KR100583584B1 - Transmission speed control device and method for reverse traffic channel in high speed wireless communication system - Google Patents

Abstract

The present invention relates to a reverse traffic channel of a specific terminal by transmission rate control information transmitted by a plurality of base stations connected to a specific terminal in a high-speed wireless communication system having a plurality of base stations and a plurality of terminals connected to each base station. An apparatus for controlling a transmission rate, wherein the specific terminal receives reverse activity bit (RAB) information provided by the plurality of connected base stations from a plurality of reverse activity (RA) channels respectively corresponding to the plurality of connected base stations. A receiving RA channel processor, a CRAB reader for reading a combined reverse activity bit (CRAB) based on each RAB information provided from the RA channel processor, a random number generator for generating a random value, and a transmission according to a current transmission rate ERI generation that generates Extended Rate Indicator (ERI) information by comparing the rate of increase or decrease rate with the random number of the random number generator A ERI storage device for storing an ERI value generated by the ERI generator, a CRAB provided from the CRAB reader, data provided from a predetermined upper layer, a random number value provided from the random number generator, and the ERI storage device. A rate controller for controlling a transmission rate using the stored ERI value used for transmitting previous packets, an ERI channel processor for transmitting ERI information provided from the ERI generator to a plurality of connected base stations through a preset ERI channel; And an RRI channel processor for transmitting reverse rate indicator (RRI) information provided from the transmission rate controller to the plurality of connected base stations through a predetermined RRI channel, and preset data for which transmission rate is determined by the transmission rate controller. Data channel processing for transmitting to the connected multiple base stations via a data channel It consists of.

Description

Apparatus and method for controlling transmission rate of reverse traffic channel in high speed wireless communication system {APPARATUS AND METHOD FOR RATE CONTROL SCHEME OF REVERSE TRAFFIC CHANNELS IN HIGH-SPEED WIRELESS COMMUNICATION SYSTEMS}             

1 is a diagram illustrating a forward channel structure and a reverse channel structure of a 1xEV-DO system;

2 is a schematic diagram illustrating transmission rate control for a reverse traffic channel of a 1xEV-DO system;

3 is a block diagram showing an internal structure of a terminal according to a conventional technique for controlling a transmission rate in a terminal;

4 is a flowchart illustrating a conventional transmission rate control method in a cellular environment step by step;

5 is a view showing an example in which the transmission rate is controlled according to the prior art;

6 is a block diagram showing the internal structure of a terminal device according to the present invention;

7 is a flowchart illustrating a method for controlling a transmission rate of a reverse traffic channel of a terminal according to the present invention;

8 and 9 are diagrams for comparing the performance of the present invention with the performance of the present invention while increasing the number of terminals in the cell.

The present invention relates to an apparatus and method for controlling a transmission speed of reverse traffic channels in a high speed wireless communication system. In particular, the present invention efficiently prevents overload of a reverse link in a high speed wireless communication system. An apparatus and method are provided for maintaining an appropriate level of system performance.

The 1xEV-DO system is one of the third generation mobile communication standards approved in October 2000 through the North American Standardization Organization called the third Generation Project Partnership 2 (3GPP2), formerly called High Data Rate (HDR). . The name 1xEV-DO itself makes it easy to see the characteristics of the system. First, '1x' indicates the frequency bandwidth of 1.25 MHz of the IS-95, which is a conventional narrowband code division multiple access (CDMA) system. In some cases, the term '1x' may mean the existing narrowband CDMA technology itself. Next, 'EV' stands for 'Evolution'. That is, it means that the system is evolved based on the 1x system, and it can be thought of as a system having a characteristic of evolving from the second generation mobile communication system to the third generation mobile communication system. Finally, 'DO' stands for 'Data Only'. In other words, unlike the existing second generation mobile communication system, it is a system for supporting only packet data communication services such as Internet service. Thus, the system uses various techniques for the transmission of packet data, but the transmission quality of real-time services such as voice is not guaranteed. In order to support real-time services and non-real-time services in the same frequency band, a standard specification called 1xEV-DV is under development. In this case, DV stands for 'Data & Voice'.

Efforts to improve the performance of the conventional second generation mobile communication system has been actively made in various equipment companies around the world since early 2000. During this time, 3GPP2 was actively debating to determine a single standard through performance evaluation between Qualcomm's HDR system and Motorola's '1xTreme system'. Later, no agreement was reached on a single standard, which led to the development of a standard for packet data services based on the most advanced HDR system at the time, the current 1xEV-DO system. The system has undergone a continuous renewal process and is approved as an official standard in October 2000. It is named C.S0024 in 3GPP2 and IS-856 in the TIA / EIA (Telecommunications Industry Association / Electronic Industries Alliance).

The 1xEV-DO focused on the performance improvement of the forward link in consideration of the generation characteristics of the Internet traffic. Therefore, the transmission speed of the forward link is higher than that of the reverse link. It can support up to 2.4Mbps on the forward link and 153.6kbps on the reverse link. In particular, the 1xEV-DO system uses a different frequency band than the existing IS-95 system. However, since some of the frequency bands allocated for the IS-95 system can be used, the same antenna system can be used. As a result, terminal and system manufacturers can rely on the same Radio Frequency (RF) components as the IS-95 to provide inexpensive IS-95 and 1xEV-DO terminals operating in dual mode. Typical technologies adopted in 1xEV-DO include adaptive modulation and coding, hybrid automatic repeat request, fast channel feedback information, and multi-user detection. detection).

The basic unit of data transmission on the forward and reverse links is called a slot, and each slot has a length of 1.666 ms. In addition, a unit consisting of 16 slots is called a frame, and may also refer to a packet itself transmitted during one frame period.

1 is a diagram illustrating a forward channel structure and a reverse channel structure of a 1xEV-DO system. The forward channel is a channel shared by all terminals in a cell, and the reverse channel may be used exclusively by each terminal.

In the figure, the forward channel is composed of a pilot channel, a medium access control (MAC) channel, a control channel, and a traffic channel. At this time, the MAC channel is composed of a reverse activity (RA) channel and a reverse power control (RPC) channel. These channels are time division multiplexed and transmitted to the terminals. The pilot channel is used for system acquisition, channel estimation, channel prediction, and the like. The RPC channel transmits 1-bit information that regulates the transmit power of the reverse traffic channel at 600 cycles per second. The RA channel transmits a reverse activity bit (RAB), which is 1 bit information that informs the terminal of the traffic load of the reverse link, to the terminal. The terminal may adjust the transmission rate according to the RAB information. The control channel basically includes a control message and a signaling message, and may transmit user traffic in some cases. The traffic channel carries user traffic and provides a variable data rate between 38.4kbps-2.4576Mbps. In particular, since the traffic channel is based on a time multiplexing scheme, data can be transmitted to only one terminal in a specific transmission period.

For reference, in 1xEV-DO, each terminal manages an active set, which includes base stations with good reception of the forward channel. When the received signal strength of the forward link exceeds the threshold, the terminal includes the base station in the active set, and when the base station received signal in the active set is lower than the threshold, the terminal removes it from the active set. In addition, the UE can select the base station having the best signal reception state within the active set and receive the data. This method reduces interference between cells in comparison with the soft hand-over method. In other words, the terminal receives data from only one base station in the active set when receiving data.

The reverse channel is composed of an access channel and a traffic channel. The access channel is used by the terminal for initiating communication with the base station or in response to a message sent to the terminal. The access channel is composed of a pilot channel and a data channel. The traffic channel is a channel used after the communication connection is established between the terminal and the base station. The traffic channel includes a pilot channel, a MAC channel, an acknowledgment (ACK) channel, and a data channel. The pilot channel is used for reverse channel estimation and coherent detection. The MAC channel consists of a Data Rate Control (DRC) channel and a Reverse Rate Indicator (RRI) channel. The terminal may indicate the base station having the best reception signal of the forward link using the DRC channel, and at the same time, transmits the data transmission rate of the forward link to the base station in consideration of the state of the forward channel to the base station. The RRI channel informs the base station of the transmission rate of the data channel being transmitted together. The RRI channel transmits information consisting of three bits, which are repeated 37 times in each frame. The reason for repeatedly transmitting the RRI information is because the RRI information is very important when decoding the reverse data at the base station. The ACK channel informs the base station whether the data received on the forward link is successful. Finally, the data channel supports five data rates between 9.6kbps and 153.6kbps. The UE determines the transmission rate of the reverse traffic channel based on the RAB information of the forward link and the unique probability model of 1xEV-DO.

Pilot, MAC, ACK, and data channels constituting the reverse traffic channel are transmitted by code division using a code having orthogonality. Exceptionally, the RRI channel belonging to the MAC channel is transmitted in time multiplexed with the pilot channel. In the case of the data channel, all five transmission rates have the same spreading factor. Therefore, in order to guarantee a high transmission rate, the higher the transmission rate is used, the higher power should be transmitted (which is the transmission characteristic of CDMA). For this reason, the 1xEV-DO standard proposes a transmission power gain compared to a pilot channel for each transmission rate.

Type R (i) of transmission rate used in reverse data channel and transmit power gain compared to pilot channel at each transmission rate are shown in Table 1. The transmit power of the DRC channel and the ACK channel is also set based on the pilot channel. Typically, the DRC channel transmits at -1.5dB gain relative to the pilot channel power, and the ACK channel transmits at 4.0dB gain. Since the RRI channel is transmitted multiplexed with the pilot channel, the transmit power is the same as that of the pilot channel.

symbol Baud rate [kbps] Transmit Power Gain over Pilot Channel R (1) 9.6 3.75 R (2) 19.2 6.75 R (3) 38.4 9.75 R (4) 76.8 13.25 R (5) 153.6 18.50

In the reverse traffic channel, the transmission power of the pilot channel, which is the transmission power reference of other channels, follows a power control scheme similar to that of the IS-95. That is, to compensate for the effects of fading experienced by the wireless channel, the transmission power is increased or decreased in units of 1 dB (or 0.5 dB) by RPC information, which is 1-bit information transmitted by one of the forward channels, the RPC channel. (600 times per second). The RPC information may be set based on a frame error rate of the corresponding UE or a signal to noise ratio (SNR) of the pilot channel.

Each terminal adjusts the transmission rate using the RAB information transmitted by the base station and a unique probability model of 1xEV-DO.

2 is a schematic diagram illustrating transmission rate control for a reverse traffic channel of a 1xEV-DO system. The RAB information transmitted by a base station informs the load of reverse link traffic, and the terminal receiving the information uses a probability model. It is possible to increase or decrease the transmission rate or to maintain the same transmission rate as before. In a single cell environment in which one base station controls several terminals, a specific transmission rate control method is as follows.

First, RAB information indicating the traffic load of reverse traffic is composed of 1-bit information. The base station may set the RAB information to 1 or 0 based on its own determination criteria. In general, if the reverse traffic load exceeds a certain threshold Lth, RAB is set to 1, and if it is lower than Lth, RAB is set to 0. Traffic load can also be used by the base station its own criteria. The sum of the reverse rate, the base station total receive power over noise, and the average data error rate during a specific period are used as the basis for the reverse traffic load. For example, if the total reverse rate is set as the traffic load, and Lth is 450 kbps, the base station transmits the RAB to 1 when the total reverse rate exceeds 450 kbps, and sets it to 0 otherwise. . The RAB information is periodically transmitted to all terminals in the cell using one of 8/16/32/64 slots.

The terminal may select a new transmission rate each time a new packet is transmitted. The new baud rate can be selected one step lower or one step higher based on the current one. In some cases, the same baud rate may be used. In addition to the RAB value, important parameters used in the transmission rate adjustment are p (i) and q (i), which are rate control probabilities stored in the terminal. These transmission rate control probabilities p (i) and q (i) are values that the base station informs the terminal, and their values differ depending on the current transmission rate R (i). The transmission rate control probability p (i) is used when the RAB value is '0', and the transmission rate control probability q (i) is used when the RAB value is '1'. To distinguish between these two types of control probabilities, p (i) is called a transmission rate increase probability and q (i) is called a transmission rate decrease probability.

Before transmitting a new packet, the UE uses the most recently received RAB value. If the value of the RAB is 0, the terminal interprets that there is a margin in the load of reverse traffic and determines whether to increase or not increase the transmission speed. That is, the terminal generates a random number between 0 and 1, and if the random number is less than the transmission rate increase probability p (i), increases the transmission rate by one step, otherwise maintains the current transmission rate. In a similar manner, if the RAB value is 1, the terminal determines whether or not to reduce the transmission speed in order to lower the reverse traffic load. In this case, the terminal generates a random number between 0 and 1, and if the value is less than q (i), the transmission rate is reduced by one step. Otherwise, the terminal maintains the current transmission rate.

The transmission rate control method in a cellular environment in which several cells exist is almost the same as the single cell environment described above. The only difference is that in the cellular environment, the terminal may receive different RAB values from several base stations in the active set. For example, suppose that three base stations are included in the active set of the terminal, and the RAB of the base stations 1 and 2 is 0, and the RAB of the base station 3 is 1 is received. If the terminal increases the transmission rate, the reverse traffic load in the region managed by the base station 3 may well exceed the threshold. In order to prevent such a situation, the terminal can increase the data transmission rate only when all RAB values sent by the base stations in the active set are set to zero. To this end, the terminal maintains a value called CRAB, which is set to 0 only when the RAB value sent from all base stations in the active set is 0, and the CRAB value is 1 when the RAB value is 1 in at least one base station. Set it. Therefore, in the cellular environment, the terminal adjusts the transmission rate according to the CRAB value considering all base stations in the active set, not the RAB value of a specific base station.

3 is a block diagram illustrating an internal structure of a terminal according to a related art for controlling a transmission speed in a terminal, and includes a receiver for receiving data through a forward link and a transmitter for transmitting data through a reverse link. In this case, the solid line arrow indicates the transfer direction of data information, and the broken line arrow indicates the transfer direction of control information.

In the figure, the physical layer 10 of the terminal performs various signal processing functions directly related to the transmission and reception of data through a wireless section. This process may include various functions such as data coding, modulation, signal processing, power control, and RF configuration. Data transmitted through the data channel is controlled by the transmission rate controller and transmitted to the base station. The rate controller receives a plurality of RAB information and random values to determine the rate. The RAB information is received through respective RA channels transmitted by several base stations at the receiver, and is read as 0 or 1 by the CRAB reader and transmitted to the transmission speed controller. In addition, the random number value transmitted to the rate controller is generated in the range between 0 and 1 in the random number generator, and used to determine the final data rate through a process of comparing with the probability of increasing or decreasing the rate. The rate controller transmits RRI information, that is, data rate information, to the base station through an RRI channel that is distinct from the data channel.

FIG. 4 is a flowchart illustrating a conventional transmission rate control method in a cellular environment, and illustrates a transmission rate determination method that is processed in a "transmission rate controller" of a terminal.

First, when the terminal transmits a packet for the first time, the terminal starts transmission using the transmission rate of R (1). The transmission rate of R (1) is also used when all packets are transmitted and then another packet starts to be transmitted. For reference, although the maximum transmission rate that the terminal can transmit is 153.6kbps, the base station may individually indicate the limit value of the transmission rate to the terminal.

In the conventional transmission rate control, the performance depends largely on the RAB value transmitted by the base station, the probability of increasing the rate, and the probability of decreasing the rate. FIG. 5 is a diagram illustrating an example in which a transmission rate is controlled according to a conventional technique, and the total reverse transmission rate is set as a reverse traffic load, and the base station sets RAB to 1 when the total reverse transmission rate exceeds 350 kbps. Otherwise set RAB to 0 (ie Lth = 350 kbps). In this example, the transmission rate increase probability and the decrease probability used by each terminal are shown in Table 2.

i One 2 3 4 5 R (i) 9.6 kbps 19.2 kbps 38.4 kbps 76.8 kbps 153.6 kbps p (i) 0.40 0.20 0.10 0.05 0 q (i) 0 0.1 0.3 0.6 0.9

As can be seen in Figure 5, the conventional rate control method operates so that the traffic load falls below the threshold when the traffic load exceeds the threshold of 350 kbps, and vice versa, resulting in an increase in the traffic load. This allows traffic loads to be maintained around 350 kbps.

Due to the inherent technical problem, the performance of CDMA system is determined by the influence of mutual interference. Since 1xEV-DO system is also based on CDMA technology, its performance is greatly influenced by the load of reverse traffic. In other words, if the load of reverse traffic exceeds a certain limit, the overall performance of the system is significantly reduced. In this case, the limit value is expressed as Lmax, and when the reverse traffic load exceeds Lmax, it is called an overload condition. Accordingly, in order to support normal reverse link performance, the 1xEV-DO system should maintain reverse traffic load lower than Lmax to prevent an overload state. However, in the conventional method, as shown in FIG. 5, the traffic vibrates based on Lth, and the amplitude of the vibration is highly dependent on parameters such as transmission rate increase probability and decrease probability. In addition, since the conventional method is based on a probabilistic model, it is not easy to always keep the traffic load below Lmax. For example, in FIG. 5, if Lmax is 400 kbps, it can be seen that the controlled reverse traffic load frequently exceeds the Lmax value. As a method of reducing the frequency of such an overload condition, there may be a method of widening the gap between Lth and Lmax by setting Lth low. However, if the value of Lth is set low, most of the reverse traffic oscillates around Lth, thereby reducing the overall performance of the 1xEV-DO reverse link. For this reason, the conventional reverse transmission rate control method is not provided with a device that can prevent the unstable operating characteristics and overload, there is a possibility that the performance of the system may be degraded.

The present invention has been made in view of the above-described drawbacks of the prior art. In a high-speed wireless communication system, terminals transmit simple operation information to a base station so that the base station can predict the next reverse traffic load, and the base station predicts the estimated next traffic. Based on the amount of load, control information that can control the transmission speed of the terminal before the reverse channel reaches an overload condition is transmitted to the terminal, thereby significantly reducing the overload probability of the reverse link and maintaining an appropriate level of reverse link performance. An object of the present invention is to provide an apparatus and method for controlling a transmission rate of a reverse traffic channel.

In order to achieve the above object, an apparatus of the present invention is a device for controlling a transmission rate of a reverse traffic channel transmitted by a plurality of terminals to a plurality of base stations in a high-speed wireless communication system,
The terminal comprises: ERI setting means for setting an Extended Rate Indicator (ERI) value indicating whether to increase the current transmission rate by one step at the next transmission rate of the terminal;
Transmitting means for transmitting the RRI information indicating the current transmission rate of the terminal and the ERI values to the plurality of base stations;
RAB receiving means for receiving a reverse activity bit (RAB) value indicating whether to increase the transmission rate according to the next traffic load information from the plurality of base stations;
And a transmission rate determining means for finally determining a next transmission rate using the RAB values received from the plurality of base stations and the ERI values.
In addition, the method of the present invention, in a method for controlling the transmission rate of a reverse traffic channel transmitted by a plurality of terminals to a plurality of base stations in a high-speed wireless communication system,
An ERI setting step of setting an extended rate indicator (ERI) value indicating whether the terminal increases the current transmission rate by one step at the next transmission rate of the terminal;
Transmitting, by the terminal, the RRI information indicating the current transmission rate of the terminal and the ERI values to the plurality of base stations;
A RAB receiving step of receiving, by the terminal, a RAB (Reverse Activity Bit) value indicating whether to accept the increase in transmission rate according to the next traffic load information from the plurality of base stations;
And a transmission rate determining step of finally determining a next transmission rate by using the RAB values received from the base stations and the ERI values.

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

First, in a high-speed wireless communication system of a cellular environment composed of a plurality of base stations and a plurality of terminals, each terminal transmits simple operation information to the base station, so that the base station can easily predict the next reverse traffic load. This operation information is 1-bit information indicating whether to increase or maintain the transmission rate higher than the current value when the terminal transmits the next packet. In the present invention, this information will be referred to as Extended Rate Indicator (ERI) information. For example, ERI = 1 means that the transmission rate will be increased. ERI = 0 means that the transmission rate will be maintained. However, the next transmission speed of the terminal is not determined through the ERI information. The terminal may increase the transmission rate only when receiving the approval of the base station. Otherwise, the terminal does not increase the transmission rate. A specific method of adjusting the transmission speed of the terminal will be described later.

The base station may combine the ERI information and the RRI information to predict the transmission rate that the corresponding terminal will use to transmit the next packet. For example, if the current transmission rate is 19.2kbps and ERI = 1 by the RRI value, the base station may know that the transmission rate used when the UE transmits the next packet is 38.4 kbps. The ERI information may be transmitted by being temporally multiplexed with the RRI channel or by adding a new reverse channel. This channel is called the "ERI channel".

6 is a block diagram showing the internal structure of a terminal apparatus according to the present invention, and comprises a receiving unit 20 and a transmitting unit 30. The receiver 20 is composed of an RA channel processor 22 and a CRAB reader 24, the transmitter 30 is a random number generator 32, ERI generator 34, ERI storage device 36, a transmission rate controller (38), data channel processor 40, RRI channel processor 42, and ERI channel processor 44. In this case, the solid line arrow indicates the transfer direction of data information, and the broken line arrow indicates the transfer direction of control information. The RA channel processor 22, the data channel processor 40, the RRI channel processor 42, and the ERI channel processor 44 correspond to the physical layer 50.

In the figure, the RA channel processor 22 in the receiver 20 receives each RAB information from a plurality of RA channels corresponding to a plurality of base stations and provides them to the CRAB reader 24. The RA channel transmits RAB, which is 1 bit information that informs the terminal of the traffic load of the reverse link, to the terminal. CRAB is 0 only when all base stations in the active set transmit RAB = 0. Otherwise, the CRAB value is 1.

The CRAB reader 24 receives each RAB information from the RA channel processor 22, reads the CRAB, and transfers the read CRAB to the transmission speed controller 38 in the transmitter 30.

Random number generator 32 generates a random value between 0 and 1.

The ERI generator 34 generates ERI information by comparing the random number value of the random number generator 32 with the rate of increase probability p (i) defined at the current rate. The ERI generator 34 sets the ERI value to 1 when the random number generated by the random number generator 32 is smaller than the transmission rate increase probability p (i), and sets the ERI value to 0 otherwise.

The ERI storage 36 stores the ERI values generated by the ERI generator 34 so that the rate controller 38 can be used to determine the rate of the next packet.

The rate controller 38 is used to transmit the CRAB delivered from the CRAB reader 24, the data provided from the upper layer, the random number value provided from the random number generator 32, and the previous packet stored in the ERI storage 36. The transmission rate is controlled using the ERI value. The transmission rate control method used in the transmission rate controller 38 will be described in detail as follows.

The base station estimates the traffic load of the reverse link through the RRI and ERI information received from all terminals. In consideration of more stable operation and uncertainty of the radio channel, the base station may set the RAB using a value smaller than Lmax as a reference value. If this value is defined as Leri, the base station sets the RAB to 0 when the traffic load is less than the Leri value, and sets the RAB to 1 otherwise. The Leri value is set equal to or less than the value of Lmax.

When the value of CRAB is 0, if only the terminals transmitted by setting ERI = 1 increase the transmission rate by one step, the traffic load of all base stations in the active set does not exceed Lmax. Therefore, if CRAB is 0, terminals transmitted with ERI = 1 are transmitted at a higher transmission rate when the next packet is transmitted, and terminals transmitted with ERI = 0 remain at the current transmission rate.

On the other hand, in the case of CRAB = 1, if the UEs transmitted by setting ERI = 1 increase the transmission speed, the reverse traffic load exceeds Lmax in the base station where RAB is set to 1. FIG. Therefore, in this case, even if the terminal is set to ERI = 1 should not increase the transmission rate. Therefore, if CRAB is 1, all terminals generate random numbers between 0 and 1 regardless of the value of ERI, and if the value is smaller than q (i), the transmission rate is reduced. Use a method to maintain speed.

The method of setting the ERI value by each terminal is made through a transmission rate increase probability p (i). That is, the terminal whose current transmission rate is R (i) generates a random number between 0 and 1 regardless of the recently received RAB value. If this value is smaller than p (i), the terminal sets ERI to 1 and transmits it. , if it is greater than p (i), send ERI by setting it to 0.

The ERI channel processor 44 receives ERI information from the ERI generator 34 and transmits the ERI information through the ERI channel.

The RRI channel processor 42 receives the RRI information, which is the transmission rate information of the data, from the transmission rate controller 38 and transmits it through the RRI channel.

The data channel processor 40 receives data whose transmission rate is determined by the transmission rate controller 38 and transmits the data through the data channel.

7 is a flowchart illustrating a method for controlling a transmission rate of a reverse traffic channel of a terminal according to the present invention step by step.

The terminal determines the ERI value by the transmission rate increasing probability p (i) before transmitting each packet. That is, the terminal generates a random number between 0 and 1, and if the random number is smaller than the transmission rate increase probability p (i), the ERI is set to 1, and if the random number is the transmission rate increase probability p (i) or more. Set ERI to 0.

The terminal transmits the ERI value and the RRI information to the base station when the packet is transmitted.

The terminal determines the CRAB based on each received RAB from a plurality of base stations, and if this value is '0', the transmission rate is increased by one step only when the transmission is set by setting ERI = 1 and the transmission is set by setting ERI to 0. In one case, the current transmission rate is used as it is.

The UE determines a CRAB based on RABs received from a plurality of base stations, and if this value is '1', generates a random number between 0 and 1 regardless of the ERI value. i) If smaller, lower the transmission rate by one step, otherwise keep the current transmission rate. The transmission rate thus determined is used as the transmission rate of the next packet.

The performance of the conventional method and the present invention described above are compared in terms of overload rate and average transmission efficiency in a single cell environment. In this case, it is assumed that Lmax = 450kbps, and the transmission rate increase probability and the decrease probability use the values in Table 2. In this case, the overload rate means the rate at which the reverse traffic load exceeds 450 kbps, and the average transmission efficiency means the average value of the sum of the reverse transmission rates. In order to consider a more realistic situation, it is assumed in this comparison that the terminals receive the RAB with a reception error rate of 5%. For example, when the base station transmits a value of RAB = 1, each terminal decodes this value to 0 with a 5% probability. Leri, which is a reference value used when the base station sets the RAB in the present invention, uses the same 450 kbps as Lmax.

8 and 9 are diagrams for comparing the performance of the present invention with the performance of the present invention while increasing the number of terminals in the cell, it can be seen that the overload rate of the proposed method is significantly lower than the conventional method in all cases. have. The conventional method with Lth = 390kbps shows almost the same average transmission efficiency as the proposed method. However, the corresponding overload rate is very high compared with the proposed method. In particular, in the conventional method, as the Lth is reduced, the overload rate gradually decreases. However, since the reverse transmission rate is also reduced, it can be seen that a method of reducing the overload rate by reducing Lth is not a good solution. From the comparison results, it can be seen that the present invention efficiently reduces the overload of the 1xEV-DO reverse traffic channel and at the same time ensures an appropriate level of performance (average transmission efficiency).

As described above, in the present invention, the base station estimates the reverse traffic load, and based on this, the base station transmits control information for controlling the transmission speed of the terminal through the forward link before the reverse channel reaches an overloaded state. Significantly reduces the link overload rate. By reducing the reverse link overload, the performance of 1xEV-DO systems using CDMA technology can be greatly improved. In particular, in the present invention, since the 1-bit information, which is the operation information of the terminal, needs to be transmitted to the base station, a large effect can be expected by minimizing the conventional system. This 1-bit information transmission can be implemented by adding a new reverse channel or extending RRI information to 4 bits (3 bits RRI information, 1 bit ERI information).

Claims (16)

An apparatus for controlling a transmission rate of a reverse traffic channel transmitted by a plurality of terminals to a plurality of base stations in a wireless communication system, The terminal comprises: ERI setting means for setting an Extended Rate Indicator (ERI) value indicating whether to increase the current transmission rate by one step at the next transmission rate of the terminal; Transmitting means for transmitting the RRI information indicating the current transmission rate of the terminal and the ERI values to the plurality of base stations; RAB receiving means for receiving a reverse activity bit (RAB) value indicating whether to increase the transmission rate according to the next traffic load information from the plurality of base stations; And a transmission rate determining means for finally determining a next transmission rate using the RAB values received from the plurality of base stations and the ERI values. The method of claim 1, wherein the base station, Traffic load measurement information of the current reverse link received from the plurality of terminals, RRI information and ERI values received from the plurality of terminals are input to predict the next traffic load of the reverse link, and from the estimated next traffic load. The apparatus for controlling the transmission rate of a reverse traffic channel in a high speed wireless communication system, wherein the RAB value is generated and transmitted to a plurality of terminals. The method of claim 1, wherein the ERI setting means, A random number generator that generates a random value between 0 and 1, ERI value by comparing the transmission rate increase probability (p (i) inherent to the current transmission rate R (i), i = 1,2,3,4,5) with the random number generated by the random number generator Transmission rate control apparatus for the reverse traffic channel in a high-speed wireless communication system, characterized in that it comprises an ERI generator for setting. The method of claim 1, wherein the transmission rate determining means, If the ERI value is a transmission rate increase value and the RAB value is a transmission rate increase acceptance value, the next transmission rate is set by one step higher than the current transmission rate, and the ERI value is not the transmission rate increase value and the RAB value is set. And a transmission rate controller for setting the next transmission rate to the current transmission rate if the transmission rate is an increase acceptance value. 5. The transmission rate determining means according to claim 4, Further comprising a random value generator for generating any random value between 0 and 1, If the RAB value is the increase rate rejection value, the rate controller decreases the transmission rate inherent to the current transmission rate R (i), i = 1, 2, 3, 4, 5 regardless of the ERI value. The apparatus for controlling a transmission speed of a reverse traffic channel in a high speed wireless communication system, characterized in that the transmission rate is reduced by comparing a probability (q (i)) with a random number value generated by the random number generator. The method of claim 1, wherein the transmission rate determining means, A CRAB reader for combining the RAB values received from the base stations and reading a CRAB value indicating acceptance of an increase in transmission rate; If the ERI value is a transmission rate increase value and the CRAB value is a transmission rate increase acceptance value, the next transmission rate is set by one step higher than the current transmission rate, and the ERI value is not a transmission rate increase value and the CRAB value is set. And a transmission rate controller for setting the next transmission rate to the current transmission rate if the transmission rate is an increase acceptance value. 7. The transmission rate determining means according to claim 6, Further comprising a random value generator for generating any random value between 0 and 1, If the CRAB value is a rate increase rejection value, the rate controller decreases a transmission rate inherent to the current transmission rate R (i), i = 1, 2, 3, 4, 5 regardless of the ERI value. The apparatus for controlling a transmission speed of a reverse traffic channel in a high speed wireless communication system, characterized in that the transmission rate is reduced by comparing a probability (q (i)) with a random number value generated by the random number generator. The apparatus of claim 1, wherein the transmission means transmits the RRI information and the ERI value by multiplexing them in time. In a wireless communication system, a method for controlling a transmission rate of a reverse traffic channel transmitted by a plurality of terminals to a plurality of base stations, An ERI setting step of setting an extended rate indicator (ERI) value indicating whether the terminal increases the current transmission rate by one step at the next transmission rate of the terminal; Transmitting, by the terminal, the RRI information indicating the current transmission speed of the terminal and the ERI values to the plurality of base stations; A RAB receiving step of receiving, by the terminal, a RAB (Reverse Activity Bit) value indicating whether to accept the increase in transmission rate according to the next traffic load information from the plurality of base stations; And a transmission rate determining step in which the terminal finally determines a next transmission rate using the RAB values received from the base stations and the ERI values. . The method of claim 9, wherein the base station, Traffic load measurement information of the current reverse link received from the plurality of terminals, RRI information and ERI values received from the plurality of terminals are input to predict the traffic load of the next reverse link, and the predicted next reverse link The RAB value is generated from the traffic load of the transmission rate control method for the reverse traffic channel in the high-speed wireless communication system, characterized in that for transmitting to a plurality of terminals. The method of claim 9, wherein the ERI setting step, A transmission rate increasing probability (p (i) inherent to the current transmission rate R (i), i = 1,2,3,4,5), and any random value generated between 0 and 1 A method of controlling the transmission rate of a reverse traffic channel in a high speed wireless communication system, characterized by setting an ERI value in comparison. The method of claim 9, wherein the transmission rate determining step, If the ERI value is a transmission rate increase value and the RAB value is a transmission rate increase acceptance value, the next transmission rate is set by one step higher than the current transmission rate, and the ERI value is not the transmission rate increase value and the RAB value is set. And a transmission rate increasing acceptance value, wherein the next transmission rate is set to the current transmission rate. The method of claim 12, wherein the transmission rate determination step, If the RAB value is a transmission rate increase rejection value, a rate of reduction rate q (i) inherent to the current transmission rate R (i), i = 1,2,3,4,5 regardless of the ERI value )), And comparing a random number generated between 0 and 1 to determine whether to reduce the transmission rate of the reverse traffic channel in the high-speed wireless communication system. The method of claim 9, wherein the transmission rate determining step, Combines the RAB values received from the plurality of base stations to read a CRAB value indicating acceptance of an increase in transmission rate, If the ERI value is a transmission rate increase value and the CRAB value is a transmission rate increase acceptance value, the next transmission rate is set by one step higher than the current transmission rate, and the ERI value is not a transmission rate increase value and the CRAB value is set. And a transmission rate increasing acceptance value, wherein the next transmission rate is set to the current transmission rate. The method of claim 14, wherein the transmission rate determining step, If the CRAB value is the transmission rate increase rejection value, the transmission rate reduction probability q (i) inherent to the current set rate R (i), i = 1, 2, 3, 4, 5 regardless of the ERI value. )), And comparing a random number generated between 0 and 1 to determine whether to reduce the transmission rate of the reverse traffic channel in the high-speed wireless communication system. 10. The method of claim 9, wherein the transmitting step transmits the multiplexed RRI information and the ERI values to the plurality of base stations.

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