CN1805316A - Uplink FDMA access method in frequency selected block transmission system - Google Patents

Abstract

The invention relates to a ascending chain circuit frequency division multiple access method of select frequency segmented transmission system, which comprises following steps: 1, accessing the mobile station into base station; the base station distributes a group of sub channels to it, and sends the information to the mobile station to request the mobile station to send the auxiliary data of channel estimation; 2, the base station processes the channel estimation to attain the channel condition of sub channel group to select the available sub channel and send the mark information of sub channel group to the mobile station; 3, the mobile station processes the orthogonal transformation on the sent signal into the time domain to be sent, and send the signal with information to the base station; 4, the base station transforms the received sampling signal to the frequency domain and frequency balances the received signal to select the available signal to attain the information data; 5, according to the demand, the base station changes the sub channel group in the communication; and the mobile station according to received information to communicate with the base station. The invention can solve the access problem when the ascending chain circuit is in the time varying condition.

Description

Uplink frequency division multiple access method of frequency-selecting block transmission system

(I) technical field

The invention relates to a broadband digital communication transmission method. Belongs to the technical field of broadband wireless communication.

(II) background of the invention

Communication technology has been developed over the last decades, particularly the nineties of the twentieth century, with profound effects on the development of people's daily lives and national economy. In the future, communication technologies are developing towards high-speed broadband, so that many broadband digital transmission technologies are receiving wide attention, and Orthogonal Frequency Division Multiplexing (OFDM) and single carrier with Frequency Domain Equalization (SC-FDE) are two broadband digital transmission technologies that are regarded by people, and both of them belong to block transmission technologies, while OFDM is far more concerned than SC-FDE at present, and become support technologies in various standards, for example: IEEE802.11a in a Wireless Local Area Network (WLAN); IEEE802.16 in Wireless Metropolitan Area Network (WMAN: Wireless Metropolisan Area Network); various high-speed Digital Subscriber lines (xDSL) in wired data transmission are standards based on OFDM technology. SC-FDE is not adopted by these standards, but is proposed as a physical layer transmission technique in IEEE802.16 in combination with OFDM.

The mathematical model of the conventional SC-FDE system is briefly described below.

In the SC-FDE system, a frame of discrete time domain signals transmitted by a transmitting end is s (N), (N is 0, 1, …, N-1), and through a multipath channel, where an impulse response of the channel is h (N), (N is 0, 1, …, L-1), interference from Additive White Gaussian Noise (AWGN) is received during signal transmission, where w (N) is assumed to be Noise, (N is 0, 1, …, N-1), and after CP is removed, a received time domain signal r (N) is:

r(n)＝s(n)*h(n)+w(n)，(n＝0，1，…，N-1) (1)

here, "*" represents a circular convolution operation.

In the base station, the r (n) signal is transformed into the frequency domain by Discrete Fourier Transform (DFT), and the frequency domain signal obtained according to the time domain convolution theorem of DFT is:

R(k)＝S(k)H(k)+W(k)，(k＝0，1，…，N-1) (2)

wherein, r (k), s (k), h (k), w (k) are r (N), s (N), h (N), w (N) are frequency domain symbols obtained by N-point DFT, and h (k), (k ═ 0, 1, …, N-1) are frequency domain responses of the channel. After zero-forcing equalization, the frequency domain signals are:

$\tilde{S}\left(k\right)=S\left(k\right)+\frac{W\left(k\right)}{H\left(k\right)}=S\left(k\right)+\tilde{W}\left(k\right),(k=\mathrm{0,1},...,N-1)...\left(3\right)$

and finally, performing Inverse Discrete Fourier Transform (IDFT) on the equalized signal, converting the equalized signal back to a time domain for judgment, and obtaining data transmitted by a transmitting end.

OFDM and SC-FDE both belong to the block transmission technology and the system they form is called a block transmission system.

Channels of broadband mobile communication generally exhibit severe frequency selective fading, and the influence of the frequency selective channels on a block transmission system is mainly expressed in that: frequency selective fading is caused by multipath propagation or delay spread of a signal, some frequency spectrum components of the signal are attenuated very low when the signal propagates in a frequency selective fading channel, and under the condition that a deep attenuation point exists in the channel, the signal is influenced more greatly, so that the signal is distorted, intersymbol interference is caused, and system performance is influenced. In many important applications of OFDM and SC-FDE (such as WLAN, WMAN, xDSL and future broadband mobile communication), there is a reverse channel, and then the transmitting end of the block transmission system can utilize the channel state information returned by the reverse channel and some adaptive techniques to improve the performance and efficiency of the whole system.

The chinese patent application No. 200410036439.6 provides a single carrier block transmission method in a frequency selection mode, which includes the following steps:

(1) after the two parties of the transceiver set up communication, the receiving end finds out M usable sub-channels from N pieces of estimated channel state information, mark usable channel and forbidden channel separately at the same time, form the mark information of sub-channel, send the mark information of sub-channel back to the sending end through the reverse channel;

(2) after receiving the sub-channel marking information sent back by the receiving end, the sending end changes the signal frequency spectrum according to the information and transmits signals by using available sub-channels;

(3) and after receiving the signals, the receiving end transforms the signals to a frequency domain, selects the signals on the available sub-channels according to the sub-channel marking information, and then balances and judges the selected signals to finally obtain the transmitted data.

In mobile communication systems, efficient multiple access techniques must be employed. The basic types of Multiple access techniques are frequency Division Multiple access fdma (frequency Division Multiple access), time Division Multiple access tdma (time Division Multiple access), and code Division Multiple access cdma (code Division Multiple access). FDMA and TDMA are simple to implement, but need to leave guard bands in the frequency domain and the time domain, respectively, and are inefficient. CDMA is a multiple access technique with significantly higher user capacity than TDMA and FDMA, but in the uplink (from mobile terminals to base stations), there is typically severe multi-user interference. Although multi-user detection techniques can be employed to combat multi-user interference, the implementation is complex; multi-carrier CDMA (MC-CDMA) also suffers from the same problems as normal CDMA. The carrier sense/collision avoidance technique in a wireless local area network is inefficient if used for multiple access for mobile communications.

Ofdma (orthogonal Frequency Division Multiple access), which is a new broadband wireless communication Multiple access technology that has attracted attention in recent years, is an OFDM-based Multiple access technology, and can be essentially regarded as a new Frequency Division Multiple access technology. OFDMA divides the entire bandwidth into a large number of narrowband subchannels, and a user allocates one or several subchannel groups, each containing a certain number of subchannels. OFDMA is simple to realize and has high spectrum utilization rate. In the uplink, there is no multi-user interference. The OFDMA scheme for establishing a subchannel set generally has two schemes, one is that a certain number of subchannels are adjacent to each other to form a subchannel set, and the second scheme is that all subchannels of the subchannel set are spread in the entire bandwidth at certain intervals. Second kindThe scheme has advantages over the first scheme, especially in frequency selective fading channels. In order to fully utilize the channel state information, a number of adaptive OFDMA techniques have been proposed, but the complexity is too high. Although the second scheme works well in frequency selective fading channel, it still suffers from the great influence of frequency selective fading, and usually needs to combine with error correcting code with strong error correcting capability to control the error performance of the system to a relatively low level (e.g. 10)^-4Below) and the code rate of such error correcting codes is generally low, e.g. generally 1/2, 1/3 or even lower, which greatly reduces the efficiency of the whole system.

Disclosure of the invention

The invention provides an uplink frequency division multiple access method of a frequency-selecting block transmission system aiming at the problems in the prior art, which can improve the error code performance of the system and further improve the frequency spectrum efficiency of the system.

The method comprises the following steps (for convenience of description, the following steps are performed for uplink communication in which one mobile station U accesses to the base station, since the access modes of the mobile stations to the base station are the same):

(1) the mobile station U sends a signal to apply for accessing the base station, the base station distributes a group of sub-channels for the base station according to the service requirement and available spectrum resources, the sub-channels are recorded as a sub-channel group U, relevant information of the sub-channel group U, namely label information of each sub-channel in the sub-channel group U, is sent to the mobile station U, and the mobile station U is requested to send auxiliary data for channel estimation;

(2) the base station carries out channel estimation, acquires the channel state information of the sub-channel group u, carries out frequency selection, selects M available sub-channels, obtains the sub-channel mark information of the sub-channel group u, and sends the sub-channel mark information of the sub-channel group u to the mobile station;

(3) the mobile station carries out orthogonal transformation on the transmitted signal according to the received subchannel marking information of the subchannel group u, maps the orthogonal transformation into an N-dimensional vector, transmits the N-dimensional vector after transforming the N-dimensional vector into a time domain, and transmits a signal carrying information to the base station;

(4) the base station transforms the received sampling signal to a frequency domain, performs frequency domain equalization on the received signal according to the sub-channel marking information of the sub-channel group u, selects M useful signals on the available sub-channels, performs orthogonal inverse transformation, transforms the useful signals back to time domain signals and completes judgment to obtain information data;

(5) according to the requirement, the base station changes the sub-channel group u to other sub-channel groups in the communication process, or keeps the sub-channel group u unchanged and only changes the sub-channel mark information in the sub-channel group u; after the change, the base station sends the changed identification information of the sub-channel group or the sub-channel marking information of the sub-channel group u to the mobile station, and the mobile station always communicates with the base station according to the recently received identification information of the sub-channel group or the sub-channel marking information.

The detailed steps of the method are as follows:

first, the following description will be made of the symbols involved:

k: the overall label of the sub-channel is that k is more than or equal to 0 and less than or equal to N-1. In a block transmission system, both communicating parties divide the entire available frequency band into N subchannels, and in a block transmission system implemented based on FFT, k is also the index of the frequency domain variable.

m: the local index of a subchannel is the index of the mth subchannel in the same subchannel group, and m is called the local index in the subchannel group.

I_u: identification information of subchannel group u, according to I_uBoth the base station and the mobile station may obtain an overall index for all subchannels in subchannel set u.

D_B(k) The method comprises the following steps Vector of N dimension, N is the number of all available sub-channels of the base station, if D_B(k)＝u，1≤u≤U_maxIndicates that the kth sub-channel belongs to the sub-channel group U, U of the Uth mobile station_maxIndicating the maximum number of users the base station is allowed to access.

D_u(m): the subchannel label array for subchannel set u. D_uWhere (m) ═ k denotes the overall index of the subchannel of subchannel group u, which is partially index m, is k. This array is stored both at the base station and at the mobile station U, the base station being based on D_B(k) Can obtain D_u(m), the mobile station U is based on the identification information I of the sub-channel group U transmitted from the base station_uTo obtain D_u(m)。

A_u(m): subchannel flag information for subchannel group u. A. the_u(m) ═ 0, indicating that the subchannel in subchannel group u, which is locally labeled m, is an unavailable subchannel; a. the_u(m) ═ 1, indicating that the subchannel in subchannel group u, which is locally labeled m, is an available subchannel.

Step (1), the mobile station U sends a signal to apply for accessing the base station, the base station allocates a group of sub-channels for the base station according to the service requirement and available spectrum resources, the sub-channels are recorded as a sub-channel group U, the related information of the sub-channel group U, namely the label information of each sub-channel in the sub-channel group U, is sent to the mobile station U, and the mobile station U is requested to send auxiliary data for channel estimation.

In a block transmission system, a base station divides the whole available frequency band into a plurality of sub-channels, and since the block transmission system needs to transform the discrete time domain signal without the CP to the discrete frequency domain by using DFT, in the discrete frequency domain, the total number of sub-channels of the base station is equal to the number of points of DFT, and each sub-channel corresponds to one point or component of DFT. The number of subchannels included in each subchannel set may vary from service to service. The distribution of the sub-channels in the same sub-channel group in the whole frequency band can be chosen in many ways, for example, the sub-channel groups of multiple users can each occupy a continuous spectrum, or the sub-channel groups of each user can be spread in the whole frequency band.

The base station distributes a group of sub-channels for the mobile station U according to the service requirement and the available frequency spectrum resource, and the sub-channels are marked as a sub-channel group U to form sub-channel identification information I of the sub-channel group U_u. For example, the base station may allocate up to 64 mobile stations with subchannel groups according to the protocol, and each subchannel may be assigned to a specific mobile stationChannel group needs 6 bits to identify, and identification information I transmitted to subchannel group u of mobile station_uI.e. the index of the subchannel set u; the number of subchannels in these subchannel groups may be the same or different; or in the case that the sub-channels in the sub-channel group u are completely randomly distributed in the whole frequency band, the identification information I of the sub-channel group u_uN bits of information are needed for marking, i.e., the base station needs to send N bits of information to the mobile station. Let D_BIs a vector used by the base station to represent the mark information of the subchannel set u, namely:

D_B＝{D_B(k)，k＝0，1…，N-1}，

D_B(k)＝u，1≤u≤U_maxindicating that the kth sub-channel belongs to the u sub-channel group, the u sub-channel group has B_uSub-channels, D_u(m)＝k，(m＝0，1，…，B_u-1) the global index k of the subchannel denoted local index m of the subchannel set u is denoted.

The mobile station U receives the identification information I of the sub-channel group U_uThen, i.e. know D_u(m)＝k，(m＝0，1，…，B_u-1) followed by transmitting assistance data for channel estimation.

And (2) the base station performs channel estimation to obtain the channel state information of the sub-channel group u, performs frequency selection to obtain the sub-channel mark information of the sub-channel group u, and sends the sub-channel mark information of the sub-channel group u to the mobile station.

There are many methods for channel estimation, such as a channel estimation method based on a training frame, an interpolation pilot symbol estimation method, and the like. And after acquiring the channel state information of the sub-channel group u, the base station performs frequency selection on the sub-channel group u. After the base station acquires the channel state information of each subchannel of the subchannel group U, according to the system performance requirement and the channel state information of each subchannel of the subchannel group U, the first M subchannels with high gains are selected as available subchannels according to the gain of the frequency domain subchannel, each subchannel in the subchannel group U is marked by one bit of information '0' or '1', subchannel marking information of the subchannel group U is formed, and the subchannel marking information is sent to the mobile station U through the channel from the base station to the mobile station U.

For example, let the vector representing the subchannel flag information for subchannel set u be:

A_u＝{A_u(m)，m＝0，1，…，B_u-1}，

A_u(m) ═ 1, indicating that the subchannel in subchannel group u, which is locally labeled m, is an available subchannel; a. the_u(M) ═ 0, which indicates that the subchannel with local label M in the subchannel group u is an unavailable subchannel, and the number of all available subchannels in the subchannel group u is recorded as M, and M can be changed in the communication process, for example, the number M of the available subchannels selected is generally different each time frequency re-selection is performed; when selecting the available sub-channel, firstly estimating the receiving signal-to-noise ratio, and determining the used modulation mode according to the receiving signal-to-noise ratio, wherein the modulation mode can also be agreed by the two communication parties in advance, and the criterion for selecting the available sub-channel is that the number of the selected available sub-channel is as large as possible on the premise of meeting the error code performance requirement of the system; the error code performance of the system is determined by the equalized signal-to-noise ratio of the system, the signal-to-noise ratio after the lowest equalization of the error code performance is called the signal-to-noise ratio after the expected equalization, and a certain margin is reserved for the signal-to-noise ratio after the equalization.

The method for calculating the received signal-to-noise ratio refers to relevant documents. Let the overall label of the M available sub-channels selected by the current frequency selection module be k_mAnd (M-0, 1, …, M-1), which are all subchannels in subchannel set u. The following briefly describes the calculation of the post-equalization signal-to-noise ratio by taking zero-forcing equalization as an example, and does not consider the influence of synchronization errors:

due to the cyclic prefix, a linear convolution of the signal and the channel impulse response can be converted into a product in the discrete frequency domain in the discrete time domain. Let S' (k), H_u(k) W (k), R' (k), (k ═ 0, 1, …, N-1) are frequency domain transmission signal, frequency domain channel complex gain, noise sum, and sum of signals in the uplink channel from the mobile station U to the base station, respectivelyThe frequency domain received signal after CP removal, where w (k), (k ═ 0, 1, …, N-1) is gaussian noise, which is generally white, i.e. the noise power on each subchannel in the frequency domain is equal, so that:

R′(k)＝S′(k)H_u(k)+W(k)，(k＝0，1，…，N-1)

after zero-forcing equalization is performed on M available subchannels in the subchannel group u, the following results are obtained:

<math> <mrow> <msup> <mover> <mi>S</mi> <mo>~</mo> </mover> <mo>&prime;</mo> </msup> <mrow> <mo>(</mo> <mi>m</mi> <mo>)</mo> </mrow> <mo>=</mo> <msup> <mi>S</mi> <mo>&prime;</mo> </msup> <mrow> <mo>(</mo> <msub> <mi>k</mi> <mi>m</mi> </msub> <mo>)</mo> </mrow> <mo>+</mo> <mfrac> <mrow> <mi>W</mi> <mrow> <mo>(</mo> <msub> <mi>k</mi> <mi>m</mi> </msub> <mo>)</mo> </mrow> </mrow> <mrow> <msub> <mi>H</mi> <mi>u</mi> </msub> <mrow> <mo>(</mo> <msub> <mi>k</mi> <mi>m</mi> </msub> <mo>)</mo> </mrow> </mrow> </mfrac> <mo>,</mo> <mrow> <mo>(</mo> <mi>m</mi> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <mi>M</mi> <mo>-</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow> </math>

the post-equalization signal-to-noise ratio is:

<math> <mrow> <msub> <mi>SNR</mi> <mi>eq</mi> </msub> <mo>=</mo> <mfrac> <mrow> <mi>E</mi> <mrow> <mo>(</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>m</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <mi>M</mi> <mo>-</mo> <mn>1</mn> </mrow> </munderover> <msup> <mrow> <mo>|</mo> <msup> <mover> <mi>S</mi> <mo>~</mo> </mover> <mo>&prime;</mo> </msup> <mrow> <mo>(</mo> <mi>m</mi> <mo>)</mo> </mrow> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mo>)</mo> </mrow> </mrow> <mrow> <mi>E</mi> <mrow> <mo>(</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>m</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <mi>M</mi> <mo>-</mo> <mn>1</mn> </mrow> </munderover> <msup> <mrow> <mo>|</mo> <mfrac> <mrow> <mi>W</mi> <mrow> <mo>(</mo> <msub> <mi>k</mi> <mi>m</mi> </msub> <mo>)</mo> </mrow> </mrow> <mrow> <msub> <mi>H</mi> <mi>u</mi> </msub> <mrow> <mo>(</mo> <msub> <mi>k</mi> <mi>m</mi> </msub> <mo>)</mo> </mrow> </mrow> </mfrac> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mo>)</mo> </mrow> </mrow> </mfrac> <mo>=</mo> <mfrac> <mrow> <mi>E</mi> <mrow> <mo>(</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>m</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <mi>M</mi> <mo>-</mo> <mn>1</mn> </mrow> </munderover> <msup> <mrow> <mo>|</mo> <msup> <mover> <mi>S</mi> <mo>~</mo> </mover> <mo>&prime;</mo> </msup> <mrow> <mo>(</mo> <mi>m</mi> <mo>)</mo> </mrow> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mo>)</mo> </mrow> </mrow> <mrow> <msubsup> <mi>&sigma;</mi> <mi>n</mi> <mn>2</mn> </msubsup> <munderover> <mi>&Sigma;</mi> <mrow> <mi>m</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <mi>M</mi> <mo>-</mo> <mn>1</mn> </mrow> </munderover> <msup> <mrow> <mo>|</mo> <mfrac> <mn>1</mn> <mrow> <msub> <mi>H</mi> <mi>u</mi> </msub> <mrow> <mo>(</mo> <msub> <mi>k</mi> <mi>m</mi> </msub> <mo>)</mo> </mrow> </mrow> </mfrac> <mo>|</mo> </mrow> <mn>2</mn> </msup> </mrow> </mfrac> </mrow> </math>

wherein, <math> <mrow> <msubsup> <mi>&sigma;</mi> <mi>n</mi> <mn>2</mn> </msubsup> <mo>=</mo> <mi>E</mi> <mrow> <mo>(</mo> <msup> <mrow> <mo>|</mo> <mi>W</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mo>)</mo> </mrow> <mo>,</mo> </mrow> </math> (k-0, 1, …, N-1) is the power of the noise on each subchannel.

Step (3): the mobile station carries out orthogonal transformation on the transmitted signal according to the received subchannel marking information of the subchannel group u, maps the orthogonal transformation into an N-dimensional vector, transmits the N-dimensional vector after transforming the N-dimensional vector into a time domain, and transmits a signal carrying information to the base station;

the mobile station U performs orthogonal transformation on the transmission signal according to the received subchannel flag information of the subchannel set U. The mobile station carries out symbol mapping according to the adopted modulation mode to form a frame of M symbols to be transmitted, carries out orthogonal transformation on the M symbols to obtain M transformation domain symbols, expands the M transformation domain symbols into N-dimensional vectors according to the sub-channel mark information to obtain a frequency domain form of a signal to be transmitted, transforms the N-dimensional frequency domain signal back to a time domain and transmits the time domain signal, when M is not an integral power of 2, the orthogonal transformation can be realized in a blocking mode, and different blocks can use the same or different orthogonal transformations.

The specific method for expanding the M transform domain symbols into N-dimensional vectors according to the channel marking information is as follows:

after receiving the subchannel marking information sent back by the base station, the mobile station U transmits signals by using only M available subchannels, thus performing M-point orthogonal transformation to transform domain for a frame of M blocks of transmission system symbols s (n), (n ═ 0, 1, …, M-1) of the mobile station:

S＝Fs

where F is an M-point orthogonal transform matrix, S ═ { S (n), { 0, 1, …, and M-1} are M time domain symbols of the block transmission system, S ═ { S (i) }, i ═ 0, 1, …, and M-1} are M transform domain symbols.

Expanding M transform domain symbols S ═ { S (M), M ═ 0, 1, …, M-1} into an N-dimensional vector S '═ { S' (k), k ═ 0, 1, …, N-1}, where M transform domain symbols correspond one-to-one to M available subchannels of subchannel group u, e.g., S corresponds to M available subchannels in order of their overall index:

kth where S 'is { S' (k), k is 0, 1 … N-1}_mOne component is equal to S (m), and zero or some non-information data is placed on the components corresponding to other sub-channels of the sub-channel group u; and all the sub-channels which do not belong to the sub-channel group u are set to be zero.

Where k is_mAnd (M-0, 1, …, M-1) is an overall index of the M available subchannels in the subchannel set U.

Then, for S' (k), (k ═ 0, 1, …, N-1), an N-point Inverse discrete Fourier Transform (hereinafter IDFT: Inverse discrete Fourier Transform) is performed, and the Inverse fast Fourier Transform (hereinafter IFFT: Inverse fast Fourier Transform) algorithm is used to realize:

<math> <mrow> <msup> <mi>s</mi> <mo>&prime;</mo> </msup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mn>1</mn> <mi>N</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <mi>N</mi> <mo>-</mo> <mn>1</mn> </mrow> </munderover> <msup> <mi>S</mi> <mo>&prime;</mo> </msup> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;</mi> </mrow> <mi>N</mi> </mfrac> <mi>nk</mi> </mrow> </msup> <mo>,</mo> <mrow> <mo>(</mo> <mi>n</mi> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <mi>N</mi> <mo>-</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow> </math>

the time domain signal is changed into a time domain signal, the IFFT points are more than N when the time domain signal is over-sampled, the high frequency part is set to be zero, and the time domain signal is sent out after being subjected to D/A conversion and then subjected to carrier modulation.

When M is not an integer power of 2, the orthogonal transformation may be implemented in blocks, different blocks may use the same or different orthogonal transformations;

and (4) converting the received sampling signals to a frequency domain by the base station, carrying out frequency domain equalization on the received signals on the subchannel group u according to the subchannel marking information of the subchannel group u, selecting M useful signals on the available subchannels, carrying out orthogonal inverse transformation, converting back to time domain signals and finishing judgment to obtain information data, wherein if M is not the integral power of 2, the original orthogonal transformation is realized by blocks, the orthogonal inverse transformation is realized by blocks, and different blocks adopt the same or different orthogonal inverse transformations according to the orthogonal transformations respectively adopted by the different blocks.

The specific implementation method for selecting the signal on the available sub-channel according to the sub-channel marking information is as follows:

the time domain discrete signal with the CP removed from the signal received by the base station is set as follows:

r′(n)＝s′(n)*h(n)+w(n)，(n＝0，1，…，N-1)

and performing N-point DFT on the obtained data:

<math> <mrow> <msup> <mi>R</mi> <mo>&prime;</mo> </msup> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <mi>N</mi> <mo>-</mo> <mn>1</mn> </mrow> </munderover> <msup> <mi>r</mi> <mo>&prime;</mo> </msup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;</mi> </mrow> <mi>N</mi> </mfrac> <mi>nk</mi> </mrow> </msup> <mo>,</mo> <mrow> <mo>(</mo> <mi>k</mi> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <mi>N</mi> <mo>-</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow> </math>

and,

R′(k)＝S′(k)H(k)+W(k)，(k＝0，1，…，N-1)

in this way, the signals r (M) on the M available subchannels can be collectively selected based on the flag information of the subchannel set u and the corresponding subchannel flag information, (M ═ 0, 1, …, M-1), and for example, for the above-mentioned spectrum transformation method, there are:

R(m)＝R′(k_m) Where k is_mAnd (M-0, 1, …, M-1) is an overall index of M available subchannels.

Equalizing the selected signal by using the channel state information of the available sub-channels in the estimated channel state information; one of three equalization modes can be selected:

1. zero forcing equalization;

2. balancing the minimum mean square error;

3. hybrid equalization, i.e., one part of the subchannels is equalized with zero-forcing and the other part of the subchannels is equalized with minimum mean square error. The equalized signal is transformed back to the time domain by an M-point orthogonal inverse transform:

r＝F^HR

wherein F^HIs the conjugate transpose of F, which is the inverse transform matrix of F. When M is not an integer power of 2, if the original orthogonal transformation is realized by blocks, the orthogonal inverse transformation is also realized by blocks, and different blocks adopt the same or different orthogonal inverse transformations according to the orthogonal transformations respectively adopted.

Step (5), according to the requirement, the base station can change the sub-channel group u to other sub-channel groups in the communication process, or keep the sub-channel group u unchanged, and only change the sub-channel mark information in the sub-channel group u; after the change, the base station sends the changed identification information of the sub-channel group or the sub-channel marking information of the sub-channel group u to the mobile station, and the mobile station always communicates with the base station according to the recently received identification information of the sub-channel group or the sub-channel marking information.

When the channel state information changes or the system needs to optimize the sub-channel group of multiple users, the base station can change the identification information of the sub-channel group u, that is, the sub-channel group u is changed into other sub-channel groups, or the identification information of the sub-channel group u is kept unchanged, only the sub-channel marking information in the sub-channel group u is changed, at this time, the previous channel marking information is inaccurate, so that the system performance is affected, at this time, frequency selection needs to be carried out again, and the second step and the third step need to be repeated.

Through the above descriptions of the steps, a new system can be constructed, but parameters affecting the error performance and the spectral efficiency of the system need to be explained:

1. determination of the number of available subchannels

The number of available subchannels is an important parameter affecting the performance of the new system. In view of the above, if only available subchannels are used for transmitting useful information, there is a problem how to determine the number of available subchannels, which is not a constant value for different channel types and at different times of a time-varying channel. According to different channel conditions, the system spectrum efficiency and performance are considered, and the selected available sub-channel number M occupies the sub-channel number B in the sub-channel group u_uThe proportion of (B) is generally between 5% and 100%.

2. Block orthogonal transformation of signals on available subchannels

Because most orthogonal transformation operations have a fast algorithm when the number of points is the integer power of 2, when the number of the orthogonal transformation points is not the integer power of 2, a blocking method can be adopted to improve the calculation efficiency.

The method divides the orthogonal transformation operation with more points but not the integer power of 2 into a plurality of orthogonal transformation operations with relatively less points; in the orthogonal transformation operation with less points, at most one point is not an integer power of 2, but the point is very small, and the rest points are all integer powers of 2, namely, the block orthogonal transformation is carried out, and various block methods are proposed to follow the following principle:

a. a block of length 16 or more, the length of which is an integer power of 2;

b. at most 1 block of length less than 16;

c. blocks of length less than 4 are not recommended;

the same processing is performed on the orthogonal inverse transformation, and the operation efficiency of the system is improved by the blocking processing.

The invention better solves the access problem of the uplink in a time-varying environment on the premise of ensuring the system performance. It can be seen from the simulation results given in the embodiments that for a single-antenna system with a signal sampling rate of 40MHz and a radio frequency bandwidth of no more than 46MHz, under the conditions that the sum Doppler frequency of an IMT 2000 mobile channel a reaches 100Hz-300Hz and the received signal-to-noise ratio is 10dB, the method provided by the present invention can ensure that the bit error rate of the system is lower than 5 × 10^-3Under the condition of (1), for a mobile station occupying 64 sub-channels, the uplink transmission rate of the system is not lower than 5.0Mbps, and the return information rate of the reverse channel does not exceed 300 Kbps.

(IV) description of the drawings

The figure is a block diagram of a system implementing the proposed method of the invention.

In the figure: 1. the system comprises a source module, a 2 symbol mapping module, a 3 FFT module (M point), a 4 signal spectrum transformation module, a 5 IFFT module (N point), a 6 Cyclic Prefix (CP) adding module, a 7D/A module, a 8 intermediate frequency and radio frequency modulation module, a 9 channel, a 10 radio frequency and intermediate frequency demodulation module, a 11A/D module, a 12 CP removing module, a 13 FFT module (N point), a 14 signal spectrum inverse transformation module, a 15 equalization module, a 16 IFFT module (M point), a 17 decision module, a 18 channel estimation module, a 19 self-adaptive frequency selection decision module, a 20 frequency selection module, a 21 reverse channel, a 22 synchronization module, a 23 multi-address access control module.

(V) detailed description of the preferred embodiments

Example (b):

the orthogonal transform employed in the embodiment is an M-point discrete fourier transform, and the corresponding inverse orthogonal transform is an inverse M-point discrete fourier transform. The embodiment does not perform the blocking process for the M-point DFT and the IDFT.

The attached drawings show a system block diagram for realizing the method provided by the invention, and the functions of all modules are as follows:

the information source module 1: and the general module generates data to be transmitted. According to the result returned by multiple access module 23 and reverse channel 21, data of length corresponding to the selected number M of available sub-channels is generated.

The symbol mapping module 2: and the universal module is used for mapping the data generated by the information source to the corresponding points of the constellation diagram according to the adopted modulation mode.

M-point FFT transform module 3: and the general module is used for transforming the M mapped signals of each frame to a frequency domain to obtain M point frequency domain signals of the signals.

The signal spectrum transformation module 4: the special module of the system, the base station sends back the sub-channel marking information through the multiple access module 23 and the reverse channel 21, the M point frequency domain signal output by the module 3 is placed on the corresponding frequency spectrum points of M available sub-channels, the corresponding frequency spectrum points of the forbidden sub-channels are set to zero, or non-information data is filled, and then the new frequency domain signal of the block transmission system of a frame of N points is obtained. This module needs to be programmed according to the method described in detail step (3) in the summary of the invention, and is implemented by a general digital signal processing chip.

N-point IFFT module 5: and the universal module is used for transforming the newly obtained frequency domain signal to the time domain.

And a CP adding module 6: and the universal module adds the cyclic prefix to each frame of obtained data.

D/A module 7: and the general module is used for converting the digital signal into an analog signal.

Intermediate frequency and radio frequency modulation module 8: and a general module, if the system is used in a wireless environment, the system needs to perform radio frequency modulation on signals to be transmitted to an antenna. Sometimes, the signal needs to be modulated to an intermediate frequency for intermediate frequency amplification, then radio frequency modulation, and finally the modulated signal is sent to an antenna for transmission.

Channel 9: and the universal module is a broadband mobile channel for transmitting signals.

Radio frequency and intermediate frequency demodulation module 10: and the general module is used for shifting the frequency spectrum of the signal received by the receiving antenna from radio frequency or intermediate frequency to low frequency in a wireless environment. Frequency offset caused during signal transmission needs to be corrected by frequency synchronization data before demodulation.

The A/D module 11: and the general module is used for converting the demodulated analog signal into a digital signal. The analog signal needs to be sampled by the a/D, and the crystal oscillator providing the clock signal needs to have the same frequency as the crystal oscillator of the D/a module of the transmitter, otherwise, a sampling rate error may result. The sampling rate synchronization is performed before the a/D.

The CP removing module 12: and the general module is used for removing the cyclic prefix. There is a problem in determining when a frame of data starts, and therefore timing synchronization is required before the CP is removed.

N-point FFT module 13: and the general module is used for transforming the CP-removed signal to a frequency domain.

The signal spectrum inverse transformation module 14: the system has special module to find out the M point frequency domain signal carried by the available sub-channel in the received signal according to the sub-channel mark information sent by the multiple access module 23 and the channel estimation module 18. This module needs to be programmed according to the method described in detail step (4) in the summary of the invention, and is implemented by a general digital signal processing chip.

The equalization module 15: the general module equalizes the signal selected by the inverse signal spectrum transform module 14 by using the available sub-channel parameters (channel state information) sent by the channel estimation module 18. The equalization mode can select one of the following three equalization modes: zero-forcing equalization, minimum mean square error equalization, and mixed mode equalization.

M-point IFFT transformation module 16: and the general module is used for transforming the M frequency domain signals of the equalized signals to a time domain.

A decision module 17: and the universal module is used for finishing the judgment of the time domain signal according to the modulation mode adopted by the system.

The channel estimation module 18: and the general module is used for acquiring the channel state. The channel state information may be obtained in different ways, such as channel prediction, an auxiliary data based channel estimation method, a decision feedback channel tracking method, etc. The embodiment provides a channel state acquisition method which is training frame and decision feedback tracking. This method is briefly described below:

the method for training frame and decision feedback tracking is that firstly, a training frame is sent to estimate a channel, and a symbol after decision is reconstructed by a following data frame according to a decision result:

assuming that the discrete time domain of the received signal is R ' (k), (k ═ 0, 1, …, N-1), and the discrete time domain is transformed into the frequency domain to obtain R ' (k), (k ═ 0, 1, …, N-1), the time domain symbol after the decision of the data frame is R ' (k), (k ═ 0, 1, …, N-1)

(M-0, 1, …, M-1), symbol mapping is performed according to the modulation scheme adopted by the mobile station, and the reconstructed symbol is obtained(M-0, 1, …, M-1) by M-point orthogonal transformation(M-0, 1, …, M-1) transform to the transform domain(M-0, 1, …, M-1), which is the frequency domain symbol reconstructed according to the decision result, and the method for tracking the channel by using the reconstructed frequency domain symbol is as follows:

<math> <mrow> <msup> <mi>H</mi> <mo>&prime;</mo> </msup> <mrow> <mo>(</mo> <mi>m</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <msup> <mi>R</mi> <mo>&prime;</mo> </msup> <mrow> <mo>(</mo> <msub> <mi>k</mi> <mi>m</mi> </msub> <mo>)</mo> </mrow> <mo>/</mo> <msup> <mover> <mi>S</mi> <mo>~</mo> </mover> <mo>&prime;</mo> </msup> <mrow> <mo>(</mo> <mi>m</mi> <mo>)</mo> </mrow> <mo>,</mo> </mtd> <mtd> <msub> <mi>A</mi> <mi>u</mi> </msub> <mrow> <mo>(</mo> <mi>m</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>1</mn> </mtd> </mtr> <mtr> <mtd> <mi>H</mi> <mrow> <mo>(</mo> <msub> <mi>k</mi> <mi>m</mi> </msub> <mo>)</mo> </mrow> <mo>,</mo> </mtd> <mtd> <msub> <mi>A</mi> <mi>u</mi> </msub> <mrow> <mo>(</mo> <mi>m</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>0</mn> </mtd> </mtr> </mtable> </mfenced> </mrow> </math>

wherein, H (k)_m) Channel state information of a previous frame for the system. Where k is_mAnd (M-0, 1, …, M-1) is an overall index of M available subchannels.

Since only a portion of the subchannels have decision symbols, tracking is only performed for the available subchannels. And after a period of time, the training frame is sent again to eliminate the error accumulation caused by tracking. It should be noted that, the tracking method does not utilize the reconstructed symbols on all available sub-channels, but only utilizes the frequency domain symbols with the amplitude greater than a certain threshold, and for the sub-channels with the amplitude less than the threshold, the frequency domain CSI is not updated, i.e. the value at the previous time is kept unchanged.

The adaptive frequency selection judging module 19: the special module of the system obtains the amplitude gain | H (k) of the sub-channel according to the CSI updated by each frame transmitted by the channel estimation or prediction module 18_i) And |, (i ═ 0, 1, …, M-1) and available subchannel flag information. Different decision rules may be used. If the judgment result is that frequency re-selection is needed, controlling the frequency selection module 20 to work; the originating always works according to the latest acquired sub-channel marking information when transmitting a new frame of data. The following is given

Implementation examples:

after acquiring the CSI on the sub-channel, the used method for determining is as follows: calculating the current signal-to-noise ratio after equalization, namely the actual signal-to-noise ratio after equalization, and making a difference value with the signal-to-noise ratio after the expected equalization, if the absolute value of the obtained difference value is greater than a threshold, re-selecting the frequency, otherwise, keeping the current channel marking information unchanged; the threshold value is 1dB in the simulation of the embodiment;

the frequency selection module 20: the system is characterized by comprising a special module, a channel state information of a subchannel group u obtained by a channel estimation module 18 selects an available subchannel, the available subchannel is marked by 1 bit information (0 or 1) according to the availability of the channel to form subchannel marking information, the subchannel marking information is simultaneously sent to a signal spectrum inverse transformation module 14, a reverse channel 21 and a self-adaptive frequency selection judgment module 19, and the signal spectrum inverse transformation module 4 of the mobile station is sent back through the reverse channel; this module needs to be programmed according to the method described in the chinese patent application No. 200410036439.6 mentioned in the background, and is implemented by a general digital signal processing chip.

Reverse channel 21: and the general module is used for transmitting the sub-channel mark information back to the mobile station.

The synchronization module 22: and the universal module is used for obtaining various synchronous data required by the system through parameter estimation. The synchronization module sends the frequency synchronization data to the radio frequency and intermediate frequency demodulation module 10; sending the sampling rate synchronization data to the analog-to-digital conversion module 11; the timing synchronization data is sent to the de-CP module 12.

The multiple access control module 23: when establishing communication, the base station obtains the channel state information of each user by the channel estimation module 18, allocates a sub-channel group to each user and makes the access of the user be quasi-synchronous access, i.e. the time for transmitting data to the mobile station by the user is controlled, the CP of different users are aligned at the base station, but the frame timing of part of users is allowed to be advanced a little (generally, several sampling values are advanced), which is the same as the access control mechanism of OFDMA. The function of the module is the same as that of a multiple access control module in OFDMA. In this embodiment, the scheme for establishing the subchannel group u is that all the subchannels of the subchannel group u are distributed in the whole bandwidth at certain intervals, the size of the interval is equal to the number of users, and the number of subchannels of all the subchannel groups u is the same.

Simulation parameters of this embodiment:

simulation environment: matlab7.0.1

Total number of subchannels: n1024

Modulation mode: QPSK, 16QAM

CP Length: 256

Data sampling rate: 40M

Maximum doppler frequency: 100Hz 200Hz 300Hz

Transmission signal-to-noise ratio: 2dB, 10dB

Time-varying channel model:

ITU IMT2000 Vehichlar Test Environment channel model A

reference is made to RECOMMENDING ITU-R M.1225GUIDELLINES FOR EVALUATION OF RADIIONTRANSMISSION TECHNOLOGIES FOR IMT-2000

The influence of synchronization errors (including carrier synchronization errors, sampling rate synchronization errors and frame timing synchronization errors) on the system is not considered in the simulation, namely, the errors of all synchronization parameters are assumed to be 0; the influence of transmission delay and transmission error code when the reverse channel transmits back the available sub-channel is not considered, that is, the transmission delay and the error code are both assumed to be 0; the influence of other non-ideal factors (such as the non-linearity of the device and the like) is not considered; the interference of co-channel cells is not considered.

And (3) simulation results:

1.64 subchannel users, subchannel groups: 1mod (16)

2.8 subchannel users, subchannel groups: 4mod (128) of the number of bits,

to avoid confusion, some of the terms mentioned in this specification are to be interpreted as follows:

symbol 1: refers to data in which information bits are modulation mapped (also referred to as symbol mapped). Typically a complex number where the real and imaginary parts are integers.

2 one frame signal: for OFDM, a frame signal refers to N symbols for IFFT at the transmitting end and N symbols for FFT at the base station after CP removal. For SC-FDE, a frame of signal refers to N information symbols between two adjacent CPs at the transmitting end, and refers to N symbols for FFT transformation after the CPs are removed at the base station. For the SC-FDE system realized by the method provided by the invention, a frame of signal refers to M symbols for FFT transformation at a transmitting end, and refers to M symbols for IFFT transformation after equalization at a base station.

3, sub-channel: for OFDM, SC-FDE baseband signals, a subchannel refers to a frequency point after the FFT of the base station. For a radio frequency channel, a subchannel refers to a segment of the frequency spectrum of the radio frequency channel.

4 subchannel group: a set of subchannels allocated to a user.

5 signal-to-noise ratio: the ratio of signal power to noise power, where the signal-to-noise ratio mentioned in the summary and claims section is log-log, without units; the signal-to-noise ratio mentioned in the examples is a logarithmic signal-to-noise ratio in dB.

6 signal-to-noise ratio after equalization: the ratio of signal power to noise power after equalization.

Desired post-equalization signal-to-noise ratio: minimum post-equalization signal-to-noise ratio for different error performance requirements.

Claims (4)

1. An uplink frequency division multiple access method of a frequency selective block transmission system, the method comprising the steps of:

(1) the mobile station U sends a signal to apply for accessing the base station, the base station distributes a group of sub-channels for the base station according to the service requirement and available spectrum resources, the sub-channels are recorded as a sub-channel group U, relevant information of the sub-channel group U, namely label information of each sub-channel in the sub-channel group U, is sent to the mobile station U, and the mobile station U is requested to send auxiliary data for channel estimation;

(2) the base station carries out channel estimation, acquires the channel state information of the sub-channel group u, carries out frequency selection, selects M available sub-channels, obtains the sub-channel mark information of the sub-channel group u, and sends the sub-channel mark information of the sub-channel group u to the mobile station;

(3) the mobile station carries out orthogonal transformation on the transmitted signal according to the received subchannel marking information of the subchannel group u, maps the orthogonal transformation into an N-dimensional vector, transmits the N-dimensional vector after transforming the N-dimensional vector into a time domain, and transmits a signal carrying information to the base station;

(4) the base station transforms the received sampling signal to a frequency domain, performs frequency domain equalization on the received signal according to the sub-channel marking information of the sub-channel group u, selects M useful signals on the available sub-channels, performs orthogonal inverse transformation, transforms the useful signals back to time domain signals and completes judgment to obtain information data;

(5) according to the requirement, the base station changes the sub-channel group u to other sub-channel groups in the communication process, or keeps the sub-channel group u unchanged and only changes the sub-channel mark information in the sub-channel group u; after the change, the base station sends the changed identification information of the sub-channel group or the sub-channel marking information of the sub-channel group u to the mobile station, and the mobile station always communicates with the base station according to the recently received identification information of the sub-channel group or the sub-channel marking information.

2. The uplink frequency division multiple access method of the frequency-selective block transmission system according to claim 1, wherein: the method for the mobile station U to perform orthogonal transformation on the transmission signal according to the received subchannel flag information of the subchannel set U in the step (3) is as follows:

the mobile station carries out symbol mapping according to the adopted modulation mode to form a frame of M symbols to be transmitted, carries out orthogonal transformation on the M symbols to obtain M transformation domain symbols, expands the M transformation domain symbols into N-dimensional vectors according to the sub-channel mark information to obtain a frequency domain form of a signal to be transmitted, transforms the N-dimensional frequency domain signal back to a time domain and transmits the time domain signal, when M is not an integral power of 2, the orthogonal transformation can be realized in a blocking way, and different blocks can use the same or different orthogonal transformations;

the specific method for expanding the M transform domain symbols into N-dimensional vectors according to the channel marking information is as follows:

after receiving the subchannel marking information sent back by the base station, the mobile station U transmits signals by using only M available subchannels, thus performing M-point orthogonal transformation to transform domain for a frame of M blocks of transmission system symbols s (n), (n ═ 0, 1, …, M-1) of the mobile station:

S＝Fs

wherein F is an M-point orthogonal transform matrix, S ═ { S (n), n ═ 0, 1, …, M-1} is M time domain symbols of the block transmission system, S ═ { S (i), i ═ 0, 1, …, M-1} is M transform domain symbols;

expanding M transform domain symbols S ═ { S (M), M ═ 0, 1, …, M-1} into an N-dimensional vector S '═ { S' (k), k ═ 0, 1, …, N-1}, where M transform domain symbols correspond one-to-one to M available subchannels of subchannel group u, e.g., S corresponds to M available subchannels in order of their overall index:

let S '{ S' (k), k ═ 0, 1 … N-1} th_mOne component is equal to S (m), and zero or some non-information data is placed on the components corresponding to other sub-channels of the sub-channel group u; all the sub-channels which do not belong to the sub-channel group u are set to be zero;

where k is_m(M-0, 1, …, M-1) is an overall index of the M available subchannels in the subchannel set U;

then, N-point inverse discrete fourier transform is performed on S' (k), (k is 0, 1, …, N-1), which can be implemented by an inverse fast fourier transform algorithm:

<math> <mrow> <msup> <mi>s</mi> <mo>&prime;</mo> </msup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mn>1</mn> <mi>N</mi> </mfrac> <munderover> <mi>&Sigma;</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <mi>N</mi> <mo>-</mo> <mn>1</mn> </mrow> </munderover> <msup> <mi>S</mi> <mo>&prime;</mo> </msup> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;</mi> </mrow> <mi>N</mi> </mfrac> <mi>nk</mi> </mrow> </msup> <mo>,</mo> </mrow> </math> (n＝0，1，…，N-1)

the time domain signal is changed into a time domain signal, the IFFT points are more than n when the time domain signal is over-sampled, the high frequency part is set to be zero, and the time domain signal is sent out after being subjected to D/A conversion and then subjected to carrier modulation.

3. The uplink frequency division multiple access method of the frequency-selective block transmission system according to claim 1, wherein: the specific implementation method for selecting the signal on the available sub-channel according to the sub-channel mark information in the step (4) is as follows:

the time domain discrete signal with the CP removed from the signal received by the base station is set as follows:

r′(n)＝s′(n)*h(n)+w(n)，(n＝0，1，…，N-1)

and performing N-point DFT on the obtained data:

<math> <mrow> <msup> <mi>R</mi> <mo>&prime;</mo> </msup> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <mi>N</mi> <mo>-</mo> <mn>1</mn> </mrow> </munderover> <msup> <mi>r</mi> <mo>&prime;</mo> </msup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;</mi> </mrow> <mi>N</mi> </mfrac> <mi>nk</mi> </mrow> </msup> <mo>,</mo> </mrow> </math> (k-0, 1, …, N-1) and,

R′(k)＝S′(k)H(k)+W(k)，(k＝0，1，…，N-1)

in this way, the signals r (M), (M ═ 0, 1, …, M-1) on the M available subchannels can be collectively selected based on the flag information of the subchannel group u and the corresponding subchannel flag information. For example, for the aforementioned spectral transformation methods, we have:

R(m)＝R′(k_m) This isRik_mAnd (M-0, 1, …, M-1) is an overall index of M available subchannels.

4. The uplink frequency division multiple access method of the frequency-selective block transmission system according to claim 1, wherein: selecting the number of available sub-channels M occupying the number of sub-channels B in the sub-channel group u in the step (4)_uBetween 5% and 100%.