WO2004059892A1

WO2004059892A1 - Access control method in cdma communication system

Info

Publication number: WO2004059892A1
Application number: PCT/CN2003/001111
Authority: WO
Inventors: Dengkun Xiao; Junli Guo
Original assignee: Da Tang Mobile Communications Equipment Co., Ltd.
Priority date: 2002-12-24
Filing date: 2003-12-24
Publication date: 2004-07-15
Also published as: AU2003292868A1; CN1182673C; CN1445952A

Abstract

The present invention relates to a kind of method of access control in CDMA communication system based on value measured actually. New subscriber sends a call request for access; radio network controller (RNC) admits or refuses the access control. The access control includes: supposing the new subscriber can be accessed, directly use the whole base station uplink received and downlink transmitted power value measured actually before the new subscriber accessed to calculate the whole base station uplink received and downlink transmitted power after the new subscriber accessed. comparing the whole base station uplink received power, the whole base station downlink transmitted power and the new subscriber's uplink original power after the new subscriber accessed with their own judge criterion respectively, if all the condition were meet then admit the access if any one of it was not meet, then refuse this can reflect interference of the subscriber needing to access and the actual change of the system load , and can full use of the system capacity with little quick calculation and actually operation.

Description

Technical Field of Admission Control in CDMA Mobile Communication System

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

In a mobile communication system, the call admission (or access) control (CAL) is to solve the problem: when there is a new call or a handover (H0) request, the wireless network controller (RNC) Accept or reject based on certain criteria. After the network accepts a new connection, the quality of service (QoS) of the existing connection and the quality of service of the newly connected user should be met. Therefore, how to maximize the system capacity without affecting the service quality of the connected users has become a major problem to be solved by call admission control.

The CAC problem is a problem that must be solved for both wired and wireless networks. Since the CDMA system is a system with limited interference, its special wireless environment makes the admission problem more complicated.

Before the emergence of ATM technology, the admission control of the wired network was relatively simple, and the network nodes decided whether to accept new calls or not according to the availability of the outgoing line and the buffer. After the emergence of ATM technology, since the network has to undertake the transmission of multiple service shield services, the acceptance of any kind of business user must consider the impact on other business users, so making admission control one of the main technologies of ATM technology .

In a narrowband-code division multiple access (N-CDMA) system, since the network mainly undertakes the transmission of single-level or two-level services, the admission of services can use a threshold-based scheme that is relatively easy to implement or a scheme based on SIR measurement. However, in the case of multi-level services, 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, it must be set Multiple SIR standards to make real-time operation Very complicated.

In the IS-95 CDMA system, most of the CACs adopt an interference threshold-based admission scheme, and often determine the threshold value according to the worst case. If the power of all existing users in the current system exceeds the given threshold, then the new user Will be rejected. This admission scheme based on interference threshold points does not consider the dynamic characteristics of the system, which reduces the capacity utilization of the system and causes a waste of resources. At the same time, it only considers the interference suffered by new users, and does not consider the impact of new user access on the system.

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.

The performance indicators related to admission control technology include call blocking rate, handover blocking rate, and so on. 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, a schematic structure of a TD-SCDMA wireless communication system is shown (only functional modules related to the technical solution of the present invention are shown). The system is composed of multiple user equipments (UEs) 100, multiple base stations (Node Bs) 110, and radio network controllers (RNCs) 120. The user equipment 100 therein can move within different cell ranges of the system. The radio network controller 120 is the core part of the system, and mainly includes three major functional parts: dynamic channel allocation 123, call access control 122, and parameter library 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; the RNC uses a certain algorithm based on the Node B measurement report, UE's carrier-to-interference ratio parameters, and other system parameters (such as the network resource usage measured by the UE). Judge with access criteria, and return the final judgment result, including access or rejection, to Node B, and then Node B to UE. If the message of successful acceptance is returned, it also includes adjustment information for transmission power and information for re-allocation of radio resources for the user equipment 100 (UE) to determine its own initial transmission power and code channel.

In the radio network controller 120, the dynamic channel allocation 123 receives an access request from the base station 110 Message, and determine a higher priority time slot 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 a fast and efficient admission control method for a code division multiple access mobile communication system, which can reflect the interference situation of the users to be accessed in real time and the actual change of the load in the system after accessing the users. Make full use of the system capacity, and have the advantages of small calculation volume, fast calculation speed, and real-time operation.

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 request for admission, and the admission request carries measurements related to admission control The 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 according to the measurement report, the carrier-to-interference ratio parameters of the new user, and other parameters of the system, which is characterized by The admission or rejection admission control further includes:

A. Calculate the total uplink received power and total downlink transmit power of the base station after accessing the new user, and use the total uplink received power and downlink transmit power values measured by the base station before the new user accesses. Initial transmit power

B. Compare the calculated total uplink receive power, total downlink transmit power, and initial uplink transmit power of the new user with their respective power discrimination criteria after accessing the new user;

C. Admission is allowed when all the power discrimination criteria are met, and one is rejected if one of them does not meet the power discrimination criteria.

In step A, the total uplink received power of the base station after accessing a new user is an increase in the total uplink received power actually measured by the base station before the new user accesses and the uplink power of the base station after the new user accesses. The sum of AP _u _ _{k + 1} ; the total downlink transmit power of the base station after accessing the new user is the total downlink transmit power actually measured by the base station before the new user accesses and the initial downlink transmit power after the new user accesses The sum of the incremental APs _{dJ + 1} , k + 1, j + 1 respectively represents new users for uplink and downlink access, u represents uplink, d represents downlink, and P represents power; The uplink initial transmit power = AP _{UJc + 1} I gu_ _{k +} l,, gu_ _{k +} i represents the uplink path loss factor of the new user.

Uplink power increment Δ after the new user accesses

Received uplink interference power

X uplink target carrier-to-interference ratio of the new user; the initial downlink transmit power increase Δ after the new user accesses (downlink interference power received by the new user X downlink target carrier-to-interference ratio of the new user) / path loss of the new user factor.

In step B, comparing the calculated total uplink receive power, total downlink transmit power, and initial uplink transmit power of the new user with the respective power discrimination criteria of the base station after accessing the new user further includes: Under the condition that the total downlink transmit power and uplink receive power of the user remain unchanged at the moment of new user access, determine whether the total uplink receive power of the base station after accessing the new user is less than a given uplink receive power threshold; Whether the total downlink transmit power of the base station after the user is less than a given downlink transmit power network value; and determining whether the uplink initial transmit power of the new user is less than or equal to its uplink transmit power alarm value and greater than or equal to its minimum transmit power.

In the technical solution of the present invention, it is assumed that the total power of the uplink received signal and the total power of the downlink transmitted signal of the existing access user remain unchanged at the instant before and after the new user accesses, and the base station uplink before the new user access can be used. The actual measured values of the total received power and the total downlink transmit power are used to approximately calculate the interference value experienced by the new user after access, so as to obtain the total uplink receive power and total downlink transmit power after the new user accesses. Then use the power discrimination criterion to make a judgment of acceptance or rejection. Therefore, the technical solution of the present invention is an admission control scheme based on actual measurements. The actual measured values are used to directly calculate the total uplink and downlink receive and transmit powers after accessing the user, so it can reflect the real-time requirements of the users to be accessed. The interference situation and the actual change of the load in the system can make full use of the system capacity.

The measurement-based CAC method of the present invention has the following characteristics:

According to the target carrier-to-interference ratio of the new user, the actual measured value of the base station is directly used to calculate the upper limit of the user to be accessed. The total received power and downlink transmitted power and the load of the system after the new user accesses are simple and easy to implement. At the same time, the calculation results can satisfy the new carrier's carrier-to-interference ratio (the ratio of carrier power to perturbation power).

According to the calculation results, it is determined whether the total power of the system after the new user accesses exceeds the power threshold (load threshold) requirement, which avoids overload caused by the new user access.

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

The measured value can reflect the interference and system load of users in the time slot to be accessed in real time

(For the FDD CDMA system, since there is no DCA command for selecting a time slot to be accessed for a new user, its CAC can directly perform admission determination in a designated cell according to the method of the present invention);

Because the actual measurement of the base station is used to approximate the interference of the user, the calculation amount of the system when accessing a new call is reduced, and it is simple, practical, and easy to implement.

In addition, the method of the invention also has the advantages of small calculation amount, fast calculation speed and real-time operation. The working principle of the method designed by the present invention is suitable for all CDMA system chargers. Brief Description of the Drawings Figure 1 is a block diagram of the principle structure of a TD-SCDMA wireless communication system;

FIG. 2 is a basic flow block diagram of the admission control method of the present invention. Mode for Carrying Out the Invention The present invention is described in detail below with reference to the drawings.

The present invention is a fast and efficient CAC method for a CDMA wireless communication system. It calculates the total downlink transmit power and total uplink receive power of a base station after a new user accesses based on actual measured values, and uses load-based discrimination criteria. Admission control for new users.

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

FIG. 2 shows the main flow of the call access control method in the present invention. It can be summarized as follows: Step 200: A new user issues a call request; Step 201: The radio network controller performs admission control in a given time slot according to the call request, and obtains a carrier-to-interference ratio parameter of a new user in a time slot to be accessed and a related measurement value of the network.

Step 202, the following measurement method is adopted, that is, first assume that the new user can access, and directly use the currently measured total uplink receive power value and the total downlink transmit power value of the base station, and after calculating the access to the new user, Total power, total downlink transmission power, and calculating the uplink initial transmission power of the new user;

Step 203: Compare the calculated total uplink receive power, total downlink transmit power, and initial uplink transmit power of the new user with the set standard according to the power discrimination criterion.

Step 204: When the calculated total uplink receive power, total downlink transmit power, and new user ’s initial uplink transmit power of the base station cannot meet the respective set standards (one of them), the base station sends the new user to the base station through the base station. The result of the rejection;

Step 205: When the calculated total uplink receive power, total downlink initial transmit power, and new user's initial uplink transmit power of the base station can meet the respective set standards, the base station and the new user are permitted to receive admission information through the base station. critical result.

The core content of the above steps includes a measurement method and judging whether the calculated total uplink and downlink power in the time slot to be accessed meets the power discrimination criterion according to the calculation result: if it is satisfied, then access is allowed; otherwise, it is rejected.

In the following, the user's uplink and downlink admission calculation process in a TD-SCDMA system is taken as an example to explain the solution of the measurement method of the present invention. The uplink admission process will be explained first.

It is assumed that when a new call arrives, there are already k users in the designated time slot of the designated cell, and the uplink carrier-to-interference ratio of the new user can be expressed by the signal power, noise, and interference (including interval interference and signal power of other users) of the new user. If new technologies such as smart antennas, joint detection, and synchronization are used, the multiple access interference processing factor added before the signal power of other users is less than one. The uplink target load ratio of new users can be expressed as:.

Among them, U represents the uplink, Γ ₊₁ represents the uplink carrier-to-interference ratio of the new user, C represents the carrier power of the new user, and / represents the interference power experienced by the new user. ^ — '= 1 _·· + 1) is the signal power of the ith user received by the base station, / „ _{Jnte +1} is the inter-cell uplink interference power, P _w is the system thermal noise power, and _ _in ^ ₊₁ is the base station The received total interference power to the new user is the processing factor of the system for uplink multiple access interference.

The core of the measurement method of the present invention is that it assumes that the uplink and downlink signal power of existing users in a given time slot of a given cell before and after the new user accesses remain unchanged, so that the interference experienced by the new user can be accessed by the new user. The actual measured values (total uplink received power and total downlink transmitted power) of the former base station are used to approximately calculate the interference value experienced by the new user after access, so as to obtain the total uplink received power and total downlink transmitted power after the new user access. Therefore, the uplink initial transmit power of the new user can be directly calculated from the measured value of the base station (the signal power of the new user received by the base station) and the uplink target carrier-to-interference ratio of the new user. If the carrier-to-interference ratio is taken as the target value, the calculated power will automatically satisfy the new user's carrier-to-interference condition. Based on these two values, the power control module further adjusts the user's transmit power in real time based on parameters such as the carrier-to-interference ratio.

Incremental uplink interference system (delta power) after the new user access caused _ΔΡ "_ ω may represent a new user to a base station received signal power, namely:

AP _U _ _M = uplink interference power received by the new user X uplink target carrier-to-interference ratio of the new user (2) where the uplink interference power received by the new user can be calculated using the measurement value of the base station. Because when the new user accesses, the interference situation may be different from the most recent measurement, the signal power of the new user received by the base station obtained in the above expression is an approximate value.

The calculation of the downlink transmit power is the same as that of the uplink, except that the path loss factor must be considered during the calculation. It is assumed that when a new call arrives, there are already j users in the designated time slot of the designated cell.

After the new user accesses, the system ’s downlink power increment Δ / ^. ₊₁ can be expressed as the signal power transmitted by the base station to the new user:

AP _d _ _M = (downlink interference power received by the new user x downlink target carrier-to-interference ratio of the new user) / Path loss factor for new users (3)

The downlink interference power received by the new user can be calculated according to the actual measurement value of the base station before accessing the new user.

In formula (3), the path loss factor of the new user is between 0 and 1. The term in the right parenthesis of formula (3) is the power expected to be received by the new user. After this term and the path loss factor are taken into account, the power value that the base station should transmit to the new user.

The formula for the downlink target carrier-to-interference ratio for new users is similar to the uplink: T-/ V P d nter + \

¹ d nter, j + " _d . P 4- / ^ _d jw

― = 1

The explanation of the terms in formula (4) is similar to the uplink: where d represents the downlink, represents the downlink target carrier-to-interference ratio of the new user, C represents the carrier power of the new user, and / represents the interference power experienced by the new user. First, '= 1.' ₊ 1) is the signal power transmitted by the base station to the i-th user, / ^ ₊₁ is the inter-cell downlink interference power to access new users, P _w is the system thermal noise power, ^ ₊₁ It is the downlink interference power received by new users after access. a _rf is the processing factor of the system for downlink multiple access interference.

In formulas (1) and (2), the processing factors "„, a _d , when the mobile communication system uses one or all of new technologies such as smart antennas, joint detection, and synchronization, its value is less than 1 or even zero ( When all are used, the processing factor tends to zero); when the system does not all adopt new technologies such as smart antennas, joint detection, and synchronization, its value is 1

The uplink initial transmit power of the new user = AP _U — _{k +} i I g _u — _{k + 1.} It can be known from formula (2) that Δρ „— _ω = uplink interference power received by the new user X uplink target carrier-to-interference ratio of the new user, That is, the initial uplink transmit power of the new user ^^ +

Is the uplink path loss factor for new users.

It should be noted that: assuming that a new user initiates a call at frame X, access to the call is performed at frame X + 1 (using the total uplink received power value actually measured by the base station before the new user does not access, and prediction calculations are required ). Base on the total received power measured by the base station at frame X and frame X-1, predict and calculate the base of frame X + 1 The total received power of the station, and then calculate the interference power caused by the base station if the new user is accessed based on the power value. Therefore, the total uplink received power of the base station after accessing the new user is the sum of the predicted total received power of the base station in the X + 1 frame and the uplink power increase AP _u _ _{k + 1} of the base station after the new user accesses, The uplink power increment AP _u _ _{k + 1} = _¾_ after the new user accesses the total received power at the X + 1 frame X the uplink target carrier-to-interference ratio of the new user.

The power discrimination criteria of the access control method of the present invention are given below. The criteria should ensure that after accessing a new user: 1) The sum of the uplink receive power and the downlink transmit power of the base station to all users does not exceed a given value. The maximum uplink receive power threshold and downlink transmit power threshold; 2) the initial uplink transmit power of a new user cannot exceed its transmit power threshold and cannot be less than its minimum transmit power; 3) assuming that the total downlink transmit power of existing users is The total uplink receive power remains unchanged at the instant of new user access. All three of the above items must be satisfied when judging, namely:

― Totala old '+ ― "Pu— threshold

Pd—totcil—old + ^ d_n jhreshold

Pk + l, m--A

In the formula ¹ ,

/ f _. "Represents the total uplink receive power and downlink transmit power when a new call arrives; A" _ _{i + 1} / AP _{rf i + 1} represents the uplink interference (power) increase and downlink initial transmit power increase caused by a new call, respectively P _tl — _thresh lP _d one by one set the power threshold (load threshold) of the total uplink receive power / downlink transmit power; / W _min / _max represents the minimum transmit power and maximum transmit power allowed by the new user ; G „— _{i + 1} represents the uplink path loss factor of the new user

(In a TD-SCDMA system, the uplink path loss factor of the user is approximately equal to the downlink path loss factor); A represents the redundancy factor of the user's transmit power, and A. ^ _{+ L max} represents the uplink transmit power threshold of the new user .

This criterion is common to all businesses. Among them, the formula (5) (7) is used for the uplink of the new user, and (6) is used for the downlink of the new user.

For various CDMA systems, the uplink and downlink admission control can be performed according to the steps in the embodiment.

Claims

Claim

1. An admission control method in a code division multiple access mobile communication system, comprising: a new user sending an admission request, the admission request carrying a measurement report related to admission control, and a carrier-to-interference ratio parameter for the new user 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 system parameters, which is characterized by the admission or rejection admission control Further includes:

A. Calculate the total uplink received power and total downlink transmit power of the base station after the new user is accessed using the actual uplink received total power and downlink transmit power measured by the base station before the new user is accessed. Initial transmit power

C. When all the power discrimination criteria are met, admission is allowed, and if one of them does not meet the power discrimination criteria, admission is refused.

2. An admission control method in a CDMA mobile communication system according to claim 1, characterized in that: in said step A, the total uplink received power of the base station after accessing a new user is The sum of the total uplink received power actually measured by the base station before the new user accesses and the uplink power increase Δ P _u — _{k + 1} of the base station after the new user accesses; the total downlink power of the base station after the new user accesses, The sum of the total downlink transmit power actually measured by the base station before the new user accesses and the downlink initial transmit power increment AP _d ₊₁ after the new user accesses, where k + 1 and j + 1 represent the uplink and downlink connections, respectively. the new users, u denotes the uplink, d represents downlink, P represents power; the new user uplink initial transmission power _{_{= AP u _ k + 1 /}} g UJc + 1, g u _ k + i represents a new The user's uplink path loss factor.

3. An admission control method in a CDMA mobile communication system according to claim 1, characterized in that: the uplink power increment after the new user accesses 厶? ^ ₊₁ = uplink interference power received by the new user X uplink target carrier-to-interference ratio of the new user; the downlink initial transmit power increase after the new user access Δ P _d ” ₊₁ = (downlink interference received by the new user Power x downlink target carrier-to-interference ratio for new users) / path loss factor for new users.

4. An admission control method in a CDMA mobile communication system according to claim 3, characterized in that: the uplink target carrier-to-interference ratio Γ _¾ " _{+1 of} the new user is calculated using the following formula:

C P .. k P .. k + \

∑ p

k P. p M „int er, & + 1

ru_i ^Γ Ν

(= 1

The downlink target carrier-to-interference ratio of the new users is calculated using the following formula

C represents the carrier power of the new user, / represents the interference power experienced by the new user, and P _UJ is the uplink and downlink signal power of the ith user received and transmitted by the base station, i = l -k + l and i = l ... I _{u nterMl} / ^ is the inter-cell uplink and downlink interference power to the new user, P _w is the system thermal noise power, and _{Α + 1} and Α_ ^ are the power of the new user received and transmitted by the base station, respectively. ― _{Int +1} and ^ _int ^. ₊₁ are the total interference power to the new user received and transmitted by the base station, respectively, and a „a _d is the processing factor of the system for uplink and downlink multiple access interference.

5. An admission control method in a code division multiple access mobile communication system according to claim 4, characterized in that: when the system adopts one or all of smart antenna, joint detection, and synchronization technologies, the new user In the formula for calculating the uplink target carrier-to-interference ratio and the downlink target carrier-to-interference ratio, the system's processing factor for multiple access interference is less than 1; When the smart antenna, joint detection, and synchronization technologies are not adopted, the calculation formula of the uplink target carrier-to-interference ratio d and the downlink target carrier-to-interference ratio 1 of the new user is as follows: 1.

6. An admission control method in a CDMA mobile communication system according to claim 1, characterized in that: in said step B, the total uplink uplink power received by the base station after accessing the new user is calculated , The total downlink transmit power, and the uplink initial transmit power of the new user compared with their respective power discrimination criteria further include: assuming that the total downlink transmit power of the existing user and the total uplink receive power remain unchanged at the instant of new user access Determining whether the total uplink receiving power of the base station after accessing the new user is less than a given uplink receiving power threshold; determining whether the total downlink transmitting power of the base station after accessing the new user is less than a given downlink transmitting power threshold; and determining a new Whether the user's uplink initial transmit power is less than or equal to its uplink transmit power threshold and at least equal to its minimum transmit power.

.

The admission control method in a CDMA mobile communication system according to claim 6, characterized in that: said judging whether the uplink initial transmit power of a new user is less than or equal to its uplink transmit power threshold and greater than Equal to its minimum transmit power is determined by

Δρ

The formula A ₊₁ , _min ≤ ~ ^ ≤A · ₊₁ , the '' in the drawing indicates the minimum transmission power of the new user k + 1, P _{k + 1} indicates the maximum uplink transmission power of the new user k + 1, and the new user k +1 uplink path loss factor, AP _u — _{k + 1} represents the increase in uplink power caused by a new user k + 1 call, A represents a redundancy factor for the transmit power of the new user, and Α · ^, represents the new user ’s Uplink transmit power threshold.