Patrik Österberg

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.

Receiver-controlled joint source/channel coding on the application level, for video streaming over WLANs

The proportion of real-time traffic, being transported over Internet protocol (IP) networks, appears to be ever increasing. Real-time traffic may, for example, be video and audio, which have real-time constraints such as maximum delay and delay jitter. Such requirements can be hard to satisfy in a wired infrastructure, and are even more so in a wireless network. Therefore there is a need to make transmission over wireless local area networks (WLANs) more reliable. The aim of this paper is to outline transmission of MPEG-4 video over an IEEE 802.11b WLAN, and to experimentally verify its efficiency. Receiver-driven layered multicast has been proposed before, for dealing with band limitations and environments with heterogeneous terminals. We extend these ideas to handle packet loss, by adding receiver-driven unequal error protection (UEP). The proposal can be viewed as receiver-controlled joint source/channel (JSC) coding on the application level.

The Updated 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 the tasks with which they are involved. In response to this growing trend, the Media Sense 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. The focus of this paper is the overall framework, the handling of user profiles, management of context information, real-time distribution and proof of concepts.

Evaluating Ubiquitous Sensor Information Sharing on the Internet-of-Things

Next generation context-aware mobile applications will require a continuous update of relevant information about a users surroundings, in order to create low latency notifications and high quality of experience. Existing mobile devices already contain a large number of built in sensors which are capable of producing huge amounts of sensor data, exceeding both the capacity of the local storage and the Internet connection. Therefore, we will in this paper study the limits when sharing contextual information from mobile devices, as well as finding the impact of this information overload for the Internet-of-Things. Furthermore, we present an evaluation model for assessing the effort required to present applications with relevant context information. In conclusion, the model shows that one feasible solution for the future Internet-of-Things is a peer-to-peer based solution which can control the flow of information without any centralized authority, to circumvent earlier limitations.

Hybrid MAC mechanism for energy efficient communication in IEEE 802.11ah

Many applications for machine-to-machine (M2M) communications are characterized by large numbers of devices with sporadic transmissions and subjected to low energy budgets. This work addresses the importance of energy consumption by proposing a new Medium Access Control (MAC) mechanism for improving the energy efficiency of IEEE 802.11ah, a standard targeting M2M communication. We propose to use the features of IEEE 802.11ah MAC to realize a hybrid contention-reservation mechanism for the transmission of uplink traffic. In the proposed mechanism, any device with a buffered packet will first notify the Access Point (AP) during a contention phase before being given a reserved timeslot for the data transmission. We develop a mathematical model to analyse the energy consumption of the proposed mechanism and of IEEE 802.11ah. The results show that for a monitoring scenario, the proposed contentionreservation mechanism reduces the energy consumption for a successful uplink data transmission by up to 55%.

Multicast-favorable max-min fairness - a general definition of multicast fairness

As video-streaming services are becoming more common, the benefit of multicast transmission is growing, because multicast is more bandwidth efficient than unicast in scenarios where many receivers simultaneously are interested in the same data. Of the same reason, the concept of multicast fairness is starting to attract attention, it might be sensible to give multicast flows higher priority and thereby create an incentive for the use of multicast transmission. Allocating link bandwidth in proportion to the logarithm of the number of receivers of a flow, which favors multicast flows without totally starving unicast flows, has been proposed in the work of A. Legout et al. (2001). That was however just as a bandwidth-allocation policy ran on the individual routers and not a definition of multicast fairness. To our knowledge, no one has yet come up with a definition of multicast fairness which prioritizes multicast flows. In this paper, we present a general multicast-fairness definition, named multicast-favorable max-min fairness (MFMF), which can be used together with any multicast-favorable function.

Ubiquitous Secure Interactions with Intelligent Artifacts on the Internet-of-Things

Intelligent artifacts are real-world objects enhanced with capabilities in order to display relevant behavior in various types of context-aware applications, such as in mHealth, commerce, or pervasive games. This can be achieved by attaching sensors and store associated information on the Internet. Interaction with such artifacts requires secure communication, to protect personal and private information. This mandates research in how to safeguard interactions via heterogeneous means of communication involving interconnected local and non-local artifacts. In response to these challenges, this paper presents key schemes to secure interaction via heterogeneous means of communication. In conclusion, the architecture can securely authenticate an intelligent artifact as well as securely exchange sensor information with other authenticated artifacts attached in an overlay. Our proof-of-concept application demonstrated in an Internet-of-Things platform validates the approach.

Bid-based cost sharing among multicast receivers

In scenarios where many receivers simultaneously are interested in the same data, multicast transmission is more bandwidth efficient than unicast. The reason is that the receivers of a multicast session share the resources through a common transmission tree. Since the resources are shared between the receivers, it is reasonable that the costs corresponding to these resources should be shared as well. This paper deals with fair cost sharing among multicast receivers, and the work is based upon the assumption that costs should be shared according to the resource usage. However, it is not for certain that an optimally fair cost allocation is most beneficial for the receivers; receivers that cannot cover their fair share of the costs may nevertheless be able to contribute to the cost sharing to some extent. We propose a cost-allocation mechanism that strives to allocate the costs fairly, but gives discount to poor receivers who at least manage to cover the additional cost of providing them with the service.

Fair Cost Sharing among Multicast Receivers

In scenarios where many receivers simultaneously are interested in the same data, multicast transmission is more bandwidth efficient than unicast. The reason is that the receivers of a multicast session share the resources through a common transmission tree. Since the resources are shared between the receivers, it is reasonable that the costs corresponding to these resources should be shared as well. This paper deals with fair cost sharing among multicast receivers. The work is based upon the assumption that costs should be shared based on resource usage. With this in mind, existing cost-allocation mechanisms are evaluated and the conclusion is that none of them is satisfactory fair. We therefore propose a new cost-allocation mechanism that allocates the costs according to the transmission path and obtained QoS level of each receiver.