as Q-learning to solve QoS provisioning for wireless adaptive multimedia. Q-learning does not require the explicit state transition model to solve the Markov decision problem; therefore more general and realistic assumptions can be applied to the underlying system model for this approach than in previous schemes. Moreover, the proposed scheme can efficiently handle the large state space and action set of the wireless adaptive multimedia QoS provisioning problem. Handoff dropping probability and average allocated bandwidth are considered as QoS constraints in our model and can be guaranteed simultaneously. Simulation results demonstrate the effectiveness of the proposed scheme in adaptive multimedia mobile communication networks.

Receiver-driven bandwidth sharing for TCP and its application to video streaming

Applications using Transmission Control Protocol (TCP), such as web-browsers, ftp, and various peer-to-peer (P2P) programs, dominate most of the Internet traffic today. In many cases, users have bandwidth-limited last mile connections to the Internet which act as network bottlenecks. Users generally run multiple concurrent networking applications that compete for the scarce bandwidth resource. Standard TCP shares bottleneck link capacity according to connection round-trip time (RTT), and consequently may result in a bandwidth partition which does not necessarily coincide with the user's desires. In this work, we present a receiver-based bandwidth sharing system (BWSS) for allocating the capacity of last-hop access links according to user preferences. Our system does not require modifications to the TCP protocol, network infrastructure or sending hosts, making it easy to deploy. By breaking fairness between flows on the access link, the BWSS can limit the throughput fluctuations of high-priority applications. We utilize the BWSS to perform efficient video streaming over TCP to receivers with bandwidth-limited last mile connections. We demonstrate the effectiveness of our proposed system through Internet experiments.

A Novel Scheme for Resource Allocation for Multimedia Wireless Networks

The third generation (3G) wireless communication systems will support multimedia traffic at a target transmission rate of up to 2 Mbps for static mobile users and 384 kbps for high mobility users. Unlike wired networks, communication entities in wireless networks change their connectivity via handoff when they move from one cell to another. The use of micro or pico-sized cells makes the role of handoff procedures very important in maintaining the service continuity and QoS guarantees to the multimedia applications. Admission control and bandwidth allocation schemes can offer wire line networks the ability to provide these guarantees. Due to host mobility, scarcity of bandwidth, and an assortment of channel impairments, the QoS provisioning is far more challenging in wireless networks than in wire line networks.This paper proposes a novel scheme for resource allocation that attempts to allocate the desired bandwidth to all the multimedia connections whether it is new connection or handoff. This is different from the rate based borrowing scheme in the sense that it does not have a reserve pool of bandwidth in the cell for Class I connections, but it reserves bandwidth in all the neighboring cells dynamically when a new connection arrives in a cell. There is a limit on the amount of bandwidth that can be reserved in a cell.Extensive simulation results show that the proposed scheme performs better than the previous known schemes in terms of bandwidth utilization, call blocking probability and call dropping probability.

The enhanced staircase broadcasting for VBR videos

One way to broadcast a popular video is to partition the video into segments, which are broadcasted on several streams periodically. The approach lets multiple users share streams; thus, the stress on the scarce bandwidth can be alleviated without sacrificing viewers' waiting time. One representative approach is the Staircase Broadcasting (SB) scheme, which requires buffering only 25% of a playing video. However, the scheme mainly supports transmission of CBR-encoded videos. In this paper, we proposed a simple VBR staircase broadcasting (SVSB) scheme, which can distribute VBR-encoded videos with small buffers. The idea behind the scheme is asynchronous downloading and playing, and hybrid division by length and size. It is simple and effective. We also applied the design to several segmented broadcasting schemes, such as the harmonic-based broadcasting, and the recursive frequency-splitting (RFS) schemes, to enable them to support VBR videos. A simulation was conducted to evaluate the schemes. The results indicated that the SVSB scheme still outperforms on required buffers, and disk transfer rate at client end. The harmonic broadcasting scheme with VBR support consumes the least bandwidth.

Allowing bit errors in speech over wireless LANs

Wireless LANs are becoming commonplace because of their ease in providing mobile communication. As use of IEEE 802.11 continues to expand, support for voice will become a desirable feature. Supporting voice conversations over a packet network is more challenging than over current circuit-switched wired networks. These challenges are particularly difficult due to the erroneous nature of a wireless channel. The IEEE 802.11 MAC layer standard requires that the receiver not accept a packet with any bit error; the source must retransmit all packets received with errors. However, digitized voice data can tolerate some error and loss without noticeable degradation in call quality. By forcing error-free reception of speech, scarce bandwidth and energy are unnecessarily expended, and the delay of the packets increases. In this paper we explore allowing bit errors in voice packets over IEEE 802.11 networks. We propose two strategies for allowing these errors and demonstrate that they both result in improved performance.

A Header Compression Algorithm for Real-Time Streams in Wireless IP Networks

In wireless IP networks, it is necessary to adopt header compression schemes for the reduction of the protocol header size in order to save the scarce wireless bandwidth resource and make real-time services economically feasible and physically realizable. However, all the existing header compression schemes have not taken wireless channel state into consideration when designed. For a better usage over wireless links, a new channel state based robust header compression algorithm (CSB-ROHC) for real-time streams in wireless IP networks such as 3G platforms is proposed and analyzed in this paper. Through adjusting the dimension of VSW in W-LSB encoding (a key parameter in header compressor) with the accurate estimation of wireless channel state, this new algorithm can achieve a good balance of compression ratio and error-resistant robustness for its adaptive usage over wireless links. The authors present simulation results that demonstrate the effectiveness of the CSB-ROHC algorithm over wireless links.

A grouping genetic algorithm for registration area planning

The enormous increase in wireless customers in recent years has taxed wireless network resources, in particular, the bandwidth available. The scarce bandwidth is not only consumed by placing and receiving calls on a portable, but by performing routine control functions to ensure universal service and increased quality of service. Among the control functions performed by a wireless network is finding the location of called mobiles. The registration area planning problem attempts to achieve this with minimal impact on the network's bandwidth. In this paper, we develop a grouping genetic algorithm to efficiently solve the registration area planning problem. The problem is NP-complete, therefore the literature has concentrated on heuristics to find good solutions in an acceptable time. The goal of registration area planning is to group wireless network cells into contiguous areas to minimize location update costs subject to paging bound and preset constraints. Therefore, the registration area planning problem is a grouping problem and grouping genetic algorithms, which have been shown to be a useful tool in solving these types of problems, are an applicable solution methodology. The proposed grouping genetic algorithm, GGARAP, has been extensively tested. Our results indicate that GGARAP is robust and finds good solutions for the registration area planning problem for a wide range of network situations. Furthermore, the computational effort involved in running GGARAP is minimal.