A novel approach based on proximal policy optimization (PPO) combined with meta-learning is proposed in this paper to effectively address the path-planning optimization problem, enabling the generation of a safe, feasible, and optimal path for an autonomous driving system (ADS). Our proposed approach aims to autonomously and efficiently generate an obstacle-free and optimal path for ADS in real-time. To achieve this, we first formulate a path-planning optimization problem to find the optimal and safe trajectory over a planning horizon while minimizing the composite cost function of the path. Then, our PPO-Meta learning-based approach is proposed to solve this problem, leveraging meta-learning and roadside unit (RSU) assisted global information to adapt to unseen scenarios quickly. Via simulations, we demonstrate that our proposed approach improves the average success rate, average navigation time, and average safety score by up to 26.98%, 11.02%, and 16.11%, respectively, compared to the closely related approaches in the literature.

In this paper, a machine-learning based prediction is applied to detect the congested roads to occur in the future, future number of vehicles, future density of the road, etc. Further working with the rerouting strategy, the alternative route can be found for vehicles so that the travel time can be shortened effectively and the traffic congestion can be alleviated greatly. Through simulations, we demonstrate that our proposed mechanism exhibits better performance with more than 10.1% improvement in the average travel time as compared to the closely related mechanisms in the literature.

Traditional beaconless geographical routing (BGR) protocols perform poorly in a heterogeneous environment due to the consideration of location solely with an assumption of homogeneous transmission. Therefore, we propose a novel BGR with consideration of the locations of candidate forwarders and different transmission ranges. Our proposed protocol, namely, the heterogeneity-aware BGR (HA-BGR), is designed for a heterogeneous mobile sensor network (MSN), where the transmission ranges of mobile sensors are different. In HA-BGR, a node takes its distance, transmission range, and progress to the destination into consideration before setting itself to be a candidate next hop and remains active. Examined by analytical and extensive simulation results, HA-BGR not only needs fewer next-hop candidates but also achieves better performance in the end-to-end delivery ratio and latency as compared to the recently proposed convex-lense decision region BGR (CDR-BGR).

Under a high-density traffic environment in a vehicular ad hoc network (VANET), many safety messages will not be verified in time and then get dropped. To touch such an issue appropriately, we aim at improving the efficiency of message verification and the number of verified safety messages. In our proposed scheme, messages are properly classified and prioritized first so that more important basic safety messages can be verified earlier. To improve batch verification, a dynamic batch verification scheme with an adjustable batch size is designed accordingly. The batch size is halved when failures of batch verification occur consecutively over a certain threshold to improve the efficiency of batch verification. On the contrary, the batch size is doubled when successes of batch verification occur consecutively over a certain threshold to increase the messages in a batch to be verified. For a failure of batch verification, a divide-and-conquer approach is utilized to find the illegitimate message(s). Via analysis, the superiority of our design over some closely related schemes in terms of verification delay and number of verified basic safety messages etc. is successfully demonstrated. By simulation, performance of our design and some closely related schemes is further investigated in realistic scenarios.

Only two types of sleep cycles with two fixed sleep periods are defined in the standard of the discontinuous reception (DRX) mechanism in LTE/LTE-A. Explicitly, such a DRX mechanism is simple but lacks flexibility. To provide flexibility, two types of dynamic and adjustable DRX (DADRX) mechanisms are proposed and investigated in this paper. The first type of DADRX extends the number of types of sleep cycles through adding different pairs of sleep cycles with different sleep periods gradually. As for the second type of DADRX, it fixes the total number of types of sleep cycles like the first-type DADRX but further employs a set of level expanding probabilities to control probabilistically the possible pairs of sleep cycles that can be reached. To enable the analytical calculation, performance metrics for the proposed DADRX mechanisms are acquired, including average response delay and average long-term power consumption. Via both analytical and simulation approaches, we investigate the dynamics of performance for the proposed DADRX mechanisms extensively. We successfully show that these two proposed mechanisms can exhibit much more flexibility than the closely related mechanisms in the literature.

Installing a mobile sink on the public vehicle, which is a path-constrained vehicle, to collect data in a mobile sensor network can lower maintenance cost. However, immediately sending the data packet to the mobile sink when it arrives does not guarantee the shortest path, leading to high energy consumption. Meanwhile, immediately sending the data packet to the closest future position of the mobile sink can guarantee the shortest path. However, the mobile sensor node, which buffers the data packet while waiting for the mobile sink to arrive, may move away from the trajectory, resulting in reduction of delivery ratio. Therefore, we shall propose to delay sending the data packet until the mobile sink approaches the position with the shortest path. It not only guarantees the shortest path but also exhibits robustness with dynamic node mobility. Via extensive simulations, we show that our proposed scheme can effectively reduce energy consumption and increase delivery ratio even for the high-speed mobile sink.

Although many researches on network mobility management have been carried out, a binding update storm, signaling overheads, and so on still exist in the past proposals. To avoid the binding update storm and to support route optimization as well as intra-domain data communication, a specifically designed solution with a distributed manner is proposed in this paper. By applying the derived analytical results, we demonstrate that the proposed solution is able to significantly outperform the closely related work in the literature.Copyright © 2012 John Wiley & Sons, Ltd.

To provide strong and reliable support for voice (VO) and video (VI) traffic in IEEE 802.11e networks, a novel scheme called multiple periods scheduling (MPS) is proposed in this paper. Because the original HCCA mode does not support VI traffic properly, a special treatment for VI traffic is introduced by MPS. According to the requirements of both VO and VI traffic, the service period for each stream is assigned by MPS individually. With the aforementioned enhancement, MPS is able to increase the number of accepted traffic streams while keeping delay and jitter at acceptable levels. To analytically demonstrate the merit of the newly proposed scheme, the optimality of MPS is proven first. Then, the optimal values of service periods are provided theoretically. Finally, we show that significant performance improvement over the related schemes in the literature can be achieved by MPS.

Focusing on the issues of security and energy efficiency, we present an energy-efficient secure routing protocol for wireless sensor networks (WSNs). With the location and energy-aware characteristics for routing, our protocol gives a better delivery rate, energy balancing, and routing efficiency. In addition, the proposed security mechanism ensures the data authenticity and confidentiality in the data delivery. Evaluating the proposed protocol through both simulation and analysis, we show that our proposed protocol can significantly outperform the closest routing protocol and security mechanism.

Considering coverage, efficiency, and durability, three nonuniform node distribution strategies for a corona-based wireless sensor network (WSN) are proposed in this paper. To derive lower bounds on sensor nodes in coronas, we investigate the optimal node placement based on coverage. We then prove the feasibility of balanced energy depletion for a primitive geometric node distribution (GND) and a primitive energy proportional node distribution (EPND). Applying the optimal node placement and GND enables us to propose the first strategy (Strategy I) to reach completely balanced energy depletion. Combining the optimal node placement, EPND, and a simple switch scheduling, the second strategy (Strategy II) and the third strategy (Strategy III) are designed for a uniform-width corona model and a nonuniform-width corona model, respectively. Although balanced energy depletion may not be reached, Strategy II achieves the longest network lifetime and Strategy III requires the fewest sensor nodes among the three strategies. Finally, the performance investigation done by both analytical and simulation approaches exhibits the superiorities of the proposed strategies over the two closest strategies in the literature in terms of number of sensor nodes, network lifetime, and residual energy.

In this paper, a three-level P2P-SIP architecture employing SIP servers is proposed for the overlay network. The proposed architecture achieves global overlay and has the capability of solving the triangular routing problem for the domain-based P2P-SIP architecture to reach route optimization. Demonstrated by our numerical results, the proposed architecture can exhibit its superiorities over the closest-related architectures in the literature in terms of message rate, latency, and physical hops count.

How to simultaneously achieve fairness and quality-of-service (QoS) guarantee in QoS-oriented wireless local area networks (LANs) is an important and challenging issue. Targeting at this goal and jointly taking priority setting, fairness, and cross-layer design into account, four scheduling schemes designed for the QoS-oriented wireless LAN mainly based on concepts of deficit count and allowance are proposed in this paper to provide better QoS and fairness. Using multiple deficit count to interframe space (IFS) and allowance to IFS mappings for different priorities, enhanced distributed deficit round robin (EDDRR) and enhanced distributed elastic round robin (EDERR) schemes are designed to reduce (or even eliminate) possible collisions, while EDDRR with backoff interval and EDERR with backoff interval schemes still keep the backoff procedure but dynamically adjust backoff intervals for nonfailure events (the events excluding collisions and failed transmissions) depending on the priority setting and deficit count or allowance with a cross-layer design. Through extensive numerical examples, we show that the proposed schemes outperform the closest scheduling schemes in the literature and exhibit much better QoS as well as station-level and flow-level fairness.

A novel software-based time multiplexing (TM) coordination mechanism for the IEEE 802.11 wireless local area network (WLAN) is proposed in this paper. By using the TM mechanism which can be easily implemented on top of the distributed coordination function (DCF) at the access point (AP) with the best features of both point coordination function (PCF) and DCF, a higher priority is naturally set to voice services over data services. Finally, our simulation results demonstrate that the TM mechanism outperforms the pure DCF and the mixture of PCF and DCF in terms of end-to-end voice delay, number of supported voice sessions, and aggregate throughput.

High altitude platform stations (HAPSs) can be displaced by stratospheric winds. In this paper, a HAPS code division multiple access (CDMA) cellular system is considered, and the impact of platform displacement on both the cell deployment movement and the uplink and downlink capacity is examined under two types of multibeam antennas. One type is that the directions of the main lobes can be adapted to make cell centers stay unchanged during platform displacement; the other is with a fixed beam projection pattern at all times. From numerical results it is observed that the former is effective in minimizing cell deployment movement, whereas the latter is advantageous to avoid capacity variations.

When the system load is high or congestion occurs, a base station (BS) in the IEEE 802.16e metropolitan area network (MAN) is not able to transmit all buffered packets to mobile stations (MSs) within a frame interval, resulting in extra energy consumption for MSs to wake up for receiving pending packets. To save energy for such a situation, we first propose a scheduling- based delay-tolerant traffic indication message (D-TIM) scheme to enable a BS to properly schedule queued packets for non-real-time variable rate (NRT-VR) and best effort (BE) using information of delay threshold (DT), which can be derived from QoS parameters, and to determine the time offset between the frame in which an MS has to wake up and the frame containing a TIM message. With the time offset, MSs are able to wake up more precisely so that energy can be efficiently saved and less packet delay can be reached. Furthermore, two variants of D- TIM are also proposed for solving the problem of higher jitter to the unsolicited grant service (UGS). Through simulation, we demonstrate that D-TIM outperforms other related schemes in the literature in terms of energy efficiency and packet delay and the two variants reduce jitter greatly as compared to D-TIM while maintaining good energy efficiency and less packet delay.

Keeping a session connected as a mobile host traverses across networks is the responsibility of a handoff management protocol. An effective protocol should support various transport protocols, require minimum changes, and manage handoff with acceptable delay and signaling cost. In this paper, a handoff management architecture that utilizes application layer gateway (ALG) and network address translation (NAT) mechanisms based on the session initiation protocol (SIP) is proposed. In addition to supporting mobility for the TCP session, the proposed architecture also optimizes real-time handoff delay by reducing delays caused by layer independency and duplication address detection (DAD) procedure and head of train delay caused by sequential execution of handoff procedures at different layers with few changes to the existing protocols and infrastructure.

Two scheduling mechanisms called enhanced distributed deficit round robin with backoff interval (EDDRR-BI) and enhanced distributed elastic round robin with backoff interval (EDERR-BI) are proposed in this paper for the IEEE 802.11e wireless LAN. EDDRR-BI and EDERR-BI take both priority which is a mean to guarantee quality of service (QoS) and fairness simultaneously into account so that QoS and fairness can be well taken care. The idea behind the proposed mechanisms mainly relies on dynamic adjustment of the backoff interval according to priority, collision rate, and deficit count or allowance. Through numerical experiments, we demonstrate that the proposed mechanisms can reach station-level fairness as well as flow-level fairness within the same (among different) access category (categories). Of course, these mechanisms outperform the related schemes in the literature.

To guarantee seamless handoffs between access points (APs) is one of the most decisive factors in providing realtime applications such as voice over Internet protocol (VoIP) in IEEE 802.11 networks. It is because in wireless local area networks (WLANs) there is no specific control channel for executing a handoff process and a mobile station (MS) has to search for new APs from channel to channel by temporarily disconnecting its association with the old AP. While previous studies are mainly focused on how to reduce the handoff latency, in this paper a channel scanning algorithm is proposed to schedule suitable time for performing a handoff process efficiently. In the proposed algorithm, the voice activity is taken into consideration, and the handoff process is performed during silent periods. Extensive simulations are conducted to investigate the performance of the proposed algorithm in terms of the handoff success probability and the packet loss rate, and the results obtained in this paper can serve as a good reference for the system design.

In a cellular code division multiple access (CDMA) system, uplink capacity is limited by interference. For a ground-based CDMA system or a high altitude platform station (HAPS) CDMA system, the interference is contributed by users in the same cell and in other cells. In this paper, a novel scheme is proposed to reduce both the same-cell and other-cell interferences in a cellular CDMA system. The proposed scheme attempts to lower the required transmitting power for each user by integrating terrestrial base stations (BSs) with a HAPS to provide two separate paths for signal reception. Numerical results show that the total interference is significantly reduced and the uplink capacity is improved under the proposed scheme, compared to either a HAPS CDMA system or a ground-based CDMA system.

High altitude platform stations (HAPSs) are widely known as an alternative means to provide broadband applications and code division multiple access (CDMA) based international mobile telecommunications-2000 (IMT-2000) communications. Previous studies have shown that platform instability caused by stratospheric winds may lead to system level performance degradation. In this paper, we propose to combat this problem by using multiple HAPSs to provide diversity of signal reception. Though the proposed scheme would enhance the reliability of service provision, the required uplink transmitting power may need to be increased to ensure that every serving HAPS receives at least the target receive power. This will elevate the interference level and may adversely affect the uplink capacity. Numerical analysis is thus performed to investigate the impact of using multiple HAPSs on the uplink capacity.

This paper aims at proposing a dynamic resource reservation scheme to enhance wireless multicasting protocols run in the hierarchical mobile IP version 6 (HMIPv6) based networks. The novelty of this scheme relies on techniques of dynamic resource reservation, priority, pre-registration, and path prediction, which are used to improve wireless multicasting and guarantee service continuity. Through numerical examples, we demonstrate that the proposed scheme performs well in terms of robustness, adaptiveness, and quality of service (QoS) guarantee.

A mobile ad hoc network (MANET) is vulnerable to malicious attacks although it is suitable for various environments because of its rapid establishment. In order to set up a secured MANET, we should not only adopt encryption and authentication, but also equip each node with an intrusion detection system to detect malicious attackers. Focusing on intrusion detection, we propose an intrusion detection system that integrates a finite state machine (FSM) and a support vector machine (SVM) to analyze traffic patterns of MANETs. Shown by numerical examples, such an intrusion detection system is able to amend drawbacks of single-technique systems and enhance usage/right of normal users as well as security of MANETs.

In this paper, we consider the uplink capacity of an integrated high altitude platform station (HAPS)-terrestrial code division multiple access (CDMA) system in which sharing band overlay configuration is used. To increase system capacity, an enhancement is investigated by assuming that directional antenna is used for high mobility users to access to the HAPS. This will lead to a reduction of not only the interference from HAPS to terrestrial, but also the interference from terrestrial to HAPS as the uplink power to HAPS can accordingly be increased. Numerical results are obtained analytically and it is shown that the system capacity can be enhanced significantly under the proposed scheme

This paper investigates the impact on the power saving mechanism (PSM) of the cellular digital packet data (CDPD) caused by random frame errors and losses. To combat such random frame errors and losses, a selective repeat (SR) protocol of automatic repeat request (ARQ) protocols in charge of recovery of garbled/lost frames is combined with the original PSM of CDPD and then study the enhanced PSM and investigate the effect of channel conditions including bit error rate and frame loss probability as well as frame buffer size and window size of SR-ARQ to the PSM through numerical examples. The results provided in this paper are able to serve as guidelines on system design and parameter setting for CDPD when an imperfect channel is taken into consideration to reflect the realistic situation.

Two reliable multicast protocols for wireless local area networks (LANs) are proposed: a leader-based protocol with a sliding window, LBPW; a leader-based protocol with a sliding window and n-fold acknowledgement reduction, LBPR(n). They are based on a previously proposed leader-based protocol (LBP). Firstly, a pipelining technique is added into the LBP to form the LBPW so as to make frame transmission efficient. Then, an acknowledgement reduction scheme is incorporated into LBPW to form LBPR(n) to alleviate the ACK/NAK implosion problem. Through numerical examples done by a simulation approach, we demonstrate that these two reliable multicast protocols outperform LBP.

We propose dynamic channel allocation schemes, which employ techniques such as channel reservation, service priority and queueing strategies (with or without threshold control) etc. Using these techniques allows system designers to differentiate quality of service (QoS) requirements (e.g., new call blocking/handoff forced termination probability and delay) required by different types of service. Via the simulation approach, the improvements offered by different strategies under different parameter sets and different network situations are investigated. The results obtained in this paper provide system designers guidelines of how to provide an excellent channel allocation scheme and how to choose suitable parameters in the integrated GSM and GPRS system.

We investigate the departure process of an ATM output buffer intaking asymptotically second-order self-similar traffic using matrix-analytic technique. The results obtained include the marginal and joint distribution of interdeparture times. We show that output and input processes asymptotically possess the same tail and smoothing effect takes place only for traffic with small Hurst parameters.