Stefan Pettersson

Improving Transmission Efficiency in H.264 Based IPTV Systems

In this paper, a novel proposal regarding the transmission of the next generation of live-TV content in an IPTV environment is presented. Today live-TV IP transmission systems utilizes a Group Of Pictures (GOP) structure in order to provide stream synchronization points for the clients. Synchronization points are used when a TV-channel switch occurs. The number of channel switches made by TV audiences have been shown to be rather rare. It is therefore redundant to send synchronization events in a GOP manner. Our proposal, Synchronization Frames for Channel Switching (SFCS), only requests synchronization points when required. Due to channel popularity distributions and the number of connected users, the total number of synchronization requests for a popular channel can increase to a level that makes SFCS less effective than GOP. Therefore, we introduce an SFCS-GOP hybrid. A complete network traffic analysis model, verified by a simple simulation environment, is also presented and the results show that the SFCS-GOP hybrid significantly increases the bandwidth utilization compared to a traditional GOP system

Distributed context support for ubiquitous mobile awareness services

Context-aware applications and services require ubiquitous access to context information about the users or sensors such as preferences, spatial & environmental data, available connectivity, and device capabilities. Systems for the brokering or the provisioning of context data via wireless networks do so with centralized servers or by employing protocols that do not scale well with real-time distribution capabilities. In other cases, such as the extending of presence systems, the data models are limited in expressive capabilities and consequently incur unnecessary signaling overhead. This paper presents a distributed protocol, the Distributed Context eXchange Protocol (DCXP), and an architecture for the real-time distribution of context information to ubiquitous mobile services: We present the architecture and its principle operation in a sample ubiquitous mobile awareness service. Preliminary results indicate that our approach scales well for the ubiquitous provision of context data in real-time to clients on the Internet via 3G wireless systems. Performed measurements show that DCXP can reduce the time to process context data with a factor of 20 compared to similar approaches.

The MediaSense Framework

Mobile telecommunication is evolving rapidly. People no longer only communicate with each other regardless of time and place, but also share other information that is important for tasks with which they are involved. In response to this growing trend the MediaSense framework addresses the intelligent delivery of any information to any host, anywhere, based on context-aware information regarding personal preferences, presence information, and sensor values. This includes another challenge to achieve seamless delivery, especially of multimedia content, and multimodal services via heterogeneous connections.

A RADIO RESOURCE MANAGEMENT CONCEPT FOR "BUNCHED" PERSONAL COMMUNICATION SYSTEMS

The radio resource management (RRM) techniques used in current 2nd generation mobile communication systems rely heavily on fixed frequency or timeslot allocation techniques which are not well suited for large variations in data rates. Spread spectrum systems proposed provide partial solutions to this problem but exhibit deficiencies when faced with uneven user populations. The overall objective of ACTS project AC090 FRAMES is to define, develop and evaluate a wideband multiple radio access scheme fulfilling the UMTS requirements. Within the project several RRM concepts have been proposed. The “bunch” concept discussed in this paper uses synchronous dynamic physical layer radio resource reservation combined with fast SIR based power control in a local cluster (“bunch”). Uncontrolled, “interbunch”, interference is handled by time/frequency hopping (“interference averaging”). In the paper some initial performance results are presented.

Bounding the Information Collection Performance of Wireless Sensor Network Routing

Wireless sensor networks have mainly been designed for information-collecting purposes, such as habitat monitoring, product process tracing, battlefield surveillance, etc. In order to support efficient communications for such networks, many routing protocols have been proposed. However, protocol designs are out-pacing formal analysis. We propose an optimization model in this paper to bound the routing performance in terms of network information collection. We first argue that a network can only be given a death sentence when it fails to satisfy the applications requirement and propose a more reasonable network lifetime definition. Then, the optimization model concerning maximizing information collection routing is presented based on this new network lifetime definition. Existing typical routing algorithms: MH, MTE, FA and MREP are simulated as references to validate the model proposed. Results show our model can provide a tight upper bound and thus can be used to evaluate existing and up-coming routing algorithms.

A comparison of radio resource management strategies in bunched systems for indoor communication

We investigate the performance of different channel selection strategies in a 3-dimensional indoor environment. The selection strategies are part of a locally centralized or bunched radio communication system using the SIR as a basis for the channel selection decisions. We evaluate the capacity and the complexity of the system for the different strategies. In the performance evaluation, fixed channel assignment (FCA) is used as a reference. The result show that the capacity is more than five times higher in the bunched system compared with the FCA system for the LNF (lowest number first) strategy. We also investigate the impact power control has on the system performance.

Sectoring of a locally centralized communication system in an indoor environment

Future indoor communication systems will support different services with varying quality demands. Centralized radio resource management (RRM) is suitable for these types of systems. With central control the existing users can be protected and given priority over new allocations. The drawback is generally considered to be increased complexity. By dividing the coverage area into smaller segments using multiple controllers, the computational complexity can be reduced. The price for reduced complexity is lost capacity compared with a single controller system. We introduce sector antennas in a locally centralized radio communication system covering one building floor and investigate their ability to increase the capacity with maintained low complexity. The results show that the capacity can be almost as high for a sectorized system with two central units as for a system using one central unit covering the floor with omnidirectional antennas. The results also indicate how well the studied wireless system can coexist with similar systems located in the vicinity. Sectoring reduces the transmitter powers and therefore improves the performance of closely located wireless networks.