KR100228012B1 - Apparatus and method for combining symbol by using memory - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to an apparatus and method for symbol combining using a memory.

2. The technical problem to be solved by the invention

SUMMARY OF THE INVENTION An object of the present invention is to provide a symbol combining apparatus and a method for combining symbols after receiving a signal during handover and performing demodulation even in an asynchronous manner.

3. Summary of Solution to Invention

The present invention provides a demodulation means for demodulating a signal received from a base station; Switching means for switching a demodulated plurality of signals; First storage means connected to the switching means for receiving and storing the switched work output; First symbol combining means for reading and combining symbols from the first storage means; Second storage means connected to the switching means for receiving and storing another switched output, and storing the output of the first symbol combining means; And second symbol combining means for reading and combining symbols from said second storage means.

4. Important uses of the invention

The present invention is used in a mobile station.

Description

Symbol combining apparatus using memory and its method

The present invention relates to a symbol combining apparatus and method for combining symbols received from base stations in a mobile station.

The conventional symbol combining apparatus for mobile stations is composed of three demodulating fingers, three first-in first-out circuits, and one symbol combiner. The conventional base station symbol combining apparatus includes four demodulating fingers, four first-in-first-out circuits, and one symbol combiner. It consists of.

In a general code division multiple access (CDMA) mobile communication network, demodulating fingers of a mobile station perform symbol-combine in a symbol combiner after receiving and demodulating signals from different paths. A deskew is responsible for aligning symbols received by different demodulating fingers according to the same reference time in order to be able to perform symbol combining. Such a desktop is implemented as a first-in first-out (FIFO), and a symbol combiner is configured to take a desired symbol from a buffer for symbol combining.

1 is a block diagram of a general deskewer used in a symbol combining apparatus.

As shown in the figure, a read pointer is controlled by a symbol combiner, a write pointer is controlled by a demodulating finger, and each FIFO has a depth of 8 symbols. It consists of a circular buffer.

When a signal is received through each modulating finger, the symbol is stored in the desktop and the write pointer is incremented by one. The received symbol is then stored at the location of the incremented write pointer. The depths of the symbols stacked on the desk corresponding to each modulation finger are different. The depth of a symbol accumulated in a deskew corresponding to a demodulating finger that despreads a signal first is greater than a depth of a symbol stacked in a desk corresponding to a demodulating finger which is later despreaded.

However, in order to combine the symbols, the symbols should be output at the same time point at the same position of each first-in first-out circuit (FIFO) in consideration of the symbol delay due to the multi-path effect.

The behavior of the desk pointer's read pointer, controlled by a symbol combiner, is

In most applications, a demodulating finger that demodulates the first arriving signal is designated as a predefined demodulating finger. The predefined demodulation finger refers to a demodulation finger whose time is tracked by a symbol combiner. A read operation is performed on the demodulating finger after data is input to all three demodulating fingers on the basis of a time delay of at least 5 symbols or more from the write pointer of the predetermined demodulating finger. Is performed simultaneously. At this time, the positions of the pointers for reading the symbols in the first-in first-out circuit (FIFO) are all the same, and the read pointer is increased by one after the read operation. The read operation that occurs next is performed on the incremented read pointer. In the predefined demodulating fingers, the time delay of the write and read pointers is fixed, and the time delays of the other two demodulating fingers are changed by slewing and time tracking. Although the time delay between the write pointer and the read pointer is usually 5 symbols in the predefined demodulation finger, 8 symbols are placed in the first-in first-out circuit under the worst condition.

In the conventional " IS-95 " method, synchronization between base stations is matched based on a global positioning system (GPS), and data is transmitted based on the synchronization. Therefore, when the mobile station requests a soft handover to the base station, each base station transmits data at the same time through the channel allocated for handover, so that the mobile station can transmit the data at the same time. The resulting time delay, even in the worst case, does not exceed eight symbols. Accordingly, symbol delay / chip delay due to cell diversity / multipath in a first-in first-out circuit that can accommodate 8 symbols corresponding to each demodulating finger It is not difficult to implement this in hardware (H / W).

However, in the base station asynchronous mode, each base station operates independently of each other without a time reference matched between the base stations. In the inter-base station asynchronous scheme, while the mobile station performs soft handover, each demodulating finger must receive data transmitted from both base stations and the symbol combiner must perform symbol combine. In this case, since the data transmitted from the two base stations are not transmitted according to the same time reference, each of the demodulating fingers of the mobile station may arrive with a significant time difference.

Accordingly, when the mobile station demodulates data based on the start of the current base station frame while performing the soft handover as shown in FIG. 2, the data transmitted from the base station to be moved in the worst case is 1 of the current base station frame. Symbol combines must be successful even if they are advanced or lag by a period of / 2.

Therefore, in the case of the base station asynchronous method, in order for the mobile station to perform the soft handover normally, a very large internal first-in first-out circuit (FIFO) may be used for the demodulating fingers to store a symbol corresponding to a maximum of about 1/2 frame. There was a problem that needed.

The present invention devised to solve the above problems, in the case of asynchronous as well as inter-base station synchronous scheme, by using a memory, after receiving a signal in a cell (demodulation) to perform demodulation after combining the symbols It is an object of the present invention to provide a symbol combining apparatus and a method for combining symbols after receiving a signal upon handover and performing demodulation.

1 is a schematic diagram of a typical deskewer used in a symbol combining apparatus.

2 is an explanatory diagram for a general symbol combining range in the symbol combining apparatus.

3A and 3B are diagrams illustrating an embodiment of a symbol combining apparatus according to the present invention.

4 is a diagram illustrating an embodiment of a memory and a second symbol combiner according to the present invention;

* Explanation of symbols for the main parts of the drawings

31,37: demodulation finger 32,38: switching unit

33,39: first-in first-out circuit 34,40: first symbol combiner

35,41: memory 36,42: second symbol combiner

In order to achieve the above object, an apparatus of the present invention is a symbol combining apparatus of a mobile station, comprising: a plurality of demodulation means for demodulating a signal received from a base station; Switching means for switching a plurality of signals output from said plurality of demodulation means; First storage means connected to the switching means for receiving and storing one output of the demodulation means switched in the switching means; First symbol combining means for reading and combining symbols from the first storage means; Second storage means connected to the switching means for receiving and storing the other output of the demodulation means switched in the switching means, and storing the output of the first symbol combining means; And second symbol combining means for reading and combining symbols from said second storage means.

On the other hand, the method of the present invention, in the symbol combining method applied to the symbol combining apparatus of the mobile station, when the three demodulating fingers hold the multipath of one base station to which the mobile station currently belongs, A first step of demodulating a signal received from the same base station, switching and storing the demodulated signal, reading and combining the stored symbols, and then storing and reading and combining the stored symbols again; And a signal received from the base station to which the mobile station currently belongs, in soft handover in which two demodulating fingers hold the multipath of the base station to which the mobile station currently belongs, and the other demodulating finger taking the path of the base station to which the mobile station will move. After demodulating and switching and storing the demodulated signal, the stored symbols are read, combined and stored again, and after the mobile station demodulates the received signal from the base station to be moved, switches and stores the demodulated signal, and stores the two stored symbols. The second step is to read and combine.

In addition, another method of the present invention is a symbol combining method applied to a symbol combining apparatus of a mobile station, wherein, when three demodulators hold a multipath of one base station to which the mobile station currently belongs, the mobile station belongs to the mobile station. Demodulating a signal received from the same base station, switching and storing the demodulated signal, and then reading and combining the stored symbols; And during soft handover in which two demodulators hold the multipath of the base station to which the mobile station currently belongs and another demodulator takes the path of the base station to which the mobile station will move, demodulating the signals received from the base station to which the mobile station currently belongs. After switching and storing the demodulated signal, the stored symbols are read, combined and stored again.The mobile station demodulates the signals received from the base station to be moved, switches and stores the demodulated signals, and then reads the two stored symbols. A second step of combining.

Hereinafter, an embodiment according to the present invention will be described in detail with reference to FIG. 3.

3A and 3B are diagrams illustrating an embodiment of a symbol combining apparatus according to the present invention.

As shown in FIG. 3A, when each demodulating finger is holding a multi-path of one base station to which the mobile station currently belongs, the three demodulating fingers 31 are the same to which the mobile station belongs. After demodulating the signal received from the base station, the switching unit 32 switches all of the outputs of the three demodulating fingers 31 to the first-in first-out circuit 33. The three first-in first-out circuits 33 corresponding to the three demodulating fingers 31 receive and store the outputs of the three demodulating fingers 31 switched by the switching unit 32. Then, the first symbol combiner 34 reads and combines the symbols at the same pointer positions of the three first-in first-out circuits 33 at the same time, and the memory 35 stores the output of the first symbol combiner 34. The second symbol combiner 36 reads symbols from the memory 35, combines them, and outputs the combined symbols.

On the other hand, as shown in Figure 3b, two demodulating fingers are holding a multi-path of the base station to which the current mobile station belongs, and another demodulating finger is a soft handover holding the path of the base station to which the mobile station will move (soft hand over), two demodulating fingers 37 demodulate a signal received from the same base station to which the mobile station currently belongs, and the other demodulating finger 37 demodulates the signal received from the base station to which the mobile station will move. do. The switching unit 38 switches the outputs of the two demodulating fingers having received the signal of the base station to which the mobile station currently belongs among the three demodulating fingers 37 to the first-in first-out circuit 39, and receives the signal of the base station to which the mobile station will move. The output of one demodulating finger is switched directly to the memory 41. Two first-in first-out circuits of the three first-in first-out circuits 39 corresponding to the three demodulating fingers 37 receive and store the outputs of the two demodulating fingers 37 switched by the switching unit 38. do. Then, the first symbol combiner 40 reads and combines symbols simultaneously at the positions of the same pointers of the two first-in first-out circuits 39, and the memory 41 stores the output of the first symbol combiner 40 and the first symbol combiner 40. The output of one demodulating finger switched by the switching unit 38 is stored, and the second symbol combiner 42 reads and combines the symbols from the memory 41 and outputs the combined symbols.

Next, the operation during handover will be described in detail. Of the three demodulating fingers 37, two demodulating fingers are assigned the channel of the base station to which the mobile station currently belongs, and the other demodulating finger is assigned the channel of the base station to which the mobile station is to move. ). In this case, since a large time delay may occur between the two demodulating fingers and the cell diversity demodulating fingers, a software symbol combine is performed in the second symbol combiner using a memory of the CPU. ).

That is, the first-in first-out circuit (FIFO) corresponding to the demodulating finger # 1 and the demodulating finger # 2 stores the symbol on the basis of the start point of the channel frame allocated to the demodulating finger corresponding thereto. The hardware symbol combiner reads the outputs of the demodulating finger # 1 and the demodulating finger # 2 from the first-in first-out circuit, combines the symbols, and stores the values in the memory of the central processing unit through direct memory access (DMA). Since the signal output from the demodulation finger # 3 has a very large time delay displacement, if the symbol value is stored in accordance with the start point of the frame assigned to the corresponding demodulation finger as above, the structure of the first-in first-out circuit has a limited size. A read operation cannot be performed simultaneously with the demodulation fingers # 1 and # 2. Accordingly, cell diversity demodulating finger # 3 should operate in a different manner than demodulation fingers # 1 and # 2. That is, the demodulation finger # 3 stores the symbol value directly in the memory of the central processing unit through direct memory access (DMA) when the frame starts without passing through the first-in first-out circuit (FIFO).

4 is a diagram illustrating an embodiment of a memory and a second symbol combiner according to the present invention.

At handover, the even values such as address (addr), address +2 (addr + 2), and address +4 (addr + 4) in FIG. 4 are output from demodulation fingers # 1 and # 2, and the combined symbol values are combined. In the odd addresses such as address + 1 (addr + 1) and address + 3 (addr + 3), the symbol value at which demodulation finger # 3 begins to demodulate at the start of the frame of its channel is stored. The software symbol combiner (second symbol combiner) combines the two values of the demodulating fingers # 1 and # 2 and the symbol values of the demodulating finger # 3 in the memory if they are stored in the memory. However, in case of no handover, the first symbol combiner may store the combined data in a memory and immediately output the data without going through the process of combining the symbols. Through this method, symbol combine is successfully performed even in the base station asynchronous method. If the software symbol combiner is implemented as a hardware symbol combiner, the modem chip may include a demodulating finger, a switching unit, a first-in first-out circuit, a first symbol combiner, a memory, and a symbol combiner (second symbol combiner). (modem chip) can be implemented in hardware.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes can be made in the art without departing from the technical spirit of the present invention. It will be apparent to those of ordinary knowledge.

As described above, the present invention is implemented in consideration of the inter-base station synchronization method, and in the inter-base station asynchronous method, unlike a conventional symbol combining apparatus capable of symbol combining only by using an internal first-in first-out circuit having a very large size, it uses software using a memory. By further performing symbol combining, symbol combining is possible not only in the base station synchronous method but also in the base station asynchronous method.

Claims (8)

In the symbol combining apparatus of a mobile station, A plurality of demodulation means for demodulating a signal received from a base station; Switching means for switching a plurality of signals output from said plurality of demodulation means; First storage means connected to the switching means for receiving and storing one output of the demodulation means switched in the switching means; First symbol combining means for reading and combining symbols from the first storage means; Second storage means connected to the switching means for receiving and storing the other output of the demodulation means switched in the switching means, and storing the output of the first symbol combining means; And Second symbol combining means for reading and combining symbols from said second storage means; Symbol combining device consisting of. The method of claim 1, The second symbol combining means, Symbol combining apparatus comprising a symbol combining operation unit implemented in hardware. The method of claim 1, The second symbol combining means, A symbol combining apparatus comprising a software symbol combiner mounted on a central processing unit. The method of claim 3, wherein The second storage means, Symbol combining apparatus characterized in that configured using the memory of the central processing unit. The method according to any one of claims 1 to 4, The plurality of demodulation means, Symbol combining device characterized in that consisting of three demodulating fingers (demodulating fingers). The method according to any one of claims 1 to 4, The switching means, Switching the output of the demodulation means receiving the signal of the base station to which the mobile station currently belongs to the first storage means, and switching the output of the demodulation means receiving the signal of the base station to which the mobile station is to move to the second storage means. Symbol combining apparatus characterized in that. In the symbol combining method applied to the symbol combining apparatus of a mobile station, When three demodulators hold the multipath of one base station to which the mobile station currently belongs, demodulate the signals received from the same base station to which the mobile station belongs, switch and store the demodulated signals, and then read the stored symbols. A first step of combining and restoring again and reading and combining the restored symbols; And In a soft handover in which two demodulators hold the multipath of the base station to which the mobile station currently belongs, and another demodulator takes the path of the base station to which the mobile station will travel, the mobile station demodulates the signal received from the base station to which it currently belongs. After switching and storing the demodulated signal, the stored symbols are read and combined, and then stored again.The mobile station demodulates the signals received from the base station to be moved, switches and stores the demodulated signals, and then reads and combines the two stored symbols. 2nd step Symbol combining method comprising a. In the symbol combining method applied to the symbol combining apparatus of a mobile station, When three demodulators hold the multipath of one base station to which the mobile station currently belongs, demodulate the signals received from the same base station to which the mobile station belongs, switch and store the demodulated signals, and then read the stored symbols. Combining the first step; And In a soft handover in which two demodulators hold the multipath of the base station to which the mobile station currently belongs, and another demodulator takes the path of the base station to which the mobile station will travel, the mobile station demodulates the signal received from the base station to which it currently belongs. After switching and storing the demodulated signal, the stored symbols are read and combined, and then stored again.The mobile station demodulates the signals received from the base station to be moved, switches and stores the demodulated signals, and then reads and combines the two stored symbols. 2nd step Symbol combining method comprising a.

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