IEEE Std 1609.3-2020 pdf download

IEEE Std 1609.3-2020 pdf download.IEEE Standard for Wireless Access in Vehicular Environments (WAVE)一Networking.
6.2.2.2.6 Timing Advertisement service request
A Timing Advertisement service request indicates to the WME that another entity wishes to have
Timing Advertisement frames transmitted on its behalf and, possibly, channel access provided.
Acceptance of a WME-TimingAdvertisementService.request results in the consideration ot the
service request in determining channel access assignments and in generating TA requests to the
MIME
6.2.2.3 Changing service requests
Upon receipt of any service request with Action equal to Change, the corresponding application service information is updated in the MIB and in the WME channel access assignment function. Changing of an ongoing WAVE Service Advertisement is covered in more detail in 6.2.4.2.2.
6.2.2.4 Deleting service requests
Upon receipt of any service request with Action equal to Delete, the corresponding applic.tion service information is removed from the MIB and from the WME channel access assignment function. Additional processing is specified in 6.2.3.6 and 6.2.4.4.
6.2.3 Channel access assignment
6.2.3.1 General
Each of the features specified in the subdauses of 6.2.3 are optional. Networking Services assigns local radio channel resources in support o1 service requests. This includes assigning radio resources to particular channels to provide data communication opportunities for the requesting entities. The primitive exchanges related to channel access assignment for provider and user service requests are illustrated in Figure 8 and described here and in more detail in the following subclauses. Additional flows are depicted in Annex E.
In general, the access assignment algorithm may give precedence to requests with higher priority. Channel service requests with a higher priority may take precedence over lower priority assignments that would interfere with ongoing channel operation. For example, SCH access in support of a user service request may tie assigned but without the requested In,,,,ediateAccess. Any prioritization of service requests, based on configuration information or information received from the requesting higher layer, is not specified in this standard.
Other factors may be considered, such as the following:
— The geographic proximity to the transmitter of the WSA
— Link quality associated with the transmitter of the WSA
— A FVhcat i n service du rat ion
After channel access has been assigned, certain events such as the following should cause the assignment to be ended, Refer to 623.6:
— Application service has been deleted (6.2.2.4)
— User service request no longer matching an available applitt*in service opportunity
(6.3)
— Need to satisfy a service request with higher priority
— Loss of lower layer synchronization indicated by receipt of MLMEXCflENDindication per IEEE Std 1609.4
— Other factors, such as poor Link Quality (63.4)
6.2.3.3 Assignments in support of provider service requests
When service channels are assigned to fulfill provider service requests, in addition to generating a series of WSAs for transmission via WSMI as specified in 6.2.4.2, the WME triggers MAC sublayer processing by sending an MLMEX-CHSTART.request to start service channel access.
6.2.4.2.2 Changing advertisements
The WME may change the .onteuts of Wa ServiceAdverticnwnt while the advertisements are ongoing. This is useful, for example, when a new provider service request is received compatible with the Channel Info Segment in an existing WSA, when one of multiple advertised services is deleted via WME-ProviderService.request with Action equal to Ilete, or if a higher layer entity changes the Provider Service Context (PSC) in the advertised appli:ation service via a WME. ProviderService.request with Action equal to Change.
The WSA header Content Count may be used by a recipient to determine whether a WSA is a repeat of a previous WSA with the same WSA Identifier (see 822.5). The sender shall increment its value each time the WSA (including the WAVEServiceAdvertisement contents or security information) changes as described in this subclause.
If changes are made to the signed portions of a Secured WSA, the advertisement is signed and secured using the Sec-SignedL)ata.request.
Changes to ongoing advertisements should be reflected in the MIB Pror’iderSert’iceRequest Table. An information flow illustrating WSA updates is illustrated in Figure 10.