CN1146147C - Method for base station to guide mobile station to reduce prefix emitted power - Google Patents

Abstract

The present invention provides a method for a base station to transmit information by an acquisition indication channel to guide a mobile station to reduce prefix emitted power. The acquisition indication information is composed of an acquisition indicating (AI) part for indicating the mobile station to transmit information or continue to transmit a prefix and a power adjustment (PA) part which is connected to the acquisition indication (AI) part and used for indicating the mobile station to reduce prefix emitted power values. When acquisition indication which is transmitted by the base station and received by the mobile station is-1, the mobile station continues to demodulate the PA part to obtain an emitted power reduced value of the mobile station which transmits the next prefix.

Description

A method for base station to instruct mobile station to reduce prefix transmission power

The present invention relates to a code division multiple access (CDMA) communication system. In more detail, the present invention relates to a method for a base station to instruct a mobile station to reduce the transmit power of a prefix through information sent on an acquisition indication channel (AICH).

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

The mobile station reads information about the cell on a broadcast channel (broadcast channel, BCCH) of the cell. The information includes: (1) the spreading code of the prefix part used by the cell/scrambling code of the message part (message); (2) the available signature (signature); (3) each access service category (access service category, ASC) of the reverse access channel (RACH) subchannel group; (4) available spreading factor of the message part; (5) interference level of the uplink in the cell; (6) main sharing control channel (common control principal channel, CCPCH); (7) transmission timing of acquisition indication channel; (8) power deviation ΔP _pm of prefix part and message part; and (9) power deviation Δ ₀ (when no acquisition indication is received power increase) and ΔP ₁ (power decrease when an acquisition indication of -1 is received).

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 as P _RACH according to the estimated value of the open-loop power. The mobile station then performs a random backoff algorithm to select a RACH sub-channel from the available ASC sub-channel group, so as to obtain an access slot (AS) in the next two frames in the selected RACH sub-channel. The mobile station then randomly selects a token from the available tokens. Finally, in the obtained uplink access time slot, the mobile station uses the selected marker to transmit the prefix with the set prefix transmission power.

The base station will send the acquisition indication through the AICH channel in the downlink access time slot corresponding to the uplink access time slot. If the mobile station does not receive an acquisition indication in the downlink access slot, it will select a new uplink access slot and increase its prefix transmission power by ΔP ₀ ; if the mobile station in the downlink access slot If the acquisition indication received by the time slot is -1, it will select a new uplink access time slot and reduce its prefix transmit power by ΔP ₁ ; if the mobile station receives If the capture indicator of the smack is +1, it will send the message 3 or 4 slots after the last prefix has been sent. The transmit power of the message part is adjusted by ΔP _pm relative to the power of the last prefix transmitted.

Fig. 1 shows the style of the capture instruction information of the AICH frame stipulated by the third generation mobile communication standardization organization (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 instruction information for a mobile station. The acquisition indication information includes an acquisition indication part (AI-part) preceding it and an empty part (empty-part) following it. The length of the former is 16 symbols (4096 chips), and the length of the latter is 4 symbols (1024 chips).

FIG. 2 shows a method for generating acquisition indication information stipulated by 3GPP. In the figure, W _i (i=1, 2, ..., 16) are 16 orthogonal codewords, and AI _i (i = 1, 2, ..., 16) are 16 acquisition indications, consisting of the first 16 symbols Constitute the AI part, which is the sum of corresponding symbols after multiplying 16 codewords W _i (i=1, 2, ..., 16) by the corresponding acquisition indication AI _i (i = 1, 2, ..., 16), And the last 4 zero symbols constitute the empty part.

In the prior art, the mobile station uses the open-loop power control method to send the initial prefix, that is, the mobile station estimates the uplink path loss according to the BCCH transmit power broadcast on the BCCH channel, and then it estimates the uplink path loss according to the uplink broadcast power on the BCCH channel. The interference level of the path determines the transmit power of the uplink prefix. However, when the frequencies of the uplink and downlink radio frequency carriers differ greatly, the error of this open-loop power estimation is large, so that the difference between the initial open-loop power estimation of the mobile station and the power required by the base station is relatively small. big. In this way, after the mobile station receives a negative acquisition indication, it needs to resend the preamble in a new uplink time slot, and its transmit power is reduced by ΔP ₁ from the power of the previous sent preamble. When the estimated value of the initial transmission power of the mobile station is too high, which is quite different from the power value required by the base station, generally the mobile station needs to reduce the transmission power of the prefix several times to reach the target value. In other words, the mobile station often cannot send a message until several prefixes have been sent. 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 in the prior art that the mobile station needs to reduce the transmission power multiple times to reach the target value, so that the mobile station can send messages without sending the prefix multiple times without increasing system resources.

The invention provides a method for the base station to send capture information through the AICH channel to instruct the mobile station to reduce the transmission power of the prefix. Using 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 adopts the selected mark and uses the set power value Send the prefix; secondly, the mobile station receives the acquisition indication information for the mobile station sent by the base station through the acquisition indication channel in the downlink access time slot corresponding to the uplink access time slot, and finally the mobile station makes different responses according to different situations, Wherein, the acquisition indication information is composed of an acquisition indication part for instructing the mobile station to send a message or continue to send a prefix, followed by a power adjustment (power adjustment, PA) part for instructing the mobile station to reduce the transmission power value of the prefix.

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

Fig. 1 shows the style of the acquisition indication information stipulated by 3GPP;

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

Fig. 3 is the style of the capture instruction information proposed by the present invention;

Fig. 4 is the first coding method of the power adjustment signal proposed by the present invention;

Fig. 5 is the second coding method of the power adjustment signal proposed by the present invention;

Fig. 6 is an example of the style of capture indication information of the present invention;

Fig. 7 is the example of the first coding method of the power regulation 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.

Referring now to FIG. 3 , this figure shows the format of the capture indication information proposed by the present invention. It can be seen from FIG. 3 that the acquisition indication frame sent via the AICH channel is two frames, the length is T (ms), and includes L access slots. The acquisition indication information in each access slot contains an acquisition indication (AI) part and a power adjustment (PA) part. The AI part has a length of M ₁ chips and contains N ₁ symbols. Here, _N1 is the length of the mark used by the mobile station, which is an integer power of 2. The spreading factor of the AI part is M ₁ /N ₁ . AI is the sum of corresponding symbols after N ₁ orthogonal codewords W _i (i=1, 2, ..., N ₁ ) are multiplied by the corresponding acquisition indication AI _i . The length of the PA part is M ₂ chips, and is used to carry 2-bit power adjustment (PA) information. When the base station thinks that the prefix transmission power of a certain mobile station is too high, it first uses the M ₁ chips of the AI part to send the acquisition indication-1 in the corresponding downlink time slot, and then uses the subsequent M ₂ chips of the PA part The chips indicate the reduction in transmit power for the mobile station when transmitting subsequent prefixes. Two schemes and their corresponding examples are listed below.

(plan 1)

As shown in Fig. 4, the M ₂ chips of the PA part include 2N ₁ symbols, and the spreading factor of each symbol is SF=M ₂ /2/N ₁ . These 2N ₁ symbols are two repetitions of a codeword W _i (W _i1 , W _i2 , . . . , W _iN1 ) of length N ₁ symbols. The codeword W _i coincides with the orthogonal codeword with Ai _i =-1 for the AI part. At this time, 2-bit power control information can be modulated on these 2N ₁ symbols. That is, if the acquisition indication corresponding to W _i (W _i1 , W _i2 ,...,W _iN1 ) of the AI part is -1, then the two codewords W _i W _i with a total length of M ₂ chips are 2 bits The modulation power adjustment indication amount b ₀ b _{1 of} , if the amount is 00, 01, 10 and 11 respectively, the mobile station will reduce the transmit power of the next prefix by ΔP ₁ , 2ΔP ₁ , 3ΔP ₁ and 4ΔP ₁ respectively. For the mobile station, if it demodulates its AI part and obtains its corresponding acquisition indication as -1, it needs to continue to demodulate the following M ₂ chips of the PA part to obtain PA information.

(Scenario 2)

As shown in Figure 5, the total length of the PA part is M ₂ chips. The first symbol b ₀ is modulated with the first M ₂ /2 chips, whose spreading code uses M ₂ /2/N ₁ repetitions of marks of length N ₁ chips. The next M ₂ /2 chips are used to modulate the second symbol b ₁ , whose spreading code uses M ₂ /2/N ₁ repetitions of marks of length N ₁ chips. Here, the signature adopted by the base station is the same as the signature of the corresponding mobile station received by the base station. If the acquisition indicator corresponding to W _i (W _i1 , W _i2 , ..., W _iN1 ) in the AI part is -1, then the power adjustment indicator b ₀ b ₁ is modulated with a total length of M ₂ chips. If the indications are 00, 01, 10 and 11 respectively, the mobile station will reduce the transmission power by ΔP ₁ , 2ΔP ₁ , 3ΔP ₁ and 4ΔP ₁ when sending the next prefix. For the mobile station, if it demodulates its AI part and obtains an acquisition indication of -1, it needs to continue to demodulate the following M ₂ chips of the PA part to obtain PA information.

Examples of the present invention are given below. As shown in Figure 6, the same parameters as those specified by 3GPP are adopted for the AICH frame and time slot, that is, the AICH frame is two frames, a total of 20 ms, and there are 15 access slots in the two frames, and each access slot The AI part is 16 code elements, a total of 4096 chips, while the PA part is 1024 chips. The AI part is the sum of corresponding symbols after multiplying 16 orthogonal codewords W _i (i=1, 2, ..., 16) by the corresponding acquisition indication AI _i , and the spreading factor of the AI signal is 256. When the base station returns an acquisition indication of -1 to the tag sent by a certain mobile station, in order to reduce the number of times the mobile station retransmits the prefix, the base station uses 1024 chips of the PA signal following the AI signal to indicate that the mobile station is How much to reduce the transmit power when the prefix portion is subsequently transmitted. Examples corresponding to the above scheme 1 and scheme 2 are described below respectively.

(Example 1)

As shown in Figure 7, 1024 chips of the PA signal correspond to 32 symbols, so its spreading factor is 32. These 32 symbols are two repetitions of a codeword W _i (W _i1 , W _i2 , . . . , W _i16 ) of length 16 symbols. This codeword agrees with the orthogonal codeword of the AI signal with Ai _i =-1. At this time, the 2-bit power adjustment indicator b ₀ b ₁ can be modulated on the 32 symbols. If the indications are 00, 01, 10 and 11 respectively, the mobile station will reduce the transmission power by ΔP ₁ , 2ΔP ₁ , 3ΔP ₁ and 4ΔP ₁ when sending the next prefix. For the mobile station, if it demodulates the 16 symbols of its AI part and gets its corresponding acquisition indication as -1, it needs to continue to demodulate the 1024 chips of the PA part following it to obtain the power Regulatory information.

(Example 2)

As shown in Figure 8, 2 symbols b ₀ b ₁ are modulated with 1024 chips of the PA part, that is, the first symbol b 0 is modulated with the first 512 chips, and the second symbol b ₀ is modulated with the last 512 chips. symbol b ₁ . Its spreading code employs 32 repetitions of marks with a length of 16 chips. Here, the signature used by the base station is the same as the signature received by the base station and sent by the corresponding mobile station. If the acquisition indicator corresponding to W _i (i=1, 2, ..., 16) in the AI part is -1, then in the 1024 chips of the PA part, the modulation power adjustment indicator b ₀ b ₁ is modulated. If the indications are 00, 01, 10 and 11 respectively, the mobile station will reduce the transmission power by ΔP ₁ , 2ΔP ₁ , 3ΔP ₁ and 4ΔP ₁ when sending the next prefix. For the mobile station, if it demodulates the 16 symbols of its AI part and gets its corresponding acquisition indication as -1, it needs to continue to demodulate the 1024 chips of the PA part following it to obtain the power Regulatory information.

Claims (6)

1. a method that is used to sew before regulating travelling carriage transmitting power is characterized in that, described method comprises the steps:

Travelling carriage is set a prefix transmitting power according to the cell information that receives;

The up access slot that described travelling carriage obtains on Reverse Access Channel with the prefix transmitting power of setting, sends prefix;

Described travelling carriage is in the descending access slot corresponding with described up access slot, by the catch indication information of AICH Acquisition Indication Channel reception from the base station, the wherein said indication information of catching comprises and catches indicating section and power adjustments part, the described indicating section of catching has the information that indication increases transmitting power, reduces one of transmitting power and maintenance transmitting power, and described power adjustments has partly comprised the information that reduces to be worth about transmitting power;

Reduce described prefix transmitting power if catch indicating section indication, so described travelling carriage reduces described prefix transmitting power according to the information that reduces to be worth about transmitting power that described power adjustments part is comprised; And

Described travelling carriage with described transmitting power through reducing, resends prefix at next ascending time slot.

2. the method for claim 1 is characterized in that, and is further comprising the steps of:

If described travelling carriage does not receive the described indication information of catching, then described prefix transmitting power is increased Δ P ₀

Described travelling carriage is at the up access slot of the next one, and the prefix transmitting power to increase resends described prefix.

3. method as claimed in claim 1 or 2 is characterized in that, and is further comprising the steps of:

If the described indicating section of catching represents to keep transmitting power, so described travelling carriage sends message behind several up access slots.

4. the method for claim 1 is characterized in that, the described indicating section of catching is total up to M ₁Individual chip comprises N ₁Individual code element, described power adjustments partly is total up to M ₂Individual chip comprises 2N ₁Individual code element is as the described orthogonal code W that catches indicating section _i(W _I1, W _I2..., W _IN1) corresponding catching be designated as at-1 o'clock, the 2N of described power adjustments part ₁Individual code element is to be N to length ₁Twice of the code word of individual code element repeated to modulate the power adjustments indicatrix b of 2 bits ₀b ₁Obtain wherein said code word and the described orthogonal code W that catches indicating section _i(W _I1, W _I2..., W _IN1) consistent.

5. the method for claim 1 is characterized in that, the described indicating section of catching is total up to M ₁Individual chip comprises N ₁Individual code element, described power adjustments partly is total up to M ₂Individual chip is when described code word W of catching indicating section _i(W _I1, W _I2..., W _IN1) corresponding described catching be designated as at-1 o'clock, at the described M of described power adjustments part ₂Modulated the power adjustments indicatrix b of 2 bits in the individual chip ₀b ₁, wherein at preceding M ₂Modulated first code element b in/2 chips ₀, at back M ₂Modulated second code element b in/2 chips ₁, it is N that spreading code all adopts length ₁The M of the mark of individual chip ₂/ 2/N ₁The described mark that inferior repetition, described base station are here adopted is identical with the mark of the travelling carriage that described base station receives.

6. as claim 4 or 5 described methods, it is characterized in that, as described power adjustments indicatrix b ₀b ₁Be respectively 00,01,10 and at 11 o'clock, then described travelling carriage reduces Δ P to the transmitting power of described next prefix respectively ₁, 2 Δ P ₁, 3 Δ P ₁With 4 Δ P ₁

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