FR2872670A1 - METHOD FOR DISTRIBUTING RADIO RESOURCES BETWEEN A PLURALITY OF MULTIPLEX TRANSPORT CHANNELS IN A PHYSICAL CHANNEL - Google Patents

Abstract

The invention relates to a method for distributing radio resources between a number M of multiplexed transport channels in a physical channel, each transport channel carrying a service and / or data having a specific QoS requirement between a user terminal and a station. The method of the invention comprises the following steps: a- estimating the QoS of each of the received transport channelsb- determining N services among the M services for which the QoS is greater than a value predetermined target, c- reducing the proportion of the physical channel allocated to the N transport channels determined in step b by modifying their rate adaptation parameters, e-performing steps c) and d) until the QoS specific to each service is reached with a minimum transmission power of the physical channel.

Description

METHOD FOR DISTRIBUTING RADIO RESOURCES BETWEEN ONE

  PLURALITY OF MULTIPLEX TRANSPORT CHANNELS IN A

PHYSICAL CHANNEL

DESCRIPTION TECHNICAL FIELD

  The invention is in the field of telecommunications and relates more specifically to a method for distributing radio resources between a number M of multiplexed transport channels in a physical channel, each transport channel carrying a service and / or data having a requirement. specific Quality of Service (QoS) between a user terminal and a base station of a cellular telecommunication network.

  The invention also relates to a mobile terminal and a base station adapted to implement the method.

  STATE OF PRIOR ART The transmission power of a mobile terminal or of a base station in a cellular telecommunication network is systematically controlled so as, on the one hand, to provide the terminal with the same quality of QoS service ( for Quality Of Service) regardless of its position in the network, and secondly, to increase battery life while avoiding unnecessarily increasing the level of interference in a cell. This control can be performed on both the uplink and the downlink.

  On the uplink, the base station ("Node B") measures the signal-to-current interference ratio (SIR) on the received signal and transmits to the terminal a command so that the latter adjusts its transmission power. On the downstream path, the mobile terminal performs similar operations for the downlink. This power control mechanism where the terminal and the base station mutually adjusts their transmit powers is known in CDMA as closed-loop power control or closed-loop power control in English.

  The commands exchanged between the base station and the terminal in order to adjust their transmission powers are based on a level of SIR (signal to interference ratio) established by a controller of the radio network RNC (for Radio Network Controller) responsible for the management radio resources in the cells he controls.

  The power control process described above can be represented by two processing loops, schematically illustrated in FIG. 1, in which quality of service measurements and power matching commands are performed simultaneously.

  The first processing loop, called the internal loop, performs a fast processing to adjust the power of the signal received by the terminal or the base station to maintain the signal-to-interference ratio (SIR) equal to a predetermined target value SIR. by the second loop.

  The second loop, called the external loop, has the function of defining the signal-to-interference ratio SIR, so as to maintain the measured block error rate on the transport blocks of the received signal (BLER for Block Error Rate). a BLERE target value ensuring the quality of service at the required level.

  As illustrated by FIG. 1, the internal loop comprises a matched filter 2, a RAKE receiver 4, a SIR interference signal ratio calculation module 6 and a control bit generation module 8 (TPC) for Transmit Power. Control).

  In addition to the filter 2 and the receiver RAKE 4, the external loop comprises a channel decoder 10, an error block detector module 12 and a comparison module 14 of the BLER with a target value BLERC for updating the SIR.

  The module 6 calculates the current SIR relating to a received signal and transmits the calculated SIR to the module 8 which generates a bit 0 If the calculated SIR is greater than the target value SIRc, or a bit 1 If the calculated SIR is less than SIRE.

  The estimation of the SIR is based on a measure of the quality of the link in terms of BLER. The optimum value of the SIR must be such that the desired quality in the link is achieved with the minimum transmit power of the base station or mobile terminal. If the estimated quality is better than the target quality, the value of the SIR is decreased, and if not, this value is increased.

  In a UMTS UTRA system, it is possible to multiplex on a single physical channel several services with different quality requirements (QoS). During the communication, the control performed by the external loop dynamically adjusts the signal-to-interference ratio SIR, so as to maintain, for each service transported via the physical channel, the block error rate measured on the transport blocks. from the received signal BLER (for Block Error Rate) to a target value BLERC. However, there can only be one target value for fast closed loop power control since all services have a common power control. This SIRE target interference signal ratio is defined according to the service requiring the highest SIR ,. As a result, the transmission power required to achieve this signal-to-interference ratio SIRc can be overvalued for other multiplexed services and requires a lower SIRc.

  This results in an imbalance between the real power requirement of the service transport channels and the power actually available for these channels.

  This imbalance of power has the effect, on the one hand, to increase the level of interference for other users of the system, and on the other hand, to limit the lifetime of the terminal battery.

  An object of the invention is to rebalance the distribution of radio resources between the different transport channels by selectively adapting the coding parameters of these transport channels so as to reduce the transmission power through the physical channel while respecting the QoS requirements for all services transmitted through this channel.

  DISCLOSURE OF THE INVENTION The invention recommends a method for distributing radio resources between a number M of multiplexed transport channels in a physical channel, each transport channel conveying a service and / or data having a specific QoS requirement between a user terminal and a base station of a cellular telecommunication network.

  The method according to the invention comprises the following steps: a - estimating the quality of service (QoS) of each of the received transport channels, b determining N services among the M services for which the QoS is greater than a predetermined target value c - reducing the proportion of the physical channel allocated to the N transport channels determined in step b by modifying their rate adaptation parameters, d - waiting for the convergence of the power control loop, e - performing the steps c and d) until the specific QoS of each service is reached with a minimum transmission power of the physical channel.

  This method further comprises a phase in which the signal-to-interference ratio (SIR) is estimated for each transport channel and the transmission power is adjusted to achieve an optimum signal-to-interference ratio (SIR, o). guaranteeing the required QoS for each of the transport channels while minimizing the power emitted.

  Preferentially, the reduction of the transmission rate in the transport channels for which the QoS is greater than a predetermined target value is achieved by a modification of a predefined rate adaptation parameter for each transport channel.

  The method according to the invention is preferably implemented in a UMTS cellular network. In this case, the rate adaptation parameter is the RM (Rate Matching) parameter defined in TS25.212.

  The invention also relates to a mobile terminal capable of exchanging with a base station, via a single physical channel, a plurality of services and / or data each having a specific QoS requirement. This terminal comprises means for dynamically and selectively adapting the data rate of a portion of the least demanding services in terms of QoS so as to reduce the transmission power without degrading the quality of the most demanding services in terms of QoS.

  The invention also relates to a base station of a cellular telecommunication network capable of exchanging with a mobile terminal, via a single physical channel, a plurality of services and / or data each having a specific QoS requirement. This base station comprises means for dynamically and selectively adapting the data rate of some of the least demanding services in terms of QoS so as to reduce the transmission power without degrading the quality of the most demanding services in terms of QoS .

BRIEF DESCRIPTION OF THE DRAWINGS

  Other characteristics and advantages of the invention will emerge from the description which follows, taken by way of non-limiting example, with reference to the appended figures in which: FIG. 1, previously described, schematically illustrates two control loops of power of the prior art, - Figure 2 shows a general flowchart illustrating the method according to the invention - Figure 3 shows an embodiment of the method according to the invention.

  DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

  The following description concerns a

  implementing the method in a UMTS cellular network in which a mobile terminal, connected to a base station, receives through a single physical connection four separate services having distinct QoS QoS requirements, such as for example a voice service, a video service, a data service and an internet connection. These services are carried in four distinct transport channels TrCH1, TrCH2, TrCH3 and TrCH4 multiplexed in the same physical channel connecting the base station and the terminal.

  Once the mobile terminal has established communication with the base station, the closed loop power control is activated. On the uplink, the base station permanently measures the signal quality in terms of signal-to-interference ratio (SIR) and sends the terminal a command on the downstream channel to ask it to either increase the transmission power if the measured SIR is below a target value SIRc, which is to decrease the transmission power if the measured SIR is greater than the target value SIRc.

  In the downlink, the fast adjustment of the target value is performed by an external loop power control performed at the mobile.

  The inner loop performs fast processing to adjust the power of the signal received by the terminal or the base station to maintain the signal-to-interference ratio (SIR) equal to a target value SIR, predetermined by the outer loop. The latter defines the signal-to-interference ratio SIR, so as to maintain the Block Error Rate (BLER) measured on the transport blocks of the signals received via each of the transport channels TrCH1, TrCH2, TrCH3 and TrCH4 at a target value BLERc.

  FIG. 2 schematically illustrates the steps of the method according to the invention for adapting the rate adaptation parameters making it possible to minimize the transmission power while ensuring the desired quality of service for each of the transport channels TrCH1, TrCH2, TrCH3 and TrCH4 .

  Step 32 consists of measuring the Block Error Rate (BLER) for the transport blocks of the signals received via each of the transport channels TrCH1, TrCH2, TrCH3 and TrCH4.

  Step 34 consists in verifying whether the BLER measured for each of the transport channels TrCH1, TrCH2, TrCH3 has at least reached the target BLER defined for each of said channels.

  If the measured BLER has not converged to the target BLER, the process is resumed from step 32.

  If the measured BLER has converged to the target BLER, the process proceeds to step 36 of determining the N transport channels having a BLER greater than a predetermined threshold to the target BLER value.

  Step 38 selectively modifies the RM (Rate Matching) parameter of these channels to be able to reduce the transmission power while continuing to guarantee the target value of the BLER for each of the transport channels.

  step 40 is to adjust all RMs by a common factor if at least one modified RM value is less than the normalized minimum RM. The common factor is chosen to ensure that all RM values are between the normalized minimum and maximum values.

  FIG. 3 schematically illustrates the evolution of the BLERs of the four transport channels TrCH1, TrCH2, TrCH3 and TrCH4 with respect to their target value BLERc as a function of the update of the rate adaptation parameters as well as that of SIRc.

  For simplicity of presentation, it is assumed that the target BLER value was the same for all transport channels.

  In FIG. 3a, the channel TrCH1 has a value of BLER for which the service transported via this channel has a quality of service lower than the target QoS, and each of the channels TrCH2, TrCH3 and TrCH4 has a value BLER for which the service transported via this channel has a higher quality of service than the target QoS.

  To achieve the target service quality of the TrCH1 channel, transmission power is increased (arrow P Figure 3b) for all transport channels.

  This increase in power has an unnecessary impact on the TrCH2, TrCH3 and TrCH4 channels which already had sufficient quality of service.

  In order to be able to reduce the transmission power without degrading the quality of the TrCH1 channel, the parameter RM (arrow D2 to D4, FIG. 3c) of the TrCH2, TrCH3 and TrCH4 channels is selectively reduced, which automatically reduces the proportion of the transmission rate. physical channel allocated to channels TrCH2, TrCH3 and TrCH4 and automatically increase the rate proportion of the physical channel allocated to channel TrCH1. This has the consequence of increasing the BLER of the channels TrCH2, TrCH3 and TrCH4 and of decreasing the BLER of the channel TrCH1 (arrow D1, FIG. 3c).

  This results in a rebalancing of the QoS between, on the one hand, the channel TrCH1, and on the other hand, the channels TrCH2, TrCH3 and TrCH4. A decrease in power (arrow P figure 3d) is then possible while continuing to guarantee the quality of service of the TrCH1 channel.

SP 25136 / HM

Claims (7)

  A method of distributing radio resources between a number M of multiplexed transport channels in a physical channel, each transport channel carrying a service and / or data having a specific QoS requirement between a user terminal and a base station a cellular telecommunication network, the method comprising the following steps: a - estimating the quality of service (QoS) of each of the received transport channels, b - determining N services among the M services for which the QoS is greater than a target value predetermined, c reduce the proportion of the physical channel allocated to the N transport channels determined in step b by modifying their rate adaptation parameters, d - wait for the convergence of the power control loop, e - perform the steps c and d) until the specific QoS of each service is reached with a minimum transmission power of the physical channel.   2. Method according to claim 1, characterized in that it further comprises a phase during which it is estimated, for each transport channel, the signal-to-interference ratio (SIR) and the transmission power is adjusted to achieve an optimal target interference signal ratio (SIRco) SP 25136 / HM 2872670 guaranteeing the required QoS for each transport channel while minimizing the power output.   3. Method according to claim 1, characterized in that step c) is performed by modifying a predefined rate adaptation parameter for each transport channel.   4. Method according to claim 3, characterized in that the cellular network is a UMTS network.   5. Method according to claim 4, characterized in that said rate adaptation parameter is the RM defined in the specification 3GPP TS 25.212.   6. Mobile terminal capable of exchanging with a base station, via a single physical channel, a plurality of services and / or data each having a specific QoS requirement, characterized in that it comprises: a) means for estimating the quality of service (QoS) of each of the received transport channels, b) means for determining N services among the M services for which the QoS is greater than a predetermined target value, c) means for reducing the proportion of the physical channel allocated to the N transport channels determined in step b by changing their rate adaptation parameter, until the specific QoS SP 25136 / HM of each service is reached with a minimum transmission power of the physical channel.   7. Base station of a cellular telecommunication network network capable of exchanging with a mobile terminal, via a single physical channel, a plurality of services and / or data each having a specific QoS requirement, characterized in that it comprises: a) means for estimating the quality of service (QoS) of each of the transport channels received, b) means for determining N services among the M services for which the QoS is greater than a predetermined target value, c) means for reducing the proportion of the physical channel allocated to the N transport channels determined in step b by modifying their rate adaptation parameter, until the specific QoS of each service is reached with a minimum transmission power the physical channel.