CN1913512A - Training character transfer method in radio communication system - Google Patents

Abstract

The invention describes a training symbol transmission method in a wireless communication system. The system includes at least two transmit antennas. The system selects subbands to transmit one or more user data signals, and the training symbols used for channel estimation and user data symbols multiplex time/frequency resources and insert them into specific time/frequency grids. In this design scheme, the training symbols adopt the continuous orthogonal transmission method, that is, the training symbols occupy the same time/frequency grid of at least two transmitting antennas, and perform orthogonal training symbol transmission on at least two consecutive time/frequency grids .

Description

Training character transfer method in a kind of wireless communication system

Technical field

The present invention relates to the training character transfer method in a kind of wireless communication system.

Background technology

In recent years, along with the continuous growth of mobile user data business demand, wireless communication system is just experiencing from the third generation (3G) three generations's (B3G) development backward.In the commercialization and the marketization that the mobile communication carrier and the equipment manufacturers of our times various countries are actively promoting 3G (Third Generation) Moblie, every industry or trade, the research and development of the B3G mobile communication system of high speed business also launch for having more high spectrum utilization and providing more for university and other scientific research institutions.In order to maximize the return of investment of operator on the frequency spectrum resource of preciousness, the B3G mobile communication system will have higher spectrum efficiency than system in the past to support the more business of high data rate (more than 100Mb/s), make multimedia services such as high speed audio frequency, video, image and Internet become possibility.These business obviously improve for the requirement of transmission of radio links ability.OFDM (OFDM) technology and show up prominently gradually in the case based on the technology such as single carrier (SC-FDE) technology of frequency domain equalization.The OFDM technology is that a plurality of parallel low rate data streams that frequency spectrum overlaps sends with data stream modulates at a high speed.Add greater than the protection of maximum multipath time delay (GI) at interval by front end, can eliminate the intersymbol interference (ISI) that causes by multidiameter delay fully, thereby greatly reduce the complexity of receiving terminal equalizer at the OFDM symbol.Single-carrier technology based on frequency domain equalization has and OFDM similar performance, efficient and signal processing complexity.Compare the advantage that also has the peak-to-average ratio aspect based on the single-carrier technology of frequency domain equalization with the OFDM technology in addition.

In order further to improve power system capacity, the B3G system extensively adopts the MIMO transmission technology.Theoretical research and facts have proved adopts the MIMO transmission will greatly improve channel capacity.

Training symbol has obtained using widely in wireless communication system, also will obtain extensive use in the B3G mobile communication system.Training symbol mainly contains two kinds of purposes:

1) is used for synchronizing process.System sends known training symbol, at receiving terminal, by carrying out related operation with this training symbol, obtain to system the time/frequency synchronously.

2) be used for channel estimation process.System sends known training symbol, at receiving terminal, by received signal and this training symbol are carried out computing, obtains the estimation for the characteristic of channel in the transmission course.

Defeated down at the multi-antenna transmitting that with MIMO is representative, training symbol be designed to a hot issue.Training symbol design in the at present domestic and international wireless communication system mainly contains two kinds:

1) the quadrature training symbol of non-intersect (disjoint) design:

In this design, system is that training symbol is reserved specific running time-frequency resource.But for fear of the phase mutual interference of many antennas training symbol transmission, in an antenna transmission training symbol, remaining antenna all sends null symbol.For example referring to 3GPP, R1-050484, Nortel, " Proposal for the downlink multiple access scheme for E-UTRA (update) " and 3GPP, R1-050485, Nortel, " Proposal for the uplinkmultiple access scheme for E-UTRA (update) ", here that described document is incorporated by reference.

2) training symbol of phase shift quadrature design:

Under desirable hypothesis prerequisite, adopt the training symbol design of phase shift quadrature can reach minimum channel estimating mean square error.For example referring to I.Barhumi, G.Leus, M.Moonen, " Optimal training design for MIMO OFDM systems inmobile wireless channels ", IEEE Trans.on Signal Processing, vol.51, pp.1615-1624, June 2003, and is here that described document is incorporated by reference.

Though adopt disjoint quadrature training symbol method for designing can avoid the signal between many antennas to disturb, because in an antenna transmission training symbol, other antennas can only send null symbol and can not make full use of frequency/time resource of reservation.Though adopt the training symbol design of phase shift quadrature can reach optimum channel estimating performance, owing to all restrictions of its too high receiver complexity and real system parameter are difficult to obtain practical application.

Summary of the invention

Above-mentioned state in view of prior art, the object of the present invention is to provide improvement training character transfer method and system in a kind of wireless communication system, wherein can either make full use of frequency/time resource, can reduce the complexity of receiver end again and avoid the restriction of real system parameter.

For achieving the above object, the face the future application of wireless communication system of the present invention proposes a kind of improved quadrature training character transfer method.This system comprises at least two transmit antennas, when training symbol and user data symbol are multiplexing/frequency resource and be inserted into when specific/frequency lattice in, the method is characterized in that, training symbol adopts continuous orthogonal transmission mode, be training symbol when taking at least two transmit antennas identical/frequency lattice, at least two when continuous/frequency lattice, carry out the training symbol transmission of quadrature.

Further, in described method, the training symbol that is transmitted is transferred to one or more receiving equipments from least two antennas, so that utilized the training symbol on each transmitting antenna to carry out channel estimating by described receiving equipment, thereby carries out the detection of subscriber signal on this basis.

Further, in described method, receive signal from least two antennas by receiving equipment, the training symbol on these antenna takies when identical/frequency lattice transmit, and the training symbol that carries out quadrature at least two when continuous/frequency lattice transmits.

Further, in described method, when one or more users' information and described training symbol are multiplexing/the frequency resource.

The present invention also provides a kind of wireless communication system that comprises at least one sub-district, comprise at least one transmitting apparatus and at least one receiving equipment, this wireless communication system is assigned with specific band resource and transmits, the running time-frequency resource of training symbol and user data symbol multiplex system, the method that the training symbol that described receiving equipment use is launched at least two antennas receives, it is characterized in that, described transmitting apparatus is configured to send by this way described training symbol, make when described training symbol takies at least two transmit antennas identical/the frequency lattice, at least two when continuous/frequency lattice, carry out the training symbol transmission of quadrature.

Description of drawings

It is example that Fig. 1 shows with two antennas, utilizes the frequency domain correlation of channel to carry out training symbol distribution schematic diagram.

It is example that Fig. 2 shows with two antennas, utilizes the relativity of time domain of channel to carry out training symbol distribution schematic diagram.

Embodiment

Be that example illustrates content of the present invention with MIMO OFDMA system below with two transmit antennas.The different sub carrier of ofdm system is distributed to different user, promptly constituted the OFDMA system.

The method for designing of training symbol as shown in Figure 1.Abscissa is the time, the corresponding OFDM symbol of each time quantum; Ordinate is a frequency, a subcarrier in the corresponding OFDM symbol of each frequency cells.The multiplexing OFDMA of user data (data) symbol and training symbol (pilot is also referred to as pilot tone) system the time/the frequency resource, promptly user data symbol and training symbol take when different/the frequency unit transmits.Training symbol the time/be inserted in the OFDM symbol to the frequency domain discontinuous and go.Training symbol takies two continuous OFDM subcarriers at frequency domain and transmits, and the training symbol on every antenna takies identical continuous subcarrier.As shown in Figure 1, the left side is that first training symbol on the antenna distributes, and the right side is that second training symbol on the antenna distributes.The the 1st, 2,6,7 and 11, the 12 3 pair of continuous sub-carriers that training symbol on two antennas has all taken the 1st and the 4th OFDM symbol transmitted.On every pair of continuous subcarrier, on two antennas symbol transmission is arranged all.Suppose p _IjBe illustrated in the individual training symbol of j (j=1,2) that transmits on i on certain OFDM symbol (i=1,2) the root antenna.Continuous quadrature training character transfer method requires:

${\left[\begin{array}{cc}{p}_{11}& p_{21}\\ p_{12}& p_{22}\end{array}\right]}^H\left[\begin{array}{cc}{p}_{11}& p_{21}\\ p_{12}& p_{22}\end{array}\right]=\mathrm{KI},---\left(1\right)$

Wherein I is a unit matrix, () ^HFor changeing order conjugate operation, p _I1And p _I2Transmit on two continuous sub-carriers, K is an arbitrary constant.

Alternatively, the training symbol design as shown in Figure 2.User data (data) symbol and the multiplexing OFDMA of training symbol (pilot) system the time/the frequency resource.Training symbol the time/be inserted in the OFDM symbol to the frequency domain discontinuous and go.Training symbol takies two continuous time quantums and transmits on specific subcarrier, and the training symbol on every antenna takies identical unit continuous time.As shown in Figure 2, the left side is that first training symbol on the antenna distributes, and the right side is that second training symbol on the antenna distributes.The the 1st, 2 and 4, the 5 two pair of continuous time quantum that training symbol on two antennas has all taken on the 1st, 6,11 subcarrier transmits.On every pair of continuous time quantum, on two antennas symbol transmission is arranged all.Suppose q _IjBe illustrated in the individual training symbol of j (j=1,2) on i on certain subcarrier (i=1,2) the root antenna.Continuous quadrature training character transfer method requires:

${\left[\begin{array}{cc}{q}_{11}& q_{21}\\ q_{12}& q_{22}\end{array}\right]}^H\left[\begin{array}{cc}{q}_{11}& q_{21}\\ q_{12}& q_{22}\end{array}\right]=\mathrm{KI},---\left(2\right)$

Wherein I is a unit matrix, () ^HFor changeing order conjugate operation, q _I1And q _I2Transmit on two continuous time quantums, K is an arbitrary constant.

Consider a MIMO OFDMA system that comprises two transmit antennas below.With Fig. 1 is example, and continuous two training symbols that transmit on first antenna can be designed as:

p ₁₁＝1+j，p ₁₂＝-1-j，

Continuous two training symbols that transmit on second antenna can be designed as:

p ₂₁＝1-j，p ₂₂＝1-j.

Can prove, the continuous training symbol mutually orthogonal that transmits on these two antennas, i.e. this design can be satisfied (1) formula.

Be the signal processing that example is described receiving terminal this training symbol is used for channel estimating below.Utilize the correlation on the frequency, suppose that promptly channel does not change on continuous two subcarriers, then training symbol designs as shown in Figure 1.Also can utilize the correlation on the time domain, suppose that promptly channel does not change on the transmission time of continuous two OFDM symbols, then training symbol designs as shown in Figure 2.

Suppose that channel does not change on continuous two subcarriers, promptly training symbol designs as shown in Figure 1.Then at receiving terminal since two antennas take when identical/frequency unit carries out training symbol to be transmitted, then the received signal on the subcarrier of first training symbol correspondence of each root antenna is:

r ₀＝p ₁₁h ₀+p ₂₁h ₁. (3)

Received signal on the subcarrier of second training symbol correspondence of each root antenna is:

r ₁＝p ₁₂h ₀+p ₂₂h ₁. (4)

(3) and (4) are expressed as matrix form is:

$\left[\begin{array}{c}{r}_0\\ r_1\end{array}\right]=\left[\begin{array}{cc}{p}_{11}& p_{21}\\ p_{12}& p_{22}\end{array}\right]\left[\begin{array}{c}{h}_0\\ h_1\end{array}\right]+\left[\begin{array}{c}{n}_0\\ n_1\end{array}\right].---\left(5\right)$

The channel estimating of receiver is following carries out:

$\left[\begin{array}{c}{\hat{h}}_0\\ {\hat{h}}_1\end{array}\right]=\frac{1}{K}{\left[\begin{array}{cc}{p}_{11}& p_{21}\\ p_{12}& p_{22}\end{array}\right]}^H\left[\begin{array}{c}{r}_0\\ r_1\end{array}\right].---\left(6\right)$

The present invention is not limited to two transmit antennas, but can be applied to the situation more than two.For example when four transmit antennas, being used for channel estimating with training sequence is example, utilize the correlation on the frequency domain, suppose that promptly channel does not change on continuous four OFDM subcarriers, then training symbol takies four continuous OFDM subcarriers at frequency domain and transmits, and the training symbol on every antenna takies identical continuous subcarrier.Continuous four training symbols of transmission should mutually orthogonal respectively on four antennas.Also can utilize the correlation on the time domain to transmit similarly.

Those skilled in the art can understand that being used for channel estimating with training symbol is example, utilizes the correlation on frequency domain or the time domain, then transmit the used continuous subcarrier of training symbol quantity or continuous time the unit quantity can be not limited to two.

Can verify, be example with the channel estimating, adopts the continuous quadrature training character transfer method among the present invention, will obtain better system error performance than discontinuous quadrature training character transfer method.On the other hand, under same system's error performance requires, adopt continuous quadrature training character transfer method to have higher bandwidth efficiency than discontinuous quadrature training character transfer method.In addition, the method of at least two antennas, transmitting training symbol simultaneously that adopts the present invention to describe, transmission method that can more discontinuous quadrature training symbol needs lower transmitting power under same performance, thereby suppresses the peak-to-average ratio of OFDMA system effectively.Adopt the continuous quadrature training character transfer method among the present invention, will have lower receiver implementation complexity than the training symbol design of phase shift quadrature.

It should be noted that, though be that example has been described embodiments of the invention here with the ofdm system, yet those skilled in the art can understand that according to the description here scope of the present invention is not limited to this, but can be applied in other wireless communication system that transmits continuous quadrature training symbol.

Claims (5)

1. the training character transfer method in the wireless communication system, this system comprises at least two transmit antennas, and select for use subband to carry out the transmission of one or more user data signals, be used for the training symbol of channel estimating and user data symbol when multiplexing/frequency resource and be inserted into when specific/the frequency lattice, the method is characterized in that, training symbol adopts continuous orthogonal transmission mode, be training symbol when taking at least two transmit antennas identical/frequency lattice, at least two when continuous/frequency lattice, carry out the training symbol transmission of quadrature.

2. according to the method for claim 1, it is characterized in that, the training symbol that is transmitted is transferred to one or more receiving equipments from least two antennas, so that utilized the training symbol on each transmitting antenna to carry out channel estimating by described receiving equipment, thereby carry out the detection of subscriber signal on this basis.

3. according to the method for claim 2, it is characterized in that, receive signal from least two antennas by receiving equipment, the training symbol on these antenna takies when identical/frequency lattice transmit, and the training symbol that carries out quadrature at least two when continuous/frequency lattice transmits.

4. according to any one method in the claim 1 to 3, it is characterized in that, when one or more users' information and described training symbol are multiplexing/the frequency resource.

5. wireless communication system that comprises at least one sub-district, comprise at least one transmitting apparatus and at least one receiving equipment, this wireless communication system is assigned with specific band resource and transmits, the running time-frequency resource of training symbol and user data symbol multiplex system, the method that the training symbol that described receiving equipment use is launched at least two antennas receives, it is characterized in that, described transmitting apparatus is configured to send by this way described training symbol, make when described training symbol takies at least two transmit antennas identical/the frequency lattice, at least two when continuous/frequency lattice, carry out the training symbol transmission of quadrature.

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