Cleaning and inspection of pipelines and gun barrels are crucial for ensuring safety and integrity to extend their lifespan. Existing automatic inspection approaches lack high robustness, as well as portability, and have movement restrictions and complexity. This study presents the design and development of a scalable, comprehensive automated inspection, cleaning, and evaluation mechanism (CAICEM) for large‐sized pipelines and barrels with diameters in the range of 105 mm–210 mm. The proposed system is divided into electrical and mechanical assemblies that are independently designed, tested, fabricated, integrated, and controlled with industrial grid controllers and processors. These actuators are suitably programmed to provide the desired actions through toggle switches on a simple housing subassembly. The stress analysis and material specifications are obtained using ANSYS to ensure robustness and practicability. Later, on‐ground testing and optimization are performed before industrial prototyping. The inspection system of the proposed mechanism includes barrel‐mounted and brush‐mounted cameras with sensors utilized to keep track of the pipeline deposits and monitor user activity. The experimental results demonstrate that the proposed mechanism is cost‐effective and achieves the desired objectives with minimum human efforts in the least possible time for both smooth and rifled large‐diameter pipes and barrels.

Aggregation-enabled wireless local area networks (WLANs) have an automatic repeat-request (ARQ) mechanism called a block acknowledgement window (BAW), which has a significant impact on frame aggregation size, throughput, and delay under noisy channel conditions. While accurate estimations of network performance are essential for traffic engineering and guaranteed quality of service, the existing mathematical modeling approaches do not include BAW operations, and thus, are not applicable to aggregation-enabled WLANs with BAW mechanism. In this paper, we propose a new and accurate Markov chain model to estimate the average aggregation size resulting from BAW operations under noisy channel conditions. The obtained average aggregation size is used in the proposed enhanced performance model of aggregation-enabled WLANs. Our numerical and simulation analysis shows that, for 50 nodes transmitting saturated uplink traffic on a channel with a packet error rate (PER) of 0.25, ignoring the BAW operations when modeling the current protocol results in throughput and access delay errors as high as 55 and 77 percent, respectively; but the proposed enhanced model, which captures the BAW's impact, produces less than 2.5 percent errors in throughput and access delay estimations.

In existing PMIP-SAE based mobile networks, all the communication traffic go through the centralized Local Mobility Anchor (LMA). Hence the central node, LMA, suffers from huge packet processing overhead and the traffic is delivered via non-optimal routes. In order to overcome these drawbacks, we apply the localized routing to mobile networks based on PMIP-SAE mobility management scheme, while introducing additional control messages of Localized Routing Initiation (LRI) and Local Routing Acknowledgment (LRA). Numerical analysis shows that our proposed scheme performs better than the existing scheme in packet delivery cost, tunneling overhead, and throughput.

For group-based mobility management in 6LoWPAN-based wireless body area networks (WBAN), some schemes using the Proxy Mobile IPv6 (PMIP) have been proposed. However, the existing PMIP-based mobility schemes tend to induce large registration delay and handover delay. To overcome such limitations, we propose a new distributed group-based mobility management scheme, in which the Local Mobility Anchor (LMA) function is implemented by each Mobile Access Gateway (MAG) and the handover operation is performed between two neighboring MAGs without the help of LMA. Besides, each MAG maintains the information of the group of mobile sensors and aggregates the Authentication-Authorization-Accounting (AAA) query messages for a group of mobile sensors as a “single” message to decrease the control overhead. By numerical analysis, it is shown that the proposed scheme can reduce the registration and handover delays, compared to the existing PMIP-based mobility schemes.

Link adaptation technologies, such as Adaptive Modulation and Coding (AMC) and Multiple-Input-Multiple-Output (MIMO), are used in advanced wireless communication systems to achieve high spectrum efficiency. Communication performance can be improved significantly by adaptive transmissions based on the quality of received signals, i.e., the signal-to-interference-plus-noise ratio (SINR). However, for multihop wireless communications, most link scheduling schemes have been developed under simplified interference models that do not account for accumulative interference and cannot fully exploit the recent advances in PHY-layer communication theory. This paper focuses on developing link scheduling schemes that can achieve optimal performance under the SINR model. One key idea is to treat an adaptive wireless link as multiple parallel virtual links with different signal quality, building on which we develop throughput-optimal scheduling schemes using a two-stage queueing structure in conjunction with recently developed carrier-sensing techniques. Furthermore, we introduce a novel three-way handshake to ensure, in a distributed manner, that all transmitting links satisfy their SINR requirements. We evaluate the proposed schemes through rigorous analysis and simulations.

In wireless sensor networks, the routing control overhead could be large because multiple relays are involved in the routing operation. In order to mitigate this problem, a promising solution is to use tier-based anycast protocols. The main shortcoming of these protocols is that they can consume a much greater amount of energy as compared with other competing protocols using deterministic routing. In this paper, we analyze, in depth, a tier-based anycast protocol and develop a new technique of improving network lifetime. Our solution is guided by our analytic framework that consists of subtiering and a new forwarding protocol called 'scheduling controlled anycast protocol'. We formulate the problem for finding an optimal duty cycle for each tier with a delay constraint as a minimax optimization problem and find its solution, which we show is unique. From the analytical results, we find that the network lifetime can be significantly extended by allocating a different duty cycle adaptively for each tier under a delay constraint. Through simulations, we verify that our duty cycle control algorithm enhances the network lifetime by approximately 70% in comparison with an optimal homogeneous duty cycle allocation. Copyright © 2012 John Wiley & Sons, Ltd.

In-network aggregation has become a promising technique for improving the energy efficiency of wireless sensor networks. Aggregating data at various nodes in the network results in a reduction in the amount of bits transmitted over the network, and hence, saves energy. In this paper, we focus on another important aspect of aggregation, i.e., delay performance. In conjunction with link scheduling, in-network aggregation can reduce the delay by lessening the demands for wireless resources and thus expediting data transmissions. We formulate the problem that minimizes the sum delay of sensed data, and analyze the performance of optimal scheduling with in-network aggregation in tree networks under the node-exclusive interference model. We provide a system wide lower bound on the delay and use it as a benchmark for evaluating different scheduling policies. We numerically evaluate the performance of myopic and non-myopic scheduling policies, where myopic one considers only the current system state for a scheduling decision while non-myopic one simulates future system states. We show that the one-step non-myopic policies can substantially improve the delay performance. In particular, the proposed non-myopic greedy scheduling achieves a good tradeoff between performance and implementability.

In this letter, we propose a power-based call admission control (CAC) scheme to accommodate multiclass traffic by directly extending the number-based CAC scheme in multicode CDMA networks, and develop some related mathematical properties. Against the conventional findings, we demonstrate that complete partitioning (CP) of the received signal power at a basestation for each traffic class can be an approach as useful as complete sharing (CS) in accommodating an appropriate number of users. The main advantage of CP scheme over CS scheme is its simplicity in resource management

Opportunistic scheduling provides an important capability of resource management for wireless systems by taking advantage of multiuser diversity, allowing delay variation in delivering data packets. Our opportunistic scheduling aims at maximizing the utility which is usually expressed as a function of user throughput. In this paper we derive an off-line optimal scheduling policy by optimization theory, and show that the policy is also optimal in opportunistic scheduling. We extend the scheduling policy by adding QoS requirements for each user. To do so, we classify opportunistic schedulers according to QoS constraints. Their optimalities are also proved through mathematical analysis. To obtain optimal scheduling policy, the parameters related to QoS should be computed, so we propose a practical algorithm for parameter adaptation and verify its performance through simulations. The results confirm that our considered opportunistic schedulers show good fairness performance and guarantee each user's QoS without any difficulty in implementation.

We introduce a utility-based radio resource management technique for multicell wireless packet networks. Assuming each base station operates to maximize its own cell utility, we try to maximize the system utility which is defined as the sum of each cell utility. By using the downlink transmit power of each base station as a control variable, we formulate a problem of system utility maximization. However, the problem is intractable because it contains non-convex functions, and, accordingly, the complexity is too high. Therefore, we first analyze a simple two-cell problem and take an intuitive approach to find its optimal solution. We extend this intuition to a general multi-cell problem and devise a simple heuristic algorithm that requires a light overhead of signaling between neighboring base stations. Through simulations, we compare, in terms of utility gain, our proposed heuristic algorithm with two competing schemes, optimal power allocation and maximum power allocation. As expected, the optimal allocation scheme shows the best performance but cannot be applied to real multi-cell problems due to its intractable complexity. Our proposed heuristic algorithm has very low complexity and its performance lies between the optimal allocation and maximum allocation schemes.

CDMA systems have a trade-off relationship between the frame error rate (FER) and the number of accepted users. Therefore, the call admission control (CAC) scheme is essential for guaranteeing the FER below the required value, which is the measure of the quality of service (QoS) in the frame level. In cellular networks, the dropping probability of handoff calls is another critical measure for QoS in the call level. There has been, nevertheless, little concern for CAC schemes guaranteeing these QoS requirements simultaneously in the CDMA cellular networks. In this paper, we propose CAC that track the time-varying capacity of CDMA systems by estimating the distribution of the total received power at a base station, thereby realizing the bandwidth reservation scheme to meet the QoS requirement for handoff calls in the call level.

An important quality-of-service (QoS) issue in wireless multimedia networks is how to control handoff drops. In this paper, we propose admission control algorithms that adaptively control the admission threshold in each cell, in order to keep the handoff dropping probability below a pre-defined level. The admission threshold is dynamically adjusted based on handoff dropping events. We first present a simple admission control scheme which brings out an important performance evaluation criterion - inter-cell fairness - and serves as a reference point. We then investigate the inter-cell unfairness problem and develop two enhanced schemes to overcome this problem. The performance of these protocols is benchmarked and compared with other competitive schemes. The results indicate that our schemes perform very well while, in addition, achieving significantly reduced complexity and signaling load.

In this paper, we consider a CDMA cellular network that has signal power as its scare resource and uses the multicode transmission scheme to support multiclass calls with different QoS requirements. By simply extending the number-based scheme to accommodate multiclass traffic, we present a power-based call admission control scheme. Contrary to the general fact that complete sharing (CS) achieves better utilization than complete partitioning (CP), our finding in this paper is somewhat unique. That is, the CP of signal power for each traffic class can accommodate a reasonably high number of users when compared with CS. This result allows us to use CP which is much easier than CS in terms of resource management. By adopting the CP technique for resource reservation in wireless CDMA networks, we can guarantee QoS of calls in terms of handoff drops with minimal complexity.