Performance evaluation of optimal decoding schemes for tail biting convolutional codes in EDGE headers

The performance of several suboptimal decoding schemes for a tail biting convolutional code used in enhanced data rates for global evolution (EDGE) headers, compared with an optimal decoding scheme, is evaluated. An interference-limited cellular radio environment is considered. The impact of mobile speed is also assessed

Performance of EGPRS incremental redundancy in interference limited environments

Incremental Redundancy (IR), an established Hybrid-ARQ technique, has been proposed as an adaptive link level mechanism in third-generation and evolved second-generation wireless systems such as the Enhanced General Packet Radio Service (EGPRS). In this paper, three alternative EGPRS Incremental Redundancy ARQ algorithms of low (IR-ARQ1), medium (IR-ARQ2) and high (IR-ARQ3) computational complexity are specified. The relative downlink performance of the specified algorithms is evaluated for interference-limited mobile radio environments with pedestrian (5 km/h) and vehicular (50 km/h) mobile speeds, using a high-speed link level simulator. For comparison, a basic Selective-Repeat ARQ algorithm (SR-ARQ) is also implemented. The algorithms are compared in terms of their throughput performance, transmission delay performance, and processing requirements. It is shown that the most significant performance improvement is from SR-ARQ to IR-ARQ1 (up to about 2dB at 5 km/h, and 5 dB at 50 km/h). The performance gains from IR-ARQ1 to IR-ARQ2, and from IR-ARQ2, to IR-ARQ3 are negligible. Overall, the results suggest that implementing a low-complexity Incremental Redundancy ARQ algorithm gives the optimal performance/complexity trade-off

Influence of incremental redundancy on the performance of TCP in enhanced general packet radio service

The incremental redundancy mechanism defined for enhanced general packet radio service (EGPRS) (also known as type-II hybrid ARQ) is considered here. The optimum packet combining strategy is identified and is then used to assess the performance of transmission control protocol/Internet protocol in the transmission of bulk data over an EGPRS system. The influence of other key system operating parameters is also assessed and a set of optimal operating parameters is derived and discussed

Packet combining strategies for EGPRS

Packet combining techniques are used to improve the performance of the hybrid ARQ mechanisms. This paper assesses the impact of several variations of packet combining, in its two basic forms (diversity combining and code combining), on a selective-repeat ARQ mechanism in an EGPRS wireless system. These variations range from the application of no packet combining at all, to the application of both diversity combining and code combining on all possible combinations of available packets. A link-level simulator for the EGPRS downlink in a typical urban mobile radio propagation environment is implemented. Mobile speeds of 5 km/h and 50 km/h are considered. It is shown that packet combining can significantly improve performance and has a greater impact at the higher speed. Furthermore, a packet combining strategy of moderate complexity is shown to be optimal in terms of the trade-off between performance, on the one hand, and the associated decoding-related processing load at the receiver, on the other

Optimisation of TCP performance over EGPRS in incremental redundancy mode

This paper investigates how to optimise TCP performance over the EGPRS (enhanced general packet radio service) downlink, when the EGPRS radio link layer is operating in pure incremental redundancy (IR) mode. Particular attention is paid to the optimal configuration of the IR algorithm itself. The influence of other key system operating parameters is also assessed. A set of optimal operating parameters is derived and discussed

Technical Efficiency and Technological Gaps of Rice Production in Anambra State, Nigeria

The traditional approach to modeling productive efficiency assumes that technology is constant across the sample. However, farms in different regions may face different production opportunities, and the technologies they employ may differ due to environmental factors. Therefore, rather than using a traditional stochastic frontier model in such cases, a stochastic meta-frontier (SMF) analysis is recommended to account for environmental factors between regions. It follows that differences in environmental factors between the upland and lowland regions in Anambra State, Nigeria, may result in farmers producing rice under different production and environmental conditions. Using the SMF model, this study, for the first time, determines technical efficiency (TE) and technological gap ratios (TGRs) of rice production from the upland and lowland regions in the Awka North Local Government Area of Anambra State, Nigeria. Our data are from a cross-section sample of randomly selected rice farmers. Results reveal that lowland regional rice producers are on average, significantly more technically efficient (91.7%) than their upland counterparts (84.2%). Additionally, mean TGRs associated with lowland rice farmers are higher (92.1%) than their corresponding upland producers (84.7%). While the upland rice producers are less technically efficient and further away from their full potential, results indicate that both sets of farmers do not use advanced technologies to match the industry’s potential. We suggest that agricultural policy should focus on providing regionally specific technologies, such as improved rice varieties that fit the working environment of the lagging area, to help rice farmers improve their resource efficiency and minimize technological gaps

What happened to patients with RMP-resistant/MDR-TB in Zambia reported as lost to follow-up from 2011 to 2014?

SETTING: University Teaching Hospital, Lusaka, and Ndola Central Hospital, Ndola, Zambia, which implemented active tracing of multidrug-resistant tuberculosis (MDR-TB) patients reported as lost to follow-up (LTFU). OBJECTIVE: To determine 1) the number of patients treated for MDR-TB between 2011 and 2014; 2) the number, proportion, month when LTFU and characteristics of patients registered as LTFU; and 3) final outcomes observed following active patient tracing. DESIGN: Retrospective cohort study. RESULTS: Of 184 patients treated for confirmed MDR-TB, 76 (41%) were reported as LTFU. From 2011 to 2014, the proportions reported each year as LTFU were respectively 21%, 47%, 51% and 39%. Of patients who were LTFU, 43 (57%) had stopped attending the clinic during the intensive phase. These patients were predominantly male, aged 15-44 years, had pulmonary disease and had failed previous treatment. Of 57 (75%) patients with known human immunodeficiency virus (HIV) status, 42 (74%) were HIV-positive, 57% of whom were on antiretroviral treatment. After active patient tracing, 29 (38%) patients could not be found and the observed outcome remained LTFU. Of the remaining 47 patients, 29 (62%) were alive and had completed or were still on treatment, 14 (30%) were alive but had stopped treatment and 4 (8%) had died. CONCLUSION: Zambia has been underreporting its favourable outcomes for MDR-TB treatment and should continue with active tracing of LTFU patients

Evaluation of the Xpert MTB/RIF Assay at a Tertiary Care Referral Hospital in a Setting Where Tuberculosis and HIV Infection Are Highly Endemic.

Background: There were 1.45 million deaths from tuberculosis (TB) in 2011. A substantial proportion of active pulmonary TB cases in countries where tuberculosis, human immunodeficiency virus (HIV) infection, and AIDS are highly endemic remain undiagnosed because of the reliance on sputum-smear microscopy. This study evaluated the performance of the Xpert MTB/RIF assay at a tertiary care referral center in Zambia, a country where the burden of TB and HIV infection is high.Methods: A total of 881 adult inpatients admitted to University Teaching Hospital in Lusaka who were able to produce sputum were enrolled and analyzed in the study, irrespective of admission diagnosis. Sputum specimens were analyzed by fluorescence smear microscopy, the Xpert MTB/RIF assay, mycobacterial growth indicator tube (MGIT) culture, and MGIT drug-susceptibility testing. The sensitivity and specificity of the Xpert MTB/RIF assay were evaluated using culture as the gold standard.Results: Culture-confirmed TB was found in 201 of 881 patients (22.8%). The specificity of the Xpert MTB/RIF assay was 95.0% (95% confidence interval [CI], 92.4%-96.8), and the sensitivity was 86.1% (95% CI, 80.3-90.4%). In sputum smear-negative, culture-positive cases, the assay was 74.7% sensitive (95% CI, 64.6%-82.8%), identifying 71 additional TB cases that were not detected by smear microscopy. A total of 18 of 111 patients with TB who were tested (16.2%) had multidrug-resistant (MDR) TB. The sensitivity and specificity of the Xpert MTB/RIF assay for detecting culture-confirmed, rifampicin-resistant TB was 81.3% (95% CI, 53.7-95.0%) and 97.5% (95% CI, 90.4-99.6%), respectively.Conclusions: The Xpert MTB/RIF assay performs better than smear microscopy in an inpatient setting in a country where TB and HIV infection are highly endemic. Assessment of its usefulness and cost-effectiveness for increased detection of TB cases missed by sputum smear and for concomitant screening for MDR TB among adult inpatients attending tertiary care referral centers in other countries with a high burden of TB and HIV infection is warranted. © 2012 Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved

Delayed second dose of oral cholera vaccine administered before high-risk period for cholera transmission: Cholera control strategy in Lusaka, 2016.

BackgroundIn April 2016, an emergency vaccination campaign using one dose of Oral Cholera Vaccine (OCV) was organized in response to a cholera outbreak that started in Lusaka in February 2016. In December 2016, a second round of vaccination was conducted, with the objective of increasing the duration of protection, before the high-risk period for cholera transmission. We assessed vaccination coverage for the first and second rounds of the OCV campaign.MethodsVaccination coverage was estimated after each round from a sample selected from targeted-areas for vaccination using a cross-sectional survey in to establish the vaccination status of the individuals recruited. The study population included all individuals older than 12 months residing in the areas targeted for vaccination. We interviewed 505 randomly selected individuals after the first round and 442 after the second round. Vaccination status was ascertained either by vaccination card or verbal reporting. Households were selected using spatial random sampling.ResultsThe vaccination coverage with two doses was 58.1% (25/43; 95%CI: 42.1-72.9) in children 1-5 years old, 59.5% (69/116; 95%CI: 49.9-68.5) in children 5-15 years old and 19.9% (56/281; 95%CI: 15.4-25.1) in adults above 15 years old. The overall dropout rate was 10.9% (95%CI: 8.1-14.1). Overall, 69.9% (n = 309/442; 95%CI: 65.4-74.1) reported to have received at least one OCV dose.ConclusionsThe areas at highest risk of suffering cholera outbreaks were targeted for vaccination obtaining relatively high vaccine coverage after each round. However, the long delay between doses in areas subject to considerable population movement resulted in many individuals receiving only one OCV dose. Additional vaccination campaigns may be required to sustain protection over time in case of persistence of risk. Further evidence is needed to establish a maximum optimal interval time of a delayed second dose and variations in different settings