Robust scheduling algorithm for Guaranteed Bit Rate services

This paper proposes a novel packet scheduling algorithm to overcome detrimental effects of channel impairments on the quality of service of delay-sensitive Guaranteed Bit Rate (GBR) services. The proposed algorithm prioritises the packets that require retransmission of Hybrid Automatic Repeat Request (HARQ) users compared to the packets of new users. The packets of new users are scheduled according to the Channel Quality Information (CQI), average throughput and packet delay information. Computer simulations have demonstrated that the proposed algorithm has 22.7% system capacity improvement over a well-known algorithm. It also tolerates for up to 200% delay of CQI and reduces the uplink signalling overhead by 150% compared to the well-known algorithm without compromising the quality of service requirements of the GBR services. Copyright © 2013 Inderscience Enterprises Ltd

Delay-Prioritized Scheduling (DPS) for real time traffic in 3GPP LTE system

Given that the co-existence of multimedia applications will be a norm in the future wireless systems, their quality of service (QoS) requirements need to be guaranteed. This has imposed new challenges in the design of packet scheduling algorithms in these systems. To address those challenges, a new packet scheduling algorithm for real time (RT) traffic in downlink third generation partnership project long term evolution (3GPP LTE) system is proposed in this paper. The proposed algorithm utilizes each user's packet delay information and its instantaneous downlink channel conditions when making scheduling decisions. Simulation results show that the proposed algorithm outperforms opportunistic scheduling and maximum-largest weighted delay first algorithms by maximizing system throughput and satisfying the QoS requirements of the RT traffic. ©2010 IEEE

Opportunistic contention-based feedback protocol for downlink OFDMA systems with mixed traffic

An opportunistic feedback protocol is proposed for orthogonal frequency division multiple access (OFDMA) systems with mixed realtime (RT) and non-realtime (NRT) traffic. This protocol allocates a dedicated feedback channel for each RT user, while it allows all NRT users to compete to send feedback via a contention-based random access feedback channel. The proposed feedback protocol requires a fixed amount of resource to carry feedback from all RT users and some selected NRT users. The probability that NRT users attempt to send feedback is based on two parameters: a channel quality threshold, and the number of subcarriers (or clusters) whose channel quality is above the threshold. Simulation results demonstrate that allocating a dedicated feedback channel for RT user improves the achievable throughput significantly compared with allocating a dedicated traffic channel. For NRT users, the achievable sum rate of the proposed protocol when the number of users is moderate (20-50 users) approaches the ideal case when the channel quality of all users is known at the base station. The sum rate also is close to the ideal case when the number contention minislots per subcarrier is as low as 2 minislot per subcarrier. © 2009 Springer-Verlag Berlin Heidelberg

Impact of primary kidney disease on the effects of empagliflozin in patients with chronic kidney disease: secondary analyses of the EMPA-KIDNEY trial

Background: The EMPA KIDNEY trial showed that empagliflozin reduced the risk of the primary composite outcome of kidney disease progression or cardiovascular death in patients with chronic kidney disease mainly through slowing progression. We aimed to assess how effects of empagliflozin might differ by primary kidney disease across its broad population. Methods: EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA). Patients were eligible if their estimated glomerular filtration rate (eGFR) was 20 to less than 45 mL/min per 1·73 m2, or 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher at screening. They were randomly assigned (1:1) to 10 mg oral empagliflozin once daily or matching placebo. Effects on kidney disease progression (defined as a sustained ≥40% eGFR decline from randomisation, end-stage kidney disease, a sustained eGFR below 10 mL/min per 1·73 m2, or death from kidney failure) were assessed using prespecified Cox models, and eGFR slope analyses used shared parameter models. Subgroup comparisons were performed by including relevant interaction terms in models. EMPA-KIDNEY is registered with ClinicalTrials.gov, NCT03594110. Findings: Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and followed up for a median of 2·0 years (IQR 1·5–2·4). Prespecified subgroupings by primary kidney disease included 2057 (31·1%) participants with diabetic kidney disease, 1669 (25·3%) with glomerular disease, 1445 (21·9%) with hypertensive or renovascular disease, and 1438 (21·8%) with other or unknown causes. Kidney disease progression occurred in 384 (11·6%) of 3304 patients in the empagliflozin group and 504 (15·2%) of 3305 patients in the placebo group (hazard ratio 0·71 [95% CI 0·62–0·81]), with no evidence that the relative effect size varied significantly by primary kidney disease (pheterogeneity=0·62). The between-group difference in chronic eGFR slopes (ie, from 2 months to final follow-up) was 1·37 mL/min per 1·73 m2 per year (95% CI 1·16–1·59), representing a 50% (42–58) reduction in the rate of chronic eGFR decline. This relative effect of empagliflozin on chronic eGFR slope was similar in analyses by different primary kidney diseases, including in explorations by type of glomerular disease and diabetes (p values for heterogeneity all >0·1). Interpretation: In a broad range of patients with chronic kidney disease at risk of progression, including a wide range of non-diabetic causes of chronic kidney disease, empagliflozin reduced risk of kidney disease progression. Relative effect sizes were broadly similar irrespective of the cause of primary kidney disease, suggesting that SGLT2 inhibitors should be part of a standard of care to minimise risk of kidney failure in chronic kidney disease. Funding: Boehringer Ingelheim, Eli Lilly, and UK Medical Research Council

Modeling and simulation of packet scheduling in the downlink long term evolution system

Long term evolution (LTE) is the next generation wireless system that uses orthogonal frequency division multiple access (OFDMA) technology in the downlink. Packet scheduling becomes paramount as the wireless systems are moving towards all IP transmissions. Since LTE system is relatively new, very little work has been published to date that can precisely model and simulate the downlink LTE system environment. This paper provides detailed descriptions on modeling and simulation of packet scheduling in the downlink LTE system using a C++ simulation tool. The tool accurately modeled the wireless system parameters and can be used for study of optimization of the LTE system. ©2009 IEEE

A study of packet scheduling with mobile cellular channel impairments

Long Term Evolution-Advanced (LTE-A) is a new radio access technology that is expected to provide better experience among the mobile cellular users. It delivers multimedia services using packet switching technology. Therefore, intelligent design of packet scheduling for the LTE-A to provide Quality of Service (QoS) comparable to fixed line services becomes crucial. However, packet scheduling over the LTE-A system faces a number of challenges. This paper studies a number of low complexity real time packet scheduling algorithms developed for the legacy mobile cellular systems. In addition to that, studies on performance impact due to mobile cellular channel impairments are presented. The study aims to identify the methods used by the existing packet scheduling algorithms as well to ascertain the performance degradations on the QoS of multimedia services due to the impact of the mobile cellular channel impairments. Future works include development of a new packet scheduling algorithm to overcome detrimental effects due to LTE-A channel impairments on the QoS of multimedia services. © 2012 IEEE

Performance analysis of two packet scheduling Algorithms in downlink 3GPP LTE system

This paper evaluates the performance of two simple packet scheduling algorithms for real-time traffic in the third generation partnership project long term evolution (3GPP LTE) system. These algorithms, known as Algorithm 1 and Algorithm 2 for this paper, were proposed to support real-time traffic in orthogonal frequency division multiple access (OFDMA) system. Simulation results show that Algorithm 1 outperforms Algorithm 2 by achieving a lower packet delay and packet loss rate while having almost similar throughput and fairness performance compared to Algorithm 2. © 2010 IEEE

Radio propagation modelling in the downlink LTE

In order to support development of third generation partnership project long term evolution (3GPP LTE) packet scheduling algorithms, research has been conducted into several radio propagation effects. The radio channels of interest are the downlink (eNodeB to user equipment) of LTE mobile networks. Through network simulator modification and repeated testing the effects of error and delay in reporting available user mobile Signal to Noise Ratio (SNR) has been investigated. Simulation results show that errors in reported SNR will increase erroneous transmission, and the effect increased with greater numbers of users. Simulations results also show that the effect of processing delay is largely dependent on the velocity of the affected mobile user. ©2010 IEEE

Analysis of hybrid ARQ in 3GPP LTE systems

The use of Hybrid ARQ in wireless networks is to provide fast re-transmits and to lower the overall error rate. The performance of HARQ schemes is a well studied field, with many results to draw from in the literature. An area that is less researched is what impact Hybrid ARQ has on LTE systems. We are, specifically, interested in looking at the system delay, but also at how HARQ behaves when used with a packet scheduler. A further area of interest is when HARQ is a drawback on the system throughput. This paper aims to look at all three of these areas. ©2010 IEEE