KR20060062420A - Apparatus and method for acquiring pilot in mobile communication system - Google Patents

Abstract

The present invention relates to a pilot acquisition apparatus and method in a mobile communication system, and more particularly, to an apparatus and method for searching for a CDMA signal using a Global Position System (GPS) searcher.

In the mobile communication system according to an embodiment of the present invention, the pilot acquisition apparatus can receive a Code Division Multiple Access (CDMA) signal and a Global Position System (GPS) signal simultaneously in the mobile communication system, When receiving the CDMA signal, the CDMA searcher searches the strength and position of the pilot signal by calculating the energy of the received signal by changing the offset of the PN sequence, and generates the CDMA PN sequence by the CDMA / GPS mode selection signal. And a GPS searcher for changing the offset of the CDMA PN sequence and calculating the energy of the received signal to search the strength and position of the pilot signal.

Navigator, Global Position System

Description

APAPATUS AND METHOD FOR ACQUIRING PILOT IN MOBILE COMMUNICATION SYSTEM}             

1 is a block diagram of a general code division multiple access (CDMA) searcher;

2 is a block diagram of a 16x speed searcher in FIG. 1;

3 is a block diagram of a GPS (Global Position System) demodulator,

4 is a block diagram of a pilot acquisition apparatus according to the present invention;

5 is a flowchart illustrating a pilot acquisition method in a mobile communication system according to an embodiment of the present invention;

6 is a flowchart illustrating a pilot acquisition method in a mobile communication system according to another embodiment of the present invention;

7 is a flowchart illustrating a pilot acquisition method in a mobile communication system according to another embodiment of the present invention.

The present invention relates to a pilot acquisition apparatus and method in a mobile communication system, and more particularly, to an apparatus and method for obtaining a pilot signal.

In general, in a code division multiple access (CDMA) communication system, a base station sends a pilot signal on a forward link, and a mobile station acquires and synchronizes a pilot signal to communicate. The mobile station includes a circuit for acquiring and tracking the pilot signal in this way, which is called a searcher. The searcher changes the offset of the PN sequence using a short PN (short pseudo-random number) code generator that is used by the base station and calculates the energy of the received signal to pilot. ) Find the strength and location of the signal. Here, the offset of each PN sequence for searching for a pilot signal is called a PN hypothesis.

Meanwhile, a linear feedback shift register (LFSR) is used as an apparatus for generating a pseudo-random sequence such as a PN sequence used in a code division multiple access communication system. A mobile cell searcher of the code division multiple access communication system detects a PN offset for a PN sequence transmitted from a plurality of base stations by using a PN sequence generator, and calculates a pilot channel energy value for the PN offset. PN synchronization is obtained between the base station and the mobile station by calculating

In the code division multiple access communication system, the searcher calculates a pilot energy value for each PN offset of the PN sequence, and the mobile station performs initial acquisition to find the PN offset and system time of the base station in an initial state. In the idle and call states, search for multipath information to allocate an optimal demodulation path to the RAKE receiver or perform soft-handoff by measuring pilot channel energy values of adjacent base stations. Do it.

The searcher in the mobile communication system has the same local short PN sequence generator as used by the base station. Using this, we generate a PN sequence corresponding to each PN offset hypothesis, perform complex multiplication with the received I / Q data, perform despreading, and accumulate a given number of times to correlate the energy for each PN offset hypothesis. Calculate the value of (correlation energy). In this case, when the frequency is not stabilized at the initial acquisition, asynchronous accumulation may be performed to accumulate several correlation energy values for the same PN offset hypothesis. The pilot channel energy value for each PN offset hypothesis calculated as described above is compared with a given energy threshold to determine whether to acquire a pilot for a specific PN offset.

1 shows the structure of a general searcher. In general, the searcher performs a search operation by a search command. The search command includes various parameters required to perform a search. The parameters that directly affect the search time are the search window size value, which indicates the number of PN offset hypotheses to search, the search speed to specify how many PN offset hypotheses are parallelized at the same time, and the amount to move to the start of the search window. There are a slew value indicating the cumulative value, an integral time value indicating the correlation cumulative number, and an accumulation value indicating the asynchronous cumulative number. Here, the slew refers to an operation of reading or laging the state of the LFSR to change the PN offset.

On the other hand, since the PN signal pattern is repeated every 32768 chips, all 32768 positions must be verified, so the number of position hypotheses becomes 32768. Since there is time to integrate for one position hypothesis, initial pilot synchronization takes considerable time. In order to reduce this time, as shown in FIG. 2, a 16x speed searcher capable of simultaneously verifying multiple positional hypotheses is used.

On the other hand, in the case of a satellite positioning system (hereinafter referred to as "GPS") searcher, various pieces of information necessary for calculating the position on the ground are transmitted from the GPS satellites. The information is modulated and transmitted in the form of a direct sequence (DS). Basically, DS is the same modulation method used in CDMA. The information transmitted from the satellite is spread by the PN sequence. Therefore, in order to demodulate information from satellites, it is necessary to first synchronize PN. This is basically the same as the pilot synchronization acquisition process in the mobile communication system. The GPS demodulator is shown in FIG. In general, the GPS searcher should receive signals from several GPS satellites at the same time for position detection, and for this purpose, as shown in FIG. 3, the input signal is divided into N channels to synchronize the PN signal of each GPS satellite. In order to detect the problem, several searcher modules are required.

In general, the size of a signal is quite small because a GPS signal is transmitted from a GPS satellite. Since the PN synchronization and demodulation need to be performed with these small signals, the GPS searcher generally uses circuits and algorithms that perform significantly better than the existing mobile network searcher.

Conventionally, the GPS operation can be performed even when making a call using a mobile communication network, but the mobile communication network explorer and the GPS explorer are designed separately, and the GPS explorer and the mobile communication network explorer do not interoperate with each other.

In addition, when a long period of fading or when the mobile terminal is powered on, pilot signal initial synchronization needs to operate even in a large number of positional hypotheses and a weak signal. It had to be detected with limited hardware, so complex algorithms had to be used.

Accordingly, an object of the present invention is to provide a pilot acquisition apparatus and method for detecting a mobile communication network pilot signal by using a GPS searcher function during initial pilot acquisition.

Another object of the present invention is to provide an apparatus and method for reducing initial synchronization time by using a function of a GPS searcher to detect a pilot communication signal when a pilot is initially acquired.

In the mobile communication system according to an embodiment of the present invention, the pilot acquisition apparatus can receive a Code Division Multiple Access (CDMA) signal and a Global Position System (GPS) signal simultaneously in the mobile communication system, When receiving the CDMA signal, the CDMA searcher searches the strength and position of the pilot signal by calculating the energy of the received signal by changing the offset of the PN sequence, and generates the CDMA PN sequence by the CDMA / GPS mode selection signal. And a GPS searcher for changing the offset of the CDMA PN sequence and calculating the energy of the received signal to search the strength and position of the pilot signal.

In addition, the method for acquiring a pilot in a mobile communication system according to an embodiment of the present invention may simultaneously receive a code division multiple access (CDMA) signal and a global position system (GPS) signal in a mobile communication system, and acquire a pilot. A method of generating a PN sequence by converting a GPS mode into a CDMA mode by using a CDMA / GPS mode selection signal, and calculating the energy of a received signal by changing an offset of the PN sequence, calculating the strength and position of a pilot signal. The method includes searching for a signal, copying the obtained pilot phase to a CDMA searcher when acquiring a pilot signal, acquiring a system, and converting a CDMA mode to a GPS mode.

In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may vary according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

In the case of GPS signals, the signal is fairly small because the signal is transmitted from the satellite. Since the PN synchronization and demodulation need to be performed with such a small signal, the GPS searcher generally uses circuits and algorithms that are significantly better than the mobile communication network searcher (hereinafter referred to as "CDMA searcher").

In addition, the actual initial synchronization occurs when the mobile terminal is first powered on, or when it is in a long fading state or cannot receive system time information. Using complex hardware to reduce initial sync time is wasteful. Therefore, the present invention intends to reduce the initial synchronization time by using the function of the GPS searcher when the pilot initial acquisition.

In addition, the present invention intends to reduce the pilot acquisition time by allowing the mobile communication network and GPS to operate simultaneously after initial synchronization acquisition. This increases the number of hypotheses that can be verified simultaneously, enabling reliable pilot signal detection without the use of complex algorithms during initial pilot detection.

In addition, in another embodiment of the present invention, when the GPS operation is not performed, by applying the GPS searcher to the search for the neighbor base station, it is possible to prevent a hand-off failure in a bad channel environment. .

Pilot acquisition device 470 in the mobile communication system according to the present invention is shown in FIG. The pilot acquisition device includes a CDMA searcher 460 and a GPS searcher 400. Unlike the existing GPS searcher, the GPS searcher 400 may use a CDMA signal or a GPS signal as an input signal by a CDMA / GPS mode selection signal. The PN sequence is generated in the PN generator 430 by the CDMA / GPS mode selection signal. That is, in case of a CDMA mode selection signal, the PN generator 430 generates a CDMA PN sequence. In addition, when the GPS mode selection signal, the PN generator 430 generates a GPS signal. In addition, by the CDMA mode selection signal, the PN generator 430 converts from the GPS mode to the CDMA mode, and the GPS searcher 400 performs the fast parallel search by the generated CDMA PN sequence. That is, after the PN generator 430 converts the GPS mode to the CDMA mode, the PN generator 430 performs the same operation as the conventional CDMA searcher. The case of CDMA 1x will be described as an example. In other systems (EV-DO, WCDMA), the detailed operation is different, but the basic concept, that is, the concept of using the GPS searcher 400 for initial acquisition of the pilot signal is the same. As a result of hypothesis verification, if the pilot signal acquisition is successful, the system enters the process of acquiring the system. When acquiring the system, the SYNC message is received from the SYNC channel. The PN offset information of the current base station is input to the synchronization message. The pilot signal is currently acquired by the GPS navigator 400, but since the CDMA navigator 460 needs to perform neighbor base station search in the future, the state of the CDMA navigator 460 is copied to the CDMA explorer 460, and the CDMA navigator 460 in the future. The pilot signal detection and the base station search is performed through

In addition, when the CDMA searcher 460 and the GPS searcher 400 are used at the same time, the number of hypotheses that can be simultaneously verified increases, thereby increasing the pilot acquisition time. If the CDMA searcher 460 detects the current pilot, the operation may be performed in the same manner as the existing operation. If the GPS searcher 400 detects the current state, the GPS searcher 400 may change the state of the GPS searcher 400 as described above. Must be copied).

Pilot acquisition method in a mobile communication system according to an embodiment of the present invention will be described with reference to FIG.

Referring to FIG. 5, in operation 501, the pilot acquisition apparatus 470 selects a CDMA signal as a channel input by the CDMA / GPS mode selection signal. The PN generator 430 of the pilot acquisition device 470 converts from the GPS mode to the CDMA mode in step 502. That is, the pilot acquisition device 470 generates the CDMA PN sequence in the PN generator 430 by the CDMA mode selection signal. Thereafter, the pilot acquisition apparatus 470 proceeds to step 503 to start a fast parallel search using the GPS searcher 400.

In operation 504, the pilot acquisition apparatus 470 determines whether the pilot acquisition is successful. If the pilot acquisition apparatus 470 does not succeed in acquiring the pilot, the process returns to step 503. However, if the GPS searcher 400 succeeds in acquiring the pilot, the process proceeds to step 505 to copy the acquired pilot phase to the CDMA searcher 460. After completing copying to the CDMA searcher 460, the CDMA processing block (not shown) acquires the system and performs slitting. Thus, pilot signal detection and base station search are made. After operation 505, the pilot acquisition apparatus 470 proceeds to operation 506 to convert from the CDMA mode to the GPS mode.                     

Meanwhile, FIG. 6 illustrates a process of hypothesis verification by simultaneously using the CDMA searcher and the GPS searcher.

Referring to FIG. 6, when the CDMA signal is received from the GPS searcher 400 in step 601, the pilot acquisition device 470 converts the GPS mode to the CDMA mode by the CDMA mode selection signal. In operation 602, the pilot acquisition apparatus 470 simultaneously performs a high-speed parallel search using the GPS searcher 400 and the CDMA searcher 460.

In operation 603, the pilot acquisition apparatus 470 determines whether the pilot acquisition is successful. If the pilot acquisition apparatus 470 does not succeed in acquiring the pilot, the process returns to step 602. However, if the GPS searcher 400 succeeds in acquiring the pilot, the pilot acquisition apparatus 470 proceeds to step 604 to determine whether the acquired pilot is obtained from the GPS searcher. If the acquired pilot is not obtained from the GPS searcher 400, the pilot acquisition device 470 proceeds to step 605 in the same manner as the existing operation. However, when the acquired pilot is obtained from the GPS searcher 400, the pilot acquisition device 470 copies the pilot phase acquired in step 606 to the CDMA searcher. After completing copying to the CDMA searcher, the CDMA processing block (not shown) acquires the system and performs slitting. Thus, pilot signal detection and base station search are made. After operation 606, the pilot acquisition apparatus 470 converts from the CDMA mode to the GPS mode in operation 607.

As shown in FIG. 6, when the hypothesis is verified by using the CDMA searcher and the GPS searcher at the same time, the number of hypotheses capable of verifying the hypothesis is increased to increase the pilot acquisition time.

On the other hand, FIG. 7 illustrates the operation of the pilot acquisition apparatus when the GPS navigator 400 is used for the detection of the neighbor base station pilot strength when the GPS navigator is not used only for initial pilot acquisition, and when the GPS is not operated. will be.

Referring to FIG. 7, the pilot acquisition apparatus 470 receives a GPS signal in operation 701 and determines whether to operate as a GPS. If it does not operate with GPS, the pilot acquisition device 470 proceeds to step 702 in the same manner as the existing operation. However, when operating with GPS, the pilot acquisition device 470 converts the GPS searcher 400 from the GPS mode to the CDMA initial synchronization mode in step 703. Thereafter, the pilot acquisition apparatus 470 detects adjacent base station pilot strength using the GPS searcher 400 and the CDMA searcher 460 simultaneously in step 704.

In this case, the number of hypotheses that can be detected at one time is increased, so that the neighbor base station pilot search can be performed more frequently than the conventional method. Therefore, it is possible to prevent a handoff determination error caused by comparing the information of the other pilot base station.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

According to the present invention, when the GPS searcher is used to detect the pilot signal, the number of hypotheses that can be verified simultaneously increases, so that the pilot signal can be reliably detected without using a complicated algorithm during the initial pilot detection.

Claims (5)

In the mobile communication system can receive a Code Division Multiple Access (CDMA) signal and a GPS (Global Position System) signal at the same time, the device for obtaining a pilot, Receiving a CDMA signal, changing the offset of the PN sequence, calculating the energy of the received signal, and searching for the strength and position of the pilot signal; And a GPS searcher for generating a CDMA PN sequence by a CDMA / GPS mode selection signal, changing the offset of the CDMA PN sequence, and calculating the energy of the received signal to search the strength and position of the pilot signal. Said device. The method of claim 1, The GPS navigator, And a PN generator for selecting a CDMA signal as an input by the CDMA selection signal and converting a GPS mode to a CDMA mode. The method of claim 1, The GPS navigator, And when the pilot signal is acquired, copy the obtained pilot phase to a CDMA searcher. The method of claim 1, And the GPS searcher is used as a CDMA searcher while a GPS operation is not performed. A method for acquiring a pilot and simultaneously receiving a code division multiple access (CDMA) signal and a global position system (GPS) signal in a mobile communication system, Generating a PN sequence by converting the GPS mode to the CDMA mode by the CDMA / GPS mode selection signal; Changing the offset of the PN sequence and calculating the energy of the received signal to search for the strength and position of the pilot signal; When the pilot signal is obtained, copying the acquired pilot phase to a CDMA searcher; The process of acquiring the system, And converting from CDMA mode to GPS mode.

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