Study of IEEE802.16e standards to improve QoS throughput and delay analysis of PMP MAC Scheduling algorithms

WiMAX has two modes of operation: Point to Multi Point (PMP) mode and Mesh mode. PMP mode consists of one BS and multiple SS.The Wi-MAX is IEEE 802.16 Wireless network standard which recently used for Broadband Wireless communication. Now days to satisfy the highest demand of broadband wireless access by using various resource of bandwidth is a biggest challenge for Researchers, in this time WiMAX (Worldwide Interoperability for Microwave Access) emerged as a better solution to fulfil that demand. To provide authentic services for voice, data and videos WiMAX define the various QoS parameters at Media Access Control (MAC) layer. WiMAX structure is based on IEEE 802.16 OSI standard and defines the PMP (Point to Multipoint) and Mesh modes for transmission of information. In this study, cross-layer scheduling algorithm for Wimax networks has been proposed

An improved resource allocation scheme for WiMAX using channel information

In recent years, tremendous progress has been made in wireless communication systems to provide wireless coverage to end users at different data rates. WiMAX technology provides wireless broadband access over an extended coverage area in both fixed and mobility environments. Most of the existing resource allocation schemes allocate resources based on respective service class of the incoming users’ requests. However, due to variation in channel conditions, user mobility and diverse resource requirements QoS based resource allocation either results in over or under utilization of allocated resources. Therefore, resource allocation is a challenging task in WiMAX. This research proposes an improved resource management mechanism that performs resource allocation by taking into consideration not only the user service class but also the respective channel status. Based on these two parameters, this research aims to achieve improved resource allocation in terms of resource utilization, fairness and network throughput. First, a Channel Based Resource Allocation scheme is introduced where priority in resource allocation is given to users’ requests with relatively higher service classes and better channel status. To maintain fairness in resource allocation process, a Fair Resource Allocation Based Service mechanism is developed where priority is given to users’ requests having less additional resources demand. Finally, to improve throughput of the network, a Channel Based Throughput Improvement approach is proposed which dynamically selects a threshold level of channel gain based on individual channel gain of users. During resource allocation process, users above the threshold level are selected for resource allocation such that priority is given to users with high channel gain. Different simulation scenario results reveal an overall improved resource utilization from 87% to 91% and the throughput improves up to 15% when compared to existing schemes. In conclusion the performance of resource utilization is improved if channel status is considered as an input parameter

An Integrated Routing and Distributed Scheduling Approach for Hybrid IEEE 802.16E Mesh Networks For Vehicular Broadband Communications

An integrated routing and distributed scheduling approach for fast deployable IEEE 802.16e networks is presented where distributed base stations with dual radios form a mesh backhaul and subscriber stations communicate through these base stations. The mesh backhaul is formed via an IEEE 802.16e mesh mode radio on each base station, while the subscriber stations communicate with base stations via PMP mode radios. The proposed routing scheme divides the deployed network into several routing zones. Each routing zone contains several base stations that form the mesh backhaul with one base station equipped with either a fiber, satellite or any other point-to-point backhaul link to reach a gateway on the core network (for example, Internet or Enterprise Network). Traffic from the subscriber stations is routed by the serving base station through the mesh to the gateway-connected base station using min-hop routing metric. Mobile IP scheme is used to assign a care-of address to a subscriber station that moves from one routing zone to the other, thereby avoiding a change in IP address for network layer applications. The scheduling approach consists of two phases. In the first phase, a centralized mesh scheduling algorithm is applied with collected information on network topology, radio parameters, and initial QoS provisioning requirements. At the same time, each base station derives a PMP schedule for actual demands from associated subscriber stations constrained by the initial mesh schedule. In the second phase, each base station monitors its carried PMP traffic load statistics; to accommodate traffic load changes in a distributed fashion, each base station lends or borrows time slots from neighboring base stations to adjust its mesh and PMP radio schedules. The distributed schedule adaptation method not only allows individual base stations to accommodate short-term increases in bandwidth demands, it also provides the means for optimizing the mesh and PMP schedules with respect to actual bandwidth demands. Several deployment strategies are considered and an analytical model is developed to identify the achievable increase in overall network throughput using the proposed scheduling approach. Simulations are run in network simulator ns-2 to verify results obtained using the analytical model

Enhancing Scheduling for IEEE 802.16 Networks

The IEEE 802.16 standard defines the specifications of the Worldwide Interoperability for Microwave Access (WiMAX) technology as a Broadband Wireless Access network. This type of networks supports multiservice traffic (data, voice and video) and guarantees the Quality of Service at the MAC layer level. However, the IEEE 802.16 standard specifies three QoS components that reside in the MAC layer such as scheduler and call admission control. Although, the IEEE 802.16 defined the function of each component but left the implementation open for vendors and operators. In this thesis, we aim to design two new scheduling algorithms that guarantee QoS in WiMAX network. The new algorithms will consider application traffic requirements, channel condition states and compliant with the standard. The first algorithm is Deadline maximum Signal to Interference Ratio (DmSIR) scheduling algorithm and it is a modified version from maximum Signal to Interference Ratio (mSIR) scheduling algorithm. The DmSIR scheduling algorithm makes scheduling decision based on two factors: the packets deadline and signal to noise ratio. The second algorithm which we named the Priority based Deficit Round Robin (PbDRR) solves the problem of long delay for non real-time traffic with low signal to noise ratio as well as giving priority to real-time traffic that approach to deadline. The PbDRR scheduling algorithm makes scheduling decision based on three factors: packets deadline, signal to noise ratio and backlog traffic. We used the NS2 network simulation to evaluate the performance of the new algorithms and three performance metrics are evaluated for this purpose. The simulation results for DmSIR shows enhancement in the performance compared to the mSIR scheduling algorithm but the non real-time traffic with low signal to noise ratio suffers from long delay. On the other hand, the simulation results for the PbDRR scheduling algorithm shows better performance than the DmSIR and Deficit Round Robin + Fragmentation (DRR+F) scheduling algorithms

Traffic Scheduling in Point-to-Multipoint OFDMA-based Systems

The new generation of wireless networks (e.g., WiMAX, LTE-Advanced, Cognitive Radio) support many high resource-consuming services (e.g., VoIP, video conference, multiplayer interactive gaming, multimedia streaming, digital video broadcasting, mobile commerce). The main problem of such networks is that the bandwidth is limited, besides to be subject to fading process, and shared among multiple users. Therefore, a combination of sophisticated transmission techniques (e.g., OFDMA) and proper packet scheduling algorithms is necessary, in order to provide applications with suitable quality of service. This Thesis addresses the problem of traffic scheduling in Point-to-Multipoint OFDMA-based systems. We formally prove that in such systems, even a simple scheduling problem of a Service Class at a time, is NP-complete, therefore, computationally intractable. An optimal solution is unfeasible in term of time, thus, fast and simple scheduling heuristics are needed. First, we address the Best Effort traffic scheduling issue, in a system adopting variable-length Frames, with the objective of producing a legal schedule (i.e., the one meeting all system constraints) of minimum length. Besides, we present fast and simple heuristics, which generate suboptimal solutions, and evaluate their performance in the average case, as in the worst one. Then, we investigate the scheduling of Real Time traffic, with the objective of meeting as many deadlines as possible, or equivalently, minimizing the packet drop ratio. Specifically, we propose two scheduling heuristics, which apply two different resource allocation mechanisms, and evaluate their average-case performance by means of a simulation experiment