Point cloud compression has become a crucial factor in immersive visual media processing and streaming. This paper presents a new open dataset called UVG-VPC for the development, evaluation, and validation of MPEG Visual Volumetric Video-based Coding (V3C) technology. The dataset is distributed under its own non-commercial license. It consists of 12 point cloud test video sequences of diverse characteristics with respect to the motion, RGB texture, 3D geometry, and surface occlusion of the points. Each sequence is 10 seconds long and comprises 250 frames captured at 25 frames per second. The sequences are voxelized with a geometry precision of 9 to 12 bits, and the voxel color attributes are represented as 8-bit RGB values. The dataset also includes associated normals that make it more suitable for evaluating point cloud compression solutions. The main objective of releasing the UVG-VPC dataset is to foster the development of V3C technologies and thereby shape the future in this field.

We propose a novel reinforcement learning approach to learning lattice codes for MIMO channels. We use the block error rate as a loss function to be minimized and compare the learnt lattices with those obtained from algebraic design methods for different SNR ranges. Our results indicate that our learnt lattices achieve close to optimal performance in some cases.

This paper presents a remote 360-degree virtual reality (VR) gaming system for mobile devices. In this end-to-end scheme, execution of VR game is off-loaded from low-power mobile devices to a remote server where the executed game is rendered based on controller orientation and actions transmitted over the network. The server is running the Unity game engine and Kvazaar video encoder. Kvazaar compresses the rendered views of the game to High Efficiency Video Coding (HEVC) video that is streamed to a player over a regular WiFi link in real time. The frontend of our proof-of-concept demonstrator setup is composed of the Samsung Galaxy S8 smartphone and Google Daydream View VR headset with a controller. The backend server is a laptop equipped with Nvidia GTX 1070 GPU and Intel i7 7820HK CPU. The system is able to run the demonstrated 360-degree shooting VR game with 1080p resolution at 30 fps while keeping motion-to-photon latency close to 50 ms. This approach lets players enter immersive gaming experience without a need to invest in all-in-one VR headsets.

When applying delay-tolerant networking concepts to communication in mobile ad-hoc networks formed between mobile users, a general assumption is that users are willing to share own resources to support communication between others. However, we cannot assume that all users are altruistic in their behavior; instead, we have to deal with users who only make a limited or no contribution to the mobile community. Nodes not participating in communication only reduce the effective node density, but do not consume resources. Others act as sources and sinks but perform only limited or no forwarding and thus may impact the overall network performance. When considering routing in mobile DTNs, such selfish nodes have to be considered. We introduce two types of selfish nodes and evaluate their impact on message delivery performance for different routing protocols by means of simulation in different synthetic mobility models and with real-world traces. We find that their impact can be surprisingly low in our scenarios, suggesting that DTN communication can be quite robust against selfishness and that controlled non-cooperative behavior may be a suitable way to overcome resource limitations, such as battery depletion.

In this paper, we study how to adapt the routing according to dynamic network conditions in wireless ad hoc networks. We present a method that dynamically chooses routing agent between ad hoc on-demand distance vector routing protocol (AODV) with TCP (end-to-end transport) and delay-tolerant networking (DTN) routing and bundle protocol (hop-by-hop transport). We use simulations to confirm that DTN routing and the bundle protocol leads to significantly shorter end-to-end delays and higher message delivery ratios than AODV and end-to-end TCP when the wireless node density is low. However, with high node density, DTN routing, especially epidemic routing, suffers from multiple bundle copies and simultaneous transmissions that lead into collisions and retransmissions at the wireless link (MAC) layer. Thus, we propose a simple adaptive scheme that uses only local information to transmit the messages from source to destination using either AODV or DTN routing, depending on current node density, message size, and path length to destination.

Mobile phones are becoming commonplace for consuming Internet content and services. However, availability, affordability, and quality of the supposedly ubiquitous cellular network infrastructure may be limited, so that delay-tolerant web access via WLAN hotspots becomes an interesting alternative, even in urban areas. In this paper we explore mobile web access using asynchronous messaging via WLAN hotspots: for nodes directly connected to an access point and nodes relying on others for message forwarding. We investigate different routing and caching approaches using real-world access point locations in Helsinki. We find that a significant number of requests can be satisfied without requiring an always-on infrastructure, provided that users are willing to tolerate some response delay; this allows offloading traffic from the cellular network. We also report on our prototype implementation of mobile DTN-based web browsing.

Delay-tolerant networking (DTN) provides a platform for applications in environments where end-to-end paths may be highly unreliable or do not exist at all. In many applications such as distributed wikis or photo sharing, users need to be able to find content even when they do not know an unambiguous identifier. In order do bring these applications to the domain of DTNs, a search scheme is required that works despite the unreliable network conditions. In this paper, we introduce a search scheme that makes no assumptions about the underlying routing protocols and the format of search requests. We evaluate different algorithms for forwarding and terminating search queries, using simulations with different classes of DTN routing protocols for different mobility scenarios.

In this paper we show how grid computing can be used to improve the operation of a medical image search system. The paper introduces the basic principles of a content-based image retrieval (CBIR) system and identifies the computationally challenging tasks in the system. For the computationally challenging tasks an efficient design is proposed that uses distributed grid computing to carry out the image processing in a distributed and efficient way. The algorithms of the search system are executed by using a real medical image collection as input and a grid computing infrastructure to provide the needed computing power. Finally, the results show how the image processing task that required tens of hours to complete can be processed by using only a fraction of the originally required computing time.

Delay-tolerant networking is used for communication in challenged environments such as MANETs, in which links are unstable and end-to-end paths between communicating nodes may not exist. Messages may be significantly larger than packets in IP networks. Large messages lead to longer transfer times rendering it more likely that a link breaks in the middle of a message transfer. This motivates investigating how to support partial message transfers through fragmentation. In this paper, we formulate fragmentation independent of routing algorithms, introduce several fragmentation strategies, and evaluate these by simulations to derive recommendations for using fragmentation in DTNs.

Today's medical institutions produce enormous amounts of data on patients, including multimedia data, which is increasingly produced in digital form. These data in their clinical context contain much information and experience that is currently not being used up to its full potential. Through the digital form the data has become accessible for automatic analysis and treatment for a variety of applications. At the same time, the variety of images produced can be confusing even for trained specialists causing an information overload exists for many medical doctors. This suggests that content-based image retrieval can be a valuable tool for helping manage these data and access the right information at the right time. This article gives a short state of the art of content-based medical image retrieval followed by a description of the medGIFT project on image retrieval with its main components. Then, several challenges are used to illustrate areas where much more work is currently needed to advance biomedical image retrieval. This shows that we have now progresses beyond the phase, where medical doctors transfer a database to computer scientists to only evaluate their algorithms. We conclude that visual information retrieval can have a real impact in the medical field if the techniques can adapt to this rapidly changing field and get integrated into the workflow in radiology and other medical fields.

Delay-tolerant networking (DTN) enables nodes to communicate by means of asynchronous messaging witout the need for an end-to-end path. Suitably designed application protocols may operate in DTNs by minimizing end-to-end interactions and using self-contained messages for communication. The store-carry-and-forward operation and message replication of many DTN routing protocols may yield multiple copies of messages spread across many nodes for an axtended period of time. We leverage these properties for application support in (mobile) intermediate DTN nodes which act as ad-hoc routers. We add explicit application hints to messages that are visible to each node, allowing them, e.g., to cache content, act as distributed storage, or perform application-specific forwarding.