Interest in broadband wireless access (BWA) has been growing due to increased user mobility and the need for data access at all times. IEEE 802.16e based WiMAX networks promise the best available quality of experience for mobile data service users. Unlike wireless LANs, WiMAX networks incorporate several quality of service (QoS) mechanisms at the Media Access Control (MAC) level for guaranteed services for data, voice and video. The problem of assuring QoS is basically that of how to allocate available resources among users in order to meet the QoS criteria such as delay, delay jitter and throughput requirements. IEEE standard does not include a standard scheduling mechanism and leaves it for implementer differentiation. Scheduling is, therefore, of special interest to all WiMAX equipment makers and service providers. This paper discusses the key issues and design factors to be considered for scheduler designers. In addition, we present an extensive survey of recent scheduling research. We classify the proposed mechanisms based on the use of channel conditions. The goals of scheduling are to achieve the optimal usage of resources, to assure the QoS guarantees, to maximize goodput and to minimize power consumption while ensuring feasible algorithm complexity and system scalability.

https://www.cse.wustl.edu/~jain//papers/ftp/sched.pdf

Scheduling in IEEE 802.16e mobile WiMAX networks: key issues and a survey

Scheduling solution for the IEEE 802.16 base station

Techniques, devices, systems, and protocols are disclosed herein that relate to data transfer between communication nodes via multiple heterogeneous paths. In various embodiments, network coding may be used to improve data flow and reliability in a multiple path scenario. Transmission control protocol (TCP) may also be used within different paths to further enhance data transfer reliability. In some embodiments, multiple levels of network coding may be provided within a transmitter in a multiple path scenario, with one level being applied across all paths and another being applied within individual paths.

Multi-path data transfer using network coding

In this work we present a link abstraction model for the simulation of downlink data transmission in LTE networks. The purpose of this model is to provide an accurate link performance metric at a low computational cost by relying solely on the knowledge of the SINR and of the modulation and coding scheme. To this aim, the model combines Mutual Information-based multi-carrier compression metrics with Link-Level performance curves matching, to obtain lookup tables that express the dependency of the Block Error Rate on the SINR values and on the modulation and coding scheme being used. In addition, we propose a 3GPP-compliant Channel Quality Indicator evaluation procedure, based on the proposed Link Abstraction Model, to be used as part of the LTE Adaptive Modulation and Coding mechanisms. Finally, we discuss how these contributions have been tested, validated and integrated in the ns-3 simulator. The link abstraction model described in this paper has been included in the official ns-3 distribution since release 3.14.

/pdf/a-lightweight-and-accurate-link-abstraction-model-for-the-15xus66qhs.pdf

A lightweight and accurate link abstraction model for the simulation of LTE networks in ns-3

A coding approach for a robust and flexible network communication protocol is described. By using coding, it is possible to eliminate the need to track packet identities, and hence, it is possible to reduce coordination overhead associated with many conventional protocols. The method and system described herein takes advantage of multiple paths, interfaces, mediums, servers, and storage locations available in a network. The proposed protocol allows quick response to congestion by load balancing over different network resources. The method also enables soft vertical hand-overs across heterogeneous networks. In one embodiment, a media file is divided into chunks and transmitted using a transport protocol tailored to meet delay requirements of media streaming applications. Also described are different coding strategies for chunk delivery based upon an urgency level of each chunk.

Coding approach for a robust and flexible communication protocol

The IEEE 802.16 technology defines the ARQ mechanism that enables a connection to resend data at the MAC level if an error is detected. In this paper, we analyze the key features and parameters of the 802.16 ARQ mechanism. In particular, we consider a choice for the ARQ feedback type, an algorithm to build block sequences, a scheduling of the ARQ feedbacks and retransmissions, the ARQ block rearrangement, ARQ transmission window and ARQ block size. We run a number of simulation scenarios to study these parameters and how they impact a performance of application protocols. The simulation results reveal that the ARQ mechanism and its correct configuration play an important role in transmitting data over wireless channels in the IEEE 802.16 networks.

Performance analysis of the ieee 802.16 arq mechanism

In the IEEE 802.16 the number of errors and the MAC PDU size have an impact on the performance of the network. We present a way to estimate the optimal PDU size and we run a number of simulation scenarios to study these parameters and how they impact on the performance of application protocols. The simulation results reveal that the channel bit error rate has a major impact on the optimal PDU size in the IEEE 802.16 networks. Also, the ARQ block rearrangement influences the performance.

Optimal MAC PDU Size in IEEE 802.16

IEEE 80216 standard defines the wireless broadband technology called WiMAX When compared to other wireless technologies, it introduces many interesting advantages at PHY, MAC, and QoS layers Heavy simulations are needed to study IEEE 80216 performance and propose further enhancements to this standard Link level simulations are not always sufficient, while system level simulators are not always accurate to capture MAC and transport protocol details We implemented a 80216 extension for the NS-2 network simulator It includes upper PHY modeling, almost all the features of the 80216 MAC layer, as well as the QoS framework This article describes the implemented features, simulation methodology, and shares our experience that can be used with other NS-2 modules An overview of research papers, where this implementation was used, is given

WINSE: WiMAX NS-2 extension

The IEEE 802.16 technology defines the ARQ mechanism that enables a connection to resend data at the MAC level if an error is detected. In this paper, we analyze the key features and parameters of the ARQ mechanism. In particular, we consider a choice for the ARQ feedback type, a scheduling of the ARQ feedbacks and retransmissions, the ARQ block rearrangement, ARQ transmission window and ARQ block size. We run a number of simulation scenarios to study these parameters and how they impact a performance of application protocols. The simulation results reveal that the ARQ mechanism plays an important role in transmitting data over wireless channels in the IEEE 802.16 networks.

Performance evaluation of the IEEE 802.16 ARQ mechanism

The IEEE 802.16 standard defines the ARQ mechanism as a part of the MAC layer. The functioning of the ARQ mechanism depends on a number of parameters. The IEEE 802.16 specification defines them but it does not provide concrete values and solutions. We ran simulation scenarios to study how the ARQ feedback intensity impacts the performance of application protocols. The simulation results reveal that a low ARQ feedback intensity results only in a marginal improvement. Though it is possible to optimize the ARQ feedback intensity, it is reasonable to rely upon more frequent ARQ feedback messages as they do not result in a performance degradation. At the same time, ARQ connections, which work on top of HARQ, can delay the ARQ feedbacks up to the ARQ retry timeout to optimize the performance.

Vitaliy Tykhomyrov

Papers

Performance analysis of the ieee 802.16 arq mechanism

Optimal MAC PDU Size in IEEE 802.16

WINSE: WiMAX NS-2 extension

Performance evaluation of the IEEE 802.16 ARQ mechanism

On ARQ feedback intensity of the IEEE 802.16 ARQ mechanism