CN100544239C - Interleaving Method for Orthogonal Frequency Division Multiplexing Communication - Google Patents

Abstract

The present invention relates to an interleaving method in an OFDM system, which utilizes a two-dimensional time-frequency structure of the OFDM system. The method comprises the following steps: dividing the available frequency band into a number of sub-bands, each sub-band comprising substantially only adjacent frequencies; mapping the sequence of constellation symbols into a sequence of OFDM cells, where an OFDM cell comprises a set of constellation symbols, after which the constellation symbols are processed only in a group-wise or OFDM cell-wise manner; and interleaving a sequence of OFDM units, where each OFDM unit may be mapped onto one of the subbands. Preferably, the last step is performed separately for the real and imaginary parts of the OFDM unit, respectively. The invention also relates to a transmitter and a system.

Description

Interleaving Method for Orthogonal Frequency Division Multiplexing Communication

technical field

The invention relates to the field of wireless communication systems, in particular to an improved interleaving method for OFDM (Orthogonal Frequency Division Multiplexing) communication.

Background technique

OFDM (Orthogonal Frequency Division Multiplexing) is a transmission technique that achieves high data rates over noisy channels with relatively low complexity, and is used in Digital Audio Broadcasting (DAB) and Digital Video Broadcasting (DVB). OFDM has some good properties, such as high spectral efficiency and robustness to channel dispersion, so it will likely be used in future broadband applications such as digital mobile wireless communications.

Briefly, in an OFDM system, the data to be transmitted is modulated and spread over a large number of carriers, and the rate of data transferred by each of these carriers is proportional to the number of carriers and thus decreases. These carriers have equal, precisely selected frequency spacing, and the frequency bands of the subcarriers are not separated but overlap. By using IFFT (Inverse Fast Fourier Transform) as the modulation, the spacing of the subcarriers is chosen in such a way that the signal modulated by a certain subcarrier is correctly recovered from the received signal, while all other signals are zero. Carrier spacing is selected to ensure its orthogonality, which is also the origin of OFDM.

A properly designed OFDM system transforms a scatter-fading channel into a flat-fading channel without advanced time-domain equalizers. This provides clear implementation advantages as no equalizer is required and thus reduces transceiver complexity, but it also results in the system not being able to obtain the frequency diversity offered by the channel. In contrast to single-carrier communication systems, for which a well-designed equalizer can capture the frequency diversity available in the channel, OFDM systems must resort to specific methods to achieve the higher order diversity performance offered by the wireless environment.

This is well known in the literature on OFDM, and an accepted method of capturing channel frequency diversity is to use a code (such as a convolutional code or a turbo code) whose output bits are modulated and spread over all subcarriers . As described in 'A comparison of a single-carrier system using a DFE and a coded OFDM system in a broadcast Rayleigh-fading charnnel' by S.K. Wilson and J.M. Cioffi (International Symposium on Information Theory (ISIT), September 1995), This method captures the available frequency diversity as long as the code's diversity multiplicity is greater than the channel's frequency diversity multiplicity.

Because OFDM effectively creates a set of flat-fading channels, any technique designed to improve communication performance over flat-fading channels can be applied to OFDM.

One way to improve the diversity performance of normally uncoded (ie no redundancy is added to the information bit stream) communication signals in flat fading channels is to increase the diversity multiplicity of the modulation symbols, ie to increase the so-called modulation diversity. This alternative is analyzed in "Signal Space Diversity: A Power-and Bandwidth-Efficient Diversity Technique for the Rayleigh Fading Channel" (IEEE Transactions on Information Theory, Vol. 44, No. 4, July 1998, Joseph Boutros and Emanuele Viterbo) Diversity technology. Modulation diversity is increased by applying some rotation to the conventional signal constellation in such a way that any two constellation points obtain the maximum number of distinct components. The fading of the transmitted signal vector is thus spread over many components and better protection against noise effects is achieved, since those components are affected by fading differently and no two points are corrupted at the same time. It is shown in this document that multidimensional QAM (Quadrature Amplitude Modulation) constellations become insensitive to fading when the modulation diversity is large.

However, the above-mentioned literature assumes ideal interleaving and does not take advantage of any special characteristics of OFDM systems, especially does not take advantage of any characteristics of multi-user OFDM systems (in a multi-user OFDM system, within each OFDM symbol interval, a single user only uses the total available part of the spectrum). The disadvantage of modulation diversity is that in the case of non-ideal interleaving, the performance gain may be insignificant.

Further related prior art is found in "On the Design of Multidimensional Signal Sets for OFDM Systems" by Dennis L. Goeckel and Ganesh Ananthaswamy (IEEE Transactions on Communications, Vol. 50, No. 3, March 2002). In this document, "combining several subcarriers, transmitting symbols from a multi-dimensional constellation" is developed for a conventional OFDM transmission system. A coded modulation technique is proposed: symbols are selected from a multi-dimensional complex signal set, and each dimension of the selected symbol is modulated with a subcarrier selected by OFDM system, thus obtaining diversity gain. In this document, the transmission of the constellation symbol components is modulated with scattered subcarriers in each OFDM symbol interval. This approach has some drawbacks. First, this document does not describe the application to multi-user systems. Even if it can be applied to a multi-user system, it is difficult to perform channel estimation due to the dispersed characteristics of sub-carriers. Second, the detection is more complicated due to the specific, non-standard, non-rotated constellation structure; third, the performance in Gaussian channels is not optimal.

On frequency-selective fading channels, a typical uncoded OFDM system achieves significantly less diversity than an uncoded single-carrier system using an appropriate channel equalizer. One way to reproduce the frequency diversity of an OFDM system is to apply coding/interleaving on the subcarriers, another way is to use a high diversity symbol constellation (a finite set of real-valued vectors to which coded bits are mapped) that has Commonly referred to as signal space diversity or component interleaving of modulation diversity, the advantage of the first method is that the diversity brought about by channel coding redundancy produces additional performance gain, but the cost is an increase in bandwidth. The advantage of the second method is that frequency diversity can be obtained without any increase in bandwidth (no redundancy). However, both methods require an appropriate interleaving scheme to decorrelate the symbols and the symbol components, respectively.

Because one interleaving scheme may yield significantly worse performance than another, it is desirable to provide an OFDM interleaving scheme that optimizes diversity performance in all coded OFDM systems including, exploiting redundant OFDM systems that use codes such as convolutional codes and OFDM systems that utilize non-redundant codes such as modulation diversity.

Further, another object is that in the case of multi-user OFDM, all users in the system can obtain diversity gain.

Therefore, there is a need for an OFDM interleaving method that can optimize the diversity performance of an OFDM system.

Contents of the invention

The object of the present invention is to provide an interleaving method in an OFDM system which optimizes the diversity performance of the diversity method used to create frequency diversity.

It is a further object of the present invention to provide diversity gain to all users of an OFDM system.

Yet another object of the present invention is to provide higher frequency diversity without requiring increased bandwidth compared to known multi-user OFDM systems. Modulation diversity does not add any redundancy to the data stream, and diversity performance gains can thus be obtained while maintaining the data rate.

According to a first aspect of the present invention, by an interleaving method in an OFDM system, a transmitter applied in an OFDM system and an OFDM for signal communication between at least one transmitter and a receiver Wireless communication system to achieve these goals.

According to the present invention, there is provided a method for interleaving in an OFDM system, wherein the method utilizes the two-dimensional time-frequency structure of the OFDM system. The method includes the steps of: dividing the available frequency band into several sub-bands, each sub-band only includes necessary adjacent frequencies; mapping the constellation symbol sequence to an OFDM unit sequence, wherein an OFDM unit is defined as a group of constellation symbols, where After the step, the constellation symbols are only processed in groups or in OFDM units; interleaving the sequence of OFDM units, where each OFDM unit can be mapped onto one of the sub-bands. Preferably, said interleaving is performed separately and separately for the real and imaginary parts of the OFDM unit.

According to an embodiment of the present invention, the step of dividing the available OFDM frequency bandwidth into several sub-bands includes: dividing the frequency band into equal-sized sub-bands. This feature provides easy management of available resources. For example, channel allocation to a large number of users can be performed in a simple manner. It is also possible to use sub-bands of unequal frequencies, and thus provide the operator of the mobile communication system with great design flexibility.

According to another embodiment of the invention, the method is performed after the constellation mapping step. Therefore, this is an additional interleaving not performed in the prior art. This additional interleaving step, taking advantage of the time-frequency correlation structure of the OFDM system, provides additional diversity.

According to another embodiment of the present invention, the step of mapping the sequence of constellation symbols includes: after the rotation of the constellation symbols and the interleaving of the components of the constellation symbols, mapping the constellation symbols onto OFDM units. According to this feature, additional interleaving is performed after the interleaving of the components of the constellation symbols, thereby providing additional diversity.

According to another embodiment of the invention, the interleaving step is a time and frequency mapping of said sequence of OFDM units, wherein each OFDM unit is assigned a unique time and frequency band within the available transmission time interval and the available frequency spectrum. By means of this, the specific time-frequency correlation of the OFDM flat-fading channel is taken into account, and an additional frequency diversity of the channel is obtained.

According to another embodiment of the present invention, the mapping method used is randomized time-frequency mapping. It can be seen that this random mapping approach provides good diversity performance, but other approaches could equally be used. For example, different users may use different mapping methods only in time or frequency.

The invention also relates to a transmitter comprising means for performing the interleaving method. The invention also relates to a communication system comprising at least one said transmitter.

The above corresponding advantages are respectively realized by the transmitter and the system provided by the embodiments of the present invention.

When the invention is applied to a turbo coding system (or other methods using soft decisions), the soft bits fed to the first stage of the iterative decoder are improved. Therefore, the decoded bits have a lower probability of error than a system that does not achieve this diversity.

Furthermore, when applied to a multi-user system, all users in the system will obtain similar diversity improvements by means of the present invention.

The present invention also provides a method that can be easily merged with existing OFDM standards, making it an attractive alternative.

Description of drawings

Figure 1 illustrates a prior art method.

Figure 2 shows the basis of an OFDM system.

Figure 3 shows the last stage of the baseband stage of an OFDM transmitter, an illustration of OFDM elements and the grouping of frequency bands according to the invention.

Figure 4 shows a typical downlink transmitter processing chain.

Figure 5 shows the final stage of the OFDM transmitter processing chain according to the invention.

Figures 6a-d illustrate an exemplary time-frequency mapping approach for use in the present invention.

Figures 7-8 show some experimental results.

Detailed ways

As explained in the introductory section, OFDM effectively creates a set of flat-fading channels, and any technique designed to improve communication performance over flat-fading channels can be applied to OFDM. However, the specific correlation structure of OFDM flat-fading channels offers special opportunities for improvement, as recognized by the inventors of the present invention. Specifically, multi-carrier systems such as OFDM have a two-dimensional structure (time dimension and frequency dimension), which provides designers with conditions for diversity gain from frequency correlation and time correlation, respectively.

In a multi-user OFDM system, a single user only uses a part of the total available spectrum in each OFDM symbol interval. It provides additional time-frequency interleaving opportunities, such as combining the existing data bit interleaving and constellation mapping, and can also obtain the potential frequency diversity gain of the channel.

As described earlier, in the paper "SignalSpace Diversity: A Power-and Bandwidth-Efficient Diversity Technique for the Rayleigh Fading Channel" by Joseph Boutros and Emanuele Viterbo (IEEE Transactions on Information Theory, Vol. 44, No. 4, July 1998) A method for achieving modulation diversity is provided. As explained earlier, the key to increasing modulation diversity is to apply some rotation to the conventional signal constellation in such a way that any two constellation points get as many distinct components as possible. Such a rotation operation will not change the performance on an AWGN (Additive White Gaussian Noise) channel, but will improve the performance on a flat Rayleigh fading channel. A basic requirement for such improved performance is that the real and imaginary parts of the transmitted signal are uncorrelated. To create this necessary condition, a so-called component interleaver is introduced in one of the quadrature branches of the signal. The component interleaver destroys the correlation between the in-phase and quadrature signal components so that only one of all the components of the transmitted constellation symbol experiences deep fading.

The method of the above prior art is shown in FIG. 1 . The inventors of the present invention have realized that this method done in accordance with the present invention can be adapted and implemented in an OFDM system. Figure 2 illustrates that the FFT (Fast Fourier Transform) and cyclic prefix in an OFDM system transforms a diffuse channel into a flat Rayleigh fading channel, and the inventors of the present invention have realized that modulation diversity is therefore applicable to OFDM systems. Accordingly, the present invention relates to a method to further improve modulation diversity gain by appropriate time-frequency interleaving in multiuser OFDM based on the spacing of OFDM elements in time and frequency compared to the modulation diversity gain described in the above references. Amplify diversity gain. The time-frequency interleaver of the OFDM unit makes the received constellation symbols of each pair of OFDM units as uncorrelated as possible in the frequency and time domains.

Referring now to Figure 3, some basic features of an OFDM transmitter as well as features according to the invention will be described. Here, an OFDM unit is defined as a set of constellation symbols mapped to one of several equal sub-bands within the total available spectrum. According to the invention, preferably the total frequency spectrum is divided into equal sub-bands. Equal frequency sub-bands are preferred as it facilitates resource management (eg easier allocation of available resources), but division into non-equal frequency sub-bands is also possible. The OFDM cells are fed into an Inverse Fast Fourier Transform (IFFT) processor where pulse formation and modulation is done. In the receiver, the reverse is done using a Fast Fourier Transform, which is well known to those skilled in the art. The signal is then fed to a parallel-serial unit (P/S), where N parallel data streams are combined into one data stream. Thereafter, the cyclic prefix is added.

Reference is now made to FIG. 4, which depicts typical processing performed by a transmitter on the downlink of a mobile communication system. The block of bits is first subjected to a Cyclic Redundancy Check (CRC) and then encoded eg using convolutional or turbo encoding. The resulting block of bits is then punctured and interleaved and mapped onto a complex constellation. After this level, there is a block of N _s complex-valued constellation symbols. Please refer to the 3rd Generation Partnership Project 3GPP TS 25.212V5.2.0 (2002-09) (eg Chapter 4.2) for details.

One embodiment of the invention is concerned with the final part of the transmitter processing chain: the mapping of N _s constellation symbols onto OFDM physical resources (characterized by subcarrier pointers and OFDM symbol spacing pointers), or physical channel mapping. However, the interleaving method according to the invention can be performed elsewhere in the transmission chain. Finally, each symbol in the N _s constellation symbols is mapped to an OFDM symbol interval and a part of FFT (subcarrier frequency) through this OFDM physical channel. The present invention subdivides the general structure of OFDM physical channel mapping into three stages, as will be described with reference to FIG. 4 .

Compared with the prior art method ("On the Design of Multidimensional Signal Sets for OFDM Systems") that uses dispersed subcarriers in each OFDM symbol interval to transmit constellation symbol components, the present invention performs grouping. While most of the sub-band frequencies are adjacent to each other, some offset frequencies may form part of a sub-band. These offset frequencies will be used for non-user traffic, such as pilot signals. Such aggregation of subcarriers simplifies channel estimation by providing better channel estimation conditions. OFDM channel estimation methods typically exploit the strong correlation of channel fading between adjacent subcarriers. Thus, knowing the attenuation at one frequency, this knowledge can be used to estimate the attenuation or fading at adjacent frequencies. Thus, the need to transmit pilot signals (ie known signal sequences) is reduced, one pilot signal per frequency does not need to be transmitted, and thus scarce resources can be saved and the data rate of user data can be increased.

Therefore, there are two contradictory aspects: on the one hand, it is desirable that the separation between groups be as large as possible in order to achieve diversity; on the other hand, it is desirable that the separation between groups is as small as possible, because this will help channel estimation . The present invention reconciles these two aspects, since the available frequency band is divided into several sub-bands (ie essentially only adjacent groups of sub-carriers are aggregated) and at the same time provides modulation diversity (by appropriate time-frequency interleaving).

As explained before, the time-frequency interleaver of the OFDM unit makes the constellation symbols received by each pair of OFDM units as uncorrelated as possible in the frequency and time domains. In particular, and with reference to Figure 4, the OFDM time-frequency interleaver according to the present invention consists of three basic stages as follows:

1. Mapping of constellation symbol sequence to OFDM unit sequence. After this stage, constellation symbols are only processed in groups or OFDM units. Specifically, after the rotation of the constellation symbol and the interleaving of the constellation symbol components, the mapping of the constellation symbol to the OFDM unit is completed.

2. OFDM unit interleaving. A sequence of OFDM units is interleaved. This is an additional (as used in the example) interleaving which is not performed in the prior art, and preferably the real and imaginary parts of the OFDM units are interleaved separately.

3. Time-frequency mapping of a sequence of OFDM elements (ie a set of constellation symbols). Wherein, each OFDM unit is assigned an available transmission time interval and a unique time and frequency band within the available spectrum.

Stages 2 and 3 provide the desired diversity gain. If the above three stages are similar for different users, all users of the system will get similar diversity improvement. For example, if the same interleaving is performed in the first two stages, and only the mapping pattern used in the third stage is different, there is an offset in time and/or frequency.

First, after constellation mapping, the resulting N _s constellation symbols are mapped onto N _OFDM OFDM units. Each OFDM cell is here just a set of constellation symbols, and generally all OFDM cells contain an equal number of constellation symbols. The constellation symbols are grouped so that each group can be mapped onto a specific frequency subband.

Second, the OFDM unit interleaver is used to optimize the performance of the bit interleaver (appeared earlier in the transmitter chain, see Figure 3) by taking into account the 2-dimensional correlation properties of the wireless channel. An OFDM unit interleaver can be described by a permutation vector I of N _OFDM consecutive OFDM units. The OFDM unit interleaver can be made explicit by setting the permutation vector I = [1 2 3 . . . N _OFDM ].

According to a preferred embodiment, the real and imaginary parts of the OFDM cells are mapped separately. Thereby a better diversity gain is obtained and more effective against the effects of noise present in the system, since neither component is assumed to experience deep fading. The real part of the signal is mapped onto one specific subband and the imaginary part onto other subbands.

Finally, the sequence of interleaved OFDM units is mapped onto a physical channel. For this purpose, the entire available OFDM frequency band is divided into N _B frequency sub-bands as described above. A single physical channel uses only 1/N _B of the total available aggregate resources for the duration of N _{sym_int} OFDM unit intervals, meaning: there may be up to N _B parallel users or up to N _B parallel physical channels for a single user , achieving extremely fast data rates for a single user.

The size of the OFDM unit (ie the number of constellation symbols) is such that each frequency sub-band contains one OFDM unit within each OFDM symbol interval. This means that a maximum of N _B parallel OFDM units can be transmitted in each OFDM symbol interval.

When performing the third stage of time-frequency (TF) mapping, each user can specify a specific pattern, see Fig. 6a-d. In Figs. 6a-d different modes for use in the third stage are illustrated and four different exemplary modes are shown, _NB = 15 and N _{sym_int} = 12 and N _OFDM = 12. Note: N _OFDM = N _{sym_int} is not necessarily the case. If these parameters are different, then N _B N _{sym_int} resources can fit N _OFDM streams over N _B OFDM units.

The randomized T-F mapping D in Fig. 6d is a preferred embodiment and shows ITU-channel VA120 (Vehicle A at 120 km/h in terms of bit error rate and frame error rate, see 3GPP TR25.890 V1.0.0 for details 2002-05) and PB3 (pedestrian B at 3km/h, details see 3GPP TR 25.890V1.0.0, 2002-05) the best performance of T-F mapping in some channel environments as shown in Fig. 6a-d A-D. Fig. 7 shows some test results illustrating the performance of the T-F mapping of Fig. 6a-d. In Fig. 7, the bit error rate (BER) at the time of mapping as shown in Fig. 6a-d for the ITU-specified channel environment (vehicle A, 120 km/h) is plotted. The randomized T-F map D in Fig. 6d is the preferred embodiment and shows the best performance in certain channel environments as can be seen in Fig. 8 . In FIG. 8 , the bit error rate (BER) of the ITU-specified channel environment (vehicle A, 120 km/h) is plotted once again when mapped as shown in FIG. 6d. Tests were performed with and without coded and with and without modulation diversity. Eight iterations are performed in the turbo decoder. As can be seen, the modulation diversity approach according to the invention greatly improves the performance.

The time-frequency mapping of OFDM cells is characterized by two parameters per OFDM cell: one indicating the OFDM symbol time interval and one indicating the selected frequency sub-band. These parameters may be grouped in the T vector of OFDM symbol interval indices contained in the range {1, N _OFDM } and the F vector of the corresponding subband indices of each OFDM cell contained in the range {1, N _B }. For the kth input of the OFDM unit, its TF mapping is determined by the corresponding T and F values at the kth position.

The mapping used will yield the best diversity performance in any channel environment. It should be so: make each pair of OFDM unit pairs receive constellation symbols as uncorrelated as possible in the frequency and time domains.

A typical way to divide the signal components is to divide them into real and imaginary components, respectively, or equivalently, into in-phase and quadrature components. When the method according to the invention combines modulation diversity to improve performance, it is important to interleave the real and imaginary parts separately. When the method according to the invention is generally used to improve the performance of coded OFDM systems, the interleaving of the sequence of OFDM units can be done in other ways.

The mapping can be done by trial-and-error in one embodiment, or by channel selection in another embodiment.

As is known in the art, soft-decision decoding brings greater determinism to the decoding, since both sign and magnitude measures of the received signal (hard-decision) are considered. In an OFDM system data is modulated onto several carriers, and different carriers will have different signal-to-noise ratios and will therefore experience different fading. Preferably, since the method according to the invention interleaves the real and imaginary parts separately on different sub-bands, there is little probability that both components are lost, or in other words, at least one uncorrupted component is received more likely. Thus, when the present invention is applied to turbo coded systems (or other systems using soft decisions), the soft bits fed to the first stage iterative decoder are improved. Therefore, the decoded bits will have a lower probability of error than a system that does not achieve this diversity.

The invention can be used in the high-speed downlink shared channel (HS-DSCH) of the third generation cellular system in the multi-user OFDM-based transmission system.

The present invention provides a method that can be easily merged with or added to existing standards, such as ETSI 3GPP TS 25 212 V5.2.0 (2009-09), 3GPP TSG RAN: Multiplexing and Channeling Encoding (FDD) (version 5). The present invention is therefore a very attractive and practical alternative.

The invention has been described in conjunction with preferred embodiments. Obviously, many alternatives, modifications, variations and uses will be apparent to those skilled in the art in view of the foregoing description. For example, the interleaving method according to the present invention has been described in connection with a channel mapping stage. However, the invention is not limited thereto, and the interleaving method according to the invention may be used for the first (and possibly only) interleaving, or as an interleaving step elsewhere in the transmission chain. Those skilled in the art can implement corresponding deinterleaving in the receiving chain.

Claims (19)

1. deinterleaving method in ofdm system is characterized in that: described method adopts the two-dimensional time-frequency structure of ofdm system, and comprises the steps:

Available band is divided into plurality of sub-bands, and each sub-band comprises adjacent frequency,

The constellation symbol sequence is mapped as the OFDM unit sequence, and wherein, defining an OFDM unit is one group of constellation symbol, and after this step, constellation symbol is only processed in the mode of group;

The OFDM unit sequence that interweaves, wherein, each OFDM unit is mapped on one of described sub-band.

2. deinterleaving method as claimed in claim 1 is characterized in that: the described step that available band is divided into plurality of sub-bands comprises: the sub-band that frequency band division is become equal sizes.

3. deinterleaving method as claimed in claim 1 is characterized in that: the described step that available band is divided into plurality of sub-bands comprises: the sub-band that frequency band division is become non-equal sizes.

4. as any one described deinterleaving method of claim 1-3, it is characterized in that: the step of the described OFDM of interweaving unit sequence comprises: interleaved signal component respectively.

5. deinterleaving method as claimed in claim 4 is characterized in that: the step of the described OFDM of interweaving unit sequence comprises: real part and imaginary part discretely interweave respectively.

6. as any one described deinterleaving method of claim 1-3, it is characterized in that: after the constellation mapping step, carry out this method.

7. as any one described deinterleaving method of claim 1-3, it is characterized in that: the step of described mapped constellation symbol sebolic addressing comprises: the rotation constellation symbol after constellation symbol mapped to the OFDM unit.

8. as any one described deinterleaving method of claim 1-3, it is characterized in that: time and frequency map that the described step that interweaves is the OFDM unit sequence, wherein, be unique time and frequency band in each OFDM unit distribution available transmission time interval and the usable spectrum.

9. as any one described deinterleaving method of claim 1-3, it is characterized in that: the mapped mode that employed each OFDM unit is mapped on one of described sub-band is randomized T/F mapping.

10. as any one described deinterleaving method of claim 1-3, it is characterized in that: this method is used for multi-user environment.

11. a transmitter that is applied in the ofdm system is characterized in that: this transmitter comprises,

Be used for available band is divided into the device of plurality of sub-bands, each sub-band comprises side frequency;

Be used for the constellation symbol sequence is mapped as the device of OFDM unit sequence, wherein, an OFDM unit is defined as one group of constellation symbol, and after this, constellation symbol is only processed in the mode of group;

Be used to the to interweave device of OFDM unit sequence, the real part and the imaginary part of the OFDM unit that interweaves discretely respectively, wherein, each OFDM unit is mapped on one of described sub-band.

12. transmitter as claimed in claim 11 is characterized in that: the described device that is used for available band is divided into plurality of sub-bands comprises, frequency band division is become the device of the sub-band of equal sizes.

13. transmitter as claimed in claim 11 is characterized in that: the described device that is used for bandwidth available is divided into plurality of sub-bands comprises, frequency band division is become the device of the sub-band of non-equal sizes.

14. as any one described transmitter of claim 11-13, it is characterized in that: the device of the described OFDM unit sequence that is used to interweave comprises and is used for the device of interleaved signal component discretely.

15. transmitter as claimed in claim 14 is characterized in that: the device of the described OFDM of interweaving unit sequence comprises the device of be used for interweaving discretely respectively real part and imaginary part.

16. as any one described transmitter of claim 11-13, it is characterized in that: the described device that is used for the mapped constellation symbol sebolic addressing comprises and being used for after the rotation constellation symbol the device of constellation symbol mapped to the OFDM unit.

17. as any one described transmitter of claim 11-13, it is characterized in that: the described device that is used to interweave comprises: be used for the time of OFDM unit sequence and the device of frequency map, wherein, each OFDM unit is assigned to unique time and the frequency band in the available transmission time interval and the usable spectrum.

18. as any one described transmitter of claim 11-13, it is characterized in that: the mapped mode that employed each OFDM unit is mapped on one of described sub-band is randomized T/F mapping.

19. an OFDM wireless communication system that is used for the signal communication between at least one transmitter and receiver, described communication system comprises any one described at least one transmitter as claim 11-18.

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