HoIP: Haptics over Internet Protocol
Applications such as telesurgery need low latency communication of haptic data between remote nodes. For the stability of the control loop, a typical round trip delay target is 5 ms or lower. In this paper, we specify an application layer protocol - Haptics over Internet Protocol (HoIP) - which is designed to allow such low latency haptic data transmission without sacrificing on the quality of haptic perception. The key ingredients of HoIP include adaptive sampling strategies for the digitization of the haptic signal, use of a multithreaded architecture at the transmitter and receiver to minimize processing delay, and use of an existing UDP implementation. In this paper, we describe in detail the frame structure used in HoIP and the rationale behind our design choices, the implementation details of HoIP at the transmitter and receiver, and report processing delay measurements done using real haptic devices and HAPI (an open source software used to interface with the haptic device). The HoIP software is entirely written in C++ and our results show that in the worst case transmitter and receiver side processing delays are less than 0.6 ms.