TW462161B - Method in a telecommunication system - Google Patents

Abstract

The present invention relates to a method for downlink power control in the base station of a code division multiple access (CDMA) communication system. The total assigned downlink power from the base station is adjusted to a maximum downlink power level by means of individually adjusting the assigned bit rates of an appropriately selected subset of downlink channels to those users having a data communication connection. Said subset is retrieved by applying suitable selection criterions for the downlink channel, e.g., the momentarily assigned bit rate, the reported pathloss, or the user subscription type.

Description

V. Description of the invention (π Scope of the invention The present invention relates to a method of a telecommunications system, and more particularly to a method for controlling downlink power in a base station of a code division multiple access (CDMA) communication system. Background of the invention In the road access (CM A) communication system, many base stations cover each geographical area and provide communication services for users in this geographical area. The characteristic of the CDM A system is to share a common transmission medium among different users. The method is: Assign special and unique code sequences to the uplink and downlink channels between the base station and user equipment. These code sequences are used by the transmitter to transform the signal into a wideband spread spectrum signal. In the receiver unit, base station or user equipment, since The wideband signal of a particular transmitter is converted into the original bandwidth using the same code sequence of the transmitter, while signals with different mines are retained as wideband signals. Therefore, the receiver interprets it as part of the background noise A special problem of the multiple access technology used in CD M A is that all users are transmitting broadband signals simultaneously and using the same bandwidth. Therefore, one of the limiting factors in the CDMA reference system is the reduced signal-to-noise ratio in the communication channel, which is due to the increased interference level caused by other transmitters. The signal interference level of each unit is from that It is caused by the transmitter of the unit and the transmitter in the nearby unit. Therefore, it is very obvious that the power control of the uplink signal and the downlink signal is very important in order to achieve a large system capacity and high service quality. The meaning is, For uplink signals, the transmission power of the user equipment must be controlled to avoid users close to service stations and users who are far away, and to limit the acceptable interference

Five 'invention description (2) has the largest number of users. For the following lines, signal power control is also necessary, that is, to minimize interference to other units and to compensate for interference from other units. In this way, the base station can perfectly serve users at any address in the cell without having a strong influence on the interference level of neighboring cells. Another important fact of downlink power control is that increasing the power value can lead to an expansion of the signal spectrum. Therefore, in order to avoid the extension of the spectrum of the total downlink signal beyond the permitted range, the range is reserved for downlink signals of the CDMA-based communication system, and the total power allocated to the downlink of the base station must be limited. Therefore, the downlink transmission power of the base station is a limited resource, so there must be a method to allocate an appropriate power level to each downlink so that the total allocated power is below the maximum power level. One of the answers to this downlink power control is to distribute the maximum downlink power to each user in a fixed way. The sum of the allocated power levels is below the maximum threshold. This allows the maximum power level to be exceeded, but due to the lack of flexibility, it still leads to a crisis of poor system capacity. SUMMARY OF THE INVENTION A first object of the present invention is an effective method for managing the resources of a base station's downlink. Another object of the present invention is to provide a method for allocating power to the downlink channels of these users with established data connections in a system with limited downlink power. Below the maximum allowed downlink power level. Another object of the present invention is to achieve a method for allocating the downlink power and adjusting the individual available downlinks of each downlink user data channel

4 6 2 16 1 V. Description of the invention (3) Power level. Another object of the present invention is to achieve a method to limit the total allocated downlink power without degrading the transmission quality of downlink user data channels. In short, these objects of the present invention can be achieved by a method that periodically implements a total distribution of downlink power and evaluates it based on radio environmental parameters and the bit rate of the downlink user data channel application. If the allocated power exceeds the maximum allowable downlink power threshold, the bit rate of the user data channel is adjusted. The invention is based on the idea that the transmission power of each downlink user data channel of the base station is related to the transmitted signal energy and the transmission bit rate. Therefore, the allocated downlink transmission power can be controlled by adjusting the signal energy or the transmission bit rate of a channel or a group of channels. The first advantage of the present invention is that the base station can manage the allocated downlink power. , Without exceeding the maximum allowed downlink transmission power. Another advantage of the present invention is that the distributed power can be adjusted based on individual user needs or network conditions without degrading channel quality. Another advantage of the present invention is to take advantage of the reduced interrupted call rate to improve the service coverage of the user. The downlink power allocated to the user data channel can be adjusted so that the number of users receiving good service quality increases significantly. Yet another advantage of the present invention is related to optimized information output and / or system capacity. These advantages, objects and novel features of the present invention will be clearer from the following detailed description and consideration of the drawings and the scope of patent application. Simple illustration of the schema

Page 7 4 6 2 1 6 1 V. Description of the invention ¢ 4) For a better understanding, please refer to the following drawings and preferred specific examples of the present invention. Figure 1 is an overview of a CDMA-based communication system, and in particular a unit including many user equipments served by a base station. FIG. 2 illustrates a specific example of the present invention. The allocated downlink power is adjusted by adjusting the bit rate, which is assigned to different downlink user data channels. Figure 3 shows a flowchart of the method of the present invention. Detailed description FIG. 1 shows a CDMA base radio communication system, which is divided into a number of units, each equipped with a base station 12 to provide communication services, that is, voice and data connections to and from user equipment 13a within the coverage area of the base station -13d. The present invention relates to user equipment 13a-13d from a downlink channel 14a-14d of a base station 12 to an established data connection. It specifically concerns the control and effective power distribution of the downlink channels that have applied for the data connection. For the base station 12, the downlink power PQUt that must be allocated in order to serve a certain number of user equipments 13a-13d in its unit can be represented by N Μ P〇ut-speech ^ i.data ^ ^ max ' The total assigned downlink power PQ1: t is the sum Pi of the transmitted power, and this sum is allocated to N downlink language channels and M downlink user data channels. The power allocated to Type 2 downlinks cannot exceed the maximum permitted downlink power level, Praax. This maximum power level is adjusted by the above-mentioned non-ideal spread spectrum. But PMX can also be defined as lower than the actual system

6 2 16 1 No. 88120440 July, fo Revised The target power level of the critical value related to the load. In this way, the total allowed downlink power can be used for a sufficiently high system capacity, and the target value can be reduced when there is less talk. Because the language connection must meet certain requirements, and a certain amount of Pspeeeh of the allowed downlink power Pmax is allocated in advance, the allowed downlink power source is reserved for the maximum available amount of downlink user data channels, and N downlink languages The channel changes. Therefore, the total downlink power of each user channel must be adjusted so as to stay below the maximum available amount of downlink power. Within the scope of the present invention, the allocated power Pi, data of each downlink user data channel is represented by the transmitted signal energy and transmission bit rate Ri of each bit E 丨, ie f Μ Σ ^ i.dale ^ Eh. R ., The first characteristic of the present invention is related to the fact that the total allocated downlink power PQut of the base station 12 can be adjusted to the maximum allowed downlink power Pmax, and it is better to adjust each downlink user data channel individually. Power level Pi.data, not the static maximum downlink power level for these channels. This means that each downlink subscriber data channel adjusts the amount of allocated power according to its special needs. The demand mainly depends on the needs of the individual users 13a-13d and the conditions of the radio environment of the channel. Other requirements may be related to total network utilization, that is, to system capacity and data output. The impact of individual users of the data connection is usually on the type of subscription, that is, on the services that can be disposed of and the quality of the services guaranteed. The environmental parameters that must be considered in relation to radio propagation conditions are general terrain characteristics and different kinds of obstacles, i.e. trees 15 or buildings 16 which can affect radio channels. by

O: \ 61 \ 6M13.ptc Page 9 2001.07.12. 009 4 6 2 16 1 V. Description of the invention (6) For some users it must be due to the environment, especially the self-service base station in the neighboring unit. The first part of the invention, its channel, but still in a flexible way, the data channel of the present invention can be changed by one or more to adjust the signal for power reduction because the frame can be output incorrectly. Therefore, the increased mobility of the transport bits 1 3 b on the better side of the boundary can quickly change and adjust the environmental parameters. Other effects are caused by the overall signal interference level, this noise or transmission from other users in the unit, this on the unit boundary, user equipment 13d may be easily from the base station 1 7 a, 1 7 b or user 18 Affected by signal interference, the quality of downlink channels may be degraded. Therefore, according to the -characteristic method, the maximum available downlink power can be used to provide individual data traffic to downlink user data. Within the limits of the permitted downlink power Praax, the above-mentioned change requirements can still be achieved. The second characteristic is related to the fact that Plidata, which is used to allocate power for each downlink user, can be adjusted by two different schemes: one is the bit energy Eb .; of the transmission signal of the downlink channel, the level. However, when the reduced power value causes the radio channel to degrade due to the -interference ratio Eb / IQ, this solution can increase the number of cases poorly, and reduce the amount of data caused by encapsulation and retransmission. The call interruption rate of units with low signal power levels will increase. Another solution is the proposal, which will adjust one or more downlink user data channel rates R; 'while the signal power is kept at a sufficiently high level * to maintain a certain target signal-to-interference ratio R, / 10. When the bit ratio is reduced, this solution also results in reduced data output; however, the transmission bit rate can be adjusted according to actual needs, while the transmission error remains unchanged. This solution is more convenient and causes fewer extra signals.

1 11__Country 1 liBHl 1 II Page 10 4 6 2 16 1 5 'Explanation of the invention (7) Figure 2 shows in the first figure the total allocated power P of a base station in the downlink. " is a function of time. The allocated downlink power includes downlink power allocated to the language connection Pspeeeh, and downlink power allocated to all data connections Pdata. To comply with the first characteristic of the present invention, the method of the present invention intends to individually adjust the power level of the downlink user data channel within the maximum available power range that can be used for data traffic. The force method is to evaluate the data channel bit rate and assign the downlink power pcut to the original setting, and control the power at a certain time t i. When necessary, the bit rate is adjusted repeatedly to conform to the second characteristic of the present invention. Such as the total allocated downlink power P. ^ Exceeds the maximum allowable downlink power level P „ax a certain value 2 1 1 as shown in the time interval (乜, ti + 1). The adjustment of the downlink user data channel shows the threshold level Pmax. Restriction. Similarly, as long as the allocated downlink power remains below a certain value of the allowed power level 2 2 1, as shown in the time interval (t), tm, the remaining power can be additionally allocated to the downlink Line user data channel. Another feature of the present invention relates to a method for selecting an appropriate downlink data channel that needs to be adjusted in order to achieve the best allocation of the maximum available downlink power resources. Selection criteria and users The requirements, radio environmental conditions, and network maintenance are as described above. In the example shown in Figures 2 12 and 2 2 2, the selection criterion applied is the bit rate (BR) assigned to the downlink user data channel [1, M]. ). If PDUt is greater than Pnax, Figure 2 12 indicates the specified bit rate. For downlink user data channels that have exceeded the maximum value, the maximum bit rate has been reduced (BU. If PQUt is less than Pmax, the graph 222 indicates that The fixed bit rate has been increased for these downlink user data channels below the maximum value to the maximum bit rate (). Other appropriate selection criteria will be described

Page 11 462161 V. Description of the invention (8) is as follows. It is the bit rate selection of each downlink user data channel in a unit, which is implemented at a certain time, that is, every 10 ms, preferably longer than the reporting time of the system power control of the uplink and downlink channels. Figure 3 is a flow chart representing the steps of the method of the present invention. First, before starting the method of the present invention, paragraph 31 calculates the environmental parameters of the radio for each downlink user data channel in order to make a bit rate selection for that channel. To maintain instantaneous transmission quality, path loss and signal-to-interference ratio must be determined. Because of the distance between the user equipment and its serving base station, the path loss corresponds to the signal attenuation. This value is calculated from the downlink signal strength, which is reported by the user equipment of the downlink channel. This signal-to-interference ratio (Eb / Itt) is calculated in the power control of the external circuit of the downlink, which control is located in the network or in the user equipment. The downlink power control can adjust the signal bit energy of the downlink channel to a sufficiently high target value to correspond to the ratio of the uplink line as instructed by the user equipment. These values are updated by the system when the decision time for the bit rate selection is short. Therefore, it can be assumed that this method is often suitable for actual rms. Other parameters that affect the radio channel are external noise, which can be assumed to be white Gaussian noise with a fixed frequency density N, and related factors, which indicate that the incorrect spreading of the downlink spreading codes between different channels is orthogonal. These values can be regarded as constant for the method of the present invention. In the next step, step 32, an original bit rate is assigned to each downlink user data channel. Therefore, the waiting channel has the highest bit rate data to be released. The lowest bit rate for channels without data transmission is not enough to maintain the power control operation of the downlink. The output traffic transmitted from a base station to all downlink user data channels in sequence can be checked by checking each downlink

苐 Page 12 4 6 2 1 6 1 V. Description of the invention (9) The output of the channel is a buffer and can be evaluated. Paragraph 3 3: From the original setting, evaluate the preliminary value of the allocated downlink power. The allocated downlink power P. The value of ^ is compared with the maximum allowed downstream power PBax in paragraph 34. If the allocated power is less than the allowed power level, the system is not currently subject to downstream power restrictions. If the estimated value of power demand is higher than the allowed downlink power, the system needs to be adjusted, that is, the bit rate of one or more of the downlink user data channels to a lower bit rate. The method is to implement the iterative procedure of the steps of selecting a sub-group of the user data channel of the next line and then selecting the bit rate of the channel (block 351), and reselecting the bit rate of these channels (block 3 5 2). Then select the bit rate. In paragraph 3 5 3, the adjustment value of the total allocated downlink power is evaluated. If Pat exceeds the allowed maximum downlink power Pnax, the iterative process is repeated. This selection can be done according to a selection criterion and described in the following methods, which can be used individually or in combination. The method of the present invention can also be performed on the allocated downlink power P. " Apply when the maximum downlink power PBax allowed is below. The remaining downlink power can be used to improve the output, that is, to increase the bit rate of all or a certain subset of downlink user data channels to improve service quality. This is accomplished by repeated reselection procedures, as described above, including selecting a subgroup of the downlink user data channel, segment 3 6 I, and reselecting the subgroup with a higher bit rate, segment 3 6 2. From the reselected bit rate, the adjusted value of the total allocated downlink power PQUt is evaluated in paragraph 3 6 3, and this iterative process is repeated until P. " Do not exceed the target value of the downstream power, paragraph 3 6 4.

Page 13 462161 V. Description of the Invention (ίο) In the first method, each downlink user data channel is treated equally at the specified downlink bit rate. Therefore, when the allocated downlink power exceeds the threshold of the maximum allowable downlink power, the allocated downlink power is adjusted by modifying the transmission characteristics of an appropriate subgroup, or by modifying the transmission characteristics of all downlink user data channels. The appropriate sub-group may arbitrarily select several downlink user data channels for restoration. In another solution, a sub-group of the index value representing the starting position of the downlink transmission buffer _ is selected cyclically for data to be sent to the downlink user data channel. In this way, each downlink user channel has a momentarily reduced bit rate within a certain time. From the perspective of a base station, this method is easy to implement and maintain; but it ignores the fact that downlink channels have different prerequisites for users at different addresses in a unit in terms of their downstream power requirements. Therefore, when the allocated downlink power level is lower than the maximum allowed downlink power level, the first method will increase the bit rate for each downlink user data channel. But it only means a small increase for each user. Therefore, another method of selecting a subgroup of downlink user data channels is that the downlink channel is the selection criterion, which is related to its physical characteristics, namely the reported path loss, the power level required by the downlink channel, or instantaneous designation. Bit rate. In the case that the allocated downlink power must be reduced, this means that the channel has an unacceptably high path loss at the border, so it must be dealt with at a lower priority because a small number of users consume most of the available downlink power. Not good for most users. Or, first, these channels are selected as the channel with the highest specified bit rate, and then the path loss is considered

Page 14 4 6 2 16 1 V. Description of the invention (π) Loss and / or required power level. From a system point of view, this method intends to maximize the number of these downlink user data channels, and the base station can provide good downlink channel quality for these channels, that is, bit rate and path loss, instead of maximizing the number of users supported. However, for users consuming too much total downlink power, the method of the present invention may indicate the need for replacement processing. When considering the cell boundary users of high-load cells, the method can start a handover to a neighboring cell with less call volume. If the bit rate is selected as a higher bit rate, it is better to choose a downlink channel that already has good quality so that it can greatly increase the service quality of these users. In addition, one method may be related to the user's order type, that is, under any conditions, at least a minimum bit rate of the main order type, or a low budget type, that is, no guarantee at the access point or bit rate. Other user-related selection criteria are packet arrival time and packet waiting time, so that the needs of individual users can be observed in a better way. This means that the status of the transmission buffer of each downlink user data channel has been applied as a selection criterion. Therefore, users who apply for a large amount of data instantaneously can be assigned a higher bit rate to implement their instantaneous requirements, and to avoid excessive traffic in the output transmission buffer of the base station. Therefore, these selection criteria can prevent some users from being ignored for a long time.

Page 15

4 6 2 1 6 € No. 88120440 ^ Ο — (ha) Symbol description 11 Unit 12 Base station 13a, 13b, 13c, 13d 14a, 14b, 14c, 14d 15 Tree 16 Building 17a, 17b Base station 18 User 211 Power offset 212,222 Figure 2 2 1 Power offset below i \ ax ft July July Correction of user equipment downlink channel

O: \ 61 \ 61413.ptc Page 15a 2001.07.12.016

Claims (1)

6. Scope of patent application 1. Stations can be used by users. Users can allocate equipment and data frequently based on the rules and regulations. For example, the line electronics group can adjust the total score to one of the downlink data. 3. 2. If you apply for it, the line electronics group refers to the channel. If you apply for the downlink of the self-confidence system, the data channel provides the total allocated power level for each time station that you set as a fixed time point. From time to time, you can use the selected downward patent range to levy the total downlink power level on time Correction method. The system includes a number of base station channels, providing communication services to the letter selection service to have a specified portion of the user equipment. During this period, each base station implements the following line channel channel assessments to determine the total allocation of downlink power. With the consent of a base station, select all or downlink subscribers. The method of bit line power of the downlink user data channel to the maximum allowed downlink item 1. If the power of the subscriber data exceeds the base station, select all or downlink users. , The step of the rate of each basic number, the method of the maximum channel frequency of the line license, the maximum data channel of the line license is set to a lower bit rate method, and the selected downlink user patent scope is adjusted to item 2 The method is to have a specified bit rate in the downlink user data channel. O: \ 61 \ 61413.ptc Page 1 2001.07.12.018 _ Case No. 88120440_July Θ_ __ VI. Select a proper number of channels to select the downlink line for the channels where the scope of patent application exceeds the threshold limit One of the user profile channels. 4 The method according to item 2 of the scope of patent application, which is characterized by selecting an appropriate number of channels from a channel of downlink user data channels with a path loss that has exceeded a threshold value to select one of the downlink user channels. group. 5. If the method in the second item of the patent application is applied, it is characterized by selecting an appropriate number of users of the unsubscribed rate subscription type in the downlink user data channel to select a subgroup of the downlink user data channel. 6. The method according to item 1 of the scope of patent application, characterized in that if the total allocated downlink power is lower than the maximum allowed downlink power level of a base station, all or a subset of downlink user channel data is selected, Specify a higher bit rate mode and adjust the selected downlink user data channel. 7. If the method of claim 6 is applied, it is characterized by selecting an appropriate number from the downlink user data channels with a specified bit rate below the threshold value to select a subgroup of the downlink user data channels. . O: \ 61 \ 6H13.ptc Page 2 2001.07.12. 019 4 6 2 16 1 _ Case No. 88120440 6 'Application for Patent Range Amendment 8. If the method of the 6th item of the patent scope is applied, it is characterized by the downlink user An appropriate number is selected from the data channels having a path loss below the threshold, and a subgroup of the downlink user data channels is selected. 9. If the method of claim 6 is applied, it is characterized in that an appropriate number is mainly selected from the channels of subscribers with prime rate subscriptions of the downlink user data channel to select the downlink user data channel to select the downlink One of the subgroups in the profile. 10. The method of item 2 or 6 of the scope of patent application, which is characterized by cyclically selecting an appropriate range from an index value indicating a starting position of a downlink transmission buffer of a downlink user data channel to select downlink user data One of the subgroups of the channel. 11. The method according to item 2 or 6 of the scope of patent application, which is characterized by randomly selecting an appropriate number of downlink user channels to select a subgroup of downlink user data channels. 1 2. If the method of item 1, 2, 3, 4, 5, 6, 7, 8, or 9 of the scope of patent application is applied, it is characterized in that it is continuously performed from the downlink user's data channel to continuously apply more than one selection Select an appropriate number of criteria to select the downlink O: \ 61 \ 61413.ptc Page 3 2001.07. 12. 020 4 6216 1 Amendment _ Case No. 88120440 VI. Scope of patent application A subgroup of user information channels. 1 3. If the method of claim 1, 2, 3, 4, 5, 6, 7, 8, or 9 of the scope of patent application, it is characterized in that the method is performed in a normal time interval, which is more than the radio channel parameters from the user equipment The reporting interval is long. 14. The method according to item 4 of the scope of patent application, which is characterized by the user equipment with the highest path loss starting to be delivered to an adjacent unit. 2001.07.12. 021