CN100461658C - Speed matching and parameter optimizing method of wide band CDMA cut-ni system - Google Patents
Speed matching and parameter optimizing method of wide band CDMA cut-ni system Download PDFInfo
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Abstract
A method of rate matched parameters optimization for a broad band CDMA access system is to get the maximum rate matched parameter combination for each channel according to code back BER limitation of every channel, the said parameter combination is got by derivation of a set of equations made up of channel rate matched gain equations. The method can get rate matched factors of the transmission channels in quantity so that the compound channel CCtr CH performance can meet the different performance requirements of transmission channels joining in complexion at the same time, unbalanced situation will not appear, when this set of rate matched factors is applied for rate matched factors is applied for rate match.
Description
The technical field is as follows:
the invention relates to a method for optimizing parameters in a Wideband Code Division Multiple Access (WCDMA) system, in particular to a method for optimizing parameters in a WCDMA system, which comprises the following steps: is a method for optimizing and configuring transmission channel RM (Rate Matching) parameter in WCDMA system.
Background art:
in the uplink and downlink flow of the physical layer baseband flow of the WCDMA system, the steps of rate matching are provided. Both the size of a Transport code block and the number of code blocks may vary within different TTIs (transmission time intervals) in the same Transport channel. If all the transmission channels are directly compounded into one physical Channel, the fact that the CCtrCH (code multiplexed Composite Transport Channel) formed by compounding can be mapped onto the physical Channel according to the frame format specified in the protocol cannot be guaranteed all the time; that is to say: the number of bits on a physical channel that can be included in a frame may be inconsistent with the number of times the composite channel requires it to transmit within a frame. The process of channel recombination must be controlled.
The size of the code stream is dynamically adjusted through bit repetition or bit stream punching, so that the finally obtained CCtrCH channel can be correctly mapped to a physical channel. In actual repetition and puncturing, the bits to be operated on are spread out over the entire transmission channel as much as possible to ensure minimal impact on decoding. The procedure of the downlink and uplink rate matching is performed in the process of calculating the rate matching operation, i.e. the procedure is broken or repeated, the formula of the number of bits is consistent, and the calculation method specified in the WCDMA protocol 3GPP TS 25.212 V4.1.0(2001-01) is as follows:
ΔNi＝Zi-Zi-1-NiWherein I1
The symbols in the formula are illustrated below:
i is a transmission channel contained in CCtrCH;
Ndatathe number of bits that each radio frame of the composite channel CCtrCH should contain according to the physical transmission limitation requirement;
Nmcorresponding to the bit number in a 10ms wireless frame for the mth transmission channel before rate matching;
RMmmatching parameters for the rate of the mth transmission channel;
ZIis an intermediate result;
ΔNIthe number of bits that are repeated (if the value is positive) or punctured (if the value is negative) by rate matching is needed for the calculated ith transport channel.
From the above formula, it can be seen that: the rate matching factor actually affects how the bit rate required by the CCtrCH is allocated to the various transport channels. The WCDMA protocol does not describe how to set the rate matching factor parameters for different transport channels. If the allocation rates cannot be equalized to the different transport channels according to the transport channel performance requirements, a composite channel with optimal performance cannot be obtained.
The invention content is as follows:
the invention mainly aims to provide a method for optimizing the rate matching parameters of transmission channels, which comprehensively considers the different performance requirements of each transmission channel, utilizes reasonable rate matching parameters to carry out rate matching operation, and distributes the rate to different transmission channels in a balanced manner, thereby obtaining the optimal composite channel performance; and respective rate matching parameter values can be calculated quantitatively according to the performance requirements of the composite individual transmission channels.
The purpose of the invention is realized as follows:
constructing and solving an equation set formed by rate matching gain equations of all the channels according to the coded bit error rate limit of all the transmission channels, and obtaining the optimal rate matching parameter combination of all the channels;
the method for constructing the equation set formed by the rate matching gain equation of the channel comprises the following steps:
when the channel gets a positive gain through a bit repetition operation:
when the channel carries out bit puncturing operation to obtain negative gain:
wherein:
q is the channel error rate after the rate matching operation;
q' is the channel error rate before the rate matching operation;
Δ Nithe bit number of the rate matching operation of the ith transmission channel is represented by bit repetition operation when the bit number is a positive value, and the bit punching operation is represented by a negative number;
Nithe bit number of a corresponding wireless frame of the ith transmission channel before rate matching is obtained;
the solving method of the channel rate matching gain equation set comprises the following steps:
step 1: initially constructing an equation set in which all channels execute bit repetition operation, namely constructing an equation set formed by rate matching gain equations in a positive gain form of all channels and solving the equation set;
step 2: solving the system of equations if all solved Δ NiIf all the channels meet the set of the structural equation set, executing bit punching operation or bit repeating operation on each channel, and if yes, starting to execute the step 4; otherwise, executing step 3;
and step 3: setting the channel corresponding to the maximum bit error rate limit to execute bit punching operation, constructing a new equation set according to new setting and executing the step 2;
and 4, step 4: according to the calculation formula of the rate matching operation bit number of each transmission channel in the WCDMA protocol 3GPP TS 25.212 V4.1.0, the delta N of each channel is calculatediAnd calculating the rate matching parameters of each channel by using the values.
Further, the method further includes calculating the bit error rate limit of each transmission channel compounded in the baseband process. If the channel quality requirement is given in the form of an error rate limit, it can be used directly. If, however, the channel quality requirement is in the form of a block error rate or frame error rate limit, the corresponding bit error rate limit is derived according to the following equation.
Wherein,
ber (Bit Error rate) is the Bit Error rate limit to be solved;
err is a given block error rate limit or frame error rate limit;
size is the length of a given code segment.
If there are multiple possible code block sizes in the format set of the transport channel, a calculation should be performed according to the probability of occurrence of the different format sets in the transport channel to obtain an expected code block size or an expected radio frame size.
Further, according to the error correction coding gain of different transmission channels, the error rate limit of the transmission channel after coding is obtained according to the error rate requirement of the transmission channel.
In the invention, the error rate requirement before coding of the transmission channel is the error rate before coding, and the error rate requirement of the transmission channel after coding is expressed as the error rate after coding. Due to the coding gain, the error rate after coding is greater than the error rate before coding.
The method of the invention can quantitatively obtain the rate matching factors of the transmission channels, and ensures that the performance of the composite channel CCtrCH can simultaneously meet different performance requirements of the transmission channels participating in multiplexing without imbalance when the rate matching is carried out by adopting the group of rate matching factors. That is to say: the quality requirement of each transmission channel for wireless transmission in the air is reduced. The invention can reduce the transmitting power of the channel, and actually improve the capacity of the system.
Description of the drawings:
FIG. 1 is a graph of 1/2 rate convolutional code error correction gain fit in accordance with the present invention.
FIG. 2 is a graph of 1/3 rate convolutional code error correction gain fit in accordance with the present invention.
FIG. 3 is a fitting curve diagram of error correction gain of Turbo coding according to the present invention.
Fig. 4 is an overall flow chart of the present invention.
Fig. 5 is a flow chart of calculating the post-coding error rate limit of each transmission channel in the present invention.
Fig. 6 is a flow chart of solving the rate matching gain equation of the channel in the present invention.
The specific implementation mode is as follows:
the invention is described in further detail below with reference to the following figures and specific examples:
the method for designing the transmission channel rate matching parameters in the system provided by the invention comprises the following steps:
first, the bit error rate limit of each transmission channel participating in multiplexing in the baseband process is calculated.
The bit error rate limit of the transmission channel reflects the performance requirement of the channel; however, the actual channel performance parameters may be given in the form of block error rate and frame error rate limits, and in this step, they need to be uniformly converted into the form of error rate limits.
The formula for this conversion is derived as follows:
defining the symbolic variables:
err: error rate given in code segment form (code block or frame);
ber: error rate;
size: the length of a given code segment;
x: the code stream length;
ErrNum: the error code segment count.
By applying statistical theory, we can derive: <math> <mrow> <mi>Err</mi> <mo>=</mo> <munder> <mi>lim</mi> <mrow> <mi>x</mi> <mo>→</mo> <mo>∞</mo> </mrow> </munder> <mfrac> <mi>ErrNum</mi> <mrow> <mi>x</mi> <mo>/</mo> <mi>Size</mi> </mrow> </mfrac> </mrow></math>
the symbol num is defined as x/Size, which is the number of segments on the code stream with length x. The bit error number on the code stream with the length of x is x multiplied by Ber. According to probability theory, when an error bit is randomly divided into num code segments, the probability that a certain code segment is not divided into the error bit is (1-1/num), and then the probability that a certain code segment is not divided into error bits for continuous times (x multiplied by Ber) is <math> <mrow> <msup> <mrow> <mo>(</mo> <mfrac> <mrow> <mi>num</mi> <mo>-</mo> <mn>1</mn> </mrow> <mi>num</mi> </mfrac> <mo>)</mo> </mrow> <mrow> <mi>x</mi> <mo>·</mo> <mi>Ber</mi> </mrow> </msup> <mo>,</mo> </mrow></math>
The most likely number of error code segments is therefore:
from this, it can be derived:
the formula for obtaining the error limit in the form of the translation code segment as the bit error rate limit is as follows:
if there are many possible code segment sizes in the format set of the transmission channel, an expected code segment size is obtained by calculation according to the probability of the code segments with different sizes appearing in the transmission channel, and then the expected code segment size is substituted into the formula to obtain the error rate limit.
Then, the error rate limit after coding of each transmission channel is calculated according to the error correction coding gain of different transmission channels.
The error correction coding gain of the individual transmission channels is taken into account to obtain their performance requirements before the rate matching operation, i.e. the post-coding error rate limit.
There are three coding schemes specified in the WCDMA protocol 3GPP TS 25.212 V4.1.0(2001-01), which are: 1/2 rate convolutional coding, 1/3 rate convolutional coding, and Turbo coding. The gains of these coding schemes differ significantly. The most accurate method for obtaining the coding gain of a certain transmission channel is to design a simulation program according to the parameters of the channel and calculate to obtain a statistical result. But is not easy to implement in practice. A simple and practical method is to design a transmission channel as a reference, and to perform simulation tests on three different coding modes specified in a protocol based on the transmission channel to obtain a coding gain test result. When the bit error rate limit after coding of a certain transmission channel needs to be solved, the bit error rate limit can be obtained only by interpolation according to data in the table. The reference channel has the following characteristics:
1) it is assumed that the error bits are uniformly distributed over the entire encoded transport channel stream. This is also true in practice, since the interleaving procedure in the physical layer causes the error distribution to be spread out.
2) The decoding algorithms are all hard decisions.
3) The convolutional coding gain simulation test of 1/2 rate and 1/3 rate in the invention is to carry out 2000 coding and decoding tests on a random binary code stream with the length of 400, and the accuracy of the obtained bit error rate result is in the level of 1e-4 accuracy; the Turbo coding gain simulation test is to perform one hundred thousand coding and decoding tests on a random code stream with the length of 1000, and the accuracy of an obtained bit error rate result is in the level of 1e-6 accuracy.
The gain data obtained by simulation under three coding modes are listed as follows:
TABLE 1
See fig. 1, 2, and 3, which are gain curves of three coding modes obtained by fitting the data in table 1.
And further substituting the coded bit error rate of each transmission channel, and solving an equation set formed by a rate matching gain equation of the channel so as to obtain the optimal rate matching parameter combination of each channel.
For convenience of explanation, the following symbolic variables are defined:
Δ Nimatching the operation bit number for the ith transmission channel rate, if the operation bit number is a positive number, executing bit repetition operation, and if the operation bit number is a negative number, executing bit punching operation;
Nicorresponding to the bit number in a wireless frame before rate matching for the ith transmission channel;
RMimatching parameters for the rate of the ith transmission channel;
Ndatathe number of bits in a radio frame on CCtrCH;
i is the number of transmission channels participating in multiplexing;
Qilimiting the coded bit error rate of the ith transmission channel;
q is the error rate limit of CCtrCH;
Xithe rate of change for the i-th transport channel rate matching operation, i.e. Δ Ni/NI；
The punture is an intermediate variable, the number of channels currently assumed to perform the puncturing operation.
The calculation method of the operation bit number of each transmission channel in the rate matching link can be derived from the formula in the WCDMA protocol 3GPP TS 25.212 V4.1.0 (2001-01):
in addition, whether the rate matching operation according to the channel is bit repetition or bit puncturing should be performed according to the following rules:
if the operation is bit repetition operation, the statistical error rate after the rate matching is Q; the statistical bit error rate before rate matching is Q'. In general,. DELTA.Ni<NiI.e. there will not be more than one bit repeated. The bit repeated demodulation results are combined to reduce the error probability by half, so the following gain equation under the bit repeated operation is obtained:
in the case of bit puncturing, the punctured bits are arbitrarily complemented to 0 or 1 at the receiver, with a probability of error of 1/2. The gain equation under the puncturing operation is:
since it is impossible to determine which channels need to perform bit puncturing and which channels need to perform bit repetition before designing the rate matching parameters, the rate matching gain equation form of each channel cannot be determined. The program flow is therefore a heuristic solution and then verification process.
Referring to fig. 4, which is a general flow chart of the present invention, the method includes the following steps:
step 1: calculating the bit error rate limit of each transmission channel participating in multiplexing in the baseband process;
step 2: calculating the error rate limit after coding of each transmission channel according to the error correction coding gain of different transmission channels;
and step 3: and solving an equation set formed by a rate matching gain equation of the channel according to the coded bit error rate of each transmission channel to obtain the optimal rate matching parameter combination of each channel.
Referring to fig. 5, which is a flowchart of calculating the post-coding error rate limit of each transmission channel in the present invention, the flowchart includes: firstly, setting a reference transmission channel; then, based on the reference channel, a simulation test is carried out on three coding modes specified in a WCDMA protocol 3GPP TS 25.212 V4.1.0(2001-01) to obtain a coding gain test data table; and finally, interpolating the coded bit error rate limit of the corresponding transmission channel according to the coding gain test data table.
Referring to fig. 6, which is a flowchart of a method for solving a rate matching gain equation of a channel according to the present invention, the method includes:
step 1: assuming that all channels will perform repeated operations, constructing an equation set solution composed of rate matching gain equations in the form of positive gains of all channels;
step 2: solving the system of equations if all solved Δ NiIf the bit puncturing operation or the bit repetition operation is performed on each channel according to the constructed equation set, starting to perform the step 4; otherwise, executing step 3;
and step 3: setting the channel corresponding to the maximum bit error rate limit as a channel for executing punching operation, constructing a new equation set and executing the step 2;
and 4, step 4: according to the calculation formula of the operation bit number of rate matching of each transmission channel in the WCDMA protocol 3GPP TS 25.212 V4.1.0(2001-01), the delta N of each channel is calculatediAnd calculating the rate matching parameters of each channel by using the values.
The method provided by the invention can accurately configure the rate matching parameter value of each transmission channel participating in multiplexing so as to enable the bit error rate limit of the composite channel to be maximum.
Finally, it should be noted that: the above embodiments are only used to illustrate the present invention and do not limit the technical solutions described in the present invention; thus, while the present invention has been described in detail with reference to the various embodiments thereof, it will be understood by those skilled in the art that the present invention may be modified and equivalents may be substituted; all such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims.
Claims (2)
1. A method for optimizing rate matching parameters of a WCDMA access system is characterized by comprising the following steps:
constructing and solving an equation set formed by rate matching gain equations of all the channels according to the coded bit error rate limit of all the transmission channels, and obtaining the optimal rate matching parameter combination of all the channels;
the method for constructing the equation set formed by the rate matching gain equation of the channel comprises the following steps:
when the channel gets a positive gain through a bit repetition operation:
when the channel carries out bit puncturing operation to obtain negative gain:
wherein:
q is the channel error rate after the rate matching operation;
q' is the channel error rate before the rate matching operation;
ΔNithe bit number of the rate matching operation of the ith transmission channel is represented by bit repetition operation when the bit number is a positive value, and the bit punching operation is represented by a negative number;
Nithe bit number of a corresponding wireless frame of the ith transmission channel before rate matching is obtained;
the solving method of the channel rate matching gain equation set comprises the following steps:
step 1: initially constructing an equation set in which all channels execute bit repetition operation, namely constructing an equation set formed by rate matching gain equations in a positive gain form of all channels and solving the equation set;
step 2: solving the system of equations if all solved Δ NiIf all the channels meet the set of the structural equation set, executing bit punching operation or bit repeating operation on each channel, and if yes, starting to execute the step 4; otherwise, executing step 3;
and step 3: setting the channel corresponding to the maximum bit error rate limit to execute bit punching operation, constructing a new equation set according to new setting and executing the step 2;
and 4, step 4: according to the calculation formula of the rate matching operation bit number of each transmission channel in the WCDMA protocol 3GPP TS 25.212 V4.1.0, the delta N of each channel is calculatediAnd calculating the rate matching parameters of each channel by using the values.
2. The method of claim 1, wherein the method comprises: when the channel quality requirement is given in the form of a block error rate or frame error rate limit, the corresponding bit error rate limit is calculated by the following formula:
wherein,
ber is the bit error rate limit to be solved;
err is a given block error rate limit or frame error rate limit;
size is the length of a given code segment.
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| CN1275873A (en) * | 1999-04-21 | 2000-12-06 | 欧洲三菱电讯公司 | Method for equalizing service of Eb/1 ratio in multiple CDMA system |
| WO2001074032A1 (en) * | 2000-03-31 | 2001-10-04 | Matsushita Electric Industrial Co., Ltd. | Method for operating rate match and rate match device |
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| CN1275873A (en) * | 1999-04-21 | 2000-12-06 | 欧洲三菱电讯公司 | Method for equalizing service of Eb/1 ratio in multiple CDMA system |
| WO2001074032A1 (en) * | 2000-03-31 | 2001-10-04 | Matsushita Electric Industrial Co., Ltd. | Method for operating rate match and rate match device |
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