FR2923964A1 - DYNAMIC METHOD FOR CONTROLLING TRANSMISSION POWER LEVEL OF COMMUNICATION TERMINALS - Google Patents

Abstract

A method for determining an instantaneous transmission power of a radio communication terminal in which said terminal realizes a control of its instantaneous transmission power as a function of a target power, said method comprising a step of regulating said instantaneous transmission power comprising an evaluation of N magnitudes to which respective indices i can be assigned, with i varying from 1 to N, respectively representative of cumulative differences between the instantaneous transmission power and a threshold average power over N time windows which are such that the duration of the time window corresponding to the magnitude of index i is less than the duration of the time window corresponding to the magnitude of index i-1, the execution of a succession of tests (E2) to check whether said respective index magnitudes i representative of the cumulative deviations are positive, starting from the index i = 1 and for successive index i, and if, for an index, the magnitude of index j is negative or zero, an interruption of the succession of tests, and the determination of a regulation factor to be applied to the target power to obtain a power instantaneous issue, according to the index j.

Description

The present invention relates to a dynamic method for regulating the transmission power level of a radio communication terminal in a radio communication network. This method is superimposed on the existing power control mechanisms and is applicable whatever the access mode, for example time division multiple access (TDMA), by the codes (CDMA for "Code Division Multiple Access" in English) or orthogonal frequency (OFDM for "Orthogonal Frequency Division Multiplexing" in English).

In the absence of the control method according to this invention, the instantaneous transmission power of a radio communication terminal varies during a communication essentially as a function of the distance between the radio communication terminal and the base stations. , conditions of propagation of the radio signal and interference generated by neighboring radio communication terminals. This power must be all the more important to ensure the quality of a communication conditions are unfavorable. In order to guarantee a target quality of service, the transmission power level is controlled by a power control algorithm which periodically determines the power to be transmitted by the terminal. The power controllers are more or less complex according to the associated quality criteria and may simply be, for example, power limiters. The periodicity for determining the power to be transmitted is generally adapted to the access modes, and mainly the power control mechanisms are chosen slowly for transmissions based on TDMA and OFDM type access, and fast for transmissions based on a CDMA type access.

There are essentially two types of power control: open loop power control and closed loop power control. The open loop power control leverages the ability of the radio communication terminal to set its instantaneous transmit power to a predefined value when establishing a communication. Closed-loop power control for uplink transmission (ie from the radio terminal to a base station) is based on the network sending instantaneous power change commands. transmission of the radio terminal to maintain for example the signal-to-noise ratio (SNR for "Signal to Noise Ratio" in English) in the uplink direction greater than or equal to a predefined threshold.

The evolution of regulatory constraints setting limits on the levels of power radiated by radio terminals in order to limit the levels of exposure to users, radio frequency spectrum pollution, or even energy consumption, now also impose on the average radiated power.

However, the current power control algorithms do not have the capacity to control the average power because it requires the short and long term prediction of the instantaneous power. This is indeed difficult to predict because it is a function including the terminal path and the behavior of other users. As a result, the existing power control algorithms can not guarantee an average transmission power, while continuing to also ensure a target quality of service. There is therefore a need for a method for determining the instantaneous transmission power of a radio terminal making it possible to respect an average transmission power constraint of this radio terminal. This method must also be capable of being implemented in any transmission device of a radio terminal operating in any type of radio network, for example cellular type mobile radio networks such as GSM (for "Global System for Mobile Communications "in English) and UMTS (for" Universal Mobile Telecommunication System "in English) and subsequent generations, wireless local area networks such WI MAX (for" Worldwide I nteroperability for Microwave Access "in English), or satellite type.

To achieve this objective, the invention proposes a method for determining the instantaneous power of a radio communication terminal in which said terminal realizes a control of its instantaneous transmission power as a function of a desired power, the method comprising a step of regulating the instantaneous transmission power comprising: an evaluation of N magnitudes to which we can assign respective indices i, with i varying from 1 to N, respectively representative of cumulative differences between the instantaneous transmission power and an average threshold power over N time windows which are such that the duration of the time window corresponding to the magnitude of index i is less than the duration of the time window corresponding to the magnitude of index i-1; the execution of a succession of tests to check whether said respective index quantities i representative of the cumulative deviations are positive, starting from the index i = 1 and for successive indices i, and - if, for an index j, the magnitude of index j is negative or zero, an interruption of the succession of tests, and the determination of a regulation factor to be applied to the target power to obtain an instantaneous transmission power, as a function of the index j.

The invention thus advantageously integrates the average transmission power constraints of a mobile radio terminal into a power control mechanism by limiting any degradation in quality of service. The observation of the differences between the average threshold power and the cumulative radiated power over different time windows makes it possible to predict the evolution of the average radiated power with respect to the fixed average power. This makes it possible, according to the various quantities evaluated, to allow specific exceedances of the average radiated power with respect to the average threshold power and to regulate the instantaneous radiated power when this is necessary.

The instantaneous transmission power being evaluated for successive instants, the regulation factor for a given instant is determined according to a regulation factor determined for a previous instant. By this, it avoids storing the history of the instantaneous transmission powers of the terminals to evaluate average powers by determining evolutionary regulatory factors associated with cumulative variables. The control factor for a given instant is further determined by an increasing function of the control factor determined for a previous instant. The successive regulation factors are thus determined in order to respect the average power constraint. The regulation factor is further reset in the case where, for the index i = 1, the magnitude of index 1 is negative or zero. As the time window 20 of index 1 is of the longest duration, the threshold mean power constraint is thus declared as complied with and the regulation factor reset to zero. A decreasing function of the regulating factor is applied to the target power, which makes it possible to limit the instantaneous power and thus to regulate the average power. The invention also relates to a device for determining an instantaneous transmission power of a radio communication terminal able to carry out a control of its power as a function of a desired power, the device comprising: evaluation means of N magnitudes of indices 1 to N representative of N cumulative differences between the instantaneous transmission power and a threshold average power over N respective time windows which are such that the duration of the time window of index i is less than the duration of the time window of index i-1, means for determining an instantaneous transmission power regulation factor adapted to: execute a series of tests in order to verify whether said respective index quantities i are representative of cumulative differences are positive, starting from the index i = 1 and for successive indices i, and ^ if, for an index j, the magnitude of index j is negative or zero, interrupt the sequence of tests, and determine a regulation factor to be applied to the target power to obtain an instantaneous transmission power, as a function of the index j. The invention also relates to a radio communication system comprising a power controller and a regulating device for determining an instantaneous transmission power. The power controller, delivering the setpoint power to the device, can be indifferently open loop or closed loop, with a frequency of determining the slow or fast reference power. The invention also relates to a communication terminal comprising the aforementioned control device, or a radio communication terminal comprising the aforementioned radio communication system.

Other features and advantages of the present invention will emerge more clearly on reading the following description of several particular embodiments, of the method for determining the instantaneous transmission power of a terminal and of the terminal itself, given in FIG. As simple illustrative and non-limiting examples, and appended drawings, in which: FIG. 1 represents the steps of the method for determining the instantaneous transmission power, according to one particular embodiment of the invention, FIG. 2 represents an example of determination of a regulation factor for the implementation of the method of FIG. 1; FIG. 3 represents a radio communication terminal for carrying out the method of FIG.

In Figure 1, there is shown the different steps of the method, according to a particular embodiment of the invention. The method is superimposed on an instantaneous power control algorithm for regularly delivering to the radio terminal a setpoint power Pcons. This reference power can be determined, in known manner, by the network, in the case of a closed loop power control, or by the terminal, in the case of an open loop power control. The periodicity T for determining the desired power depends on the characteristics of the radio system. The determination of the desired power being well known to those skilled in the art and not being the subject of the invention, it will not be described in more detail. For more information on this subject, please refer to the following documents: "Power Contrai in UMTS release'99", presented by authors MPJ Baker and TJ Moulsley at the conference "First international conference on 3G communication technologies "in March 2000, or the work of M. Mouly and MB Pautet entitled" The GSM System for Mobile Communication "published by the authors in 1992. Referring to Figure 1, the method comprises a first step El d evaluating, for a time tk, N magnitudes G (tk) of index i, with i varying from 1 to N, representative of cumulative differences between the instantaneous transmission power P (tk) of the radio terminal at instant tk and a threshold mean power Pseuil over N time windows. The average power set Pseuil corresponds to the average power requirement that the radio terminal must respect and corresponding to a measurement time over a duration Tseuii.

The evaluation time windows of the quantities G (tk), noted here f ;, with i varying from 1 to N, are such that the duration of the time window f; of index i is less than the duration of the time window f; _1 of index i-1.

The magnitudes representative of the cumulative differences between the instantaneous transmission power P (tk) of the radio terminal at the instant tk and the mean fixed power Pseuil are such that: G (tk) = G (tk-1) + (P ( tk) - Pseuil) i = 1, .. N Take as an illustrative example the particular case where N = 3, the power control being for example carried out in a closed loop. Three time windows f1, f2, f3 are used. Their respective durations are here: - For the window f1: Tseuil / 2 seconds allowing to have a long term estimate of the evolution of the mean power emitted compared to the average threshold power Pseuil, -For the window f2: Tseuil / 10 seconds allowing to have a medium term estimate, and - for the window f3: Tseuil / 60 seconds allowing to have a short term estimate. The method then comprises a test step E2, iterative on the indices i ranging from 1 to N, consisting in checking whether the magnitude G (tk) is positive, starting from i = 1 and for the successive indices i, in other words for i = 1, 2, ..., N. This test is repeated for the successive indices i, in ascending order, as long as the magnitude G (tk) is positive. If, for a given index j, the quantity tested q (tk) is negative or zero, the execution of the succession of tests is interrupted and the method proceeds to a step E3. During this step E3, a regulation factor R (tk) of the instantaneous power for the moment tk is determined from the regulation factor determined for the previous instant tk-1 by application of a regulation function Ui increasing corresponding to the index j for which the corresponding magnitude C (tk) caused the interruption of the succession of tests. Alternatively, the magnitude sign test G (tk) is reiterated in the ascending order of the indices as long as the magnitude G (tk) is positive or zero. The regulation factor at time tk is thus a function of the factor. defined for a previous instant R (tk_l) according to the following equation: R (tk) = Uj (R (tk-1)), by way of illustrative and nonlimiting example, the functions U ;, for i variant from 1 to N, are increasing affine functions defined by the parameters A and B ;: R (tk) = AR (tk_1) + B,

In the aforementioned example in which N = 3, the parameters of the regulation functions U i, i ranging from 1 to 3, are set to the values Al = O, B1 = 0, A2 = 1, B2 = 1, A3 = 1 and B3 = 2. Of course, we could choose other values.

On the other hand, the number of parameters of the regulation functions depends on the type of function chosen. Thus two regulation parameters are defined for each index i in this particular example of using an affine function. The regulation factor is also reset, that is to say reset if the test step is interrupted for the magnitude of index 1, ie if the magnitude CG (tk) which corresponds to the cumulative deviations evaluated over the time window of longer duration is negative or zero. This reset is implemented by applying the constant function U1 (R (tk)) = 0, corresponding to parameters A1 and B1 zero in the particular case of the choice of the affine control functions.

If no quantity C, (tk), for i varying from 1 to N, has made it possible to interrupt the execution of the succession of tests of step E2, the regulation factor is determined during a step E4 by applying an increasing regulating function UN + 1. With reference to the above example for which N = 3, the function UN + 1 is chosen affine with the parameters A4 = 1 and B4 = 4.

As described in FIG. 2, referring to the aforementioned example where N = 3 and the regulation functions are affine, if the magnitude C, (tk) is positive and the magnitude C2 (tk) is negative or zero, the regulation is given by R (tk) = R (tk_1) +1. If the quantities C1 (tk) and C2 (tk) are positive, the regulation factor is given respectively by R (tk) = R (tk_1) +2 and R (tk) = R (tk_1) +4 according to the sign of the size C3 (tk). The regulating factor is, on the other hand, reset to a zero value if the quantity C1 (tk) is negative or zero.

Following the determination of the regulation factor for the instant tk, the radio terminal decreases its instantaneous transmission power P (tk) below the setpoint power in a step E5 by applying a decreasing attenuation function H. according to the regulation factor. As an illustrative and nonlimiting example, the instantaneous power is given by: Pe (tk) = Pcons 1+ gx N (tk) The constant g aimed at weighting the regulation factor. This constant is set at 0.03 in the above example. The method for determining the instantaneous power is then reiterated for the following instants tk + 1, tk + 2, ..., during the communication time of the radio terminal.

The number N of quantities to be evaluated, the duration of time windows, the type of regulation function and the associated parameters and the attenuation function H are here determined in advance by simulations carried out for different levels of target quality of service by example defined according to a signal-to-noise floor ratio. Thus, the choice of regulation parameters achieves the best compromise between the objectives of quality of service and compliance with the threshold power threshold constraint. These parameters can be configurable and updated, for example, following the modification of the constraints on the average threshold power to be respected. The regulation of the instantaneous power will be all the more effective if the number N is large. However, the larger N is, the greater the number of variables to be considered and the volume of calculations to be performed. However, it is possible to limit the complexity of the receiver and choose for example to evaluate only 2 sizes. In this case, step E2 comprises a test on the sign of the first quantity Cl (tk) and if this quantity is negative, or else negative or zero, the regulation factor is determined as a function of the sign of the second quantity C2 (tk).

A radio communication terminal will now be described with reference to FIG. 3. For the sake of clarity, only the elements of the radio communication terminal related to the invention will be explained. The radio communication terminal comprises a module 50 for determining the instantaneous power which comprises the following elements: a brick 51 for evaluating the N magnitudes representative of the cumulative differences between the instantaneous transmission power and the average power set on the N time windows, - a brick 52 for determining an instantaneous power regulation factor, - a brick 53 for determining the instantaneous transmission power of the terminal after regulation, - a brick 54 for storage.

The brick 51 is arranged to evaluate at successive instants tk the N magnitudes C, (tk), i ranging from 1 to N, representative of the cumulative differences between the instantaneous emission power P (tk) and the average threshold power Pseu the N respective time windows f;, such as the duration of the time window f; is less than the duration of the time window f; _ ,. The brick 52 for determining a regulation factor is arranged to execute the series of tests on the values of the magnitudes G (tk) for the indices i varying from 1 to N, and to assign a regulation factor according to the index j for which the value of the index magnitude ja interrupted the succession of tests. The brick 53 is able to modify the value of the transmission power of the radio communication terminal as a function of the regulation factor, the attenuation function H and the target power delivered by a power control module in the terminal or delivered by the network. Process configuration parameters are stored in the brick 54, for example the duration of the time windows f; the parameters of the regulation functions, the parameters of the attenuation function H. The brick 54 also stores the quantities representative of the accumulated deviations and the regulation factor determined at a previous time. The terminal comprises a central control unit, not shown, to which the elements of the module 50 are connected and intended to control the operation of these elements.

In a particular embodiment of the invention, the various steps of the method for determining the instantaneous power are implemented by a computer program loaded into a radio communication terminal or a computer system of a terminal simulator. radio communication for example. The module 50 is in this case a software module comprising software instructions for controlling the execution by the radio communication terminal of the steps of the previously described method. Accordingly, the invention also applies to a computer program, including a computer program on or in an information recording medium, adapted to implement the invention. This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code such as in a partially compiled form, or in any other form desirable to implement the method according to the invention. The information recording medium may be any entity or device capable of storing the program. For example, the medium may comprise storage means or recording medium on which is stored the computer program according to the invention, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or a USB key, or a magnetic recording medium, for example a diskette (floppy disc) or a hard disk. On the other hand, the information medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means. The program according to the invention can in particular be downloaded to an Internet type network. Alternatively, the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method according to the invention.

Claims (11)

A method for determining an instantaneous transmitting power of a radio communication terminal in which said terminal realizes a control of its instantaneous transmission power as a function of a reference power (Pcons), said method being characterized in that it comprises a step of regulating said instantaneous transmission power comprising: - an evaluation (El) of N magnitudes (C; (tk)) to which we can assign respective indices i, with i varying from 1 to N, respectively representative of cumulative differences between the instantaneous transmission power and a threshold average power (Pneu ;,) over N time windows (f;) which are such that the duration of the time window corresponding to the index magnitude i is less than the duration of the time window corresponding to the magnitude of index i-1; the execution of a succession of tests (E2) for verifying whether said respective index quantities i representative of the cumulative deviations are positive, starting from the index i = 1 and for successive indices i, and -si, for an index j, the magnitude of index j is negative or zero, an interruption of the succession of tests and the determination (E3) of a regulation factor to be applied to the reference power (Pcons) to obtain a power of d instantaneous issue, according to the index j. 2. The method as claimed in claim 1, and in which, the instantaneous transmission power being evaluated for successive instants (tk), the regulation factor R (tk) for a given instant (tk) is determined according to a factor determined for a previous instant (tk_l). 3 - Process according to one of claims 1 to 2 wherein the regulation factor for a given instant (tk) is determined by an increasing function of the regulation factor determined for a previous instant (tk_l). 4- Method according to one of claims 1 to 3, wherein the regulation factor is reset in the case where, for the index i = 1, said magnitude index 1 is negative or zero. 5. Method according to one of claims 1 to 4, wherein a decreasing function (H) of the regulation factor is applied to the desired power (Pcons). Device for determining an instantaneous transmitting power of a radio communication terminal able to carry out a control of its power as a function of a reference power (Pcons), said device comprising: N evaluation means magnitudes (G (tk)) of indices 1 to N representative of N cumulative differences between the instantaneous transmission power and a threshold mean power (P i) over N respective time windows (f i) which are such that the duration of the time window of index i is less than the duration of the time window of index i-1, - means for determining an instantaneous transmission power control factor adapted to: ^ execute a succession of tests in order to check whether said respective index magnitudes i representative of the cumulative deviations are positive, starting from the index i = 1 and for successive indices i, and ^ if, for an index j, the magnitude of index j is negative or null e, interrupt the succession of tests, and determine a regulation factor to be applied to the nominal power (Pcons) to obtain an instantaneous transmission power, as a function of the index j. A radio communication system comprising a power controller and a device for determining an instantaneous transmission power as defined in claim 6. 8- Radio communication terminal comprising a device for determining an instantaneous transmission power, as defined in claim 6. 9- radio communication terminal comprising a radio communication system as defined in claim 7. A computer program for a device capable of determining instantaneous transmission power, comprising software instructions for controlling the execution of the steps of the method defined in claim 1, when said program is executed by the device. 11- Data carrier in which the computer program according to claim 10 is registered.