KR19990066576A - Pilot diversity system that combines the concept of pilot channel and pilot symbol in the forward direction of DS / CDMA system - Google Patents

Abstract

Pilot diversity that improves the functionality of CDMA systems by mixing pilot channels and pilot symbols in the forward direction of DS / CDMA systems that can meet the requirements of forward capacity maximization of DS / CDMA systems and maximize subscriber capacity. System is disclosed. By using both pilot channels and pilot symbols in the forward direction, the pilot channel is used for handoff and initial synchronization to take advantage of the inter-base station synchronization system, and when the traffic channel is detected, the pilot symbol is used to perform periodic phase prediction. Therefore, the pilot channel is used only for the purpose of initial synchronization. Therefore, after initial synchronization using the pilot channel, the pilot channel is reduced in power size to reduce the interference of the pilot channel on the traffic channels in the forward direction with a small amount of power. It can be minimized.

Description

Pilot diversity system that combines the concept of pilot channel and pilot symbol in the forward direction of DS / CDMA system

The present invention relates to a DS / CDMA system, and more particularly, to a pilot channel in a forward direction of a DS / CDMA system capable of meeting the requirements of forward capacity maximization of a DS / CDMA system and maximizing subscriber capacity. The present invention relates to a pilot diversity system in which pilot symbols are mixed to improve a function of a CDMA system.

In general, a channel formed between the base station and the mobile station includes a forward channel formed by transmitting data information from the base station in the direction of the mobile station, and a reverse channel formed by transmitting data information from the mobile station to the base station. Divided into. In addition, the forward channel includes a pilot channel, a sync channel, a pasing channel, and a traffic channel, and the pilot channel, the synchronization channel, and the paging channel are between all mobile stations in one base station. Are used jointly, one traffic channel is assigned to each mobile station. The reverse channel includes an access channel and a traffic channel. The pilot channel constituting the forward channel continues to transmit information. When the pilot channel is directed toward the mobile station to be isotropic from the base station, the receiving mobile station detects the pilot power of the received pilot channel and measures the distance of the mobile station. . Since the power occupied by the pilot channel corresponds to 20 to 30% compared to other channels forming the forward channel, interference occurs between the multipath components of the pilot signal and other channels. On the other hand, since pilot symbols used in asynchronous systems between base stations are inserted and shot in the middle of other data constituting the traffic channel, it is very difficult to insert and play pilot symbols in the middle of the data constituting the traffic channel. have. In other words, a pilot channel is used in a synchronous CDMA system between base stations and a pilot symbol is used in an asynchronous CDMA system between base stations, but the pilot power of the pilot channel is too large to be compared with other channels. It is difficult to prevent interference, and it does not overcome the disadvantages of each system, which is difficult to insert pilot symbols between data forming the traffic channel.

Accordingly, the present invention has been made to solve the above problems, an object of the present invention is to mix the advantages of the inter-base station synchronous CDMA system and the inter-base station asynchronous CDMA system DS / CDMA that can improve the performance of the CDMA system In the forward direction of the system, the concept of the pilot channel and the pilot symbol is to provide a mixed pilot diversity system.

1 (a) is a diagram showing a forward channel structure according to the present invention.

1 (b) is a view showing a reverse channel structure according to the present invention.

2 is a block diagram showing a base station transmitter in accordance with the present invention.

3 is a block diagram showing a mobile station receiving end according to the present invention.

<Description of the reference numerals for the main parts of the drawings>

10: pilot channel 20: pilot symbol

30: traffic channel 40: transmitter

50: sync channel correlator 60: pilot channel correlator

70: Paging / Traffic Channel Correlator

In order to achieve the above object, the present invention uses a pilot channel for handoff or initial synchronization in a forward direction transmitted from a base station to a mobile station, and uses a pilot symbol for detecting a traffic channel for transmitting data such as a voice signal. Provided is a pilot diversity system in which a concept of a pilot channel and a pilot symbol are mixed in a forward direction of a DS / CDMA system.

According to the present invention, by utilizing both pilot channels and pilot symbols in the forward direction, the pilot channel is used for handoff or initial synchronization, and the advantages of the inter-base station synchronization system can be utilized. Periodic phase prediction is performed using symbols. Therefore, the pilot channel is used only for the purpose of initial synchronization. Therefore, after initial synchronization using the pilot channel, the pilot channel is reduced in power size to reduce the interference of the pilot channel on the traffic channels in the forward direction with a small amount of power. It can be minimized.

Hereinafter, a preferred embodiment of a pilot diversity system in which a concept of a pilot channel and a pilot symbol is mixed in a forward direction of a DS / CDMA system according to the present invention will be described in detail with reference to the accompanying drawings.

1 (a) is a diagram showing a forward channel structure according to the present invention.

1 (b) is a view showing a reverse channel structure according to the present invention.

2 is a block diagram showing a base station transmitter in accordance with the present invention.

3 is a block diagram showing a mobile station receiving end according to the present invention.

Referring to Figures 1 (a) to 3, first, Table 1 summarizes the advantages of using the pilot channel and the pilot symbol.

Table 1. Comparison of Systems Using Pilot Channels and Pilot Symbols

Pilot channel Pilot symbol Advantages 1. Synchronization method between base stations 2. Fast initial sync 3. Easy handoff control Easy acquisition of traffic channel phase information (phase, timing for synchronization detection, frequency shift, etc.) 2. Reverse Direction Antenna Available

First, in case of using a pilot channel, it is easy to secure synchronization between base stations and has advantages of fast initial synchronization acquisition. In addition, since the base station synchronization method can be applied, there is an advantage that the control mechanism is easy during handoff. On the other hand, when the pilot symbol is used, the pilot symbol is inserted between data, which is information on each traffic channel, so that phase information of the traffic channel can be easily obtained. Here, the phase information means to extract phase, synchronization detection timing, frequency shift, and the like. In addition, since the reverse link has an advantage of using an array antenna, only a beam corresponding to the user arrives, thereby reducing multi-user interference between traffic channels in the reverse direction.

1 illustrates a method of allocating forward and reverse pilot signals according to the present invention. First, in the forward direction, pilot channels and pilot symbols are transmitted in a mixed form. The concept of the pilot channel 10 in the forward direction is applied to the existing commercial system and has advantages such as synchronization between base stations, fast initial synchronization acquisition, and easy handoff. The use of the pilot symbol 20 in the forward direction is a concept proposed by the present invention. Since each pilot information is transmitted in the form of a symbol for each channel, phase information necessary for demodulation of the traffic channel 30 can be predicted periodically. . The reverse channel structure is illustrated in FIG. The pilot signal in the reverse channel applies only the concept of the pilot symbol 20, which is a conventionally proposed scheme. This is the same concept as the conventional method because only the pilot symbol 20 is applied to the allocation of independent pilot channels for each mobile station in the reverse direction because of the problem of overall capacity reduction.

FIG. 2 is a block diagram illustrating how the pilot channel 10 and the pilot symbol 20 described in FIG. 1 are applied to the actual transmitter 40. The pilot channel is divided into Walsh codes (W _S , W _P , and W _t ) as in the conventional method, and forms an independent channel. On the other hand, the pilot symbol 20 is periodically muxed to the traffic channel 30, but the addition period of the pilot information can be arbitrarily determined. If the pilot symbol 20 is added densely, it may be accurate to predict the change of the channel, but it has the disadvantage of slowing down the transmission speed of the traffic data, and if it is loosely added, the pilot symbol may not properly follow the time-varying channel. The addition period of is important to get the optimal period through simulation. Adding a pilot symbol concept as described above has advantages over a forward link using only a pilot channel. That is, when only the pilot channel is used, first, the pilot channel 10 is required for initial synchronization, and even when the traffic channel 30 is detected after the initial synchronization, the pilot channel 10 continues to predict the phase shift of the traffic information. ) Is required. In addition, the accuracy of the prediction of the phase shift affects the performance of the traffic information detection, so that the burden of maintaining the pilot channel power higher than that of the traffic channel is generated. In practice, the system uses about 30 to 40% of the total cell power. This figure is the main cause of forward capacity reduction because the multipath component of the pilot channel in the forward acts as a large interference to the traffic channels. However, in the present invention in which the pilot symbol 20 and the pilot channel 10 are used at the same time, the periodic phase prediction is performed by using the pilot symbol 20 when the traffic channel is detected. Therefore, since the pilot channel 10 is used only for the purpose of initial synchronization and the like, a small amount of power can be allocated to minimize the interference on the traffic channels.

3 illustrates a process of recovering a pilot channel and a pilot symbol when they are received by the mobile station in a mixed form. First, the synchronization channel correlator 50 recovers synchronization information on a signal to be detected, and the pilot channel correlator 60 independently detects pilot information transmitted from a pilot channel of a transmitter. It contains information that can infer the strength (RSSI), timing (Timing) and phase information (Phase), frequency control value (AFC) of the received signal. Finally, the paging / traffic channel correlator 70 extracts pilot symbols inserted in the middle of each traffic information, and independently predicts the channel status by using the pilot information. Therefore, in order to finally detect the traffic data (demodulated data), channel information obtained from the pilot symbol is used as the main information, and channel information obtained from the pilot channel can be used for more accurate channel prediction.

As can be seen from the above description, the present invention utilizes both a pilot channel and a pilot symbol in the forward direction to take advantage of the inter-base station synchronization system by using a pilot channel for handoff or initial synchronization, and for the detection of a traffic channel. Periodic phase prediction is performed using symbols. Therefore, the pilot channel is used only for the purpose of initial synchronization. Therefore, after initial synchronization using the pilot channel, the pilot channel is reduced in power size to reduce the interference of the pilot channel on the traffic channels in the forward direction with a small amount of power. It can be minimized.

Claims (3)

In the forward direction of a DS / CDMA system, a pilot channel is used for handoff or initial synchronization in a forward direction transmitted from a base station to a mobile station, and a pilot symbol is used for detecting a traffic channel for transmitting data such as a voice signal. Pilot diversity system that combines the concept of pilot channel and pilot symbol. 2. The pilot diversity system of claim 1, wherein the pilot channel and pilot symbols are mixed in the forward direction of the DS / CDMA system, characterized in that, when detecting the traffic channel, the power size of the pilot channel is reduced to a low value. 2. The method of claim 1, wherein the pilot symbols inserted into the traffic channel are precisely synchronized when inserted in the traffic channel, and the synchronization is difficult to be synchronized instead of being accelerated when loosely inserted. A pilot diversity system in which a pilot channel and a pilot symbol are mixed in a forward direction of a DS / CDMA system.