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Identification and authentication are two essential features for traditional random access protocols. In ALOHA-based random access, the packets usually include a field with a unique user address. However, when the number of users is massive and relatively small packets are transmitted, the overhead of including such field becomes restrictive. In unsourced random access (U-RA), the packets do not include any address field for the user, which maximizes the number of useful bits that are transmitted. However, by definition an U-RA protocol does not provide user identification. This letter presents a scheme that builds upon an underlying U-RA protocol and solves the problem of user identification and authentication. In our scheme, the users generate a message authentication code (MAC) that provides these functionalities without violating the main principle of unsourced random access: the selection of codewords from a common codebook is i.i.d. among all users.

In this work we investigate the reliability aspects of uplink multi-user MIMO communication over a preallocated pool of time-frequency resources shared by a group of ultra-reliable low-latency devices. To achieve sufficient diversity, users perform multiple transmissions of their packets over a shared pool of time-frequency resources in a non-orthogonal manner. The preallocation allows users to employ fast, grant-free type of access, while sharing improves the overall spectral efficiency. The multiple transmit opportunities enhance the robustness of communication through incremental redundancy. On the base station side, we consider the performance of a minimum mean square error (MMSE) receiver, chosen for its relative simplicity.In addition to a baseline scheme in which devices randomly select the resources without coordination, we consider two other approaches based on preassigned access patterns: i) one in which all resources are utilized evenly and with equal power, and ii) another, where the spectrum is divided into high and low contention portions and users benefit from having few reliable transmissions and few diversity resources. In particular, we focus on evaluating the performance limits of the schemes as the number of antennas at the base station grows.

5G features flagship use cases with ultra reliable low latency communication (URLLC), supported through high diversity. When multiple URLLC connections are only intermittently active, dedicating many diversity resources to a single connection leads to inefficient operation. We address this problem through shared diversity resources and compare it to per-link dedicated diversity. Two receiver types are considered, minimum mean squared error (MMSE) and MMSE successive interference cancelation. Outage probability is evaluated by assuming channel estimation errors. The results show that it is possible to remain close to the reliability of reference system with a relatively low amount of pre-allocated resources.

Security and reliability are crucial requirements of modern information systems. Therefore, appropriate error detection mechanisms are necessary, in particular in systems processing confidential or private information, i.e. modern encryptors. This paper discusses error detection in software and hardware encryption. Cryptography basics, error detection algorithms and concurrent error detection methods are introduced first. Next, the authors describe software implementation of a prototype and present results of tests. Analysis of the results is used to assess basic error detection algorithms. Additionally, hardware-based error detection methods have been implemented in an FPGA device. The final section presents functional tests and overheads of implemented methods. Analysis of device utilization makes it possible to evaluate the error detection algorithms.

URLLC is an important new feature brought by 5G, with a potential to support a vast set of applications that rely on mission-critical links. In this article, we first discuss the principles for supporting URLLC from the perspective of the traditional assumptions and models applied in communication/information theory. We then discuss how these principles are applied in various elements of system design, such as use of various diversity sources, design of packets, and access protocols. The important message is that there is a need to optimize the transmission of signaling information, as well as a need for lean use of various sources of diversity.

We study coded multichannel random access schemes for ultra-reliable low-latency uplink transmissions. We concentrate on non-orthogonal access in the frequency domain, where users transmit over multiple orthogonal subchannels and inter-user collisions limit the available diversity. Two different models for contention-based random access over Rayleigh fading resources are investigated. First, a collision model is considered, in which the packet is replicated onto $K$ available resources, $K' \leq K$ of which are received without collision, and treated as diversity branches by a maximum-ratio combining (MRC) receiver. The resulting diversity degree $K'$ depends on the arrival process and coding strategy. In the second model, the slots subject to collisions are also used for MRC, such that the number of diversity branches $K$ is constant, but the resulting combined signal is affected by multiple access interference. In both models, the performance of random and deterministic repetition coding is compared. The results show that the deterministic coding approach can lead to a significantly superior performance when the arrival rate of the intermittent URLLC transmissions is low., 2019 IEEE 20th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC) - Special Session on Signal Processing for NOMA Communication Systems