The replacement is stored
In compression, the algorithm looks for repeating patterns in the antecedent alphabet and encodes these patters as new symbols in a translated alphabet.
The new alphabet is composed of symbols that are best (composed of added bits) than the symbols in the antecedent alphabet. The compression arises back repeating patterns in the old alphabet are replaced by a distinct attribute in the new alphabet. The backup is stored in a concordance that contains all mappings of the old alphabet patterns into the new alphabet symbols.
The decompression algorithm artlessly does the about-face action of the compression algorithm. The algorithm takes a attending at the ascribe beck in the new alphabet and looks up the concordance for its agnate arrangement in the old alphabet.
Unlike Huffman coding, LZW compression does not use anticipation assay and ciphering on the antecedent data, defective alone to attending at repeating patterns in the antecedent alphabet. LZW works best on streams that accommodate assorted repeating patterns such as argument files.
Huffman coding on the alternative duke works best on streams area there is a alterity in about frequencies amid symbols. In LZW, a concordance is acclimated to map patterns in the old alphabet to symbols in the new alphabet, the concordance actuality complete from repeating patterns.
In Huffman, attribute mappings are based on the frequencies of the symbols in the antecedent alphabet. Additionally, the bit breadth of the new symbols in LZW is connected while the bit breadth for the new symbols in Huffman is variable, depending on the abundance of the antecedent symbols.
Wireless Mobile Ad-hoc Networks (MANET) and Wireless Sensor Networks are two agnate kinds of wireless technology. A MANET is a self-configuring arrangement the aftereffect actuality an approximate topology. There is no anchored basement amid the nodes and their alone accord to anniversary alternative is their adjacency to one another.
However, that may not be accurate for sensor networks. Some sensor arrangement protocols specify a specific topology. In the case of IEEE 802.15.4, it allows for two kinds of topologies, a arena cartography and a associate to associate topology.
Another aberration is complexity. The nodes of sensor networks are about abundant simpler than in MANETs. Sensor nodes about accommodate alone a transceiver bore for communication, a sensor and a microcontroller.
This is because of the almost simpler uses for the sensor such as abstracts accumulating and gathering. In contrast, nodes of a MANET will about be added complex, actuality fabricated up of complete laptops, PDAs or alternative aerial akin advice devices.
A third aberration is in the abstracts rates. Sensor networks are about low abstracts bulk systems while MANETs accept college abstracts rates. Bit ante in MANETs like 802.11 are abstinent in Mbps while those in 802.15.4 and Zigbee are in kbps only. Fourth is ability consumption, MANET nodes are advised to be mains powered or alone to be codicillary on batteries for a abbreviate bulk of time (generally a few hours).
On the alternative hand, sensor networks will about use low ability apparatus to amplitude the ability of the array for weeks or months on end. Lastly, in MANETs, nodes are envisioned to be consistently sending abstracts to one addition while in sensor networks, nodes are accepted to be in a beddy-bye or quiet approach for best of the time.
This is due to the bulk of abstracts exchanged in MANETs compared to sensor networks which may alone charge to bandy abstracts to the server on defined times.
If we booty the archetype of the ZigBee sensor arrangement protocol, we can see three layers from the OSI archetypal at assignment in the ZigBee protocol. In the ZigBee protocol, its uses the IEEE 802.15.4 accepted for the PHY and MAC allocation of the DLL layer. The ZigBee blueprint on the alternative duke serves as the high layers for the wireless sensor network.
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