Transmission Timing Control Research Articles

Transmission Timing Control among Both Aperiodic and Periodic Flows for Reliable Transfer by Restricted Packet Loss and within Permissible Delay in Wireless Sensor Networks

Nowadays, in various wireless sensor networks, both aperiodically generated packets like event detections and periodically generated ones for environmental, machinery, vital monitoring, etc. are transferred. Thus, packet loss caused by collision should be suppressed among aperiodic and periodic packets. In addition, some packets for wireless applications such as factory IoT must be transferred within permissible end-to-end delays, in addition to improving packet loss. In this paper, we propose transmission timing control of both aperiodic and periodic packets at an upper layer of medium access control (MAC). First, to suppress packet loss caused by collision, transmission timings of aperiodic and periodic packets are distributed on the time axis. Then, transmission timings of delay-bounded packets with permissible delays are assigned within the bounded periods so that transfer within their permissible delays is possible to maximally satisfy their permissible delays. Such control at an upper layer has advantages of no modification to the MAC layer standardized by IEEE 802.11, 802.15.4, etc. and low sensor node cost, whereas existing approaches at the MAC layer rely on MAC modifications and time synchronization among all sensor nodes. Performance evaluation verifies that the proposed transmission timing control improves packet loss rate regardless of the presence or absence of packet's periodicity and permissible delay, and restricts average transfer delay of delay-bounded packets within their permissible delays comparably to a greedy approach that transmits delay-bounded packets to the MAC layer immediately when they are generated at an upper layer.

Dynamic Beacon Distribution Mechanism for Internet of Vehicles: An Analytical Study

In the last decade, with the arrival of the 5G communication technology and the increasing numbers of vehicles being connected to the internet, conventional vehicle ad-hoc networks (VANETs) are evolving towards the internet of vehicles (IoV), which makes the co-existence of IEEE 802.11p and 5G-based technologies very important for the design of a heterogeneous IoV system that takes advantage of both. The IEEE 802.11p standard is still the best candidate to support direct communications for safety critical services. In fact, both the ETSI ITS-G5 and the IEEE 1609 standard families adopt the IEEE 802.11p standard as a medium access control (MAC) mechanism, and they require vehicles to exchange periodic awareness messages to avoid dangerous situations. When the density of vehicles increases, the MAC layer will suffer from radio channel congestion problems, and this may affect the various VANET applications, especially safety applications. Therefore, the decentralized congestion control (DCC) mechanism has been specified by ETSI to mitigate the channel congestion; this was achieved by adapting the transmission parameters, such as the transmit power and data-rate. However, many research studies have demonstrated limitations and a low performance of DCC, especially when the channel load is extremely high. To deal with this, in this paper, we investigate a new promising technique, called the transmission timing control (TTC), to control the channel load for periodic cooperative awareness. It consists of spreading the transmissions over time in order to avoid contention on the transmission channel. The objective of the paper is to propose an analytical study to calculate the probability of successful transmission using TTC. The demonstrated results show the efficiency of our timing control-enabled scheme to deal with the channel load on top of different conditions.

Analysis of Congestion Control Mechanisms for Cooperative Awareness in IoV Environments

Traditional vehicle ad hoc networks (VANETs) have evolved toward the Internet of Vehicles (IoV) during the past ten years with the introduction of 5G communication technology and the growing number of vehicles linked to the Internet. The coexistence of IEEE 802.11p and 5G becomes critical to build a heterogeneous IoV system that benefits from both technologies, being that the IEEE 802.11p standard remains the best option for direct communications and safety-critical applications. The IEEE 1609 standard family and the ETSI ITS-G5 standard family both use the IEEE 802.11p standard as a MAC mechanism. To avoid dangerous situations, vehicles require the periodic exchange of awareness messages. With the increase in vehicle density, the MAC layer will suffer from radio channel congestion problems, which in turn will have a negative impact on the safety application requirements. Therefore, the decentralized congestion control (DCC) mechanism has been specified by ETSI to mitigate channel congestion; this was achieved by adapting transmission parameters such as transmit power and data rate. However, several studies have demonstrated that DCC has drawbacks and suffers from poor performance when the channel load is very high. This paper investigates a new promising DCC technique called transmission timing control (TTC), to reduce the channel load for periodic cooperative awareness. It consists of spreading the transmissions over time to avoid contention on the transmission channel. The objective of the paper is to propose an analytical study to calculate the probability of successful transmission using TTC. Obtained results showed a convergence between the applied experiments and our mathematical model, achieving an error margin of only 5%, which confirms the validity of the equation proposed.

Frequency Discrimination Method Using Asymmetric Transmission Time in FSK Radar

A frequency discrimination method based on transmission time control is proposed for effective absolute distance measurement using frequency-shift keying (FSK) radar. In FSK radar, each frequency is transmitted for different durations using an asymmetric control signal. The phase difference at each frequency is effectively obtained by counting the different numbers of samples obtained after envelope detection in the baseband signal. The proposed method can easily and rapidly distinguish the phase difference for each frequency. This makes it simple to measure the absolute distance up to the maximum unambiguous range. The absolute distance measured using FSK radar with a frequency spacing of 150 MHz showed an accuracy of 97.08% in the full unambiguous range. The distance measurement results prove that the proposed method using FSK radar is useful for presenting the maximum unambiguous range.

Ultra-low-latency 8K-video-transmission System Utilizing Whitebox Transponder with Disaggregation Configuration

The demand for low-latency transmission of large-capacity video, such as 4K and 8K, is increasing for various applications such as live-broadcast program production, sports viewing, and medical care. In the broadcast industry, low-latency video transmission is required in remote production, an emerging workflow for outside broadcasting. For ideal remote production, long-distance transmission of uncompressed 8K60p video signals, ultra-low latency less than 16.7 ms, and PTP synchronization through network are required; however, no existing video-transmission system fully satisfy these requirements. We focused on optical transport technologies capable of long-distance and large-capacity communication, which were previously used only in telecommunication-carrier networks. To fully utilize optical transport technologies, we propose the first-ever video-transmission system architecture capable of sending and receiving uncompressed 8K video directly through large-capacity optical paths. A transmission timing control in seamless protection switching is also proposed to improve the tolerance to network impairment. As a means of implementation, we focused on whitebox transponder, an emerging type of optical transponder with a disaggregation configuration. The disaggregation configuration enables flexible configuration changes, additional implementations, and cost reduction by separating various functions of optical transponders and controlling them with a standardized interface. We implemented the ultra-low-latency video-transmission system utilizing whitebox transponder Galileo. We developed a hardware plug-in unit for video transmission (VideoPIU), and software to control the VideoPIU. In the video-transmission experiments with 120-km optical fiber, we confirmed that it was capable of transmitting uncompressed 8K60p video stably in 1.3 ms latency and highly accurate PTP synchronization through the optical network, which was required in the ideal remote production. In addition, the application to immersive sports viewing is also presented. Consequently, excellent potential to support the unprecedented applications is demonstrated.

Energy-Efficient Resource Allocation in Radio-Frequency-Powered Cognitive Radio Network for Connected Vehicles

Radio-frequency-energy-powered cognitive radio network (RF-CRN) is being taken seriously in Connected Vehicles, especially in 5G network, which can better address the challenges of energy limitation and spectrum scarcity. However, the energy efficiency (EE) of the RF-CRN wherein multiple secondary users (SUs) share the same channel is rarely presented. In this article, we consider a RF-CRN in which SUs first harvest energy from RF signals originating from a primary network (PN) and then utilize the available energy in the battery to transmit data. Since all SUs can access the authorized spectrum for transmission simultaneously, co-frequency interference (Co-FI) occurs among SUs. Given the quality of service (QoS) requirement, our goal is to achieve the maximum EE of the RF-CRN by jointly optimizing transmission time and power control. To this end, a resource allocation scheme referred to as approximate convex policy for co-frequency interference (CO-ACP) is proposed. Specifically, the EE problem is firstly converted into a convex one by CO-ACP. Then, we utilize Frank-Wolfe (FW) and one-dimensional linear programming to obtain the optimal solution. Simulation results demonstrate that a tight lower-bound optimum solution for the non-convex EE maximization can be achieved by CO-ACP. Moreover, the CO-ACP provides meaningful system features, such as the number of SUs, energy harvesting efficiency, and the battery energy state of the SUs under different RF-CRN scenarios, providing a clear reference for future deployment of RF-CRN.

Adaptive Channel Selection and Transmission Timing Control for Simultaneous Receiving and Sending in Relay-Based UAV Network

Recently, the demand for technology that can wirelessly transmit images taken by unmanned aerial vehicles (UAVs) has increased. Relay transmission technology is attracting particular attention, as it can provide wireless transmission to remote locations even in environments lacking infrastructure. Here, we focus on further developing an existing relay transmission system, namely, the simultaneous reception and transmission method, using multiple frequency bands. In this method, a relay node receives data from a source node and simultaneously transmits data to a destination node using another channel. This technology has the advantages of high frequency utilization efficiency and a short transmission time; however, buffer overflow at the relay node may remain, which could contribute to video quality degradation. Thus, we propose a buffer control method involving two proposed elements: a channel selection method, and a transmission start timing control method. By applying these two methods, we show that the buffer overflow rate at the relay node is decreased, and the amount of data that can be received by the destination node is maximized within the assigned sub frame. Ultimately, these results can contribute to improving the quality of videos transmitted in real-time using relay transmission with UAVs.

Probe/PreAck: A Joint Solution for Mitigating Hidden and Exposed Node Problems and Enhancing Spatial Reuse in Dense WLANs

In dense wireless local area networks (WLANs), the primary causes of interference and hindrance to spatial reuse are the well-known hidden node problem (HNP) and the exposed node problem (ENP). In this paper, we propose a joint solution to these problems. The proposed mechanism, referred to as Probe/PreAck (PR/PA), utilizes the concept of a two-way handshake for efficient channel reservation and spatial reuse by means of two control frames called PR and PA. The PR frame is designed for the semi-reservation of a channel initiated by a transmitting node, while the PA frame is used for the receiver-oriented permission of a channel reservation. Once a transmitting node advertises a PR frame, the channel is temporarily reserved, and the channel reservation is finally completed after the node receives the corresponding PA frame. Otherwise, the channel reservation is immediately released. Unlike the ready-to-send/clear-to-send mechanism, which is a well-known solution to HNP, the proposed mechanism does not unnecessarily prevent nodes from accessing the channel but selectively blocks transmitting and receiving nodes when they overhear the PA and PR frames transmitted by neighboring nodes, respectively. In this way, the proposed PR/PA mechanism effectively deals with both HNP and ENP in a unified framework. We further enhance the PR/PA mechanism by devising an immediate destination switching scheme, which is implemented in access points (APs) to improve the downlink throughput. If an AP fails to complete the exchange of PR and PA frames with a specific destination, it sends another PR frame to a different destination node without performing a new back-off procedure. Moreover, we adopt the transmission time control scheme to assure successful spatial reuse in multiple basic service set (BSS) WLANs. By adjusting the transmission time of the data frames simultaneously transmitted in different BSSs, severe interference between the data and acknowledgment frames can be avoided. The results of a simulation study confirmed that the proposed mechanism outperformed conventional mechanisms in dense multi-BSS WLANs; the downlink throughput was increased by more than 10 times while the overall network throughput was increased by approximately 50%.

Enhanced Dual Carrier Sensing With Transmission Time Control for Fair Spatial Reuse in Heterogeneous and Dense WLANs

In this paper, we focus on fairness and spatial reuse in heterogeneous and dense wireless local area networks (WLANs) where stations (STAs) have different capabilities of carrier sensing and basic service sets (BSSs) are densely deployed. First, we show a serious problem of unfairness arising when STAs with different carrier sensing threshold (CSTH) coexist and compete for channel access. To cope with this problem, a dual carrier sensing mechanism has been proposed in the on-going IEEE 802.11ax standardization. This mechanism uses two differentiated CSTHs: a conservative CSTH for fairness among intra-BSS STAs and an aggressive CSTH for spatial reuse by inter-BSS STAs. This dual carrier sensing mechanism may be effective in improving fairness. However, we show that its gain is marginal in terms of spatial reuse because an acknowledgment (ACK) frame is liable to be corrupted due to interference from a data frame transmitted by an inter-BSS STA. In order to avoid ACK corruption, we enhanced the dual carrier sensing mechanism by controlling the transmission time of the data frame. Depending on the receiving signal strength of data frame transmitted by an inter-BSS STA, the proposed mechanism selectively adjusts the concurrent transmission time of the data frame so that ACK frames can be successfully delivered. Results from simulation confirmed the outstanding performance of the proposed mechanism in heterogeneous and dense WLANs; compared with conventional mechanisms, the total throughput was considerably increased by more than two-fold while the fairness among the STAs was improved.

Energy efficient resource allocation in timesharing multiuser systems with hybrid energy harvesting transmitter

An energy efficient resource allocation scheme in timesharing multiuser system with a hybrid energy harvesting transmitter is studied in this paper. Specially, the operation energy of system is supplied by constant energy and energy harvesting, which harvests energy from external environment. Our goal is to maximize the energy efficiency of timesharing multiuser systems by considering jointly allocation of transmission time and power control in an off-line manner. The original nonconvex objective function is transformed into convex optimization problem via the fractional programming approach. Then, we solve the convex problem by Lagrange dual decomposition method. Simulation results show that the proposed energy efficient resource allocation scheme has a better performance than the scheme which decomposes optimization problem into two parts (power allocation, time allocation) to solve iteratively.

Switched Control of a Time Delayed Compass Gait Robot

the analysis and control of delayed systems are becoming more and more research topics in progress. This is mainly due to the fact that the delay is frequently encountered in technological systems. Most control command laws are based on current digital computers and delays are intrinsic to the process or in the control loop caused by the transmission time control sequences, or computing time. In other hand, the controls of humanoid walking robot present a common problem in robotics because it involves physical interaction between an articulated system and its environment. This close relationship is actually a common set of fundamental problems such as the implementation of robust stable dynamic control. This paper presents acomplete approach, based on switched system theory, for the stabilization of a compass gait robot subject to time delays transmission. The multiple feedback gains designed are based on multiple linear systems governed by a switching control law. The establishment of control law in real time is affected by the unknown pounded random delay. The results obtained from this method show that the control law stabilize the compass robot walk despite a varying delay reaching six times sampling period.

Stabilization of a Nonlinear Delay System

Problem statement: The analysis and control of delayed systems are becoming more and more research topics in progress. This is mainly due to the fact that the delay is frequently encountered in technological systems. This can affect their significantly operations. Most control command laws are based on current digital computers and delays are intrinsic to the process or in the control loop caused by the transmission time control sequences, or computing time. The delay may affect one or more states of the considered system. It may also affect the establishment of the command. Several studies have investigated the stability of delay systems under the assumption that the delay is a variable phenomenon; such variation is considered to be bounded or limited to facilitate analysis of the system. In this study we propose a modelling of delayed system by using the multimodels and switched system theory. The analysis of stability is based on the use of second Lyapunov method. The issued stability conditions are expressed as Bilinear Matrix Inequalities impossible to resolve. That’s why we propose the same original relaxations to come over this difficulty, an example of induction machine is given to illustrate over approach. Approach: We propose to use the control theory developed for switched systems to synthesis a control laws for the stabilisation of delays system. Results: We stabilize the induction machine around many operating points despite the non linearities. Conclusion: The developed method is less conservative and less pessimistic than the used classical methods.

The Principle and System Design of Self-Cleaning Filter

This paper describes the self-cleaning filter structure, working principal and the main parameters, and it describes the hardware, control theory and software design process. Pressure transmission control method, time control, automatically open and close cleaning and sewage systems are used in automatic self-cleaning filter, which fully realizes unmanned operation, stable and reliable. There are some reference values in this article for the depth understanding of design and development the automatic cleaning filters.

A Low-Energy Inductive Coupling Transceiver With Cm-Range 50-Mbps Data Communication in Mobile Device Applications

A low-energy inductive coupling transceiver is proposed for Cm-range multimedia data transmission in mobile device applications. The Transmission Time Control (TTC) scheme is proposed to reduce the transmitter energy consumption to 0.475 pJ/b, and the Adaptive Gain Control (AGC) scheme is adopted to make the receiver energy consumption be 0.825 pJ/b. The planar-type inductor with self-resonance frequency of about 200 MHz fabricated on the flexible substrate achieves a data rate over 50 Mbps. To compensate for the weakly coupled channel, the receiver sensitivity is enhanced by the differential detection method (DDM) of the nodal voltages across the receiver inductor. With this method, the communication distance is increased up to 7 cm, and channel misalignment tolerance is enhanced up to 2 cm. The proposed transceiver is implemented within 1.5 × 2.37 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in 0.18-μ m CMOS process and operates with 1-V supply.

Transmission error analysis and avoidance for IEEE 802.15.4 wireless sensors on rotating structures

Wireless sensors are increasingly adopted in manufacturing and vehicular systems for monitoring critical components under continuous operation. Many such components move rapidly and frequently in metallic containments with challenging radio propagation characteristics. For wireless sensors mounted on rotating structures, previous experimental studies observed an eminent increase in packet transmission errors at higher rotation speeds. Such errors were found to occur at specific locations around the rotating spindle's periphery and such locations depended sensitively on sensor location and surrounding geometry. This paper analyses the expected packet error rates with different rotation speeds and error region distributions, and proposes a transmission error avoidance approach based on online error pattern inference and transmission time control for IEEE 802.15.4 compatible sensor radios. Simulation studies showed a 50% error reduction and up to 75% throughput increase; higher throughput gains are expected for applications with more frequent and larger size data transmissions.

EACLE : Energy-Aware Clustering Scheme with Transmission Power Control for Sensor Networks

In this paper, we propose a new energy efficient clustering scheme with transmission power control named "EACLE" (Energy-Aware CLustering scheme with transmission power control for sEnsor networks) for wireless sensor networks, which are composed of the following three components; "EACLE clustering" is a distributed clustering method by means of transmission power control, "EACLE routing" builds a tree rooted at a sink node and sets the paths from sensor nodes taking energy saving into consideration, and "EACLE transmission timing control" changes the transmission timing with different levels of transmission power to avoid packet collisions and facilitates packet binding. With an indoor wireless channel model which we obtained from channel measurement campaigns in rooms and corridors and an energy consumption model which we obtained from a measurement of a chipset, we performed computer simulations to investigate the performance of EACLE in a realistic environment. Our simulation results indicate that EACLE outperforms a conventional scheme such as EAD (Energy-Aware Data-centric routing) in terms of communication success rate and energy consumption. Furthermore, we fully discuss the impact of transmission power and timing control on the performance of EACLE.

Capacity analysis of an uplink synchronized multicarrier DS-CDMA system

An uplink synchronous transmission scheme has been proposed for DS-CDMA systems to increase the uplink capacity through transmission timing control and a proper code usage. Since the scheme suppresses the interference along the first paths of other users, it can achieve a significant capacity increase when combined with a multicarrier (MC) technique. This article mathematically compares the proposed uplink synchronized MC DS-CDMA system with conventional DS-CDMA and MC DS-CDMA systems in terms of the maximum number of users.