29918395
A Work-Time Optimal Algorithm for Computing All String Covers
In recent study of repetitive structures of strings, generalized notions of periods have been introduced. A typical regularity, the period u of a given string x, grasps the repetitiveness of x since x is a prefix of a string constructed by concatenations of u. A substring w of x is called a cover of x if x can be constructed by concatenations and superpositions of w. The notion “cover” is a generalization of periods in the sense that superpositions as well as concatenations are considered to define it, whereas only concatenations are considered for periods. 
 
We consider the all-covers problem, i.e., that of computing all the covers of a given string of length n. We present an optimal O(log log n)-time CRCW PRAM algorithm for the all-covers problem. Since there is an Ω(log log n) lower bound on the time complexity of the all-covers problem, our algorithm is work-time optimal.
44748347
A Linear-Time Algorithm for Concave One-Dimensional Dynamic Programming
37635676
Efficient Algorithms for Approximate String Matching with Swaps
Most research on the edit distance problem and thek-differences problem considered the set of edit operations consisting of changes, insertions, and deletions. In this paper we include theswapoperation that interchanges two adjacent characters into the set of allowable edit operations, and we present anO(tmin(m,n))-time algorithm for the extended edit distance problem, wheretis the edit distance between the given strings, and anO(kn)-time algorithm for the extendedk-differences problem. That is, we add swaps into the set of edit operations without increasing the time complexities of previous algorithms that consider only changes, insertions, and deletions for the edit distance andk-differences problems.
37313687
Performance evaluation of optimal aggregate-flow scheduling: a simulation study
Providing scalable QoS-sensitive services to applications with varying degrees of elasticity using aggregate-flow scheduling is a challenging problem. In a previous paper [Proc. IEEE/IFIP Int. Workshop Quality Service (2000) 211], we advanced a theoretical framework where an optimal differentiated services provisioning problem is formulated and solved to yield solutions for optimal per-hop control. In this paper, we extend our previous work by investigating performance evaluation and implementation issues associated with the induced optimal differentiated services architecture. We design a system that realizes the optimal per-hop control coupled with end-to-end adaptive QoS control, and implement a practical enhancement by introducing a scaling function which is applied to the TOS field label value in the IP header at each router. The scaling function allows the service provider to configure the per-hop control so as to export customized QoS separation-essential when shaping end-to-end absolute QoS over per-hop relative QoS-commensurate with the QoS profiles of the service provider's user base. We use simulation to study the structural and dynamical properties of differentiated services as affected by optimal aggregate-flow per-hop control.
14470122
An architecture for noncooperative QoS provision in many-switch systems
With the proliferation of high-speed networks and networked services, provisioning differentiated services to a diverse user base with heterogeneous QoS requirements has become an important problem. The traditional approach of resource reservation and admission control provides both guarantees and graded services, however, at the cost of potentially underutilized resources and limited scalability. We describe a WAN QoS provision architecture that adaptively organizes best-effort bandwidth into stratified services with graded QoS properties such that the QoS needs of a diverse user base can be effectively met. This architecture-SBS (stratified best-effort service)-promotes a simple user/simple network realization where neither the user nor the network is burdened with complex computational responsibilities. SBS is scalable, efficient, and adaptive, and it complements the guaranteed service architecture, sharing a common network substrate comprised of GPS routers. It is also a functional complement, provisioning QoS efficiently commensurate with user needs, albeit at the cost of weaker protection. SBS is suited to noncooperative network environments where users behave selfishly and resource contention resolution is mediated by the principle of competitive interaction. A principal feature of SBS is the transformation of user-centric QoS provision mechanisms-a defining characteristic of competitive interaction entailing intimate user control of internal network resources-into network-centric mechanisms while preserving the former's resource allocation paradigm. End-to-end QoS control is facilitated by decentralized control based on Lagrangian optimization-achieve a target end-to-end QoS at minimum cost or resource usage-which, in turn, is amenable to distributed implementation. SBS achieves per-flow QoS control with zero per-flow state at routers and a packet header whose size is independent of hop count. SBS, in spite of foregoing both resource reservation and admission control, is able to provision stable, graded QoS.
20327349
Analysis and design of the virtual rate control algorithm for stabilizing queues in TCP networks
The virtual rate control (VRC) algorithm has been proposed for active queue management (AQM) in TCP networks. VRC, a rate-based control mechanism, responds quickly to traffic changes, thus allowing for high utilization and small loss. It can effectively stabilize both the input rate and the queue length around their target levels. In this paper, we analyze the stability of the VRC algorithm based on a linearized TCP model with time delay and provide a design guideline for parameter setting to make the overall system stable. Finally, we confirm the validity of our analysis and the effectiveness of VRC compared to RED, PI, REM, and AVQ through extensive ns-2 simulations.
14489739
Robust playout mechanism for Internet audio applications
In Internet audio applications, delay and delay jitter affect mostly the applications' quality of service. Since packet delays are different and changing over time, the receiver needs to buffer some amount of packets before playout. Therefore, the amount of buffered packets and the timing of playout are very important for the performance of applications. We adopt an autoregressive (AR) model for estimation of packet delay and deploy a robust identification algorithm for adjustment of the parameters of the AR process. In our preliminary experiments, this robust algorithm leads to better performance when the noise is correlated and/or non-stationary, and also it is robust to model uncertainties.
35766217
Efficient Shaping of User-Specified QoS Using Aggregate-Flow Control
Architecting networks capable of providing scalable, efficient, and fair services to users with diverse QoS requirements is a pressing problem. The two principal issues are: design of "good" per-hop behavior and edge control. In previous work [2,3], we studied aggregate-flow QoS control from a noncooperative resource provisioning context. In [20], the framework was generalized by, one, solving an optimal aggregate-flow per-hop behavior problem, and two, showing how it can be used coupled with end-to-end label control to facilitate scalable and fair QoS when driven by selfish users and service providers. In this paper, we focus on optimal aggregate-flow per-hop control and complement analysis by experimental performance evaluation. We show that user-specified, diverse QoS is efficiently facilitated over the optimal per-hop behavior network substrate using adaptive label control end-to-end.