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In this paper we investigate the problem of finding a layer-2 network topology when the information available from SNMP MIB is incomplete. We prove that finding a network topology in this case is NP-hard. We further prove that deciding whether the given information defines a unique network topology is a co-NP-hard problem. We show that if there is a single node r such that every other network node...
Assuring cryptographic integrity of mutable fields in any on-demand ad hoc routing protocol is more challenging than that of non mutable fields. We propose an efficient authentication strategy for this purpose, which leverages a proposed broadcast encryption (BE) scheme. We investigate some shortcomings of SAODV, a popular secure extension of the ad hoc on-demand distance vector (AODV) protocol and...
We present an "opportunistic" scheduling policy with the objective of improving delay performance for time-sensitive users in wireless networks. Since packet delay depends on both resource allocation and time-varying capacity of wireless channels, we introduce a search radius (SR) into the framework of packet fair queueing (PFQ) and employ maximum relative SNR (Max-rSNR) as scheduling rule...
In most designed adaptive modulation and coding (AMC) schemes the data link layer transmission rate is adapted only against physical layer channel variation. The highly fluctuating queuing process at the data link layer is not fully investigated. In this study, we first research on more advanced AMC mode selection algorithms and then propose a two-dimensional cross- layer optimization scheme. This...
The current system design of mobile ad hoc networks (MANET), derived from their traditional fixed counterparts, cannot fully meet the requirements inherent to the dynamic nature of such networks. Cross-layer (CL) designs, a modification of the classic protocol stack, are envisioned as a solution for this problem. Many CL design approaches are proposed, each for a different optimization purpose. Mobile...
The problem of dynamic bandwidth allocation (DBA) is inherent to systems that employ bandwidth on demand (BoD). An important issue in such systems is to be able to react efficiently to the always-changing traffic requests of users. Moreover, it is realistic to assume large populations sharing system resources and thus efficient methods to distribute bandwidth are mandatory. Further desirable system...
In next generation wireless networks, a variety of heterogeneous radio access technologies are expected to be available simultaneously within a single wireless terminal. This paper addresses the challenge of link aggregation in multi-access networks, where a key issue is how to optimally aggregate bandwidth offered by the individual radio link. Effective link throughput model is employed as a common...
As the Internet grows in size and bandwidth, a variety of real time applications such as voice over IP (VoIP) and video conferences require low latency, bandwidth guarantee and delay bounded service constraints. Because current Internet provides only offer best effort services, packet scheduling algorithms supporting quality of service (QoS) requirements play an important part in switches and routers...
Traffic grooming techniques are used to combine low-speed data streams onto high-speed lightpaths with the objective of minimizing the network cost, or maximizing the network throughput. In this paper, we first present an efficient integer linear program (ILP) formulation for traffic grooming on mesh WDM networks. Our formulation can be easily modified to implement different objective functions. Unlike...
Traffic flow measurement is essential to implement QoS control in the Internet. Flow monitoring system collects and stores sampled flow states in a flow table (FT) and the entries are renewed at every packet sampling. Entries in the FT are checked and removed when no packets are sampled within a predetermined timeout. We propose an efficient timeout checking mechanism based on checking a small number...
This work is concerned with defining a performanceindex that can be used as an objective measure in the evaluation and comparison of ad hoc networking protocols. Specifically, we introduce a performance index that aggregates performance results from multiple response metrics into a single scalar value that quantifies overall system performance, leading to more objective evaluations and comparisons...
Orthogonal frequency-division multiplexing (OFDM) with multiple transmit and receive antennas (MIMO-OFDM) and adaptive bit-loading (ABL) offers reliable high-data rate communication for systems with moderate mobility as considered in e.g. IEEE 802.16e. In this paper, we propose and optimize wrapped space-time coding (WSTC) for bit-loaded MIMO-OFDM. We further optimize V-BLAST with ABL by mitigating...
Many P2P-based storage systems use distributed indexing service for searching documents. There are two security issues when the nodes providing the index service are compromised by adversaries. First, the adversaries may delete the indexes or stop the program of indexing service, making the affected documents disappear in the search infrastructure. Second, the adversaries may leak the locations of...
A serial sum-product architecture for low-density parity-check (LDPC) codes is presented. In the proposed architecture, a standard bit node processing unit computes the bit to check node messages sequentially, while the check node computations are broken up into several steps and computed on the fly. This bit node centric architecture requires considerably less memory compared to other serial architectures,...
Recently, peer-to-peer systems have become one of the most popular distributed applications. Many previous works have investigated identifier-based indexing systems that support a query-by-identifier service. However, clients usually have only partial information about an object, and prefer to query by keywords. In this paper, we propose a small-world-based keyword search system (SW-KSS) that provides...
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