KR100312307B1 - Method for transmitting forward link frames which consist of time slots - Google Patents

Abstract

In the code division multiple access method, the transmission power of the control information bit group of each mobile station in the service cell is changed and transmitted by varying and transmitting the transmission position of the unencoded control information bit group in the transmission slot according to the usage status of the mobile stations. Is distributed in the transmission slot. This can minimize the reception interference power for the mobile station of the adjacent cell.

Description

METHODS FOR TRANSMITTING FORWARD LINK FRAMES WHICH CONSIST OF TIME SLOTS}

The present invention relates to a forward transmission method of a digital mobile communication system. In particular, in a code division multiple access communication system using an inter-base station synchronization method, a position of a control information bit group transmitted to a mobile station through a transmission slot within a transmission slot The present invention relates to a forward frame transmission method of variable transmission.

In the digital mobile communication system, the transmission of information may be performed in units of frames. The information may be user data such as voice data and packet data, and control data such as power control command, data transmission rate, and the like.

In addition, the time period of the frame is different depending on the system can be divided into time intervals, such as 10mS, 20mS. The frame may be configured of a plurality of time slots (hereinafter referred to as 'transmission slots'). On the other hand, the reason why the frame is composed of a plurality of time slots is that the transmission time of the transmitted data is shorter than the time interval of the frame. Because.

1 illustrates an example of a forward transmission frame structure of a digital mobile communication system.

As shown, the minimum unit of transmission may be the transmission slot 110 of 0.625mS time. And the frame 120 of the 10mS time period may be composed of the 16 slots. The superframe 130 of the 720mS time period may include 72 frames.

Each transmission slot 110 may be composed of control information and user data. In addition, the control information may be transmitted in a state in which no Forward Error Correction (FEC) channel encoding is performed. This is for quickly processing control information without performing a channel decoding process on the receiving side. On the other hand, at this time, the base station transmits the control information at a greater power than the user data in order to make the control information robust to bit errors.

On the other hand, in the case of the forward transmission frame of asynchronous UMTS (Universal Mobile Telecommunication Systems), the third generation mobile communication system in Europe currently being standardized, the control information in the transmission slot 110 of each 0.625mS time is the transmission slot time interval unit Transmission Power Control Command Bit (TPC) to control the transmission power, and a pilot bit to compensate for fading and phase distortion occurring on the mobile radio channel. Pilot Bit) and a Transport Format Indicator (TFI) bit indicating the transmission rate of the frame. The control information is referred to as a dedicated physical control channel (hereinafter referred to as 'DPCCH'). The user data in the transmission slot 110 for each 0.625mS time is user data such as voice data, packet data, and circuit data, and is called a dedicated physical data channel (hereinafter referred to as 'DPDCH'). .

In addition, the base station can perform spread modulation and digital modulation of a quadrature phase shift keying (QPSK) method using a DS (direct sequence) code. Transmit to mobile stations.

FIG. 2 is a diagram illustrating the relative magnitudes of the transmission powers of the DPCCH and DPDCH of the forward transmission frame received by each mobile station in the CDMA mobile communication system on the transmission slot time interval axis.

As shown, the transmit power of the DPCCH is relatively greater than the transmit power of the DPDCH. It controls transmit power in units of pilot bits and transmission slot time intervals for synchronous demodulation, which allows the receiving end to compensate for fading and phase distortion information occurring on a mobile radio channel. This is because a transmission power control command bit and a transport format indicator (TFI) bit indicating a transmission rate of a frame are not FEC (Forward Error Correction) channel encoding. As a result, the UMTS system transmits the DPCCH to the mobile stations with a relatively larger transmission power of the DPCCH than the transmission power of the DPDCH, with the intention of being robust to bit errors that may occur in the radio transmission.

On the other hand, the transmission power of the illustrated DPCCH and DPDCH in a certain service area is received as interference power to mobile stations in adjacent cells that are not the service area. That is, in the CDMA mobile communication system, the frequencies used in the serving cell region and the neighboring cell region are the same. Therefore, the control of the interference power becomes a very important factor in the service capacity and performance of the system. However, the UMTS mobile communication system assumes an asynchronous base station system. As a result, each asynchronous base station system transmits its own superframe without time synchronization between the base stations. Therefore, the large transmission power of the DPCCH shown in FIG. 2 transmitted from adjacent base stations respectively is received at different arrival times to the corresponding mobile station in a given serving cell, and in this case, the interference power of the received signal of the corresponding mobile station is Central. According to Limit Theory, it becomes Additive White Gaussian Noise.

On the other hand, when using the asynchronous UMTS forward transmission frame in the CDMA mobile communication system using the inter-base station synchronization method, which is time-synchronized with each other, as shown in FIG. Each transmission slot in the transmission frame is received at about the same time. The arrival time of each transmission slot received by each mobile station varies slightly depending on the propagation delay time according to the location of the mobile station and the base stations. However, this propagation delay time can be ignored because it is very short compared to the transmission time interval of the DPCCH. That is, in the case of using the asynchronous UMTS forward transmission frame in the CDMA mobile communication system using the inter-base station synchronization method, the transmission power of the transmission slot received at nearly the same time from neighboring base stations directly affects the received signal of each mobile station. It acts as an interference power. In particular, since the transmit power of the DPCCH is larger than that of the DPDCH, the influence of the received interference power during the time period of the DPCCH in the corresponding transmission slot is greater.

That is, in the case of using the asynchronous UMTS forward transmission frame in a synchronous CDMA mobile communication system in which time synchronization is performed between base stations, a plurality of mobile stations in adjacent cells will make a call when the position of the DPCCH in the transmission slot is fixed as in the related art. The result is that certain mobile stations in the serving cell will receive the received interference power combined with the DPCCHs of each of the mobile stations during the DPCCH time period. Accordingly, it can be seen that in a synchronous CDMA mobile communication system, mobile stations of adjacent cells are affected by very high reception interference power during the DPCCH time period in the transmission slot.

Therefore, mobile stations located at the boundary area between the cell or the communication traffic of neighboring base stations are not able to correctly receive the transmission slot or DPCCH transmitted from the base station in the serving cell due to the interference power. Incorrect reception of the DPCCH causes system call capacity deterioration due to synchronous demodulation performance degradation and incorrect power control due to power control bit decoding error. In addition, incorrect reception of the DPCCH can result in poor call quality and call breakage.

Accordingly, an object of the present invention is to provide a forward frame transmission method capable of minimizing reception interference power by signals transmitted to mobile stations of an adjacent cell in a code division multiple access mobile communication system using an inter-base station synchronization method. Is in.

Another object of the present invention is to change the transmission position on the transmission slot of each control information bit group transmitted to the mobile stations according to the usage state of the mobile stations in the code division multiple access method using the base station synchronization method. The present invention provides a method for forward frame transmission.

In addition, another object of the present invention is to provide a mobile communication system corresponding to a base station in a serving cell in a code division multiple access type mobile communication system using an inter-base station synchronization scheme and transmitting control information transmitted to each of the mobile devices through different transmission slots. The present invention provides a method of receiving transmission position information of a control information bit group in a transmission slot and receiving the corresponding transmission slot according to the received transmission position information.

In order to achieve the above object, the present invention provides a method for transmitting a forward frame composed of a plurality of transmission slot units in a code division multiple access mobile communication system. And a second step of determining a transmission position of the control information bit group, a second step of transmitting a transmission position of the control information bit group in the determined transmission slot to the call originating mobile station, and the determined control information bit group. According to the transmission position of the characterized in that the third step of transmitting the corresponding transmission slot.

1 is a diagram illustrating an example of a structure of a forward transmission frame of a digital mobile communication system.

2 is a diagram showing the relative magnitudes of the transmit powers of the DPCCH and DPDCH of an asynchronous UMTS forward transmission frame received by each mobile station in a synchronous CDMA mobile communication system on a transmission slot time interval axis;

3 is a diagram illustrating a process in which a base station of a synchronous CDMA mobile communication system transmits a variable position of a DPCCH in a corresponding transmission slot to respective mobile stations in its cell according to an embodiment of the present invention.

FIG. 4 conceptually illustrates the magnitude of transmit power from a base station within a transmission slot time interval when a plurality of mobile stations assuming the same data rate when using a forward frame transmission method according to an embodiment of the present invention. drawing.

5 is a flowchart illustrating a method of transmitting a forward frame by a base station in a CDMA mobile communication system according to an embodiment of the present invention.

6 is a flowchart illustrating a method of receiving a forward frame of a mobile station in a CDMA mobile communication system according to an embodiment of the present invention.

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 the following description of the present invention, detailed descriptions of related well-known functions or configurations are omitted when it is determined that the detailed description may unnecessarily obscure the subject matter of the present invention.

3 is a diagram illustrating a process in which a base station of a CDMA mobile communication system adopting an inter-base station synchronization method transmits a variable position of a DPCCH in a corresponding transmission slot to respective mobile stations in its cell according to an embodiment of the present invention. to be. Hereinafter, a description will be given with reference to FIGS. 1 and 2.

As shown in FIG. 3, the base station according to an embodiment of the present invention changes the position of the slot in the slot according to the usage state of the mobile stations in the transmission position of the control information bit group without channel coding in the transmission slot. To transmit. As a result, since the transmission power of the DPCCH for each mobile station in the serving cell is distributed in the transmission slot, the interference power on the received signal of the mobile station of the adjacent cell can be significantly reduced.

On the other hand, the number of DPCCH variable positions in the transmission slot can be represented by a maximum integer that does not exceed the result of dividing the time interval of the transmission slot by the DPCCH time interval. For example, if the time period of a given DPCCH is 0.06mS, 0.625 [mS] /0.06 [mS] = 10.42, that is, the maximum integer 10 is the number of variable positions where the DPCCH can be inserted in one transmission slot.

That is, the base station according to an embodiment of the present invention, when a new call (Call) occurs, checks the currently used DPCCH variable position in the transmission slot. If there is an unused location, the base station determines the DPCCH transmission location at the unused location for the currently requested call and transmits the corresponding transmission slot to the corresponding call originating mobile station. If all DPCCH transmittable positions are in use in the transmission slot, the base station allocates the duplicated DPCCH transmission positions but minimizes the overlapping positions in order to minimize interference power.

On the other hand, in order for the base station and the mobile station according to the embodiment of the present invention to transmit / receive mutual signals, the mobile station needs to know the transmission position of the DPCCH of the transmission slot that it receives. In general, call generation in a mobile communication system is caused by a call of a mobile station or a call of a base station. In order to connect a normal call, the base station and the mobile station transmit / receive various control and signaling messages through a common control channel or a dedicated control channel before transmitting / receiving subscriber data traffic. It is common to receive. Therefore, before the call is set up, the base station can inform the mobile station of the transmission position of the DPCCH in the determined transmission slot through a common control channel or a dedicated control channel.

FIG. 4 conceptually illustrates the magnitude of transmit power from a base station within a transmission slot time interval when a plurality of mobile stations assuming the same data rate when using a forward frame transmission method according to an embodiment of the present invention. Drawing.

As shown, according to the forward frame transmission method according to an embodiment of the present invention, since the transmission power of the DPCCH for each mobile station in the serving cell is distributed within the time slot of the transmission slot, the transmission power of the DPCCH is transmitted over the entire transmission slot time interval. It is distributed uniformly. Therefore, in the CDMA mobile communication system using the inter-base station synchronization scheme, the transmission power of the DPCCH from the base stations of the neighboring cells received by the predetermined mobile station is also distributed within the time slot of one transmission slot.

If the number of DPCCH variable positions is N and the number of busy mobile stations having the same data rate is also N, the DPCCH required transmission power is And the DPDCH request transmit power Let's say In this case, according to the forward frame transmission method according to an embodiment of the present invention, as shown in FIG. 3, the base station transmits a constant transmission power as shown in Equation 1 to the mobile stations in the serving cell over the entire time slot of the transmission slot. Send the slot.

Here, N in Equation 1 means the number of mobile stations in a call having the same data rate in a predetermined serving cell. Is the DPDCH required transmission power, Means DPCCH required transmission power.

In contrast, in a synchronous CDMA mobile communication system in which time synchronization is performed between base stations, when a non-synchronous and forward frame structure of a plurality of transmission slot units is used, such as a UMTS mobile communication system, channel coding is performed in a transmission slot as in the prior art. If the position of the DPCCH, which is not a group of control information bits, is fixed, as shown in FIG. Will be transmitted.

Here, N in Equation 2 means the number of mobile stations in a call having the same data rate in a predetermined serving cell. Means DPCCH required transmission power.

For example, the required transmit power of the DPCCH is twice that of the DPDCH (in the current code division multiple access mobile communication system of the commercial IS-95 standard, the energy of the TPC bits is transmitted about twice as large as the user data bit energy). If the number of mobile stations in a given serving cell is 30, the transmit power during the DPCCH time period according to the conventional method is directly proportional to the interference power received by the predetermined mobile station located in the adjacent cell is expressed by Equation 3 below. .

Here, 30 in Equation 3 refers to the number of mobile stations in a predetermined serving cell. Is the DPCCH required transmission power converted into DPDCH required transmission power.

In contrast, according to the forward frame transmission method according to an embodiment of the present invention, the transmission power over the transmission slot time period directly proportional to the interference power received by a mobile station located in an adjacent cell is expressed by Equation 4 below. .

Where <Equation 4> Denotes the magnitude of DPDCH transmit power according to an embodiment of the present invention during a fixed DPCCH time period. Is the DPCCH required transmission power converted into DPDCH required transmission power.

In contrast to the above Equations 3 and 4, the forward frame transmission method according to an embodiment of the present invention uses a forward frame structure of a plurality of transmission slot units, such as asynchronous, such as a UMTS mobile communication system. In this case, it can be seen that the reception interference power of mobile stations located in other cells can be reduced by about 50%.

5 is a flowchart illustrating a method of transmitting a forward frame by a base station in a CDMA mobile communication system according to an embodiment of the present invention. Hereinafter, a description will be given with reference to FIGS. 1 to 4.

In step 510, the base station checks whether a call has occurred. When the call is generated, the base station checks whether the current DPCCH variable positions in the transmission slot are used in step 520. In this case, the inspection operation may be determined as a variable position that does not use the transmission position of the corresponding DPCCH. The check operation may determine that the transmission position of the corresponding DPCCH is the least redundantly allocated DPCCH variable position in order to minimize the interference power if all transmittable DPCCH variable positions are used in the transmission slot.

In step 530, the base station transmits the DPCCH transmission position in the transmission slot determined in step 520 to the mobile station. In this case, the transmission operation may be performed through a common control channel or a dedicated control channel.

In step 540, the base station transmits the corresponding transmission slot to the corresponding mobile station according to the DPCCH transmission location determined in step 520.

6 is a flowchart illustrating a method of receiving a forward frame by a mobile station in a CDMA mobile communication system according to an embodiment of the present invention. Hereinafter, a description will be given with reference to FIGS. 1 to 5.

In step 610, the mobile station checks whether a call has occurred. When the call is generated, the mobile station receives transmission location information of the DPCCH from the base station in the serving cell in step 620. In this case, the receiving operation may be performed through a common control channel or a dedicated control channel. In step 630, the mobile station receives the corresponding transmission slot according to the transmission position of the DPCCH received in step 620.

1 to 6, in the CDMA mobile communication system according to the embodiment of the present invention, in the forward frame transmission method, the base station transmits the transmission position of the DPCCH in the transmission slot in accordance with the position usage state for the mobile stations. . As a result, the transmission power of the DPCCH for each mobile station in the serving cell is distributed in the transmission slot, thereby significantly reducing the interference power on the received signal of the mobile station of the neighboring cell. In this case, the number of variable positions of the DPCCH in the transmission slot may be represented by a maximum integer not exceeding the result of dividing the time interval of the transmission slot by the DPCCH time interval. Also, the base station may check whether the current DPCCH variable positions in the transmission slot are used, and transmit the determined DPCCH transmission position to the corresponding mobile station through the common control channel or the dedicated control channel.

Meanwhile, in the detailed description of the present invention, an asynchronous UMTS forward transmission frame has been described as an example of a forward transmission frame composed of a plurality of transmission slot units in a code division multiple access mobile communication system. Of course, many modifications are possible without departing from the scope of the invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, according to the present invention, in a forward frame transmission in units of a plurality of transmission slots, a service cell is transmitted by varying a transmission position of a group of control information bits that are not channel coded according to a usage state of mobile stations in the transmission slot. The transmission power of the control information bit group for each mobile station in the apparatus is distributed in the corresponding transmission slot. Therefore, the present invention has the advantage of significantly reducing the interference power on the received signal of the mobile station of the adjacent cell.

Claims (14)

In the forward frame transmission method consisting of a plurality of transmission slot units in a code division multiple access mobile communication system, A first step of checking whether a variable position of a current control information bit group is used in a corresponding transmission slot and determining a transmission position of the corresponding control information bit group when a call is generated; Transmitting a transmission position of the control information bit group in the determined transmission slot to a call originating mobile station; And transmitting the corresponding transmission slot according to the determined transmission position of the control information bit group. The method of claim 1, wherein the control information bit group, A forward frame transmission method characterized in that no channel coding is performed. The variable position number of the control information bit group in the transmission slot, And a maximum integer not exceeding a result obtained by dividing the transmission slot time period by the time period of the control information bit group. The method of claim 3, wherein the determination of the transmission position of the control information bit group in the first step, And a variable position which is not used as a transmission position of the current control information bit group among the variable positions in the corresponding transmission slot. The method of claim 4, wherein the transmission position determination of the corresponding control information bit group of the first step, And if the variable positions of all the transmittable control information bit groups are in use in the corresponding transmission slot, a variable position allocated less frequently among the transmittable variable positions. The method of claim 5, wherein the second step of the transmission operation, A forward frame transmission method comprising a common control channel and a dedicated control channel. The mobile terminal of claim 6, wherein the call originating mobile station comprises: Receiving transmission position information of a control information bit group in a corresponding transmission slot from a base station in a serving cell, and receiving the corresponding transmission slot according to the received transmission position information. In the forward frame transmission method of the asynchronous and composed of a plurality of transmission slot units in a synchronous code division multiple access mobile communication system, A first step of checking whether a variable position of a current control information bit group is used in a corresponding transmission slot and determining a transmission position of the corresponding control information bit group when a call is generated; Transmitting a transmission position of the control information bit group in the determined transmission slot to a call originating mobile station; And transmitting the corresponding transmission slot according to the determined transmission position of the control information bit group. The method of claim 8, wherein the control information bit group, A forward frame transmission method characterized in that no channel coding is performed. 10. The method of claim 9, wherein the number of variable positions of the control information bit group in the transmission slot is And a maximum integer not exceeding a result obtained by dividing the transmission slot time period by the time period of the control information bit group. 11. The method of claim 10, wherein the transmission position determination of the corresponding control information bit group of the first step, And a variable position which is not used as a transmission position of the current control information bit group among the variable positions in the corresponding transmission slot. 12. The method of claim 11, wherein the determination of the transmission position of the corresponding control information bit group in the first step comprises: And if the variable positions of all the transmittable control information bit groups are in use in the corresponding transmission slot, a variable position allocated less frequently among the transmittable variable positions. The method of claim 12, wherein the second step of the transmission operation, A forward frame transmission method comprising a common control channel and a dedicated control channel. The method of claim 13, wherein the call originating mobile station, Receiving transmission position information of a control information bit group in a corresponding transmission slot from a base station in a serving cell, and receiving the corresponding transmission slot according to the received transmission position information.