Thushara Weerawardane

Multi-QoS-Aware Fair Scheduling for LTE

the MAC scheduler is an important and crucial entity of the Long Term Evolution (LTE) and is responsible for efficiently allocating the radio resources among mobile users who have different QoS demands. The scheduler takes different considerations into account such as throughput and fairness when deciding the allocation of the scarce radio resources. LTE is an all IP packet system in which guaranteeing QoS is a real challenge. Therefore the LTE MAC scheduler should consider not only the throughput optimization but also the QoS differentiations in an effective manner. In this paper, we propose a novel LTE downlink MAC scheduling algorithm. The proposed scheduler differentiates between the different QoS classes and their requirements. Two different QoS classifications are considered: Guaranteed Bit Rate (GBR) and non Guaranteed Bit Rate (non-GBR). The proposed scheduler also considers the different users channel conditions and tries to create a balance between the QoS guarantees and the multi-user diversity in a proportional fair manner. The simulation analysis confirms that guaranteeing the different QoS requirements is possible.

Preventive and Reactive Based TNL Congestion Control Impact on the HSDPA Performance

High speed downlink packet access (HSDPA) is an extension of the Universal Mobile Telecommunications System (UMTS) technology of 3GPP Rel-99, with the objective to increase the data rate and reduce the latency in the downlink. The main focus of the work presented is to analyse the effect of congestion at the Iub interface on the HSDPA performance. The data flows should be adequately controlled in order to avoid congestion in the transport network. The 3GPP (3rd Generation Partnership Project) Rel. 5 specifications highlight two congestion detection mechanisms which are based on the frame sequence number (FSN) and the delay reference time (DRT) fields of HSDPA data frame. In addition to these, a third congestion detection mechanism based of Checksum of HSDPA data frame is considered. This paper discusses a congestion control scheme deploying all three congestion detection methods. It is shown, that a congestion control algorithm can effectively work using these congestion detection triggers and can control the offered load to the transport network. The simulation results presented in this paper confirm that the congestion in the transport network can be avoided, and hence the performance of HSDPA network can be significantly improved in all aspects.

Performance evaluation of bandwidth and qos aware LTE uplink scheduler

A Long Term Evolution (LTE) eNodeB Medium Access Control (MAC) uplink scheduler is proposed in this paper for Single Carrier Frequency Division Multiple Access (SC-FDMA) as the uplink transmission scheme. Uplink scheduling algorithms available in literature commonly do not consider all the essential features of the LTE uplink. The proposed scheduler is shown to provide efficient allocation of radio resources to User Equipments (UEs) according to Quality of Service (QoS) of various traffic classes and the instantaneous channel conditions. The scheduler functionality is divided into Time Domain Packet Scheduling (TDPS) and Frequency Domain Packet Scheduling (FDPS). The proposed scheduler also supports multi-bearer UEs. The performance of the proposed scheduler is compared with common TDPS schedulers like Blind Equal Throughput (BET), Maximum Throughput (MT) and Proportional Fair (PF). The results show that the proposed scheduler guarantees provision of QoS to UEs and achieves an acceptable performance in terms of throughput.

Dimensioning of the LTE S1 interface

This paper presents analytical models to dimension the transport bandwidths for the S1 interface in the Long Term Evolution (LTE) Network. In this paper, we consider two major traffic types: elastic traffic and real time traffic. For each type of traffic, individual dimensioning models are proposed. For validating these analytical dimensioning models, a developed LTE system simulation model is used. The simulation results demonstrate that the proposed models can properly estimate the required performances and thus be able to be used for link dimensioning for various traffic and network scenarios.

Design and performance analysis of bandwidth and QoS aware LTE uplink scheduler in heterogeneous traffic environment

Long Term Evolution (LTE) uses Single Carrier Frequency Division Multiple Access (SC-FDMA) as the uplink transmission scheme. The Quality of Service (QoS) provision is one of the primary objectives of the wireless network operators. In this paper, the end-to-end QoS performance of Bandwidth and QoS Aware (BQA) scheduler for LTE uplink is evaluated in heterogeneous traffic environment. The BQA scheduler is designed to provide efficient allocation of radio resources to users according to the QoS requirements of various traffic classes and the instantaneous channel conditions. The user QoS provision is ensured by using dynamic QoS weights. Additionally, the delay sensitive traffic is facilitated by employing delay thresholds. The BQA scheduler algorithm supports multi-bearer users. The end-to-end QoS performance of the scheduler is analyzed in several simulation scenarios. The results show that the proposed scheduler guarantees provision of QoS to users.

Optimized service aware LTE MAC scheduler with comparison against other well known schedulers

Long Term Evolution (LTE) is the latest deployed broadband wireless technology from the 3rd Generation Partner Ship Project (3GPP) family. Nowadays there is an increased demand on the QoS requirements and inherently on further optimizing the usage of not only the scarce radio resources but also the overall network performance over the flat IP network more efficiently. Traditional scheduling algorithms are not able to fulfill such complex requirements. In this paper an Optimized Service Aware (OSA) scheduling algorithm is proposed, aiming at addressing the aforementioned challenges. It consists of three main functional units. The paper presents through simulations that the proposed OSA algorithm is able to achieve optimum radio and end user performance. The performance of the OSA is compared against other well-known scheduling algorithms: Weighted Blind-Equal Throughput (w-BET), Weighted Maximum Throughput (w-MaxT), and Weighted Proportional Fair (w-PF).

Intelligent traffic enforcement for LTE backhaul

There has been a lot of research focusing on optimizing the Long Term Evolution (LTE) networks performance. A large part of this research focused on how to optimize the LTE radio interface to efficiently distribute the scarce radio resources among the LTE users. Since LTE offers a diverse amount of services, the Quality of Service (QoS) differentiation is a major challenge. QoS is handled in LTE at different levels; the most important one is the radio scheduler. The QoS aware radio scheduler is designed to guarantee different service requirements. However, if the LTE radio interface is fully optimized towards QoS guarantees, what happen when the LTE transport network runs into congestion? Congestion can happen at any point in the network, and normally congested LTE backhaul tends to create large unfairness among the users, even among the ones with the same QoS class. The LTE transport congestion can occur at any router in the backhaul network. In this paper, we present two novel algorithms, which focus on the LTE transport congestion. The first algorithm is a congestion detection mechanism (CD) that identifies the transport network congestion as early as possible, and triggers the congestion control function. The second algorithm preserves and optimizes the QoS performance of each user over the transport to match the radio scheduler service differentiation, i.e., achieving fairness among the users in the same QoS demand and guaranteeing the enforced radio QoS weights for different service classes.

Dimensioning of the LTE access transport network for elastic internet traffic

This paper proposes efficient analytical models to dimension the required transport bandwidths for the Long Term Evolution (LTE) access network for the elastic Internet traffic (which is carried by the TCP protocol). The dimensioning models are based on the use of Processor Sharing queuing theory to guarantee a desired end-to-end application QoS target. For validating the analytical dimensioning models, a developed LTE system simulation model is used. Extensive simulations are performed with various traffic and network scenarios. The analytical results derived from the proposed dimensioning models are compared against the simulation results. The presented results demonstrate that the proposed analytical models can appropriately estimate the application performances of different QoS priorities and thus be used for the link dimensioning for various traffic and network scenarios.

HSUPA backhaul bandwidth dimensioning

HSUPA (High Speed Uplink Packet Access) is introduced by the 3GPP Release 6 to enhance the UMTS uplink with higher data rates, reduced latency and increased capacity. This paper discusses the dimensioning of the backhaul resources on the ATM-based Iub interface in UMTS HSUPA networks. The main focuses of this paper is to (1) analyze the important factors that have influence on the transport network dimensioning and further investigate their impacts; (2) estimate the required backhaul bandwidth as a function of user QoS requirements; (3) discuss the impact when including HSDPA traffic on the downlink. In addition, this paper also provides insights of HSUPA air interface given diverse user applications as well as different number of users within one cell. The investigations and dimensioning are based on simulations.

Effect of the RLC and TNL congestion control on the HSUPA network performance

This paper focuses on the impact of the radio link control protocol (RLC) combined with the Iub congestion control on the performance of high speed uplink packet access (HSUPA) networks. The paper investigates the performance enhancement achieved by the RLC AM (acknowledged mode) with the deployment of the Iub congestion control in the HSUPA network. To show the effect of the RLC AM in the uplink, it was compared against the RLC TM (transparent mode). Although RLC TM is not part of the HSPA specification but the aim of the comparison is to highlight and sustain the advantages gained by deploying the RLC AM. The investigations are carried out for a limited TNL network offering a low Iub link bandwidth (which is usually the case for most operators due to high cost of the Iub link), where RLC AM can effectively work with the TNL congestion control in order to optimize the end user goodput performance and the efficient utilization of the overall network resources. This paper also compares the performance of the RLC AM with two different configurations, one combined with the Iub congestion control and another without the Iub congestion control.