Channel aware optimized proportional fair scheduler for LTE downlink

In this paper, we investigate adaptive resource allocation in downlink transmission of orthogonal frequency division multiple access (OFDMA) networks. A block-level resource allocation scheme is developed to maximize the overall throughput of the networks. We focus on application in long term evolution (LTE) systems where all resource blocks (RB's) allocated to the same user must use the same modulation and coding scheme (MCS). The complexity of such optimization problem is usually high. In order to reduce the complexity, we divide the original optimization problem into two suboptimal ones. We first allocate appropriate RB's to users with the best channel quality and then perform power allocation. Finally, a more effective MCS is selected, which not only ensures block-error rate (BLER) performance of RB with the poor channel condition but also makes full use of the RB's with good channel condition. Simulation results show that the proposed resource allocation scheme can improve the overall throughput of the network by 20% compared with the existing scheme when the number of users is 4 and SINR = 10 dB.

The demand for faster internet connections to access wireless multimedia applications, Aeronautical Communication Networks (ACNs) and internet services has resulted into rise of developing broadband wireless technologies in recent years. The demand for higher data rates was the backbone for developing wireless communication technologies such as Worldwide Interoperability for Microwave Access (WiMAX), Long Term Evolution (LTE) and High-Speed Packet Access (HSPA). The big challenge with wireless communications lies with providing Quality of Service (QoS) under various environmental challenges and maximizing resource utilization at the same time. In wireless communication, the support for QoS is difficult due to the unpredictable nature of wireless channels. Opportunistic Scheduling plays a big role towards meeting QoS requirements and managing resources in aeronautical communication networks. Various opportunistic schedulers focus on increasing the system capacity of a wireless communication network, while some aim on improving the system’s fairness and throughput. With such interest in opportunistic scheduling, the paper focuses on reviewing recently proposed opportunistic scheduling algorithms, the objectives they were designed for, and their shortcomings. An effective opportunistic scheduling algorithm with hierarchical modulation technique is presented in this paper. The algorithm focuses on the ability to allocate resources between two users with different channel conditions; that is a user with good channel conditions and a user with bad channel conditions, to maximize the system’s throughput and maintain fairness.

In traditional wireless multicast systems, the system is optimized to provide high reliability to users with the worst channel conditions. However this results in a waste of available bandwidth for users with a good channel conditions. In particular for transmission of video, this wasted bandwidth can be used to deliver higher quality video to some of the users. This paper addresses this problem by using diversity embedded space time codes (DESTC) to send multiple layers of video simultaneously. DESTC provides unequal error protection to different video layers, thereby delivering high quality video to users with good channel conditions while still providing acceptable quality to users with poor channel conditions. The performance of DESTC is compared to a single-layer orthogonal space-time code used for single-layer video delivery as well as layered video delivery with time division multiplexing. The results show that the use of DESTC is advantageous over both strategies in multicast video delivery.

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Evolved UMTS terrestrial radio access network (EUTRAN) offers high uplink and downlink throughput. In this paper, we investigate the performance of five different schedulers of media access control for resource allocation, such as round robin (RB), proportional fair (PF), best channel quality indicator (CQI), max transmission point (TP) and resource fair (RF). On comparing the performance of resource allocation schedulers in the indistinguishable arrangement, we found the proportional fair (PF) offers balance in terms of individual metrics. Furthermore, we analyse the effect of feedback transmission time interval (TTI) delay on two typical EUTRAN networks referred to as long term evolution (LTE) and LTE-Advance (LTE-A). We evaluate the performance of the PF scheduler for both networks under varying feedback delay in TTI. Simulated results show that the delay in TTI affects the performance of resource allocation. Feedback delay improves network performance by compensating effect of imperfect channel.

Recently, there has been a tremendous increase in mobile data usage with widespread proliferation of smartphone like devices and increasing popularity of video streaming services such as YouTube. This is already causing overloading of 3G cellular access networks. It is estimated that even the 4G LTE (Long Term Evolution) technology which has significantly higher spectral efficiency than 3G will also face overloading in near future. As a result, it has become important to find out ways and means of offloading the traffic from the LTE network. One possible solution is offloading it to Wi-Fi to gain extra capacity and improve overall network performance. In this paper we have considered an outdoor macro cell LTE Network being offloaded by a Wi-Fi network. We study the loading of LTE Network in different types of user and traffic distribution and investigate how offload to Wi-Fi APs can help in easing the congestion in LTE network and thereby lead to better per user throughputs and better quality of experience to end users using NS-3. Also, among the various scheduling algorithms that have been defined for efficient resource allocation in LTE, three schedulers have been considered: Round Robin (RR), Proportional Fair (PF) and Priority Set Scheduler (PSS) schedulers and their performance has been evaluated in the offloading scenario.

This study focuses on managing equity-conscious radio resources in OFDMA-based WIMAX networks with comparison of three algorithms, Max Rate, RR and PFS. Hence WiMAX Forum has been formed, which promotes the technology and provides compatibility and teroperability for 802.16-based products. The problem in heterogeneous WiMAX, users may possess different transmit power capabilities and experience independent channel realizations. As a result, those with lower power Capabilities or poor channel conditions will starve throughput share. It is observed that users with better channel conditions always dominate usage of the spectrum, causing low throughput for users with poor channel conditions. This paper studied the performance of downlink scheduling algorithms that perform radio resource allocation in order to improve the performance of the WiMAX system. These algorithms are Max Rate, Round Robin, and Proportional Fair. In addition, scheduling algorithm was implementing in order to explain the fairness concept. The algorithms were comparing to each other in terms of system throughput and fairness index. The performance evaluations are carrying out using MATLAB software. Simultaneous results show that the most suitable scheduling algorithm in terms of fairness index and system throughput for the WiMAX network is proportional fair. Meanwhile, Max Rate provides the highest throughput, even though the number of users is increased.

In this paper, a Long-Term Evolution-Advanced (LTE-A) Modified Best Channel Quality Indicator (M-BCQI) Scheduler is proposed for enhanced cell edge throughput performance. The scheduling algorithm utilizes two time slots, each of 0.5 ms in length, with the First Time Slot (FTS) implemented with the Best Channel Quality Indicator (BCQI) algorithm has a CQI-focused Resource Block (RB) allocation mechanism, while the Robin (RR) algorithm is the mechanism used in the Second Time Slot (STS) for RB allocation. Vienna LTE system level simulator was used for the proposed scheduling algorithm assessment. The results obtained showed significant improvement, indicating 44% superior cell edge performance and 56 % better fairness index in comparison to BCQI. However, M-BCQI slightly underperformed by 4.2% in terms of average throughput in comparison to BCQI and by 7% in comparison to RR in terms of fairness index.

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A new concept such as smart city was introduced in the last years where the Intelligent Transportation system (ITS ) plays a critical role to provide road safety and manage Vehicular Ad Hoc Networks (VANETs) traffic. Nevertheless, VANETs have significant constraints like nodes high mobility, intermittent connectivity, variable network density and heterogeneity. However, the different types of traffic, the different Quality of Service requirements, the need to exchange mobile data, multi-services and data diversity leads mainly to load and time constraints in this specific and stringent type of networks. The main characteristic of this kind of networks is the very changing topology that poses supplementary constraints and makes achieving QoS constraints a very challenging task. In VANET network the vehicle generated traffic will be transferred to the data center from road side unit to the base station by using Long Term Evolution (LTE) in an urban area. Despite LTE has a larger system capacity and it provides a higher transmission speed, the network performance is affected by the implemented scheduling algorithm. In this context, we study the efficiency of LTE scheduler algorithms such as Proportional Fairness, Round Robin, Priority Set Scheduler, Maximum Throughput Scheduler and Throughput to Average Scheduler and Blind Equal Throughput mainly at the road side unit using Network Simulator 3(NS3) to determinate the most suitable scheduler for VANET traffic. Results demonstrate that the round robin algorithm is more effective for volumetric VANET traffic in terms of throughput, delay, packet loss rate and fairness.

[ Abstract] In this paper, we propose a channel change detection mechanism implemented at UE to support feedback implosion suppression algorithm for reliable transmission of multicast data over GEO satellite networks. In this framework, reliability is guaranteed via MFTP that retransmits lost segments to the multicast group. A channel-aware scheduling mechanism is used at the Gateway that behaves like a switch to allow downlink transmissions of MFTP packets. The scheduler uses CSI values collected from group members through the CSI collection policy before making a decision as to whether or not to transmit a multicast packet in the forward link. As such, the scheduling algorithm aims at avoiding unfavorable channel conditions to reduce the forward link resources that would be wasted for retransmissions and to allow downlink transmissions only when users are in good channel condition, in the face of L-band mobile satellite channel conditions. The integration of channel-aware scheduling algorithm and CSI collection policy aims to reduce session duration and traffic volume in the return link by updating only relevant information back to Gateway. In order to achieve this objective, change detection mechanism is proposed. The performance parameters such as change detection rate and downlink resource utilization are analyzed. Two change detection algorithms are compared; it is shown that there is a trade-off in performance, in particular between uplink signalling load and downlink resource utilization. The work presented in this paper is executed within IST SatNEx II (EU IST FP6 – Contract No. 027393), JA2330 “Radio Resource Allocation and Adaptation” activity. Nomenclature

In an urban environment, vehicle mobility is limited by road structure and obstacles. This gives rise to extremely challenging network design for large data transfers due to unpredictable network dynamics, limited connection lifetime and unstable channel conditions. Conventional approaches using retransmission schemes do not perform well in these conditions due to nodes leaving the network in the middle of the download. Rateless codes have been identified as a solution to address interrupted downloads with minimal handshaking and overhead requirements. Varying channel conditions calls for the need of multi-rate vehicular communications, where low rate robust communication is used when bad channel is experienced and higher rate modulation is used in good channel conditions. This paper presents a novel coding scheme based on systematic raptor codes for multihop data dissemination that is based on multi-rate vehicular communications. With this scheme, even vehicles which are outside the roadside infrastructure coverage can be provided with reliable access to infrastructure services.

Time-domain inter-cell interference coordination, so called eICIC, has been introduced in Long Term Evolution-Advanced (LTE-Advanced) system as a throughput improvement method for heterogeneous network, where a lot of low power nodes (LPNs) are located in the coverage area of high power base station (Marco-BS). eICIC enables Macro-BSs to configure almost blank subframe (ABS), in which Marco-BSs reduce their transmit power or mute data transmission so as to reduce interference to the users served by LPNs. However, the improvement of the overall throughput is affected by the ABS setting. This paper proposes a novel user throughput estimation method for LTE-Advanced system where ABS and proportional fairness scheduler are applied. Numerical results show that the proposed method accurately estimates the user throughput for arbitrary ABS ratio with the estimation error of 1-7% for cell edge user throughput and around 1% for average user throughput, respectively. As a result, using the proposed method, Macro-BSs can decide proper ABS ratio to maximize cell edge or average user throughput.

The preference improvement resulting from modifications to the original ARQ scheme proposed by E.J. Weldon (1982) for use in systems with finite-receiver buffers was analyzed in a previous paper. A modification involving the use of parity retransmission is studied. One drawback of using forward error correcting (FEC) codes is that the parity bits result in a degradation in efficiency under good channel conditions: the maximum throughput is limited to the FEC code rate. Two type II ARQ schemes which overcome this problem are studied. Lower bounds on the throughputs of the two schemes are obtained. The throughput of the type II ARQ scheme is no longer limited by one-half the rate of the FEC code used. Under good channel conditions, the throughput with the type II ARQ scheme is equivalent to not using FEC; as the channel degrades, it approaches the throughput with a rate one-half FEC code.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Smart Grid is a new standard or digital technology which allows both way of communication between utility and customers. Smart grid is also a framework of new equipment, technologies, automatic operations and controls which is very similar to the internet, however in this regard for rapidly changing loads the grid will be digitally reactive by combining these technologies. For digitalization of smart grid, a faster, and wireless but reliable communication is necessary. On that account LTE could be a better option. Long-Term Evolution (LTE) is a new grade for faster and seamless communication for smart devices and data terminals. In this regard, different scheduling tackles are very helpful. This paper discusses about two very common scheduling algorithms and those are Best Channel Quality Indicator (Best CQI) and Proportional Fair (PF). From simulation it is possible to find out their throughput and BLER (Block Error Rate) by using Transmit Diversity (TxD) and Open Loop Spatial Multiplexing (OLSM). Each time cross relation can be carried out for better comparison experiments.