JP2005229393A - Communication terminal device and tfc selecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To select a TFC which is suitable for channel quality at the time of transmission by following an environmental change. <P>SOLUTION: A required SIR calculating part 170 regulates a target BLER (Target Block Error Rate), on the basis of communication quality (QoS) and calculates a required SIR necessary for satisfying the target BLER concerning DPCCH and each TFC. An offset calculating part 171 calculates a difference between the required SIR of each TFC and the required SIR of DPCCH as the offset of each TFC. A transmission power calculating part 172 calculates transmission power of each TFC by adding the offset of each TFC to the transmission power of DPCCH. An upper limit value calculating part 173 calculates the upper limit value of the transmission power of the TFC by subtracting the transmission power of DPCCH from total transmission power. A TFC selecting part 174 selects one TFC from the TFCs of the transmission power being less than the upper limit value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a communication terminal apparatus used in a CDMA wireless communication system and a TFC selection method thereof.

  As a technique for transmitting packet data on the downlink in the WCDMA system, a high-speed packet transmission system called HSDPA (High-Speed Downlink Packet Access) is known. Also, studies are being made on increasing the packet transmission speed and reducing the delay on the uplink called Uplink Enhancement.

  In the uplink of a wireless communication system, if the total transmission power of the communication terminal device exceeds the maximum transmission power, control such as stopping the transmission of any channel or lowering the transmission rate is performed. Must not exceed the maximum transmission power. In the W-CDMA 3GPP Release 99 specification, Transport Format Combination Selection (hereinafter referred to as “TFC selection”) is standardized as a method for realizing this in Uplink Enhancement.

  In TFC selection, when a communication terminal apparatus multiplexes and transmits data using a plurality of DCHs (dedicated channels), a transport format (Transport Format: hereinafter referred to as “TF”) indicating the amount of data to be transmitted on each DCH. For each Transport Format Combination (hereinafter abbreviated as “TFC”), it is determined whether or not the total transmission power does not exceed the maximum transmission power, and a transmittable TFC is selected. To do. In the following description, a set of all TFCs is called a TFCS (Transport Format Combination Set).

  Hereinafter, TFC selection will be specifically described with reference to the drawings. FIG. 8 shows a case where there are two DCHs, DCH # 1 has three TFs, and DCH # 2 has two TFs (FIG. 8A). In this case, as shown in FIG. 8B, there are six TFCs TFC1 to TFC6. In FIGS. 8A and 8B, the number of bits of each TF is represented by the length of the horizontal axis.

  Here, it is necessary to increase the transmission rate as the number of bits that must be transmitted per unit time increases. In order to obtain a predetermined quality, the transmission power must be increased as the transmission rate increases. In FIG. 8C, the transmission power of each TFC is represented by the length of the horizontal axis, and the dotted line indicates the maximum transmission power Pmax.

  In the case of FIG. 8C, the communication terminal apparatus determines that transmission is possible because the total transmission power is lower than the maximum transmission power Pmax in TFC1 to TFC3 in TFCS, and the total transmission power is the maximum transmission power Pmax in TFC4 to TFC6 in TFCS. It is determined that transmission is impossible because the transmission power is insufficient. Then, the communication terminal apparatus selects one TFC from TFC1 to TFC3 determined to be transmittable.

  Next, a detection function and a TFCS restriction function in TFC selection of Release 99 will be described with reference to the drawings.

  As shown in the state transition diagram of FIG. 9, the communication terminal apparatus detects an Elimination criterion / Recovery criterion for all TFCs for every frame (= 15 slots) as a detection function. Specifically, for a TFC that is in a supported state (transmission enabled state), at least X [slot] (X is the last consecutive Y [slot] that the transmission power required for the TFC exceeds the maximum transmission power. If it does not have to be continuous, the Elimination criterion is detected, and a transition is made to the excess power state. In addition, for a TFC in the excess power state, when there is a continuous Z [slot] immediately before that the transmission power required for the TFC does not exceed the maximum transmission power, the recovery criterion is detected, and the state transits to the supported state. . Note that the parameters X, Y, and Z have values shown in FIG. 10 as default values.

  In addition, as a TFCS restriction function, the communication terminal apparatus prohibits transmission in the blocked state (transmission stopped state) and transmits in the supported state for every TFC every frame (= 15 slots). The restriction process is performed.

FIG. 11 is a diagram illustrating the timing of the TFCS restriction function. As shown in FIG. 11, in the conventional TFC selection method, after transitioning to the _supported state by the detection function, transition to the _supported state by the TFCS limiting function after T _{delay_transition} (default value is 60 ms). _Further, after the transition to the _excess power state by the detection function, the transition to the _blocked state by the TFCS limiting function is _made after T _{delay_transition} .
3GPP Release99 TR25.896

  However, in the conventional TFC selection method, since it takes a predetermined time from the transition of the state by the detection function to the transition of the state by the TFCS limiting function, it can follow the environmental change in an environment where fading fluctuation is severe. Cannot be selected, and a TFC suitable for the channel quality at the time of transmission cannot be selected. As a result, errors are often detected in the base station apparatus, and it is considered that the throughput of the entire system is reduced.

  The present invention has been made in view of such points, and it is an object of the present invention to provide a communication terminal apparatus and a TFC selection method capable of following a change in environment and selecting a TFC suitable for channel quality at the time of transmission. To do.

  In order to solve this problem, the communication terminal apparatus of the present invention includes transmission power calculation means for calculating the transmission power of each TFC by adding the offset of each TFC (Transport Format Combination) to the transmission power of the dedicated control channel. An upper limit value calculating means for subtracting the transmission power of the dedicated control channel from the total transmission power to calculate the upper limit value of the TFC transmission power, and selecting one TFC from the TFCs having a transmission power lower than the upper limit value And a TFC selection unit.

  With this configuration, TFC selection can be performed on a slot-by-slot basis, so that even under an environment where fading fluctuations are severe, it is possible to perform TFC selection suitable for channel quality at the time of transmission, and to perform system-wide selection. Throughput can be improved.

  The communication terminal apparatus of the present invention includes an offset adjustment unit that adjusts the offset by adding an adjustment value to the offset of each TFC, and the transmission power calculation unit uses the offset after the adjustment to each TFC. A configuration for calculating transmission power is adopted.

  With this configuration, the offset used when calculating the TFC transmission power can be adjusted, and the TFC transmission power can be increased when the propagation environment is bad. Can be improved.

  The communication terminal apparatus of the present invention, for the dedicated control channel and each TFC, required SIR calculation means for calculating a required SIR that is a SIR (ratio of desired wave power and interference wave power) that satisfies a target block error rate; An offset calculating means is provided that calculates a difference between the required SIR of each TFC and the required SIR of the dedicated control channel as an offset of each TFC.

  With this configuration, since the offset of each TFC can be the difference between the required SIR of each TFC and the SIR of the dedicated control channel, an appropriate TFC offset that can satisfy a predetermined communication quality is set. Can do.

  The communication terminal apparatus of the present invention subtracts the propagation loss from the upper limit value of the TFC transmission power to calculate an expected maximum received power that is a maximum received power of the TFC that can be received by the base station apparatus, and the expected maximum received power Expected SIR calculating means for calculating an expected SIR that is a minimum necessary SIR that is expected to obtain a predetermined quality in the base station apparatus by dividing power by the total target interference power value in the base station apparatus. The TFC selection means adopts a configuration in which one TFC is selected from TFCs whose transmission power is lower than the upper limit value and whose required SIR is lower than the expected SIR.

  With this configuration, in addition to the transmission power of each TFC calculated using the transmission power and offset of the dedicated control channel, TFC selection is performed based on the relationship between the expected SIR required in the base station apparatus and the required SIR of each TFC. Therefore, more accurate TFC selection can be performed.

  The communication terminal apparatus according to the present invention calculates a propagation loss by subtracting the reception power of the common control channel from the transmission power of the common control channel included in the data of the common control channel transmitted from the base station apparatus. A configuration including loss calculation means is adopted.

  With this configuration, since the common control channel has higher power and longer symbols than the pilot symbol of the uplink dedicated channel, a highly reliable value can be obtained.

  In the communication terminal apparatus of the present invention, the TFC selection means may increase the TFC level when the base station apparatus can correctly demodulate the packet data, and correctly demodulate the packet data at the base station apparatus. If an error cannot be detected, a configuration in which the TFC level is lowered is adopted.

  With this configuration, the selected TFC can be adjusted and the TFC level can be lowered when the propagation environment is bad. Therefore, it is possible to suppress the error occurrence rate in the base station apparatus and improve the throughput of the communication system.

  The TFC selection method of the present invention includes the step of calculating the transmission power of each TFC by adding the offset of each TFC (Transport Format Combination) to the transmission power of the dedicated control channel, and the total control power of the dedicated control channel. A method comprising: subtracting transmission power to calculate an upper limit value of TFC transmission power; and selecting one TFC from TFCs having transmission power lower than the upper limit value.

  By this method, TFC selection can be performed on a slot basis, so that even under an environment where fading fluctuation is severe, it is possible to perform the TFC selection suitable for the channel quality at the time of transmission, following the change in the environment. Throughput can be improved.

  According to the present invention, since TFC selection can be performed on a slot basis, TFC selection suitable for channel quality at the time of transmission can be performed even under an environment where fading fluctuation is severe, and TFC selection suitable for transmission can be performed. Overall throughput can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a communication terminal apparatus according to Embodiment 1 of the present invention.

  First, the configuration of the receiving unit of the communication terminal apparatus in FIG. 1 will be described.

  Reception radio section 102 down-converts the signal received by antenna 101 into a baseband signal and performs A / D conversion processing.

  Despreading section 103 performs despreading processing on the output signal of reception radio section 102 with a DCH spreading code. Demodulation section 104 performs demodulation processing on the output signal of despreading section 103. Channel decoding section 105 performs a decoding process on the output signal of demodulation section 104 and extracts received DCH data, ACK / NACK, and uplink transmission power control command (hereinafter referred to as “UL-TPC”). The ACK / NACK is input to the buffers 176-1 to 176-N. The UL-TPC is input to the transmission power control unit 154. Note that ACK is a signal indicating that packet data can be correctly demodulated in the base station apparatus, and NACK is a signal that cannot be demodulated correctly in the base station apparatus and an error is detected. This is a signal indicating this.

  The SIR measurement unit 106 measures the desired signal power of the output signal of the despreading unit 103, calculates the interference signal power from the dispersion value of the desired signal power, and calculates the ratio between the desired signal power and the interference signal power (hereinafter referred to as “SIR”). ”). The TPC generation unit 107 generates a downlink transmission power control command (hereinafter referred to as “DL-TPC”) instructing increase / decrease in downlink transmission power based on the magnitude relationship between the downlink reception SIR and the target SIR. . The DL-TPC is input to the channel encoding unit 151.

  Despreading section 109 performs despreading processing on the output signal of reception radio section 102 with a spreading code for CPICH (common control channel). The demodulation unit 110 demodulates the output signal of the despreading unit 109. The channel decoding unit 111 performs decoding and takes out CPICH data.

  Next, the configuration of the transmission unit of the communication terminal apparatus in FIG. 1 will be described.

  Channel encoding section 151 performs encoding processing on pilot symbols (PILOT) and DL-TPC. The modulation unit 152 performs modulation processing on the output signal of the channel encoding unit 151. The spreading unit 153 performs spreading processing on the output signal of the modulation unit 152. The transmission power control unit 154 increases or decreases the stored transmission power based on UL-TPC, and controls the amplification unit 155. The amplification unit 155 amplifies the output signal of the spreading unit 153 based on the control of the transmission power control unit 154, and outputs the amplified signal to the transmission radio unit 182 as a DPCCH (Dedicated Control Channel) signal.

  The required SIR calculation unit 170 defines a target BLER (Target Block Error Rate) based on the communication quality (QoS). Further, as shown in FIG. 2, the required SIR calculation unit 170 internally stores a table indicating the correlation between SIR and BLER for DPCCH and each TFC (201 to 206 in FIG. 2), and for DPCCH and each TFC. 2 is calculated (hereinafter referred to as “required SIR”) to satisfy the target BLER indicated by the broken line in FIG. 2 (207 to 212 in FIG. 2), and the calculation result is output to the offset calculation unit 171.

  The offset calculation unit 171 outputs the difference (213 to 217 in FIG. 2) between the required SIR of each TFC output from the required SIR calculation unit 170 and the required SIR of DPCCH to the transmission power calculation unit 172 as an offset of each TFC. .

  The transmission power calculation unit 172 calculates the transmission power of each TFC by adding the offset of each TFC to the transmission power of the DPCCH. As a result, the transmission power of each TFC has a predetermined offset with respect to the transmission power of the DPCCH, as shown in FIG. The transmission power calculation unit 172 outputs the calculated transmission power of each TFC to the TFC selection unit 174.

  Upper limit calculation section 173 calculates the upper limit value of the TFC transmission power by subtracting the DPCCH transmission power from the total transmission power, and outputs the calculated upper limit value to TFC selection section 174.

  The TFC selection unit 174 selects one TFC from TFCs having transmission power lower than the upper limit value, and outputs the selected TFC to the TFC determination unit 175. Further, the TFC selection unit 174 outputs the transmission power of the selected TFC to the transmission power control unit 180.

  The TFC determination unit 175 determines each TF of the TFC selected by the TFC selection unit 174 based on the target value (Target RoT) of the total received interference power (Rise over Thermal noise) of the uplink in the base station apparatus, etc. The corresponding buffer 176-1 to 176-N is instructed.

  Each buffer 176-1 to 176 -N temporarily stores data of corresponding DCH # 1 to #N, and outputs data corresponding to TF instructed from TFC determination unit 175 described later to channel encoding unit 177. To do. Each buffer 176-1 to 176 -N outputs data (new data) that has not yet been transmitted when ACK is input, and data that has already been transmitted (retransmission data) when NACK is input. Output.

  The channel encoding unit 177 performs an encoding process on the output signals of the buffers 176-1 to 176-N. Modulation section 178 performs modulation processing on the output signal of channel encoding section 177. The spreading unit 179 performs spreading processing on the output signal of the modulation unit 178. The transmission power control unit 180 controls the amplification unit 181 so that the transmission power output from the TFC selection unit 174 is obtained. The amplification unit 181 amplifies the output signal of the spreading unit 179 based on the control of the transmission power control unit 180, and outputs the amplified signal to the transmission radio unit 182 as a DPDCH (Dedicated Data Channel) signal.

  Transmission radio section 182 multiplexes DPCCH and DPDCH signals, performs D / A conversion processing and up-conversion, and transmits the signals wirelessly from antenna 101.

  As described above, according to the present embodiment, DL-TPC is received for each slot by performing TFC selection based on the transmission power of each TFC calculated using the transmission power and offset of the DPCCH. , DPCCH and DPDCH transmission power control and TFC selection can also be performed on a slot-by-slot basis, so that even in environments where fading fluctuations are severe, it can follow changes in the environment and perform TFC selection suitable for channel quality during transmission It is possible to improve the throughput of the entire system.

  Further, by setting the offset of each TFC as the difference between the required SIR of each TFC and the SIR of the DPCCH, an appropriate TFC offset that can satisfy a predetermined communication quality can be set.

  In the present invention, the offset calculation method is not limited to the method of the present embodiment, and other calculation methods may be used, and the offset may be fixed.

(Embodiment 2)
FIG. 4 is a block diagram showing a configuration of the communication terminal apparatus according to the present embodiment. In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG.

  The communication terminal apparatus of FIG. 4 has a configuration in which a received power measurement unit 401, a propagation loss calculation unit 451, and an expected SIR calculation unit 452 are added as compared with FIG. 4 is different from that in FIG. 1 in the operation of the TFC selection unit 174.

  The required SIR calculation unit 170 outputs the required SIR calculated for the DPCCH and each TFC to the offset calculation unit 171 and the TFC selection unit 174.

  Received power measuring section 401 measures CPICH received power (hereinafter referred to as “PRX-BS”) and outputs the measured PRX-BS to propagation loss calculating section 451.

  The propagation loss calculation unit 451 calculates the propagation loss by subtracting the PRX-BS output from the reception power measurement unit 401 from the CPICH transmission power (hereinafter referred to as “PTX-BS”) included in the CPICH data. The calculated propagation loss is output to the predicted SIR calculation unit 452. Here, as a merit of calculating propagation loss using CPICH, CPICH has higher power and longer symbols than pilot symbols of uplink dedicated channels, and therefore, a high value can be obtained. . In the case of FDD, since the frequency is different between the uplink and the downlink, the propagation loss is slightly different, but the difference is small.

  The upper limit calculation unit 173 outputs the calculated upper limit value of the TFC transmission power to the TFC selection unit 174 and the expected SIR calculation unit 452.

  The predicted SIR calculation unit 452 subtracts the propagation loss from the upper limit value of the TFC transmission power, and calculates the maximum received power of the TFC that can be received by the base station apparatus (hereinafter referred to as “expected maximum received power”). Then, the predicted SIR calculation unit 452 divides the predicted maximum received power by the total target interference power value (RoT) included in the CPICH data, so that the required minimum expected to obtain a predetermined quality in the base station apparatus. The limit SIR (hereinafter referred to as “expected SIR”) is calculated, and the calculated predicted SIR is output to the TFC selection unit 174.

  The TFC selection unit 174 selects one TFC from TFCs whose transmission power falls below the upper limit value and whose required SIR is lower than the expected SIR, and outputs the selected TFC to the TFC determination unit 175. Further, the TFC selection unit 174 outputs the transmission power of the selected TFC to the transmission power control unit 180.

  As described above, according to the present embodiment, in addition to the transmission power of each TFC calculated using the transmission power and offset of the DPCCH, based on the relationship between the predicted SIR required in the base station apparatus and the required SIR of each TFC. By performing TFC selection, in addition to the effects of the first embodiment, it is possible to perform TFC selection that is more accurate than that of the first embodiment.

(Embodiment 3)
In the third embodiment, a case will be described in which the offset when calculating the transmission power of each TFC is adjusted during communication.

  FIG. 5 is a block diagram showing a configuration of the communication terminal apparatus according to the present embodiment. In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG.

  The communication terminal apparatus in FIG. 5 has a configuration in which an offset adjustment unit 551 is added as compared with FIG.

  The offset calculation unit 171 outputs the offset of each TFC to the offset adjustment unit 551.

  The offset adjustment unit 551 stores a table in which each TFC, the offset, and the offset adjustment value shown in FIG. 6 are associated with each other, and adds the adjustment value (Δ1 to Δ6) to each TFC offset (offset1 to offset6). Thus, the offset is adjusted, and the adjusted offset is output to the transmission power calculation unit 172.

  Note that, as an offset adjustment method in the offset adjustment unit 551, it is conceivable that the adjustment value is decreased when ACK is returned from the base station apparatus, and is increased when NACK is returned.

  As described above, according to the present embodiment, it is possible to adjust the offset used when calculating the TFC transmission power and increase the TFC transmission power when the propagation environment is bad. The rate can be suppressed and the throughput of the communication system can be improved.

  Note that Embodiment 3 can be combined with Embodiment 2.

(Embodiment 4)
The fourth embodiment will explain a case where the selected TFC is adjusted based on ACK / NACK or the like returned from the base station apparatus.

  FIG. 7 is a block diagram showing a configuration of the communication terminal apparatus according to the present embodiment. In FIG. 7, the same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG.

  The communication terminal device of FIG. 7 is different from that of FIG. 1 in the operation of the TFC selection unit 174.

  First, the TFC selection unit 174 selects one TFC from among TFCs having transmission power lower than the upper limit value. Then, the TFC selection unit 174 adjusts the TFC so as to increase the TFC level when the ACK is returned from the base station apparatus, and decreases the TFC level when the NACK is returned, and the adjusted TFC. Is output to the TFC determination unit 175.

  As described above, according to this embodiment, the selected TFC can be adjusted, and the TFC level can be lowered when the propagation environment is bad. Can be improved.

  Note that Embodiment 4 can be combined with Embodiments 2 and 3.

  The present invention is used in a CDMA wireless communication system and is suitable for use in a communication terminal apparatus that performs TFC selection.

The block diagram which shows the structure of the communication terminal device which concerns on Embodiment 1 of this invention. Table showing correlation between SIR and BLER The figure which shows the relationship between the transmission power of TFC and the transmission power of DPCCH The block diagram which shows the structure of the communication terminal device which concerns on Embodiment 2 of this invention. The block diagram which shows the structure of the communication terminal device which concerns on Embodiment 3 of this invention. The table figure which matched each TFC, offset, and the adjustment value of offset of the communication terminal device which concerns on Embodiment 3 of this invention. Block diagram showing a configuration of a communication terminal apparatus according to Embodiment 4 of the present invention Diagram for explaining TFC selection State transition diagram showing TFC selection detection and TFCS restriction functions Diagram showing parameters in TFC selection The figure which shows the relationship between the state transition of TFC selection and delay

Explanation of symbols

151, 177 Channel encoding unit 152, 178 Modulation unit 153, 179 Spreading unit 154, 180 Transmission power control unit 155, 181 Amplification unit 171 Offset calculation unit 172 Transmission power calculation unit 174 TFC selection unit 175 TFC determination unit 176 Buffer 182 Transmission radio Unit 401 Received power measurement unit 451 Propagation loss calculation unit 452 Expected SIR calculation unit 551 Offset adjustment unit

Claims (7)

Transmission power calculating means for calculating the transmission power of each TFC by adding the offset of each TFC (Transport Format Combination) to the transmission power of the dedicated control channel;
Upper limit calculation means for subtracting the transmission power of the dedicated control channel from the total transmission power to calculate the upper limit value of the TFC transmission power;
TFC selection means for selecting one TFC from TFCs having transmission power lower than the upper limit value. An offset adjusting means for adjusting the offset by adding an adjustment value to the offset of each TFC;
The communication terminal apparatus according to claim 1, wherein the transmission power calculation means calculates transmission power of each TFC using the adjusted offset. A required SIR calculating means for calculating a required SIR that is a SIR (ratio of desired wave power and interference wave power) that satisfies a target block error rate for the dedicated control channel and each TFC;
The communication terminal according to claim 1, further comprising: an offset calculating unit that calculates a difference between the required SIR of each TFC and the required SIR of the dedicated control channel as an offset of each TFC. apparatus. By subtracting the propagation loss from the upper limit value of the TFC transmission power, the expected maximum received power that is the maximum received power of the TFC that can be received by the base station apparatus is calculated, and the predicted maximum received power is An expected SIR calculating means for calculating an expected SIR, which is a minimum necessary SIR expected to obtain a predetermined quality by dividing by the target interference power value,
4. The communication terminal apparatus according to claim 3, wherein the TFC selection means selects one TFC from TFCs whose transmission power is lower than the upper limit value and whose required SIR is lower than the expected SIR.   Propagation loss calculating means for calculating the propagation loss by subtracting the reception power of the common control channel from the transmission power of the common control channel included in the data of the common control channel transmitted from the base station apparatus. The communication terminal apparatus according to claim 4, characterized in that:   The TFC selection means increases the TFC level when the base station apparatus can correctly demodulate the packet data, and the base station apparatus cannot demodulate the packet data correctly and an error is detected. 6. The communication terminal apparatus according to claim 1, wherein the TFC level is lowered. Calculating the transmission power of each TFC by adding the offset of each TFC (Transport Format Combination) to the transmission power of the dedicated control channel;
Subtracting the transmission power of the dedicated control channel from the total transmission power to calculate the upper limit value of the TFC transmission power;
Selecting one TFC from among TFCs having a transmission power lower than the upper limit value.

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