CN101330356A - Device and method for transmitting broadcast information in wireless communication system - Google Patents

Abstract

The present invention provides a method for transmitting broadcast information in a wireless communication system, comprising steps: a) the base station selects the channelization code used by the primary broadcast channel of the cell according to the cell identifier of the physical layer of the cell; b) the base station The channelization code is used to spread and transmit the primary broadcast channel of the cell. Compared with other methods for transmitting broadcast information, the present invention can effectively eliminate the interference generated by the broadcast channels of adjacent cells in the synchronous network, improve the accuracy of user equipment receiving broadcast information, reduce the time for cell search, and further improve the efficiency of the system. Spectrum utilization.

Description

Device and method for transmitting broadcast information in wireless communication system

technical field

The present invention relates to a wireless communication system, in particular to a device and method for transmitting broadcast information in the wireless communication system.

Background technique

Now, the 3GPP standardization organization has embarked on a long-term evolution (LTE, Long Term Evolution) of its existing system specifications. Among the many physical layer transmission technologies, downlink transmission technology based on Orthogonal Frequency Division Multiplexing (hereinafter referred to as OFDM) and single carrier frequency division multiple access (Single Carrier Frequency Division Multiple Access, hereinafter referred to as SC) -FDMA) uplink transmission technology is a research hotspot. OFDM technology is essentially a multi-carrier modulation communication technology. Its basic principle is to decompose a high-rate data stream into several low-rate data streams and transmit them simultaneously on a group of mutually orthogonal sub-carriers. OFDM technology has performance advantages in many aspects due to its multi-carrier nature. SC-FDMA technology is essentially a single-carrier transmission technology, and its signal peak-to-average ratio (Peak to Average Power Ratio, hereinafter referred to as PAPR) is relatively low, so that the power amplifier of the mobile terminal can work with higher efficiency and expand the coverage of the cell. Coverage, while adding cyclic prefix (Cyclic Prefix) and frequency domain equalization, its processing complexity is relatively low.

Wireless communication systems can be classified into Frequency Division Duplex (FDD) and Time Division Duplex (TDD) according to their duplex modes. The FDD duplex mode means that the communication in two directions in the wireless system is completed on two frequencies separated by a certain distance, so that the communication entity can complete the receiving and sending operations at the same time. The TDD duplex mode means that the communication in the two directions in the wireless system is completed on the same frequency, so that the communication entity cannot perform receiving and sending operations at the same time, that is, the receiving and sending operations are separated in time. There are two frame structures in LTE: Type 1 Frame Structure and Type 2 Frame Structure. There are two duplex modes of FDD and TDD in the type 1 frame structure, but there is only one duplex mode of TDD in the type 2 frame structure. These two structures will be given separately below.

According to the existing discussion results about LTE, as shown in Figure 1, the downlink frame structure of LTE type 1 is shown. The radio resources in the LTE system refer to the time and frequency resources that the system or user equipment can occupy. The radio frame ( Radio Frame) (101-103) as a unit to distinguish, the time length of the wireless frame is the same as the time length of the wireless frame of the WCDMA system, that is, its time length is 10ms; each frame is subdivided into multiple time slots (Slot) (104-107), the current assumption is that each radio frame contains 20 time slots, and the time length of the time slot is 0.5ms; for FDD duplex mode, each time slot contains multiple OFDM symbols, and for TDD duplex In the work mode, each downlink time slot also includes multiple OFDM symbols. According to current assumptions, the time length of an effective OFDM symbol in an LTE system is about 66.7 μs. There are two kinds of CP time lengths of OFDM symbols, that is, the time length of normal CP (Normal CP, also called short CP) is about 4.8 μs, and the time length of extended CP (Extended CP, also called long CP) is about 16.7 μs, the extended CP time slot is used for multi-cell broadcast/multicast and the situation of very large cell radius, the general CP time slot (108) contains 7 OFDM symbols, and the extended CP time slot (109) contains 6 OFDM symbols. Two slots make up a subframe. That is, slot 0 and slot 1 form subframe 0, slot 2 and slot 3 form subframe 1, and so on.

According to the discussion result of current LTE, Fig. 2 is the downlink frame structure of LTE type 2, and the time length of the radio frame (radio frame) (201-203) is 10ms; each frame is equally divided into two 5ms half-frames (half- frame) (204, 205); each half frame includes 7 time slots (206-212) and three special domains, namely downlink pilot time slot (DwPTS) (213), guard interval (GP) (214) and Uplink Pilot Time Slot (UpPTS) (215). In addition, time slot 0 (206) and DwPTS of each half-frame are fixedly used for downlink transmission, and UpPTS and time slot 1 (207) of each half-frame are fixedly used for uplink transmission. Taking the sampling frequency as 30.72MHz as an example, each time slot (206~212) contains 20736 samples and the time is 0.625ms; DwPTS contains 2572 samples and the time is about 83.7μs; GP contains 1536 samples and the time is 50μs; UpPTS contains 4340 samples and takes about 141.3 μs. Same as the FDD system, the time length of the effective OFDM symbol is about 66.7 μs, and the time length of the CP of the OFDM symbol can be two kinds. The time length of the general CP is about 7.29 μs, and the time length of the extended CP is about 16.67 μs. A normal CP slot (216) contains 9 OFDM symbols and a slot interval (TI) (218), and an extended CP slot (217) contains 8 OFDM symbols and a TI (219). Note that the time lengths of the two TIs (218, 219) are not equal. According to the current discussion results, each time slot is a subframe, so in the description of the type 2 frame structure in this patent, time slots and subframes are equivalent and can be used interchangeably.

In an OFDM system, if user data is mapped to continuous subcarriers, it is localized transmission. If user data is mapped to dispersed subcarriers, it is distributed transmission. Subcarriers used by user equipments in the same cell usually do not overlap, and this resource allocation method is called orthogonal resource allocation in the frequency domain. The orthogonal resource allocation method in the time domain is that the base station uses different time slots or OFDM symbols to transmit data to user equipment in the same cell. Combining resource allocation methods in the frequency domain and time domain, downlink resources can be allocated to users in the form of two-dimensional grids in the time domain and frequency domain in the OFDM system.

In the current discussion on transmit diversity in LTE, when a base station is configured with multiple transmit antennas, one transmit diversity method is transmit diversity based on space frequency block coding (SFBC). The principle of SFBC is to jointly encode and transmit signals on two antennas and two subcarriers in the same OFDM symbol, and its minimum allocation unit is two subcarriers that are adjacent or very close in frequency domain, so The channel characteristics on the subcarriers are basically the same.

In this patent, when referring to multiple entities, use 0 as the reference method: that is, use antenna 0, time slot 0, subframe 0, and OFDM symbol 0 to refer to the first antenna and the first time slot respectively. , the first subframe, and the first OFDM symbol.

The progress of cell search in the current LTE discussion is: there are 510 physical layer cell identities (Physical Layer Cell Identity), and these 510 physical layer cell identities are divided into 170 physical layer cell identity groups (Physical Layer Cell Identity Group ), wherein each physical layer cell identity group contains 3 physical layer cell identity. In this grouping mode, each physical layer cell ID belongs to only one physical layer cell ID group. In this way, each physical layer cell identity is represented by two numbers, one of which has a value of 0 to 169, which is used to indicate the physical layer cell identity group, and the other number, which has a value of 0 to 2, is used to indicate The physical layer identifier within the physical layer cell identifier group.

The cell-related reference signal in LTE adopts a two-dimensional reference signal sequence r _m,n (i), where i is a time slot number. The sequence is generated according to the following formula: $r_{m,\mathrm{no}}\left(i\right)=r_{m,\mathrm{no}}^{\mathrm{OS}}\×r_{m,\mathrm{no}}^{\mathrm{PRS}}\left(i\right),$ where r _{m, n} ^OS is a two-dimensional orthogonal sequence, and r _{m, n} ^PRS (i) is a two-dimensional pseudo-random sequence. There are 3 different 2D orthogonal sequences and 170 2D pseudorandom sequences. The 3 identities in the physical layer cell id group are in one-to-one correspondence with the 3 two-dimensional orthogonal sequences.

In the current LTE discussion, system broadcast information can be transmitted in a primary broadcast channel (Primary Broadcast Channel, hereinafter referred to as P-BCH) and a secondary broadcast channel (Secondary Broadcast Channel, hereinafter referred to as S-BCH). For P-BCH, the current assumption is that the transmission time interval (Transmission Time Interval, hereinafter referred to as TTI) of P-BCH is 40 milliseconds, and P-BCH is transmitted in subframe 0 of each radio frame. A current way of transmitting P-BCH is that the content of the 4 transmissions in the TTI of P-BCH is exactly the same: that is, the modulation symbols of the P-BCH transmitted on the same OFDM symbol and subcarrier in 4 frames are exactly the same. same. The disadvantage of this method is that for a synchronous network, when the mobile speed of the user equipment is slow, since the modulation symbol of the received P-BCH of the adjacent cell does not change much between each frame, the P-BCH of the adjacent cell The interference generated by the P-BCH is coherently superimposed when the user equipment receives the P-BCH of the local cell, thereby reducing the processing gain brought by the four transmissions.

Contents of the invention

The object of the present invention is to provide a device and method for transmitting broadcast information in a wireless communication system.

According to one aspect of the present invention, a method for transmitting broadcast information in a wireless communication system includes the steps of:

a) The base station selects the channelization code used by the primary broadcast channel of the cell according to the physical layer cell identity of the cell;

b) The base station uses the channelization code to spread and transmit the primary broadcast channel of the cell.

According to another aspect of the present invention, a method for receiving broadcast information in a wireless communication system includes the steps of:

a) The user equipment selects the channelization code used by the primary broadcast channel of the cell according to the physical layer cell identity of the cell;

b) The user equipment uses the channelization code to despread the primary broadcast channel of the cell.

According to another aspect of the present invention, a device for transmitting broadcast information by a base station in a wireless communication system includes an IFFT module, and further includes:

A weighting factor controller module, configured to extract a weighting factor from the channelization code according to the position of the radio frame in the main broadcast channel TTI;

A multiplication weighting factor module, used for multiplying the modulated main broadcast channel data by a weighting factor when transmitting the main broadcast channel;

The IFFT module performs IFFT operation on the main broadcast channel modulation symbol multiplied by the weighting factor after subcarrier mapping to realize OFDM modulation.

According to another aspect of the present invention, a device for transmitting broadcast information by a base station in a wireless communication system includes an IFFT module, and further includes:

A channelization code element selection controller module, used to extract elements from the channelization code according to the position of the radio frame in the main broadcast channel TTI to generate a sequence S ^B ;

An XOR module, used to XOR each corresponding bit of the sequence S ^A and S ^B to obtain the scrambling code sequence S;

A scrambling module, configured to scramble the coded and rate-matched main broadcast channel bits with sequence S when transmitting the main broadcast channel;

The IFFT module performs IFFT operation on the main broadcast channel symbols after scrambling, modulation and subcarrier mapping to realize OFDM modulation.

Compared with other methods for transmitting broadcast information, the present invention can effectively eliminate the interference generated by the broadcast channels of adjacent cells in the synchronous network, improve the accuracy of user equipment receiving broadcast information, reduce the time for cell search, and further improve the efficiency of the system. Spectrum utilization.

Description of drawings

Fig. 1 is the downlink frame structure of LTE type 1;

Fig. 2 is the downlink frame structure of LTE type 2;

Fig. 3 is a schematic diagram of spread spectrum implementation;

FIG. 4 is a schematic diagram of a first implementation of time-domain spread spectrum;

Fig. 5 is the encoding chain diagram of the implementation mode 1 of time-domain spreading;

Fig. 6 is the encoding chain diagram of the realization mode 2 of time-domain spread spectrum;

FIG. 7 is a schematic diagram of a second implementation manner of frequency domain spreading.

Detailed ways

The method for transmitting broadcast information proposed by the present invention is that the base station transmits the P-BCH in a spreading manner. Since the base station selects the channelization code used in spreading according to the physical layer cell identity of the cell, the user equipment receives the P-BCH through despreading (Despreading), which can effectively reduce the noise of adjacent cells in the synchronous network. Interference generated by P-BCH.

It is worth noting that the spread spectrum mentioned in this article refers to the spread spectrum in a broad sense, and its meaning refers to the process of spreading a modulation symbol into multiple modulation symbols through a specific channelization code, that is, the spread spectrum operation can be implemented in the time domain. It can be implemented in the frequency domain or in the time-frequency domain. As shown in FIG. 3 , if the data 301 is set to a ₀ , and the channelization code 302 is set to 1-11-1, then the modulation symbol after spectrum spreading is a ₀ -a ₀ a ₀ -a ₀ . The time domain spread spectrum operation is to transmit the modulated symbols after the same modulation symbol is spread at different times, the frequency domain spread spectrum operation is to transmit the modulated symbols after the same modulation symbol is spread in different subcarriers, and the time frequency domain It spreads the modulation symbols of the same modulation symbol and transmits them at different times and subcarriers.

的各行进行DFT操作后的各行的集合。以N＝4为例，

因此对该矩阵的每一行进行DFT操作后，可得到4个信道化码，分别为1 1 1 1，1 -j -1 j，1-1 1-1和1 j -1 -j。对于N＝3，得到的3个信道化码为1 1 1，1e^j/4π/3e^j2π/3，和1 e^j2π/3e^j4π/3。需要注意的是，DFT码对应于任意自然数，均有相对应长度的码字。第三种是由CAZAC(Constant AmplitudeZero Autocorrelation)序列产生的扩频码。CAZAC序列在时域和频域都具有恒定的包络，其循环自相关函数为0，并且其循环互相关函数为一个很小的常数值。其中的一种为Zadoff-Chu序列。长度为N_ZC，第u个根的Zadoff-Chu序列为 $x_u\left(n\right)=e^{-j\frac{\text{\πun}(n+1)}{N_{\mathrm{ZC}}}},$ 0≤n≤N_ZC-1。由CAZAC序列产生扩频码的方式是利用一个特定的CAZAC序列的所有的循环移位。The code words used for spreading are usually called spreading codes. There are many types of spreading codes, and corresponding to each type, corresponding to a specific length, each type has multiple codewords, each of which is called a channelization code. Generally speaking, the number of channelization codes is the same as the length of the channelization codes. Several commonly used spreading codes are described below. The first type is Orthogonal Variable Spreading Factor Code (Orthogonal Variable Spreading Factor Code, hereinafter referred to as OVSF code). An OVSF code of length 2 contains 2 channelization codes, 11 and 1-1, respectively. An OVSF code with a length of 4 contains 4 channelization codes, namely 1 1 1 1, 1 1-1-1, 1-1 1-1 and 1-1-1 1. The OVSF code has a corresponding codeword for any length of a power of 2. In addition, OVSF codes are also called Walsh codes by changing the arrangement of channelization codes. The second type is a discrete Fourier transform code (Discrete Fourier Transformation Code, hereinafter referred to as a DFT code). The codeword is constructed in such a way that, corresponding to any code length N, the set of all channelization codes is a pair matrix

The set of each row after performing DFT operation on each row of . Taking N=4 as an example,

Therefore, after the DFT operation is performed on each row of the matrix, four channelization codes can be obtained, namely 1 1 1 1, 1 -j -1 j, 1-1 1-1 and 1 j -1 -j. For N=3, the obtained 3 channelization codes are 1 1 1, 1 e ^j/4π/3 e ^j2π/3 , and 1 e ^j2π/3 e ^j4π/3 . It should be noted that the DFT code corresponds to any natural number and has a code word of a corresponding length. The third type is a spreading code generated by a CAZAC (Constant Amplitude Zero Autocorrelation) sequence. The CAZAC sequence has a constant envelope in both the time domain and the frequency domain, its circular autocorrelation function is 0, and its circular cross-correlation function is a small constant value. One of these is the Zadoff-Chu sequence. With length N _ZC , the Zadoff-Chu sequence of the uth root is $x_u\left(\mathrm{no}\right)=e^{-j\frac{\text{\πun}(\mathrm{no}+1)}{N_{\mathrm{ZC}}}},$ 0≤n≤N _ZC -1. The way to generate spreading codes from CAZAC sequences is to use all the cyclic shifts of a particular CAZAC sequence.

Corresponding to a specific set of channelization codes, it is usually necessary to use an index to indicate a specific channelization code used, and the index is called a channelization code index. For example, corresponding to an OVSF code with a length of 4, you can use ch ₀ to indicate the channelization code 1 1 1 1, ch ₁ to indicate the channelization code 1 1 -1 -1, and ch ₂ to indicate the channelization code 1 -1 1 - 1, ch ₃ to indicate the channelization code 1 -1 -1 1.

It should be noted that the various spreading codes described above only give general definitions. In fact, according to a set of channelization codes, three basic transformations can be performed to obtain another set of channelization codes. One way of transformation is to exchange the index of the channelization code, one way is to multiply all the elements in one or more channelization codes in the channelization code set by -1, and the other way is to multiply the channelization code All channelization codes in the set undergo a cyclic shift of the same length. For example, corresponding to the set CS ₁ 1 1 1 1, 1 1 -1 -1, 1 -1 1 -1 and 1 -1 -1 1 of channelization codes composed of OVSF with length 4. By exchanging the channelization codes indicated by ch ₀ and ch ₃ , another set CS ₂ 1 -1 -1 1, 1 1 -1 -1, 1 -1 1 -1 and 1 1 1 1 can be obtained. Multiplying all elements in ch ₁ and ch ₂ in CS ₂ by -1, you can get another set CS ₃ 1 -1 -1 1, -1 -1 1 1, -1 1 -1 1 and 1 1 1 1. Then all the channelization codes in CS ₃ are cyclically shifted right by one bit, and CS ₄ -1 -1 1 1, -1 1 1 -1, 1 -1 1 -1 and 1 1 1 1 can be obtained. For the set of channelization codes that the spreading code described in the present invention produces, carry out above-mentioned three kinds of transformations (three kinds of transformations can be implemented independently, also can use in combination, and each kind of transformation can be implemented multiple times) the channel produced The set of coding codes, the method and the device described in the present invention are also applicable, so the following will not describe them one by one.

In step a) of the present invention, the manner in which the base station selects the channelization code used by the P-BCH of the cell according to the physical layer cell identity of the cell is as follows. The physical layer cell identity of the set cell is cell _i (0≤i≤N _cell ), where N _cell is the number of different physical layer cell identity (according to the current LTE discussion results, N _cell =510 in LTE) , and the number of channelization codes is R, then the channelization code used by the P-BCH of the cell is ch _1modR . Where amodb represents the remainder of dividing a by b. Corresponding to LTE, each physical layer cell identity is set to be represented by cell_group _j (0≤j≤169) and k (0≤k≤2), where cell_group _j is used to indicate the physical layer cell identity group, and k It is used to indicate the physical layer identity in the physical layer cell identity group. In this way, when the physical layer cell identity of a cell is represented by cell_group _j and k, its physical layer cell identity is cell _j*3+k , so the channelization code used by the P-BCH of this cell is ch _{(j*3 +k) mod R} . In particular, when R=3, the channelization code is ch _k , that is, the channelization code is uniquely determined by the physical layer identity k of the cell in the physical layer cell identity group. Another way to select the channelization code is that the channelization code is uniquely determined by the physical layer cell identity group of the cell. One implementation of this method is that when the physical layer cell identity group of the cell is cell_group _j (0≤j≤169), and the number of channelization codes is R, the channelization code used by the P-BCH of the cell is ch _jmodR .

In step b) of the present invention, the base station uses the channelization code to spread and transmit the P-BCH of the cell. According to the above, the P-BCH can be spread in the time domain, frequency domain, and time-frequency domain, and the three methods will be described below.

1. Time-domain spread spectrum. Corresponding to P-BCH transmission, there are two ways to implement time-domain spread spectrum. The first implementation is to perform the same channel coding, rate matching, scrambling and modulation operations on the P-BCH data transmitted in each wireless frame, and finally map the selected channelization codes to the subcarriers An element of is used as a weighting factor to multiply each modulation symbol, and the index of the used element is determined by the position of the frame in the P-BCH TTI. It is assumed that in one TTI, the P-BCH is transmitted in M radio frames, and the channelization codes are set as w ₀ ...w _M-1 . Assuming that the order of the current radio frame in the TTI for transmitting the P-BCH is f (0≤f≤M-1), the weighting factor used by the radio frame is w _f . For example, when M=2, set the starting frame of P-BCH in one TTI as radio frame i, and P-BCH is transmitted in radio frames i and i+2, then for radio frame i, the weighting factor is w ₀ , for radio frame i+2, the weighting factor is w ₁ . When M=4, set the starting frame of P-BCH in one TTI as radio frame i, and P-BCH is transmitted in 4 radio frames, then for radio frame i, the weighting factor is w ₀ , for radio For frame i+1, the weighting factor is w ₁ , for wireless frame i+2, the weighting factor is w ₂ , and for wireless frame i+3, the weighting factor is w ₃ . The operation schematic diagram corresponding to this mode is shown in FIG. 4 , and the corresponding coding chain is shown in FIG. 5 . In the schematic diagram, the P-BCH is transmitted using four radio frames in a TTI of the P-BCH as an example. This patent is also applicable to the situation of using two frames or three frames to transmit P-BCH. In Figure 4, the start frame of the TTI of P-BCH is set as 401 radio frame i, and the channelization code is set as w ₀ w ₁ w ₂ w ₃ , then the P-BCH transmitted in 401 radio frame i The modulation symbols of BCH are multiplied by w ₀ , the modulation symbols of P-BCH transmitted in 402 radio frame i+1 are multiplied by w ₁ , and the modulation symbols of P-BCH transmitted in 403 radio frame i+2 are multiplied by With w ₂ , the modulation symbols of the P-BCH transmitted in radio frame i+3 in 404 are all multiplied by w ₃ . In Fig. 5, only the modules in the encoding chain related to this patent are shown. CRC is added to P-BCH information in module 501 , and then channel coding is performed in module 502 . According to the current discussion results of LTE, convolutional coding is adopted for channel coding. The coded data is rate matched in module 503 . According to the specific implementation manner of the rate matching module, the rate matching module can also realize the function of interleaving at the same time. When the rate matching module does not have an interleaving function, a separate interleaving module may be required in the encoding link, which is not shown separately in FIG. 5 . The rate-matched data is scrambled in module 504, and it should be noted that the scrambling code is the same in each wireless frame. The scrambled data is modulated in module 505, and the result of the current LTE discussion is to use QPSK modulation. The modulated data is multiplied by weighting factors in block 506 . Module 507 extracts the weighting factor from the channelization code according to the position of the radio frame in the P-BCH TTI. The data multiplied by the weighting factor is mapped to subcarriers in module 508 , and then IFFT operation is performed in module 509 .

为比特异或操作(与二进制加法或减法等效，即 $0\⊗0=0,$ $0\⊗1=1,$ $1\⊗0=1,$ $1\⊗1=0$ )，序列S^A为P-BCH TTI内传输P-BCH的各个无线帧内相同的扰码序列，而序列S^B由所选择的信道化码获得。序列S^B由所选择的信道化码中的一个元素经过变换后重复L次获得，而所使用的元素的索引由该帧在P-BCH TTI中的位置所决定。本方法仅适用于所有信道化码的元素为+1和-1的情形。上述的变换为：当元素为+1时，将其映射为0，而当元素为-1时，将其映射为1。例如当L＝8时，当元素为+1时，S^B为0 0 0 0 0 0 0 0，而当元素为-1时，S^B为1 1 1 1 1 1 1 1。上述的决定所使用的元素的索引由该无线帧在P-BCH TTI中的位置所决定的方法与第一种实现方式类似，说明如下。设定在一个TTI中，P-BCH在M个无线帧内传输，并且设定信道化码为w₀…w_M-1。设定当前无线帧在传输P-BCH的TTI内的次序为f(0≤f≤M-1)，则该无线帧所使用的元素为w_f。例如当M＝2时，设定P-BCH在一个TTI内的起始帧为无线帧i，并且P-BCH在无线帧i和i+2内传输，则对于无线帧i，元素为w₀，对于无线帧i+2，元素为w₁。当M＝4时，设定P-BCH在一个TTI内的起始帧为无线帧i，并且P-BCH在4个无线帧内传输，则对于无线帧i，元素为w₀，对于无线帧i+1，元素为w₁，对于无线帧i+2，元素为w₂，对于无线帧i+3，元素为w₃。对应于该方式的编码链路如图6所示。在图6中，仅给出了与本专利相关的编码链路中的模块。P-BCH信息在模块601内添加CRC，进而在模块602内进行信道编码。根据LTE当前的讨论结果，信道编码采用了卷积编码。编码后的数据在模块603内进行速率匹配。根据速率匹配模块的具体实现方式，速率匹配模块同时也可以实现交织的功能。当速率匹配模块不具备交织的功能时，编码链路中可能需要单独的交织模块，在图6中没有单独显示。速率匹配后的数据在模块606中加扰，加扰所使用的扰码由序列S^A和S^B通过异或器605将每个对应比特对应异或所获得，而模块604根据无线帧在P-BCH TTI中的位置从信道化码中提取元素产生序列S^B。加扰后的数据在模块607中调制，目前LTE讨论的结果是使用QPSK调制。调制后的数据在模块608内映射到子载波，然后在模块609内进行IFFT操作。The second implementation is to perform the same channel coding and rate matching operation for the P-BCH data transmitted in each wireless frame, and the scrambling code S _i (0≤i≤L) used for scrambling is two sequences S _i ^A (0≤i≤L) and S _i ^B (0≤i≤L) perform XOR operation on each bit, that is $S_i=S_i^A\⊗S_i^B,$ where L is the length of the scrambling code sequence,

is a bit XOR operation (equivalent to binary addition or subtraction, ie $0\⊗0=0,$ $0\⊗1=1,$ $1\⊗0=1,$ $1\⊗1=0$ ), the sequence S ^A is the same scrambling code sequence in each radio frame transmitting the P-BCH in the P-BCH TTI, and the sequence S ^B is obtained by the selected channelization code. The sequence S ^B is obtained by repeating an element in the selected channelization code L times after transformation, and the index of the element used is determined by the position of the frame in the P-BCH TTI. This method is only applicable when the elements of all channelization codes are +1 and -1. The above transformation is: when the element is +1, it is mapped to 0, and when the element is -1, it is mapped to 1. For example, when L=8, when the element is +1, S ^B is 0 0 0 0 0 0 0 0, and when the element is -1, S ^B is 1 1 1 1 1 1 1 1. The above method in which the index of the element used for determining is determined by the position of the radio frame in the P-BCH TTI is similar to the first implementation manner, and is described as follows. It is assumed that in one TTI, the P-BCH is transmitted in M radio frames, and the channelization codes are set as w ₀ ...w _M-1 . Assuming that the order of the current radio frame in the TTI for transmitting the P-BCH is f (0≤f≤M-1), the element used by the radio frame is w _f . For example, when M=2, set the start frame of P-BCH in one TTI as radio frame i, and P-BCH is transmitted in radio frames i and i+2, then for radio frame i, the element is w ₀ , for wireless frame i+2, the element is w ₁ . When M=4, set the start frame of P-BCH in one TTI as radio frame i, and P-BCH is transmitted in 4 radio frames, then for radio frame i, the element is w ₀ , for radio frame For i+1, the element is w ₁ , for radio frame i+2, the element is w ₂ , and for radio frame i+3, the element is w ₃ . The coding chain corresponding to this method is shown in Figure 6 . In Fig. 6, only the modules in the coding chain related to this patent are shown. CRC is added to P-BCH information in module 601 , and then channel coding is performed in module 602 . According to the current discussion results of LTE, convolutional coding is adopted for channel coding. The coded data is rate-matched in module 603 . According to the specific implementation manner of the rate matching module, the rate matching module can also realize the function of interleaving at the same time. When the rate matching module does not have an interleaving function, a separate interleaving module may be required in the encoding link, which is not shown separately in FIG. 6 . The rate-matched data is scrambled in module 606, and the scrambling code used for scrambling is obtained by XORing each corresponding bit through the sequence ^SA and S ^B through the exclusive OR device 605, and the module 604 is based on the wireless frame at P - Position in BCH TTI The elements are extracted from the channelization code to generate the sequence S ^B . The scrambled data is modulated in module 607, and the result of the current LTE discussion is to use QPSK modulation. The modulated data is mapped to subcarriers in block 608 , and then IFFT operation is performed in block 609 .

In the way of time-domain spreading, OVSF codes, DFT codes, spreading codes generated by CAZAC sequences, etc. can be used for spreading. In addition, scrambling codes can also be used for spreading. The scrambling code referred to here means that different codewords do not satisfy the principle of orthogonality. In addition, when using 4 radio frames in a P-BCH TTI to transmit P-BCH, a spreading code design is to use a spreading code with a length of 4, and the spreading code only contains 3 channelization code. In one design, the channelization codes used are 1 -1 1 1, 1 1 -1 1 and 1 1 1 -1. The advantage of this channelization code is that the boundary of P-BCHTTI can be detected by all three channelization codes because the element -1 appears only once. For example, when the channelization code is 1 -1 1 1, when the user equipment detects that the element of the channelization code used in the current frame is -1, it can be concluded that the start frame of the current TTI is the previous radio frame .

Second, the frequency domain spread spectrum. Corresponding to P-BCH transmission, there are two implementations of frequency domain spreading. The first implementation manner is that the data after frequency domain spreading is transmitted in the entire TTI of the P-BCH. In this way, the number of bits after rate matching is set to N _{rate-matching} , the spreading factor is SF, and the number of physical bits for transmitting P-BCH provided in P-BCHTTI is N _TTI , then the three A relational expression is satisfied: N _TTI =N _{rate-matching} *SF. The second implementation mode is that the data after frequency domain spreading is divided into two transmissions, and the same modulation symbol is mapped to different subcarriers between the two transmissions. In this mode, the number of bits after rate matching is set to N _{rate-matching} , the spreading factor is SF, and the number of physical bits for transmitting P-BCH provided in the P-BCH TTI is N _TTI , then one of the three satisfies the relational expression: N _TTI =2*N _{rate-matching} *SF. One kind of mapping relationship is to adopt the way of circular shift. The operation diagram corresponding to this mode is shown in FIG. 7 . In the schematic diagram, the P-BCH is transmitted using four radio frames in a TTI of the P-BCH as an example. This patent is also applicable to the case of using two frames to transmit P-BCH. In FIG. 7 , the P-BCH modulation symbols are spread using a spreading code with a spreading value of 4. During transmission, the data transmitted in 703 radio frame i+2 is the cyclic shift of the data transmitted in 701 radio frame i, and the data transmitted in 704 radio frame i+3 is in 702 radio frame i+1 Cyclic shift of transmitted data.

When the SFBC transmit diversity technology is used, since the adjacent subcarriers are encoded by SFBC, the spread spectrum operation is performed in groups of two or four subcarriers, that is, two or four subcarriers are multiplied by the same channel elements in the code.

Three, time-frequency domain spread spectrum.

The time-frequency domain spread spectrum operation is to disperse the spread modulation symbols of the same modulation symbol at different times and sub-carriers for transmission. In particular, when the spreading factor is 4, spread spectrum is performed in units of 4 subcarriers in a 2x2 time-frequency grid formed by two OFDM symbols in the time domain and two subcarriers in the frequency domain.

The operation of the user equipment is: the user equipment selects the channelization code used by the primary broadcast channel of the cell according to the physical layer cell identity of the cell. The user equipment is usually based on the physical layer cell identity obtained from the primary synchronization channel and the secondary synchronization channel during the cell search. The user equipment may also further obtain the physical layer cell identity according to the downlink reference signal. After the user equipment acquires the channelization code, the user equipment uses the channelization code to despread the primary broadcast channel of the cell, and performs further operations such as decoding.

Example

This section presents an embodiment of the invention. In order to avoid making the description of this patent too lengthy, in the following description, detailed descriptions of functions or devices that are well known to the public are omitted.

In this embodiment, it is set to adopt the second method of time-domain spread spectrum. It is set that four radio frames are used to transmit the P-BCH in the TTI of the P-BCH, and the sets of channelization codes used are 1 -1 1 1, 1 1 -1 1 and 1 1 1 -1. It is set to use k to indicate the physical layer identity in the physical layer cell identity group. In this way, when k=2, the channelization code is 1 1 1 -1. Therefore, when transmitting P-BCH, the base station selects the used channelization code elements according to the channelization code 1 1 1 -1 according to the coding chain diagram shown in FIG. 6 , thereby correspondingly generating the sequence S ^B . Set the start frame of P-BCH in one TTI as radio frame i, then for radio frame i, S ^B is 0 0 0 0 0 0 0..., for radio frame i+1, S ^B is 0 0 0 0 0 0 0..., for radio frame i+2, S ^B is 0 0 0 0 0 0 0..., for radio frame i+3, S ^B is 1 1 1 1 1 1.... Suppose S ^A is 0 1 1 0 1 1 1..., then for wireless frame i, the scrambling code sequence S is 0 1 1 0 1 1 1..., for wireless frame i+1, the scrambling code sequence S is 0 1 1 0 1 1 1..., for wireless frame i+2, the scrambling code sequence S is 0 1 1 0 1 1 1..., for wireless frame i+3, the scrambling code sequence S is 1 0 0 1 0 0 0.... The base station thus performs a scrambling operation using the corresponding scrambling code sequence.

The operation of the user equipment is: according to k=2, the user equipment determines that the channelization code used by the P-BCH is 111-1. When the user equipment detects the P-BCH for the first time, the user equipment detects the P-BCH according to two different assumptions that S ^B is 0 0 0 0 0 0 0... and S ^B is 1 1 1 1 1 1 1.... When the decoded data corresponding to any one of the hypotheses passes the CRC check, the user equipment considers that the P-BCH is received correctly. When neither of the two assumptions can result in correct reception of the P-BCH, the user equipment continues to receive the P-BCH in the next radio frame. The user equipment correlates the two received P-BCH modulation symbols after channel estimation to determine the phase difference between the two transmissions. If the judgment result indicates that there is no phase difference between the two transmissions, soft-combining the two received symbols . If the judgment result shows that the phases of the two transmissions are opposite, the user equipment inverts the phases of one received symbol and combines it with the other. The user equipment then decodes and receives the combined symbols according to two hypotheses respectively. The user equipment continues this process until it receives the P-BCH correctly.

Claims (33)

1. A method for transmitting broadcast information in a wireless communication system, comprising the steps of: a) The base station selects the channelization code used by the primary broadcast channel of the cell according to the physical layer cell identity of the cell; b) The base station uses the channelization code to spread and transmit the primary broadcast channel of the cell. 2. The method according to claim 1, characterized in that in step a), the manner in which the base station selects the channelization code according to the physical layer cell identity of the cell is: the physical layer cell identity of the setting cell is cell _i (0≤i≤N _cell ), where N _cell is the number of different physical layer cell identities, and the number of channelization codes is R, then the channelization code used by the P-BCH of this cell is ch _imodR . 3. method according to claim 1, it is characterized in that in step a), the mode that described base station selects channelization code according to the physical layer cell identification of subdistrict is: set each physical layer cell identification by cell_group _j (0≤j≤169) and k(0≤k≤2), where cell_group _j is used to indicate the physical layer cell identity group, and k is used to indicate the physical layer identity in the physical layer cell identity group, channelization The number of codes is R, and the channelization code used by the P-BCH of the cell is ch _(j*3+k)modR . 4. The method according to claim 1, wherein in step a), the mode in which the base station selects the channelization code according to the physical layer cell identity of the cell is: when the number of channelization codes is R= 3, the channelization code used by the P-BCH of the cell is uniquely determined by the physical layer identifier k of the cell in the physical layer cell identifier group. 5. The method according to claim 1, wherein in step a), the mode in which the base station selects the channelization code according to the physical layer cell identity of the cell is: the channelization code is selected by the physical layer cell of the cell The identity group is uniquely determined. 6. The method according to claim 4, wherein when the physical layer cell identification group of the subdistrict is cell_group _j (0≤j≤169), and the number of channelization codes is R, the P-BCH of the subdistrict The channelization code used is ch _jmodR . 7. The method according to claim 1, characterized in that in step b), the spreading code used for said spreading is OVSF code. 8. The method according to claim 1, characterized in that in step b), the spreading code used for said spreading is a DFT code. 9. The method according to claim 1), characterized in that in step b), the spreading code used for said spreading is generated by a CAZAC sequence. 10. The method according to claim 9, characterized in that the CAZAC sequence is a Zadoff-Chu sequence. 11. The method according to claim 1, characterized in that in step b), said spreading is spreading in time domain. 12. The method according to claim 11, characterized in that the time-domain spread spectrum operation is to perform the same channel coding, rate matching, scrambling and modulation for the P-BCH data transmitted in each wireless frame operation, and finally multiply each modulation symbol by an element of the selected channelization code as a weighting factor before mapping to subcarriers, and the index of the element used is determined by the position of the frame in the P-BCH TTI . 13. The method according to claim 12, characterized in that the algorithm of the index of the elements of the channelization code used by the decision weighting factor is: set in one TTI, P-BCH in M radio frames transmission, and the channelization code is w ₀ ...w _M-1 , and the order of the current radio frame in the TTI of P-BCH transmission is f (0≤f≤M-1), then the radio frame used The weighting factor is w _f . 14. The method according to claim 13, wherein when M=2, the start frame of P-BCH in one TTI is set as radio frame i, and P-BCH is in radio frame i and i+2 Intra transmission, then for radio frame i, the weighting factor is w ₀ , and for radio frame i+2, the weighting factor is w ₁ . 15. The method according to claim 13, wherein when M=4, the initial frame of P-BCH in one TTI is set as radio frame i, and P-BCH is transmitted in 4 radio frames, Then for wireless frame i, the weighting factor is w ₀ , for wireless frame i+1, the weighting factor is w ₁ , for wireless frame i+2, the weighting factor is w ₂ , for wireless frame i+3, the weighting factor is w ₃ . 16. The method according to claim 11, characterized in that the time-domain spread spectrum operation is for the P-BCH data transmitted in each wireless frame, the same channel coding, rate matching operation, and scrambling the The scrambling code S _i (0≤i≤L) used is obtained by performing an XOR operation on each bit of two sequences S _i ^A (0≤i≤L) and S _i ^B (0≤i≤L), namely $S_i=S_i^A\⊗S_i^B,$ where L is the length of the scrambling code sequence,

For the bit XOR operation, the sequence ^SA is the same scrambling code sequence in each radio frame transmitting P-BCH in the P-BCH TTI, and the sequence S ^B is obtained by the selected channelization code. 17. The method according to claim 16, characterized in that said sequence S ^B is obtained by repeating L times of an element in the selected channelization code after transformation, and the index of the used element is determined by the frame in Determined by the position in the P-BCH TTI. 18. The method according to claim 17, wherein the transformation is as follows: when an element is +1, it is mapped to 0, and when the element is -1, it is mapped to 1. 19. The method according to claim 17, characterized in that the index of the element used in the decision is determined by the position of the radio frame in the P-BCH TTI. The algorithm is: set in a TTI, P - BCH is transmitted in M radio frames, and the channelization code is set to w ₀ ...w _M-1 . And the order of the current radio frame in the TTI for transmitting the P-BCH is f (0≤f≤M-1), then the element used by the radio frame is w _f . 20. The method according to claim 19, wherein when M=2, the start frame of P-BCH in one TTI is set as radio frame i, and P-BCH is in radio frame i and i+2 For intra-transmission, for wireless frame i, the element is w ₀ , and for wireless frame i+2, the element is w ₁ . 21. The method according to claim 19, wherein when M=4, the initial frame of P-BCH in one TTI is set as radio frame i, and P-BCH is transmitted in 4 radio frames, Then for wireless frame i, the element is w ₀ , for wireless frame i+1, the element is w ₁ , for wireless frame i+2, the element is w ₂ , and for wireless frame i+3, the element is w ₃ . 22. The method according to claim 11, characterized in that a scrambling code is used for spreading. 23. The method according to claim 11, characterized in that the channelization codes included in the spreading codes used are 1-111, 11-11 and 111-1 or equivalent spreading codes obtained through various transformations. 24. The method according to claim 1, characterized in that in step b), said spreading is performing spreading in the frequency domain. 25. The method according to claim 24, characterized in that the frequency domain spreading operation is that the data after frequency domain spreading is transmitted in the entire TTI of the P-BCH. 26. The method according to claim 24, characterized in that the frequency domain spread spectrum operation is divided into two transmissions of the frequency domain spread data, and the same modulation symbol is mapped to different subcarriers between the two transmissions superior. 27. The method according to claim 26, characterized in that two transmissions are performed in a cyclic shift manner. 28. The method according to claim 24, characterized in that when the SFBC transmit diversity technique is adopted, the spread spectrum operation is carried out in groups of two or four subcarriers. 29. The method according to claim 1, characterized in that in step b), said spreading is carried out in the time-frequency domain. 30. method according to claim 29, it is characterized in that when spreading factor is 4, with two OFDM symbols on the time domain and the 4 in the 2x2 time-frequency grid that two subcarriers on the frequency domain are formed The subcarriers are used for spreading. 31. A method for receiving broadcast information in a wireless communication system, comprising the steps of: a) The user equipment selects the channelization code used by the primary broadcast channel of the cell according to the physical layer cell identity of the cell; b) The user equipment uses the channelization code to despread the primary broadcast channel of the cell. 32. A device for transmitting broadcast information by a base station in a wireless communication system, comprising an IFFT module, and further comprising: A weighting factor controller module, configured to extract a weighting factor from the channelization code according to the position of the radio frame in the main broadcast channel TTI; A multiplication weighting factor module, used for multiplying the modulated main broadcast channel data by a weighting factor when transmitting the main broadcast channel; The IFFT module performs IFFT operation on the main broadcast channel modulation symbol multiplied by the weighting factor after subcarrier mapping to realize OFDM modulation. 33. A device for transmitting broadcast information by a base station in a wireless communication system, comprising an IFFT module, and further comprising: A channelization code element selection controller module, used to extract elements from the channelization code according to the position of the radio frame in the main broadcast channel TTI to generate a sequence S ^B ; An XOR module, used to XOR each corresponding bit of the sequence S ^A and S ^B to obtain the scrambling code sequence S; A scrambling module, configured to scramble the coded and rate-matched main broadcast channel bits with sequence S when transmitting the main broadcast channel; The IFFT module performs IFFT operation on the main broadcast channel symbols after scrambling, modulation and subcarrier mapping to realize OFDM modulation.

Images