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A TDD frame structure of IEEE 802.16 standard
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IEEE 802.16 (WiMAX) is considered as one of the most promising wireless access technologies supporting highcapacity and long-distance communications as well as user mobility. A problem that should be addressed in the context of multi-access communications is the efficient accommodation of traffic requests to the downlink subframe. The allocation op...
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Citations
... An Adaptive Split Ratio (ASR) scheme is proposed which adjusts the bandwidth ratio of DL to UL adaptively accord-ing to the current traffic profile, wireless interference, and transport layer parameters, so as to maximize the aggregate throughput of TCP based traffic. Similar works in [19] and [20] also deal with dynamic and efficient DL TDD mapping schemes. ...
In this paper, we study the aggregation between the FDD and TDD spectrum bands within the context of 3GPP LTE-A system. To be specific, we first provide a cross-layer design analysis to obtain the achievable throughput using the TDD mode for transmission in LTE-A system. Under particular QoS requirements and certain channel conditions, the achievable throughput is derived and evaluated. The QoS requirements originate from the upper layers, where the file size, the TCP window size and the latency for efficient transmission are incorporated in the final formulation. Having obtained the formulation, simulation results highlight the impact of the QoS parameters to different TDD frame formats. We therefore propose a framework for TDD frame adaptation within the LTE-A system. The aim of this framework is to provide the options of choosing different TDD frame formats by calculating the DL:UL subframes ratio under certain channel conditions and QoS requirements. Simulation results are carried out, which reveal the probability of choosing the different TDD frame formats from the system under certain channel conditions and QoS requirements.
... Our previous work includes the design of various mapping schemes giving emphasis to the fairness issue [30] and the QoS provisioning issue [31]. Nonetheless, recent studies on determining the channel split ratio in WiMAX wireless networks [32][33][34] indicate a compelling research area in OFDMA-based BWA networks. ...
Worldwide Interoperability for Microwave Access (WiMAX) family of standards have introduced a flexible, efficient, and robust wireless interface. Among other interesting features, WiMAX access networks bring into play a flexible determination of the ratio between the downlink and the uplink directions, allowing a relation width from 3:1 to 1:1 respectively. However, this promising feature is not properly utilized, since hitherto scheduling and mapping schemes proposed neglect it. In this work, this challenging issue is effectively addressed by proposing an adaptive model that attempts to adequately adjust the downlink-to-uplink sub-frame width ratio according to the current traffic conditions. In the context of a mobile WiMAX wireless access network, the Base Station is enhanced with an error-aware Learning Automaton in order to be able to identify the magnitude of the incoming and the outgoing traffic flows and in turn to suitably define the ratio on a frame-by-frame basis. The model designed is extensively evaluated under realistic and dynamic scenarios and the results indicate that its performance is clearly improved compared to schemes having predefined, fixed ratio values. K e y w o r d s -IEEE 802.16, Learning Automata, mapping, OFDMA, WiMAX
... The same shortcoming arises in the work in [8], where the fairness issue is explicitly examined. Finally, our extension in [9] takes into account only the deadline of sensitive requests, without dealing with the service class issue. ...
Mobile Worldwide Interoperability for Microwave Access (WiMAX) constitutes an attractive trademark for
supporting wireless access to Intranets and the Internet. Scheduling and mapping processes are of paramount importance since they dramatically affect the network performance. This work endeavors to provide a robust mapping scheme for the downlink sub-frame with respect to various Quality of Service (QoS) constraints. Each downlink request creates rectangular regions, called Horizons, and the mapping technique applies a persistent probing of the Horizons recorded. The evaluation experiments conducted
indicate that the scheme designed beneficially affects the system performance.
... Since constructing bursts that maximizes throughput is NP-hard [2], proposed algorithms can be classified as Max Matching solutions [4][5][6][7][8][9] or as Bin Packing solutions [2,[16][17][18][19][20][21][22]. The objective of Max Matching solutions for burst construction is to assign bursts to their best quality subchannels [4][5][6][7][8][9]. ...
... Burst construction, however, can be considered a process of placing items of variable lengths, widths, and values in a two-dimensional area such that the total value of all items in the area is maximized [2,[15][16][17][18][19][20][21][22]. Thus, they transform this problem into a Bin Packing problem and find the best shape and position of each burst in the bandwidth area to maximize the overall throughput of all constructed bursts. ...
... This procedure ends when the required number of slots is fulfilled. Instead of a horizontal direction used in [2,18], the studies designed the approaches that construct bursts following a vertical direction [15][16][17]. Cicconetti further provided two algorithms, Tiles and Stripes, where the former adopts a horizontal-vertical direction and the latter uses a vertical direction [19]. ...
Many burst construction algorithms for Orthogonal Frequency Division Multiple Access (OFDMA) were proposed. However, these algorithms do not meet the uplink burst characteristics specified in the IEEE 802.16 standard. This paper therefore proposes the Best Sub channel Oriented algorithm (BSO). BSO not only complies with uplink burst characteristics, but also obtains high throughput by considering the issues of internal fragmentation, external fragmentation, and good-sub channels exploring. BSO shrinks the burst area to avoid internal fragmentation, if the requested bandwidth has been satisfied. BSO minimizes the external fragmentation by evaluating all divided bandwidth areas and shrinking the burst area to fit into a proper available bandwidth area if no available area can accommodate it. To explore the good sub channels, BSO analyzes the channel quality of sub channels and constructs the burst on the sub channels which provide largest throughput. The simulation results under a heavy load indicate that BSO achieves 2 times the throughput achieved by Raster, a conventional algorithm.
... However, the traditional studies in operational research are not applicable for the burst construction because they focus on packing objects with fixed shapes and values131415 . Thus, a number of algorithms were proposed [10,11,161718192021 . The eOCSA algorithm proposed by So-In et al. [10] constructs the first burst in the bottom right-hand corner of the available bandwidth area, and subsequently constructs another burst if the available bandwidth area above the previous burst is sufficient. ...
... Otherwise, eOCSA subsequently constructs the burst on the left-hand edge of the previous burst. The approaches161718 were designed in a method similar to eOCSA, but with minor modifications . Cicconetti et al. [19] further evaluated the internal fragmentation of the burst constructed in different directions, that is, vertical direction or horizontal direction , and subsequently selected the direction that experienced less fragmentation to construct the burst. ...
Several burst construction algorithms for orthogonal frequency division multiple access were proposed. However, these algorithms did not meet the downlink burst characteristics specified in the IEEE 802.16 standard. This article therefore proposes the best corner-oriented algorithm (BCO). BCO not only complies with downlink burst characteristics, but also considers the three issues to obtain high throughput, as follows: BCO maintains all free slots as a continuous area by constructing each burst in the corner of the available bandwidth area for minimizing external fragmentation; BCO shrinks the burst area to minimize internal fragmentation, if the requested bandwidth has been satisfied; and for exploring the continuous subchannels with good channel quality, BCO ensures that the burst adopts an optimal modulation coding scheme by selecting the excellent corner that can generate the maximal throughput. The simulation results indicate that BCO achieves 2-9 times the throughput achieved by the previous algorithms under a heavy load.
The IEEE 802.16e standard known as Mobile WiMAX has recently been introduced. It is considered as one of the most promising wireless access technologies supporting high data throughput with low cost of deployment. Mobile WiMAX makes use of Orthogonal Frequency-Division Multiple Access (OFDMA) digital modulation scheme as the transmission method. With the constraint requires that all requests have to be mapped as a rectangle, it is shown that finding an optimum mapping solution is an NP-complete problem. Many burst mapping algorithms have been proposed, but none considered the case with prioritized requests. This paper presents an efficient packing algorithm for two-level requests with two targets: (1) map high (MUST part) priority data as much as possible; and (2) achieve high efficiency, reduces the number of unused slots, and minimizes the mapping information overhead. Simulation results show that the proposed algorithm achieves high efficiency.
IEEE 802.16 OFDMA systems have gained much attention for their ability to support high transmission rates and broadband services. For multiuser environments, IEEE 802.16 OFDMA systems require a resource allocation algorithm to use the limited downlink resource efficiently. One of the main problems to increase the resource utilization and throughput is how to construct two-dimensional blocks that realize time and frequency dimensions to multi-users. However, mapping a rectangular shape (i.e. two-dimensional burst) that not enough to utilize some flows in downlink frame, decreases total throughput and is crucial for Quality of Service (QoS) that support real-time applications. In this paper, we propose a low complexity algorithm called Best Edge Block Oriented (BEBO) which complies with 802.16 downlink burst characteristics with assurance of real time throughput. The proposed algorithm reduce the unserved slots by assembling bursts in the edge of the free spaces for reducing outdoor spaces from other bursts; and enlarge the internal burst size gradually to minimize the internal free spaces for a given request size with priority level and channel state information considerations. Simulation results show that the burst construction mechanism result is competitive.
WiMAX technology provides a Quality of Service (QoS) system that allows system operators to configure a network to provide maximum performance compared to conventional Best Effort (BE) systems. In this paper, we address the increase in number of data rich mobile devices and the performance issues associated with Video On Demand (VOD) multimedia traffic over a WiMAX network. We present the results of application testing using WiMAX protocol where the main focus is to show how utilizing a QoS system can benefit streaming real time multimedia. The results show how WiMAX technology is beneficial to multimedia applications.
The IEEE 802.16e standard, which adopts OFDMA PHY and is generally known as Mobile WiMAX, has grabbed the attention of wireless communication industry for the past few years. It is a technology optimized for IP-based high speed long-distance wireless broadband access. In the downlink of Mobile WiMAX systems, data requests have to be mapped into rectangular regions. Such a constraint results in an NP-complete problem in order to maximize throughput. Several heuristic data mapping algorithms were proposed trying to achieve high system throughput. Most of the algorithms handle only one type of data. In a previous paper, we presented a data mapping algorithm which maps two levels of requests, i.e., urgent and non-urgent data. However, only the numbers of required slots were considered in determining the order of data mapping. In this paper, we propose an enhanced version which considers both the number of required slots and the Modulation and Coding Scheme (MCS) for each mobile station. Simulation results show that, compared with previous design, the enhanced algorithm serves more urgent data with higher throughput.
Various burst construction algorithms for Orthogonal Frequency Division Multiple Access (OFDMA) were proposed. However, these algorithms did not consider the downlink burst characteristics that are specified in IEEE 802.16 standard. This work therefore presents the Best Block-Oriented (BBO) algorithm. BBO not only complies with the downlink burst characteristics, but also addresses three further issues that are important to obtain high throughput: BBO reduces external fragment by shrinking a burst to fit into the available bandwidth area if the available area is otherwise insufficient to accommodate it; BBO shrinks the burst area to minimize internal fragment if the requested bandwidth has been satisfied; to find the subchannels that have good channel quality, BBO evaluates the channel quality of subchannels and constructs the burst in the subchannels that provide the highest throughput. Simulation results show that BBO yields 1.2–9 times the throughput that has been achieved using previous algorithms under a heavy load.
