WO2008022598A1

WO2008022598A1 - A testing method, terminal and network side device for random access

Info

Publication number: WO2008022598A1
Application number: PCT/CN2007/070506
Authority: WO
Inventors: Bin Li; Wei Ruan
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2006-08-18
Filing date: 2007-08-17
Publication date: 2008-02-28
Also published as: CN101128004B; CN101128004A

Abstract

In the wireless communication area, a testing method, terminal and network side device for random access are provided, which are used for largely reducing the amount of calculation when the network side tests the random access, and simplifying the relevant devices. In the invention, by transmitting OFDM signal containing a signature sequence in the full frequency band, it is possible to testing the signature sequence in time-domain. The signature sequence may be transmitted on the serial sub-carriers, then it is tested in the manner of direct time-domain relation. The signature sequence also may be transmitted on the sub-carriers with equal interval, then it is tested in the manner of time-domain difference relation. A more subsequent OFDM symbol may be used for pre-kept protection time and without carrying data, after the OFDM symbols carrying the signature sequence are finished transmitting. Also, several OFDM symbols can be delayed randomly, before the OFDM symbols carrying the signature sequence are transmitted.

Description

Random access detection method, terminal and network side device

This application claims the priority of the Chinese patent application filed on August 18, 2006, the Chinese Patent Office, Application No. 200610115131.X, entitled "Random Access Detection Method, Terminal and Network Side Equipment", all contents thereof This is incorporated herein by reference.

Technical field

The present invention relates to the field of wireless communications, and in particular to a detection technique for random access in an OFDM-based system.

Background technique

With the advancement of mobile communication technology, the number of mobile users has increased dramatically, and current wireless mobile communication systems need to support a certain number of terminals. That is to say, the system needs to contain a certain number of base stations, and each base station needs to communicate with a certain number of terminals at the same time.

Since the terminal is randomly dispersed in the coverage of the base station of the entire communication system, when the terminal needs to communicate with the base station, a random access procedure needs to be initiated. Therefore, random access technology plays an important role in various wireless communication multiple access systems. The following is a brief description of the access control technology in the mobile communication system.

In a mobile communication system, when a terminal moves in each neighboring cell, after entering a cell to complete location registration, the terminal resides in the cell and enters an idle state, which is also referred to as a current cell of the terminal. . In the idle state, if the terminal performs the cell location update process, or needs to respond to the paging of the cell, or needs to establish a call with other terminals, including a service request, a short message request, etc., the terminal sends the message to the current cell base station. Access request. It should be noted that the random access process is initiated by the terminal. The terminal sends an access request to the cell base station on the random access channel to perform access probe. When the network side receives the access request of the terminal, it allocates a message to the terminal back channel on a common channel, and then the terminal and the base station perform data interaction on the allocated specific channel. It should also be noted that the random access procedure initiated by the terminal is performed according to the access resources of the current cell base station and according to a specific algorithm. The terminal selects an access slot in the available access resources, and the selection is random. After receiving the access probe of the terminal, the base station sends an access indication message to the terminal, indicating whether the current terminal is connected. Successful. If the random access is unsuccessful, the terminal cannot perform data interaction with the current cell, and cannot complete the function of call or data transmission.

The random access channel usually consists of a random access prefix and a random access message. Random access The function of the prefix is to implement uplink synchronization, carrying random identification numbers and other information. The random access message part usually carries connection request information and the like. The random access prefix is also called a random access probe.

The design of the random access prefix needs to consider the difficulty of capturing the prefix sequence by the base station, the complexity of the base station detection, the anti-interference performance, and the performance in different transmission environments.

Currently, in the wireless communication protocol C802.20, the design of transmitting a random access prefix on the transmitting end is as shown in the figure.

1 is shown. First, the sender selects a signature sequence from the candidate signature sequences. In this scheme, a 1024-bit Walsh code (Wash code) is used as the signature sequence. The 1024-bit signature sequence is scrambled and then arranged into a matrix of 128 rows and 8 columns. Each column undergoes a 128-point Discrete Fourier Transform ("DFT") transformation. The 128 data obtained after the transformation is mapped to consecutive 128 subcarriers of an Orthogonal Frequency Division Multiplexing (OFDM) system, and then subjected to OFDM modulation, for example, by 512-point inverse fast Fourier transform ( Inverse Fast Fourier Transform ("IFFT") is transformed, and the cyclic prefix is sent as a random access prefix through the antenna. A total of 8 columns are transmitted, occupying 8 OFDM symbols. In 802.20, a physical frame is included. 8 OFDM symbols, so the transmission of the random access prefix occupies 128 subcarriers on one physical frame.

The design of receiving the random access prefix at the receiving end is as shown in FIG. 2, firstly, the signal received by the antenna is demodulated by OFDM, for example, after circling and embedding, performing 512-point Fast Fourier Transform ("FFT" for short). Then, the prefix data is extracted from the corresponding 128 subcarriers at the time of transmission, and a column is formed, and 8 columns of data are extracted, and 128 points of Inverse Discrete Fourier Transform (IDFT) are obtained, respectively, and 128 are obtained respectively. Demodulated signature sequence data. The demodulated signature sequence data of eight columns of 128 elements is rearranged and restored into a sequence of scrambled 1024 elements, which is subjected to descrambling and correlation detection of a 1024-bit Walsh code to obtain a detection signal. Determining whether to capture the prefix according to whether the detection signal exceeds the threshold. If the detection signal exceeds the threshold, it is considered to capture the prefix, and the base station as the receiving end sends the acknowledgement information to the terminal as the transmitting end on the downlink channel, if the detection signal is not exceeded. The value is considered to be not captured.

Since the terminal does not implement uplink synchronization when transmitting the prefix sequence, the base station needs to perform timing shift on the signal received by the antenna, and then perform correlation detection after OFDM demodulation or the like.

In practical applications, the following problems exist: (1) The calculation amount at the receiving end is very large, and the receiving structure is complicated. Since the random access prefix is transmitted only on 128 subcarriers of all 512 OFDM subcarriers, and the uplink sequence is not implemented when the prefix sequence is transmitted, the timing information is unknown, and therefore, the receiving end is performing time synchronization. At this time, it is necessary to re-execute 512-point FFT operation, 128-point IDFT operation and Walsh code correlation operation for each newly received signal sample point, which results in a huge computational amount at the receiving end, and has to have extremely complicated reception. Machine structure.

(2) Poor performance at high speeds. Since the transmitted Walsh code occupies 8 OFDM symbols, when the terminal is moving at a high speed, the channel characteristics change greatly. When the receiving end performs Walsh code correlation, the correlation peak will greatly decrease due to the great change of the channel characteristics, thereby affecting performance. . In addition, the detection performance will drop significantly.

(3) The interference to other terminals is serious. Since the Walsh code is transmitted in the entire subframe, the timing error in the reverse access usually caused mainly by the propagation delay is not considered. Therefore, the random access prefix will be next to the frame if there is an inevitable time error. Other terminals cause severe interference.

Summary of the invention

The present invention provides a method for detecting random access, a terminal, and a network side device, so that the calculation amount when the network side detects random access is greatly reduced, and the related device is simplified.

The present invention provides a method for detecting random access in an OFDM-based system, which includes the following steps:

The terminal transmits the signature sequence in the entire frequency band by using OFDM;

After the network side removes the received signal from the cyclic prefix, the signature sequence is detected in the time domain.

The present invention also provides a method for detecting random access in an OFDM-based system, comprising: removing the received signal from a cyclic prefix and detecting the signature sequence in a time domain.

The invention also provides an OFDM-based terminal, comprising:

Generating a unit of the signature sequence;

Modulating the generated signature sequence into units of OFDM signals;

A unit that transmits the OFDM signal in a full frequency band.

The present invention also provides an OFDM-based network side device, including: a unit that receives an OFDM signal;

Remove the received signal from the unit of the cyclic prefix;

The unit of the signature sequence is detected in the time domain for the signal from which the cyclic prefix is removed.

By comparison, it can be found that the main difference between the technical solution of the present invention and the prior art is that it is possible to detect a signature sequence in the time domain by transmitting an OFDM signal containing a signature sequence in the entire frequency band. Since the correlation operation is not required for all possible timing sequences for all possible timing shifts, the detection in the time domain greatly reduces the amount of computation on the network side. All-band transmission means that all subcarriers are used to transmit a prefix containing a signature sequence. The signature sequence can be mapped to all subcarriers, or only to a part of subcarriers, and other subcarriers do not carry data.

Since the signature sequence is transmitted in the full frequency band, the present invention can complete the transmission of the signature sequence with fewer symbols than the prior art, and the signature sequence can be obtained with a lower moving speed of the terminal. Better detection results.

The signature sequence can be sent on consecutive subcarriers and detected by direct time domain correlation, which facilitates direct acquisition of the signature sequence and timing correction information.

The signature sequence can also be transmitted on equally spaced subcarriers and detected by time domain differential correlation. Compared with the direct time domain correlation method, the time domain differential correlation method can detect whether there is a prefix with a smaller amount of calculation, and further identify a specific signature sequence only when there is a prefix, so that the terminal access is not frequent. In the case, the total amount of computation associated with random access detection is small.

After the OFDM symbol carrying the signature sequence is sent, one subsequent OFDM symbol is occupied as the reserved guard time, and no data is carried. During random access, because the terminal and the base station are not synchronized in time, the reserved guard time can prevent the random access prefix from interfering with the traffic channel and ensure the performance of the traffic channel.

It is also possible to randomly delay several OFDM symbols before the OFDM symbol carrying the signature sequence is transmitted, thereby reducing the chance of random access prefix detection colliding with each other.

DRAWINGS

1 is a schematic diagram of a terminal transmitting a random access prefix according to the prior art;

2 is a schematic diagram of receiving a random access prefix by a network side according to the prior art;

3 is a flowchart of a method for detecting random access in an OFDM-based system according to a first embodiment of the present invention; 4 is a schematic diagram of a terminal transmitting a random access prefix in a method for detecting random access in an OFDM-based system according to a first embodiment of the present invention;

5 is a schematic diagram of a network side receiving a random access prefix in a method for detecting random access in an OFDM-based system according to a first embodiment of the present invention;

6 is a flowchart of a method for detecting random access in an OFDM-based system according to a second embodiment of the present invention;

7 is a schematic diagram of a network side receiving a random access prefix in a method for detecting random access in an OFDM-based system according to a second embodiment of the present invention.

detailed description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings.

In the present invention, the terminal maps the generated signature sequence to consecutive subcarriers, or maps to a part of the subcarriers at equal intervals, and the other subcarriers do not carry data, and the OFDM signal containing the signature sequence is transmitted in the entire frequency band, so that The receiving end can detect the signature sequence in a direct time domain correlation manner or in a time domain differential correlation manner, thereby avoiding performing related operations on all possible signature sequences for all possible timing shifts, thereby greatly reducing the calculation amount on the network side. .

The present invention has been briefly described above. Hereinafter, a method for detecting random access in an OFDM-based system according to a first embodiment of the present invention will be described in detail.

As shown in FIG. 3, in step 301, the terminal generates a signature sequence. Specifically, the terminal generates a signature sequence of length m*N ₂ bits, that is, the signature sequence is composed of sub-sequences of length m of ^ ₂ . Where m is an integer greater than or equal to 1, and ^ is the number of subcarriers available in each OFDM symbol of the OFDM system, the number of subcarriers being less than or equal to the total number of subcarriers included in each OFDM symbol of the OFDM system. Each of the sub-sequences constituting the signature sequence includes: a GCL sequence, a Walsh code or a DFT-transformed Walsh code, a PN sequence, or a DFT-transformed PN sequence. The subsequences constituting the same signature sequence may be the same or different, for example, a GCL sequence repeated by two columns in the same signature sequence.

Next, proceeding to step 302, the terminal maps the signature sequence to consecutive subcarriers and transmits the OFDM method in the entire frequency band. Specifically, the signature sequence generated by the terminal and having a length of m*N ₂ bits may be arranged into an array of N ₂ rows and m columns, and each of the columns is mapped to all of the OFDM symbols. On the available subcarriers, the m columns are mapped to m consecutive OFDM symbols, which are transmitted through the antenna after OFDM modulation, as shown in FIG. In this embodiment, the signature sequence is transmitted by using all available subcarriers in the OFDM symbol. Therefore, the signature sequence is transmitted in only part of the frequency band in the prior art, and the signature sequence can be completed with fewer symbols in this embodiment. The transmission can still obtain better detection results when the terminal moves at a higher speed.

It is not difficult to find that the value of m is actually related to the moving speed of the terminal. The higher the speed of the terminal moves, the smaller the value of the selected m is. For example, for a system with 5M bandwidth and 512 subcarriers, if m is less than or equal to 4, that is, transmission of the signature sequence is completed by 4 or less OFDM symbols, better performance can be obtained even at a speed of 300 km/h. .

Then, proceeding to step 303, the network side removes the cyclic prefix from the received signal, and performs a detection signature sequence in a direct time domain correlation manner, as shown in FIG. 5. Specifically, since the terminal transmits the generated signature sequence through all available subcarriers in the OFDM symbol, even if the number of subcarriers available in each OFDM symbol is smaller than the total number of subcarriers included in each OFDM symbol of the OFDM system The signature sequence as a random access prefix still occupies the entire frequency band. Therefore, the network side can detect the received signal by using the direct time domain correlation method after removing the cyclic prefix, and does not need to perform related operations on all candidate signature sequences for all possible timing shifts, thereby greatly reducing The amount of calculation on the network side.

Next, proceeding to step 304, the network side determines whether a random access prefix is captured. Specifically, the network side determines whether a random access prefix is captured based on the result of detecting the signature sequence in the time domain, and if yes, proceeds to step 305, otherwise, the flow ends.

In step 305, the network side acquires the corresponding signature sequence number and timing correction information. Specifically, if the network side determines that a random access prefix is captured based on the result of detecting the signature sequence in the time domain, the corresponding signature sequence number and timing correction information are obtained. Since the terminal transmits the signature sequence 歹 |J on consecutive subcarriers, the network side can directly detect the signature sequence and the timing correction information by means of direct time domain correlation.

A method for detecting random access in a system based on OFDM according to a second embodiment of the present invention is shown in FIG. 6.

In step 601, the terminal generates a signature sequence. Specifically, the terminal generates a signature sequence of length m*(N ₂ /2) bits, that is, the signature sequence is composed of sub-sequences of length m segments. Where m is an integer greater than or equal to 1, and N ₂ is the number of subcarriers available in each OFDM symbol of the OFDM system, the number of subcarriers being less than or equal to the total number of subcarriers included in each OFDM symbol of the OFDM system. Each of the sub-sequences constituting the signature sequence includes: a GCL sequence, a Walsh code or a DFT-transformed Walsh code, a PN sequence, or a DFT-transformed PN sequence. The subsequences constituting the same signature sequence may be the same or different, for example, a GCL sequence repeated by two columns in the same signature sequence.

Next, proceeding to step 602, the terminal maps the signature sequence to equally available subcarriers, and transmits the OFDM in the full frequency band. Specifically, the signature sequence generated by the terminal with the length m*N ₂ /2 bits may be arranged into an array of N ₂ /2 rows and m columns, and each of the columns is respectively mapped to an equally spaced available subcarrier of one OFDM symbol. On, for example, only on odd or only on even available subcarriers, the other available subcarriers that are mapped to do not carry data. And mapping the m columns to m consecutive OFDM symbols to generate two identical signals in the time domain so that the network side performs simple correlation processing on the time domain to obtain timing synchronization. After the signature sequence of the N ₂ /2 rows and m columns is mapped onto the equally available available subcarriers, OFDM modulation is performed and transmitted through the antenna. The value of m is still related to the moving speed of the terminal. The higher the speed of the terminal moves, the smaller the value of the selected m is. For example, for a system with 5M bandwidth and 512 subcarriers, if m is less than or equal to 4, that is, transmission of the signature sequence is completed by 4 or less OFDM symbols, good performance can be obtained even at a speed of 300 km/h. .

It should be noted that in the present embodiment, a signature sequence having a length of m*N ₂ /2 bits is taken as an example. However, in practical applications, the length of the subsequence in the signature sequence may be set to fewer bits. Each of the subsequences is mapped to equally spaced available subcarriers of one OFDM symbol, such as 3 subcarriers.

In step 603, after the network side de-cycles the received signal, the network detects the signature sequence by means of time-domain differential correlation, as shown in FIG. 7. Specifically, the network side separately samples the first half and the second half of the time domain signal for each OFDM time domain signal, and then performs correlation detection on the two signals, and accumulates the detection energy on the m OFDM symbols to generate Differential detection. Since the terminal maps the signature sequence to the equally available available subcarriers, the other available subcarriers that are mapped do not carry data. Therefore, even if the number of subcarriers available in each OFDM symbol is smaller than the total number of subcarriers included in each OFDM symbol of the OFDM system, the signature sequence as a random access prefix still occupies the entire frequency band. Place Therefore, the network side does not need to perform related operations on all candidate signature sequences for all possible timing shifts, which greatly reduces the amount of computation on the network side.

Next, proceeding to step 604, the network side decides whether a random access prefix is captured. Specifically, the network side determines whether a random access prefix is captured based on the result of detecting the signature sequence in the time domain, and if yes, proceeds to step 605; otherwise, the flow ends.

In step 605, the network side acquires corresponding timing correction information. Specifically, if the network side determines that a random access prefix is captured based on the result of detecting the signature sequence in the time domain, the corresponding timing correction information is acquired.

Next, proceeding to step 606, the network side recognizes the signature sequence. Specifically, the network side corrects the received signal after the cyclic prefix is removed based on the acquired timing correction information, thereby identifying the signature sequence, as shown in FIG. For example, the candidate signature sequence and the received signal correlation may be used to detect whether the output energy exceeds the threshold value to identify the signature sequence; or a specific detector may be selected according to the characteristics of the signature sequence, such as Walsh sequence detection by Hadmar transform The GCL sequence is detected by a differential coding-reverse complex leaf transform method to identify the signature sequence.

In this embodiment, since the terminal sends the signature sequence on the equally spaced subcarriers, the network side can detect whether there is a prefix with a smaller computation amount in a time domain differential correlation manner, and further identify only when there is a prefix. A specific signature sequence is generated, so that the total amount of computation associated with random access detection is small in the case where the terminal access is not frequent.

In the third embodiment of the present invention, the method for detecting random access in the OFDM-based system, based on the first or second embodiment, reserves the OFDM symbol as the guard time and does not carry the service data.

Specifically, if the physical channel resource allocated by the system to the random access channel occupies ₂ consecutive OFDM symbols, the random access prefix is designed.

Contiguous OFDM symbols, M ₂ ≥ + 1.

The signature sequence is transmitted with consecutive delays τ symbols in consecutive OFDM symbols, that is, within [ , +Λ^ - 1] symbols, where τ is an integer greater than or equal to 0, +Λ^ - 1≤ Μ ₂ - 1 , the last OFDM symbol that does not carry the signature sequence is reserved as the guard time and does not carry data.

When the terminal is not synchronized with the base station during random access, the reserved guard time can prevent the random access prefix from interfering with the traffic channel and ensure the performance of the traffic channel. Moreover, by randomly delaying a number of OFDM symbols, the chance of random access prefix detection colliding with each other can be effectively reduced. A fourth embodiment of the present invention is directed to an OFDM-based terminal, including a unit for generating a signature sequence, a unit for modulating the generated signature sequence into an OFDM signal, and a unit for transmitting an OFDM signal in the entire frequency band.

Specifically, the unit that modulates the generated signature sequence into an OFDM signal maps the signature sequence on consecutive subcarriers, or maps the signature sequence on equally spaced subcarriers, and the remaining subcarriers are filled with 0, and the actual bearer signature is actually carried. The number of subcarriers in the sequence is less than or equal to the number of subcarriers in the full band.

Then, the signature sequence is transmitted in consecutive OFDM symbols by the unit that transmits the OFDM signal in the full frequency band, and the number of OFDM symbols of the actual transmission signature sequence is smaller than the number N of consecutive OFDM symbols allocated by the system to the random access channel, and the signature is not carried. The OFDM symbols of the sequence do not carry data. Among them, the signature sequence uses a random delay τ symbols, which are transmitted in the [τ, τ+Μ-l] symbol, τ is an integer greater than or equal to 0, and τ+Μ-1≤Ν-1.

By transmitting the OFDM signal containing the signature sequence in the full frequency band, it is possible to detect the signature sequence in the time domain, so that the network side does not need to perform related operations on all candidate timing sequences for all possible timing shifts when detecting random access. , greatly reducing the amount of calculations and simplifying related equipment. Moreover, by using the reserved guard time, the interference of the random access prefix on the traffic channel can be prevented, and the performance of the traffic channel can be ensured, and the random delay is also beneficial to reduce the chance of the random access prefix detection colliding with each other.

A fifth embodiment of the present invention is directed to an OFDM-based network side device, comprising: a unit for receiving an OFDM signal, a unit for removing a received signal from a cyclic prefix, and a unit for detecting a signature sequence for a signal for removing a cyclic prefix in a time domain, And according to the result of detecting the signature sequence in the time domain, it is determined whether a random access prefix is captured, and if it is determined that a random access prefix is captured, the corresponding unit of the signature sequence number and the timing correction information is output. The unit for detecting the signature sequence in the time domain for the signal with the cyclic prefix removed detects the signature sequence by direct time domain correlation.

The network side device detects the signature sequence by direct time domain correlation, which can greatly reduce the calculation amount when detecting random access, and is convenient for directly obtaining the signature sequence and the timing correction information.

A sixth embodiment of the present invention is a network side device based on OFDM, comprising: a unit for receiving an OFDM signal, a unit for removing a received signal from a cyclic prefix, and a unit for detecting a signature sequence for a signal for removing a cyclic prefix in a time domain, According to the result of detecting the signature sequence in the time domain, it is determined whether a random access prefix is captured, and if it is determined that a random access prefix is captured, a corresponding timing correction information is output. And correcting the signal after removing the cyclic prefix according to the timing correction information and identifying the signature sequence

It is detected whether there is a prefix, and the specific signature sequence is further identified only when there is a prefix, so that the total amount of calculation related to random access detection is small when the terminal access is not frequent.

While the invention has been illustrated and described with reference to the preferred embodiments embodiments The spirit and scope of the invention.

Claims

Rights request

A method for detecting random access in an OFDM-based system, characterized in that it comprises the following steps:

The method for detecting random access in an OFDM-based system according to claim 1, wherein the signature sequence is one of the following:

GCL sequence, Walsh code, Walsh code after discrete Fourier transform, PN sequence, or PN sequence subjected to discrete Fourier transform.

The method for detecting random access in an OFDM-based system according to claim 1, wherein the terminal maps the signature sequence on consecutive subcarriers for transmission;

The network side detects the signature sequence by direct time domain correlation.

4. The method for detecting random access in an OFDM-based system according to claim 3, further comprising the steps of:

The network side determines whether a random access prefix is captured according to the result of detecting the signature sequence in the time domain, and if it is determined that a random access prefix is captured, outputs a corresponding signature sequence number and timing correction information.

The method for detecting random access in an OFDM-based system according to claim 1, wherein the terminal maps the signature sequence on equally spaced subcarriers, and the remaining subcarriers are filled with zeros;

6. The method for detecting random access in an OFDM-based system according to claim 5, further comprising the steps of:

The network side determines whether a random access prefix is captured according to the result of detecting the signature sequence in the time domain, and if it is determined that a random access prefix is captured, outputs corresponding timing correction information, according to the timing correction information. The signal after the cyclic prefix is removed is corrected and the signature sequence is identified.

7. The method for detecting random access in an OFDM-based system according to claim 6, wherein the signature sequence is identified by one of:

Correlating the candidate signature sequence with the received signal to detect whether the output energy exceeds a threshold; In the case where the signature sequence is a Walsh sequence, it is identified by means of Hadmar transform; and when the signature sequence is a GCL sequence, it is identified by means of differential coding-inverse complex leaf transform.

The method for detecting random access in an OFDM-based system according to claim 1, wherein the number of subcarriers actually carrying the signature sequence is less than or equal to the number of subcarriers of the full frequency band.

The method for detecting random access in an OFDM-based system according to any one of claims 1 to 8, wherein the signature sequence is composed of at least one subsequence, each subsequence being within one OFDM symbol Send, the sub-sequences that make up the same signature sequence are the same or different.

The method for detecting random access in an OFDM-based system according to claim 9, wherein the signature sequence is transmitted in consecutive OFDM symbols, and the number of OFDM symbols actually transmitting the signature sequence is smaller than a system. The number of consecutive OFDM symbols assigned to the random access channel is N, and the OFDM symbol not carrying the signature sequence does not carry service data.

The method for detecting random access in an OFDM-based system according to claim 10, wherein the signature sequence uses a random delay τ symbols within the [τ, τ+Μ-l] symbol. Transmitted, where τ is an integer greater than or equal to 0, and τ+Μ-1≤Ν-1;

The last OFDM symbol in the consecutive OFDM symbols does not carry service data.

12. A method for detecting random access in an OFDM-based system, comprising: removing the received signal from a cyclic prefix and detecting the signature sequence in a time domain.

13. The method for detecting random access in an OFDM-based system according to claim 12, wherein:

When the signature sequence is mapped for transmission on consecutive subcarriers, the signature sequence is detected by direct time domain correlation.

The method for detecting random access in an OFDM-based system according to claim 13, further comprising:

According to the result of detecting the signature sequence in the time domain, it is determined whether a random access prefix is captured, and if it is determined that a random access prefix is captured, the corresponding signature sequence number and timing correction information are output.

15. The method for detecting random access in an OFDM-based system according to claim 12, wherein: When the signature sequence mapping is transmitted on equally spaced subcarriers, and the remaining subcarriers are zero filled, the signature sequence is detected by a time domain differential correlation.

The method for detecting random access in an OFDM-based system according to claim 15, further comprising:

Determining whether a random access prefix is captured according to a result of detecting the signature sequence in the time domain, if it is determined that a random access prefix is captured, outputting corresponding timing correction information, and correcting the removal cycle according to the timing correction information The signal after the prefix and identifies the signature sequence.

The method for detecting random access in an OFDM-based system according to claim 16, wherein the signature sequence is identified by one of the following methods:

Correlating the candidate signature sequence with the received signal to detect whether the output energy exceeds a threshold;

In the case where the signature sequence is a Walsh sequence, it is identified by means of Hadmar transform; when the signature sequence is a GCL sequence, it is identified by means of differential coding-inverse complex leaf transform.

The method for detecting random access in an OFDM-based system according to claim 12, wherein the number of subcarriers actually carrying the signature sequence is less than or equal to the number of subcarriers of the full frequency band.

The method for detecting random access in an OFDM-based system according to any one of claims 12 to 18, wherein the signature sequence is composed of at least one subsequence, each subsequence being within one OFDM symbol Send, the sub-sequences that make up the same signature sequence are the same or different.

The method for detecting random access in an OFDM-based system according to claim 19, wherein the signature sequence is transmitted in consecutive OFDM symbols, and the number of OFDM symbols actually transmitting the signature sequence is smaller than a system. The number of consecutive OFDM symbols assigned to the random access channel is N, and the OFDM symbol not carrying the signature sequence does not carry service data.

The method for detecting random access in an OFDM-based system according to claim 20, wherein the signature sequence uses a random delay τ symbols within the [τ, τ+Μ-l] symbol Transmitted, where τ is an integer greater than or equal to 0, and τ+Μ-1≤Ν-1;

22. An OFDM-based terminal, comprising:

Generating a unit of the signature sequence; Modulating the generated signature sequence into units of an OFDM signal;

A unit that transmits the OFDM signal in a full frequency band.

The OFDM-based terminal according to claim 22, wherein the signature sequence is transmitted in consecutive OFDM symbols, and the number M of OFDM symbols actually transmitting the signature sequence is smaller than a system allocated to a random access channel. The number of consecutive OFDM symbols N, the OFDM symbol that does not carry the signature sequence does not carry data; wherein the signature sequence is transmitted within a [τ, τ+Μ-l] symbol by using a random delay τ symbols, where τ is an integer greater than or equal to 0, and τ + Μ -1 ≤ Ν-1.

The OFDM-based terminal according to claim 22, wherein the number of subcarriers actually carrying the signature sequence is less than or equal to the number of subcarriers of the full frequency band.

The OFDM-based terminal according to claim 22, wherein the unit that modulates the signature sequence into an OFDM signal maps the signature sequence to a subcarrier in one of the following ways:

Mapping the signature sequence on consecutive subcarriers; or

The signature sequence is mapped and transmitted on equally spaced subcarriers, and the remaining subcarriers are filled with zeros.

26. An OFDM-based network side device, comprising:

a unit that receives an OFDM signal;

Remove the received signal from the unit of the cyclic prefix;

The OFDM-based network side device according to claim 26, wherein the unit that detects the signature sequence in the time domain by detecting the signal that removes the cyclic prefix detects the signature by direct time domain correlation. sequence.

The OFDM-based network side device according to claim 27, further comprising: determining whether a random access prefix is captured according to a result of detecting the signature sequence in a time domain, and determining that there is random A unit that outputs a corresponding signature sequence number and timing correction information when the access prefix is captured.

The OFDM-based network side device according to claim 26, wherein the signature sequence is detected in a manner.

30. The OFDM-based network side device according to claim 29, further comprising Contains:

Determining whether a random access prefix is captured according to a result of detecting the signature sequence in the time domain, and outputting a unit of timing correction information when determining that a random access prefix is captured;

The signal after the cyclic prefix is removed is corrected based on the timing correction information and the unit of the signature sequence is identified.