KR102002847B1 - Method and apparatus for setting frequency resource of uplink control channel - Google Patents

Abstract

A method and an apparatus for estimating an uplink frequency offset of a mobile communication system are provided. The base station receives an uplink synchronization signal transmitted in an uplink control channel frequency in a downlink-uplink switch slot period from the terminal, and estimates an uplink frequency offset based on the uplink synchronization signal.

Description

TECHNICAL FIELD The present invention relates to a method and apparatus for estimating an uplink frequency offset in a mobile communication system,

The present invention relates to a method and apparatus for estimating uplink frequency offset in a mobile communication system.

In cellular mobile communication, a frequency offset between a base station and a terminal affects a transmission error rate, and data transmission is impossible when an offset of a certain level or more occurs. Therefore, transmission standards and algorithms are needed to overcome these problems.

In 3GPP LTE (Long Term Evolution) and LTE Advanced, the downlink can estimate and compensate time and frequency offset using a synchronization signal transmitted periodically. For each uncompensated residual offset, each terminal estimates and restores the residual frequency offset using a cell-specific reference signal or a demodulation reference signal. frequency Compensation for offsets can be done by changing the carrier frequency of the terminal RF stage or by compensating in the signal processing stage of the baseband modem.

However, the uplink can not estimate and compensate for the frequency offset in the same manner as the downlink. This is because a plurality of terminals transmit signals on the uplink, and the base station demodulates them, resulting in frequency offsets as many as the number of terminals. Therefore, frequency offset estimation and compensation processes are different.

In case of LTE, the downlink uses OFDMA (Orthogonal Frequency Division Multiple Access) and the uplink uses SC-FDMA (Single Carrier Frequency Division Multiple Access). In the LTE uplink, a demodulation reference signal (DMRS), which is a demodulation reference signal, is transmitted, and a frequency offset can be obtained using the DMRS signal.

When two terminals transmit data frames to the base station in the uplink, the base station compensates for the frequency offset (refer to " Carrier frequency offset compensation for OFDM-FDMA systems, " IEEE Communications Letters, Vol. , No. 12, Dec. 2000). Specifically, in the uplink, a carrier wave is removed using a received signal for each terminal, converted into a digital signal, and then a digital signal is estimated using an estimated frequency offset However, considering that some performance degradation due to frequency offset is taken into consideration, it is not possible to use a separate compensation circuit in the base station However, if the frequency offset further increases, communication becomes impossible.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and apparatus for reducing hardware complexity and improving frequency offset estimation performance when estimating and compensating a frequency offset of an uplink terminal in an OFDMA multiple access based mobile communication system .

A method for estimating an uplink frequency offset in a mobile communication system is provided. A method for estimating an uplink frequency offset in a downlink- Receiving a synchronization signal; And estimating an uplink frequency offset based on the uplink synchronization signal.

The uplink synchronization signal may be transmitted over two or more consecutive symbol periods.

In this case, the step of estimating the uplink frequency offset may include: obtaining a phase difference between the symbols using an uplink synchronization signal received at an uplink control channel frequency and a spreading code stored in advance, The link frequency offset can be estimated.

The method may further include the step of the base station feedbacking the frequency offset information estimated for each terminal to the terminals through the downlink control channel.

The feedback step separates and quantizes the estimated frequency offset into a plurality of areas, and transmits the quantized frequency offset information to the control information of the downlink control channel.

The method may further include the steps of the terminal receiving and decoding the downlink control channel to obtain the frequency offset estimation information; And compensating the frequency offset of the signal based on the frequency offset estimation information in the next uplink interval and transmitting the compensated signal.

According to another aspect of the present invention, there is provided a base station including: a base station that estimates an uplink frequency offset in a mobile communication system; an RF unit that transmits and receives signals through an antenna; Wherein the signal processor is configured to estimate an uplink frequency offset based on an uplink synchronization signal transmitted in an uplink control channel frequency in a downlink-uplink switch slot period from a terminal.

The base station may further include a memory, and the signal processor estimates an uplink frequency offset of the MS using the uplink synchronization signal transmitted over two consecutive symbol periods and the spreading code stored in the memory, And store it in the memory.

The signal processing unit is configured to feed back the frequency offset information estimated for each UE to the UEs through a downlink control channel, and the frequency offset information may be added to the control information of the downlink control channel.

According to another aspect of the present invention, there is provided a mobile communication system including an RF unit transmitting and receiving a signal through an antenna in a mobile communication system, and a frequency offset compensator connected to the RF converter, Wherein the signal processor is configured to generate an uplink synchronization signal transmitted in an uplink control channel frequency in a downlink to uplink switch slot and transmit the uplink synchronization signal through the RF unit, And decodes the downlink control channel received through the RF unit to obtain frequency offset information based on the uplink decoded signal.

The uplink synchronization signal may be transmitted over two or more consecutive symbol periods. The signal processing unit may generate an independent sequence orthogonal to the sequence of the other terminals on the frequency axis, multiplex the uplink synchronization signals, and transmit the multiplexed uplink synchronization signals.

The terminal may further include a memory, wherein the signal processing unit stores the acquired frequency offset estimation information in the memory, and calculates a frequency of a signal based on frequency offset estimation information stored in the memory in a next uplink interval, Can be configured to compensate for the offset.

According to the embodiment of the present invention, in OFDMA mobile communication system, the frequency offset due to the Doppler frequency transition occurring in the terminal moving at high speed can be accurately estimated and compensated. Therefore, deterioration of communication performance caused by the frequency offset of the base station and the terminal can be prevented.

In particular, it is possible to widen the estimation range of the uplink frequency offset and easily compensate for the frequency offset with small hardware.

1 is a diagram illustrating an uplink channel of a mobile communication system.
2 is a diagram illustrating a frame structure of a mobile communication system according to an embodiment of the present invention.
3 is a diagram illustrating transmission channels and signals of a special subframe according to an embodiment of the present invention.
4 is a diagram illustrating an uplink synchronization signal according to an embodiment of the present invention.
5 is a diagram illustrating a frequency offset estimation process according to an embodiment of the present invention.
6 is a diagram illustrating a process of acquiring frequency offset information of a UE according to an embodiment of the present invention.
FIG. 7 is a diagram illustrating an example of a process for compensating a frequency offset in a baseband in an embodiment of the present invention. FIG.
8 is a flowchart of a frequency offset estimation and compensation method according to an embodiment of the present invention.
9 is a structural diagram of a terminal according to an embodiment of the present invention.
10 is a structural diagram of a base station according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when an element is referred to as "comprising ", it means that it can include other elements as well, without excluding other elements unless specifically stated otherwise.

Throughout the specification, a terminal is referred to as a mobile terminal (MT), a mobile station (MS), an advanced mobile station (AMS), a high reliability mobile station (HR- A subscriber station (SS), a portable subscriber station (PSS), an access terminal (AT), a user equipment (UE) , HR-MS, SS, PSS, AT, UE, and the like.

Also, a base station (BS) is an advanced base station (ABS), a high reliability base station (HR-BS), a node B, an evolved node B, eNodeB), an access point (AP), a radio access station (RAS), a base transceiver station (BTS), a mobile multihop relay (MMR) (RS), a relay node (RN) serving as a base station, an advanced relay station (ARS) serving as a base station, a high reliability relay station (HR) A femto BS, a home Node B, a HNB, a pico BS, a metro BS, a micro BS, ), Etc., and all or all of ABS, Node B, eNodeB, AP, RAS, BTS, MMR-BS, RS, RN, ARS, HR- And may include negative functionality.

Hereinafter, a method and apparatus for estimating uplink frequency offset in a mobile communication system according to an embodiment of the present invention will be described with reference to the drawings.

1 is a diagram illustrating an uplink channel of a mobile communication system.

In a mobile communication system using OFDMA (Orthogonal Frequency Division Multiple Access) as a downlink and a Single Carrier Frequency Division Multiple Access (SC-FDMA) as an uplink, an uplink channel is given as shown in FIG. .

1, when a physical uplink shared channel (PUSCH) and a physical uplink control channel (PUCCH) are allocated to a time-frequency resource of one subframe in an uplink, . PUSCH, a downlink demodulation reference signal (DMRS) is transmitted once in each slot. In case of PUCCH, the DMRS is transmitted twice in each slot. By using this DMRS signal, a frequency offset can be obtained.

를 다음과 같이 정의할 수 있다. The frequency offset estimation performance is better as the number of times of DMRS is larger, and the maximum error estimation range is larger as the time interval of DMRS is smaller. In OFDM systems, the normalized frequency offset

Can be defined as follows.

는 서브반송파 주파수 폭을 나타내고,

는 주파수 옵셋을 나타낸다. here

Represents the subcarrier frequency width,

Represents a frequency offset.

를 구할 수 있다. 이 위상 차를 이용하여, 주파수 옵셋은 다음과 같이 구할 수 있다. A correlation method is generally used for frequency offset estimation. The correlation method is based on the correlation between the OFDM symbols received through the correlation of the DMRS

Can be obtained. Using this phase difference, the frequency offset can be obtained as follows.

는 FFT(fast fourier transform) 포인트 수를 나타내고,

는 위상 차를 나타내며,

은 DMRS 간 시간 샘플 간격을 나타낸다. here

Represents the number of FFT (fast fourier transform) points,

Represents the phase difference,

Represents the time sample interval between DMRSs.

In this method, the frequency offset estimation range increases as the DMRS interval approaches.

In the embodiment of the present invention, a new signal is defined and used in order to estimate the frequency offset in the uplink. Hereinafter, for convenience of explanation, a signal for estimating the uplink frequency offset is referred to as an " uplink synchronization signal ".

In addition, LTE (Long Term Evolution) and LTE Advanced technologies of 3GPP (3rd Generation Partnership Project) are exemplified in the embodiment of the present invention, but the mobile communication system according to the present invention is not limited to this.

The LTE specification supports both frequency division duplex (FDD) and time division duplex (TDD).

2 is a diagram illustrating a frame structure of a mobile communication system according to an embodiment of the present invention.

As shown in FIG. 2, the TDD-based frame includes a DL subframe, a UL subframe, and a special subframe. Switching from downlink to uplink is done in a special subframe. The special subframe is divided into three parts: a downlink portion (also called a downlink pilot time slot (DwPTS)), a guard period (GP), and an uplink portion (named UpPTS) . In the protection period, switching is actually performed without signal transmission.

The physical downlink shared channel (PDSCH) is transmitted in the data area, and the physical downlink control channel (PDCCH), physical control channel (PCFICH) Format Indicator Channel) and PHICH (Physical Hybrid-ARQ Indicator Channel) are transmitted.

(PUSCH), a Physical Uplink Control Channel (PUCCH), a Physical Random Access Channel (PRACH), and a SRS (Sounding Reference Signal) in the uplink subframe .

3 is a diagram illustrating transmission channels and signals of a special subframe according to an embodiment of the present invention.

3, a PDSCH is transmitted in a downlink part of a special subframe, a PRACH (for example, a shortened physical random access channel) is transmitted in an uplink part of a special subframe, Or SRS is transmitted.

In the LTE-based mobile communication system having such a frame structure, the downlink can estimate and compensate time and frequency offsets using a periodically transmitted synchronization signal. For each uncompensated residual offset, each terminal estimates and restores the residual frequency offset using a cell-specific reference signal or a demodulation reference signal. In the uplink, the UE transmits a random access channel (PRACH) for frame time synchronization with the base station, and performs coherent demodulation using a demodulation reference signal when transmitting PUSCH or PUCCH .

In the uplink, the UE transmits the PUSCH, the PUCCH, the random access channel, the SRS, the general data to the PUSCH, and the control information to the PUCCH. The PUCCH transmits ACK / NACK (Acknowledgment / Negative-ACK), a scheduling request, channel state information, and the like. PUCCH is allocated from both edge frequency resource blocks of the transmission band and the inner frequency resource block is allocated to the PUSCH. The SRS is transmitted by the UE so that the BS can check the channel status, and there is no need to transmit the SRS simultaneously with another physical channel. SRS can be allocated to all frequency resources, SRS is allocated to the last DFTS-OFDM symbol in the slot, and the PUSCH of all other UEs in the cell does not transmit the last DFTS-OFDM symbol.

In this uplink, in the embodiment of the present invention, an uplink synchronization signal (USS) is used to estimate a frequency offset.

In the LTE-based mobile communication system, the UE transmits a random access channel in the uplink. The base station estimates a time offset based on the random access channel and transmits a signal (time advance) for compensating the time offset to the terminal. The uplink frequency offset compensation starts with compensating the coarse frequency offset in the downlink reception process. After the course frequency offset compensation, the remaining frequency offsets can be compensated using the demodulation reference signal included in the PUSCH and PUCCH. In this embodiment of the present invention, a new uplink synchronization signal is further defined and used in order to improve the frequency offset estimation performance.

4 is a diagram illustrating an uplink synchronization signal according to an embodiment of the present invention.

In the special subframe (or slot) as shown in FIG. 4, the uplink synchronization signal USS according to the embodiment of the present invention includes a downlink-uplink switching slot That is, the uplink part (UpPTS) constituting the special subframe is allocated, and more than two consecutive OFDM symbol intervals are allocated. The uplink control channel resource is used as the frequency resource of the uplink synchronization signal USS. The MS transmits the uplink synchronization signal USS, and the synchronization signals of the MSs are spread and transmitted in units of frequency.

PRACH or SRS is transmitted to the uplink part of the special subframe. The SRS is used by the base station to determine the status of the transport channel. However, in the case of the uplink control channel (PUCCH), since multiple terminals use a common resource, there is no need to separately perform scheduling using a channel condition. In the embodiment of the present invention, the uplink synchronization signal is transmitted using the frequency that does not require the scheduling. That is, as shown in FIG. 4, an uplink synchronization signal is transmitted through an uplink control channel (PUCCH) resource, thereby not affecting the existing frame structure. Since the special subframe, i.e., the downlink-uplink switching slot, is used, there is an advantage that it does not affect the frame structure of other slots.

인 코드에 선형으로 위상 회전을 가하면 새로운 직교 시퀀스를 만들 수 있다.

가 i 번째 서브반송파의 기본 시퀀스 일 때, 새로운 시퀀스의 i 번째 서브반송파 신호

는 다음 식과 같이 나타낼 수 있다. The uplink synchronization signal according to the embodiment of the present invention is multiplexed in the frequency axis by an orthogonal code division multiplexing (CDM) scheme. In the conventional uplink control channel (PUCCH) requiring multiplexing, both the frequency axis and the time axis use the OCDM scheme. The frequency axis OCDM scheme can use a sequence in which the terminals are orthogonal to each other. Or by applying a phase rotation in the frequency domain linearly to the same sequence (e.g., ZC (zadoff-chu) sequence). For example,

A linear orthogonal sequence can be created by applying a phase rotation to the encode.

Carrier signal of the i < th > sub-carrier,

Can be expressed by the following equation.

이다. 이 경우, 총

의 독립적인 시퀀스가 생성가능하고, 각 시퀀스는 서로 다른 단말에 할당될 수 있다.here,

to be. In this case,

Can be generated, and each sequence can be assigned to a different terminal.

Meanwhile, in the time-axis OCDM scheme, each OFDM symbol is spread using an orthogonal block code. A Walsh code or a discrete Fourier transform (DFT) code may be used as the orthogonal block code.

However, it is preferable that only the frequency axis OCDM method is used for the uplink synchronous signal transmission. This is because the time-axis OCDM has a problem in that when the channel changes in time due to the Doppler effect during transmission, the multiplexed signal maintains orthogonality. Therefore, in the embodiment of the present invention, the uplink synchronization signal is multiplexed using the frequency-axis OCDM scheme.

As described above, since the frame structure according to the embodiment of the present invention uses only unused frequency resources, it does not affect existing transmission channels.

On the other hand, according to Equation (2), when the reference signal such as the DMRS is transmitted with a small symbol interval, the frequency offset estimation range can be widened. In an embodiment of the present invention, when a frequency offset is estimated using a reference symbol correlation method by allocating and transmitting an uplink synchronous signal over two consecutive OFDM symbols, the frequency offset estimation range can be maximized.

Next, a method of estimating a frequency offset using an uplink synchronization signal according to an embodiment of the present invention will be described.

5 is a diagram illustrating a frequency offset estimation process according to an embodiment of the present invention.

As shown in FIG. 5, M terminals transmit an uplink synchronization signal during two OFDM symbols, and the uplink synchronization signal is transmitted to the base station through the corresponding channel.

A frequency offset occurs between the base station and the terminal due to a difference in carrier frequency and a frequency error due to a Doppler shift occurs according to the speed of the terminal. Accordingly, the base station receiving the uplink synchronization signal estimates a frequency offset for all terminals. Here, the base station estimates the frequency offset using the correlation method for the uplink synchronization signal.

Specifically, since the base station has a frequency-axis spreading code for all terminals, a correlation value between the uplink synchronization signal received from the terminal and the spreading code for the terminal is calculated, and the calculated value is added by the frequency unit Despreading method.

Through this correlation and despreading process, two complex values for two OFDM symbols are obtained for each terminal. Thereafter, the amount of change of the two complex values is calculated, and the phase difference between the respective symbols is obtained based on the calculated amount of change. Then, the phase difference is applied to the above equation (2) to obtain an estimate of the frequency offset.

Next, the base station feeds back the estimated frequency offset to the terminal. To this end, the base station according to an embodiment of the present invention uses a downlink control channel (PDCCH) as a channel for feedback.

The information of the downlink control channel is called DCI (downlink control information), and the DCI includes information related to resource allocation for the PDSCH, resource allocation for the PUSCH, and transmission power of the UE. A CRC (cyclic redundancy check) generated with a specific value of each terminal is added to the DL control channel. The downlink control channel is transmitted in one to four OFDM symbol intervals, and a plurality of DCIs for a plurality of terminals are multiplexed and transmitted over the entire frequency band.

In the embodiment of the present invention, the frequency offset estimation value estimated based on the uplink synchronization signal is added to the downlink control channel information (DCI) and transmitted. For example, the estimated frequency offset values (-π / 2 to? / 2) are divided into a plurality of (16) regions, quantized into 4 bits each, and 4 bits of quantized information are added to DCI.

A UE according to an embodiment of the present invention receives a downlink control channel including frequency offset information estimated based on an uplink synchronization signal, and the UE demodulates a downlink control channel to search for frequency offset information. Specifically, the UE receiving the DL control channel performs blind decoding on 1 to 4 OFDM symbol intervals to acquire a corresponding DCI. If the DCI obtained by decoding is CRC checked and succeeded, the DCI is recognized as control information for the DCI. And obtains and stores frequency offset information included in the control information DCI of the mobile station.

Based on this process, after obtaining the frequency offset information based on the uplink synchronization signal, the terminal compensates the frequency offset in the next uplink slot period and transmits the signal.

6 is a diagram illustrating a process of acquiring frequency offset information of a UE according to an embodiment of the present invention.

The base station generates and transmits a downlink control channel including frequency offset information (CFO_0, CFO_1, ..., CFO_M) for M terminals, and the downlink control channel transmits a plurality of, for example, four OFDM symbols do.

The UEs receiving the downlink control channel decode their downlink control channel information. Each terminal acquires and stores a frequency offset from its own downlink control channel information.

)으로 치환된다. 단말은 치환된 대표값을 이용하여 다음 상향링크 시점에 주파수 옵셋을 보상한다. 주파수 옵셋을 보상 처리는 베이스 밴드(baseband) 모뎀에서 할 수 있고, RF 단에서 수행할 수 있다. In an exemplary embodiment of the present invention, the UE calculates quantized frequency offset information, which is obtained from the downlink control channel information,

). The MS compensates the frequency offset at the next uplink time using the replaced representative value. Compensation for the frequency offset can be done at the baseband modem and at the RF stage.

FIG. 7 is a diagram illustrating an example of a process for compensating a frequency offset in a baseband in an embodiment of the present invention. FIG.

As shown in FIG. 7, in the uplink, a frequency offset compensation process for a signal to be transmitted can be performed in the base band. In this case, the frequency offset compensator is located after the inverse discrete transform (IDFT) and parallel / serial (P / S) blocks.

를 사용하여 주파수 옵셋 보상 처리를 수행하며, 구체적으로, IDFT 이후 시간 영역에서 해당 신호에 보상값

를 곱한다. 여기서 n은 슬롯내부 샘플 번호를 나타내고, N은 FFT 포인트의 수를 나타낸다. The frequency offset compensator compares the frequency offset information obtained from the downlink control channel information

To perform frequency offset compensation processing. Specifically, in the time domain after the IDFT, a compensation value

Lt; / RTI > Where n is the number of samples in the slot and N is the number of FFT points.

만큼 변화시킨다. RF 단은 반송파 주파수를 (

)로 바꿔서 전송한다. Alternatively, frequency offset compensation may be performed at the RF stage. At this time, the baseband outputs the signal of the RF stage

. The RF stage converts the carrier frequency (

).

8 is a flowchart of a frequency offset estimation and compensation method according to an embodiment of the present invention.

As shown in FIG. 8, the terminal 1 transmits the uplink synchronization signal to the base station using the uplink control channel frequency in the downlink-uplink switch slot period (S100). In particular, the terminal 1 allocates and transmits an uplink synchronization signal over two consecutive OFDM symbol intervals. The terminal generates an independent sequence orthogonal to the sequence of the other terminals on the frequency axis, multiplexes the uplink synchronization signals, and transmits the multiplexed signals.

The base station 2 receives uplink synchronization signals from the UEs and estimates a frequency offset for each UE using a correlation method or the like (S110, S120).

Then, the base station 2 feeds back the frequency offset information estimated for each terminal to the terminals through the downlink control channel (S130). That is, the estimated frequency offset estimation value is divided into a plurality of regions, quantized, and then added to the control information DCI of the DL control channel.

The terminal 1 receives and decodes the control information transmitted through the downlink control channel to obtain frequency offset information (S140, S150). Based on the obtained frequency offset information, the frequency offset of the signal is compensated in the next uplink slot and transmitted (S160).

9 is a structural diagram of a terminal according to an embodiment of the present invention.

9, the terminal 1 according to the embodiment of the present invention includes a signal processing unit 110, a memory 120, and a radio frequency (RF) unit 130. The signal processing unit 110 may be configured to implement the method described above based on FIG. 2 to FIG.

Specifically, the signal processing unit 110 generates an uplink synchronization signal transmitted in an uplink control channel frequency in an uplink interval of a downlink-uplink switching slot, and transmits the uplink synchronization signal to the RF unit 130. Upon receiving the downlink control channel through the RF unit 130, the signal processing unit 110 decodes the received downlink control channel to obtain frequency offset information, stores the information in the memory 120, Compensates the frequency offset of the uplink signal based on the frequency offset information stored in the memory 120, and transmits the compensated signal to the RF unit 130.

The memory 120 is connected to the signal processing unit 110 and stores various information related to the operation of the signal processing unit 110. [ The RF unit 130 is connected to the signal processing unit 110 and performs processing for transmitting or receiving a radio signal. Since the signal transmission and the signal reception processing are known technologies, detailed description thereof will be omitted here.

10 is a structural diagram of a base station according to an embodiment of the present invention.

10, the base station 2 according to the embodiment of the present invention includes a signal processing unit 210, a memory 220, and an RF unit 230. [ The signal processing unit 210 may be configured to implement the method described above based on FIGS.

Specifically, the signal processing unit 210 uses the uplink synchronization signal received at the uplink control channel frequency in the uplink interval of the downlink-uplink switching slot and the spreading code stored in the memory 220, Estimates an offset, and stores it in the memory 220. When transmitting the downlink control channel to the corresponding terminal, the signal processing unit 210 generates a downlink control channel signal by adding frequency offset information to the downlink control channel information, and transmits the downlink control channel signal to the RF unit 230 ).

The memory 220 is connected to the signal processing unit 210 and stores various information related to the operation of the signal processing unit 210. The RF unit 230 is connected to the signal processing unit 210 and performs processing for transmitting or receiving a radio signal. Since the signal transmission and the signal reception processing are known technologies, detailed description thereof will be omitted here.

The embodiments of the present invention are not limited to the above-described apparatuses and / or methods, but may be implemented through a program for realizing functions corresponding to the configuration of the embodiment of the present invention, a recording medium on which the program is recorded And such an embodiment can be easily implemented by those skilled in the art from the description of the embodiments described above.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims (13)

In a method for estimating an uplink frequency offset in a mobile communication system,
Receiving, by a Node B, an uplink synchronization signal transmitted in an uplink control channel frequency in a downlink-uplink switch slot period; And
Estimating an uplink frequency offset based on the uplink synchronization signal
/ RTI > The method according to claim 1,
Wherein the uplink synchronization signal is transmitted over two consecutive symbol periods. 3. The method of claim 2,
Wherein the step of estimating the uplink frequency offset comprises:
A frequency offset estimation method for estimating an uplink frequency offset of a terminal based on a phase difference between the symbols using an uplink synchronization signal received at an uplink control channel frequency and a spreading code stored in advance. The method according to claim 1,
The base station feedbacks the frequency offset information estimated for each terminal to the terminals through the downlink control channel
And estimating the frequency offset. 5. The method of claim 4,
Wherein the feedback step comprises:
Dividing the quantized frequency offset into a plurality of regions, quantizing the quantized frequency offset, adding the quantized frequency offset information to the control information of the downlink control channel, and transmitting the frequency offset information. 5. The method of claim 4,
The UE receiving and decoding the downlink control channel to obtain the frequency offset information; And
The UE compensates the frequency offset of the signal based on the frequency offset information in the next uplink interval and transmits
And estimating the frequency offset. In a base station that estimates an uplink frequency offset in a mobile communication system,
An RF unit for transmitting and receiving signals through an antenna, and
And a signal processing unit connected to the RF unit and performing an uplink frequency offset estimation,
Wherein the signal processor is configured to estimate an uplink frequency offset based on an uplink synchronization signal transmitted in an uplink control channel frequency in a downlink-uplink switch slot period from a terminal. 8. The method of claim 7,
Further comprising a memory,
Wherein the signal processor is configured to estimate an uplink frequency offset of a terminal using the uplink synchronization signal transmitted over consecutive two symbol intervals and a spreading code stored in the memory and to store the offset in the memory. 8. The method of claim 7,
Wherein the signal processor is configured to feed back the frequency offset information estimated for each terminal to the UEs through a downlink control channel and the frequency offset information is added to control information of a downlink control channel. In a terminal in a mobile communication system,
An RF unit for transmitting and receiving signals through an antenna, and
And a signal processor coupled to the RF unit for obtaining frequency offset information and performing frequency offset compensation based on the frequency offset information,
The signal processing unit is configured to generate an uplink synchronization signal transmitted in an uplink control channel frequency in a downlink-uplink switching slot period and transmit the uplink synchronization signal through the RF unit, and further, And decode the control channel to obtain frequency offset information based on the uplink synchronization signal. The method of claim 10, wherein
Wherein the uplink synchronization signal is transmitted over two consecutive symbol periods. 11. The method of claim 10,
Wherein the signal processing unit is configured to generate an independent sequence orthogonal to a sequence of other terminals on a frequency axis and to multiplex and transmit the uplink synchronization signal. 11. The method of claim 10,
Further comprising a memory,
Wherein the signal processor is configured to store the acquired frequency offset information in the memory and compensate for a frequency offset of the signal based on frequency offset information stored in the memory in a next uplink interval.

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