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

Performance analysis of EXP/PF and M-LWDF in downlink 3GPP LTE system

This paper investigates the performance of exponential/proportional fair (EXP/PF) and maximum-largest weighted delay first (M-LWDF) scheduling algorithms in the third generation partnership project long term evolution (3GPP LTE) providing packet-switched multimedia services. It, then, identifies a suitable packet scheduling algorithm on a basis of their performance evaluation. The performance evaluation is conducted in terms of system throughput, average real time (RT) and non-real time (NRT) throughput, packet loss for RT service and fairness for NRT service. A video streaming traffic is used to model the RT service, while a web-browsing traffic is modelled for NRT service. Simulation results show that at lower load M-LWDF algorithm provides better performance than EXP/PF while as the load increases the EXP/PF gives better performance. ©2009 IEEE

Performance of Well Known Packet Scheduling Algorithms in the Downlink 3GPP LTE System

This paper investigates the performance of well known packet scheduling algorithms developed for single carrier wireless systems from a real time video streaming perspective. The performance evaluation is conducted using the downlink third generation partnership project long term evolution (3GPP LTE) system as the simulation platform. This paper contributes to the identification of a suitable packet scheduling algorithm for use in the downlink 3GPP LTE system supporting video streaming services. Simulation results show that, in the downlink 3GPP LTE system supporting video streaming services, maximum-largest weighted delay first (M-LWDF) algorithm outperforms other packet scheduling algorithms by providing a higher system throughput, supporting a higher number of users and guaranteeing fairness at a satisfactory level

Impact of soft handover and pilot pollution on video telephony in a commercial network

Soft handover (SHO) provides better support for user mobility. The quality of service (QoS) to the mobile wireless subscribers can also grant benefits from SHO. To analyze the impact of SHO on the circuit switched (CS) video telephony (VT); real-time measurements have been conducted on a commercial WCDMA mobile network in the CBD of Sydney, Australia. Live measurement provides a practical approach to evaluate performance of commercial network. The obtained SHO gain implies that better QoS can be achieved. Furthermore, the negative impact of pilot pollution on radio link quality has been demonstrated in this paper. ©2010 IEEE

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

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

Impact of CQI feedback rate/delay on scheduling video streaming services in LTE downlink

The major attraction of the next generation wireless systems such as the third generation partnership project (3GPP) Long Term Evolution (LTE) is the availability of high data-rate video services at high user velocities. However, it is quite a challenge to provide the required level of quality of service (QoS) and maintain the planned system performance due to limited radio resources, unreliable radio propagation channel and high user demands. This paper analyses the impact of channel quality indicator (CQI) delay and its aperiodic reporting rate on the performance of a well known scheduling algorithm serving video streaming users at different velocities. The analysis will be compared against the system having perfect and delayed channel knowledge at each scheduling instance. We then recommend the minimum rate requirement of aperiodic CQI reports to maintain the required QoS for a certain number of video streaming users. © 2010 IEEE