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| 2. |
- Bengtsson, Jerker
(författare)
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Models and Methods for Development of DSP Applications on Manycore Processors
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Advanced digital signal processing systems require specialized high-performance embedded computer architectures. The term high-performance translates to large amounts of data and computations per time unit. The term embedded further implies requirements on physical size and power efficiency. Thus the requirements are of both functional and non-functional nature. This thesis addresses the development of high-performance digital signal processing systems relying on manycore technology. We propose building two-level hierarchical computer architectures for this domain of applications. Further, we outline a tool flow based on methods and analysis techniques for automated, multi-objective mapping of such applications on distributed memory manycore processors. In particular, the focus is put on how to provide a means for tunable strategies for mapping of task graphs on array structured distributed memory manycores, with respect to given application constraints. We argue for code mapping strategies based on predicted execution performance, which can be used in an auto-tuning feedback loop or to guide manual tuning directed by the programmer. Automated parallelization, optimisation and mapping to a manycore processor benefits from the use of a concurrent programming model as the starting point. Such a model allows the programmer to express different types and granularities of parallelism as well as computation characteristics of importance in the addressed class of applications. The programming model should also abstract away machine dependent hardware details. The analytical study of WCDMA baseband processing in radio base stations, presented in this thesis, suggests dataflow models as a good match to the characteristics of the application and as execution model abstracting computations on a manycore. Construction of portable tools further requires a manycore machine model and an intermediate representation. The models are needed in order to decouple algorithms, used to transform and map application software, from hardware. We propose a manycore machine model that captures common hardware resources, as well as resource dependent performance metrics for parallel computation and communication. Further, we have developed a multifunctional intermediate representation, which can be used as source for code generation and for dynamic execution analysis. Finally, we demonstrate how we can dynamically analyse execution using abstract interpretation on the intermediate representation. It is shown that the performance predictions can be used to accurately rank different mappings by best throughput or shortest end-to-end computation latency.
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| 4. |
- Nilsson, Björn, et al.
(författare)
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A snoozing frequency binary tree protocol
- 2010
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Ingår i: The Third International EURASIP Workshop on RFID Technology, La Manga del Mar Menor, Cartagena, Spain, 6-7 Sept, 2010.
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Konferensbidrag (refereegranskat)abstract
- In this paper we describe and evaluate anenhanced version of an active RFID wake-up and tag IDextraction radio communication protocol. The enhancedprotocol further reduces the transponders’ power consumption(prolonging their battery lifetime). The protocol uses afrequency binary tree method for extracting the identificationnumber of each transponder. This protocol is enhanced byextending it with a framed slotted medium access controlmethod which decreases the number of activations of eachtransponder during tag ID extractions. Using this medium accessmethod, the average number of transponder activations isdecreased with a factor of 2.5 compared to the original protocol.The resulting increase in ID read-out delay is 0.9%, on average.
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| 5. |
- Nilsson, Björn, 1965-, et al.
(författare)
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An active backscatter wake-up and tag identification extraction protocol for low cost and low power active RFID
- 2010
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Ingår i: Proceedings of 2010 IEEE International Conference on RFID-Technology and Applications, RFID-TA 2010. - Piscataway, NJ : IEEE Press. - 9781424466986 - 9781424467006 ; , s. 86-91
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Konferensbidrag (refereegranskat)abstract
- In this paper we present a Radio Frequency Identification (RFID) protocol used to wake up and extract the ID of every tag (or a subset thereof) within reach of a reader in an active backscatter RFID system. We also study the effect on tag energy cost and read-out delay incurred when using the protocol, which is based on a frequency binary tree. Simulations show that, when using the 2.45 GHz ISM band, more than 1500 tags can be read per second.With a population of 1000 tags, the average read-out delay is 319 ms, and the expected lifetime of the RFID tags is estimated to be more than 2.5 years, even in a scenario when they are read out very often.
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| 7. |
- Nilsson, Björn, et al.
(författare)
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An Energy and Application Scenario Aware Active RFID Protocol
- 2010
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Ingår i: EURASIP Journal on Wireless Communications and Networking. - New York : Hindawi Publishing Corporation. - 1687-1472 .- 1687-1499. ; 2010:Article ID 432938, s. 15-
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Tidskriftsartikel (refereegranskat)abstract
- The communication protocol used is a key issue in order to make the most of the advantages of active RFID technologies. In this paper we introduce a carrier sense medium access data communication protocol that dynamically adjusts its back-off algorithm to best suit the actual application at hand. Based on a simulation study of the effect on tag energy cost, read-out delay, and message throughput incurred by some typical back-off algorithms in a CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) active RFID protocol, we conclude that by dynamic tuning of the initial contention window size and back-off interval coefficient, tag energy consumption and read-out delay can be significantly lowered. We show that it is possible to decrease the energy consumption per tag payload delivery with more than 10 times, resulting in a 50% increase in tag battery lifetime. We also discuss the advantage of being able to predict the number of tags present at the RFID-reader as well as ways of doing it.
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| 8. |
- Nilsson, Björn, et al.
(författare)
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Protocols for active RFID - the energy consumption aspect
- 2007
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Ingår i: 2007 Symposium on Industrial Embedded Systems Proceedings. - Piscataway, N.J. : IEEE Press. - 1424408407 ; , s. 41-48
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Konferensbidrag (refereegranskat)abstract
- The use of Radio Frequency Identification systems (RFID) is growing rapidly. Today, mostly “passive” RFID systems are used because no onboard energy source is needed on the transponders. However, “active” RFID technology, with onboard power sources in the transponders, gives a range of opportunities not possible with passive systems. To obtain energy efficiency in an Active RFID system the protocol to be used should be carefully designed with energy optimization in mind. This paper describes how energy consumption can be calculated, to be used in protocol definition, and how evaluation of protocol in this respect can be made. The performance of such a new protocol, in terms of energy efficiency, aggregated throughput, delay, and number of air collisions is evaluated and compared to an existing, commercially available protocol for Active RFID, as well as to the IEEE standard 802.15.4 (used e.g. in the Zigbee mediumaccess layer).
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| 9. |
- Nilsson, Björn, et al.
(författare)
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Selecting back off algorithm in active RFID CSMA/CA based medium-access protocols
- 2008
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Ingår i: International Symposium on Industrial Embedded Systems, 2008. SIES 2008. - Piscataway, N.J. : IEEE Press. - 9781424419944 ; , s. 265-270, s. 265-270
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Konferensbidrag (refereegranskat)abstract
- Active radio frequency identification (A-RFID) is a technology where the tags (transponders) carry an on board energy source for powering the radio, processor circuits, and sensors. Besides offering longer working distance between RFID-reader and tag than passive RFID, this also enables the tags to do sensor measurements, calculations and storage even when no RFID-reader is in the vicinity of the tags. In this paper we study the effect on tag energy cost and read out delay incurred by some typical back-off algorithms (constant, linear, and exponential) used in a contention based CSMA/CA (carrier sense multiple access/collision avoidance) protocol for A-RFID communication.
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| 10. |
- Nilsson, Björn, et al.
(författare)
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Towards an Energy Efficient Protocol for Active RFID
- 2006
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Ingår i: International Symposium on Industrial Embedded Systems, 2006. IES '06. - Piscataway, N.J. : IEEE Press. - 142440777X ; , s. 1-4
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Konferensbidrag (refereegranskat)abstract
- The use of radio frequency identification systems (RFID) is growing rapidly. Today, mostly "passive" RFID systems are used because no onboard energy source is needed on the transponders. However, "active " RFID with onboard power source gives a new range of opportunities not possible with passive systems. To obtain energy efficiency in an active RFID system a protocol should be designed that is optimized with energy in mind. This paper describes the on-going work of defining and evaluating such a protocol. The protocol's performance in terms of energy efficiency, aggregated throughput, delay, and number of air collisions is evaluated and compared to that of the medium-access layer in 802.15.4 Zigbee, and also to a commercially available protocol from Free2move.
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