IEEE 1609.4:2016 pdf free download – IEEE Standard for Wireless Access inVehicular Environments (WAVE) – Multi-Channel Operation
4.1 Overview
WAVE provides a communication protocol stack optimized for the vehicular environment, employing bothcustomized and general-purpose elements, as illustrated in Figure 1 and Figure 2.WAVE supports both IP-and non-IP-based data transfers， although individual devices might support only one networking stack.Non-IP-based data transfers are supported through the WAVE Short Message Protocol (WSMP) specifiedin IEEE Std 1609.3.Channel coordination is a collection of extensions to the IEEE 802.11 MAC. TheWAVE Management Entity (WME) and corresponding network services are specified in IEEE Std 1609.3.WAVE security services are specified in IEEE Std 1609.2.IEEE Std 1609.0 provides a description of theWAVE system architecture and operations.
To operate over multiple wireless channels while OCBActivated,there is a need to perform channelcoordination. OCBActivated indicates communication outside the context of a basic service set as specifiedin IEEE Std 802.11 (by setting dot11OCBActivated to TRUE) (i.e.，WAVE operation). Channelcoordination is specified in this standard and consists of additional features for OCBActivatedcommunication in the MAC sublayer specified in IEEE Std 802.11.Both data plane and managemententities are included as shown in Figure 2. These features are introduced in 4.2 and specified in Clause 5and Clause 6.
The scope of this standard is shown in Figure 2.This standard specifies extensions to the IEEE 802.11MAC sublayer.These extensions include channel coordination features in support of multi-channeloperation (see 5.2) and additions to the primitives used for transmitting data (see 5.3).The result is anextended variant of the MAC sublayer specified in TEEE Std 802.11 rather than a new sublayer in theprotocol stack.
The MAC and PHY layers conceptually include management entities, called MAC sublayer managementand PHY layer management entities (MLME and PLME, respectively).These management entities providethe layer management service interfaces through which layer management functions may be invoked. InClause 6, this document specifies an extension to the IEEE 802.11 MLME to provide channel coordination.The interactions between the various entities are through service access point (SAPs) across which definedprimitives are exchanged; see Clause 7.
5.1 General
WAVE devices shall communicate outside the context of an IEEE 802.11 basic service set (i.e.,withdot11OCBActivated equal true)， as specified in IEEE Std 802.11. A transmitting WAVE device shallsupport WSMP traffic, IP traffic, or both.
A conceptual diagram of a WAVE multi-channel MAC internal architecture is shown in Figure 3. Thisdiagram facilitatcs the specification of the following transmit operations: channel routing, data queueingand prioritization， and channel coordination.Actual implementations may depart from this conceptualdiagram. A WAVE MAC entity uses one or more instances of the MAC sublayer entity specified in IEEEStd 802.11, communicating outside the context of a basic service set,with the extensions defined herein.There are two IEEE Std 802.11 MAC entities in the conceptual diagram described in this clause: one forthe CCH and one for a SCH. Data is prioritized according to access category (directly related to userpriority),as indicated by the queues shown in Figure 3, which provide different contention andtransmission parameters for data frames with different priorities. Prioritization is further specified in 5.4.
There are three types of over the air information specified by IEEE Std 802.1 1 : management frames, dataframes, and control frames. Control frames may be used per IEEE Std 802.11 and are not addressed in thisstandard. Management frames used by WAVE enter the data plane at the MAC layer. The onlymanagement frame specified for use by a WAVE device is the TA frame specified in TEEE Std 802.11.Timing Advertisement frames are used to distribute time synchronization information as specified in 6.2.