1. Field of the Invention
The present invention relates to power line communication in which transmission and reception of desired data are carried out using a power line as a communication channel, and more particularly to an apparatus and a method for adaptively detecting received signals for power line communication, which are capable of stably receiving desired data transmitted via a power line irrespective of variations in channel characteristics.
2. Description of the Related Art
The use of a power line as a communication channel provides a remarkable advantage in that additional expenses are not required for the construction of a new communication channel. That is, since power lines to supply electricity have been distributed over most areas in the world, those areas are not different from having already been equipped with a communication channel.
However, originally, power lines are not intended for a communication channel, but for the supply of electricity. For this reason, such power lines exhibit degraded characteristics for a communication channel. For example, where diverse electric home appliances are operated using electric power supplied through a power line, noise may be generated by such operation. This noise may be induced into the power line, thereby varying the communication channel characteristics of the power line. As a result, loss of data transmitted on the power line may occur.
Therefore, it is necessary to accurately check the channel characteristics of the power line for power line communication in order to apply a desired algorithm meeting the checked channel characteristics.
In order to reduce the data loss resulting from noise on power lines, communication technologies using a spread spectrum technique have been proposed.
The spread spectrum technique is a method in which pseudo noise is added to transmitted signals. This technique has mainly been used for military systems because it provides characteristics strong against noise. Among such spread spectrum techniques, there are a direct sequence (DS) method, a frequency hopping (FH) method, and a chirp method.
In particular, power line communication systems using the chirp method have an advantage in that it provides characteristics strong against noise, as compared with other spread spectrum techniques, even though it exhibits inferior characteristics in terms of transmission rate. Thus, this technique may be more suitable for the channel environment using power lines.
Generally, a chirp signal used on power lines has a frequency sustained at 100 to 400 kHz for 100 μs, varied between 200 kHz and 400 kHz, and then varied between 100 kHz and 200 kHz. Power line communication systems using the chirp method conduct data transmission and reception operations using chirp signals of the same type in a certain frequency band.
However, the load attenuating characteristics of power lines are non-uniform in the entire frequency band. As shown in FIG. 1, power lines exhibit a severe variation in load attenuating characteristics. For this reason, loss of transmitted data occurs in a particular frequency band.
In particular, in the case of a power line communication system which shows various attenuation characteristics, depending on the sort of electric appliances in use or the installation place, it may be impossible to detect received signals because data loss occurs in the frequency band exhibiting a severe attenuation, for a particular frequency band or particular chirp signal.
In communication systems using a spread spectrum technique, it is necessary to use a signal tracking circuit for detecting received signals. This signal tracking circuit tends to be complicated because it should conduct a comparison of received signals with a reference value and a calculation of a maximum value. For this reason, there is a limitation to reducing the manufacturing costs.