CN1327730C - Radio communication equipment and method - Google Patents

Abstract

In a communication system having a base station with multiple transmit antennas and a mobile station with at least one single receive antenna, a method and apparatus for obtaining combined beamforming and transmit diversity for a frequency-selective fading channel, the method comprising the steps : Provide a signal to be transmitted; perform space-time encoding on the signal to generate at least two separate signals, each on a respective output; send each output signal to a multi-access transmit processor to generate an output signal; Apply respective selected transmit beamforming weights to each output signal; send each weighted signal to a signal combiner, perform a signal summation function, and generate a signal for transmission; send the summed signal to multiple Each antenna in the transmitting antenna transmits; transmits a signal through each physical channel; receives the transmitted signal in at least one single receiving antenna; sends the transmitted signal to a multi-access receiving processor to generate an output signal ; and performing space-time decoding on the received signal.

Description

Wireless Telecom Equipment and method

Technical field

The present invention relates in general to wireless communication system, and relates to the performance of improving wireless communication system downlink more especially.

Background technology

Wireless mobile communications can be subjected to four kinds of main infringements: path loss, multipath fading, intersymbol interference (ISI) and road interference altogether.Adaptive antenna can be used to suppress the influence of these factors, to improve the performance of wireless communication system.Have two types adaptive antenna: diversity antenna and beam form antenna.In diversity aerial system,, need obtain a plurality of low relevant or fading channels independently, to obtain diversity gain in order to compensate multipath fading.On the other hand, beam forms antenna by utilizing spatial directivity, can provide beam to form gain, so just compensating for path loss to a certain extent, and suppress to be total to the road and disturb.

In diversity aerial system, particularly for low-angle expansion environment, for obtain low relevant/fading channel independently, require antenna distance to want enough (for example 10 λ) greatly usually.Need obtain spatial directivity yet beam forms antenna, so the signal that all antennas receive and/or send must be correlated with.This just means: form antenna for beam, antenna distance is less usually, is half wavelength to even linear array (ULA) for example.Because diversity aerial system and beam form the conflict between the desired antenna distance of system, therefore there is the defective that can not obtain diversity gain and beam formation gain simultaneously.

Summary of the invention

One object of the present invention is that seeking to provide a kind of can form the wireless communication system that obtains advantage the gain from diversity gain and beam simultaneously.

Correspondingly, one aspect of the present invention is provided at possesses the method that obtains to send diversity gain in base station that multiple transmit antennas is arranged and the communications of Mobile Terminals system that single reception antenna is arranged, and comprises step in this method: provide the signal s that will be sent out (n); Signal s (n) is carried out Space Time Coding, generate at least two independent signal s ₁(n), s ₂(n), each signal is in output separately; Each output signal s ₁(n), s ₂(n) deliver to and have function g separately ₁(k), g ₂(k) ZF pre equalizer generates output signal x ₁(n), x ₂(n); The output signal x of each pre equalizer ₁(n), x ₂(n) deliver to transmitting antenna; By physical channel h separately ₁(k), h ₂(k), send output signal x ₁(n), x ₂(n); In single reception antenna, receive output signal x ₁(n), x ₂(n); And decode when carrying out sky to received signal, wherein select the function g of ZF pre equalizer ₁(k), g ₂(k), make each physical channel h ₁(k), h ₂(k) channel response g ₁(k) * h ₁(k), g ₂(k) * h ₂(k) be falt fading channel.

Communication system is tdd systems preferably, and also comprises in this method and obtain real channel coefficients from the uplink channel coefficient, the function g of selective pre equalizer ₁(k), g ₂(k) step of Shi Yonging.

Be from the uplink channel coefficient, to obtain using in the step of real channel coefficients training symbol easily from uplink channel.

Benefit is, obtains using blind technology in the step of real channel coefficients from the uplink channel coefficient.

Communication system is frequency division duplex system preferably, and also comprise step in this method: send one group of training symbol by reception antenna to portable terminal, estimate real channel coefficients by portable terminal, and the channel coefficients feedback information is gone back to the base station, and obtain this real channel coefficients.

Another aspect of the present invention is provided for by physical channel h ₁(k), h ₂(k), the base station that multiple transmit antennas is arranged with the portable terminal that possesses single reception antenna communicates comprises in this base station:

Possess the input that will be sent out signal s (n) and the Space Time Coding device of at least two outputs, each output generates independent signal s ₁(n), s ₂(n); At least two ZF pre equalizers, each all is fed the output signal s with separately ₁(n), s ₂And possess separately function g (n), ₁(k), g ₂(k), to generate output signal x ₁(n), x ₂(n); And at least two transmitting antennas, each all is fed the output signal x with each pre equalizer ₁(n), x ₂(n), wherein select the function g of ZF pre equalizer ₁(k), g ₂(k), make each physical channel h ₁(k), h ₂(k) channel response g ₁(k) * h ₁(k), g ₂(k) * h ₂(k) be falt fading channel.

Decoder when portable terminal preferably possesses single reception antenna and sky is to decode to the signal that receives from the base station.

Another aspect of the present invention is to possess the base station that multiple transmit antennas is arranged and having in the communications of Mobile Terminals system of single reception antenna, be provided as frequency selective fading channels and obtain the method that the combination beam formed and sent diversity, comprise step in this method: provide the signal S that will be sent out (n; K); To signal S (n; K) carry out Space Time Coding, to generate at least two independent signal S ₁(n; K), S ₂(n; K), each signal is in output separately; Each output signal S ₁(n; K), S ₂(n; K) give the transmission processor, to generate output signal X ₁(n; K), X ₂(n; K); To each output signal X ₁(n; K), X ₂(n; K) use selected separately transmission beam and form weights; Each weighted signal is delivered to the signal combiner, carry out the summation function of signal, and generate the signal X (n that is used to send; K); The signal X (n of summation; K) send to each antenna in the multiple transmit antennas, send; Through physical channel h (n separately; K) send signal X (n; K); In single reception antenna, receive this signal Y (n that receives; K); The signal Y (n that receives; K) deliver to receiving processor, to generate output signal; And decode when carrying out sky to received signal.

Preferably select each to send beam and form weights, as with physical channel h (n; K) two corresponding characteristic vectors of eigenvalue of maximum in the downlink channel covariance matrix (DCCM).

Easily, physical channel h (n; K) penetrate footpath (ray) h by two time delays in ₁(n; K), h ₂(n; K) form, and the transmission processor does not add Cyclic Prefix, and before using selected separately transmission beam formation weights, send the time-delay of one of them output signal of processor through Δ τ, select beam to form weights, make time delayed signal or its pay upright leaf inverse transformation (IFFT) fast only by a channel h between base station multiple transmit antennas and the reception antenna ₁(n; K), and not delayed signal or its IFFT are only through another channel h between base station multiple transmit antennas and the reception antenna ₂(n; Decoding was to recover to be sent out two different channels of signal when k), establishment can be passed through sky thus.

Benefit is physical channel h (n; K) by two time delays, the collection bunch penetrate the footpath h ₁(n; K) and h ₂(n; K) form, send processor and possess the Cyclic Prefix that length is Δ Ψ, and before using each selecteed transmission beam formation weights, will be from one of them output signal that sends processor through the time-delay of Ψ, select beam to form weights, make time delayed signal or its pay upright leaf inverse transformation (IFFT) fast only by a channel h between base station multiple transmit antennas and the reception antenna ₁(n; K), and not delayed signal or its IFFT are only through another channel h between base station multiple transmit antennas and the reception antenna ₂(n; Decoding was to recover to be sent out two different channels of signal when k), establishment can be passed through sky thus.

Preferably also comprise step in this method: be channel h (n; K) estimating power-delay-DOA distributes; And on the basis of this distribution, determining will be by sending the circulating prefix-length Δ Ψ that processor adds; Determine time delay Ψ; And determine to send beam and form weights.

Benefit is also to comprise estimating down-ward link channel covariance matrix (DCCM) from uplink channel covariance matrix (UCCM) in this method, with the step of structure transmission beam formation weights.

Easily, also comprise step in this method: estimating down-ward link channel covariance matrix (DCCM) from uplink channel covariance matrix (UCCM) sends beam with structure and forms weights; Be channel h (n; K) estimating power-delay-DOA distributes; And on the basis that distributes, determine by sending the circulating prefix-length Δ Ψ that processor adds; Determine time delay Ψ; And determine to send beam and form weights.

Another aspect of the present invention is provided for penetrating footpath h by possessing two time delays ₁(n; K) and h ₂(n; K) physical channel h (n; K), the base station that multiple transmit antennas is arranged with the portable terminal that possesses single reception antenna communicates comprises in this base station:

Possess the input that will be sent out signal and the Space Time Coding device of at least two outputs, each output generates independent signal; At least two transmission processors, each all receives one of output from each Space Time Coding device respectively; At least two send beam formation device, and each all receives each output that sends processor, and its application transmission beam is formed weights; Form the signal combiner of device received signal from beam, can be used to carry out from this beam form device signal summing function and generate signal and send by multiple transmit antennas.

The delay of Δ τ preferably is placed in one of this transmission processor output and beam forms between the device, making can be before using selected separately transmission beam formation weights, from the signal output time-delay Δ τ that sends processor, wherein send processor and do not add Cyclic Prefix.

Easily, the delay of Ψ preferably is placed in and sends between one of processor output and the beam formation device, making can be before using selected separately transmission beam formation weights, and export time-delay Ψ from the signal that sends processor, the circulating prefix-length that sends processor is Δ Ψ.

Benefit is to be provided as channel h (n; K) determine the processor that power-delay-DOA distributes and estimates, and on the basis that distributes, determining will be by sending the circulating prefix-length Δ Ψ that processor adds; Time delay Ψ; And the transmission beam forms weights.

Easily, provide processor, with estimating down-ward link channel covariance matrix (DCCM) from uplink channel covariance matrix (UCCM), structure sends beam and forms weights.

Preferably also be included as channel h (n in the base station; K) determine power-delay-DOA estimation that distributes; And on the basis that distributes, determining will be by sending the circulating prefix-length Δ Ψ that processor adds; Time delay Ψ; And the first processor that sends beam formation weights; And from uplink channel covariance matrix (UCCM) estimating down-ward link channel covariance matrix (DCCM), structure sends second processor that beam forms weights.

Easily, can from the group of forming by OFDM, CDMA and TDMA processor, select to send and receiving processor.

Benefit is, comprises base station and portable terminal in the communication system, this portable terminal possesses single reception antenna, generate output signal receiving processor and to output signal decode empty the time decoder.

Another aspect of the present invention is to possess the base station that multiple transmit antennas is arranged and having in the communications of Mobile Terminals system of single reception antenna, be provided as frequency selective fading channels and obtain the method that the combination beam formed and sent diversity, comprise step in this method: provide the signal s that will be sent out (n); The signal s (n) that will be sent out is carried out Space Time Coding, to generate at least two independent signal s ₁(n), s ₂(n), each signal is in output separately; Make a output signal in the output signal of Space Time Coding through the time-delay of Δ τ; Selected transmission beam is separately formed weights to be applied to through postponing and not delayed signal; Each weighted signal is delivered to the signal combiner,, and generate the signal that is used to send with the summation function of execution signal; Give each antenna in the multiple transmit antennas signal of summation, send; Penetrate footpath h through possessing two time delays ₁(k) and h ₂(k) physical channel h (k) sends the signal of this summation; On the essentially identical time, in single reception antenna, receive the fundamental component that is sent out signal; And decode when carrying out sky to received signal.

Preferably select to send beam and form weights, make and only penetrate footpath h through one between base station multiple transmit antennas and the reception antenna through the signal that postpones ₁(k), and not delayed signal is only penetrated footpath h through between base station multiple transmit antennas and the reception antenna another ₂(k).

Easily, time-delay Δ τ can obtain from downlink channel information.

Another aspect of the present invention is provided for penetrating footpath h by possessing two time delays ₁(k), h ₂(k) physical channel h (k), the base station that multiple transmit antennas is arranged with the portable terminal that possesses single reception antenna communicates comprises in this base station:

Possess the input that will be sent out signal and the Space Time Coding device of at least two outputs, each output generates independent signal; At least two send beam formation device, and each all receives the output from the Space Time Coding device, and it is used transmission beam formation weights; The signal combiner, form the device received signal from beam, and can be used to carry out the summation function that forms the signal of device from beam, with generate signal by each transmission in the multiple transmit antennas, wherein time delay Δ τ is placed between Space Time Coding device and one of them beam formation device, make and to receive the fundamental component that is sent out signal at single reception antenna place in the essentially identical time.

Preferably comprise the base station in the communication system and possess single reception antenna and to the signal that receives decode empty the time decoder portable terminal.

A target of the present invention is exactly to seek to obtain diversity gain, beam formation gain by using the base station of multi-antenna array simultaneously at portable terminal, and, reduce the time delay expansion.

The benefit of the embodiment of the invention is as follows:

Can obtain beam simultaneously forms gain and sends diversity.

On the basis that power time delay DOA distributes, can reduce the time delay expansion adaptively.

Penetrate in the environment of footpath two, frequency selective fading channels is converted into falt fading channel, still can keep the path diversity gain.

In the environment of hilly country (HT), can be converted to a hour delay extended channel to the long time delay extended channel, still can keep the path diversity gain.

By beam formation and transmission diversity that the time delay expansion reduces and makes up, system of the present invention provides spectral efficient, and consumes less transmitted power.

System of the present invention also adopts Adaptive Modulation, further to improve spectrum efficiency based on diversity order and channel conditions.

Portable terminal all is subjected to the restriction of its physical size and the power of battery usually.System of the present invention is in the base station, rather than implements complicated processing at portable terminal.The complexity of portable terminal just can be lowered like this.

System of the present invention also can be advantageously applied to the application that requires the downlink transmission high data rate.For example, comprise during these are used that the interior high-speed downlink packet of third generation partner plan (3GPP) inserts (HSDPA), wireless Internet and wireless multimedia communication.

Description of drawings

In order to understand the present invention more easily, by example, with reference to the accompanying drawings, embodiments of the invention are described now, in the accompanying drawing:

Fig. 1 (prior art) is the general block diagram that the displacement of explanation Alamouti sends deversity scheme;

Fig. 2 illustrates for frequency selective fading channels, utilizes the transmission diversity that possesses preequalization to realize the general block diagram of method of the present invention;

Fig. 3 (prior art) is that explanation is at (a) transmitter; (b) the receiver place has the general block diagram of the OFDM (OFDM) that sends diversity;

Fig. 4 (prior art) illustrates that for falt fading channel the combination beam forms and send the general block diagram of the OFDM of diversity;

Fig. 5 is that explanation is at (a) transmitter; (b) the receiver place utilizes beam formation that has combination and the OFDM that sends diversity to realize the general block diagram of method of the present invention;

Fig. 6 is that explanation is penetrated footpath (TR) frequency selective fading channels for two, at (a) transmitter; (b) the receiver place utilizes the combination beam to form and send the general block diagram that diversity realizes method of the present invention;

Fig. 7 is that explanation is penetrated footpath (TR) model for two, at (a) transmitter; (b) the receiver place utilizes beam formation that has combination and the OFDM that sends diversity to realize the general block diagram of method of the present invention;

Fig. 8 explanation is for the model of hilly country (HR), at (a) transmitter; (b) the receiver place utilizes beam formation that has combination and the OFDM that sends diversity to realize the general block diagram of method of the present invention; And

Fig. 9 is that explanation is at (a) transmitter; (b) the receiver place utilizes the beam formation, transmission diversity and the Adaptive Time Delay that possess combination to expand the general block diagram that the OFDM that reduces realizes method of the present invention.

Embodiment

The present invention is centered around and uses many antennas in the base station, to improve the performance of wireless communication system downlink.In the interference effect condition of limited, it is that effectively particularly in multimedia communication, this point is very important that the down link beam forms.When receive diversity can not be realized, particularly for the portable terminal that size and/or Power Limitation are arranged, sending diversity was a kind of very effective technology.Even but in the receive diversity time spent, it also can be used to further improve down-link performance.

In multipath propagation environment, receiver obtains to be sent out several time delays, the amplitude convergent-divergent and the relevant version of arrival direction (DOA) of signal.When the interval of the maximum delay in-less-than symbol between the signal version that arrives at first along each path and arrive at last, these paths are nondecomposable in time domain.Yet because they are from different DOA, so these paths are decomposable in spatial domain.Because each path may experience independently decline, therefore utilize beam to form aerial array, can obtain several independent channels, can use the transmission diversity to it.

When maximum is-greater-than symbol in relative time delay interval, can observe a frequency selective fading channels.Frequency selectivity helps obtaining diversity, yet it also can bring need repressed intersymbol interference (ISI) in receiver.When message transmission rate increased, it is more and more general that this phenomenon can become.A kind of method that suppresses ISI adopts equalizer exactly in receiver.Yet the performance of equalizer will depend on the frequency response of wireless channel.Particularly when there was deep space (deep null) in the frequency response of channel in special frequency channel, balanced output will cause noise to strengthen, and its effect can reduce by the resulting diversity gain of frequency selectivity.On the other hand, when decision-directed symbol was used as reference signal, adaptive equalizer usually can quicken Error propagation problems, and if time delay expansion bigger, then the complexity of equalizer can be bigger.

Another method that reduces ISI is utilized adaptive antenna exactly in the base station, go to reduce the time delay expansion.For example, if arrival direction (DOA) information of each time delay version of the known received signal in base station, then it can form beam at a paths, and at the DOA in other path, arranging antenna gain is zero or very little.In this mode, portable terminal receives only each paths that is sent out signal.Although the input of this method is very simple,, therefore sacrificed diversity gain owing to can only utilize a paths.

Compare with receive diversity, send diversity and more paid attention in the past few decades." A new bandwidth efficient transmit antennamodulation diversity scheme for linear digital modulation (being used for linear digital new transmitting antenna modulation diversity scheme modulation, bandwidth efficient) " (Proc.ofICC ' 93 of A.Wittneben, the 1630-1634 page or leaf, 1993) in the time delay diversity set forth be exactly early stage a kind of transmission diversity technique of utilizing multiple transmit antennas.This method is deformed into frequency selective fading channels to falt fading channel, thereby utilizes frequency diversity.In order to compensate the ISI that non-natural cause is introduced, in portable terminal, provide equalizer.The performance of equalizer depends on the frequency characteristic of channel.And when the decision-directed symbol was used as reference signal, adaptive equalizer usually can quicken Error propagation problems.In fact, when maximum doppler frequency surpasses 40Hz, the performance of this deversity scheme even also poorer than not adopting diversity, " Feasibility of transmit diversity for IS-136 TDMA systems (sending the feasibility of diversity in the IS-136 tdma system) " (Proc.of VTC ' 98 referring to Y.C.Liang, Y.Li and K.J.R.Liu, the 2321-2324 page or leaf, 1998) in explanation.At S.M.Alamouti " A simpletransmit diversity technique for wireless communications (the simple transmission diversity technique that is used for radio communication) " (IEEE Journal of Selected Areasin Communications, 16 volumes, 8 phases, the 1451-1458 page or leaf, in October, 1998) in, Alamouti proposes a kind of displacement deversity scheme, and its performance classes is similar to high specific and merges (MRC) receive diversity.This method is only required simple receiver structure.More general transmission deversity scheme is called as space-time coding method, see " Space-time codes for high data rate wireless communication:Performance analysis and code construction (Space Time Coding that is used for high data rate wireless communication: performance evaluation and coding constitute) " (IEEE trans On InformationTheory of V.Tarokh, N.Seshadri and A.R.Calderbank, 44 volumes, 3 phases, the 744-765 page or leaf, in March, 1998).Space Time Coding comprises space-time grid coding (STTC) and space-time block code (STBC).In fact, the displacement diversity is exactly the simplest class STBC.

Provide the displacement deversity scheme that base station (BS) is furnished with two transmitting antennas 1,2 in the Alamouti displacement deversity scheme illustrated in fig. 1.The signal s (n) that is sent out at first encodes in Space Time Coding module 3.Space Time Coding module 3 is carried out work in the following manner.It possesses an input port and two output ports.Input port accepts to be sent out sequence s (0), s (1) ....In response, two output ports provide separately output signal s at moment t=n and t=n+1 ₁(t) and s ₂(t), wherein n is an even number, and is as follows

	t＝n	t＝n+1
			s 1(t)	s(n)/	s *(n+1)/
s 2(t)	s(n+1)/	-s *(n)/

At moment t=n and t=n+1, the received signal of single reception antenna 4 of portable terminal is:

x(n)＝α ₁s ₁(n)+α ₂s ₂(n)+w(n) (1)

x(n+1)＝α ₁s ₁(n+1)+α ₂s ₂(n+1)+w(n+1) (2)

α wherein ₁And α ₂It is respectively respective channel response from two transmitting antennas 1,2 to reception antenna 4; W (n) is additive white Gaussian noise (AWGN).

Subsequently, the signal that receives in the following manner, decoder module is decoded during by sky.Particularly, formula (1) and (2) can be written as matrix form:

$\left[\begin{array}{c}x\left(n\right)\\ x(n-1)\end{array}\right]=\frac{1}{\sqrt{2}}\left[\begin{array}{cc}s\left(n\right)& s(n+1)\\ s*(n+1)& -s*\left(n\right)\end{array}\right]\left[\begin{array}{c}{\mathrm{\α}}_1\\ {\mathrm{\α}}_2\end{array}\right]+\left[\begin{array}{c}w\left(n\right)\\ w(n+1)\end{array}\right]---\left(3\right)$

$\left[\begin{array}{c}x\left(n\right)\\ x*(n+1)\end{array}\right]=\frac{1}{\sqrt{2}}\left[\begin{array}{cc}{\mathrm{\α}}_1& {\mathrm{\α}}_2\\ -{\mathrm{\α}}_2^{*}& {\mathrm{\α}}_1^{*}\end{array}\right]\left[\begin{array}{c}s\left(n\right)\\ s(n+1)\end{array}\right]+\left[\begin{array}{c}w\left(n\right)\\ w*(n+1)\end{array}\right]---\left(4\right)$

Therefore, can utilize training symbol, estimate channel coefficients by equation (3); And equation (4) can be used as signal estimation/detection.The sort signal detection method also is known as permutation decoding.

Be noted that and require use the time delay diversity technique of complicated equalizer opposite that the channel estimating of displacement diversity and input only comprise very simple numerical operation at the receiver place.In addition, compare with the reception diversity technology of single transmit machine/two receivers, although there is the performance loss of 3dB in the displacement deversity scheme, it still can obtain and adopt high specific to merge the diversity gain of the reception diversity technology equivalent amount level of (MRC) scheme.

The displacement diversity can be extended to space-time block code (STBC) and space-time grid coding (STTC).All these codings can obtain to send diversity in flat fading environment.

An example of the present invention is exactly that the deversity scheme of Alamouti is applied to frequency selective fading channels.When time delay expansion is-greater-than symbol interval, can observe frequency selective fading channels.Fig. 2 illustrates the system model that the Alamouti deversity scheme is applied to frequency selective fading channels.Be sent out signal s (n) at first in coding module 3, utilize the Alamouti sign indicating number to encode, two branch roads outputs are respectively s ₁(n) and s ₂(n).S then ₁(n) and s ₂(n) be sent to two and have function g ₁(k), g ₂(k) pre equalizer 6,7 generates two output sequence y ₁(n) and y ₂(n).y ₁(n) and y ₂(n) finally through ovennodulation, and up-convert to the RF signal, by as physical channel h ₁(k) and h ₂(k) transmitting antenna 1,2 sends out.

The function g of pre equalizer 6,7 ₁(k) and g ₂(k) be used to respectively to two physical channel h ₁(k) and h ₂(k) carry out preequalization.By the preequalization of design employing Zero Forcing, present whole channel response g ₁(k) * h ₁(k) and g ₂(k) * h ₂(k) all be falt fading channel, the coding/decoding method of Alamouti can use for it.Here, " * " expression convolution algorithm.

In order to design pre equalizer 6,7, base station/transmitting antenna 1,2 should known real channel coefficients h ₁(k) and h ₂(k).Can accomplish this point by dual mode.For time division duplex (TDD) system, downlink channel coefficients is identical with the uplink channel coefficient, can obtain from the up link of utilizing training symbol or blind technology (up to fixing scaler).For Frequency Division Duplexing (FDD) (FDD) system, the base station sends one group of training symbol to portable terminal, estimate then, and to the base station feedback downlink channel information.

Said method also is applicable to other Space Time Coding.

OFDM (OFDM) is a kind of generally acknowledged known and effective method that overcomes the long time delay scaling problem.Combination OFDM and transmission deversity scheme not only suppress bigger time delay expansion, can also obtain to send diversity gain.Fig. 3 provides " Channel estimation for OFDM systems withtransmitter diversity in mobile wireless channels (channel estimating of the ofdm system that possesses transmitter diversity in the mobile radio channel) " (the IEEE Journal ofSelected Areas in Communications as Y.Li, N.Seshadri and S.Ariyavisitakul, 17 volumes, 3 phases, the 461-471 page or leaf, in March, 1999) describe in, be furnished with the ofdm system of the prior art of two antenna transmission diversity.Signal S (the n that is sent out; K) at first utilize the Space Time Coding in the coding module 3 to encode, generate two branch road output S ₁(n; K) and S ₂(n; K).S ₁(n; K) and S ₂(n; K) be sent to each conventional OFDM then and send processor 8,9, their output is finally modulated and up-convert to the RF signal, sends by transmitting antenna 1,2.

At single antenna receiver 4 places of travelling carriage, the signal that receives is transmitted to conventional OFDM receiver processor 10, follows decoder module 5 when the sky.In particular, rapid fourier change (FFT) output becomes:

X(n；k)＝H ₁(n；k)S ₁(n；k)+H ₂(n；k)S ₂(n；k)+W(n；k) (5)

X(n；k+1)＝H ₁(n；k+1)S ₁(n；k+1)+H ₂(n；k+1)S ₂(n；k+1)+W(n；k+1)

(6)

In (5) and (6), H ₁(n; K) and H ₂(n; K) be channel impulse response h between transmitting antenna 1 and the reception antenna 4 respectively ₁(n; K) and the channel impulse response h between transmitting antenna 2 and the reception antenna 4 ₂(n; K) Fourier transformation; W (n; K) be the additive noise w (n that reception antenna 4 receives; K) FFT output.

If select the S of moment t=k and t=k+1 as follows ₁(n; T), S ₂(n; T), then can easily use the permutation decoding method, wherein k is an even number:

	t＝k	t＝k+1
			S 1(n；t)	S(n；k)/	S *(n；k+1)/
S 2(n；t)	S(n；k+1)/	-S *(n；k)/

Prior art: for falt fading channel, the beam of combination forms and sends diversity.

Above-mentioned three kinds of methods (Alamouti displacement deversity scheme, be applied to the deversity scheme of frequency selective fading channels and be furnished with the OFDM that sends diversity) can be for falt fading channel, or frequency selective fading channels obtains to send diversity gain.Transmitting antenna belongs to diversity antenna, and promptly antenna distance is bigger, for example typically is 10 times wavelength.

Fig. 4 provides " Adaptiveantennas for space-time coding over block invariant multipathfading channels (adaptive antenna that is used for Space Time Coding on the constant multipath channel of part) " (the Proc.of IEEE VTC as R.Negi, A.M.Tehrani and J.Cioffi, the 70-74 page or leaf, 1999) middle elaboration, for the combination beam formation of falt fading channel and the known system of transmission diversity.The signal s (n) that is sent out generates two branch road output s at first through using Space Time Coding device module 3 codings ₁(n) and s ₂(n).s ₁(n) and s ₂(n) be sent to two then respectively and send beam formation device 11,12w ₁And w ₂, to follow by signal combiner 13, it carries out the simple summation function of two inputs, generates the signal x (n) that is used to send, and its vector form is:

$x\left(n\right)=w_1^H{s}_1\left(n\right)+w_2^H{S}_2\left(n\right)---\left(7\right)$

In order to obtain spatial selectivity, antenna distance d is set to less, and the number of for example half wavelength, and transmitting antenna 1A, 1B, 2, M is greater than 2.This is that beam forms aerial array, rather than diversity antenna array.Suppose that physical channel is made up of the path of L apart, its fading coefficients and DOA are expressed as (α _k(t), θ _k), k=1 wherein ..., L.If arrive the maximum delay in-less-than symbol interval in path relatively at first, then can observe falt fading channel, and instantaneous channel response h _d(t) can be expressed as follows:

$h_d\left(t\right)=\underset{k=1}{\overset{L}{\mathrm{\Σ}}}{\mathrm{\α}}_k\left(t\right){\mathrm{\α}}_d\left({\mathrm{\θ}}_k\right)---\left(8\right)$

A wherein _d(θ _k) be at DOA θ _kThe down link steering vector at place.The received signal y of portable terminal (n) is expressed as:

$y\left(n\right)=w_1^H{h}_d\left(t\right)s_1\left(n\right)+w_2^H{h}_d\left(t\right)s_2\left(n\right)+w\left(n\right)---\left(9\right)$

By being expressed as β ₁(t)=w ₁ ^Hh _d(t), β ₂(t)=w ₂ ^Hh _d(t), the maximum of cost function as calculated, estimate to send beam and form weights:

J＝E|β ₁(t)| ²+E|β ₂(t)| ² (10)

$s.t.E\left[{\mathrm{\β}}_1\left(t\right){\mathrm{\β}}_2^{*}\left(t\right)\right]=0---\left(11\right)$

By maximization (10), can obtain maximum average signal-to-noise ratio (SNR); And condition (11) can be guaranteed β ₁(t) and β ₂(t) be that statistics is incoherent, therefore can obtain maximum diversity gain.

Relatively (9) and (1) form by means of the down link beam, two uncorrelated fading channel β of statistics ₁(t) and β ₂(t) manually generate, decoding is to recover to be sent out signal s (n) in the time of can using sky to it.For the Alamouti deversity scheme, use permutation decoding.

Best send beam to form weight vector be the corresponding characteristic vector of characteristic value with two maximums of downlink channel covariance matrix (DCCM):

$R_d=E\left[h_d\left(t\right)h_d^H\left(t\right)\right]---\left(12\right)$

Wherein to all fading coefficients calculation expectation values.Suppose that all paths all have identical average power, perhaps E| α _k(t) ²=1/L, then DCCM is provided by following formula:

$R_d=\frac{1}{L}\underset{k=1}{\overset{L}{\mathrm{\Σ}}}{\mathrm{\α}}_d\left({\mathrm{\θ}}_k\right){\mathrm{\α}}_d^H\left({\mathrm{\θ}}_k\right)---\left(13\right)$

For TDD, DCCM is identical with uplink channel covariance matrix (UCCM).For FDD, have two kinds of methods and estimate DCCM, they all are based on the following fact, i.e. up link and the identical DOA of down link signal process.First method at first goes to estimate all paths according to the uplink signal that receives DOA constructs down link steering vector a then _d(θ _k) and utilize equation (13) further to construct DCCM R _dThe frequency calibration that " Downlink beamforming methods for capacityenhancement in wireless communication systems (being used for improving the down link beam formation method of capacity in the wireless communication system) " (the Singapore patent application No.9904733.4) of the second method utilization such as Y-C.Liang and F.Chin sets forth is handled, and directly estimates DCCM from UCCM.This method need not comprise DOA estimate with and related, therefore realize easily.

This system can obtain diversity gain simultaneously for flat fading environment and beam forms gain, but expects that system extension in the frequency selective fading environment.

For there not being beam-forming mobile radio telecommunications, two penetrate directly, and (TR) model, typical urban district (TU) model and knob (HT) model are that three kinds of power commonly used-delay distributes.When adding the formation of down link beam, need to consider that power-delay-DOA distributes.In the picocell, Microcell and the macrocell that adopt the TU model, the correlation between path delay and the DOA is lower.Yet in the macrocell that adopts TR and HR model, say on the path delay statistics usually and will depend on DOA.Below we provide, can have different schemes for varying environment, form and send diversity gain to obtain the combination beam, and maximum spectral efficiency.

Another example of the present invention utilizes OFDM, forms and send diversity with the beam that obtains combination.

For frequency selective fading channels, utilize OFDM can obtain to make up beam and form and send diversity.Fig. 5 provides the ofdm system that the beam that possesses combination formed and sent diversity.Although select OFDM to show how to reduce the time delay expansion as an example, form and send diversity gain and still keep beam simultaneously, but other example is other multi carrier modulation scheme, for example the single-carrier system of MC-CDMA, MC-DS-CDMA and employing Cyclic Prefix.

Signal S (the n that is sent out on k the single-tone (tone) in n piece; K) at first utilize the Space Time Coding in the coding module 3 to encode, generate two branch road output S at the place, base station ₁(n; K) and S ₂(n; K).S ₁(n; K) and S ₂(n; K) be sent to normal separately OFDM and send processor 8,9, be two afterwards respectively and send beam formation device 10,11 (w ₁And w ₂).Beam forms output and is finally merged in combiner 13, and sends through transmitting antenna 1A, the 1B, 2 of base-station antenna array.

Adopt base- station antenna array 1A, 1B, 2, the complex radical band of wireless channel impulse response is represented to be described as following vector form:

$h_d(t;\mathrm{\τ})=\underset{m}{\mathrm{\Σ}}\underset{l}{\mathrm{\Σ}}{\mathrm{\γ}}_{m,l}\left(t\right){\mathrm{\α}}_d\left({\mathrm{\θ}}_{m,l}\right)\mathrm{\δ}(\mathrm{\τ}-{\mathrm{\τ}}_m)---\left(14\right)$

τ wherein _mThe time delay of decomposable m paths on the express time, γ _{M, l}(t) and a _d(θ _{M, l}) be multiple amplitude and down link steering vector corresponding to the 1st DOA in the m bar time delay path.Because vehicle is mobile, γ _{M, l}(t) be the steadily multiple Gaussian process in (WSS) arrowband of broad sense, its average is zero, and for different m and l, is to add up independently.Suppose all γ _{M, l}(t) all possess identical normalization correlation function r (t) (r (0)=1), but have different average power σ _{M, l} ², then

$E\left[{\mathrm{\γ}}_{m,l}(t+\mathrm{\Δt}){\mathrm{\γ}}_{m,l}^{*}\left(t\right)\right]={\mathrm{\σ}}_{m,l}^{2}r\left(\mathrm{\Δt}\right)---\left(15\right)$

At moment t, h (t; Fourier transformation τ) (FFT) is provided by following formula:

$H_d(t;f)={\&Integral;}_{-\&infin;}^{\&infin;}{h}_d(t;\mathrm{\&tau;})e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C0212652200351.png,C0212652200371.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;f\&tau;}}\mathrm{d\&tau;}=\underset{m}{\mathrm{\&Sigma;}}\underset{l}{\mathrm{\&Sigma;}}{\mathrm{\&gamma;}}_{m,l}\left(t\right){\mathrm{\&alpha;}}_d\left({\mathrm{\&theta;}}_{m,l}\right)e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C0212652200351.png,C0212652200371.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;f}{\mathrm{\&tau;}}_m}---\left(16\right)$

For block length is T _b, the single-tone spacing is f _tOfdm system, H (t; F) centrifugal pump is:

$H_d[n;k]\underset{=}{\mathrm{\&Delta;}}{H}_d(n{T}_b;k{f}_t)=\underset{m}{\mathrm{\&Sigma;}}\underset{l}{\mathrm{\&Sigma;}}{\mathrm{\&gamma;}}_{m,l}\left(n{T}_s\right){\mathrm{\&alpha;}}_d\left({\mathrm{\&theta;}}_{m.l}\right)e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C0212652200351.png,C0212652200371.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;k}{f}_t{\mathrm{\&tau;}}_m}---\left(17\right)$

Concerning different time and frequency, the correlation function matrix of frequency response is like this

$r_d[\mathrm{\&Delta;n};\mathrm{\&Delta;k}]=E\left[H_d\right[n+\mathrm{\&Delta;n};k+\mathrm{\&Delta;k}\left]H_d^H\right[n;k\left]\right]=r\left(\mathrm{\&Delta;n}{T}_b\right)\underset{m}{\mathrm{\&Sigma;}}{e}^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C0212652200351.png,C0212652200371.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;\&Delta;k}{f}_t{\mathrm{\&tau;}}_m}{R}_{d,m---\left(18\right)}$

Wherein $R_{d,m}=\underset{l}{\mathrm{\&Sigma;}}{\mathrm{\&sigma;}}_{m,\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="C0212652200351.png,C0212652200371.png"\; state="\{\{state\}\}">l</figure-callout>}}^2{\mathrm{\&alpha;}}_d\left({\mathrm{\&theta;}}_{m,l}\right){\mathrm{\&alpha;}}_d^H\left({\mathrm{\&theta;}}_{m,l}\right)$ It is downlink channel covariance matrix corresponding to m bar time delay path.Note, when Δ n=0 and Δ k=0

$r_d[0;0]=\underset{m}{\mathrm{\&Sigma;}}\underset{l}{\mathrm{\&Sigma;}}{\mathrm{\&sigma;}}_{m,\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="C0212652200351.png,C0212652200371.png"\; state="\{\{state\}\}">l</figure-callout>}}^2{\mathrm{\&alpha;}}_d\left({\mathrm{\&theta;}}_{m.l}\right){\mathrm{\&alpha;}}_d^H\left({\mathrm{\&theta;}}_{m,l}\right)\underset{=}{\mathrm{\&Delta;}}{R}_d---\left(19\right)$

At the single antenna 4 of portable terminal, the signal of reception at first is sent to conventional OFDM receiving processor 10, follows by permutation decoding device 5.In conventional OFDM receiving processor, FFT output becomes:

$X[n;k]{=w}_1^H{H}_d[n;k]S_1[n;k]+w_2^H{H}_d[n;k]S_2[n;k]+W[n;k]---\left(20\right)$

$X[n;k+1]=w_1^H{H}_d[n;k+1]S_1[n;k+1]+w_2^H{H}_d[n;k+1]S_2[n;k+1]+W[n;k+1]---\left(21\right)$

W[n wherein; K] be the AWGN of zero-mean.

By expression β ₁(t)=w ₁ ^HH _d[n; K], β ₂(t)=w ₂ ^HH _d[n; K], estimate that through the maximization cost function beam forms weights:

J＝E|β ₁| ²+E|β ₂| ² (22)

$s.t.E\left[{\mathrm{\&beta;}}_1{\mathrm{\&beta;}}_2^{*}\right]=0---\left(23\right)$

Once more, by maximization equation (22), can obtain maximum average SNR; And condition (23) can be guaranteed β ₁And β ₂Be that statistics is incoherent, therefore can obtain maximum diversity gain.

The optimum beam formation weight vector that sends is and downlink channel covariance matrix (DCCM) R _dThe corresponding characteristic vector of characteristic value of two maximums:

$R_d=E\left[H_d\right[n;k\left]H_d^H\right[n;k\left]\right]---\left(24\right)$

Relatively equation (20) and (21) and equation (5) and (6) form by means of the down link beam, generate two irrelevant fading channels, and decoding is to recover to be sent out signal in the time of can using sky to it.If select S in the following manner ₁(n; K) and S ₂(n; K), then can adopt the permutation decoding method:

	t＝k	t＝k+1
			S 1(n；t)	s(n；k)/	s *(n；k+1)/
S 2(n；t)	s(n；k+1)/	-s *(n；k)/

The transmitting frequency calibration method that is used for the DCCM estimation of OFDM

Form weights in order to generate the down link beam, at first need to construct DCCM.Adopt frequency calibration (FC) method of " Downlink beamforming methods for capacityenhancement in wireless communication systems (being used for improving the down link beam formation method of capacity in the wireless communication system) " (Singapore patent application No.9904733.4) elaboration of Y-C.Liang and F.Chin.

Utilize similar method, we can be provided the correlation function matrix of the uplink frequency response of different time and frequency by following formula:

$r_u[\mathrm{\&Delta;n};\mathrm{\&Delta;k}]=E\left[H_u\right[n+\mathrm{\&Delta;n};k+\mathrm{\&Delta;k}\left]H_u^H\right[n;k\left]\right]=r\left(\mathrm{\&Delta;n}{T}_b\right)\underset{m}{\mathrm{\&Sigma;}}{e}^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C0212652200351.png,C0212652200371.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;\&Delta;k}{f}_t{\mathrm{\&tau;}}_m}{R}_{u,m}---\left(25\right)$

Wherein $R_{u,m}=\underset{l}{\mathrm{\&Sigma;}}{\mathrm{\&sigma;}}_{m,\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="C0212652200351.png,C0212652200371.png"\; state="\{\{state\}\}">l</figure-callout>}}^2{\mathrm{\&alpha;}}_u\left({\mathrm{\&theta;}}_{m,l}\right){\mathrm{\&alpha;}}_u^H({\mathrm{\&theta;}}_{m,l})$ It is uplink channel covariance matrix corresponding to m bar time-delay path.Note, when Δ n=0 and Δ k=0

$r_u[0;0]=\underset{m}{\mathrm{\&Sigma;}}\underset{l}{\mathrm{\&Sigma;}}{\mathrm{\&sigma;}}_{m,\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="C0212652200351.png,C0212652200371.png"\; state="\{\{state\}\}">l</figure-callout>}}^2{\mathrm{\&alpha;}}_u({\mathrm{\&theta;}}_{m,l}{)\mathrm{\&alpha;}}_u^H\left({\mathrm{\&theta;}}_{m,l}\right)\underset{=}{\mathrm{\&Delta;}}{R}_u---\left(26\right)$

Compare equation (19) and (26), frequency calibration (FC) method of " Downlinkbeamforming methods for capacity enhancement in wirelesscommunication systems (being used for improving the down link beam formation method of capacity in the wireless communication system) " (Singapore patent application No.9904733.4) design of Y-C.Liang and F.Chin can be used to estimate DCCM from UCCM.

This system forms gain for ofdm system provides diversity gain and beam.In this system, the length of Cyclic Prefix determined by the greatest physical time delay, and with conventional ofdm system in identical.Like this, it can easily be applied to DOA and delay statistics independently in the environment.

When the DOA in path is adding up relevant with the path delay of time, for example in TR and HR environment, then not only can obtain beam simultaneously and form gain and diversity gain, also reduced Cyclic Prefix, can improve spectrum efficiency like this.

Another example of the present invention is penetrated the directly frequency selective fading channels of (TR) model at two, utilizes the beam of combination to form and send diversity.

Suppose that physical channel follows the TR model.Adopt base-station antenna array, the complex radical band of wireless channel impulse response is represented to be described as following vector form:

$h_d(t;\mathrm{\&tau;})=\underset{m=1}{\overset{2}{\mathrm{\&Sigma;}}}{h}_{d,m}\left(t\right)\mathrm{\&delta;}(\mathrm{\&tau;}-{\mathrm{\&tau;}}_m)---\left(27\right)$

Have

$h_{d,m}\left(t\right)=\underset{l}{\mathrm{\&Sigma;}}{\mathrm{\&gamma;}}_{m,l}\left(t\right){\mathrm{\&alpha;}}_d\left({\mathrm{\&theta;}}_{m,l}\right)---\left(28\right)$

τ wherein _mThe time delay of decomposable m paths on the express time, γ _{M, l}(t) and a _d(θ _{M, l}) be multiple amplitude and down link steering vector corresponding to the 1st DOA in the m bar time delay path.Because vehicle is mobile, γ _{M, l}(t) be the steadily multiple Gaussian process in (WSS) arrowband of broad sense, its average is zero, and for different m and l, is to add up independently.Suppose all γ _{M, l}(t) all possess identical normalization correlation function r (t) (r (0)=1), but different average power σ is arranged _{M, l} ², then

$E\left[{\mathrm{\&gamma;}}_{m,l}(t+\mathrm{\&Delta;t}){\mathrm{\&gamma;}}_{m,l}^{*}\left(t\right)\right]={\mathrm{\&sigma;}}_{m,l}^{2}r\left(\mathrm{\&Delta;t}\right)--\left(29\right)$

As Δ τ=τ ₂-τ ₁During the is-greater-than symbol interval, there is ISI.Adopt the combination beam to form and diversity technique,, then may be converted to falt fading channel to frequency selective fading channels, still keep the transmission diversity if two to penetrate the footpath be apart.

Fig. 6 provides for two and penetrates the footpath frequency selective fading channels, has the communication system that the combination beam formed and sent diversity.The signal s (n) that is sent out at first encodes with Space Time Coding in coding module 3, and two branch roads are output as s ₁(n) and s ₂(n).S then ₁(n) be fed through postponing 14, s ₁(n) time-delay Δ τ generates x ₁And then be sent to and send beam and form device 11 (w (n), ₁).Second branch road output s ₂(n) directly delivered to another and sent beam formation device 12 (w ₂).Then, the combination beam forms output in combiner 13, and is sent by antenna 1A, 1B, 2, generates following transmission signal:

$x\left(n\right)=w_1^H{x}_1\left(n\right)+w_2^H{s}_2\left(n\right)---\left(30\right)$

The signal y (n) that receives at portable terminal single antenna 4 places is provided by following formula:

$y\left(n\right)=w_1^H{h}_{d,1}{x}_1\left(n\right)+w_1^H{h}_{d,2}{x}_1(n-\mathrm{\&Delta;\&tau;})$

$+w_2^H{h}_{d,1}{s}_2\left(n\right)+w_2^H{h}_{d,2}{s}_2(n-\mathrm{\&Delta;\&tau;})+w\left(n\right)---\left(31\right)$

Expression z (n)=y (n+ Δ τ), and consider two pre-aligns that are sent out signal, obtain

$z\left(n\right)=w_1^H{h}_{d,1}{s}_1\left(n\right)+w_1^H{h}_{d,2}{s}_1(n-\mathrm{\&Delta;\&tau;})$

$+w_2^H{h}_{d,1}{s}_2(n+\mathrm{\&Delta;\&tau;})+w_2^H{h}_{d,2}{s}_2\left(n\right)+w(n+\mathrm{\&Delta;\&tau;})---\left(32\right)$

Select beam to form weights, make the branch road output s that wins ₁(n) only through the first path h between base-station antenna array and the reception antenna 4 _{D, 1}And second branch road output s ₂(n) only through the second path h between base-station antenna array and the reception antenna 4 _{D, 2}On the mathematics,

$\left\{\begin{array}{c}{w}_1^H{h}_{d,2}=0\\ {\left|w_1^H{h}_{d,1}\right|}^2=\max \end{array}\right.$

With

$\left\{\begin{array}{c}{w}_2^H{h}_{d,1}=0\\ {\left|w_2^H{h}_{d,2}\right|}^2=\max \end{array}\right.$

In this case, the ISI item can be suppressed fully, and z (n) can be written as

$z\left(n\right)=w_1^H{h}_{d,1}{s}_1\left(n\right)+w_2^H{h}_{d,2}{s}_2\left(n\right)+w(n+\mathrm{\&Delta;\&tau;})---\left(33\right)$

Like this, frequency selective fading channels just is converted into falt fading channel now, wherein can use the transmission deversity scheme.

Easily, by maximizing average transmission SINR function, select to send beam-forming weights:

$J_1\left(w_1\right)=\frac{w_1^H{R}_{d,1}{w}_1}{w_1^H{R}_{d,2}{\mathrm{<figure-callout\; id="1"\; label="w"\; filenames="C0212652200351.png"\; state="\{\{state\}\}">w</figure-callout>}}_1}$ With $J_2\left(w_1\right)=\frac{w_2^H{R}_{d,2}{w}_2}{w_2^H{R}_{d,1}{\mathrm{<figure-callout\; id="2"\; label="w"\; filenames="C0212652200351.png,C0212652200371.png"\; state="\{\{state\}\}">w</figure-callout>}}_2}$

Wherein

$R_{d,m}=E\left[h_{d,m}\left(t\right)h_{d,m}^H\left(t\right)\right]=\underset{l}{\mathrm{\&Sigma;}}{\mathrm{\&sigma;}}_{m,l}^2{a}_d\left({\mathrm{\&theta;}}_{m,l}\right)a_d^H\left({\mathrm{\&theta;}}_{m,l}\right)---\left(34\right)$

It is the downlink channel covariance matrix of m paths.

Preferably, select to send beam-forming weights, promptly by the average received SINR at maximization mobile receiver place

$J=\frac{w_1^H{R}_{d,1}{\mathrm{<figure-callout\; id="1"\; label="w"\; filenames="C0212652200351.png"\; state="\{\{state\}\}">w</figure-callout>}}_1+w_2^H{R}_{d,2}{w}_2}{w_1^H{R}_{d,2}{\mathrm{<figure-callout\; id="1"\; label="w"\; filenames="C0212652200351.png"\; state="\{\{state\}\}">w</figure-callout>}}_1+w_2^H{R}_{d,1}{\mathrm{<figure-callout\; id="2"\; label="w"\; filenames="C0212652200351.png,C0212652200371.png"\; state="\{\{state\}\}">w</figure-callout>}}_2+{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="C0212652200351.png,C0212652200371.png"\; state="\{\{state\}\}">n</figure-callout>}}^2},---\left(35\right)$

Benefit is to send beam and form weight w _mCan selectedly be used as R _{D, m}Main characteristic vector.

Once more, the transmitting frequency calibration method of Y-C.Liang and F.Chin " Downlink beamforming methodsfor capacity enhancement in wireless communication systems (being used for improving the down link beam formation method of capacity in the wireless communication system) " (Singapore patent application No.9904733.4) elaboration can be used to directly estimate DCCM from UCCM.

The above-mentioned method that is used to obtain to make up beam formation and send diversity gain can be known as pre-align (PAL) method.S ₁(n) purpose of time-delay Δ τ is to guarantee two sequence s ₁(n) and s ₂(n) fundamental component can reach receiver simultaneously.Therefore, the time delay expansion has been reduced to zero.On the other hand, beam forms and is used to minimize the ISI influence, and manually generates two unrelated signals, can obtain to send diversity gain to it.

The PAL method requires to be included in the time delay information Δ τ in downlink power-delay-DOA (PDD) distribution.Become when being even PDD distributes, its variation in time also is slowly.And down link PDD distributes almost identical with up link PDD distribution, and this can estimate from the uplink signal that receives.

The PAL method also can be used to penetrate footpath quantity more than in 2 the system.In this case, require Space Time Coding output branch road, and except that first output, each is exported corresponding to a time delay more than two.

If the quantity of Space Time Coding output is (for example 2) that fix, then form weights in order to generate time delay Δ τ and to send beam, can select two mainly to penetrate the footpath.Because the sum of branch has been reduced, so the direct application of this system will reduce the interference between the interior branch of CDMA exactly.

Conventional, when penetrating the footpath by many, physical channel h (k) forms, wherein mainly penetrate footpath h for two ₁(k), h ₂When (k) being delayed Δ τ, select beam to form weights, make the signal that is delayed only penetrate footpath h through one between base station multiple transmit antennas and the reception antenna ₁(k), the signal that is not delayed is only penetrated footpath h through between base station multiple transmit antennas and the reception antenna another ₂(k).

Benefit is, forms when physical channel h (k) penetrates the footpath by many, wherein mainly penetrates directly h for two ₁(k), h ₂When (k) being delayed Δ τ, select beam to form weights, make and penetrate the average transmission SINR function maximum that the footpath is located in the base station for every.

Benefit is, forms when physical channel h (k) penetrates the footpath by many, wherein mainly penetrates directly h for two ₁(k), h ₂When (k) being delayed Δ τ, select beam to form weights, make in the average received SINR at portable terminal place function maximum.

Another example of the present invention is penetrated the directly frequency selective fading channels of (TR) model for two, utilizes the beam that has combination to form and send the OFDM of diversity.

In OFDM, can directly utilize the time delay expansion to reduce.In typical ofdm system, in order to remove ISI and to guarantee orthogonality between each subchannel, and add Cyclic Prefix.The length of Cyclic Prefix should be greater than maximum delay, and it can reach 40 μ s in the mobile radio telecommunications environment.Add Cyclic Prefix and not only reduced spectrum efficiency, also can take a part of transmitting power.If when keeping identical performance, can reduce the length of Cyclic Prefix, then can improve the spectrum efficiency and the effect of ofdm system greatly.

Suppose that it is (α that physical channel is followed parameter _k, θ _k, τ _k) the TR model, k=1,2 and τ ₁＜τ ₂α _kBe add up independently, zero-mean, variance is σ _k ²Multiple Gaussian process.As Δ τ=τ ₂-τ ₁During greater than bandwidth reciprocal, there is ISI.

Fig. 7 illustrates that realization is of the present invention, for the ofdm system that the combination beam formed and sent diversity that has of TR model.K single-tone is sent out signal S (n in n piece; K) at first encode, generate two branch road output S with the Space Time Coding in the coding module 3 ₁(n; K) and S ₂(n; K).Two branch road output S ₁(n; K) and S ₂(n; K) do not add Cyclic Prefix, the OFDM that is sent to separately sends processor 8,9.S then ₁(n; K) in the time delay that postpones process Δ τ in 14, generate X ₁(n; K), the latter is sent to again and sends beam formation device 11 (w ₁).Second branch road output S ₂(n; K) directly delivered to another and sent beam formation device 12 (w ₂).Then, beam forms output and is combined, and sends on base station transmit antenna array 1A, 1B, 2, obtains the following signal that is sent out:

$x(n;k)=w_1^H{x}_1(n;k)+w_2^H{s}_2(n;k)---\left(36\right)$

At portable terminal single antenna 4 places, the signal that receives at first is sent to conventional OFDM receiving processor 10.Select beam to form weights, make the branch road output S that wins ₁(n; K) or its anti-FFT (IFFT) s ₁(n; K) only through the first path h between base-station antenna array and the reception antenna 4 ₁(n; And second branch road output S k), ₂(n; K) or its anti-FFT (IFFT) s ₂(n; K) only through the second path h between base-station antenna array and the reception antenna 4 ₂(n; K).In case suitably selected the transmission beam to form weights, become in the FFT of travelling carriage place received signal output

Relatively equation (37) and equation (5) form by means of the down link beam, and decoding was to recover to be sent out two different channels of signal when manual creation can be carried out sky by module 5.And, if select S as follows ₁(n; K) and S ₂(n; K), then can easily adopt the permutation decoding method:

	t＝k	t＝k+1
			S 1(n；t)	s(n；k)/	s *(n；k+1)/
S 2(n；t)	s(n；k+1)/	-s *(n；k)/

The combination beam forms and when sending the ofdm system of diversity, do not need to add Cyclic Prefix when PAL is applied to the TR model had.Such benefit is: send the raising of diversity, beam formation gain and spectrum efficiency.

Easily, can select beam to form weights by the average SINR function that sends of maximization.

Preferably, select to send beam-forming weights by the average received SINR of maximization mobile receiver.

Benefit is to send beam and form weight w _mCan selectedly be used as R _{D, m}Main characteristic vector.

Once more, the transmitting frequency calibration method of Y-C.Liang and F.Chin " Downlink beamforming methodsfor capacity enhancement in wireless communication systems (being used for improving the down link beam formation method of capacity in the wireless communication system) " (Singapore patent application No.9904733.4) elaboration can be used to directly estimate DCCM from UCCM.

Provide below and utilize the expansion of this time delay to reduce the spectrum efficiency that method carries out and the comparison of power-saving.

Another example of the present invention utilizes the beam that has combination to form and send the OFDM of diversity at the frequency selective fading channels of mountain area, hills (HT) model.

Even maximum delay reaches 40 μ s, the wireless channel that satisfies the HT model also can be described by the path of several leading collection bunch, and each path all has a little time delay expansion.These the collection bunch the path also all be apart.For the distribute OFDM of (its maximum delay is 20 μ s, and the maximum delay expansion in each path that is collected bunch is 2 μ s) of typical HT power-delay is arranged, in order to remove ISI, the minimum length of signal prefix is 20 μ s.Yet adopt the PAL method, the duration of Cyclic Prefix can be reduced to 2 μ s.

Suppose that these two paths by collection bunch are delayed Ψ, and for easy, suppose that the time delay expansion in the path that each is collected bunch is Δ Ψ.The impulse response of time varying channel can be described as

h(t；τ)＝h ₁(t；τ)[u(τ)-u(τ-ΔΨ)]+h ₂(t；τ-Ψ)[u(τ-Ψ)-u(τ-Ψ-ΔΨ)] (38)

H wherein ₁(t; τ) and h ₂(t; τ) correspond respectively to first and second by the channel response in path of collection bunch; And u (x) is a unit step function.

Fig. 8 be given in the coder module 3 realize of the present invention, for the ofdm system that the combination beam formed and sent diversity that has of knob (HT) model.Signal S (the n that will be sent out in k the single-tone in n piece; K) at first in coder module 3, encode, generate two branch road output S by Space Time Coding ₁(n; K) and S ₂(n; K), the conventional OFDM that transfers them to then separately sends processor 8,9, and its circulating prefix-length is Δ Ψ, rather than Ψ+Δ Ψ.The output of first branch road is postponing to be delayed Ψ in 15 then, and the output of second branch road remains unchanged.Afterwards, signal is sent to respectively and is sent beam formation device 11,12 (w separately ₁And w ₂).Then, the combination beam forms output in combiner 13, and sends through base station transmit antenna array 1A, 1B, 2.

Select beam to form weights, make the branch road input of winning, and the input of second branch road promptly selects beam to form weights only through second by the path of collection bunch, makes the branch road output s that wins only through first by the path of collection bunch ₁(n) only through the first path h between base-station antenna array and the reception antenna 4 _{D, 1}, and second branch road output s ₂(n) only through the second path h between base-station antenna array and the reception antenna 4 _{D, 2}The signal that receives at portable terminal single antenna 4 places at first is sent to conventional OFDM receiving processor 10, follows decoder module 5 when the sky.In conventional OFDM receiving processor 10, the received signal after the FFT becomes:

Wherein  x  represents to be not more than the maximum integer of x.Relatively equation (39) and equation (5) form by means of the down link beam, and decoding is to recover to be sent out two different channels of signal when manually generating through sky.If select S as follows ₁(n; K) and S ₂(n; K), then can easily adopt the permutation decoding method:

	t＝k	t＝k+1
			S 1(n；t)	s(n；k)/	s *(n；k+1)/
S 2(n；t)	s(n；k+1)/	-s *(n；k)/

Easily, can select to send beam and form weights by the average SINR function that sends of maximization.

Preferably, select to send beam and form weights by the average received SINR of maximization mobile receiver.

Benefit is to send beam and form weight w _mCan selectedly be used as R _{D, m}Main characteristic vector.

As mentioned above, under the more different subsequently circulating prefix-length conditions, the spectrum efficiency of ofdm system.

Parameter is bandwidth B=800kHz, maximum delay=40.For the HT model, the expansion of the maximum delay in the path of every collection bunch is 5.In order to make single-tone mutually orthogonal, symbol duration is N/B, and wherein N is the number of single-tone in each OFDM symbol.The total length of piece is symbol duration and additional protection interval sum, and for the TR of the OFDM that does not adopt PAL, the HT that adopts PAL and employing PAL, it is respectively 40,5,0.

QPSK modulation, the not coding transmission data rate of the ofdm system of different single-tone numbers are adopted in explanation in the Table I.Can see that under given modulation scheme and identical single-tone quantity term, by adopting PAL, for the TR environment, transmitted data rates can be increased to 1.6Mbps, and is independent of the value of N.For the HT that adopts PAL, and do not adopt comparing of PAL, spectrum efficiency also can increase.

Table I: transmitted data rates relatively

	N＝128	N＝64	N＝32
				Do not adopt PAL	1.28Mbps	1.07Mbps	800kbps
Adopt the HT of PAL	1.55Mbps	1.51Mbps	1.42Mbps
				Adopt the TR of PAL	1.6Mbps	1.6Mbps	1.6Mbps

The power that relatively has different Cyclic Prefix in OFDM System to save below:

Owing to add Cyclic Prefix, effectively E _b/ N ₀Be less than the E of actual transmission _b/ N ₀Along with reducing of time delay expansion, can more effectively use transmitted power.The Table II explanation is compared with conventional ofdm system, in each OFDM piece, and under the different single-tone quantity terms, the power that the ofdm system that adopts PAL to reduce the time delay expansion is saved.

Table II: power-saving

	N＝128	N＝64	N＝32
				Adopt the HT of PAL	0.84dB	1.5dB	2.5dB
Adopt the TR of PAL	0.97dB	1.76dB	3.0dB

Beam forms and diversity gain:

There has been the beam of combination to form and diversity gain, will have required less E in order to make system reach desired given bit error rate (BER) _b/ N ₀Perhaps, adopt the more high modulation scheme of 128 QAM for example or 256 QAM, beam forms and diversity gain can be converted into higher spectrum efficiency.

Another embodiment of the present invention relates to the Adaptive Time Delay expansion of adopting formation of combination beam and diversity gain and reduces:

The foregoing description all designs at varying environment.In actual applications, because the moving of vehicle, power-delays-DOA (PDD) distributes all can relative time and change, and like this in order to obtain maximum spectral efficiency, time delay is expanded and reduced scheme and should correspondingly follow this variation.Provide among Fig. 9 to down link adopt of the present invention, have the combination beam and form, send the ofdm system that diversity and Adaptive Time Delay expansion reduce.The OFMD system of Fig. 9 comprises the system of Fig. 8, but the estimation that replenished wherein that UCCM estimates and power-delay-DOA distributes.Like this, except Fig. 8 system provided functional, this system also possesses following functional:

According to the uplink signal that the base station receives, utilize training sequence or blind technology, for each RX path estimation time delay with reach direction (DOA) information.On the basis of estimation time delay and DOA information, can estimating uplink power-delay-DOA (PDD) distributes, and the UCCM in each path that is collected bunch;

Distribute based on up link PDD, can determine following parameter: the maximum delay in the path of the time delay in diversity order, path that each is collected bunch and this collection bunch is expanded;

Up link PDD distribution is used to design Adaptive Time Delay and reduces scheme, thereby design self adaptation Cyclic Prefix adds scheme;

Utilize the FC method of " Downlink beamforming methodsfor capacity enhancement in wireless communication systems (being used for improving the down link beam formation method of capacity in the wireless communication system) " (Singapore patent application No.9904733.4) elaboration of Y-C.Liang and F.Chin, estimate the DCCM in the path that each is collected bunch according to corresponding UCCM, be applied to structure with time delay information then and send beam and form weights;

The base station is notified to MS to the length of the Cyclic Prefix that adds;

Adaptive Modulation also is used to further improve spectrum efficiency on the basis of diversity order/channel conditions.Especially, on the basis that up link PDD distributes, determine that maximum can realize diversity order.If can realize that diversity order is bigger, then can adopt higher modulation scheme; Otherwise, adopt lower modulation scheme.

Should be noted that, depend on the diversity order that will obtain, the branch road output number in the module 3 after the Space Time Coding can be greater than 2.

More than describe and consider that the combination beam of implementing forms, sends diversity and the time delay expansion reduces in the base station.In fact, in portable terminal, also can add a plurality of diversity antennas, to obtain receive diversity.In this case, can obtain bigger diversity gain:

Even OFDM is used to show how to reduce the time delay expansion, its still can be kept simultaneously beam and form and send diversity gain, the elaboration among the application also can be used to other for example MC-CDMA, MC-DS-CDMA multi carrier modulation scheme and possess in the single-carrier system of Cyclic Prefix.

In multi-user environment, can consider channel/DOA information of all users, generate beam and form weights; Therefore, the application's elaboration also is applicable to different multiple access access schemes, for example time division multiple access multiplexing (TDMA), frequency division multiple access multiplexing (FDMA) and CDMA multiplexing (CDMA).

" comprise " and mean " comprise or by ... form ".

In above description or subsequently claim or accompanying drawing, with its peculiar form, perhaps to carry out the device of the function of being set forth, perhaps set forth result's method or the feature that process is set forth to reach, can be according to suitable mode, individually or make up this feature ground, be used to realize the present invention with various forms.

Claims (35)

1. In a communication system having a base station with multiple transmit antennas and a mobile terminal with at least one single receive antenna, a method for obtaining transmit diversity gain for a frequency-selective fading channel, comprising the steps of: Provide the signal s(n) to be sent; space-time encoding the signal s(n) to generate at least two separate signals s ₁ (n), s ₂ (n), each on a respective output; Send each output signal s ₁ (n), s ₂ (n) to a zero-forcing pre-equalizer with respective functions g ₁ (k), g ₂ (k) to generate output signals x ₁ (n), x ₂ (n); Send the output signals x ₁ (n) and x ₂ (n) of each pre-equalizer to the transmitting antenna; transmit output signals x ₁ (n), x ₂ (n) via respective physical channels h ₁ (k), h ₂ (k); Receive the output signals x ₁ (n), x ₂ (n) at at least one single receive antenna; and space-time decode the received signals, where Select the functions g ₁ (k) and g ₂ (k) of the zero-forcing pre-equalizer so that the channel responses of each physical channel h ₁ (k) and h ₂ (k) g ₁ (k)*h ₁ (k), g ₂ (k)*h ₂ (k) is a flat fading channel; and The real channel coefficients are obtained from the uplink channel coefficients for the functions g ₁ (k), g ₂ (k) to select the pre-equalizer. 2. The method according to claim 1, wherein the step of deriving the true channel coefficients from the uplink channel coefficients uses training symbols from the uplink channel. 3. The method according to claim 1, wherein a blinding technique is used in the step of deriving the true channel coefficients from the uplink channel coefficients. 4. The method according to claim 1, wherein the communication system is a frequency-division duplex system, and the method also includes sending a group of training symbols to a receiving antenna of the mobile terminal, the mobile terminal estimates the true channel coefficients, and the channel coefficient information Feedback to the base station to obtain the real channel coefficient. 5. A base station with multiple transmit antennas communicating with a mobile terminal having at least one single receive antenna via physical channels h ₁ (k) and h ₂ (k), the base station comprising: a space-time encoder having an input to be transmitted a signal s(n) and at least two outputs, each output generating a separate signal s ₁ (n), s ₂ (n); At least two zero-forcing pre-equalizers, each fed with a respective output signal s ₁ (n), s ₂ (n), and having a respective function g ₁ (k), g ₂ (k), generate an output Signals x ₁ (n), x ₂ (n); where the true channel coefficients are derived from the uplink channel coefficients for the functions g ₁ (k), g ₂ (k) that select the pre-equalizer; and At least two transmit antennas, each fed with an output signal x ₁ (n), x ₂ (n) of a respective pre-equalizer, where the functions g ₁ (k), g ₂ (k ), so that the channel responses g ₁ (k)*h 1 (k), _{g 2} (k)*h ₂ (k) of each physical channel h ₁ (k) and h ₂ (k) are flat fading channels. 6. A communication system comprising a base station according to claim 5 and a mobile terminal having at least one single receive antenna and a space-time decoder for decoding signals received from the base station. 7. In a communication system having a base station with multiple transmit antennas and a mobile terminal with at least one single receive antenna, a method for obtaining combined beamforming and transmit diversity for a frequency-selective fading channel, the method comprising the steps of: Provide the signal S(n;k) to be sent; space-time encoding the signal S(n;k) to generate at least two separate signals S ₁ (n;k), S ₂ (n;k), each on a respective output; Sending each output signal S ₁ (n; k), S ₂ (n; k) to a transmit processor to generate output signals X ₁ (n; k), X ₂ (n; k); Applying a respective selected transmit beamforming weight to each output signal X ₁ (n; k), X ₂ (n; k); Send each weighted signal to the signal combiner, perform the summation function of the signal, and generate the signal X(n; k) for transmission; Send the summed signal X(n; k) to each antenna in the multi-transmission antennas for transmission; Send a signal X(n; k) through the physical channel h(n; k), where the physical channel h(n; k) consists of two delay paths h ₁ (n; k), h ₂ (n; k) composition; receiving the received signal Y(n;k) at at least one single receive antenna; sending the received signal Y(n; k) to a receiving processor to generate an output signal; and performing space-time decoding on the received signal; wherein The transmit processor does not add a cyclic prefix, and one of the output signals from the transmit processor is delayed by Δτ before applying the respective selected transmit beamforming weights. 8. The method according to claim 7, wherein each transmit beamforming weight is selected as the two largest eigenvalues corresponding to the downlink channel covariance matrix (DCCM) of the physical channel h(n; k) Feature vector. 9. The method of claim 7, wherein the transmit and receive processors are selected from the group consisting of OFDM, MC-CDMA, MC-DS-CDMA and single carrier systems with cyclic prefix. 10. The method according to claim 7, wherein the physical channel h(n; k) consists of two delay paths h ₁ (n; k) and h ₂ (n; k) with a time delay of Δτ, and the selected rays Beamforming weights such that the average transmit SINR function at the base station is maximized for each beam. 11. The method according to claim 7, wherein the physical channel h(n; k) consists of two delay paths h ₁ (n; k), h ₂ (n; k) with a delay of Δτ, the beam selected The weights are formed such that the average received SINR function at the mobile terminal is maximized. 12. The method according to claim 7, wherein the physical channel h(n; k) is composed of two delay paths h ₁ (n; k), h ₂ (n; k) with a delay of Δτ, for each A beam-forming weight is selected for a beam as the principal eigenvector of the downlink channel covariance matrix (DCCM) corresponding to that beam. 13. In a communication system having a base station with multiple transmit antennas and a mobile terminal with at least one single receive antenna, a method for obtaining combined beamforming and transmit diversity for a frequency-selective fading channel, the method comprising the steps of: Provide the signal S(n;k) to be sent; space-time encoding the signal S(n;k) to generate at least two separate signals S ₁ (n;k), S ₂ (n;k), each on a respective output; Sending each output signal S ₁ (n; k), S ₂ (n; k) to a transmit processor to generate output signals X ₁ (n; k), X ₂ (n; k); Applying a respective selected transmit beamforming weight to each output signal X ₁ (n; k), X ₂ (n; k); Send each weighted signal to the signal combiner, perform the summation function of the signal, and generate the signal X(n; k) for transmission; Send the summed signal X(n; k) to each antenna in the multi-transmission antennas for transmission; Send a signal X(n; k) through the physical channel h(n; k); receiving the received signal Y(n;k) at at least one single receive antenna; sending the received signal Y(n; k) to a receiving processor to generate an output signal; and performing space-time decoding on the received signal; The physical channel h(n; k) is composed of two delay paths h ₁ (n; k) and h ₂ (n; k) with a delay of Δτ, and the beamforming weights are selected such that the delayed signal or Its inverse fast Fourier transform (IFFT) only passes through a channel h ₁ (n; k) between the base station's multiple transmit antennas and the receive antenna, while the undelayed signal or its IFFT only passes through the base station's multiple transmit antennas and receive antennas Another channel h ₂ (n; k) between , thus creating two different channels that can be space-time decoded to recover the transmitted signal. 14. The method according to claim 13, wherein each transmit beamforming weight is selected as the two largest eigenvalues corresponding to the downlink channel covariance matrix (DCCM) of the physical channel h(n; k) Feature vector. 15. In a communication system having a base station with multiple transmit antennas and a mobile terminal with at least one single receive antenna, a method for obtaining combined beamforming and transmit diversity for a frequency-selective fading channel, the method comprising the steps of: Provide the signal S(n;k) to be sent; space-time encoding the signal S(n;k) to generate at least two separate signals S ₁ (n;k), S ₂ (n;k), each on a respective output; Sending each output signal S ₁ (n; k), S ₂ (n; k) to a transmit processor to generate output signals X ₁ (n; k), X ₂ (n; k); Applying a respective selected transmit beamforming weight to each output signal X ₁ (n; k), X ₂ (n; k); Send each weighted signal to the signal combiner, perform the summation function of the signal, and generate the signal X(n; k) for transmission; Send the summed signal X(n; k) to each antenna in the multi-transmission antennas for transmission; Send a signal X(n; k) through the physical channel h(n; k); receiving the received signal Y(n;k) at at least one single receive antenna; sending the received signal Y(n; k) to a receiving processor to generate an output signal; and performing space-time decoding on the received signal; where the physical channel h(n;k) consists of two clustered beam paths h ₁ (n;k) and h ₂ (n;k) with a delay of Ψ, the maximum exceeding time of the cluster By ΔΨ, the transmit processors are provided with a cyclic prefix of length ΔΨ, and one of the output signals from the transmit processors is delayed by Ψ before applying the respective selected transmit beamforming weights. 16. The method according to claim 15, wherein the beamforming weights are selected such that the delayed signal or its inverse fast Fourier transform (IFFT) passes only through one channel h ₁ (n; k), while the undelayed signal or its IFFT only passes through another channel h ₂ (n; k) between the multiple transmit and receive antennas of the base station, thus creating two channels that can be space-time decoded to recover the transmitted signal different channels. 17. The method of claim 15, wherein the beamforming weights are chosen such that the average transmit SINR function at the base station is maximized for each clustered path. 18. The method of claim 15, wherein the beamforming weights are chosen such that the average received SINR function at the mobile terminal is maximized. 19. The method of claim 15, wherein beamforming weights are selected for each clustered path as the principal eigenvectors of the downlink channel covariance matrix (DCCM) corresponding to the clustered paths . 20. The method according to claim 15, further comprising the steps of: Estimate the power-delay-DOA distribution for the channel h(n; k); and on the basis of this distribution, determine the cyclic prefix ΔΨ to be added by the transmit processor; determine the delay Ψ; the diversity magnitude and the modulation scheme; and determine the transmit radio bundle forming weights. 21. The method of claim 20, further comprising the step of estimating the downlink channel covariance matrix (DCCM) from the uplink channel covariance matrix (UCCM) to construct transmit beamforming weights. 22. The method of claim 21, further comprising the step of determining the diversity magnitude and the modulation scheme on a distribution basis. 23. The method according to claim 15, wherein each transmit beamforming weight is selected as the two largest eigenvalues corresponding to the downlink channel covariance matrix (DCCM) of the physical channel h(n; k) Feature vector. 24. A base station with multiple transmit antennas for communicating with a mobile terminal having at least one single receive antenna via a physical channel h(k), the base station comprising: a space-time encoder having an input to be signaled and at least two outputs, each output generating a separate signal; at least two transmit processors, each receiving one of the outputs of a respective space-time encoder; at least two transmit beamformers each receiving the output of a respective transmit processor and applying transmit beamforming weights thereto; a signal combiner receiving signals from the beamformers and operable to perform a signal summation function from the beamformers and generate signals for transmission by the multiple transmit antennas; The physical channel h(n; k) consists of two delay paths h ₁ (n; k) and h ₂ (n; k) with a delay of Δτ, including A delay of Δτ between one of the outputs and the beamformer such that the signal output from the transmit processor is delayed by Δτ before applying the respective selected transmit beamforming weights, wherein the transmit processor does not add a cyclic prefix . 25. A communication system comprising the base station of claim 24 and a mobile terminal having at least one single receive antenna, a receive processor for generating the output signal and a space-time decoder for decoding the output signal. 26. A base station with multiple transmit antennas for communicating with a mobile terminal having at least one single receive antenna via a physical channel h(k), the base station comprising: a space-time encoder having an input to be signaled and at least two outputs, each output generating a separate signal; at least two transmit processors, each receiving one of the outputs of a respective space-time encoder; at least two transmit beamformers each receiving the output of a respective transmit processor and applying transmit beamforming weights thereto; a signal combiner receiving signals from the beamformers and operable to perform a signal summation function from the beamformers and generate signals for transmission by the multiple transmit antennas; where the physical channel h(n;k) consists of two delayed, clustered paths h ₁ (n;k) and h ₂ (n;k) with delay Ψ, the maximum excess delay of the cluster is ΔΨ, also including a delay of Ψ placed between one of the multi-access transmit processor outputs and the beamformer so that The signal output delay of the processor is Ψ, and the sending processor has a cyclic prefix of length ΔΨ. 27. A base station with multiple transmit antennas for communicating with a mobile terminal having at least one single receive antenna via a physical channel h(k), the base station comprising: a space-time encoder having an input to be signaled and at least two outputs, each output generating a separate signal; at least two transmit processors, each receiving one of the outputs of a respective space-time encoder; at least two transmit beamformers each receiving the output of a respective transmit processor and applying transmit beamforming weights thereto; a signal combiner that receives signals from the beamformers and is operable to perform a signal summation function from the beamformers and generate signals for transmission by the multiple transmit antennas; and A first processor that determines a power-delay-DOA distribution estimate for channel h(n; k); and on the basis of this distribution, determines: cyclic prefix length ΔΨ added by the transmit processor; delay Ψ; diversity magnitude and modulation schemes; and transmit beamforming weights. 28. The base station of claim 27, further comprising a second processor that estimates the downlink channel covariance matrix (DCCM) from the uplink channel covariance matrix (UCCM) to construct transmit beamforming weights. 29. The base station of claim 15, wherein the transmit and receive processors are selected from the group consisting of OFDM, MC-CDMA, MC-DS-CDMA, and single carrier systems with cyclic prefix. 30. A communication system comprising the base station of claim 26 and a mobile terminal having at least one single receive antenna, a receive processor for generating an output signal, and a space-time decoder for decoding the output signal. 31. A communication system comprising the base station of claim 27 and a mobile terminal having at least one single receive antenna, a receive processor for generating the output signal and a space-time decoder for decoding the output signal. 32. In a communication system having a base station with multiple transmit antennas and a mobile terminal with at least one single receive antenna, a method for obtaining combined beamforming and transmit diversity for a frequency-selective fading channel, the method comprising the steps of: Provide the signal s(n) to be sent; space-time encoding the signal s(n) to be transmitted, generating at least two separate signals s ₁ (n), s ₂ (n), each on a respective output; Delaying one of the space-time encoded output signals by Δτ; applying respective selected transmit beamforming weights to the delayed and non-delayed signals; Send each weighted signal to a signal combiner, perform the summation function of the signal, and generate a signal for transmission; sending the summed signal to each antenna in the multi-transmission antennas for transmission; sending the summed signal over the physical channel h(k); receiving the main components of the transmitted signal at at least one single receive antenna at substantially the same time; and performing space-time decoding on the received signal; The physical channel h(k) is composed of two delay paths h ₁ (k) and h ₂ (k) with a delay of Δτ, and the beamforming weights are selected so that the delayed signal only passes through the multi-transmission antennas of the base station One path h ₁ (k) between the receiving antenna and the receiving antenna, and the undelayed signal only passes through another path h ₂ (k) between the transmitting antenna and the receiving antenna of the base station. 33. In a communication system having a base station with multiple transmit antennas and a mobile terminal with at least one single receive antenna, a method for obtaining combined beamforming and transmit diversity for a frequency-selective fading channel, the method comprising the steps of: Provide the signal s(n) to be sent; space-time encoding the signal s(n) to be transmitted, generating at least two separate signals s ₁ (n), s ₂ (n), each on a respective output; Delaying one of the space-time encoded output signals by Δτ; applying respective selected transmit beamforming weights to the delayed and non-delayed signals; Send each weighted signal to a signal combiner, perform the summation function of the signal, and generate a signal for transmission; sending the summed signal to each antenna in the multi-transmission antennas for transmission; sending the summed signal over the physical channel h(k); receiving the main components of the transmitted signal at at least one single receive antenna at substantially the same time; and performing space-time decoding on the received signal; The physical channel h(k) is composed of multiple paths, and the two main paths h ₁ (k) and h ₂ (k) are delayed by Δτ, and the beamforming weights are selected so that the delayed signal only passes through the base station One radiation path h ₁ (k) between the transmitting antenna and the receiving antenna, and the undelayed signal only passes through another radiation path h ₂ (k) between the transmitting antenna and the receiving antenna of the base station. 34. A base station with multiple transmitting antennas that communicates with a mobile terminal having at least one single receiving antenna through a physical channel h(k) having two delay paths h ₁ (k) and h ₂ (k) , the base station includes: a space-time encoder having an input to be signaled and at least two outputs, each output generating a separate signal; at least two transmit beamformers each receiving an output from the space-time encoder and applying transmit beamforming weights thereto; a signal combiner that receives signals from the beamformers and is operable to perform a summation function of the signals from the beamformers and generate signals for transmission by each of the multiple transmit antennas, wherein the delay of Δτ is set to between the space-time encoder and one of the beamformers such that the main components of the transmitted signal are received at the at least one single receive antenna at substantially the same time. 35. A communication system comprising the base station of claim 24 and a mobile terminal provided with at least one single receive antenna, and a space-time decoder for decoding the received signal.

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