A Multistage Method for SCMA Codebook Design Based on MDS Codes

Sparse Code Multiple Access (SCMA) has been recently proposed for the future generation of wireless communication standards. SCMA system design involves specifying several parameters. In order to simplify the procedure, most works consider a multistage design approach. Two main stages are usually emphasized in these methods: sparse signatures design (equivalently, resource allocation) and codebook design. In this paper, we present a novel SCMA codebook design method. The proposed method considers SCMA codebooks structured with an underlying vector space obtained from classical block codes. In particular, when using maximum distance separable (MDS) codes, our proposed design provides maximum signal-space diversity with a relatively small alphabet. The use of small alphabets also helps to maintain desired properties in the codebooks, such as low peak-to-average power ratio and low-complexity detection.Comment: Submitted to IEEE Wireless Communication Letter

Random graph model with power-law distributed triangle subgraphs

Clustering is well-known to play a prominent role in the description and understanding of complex networks, and a large spectrum of tools and ideas have been introduced to this end. In particular, it has been recognized that the abundance of small subgraphs is important. Here, we study the arrangement of triangles in a model for scale-free random graphs and determine the asymptotic behavior of the clustering coefficient, the average number of triangles, as well as the number of triangles attached to the vertex of maximum degree. We prove that triangles are power-law distributed among vertices and characterized by both vertex and edge coagulation when the degree exponent satisfies $2<\beta<2.5$; furthermore, a finite density of triangles appears as $\beta=2+1/3$.Comment: 4 pages, 2 figure; v2: major conceptual change

Nutrient use efficiency of two improved cultivars of Taro (Colocasia esculenta) under screen house conditions in Samoa

Taro (Colocasia esculenta (L.) Schott) is a staple crop of many of the South Pacific nations with an ever increasing export demand. In recent years, yields of taro have increased dramatically through breeding and selection. However, selections of improved lines are often entirely based on final yield. There are many physiological pathways by which increased potential yield may be achieved. Factors such as the accumulation of dry matter and nutrient use efficiency, merit investigation. Two improved (blight resistant) taro cultivars were planted and harvested for biomass measurements on a monthly basis for a total of eight months (30-240 days after planting) through destructive sampling. At each harvest, plants were separated into various plant parts and their dry matter accumulation and nutrient content were determined. Comparatively, cultivar Samoa 2 showed significantly higher uptake of N (25%), P (37.5%), K (33%), Mg (36.4%), Mn (22.7%) and Zn (48.3%) than cultivar Samoa 1. Even though maximum levels of total plant uptake of nutrients by the two cultivars did not differ between the cultivars, cultivar Samoa 1 plants absorbed 17% less N, 26% less P and 20% less K than those of cultivar Samoa 2 with the uptake uniformly distributed over the entire life cycle of the crop. Although cultivar Samoa 2 resulted in higher total plant (19.6%) and corm dry matter (10.4%) productions, cultivar Samoa 1 had a higher nutrient use efficiency, (kg of edible dry matter produced per kg of nutrient taken up), for N, P, K, Mg, Mn and Cu over cultivar Samoa 2. However, for Ca, Fe and Zn. Cultivar Samoa 2 had a higher nutrient use efficiency over cultivar Samoa 1. Based on nutrient use efficiency of the cultivars, Samoa 1 is recommended for marginal to rich soils while Samoa 2 for good to rich soils

Escenarios socioeconómicos futuros para la agricultura y seguridad alimentaria y nutricional en Nicaragua al 2050

En este documento se presentan y analizan doce (12) escenarios socioeconómicos sobre el futuro de la agricultura y la seguridad alimentaria nutricional en el corredor seco de Nicaragua al año 2050. A través de estos escenarios se pretende apoyar la toma decisiones en el país para mejorar la resiliencia del sector frente al cambio climático, buscando promover su uso en la formulación de programas, políticas y proyectos. El abordaje metodológico para la creación de los escenarios presentados tuvo como pilar fundamental la identificación y análisis de los factores contextuales que se estima cambiarán e impactarán el sector agropecuario y la seguridad alimentaria en el corredor seco de Nicaragua hasta el año 2050. Esto se logró mediante un proceso sistemático y participativo a través de entrevistas semi estructuradas con informantes claves del país expertos en el nexo agricultura, SAN y el medio ambiente. De los 17 factores de cambio que se identificaron, se priorizaron los más relevantes e inciertos, cuales formaron la base para la construcción de doce escenarios que exploran el futuro de recursos hídricos, gobernanza y políticas públicas, inestabilidad política, conflictividad social y vulne- rabilidad, practicas productivas, inversión y financiamiento y degradación ambiental. La exploración de escenarios futuros permite conocer las incertidumbres que podrían impactar de manera negativa o positiva la efectividad de las inversiones que se pretenden hacer para fomentar la resiliencia de los productores de la zona del corredor seco de Nicaragua, frente la variabilidad y vulnerabilidad climática. El documento señala aspectos que son relevantes tanto como problemáticos para el futuro de la agricultura y la seguridad alimentaria de este territorio, como también posibles soluciones para aprovechar las oportunidades identificadas y prepararse para los retos que plantean los distintos escenarios considerados

Perceptions of Fishermen Households on the Long-Term Impact of Coastal Resources Management in Panguil Bay

Coastal resources management (CRM) has flourished as a management approach for attaining a more sustainable form of economic development in the coastal areas of the Philippines. Its proliferation, coupled with the reasonably long time it has been in implementation, now calls for an evaluation of its long-term impact as a management and development approach. In this study, the long-term impact of CRM is evaluated not from the perspectives of technical people but based on the perception of its intended primary beneficiaries--the fishermen households. It does so not by looking into a specific CRM program or project but by observing the succession of CRM activities conducted in a single coastal area--Panguil Bay, Mindanao--over many years. The objectives were to ascertain if CRM works, identify its major constraints if it does not, and recommend future courses of actions to address the constraints.coastal resources management, long-term impact indicators, ladder diagram, Panguil Bay

Perceptions of Fishermen Households on the Long-Term Impact of Coastal Resources Management in Panguil Bay

Coastal resources management (CRM) has flourished as a management approach for attaining a more sustainable form of economic development in the coastal areas of the Philippines. Its proliferation, coupled with the reasonably long time it has been in implementation, now calls for an evaluation of its long-term impact as a management and development approach. In this study, the long-term impact of CRM is evaluated not from the perspectives of technical people but based on the perception of its intended primary beneficiaries--the fishermen households. It does so not by looking into a specific CRM program or project but by observing the succession of CRM activities conducted in a single coastal area--Panguil Bay, Mindanao--over many years. The objectives were to ascertain if CRM works, identify its major constraints if it does not, and recommend future courses of actions to address the constraints.coastal resources management, long-term impact indicators, ladder diagram, Panguil Bay