Abstract-The throughput of multicell systems is inherently limited by interference and the available communication resources.Coordinated resource allocation is the key to efficient performance, but the demand on backhaul signaling and computational resources grows rapidly with number of cells, terminals, and subcarriers. To handle this, we propose a novel multicell framework with dynamic cooperation clusters where each terminal is jointly served by a small set of base stations. Each base station coordinates interference to neighboring terminals only, thus limiting backhaul signalling and making the framework scalable. This framework can describe anything from interference channels to ideal joint multicell transmission. The resource allocation (i.e., precoding and scheduling) is formulated as an optimization problem (P1) with performance described by arbitrary monotonic functions of the signal-to-interference-and-noise ratios (SINRs) and arbitrary linear power constraints. Although (P1) is nonconvex and difficult to solve optimally, we are able to prove: 1) optimality of single-stream beamforming; 2) conditions for full power usage; and 3) a precoding parametrization based on a few parameters between zero and one. These optimality properties are used to propose low-complexity strategies: both a centralized scheme and a distributed version that only requires local channel knowledge and processing. We evaluate the performance on measured multicell channels and observe that the proposed strategies achieve close-to-optimal performance among centralized and distributed solutions, respectively. In addition, we show that multicell interference coordination can give substantial improvements in sum performance, but that joint transmission is very sensitive to synchronization errors and that some terminals can experience performance degradations.

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The introduction of 8x8 MIMO and carrier aggregation in the 3GPP LTE Rel. 10 opens up for increased user throughput. The potential gains using these techniques have been evaluated in a field measurement campaign with a testbed implementation. A downlink throughput exceeding 1 Gbps has been achieved combining 8x8 MIMO in an outdoor macro scenario with carrier aggregation using three component carriers (3x20 MHz). The relation between the achievable throughput and the channel richness arising from the physical environment and antenna spacing was demonstrated. The performance of MIMO setups ranging from 1x2 up to 8x8 was evaluated in indoor-toindoor, outdoor-to-indoor, and outdoor-to-outdoor deployments. It was observed that each added transmit or receive antenna increased the throughput. These gains were achieved with a compact UE antenna that is reasonable in size for implementation in a consumer device.

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The objective of this paper is to improve the knowledge on directional channel characteristics at the base station, particularly concerning elevation. For this purpose a channel measurement campaign has been performed. A powerful new method for super-resolution channel estimation has been used to get a detailed picture of the directional characteristics of the channel. This has further led to improved knowledge of when processes like diffraction over rooftops and/or specular reflections are important. The findings herein have been incorporated into a model for the elevation angle dispersion which is proposed as an extension to some commonly used directional channel models such as the ITU-IMT-Advanced model. I.

Since the first generation of cellular networks was rolled out, the priority has been to improve the connectivity and capacity of densely populated areas, such as urban centers, whereas rural areas received less attention. The lower subscriber density of such areas makes it difficult to get a positive business case with current wireless technologies and current cost structures. Base stations are deployed more sparsely in rural areas and are typically shared by several operators and are thus not able to provide high-performance connectivity, compared to urban areas, resulting in a connectivity gap. Third Generation Partnership Project (3GPP) is currently introducing Non-Terrestrial Networks (NTN) in 5G NR scope with Release 17 for broadband services, and this development will likely continue in 6G networks. In parallel, Sparse Terrestrial Networks (STN) using high towers and large antenna arrays, are being developed to deliver very long transmission ranges. In this paper we discuss the characteristics and the expected performance of networks based on satellites or terrestrial large cell networks, in relation to the traffic density and required infrastructure, with a focus on remote and sparsely populated areas. The two solutions are found to deliver in complementary traffic and partly different use case scenarios.