Modifications of pilot patterns for channel estimation in networks 802.11P standards

Prototypes of 802.11p communication protocols in Vehicular Ad Hoc Network networks were created to work with fixed or slow moving vehicles and, therefore, did not take into account the negative impact of high speed vehicles on the characteristics of Vehicle 2 Vehicle radio channels (communication channels between mobile vehicles). «Cross layered methods» modify of the Wireless Local Area Network frame structure, which do not affect the standardized procedures and characteristics of the two lower layers (physical and medium access control). In this paper, the concept of «cross layered» modification contains two differences from the solutions: first of all, the inclusion of additional pilot signals for channel estimation, that reduce the speed of information transfer is carried out only when exceeding a certain threshold of high speeds interacting mobile vehicles in the Wireless Local Area Network coverage area, which leads to the appearance of rapid fades in the channel. Secondly, additional pilot signals have a regular hexagonal configuration, which allows to obtain the channel state information by linear 2×1D interpolation. Parameters, characterizing the spreading of the channel in time and frequency, are random variables that are depended on environmental factors. The system designer always faces the problem of parameter selection Nt and Nf distance between pilots along the axes of time and frequency. Creating a pilot signals grid that adapts to changes in channel parameters can be a solution to this problem. To determine the appropriateness of the introduction of adaptation, it is necessary to assess how much the assessment of the estimation state of the channel deteriorates when it used and with the actual values spreading in the radio channel.