Method of generating code sequence and method of transmitting signal using the same

Abstract

A method of generating a code sequence and method of adding additional information using the same are disclosed, by which a code sequence usable for a channel for synchronization is generated and by which a synchronization channel is established using the generated sequence. The present invention, in which the additional information is added to a cell common sequence for time synchronization and frequency synchronization, includes the steps of generating the sequence repeated in time domain as many as a specific count, masking the sequence using a code corresponding to the additional information to be added, and transmitting a signal including the masked sequence to a receiving end.

Description

In Formula 9C, ‘h(n)’ indicates an impulse response of channel, ‘n(n)’ indicates AWGN, and ‘*’ indicates a convolutional operation. A result of Formula 9C can be represented as Formula 9D.
r_psch(k)=P_bit(k)*H(k)+N(k)  [Formula 9D]

In Formula 9D, a signal indicates a frequency domain signal. In this case, ‘H(k)’ indicates a frequency response of channel and ‘N(k)’ indicates AWGN. Time and frequency domain signals received on S-SCH are represented as Formula 9E and Formula 9F, respectively.
r_ssch(n)=s(n)*h(n)+h(n)  [Formula 9E]
R_ssch(k)=S(k)*H(k)+N(k)  [Formula 9F]

In Formula 9E and Formula 9F, ‘S(k)’ indicates an S-SCH signal transmitted in frequency domain and ‘s(n)’ indicates an S-SCH signal transmitted in time domain.

According to the above assumptions, channel estimation is executed in S-SCH. For instance, LS (least square) channel estimation can be executed according to Formula 9G.

$\begin{array}{cc}\widehat{H\left(k\right)}=\frac{R_{\mathrm{ssch}}\left(k\right)}{S\left(k\right)}& \left[\mathrm{Formula}9G\right]\end{array}$

In Formula 9G, as mentioned in the foregoing description, since the detection for cell ID has been completed, ‘S(k)’ is a value already known by the receiving end.

P-SCH is recovered as Formula 9H using the estimated radio channel.
R_eq(k)=R_psch(k)/H{circumflex over (()}{circumflex over (k)}=P_bit(k)+N(k)/H{circumflex over (()}{circumflex over (k)}  [Formula 9H]

It is able to detect added bit information by Formula 9I using ‘R_eq(k)’ of which channel is compensated for.

$\begin{array}{cc}\hat{m}=\frac{M}{2\pi }\arg \left\{\frac{1}{N}\sum _{k=0}^{N-1}{R}_{\mathrm{eq}}\left(k\right)P\left(k\right)\right\}& \left[\mathrm{Formula}9I\right]\end{array}$

In Formula 9I, ‘arg { }’ indicates a phase component. And, ‘{ }’ indicates a complex result value of correlation.

The aforesaid additional information adding method is applicable to the hybrid SCH or the non-hierarchical SCH. Namely, by an operation of rotation by a phase corresponding to the additional information, it is able to add the additional information.

Hereinafter, a new method in which the first to third methods and the fourth method are combined together is proposed as follows.

A fifth method in the following description relates to a method of adding additional information using both code masking and micro-constellation modulation.

5. Fifth Method

First of all, it is preferable that a fifth method is applied to a sequence having a repetitive structure in time domain. For instance, the fifth method is applied to hybrid SCH as follows.

Three methods of adding additional information by masking are proposed. The fifth method can use one of the three methods of adding addition information. Hereinafter, a method which uses the third method is explained.

According to the aforesaid third method, in case of allocating a sequence to an odd-order frequency index, additional information ‘1’ (or ‘0’) is indicated. In case of allocating a sequence to an even-order frequency index, additional information ‘0’ (or ‘1’) is indicated.

According to the aforesaid explanation, if a sequence is allocated to an odd-order frequency index, a [C|−C] type waveform, as mentioned in (c) of FIG. 11, is formed in time domain. If a sequence is allocated to an even-order frequency index, a [B|B] type waveform, as mentioned in (b) of FIG. 11, is formed in time domain.

In addition, micro-constellation modulation can be performed on the corresponding result. In particular, by rotating a phase by 0° or 180°, it is able to add additional information.

FIG. 18 is a diagram of examples by both a third method of the present embodiment and micro-constellation modulation.

Referring to FIG. 18, in case that added additional information is ‘00’, a sequence type is [B|B]. So, MSB of additional information is decided as ‘0’. Meanwhile, since a phase is changed by 0° according to micro-constellation modulation, LSB of additional information is decided as ‘0’.

In case that added additional information is ‘01’, a sequence type is [B|B]. So, MSB of additional information is decided as ‘0’. Meanwhile, since a phase is changed by 180° according to micro-constellation modulation, LSB of additional information is decided as ‘1’.

In case that added additional information is ‘10’, a sequence type is [C|−C]. So, MSB of additional information is decided as ‘1’. Meanwhile, since a phase is changed by 0° according to micro-constellation modulation, LSB of additional information is decided as ‘0’.

In case that added additional information is ‘11’, a sequence type is [C|−C]. So, MSB of additional information is decided as ‘1’. Meanwhile, since a phase is changed by 180° according to micro-constellation modulation, LSB of additional information is decided as ‘1’.

In order to detect additional information by the fifth method, it is decided whether a sequence has a [B|B] type or a [C|−C] type and a phase value rotated by micro-constellation modulation is then calculated.

The fourth and fifth methods of the present embodiment are characterized in using micro-constellation modulation.

In the above examples, a case that a count of added additional informations corresponds to a power of 2, which does not put limitation on the present embodiment.

Namely, it is able to convert Formula 9A to Formula 10A.

$\begin{array}{cc}{P}_{\mathrm{bit}\left(n\right)}=e^{j\frac{2\pi m}{X}}p\left(n\right)n=0,1,\dots ,N-1m=0,1,\dots ,X-1& \left[\mathrm{Formula}10A\right]\end{array}$

And, it is able to convert Formula 9B to Formula 10B.

$\begin{array}{cc}{P}_{\mathrm{bit}\left(k\right)}{e}^{j\frac{2\pi m}{X}}P\left(k\right)k=0,1,\dots ,N-1m=0,1,\dots ,X-1& \left[\mathrm{Formula}10B\right]\end{array}$

In this case, Formulas 9C to 9H are applied as they are. And, Formula 91 is converted to Formula 10C to be applied.

$\begin{array}{cc}\hat{m}=\frac{X}{2\pi }\arg \left\{\frac{1}{N}\sum _{k=0}^{N-1}{R}_{\mathrm{eq}}\left(k\right)P\left(k\right)\right\}& \left[\mathrm{Formula}10C\right]\end{array}$

The above-explained example shown in FIG. 18 is applicable to hierarchical or non-hierarchical SCH.

In case that additional information is added through non-hierarchical SCH, it is able to reconstruct the additional information by the following operation.

First of all, an operation of adding additional information by a transmitting end is identically applied to the non-hierarchical SCH or other SCHs.

A receiving end is able to detect initial synchronization based on auto-correlation. And, the receiving end is able to acquire frequency synchronization.

Subsequently, the receiving end detects a sequence index used for SCH. The receiving end performs integer-times frequency offset estimation using the detected sequence index. The receiving end then corrects the estimated offset.

The receiving end estimates a channel using the detected sequence and then compensates for the channel.

After completion of the channel estimation, additional information by micro-constellation modulation is obtained.

In the fourth or fifth method of the present embodiment, micro-constellation modulation is able to use a plus phase value or a minus phase value. Namely, it is able to convert Formula 10A and Formula 10B to Formula 11A and Formula 11B, respectively.

$\begin{array}{cc}{P}_{\mathrm{bit}\left(n\right)}=e^{-j\frac{2\pi m}{X}}p\left(n\right)n=0,1,\dots ,N-1m=0,1,\dots ,X-1& \left[\mathrm{Formula}11A\right]\\ P_{\mathrm{bit}\left(k\right)}{e}^{-j\frac{2\pi m}{X}}P\left(k\right)k=0,1,\dots ,N-1m=0,1,\dots ,X-1& \left[\mathrm{Formula}11B\right]\end{array}$

And, it is able to convert Formula 10C to Formula 11C.

$\begin{array}{cc}\hat{m}=-\frac{X}{2\pi }\arg \left\{\frac{1}{N}\sum _{k=0}^{N-1}{R}_{\mathrm{eq}}\left(k\right)P\left(k\right)\right\}& \left[\mathrm{Formula}11C\right]\end{array}$

In a constellation map, a phase of each symbol (e.g., QPSK symbol, etc.) can be rotated clockwise or counterclockwise by micro-constellation modulation.

The additional information inserting method has the following advantages. First of all, it is able to insert additional bit information without changing a previous structure. Secondly, additional complexity is prevented from taking place.

The additional information added by the present method is explained as follows.

First of all, no limitation is put on a type of the additional information. And, various kinds of information for communications can be included. For instance, it is able to use the additional information as information for a length of cyclic prefix (hereinafter abbreviated CP). For instance, cyclic prefixes can be classified into short CP and long CP according to their lengths. In this case, it is able to represent a type of CP via the additional information.

And, the information may include information for an antenna mode. In particular, the information is able to indicate whether an antenna is a single antenna or a multi-antenna.

Besides, various kinds of information are possible. For instance, various kinds of information such as subframe synchronization information (indicating whether a first subframe of Nth radio frame or a second subframe of Nth radio frame), BCH bandwidth (1.25 MHz or 5 MHz) and the like can be included. And, cell group ID information can be additionally inserted.

FIG. 19 is a flowchart of a method of generating a sequence for a synchronization channel according to an embodiment of the present invention. FIG. 19 shows an example of P-SCH among sequences for synchronization channels.

Referring to FIG. 19, according to the above-explained five kinds of methods, a sequence for a synchronization channel (e.g., P-SCH sequence, S-SCH sequence, hybrid sequence, non-hierarchical SCH sequence) is generated. And, additional information is then inserted in the generated sequence (S1001). The additional information inserting step is carried out by one of the above-explained five kinds of methods. In particular, masking for codes is used, the additional information inserting scheme using micro-constellation modulation is used, or both of the masking and the micro-constellation modulation are used.

The P-SCH generated by the above step is transformed into a time domain sequence by steps S1003 to S1009 corresponding to the aforesaid steps S103 to S106 of FIG. 10 and is then transmitted to a user equipment.

A communication apparatus according to the present embodiment is able to include independent modules for the respective steps.

FIG. 20 is a block diagram of a transmitting apparatus according to an embodiment of the present invention.

Referring to FIG. 20, a transmitting apparatus according to an embodiment of the present invention may include a sequence generation & additional information insertion module 21 according to one of the five kinds of methods, an FFT module 22, a DC & guard subcarrier inserting module 23, a PAPR scheme applying module 24 and an IFFT module 25.

And, the communication apparatus according to the present invention can be implemented according to FIG. 21.

FIG. 21 is a block diagram of a communication apparatus for transmitting P-SCH according to the present invention.

Referring to FIG. 21, a communication apparatus for transmitting P-SCH according to the present invention includes a serial-to-parallel converting unit 11, a subchannel mapping & PAPR enhancement module 12 performing symbol-to-subcarrier mapping and PAPR enhancement, an IFFT module 13 performing IFFT, a parallel-to-serial converting module 14, and a CP inserting module 15 inserting a cyclic prefix.

An output signal by the steps S1001 to S1009 is inputted to the apparatus shown in FIG. 21 and is then transmitted to a receiving end. Yet, since the step S107 is performed by the apparatus shown in FIG. 15, if the output signal is transmitted by the apparatus shown in FIG. 21, it is able to omit the step S1007. Moreover, since an operation of inserting the guard subcarrier in the step S1005 can be implemented by a filter (not shown in the drawing) separately provided to the apparatus shown in FIG. 21, it is able to omit the guard subcarrier inserting operation.

Claims

1. A method of transmitting a cell common sequence for synchronization by a transmitter, the method comprising:

acquiring the cell common sequence generated such that a frequency index with a constant interval is allocated to each sample of the cell common sequence in a frequency domain and the cell common sequence is masked with a code for a specific information; and

transmitting the acquired cell common sequence to a receiver.

2. The method of claim 1, wherein the masking comprises multiplying each sample of the cell common sequence by each sample of the code.

3. The method of claim 1, wherein the interval depends on the specific count.

4. The method of claim 1, wherein the acquired cell common sequence is transmitted as secondary synchronization channel (S-SCH) signals.

5. The method of claim 1, wherein the transmitting comprises transmitting the signal using a plurality of orthogonal subcarriers.

6. The method of claim 1, wherein the cell common sequence comprises at least one of

a first sequence generated such that a frequency index with an even number is allocated to each sample of the first sequence, and

a second sequence generated such that a frequency index with an odd number is allocated to each sample of the second sequence.

7. The method of claim 1, wherein the specific information comprises information indicating a subframe number via which the cell common sequence is transmitted.

8. The method of claim 1, wherein the cell common sequence is generated to have guard subcarriers.

9. The method of claim 1, wherein the cell common sequence is transmitted such that no sample of the cell common sequence is transmitted via DC subcarrier.

10. A transmitter transmitting a cell common sequence for synchronization, the transmitter comprising:

a sequence generating module for acquiring the cell common sequence generated such that a frequency index with a constant interval is allocated to each sample of the cell common sequence in a frequency domain and the cell common sequence is masked with a code for a specific information; and

a transmitting module for transmitting the acquired cell common sequence to a receiver.

11. The transmitter of claim 10, wherein the acquired cell common sequence is transmitted as secondary synchronization channel (S-SCH) signals.

12. The transmitter of claim 10, wherein the cell common sequence comprises at least one of

a first sequence generated such that a frequency index with an even number is allocated to each sample of the first sequence, and

a second sequence generated such that a frequency index with an odd number is allocated to each sample of the second sequence.

13. The transmitter of claim 10, wherein the specific information comprises information indicating a subframe number via which the cell common sequence is transmitted.

14. The transmitter of claim 10, wherein the cell common sequence is generated to have guard subcarriers.

15. The transmitter of claim 10, wherein the cell common sequence is transmitted such that no sample of the cell common sequence is transmitted via DC subcarrier.