Grant-Free Massive MTC-Enabled Massive MIMO: A Compressive Sensing Approach

A key challenge of massive MTC (mMTC), is the joint detection of device activity and decoding of data. The sparse characteristics of mMTC makes compressed sensing (CS) approaches a promising solution to the device detection problem. However, utilizing CS-based approaches for device detection along with channel estimation, and using the acquired estimates for coherent data transmission is suboptimal, especially when the goal is to convey only a few bits of data. First, we focus on the coherent transmission and demonstrate that it is possible to obtain more accurate channel state information by combining conventional estimators with CS-based techniques. Moreover, we illustrate that even simple power control techniques can enhance the device detection performance in mMTC setups. Second, we devise a new non-coherent transmission scheme for mMTC and specifically for grant-free random access. We design an algorithm that jointly detects device activity along with embedded information bits. The approach leverages elements from the approximate message passing (AMP) algorithm, and exploits the structured sparsity introduced by the non-coherent transmission scheme. Our analysis reveals that the proposed approach has superior performance compared to application of the original AMP approach.Comment: Submitted to IEEE Transactions on Communication

Mapping as Performing Place

Mapping is an emerging act in contemporary discourse to understand, criticize, and re-imagine complex cultural, social, and physical relationships in the built environment. Maps are documents nearly as old as the human history in representing the relationships of people to land. Yet, mapping rather than map-making is a newly created concept as an alternative way of thinking about this relationship. Mapping refers less to a representation than a performance, in which the maker, place, and the product redefine, reposition and reproduce each other in the process. Mapping may allow developing an embodied and critical understanding of place, which is continuously created through the existence, experiences, and design activities of people. On the contrary, mapping has become a frequently used word for diverse situations, some of which refer to data visualization rather than performing place, and some others hardly differ from traditional map-making practices in terms of how they reproduce dominant control mechanisms. Here, I will be discussing the ways in which mapping differs from map-making and transforms contemporary theories and practices. I will start with defining the difference of map-making and mapping and point out the ways in which mapping as a metaphor traverses and connects different disciplines, theories and practices. Next, I will argue that the shift from map-making to mapping both transforms our worldview, our understanding of space and time, and also our understanding of producing and using maps. I will point out that mapping refers to a performance rather than a representation, as such it helps us conceptualize a dynamic and embodied relationship of one to her/his environment, and an active spatiotemporality

Demonstrating genuine multipartite entanglement and nonseparability without shared reference frames

Multipartite nonlocality is of great fundamental interest and constitutes a useful resource for many quantum information protocols. However, demonstrating it in practice, by violating a Bell inequality, can be difficult. In particular, standard experimental setups require the alignment of distant parties' reference frames, which can be challenging or impossible in practice. In this work we study the violation of certain Bell inequalities, namely the Mermin, Mermin-Klyshko and Svetlichny inequalities, without shared reference frames, when parties share a Greenberger-Horne-Zeilinger (GHZ) state. Furthermore, we analyse how these violations demonstrate genuine multipartite features of entanglement and nonlocality. For 3, 4 and 5 parties, we show that it is possible to violate these inequalities with high probability, when the parties choose their measurements from the three Pauli operators, defined only with respect to their local frames. Moreover, the probability of violation, and the amount of violation, are increased when each party chooses their measurements from the four operators describing the vertices of a tetrahedron. We also consider how many randomly chosen measurement directions are needed to violate the Bell inequalities with high probability. We see that the obtained levels of violation are sufficient to also demonstrate genuine multipartite entanglement and nonseparability. Finally, we show analytically that choosing from two measurement settings per party is sufficient to demonstrate the maximum degree of genuine multipartite entanglement and nonseparability with certainty when the parties' reference frames are aligned in one direction so that they differ only in rotations around one axis

Cultural Value Orientation, Social Networking Site (SNS) Use, and Homesickness in International Students

This study explores the relations between cultural value orientation, social networking site (SNS) usage intensity, and homesickness among a sample of international students studying in the United States. The results of this study determined that individuals high in collectivism and familism reported significantly more SNS usage in general. Other results revealed that students with high levels of individualism had significantly lower levels of homesickness. In addition, students with higher levels of homesickness reported a higher level of SNS usage with people back home. Based on the results this paper discusses implications and suggest interventions that could be used with international students