Hans D. Schotten

Scenarios for 5G mobile and wireless communications: the vision of the METIS project

METIS is the EU flagship 5G project with the objective of laying the foundation for 5G systems and building consensus prior to standardization. The METIS overall approach toward 5G builds on the evolution of existing technologies complemented by new radio concepts that are designed to meet the new and challenging requirements of use cases todays radio access networks cannot support. The integration of these new radio concepts, such as massive MIMO, ultra dense networks, moving networks, and device-to-device, ultra reliable, and massive machine communications, will allow 5G to support the expected increase in mobile data volume while broadening the range of application domains that mobile communications can support beyond 2020. In this article, we describe the scenarios identified for the purpose of driving the 5G research direction. Furthermore, we give initial directions for the technology components (e.g., link level components, multinode/multiantenna, multi-RAT, and multi-layer networks and spectrum handling) that will allow the fulfillment of the requirements of the identified 5G scenarios.

Access Schemes for Mobile Cloud Computing

Mobile Cloud Computing is widely accepted as a concept that can significantly improve the user experience when accessing mobile services. By removing the limitations of mobile devices with respect to storage and computing capabilities and providing a new level of security by a centralized maintenance of security-critical software for e.g. mobile payment applications, it is expected that it will find broad acceptance on the business as well as consumer side. Research indicates [1] that Mobile Cloud Computing will additionally help to make visions of context services become reality. However, Mobile Cloud Computing concepts rely on an always-on connectivity and will need to provide a scalable and - when requested - quality mobile access. ”Intelligent access” schemes meeting these requirements will be discussed in this paper. They exploit the specific information available by the ”Mobile Cloud Controller”, i.e., theusers’ location, context, and requested services, and significantly evolve the Heterogeneous Access Management schemes developed for the traditional heterogeneous access scenarios. In order to evaluate the performance of these intelligent radio access management concepts in the framework of mobile cloud computing, a specialized radio network simulator will be introduced. It will be shown that a Mobile Cloud Controller establishing a Context Management Architecture can provide the requested availability and quality of mobile connectivity.

The Foundation of the Mobile and Wireless Communications System for 2020 and Beyond: Challenges, Enablers and Technology Solutions

In 2020, mobile and wireless traffic volume is expected to increase thousand-fold over 2010 figures. Moreover, an increase in the number of wirelessly-connected devices to counts in the tens of billions will have a profound impact on society. Massive machine communication, forming the basis for the Internet of Things, will make our everyday life more efficient, comfortable and safer, through a wide range of applications including traffic safety and medical services. The variety of applications and data traffic types will be significantly larger than today, and will result in more diverse requirements on services, devices and networks. METIS is set up by leading global players to prepare the migration towards tomorrows multi-purpose global communication infrastructure, serving humans and things. The main objective of METIS is to lay the foundation for this future global mobile and wireless communications system, and to generate a global consensus here. In particular, METIS will provide new solutions which fit the needs beyond 2020.

Efficient implementation of linear multiuser detectors for asynchronous CDMA systems by linear interference cancellation

The decorrelating and the linear, minimum mean-squared error (MMSE) detector for asynchronous code-division multiple-access communications are ideally infinite memory-length detectors. Finite memory approximations of these detectors require the inversion of a correlation matrix whose dimension is given by the product of the number of active users and the length of the processing window. With increasing number of active users or increasing length of the processing window, the calculation of the inverse may soon become numerically very expensive. In this paper, we prove that the decorrelating and the linear MMSE detector can both be realized by linear multistage interference cancellation algorithms with ideally an infinite number of stages. It will be shown that depending on the signal-to-noise ratio, the number of active users, and the choice of the cancellation algorithm, only a few stages are necessary to obtain the same BER performance as with the ideal detectors. The computational costs for one stage of a linear interference cancellation algorithm are essentially given by one matrix-vector multiplication. Thus, the computational complexity can be reduced considerably. Since each stage introduces a time delay equivalent to the bit duration, the number of stages also determines the detection delay. Because a few stages are sufficient, this approach can also be used to obtain receiver structures with low memory consumption and detection delay.

Coded aperture imaging with multiple measurements

In coded aperture imaging, only aperture arrays consisting of (0, 1) elements are physically realizable. If multiple coded images are obtained with different aperture masks and the resulting detector images are suitably combined, a larger variety of aperture arrays, such as multilevel, complex-valued, vector-valued, or complementary arrays becomes applicable. We present a general theory of coded aperture imaging with multiple measurements. An image reconstruction scheme from the coded images is described that results in a maximum signal-to-noise ratio. Also, the design of sets of aperture arrays is addressed and explicitly solved for several important cases. It is shown how known classes of correlation arrays can be beneficially applied to coded aperture imaging.

Exploiting the data-rate potential of MIMO channels: multi-stratum space-time coding

There is a high potential with respect to Shannon capacity in having a multiple-input multiple-output (MIMO) channel. In this paper a new MIMO coding approach, called multi-stratum space-time coding (MSSTC) is presented The principle of MSSTC is to partition the data stream and to transmit the substreams on separate strata. The transmission on every stratum is based on space-time block coding (STBC) yielding full diversity. Orthogonal superposition of the strata results in independent transmit symbols and enables therefore a high data rate. Decoding may be done successively stratum by stratum yielding reasonable receiver complexity. The structural properties inherent in MSSTC make it a robust scheme for varying channel conditions. A Shannon capacity comparison to other MIMO schemes like V- and D-BLAST is presented showing the robustness of MSSTC in different environments.

Uniformly Redundant Arrays

Uniformly Redundant Arrays (URAs) are two–dimensional binary arrays with constant sidelobes of their periodic autocorrelation function. They are widely agreed upon to be optimum mask patterns for coded aperture imaging, particularly in imaging systems with a cyclic coded mask. In this paper, a survey of all currently known construction methods for URAs is given and the sizes and open fractions of the arrays resulting from each construction method are pointed out. Alternatives to URAs for situations in which a URA does not exist, are discussed.

Optimum complementary sets and quadriphase sequences derived from q-ary m-sequences

Sequences with perfect correlation properties (i.e., vanishing sidelobes of their autocorrelation function) are applied in navigational systems, in synchronization, and for system measurement and identification. Since only one periodic perfect binary sequence (length N=4) is known, on the one hand polyphase sequences with a larger phase alphabet, especially quadriphase sequences, and on the other hand so-called complementary sets of sequences have been applied (Golay 1961). Pairs of sequences are called aperiodic or periodic complementary sets (ACS or PCS) if the sum of their aperiodic or periodic respectively autocorrelation functions is a delta function. Complementary pairs of binary sequences cannot exist for all lengths. Therefore, sets of ternary sequences with the elements -1, 0 and 1 have been investigated. Since for technical reasons the number of zero-elements should be as small as possible, ternary complementary sets are called optimum if no set with a smaller number of zero-elements exists. Ternary aperiodic complementary sets have been investigated in Garvish and Lempel (1994). In this paper, the construction of new optimum PCS and almost perfect quadriphase sequences is described.

Improving channel reciprocity for effective key management systems

We propose a secret key management system for wireless ad-hoc networks, by utilizing the random and reciprocal variations of the wireless channel. We record the variations of the received signal strength and pre-process it before quantizing. The pre-processing of channel measurements improves the channel reciprocity. The quantized preliminary keys are then synchronized and their privacy is amplified to obtain, a final secure key. We validate the proposed method on an testbed and evaluate its performance. We also compare our method to other existing methods to show a significant improvement in the performance of key generation.

The SELFNET approach for autonomic management in an NFV/SDN networking paradigm

To meet the challenging key performance indicators of the fifth generation (5G) system, the network infrastructure becomes more heterogeneous and complex. This will bring a high pressure on the reduction of OPEX and the improvement of the user experience. Hence, shifting todays manual and semi-automatic network management into an autonomic and intelligent framework will play a vital role in the upcoming 5G system. Based on the cutting-edge technologies, such as Software-Defined Networking and Network Function Virtualization, a novel management framework upon the software-defined and Virtualized Network is proposed by EU H2020 SELFNET project. In the paper, the reference architecture of SELFNET, which is divided into Infrastructure Layer, Virtualized Network Layer, SON Control Layer, SON Autonomic Layer, NFV Orchestration and Management Layer, and Access Layer, will be presented.