CN1925352A - Realization Method of HSUPA Outer Loop Power Control - Google Patents

Abstract

The invention discloses an HSUPA outer loop power control method in a mobile communication system. A radio network controller RNC uses the block error rate BLER of DCH to control the outer loop. The protocol data unit PDU reported by the base station also reports the measured total broadband receiving power RTWP of the cell to the RNC, and the RNC uses the PDU or retransmission information to calculate the BLER and residual BLER of the E-DCH; then the RNC uses the BLER, residual BLER and RTWP Adjust the power offset and the maximum number of retransmissions; finally, the RNC sends the RRC command to the UE to reconfigure the power offset and the maximum number of retransmissions of the E-DCH, and the reconfiguration data assists the UE in TFC selection, and the UE will select the E-TFC and power offset are applied to the physical channel, thereby completing the outer loop power control.

Description

Realization Method of HSUPA Outer Loop Power Control

technical field

The invention belongs to an outer loop power control method of an uplink physical channel with ARQ retransmission in a mobile communication system, and is particularly aimed at the outer loop power control of HSUPA (uplink enhanced channel) in a WCDMA system.

Background technique

In R99, the outer loop power control is carried out in the RNC (Radio Network Controller), and the user configures different target BLER (block error rate) for different service types, and the Node B (base station) controls each DCH (dedicated channel) TTI (Transmission Time Interval) performs CRC (Cyclic Redundancy Check) check and reports the result to RNC, and RNC compares the BLER of the data channel with the target BLER by reporting the information.

If the BLER is greater than the target BLER, the RNC increases the SIRtarget (target signal-to-interference ratio) by one step; if the BLER is smaller than the target BLER, the RNC decreases the SIRtarget by one step.

Besides BLER, BER and FER can also be used for outer loop power control.

HSUPA was proposed in R6, and it uses some key technologies: Node B-controlled scheduling technology; HARQ (hybrid ARQ) technology combined with soft combination; shorter TTI technology (2ms TTI).

HSUPA can make full use of the UE's transmit power resources to maximize the transmission of packet services. Since uplink interference is limited, if the uplink interference exceeds a threshold, the performance of the uplink channel will be greatly reduced. In order to prevent the uplink interference from exceeding the threshold, the Node B needs to measure the uplink interference and report it to the RNC for RRM (Radio Resource Management) control. In HSUPA, the measured value is RTWP (Received total wide band power, total broadband received power).

The channel for HSUPA to transmit uplink data is E-DCH. Since E-DCH and DCH are different in TTI length, target BLER and active set size, their outer loop power control is different. The difference in the TTI length of the DCH and the E-DCH leads to different interleaving gains for the two channels, and the DCH with a longer TTI has a greater interleaving gain.

Different target BLERs require that the RNC should have the ability to control the BLERs of DCH and E-DCH respectively. In soft handover, the active set sizes of E-DCH and DCH may be different, so when both DCH and E-DCH are configured to transmit data, the two channels will have significantly different macrodiversity gains.

The most obvious difference between E-DCH and DCH is that E-DCH has HARQ retransmission, but DCH does not. From the perspective of the outer loop power control entity and the RLC (radio link control) entity, the DCH has the same block error rate (consistent with the actual channel BLER). After E-DCH is introduced, since the MAC layer adopts the HARQ protocol, the BLER seen from the outer loop power control entity or RLC entity is the residual BLER, which is the block error rate after soft combining, which is different from the BLER of the actual channel. Obviously, the residual BLER is much smaller than the channel BLER, so it is very likely that the residual BLER has been kept at a very low level, so that the outer loop power control will think that the BLER is very good and cannot effectively perform the outer loop power control operation.

The basic idea of the outer loop power control of E-DCH is mentioned in the R6 agreement: DPCCH (Dedicated Control Channel) assists E-DCH in power control, and the power control of DPCCH is the same as R99. In the presence of DCH, control the SIRtarget of DPCCH according to the outer loop of BLER of DCH, and reconfigure the power offset (PO) of E-DCH through RRC to ensure the service quality of E-DCH; in the case of no need for DCH In this case, a zero transmission block may be required to assist the outer loop power control of the E-DCH.

The information provided by Node B to RNC includes each PDU (protocol data unit) transmitted to RNC and the number of transmissions required for correct decoding of this PDU.

The RNC maintains the latest E-DCH power offset based on the information provided by the Node B, and may decide to transmit the updated power offset attribute to the UE.

The UE receives the power offset from the RNC, which is added to the reference power offset previously calculated for different E-TFCs (transport format combinations).

Then the UE selects the E-TFC, taking into account the obtained power offset, the remaining power of the UE and the total amount of data to be transmitted.

Patent WO 2004/091114 mentions that the number of retransmissions can be used as a weight to adjust the SIRtarget to perform uplink outer loop power control. The method provided by this patent uses RTWP, the maximum number of retransmissions and the reported actual number of retransmissions to jointly perform outer loop power control, which can optimize the number of retransmissions and improve user throughput.

Due to the existence of the ARQ mechanism, the channel performance is mainly related to the target BLER and the residual target BLER. Excessive residual BLER will cause RLC retransmission. Therefore, it is first necessary to ensure that the residual BLER meets the requirements of the target value.

On the premise of ensuring the residual BLER, if a smaller number of retransmissions is used, although the transmission delay of the channel is reduced, the increased channel transmission power will cause interference to other users; if a larger number of retransmissions is used, although the transmission delay of the channel is reduced The transmission power of the channel is increased, but the transmission delay of the channel is increased.

Adjusting the channel power and adjusting the maximum number of retransmissions can both change the residual BLER, and they can be combined for outer loop power control. At the same time, since the method of increasing the power will increase the uplink interference, the uplink interference will also affect the way to adjust the residual BLER.

Contents of the invention

In order to overcome the above-mentioned problems in the prior art, the present invention provides an HSUPA outer loop power control method that is easy to implement and has good throughput performance.

The HSUPA outer loop power control method of the present invention utilizes the reported transmission times, the measured and reported RTWP and the maximum retransmission times to jointly control the HSUPA outer loop power.

HSUPA outer loop power control realization method of the present invention, comprises the following steps:

Step 1. Set initial values, including target block error rate, target residual block error rate, interference threshold, and initial power offset;

Step 2, the base station reports the number of transmissions required for correct decoding of the protocol data unit to the wireless network controller together with the protocol data unit, and the wireless network controller records the outer loop power control parameters reported within a certain time window,

The outer loop power control parameters include the number of E-DCH retransmissions and the total broadband receiving power;

Step 3. Calculate the block error rate and residual block error rate within the time window through the reported number of transmissions;

Step 4, comparing the residual block error rate with the target residual block error rate,

When the residual block error rate is greater than the target residual block error rate, if the reported broadband received total power exceeds the interference judgment threshold, then increase the maximum number of retransmissions, otherwise the power offset (PO) increases by step1;

When the residual block error rate is less than the target residual block error rate, if the reported RTWP exceeds the interference judgment threshold, the power offset (PO) is reduced by step2; otherwise, the maximum number of retransmissions is reduced;

Step 5. Send the adjusted power offset value and the maximum number of retransmissions to the UE through a downlink command, and the UE selects and adjusts its transmit power through the TFC.

In step 3, if there is a DCH channel, calculate the block error rate of the DCH through the cyclic redundancy check instruction, and perform power control on the DCH according to the power control method of R99.

The block error rate and residual block error rate can be obtained by the following formula:

$\mathrm{<span\; class="notranslate">\; BLER</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; k</span>}}{\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}$

In the formula, m is the number of PDU packets processed in the time window;

N _i is the number of times each PDU packet is transmitted;

k is the number of PDU packets that have reached the maximum number of retransmissions but have not been correctly decoded.

If the maximum number of retransmissions is reached but there are no correctly decoded PDUs, the residual block error rate is 1, otherwise it is 0.

The step1=k1×ΔBLER,

k1 is the up-regulation coefficient, which can be obtained by simulation;

ΔBLER = BLER - target BLER;

The PO=min(PO+step1, MaxPO),

MaxPO is the maximum power shift value set by the system.

The step2=k2×ΔBLER,

K2 is the down-regulation coefficient, which can be obtained by simulation;

ΔBLER = BLER - target BLER;

The PO=max(PO-step2, MinPO),

MinPO is the minimum power offset value set by the system.

The interference decision threshold is set to be less than or equal to the interference threshold.

By adopting the method of the invention, not only the method is easy to realize, but also has good throughput performance.

Description of drawings

Fig. 1 is the overall flowchart of HSUPA power control of the present invention;

Fig. 2 is a flow chart of the outer loop power control method of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and the embodiment of HSUPA outer loop power control.

Accompanying drawing 1 illustrates the overall flowchart of HSUPA power control.

In this example, the UE transmits DCH and E-DCH, and DCH performs power control according to the R99 protocol: Node B uses the SIR of DPCCH to perform inner-loop power control, and RNC uses DCH BLER to perform outer-loop power control.

Node B reports the number of PDU transmissions to the RNC, and also reports the measured RTWP of the cell to the RNC, and the RNC uses the PDU and retransmission information to calculate the target BLER and target residual BLER of the E-DCH; then the RNC uses the target BLER, target residual BLER and RTWP adjusts the power offset and the maximum number of retransmissions; finally, the RNC sends an RRC command to the UE to reconfigure the power offset and the maximum number of retransmissions of the E-DCH, and the reconfiguration data assists the UE in TFC selection, and the UE will select the E-DCH TFC and power offset are applied to the physical channel to complete the outer loop power control.

Wherein, the reconfigured power offset is the difference between the power offset required by the E-DCH and the reference E-TFC power offset, and the reference power offset is set by the RNC for the specified E-TFC.

Accompanying drawing 2 has illustrated HSUPA outer loop power control method flow chart, and this figure has specifically described RNC processing procedure among Fig. 1:

Step 20 sets the target BLER, target residual BLER, interference threshold, and initial power offset. The setting of the target residual BLER will affect RLC retransmission; the setting of the target BLER will reflect the link performance before HARQ retransmission; the interference threshold reflects the uplink interference In the limit case of , there may be a certain margin in the actual situation. If the interference threshold is set to I _max , the interference decision threshold is I _max -ΔI. ΔI≥0 can be determined by simulation; the initial power offset is set by the RNC for each MAC-d flow, and the initial power offset is the power offset value relative to the reference E-TFC power offset. The above parameters can be set and optimized according to simulation and actual measurement.

Step 201 records the number of retransmissions used by each E-DCH PDU packet and the CRCI (CRC indication) of the DCH channel in a certain time window, and obtains RTWP from the Node B measurement report, and the RTWP value is reported periodically.

Step 202 calculates the BLER and residual BLER of the E-DCH. If there is a DCH channel, the BLER of the DCH is calculated through CRCI, and the inner and outer loop power control of the DCH is performed according to the power control algorithm of R99.

The BLER and residual BLER of E-DCH can be obtained by the following formula:

$\mathrm{<span\; class="notranslate">\; BLER</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; k</span>}}{\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; ,</span>$

In the formula, m is the number of PDU packets processed in the time window;

N _i is the number of transmissions required for correct decoding of each PDU packet;

k is the number of PDU packets that have reached the maximum number of retransmissions but have not been correctly decoded.

Step 203 judges whether the residual BLER is greater than the target residual BLER, if the residual BLER is greater than the target residual BLER, go to step 204; otherwise, go to step 207.

Step 204 judges whether the RTWP is greater than or equal to the interference judgment threshold, and if the RTWP is greater than or equal to the interference judgment threshold, proceed to step 206 ; otherwise, proceed to step 205 .

Step 205 calculates the power offset upward adjustment step step1, and makes PO=min(PO+step1, MaxPO), where MaxPO is the maximum power offset value set by the system, and min is a function to obtain the minimum value. Step1 can be calculated as follows:

step1=k1×ΔBLER

In the formula, k1 is the up-regulation coefficient, which can be obtained by simulation;

ΔBLER = BLER - target BLER.

Step 206 adjusts the maximum number of retransmissions. If the maximum number of retransmissions is not greater than 15 (HSUPA maximum number of retransmissions), then the maximum number of retransmissions +1. A higher residual BLER is obtained by increasing the number of retransmissions.

Step 207 judges whether the RTWP is greater than or equal to the interference judgment threshold, and if the RTWP is greater than or equal to the interference judgment threshold, proceed to step 208 ; otherwise, proceed to step 209 .

Step 208 calculates the power offset down-adjustment step length step2, and makes PO=max(PO-step2, MinPO), where MinPO is the minimum power offset value set by the system, and max is a function to obtain the maximum value. Step2 can be calculated as follows:

step2=k2×ΔBLER

In the formula, k2 is the down-regulation coefficient, which can be obtained by simulation;

ΔBLER = target BLER - BLER.

Step 206 adjusts the maximum number of retransmissions. If the maximum number of retransmissions is not equal to 0, then the maximum number of retransmissions -1. Doing so reduces the transmission delay.

Finally, the RNC sends the calculated power offset and the maximum number of retransmissions to the UE through downlink signaling.

Claims (7)

1, a kind of HSUPA outer loop power control implementation method is characterized in that, comprises as follows: Step 1. Set initial values, including target block error rate, target residual block error rate, interference threshold, and initial power offset; Step 2, the base station reports the number of transmissions required for correct decoding of the protocol data unit to the radio network controller together with the protocol data unit, and the radio network controller records the outer loop power control parameters reported within a certain time window, the outer loop power control The parameters include the number of E-DCH retransmissions and the total power of broadband reception; Step 3. Calculate the block error rate and residual block error rate within the time window through the reported number of transmissions; Step 4. Compare the residual block error rate and the target residual block error rate. If the residual block error rate is greater than the target residual block error rate, if the reported broadband receiving total power exceeds the interference judgment threshold, increase the maximum number of retransmissions, otherwise The power offset PO is increased by step1; when the residual block error rate is less than the target residual block error rate, if the reported RTWP exceeds the interference judgment threshold, the power offset is reduced by step2; otherwise, the maximum number of retransmissions is reduced; Step 5. Send the adjusted power offset value and the maximum number of retransmissions to the UE through a downlink command, and the UE selects and adjusts its transmit power through the TFC. 2, the HSUPA outer loop power control implementation method as claimed in claim 1, is characterized in that: In the step 3, if there is a DCH channel, calculate the block error rate of the DCH through the cyclic redundancy check instruction, and perform power control on the DCH according to the power control method of R99. 3, the HSUPA outer loop power control implementation method as claimed in claim 1, is characterized in that: The block error rate and residual block error rate can be obtained by the following formula: $\mathrm{<span\; class="notranslate">\; BLER</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; k</span>}}{\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}$ residual $\mathrm{BLER}=\frac{k}{m}$ In the formula, m is the number of PDU packets processed in the time window; N _i is the number of times each PDU packet is transmitted; k is the number of PDU packets that have reached the maximum number of retransmissions but have not been correctly decoded. 4. The HSUPA outer loop power control implementation method as claimed in claim 3, characterized in that: If the maximum number of retransmissions is reached but there are no correctly decoded PDUs, the residual block error rate is 1, otherwise it is 0. 5. The HSUPA outer loop power control implementation method as claimed in claim 1, characterized in that: The step1=k1×ΔBLER, k1 is the up-regulation coefficient; ΔBLER=BLER-target BLER; The PO=min(PO+step1, MaxPO), MaxPO is the maximum power shift value set by the system. 6. The HSUPA outer loop power control implementation method as claimed in claim 1, characterized in that: The step2=k2×ΔBLER, K2 is the down-regulation coefficient; ΔBLER=BLER-target BLER; The PO=max(PO-step2, MinPO), MinPO is the minimum power offset value set by the system. 7. The HSUPA outer loop power control implementation method as claimed in claim 1 or 5 or 6, characterized in that: The interference decision threshold is set to be less than or equal to the interference threshold.

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