Network load and packet loss optimization during handoff using multi-scan approach

Handoff is a critical function that enables mobile nodes to stay connected to the wireless network by switching the data connection from one WLAN to another. During handoff the communication may be degraded or interrupted due to the high packets loss. To prevent packet loss during handoff, a handoff management scheme that employs a transport protocol has been proposed. It supports multiple connections for Voice Over IP communication and makes handoff decision based on the number of frame retransmission on the MAC layer. Moreover, the handoff scheme uses the multi-scan technique that enables mobile nodes to use two WLAN interfaces for channel scanning and multi-path transmission rather than single WLAN interface. This technique introduces extra network overhead during multi-path transmission. This work optimizes the network overhead and packet loss and keeps VoIP communication at an acceptable level

What Gets Measured Gets Treated? A composite Measure of Child Malnutrition and its Determinants

Micronutrient deficiencies in children are a major health problem at a global level. There are various avenues for solving this multidimensional problem, but all require an accurate assessment of the level of the deficiency. In this study, we assessed the prevalence of four essential micronutrients deficiencies using defined cutoff values and determine an aggregate burden of malnutrition named as the Composite Index of Micronutrient Deficiencies (CIMND). We used the National Nutrient Survey 2011 from Pakistan (n = 7,173) to develop this new index. We also built a multinomial logistic regression model to express the probability of an infant falling into a particular category of CIMND as a function of various covariates. Concomitant deficiencies of three micronutrients have the highest percentage (38.6%) among all other levels of malnutrition. Children of rural households are less malnourished.Food security did not prove to be a strong predictor of child malnutrition while demographic and economic dependency showed negative associations with undernourishment.   Keywords: micronutrient deficiency; operationalization; stunting; wasting; underweight

SRA-MSDU: Enhanced A-MSDU frame aggregation with selective retransmission in 802.11n wireless networks

The main goal of the IEEE 802.11n standard is to achieve more than 100 Mbps of throughput at the MAC service access point. This high throughput has been achieved via many enhancements in both the physical and MAC layers. One of the MAC enhancements is the frame aggregation in which multiple frames are concatenated into a single large frame before being transmitted. The 802.11n MAC layer defines two types of aggregation, aggregate MAC service data unit (A-MSDU) and aggregate MAC protocol data unit (A-MPDU). The A-MPDU outperforms A-MSDU due to its large aggregation size and the subframes retransmission in erroneous channels. However, in error free channels and under the same aggregation size the A-MSDU performs better than the A-MPDU due to its smaller headers. Thus, adding a selective retransmission capability to the A-MSDU would improve the system performance. In this paper, we have proposed an MSDU frame aggregation scheme that enables selective retransmission at the MSDU level without altering the original MAC header. In this proposed scheme an implicit sequence control mechanism has been introduced in order to keep the frames in sequence and preserve their correct order at the receiver side. The results show that the proposed scheme improves the system performance in terms of throughput and delay even under highly erroneous channels

An enhanced A-MSDU frame aggretation scheme for 802.11n wireless networks

The main goal of the IEEE 802.11n standard is to achieve a minimum throughput of 100 Mbps at the MAC service access point. This high throughput has been achieved via many enhancements in both the physical and MAC layers. A key enhancement at the MAC layer is frame aggregation in which the timing and headers overheads of the legacy MAC are reduced by aggregating multiple frames into a single large frame before being transmitted. Two aggregation schemes have been defined by the 802.11n standard, aggregate MAC service data unit (A-MSDU) and aggregate MAC protocol data unit (A-MPDU). As a consequence of the aggregation, newaggregation headers are introduced and become parts of the transmitted frame. Even though these headers are small compared to the legacy headers they still have a negative impact on the network performance, especially when aggregating frames of small payload. Moreover, the A-MSDU is highly influenced by the channel condition due mainly to lack of subframes sequence control and retransmission. In this paper, we have proposed an aggregation scheme (mA-MSDU) that reduces the aggregation headers and implements a retransmission control over the individual subframes at the MSDU level. The analysis and simulations results show the significance of the proposed scheme, specifically for applications that have a small frame size such as VoIP

Frame aggregation in wireless networks: techniques and issues

The timing and headers overheads of IEEE 802.11 PHY and MAC layers consume a large part of the channel time leading to performance degradation especially at higher data rates. Several enhancements at both the PHY and MAC layers have been proposed in order to reduce these overheads and increase the channel utilization. A key enhancement is frame aggregation in which the timing and headers overheads are reduced by aggregating multiple frames into a single large frame and then transmit it in a single channel access. This paper addresses the frame aggregation techniques that have been proposed for the next generation wireless networks and the aggregation techniques that are adopted by IEEE 802.11n standard. It also high-lights the aggregation issues that need to be investigated in order to further enhance the frame aggregation performance

Physico-Chemical and Microbial Analysis of Drinking Water of Four Springs of Danyore Gilgit Baltistan Pakistan

Drinking water of good quality is essential for human physiology whose continual existence depends on the availability of water and any sort of contamination in water which is above the standard limits set by International water regulating agencies can lead to water related diseases. So, the present investigation was conducted to determine the physico-chemical and bacteriological contents of four springs i.e.Heshi spring 1, Heshi spring 2, Kitaab Roong, and Kooti spring and its distribution system such as water reservoir inlet, outlet, mid and end point of distribution systems, junction where it merge with glacier water. The temperature was in a range of 13oC - 22oC. The turbidity of water samples fluctuate from 0.02NTU-1.99NTU. The pH value was in a range of 6.2-7.1. Electrical conductivity range of minimum 122µS/cm to a maximum of 600µS/cm. The TDS of all water samples ranging from minimum of 164-513mg/l. The amount of reactive ortho phosphate was in a range of 26mg/l to 59mg/L. The amount of total phosphorous was in a range of minimum 23m/L to maximum of 120mg/L. The total bacterial count was in a range of 11CFU/100ml to 83 CFU/100ml.The findings showed there should be comprehensive standardization of drinking water of Danyore village according to guidelines of WHO water quality standards and make it safe for human consumption

Two-level frame aggregation scheme under unreliable channel conditions for IEEE 802.11n WLANs: a survey

Frame Aggregation schemes defined by IEEE 802.11n is the combination of the Aggregate MAC Service Data Unit (A-MSDU) and MAC Protocol Data Unit (A- MPDU). The units are aimed at maximizing Wireless Local Area Networks (WLANs) efficiency at Media Access Control (MAC) level, via the sharing of headers and timing overheads. Moreover, the combination of A-MSDU and A-MPDU is known as Two-level frame aggregation. In spite of their abilities in improving the throughput of MAC Layer, the scheme is still limited by other overheads as a result of aggregation which affects the system performance. Block Acknowledgement (Block ACK) and Frame aggregation were introduced in order to minimize MAC Layer overheads. Still, there are some parameters that affect the aggregation performance, such as aggregate length, sub frame size and channel condition overheads. A-MPDU in other hand minimizes the effect of error condition through sub frame transmission. Therefore, A- MPDU aggregation performances, its limitations, and its promising performances motivated this survey to focus on enhancing Aggregation Mac Protocol Data Unit (eA-MPDU) performance by minimizing the headers overheads of the Two-Level Frame Aggregation Scheme, for the reduction of the channel noise, which by its role will increase the Signal Noise Ratio (SNR) and improve the throughput

Antimicrobial Activities of Novel Bis-Piperidinium Compounds

SHORT COMMUNICATION e quaternary nitrogen group is an essential component for many biologically active compounds synthesized so far. Quaternary ammonium compounds (QACs) play an important role in living processes such as transmethylation reaction of lipid metabolism (cholin), nerve impulse transmission (acetylcholine) or metabolism of carbohydrates (from vitamins to carboxylases) Antibacterial activity of long-chain quaternary ammonium compounds was reported for the first time by Given this very brief literature review, little data describing the antimicrobial properties of piperidinium compounds is available. To study antibacterial and antifungal properties of bis-piperidinium compounds, we synthesized two new series of compounds (2-13 and 15-26) and investigated their properties. Twenty four bis-piperidinium compounds (2-13 and 15-26) were synthesized from readily available starting materials and tested for their antimicrobial properties. e synthesis of bis-piperidinium compounds are shown as Antimicrobial Activities of Novel Bis-Piperidinium Compounds K e y w o r d s: bis-piperidinium, quaternary ammonium, piperidinium, antimicrobial activity * Correspondending author: M

Costs of coexistence : understanding the drivers of tolerance towards Asian elephants Elephas maximus in rural Bangladesh

CITATION: Saif, O. et al. 2020. Costs of coexistence : understanding the drivers of tolerance towards Asian elephants Elephas maximus in rural Bangladesh. Oryx, 54(5):603-611, doi:10.1017/S0030605318001072.The original publication is available at https://www.oryxthejournal.orgHabitat degradation and fragmentation have heightened the importance of understanding human tolerance towards wildlife, as the fate of wildlife in multi-use landscapes depends on people's capacity for coexistence. We applied the wildlife tolerance model to examine drivers of tolerance towards Asian elephants Elephas maximus in rural Bangladesh, interviewing local people in 17 villages. We used structural equation modelling to identify causal pathways in which elephant-related exposure, positive and negative interactions, costs and benefits (tangible and intangible) contributed to tolerance. Contrary to expectations, monetary costs were non-significant in shaping tolerance despite major impacts on livelihoods. Instead, intangible costs and intangible benefits were significant factors determining tolerance. Furthermore, reducing people's exposure to elephants would not necessarily affect tolerance, nor would increasing positive interactions. We discuss how the socio-economic and bio-cultural dynamics of local communities can explain these results, and demonstrate how our model can be used to incorporate such complexities into conservation decision-making. For instance, compensation schemes aim to recompense monetary losses and direct damages, to improve tolerance, whereas our results suggest a more effective approach would be to enhance resilience to non-monetary costs and improve perceived benefits. We conclude that future studies should pay increased attention to intangible costs and consider the less direct drivers of tolerance. Through repeated testing of universal models such as that presented here, broad trends may emerge that will facilitate the application of policies across contexts and landscapes.Publisher's versio

Impact of aggregation headers on aggregating small MSDUs in 802.11n WLANs

The main goal of the IEEE 802.11n standard is to achieve more than 100Mbps of throughput at the MAC service access point. This high throughput has been achieved via many enhancements in both the physical and MAC layers. A key enhancement is frame aggregation which reduces the overheads and increases the channel utilization efficiency. The MAC layer defines A-MSDU and A-MPDU frame aggregations in which MAC overheads are squeezed by aggregating multiple frames into a single large frame before being transmitted. As a consequence of the aggregation, new aggregation headers are introduced and become parts of the transmitted frame. The existence of such headers will have a negative impact on the performance, especially when aggregating frames of small payloads. In this paper, we have analysed the aggregation headers of the 802.11n aggregation schemes and introduced an MSDU frame aggregation that reduces the header's overhead and supports the applications that have a small frame size such as VoIP