Integrated Sensing and Communication (ISAC) is among the early feature areas being explored for 6G in 3GPP standards. It involves the seamless integration of communication and sensing functions within a unified system architecture, where a single base station (also known as gNB), is inherently capable of supporting both roles. This paper reviews recent developments in ISAC within 3GPP, focusing on key use cases and relevant channel models, including target and background environment channels. It provides an overview of different sensing topologies and outlines ISAC requirements across various deployment contexts. The discussion then extends to link budget analysis, waveform design, beamforming strategies, and associated hardware considerations. Lastly, the paper highlights several Proof-of-Concept (PoC) systems that showcase practical implementations of ISAC concepts.

Integrated sensing and communications (ISAC) will be deployed into cellular communication systems possibly already with 5G-A and surely in 6G. This paper discusses ISAC use cases, key technology building blocks for system design with solutions and open research questions. Furthermore, we introduce our proof-of-concept (PoC) based on commercially available 5G communications hardware at mm-Wave frequencies, with sensing-specific algorithmic extensions. This new ISAC PoC can perform jointly high data-rate communications and OFDM radar sensing in the same frequency band. Initial pedestrian detection results are shown, indicating the practicability of ISAC in future cellular networks. The results also indicate our achievable sensing range and provide hints to the achievable range estimation accuracy, based on the stability of the PoC system communications hardware.

Integrated Sensing And Communication (ISAC)forms a symbiosis between the human need for communication and the need for increasing productivity, by extracting environmental information leveraging the communication network. As multiple sensory already create a perception of the environment, an investigation into the advantages of ISAC compare to such modalities is required. Therefore, we introduce MaxRay, an ISAC framework allowing to simulate communication, sensing, and additional sensory jointly. Emphasizing the challenges for creating such sensing networks, we introduce the required propagation properties for sensing and how they are leveraged. To compare the performance of the different sensing techniques, we analyze four commonly used metrics used in different fields and evaluate their advantages and disadvantages for sensing. We depict that a metric based on prominence is suitable to cover most algorithms. Further we highlight the requirement of clutter removal algorithms, using two standard clutter removal techniques to detect a target in a typical industrial scenario. In general a versatile framework, allowing to create automatically labeled datasets to investigate a large variety of tasks is demonstrated.

The 6th Generation (6G) radio access technology is expected to support extreme communication requirements in terms of throughput, latency and reliability, which can only be achieved by providing capillary wireless coverage. In this paper, we present our vision for short-range low power 6G 'in-X' subnetworks, with the 'X' standing for the entity in which the cell in which the subnetwork is deployed, e.g., a production module, a robot, a vehicle, a house or even a human body. Such cells can support services that can be life-critical and that traditionally relied on wired systems. We discuss potential deployment options, as well as candidate air interface components and spectrum bands. Interference management is identified as a major challenge in dense deployments, which needs to handle also non-cellular types of interference like jamming attacks and impulsive noise. A qualitative example of interference-robust system design is also presented.

The current standard IEEE 802.16e [1], base of the well-known WiMAX Mobile System Profile [2], provides Orthogonal Frequency Division Multiple Access (OFDMA) allowing efficient resource sharing and coping with multipath propagation in dense urban environments. OFDMA is also a dominant candidate for future 4G wireless communication systems. However, in cellular networks without explicit precaution co-channel interference causes severe performance degradation in terms of coverage and data throughput, particularly in systems with low frequency reuse factor.

Massive multiple-input multiple-output (MIMO), the cornerstone of 5G, is in theory well understood, but many parts of the practical challenge remain unclear, e.g. what antenna configuration is suitable for which scenario. Inheriting from the over-provisioning of antennas and thus the possibility of creating an ultra-reliable wireless link, Massive MIMO is also intended for industrial scenarios. In these environments, a large number of reflectors, movements, and distortions are to be expected, which results in a high variation of fading and propagation delay. We show that in the case of distributed antennas these channel outages through fading/blockage are minimized Comparing this case to the standard co-located approach, the link-reliability is increased by more than 3 dB for the same amount of antennas. This is verified in two different, yet typical, future factory environments by using standard channel parameters. Through these measurements we show that the requirement of perfectly syncing the distributed antenna arrays can be relaxed, still achieving reasonable gains.

Robust and versatile localization techniques are the key to the success of the next industrial revolution. Yet, it is uncertain which combination of sensors will be the most robust and valuable. Thus, we present a versatile and reproducible measurement system incorporating a manifold number of state-of-the art sensors to compare and fuse the raw input data. It is shown that some techniques show very good results on the same scenario and data-set, but fall apart on translating to a slightly different scenario. In general we show that the vanilla approach to fuse the raw data achieves reasonable results in the generalization domain, demonstrating that radio frequency (RF) localization techniques in combination with an inertial measurement unit (IMU) could result in a very robust and promising candidate for solving this challenging task.

In cyclic-prefix orthogonal frequency-division multiplexing (CP-OFDM)-based radio access, the coexistence of different technologies without precise time-frequency synchronization is limited due to high out-of-band (OOB) emissions. Therefore, the spectrum enhancement techniques play a key role in relaxing the synchronization and power control requirements. This allows a higher degree of opportunistic spectrum use with minimized interference. In addition, all the transmitting devices have to fulfill specific transmitted signal quality requirements, including the maximum OOB radiated signal power. With the orthogonal frequency-division multiplexing (OFDM)-based radio access, some additional signal processing for improved spectrum containment is commonly needed to achieve these requirements. The filtering and time-domain windowing are two fundamentally different approaches for spectrum enhancement. The filtered OFDM (F-OFDM) provides better spectrum localization than the time-windowing schemes [such as windowed overlap-add (WOLA)], with the cost of higher complexity. This article introduces low-complexity solutions for spectrally enhanced narrowband OFDM transmitters based on the use of lookup tables (LUTs). The proposed LUT approach, requiring only memory units and a low number of additions, allows to avoid all computationally expensive operations in online transmitter processing, as it builds the transmitted signal by summing the stored partial waveforms optimized offline. In certain cases, completely multiplication- and summation-free designs are possible. The transmitters of narrowband Internet of Things (NB-IoT) devices are natural applications for the proposed LUT approach, as they require additional digital baseband signal processing to reach the emission requirements. It is shown that the proposed LUT schemes can provide significant savings in real-time computations of NB-IoT devices, while fulfilling the 3GPP requirements.

In cyclic-prefix orthogonal frequency-division multiplexing (CP-OFDM) based radio access, the coexistence of different systems without precise time-frequency synchronization is limited due to high out-of-band emissions. Therefore, filtered-OFDM (F-OFDM) type spectrum enhancement can play a key role to relax the synchronization requirements as it provides well-contained spectrum through subband based filtering. This allows higher degree of flexible and dynamic spectrum use with minimized interference. However, this approach increases computational complexity compared with CP-OFDM. This paper presents a low-complexity solution for narrow-band F-OFDM transmitters based on the use of a look-up table (LUT) to store the F-OFDM waveform. This approach can be applied equally well for filtered version of the discrete Fourier transform-spread-OFDM (DFT-s-OFDM) waveform with small number of subcarriers. DFT-s-OFDM is commonly used in the uplink of OFDM-based systems to mitigate high peak-to-average power ratio (PAPR) of OFDM. The scheme is particularly interesting for the transmitters of Internet-of-Things (IoT) or massive machine type communication (mMTC) devices operating at low data rate. The LUT approach requires only memory units and relatively low number of additions. Moreover, we propose a low-complexity solution to deal with the CP-length variations within the transmission frame. The required memory wordlengths are evaluated through simulations. Comparisons with time-domain filtering and fast-convolution-based filtering solutions are included as well.

This chapter ventures in detail into antenna design, analog, digital and hybrid beamforming, covers novel physical layer (PHY), media access control (MAC), design paradigms and specific solutions for serving and multiplexing the main service types envisioned for 5th generation (5G). The support of multiple antennas both at the base station (BS) and at the device will be a fundamental corner stone of 5G. The chapter covers relevant criteria for the PHY and MAC design, including considerations of harmonization, for instance between different radio access technologies (RATs). It provides a more in-depth analysis of the waveform candidates and means for multiplexing user transmissions. The chapter delves into details on waveforms, numerology, modulation schemes, and coding approaches. It also provides more details on the related options that can be drawn from both forward error correction (FEC) and hybrid automatic repeat request (HARQ), and the respective interdependencies.

ONE5G (E2E-aware Optimizations and advancements for the Network Edge of 5G New Radio) is an European funded collaborative project, aiming at designing Radio Access Network (RAN) enhancements to address the multiplicity of services and deployment scenarios for 5G. The project will build upon the specification already defined in 3GPP to propose advanced link techniques and optimization schemes taking into account an end-to- end (E2E) performance view. This paper describes the scenarios considered in the project and the set of uses cases considered, as well as the approach to define Key Performance Indicators reflecting the E2E performance. The technical areas investigated in the project are presented, as well as the planned prototypes.

Fundamental research for 5G is well under way, and mobile communication networks on the brink toward a new innovation cycle including intriguing application visions such as Gigabit wireless connectivity, Internet of Things, and Tactile Internet. From a technical perspective it seems to be utmost challenging to provide uniform service experience to users under the premises of heterogeneous networking or future small-cell scenarios. Not only must the network operators be well prepared to take on the challenge of a much higher per-user rate and increasing overall required bandwidth but also to realize service differentiation with very different (virtually contradicting) application requirements. Consequently, the radio access has to be flexible, scalable, content aware, robust, reliable, and efficient in terms of energy and spectrum. In fact, with the limitations of current 4G system outlined in this chapter, the requirements will put further pressure on the common value chains on which the operators rely in order to compensate for investment costs for future user services. Hence, there is a clear motivation for an innovative and in part disruptive redesign of the physical (PHY) layer as presented in this chapter.

One of the key use cases of fifth generation of mobile radio (5G) is to deliver ultra-reliable low latency communication (URLLC). Besides antenna- and frequency diversity techniques, hybrid automatic repeat request (HARQ) is a powerful tool to increase reliability. However, due to the low latency requirement, only a very small number of retransmissions can be carried out. In this paper, we consider the help of additional supporting user equipment (sUE) devices. The sUE listens to the transmitter user equipment (tUE) and relays the retransmitted data in case the transmission fails between the tUE and the base station. The proposed approach improves reliability since the sUE offers an additional source of antenna diversity, and it can provide benefits because of better path gain conditions compared to the tUE. Hence, the number of required transmissions will be significantly reduced thanks to the side-link assistance. In this way, the complete setup can be considered as a distributed smart antenna system. The simulation results show that the considered sidelink-assisted framework achieves a significant reduction of the latency compared to the scenario relying on direct-link-only.

Upcoming fifth generation (5G) cellular networks will demand more from the physical layer (PHY) than current- generation Orthogonal Frequency Division Multiplexing (OFDM) can deliver. The 5G waveform candidate Universal Filtered OFDM (UF-OFDM) is designed to provide the flexibility required for future applications. However, the introduction of subband filters in UFMC can increase implementation complexity and low-complexity solutions need to be found. State-of-the-art technologies provide an algorithm that performs shorter-length FFTs that can reduce complexity to two to ten times that of OFDM (depending on the allocation sizes), at the cost of only approximating the exact UFMC signal. In this paper we propose a new approximation of the UFMC signal which bases on the similarity of adjacent subcarriers that can be implemented with reduced number of operations. Analysis show that the system can be implemented with only 20% more operations than standard OFDM when accepting some increase in the subband bandwidth. A more accurate solution can be implemented at roughly 3.6 times OFDM complexity. The results can reduce implementation costs for future mobile devices.

—The advent of a new generation of wireless cellular communication networks (5G) is currently being discussed both in research and standardization, while 4G is continuously evolving. Within the overall 5GPPP framework, FANTASTIC-5G is the project dealing with the design of the multi-service air interface for below 6 GHz. Ultimate target of the project is to allow the system to adapt to any means arising from diverse service requirements and device capabilities, various deployment and environment settings and mobility levels. Additionally, the ambition of the project is to have an impact to standardization. Therefore, we focus on technologies being relevant for standardization instead of proprietary elements. This paper provides some insights on the project itself and on the concepts being worked on.

This chapter provides fundamental indications about wireless communications beyond LTE/LTE-A (5G). We start by identifying the drivers for making the transition to 5G networks, and we make clear that the strict paradigm of synchronism and orthogonality as applied in LTE prevents efficiency and scalability. We challenge this paradigm and propose new key PHY-layer technology components, the core being a unified frame structure concept, which supports an integrated 5G air interface, capable of dealing both with broadband data services and small packet services within the same band. It is essential for this concept to introduce waveforms that are more robust than OFDM, for example with respect to time-frequency misalignment. Encouraging candidate waveform technologies are presented and discussed with their respective results. This goes along with the corresponding multiple access technologies, using multi-layered signals and advanced multi-user receivers. In addition, we introduce new strategies to enable "one shot transmission", with greatly reduced control signaling, particularly for sporadic traffic. These components enable an efficient and scalable air interface supporting the highly varying set of requirements originating from the 5G drivers.

Universal Filtered Orthogonal Frequency Division Multiplexing (UF-OFDM) is considered as a promising 5G waveform candidate. It requires a relatively simple transceiver structure, while achieving much better spectral properties compared to CP-OFDM. During the early deployment of 5G systems, many frequency bands will still be occupied by 4G systems, using the legacy CP-OFDM waveform. The main focus in this work lies on using the uplink shared channel (PUSCH) with both waveforms on the same carrier. We analyze the impact of inter-carrier interference (ICI) leakage on the performance of both receivers for neighboring allocations using the different waveforms. We also propose two techniques to mitigate the effect of ICI between both waveforms, namely: 1-delaying the transmitted UF-OFDM signal relative to the transmitted CPOFDM signal to reduce the ICI on the CP-OFDM receiver and 2-windowing at the UF-OFDM receiver to suppress the power spectral leakage from the CP-OFDM signal.

This paper provides indications and simulative performance evaluations of how a wireless system can profit from being able to support various subcarrier spacings concurrently. We show that with using this degree of freedom high Doppler, low latency and extended coverage scenarios are improved. In our investigations we consider different options for multi-carrier numerology, frame design and pilot placement. Based on our investigation results and general considerations we propose a set of numerology settings for 5G. Furthermore we propose a tiling concept, enabling the parallel usage of different user-specific numerologies.