Message communication in WSN is much alike the way we communicate words with others. In WSN, the technical terminology of this situation is called ‘Routing‘, whereas in our normal conversation, we understand this as ‘Speaking‘. The aim of both cases is same: to convey message to the other party! In fact, in a closer look, the way we or they convey messages also shows similarity. Let’s take a look in human conversation. Someone could only speak out the words (i.e., messages) to other if the other person just be in front of him or her. He just could ‘directly‘ speak the words out. Similarly in WSN, a sensor device or called ‘mote’, after transmitting a message out, it is straight away received by other mote which is located in it’s transmission range. Visually, it can be shown as: source mote –> destination mote. Technically, we termed this as Direct Transmission (DT); it is a single-hop message passing.
Back to the human scenario, however, someone’s voice (words) could not be heard by the other person if the other person not being just in front of him as in the previous scenario, or being in a place that his voice cannot be heard. Two simple solutions in this case is either to use a telephone to ‘convey’ the message to the other person, or tell the words to someone and asked him to pass the words to the intended recipient. We see in this scenario, the need of intermediate persons. Synonymous in WSN, in short, this situation can be shown as: source mote –> intermediate motes –> destination mote. Since the source mote and the destination mote is not within communication range, without the intermediate motes, messages has no way to reach the destination mote. Again technically, this kind of message passing through intermediate motes is known as Minimum Transmission Energy (MTE); it is a multi-hop message passing.
These are two basic communication methods practicing by us human and they motes. However, there exist a different kind of ‘dialect’ or ‘pattern’ of the communication. Let’s for the final straw, for instance in human conversation, someone could just firstly form a group of people (say, 5 persons in a group), with every person votes to elect a leader person. Note, other people around also do the same thing that forming their own group. Anyone in the group that has words to convey to the other person somewhere, simply first tells the words to the leader. The leader keeps all words, while in some cases can do an extra task such as eliminating any redundant words that may have, and then just forward the words to the other leader in the other group around. The other leader in that group finally deliver the source words to the intended person. Recall the multi-hopping method, this scenario merely same in the leader-motes communication, with pretty small differences compared to the MTE method. Comparably, this kind of message passing can be shown as: source mote –> leader motes (from a group of intermediate motes) –> destination mote, and in WSN terminology, it is known as Clustering; it is a grouped multi-hop message passing.
In conclusion, these are kind of protocols exist in human and motes communication with one similar objective: to successfully convey messages to the others. However, the process is not as simple as it may be seen, due to an ‘external forces’ the conveyed words may experienced while in the transmission. We will see that in my next blog … cheers.