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We describe a prototype implementation of a future mobile phone called CyPhone. In addition to voice calls, it has been designed to support context-specific and multi-user multimedia services in an augmented reality manner. Context-awareness has been implemented with GPS-based navigation techniques and a registration algorithm, capable of detecting a predefined 3-D model or a landmark in the environment. A new adaptive transport protocol has been developed to support real-time packet-switched data transfer between concurrent users of mobile augmented reality applications. The prototype itself is based on PC/104+ architecture. As a case example we describe an augmented reality-based personal navigation service.

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In this paper we describe a new adaptive streaming protocol for mobile augmented reality applications. Mobile augmented reality is typically a multi-user environment, where users interact with each other using shared computer-generated virtual objects. One application area of mobile augmented reality is concurrent design and engineering, where the consistency of shared objects is maintained with a real-time streaming protocol. The protocol adapts the stream of update messages according to the wireless link quality. Adaptation means the adjusting of transmission speed to maximize reliability and to minimize packet delivery latencies and their variation, jitter. Conventional streaming protocols use an end-to-end feedback channel to transmit network quality parameters used in adaptation. However, this causes unnecessary delays and decreases the reliability, because feedback messages have to be transmitted over a wireless media. We present a new approach, in which the adaptation is based on the link quality parameters, stored in a base station. No high protocol layer wireless feedback channel is required, which makes the adaptation fast. We justify the feasibility of our protocol by comparing its performance with the most common transport-layer streaming protocols and show that faster adaptation reduces the number oflost packets and jitter in the network.