Modeling energy consumption of dual-hop relay based MAC protocols in ad hoc networks

Given that the next and current generation networks will coexist for a considerable period of time, it is important to improve the performance of existing networks. One such improvement recently proposed is to enhance the throughput of ad hoc networks by using dual-hop relay-based transmission schemes. Since in ad hoc networks throughput is normally related to their energy consumption, it is important to examine the impact of using relay-based transmissions on energy consumption. In this paper, we present an analytical energy consumption model for dual-hop relay-based medium access control (MAC) protocols. Based on the recently reported relay-enabled Distributed Coordination Function (rDCF), we have shown the efficacy of the proposed analytical model. This is a generalized model and can be used to predict energy consumption in saturated relay-based ad hoc networks. This model can predict energy consumption in ideal environment and with transmission errors. It is shown that using a relay results in not only better throughput but also better energy efficiency. Copyright (C) 2009 Rizwan Ahmad et al.

Infant Attachment Security and the Timing of Puberty: Testing an Evolutionary Hypothesis

Life-history theories of the early programming of human reproductive strategy stipulate that early rearing experience, including that reflected in infant-parent attachment security, regulates psychological, behavioral, and reproductive development. We tested the hypothesis that infant attachment insecurity, compared with infant attachment security, at the age of 15 months predicts earlier pubertal maturation. Focusing on 373 White females enrolled in the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development, we gathered data from annual physical exams from the ages of 9½ years to 15½ years and from self-reported age of menarche. Results revealed that individuals who had been insecure infants initiated and completed pubertal development earlier and had an earlier age of menarche compared with individuals who had been secure infants, even after accounting for age of menarche in the infants’ mothers. These results support a conditional-adaptational view of individual differences in attachment security and raise questions about the biological mechanisms responsible for the attachment effects we discerned.