Browsing by Author "Chaves, Ricardo"
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- An efficient scalable RNS architecture for large dynamic rangesPublication . Miguens Matutino, Pedro; Chaves, Ricardo; Sousa, LeonelThis paper proposes an efficient scalable Residue Number System (RNS) architecture supporting moduli sets with an arbitrary number of channels, allowing to achieve larger dynamic range and a higher level of parallelism. The proposed architecture allows the forward and reverse RNS conversion, by reusing the arithmetic channel units. The arithmetic operations supported at the channel level include addition, subtraction, and multiplication with accumulation capability. For the reverse conversion two algorithms are considered, one based on the Chinese Remainder Theorem and the other one on Mixed-Radix-Conversion, leading to implementations optimized for delay and required circuit area. With the proposed architecture a complete and compact RNS platform is achieved. Experimental results suggest gains of 17 % in the delay in the arithmetic operations, with an area reduction of 23 % regarding the RNS state of the art. When compared with a binary system the proposed architecture allows to perform the same computation 20 times faster alongside with only 10 % of the circuit area resources.
- Arithmetic-based binary-to-RNS converter modulo {2(n)+/- k} for jn-Bit dynamic rangePublication . Miguens Matutino, Pedro; Chaves, Ricardo; Sousa, LeonelIn this brief, a read-only-memoryless structure for binary-to-residue number system (RNS) conversion modulo {2(n) +/- k} is proposed. This structure is based only on adders and constant multipliers. This brief is motivated by the existing {2(n) +/- k} binary-to-RNS converters, which are particular inefficient for larger values of n. The experimental results obtained for 4n and 8n bits of dynamic range suggest that the proposed conversion structures are able to significantly improve the forward conversion efficiency, with an AT metric improvement above 100%, regarding the related state of the art. Delay improvements of 2.17 times with only 5% area increase can be achieved if a proper selection of the {2(n) +/- k} moduli is performed.
- A Compact and Scalable RNS ArchitecturePublication . Miguens Matutino, Pedro; Chaves, Ricardo; Sousa, LeonelThis paper proposes a unified architecture for designing Residue Number System (RNS) based processors for moduli sets with an arbitrary number of channels. Recently, new RNS moduli sets have been proposed in order to increase the dynamic range and reduce the width of the channels. The proposed architecture allows designing forward and reverse RNS converters, as well as the arithmetic operators of each modulo channel. The forward and reverse conversions are implemented using channel arithmetic units, resulting in a very compact architecture. Moreover, the arithmetic operations supported at the channel level include addition, subtraction, and multiplication with accumulation capability. The presented results suggest that the proposed RNS architecture leads to compact and scalable implementations, with competitive, or even better, performance when compared with the related state of the art, considering fixed moduli sets. Experimental results suggest gains of 17% in the delay of arithmetic operations, with an area reduction of 23% regarding the state of the art.
- EmuCD: an emulator for content dissemination protocols in vehicular networksPublication . Chaves, Ricardo; Senna, Carlos; Luís, Miguel; Sargento, Susana; Moreira, André; Recharte, Diogo; Matos, RicardoThe development of protocols for mobile networks, especially for vehicular ad-hoc networks (VANETs), presents great challenges in terms of testing in real conditions. Using a production network for testing communication protocols may not be feasible, and the use of small networks does not meet the requirements for mobility and scale found in real networks. The alternative is to use simulators and emulators, but vehicular network simulators do not meet all the requirements for effective testing. Aspects closely linked to the behaviour of the network nodes (mobility, radio communication capabilities, etc.) are particularly important in mobile networks, where a delay tolerance capability is desired. This paper proposes a distributed emulator, EmuCD, where each network node is built in a container that consumes a data trace that defines the node's mobility and connectivity in a real network (but also allowing the use of data from simulated networks). The emulated nodes interact directly with the container's operating system, updating the network conditions at each step of the emulation. In this way, our emulator allows the development and testing of protocols, without any relation to the emulator, whose code is directly portable to any hardware without requiring changes or customizations. Using the facilities of our emulator, we tested InterPlanetary File System (IPFS), Sprinkler and BitTorrent content dissemination protocols with real mobility and connectivity data from a real vehicular network. The tests with a real VANET and with the emulator have shown that, under similar conditions, EmuCD performs closely to the real VANET, only lacking in the finer details that are extremely hard to emulate, such as varying loads in the hardware.
- Pipelined FPGA coprocessor for elliptic curve cryptography based on residue number systemPublication . Miguens Matutino, Pedro; Araújo, Juvenal; Sousa, Leonel; Chaves, RicardoIn this paper a novel pipelined FPGA coprocessor for ECC is proposed, exploiting the parallelism capabilities of RNS to the computation of large operand algorithms. This intrinsic characteristic of representing large integer numbers as a set of smaller and independent values allows for the parallelization of the computationally heavy large operand multiplications, required in asymmetrical cryptographic algorithms. Towards a compact and performance efficient design, the RNS coprocessor supports a single highly pipelined multi-modulo arithmetic unit. Implementation results, on FPGA of this RNS based ECC coprocessor, suggest one of the smallest programmable designs with a proportional performance when compared with related state of the art. Additionally, the resulting architecture allows for the computation of varying key sizes without changing the design or its implementation.
- ROM-less RNS-to-binary converter moduli {22N − 1, 22N + 1, 2N − 3, 2N + 3}Publication . Miguens Matutino, Pedro; Chaves, Ricardo; Sousa, LeonelIn this paper, a novel ROM-less RNS-to-binary converter is proposed, using a new balanced moduli set {22n-1, 22n + 1, 2n-3, 2n + 3} for n even. The proposed converter is implemented with a two stage ROM-less approach, which computes the value of X based only in arithmetic operations, without using lookup tables. Experimental results for 24 to 120 bits of Dynamic Range, show that the proposed converter structure allows a balanced system with 20% faster arithmetic channels regarding the related state of the art, while requiring similar area resources. This improvement in the channel's performance is enough to offset the higher conversion costs of the proposed converter. Furthermore, up to 20% better Power-Delay-Product efficiency metric can be achieved for the full RNS architecture using the proposed moduli set. © 2014 IEEE.
- When backscatter communication meets vehicular networks: boosting crosswalk awarenessPublication . Pereira, Felisberto; Sampaio, Hugo; Chaves, Ricardo; Correia, Ricardo; Luís, Miguel; Sargento, Susana; Jordão, Marina; Almeida, Luís; Senna, Carlos; Oliveira, Arnaldo S. R.; Carvalho, Nuno BorgesThe research of safety applications in vehicular networks has been a popular research topic in an effort to reduce the number of road victims. Advances on vehicular communications are facilitating information sharing through real time communications, critical for the development of driving assistance systems. However, the communication by itself is not enough to reach the most desired target as we need to know which safety-related information should be disseminated. In this work, we bring passive sensors and backscatter communication to the vehicular network world. The idea is to increase the driver (or vehicle) awareness regarding the presence of pedestrians in a crosswalk. Passive sensors and backscatter communication technologies are used for the pedestrians’ detection phase, while the vehicular network is used during the dissemination of the detection information to surrounding vehicles. The proposed solution was validated through end-to-end experimentation, with real hardware and in a real crosswalk with real pedestrians and vehicles, demonstrating its applicability.