KR19990033607A - Base Station Asynchronous Method for Wideband Code Division Multiple Access with Short Cycle Extension Gold Code - Google Patents

Abstract

The present invention relates to a base station asynchronous method for wideband code division multiple access (hereinafter referred to as " W-CDMA "), a promising candidate multiple access technology for next generation mobile communication.

The present invention distinguishes each base station using different extended gold codes having a length of 2 ⁿ , which is a short cycle, ^{wherein the} extended gold code having the period of 2 ⁿ is allocated to the end of a gold code having a period of 2 ⁿ - 1 Quot; 0 ", and each of the base stations uses two of the extended Gold codes as pilot I and Q code sequences, and in the mobile station after completion of the pilot search, Channel wide band code-division multiple access (W-CDMA) base station asynchronous method using a short-term extended gold code.

The present invention basically does not require synchronization between the base stations and thus does not require a GPS receiver. Therefore, it is easy to install various types of base stations such as macro cell, micro cell and indoor small cell. In addition, since the cross-correlation property for distinguishing each base station is very good, the cycle is short, and the extended gold code that can generate multiple codes simultaneously is used, there is a remarkable effect that the initial system acquisition time of the mobile station is extremely short .

Description

Base Station Asynchronous Method for Wideband Code Division Multiple Access with Short Cycle Extension Gold Code

The present invention relates to a base station asynchronous method for wideband code division multiple access (hereinafter referred to as " W-CDMA "), a promising candidate multiple access technology for next generation mobile communication.

Currently, the second generation digital cellular or personal communication service (hereinafter referred to as "PCS") system of the country has a wireless interface part corresponding to a standard of TIA / EIA (Telecommunications Industry Association / Electronic Industries Association) Narrowband direct sequence code division multiple access (hereinafter referred to as " narrow band CDMA ") system conforming to IS-95 and J-STD-008 of the American National Standards Institute has a transmission bandwidth of 1.25 MHz, chip) transfer rate is 1.2288 Mcps.

Another feature in operating the conventional narrowband CDMA system is that all base stations are synchronized with a base station using a receiver of a Global Positioning System (hereinafter referred to as " GPS ") . Therefore, in order to acquire the initial system time and soft handoff of the mobile station, synchronization between the base stations must be performed first. Where each base station ²¹⁵ cycles (26.666 msec ..), a pair of longest-length sequence of strain having: are distinguished by varying the phase (Offset) of the system time of the (Maximal Length Sequence hereinafter referred to as "M sequence") . Here, all base stations use the same code.

FIG. 1 shows a conventional narrowband CDMA base station system using the GPS receiver, and FIG. 2 shows a base station time alignment of a conventional narrowband CDMA system. Here, all the base stations distinguish the respective base stations by making the phases of the pair of M sequences different for the system time synchronized in advance.

Meanwhile, the wireless transmission technology being developed for the next generation mobile communication (IMT-2000) in the domestic, Japan, and USA is a W-CDMA technology supporting a transmission bandwidth of 5 MHz or more. It is being developed to enable high-speed data transmission such as image and video.

However, since the conventional narrowband CDMA system is designed for voice-oriented communication, the maximum data transmission rate is limited to 9.6 or 14.4 Kbps, which is not suitable for a next generation mobile communication system requiring a high data rate have. In addition, in the case of a base station which can not receive GPS, the conventional system can not synchronize between the base stations, so soft handoff with the adjacent base station is almost impossible and essentially requires a GPS receiver. There is a problem that it is difficult to install various types of base stations.

Therefore, the present invention provides a W-CDMA system for W-CDMA, which is a promising candidate multiple access technology for next generation mobile communication capable of acquiring initial system time and soft handoff of a mobile station without synchronization between base stations, To provide an asynchronous method.

1 is a block diagram of a conventional narrowband code division multiple access (CDMA) system in which base station synchronization is maintained using a global positioning system and base stations are discriminated by using a phase difference of the same code for absolute time Schematic of

FIG. 2 is a time chart showing a base station transmission time and a frame alignment of a forward channel in a conventional narrowband CDMA system.

Figure 3 is a schematic diagram of a system of the present invention that operates with base station asynchronous,

4 is a time chart of the present invention showing the transmission time of the asynchronous base station system and the frame alignment of the forward channel

5 is a schematic diagram showing a common portion of a forward channel of the present invention

6 is a schematic diagram showing the structure of a pilot channel of the present invention

7 is a schematic diagram showing the structure of a synchronization channel of the present invention

8 is an exemplary diagram showing an embodiment of a Gold Code generator of the present invention.

9 is a schematic diagram illustrating one embodiment of an I and Q pilot gold code generator of the present invention

10 is a schematic diagram illustrating a Multiple Gold Code generator for pilot acquisition of a mobile station of the present invention;

11 is a flowchart showing an initial base station synchronization acquisition procedure of the mobile station of the present invention

The fundamental principle of the present invention to achieve the above-mentioned object is that as shown in FIG. 3 and FIG. 4, the distinction between the base stations is performed by using different codes having short cycles without synchronization between the base stations . Each base station has a reference time (frame time) of the base station itself of 10 msec as shown in FIG. 4, and the reference time is independent from one base station to another.

In the base station asynchronous method of the present invention, the forward channel includes a pilot channel, a synchronization channel, a paging channel, and a call channel. Each channel is divided into Walsh codes and has a common portion as shown in FIG. The pilot channel allows the mobile station to perform base station synchronization acquisition and coherent demodulation and soft handoff. The pilot channel is subjected to QPSK modulation by Pilot I and Q codes as shown in FIG. 5 through spreading by 0 Ws code to an unmodulated data symbol as shown in FIG.

Each base station uses two unique extensible Gold codes with 2 ⁹ chip lengths as pilot I and Q codes in FIG. Where there holding one embodiment, if the length is ²⁹ in a, it not necessarily required ²⁹ days, are also possible, such as the length 2 ¹⁰ and 2 ^11. However, the length of codes used by each base station should be the same.

Turning to the example of the enhanced generation Gold code having a length less than ²⁹ set, Extended Gold code having a first length ²⁹ is ²⁹ - 1 is obtained by adding at the end a 0 of 1 Gold code having a length of. A Gold code set with a length of 2 ⁹ - 1 is generated from two M sequences with the following generator polynomials.

f ₁ (D) = 1 + D ⁴ + D ⁹

f ₂ (D) = 1 + D ⁴ + D ⁵ + D ⁸ + D ⁹

In Equation (1), D is a delay factor, and the two M sequences having the generator polynomial have a period of 2 ⁹ -1 and satisfy the necessary and sufficient condition for generating a Gold sequence.

If the M sequences generated by the generator polynomial are expressed as m ₁ (D) and m ₂ (D), respectively, the number of gold sequences that can be generated from the two M sequences is 513 as follows.

FIG. 8 shows an exemplary structure of a typical shift register for generating the gold codes given by the above equation.

The value of [a ₀ a ₁ a ₂ a ₃ a ₄ a ₅ a ₆ a ₇ a ₈ ] has a value of [1 0 0 0 0 0 0] at the start of the base station time of 10 msec. On the other hand, the value of [b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ b ₆ b ₇ b ₈ ] has a value corresponding to the extended gold code used for each base station at the starting point of 10 msec base station time.

The extended gold code used in the I and Q pilot pn (PN) codes to distinguish each base station adds orthogonality between the codes by adding one zero to the end of each of the 512 gold codes except m ₂ (D) ≪ / RTI > The expanded gold code m ₁ (D) + D ⁱ m ₂ (D) is defined as g _i (D), and the two extended gold codes are numbered as shown in Table 1 below.

Code pair number I channel pilot code Q-channel pilot code Code pair 0 g ₀ (D) g ₁ (D) Code pair 1 g ₂ (D) g ₃ (D) ... ... ... Code pair k g _2k (D) g _{2k + 1} (D) ... ... ... Code pair 254 g ₅₀₈ (D) g ₅₀₉ (D) Code pair 255 g ₅₁₀ (D) g (D)

Each base station selects one of the 256 code pairs in Table 1 and uses it as a pilot peen (PN) code pair.

FIG. 9 shows an embodiment of a gold code generator for generating the pilot code pair mentioned in Table 1 above.

The major advantage of the extended Gold code is that the cross-correlation between the different codes is very good, and that multiple codes can be simultaneously generated without increasing the complexity. Therefore, the mobile station can easily obtain the initial synchronization of the pilot using the characteristics of the extended Gold code.

FIG. 10 shows an embodiment of a multiple gold code generator of a mobile station generating a plurality of gold codes at a time. The extended gold code is obtained by adding 0 to the end of the gold code as above.

Hereinafter, the initial base station synchronization acquisition procedure of the mobile station in the asynchronous method of the present invention having the extended Gold code will be described with reference to the flowchart of FIG.

First, when the power is turned on, the terminal assigns the first k code pairs to the parallel correlator. The parallel correlator performs parallel correlation on the first of the whole period (2 ⁿ chips).

The mobile station then compares the k correlator outputs against a preset threshold value in the memory. If none of the k correlator outputs is greater than the threshold value, the mobile station updates the timing of the code generator to half-chip (1/2 chip), and then performs parallel correlation. If none of the correlator outputs is greater than the threshold value, the above process is repeated.

If the code is not found until the end of the code period (512 chips), the mobile station allocates the next k codes to the parallel correlator, and then repeats the above process.

If the output value of the correlator is larger than the threshold value during the above process, the mobile station enters the confirmation mode. If it is a false alarm, the above process is performed again, and if it is true (True), synchronization channel data demodulation is performed immediately.

Through synchronization channel data demodulation, the mobile station acquires a 10 msec base station (typically the nearest base station) time. The frame of the synchronization channel has a length of 10 msec, and the start point of the frame is aligned with the base station time reference. And inserts eight " 1 " s at the start position of the synchronization channel frame to provide 10 msec base station time information to the mobile station that has acquired the pilot. FIG. 4 shows a structure of a sync channel frame in which eight "1" s are inserted, and FIG. 7 shows a structure of a sync channel. After acquiring the 10 msec base station time through the synchronization channel, the mobile station enters an idle state. In the idle state, the mobile station acquires all information of the system through the paging channel.

Therefore, since the present invention is essentially asynchronous, it is possible to acquire initial system time and soft handoff of a mobile station without synchronizing between base stations without requiring a GPS receiver, and various types of base station installation such as macrocell, microcell, It is possible to generate multiple codes at the same time without increasing the complexity and to use the extended gold code having a short cycle as the pilot sequence (PN) (IMT-2000), which has a short initial system acquisition time compared with the synchronous method and can transmit data at high speed, can be used as a core technology of the radio transmission technology for the next generation mobile communication .

Claims (1)

The base station asynchronous method for wideband code division multiple access method for transmission of high-speed data, but distinguishes the base stations using different extended Gold code having a short period of 2 ⁿ long, the period is 2 ⁿ of extended Gold Code is created by adding a " 0 " to the end of the Gold code having a period of 2 ^{< n} > -1 and each of the base stations uses two of the extended Gold codes as pilot I and Q code sequences, respectively And a base station asynchronous method for a multi-band code division multiple access method using a short period extended Gold code, the base station asynchronous method comprising: