Timo Vanhatupa

Genetic Algorithm to Optimize Node Placement and Configuration for WLAN Planning

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

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

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

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

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.

Multihop IEEE 802.11b WLAN Performance for VoIP

This paper evaluates the performance of IEEE 802.11b WLAN for supporting multihop voice over IP (VoIP) service. Evaluation is carried out using the NS-2 network simulator and the mean opinion score (MOS) as a criteria for measuring the quality of a VoIP connection. The results show that the mean number of hops between a VoIP transmitter and receiver has the main effect on the number of calls with acceptable quality. On a small network where connections cause interference to each other already three hops cause problems. The mean number of hops can be decreased with a supporting access point (AP) infrastructure. Also the type of interfering traffic affects. The voice quality in VoIP is sensitive to transmission losses, and VoIP cannot compete equally with high data rate applications

Windows NT software design and implementation for a wireless LAN base station

This paper introduces the architecture of a base station designed for a new Wireless Local Area Network (WLAN). The emphasis is on the software but also backgrounds for the design choices made are discussed. The main design objective has been to develop a simple and low-cost system while maintaining suitability for a large variety of applications, ranging from wireless sensors to multimedia workstations. A base station is implemented by attaching a custom WLAN adapter card into a PC. The network adapter consists of a custom wireless Medium Access Control (MAC) protocol and a standard low-power radio subsystem. The PC hosts other wireless network related functions, such as management of a wireless cell and bridging of data between the wireless network and a wired LAN. Currently, a demonstrator network is being implemented. Components implemented for a base station contain the network adapter card, a Windows NT device driver, and a management application that is a user mode program needed for configuring and managing the network interface hardware and the MAC protocol. In addition, a Windows NT protocol driver has been developed for implementing the data exchange between the device driver and the management application.

Frequency management tool for multi-cell WLAN performance optimization

Careful configuration of frequencies for WLAN access points (AP) is crucial for ensuring the optimal performance of the network. Thus, advanced tools for WLAN frequency management tasks are needed. This paper presents a practical tool for the frequency management in IEEE 802.11 WLANs. The tool minimizes the interference between APs and consequently maximizes the effective capacity of the network. It also contains a graphical user interface (GUI) showing an illustrative view of the network state in frequency domain. The tool has been designed for administrators of medium and large WLAN networks, such as used in companies, airports, and campus areas. In the presented case, the throughput of the optimized network was 60 % higher compared to the original network with random channels

Architecture for a Windows NT wireless LAN multimedia terminal

The support for multimedia services in wireless access networks is challenging to implement, due to an unreliable and bandwidth-limited wireless medium. In addition, the widely used applications and protocols generally lack the support for quality-of-service (QoS) parameters. This paper presents the architecture of a multimedia wireless LAN terminal. The terminal is implemented using a custom network demonstrator platform connected to a Windows NT workstation. The system provides a separate management plane for configuring the service parameters of a proprietary wireless medium access control (MAC) protocol. Also, native applications that are capable of accessing the MAC QoS parameters directly are supported.

Design of a Manageable WLAN Access Point

This paper presents the design and prototype implementation of a manageable WLAN Access Point (mAP). mAP has been developed for managing WLAN Quality of Service (QoS), frequency selection, client configuration, and for collecting a wide range of management information. The prototype is implemented using a Linux platform. With the presented architecture, the mAP functionality can be easily extended by adding new management functions and automated services.