The different flavors of today's and future multilayer transmission networks are analyzed highlighting the main infrastructure, capital expenditure (CAPEX) and operational expenditure (OPEX) contributions to total cost of ownership (TCO). Depending on different carrier requirements, critical parameters and general design rules for optimum overall cost positions are discussed. To illustrate and evaluate the impact of given boundary conditions, some case studies will be presented where new technologies lead to significant OPEX/CAPEX savings.
Location of mobile users is a common implemented issue in modern personal communication networks (PCN). Location may have several purposes in a wireless network, for example authentication of users to deliver incoming calls to destination users, and to make a more efficient use of network resources. In a practical wireless network the location algorithms need to keep track of mobile users in a dynamic manner. In this paper, we present an analytic model for the dynamic movement-based location algorithm for PCN's. Our model is based on renewal theory arguments and it is general enough to include a variety of probability distributions for modelling residence times in location areas and intercall times.
Delivering proper management into the flat structured mobile communities is crucial for improving users experience and increase applications diversity in mobile networks. The available P2P applications do application-centric management, but it cannot replace network-wide management, especially when a number of different applications are used simultaneously in the network. The network-wide management is the key element required for a smooth transition from standalone P2P applications to the self-organizing mobile communities that maintain various services with quality and security guaranties. The classical centralized network management solutions are not applicable in the flat structured mobile communities due to the decentralized nature and high mobility of the underlying networks. Also the basic network management tasks have to be revised taking into account specialties of the flat structured mobile communities. The network performance management becomes more dependent on the current nodes' context, which also requires extension of the configuration management functionality. The fault management has to take into account high mobility of the network nodes. The performance and accounting managements are mainly targeted in maintain an efficient and fair access to the resources within the community, however they also allow unbalanced resource use of the nodes that explicitly permit it, e.g. as a voluntary donation to the community or due to the profession (commercial) reasons. The security management must implement the new trust models, which are based on the community feedback, professional authorization, and a mix of both. For fulfilling these and another specialties of the flat structured mobile communities, a new network management solution is demanded. The paper presents a distributed network management solution for flat structured mobile communities. Also the paper points out possible network management roles for the different parties (e.g. operators, service providing hubs/super nodes, etc.) involved in a service providing chain.
We present the modeling and evaluation in the integrated cellular
and ad hoc network system. The system is modeled using queueing theory and we derive some characteristic values. As regards a system model of two cells, M channels are assigned to each cell and a relay station is set in the overlapped area of two cells. New calls in cellA can be relayed to cellB if the channels in cellA are all busy and the mobile stations are in the covered area by a relay station. Handoff calls select the channels of the cell that the number of empty channels are more in the two cells.
If the channels of the both cells are all busy, handoff calls can wait in a queue with the capacity Q while mobile stations are in the handoff area. However, so as not to make handoff calls possess channels prior to new calls, we manage it with the method being different from the other researches. This system is more flexible than cellular networks, the bias of traffic gets smaller and it leads to an efficient channel using. We model and evaluate our system
by assuming that the dwelling time is distributed with non-exponential distribution as well as exponential one. In numerical results, we compare the characteristic values in our system with those in non-relaying system, see how the characteristic values are affected when the covered area by a relay station changes, and verify the effectiveness of our system.
Fast rerouting is a critical traffic engineering operation in the MPLS networks. To implement the Mobile IP service over the MPLS network, one can collaborate with the fast rerouting operation to enhance the availability and survivability. MPLS can protect critical LSP tunnel between Home Agent (HA) and Foreign Agent (FA) using the fast rerouting scheme. In this paper, we propose a simple but efficient algorithm to address the triangle routing problem for the Mobile IP over the MPLS networks. We consider this routing issue as a link weighting and capacity assignment (LW-CA) problem. The derived solution is used to plan the fast restoration mechanism to protect the link or node failure. In this paper, we first model the LW-CA problem as a mixed integer optimization problem. Our goal is to minimize the call blocking probability on the most congested working truck for the mobile IP connections. Many existing network topologies are used to evaluate the performance of our scheme. Results show that our proposed scheme can obtain the best performance in terms of the smallest blocking probability compared to other schemes.
Backbones infrastructures in wireless sensor networks reduce the communication overhead and energy consumption. In this paper, we present BackBone Routing (BBR), a fully distributed protocol for construction and rotation of backbone networks. BBR reduces energy consumption without significantly diminishing the capacity or connectivity of the network. Another key feature of BBR is its energy balancing nature by distributing the role of being Backbone Node among all the nodes. BBR builds on the observation that when a region of a shared-channel wireless network has a sufficient density of nodes, only a small number of them need be on at any time to forward traffic for active connections. Improvement in system lifetime due to BBR increases as the ratio of idle-to-sleep energy consumption increases, and increases as the density of the network increases. Our experiments show that BBR is more efficient in saving energy and extending network life without deteriorating network performance when compared with geographical shortest path routing.
Location-awareness is a key enabler for using energy-conserving protocols and other location-based services in Wireless Sensor Networks (WSN). Due to the ad hoc nature of WSN, and resource-constrained sensor nodes, the localization technique must be infrastructure-free, computationally simple, and energy-efficient. In this paper we present an ad hoc localization technique that satisfies these requirements. The proposed localization technique is infrastructure-free, anchor-free, and is computationally efficient with reduced communication. We use a novel combination of TOA/TDOA and AOA ranging techniques to detect and estimate ranges between neighbors. Using this information we construct unidirectional coordinate systems to avoid the reflection ambiguity. This reduces the amount of information, and thus communication, required to induce location-awareness in sensor nodes. We then compute node positions using a transformation matrix [T] which reduces the computational complexity of the localization algorithm while computing positions relative to the fixed coordinate system.
Recent advances in wireless communications and microelectro-mechanical systems have motivated the development of extremely small, low-cost sensors that possess sensing, signal processing and wireless communication capabilities. A wireless network consisting of a large number of small sensors with low-power transceivers can be an effective tool for gathering data in a variety of environments. The data collected by each sensor is communicated through the network to a single processing center that uses all reported data to determine characteristics of the environment or detect an event. The communication or message passing process must be designed to conserve the limited energy resources of the sensors. Clustering sensors into groups, so that sensors communicate information only to clusterheads and then the clusterheads communicate the aggregated information to the processing center, may save energy. In this paper, we propose a distributed, randomized clustering algorithm to organize the sensors in a wireless sensor network into clusters. Our algorithm generates a hierarchy of clusterheads and observes that the energy savings increase with the number of levels in the hierarchy. Results in stochastic geometry are used to derive solutions for the values of parameters of our algorithm that minimize the total energy spent in the network when all sensors report data through the clusterheads to the processing center.
As the telecom industry responds with technological innovations to requests for higher data rates, increased number of wavelengths at higher densities, longer transmission distances and more intelligence for next generation optical networks, new monitoring schemes based on monitoring and tracking of each wavelength need to be developed and deployed. An optical layer monitoring scheme, based on tracking key optical parameters per each wavelength, is considered to be one of enablers for the transformation of today's opaque networks to dynamic, agile future networks. Ever-tighter network monitoring and control will be required to fulfill customer Service Level Agreements (SLAs). A wavelength monitoring and tracking concept was developed as a three-step approach. It started with the identification of all critical parameters required to obtain sufficient information about each wavelength; followed by the deployment of a cost-efficient device to provide simultaneous, accurate measurements in real-time of all critical parameters; and finally, the formulation of a specification for wavelength monitoring and tracking devices for real-time, simultaneous measurements and processing the data. A prototype solution based on a commercially available integrated modular spectrometer within a testbed environment associated with the all-optical network (AON) demonstrator program was used to verify and validate the wavelength monitoring and tracking concept. The developed concept verified that it can manage tracking of 32 wavelengths within a wavelength division multiplexing network. The developed concept presented in this paper can be used inside the transparent domains of networks to detect, identify and locate signal degradations in real-time, even sometimes to recognize the cause of the failure. Aside from the reduction of operational expenses due to the elimination of the need for operators at every site and skilled field technicians to isolate and repair faults, the developed wavelength monitoring concept provides critical inputs for protection switching, line equalization and span monitoring. Additionally, it can unlock the capabilities of tunable technologies, ensuring network agility. Finally, further developments of the presented concept might enable building and controlling of complex network topologies while efficiently maintaining a high quality of service (QoS).
The ever increasing demand of the bandwidth has been efficiently fulfilled by the advent of Wavelength Division Multiplexing (WDM), which efficiently utilizes the available bandwidth of fiber links. The performance of these networks can be drastically improved by using efficient message scheduling and/or sequencing algorithm(s), to reduce the delay experienced by the packets and also to distribute the load among the available channels, to get maximum channel utilization. In this research we modeled protocols, which can improve network performance, as each of them may perform better in different operating circumstances. Several conditions were studied and performance of these algorithms has been compared, using our modeling tools. Most of the schemes proposed earlier ignored some parameters (e.g. tuning times of the transmitters and the receivers) or had some unrealistic assumptions, which will be discussed later in the paper. We tried to simulate more realistic scenarios. The parameters, which are monitored during the simulations, are average delay, throughput and channel utilization by changing the values of packet generation rate, number of available channels, transmitter and receiver tuning times. To verify the simulations we also developed a math model without making any unrealistic assumptions. Extensive simulations were conducted and a detailed study of the protocols is made possible.
Recent and future communications networks have to provide QoS guarantees for a rapidly growing number of various telecommunication services, which can be ensured by application of an efficient MAC layer. Particularly, per-packet reservation MAC protocols are efficient ensuring a good network utilization and realization of QoS for various telecommunications services. However, per-packet reservation protocols suffers from an unfairness because network stations achieve different relative data throughput depending on the traffic characteristics of used services. A fair scheduling between network stations can be ensured if offered data rate per station is known, which is unfortunately not the case. In this investigation it is shown that the offered data rate can be successfully estimated by calculation of so-called effective requesting period per network station, which can be used for implementation of a fair scheduling mechanism. The results show a significant improvement of the fairness behavior in the network if the fair scheduling is applied.
With the increasing diversity of network applications, it has become crucial for the Internet to offer various services. In the Internet a simple shortest path routing algorithm is employed, however, it may not be adequate in networks that provide Quality of Service (QoS) guarantees to applications such as real time applications. Since the goal of the QoS routing is to find a path that satisfies the given requirements and may increase the global network resource utilization, an advanced QoS-aware routing technology in the current IP networks is needed to realize next generation ubiquitous networks. In this paper, we propose a distributed link state QoS routing with multiple routing tables obtained upon different link costs to effectively accommodate multi-class traffic such as real time QoS traffic and best-effort traffic. Selecting a path for QoS traffic can have an effect on overall the network. Therefore, how much QoS traffic has to be routed on the shortest path will have an impact on the behavior of Best Effort Traffic. For that we used a dynamic threshold based on network state to split QoS traffic between alternatives path. The significance of the proposed scheme lies in reducing the packet loss probability of the QoS traffic. This scheme can prevent the QoS traffic from concentrating on some links and allow at the same time to improve the best-effort traffic throughput. We investigate the characteristics of the proposed multi-class routing schemes by computer simulations. We have found that both packet loss of QoS traffic and the throughput of Best-Effort can be improved by using the proposed scheme.
In this paper, Just-In-Time (JIT), Just-Enough-Time (JET) and Horizon signalling schemes for Optical Burst Switched Networks (OBS) are presented. These signaling schemes run over a core dWDM network and a network architecture based on Optical Burst Switches (OBS) is proposed to support IP, ATM and Burst traffic. In IP and ATM traffic several packets are assembled in a single packet called burst and the burst contention is handled by burst dropping. The burst length distribution in IP traffic is arbitrary between 0 and 1, and is fixed in ATM traffic at 0,5. Burst traffic on the other hand is arbitrary between 1 and 5. The Setup and Setup ack length distributions are arbitrary. We apply the Poisson model with rate λ and Self-Similar model with pareto distribution rate α to identify inter-arrival times in these protocols. We consider a communication between a source client node and a destination client node over an ingress and one or more multiple intermediate switches.We use buffering only in the ingress node. The communication is based on single burst connections in which, the connection is set up just before sending a burst and then closed as soon as the burst is sent. Our analysis accounts for several important parameters, including the burst setup, burst setup ack, keepalive messages and the optical switching protocol. We compare the performance of the three signalling schemes on the network under as burst dropping probability under a range of network scenarios.
TCP tunnel is a technology that aggregates and transfers packets sent between end hosts as a single TCP connection. By using a TCP tunnel, the fairness among aggregated flows can be improved and several protocols can be transparently transmitted through a firewall. Currently, many applications such as SSH, VTun, and HTun use a TCP tunnel. However, since most applications running on end hosts generally use TCP, two TCP congestion controls (i.e., end-to-end TCP and tunnel TCP) operate simultaneously and interfere each other. Under certain conditions, it has been known that using a TCP tunnel severely degrades the end-to-end TCP performance. Namely, it has known that using a TCP tunnel drastically degrades the end-to-end TCP throughput for some time, which is called TCP meltdown problem. On the contrary, under other conditions, it has been known that using a TCP tunnel significantly improves the end-to-end TCP performance. However, it is still an open issue --- how, when, and why is a TCP tunnel malicious for end-to-end TCP performance? In this paper, we therefore investigate effect of TCP tunnel on end-to-end TCP performance using simulation experiments. Specifically, we quantitatively reveal effects of several factors (e.g., the propagation delay, usage of SACK option, TCP socket buffer size, and sender buffer size of TCP tunnel) on performance of end-to-end TCP and tunnel TCP.
Multi-channel medium access control (MAC) protocols have been developed to overcome the contention/collision problems that arise with single channel MAC protocols in ad-hoc wireless networks. In most of the currently available schemes, a single pre-assigned control channel carries all the control packets (RTS/CTS/RES) for data communication. One of the problems identified with this method is that as the number of nodes in a system increases, the throughput drops significantly due to heavy contention on the control channel. Moreover, even if several data channels are available in the system, many of them remain underutilized due to the unavailability of the control channel. This paper presents SU-MAC, a Smart Utilization MAC protocol, that assigns the available multi-channels dynamically. Our protocol combines the control and available data channel bandwidth to send control information and thus avoids blockage of the control channel for long periods. A power control scheme is also used as well to reduce interference and to effectively re-use the available bandwidth. Simulation results show that our SU-MAC protocol is promising in terms of reduced contention at the control channel and improved throughput because of channel re-use.
Choosing a minimum-cost link topology for a network, given a set of nodes and given the node-to-node traffic that must be routed, is a difficult combinatorial problem. In the network design literature, many different approaches, based on a variety of assumptions, have been proposed for this type of problem. The unique features of Internet Protocol (IP) networks make the link topology design problem especially challenging. In this paper, we discuss some of these features and explain why assumptions commonly found in the link topology design literature often fail to capture the behavior of IP traffic. We discuss possible heuristic approaches to link topology selection that take the particular features of IP into account.
With the rapid development of computer and wireless communication technologies, the wireless ad hoc networks are receiving an increasing amount of attention due to its deployment and administration flexibilities. Thus various routing protocols have been developed for wireless ad hoc networks in recent years. This paper presents the results of simulation comparing three multi-hop wireless ad hoc network routing protocols that cover a range of single-path and multi-path source routing design choices: DSR, MSR and BSR. Simulation results demonstrate the performances of DSR, MSR and BSR revealed four interesting insights: (1) In lower mobility situations, multi-path routing MSR and BSR have similar performance as DSR, and three routing protocols being considered all have good performances. (2) In moderate situations of load and mobility, the performances of MSR and BSR are much more superior when compared to that of single-path DSR. And MSR has similar performance as BSR. (3) In heavy load and high mobility situations, BSR performs better than DSR and MSR. (4) In more challenging situations of high mobility, none of the routing protocols considered in this paper can respond to the dynamics in the network topology. The performances of DSR, MSR and BSR are all less than satisfactory.
Reliable transport protocols such as TCP are tuned to perform well in traditional networks where packet losses occur mostly because of congestion. However, networks with wireless and other lossy links also suffer from significant non-congestion-related losses due to reasons such as bit errors and handoffs. TCP responds to all losses by invoking congestion control and avoidance algorithms, resulting in degraded end-to-end performance in wireless and lossy networks. In case of wired-wireless interaction (WLANs), the wireless link is assumed to be the last hop where most of the loss and delay occurs. Since the mobile host is adjacent to the wireless hops, it is obviously better equipped to obtain first-hand knowledge of the wireless links. In the paper, we proposed a mobile-host-centric transport protocol called MCP (Mobile-host Control Protocol) that is like TCP in its general behavior, but allows for better congestion control and loss recovery in mobile wireless networks. The MCP shifts most transport layer control policies to the mobile host side under all cases (mobile host is a sender or receiver, fixed or mobile, and so on). Therefore, mobile stations can make better transport layer control in time based on the condition of wireless link.
In recent years, AQM (Active Queue Management) mechanisms, which support the end-to-end congestion control mechanism of TCP (Transmission Control Protocol), have been widely studied in the literature. AQM mechanism is a congestion controller at a router for suppressing and stabilizing its queue length (i.e., the number of packets in the buffer) by actively discarding arriving packets. Although a number of AQM mechanisms have been proposed, behaviors of those AQM mechanisms other than RED (Random Early Detection) have not been fully investigated. In this paper, using fluid-flow approximation, we analyze steady state behavior of DRED (Dynamic RED), which is designed with a control theoretic approach. More specifically, we model several network components such as congestion control mechanism of TCP, DRED router, and link propagation delay as independent SISO (Single-Input Single-Output) continuous-time systems. By interconnecting those SISO models, we obtain a continuous-time model for the entire network. Unlike other fluid-based modeling approaches, our analytic approach is scalable; our analytic approach is scalable in terms of the number of TCP connections and DRED routers since both input and output of all continuous-time systems are uniformly defined as a packet transmission rate. By performing steady-state analysis, we derive TCP throughput, average queue length of DRED router, and packet loss probability. Through several numerical examples, we quantitatively show that DRED has an intrinsic problem in high-speed networks; i.e., DRED cannot stabilize its queue length when the bottleneck link bandwidth is high. We also validate accuracy of our analytic approach by comparing analytic results with simulation ones.
Resilient packet ring (RPR), defined under IEEE 802.17, is a new kind of metropolitan area network technology. Fairness algorithm is one key technology of RPR. Presently, fairness algorithms found in RPR draft and related publications (e.g., DVSR algorithm) have some critical and common limitations, such as oscillation of the allocated bandwidth, high computation complexity or not get high bandwidth utilization. In this paper, we propose a new GPS-based algorithm, FBDRR algorithm, with a view to overcome these limitations. GPS is an ideal scheduling algorithm that can fairly allocate bandwidth to different flows and can also isolate vicious users. Its principle is that when downstream has high demand and make network congested and lost some frames, the low demand traffic from upstream node will has the same loss rate with the downstream one, and if one node does not constrain its stream to its fair share bandwidth, then it can use all of the bandwidth for C class if ring priority scheduling algorithm is used. We analyze the stability of this algorithm. Theoretical analysis and simulation results demonstrate that with this fairness algorithm, each node on the ring can remotely approximate the ideal fair rate for its own traffic at each downstream link, and there is no permanent oscillation, i.e., satisfied stability.
Buffered crossbar switch is becoming attractive due to its feature of distributed scheduling, which makes the scheduler more scalable than that in an un-buffered crossbar switch. However, previous researches on buffered crossbar switches mainly aimed at improving the throughput and cell delay performance, scarcely at the fairness and bandwidth guarantee. In this paper, we discuss the necessities of providing bandwidth guarantee in buffered crossbar switches, and propose a novel RR_MCF algorithm. RR_MCF uses a simple round robin policy at input scheduling, and a most credit first policy at output scheduling. By given a predetermined reserved bandwidth matrix, simulations show RR_MCF could provide good bandwidth guarantee for each flow, even with the presence of ill-behaved flows.