WO2001045436A1

WO2001045436A1 - A method of indicating a mobile station by a base station to reduce preamble transmission power

Info

Publication number: WO2001045436A1
Application number: PCT/CN2000/000204
Authority: WO
Inventors: Chaobin Yang; Yuhong Wang
Original assignee: Huawei Technologies Co., Ltd
Priority date: 1999-12-13
Filing date: 2000-07-17
Publication date: 2001-06-21
Also published as: CN1300138A; CN1146147C; AU6145700A

Abstract

The present invention gives a method by which a base station through an acquisition indication channel sends information to indicate a mobile station to reduce preamble transmission power. The acquisition indication information is composed of an acquisition indication (AI) portion for indicating mobile stations to send message or continue to send preamble, and a power adjustment (PA) portion for indicating mobile stations to reduce the preamble transmission power value, which follows with the AI portion. When the acquisition indication is -1, which is received by the mobile station and sent from the base station, the mobile station continues to demodulate the PA portion, in order to obtain the reduction value of transmission power when the mobile station sends the next preamble.

Description

Method for instructing mobile station to reduce prefix transmission power by base station TECHNICAL FIELD

The present invention relates to a code division multiple access (CDMA) communication system, and in more detail, the present invention relates to a method for a base station to instruct a mobile station to reduce a prefix transmission power by using information transmitted on an acquisition indication channel (AICH). Background technique

In an asynchronous code division multiple access communication system, a mobile station first establishes synchronization with a cell through a cell search, and then sends a preamble on a reverse access channel (RACH), and the base station sends the preamble on the acquisition indicator channel. Send acquisition indication ( ^ac q ^uisition indication, AI) information. The process is roughly as follows.

The mobile station reads information about the cell on the broadcast channel (BCCH) of the cell. The information includes: (1) the spreading code / message scrambling code of the prefix part used by the cell; (2) the available signature; (3) each type of access service class is ij ( access service category (ASC) sub-channel group of reverse access channel (RACH); (4) spreading factor available in the message part; (5) uplink interference level in the cell; (6) main Common Control Channel (Primary Common Control Physical Channel 1) (7) Acquisition transmission timing of the indication channel; (8) Power deviation Δν ,,, Ι of the prefix part and the message part; and (9) Power offset Δ. | ( The amount of power increase when no capture instruction is received) and \ ^ | (the amount of power decrease when a capture instruction is received-1).

After reading the cell information, the mobile station first randomly selects a prefix spreading code from the available spreading codes, and sets the transmit power of the prefix to P _RACH according to the estimated open-loop power. The mobile station then implements a random backoff algorithm to select a RACH subchannel from the available ASC subchannel groups, thereby obtaining an access slot (AS) in the next two frames from the selected RACH subchannel. The mobile station then randomly selects one of the available tags. The mobile station finally uses the selected mark at the obtained uplink access time slot to send the prefix with the set prefix transmission power.

The base station will send an acquisition indication through the AICH channel in the downlink access slot corresponding to the uplink access slot. If the mobile station does not receive an acquisition indication in this downlink access slot, it will select a new uplink access slot and increase its prefix transmit power by A. |; If the acquisition indication received by the mobile station in this downlink access slot is-1, it will select a new uplink access slot and reduce its prefix transmit power by Δ ^ |; The acquisition indication received by the mobile station in this downlink access slot is + 1, then it will Send the message after ³ or ⁴ time slots of the last prefix have been transmitted. The transmission power of the message part is adjusted to Δ ^ _ „, relative to the power of the last prefix sent.

FIG. 1 shows a style of acquisition indication information of an AICH frame specified by the Third Generation Partnership Project (Third Generation Partnership Project, 3GPP). The length of the two AICH frames is 20 ms, including 15 access time slots, and each time slot contains acquisition indication information for a mobile station. The capture instruction information includes a previous capture instruction part (Al-part) and a subsequent empty part (empty- _par t). The former is 16 symbols (4096 chips) in length, and the latter is 4 symbols (1024 chips) in length.

FIG. 2 illustrates a method of generating capture indication information specified by 3GPP. In the figure, W 1, 2, ···, 16) are 16 orthogonal codewords,

, 2, 16) are 16 capture instructions, and the AI part is composed of the first 16 symbols. It is 16 codewords Wi (i = 1, 2, ..., 16) times the corresponding capture instruction AIi (i = l , 2, ..., 16), and the last 4 zero symbols constitute the empty part.

In the prior art, the mobile station uses an open-loop power control method to send the initial prefix, that is, the mobile station estimates the uplink path loss based on the BCCH transmit power broadcasted by the BCCH channel, and then it

The uplink interference level broadcast on the BCCH channel determines the transmit power of the uplink prefix. However, when the frequency difference between the uplink and downlink RF carriers is large, the error of this open-loop power estimation is large, so that the initial open-loop power estimation of the mobile station differs from the power required to be received by the base station. Big. In this way, after receiving the negative acquisition indication, the mobile station must resend the prefix in the new uplink time slot, and its transmission power is reduced by Δ / ^ from the power of the previous transmitted prefix. When the initial transmission power estimate of the mobile station is too high, When the difference between the received power value required by the base station is large, the mobile station generally needs to reduce the transmission power of the prefix multiple times to reach the target value. In other words, the mobile station often has to send several prefixes before sending a message. This not only reduces access efficiency, wastes system resources, increases interference to the system, but also reduces system capacity.

The purpose of the present invention is to overcome the disadvantage that the mobile station needs to reduce the transmission power of the reverse access channel prefix part multiple times according to the BCCH information in the prior art to reach the system target value. Power method. In this method, without increasing system resources, the mobile station can send subsequent message parts without sending and adjusting the prefix part of the reverse access channel multiple times, thereby reducing the time of reverse access. Reducing interference to other users is beneficial to increasing system capacity. Summary of the Invention

The present invention provides a method for instructing a mobile station to reduce a prefix transmission power by sending acquisition information through a base station via an AICH channel. With the method of the present invention, the mobile station first sets the prefix transmission power value according to the received cell information, and the uplink access time slot obtained on the reverse access channel uses the selected mark to set The mobile station receives the acquisition instruction information sent by the base station via the acquisition instruction channel in the downlink access slot corresponding to the uplink access slot, and finally the mobile station makes Different responses, where the acquisition instruction information is composed of an acquisition instruction part for instructing the mobile station to send a message or continue to transmit a prefix, and a power adjustment (PA) for instructing the mobile station to decrease the transmission power value of the prefix that follows. ) Part of the composition. Overview of the drawings

Hereinafter, the method of the present invention will be described in detail with reference to the drawings. In these drawings:

FIG. 1 shows a style of the capture indication information specified by 3 GPP;

FIG. 2 shows a method for generating capture indication information specified by 3 GPP;

FIG. 3 is a style of capturing indication information proposed by the present invention;

⁴ is a first encoding method of a power adjustment signal according to the present invention;

5 is a second encoding method of a power adjustment signal according to the present invention;

FIG. 6 is an example of a style of capturing indication information of the present invention;

FIG. 7 is an example of a first encoding method of a power adjustment signal of the present invention; and

Fig. 8 is an example of the second encoding method of the power adjustment signal of the present invention. The best embodiment of the present invention

Referring now to FIG. 3, this figure shows a style of capture indication information proposed by the present invention. It can be seen from FIG. 3 that the acquisition indication frame sent through the AICH channel is two frames, the length is T (ms), and it includes L access time slots. The acquisition indication information in each access slot includes an acquisition indication ( ^AI ) part and a power adjustment ( ^PA ) part. The length of the ^AI part is ^^ chips and contains 1 ^ symbols. Here, ^ is the length of the marker used by the mobile station, which is an integer power of two. The spreading factor of the AI part is M, / N 81 is an orthogonal codeword

1, 2, ..., Ni) multiplied by the sum of the corresponding symbols after the corresponding acquisition indication Ali. The length of the PA part is ₂ ^ ₂ chips and is used to carry 2 bits of power adjustment (PA) information. When the base station considers that the transmission power of the prefix of a certain mobile station is too high, it first sends the capture indication-1 with the chips of the AI part in the corresponding downlink time slot, and then uses the M ₂ codes of the PA part following it. The slice indicates a decrease in the transmission power of the mobile station when transmitting subsequent prefixes. Below are two scenarios and their corresponding examples.

(plan 1 )

As shown in FIG. 4, the M ₂ chips in the PA part include 2N i symbols, and the spreading factor SF of each symbol is SF = 2/2 / N, which is 2N. Each symbol is ^ symbols long. The code words W ^^, _Wi2 , ..., _WiNl ) are repeated twice. The code word Wi coincides with an orthogonal code word having Ai-1 in the AI part. At this time, 2 can be modulated on this symbol Bit power control information. That is, if the capture indication corresponding to Wi (W _i W _i2 , —, W _iN ,) in the AI part is -1, then two codewords with a total length of ₂ chips are 2 bits of modulation power adjustment indication Quantity bob !, if the quantities are 00, 01, 10, and 11, respectively, the mobile station reduces the transmit power of the next prefix by Δ, |, 2Δ ^ |, 3ΔP, |, and 4Δ ^ |. For a mobile station, if it demodulate its A1 part and obtains its corresponding acquisition indication as -1, it needs to continue to demodulate the M ₂ chips of the subsequent PA part to obtain the PA information. (Scenario 2)

As shown in FIG. 5, the total length of the PA part is M ₂ chips. Beginning with Μ _2/2 chips of the first modulation symbol b. Which uses the spreading code length of chips labeled 1 ^ ₂ / ^ 2 replicates. With subsequent M _2/2 chips of the second modulation symbol using a spreading code which b !, length of marker chips! ^ /? ^^ underrepeated. Here, the label used by the base station is the same as the label of the corresponding mobile station received by the base station. If the AI part _{_{Wi (W H, W i2,}} ..., W iNl) acquisition indicator corresponding to -1, M ₂ modulation chips power adjustment indicating amount of the total length of b. b ,. If the indications are 00, 01, 10, and 11, respectively, the mobile station will reduce the transmit power by Δ ^, ^2Δ ^ |, 3Δ ^, and 4ΔP, | when transmitting the next prefix. For a mobile station, if the demodulation of its A1 part gets a capture indication of -1, it also needs to continue to demodulate the M ₂ chips of the subsequent PA part to obtain the PA information.

Examples of the present invention are given below. As shown in FIG. 6, the same parameters as the 3GPP regulations are adopted for AICH frames and time slots, that is, the AICH frame is two frames with a total length of 20 ms. There are 15 access time slots in the two frames, and each access time slot The AI part is 16 symbols with a total of 4096 chips, while the PA part is 1024 chips. The AI part is 16 orthogonal codewords Wi (i = 1, 2, ..., 16) multiplied by the corresponding acquisition indication AI; the sum of the corresponding corresponding symbols later, the spreading factor of the AI signal is 256. When the base station returns a capture indication of a marker sent by a mobile station to -1, in order to reduce the number of times the mobile station resends the prefix, the base station uses 102 ⁴ chips of the PA signal after the AI signal to indicate the mobile station How much the transmit power is reduced when the prefix part is subsequently transmitted. Examples corresponding to the above-mentioned schemes 1 and 2 will be described below.

(Example 1)

As shown in FIG. 7, 1024 chips of the PA signal correspond to 32 symbols, so the spreading factor is 32. This length is 32 symbols to 16 symbols codeword _{_{^ (\ η, W i2,}} ..., W il6) twice. The codeword is related to the AI signal

The -1 orthogonal codewords agree. At this time, a 2-bit power adjustment indicator bob! Can be modulated on the 32 symbols. If the indicators are 00, 01, 10, and 11, respectively, the mobile station will separate the transmit power when transmitting the next prefix. Decrease Δ ^ |, 2Δ ^ |, 3ΔP, | ¾] 4Δ ₁ | „For a mobile station, if it demodulates the 16 symbols of its ΑΙ section and obtains its corresponding acquisition indication as -1, it needs Continue demodulating the 102 ⁴ chips of the PA part connected to it to obtain the power adjustment information.

(Example 2) As shown in FIG. 8, two symbols bab !, gf] are modulated with 1024 chips of the PA part, and the first symbol b is modulated with the first 512 chips. The second symbol bi is modulated with the last 512 chips. The spreading code uses 32 repetitions of the mark with a length of 16 chips. Here, the label used by the base station is the same as the label sent by the corresponding mobile station received by the base station. If W i = 1, 2, ..., 16) in the AI part, the corresponding capture indication is -1, then in the 1024 chips of the PA part, the modulation power adjustment indication amount bab ^ If the indication amounts are 00, 01, respectively , 10 and

11, then the mobile station will reduce the transmit power by Δ |, ² ^ |, 3Δ |, and Δ, | Δ when transmitting the next prefix. For a mobile station, if the 16 symbols of the ΑΙ part are demodulated, Its corresponding acquisition indication is -1, then it also needs to continue demodulating the 1024 chips of the PA part connected to it to obtain the power adjustment signal.

Industrial applicability

The present invention solves the problem that the current mobile station needs to reduce the transmission power multiple times to reach the target value, so that the mobile station can send a message without sending a prefix multiple times without increasing system resources.

Claims

Rights request

1. A method for instructing a mobile station to reduce transmission power by sending acquisition indication information by a base station through an acquisition indication channel, the method comprising the following steps:

The mobile station sets a prefix transmission power value according to the received cell information, and uses the selected mark to send the uplink access time slot obtained on the reverse access channel to the preset transmission power value of the prefix. Prefix

Receiving, by the mobile station, the acquisition indication information for the mobile station sent by the base station via the acquisition indication channel in a downlink access slot corresponding to the uplink access slot; and

The mobile station responds differently according to different situations encountered in receiving the acquisition instruction information, and the method is characterized in that the acquisition instruction information is composed of an acquisition instruction part for instructing the mobile station to respond and immediately after it The power adjustment part is used to instruct the mobile station to reduce the value of the prefix transmission power.

2. The method according to claim 1, wherein the different responses made by the mobile station are:

When the mobile station does not receive the acquisition indication information, it will increase the transmission power of the prefix by Δ when it sends the prefix in the next uplink access slot. |;

When the acquisition indication corresponding to the acquisition indication part received by the mobile station is +1, it will send a message after several uplink access time slots;

When the acquisition indication corresponding to the acquisition indication part received by the mobile station is -1, it will reduce the prefix transmission power when the prefix is transmitted in the next uplink slot,

It is characterized in that the reduction value of the prefix transmission power is indicated by the power adjustment section of the acquisition instruction information.

3. The method according to claim 1, wherein the capture indication portion is a total of Mi chips, including ^ symbols, and the power adjustment portion is a total of M ₂ chips, including 21 ^ Symbols, the symbols are of length! Two codeword Wi Vi ^ symbols _{_{,, W i2, ..., W iNl}} ) is repeated, the codeword indicating the capture portion having Ali = - consistent orthogonal code word 1, when the When the capture indication corresponding to the code word Wi (W, _Wi2 ... ..., \ _ViNl) in the capture instruction portion is -1, then in the M ^, chip of the power adjustment portion Modulates the 2-bit power adjustment indicator b ^

4. The method according to claim 1, wherein the capture indication portion is a total of chips, including ^ symbols, and the power adjustment portion is a total of M ₂ chips, using a pre-M ₂ / 2 yards chip modulated first symbol b _Q, with the M _2/2 chips of the second modulation symbol b _h spreading code length are used to mark the chips ^ M _2/2 / N ₁ repetition, the tag adopted by the base station here is the same as the tag of the mobile station received by the base station, and when the code word Wi (W _n . W _i2 , .... W _{iN of} the acquisition indication part) _{l) the} corresponding capturing finger When it is shown as -1, then a 2-bit power adjustment indication r¾-b ₀ b is modulated in the M ₂ chips of the power adjustment part; _o

5. The method according to claim 3 or ⁴ , wherein when the power adjustment indicator bob is 00, 01, 10, and 11, respectively, the mobile station transmits the next prefix. Power decreases by Δ, |, Δ, |, 3Δ, ^ ρ4Δ, | _ο