HK1096205A - Initial downlink transmit power adjustment for non-real-time services - Google Patents

Description

Preliminary downlink transmit power adjustment for non-real time services

Technical Field

The present invention relates to adjusting initial downlink transmit power in a cellular network, and more particularly to adjusting initial downlink transmit power for non-real time services to improve the perceived quality of the service.

Background

Because of the bursty nature of non-real time (NRT) services, the configuration of physical resources for NRT services is also bursty and transitory. For each configuration, the accuracy of the preliminary downlink transmit power is important to the quality of experience of the service for that configuration, such as the block error rate (BLER). Today, the preliminary downlink transmit power is estimated by the controlling radio network controller (C-RNC) using two different architectures depending on the availability of measurements.

Because of factors such as fading, mobility, measurement reporting delays, and errors, the preliminary downlink transmit power may be significantly different from the power actually required to support the signal-to-interference ratio (SIR). If the initial downlink transmit power is significantly lower than the actual required power, the actual SIR in the configuration start time is much lower than the required SIR, which causes many transmission errors. Since the configuration of NRT services is typically short-lived, errors encountered during the configuration start time may not be amortized over the short configuration duration to meet the necessary BLER.

Disclosure of Invention

The present invention proposes a solution for cellular networks to adjust the initial downlink transmit power of non-real time services to improve the experienced quality of service.

A method for initial downlink transmit power adjustment for non-real time services in a wireless communication network begins by estimating an initial downlink transmit power level for the non-real time services. The estimated power level is then compared to a threshold. It is determined whether an increase in the estimated power level will affect neighboring cells (cells). If an increase does not affect neighboring cells, the preliminary downlink transmit power level is adjusted by a predetermined amount.

A method for initial downlink transmit power adjustment for non-real time services in a wireless communication network begins by estimating an initial downlink transmit power level for the non-real time services. An estimated timeslot carrier power is calculated and compared to a threshold. The preliminary downlink transmit power is adjusted based on the comparison. The preliminary downlink transmit power may be increased or maintained at a preliminary set point based on a threshold used for the comparison.

Drawings

The invention will be more fully understood from the following description of preferred embodiments, given by way of example, and with reference to the accompanying drawings, in which:

fig. 1 is a flow diagram of a general strategy for preliminary downlink transmit power adjustment for non-real time services; and is

Fig. 2 is a flow diagram of the implementation of the strategy of fig. 1 in a Wideband Code Division Multiple Access (WCDMA) Time Division Duplex (TDD) system.

Fig. 3 is a block diagram of a system that utilizes preliminary downlink transmit power adjustment for non-real time services.

Detailed Description

Fig. 1 is a flow diagram of a method 100 for estimating preliminary downlink transmit power by a C-RNC that uses either a full measurement type algorithm or a common measurement type algorithm. The full measurement type algorithm is used when both dedicated and common measurements are available to the RNC, whereas the common measurement type algorithm is used when only common measurements are available to the RNC. The method 100 begins by the C-RNC estimating a preliminary downlink transmission power for the NRT service (step 102). The estimated preliminary downlink transmit power is compared to a threshold (step 104) and the method is terminated if the estimated power is above the threshold (step 106).

If the estimated power is below the threshold (step 104), it is determined whether an increase in preliminary downlink transmit power will significantly degrade service in neighboring cells (step 108). If service in the neighboring cell is significantly degraded, no power adjustments are made and the method is terminated (step 106). However, if service in a neighboring cell does not significantly degrade, the preliminary downlink transmit power is increased by a particular amount depending on the threshold encountered in step 104 (step 110). The method is then terminated (step 106).

Intuitively, increasing the preliminary downlink transmit power appropriately when conditions warrant may improve performance. In one embodiment, the preliminary downlink transmit power is increased only when the following conditions are met:

1) the preliminary downlink transmission power estimated by the C-RNC is below a certain threshold.

2) The initial increase in downlink transmit power will not significantly degrade service in neighboring cells (e.g., causing congestion). This effect can be measured by the carrier power of a neighboring Base Station (BS) or by downlink interference.

It is also possible that there are multiple thresholds for the preliminary downlink transmit power. Each threshold has an amount of transmit power increase associated with it. The amount of increase and the values of these thresholds also depend on the required BLER for NRT services, since the required BLER is a pointer to the tolerance of preliminary transmission errors.

A solution to the preliminary downlink transmission power problem for NRT services in WCDMA TDD systems is shown in fig. 2. A method 200 begins by estimating, by a C-RNC, a preliminary downlink transmission power for an NRT service (step 202). Next, it is determined whether the estimated timeslot carrier power, which is equal to the estimated preliminary downlink transmission power plus the current timeslot carrier power, is below a certain threshold (step 204). If the estimated timeslot carrier power is less than the minimum node-B carrier power, the preliminary downlink transmission power is increased such that the total timeslot carrier power is equal to the minimum node-B carrier power plus a margin value, Marginlow (step 206). Marginlow is a design parameter with typical values in the 2-5dB range. The lower the value of the required BLER, the higher the value of Marginlow. The method is then terminated (step 208). If the estimated timeslot carrier power is greater than the minimum node-B carrier power but less than a carrier threshold (ThresOwn _ CaPwr; step 204), it is determined whether the average timeslot carrier power of neighboring cells is below a certain threshold threesenighbor _ CaPwr (step 210). Alternatively, the Interference Signal Code Power (ISCP) ThresNeighbor _ ISCP of the wireless transmit/receive unit (WTRU) in the time slot of the unit may be utilized. These thresholds are jointly determined by the maximum allowed timeslot carrier power of the node B and the required BLER for NRT service. The higher the maximum allowed slot carrier power, the higher these thresholds will be. Furthermore, the lower the value of the necessary BLER, the higher these thresholds will be.

If the average timeslot carrier power is lower than threeseneighbor _ CaPwr, the preliminary downlink transmission power is increased such that the total timeslot carrier power equals the greater of: the minimum node-B carrier power plus a margin value, margin, or the original estimated total timeslot carrier power plus a margin value, margin (step 212). Marginmedium is determined to be a maximum margin such that interference due to the minimum node B carrier power plus Marginmedium does not cause the slot carrier power of a neighboring cell to approach its maximum allowed value. The marginogical is determined to be a maximum margin such that interference due to the B-node carrier power at ThresOwn _ CaPwr plus marginogical does not cause the slot carrier power of a neighboring cell to approach its maximum allowed value. The method is then terminated (step 208).

If the average timeslot carrier power of the neighboring cells is greater than threeseneighborcapwr in step 210, no adjustment is made to the preliminary downlink transmit power (step 214) and the method is terminated (step 208). If the estimated timeslot carrier power is greater than the carrier power threshold (ThresOwn _ CaPwr; step 204), no adjustment is made to the preliminary downlink transmission power (step 214) and the method is terminated (step 208).

It should be understood that all parameters used in method 200 (i.e., the margin and threshold) are directly or indirectly related to BLER. Practically speaking, all parameters can be fine-tuned through simulation or field test/experiment.

Fig. 3 is a block diagram of an embodiment of preliminary downlink transmit power adjustment for non-real time services. A C-RNC300 receives NRT data. A media access controller 308 arranges the NRT data for transmission. The C-RNC300 also has a preliminary NRT transmission power determining means 310 for determining a preliminary transmission power level of the NRT data.

The scheduled NRT data is sent to the node B302 for physical layer processing 312 to format it for transmission over the air interface 306. A preliminary NRT transmit power adjustment means 314 adjusts the preliminary transmit power level estimate as previously described. The adjusted preliminary transmission power level determination is used to adjust the gain of an amplifier 316. The amplified NRT signal is radiated by an antenna 318 or an array of antennas via the air interface 306. The WTRU 304 receives the NRT signal using its antenna 320 or antenna array and recovers the NRT data using an NRT receiver 322.

While the particular embodiments of the present invention have been illustrated in the drawings and described in the text, numerous modifications and variations could be made by those skilled in the art without departing from the scope of the invention. The foregoing description is by way of example only, and is not intended as limiting the invention in any way.

Claims (8)

1. A method for performing preliminary downlink transmit power adjustment for a non-real time service in a wireless communication network, comprising:

estimating a preliminary downlink transmission power level for the non-real time service;

comparing the estimated power level to a threshold;

determining whether an increase in the estimated power level would degrade service in a neighboring cell; and

adjusting the preliminary downlink transmit power level by a predetermined amount based on the determining step.

2. A method for performing preliminary downlink transmit power adjustment for a non-real time service in a wireless communication network, comprising:

estimating a preliminary downlink transmission power level for the non-real time service;

calculating an estimated time slot carrier power;

comparing the estimated time slot carrier power with a threshold value; and

adjusting the preliminary downlink transmission power based on the comparison result.

3. The method of claim 2 wherein said calculating step includes adding said estimated preliminary downlink transmission power to a current time slot carrier power.

4. The method of claim 2 wherein said comparing step comprises comparing said estimated timeslot carrier power to a minimum carrier power level for a node B.

5. The method of claim 4, wherein the adjusting step comprises increasing the preliminary downlink transmit power such that a total carrier power equals the minimum carrier power plus a margin.

6. The method of claim 2 wherein the comparing step comprises determining whether the estimated timeslot carrier power is greater than a minimum carrier power level for a node B and less than a carrier power threshold.

7. The method of claim 6, wherein the adjusting step comprises:

judging whether the average time slot carrier power of adjacent units is less than a threshold value; and

if the average timeslot carrier power is below the threshold, increasing the preliminary downlink transmission power, thereby making a total carrier power equal to the greater of: the minimum carrier power plus a first margin value, and the estimated timeslot carrier power plus a second margin value.

8. The method of claim 2 wherein said comparing step comprises comparing said estimated timeslot carrier power to a carrier power threshold.