CN103036839A

CN103036839A - Wireless client device for compensating MU-MAS communication, dynamic adapting MU-MAS communication system

Info

Publication number: CN103036839A
Application number: CN2012104649746A
Authority: CN
Inventors: A·福伦扎; R·W·J·希思; S·G·帕尔曼; R·范德拉恩; J·斯佩克
Original assignee: Rearden LLC
Current assignee: Rearden LLC
Priority date: 2007-08-20
Filing date: 2008-08-20
Publication date: 2013-04-10
Anticipated expiration: 2028-08-20
Also published as: KR101805345B1; KR101598324B1; KR20160136476A; KR20150018900A; CN103501193A; RU2016107617A; KR20150136548A; RU2580324C2; CA3025857A1; CA3025857C; JP2015216699A; JP2020127215A; CN103036839B; JP2017085589A; RU2016107617A3; JP6922027B2; CA2937021C; RU2700568C2; CN103117975B; CN103117975A

Abstract

A wireless client device for compensating MU-MAS communication and a dynamic adapting MU-MAS communication system is described. The wireless client device for compensating MU-MAS communication comprises one or more RF units for receiving signals sent by one or more MU-MAS emitter units and down converting the signals to a base band; one or more analog-digital (A/D) converting unit for receiving down converted signals and converting the analog signals into digital signals; a frequency/phase offset estimation/ compensation unit for estimating frequency/phase offset and feeding the information back to the emitter for pre- compensation; one or more OFDM units for removing recycling prefix and rapidly conducting Fourier transform on the digital signals to report signals in frequency domain; a signal channel estimation unit for receiving signals output by the one or more OFDM units during a training period and respondingly calculating signal channel estimation data; and a feedback generating unit for sending the signal channel estimation data to a base station and pre-encoding the signals before the signal is sent to the wireless client device.

Description

The wireless client device of compensation MU-MAS communication, dynamically adapting MU-MAS communication system

The application be that on 08 20th, 2008, application number are 200880102933.4 the applying date, name is called the dividing an application of application for a patent for invention of " system and method for distributed input distributed output wireless communications ".

Priority request

The application is the application NO.10/902 that submitted to July 30 in 2004,978 continuation application.

Technical field

The present invention relates generally to field of wireless communications.Especially, the present invention relates to system and method for the radio communication of the distributed input distributed output of using the space-time code technology.

Background technology

The space-time code of signal of communication

Space multiplex (MUX) and space-time code are newer development known in the wireless technology.Owing to having several antennas to be used in each terminal, so a kind of space-time code of specific type is called as " multi-input multi output " (MIMO).By coming sending and receiving with a plurality of antennas, a plurality of independently radio waves can transmit in identical frequency range simultaneously.Following article provides the general introduction of MIMO.

IEEE member David Gesbert, IEEE member Mansoor Shafi, IEEE member Da-shanShiu,, IEEE member Peter J.Smith and the senior member Ayman of IEEE Naguib IEEEJOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL.21, NO.3, APRIL 2003: " From theory to Practice:An Overview of MIMO Space-TimeCoded Wireless Systems ".

The IEEE TRANSCTIONS ONCOMMUNICATIONS of IEEE member David Gesbert, IEEE member Helmut Bolcskei, Dhananijay A.Gore and IEEE member Arogyaswami J.Paulraj, VOL.50, NO.12, DECEMBER 2000: " Outdoor MIMOWireless Channels:Models and Performance Prediction ".

Basically, the MIMO technology is based on for the application that produces the spatially distributed antenna of spatial data arranged side by side in common band.Radio wave is propagated by this way, thereby can separate and the demodulation individual signals at receiver, even they transmit in identical frequency band, this can cause the communication channel of independent on a plurality of statistical significances (namely effectively separating).Therefore, compare (namely with the standard wireless communication system that makes great efforts the inhibition multipath signal, a plurality of delay time signals of same frequency, and amplitude and phase place exist to be revised), MIMO can depend on irrelevant or weak relevant multipath signal, realizes higher throughput and the signal to noise ratio of improvement in given frequency band.Example shows, under the power condition suitable with signal to noise ratio (snr), the MIMO technology has realized higher throughput (throughput), and traditional non-mimo system only can be realized lower throughput.Qualcomm's (high pass is maximum wireless technology supplier) website Http:// www.cdmatech.com/products/what_mimo_delivers.jsp:Subscript is entitled as has described this function on the page of " What MIMO Delivers ": " MIMO is the onlymultiple antenna technique that increases spectral capacity by delivering two ormore times the peak data rate of a system per channel or per MHz of spectrum.To be more specific, for wireless LAN or Wi- Applications QUALCOMM'sfourth generation MIMO technology delivers speeds of 315Mbps in 36MHz ofspectrum or 8.8Mbps/MHz.Compare this to the peak capacity of 802.1 1a/g (even with beam-forming or diversity techniques) which delivers only 54Mbps in17MHz of spectrum or 3.18Mbps/MHz ".

Usually on, owing to several reasons, mimo system is less than the actual property restriction (so the improvement in the network is less than 10 * throughput) of 10 antennas facing to each device:

1. physical restriction: must have enough intervals between the MIMO antenna on the setter, thus each receiving and counting signal independently.Even although when the antenna spacing of wavelength mark, still can see the improvement of MIMO throughput, when antenna more near the time efficient worsen rapidly, this has caused lower MIMO throughput multiplication device.

Referring to for example below with reference to document:

[1]D.-S.Shiu，G.J.Foschini，M.J.Gans，and J.M.Kahn，“Fadingcorrelation and its effect on the capacity of multielement antenna systems，”IEEE Trans.Comm.，vol.48，no.3，pp.502-513，Mar.2000.

[2]V.Pohl，V.Jungnickel，T.Haustein，and C.von Helmolt，“Antennaspacing in MIMO indoor channels，”Proc.IEEE Veh.Technol.Conf.，vol.2，pp.749-753，May 2002.

[3]M.Stoytchev，H.Safar，A.L.Moustakas，and S.Simon，“Compactantenna arrays for MIMO applications，”Proc.IEEE Antennas and Prop.Symp.，vol.3，pp.708-711，July 2001.

[4]A.Forenza and R.W.Heath Jr.，“Impact of antenna geometry onMIMO communication in indoor clustered channels，”Proc.IEEE Antennasand Prop.Symp.，vol.2，pp.1700-1703，June 2004.

In addition, for little antenna spacing, coupling effect each other may reduce the performance of mimo system.

Referring to for example below with reference to document:

[5]M.J.Fakhereddin and K.R.Dandekar，“Combined effect ofpolarization diversity and mutual coupling on MIMO capacity，”Proc.IEEEAntennas and Prop.Symp.，vol.2，pp.495-498，June 2003.

[7]P.N.Fletcher，M.Dean，and A.R.Nix，“Mutual coupling in multi-element array antennas and its influence on MIMO channel capacity，”IEEEElectronics Letters，vol.39，pp.342-344，Feb.2003.

[8]V.Jungnickel，V.Pohl，and C.Von Helmolt，“Capacity of MIMOsystems with closely spaced antennas，”IEEE Comm.Lett.，vol.7，pp.361-363，Aug.2003.

[10]J.W.Wallace and M.A.Jensen，“Termination-dependent diversityperformance of coupled antennas：Network theory analysis，”IEEE Trans.Antennas Propagat.，vol.52，pp.98-105，Jan.2004.

[13]C.Waldschmidt，S.Schulteis，and W.Wiesbeck，“Complete RFsystem model for analysis of compact MIMO arrays，”IEEE Trans.on Veh.Technol.，vol.53，pp.579-586，May 2004.

[14]M.L.Morris and M.A.Jensen,“Network model for MIMO systemswith coupled antennas and noisy amplifiers，”IEEE Trans.AntennasPropagat.，vol.53，pp.545-552，Jan.2005.

And crowded to together the time when antenna, antenna must be done littlely usually, and this also can affect antenna efficiency.

Referring to for example below with reference to document:

[15]H.A.Wheeler，“Small antennas，”IEEE Trans.AntennasPropagat.，vol.AP-23，n.4，pp.462-469，July 1975.

[16]J.S.McLean，“A re-examination of the fundamental limits on theradiation Q of electrically small antennas，”IEEE Trans.Antennas Propagat.，vol.44，n.5，pp.672-676，May 1996.

At last, with lower frequency and longer wavelength, the physical size of MIMO device just becomes and is difficult to process.An extreme example is at the HF wave band, and MIMO device antenna must 10 meters or larger distance separated from each other here.

2. noise limit.The receiver of each MIMO/transmitter subsystem produces the noise of certain level.When increasing this subsystem closed on mutually placement, background noise will rise.Simultaneously, when needs identify more unlike signals from multiple-antenna MIMO system when, just require lower background noise.

3. cost and Power Limitation.Although cost and power consumption were not focuses during some MIMO used, in typical wireless product, when developing a kind of successful product, cost and power consumption all are vital restraining factors.For each MIMO antenna, the RF subsystem that need to separate comprises the mould of separation-number (A/D) and number-Mo (D/A) transducer.Unlike a lot of aspects of the digital system of weighing scale with Moore's Law (observed result of the experience aspect that cofounder Gordon mole of Intel has been done, the transistor size on the integrated circuit of microdevice approximately just can quadruple every 24 months; The source: http://www.intel.com/technology/mooreslaw/), intensive like this analog subsystem has certain physical structure size and power requirement usually, and its size and cost and power linear are proportional.Therefore, compare with single antenna devices, many antennas MIMO device will become extremely expensive and have surprising energy consumption.

As top result, most of mimo systems of today expection are on the grade of 2 to 4 antennas, some SNR(signal to noise ratios that cause the rising of 2 to 4 times of throughputs and cause owing to the diversity benefit of multiaerial system) rising.Anticipated the mimo system (particularly because shorter wavelength and nearer antenna spacing on higher microwave frequency) of 10 antennas, but except special for some and to the insensitive application of cost, it is very unpractiaca surpassing 10 antennas.

Virtual antenna array

A kind of special applications of the technology of MIMO type is virtual antenna array.Advised this system in the research file that Euroscience technical field research cooperation tissue proposes, EURO, Barcelona, Spain, 15-17 day in January, 2003: Center for Telecommunication Research, King ' s CollegeLondon, UK: " A step towards MIMO:Virtual Antenna Arrays ", Mischa Dohler﹠amp; Hamid Aghvami.

Described in file, virtual antenna array is cooperation wireless device system (for example cell phone), its mutually communication on the communication channel of separating (mutually enough closing on if work as them), rather than on their main communication channels with their base station communication, so that the work of collaborative ground (for example, if they are the GSM cell phones in the UHF wave band, this can be the wireless wave band of industrial scientific medical (ISM) of 5GHz so).By forwarding information between the several devices in the mutual relaying scope (except in the scope of base station), just look like they be that to have physically a device job of a plurality of antennas the same so that single antenna devices realizes the throughput hoisting as the MIMO potentially.

Yet in fact, the extremely difficult realization of such system and use are limited.At first, must keep each device the rarest present two different communication paths to promote to realize throughput, the availability of its second repeated link often is uncertain.And, have the second communication subsystem and larger computation requirement is arranged owing to they are minimum, so this device being more expensive, physical size is larger, and consumes more power.In addition, by a plurality of communication links, this system depends on very complicated systematic live collaboration potentially.At last, because simultaneous channel usage (for example increases, use the simultaneous call transmission of MIMO technology), computation burden for each device has also just increased (the linearity increase with the channel utilization forms exponent increase usually), and this is very unpractiaca to the portable unit with strict power and size restrictions.

Summary of the invention

The invention provides a kind of in system, the use with the frequency that is used for compensation multi-user multi-aerial system MU-MAS communication and the wireless client device of phase deviation, this wireless client device comprises: one or more RF unit, be used for receiving the signal that sends from one or more MU-MAS transmitter units, and described signal down is transformed into base band; One or more moduluses (A/D) converting unit is used for receiving the signal after frequency reducing is changed and this signal from analog signal is converted to digital signal; Frequency/phase bias estimation/compensating unit is used for estimated frequency and/or phase deviation and information is fed back to transmitter to be used for precompensation; One or more OFDM unit is used for removing Cyclic Prefix and carries out fast Fourier transform (FFT) with the signal of report frequency domain in described digital signal; Channel estimating unit, the signal that is used for receiving during cycle of training from the output of described one or more OFDM unit also responsively calculates channel evaluation data; And feedback maker unit, be used for that described channel evaluation data is sent to the base station and use to be used for before signal is sent to described wireless client device, signal being carried out precoding.

The present invention also provides a kind of and used to be used for the unbalanced wireless client device of inphase quadrature (I/Q) of compensation multi-user multi-aerial system MU-MAS communication in system, this wireless client device comprises: one or more RF unit, be used for receiving the signal that sends from one or more MU-MAS transmitter units, and described signal down is transformed into base band; One or more moduluses (A/D) converting unit is used for receiving the signal after frequency reducing is changed and this signal from analog signal is converted to digital signal;

One or more OFDM unit is used for removing Cyclic Prefix and carries out fast Fourier transform (FFT) with the signal of report frequency domain in described digital signal; I/Q channel perception estimation unit receives during cycle of training from the signal of described one or more OFDM unit output and also responsively calculates channel evaluation data; And feedback maker unit, be used for that described channel evaluation data is sent to the base station and use to be used for before signal is sent to described wireless client device, signal being carried out precoding.

The present invention also provides a kind of wireless client device of using with the communication characteristic that is used for dynamically adapting multi-user multi-aerial system MU-MAS communication system in system, this wireless client device comprises: one or more RF unit, be used for receiving the signal that sends from one or more MU-MAS transmitter units, and described signal down is transformed into base band; One or more moduluses (A/D) converting unit is used for receiving the signal after frequency reducing is changed and this signal from analog signal is converted to digital signal; One or more OFDM unit is used for removing Cyclic Prefix and carries out fast Fourier transform (FFT) with the signal of report frequency domain in described digital signal; Channel estimator, the signal that is used for receiving during cycle of training from the output of described one or more OFDM unit also responsively calculates the link-quality matrix; And feedback maker unit, be used for that described link-quality matrix is sent to the base station and use to be used for before signal is sent to described wireless client device, signal being carried out modulation/coding, precoding and user selection.

Described a kind of for sending the frequency of multiaerial system (MAS) of (" MU-MAS ") and the system and method that phase deviation compensates to having multi-user (MU).For example, method according to one embodiment of the present invention comprises: will be sent to from the training signal of each antenna of base station one or each wireless client device in a plurality of wireless client device, in this customer set up one or each customer set up are analyzed each training signal with the generated frequency bias compensation data, and in place, base station receive frequency bias compensation data; Calculate MU-MAS precoder weight with the frequency shift (FS) at pre-elimination transmitter place based on described frequency offset compensation data; Use described MU-MAS precoder weight that training signal is carried out precoding, to generate the precoding training signal for each antenna of base station; To send to from the training signal after the precoding of each antenna of described base station each wireless client device in described a plurality of wireless client device, each customer set up is analyzed each training signal with generation channel characteristics data, and receives described channel characteristics data in described base station; Calculate a plurality of MU-MAS precoding weights based on these channel characteristics data, this MU-MAS precoder weight is calculated to be used for the pre-interference of eliminating between frequency and phase deviation and/or the user; Come data are carried out precoding with MU-MAS precoder weight, to generate for the data-signal after the precoding of each antenna of base station; And each antenna by the base station of the pre-code data signal after the described precoding is sent to its each client device.

Description of drawings

By reference to the accompanying drawings, below detailed description can obtain the present invention is better understood, wherein:

Fig. 1 has shown the mimo system of prior art.

Fig. 2 has shown the N antenna base station that communicates with a plurality of single antenna customer set ups.

Fig. 3 has shown the base station of three antennas that communicate with three single antenna customer set ups.

Fig. 4 has shown the training signal technology of using in one embodiment of the present of invention.

Fig. 5 has shown the channel characteristics data that are transferred to according to an embodiment of the invention the base station from customer set up.

Fig. 6 has shown the distributed output of multiple according to an embodiment of the invention input (" MIDO ") downlink transfer.

Fig. 7 has shown according to an embodiment of the invention multi-input multi output (" MIMO ") uplink.

Fig. 8 has shown the base station of circulating to distribute throughput by different customers according to an embodiment of the invention.

Fig. 9 has shown the client's grouping based on closing on according to an embodiment of the invention.

Figure 10 has shown the embodiments of the invention that use in the NVIS system.

Figure 11 has shown the execution mode of the DIDO transmitter with I/Q compensate function unit.

Figure 12 has shown the DIDO receiver with I/Q compensate function unit.

Figure 13 has shown a kind of execution mode of the DIDO-OFDM system with I/Q compensation.

Figure 14 has shown in the situation that have and do not have a kind of execution mode of I/Q compensation DIDO 2 * 2 performances (performance).

Figure 15 has shown in the situation that have and do not have a kind of execution mode of I/Q compensation DIDO 2 * 2 performances.

Figure 16 has shown in the situation that have and do not have I/Q compensation for the SER(symbol error rate of different Q AM planisphere) a kind of execution mode.

Figure 17 has shown in the situation that the different user devices position has and do not have a kind of execution mode of I/Q compensation DIDO2 * 2 performances.

Figure 18 has shown in the situation that desirable (i.i.d.(independent and with distributing)) have and do not have a kind of execution mode of I/Q compensation SER in the channel.

Figure 19 has shown a kind of execution mode of the transmitter architecture of self adaptation DIDO system.

Figure 20 has shown a kind of execution mode of the receiver architecture of self adaptation DIDO system.

Figure 21 has shown a kind of execution mode of the method for self adaptation DIDO-OFDM.

Figure 22 has shown a kind of execution mode of the antenna arrangement that is used for the DIDO measurement.

Figure 23 has shown the execution mode that is used for the array configurations of different stage (order) DIDO system.

Figure 24 has shown the performance of different stage DIDO system.

Figure 25 has shown a kind of execution mode of the aerial array that is used for the DIDO measurement.

Figure 26 has shown a kind of execution mode of the functional relation of DIDO 2 * 2 performances that 4-QAM and 1/2FEC lead and location of user equipment.

Figure 27 has shown a kind of execution mode of the antenna arrangement that is used for the DIDO measurement.

Figure 28 has shown how DIDO 8 * 8 in one embodiment produces the SE larger than the DIDO 2 * 2 with low TX power demand.

Figure 29 has shown at a kind of execution mode with DIDO 2 * 2 performances in day line options situation.

Figure 30 has shown average BER (BER) performance of different DIDO pre-coding schemes in the i.i.d. channel.

Figure 31 has shown the functional relation between the quantity of extra transmitting antenna in the snr gain of ASel and the i.i.d. channel.

Figure 32 shown in the situation that have 1 and 2 exterior antenna SNR threshold value in the i.i.d. channel and be used for block diagonalization (BD) and the number of users (M) of ASel between functional relation.

Figure 33 has shown for being positioned at the equal angular direction and having two users' of different angles expansion (AS) value BER and every user's average SNR.

Figure 34 has shown the result similar with Figure 33, but has higher angle intervals between the user.

Figure 35 has drawn the different value for user's average arrival angle (AOA), the functional relation between AS and the SNR threshold value.

Figure 36 has shown the SNR threshold value for 5 users' exemplary cases.

Figure 37 provides in the situation that have 1 and 2 additional antenna, the comparison of SNR threshold value BD and ASel for 2 users' situation.

Figure 38 has shown the result similar with Figure 37, but for 5 users' situation.

Figure 39 has shown the SNR threshold value for the BD scheme with different AS values.

Figure 40 shown for the BD with 1 and 2 additional antenna and ASel, the SNR threshold value in having AS=0.1 ° space correlation channel.

Figure 41 has shown the calculating for the SNR threshold value of two other channel conditions of AS=5 °.

Figure 42 has shown the calculating for the SNR threshold value of two other channel conditions of AS=10 °.

Figure 43-Figure 44 has shown respectively in the situation that 1 and 2 additional antenna, the functional relation between the angle spread (AS) of SNR threshold value and number of users (M) and BD and ASel scheme.

Figure 45 has shown the receiver that is equipped with frequency offset estimator/compensator;

Figure 46 has shown DIDO 2 * 2 system models according to one embodiment of the present invention.

Figure 47 has shown the method according to one embodiment of the present invention.

Figure 48 has shown in the situation that have and do not have frequency shift (FS), the SER result of DIDO 2 * 2 systems.

Figure 49 compares the SNR threshold performance of different DIDO schemes.

Figure 50 amount of overhead that the distinct methods execution mode is required compares.

Figure 51 has shown at f _MaxThe small frequency of=2Hz skew and do not have emulation in the situation of integer offset correction.

Figure 52 has shown the result when closing the integer offset estimator.

Embodiment

In the following description, for the purpose of explaining, in order providing the present invention to be understood thoroughly, to have illustrated a plurality of specific details.Yet, it is apparent that, for the one of ordinary skilled in the art, even without some specific details, still can realize the present invention.In addition, known construction and device is shown as the block diagram form, to avoid ultimata obfuscation of the present invention.

Fig. 1 has shown the prior art mimo system with transmitting antenna 104 and reception antenna 105.The throughput of such system can be realized 3 times of the common throughput of realizing in available channel.Have multiple diverse ways to realize the details of this mimo system, it had description in the publication document about this theme, and following explanation will be described such method.

Before data were transmitted in the mimo system of Fig. 1, channel was by " characterization ".This is by realizing beginning that " training signal " is transferred to each receiver 105 from each transmitting antenna 104.Training signal has coding and mod subsystem 102 to generate, and is converted to analog signal by the D/A converter (not shown), then is converted to the RF signal by each transmitter 103 from baseband signal.Each reception antenna 105 that is coupled to its RF receiver 106 receives each training signal and is converted into baseband signal.Baseband signal is converted to digital signal by the D/A converter (not shown), then this training signal of signal processing subsystem 107 characterizations.The feature of each signal can comprise several factors, and for example, it comprises, with respect to phase place and amplitude, absolute reference signal, relative reference signal, feature noise or other factors of the reference signal of receiver inside.The feature of each signal is normally defined the phase place of the several aspects of performance signal when signal transmits by channel and the vector of amplitude variations.For example, in the modulation signal of quadrature amplitude modulation (" QAM "), described feature may be the phase place of several multipaths reflection of signal and the vector of amplitude excursion.The another one example is that in the signal of OFDM (" OFDM ") modulation, it may be several in the OFDM frequency spectrum or the phase place of all single component signals (sub-signal) and the vector of amplitude excursion.

Signal processing subsystem 107 will be stored by the channel characteristics that each reception antenna 105 and corresponding receiver 106 receive.Three all transmitting antennas 104 are finished after their the training signal transmission, signal processing subsystem 107 will have been stored three for each channel characteristics in three reception antennas 105, this has formed 3 * 3 matrix 108, and it is expressed as channel characteristics matrix " H ".The matrix element H that each is independent _{I, j}It is the channel characteristics of the training signal transmission of the transmit antenna 104i that receives of reception antenna 105j.

In this, signal processing subsystem 107 inverts to produce H with matrix H 108 ^-1, and wait for from the transmission of the real data of transmitting antenna 104.Note, the multiple existing MIMO technology of describing in available document can be used for guaranteeing that H matrix 108 is reversible.

The content of the data that transmit in force, (payload) is delivered to data input subsystem 100.Then before delivering to coding and mod subsystem 102, it is assigned with device (splitter) 101 and is divided into three parts.For example, if content is the ASCII bit of " abcdef ", it just can be assigned with device and be divided into three sub-contents " ad ", " be " and " cf ".Then, every sub-content sends to separately coding and mod subsystem 102.

By using the statistical independence that is fit to each signal and the coded system of error correcting capability, individually every sub-content encoded.These comprise, and are not limited only to, Reed-Solomon coding, Viterbi coding (Viterbi coding) and strengthen encode (Turbo Codes).At last, use in the sub-content of the suitable modulator approach of channel after to these three codings each is modulated.Exemplary modulator approach is differential phase keying (DPSK) modulation (" DPSK "), 64-QAM modulation and OFDM.Here it should be noted, diversity gain that MIMO provides allows the modulation constellation of higher plate number, and described modulation constellation is in the single output of the single input of the SISO(that uses same channel) also be feasible in the system.Then, the signal after each coding and the modulation transfers out by its antenna 104, after the D/A conversion that described transmission is followed at D/A converting unit (not shown) and the RF of each transmitter 103 generate.

Suppose to have enough space diversitys to be present between the sending and receiving antenna, each reception antenna 105 will receive from antenna 104 various combination of three signal transmissions.Each RF receiver 106 receives and converts them to baseband signal with each signal, and then the A/D converter (not shown) carries out digitlization to signal again.If y _nThe signal that is received by n reception antenna 105, x _nBe the signal that is sent by n transmitting antenna 104, N is noise, and this just can describe with following equation so.

y ₁=x ₁H ₁₁+x ₂H ₁₂+x ₃H ₁₃+N

y ₂=x ₁H ₁₂+x ₂H ₂₂+x ₃H ₂₃+N

y ₃=x ₁H ₁₃+x ₂H ₃₂+x ₃H ₃₃+N

Suppose that this is a system with three equatioies of three unknown quantitys, Here it is so, and signal processing subsystem 107 is derived x ₁, x ₂And x ₃Linear algebra problem (suppose N in enough low level, allow signal is decoded):

x ₁=y ₁H ^-1 ₁₁+y ₂H ^-1 ₁₂+y ₃H ^-1 ₁₃

x ₂=y ₁H ^-1 ₂₁+y ₂H ^-1 ₂₂+y ₃H ^-1 ₂₃

x ₃=y ₁H ^-1 ₃₁+y ₂H ^-1 ₃₂+y ₃H ^-1 ₃₃

In case derive the signal x of three transmission _n, they are just by signal processing subsystem 107 demodulation, decoding and error correction, three bit streams that separate to recover former cause distributor 101.These bit streams merge in combiner unit 108, and are output as single data stream from data output 109.The supposing the system robustness can overcome noise induced damage, so the bit streams that produce of data output 109 will be incorporated into data input 100 in bit stream the same.

Although described prior art systems is usually effectively until four antennas, perhaps until 10 more than antenna, owing to describing in the background parts of the disclosure, it becomes very unactual when having a large amount of antennas (for example 25,100 or 1000).

Usually, such prior art systems is two-way, and return path realizes in identical mode, but conversely, all has the sending and receiving subsystem in each side of communication channel.

Fig. 2 has shown one embodiment of the present of invention, and therein, base station (BS) 200 disposes wide area network (WAN) interface (for example connecting at a high speed by T1 or other) 201 and provide (N) antenna 202 of some.We use term " base station " to refer to any wireless site that carries out radio communication with one group of client of fixed position for the time being.The example of base station can be the access point in the wireless lan (wlan), or WAN antenna or aerial array.Some customer set up 203-207 are arranged, and each has single antenna, and base station 200 is served them by wireless mode.Although the purpose for this example, be very easy to expect being positioned at the base station of office environment, in this environment, its user's set 203-207 for the personal computer that is equipped with wireless network provides service, but this structure will apply to a large amount of applicable cases, indoor and outdoors, here wireless client is served in the base station.For example, described base station can be positioned on the cellular tower, perhaps is positioned on the television broadcast towers.In one embodiment, base station 200 is placed in ground, be used for (for example frequency of 24MHz) up transmission of HF frequency, so that signal is returned from ionospheric reflection, as proposing on April 20th, 2004, sequence number is No.10/817,731, what pending application was described when exercise question was SYSTEM AND METHOD FOR ENHANCING NEAR VERTICALINCIDENTCE SKYWAVE (" NVIS ") COMMUNICATION USINGSPACE-TIME CODING is the same, it is by dispensing the application agent, here as a reference.

Some details that interrelates with base station 200 and illustrated customer set up only are the purposes for illustration, rather than cardinal principle according to the present invention is essential.For example, this base station can be connected in a plurality of dissimilar wide area networks via wan interface 201, and it comprises private wide area network, and for example those are used for the wide area network that digital video sends.Similarly, customer set up can be wireless data processing and/or the communicator of any kind, and it comprises, and not only is confined to cell phone, personal digital assistant (" PDA "), receiver and wireless camera.

In one embodiment, the n of a base station antenna 202 spatially separates, thus the relevant signal of each sending and receiving non-space, just look like described base station be that the transceiver of prior art MIMO is the same.Described in background technology, antenna is with i.e. 1/6 wavelength of λ/6() the interval experiment of placing makes, it has successfully realized the throughput hoisting from MIMO, but in general, these antenna for base station are further separated, the performance of system is just better, λ/2nd, gratifying minimum range.Certainly, cardinal principle of the present invention is not limited to any specific separation between antenna.

Note, single base station 200 can be positioned over far distance with its antenna well.For example, in the HF frequency spectrum, antenna can have 10 meters or farther (for example, mention NVIS realize in) in the above.If use 100 such antennas, the aerial array of this base station just can occupy several square kilometres area.

Except space diversity reception to communicate, in order to improve the effective throughput of system, one embodiment of the present of invention are with polarizations.Improving channel capacity by polarization is a kind of known technology, and it was used a lot of years by satellite television providers.Use Polarization technique, can make a plurality of (for example three) base stations or user antenna very approaching with each other, and it is relevant to remain non-space.Although traditional RF system mostly just benefits from two dimension (for example x and the y) diversity of polarization, structure described herein can further be benefited from three-dimensional (x, y and the z) diversity of polarization.

Except space and polarization diversity, one embodiment of the present invention adopt the antenna pattern (pattern) that is close to quadrature, to improve link performance via the directional diagram diversity.The directional diagram diversity can be improved capacity and the bit error rate performance of mimo system, and it can be referring to following article than the advantage of other diversity antenna technologies:

[17]L.Dong，H.Ling，and R.W.Heath Jr.，“Multiple-input multiple-output

wireless communication systems using antenna pattern diversity，”Proc.IEEE Glob.Telecom.Conf.，vol.1，pp.997-1001，Nov.2002.

[18]R.Vaughan，“Switched parasitic elements for antenna diversity，”IEEE

Trans.Antennas Propagat.，vol.47，pp.399-405，Feb.1999.

[19]P.Mattheijssen，M.H.A.J.Herben，G.Dolmans，and L.Leyten，“Antenna-pattern diversity versus space diversity for use at handhelds，”IEEETrans.on Veh.Technol.，vol.53，pp.1035-1042，July 2004.

[20]C.B.Dietrich Jr，K.Dietze，J.R.Nealy，and W.L.Stutzman，“Spatial，polarization，and pattern diversity for wireless handheld terminals，”Proc.IEEE Antennas and Prop.Symp.，vol.49，pp.1271-1281，Sep.2001.

[21]A.Forenza and R.W.Heath，Jr.，“Benefit of Pattern Diversity Via2-element Array of Circular Patch Antennas in Indoor Clustered MIMOChannels″，IEEE Trans.on Communications，vol.54，no.5，pp.943-954，May2006.

By using the directional diagram diversity, can be so that a plurality of base station or user antenna be very approaching each other, and however also can spatially not be associated.

Fig. 3 provides the additional detail of the embodiment of the base station 200 shown in Fig. 2 and customer set up 203-207.For the purpose of simplifying, this base station 300 only is shown as three antennas 305 and three customer set up 306-308.Yet, it should be noted that embodiments of the invention described herein can be with the antenna 305(of unlimited amount almost namely, only by can with space and noise limit) and customer set up 306-308 realize.

Fig. 3 and prior art MIMO structure shown in Figure 1 are similar, and wherein, both have three antennas at each end of communication channel.Significant difference is, in the mimo system of prior art, three antennas 105 on Fig. 1 right side are fixed range (for example, being integrated in the single device) between mutually, are processed signal processing subsystem 107 together from the signal that each antenna 105 receives.By contrast, in Fig. 3, each is coupled to three antennas on figure right side 309 on the different customer set up 306-308, and each described customer set up can be distributed in the scope of base station 305 Anywhere.Like this, the signal that receives of each customer set up can encode at it, be independent of other two signals that receive in the modulation, signal processing subsystem 311 and processed.Therefore, compare with " MIMO " system of the multiple output of multiple input (being antenna 105) (being antenna 104), Fig. 3 has shown the distributed output of multiple input (being antenna 305) (being antenna 305) system, below refers to " MIDO " system.

Note, the application uses the term usage different from application before, to meet better academia and industrial practice.Application NO.10/817 at the common pending trial of being entitled as of submitting in 20 days April in 2004 of quoting before " SYSTEM ANDMETHOD FOR ENHANCING NEAR VERTICAL INCIDENCE SKYWAVE(" NVIS ") COMMUNICATION USING SPACE-TIME CODING ", the application NO.10/902 that on July 30th, 731 and 2004 submitted to, 978(the application is the continuation application of this application) in, " input " and " output " is (at SIMO, MISO, in the environment of DIMO and MIDO) the meaning and this term expressing the meaning in this application be opposite.In application before, " input " refers to input to the wireless signal of reception antenna (for example, the antenna 309 among Fig. 3), and " output " refers to the wireless signal of transmitting antenna (for example, antenna 305) output.In academia and wireless industry, usually use the antisense of " input " and " output ", wherein " input " refer to input to channel wireless signal (namely, wireless signal from antenna 305 transmissions), and " output " refers to the wireless signal (that is, antenna 309 receive wireless signal) from channel output.The application adopts this term usage, and the usage in the application of quoting before this usage and this section is opposite.Therefore, below illustrated the term usage equivalent form of value between several applications:

10/817,731 and 10/902,978 the application

SIMO = MISO

MISO = SIMO

DIMO = MIDO

MIDO = DIMO

MIDO structure shown in Figure 3 has realized being similar to MIMO for the transmitting antenna of giving determined number and has promoted at the capacity that the SISO system realizes.Yet, the difference of MIMO and specific MIDO embodiment shown in Figure 3 is, for realizing that the capacity that a plurality of antenna for base station provide promotes, each MIDO customer set up 306-308 only requires single receive antenna, and for MIMO, each customer set up requires and the as many reception antenna of capacity multiple of wishing to realize at least.Suppose usually to have a restriction of carrying out, its restriction can be placed how many antennas (as explaining) at customer set up in background technology, and this just is limited in mimo system between 4 to 10 antennas (4 times to 10 times capacity) on the typical case.Because base station 300 from fixing and fill dynamic location-based service in a lot of customer set ups, expands to 10 antennas that surpass far away with it usually, and with suitable be very actual apart from separate antenna with the implementation space diversity.As described, each antenna arrangement has the disposal ability of transceiver 304 and a part of coding, modulation and Signal Processing Element 303.It should be noted that, in this embodiment, no matter how many base stations 300 expands, and each customer set up 306-308 will only require an antenna 309, therefore the cost for alone family customer set up 306-308 will be very low, and the cost of base station 300 can be shared in the user of large cardinal.

In Fig. 4 to Fig. 6, shown example how to finish from the base station 300 to customer set up 306-308 MIDO transmission.

In one embodiment of the invention, before the MIDO transmission beginning, channel is characterized.For mimo system, 405 pairs of training signals of each antenna transmit one by one.Fig. 4 has only shown the transmission of first training signal, but for three antennas 405, has three transmission that separate.Each training signal is generated by coding, modulation and signal processing subsystem 403, converts analog signal to by D/A converter, and sends by each RF transceiver 404 as the RF signal.Available various coding, modulation and signal processing technology comprise, and be not limited to those above-described technology (for example, Reed Solomon, Viterbi coding (Viterbi Coding); QAM, DPSK, QPSK modulation etc.).

Each customer set up 406-408 receives training signal and converts this training signal to baseband signal by transceiver 410 by its antenna 409.The place that the A/D converter (not shown) is encoded at this signal, modulation and signal processing subsystem 411 processed converts thereof into digital signal.Then the feature (for example, above-mentioned phase place and the amplitude distortion of identification) of signal characteristic logical block 320 identification gained signals also is stored in this feature in the memory.This characteristic processing process is similar to the processing procedure of the mimo system of prior art, and a significant difference is that each customer set up only calculates an one antenna, rather than the characteristic vector of n antenna.For example, the described training signal of known mode is with coding, modulation and signal processing subsystem 420 initialization of customer set up 406 (when producing by receiving it in the information that sends, or by other initialization process).When antenna 405 sends this training signal with known mode, coding, modulation and signal processing subsystem 420 usefulness correlation methods find the strongest training signal receiving mode, it preserves phase place and amplitude excursion, and then it cuts this pattern in the middle of the signal that receives.Next, it finds second strong cohesiveness relevant with described training signal to receive pattern, and phase place and amplitude excursion are preserved, and then it cuts the second strong mode from the described signal that receives.This processing is carried out always, drops under the given background noise until preserved the phase place of certain fixed qty and amplitude excursion (for example, 8) or detectable training signal pattern.The vector of this phase/amplitude skew becomes the element H of vector 413 ₁₁Meanwhile, customer set up 407 and 408 coding, modulation and signal processing subsystem are carried out same processing, produce their vector element H ₂₁And H ₃₁

The memory that channel characteristics is deposited can be nonvolatile memory, for example flash memory, or hard disk, and/or volatile memory, for example random access memory (for example, SDRAM, RDAM).In addition, different user's sets can be stored characteristic information (for example PDA uses flash memory, and notebook computer uses hard disk) with dissimilar memory simultaneously.On various customer set ups or base station, ultimata of the present invention is not limited to the storing mechanism of any particular type.

As mentioned above, according to employed scheme, because each customer set up 406-408 only has an antenna, each only stores 1 * 3 row 413-415 of H matrix.Fig. 4 has shown the stage after the transmission of the first training signal, and here, the first row of 1 * 3 row 413-415 has been stored the channel characteristics information of first antenna of three antenna for base station 405.All the other two row have been stored from the channel characteristics of ensuing two training signals transmission of all the other two antenna for base station.Note, for the purpose of illustration, described three time tranfers that the training signal pattern is being separated.Thereby if selected three training signal patterns uncorrelated mutually, they can transmit simultaneously so, therefore reduce the training time.

As shown in Figure 5, after all three pilot transmission were finished, 1 * 3 row 513-515 of the matrix H that each customer set up 506-508 will store sent it back base station 500.For the purpose of simplifying, in Fig. 5, only show a customer set up 506 and transmit its characteristic information.In conjunction with suitable error correction coding (for example Reed Solomon, Viterbi coding (Viterbi Coding) and/or enhancing coding (TurboCodes)), can use suitable modulator approach (for example DPSK, 64QAM, OFDM) to guarantee that base station 500 receives the data among the row 513-515 exactly.

Among Fig. 5, although all three antennas 505 demonstrate the reception signal, for the transmission that receives per 1 * 3 row 513-515, the single antenna of base station 500 and single transceiver are enough.Yet, under certain condition, receiving each transmission (that is, using single input multiple output (" SIMO ") treatment technology of prior art in coding, modulation and signal processing subsystem 503) with a lot of or all antennas 505 and transceiver 504 can realize than single antenna 505 and transceiver 504 better signal to noise ratio (snr)s.

When coding, modulation and the signal processing subsystem 503 of base station 500 received described 1 * 3 row 513-515 from each customer set up 507-508, it deposited described 1 * 3 row 513-515 in 3 * 3 the H matrix 516.For customer set up, storage matrix 516 can be come with a lot of different memory technologies in the base station, and it includes, but are not limited to, nonvolatile mass storage (for example hard disk) and/or volatile memory (for example SDRAM).Fig. 5 has shown that the base station has received and stored the stage from 1 * 3 row 513 of customer set up 509.When 1 * 3

row

514 and 515 transmitted from all the other customer set ups, they can be transmitted and be kept in the H matrix 516, until whole H matrix 516 is stored.

With reference to figure 6, the embodiment of 600 to customer set up 606-608 MIDO transmission will be described now from the base station.Because each customer set up 606-608 independently installs, so each device receives different transfer of data.Like this, the embodiment of base station 600 comprises between wan interface 601 and coding, modulation and signal processing subsystem 603 they is communicated the router 602 of contact, it receives a plurality of data flow (form is bit stream) from wan interface 601, correspond respectively to each customer set up 606-608 with described data flow by the data flow u that separates ₁-u ₃Send.For this purpose, this router 602 can use various known route technologies.

As shown in Figure 6, with described three bit streams, u ₁-u ₃Route is advanced in described coding, modulation and the signal processing subsystem 603, they are encoded to add up independently error correction stream (for example, use ReedSolomon, Viterbi or strengthen coding), and use the suitable modulator approach of channel (for example DPSK, 64QAM or OFDM) they modulation.In addition, the embodiment that Fig. 6 shows comprises signal precoding logical block 630, and based on signal characteristic matrix 616, this signal precoding logical block 630 is used for the signal that sends from each antenna 605 is carried out unique coding.Especially, in this embodiment, precoding logical block 630 is with three bit stream u among Fig. 6 ₁-u ₃Multiply by mutually with the inverse matrix of H matrix 616 and to generate three new bit stream u' ₁-u' ₃, rather than each coding and the bit stream modulated be routed to antenna (as doing among Fig. 1) separately.Then, the D/A converter (not shown) is changed to analog signal with described three precoding bit circulation, and transceiver 604 and antenna 605 send it as the RF signal.

Before explaining how customer set up 606-608 receives described special stream, will the operation of precoding module 630 execution be described.Be similar to the example of MIMO among top Fig. 1, the coding of each bit stream and the signal of modulating will be expressed as u in three original bit stream _nIn the embodiment shown in fig. 6, each u _iComprise the data that three bit streams of 602 routes of router come, each such bit stream will become three user's set 606-608 one of them.

Yet, do not resemble the MIMO example among Fig. 1, there, each x _iThere is each antenna 104 to send, in embodiments of the invention shown in Figure 6, receives each u at each customer set up antenna 609 _i(adding noise N any in the upper signal channel).For realizing such result, (we are expressed as v with it in the output of each in three antennas 605 _i) be u _iFunction with the H matrix of each customer set up of characterization.In an embodiment, the precoding logical block 630 in coding, modulation and the signal processing subsystem is calculated each v by carrying out following equation _i:

v ₁＝u ₁H ^-1 ₁₁+u ₂H ^-1 ₁₂+u ₃H ^-1 ₁₃

v ₂＝u ₁H ^-1 ₂₁+u ₂H ^-1 ₂₂+u ₃H ^-1 ₂₃

v ₃＝u ₁H ^-1 ₃₁+u ₂H ^-1 ₃₂+u ₃H ^-1 ₃₃

Therefore, unlike MIMO, there, channel calculates each x with after the signal conversion at receiver _i, and embodiments of the invention described herein were found the solution each v at transmitter before channel is with the signal conversion _iEach antenna 609 receives the u that is used for other antenna 609 from other _N-1The u that separates in the bit stream _iThe signal that each transceiver 610 will respectively receive converts baseband signal to, and the A/D converter (not shown) carries out digitlization to it here, and each coding, modulation and signal processing subsystem 611 are to its x _iBit stream carries out the demodulation code, and its bit stream is for example delivered to data-interface 612(that customer set up uses, the application program on the customer set up).

Embodiments of the invention described herein can be realized with multiple different coding and modulator approach.For example, in OFDM realized, its intermediate frequency spectrum was divided into a plurality of minutes frequency bands, and technology described herein can be used for each independent minute frequency band of characterization.Yet as mentioned above, cardinal principle of the present invention is not limited to any specific modulator approach.

If customer set up 606-608 is portable data processing device, for example PDA, notebook computer and/or wireless telephonic words, because customer set up may be from a position movement to another one, then channel characteristics can change by frequent occurrence so.Like this, in one embodiment of the invention, the channel characteristics matrix 616 of base station is constantly upgraded.In one embodiment, new training signal is sent to each customer set up in base station 600 periodically (per 250 milliseconds), each customer set up with its channel characteristics vector constantly send it back base station 600 with guarantee channel characteristics keep accurately (for example, if thereby environment change or customer set up move have influence on channel).In one embodiment, in sending to the actual data signal of each customer set up, training signal is interweaved.Typically, the throughput of described training signal is far below the throughput of described data-signal, so this throughput almost not impact total on system.Correspondingly, in this embodiment, channel characteristics matrix 616 can constantly be upgraded when initiatively communicating with each customer set up in the base station, thus when customer set up from a position movement to next position, thereby or environment change and keep accurately channel characteristics when having influence on channel.

One embodiment of the present of invention shown in Fig. 7 are improved uplink communication channel (that is, from customer set up 706-708 to the base station 700 channel) with the MIMO technology.In this embodiment, the uplink channel characteristics logical block in the base station 741 is constantly analyzed and characterization the channel that comes from each customer set up.Especially, each customer set up 706-708 sends training signal to base station 700, and there channel characteristics logical block 741 analyzes to produce the channel characteristics matrix 741 of N * M, and N is the quantity of customer set up here, and M is the quantity of the employed antenna in base station.Embodiment shown in Figure 7 uses three antennas 705 and three customer set up 706-708 in the base station, this has caused depositing in 3 * 3 channel characteristics matrixes 741 of base station 700.Customer set up can be used for MIMO uplink shown in Figure 7 data are sent it back base station 700 and the channel characteristics vector is sent back base station 700, as shown in Figure 5.But different with embodiment shown in Figure 5 is, in Fig. 5, the channel characteristics vector of each customer set up transmitted with the time of separating, and method shown in Figure 7 allows from a plurality of customer set ups simultaneously the channel characteristics vector to be transmitted go back to base station 700, thereby greatly reduces the channel characteristics vector to the impact of Return Channel throughput.

As mentioned above, the feature of each signal can comprise several factors, and for example, it comprises phase place and amplitude with respect to the reference signal of receiver inside, absolute reference signal, relative reference signal, feature noise or other factors.For example, in the signal that quadrature amplitude modulation is modulated, described feature can be phase place and the amplitude excursion vector of several multipath reflections of signal.Another example is that in the signal that OFDM is modulated, described feature can be phase place and the amplitude excursion vector of several in the OFDM frequency spectrum or all single component signals.Described training signal can be generated by coding and the mod subsystem 711 of each customer set up, and the D/A converter (not shown) converts this training signal to analog signal, and then the transmitter 709 of each customer set up converts it to RF signal from baseband signal.In one embodiment, in order to ensure training signal synchronously, customer set up only transmits training signal (for example, in the situation that circulation (round robin)) in base station requests.In addition, can interweave to training signal the actual data signal that sends from each customer set up, perhaps training signal can transmit together with described actual data signal.Therefore, even customer set up 706-708 is mobile, uplink channel characteristics logical block 741 also can be transmitted continuously and analyze this training signal, thereby guarantees that channel characteristics matrix 741 keeps upgrading.

Total channel capacity that previous embodiment of the present invention is supported can be defined as min(N, M), here, M is the quantity of customer set up, and N is the quantity of antenna for base station.That is to say, capacity is limited by the antenna amount of base station side or customer side.So, one embodiment of the present of invention guarantee to be no more than min(N, M with simultaneous techniques within preset time) individual antenna is in sending/receiving.

In typical situation, the quantity of the antenna 705 of base station 700 will be less than the quantity of customer set up 706-708.Fig. 8 has shown an exemplary situation, and it allows 5 customer set up 804-808 and the base station with three antennas 802 to communicate.In this embodiment, determine the quantity of total customer set up 804-808 and (for example detect necessary channel characteristics information, top description) afterwards, first crowd of three client 810(that communicate with it selected because min(N in base station 800, M)=3, so be three clients in this example).After the fixed time of having communicated by letter with first crowd of client 810, three clients 811 that the base station just selects another group to communicate with.For the uniform distribution communication channel, two customer set ups 807,808 in first group are selected not to be included in base station 800.In addition, because extra antenna is available, the extra customer set up 806 in first group is just selected to be included in base station 800.In one embodiment, circulating the client masses by this way in base station 800, thereby can effectively distribute to the in time throughput of equal number of each client.For example, for the uniform distribution throughput, any combination (that is, owing to customer set up 806 is used for communicating with the base station in two circulations of beginning) of three customer set ups except customer set up 806 can then be selected in the base station.

In one embodiment, except the data communication of standard, the base station can be transmitted training signal with aforementioned techniques and be received training signal and signal characteristic data to each customer set up with from each customer set up.

In one embodiment, some customer set up or customer set up group can be assigned to the throughput of varying level, for example, can distinguish order of priority to customer set up, thereby the client that the customer set up that can guarantee high priority relatively must lower priority fills the family more communication cycle (that is, more throughput) is arranged.Variable based on some, can select client " priority ", described variable comprises, for example, the user to the subscription fee of wireless bandwidth (for example, being used for being willing to mean additional throughput pays more), and/or communication to/from data type (for example, the real time communication, such as call voice and video of customer set up, acquisition is higher than the priority of non-realtime traffic, for example Email).

In the present load that requires based on each customer set up, among the embodiment of base station dynamic assignment throughput.For example, if customer set up 804 live video streams, and other device 805-808 is carrying out for example non real-time function of Email, base station 800 distributes relatively many throughputs can for this client 804 so.Yet, it should be noted, cardinal principle of the present invention is not limited to any specific throughput distribution technology.

As shown in Figure 9, two customer set ups 907,908 can be very approaching, so that described client's channel characteristics is the same actually.As a result, the base station will receive and store two customer set ups 907,908 the channel characteristics that in fact equates vector, so this can not produce the signal unique, spatial distribution for each client.Correspondingly, in one embodiment, the base station will guarantee that any two or more customer set ups that the phase mutual edge distance approaches very much are assigned to different groups.For example, in Fig. 9, at first communicate by letter with customer set up 904,905 and 908 first group 910 in base station 900, then communicates by letter with customer set up 905,906,907 second group 911, and this has guaranteed that customer set up 907 is with 908 in different groups.

Selectively, in one embodiment, 900 whiles of base station and customer set up 907 and 908 communicate, but come to carry out multiplexing to communication channel with known multi-channel Technology.For example, the base station can use time division multiplexing (" TDM "), frequency division multiplexing (" FDM ") or code division multiple access (" CDMA ") technology to come separately signal single, space correlation between the customer set up 907 and 908.

Although above-mentioned each customer set up is equipped with single antenna, can be by realizing that with the customer set up with a plurality of antennas cardinal principle of the present invention is to improve throughput.For example, in the time of on being used in above-mentioned wireless system, the client with 2 antennas will realize 2 times throughput hoisting, and the client with 3 antennas will realize 3 times throughput hoisting, etc. (that is, supposing that space and angular separation between the antenna are enough).When circulating by the customer set up with a plurality of antennas, same general rule can be used in the base station.For example, it can regard each antenna as client separately, and gives that " client " with throughput distribution, just (for example, guarantees that each client provides enough or suitable communication cycle) as it is any other client.

As mentioned above, one embodiment of the present of invention use above-mentioned MIDO and/or MIMO signal transmission technology to improve signal to noise ratio and throughput near vertical incident sky wave (" NVIS ").With reference to Figure 10, in one embodiment of the invention, a NVIS base station 1001 that is equipped with the matrix of N antenna 1002 is used for communicating with M customer set up 1004.The antenna 1004 of described NVIS antenna 1002 and multiple user's set is approximately to become 15 degree with interior angle signal uplink to be transmitted the NVIS that obtains to want and drops to the surface wave disturbing effect minimum with vertical direction.In one embodiment, antenna 1002 and customer set up 1004 uses assigned frequency in the NVIS frequency spectrum of above-mentioned multiple MIDO and MIMO technology (for example in carrier frequency or be lower than the frequency of 23MHz, but be usually less than on the frequency of 10MHz) a plurality of independently data flow 1006 of support, thereby significantly improved throughput in assigned frequency (that is, with add up independently the quantity of data flow is directly proportional).

The described NVIS antenna of serving given base station can have far physical distance each other.Suppose to be lower than the long wavelength of 10MHz and the long distance (300 miles round distances) that signal is propagated, the hundreds of code, or even several miles antenna physical separation can provide benefit in diversity.Under such condition, independent aerial signal can be withdrawn into the center, with traditional wired or wireless communication system it is processed.Selectively, each antenna can have local device and process its signal, then with traditional wired or wireless communication system this transfer of data is gone back to the center.In one embodiment of the invention, NVIS base station 1001 has to internet 1010(or other wide area network) wideband link 1015, thereby offer customer set up 1003 long-range, at a high speed, wireless network access.

In one embodiment, base station and/or user can utilize polarization/direction figure diversity (patterndiversity) technology, with when diversity being provided and promoting throughput, reduce array size and/or user distance.For example, in the DIMO system with HF transmission, because polarization/direction figure diversity, the user can be positioned at same position and their signal can not be associated.Especially, by using the directional diagram diversity, a user can communicate with the base station via earthwave, and other users can communicate with the base station via NVIS.

Additional execution mode of the present invention

I, Utilize the I/Q imbalance to carry out the DIDO-OFDM precoding

One embodiment of the present invention adopt to be used for the system and method that inphase quadrature (I/Q) imbalance to distributed input distributed output (DIDO) system with OFDM (OFDM) compensates.In brief, according to present embodiment, subscriber equipment estimates channel, and with this information feedback to the base station; The base station calculates pre-coding matrix, to eliminate between the carrier wave that the I/Q imbalance caused and the interference between the user; And parallel data stream is sent to a plurality of subscriber equipmenies via the DIDO precoding; This subscriber equipment forces (ZF), least mean-square error (MMSE) or maximum likelihood (ML) receiver to come data are carried out demodulation via zero, to suppress residual interference.

As detailed below, some notable features of this execution mode of the present invention include, but are not limited to:

Precoding be used for to eliminate ofdm system from mirror image transfer (mirror tone) inter-carrier interference (ICI) (because of I/Q do not mate caused);

Precoding with inter-user interference that be used for to eliminate the DIDO-OFDM system and ICI(because of I/Q do not mate caused);

Be used for via the ZF receiver of the DIDO-OFDM system that adopts block diagonalization (BD) eliminate ICI(because of I/Q do not mate cause) technology;

Be used for via the precoding (at the transmitter place) of DIDO-OFDM system and ZF or MMSE filter (at the receiver place) eliminate inter-user interference and ICI(because of I/Q do not mate cause) technology;

Be used for via the precoding (at the transmitter place) of DIDO-OFDM system and the nonlinear detector (at the receiver place) that is similar to maximum likelihood (ML) detector eliminate inter-user interference and ICI(because of I/Q do not mate cause) technology;

Use based on the precoding of channel condition information with the inter-carrier interference (ICI) that is used for eliminating ofdm system and transfers from mirror image (because of I/Q do not mate caused);

Use based on the precoding of channel condition information with the inter-carrier interference (ICI) that is used for eliminating the DIDO-OFDM system and transfers from mirror image (because of I/Q do not mate caused);

Use I/Q not mate known DIDO precoder (I/Q mismatch aware DIDOprecoder) at the place, base station, and use the known DIDO receiver of I/Q at the user terminal place;

Use I/Q not mate known DIDO precoder (I/Q mismatch aware DIDOprecoder) at the place, base station, use the known DIDO receiver of I/Q at the user terminal place, and use I/Q known channel estimator;

Use I/Q not mate known DIDO precoder at the place, base station, use the known DIDO receiver of I/Q at the user terminal place, and use I/Q known channel estimator and the known DIDO feedback of I/Q maker (this maker is sent to website with channel condition information from user terminal);

Use I/Q not mate known DIDO precoder at the place, base station, and the known DIDO configurator of use I/Q (this configurator is carried out various functions with the I/Q channel information, comprises user selection, adaptive coding and modulation, the mapping of empty time-frequency or precoder selection);

Use the known DIDO receiver of I/Q (this receiver is eliminated ICI(via the ZF receiver in the DIDO-OFDM system that adopts block diagonalization (BD) precoder and do not caused because I/Q does not mate institute));

Use the known DIDO receiver of I/Q (this receiver via the precoding in the DIDO-OFDM system (at the transmitter place) and the nonlinear detector (at the receiver place) that is similar to maximum likelihood (ML) detector eliminate inter-user interference and ICI(because of I/Q do not mate do not cause)); And

Use the known DIDO receiver of I/Q (this receiver is eliminated ICI(via the ZF in the DIDO-OFDM system or MMSE filter and do not caused because I/Q does not mate institute)).

A, Background

The sending and receiving signal of exemplary radio communication system comprises inphase quadrature (I/Q) component.In the system of reality, this inphase quadrature component may the distortion owing to the defective in mixing and the baseband operations.These distortions (distortion) show as I/Q phase place, gain and delay and do not mate.Unbalance in phase is caused by the sine in the modulator/demodulator (sine) and the incorrect quadrature of cosine (cosine).Gain is uneven to be caused by the different amplification between the inphase quadrature component.Because the I in the analog circuit and the delay between the Q track (rail) are different, also may have additional distortion, this distortion is referred to as to postpone uneven.

In OFDM (OFDM) system, the intercarrier uneven (ICI) that the I/Q imbalance can cause coming spontaneous emission to be transferred.This impact has obtained research in some data, and in following information, the I/Q that has proposed to be used for the single output of single input SISO-OFDM system does not mate the method that compensates: M.D.Benedetto and P.Mandarini, " Analysis of the effect of the I/Qbaseband filter mismatch in an OFDM modem; " Wireless personalcommunications, pp.175-186,2000; S.Schuchert and R.Hasholzner, " A novelI/Q imbalance compensation scheme for the reception of OFDM signals, " IEEETransaction on Consumer Electronics, Aug.2001; M.Valkama, M.Renfors and V.Koivunen, " Advanced methods for I/Q imbalance compensation incommunication receivers, " IEEE Trans.Sig.Proc, Oct.2001; R.Rao and B.Daneshrad, " Analysis of I/Q mismatch and a cancellation scheme for OFDMsystems, " IST Mobile Communication Summit, June 2004; A.Tarighat, R.Bagheri and A.H.Sayed, " Compensation schemes and performance analysis of IQimbalances in OFDM receivers, " Signal Processing, IEEE Transactions on[also can be referring to Acoustics, Speech, and Signal Processing, IEEE Transactions on], vol.53, pp.3257-3268, Aug.2005.

The expansion of this work to multiple-input and multiple-output MIMO-OFDM system has been shown: R.Rao and B.Daneshrad in the following information, " I/Q mismatch cancellation for MIMO OFDM systems; " in Personal, Indoor and Mobile Radio Communications, 2004; PIMRC 2004.15th IEEE International Symposium on, vol.4,2004, pp.2710-2714.For spatial reuse (SM), see also R.M.Rao, W.Zhu, S.Lang, C.Oberli, D.Browne, J.Bhatia, J.F.Frigon, J.Wang, P; Gupta, H.Lee, D.N.Liu, S.G.Wong, M.Fitz, B.Daneshrad, and O.Takeshita, " Multiantenna testbeds for research and education inwireless communications; " IEEE Communications Magazine, vol.42, no.12, pp.72-81, Dec.2004; S.Lang, M.R.Rao and B.Daneshrad, " Design anddevelopment of a 5.25GHz software defined wireless OFDM communicationplatform; " IEEE Communications Magazine, vol.42, no.6, pp.6-12, June 2004; For orthogonal space time packet (OSTBC), see also A.Tarighat and A.H.Sayed, " MIMOOFDM receivers for systems with IQ imbalances, " IEEE Trans.Sig.Proc, vol.53, pp.3583-3596, Sep.2005.

Unfortunately, the data that does not exist at present introduction how the gain of the I/Q in distributed input distributed output (DIDO) communication system and unbalance in phase error to be proofreaied and correct.The embodiment of the present invention of the following stated provides a kind of scheme that addresses these problems.

The DIDO system comprises that one has the base station of spaced antenna, the Radio Resource that this base station is same as traditional SIO system in utilization (namely, identical time slot duration and frequency band), send parallel data stream (through precoding) to a plurality of users, to strengthen downlink throughput.The application No.10/902 that is entitled as " System and Method for DistributedInput-Distributed Output Wireless Communications " that S.G.Perlman and T.Cotter submitted to July 30 in 2004,978(" in first to file ") provided the detailed description of DIDO system, this application has been transferred to the application's assignee, and this application is incorporated into this as a reference.

Exist various ways to realize the DIDO precoder.A kind of scheme is the block diagonalization (BD) described in the following information: Q.H.Spencer, A.L.Swindlehurst and M.Haardt, " Zero forcingmethods for downlink spatial multiplexing in multiuser MIMO channels; " IEEETrans.Sig.Proc, vol.52, pp.461-471, Feb.2004; K.K.Wong, R.D.Murch, and K.B.Letaief, " A joint channel diagonalization for multiuser MIMO antennasystems, " IEEE Trans.Wireless Comm., vol.2, pp.773-786, JuI 2003; L.U.Choi and R.D.Murch, " A transmit preprocessing technique for multiuser MIMOsystems using a decomposition approach, " IEEE Trans.Wireless Comm., vol.3, pp.20-24, Jan 2004; Z.Shen, J.G.Andrews, R.W.Heath and B.L.Evans, " Lowcomplexity user selection algorithms for multiuser MIMO systems with blockdiagonalization; " be accepted and be published in IEEE Trans.Sig.Proc, Sep.2005; Z.Shen, R.Chen, J.G.Andrews, R.W.Heath and B.L.Evans, " Sum capacity of multiuserMIMO broadcast channels with block diagonalization, " is submitted to IEEE Trans.Wireless Comm., Oct.2005; R.Chen, R.W.Heath, and J.G.Andrews, " Transmitselection diversity for unitary precoded multiuser spatial multiplexing systemswith linear receivers; " be accepted the Trans to IEEE, on Signal Processing, 2005.The method that is used for the I/Q compensation given in these materials has been imagined the BD precoder, and this precoder can be expanded any type to the DIDO precoding.

In the DIDO-OFDM system, I/Q does not mate can cause two kinds of impact: ICI and inter-user interference.With similar in the SISO-OFDM system, the former is because the interference of transferring from mirror image causes.The latter is due to the fact that and causes, namely I/Q does not mate the quadrature that can destroy the DIDO precoder, disturbs thereby produce between the user.Can by method described herein, eliminate this two class at the transmitter and receiver place and disturb.Describe three kinds of methods that are used for the I/Q compensation of DIDO-OFDM system at this, and do not mated for having and not having I/Q, compared their performance.Based on utilizing the performed emulation of DIDO-OFDM prototype and actual measurement, showed the result.

Present embodiment is the expansion in first to file.Especially, these execution modes are relevant with the following characteristics in first to file:

System described in first to file, wherein the I/Q track can be subject to gaining and the impact of unbalance in phase;

At the transmitter place, use the training signal that adopts for channel estimating to calculate and have the DIDO precoder that I/Q compensates; And

The signal characteristic data have been considered the distortion that causes owing to the I/Q imbalance, and at the transmitter place, according to the method that this material proposes, calculate the DIDO precoder with these signal characteristic data.

B, Embodiments of the present invention

At first, Mathematical Modeling of the present invention and framework will be described.

Before showing this programme, explain that the core mathematics concept is very useful.We come it is made an explanation by hypothesis I/Q gain and unbalance in phase (do not comprise phase delay in this description, but this phase delay will be processed automatically in the algorithm of DIDO-OFDM form).For explaining basic thought, suppose that we want two plural s=s _I+ js _QAnd h=h _I+ jh _QMultiply each other, and so that x=h*s.We represent the inphase quadrature component with subscript.Call following equation:

x _I＝s _Ih _I-s _Qh _Q

And

x _Q＝s _Ih _Q+s _Qh _I

Its matrix form can be rewritten as:

[\begin{matrix} x_{I} \\ x_{Q} \end{matrix}] = [\begin{matrix} h_{I} & - h_{Q} \\ h_{Q} & h_{I} \end{matrix}] [\begin{matrix} s_{I} \\ s_{Q} \end{matrix}]

Come mark normalization conversion by channel matrix (H).Suppose that now s is the symbol that sends, and h is channel.Can come modeling is carried out in the existence of I/Q gain and unbalance in phase by creating following non-normalized conversion:

[\begin{matrix} x_{I} \\ x_{Q} \end{matrix}] = [\begin{matrix} h_{11} & h_{12} \\ h_{21} & h_{22} \end{matrix}] [\begin{matrix} s_{I} \\ s_{Q} \end{matrix}] - - - (A)

The effect of this skill is to confirm and can be written as:

[\begin{matrix} h_{11} & - h_{12} \\ h_{21} & h_{22} \end{matrix}] = \frac{1}{2} [\begin{matrix} h_{11} + h_{22} & h_{12} - h_{21} \\ - (h_{12} - h_{21}) & h_{11} + h_{22} \end{matrix}] + \frac{1}{2} [\begin{matrix} h_{11} - h_{22} & h_{12} + h_{21} \\ h_{12} + h_{21} & h_{22} - h_{11} \end{matrix}]

= \frac{1}{2} [\begin{matrix} h_{11} + h_{22} & h_{12} - h_{21} \\ - (h_{12} - h_{21}) & h_{11} + h_{22} \end{matrix}] + \frac{1}{2} [\begin{matrix} h_{11} - h_{22} & - (h_{12} + h_{21}) \\ h_{12} + h_{21} & h_{11} - h_{22} \end{matrix}] [\begin{matrix} 1 & 0 \\ 0 & - 1 \end{matrix}]

Now (A) rewritten:

[\begin{matrix} x_{I} \\ x_{Q} \end{matrix}] = \frac{1}{2} [\begin{matrix} h_{11} + h_{22} & h_{12} - h_{21} \\ - (h_{12} - h_{21}) & h_{11} + h_{22} \end{matrix}] [\begin{matrix} s_{I} \\ s_{Q} \end{matrix}] + \frac{1}{2} [\begin{matrix} h_{11} - h_{22} & - (h_{12} + h_{21}) \\ h_{12} + h_{21} & h_{11} - h_{22} \end{matrix}] [\begin{matrix} 1 & 0 \\ 0 & - 1 \end{matrix}] [\begin{matrix} s_{I} \\ s_{Q} \end{matrix}]

= \frac{1}{2} [\begin{matrix} h_{11} + h_{22} & h_{12} - h_{21} \\ - (h_{12} - h_{21}) & h_{11} + h_{22} \end{matrix}] [\begin{matrix} s_{I} \\ s_{Q} \end{matrix}] + \frac{1}{2} [\begin{matrix} h_{11} - h_{22} & - (h_{12} - h_{21}) \\ h_{12} + h_{21} & h_{11} - h_{22} \end{matrix}] [\begin{matrix} s_{I} \\ - s_{Q} \end{matrix}]

We carry out giving a definition:

H_{e} = \frac{1}{2} [\begin{matrix} h_{11} + h_{22} & h_{12} - h_{21} \\ - (h_{12} - h_{21}) & h_{11} + h_{22} \end{matrix}]

And

H_{c} = \frac{1}{2} [\begin{matrix} h_{11} - h_{22} & - (h_{12} + h_{21}) \\ h_{12} + h_{21} & h_{11} - h_{22} \end{matrix}]

These two matrixes have the normalization structure, therefore can be represented as plural form:

h _e=h ₁₁+h ₂₂+j(h ₂₁-h ₁₂)

And

h _c=h ₁₁-h ₂₂+j(h ₂₁+h ₁₂)

By using all these knowledge, we can derive back effective equation and have two channel (equivalent channels h _eWith conjugation channel h _c) the scalar form.Therefore, the efficient transformation in (5) becomes:

x=h _es+h _cs ^*

We are called equivalent channels with the first channel, and second channel is called the conjugation channel.If there is no I/Q gain and unbalance in phase then should be the channel that we will observe by the equivalence channel.

By using similar argument, the Input output Relationship with the discrete time MIMON of I/Q gain and unbalance in phase * M system can be shown (by set up their matrix corresponding form with the scalar equivalent form of value):

x [t] = Σ_{l = 0}^{L} h_{e} [l] s [t - l] + h_{c} [l] s^{*} [t - l]

Wherein, t is the discrete time index, h _e, h _c∈ C ^{M * N}, s=[s ₁..., s _N], x=[x ₁..., x _M] and L be channel tap (channel tap) number.

In the DIDO-OFDM system, represented the signal that receives in the frequency domain.If satisfy following equation, then from the signal and systems re invocation:

FFT _K{ s[t] }=S[k] FFT then _K{ s ^*[t] }=S ^*[(k)]=S ^*[K-k] for k=0,1 ..., K-1

Utilize OFDM, for subcarrier k, the Input output Relationship of equal value of MIMO-OFDM system is:

\overset{&OverBar;}{x} [k] = H_{e} [k] \overset{&OverBar;}{s} [k] + H_{c} [k] {\overset{&OverBar;}{s}}^{*} [K - k] - - - (1)

Wherein, k=0,1 ..., K-1 is OFDM subcarrier index, H _eAnd H _cRepresent respectively of equal value and conjugation channel matrix, be defined as follows:

H_{e} [k] = Σ_{l = 0}^{L} h_{e} [l] e^{- j \frac{2 Πk}{K} l}

And

H_{c} [k] = Σ_{l = 0}^{L} h_{c} [l] e^{- j \frac{2 Πk}{K} l}

(1) the second base value in is the interference of transferring from mirror image.Can come it is processed by making up following repeatedly formula (stacked) matrix system (please carefully noting conjugate):

[\begin{matrix} \overset{&OverBar;}{x} [k] \\ {\overset{&OverBar;}{x}}^{*} [K - k] \end{matrix}] = [\begin{matrix} H_{e} [k] & H_{c} [k] \\ H_{c}^{*} [K - k] & H_{e}^{*} [K - k] \end{matrix}] [\begin{matrix} \overset{&OverBar;}{s} [k] \\ {\overset{&OverBar;}{s}}^{*} [K - k] \end{matrix}]

Wherein

With

Be respectively the vector of sending and receiving symbol in frequency domain.

By using the method, can set up active matrix, to be used for the DIDO operation.For example, utilize DIDO 2 * 2 Input output Relationships (supposing that each user has single receive antenna), first user equipment can be considered following equation (when not having noise):

[\begin{matrix} {\overset{&OverBar;}{x}}_{1} [k] \\ {\overset{&OverBar;}{x}}_{1}^{*} [K - k] \end{matrix}] = [\begin{matrix} H_{e}^{(1)} [k] & H_{c}^{(1)} [k] \\ H_{c}^{(1) *} [K - k] & H_{e}^{(1) *} [K - k] \end{matrix}] W [\begin{matrix} {\overset{&OverBar;}{s}}_{1} [k] \\ {\overset{&OverBar;}{s}}_{1}^{*} [K - k] \\ {\overset{&OverBar;}{s}}_{2} [k] \\ {\overset{&OverBar;}{s}}_{2}^{*} [K - k] \end{matrix}] - - - (2)

And the second user notes following equation:

[\begin{matrix} {\overset{&OverBar;}{x}}_{2} [k] \\ {\overset{&OverBar;}{x}}_{2}^{*} [K - k] \end{matrix}] = [\begin{matrix} H_{e}^{(2)} [k] & H_{c}^{(2)} [k] \\ H_{c}^{(2) *} [K - k] & H_{e}^{(2) *} [K - k] \end{matrix}] W [\begin{matrix} {\overset{&OverBar;}{s}}_{1} [k] \\ {\overset{&OverBar;}{s}}_{1}^{*} [K - k] \\ {\overset{&OverBar;}{s}}_{2} [k] \\ {\overset{&OverBar;}{s}}_{2}^{*} [K - k] \end{matrix}] - - - (3)

Wherein,

Represent respectively matrix H _eAnd H _cM capable, and W ∈ C ^4x4Be the DIDO pre-coding matrix.According to (2) and (3), can notice the symbol that user m receives

(that is the inter-carrier interference of, transferring from mirror image (that is, to be subjected to two interference sources that the I/Q imbalance causes

) and inter-user interference (that is, And

P ≠ m)) impact.(3) the DIDO pre-coding matrix W in is designed to eliminate this two distracters.

There are a plurality of different execution modes in the DIDO precoder that can be used for herein, and this depends on the applied joint-detection in receiver place.In one embodiment, can adopt according to composite channel

(but not ) block diagonalization (BD) that calculates (for example sees also, Q.H.Spencer, A.L.Swindlehurst, and M.Haardt, " Zeroforcing methods for downlink spatialmultiplexing in multiuser MIMO channels, " IEEE Trans.Sig.Proc, vol.52, pp.461-471, Feb.2004.K.K; Wong, R.D.Murch, and K.B.Letaief, " A jointchannel diagonalization for multiuser MIMO antenna systems, " IEEE Trans.Wireless Comm., vol.2, pp.773-786, JuI 2003; L.U.Choi and R.D.Murch, " Atransmit preprocessing technique for multiuser MIMO systems using adecomposition approach, " IEEE Trans.Wireless Comm., vol.3, pp.20-24, Jan2004; Z.Shen, J.G.Andrews, R.W.Heath, with B.L Evans, " Low complexityuser selection algorithms for multiuser MIMO systems with blockdiagonalization; " be accepted and be published in IEEE Trans.Sig.Proc, Sep.2005; Z.Shen, R.Chen, J.G.Andrews, R.W.Heath, and B.L Evans, " Sum capacity of multiuserMIMO broadcast channels with block diagonalization; " be submitted to IEEE Trans.Wireless Comm., Oct.2005).Therefore, precoder is selected by the DIDO system at present, so that:

H_{w} \overset{Δ}{=} [\begin{matrix} H_{e}^{(1)} [k] & H_{c}^{(1)} [k] \\ H_{c}^{(1) *} [K - k] & H_{e}^{(1) *} [K - k] \\ H_{e}^{(2)} [k] & H_{c}^{(2)} [k] \\ H_{c}^{(2) *} [K - k] & H_{e}^{(2) *} [K - k] \end{matrix}] W = [\begin{matrix} α_{1,1} & 0 & 0 & 0 \\ 0 & α_{1,2} & 0 & 0 \\ 0 & 0 & α_{2,1} & 0 \\ 0 & 0 & 0 & α_{2,2} \end{matrix}] \overset{Δ}{=} [\begin{matrix} H_{w}^{(1,1)} & H_{w}^{(1,2)} \\ H_{w}^{(2,1)} & H_{w}^{(2,2)} \end{matrix}] - - - (4)

Wherein, α _{I, j}Be constant, and

The method is very useful, because by using this precoder, keeps intact aspect other of DIDO precoder because the impact of having eliminated I/Q gain and unbalance in phase fully at the transmitter place can make.

Also the DIDO precoder can be designed to eliminate in advance inter-user interference, and not eliminate in advance the ICI that causes because of the IQ imbalance.Utilize the method, one of receiving filter that receiver (but not transmitter) can be by adopting the following stated comes the IQ imbalance is compensated.Therefore, the Precoding Design standard in (4) can be modified to:

H_{w} \overset{Δ}{=} [\begin{matrix} H_{e}^{(1)} [k] & H_{c}^{(1)} [k] \\ H_{c}^{(1) *} [K - k] & H_{e}^{(1) *} [K - k] \\ H_{e}^{(2)} [k] & H_{c}^{(2)} [k] \\ H_{c}^{(2) *} [K - k] & H_{e}^{(2) *} [K - k] \end{matrix}] W = [\begin{matrix} α_{1,1} & α_{1,2} & 0 & 0 \\ α_{2,1} & α_{2,2} & 0 & 0 \\ 0 & 0 & α_{3,3} & α_{3,4} \\ 0 & 0 & α_{4,3} & α_{4,4} \end{matrix}] \overset{Δ}{=} [\begin{matrix} H_{w}^{(1,1)} & H_{w}^{(1,2)} \\ H_{w}^{(2,1)} & H_{w}^{(2,2)} \end{matrix}] - - - (5)

{\overset{&OverBar;}{x}}_{1} [k] = [\begin{matrix} H_{w}^{(1,1)} & H_{w}^{(1,2)} \end{matrix}] [\frac{{\overset{&OverBar;}{s}}_{1}}{{\overset{&OverBar;}{s}}_{2}} \frac{[k]}{[k]}] - - - (6)

And

{\overset{&OverBar;}{x}}_{2} [k] = [\begin{matrix} H_{w}^{(2,1)} & H_{w}^{(2,2)} \end{matrix}] [\frac{{\overset{&OverBar;}{s}}_{1}}{{\overset{&OverBar;}{s}}_{2}} \frac{[k]}{[k]}] - - - (7)

Wherein for m transmitted signal,

And

The symbolic vector that receives for user m.At receiver side, for to sending symbolic vector

Estimate, user m adopts the ZF filter, and estimated symbolic vector is given as:

Although the easy to understand of ZF filter, receiver also can be used other filters known in those skilled in the art of any amount.A kind of masses are chosen as the MMSE filter, wherein:

And ρ is signal to noise ratio.Alternatively, the user can carry out maximum likelihood symbol detection (perhaps ball decoder, iteration change).For example, first user can use the ML receiver, and finds the solution following optimization:

{\hat{s}}_{m}^{(ML)} [k] = \arg \min_{s}_{1}, s_{2} &Element; S ||\begin{matrix} {\overset{&OverBar;}{y}}_{1} [k] - [\begin{matrix} H_{w}^{(1,1)} & H_{w}^{(1,2)} \end{matrix}] [\begin{matrix} s_{1} [k] \\ s_{2} [k] \end{matrix}] \end{matrix}|| - - - (10)

Wherein, S is the set of all possible vectorial s, and depends on constellation sizes.This ML receiver provides preferably performance, but requires higher complexity at the receiver place.Similar one group of equation can be applicable to the second user.

Note, in (6) and (7)

With

Be assumed to be and have zero.This hypothesis only under the emission precoder can be eliminated for the situation of the inter-user interference of the standard in (4) fully effectively.Similarly, With

Only can eliminate in the situation of inter-carrier interference (that is, from mirror image transfer) fully at the emission precoder is diagonal matrix.

Figure 13 has shown a kind of execution mode of the framework of the DIDO-OFDM system with I/Q compensation, and described DIDO-OFDM system comprises IQ-DIDO precoder 1302, the transmitting channel 1304 that is positioned at base station (BS), the channel estimating logical one 306 that is positioned at subscriber equipment and ZF, MMSE or ML receiver 1308.Described channel estimating logical one 306 via training signal to channel

With

Estimate, and these estimations are fed back to precoder in the AP.BS calculates DIDO precoder weight (matrix W), eliminating in advance interference and the user's interference that is caused because of I/Q gain and unbalance in phase, and data communication device is crossed wireless channel 1304 is sent to the user.Subscriber equipment m adopts ZF, MMSE or ML receiver 1308, eliminates residual interference by the channel estimating that range site 1304 provides, and data are carried out demodulation.

Can adopt following three execution modes to realize this I/Q backoff algorithm.

Method 1-TX compensation: in this embodiment, transmitter calculates pre-coding matrix according to the standard in (4).At the receiver place, subscriber equipment adopts " simplification " ZF receiver, wherein

With

Be assumed to be diagonal matrix.Therefore, formula (8) is reduced to:

{\hat{s}}_{m} [k] = [\begin{matrix} 1 / α_{m, 1} & 0 \\ 0 & 1 / α_{m, 2} \end{matrix}] {\overset{&OverBar;}{x}}_{m} [k] - - - (10)

Method 2-RX compensation: in this embodiment, transmitter is based on R.Chen, R.W.Heath, andJ.G.Andrews, " Transmit selection diversity for unitary precoded multiuserspatial multiplexing systems with linear receivers; " accepted to IEEE Trans, onSignal Processing, the traditional B D method of describing in 2005, calculate pre-coding matrix, and do not eliminate intercarrier and inter-user interference for the standard in (4).Utilize the method, the pre-coding matrix in (2) and (3) is reduced to:

W = [\begin{matrix} w_{1,1} [k] & 0 & w_{1,2} [k] & 0 \\ 0 & w_{1,1}^{*} [K - k] & 0 & w_{1,2}^{*} [K - k] \\ w_{2,1} [k] & 0 & w_{2,2} [k] & 0 \\ 0 & w_{2,1}^{*} [K - k] & 0 & w_{2,2}^{*} [K - k] \end{matrix}] - - - (12)

At the receiver place, subscriber equipment adopts the ZF filter as in (8).Note, the method is such not as above-mentioned method 1, eliminates in advance interference at the transmitter place.Therefore, it eliminates inter-carrier interference at the receiver place, but can not eliminate inter-user interference.In addition, require feedback than method 1

With In method 2, the user only needs to feed back the vector for transmitter

To calculate the DIDO precoder.Therefore, method 2 is particularly suitable for having the DIDO system of low-rate feedback channel.On the other hand, method 2 needs the subscriber equipment place to have higher a little computation complexity, to calculate the ZF receiver in (8) (but not (11)).

Method 3-TX-RX compensation: in one embodiment, above-mentioned two methods are merged.Transmitter calculates pre-coding matrix as (4), and receiver estimates sending symbol according to (8).

I/Q uneven (no matter being that unbalance in phase, gain are uneven, or be to postpone imbalance) can cause harmful degradation to the signal quality in the wireless communication system.For this reason, circuit in the past all is designed to have lower imbalance.Yet, as mentioned above, can by using Digital Signal Processing and/or the specific receiver of emission precoded form, revise this problem.One embodiment of the present invention comprise the system with a plurality of new functional units, and each unit is for realizing that the I/Q correction in ofdm communication system or the DIDO-OFDM communication system all is very important.

One embodiment of the present invention are used the precoding based on channel condition information, to eliminate the inter-carrier interference (ICI) (not causing because I/Q does not mate) of transferring from mirror image in the ofdm system.As shown in figure 11, the known precoding unit 1108 of a plurality of map unit 1106, DIDO IQ, a plurality of RF transmitter unit 1114, user feedback unit 1112 and the DIDO configurator unit 1110 that comprise subscriber selector unit 1102, a plurality of coded modulation unit 1104, correspondence according to the DIDO transmitter of present embodiment.

The feedback information that described subscriber selector unit 1102 obtains based on feedback unit 1112 is selected and a plurality of user U ₁-U _MThe data that are associated, and this information offered each coded modulation unit 1104 in a plurality of coded modulation unit 1104.Encode and demodulation to each user's information bit in each coded modulation unit 1104, and they are sent to map unit 1106.This map unit 1106 maps to complex symbol with input bit, and the result is sent to the known precoding unit 1108 of DIDO IQ.The channel condition information that the known precoding unit 1108 of this DIDO IQ utilizes feedback unit 1112 to obtain from the user is calculated the known precoding weight of DIDO IQ, and the incoming symbol of obtaining from map unit 1106 is carried out precoding.Each pre-code data stream is sent to OFDM unit 1115 by the known precoding unit 1108 of DIDO IQ, and this OFDM unit 1115 calculates IFFT, and adds Cyclic Prefix.This information is sent to D/A unit 1116, and this D/A unit 1116 carries out digital-to-analogue conversion, and sends it to RF unit 1114.This RF unit 1114 to intermediate frequency/radio frequency, and sends it to transmitting antenna with the baseband signal raising frequency.

Described precoder is transferred routine mediation mirror image and is operated together, and I/Q is uneven with compensation.Can use the precoder design standard of any amount, comprise ZF, MMSE or weighting MMSE design.In a preferred embodiment, precoder can remove fully because I/Q does not mate the ICI that causes, thereby so that receiver does not need to carry out any ancillary relief.

In one embodiment, described precoder uses the block diagonalization standard, with not exclusively eliminating in each user's the I/Q impact situation of (this needs accessory receiver to process), eliminates inter-user interference fully.In another embodiment, described precoder is eliminated inter-user interference and the ICI interference that causes because of the I/Q imbalance fully with zero pressure standard.This execution mode can use at the receiver place traditional DIDO-OFDM processor.

One embodiment of the present invention are used the precoding based on channel condition information, with eliminate the inter-carrier interference (ICI) of transferring from mirror image in the DIDO-OFDM system (because of I/Q do not mate caused), and each user adopts the known DIDO receiver of IQ.As shown in figure 12, in one embodiment of the invention, system's (comprising receiver 1202) comprises a plurality of RF unit 1208, correspondingly a plurality of A/D unit 1210, IQ known channel estimator 1204 and DIDO feedback maker unit 1206.

Described RF unit 1208 receives the signal that sends from DIDO transmitter unit 1114, and this signal down to base band, and is offered A/D unit 1210 with the signal after this frequency reducing.Afterwards, 1210 pairs of these signals in this A/D unit carry out analog-to-digital conversion, and send it to OFDM unit 1213.This OFDM unit 1213 removes Cyclic Prefix, and carries out FFT, so that this signal is reported to frequency domain.During cycle of training, OFDM unit 1213 is sent to IQ known channel estimation unit 1204 with output, and this IQ known channel estimation unit 1204 calculates channel estimating in frequency domain.Alternatively, can in time domain, calculate described channel estimating.During the data cycle (data period), OFDM unit 1213 is sent to the known receiver unit 1202 of IQ with output.The known receiver unit of this IQ calculates the IQ receiver, and described signal is carried out demodulate/decode, to obtain data 1214.Described IQ known channel estimation unit 1204 sends described channel estimating to DIDO feedback maker unit 1206, and this feedback maker unit 1204 can quantize described channel estimating, and via FEEDBACK CONTROL channel 1112 it is beamed back transmitter.

Receiver 1202 shown in Figure 12 can be in the lower work of the standard known in those skilled in the art (comprising ZF, MMSE, maximum likelihood or MAP receiver) of any amount.In a preferred embodiment, receiver is eliminated the ICI that causes because of the IQ imbalance on the mirror image accent with the MMSE filter.In another preferred embodiment, the receiver symbol that the nonlinear detector that is similar to maximum likelihood searching comes the joint-detection mirror image to transfer.The method has good performance, but has higher complexity.

In one embodiment, determine the receiver coefficient with IQ known channel estimator 1204, to remove ICI.Therefore, we required the DIDO-OFDM system (use based on the precoding of channel condition information eliminate the inter-carrier interference (ICI) of transferring from mirror image (because of I/Q do not mate cause)), the rights and interests of the known DIDO receiver of IQ and IQ known channel estimator.Described channel estimator can use traditional training signal, maybe can use the training signal of the special structure that sends at the inphase quadrature signal.The algorithm for estimating of any amount be can implement, least square method, MMSE or maximum likelihood comprised.Described IQ known channel estimator provides input for the known receiver of IQ.

Channel condition information can be provided for website by channel reciprocity or by feedback channel.One embodiment of the present invention comprises the DIDO-OFDM system, and this system has the known precoder of I/Q, and the known feedback channel of I/Q that is used for transferring to from the channel condition information of user's terminal website.This feedback channel can be physics or logical control channel.It can be by special-purpose or shared in RACH.Can generate feedback information by the DIDO feedback maker that user's terminal (we have also required the rights and interests of this user terminal) located.Described DIDO feedback maker with the output of described I/Q known channel estimator as input.But its quantized channel coefficient maybe can use any amount Limited Feedback algorithm known in the field.

User's distribution, modulation and encoding rate, can change according to the result of described DIDO feedback maker to the mapping of space-time frequency coding time slot.Therefore, one execution mode comprises the known DIDO configurator of IQ, this configurator is used from one or more users' IQ known channel and is estimated to configure the known precoder of DIDO IQ, the user's that selection modulation rate, encoding rate, permission send subset and their mapping to the space-time frequency coding time slot.

In order to estimate the performance of the compensation method that proposes, will compare three DIDO 2 * 2 systems:

1, having I/Q does not mate: send by all accent (transferring except DC is in harmonious proportion the edge), and I/Q is not mated and compensate;

2, has I/Q compensation: send by all row of transferring in, and come I/Q do not mated by use above-mentioned " method 1 " and compensate;

3, desirable: as only to transfer in row by odd number and send, to avoid inter-user interference and not mate intercarrier (that is, transferring from the mirror image) interference that is caused because of I/Q.

After this, showed in the true propagation situation and utilize the DIDO-OFDM prototype to measure the result who obtains.Figure 14 has illustrated the 64-QAM planisphere that obtains from above-mentioned three systems.These planispheres be in the situation that same customer location and fixedly average signal-to-noise ratio (~ 45dB) obtain.The first planisphere 1401 is very noisy (because the uneven cause of I/Q is from interference of mirror image accent).The second planisphere 1402 shows some improvement (because I/Q compensation).Note, the second planisphere 1402 is the ideal situation shown in the planisphere 1403 pure like that (owing to having the phase noise that may produce inter-carrier interference (ICI)) not.

Figure 15 shows to have and not to have in the unmatched situation of I/Q the average SER(symbol error rate of DIDO 2 * 2 systems of 64-QAM and 3/4 encoding rate) 1501 and every user's goodput (goodput) 1502.The OFDM bandwidth is 250KHZ, has 64 and transfers and circulating prefix-length L _Cp=4.Because in the ideal case, we only send data by the subset of transferring, and therefore estimate SER and goodput performance according to the transmitting power (but not total transmitting power) of average every accent, to guarantee the fair comparison between the different situations.In addition, in following result, we use the normalized value (indicating with decibel) of transmitting power, because the target of ours is relatively (but not absolute) performance of comparison different schemes herein.Figure 15 shows and exists in the unbalanced situation of I/Q, saturated and miss the mark SER(~ 10 of SER ^-2), this and A.Tarighat and A.H.Sayed, " MIMO OFDM receiversfor systems with IQ imbalances, " IEEE Trans.Sig.Proc, vol.53, pp.3583-3596, the result who reports among the Sep.2005 is consistent.This saturation effect is due to the fact that and causes, and namely signal power and interference power (transferring from mirror image) increase along with the increase of TX power.Yet the I/Q compensation method of passing through to propose can be eliminated interference, and obtains preferably SER performance.Note, because the 64-QAM modulation needs larger transmitting power, therefore, can cause SER can have trickle increase at high SNR place because of the amplitude saturation effect among the DAC.

In addition, can be observed, in the situation that there is the I/Q compensation, the SER performance is very near ideal situation.Between these two kinds of situations, the 2dB gap of TX power is owing to phase noise (this phase noise may produce additional interference between adjacent OFDM is transferred) causes.At last, goodput curve 1502 shows when using the I/Q method, and it can send the data of twice than ideal situation, and only odd number is transferred (for ideal situation) because we have used all data accent.

Figure 16 illustrates in the situation that have the I/Q compensation or do not have I/Q compensation, the SER performance of different Q AM planisphere.We can be observed, and in this execution mode, the method that proposes is particularly advantageous for the 64-QAM planisphere.For 4-QAM and 16-QAM, I/Q compensation method meeting produces than having the worse performance of the unmatched situation of I/Q, and this may be because the method that proposes requires larger power to carry out the data transmission and eliminates from the interference that mirror image is transferred.In addition, because the larger minimum range between the constellation point, 4-QAM and 16-QAM also are subject to the unmatched impact of I/Q like that not as 64-QAM.Referring to A.Tarighat, R.Bagheri, and A.H.Sayed, " Compensation schemes and performance analysis of IQ imbalances in OFDMreceivers; " Signal Processing, IEEE Transactions on[also can be referring to Acoustics, Speech, and Signal Processing, IEEE Transactions on], vol.53, pp.3257-3268, Aug.2005.Observable Figure 16 and draw this conclusion by I/Q not being mated compare with ideal situation for 4-QAM and 16-QAM also.Therefore, for the situation of 4-QAM and 16-QAM, have and disturb the needed secondary power of DIDO precoder of eliminating (transferring from mirror image) not go bail for for the slight interests of I/Q compensation.Note, can solve this problem by adopting above-mentioned I/Q compensation method 2 and 3.

At last, under different propagation conditions, measured the relative SER performance of above-mentioned three methods.Also described and have the SER performance of the unmatched situation of I/Q, for your guidance.It is that 450.5MHZ and bandwidth are 64-QAM DIDO 2 * 2 systems of 250KHz that Figure 17 has illustrated for carrier frequency, at two SER that different customer locations is measured.In the position 1, the user be in chummery not and be in NLOS(ignore apart from) BS of state is at a distance of ~ 6 λ.In the position 2, the user with have the LOS(sighting distance) BS at a distance of ~ λ.

Figure 17 shows all three kinds of compensation methodes and all has outstanding performance than situation about not compensating.Yet, it should be noted, under any channel conditions, method 3 is all better than other two kinds of

compensation methodes.Method

1 and 2 relative performance depend on propagation condition.By the actual measurement activity, can draw method 1 surpasses method 2 substantially, because it has eliminated the inter-user interference that (at the transmitter place) I/O imbalance causes in advance.When this inter-user interference was very little, shown in the curve chart 1702 of Figure 17, method 2 can surpass method 1, because it can not suffer to compensate the power loss that precoder causes because of I/Q.

Up to the present, by only considering limited group of propagation situation (as shown in figure 17) distinct methods is compared.After this, at desirable i.i.d.(independence and tool with distributing) measure the relative performance of these methods in the channel.Utilization transmits and receives I/Q phase place and the gain imbalance of side and comes emulation DIDO-OFDM system.Figure 18 shows in the situation that only launch pusher side has gain balance (that is, have gain 0.8 at the I of the first transmitting chain rail, have gain 1 at other rails), the performance of the method that proposes.Can find out, method 3 has surpassed every other method.In addition, obtain the result with 2 places, position in the curve chart 1702 of Figure 17 and compare, in the i.i.d. channel, method 1 comparable method 2 is carried out better.

Therefore, provided the I/Q that three kinds of novel methods compensate in the above-mentioned DIDO-OFDM system uneven, method 3 surpasses other compensation methodes that propose.In having the system of low-rate feedback channel, but using method 2 reduces the required feedback quantity of DIDO precoding, but can cause relatively poor SER performance.

II, Self adaptation DIDO delivery plan

Use description to strengthen another execution mode of system and method for the performance of distributed input distributed output (DIDO) system.The method is dynamically given different subscriber equipmenies with allocation of radio resources by following the tracks of the channel status that changes, to increase throughput when satisfying some target error rate.Described subscriber equipment is estimated channel quality, and it is fed back to base station (BS); Process the channel quality that is obtained from subscriber equipment this base station, to select to be used for optimal user cluster tool, DIDO scheme, modulation/coding scheme (MCS) and the array configurations of next time transmission; Described base station is sent to parallel data via precoding a plurality of subscriber equipmenies, and signal is demodulated at the receiver place.

Also describe one and be the system of the effective Resources allocation of DIDO Radio Link.This system comprises the DIDO base station with DIDO configurator, and process the feedback that receives personal family this base station, to select to be used for optimal user set, DIDO scheme, modulation/coding scheme (MCS) and the array configurations of next time transmission; Receiver in the DIDO system, this receiver is measured channel and other relevant parameters, to generate the DIDO feedback signal; And DIDO FEEDBACK CONTROL channel, being used for will be from user's transmission of feedback information to the base station.

As detailed in the following, some notable features of this execution mode of the present invention can include, but are not limited to:

Be used for based on channel quality information, select adaptively number of users, DIDO delivery plan (namely, it line options or multiplexing), modulation/coding scheme (MCS) and array configurations, minimizing SER, or maximize every user's spectrum efficiency or the technology of downlink tone spectrum efficiency;

Be used for defining many group DIDO sending modes with the technology as the combination of DIDO scheme and MCS;

Be used for according to channel status different DIDO patterns being assigned to the technology of different time slots, OFDM mediation DIDO subflow;

Be used for based on the channel quality of different user different DIDO patterns dynamically being assigned to the technology of different user;

Be used for self adaptation DIDO being switched the standard that activates based on the link quality metric of calculating in time domain, frequency domain and spatial domain;

Be used for self adaptation DIDO being switched the standard that activates based on look-up table.

As shown in figure 19 have a DIDO system of DIDO configurator at base station place, this system can be based on channel quality information, select adaptively number of users, DIDO delivery plan (namely, it line options or multiplexing), modulation/coding scheme (MCS) and array configurations, minimizing SER, or maximize every user's spectrum efficiency or downlink tone spectrum efficiency;

Having the DIDO configurator at base station place and having the DIDO system of DIDO feedback maker at each subscriber equipment place as shown in figure 20, this system uses estimated channel conditions and/or other parameters (being similar to estimated SNR) at receiver place, inputs to the feedback message of DIDO configurator with generation.

DIDO system, this system have DIDO configurator (at the place, base station), DIDO feedback maker and DIDO FEEDBACK CONTROL channel (this DIDO feedback channel is used for the DIDO specific configuration information is transferred to the base station from the user).

A, Background

In multiple-input and multiple-output (MIMO) system, (for example can conceive diversity scheme, orthogonal space time packet (OSTBC) is (referring to V.Tarokh, H.Jafarkhani, and A.R.Calderbank, " Spacetime block codes from orthogonal designs; " IEEE Trans.Info.Th., vol.45, pp.1456-467, JuI.1999) or day line options (referring to R.W.Heath Jr., S.Sandhu, andA.J.Paulraj, " Antenna selection for spatial multiplexing systems with linearreceivers; " IEEE Trans.Comm., vol.5, pp.142-144, Apr.2001), to prevent fading channel, improve link reliability (this reliability can be exchanged into better coverage rate).On the other hand, spatial reuse (SM) can send with a plurality of parallel datas and strengthen throughput of system as means.Referring to G.J.Foschini, G.D.Golden, R.A.Valenzuela, and P.W.Wolniansky, " Simplifiedprocessing for high spectral effciency wireless communication employingmultielement arrays, " IEEE Jour.Select.Areas in Comm., vol.17, no.1 1, pp.1841-1852, Nov.1999.According to deriving from L.Zheng and D.N.C.Tse, " Diversity andmultiplexing:a fundamental tradeoff in multiple antenna channels; " IEEE Trans.Info.Th., vol.49, no.5, pp.1073-1096, the theoretical diversity of May 2003/multiplexing compromise, these benefits can realize in mimo system simultaneously.One actual form of implementation is carried out self adaptation and is switched for by following the tracks of the channel status that changes between diversity and multiplexing delivery plan.

A large amount of adaptive MIMO transmission technologies have now been proposed.R.W.Heath and A.J.Paulraj, " Switching between diversity and multiplexing in MIMO systems; " IEEETrans.Comm., vol.53, no.6, pp.962-968, the diversity among the Jun.2005/multiplexing changing method is designed to based on instantaneous channel quality information, improves the BER(bit error rate that sends for fixed rate).Alternatively, can be such as S.Catreux, V.Erceg, D.Gesbert, and R.W.Heath.Jr., " Adaptive modulation and MIMO coding for broadband wireless datanetworks, " IEEE Comm.Mag., vol.2, pp.108-1 15, like that, adopt statistic channel information to come self adaptation is activated among the June 2002 (" Catreux "), thereby reduce the quantity of feedback overhead and control message.When the self adaptation transmission algorithm among the Catreux is designed to based on channel/frequency selects designator, for the predeterminated target error rate in OFDM (OFDM) system, strengthens spectrum efficiency.Also for narrowband systems, proposed similarly to hang down the feedback adaptive method, the method utilizes the channel space selectivity to switch between diversity scheme and spatial reuse.Referring to for example A.Forenza, M.R.McKay, A.Pandharipande, R.W.Heath.Jr., and I.B.Collings, " Adaptive MIMOtransmission for exploiting the capacity of spatially correlated channels, " accepted to the IEEE Trans, on Veh.Tech., Mar.2007; M.R.McKay, I.B.Collings, A.Forenza, and R.W.Heath.Jr., " Multiplexing/beamformingswitching for coded MIMO in spatially correlated Rayleigh channels; " be accepted the Trans to IEEE, on Veh.Tech., Dec.2007; A.Forenza, M.R.McKay, R.W.Heath.Jr., and I.B.Collings, " Switching between OSTBC and spatial multiplexing withlinear receivers in spatially correlated MIMO channels, " Proc.IEEE Veh.Technol.Conf., vol.3, pp.1387-1391, May 2006; M.R.McKay, I.B.Collings, A.Forenza, with R.W.Heath Jr., " A throughput-based adaptive MIMO BICMapproach for spatially correlated channels, " appears at Proc.IEEE ICC, and June 2006.

In this data, we extend to the DIDO-OFDM system with the working range that represents in various previous the disclosing.Referring to for example R.W.Heath and A.J.Paulraj, " Switching betweendiversity and multiplexing in MIMO systems, " IEEE Trans.Comm., vol.53, no.6, pp.962-968, Jun.2005; S.Catreux, V.Erceg, D.Gesbert, with R.W.Heath Jr., " Adaptive modulation and MIMO coding for broadband wireless datanetworks, " IEEE Comm.Mag., vol.2, pp.108-1 15, and June 2002; A.Forenza, M.R.McKay, A.Pandharipande, R.W.Heath Jr., and I.B.Collings, " AdaptiveMIMO transmission for exploiting the capacity of spatially correlated channels, " IEEE Trans, on Veh.Tech., vol.56, n.2, pp.619-630, Mar.2007; M.R.McKay, I.B.Collings, A.Forenza, with R.W.Heath Jr., " Multiplexing/beamformingswitching for coded MIMO in spatially correlated Rayleigh channels; " be accepted the Trans to IEEE, on Veh.Tech., Dec.2007; A.Forenza, M.R.McKay, R.W.HeathJr., and I.B.Collings, " Switching between OSTBC and spatial multiplexing withlinear receivers in spatially correlated MIMO channels, " Proc.IEEE Veh.Technol.Conf., vol.3, pp.1387-1391, May 2006; M.R.McKay, I.B.Collings, A.Forenza, with R.W.Heath Jr., " A throughput-based adaptive MIMO BICMapproach for spatially correlated channels, " appears at Proc.IEEE ICC, and June 2006.

Described NEW ADAPTIVE DIDO sending strategy at this, this strategy comes the improved system performance to switch as a kind of means between the transmitting antenna of the user of varying number, varying number and delivery plan based on channel quality information.Note, M.Sharif and B.Hassibi, " On the capacity ofMIMO broadcast channel with partial side information; " IEEE Trans.Info.Th., vol.51, p.506522, Feb.2005 and W.Choi, A.Forenza, J.G.Andrews, and R.W.Heath Jr., " Opportunistic space division multiple access with beam selection; " appear at IEEE Trans, proposed the scheme of adaptively selected user in multi-user MIMO system among the on Communications.Yet, opportunistic (opportunistic) space division multiplexing access (OSDMA) scheme during these are open is designed to by utilizing multi-user diversity to maximize total capacity, and they only can realize the part of theory capacity of dirty paper (dirty paper) code, because do not eliminate fully in advance interference at the transmitter place.In DIDO transmission algorithm described herein, adopt block diagonalization to eliminate in advance inter-user interference.Yet the self adaptation sending strategy that proposes can be applied to any DIDO system, need not to consider the type of precoding technique.

Present patent application has been described the invention described above and in the expansion of the execution mode of first to file, has been included but not limited to following supplementary features:

1, can adopt the training symbol that in first to file, is used for channel estimating to come the link quality metric of self adaptation DIDO scheme is estimated by wireless client device.

2, as described in the first to file, the base station receives the signal characteristic data from client device.In current execution mode, the signal characteristic data are defined as for the link quality metric that self adaptation is activated.

3, described one in first to file and be used for selecting the mechanism of antenna and number of users, and defined throughput distribution.In addition, can be as in first to file, the throughput of different stage dynamically is assigned to different clients.Current execution mode of the present invention has defined the novel standard relevant with this selection and throughput distribution.

B, Embodiments of the present invention

The target of the self adaptation DIDO technology that proposes is by the Radio Resource dynamic assignment in time, frequency and the space is strengthened every user's spectrum efficiency or downlink tone spectrum efficiency to the different user in the system.This integral body self adaptation standard is used for improving throughput when satisfying target error rate.According to spread state, also can improve with this adaptive algorithm user's link-quality (or coverage rate) via diversity scheme.The flow chart description that Figure 21 shows the step of self adaptation DIDO scheme.

2102, base station (BS) collects from all users' channel condition information.2104, according to the CSI that receives, link quality metric is calculated in time domain/frequency domain/spatial domain in the base station.2106, with these link quality metric select will be in next transmission serviced user, and for each user's sending mode.Note, sending mode comprises the various combination of modulation/coding and DIDO scheme.At last, send data to the user at 2108, BS via the DIDO precoding.

2102, base station selected channel condition information from all subscriber equipmenies (CSI).2104, the instantaneous of all subscriber equipmenies or statistical channel quality are determined with this CSI in the base station.In the DIDO-OFDM system, can estimate channel quality (or link quality metric) in time domain, frequency domain and spatial domain.Afterwards, 2106, optimal user subset and the sending mode that is used for current spread state are determined with link quality metric in the base station.The set of DIDO sending mode is combined into the combination of DIDO scheme (that is, day line options or multiplexing), modulation/coding scheme (MCS) and array configurations.2108, by using selected user quantity and sending mode, send data to subscriber equipment.

Can carry out model selection by look-up table (LUT) (this look-up table be based on bit error rate performance in the different communication environments of DIDO system be pre-calculated).These LUT map to bit error rate performance with channel quality information.In order to make up LUT, can estimate the DIDO system according to SNR and propagate bit error rate performance in the situation in difference.Can find out from ber curve, can calculate and realize the required minimum SNR of a certain predeterminated target error rate.We are the SNR threshold value with this SNR requirement definition.Afterwards, estimate the SNR threshold value in different propagation situations and for different DIDO sending modes, and it is stored among the LUT.For example, can make up LUT with SER result among Figure 24 and Figure 26.Afterwards, according to this LUT, the sending mode for active user can be selected in the base station, and this pattern can improve throughput when satisfying the predeterminated target error rate.At last, the base station sends data to selected user via the DIDO precoding.Note, different DIDO patterns can be assigned to different time slots, OFDM accent and DIDO subflow, so that can carry out self adaptation in time domain, frequency domain and spatial domain.

Figure 19-Figure 20 has shown a kind of execution mode that adopts the adaptive system of DIDO.Introduced the DIDO adaptive algorithm that some new functional units are implemented to propose.Particularly, in one embodiment, the channel quality information 1912 that DIDO configurator 1910 can provide based on subscriber equipment is carried out several functions, comprise and select number of users, DIDO delivery plan (that is, day line options and multiplexing), modulation/coding scheme (MCS) and array configurations.

Subscriber selector unit 1902 is selected and a plurality of user U based on the feedback information that is obtained by DIDO configurator 1910 ₁-U _MThe data that are associated, and provide each coded modulation unit in every a plurality of coded modulation unit 1904 with this information.Encode to each user's information bit and modulate in each coded modulation unit 1904, and they are sent to map unit 1906.This map unit 1906 maps to complex symbol with input bit, and sends it to precoding unit 1908.Coded modulation unit 1904 and map unit 1906 are all utilized the information that is obtained from DIDO configurator unit 1910, are chosen as the modulation/coding scheme type that each user adopts.Described information can be calculated by the channel quality information of configurator unit 1910 by each user of utilizing feedback unit 1912 and providing.DIDO precoding unit 1908 utilizes the information of being obtained by DIDO configurator unit 1910 to calculate the DIDO precoding weight, and the incoming symbol that is obtained from map unit 1906 is carried out precoding.Be sent to OFDM unit 1915 by the data flow of DIDO precoding unit 1906 after with each precoding, this OFDM unit 1915 calculates IFFT and also adds Cyclic Prefix.This information is sent to D/A unit 1916, and this D/A unit 1916 carries out digital-to-analogue conversion, and final analog signal is sent to RF unit 1914.This RF unit 1914 to intermediate frequency/radio frequency, and sends it to transmitting antenna with the baseband signal raising frequency.

The RF unit 2008 of each client device receives the signal that sends from DIDO transmitter unit 1914, and this signal down to base band, and is offered A/D unit 2010 with the signal after the frequency reducing.Afterwards, this A/D unit 2010 is converted to numeral with this signal from analog, and sends it to OFDM unit 2013.This OFDM unit 2013 removes Cyclic Prefix, and carries out FFT, so that signal is reported to frequency domain.In cycle of training, OFDM unit 2013 is sent to channel estimating unit 2004 with output, and this channel estimating unit 2004 is calculated channel estimating in frequency domain.Alternatively, can calculate channel estimating in time domain.During the data cycle, OFDM unit 2013 is sent to receiver unit 2002 with output, and 2002 pairs of signals of this receiver unit carry out demodulate/decode, to obtain data 2014.Described channel estimating unit 2004 is sent to DIDO feedback maker unit 2006 with channel estimating, and this DIDO feedback maker unit 2006 can quantize channel estimating, and via FEEDBACK CONTROL channel 1912 it is beamed back transmitter.

Described DIDO configurator 1910 can use the information that obtains at base station place, or in a preferred embodiment, the extra DIDO feedback maker 2006(that works in each subscriber equipment place that uses is referring to Figure 20) output.The channel conditions 2004 that these DIDO feedback maker 2006 usefulness are estimated and/or other parameters that are similar to estimated SNR at receiver place generate the feedback message that will be input to DIDO configurator 1910.Described DIDO feedback maker 2006 can be at the receiver place compresses, quantizes information and/or use Limited Feedback strategies more known in the field.

Described DIDO configurator 1910 can use the information of recovering from DIDO FEEDBACK CONTROL channel 1912.DIDO FEEDBACK CONTROL channel is the logic OR physical control channel, and the output that this channel can be used for DIDO is fed back maker 2006 is sent to the base station from the user.Control channel 1912 can be implemented in the mode known in the field of any amount, and can be the logic OR physical control channel.As physical channel, it can comprise the dedicated time slot that is assigned to the user/frequency gap.Its RACH that all users share of also can serving as reasons.Described control channel can be by pre-assigned, or can be created by the bit (stealing bits) of occupying of predetermined way in the existing control channel.

In the following discussion, will in true communication environments, describe by utilizing the DIDO-OFDM prototype to measure the result who obtains.These results have shown the realizability of potential gain in the self adaptation DIDO system.The performance that at first represents different stage DIDO system shows to increase antenna/user quantity, to realize larger downlink throughput.Afterwards, describe the DIDO performance relevant with the position of subscriber equipment, show the channel status that the needs tracking changes.At last, the performance of the DIDO system that adopts diversity technique is described.

The performance of ⅰ, different stage DIDO system

Utilize increasing transmitting antenna (N=M, wherein M is number of users) to estimate the performance of different DIDO system.The performance of following system is compared: SISO, DIDO 2 * 2, DIDO 4 * 4, DIDO 6 * 6 and DIDO 8 * 8.DIDO N * M refers to have at the BS place N transmitting antenna and M user's DIDO.

Figure 22 has shown the transmit/receive antenna layout.Configure to arrange transmitting antenna 2201 with square array, and the user is positioned at around the emission array.At Figure 22, T refers to " emission " antenna, and U refers to " subscriber equipment " 2202.

Different antennae subset in 8 yuan of emission arrays is in active state, and this depends on for the selected N value of different measuring.For each DIDO rank (N), selection can to the fixed size of 8 element array constraint institute for the antenna subset that covers of maximum truly area.This standard is supposed to strengthen the space diversity of given N value.

Figure 23 shows for different other array configurations of DIDO level that are fit to available true area (that is, dotted line).Square empty frame has 24 " * 24 " size, corresponding to the 450MHz carrier frequency ~ λ * λ.

Based on the commentary relevant with Figure 23 and with reference to Figure 22, now will define and following system in the performance of each system:

SISO(2301 with T1 and U1)

Have T1,2 and U1,2 DIDO 2 * 2(2302)

Have T1,2,3,4 and U1,2,3,4 DIDO 4 * 4(2303)

Have T1,2,3,4,5,6 and U1,2,3,4,5,6 DIDO 6 * 6(2304)

Have T1,2,3,4,5,6,7,8 and U1,2,3,4,5,6,7,8 DIDO 8 * 8(2305)

Figure 24 shows in 4-QAM and 1/2FEC(forward error correction) in the rate situation, SER, BER, SE(spectrum efficiency in the above-mentioned DIDO system) and the functional relation of goodput performance and emission (TX) power.Observation draws, and SER and BER performance can descend because the N value increases.This impact is caused by following two phenomenons: for fixing TX power, the input power of DIDO array can be divided between increasing user's (or data flow); Space diversity can reduce along with the increase of the number of users in the actual DIDO channel.

As shown in figure 24, in order to compare the relative performance of different stage DIDO system, target BER is fixed as 10 ^-4(this value can change according to system), this is worth roughly corresponding to SER=10 ^-2We will be referred to as corresponding to the TX performance number of this target TX power threshold (TPT).For any N, if TX power is lower than TPT, we suppose and can not send under the DIDO level n, and we need to switch to other DIDO of even lower level.In addition, at Figure 24, observable draws, and when TX power surpassed TPT for any N value, SE and goodput performance can reach capacity.According to these results, the self adaptation sending strategy can be designed between different stage DIDO, switch, to strengthen for fixedly SE or the goodput of the predeterminated target error rate.

Performance under ⅱ, the user variable situation

The target of this test is, via carry out emulation in the space correlation channel, estimates the DIDO performance of different user position.DIDO 2 * 2 systems are regarded as having 4QAM and 1/2FEC leads.As shown in figure 25, user 1 is positioned at the side of emission array and penetrates (broadside) direction, and user 2 position is penetrated direction from side and become end-fire (endfire) direction.Transmitting antenna interval-λ/2, and-2.5 λ of being separated by with the user.

Figure 26 shows the diverse location for subscriber equipment 2, SER and every user's SE result.Penetrate orientation measurement from the limit of emission array, the arrival angle (AOA) of subscriber equipment is 0 ° to 90 °.Observation draws, and along with the angular distance increase of subscriber equipment, the DIDO performance will promote, because the DIDO channel memory is in larger diversity.In addition, at target SER=10 ^-2There is the gap of 10dB in the place between AOA2=0 ° and the AOA2=90 ° of both of these case.Among this result and Figure 35 for 10 ° of angle spread to obtain simulation result consistent.In addition, note, for AOA1=AOA2=0 ° situation, may have coupling effect (adjoining institute causes because of their antenna) between two users, these may be so that their performance be different from the simulation result among Figure 35.

ⅲ, for the preferred situation of DIDO 8 * 8

Figure 24 has shown that DIDO 8 * 8 produces the SE larger than even lower level DIDO, but has higher TX power demand.The target of this analysis is to illustrate this situation that exists, and namely DIDO 8 * 8 but also aspect TX power demand (or TPT), surpasses DIDO2 * 2, to realize described peak value SE not only aspect peaks spectrum efficient (SE).

Note, desirable at i.i.d.() in the channel, the gap of TX power existence ~ 6dB between the SE of DIDO 8 * 8 and DIDO 2 * 2.This gap causes because of this fact, and namely DIDO 8 * 8 is cut apart TX power between 8 data flow, and DIDO 2 * 2 is only cut apart between two stream.This result is illustrated via the emulation among Figure 32.

Yet in the space correlation channel, TPT is the function of communication environments characteristic (for example, array is towards, customer location, angle spread).For example, Figure 35 show for the low angle between two different user devices positions expansion ~ the 15dB gap.Showed similar result among the application Figure 26.

Be similar to mimo system, when the user was positioned at the end-on direction of TX array, the performance of DIDO system can descend (causing because lacking diversity).This impact can draw by utilizing current DIDO prototype to measure to observe.Therefore, a kind of DIDO of illustrating 8 * 8 surpasses the mode of DIDO 2 * 2 for the user being placed the end-on direction with respect to DIDO 2 * 2 arrays.In this situation, DIDO 8 * 8 has surpassed DIDO 2 * 2, because the 8-aerial array provides higher diversity.

In this is analyzed, considered following system:

The every time slot of DIDO 8 * 8(of system 1:4-QAM sends 8 parallel data streams);

Per 4 time slots of DIDO 2 * 2(of system 2:64-QAM once send sending user X and Y).For this system, we consider four kinds of combinations of TX and RX aerial position: a) T1, T2U1,2(end-on direction); B) T3, T4U3,4(end-on direction); C) T5, T6U5,6(and end-on direction be separated by ~ and 30 °); D) T7, T8U7,8(NLOS(ignore distance));

The DIDO 8 * 8 of system 3:64-QAM; And

Per 8 time slots of MISO 8 * 1(of system 4:64-QAM once send sending user X).

For all these situations, use 3/4 FEC to lead.

Figure 27 has illustrated user's position.

In Figure 28, SER result shows because the gap (similar to the simulation result in Figure 35) of a ~ 15dB between the 2a of system and 2c of different array directions and customer location.The first subgraph in the second row shows the value (that is, corresponding to BER 1e-4) of the saturated TX power of SE curve.We observe system 1 than system 2 for lower TX power demand (less than ~ 5dB) produced each larger user SE.And, because the spatial multiplexing gain of DIDO 8 * 8 on DIDO 2 * 2, DIDO8 * 8 than the benefit of DIDO 2 * 2 for the DL(down link) more obvious SE and the DL goodput.Because the array gain (that is, having the MRC of MISO 8 * 1) of beam forming, system 4 has lower TX power demand (less than 8dB) than system 1.But system 4 only produced than system 1 each user SE 1/3.System 2 is than the poor performance (that is, having produced lower SE for larger TX power demand) of system 1.At last, system 3 than system 1 for larger TX power demand (~ 15dB) produced much bigger SE(because the modulation of larger exponent number (larger order)).

According to these results, can infer to draw a conclusion:

A kind of channel conditions is confirmed to be DIDO 8 * 8 and has namely produced larger SE for lower TX power demand better than DIDO 2 * 2();

In this channel conditions, DIDO 8 * 8 has produced each larger user SE and DL SE than DIDO 2 * 2 and MISO 8 * 1; And

Can by take larger TX power demand (greater than ~ 15dB) use high order modulation (be 64-QAM, rather than 4-QAM) as cost and further increase the performance of DIDO 8 * 8.

Iv. the DIDO that has day line options

Below, we are evaluated at the benefit in the Antenna Selection Algorithem of describing on the Signal Processing that is received by the IEEE journal in " the Transmit selection diversityfor unitary precoded multiuser spatial multiplexing systems with linear receivers " that delivered by R.Chen, R.W.Heath and J.G.Andrews in 2005.We lead to present result for a specific DIDO system with the FEC of two users, 4-QAM and 1/2.Following system is compared in Figure 27:

Have T1,2 and U1,2 DIDO 2 * 2; And

Have T1,2,3 and U1, the DIDO 3 * 2 of 2 use sky line options.

Identical among position of transmitting antenna and user device location and Figure 27.

Figure 29 shows the DIDO 3 * 2 with day line options and compares with DIDO 2 * 2 systems (not having selection) and can provide ~ gain of 5dB.Notice that channel almost is static (namely not having Doppler effect), so selection algorithm is applicable to path loss and channel space-related, rather than fast decay.We should see different gains in having much higher general situation of strangling effect.And, in this particular experiment, observe Antenna Selection Algorithem and

select antenna

2 and 3 to be used for sending.

Iv. the SNR threshold value that is used for LUT

Selecting [0171], we have stated that model selection realizes by LUT.LUT can come by precomputation to realize being used for the specific predefined target error rate performance of DIDO sending mode in different communication environments by assessment SNR threshold value.Below, we provide the performance that has and do not have the DIDO system of day line options and transformable number of users, and described performance can be as the guidance of structure LUT.Although Figure 24, Figure 26, Figure 28, Figure 29 are by obtaining with the actual measurement of DIDO prototype, following figure obtains by emulation.Following BER result's hypothesis does not have FEC.

Figure 30 shows the average BER performance of DIDO pre-coding schemes different in the independent same distribution channel.The curve that indicates " not having to select " refers to use the situation of BD.In same figure, the performance of day line options (ASel) is illustrated for the additional antenna (for the user of varying number) of varying number.Can find out, along with the quantity growth of additional antenna, ASel provides better diversity gain (take the BER slope of a curve in high SNR district as feature), has produced better covering.For example, if we are fixed to 10 with target BER ^-2(for the actual value of uncoded system) then gained along with the quantity growth of antenna by the SNR that ASel provides.

Figure 31 shows the SNR gain for the ASel of the function of the quantity of the extra transmitting antenna of conduct in the independent same distribution channel of different target BER.Can find out, only by adding 1 or 2 antenna, ASel compares with BD and has produced huge SNR gain.In following part, we will be only for the situation of 1 or 2 additional antenna by target BER is fixed to 10-2(for uncoded system) assess the performance of ASel.

Figure 32 shows the SNR threshold value as the function of number of users (M) for the BD that has 1 and 2 additional antenna in the independent same distribution channel and ASel.We observe because for the user's of larger amt larger reception SNR demand, the SNR threshold value is along with M increases.Note, we suppose to be fixing total transmitting power (with the transmitting antenna of varying number) for the user of any amount.In addition, Figure 32 shows because the gain of day line options is constant for the user of any amount in the independent same distribution channel.

Below, we show the performance of the DIDO system in spatial correlation channel.We are by each user's of COST-259 spatial Channel Model emulation of describing in " Channel models for link and system level simulations " that IEEE 802.16Broadband Wireless Access Working Group delivers in September, 2004 at X.Zhuang, F.W.Vook, K.L.Baum, T.A.Thomas and M.Cudak channel.We generate the single group who is used for each user.As a kind of case study, we have supposed the NLOS channel, at transmitter uniform linear array (ULA) are arranged, and element spacing is 0.5 λ.For the situation of 2 custom systems, we come emulation group with the AOA1 that arrives and the average angle of AOA2 respectively for the first and second users.AOA is with respect to the side surface direction of ULA and measured.As the user who has in system more than two, we generate has at scope [φ _m, φ _m] in user's the group of evenly spaced average A OA, wherein our definition

Φ_{M} = \frac{Δφ (M - 1)}{2} - - - (13)

K is user's quantity, and △ φ is the angular distance between user's the average A OA.Note angular range [φ _m, φ _m] center is 0 °, penetrates direction corresponding to the side of ULA.Below, we with BD and ASel delivery plan and different numbers of users study as channel angle distribute (AS) and the user between the BER performance of DIDO system of function of angular distance.

Figure 33 shows the BER with respect to each user's average SNR be used to two users with different AS values that are positioned at same angle direction (namely penetrating direction with respect to the side of ULA, AOA1=AOA2=0 °).Can find out, along with AS increases, BER performance improvement and near the independent same distribution situation.In fact, higher AS has produced less covering between two users' feature mode and the better performance of BD precoder in statistics.

Figure 34 shows the result similar to Figure 33, but has higher angular distance between the user.We consider AOA1=0 °, AOA2=90 ° (i.e. 90 ° of angular distances).In the situation of low AS, realized best performance.In fact, for the situation of high angular distance, when angular distance is low, less crossover is arranged between user's feature mode.What is interesting is, we observe for the identical reason of just having mentioned, and the BER performance in low AS is better than the independent same distribution channel.

Next, for 10 in the different relevant situation ^-2Target BER, we calculate the SNR threshold value.Figure 35 has drawn the SNR threshold value as the function of AS for the different value of user's average A OA.For low user's angular distance, the reliable transmission with rational SNR demand (being 18dB) is possible for the channel take high AS as feature only.On the other hand, when the user spatially separates, need less SNR to satisfy identical target BER.

Figure 36 shows the SNR threshold value for 5 users' situation.Generate user's average A OA of the value with different angular distance △ φ according to the definition in (13).We observe for △ φ=0 ° and AS＜15 °, because the little angular distance between the user, the BD poor performance does not satisfy target BER.For the AS that increases, the SNR demand that satisfies fixing target BER reduces.On the other hand, for △ φ=30 °, obtain minimum SNR demand at low AS, consistent with result among Figure 35.Along with AS increases, the SNR threshold value is saturated in the independent same distribution channel.Note having 5 users' △ φ=30 ° of AOA scopes corresponding to [60 °, 60 °], this is typical for the base station in the cellular system with 120 ° of sector elements.

Next, we have studied the performance of the ASel delivery plan in spatial correlation channel.Figure 37 has compared the SNR threshold value for the BD with 1 and 2 additional antenna and the ASel of two user situations.We have considered two kinds of different situations of the angular distance between the user: { AOA1=0 °, AOA2=0 ° } and { AOA1=0 °, AOA2=90 ° }.Be used for the curve of BD scheme (namely not having a day line options) with identical at Figure 35.We observe the 10dB of SNR gain ASel has produced respectively 8dB with 1 and 2 additional antenna and to(for) high AS.Along with AS reduces, on the BD since the gain of ASel because the quantity minimizing of the degree of freedom in the MIMO broadcast channel becomes less.What is interesting is, for AS=0 ° (namely close to the LOS channel) and situation { AOA1=0 °, AOA2=90 ° }, ASel does not provide because any gain of the difference in spatial domain.Figure 38 shows the result similar to Figure 37, but for 5 users' situation.

We have calculated as the SNR threshold value of the function of the number of users (M) in system for BD and ASel delivery plan and (have supposed 10 ^-2General objectives BER).The SNR threshold value is corresponding to average SNR, so that total transmitting power is constant for any M.We suppose at azimuth coverage [φ _m, φ _m]=[-60 °, 60 °] in largest interval between the average A OA of each customer group.Then, the angular distance between the user is △ φ=120 °/(M-1).

Figure 39 shows the SNR threshold value for the BD scheme with different AS values.We observe owing to the large angular distance between the user, and AS=0.1 ° (i.e. low angular spread) for the user with less quantity (being K≤20) obtains minimum SNR demand.Yet, for M〉and 50, because △ φ is very little and BD can not carry out, the SNR demand is far longer than 40dB.In addition, for AS〉10 °, the SNR threshold value almost keeps constant for any M, and the DIDO system in spatial correlation channel is near the performance of independent same distribution channel.

For the value that reduces the SNR threshold value and the performance of improving the DIDO system, we use the ASel delivery plan.Figure 40 shows the SNR threshold value in having AS=0.1 ° spatial correlation channel for the BD with 1 and 2 additional antenna and ASel.For reference, we have also reported the curve that is used for independent same distribution situation shown in Figure 32.Can see, for less user (being M≤10), owing to lacking diversity in the DIDO broadcast channel, a day line options does not help to reduce the SNR demand.Along with number of users increases, ASel is benefited from multi-user diversity, has produced SNR gain (being 4dB for M=20 namely).In addition, for M≤20, the performance of the ASel with 1 or 2 additional antenna in high spatial correlation channel is identical.

Then we calculate the SNR threshold value for two kinds of other channel conditions: among the AS=5 among Figure 41 ° and Figure 42 AS=10 °.Figure 41 compares with Figure 40, shows owing to larger angular spread, and ASel has produced and also has been used for the relatively user's of small number (being M≤10) SNR gain.As reporting in Figure 42, for AS=10 °, the SNR threshold value further reduces, because the gain of ASel becomes higher.

At last, we have summed up the result who proposes for correlated channels at present.Figure 43 and Figure 44 show the conduct that has respectively 1 and 2 additional antenna for the SNR threshold value of the function of the number of users (M) of BD and ASel scheme and angular spread (AS).Note, AS=30 ° situation is in fact corresponding to the independent same distribution channel, and we use this value of AS to be used for diagrammatic representation in the drawings.We observe, although BD is affected by channel space-related, ASel has produced the almost identical performance for any AS.In addition, for AS=0.1 °, because multi-user diversity, ASel is similar to the BD performance for low M, and is M 〉=20 for large M() above BD.

Figure 49 has compared the performance of DIDO schemes different aspect the SNR threshold value.The DIDO scheme of considering is: BD, ASel, the BD with feature mode selection (BD-ESel) and high specific merge (MRC).Notice that MRC does not eliminate the interference (unlike other method) at the transmitter place in advance, but in the situation that the user is separated the gain that provides larger by the space.In Figure 49, we have drawn when two users lay respectively at the side of emission array and have penetrated direction when becoming-30 ° and 30 °, for DIDO N * 2 systems for target BER=10 ^-2The SNR threshold value.We observe, and for low AS, the MRC scheme is compared the gain that 3dB is provided with other scheme, because user's space channel is separated well, the impact of the interference between the user is very little.Note, the gain of the MRC on DIDO N * 2 is because array gain.For greater than 20 ° AS, the QR-ASel scheme surpasses other scheme and compares the gain that has produced about 10dB with the selectable BD 2 * 2 of tool not.QR-ASel and BD-ESel provide about identical performance for the arbitrary value of AS.

Above-described is new self adaptation transmission technology for the DIDO system.The method dynamic translation between the DIDO sending mode strengthens throughput for fixing target error rate to different users.The performance of the DIDO system of different stage is measured under different propagation conditions, and the huge gain of observing in throughput can realize as DIDO pattern and the number of users of the function of propagation condition by Dynamic Selection.

III. the precompensation of frequency and phase difference

A. background

As described above, wireless communication system comes transmission information with carrier wave.These carrier waves are normally sinusoidal wave, and its amplitude and/or phase response are in the information that is sent out and modulated.Sinusoidal wave nominal frequency is known as carrier frequency.In order to create this waveform, transmitter synthesizes one or two sine wave, and creates the signal after the modulation that overlaps on the sine wave with designated carrier frequency with up-conversion.This can realize by direct conversion, and wherein, signal is directly modulated on carrier wave or by a plurality of up-conversion stage.In order to process this waveform, receiver must the received RF signal of demodulation, and effectively removes modulated carrier.This needs the synthetic one or more sinusoidal signals of receiver to be reversed in the modulated process at transmitter place, is known as the frequency reducing conversion.Regrettably, the sine wave signal that generates at transmitter and receiver obtains from different reference oscillators.There is not reference oscillator to create the frequency reference of perfect (perfect); In fact, usually and actual frequency some deviations are arranged.

In wireless communication system, created the phenomenon that is known as carrier frequency shift or simple frequency shift (FS) at the receiver place in the difference of the output of the reference oscillator at transmitter and receiver place.In essence, after the frequency reducing conversion, some residue modulation (corresponding to the difference in the sending and receiving carrier wave) are arranged in the signal that receives.The distortion that this has created in the signal that receives has caused higher bit error rate and lower throughput.

Existence is for the treatment of the different technologies of carrier frequency shift.Most methods is estimated the carrier frequency shift at the receiver place, then uses the offset correction of carrier frequency algorithm.It is blindness (blind) that the Carrier frequency offset estimation algorithm uses following methods: offset-QAM (T.Fusco and M.Tanda, " BlindFrequency-offset Estimation for OFDM/OQAM Systems; " Signal Processing, IEEE Transactions on[is also referring to Acoustics, Speech, and Signal Processing, IEEETransactions on], vol.55, pp.1828-1838,2007); Cyclophysis (E.Serpedin, A.Chevreuil, G.B.Giannakis and P.Loubaton, " Blind channel and carrier frequencyoffset estimation using periodic modulation precoders; " Signal Processing, IEEETransactions on[be also referring to Acoustics, Speech, and Signal Processing, IEEETransactions on], vol.48, no.8, pp.2389-2405, Aug.2000); Perhaps Cyclic Prefix (the J.J.van de Beek in OFDM (OFDM) structural approach, M.Sandell and P.O.Borjesson, " ML estimation of time and frequency offset in OFDM systems, " Signal Processing, IEEE Transactions on[is also referring to Acoustics, Speech, and SignalProcessing, IEEE Transactions on], vol.45, no.7, pp.1800-1805, July 1997; U.Tureli, H.Liu and M.D.Zoltowski, " OFDM blind carrier offset estimation:ESPRIT, " IEEE Trans.Commun., vol.48, no.9, pp.1459-1461, Sept.2000; M.Luise, M.Marselli and R.Reggiannini, " Low-complexity blind carrier frequencyrecovery for OFDM signals over frequency-selective radio channels; " IEEE Trans.Commun., vol.50, no.7, pp.1182-1188, July 2002).

Replacedly, special-purpose training signal can be utilized, data symbol (the P.H.Moose that comprises repetition, " A technique for orthogonal frequency division multiplexing frequency offsetcorrection; " IEEE Trans.Commun., vol.42, no.10, pp.2908-2914, Oct.1994); Two different symbols (T.M.Schmidl and D.C.Cox, " Robust frequency and timingsynchronization for OFDM, " IEEE Trans.Commun., vol.45, no.12, pp.1613-1621, Dec.1997); Known symbol sebolic addressing (M.Luise and R.Reggiannini, " the Carrier frequency acquisition and tracking for OFDM systems that perhaps periodically inserts, " IEEE Trans.Commun., vol.44, no.11, pp.1590-1598, Nov.1996).Correction can occur in the analog or digital mode.Receiver can also be offset to eliminate with the signal that Carrier frequency offset estimation comes precorrection to send.Because multicarrier and ofdm system are to the sensitivity of frequency shift (FS), offset correction of carrier frequency is extensively studied (J.J.van de Beek for multicarrier and ofdm system, M.Sandell and P.O.Borjesson, " ML estimation of time and frequency offset inOFDM systems; " Signal Processing, IEEE Transactions on[is also referring to Acoustics, Speech, and Signal Processing, IEEE Transactions on], vol.45, no.7, pp.1800-1805, July 1997; U.Tureli, H.Liu and M.D.Zoltowski, " OFDM blindcarrier offset estimation:ESPRIT, " IEEE Trans.Commun., vol.48, no.9, pp.1459-1461, Sept.2000; T.M.Schmidl and D.C.Cox, " Robust frequency andtiming synchronization for OFDM, " IEEE Trans.Commun., vol.45, no.12, pp.1613-1621, Dec.1997; M.Luise, M.Marselli and R.Reggiannini, " Low-complexity blind carrier frequency recovery for OFDM signals overfrequency-selective radio channels; " IEEE Trans.Commun., vol.50, no.7, pp.1182-1 188, July 2002).

Frequency offset estimation and proofread and correct for multiple antenna communication or MIMO(multiple-input and multiple-output more generally) system is important problem.In mimo system, transmitting antenna is locked into a frequency reference, and receiver is locked into another frequency reference, and single skew is arranged between transmitter and receiver.Having proposed several algorithms uses training signal to process this problem (K.Lee and J.Chun, " Frequency-offset estimation for MIMO and OFDM systems using orthogonaltraining sequences; " IEEE Trans.Veh.Technol., vol.56, no.1, pp.146-156, Jan.2007; M.Ghogho and A.Swami, " Training design for multipath channel andfrequency offset estimation in MIMO systems; " Signal Processing, IEEETransactions on[be also referring to Acoustics, Speech, and Signal Processing, IEEETransactions on], vol.54, no.10, pp.3957-3965, Oct.2006; And adaptivetracking C.Oberli and B.Daneshrad, " Maximum likelihood tracking algorithms forMIMOOFDM; " in Communications, 2004IEEE International Conference on, vol.4, June 20-24,2004, pp.2468-2472).Run into prior problem in mimo system, wherein, transmitting antenna is not locked into same frequency reference, but reception antenna is locked into together.In fact this occur in the up link of space division multiple access access (SDMA) system, and the SDMA system is regarded as mimo system, and wherein different user is corresponding to different transmitting antennas.In this case, the compensation of frequency shift (FS) is more complicated.Particularly, frequency shift (FS) has created the interference in the different MIMO that is sent out stream.Can be with estimating uniting of complexity and equalization algorithm is proofreaied and correct (A.Kannan, T.P.Krauss and M.D.Zoltowski, " Separation of cochannel signals under imperfecttiming and carrier synchronization; " IEEE Trans.Veh.Technol., vol.50, no.1, pp.79-96, Jan.2001), and the equilibrium after Frequency offset estimation (T.Tang and R.W.Heath, " Joint frequency offset estimation and interference cancellation forMIMO-OFDM systems[mobile radio], " 2004.VTC2004-Fall.2004IEEE 60 ^ThVehicular Technology Conference, vol.3, pp.1553-1557, Sept.26-29,2004; X.Dai, " Carrier frequency offset estimation for OFDM/SDMA systems usingconsecutive pilots, " IEEE Proceedings-Communications, vol.152, pp.624-632, Oct.7,2005).A few thing has been processed the relevant issues of excess phase shift and tracking error, wherein excess phase shift is estimated after Frequency offset estimation and is compensated, but up link (the L Haring of SDMAOFDMA system has only been considered in this work, S.Bieder and A.Czylwik, " Residual carrierand sampling frequency synchronization in multiuser OFDM systems; " 2006.VTC 2006-Spring.IEEE 63rd Vehicular Technology Conference, vol.4, pp.1937-1941,2006).When all transmitted and received antenna and have different frequency references, the most serious situation occured in mimo system.Asymptotic analysis (O.Besson and the P.Stoica of the evaluated error in the flat fading channel have only been processed about the only available work of this topic, " On parameterestimation of MIMO flat-fading channels with frequency offsets; " SignalProcessing, IEEE Transactions on[is also referring to Acoustics, Speech, and SignalProcessing, IEEE Transactions on], vol.51, no.3, pp.602-613, Mar.2003).

When the different transmit antennas of mimo system does not have identical frequency reference, and reception antenna is independently during processing signals, and situation about having been furtherd investigate occurs.This occurs in to be known as in distributed input and output (DIDO) communication system (being also referred to as in the literature the MIMO broadcast channel) and occurs.The DIDO system comprises an access point with spaced antenna, described antenna sends data streams in parallel (via precoding) strengthens down link to a plurality of users throughput, uses this moment identical Radio Resource (being identical time slot duration and frequency band) as conventional SISO system.The DIDO system is described in detail in S.G.Perlman and T.Cotter, proposes in the U.S. Patent application 20060023803 that is entitled as " System and method fordistributed input-distributed output wireless communications " of submitting in July, 2004.The mode that many enforcement DIDO precoders are arranged.A solution is block diagonalization (BD), in for example with Publication about Document, describe: Q.H.Spencer, A.L.Swindlehurst and M.Haardt, " Zero-forcing methods for downlink spatial multiplexing inmultiuser MIMO channels; " IEEE Trans.Sig.Proc, vol.52, pp.461-471, Feb.2004; K.K.Wong, R.D.Murch and K.B.Letaief, " A joint-channeldiagonalization for multiuser MIMO antenna systems, " IEEE Trans.WirelessComm., vol.2, pp.773-786, JuI 2003; L.U.Choi and R.D.Murch, " A transmitpreprocessing technique for multiuser MIMO systems using a decompositionapproach, " IEEE Trans.Wireless Comm., vol.3, pp.20-24, Jan 2004; Z.Shen, J.G.Andrews, R.W.Heath and B.L Evans, " Low complexity user selectionalgorithms for multiuser MIMO systems with block diagonalization; " be accepted and be published in IEEE Trans.Sig.Proc, Sep.2005; Z.Shen, R.Chen, J.G.Andrews, R.W.Heath and B.L Evans, " Sum capacity of multiuser MIMO broadcast channels withblock diagonalization " is submitted to IEEE Trans.Wireless Comm., Oct.2005; R.Chen, R.W.Heath and J.G.Andrews, " Transmit selection diversity for unitaryprecoded multiuser spatial multiplexing systems with linear receivers; " be accepted the Trans to IEEE, on Signal Processing, 2005.

In the DIDO system, the transmission precoding is used to separate the data flow for different user.When the transmitting antenna rf chain was not shared same frequency reference, carrier frequency shift had caused the several problems relevant with System Implementation.When this occured, each antenna effectively sent with slightly different carrier frequency.The integrality that this has destroyed the DIDO precoder causes each user to suffer extra interference.The below proposes is several solutions to this problem.In an execution mode of solution, the DIDO transmitting antenna is shared a frequency reference by wired, optics or wireless network.In another execution mode of solution, one or more user's estimated frequency offset differences (antenna between skew in relative different) and this information is sent it back transmitter.Then transmitter precorrection frequency shift (FS) and proceed to estimate phase place for the training of DIDO and precoder.This execution mode exists at feedback channel problem when postponing.Reason is that the residual phase error that is created by trimming process possible be arranged, and this trimming process is not considered channel estimating subsequently.In order to address this problem, an other execution mode uses new frequency shift (FS) and phase estimating device, has solved this problem by estimated delay.Provide the result based on emulation with by the actual measurement that the DIDO-OFDM prototype is carried out.

The frequency that proposes in this document and phase deviation compensation method may be to because the evaluated error of the noise at receiver place be relatively sensitiveer.Therefore, another execution mode has proposed to be used for the method that the time and frequency shift is estimated, and is also very strong under low SNR condition.

The different methods that is used for time of implementation and Frequency offset estimation is arranged.Because its sensitivity to synchronous error, the many methods in these methods propose for the OFDM waveform specially.

These algorithms typically do not use the structure of OFDM waveform, generally are enough for single carrier wave and multicarrier waveform therefore.The algorithm that the following describes use known fiducial mark (for example, training data) with the class of assisting synchronous technology among.Many methods are that the expansion of the frequency offset estimator of Moose (is seen P.H.Moose, " A technique for orthogonal frequency divisionmultiplexing frequency offset correction; " IEEE Trans.Commun., vol.42, no.10, pp.2908-2914, Oct.1994).Moose has proposed with the training signal of two repetitions and has used the phase difference between received signal to obtain frequency shift (FS).The method of Moose only can be proofreaied and correct mark (fractional) frequency shift (FS).The expansion of the method for Moose proposes (T.M.Schmidl and D.C.Cox, " Robust frequency and timing synchronization forOFDM, " IEEE Trans.Commun. by Schmidl and Cox, vol.45, no.12, pp.1613-1621, Dec.1997).Their main innovation is to use the OFDM symbol of one-period and the training symbol of other differential coding.The integer offset correction that differential coding in second symbol is realized.Coulson has considered at T.M.Schmidl and D.C.Cox, " Robust frequency and timing synchronization forOFDM; " IEEE Trans.Commun., vol.45, no.12, pp.1613-1621, the similar setting of describing among the Dec.1997, and at A.J.Coulson, " Maximum likelihood synchronization forOFDM using a pilot symbol:analysis; " IEEE J.Select.Areas Commun., vol.19, no.12, pp.2495-2503, Dec.2001 and A.J.Coulson, " Maximum likelihoodsynchronization for OFDM using a pilot symbol:algorithms, " IEEE J.Select.Areas Commun., vol.19, no.12, pp.2486-2494 provides the detailed discussion of algorithm and analysis among the Dec.2001.A main difference is the correlation properties that Coulson has used the maximal-length sequence of repetition to provide.He also advises using linear frequency modulation (chirp) signal, because its constant envelope properties in time domain and frequency domain.Coulson has considered actual details but has not comprised the integer estimation.The training signal of a plurality of repetitions is by Minn et.al.in H.Minn, V.K.Bhargava and K.B.Letaief, " A robust timing and frequency synchronization for OFDM systems; " IEEETrans.Wireless Commun., vol.2, no.4, pp.822-839, July 2003 considers, but the structure of training does not have optimised.Shi and Serpedin have proposed some optimalitys (K.Shi and E.Serpedin that training structure has the idea that forms frame synchronization, " Coarse frame and carriersynchronization of OFDM systems:a new metric and comparison; " IEEE Trans.Wireless Commun., vol.3, no.4, pp.1271-1284, July 2004).An embodiment of the invention have used the method for Shi and Serpedin to carry out frame synchronization and fractional frequency bias estimation.

Many methods in the literature concentrate on frame synchronization and the fractional frequency offset correction.The integer offset correction uses at T.M.Schmidl and D.C.Cox, " Robust frequency and timingsynchronization for OFDM, " IEEE Trans.Commun., vol.45, no.12, pp.1613-1621, the other training symbol among the Dec.1997 is solved.For example, Morrelli etc. are at M.Morelli, A.N.D'Andrea and U.Mengali, " Frequency ambiguity resolution inOFDM systems, " IEEE Commun.Lett., vol.4, no.4, pp.134-136 has obtained T.M.Schmidl and D.C.Cox among the Apr.2000, " Robust frequency and timingsynchronization for OFDM; " IEEE Trans.Commun., vol.45, no.12, pp.1613-1621, the improvement version of Dec.1997.Use the interchangeable method of different preamble structures to propose (M.Morelli and U.Mengali by Morelli and Mengali, " An improvedfrequency offset estimator for OFDM applications; " IEEE Commun.Lett., vol.3, no.3, pp.75-77, Mar.1999).This method has used the correlation between M identical training symbol that repeats to increase by the M factor scope of fractional frequency offset estimator.This is best linear unbias estimator and has accepted maximum skew (having suitable design), but the timing synchronization that does not provide.

System is described

An embodiment of the invention are used based on the precoding of channel condition information and are eliminated frequency and phase deviation in the DIDO system.See Figure 11 and for the top associated description of the description of this execution mode.

In an embodiment of the invention, each user uses the receiver that is equipped with frequency offset estimator/compensator.Go out as shown in Figure 45, in an embodiment of the invention, the system that comprises receiver comprises a plurality of RF unit 4508, corresponding a plurality of A/D unit 4510, the receiver that is equipped with frequency offset estimator/compensator 4512 and DIDO feedback maker unit 4506.

RF unit 4508 receives the signal that sends from the DIDO transmitter unit, and signal down is transformed into base band, and the signal after the frequency reducing conversion is provided to A/D unit 4510.Then A/D unit 4510 is converted to numeral with signal from analog, and it is sent to frequency offset estimator/compensator units 4512.The skew of frequency offset estimator/compensator units 4512 estimated frequencies and compensating frequency deviation, as described here, the signal after then will compensating sends to OFDM unit 4513.OFDM unit 4513 removes Cyclic Prefix and moves fast Fourier transform (FFT) signal is reported to frequency domain.At training period, OFDM unit 4513 sends to channel estimating unit 4504 with output and calculates channel estimating in frequency domain.Replacedly, channel estimating can be calculated in time domain.During the data cycle, OFDM unit 4513 sends to DIDO receiver unit 4502 with output, and 4502 pairs of signals of this DIDO receiver unit carry out demodulate/decode to obtain data.Channel estimating unit 4504 sends to DIDO feedback maker unit 4506 with channel estimating, and this DIDO feedback maker unit 4506 can quantized channel be estimated and via the FEEDBACK CONTROL channel they sent it back transmitter, goes out as shown.

Description to an execution mode of the algorithm that is used for DIDO 2 * 2 situations

What the following describes is execution mode for the algorithm of the frequency/phase migration of DIDO system.The DIDO system model begins in the situation that have and do not have frequency/phase skew and be described.For easy, provide the particular implementation of DIDO 2 * 2 systems.Yet basic principle of the present invention can also be implemented in high-order DIDO system.

Has/do not have the DIDO system model of frequency and phase deviation

The received signal of DIDO 2 * 2 can be write as for first user:

r ₁[t]＝h ₁₁(w ₁₁x ₁[t]+w ₂₁x ₂[t])+h ₁₂(w ₁₂x ₁[t]+w ₂₂x ₂[t]) （1）

And write as for second user:

r ₂[t]＝h ₂₁(w ₁₁x ₁[t]+w ₂₁x ₂[t])+h ₂₂(w ₁₂x ₁[t]+w ₂₂x ₂[t]) （2）

Wherein t is the discrete time index, h _MnAnd w _MnRespectively channel and the DIDO precoding weight between m user and n transmitting antenna, x _mIt is the transmitted signal for user m.Note h _MnAnd w _MnBe not the function of t, the cycle between training and data transmission is constant because we suppose channel.

When frequency and phase deviation existed, the signal that receives was represented as

r_{1} [t] = e^{j (ω_{U 1} - ω_{T 1}) T_{s} (t - t_{11})} h_{11} (w_{11} x_{1} [t] + w_{21} x_{2} [t]) + e^{j^{(ω_{U 1} - ω_{T 2}) T_{s} ({t - t}_{12})}} h_{12} (w_{12} x_{1} [t] + w_{22} x_{2} [t]) - - - (3)

And

r_{2} [t] = e^{j (ω_{U 2} - ω_{T 1}) T_{s} (t - t_{21})} h_{21} (w_{11} x_{1} [t] + w_{21} x_{2} [t]) + e^{j^{(ω_{U 2} - ω_{T 2}) T_{s} ({t - t}_{22})}} h_{22} (w_{12} x_{1} [t] + w_{22} x_{2} [t]) - - - (4)

Wherein, T _sThe is-symbol cycle; For n transmitting antenna, ω _Tn=2 ∏ f _TnFor m user, ω _Um=2 ∏ f _UmAnd f _TnAnd f _UmIt is respectively the practical carrier frequency (by bias effect) for n transmitting antenna and m user.Value t _MnBe illustrated in channel h _MnOn cause the random delay of phase deviation.Figure 46 has drawn DIDO 2 * 2 system models.

For the time, we use to give a definition:

Δω _mn＝ω _Um-ω _Tn （5）

To be used for being illustrated in the frequency shift (FS) between m user and n the transmitting antenna.

The description of an embodiment of the invention

Method according to an embodiment of the invention is illustrated in Figure 47.The method comprises that following general step (comprises substep, as shown): the cycle of training 4701 that is used for Frequency offset estimation; The cycle of training 4702 that is used for channel estimating; Data via the balanced DIDO precoding of tool send 4703.These steps are described in detail in the following.

(a) be used for the cycle of training (4701) of Frequency offset estimation

During the first cycle of training, the base station will send to from one or more training signals of each transmitting antenna one (4701a) among the user.As described here, " user " is wireless client device.For the situation of DIDO 2 * 2, the signal that is received by m user is provided by following:

r_{m} [t] = e^{jΔ ω_{m 1} T_{s} (t - t_{m 1})} h_{m 1} p_{1} [t] + e^{jΔ ω_{m 2} T_{s} (t - t_{m 2})} h_{m 2} p_{2} [t] - - - (6)

Wherein, p ₁And p ₂It is respectively the training sequence that sends from the first and second antennas.

M user can use the frequency offset estimator convolution of training sequence (namely by) of any type and estimate shifted by delta ω _MlWith Δ ω _M2Then, according to these values, the user calculates two frequency shift (FS)s between the transmitting antenna:

Δω _T＝Δω _m2-Δω _m1＝ω _T1-ω _T2 （7）

At last, the value in (7) is fed back to base station (4701b).

Note the p in (6) ₁And p ₂Being designed to is quadrature, thereby the user can estimate Δ ω _MlWith Δ ω _M2Replacedly, in one embodiment, identical training sequence is used in two continuous time slots, and the user therefrom estimates skew.In addition, in order to improve the estimation of the skew in (7), above-described identical calculating can be done for all users (not only for m user) of DIDO system, and last estimation can be (after the weighting) mean value from the value of all users' acquisitions.Yet this solution needs more computing time and feedback quantity.At last, the renewal of Frequency offset estimation only just needs when the frequency shift (FS) temporal evolution.Therefore, according to the stability of the clock at transmitter place, the step 4701 of algorithm can be performed in long-term basis (namely sending for each data), so that above-mentioned feedback reduces.

(b) be used for the cycle of training (4702) of channel estimating

During the second cycle of training, the base station at first maybe must have the frequency shift (FS) feedback of the value (7) from m user or from a plurality of users.Value in (7) is used to precompensation in the frequency shift (FS) of transmitting terminal.Then, the base station sends to all users with training data and comes for channel estimating (4702a).

For DIDO 2 * 2 systems, the signal that receives at first user place is provided by following:

r_{1} [t] = e^{jΔ ω_{11} T_{s} (t - {\tilde{t}}_{11})} h_{11} p_{1} [t] + e^{jΔ ω_{12} T_{s} (t - {\tilde{t}}_{12})} h_{12} e^{- jΔ ω_{T} T_{s} t} p_{2} [t] - - - (8)

And second user place:

r_{2} [t] = e^{jΔ ω_{21} T_{s} (t - {\tilde{t}}_{21})} h_{21} p_{1} [t] + e^{jΔ ω_{22} T_{s} (t - {\tilde{t}}_{22})} h_{22} e^{- jΔ ω_{T} T_{s} t} p_{2} [t] - - - (9)

Wherein,

And Δ t is the random or known delay between first transmission and second of base station sends.In addition, p ₁And p ₂It is respectively the training sequence from the transmission of the first and second antennas of user's frequency shift (FS) and channel estimating.

Note, precompensation only is applied to the second antenna in this embodiment.

Launch (8), we obtain

r_{1} [t] = e^{jΔ ω_{11} T_{s} t} e^{{jθ}_{11}} [h_{11} p_{1} [t] + e^{j (θ_{12} - θ_{11})} h_{12} p_{2} [t]] - - - (10)

Similarly for the second user:

r_{2} [t] = e^{jΔ ω_{21} T_{s} t} e^{{jθ}_{21}} [h_{21} p_{1} [t] + e^{j (θ_{22} - θ_{21})} h_{22} p_{2} [t]] - - - (11)

Wherein,

θ_{mn} = - Δ ω_{mn} T_{s} {\tilde{t}}_{mn} .

At receiving terminal, the user is by using training sequence p ₁And p ₂Come compensating frequency offset residue.Then, the user estimates (4702b) by the trained vector channel:

h_{1} = [\begin{matrix} h_{11} \\ e^{j (θ_{12} - θ_{11})} h_{12} \end{matrix}]

h_{2} = [\begin{matrix} h_{21} \\ e^{j (θ_{22} - θ_{21})} h_{22} \end{matrix}] - - - (12)

These channels in (12) or channel condition information (CSI) are fed back to base station (4702b), calculate the DIDO precoder as described in base station such as the lower part.

(c) has the DIDO precoding (4703) of precompensation

The base station receives the channel condition information (CSI) (12) and calculates the weight (4703a) of precoding by block diagonalization (BD) from the user, so that

w_{1}^{T} h_{2} = 0,

w_{2}^{T} h_{1} = 0 - - - (13)

Wherein, vector h ₁In (12), be defined, and w _m=[w _M1, w _M2].Note, the present invention who proposes in the disclosure can be used in any other DIDO method for precoding except BD.The precompensation frequency shift (FS) is also come by the estimation in the use (7) in the base station, and by estimating delay (the Δ t between the second training transmission and the current transmission ₀) come precompensation phase deviation (4703a).At last, the base station sends to user (4703b) via the DIDO precoder with data.

After process of transmitting, the signal that receives at user 1 place is provided by following:

r_{1} [t] = e^{jΔ ω_{11} T_{s} (t - {\tilde{t}}_{11} - {Δt}_{o})} h_{11} [w_{11} x_{1} [t] + w_{21} x_{2} [t]]

= e^{jΔ ω_{12} T_{s} (t - {\tilde{t}}_{12} - Δ t_{o})} h_{12} e^{- jΔ ω_{T} T_{S} (t - {Δt}_{o})} [w_{12} x_{1} [t] + w_{22} x_{2} [t]]

= γ_{1} [t] [h_{11} (w_{11} x_{1} [t] + w_{21} x_{2} [t]) + e^{j (Δ ω_{11} t_{11} - Δ ω_{12} t_{12}) T_{s}} h_{12} (w_{12} x_{1} [t] + w_{22} x_{2} [t])]

= γ_{1} [t] [(h_{11} w_{11} + e^{j (θ_{12} - θ_{11})} h_{12} w_{12}) x_{1} [t] + (h_{11} w_{21} + e^{j (θ_{12} - θ_{11})} h_{12} w_{22}) x_{2} [t]] - - - (14)

Wherein,

Use attribute (13), we obtain

r_{1} [t] = γ_{1} [t] w_{1}^{T} h_{1} x_{1} [t] - - - (15)

Similarly, for user 2, we obtain:

r_{2} [t] = e^{jΔ ω_{21} T_{s} (t - {\tilde{t}}_{21} - {Δt}_{o})} h_{21} [w_{11} x_{1} [t] + w_{21} x_{2} [t]]

+ e^{jΔ ω_{22} T_{s} (t - {\tilde{t}}_{22} - Δ t_{o})} h_{22} e^{- jΔ ω_{T} T_{s} (t - {Δt}_{o})} [w_{12} x_{1} [t] + w_{22} x_{2} [t]] - - - (16)

Launch (16):

r_{2} [t] = γ_{2} [t] w_{2}^{T} h_{2} x_{2} [t] - - - (17)

Wherein,

γ_{2} [t] = e^{jΔ ω_{21} T_{s} (t - {\tilde{t}}_{21} - Δ t_{o})} .

At last, the user calculates frequency offset residue and channel estimating is come demodulated data stream x ₁[t] and x ₂[t] (4703c).

Be generalized to DIDO N * M

In this part, the technology of before describing is generalized to the DIDO system with N transmitting antenna and M user.

I. the cycle of training of user's Frequency offset estimation

During the first cycle of training, owing to being provided by following from the signal that is received by m user of the training sequence of N antenna transmission:

r_{m} [t] = Σ_{n = 1}^{N} e^{jΔ ω_{mn} T_{s} (t - t_{mn})} h_{mn} p_{n} [t] - - - (18)

Wherein, p _nIt is the training sequence that sends from n antenna.

Estimating shifted by delta ω _MnAfterwards,

M user calculates the frequency shift (FS) between first and n the transmitting antenna:

Δω _T，1n＝Δω _mn-Δω _m1＝ω _T1-ω _Tn （19）

At last, the value in (19) is fed back to the base station.

Ii. the cycle of training that is used for channel estimating

During the second cycle of training, at first feed back from m user or from the frequency shift (FS) that a plurality of users' acquisitions have the value (19) the base station.Value in (19) is used to precompensation in the frequency shift (FS) of transmitting terminal.Then, the base station sends to all users with training data and comes for channel estimating.

For DIDO N * M system, the signal that receives at m user place is provided by following:

r_{m} [t] = e^{jΔ ω_{m 1} T_{S} (t - {\tilde{t}}_{m 1})} h_{m 1} p_{1} [t] + Σ_{n = 2}^{N} e^{jΔ ω_{mn} T_{s} (t - {\tilde{t}}_{mn})} h_{mn} e^{- jΔ ω_{T, 1 n} T_{s} t} p_{n} [t]

= e^{jΔ ω_{m 1} T_{s} (t - {\tilde{t}}_{m 1})} [h_{m 1} p_{1} [t] + Σ_{n = 2}^{N} e^{j (θ_{mn} - θ_{m 1})} h_{mn} p_{n} [t]]

= e^{jΔ ω_{m 1} T_{s} (t - {\tilde{t}}_{m 1})} Σ_{n = 1}^{N} e^{j (θ_{mn} - θ_{m 1})} h_{mn} p_{n} [t] - - - (20)

Wherein,

And Δ t is the random or known delay between first and second of base station sends.In addition, P _nIt is the training sequence from n antenna transmission for frequency shift (FS) and channel estimating.

At receiver side, the user is by using training sequence P _nCome compensating frequency offset residue.Then, each user m estimates by the trained vector channel:

h_{m} = [\begin{matrix} h_{m 1} \\ e^{j (θ_{m 2} - θ_{m 1})} h_{m 2} \\ . \\ . \\ . \\ e^{j (θ_{mN} - θ_{m 1})} h_{mN} \end{matrix}] - - - (21)

And feeding back to the base station, the DIDO precoder is calculated in the base station as described in following part.

Iii. the DIDO precoding that has precompensation

The base station receives the channel condition information (CSI) (12) and calculates the weight of precoding by block diagonalization (BD) from the user, so that

w_{m}^{T} h_{l} = 0, &ForAll; m &NotEqual; l, m = 1, . . ., M - - - (22)

Wherein, vector h _mIn (21), be defined, and w _m=[w _M1, w _M2..., w _MN].The precompensation frequency shift (FS) is also come by the estimation in the use (19) in the base station, and by estimating delay (the Δ t between the second training transmission and the current transmission ₀) come precompensation phase deviation.At last, the base station sends to the user via the DIDO precoder with data.

After process of transmitting, the signal that receives at user i place is provided by following:

r_{i} [t] = e^{jΔ ω_{i 1} T_{s} (t - {\tilde{t}}_{i 1} - Δ t_{o})} h_{i 1} Σ_{m = 1}^{M} w_{m 1} x_{m} [t] +

+ Σ_{n = 2}^{N} e^{jΔ ω_{in} T_{s} (t - {\tilde{t}}_{in} - Δ t_{o})} h_{in} e^{- jΔ ω_{T, 1 n} T_{s} (t - {Δ t}_{o})} Σ_{m = 1}^{M} w_{mn} x_{m} [t]

= e^{jΔ ω_{i 1} T_{s} (t - Δ t_{o})} e^{- jΔ ω_{i 1} T_{s} {\tilde{t}}_{i 1}} h_{i 1} Σ_{m = 1}^{M} w_{m 1} x_{m} [t]

+ Σ_{n = 2}^{N} e^{jΔ ω_{i 1} T_{s} (t - Δ t_{o})} e^{- j {Δω}_{in} T_{s} {\tilde{t}}_{in}} h_{in} Σ_{m = 1}^{M} w_{mn} x_{m} [t]

= γ_{i} [t] [h_{i 1} Σ_{m = 1}^{M} w_{m 1} x_{m} [t] + Σ_{n = 2}^{N} e^{j (θ_{in} - θ_{i 1})} h_{in} Σ_{m = 1}^{M} w_{m 1} x_{m} [t]]

= γ_{i} [t] [Σ_{n = 1}^{N} e^{j (θ_{in} - θ_{i 1})} h_{in} Σ_{m = 1}^{M} w_{mn} x_{m} [t]]

= γ_{i} [t] Σ_{m = 1}^{M} [Σ_{n = 1}^{N} e^{j (θ_{in} - θ_{i 1})} h_{in} w_{mn}] x_{m} [t]

= γ_{i} [t] Σ_{m = 1}^{M} w_{m}^{T} h_{i} x_{m} [t] - - - (23)

Wherein,

Use attribute (22), we obtain:

r_{i} [t] = γ_{i} [t] w_{i}^{T} h_{i} x_{i} [t] - - - (24)

At last, the user calculates frequency offset residue and channel estimating is come demodulated data stream x _i[t].

The result

Figure 48 shows the SER result who has and do not have DIDO 2 * 2 systems of frequency shift (FS).Can see, the method that proposes has been eliminated the frequency/phase skew fully, has produced the SER identical with the system that does not have skew.

Next, we assess the compensation method that proposes for frequency offset error and/or the real-time sensitivity of the fluctuation of skew.Therefore, we are rewritten as (14):

r_{1} [t] = e^{j {Δω}_{11} T_{s} (t - {\tilde{t}}_{11} - Δ t_{o})} h_{11} [w_{11} x_{1} [t] + w_{21} x_{2} [t]]

{+ e}^{j {Δω}_{12} T_{s} (t - {\tilde{t}}_{12} - Δ t_{o})} h_{12} e^{- j (Δ ω_{T} + 2 Π &Element;) T_{s} (t - Δ t_{o})} [w_{12} x_{1} [t] + w_{22} x_{2} [t]] - - - (25)

Wherein, ε represents to train and evaluated error and/or the variation of the frequency shift (FS) of data between sending.Note, the effect of ε is the orthogonal property that destroys in (13), so that the distracter in (14) and (16) is not eliminated fully in advance at the transmitter place.Because like this, the SER performance reduces along with the ε value that increases.

Figure 48 shows the SER performance for the frequency offset compensation method of different ∈ values.These results suppose T _s=0.3ms(namely has the signal of 3KHz bandwidth).We observe, for ε=0.001Hz(or still less), the SER performance is similar to the situation that does not have skew.

F. be used for the description of an execution mode of the algorithm that the time and frequency shift estimates

Below, we describe the other execution mode (4701b among Figure 47) of time of implementation and Frequency offset estimation.The structure that transmits of considering is at H.Minn, V.K.Bhargava and K.B.Letaief, " A robust timing and frequency synchronization for OFDM systems; " IEEETrans.Wireless Commun., vol.2, no.4, pp.822-839 proposes among the July 2003, at K.Shi and E.Serpedin, " Coarse frame and carrier synchronization of OFDM systems:a new metric and comparison; " IEEE Trans.Wireless Commun., vol.3, no.4, pp.1271-1284 is studied in great detail among the July 2004.Usually the sequence that has good association attributes is used to training.For example, for our system, the Chu sequence is used, the Chu sequence is as at D.Chu, " Polyphasecodes with good periodic correlation properties (corresp.), " IEEE Trans.Inform.Theory, vol.18, no.4, pp.531-532 is described among the July 1972.These sequences have interesting attribute, and namely they have perfect circular correlation.Allow L _CpThe length of expression Cyclic Prefix, N _tThe length of expression component training sequence.So that N _t=M _t, M wherein _tThe length of training sequence.Under these hypothesis, the symbol sebolic addressing that is used for the beginning that sends can be write as:

S[n]=t[n-N _t] for n=-1 ... ,-L _Cp

S[n]=t[n] for n=0 ..., N _t-1

S[n]=t[n-N _t] for n=N _t..., 2N _t-1

S[n]=-t[n-2N _t] for n=2N _t..., 3N _t-1

S[n]=t[n-3N _t] for n=3N _t..., 4N _t-1

The structure of noting this training signal can be expanded to other length, but has repeated block structure.For example, in order to use 16 training signals, we consider a kind of structure, for example:

[CP,B,B,-B,B,B,B,-B,B,-B,-B,B,-B,B,B,-B,B,]。

By using this structure, and make N _t=4M _t, all algorithms that will describe can be in the situation that there be modification to be used.Effectively, our repetition training sequence.This is particularly useful in the suitable disabled situation of training signal possibility.

After the filtering that symbol rate is mated and down sample, the received signal below considering:

r [n] = e^{2 πϵn} Σ_{l = 0}^{L} h [l] s [n - l - Δ] + v [n]

Wherein ε is unknown discrete time frequency shift (FS), and Δ is unknown vertical shift, h[l] be unknown discrete time channel coefficients, and v[n] be additional noise.In order to explain the key idea in the following part, ignore the existence of additional noise.

I. rough frame synchronization

The purpose of rough frame synchronization is to solve unknown vertical shift Δ.Let us is made giving a definition:

r ₁[n]：＝[r[n]，r[n+1]，...，r[n+N _t-1]] ^T，

{\overset{&OverBar;}{r}}_{1} [n] : = {[r [n + L_{cp}], r [n + 1], . . ., r [n + N_{t} - 1]]}^{T},

r ₂[n]：＝[r[n+N _t]，r[n+1+N _t]，...，r[n+2N _t-1]] ^T，

{\overset{&OverBar;}{r}}_{2} [n] : = {[r [n + L_{cp} + N_{t}], r [n + 1 + L_{cp} + N_{t}], . . ., r [n + {L_{cp} + 2 N}_{t} - 1]]}^{T},

r ₃[n]：＝[r[n+2N _t]，r[n+1+2N _t]，...，r[n+3N _t-1]] ^T，

{\overset{&OverBar;}{r}}_{3} [n] : = {[r [n + L_{cp} + 2 N_{t}], r [n + L_{cp} + 1 + {2 N}_{t}], . . ., r [n + {L_{cp} + 3 N}_{t} - 1]]}^{T},

r ₄[n]：＝[r[n+3N _t]，r[n+1+3N _t]，...，r[n+4N _t-1]] ^T，

{\overset{&OverBar;}{r}}_{4} [n] : = {[r [n + L_{cp} + 3 N_{t}], r [n + L_{cp} + 1 + {3 N}_{t}], . . ., r [n + {L_{cp} + 4 N}_{t} - 1]]}^{T},

The rough frame synchronization algorithm that proposes is from K.Shi and E.Serpedin, " Coarse frame andcarrier synchronization of OFDM systems:a new metric and comparison; " IEEETrans.Wireless Commun., vol.3, no.4, pp.1271-1284, the algorithm among the July 2004 takes a hint, and obtains according to maximum-likelihood criterion.

The improved rough frame synchronization of method 1-: rough frame synchronization estimator has solved following optimization:

\hat{Δ} = \arg \max_{k &Element; Z} \frac{| P_{1} (k) | + | P_{2} (k) | + | P_{3} (k) |}{{| | r_{1} | |}^{2} + {| | r_{2} | |}^{2} + {| | r_{3} | |}^{2} + {| | r_{4} | |}^{2} + \frac{1}{2} ({| | {\overset{&OverBar;}{r}}_{1} | |}^{2} + {| | {\overset{&OverBar;}{r}}_{2} | |}^{2} + {| | {\overset{&OverBar;}{r}}_{3} | |}^{2} + {| | {\overset{&OverBar;}{r}}_{4} | |}^{2})}

Wherein,

P_{1} [k] = r_{1}^{*} [k] r_{2} [k] - r_{3}^{*} [k] r_{4} [k] - {\overset{&OverBar;}{r}}_{2}^{*} [k] {\overset{&OverBar;}{r}}_{3} [k]

P_{2} [k] = r_{2}^{*} [k] r_{4} [k] - r_{1}^{*} [k] r_{3} [k]

P_{3} [k] = {\overset{&OverBar;}{r}}_{4}^{*} [k] {\overset{&OverBar;}{r}}_{4} [k],

So that the signal that is corrected is defined as:

Other correction term is used to the little inceptive impulse in the compensate for channel and can be conditioned based on application.This extra delay will be included in the channel afterwards.

Ii. fractional frequency offset correction

The fractional frequency offset correction is after rough frame synchronization piece.

The improved fractional frequency offset correction of method 2-: the fractional frequency skew is following solution:

This is known as the fractional frequency skew, because algorithm only can correcting offset

| {\hat{e}}_{f} | < \frac{1}{2 N_{t}}

This problem will be solved in next part.Allow the fine frequency offset correction signal be defined as:

r_{f} [n] = e^{- j 2 π {\hat{ϵ}}_{f}} r_{c} [n]

Note,

method

1 and 2 is for the preferably K.Shi that works in frequency selective channel, E.Serpedin, " Coarse frame and carrier synchronization of OFDM systems:a newmetric and comparison; " IEEE Trans.Wireless Commun., vol.3, no.4, pp.1271-1284, the improvement of July 2004.Here one special innovation be used r recited above and

The estimator of use before having improved the sampling that the internal symbol interference is affected because it has been ignored.

Iii. integer frequency deviation is proofreaied and correct

In order to proofread and correct integer frequency deviation, be necessary to write an equivalent system model that is used for signal received after fine frequency offset is proofreaied and correct.The timing error that keeps is absorbed in the channel, is not had noisy received signal to have following structure:

r_{f} [n] = e^{j 2 π \frac{nk}{N_{s}}} Σ_{l = 0}^{L_{cp}} g [l] s [n - l]

N=0 wherein, 1 ..., 4N _t– 1.Integer frequency deviation is k, and unknown equivalent channels is g[l].

The improved integer frequency deviation of method 3-is proofreaied and correct: integer frequency deviation is following solution:

\hat{k} = \arg \max_{m = 0,1, . . ., N_{t} - 1} {r * D [k] S (S * S)}^{- 1} S * D [k] * r

Wherein:

r＝D[k]Sg

D [k] : = diag {1, e^{j 2 π \frac{n 1}{N_{t}}}, . . ., e^{j 2 π \frac{n (4 N_{t} - 1)}{N_{t}}}}

S : = [\begin{matrix} s [0] & s [- 1] & . . . & . . . & s [- L_{cp}] \\ s [1] & s [0] & s [- 1] & . . . & s [- L_{cp} + 1] \\ s [4 N_{t} - 1] & s [4 N_{t} - 2] & s [4 N_{t} - 3] & . . . & s [4 N_{t} - 1 - L_{cp}] \end{matrix}]

g : = [\begin{matrix} g [0] \\ g [1] \\ . \\ . \\ . \\ g [L_{cp}] \end{matrix}]

This has provided the estimation of total frequency shift (FS):

\hat{e} = \frac{\hat{k}}{N_{t}} + {\hat{e}}_{f}

In fact, method 3 has very high complexity.In order to reduce complexity, can make following observation.At first, product S (S*S) ^-1S can be by precomputation.Regrettably, this has still stayed sizable matrix multiplication.Adopt alternatively the observation with the training sequence that proposes, S*S ≈ I.This has produced the method for the support type of following reduction.

The improved integer frequency deviation of method 4-low-complexity is proofreaied and correct:

The integer frequency deviation estimator of low-complexity has solved

\hat{k} = \arg \max_{m = 0,1, . . ., N_{t} - 1} (S * D [k] * r) * (S * D [k] * r)

Iv. result

In this part, we have compared the performance of the different estimators that proposes.

At first, in Figure 50, we have compared the amount of every kind of needed expense of method.Notice that two kinds of new methods have reduced by 10 times to 20 times with expense.For the performance of more different estimators, the MonteCarlo experiment is performed.The setting of considering is that our the common NVIS from the linear modulation of the symbol rate with 3K symbol per second structure sends waveform, and corresponding to the pass band width of 3KHz, and the cosine impulse that rises is shaped.Realize for each Monte Carlo, frequency shift (FS) is from [f _Max, f _Max] on even distribution and generate.

Has f _MaxThe little frequency shift (FS) of=2Hz and do not have the emulation of integer offset correction in Figure 51, to be illustrated.Can find out to have N from this Performance Ratio _t/ M _t=1 performance is slightly demoted from original estimator, although reduced in fact expense.Has N _t/ M _t=4 performance is better, almost is 10dB.Because the error in the integer bias estimation, all curves have experienced complications at low SNR point.Little error in the integer skew can create large frequency error and large splicing square error.The integer offset correction can be closed to improve performance in little skew.

In the situation that multi-path channel exists, the performance of frequency offset estimator generally reduces.Yet, in Figure 52, close the integer offset estimator and represented extraordinary performance.Therefore, in multi-path channel, the improved fine correction algorithm after the rough correction of carrying out robust is prior.Note, have N _t/ M _t=4 offset behavior is much better in the multipath situation.

The various steps that propose above embodiments of the present invention can comprise.Described step can realize in the mode of machine-executable instruction, and described instruction is so that universal or special processor is carried out particular step.For example, the interior various assemblies of described base station/AP and customer set up may be implemented as the software of carrying out at universal or special processor in the above.For fear of the fuzzy parties concerned of the present invention, from figure, save such as the various known individual calculus thermomechanical components of computer storage, hard disk, input unit etc.

Replacedly, the specialized hardware components (for example application-specific integrated circuit (ASIC) (ASIC)) of the hardwired logic that in one embodiment, shown various functional module and correlation step can be by comprising execution in step here or be performed by the combination in any of programmed computer components and custom hardware components.

In one embodiment, allly encode as described above, the particular module of modulation and signal processing logic 903 can be implemented in programmable digital signal processor (DSP) (or DSP group), described DSP for example use Texas Instrument (Texas Instruments) the TMS320x framework DSP(for example, TMS320C6000, TMS320C5000 etc.).DSP in this embodiment can be embedded in the package card of personal computer, for example, and pci card.Certainly, in the situation that basic principle according to the invention, various DSP framework can be used.

Various parts of the present invention also may be provided in the machine readable media for the storage machine-executable instruction.Machine readable media can include but not limited to flash memory, CD, CD-ROM, DVD ROM, RAM, EPROM, EEPROM, magnetic card or optical card, communication media or be suitable for the machine readable media of other type of store electrons instruction.For example, the present invention can be downloaded and be computer program, this computer program can be by being included in carrier wave or other communication media the mode of data-signal be sent to requesting computer (for example client) via communication link (for example, modulator-demodulator or network connection) from remote computer (for example server).

Spread all over aforementioned description, for the purpose of explaining, many specific detail are suggested to provide the complete understanding of native system and method.Yet, be implemented in the situation of some that it will be apparent to one skilled in the art that system and method can be in not having these specific detail.Therefore, scope of the present invention and essence should be judged according to claims.

In addition, in aforementioned description, many documents are cited to provide of the present invention and more fully understand.All these lists of references of quoting are integrated among the application by reference.

Claims

1. one kind is used to be used for compensating the frequency of multi-user multi-aerial system MU-MAS communication and the wireless client device of phase deviation in system, and this wireless client device comprises:

One or more RF unit is used for receiving the signal that sends from one or more MU-MAS transmitter units, and described signal down is transformed into base band;

One or more moduluses (A/D) converting unit is used for receiving the signal after frequency reducing is changed and this signal from analog signal is converted to digital signal;

Frequency/phase bias estimation/compensating unit is used for estimated frequency and/or phase deviation and information is fed back to transmitter to be used for precompensation;

One or more OFDM unit is used for removing Cyclic Prefix and carries out fast Fourier transform (FFT) with the signal of report frequency domain in described digital signal;

Channel estimating unit, the signal that is used for receiving during cycle of training from the output of described one or more OFDM unit also responsively calculates channel evaluation data; And

Feedback maker unit is used for that described channel evaluation data is sent to the base station and uses to be used for before signal is sent to described wireless client device signal being carried out precoding.

2. wireless client device according to claim 1, wherein channel estimating is calculated in time domain by the input that uses described OFDM unit.

3. wireless client device according to claim 1, wherein said feedback maker unit also comprises logic, this logic is used for before sending to described base station frequency shift (FS) and channel estimating being quantized.

4. wireless client device according to claim 1, this wireless client device also comprises: receiver unit, this receiver unit is used for receiving the output from described OFDM unit, and responsively calculates receiver and signal is carried out demodulate/decode to obtain the estimation to the data that sent.

5. wireless client device according to claim 4, wherein said receiver unit are that least mean-square error (MMSE) receiver, zero is forced (ZF) receiver, maximum likelihood (ML) or MAP receiver.

6. wireless client device according to claim 1, wherein said MU-MAS communication comprises DIDO communication, and wherein said one or more RF unit receives the signal that sends from one or more DIDO transmitter units and this signal down is transformed into base band.

7. wireless client device according to claim 1, wherein said frequency/phase bias estimation/compensating unit carry out the method, the method that is used for the fractional frequency offset correction that are used for rough frame synchronization, be used for the method that integer frequency deviation proofreaies and correct and/or be used for the method that integer frequency deviation is proofreaied and correct.

8. one kind is used to be used for the unbalanced wireless client device of inphase quadrature (I/Q) of compensation multi-user multi-aerial system MU-MAS communication in system, and this wireless client device comprises:

I/Q channel perception estimation unit receives during cycle of training from the signal of described one or more OFDM unit output and also responsively calculates channel evaluation data; And

9. wireless client device according to claim 8, wherein channel estimating is calculated in time domain by the input that uses described OFDM unit.

10. wireless client device according to claim 8, wherein said feedback maker unit also comprises logic, this logic is used for before sending to described base station channel estimating being quantized.

11. wireless client device according to claim 8, this wireless client device also comprises:

I/Q perception receiver unit is used for receiving the output from described OFDM unit, and responsively calculates the IQ receiver and signal is carried out demodulate/decode to obtain the estimation to the data that sent.

12. being least mean-square error (MMSE) receivers, zero, wireless client device according to claim 10, wherein said I/Q perception receiver unit force (ZF) receiver, maximum likelihood (ML) or MAP receiver.

13. wireless client device according to claim 10, wherein said I/Q perception receiver unit comprise that MMSE or ZF filter are to eliminate the inter-carrier interference (ICI) that is caused by the I/Q imbalance on the mirror image accent.

14. wireless client device according to claim 10, wherein said I/Q perception receiver unit comprise the symbol that nonlinear detector (being ML) comes the joint-detection mirror image to transfer.

15. wireless client device according to claim 10, wherein said I/Q channel perception estimation unit calculate I/Q perception receiver unit can with coefficient to remove inter-carrier interference (ICI).

16. one kind is used the wireless client device with the communication characteristic that is used for dynamically adapting multi-user multi-aerial system MU-MAS communication system in system, this wireless client device comprises:

Channel estimator, the signal that is used for receiving during cycle of training from the output of described one or more OFDM unit also responsively calculates the link-quality matrix; And

Feedback maker unit is used for that described link-quality matrix is sent to the base station and uses to be used for before signal is sent to described wireless client device signal being carried out modulation/coding, precoding and user selection.

17. wireless client device according to claim 16, wherein channel estimating is calculated in time domain by the input that uses described OFDM unit.

18. wireless client device according to claim 16, wherein said feedback maker unit also comprises logic, and this logic is used for before sending to described base station channel estimating and/or described link-quality matrix being quantized.

19. wireless client device according to claim 16, this wireless client device also comprises:

Receiver unit is used for receiving the output from described OFDM unit, and responsively signal is carried out demodulate/decode to obtain the estimation to the data that sent.

20. being least mean-square error (MMSE) receivers, zero, wireless client device according to claim 18, wherein said receiver unit force (ZF) receiver, maximum likelihood (ML) or MAP receiver.

21. wireless client device according to claim 17, wherein said MU-MAS configurator unit or described channel estimator unit use respectively polarization and/or directional diagram diversity technique as the method that reduces array sizes, obtain simultaneously the diversity on Radio Link.

22. wireless client device according to claim 16, wherein communicating by letter occurs with the method as increase diversity and downlink throughput via NVIS and/or earthwave.

23. wireless client device according to claim 16, wherein the directional diagram diversity is used to communicate via earthwave and specific user with via NVIS and other users respectively.

24. described wireless client device according to claim 23, wherein each customer end adopted earthwave separates the method for the space diversity that is used as increasing link with the space of NVIS link.