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Field measurements of signal strength is one of the basic techniques for coverage determination of a cellular network. In this paper, we report on the experimental study of the signal strength measurements in a typical worldwide interoperability for microwave access network operating at 2.62 GHz installed for fixed wireless access in the district of Greater Noida, Uttar Pradesh, India. The experimental data are analyzed for deriving characteristic parameters of the radio propagation environment. The characteristic parameters include path loss exponent and standard deviation of shadow fading. Having derived the characteristic parameters, we propose path loss models for the cellular network. The study also aims at the determination of network coverage for the given system parameters. Results and their analysis are utilized for network planning and optimization of the system parameters for the installed cellular network. [ABSTRACT FROM AUTHOR]

This paper proposes a carrier frequency offset (CFO) estimation scheme for OFDM systems over fast fading channels. In the proposed scheme, exploiting the multiple preambles with the identical values, we estimate the CFO over fast fading channels. In particular, we improve the performance of the CFO estimator by applying the overlapped windows to preambles. Through simulations, we validate the proposed estimation scheme by showing the effectiveness of the proposed estimator. [ABSTRACT FROM AUTHOR]

Currently most existing entity authentication protocols can not guarantee anonymity against compromised verifier in semi-honest model. To solve the question, this paper puts forward a shared certificate entity authentication model, by which some qualities for anonymous entity authentication in semi-honest situation are suggested reasonably. On basis of our proposed model, this paper designs two anonymous entity authentication protocols including an anonymous shared certificate bi-entity authentication protocol and an anonymous shared certificate multi-entity authentication protocol. In proposed protocols it is only single certificate that is used to verify identity correctly and anonymously for legitimate users who has different identity secret. Any compromised verifier has capability to verify correctly whether the user identity is legitimate or not, but it is difficult for it to judge which legitimate user has been verified and distinguish who the verifying user is in particular, therefore attacker does not learn any useful information from legitimate user by spying upon the information of public channel or compromising the certificate. So the security requirements of anonymous entity authentication are achieved successfully, meanwhile the proposed model is more feasibly and effective than zero knowledge protocol in practical applications. [ABSTRACT FROM AUTHOR]

Long term evolution (LTE) Advanced is a well designed system that meets the requirements of 4G cellular systems. Its standard specification has been lately released. One of its main features is supporting relaying topology inspired from ad hoc multihop networks. This paper is a survey upon the relaying architecture of LTE Advanced standard based on 3GPP Release 10 specifications. A comparison with other relaying architectures, i.e. IEEE 802.16m and IEEE 802.11s is handled. The originality of this work is in involving comparison with multihop architecture supported by IEEE 802.11s based wireless mesh networks. Several similarities are noted and differences are pointed out. [ABSTRACT FROM AUTHOR]

In this paper, a novel semi-orthogonal distributed Alamouti space-time codes transmission protocol is proposed for a four nodes cooperative communication system consisting of one source, one destination and two semi blind relays over block fading channels. In particular, by semi-orthogonal we mean two orthogonal frequency bands are invoked, one of which is for the transmission by the source node, while the other one is shared simultaneously by the two relay-destination links. Moreover, analytical performances of the proposed semi-orthogonal scheme are investigated in this paper. Specifically, the theoretical expressions of the exact SER and diversity order are presented. Our proposed scheme is capable of achieving higher spectral efficiency and remaining the same diversity order compared to the existing orthogonal one, while attaining better symbol error rate performance and higher diversity order against the non-orthogonal design. Finally, simulation results prove the correctness of the above conclusions and also verify our derivation for the analytical performances. [ABSTRACT FROM AUTHOR]

The paper presents a new steganographic method called RSTEG (retransmission steganography), which is intended for a broad class of protocols that utilises retransmission mechanisms. The main innovation of RSTEG is to not acknowledge a successfully received packet in order to intentionally invoke retransmission. The retransmitted packet carries a steganogram instead of user data in the payload field. RSTEG is presented in the broad context of network steganography, and the utilisation of RSTEG for TCP (transmission control protocol) retransmission mechanisms is described in detail. Simulation results are also presented with the main aim of measuring and comparing the steganographic bandwidth of the proposed method for different TCP retransmission mechanisms, as well as to determine the influence of RSTEG on the network retransmission level. [ABSTRACT FROM AUTHOR]

High data rate wireless technologies are now becoming a reality, and have spurred the development of new applications that were previously hindered by the lack of capacity. In particular, it is now possible to stream high definition movies from a laptop to a sound system and flat screen television seamlessly. One of the key enablers of such applications is the IEEE 802.15.3 medium access control (MAC) protocol, which is designed to support bandwidth intensive applications in wireless personal area networks (WPANs). A key observation is that a significant number of multi-media applications rely on the transmission control protocol (TCP). Unfortunately, little works have conducted a thorough performance study of TCP over the IEEE 802.15.3 MAC. Moreover, the IEEE 802.15.3 specification does not specify any strategies for allocating time slots. This paper therefore contributes to the current state-of-the-art in the following manners. From our extensive analytical and simulation studies, we reveal the impacts of different channel time allocation methods and acknowledgment policies on the performance of TCP, with particular attention on round trip time, congestion window growth, and packet recovery. We then present the following guidance to application developers: (1) channel time allocations (CTAs) should be distributed evenly over the superframe and have durations determined by TCP’s maximum congestion window, (2) CTA positioning has no impact on TCP’s performance, and (3) the specified delayed acknowledgment policy needs to be augmented with an adaptive algorithm that adjusts its burst size dynamically to varying bit error rate (BER). [ABSTRACT FROM AUTHOR]

We evaluate the performance of realistic wireless sensor networks in indoor scenarios. Most of the considered networks are formed by nodes using the Zigbee communication protocol. For comparison, we also analyze networks based on the proprietary standard Z-Wave. Two main groups of network scenarios are proposed: (i) scenarios with direct transmissions between the remote nodes and the network coordinator, and (ii) scenarios with routers, which relay the packets between the remote nodes and the coordinator. The sensor networks of interest are evaluated considering different performance metrics. In particular, we show how the received signal strength indication (RSSI) behaves in the considered scenarios. Then, the network behavior is characterized in terms of end-to-end delay and throughput. In order to confirm the experiments, analytical and simulation results are also derived. [ABSTRACT FROM AUTHOR]

Distributed queuing is a fundamental coordination problem that arises in a variety of applications, including distributed directories, totally ordered multicast, and distributed mutual exclusion. The arrow protocol is a solution to distributed queuing that is based on path reversal on a pre-selected spanning tree of the network. We present a novel and comprehensive competitive analysis of the arrow protocol. We consider the total cost of handling a finite number of queuing requests, which may or may not be issued concurrently, and show that the arrow protocol is $O(s\cdot \log D)$ -competitive to the optimal queuing protocol, where s and D are the stretch and the diameter, respectively, of the spanning tree. In addition, we show that our analysis is almost tight by proving that for every spanning tree chosen for execution, the arrow protocol is $\Omega(s \cdot \log(D/s)/{\log}\log(D/s))$ -competitive to the optimal queuing protocol. Our analysis reveals an intriguing connection between the arrow protocol and the nearest neighbor traveling salesperson tour on an appropriately defined graph. [ABSTRACT FROM AUTHOR]

We study the problem of how resilient networks are to node faults. Specifically, we investigate the question of how many faults a network can sustain and still contain a large (i.e., linear-sized) connected component with approximately the same expansion as the original fault-free network. We use a pruning technique that culls away those parts of the faulty network that have poor expansion. The faults may occur at random or be caused by an adversary. Our techniques apply in either case. In the adversarial setting we prove that for every network with expansion $\alpha,$ a large connected component with basically the same expansion as the original network exists for up to a constant times $\alpha \cdot n$ faults. We show this result is tight in the sense that every graph G of size n and uniform expansion $\alpha(\cdot)$ can be broken into components of size o(n) with $\omega(\alpha(n) \cdot n)$ faults. Unlike the adversarial case, the expansion of a graph gives a very weak bound on its resilience to random faults. While it is the case, as before, that there are networks of uniform expansion $\Omega(1/{\rm log}\, n)$ that are not resilient against a fault probability of a constant times $1/{\log}\, n,$ it is also observed that there are networks of uniform expansion $O(1/\sqrt{n})$ that are resilient against a constant fault probability. Thus, we introduce a different parameter, called the span of a graph, which gives us a more precise handle on the maximum fault probability. We use the span to show the first known results for the effect of random faults on the expansion of d-dimensional meshes. [ABSTRACT FROM AUTHOR]

In this paper, we present an energy conservation scheme for wireless ad hoc and sensor networks using gossiping to place nodes in an energy saving sleep state. The technique is termed the Gossip-based Sleep Protocol (GSP).With GSP, each node randomly goes to sleep for some time with gossip sleep probability p. GSP is based on the observation that in a well connected network there are usually many paths between a source and destination, so a percentage of nodes can be in an energy conserving sleep mode without losing network connectivity. GSP needs few operations, scales to large networks and does not require a wireless node to maintain the states of other nodes. We propose two versions of GSP, one for synchronous networks and one for asynchronous networks, and afterward extend GSP to adapt to network traffic conditions. We show the advantages of the GSP approach through both simulations and analysis. [ABSTRACT FROM AUTHOR]

In our study, we investigate a packet-level protocol parallelization approach, which works by parallel multithreading the protocol execution such that packets within and among connections are processed in parallel using distinct processors/threads. The major advantage of this approach is its high scalability—with proper scheduling, more protocol connections, and hence more requests, can be supported by using more threads. In this paper, we present results of our detailed simulations using the NS-2 platform for reliably transferring video stream data in a client-server system. Different types of parameters are used to measure the performance. The parameters include available network bandwidth, different number of TCP connections, and different video sources. Our results show that a parallel approach can indeed significantly enhance the playback quality. [ABSTRACT FROM AUTHOR]

The problem of operation and maintenance (OAM) in optical burst switched (OBS) networks is not addressed by the optical-networking community even though OBS has been gaining research interest in recent years. In this paper, we introduce a functional model of OBS networks and an OAM architecture that is designed to meet the operational requirements based on this model. We present the first framework to realize OAM in OBS networks, including OAM activities, OAM-aware OBS nodes, OAM information and communication models and protocols. A number of practical examples of possible network failures and the corresponding reactions are presented. [ABSTRACT FROM AUTHOR]

We study an Adaptive Window Protocol (AWP) with general increase and decrease profiles in the presence of window dependent random losses. We derive a steady-state Kolmogorov equation, and then obtain its solution in analytic form for particular TCP versions proposed for high speed networks, such as Scalable TCP and HighSpeed TCP. We also relate window evolution under an AWP to workload process in queueing systems; this observation gives us a way to compare various AWP protocols. [ABSTRACT FROM AUTHOR]

This paper investigates the performance of two TCP enhancements (i.e., Scalable TCP and HighSpeed TCP), recently proposed for high-speed backbone networks with a very large bandwidth-delay product, in a geostationary satellite environment. Both persistent and elastic traffic patterns are considered, performance being evaluated in terms of TCP throughput and mean session delay, respectively. The impact of channel characteristics (packet error rate, correlation between successive losses) is widely discussed. Fairness issues are also accounted for, together with the impact of some system parameters, such as the satellite link bandwidth. Extensive comparisons are carried out among Scalable TCP, HighSpeed TCP and other congestion control schemes. The obtained results show the soundness for the use of such protocols in geostationary satellite networks. Indeed, both protocols permit to improve the performance of TCP connections in a wide range of channel conditions, showing (especially Scalable TCP) to be able to cope well with rainy conditions and to exploit a future increase in the satellite link capacity. [ABSTRACT FROM AUTHOR]

This study proposes an algorithm of the maximum value accumulation method that uses the SNMP MIB II to calculate the line utilization on a network based on TCP/IP protocol. There are four types of algorithms to calculate it; the utilization accumulation method, the utilization midterm calculation method, the maximum calculation method, and the maximum accumulation method. The first two methods are not suitable to detect the faults or process the transmission delays in that they are to be followed by their line utilization, if applicable. On the contrary, the other two whose calculations are based on their accumulated amount of bytes, can be used to not only detect the faults but also compensate for the packet delays. The calculations of the line utilization have their practical uses in the capacity planning, the best calculation algorithm for which the maximum accumulation method would serve as. Its practicability includes coping with system faults, line and routing faults and wraparound of the MIB variables, along with its availability as an indicator for the bandwidth upgrade. The study includes its comparison of the latter two methods above by collecting the current traffic on a TCP/IP network to work on the characteristics of the proposed algorithm, as would help a network manager understand the current status of the line capacity to use series of data as an indicator in the line capacity planning. [ABSTRACT FROM AUTHOR]

The routing of traffic between Interact domains, or Autonomous Systems (ASs), a task known as interdomain routing, is currently handled by the Border Gateway Protocol (BGP). In this paper, we address the problem of interdomain routing from a mechanism-design point of view. The application of mechanism-design principles to the study of routing is the subject of earlier work by Nisan and Ronen [16] and Hershberger and Suri [12]. In this paper, we formulate and solve a version of the routing-mechanism design problem that is different from the previously studied version in three ways that make it more accurately reflective of real-world interdomain routing: (1) we treat the nodes as strategic agents, rather than the links; (2) our mechanism computes lowest-cost routes for all source-destination pairs and payments for transit nodes on all of the routes (rather than computing routes and payments for only one source-destination pair at a time, as is done in [12, 16]); (3) we show how to compute our mechanism with a distributed algorithm that is a straightforward extension to BGP and causes only modest increases in routing-table size and convergence time (in contrast with the centralized algorithms used in [12, 16]). This approach of using an existing protocol as a substrate for distributed computation may prove useful in future development of Internet algorithms generally, not only for routing or pricing problems. Our design and analysis of a strategyproof, BGP-based routing mechanism provides a new, promising direction in distributed algorithmic mechanism design, which has heretofore been focused mainly on multicast cost sharing. [ABSTRACT FROM AUTHOR]

Abstract A lot of ongoing work is geared towards improving the reliability, performance and QoS characteristics of service provider IP networks. In contrast, we propose novel enterprise-based techniques that exploit the fact that many enterprises are multi/dual-homed. In a form of service-aware routing, certain (e.g., VoIP) packets are duplicated (e.g., at one edge router) and sent over multiple service providers. After traversing the service provider networks, only the first-to-arrive packets are kept and the later-arriving copies are discarded. In so doing, the result is not only better protection against node and link failures, and packet losses and errors, but also better QoS performance under normal (fault-free) operation. The packet-duplication process can be policy-based and take into account costs, bandwidth, and priority issues, permitting the system to behave like a simple smart router that automatically and continually makes use of the best (lowest-delay) service provider. In this paper, we present the main ideas behind the proposal, along with some initial analytical and experimental/simulation results and insights from a Linux-based implementation. [ABSTRACT FROM AUTHOR]

In this paper, an authenticated tripartite key agreement protocol is proposed, which is an ID-based one with pairings. This protocol involves only one round. The authenticity of the protocol is assured by a special signature scheme, so that messages carrying the information of two ephemeral keys can be broadcasted authentically by an entity. Consequently, one instance of the protocol results in eight session keys for three entities. In other word, one instance of the protocol generates a session key, which is eight times longer than those obtained from traditional key agreement protocols. Security attributes of the protocol are presented, and the computational overhead and bandwidth of the broadcast messages are analyzed as well. [ABSTRACT FROM AUTHOR]

An analytical model of TCP (Transport Control Protocol) over an end-to-end path with random abrupt round-trip time (RTT) changes is presented. Modeling the RTT as a stochastic process, we analytically quantify and compare between the degree of degradation of the steady-state average throughput and window size due to spurious retransmissions for the different versions of TCP (Reno/NewReno versus Tahoe). The modeling methodology in this paper is used for evaluating different design alternatives for TCP for highly dynamic networks. [ABSTRACT FROM AUTHOR]