Frank Haizhon Li

On optimizing backoff counter reservation and classifying stations for the IEEE 802.11 distributed wireless LANs

In this paper, we propose a novel contention-based protocol called backoff counter reservation and classifying stations for the IEEE 802.11 distributed coordination function (DCF). In the proposed scheme, each station has three states: idle, reserved, and contentious. A station is in the idle state if it has no frame ready to transmit. A station is in the reserved state if it has a frame ready to transmit and this frames backoff counter has been successfully announced through the previous successfully transmitted frame so that other stations know this information. A station is in the contentious state if it has a frame ready to transmit, but this frames backoff counter has not been successfully announced to other stations. All the stations in the idle state, the reserved state, and the contentious state form an idle group, a reserved group, and a contentious group, respectively. Two backoff schemes are proposed in the BCR-CS protocol based on the number of stations in the contentious group including the optimal pseudo-p-persistent scheme. The proposed schemes are compared with the DCF and the enhanced collision avoidance (ECA) scheme in the literature. Extensive simulations and some analytical analysts are carried out. Our results show that all proposed schemes outperform both the DCF and the ECA, and the BCR-CS with optimal pseudo-p-persistent scheme is the best scheme among the four schemes

Bandwidth Sharing Schemes for Multimedia Traffic in the IEEE 802.11e Contention-Based WLANs

Bandwidth allocation schemes have been well studied for mobile cellular networks. However, there is no study about this aspect reported for IEEE 802.11 contention-based distributed wireless LANs. In cellular networks, bandwidth is deterministic in terms of the number of channels by frequency division, time division, or code division. On the contrary, bandwidth allocation in contention- based distributed wireless LANs is extremely challenging due to its contention-based nature, packet-based network, and the most important aspect: only one channel is available, competed for by an unknown number of stations. As a consequence, guaranteeing bandwidth and allocating bandwidth are both challenging issues. In this paper, we address these difficult issues. We propose and study nine bandwidth allocation schemes, called sharing schemes, with guaranteed Quality of Service (QoS) for integrated voice/video/data traffic in IEEE 802.11e contention-based distributed wireless LANs. A guard period is proposed to prevent bandwidth allocation from overprovisioning and is for best-effort data traffic. Our study and analysis show that the guard period is a key concept for QoS guarantees in a contention-based channel. The proposed schemes are compared and evaluated via extensive simulations.

Handbook on Sensor Networks

Sensor networks have many interesting applications with great utility; however, their actually deployment and realization rely on continuous innovations and solutions to many challenging problems. Thus, sensor networks have recently attracted the attention of many researchers and practitioners. The compilation of the Handbook on Sensor Networks will meet the demand of the sensor network community for a comprehensive reference and summary of the current state of the area. The Handbook on Sensor Networks is a collection of approximately 40 chapters on sensor network theory and applications. The book spans a wide spectrum and includes topics in medium access control, routing, security and privacy, coverage and connectivity, modeling and simulations, multimedia, energy efficiency, localization and tracking, design and implementation, as well as sensor network applications.

Variable bit rate VOiP in IEEE 802.11e wireless LANs

WLANs have become a ubiquitous networking technology deployed everywhere. Meanwhile. VoIP is one popular application and a viable alternative to traditional telephony systems due to its cost efficiency. VoIP over WLAN (VoWLAN) has been emerging as an infrastructure to provide low-cost wireless voice services. However, VoWLAN poses significant challenges due to the characteristics of contention-based protocols and wireless networks. In this article we propose two mechanisms to provide quality of service for variable bit rate VoIP in IEEE 802.11e contention-based channel access WLANs: access time-based admission control and access point dynamic access. Simulation results are conducted to study these schemes.

Handbook of Security and Networks

This valuable handbook is a comprehensive compilation of state-of-art advances on security in computer networks. More than 40 internationally recognized authorities in the field of security and networks contribute articles in their areas of expertise. These international researchers and practitioners are from highly-respected universities, renowned research institutions and IT companies from all over the world. Each self-contained chapter covers one essential research topic on security in computer networks. Through the efforts of all the authors, all chapters are written in a uniformed style; each containing a comprehensive overview, the latest pioneering work and future research direction of a research topic.

Contention-based QoS MAC mechanisms for VBR VoIP in IEEE 802.11e wireless LANs

In this paper, We propose two contention-based medium access control (MAC) mechanisms to provide quality of service (QoS) for variable bit rate (VBR) voice over IP (VoIP) in IEEE 802.11e contention-based channel access (EDCA) wireless LANs (WLANs): Access time-based admission control (ATAC) and access point dynamic access (AP-DA). Simulation results indicate that the proposed mechanisms offer a satisfactory solution for QoS of VBR VoIP; the ATAC algorithm outperforms the EDCA and significantly improves QOS of VBR VoIP sessions in terms of average delay and delay distribution; and the AP-DA algorithm effectively balances downlink and uplink VoIP sessions. Keywords-VoIP, QoS, IEEE 802.11e WLAN; Admission Control

Isolate Safe Area Detection for Rescue in Wireless Sensor Networks

Isolate safe area detection is significant for various applications of wireless sensor networks since it can provide precious information for the rescue crew to save trapped persons. We propose a centralized method to detect isolate safe areas via discovering holes in event areas. In order to shorten the detection delay, a distributed method is also studied. Detecting isolate safe areas in a building is addressed specially since the regular detecting method is not applicable. Our simulation results show that the distributed method can detect all isolate safe areas in acceptable short delay.

Dynamic Bandwidth Partition with Finer-Tune (DP-FT) Scheme for Multimedia IEEE 802.11e WLANs

In mobile cellular networks, bandwidth is deterministic in terms of number of channels by frequency division, time division, or code division. On the other hand, bandwidth partition schemes in the contention-based medium access control (MAC) in distributed wireless LANs are extremely challenging due to the contention-based nature. In this paper, we propose and study a dynamic bandwidth partition with finer-tune (DP-FT) scheme for integrated voice/video/data traffic in the IEEE 802.11e wireless LANs.