KR20020060462A - Demodulation Track System of CDMA Modem ASIC - Google Patents

Abstract

PURPOSE: A demodulation tracking system of a code division multiple access modem custom integrated circuit is provided to increase available rake and perform rake as much as possible within the fixed time by constructing three despreaders parallel at one rake per one path. CONSTITUTION: On time spread, -1/2 chip spread, and +1/2 chip spread signals received from a plurality of paths through an antenna, are input to one rake per one path. Three parallel despreaders(1-3) receive the spread signals for automatically controlling the spread signals and calculating offsets of -1/2 chip spread signal and +1/2 chip spread signal by using the on time spread signal. A path tracking algorithm receives the calculated signals and detects energy of input signals for outputting a rake offset control signal tracking movement of a path loading data.

Description

Code Division Multiple Access Modem Demodulation Tracking System for On-Demand Integrated Circuits {Demodulation Track System of CDMA Modem ASIC}

The present invention relates to a demodulation tracking system for a CDMA modem on-demand integrated circuit, and more particularly, to a CDMA modem on-demand that can quickly track a path carrying actual information among signals received through a non-uniform multipath between a base station and a terminal station. A demodulation tracking system for an integrated circuit.

In general, the most influential factor affecting transmission quality when communicating using electromagnetic waves is fading due to multipath.

Fading by the multipath is caused by a phase difference (time delay difference) of a signal arriving at a receiver in different paths.

This fading reduces the size of the signal, which in turn worsens the signal to interference ratio (C / I), causing intensive transmission errors.

In addition, the time delay generates inter-symbol interference (ISI), and in a communication method using radio waves, fading is overcome by using a diversity scheme, and an equalizer (compensating for the time delay) is used. equalizer) to reduce the interference between signals.

Therefore, in order to reduce the influence of the multipath, a CDMA method uses a rake receiver that independently tracks a plurality of multipath arrival signals. The use of the rake receiver is an important feature of the CDMA method.

The rake receiver refers to a receiver having a function capable of separating multiple signals having a time difference (delay). As shown in FIG. 1, the receiver receives an antenna from multiple paths (Path1, 2, 3). It consists of several correlators 1-n that despread and demodulate the spread CDMA demodulated signal received through it, which is one of the characteristics obtained by the spread spectrum principle of CDMA.

In addition to receiving different signals with a time delay, the rake receiver is also used to receive signals from different base stations together during soft handoff.

As such, each correlator of the rake receiver performs spreading with a different PN offset.

The time delay of the signal received through each of the paths is changed little by little depending on the mobility of the terminal station and the change of surrounding conditions.

Therefore, the base station needs a device that tracks a path for recognizing such a change and demodulating a signal of a correct time delay with respect to a signal received through each path. The device is a tracker of a rake receiver.

Such a tracker observes the change in the time delay of the path currently being held by the base station and, if there is a change around the path containing the actual information, ± 1/2 PN chip with respect to the PN offset of the correlator. Spread the time delay to observe the change of the signal level extracted at each point, detect the energy of the signal, and use it to track the movement of the path containing information (phase change of the received signal) .

As shown in FIG. 2, the tracker for tracking the information-carrying path requires three rakes (rake1-3), or spreaders1-3, per path. It is configured to control each of the three rakes per path through.

As shown in FIG. 3, each of the rakes is internally configured in series so that each rake includes three rakes, that is, an nth rake, an (n + 1) th rake, and an (n + 2) th rake. Time sharing is used for on time spreading, -1/2 chip spreading, and +1/2 chip spreading, respectively.

Therefore, the conventional tracker has to control three rakes per path one by one, so the amount of software operation is increased, or three rakes are divided by time, so the number of available rakes within a predetermined time is reduced. It became.

Accordingly, an object of the present invention is to track a spreader that can perform a large amount of rake as much as possible within a predetermined time by controlling the three spreading signals in parallel to the rake received through a path in which the receiving time that changes from time to time is not constant Is to provide.

In order to realize the above object, the present invention is characterized in that three spreaders for despreading and demodulating three spreading signals on one rake in one path received through an antenna from a plurality of paths are configured in parallel. .

1 is a receiving block diagram of a typical multipath rake receiving system.

2 is a block diagram of a demodulation tracking system of a conventional CDMA modem application specific integrated circuit.

3 is a diagram of a demodulation tracking system of a conventional CDMA modem application specific integrated circuit.

4 is a diagram of a demodulation tracking system of a CDMA modem application specific integrated circuit of the present invention.

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5 is a block diagram of a demodulation tracking system of a CDMA modem application specific integrated circuit of the present invention.

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

despreader 1-3; Diffuser PTA; Route tracking algorithm

Hereinafter, described in detail with reference to the accompanying drawings, preferred embodiments of the present invention.

4 is a diagram of a demodulation tracking system of a CDMA modem application specific integrated circuit of the present invention, and FIG. 5 is a block diagram of a demodulation tracking system of a CDMA modem application specific integrated circuit of the present invention, wherein an antenna (ant) is selected from a plurality of paths. Three time-decoded demodulated signals spread through the time spread on one rake in one path, -1/2 chip spread, and +1/2 chip spread A diffuser 1-3; The three spreaders (despreaders 1-3) are configured with a path tracking algorithm (PTA) that detects the energy of the spread demodulated signal and outputs a rake offset control signal that tracks the movement of the path containing the information.

Three spreaders 1-3 formed in one rake in one path are configured in parallel.

The three spreaders 1-3 are configured to automatically control -1/2 chip spreading and +1/2 chip spreading during on-time spreading control.

According to the present invention configured as described above, the on-time spreading -1/2 chip spreading and the +1/2 chip spreading signal received through the antenna ant from a plurality of paths generated between the base station and the terminal are one. It is input to one rake per path of.

As shown in FIG. 5, the spreading signal input to the one rake is divided into a time spreading -1/2 chip spreading and a +1/2 chip spreading signal, and the on-time spreader configured in parallel (despreader1). ), -1/2 chip spreader (despreader2), +1/2 chip spreader (despreader3) are input in parallel.

Therefore, the three spreaders 1-3 automatically control the parallel input on time spread signal, -1/2 chip spread signal, and +1/2 chip spread signal at a time. In this case, the three spreaders (despreaders 1-3) calculate the offset of the -1/2 chip spread signal and the +1/2 chip spread signal by using the input on-time spread signals.

The signals calculated by the three spreaders 1-3 are input to the path tracking algorithm PTA, and the path tracking algorithm PTA detects the energy of the input signal and tracks the movement of the path containing the information. The rake offset control signal is output.

As described above, in the present invention, three spreaders are configured in parallel on one rake in one path with respect to information received through an antenna from multiple paths so that three spread signals are inputted at one time to despread and demodulate. This not only increases the total available rake, but also provides the effect of performing as much of the rake as possible within a given time on the route containing the actual information received.

Claims (3)

Three spreaders for time-dividing and demodulating the spread signals received through the antennas from the plurality of paths into time spread, -1/2 chip spread, and +1/2 chip spread in one rake in one path; And a path tracking algorithm for detecting the energy of the spread demodulated signal in the three spreaders and tracking the movement of the path carrying the information. The demodulation tracking system of a CDMA modem application specific integrated circuit according to claim 1, wherein the three spreaders are configured in parallel. The CDMA modem on-demand integrated circuit of claim 1, wherein the three spreaders are configured to automatically control -1/2 chip spreading and +1/2 chip spreading during on-time spreading control. Demodulation Tracking System.