KR20030072857A - Resource management method and apparatus in a mobile communication system providing voice and data services - Google Patents

Abstract

PURPOSE: A method for managing resources of a mobile communication system supplying voice and data services is provided to analyze a requested call, and to determine whether to accept the call according to transmission power of a BTS, thereby supplying differential resource management services for a newly initiated call and an ongoing call. CONSTITUTION: A call request receiver decides whether a call request is received(201). If so, a call analyzer decides a service kind of the requested call(202). If the call is a voice call, the call analyzer decides whether the call is a new call or an ongoing handoff call(203). If the call is the new call, a call acceptance determiner decides whether a formula condition is satisfied(205). If so, the call acceptance determiner determines to accept the call(205). If the condition is not satisfied, the call acceptance determiner determines to reject the call(206). If the call is the ongoing handoff call, the call acceptance determiner decides whether another formula condition is satisfied(207). If so, the call acceptance determiner determines to accept the call(208), and if not, the call acceptance determiner determines to reject the call(209).

Description

RESOURCE MANAGEMENT METHOD AND APPARATUS IN A MOBILE COMMUNICATION SYSTEM PROVIDING VOICE AND DATA SERVICES}

The present invention relates to efficient radio resource management of a mobile communication system, and more particularly, to a method and apparatus for controlling call acceptance and managing orthogonal code assignment in a mobile communication system for voice and data services.

Typical mobile communication systems, such as IS-95-based code division multiple access (CDMA) communication systems, only support voice services. However, as communication technology has developed along with user demands, mobile communication systems have also been developed to support data services.

Mobile communication systems that support multi-media services, including voice and data services (e.g., mobile communication systems based on IS-2000) support voice and data services to multiple users using the same frequency band. do. In this case, a time division multiplexing (TDM) method or a code division multiplexing (CDM) method is a representative example of a system for supporting voice and data services to a plurality of users using the same frequency band. However, a problem arises in that the above methods cannot provide sufficient services to many users. In other words, when the service is to be provided to more users, the above-mentioned time division or code division alone has a limit in accommodating many users. Thus, there is a need for a method for accommodating more users.

On the other hand, in the second generation CDMA mobile communication system based on IS-95B, several low-speed channels are bundled to provide high-speed data service. At this time, each low-speed channel (SCCH: Supplemental Code Channel) is the same as a channel used for voice service (FCH: Fundamental Channel), and as a result, it is difficult to manage resources differently for voice and data.

On the other hand, in the third generation CDMA mobile communication system based on IS-2000, differential services for voice and data services are enabled by introducing a supplemental channel (SCH) for high-speed data services. However, it has only recently begun to provide high-speed data services in a mobile communication environment, and there are few studies for efficient high-speed data services. Moreover, there are few studies on how to achieve the opposite goals of guaranteeing voice service quality and providing high speed data service in a mixed voice and data service environment.

Accordingly, an object of the present invention is to provide a method and apparatus for efficiently managing radio resources in a mobile communication system providing voice and data services.

Another object of the present invention is to provide a method and apparatus for efficient high speed data service while minimizing the impact on existing voice services in a mobile communication system providing voice and data services.

Another object of the present invention is to provide a method and apparatus for call admission control and orthogonal code management for optimizing high-speed data services while providing priority for voice services in a mobile communication system providing voice and data services. .

Another object of the present invention is to provide a method and apparatus for a flexible resource distribution / allocation function for radio resources used for voice service and data service in a mobile communication system providing voice and data service.

It is still another object of the present invention to provide a voice and data service in a mobile communication system, as well as a differentiated service of a voice service and a data service, as well as a method for making a differentiated resource management service for a newly started call and a call already in service. And providing an apparatus.

The present invention for achieving these objectives proposes a method for efficient radio resource management in a mobile communication system such as CDMA mixed voice and data services. The method for controlling the acceptance of a requested call in accordance with the present invention comprises the steps of analyzing the requested call when a call is requested and based on the transmit power of the base station determined according to the analysis result of the requested call. It includes the process of determining acceptance of the call. The process of determining acceptance of the requested call is as follows. If the condition is met, it is decided to accept the requested call. In the above formula, Is a preset threshold, Is the sum of power in use for voice and low-speed data calls and power for overhead channels, Is the amount of power needed to service new calls, Is the reserve power. The threshold is determined by a preset ratio of the total transmit power of the base station. The set rate is set differently for the call for the voice service and the call for the data service. The reserve power is determined differently for each of the newly starting call and the call already in progress. The reserve power for the call already in progress is greater than the reserve power for the newly starting call.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that those skilled in the art may better understand the detailed description of the invention that follows.

Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. Those skilled in the art should recognize that the disclosed concepts and specific embodiments of the invention may be readily used as a basis for modifying or designing other structures for achieving the same purposes of the present invention. Those skilled in the art should also recognize that structures equivalent to the invention do not depart from the spirit and scope of the broadest form of the invention.

1 is a view for explaining the principle of the call admission control operation according to an embodiment of the present invention.

2 is a view showing the configuration of a call admission control device according to an embodiment of the present invention.

3A and 3B illustrate a processing flow of a call admission control operation according to an embodiment of the present invention.

4 is a diagram illustrating a principle of resource allocation for a high speed data service according to an exemplary embodiment of the present invention.

5 is a state transition diagram by voice call arrival / end according to an embodiment of the present invention.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings. It should be noted that the same reference numerals and the same elements among the drawings are represented by the same reference numerals and symbols as much as possible even though they are shown in different drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

The present invention for guaranteeing voice service quality and providing high-speed data service in a mobile communication system such as a CDMA communication system having a mixed voice and data service, which will be described below, includes (1) a call admission control scheme and a call admission control scheme. (2) Orthogonal Code Allocation Scheme. As the orthogonal code, a case of a Walsh code will be described.

The call admission control refers to a process of determining whether to accept a service request when a new service request arrives in order to guarantee the quality of an existing service call. This call admission control can selectively accommodate voice services and data services, and can also selectively accept newly initiated calls and ongoing calls. The present invention proposes a technique for performing call admission control based on power, which is a resource for determining capacity of a CDMA mobile communication system in most cases.

In a CDMA communication system, the traffic link between a base station and a mobile station is distinguished by a Walsh code based on a Hadamard matrix. This Walsh code is not an infinite resource and is a finite resource having only 64 in total based on the 9.6kbps traffic channel. In addition, a large number of Walsh codes are required when performing a high speed data service. For example, 16 Walsh codes for 9.6 kbps are used for 153.6 kbps data communication. Therefore, there is a need to efficiently manage Walsh codes as a high speed data service is introduced. The present invention proposes a Walsh code management scheme for enabling high-speed data service while guaranteeing priority for voice.

A. Call Admission Control Technique

The capacity of a communication system based on the code division multiple access (CDMA) scheme is variable, unlike the frequency division multiple access (FDMA) or the time division multiple access (TDMA) scheme. That is, if the location of the mobile station is located in a good link state on the base station antenna and the line of sight (LOS), it can accommodate a large number of users and vice versa. In addition, accepting users beyond the capacity of the communication system adversely affects the call quality of other users who are already receiving service. For this reason, the effective call admission control technique is very important in terms of system capacity and quality in CDMA based mobile communication systems.

Important resources of the mobile communication system include base station transmit power, orthogonal code (eg Walsh code), base station transceiver subsystem (BTS)-transmission line, base station controller (BSC), vocoder, channel Cards. Among these resources, the call admission control scheme proposed by the present invention is characterized by performing call admission control based on the base station transmit power. Based on the transmission power of the base station, most of the traffic of the mobile communication data service is performed through the downlink or forward link between the base station and the mobile station, and the resource for determining the capacity of the downlink is the base station transmission power. Because it is. In addition, the call admission control scheme proposed by the present invention provides the following types of services in order to not only selectively accept voice services and data services but also to prioritize newly initiated calls of ongoing calls. The call admission control technique is applied differently by dividing into four categories. (1) a newly initiated voice call, (2) a newly initiated data call, (3) an ongoing voice call, and (4) a data call already in progress (ongoing data call).

The call admission control scheme based on the base station transmit power proposed in the present invention is performed when the condition defined by Equation 1 below is satisfied.

Equation 1 is a conditional expression for determining whether a new service request is accepted. The sum of the current base station transmission power (fdch_pwr_sum), power required for a new service (init_tx_gain), and backup power (P _GURRD ) is previously determined. It is determined whether the service request is accepted based on whether or not the set threshold P _ALLOWED is exceeded. That is, the base station of the mobile communication system determines when the call is requested when the condition based on the transmission power of the base station is satisfied, as shown in Equation 1 above.

In Equation 1, fch_pwr_sum is a sum of power used for voice and low-speed data calls and power used for an overhead channel, and may be expressed as Equation 2 below. For reference, in IS-2000, which is a standard of the third generation synchronous CDMA mobile communication system, there is a fundamental channel (FCH) as a voice and low-speed data channel, and a supplemental channel (SCH) as a high-speed data channel. In addition, the overhead channel includes a pilot channel, a sync channel, a paging channel, and the like.

here,

In Equation 1, the init_tx_gain value is an amount of power required for a service for a new call, and includes a coding type (eg, convolutional coding or turbo coding) and a radio resource. The configuration may be set to a different value according to a radio configuration (RC1, RC2, RC3, RC4, RC5), transmission diversity or the like.

In Equation 1, P _GURRD is a guard power in response to a change in base station transmission power according to a dynamic wireless environment. By changing this value, a newly initiated call and an ongoing call ( The priority of an ongoing call can be set differently. P _GURRD can be expressed as the following Equation 3 when the reserve power for the newly starting call and the ongoing call are set differently.

In Equation 3, P _MAX denotes the total amount of transmit power that can be transmitted from the base station, and R _{F_FD_V_NEW_GP} may be expressed as a percentage (%) of P _MAX as a reserve power ratio for a newly started call. In addition, R _{F_FD_V_HANDOFF_GP} is the reserve power ratio for the call already in progress. In general, the relation of (R _{F_FD_V_NEW_GP} > R _{F_FD_V_HANDOFF_GP} ) is established because the priority of the call already in progress is higher than the priority of the newly starting call.

P _{ALLOWED, which} is the left side of Equation 1, may be set as a specific ratio with respect to the total transmission power of the base station as a threshold for accepting a new call. By setting a specific ratio differently for the voice service and the data service, the priority of the voice service and the data service can be set differently, which is expressed in the following equation.

1 is a view for explaining the principle of the call admission control operation according to an embodiment of the present invention, it shows a range of a new accepted call according to the value of the right side of the equation (1).

_Assuming that P _{V_ALLOWED} > P _{D_ALLOWED} is set in FIG. 1, if the value of the right side of Equation 1 is larger than P _{V_ALLOWED} , both the voice call and the data call are not newly accepted, and the value of the right side of P _{D_ALLOWED} is not included. If this is small, both the voice call and the data call are newly accepted. On the other hand, if the value on the right side of Equation 1 is distributed between P _{V_ALLOWED} and P _{D_ALLOWED} values, only the voice call is newly accepted. By applying different threshold values for voice calls and data calls, priority can be given to voice calls and data calls. In addition, when calculating the reserve power P _GURRD included in the value on the right side of Equation 1, the priority of the new call and the call in progress is also different by applying the reserve power for the new call and the call already in progress. can do.

Finally, a call applied according to four different service types ((1) newly initiated voice call (2) newly initiated data call (3) ongoing voice call (4) ongoing data call) by the call admission control scheme described above. When the expressions of the admission control conditions are made, the following equations (5) to (8) are shown, respectively.

2 is a diagram showing the configuration of a call admission control device according to an embodiment of the present invention.

Referring to FIG. 2, the call admission control apparatus of the present invention includes a call request receiver 110, a requested call analyzer 120, and a call accept determiner 130. The call admission control device is a component included in a base station of a mobile communication system. The call request receiving unit 110 receives a call request from a mobile station (terminal) not shown. The requested call analyzer 120 analyzes the requested call when a call request is received by the call request receiver 110. The call acceptance determination unit 130 determines the acceptance of the requested call based on the transmission power of the base station determined according to the analysis result of the requested call. The call acceptance determination unit 130 determines to accept the requested call when the condition of Equation 1 is satisfied. In Equation 1, the threshold is determined by a preset ratio of the total transmission power of the base station. The set rate is set differently for the call for the voice service and the call for the data service. The reserve power is determined differently for each of the newly starting call and the call already in progress. The reserve power for the call already in progress is preferably determined to be greater than the reserve power for the newly starting call. The call acceptance determination operation by the call acceptance determination unit 130 is determined according to the analysis result of the requested call as described above. The call acceptance determination operation according to the analysis result by the call acceptance determination unit 130 is expressed as described in Equations 5 to 8 above.

3A and 3B illustrate a process flow of a call admission control operation according to an embodiment of the present invention.

3A and 3B are performed by the call request receiver 110, the requested call analyzer 120, and the call accept determiner 130 of FIG. It shows the operation flow of call admission control algorithm. The base station determines whether the call is accepted by applying the above-described equations described and described according to whether the received service request is a voice call / data call and a new call / handoff call.

In step 201 of FIG. 3A, the call request receiver 110 determines whether a call request is received. When the call request is received, the call analyzer 120 determines the service type of the requested call in step 202. If the service request call is a voice call, the process proceeds to step 203, and if the service call is a data call, proceeds to step 210 of FIG.

In step 203, the call analyzer 120 determines whether the requested call type is a new call or a handoff call already in progress. If the requested call is a new call, the call acceptance determining unit 130 determines whether the condition of Equation 5 is satisfied in step 204. If satisfied, it is determined to accept the requested call in step 205, and if not satisfied, it is determined to reject the requested call in step 206. If the requested call is a new call, the call acceptance determining unit 130 determines whether the condition of Equation 6 is satisfied in step 207. If it is satisfied, it is decided to accept the requested call in step 208, and if it is not satisfied, it is determined to reject the requested call in step 209.

In step 210, the call analyzer 120 determines whether the requested call type is a new call or a handoff call already in progress. If the requested call is a new call, the call acceptance determining unit 130 determines whether the condition of Equation 7 is satisfied in step 211. If satisfied, it is determined to accept the requested call in step 212, and if not satisfied, it is determined to reject the requested call in step 213. If the requested call is a new call, the call acceptance determining unit 130 determines whether the condition of Equation 8 is satisfied in step 214. If satisfied, in step 209 it is determined to accept the requested call, and if not satisfied in step 210 it is determined to reject the requested call.

B. Orthogonal Code Allocation Scheme

In the CDMA wireless mobile communication scheme, an orthogonal code for distinguishing a traffic link between a base station and a mobile station is typically a Walsh code. In the following the orthogonal code will be described as a Walsh code, but it should be noted that the same can be used for other orthogonal codes equivalent thereto. The Walsh code may be represented in the form of a binary tree having 64 leaf nodes. For example, when using Radio Configuration 4, it has 128 leaf nodes. Table 1 below shows the binary tree-shaped Walsh codes generated by the Hadamard matrix. The Walsh code corresponding to the leaf node is used for voice and 9.6kbps low speed data communication, and the higher node is used for high speed data communication. If a 19.2 kbps data communication is performed, Walsh codes corresponding to two leaf nodes are used, and a 4bit Walsh code corresponding to 16 leaf nodes is required for 153.6 kbps high speed data communication. At this time, if any one of the leaf nodes corresponding to 153.6 kbps Walsh code is in use, the corresponding Walsh code cannot be used. Therefore, if the Walsh code is not managed efficiently, high-speed data communication cannot be performed due to lack of Walsh code due to fragmentation. .

In a mixed voice and high-speed data service, an efficient Walsh code allocation scheme must satisfy the following requirements.

[Condition 1]: Minimize the high-speed data communication service failure due to the fragmentation of Walsh code.

[Condition 2]: Must provide maximum high speed data communication service without affecting voice service.

[Condition 3]: The increase in blocking probability of voice service due to lack of Walsh code allocated for high speed data communication service should be minimized.

In the present invention, the proposed Walsh code allocation scheme allocates Walsh codes based on the following principles to satisfy the above requirements.

[Principle 1]: When the Walsh code for voice and low-speed data communication service is allocated in order to satisfy the condition 1, the Walsh code is allocated in a place where there are many subloads. To this end, a subload corresponding to a subtree must be managed for each Walsh code size. For example, if a subload is managed for each subtree having a Walsh code size of 4 bits, the subload is managed for each subtree corresponding to the Walsh codes 0, 2, 1, and 3 in Table 1 below. Done. Here, assuming that a single Walsh code having a 128-bit Walsh code size is allocated as a unit of a subload value, each subtree has a value between '0' and '32' as a subload value. do. The Walsh code is managed in units of subcells. In general, all base stations transmit overhead channels (pilot, paging, sync) in units of subcells. The Walsh codes occupied by each overhead channel are 64-bit Walsh codes, which are '0' (= pilot), '1' (= paging), and '32' (= sync) times. In this situation, if there is no call except for the overhead channel in a specific subcell, the value of the subload having a Walsh code size of each 4-bit subtree is (4, 0, 2, 0). This can be seen through. In the situation of having such a subload value, two Walsh codes that can be allocated for the SCH of 153.6 kbps transmission rate are '2' and '3'. In this situation, when a new voice call arrives, the Walsh codes corresponding to the subtrees of Walsh codes '2' and '3' are reduced to one Walsh code for 153.6kbps SCH. To prevent this situation, the Walsh codes corresponding to the subtrees of Walsh codes '0' and '1', which cannot be 153.6 kbps SCH due to the overhead channel, rather than the subtrees of Walsh codes '2' and '3', must be allocated. . In order to generalize the above allocation method to prevent the inability to allocate high-speed data service Walsh codes due to fragmentation, the Walsh codes in subtrees with high subload values should be allocated first for FCH channels for voice and low-speed data services. do.

[Principle 2]: In order to satisfy [Condition 2], resource (walsh code, power, etc.) allocation for high speed data communication is performed periodically. At this time, except for resources used for voice and low-speed data services using FCH, resource allocation for high-speed data services using SCH is performed within available resources. To this end, it is necessary to understand the resource allocation state in use for voice and low-speed data services during periodic high-speed data service scheduling.

4 is a diagram illustrating a principle of resource allocation for a high speed data service according to an exemplary embodiment of the present invention. Resource allocation for a high speed data service according to [Principle 2] of the present invention is shown as a time base. This figure shows that Walsh codes are allocated for the SCH except for the Walsh codes being used for the FCH, and a few Walsh codes are reserved for the FCH allocation request that arrives during the scheduling period.

[Principle 3]: In order to satisfy [Condition 3], some Walsh codes are reserved for the voice service request that will arrive during the next cycle when allocating resources for high speed data communication. The number of Walsh codes to reserve is: (1) scheduling period (T), (2) voice service request arrival rate (λ) at the time of the most traffic, (3) voice service blocking probability (B) to be satisfied, (4 ) Can be calculated by the total number of Walsh codes (N), (5) the number of Walsh codes (I) currently being used for voice, (6) the average voice service duration (1 / μ), and the like.

5 is a state transition diagram of voice call arrival / end according to an embodiment of the present invention.

In FIG. 5, the state 'I' means that I Walsh codes are used for voice. Assuming the current state 'I', the voice call blocking probability due to voice call arrival after T hours can be expressed as Equation 9 below.

In Equation 9, B (t) has a value equal to P _iN (t) as a probability of being in state N at time t when it is in state I at time zero. P _iN (t) is represented by the matrix P (t) = P _ij (t) = e ^Qt by the Colmogorov equation. Q is a transition rate matrix, and the Q value for the Markov model of FIG. 4 is expressed by Equation 10 below.

In Equation 10, Q is expressed as a determinant of (N + 1) * (N + 1), but only a part of it is indicated above for convenience. Since e ^Qt is difficult to find by itself, it is generally expressed by the eigen value and eigen vector of Q. Also, the square matrix Q is represented by an eigenvalue matrix and an eigenvector, as shown in Equation 11 below.

In Equation 11, S is a matrix in which each column vector is an eigenvector, and ∧ is a matrix in which a diagonal circle has an eigenvalue and the remaining elements are zero. The characteristic of S is expressed as Q ⁿ = S Λ ⁿ S ^-1 and similarly can be expressed as e ^Qt = S e ^Λt S ^-1 . Where e ^Λt is a determinant such as < Equation 12 &gt;, wherein λ1, λ2, λ3, etc. are eigenvalues of Q.

Finally, P (t) is expressed by the eigenvalues and eigenvectors of Q in the above equation, and the specific values must be solved for higher order equations of (N + 1) order. However, these higher-order equations are not solved by general equations and can be solved by approximate methods such as Newton's method.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

As described above, the effects of the call admission control scheme and the orthogonal code (e.g. Walsh code) allocation scheme in a mobile communication system such as a CDMA communication system in which the voice and high-speed data communication service proposed by the present invention are mixed are as follows. same.

(1) It can provide flexible resource distribution function for voice service and data service.

(2) Provide differentiated resource management services for newly initiated calls and ongoing calls already in service.

(3) The impact of high speed data service on voice service can be minimized.

(4) It is possible to provide the maximum possible high speed data communication service while minimizing the impact on the voice service.

Claims (12)

A method of controlling acceptance of a requested call at a base station of a mobile communication system providing a voice service and a data service, Analyzing the requested call when a call is requested, And determining acceptance of the requested call based on the transmission power of the base station determined according to the analysis result of the requested call. The method of claim 1, wherein determining the acceptance of the requested call comprises: And determining to accept the requested call when the condition of Equation 13 below is satisfied. here, Is a preset threshold, Is the sum of power in use for voice and low-speed data calls and power for overhead channels, Is the amount of power needed to service new calls, Is the reserve power. 3. The method as claimed in claim 2, wherein the threshold is determined by a preset ratio of total transmission power of the base station. 4. The method of claim 3, wherein the set rate is set differently for a call for the voice service and a call for the data service. 3. The method as claimed in claim 2, wherein the reserve power is determined differently for each of the newly starting call and the call already in progress. 6. The method of claim 5, wherein the reserve power for the call already in progress is greater than the reserve power for the newly starting call. A base station apparatus for controlling acceptance of a requested call in a mobile communication system providing a voice service and a data service, A call request receiving unit for receiving a call request; A call analyzer for analyzing the requested call when a call request is received at the call request receiver; And a call admission determination unit for determining acceptance of the requested call based on a transmission power of the base station determined according to the analysis result of the requested call. 8. The apparatus as claimed in claim 7, wherein the call acceptance determining unit determines to accept the requested call when the condition of Equation 14 below is satisfied. here, Is a preset threshold, Is the sum of power in use for voice and low-speed data calls and power for overhead channels, Is the amount of power needed to service new calls, Is the reserve power. 9. The apparatus as claimed in claim 8, wherein the threshold is determined by a preset ratio of total transmission power of the base station. 10. The apparatus of claim 9, wherein the set rate is set differently for a call for the voice service and a call for the data service. 10. The apparatus of claim 8, wherein the reserve power is determined differently for each of the newly starting call and the call already in progress. 12. The apparatus of claim 11, wherein the reserve power for the call already in progress is greater than the reserve power for the new call.