CN101282319B - Method for expanding band width of broadband radio communication system based on OFDM technique - Google Patents

Abstract

The invention relates to a bandwidth expanding method of a broadband wireless communication system based on the OFDM technology, comprising: after adjacent other wireless system releases a bandwidth, a spectral bandwidth of the broadband wireless communication system is expanded; a corresponding IFFT point is calculated according to the expanded spectral bandwidth, and the expanded IFFT point N of the broadband wireless communication system, namely a sub-carrier number comprised by the broadband wireless communication system is determined; in N sub-carriers, data is only modulated on the whole or a portion of sub-carriers in sub-carriers corresponding with the expanded bandwidth. The invention can fully and effectively make use of a scattered bandwidth near an evolvement system bandwidth.

Description

A kind of method for expanding band width of broadband radio communication system based on the OFDM technology

Technical field

The present invention relates to orthogonal frequency division multiplex OFDM, be specifically related to a kind of method for expanding band width of broadband radio communication system based on the OFDM technology.

Background technology

IMT Advanced GSM is the wideband wireless mobile communication technology in the 4th generation, at present the ITU of International Telecommunications Union the 4th generation mobile system 4G standard of formulation that begun one's study.The target of 4G is to make the mobile user data transmission rate reach 100Mbit/s before 2010, and the stationary user message transmission rate reaches 1Gbit/s.For this reason, the bandwidth of 4G can be up to 100MHz.Because GSM is smooth evolution, so, in order to protect benefits of operators, in the regular hour, the 4th generation communication system and 3-G (Generation Three mobile communication system), comprise TD-SCDMA system or 802.16E system etc., will coexist.When the carrier wave of IMT Advanced GSM and adjacent TD-SCDMA or the coexistence of 802.16E carrier wave; Operator is according to TD-SCDMA or the professional needs that shift toward IMT Advanced (4G) of 802.16e, the frequency resource that need effectively utilize TD-SCDMA or 802.16E to discharge.

As shown in Figure 1; Suppose IMT Advanced (4G) system of 20MHz bandwidth and the TD-SCDMA system adjacent frequency coexistence of 3 carrier frequency total bandwidth 5MHz; Operator divides three phases that three carrier frequency of TD-SCDMA are discharged, like this according to the professional needs that shift toward IMT Advanced (4G) of TD-SCDMA; At three phases, the available bandwidth of IMT Advanced (4G) expands to 21.6MHz and 23.2MHz respectively from 20MHz.Because the design bandwidth of IMT Advanced (4G) is 5,10MHz; Fixed-bandwidth such as 20MHz and 40MHz series; So; The frequency bandwidth that the original big bandwidth of little bandwidth that TD-SCDMA progressively discharges and IMT Advanced (4G) is formed is not the design bandwidth series of IMT Advanced (4G), make frequency spectrum resource can not be by in time, effectively and fully utilize.

Bandwidth expansion for other evolution system also has same problem.

Summary of the invention

The technical issues that need to address of the present invention provide a kind of broadband wireless communications bandwidth extended method based on the OFDM technology, can fully and effectively utilize the fragmentary bandwidth adjacent with the evolution system bandwidth.

Above-mentioned technical problem of the present invention solves like this, and a kind of method for expanding band width of broadband radio communication system based on the OFDM technology is provided, and it is characterized in that, may further comprise the steps:

(a) after adjacent other wireless communication systems discharged bandwidth

, the spectral bandwidth of expanding said system of broadband wireless communication was the bandwidth of this system of broadband wireless communication before this expansion to

;

(b) calculate according to the spectral bandwidth

after the expansion that corresponding IFFT counts

and confirm the IFFT points N of the said system of broadband wireless communication in expansion back; Also be its sub-carrier number that comprises, N is more than or equal to

(c) in the N number of sub-carrier, modulating data on all or part of subcarrier in frequency band pairing number of sub-carrier after expansion only.

Further, said method also can have following characteristics: the said system of broadband wireless communication of spread bandwidth is IMT Advanced system or IEEE802.16m system, and the bandwidth before this system extension is 20MHz, 40MHz, 60MHz, 80MHz or 100MHz.

Further, said method also can have following characteristics: the said wireless communication system that discharges bandwidth is TD-SCDMA, 802.16e or WCDMA or CDMA2000 system.

Further, said method also can have following characteristics: the frequency band before bandwidth that said wireless communication system the discharges place frequency band of release bandwidth and the expansion of said system of broadband wireless communication is adjacent.

Further, said method also can have following characteristics: have in the step (b):

${\left\{N_{\mathrm{FFT}}^{4G}\right\}}_2=\frac{n_1\×W_2^{4G}}{{\mathrm{\Δf}}_1}$

Wherein, n ₁Be the over-sampling rate of the said system of broadband wireless communication of spread bandwidth, Δ f ₁Subcarrier spacing for the said system of broadband wireless communication of spread bandwidth.

Further; Said method also can have following characteristics: in the step (b),

Further, said method also can have following characteristics: have in the step (b):

$N=2\×{\left\{N_{\mathrm{FFT}}^{4G}\right\}}_1,$ Wherein

${\left\{N_{\mathrm{FFT}}^{4G}\right\}}_1=\frac{n_1\×W_1^{4G}}{\mathrm{\Δ}{f}_1}$

Wherein, n ₁Be the over-sampling rate of the said system of broadband wireless communication of spread bandwidth, Δ f ₁Subcarrier spacing for the said system of broadband wireless communication of spread bandwidth.

Further; Said method also can have following characteristics: when adjacent other wireless systems discharge bandwidth once more; The spectral bandwidth of said system of broadband wireless communication is expanded to once more the bandwidth sum that this time discharges after bandwidth and expansion last time; Count like the IFFT after the last time expansion and to count more than or equal to the pairing IFFT of expansion back bandwidth once more; Then bandwidth belongs to modulating data on the subcarrier all or part of in the corresponding subcarrier of frequency band after expanding once more, has wherein increased all or part of subcarrier that this time discharges bandwidth place frequency band correspondence, power zero setting on all the other subcarriers; Bandwidth after the pairing IFFT of the said bandwidth of expansion back once more counts and equals system's over-sampling rate and multiply by this and expand once more, the value that obtains divided by the subcarrier spacing of system again.

Further; Said method also can have following characteristics: when adjacent other wireless systems discharge bandwidth once more; The spectral bandwidth of said system of broadband wireless communication is expanded to once more the bandwidth sum that this time discharges after bandwidth and expansion last time; Count like the IFFT after the last time expansion and to count less than the pairing IFFT of expansion back bandwidth once more; Then handle the bandwidth after the pairing IFFT of the said bandwidth of expansion back once more counts and equals system's over-sampling rate and multiply by this and expand once more, the value that obtains divided by the subcarrier spacing of system again by the mode of above-mentioned steps (a)～step (c).

Further, said method also can have following characteristics: after expansion, in the pairing subcarrier of frequency band the protection subcarrier is set, the protection sub-carrier power is put 0, modulating data on the subcarrier of remainder.

Further, said method also can have following characteristics: said power put 0 subcarrier be included in exceed under the over-sampling situation said expansion back frequency band the subcarrier outside the corresponding subcarrier.

Further, said method also can have following characteristics: will expand power zero setting on the subcarrier outside the frequency band of back in the step (c).

Further, said method also can have following characteristics: the sample frequency of the said wireless system of release bandwidth and the said system of broadband wireless communication of spread bandwidth is identical with subcarrier spacing.

The invention enables the system works bandwidth not receive the restriction of fixed standard series bandwidth, it is wide convenient and swift and fully to effectively utilize the adjacent zeros star braid, can satisfy operator progressively upgrade communication apparatus, protect the needs of its network investment; In addition; When being the system of 802.16e for adjacent sub-carrier; If the sample frequency of IMTAdvanced (4G) and subcarrier spacing are identical with the 802.16e system; Just can guarantee to receive the subcarrier of subcarrier and former 802.16E of IMT Advanced (4G) after the new bandwidth mutually orthogonal,, then receive the use that does not influence the 802.16e terminal after the new bandwidth if contain the bandwidth of promising 802.16e terminal distribution in IMT Advanced (4G) system before the original absorption band.

Description of drawings

Further the present invention is elaborated below in conjunction with accompanying drawing and specific embodiment.

The little bandwidth that Fig. 1 progressively discharges for TD-SCDMA incorporates the IMT-Advanced system schematic gradually.

Fig. 2 is that the IMT-Advanced system of 20MHz passes through 2048 the formed subcarrier sketch map of IFFT conversion.

Fig. 3 merges after the adjacent 5MHzTD-SCDMA system formed subcarrier of IFFT conversion and power zero setting sketch map through 4096 for adopting the IMT-Advanced system of 20MHz behind the present invention.

Fig. 4 merges IFFT conversion formed subcarrier and the power zero setting sketch map of adjacent 5MHz TD-SCDMA system through 4096 for adopting the 20MHz IMT-Advanced system that has boundary belt behind the present invention.

Fig. 5-1 and Fig. 5-2 merge IFFT conversion formed subcarrier and the power zero setting sketch map of adjacent 5MHz TD-SCDMA system through 4096 for adopting the 20MHz IMT-Advanced system that has over-sampling behind the present invention.

Embodiment

Frequency division multiplexing Orthogonal Frequency Division Multiplexing is called for short the OFDM technology, is the high speed transmission technology under a kind of wireless environment.The frequency response curve of wireless channel is non-flat forms mostly, and the main thought of OFDM technology is divided into many orthogonal sub-channels with given channel exactly in frequency domain, on each subchannel, uses a number of sub-carrier to modulate, and each subcarrier parallel transmission.Like this, although total channel be non-flat forms, have frequency selectivity; But each subchannel is a relatively flat; What on each subchannel, carry out is narrow band transmission, and signal bandwidth is less than the respective bandwidth of channel, so the just interference between the erasure signal waveform greatly.Because the carrier wave of each subchannel is mutually orthogonal in ofdm system, so their frequency spectrum is overlapped, has so not only reduced the phase mutual interference between subcarrier, improved the availability of frequency spectrum simultaneously again.

(2) the OFDM modulation can realize given channel is divided into many orthogonal sub-carriers through IFFT, and its expression formula is:

$x_N\left(m\right)=\frac{1}{\sqrt{N}}\underset{i=0}{\overset{N-1}{\mathrm{\Σ}}}s\left(i\right)e^{j(2\mathrm{\π}/N)\mathrm{im}}---\left(4\right)$

Wherein, N is a sub-carrier number, also is counting of IFFT conversion.S (i) is that binary data carries out the data symbol after the digital modulation, x on the i number of sub-carrier _N(m) be the signal after the modulation.

Below, the contractility Scalability characteristic that present embodiment utilizes OFDM to have is described, make the evolution system and other system's adjacent frequency coexistence that adopt the OFDM technology can carry out the bandwidth expansion.Is that example describes with IMTAdvanced (4G) with the TD-SCDMA system.

When coexisting with TD-SCDMA or 802.16E (3G) adjacent carrier with IMT Advanced (4G); The frequency resource of effectively utilizing TD-SCDMA or 802.16E to discharge; Form complete IMT Advanced (4G) frequency band; And the method that can be used effectively, be that example comprises following concrete steps with the TD-SCDMA system:

Step 1, new spectral bandwidth

is merged into wherein with original spectral bandwidth

and the spectral bandwidth that adjacent TD-SCDMA discharges in IMT Advanced (4G) base station on frequency:

$W_2^{4G}=W_1^{4G}+W_1^{3G}---\left(1\right);$

Step 2 is in new spectral bandwidth

On, confirm the points N of rapid fourier change IFFT to that is to say sub-carrier number, a kind of mode be from

Increase to

Promptly $N={\left\{N_{\mathrm{FFT}}^{4G}\right\}}_2,$ Wherein:

${\left\{N_{\mathrm{FFT}}^{4G}\right\}}_1=\frac{n_1\×W_1^{4G}}{\mathrm{\Δ}{f}_1}---\left(2\right);$

${\left\{N_{\mathrm{FFT}}^{4G}\right\}}_2=\frac{n_1\×W_2^{4G}}{\mathrm{\Δ}{f}_1}---\left(3\right);$

n ₁Be over-sampling rate, Δ f ₁Be subcarrier spacing.

Another kind of mode is, when $\frac{W_2^{4G}}{W_1^{4G}}<2$ The time, in new spectral bandwidth

On, also can with rapid fourier change IFFT count from

Increase to Promptly $N={2\&times;\left\{N_{\mathrm{FFT}}^{4G}\right\}}_1;$

Step 3; In the N number of sub-carrier; Only modulating data on frequency band after the expansion pairing

number of sub-carrier will be positioned at the sub-carrier power zero setting outside the band system band.

IMT-Advanced system with 20Mhz is an example, through 2048 FTT conversion, is the subcarrier of 2048 independences, quadrature with the IMT-Advanced frequency band transformation of 20MHz.Shown in the vertical arrows among Fig. 2.Decimation factor n during hypothesis is schemed here ₁Be 1.

Adjacent frequency is an example when the IMT-Advanced of 20Mhz system and TD-SCDMA system, and establishing the adjacent bandwidth of TD-SCDMA system is 5MHz.

When the TD-SCDMA of 5MHz bandwidth system discharged the frequency spectrum of 5MHz, the IMT-Advanced system was at first with original 20Mhz bandwidth and the adjacent full frequency band of forming 25Mhz frequently of the 5MHz that discharges.

Because the frequency spectrum of 25Mhz bandwidth is not the working band series of IMT-Advanced, like 20Mhz, 40Mhz, 80Mhz, 100Mhz.So,, still can not directly make full use of for the standard OFDM modulator in the IMT-Advanced system although the 25Mhz bandwidth is a full frequency band.

Adopt method of the present invention,,, the IMT-Advanced full frequency band of 25MHz is transformed to the subcarrier of 4096 independences, quadrature through the FTT conversion that 2x2048=4096 is ordered to the full frequency band of 25Mhz.As shown in Figure 3.

On 4096 number of sub-carrier, only to 2560 number of sub-carrier modulating datas in the 25MHz frequency band, power zero setting on all the other 1536 number of sub-carrier is shown in the round dot on Fig. 3 medium frequency axle.

Method of the present invention is equally applicable to have the IMT-Advanced system scenario of boundary belt, in this situation, and power zero setting on the corresponding protection subcarrier of boundary belt.Shown in the blockage on Fig. 4 medium frequency axle.

Method of the present invention is equally applicable to the IFFT over-sampling situation (n in the formula 2 ₁Greater than 1).In this situation, will be positioned at power zero setting on the subcarrier outside the band system band, shown in the rhombus blockage on Fig. 5-1 and Fig. 5-2 medium frequency axle.

After bandwidth of expansion; When discharging bandwidth once more like adjacent other wireless systems; Then the spectral bandwidth of said system of broadband wireless communication is expanded to the bandwidth sum that this time discharges after bandwidth and expansion last time once more; With sub-carrier number possibly comprise the subcarrier of the bandwidth place frequency band that once more discharge because the IFFT that was adopted during spread bandwidth last time counts this moment, and therefore two kinds of different processing are arranged:

Count like the IFFT after the last time expansion and to count more than or equal to the pairing IFFT of expansion back bandwidth once more; Then bandwidth belongs to modulating data on the subcarrier all or part of in the corresponding subcarrier of frequency band after expanding once more; Wherein increased and this time discharged the corresponding all or part of subcarrier of bandwidth place frequency band; Power zero setting on all the other subcarriers; Bandwidth after the pairing IFFT of the said bandwidth of expansion back once more counts and equals system's over-sampling rate and multiply by this and expand once more, the value that obtains divided by the subcarrier spacing of system again.

Count like the IFFT after the last time expansion and to count less than the pairing IFFT of expansion back bandwidth once more; Then handle to the mode of step 3 by above-mentioned steps one; Bandwidth after the pairing IFFT of the said bandwidth of expansion back once more counts and equals system's over-sampling rate and multiply by this and expand once more, the value that obtains divided by the subcarrier spacing of system again.

Method of the present invention is used when being equally applicable to adopt other system of broadband wireless communication spread bandwidth of OFDM modulation technique.Like 802.16m system etc., its bandwidth can be 20MHz, 40MHz, 60MHz, 80MHz or 100MHz.And the wireless system that expansion has bandwidth to come from comprises TD-SCDMA, 802.16E, WCDMA or CDMA2000 system etc.

In addition, those of ordinary skill in the art are understood that and the present invention includes but be not restricted to above embodiment that other various application also can be arranged, and its equivalence changes and distortion also should be included in the protection range of accompanying claims of the present invention.

Claims (11)

1. the method for expanding band width of broadband radio communication system based on the OFDM technology is characterized in that, may further comprise the steps:

(a) after adjacent other wireless communication systems discharged bandwidth

, the spectral bandwidth of expanding said system of broadband wireless communication was the bandwidth of this system of broadband wireless communication before this expansion to ;

(b) according to the spectral bandwidth after the expansion

Calculating corresponding IFFT counts

And confirm the IFFT points N of the said system of broadband wireless communication in expansion back, also be its sub-carrier number that comprises, N more than or equal to Said IFFT counts

Perhaps said IFFT counts Wherein

n ₁Be the over-sampling rate of the said system of broadband wireless communication of spread bandwidth, Δ f ₁Subcarrier spacing for the said system of broadband wireless communication of spread bandwidth;

(c) in the N number of sub-carrier, modulating data on all or part of subcarrier in frequency band pairing

number of sub-carrier after expansion only.

2. method according to claim 1 is characterized in that, the said system of broadband wireless communication of spread bandwidth is IMT Advanced system or IEEE802.16m system, and the bandwidth before this system extension is 20MHz, 40MHz, 60MHz, 80MHz or 100MHz.

3. method according to claim 1 is characterized in that, the said wireless communication system that discharges bandwidth is TD-SCDMA, 802.16e or WCDMA or CDMA2000 system.

4. method according to claim 1 is characterized in that, the frequency band before bandwidth that said wireless communication system the discharges place frequency band of release bandwidth and the expansion of said system of broadband wireless communication is adjacent.

5. method according to claim 1 is characterized in that, has in the step (b):

${\left\{N_{\mathrm{FFT}}^{4G}\right\}}_2=\frac{n_1\&times;W_2^{4G}}{\mathrm{\&Delta;}{f}_1}$

Wherein, n ₁Be the over-sampling rate of the said system of broadband wireless communication of spread bandwidth, Δ f ₁Subcarrier spacing for the said system of broadband wireless communication of spread bandwidth.

6. method according to claim 1; It is characterized in that; When adjacent other wireless systems discharge bandwidth once more; The spectral bandwidth of said system of broadband wireless communication is expanded to the bandwidth sum that this time discharges after bandwidth and expansion last time once more, count like the IFFT after expansion last time and count, then modulating data on all or part of subcarrier in the subcarrier that expansion back bandwidth place frequency band is corresponding once more more than or equal to the pairing IFFT of expansion back bandwidth once more; Wherein increased and this time discharged the corresponding all or part of subcarrier of bandwidth place frequency band; Power zero setting on all the other subcarriers, the bandwidth after the pairing IFFT of the said bandwidth of expansion back once more counts and equals system's over-sampling rate and multiply by this and expand once more, the value that obtains divided by the subcarrier spacing of system again.

7. method according to claim 1; It is characterized in that; When adjacent other wireless systems discharge bandwidth once more; The spectral bandwidth of said system of broadband wireless communication is expanded to the bandwidth sum that this time discharges after bandwidth and expansion last time once more, count like the IFFT after expansion last time and count, then handle by the mode of above-mentioned steps (a)～step (c) less than the pairing IFFT of expansion back bandwidth once more; Bandwidth after the pairing IFFT of the said bandwidth of expansion back once more counts and equals system's over-sampling rate and multiply by this and expand once more, the value that obtains divided by the subcarrier spacing of system again.

8. method according to claim 1 is characterized in that, after expansion, in the pairing subcarrier of frequency band the protection subcarrier is set, and the protection sub-carrier power is put 0, modulating data on the subcarrier of remainder.

9. method according to claim 8 is characterized in that, said power put 0 subcarrier be included in exceed under the over-sampling situation said expansion back frequency band the subcarrier outside the corresponding subcarrier.

10. method according to claim 1 is characterized in that, will expand power zero setting on the subcarrier outside the frequency band of back in the step (c).

11. method according to claim 1 is characterized in that, the sample frequency of the said wireless system of release bandwidth and the said system of broadband wireless communication of spread bandwidth is identical with subcarrier spacing.

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