Hi

If the vehicles are far from the transmission you should use multi-hop broadcasting.You can see this paper :

http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=4300825&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D4300825

Have you any problem in implementation in ns2?

Yes I have problems in the implementation in Ns2. The problem is that when I use routing protocols such as AODV or DSR, I should use a code to send packets from one node to another (constant bit rate) such as the code below. But the scenario that I just want one node to send a single packet to all the nodes and all the nodes are able to reply back. (The packet should travel to all the nodes in the simulation (map) or the packet can travel for a certain distance and then dropped). 

#I donot need to do code like that below

set udp_(0) [new Agent/UDP]

$ns_ attach-agent $node_(1) $udp_(0)

set null_(0) [new Agent/Null]

$ns_ attach-agent $node_(2) $null_(0)

set cbr_(0) [new Application/Traffic/CBR]

$cbr_(0) set packetSize_ 512

$cbr_(0) set interval_ 0.25

$cbr_(0) set random_ 1

$cbr_(0) set maxpkts_ 10000

$cbr_(0) attach-agent $udp_(0)

$ns_ connect $udp_(0) $null_(0)

$ns_ at 2.5568388786897245 "$cbr_(0) start"

Any Ideas?

You want to send just one packet to all of nodes?

Yes .. I am supposed to make a scheme where one node send a packet to all nodes in the map and all nodes reply by one packet. This is a simple scenario but i can extended it later

I think this link:

http://www.pudn.com/downloads155/sourcecode/comm/wireless/detail689495.html

or this implementation:

http://www.math.unipd.it/~cpalazzi/fastbroadcast.html

can be usefull for you.You should modify this codes...

I will give them a try Minoo and reply back to you soon

Minoo, Both the links use a constant bit rate to send packets. I donot think this will solve the problem

$game($i) set bmsg-interval_ $cbr_interval

$game($i) attach-agent $udp($i)

In vanet you have platoon,it means all of node may be not in one node's communication range...and you want to simulate this broadcasting in 1*1 km...Do you set mobility? All of protocols that I know sending many packet for broadcasting,because in wireless invironment we have loss in link...

I think you should create minimmum spaning tree in your network and careat link between the nodes with help of minimmum spaning tree...but if you have mobility,it's not usefull!!!

I didn't understand detailed....Is it usefull to creat n link that have 1 sender and n-1 reciever for broadcasting that you want?

 Regarding the  mobility, yes the vehicles are moving. Iam trying to let a node or a group of nodes to be able to communicate with other nodes within a specific distance apart for example the nodes can be able to send and receive messages with the upfront nodes for a distance of 1 Km or 2 Km or any distance. This is necessary in traffic management scheme because vehicles should know the traffic conditions in 1km apart. Is that clear?

This problem can be seen as distance based routing protocol where packets should be broadcasted to the vehicles in a certain distance , If the packet exceeds this distance nodes should drop it. Any ideas?

Do you think Geographic Routing such as Preferred Group Broadcast (PGB) will be useful?

You can set communication range.If two nodes aren't in their communication and any node doesn't existence between their that forwarding the packet,it will be drop.Is it your aim?

May be the geographic routing can help but i am not sure if it is implemented in NS2 or not. Do you think it is implemented?

Hello sir, I have the same problem about how to broadcast security message in VANET.

Could you please help me?

Thanks in advance...