The most wide-spread wireless technologies are 3GPP cellular networking solutions (e.g., LTE-A) and IEEE WLAN solutions (e.g., WiFi). Traditionally, these two served distinct purposes. Cellular systems were commonly used for outdoor and long-range communication with limited data-rate, whereas WiFi networks provided short-range communication within residential and office environments. The operational distinction between these two technologies has (almost) disappeared within the past few years, encouraging a more seamless multi-RAT capability in 5G networks. In this poster, we illustrate and evaluate a full-stack and real-time implementation of a multi-RAT system, whose implementation will be publicly made available.

Spatially-coupled regular LDPC code ensembles have outstanding performance with belief propagation decoding and can perform arbitrarily close to the Shannon limit without requiring irregular graph structures. In this paper, we are concerned with the performance and complexity of spatially-coupled ensembles with a rate-compatibility constraint. Spatially-coupled regular ensembles that support rate-compatibility through extension have been proposed before and show very good performance if the node degrees and the coupling width are chosen appropriately. But due to the strict constraint of maintaining a regular degree, there exist certain unfavorable rates that exhibit bad performance and high decoding complexity. We introduce an altered LDPC ensemble construction that changes the evolution of degrees over subsequent incremental redundancy steps in such a way, that the degrees can be kept low to achieve outstanding performance close to Shannon limit for all rates. These ensembles always outperform their regular counterparts at small coupling width.

Spatially coupled regular LDPC code ensembles have outstanding performance with belief propagation decoding and can perform close to the Shannon limit. In this paper we investigate the suitability of coupled regular LDPC code ensembles with respect to rate-flexibility. Regular ensembles with good performance and low complexity exist for a variety of specific code rates. On the other hand it can be observed that outside this set of favorable rational rates the complexity and performance penalty become unreasonably high. We therefore propose ensembles with slight irregularity that allow us to smoothly cover the complete range of rational rates. Our simple construction allows a performance with negligible gap to the Shannon limit while maintaining complexity as low as for the best regular code ensembles. At the same time the construction guarantees that asymptotically the minimum distance grows linearly with the length of the coupled blocks.

The field of machine-to-machine (M2M) communications has gained wide popularity and is steadily growing. This paper studies the feasibility of using the Global System for Mobile Communications and in particular the General Packet Radio Service (GPRS) for a low data rate long- lasting battery-powered operation of M2M devices. A model is introduced to estimate the power consumption of a GPRS connection. It allows the identification and evaluation of optimizations of the data transmission procedures. Two M2M modes of GPRS operation are introduced. For applications with frequent transmissions, an Always- on-mode turns out to be most reasonable. For infrequent transmissions, e.g., one transmission every 2 hours, an On/off-mode reduces the power consumption of M2M devices by 93% as compared to the Always-on-mode. With a 3-cell battery providing 25.9 Wh of energy and considering only the power consumption of the communication module, a battery lifetime of up to 5 years is feasible. Measurements show that usually 40% of the energy spent for a short data transmission is wasted by one particular GPRS procedure called non-DRX period. Avoiding this saves up to 35% of total average power, depending on the rate of data transmissions.