CN101378283A - Diversity method for MIMO-OFDM system base on null-frequency encode - Google Patents

Abstract

The invention discloses a diversifying method of an MIMO-OFDM system based on space-frequency coding, when the transmitting antenna is more than 2, better frequency gain effect can still be obtained. The diversifying method comprises that: after rearranging data in a data packet needed to be transmitted, a transmitting party carries out space-frequency coding to the data and then transmits the data; the rearrangement is used for causing the data transmitted by each antenna on sub-carriers with the same frequency points to be different; when receiving the data, a receiving party carries out de-rearrangement according to the rearrangement manner of the transmitting party after the receiving of all the data packets is finished, and carries out space-frequency decoding after the same user data is obtained on the corresponding sub-carriers so as to obtain the original user data.

Description

Deversity scheme based on the MIMO-OFDM system of space-frequency coding

Technical field

The present invention relates to the diversity technique of wireless telecommunication system, especially relate to the deversity scheme of employing based on multi-input multi-output-orthogonal frequency division multiplexing (MIMO-OFDM) system of space-frequency coding (SFBC).

Background technology

Follow-on wireless communication system will provide better speech quality, faster data transmission rate.But, the time multipath transmission environment, limited bandwidth resources and the user that become make above-mentioned requirements implement very difficulty to the demand of service.Effective ways that address these problems are to adopt diversity technique.

The empty time-code of Alamouti scheme is because of its simplicity of design, and decoding has conveniently obtained to use widely in MIMO (MultipleInput Multiple Output) system.Agrawal etc. have proposed empty time-code and OFDM (OFDM, Orthogonal Frequency Division Multiplexing) scheme-space-frequency coding (SFBC of combining of modulation technique, Space Frequency Block Codes), thus make system can obtain higher spectrum efficiency, transmission rate and communication quality.But have only when number of transmit antennas is 2, Alamouti just can give full play to its advantage, reaching encoder matrix quadrature and code rate simultaneously is 1 these two effects, when transmitting antenna greater than 2 the time, just must among encoder matrix quadrature and code rate are 1 these two requirements, select one, and this all can reduce the performance of empty time-code.Therefore need a kind of diversity mode that is suitable for a plurality of antennas, overcome the limitation that the Alamouti scheme can only could be brought into play its advantage fully at 2 system of transmit antennas.In addition, the SFBC of Alamouti scheme coding, the prerequisite of the simplification maximum-likelihood decoding of its correspondence is that channel variation is little between the hypothesis adjacent sub-carrier.But when the channel variation between adjacent sub-carrier is little, be the effect that can't embody frequency diversity and time diversity.

Summary of the invention

The technical problem to be solved in the present invention provides a kind of deversity scheme of the MIMO-OFDM system based on space-frequency coding, greater than 2 o'clock, still can obtain frequency gain effect preferably at transmitting antenna.

The present invention at transmitting antenna greater than 2 MIMO-OFDM system, design a kind of deversity scheme of suitable a plurality of antennas of the SFBC coding based on the Alamouti scheme, overcome the limitation that the Alamouti scheme can only could be brought into play its advantage fully at 2 system of transmit antennas.Diversity scheme of the present invention is that data flow to be encoded is at first reset, and the SFBC coding that will carry out the Alamouti scheme respectively through the sequence of resetting and former sequence, thus the diversity when realizing greater than 2 antennas.

In order to solve the problems of the technologies described above, the invention provides a kind of emission diversity method of the multi-input multi-output-orthogonal frequency division multiplexing system based on space-frequency coding, comprising:

Carry out space-frequency coding again after data in the packet that emission side sends needs are reset and send, described rearrangement is used to data difference that each antenna is sent on identical frequency subcarrier.

Further, said method also can have following characteristics, and reset data emission side, the data difference that each antenna is sent on identical frequency subcarrier, and guarantee that the different sub carrier that sends same data differs x coherence bandwidth cycle, wherein x 〉=1 at least.

Further, said method also can have following characteristics, and described method further may further comprise the steps: (a) initial data in emission side's packet that needs are sent is carried out n rearrangement and is obtained the n circuit-switched data, and described rearrangement frequency n determines according to antenna number m, wherein n is an integer, and

, in the formula

Expression rounds downwards; (b) emission side carries out space-frequency coding to the described initial data that need to send and the n circuit-switched data after the described rearrangement and obtains 2 (n+1) circuit-switched data; (c) emission side is sending through the data behind the coding on the antenna.

Further, said method also can have following characteristics, when described antenna number m is even number, in described step (a), gets the rearrangement number of times $n=\frac{m}{2}-1$ In described step (c), just on the individual antenna of the m=2 of correspondence (n+1), send through 2 (n+1) circuit-switched data behind the coding.

Further, said method also can have following characteristics, when described antenna number m is odd number, in described step (a), gets the rearrangement number of times

, in the formula Expression rounds downwards; In described step (c), send on the individual antenna of 2 (n+1) of correspondence through 2 (n+1) circuit-switched data behind the coding, simultaneously, emission side sends on the individual antenna of m-2 (n+1) in the described step (b) through any circuit-switched data behind the coding.

Further, said method also can have following characteristics, and in described step (c), emission side sends on the individual antenna of m-2 (n+1) in the described step (b) through the initial data behind the coding.

Further, said method also can have following characteristics, and described rearrangement adopts the frequency domain cyclic shift to carry out.

In order to solve the problems of the technologies described above, the present invention also provides a kind of deversity scheme of the multi-input multi-output-orthogonal frequency division multiplexing system based on space-frequency coding, may further comprise the steps:

Emission side carries out space-frequency coding again after the data in the packet that needs are sent are reset and sends when sending data, and described rearrangement is used to data difference that each antenna is sent on identical frequency subcarrier; The recipient after each packet finishes receiving, separates rearrangement according to the rearrangement mode of emission side when receiving data, carry out sky decoding frequently again after corresponding subcarrier obtains identical user data, obtains original user data.

Further, said method also can have following characteristics: the data difference that each antenna is sent is reset by emission side on identical frequency subcarrier to data when sending data, and guarantee that the different sub carrier that sends same data differs x coherence bandwidth cycle, wherein x 〉=1 at least.

Further, said method also can have following characteristics, emission side is when sending data, further may further comprise the steps: (a) emission side is when sending data, initial data in the packet of needs transmission is carried out n rearrangement obtain the n circuit-switched data, described rearrangement frequency n is according to antenna number m decision, and wherein n is an integer, and

, in the formula Expression rounds downwards; (b) emission side carries out space-frequency coding to the described initial data that need to send and the n circuit-switched data after the described rearrangement and obtains 2 (n+1) circuit-switched data; (c) emission side is sending through the data behind the coding on the antenna.

Further, said method also can have following characteristics, when described antenna number m is even number, in described step (a), gets the rearrangement number of times $n=\frac{m}{2}-1$ In described step (c), just on the individual antenna of the m=2 of correspondence (n+1), send through 2 (n+1) circuit-switched data behind the coding.

Further, said method also can have following characteristics, when described antenna number m is odd number, in described step (a), gets the rearrangement number of times

, in the formula

Expression rounds downwards; In described step (c), send on the individual antenna of 2 (n+1) of correspondence through 2 (n+1) circuit-switched data behind the coding, simultaneously, emission side sends on the individual antenna of m-2 (n+1) in the described step (b) through any circuit-switched data behind the coding.

Further, said method also can have following characteristics, and in described step (c), emission side sends on the individual antenna of m-2 (n+1) in the described step (b) through the initial data behind the coding.

Further, said method also can have following characteristics, and described rearrangement adopts the frequency domain cyclic shift to carry out.

Adopt the method for the invention, SFBC coding and antenna grouping combination with the Alamouti scheme, simultaneously frequency domain sequence is reset, same data can be transmitted at different subcarriers, SFBC coding with respect to the Alamouti scheme, the bright diversity scheme of we can embody the effect of frequency diversity, can improve the effect of diversity gain to a certain extent.

Description of drawings

Fig. 1 is the transmitter principle structure chart of the MIMO-OFDM system of present embodiment deversity scheme;

Fig. 2 is the flow chart of present embodiment emission diversity method;

Fig. 3 be the present embodiment deversity scheme under 4 antenna situations with prior art in the performance comparison curves of SFBC+FSTD (Space Frequency Block Coding+frequency inverted transmit diversity) deversity scheme.

Embodiment

Present embodiment is in conjunction with the current design philosophy based on the SFBC diversity, greater than 2 MIMO-OFDM system, designs a kind of antenna number that is applicable to greater than 2 o'clock deversity scheme at transmitting antenna, effect that can the better utilization frequency diversity.

Present embodiment is by resetting former data at frequency domain, and data after resetting and former data are carried out the SFBC coding, thereby realizes the effect of antenna number greater than 2 o'clock grouping SFBC coding.

Fig. 1 is the schematic diagram of transmitter emission in the deversity scheme of resetting based on subcarrier in the present embodiment, and establishing certain user's data waiting for transmission is S=[s ₁, s ₂..., s _k..., s _N], wherein, k is arbitrary numerical value in 1 to N, and the hypothesis number of transmit antennas is N _t, N in the present embodiment _tBe even number.Described emission diversity method may further comprise the steps as shown in Figure 2:

Step 110, the emission root is according to number of transmit antennas N _t, calculate the number of times of resetting

In the formula

Expression rounds downwards;

Step 120, emission side carries out initial data S Inferior rearrangement (being also referred to as subcarrier resets) obtains n circuit-switched data S ₁, S ₂..., S _n

The method of resetting has a variety of, as adopting the frequency domain cyclic shift.But in the rearrangement process, should guarantee the principle that same data should not repeat to send at same subcarrier, be that same data should send at different subcarriers, in order to guarantee to obtain maximum frequency diversity gain, the different sub carrier that sends same data is set differs x coherence bandwidth cycle, wherein x 〉=1 at least.The mode of resetting is transparent to receiving-transmitting sides.

Step 130, emission side is to initial data S and each the circuit-switched data S through resetting ₁, S ₂..., S _nCarry out the SFBC coding respectively, obtain the emission data of 2 (n+1) road antenna;

Step 140, the data vector of establishing after initial data is encoded is $\left[\begin{array}{c}{\mathrm{<figure-callout\; id="0"\; label="S"\; filenames="A200710147960E00141.png"\; state="\{\{state\}\}">S</figure-callout>}}_0^1\\ {\mathrm{<figure-callout\; id="0"\; label="S"\; filenames="A200710147960E00141.png"\; state="\{\{state\}\}">S</figure-callout>}}_0^2\end{array}\right]$ , through the data vector after resetting be $\left[\begin{array}{c}{S}_1^1\\ S_1^2\end{array}\right],\left[\begin{array}{c}{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="A200710147960E00141.png"\; state="\{\{state\}\}">S</figure-callout>}}_2^1\\ {\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="A200710147960E00141.png"\; state="\{\{state\}\}">S</figure-callout>}}_2^2\end{array}\right],\&CenterDot;\&CenterDot;\&CenterDot;,\left[\begin{array}{c}{S}_n^1\\ {\mathrm{<figure-callout\; id="2"\; label="S\; n"\; filenames="A200710147960E00141.png"\; state="\{\{state\}\}">S</figure-callout>}}_n^{}\end{array}\right]$ , wherein the subscript n of S represents that this data vector is generated by the n circuit-switched data, wherein 0 expression is generated by initial data; Two data that subscript 1 or 2 expressions obtain after encoding through SFBC are organized into following form with it $\left[\begin{array}{c}{\mathrm{<figure-callout\; id="0"\; label="S"\; filenames="A200710147960E00141.png"\; state="\{\{state\}\}">S</figure-callout>}}_0^1\\ {\mathrm{<figure-callout\; id="0"\; label="S"\; filenames="A200710147960E00141.png"\; state="\{\{state\}\}">S</figure-callout>}}_0^2\\ S_1^1\\ S_1^2\\ {\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="A200710147960E00141.png"\; state="\{\{state\}\}">S</figure-callout>}}_2^1\\ {\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="A200710147960E00141.png"\; state="\{\{state\}\}">S</figure-callout>}}_2^2\\ -----\\ S_n^1\\ {\mathrm{<figure-callout\; id="2"\; label="S\; n"\; filenames="A200710147960E00141.png"\; state="\{\{state\}\}">S</figure-callout>}}_n^{}\end{array}\right],$ With the corresponding antenna emission of each row in correspondence.

When the antenna number is even number, i.e. N _tDuring=2 (n+1), just can on the individual antenna of 2 (n+1), send through the data behind the coding; And when the antenna number is odd number, i.e. N _t=2 (n+1)+1 o'clock then can send on a remaining antenna through any circuit-switched data behind the SFBC coding in the step 130, preferably through the initial data behind the coding.For example, the antenna number is 3 o'clock, resets frequency n=0, can send on the remaining antenna through any circuit-switched data behind the SFBC coding.

The two paths of data that same circuit-switched data obtains after encoding through SFBC is one group of little antenna transmission of correlation between antenna as far as possible.

In other embodiments, reset number of times also can less than

, like this, in step 140, emission side is when sending data, and remaining antenna can be used for sending arbitrary road or a few circuit-switched data behind the coding, as long as guarantee that the data that send with the frequency subcarrier are different.

Be that example describes with 4 antennas below, number of transmit antennas is 4, then needs initial data is once reset.To S=[s ₁, s ₂..., s _k..., s _N] reset, for analyzing for simplicity, suppose that here the rearrangement mode is the frequency domain cyclic shift, after through rearrangement, data become two-way, and form is as follows: $S\&prime;=\left[\begin{array}{c}{s}_1,{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="A200710147960E00141.png"\; state="\{\{state\}\}">s</figure-callout>}}_2,\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;,s_k,\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;,s_N\\ s_k,s_{k+1},\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;,s_1,{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="A200710147960E00141.png"\; state="\{\{state\}\}">s</figure-callout>}}_2,\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;,s_{k-1}\end{array}\right];$

Then S ＇ is carried out the SFBC coding, the mode of coding has two kinds:

A kind of is order $S\&prime;=\left[\begin{array}{c}{S}_1\\ {\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="A200710147960E00141.png"\; state="\{\{state\}\}">S</figure-callout>}}_2\end{array}\right]$ , respectively to S ₁And S ₂Carry out the Alamouti coding, the emission data format that obtains each antenna is: $\left|\begin{array}{cccccc}{s}_1& -{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="A200710147960E00141.png"\; state="\{\{state\}\}">s</figure-callout>}}_2^{*}& \&CenterDot;\&CenterDot;\&CenterDot;& s_k& -s_{k+1}^{*}& \&CenterDot;\&CenterDot;\&CenterDot;\\ s_2& s_1^{*}& \&CenterDot;\&CenterDot;\&CenterDot;& s_{k+1}& s_k^{*}& \&CenterDot;\&CenterDot;\&CenterDot;\\ s_k& -s_{k+1}^{*}& \&CenterDot;\&CenterDot;\&CenterDot;& s_1& -{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="A200710147960E00141.png"\; state="\{\{state\}\}">s</figure-callout>}}_2^{*}& \&CenterDot;\&CenterDot;\&CenterDot;\\ s_{k+1}& s_k^{*}& \&CenterDot;\&CenterDot;\&CenterDot;& s_2& s_1^{*}& \&CenterDot;\&CenterDot;\&CenterDot;\end{array}\right|;$

Another mode is to make S ＇=[v ₁, v ₂..., v _k..., v _N], v wherein _iBe column vector or matrix, and the v among the S ＇ is carried out the Alamouti coding, the emission data format that obtains each antenna is:

$\left|\begin{array}{cccccc}{s}_1& -{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="A200710147960E00141.png"\; state="\{\{state\}\}">s</figure-callout>}}_2^{*}& \&CenterDot;\&CenterDot;\&CenterDot;& s_k& -s_{k+1}^{*}& \&CenterDot;\&CenterDot;\&CenterDot;\\ s_k& -s_{k+1}^{*}& \&CenterDot;\&CenterDot;\&CenterDot;& s_1& {-\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="A200710147960E00141.png"\; state="\{\{state\}\}">s</figure-callout>}}_2^{*}& \&CenterDot;\&CenterDot;\&CenterDot;\\ s_2& s_1^{*}& \&CenterDot;\&CenterDot;\&CenterDot;& s_{k+1}& s_k^{*}& \&CenterDot;\&CenterDot;\&CenterDot;\\ s_{k+1}& s_k^{*}& \&CenterDot;\&CenterDot;\&CenterDot;& s_2& s_1^{*}& \&CenterDot;\&CenterDot;\&CenterDot;\end{array}\right|;$

At last according to emission data format emission data.

Be adopted as the present embodiment deversity scheme under 4 antenna situations with prior art in the SFBC+FSTD deversity scheme the performance comparison curves as shown in Figure 3, wherein the diversity matrix of SFBC+FSTD is: $\left[\begin{array}{cccc}{S}_1& -{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="A200710147960E00141.png"\; state="\{\{state\}\}">S</figure-callout>}}_2^{*}& 0& 0\\ S_2& S_1^{*}& 0& 0\\ 0& 0& S_3& -{\mathrm{<figure-callout\; id="4"\; label="S"\; filenames="A200710147960E00141.png"\; state="\{\{state\}\}">S</figure-callout>}}_4^{*}\\ 0& 0& S_4& S_3^{*}\end{array}\right]$ , deversity scheme of the present invention is adopted in " SFR_SFBC " expression.From simulation result, method of the present invention can obtain the diversity gain bigger than SFBC+FSTD.

In deversity scheme, corresponding to above-mentioned emission diversity method, the recipient is when receiving data, after each packet finishes receiving, rearrangement mode according to emission side is separated rearrangement, after corresponding subcarrier obtains identical user data, carry out the SFBC decoding again, finally obtain original user data.Method of reseptance can adopt prior art as Alamouti, MMSE (least mean-square error) algorithm, ZF (ZF) algorithm, maximum likelihood code calculation etc.

Certainly; the present invention also can have other various embodiments; under the situation that does not deviate from spirit of the present invention and essence thereof; those of ordinary skill in the art work as can make various corresponding changes and distortion according to the present invention, but these corresponding changes and distortion all should belong to the protection range of the appended claim of the present invention.

For example, the present invention goes for antenna number greater than 2 situation, and not only is confined to the situation of 4 antennas among the embodiment.

For another example, to the mode of resetting, resetting with circulation herein is that example describes, this is just in order to illustrate the principle of this diversity scheme, real system is not limited to the mode that above-mentioned circulation is reset, and should should differ coherence bandwidth at least in the different sub carrier that different subcarriers sent and sent same data as long as guarantee same data.

Claims (14)

1, a kind of emission diversity method of the multi-input multi-output-orthogonal frequency division multiplexing system based on space-frequency coding is characterized in that,

Carry out space-frequency coding again after data in the packet that emission side sends needs are reset and send, described rearrangement is used to data difference that each antenna is sent on identical frequency subcarrier.

2, the method for claim 1 is characterized in that,

Reset data emission side, the data difference that each antenna is sent on identical frequency subcarrier, and guarantee that the different sub carrier that sends same data differs x coherence bandwidth cycle, wherein x 〉=1 at least.

3, method as claimed in claim 1 or 2 is characterized in that, described method further may further comprise the steps:

(a) initial data in emission side's packet that needs are sent is carried out resetting for n time and is obtained the n circuit-switched data, and described rearrangement frequency n determines that according to antenna number m wherein n is an integer, and

In the formula Expression rounds downwards;

(b) emission side carries out space-frequency coding to the described initial data that need to send and the n circuit-switched data after the described rearrangement and obtains 2 (n+1) circuit-switched data;

(c) emission side is sending through the data behind the coding on the antenna.

4, method as claimed in claim 3 is characterized in that, when described antenna number m is even number, in described step (a), gets the rearrangement number of times $n=\frac{m}{2}-1;$ In described step (c), just on the individual antenna of the m=2 of correspondence (n+1), send through 2 (n+1) circuit-switched data behind the coding.

5, method as claimed in claim 3 is characterized in that,

When described antenna number m is odd number, in described step (a), get the rearrangement number of times

In the formula

Expression rounds downwards; In described step (c), send on the individual antenna of 2 (n+1) of correspondence through 2 (n+1) circuit-switched data behind the coding, simultaneously, emission side sends on the individual antenna of m-2 (n+1) in the described step (b) through any circuit-switched data behind the coding.

6, method as claimed in claim 5 is characterized in that,

In described step (c), emission side sends on the individual antenna of m-2 (n+1) in the described step (b) through the initial data behind the coding.

7, method as claimed in claim 3 is characterized in that, described rearrangement adopts the frequency domain cyclic shift to carry out.

8, a kind of deversity scheme of the multi-input multi-output-orthogonal frequency division multiplexing system based on space-frequency coding is characterized in that, may further comprise the steps:

Emission side carries out space-frequency coding again after the data in the packet that needs are sent are reset and sends when sending data, and described rearrangement is used to data difference that each antenna is sent on identical frequency subcarrier;

The recipient after each packet finishes receiving, separates rearrangement according to the rearrangement mode of emission side when receiving data, carry out sky decoding frequently again after corresponding subcarrier obtains identical user data, obtains original user data.

9, method as claimed in claim 8 is characterized in that,

Reset data when sending data emission side, the data difference that each antenna is sent on identical frequency subcarrier, and guarantee that the different sub carrier that sends same data differs x coherence bandwidth cycle, wherein x 〉=1 at least.

10, method as claimed in claim 9 is characterized in that, emission side further may further comprise the steps when sending data:

(a) emission side carries out n rearrangement to the initial data in the packet of needs transmission and obtains the n circuit-switched data when sending data, and described rearrangement frequency n is according to antenna number m decision, and wherein n is an integer, and

In the formula Expression rounds downwards;

(b) emission side carries out space-frequency coding to the described initial data that need to send and the n circuit-switched data after the described rearrangement and obtains 2 (n+1) circuit-switched data;

(c) emission side is sending through the data behind the coding on the antenna.

11, method as claimed in claim 10 is characterized in that,

When described antenna number m is even number, in described step (a), get the rearrangement number of times $n=\frac{m}{2}-1;$ In described step (c), just on the individual antenna of the m=2 of correspondence (n+1), send through 2 (n+1) circuit-switched data behind the coding.

12, method as claimed in claim 10 is characterized in that,

When described antenna number m is odd number, in described step (a), get the rearrangement number of times

In the formula Expression rounds downwards; In described step (c), send on the individual antenna of 2 (n+1) of correspondence through 2 (n+1) circuit-switched data behind the coding, simultaneously, emission side sends on the individual antenna of m-2 (n+1) in the described step (b) through any circuit-switched data behind the coding.

13, method as claimed in claim 12 is characterized in that,

In described step (c), emission side sends on the individual antenna of m-2 (n+1) in the described step (b) through the initial data behind the coding.

14, method as claimed in claim 10 is characterized in that, described rearrangement adopts the frequency domain cyclic shift to carry out.

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