Abstract
Vehicular communications will foster mobility services and enable mass adoption of future autonomous vehicles, interchanging huge amount of data acquired from vehicles’ sensors. 3GPP Release 14 presents the first standard for supporting V2X in LTE. Several enhancements are introduced, including a new arrangement of the physical resource grid, where subchannels are the minimum resource unit instead of Resource Blocks. The resource grid is defined by several design parameters, some of them with constraints imposed by 3GPP specifications, that affect the maximum message transmission rate and efficiency of the system. Moreover, the optimum choice of these parameters is closely linked to message length, which is another variable parameter. This paper provides an analysis of the relationship between these design parameters (Resource Block per Subchannel, Transport Block Size Index, and coding rate), message size, and the system’s maximum capacity and efficiency. In doing so, we do not consider channel reuse or radio transmission characteristics because the focus of this paper is trying to find the resource grid design parameters that optimize system capacity, which is a very important aspect to consider by V2X operators.
Highlights
The ecosystem of vehicular networks opens a wide horizon of new opportunities in different sectors as in businesses and application development, which include artificial intelligence algorithms, communication protocol integration, and new wireless technologies to communicate with vehicles, pedestrians, road infrastructure, and management centres
The efficiency of the resource grid is affected and decreased by three factors: the coding rate described in Section 5, the two Resource Blocks (RBs) that are automatically dedicated for control in each message transmission, and, depending on the size of the subchannels and the size of the message, the unused space on the Transport Block (TB)
We have investigated the effect of resource grid design parameters in the capacity and efficiency of Long-Term Evolution- (LTE-)V2X as it will be used to transmit different types of data in vehicular networks, from position or speed of the vehicle up to much of its sensor data
Summary
The ecosystem of vehicular networks opens a wide horizon of new opportunities in different sectors as in businesses and application development, which include artificial intelligence algorithms, communication protocol integration, and new wireless technologies to communicate with vehicles, pedestrians, road infrastructure, and management centres. The basic cases are, for Europe, the Cooperative Awareness Message (CAM) defined by the European Telecommunications Standards Institute (ETSI) and, for the United States of America (USA), the Basic Safety Message (BSM) defined by the Society of Automotive Engineers (SAE), both of them transmitted with a periodicity of 1-10 Hz, which report the position, speed, and direction of a vehicle Both organizations have standardized several more messages, and some others are nowadays under development, as, for instance, the so-called Collective Perception Messages (CPM) where vehicles will interchange information acquired with their onboard sensors, such as objects in the road, their dimensions, presence of pedestrians, and distances between the object and the transmitting vehicle. Some of them will be transmitted much more often than others
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