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39
Wireless Access to Internet via Bluetooth: Performance Evaluation of the EDC Scheduling Algorithm
 In Proceedings of the First Workshop on Wireless Mobile Internet
, 2001
"... Bluetooth is an emerging technology for constructing adhoc wireless Personal Area Networks (WPANs). In this paper we analyze an innovative scheduling algorithm for asynchronous data traffic specifically tailored to the Bluetooth characteristic. This algorithm, named Efficient DoubleCycle (EDC), dyn ..."
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Cited by 23 (2 self)
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Bluetooth is an emerging technology for constructing adhoc wireless Personal Area Networks (WPANs). In this paper we analyze an innovative scheduling algorithm for asynchronous data traffic specifically tailored to the Bluetooth characteristic. This algorithm, named Efficient DoubleCycle (EDC), dynamically adapts the polling frequency to the traffic conditions. By considering a scenario where a Bluetooth master is used as wireless access point to the Internet, we show that our EDC scheduler significantly enhances the system performance with regard to a Round Robin (RR) scheduler.
Performance Evaluation of Bluetooth Polling Schemes: An Analytical Approach
 ACM/Kluwer MONET
, 2004
"... In the recent years, many polling schemes for Bluetooth networks have been proposed and evaluated. To the authors knowledge, however, analysis has been carried out mainly through computer simulations and, up to now, no mathematical treatment of this topic has been presented. In this paper, we propos ..."
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Cited by 16 (0 self)
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In the recent years, many polling schemes for Bluetooth networks have been proposed and evaluated. To the authors knowledge, however, analysis has been carried out mainly through computer simulations and, up to now, no mathematical treatment of this topic has been presented. In this paper, we propose an analytical framework for performance evaluation of polling algorithms in Bluetooth piconets. The analysis is carried out by resorting to an effective and simple mathematical method, called Equilibrium Point Analysis. The system is modelled as a multidimensional finite Markov chain and performance metrics are evaluated at the equilibrium state. The analysis is focused on three classical polling schemes, namely Pure Round Robin, Gated Round Robin and Exhaustive Round Robin, which are compared in terms of packet delay, channel utilization, and fairness among users. Both analytical and simulation results are presented for three relevant scenarios, in order to validate the accuracy of the analysis proposed. Keywords: Bluetooth, polling schemes, equilibrium point analysis, performance evaluation 1.
Weighted Capacitated, Priority, and Geometric Set Cover via Improved QuasiUniform Sampling
, 2011
"... The minimumweight set cover problem is widely known to be O(log n)approximable, with no improvement possible in the general case. We take the approach of exploiting problem structure to achieve better results, by providing a geometryinspired algorithm whose approximation guarantee depends solely ..."
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Cited by 13 (1 self)
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The minimumweight set cover problem is widely known to be O(log n)approximable, with no improvement possible in the general case. We take the approach of exploiting problem structure to achieve better results, by providing a geometryinspired algorithm whose approximation guarantee depends solely on an instancespecific combinatorial property known as shallow cell complexity (SCC). Roughly speaking, a set cover instance has low SCC if any columninduced submatrix of the corresponding elementset incidence matrix has few distinct rows. By adapting and improving Varadarajan’s recent quasiuniform random sampling method for weighted geometric covering problems, we obtain strong approximation algorithms for a structurally rich class of weighted covering problems with low SCC. We also show how to derandomize our algorithm. Our main result has several immediate consequences. Among them, we settle an open question of Chakrabarty et al. [8] by showing that weighted instances of the capacitated covering problem with underlying network structure have O(1)approximations. Additionally, our improvements to Varadarajan’s sampling framework yield several new results for weighted geometric set cover, hitting set, and dominating set problems. In particular, for weighted covering problems exhibiting linear (or nearlinear) union complexity, we obtain approximability results agreeing with those known for the unweighted case. For example, we obtain a constant approximation for the weighted disk cover problem, improving upon the 2 O(log ∗ n)approximation known prior to our work and matching the O(1)approximation known for the unweighted variant.
Exact Algorithms and APXHardness Results for Geometric Set Cover
, 2011
"... We study several geometric set cover problems in which the goal is to compute a minimum cover of a given set of points in Euclidean space by a family of geometric objects. We give a short proof that this problem is APXhard when the objects are axisaligned fat rectangles, even when each rectangle i ..."
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Cited by 9 (0 self)
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We study several geometric set cover problems in which the goal is to compute a minimum cover of a given set of points in Euclidean space by a family of geometric objects. We give a short proof that this problem is APXhard when the objects are axisaligned fat rectangles, even when each rectangle is an ǫperturbed copy of a single unit square. We extend this result to several other classes of objects including almostcircular ellipses, axisaligned slabs, downward shadows of line segments, downward shadows of graphs of cubic functions, 3dimensional unit balls, and axisaligned cubes, as well as some related hitting set problems. Our hardness results are all proven by encoding a highly structured minimum vertex cover problem which we believe may be of independent interest. In contrast, we give a polynomialtime dynamic programming algorithm for 2dimensional set cover where the objects are pseudodisks containing the origin or are downward shadows of pairwise 2intersecting xmonotone curves. Our algorithm extends to the weighted case where a minimumcost cover is required.
Universal sequencing on an unreliable machine
, 2011
"... We consider scheduling on an unreliable machine that may experience unexpected changes in processing speed or even full breakdowns. We aim for a universal solution that performs well without adaptation for any possible machine behavior. Our objective is to minimize ∑ wjf(Cj) for any nondecreasing, ..."
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Cited by 6 (2 self)
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We consider scheduling on an unreliable machine that may experience unexpected changes in processing speed or even full breakdowns. We aim for a universal solution that performs well without adaptation for any possible machine behavior. Our objective is to minimize ∑ wjf(Cj) for any nondecreasing, nonnegative, differentiable cost function f(Cj). We design a deterministic algorithm that finds a universal scheduling sequence with a solution value within 4 times the value of an optimal clairvoyant algorithm that knows the machine behavior in advance. A randomized version of this algorithm attains in expectation a ratio of e. We also show that both results are best possible among all universal solutions. Our algorithms can be adapted to run in polynomial time with slightly increased cost. When jobs have individual release dates, the situation changes drastically. Even if all weights are equal, there are instances for which any universal solution is a factor of Ω(log n / log log n) worse than an optimal sequence for any unbounded cost function. Motivated by this hardness, we study the special case when the processing time of each job is proportional to its weight. We present a nontrivial algorithm with a small constant performance guarantee.
Online Scheduling with General Cost Functions
"... We consider a general online scheduling problem on a single machine with the objective of minimizing j wjg(Fj), where wj is the weight/importance of job Jj, Fj is the flow time of the job in the schedule, and g is an arbitrary nondecreasing cost function. Numerous natural scheduling objectives are ..."
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Cited by 6 (4 self)
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We consider a general online scheduling problem on a single machine with the objective of minimizing j wjg(Fj), where wj is the weight/importance of job Jj, Fj is the flow time of the job in the schedule, and g is an arbitrary nondecreasing cost function. Numerous natural scheduling objectives are special cases of this general objective. We show that the scheduling algorithm Highest Density First (HDF) is (2+ɛ)speed O(1)competitive for all cost functions g simultaneously. We give lower bounds that show the HDF algorithm and this analysis are essentially optimal. Finally, we show scalable algorithms are achievable in some special cases. 1
A fair and traffic dependent polling scheme for bluetooth
 in Proc. of the joint IEEE conferences ICWLHN 2002 and ICN 2002
, 2002
"... Bluetooth [1] is a universal radio interface in the 2.4 GHz ISM frequency band, which will enable users to connect a wide range of small electronic devices such as notebook computers, cellular phones and other portable handheld devices easily and quickly, without the need for cables. The key disting ..."
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Cited by 5 (3 self)
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Bluetooth [1] is a universal radio interface in the 2.4 GHz ISM frequency band, which will enable users to connect a wide range of small electronic devices such as notebook computers, cellular phones and other portable handheld devices easily and quickly, without the need for cables. The key distinguishing features of Bluetooth are its minimal hardware dimensions, low
An efficient link polling policy by pattern matching for Bluetooth piconets
 in Proc. of the 36th Hawaii International Conference on System Sciences
, 2003
"... Bluetooth has a master–slave configuration called a piconet. Unspecified in the Bluetooth standard, the link polling policy adopted by a master may significantly influence the bandwidth utilization of a piconet. Several works have been dedicated to this issue. However, none of them addresses the asy ..."
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Cited by 4 (0 self)
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Bluetooth has a master–slave configuration called a piconet. Unspecified in the Bluetooth standard, the link polling policy adopted by a master may significantly influence the bandwidth utilization of a piconet. Several works have been dedicated to this issue. However, none of them addresses the asymmetry of traffics between masters and slaves, and the different data packet types provided by Bluetooth are not fully exploited. In this paper, we propose an efficient pattern matching polling (PMP) policy for data link scheduling that properly resolves these deficiencies. A polling pattern is a sequence of Bluetooth packets of different type combinations (e.g. DH1/DH3/DH5/DM1/DM3/DM5) to be exchanged by a master–slave pair that can properly reflect the traffic ratio (i.e. asymmetry) of the pair. By judiciously selecting a proper polling pattern together with polling times for the link, the precious wireless bandwidth can be better utilized. The ultimate goal is to reduce the unfilled, or even null, payloads in each busy slot. In addition, an overflow mechanism is included to handle unpredictable traffic dynamics. Extensive simulations are presented to justify the capability of PMP in handling regular as well as bursty traffics. 1.
On capacitated set cover problems
 APPROX
"... Abstract. Recently, Chakrabarty et al. [5] initiated a systematic study of capacitated set cover problems, and considered the question of how their approximability relates to that of the uncapacitated problem on the same underlying set system. Here, we investigate this connection further and give se ..."
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Cited by 2 (1 self)
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Abstract. Recently, Chakrabarty et al. [5] initiated a systematic study of capacitated set cover problems, and considered the question of how their approximability relates to that of the uncapacitated problem on the same underlying set system. Here, we investigate this connection further and give several results, both positive and negative. In particular, we show that if the underlying set system satisfies a certain hereditary property, then the approximability of the capacitated problem is closely related to that of the uncapacitated version. We also give related lower bounds, and show that the hereditary property is necessary to obtain nontrivial results. Finally, we give some results for capacitated covering problems on set systems with low hereditary discrepancy and low VC dimension. 1