arXiv subjects

Bogdan S. Chlebus

Publications and source records attributed to Bogdan S. Chlebus.

21 records · Page 2Linked to original sources

arXiv2017

Maximum Throughput of Multiple Access Channels in Adversarial Environments

We consider deterministic distributed broadcasting on multiple access channels in the framework of adversarial queuing. Packets are injected dynamically by an adversary that is constrained by the injection rate and the number of packets that may be injected simultaneously; the latter we call burstiness. The maximum injection rate that an algorithm can handle in a stable manner is called the throughput of the algorithm. We develop an algorithm that achieves throughput $1$ for any number of stations against leaky-bucket adversaries. The algorithm has $O(n^2+\text{burstiness})$ packets queued simultaneously at any time, where $n$ is the number of stations; this upper bound is proved to be best possible. An algorithm is called fair when each packet is eventually broadcast. We show that no algorithm can be both stable and fair for a system of at least two stations against leaky-bucket adversaries. We study in detail small systems of exactly two and three stations against window adversaries to exhibit differences in quality of broadcast among classes of algorithms. For two stations, we show that fair latency can be achieved by a full sensing algorithm, while there is no stable acknowledgment based algorithm. For three stations, we show that fair latency can be achieved by a general algorithm, while no full sensing algorithm can be stable. Finally, we show that algorithms that either are fair or do not have the queue sizes affect the order of transmissions cannot be stable in systems of at least four stations against window adversaries.

cs.NI↗

arXiv2016

Anonymous Processors with Synchronous Shared Memory

We consider synchronous distributed systems in which anonymous processors communicate by shared read-write variables. The goal is to have all the processors assign unique names to themselves. We consider the instances of this problem determined by whether the number $n$ is known or not, and whether concurrently attempting to write distinct values into the same memory cell is allowed or not, and whether the number of shared variables is a constant independent of $n$ or it is unbounded. For known $n$, we give Las Vegas algorithms that operate in the optimum expected time, as determined by the amount of available shared memory, and use the optimum $O(n\log n)$ expected number of random bits. For unknown $n$, we give Monte Carlo algorithms that produce correct output upon termination with probabilities that are $1-n^{-Ω(1)}$, which is best possible when terminating almost surely and using $O(n\log n)$ random bits.

cs.DC↗

arXiv2016

Universal Routing in Multi-hop Radio Networks

In this article we introduce a new model to study stability in multi-hop wireless networks in the framework of adversarial queueing. In such a model, a routing protocol consists of three components: a transmission policy, a scheduling policy to select the packet to transmit form a set of packets parked at a node, and a hearing control mechanism to coordinate transmissions with scheduling. For such a setting, we propose a definition of universal stability that takes into account not only the scheduling policies (as in the standard wireline adversarial model), but also the transmission policies. First, we show that any scheduling policy that is unstable in the classical wireline adversarial model remains unstable in the multi-hop radio network model, even in scenarios free of inter- ferences. Then, we show that both SIS and LIS (two well-known universally stable scheduling policies in the wireline adversarial model) remain stable in the multi-hop radio network model, provided a proactive hearing control is used. In contrast, such scheduling policies turn out to be unstable when using a reactive hearing control. However, the scheduling policy LIS can be enforced to be universally stable provided ties are resolved in a permanent manner. Such a situation doesn't hold in the case of SIS, which remains unstable regardless of how ties are resolved. Furthermore, for some transmission policies which we call regular, we also show that all scheduling policies that are universally stable when using proactive hearing control (which include SIS and LIS) remain universally stable when using reactive hearing control.

cs.NI↗