The effects of microwave oven over the IEEE 802.11 FHSS wireless LAN card

[[abstract]]We have investigated the effects of microwave ovens over the IEEE 802.11 FHSS wireless LAN card. The measured MAC frame error rate (FER) is affected by the microwave ovens. The signal spectrum radiated from the microwave oven can be used to verify the measured FER data. The performance of the specific bands assigned to some geographic locations in the IEEE 802.11 standard have been discussed in the paper. From these measurement results we can obtain that the performance of some channels within the IEEE 802.11 FHSS wireless LAN card can be seriously deteriorated. Therefore, the location of the microwave oven and the specific channels for the wireless LAN card should be pre-determined according to the experience guideline.[[conferencetype]]國際[[conferencedate]]19991018~19991022[[booktype]]紙本[[conferencelocation]]Beijing, Chin

Design and analysis of MAC protocols for wireless networks

During the last few years, wireless networking has attracted much of the research and industry interest. In addition, almost all current wireless devices are based on the IEEE 802.11 and IEEE 802.16 standards for the local and metropolitan area networks (LAN/MAN) respectively. Both of these standards define the medium access control layer (MAC) and physical layer (PHY) parts of a wireless user. In a wireless network, the MAC protocol plays a significant role in determining the performance of the whole network and individual users. Accordingly, many challenges are addressed by research to improve the performance of MAC operations in IEEE 802.11 and IEEE 802.16 standards. Such performance is measured using different metrics like the throughput, fairness, delay, utilization, and drop rate. We propose new protocols and solutions to enhance the performance of an IEEE 802.11 WLAN (wireless LAN) network, and to enhance the utilization of an IEEE 802.16e WMAN (wireless MAN). First, we propose a new protocol called HDCF (High-performance Distributed Coordination Function), to address the problem of wasted time, or idle slots and collided frames, in contention resolution of the IEEE 802.11 DCF. Second, we propose a simple protocol that enhances the performance of DCF in the existence of the hidden terminal problem. Opposite to other approaches, the proposed protocol attempts to benefit from the hidden terminal problem. Third, we propose two variants of a simple though effective distributed scheme, called NZ-ACK (Non Zero-Acknowledgement), to address the effects of coexisting IEEE 802.11e EDCA and IEEE 802.11 DCF devices. Finally, we investigate encouraging ertPS (enhanced real time Polling Service) connections, in an IEEE 802.16e, network to benefit from contention, and we aim at improving the network performance without violating any delay requirements of voice applications

PLFC: the packet length fuzzy controller to improve the performance of WLAN under the interference of microwave oven

[[abstract]]We design a novel fuzzy controller to dynamically adjust the packet length to protect against the interference from microwave oven over the IEEE 802.11 FHSS (frequency hopping spread spectrum) wireless LAN card. The idea of adjusting the packet length under the noise environment from the measurement results about the effects of microwave ovens over the wireless LAN card is referred by Lee, Sheu, Chen, Yu and Huaung (see APCC/OECC'99, p.817-820, 1999). Simulation results show that the designed fuzzy controller can effectively improve the transmission performance in terms of network throughput[[abstract]]In this paper, we have investigated the effects of microwave ovens over the IEEE 802.11 FHSS (Frequency Hopping Spread Spectrum) wireless LAN card. The measured MAC Frame Error Rate (FER) and UDP Packet Error Rate (PER) are affected by the microwave ovens. From these measurement results we know that the performance of some channels within the IEEE 802.11 FHSS wireless LAN card can be seriously deteriorated. Furthermore, decreasing the packet length would improve the transmission performance from the PER measurement results. Therefore, we design a novel fuzzy controller to dynamically adjust the packet length to against the interference from microwave oven. Simulation results show that the designed fuzzy controller can effectively improve the transmission performance in terms of throughput.[[sponsorship]]教育部; 淡江大學 資訊工程系; 行政院國家學委員會工程處[[conferencetype]]國內[[conferencetkucampus]]淡水校園[[conferencedate]]19991220~19991221[[booktype]]紙本[[conferencelocation]]臺北縣, 臺

Spectrum Utilization and Congestion of IEEE 802.11 Networks in the 2.4 GHz ISM Band

Wi-Fi technology, plays a major role in society thanks to its widespread availability, ease of use and low cost. To assure its long term viability in terms of capacity and ability to share the spectrum efficiently, it is of paramount to study the spectrum utilization and congestion mechanisms in live environments. In this paper the service level in the 2.4 GHz ISM band is investigated with focus on todays IEEE 802.11 WLAN systems with support for the 802.11e extension. Here service level means the overall Quality of Service (QoS), i.e. can all devices fulfill their communication needs? A crosslayer approach is used, since the service level can be measured at several levels of the protocol stack. The focus is on monitoring at both the Physical (PHY) and the Medium Access Control (MAC) link layer simultaneously by performing respectively power measurements with a spectrum analyzer to assess spectrum utilization and packet sniffing to measure the congestion. Compared to traditional QoS analysis in 802.11 networks, packet sniffing allows to study the occurring congestion mechanisms more thoroughly. The monitoring is applied for the following two cases. First the influence of interference between WLAN networks sharing the same radio channel is investigated in a controlled environment. It turns out that retry rate, Clear-ToSend (CTS), Request-To-Send (RTS) and (Block) Acknowledgment (ACK) frames can be used to identify congestion, whereas the spectrum analyzer is employed to identify the source of interference. Secondly, live measurements are performed at three locations to identify this type of interference in real-live situations. Results show inefficient use of the wireless medium in certain scenarios, due to a large portion of management and control frames compared to data content frames (i.e. only 21% of the frames is identified as data frames)

Improving multiple broadcasting of multimedia traffic in wireless ad-hoc networks

The increasing use of multimedia streaming applications in addition with advent of internet television and radio, demands from today's wireless networks to handle with reliability multiple broadcasting and multicasting sources. However, the way that 802.11 standard, which is the primary technology in wireless networking, handle this type of traffic raises a series of problems mainly related to the lack of an effective feedback mechanism. This lack in turn, limits the capability of random backoff process to eliminate collisions and reduce reliability and fairness. This inherited drawback of the standard is affecting the way broadcast and multicast traffic is transmitted as well as the overall performance of the network. In this paper initially we are highlighting the drawback of the IEEE 802.11 MAC algorithm in handling multiple stations “media type” data broadcasting in an ad-hoc wireless network. Then, we propose two different approaches in alleviating these problems. The first approach is the simple linear increase of the contention window (CW) while the second propose a linear increase of the CW implementing an exclusive backoff number allocation (EBNA) algorithm. In addition we are modifying the 802.11 medium access control (MAC) algorithm to use the clear to send to self (CTS-to-Self) protection mechanism prior to every transmission. Both the above techniques are simulated and compared with the classic 802.11 MAC. The results show that the overall performance of the network can be improved using these alternative MAC methods