KR20050006641A - Apparatus and Method for Transmitting and Receiving Rate Control Bit in a Mobile Communication System - Google Patents

Abstract

PURPOSE: An apparatus and a method for transmitting/receiving an RCB(Rate Control Bit) in a mobile communication system are provided to reduce power of a base station required for the transmission of an reverse-RCB to increase a forward throughput. CONSTITUTION: An RCB generator(201) generates an RCB for controlling a data rate in transmitting reverse packet data of a mobile terminal. A spreading unit(202) spreads the RCB to output it through a radio channel. A transmission power controller(203) outputs a control signal demanding that the RCB should not be transmitted, when information that the data rate cannot be increased any higher is received from the mobile terminal.

Description

Apparatus and Method for Transmitting and Receiving Rate Control Bit in a Mobile Communication System}

The present invention relates to an apparatus and a method for transmitting and receiving a rate control bit in a mobile communication system, and more particularly, to an apparatus and a method for transmitting and receiving a rate control bit in a mobile communication system for efficiently transmitting and receiving a rate control bit.

In general, mobile communication systems use finite resources to achieve maximum efficiency. In the mobile communication system, transmission may be classified into forward transmission and reverse transmission. Here, forward transmission means transmission from the base station to the mobile terminal, and reverse transmission means transmission from the mobile terminal to the base station.

Among the limited resources in the forward transmission is the power of the base station. The larger the power of the base station, the greater the amount of interference on the neighboring base station, so it should be limited to an appropriate value. However, there is a limit to the data rate that can be obtained with base station power. Therefore, the forward direction of the mobile communication system should be designed to overcome the above limitations.

On the other hand, there is interference among the limiting factors of reverse resources. This is because signals for mobile terminals transmitting in the reverse direction cause interference with one base station. When a plurality of mobile terminals exist in one base station, one mobile terminal transmits using high power to obtain a high data rate. A high power signal will then be received from the mobile terminal at the base station in communication with the mobile terminal. In addition, the high power generates a large amount of interference in signals of other mobile terminals. If a plurality of mobile terminals attempt to transmit data at a high data rate at the same time, the total amount of reverse interference becomes very large, and thus the probability of successfully receiving the signals of all mobile terminals decreases. Therefore, in order to maximize the throughput of the mobile communication system, the base station efficiently adjusts the total reverse interference amount. In addition, the base station must efficiently manage the data rate of the various mobile terminals.

FIG. 1 is a diagram for explaining why a base station should efficiently adjust reverse transmission of various mobile terminals as described above. A portion indicated by a dotted line in FIG. 1 represents a target system load or a target rise over thermal (RoT) of a base station. RoT is a measure of the total reverse interference amount, and means the sum of the total noise received by the base station versus the thermal noise power.

Here, the reason why the base station should manage the target system load or target RoT is as follows. In general, mobile communication systems support power control to guarantee the quality of a reverse or forward link. If the base station does not manage the sum of the load of the reverse system or the total reverse signal received at a specific value or less and the value becomes very large, the amount of mutual interference increases. Therefore, the signal to noise power ratio (SNR) for the signals of all mobile terminals is reduced. In this case, in order to maintain communication quality of each link, various mobile terminals continue to increase power. In this way, a vicious cycle causing an increase in the amount of interference is repeated, making communication impossible. As an example of data rate, when one mobile terminal uses high power to obtain a high data rate, the amount of reverse interference is greatly increased due to the mobile terminal, and other mobile terminals maintain their link quality. To increase the power. This in turn increases the overall reverse amount of interference, thereby causing a vicious cycle. Therefore, in order to prevent such a vicious cycle, the base station efficiently controls the data rates of all mobile terminals so that the reverse load does not exceed the target system load. In addition, the base station efficiently controls the data rates of all mobile terminals to maintain the sum of the total reverse received signals so as not to exceed the target RoT.

As shown in FIG. 1, the reverse transmission generating the reverse interference amount is classified into inter-cell interference, voice or circuit channel interference, packet data channel interference, and the like. do.

The intra-cell interference refers to the amount of interference caused by signals received from mobile terminals communicating with other base stations. The amount of interference in the cell changes over time. In addition, since the amount of interference in a cell is interference from mobile terminals communicating with other base stations, it is not a value that can be controlled by a reference base station and is not a value that can be accurately predicted.

The voice or circuit channel interference refers to interference generated from a voice channel or another circuit-based channel. Since the voice or circuit channel is a channel allocated by the base station, the base station can estimate an approximate amount of interference. In general, voice or circuit channels have priority over packet data channels.

The packet data channel interference refers to the amount of interference generated from the packet data channel. Typically, the base station subtracts the amount of intra-cell interference and voice or circuit channel interference from the base station total target system load or target RoT, and then allocates the remaining amount to the packet data channel. At this time, the base station adjusts the amount of interference generated from the packet data channel to subtract the amount of intra-cell interference and voice or line channel interference from the total target system load or target RoT, and then allocates the remaining amount to the packet data channel. In this case, the base station should control the amount of interference generated from the packet data channel to control the total target system load or target RoT so as not to exceed the total target system load or target RoT.

The base station adjusts the total amount of reverse interference by controlling the data rate of packet data transmission of the reverse mobile stations, that is, reverse packet data transmission of the mobile terminals, based on the target system load or the target RoT.

In a typical mobile communication system, a base station controls a rate through a forward rate control channel (F-RCCH) (hereinafter referred to as a "rate rate control channel") in order to control the data rate of reverse packet data transmission of mobile stations. Transmit bit (Rate Control Bit: RCB). The rate control bit has a value of +1 or -1, and when the rate control bit value is "+1", the mobile station increases the data rate of the mobile terminal by one step in the next transmission interval. If the rate control bit value is "-1", the mobile terminal decreases the data rate of the mobile terminal by one step in the next transmission interval.

In general, a rate control bit transmitted by a base station to control reverse data rates of mobile terminals is transmitted for each physical layer unit (hereinafter referred to as a "frame"). That is, the base station continuously controls the transmission rate of a specific terminal through the transmission rate control bit. For example, the reverse data rate is composed of 9.6kbps, 19.2kbps, 38.4kbps, 79.8kbps, 153.8kbps and the like. Here, assume that the mobile terminal A is transmitting data at a data rate of 9.6 kbps in the i-th frame. If the base station continuously transmits the rate control bits of +1, +1, +1, -1, -1, ... to control the data rate of the terminal A, the base station transmits to the command of the rate control bits of the mobile terminal. Therefore, packet data is transmitted at data rates of 19.2kbps, 38.4kbps, 79.8kbps, 38.4kbps, and 19.2kbps from the i + 1th frame.

In the mobile communication system performing the reverse rate control as described above, the mobile terminal transmits feedback information on whether it wants to raise or lower the data rate at the data rate currently being transmitted. The feedback information is commonly referred to as increase availability bit (IAB). The IAB is typically determined from the transmission power value of the mobile terminal and the amount of packet data stored in the mobile terminal's buffer. For example, the maximum transmission power of the mobile terminal is finite, and when the channel situation of the mobile terminal is very poor, and thus, a very high transmission power is used by the power control, the mobile terminal can no longer increase the data rate. On the other hand, even if the transmission power of the mobile terminal is sufficient, the amount of packet data stored in the buffer of the mobile terminal is small, and thus it may not be necessary to increase the data rate any more. As described above, the mobile station transmits information on whether to increase or decrease the data rate at the data rate it is currently transmitting to the base station through the IAB, and the base station receives the IAB from various mobile terminals, Determine whether to increase or decrease the data rate for the mobile terminal. According to the determination, the base station determines the value of the data rate control bits of each mobile terminal and transmits the determined data rate control bits through the rate control channel.

However, if the base station transmits a rate control bit of "+1" to the mobile terminals fed back the IAB including the information that the data rate can no longer be increased, the mobile terminal may receive a command to increase the data rate. In some cases, the data rate cannot be increased in consideration of its own power situation or the data in the buffer. Therefore, when the base station transmits a rate control bit of "+1" to the mobile terminal fed back the IAB of "-1", there is a problem in wasting the base station power.

In addition, in the reverse rate control method as described above, the base station should transmit the determined data rate control bits for each frame by the number of mobile terminals to control the reverse rate. For example, when the number of mobile terminals receiving data service from a specific base station is 20, the base station should transmit 20 bit rate control bits every frame. In this case, since the base station must transmit the reverse rate control bits as many as the number of mobile terminals to control the reverse rate in each frame, the transmission power of the reverse rate control bits was wasted.

Accordingly, it is an object of the present invention to reduce base station power that must do reverse rate control bits.

Another object of the present invention is to increase the forward throughput by using it on another channel (e.g., forward packet data channel) with the base station power required to transmit the saved reverse rate control bits.

In the mobile communication system according to an embodiment of the present invention, the rate control bit transmitting apparatus is a rate control bit transmitting apparatus for transmitting a rate control bit indicating whether or not to increase or decrease the data rate of a specific mobile terminal in the mobile communication system, A rate control bit generator for generating a rate control bit for controlling a data rate of reverse packet data transmission of a mobile terminal, a spreader for spreading and outputting the rate control bit for transmission in a wireless channel, and data from the mobile terminal And a transmission power control unit for outputting a control signal so as not to transmit the transmission rate control bit when receiving the information indicating that the transmission rate can no longer be increased.

In addition, the method for transmitting a rate control bit in a mobile communication system according to an embodiment of the present invention relates to a method for transmitting a rate control bit in a rate control bit transmitting apparatus indicating whether a data rate of a specific mobile terminal is increased or decreased in a mobile communication system. The method may include generating a rate control bit for controlling a data rate of reverse packet data transmission of the mobile terminal, spreading and outputting the rate control bit for transmission on a wireless channel, and transmitting a data rate from the mobile terminal. When receiving the information that can not increase any more characterized in that it comprises the step of controlling not to transmit the rate control bit.

1 is a graph illustrating a factor causing a reverse interference amount in a general mobile communication system;

2 is a structural diagram showing a rate control bit transmitter according to an embodiment of the present invention;

3 is a structural diagram showing a rate control bit receiver according to another embodiment of the present invention;

4 is a flowchart illustrating a method of transmitting a rate control bit according to an embodiment of the present invention;

5 is a flowchart illustrating a method of receiving a rate control bit according to another embodiment of the present invention.

In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

As shown in FIG. 2, a rate control bit transmitter according to an exemplary embodiment of the present invention includes a rate control bit generator 201, a spreader 202, a transmit power controller 203, and a transmitter 204.

The rate control bit generator 201 generates and outputs a rate control bit when it is determined whether to lower or raise the data rate by a scheduler (not shown) in the rate control bit transmitter (base station). The spreader 202 receives the rate control bits and spreads them for output over a wireless channel. The transmission power control unit 203 inspects the IAB in an IAB storage unit (not shown), which stores the IAB received from a specific mobile terminal, and controls the transmission power according to the test result and outputs the IAB. That is, when the IAB received from the specific mobile terminal is " -1 ", the generated rate control bit is obtained by setting the gain of the rate control channel, which is a channel through which the rate control bit is transmitted, to " 0 " Do not send it. However, when the IAB received from a specific mobile terminal is " + 1 ", the power is controlled and output to a different power value according to the reception environment of the mobile terminal. The transmitter 204 transmits a rate control bit output from the transmit power controller 203 through a wireless channel.

As shown in FIG. 3, the rate control bit receiver according to another embodiment of the present invention includes an IAB storage unit 301, a rate control bit reception control unit 302, a switch unit 303, a despreader 304, a determiner. 305 is provided.

The IAB storage unit 301 receives and stores the IAB, which is feedback information on whether to increase or decrease the data rate from the data rate transmitted by the mobile terminal.

The rate control bit receiving controller 302 extracts the IAB value previously transmitted from the IAB storage unit 301 and determines whether to receive the rate control bit according to the extracted IAB value. In addition, the switch is controlled depending on whether the rate control bit is received. That is, when the previously transmitted IAB value is "-1", the switch is controlled so as not to receive the rate control bit from the base station. If the value of the previously transmitted IAB is "-1", the mobile terminal determines a data rate lower than the previously transmitted data rate. However, if the previously transmitted IAB value is "+1", the switch is controlled to receive a rate control bit from the base station. The switch unit 303 is turned on or off depending on whether the rate control bit is determined by the rate control bit receiving control unit 302. That is, the rate control bit reception control unit 302 switches to "ON" when it is determined to receive the rate control bits from the base station, and switches to "OFF" when it is determined not to receive the rate control bits. The despreader 304 despreads and outputs the rate control bits received through the rate control channel. The determiner 305 receives the output of the despreader 304 and determines whether the value of the transmitted rate control bit is "1" or "-1". Although not shown in FIG. 3, the mobile station determines a data rate of data to be transmitted according to a rate control bit value output from the determiner 305.

A transmission rate control bit transmission method according to an embodiment of the present invention will be described with reference to the flowchart of FIG. 4.

First, the rate control bit transmitter is in a standby state at step 401. The rate control bit determines whether it is time to transmit the rate control bit in step 402 during the standby state. If it is not the time to transmit the rate control bits, the rate control bit transmitter proceeds to step 401 to maintain a standby state. However, when it is time to transmit the rate control bits, the rate control bit transmitter performs the following operations. First, the rate control bit generator 201 proceeds to step 403 to generate a rate control bit according to the data rate determined by the scheduler (not shown). The spreader 202 spreads and outputs the spread rate control bit in step 404 to transmit the generated bit rate control bit through a wireless channel. In step 405, the transmission power control unit 203 determines whether the IAB received from the mobile terminal is "-1". If the IAB received from the mobile terminal is " -1 ", the transmit power controller 203 proceeds to step 406 in which the gain of the rate control channel, which is a channel through which a rate control bit is transmitted, is transmitted to the mobile terminal. In order to control the control, the generated rate control bit is not transmitted. However, if the IAB received from the mobile terminal is not "-1", the transmission power control unit 203 proceeds to step 407 to determine whether the IAB received from the mobile terminal is "+1". When the IAB received from the mobile terminal is "+1", the transmit power controller 203 outputs power by controlling different power values according to the reception environment of the mobile terminal in step 408. The transmitter 204 transmits a rate control bit output from the transmit power controller 203 through a wireless channel.

A method of receiving a rate control bit according to another embodiment of the present invention will be described with reference to the flowchart of FIG. 5.

The rate control bit receiver performs the following operation to receive the rate control bit. First, the IAB storage unit 301 extracts the IAB previously transmitted to the base station in step 501. In operation 502, the rate control bit reception controller 302 determines whether the IAB previously transmitted to the base station is "-1". If the previously transmitted IAB is "-1", the rate control bit receiving control unit 302 proceeds to step 503 and outputs a control signal for setting the switch unit 303 to "OFF". By setting the switch to " OFF " as described above, the rate control bit cannot be received from the base station. Thereafter, the mobile terminal proceeds to step 504 to reduce the rate control bit to determine a data rate reduced from the previously transmitted data rate, and to transmit packet data at the determined data rate . However, if the previously transmitted IAB is not "-1", the rate control bit receiving control unit 302 proceeds to step 505 and outputs a control signal for setting the switch unit 303 to "ON". By setting the switch to "ON" as described above, it is possible to receive the rate control bits from the base station. Thus, the previously transmitted IAB determines whether or not to receive the rate control bits from the base station.

After operation 505, the despreader 304 proceeds to operation 506 to despread and output the rate control bits received through the rate control channel. Thereafter, the determiner 305 determines whether the rate control bit received in step 507 is "+1". If the received rate control bit is "+1", the determiner 305 proceeds to step 508 to increase the data rate in the next transmission interval. However, if the received rate control bit is not "+1", the determiner 305 determines whether the received rate control bit is "-1" in step 509. If the received rate control bit is "-1", the determiner 305 reduces the data rate in the next transmission section in step 510.

Accordingly, the rate control bit receiver (mobile terminal) determines whether to receive the rate control bit received from the base station according to the previously transmitted IAB value.

The present invention can conserve resources of the base station by controlling the base station not to transmit the reverse rate control bit every frame and not to transmit the rate control bit in certain circumstances.

Claims (12)

An apparatus for transmitting a rate control bit for transmitting a rate control bit indicating whether a data rate of a specific mobile terminal is increased or decreased in a mobile communication system, A rate control bit generator for generating a rate control bit for controlling a data rate of reverse packet data transmission of the mobile terminal; A spreader configured to spread and output the rate control bits for transmission on a wireless channel; And a transmission power control unit for outputting a control signal so as not to transmit the transmission rate control bit when receiving the information indicating that the data transmission rate can no longer be increased from the mobile terminal. Device. The method of claim 1, And receiving the information indicating that the data rate can no longer be increased from the mobile terminal, setting a gain of a rate control channel through which a rate control bit is transmitted to the mobile terminal as "0". Apparatus for transmitting rate control bits in a mobile communication system. An apparatus for receiving a rate control bit for receiving a rate control bit including increase / decrease information of a data rate in a mobile communication system, An IAB storage unit for storing the IAB transmitted to the base station, A rate control bit reception control unit for inspecting a previously transmitted IAB in the IAB storage unit and outputting a control signal for determining whether to receive a rate control bit according to the previously transmitted IAB value; And a switch unit for turning on or off according to a control signal output from the rate control bit receiving control unit. The method of claim 3, wherein The rate control bit receiving control unit outputs a control signal for setting the switch to "OFF" when the previously transmitted IAB is "-1", so that the mobile station does not receive the rate control bit from the base station. Device for receiving rate control bits in the system. The method of claim 3, wherein The rate control bit receiving control unit outputs a control signal for setting the switch to "ON" when the previously transmitted IAB is "+1", and receives the rate control bit from the base station. Device for receiving rate control bits. A method of transmitting a rate control bit in a rate control bit transmitting apparatus indicating whether a data rate of a specific mobile terminal is increased or decreased in a mobile communication system, Generating a rate control bit for controlling a data rate of reverse packet data transmission of the mobile terminal; Spreading and outputting the rate control bits for transmission over a wireless channel; And controlling the transmission rate control bit not to be transmitted when receiving information indicating that the data rate can no longer be increased from the mobile terminal. The method of claim 6, If the mobile station receives information indicating that the data rate can no longer be increased, the method further includes setting a gain of a rate control channel through which a rate control bit is transmitted to the mobile station to "0". A method of transmitting rate control bits in a mobile communication system. A method of receiving a rate control bit in a rate control bit receiving apparatus for receiving a rate control bit including increase / decrease information of a data rate in a mobile communication system, Checking the IAB previously sent to the base station, Determining whether to receive a rate control bit according to the IAB value previously transmitted to the base station; And turning on or off a switch according to whether the determined rate control bit is received. The method of claim 8, Outputting a control signal for setting the switch to "OFF" when the IAB previously transmitted to the base station is "-1"; And receiving the rate control bits from the base station according to the control signal. The method of claim 8, Outputting a control signal for setting the switch to “ON” when the IAB previously transmitted to the base station is “+1”; Receiving a rate control bit from a base station according to the control signal; Despreading and outputting the received rate control bits; Determining the despread rate control bits; The method of claim 1, further comprising increasing / decreasing the data rate according to the determination result. A method of transmitting a rate control bit in a rate control bit transmitting apparatus indicating whether a data rate of a specific mobile terminal is increased or decreased in a mobile communication system, Generating a rate control bit for controlling a data rate of reverse packet data transmission of the mobile terminal; And determining whether to transmit the generated rate control bit from the information received from the mobile terminal. A method of receiving a rate control bit in a rate control bit receiving apparatus for receiving a rate control bit including increase / decrease information of a data rate in a mobile communication system, Checking the IAB previously sent to the base station, And determining whether to receive a rate control bit according to the IAB value previously transmitted to the base station.