JP4968244B2 - Cellular system, communication control method thereof, and base station used therefor - Google Patents

Description

  The present invention relates to a cellular system, a communication control method thereof, and a base station used therefor, and more particularly to a high-speed downlink packet access (HSDPA) cellular system, a communication control method thereof, and a base station used therefor. .

  HSDPA that transmits high-speed data on a downlink from a base station to a mobile station in a cellular system has been proposed by 3GPP (3rd Generation Pertnership Project). In this HSDPA, a high-speed physical downlink shared channel (HS-PDSCH) is used for downlink transmission from a base station to a mobile station. This HS-PDSCH is used for data transmission from each base station to a plurality of mobile stations. For this purpose, the base station or its control station determines a schedule for performing data transmission to each of the plurality of mobile stations. Thus, data is transmitted at a different timing (time division method) for each mobile station.

  In order to control such data transmission from the base station to the mobile station, each base station sets a DPCH (Dedicated Physical Channel), which is a dedicated channel, with each of the plurality of mobile stations. The DPCH is used to transmit control information from the base station to the mobile station using the downlink signal and to transmit a control signal from the mobile station to the base station using the uplink signal.

  In each mobile station, the rate of time for receiving data using the HS-PDSCH is small, but the DPCH is continuously set up with the base station even in the data standby state where data is not received, and the data Data transmission can be started in a short time. For this reason, each base station simultaneously transmits one mobile station at a time, but a large number of mobile stations are in a data standby state and set up DPCH with the base station.

  In the cellular system, there is a technique called soft handover in which a mobile station sets a channel simultaneously with a plurality of base stations. Each base station transmits a common pilot signal with a predetermined power, and the mobile station sets up a DPCH with a base station having the maximum reception power of the common pilot signal, but in soft handover, the reception power of the common pilot signal is set. When there is another base station having a small difference, the DPCH is set with the other base station, and the DPCH is set with a plurality of base stations. In the following description, a base station that sets DPCH during soft handover is referred to as a connected base station.

  In the cellular system, a technique called high-speed closed loop transmission power control is applied. This high-speed closed loop transmission power control is applied to both the uplink and the downlink for the DPCH. In DPCH uplink transmission power control, the base station measures the received SIR (Signal to Interference Ratio) using an individual pilot signal included in the uplink signal, and compares the measured value with a predetermined target SIR. . If the measured value is smaller than the target SIR, a TPC (Transmit Power Control) bit indicating an increase in power is included in the downlink signal of the DPCH in other cases, and a TPC bit indicating a decrease in power is notified to the mobile station. To do. Then, the mobile station receives the TPC bit and increases or decreases the transmission power according to the TPC bit.

  When this uplink transmission power control is used together with soft handover, the mobile station receives a TPC bit from each of a plurality of connected base stations, and when at least one TPC bit indicates a power decrease, the transmission power of the DPCH In other cases (that is, when all TPC bits are increased in power), the transmission power of DPCH is increased. By performing such transmission power control, the reception quality of the uplink signal satisfies the target SIR in at least one connected base station, and at the same time, the reception quality of the uplink signal satisfies the target SIR in all the connected base stations. It is prevented that the interference wave power of the uplink is increased.

  On the other hand, in downlink transmission power control of DPCH, the mobile station measures the received SIR using an individual pilot signal included in the downlink signal, and compares the measured value with a predetermined target SIR. If the measured value is smaller than the target SIR, a TPC bit indicating an increase in power is included in the uplink signal on the DPCH, and a TPC bit indicating a decrease in power is reported to the base station. Then, the base station receives the TPC bit, and increases or decreases the transmission power according to the TPC bit.

  When this downlink transmission power control is used together with soft handover, the mobile station receives and synthesizes DPCH downlink signals from each of a plurality of connected base stations, and combines the received downlink signal reception SIR. The TPC bit is determined by comparison with the target SIR. Then, a common TPC bit is transmitted to a plurality of connected base stations, and each of the connected base stations increases or decreases transmission power according to the TPC bit. In this way, all connected base stations increase / decrease the transmission power according to a common TPC bit, thereby maintaining a balance of transmission power between the connected base stations, and a connected base station that minimizes the propagation loss with the mobile station. The downlink signal to be transmitted is received by the mobile station with a good quality to prevent the transmission power of the downlink signal from increasing more than necessary, and the interference signal power of the downlink is not increased. .

  The transmission power control and soft handover described above are used as a radio access method, particularly in a CDMA (Code Division Multiple Access) cellular system, by reducing the transmission power to reduce the interference wave power, thereby reducing the line capacity. It is an effective technology for increasing

  Here, during the soft handover, the mobile station (MS) 3 is connected to the DPCH simultaneously with a plurality of connected base stations (BS) 1 and 2, as shown in FIG. HS-PDSCH is connected to only one base station (base station 1 in the figure). As described above, the mobile station 3 receives acknowledgment (ACK / NACK: Acknowledge / Non-Acknowledge) information indicating whether or not the packet transmitted by the HS-PDSCH has been received without error. The reception confirmation notification information uses an uplink HS-DPCCH (High-Speed Dedicated Physical Control Channel: HS-PDSCH dedicated control channel including packet transmission control information). Sent.

  The relationship between the uplink HS-DPCCH and the uplink DPCH is as shown in FIG. 11, and the DPCH is composed of a DPCCH (Dedicated Physical Control Channel) and a DPDCH (Dedicated Physical Data Channel). The DPCCH includes a dedicated pilot channel (Pilot), a TPC bit, and FBI (Feed Back Information). DPDCH is data and includes user information and control information. The DPCCH and DPDCH are transmitted after being orthogonally modulated and multiplexed.

  HS-DPCCH is assigned slot lengths corresponding to three slots of DPCCH and DPDCH, and includes the above-described acknowledgment (ACK / NACK) information and CQI (Channel Quality Indicator) indicating downlink quality. ing. This HS-DPCCH is transmitted by DPCH and code multiplexing. And since the determination of the ACK (acceptance) / NACK (non-acceptance) signal included in this HS-DPCCH is performed only by the base station transmitting the HS-PDSCH, that is, the packet transmission base station, Diversity synthesis is not performed.

On the other hand, as shown in FIG. 10, the uplink DPCH undergoes diversity combining between the connected base stations 1 and 2 in the radio network control station (RNC) 10, and this DPCH is, as described above, High-speed closed-loop transmission power control is performed to achieve a predetermined reception quality. The transmission power PH of the HS-DPCCH is transmitted with a power obtained by adding a predetermined offset power Δ to the transmission power PD of the DPCH. It has become so. That is,
PH = PD + Δ (1)
Sent in a relationship.

In addition, there exist patent document 1 and nonpatent literature 1 as a related technique.
JP 2001-274748 A Samsung, UL Power Control for HSDPA, 3GPP TSG-RAN WG1 # 22, November 19, 2001

In this way, based on ACK / NACK transmitted from the mobile station using HS-PDCCH, the packet transmission base station determines whether or not the packet has been correctly received by the mobile station. , it is assumed that the packet corresponding thereto can not be received correctly at the mobile station performs a retransmission of the packet, so as to prevent packet loss.

  Here, in particular, when NACK is mistaken for ACK, the base station will transmit the next packet even though the packet is not correctly received. Packets are lost without being retransmitted and lost at the mobile station. Therefore, the reception error rate for NACK needs to be sufficiently smaller than that for ACK, in other words, the reception quality of the ACK / NACK signal at the packet transmission base station needs to be sufficiently high. .

  However, if no measures are taken, the reception quality of ACK / NACK is lowered by the operation described below.

  During execution of the soft handover, the transmission power of the UL (Up-Link) DPCH serving as a reference for the transmission power of the HS-DPCCH is controlled as follows. When the reception SIR of the UL DPCH is larger than the reference SIR, the connecting base station transmits a TPC signal that decreases power, and when the combined received SIR is smaller than the reference SIR, the connecting base station transmits a TPC signal that increases power. Send.

  Further, the mobile station that is executing the soft handover receives the TPC signal from each connected base station, increases the transmission power when all the TPC signals are increased in power, and at least one TPC signal is decreased in power. Sometimes the transmission power is reduced. At this time, even if the reception SIR of the UL DPCH of the packet transmission base station is less than the reference SIR, if the reception SIR of the UL DPCH of other base stations is equal to or greater than the reference SIR, at least one TPC signal for the mobile station is Since the power decreases, the mobile station decreases the transmission power of the UL DPCH, and the reception SIR of the UL DPCH of the packet transmission base station further decreases. Accordingly, the reception quality of the HS-DPCCH is degraded.

  Thus, during soft handover, because of the TPC signal other than the packet transmission base station, there is a problem that the reception quality of the HS-DPCCH deteriorates and the reception error of ACK / NACK is likely to occur.

  During execution of soft handover, transmission power of DL (Down-Link) DPCH including a TPC signal for controlling transmission power of UL DPCH is controlled as follows. The mobile station executing the soft handover combines the DL DPCHs transmitted from the connected base stations, and when the combined SIR is larger than the reference SIR, transmits a TPC signal for reducing the power. When the received SIR is smaller than the reference SIR, a TPC signal for increasing power is transmitted, and each base station controls transmission power according to the TPC signal.

  At this time, even if the reception SIR of the DL DPCH of the packet transmission base station is smaller than the reference SIR, if the reception SIR of the DL DPCH of the other base station is large, the combined reception SIR becomes larger than the reference SIR. Therefore, each base station decreases the DL DPCH transmission power, and the DL DPCH reception SIR of the packet transmission base station further decreases. Therefore, the reception quality of the TPC signal transmitted from the packet transmission base station is lowered, and the reception error of the TPC signal is increased. At this time, even if the packet transmission base station transmits the TPC signal for increasing the transmission power of the mobile station in order to increase the reception SIR of the UL DPCH, the reception SIR of the UL DPCH is reduced due to an error in the TPC signal. Accordingly, there is a problem that the reception quality of the HS-DPCCH is lowered accordingly, and reception errors of ACK / NACK are likely to occur.

  In particular, in each base station, when a TPC signal reception error occurs, the transmission power of the DL DPCH of the packet transmission base station becomes smaller than the transmission power of the DL DPCH of another base station, and the above problem occurs. It becomes easy.

  The following two methods can be considered as conventional methods for improving the above problems. As a first method, when the mobile station is in the soft handover state, there is a method for increasing the value of the offset power Δ of the HS-DPCCH than in the non-soft handover state. In this method, the appropriate Δ differs depending on the number of connected base stations, the UL reception quality of the link transmitting the packet, and the like, so that it is difficult to determine the optimal Δ increment. . Further, in order to sufficiently reduce the reception error rate of ACK / NACK, it is necessary to increase the value of Δ with a margin, the uplink transmission power becomes larger than necessary, and the power consumption of the mobile station increases. There is a disadvantage that the interference power of the uplink increases.

  Furthermore, since the transmission power of the HS-DPCCH is larger than that of the DPCCH, there is a disadvantage that the reception quality of the pilot signal of the DPCCH deteriorates and the channel estimation accuracy deteriorates. In order to clear the above-described drawbacks, it is conceivable to add a pilot signal to the HS-DPCCH. However, since a pilot signal that is used only during the soft handover is always transmitted, there is a problem in that resource use efficiency decreases.

  As a second method, during SHO, the packet transmission base station generates a signal TPC-HS for high-speed closed-loop control type transmission power control for the reception quality of HS-DPCCH, and moves either or both of the normal TPC signals. There is a method of transmitting to the station. In this method, the target SIR has to be set to a more demanding quality so that both the quality of the ACK signal and the NACK signal is satisfied in the packet transmission base station. Therefore, there is a drawback that an excessive transmission signal is consumed. Also, when transmitting TPC-HS instead of normal TPC, HS-DPCCH power is increased to cause interference, resulting in a drawback that the normal DPCCH channel estimation accuracy deteriorates. Furthermore, when TPC-HS is transmitted separately from normal TPC, there is a drawback that the slot format needs to be changed.

  An object of the present invention is to receive, at a high quality, an ACK / NACK signal for a packet receipt confirmation notification transmitted from a mobile station to a base station while solving the above-described various conventional problems. It is to provide a base station in a possible cellular system.

  The cellular system according to the present invention includes a mobile station and a plurality of base stations that are in soft handover state with the mobile station and set up dedicated channels with the mobile station, and the dedicated channels include uplink and downlink dedicated channels, These dedicated channels contain transmission power control information for other dedicated channels, and only a specific base station among base stations in soft handover state sets a shared channel with the mobile station and transmits packets. And a means for controlling the target reception quality of the dedicated channel at the base station to be changed from a first value to a second value larger than that during the packet transmission. It is characterized by that.

  The communication control method according to the present invention includes a mobile station and a plurality of base stations that are in a soft handover state with the mobile station and set up dedicated channels with the mobile station, and the dedicated channels include uplink and downlink dedicated channels. These dedicated channels contain transmission power control information for other dedicated channels, and only a specific base station among the base stations in the soft handover state sets up a shared channel with the mobile station. A communication control method in a cellular system configured to perform transmission, wherein during the packet transmission, the target reception quality of the dedicated channel at the base station is changed from a first value to a second value higher than the first value. It has the step to control, It is characterized by the above-mentioned.

  The base station according to the present invention includes a mobile station and a plurality of base stations that are in a soft handover state with the mobile station and set up dedicated channels with the mobile station, and the dedicated channels include uplink and downlink dedicated channels, These dedicated channels contain transmission power control information for other dedicated channels, and only a specific base station among base stations in soft handover state sets a shared channel with the mobile station and transmits packets. A packet transmission base station in a cellular system adapted to perform the target reception quality of the dedicated channel at the base station during the packet transmission from a first value to a larger second value It has the means to control, It is characterized by the above-mentioned.

  According to the present invention, the packet transmission base station can receive the HS-DPCCH with sufficient quality even when the mobile station is in the soft handover state and sets the DPCH with a plurality of base stations. Therefore, there is an effect that the error rate of the ACK / NACK signal indicating whether or not normal reception of the packet included in the HS-DPCCH is reduced, packet loss is eliminated, and throughput can be improved.

  In addition, the above-described control for reducing the error rate of the ACK / NACK signal is performed only in the soft handover state and during packet transmission / reception, and the control is performed while waiting for a packet whose time ratio is larger than the time during packet transmission / reception. Therefore, the error rate of the ACK / NACK signal can be reduced without causing an increase in transmission power, and the diversity effect at the time of UL / DL DPCH soft handover is not impaired.

  Embodiments 1 to 5 of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing an example of a cellular system to which all of the first to fifth embodiments of the present invention are applied. Referring to the figure, the cellular system includes a base station 1, a base station 2, and mobile stations 3, 4, and 5. Note that the base station 1 and the base station 2 are provided in different cells. Further, in this example, a case where two base stations 1 and 2 exist for three mobile stations 3, 4, and 5 will be described, but the present invention is not limited to this, and three mobile stations 3 , 4 and 5 can also be applied when there are three or more base stations. In general, there are many mobile stations for one base station.

  The present invention can also be applied to the case where there are four or more mobile stations in the transmission system, and the figure shows an example in which three mobile stations 3, 4, and 5 exist. . A CDMA (Code Division Multiple Access) method is used as a wireless access method between the base station and the mobile stations 3, 4, and 5.

  The figure shows an HS-PDSCH signal from the base station 1 to the mobile station 3, a DPCH1 (DL: Down-Link: transmission from the base station to the mobile station) signal, and a CPICH1 (Common Pilot Channel 1) signal. Is transmitted from the mobile station 3 to the base station 1, and a signal of DPCH 1 (UL: Up-Link: transmission from the mobile station to the base station) is transmitted. In addition, the HS-DPCCH (UL) signal illustrated in FIG. 11 is transmitted from the mobile station 3 to the base station 1.

  Similarly, a DPCH2 (DL) signal and a CPICH2 signal are transmitted from the base station 2 to the mobile station 3, and a DPCH2 (UL) signal is transmitted from the mobile station 3 to the base station 2. Yes. This DPCH2 (UL) is the same as DPCH1 (UL) as a transmission signal of the mobile station, although the receiving base station is different from DPCH1 (UL). That is, the HS-DPSCH signal and the CPICH signal are unidirectional signals, and the DPCH signal is a bidirectional signal.

  HS-PDSCH is a high-speed channel and is used for transmitting and receiving large files such as moving images in a short time. CPICH is a common pilot channel (DL only), and a common pilot signal is constantly transmitted from the base stations 1 and 2 to the mobile station 3 via this channel.

  Further, DPCH is an individual (physical) channel (UL and DL), and is configured by DPCCH and DPDCH, as described in FIG. Further, as described above, the HS-DPCCH includes an ACK / NACK signal and CQI indicating the quality of the downlink propagation path, and the relationship between the transmission power and the DPCCH is expressed by the above equation. As shown in (1).

  Next, operations common to all of the first to fifth embodiments will be described. Each base station 1 and 2 transmits CPICH 1 and 2 respectively, and this CPICH is spread by a different scramble code for each cell, and each mobile station identifies a cell by a difference in scramble code. When each mobile station receives downlink data, it sets a DPCH (UL / DL) with one or a plurality of base stations and waits for data reception.

  When the difference in CPICH received power between the mobile station 3 and the base stations 1 and 2 is equal to or less than a predetermined value, not only the base station 1 but also the base station 2 sets DPCH, and a plurality of base stations 1 , 2 and DPCH are set (soft handover).

  The UL and DL DPCHs include a dedicated pilot signal (Pilot) composed of a predetermined bit sequence. The UL DPCH transmission power is controlled by high-speed closed-loop transmission power control. In this control, the base station measures the DPCH reception SIR using the UL DPCH dedicated pilot signal, and the measured value and The target SIR of the base station is compared. If the measured value is smaller than the target SIR, the TPC bit of “Power Up” is notified to the mobile station 3 using the DPCH 1 and 2 of the DL, otherwise the TPC bit of “Power Down” is notified. The value of the target SIR is notified from the radio network control station RNC (10 in FIG. 10).

  Each base station transmits HS-PDSCH, which is a higher-speed channel than DPCH and is transmitted with higher power than DL DPCH. Each base station uses one HS-PDSCH for data transmission to a plurality of mobile stations. The RNC or base station determines a schedule for data transmission to each mobile station, and performs data transmission at a different timing for each mobile station. That is, as an example, the HS-PDSCH is first transmitted to the mobile station 3, and after the transmission is finished, the HS-PDSCH is transmitted to the mobile station 4, and after the transmission is finished, HS-PDSCH is transmitted to the mobile station 5.

  When data to be transmitted from the communication network to the mobile station 3 arrives at the RNC, the RNC sends the data to the base station 1 or 2 where the mobile station 3 has set DPCH. In this case, the data is sent to the base station 1.

  The above is the operation common to all of the first to fifth embodiments. Hereinafter, the first embodiment will be described with reference to the sequence diagram of FIG. When data to be transmitted from the communication network to the mobile station (MS) 3 arrives at the RNC, the RCN sends the data to the base station (BS) where the mobile station 3 has set DPCH. In this case, it is assumed that data is sent to the base station 1 (step S10).

The base station 1 gives a notice to the effect that data is transferred to the mobile station 3 (step S11). Thereafter, the base station 1 increases the SIR for the reception quality of the UL DPCH by a predetermined value (step S12). Further, the transmission power of the TPC bit transmitted on the DL DPCH is increased by a predetermined value and transmitted ( step S13). Furthermore, the reference power for power balancing is increased by a predetermined value, and the transmission power of the DL DPCH is also increased by a predetermined value (step S14).

  This power balancing is specified in 3GPP (3rd Generation Partnership Project), and the DL DPCH transmission power is slowly brought close to the reference power so as not to affect the closed-loop transmission power control. This is to balance the transmission power between base stations. The reference power used for the balancing adjustment is increased by a predetermined value at the packet transmission base station 1.

  In the mobile station 3, after receiving the data transfer advance notice from the base station 1, the transmission power of the UL DPCH transmitted by the own station is controlled only in accordance with the TPC signal transmitted by the packet transmission base station 1 (step S15). .

  In the above state, the first packet # 1 obtained by dividing the data into blocks from the base station 1 is transmitted to the mobile station 3 using the HS-PDSCH (step S16), and the mobile station 3 correctly transmits the packet # 1. If received, ACK is transmitted to base station 1 using HS-DPCCH (step S17). Thereafter, similarly, packet # 2 is transmitted from the base station 1 (step S18), and ACK is transmitted from the mobile station 3 to the base station 1 (step S19).

When the data transmission is completed, the base station 1 notifies the mobile station 3 of the end of data (End of Data) (step S20). In response to the end of data transmission, the base station 1 performs processing for returning the values changed in steps S12 to S14 to the original state (step S21). Also, in the mobile station 3, the UL DPCH transmission power is controlled only by the TPC of the packet transmission base station 1 in step S15, but the UL DPCH is used using the TPCs of all the base stations during soft handover. The transmission power is controlled to return to the original state (step S22). Note that, instead of notifying the end of data, when the packet has not been transmitted for a predetermined time, it is possible to return to the original state before the packet transmission.

  As shown in step S15 described above, the UL DPCH in the packet transmission base station 1 becomes the target quality by performing the transmission power control of the UL DPCH transmitted by the mobile station 3 using only the TPC signal of the packet transmission base station 1. In order to be able to control the transmission power of the mobile station so as to satisfy Quality also satisfies the target quality. As a result, the reception accuracy of the ACK / NACK signal is improved, and the throughput of data transmission by HS-DPSCH is increased.

  Further, the packet transmission base station 1 increases the transmission power of the TPC signal transmitted by the DL DPCH (step S13), or increases the reference power for power balancing and the transmission power of the DL DPCH (step S14). In order to reduce the reception error rate of the TPC signal transmitted by the base station 1 and improve the accuracy of transmission power control in the mobile station 3, it is possible to further improve the reception quality of the ACK / NACK signal in the packet transmission base station 1 Become. Further, in the packet transmission base station 1, the reception quality of the ACK / NACK signal at the base station 1 can be improved by increasing the UL DPCH target SIR (step S12).

  According to the first embodiment, it is not necessary to change the slot format as in the conventional second method, and the offset power values of DPCH and HS-DPCCH are fixed. The channel estimation accuracy does not deteriorate due to the deterioration of the reception quality of the DPCH pilot signal as in the second method, and therefore it is not necessary to put the pilot signal in the HS-DPCCH. In the first embodiment, the processing in steps S12 to S15 is applied only during packet transmission / reception, and the time ratio is larger than the time during packet transmission / reception. No increase in interference occurs.

  Note that the object of the present invention can be achieved only by the operation in the mobile station 3 in step S15, and even if the operation in step S15 and the operation in the packet transmission base station 1 in step S12 are combined, the present invention can be achieved. The objective of can be achieved. In addition, the object of the present invention can be achieved only by performing the operation of step S13 and the operation of step S14 independently in the packet transmission base station 1. Furthermore, it is only necessary to increase the reference power for power balancing in step S14.

  3 and 4 respectively show schematic functional block diagrams of the base station and the mobile station for realizing the first embodiment. Referring to FIG. 3, in the base station, a received signal from the antenna 11 is input to a receiving unit 13 via an antenna duplexer (DUP: Duplexer) 12, and processing such as amplification, frequency conversion, and demodulation is performed. The demodulated output is separated into user information and various control information by a channel separator 14. The control information is input to the control unit (CPU) 15, and processes such as steps S 12 to S 14 and S 21 shown in the sequence diagram of FIG. 2 are executed according to a program procedure stored in the memory 16 in advance.

  On the other hand, user information and control information for the mobile station are combined by the channel combining unit 17, amplified by the amplifying unit 18 and supplied to the transmitting unit 19, and subjected to processing such as modulation and frequency conversion, and then the antenna duplexer 12 and the antenna. 11 is transmitted.

  Referring to FIG. 4, in the mobile station, the received signal from the antenna 21 is supplied to the receiving unit 23 via the antenna duplexer 22, and processing such as amplification, frequency conversion, and demodulation is performed. The demodulated output is separated by the channel separator 24 into user information and TPC signals as control information. The TPC signal is input to the control unit (CPU) 25, and the processes of steps S15 and S22 shown in the sequence diagram of FIG. 2 are executed according to a program procedure stored in the memory 26 in advance.

  On the other hand, user information and control information for the base station are combined by the channel combining unit 27, amplified by the amplifying unit 28, supplied to the transmitting unit 29, and subjected to processing such as modulation and frequency conversion, and the antenna duplexer 22 and the antenna. 21 is transmitted.

  Next, Embodiment 2 of the present invention will be described with reference to the operation sequence diagram of FIG. When data to be transmitted from the communication network to the mobile station 3 arrives at the RNC, the RNC sends the data to the base station where the mobile station 3 has set DPCH. In this case, data is sent to the base station 1 (step S30).

  The base station 1 gives a notice to the effect that data is transferred to the mobile station 3 (step S31). Thereafter, the base station 1 increases the target value SIR for the reception quality of the UL DPCH by a predetermined value (step S32). On the other hand, when receiving a data transfer advance notice from the base station 1, the mobile station 3 controls the transmission power of the UL DPCH transmitted by the mobile station 3 only in accordance with the TPC signal transmitted by the packet communication base station 1 (step S33). . In addition, the mobile station 3 increases the target SIR of DL DPCH by a predetermined value (step S34).

Furthermore, the mobile station 3 controls the transmission power control of the UL DPCH in the local station to be larger than the decrease, so that the increase / decrease of the control step is asymmetric (step S35). That is, if the increase step is ΔPup and the decrease step is ΔPdown,
ΔPup> ΔPdown
It is made to become.

  Furthermore, the mobile station 3 generates a TPC signal for DL DPCH power control based on the reception SIR of only the DL DPCH transmitted from the packet transmission base station 1 (step S36).

  Thereafter, the packets # 1 and # 2 obtained by dividing the data into blocks from the base station 1 are transmitted to the mobile station 3 using the HS-PDSCH (steps S37 and S39), and the mobile station 3 transmits each packet to the base station 1. An ACK signal indicating that the packet has been received is transmitted using HS-DPCCH (steps S38 and S40). When the data transmission is completed, the base station 1 notifies the mobile station 3 of the end of data (step S41). In response to the end of the data, the base station 1 returns the value changed in step S32 (step S42), and the mobile station 3 returns the process changed in steps S33 to S36 (step S43). . In this embodiment as well, instead of notifying the end of data, when a packet has not been transmitted for a predetermined time, it is possible to return to the original state before packet transmission.

  In the second embodiment, in addition to performing the same processing (S32 and S33) as steps S12 and S15 of the sequence diagram in FIG. 2 of the first embodiment, the mobile station 3 further performs the target SIR of DL DPCH. (Step S34), the reception quality of the TPC signal received by the mobile station is improved, and the accuracy of UL transmission power control is increased. Therefore, the reception quality of the ACK / NACK signal at the packet transmission base station is improved.

  Further, by making the control step of the UL DPCH transmission power at the mobile station 3 asymmetric, and increasing the increase step greater than the decrease step (step S35), the transmission power is increased so that the required reception quality can be obtained immediately. It becomes possible. Therefore, the required quality can be maintained even in a short transmission time such as a packet. Further, by generating a TPC signal based on the reception SIR of only the DL DPCH from the packet transmission base station (step S36), the reception quality of the DL DPCH at the mobile station is increased, and the TPC signal included in the TPC signal is accurately detected. As a result, the HS-DPCCH transmitted from the mobile station can be accurately received by the base station 1.

  In the second embodiment, the process of steps S32 to S36 is applied only during packet transmission / reception, and the time ratio is larger than the time during packet transmission / reception. No increase in interference occurs.

  In the mobile station 3, the object of the present invention can be achieved only by performing the operation of step S34 and the operation of step S36 independently of each other. The object of the present invention is to combine the operation of step S32 in the packet transmission base station 1 with the operation of step S33 in the mobile station 3 and further combine the operation of step S35 in the mobile station 3. It can be achieved.

  It is obvious that the schematic functional block diagrams shown in FIGS. 3 and 4 can be applied to the base station and the mobile station for realizing the second embodiment.

  Next, Embodiment 3 according to the present invention will be described with reference to the flowcharts of FIGS. FIG. 6 is an operation flow in the mobile station. In response to the data transfer advance notice from the packet transmission base station 1 (step S51), the mobile station 3 transmits the connection base stations 1 and 2 with a predetermined transmission power. The increment of the offset power ΔSHO of the HS-DPCCH is determined according to the quality of the DL. Specifically, the received powers RP1 and RP2 of the common pilot signal from the connected base stations 1 and 2 in the soft handover state are measured (step S52), and the DL quality is determined.

The increment of the offset power ΔSHO of the HS-DPCCH is determined according to the received powers RP1 and RP2 (step S53). Specifically,
ΔSHO = ΔNON-SHO + ₁₀ log ₁₀ {max (RP1, RP2) / RP1}
(DB) (2)
The offset power ΔSHO is calculated by the following formula. Here, ΔNON-SHO is the offset power when not in the soft handover state, and max (RP1, RP2) indicates the maximum of RP1, RP2.

Therefore, if RP1> RP2, ΔSHO = ΔNON-SHO, and if RP1 <RP2,
ΔSHO = ΔNON-SHO + ₁₀ log ₁₀ (RP2 / RP1) (3)
Thus, the second term on the right side is the increment of the offset power. The offset power is increased by the determined increment, and the HS-DPCCH is transmitted (step S54).

  FIG. 7 is an operation flow of the packet transmission base station according to the third embodiment. The flow of FIG. 7 is common to the operation of the base station of the fourth embodiment. Referring to FIG. 7, in response to reception of the HS-DPCCH (step S61), an ACK / NACK determination is performed, and if it is determined to be “NACK” (“N” in step S62), normal processing is performed. (Step S63). That is, since it is “NACK”, the corresponding packet is retransmitted.

  When it is determined as “ACK” in step S62, the packet transmission in the UL is determined according to the reliability of the reception determination result of HS-DPCCH ACK / NACK. That is, the reliability of the ACK / NACK reception determination result is detected (step S64), and this reliability is compared with a predetermined threshold (step S65). If the reliability is higher than the threshold, the process proceeds to normal processing (step S63). If the reliability is low, it is always determined that the signal is NACK regardless of the ACK / NACK signal (step S66). Therefore, the corresponding packet is retransmitted (step S67).

  According to the third embodiment, compared to other base stations among the connected base stations, the offset is larger depending on the UL propagation loss (line quality) of the packet transmission base station, that is, if the propagation loss is large. If the power (ΔSHO) is small, a smaller offset power is set, so that it is possible to compensate for reception quality deterioration of the ACK / NACK signal due to propagation loss. Further, in the ACK / NACK determination at the packet transmission base station, if it is erroneously determined that NACK is ACK, packet loss occurs, but if it is determined that it is ACK, it depends on the reliability of the reception determination result. By always determining NACK, the NACK error rate can be reduced, the packet loss rate can be reduced, and the throughput can be improved.

  In this embodiment, the number of base stations in the soft handover state is 2. However, when the number is 3 or more, max {PR1, PR2} in the above formula (2) is max {PR1, PR2, PR3,. It is clear that ...

  6 and 7 can be realized by the functional blocks shown in FIGS. 3 and 4.

Embodiment 4 of the present invention will be described. FIG. 8 is an operation flowchart of the mobile station according to the fourth embodiment. In response to the data transfer notice (step S71), the mobile station determines the increment of the HS-DPCCH offset power ΔSHO according to the number N of base stations in soft handover (step S72). In particular,
ΔSHO = ΔNON-SHO + ₁₀ log ₁₀ N (dB) (4)
The offset power is calculated according to the following formula, and therefore, the increment of the offset power is the second term on the right side of the formula (4). The HS-DPCCH is transmitted with the offset power of equation (4) increased by this increment (step S73). The operation flow of the packet transmission base station in the fourth embodiment is the same as that in FIG.

  The fourth embodiment has the following effects. That is, if the number N of base stations in soft handover becomes large, the DPCH reception diversity gain becomes large and the transmission power of the DPCH decreases. However, if this number N increases, Accordingly, since the HS-DPCCH offset power increment is also increased, the HS-DPCCH reception quality can be controlled to a required value regardless of the number of base stations during soft handover.

  Further, when it is determined as ACK in the base station, the NACK error rate is reduced by always determining NACK according to the reliability of the reception determination result of HS-DPCCH ACK / NACK, and the packet loss rate is reduced. Can be reduced and the reliability of the HS-DPCCH ACK / NACK reception determination result is not always calculated, but only when it is determined as ACK, so that the load for the calculation can be reduced. become.

  Further, in the fourth embodiment, the mobile station applies the processing of FIG. 8 only during packet reception, and the time ratio is larger than the time during packet reception. In the meantime, no increase in interference occurs. Of course, the operation of the fourth embodiment can also be realized by the functional blocks shown in FIGS.

A fifth embodiment of the present invention will be described. In the fifth embodiment, as shown in FIG. 10, the uplink DPCH is subjected to diversity combining between the connecting base stations 1 and 2 in the radio network control station (RNC) 10, and this DPCH is usually Control is performed so as to obtain a predetermined reception quality by high-speed closed loop transmission power control. Specifically, the mobile station increases or decreases the transmission power of the DPCCH according to the TPC bit transmitted from the base station, and the transmission power PDDPCH of the DPDCH is transmitted with the power obtained by adding a predetermined offset value Δ1 to the transmission power PDPCCH of the DPCCH. It has come to be. That is,
PDDPCH = PDPCCH + Δ1 (dB) (5)
Sent in a relationship.

Further, the transmission power PH of the HS-DPCCH is transmitted with a power obtained by adding a predetermined offset value Δ2 to the transmission power PDPCCH of the DPCCH. That is,
PH = PDPCCH + Δ2 (dB) (6)
Sent in a relationship. However, in Equations (5) and (6), each value is a decibel value.

  This operation is substantially the same as that of the first embodiment. However, in the fifth embodiment, when the transmission power of the mobile station is limited to a predetermined maximum value, the HS-DPCCH transmission power is given priority. And transmission power of DPDCH is suppressed. Except this point, the second embodiment is the same as the first embodiment. Control for suppressing the transmission power of the DPDCH is performed in the control unit 25 of the mobile station in FIG.

  FIG. 9 is a flowchart of transmission power suppression of DPDCH in the fifth embodiment. Referring to FIG. 9, the mobile station receives the TPC bit (step S81), calculates the total transmission power of the DPCCH and HS-DPCCH (step S82), and calculates the maximum transmission power that can be allocated to the DPDCH (step S83). ). This DPDCH maximum transmission power is obtained by subtracting the total transmission power of DPCCH and HS-DPCCH from a predetermined maximum value of transmission power.

  If the DPDCH transmission power calculated by equation (5) does not exceed the DPDCH maximum transmission power, the DPDCH transmission power is set to a value calculated by equation (5) (step S85), and equation (5) When the DPDCH transmission power calculated by the above exceeds the DPDCH maximum transmission power, the DPDCH transmission power is suppressed to the DPDCH maximum transmission power (step S86).

  As a method for suppressing the transmission power of DPDCH, the offset value Δ1 in equation (5) may be temporarily reduced when the total transmission power of the mobile station approaches a predetermined maximum value. .

  The fifth embodiment has the following effects. That is, when the propagation loss from the mobile station to the base station is large or when the interference wave power received by the packet transmission base station is large, the mobile station needs to transmit the HS-DPCCH with a large transmission power. If the ratio of the transmission power of DPDCH is kept constant, the transmission power of the mobile station reaches a predetermined maximum value, so that the transmission power of HS-DPCCH cannot be increased sufficiently. There is a possibility that the reception quality of the included ACK / NACK signal deteriorates.

  However, in the fifth embodiment, when the transmission power of the mobile station is limited to a predetermined maximum value, the transmission power that can be allocated to the HS-DPCCH is increased to suppress the transmission power of the DPDCH, The possibility that the reception quality of the ACK / NACK signal deteriorates is reduced. As a result, the reception quality of the ACK / NACK signal is improved at the packet transmission base station, and the throughput of data transmission by HS-DPSCH increases.

  In the fifth embodiment, in the soft handover state in which the mobile station sets up dedicated channels with a plurality of base stations, the TPC signal of the packet transmitting base station is received during packet reception as shown in step S15 of the first embodiment. Only, the transmission power control of the UL DPCH transmitted by the mobile station is performed. At this time, among the base stations in soft handover state with the mobile station, the packet transmission is performed even though the reception quality of the DPCCH and DPDCH satisfies the predetermined quality target in the base stations other than the packet transmission base station. Since the reception quality of the DPCCH and DPDCH at the base station does not satisfy a predetermined quality target, the mobile station may increase the transmission power of the DPCCH and DPDCH. In this case, the transmission power of DPDCH is increased more than necessary. This is because DPDCH received by a plurality of base stations in the soft handover state is diversity combined. Therefore, in the soft handover state, there is a relatively high possibility that the transmission power of the mobile station is limited to a predetermined maximum value.

  However, in the fifth embodiment, the transmission power of the HS-DPCCH is not limited by the maximum value of the transmission power of the mobile station by suppressing the transmission power of the DPDCH. Therefore, particularly in the soft handover state, the effect of improving the reception quality of the ACK / NACK signal at the packet transmission base station is increased.

It is the schematic of the cellular system with which the Example of this invention is applied. It is a sequence diagram which shows operation | movement of Example 1 of this invention. It is a block diagram of the base station in the Example of this invention. It is a block diagram of the mobile station in the Example of this invention. It is a sequence diagram which shows operation | movement of Example 2 of this invention. It is a flowchart which shows operation | movement of the mobile station in Example 3 of this invention. It is a flowchart which shows operation | movement of the base station in Example 3, 4 of this invention. It is a flowchart which shows operation | movement of the mobile station in Example 4 of this invention. It is a flowchart which shows operation | movement of the mobile station in Example 5 of this invention. It is the schematic for demonstrating the general operation | movement in a cellular system. It is a format figure for demonstrating the relationship between UL DPCH and HS-DPCCH in a HSDPA system.

Explanation of symbols

1, 2 Base station (BS)
3-5 Mobile station (MS)
10 RNC
11,21 antenna 12,22 antenna duplexer (DUP)
13, 23 Reception unit 14, 24 Channel separation unit 15, 25 Control unit (CPU)
16, 26 Memory 17, 27 Channel combiner 18, 28 Amplifier 19, 29 Transmitter

Claims (3)

A mobile station and a plurality of base stations that are in a soft handover state with the mobile station and set up dedicated channels with the mobile station, and the dedicated channels include uplink and downlink dedicated channels, and these dedicated channels Cellular system that includes transmission power control information for other dedicated channels, and only a specific base station among base stations in a soft handover state sets a shared channel with the mobile station to perform packet transmission Because
A cellular system comprising: means for controlling to change the target reception quality at the base station of the dedicated channel from a first value to a second value higher than the target value during the packet transmission. A mobile station and a plurality of base stations that are in a soft handover state with the mobile station and set up dedicated channels with the mobile station, and the dedicated channels include uplink and downlink dedicated channels, and these dedicated channels Cellular system that includes transmission power control information for other dedicated channels, and only a specific base station among base stations in a soft handover state sets a shared channel with the mobile station to perform packet transmission A communication control method in
A communication control method, comprising: a step of changing the target reception quality of the dedicated channel at the base station from the first value to a second value higher than the target value during the packet transmission. A mobile station and a plurality of base stations that are in a soft handover state with the mobile station and set up dedicated channels with the mobile station, and the dedicated channels include uplink and downlink dedicated channels, and these dedicated channels Cellular system that includes transmission power control information for other dedicated channels, and only a specific base station among base stations in a soft handover state sets a shared channel with the mobile station to perform packet transmission A packet transmission base station in
A base station comprising means for changing and controlling the target reception quality at the base station of the dedicated channel from a first value to a second value larger than that during the packet transmission.

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