JP2005223671A - Apparatus and method for estimating channel, and base station device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a channel estimation apparatus capable of increasing estimation precision in the channel estimate of a reception signal without decreasing communication throughput even if allowable processing delay time is extremely short, for example, 1 slot or less. <P>SOLUTION: A weighting factor calculator 106 calculates a weighting factor to the reception signal of three slots, namely a reference slot retained at a weighting adder 107 according to the amount of variation in a phase inputted from a maximum Doppler frequency detector 105, and a slot before and after the reference slot, and informs the weighting adder 107 of the three calculated weighting factors. The weighting factor calculator 106 calculates only a weighting factor to the reception signal of the two slots, namely the reference slot and the slot before the reference one, when a demodulation timing detector 104 informs the weighting factor calculator 106 of demodulation start timing, and inputs the two calculated weighting factors and the arrival information of the demodulation start timing into the weighting adder 107. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a channel estimation apparatus, a base station apparatus, and a channel estimation method used in a W-CDMA (Wideband Code Division Multiple Access) type digital wireless communication system.

  A conventional channel estimation apparatus calculates a channel estimation value by weighting pilot symbols included in a received signal in units of slots and adding the weighted received signals for a plurality of slots. In such a channel estimation device, the estimation accuracy is improved by adjusting the average length (slot length and weighting factor) used to calculate the channel estimation value according to the maximum Doppler frequency (fD) of the received signal. (For example, refer to Patent Document 1 and Non-Patent Document 1).

  FIG. 5 shows a configuration of a conventional general channel estimation apparatus 10. The channel estimation device 10 includes a correlator 11, a multiplier 12, an in-phase addition unit 13, an fD detection unit 14, a weight coefficient calculation unit 15, and a weighting addition unit 16.

  The correlator 11 performs a despreading process on the reception signal input from a reception processing unit (not shown), and inputs the reception signal subjected to the despreading process to the multiplier 12 and the fD detection unit 14 respectively.

  The multiplier 12 multiplies the pilot portion (known signal portion) of the received signal input from the correlator 11 by the pilot pattern (PL pattern), and inputs the received signal multiplied by the PL pattern to the in-phase addition unit 13. .

  The in-phase addition unit 13 calculates the in-phase addition value (available as a channel estimation value) of each slot by in-phase addition of the received signal input from the multiplier 12 for each slot, and calculates the in-phase addition of each calculated slot. The value is input to the weighted addition unit 16. Note that the multiplication of the PL pattern in the multiplier 12 and the in-phase addition in the in-phase addition unit 13 are processing in slot units, and multiplication and in-phase addition are performed in each slot.

  The fD detection unit 14 detects the fD of the received signal input from the correlator 11, converts the detected fD into a phase variation amount, and then inputs the phase variation amount to the weight coefficient calculation unit 15.

  The weighting factor calculation unit 15 calculates a weighting factor by which each slot is multiplied according to the phase fluctuation amount input from the fD detection unit 14 and notifies the weighting addition unit 16 of the calculated weighting factor sequentially.

The weighting addition unit 16 holds the reception signal input from the in-phase addition unit 13 for a predetermined number of slots, and multiplies each of the held slots by the weighting factor of each slot notified from the weighting factor calculation unit 15. Then, the product is averaged after adding a plurality of slots, and the channel estimation value (slot average channel estimation value) of the received signal in each slot is calculated. More specifically, the weighting addition unit 16 calculates the channel estimation value for a certain slot (hereinafter referred to as “reference slot”) of the received signal input from the in-phase addition unit 13, and the reference slot and its reference slot. The received signals for a total of three slots, one for each slot before and after, are held, and the weighting factor notified from the weighting factor calculation unit 15 at the timing when the subsequent slot of the reference slot is input from the in-phase addition unit 13 is represented by three slots. Multiply each and add and average the three products. In this way, the weighting factor calculation unit 15 and the weighting addition unit 16 calculate the channel estimation value of the received signal of the reference slot using not only the reference slot but also the slots before and after the reference slot. It can suppress that the demodulation accuracy of a received signal deteriorates. Therefore, the weighted addition process in the weighted addition unit 16 is a process between a plurality of slots. Then, the weighting addition unit 16 sequentially inputs the calculated channel estimation value of the reference channel to a baseband unit (not shown) with a delay of one slot from the timing at which the in-phase addition value of the reference slot is input from the in-phase addition unit 13. Note that the baseband unit uses this channel estimation value to demodulate the received signal.
JP 2002-33780 A Supervised by Keiji Tachikawa, “W-CDMA mobile communication system”, Maruzen, June 25, 2001, p. 57-59

  However, in the conventional channel estimation apparatus 10, when the allowable processing delay time is short, that is, when the period from when the received signal is input to the channel estimation apparatus 10 until the demodulation is started is short, the weighting addition unit Due to the time lag caused by 16, the generation of the channel estimation value is not in time for the demodulation start timing of the received signal, resulting in a problem that the demodulation accuracy of the received signal is lowered and the communication throughput is lowered.

  For example, in 3GPP (3rd Generation Partnership Project), about HARQ-ACK (Hybrid-ARQ Acknowledgement) and CQI (Channel Quality Indicator) information transmitted by HS-DPCCH (Dedicated Physical Control Channel (uplink) for HS-DSCH) Processing delay time is specified. That is, in 3GPP, permissible times from completion of reception of HARQ-ACK and CQI to demodulation, reflection of decoding results, scheduling, and transmission by HS-SCCH (Shared Control Physical Channel for HS-DSCH) are defined.

  The present invention has been made in view of such a point, and even when the allowable processing delay time is extremely short, for example, 1 slot or less, the channel estimation value of the received signal is estimated without reducing the communication throughput. An object of the present invention is to provide a channel estimation apparatus capable of improving accuracy.

  A channel estimation apparatus according to the present invention calculates a product for each slot by multiplying a demodulation timing detection means for detecting a demodulation start timing of a received signal and the received signal and a weighting factor for each slot of the received signal. When the channel estimation value of the reference slot is calculated by adding the product of the reference slot and the product of the slots before and after the reference slot, the reference slot received after the detected demodulation start timing And a weighted addition means for excluding the subsequent slot from the addition target in the calculation of the channel estimation value of the reference slot.

  The channel estimation apparatus according to the present invention employs a configuration in which, in the above invention, the demodulation timing detection means detects the demodulation start timing by determining a communication system of the received signal.

  The base station apparatus according to the present invention employs a configuration including the channel estimation apparatus according to the present invention.

  In the channel estimation method according to the present invention, a demodulation timing detection step for detecting a demodulation start timing of a received signal and a product for each slot are calculated by multiplying the received signal by a weighting factor for each slot of the received signal. When the channel estimation value of the reference slot is calculated by adding the product of the reference slot and the product of the slots before and after the reference slot, the reference slot received after the detected demodulation start timing A weighting and adding step of excluding the subsequent slot from the addition target in the calculation of the channel estimation value of the reference slot.

  According to the present invention, since the channel estimation device grasps the demodulation start timing of the received signal in advance and adjusts the generation timing of the channel estimation value, the processing delay time allowed for the channel estimation device is extremely short, for example, 1 slot or less. Even in this case, it is possible to improve the demodulation accuracy of the received signal by improving the estimation accuracy of the channel estimation value of the received signal without reducing the communication throughput.

  The essence of the present invention is to determine the demodulation start timing of a received signal in advance and adjust the calculation timing of the channel estimation value of the received signal, thereby estimating the channel corresponding to that slot before the demodulation start timing of the received signal of a certain slot. It is to calculate the value reliably.

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

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of channel estimation apparatus 100 according to Embodiment 1 of the present invention. Channel estimation apparatus 100 is used by being incorporated in a wireless communication apparatus such as a base station apparatus or a mobile station apparatus.

  In the present embodiment, the received signal of the reference slot is obtained by multiplying the channel estimation values of the received signal of the reference slot and the preceding and subsequent slots by a weighting factor and averaging the products of the three slots. Assume that the slot average channel estimation value is calculated.

  The channel estimation apparatus 100 includes a correlator 101, a multiplier 102, an in-phase addition unit 103, a demodulation timing detection unit 104, an fD detection unit 105, a weight coefficient calculation unit 106, and a weighting addition unit 107.

  Correlator 101 performs despreading processing on the reception signal input from a reception processing unit (not shown), and inputs the despread reception signal to multiplier 102, demodulation timing detection unit 104, and fD detection unit 105, respectively. .

  Multiplier 102 multiplies the pilot portion (known signal portion) of the received signal input from correlator 101 by the PL pattern, and inputs the received signal multiplied by the PL pattern to in-phase addition section 103.

  The in-phase addition unit 103 calculates the in-phase addition value (available as a channel estimation value) of each slot by in-phase addition of the received signal input from the multiplier 102 for each slot, and calculates the in-phase addition of each slot thus calculated. The value is input to the weighted addition unit 107.

  The demodulation timing detection unit 104 includes channel information of a reception signal input from the correlator 101 and a reception signal input from a baseband unit (not shown) (including period information of a demodulation start timing that varies depending on a communication method of the reception signal). , The arrival time of the demodulation start timing is detected, and when the received signal of the slot (reference slot) immediately before the demodulation start timing arrives is input from the correlator 101, the weight coefficient calculation unit 106 Notify that the demodulation start timing has arrived.

  The fD detection unit 105 detects the fD of the received signal input from the correlator 101, converts the detected fD into a phase variation amount, and then inputs the phase variation amount to the weight coefficient calculation unit 106.

  The weighting factor calculation unit 106 performs a total of three slots of received signals including the reference slot held in the weighting addition unit 107 and one slot before and after the reference slot according to the phase fluctuation amount input from the fD detection unit 105. A weighting factor is calculated, and the calculated three weighting factors are sequentially notified to the weighting addition unit 107. Further, when the demodulation timing detection unit 104 is notified of the demodulation start timing, the weighting factor calculation unit 106 calculates only the weighting factor for the received signals of a total of two slots, that is, the reference slot and the previous slot, and calculates the calculated 2 The two weighting factors and the arrival information at the demodulation start timing are input to the weighting addition unit 107.

  The weighting addition unit 107 holds the received signal input from the in-phase addition unit 103 for a total of three slots, that is, the reference slot and one slot before and after the reference slot. The channel estimation value of the received signal of the reference slot is calculated by multiplying the notified weighting coefficients, adding the products for three slots, and then averaging. Then, the weighted addition unit 107 inputs the channel estimation value of the received signal of the reference slot to the baseband unit (not shown) immediately after calculation.

  Further, when the weighting coefficient calculating unit 106 receives the weighting coefficient for the received signals of the total of two slots, that is, the reference slot and the previous slot, and the arrival information of the demodulation start timing, from the weighting coefficient calculating unit 106, Without waiting until the in-phase addition value of the subsequent slot is input from the in-phase addition unit 103, the received signals of the reference slot and the previous slot are immediately multiplied by the weighting factor, and the two products are added and averaged. A channel estimation value of the received signal of the reference slot is calculated. Therefore, when arrival information of the demodulation start timing is input from the weighting factor calculation unit 106 to the weighting addition unit 107, the channel estimation value of the reception signal of the reference slot, the channel estimation value of the reception signal of the previous slot of the reference slot, These two channel estimation values are simultaneously input to a baseband unit (not shown).

  Next, the operation of the channel estimation apparatus 100 will be described more specifically with reference to FIG. FIG. 2 shows the relationship between each slot of a received signal used for CQI demodulation and the timing at which the CQI demodulation is actually started, that is, the demodulation start timing, taking CQI demodulation specified by 3GPP as an example. FIG.

  In 3GPP, the mobile station apparatus transmits to the base station apparatus 2-slot CQI (Slot # m-1 and Slot # m in FIG. 2) encoded by HS-DPCCH and 1-slot HARQ-ACK (in FIG. 2). Slot # m-2) is transmitted alternately. Therefore, CQI is based on HS-DPCCH in units of 3 slots (Slot # m-2 to Slot # m in FIG. 2), and 2 slots (Slot # m-1 and Slot # m in FIG. 2) are used. Will be sent. In 3GPP, since the CQI is encoded to a length of 2 slots, the reception signals of the 2 slots (Slot # m-1 and Slot # m in FIG. 2) are received for the CQI demodulation. Will be started after.

  Here, the demodulation timing detection unit 104 determines that the currently received channel is the HS-DPCCH based on the channel information input from the baseband unit, and the CQI is 2 in units of 3 slots. Understand that the slot is occupied and transmitted. Further, the demodulation timing detection unit 104 identifies whether the currently received reception signal is CQI or HARQ-ACK based on the reception signal input from the correlator 101, and further performs communication by the channel estimation apparatus 100. A demodulation start timing of CQI that does not decrease the throughput is detected, and a remaining period until the detected demodulation start timing is calculated.

  If demodulation is started immediately after receiving two CQI slots (Slot # m-1 and Slot # m in FIG. 2), no delay occurs in CQI generation. It is assumed that the time point 104 completes reception of two CQI slots (Slot # m-1 and Slot # m in FIG. 2) as a demodulation start timing.

  Then, the demodulation timing detection unit 104 notifies the detected demodulation start timing to the weighting factor calculation unit 106, and the weighting factor calculation unit 106 that has received the notification notifies the first half slot of CQI (Slot # m-1 in FIG. 2). Is the reference slot (Slot # m-1 in FIG. 2) and one slot before and after that (Slot # m-2 and Slot # m in FIG. 2) for a total of 3 slots received. A weighting factor for the signal is calculated and input to the weighting addition unit 107 immediately after the calculation. On the other hand, when the weighting factor calculation unit 106 sets the second half slot of CQI (Slot # m in FIG. 2) as a reference slot, the reference slot (Slot # m in FIG. 2) and its previous slot (in FIG. 2) The weighting coefficients for the two slots (Slot # m-1) are calculated, and the weighting coefficients are input to the weighting addition unit 107 immediately after the calculation. Therefore, the weights in the two cases of the case where the first slot of CQI (Slot # m-1 in FIG. 2) is used as a reference slot and the case where the latter slot of CQI (Slot # m in FIG. 2) is used as a reference slot. Coefficients are simultaneously input from the weighting coefficient calculation unit 106 to the weighting addition unit 107.

  The weighting addition unit 107 uses the weighting factors in the two cases input simultaneously from the weighting factor calculation unit 106 at the demodulation start timing, and uses the first half slot (Slot # m-1 in FIG. 2) and the second half slot ( The slot average channel estimated values of (Slot # m) in FIG. 2 are calculated, and these channel estimated values are input to a baseband unit (not shown) immediately after the calculation. Then, in the baseband unit, CQI demodulation is performed using the channel estimation value input from the weighted addition unit 107.

  Therefore, channel estimation apparatus 100 according to the present embodiment calculates a product for each slot by multiplying the received signal of each slot by a weighting factor, and calculates the product of the reference slot and the slot before and after the reference slot. When calculating the channel estimation value of the received signal of the reference slot by averaging the product and adding, the subsequent slot received after the demodulation start timing is excluded from the addition target in calculating the channel estimation value of the reference slot Will do.

  As described above, according to channel estimation apparatus 100 according to the present embodiment, when the latter half slot of CQI (Slot # m in FIG. 2) is used as a reference slot, the latter slot of the reference slot (in FIG. 2) Although Slot # m + 1) cannot be used to calculate the channel estimation value, channel estimation is performed using two slots, the reference slot (Slot # m in FIG. 2) and the previous slot (Slot # m-1 in FIG. 2). Since the value can be calculated, the CQI demodulation accuracy can be improved without reducing the communication throughput.

  FIG. 3 shows simulation results of error determination rates when CQI transmitted on HS-DPCCH is demodulated and decoded for channel estimation apparatus 100 according to the present embodiment and conventional channel estimation apparatus 10. In this simulation, it is assumed that a path search is performed on a wireless signal transmitted from a wireless communication device moving at 45 km / h. Since the conventional channel estimation apparatus 10 cannot detect the demodulation start timing, the channel estimation value is calculated based on only the reference slot (no slots before and after it) for all slots.

  In FIG. 3, the simulation results for the channel estimation apparatus 100 according to the present embodiment are indicated by black squares (♦), and the simulation results for the conventional channel estimation apparatus 10 are indicated by black circles (●). From FIG. 3, it can be seen that the required Ec / N0 is 1.5 dB lower than the CQI error determination rate by the conventional channel estimation device 10 for the CQI error determination rate by the channel estimation device 100. Here, since Ec / N0 is a ratio representing the received signal power / interference wave power, if the CQI error determination rate is the same, the estimation accuracy of the channel estimation value is higher as Ec / N0 is lower.

  Note that channel estimation apparatus 100 according to the present embodiment may be modified or applied as follows.

  In the present embodiment, the weighted adder 107 multiplies the received signals of a total of three slots, that is, the reference slot and the preceding and succeeding slots by a weighting factor, and averages the products after the addition, thereby averaging the reference slots. However, the present invention is not limited to this case. For example, the channel estimation value is calculated according to the processing delay time allowed for the channel estimation apparatus 100. The number of later slots of the reference slot used may be changed. In other words, when calculating the channel estimation value of the received signal of the reference slot, in view of the timing relationship between the reference slot and the demodulation start timing, the reference slot to be added and averaged within a range that does not reduce the communication throughput. You may increase the number of slots of the front and back slots. Thus, by increasing the number of slots before and after the reference slot that is the target of addition averaging, it is possible to further improve the estimation accuracy of the channel estimation value of the received signal in the reference slot.

  Further, in the present embodiment, the weighted adder 107 multiplies the received signals of a total of three slots, ie, the reference slot and one slot before and after the reference slot, by weighting factors, and averages the products of the reference slots. However, the present invention is not limited to this case. For example, without averaging the products of the three slots, the sum is calculated as the reference slot. You may use as a channel estimation value of a received signal.

  In the present embodiment, the case where channel estimation apparatus 100 mounted on the base station apparatus detects the demodulation start timing and demodulates the CQI transmitted by HS-DPCCH has been described. For example, the channel estimation apparatus 100 may demodulate HARQ-ACK transmitted on the HS-DPCCH. If it is the channel estimation apparatus 100, the effect | action and effect similar to the case of CQI can be show | played also about HARQ-ACK transmitted by HS-DPCCH.

(Embodiment 2)
In Embodiment 2 according to the present invention, in the case of “Repetition Factor = 2” in which the same radio signal, which is a communication method defined by 3GPP, is repeatedly transmitted twice, a mode in which CQI is demodulated using channel estimation apparatus 100 Will be described.

  FIG. 4 is a timing diagram showing the relationship between each slot of the received signal used for CQI demodulation and the CQI demodulation start timing when Repetition Factor = 2. In the case of Repetition Factor = 2, after 3 slots consisting of HARQ-ACK and CQI are repeatedly transmitted twice, that is, after Slot # m-5 to Slot # m are transmitted in FIG. 4, CQI demodulation is performed. Be started. Therefore, in this embodiment, the CQI demodulation start timing arrives at a 6-slot period.

  Here, the fact that the communication method of the received signal is Repetition Factor = 2 can be determined by demodulating and decoding pilot symbols included in each slot of the received signal. Therefore, in the present embodiment, when the channel information of the received signal is input from the baseband unit (not shown) to the demodulation timing detecting unit 104, the demodulation timing detecting unit 104 has the communication method of the received signal with Repetition Factor = 2. It is discriminated that there is, and further, the demodulation start timing at Repetition Factor = 2 is detected.

  In this embodiment, Slot # m + 1 cannot be used in the calculation of the channel estimation value of the CQI of Slot # m. However, when Slot # m-5 to Slot # m-1 are used as reference slots, the reference The channel estimation value can be calculated using one slot before and after the slot. Therefore, in the present embodiment, by using channel estimation apparatus 100, CQI demodulation accuracy can be improved without reducing communication throughput.

  In the present embodiment, as in the first embodiment, for example, HARQ-ACK transmitted using HS-DPCCH instead of CQI may be demodulated. If it is the channel estimation apparatus 100, the effect | action and effect similar to the case of CQI can be show | played also about HARQ-ACK transmitted by Repetition Factor = 2.

  The channel estimation device, the base station device, and the channel estimation method according to the present invention have the effect that the estimation accuracy of the channel estimation value can be improved and the demodulation accuracy of the received signal can be improved without reducing the communication throughput. However, it is useful in a W-CDMA digital wireless communication system or the like.

The block diagram which shows the structure of the channel estimation apparatus which concerns on this invention The figure which shows the timing relationship between each slot of the received signal in Embodiment 1, and a demodulation start timing The figure which shows a mode that the estimation accuracy of a channel estimation value improves with the channel estimation apparatus which concerns on Embodiment 1. FIG. The figure which shows the timing relationship between each slot of the received signal in Embodiment 2, and a demodulation start timing The block diagram which shows the structure of the conventional channel estimation apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Channel estimation apparatus 101 Correlator 102 Multiplier 103 In-phase addition part 104 Demodulation timing detection part 105 Maximum Doppler frequency (fD) detection part 106 Weight coefficient calculation part 107 Weighting addition part

Claims (4)

Demodulation timing detection means for detecting the demodulation start timing of the received signal;
The product of each slot is calculated by multiplying the received signal by a weighting factor for each slot of the received signal, and the product of the reference slot and the products of the slots before and after the reference slot are added to the reference Weighted addition means for excluding a slot after the reference slot received after the detected demodulation start timing from an addition target in the calculation of the channel estimation value of the reference slot when calculating the channel estimation value of the slot A channel estimation apparatus comprising:   The channel estimation apparatus according to claim 1, wherein the demodulation timing detection means detects the demodulation start timing by determining a communication system of the received signal.   A base station apparatus comprising the channel estimation apparatus according to claim 1. A demodulation timing detection step for detecting a demodulation start timing of the received signal;
The product of each slot is calculated by multiplying the received signal by a weighting factor for each slot of the received signal, and the product of the reference slot and the products of the slots before and after the reference slot are added to the reference A weighted addition step of excluding a slot after the reference slot received after the detected demodulation start timing from an addition target in the calculation of the channel estimation value of the reference slot when calculating the channel estimation value of the slot A channel estimation method comprising:

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