CN1373574A - SIR measuring method and device for WCDMA downlink (forward) link - Google Patents

Abstract

The present invention proposes an SIR measurement method applied to the downlink of a WCDMA system: after correcting the SIR measurement parameters, the UE (user equipment) performs respective SIR measurements on the signals from different paths before RAKE combination, and the total received signal SIR is the sum of the signals of each path. The invention uses single-path SIR measurement as a module, and adjusts a specific DIR measurement device according to system requirements: including a SIR parameter corrector, L single-path SIR measurement modules, and an SIR combiner.

Description

SIR measurement method and device for WCDMA downlink (forward) link

(1) Technical field:

The invention relates to an inner loop SIR measurement method and device in downlink (forward) link power control of a WCDMA (wideband code division multiple access) system.

(two) background technology:

CDMA system is a co-frequency self-interference system. In order to overcome the near-far problem and fast fading, power control has been introduced and has been paid much attention. Since the multiple access interference (MAI) generated by multiple users sharing the same frequency band greatly limits the system capacity of CDMA, many studies focus on the power control of the reverse link. In fact, the downlink also has interference and fading, especially in order to realize high-quality broadband multimedia integrated services in the WCDMA system, in order to optimize the communication quality of different services and maximize the system capacity, it is necessary to adopt downlink power control. The present invention is proposed under the research and development of the commercialized WCDMA communication system.

It is stipulated in the 3GPP agreement that the downlink of the WCDMA system is implemented based on QoS (Quality of Service) and fast closed-loop power control with a fixed step length. In the power control of the forward link, it is generally considered that the UE is in a non-soft handover area, that is, the UE communicates with only one base station; when the UE is in a soft handover area, it first identifies the primary cell through the ID numbers of each cell. If the UE is determined to be a non-primary cell, power transmission will be cut off, and the UE will only perform forward power control with the primary cell. Based on this, we determined the fixed-step fast closed-loop power control scheme of the inner loop + outer loop, and changed the transmission power of the signal through power control to keep the SIR (the ratio of the signal to the average interference plus background noise) measured by the inner loop at the outer loop. The target SIR given by the ring, so as to meet the quality of service requirements. Among them, the SIR measurement of the inner loop is the basis for the good operation of the power control mechanism. Without accurate SIR measurement of the inner loop, the comparison of the SIR of the inner and outer loops is meaningless, and it is impossible to talk about power control with good performance.

The research work of baseband SIR measurement has always been valued by scholars from various countries, but most of them are theoretical studies, and these studies are carried out on the premise that the channel characteristics can be accurately estimated and the received signal can be accurately measured. In fact, it is impossible to measure the received signal without errors due to the limitation of the measurement method and the accuracy of the measurement tools that can be realized. Generally, it is theoretically believed that ideal channel estimation utilizes the overall statistical characteristics of multiple access interference plus background noise, but the fast closed-loop power control mechanism (ie DPC_MODE=0) required by 3GPP requires UE (user equipment) to give A TPC command (transmission power control command) is issued, that is, an inner loop SIR measurement value is required to be given per time slot, which makes the actual channel estimation sample size not large enough (up to 2560 chips); and, now There is an agreement that stipulates that the proportion of the number of pilot symbols corresponding to the downlink to the total number of symbols per slot (see attached table 1) is not large, that is, the sample size used for inner-loop SIR measurement is smaller, which will inevitably lead to channel estimation errors. Therefore, in order to obtain a high-precision inner-loop SIR measurement value in the fast closed-loop power control of the downlink of the WCDMA system, we can only seek a SIR measurement method with better performance: it must not only have higher-precision measurement performance, but also need It is convenient for hardware implementation and has better operability.

Therefore, we set out from the introduction of reducing the error as far as possible, break away from the traditional algorithm idea of combining first and then dividing, and propose the present invention according to the frame structure of the WCDMA system: the inner loop in the downlink power control with the idea of dividing first and then combining algorithm SIR measurement method. Its performance is simulated, studied, and compared with the measurement method of classical inner-ring SIR in [1]. The results show that the present invention is not only easy to implement modularization, but also better than the method proposed in [1] in terms of measurement performance (see the effect of the invention for details).

The present invention is based on the WCDMA system downlink dedicated physical channel frame structure stipulated by the 3GPP agreement, and considers the reality that there must be errors in actual channel estimation, and proposes the WCDMA system downlink power for the pursuit of high precision and hardware operation flexibility. Inner loop SIR measurement method and device in control. Simulation results show that the invention can well realize the downlink QoS-based closed-loop power control of the WCDMA system, thereby maximizing the system capacity.

(3) Contents of the invention:

The application field of the SIR measurement method designed by the present invention is the baseband SIR measurement of the communication system with the frame structure in Fig. 1, and is especially suitable for the inner loop SIR measurement in the downlink power control of the WCDMA communication system. The present invention first provides the selection method of the modified pilot symbol d _pilot based on the frame structure in Fig. 1, and proposes the SIR measurement idea on this basis: before RAKE is combined, the DPCH complex signals from different paths are separately measured for SIR , the total SIR of the received signal is the sum of the SIRs of each path signal. This method uses single-path measurement as a module, the algorithm is simple and flexible, and the measurement accuracy is improved by reducing the introduction of channel estimation errors.

The specific method flow is as follows: (Measurement takes time slot as the unit, may as well take the SIR measurement of the Kth time slot of the base station as an example to illustrate)

1. At the receiving end of the UE, the received multipath mixed signal from the base station of the cell is decomposed into L single-path despread signals and SIR measurement parameters by the receiving and processing device: the number of RAKE combined paths L, the pilot frequency symbol, the number of pilot symbols, and channel estimation for each path.

2. The I-branch pilot symbol obtained from 1 is corrected by the SIR measurement parameter modifier to obtain a modified pilot symbol, which is input into the single-path SIR measurement module together with the other three parameters obtained from 1.

3. Input each single-path K-th time slot obtained from 1 into each single-path SIR measurement module, and perform single-path SIR measurement of L K-th time slots in parallel.

The specific steps of single-path SIR measurement are as follows:

(1) Measure the single-path instantaneous signal power of the Kth time slot with a single-path instantaneous signal power measuring instrument ${\tilde{S}}_{\mathrm{downlink},l}\left(k\right);$

(2) Measure the single-path instantaneous multiple access interference and background noise power of the Kth time slot with a single-path instantaneous multiple access interference and background noise power measuring device

(3) Combine (2) to get instantaneous multiple access interference and background noise power The input noise averager (E1.3) and the average multiple access interference and background noise power I _{downlink, l} (k-1) obtained in the previous (K-1th) time slot carry out weighted average to obtain the Kth time slot Single-path average multiple access interference and background noise power (abbreviated as average noise power) I _{downlink, l} (k);

(4) The single-path instantaneous signal power of the Kth time slot obtained by (1) Divide by (3) to obtain the single-path average noise power I _{downlink, l} (k) of the Kth time slot, and then obtain the single-path SIR measurement value SIR _{downlink, l} (k) of the user's K-th time slot.

4. Input the single-path SIR measurement value of the L Kth time slot obtained from 1 into the SIR combiner for addition, and obtain the uplink SIR measurement value SIR _downlink (k) of the user's Kth time slot.

It can be seen that the SIR measurement device of the WCDMA system downlink (forward) link includes: SIR measurement parameter modifier, single-path SIR measurement module (including single-path instantaneous signal power measuring device, single-path instantaneous multiple access interference and background noise power measurement device, noise averager, single-path SIR divider) and SIR combiner. The number L of single-path SIR measurement modules required in a specific application is determined by the system requirements, which is equal to the number of RAKE combined paths required by the system.

，由k决定，也即由不同业务选用不同的扩频因子SF=256/2^k决定，它不影响用本发明进行SIR的测量。In Figure 1, the downlink dedicated physical channel DPCH, which is composed of DPCCH and DPDCH time division multiplexing, is formed by serial/parallel conversion. The two-way signals are I/Q multiplexed in each radio frame, because the I-way and Q-way signals use the same Therefore, it is required that the I channel and the Q channel have the same frame structure, that is, the number of pilot symbols of the I and Q channels is the same, and the N _pilot is 1, 2, 4, and 8. The composition of data dmta is determined by the upper layer, which can include TFCI (transport format combination indication), TPC (transmission power control) and transmitted information, the number of bits

, is determined by k, that is, it is determined by the selection of different spreading factors SF=256/2 ^k for different services, which does not affect the SIR measurement performed by the present invention.

Fig. 4 shows the SIR measuring device of the present invention, which embodies the innovative idea of the present invention: before RAKE combining, the signals from different paths are respectively measured for SIR, and the total SIR of the received signal is the sum of the SIRs of the signals of each path. The measurement unit is a time slot (1 slot in the WCDMA forward link DPCH is equal to The entities included in the SIR measurement device of the present invention include a SIR measurement parameter corrector (E2), L single-path SIR measurement modules (E1) and a SIR combiner (E3). L is the number of paths that the system requires RAKE to merge. Among them, the single-path SIR measurement module (E1) includes: single-path instantaneous signal power measurer (E1.1), single-path instantaneous multiple access interference and background noise power measurer (E1.2), noise averager (E1.3 ), a single-path SIR divider (E1.4); the SIR combiner (E3) is an adder; the SIR measurement parameter corrector (E2) includes a multiplier (E2.1).

FIG. 5 describes the specific structure of the single-path SIR measurement module (E1) as shown in FIG. 4 .

Among them, the single-path instantaneous signal power measuring device (E1.1) includes: multiplier (E1.11), N _pilot sign integral averager (E1.12), complex modulo device (E1.13), squarer (E1. 14);

The single-path instantaneous multiple access interference and background noise power measurer (E1.2) includes: subtractor (E1.21), complex modulo device (E1.22), squarer (E1.23), N _pilot sign integral average device (E1.24);

Noise averager (E1.3) includes: multiplier (E1.31), multiplier (E1.32), squarer (E1.33), delayer (E1.34);

The single-path SIR phase divider (E1.4) includes: a divider (E1.41).

When fully synchronized, the base station receiver obtains RAKE combined path number L (I2.1), pilot symbol (I2.2), pilot symbol number (I2.3) and channel estimation of each path (I2. 4), and decompose a user's multipath mixed signal into single-path despread signals.

输入噪声平均器(E1.3)中的乘法器(E1.31)与(1-α)相乘，结果送入加法器(E1.33)做被加数，在另一个乘法器(E1.32)中前一时隙(即第K-1时隙)的平均多址干扰和背景噪声功率I_downlink，l(k-1)(即由前一时隙加法器(E1.33)的输出结果经过延时器(E1.34)延时1时隙得到的)与α因子相乘，结果送入加法器(E1.33)做加数；这里，α为遗忘因子，取值0--1之间，一般取0.99或0.999以平滑由于功率控制而导致多址干扰功率波动对求平均噪声功率的影响。加法器(E1.33)的输出结果就是第1径第K时隙平均噪声功率 I_downlink，l(k)。在单径SIR相除器(E1.4)中，把第1径第K时隙瞬时信号功率

送入除法器(E1.41)做被除数，第1径第K时隙平均噪声功率 I_downlink，l(k)送入除法器(E1.41)做除数，二者相除的结果就是第1径第K时隙的SIR测量值SIR_downlink，l(k)。The Kth time slot of the 1st path DPCH despread complex signal enters the single path SIR measurement module (E1) to obtain the 1st path SIR _{downlink, the processing procedure of l} (k) as follows: the 1st path DPCH despread complex signal The Kth time slot and the modified pilot symbol are input into the multiplier (E1.11), and the bit-by-bit multiplication results are respectively input into the N _pilot symbol integral averager (E1.12) and the single-path instantaneous multiple access interference and background noise power are calculated. The subtractor (E1.21) in the measurer (E1.2) acts as the minuend. The N _pilot data are integrated and averaged in the N _pilot symbolic integral averager (E1.12) of the single-path instantaneous signal power measuring device (E1.1), and the average value is input into the complex number modulo device (E1.13) for modulo calculation Enter the squarer (E1.14) to get the square value, and sample every time slot to get the instantaneous signal power of the 1st path and the Kth time slot . In the subtractor (E1.21) in the single-path instantaneous multiple access interference and background noise power measurer (E1.2), the channel estimate of the first path is used as a subtrahend, and the subtraction result is input to the complex modulus device (E1.22) After calculating the modulus, enter the squarer (E1.23) to obtain the square value, and then enter the N _pilot symbolic integral averager (E1.24) to perform the integral average of N _pilot data, and calculate the result for each time slot Sampling to obtain the instantaneous multiple access interference and background noise power of the first path Kth time slot . Bundle

The multiplier (E1.31) in the input noise averager (E1.3) is multiplied by (1-α), and the result is sent to the adder (E1.33) as the summand, and in another multiplier (E1. 32) in the previous time slot (i.e. the K-1th time slot) average multiple access interference and background noise power _{Idownlink, l} (k-1) (i.e. by the output of the previous time slot adder (E1.33) through The delay (E1.34) obtained by delaying 1 time slot) is multiplied by the α factor, and the result is sent to the adder (E1.33) as an addend; here, α is the forgetting factor, which takes a value between 0 and 1. Generally, 0.99 or 0.999 is used to smooth the influence of multiple access interference power fluctuations on the average noise power due to power control. The output result of the adder (E1.33) is the average noise power I _{downlink, l} (k) of the first path and the Kth time slot. In the single-path SIR phase divider (E1.4), the instantaneous signal power of the first path K time slot

Send it to the divider (E1.41) as the dividend, the average noise power I _{downlink of the Kth time slot of the first path, l} (k) is sent to the divider (E1.41) as the divisor, and the result of dividing the two is the first The SIR measurement value SIR _{downlink of the Kth time slot, l} (k).

At the same time, the L single-path SIR measurement values SIR _{downlink obtained in parallel processing, l} (k) (l=1--L) are input to the SIR combiner (E3) to add, and the Kth hour of the required cell base station is obtained. Gap SIR measurements.

Beneficial effects of the present invention: (1) The present invention takes the single path before the RAKE merger as the object, and it is easy to realize modularization. When the number of RAKE combined paths changes, the present invention meets the requirements by adding and deleting single-path SIR measurement modules. (2) In terms of measurement performance, the present invention directly performs SIR measurement on the received despread signals of each path. In this way, the secondary introduction of the channel estimation error can be avoided, and the measurement accuracy of the SIR can be improved. Further, with the high-precision SIR measurement as the core of the inner loop power control, implementing the closed loop power control of the forward link of the WCDMA system can better guarantee the QoS, thus greatly improving the system capacity.

(4) Description of drawings:

Fig. 1 is the frame structure that applies the present invention to carry out SIR measurement;

Fig. 2 is a block diagram of the WCDMA forward link system applying the present invention;

Fig. 3 is the WCDMA downlink closed-loop power control of the base station based on the present invention;

Fig. 4 is device block diagram of the present invention;

FIG. 5 is a single-path SIR measurement module in the present invention.

The relation between each accompanying drawing is that shown in Fig. 1 is I (BT15) and Q (BT16) in Fig. 2; Fig. 3 is the closed-loop power control (MR1) based on the present invention of the base station in Fig. 2; Fig. 4 is the SIR measurement device (MR114) in Figure 3; Figure 5 is the single-path SIR measurement module (E1) in Figure 4.

(5) Specific implementation methods:

Fig. 3 is the closed-loop power control mechanism of the UE based on the present invention. In order to meet the QoS (service quality)-based fixed-step fast power control required by the 3GPP protocol, the structure of the inner loop + outer loop is adopted: the inner loop gives the measured SIR Measured value (MR115), the outer loop includes RAKE combination (MR105), decoder (MR106), error block detection (MR107), low-pass filter (MR108), comparator (MR110), outer loop target SIR generator ( MR111), delayer (MR112) and other entities, give the target SIR (MR113) according to the block error rate (BLER) (MR109) required by different services, and compare the inner ring SIR measurement value with the target SIR to obtain the power control command (TPC ) (BT29), forming a loop to control the base station power transmission controller (BT1). Wherein the special feature is that the measurement (MR114) of the inner ring SIR is exactly the present invention (seeing in Figure 4); therefore, the input point of the inner ring is before the RAKE combiner (MR104), and each single-path despreading signal of the input The inner loop SIR measurements are processed in parallel. The closed-loop power control mechanism based on the present invention as shown in FIG. 3 can provide high-precision inner-loop SIR, thereby better meeting the requirements of different services (see the effect of the invention).

，这里，k为时隙，p(k)为基站DPCH发出的功率(单位dBm)；Δ为最小功率调整步长，取值为1dB或0.5dB；TPC_command为功率控制命令(BT29)，取值+1(当图3中目标SIR(R113)＞内环SIR测量值(R115)时)或-1(当图3中目标SIR(R113)＜内环SIR测量值(R115)时)。在如图2的WCDMA前向链路系统的功率控制中应用本发明可取得很好的效果。What Fig. 2 provided is the block diagram of the WCDMA forward link system implementing the present invention. According to the 3GPP protocol, the base station at the sending end first performs baseband processing on the information to be transmitted, including adding CRC (cyclic redundancy check) code (BT10), tail bit (BT11), channel coding (BT12), interleaving (BT13), string And transform (BT14), spread spectrum (BT18 and BT19), scramble (BT22), perform QPSK modulation (BT27 and BT28) after passing through the shaping filter (BT23 and BT24), and then send it to the power amplifier (BT34) to amplify and transmit. Wherein, the spreading code is an OVSF code (orthogonal variable spreading factor code), and a code word other than C _ch,256,0 for the main CPICH and C _ch,256,1 for the main CCPCH is selected. The complex signal I+jQ formed by the I channel and the Q channel is complex multiplied by the complex scrambling code (T23). It should be noted that: the base station power transmission controller (BT1) adjusts the transmission power of the base station DPCH according to the received power control command (BT29) from the closed-loop power control (MR1) based on the present invention at the MS end. The base station power transmission controller (BT1) includes a multiplier (BT30), a delayer (BT32), an adder (BT33) and a power amplifier (BT34). Its control mechanism satisfies the

, where k is a time slot, and p(k) is the power (in dBm) sent by the base station DPCH; Δ is the minimum power adjustment step size, with a value of 1dB or 0.5dB; TPC _command is a power control command (BT29), which takes Value +1 (when the target SIR (R113) in Figure 3 > the measured value of the inner ring SIR (R115)) or -1 (when the target SIR (R113) in Figure 3 < the measured value of the inner ring SIR (R115)). Applying the present invention to the power control of the WCDMA forward link system as shown in FIG. 2 can achieve good results.

Claims (7)

1. The SIR measurement method of CDMA system downlink (forward) link, it is characterized in that: (1) At the receiving end of the UE, decompose the received multipath mixed signal from the base station of the cell into L single-path despreading signals and SIR measurement parameters through the receiving and processing device: RAKE combining path number L, deriving Frequency symbols, number of pilot symbols, and channel estimation for each path; (2) the I-branch pilot symbol obtained by (1) is corrected to obtain the revised pilot symbol through the SIR measurement parameter corrector, and it and the other three parameters obtained by (1) are input into the single-path SIR measurement module; (3) Input each single-path Kth time slot obtained from (1) into each single-path SIR measurement module, and perform single-path SIR measurement of L K-th time slots in parallel. 2. the SIR measurement method of WCDMA system downlink (forward) link as claimed in claim 1, is characterized in that, carries out according to the following steps: (1) Measure the single-path instantaneous signal power of the Kth time slot with a single-path instantaneous signal power measuring instrument ${\tilde{S}}_{\mathrm{downlink},l}\left(k\right);$ (2) Measure the single-path instantaneous multiple access interference and background noise power of the Kth time slot with a single-path instantaneous multiple access interference and background noise power measuring device (3) Combine (2) to get instantaneous multiple access interference and background noise power

The input noise averager (E1.3) and the average multiple access interference and background noise power I _{downlink, l} (k-1) obtained in the previous (K-1th) time slot carry out weighted average to obtain the Kth time slot Single-path average multiple access interference and background noise power (abbreviated as average noise power) I _{downlink, l} (k); (4) The single-path instantaneous signal power of the Kth time slot obtained by (1) Divide by (3) to obtain the single-path average noise power I _{downlink, l} (k) of the Kth time slot, and then obtain the single-path SIR measurement value SIR _{downlink, l} (k) of the user's K-th time slot. 3. The SIR measurement device of WCDMA system downlink (forward) link is characterized in that: comprise SIR measurement parameter corrector, single-path SIR measurement module (comprising single-path instantaneous signal power measurer, single-path instantaneous multiple access interference and background Noise power measurer, noise averager, single-path SIR phase divider) and SIR combiner, the number L of single-path SIR measurement modules required in a specific application is determined by the system requirements, which is equal to the number of RAKE combined paths required by the system. 4. the SIR measurement device of WCDMA system downlink (forward) link as claimed in claim 3, is characterized in that: single-path SIR measurement module (E1) comprises: single-path instantaneous signal power measurer (E1.1), Single-path instantaneous multiple access interference and background noise power measurer (E1.2), noise averager (E1.3), single-path SIR phase divider (E1.4); SIR combiner (E3) is an adder; The SIR measurement parameter corrector (E2) includes a multiplier (E2.1). 5. the SIR measurement device of WCDMA system downlink (forward) link as claimed in claim 3, is characterized in that, single-path instantaneous signal power measurer (E1.1) comprises: multiplier (E1.11), N _Pilot sign integral averager (E1.12), complex modulo device (E1.13), squarer (E1.14). 6. the SIR measuring device of WCDMA system downlink (forward) link as claimed in claim 3, is characterized in that, single-path instantaneous multiple access interference and background noise power measurer (E1.2) comprise: subtractor (E1 .21), complex number modulus device (E1.22), squarer (E1.23), N _pilot sign integral averager (E1.24). 7. the SIR measuring device of WCDMA system downlink (forward) link as claimed in claim 3, is characterized in that, noise averager (E1.3) comprises: multiplier (E1.31), multiplier (E1. 32), squarer (E1.33), delayer (E1.34).

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