Tham khảo tài liệu 'the_handbook_of_ad_hoc_wireless_networks_7', công nghệ thông tin, quản trị mạng phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Simpo PDF Merge and Split Unregistered Version - http a Broadcast storm b Counter-based scheme Note that the extra coverage area by A show in grey is too little to warrant a transmission c Distance-based scheme If the distance d between A and B is small then there is only marginal difference in their coverage areas FIGURE a Broadcast storm b Counter-based scheme Note that the extra coverage area by A shown in gray is too little to warrant a transmission c Distance-based scheme If the distance d between A and B is small then there is only marginal difference in their coverage areas. RREQs they receive for the first time some of the rebroadcasts may be redundant. As shown in Fig. suppose Node A broadcasts a new RREQ to Nodes B and C which in turn rebroadcast to Node D. Hence Node D receives two copies of the same RREQ one of which is redundant. Moreover if Nodes B and C are close to each other and both transmit at the same time channel contention could occur. Further RTS CTS exchange is not used in broadcast transmission. If the underlying MAC does not provide collision detection capability . CSMA CA cannot listen while sending packet collisions could be damaging. The resulting redundancy contention and collisions constitute what is called the broadcast storm problem 8 . Several schemes are proposed by the authors to alleviate this problem 1. Probabilistic 2. Counter-based 3. Distance-based 4. Location-based 5. Cluster-based Below is a concise description of these schemes. In the probabilistic scheme each node rebroadcasts the message it received for the first time with some fixed probability p. 2003 by CRC Press LLC Simpo PDF Merge and Split Unregistered Version - http In the counter-based scheme each node rebroadcasts the message only if the same message has not been heard for more than C times before it itself can transmit. The assumption made by the node is that if the message has been rebroadcast several times by .
