Touch is currently seen as the modality that will complement audition and vision as a third media stream over the Internet in a variety of future haptic applications which will allow full immersion and that will, in many ways, impact society. Nevertheless, the high requirements of these applications demand networks which allow ultra-reliable and low-latency communication (URLLC) for the challenging task of applying the required Quality of Service (QoS) for maintaining the user’s Quality of Experience (QoE) at optimum levels. In this survey, we enlist, discuss and evaluate methodologies and technologies of the necessary infrastructure for haptic communication. Furthermore, we focus on how the fifth generation (5G) of mobile networks will allow haptic applications to take life, in combination with the haptic data communication protocols, bilateral teleoperation control schemes and haptic data processing needed. Finally, we state the lessons learned throughout the surveyed research material along with the future challenges and infer our conclusions.

Bilateral teleoperation systems with haptic feedback allow human users to interact with objects or perform complex tasks in remote or inaccessible environments. Communication delays in teleoperation systems jeopardize system stability and transparency, leading to degraded system performance and poor user experience. In this paper, we provide a survey of the model-mediated teleoperation (MMT) approach, which has been developed to guarantee both system stability and transparency in the presence of arbitrary communication delays. This survey focuses on two major parts: 1) the historical development of the MMT approach from the late 1980s to the present and 2) the main challenges facing the design of a reliable MMT system. Along with the discussion of the MMT challenges and the proposed solutions, a series of experiments has been conducted to compare the performance between the existing techniques and to supply data that were missing in the previous studies on the MMT approach.

In this paper, we extend the concept of model-mediated teleoperation for complex environments and six degrees of freedom interaction using point cloud surface models. In our system, a time-of-flight camera is used to capture a high-resolution point cloud model of the object surface. The point cloud model and the physical properties of the object (stiffness and surface friction coefficient) are estimated at the slave side in real-time and transmitted to the master side using the modeling and updating algorithm proposed in this paper. The proposed algorithm adaptively controls the updating of the point cloud model and the object properties according to the slave movements and by exploiting known limitations of human haptic perception. As a result, perceptually irrelevant transmissions are avoided, and thus the packet rate in the communication channel is substantially reduced. In addition, a simple point cloud-based haptic rendering algorithm is adopted to generate the force feedback signals directly from the point cloud model without first converting it into a 3-D mesh. In the experimental evaluation, the system stability and transparency are verified in the presence of a round-trip communication delay of up to 1000 ms. Furthermore, by exploiting the limits of human haptic perception, the presented system allows for a significant haptic data reduction of about 90% for teleoperation systems with time delay.

This article proposes an application-layer multiplexing scheme for teleoperation systems with multimodal feedback (video, audio, and haptics). The available transmission resources are carefully allocated to avoid delay-jitter for the haptic signal potentially caused by the size and arrival time of the video and audio data. The multiplexing scheme gives high priority to the haptic signal and applies a preemptive-resume scheduling strategy to stream the audio and video data. The proposed approach estimates the available transmission rate in real time and adapts the video bitrate, data throughput, and force buffer size accordingly. Furthermore, the proposed scheme detects sudden transmission rate drops and applies congestion control to avoid abrupt delay increases and converge promptly to the altered transmission rate. The performance of the proposed scheme is measured objectively in terms of end-to-end signal latencies, packet rates, and peak signal-to-noise ratio (PSNR) for visual quality. Moreover, peak-delay and convergence time measurements are carried out to investigate the performance of the congestion control mode of the system.

We study the combination of the perceptual deadband (PD)-based haptic packet rate reduction scheme with the time domain passivity approach (TDPA) for time-delayed teleoperation and propose a novel energy prediction (EP) scheme that deals with the conservative behavior of the resulting controller. The PD approach leads to irregular packet transmission, resulting in degraded system transparency and reduced teleoperation quality when the PD approach is combined with the TDPA. The proposed method (PD+TDPA+EP) adaptively predicts the system energy during communication interruptions and allows for larger energy output. This achieves less conservative control and improves the teleoperation quality. Evaluation of the displayed impedance shows that the PD+TDPA+EP method achieves improved system transparency, both objectively and subjectively, when compared with related approaches from literature. According to a subjective user study, the PD+TDPA+EP method allows for a high packet rate reduction (up to 80 percent) without noticeably distorting the perceived interaction quality. We also show that the PD+TDPA+EP method is preferred over related approaches from literature in a direct comparison test. Thus, with the proposed PD+TDPA+EP method, a high data reduction and a high teleoperation quality are simultaneously achieved for time-delayed teleoperation.

Networked teleoperation with haptic feedback is a prime example for the emerging Tactile Internet, which requires a careful orchestration of haptic communication and control. One major challenge in this context is how to maximize the user's quality-of-experience (QoE) while ensuring at the same time the stability of the global control loop in the presence of communication delay. In this paper, we propose a dynamic control scheme switching strategy for teleoperation systems, which maximizes the QoE for time-varying communication delay. In order to validate the feasibility of the proposed approach, we perform a dedicated case study for a virtual teleoperation environment consisting of a one-dimensional spring-damper system, and conduct extensive subjective tests under various delay conditions for two control schemes : (1) teleoperation with the time-domain passivity approach (TDPA), which is highly delay-sensitive but supports highly dynamic interaction between the operator and a potentially quickly changing remote environment; (2) model-mediated teleoperation (MMT), which is tolerable to relatively larger communication delays, but unsuitable for quickly changing, highly dynamic remote environments. For both schemes, we use recently proposed extensions, which incorporate perceptual data reduction to reduce the required packet rate between the operator and the teleoperator. One key contribution of this paper lies in the exploration of the intrinsic relationship among QoE, communication delay and the control schemes which provides a fundamental guidance, not only to this research, but also to the future joint optimization of communication and control for time-delayed teleoperation systems.