scope:

The present document summarises the result from performance evaluations of CSMA and two time slotted MAC approaches through simulations. Two different time slotted MAC approaches, self-organizing time division multiple access (STDMA) and mobile slotted Aloha (MS-Aloha), have been considered in two different scenarios; highway and urban. CSMA, the MAC algorithm proposed for the current generation of vehicular ad hoc networks (VANETs) has been used as a benchmark. Packet reception probability at different distances from the transmitter together with the channel access delay has been used as performance measures. The purpose is first and foremost to evaluate the scalability of the resulting system, as initial results have shown that CSMA may degrade in performance when the number of vehicles equipped with cooperative ITS units increase.

NOTE 1: Håkan Lans holds a patent on STDMA [i.25], which expires in July 2012. The patent has been re-examined in the US cancelling all claims on March 30, 2011.

NOTE 2: A European patent procedure has been started by ISMB on MS-Aloha techniques (European patent request filed with number 10163964.9, May 26, 2010). They have received in September 2011 Communication Under Rule 71(3) EPC of the intention to grant a patent.