KR100551868B1 - Method for power control using linear predictor coefficient in imt2000 - Google Patents

Abstract

The present invention relates to a power control method in which power control between a base station (or control station) and a mobile station (user terminal) is modified to have more efficient, simpler and better performance in defining the specification of IMT2000 (WCDMA). In particular, power control is performed using a linear predictor coefficient (LPC).

When the power control is performed in the forward and reverse links between the base station and the mobile station, the present invention estimates direct power or Eb / No (Error Rate) using a linear prediction coefficient at each of the base station and the mobile station. By adjusting the power of the forward and reverse links with a compensating technique, it is relatively simple and substantial compared to conventional power control. In the present invention, it is not important to use any parameters, but assumes that the power itself has quasi stationary characteristics. Therefore, power control is performed by applying LPC in open or internal loop power control. Therefore, it is possible to directly control the power between the mobile station and the base station, enable fast power control, and have simpler and better performance.

Mobile communication power control, IMT2000 power control

Description

Power control method using linear predictive coefficient {METHOD FOR POWER CONTROL USING LINEAR PREDICTOR COEFFICIENT IN IMT2000}

1 is a view showing a conventional internal rope power control method

2 is a view showing a power control method using a linear prediction coefficient of the present invention

3 is a flowchart of a power control method using a linear prediction coefficient of the present invention.

The present invention relates to a method for forward and reverse power control between a base station and a mobile station in a mobile communication system. In particular, an adjustment of power to be transmitted to the forward and reverse links and a necessary power control command using a linear predictor coefficient (LPC) are performed. The present invention relates to a power control method that is efficient, simple and has better performance.

The present invention is a power control method using a linear predictive coefficient in defining the specification of IMT 2000 (WCDMA) in a mobile communication system, for example, a power modified to show an efficient, simple and better performance. Control algorithm.

Looking at the power control method between the mobile station and the base station in the conventional mobile communication system, the cellular and PCS is based on the reverse link closed loop power control (Power Control) based on the power control.

In the case of reverse power control, the base station transmits to the mobile station in the forward direction every 1.25ms whether the signal strength (Eb / No) of the received mobile station is high or low, and the mobile station receives this information and transmits the signal to itself. It can control the output of fast.

Also, in the case of forward power control, the base station informs the base station to allocate a larger output to the forward call channel for a mobile station that is far from the base station or has a poor propagation condition, and vice versa to allocate a smaller output. This is a method for maximizing forward call capacity and call capacity of an adjacent cell.

IMT 2000 combines this and applies forward and reverse in a similar fashion as Innr Loop Power Control. That is, the information between the two (mobile station and the base station) for power control can be informed to each other and by using it as a parameter for power control, the output of each other can be adjusted.

In such power control, near and wave causing a difference in signal power according to a distance between a user equipment (UE) and a base station (UTRAN: UMTS Terrestrial Radio Access Network) in uplink or downlink. (Near and Far) problem, and each mobile station has a fading according to the mobile communication environment. In order to overcome this environment and maximize subscriber acceptance, very large operating range and sophisticated power control are required. The transmit power of the mobile stations should also be adjusted so that the transmit powers of the mobile stations have the same power and a minimum signal to interference ratio when they are received at the base station.

In order to perform the power control in consideration of this point, the base station monitors the state of the receiving side (ie, the mobile station) to obtain error information, compares the error information with a predetermined value, and commands the mobile station using the power control bit according to the result. The mobile station receives this power control command to adjust the transmit power. This is defined in the 3GPP specification (TS 25.214v3.20 (2000-3)) as a conventional inner loop power control technique.

According to the conventional IMT2000 3GPP specification, the power control is configured as follows, and the operation of this technology has the dedicated physical channel (DPCH), which is the most important physical channel, and power in the uplink and downlink. The control process will be described in more detail with reference to FIG. 1 as follows.

A base station having a target SIR_target (Signal to Interference Ratio) determined by an access network receives a signal of a mobile station that is actually measured in order to adjust the transmission signal strength of the mobile station to this value, and measures the SIR value. The value is compared with the target value. As a result of the comparison, if the measured SIR value is smaller than the target SIR_target, the transmit power control command is set to '0' and the base station transmits the TPC command to the reverse DPCH channel every slot when the base station transmits to the mobile station. If the measured SIR value is larger than the target SIR_target, the TPC command is set to '1' and the base station transmits this information per slot in the reverse DPCH channel when transmitting to the mobile station.

The mobile station receives this TPC command and uses one of two PCAs (Power Control Algorothm) to make the value TPC_cmd. Then, the TPC_cmd value is multiplied by the step value of the power to be adjusted to determine the power of the DPCH to be transmitted in the uplink.

The ΔTPC value determined by the control station is 1 dB or 2 dB, and ΔDPCCH = ΔTPC × TPC_cmd, and has a value of −2 to 2 dB (DPCCH: Dedicated Physical Control Channel). Also, PCA1 recognition or PCA2 is determined by the base station (UTRAN) and given to the mobile station (UE).

First, the case of Power Control Algorith 1 (PCA1) will be described.

This case is divided into a case where the mobile station is not a soft handover and a case where the mobile station is a soft handover.

One). The mobile station is not a soft handover; In this case, the mobile station will receive one TPC command in each slot. In this case, if the TPC command is '0', TPC_cmd is -1, and if the TPC command is 1, TPC_cmd is 1. And if ΔTPC is 1dB, the ΔDPCCH value will be -1 or 1dB.

2). The mobile station is in soft handover; In this case, TPC commands from several active cells are received. If this is called TPC_i command (0 <i <N (number of cells)), W _i (0 <i <N (number of cells)) We create a soft symbol decision called) and determine the TPC_cmd value by calculating TPC_cmd = γ (W ₁ , W ₂ , ..., W _N ).

Here, the function γ will satisfy the following Criteria. The probability is that if the N TPCi instructions are random and there is no correlation, then the probability that the output of the function is 1 is 1/2 ^N , and the probability that it is -1 is less than 1/2. do.

Next, also in the case of PCA2 (Power Control Algorithm 2), the case where the mobile station is not soft handover and the case where it is soft handover will be described respectively.

One). The mobile station is not soft handover; In this case, the mobile station will receive one TPC command for each slot so that it does not span frame boundaries using a 5-slot cycle. Of the 5 TPC_cmds, the first 4 TPC_cmds are fixed to 0. If the 5th TPC command is 0, TPC_cmd is -1. If the 5th TPC command is 1, TPC_cmd is 1. If ΔTPC is 1dB, only the last 5th ΔDPCCH value will be -1 or 1dB and the first 4 values will be 0.

2). The mobile station is in soft handover; In this case, TPC commands from several active cells are received. If this is called TPC_i command (0 <i <N (number of cells)), W _i (0 <i <N (number of cells)) for each value Create a soft symbol decision, and determine the TPC_cmd value by calculating TPC_cmd = γ (W ₁ , W ₂ , ..., W _N ). Each TPC_i instruction uses three slot cycles.

That is, likewise, each of the first two TPC_i_cmds is fixed to 0 and the other TPC_cmd is used. The UE first makes each TPC_cmd_i, one temporary TPC command, and applies TPC_temp_i to 1 if all three hard decisions are applied, and TPC_temp_i to 1, to 0. Neither of these will make TPC_temp_i zero.

Eventually, we will apply the power function to the third slot only.

TPC_cmd (3 ^rd ) = Υ (TPC_temp ₁ , TPC_temp ₂ , ..., TPC_temp _N ). Again, the function 것이다 will satisfy the following creteria: If 1 / N∑TPC_temp_i> 1/2, then TPC_cmd = 1; if 1 / N∑TPC_temp_i <-1/2, TPC_cmd = -1; otherwise, 0.

Multiply this by ΔTPC and the desired ΔTPCCH value will be -1 or 1 dB.

The conventional power control technique as described above is stable in power control due to the small value of ΔTPC, but it may take a long time to reach the target power value, and also considering the delay in the mobile communication ring which is difficult to predict. Since the power of the last slot is always calculated and the value is used for the current slot transmission, the radio waves have to go around one loop to control the power.

In addition, the complexity of the implementation due to too many parameters, especially PCA1, PCA2, etc., is simple, and it is difficult to actually apply it to the IMT2000 which will require more sophisticated power control.

According to the present invention, in performing power control of a mobile communication system, the mobile station and the base station perform power control using values predicted in advance of future power control information of the forward and reverse links using linear prediction coefficients. In this paper, we propose a power control method using linear predictive coefficients to improve the adaptability of power control and achieve more precise, simple, and high performance power control.

Power control method using a linear prediction coefficient of the present invention, (a). Receiving, at the base station, an initial power control preamble from the mobile station, generating a backward TPC command using a linear prediction coefficient, and transmitting the generated backward TPC command to the mobile station, (b). Generating, by the mobile station, a forward TPC variation command using a linear predictive coefficient according to the response, and transmitting to the base station, (c). Adjusting, by the base station, power to be transmitted in the reverse direction by using the forward TPC change command, and generating and transmitting a reverse TPC change command by using a linear prediction coefficient to the base station, (d). Adjusting, by the mobile station, the power to be transmitted in the reverse direction using the reverse TPC fluctuation command, and generating a forward TPC fluctuation command using a linear prediction coefficient and transmitting the result to the mobile station; Power control method using a linear prediction coefficient, characterized in that comprises a.

In the present invention, the forward TPC command is a power control method using a linear prediction coefficient, characterized in that the transmission on the TPC field of the DL_DPCCH.

Hereinafter, a power control method using a linear prediction coefficient of the present invention will be described in detail with reference to the accompanying drawings.

The present invention considers a more realistic scheme among power control algorithms.

In other words, if you look at the usage environment of the mobile station, the mobile station may randomly move, walk, stand, sit, or move in a car. At this time, the power of the signal transmitted while moving is 2 to 4 squared of the distance. Inversely we know inversely, and we also start with the assumption that the signal can be quasi-Stationary if considered in a short span.

In other words, by observing the previous signals can be interpreted to mean that you already know that the current signal will not be significantly different from the previous signal.

Of course, there are exceptions, but it can be seen that the step difference in power control described in IMT 2000 is configured to 1 dB or 2 dB per slot when ΔTPC is viewed. Of course, it is true that a sudden increase or decrease in power can interfere with adjacent cells, but it would be more effective to quickly adjust the power to a more realistic value than just 1 dB or 2 dB.

Therefore, in the present invention, the linear signal coefficient (LPC: Linear Predictor Coefficient), which is a signal processing algorithm mainly used in speech signal processing, is used to know the prediction of the next signal in advance, and the direct power difference is calculated using the linear prediction coefficient. It also sends the value. In other words, change PCA using LPC.

LPC is an algorithm having the concept of inferring a current signal from previous signals, and can be expressed by the following equation.

[x (t): original signal level at t seconds, a (i): LPC coefficient, e (t): residual signal level at t seconds]

As shown in Equation 1, a (i), which is a coefficient for minimizing the residual signal, can be obtained.In the present invention, the coefficient of the next signal is estimated using the LCP, not the coefficient. As we know it, we can use that to generate TPC instructions so we can get closer to the actual value we want.

However, to solve p simultaneous equations, the complexity of O (p ³ ) or the algorithm proposed by Durbin is a recursive method to obtain linear coefficients and estimates, which is less computational than the direct method of solving linear equations using matrices. Requires O (p ² ). In practice, the delay for this calculation is taken into account, and this module would be possible by configuring the hardware and adjusting the number of previous signals (p).

The actual operation will be described with reference to Figs. 2 and 3 by applying the power control of the DPCH of IMT 2000 (WCDMA).

First, in order to maintain the LPC coefficient, since the slot has 5 slots per frame, it is kept below 15. In practice, it should be smaller than this to minimize the delay in solving simultaneous equations. This is an essential requirement for fast power control. First, before entering the inner loop power control, the UE will perform Initial Ordinary Power Control in the reverse direction (UL), which means that the DPCH is reversed only when the base station responds to the power preamble. Will send. Serving cells of the base station UTRAN receiving this will measure the UL SIR value UL_SIR_est using the pilot signal of the received UL_DPCCH. Looking at this as x (t) of Equation 1, Equation 2 below.

[t: slot number, est: prediction, cal: calculation]

The cells active in Equation 2 could predict the SIR value of UL_DPCCH in advance with UL_SIR_cal (t), which is a calculated value using LCP, which is expected to be the power ratio of the next reverse link (UL) signal. The required ΔUL_SIR difference can be calculated by comparing with the UL_SIR_target value already provided by the network), and the power of the required ΔUL_DPCCH can be obtained as follows.

That is, ΔUL_SIR = UL_SIR_target-UL_SIR_cal (t).

In fact, knowing the SIR value can find the power of the interference signal and this signal, and it is slightly different depending on which channel, but in the end, the SIR itself represents the ratio of the power of the signal to the reference signal. It can be seen.

That is, ΔUL_DPCCH_power = ΔUL_SIR × ΔUL_Interference_power.

Here, the ΔUL_DPCCH_power or ΔUL_SIR value is set by the ΔUL_TPC command and transmitted in every slot by being loaded in the TPC field of the DPCCH of the downlink (DL: Downlink).

This enables direct and fast power control, and the existing DL_DPCH has a TPC field of 2, 4, 8, 16 bits for the slot format, and even with this, the maximum ΔUL_TPC command value is -127 to 128 dB (16 bits). If you can control). Alternatively, you can adjust the value from -31 to 32 dB in 0.25 or 0.5 dB increments for more precise and dynamic power control.

As above, the mobile station UE receives the ΔUL_TPC command through the DL_DPCCH channel and obtains DL_SIR_est (t) using Equation 3 below.

[t: slot number, est: prediction, cal: calculation]

In Equation 3, the UE can predict the SIR value of the DL_DPCCH in advance using DL_SIR_cal (t), which is a calculated value using the LPC expected as the power ratio of the next forward link (DL) signal. The required ΔDL_SIR difference can be calculated by comparing the DL_SIR_target value already given by (network), and the power of the required ΔDL_DPCCH can be calculated as ΔDL_SIR = DL_SIR_target-DL_SIR_cal (t).

In fact, knowing the SIR value can find the power of the interference signal and the present signal, and it is slightly different depending on which channel, but in the end, the SIR itself represents the power ratio of the present signal and the reference interference signal power, so that the power value of the desired channel can be known. .

That is, ΔDL_DPCCH_power = ΔDL_SIR × ΔDL_Interference_power.

Herein, the mobile station sets the ΔDL_DPCCH_power or ΔDL_SIR value with the ΔDL_TPC command and loads it in the TPC field of the DPCCH of the reverse link (UL: Uplink) and transmits it every slot. This enables direct and fast power control, and the existing UL_DPCH has a 1-bit or 2-bit TPC field for the slot format, which can be used to increase the maximum ΔDL_TPC command value by -2 to 2 dB (for more than 2 bits). Can be controlled).

On the mobile station (UE) side, the UTRAN of the forward link is more controlled than the power operation of the base station (UTRAN). However, if a larger operating range is allocated, more bits are allocated. Power control can be done.

Then, in practice, PCA1 and 2 can directly and quickly control power since the PTC command itself becomes ΔTPC × TPC_cmd and finally represents ΔDPCCH_power. In addition, PCA is not needed, and parameters such as ΔTPC are also reduced, making it simpler and expecting the LPC algorithm instead.

Considering the operation during soft handover, when the mobile station UE receives ΔUL_TPC_cmd sent from several cells, the mobile station UE measures each DL_SIR_est (t, k) (k: 1 to N (Serving Cell Number)). The calculated values are compared with each other, and handover is performed to the cell with the smallest DL_SIR_est (t, k) .In the UL_TPC field, this ΔDL_TPC command is sent and the cell is a primary cell as a temporary ID. Broadcasting to the cells. Subsequent operations are again the same as the power control algorithms of the forward link (UL) and reverse link (DL) above.

In Compressed Mode, several frames are compressed and have a transmission gap, which is the time from transmission time to transmission again. In this case, the next expected ΔTPC command calculated before the transmission gap (TG). To compensate for the pilot bit power generated by operating in compression mode, we add ΔPILOT_Power plus. Subsequent operations are again the same as the power control algorithms of the forward link (UL) and reverse link (DL) above.

That is, ΔDPCCH (t) = ΔDPCCH (t-1) + ΔPILOT (t).

According to the present invention, it is possible to perform more dynamic and sophisticated power control than the conventional method, and it is simpler and has better performance than the conventional method, and can directly control power between the mobile station UE and the base station UTRAN. It enables power control and may have more user control rights in the base station UTRAN.

This sophisticated approach also reduces the effects of interference, increasing user capacity, and facilitating rapid power control due to sudden user disconnections or rapid user movements during handovers.

And with advances in hardware, rapid power control will be possible, enabling higher transmission rates.

Claims (2)

(a). Receiving, at the base station, an initial power control preamble from the mobile station, generating a backward TPC command using a linear prediction coefficient, and transmitting the generated backward TPC command to the mobile station, (b). Generating, by the mobile station, a forward TPC variation command using a linear predictive coefficient according to the response, and transmitting to the base station, (c). Adjusting, by the base station, power to be transmitted in the reverse direction by using the forward TPC change command, and generating and transmitting a reverse TPC change command by using a linear prediction coefficient to the base station, (d). Adjusting, by the mobile station, the power to be transmitted in the reverse direction using the reverse TPC fluctuation command, and generating a forward TPC fluctuation command using a linear prediction coefficient and transmitting the result to the mobile station; Power control method using a linear prediction coefficient, characterized in that comprises a. The method of claim 1, wherein the forward TPC command is transmitted in a TPC field of DL_DPCCH.

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