This paper introduces an Integrated Sensing and Communication (ISAC) approach to safeguard communication User Equipment (UE) from approaching objects or people, such as potential blockers, without the need to scan the entire environment, while providing continuous communication services. The proposed UE-centered ISAC system utilizes a communication-centric waveform, transmitted through guard beams to monitor the area within the UE proximity. These guard beams are generated through a multi-beamforming technique employing a shared analog array that also generates the communication beam. The parameters for generating the guard beams are optimized to maximize sensing coverage while adhering to the communication Signal-to-Noise Ratio (SNR) constraints. In comparison to the detection using the communication-beam-only system, our optimized guard beams enhance the detection range and coverage area by over 1.5 times while maintaining the required communication SNR. Our multi-stage sensing pipeline applied to the guard beams significantly reduces the complexity of sensing signal processing required to detect approaching blockers while maintaining accuracy comparable to that of exhaustive scanning based on the grid-searching method. Furthermore, the guard beams approach reduces the impact on communication SNR by 0.7 dB factor compared to exhaustive scanning with a balanced communication-sensing power allocation, offering a less pronounced impact on the communication performance in an ISAC system.

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This paper studies a promising use case of a private 5G network for the sports industry: wearable bodycams and sensors in a football match. This use case requires a reliable and dedicated massive MIMO network to provide uniform coverage with a high capacity in the whole pitch area. The coverage of co-located and distributed (cell-free) massive MIMO, differing in the configuration of base station antenna placement inside the stadium, are evaluated through ray tracing using a 3D stadium model and players' mobility dataset. The results give insight into how distributed antennas inside the stadium should be deployed to enhance the uniform coverage of moving wearable devices. Besides that, the uplink capacity performance and the impact of channel aging on the capacity are also evaluated. The results demonstrate the advantages and disadvantages of different base station antenna distribution strategies in terms of coverage, capacity and channel aging impact.@en

We exploit a dense cell-free mmWave network where User Equipments (UEs) are served by multiple highly directional beams provided by multiple Base Stations (BSs) simultaneously. Such multi-beam scenarios can either offer high spectral efficiency when different information is transmitted through each beam or a diversity gain when each beam transmits the same information. However, this increased spectral efficiency or diversity gain costs a more complex network association phase. A UE requires finding multiple nearby serving BSs and determining the optimal beam pair for each one. Thus, an efficient association process is urgently needed. In this work, we propose a UE-initiated association method for dense cell-free mmWave networks. We design an efficient beam training mechanism with multiple BSs using hybrid beamforming. We evaluate the proposed association method under different network configurations. The simulation results show that compared to traditional solutions, our proposed association method can lead to maximally 100% faster beam training and reduce energy consumption by up to 77%. The proposed UE-initiated association method is also scalable to the number of RF chains and antennas at BSs and UEs, making it very suitable for dense cell-free networks.@en

The link misalignment and high susceptibility to blockages are the biggest hurdles in realizing 60-GHz-based wireless local area networks (WLANs). However, much of the previous studies investigating 60 GHz alignment and blockage issues do not provide an accurate quantitative evaluation from the perspective of WLANs. In this article, we present an in-depth quantitative evaluation of commodity IEEE 802.11ad devices by forming a 60-GHz WLAN with two docking stations mimicking as access points (APs). Through extensive experiments, we provide important insights about directional coverage pattern of antennas, communication range, and cochannel interference and blockages. We are able to measure the IEEE 802.11ad link alignment and association overheads in absolute time units. With a very high accuracy (96%-97%), our blockage characterization can differentiate between temporary and permanent blockages caused by humans in the indoor environment, which is a key insight. Utilizing our blockage characterization, we also demonstrate intelligent handoff to alternate APs using consumer-grade IEEE 802.11ad devices. Our blockage-induced handoff experiments provide important insights that would be helpful in integrating millimeter wave-based WLANs into future wireless networks.

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