Jacir Luiz Bordim

Energy-Efficient Initialization Protocols for Ad-hoc Radio Networks

The main contribution of this work is to propose energy-efficient randomized initialization protocols for ad-hoc radio networks (ARN, for short). First, we show that if the number n of stations is known beforehand, the single-channel ARN can be initialized by a protocol that terminates, with high probability, in O(n) time slots with no station being awake for more than O(log n) time slots. We then go on to address the case where the number n of stations in the ARN is not known beforehand. We begin by discussing, an elegant protocol that provides a tight approximation of n. Interestingly, this protocol terminates, with high probability, in O((log n)2) time slots and no station has to be awake for more than O(log n) time slots. We use this protocol to design an energy-efficient initialization protocol that terminates, with high probability, in O(n) time slots with no station being awake for more than O(log n) time slots. Finally, we design an energy-efficient initialization protocol for the k-channel ARN that terminates, with high probability, in O(n/k + log n) time slots, with no station being awake for more than O(log n) time slots.

INSTANCE-SPECIFIC SOLUTIONS FOR ACCELERATING THE CKY PARSING OF LARGE CONTEXT-FREE GRAMMARS

The main contribution of this paper is an FPGA-based implementation of an instance-specific hardware which accelerates the CKY (Cocke-Kasami- Younger) parsing of context-free grammars. Given a context-free grammar G and a string x, the CKY parsing determines whether G derives x. We developed a hardware generator that creates a Verilog HDL source to perform the CKY parsing for any fixed context-free grammar G. The generated source is embedded in an FPGA using the design software provided by the FPGA vendor. The results show that our instance-specific hardware solution attains an astonishing speed-up factor of up to 3,700 over traditional software solutions.

Fundamental protocols for wireless sensor networks

The main contribution of this work is to present energyefficient protocols that compute the sum of n numbers over any commutative and associative binary operator stored in n wireless sensor nodes arranged in a two-dimensional grid of size √ n × √ n. We first present a protocol that computes the sum in O(r 2 +( n r2) 1 3) time slots with no sensor node being awake for more than O(1) time slots, where r is the transmission range of the sensor nodes. We then show a fault-tolerant protocol that computes the sum in the same number of time slots with no sensor node being awake for more than O(log r) time slots.

Accelerating the CKY Parsing Using FPGAs

The main contribution of this paper is to present an FPGA-based implementation of an instance-specific hardware which accelerates the CKY (Cook-Kasami-Younger) parsing for context-free grammars. Given a context-free grammar G and a string x, the CKY parsing determines if G derives x. We have developed a hardware generator that creates a Verilog HDL source to perform the CKY parsing for any given context-free grammar G. The created source is embedded in an FPGA using the design software provided by the FPGA vendor. We evaluated the instance-specific hardware, generated by our hardware generator, using a timing analyzer and tested it using the Altera FPGAs. The generated hardware attains a speed-up factor of approximately 750 over the software CKY parsing algorithm. Hence, we believe that our approach is a promising solution for the CKY parsing.

Sorting on single-channel wireless sensor networks

A wireless sensor network is a distributed system which consists of a base station and a number of wireless sensors nodes endowed with radio transceivers. The main contribution of this work is to present a sorting protocol for multi-hop wireless sensor networks. Our protocol sorts n elements which are initially loaded in n sensor nodes that are organized in a two-dimensional plane of size /spl radic/n/spl times//spl radic/n. The sorting protocol proposed here sorts the n elements in O(r/spl radic/n) time slots when /spl radic/n > r, where r is the transmission range of the sensor nodes.

Topology Control in Cooperative Ad Hoc Wireless Networks

Cooperative communication (CC) is a technique that exploits spatial diversity allowing multiple nodes to cooperatively relay signals to the receiver so that it can combine the received signals to obtain the original message. CC can be combined with topology control to increase connectivity at the cost of a small increase in energy consumption. This work focuses on exploring CC to improve the connectivity with a sink node in ad hoc wireless networks. More precisely, this work proposes a new technique, named CoopSink, that combines CC and topology control techniques to increase connectivity to a sink node while ensuring energy-efficient routes. Simulation results show that connectivity and routing to the sink cost can be improved up to 6.8 and 2.3 times, respectively, when compared with other similar strategies.

Admission control and simple class based QoS provisioning for mobile ad hoc network

In this paper, we present a network layer based admission control and simple class based service differentiation model to support QoS in mobile ad hoc networks. Our admission control procedure works along with the route finding phase of reactive routing protocols for mobile ad hoc networks (AODV, DSR etc). We also propose a simple class based service differentiation system to support QoS once a traffic is admitted by our admission controller. The proposed service differentiation is based on a DiffServ model and includes modifications like configuration of each node with edge and core functionality, dynamic selection of edge/core functionality, and use of minimal and simple classes. Simulation results show that our system allows seven times more real time traffic in the network than the proposed QoS for the AODV model while satisfying the demanded end-to-end delay and providing low jitter.

Doubly-logarithmic energy-efficient initialization protocols for single-hop radio networks

A radio network is a distributed system with no central shared resource, consisting of n stations each equipped with a radio transceiver. One of the most important parameters to evaluate protocols in the radio networks is the number of awake time slots in which each individual station sends/receives a data packet. We are interested in devising energy-efficient initialization protocols in the single-hop radio network (RN, for short) that assign unique IDs in the range [1, n] to the n stations using few awake time slots. It is known that the RN can be initialized in O(log log n) awake time slots, with high probability, if every station knows the number n of stations in the RN. Also, it has been shown that the RN can be initialized in O(log n) awake time slots even if no station knows n. However, it has been open whether the initialization can be performed in O(log log n) awake time slots when no station knows n.Our main contribution is to provide the breakthrough: we show that even if no station knows n, the RN can be initialized by our protocol that terminates, with high probability, in O(n) time slots with no station being awake for more than O(log log n) time slots. We then go on to design an initialization protocol for the k-channel RN that terminates, with high probability, in O(n/k+(log n)2) time slots with no station being awake for more than O(log log n) time slots.

IEEE802.11b/g Standard: Theoretical Maximum Throughput

Estimating the throughput of an WiFi connection can be quite complex, even when considering simplified scenarios. Indeed, the varying number of parameters specified in the standards makes it hard to understand their impact in terms of delay and throughput. The main contribution of this work is to present a simple scheme to compute the exact maximum throughput for an IEEE 802.11g network. The proposed scheme incorporates all the timings and settings which allows one to calculate the throughput for different channel spacing and modulation techniques specified in the standard. Numerical and experimental results showing the accuracy of the proposed scheme are also presented.

An Energy Efficient Leader Election Protocol for Radio Network with a Single Transceiver

In this work we present an energy efficient leader election protocol for anonymous radio network populated with n mobile stations. Previously, Nakano and Olariu have presented a leader election protocol that terminates, with probability exceeding 1 - 1/f (f ≥ 1), in log logn + o(log log n)+ O(log f) time slots [14]. As the above protocol works under the assumption that every station has the ability to transmit and monitor the channel at the same time, it requires every station to be equipped with two transceivers. This assumption, however, is unrealistic for most mobile stations due to constraints in cost, size, and energy dissipation. Our main contribution is to show that it is possible to elect a leader in an anonymous radio network where each station is equipped with a single transceiver. Quite surprisingly, although every station has only one transceiver, our leader election protocol still runs, with probability exceeding 1 - 1/f(f ≥ 1), in log log n + o(log logn)+ O(log f) time slots. Moreover, our leader election protocol needs only expected O(n) total awake time slots, while Nakano and Olarius protocol needs expected O(nlog logn) total awake time slots. Since every leader election protocol needs at least Ω(n) awake time slots, our leader election protocol is optimal in terms of the expected awake time slots.