Timo Vanhatupa

Bio: Timo Vanhatupa is an academic researcher from Tampere University of Technology. The author has contributed to research in topic(s): Wi-Fi & Wireless LAN controller. The author has an hindex of 8, co-authored 14 publication(s) receiving 428 citation(s).

Genetic Algorithm to Optimize Node Placement and Configuration for WLAN Planning

Abstract: This paper presents a novel algorithm to rapidly create a high quality network plan for IEEE 802.11 based WLAN according to assigned design requirements. The algorithm uses a Genetic Algorithm (GA) to explore the design space, and a IEEE 802.11 rate adaptation aware QoS estimation functionality to provide feedback for the algorithm and for a network designer. The algorithm selects AP devices, locations, antennas, as well as AP configuration including transmission power and frequency channel. The algorithm was used in WLAN planning for a suburb, which is under development in Tampere-Lempaala area in Finland. Compared to manual network planning, the developed algorithm was able to create a network plan with 133 % capacity, 98 % coverage, and 93 % cost. Manually the corresponding network planning took hours, whereas the algorithm computation time was 15 minutes.

Software and hardware prototypes of the IEEE 1588 precision time protocol on wireless LAN

Abstract: IEEE 1588 is a standard for precise clock synchronization for networked measurement and control systems in LAN environment. This paper presents the design and implementation of two IEEE 1588 prototypes for wireless LAN (WLAN). The first one is implemented using a Linux PC platform and a standard IEEE 802.11 WLAN with modifications to the network device driver. The second prototype is implemented using an embedded WLAN development board that implements the synchronization functionality using an embedded processor with programmable logic device (PLD) circuits. The measured results show that 1.1 ns average clock offset can be reached on HW based implementation, while Linux PC network driver enables 660 ns with a standard WLAN. Although WLAN is an extremely difficult environment for the synchronization, the results achieved with the prototype are fully comparable to those achieved with wired LAN implementations

Performance model for IEEE 802.11s wireless mesh network deployment design

Abstract: This paper presents a performance model developed for the deployment design of IEEE 802.11s Wireless Mesh Networks (WMN). The model contains seven metrics to analyze the state of WMN, and novel mechanisms to use multiple evaluation criteria in WMN performance optimization. The model can be used with various optimization algorithms. In this work, two example algorithms for channel assignment and minimizing the number of mesh Access Points (APs) have been developed. A prototype has been implemented with Java, evaluated by optimizing a network topology with different criteria and verified with NS-2 simulations. According to the results, multirate operation, interference aware routing, and the use of multiple evaluation criteria are crucial in WMN deployment design. By channel assignment and removing useless APs, the capacity increase in the presented simulations was between 230% and 470% compared to a single channel configuration. At the same time, the coverage was kept high and the traffic distribution fair among the APs.

Precision Time Protocol Prototype on Wireless LAN

Abstract: IEEE 1588 is a new standard for precise clock synchronization for networked measurement and control systems in LAN environment. This paper presents the design and implementation of an IEEE 1588 PC software prototype for Wireless LANs (WLAN). Accuracy is improved using two new developed methods for outbound latency estimation. In addition, an algorithm for adjusting the local clock is presented. The achieved accuracy is measured and compared between WLAN and fixed LAN environments. The results show that 2.8 μs average clock offset can be reached on WLAN, while wired Ethernet connection enables 2.5 μs.

Evaluation of throughput estimation models and algorithms for WLAN frequency planning

Abstract: Frequency optimization is required to maximize the WLAN throughput in environments where several networks coexist. This paper evaluates four throughput estimation models and two optimization algorithms. Throughput is selected as the optimization criteria for channel assignment. Thus, the result of a throughput estimation model is used as an input for an optimization algorithm. The target is a frequency plan that maximizes multi-cell WLAN throughput. The throughput estimation models are based on radio spectrum usage, practical throughput measurements, WLAN protocol behavior, and theoretical coverage estimations. The models use separate functions for defining the minimum channel distance. In the evaluation, Genetic Algorithm (GA) and a distributed optimization algorithm produce the final frequency plan. A dedicated simulator has been implemented for comparing the throughput estimation models. Usage of a throughput estimation model for frequency optimization in a real WLAN implementation has also been evaluated with a hardware prototype. As overall simulation results, the evaluated throughput estimation models did not produce significant WLAN throughput improvements compared to each other. Still, the selection of the throughput estimation model and optimization algorithm pair is significant, since certain combinations cause poor results.

Genetic Algorithm to Optimize Node Placement and Configuration for WLAN Planning

Abstract: This paper presents a novel algorithm to rapidly create a high quality network plan for IEEE 802.11 based WLAN according to assigned design requirements. The algorithm uses a Genetic Algorithm (GA) to explore the design space, and a IEEE 802.11 rate adaptation aware QoS estimation functionality to provide feedback for the algorithm and for a network designer. The algorithm selects AP devices, locations, antennas, as well as AP configuration including transmission power and frequency channel. The algorithm was used in WLAN planning for a suburb, which is under development in Tampere-Lempaala area in Finland. Compared to manual network planning, the developed algorithm was able to create a network plan with 133 % capacity, 98 % coverage, and 93 % cost. Manually the corresponding network planning took hours, whereas the algorithm computation time was 15 minutes.

Wireless Mesh Networks Design — A Survey

Abstract: With the advances in wireless technologies and the explosive growth of the Internet, wireless networks, especially Wireless Mesh Networks (WMNs), are going through an important evolution. Designing efficient WMNs has become a major task for networks operators. Over the last few years, a plethora of studies has been carried out to improve the efficiency of wireless networks. However, only a few studies are related to WMNs design and are mainly concerned with protocol design and routing metrics optimization. In this paper, we survey different aspects of WMNs design and examine various methods that have been proposed either to improve the performance of an already deployed network or to improve its performance by a careful planning of its deployment.

INSIDE Windows NT

Abstract: This tutorial and reference sets out to instruct users in organizing and managing multiple tasks, and multiple programs, in Windows. It focuses on sharing and transferring data and graphics between Windows applications, either using a single computer, or by sharing across a network.

An Implementation of IEEE 1588 Over IEEE 802.11b for Synchronization of Wireless Local Area Network Nodes

Abstract: IEEE 1588 is a new standard to synchronize independent clocks running on separate nodes of a distributed measurement and control system. It is intended for high-accuracy implementations on compact systems such as a single subnet. This paper examines potential accuracy limitations introduced by the physical layer of the IEEE 802.11b wireless local area network. Experimental results are presented that show that these limitations do not preclude clock-synchronization accuracy of several hundred nanoseconds.

Time synchronization, deterministic data delivery and redundancy for cascaded nodes on full duplex ethernet networks

Abstract: A method and circuit for precisely synchronizing clocks in separate nodes on a communication network is provided by adjusting timestamps and related data in network messages. The circuit will allow a daisy-chain connection of the nodes and will forward time synchronization frames while accounting for delays in a manner that does not use boundary clocks, but does not depart from the IEEE 1588 standard protocol. The delays will be added on the fly to synchronization packets and the IP checksum and frame CRC will be adjusted. Deterministic data delivery and redundant data paths are also provided in a full duplex Ethernet network.