WO2004068759A1

WO2004068759A1 - A method of call admission control in coma mobile communication system

Info

Publication number: WO2004068759A1
Application number: PCT/CN2003/001112
Authority: WO
Inventors: Dengkun Xiao
Original assignee: Da Tang Mobile Communications Equipment Co., Ltd.
Priority date: 2002-12-24
Filing date: 2003-12-24
Publication date: 2004-08-12
Also published as: CN1172473C; AU2003296203A1; CN1445951A

Abstract

The present invention relates to a method of call admission control in CDMA mobile communication system, it is based on the method of matrix calculatation. A new user sends a call request for requesting admission; the radio network controller performs the admission control including acception and reject. The admission control includes: taking the expression of total power for all user signals in the cell and access slot in which the new user is located P0(A)-1, Iinter; judging whether solving the adverse matrix (A)-1; if the adverse matrix (A)-1 cannot be solved, the system will reject the new user; if the adverse matrix (A)-1 can be solved, further calculate the uplingk receiption total power and downlink transmission total power of the base station which is accessed by a new user, as well as the uplink initial transmission power of the new user, and compare the power judgement criterion of each other; if all the power meet the power judgement criterion, allowing admission, if one of the above mentioned don’t meet the power judgement criterion, the rejecting admission. The system can meet the SIR condition automatically, simplify the openloop power control of the system, reduce the burden of the radio network controller and reduce the process of the signalling.

Description

Admission control method in CDMA mobile communication system

Technical field

The present invention relates to mobile communication technology, and more particularly to an admission control method in a code division multiple access (CDMA) mobile communication system. The working principle of the method of the present invention can be applied to all code division multiple access mobile communication systems. Background of the invention

The call admission (or access) control (CALC) problem is a problem that must be solved for both wired and wireless networks.

In a mobile communication system, the problem that CAC needs to solve is: When a new call or a handover (H0) initiates a request, the radio network controller (RNC) accepts or rejects it according to certain criteria. After the network accepts the new connection, the amount of user service shield (Quality of Service, QoS for short) of the existing connection and the quality of service of the user of the new connection should be met.

C. A is a modulation and multiple access technology based on spread-spectrum communication. In a CDMA communication system, a base station and a user equipment use the same radio frequency band. As a system with limited interference, its special wireless environment To make the admission problem more complicated, how to maximize the system capacity without affecting the quality of service of connected users has become the main problem to be solved by call admission control.

Before the emergence of ATM technology, the admission control of the wired network was relatively simple, and the network nodes decided to accept new calls based on the outgoing line and the occupancy of the buffer. After the emergence of ATM technology, since the network has to undertake the transmission of multiple quality of service services, the acceptance of any one type of service user must consider the impact on other service users. Therefore, admission control has become one of the main technologies of ATM technology.

In N-CDMA (narrowband-code division multiple access) systems, because the network is mainly responsible for single-level or For the transmission of two-level services, the acceptance of services can adopt a relatively easy-to-implement threshold-based solution or an SIR (or uplink-to-downlink carrier-to-interference ratio, that is, the ratio of carrier power to interference power) measurement, but in multi-level services In the case of these solutions, these solutions will face many difficulties: Because different services have different QOS characteristics, if a threshold-based solution is adopted, multiple thresholds must be set; if a SIR measurement-based solution is adopted, multiple SIR standards must be set, This complicates real-time operations.

In IS-95 CDMA systems, CAC mostly adopts interference threshold-based admission schemes, and often sets the threshold value according to the worst case. If the power of all existing users in the current system exceeds the given threshold, the new user will Will be rejected. This interference threshold-based admission scheme does not consider the dynamic characteristics of the system, which reduces the capacity utilization of the system, resulting in waste of resources. In addition, because the user's signal-to-interference ratio is not considered during access, the SIR parameters of all users cannot be guaranteed. Can be satisfied.

In principle, the acceptance in the static environment is the capacity domain, but for a long time, the capacity research of the system has been limited to the static environment, and the admission control study must consider both the static environment and the dynamic environment during handover. Consider the operability of the solution.

When the CAC initially accesses the terminal equipment (UE), establishes a radio bearer, switches over, and the UE in the connected mode needs to add services, it invokes the corresponding algorithm to make or accept or reject according to parameters such as QoS and radio resource usage. judgment. Under different system characteristics and network operation environments, different access control schemes can be adopted.

The performance indicators involved in admission control technology include call blocking rate, handoff blocking rate, and call drop rate. In theory, the key technologies involved in CDMA have an impact on admission control. Among the most closely related technologies are power control, resource allocation, handover, and topology.

Referring to FIG. 1, the schematic structure of a TD-SC response A wireless communication system is shown (only functional modules related to the technical solution of the present invention are given). The system is composed of multiple user equipments (UEs) 100, multiple base stations (Node Bs) 110, and radio network controllers (RNCs) 120. Users The device 100 can move within different cell ranges of the system. The radio network controller 120 is a core part of the system, and mainly includes three major function parts: dynamic channel allocation 123, call access control 122, and parameter database 121, which are framed by dashed lines.

The process of the system for admission control is: the user equipment 100 (UE) sends a call request to the network side (radio access network RAN) through the base station 110 (Node B), and the call request carries a measurement report related to access control And carrier-to-interference ratio parameters; Node B reports measurement reports related to admission control; RNC according to the ode B measurement report, UE's carrier-to-interference ratio parameters, and other system parameters (network resource usage measured by the UE, etc.) The algorithm and the access criteria are used to judge, and the final judgment result, including access or rejection, is returned to the Node B, and then the Node B is returned to the UE. If the message that the admission is successful is returned, it also includes the adjustment signal for the transmission power and the information on the reallocation of the radio resources, so that the user equipment 100 (UE) determines its own initial transmission power and code channel.

In the radio network controller 120, the dynamic channel allocation 123 receives the access application message sent by the base station 110, and determines a time slot with a higher priority as the user's access time slot. The parameter library 121 contains three types of parameters: channel model parameters, service model parameters, and system model parameters. The parameter database 121 refreshes parameters in the network according to the measurement reports of the user equipment 100 and the base station 110. The call access control 122 performs an admission decision in the time slot selected by the dynamic channel allocation 123 according to the network parameters in the parameter database 121, and returns the decision result to the dynamic channel allocation 123. The dynamic channel allocation 123 sends a return message of the access application to the base station 110 according to the decision result. Summary of the Invention

The purpose of the present invention is to design an admission control method for a CDMA mobile communication system. While making an admission or rejection decision for a new user call, it can satisfy the SIR parameters of all users, and can also directly obtain access for new users. All users in the system (including connected users and New user), and obtain the initial transmit power that meets the new user's carrier-to-interference ratio.

The technical solution for achieving the purpose of the present invention is as follows: An admission control method in a code division multiple access mobile communication system includes: a new user sends a call request requesting admission control, and the call request is associated with admission control According to the measurement report, the carrier-to-interference ratio parameters of the new user, and other parameters of the system, the radio network controller performs admission control including admission or rejection, It is characterized in that said admission control of admission or rejection further includes:

A. Under the assumption of the new user to access, the user is to take a new cell where access slot by the expression of a column vector signal power of all users existing composition of the new user / ^) ^--1 ./^, where A is a coefficient matrix related to the total number of access users and their target carrier-to-interference ratio, and the vector I _in r describes the interval interference experienced by all access users;

B. Determine whether the inverse matrix Y of the coefficient matrix A can be solved;

C When the inverse matrix of the coefficient matrix A cannot be solved) ^-1 , the system refuses to accept the new user;

D. When the inverse matrix of the coefficient matrix A can be solved, further calculate the total uplink received power of the base station after accessing the new user, the total downlink transmission power, and the initial uplink transmission power of the new user, and compare with the respective power discrimination criteria;

E. When all the power discrimination criteria are met, admission is allowed, as long as one of the power discrimination criteria is not met, the admission is refused.

In the step A, the expression of the signal power of the access user includes the signal power received by the base station in the uplink case including the existing user and the new user, and the signal power transmitted by the base station in the downlink case to the existing user and the new user. The signal power of the new user is P „= (4) — ^. And p _d- {A _d y-^^ u means uplink, and d means downlink; In step B, it is judged whether the inverse matrices J- ¹ and (A) ^-1 can be solved, respectively;

In step C, when the inverse matrix () ^-1 or () ^-1 cannot be solved, the system refuses to accept the new user;

In step D, when the inverse matrices ¹ and ¹ can be solved at the same time, the step is continuously performed.

The method of the present invention uses a matrix method (hence the CAC method based on matrix calculation) to calculate The uplink receive power and the downlink transmit power adopt the discrimination criterion based on the load (power threshold) to control admission or rejection. In the matrix, the target carrier-to-interference ratio of each user is used to participate in the calculation, so that the carrier-to-interference ratio of all users is satisfied; the decision criterion is to meet the system load limit as the goal, so it can meet the system load requirements.

The method of the present invention has the following characteristics: The adopted matrix method can directly calculate a new power balance point for all users (including connected users and new users) in the system after the new user is accessed; Than the initial transmit power of the condition. Before solving the user signal power expression P = (AY-l _mr , first solve the inverse matrix of the coefficient matrix A (AY, when it cannot be solved, reject it without continuing to calculate the power P, which simplifies the admission control process.

The advantages of the matrix method and the power discrimination criterion in the present invention are:

It can guarantee the carrier-to-interference ratio parameters of the connected users. The matrix method combines the carrier-to-interference ratio parameters of all users with the calculation of the transmission power. The calculated transmission power must meet the user's SIR, thereby reducing the access due to new calls The rate of dropped calls; it can reduce system overhead after access.

The method of the present invention not only calculates the initial downlink transmission power for the new user and the uplink transmission power for the new user, but also obtains the cell where the new user is located (the time when the TDD system is located). Gap) Power balance point for existing users. Brief description of the drawings

Figure 1 is a schematic block diagram of the TD-SCDMA wireless communication system

FIG. 2 is a basic flow block diagram of the admission control method of the present invention. Mode of Carrying Out the Invention

The matrix-based CAC method embodies the idea that the SIR value of each connected user and new user can use the user ’s own useful signal strength, noise, and interference (including inter-cell interference and other users ’signal strength The user). Considering: The value of noise is small and can be ignored; Inter-cell interference changes very slowly (If new technologies such as smart antennas, multi-user detection, and uplink synchronization are used, the interference value will be small, which is reflected in the multi-access interference processing factor „All features are less than .1. If these new technologies are not adopted, the multiple access interference processing factor is 1). Therefore, the signal power of each user can use its carrier-to-interference ratio, inter-cell interference, and the same Signal power of other users in the time slot.

The above line situation (represented by u) is taken as an example. By synchronizing the power expressions of all users in the same time slot and sorting them out, the equation of the coefficient matrix A of the following formula (1) can be obtained:

Α · P = Ι „int (1)

Where

It is assumed that when a new user's call arrives, k users have been accessed in the designated time slot of the designated cell, and the new user is the k + 1th user. In the above formula, „is the system's processing factor for multiple access interference, and it is the target value of the uplink carrier-to-interference ratio (SIR) of the i-th user (i-1, .., k + 1), and the service type Related, such as voice, video, etc., a service type corresponds to a constant. In the above formula, the coefficient matrix reflects the system's ability to suppress interference and the SIR requirements of each user, where the elements on the diagonals in each row represent the The user's SIR requirements, other elements indicate the system's ability to suppress interference, all are -1. The vector / „represents the interval interference received by the base station and can be measured. For all users, this value can be considered constant. The vector P represents the sum of the signal powers of all users received by the base station. (K + 1) (k + 1) indicates that the matrix has (k + 1) rows and (k + 1) columns, and (k + 1) X 1 indicates that the matrix has (k + 1) rows and 1 column. Where T indicates that the matrix is transposed.

The solution idea of the downlink and uplink is the same, but the meaning of the vector P is different. For the uplink case, P represents the signal power of each user received by the base station; for the downlink case, P represents the signal power transmitted by the base station to each user. In the downlink, the equation of the coefficient matrix A also takes into account the path loss factor.

In the case of the downlink (represented by d), by combining the power expressions of all users in the same time slot and sorting them out, a matrix equation of the following formula (2) can be obtained:

= (2)

Where

It is assumed that when a new user's call arrives, j users have been accessed in the designated time slot of the designated cell, and the new user is the j + 1th user. In the above formula, £ ^^ [01] is the UE's processing factor for multiple access interference. "The value is a symbol for sgn." Is the target value of the downlink carrier-to-interference ratio (SIR) of the i-th user (i = l ... j + l), related to the service type, such as voice, video, etc., one service type corresponds to a constant.

The signal power sent by the base station to user i; g _rf — is the path loss factor from the base station (Node B) to the i-th user; received for the i-th mobile terminal user (UE) in the specified access slot Interval interference values (i = l ... j + 1) can be measured. (j + 1) X (j + 1) indicates that the matrix has (j + 1) rows and (j + 1) columns, and U + 1) xl indicates that the matrix has (j + 1) rows and 1 column. The superscript T in the formula indicates that the matrix is transposed.

By formula (1) (2), the signal power of all users in the same time slot of a cell can be obtained by solving formula (3):

If the carrier-to-interference ratios in matrix A are taken as their respective target values, the resulting vector P will automatically satisfy the user's carrier-to-interference conditions.

By solving the inverse matrix of ^)- ¹ , it can be determined whether the system can reach a new dynamic power balance point after adding a new user. If (^)- ¹ cannot be solved (that is, the inverse matrix does not exist), it means that the system cannot accept The user refuses to accept; if ^)- ¹ can be solved, it is necessary to further determine whether the transmit power of the new user exceeds the maximum transmit power allowed by the user, and determine the total uplink receive power and downlink of the base station after accessing the new user. Whether the total transmission power can meet the set power threshold, and the user is allowed to be admitted only when all the above conditions are met. Up In the above-mentioned judgment, in the process of judging whether the inverse matrix) ^-1 exists, it also includes separate judgments in the uplink and downlink cases. Only when the inverse matrix exists in both the uplink and downlink cases, the next step is performed. In subsequent judgments, if one does not exist, the new user is rejected.

When the inverse matrix) ^-1 (uplink, downlink) can be solved, according to the access criterion of the present invention, whether to allow admission is determined.

An application example of the method of the present invention in a TD-SCDMA system (structure in FIG. 1) will be described below, and the present invention will be further described with reference to the accompanying drawings.

Referring to FIG. 2, the main flow of the call access control method in the present invention is shown. The call admission control method can be summarized as the following steps:

Step 200: Receive a DCA command, that is, a given CAC time slot and a command for determining admission in this time slot;

Step 201: Obtain a carrier-to-interference (or SIR) parameter of a connected user and a newly accessed user in a time slot to be accessed, and a related measurement value of a network;

Step 202: Assuming that new users can access, use a matrix method to calculate the total uplink receive power of the base station after all users (including connected users and new users) have accessed, the total downlink transmit power of the base station, and the uplink initial transmit power of the new user. ;

Step 203: The calculated sum of the uplink signal powers of all users received by the base station, the base station compares the sum of the downlink transmission power of all users and the initial uplink transmission power of the new user with their respective power discrimination criteria, and both meet the criteria. When the access is allowed (step 205), one of them does not meet the discrimination criteria and refuses (step 204, waiting to accept the next DCA command λ) The power discrimination criterion of the access control method of the present invention should ensure that after accessing a new user: 1 ) The sum of the uplink receive power of the base station to all users does not exceed a given uplink power threshold, and the uplink transmit power of the user does not exceed its own uplink transmit power threshold and is not lower than its own minimum transmit power; 2) the base station to all users The sum of the downlink transmit power does not exceed the given The downlink power threshold; 3) The uplink and downlink powers of existing users after accessing new users are recalculated according to their respective target carrier-to-interference ratios. This criterion is common to all businesses.

k + l

Pu—threshold (4) + i

Corpse '' Pd threshold (5),

p _UJmsMd lP _dJhreshold represents the power threshold (load threshold) of the total uplink power received by the base station / the total downlink power transmitted by the base station. p _{i + l min} is the minimum transmit power allowed by the new user, and is the maximum transmit power allowed by the new user. _ω is the signal power of the new user received by the base station, is the uplink path loss factor of the new user, Α is the redundancy factor of the transmission power of the new user, and β _χ . ₊₁ , _max is the uplink transmission power threshold of the new user.

Formulas (4) (6) are used for the uplink, and (5) are used for the downlink.

The access control method of the present invention uses a matrix-based method to calculate the uplink and downlink receive power and transmit power after accessing a new user, and calculates the initial transmit power of a new user. The target carrier-to-interference ratio of all users in the gap is the premise of calculation, so the calculation results obtained automatically meet the carrier-to-interference condition. If a new call can be accessed, both the uplink power it sends to Node B and the downlink power it sends to it can be easily calculated. By adopting the method of the present invention, the open-loop power control of the system can be simplified, the burden on the RNC can be reduced, and the network signaling process can be reduced.

The working principle of the matrix-based calculation method of the present invention is suitable for all CDMA systems. In the case of FDD CDMA, since there is no DCA command for selecting a time slot to be accessed for a new user, its CAC can directly perform admission control in a designated cell according to the method of the present invention (including calculation of power and discrimination criteria).

Claims

Claim

1. An admission control method in a code division multiple access mobile communication system, comprising: a new user sending a call request requesting admission control, wherein the call request carries a measurement report related to admission control, and a new user's carrier Ratio parameter and other parameters of the system; the radio network controller performs admission control including admission or rejection according to the measurement report, the new user's carrier-to-interference ratio parameter, and other parameters of the system, and is characterized by the admission or rejection Admission control further includes:

A. Under the assumption that new users can access, take the column vector expression P = (AY · I _inter , where A is a coefficient matrix related to the total number of access users and their target carrier-to-interference ratio, and the vector I _int „describes the interval interference experienced by all access users;

B. Determine whether the inverse matrix of the coefficient matrix A can be solved) ^-1 ;

D. When the inverse matrix of the coefficient matrix A can be solved)-†, further calculate the total uplink receive power, the total downlink transmit power, and the initial uplink transmit power of the new user after accessing the new user, and perform the calculation with the respective power discrimination criteria. Comparison

E. Admittance is allowed when all the power discrimination criteria are met, and as long as one item does not meet the power discrimination criteria, admission is refused.

The admission control method in the CDMA mobile communication system according to claim 1, characterized in that: in the step A, the expression of the signal power of the access user includes a base station in an uplink case. The received signal power including the existing user and the new user, and the signal power transmitted by the base station to the existing user and the new user in the downlink case are '= (4) —' ^ and Α =) — ' Λ- _inte ,., U represents uplink, d represents downlink; In the step B, it is determined whether the inverse matrices (4) ^-1 and (Λ) ^-1 can be solved;

In step C, when the inverse matrix or ()-^^ cannot be solved, the system refuses to accept the new user;

The admission control method in a CDMA mobile communication system according to claim 2, characterized in that: in said step A, in the uplink case, the coefficient matrix and the signal power of all users received by the base station And interval interference are:

A, =

-1 (¾ + 1><1

^ ut er _int er \ '_ int er2 ^ "_ int er {k + \) / (^ + i ^ i where k + 1 is the new user, α„ is the processing factor of the system for multiple access interference, is the i-th The target value of the uplink carrier-to-interference ratio of each user; A, is the signal power of user i received by the base station, / „— _in , _v . Is the interval interference value of the i-th user, i = l ... k + 1; downlink In this case, the coefficient matrix, the signal power transmitted by the base station to all users, and the interval interference are:.

pd = (p _d ,, ΡΛ ― V, SOl々 ₊ i) where j + 1 is the new user, a _rf is the system's processing factor for multiple access interference, _, is the target value of the downlink carrier-to-interference ratio of the i-th user, and is sent by the base station to signal power of user i; is the loss from the base station to the i-th user path factor; / _d _ _in, the downlink inter-cell interference value of the i th user suffered, i = l .. j + l ...

4. An admission control method in a CDMA mobile communication system according to claim 1, characterized in that: in said step D, the total uplink received power of the base station after accessing a new user is calculated and discriminated from the power The criteria are compared using the formula P „— _; ^.

P _UJ is the uplink power of the i-th user received by the base station, i =:. K + l, Pn ,,. _w is the set received power threshold of the base station after accessing the new user; calculating the total downlink transmit power of the base station after accessing the new user and comparing it with the power discrimination criterion is performed using the formula P _d P _{d lhresh} , P _rf Is the downlink transmit power of the base station to the i-th user, i = l ~ j + l, P _d — the first is the threshold of the downlink transmit power of the base station after accessing the new user; calculating the uplink initial transmit power of the new user, and The comparison with the power discrimination criterion is to use the formula _{A + l min}

Carried out, _w _ _min new user is allowed minimum transmit power, the new user is the maximum allowed transmit power,; ^ i is the new user station received signal _power, g "- ω is the new uplink user The path loss factor, Α, is a redundancy factor for the transmission power of the new user, β, ■ Α _{+ 1} , and is the uplink transmission power threshold of the new user.