VHDL IMPLIMENTATION OF LZW COMPRESSION ALGORITHM

Abstract

The adaptive Lempel-Ziv-Welch general-purpose algorithm and its implementation
suitable for packet radio telephone transmission, and archival storage. While the statistical variablelength
Huffman technique compresses text by 20%,the LZW technique can compress data (text,
numeric, mixed, and bit-mapped images)by 40 to 60%.
The adaptive LZW algorithm has very simple logic, leading to inexpensive and fast
implementations. Good LXW implementations use 9- to 16-bit codes, handling most applications.A12-
bit code is suitable for medium-size files. Efficiency improves with larger codes. A tight coding of the
algorithm can compress 75 Kbytes in a second on a 1-MIPS machine.
This project is implemented using VHDL &simulation results are verified. It encourages
concurrent development in the area of data compression. The further enhancement of this project is to
achieve more percentage of compression with less hardware.

THYRISTOR SWITCHED REACTIVE POWER COMPENSATION
Block Diagram of Thyristor switched RPC System.
In addition to not being able to achieve the desired power factor it is also possible
that the use of fixed compensation can also result in leading power factor under
certain load conditions. This is also unhealthy for the installation as it can result in
over voltage, saturation of transformers, etc. It is therefore necessary to automatically

vary without manual intervention, the compensation to suit the load requirements.
Some loads (such as welding equipments, injection moulding equipment, starting of
large induction motors, traction loads) which demand, under certain operating
conditions, large amount of reactive power for very short duration of time. Thyristor
switched automatic power factor correction system (Fig) is used in this application
which have a response time in milliseconds. In this system, it is possible to switch in
capacitors such that the inrush transient currents are totally eliminated. In addition
the capacitors can be switched repetitively intent any limits since, there is no need
for allowing discharge of the capacitor before it is switched in.