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Process

  1. The full data packet is sent by the initial sender.
  2. Any nodes that provide progress towards the destination consider themselves appropriate as a next hop and begin a countdown timer.
  3. When the countdown is complete, the data is resent either to the next hop or destination.
  4. Any node that overhears the packet being resent cancels their own timer whilst the sender interprets this as an acknowledgement and assumes the first hop has received the packet successfully.

If the initial sender doesn’t overhear the data packet being forwarded within the time Tmax, it will attempt to send the packet another 5 times before discarding the data packet.

Advantages

There has been a study regarding packet length and how it affects the reliability of transmission. It has been shown that smaller packets are more likely to be delivered than larger ones[3]. Because this algorithm sends the full data packet straight away, this means it will choose a next hop with a stable connection every time.

The BLR protocol uses the full data packet as its initial broadcast and also uses subsequent broadcasts of the data packet as passive acknowledgements. This reduces the amount of control packets required and this is a highly desirable characteristic as one of the major goals of research in this area is to minimize the amount messages required to transfer information, both to save power and reduce the chances of collisions.

Disadvantages

Although the use of subsequent broadcasts of the data packet as a passive acknowledgement may be advantages in some respects, it also results in multiple neighbours forwarding the message. This occurs when both nodes are within range of the initial sender, but not within range of each other. The following diagram illustrates this scenario:

Although the sender has detected 2 potential next hops, because A can’t overhear B forwarding the packet and vice versa, a duplicate message will be produced.

-- XiaohongWu - 2012-01-31

Topic revision: r1 - 2012-01-31 - XiaohongWu
 
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