KR100661345B1 - Data transmission method in time division multiple access handoff region - Google Patents

Abstract

According to the present invention, a downlink transmission having only a multiplexing (TDM) interval in a cellular mobile communication system in which one frequency band is divided in time and multiplexes (TDM) or multiple access (TDMA) as a basic unit is performed. By inserting a multiple access (TDMA) interval into the CDMA to acquire synchronization with the base station through individual preambles, data transmission is performed in a handoff region of a time division multiple access scheme in which no transmission delay or loss occurs in the handoff region. As for the method,

According to the present invention, by using the TDMA interval for downlink data transmission during handoff in a cellular mobile communication system of time division multiple access, there is an effect of minimizing data transmission interruption or transmission delay during handoff.

Description

Method for Transmitting a Data at Handoff Area in Time Division Multiplexing Access Type}

1 shows the structure of a typical TDMA TDD frame,

2 illustrates a TDMA TDD frame structure of downlink transmission applied to a data transmission method in a TDMA handoff region according to an embodiment of the present invention.

3 illustrates a burst structure of a TDMA transmission data interval in a TDMA TDD frame of downlink transmission according to an embodiment of the present invention.

4 shows the position of a mobile terminal in two adjacent cells and received signal strength at that time in a downlink handoff region of a TDMA TDD system having a TDMA interval,

5 illustrates a handoff method when the mobile terminal moves from cell # 1 to cell # 2.

6 shows a data transmission process using diversity in a handoff region,

7 is a diagram illustrating a data transmission method through transmission cell selection in a handoff region.

The present invention relates to a data transmission method in a handoff region of a time division multiple access method. More particularly, the present invention relates to a time slot multiplexing (TDM) or multiple access based on time slots. In a cellular mobile communication system (TDMA), a multiple access (TDMA) section is inserted into a downlink having only a multiplexing (TDM) section to obtain synchronization with a base station through individual preambles, thereby allowing data to be The present invention relates to a data transmission method in a time division multiple access type handoff region in which transmission delay or loss does not occur.

In the cellular mobile communication system, the TDMA TDD scheme can dynamically allocate the uplink and downlink time intervals according to the amount of traffic between uplink and downlink. It is advantageous for the transmission of data of nature.

Figure 1 shows the structure of a typical TDMA TDD frame.

As shown in FIG. 1, one TDMA TDD frame has a downlink subframe, an uplink subframe, and a guard interval, and the downlink subframe has a base station / frame information section and a downlink transmission data section (TDM), and an uplink subframe. Has a contention period and an uplink transmission period (TDMA). Major systems that apply the TDMA TDD scheme include WLAN or WMAN technologies such as HIPERLAN / 2, HIPERMAN, and IEEE 802.16.

However, in the TDMA TDD cellular mobile communication system, handoff between cells is performed by acquiring the information of the neighbor cells. Since the frequency reuse coefficient of the TDMA is not 1, first, switching to the neighbor base station frequency in a section without data transmission and reception (Frequency Switching) After scanning, if the signal strength of the neighboring base station is greater than the signal strength of the serving base station, the procedure of handing off to the target base station is performed.

In this process, in the existing TDMA TDD system, the serving base station must store data to be transmitted to the mobile station scanning the neighboring base station for handoff during the scan period and transmit the data using the non-scanning period. Data transmission must be stopped during the scan interval. As shown in FIG. 1, in the downlink transmission having only the multiplexing (TDM) interval, the TDM interval is synchronized with the serving base station through the preamp. When the neighboring base station is scanned and the frequency is switched, it is transmitted from the serving base station. This is because the synchronization of the downlink is lost.

Therefore, there is a difficulty in optimizing parameters for scanning in order to perform handoff, and as the scan interval, period, and frequency increase and increase, it is possible to avoid performance degradation of relatively transmission delay sensitive data service such as voice or streaming. In addition, since downlink transmission must be stopped during the handoff, there is a problem in that data transmission is interrupted or a transmission delay occurs in the handoff region.

In order to solve the above problems, the present invention provides a multiplexing (TDM) in a cellular mobile communication system in which one frequency band is divided in time so that time slots are multiplexed (TDM) or multiple access (TDMA) as a basic unit. By inserting a multiple access (TDMA) section into the downlink transmission having only a section, and obtaining synchronization with the base station through a separate preamble, the time division multiple access method handoff so that no transmission delay or loss of data occurs even in the handoff region The purpose is to provide a data transmission method in the area.

In order to achieve the above object, a data transmission method in a time division multiple access method handoff region according to the present invention includes a downlink sub data interval, an uplink sub data interval, and a guard interval. A frame information section, a time division multiplexing (TDM) transmission data section, and a time division multiple access (TDMA) transmission data section, and the uplink sub data section is characterized by consisting of a contention section and an uplink transmission section (TDMA). .

In addition, the time-division multiple access method handoff method according to the second object of the present invention, the first step of measuring the signal strength of the serving base station, if the weak request for the adjacent channel scan to be approved to select a target base station; Transmitting information of the target base station to the serving base station, and transmitting information of the mobile terminal from the serving base station to the target base station; A third step of requesting access from the mobile terminal to the target base station; And a fourth step of changing the target base station to a new serving base station and releasing the connection with the serving base station through a downlink time division multiple access (TDMA) transmission data interval.

In addition, the data transmission method using the diversity in the handoff region according to the third object of the present invention, when the mobile terminal is in the cell region of the serving base station, the downlink time division multiplexed (TDM) transmission data interval from the serving base station; Receiving a data through a first step; The mobile terminal enters a handoff area, scans a neighbor base station, discovers a neighbor base station having a predetermined level or more signal quality, informs the serving base station of the neighbor base station, sets a target base station, and then establishes a connection. Attempting a second step; And a third step of transmitting data through a downlink time division multiple access (TDMA) transmission data interval having a predetermined time difference between the serving base station and the target base station when data to be transmitted to the mobile terminal is transmitted downward. It is characterized by.

In addition, according to the fourth aspect of the present invention, a method for transmitting data through transmission cell selection in a handoff region includes downlink time division multiplexing (TDM) transmission data interval from the serving base station when the mobile terminal is in the cell region of the serving base station. Receiving a data through a first step; The mobile terminal enters a handoff region, scans a neighbor base station, discovers a neighbor base station having a predetermined level or more signal quality, informs the serving base station of the neighbor base station, and sets a target base station. Two steps; A third step of transmitting, by the mobile terminal, optimal cell information obtained by measuring signal quality for a short time to the serving base station and the target base station; And a fourth step of the mobile terminal receiving data from an optimal base station corresponding to the optimal cell information among the serving base station and the target base station.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even if displayed on different drawings.

In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

2 illustrates a TDMA TDD frame structure of downlink transmission applied to a data transmission method in a handoff region of a time division multiple access method according to an embodiment of the present invention.

The TDMA TDD frame of downlink transmission according to the embodiment of the present invention has a structure in which a downlink data interval (TDMA) is inserted into a downlink subframe. That is, in the downlink according to the present invention, one TDMA TDD frame has a downlink subframe, an uplink subframe, and a guard interval, where the downlink subframe includes a base station / frame information section, a TDM downlink data interval, and a TDMA downlink transmission data. And an uplink subframe has a contention section and an uplink transmission section (TDMA).

When the TDMA interval is inserted in the downlink transmission, synchronization with the base station can be obtained through individual preambles included in each TDMA downlink burst.

3 illustrates a burst structure of a TDMA transmission data interval in a TDMA TDD frame of downlink transmission according to an embodiment of the present invention.

In FIG. 3, downlink transmission data of a mobile terminal requiring scanning of an adjacent base station for handoff is transmitted in a downlink TDMA burst period of a downlink transmission interval.

The downlink TDMA burst is transmitted by inserting a preamble into each downlink data of each base station, unlike a TDM burst period in a conventional TDMA TDD system in which a plurality of base station downlink data are multiplexed and transmitted in one preamble. Even if the initial synchronization with the base station is lost as a downlink burst period, synchronization can be obtained through individual preambles and the downlink data can be recovered.

The downlink TDMA burst is divided into a preamble and a dataload. As described above, the preamble may be different from the preamble located at the start of the frame as an interval for obtaining synchronization with the base station. That is, in the TDMA burst, a short preamble can be used as compared to the frame start preamble. The data section includes all data transmitted to the base station such as control information and service data. Therefore, the downlink TDMA burst needs to allocate more time intervals than the downlink TDMA burst in order to transmit service data of the same size. However, since the number of mobile terminals located at the cell boundary will be smaller than the total number of mobile terminals in the cell, increasing the downward TDMA burst period sufficiently may reduce the cell throughput. To solve this problem, the data transmission rate of the downlink TDMA burst section is set higher than the downlink TDM burst section having the same wireless channel environment. Here, the downlink TDMA burst period is transmitted at a higher transmit power than the downlink TDM burst period. This satisfies the additional signal-to-noise ratio (SN) requirements resulting from higher data rates.

4 shows the position of a mobile terminal in two adjacent cells and received signal strength at that time in a handoff region of a downlink transmission of a TDMA TDD system having a TDMA interval.

In the TDMA TDD system, the frequency reuse factor is not 1, so that two adjacent cells have different operating frequencies. When a mobile terminal moving from cell # 1 to cell # 2 receives data through the base station of cell # 1 and enters the handoff area, the mobile terminal stays connected with both the base stations of cell # 1 and cell # 2. When entering the cell # 2 out of the off area, the connection with the base station of cell # 1 is released and only the connection with the base station of cell # 2 is maintained.

5 illustrates a handoff method when the mobile terminal moves from cell # 1 to cell # 2.

The mobile terminal periodically measures signal quality such as signal strength, signal-to-noise ratio (SNR or CIR), and frame error rate of the serving base station (base station of cell # 1) (S502). When the mobile terminal reaches point (b) of FIG. 4 and the signal quality drops below a predetermined level, the mobile terminal requests a scan from the serving base station to the neighbor base station and receives an approval from the neighbor base station (S504).

When receiving the approval from the neighboring base station, the mobile station scans by switching the frequency to the candidate frequency (S506). In this case, the serving base station may transmit the operating frequency information of the adjacent base station in advance through the base station information transmission interval. The mobile terminal discovering cell # 2 through the scan informs the serving base station (cell # 1) that the base station of cell # 2 is the target base station, and attempts to access the target base station (cell # 2) (S508). At this time, the mobile terminal informs the target base station of the downlink TDMA period in which data is transmitted to the serving base station, so that the downlink TDMA transmission interval different from the serving base station can be allocated. Such information may be informed by transmission of information between base stations through a backbone network as shown in FIG. 5 (S510).

Subsequently, the mobile terminal requests access to the target base station through an upcoming contention period, a downlink frame information transmission period, or a TDMA period, and the target base station approves this (S512). The mobile terminal measures signal strengths of the serving base station (cell # 1) and the target base station (cell # 2) (S514).

When the mobile terminal passes point (c), the signal quality of the target base station (cell # 2) is superior to that of the existing serving base station (cell # 1). You will be asked to change the name to. If necessary, the two base stations negotiate between the two base stations for the role change and notify the mobile terminal that the change of the target base station and the serving base station is completed (S516). When the mobile station having changed the serving base station passes the point (d), when the mobile terminal exits the handoff area and enters the cell # 2 area, the mobile terminal requests to disconnect from the target base station of the cell # 1, and the target base station grants the approval. The mobile terminal receives data and information from only the new serving base station (cell # 2) (S518).

6 shows a data transmission process using diversity in the handoff region.

When the mobile terminal is in the region of cell # 1, the mobile station receives data from the serving base station by the downlink TDM interval (S602). After the mobile terminal enters the handoff area via point (b), the mobile terminal scans the neighbor base station. If it finds a neighbor base station with a certain level of signal quality, it informs the serving base station and targets it. After determining the base station, an access is attempted (S604).

From this point, when the serving base station and the target base station arrive at the data to be transmitted downward, the data is transmitted through the downlink TDMA section having a predetermined time difference. When the downlink data arrives at the serving base station only, the target is transmitted through the backbone network. Transfer to the base station (S606).

The order of sending data from each base station to the mobile terminal is determined through negotiation. In FIG. 6, the serving base station always transmits downlink data before the target base station (S608). In addition, the target base station also transmits data information to the serving base station through the backbone network (S610).

The mobile terminal first switches to the operating frequency of the serving base station to receive the data, and then switches to the operating frequency of the target base station to receive the data (S612). The two signals at baseband match and can be restored by combining or selecting them. When the mobile terminal passes through point (c) of FIG. 4, since the target base station and the serving base station are changed, the downlink data transmission order is also changed, and the two signals are sequentially received accordingly. At this time, the method of receiving and restoring data is the same. When the mobile terminal passes point (d) of FIG. 4, the mobile terminal releases the connection with the target base station that was the existing serving base station and receives data from only the new serving base station. From this time, the downlink TDM interval is used (S614). .

7 illustrates a data transmission method through transmission cell selection in a handoff region.

When the mobile terminal is in the region of cell # 1, it receives data through the downlink TDM interval (S702). After the mobile terminal enters the handoff area via point (b), the mobile terminal scans the neighbor base station. If it finds a neighbor base station with a certain level of signal quality, it informs the serving base station and targets it. After determining the base station, an access is attempted (S704).

In a long time average in the handoff region, the signal quality of the serving base station generally remains better than the target base station, but in the short time average, the order of the two signal qualities may continue to change. Therefore, the mobile terminal transmits the optimal cell information obtained by measuring the signal quality for a short time such as one frame period to the serving base station and the target base station (S706).

Thereafter, the mobile terminal can receive data from an optimal base station between the serving base station and the target base station. In this case, when the mobile terminal is located at point (b) of FIG. 4, since the serving base station cell becomes the optimum cell rather than the target base station, data is received through the downlink TDMA interval from the serving base station BS1, which is the base station of the optimal cell. (S708).

However, when the mobile terminal transmits the optimal cell information to the serving base station and the target base station (S710) and passes the point (c) of FIG. 4 in the handoff region, if the target base station is selected as the optimal base station by the optimal cell information, Since the target base station is switched to a new serving base station, the mobile terminal receives data from the new serving base station BS2 of the optimal cell (S712). Of course, in this case, the downlink data transmission uses the downlink TDMA transmission interval of each base station. Data reception in the remaining areas is the same (S714).

Although the above-described data transmission has been described based on downlink data, the same principle may be used for uplink data transmission.

As described above, according to the present invention, a multiplexing (TDM) interval in a cellular mobile communication system in which one frequency band is divided in time and multiplexes (TDM) or multiple access (TDMA) as a basic unit. By inserting a multiple access (TDMA) section into a downlink transmission with only transmission to obtain synchronization with a base station through individual preambles, the time division multiple access method handoff region does not cause data transmission delay or loss even in the handoff region. The data transmission method can be realized.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention.

Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments.

The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

As described above, according to the present invention, by using the TDMA interval for downlink data transmission during handoff in a cellular mobile communication system of time division multiple access, disconnection or transmission delay of data transmission during handoff can be minimized. It has an effect.

Claims (10)

It consists of a downlink sub data interval, an uplink sub data interval and a guard interval, The downlink sub data section includes a base station / frame information section, a time division multiplexing (TDM) transmission data section, and a time division multiple access (TDMA) transmission data section, and the uplink sub data section includes a contention section and an uplink transmission section. (TDMA) A data transmission method in a time division multiple access method handoff area. The method of claim 1, The time division multiple access (TDMA) transmission data interval is a downlink burst period in which the preamble is inserted into the downlink transmission data of each base station and transmitted, respectively, even though the initial synchronization with the base station is lost, the synchronization is acquired through the individual preamble and downlink data is transmitted. A data transmission method in a handoff region of time division multiple access scheme, characterized by restoring. The method of claim 2, The downlink burst period is composed of a preamble and a data period (Payload), The preamble is different from the preamble located at the beginning of the frame, and may use a short preamble compared to the frame start preamble. The data section includes control information and service data, The data transmission rate of the time division multiple access (TDMA) transmission data interval is set higher than the time division multiple access (TDM) transmission data interval having the same wireless channel environment, wherein the time division multiple access (TDMA) transmission data interval Is a data transmission method in a time division multiple access method handoff region, characterized in that the transmission is transmitted at a higher transmission power than the time division multiplexing (TDM) transmission data interval. A method for performing handoff of a mobile terminal in a time division multiple access method, A first step of measuring a signal strength of the serving base station and selecting a target base station by requesting and receiving an adjacent channel scan when the signal strength is weak; Transmitting information of the target base station to the serving base station, and transmitting information of the mobile terminal from the serving base station to the target base station; A third step of requesting access from the mobile terminal to the target base station; And And a fourth step of changing the target base station to a new serving base station and releasing the connection with the serving base station through a downlink time division multiple access (TDMA) transmission data interval. Off way. The method of claim 4, wherein The first step is performed through a downlink time division multiplexing (TDM) transmission data interval, and the second step is transmitting information of the target base station through an uplink time division multiple access (TDMA) transmission data interval, and the serving base station. In the time division multiple access method handoff method characterized in that for transmitting the information of the mobile terminal to the target base station via a backbone (Backbone) network. A first step of receiving data through a TDM transmission data interval from the serving base station when the mobile terminal is in a cell region of the serving base station; The mobile terminal enters a handoff area, scans a neighbor base station, discovers a neighbor base station having a predetermined level or more signal quality, informs the serving base station of the neighbor base station, sets a target base station, and then establishes a connection. Attempting a second step; And And a third step of transmitting data through the TDMA transmission data section having a predetermined time difference between the serving base station and the target base station when data to be transmitted to the mobile terminal is transmitted downward. A data transmission method using diversity in a handoff region. The method of claim 6, And the serving base station always transmits downlink data prior to the target base station. The method of claim 6, The mobile terminal first switches to the operating frequency of the serving base station to receive data, and then switches to the operating frequency of the target base station to receive data. . A first step of receiving data through a TDM transmission data interval from the serving base station when the mobile terminal is in a cell region of the serving base station; A second step in which the mobile terminal enters a handoff area and scans a neighbor base station, discovers a neighbor base station having a predetermined level or more signal, informs the serving base station of the neighbor base station, and sets a target base station; step; A third step of transmitting, by the mobile terminal, optimal cell information obtained by measuring signal quality for a short time to the serving base station and the target base station; And And a fourth step of the mobile terminal receiving data from an optimal base station corresponding to the optimal cell information among the serving base station and the target base station. The method of claim 9, In the fourth step, when the serving base station corresponds to the optimal cell information, the data is received from the serving base station through a downlink time division multiple access (TDMA) data transmission interval, In case the target base station corresponds to the optimal cell information, the target base station is switched to a new serving base station, and data is received from the new serving base station through a downlink time division multiple access (TDMA) transmission data interval. A data transmission method through transmission cell selection in the handoff region.

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