Tomas Jönsson

AC Grid with Embedded VSC-HVDC for Secure and Efficient Power Delivery

Increased bulk power transactions in competitive energy markets together with large scale integration of renewable energy sources are posing challenges to high-voltage transmission systems. Environmental constraints and energy efficiency requirements also have significant effects on future transmission infrastructure development. This paper reviews the recent development in HVDC technologies and discusses the needs of the hybrid AC/DC grid structure for future power systems with focus on VSC-HVDC applications in meshed AC grid. It has also been recognized that hybrid AC/DC transmission system together with the wide area measurement system (WAMS) could effectively manage the overall power grid operation security and efficiency under uncertain supply and demand conditions.

LTE evolution towards IMT-advanced and commercial network performance

This paper provides a high-level overview of Long Term Evolution (LTE) Rel-10, sometimes referred to as LTE-Advanced. First, a brief overview of LTE and some of its technologies are given and then the International Mobile Telecommunications (IMT)-Advanced requirements are discussed. LTE Rel-10 enhances the LTE with carrier aggregation, improved multi-antenna support, relaying and improved support for heterogeneous deployments. The paper is concluded with measurements from the first commercial LTE network, showing that live LTE network performance is well aligned with expectations.

The LTE radio interface - key characteristics and performance

Mobile broadband usage is taking off, demanding improved services and increased capacity of mobile networks. To meet these requirements, 3GPP has defined LTE (the 3GPP Long Term Evolution). This paper presents some key characteristics of the LTE radio interface, including physical layer and radio resource management functions, and evaluates their impact on system performance. As compared to a reference system with more basic characteristics, represented by mobile WiMax, results point to a combined gain in spectrum efficiency of 60% in downlink and 100% in uplink. Cell-edge bitrate gains are about 100% in both downlink and uplink. A closer analysis of the individual system characteristics indicates that these performance differences are due to rather uniform contributions from a set of distinctive features.

High capacity strategies for GSM/EDGE - impacts on data traffic performance

GSM is the worlds most widespread cellular technology. With EDGE packet data, an attractive solution to offer 3rd generation cellular services in existing GSM networks is provided. The introduction of new services into an existing network typically leads to increased capacity demands, since more users of different service types need to coexist in a limited spectrum, while the existing speech service is required to function at least as well as before. In GSM/EDGE systems, the highest capacity is reached in interference-limited scenarios, typically realized with tight frequency reuse and fractional loading; see for example P. de Bruin et al. (IEEE Vehicular Society News, vol.49, no.1, 2002). In such systems, methods for mitigating interference are needed to achieve maximum performance. Strategies for frequency hopping, inter-cell synchronization and MAIO (mobile allocation index offset) planning becomes increasingly important. The paper examines the impact these methods have on EDGE packet data performance. It is shown that packet data traffic responds differently than speech to interference diversity, mainly due to differences in channel coding and radio protocol characteristics. However, it is demonstrated that the intercell synchronization and MAIO planning strategies preferred for pure speech networks also offer substantial performance improvements for EDGE packet data.

Adaptive Video with SCReAM over LTE for Remote-Operated Working Machines

Remote operation is a step toward the automation of mobile working machines. Safe and efficient teleremote operation requires good-quality video feedback. Varying radio conditions make it desirable ...

Real Life LTE In-Building Deployment Demonstrating Multi-Cell Capacity

In Building Solutions (IBS) are a well-established approach to providing indoor cellular coverage. The increasing wireless mobile broadband traffic and the fact that most broadband data is consumed indoors increases the interest to understand the IBS capacity potential. For a given available spectrum, a straightforward capacity solution is cell-splitting. In this paper, measurement results from a full-scale real life deployment with a Long Term Evolution (LTE) IBS solution are presented. Two cell-splitting scenarios in a three floor, 7500 m2 office building have been tested, both by collecting traffic and radio statistics from actual users, as well as performing controlled walk-tests in the building. It is found that cell splitting is an excellent way to enable increased indoor capacity. The isolation between floors as well as within a floor is higher than in a typical macro scenario. High throughput and fraction of spatial multiplexing is maintained even with artificially generated 100% activity. The capacity is assessed to around 2 kbps/m2/MHz with a 6 cell solution.