问题
I'm new to SUMO, Veins, OMNET++ and simulations with a bit background of networks. I have successfully setup environment and run veins 4.6 demo application. On google found that unlike RSU, Car modules are added on the fly.
In demo example car nodes send Airframe11p message, i'm not getting where this message is being populated because in TraCIDemo11p.cc methods (onWSA, onWSM, handleSelfMsg, handlePositionUpdate) we are dealing with WSM message types and BaseWaveApplLayer::checkAndTrackPacket methods ensures that message being sent is either BSM, WSM or WSA.
In veins\src\veins\modules\messages AirFrame11p.msg file exists but on finding references of "AirFrame11p" in project, matches are found in AirFrame11p_m.h and AirFrame11p_m.cc only. If demo is not using these files then for what purpose these files are added? and from where simulation gets the annotation of AirFrame11p.
I'm trying to simulate a car accident scenario without RSU using V2V communication, have replaced demo map with mine, generated random routes, now trying to remove RSU from demo application and exploring to send customized messages (including geo location, speed, direction, time etc) to nearby vehicles in specified range e.g. 100 meters using WiFi direct.
If i'm confusing something then please guide me. Thanks.
回答1:
The short answer: The AirFrame11p message is a lower level message that encapsulates the upper layer messages. Just use the application message type that is appropriate for your application. If you want to replace the physical layer with WiFi direct instead of 11p, and you're starting from scratch, you're probably in for quite a bit of work, since the VEINS PHY implementation is very intricate. If you have an existing implementation of WiFi direct, it may be worth investigating the integration of VEINS' TraCI implementation with that code.
Encapsulation in VEINS
You are correct that the message types at the application layer are more diverse -- these message types (BSM and WSM) are used to encapsulate "application" behavior; it's just not very well visualized in the simulation execution. You can pause the simulation and look (for example) under scheduled events, where the queued packets can be examined visually.
Unlike regular networks, where such messages would be packaged in IP, MAC and PHY encapsulations, VEINS uses the following encapsulation process: BSMs are packaged in MAC frames (80211Pkt), which in turn are encapsulated by AirFrame11p signals. So basically, you should choose the correct message type for your application.
Footnote regarding application behavior:
Technically speaking, these messages would be more correctly placed at the Facilities layer (see e.g. ETSI's spec), since the periodic exchange of messages provides data stored in the facilities layer, which is then used by cITS/VANET applications that run on top. If you need this, look at Artery (as Ventu suggested in the comments).
来源:https://stackoverflow.com/questions/48850378/which-file-to-extend-for-customized-messages-in-veins-what-is-the-purpose-of-ai