KR100348279B1 - Soft Handover using Rate Matching for WCDMA - Google Patents

Abstract

The present invention relates to WCDMA, and more particularly to soft handover using rate matching in WCDMA that transmits different codewords for each base station using rate matching in implementing soft handover in which different codewords are transmitted for different base stations . In the soft handover according to the present invention, the first systematic bit and the first and third parity bits in the bit stream channel-coded by the turbo code are composed of the first codeword, and the second systematic bit, And the second and fourth parity bits are composed of a second codeword, and the first base station and the second base station alternately transmit the two codewords to the terminal. Therefore, since the puncturing pattern in each base station can be different, the present invention can reduce the loss due to puncturing by combining data transmitted from each base station at the receiving end. In applying the soft handover to the 3GPP system, it is possible to obtain a larger gain at a code rate of 1/3 or more by changing the puncturing pattern at each base station, and at the receiver, It is possible to obtain a gain that can be obtained at a 1/6 code rate.

Description

Soft Handover using Rate Matching for WCDMA using Rate Matching in WCDMA [

The present invention relates to WCDMA, and more particularly to soft handover using rate matching in WCDMA that transmits different codewords for each base station using rate matching in implementing soft handover in which different codewords are transmitted for different base stations .

In general, when a terminal approaches near another cell area having the same CDMA frequency during a call, the terminal detects that the signal strength of the pilot of the new cell is sufficiently high and informs the current cell of this fact. The new cell then opens the call channel to the terminal. At this time, the terminal is opening a call channel with two cells at the same time. The terminal can receive the same traffic data from two cells and benefit from soft combining.

Specifically, in the prior art, a soft handover is performed as follows. Hereinafter, it is assumed that the position of the transmission channel is fixed.

The traffic data transmitted from the WCDMA base station to the MS uses a channel code and rate-matched to map the channel-encoded traffic data to a physical channel.

1 is a block diagram illustrating a handover of a base station having a code rate of 1/3 according to a conventional technique.

Referring to FIG. 1, when the terminal receives traffic data simultaneously from two base stations while moving, traffic data transmitted from the first base station is transmitted to the systematic bit X ₁ of the first constituent encoder 101, 1 codeword composed of one parity bit Y ₁ and a second parity bit Y ₂ of the second constituent encoder 102 is generated.

Since it has generated more bits than the data rate actually transmitted, this code word is punctured and transmitted to the specific terminal at the data rate specified in the specification.

At this time, the first puncturing device 103 and the second puncturing device 104 transmit the different codewords to the specific terminal simultaneously, and the specific terminal receives the two codewords, To obtain a coding gain by puncturing.

The first puncturing unit 103 and the second puncturing unit 104 alternately use the following two patterns in order not to overlap the puncturing pattern with other base stations.

Accordingly, a specific terminal acquires loss of traffic data due to puncturing in receiving traffic data.

Here, the multiplexers 105 and 106 serve to control the traffic data so that the first base station and the second base station transmit different codewords.

The data rate actually transmitted in one base station is 2Rd. Where Rd is the transmission rate of the information to be transmitted.

1, the puncturing devices 103, 104, 203 and 204 use the following puncturing algorithm.

That is, conventionally, a rate matching process is performed through uniform symbol repetition or uniform puncturing, and the algorithm is as follows.

Algorithm for uniform puncturing process

e = eini - initial error of current and desired puncturing rate

m = 1 - the index of the current bit

do while m ≤ X _i

e = e - e _minus - error update

if e ≤ 0 then - determine whether to puncture bit number m

set bit x _{i, m} to δwhere δ ∈ {0, 1}

e = e + e _plus - error update

end if

m = m + 1 - next bit

end do

Algorithm for uniform symbol repetition

else

e = e _ini - initial error of current and desired puncturing rate

m = 1 - the index of the current bit

do while m ≤ Xi

e = e - e _minus - error update

do while e ≤ 0 - Determine whether to repeat bit number m

repeat bit x _{i, m}

e = e + e _plus - error update

end do

m = m + 1 - next bit

end do

end if

In the algorithm for uniform symbol repetition, the repeated bits immediately follow the original bits.

The parameters that change puncturing or repetition patterns in the two algorithms are e _ini , e _minus , and e _plus . These values allow the symbol repetition or puncturing process according to the above algorithm to be uniformly arranged with respect to the entire data bit sequence by the following mathematical expression conditions.

A has 2 for the first parity bit Y ₁ and a has 1 for Y ₂ .

In Equation (1) Represents the amount of symbol repetition or puncturing for transmission channel i, b represents systematic bits and parity bits, b represents systematic bits when b is 1, parity Lt; / RTI >

= , for Y ₁

= , for Y ₂

In Equation (2), TTI denotes a transport time interval (TTI), index i denotes a number of a transport channel, and is a value indicating a transport format that can be received in a TTI of a transport format set.

That is, in Equation (2), N _max denotes a transmission format set The maximum block size " Quot; is a value having a maximum value among the values divided by three.

In Equation (4), e _ini represents an initial error rate value.

e _ini = N _max

In Equation (5), e _plus is a function of puncturing the m-th bit of the transmission channel i when the bit index m is less than or equal to X _i and the value of " e - _minus & Is an offset value for updating.

e _plus = a x N _max

In Equation (6), e _minus is an offset of the initial error rate value updated when the bit index m is smaller than or equal to the X _i , and uses the initial error rate e by a multiple.

Thus, in the case of puncturing caused by rate matching, when puncturing is performed using a 1/3 coding rate and a coding rate greater than 1/3 using the same parameters, When puncturing is performed, no coding gain occurs.

Also, in the case of the 1/2 coding rate in the WCDMA system, coding gain is obtained through puncturing by rate matching, but in this case, a process of making different puncturing patterns in each base station is required.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide an apparatus and method for performing rate matching in which rate matching is performed so as to generate a coding gain even at a coding rate lower than 1/3, Hand soft handover.

Another object of the present invention is to provide inter-base station soft handover with rate matching that provides different puncturing patterns for coding gain at half rate.

According to an aspect of the present invention, a first systematic bit, a first parity bit, and a third parity bit in a bit stream channel-coded by a turbo code are composed of a first codeword, 2 systematic bits and a second and a fourth parity bits in a second codeword so that the first and second base stations periodically alternately transmit the two codewords to the terminal.

Preferably, the first and third parity bits and the second and fourth parity bits are punctured with different puncturing patterns and transmitted to the mobile station.

(2, 1) or (1) in the first base station (first parity bit, third parity bit) or (second parity bit, fourth parity bit) , 2), or has an initial error rate value e _ini for the first parity bit, an update offset value e _minus for the initial error rate value, and an initial error rate for the third parity bit, so as to have the different puncturing patterns, Value update offset value e _minus2 and the puncturing distance D, the initial error rate value for the second parity bit or the fourth parity bit is set to " e _ini- e _minus "Or" e _ini -e _minus2 Quot; is used.

And e _plus or e _plus2 which is an update offset value of another initial error rate of the first parity bit and the third parity bit when the initial error rate value of the second parity bit or the fourth parity bit becomes 0, , " &Quot;

1 is a block diagram illustrating a handover of a base station having a code rate of 1/3 according to a conventional technique.

FIG. 2 is a block diagram for a handover of a base station having a code rate of 1/6 according to the present invention; FIG.

3 is a block diagram for soft handover in a first base station according to the present invention;

4 is a block diagram for soft handover in a second base station according to the present invention;

Description of the Related Art [0002]

301, 401:

302, 402:

303, 304, 403, 404:

305,405: Collector

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

In the present invention, turbo-coded data at 1/6 rate is used as the input of the rate matching block. In the conventional data transmission by the turbo code, two constituent encoders having a 1/2 rate are connected in parallel to generate 1/4 rate data, and when it is mapped to a physical channel for transmission, the data is output from the second constituent encoder Since the method of not transmitting the second systematic bit was used, the data was transmitted at substantially 1/3 rate.

However, in the present invention, data generated at 1/6 rate is used as it is.

FIG. 2 is a block diagram for handover of a base station having a code rate of 1/6 according to the present invention.

2, when the terminal receives traffic data simultaneously from two base stations while the mobile terminal is moving, the traffic data transmitted from the first base station is transmitted to the first systematic bit X ₁ of the first constituent encoder 201 A first parity bit Y ₁ and a second parity bit Y ₂ , a second systematic bit X ₁ 'of a second constituent encoder 102, a third parity bit Y ₃ , And a fourth parity bit (Y ₄ ).

Since this generates more bits than the data rate actually transmitted, this code word is punctured and punctured at the data rate specified in the specification, and transmitted to the specific terminal.

At this time, the first puncturing device 203 and the second puncturing device 204 differ in the puncturing pattern, so that the first base station and the second base station simultaneously transmit different codewords to a specific terminal, Soft-combine these two codewords to obtain a coding gain.

The first puncturing unit 203 and the second punting unit 204 perform puncturing by using the following puncturing pattern as a pair so as not to overlap the puncturing patterns with other base stations.

P1 = , P2 =

Accordingly, in receiving a traffic data, a specific terminal obtains a coding gain from loss information generated by puncturing.

Here, the multiplexers 205 and 206 serve to control the traffic data so that the first base station and the second base station transmit different codewords.

For example, when it is assumed that two base stations, the first base station at the time _{T (X 1 (T),} Y 1 (T), Y 3 (T)), the time _{2T (X 2 (2T),} Y 2 (2T), and Y ₄ (2T) are punctured and transmitted.

On the other hand, the time T in the other second base station _{(X 2 (T), Y} 2 (T), Y 4 (T)), the time _{2T (X 1 (2T),} Y 1 (2T), Y 3 (2T )) ≪ / RTI > sequence.

Then, the puncturing pattern used for the puncturing allows the different base stations to be transmitted without having the same puncturing pattern while the P2 and P2 are operated as a pair.

P3 = , P4 =

3 is a block diagram for soft handover in a first base station according to the present invention.

4 is a block diagram for soft handover in a second base station according to the present invention.

Referring to FIG. 3, the first systematic bit X ₁ is directly transmitted to the aggregator 305 by the bit separator 302, and the first, The three parity bits (Y _1, Y ₃ ) are transmitted to the aggregator 305 after puncturing by the rate matchers 303, 304.

After the time interval T, the second systematic bit X ₂ is directly transmitted to the aggregator 305, and the second and fourth parity bits Y _{2 and} Y ₄ are transmitted to the rate matchers 303 and 304 And then sent to the aggregator 305.

4, the second systematic bit X ₂ is first transmitted to the aggregator 405 by the bit separator 402 and the second and fourth parity bits Y _{2 and} Y ₄ Are sent to the rate matchers 403 and 404, and puncturing is performed before being transmitted to the aggregator 405.

After the time interval T, the first systematic bit X ₁ is directly transmitted to the aggregator 405 by the bit separator 402, and the first and third parities The bits Y _{1 and} Y ₃ are transmitted to the aggregator 405 after the puncturing is performed by the rate matchers 403 and 404.

That is, in FIG. 3 and FIG. 4, data transmitted from the first base station and the second base station at any arbitrary time can be regarded as data transmitted at 1/3 rate to different polynomials.

For example, transmission from the first base station at any time T (X _1, Y _1, Y ₃₎ Transfer If the other second base station (X _2, Y _2, Y ₄₎ a, and the next moment (X ₂ , Y ₂ , and Y ₄ ) are transmitted from the second base station to the first base station (X ₁ , Y ₁ , Y ₃ ).

The data in () in FIG. 3 and FIG. 4 represents a data string input to the rate matching block at the next instant. In order to illustrate each operation, this situation should be avoided because the code symbols in the same codeword are punctured if Y ₁ and Y ₃ (Y ₂ and Y ₄ ) have the same puncturing pattern at the first base station.

Similarly, if Y ₂ and Y ₄ have the same puncturing pattern in Y ₂ and Y ₄ (Y ₁ and Y ₃ ) at the second base station, the code symbol is punctured in the same codeword and this situation should be avoided.

To this end, in the present invention, different puncturing patterns are obtained from two base stations using a uniform puncturing algorithm among rate matching methods generally used for changing parameters of a rate matching algorithm.

Algorithm for uniform puncturing process

e = eini - initial error of current and desired puncturing rate

m = 1 - the index of the current bit

do while m ≤ X _i

e = e - e _minus - error update

if e ≤ 0 then - determine whether to puncture bit number m

set bit x _{i, m} to δwhere δ ≠ {0, 1}

e = e + e _plus - error update

end if

m = m + 1 - next bit

end do

In the above algorithm, e _ini represents the initial error rate value.

E _plus is an offset value for updating e after puncturing the mth bit of transmission channel i when the value of " e - _minus " is less than or equal to zero.

E _minus is an offset of the initial error rate value to be updated, and uses the initial error rate e multiplied by a.

That is, changing the puncturing pattern in the rate-matching algorithm is possible by changing the value of e _ini or the value of e _plus , e _minus .

Then, parameters should be changed considering the following points.

1) Perform puncturing evenly on the output values of each polynomial.

2) Output values (Y ₁ and Y ₃ (Y ₂ and Y ₄ )), Y ₂ and Y ₄ (Y ₁ and Y ₃ ) of polynomials at each base station are not punctured simultaneously.

3) The output values (Y ₁ and Y ₂ (Y ₃ and Y ₄ )), Y ₃ and Y ₄ (Y ₁ and Y ₂ ) of the polynomials between base stations are not punctured simultaneously, The puncturing bits must be uniformly arranged.

The above conditions 1 and 2 are conditions of the existing rate matching algorithm. The third condition is a condition to be newly assumed when the present invention is considered.

The reason for the third condition is that the data pair in the third condition is a symbol of the same code word.

Therefore, in order to satisfy such a condition, the present invention generates data according to different puncturing patterns of the respective base stations according to the following two embodiments.

First Embodiment

In the uniform puncturing algorithm, the puncturing pattern is changed by changing the values of e _minus and e _plus . To do this, change the value of a in the parameter.

That is, a has a value of 2 in the case of puncturing Y ₁ (Y ₂ ) in the first base station, and a has a value of 1 in the case of puncturing of Y ₃ (Y ₄ ). In the second base station, a has a value of 1 in the case of Y ₂ (Y ₁ ) puncturing and a has a value of 2 in the case of puncturing of Y ₄ (Y ₃ ).

When two or more base stations are considered in the first embodiment, there is a method of cyclically arranging the above two, and there is a method of creating a new pattern.

To create a new pattern, you can set another a value for polynomials that make up the same codeword. When this method is applied, the puncturing pattern changes depending on the position of a value.

Second Embodiment

In order to satisfy the above algorithm and conditions, the present invention proposes the following second embodiment.

That is, in the uniform puncturing algorithm, another puncturing pattern can be generated by changing the _ini value. This computes the e _ini value when shifted left in the current puncturing pattern.

Therefore, in order to set different e _ini values, each base station sets e _ini , e _plus and e _minus corresponding to Y ₁ (Y ₃ ), sets a value corresponding to Y ₃ (Y ₁ ) to e _ini2 , e _plus2 , and e _minus2 . In this case, the e _ini values of Y ₂ and Y ₄ can be set as follows.

, For Y ₂ (Y ₄ )

, for Y ₄ (Y ₂ )

If the above result is 0, add e _plus or e _plus2 for each.

Where D is a value representing the average bit interval between punctured bits and is defined as follows.

In Equation (9), N _{max denotes} e _ini . And, " Represents the amount of symbol repetition or puncturing for transmission channel i, b represents systematic bits and parity bits, b represents systematic bits when b is 1, parity Lt; / RTI >

That is, when there are two or more base stations in Equation (9) and two or more patterns are formed, another pattern can be obtained by setting different values instead of D / 2.

Even if the same polynomial is used instead of using different polynomials in each base station, if different puncturing patterns of the base stations are used differently, the gain can be obtained by restoring the loss due to puncturing .

Even when the position of the transport channel is variable, performance gain can be obtained by applying the same method.

As described above, the present invention can make different puncturing patterns in each base station in the proposed manner. Thus, by combining data transmitted from each base station at the receiving end, loss caused by puncturing can be reduced.

In applying the soft handover to the 3GPP system, a larger gain can be obtained at a code rate of ⅓ or more by changing the puncturing pattern at each base station.

At the receiver, since it is effective to receive a code word coded at 1/6, it is possible to obtain a gain at a 1/6 code rate.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments but should be determined by the claims.

Claims (6)

The first systematic bit and the first and third parity bits in the bit-stream coded by turbo-code are constituted by a first codeword, and the second systematic bit and the second and fourth parity bits are set in the second codeword Code words, and the first base station and the second base station alternately transmit the two codewords periodically to the mobile station. 2. The soft handover according to claim 1, wherein the first and third parity bits, the second and fourth parity bits are punctured in different puncturing patterns and transmitted to the mobile station. 3. The method of claim 2, wherein the first base station (first parity bit, third parity bit) or (second parity bit, fourth parity bit) is set to a value of "a" , 1) or (1, 2). 3. The method of claim 2, further comprising: determining an initial error rate value e _ini for the first parity bit, an update offset value e _minus for the initial error rate value, and an initial error rate value for the third parity bit, For the update offset value e _minus2 and the puncturing distance D, the initial error rate value for the second parity bit or the fourth parity bit is set to " e _ini- e _minus "Or" e _ini -e _minus2 Quot; soft handover between base stations using rate matching. 5. The method of claim 4, wherein when the initial error rate of the second parity bit or the fourth parity bit is 0, e _plus or e _plus2, which is another update offset value of the initial error rate of the first parity bit and the third parity bit, Base station soft handover using rate matching. 5. The method of claim 4, wherein D is " Quot; soft handover between base stations using rate matching.