KR20060094695A - Method of alternative adaptation of radio access techniques in mobile communications system - Google Patents

Abstract

The present invention is a cellular wireless mobile communication that can selectively apply the optimal wireless access method according to the change of wireless channel environment by implementing a combined system that can utilize the advantages of OFDMA technology in the current CDMA system and future broadband The present invention relates to a method of selectively applying a wireless access method of a system. Selective application method of a wireless access method of a cellular wireless mobile communication system according to the present invention, selectively at least two or more different types of radio access (radio access) method between the base station and the terminal in the same cell (cell) Characterized in that communication is performed.

Mobile communication, cellular, wireless access, CDMA, OFDMA

Description

Method of alternative adaptation of radio access techniques in mobile communications system

1 is a view for explaining the concept of a preferred embodiment of the present invention.

2 is a view for explaining a process of performing a handover with another system in an embodiment of the present invention.

The present invention relates to a wireless mobile communication system. More specifically, the present invention implements a combined system that can utilize the advantages of the OFDMA technology in the current CDMA system and the future broadband is able to selectively apply the optimal radio access method according to the changes in the radio channel environment The present invention relates to a method of selectively applying a wireless access method of a cellular wireless mobile communication system.

In the future, mobile communication systems will evolve into broadband systems according to the high data rate demands of users. As a technology suitable for a wideband system, the radio technology of Orthodgonal Frequency Division Multiplexing Access (OFDMA) has become a certain trend, and some standards have already been adopted for practical use. However, unlike Code Division Multiple Access (CDMA), there are still many problems to be solved in order to apply OFDMA technology to a cellular mobile communication system. In particular, due to the characteristics of the cellular structure, inter-cell interference problems are the biggest issues, and uplink synchronization problems, peak-to-average ratio (PAPR), frequency and time offset problems, etc. remain to be solved. In particular, in order to apply OFDMA technology to a broadband cellular mobile communication system, it is most urgent to minimize or eliminate inter-cell interference while maximizing frequency utilization efficiency in a cellular structure.

In the conventional mobile communication system, the CDMA system and the TDMA (Time Division Multiple Access) system are mainly mainstream. CDMA is used in synchronous systems centered in the United States and Korea, and TDMA is used in GSM systems centered in Europe. In addition, wideband CDMA technology is applied in the third generation system. These include WCDMA technology of 3rd Generation Partnership Project (3GPP), a standardization body of 3G asynchronous mobile communication systems, and cdma2000 technology of 3G Generation 2 (3GPP2), a standardization group of 3G synchronous mobile communication systems.

The CDMA method uses various orthogonal codes to distinguish various data channels, control channels, users, and cells. In a cellular communication system composed of multiple adjacent cells, the system is designed to use the frequency used in one cell in neighboring cells as much as possible in order to improve the frequency usage efficiency. In the case of using different codes among cells, the CDMA method can maximize the frequency allocated in the current cell without interference from neighboring cells if the inter-code orthogonality is guaranteed. However, in practice, inter-cell orthogonality is not completely guaranteed due to various channel changes, and thus some interference occurs at the cell edge.

OFDMA technology uses frequency division multiplexing (FDM) to distinguish multiple channels, users, and sectors and is expected to be used in future broadband wireless access systems. However, when applied to a cellular system, it is impossible to freely use all frequencies allocated to a current cell independently of adjacent cells while maintaining a frequency reuse ratio of 1. Because frequency is a method of distinguishing cells, if a frequency currently used in an adjacent cell is used in a current cell, co-channel interference occurs and performance is degraded.

Therefore, frequency allocation must be made from time to time in order to prevent the use of the same frequency among adjacent cells by interworking with each other. Another method is to use a frequency hopping method that prevents the use of the same channel as much as possible while frequently changing frequency allocation independently. However, in the interference coping scheme, when the cell load increases, the co-channel interference (interference between adjacent cells using the same frequency band) is greatly increased, thereby rapidly degrading system performance. That is, the OFDMA cellular system can theoretically not achieve better performance than the CDMA scheme while maintaining frequency utilization 1 in all cells under the same frequency allocation band.

The present invention has been made to solve the problems of the prior art as described above, and an object of the present invention is to selectively apply the CDMA technique and the OFDMA technique in accordance with changes in the wireless channel environment, thereby eliminating or suppressing inter-cell interference of CDMA. The present invention provides a selective application method of a wireless access method of a cellular wireless mobile communication system that can minimize interference between adjacent cells and simultaneously exhibit high-speed transmission capability of the OFDMA scheme.

The present invention provides a method for improving cell throughput by actively coping with channel environment changes by selectively using two or more different radio access technologies such as CDMA radio access technology and OFDMA radio access technology in the same cell. It is about.

In one aspect of the present invention, a method for selectively applying a radio access method of a cellular wireless mobile communication system according to the present invention may include at least two or more different types of radio connections between a base station and a terminal within a same cell. It is characterized by performing communication by selectively using a radio access) method.

In another aspect of the present invention, a method for selectively applying a wireless access method of a cellular wireless mobile communication system according to the present invention may include: In a cellular wireless mobile communication system, a terminal in a specific cell is connected to a base station using a first wireless access method. Communicating; And communicating with the base station by the terminal using a second wireless access scheme that is different from the first wireless access scheme in the specific cell.

In another aspect of the present invention, a method for selectively applying a wireless access method of a cellular wireless mobile communication system according to the present invention includes: at least one or more base stations in a cell using a first wireless access method in a cellular wireless mobile communication system; Communicating with a terminal; And the base station communicating with at least one other terminal using a second wireless access method that is different from the first wireless access method.

Preferably, the first radio access method is a CDMA method, and the second radio access method is an OFDMA method. Alternatively, the first radio access method may be an OFDMA method, and the second radio access method may be a CDMA method.

The construction, operation and other features of the present invention will be readily understood by the preferred embodiments of the present invention described below with reference to the accompanying drawings.

1 is a view for explaining the concept of a preferred embodiment of the present invention. In FIG. 1, each cell is divided into a region using an OFDMA scheme and a region using a CDMA scheme in a mobile communication system divided into a plurality of cells. In other words, in the region using the OFDMA scheme, data transmission through all channels including the traffic channel and the control channel between the terminal and the base station is performed by the OFDMA scheme, and in the region using the CDMA scheme, data transmission between the terminal and the base station is performed by CDMA. It is performed by the method.

The criteria for distinguishing the CDMA scheme and the OFDMA scheme may be made by various methods. One of the methods is a location-based method. The cell is divided into a cell center part and a peripheral part by comparing the strength and threshold of a specific signal such as a pilot signal, and the OFDMA method is applied to the center part. This is a method using the CDMA method. The cell center and cell side portions are examples where the above technique is applicable, and may not necessarily be clearly distinguished locally. That is, the possibility that the area where the reference value (measured value) to which the threshold value is compared with the threshold value exceeds the threshold value does not necessarily coincide with the cell center and edge is not excluded. This means that since the channel environment can be greatly changed by various factors (building, forest, moving speed, etc.) existing in and outside of the cell, the area to which OFDMA and CDMA can be applied can change from time to time. In addition, it operates based on CDMA even in the case of handover occurring in an area where interference is very severe.

It is a standard that distinguishes between CDMA and OFDMA. It can be used not only for signal strength, but also for location information, quality of service (QoS), bit error rate (BER), and frame error rate (FER). Do. In more detail, in the case of location information, one cell is divided into a region to which CDMA is applied and an region to which OFDMA is applied according to a position from a base station. It is a method of reporting its location to the base station periodically or aperiodically and selecting a radio access method according to the location. In the case of the bit error rate or frame error rate, the bit error rate or frame error rate is compared with a specific threshold and divided into two regions according to the result, similarly to the case of reference based on the strength of a specific signal. As an additional example, a method of determining whether to convert between two systems by measuring the strength of an OFDM pilot signal after temporarily stopping WCDMA transmission using a compressed mode used in a 3GPP WCDMA system.

In addition, the unit selectively applying the OFDMA method and the CDMA method may determine whether to use the OFDMA method or the CDMA method by grouping each service unit or two or more terminals in addition to each terminal unit.

In FIG. 1, the boundary line (indicated by the dotted line in FIG. 1) of the radio access method in each cell may vary according to the selection criteria of the radio access method as described above. However, in the switching process between the OFDMA method and the CDMA method, a hysteresis method is applied between the threshold value and the comparison target value (for example, signal quality measurement value, BER, FER, etc.) as the selection criterion near the selection boundary line. It is desirable to minimize system load due to pin pong effects that may occur.

In a preferred embodiment of the present invention, the choice of whether a terminal in a specific cell communicates with the base station by the OFDMA scheme or the base station by the CDMA scheme may be made in the system access step. That is, power is applied to the terminal to initialize the state of the terminal and select a system by a predetermined method (for example, a signal by transmitting information about a current position of the terminal and transmitting a training signal. Checking the strength, BER, FER, etc.) It is possible to determine whether the terminal and the base station communicate by OFDMA or CDMA. When the wireless access method between the terminal and the base station is determined, the subsequent procedure may be performed such as synchronization with the system according to each method. Detailed description thereof will be omitted.

When a UE located in an area to which the OFDMA method is applied in a specific cell moves to an area in which the CDMA method is more favorable, or vice versa, two methods may be used. One is a method of communicating with a base station while maintaining the original radio access method in spite of a change of the area, and the other is a method of communicating with a base station by changing the radio access method when the area is changed.

In each cell, an OFDMA method and a CDMA method can be used simultaneously in a method of allocating different frequency bands to the OFDMA method and the CDMA method, and using the same frequency band for both methods, but using a separate code for the OFDMA method. There may be a method of realizing such that it can be distinguished by the allocated code and the channels used by CDMA. If they share the same frequency, additional processing is required. As a method of distinguishing an OFDM modulated signal from a CDMA modulated signal, first, a method of spreading OFDM symbol sample values to maintain orthogonality. Second, there is a method of using an analog orthogonal signal that can distinguish between a signal after OFDM modulation and a CMDA modulated signal.

In addition, in terms of interference problem, inter-cell handover is preferably performed by CDMA. However, FIG. 2 shows an example of a configuration in which all cells selectively use OFDM and CDMA based on a specific criterion in the example of a cell radio access method divided into two regions in one cell according to the present invention. According to FIG. 2, inter-cell handover is performed based on CDMA, but is not limited thereto. Although the OFDM scheme is always advantageous throughout the cell, if the neighbor cell is a cell that supports only CDMA, it is also possible to support CDMA-CDMA handover after converting the OFDM scheme of the current cell to CDMA. In addition, if a neighbor cell supports only OFDM, it is also possible to support OFDM-OFDM handover. That is, it is also possible to forcibly apply OFDMA or CDMA regardless of the method selection criteria.

 It is apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit and essential features of the present invention. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

According to the selective application method of the wireless access method of the cellular wireless mobile communication system according to the present invention, the currently operating CDMA system and the promising technology in the future broadband are implemented to change the wireless channel environment by implementing a combined system that can take advantage of the OFDMA technology. Therefore, the optimal wireless access scheme can be selectively applied, which can provide better service quality.

Claims (29)

In a cellular wireless mobile communication system, A method of selectively applying a radio access method, characterized in that communication is performed between a base station and a terminal by using at least two radio access methods of different types selectively in the same cell. The method of claim 1, The at least two radio access schemes include code division multiple access (CDMA) and orthogonal frequency division multiple access (OFDMA). The method of claim 1, The selective use of the at least two radio access method is determined according to the size (strength or strength) of the characteristic signal transmitted between the base station and the terminal. The method of claim 3, The specific signal is a pilot signal (pilot signal), characterized in that the selective application method of the wireless access method. The method of claim 1, The selective use of the at least two radio access schemes is determined according to the quality of the data channel established between the base station and the terminal. The method of claim 5, The quality of the data channel may be any one of signal strength, bit error rate (BER), frame error rate (FER), quality of service (QoS), throughput, and outrage probability. The method of claim 1, The selective use of the at least two radio access method is a selective application method of the radio access method, characterized in that made on a per terminal basis. The method of claim 1, The selective use of the at least two radio access methods is a selective application method of a radio access method, characterized in that each service criteria provided by the base station. The method of claim 1, Selective use of the at least two radio access method is a selective application method of a radio access method, characterized in that the unit group. The method of claim 1, The method of selectively applying a radio access method, characterized in that different frequency bands are used between the at least two radio access methods. The method of claim 1, The at least two radio access methods use the same frequency band, but the selective application method of a radio access method characterized in that the communication by applying an orthogonal code or orthogonal technology that can distinguish the two access methods. The method according to any one of claims 3 to 6, Selective application method of the wireless access method, characterized in that the OFDMA method is used in a region of a certain range based on a specific reference value, and the CDMA method in other regions. The method of claim 12, When the terminal performs the handover (handover), the selective application method of the radio access method, characterized in that performed by the CDMA method. The method of claim 1, And if the terminal performs handover between the current cell and the OFDMA-based cell, performing the handover by the OFDMA scheme. In a cellular wireless mobile communication system, A terminal in a specific cell communicating with a base station using a first wireless access scheme; And And selectively communicating with the base station by the terminal using a second wireless access scheme that is different from the first wireless access scheme within the specific cell. In a cellular wireless mobile communication system, The base station communicating with at least one terminal in the cell using a first wireless access scheme; And And the base station communicating with at least one or more other terminals using a second wireless access method different from the first wireless access method. The method according to claim 15 or 16, The first radio access method is a CDMA method, and the second radio access method is a selective application method of the radio access method, characterized in that the OFDMA method. The method of claim 17, The use of the CDMA method or the OFDMA method is a selective application method of a radio access method, characterized in that determined according to the magnitude of the feature signal transmitted between the base station and the terminal. The method of claim 18, The specific signal is a pilot signal (pilot signal), characterized in that the selective application method of the wireless access method. The method of claim 17, The use of the CDMA scheme or the OFDMA scheme is selectively applied according to the quality of the data channel established between the base station and the terminal. The method of claim 20, The quality of the data channel may be any one of signal strength, bit error rate (BER), frame error rate (FER), quality of service (QoS), throughput, and outrage probability. The method of claim 17, The use of the CDMA method or the OFDMA method is a selective application method of a radio access method, characterized in that made on a per terminal basis. The method of claim 1, The use of the CDMA method or the OFDMA method is selective application method of a radio access method, characterized in that each service standard provided by the base station. The method of claim 17, The use of the CDMA method or the OFDMA method is a selective application method of a wireless access method, characterized in that the unit of the terminal group. The method of claim 17, Selective application method of a wireless access method, characterized in that different frequency bands are used between the CDMA or OFDMA.  The method of claim 17,  The CDMA method or the OFDMA method uses the same frequency band, but the selective application method of the radio access method characterized in that the communication by applying an orthogonal code or an orthogonal signal that can distinguish the two access methods. The method of claim 17, Selective application method of the wireless access method, characterized in that the OFDMA method is used in a region of a certain range based on a specific reference value, and the CDMA method in other regions. The method of claim 27, When the terminal performs the handover (handover), the selective application method of the radio access method, characterized in that performed by the CDMA method. The method of claim 17, And if the terminal performs handover between the current cell and the OFDMA-based cell, performing the handover by the OFDMA scheme.

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