ABI - Algorithms for Broadband Infrastructure

General research areas of ABI

The project studies various kinds of algorithms used in broadband networking and network management. The emphasis is on performance aspects - development of provably effective techniques, and assessment of their performance. The main approach is modelling and analysis, but the project includes also prototype software development and simulation.

The project has three focus areas:

• algorithms for wireless access networks
• algorithms for overlay networking
• algorithms for traffic measurement and analysis

Research areas in the TKK subproject

The TKK subproject is mostly involved in research related to wireless access networks and overlay networks. Some details and motivation for the tasks are provided below. For actual results from the TKK subproject, please see the publications.

Wireless access networks

As the end usage of telecommunication systems and data networks is shifting more and more towards mobile and nomadic terminals, the wireless access is becoming a critical component in the network, which largely determines the system's capacity. Besides new technological solutions and more efficient use of the radio spectrum, it is equally important that the systems are designed and operated in the best possible way from the traffic point of view in order to optimize the performance. In some situations even multi-hop wireless access networks, often called wireless mesh networks, can be beneficial, which may call for new architectural solutions. The use of novel FEC codes (of the fountain code type) can also open new possibilities to mitigate inevitable losses in the radio channel in a bandwidth saving way. Load balancing and inter-node coordination are further techniques that can be used to improve the performance of the system.

The work in the TKK subproject in 2006 focuses on the following:

• Models are developed that take into account flow-level QoS and the impact of wireless link interference. These models are used in the formulation of dimensioning problems that can be used in designing wireless mesh networks.
• The application of fountain codes in wireless networking is considered. Fountain codes are especially suited for situations with the possibility of high packet losses, which is the case when operating wireless networks near their performance limits. In extreme situations there is no need for a backward channel to exist, enabling an efficient end-to-end software FEC mode of operation.

Overlay networks

The work in the TKK subproject in 2006 focuses on the following:

• The on-going research on the optimization of existing fountain coding schemes is continued. Additionally, new coding concepts and schemes are developed.
• The dynamical behavior of a BitTorrent-type p2p network will be analyzed, including such features as time-dependent arrival rates (i.e. flash crowd), division of the file into chunks and availability of the whole file. The aim is also to develop a realistic spatio-temporal model for the system and study different peer selection strategies from traffic engineering point of view. Particular attention will be given to the problem that the topology of the overlay network can differ strongly from the topology of the underlying network, causing the transfer of large amounts of traffic along too long distances. The questions include the estimation of the gain achievable with better, location-aware algorithms, and spatial modelling.

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