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Background Chronic undernutrition in children continues to be a global public health concern. Ethiopia has documented a significant decline in the prevalence of childhood stunting, a measure of chronic undernutrition, over the last 20 y. Objectives The aim of this research was to conduct a systematic assessment of the determinants that have driven child stunting reduction in Ethiopia from 2000 to 2016, focused on the national, community, household, and individual level. Methods This study employed both quantitative and qualitative methods. Specifically, a systematic literature review, retrospective quantitative data analysis using Demographic and Health Surveys from 2000–2016, qualitative data collection and analysis, and analyses of key nutrition-specific and -sensitive policies and programs were undertaken. Results National stunting prevalence improved from 51% in 2000 to 32% in 2016. Regional variations exist, as do pro-rich, pro-urban, and pro-educated inequalities. Child height-for-age z score (HAZ) decomposition explained >100% of predicted change in mean HAZ between 2000 and 2016, with key factors including increases in total consumable crop yield (32% of change), increased number of health workers (28%), reduction in open defecation (13%), parental education (10%), maternal nutrition (5%), economic improvement (4%), and reduced diarrhea incidence (4%). Policies and programs that were key to stunting decline focused on promoting rural agriculture to improve food security; decentralization of the health system, incorporating health extension workers to improve rural access to health services and reduce open defecation; multisectoral poverty reduction strategies; and a commitment to improving girls’ education. Interviews with national and regional stakeholders and mothers in communities presented improvements in health service access, women and girls’ education, improved agricultural production, and improved sanitation and child care practices as drivers of stunting reduction. Conclusions Ethiopia's stunting decline was driven by both nutrition-specific and -sensitive sectors, with particular focus on the agriculture sector, health care access, sanitation, and education.

Objectives Staging sexual maturation is an integral component of adolescent research. The Pubertal Development Scale (PDS) is commonly used as a puberty self-assessment tool because it avoids the use of images. Among the youth living in rural Pakistan, we determined the accuracy of self-reported pubertal assessments using a modified PDS compared to the ‘gold standard’ of physically assessed Tanner stages by a physician. Methods The strength of agreement between self-assessed puberty using a modified PDS and the ‘gold’ standard of physician-assessed Tanner stages was reported using weighted kappa (κ w) for girls (n = 723) of 9.0–14.9 years of age or boys (n = 662) of 10.0–15.9 years of age living in the rural District of Matiari. Results Agreement between the gold standard and self-assessment for puberty was substantial, with a κ w of 0.73 (95% confidence interval [CI]: 0.67; 0.79) for girls and a κ w of 0.61 (95% CI: 0.55; 0.66) for boys. Substantial agreement was observed for both boys and girls classified as thinness but only for girls with a normal body mass index. Those who were classified as severely thin had moderate agreement. The prevalence of overestimation was 18.5% (95% CI: 15.9–21.5) for girls and 2.7% (95% CI: 1.7–4.3) for boys, while the prevalence of underestimation estimation was 8.0% (95% CI: 6.2–10.2) for girls and 29.0% (95% CI: 25.8–32.6) for boys. Conclusions Most girls and boys assessed their pubertal development with substantial agreement with physician assessment. Girls were better able to assess their puberty, but they were more likely to overestimate. Agreement for boys was also substantial, but they were more likely to underestimate their pubertal development. In this rural Pakistan population, the PDS seems to be a promising tool for self-assessed puberty.

Context Clinicians, researchers, and global health advocates often include pubertal development in outcomes. However, assessments of pubertal stage can be challenging because of the sensitive nature and feasibility of clinical examinations, especially in larger settings. Objective To determine the accuracy of self-assessed Tanner staging when compared with physically assessed Tanner stages by a clinician. Data Sources MEDLINE, PubMed, Embase, Web of Science, Scopus, the Cochrane Library, CINAHL. Study Selection Studies were included if they reported 5 × 5 tables of self-assessment compared to clinician–assessment for the 5-stage Tanner scale. Data Extraction We extracted data to generate complete 5 × 5 tables for each study, including any subgroup eligible for the analysis, such as overweight/obese youth. Data Synthesis After screening, 22 studies representing 21,801 participants met our inclusion criteria for the meta-analysis. Overall agreement was moderate or substantial between the 2 assessments, with breast stage 1, female pubic hair 1, male pubic hair 1, and male pubic hair 5 having the highest agreement. When stages were collapsed into pre- (Tanner stage 1), in (stages 2,3), and completing (stages 4,5) puberty, levels of agreement improved, especially for pre- and completing pubertal development. Most included studies comprised Caucasian youth. More studies are needed which include a broader range of geographic and socioeconomic settings, as well as a greater diversity of racial/ethnic groups. Conclusions Self-assessment of puberty is most accurate when identifying Tanner stage 1, Tanner stage 5 and when development is categorized into prepuberty, in, and completing puberty phases. Use of self-assessment data should be structured accordingly. Protocol Registration PROSPERO # CRD42018100205

BACKGROUND Senegal has been an exemplar country in the West African region, reducing child stunting prevalence by 17.9% from 1992 to 2017. OBJECTIVES In this study, we aimed to conduct a systematic in-depth assessment of factors at the national, community, household, and individual levels to determine the key enablers of Senegal's success in reducing stunting in children

Background Chronic malnutrition among infants and children continues to represent a global public health concern. The Kyrgyz Republic has achieved rapid declines in stunting over the last 20 y, despite modest increases in gross domestic product per capita. Objective This study aimed to conduct a systematic, in-depth assessment of national, community, household, and individual drivers of nutrition change and stunting reduction, as well as nutrition-specific and -sensitive policies and programs, in the Kyrgyz Republic. Methods This mixed methods study employed 4 inquiry methods, including: 1) a systematic scoping literature review; 2) retrospective quantitative data analyses, including linear regression multivariable hierarchical modeling, difference-in-difference analysis, and Oaxaca-Blinder decomposition; 3) qualitative data collection and analysis; and 4) analysis of key nutrition-specific and -sensitive policies and programs. Results Stunting prevalence has decreased in the Kyrgyz Republic, however, subnational variations and inequities persist. Child growth Victora curves show improvements in height-for-age z-scores (HAZ) for children in the Kyrgyz Republic between 1997 and 2014, indicating increased intrauterine growth and population health improvements. The decomposition analysis explained 88.9% (0.637 SD increase) of the predicted change in HAZ for children under 3 y (1997-2012). Key factors included poverty (61%), maternal nutrition (14%), paternal education (6%), fertility (6%), maternal age (3%), and wealth accumulation (2%). Qualitative analysis revealed poverty reduction, increased migration and remittances, food security, and maternal nutrition as key drivers of stunting decline. Systematic scoping literature review findings supported quantitative and qualitative results, and indicated that land reforms and improved food security represented important factors. Key nutrition-specific and -sensitive policies and programs implemented involved breastfeeding promotion, social protection schemes, and land and health sector reforms. Conclusions Improvements in stunting were achieved amidst political and economic changes. Multilevel enablers, including poverty reduction, improved food security, and introduction of land and health reforms have contributed to improvements in health, nutrition, and stunting among children in the Kyrgyz Republic.

The authors investigate quantisation and feedback of channel state information in a multiuser (MU) multiple-input multiple-output (MIMO) system. Each user may receive multiple data streams. The authors design minimises the sum mean squared error (SMSE) while accounting for the imperfections in channel state information (CSI) at the transmitter. This study makes three contributions: first, the authors provide an end-to-end SMSE transceiver design that incorporates receiver combining, feedback policy and transmit precoder design with channel uncertainty. This enables the proposed transceiver to outperform the previously derived limited feedback MU linear transceivers. Second, the authors remove dimensionality constraints on the MIMO system, for the scenario with multiple data streams per user, using a combination of maximum expected signal combining and minimum MSE receiver. This makes each user's feedback independent of the others and the resulting feedback overhead scales linearly with the number of data streams instead of the number of receiving antennas. Finally, the authors analyse the SMSE of the proposed algorithm at high signal-to-noise ratio (SNR) and large number of transmit antennas. As an aside, the authors show analytically why the bit error rate, in the high SNR regime, increases if quantisation error is ignored.

The penetration of wireless broadband services in remote areas has primarily been limited due to the lack of economic incentives that service providers encounter in sparsely populated areas. Besides, wireless backhaul links like satellite and microwave are either expensive or require strict line of sight communication making them unattractive. TV white space channels with their desirable radio propagation characteristics can provide an excellent alternative for engineering backhaul networks in areas that lack abundant infrastructure. Specifically, TV white space channels can provide “free wireless backhaul pipes” to transport aggregated traffic from broadband sources to fiber access points. In this paper, we investigate the feasibility of multi-hop wireless backhaul in the available white space channels by using noncontiguous Orthogonal Frequency Division Multiple Access (NC-OFDMA) transmissions between fixed backhaul towers. Specifically, we consider joint power control, scheduling and routing strategies to maximize the minimum rate across broadband towers in the network. Depending on the population density and traffic demands of the location under consideration, we discuss the suitable choice of cell size for the backhaul network. Using the example of available TV white space channels in Wichita, Kansas (a small city located in central USA), we provide illustrative numerical examples for designing such wireless backhaul network.

Small cells have been proposed as a vehicle for wireless networks to keep up with surging demand. Small cells come with a significant challenge of providing backhaul to transport data to(from) a gateway node in the core network. Fiber based backhaul offers the high rates needed to meet this requirement, but is costly and time-consuming to deploy, when not readily available. Wireless backhaul is an attractive option for small cells as it provides a less expensive and easy-to-deploy alternative to fiber. However, there are multitude of bands and features (e.g. LOS/NLOS, spatial multiplexing etc.) associated with wireless backhaul that need to be used intelligently for small cells. Candidate bands include: sub-6 GHz band that is useful in non-line-of-sight (NLOS) scenarios, microwave band (6-42 GHz) that is useful in point-to-point line-of-sight (LOS) scenarios, and millimeter wave bands (e.g. 60, 70 and 80 GHz) that are recently being commercially used in LOS scenarios. In many deployment topologies, it is advantageous to use aggregator nodes, located at the roof tops of tall buildings near small cells. These nodes can provide high data rate to multiple small cells in NLOS paths, sustain the same data rate to gateway nodes using LOS paths and take advantage of all available bands. This work performs the joint cost optimal aggregator node placement, power allocation, channel scheduling and routing to optimize the wireless backhaul network. We formulate mixed integer nonlinear programs (MINLP) to capture the different interference and multiplexing patterns at sub-6 GHz and microwave band. We solve the MINLP through linear relaxation and branch-and-bound algorithm and apply our algorithm in an example wireless backhaul network of downtown Manhattan., Comment: Invited paper at Conference on Information Science & Systems (CISS) 2014

Wireless systems are getting deployed in many new environments with different antenna heights, frequency bands and multipath conditions. This has led to an increasing demand for more channel measurements to understand wireless propagation in specific environments and assist deployment engineering. We design and implement a rapid wireless channel sounding system, using the Universal Software Radio Peripheral (USRP) and GNU Radio software, to address these demands. Our design measures channel propagation characteristics simultaneously from multiple transmitter locations. The system consists of multiple battery-powered transmitters and receivers. Therefore, we can set-up the channel sounder rapidly at a field location and measure expeditiously by analyzing different transmitters signals during a single walk or drive through the environment. Our design can be used for both indoor and outdoor channel measurements in the frequency range of 1 MHz to 6 GHz. We expect that the proposed approach, with a few further refinements, can transform the task of propagation measurement as a routine part of day-to-day wireless network engineering., Submitted to ICC 2013 (2012 AT\&T Intellectual Property. All rights reserved.)

In this paper, we design and implement time exchange (TE) based cooperative forwarding where nodes use transmission time slots as incentives for relaying. We focus on distributed joint time slot exchange and relay selection in the sum goodput maximization of the overall network. We formulate the design objective as a mixed integer nonlinear programming (MINLP) problem and provide a polynomial time distributed solution of the MINLP. We implement the designed algorithm in the software defined radio enabled USRP nodes of the ORBIT indoor wireless testbed. The ORBIT grid is used as a global control plane for exchange of control information between the USRP nodes. Experimental results suggest that TE can significantly increase the sum goodput of the network. We also demonstrate the performance of a goodput optimization algorithm that is proportionally fair., Accepted in 2012 Military Communications Conference

In the context of a time-varying multiuser multiple-input-multiple-output (MIMO) system, we design recursive least squares based adaptive predictors and differential quantizers to minimize the sum mean squared error of the overall system. Using the fact that the scalar entries of the left singular matrix of a Gaussian MIMO channel becomes almost Gaussian distributed even for a small number of transmit antennas, we perform adaptive differential quantization of the relevant singular matrix entries. Compared to the algorithms in the existing differential feedback literature, our proposed quantizer provides three advantages: first, the controller parameters are flexible enough to adapt themselves to different vehicle speeds; second, the model is backward adaptive i.e., the base station and receiver can agree upon the predictor and variance estimator coefficients without explicit exchange of the parameters; third, it can accurately model the system even when the correlation between two successive channel samples becomes as low as 0.05. Our simulation results show that our proposed method can reduce the required feedback by several kilobits per second for vehicle speeds up to 20 km/h (channel tracker) and 10 km/h (singular vector tracker). The proposed system also outperforms a fixed quantizer, with same feedback overhead, in terms of bit error rate up to 30 km/h., Comment: IEEE 22nd International Conference on Personal, Indoor and Mobile Radio Communications (2011)

We investigate an incentive mechanism called Bandwidth Exchange (BE) for cooperative forwarding where transmission bandwidth is used as a flexible resource. We focus on a network where two nodes, communicating with the base station (BS) / access point (AP), initially get optimal amount of bandwidth based on direct path transmission and then use their individual bandwidths as flexible incentives for two hop relaying. In our proposed scenario, the forwarder node sends its own data along with the data of the sender in exchange for additional transmission bandwidth, provided by the sender. We compare the performance of the proposed mechanism with optimal bandwidth and power allocation based direct transmission. We use sum rate, max-min rate and min-max power as the evaluation criteria and prove the convex/concave nature of the optimization problem formulations. Our numerical analysis shows that the BE based cooperative forwarding extends the coverage in wireless networks when the far node falls in outage under direct transmission. Further, BE significantly improves the max-min rate and min-max power performance of the network.

We design an end-to-end linear transceiver in the downlink of a multi-user multiple-input multiple-output (MIMO) system with multiple data streams per user and quantized channel state information at the transmitter. We minimize the sum mean squared error (SMSE) under a sum power constraint with quantization based on the mean squared inner product. We make three contributions: (i) we remove dimensionality constraints on the MIMO configuration and the resulting feedback overhead scales linearly with the number of data streams; (ii) we use the combination of eigenmode combining and minimum mean square error receiver that makes user's feedback mutually independent; (iii) we analyze SMSE at high signal-to-noise ratio and large number of transmit antennas and derive an approximate SMSE floor.