The importance of wireless sensor networks in structural health monitoring is unceasingly growing, because of the increasing demand for both safety and security in the cities. The speedy growth of ...

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Wireless sensor network for structural health monitoring: A contemporary review of technologies, challenges, and future direction:

During the last years, the growth of wireless traffic pushed the wireless community to search for solutions that can assist in a more efficient management of the spectrum. Toward this direction, the operation of long term evolution (LTE) in unlicensed spectrum (LTE-U) has been proposed. Targeting a global solution that respects the regional regulations worldwide, 3GPP has published the LTE licensed assisted access (LAA) standard. According to LTE LAA, a listen before talk (LBT) procedure must precede any LTE transmission burst in the unlicensed spectrum. However, the proposed standard may cause coexistence issues between LTE and Wi-Fi, especially in the case that the latter does not use frame aggregation. Toward the provision of a balanced channel access, we have proposed mLTE-U that is an adaptive LTE LBT scheme. According to mLTE-U, LTE uses a variable transmission opportunity (TXOP), followed by a variable muting period. This muting period can be exploited by co-located Wi-Fi networks to gain access to the medium. In this paper, the system model of the mLTE-U scheme in coexistence with Wi-Fi is studied. In addition, mLTE-U is enhanced with a Q-learning technique that is used for autonomous selection of the appropriate combinations of TXOP and muting period that can provide fair coexistence between co-located mLTE-U and Wi-Fi networks. Simulation results showcase the performance of the proposed model and reveal the benefit of using Q-learning for self-adaptation of mLTE-U to the changes of the dynamic wireless environment, toward fair coexistence with Wi-Fi. Finally, the Q-learning mechanism is compared with conventional selection schemes showing the superior performance of the proposed model over less complex mechanisms.

https://biblio.ugent.be/publication/8566955/file/8566956.pdf

A Q-Learning Scheme for Fair Coexistence Between LTE and Wi-Fi in Unlicensed Spectrum

The use of directional antennas in millimeter-wave communication promises high spatial reuse at multi-gigabit-per-second data rates in dense wireless networks. Existing work studies such networks using commercial hardware but is limited to individual links. Moreover, such hardware typically allows for little or no control of the lower layers of the protocol stack. In this paper, We study the performance of dense millimeterwave deployments featuring up to eight stations. To this end, we use a practical IEEE 802.11ad millimeter-wave testbed that allows access to the lower layer parameters of each station. This enables us to analyze the impact of these parameters on upper layer performance. We study, for first time to our best knowledge, issues such as the impact of channel contention on the buffer size at the transport layer, the effect of frame aggregation, and the efficiency of spatial sharing. Our results show that using large buffer sizes with TCP is harmful due to channel contention despite the multi-gigabit-per-second data rates. Further, frame aggregation is only beneficial up to a certain level due to higher error rates for large frames. Finally, we also study delay, showing that the regular beacon transmission time can degrade performance.

Medium Access and Transport Protocol Aspects in Practical 802.11 ad Networks

As wireless technologies have been improving in recent years, a mobility management mechanism is required to provide seamless and ubiquitous mobility for end users who are roaming among points of attachment in wireless networks. Thus, Mobile IPv6 was developed by the Internet Engineering Task Force (IETF) to support the mobility service. However, Mobile IPv6 is unable to fulfill the requirements of real-time applications, such as video streaming service and voice over IP service, due to its high handover (HO) latency. To address this problem, Proxy Mobile IPv6 (PMIPv6) has been introduced by the IETF. In PMIPv6, which is a network-based approach, the serving network controls mobility management on behalf of the mobile node (MN). Thus, the MN is not required to participate in any mobility-related signaling. However, the PMIPv6 still suffers from lengthy HO latency and packet loss during a HO. This paper explores an elaborated survey on the HO procedure of PMIPv6 protocols and proposed approaches accompanied by a discussion about their points of weakness.

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A Survey on Proxy Mobile IPv6 Handover

To provide satisfactory Quality of Service (QoS) on the move, efficient mobility management is indispensable to provide mobile users with seamless and ubiquitous wireless connectivity. However, both the conventional centralized mobility architecture and the upcoming distributed mobility management face fundamental challenges such as sub-optimal routing, scalability, and so on. The emerging software-defined networking (SDN) architecture can efficiently manage network operations, and accordingly provides a new direction to address the challenges in mobility management. In this paper, we propose an SDN-based Mobility Management (SDN-MM) scheme to support seamless Intro/Inter domain handover with route optimization. SDN-MM decouples mobility management and packet forwarding functions by installing route optimizing and mobility control logics in an SDN controller, but exempting it from traffic redirecting. In SDN-MM, a comprehensive set of signaling operations are designed in order to provide transparent and efficient mobility support for ongoing sessions in each handover scenario, which prevents packet loss and tunneling overhead, and accordingly provide improved QoS to mobile users. For data communications, an SDN controller in SDN-MM pre-calculates the optimal end-to-end route before a handover, and decides whether to migrate traffic to the route by balancing the performance gain and the signaling overhead, which greatly improves bandwidth resource utilization. Finally, we develop a novel analytical model to evaluate the performance of SDN-MM, including signaling overhead, handover latency, and packet delivery cost. The simulation results have been provided to demonstrate that the proposed SDN-MM can greatly improve handover performance and maintain high resource utilization efficiency as well.

Mobility Management for Intro/Inter Domain Handover in Software-Defined Networks

The main goal of the IEEE 802.11n standard is to achieve a minimum throughput of 100 Mbps at the MAC service access point. This high throughput has been achieved via many enhancements in both the physical and MAC layers. A key enhancement at the MAC layer is frame aggregation in which the timing and headers overheads of the legacy MAC are reduced by aggregating multiple frames into a single large frame before being transmitted. Two aggregation schemes have been defined by the 802.11n standard, aggregate MAC service data unit (A-MSDU) and aggregate MAC protocol data unit (A-MPDU). As a consequence of the aggregation, new aggregation headers are introduced and become parts of the transmitted frame. Even though these headers are small compared to the legacy headers they still have a negative impact on the network performance, especially when aggregating frames of small payload. Moreover, the A-MSDU is highly influenced by the channel condition due mainly to lack of subframes sequence control and retransmission. In this paper, we have proposed an aggregation scheme (mA-MSDU) that reduces the aggregation headers and implements a retransmission control over the individual subframes at the MSDU level. The analysis and simulations results show the significance of the proposed scheme, specifically for applications that have a small frame size such as VoIP.

An Enhanced A-MSDU Frame Aggregation Scheme for 802.11n Wireless Networks

The timing and headers overheads of IEEE 802.11 PHY and MAC layers consume a large part of the chan-nel time leading to performance degradation especially at higher data rates. Several enhancements at both the PHY and MAC layers have been proposed in order to reduce these overheads and increase the channel utilization. A key enhancement is frame aggregation in which the timing and headers overheads are reduced by aggregating multiple frames into a single large frame and then transmit it in a single channel access. This paper addresses the frame aggregation techniques that have been proposed for the next generation wireless networks and the aggregation techniques that are adopted by IEEE 802.11n standard. It also high-lights the aggregation issues that need to be investigated in order to further enhance the frame aggregation performance.

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Frame aggregation in wireless networks: techniques and issues

As a network-based localized mobility management protocol, Proxy Mobile IPv6 (PMIPv6) enables a Mobile Host (MH) to roam within a localized domain without MH intervention in the mobility-related signalling. However, the PMIPv6 maintains MH mobility support in a restriction domain. Therefore, whenever the MH roams away from the PMIPv6 domain, its reachability status will be broken-down causing high handover latency and inevitable traffic loss for its communication session. This article proposes a proactive mechanism to mange the MH handover and maintain its data session continually across inter-PMIPv6-domains. The proposed mechanism introduces an intermediate global mobility anchor entity, called, which is responsible to coordinate MH handover as well as redirect its traffic across inter-PMIPv6-domains. Through various simulation evaluations, via ns-2, several experiments were conducted, revealing numerous results that verify the proposed mechanism superior performance over the conventional inter-PMIPv6-domain handover schemes in terms of handover latency, achieved throughput, protocol signalling cost and end-to-end traffic delivery latency.

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Enhancing inter-PMIPv6-domain for superior handover performance across IP-based wireless domain networks

Typical PMIPv6 supports mobility management for the Mobile Host (MH) in localized domains over variant Wireless Local Area Network technologies. The typical PMIPv6 adopted in reactive mode in which break-before-make technique may concern, which results in long disruption latency and inevitable data traffic loss that negatively affects MH's communication performance. This article proposes a proactive latency low handover mechanism, which corresponds to make-before-break technique in order to support MH's seamless and fast roaming in PMIPv6 network. The proposed mechanism proactively performs a pre-registration and pre-access authentication processes tightly together intended for the MH in advance of a handover situation involved in typical PMIPv6, thereby enabling the MH to re-configure its interface more quickly after a handover. Consequently, the associated mobility-related signallings along with their latencies are reduced significantly and the continuity of the MH communication session is granted. Furthermore, an efficient buffering technique with optimized functions is introduced at the MH's anchor mobility entity to prevent data traffic loss and save their transmission cost. Through various simulation evaluations via ns-2, we study and analyse different mobility aspects, such as handover latency, data traffic loss, throughput, end-to-end traffic delay, traffic transmission cost and signalling cost, with respect to different traffic sources like CBR-UDP and FTP-TCP. Several experiments were conducted, revealing numerous results that verify the proposed mechanisms' superior performance over existing scheme.

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Latency Low Handover Mechanism Considering Data Traffic Lost Preventing for Proxy Mobile IPv6 Over WLAN

In this paper, we study the impact of multi-radio multi-channel Wireless Mesh Networks (WMNs) characteristics on the performance of Expected Transmission Count based metrics (ETX-based). Many characteristics of multi-radio multi-channel WMNs such as channel switching, an absence of a direct connection between neighbors, and difficulty of measuring the packet loss probability in the both forward and reverse direction may affect the performance of ETX-based metrics in hybrid multi-radio multi-channel WMNs compared to static multi-radio multi-channel WMNs. Through simulation experiments, we compared the performance of ETX-based metrics with Hop count metric. The experiment result shows the superior improvement of hope count metrics over ETX-based metrics in terms of packet delivery ratio, goodput, and end-to-end delay. From the results, we concluded that major causes of the poor performance of ETX-based metrics in a multi-radio multi-channel WMNs are the extra delay caused by interface switching between channels and the inaccurate value of the ETX-based metrics.

Nor Asila Wati Abdul Hamid

Papers

An Enhanced A-MSDU Frame Aggregation Scheme for 802.11n Wireless Networks

Frame aggregation in wireless networks: techniques and issues

Enhancing inter-PMIPv6-domain for superior handover performance across IP-based wireless domain networks

Latency Low Handover Mechanism Considering Data Traffic Lost Preventing for Proxy Mobile IPv6 Over WLAN

Impact of the Hybrid Multi-channel Multi-interface Wireless Mesh Network on ETX-Based Metrics Performance