s decremented by one. When it is equal to zero, new resources must be selected and reserved with probability (1 - p) where the UE/vehicle can set the value of p between 0 and 0.8. New resources also need to be reserved, if the size of the packet to be transmitted does not fit in the subchannel(s) previously reserved. The reselection counter is randomly chosen every time that new resources are reserved. Packets can be transmitted every 100 subframes or in multiples of 100 subframes with a minimum of one packet per subframe. Each UE/vehicle includes its packet transmission interval in the resource reserva- tion field of its SCI. The semi-persistent reservation of resources and the inclusion of the Vehicle-to-Everything (V2X) Communications reselection counter and packet transmission interval in the SCI would help other vehicles to estimate the [potentially] unused subchannels when making their own reservation, resulting in reduced risk of packet collision. Let us assume that a vehicle needs to reserve new subchannels at time Treservation It can reserve subchannels between Treservation and the maximum latency of 100 ms. This interval is referred to as the selection window (see Fig. 7.19). Within the selection window, the vehicle identifies candidate single-subframe resources (CSR) to be reserved by all groups of adja- cent subchannels within the same subframe where the SCI + TB information to be transmit- ted would fit. The vehicle analyzes the information it has received in the previous 1000 subframes before time instant Treservation and creates a list of permissible CSRs. LTE V2X mode 4 provides an option for each packet to be transmitted twice to increase the reliability. The sensing-based SPS scheme randomly selects a CSR from a candidate list for the redundant transmission of the SCI + TB. 3GPP Rel-14 includes a variant of the sensing- based SPS scheme for pedestrian-to-vehicle communications, where pedestrians broadcast their presence using mobile devices. Since the sensing process increases the battery con- s