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We develop analytical models for estimating the energy spent by stations (STAs) in infrastructure WLANs when performing TCP controlled file downloads. We focus on the energy spent in radio communication when the STAs are in the Continuously Active Mode (CAM), or in the static Power Save Mode (PSM). Our approach is to develop accurate models for obtaining the fraction of times the STA radios spend in idling, receiving and transmitting. We discuss two traffic models for each mode of operation: (i) each STA performs one large file download, and (ii) the STAs perform short file transfers. We evaluate the rate of STA energy expenditure with long file downloads, and show that static PSM is worse than just using CAM. For short file downloads we compute the number of file downloads that can be completed with given battery capacity, and show that PSM performs better than CAM for this case. We provide a validation of our analytical models using the NS-2 simulator [1].

Background: Breast milk contains balanced nutrients for the complete growth of body and brain of neonates and infants. Breast feeding is rich in anti-infective factors and improves immune system, thus reducing the child mortality rate. Objective of present work was to study the effect of antenatal breast milk expression at term in improving lactational performance as compared to control group.Methods: The prospective, comparative study was conducted for 2 years to observe effects of antenatal expression of breast milk on postnatal lactational performance in a tertiary care centre   in Central India.  200 Subjects after 37 weeks of pregnancy divided in two groups of 100 each 1) study group 2) control group by systematic random sampling technique. Prior examination was done to exclude any inverted or cracked nipples and appropriate treatment instituted. The women with diseased breast and conditions, high risk pregnancy, congenitally anomalous fetus and drugs affecting lactation were excluded from study. Study group women were counselled to express milk 2-3 times every day preferably during bathing. All women were followed up in hospital and postnatal lactation performance was observed in both groups.Results: The study group did not find it difficult to initiate breast feeding after vaginal or caesarean delivery  and in 78% of patients time interval from initiation of lactation to establishment of lactation was less than half hour as compared to control group (38%) P value <0.001. Statistical analysis showed significant difference in the results of those groups.Conclusions: Daily antenatal breast milk expression after 37 weeks of pregnancy significantly reduced the time for establishing full breast feeding and reduced breast feeding failures.

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We focus on the energy spent in radio communication by the stations (STAs) in an IEEE 802.11 infrastructure WLAN. All the STAs are engaged in web browsing, which is characterized by a short file downloads over TCP, with short duration of inactivity or think time in between two file downloads. Under this traffic, Static PSM (SPSM) performs better than CAM, since the STAs in SPSM can switch to low power state (sleep) during think times while in CAM they have to be in the active state all the time. In spite of this gain, performance of SPSM degrades due to congestion, as the number of STAs associated with the access point (AP) increases. To address this problem, we propose an algorithm, which we call opportunistic PSM (OPSM). We show through simulations that OPSM performs better than SPSM under the aforementioned TCP traffic. The performance gain achieved by OPSM over SPSM increases as the mean file size requested by the STAs or the number of STAs associated with the AP increases. We implemented OPSM in NS-2.33, and to compare the performance of OPSM and SPSM, we evaluate the number of file downloads that can be completed with a given battery capacity and the average time taken to download a file.