KR20000052223A - Dynamic Signal Processing Method for lower Power Demodulation - Google Patents

Abstract

PURPOSE: A method of demodulating the low electric power signal is provided to control the speed of CDMA signal process dynamically according to the peculiarity of wireless channel. CONSTITUTION: A method of demodulating the low electric power signal comprises the steps of: performing the intended symbol process according to the transmission speed of the given data; performing signal process by transforming to the pilot accumulation cycle according to the wireless channel change emerging conflictingly to the transmission speed of available data; distributing the designated operation for the above process.

Description

Dynamic Signal Processing Method for lower Power Demodulation

The present invention relates to a CDMA communication system, and more particularly, to a low power signal demodulation method for dynamically controlling the CDMA signal processing speed according to the characteristics of a wireless channel.

According to the existing IS-95 standard, a forward link demodulation method of a CDMA communication system uses a coherent method of extracting phase information using a pilot signal of a forward link.

The pilot signal received by the CDMA signal demodulator includes information on the signal phase and signal strength of each path by the multipath, and therefore the pilot signal is used as a reference signal for timing synchronization.

In order to extract the phase information from the received pilot signal, a module called a pilot filter is statistically averaging the I channel and the Q channel. Magnitude is the signal strength, and the angle on the polar coordination of the output vector is the signal phase.

In addition, since the error of the reception frequency is proportional to the phase change rate, the signal phase of each path by the multiple paths is also used to estimate the frequency error of the reception signal.

In addition, the demodulation device requires a device for timing synchronization, which is divided into initial acquisition and time tracking. Once the initial synchronization is performed by a module called a searcher, a correct signal reception is performed. In order to achieve this, the timing synchronization must be maintained continuously. For this purpose, a reception method called Early / Late is generally used.

An early receiver is a receiver that receives signals at an earlier timing than on-time, and a late receiver is a receiver that receives signals at a later timing than the original timing.

The early / late sync circuit detects the timing error of the received signal by using the energy difference between the two receivers, and uses the detected timing error to close the closed loop control scheme such as a phase locked loop (PLL). Correct the timing error by -loop control.

1 is a block diagram showing a partial configuration of a CDMA signal demodulation device according to the prior art.

Referring to FIG. 1, the device configuration shown in FIG. 1 may be broadly divided into a unit for processing a PN chip for CDMA signal processing and a unit for processing a plurality of PN chips in an accumulated symbol unit according to a signal processing period. have.

PN chip processing units include despreaders (10, 20, 30), Walsh symbol accumulators (13, 14), a pilot filter (11), and a complex quadrature phase shift keying despreader (Complex QPSK Despreader). There are early chip accumulators 21 and 22 and late chip accumulators 31 and 32.

The despreaders 10, 20, and 30 use a correlator together with the accumulators 13, 14, 21, 22, 31, and 32 at the rear end using a PN code synchronized with the received signal. Plays the role of.

Here, the periods of the Walsh symbol accumulators 13 and 14 are equal to the symbol length. In the CDMA method such as IMT-2000, the Walsh symbol accumulators 13 and 14 must simultaneously provide data services as well as voice services. The period of 14) varies depending on the data rate.

By way of example, data rates typically range from several Kbps to several Mbps, so that symbol lengths vary from a few chips to thousands of chips at a PN chip rate of 1.2288 MHz.

On the other hand, the pilot filter 11, the early chip accumulators 21 and 22 and the late chip accumulators 31 and 32 should be subjected to signal processing to adapt to the fastest changing wireless environment.

Currently, high-speed wireless data communication environment can provide data service only while moving at a low speed due to the characteristics of a wireless channel, and low-speed communication services such as voice can be provided while moving at high speed.

However, in the conventional demodulation device, the signal is not required to use the correlation between the data rate and the radio channel change. Therefore, higher signal processing capability is required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and a low-power signal demodulation method suitable for satisfying both high-speed data service and voice service with minimum signal processing capability is made using the inverse relationship between data transmission speed and wireless channel change. The purpose is to provide.

According to an aspect of the present invention for achieving the above object, a pilot signal processing is performed according to a pilot accumulation period contrary to the symbol period while simultaneously performing a corresponding symbol processing according to a given symbol period in consideration of a change in a radio channel. And then

In order to dedicate the corresponding operations for the symbol processing and the pilot signal processing in consideration of the change in the radio channel.

Preferably, each processing period for the symbol processing and the pilot signal processing is varied according to the radio channel change and the symbol length to be processed, respectively.

1 is a block diagram showing a partial configuration of a CDMA signal demodulation device according to the prior art;

2 is a block diagram showing a device configuration for explaining the CDMA signal demodulation method according to the present invention;

* Description of the symbols for the main parts of the drawings *

100: symbol processing front end

200: pilot signal processing front end

300: demodulation signal processing unit

Hereinafter, a preferred embodiment of a low power signal demodulation method according to the present invention will be described with reference to the accompanying drawings.

The transmission rate of data and the change in radio channel are generally inversely related. Therefore, it is not necessary for the signal demodulation device for data processing at various speeds to simultaneously adapt to high-speed data reception and fast radio channel change.

In this regard, in the low-power signal demodulation according to the present invention, since wireless data service is possible only when a change in a wireless channel occurs slowly, instead of slowing down pilot signal processing and speeding up symbol processing, and supporting a low speed voice service. In this case, it needs to be able to adapt to a fast radio channel change, so that the pilot signal processing is quick.

That is, in the CDMA signal demodulation according to the present invention, pilot signal processing such as phase estimation, frequency tracking, and time tracking is varied according to the length of the symbol.

In addition, in the present invention, as the symbol length becomes shorter, the pilot signal processing period is increased.

As such, when the low power signal demodulation method according to the present invention is applied, pilot signal processing or symbol processing is performed in consideration of data transmission speed and radio channel change, thereby satisfying both high speed data service and voice service with minimum signal processing capability. Can be.

Further, since the power consumption of the digital circuit is proportional to the operation speed of the signal demodulation device, the low power signal demodulation device according to the present invention can be realized.

2 is a block diagram showing an apparatus configuration for explaining a CDMA signal demodulation method according to the present invention.

Referring to FIG. 2, the CDMA signal demodulation device according to the present invention is a symbol processing front end part 100 for receiving a symbol period for receiving data and a pilot signal processing front end part for maintaining a link of a wireless channel, like a general signal demodulation device. 200, and there is a demodulation signal processing apparatus 300 after these stages.

Here, the symbol processing front end unit 100 and the pilot signal processing front end unit 200 are shared to dynamically allocate two types of signal processing.

The demodulation signal processing apparatus 300 processes the output signals of the symbol processing front end 100 and the pilot signal processing front end 200 generated by processing in units of PN chips at lower speeds, instead of processing the output signals of the front end parts 100 and 200. It handles several signals in common.

In general, the demodulation signal processing unit 300 is designed to quickly perform multiply and accumulation (MAC) which is commonly used in a digital processor (not shown).

In the low power signal demodulation method according to the present invention, when performing a pilot signal processing procedure such as pilot filtering, early chip accumulation, late chip accumulation, or the like, the signal processing period of the pilot signal processing front end unit 100 is performed in the case of a voice service. As the symbol length increases, the signal processing period is extended without being fixed at a speed that can adapt to a fast radio channel change.

This is because the demodulation signal processing unit 300 with limited signal processing capability performs more processing in processing the signal of the high speed symbol processing front end 100 instead of slowly processing the signal of the pilot signal processing front end 200. To allow them to spend

As described above, according to the low-power signal demodulation method of the present invention, a high-speed data service and a voice service can be processed without degrading performance with minimum signal processing capability by using an inverse relationship between a communication data rate and a change in a wireless channel.

Therefore, it has the same circuit configuration as that of the conventional signal demodulation device, but has a much smaller circuit configuration, and has the effect that the signal demodulation device can be miniaturized and reduced in price.

In particular, since the power consumption is reduced, it can be very useful for small mobile terminals.

Claims (2)

In consideration of the change in the radio channel, the corresponding symbol processing is performed according to the given symbol period and the pilot signal processing is performed according to the pilot accumulation period given in opposition to the symbol period. And decompressing respective corresponding operations for the symbol processing and the pilot signal processing in consideration of the change of the radio channel. The low power signal demodulation method according to claim 1, wherein each processing period for the symbol processing and the pilot signal processing is varied according to the radio channel change and the processed symbol length.