KR100675133B1 - Method for reallocating of down link OVSF codes in WCDMA system - Google Patents

Abstract

The present invention provides a method for reassigning downlink orthogonal spreading coefficient codes in a WCDMA system, comprising: a start point determining step of determining a start point of code reassignment using a single code; And a reassignment step of reallocating the downlink orthogonal spreading factor code after the initiation time determination step, thereby reducing resource downlink OVSF code reallocation and minimizing the blocking rate of calls with high transmission rates. It will be possible.

Description

Method for reallocating downlink OVSF codes in WCDMA system

1 is a block diagram of a typical WCDMA system,

2 is a structural diagram showing a structure of a general OVSF code,

3 is a schematic diagram showing an example of allocation of a general OVSF code;

4 is a flowchart illustrating a reassignment method of a downlink orthogonal spreading spreading code in a WCDMA system according to the present invention;

FIG. 5 is a detailed flowchart of a start point determining step of FIG. 4;

FIG. 6 is a detailed flowchart of the reassignment step in FIG. 4.

7 is a graph comparing the number of times of performing code handover according to the present invention and the prior art,

8 is a graph comparing the overall call blocking rate according to the present invention and the prior art,

9 is a graph comparing the call blocking rate of an arc having a minimum diffusion coefficient according to the present invention and the prior art,

FIG. 10 is a graph comparing the code blocking rate of a call having a minimum diffusion coefficient according to the present invention and the prior art. FIG.

Explanation of symbols on the main parts of the drawings

10: terminal equipment (UE)

20: wireless access network (RAN)

30: Core Network (CS)

The present invention relates to a method for reassigning downlink Orthogonal Variable Spreading Factor (WDDMA) codes in a wideband code division multiple access (WCDMA) system, and in particular, downlink OVSF code reassignment. The present invention relates to a method for reallocating downlink orthogonal spreading spreading codes in a WCDMA system that is suitable for efficient use of resources by reducing an allocation rate and minimizing a blocking rate of a call having a high transmission rate.

In general, the third generation asynchronous system (Universal Mobile Telecommunications System) is a third generation mobile communication system evolved from the European standard (Global System for Mobile communications) GSM, based on the GSM core radio access network (Radio Access Network, RAN ) Provides various services by combining WCDMA technology.

1 is a block diagram of a typical WCDMA system, showing the interface name of UMTS and the configuration of the system.

Here, reference numeral 10 denotes a user equipment (UE), 20 denotes a radio access network (RAN), and 30 denotes a core network (CN).

As described above, the asynchronous system is mainly composed of a terminal device 10, a wireless access network 20, and a core network 30. The wireless access network 20 includes a base station Node B and a base station controller RNC.

The radio access network 20 is connected to three core networks 30. Thus, the circuit switched is connected to the CS (Circuit Switched) domain (CS), the packet switched is connected to the PS (Packet Switched), and the broadcast service is connected to the BC (Broadcasting) domain.

In the radio access network 20, the RNC controls components in the RNS to dynamically allocate radio resources of a UMTS Radio Access Network (UTRAN). And it performs the switching function to deliver the data transmitted through the UTRAN to the appropriate node. Since the RNC is directly connected to the core network 30, the RNC serves as an access point of a service for all services provided through the core network 30.

Node B in the radio access network 20 serves as a physical layer on the Uu interface, and is responsible for transmitting and receiving data through the air interface. The Node B sets wireless physical channels necessary for data exchange with the terminal according to the control information transmitted from the RNC, converts the data transmitted from the upper protocol into a wireless environment, and transmits the data to the terminal 10. The data received from the terminal 10 is transmitted to the upper layer protocol of the RNC.

The terminal 10 includes a UMTS Subscriber Identity Module (USIM) therein. Since the USIM card can be separated from the UE, a standard interface called Cu is defined between the two.

The USIM is a part storing user's unique information and may be separated from the terminal. The USIM may be somewhat ambiguous, but in practice it takes the form of a physical integrated card (IC) card. The IC card can include various applications or multiple USIM functions.

The core network 30 includes all network components related to call control, session management, mobility management, and switching in the network.

The core network components can be divided into nodes belonging to a circuit switched (CS) area, a packet switched (PS) area, and a register area.

The circuit switched (CS) area consists of a Mobile Switching Center / Visitor Location Register (MSC / VLR) and a Gateway Mobile Switching Center (GMSC), which can be physically located in the same equipment. The MSC / VLR manages circuit-switched connections, and manages data security as well as mobility management such as location update, location registration, and paging. The GMSC acts as a path through which the circuit switched area is connected to the external network.

The packet switched (PS) area is provided through a Serving GPRS Support Node (SGSN) and a Gateway GPRS Support Node (GGSN). SGSN manages and supports packet switched services destined for UTRAN. And it includes a function such as routing area update (Routing Area Update), location information registration, call for the mobility management of the terminal receiving the packet exchange service. GGSN acts as a path to connect the packet switched area to other packet switched networks such as the Internet.

The Iu interface is used as the name of the radio access network 20 and the core network 30, and the Iub / Iur is the interface name between systems in the UTRAN.

The air interface, named Uu, is an interface that incorporates WCDMA technology.

Resources used for WCDMA include transmit power, pseudo noise code (PN), and OVSF code.

2 is a structural diagram showing a structure of a general OVSF code.

Unlike the second generation method, the OVSF code is designed to smoothly support various transmission rates, adjusts the spread rate in the radio physical layer, and guarantees orthogonality according to the code number.

The OVSF code is distinguished by a spreading factor (SF) and a code number.

Thus, if the spreading factor is i and the code number is j, the OVSF code is represented by Ci, j. In the downlink, the spreading factor has a value between 4 and 512. The smaller the spreading factor is, the higher the transmission rate is.

The OVSF code has a format in which one code is divided into two codes as shown in FIG. 2 and has the following characteristics.

First, the code number of each spreading coefficient has the same value as the corresponding spreading coefficient.

Second, the signs of the same spreading coefficients are orthogonal to each other.

Third, the signs of different diffusion coefficients should not be connected up and down, and are orthogonal to each other.

Due to the first and second characteristics, there can be up to 128 users with a spreading factor of 128 (except for codes used as common channels), and the codes of the same spreading coefficients are orthogonal, so the same performance is obtained using any code allocation method. .

If there are users with various data rates, the performance varies depending on the allocation method by the third characteristic.

3 is a schematic diagram showing an example of allocation of a general OVSF code.

Thus, for example, as shown in FIG. 3, when a call requesting a spreading factor 64 is assigned to a number 4, a call requiring a spreading factor 32 must be blocked because it cannot be assigned to a number 2 because the number 4 occupies first. . However, if a call having a spreading factor of 128 is assigned to 12 and 13 and a call having a spreading factor of 64 is assigned to 7, then a call having a spreading factor of 32 can be accepted twice.

Sign allocation methods are largely random, left most, and crowded first.

The crowded first method performs the best here, but the OVSF code is not always optimal because of the irregular call release during system operation. As a result, Code Blocking is a problem that can not be used by an already assigned OVSF code.

In order to solve this problem, a code reallocation method should be applied.

That is, as shown in FIG. 3, in order to prevent the call having the spreading factor 32 from being blocked when each call is assigned to 4, 12, and 14, the 14 calls to 13 and the 4 calls to 7 The move is called code reallocation, and the following methods exist.

First, DCA (Dynamic Code Assignment)

Second, sparest-first

Like the code assignment method, the code reassignment method has a great influence on the efficiency of OVSF code usage, and therefore, it should be considered and evaluated in various aspects.

The prior art DCA and the sparse-first method will be described in more detail as follows.

First, the DCA method is a method of reassigning lower codes that cause code blocking when a call is set up so that the code of the corresponding spreading coefficient has a free space.

To use this method, first find the code that minimizes the reassignment number of the lower code.

Therefore, the use efficiency of the OVSF code is good.

However, the code assignment for the new call was delayed until the lower codes completed the reassignment procedure.

Also, if any one of the sub-code reassignment process fails, the code assignment for the new incoming call cannot be performed.

The second, sparse-first method, is a code reassignment scheme to keep the OVSF code as optimal as possible before new calls arrive.

This is a method of reallocating the voice code having the smallest code value among the OVSF codes as the released code whenever the voice code (SF = 128) having the largest spreading factor among the traffic is released.

The sign value is calculated by virtually assigning its spreading coefficient where the call is set and 0 where it is not set, and summing it to the higher sign.

However, this conventional technology has the following problems.

First, the DCS method, which performs the code reassignment during call setup, affects the call setup time, and code handover occurs more frequently than other methods, so the performance of OVSF code is good. There was a problem that was difficult to apply in the actual situation.

In addition, the second method, the sparseist-first method, does not affect the call setup time because the number of code reallocations is reduced and the number of code reallocations are performed during the call release. However, as the number of call releases increases, the reassignment increases. If there is no call with the maximum spreading coefficient in any cell connected to the controller, there is a problem that no code reallocation occurs.

Accordingly, the present invention has been proposed to solve the above-mentioned conventional problems, and an object of the present invention is to reduce the downlink OVSF code reallocation rate and to minimize the blocking rate of a call having a high transmission rate so that the resource can be efficiently used. The present invention provides a method for reallocating a downlink orthogonal spreading spreading code in a WCDMA system.

In order to achieve the above object, in the WCDMA system according to an embodiment of the present invention, a method for reassigning a downlink orthogonal variable spreading coefficient code is provided.

A start time determining step of determining a start point of code reallocation using a single code; And a reassignment step of reallocating a downlink orthogonal variable spreading factor code after the start point determining step.

Hereinafter, an embodiment according to the present invention as described above with reference to the technical concept of the method of reallocating the downlink orthogonal variable spreading coefficient code in the WCDMA system as follows.

4 is a flowchart illustrating a reassignment method of a downlink orthogonal variable spreading coefficient code in a WCDMA system according to the present invention.

As shown therein, a start time determination step (ST10) for determining the start time of code reallocation using a single code; And a reassignment step (ST20) of reassigning the downlink orthogonal variable spreading factor code after the start point determining step.

In the above-described start point determining step (ST10), the single code is performed only for a call having a specific spreading factor except for a call having a minimum spreading factor.

In the above-described start point determining step (ST10), the single code is managed for each spreading coefficient.

FIG. 5 is a detailed flowchart of a start point determining step in FIG. 4.

As shown therein, when detecting a code assignment or release, a first step (ST11 to ST13) of calculating a single code and comparing the calculated value of the single code with a threshold value; As a result of the comparison after the first step, if the threshold value is high, the method returns to the first step; if the threshold value is not high, the second step (ST14) of reallocating a code and then returning to the first step is performed.

The reassignment step (ST20) includes reassigning two single codes into one fully allocated code.

The reassignment step ST20 may include managing each of the spreading coefficients and individually reassigning them.

In the reassignment step (ST20), the call having the minimum spreading coefficient set in the system when performing code handover at the time of reassignment includes performing only the call having a specific spreading factor except in the reassignment. .

FIG. 6 is a detailed flowchart of the reassignment step in FIG. 4.

As shown therein, the eleventh step ST21 of setting the diffusion coefficient SF to 4; A twelfth step of determining whether the diffusion coefficient is greater than 512; A thirteenth step (ST23) (ST24) for terminating if the diffusion coefficient exceeds 512 and calculating a single code from a diffusion coefficient (SF) if the diffusion coefficient does not exceed 512; A fourteenth step (ST25) for returning to the twelfth step after doubling the value of the diffusion coefficient (SF) if the singular calculated value is not two or more; If the single sign calculation value is 2 or more, a 15th step ST26 is performed to move the right single sign to the leftmost single sign and reallocate it.

An operation of a method for reassigning a downlink orthogonal variable spreading coefficient code in a WCDMA system according to the present invention configured as described above will be described in detail with reference to the accompanying drawings.

First, the present invention is intended to efficiently use resources by reducing the downlink OVSF code reallocation rate and minimizing the blocking rate of a call having a high transmission rate.

Thus, the present invention is largely composed of a start point determination step for the reassignment time and a reassignment step for the reassignment method.

FIG. 5 is a flowchart for determining when to start code reassignment, and FIG. 6 illustrates a method of reallocating when code reassignment is started.

In order to compensate for the problems of the prior art, a new coefficient of measurement called a fragment code is used.

One code of OVSF is divided into two codes. One code is set and used, and the other code is assigned a single code. That is, the single code means, for example, in Fig. 3, two derivatives derived from the same code, such as 4 and 5 for the diffusion coefficient 64 and 12 and 13 or 14 and 15 for the diffusion coefficient 128. One of the two symbols is assigned, but the other is a pair of symbols that can be assigned.

The base station controller calculates this single code and compares it with a preset threshold value to start code reallocation. However, since the change of the single code is generated by the code assignment or release, the calculation of the single code is performed at the time of code assignment and release.

Here, code allocation refers to distributing one OVSF code for each user when a call is started to improve the utilization rate of downlink OVSF among radio resources of WCDMA.

Code reallocation refers to a move of a code number set to another number having the same spreading factor in order to prevent an OVSF currently in use because the call has expired.

Therefore, in the start point determining step (ST10), the start point of code reallocation is determined using the single code.

In the start point determining step (ST10), the single code is performed only for a call having a specific spreading factor except for a call having a minimum spreading factor.

In addition, the start time determining step (ST10) manages a single code for each spreading coefficient.

The operation of the start point determination step will be described in more detail with reference to FIG. 5 as follows.

First, the code allocation or release is detected (ST11).

Then, the single sign is calculated (ST12).

The calculated value of the single sign and the threshold value are compared (ST13).

If the threshold is high as a result of comparison, it detects sign assignment or release again.

If the threshold is not high as a result of the comparison, the code is reassigned (ST14). Then it detects sign assignment or release again.

Therefore, in the start point determining step, in order to improve the problem of the conventional code reassignment method, a measurement coefficient called a single code is used. When the result of FIG. 5 determines the code reassignment, the value of the single code becomes smaller than the threshold value through the method of removing the single code.

To this end, in the reassignment step (ST20), the downlink orthogonal variable spreading factor code is reallocated.

The reassignment step ST20 combines two single codes and reallocates them into one fully allocated code.

In addition, the reassignment step (ST20) is managed for each spreading coefficient to individually reassign.

The reassignment step ST20 performs only the calls with a specific spreading factor, except for the reassignment, when the code handover is performed during the reassignment.

This will be described in more detail with reference to FIG. 6 as follows.

First, the diffusion coefficient SF is set to 4 (ST21). As a result, calls with the smallest diffusion coefficient are excluded from reassignment.

Then, it is determined whether the diffusion coefficient exceeds 512 (ST22).

If the diffusion coefficient exceeds 512, it is terminated.

If the diffusion coefficient does not exceed 512, a single code is calculated from the diffusion coefficient (SF) (ST23).

Then, it is determined whether the singular signed value is 2 or more (ST24).

If the unsigned calculation value is not 2 or more, the value of the diffusion coefficient (SF) is doubled (ST25). Then determine if the diffusion coefficient exceeds 512.

If the single sign calculation is 2 or more, the right single sign is reassigned by the Left Most method. This means that if two or more single codes are found, they are reassigned by moving the rightmost single sign to the leftmost single code. For example, in FIG. 3, the single sign consisting of 14 and 15 positioned to the right of the spreading coefficient 128 is moved to the single sign consisting of 12 and 13 so that 12 and 13 are sequentially assigned.

In order to remove the single code, it is checked whether there are two or more single codes from the smallest spreading factor (where the data rate is high). If no single codes are found, the smallest spreading factor is checked. If more than one singular code is found, the singular code is reduced by shifting the rightmost single code to the leftmost single code and reallocating it.

As such, the present invention uses resources efficiently by reducing the downlink OVSF code reallocation rate and minimizing the blocking rate of calls with high transmission rates.

Although the preferred embodiment of the present invention has been described above, the present invention may use various changes, modifications, and equivalents. It is clear that the present invention can be applied in the same manner by appropriately modifying the above embodiments. Accordingly, the above description does not limit the scope of the invention as defined by the limitations of the following claims.

As described above, in the WCDMA system according to the present invention, the method for reallocating the downlink orthogonal spreading spreading code can efficiently use resources by reducing the downlink OVSF code reallocation rate and minimizing the blocking rate of a call having a high data rate. It is effective.

7 is a graph comparing the number of times of code handover execution according to the present invention and the prior art, FIG. 8 is a graph comparing the overall call blocking rate according to the present invention and the prior art, and FIG. FIG. 10 is a graph comparing a call blocking rate of an arc having a minimum diffusion coefficient according to the present invention, and FIG.

In order to compare the present invention with sparse-first, which is a code reassignment scheme, FIGS. 7 to 10 generate a call having spreading coefficients of 128, 64, 32, and 16, and assume the same call attempt rate and resource occupancy. This is the result of the experiment.

Code blocking here means that the OVSF is not optimal and cannot accept the call.                     

Call blocking also refers to a case in which the OVSF fails to maintain an optimal state or all OVSFs are in use and thus cannot accept the call.

Code handover refers to the number of times a code is changed from one code to another through code reallocation.

Therefore, code handover generated by the code reassignment method is a factor that can cause a decrease in the voice quality and a load of throughput. According to the present invention, it can be confirmed that the system load is significantly less and in case of congestion. The blocking rate was also improved.

In particular, it can be seen that the call blocking and sign blocking of the call having a spreading factor of 16 (128kbps) has an improvement effect, and the sign blocking has an effect of about 50% reduction than the sparseist-first.

Claims (8)

A start time determining step of determining a start point of code reallocation using a single code; And reallocating a downlink orthogonal spreading spreading factor code after the start point determining step, the method of reallocating a downlink orthogonal spreading spreading code in the WCDMA system. The method of claim 1, wherein the starting point determination step, A method of reassigning a downlink orthogonal spreading factor code in a WCDMA system, comprising performing a single code only for a call having a specific spreading factor except for a call having a minimum spreading factor. The method of claim 1, wherein the starting point determination step, A method of reassigning a downlink orthogonal spreading coefficient code in a WCDMA system, comprising managing a single code for each spreading coefficient. The method of claim 1, wherein the starting point determining step comprises: A first step of calculating a single code and comparing a calculated value of the single code and a threshold value upon detecting a code assignment or release; And a second step of returning to the first step if the threshold value is high, and reassigning the sign if the threshold value is not high, and returning to the first step if the comparison result after the first step is performed. Reassignment of Downlink Orthogonal Variable Spreading Factor Codes in WCDMA Systems. The method of claim 1, wherein the reassignment step, A method for reallocating a downlink orthogonal spreading coefficient code in a WCDMA system, comprising: integrating two single codes and reallocating the code to a fully allocated single code. The method of claim 1, wherein the reassignment step, A method of reassigning a downlink orthogonal spreading factor code in a WCDMA system, characterized in that it is performed according to spreading factor and individually reassignment. The method of claim 1, wherein the reassignment step, When performing code handover during reassignment, calls with the smallest spreading factor set in the system are included, except for reassignment, only for calls with a specific spreading factor. Reassignment of Link Orthogonal Variable Diffusion Coefficient Codes. The method of claim 1 or claim 5, wherein the reassignment step, An eleventh step of setting the diffusion coefficient to 4; A twelfth step of determining whether the diffusion coefficient is greater than 512; A thirteenth step of terminating if the diffusion coefficient is greater than 512; calculating a single code from the diffusion coefficient and determining whether the single code calculation value is 2 or more if the diffusion coefficient is not greater than 512; A fourteenth step of returning to the twelfth step after doubling the value of the diffusion coefficient if the singular calculated value is not two or more; Reassignment of the downlink orthogonal spreading coefficient code in the WCDMA system, comprising: a 15 th step of reassigning the single singular code to the leftmost single code when the single code calculation value is 2 or more; Way.

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