KR100391809B1 - Method for controlling of the data transmission speed of forward channel in communication system - Google Patents

Abstract

The present invention relates to a data rate control method for improving system performance by actively performing forward data rate control according to a channel environment in a communication system (1xHDR system) for high speed data service. In the communication system for data service, the forward data rate control is actively performed according to the channel environment so that each user can be assigned an optimal data rate and can transmit and receive data without retransmission. In addition, it is possible to respond to a changing environment more quickly by using a wireless channel measurement technique, and to accurately predict the channel environment to improve the transmission efficiency (throughput) to contribute to the capacity increase.

Description

Method for controlling of the data transmission speed of forward channel in communication system

The present invention relates to a forward data rate control method in a communication system (especially, 1xHDR (1x-EV-DO) system) for high-speed data service, and in particular, each user by actively performing data rate control according to a channel environment. It can assign the optimal data transmission rate to users and perform transmission and reception without retransmission of data, improve system performance, and respond to changing environment faster by using wireless channel measurement technique, By predicting, the transmission efficiency can be improved.

In general, High Data Rate (HDR) is a new technology for Qualcomm's newly introduced packet wireless data transmission, which has successfully commercialized Code Division Multiple Access (CDMA) technology and prepared the rapid spread of CDMA technology worldwide. It is a technology that enables data transmission. This HDR system is optimized only for high-speed packet transmission and uses the same frequency band (1.25MHz) as the current IS-95 system.

The theoretical maximum transmission speed of IS-95, which has already started to use in Korea, is 115.2 Kbps (currently being serviced at 57.6 Kbps) or CDMA-2000 (IS-95C) 1xRTT (Radio Transmission Technology), which is commercially available. Compared to the speed of 144Kbps, the maximum transmission speed of HDR is very high.

In addition, since the 1xRTT system supports both voice and data, there is a limitation in transmitting high-speed data in the 1.25MHz band. When this service becomes commercially available, high-speed Internet service comparable to ADSL, cable modem, etc. will be provided at a low price regardless of the location, and it will change the existing 'wireless internet' concept that was provided at a low speed on a small terminal screen. .

Access Points of the system configuration of the HDR (Access Points) is equipment that serves as a base station (BTS) of the IS-95 system is embedded in the BSC that controls the session (session) inside. Therefore, HDR can be configured by simply connecting the access point to the router and the carrier network for billing, user authentication, and data service.

The access point supports up to three sectors in one frequency assignment and can be installed in the current IS-95 base station. HDR access points share the same antenna and occupy less space because they have the same RF characteristics as IS-95, allowing them to be installed inside existing base stations without the need for additional base station construction.

In the channel structure of HDR, the forward link is different from the existing IS-95, and the reverse link is not much different. The biggest feature of the forward link is that users are separated by time slots, not by orthogonal codes. One time slot is 1.67 msec. At any moment, only one person occupies the channel, so there is little interference from other users, and no power control allows the access point (AP) to always transmit the signal at full power. The lack of power control is designed to maximize the benefits of packet transmission. For IS-95 systems, the same data rate must be guaranteed for all users, but not for packet transmission. Thus, a user who receives a strong signal can receive a higher data rate, while a user who receives a weaker signal compensates for an unequal data rate by allocating more time slots instead. However, there is also a problem that it is difficult to provide a high-speed service to the user far from the base station because the power control is not performed.

In the structure of the forward link channel of HDR, the IS-95 system transmits signals to all users at the same time, and pilot signals are also transmitted at the same time, which causes interference with pilot signals and waste of propagation power.

Since HDR uses Burst Pilot, the pilot signal is transmitted at maximum output, so it is possible to accurately measure the strength of the signal, reduce the error rate, and reduce the interference caused by the pilot signal. have. In addition, since the synchronous system also generates pilot signals of neighbor cells at the same time, it can be said that interference by pilot signals of neighbor cells is minimized.

HDR's forward link can receive services from as low as 38.4 Kbps to as high as 2.5 Mbps, depending on the signal strength the terminal receives.

The reverse link in HDR is similar to the reverse link in IS-95 systems and uses user pilot signals to improve performance. It also uses the power control method of the traditional IS-95 and provides services from 9.6Kbps to 307.2Kbps.

HDR systems are IP-based systems that are bursty and optimized for delay-insensitive packet transmission. The high-speed data transmission technology of HDR enables the mega-class data transmission that could be expected in the IMT-2000, so multimedia services such as real-time video through a video phone or a terminal are expected to be possible.

In general, a 1xHDR system is a system for serving high-speed packet data. As shown in FIG. 1, an access terminal (AT) 100 and an access network (AN) 200 are largely illustrated in FIG. 1. Consists of

1 is a block diagram showing the basic structure of a general 1xHDR system.

First, data that can be transmitted through the forward call channel can be serviced at speeds of 38.4, 76.8, 153.6, 307.2, 614.4, 921.6, 1228.8, and 2457.6 kbps.

At this time, the data rate of the forward call channel maintains an appropriate call quality while serving a variable data rate by performing a high speed data service in a good environment and a low speed data service in a poor environment according to a wireless channel environment.

In the 1xHDR (1x-EV-DO) system, which is newly defined for the high-speed data service, the forward data rate determination is configured as follows.

The access terminal (AT) 100 calculates a received signal-to-interference ratio (hereinafter, abbreviated as "C / I") value of the received signal, and calculates a DRC (DRC) value from the calculated C / I value. Data Rate Control) Symbol is determined. The determined 4-bit DRC symbol is reported to the access network (AN, base station) 200 through the DRC channel of the reverse link, the access network 200 according to the received DRC symbol to the forward data rate Will be decided.

However, since the forward channel data rate control algorithm using the DRC symbol defined in the communication (1xHDR) system standard is simple as described above, the data rate control algorithm that reflects only the channel environment at the time of C / I calculation is used to determine the channel environment. It is difficult to predict the change according to the prediction, and also, a problem arises in that the data rate cannot be controlled actively due to the change in the channel environment.

Accordingly, the present invention is proposed to solve the above problems of the prior art,

An object of the present invention is a carrier to interference for which an access terminal (AT) is currently received in determining a data rate control (DRC) symbol used for forward data rate control in a communication (1xHDR) system. Forward in a 1xHDR system that enables forward channel data rate control more actively in response to channel environment changes by using C / I values previously received as well as ratio values. The present invention provides a method of controlling a data rate of a channel.

The present invention for achieving the above object,

A first process of calculating a received carrier to interference ratio (C / I) value at an access terminal;

A second process of determining a data rate control (DRC) symbol value according to the calculated C / I value;

A third process of storing a received C / I value on a stack after determining the DRC symbol value;

A fourth process of performing an algorithm for changing the DRC symbol value after storing the C / I value;

The method comprises a fifth step of adjusting a DRC symbol value determined according to the algorithm and transmitting the adjusted DRC symbol value.

On the other hand, the fourth process,

Checking the continuous increase / decrease of the C / I values stored in the stack;

Checking whether the C / I value stored in the stack is continuously increased, and as a result, if the C / I value stored in the stack increases, increasing the DRC symbol value by one step faster;

Checking whether the C / I value stored in the stack is continuously decreased if the C / I value does not increase, and if the result decreases, decreasing the DRC symbol value by one step;

If not included in the two cases it is characterized in that the method configuration consists of maintaining the DRC symbol value as it is.

In addition, the fourth process,

Checking the continuous increase / decrease of the C / I values stored in the stack;

Checking whether the C / I value stored in the stack is continuously increased, and as a result, if the C / I value stored in the stack increases, increasing the DRC symbol value by one step faster;

Checking whether the C / I value stored in the stack is continuously decreased if the C / I value does not increase, and if the result decreases, decreasing the DRC symbol value by one step;

If not included in the two cases it is characterized in that the method configuration consists of maintaining the DRC symbol value as it is.

1 is a block diagram schematically showing the basic structure of a general communication system,

2 is a flowchart illustrating a method of controlling a forward data rate in a communication system according to the present invention;

3 is a block diagram showing the configuration of a stack for storing received C / I values according to the present invention;

4 is a flowchart illustrating a first algorithm for controlling forward data rate in the communication system according to FIG. 2;

5 is a flowchart illustrating a second algorithm for controlling forward data rate in the communication system according to FIG. 2.

<Explanation of symbols for the main parts of the drawings>

100 ..... Access Terminal

200 ..... Access Network

Hereinafter, a preferred embodiment of the <data transmission rate control method of the forward channel in the 1xHDR system> of the present invention according to the above technical concept will be described in detail with reference to the accompanying drawings.

First, in the HDR system applied to the present invention, a coding rate (1/4, 3/8, 1/2), a modulation scheme (QPSK, 8PSK, 16QAM), and a packet are repeatedly transmitted according to a channel state. It refers to a system capable of transmitting data at 13 data rates according to the combination of the number of slots. In order to select the forward data rate, the base station determines whether the terminal has a received signal to interference ratio of the forward pilot channel. C / I ") and predict the change of the next channel to request the data rate of the forward traffic channel, and the terminal sends data to the receiver of the forward traffic channel and the eight valid sectors through the DRC channel. Ie, the terminal measures the pilot channel C / I of the effective sectors to determine the data rate and sector, and thus transmits the determined data. The information is a 4-bit DRC symbol, and the cell selection information is configured to transmit DRC information to a base station by using a 3-bit index that determines an 8-bit orthogonal spreading code. The present invention also provides 1xHDR (1x-EV-). In the DO system, the forward data rate control algorithm is performed in the access terminal (AT) 100 and is configured in two ways as follows.

2 is a flowchart illustrating a method of controlling a forward data rate in a 1xHDR system according to the present invention.

As shown therein, in step ST11, the access carrier (AT) 100 calculates a received carrier to interference ratio (C / I) value, and in step ST12, the data rate control according to the calculated C / I value. ) Determines the symbol value.

If the DRC symbol value is determined in step ST13, the received C / I value is stored in a stack, and in step ST14, an algorithm for changing the DRC symbol value is performed.

Next, after performing the algorithm in step ST15, the modified DRC symbol value is adjusted, and in step ST16, the adjusted DRC symbol value is transmitted.

3 is a diagram illustrating a configuration of a stack storing a received C / I value according to the present invention.

As shown therein, the access terminal stores a previously received C / I value (n0 to nk) on the stack for a period of time, and when a new C / I value (n0) is received, the previously stored receive C / The first received C / I value (n1 to nk) is sequentially stored in the next step one by one step, and the oldest C / I value (nk) is removed.

4 is a flowchart illustrating a first algorithm for controlling a data rate of a forward channel in the 1xHDR system according to FIG. 2.

As shown therein, step ST21 for calculating a difference between a current received C / I value and a previous received C / I value, steps ST22 and ST24 for comparing the calculated difference value with a predetermined threshold value, and the comparison result Step ST23 to increase the DRC symbol value by one step if larger than the predetermined threshold value; and step ST25 to decrease the DRC symbol value by one step if the comparison result is smaller than the predetermined threshold value; In step ST26, the DRC symbol value is retained.

Referring to the data transmission rate control method according to the present invention having such a configuration in detail as follows.

The access terminal (AT) 100 determines a DRC symbol according to the received C / I value. The access terminal (AT) 100 determines not only the C / I value at the time of determining the DRC symbol but also the previously received C / I value. The DRC symbol is determined. If the current predicted C / I value is greater than a certain threshold (Threshold_Up) than the previous received C / I value, the DRC symbol is one step ahead of the data rate assigned to the currently predicted C / I value (Step1_Fast). If a data rate is assigned and the predicted C / I value is less than a certain threshold (Threshold_Down) below the previously received C / I value, the DRC symbol is one step slower than the data rate assigned to the currently predicted C / I value. Step1_Slow) Allocate a data rate. This is to improve channel efficiency by allocating DRC symbols more proactively in the rapidly changing channel conditions.

FIG. 5 is a flowchart illustrating a second algorithm for controlling a data rate of a forward channel in the 1xHDR system according to FIG. 2.

As shown therein, step ST31 of checking the continuously increasing / decreasing state of the C / I value stored in the stack, and checking whether the C / I value stored in the stack is continuously increased (ST32) and if the result is increased, DRC A step ST33 of increasing the symbol value by one step, a step of checking whether the C / I value stored in the stack continuously decreases, and a step ST35 of decreasing the DRC symbol value by one step if the result decreases; If not included in the case, step ST36 for maintaining the DRC symbol value as it is.

Referring to the data transmission rate control method according to the present invention having such a configuration in detail as follows.

As described above, the DRC symbol is determined using the C / I value stored in the stack. If the C / I value stored in the stack is in a continuous decreasing trend and the currently received C / I value is also reduced from the previously received C / I value, it is one step slower than the data rate assigned to the currently predicted C / I value (Step2_Slow). ) Allocate a data rate, and if the C / I values stored on the stack are in a continuous trend of increase and the currently received C / I values have also increased above the previously received C / I values, they are assigned to the currently predicted C / I values. Allocate a data rate one step ahead of the data rate (Step 2 Fast). This improves channel efficiency by allocating DRC symbols more actively in environments with increasingly good or worsening channel conditions.

As described above, in the present invention, the first algorithm (FIG. 4) and the second algorithm (FIG. 5) may be performed simultaneously or separately in FIGS. 4 and 5, respectively. It can predict the rapid change of the channel environment and the overall change trend, thereby improving the performance of the 1xHDR forward system.

According to the present invention "method of controlling the data rate of the forward channel in the 1xHDR system" described above, by improving the forward system performance can be applied to the system without a change in the 1xHDR standard, it can greatly contribute to the improvement of the forward link system performance Has the advantage.

In addition, since the algorithm is simple to implement, there is an advantage of reducing the cost required to improve the performance of the forward link system.

In addition, by applying the data rate control algorithm of the forward channel in the 1xHDR system, it is possible to properly control the data rate of the forward channel according to the call channel wireless environment to maintain the appropriate call channel quality, By providing it, there is an advantage that the system efficiency other than the call quality can be increased.

Claims (6)

In a communication (1xHDR) system consisting of an access terminal and an access network, the data rate control method of the forward channel, Calculating a received carrier to interference ratio (C / I) value at an access terminal; Determining a data rate control (DRC) symbol value according to the calculated C / I value; A third step of storing a received C / I value on a stack after determining the DRC symbol value; A fourth step of performing an algorithm for changing the DRC symbol value after storing the C / I value; And adjusting a DRC symbol value determined according to the algorithm, and transmitting the adjusted DRC symbol value to a data transmission rate adjustment value of a forward channel. Control method. The method of claim 1, wherein the third process comprises: The access terminal stores a previously received C / I value on the stack for a period of time, when a new C / I value is received, at a stack position of the previously stored received C / I value, and stores the previously received C / I value. A method of controlling the data rate of a forward channel in a communication system, wherein the I value is sequentially stored in the next step and the oldest C / I value is removed. The method of claim 1, wherein the fourth process, A first algorithm for calculating a difference between a current received C / I value and a previous C / I value and changing a DRC symbol value according to the difference value; and a DRC symbol value according to an increase or decrease of the C / I value stored in the stack. And a second algorithm for changing the data rate of the forward channel in the communication system. The method of claim 3, wherein the first algorithm, Calculating a difference between a current received C / I value and a previous received C / I value; Comparing the calculated difference value with a predetermined threshold value; If the comparison result is greater than a predetermined threshold, increasing the DRC symbol value by one step; If the comparison result is less than a certain threshold, decreasing the DRC symbol value by one step; If not included in the two cases, the method comprising the step of maintaining the DRC symbol value intact in the communication system, characterized in that the data transmission rate control method of the forward channel. The method of claim 3, wherein the second algorithm, Confirming the continuous increase / decrease state of the C / I value stored in the stack; Checking whether the C / I value stored in the stack is continuously increased, and as a result, increasing the DRC symbol value by one step if the C / I value stored in the stack is increased; Checking whether the C / I value stored in the stack is continuously decreased if the C / I value does not increase, and if so, decreasing the DRC symbol value by one step; If not included in the two cases, the method comprising the step of maintaining the DRC symbol value intact in the communication system, characterized in that the data transmission rate control method of the forward channel. The method of claim 1, wherein the changing of the DRC symbol value of the fourth process, The first algorithm for changing the DRC symbol value according to the calculated value and the second algorithm for changing the DRC symbol value according to the increase / decrease of the C / I value stored in the stack may be performed simultaneously or independently. A data rate control method of a forward channel in a communication system, characterized in that.