WO2005032011A1

WO2005032011A1 - Method of controlling power in a w-cdma mobile communication system

Info

Publication number: WO2005032011A1
Application number: PCT/KR2004/002470
Authority: WO
Inventors: Dong Keun Kim
Original assignee: Utstarcom Korea Limited
Priority date: 2003-09-30
Filing date: 2004-09-24
Publication date: 2005-04-07
Also published as: JP2007507153A; KR20050031550A; US20080049698A1

Abstract

The present invention is related to a backward outer-loop power control method in a wideband CDMA mobile communication system for improving backward call quality and capacity of an IMT-2000 asynchronous system. In accordance with the present invention, the power control is optimized by examining the field transmitted through the backward Dedicated Physical Control Channel (DPCCH), as well as the CRC examination of the uplink data frame received, thus setting the optimum target SIR.

Description

Description METHOD OF CONTROLLING POWER IN A W-CDMA MOBILE COMMUNICATION SYSTEM Technical Field

[1] The present invention generaly relates to a backward outer-bop power control method, and more particularly to a backward outer-bop power control method in a wideband CDMA mobile communication system for improving backward cal quality and capacity of an IMT-2000 asynchronous system. Background Art

[2] Generaly, a CDMA system uses forward (from a base station to a mobile) and backward (from a mobile to a base station) power control to obtain large capacity, good cal quality and so on. The objective of the transmission power control of mobile units is that a receiver of the base station receives every signal of nominal intensity from the mobile units. Regardless of the positioning of the mobile units and propagation bss, the transmitting signals of each mobile unit need to be received at the same intensity. If every transmission power of mobile units in an area is controled similar to the above, then the total received power is the multiplication of the nominal received power and the number of the mobile units.

[3] There are three types of power control: open-bop power control, cbsed-bop (inner-bop or fast), and outer-bop power control. Among them, the outer-bop power control set a target Signa o-Interference Ratio reference vabe (hereinafter, "SIR Target ") that is used for the dosed-bop power control to a desired standard vabe of the cal quality. That is, the outer-bop power control cbes not fix the SIR vabe to a Target specific vabe, but varies the SLR to maintain a BLER measured at every certain Target time period at a target BLER according to the communication environment.

[4] Hg. 1 shows a structure of an UMTS Terrestrial Rado Access Network (UTRAN) in a typical WCDMA mobile communication system.

[5] Reference numeral 100 designates a core network, reference numeral 200 designates a UTRAN, and reference numerals 210 and 220 designate RNSs, which play the rde of base stations/control stations. Further, reference numeral 211 designates a Rado Network Contrder (RNC) in the RNS, reference numerals 212 and 213 designate N)de-B connected to the RNS, and reference numeral 300 designates an User equipment (UE) (UE) such as a mobile unit.

[6] The conventional dosed-bop power control, which produces instruction bits for Transmit Power Contrd (TPC) in the backward transmission, is performed at N)de-Bs in Eg. 1. The conventional outer4oop power contrd is performed at Rado Network Controlers (RNCs). [7] To set the SIR of the base station, RNC 211 is informed whether a frame error Target exists by examining Cyclic Redundancy Checksum (CRC) in received data frames at N)de-B. The SIR is set accordng to the error existence of the frame. Target

[8] Rg. 4 is a flow chart showing the outerbop power contrd method in a conventional WCDMA mobile communication system.

[9] As shown in the drawing, the method comprises the steps of: initializing parameters (Sll); setting a SIR and a target Bbck Error Rate (BLER) (S12); estimating a Target received SIR (SI 3); comparing the estimated SIR with the SIR (SI 4); instructing a Target user equipment (UE) (UE) to bwer transmission power if the estimated SIR is greater than the SIR (S15); bwering the transmission power at the user equipment (UE) Target (S16); instructing the user equipment (UE) (UE) to raise the transmission power if the estimated SIR is not greater than the target SIR (S17); raising the transmission power at the user equipment (UE) (UE) (SI 8); checking if an uplink frame is received (S19); checking if received data has any frame error in case the uplink frame has been received (S20); bwering the SIR by a predetermined vabe when it is determined Target that the received data has no frame error (S21); raising the target SIR if it is determined that a pflot error has occurred accordng to the result of the pflot error check (S22).

[10] More detailed explanation on the outer-bop power contrd method in a conventional WCDMA mobile communication system is provided bebw.

[11] Rrst, at step Sll, parameters are initialized. At step S 12, the SIR and the target Target BLER are set. Then, at step SI 3, the received SIR is estimated. At step S14, the estimated SIR and the target SIR are compared each other. [ 12] After the two vabes are compared, if the estimated SIR is greater than the SIR , Target then the contrd is transferred to step SI 5, where the user equipment (UE) is instructed to bwer the transmission power. Upon receiving such instruction, the user equipment (UE) bwers the transmission power at step S16. Further, after the two vabes are compared, if the estimated SIR is not greater than the SIR , then the contrd is Target transferred to step S17, where the user equipment (UE) is instructed to raise the transmission power. Upon receiving such instruction, the user equipment (UE) raises the transmission power at step SI 8. [ 13] Then, it is checked if an uplink frame is received at step S 19. If the uplink frame has been received, then it is checked if the received data has any frame error by examining CRC of the transmitted data [the data transmitted in backward Dedcated Physical Data Channel (DPDCH)] at step S20. The SIR is bwered at step S21 Target when it is determined that the received data has no frame error. Otherwise, the SIR Target is raised at step S22 when it is determined that the received data has a frame error. [14] More specifϊcaly, in the conventional outer-bop power contrd method, to set SIR , the RNC is informed whether any frame error exists by examining Cydic Target Redundancy Checksum (CRC) in the received data frames at N)de-B. The SIR is Target set accordng to the target BLER.

[15] Because many mobile units and base stations use the same frequency channel simultaneously and interferences among the mobile units that use the same frequency channel increases in the CDMA mobile communication, the cal quality worsens. The system capacity is maximized when the mobile units transmit power with the minimum Signa o-Interference Ratio by contrd over al the mobile units.

[16] The key factor to the cal quality that the user undergoes is determined not by the SIR, but by the BLER. In an area where fadng is severe, the BLER may be bw even though the SIR is high. In a line of sight area between a base station and a mobile unit, the BLER may be high even though the SIR is bw.

[17] However, the conventional power contrd method is dsadvantageous in that mobile units that output unnecessary power decrease the cal quality of others or itself and the system capacity. This is because the conventional method controled the outer-foop power with the SLR only, and thus cannot set an SIR correspondng to the target BLER. Disclosure of Invention Technical Problem

[18] Accordngry, the present invention is provided to sdve the above-described problems of the prior art. The objective of the present invention is to provide a backward outer-bop power contrd method in a wideband CDMA mobile communication system for improving backward cal quality and capacity of an IMT-2000 asynchronous system. Technical Solution

[19] In accordance with the present invention, the power contrd is optimized by examining the field transmitted through the backward Dedcated Physical Contrd Channel (DPCCH), as wel as the CRC examination of the uplink data frame received, thus setting the optimum SLR target Brief Description of the Drawings

[20] The above objective and features of the present invention wϋ become more apparent from the fdbwing description of the preferred embodment provided in conjunction with the accompanying drawings.

[21] Rg. 1 is a bbck dagram showing a structure of UTRAN in a general WCDMA system.

[22] Rg. 2 shows a structure of a general backward DPDCH/DPCCH.

[23] Rg. 3 shows a structure of a backward data frame in a general frame protocd.

[24] Rg. 4 is a flow chart showing an outer-bop power contrd method in the conventional WCDMA mobile communication system.

[25] Rg. 5 is a flow chart showing a backward outer-bop power contrd method in the WCDMA mobile communication system accordng to an embodment of the present invention.

[26] Rg. 6 shows a structure of a backward DPCCH frame.

[27] Rg. 7 shows a pflot pattern of a backward DPCCH channel when N_pflot is 3, 4, 5 and 6.

[28] Rg. 8 shows a pflot pattern of a backward DPCCH channel when N_pflot is 7 and 8.

[29] Rg. 9 is a flow chart showing patterns of error occurrence examined by CRC and a pibt fiekt. Best Mode for Carrying Out the Invention

[30] An embodment of the present invention is described in detail in the fdbwing description with reference to the appended drawings.

[31] Rg. 5 is a flow chart showing the outer-bop power contrd method in a WCDMA mobile communication system.

[32] As shown in the drawing, the method accordng to an embodment of the present invention comprises the steps of: initializing parameters (S101); setting a SLR target (S102); estimating a received SLR (S103); comparing the estimated SLR with the SLR (S104); instructing a user equipment (UE) (UE) such as a mobile unit to bwer a target transmission power if the estimated SLR is greater than the SLR (S105); bwering target the transmission power at the user equipment (UE) (UE) (SI 06); instructing the user equipment (UE) (UE) to raise the transmission power if the estimated SLR is not greater than the SLR (S107); raising the transmission power at the user equipment target (UE) (UE) (SI 08); checking if an uplink frame is received (SI 09); checking if received data has any frame error in case uplink frame have been received (SI 10); bwering the SIR by a predetermined vabe ("X" dB) when it is determined that the target received data has no frame error (Sil l); checking if a pflot error has occurred in case a frame error was found in the received data (SI 12); raising the SLR by a first pre- target determined vabe ("Y" dB) if it is determined that no pflot error has occurred accordng to the result of the pflot error check (SI 13); and raising the SLR by a second pre- target determined vabe ("Z" dB), which is greater than the first predetermined vabe ("Y" dB), if it is checked that a pflot error has occurred accordng to the result of the pflot error check (SI 14). [33] More detailed explanation on the outer-bop power contrd method in a WCDMA mobile communication system accordng to the embodment of the present invention is provided bebw. [34] Rrst, at step S101, parameters are init zed. At step S102, the SLR is set. The Target SLR is set as the one that is set last time and at the time of system initidization, the Target SLR is set to a predetermined vabe. Then, at step S103, the received SIR is Target estimated. At SI 04, the estimated SIR and the SLR are compared each other. Target

[35] After the two vabes are compared, if the estimated SLR is greater than the SLR , Target the contrd is transferred to step SI 05, where the user equipment (UE) is instructed to bwer the transmission power. Upon receiving the instruction, the user equipment (UE) bwers the transmission power at step S106. Further, after the two vabes are compared, if the estimated SLR is not greater than the SLR , then the contrd is Target transferred to step S107, where the user equipment (UE) is instructed to raise the transmission power. Upon receiving the instruction, the user equipment (UE) raises the transmission power at step S108. Then, it is checked if an uplink frame is received at step S 109. In case the uplink frame has been received, it is checked if received data has any frame error by examining CRC of the transmitted data [the data transmitted in backward Dedcated Physical Data Channel (DPDCH)] at step SI 10. [36] The SLR is bwered by a predetermined vabe ("X" dB) at step Sil l when it is Target determined that the received data has no frame error. A pflot field is examined at S 112 in case a frame error is found in the received data. The SLR is raised by a first pre- Target determined vabe ("Y" dB) at step SI 13 if it is determined that no pflot error has occurred accordng to the result of the pflot error check. Otherwise, the SIR is Target raised by a second predetermined vabe ("Z" dB), which is greater than the first predetermined vabe ("Y" dB), at step S 114 if it is determined that a pflot error has occurred accordng to the result of the pflot error check. [37] That is, the embodment of the present invention determines if the received frame has an error by examining the CRC of the backward DPDCH frame in channel card of N)de-B to set SLR . The result of the CRC examination is informed to RNC by Target "CRC1" field shown in Rg. 3, which is a backward data frame of frame protocd defined in the standard. [38] SLR set by the outer-bop power contrd in Rg. 5 is transmitted to N)de-B by Target "UL Outer bop power contrd" frame in the frame protocd. This is to maintain the target BLER accordng to the error existence of the frame that is received by the "CRC1" fieH in Rg. 3. [39] Ln the embodment of the present invention, the error existence of the DPCCH frame through the examination of the backward DPCCH pflot field, as wel as the result of the CRC examination of the DPDCH frame, is used for the outer-bop power contrd. The information on the error existence on the pflot field is informed to RNC by "Spare Extension" field in Rg. 3, and thus is used as a vabe to set the SLR . The Target error existence of the pflot field can be determined by comparing the received pilot fields to the pflot patterns in Rgs. 7 and 9 accordng to the sbt format of Rg. 6. [40] The reason for bwering the SLR accordng to the error existence of the CRC Target and the pflot field is that the cal quality felt by the user is determined by the target BLER through examination of the CRC in the data transmitted by the DPDCH channel. [41] Further, the reason for raising the SLR to a dfferent vabe is as fdbws. Higher Target gain is applied to the backward DPCCH channel to reduce the errors because it transmits contrd data of the DPDCH channel. Therefore, the channel environment of pattern 4 is worse than that of pattern 3. To compensate the dfference of the channel environments, the SIR is adjusted accordng to the channel environment by setting Target the second predetermined vabe ("Z" dB) greater than the first predetermined vabe ("Y" dB). [42] Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. Therefore, the scope of the appended claims should not be limited to the description of the preferred versions contained therein.

Claims

[1] A method of controling power in a W-CDMA mobile communication system, the method comprising the steps of: estimating a Signa o-Interference Ratio (SLR) after initializing parameters and setting a target SLR; comparing the estimated SLR with the target SLR; instructing a user equipment (UE) to bwer transmission power if the estimated SLR is greater than the target SLR; instructing the user equipment (UE) to raise the transmission power if the estimated SLR is not greater than the target SLR; checking if received data has any frame error in case uplink data has been received; bwering the target SLR by a predetermined vabe when it is determined that the received data has no frame error; raising the target SLR by a first predetermined vabe ("Y") if it is determined that no pflot error has occurred in case a frame error was found in the received data; and raising the target SLR by a second predetermined vabe ("Z") if it is determined that a pflot error has occurred in case a frame error was found in the received data. [2] The method accordng to Claim 1, wherein the second predetermined vabe is greater than the first predetermined vabe.