Smart antennas

Smart antennas have become an essential paradigm for the enhancement of capacity in cellular communications systems. In 2nd Generation Systems smart antennas were aiming at increasing capacity either by reuse within ceN (Space Division Multiple Access SDMA) or by intercell interference reduction (Spatial Filtering for Interference Reduction SFIR). Later in 3rd Generation UMTS UTRA (Universal Terrestrial Radio Access) smart antenna concepts evolved from pure beamforming techniques merely based on directional information of the radio channel to more general spacetime processing concepts which exploit a variety of available processing gains and sources of diversity. As a natural consequence the adaptive antenna and smart antenna concepts in mobile communication systems have become a hot topic in the Technical Specification Groups for Radio Access at 3GPP (Third Generation Partnership Project) who shall prepare, approve and maintain the 3GPP Technical Specifidations and Technical Reports. In this Special Issue of the European Transactions on Telecommunications journal, ainied at presenting original results in the field of Smart Antennas, contributions are collected, which emerged from a special session of the World Micro-Technologies Congress (Hannover, Germany, 2000) which has been incorporated within EXPO 2000. The presented selection of papers comprises almost all varieties of considering and deploying smart antenna concepts in mobile communication systems both in radio layer 1 and 2. The first three papers explicitely refer to applications ofsmart antennas for UTRA FDD and UTRA TDD. The first paper, by C. Brunner, W. Utschick, and J.A. Nossek, presents an overview of eigenbeamfoning concepts in the uplink and downlink techniques for UTRA FDD; the focal point of the paper is the efficient use of short-term and long-term properties of the radio channel. In the second paper, A. Jarosch and D. Dahlhaus focus on the downlink in UTR4 FDD; simple linear demodulation schemes exploiting the space and time diversity of the mobile radic channel are derived. Smart Antennas for UTRA TDD is the tenor of the paper by M. Haardt, C.F. Mecklenbr8ucker, M. Vollmer, and P. Slanina: here both uplink and downlink techniques are discussed; whereas in the uplink the emphasis is on joint detection techniques and its efficient implementation, br the downlink again the efficient use of short-term and long-term properties of the radio channel is discussed. The next two contributions are devoted to more principal investigations of downlink processing. First, H. Troger, T. Weber, M. Meurer, and P. W. Baier present a performance survey of Joint Transmission, a novel downlink transmission scheme, by exemplary system assessments and comparisons. In the next paper, by H. Boche and M. Schubert, the problem of joint downlink beamforming and power control in wireless communication systems is addressed. The third selection of papers contains two prospective topics of smart antennas in wireless communications. In the first paper, R.S. Thoma, D. Hampicke, A. Richter, and G. Sommerkorn present a new real-time MIMO vector radio channel sounder; the proposed MIMO measurement principle can be exploited to estimate channel properties at both ends of the wireless link simultaneously, and thus, dramatically enhance overall resolution of the multi path parameters. Finally, very promising strategies for radio resource management using smart antenna cellular networks are discussed by C. Hartmann and J. EberspZicher, the focus is on adaptive strategies which combine spatial reuse within the cell with dynamic inter-cell channel allocation. We would like to take this room to thank the Editor-in-Chief of the European Transactions on Telecommunications for the opportunity of publishing this Special Issue, as well as the editorial staff at ETT for their assistance during the preparation of the issue and we are especially indebted to the reviewers for their critical comments and their constructive suggestions. We also wish to express'our sincere appreciation to all the authors of this Issue, whose contributions made tis work an important document of recent theoretical and practical advancement of smart antenna concepts.