Multiple-input multiple-output (MIMO) technology is maturing and is being incorporated into emerging wireless broadband standards like long-term evolution (LTE) [1]. For example, the LTE standard allows for up to eight antenna ports at the base station. Basically, the more antennas the transmitter/receiver is equipped with, and the more degrees of freedom that the propagation channel can provide, the better the performance in terms of data rate or link reliability. More precisely, on a quasi static channel where a code word spans across only one time and frequency coherence interval, the reliability of a point-to-point MIMO link scales according to Prob(link outage) ` SNR-ntnr where nt and nr are the numbers of transmit and receive antennas, respectively, and signal-to-noise ratio is denoted by SNR. On a channel that varies rapidly as a function of time and frequency, and where circumstances permit coding across many channel coherence intervals, the achievable rate scales as min(nt, nr) log(1 + SNR). The gains in multiuser systems are even more impressive, because such systems offer the possibility to transmit simultaneously to several users and the flexibility to select what users to schedule for reception at any given point in time [2].

/pdf/scaling-up-mimo-opportunities-and-challenges-with-very-large-puqp9v7gzk.pdf

Scaling Up MIMO: Opportunities and Challenges with Very Large Arrays

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Table Of Integrals Series And Products

Information Theory and Reliable Communication

The objective of this paper is to give a comprehensive introduction to applied cryptography with an engineer or computer scientist in mind. The emphasis is on the knowledge needed to create practical systems which supports integrity, confidentiality, or authenticity. Topics covered includes an introduction to the concepts in cryptography, attacks against cryptographic systems, key use and handling, random bit generation, encryption modes, and message authentication codes. Recommendations on algorithms and further reading is given in the end of the paper. This paper should make the reader able to build, understand and evaluate system descriptions and designs based on the cryptographic components described in the paper.

[서평]「Applied Cryptography」

The presence of both multiple-access interference (MAI) and intersymbol interference (ISI) constitutes a major impediment to reliable communications in multipath code-division multiple-access (CDMA) channels. In this paper, an iterative receiver structure is proposed for decoding multiuser information data in a convolutionally coded asynchronous multipath DS-CDMA system. The receiver performs two successive soft-output decisions, achieved by a soft-input soft-output (SISO) multiuser detector and a bank of single-user SISO channel decoders, through an iterative process. At each iteration, extrinsic information is extracted from detection and decoding stages and is then used as a priori information in the next iteration, just as in turbo decoding. Given the multipath CDMA channel model, a direct implementation of a sliding-window SISO multiuser detector has a prohibitive computational complexity. A low-complexity SISO multiuser detector is developed based on a novel nonlinear interference suppression technique, which makes use of both soft interference cancellation and instantaneous linear minimum mean-square error filtering. The properties of such a nonlinear interference suppressor are examined, and an efficient recursive implementation is derived. Simulation results demonstrate that the proposed low complexity iterative receiver structure for interference suppression and decoding offers significant performance gain over the traditional noniterative receiver structure. Moreover, at high signal-to-noise ratio, the detrimental effects of MAI and ISI in the channel can almost be completely overcome by iterative processing, and single-user performance can be approached.

/pdf/iterative-turbo-soft-interference-cancellation-and-decoding-4ha12irymu.pdf

Iterative (turbo) soft interference cancellation and decoding for coded CDMA

We introduce π/2-shifted Phase Shift Keying on the Hypersphere (π/2-PSKH), a new modulation scheme for Multiple-Input Multiple-Output (mIMO) systems. π/2-PSKH is a multidimensional extension of shifted QAM which allows to use load-modulated MIMO transmitters with a highly efficient power amplifier with reduced backoff. We propose π/2-PSKH constellations and explain how a π/2-PSKH signal is generated. The signal point sequence for π/2-PSKH is time-varying and as such has an inherent code. For the receiver, three algorithms are introduced and numerical simulations are used to examine their performance. These algorithms are further modified in order to reduce their complexity. We discuss the effect of this complexity reduction and the trade-off between receiver complexity and performance. It is shown that due to its inherent code, π/2-PSKH shows excellent performance in terms of power efficiency even if used with conventional amplifiers.

π/2-shifted phase shift keying on the hypersphere: Transmitter and receiver algorithms

In this paper, we show that Orthogonal Frequency Division Multiplexing (OFDM) is not well suited for transmission over wireless channels with intersymbol interference (ISI), if a low delay constraint prohibits the use of channel codes with long code words. We compare OFDM with single-carrier transmission for scenarios with very short block lengths and different code rates. The single-carrier receive signal is equalized and decoded using either a Turbo scheme or a so-called matched decoder, which combines channel equalization and decoding and allows for a flexible trade-off between complexity and performance. Our results show that OFDM suffers from severe losses compared to single-carrier transmission if a very low latency—corresponding to a very short block length—is required. This effect is most pronounced for high code rates.

Comparison of OFDM and Single-Carrier Transmission for Ultra-Low Delay Applications

Bei einem Sende/Empfangs-Konzept wird ein Redundanz-hinzufugender Codierer mit einer Coderate kleiner oder gleich 0,5 verwendet, um zwei Datenstrome fur zwei unterschiedliche Sender zu erhalten, die an raumlich unterschiedlichen Positionen angeordnet sind. In a transmission / reception concept, a redundancy-adding Direction encoder with a code rate is less than or equal to 0.5 is used to obtain two data streams to two different stations, which are located at spatially different positions. Beide Sender senden in demselben Frequenzband. Both stations broadcast in the same frequency band. Im Empfanger wird das Empfangssignal von einem ersten Abtaster synchron zum ersten Sender abgetastet, und von einem zweiten Abtaster synchron zum zweiten Sender abgetastet, um ein erstes und zweites Empfangssignal zu erhalten, welche einem Trellis-Decodierer zugefuhrt werden, um eine decodierte erste und zweite Empfangs-Untergruppe von Codeeinheiten zu erhalten, welche wiederum einer Berechnungseinrichtung zugefuhrt werden, um die Interferenzsignale zu berechnen, die dann zur Interferenzreduktion mit den entsprechenden Empfangssignalen kombiniert werden. In the receiver the received signal by a first scanner is scanned synchronously to the first transmitter, and scanned by a second scanner in synchronism with the second transmitter, to obtain a first and a second reception signal which are fed to a trellis decoder to provide a decoded first and second receiving to obtain subgroup of code units, which in turn are fed to a calculating means to calculate the interference signals, which are then combined into interference reduction with the corresponding received signals. Das iterative Konzept ermoglicht eine Interferenzreduktion fur Empfangssignale, die von zwei raumlich getrennten, jedoch beide im gleichen Frequenzband sendenden Sendern bestimmt werden. The iterative approach allows for interference reduction for receiving signals, which are determined by two spatially separated but both transmitting in the same frequency band transmitters. Das Empfangerkonzept zeigt eine schnelle Konvergenz und ermoglicht somit, das die beiden Sender im selben Frequenzband senden, was in einer Reduzierung der benotigten Bandbreite um die Halfte im Vergleich zu einem entsprechenden Senderkonzept resultiert, bei dem der erste und der zweite Sender bei unterschiedlichen Frequenzen senden. The receiver concept shows a fast convergence and therefore allows that the two transmitters transmit in the same frequency band, resulting in a reduction in the required bandwidth by half as compared to a corresponding transmitter concept at the sending of the first and second transmitters at different frequencies.

Sendevorrichtung und Empfangsvorrichtung Transmitting device and receiving device

In layered communication networks there are only connections between intermediate nodes in adjacent layers. Applying network coding to such networks provides a number of benefits in theory as well as in practice. We propose a "layering procedure" to transform an arbitrary network into a layered structure. Furthermore, we derive a "forward-backward duality" for linear network codes, which can be seen as an analogon to the "uplink-downlink duality" in MIMO communication systems.

Layering of Communication Networks and a Forward-Backward Duality.

Reliability-Based Hybrid Automated Repeat reQuest (RB-HARQ) strongly improves the throughput of a communications system by identifying and retransmitting the symbols deemed most unreliable after decoding the initial transmission. Additional soft-value processing, large feedback messages and many retransmissions are required to achieve a high throughput. We compare a variant of RB-HARQ designed for limited feedback with a new low-overhead, clustered Parity-Based Partial-Retransmission (PBPR) HARQ scheme. The new scheme selects symbols connected to unsatisfied parity checks and intersects this set with a subset of all symbols consisting of uniformly distributed information or parity symbols to improve the throughput. Since clustered HARQ schemes work best with codes exhibiting high intra-codeword correlations, we use Spatially-Coupled Low-Density Parity-Check (SC-LDPC) codes for evaluation.

Johannes B. Huber

Papers

π/2-shifted phase shift keying on the hypersphere: Transmitter and receiver algorithms

Comparison of OFDM and Single-Carrier Transmission for Ultra-Low Delay Applications

Sendevorrichtung und Empfangsvorrichtung Transmitting device and receiving device

Layering of Communication Networks and a Forward-Backward Duality.

Limited-Feedback Parity-Based Hybrid ARQ Using Spatially-Coupled LDPC Codes