The density of nodes in mobile communication networks as well as the requirement for data throughput has increased steadily in the last decades. Since the available frequency spectrum is limited and bandwidth is a scarce resource, future communication systems are expected to utilize it as efficient as possible. In future systems, increased spectral efficiency (more bits per second per Hertz of bandwidth) as well as improved link reliability become even more important. In order to meet the continuously growing demands, extensive efforts are made to develop new standards for the evolution of existing third generation (3G) technologies. The next steps in the development of future cellular networks are the implementation of 3GPP long term evolution (LTE) technology and its upcoming fourth generation (4G) successor LTE-Advanced. The aim of next generation technologies is to provide mobile users with high data rates that meet the requirements for future cellular networks. LTE-Advanced offers higher bandwidths as compared to 3G technologies, but the carrier frequency is expected to be increased (possibly to 2.6 GHz). Since transmission at higher frequencies may reduce coverage range due to increased attenuation, concepts to mitigate this effect are required to fulfill the demands on 4G systems also at the cell edges. Recent research results show that cooperative schemes can solve many of the issues faced by future wireless networks. Such cooperative schemes can include cooperation among several base stations or between mobile user equipment in order to form distributed multiple-input multiple-output (MIMO) arrays to achieve higher spectral efficiency and/or data rates. Other schemes make use of one or several (cooperating) relay stations that increase data rates over larger distances.
The aim of this project is to develop cooperative methods for implementation in LTE-Advanced based cellular networks. The schemes are required to fulfill the demands of 4G systems as defined by the International Telecommunication Union (ITU), while the costs such as the required infrastructure (e.g. number of base stations), backhaul traffic, delay, or financial costs should be minimized. Such costs might be reduced by sophisticated cooperative schemes. Recent academic results suggest a huge potential for performance increase in cooperative communication networks. Relay based concepts and multinode cooperation are expected to be key enablers for high spectral efficiency, large coverage, and low latency. The expected gains should be investigated under realistic conditions. The concepts developed in this project should be applicable specifically for LTE and LTE-Advanced networks. In particular, we focus on three different scenarios:
A: Cooperation between base stations and possibly also between mobile user stations in micro- and femtocells,
B: Multinode cooperation with the use of additional nodes acting as relays in macrocells as well as in micro- and femtocells, and