Mac Protocols For Wireless Sensor Networks Over Radio-over-fiber Links

In this paper, two Medium Access Control (MAC) protocols exclusively tailored to WSNs over RoF (RWSNs) namely SPP-MAC (Scheduled Priority Polling Medium Access Control) (polling-based) and HMARS (Hybrid Medium Access Control for Hybrid Radio-over-Fiber Wireless Sensor Network Architecture) (hybrid-based) are proposed. They deal with the main problems in RWSNs i.e. the delay imposed by optical fiber and the existence of two collision domains: the wireless and the fiber optical links. The performance of these two protocols evince their effectiveness for the connection of WSNs by RoF links. © 2012 IEEE.254259Estrin, D., Govindan, R., Heidemann, J., Kumar, S., Next century challenges: Scalable coordination in sensor networks (1999) Proceedings of the 5th Annual ACM/IEEE International Conference on Mobile Computing and Networking, MobiCom '99, pp. 263-270. , (New York, NY, USA), ACMPottie, G.J., Kaiser, W.J., Wireless integrated network sensors (2000) Commun. ACM, 43, pp. 51-58. , MayFanimokun, A., Frolik, J., Effects of natural propagation environments on wireless sensor network coverage area (2003) Proceedings of the 35th Southeastern Symposium, pp. 16-20Hossen, M., Jang, B.-J., Kim, K.-D., Park, Y., Extension of wireless sensor network by employing rof-based 4g network (2009) Advanced Communication Technology, 2009. ICACT 2009. 11th International Conference on, 1, pp. 275-278. , febTang, J., Jin, X., Zhang, Y., Zhang, X., Cai, W., A hybrid radio over fiber wireless sensor network architecture (2007) Wireless Communications, Networking and Mobile Computing, 2007. WiCom 2007. International Conference on, pp. 2675-2678. , septFernando, X.N., Anpalagan, A., (2004) On the Design of Optical Fiber Based Wireless Access Systems, pp. 3550-3555Gerstel, O., Li, B., McGuire, A., Rouskas, G.N., Sivalingam, K., Zhang, Z., Special issue on protocols and architectures for next generation optical WDM networks (2000) IEEE Journal Selected Areas in Communications, , OctoberYe, W., Heidemann, J., Estrin, D., An energy-efficient MAC protocol for wireless sensor netwoks (2002) Annual Koint Conference of the Computer and Communicaton Societies (INFOCOM), 3, pp. 1567-1576. , (New York, NY, USA), NovemberVan Dam, T., Langendoen, K., An adaptive energy-efficient mac protocol for wireless sensor networks (2003) Proceedings of the 1st International Conference on Embedded Networked Sensor Systems, SenSys '03, pp. 171-180. , (New York, NY, USA), ACMLu, G., Krishnamachari, B., Raghavendra, C.S., An adaptive energy-efficient and low-latency MAC for data gathering in sensor networks (2004) WMAN, , (Santa Fe, NM, USA), AprilPolastre, J., Hill, J., Culler, D., Versatile low power media access for wireless sensor networks (2004) Proceedings of the 2nd International Conference on Embedded Networked Sensor Systems, SenSys '04, pp. 95-107. , (New York, NY, USA), ACMLin, P., Qiao, C., Wang, X., Medium access control with a dynamic duty cycle for sensor networks (2004) IEEE Wireless Communications and Networking Conference (WCNC), 3, pp. 1534-1536. , (Atlanta, GA, USA), MarchBurttner, M., Yee, E., Anderson, G.V., Han, R., X-MAC: A short preamble MAC protocol for duty-cycled wireless sensor networks (2006) 4th International Conference on Embedded Networked Sensor Systems (SenSys)(2006) 802.15.4-2006 IEEE Standard for Information TechnologyRoedig, U., Barroso, A., Sreenan, C.J., F-MAC: A deterministic media access control protocol without time syncronization (2006) European Conference on Wireless Sensor Networks (EWSN), pp. 276-291. , (Zurich, Switzerland), FebruarySchurgers, C., Tsiatsis, V., Ganeriwal, S., Srivastava, M., Optimizing sensor networks in the energy-latency-density design space (2002) IEEE Trans. Mobile Comput., pp. 70-80. , JanuaryGomes, P., Da Fonseca, N., Branquinho, O., Analysis of performance degradation in Radio-over-Fiber systems based on IEEE 802.16 protocol (2009) LATINCOM '09. IEEE Latin-American Conference on Communications 2009, pp. 1-6. , septDas, A., Mamd, M., Nkansah, A., Gomes, N.J., Effects on IEEE 802.11 MAC throughput in wireless LAN over fiber systems (2007) Journal of Lightwave Technology, 25, pp. 3321-3328. , Novembe

Residual leaf area index as strategy to management of pasture: structure of Tanzania grass

O estudo visa avaliar mudanças na estrutura do pasto de capim Tanzânia sob sistema de lotação intermitente em resposta a diferentes índices de área foliar residual. O experimento foi conduzido no período de outubro/2009 a maio/2011, usando três índices de área foliar residual (0,8 – 1,6 – 2,4 IAFr). O período de descanso foi adotado segundo o critério de 95% de interceptação luminosa. Amostras de forragem foram colhidas em pontos de altura média, pesadas e retirada uma subamostra para a separação dos componentes morfológicos, para estimar as características estruturais e produtivas. No pré-pastejo, não houve efeito do índice de área foliar residual na massa seca de forragem de capim Tanzânia. No pós-pastejo, a massa seca de folhas aumentou com os IAFr testados e a massa seca de colmos foi similar. O uso do índice de área foliar residual como ferramenta para auxiliar no manejo de pastos é efetivo e modifica a estrutura do pasto3The study aims to evaluate changes structural in Tanzania grass pasture under intermittent stocking in response to different levels of residual leaf area. The experiment was carried out from the October/2009 May/2011, testing three levels of residue leaf area (0.8 - 1.6 to 2.4). The rest period was adopted according to the criterion of 95% light interception. Forage samples were harvest at points of average height, after, taken out a subsample for the separation of the morphological components to estimate the structural characteristics and productive. In the pre-grazing, there wasn't effect of leaf area index in residual dry matter forage grass Tanzania. In the post-grazing, the dry mass of leaves increased with the treatments and the dry mass of stems was similar. The use of residual leaf area index as tool to management of pastures is effective and modifies the structure of the pasture. © 2019 Universidade Federal Rural de Pernambuc