Power control method and radio network controller

This application claims the benefit of People's Republic of China application Serial No. 201110269143.9, filed Sep. 13, 2011, the disclosure of which is incorporated by reference herein in its entirety.

1. Field of the Invention

The invention relates in general to a power control method and a radio network controller (RNC), and more particularly to a power control method and an RNC for performing an outer loop power control operation.

2. Description of the Related Art

With advancements in technologies, the 3 rd Generation Partnership Project (3GPP) protocol is prevalent in applications of macrocells and femtocells to bring convenience to the daily life. In current techniques, power control mechanisms in 3GPP compliant communication systems can be categorized into open loop power control and closed loop power control. The closed loop power control is further divided into inner loop power control and outer loop power control.

In general, the inner loop power control compensates fast fading of a signal by adjusting transmission power of a user equipment (UE) or a base station, whereas the outer loop ensures that a communication system is offered with adequate quality having an acceptable transmission error rate by controlling a target value of a signal-to-interference ratio (SIR). As the 3GPP continues to prevail, it is a common goal of manufacturers to provide an even more efficient power control method.

The invention is directed to a power control method and a radio network controller (RNC) for performing a power control operation between the RNC and a node B. In the control method and the RNC of the present invention, a packet error rate threshold is calculated with reference to a target block error rate (BLER) and a precision of the target BLER, and an accumulated received packet count and an accumulated packet error count are also correspondingly calculated. Further, in the control method and the RNC of the present invention, it is determined whether to increase a target signal-to-interference ratio (SIR) of the node B through determining whether the accumulated packet error count is greater than a product of the accumulated received packet count and the packet error rate threshold. Therefore, compared to a conventional power control method, the power control method and the RNC of the present invention determine whether to increase the target SIR of the node B with reference to the accumulated packet error count and the product of the accumulated received packet count and the error packet error threshold.

According to an aspect of the present invention, a power control method for is provided. The method is applied to an RNC to perform a power control operation between the RNC and a node B. The method includes steps of: calculating a packet error rate threshold and a base received packet count according to a target BLER and a precision of the target BLER; obtaining a received packet count and a packet error count in an operation period of the RNC, and adding received packet count and the packet error count to an accumulated received packet count and an accumulated packet error count, respectively; determining whether the accumulated packet error count is greater than a product of the accumulated received packet count and the packet error rate threshold; increasing a target SIR of the node B when the accumulated packet error count is greater than the product of the previous step; determining whether the accumulated received packet count is greater than or equal to a product of the base received packet count and a threshold parameter; decreasing the target SIR of the node B when the accumulated received packet count is greater than or equal to the product of the previous step; determining whether the target SIR is adjusted in one of the foregoing steps of increasing or decreasing the target SIR; and if so, resetting the accumulated received packet count and the accumulated packet error count.

According to another aspect of the present invention, an RNC is provided. The RNC includes an initial configuration unit, a data preparing unit, a first increase determination unit, a decrease determination unit and a reset unit. The initial configuration unit calculates a packet error rate threshold and a base received packet count according to a target BLER and a precision of the target BLER. The data preparing unit obtains a received packet count and a packet error count in an operation period of the RNC, and respectively adds the received packet count and the packet error count to an accumulated received packet count and an accumulated packet error count. The first increase determination unit determines whether the accumulated packet error count is greater than a product of the accumulated received packet count and the packet error rate threshold, and increases a target SIR of the node B when the accumulated packet error count is greater than the product. The decrease determination unit determines whether the accumulated received packet count is greater than or equal to a product of the base received packet count and a threshold parameter, and decreases the target SIR of the node B when the accumulated received packet count is greater than the product. The reset unit determines whether the first increase determination unit or the decrease determination unit adjusts the target SIR, and resets the accumulated received packet count and the accumulated packet error count when the first increase determination unit or the decrease determination unit adjusts the target SIR.

Therefore, in the power control method and the RNC of the present invention, the RNC calculates the packet error rate threshold with reference to the target BLER and the precision of the target BLER, and correspondingly calculates the accumulated received packet count and the accumulated packet error count. In addition, in the power control method and the RNC of the present invention, the RNC further determines whether to increase the target SIR of the node B by determining whether the accumulated packet error count is greater than the product of the accumulated received packet and the packet error rate threshold. Compared to a conventional power control method, the power control method and the RNC of some embodiments determine whether to increase the target SIR of the node B with reference to the accumulated packet error count and the product of the accumulated received packet count and the error packet error threshold.

The above and other aspects of the invention will become better understood with regard to the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.

FIG. 1 is a block diagram of a radio communication system according to one embodiment of the present invention.

FIG. 2 is a detailed block diagram of an RNC 30 in FIG. 1 .

FIG. 3 is a detailed block diagram of an increase determination unit 30 c in FIG. 2 .

FIG. 4 is a detailed block diagram of a decrease determination unit 30 d in FIG. 2 .

FIG. 5 is a detailed block diagram of an RNC 50 according to another embodiment of the present invention.

FIG. 6 is a flowchart of a power control method according to one embodiment of the present invention.

FIG. 1 shows a block diagram of a radio communication system according to one embodiment of the present invention. A radio communication system 1 according to this embodiment includes a user equipment (UE) 10 , a node B 20 and a radio network controller (RNC) 30 . For example, the radio communication system 1 is compliant to the 3 rd Generation Partnership Project (3GPP) protocol, and the UE 10 is a handheld device such as a mobile phone capable of 3GPP communication operations.

In one embodiment, the node B 20 and the RNC 30 may be implemented by way of a femtocell to provide services to a UE located in a smaller area. The node B 20 may be low-level protocols of the femtocell and the RNC 30 may be a main control mechanism of the femtocell. For example, the femtocell may operate in a hybrid mode to provide services to UEs with very-important-person (VIP) and non-very-important-person (NVIP) identities.

The RNC 30 performs a power control operation between the RNC 30 and the node B, e.g., outer loop power control. FIG. 2 shows a detailed block diagram of the RNC 30 in FIG. 1 . The RNC 30 includes an initial configuration unit 30 a , a data preparing unit 30 b , an increase determination unit 30 c , a decrease determination unit 30 d and a reset unit 30 e.

The initial configuration unit 30 a calculates multiple initial parameters according to a target block error rate (BLER) (denoted by BLER_T) and a precision of the target BLER (BLER_T). For example, the target BLER (BLER_T) is determined by a user through an operation, administration and maintenance (OAM) unit. For example, the target BLER (BLER_T) is 0.1%; i.e., a corresponding precision of the target BLER (BLER_T) is 1/1000.

For example, the initial parameters determined by the initial configuration unit 30 a include a packet error rate threshold (ERR_PER_RECV), a base received packet count (RECV_COUNT) and a tolerable packet error count (ERR_COUNT). For example, the base received packet count (RECV_COUNT) is an inverse value of the target BLER (BLER_T). Taking the example of the target BLER (BLER_T) being 0.1% for instance, the precision of the target BLER (BLER_T) is 1/1000, and the corresponding base received packet count (RECV_COUNT) is 1000.

For example, a VIP UE and an NVIP UE respectively correspond to the different tolerable packet error counts ERR_COUNT VIP and ERR_COUNT NVIP, and different packet error rate thresholds ERR_PER_RECV_VIP and ERR_PER_RECV_NVIP. In the following description, details of how the initial configuration unit 30 a calculates the tolerable error rate counts ERR_COUNT_VIP and ERR_COUNT_NVIP as well as the packet error rate thresholds ERR_PER_RECV_VIP and ERR_PER_RECV_NVIP shall be exemplified.

For example, the initial configuration unit 30 a calculates the packet error rate threshold (ERR_PER_RECV_VIP) and the tolerable error rate count (ERR_COUNT_VIP) according to equations (1) to (4):

ERR_COUNT_BASE=RECV_COUNT×BLER_T  (1)

ERR_FLOAT_VIP=ERR_COUNT_BASE×VIP_RATE  (2)

ERR_COUNT_VIP=ERR_COUNT_BASE+ERR_FLOAT_VIP  (3)

ERR_PER_RECV_VIP=ERR_COUNT_VIP/RECV_COUNT  (4)

For example, under a condition that the packet error rate corresponds to the target BLER (BLER_T), ERR_COUNT_BASE indicates a packet error count in packets which may occur each time one base received packet count RECV_COUNT (e.g., 1000) of packets are received. VIP_RATE and ERR_FLOAT_VIP respectively indicate a floating rate of packet error rate and a packet error count range for the VIP UE. The tolerable packet error count ERR_COUNT_VIP indicates a total count of error packets which may occur every time one base received packet count RECV_COUNT (e.g., 1000) of packets are received, with respect to the VIP UE.

The initial configuration unit 30 a calculates the tolerable error rate count (ERR_COUNT_NVIP) and the packet error rate threshold (ERR_PER_RECV_NVIP) according to equations (5) to (7):

ERR_FLOAT_NVIP=ERR_COUNT_BASE×NVIP_RATE  (5)

ERR_COUNT_VNIP=ERR_COUNT_BASE+ERR_FLOAT_NVIP  (6)

ERR_PER_RECV_NVIP=ERR_COUNT_NVIP/RECV_COUNT  (7)

Similarly, NVIP_RATE and ERR_FLOAT_NVIP respectively indicate a floating rate of packet error rate and a packet error count range for the NVIP UE, and the tolerable packet error count (ERR_COUNT_NVIP) indicates a total count of error packets which may occur every time one base received packet count RECV_COUNT (e.g. 1000) of packets are received, with respect to the NVIP UE.

The data preparing unit 30 b obtains the received packet count (RECV_T) and the packet error count (ERR_T) in an operation period (OLPC_T) of the RNC 30 , and adds the received packet count (RECV_T) and the packet error count (ERR_T) to an accumulated received packet count (RECV_ALL) and an accumulated packet error count (ERR_ALL), respectively.

The increase determination unit 30 c determines whether the accumulated packet error count (ERR_ALL) is greater than a product of the accumulated received packet count (RECV_ALL) and the packet error rate threshold. For example, when a UE has the identity of VIP, a determination condition of the increase determination unit 30 c may be represented by equation (8):

ERR_ALL >RECV_ALL×ERR_PER_RECV_VIP  (8)

Similarly, if a UE has the identity of NVIPUE, the determination condition of the increase determination unit 30 c may be represented by equation (9):

ERR_ALL >RECV_ALL×ERR_PER_RECV_NVIP  (9)

When the accumulated packet error count (ERR_ALL) is greater than the product, the increase determination unit 30 c increases a target signal-to-interference ratio (SIR) of the node B.

FIG. 3 shows a detailed block diagram of the increase determination unit 30 c in FIG. 2 . For example, the increase determination unit 30 c includes a parameter determining sub-unit 30 c 1 , step determining sub-units 30 c 2 and 30 c 3 , and an adjusting sub-unit 30 c 4 . The parameter determining sub-unit 30 c 1 determines a fast factor parameter (FAST_FACTOR), a slow factor parameter (SLOW_FACTOR), and a step size (STEP). For example, the fast and slow factor parameters (FAST_FACTOR) and (SLOW_FACTOR) are natural numbers greater than 0 and smaller than or equal to 20, and the fast factor parameter (FAST_FACTOR) is greater than the slow factor parameter (SLOW_FACTOR). In one embodiment, the fast and slow factor parameters (FAST_FACTOR) and (SLOW_FACTOR) respectively equal 6 and 2.

The step determining sub-unit 30 c 2 generates a fast increase step (FAST_STEP(UP)) according to the fast factor parameter (FAST_FACTOR) and the step size (STEP). Similarly, the step adjusting sub-unit 30 c 3 generates a slow increase step (SLOW_STEP(UP)) according to the slow factor parameter (SLOW_FACTOR) and the step size (STEP).

The adjusting sub-unit 30 c 4 increases the target SIR corresponding to the VIP UE according to the fast increase step (FAST_STEP(UP)), and increases the target SIR corresponding to the NVIP UE according to the slow increase step (SLOW_STEP(UP)).

The decrease determination unit 30 d determines whether the accumulated received packet count (RECV_ALL) is greater than a product of the base received packet count (RECV_COUNT) and a threshold parameter (OLPC_OK_RATE). For example, a determination condition of the decrease determination unit 30 d is represented as equation (10):

RECV_ALL ≧RECV_COUNT×OLPC_OK_RATE  (10)

When the accumulated packet error count (RECV_ALL) is greater than the product, the decreasing determination unit 30 d decreases the target SIR (SIR_T) of the node B. The threshold parameter OLPC_OK_RATE may be any natural number, and is utilized for determining a possibility that the decrease determination unit 30 d decreases the target SIR (SIR_T). For example, when the threshold parameter OLPC_OK_RATE is low, the product of the base received packet count RECV_COUNT and the threshold parameter OLPC_OK_RATE is smaller, so that the decrease determination unit 30 d is allowed to more sensitively decrease the target SIR (SIR_T).

In contrast, when the threshold parameter OLPC_OK_RATE is high, the product of the base received packet count RECV_COUNT and the threshold parameter OLPC_OK_RATE gets larger. The larger product correspondingly lowers the possibility that the decrease determination unit 30 d decreases the target SIR (SIR_T), so that the target SIR (SIR_T) is likely maintained at a higher value.

FIG. 4 shows a detailed block diagram of the decrease determination unit 30 d in FIG. 2 . For example, the decrease determination unit 30 d includes a parameter determining sub-unit 30 d 1 , step determining sub-units 30 d 2 and 30 d 3 , and an adjusting sub-unit 30 d 4 . Similar to the parameter determining sub-unit 30 c 1 , the parameter determining sub-unit 30 d 1 determines the fast factor parameter (FAST_FACTOR), the slow factor parameter (SLOW_FACTOR) and the step size (STEP).

The step determining sub-unit 30 d 2 generates a slow decrease step (SLOW_STEP(DOWN)) according to the slow factor parameter (SLOW_FACTOR) and the step size (STEP). Similarly, the step adjusting sub-unit 30 d 3 generates a fast decrease step (FAST_STEP(DOWN)) according to the fast factor parameter (FAST_FACTOR) and the step size (STEP).

The adjusting sub-unit 30 d 4 decreases the target SIR corresponding to the VIP UE according to the slow decrease step (SLOW_STEP(DOWN)), and decreases the target SIR corresponding to the NVIP UE according to the fast decrease step (FAST_STEP(DOWN)).

In other words, similar to the increase determination unit 30 c , the decrease determination unit 30 d may also adjust a corresponding target SIR, with respect to any UE with different identity, according to different step sizes. More specifically, the decrease determination unit 30 d decreases the target SIR of a VIP UE according to the slow decrease step (SLOW_STEP(DOWN)) (corresponding to a smaller value), and decreases the target SIR of an NVIP UE according to the fast decrease step (FAST_STEP(DOWN)) (corresponding to a larger value).

The reset unit 30 e determines whether the increase and decrease determination units 30 c and 30 d adjust the target SIR (SIR_T). When the increase and decrease determination units 30 c and 30 d adjust the target SIR (SIR_T), the reset unit 30 e correspondingly resets the accumulated received packet count (RECV_ALL) and the accumulated packet error count (ERR_ALL). When the increase and decrease determination units 30 c and 30 d do not adjust the target SIR (SIR_T), the reset unit 30 e further determines whether the accumulated received packet count (RECV_ALL) is greater than or equal to the base received packet count (RECV_COUNT). When the accumulated received packet count (RECV_ALL) is greater than or equal to the base received packet count (RECV_COUNT), the reset unit 30 e also resets the accumulated received packet count (RECV_ALL) and the accumulated packet error count (ERR_ALL).

After the reset operations of the reset unit 30 e , the data preparing unit 30 b , the increase determination unit 30 c and the decrease determination unit 30 d may further iterate the corresponding steps to perform loop control with respect to the target SIR (SIR_T).

It should be noted that the example of the RNC 30 shown in FIG. 2 is used for illustrative purposes rather than limiting the present invention thereto. Referring to FIG. 5 showing another embodiment, an RNC 50 may include an increase determination unit 50 f , which determines whether to increase the target SIR (SIR_T) of the node 20 with reference to the accumulated packet error count (ERR_ALL) and the tolerable packet error count (ERR_COUNT).

Further, determination operations of the increase determination unit 50 f may be represented by equation (11) or (12):

ERR_ALL ≧ERR_COUNT_VIP  (11)

ERR_ALL ≧ERR_COUNT_NVIP  (12)

In other words, for the VIP UE, the increase determination unit 50 f determines whether to increase the target SIR (SIR_T) according to a condition of whether the accumulated packet error count (ERR_ALL) is greater than or equal to the tolerable packet error count (ERR_COUNT_VIP); for the NVIP UE, the increase determination unit 50 f determines whether to increase the target SIR (SIR_T) according to a condition of whether the accumulated packet error count (ERR_ALL) is greater than or equal to the tolerable packet error count (ERR_COUNT_NVIP).

Referring to FIG. 5 , the RNC 50 includes two different increase determination units 50 c and 50 f . For example, a user may selectively enable one or both of the increase determination units 50 c and 50 f to correspondingly increase an associated target SIR (SIR_T).

For example, similar to the increase determination unit 30 c , the increase determination unit 50 f including sub-units shown in FIG. 3 may also determine a step size for increasing the target SIR (SIR_T).

FIG. 6 shows a flowchart of a power control method according to one embodiment of the present invention. The method includes the following steps, e.g., for outer loop power control. In step (a), the initial configuration unit 30 a calculates a corresponding packet error rate threshold (ERR_PER_RECV), a base received packet count (RECV_COUNT) and a tolerable packet error count (ERR_COUNT) according to a target BLER (BLER_T) and a precision of the target BLER (BLER_T).

In step (b), the data preparing unit 30 b obtains a received packet count (RECV_T) and a packet error count (ERR_T) within an operation period of the RNC 30 , and respectively adds the received packet count (RECV_T) and the packet error count (ERR_T) to an accumulated received packet count (RECV_ALL) and an accumulated packet error count (ERR_ALL).

In step (c), the increase determination unit 30 c determines whether the accumulated packet error count (ERR_ALL) is greater than a product of the accumulated received packet count (RECV_ALL) and a packet error rate threshold (ERR_PER_RECV), and increase a target SIR (SIR_T) of the node B 20 when the accumulated packet error count (ERR_ALL) is greater than the product.

In step (d), the decrease determination unit 30 d determines whether the accumulated received packet count (RECV_ALL) is greater than or equal to a product of the base received packet count (RECV_COUNT) and a threshold parameter (VIP_RATE) (or (NVIP_RATE)), and decreases the target SIR (SIR_T) of the node B when the accumulated received packet count (RECV_ALL) is greater than or equal to the product.

In step (e), the reset unit 30 e determines whether the target SIR (SIR_T) is adjusted in step (c) or step (d). When the target SIR (SIR_T) is adjusted, step (f) is performed to reset the accumulated received packet count (RECV_ALL) and the accumulated packet error count (ERR_ALL).

When the target SIR (SIR_T) is not adjusted in step (c) or step (d), step (g) is performed. In step (g), the reset unit 30 e further determines whether the accumulated received packet count (RECV_ALL) is greater than or equal to the base received packet count (RECV_COUNT). When the accumulated received packet count (RECV_ALL) is greater than or equal to the base received packet count (RECV_COUNT), step (h) is performed, in which the reset unit 30 e resets the accumulated received packet count (RECV_ALL) and the accumulated packet error count (ERR_ALL). When the accumulated received packet count (RECV_ALL) is not greater than the base received packet count (RECV_COUNT) after steps (f) and (h), the power control method iterates steps (b) to (f) to perform loop control on the target SIR (SIR_T).

Therefore, in the power control method and the RNC disclosed by the embodiment of the present invention, the RNC calculates the packet error rate threshold with reference to the target BLER and the precision of the target BLER, and correspondingly calculates the accumulated received packet count and the accumulated packet error count. In addition, in the power control method and the RNC disclosed by the embodiment of the present invention, the RNC further determines whether to increase the target SIR of the node B by determining whether the accumulated packet error count is greater than the product of the accumulated received packet and the packet error rate threshold. Compared to a conventional power control method, the power control method and the RNC disclosed by the embodiment of the present invention determine whether to increase the target SIR of the node B with reference to the accumulated packet error count and the product of the accumulated received packet count and the error packet error threshold.

Further, in the power control method and the RNC disclosed by the embodiment of the present invention, the increase and decrease determination units determine different step sizes for UEs having different identities by using two different step determining sub-units, thereby adjusting the corresponding target SIR according to different step sizes. Therefore, compared to a conventional power control method, the power control method and the RNC disclosed by the embodiment of the present invention is further advantaged by offering diversified power adjustment solutions for adapting to UEs with different identities.

While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.