# Two-Level Sharing and Extraction of Sensing Information with Hybrid V2X Communications
## 1 Introduction  
Networking vehicles via vehicle-to-everything (V2X) communications facilitates connection among vehicles, edge servers, and cloud services. Edge servers for V2X communications play a key role in the coordination of vehicle traveling, communication quality control, and the perception of road conditions [1, 2]. Furthermore, the trends of autonomous driving brings out more challenging issues in sensing, perception, and cooperation in V2X networks. With the advances in sensing technologies, a vehicle can be equipped with various sensors, such as LiDARs, radars, cameras, and wireless RF sensors. The integration of V2X communications and the distributed sensing at vehicles is important to improve awareness and driving safety, as well as the communication quality for vehicle-to-infrastructure (V2I), vehicle-to-vehicle (V2V), and vehicle-to-network (V2N) communications [3]. Extending sensing-perception is desired due to the limited capacity of one sensor and one vehicle. The collective perception among vehicles allows vehicles to share sensing information and increase the awareness of other vehicles and obstacles [4]. In order to enable the efficiency of communication and computing in collective perception, a number of studies have been carried out, including congestion control and redundancy mitigation [5, 6]. Besides collective perception in V2X, there are also other efforts in extending sensing and perception in information and communication technology (ICT) systems to increase sensing recognition accuracy and spectrum sensing coverage. For instance, the clustering method has been examined in cognitive radio to increase the reliability and accuracy in identifying the existence of primary users [7, 8]. Furthermore, station-based multi-bandsensing has been utilized in a WLAN to improve the spatial-and-spectrum coverage of wireless sensing in a Basic Service Set (BSS) [9]. On the other hand, the specified cooperation structure, such as cluster and WLAN BSS, is not available and may be not practical for cooperation among vehicles due to the management cost and the lack of information of nearby vehicles, such as their IP addresses. In this paper, we attempt to examine the functionality of extended sensing-perception at V2X edge servers, which are expected to support reliable communications to vehicles and maneuver coordination. The general sensing information at vehicles refers to the numerical sensing results that indicate the communication quality, free space size, or distance between vehicles. For instance, the sensing information to collect and extract from vehicles can be a received signal strength indicator (RSSI) of a vehicle, or the free space size in a certain direction towards a vehicle [10; 11; 12]. An edge server increases its sensing-perception capacity by collecting and extracting sensing information from vehicles. The object information that needs to be extracted from vehicles to an edge server is the summary or statistical feature of the distributed sensing results of vehicles, such as the minimum or maximum of the sensing values among vehicles. These extracted sensing results is expected to facilitate the broadcast reliability, maneuver cooperation, and improve the awareness of road traffic conditions. We illustrate the application examples of the extended sensing-perception at a server based on distributed sensing information of communication quality and free space at vehicles. The first example is a reliable broadcast at a base station or access point (BS/AP) of an edge server. A broadcast is an important communication method in V2X and involves a number of unspecified destinations. Each vehicle monitors the communication quality, e.g., of the RSSI or the Reference Signal Received Power (RSRP), when receiving broadcast packets from the BS/AP of the edge server. By retrieving the distributed sensing results from vehicles, such as the minimum RSSI or RSRP, the edge server makes appropriate adjustments for a reliable broadcast.