Chakchai So-In

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

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.

Capacity evaluation for IEEE 802.16e mobile WiMAX

We present a simple analytical method for capacity evaluation of IEEE 802.16e Mobile WiMAX networks. Various overheads that impact the capacity are explained and methods to reduce these overheads are also presented. The advantage of a simple model is that the effect of each decision and sensitivity to various parameters can be seen easily. We illustrate the model by estimating the capacity for three sample applications--Mobile TV, VoIP, and data. The analysis process helps explain various features of IEEE 802.16e Mobile WiMAX. It is shown that proper use of overhead reducing mechanisms and proper scheduling can make an order of magnitude difference in performance. This capacity evaluation method can also be used for validation of simulation models.

eOCSA: An algorithm for burst mapping with strict QoS requirements in IEEE 802.16e Mobile WiMAX networks

Mobile WiMAX systems based on the IEEE 802.16e standard require all downlink allocations to be mapped to a rectangular region in the two dimensional subcarrier-time map. Many published resource allocation schemes ignore this requirement. It is possible that the allocations when mapped to rectangular regions may exceed the capacity of the downlink frame, and the QoS of some flows may be violated. The rectangle mapping problem is a variation of the bin or strip packing problem, which is known to be NP-complete. In a previous paper, an algorithm called OCSA (One Column Striping with non-increasing Area first mapping) for rectangular mapping was introduced. In this paper, we propose an enhanced version of the algorithm. Similar to OCSA, the enhanced algorithm is also simple and fast to implement; however, eOCSA considers the allocation of an additional resource to ensure the QoS. eOCSA also avoids an enumeration process and so lowers the complexity to O(n2).

System-level modeling of IEEE 802.16E mobile wimax networks: Key issues

WiMAX has attracted a lot of attention recently in the telecommunication community including researchers, product developers, and service providers. Numerous papers have been published on various design issues of WiMAX networks. Since the issues being discussed are usually ahead of product availability, most of these studies require simulation. It is important to have some common features among these models so that their results can be compared. Therefore, the Application Working Group of the WiMAX Forum has developed a standard simulation methodology that describes the key features to be simulated, the method of simulating these features, and various parameter values to be used. This system-level methodology has been used in several public and commercial WiMAX simulation models. This article presents a summary of the simulation methodology, and discusses the key issues and common mistakes in simulating various features of network configuration, and the physical, MAC, and application layers.

MILSA: A New Evolutionary Architecture for Scalability, Mobility, and Multihoming in the Future Internet

Many challenges to the Internet including global routing scalability have drawn significant attention from both industry and academia, and have generated several new ideas for the next generation. MILSA (Mobility and Multihoming supporting Identifier Locator Split Architecture) and related enhancements are designed to address the naming, addressing, and routing scalability challenges, provide mobility and multihoming support, and easy transition from the current Internet. In this paper, we synthesize our research into a multiple-tier realm-based framework and present the fundamental principles behind the architecture. Through detailed presentation of these principles and different aspects of our architecture, the underlying design rationale is justified. We also discuss how our proposal can meet the IRTF RRG design goals. As an evolutionary architecture, MILSA balances the high-level long-run architecture design with ease of transition considerations. Additionally, detailed evaluation of the current inter-domain routing system and the achievable improvements deploying our architecture is presented that reveals the roots of the current difficulties and helps to shape our deployment strategy.

Modeling and resource allocation for mobile video over WiMAX broadband wireless networks

The key to proper resource allocation for mobile video on wireless networks is to have a good model for the resource demands. In this paper, we present the results of analysis of a number of mobile video streams and show that a simple seasonal ARIMA model (SAM) can provide a very good representation for both MPEG4-Part2 and MPEG4-Part10 videos, the formats that are commonly used for mobile videos. The model has been implemented to provide both video frame and RTP packet generators. The model can be used to represent different movies and can be easily adjusted to produce different workloads for simulation studies. We use the SAM generator to compare the performance of three different scheduling methods for video over WiMAX networks: Earliest Deadline First (EDF), Deficit Round Robin (DRR) and a combination of the two. The results show that under overload, EDF introduces unfairness. DRR with deadline is fair and gives the best performance.

Capacity estimation and TCP performance enhancement over mobile WiMAX networks

The mobile WiMax system is based on IEEE 802.16e, which defines radio interface supporting several classes of Internet Protocol applications and services. While the mobile WiMax system is being deployed, IEEE 802.16m TG is developing an amendment to the IEEE 802.16e to greatly improve the system performance, and it is focusing not only on the PHY and MAC performance but also on a level of end-to-end performance improvement that includes the scope of the network and application to embrace the strong market request and interest. To evaluate the mobile WiMax system capacity and performance, all the aspects of performance evaluation - from air link to application - are required. For the network and application-level capacity and performance analysis, we first provide an overview of mobile WiMAX systems, especially of the OFDMA/TDD systems of IEEE 802.16e and then describe subscriber and application profiles that include traffic-mix ratio, data-session attempts for applications, diurnal-application traffic distribution, and the application-traffic model. Afterward, the simulation results of network- traffic characteristics and demand estimation are provided. Finally, in the last section, we provide simulation results of end-to-end application performance evaluation using the examples of VoIP and a TCP/IP performance-enhancement method that can be implemented in the mobile WiMAX MAC or MAC/IP cross layer.

OCSA: An algorithm for burst mapping in IEEE 802.16e mobile WiMAX networks

Most of IEEE 802.16e resource allocation proposals only focus on how to allocate the resources to meet QoS parameters such as throughput, delay, and delay-jitter. As described in the standard, the mapping from the allocation into downlink subframe for each burst needs to be in a rectangular shape. The rectangular mapping problem is a variation of a bin or strip packing problem, which is known to be NP complete. However, the mapping decision needs to be made within a few milliseconds for each Mobile WiMAX frame. In this paper, we introduce a heuristic algorithm, called One Column Striping with non-increasing Area first mapping (OCSA). The algorithm is fast and simple to implement and minimizes the unused slots in the frame.

Future wireless networks: key issues and a survey (ID/locator split perspective)

Future wireless networks (FWNs) are expected to be a convergence of different kinds of wireless technologies, such as cellular technologies, wireless local area networks (WLANs), wireless metropolitan area networks, wireless sensor networks, and traditional wired networks. The internet protocol (IP) will be potentially adopted as the common networking protocol for diverse networking technologies including the next generation of cellular networks using system architecture evolution (SAE). However, the IP architecture has several known challenges, such as mobility, multihoming, routing scalability, location privacy, path preference selection, etc. One of the greatest problems preventing the networks from overcoming these challenges is that the IP address is contextually overloaded, both as locators and identifiers. As a result, in this paper, we describe the issues of all-IP wireless networks, and survey recent proposals focusing on IP address overloading that can be applied to FWNs.

An Explicit Rate Control Framework for Lossless Ethernet Operation

In this paper, an explicit rate control framework for Ethernet applications, especially data centers, is described. The framework guarantees zero packet drops at the congested switch and fast convergence to fair and stable state. In order to manage the congestion, design choices on 2-point and 3- point structures, the reactive and proactive signaling, explicit and implicit rate controls are compared. Then the core component of the framework, queue control, is carefully studied. Furthermore, we show that this framework can seamlessly cooperate with IEEE 802.3x PAUSE mechanism to recover from severe congestion scenarios. Numerical results are provided to support the claims.