Studying and improving the performance of ETSI ITS contention-based forwarding (CBF) in urban and highway scenarios: S-FoT+

Evaluation of Greedy and CBF for ETSI non-area GeoNetworking: The impact of DCC

“…The impairments of area forwarding algorithms, Area CBF and Simple area forwarding, have been analyzed thoroughly [8,9,10,11,12,13,14,15]. These works reveal inefficiencies such as redundant retransmissions due to Decentralized Congestion Control (DCC) queues [15,16], the need for persistent duplicate packet detection [12,14], or poor dissemination coverage [8,9,11,15,17]. These papers have also proposed a number of enhancements to ETSI Area CBF to overcome the shortcomings identified.…”

“…The ETSI Area CBF algorithm has been evaluated in recent works [14,15,25]. The work in [14,15] identifies several phenomena affecting CBF due to the interaction between layers in the architecture that make ETSI CBF inefficient, and proposes improvements to solve the detected problems.…”

“…The ETSI Area CBF algorithm has been evaluated in recent works [14,15,25]. The work in [14,15] identifies several phenomena affecting CBF due to the interaction between layers in the architecture that make ETSI CBF inefficient, and proposes improvements to solve the detected problems. In particular, the performance of ETSI Area CBF is affected by the interaction between the Network & Transport (where GeoNetworking resides) and Access layers.…”

“…In particular, the performance of ETSI Area CBF is affected by the interaction between the Network & Transport (where GeoNetworking resides) and Access layers. The difference between the time a packet is expected to be transmitted and the actual time it occurs -since a transmission can be delayed by DCC -causes different phenomena explored in [14,15,25], which in turn affects the behavior of CBF, drifting away from what it is expected toward a highly inefficient performance. For example, the optimal forwarder might see its transmission delayed by DCC, and then sub-optimal forwarders do not cancel their CBF timers, send their packets to the Access layer and, given a set of circumstances, forward a message that breaks the expected system behavior.…”

“…In some cases, the message might not even be transmitted, since forwarding occurs with low priority. Forward on Time (FoT), presented in [14] uses the Cross-layer DCC information available at the Management Entity to: 1) calculate the CBF timer (choosing the maximum between the distance-based timer and the time to the next allowed transmission), and 2) decide when to move a packet from the CBF buffer to the Access layer (i.e., only if the time to the next allowed transmission is zero, or if it has already passed and no transmission occurred, as proposed in the FoT+ mechanism from [15]). Thus, if a candidate with better possibilities to access the medium is able to forward the packet (thus becoming the best candidate when network congestion is high), the rest of the candidates, if they are worse forwarders, will be able to cancel their copies in their CBF buffers.…”