Alexander Sayenko

Ensuring the QoS requirements in 802.16 scheduling

IEEE 802.16 standard defines the wireless broadband access network technology called WiMAX. WiMAX introduces several interesting advantages, and one of them is the support for QoS at the MAC level. For these purposes, the base station must allocate slots based on some algorithm. We propose a simple, yet efficient, solution for the WiMAX base station that is capable of allocating slots based on the QoS requirements, bandwidth request sizes, and the WiMAX network parameters. To test the proposed solution, we have implemented the WiMAX MAC layer in the NS-2 simulator. Several simulation scenarios are presented that demonstrate how the scheduling solution allocates resources in various cases. Simulation results reveal the proposed scheduling solution is ensures the QoS requirements of all the WiMAX service classes and shares fairly free resources achieving the work-conserving behaviour.

Scheduling solution for the IEEE 802.16 base station

The IEEE 802.16 standard defines a wireless broadband access network technology called WiMAX. It introduces several advantages, one of which is the support for QoS at the MAC level. To ensure meeting the QoS requirements, the 802.16 base station must run some algorithm to allocate slots between connections. This algorithm is not defined in the 802.16 specification but rather is open for alternative implementations. We propose a simple, yet efficient, solution that is capable of allocating slots based on the QoS requirements, bandwidth request sizes, and the 802.16 network parameters. To test the proposed solution, we have implemented the 802.16 MAC and PHY layers in the NS-2 simulator. Several simulation scenarios are presented that demonstrate how the scheduling solution allocates resources in various cases. According to the simulation results, the proposed scheduling solution ensures the QoS requirements of all 802.16 service classes. The solution shares free resources fairly and demonstrates work-conserving behaviour.

Comparison of Different Scheduling Algorithms for WiMAX Base Station: Deficit Round-Robin vs. Proportional Fair vs. Weighted Deficit Round-Robin

In this paper, we present a performance comparison of different WiMAX base station (BS) scheduling algorithms: deficit round-robin (DRR) vs. proportional fair (PF) vs. weighted deficit round-robin (WDRR). Our simulations show that when the radio channel conditions are taken into account (in PF and WDRR schedulers), the improvements in throughput can be considerable.

Performance analysis of the ieee 802.16 arq mechanism

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.

Active Queue Management for Reducing Downlink Delays in WiMAX

In WiMAX networks, the base station (BS) is a likely bottleneck for downlink (DL) TCP connections due to difference in available bandwidth between the fixed network and the wireless link. This may result in buffer overflows or excessive delays at the BS, as these buffers are connection-specific. In order to avoid buffer overflows, different active queue management (AQM) methods may be applied at the BS. This paper presents an analysis of several AQM mechanisms and proves that they are indeed very useful: AQM reduces considerably DL delays at the WiMAX BS without sacrificing TCP goodput.

WINSE: WiMAX NS-2 extension

IEEE 802.16 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 802.16 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 802.16 extension for the NS-2 network simulator. It includes upper PHY modeling, almost all the features of the 802.16 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.

Optimal MAC PDU Size in IEEE 802.16

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.

On Contention Resolution Parameters for the IEEE 802.16 Base Station

In the IEEE 802.16 networks, the base station allocates resources to subscriber stations based on their QoS requirements and bandwidth request sizes. A subscriber station can send a bandwidth request when it has an uplink grant allocated by the base station or by taking part in the contention resolution mechanism. This paper presents analytical calculations for parameters that control the contention resolution process in the IEEE 802.16 networks. In particular, the backoff start/end values and the number of the request transmission opportunities are considered. Simulation results confirm the correctness of theoretical calculations. They also reveal that the adaptive parameter tuning results in a better throughput when compared to a static configuration. At the same time, all the timing requirements are met.

ARQ Aware Scheduling for the IEEE 802.16 Base Station

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 ARQ aware scheduling for the 802.16 base station. In particular, we consider how the BS scheduler can account for the ARQ block size, absence of the ARQ block rearrangement, and the ARQ transmission window. We propose a set of constraints that can be applied to any base station scheduler algorithm. To test them, we run a number of simulation scenarios. The simulations results confirm that the ARQ aware scheduling can improve the overall performance.

Adaptive weighted fair scheduling method for channel allocation

Different applications, such as voice over IP and video-on-demand, need different quality of service parameters (e.g., guaranteed bandwidth, delay, and latency) from the networks. The customers with different needs pay different prices to the service provider, who must share resources in a plausible way. In a router, packets are queued using a multi-queue system, where each queue can correspond to one service class. This paper presents an adaptive weighted fair queue based algorithm for channel allocation. The weights in gradient type algorithms are adapted by using revenue as a target function.