Circuits over Packets

Circuits over packets was a joint project between Siemens Electronic House Zürich-Altstetten (Hr. P. Marending) and ETH Zürich (Prof. Dr. B. Plattner, Dr. U. Fiedler) with the goal of connecting existing GSM/UMTS base stations over packet-switched networks such as metropolitan Gigabit Ethernets.

The possibility to use existing Ethernets instead of dedicated SDH/PDH circuits to connect GSM/UMTS base stations and PBX triggers cost savings for base station operators.

The challenge of this project was to seamlessly integrate the packet-based Ethernet into the existing circuit-based telephone infrastructure and synchronizing frequencies on both ends. Another problem was to show that a sufficient quality of service (QoS) can be guaranteed even with bursts of traffic on the Ethernet.

To solve these problems, we developed, tested and implemented algorithms for hardware circuit emulation adapters (CEAs), which transform the signals of base stations, send and receive Ethernet frames and maintain the frequency within the bounds allowed. Measurements on the ETH network together with tests on a specifically designed network emulator showedthat QoS requirements were met. Our CEAs allowed for multiple parallel circuits and outperformed those of competitors.

The project was a complete success. The feasibility to use existing Metropolitan Gigabit Ethernets instead of dedicated SDH/PDH circuits to connect GSM/UMTS base stations has been proven which is a basis to trigger savings. Moreover, Siemens received a fully fledged circuit emulation adapter. Additionally, we developed a network emulator that Siemens is currently employed in further developments.

TOWN

TOWN (telephony over wireless metropolitan networks) was a project among Ascom (Schweiz) AG (Hr. J. Furrer), ETH Zurich (Prof. Dr. B. Plattner) and BFH-TI Biel/Bienne (Prof. Dr. U. Fiedler). In this project, we developed and tested a self organizing ad-hoc network based on WiMAX (IEEE 802.16-2004). This network allows dynamic backhaul telephone networks in areas where no infrastructure can be used.. Such a network is especially useful in disaster recovery, public safety, or military applications.

The challenges of this project were the development of a distributed topology construction algorithm that maximizes throughput and balances load in a way that new routers can join at any time.

After conducting initial simulations to assess the performance of the algorithm, we designed a protocol for distributed implementation of the algorithm. We then successfully tested our protocol implementation in a virtual test environment on a high-end PC with VMware. before Ascom conducted a field test.

Ascom is currently finalizing a product that contains our implementation.

Other Projects

Moreover, Ulrich Fiedler conducted projects that are subject to non-disclosure agreements and may thus not be listed on this page.