Timo Hämäläinen

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.

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.

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.

Pricing model for 3G/4G networks

Pricing of the future multimedia services in the 3G/4G networks will play a key role from operators point of view to achieve the maximum revenue and maximizing ROY. On the other hand pricing of the various new services is a very important issue to subscribers and especially the pricing versus the acceptance of services will be a very delicate and important matter that must be dealt very gently. This paper introduces models for the 3G/4G service pricing including QoS.

Analysis of HTTP Requests for Anomaly Detection of Web Attacks

Attacks against web servers and web-based applications remain a serious global network security threat. Attackers are able to compromise web services, collect confidential information from web data bases, interrupt or completely paralyze web servers. In this study, we consider the analysis of HTTP logs for the detection of network intrusions. First, a training set of HTTP requests which does not contain any attacks is analyzed. When all relevant information has been extracted from the logs, several clustering and anomaly detection algorithms are employed to describe the model of normal users behavior. This model is then used to detect network attacks as deviations from the norms in an online mode. The simulation results presented show that, compared to other data mining algorithms, the method results in a higher accuracy rate.

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.

Performance evaluation 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 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.

Adaptive contention resolution parameters for the IEEE 802.16 networks

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 request transmission opportunities are considered. The 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.