CN101610234B - Pilot transmission schemes for wireless multi-carrier communication systems - Google Patents

Abstract

Pilot transmission schemes suitable for use in wireless multi-carrier (e.g., OFDM) communication systems. These pilot transmission schemes may utilize frequency, time, or both frequency and time orthogonality to achieve orthogonality among the pilots transmitted by multiple base stations on the downlink. Frequency orthogonality is achieved by transmitting pilots on disjoint sets of subbands. Time orthogonality is achieved by transmitting pilots using different orthogonal codes (e.g., Walsh codes). The pilots may also be scrambled with different scrambling codes, which are used to randomize pilot interference and to enable identification of the transmitters of these pilots. Pilot interference cancellation may be performed to improve performance since subbands used for data transmission by one transmitter may also be used for pilot transmission by another transmitter. Pilot interference is estimated and then subtracted from received symbols to obtain pilot-canceled symbols having improved quality.

Description

The pilot frequency transmission method of wireless multi-carrier communication system and device

The application is that application number is 200480004741.1, international filing date is 2004.01.07, denomination of invention is divided an application for the application for a patent for invention of " pilot transmission schemes of wireless multi-carrier communication system ".

The application requires in interim U. S. application sequence number 60/438; 601 priority; The latter is entitled as " PilotTransmission Schemes for Wireless Multi-Carrier CommunicationSystems "; Be filed on January 7th, 2003, transferred assignee of the present invention, and be incorporated herein by reference fully at this.

Technical field

The present invention relates generally to communication, relate in particular to the pilot transmission schemes that is used for wireless multi-carrier communication system.

Background technology

Multi-carrier communications systems uses a plurality of carrier waves to be used for transfer of data to single endpoint.These a plurality of carrier waves can be used for like OFDM (OFDM) or some other multi-carrier modulation technologies.OFDM is divided into a plurality of (N) orthogonal subbands with the total system bandwidth effectively, and they also become tone, frequency section and frequency subchannels.In OFDM, each subband is associated with the corresponding carrier wave of modulating data above that.

In wireless communication system, the data that send are managed (for example encode and modulate) everywhere at transmitter, and upconvert to radio frequency (RF) carrier signal to generate the RF modulated signal.The RF modulated signal is sent out on wireless channel then and can arrives receiver through a plurality of propagation paths.The characteristic of propagation path usually since a plurality of factors along with the time changes, said factor is such as for example decay, multipath and external disturbance.Therefore, the RF modulated signal of transmission possibly experience different channels condition (for example different decay and multipath effect), and possibly be associated in different complex gain and signal to noise ratio (snr) in time.

In wireless communication system, pilot tone often sends to receiver (for example terminal) from transmitter (for example base station) and realizes a plurality of functions to help receiver.Pilot tone generally generates and handles in known manner based on known code element.Pilot tone can be used for that channel estimating, timing and frequency are obtained by receiver, the coherence data demodulation, receive signal strength measurement etc.

In the pilot transmission schemes design of multi-carrier communications systems, face multiple challenge.A kind of consideration is because pilot transmission is represented expense system in, and expectation minimizes pilot transmission as far as possible and the while still provides the performance of expection.Another consideration is the pilot tone that the send mode of pilot tone will make intrasystem reception function detect and interior each transmitter of distinguishing system sends.And pilot transmission schemes need solve the additional dimension of a plurality of carrier waves foundation of multicarrier system.

Therefore in this area a kind of needs to pilot transmission schemes in the multi-carrier communications systems are arranged.

Summary of the invention

At this pilot transmission schemes that is suitable for use in wireless multi-carrier communication system (for example ofdm system) is provided.These pilot transmission schemes can utilize frequency orthogonal property, time quadrature property or both are with the orthogonality between the pilot tone that obtains to be sent by a plurality of base stations on the down link.Frequency orthogonal property can obtain through on the sets of subbands that separates, sending pilot tone from different base stations.Time quadrature property can obtain through using different orthogonal sign indicating number (for example Walsh sign indicating number) to send pilot tone.Pilot tone can also be carried out scrambler with different scramblers, and said scrambler is used for the randomization Pilot Interference and makes the transmitter identity of these pilot tones of ability identification.

Pilot transmission schemes described here has made things convenient for channel estimating and detection of pilot effectively.The pilot frequency intensity that these schemes allow intrasystem terminal can obtain base station in high-quality broad-band channel estimation and the system is estimated.These estimations can be used to realize coherence data demodulation, soft handover and direct-cut operation, be described below.

At this estimation and the cancellation techniques of Pilot Interference are provided also.Can realize that Pilot Interference offsets improving performance, because the subband that is used for data or pilot transmission by a transmitter can also be used for pilot transmission by another transmitter (i.e. " interference " transmitter).The estimation of Pilot Interference can realize in the following manner: obtain the estimation of channel to interference source; The same way as that realizes with jamming transmitter generates pilot tone; And the pilot tone that generates multiply by channel estimating.Pilot Interference is deducted with the pilot tone behind the acquisition quality improvement from the code element that receives then offsets the back code element.

Various aspects of the present invention and embodiment are in following detailed description.

Characteristic of the present invention, characteristic and advantage become clearer from the detailed description below in conjunction with accompanying drawing, reference character identical among the figure identifies homologue, wherein:

Brief description of the drawings

Fig. 1 illustrates the wireless multiple access multi-carrier communications systems;

Fig. 2 A illustrates the OFDM sub band structure;

Fig. 2 B illustrates the individual sets of subbands that separates based on the T of the OFDM sub band structure shown in Fig. 2;

Fig. 3 A and 3B are depicted as the 9-sector 3-cell cluster and the corresponding exemplary sub-band of 21-sector 7-cell cluster that obtain frequency orthogonal property and distribute;

The example allocation that Fig. 4 A and 4B illustrate orthogonal code respectively obtains time quadrature property with the 3-sector 1-cell cluster that each sector is had an antenna and two antennas;

Fig. 4 C and 4D illustrate the subband and the orthogonal code example allocation of 9-sector 3-cell cluster and 21-sector 7-cell cluster respectively, to obtain frequency and time quadrature property;

Fig. 5 illustrates the example system layout, and wherein different scramblers is assigned to each 7-cell cluster;

Fig. 6 A and 6B illustrate respectively to the lock-out pulse pilot transmission schemes and synchronously the CP continuous pilot transmission plan from the pilot transmission of a plurality of sectors;

Fig. 7 illustrates the block diagram at base station and terminal;

Fig. 8 illustrates the block diagram of base station internal modulator;

Fig. 9 A and 9B illustrate the block diagram of two embodiment of demodulator in the terminal; And

Figure 10 illustrates the block diagram of the Pilot Interference canceller in the demodulator.

Embodiment

" example " speech is used herein to finger " as example, instance or explanation ".Anyly not necessarily to be understood that to be superior to other embodiment or design in this embodiment or design that is described as " example ".

Fig. 1 illustrates wireless multiple access multi-carrier communications systems 100, and said system supports a plurality of users, and can realize pilot transmission schemes described here.System 100 comprises a plurality of base stations 110, and they support the communication at a plurality of terminals 120.The base station is the fixed station that is used for terminal communication, and can also be called access point, Node B or some other terms.

Illustrate like Fig. 1, each terminal 120 can be dispersed in the system, and each terminal can be fixing (promptly static) or move.The terminal can also be called as mobile radio station, distant station, subscriber equipment (UE), Wireless Telecom Equipment, access terminal or some other terms.Can communicate by letter at any given time with a plurality of base stations on down link and/or up link in each terminal.Down link (being forward link) refers to the communication link from the base station to the terminal, and up link (being reverse link) refers to the communication link from terminal to base station.In Fig. 1, terminal 120a to 120o receive pilot tone, signaling and from the base station 110a to the possible user's particular data transmission of 110g.

System controller (in Fig. 1, not illustrating) generally is coupled to base station 110; And can be designed to realize a plurality of functions; Realize coordinating and control for the base station of being coupled to it such as (1), (2) are with data route between these base stations, and the terminal of these base station services is inserted and controlled in (3).

System 100 can be the wireless system of cellular system or some other types.System 100 can also be designed to realize any standard and design, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA) etc.The CDMA standard comprises IS-95, cdma2000, IS-856, W-CDMA and TS-CDMA, and the TDMA standard comprises GSM.These standards are many knowledges in this area.

Intrasystem each base station 110 provides the covering of specific geographic area 102.The overlay area of each base station can be defined as the zone that terminal for example can obtain specified service class (GoS).The size of the overlay area of each base station and shape generally depend on various factors, such as landform, barrier etc.For succinctly, the overlay area of each base station is represented with desirable hexagon usually.Base station and/or its overlay area generally are commonly called " sub-district ", depend on the context that this term uses.

In the General System arrangement, for the increase capacity, the overlay area of each base station can be divided into a plurality of sectors.If each sub-district is divided into three sectors, then each sector of the sub-district of sectorization representes that with 120 desirable degree wedge shapes it is 1/3 of sub-district usually.In actual arrangement, the overlay area of each base station has usually and is different from desirable hexagonal shape, and the shape of each sector usually is different from 120 desirable wedge shapes.And the sector of sectorized cells is generally located overlapping on the edge of.Each sector can be served by corresponding base transceiver subsystem (BTS).For through the sub-district of sectorization, the base station of this sub-district generally includes BTS of the sector of all these sub-districts of service." sector " term also be often used in refer to BTS with and/or its overlay area, this depends on the environment that this term uses.

For succinctly, below describe each sub-district of hypothesis and be divided into three sectors, and its BTS is positioned at the base station of this sub-district.This base station is positioned at the center of sub-district.And for succinctly, in the following description, " base station " speech generally is used for the fixedly fixed station of Serving cell and the fixed station of serving sector.

For cdma system, the pilot tone that send each base station is being dispersed on the channel on the whole system bandwidth before the transmission on the wireless channel.In end, the pilot tone that send each base station can be received with low signal-to-noise ratio (SNR).Yet the complementation that realize at the terminal goes extended operation that processing gain is provided, and this has relied on much noise and disturbed condition recovers pilot tone down.For multicarrier system, generally can not realize handling like the Direct swquence spread spectrum that uses in the CDMA to pilot tone.Thereby must use other devices to send pilot tone from each base station, make it easily to be detected by intrasystem terminal.

At this pilot transmission schemes that is applicable to multi-carrier communications systems is provided, such as illustrate in Fig. 1 that.As stated, send the various functions of pilot tone, such as regularly and frequency is obtained, channel estimating, coherence data demodulation etc. to support that normal system operation possibly need.Can also with some other multi-carrier modulation technologies a plurality of carrier waves be provided by OFDM.Pilot transmission schemes described here is applicable to down link well, also can be used for up link.

For clear, pilot transmission schemes is that the down link of ofdm system is described specially.This ofdm system has N orthogonal subbands.An OFDM code element can be sent in each OFDM code element in each base station in period, the following description.

I. pilot transmission is constructed

Form 1 has been listed pilot transmission schemes operable three kinds " structures ".

Form 1

Structure	Describe
		Frequency orthogonal property	Send pilot tone on the sets of subbands to obtain the frequency domain orthogonality of pilot transmission by different base station in different separating
Time quadrature property	By different base station is that pilot tone uses different orthogonal sign indicating number (for example Walsh sign indicating number) to obtain the time domain orthogonal property of pilot transmission
		Scrambler	By different base station is that pilot tone uses different scrambling codes to be used for randomize pilot interference and base station identity sign

Quadrature with disturb " sign indicating number " and also be called as " sequence " in the following description.Each that list in the form 1 is structured in following detailed description.The processing of base station and these structures of end is also in following description.

Various pilot transmission schemes can also be based on any one or any Combination Design of these structures.For example, pilot transmission schemes can use (1) frequency and time quadrature property, (2) frequency orthogonal property and scrambler, (3) frequency orthogonal, time quadrature property and scrambler, or (4) some other combinations.

1. frequency orthogonal property

Frequency orthogonal property can be used to avoid a plurality of base stations to carry out the interference that pilot transmission causes simultaneously.For frequency orthogonal property, pilot tone is sent in the different sub-band set by a plurality of base stations, and said sets of subbands is that " separating " (separating in following description) is to avoid interference.Frequency orthogonal performance accomplished in various ways, some is described below.

Fig. 2 A illustrates OFDM sub band structure 200, and this structure can be used for multicarrier system 100.There is total system bandwidth W MHz in system, and it is divided into N orthogonal subbands using OFDM.In general ofdm system, have only M to be used for pilot tone and transfer of data, wherein M＜N in N total subband.A remaining N-M subband is not used in pilot/data transmission, covers requirement and meet frequency spectrum as protection with the permission system.M available subband comprises subband F to F+M-1, and wherein F is an integer, and general selection makes M available subband concentrate on the center of operational frequency bands.

Fig. 2 A also illustrates the embodiment of M available subband of a division pilot transmission.In this embodiment, M available subband is divided into K group when beginning, and each group comprises T subband continuously.Generally, each can be the integer greater than for K, T and M, and KT≤M.T subband in each group is assigned to T set then, makes that i subband in each group is assigned to i set.

Fig. 2 B illustrates the T subband set that generates based on the division shown in Fig. 2 A and closes.K subband in each T set illustrates with dash box.For this embodiment, K subband in each set evenly distributes on M available subband, and the continuous intersubband in the set is separated by T intersubband.The T subband set is closed and can be assigned to T sub-district or pilot transmission is carried out in T sector.Pilot tone can only be sent in each sub-district or sector on the subband in the set of distributing to this cell/section.

As a particular example, multicarrier system can have 512 subbands, and they are assigned with the index with 1 to 512.In these 512 subbands, can also distribute 50 subbands for the pilot transmission in each sector.Therefore, these 512 subbands can also be used to form the set (being T=9 and K=50) of 9 50 subbands, as illustrating in the form 2.

Form 2

These 9 subband set are closed and can be assigned to 9 different sectors then and carry out pilot transmission.

Generally, M available subband can be assigned to T set in every way, and this within the scope of the invention.T set can comprise the subband of identical or different quantity.And the subband in each set can be evenly or is distributed in unevenly on M the available subband.The T subband set is closed each other and " is separated ", to avoid interference.Sets of subbands is spaced from each other, and makes each of M available subband be assigned to maximum set.Each set comprises that also the subband of sufficient amount is so that channel can be described based on the pilot transmission on these subbands only in the terminal.Generally, the set quantity of formation and the number of sub-bands (being the particular value of T and K) that is included in each set possibly depend on various factors, such as:

● the quantity of available subband in the system;

● the time delay expansion of system and coherence bandwidth, this largest interval of having confirmed CP continuous pilot intersubband in each set is to avoid mis-behave;

● obtain frequency orthogonal property bunch size; And

● whether time quadrature property also is used for pilot transmission.

The Cyclic Prefix of OFDM code element (being described below) can be defined as and comprise C _pIndividual sampling, wherein C _pBased on the time delay expansion of system and, make Cyclic Prefix comprise the pith of all multipath energy through suitable selection.For fear of mis-behave, the selection of the number of sub-bands in each set (K) can be so that K>=C _p, and these subbands can be evenly distributed on the system operation bandwidth.The maximum number that separates set that can form in this case, is N/C _pFor example, if N=256, and C _p=16, then can form nearly 16 subband set and close.Can also form number still less separate set, wherein each set comprises more than C _pSubclass.In this case, comprise that the sub band number that requires more than minimum can be so that pilot reception has higher signal quality, thereby channel estimating that can be improved and pilot frequency intensity are estimated.Perhaps, can form and more separate the set number, each set comprises and is less than C _pIndividual subband.In this case, comprise that being less than the minimum sub band number that requires possibly cause the characteristic of frequency selectivity of operational frequency bands insufficient, and the deterioration of some performance possibly take place.

For succinctly, each that describe below that hypothesis T subband set closes comprises K subband, and the interior subband of each set distributes equably and is spaced apart T subband (illustrating like Fig. 2 B), and KT=M.The set number that forms depend on the desired frequency orthogonality and bunch size, like the following stated.

Fig. 3 A illustrate the exemplary sub-band branch be equipped with obtain to have to 3 sub-districts bunch frequency orthogonal property, wherein each sub-district comprises 3 sectors (being 9-sector 3-cell cluster).Each of 9 sectors in bunch is assigned with of closing with 9 subband set (can for example as forming in the form 2) with illustrating.The sets of subbands of distributing to each sector is represented by the digital reference adjacent to the arrow of Fig. 3 A.Its pilot tone is only sent on the subband in the set of its distribution then in each sector.9 sectors in bunch can separate at 9 simultaneously sends its pilot tone on the sets of subbands, and obtains the frequency domain orthogonality simultaneously and avoid interference.

Fig. 3 B illustrates the exemplary sub-band distribution and thinks bunch acquisition frequency orthogonal property that has 7 sub-districts, and wherein each sub-district comprises 3 sectors (being 21-sector 7-cell cluster).Bunch in each of 21 sectors be assigned with one that closes with 21 subband set.21 sectors in bunch can separate at 21 subbands simultaneously sends its pilot tone simultaneously in the set, and obtains the orthogonality in the frequency domain simultaneously and avoid interference.

Generally, bunch can be defined as and to comprise any amount of sub-district, and each sub-district can comprise any amount of sector.As an example, bunch can be defined as and to comprise 1,2,3,7 or 19 sub-districts.Bunch size can depend on various factors, such as act as listed above.

Can also be for being that pilot tone and transfer of data use the system of a plurality of antennas to obtain frequency orthogonal property at each place, sector, to obtain spatial dispersion property and to improve reliability.For example, each sector can use space-time emission diversity (STTD) scheme or Almouti scheme from two antenna transmission data.The STTD scheme is in 3G TS25.211 and in interim U.S. Patent Application Serial Number 60/421; Describe in 309, the latter is entitled as " MIMOWLAN system ", is filed on October 25th, 2002; Transferred assignee of the present invention at this, and be hereby incorporated by.The Alamouti scheme is described in being entitled as " A Simple TransmitDiversity Technique for Wireless Communications " by S.M.Alamouti, and this article is published in IEEE JSAC, and Oct.1998 is also comprised as a reference at this.For the system of the sector that has a plurality of antennas, each antenna can be assigned with different subsets to be gathered.

2. time quadrature property

Time quadrature property can realize through the pilot tone with each sub-district of different orthogonal sign indicating number " covering " or sector.In end, can " go to cover " and recover receiving signal through the same orthogonal code used with this cell/section from the pilot tone of each cell/section.Overwrite procedure is that all Q chip that the given pilot tone that will send or data symbols multiply by (promptly having Q pilot/data code element set of given value) Q chip orthogonal sequence covers the back code element to obtain Q, and said code element is by further also transmission subsequently of processing.Go overwrite procedure be Q chip of the code element that the receives orthogonal sequence that multiply by (a) identical Q chip and (b) complex conjugate (or complex conjugate of Q pilot/data code element) of pilot tone or data symbols go to cover code element to obtain Q, they are then through adding up with the pilot tone that obtains to send or the estimation of data symbols.It is known covering and going to cover in this area, and in following description.Go to cover and remove or offset the pilot tone of sending by other cell/sections that use the different orthogonal sign indicating number for its pilot tone.Like this, can realize from the orthogonality between the pilot transmission of a plurality of cell/sections.

Validity through the pilot tone orthogonality that covers can depend on to have base station information regularly.Can obtain time quadrature property for the sector of same cells, because operate simultaneously these sectors.Sub-district in each bunch or intrasystem all sub-districts can also be operated simultaneously to allow for the pilot tone of sending these sub-districts and obtained time quadrature property.

Time quadrature property can use all kinds orthogonal code to obtain, such as Walsh sign indicating number and orthogonal variable spreading factor (OVSF) sign indicating number.The length that is used for the orthogonal code that pilot tone covers depends on the quantity of the orthogonal code of requirement, this then depend on obtain time quadrature property bunch size.For example, if to having the sub-district expected time orthogonality of 3 sectors, then need 3 orthogonal codes (being the sign indicating number in each sector), and each orthogonal code has 4 chip lengths.

Form 3 has been listed and can be assigned to nearly 4 chip Walsh sign indicating numbers of four different sectors, sub-district or antennas.

Form 3

The Walsh sign indicating number	Value
		W 1(n)	1111
W 2(n)	11-1-1
		W 3(n)	1-11-1
W 4(n)	1-1-11

Specific Walsh sign indicating number can be assigned to each sector or each antenna of given sub-district.The value of " 1 " of Walsh sign indicating number can indicate pilot frequency code element contrary (promptly $p_k\left(n\right)\⇒-p_k\left(n\right)$ ), and value " 1 " possibly indicated no contrary.Identical Walsh sign indicating number can be applied to each subband that is used for pilot transmission.For each pilot subbands, four chips of Walsh sign indicating number are applied to four pilot frequency code elements that will in four continuous OFDM code element periods, send.Therefore the length of Walsh sign indicating number be T _w=4T _Sym, T wherein _SymRepresent an OFDM code element period.If pilot transmission is longer than four OFDM code element periods, then identical Walsh sign indicating number can repeat repeatedly on demand.The Walsh sign indicating number also is called as Walsh sequence or Walsh code element, and T _wRepresent a Walsh code element period.

Fig. 4 A illustrates the example orthogonal code division and is equipped with the time quadrature property (be 3-sector 1-cell cluster) of acquisition to the sub-district that has three sectors.Each of three sectors in the sub-district is assigned with different orthogonal codes.Three orthogonal codes distributing to 3 sectors are denoted as A, B and C.As representing in Fig. 4 A that the same sub-band set can be used by all three sectors in the sub-district.Be to obtain time domain orthogonal property through using the different orthogonal sign indicating number then from the pilot transmission that send these three sectors.

Fig. 4 B illustrates the example orthogonal code division and is equipped with the time quadrature property that acquisition has the sub-district of three sectors, and each sector uses two antennas to be used for pilot tone and transfer of data.Each of three sectors is assigned with two orthogonal codes sign indicating number of each antenna in the sub-district.The three pair of orthogonal sign indicating numbers of distributing to three sectors are marked as A/B, C/D and E/F.3 sector cells require six orthogonal codes altogether then, and each orthogonal code length is 8 chips.

Time quadrature property characteristic possibly worsen owing to temporary transient variation the in the propagation path of base station and terminal room.Therefore, short orthogonal code is used in expectation, makes propagation path substantially constant duration of orthogonal code.

3. the frequency and the time quadrature property that make up

Can be pilot transmission frequency of utilization and the combination of time quadrature property.In one embodiment, for bunch in a plurality of sub-districts obtain frequency orthogonal property, be that a plurality of sectors in each sub-district obtain time quadrature property.

Fig. 4 C is depicted as the exemplary sub-band and sign indicating number distribution that 9-sector 3 cell clusters obtain frequency and time quadrature property.Each of three sub-districts in bunch is assigned with different sets of subbands to obtain the frequency orthogonal property of these three minizones.Three sectors of each sub-district also are assigned with three different orthogonal codes to obtain three time quadrature property between the sector.Each sector of each sub-district can be used the orthogonal code of its distribution to send its pilot tone then and also only sent on the subband in the set of distributing to its sub-district.Obtained in this bunch orthogonality then, and avoided interference from the pilot transmission of nine sectors.

Fig. 4 D is depicted as the exemplary sub-band and sign indicating number distribution that 21-sector 7-cell cluster obtains frequency and time quadrature property.。Each of seven sub-districts in bunch is assigned with different sets of subbands.Three sectors of each sub-district also are assigned with different orthogonal codes.Each sector of each sub-district can be used orthogonal code its pilot tone of transmission of its distribution and only on the subband that distributes, sent then.

Can also obtain frequency and time quadrature property with some other modes, and this within the scope of the invention.For example, a plurality of sub-districts can be assigned with identical sets of subbands but different orthogonal codes.As another example, a plurality of sets of subbands can be assigned to a plurality of sectors of same cells, and bunch in different districts can be assigned with different orthogonal codes.

For the system of the sector that has a plurality of antennas, can be pilot transmission acquisition orthogonality in many ways from a plurality of antennas.In one embodiment, each sub-district is assigned with a subband set and closes, and each antenna in the sub-district is assigned with different orthogonal codes.If each sector comprises two antennas, then each sector can be assigned with the pair of orthogonal sign indicating number, illustrates like Fig. 4 B.In another embodiment, a plurality of sectors of sub-district are assigned with different orthogonal codes, and a plurality of antennas of each sector are assigned with different sets of subbands.Identical sets of subbands can be used for all sectors of same cells, and divides the antenna that is equipped with the same sub-band set to be assigned with different orthogonal codes.For example, for the 3-sector cell, each sector comprises two antennas, can two subband set be closed (for example gathering 1 and 2) and distribute to two antennas of each sub-district, and three sectors can be assigned with orthogonal code A, B and C.A sector of sub-district can be assigned with sets of subbands/orthogonal code 1-A and 2-A, and second sector can be assigned with 1-B and 2-B, and the 3rd sector can be assigned with 1-C and 2-C.

4. scrambler

Scrambler can be used for the randomization Pilot Interference and can carry out identify label to the base station.Different scramblers can be assigned to each sector, each sub-district or each bunch.Scrambler can be pseudo random number (PN) sequence or some other unique sequences.Scrambler can be applied to the pilot tone (for example before orthogonal code covers) in the frequency domain, like the following stated.Scrambler can also be applied in the time domain and (for example handle the back at OFDM), should be greater than the OFDM code check with the reserve frequency orthogonality in this situation scrambler speed.The complementary processing then realized to recover pilot tone by the terminal.The scrambler of base station and end with go scrambler to handle following the description.

Fig. 5 illustrates example system layout 500, and wherein different scramblers is assigned to each 7-cell cluster.Each bunch of cloth intra-office drawn with heavy line.Example bunch illustrates with seven shade sub-districts.For this embodiment, seven sub-districts in each bunch are assigned with different sets of subbands (being marked as 1 to 7), and three sectors in each sub-district are assigned with different orthogonal codes (being denoted as A, B and C).Can be identified as the sets of subbands that the sub-district under the sector is distributed in (1) from the pilot transmission of each sector of cloth intra-office, the orthogonal code of sector is distributed in (2), and (3) distribute under the sector bunch scrambler.Other system layouts with different sub-band, orthogonal code and scrambler distribution can also be developed, and this within the scope of the present invention.

Illustrate like Fig. 5, the terminal in the given sector only can receive from other and be assigned with the Pilot Interference with the sector of same sub-band set and same orthogonal code.For example, being marked as that terminal in the sector of 1-A only can receive from the layout internal labeling is the Pilot Interference of other sectors of 1-A.

Each scrambler S _i(n) be the sequence of unique code chip, wherein n is the chip index of sequence.In one embodiment, each scrambler chip is that form does

Complex values, s wherein _i(n) and

Each value can be 1 or-1.In other embodiments, scrambler can be defined with some other modes, and sign indicating number chip value or be real number or for plural.

Scrambler can be realized in many ways, depends on the characteristic of wireless channel.Generally, channel should be on the whole duration that each scrambler chip is employed substantially constant.The substantially invariable time interval of channel is called as coherence time and can representes with τ.The lengths table of orthogonal code is shown T _w, wherein for the 4 chip Walsh sequence T that illustrate in the form 3 _w=4T _Sym

For the first scrambler scheme, if be far longer than the coherence time of channel orthogonal code length (be τ＞＞T _w), then scrambler can be employed on a plurality of orthogonal sequences.Particularly, can be applied to length be T to each scrambler chip _wAn orthogonal sequence on.Identical scrambler chip can be applied to each of K subband being used for pilot transmission.For the example Walsh sequence shown in the form 3, each scrambler chip is applied to four Walsh sign indicating number chips, and said chip is applied to four pilot frequency code elements in four continuous OFDM code element periods, sending.

For the first scrambler scheme, in order to recover the pilot tone from particular sector, the terminal can use orthogonal code and the scrambler of distributing to this sector to realize that it is that scrambler removes scrambler then that orthogonal code goes to cover.The terminal can also realize on all or part of scrambler sequence that coherent integration is to recover pilot tone and to distinguish " channel altogether " sector (promptly be assigned with same sub-band and gather but the sector of different orthogonal sign indicating number and/or scrambler).Coherent integration process refers to the process that a plurality of complex-valued symbols make up with the mode of considering its phase information.

For the second scrambler scheme, if the coherence time of channel is very short, makes the terminal to go up and realize coherent integration that then each scrambler chip can be applied to a quadrature chip at single orthogonal sequence (or a Walsh code element).Identical or different scrambler chip can be used for K pilot subbands.For example, for the example that illustrates in the form 34 chip Walsh sequences, scrambler can be used the definition of 4-K length.The one K scrambler chip can be used for K pilot subbands of a Walsh sign indicating number chip; Next K scrambler chip can be used for K pilot subbands of the 2nd Walsh sign indicating number chip; Then K scrambler chip can be used for K pilot subbands of the 3rd Walsh sign indicating number chip, and last K scrambler chip can be used for the 4th and K pilot subbands of Walsh sign indicating number chip at last.

For two kind of second scrambler scheme, identical scrambler sequence can be used by all base stations that will obtain time quadrature property.Scrambler provides randomize pilot interference.Because identical scrambler sequence used by a plurality of base stations, each base station can be by the orthogonal code sign of its distribution, possibly be scrambler with and the sets of pilot subbands of distribution.

For the scrambler scheme, in order to recover pilot tone, the terminal can be estimated for each pilot subbands derives pilot tone, be described below.Receiver then can (1) estimates to obtain each channel response estimation of a plurality of pilot tones and data subband based on the pilot tone of all K pilot subbands; And (2) obtain to receive pilot power and estimate that this is the quadratic sum of the pilot tone estimation amplitude of all K pilot subbands.The processing that carry out pilot tone at the terminal is described in detail as follows.

II. pilot transmission schemes

Pilot tone can be sent on down link to make things convenient for pilot detection and channel estimating by the base station in every way.Pilot detection can be used to make things convenient for system synchronization (frequency is obtained with timing), direct-cut operation and soft handover.Channel estimating can be used to make things convenient for the coherence data demodulation.Form 4 is listed four example pilot transmission schemes of multi-carrier communications systems

Form 4

For the pulse guide-frequency structure, each sector at the appointed time at interval or time slot (rather than continuously) send its pilot tone with impulse form.Pilot tone and data can be sent with time division multiplexing (TDM) mode in each sector.For the CP continuous pilot structure, each sector is sent its pilot tone continuously on its sets of pilot subbands that is assigned with.Data can be sent not specifying on the available subband of the residue that is used for pilot transmission in each sector.

For synchro system, the timing of all sectors of all sub-districts is synchronized (for example based on gps time or some other public timing resources) in the system.For asynchronous system, all sectors of each sub-district regularly can be synchronized, but the timing of different districts is asynchronous in the system.

For the lock-out pulse pilot transmission schemes, sector and sub-district are synchronous in the system, and in identical assigned timeslot with its pilot tone of pulsing.For this scheme, all sectors are sent its pilot tone simultaneously, but pilot tone through the set that separates of using pilot subbands and/or orthogonal code orthogonalization.Data are not during the pilot transmission period, to be sent out.The terminal can obtain higher-quality channel estimating for different sectors, because do not receive any interference from transfer of data.And, the channel estimating of given sector can be further interference through the pilot tone of sending by other sectors on the collection that offsets comfortable same pilot subband improve, wherein used interference cancellation technology as described below.

Fig. 6 A illustrates the transmission from the pilot tone of a plurality of sectors of lock-out pulse pilot transmission schemes.For this scheme, the sector is at the pulse T of specific duration _PilotSend its pilot tone on the sets of subbands that the inherence separates, interpulse specified time interval is T _IntAs pointing out in Fig. 6 A that the timing of sector is synchronous, make pilot pulse roughly locate it in its transmission time.Data can be sent in all available subbands in the time interval between pilot pulse in each sector.(for succinctly, frequency and time are not to draw in proportion in Fig. 6 A and Fig. 6 B).

For synchronous CP continuous pilot transmission plan, intrasystem sector and sub-district are synchronous, and its pilot tone of transmission on the sets of pilot subbands is being specified continuously in each sector.For this scheme, can further pass through to use the different orthogonal sign indicating number and quadrature from the pilot tone of different sectors.For each sector, data are not sent on the sets of subbands of pilot transmission appointment.

Fig. 6 B illustrates in the synchronous CP continuous pilot transmission plan pilot transmission from a plurality of sectors.For this scheme, the sector is sent its pilot tone continuously on the sets of subbands that separates.Each sector can not be to specify on other subbands that are used for pilot transmission to send data.Illustrate like Fig. 6 B, the timing of sector is synchronous.

For the asynchronous pulse pilot transmission schemes, the sets of pilot subbands separate with its pilot tone of pulsing, and is used in intrasystem sector in assigned timeslot.Sector in each sub-district can be further through using its pilot tone of different orthogonal sign indicating number orthogonalization.Yet, because the sub-district is without synchronously, from the pilot tone of different districts can be at the different time place incoming terminal, the search to these pilot pulses need be realized in the terminal.And, because the sub-district is without synchronously, possibly disturb with pilot transmission from the sector of other sub-districts from the transfer of data of sector in the sub-district, vice versa.

For asynchronous CP continuous pilot transmission plan, intrasystem sector and sub-district are not synchronous, and its pilot tone of transmission on the sets of pilot subbands is being specified continuously in each sector.Equally, the sector in each sub-district can be through using its pilot tone of different orthogonal sign indicating number orthogonalization.Because the sub-district is without synchronously, the terminal can need the sequential of definite each sector of recovering.

For the lock-out pulse pilot transmission schemes, the minimal degradation that the pilot tone of each sector experience is disturbed from cochannel is promptly from the interference that is assigned with other sectors of same pilot subband and orthogonal code.For synchronous CP continuous pilot transmission plan, the pilot tone of each sector experience cochannel disturbs the deterioration that causes, said interference is because the transfer of data of adjacent sectors on this pilot subbands causes.For asynchronous pulse/CP continuous pilot transmission plan; The pilot tone experience of each sector is disturbed the deterioration that causes from cochannel; Said interference is owing to disturb between the transfer of data loading wave that causes of asynchronous OFDM symbol timing cause that wherein inter-carrier interference does not exist under no multipath situation.

Handle in following detailed description at the receiver of end for each of these pilot transmission schemes.

No matter the pilot transmission schemes of selecting for use, pilot subbands can be assigned to the sector in every way.In one embodiment, distributing to each sector carries out the sets of subbands of pilot transmission and fixes.In another embodiment, each sector is in the different sub-band set at different time-gap and sends its pilot tone.This embodiment can allow the terminal to obtain the channel estimating of better sector.

III. system

Fig. 7 illustrates the embodiment block diagram of multi-carrier communications systems 100 interior base station 110x and terminal 120x.For succinctly, base station 110x is that an antenna is realized handling and comprising in a sector.

On down link, the 110x place in the base station, emission (TX) data processor 714 receives traffic data and slave controller 730 reception signalings and other data from data source 712.The format of the 714 pairs of data of TX data processor, coding, intersect and modulation (being symbol mapped) so that data modulation symbols or data symbols only to be provided.Modulator (MOD) 720 receives and with multiplexed these data symbols of pilot frequency code element, realizes the processing of requirement, and OFDM is provided stream.The processing of modulator 720 is described as follows.Transmitter unit (TMTR) 722 is handled the OFDM stream then so that down link signal to be provided, and they send to the terminal from antenna 724 subsequently.

The 120x place at the terminal, a plurality of base stations are that the down link signal that send a plurality of sectors is received by antenna 752.The signal that receives is handled (for example amplification, filtering, frequency down conversion and digitlization) so that sampling to be provided through receiver unit (RCVR) 754.Demodulator (DEMOD) 760 thinks that to handle sampling with the complementary mode of modulator 720 realizations the sector of recovery provides pilot frequency intensity to estimate and data symbols is estimated then.Receive (RX) data processor 762 and further handles (for example code element is gone mapping, gone to intersect and decoding) data symbols and estimate so that data after the decoding to be provided, these data are provided for data sink 764 then and store and/or offer controller 770 and further handle.

The processing of up link maybe be identical or different with the processing of down link.Data and signaling are handled (for example encode, intersect and modulate) so that data symbols to be provided by TX data processor 784, said code element and pilot frequency code element multiplexed and further by modulator 790 processing so that transmit symbol to be provided.Modulator 790 can be realized OFDM processing, CDMA processing etc., and this depends on the specific modulation technology that is used for up link.Transmitter unit 792 is further handled transmit symbol to generate uplink signal, and said signal is sent out from antenna 752 then.

The 110x place in the base station come the uplink signal of self terminal to be received by antenna 724, and the signal that receives is handled so that sampling to be provided by receiver unit 738.Sampling is further handled to provide data symbols to estimate by demodulator 740, and said estimation is further handled with data after the decoding that each terminal that is resumed is provided by RX data processor 742.Decoding back data can be provided for data sink 744 to store and/or to offer controller 730 with further processing.

Controller 730 and 770 is controlled at base station and the corresponding various processing unit operation of end.Data and program code that memory cell 732 and 772 storages are used by controller 730 and 770 respectively.

1. base station pilot is handled

Fig. 8 illustrates the block diagram of the embodiment of modulator 720.In this embodiment, pilot transmission occurs on K the sets of pilot subbands that is assigned to i sector.Pilot frequency code element is used N _wThe Walsh sign indicating number W of chip _i(n) cover and with the scrambler S that distributes to i sector _i(n) scrambler.

Generally, identical pilot frequency code element can be used for all pilot subbands or different pilot frequency code element can be used for different pilot subbands.Pilot frequency code element is based on the modulated symbol (said scheme such as BPSK, QPSK or M-QAM) that certain modulation schemes derives, i.e. the complex values of any in the signal constellation which of corresponding modulating scheme.And identical pilot frequency code element can be used by all sectors, or different pilot frequency code element can be used by different sectors.In one embodiment, be M in the system M the pilot frequency code element set that available subband definition is specific.The pilot frequency code element that use each sector depends on the sets of pilot subbands of distributing to this sector.In any case there is the priori of the pilot frequency code element that use the sector in the system at the terminal in the system.

In modulator 720, by the pilot frequency code element p of i sector transmission _i(n) be provided for demultiplexer (Demux) 812 and be decomposed into K pilot frequency code element stream of K pilot subbands by multichannel.For each OFDM code element period, identical pilot frequency code element can be launched on all K pilot subbands, and perhaps K pilot frequency code element set can be sent on K pilot subbands.Under any circumstance, each of K pilot frequency code element stream is provided for corresponding TX pilot subbands processor 820, and this processor is that the pilot subbands of its distribution is handled pilot frequency code element.

In each TX pilot subbands processor 820, the pilot frequency code element p of k the pilot subbands that is assigned with _{I, k}(n) be provided for complex multiplier 822 and multiply by the scrambler segmentation S of k pilot subbands _{I, k}(n).Scrambler can accomplished in various ways.For example, scrambler can be so that each scrambler chip be applied to each the whole Walsh sequence W of (1) K pilot subbands _i(n) (for the first above-mentioned scrambler scheme); (2) a Walsh sign indicating number chip in a pilot subbands (for the second above-mentioned scrambler scheme); (3) a Walsh sign indicating number chip of all K pilot subbands, or some other the combination of (4) Walsh sign indicating number chip and pilot subbands.

K TX pilot subbands processor 820a can be identical or different to K segmentation of the scrambler chip of 820k use, and this depends on the specific scramble codes scheme of realization.For the first scrambler scheme, identical scrambler sequence is used for each of K pilot subbands, and each scrambler chip is applied to N _wIndividual CP continuous pilot code element, this is through at N _wKeep the constant realization of scrambler chip on the individual continuous OFDM code-element period.For the second scrambler scheme, scrambler sequence S _i(n) be divided into K scrambler segmentation (for example as above describing), segmentation of each of K pilot subbands for the second scrambler scheme.Each scrambler chip is applied to a pilot frequency code element of a pilot subbands then.

Be provided for multiplier 824 then also with Walsh sign indicating number W from pilot frequency code element behind the scrambler of multiplier 822 _i(n) cover.This covering is through will be at N _wThe N that sends in the individual continuous OFDM code element period _wIndividual scrambler pilot frequency code element multiply by Walsh sign indicating number W _i(n) N _wIndividual chip multiplies each other and realizes, wherein for the example Walsh sign indicating number that illustrates in the form 3, N _w=4.The pilot frequency code element that covers is used gain G by multiplier 826 then _PilotCarry out proportional zoom, this has confirmed to be used for the amount of transmission power of pilot transmission.Generally, total transmitting power P of each sector or each antenna _TotalReceive the constraint of code requirement for example and/or power amplifier restriction.This total transmitting power P _TotalPart be that pilot transmission is distributed, and remaining power can be used for transfer of data.The power of amount P that is used for pilot transmission _PilotSelection can minimize the Pilot Interference of other sectors simultaneously so that quicken the pilot detection at terminal in the sector/obtain to transfer of data.Pilot power P _PilotCan be fixing or variation, and gain G _PilotBased on pilot power P _PilotConfirm.Be provided for MxN switch 848 then from K TX pilot subbands processor 820a pilot frequency code element after the processing of 820k.

For nearly (M-K) the individual subband that will be used for transfer of data, be by the data symbols d of i sector transmission _i(n) be provided for demultiplexer 832 and be decomposed into nearly (M-K) individual data code element stream by multichannel.Each data symbols also is based on the modulated symbol (said scheme such as BPSK, QPSK or M-QAM) that certain modulation schemes derives.Identical or different modulation scheme can be used for pilot tone or data symbols.Each data symbols stream is provided for corresponding TX data subband processor 840, the data subband deal with data code element of said processor for distributing.Each processor 840 can be realized Walsh covering, scrambler, proportional zoom, some other processing or not do any processing.Also be provided for switch 848 from (M-K) individual data subband processor 840a data symbols after the processing of 840q.

848 pairs of switchs make these code elements be provided for the pilot tone and the data subband of its appointment from pilot frequency code element after the processing of K TX pilot subbands processor 820 and from data symbols ordering after the processing of (M-K) individual TX data subband processor 840.Switch 848 also is provided as zero signal value to each untapped subband.For each OFDM code element period, switch 848 anti-fast Flourier inversionization (IFFT) unit 850 provide N the output symbol set (comprise and handle back pilot tone and data symbols and zero) of N total subband.

In IFFT unit 850, the N of each OFDM code element period code element uses invert fast fourier transformation to be switched to time domain to obtain to comprise " conversion " back code element of N time-domain sampling.In order to eliminate the inter symbol interference (ISI) that frequency selective attenuation causes, the part of code element is repeated to form corresponding OFDM code element by Cyclic Prefix generator 852 after each conversion, and this comprises N+C _pIndividual sampling, wherein C _pIt is the hits of repetition.The part that repeats is commonly called Cyclic Prefix.The duration of a corresponding OFDM code element of OFDM code element period.Cyclic Prefix generator 852 provides OFDM stream for transmission on an antenna.

If the sector has a plurality of antennas, then can realize identical pilot tone processing as shown in Figure 8 to each antenna.Particularly, the pilot frequency code element of each antenna covers with the Walsh sign indicating number, uses the scrambler scrambler, and is multiplexed on K the sets of pilot subbands distributing to this antenna.The special pilot transmission plan that depends on realization can be distributed to the identical or different Walsh sign indicating number of a plurality of antennas, can use identical or different scrambler to antenna, and can use identical or different sets of subbands for antenna.Data symbols can be handled on a plurality of antennas, to transmit, like what in aforesaid U.S. Provisional Patent Application sequence number 60/421309, describe according to STTD or Alamouti scheme.

2. the terminal pilot tone is handled

Fig. 9 A illustrates the embodiment block diagram of demodulator 760a, and this demodulator can be used for aforesaid lock-out pulse pilot transmission schemes, wherein the sector in assigned timeslot with its pilot tone of pulsing.For each pilot pulse, demodulator 760a can realize handling to recover the pilot tone from a plurality of sector transmission.

In demodulator 760a, the OFDM code element that receives is provided for cyclic prefix removal unit 912, and it has removed the Cyclic Prefix that invests on each OFDM code element to obtain the corresponding code element after the conversion that receives.FFT unit 914 receives conversion back code element with each then and is transformed into frequency domain and receives code element with N of obtaining N total subband.NxM switch 916 provides the code element that receives of each K sets of pilot subbands to K RX pilot subbands processor 920aa to the corresponding set 918 of 920ak, and wherein each pilot subbands in the pair set has a processor 920.For the lock-out pulse pilot transmission schemes, separating on the sets of subbands from a plurality of sectors reception pilot tones.RX pilot subbands processor sets can be used to each sector that will recover then and realizes the pilot tone processing.(for example from different districts or bunch) can be with the transmission of different orthogonal sign indicating number in the same sub-band set because a plurality of sectors, and a plurality of RX pilot subbands processor sets can also be used to handle given sets of pilot subbands.For succinctly, in Fig. 9 A, a RX pilot subbands processor sets only is shown for each sets of pilot subbands.

The pilot tone at terminal is handled the pilot tone that realizes with the sector and is handled complementation, and further depends on the characteristic of channel.In order to improve the pilot detection performance and to distinguish the pilot tone that send different sectors better, expectation can realize coherent integration on OFDM code element period as much as possible and pilot subbands as much as possible.Yet the amount of the coherent integration that in time domain and frequency domain, realizes depends on the coherence time and the coherence bandwidth of channel respectively.Particularly, the duration of coherent integration (promptly can realize the OFDM code element number of coherent integration above that) should be less than the coherence time (being the substantially invariable duration of channel) of channel.And comprising can be by coherently the frequency range of the subband of interpolation should be less than the coherence bandwidth of channel.Coherence bandwidth is the substantially invariable frequency band of channel within it, and relevant with the time delay expansion of channel.

The pilot tone that illustrates in Fig. 9 A is handled and on single Walsh code element period and single pilot subbands, is realized coherent integration.For succinctly, the pilot tone of given sector i is handled following the description.In being used for each RX pilot subbands processor 920 of sector i, k the pilot subbands that is assigned with receive code element r _k(n) be provided for multiplier 922, and multiply by the Walsh sign indicating number W of this sector i _i(n).The code element of going to cover is provided for complex multiplier 924 then and multiply by the complex conjugate S of scrambler chip _{I, k} ^*(n), it is used for k subband in n OFDM code element period by sector i.Go the mode of scrambler realization and the scrambler complementation that sector i realizes.For the first scrambler scheme, each scrambler chip is through keeping the scrambler chip at N _wThe individual continuous OFDM code element period goes up constant and is applied to N _wIndividually go to cover code element continuously.For the second scrambler scheme, a scrambler segmentation is used for each of K pilot subbands, and of in a pilot subbands, being applied to from multiplier 922 of each scrambler chip goes to cover code element.Going the scrambler code element to be provided for complex multiplier 926 then and multiply by the complex conjugate p of pilot frequency code element from multiplier 924 _{I, k} ^*(n), this pilot frequency code element is sent on k subband by sector I in n OFDM code-element period.Output from multiplier 926 is added up on each Walsh code element period so that the pilot tone estimation

of this Walsh code element period to be provided by accumulator (ACC) 928 then

Multiplier 922,924 and 926 (is 1/T with the operation of OFDM chip rate _Sym).Accumulator 928 is realized adding up with the OFDM chip rate, but for each Walsh code element period provide pilot tone estimate and each Walsh code element period begin be eliminated.Filter 930 (is 1/T with unit 932 with the operation of Walsh chip rate _w, or be 1/4T for 4 chip Walsh sequences _Sym).

From the accumulator 928 pilot estimates?

can be further filtered by the filter 930 to the sector i provides the k th sub-band pilot channel estimation?

filter 930 can be used accumulators, finite impulse response (FIR) filter control, infinite impulse response (IIR) filter or some other type filter implementation.Calculation unit 932 from the accumulator 928 pilot estimates? i squared amplitude distribution sector that the k-th band provides pilot strength estimate?

For each OFDM code element period of pilot transmission; The pilot frequency intensity of all K pilot subbands of summer 934 reception sector i is estimated

and to its summation with the pilot frequency intensity that obtains this OFDM code element period estimate

accumulator 938 add up then on the part or all of pilot transmission gap pilot frequency intensity is estimated thinks that sector i for example provides that final pilot frequency intensity is estimated

, accumulator 938 can be realized adding up in whole pilot pulse.Accumulator 928 is realized coherent integration and accumulator 938 realization non-coherent integrations.

If allow the coherence time of wireless channel, coherent integration can also realize on a plurality of Walsh code element periods.In this case, the pilot tone of a plurality of Walsh code element periods is estimated to be added up (for example through accumulator 928), and the estimation that produces can be provided for filter 930 and 932.If the coherence bandwidth of wireless channel allows, coherent integration can also realize (for example some or all of K pilot subbands) on a plurality of pilot subbands.In this case, can be for many pilot subbands add up, amplitude square is estimated (for example through unshowned accumulator in another Fig. 9) and offered summer 934 from the pilot tone of accumulator 928.The frequency range that comprises pilot subbands should wherein realize coherent integration less than the wireless channel coherence bandwidth on this frequency range.Can realize the pilot frequency intensity estimation of coherent integration in the frequency domain, obtain channel estimating but be generally single subband to be improved.If the coherence time of wireless channel and coherence bandwidth allow, coherent integration can also realize on a plurality of Walsh code element periods and a plurality of pilot subbands, estimates with the pilot frequency intensity that improvement is provided.

Above-mentioned pilot tone is handled the channel estimating of K the pilot subbands that sector i is provided.The channel estimating of the residue M-K of a sector i subband can obtain based on the channel estimating (for example inserting through interior) of K the pilot subbands of sector i.Describe in U.S. Patent Application Serial Number 60/422362 and 60/427896 estimate the technology of channel estimating based on all M subbands of the channel estimating of K subband; The former is entitled as " ChannelEstimation for OFDM Communication Systems "; Be filed on October 29th, 2002; The latter is entitled as " Reduced Complexity Channel Estimation for WirelessCommunications Systems "; Be filed on November 19th, 2002, both are transferred assignee of the present invention and are comprised as a reference at this.Signal is estimated to be used for data demodulates and other purposes.

The channel estimating whole or a subclass of the M of sector i available subband can be used to the transfer of data that i receives from the sector and realizes the coherence data demodulation.Can also obtain channel estimating for intrasystem a plurality of sectors.For each sector, pilot tone is handled the Walsh sequence W that uses with this sector _i(n), scrambler S _i(n) and pilot frequency code element p _i(n) realize.

Above-mentioned pilot tone is handled the pilot frequency intensity that sector i also is provided and is estimated.Pilot frequency intensity is estimated and can be obtained for intrasystem a plurality of sectors.The pilot frequency intensity of a plurality of sectors estimates can be used for confirming to receive the best sector of transfer of data, to switch to another sector (for example for portable terminal) and other purposes of possibility from a sector.

For the lock-out pulse pilot transmission schemes, demodulator 760a only realizes the pilot tone processing in the time slot that pilot tone is sent by the sector.The channel estimating of one or more sectors can be used for the coherence data demodulation of the transfer of data that realization receives from one or more sectors in the period between pilot pulse.

Fig. 9 A illustrates example pilot tone treatment technology, and this technology can be realized by the terminal.Can also use other pilot tone treatment technologies, and this within the scope of the present invention.For succinctly, in Fig. 9 A, only show the pilot tone processing of demodulator 760a.Data processing can be realized with mode as described below by demodulator 760a.

Fig. 9 B illustrates the embodiment block diagram of demodulator 760b, and this can be used for above-mentioned synchronous CP continuous pilot transmission plan, and wherein pilot tone is sent continuously in each sector in it specifies sets of pilot subbands, and on remaining subband, sends data.In the following description, demodulator 760b recovers pilot tone and the data by given sector i transmission.

In demodulator 760b, the OFDM code element that receives is handled by cyclic prefix removal unit 912 and FFT unit 914 in the above described manner.Switch 916 provides the code element that receives of K pilot subbands to K RX pilot subbands processor 920a to 920k then, and the code element that provides M-K residue subband to receive to 940q to M-K Pilot Interference canceller 940a.

The mode that each RX pilot subbands processor 920 is described with Fig. 9 A is the pilot tone processing that sector i realizes a pilot subbands.Yet; Because the pilot subbands of sector i can be by other sectors as data subband; Coherent integration can realize on longer time slot that (for example a plurality of Walsh code element period) is to offset the interference that causes owing to other sectors of data code elements; Determine coherence time by channel to obtain

the coherent integration time slot of pilot tone estimation more accurately, and should be less than this coherence time.

In each RX pilot subbands processor 920, multiplier 922,924 and 926 (is 1/T with the operation of OFDM chip rate _Sym) and the Walsh sequence W of realization and sector i _i(n), scrambler S _i(n) and pilot frequency code element p _i(n) multiplication.Accumulator 928 adds up with OFDM chip rate operation and on one or (best) a plurality of Walsh code element periods and thinks that from the output of multiplier 926 each gap of adding up provides pilot tone to estimate that

filter 930 is to add up th rate and filter that pilot tone is estimated and can further be processed (slotting for example) channel estimating with the acquisition data subband with the channel estimating of channel estimating

all K pilot subbands of k subband that sector i is provided, as stated.Unit 932, adder 934 and accumulator 938 also are that sector i provides pilot frequency intensity estimation with the th rate that adds up

For the CP continuous pilot transmission plan, demodulator 760b can handle in the free pilot tone that realizes of institute during communication session.The channel estimating of sector i can be used to be implemented in the coherence data demodulation of the transfer of data that receives on the data subband from sector i.Data processing can realize as follows.

For succinctly, have only the set of one K RX pilot subbands processor 920 and being integrated in Fig. 9 B of a M-K Pilot Interference canceller 940 to illustrate.Demodulator 760b can also use a plurality of RX pilot subbands processor sets and the set of a plurality of M-K Pilot Interference canceller to realize, to handle pilot tone and the transfer of data from a plurality of sectors with setting out.

Demodulator 760a and 760b can also be used to above-mentioned asynchronous pulse/CP continuous pilot transmission plan and realize the pilot tone processing.If the sector is asynchronous, then the terminal can need the timing of definite each sector that will recover.This can obtain through using (sliding) correlator that slides, and it is used that this is similar to cdma system.Then, the processing of each sector can realize according to the timing of this sector.Particularly FFT operation, Walsh sequence W _i(n) remove to cover and use scrambler S _i(n) the scrambler that goes is all realized according to the timing of the sector that will recover.And; Coherent integration can on the longer time period, realize (for example a plurality of Walsh code element period) to offset because the interference that the data symbols that send other sectors causes makes that pilot tone is estimated

for the sector that will recover obtains more accurately

For the asynchronous pulse pilot transmission schemes, the pilot tone of each sector handle can realize as follows (1) in the time slot when pilot tone is sent by the sector, realize and (2) based on the timing realization of this sector.For asynchronous CP continuous pilot transmission plan, the pilot tone of each sector is handled and can be realized if having time in institute based on the timing of this sector.

3. the terminal Pilot Interference offsets

As stated, the pilot transmission from sector in the system can be so that the subband that the pilot transmission of given sector i is used can also be used for the pilot transmission of other sectors.For this sector i, represent an interference from the pilot transmission of other sectors on its pilot subbands, if said interference is offseted effectively, can improve channel estimating and the pilot frequency intensity of this sector i and estimate.And the subband that sector i is used for transfer of data can also be used for the pilot transmission (for example for the CP continuous pilot transmission plan) of other sectors.For this sector i, on its data subband, represent an interference from the pilot transmission of other sectors, if being cancelled effectively, said interference can improve data performance.

For example, the terminal can be from the sector 1 receives transfer of data, the pilot tone of sector 1 on sets of subbands 1, sends (for example for the subband 10,20,30 of the example ofdm system that illustrates in form 2 and Fig. 2 B ... 500).The pilot tone that send other sectors is also known at this terminal.Some of these pilot tones can not be sent out on sets of subbands 1, and for example adjacent sectors 2 possibly gone up in sets of subbands 2 (for example subband 11,21,31...501) and send pilot tone.General sector 1 uses the terminal of nearly all not available subband in sets of subbands 1 in its overlay area to send data.Therefore, the subband (can be used for pilot transmission by sector 2) in the set 2 can be by sector 1 as data subband.Pilot transmission on the subband in the set 2 that use sector 2 can become the interference of sector 1 to transfer of data on these same sub-band.

The terminal generally knows that the pilot transmission of sector 2 on sets of subbands 2.Therefore, the terminal can be estimated from subband in set 2 from the Pilot Interference of sector 2.Pilot Interference is estimated to obtain in the following manner (1) and is estimated 2 channels to the terminal of gathering each subband in 2 from the sector; (2) serve as that each subband in the set 2 generate the pilot frequency code element of handling back (promptly through scrambler and covering) with the same way as that realizes like sector 2, and (3) pilot frequency code element after with channel estimating these being handled carry out proportional zoom.The Pilot Interference of each subband is estimated to deduct the code element with the pilot tone that obtains this subband from receiving of same sub-band then to offset the back code element in the set 2 of sector 2.

Generally, can carry out downlink pilot or transfer of data when also being used for the pilot transmission of down link of another sector being used for a sector arbitrarily, realize that Pilot Interference offsets, wherein said pilot tone is that the terminal is known.Generally, the pilot tone that send another sector can be known in the terminal, because this information is used to make things convenient for auxiliary switching the in terminal between the sector.The pilot power that the terminal general measure receives from its current service sector and are the pilot tones that the sector receives of closing on of handoff candidate from other.Pilot power is measured the sector that can be used to ask to switch to better services then by the terminal.

Pilot Interference offsets can be for pilot subbands realizes estimating to obtain higher-quality pilot tone, owing to from other sectors the interference that this pilot tone causes is removed.For example, for the lock-out pulse pilot transmission schemes, all sectors are sent its pilot tone simultaneously, in this case, can realize that Pilot Interference offsets with the channel estimating after the improvement that obtains selected sector.Pilot Interference offsets and can also realize estimating to obtain higher-quality data symbols for data subband, has wherein removed from the interference of other sector pilot tones to this pilot tone.For succinctly, below pilot cancellation is described for data subband.

Get back to Fig. 9 B, (M-K) each the code element that receives of data subband is provided for corresponding Pilot Interference canceller 940.Each canceller 940 estimation terminal estimates that from the pilot tone that each interference sector receives said interference is designated will to be offseted.Each canceller 940 (1) then specifies interference sectors to obtain total Pilot Interference for all to estimate, and (2) offset from the total Pilot Interference that receives code element and estimate, thinks that the data subband of distribution provides pilot tone to offset the back code element.

Figure 10 illustrates the embodiment block diagram of Pilot Interference canceller 940x, and this Pilot Interference canceller 940a that can be used for Fig. 9 is to each of 940q.Pilot Interference offsets in frequency domain and realizes after the FFT.Canceller 940x is that a data subband realizes that Pilot Interference offsets.

In Pilot Interference canceller 940x, the code element that receives of the subband that is assigned with is provided for L Pilot Interference estimator 1020a to 10201, wherein L can be any zero or bigger integer.Each estimator 1020 is estimated to bring the Pilot Interference from j the interference sector that is assigned with up at k the son that distributes, and will offer Pilot Interference estimation

for the subband and the sector of its distribution

In each estimator 1020, k the subband that is assigned with receive code element r _k(n) be provided for multiplier 1022 and multiply by the Walsh sign indicating number W that j interference sector uses _j(n).The complex conjugate S of scrambler chip is multiply by in the output of multiplier 1022 then by complex multiplier 1024 _{I, k} ^*(n), said scrambler is used for k subband by j interference sector.The code element behind the scrambler of going from multiplier 1024 multiply by the complex conjugate p of pilot frequency code element then by multiplier 1026 _{I, k} ^*(n), said code element is sent on k subband by j interference sector.

The output from the multiplier 1026 and 1028 by the accumulator at each Walsh symbol period that accumulate on the Walsh symbol period of the k-th sub-band to provide the pilot estimates?

from the pilot accumulator 1028 estimates further by the filter 1030 the k th sub-band filter that provides the j-th interfering sector channel estimation?

filter 1030 can be used accumulator, FIR filter or IIR filter implementation.The response of filter 1030 (for example adding up the duration) can be depended on the speed of fading channel.

In order to be the estimation of j interference sector derivation Pilot Interference

J the pilot frequency code element p that use the sector _{I, k}(n) scrambler chip S multiply by by multiplier 1034 in (1) _{I, k}(n), (2) are by multiplier 1036 usefulness Walsh sign indicating number W _j(n) cover, and channel estimating multiply by by multiplier 1038 in (3) Estimate to estimate with the total Pilot Interference that obtains k subband by summer 1042 summations then from the Pilot Interference of all estimators that are assigned with 1020

Total Pilot Interference is estimated

Then by the code element r of summer 1044 from receiving _k(n) deduct in the pilot tone that obtains k subband and offset the back code element.

Get back to Fig. 9, the offseting the back code element from Pilot Interference canceller 940a to the pilot tone of 940q and offered M-K RX data subband processor 980a respectively of M-K data subband to 980q.Each processor 980 is handled pilot tone for the data subband that distributes and is offseted the back code element, the complementation that its processing mode and Fig. 8 inner treater 840 are realized.Each processor 980 can also be realized the coherence data demodulation with the dot product of the channel estimating of the data subband of distribution through the code element after calculating pilot tone and offseting, with provide data symbols estimation

they are estimations of the data symbols of on this subband, sending.The channel estimating of i the sectors of data subband that recovers can be based upon the channel estimating of pilot subbands acquisition and derive (inserting in for example using).

Multiplexer 990 receive then from RX data subband processor 980a to the data symbols of 980q and it is carried out multiplexed, with i the sectors of data symbol estimation

that recovery is provided

Above-mentioned Pilot Interference cancellation techniques can directly expand to a plurality of reception antenna situation of end.In this case, can realize identical pilot tone processing for the signal that receives that obtains from each terminal antenna.The pilot tone of each antenna offsets the back code element can also further carry out coherent demodulation so that the data symbols estimation of this antenna to be provided with channel estimating.Estimate that from the data symbols of all antennas also combination is to provide the final data symbol estimation through weighting then, said symbol estimation is decoded then.

Above-mentioned pilot transmission and Pilot Interference cancellation techniques can be realized by variety of way.For example, the pilot transmission at access point place handle pilot detection with end offset processing with Pilot Interference can be with hardware, software or the interior realization of its combination.Realize for hardware, be used to transmission and handle pilot tone and be used for the element that Pilot Interference offsets and can in following element, realize: one or more application-specific integrated circuit (ASIC)s (ASIC), digital signal processor (DSP), digital signal processing appts (DSPD), programmable logic device (PLD), field programmable gate array (FPGA), processor, controller, microcontroller, microprocessor and other are used to realize in the electronic unit of above-mentioned functions or its combination.

Realize that for software pilot transmission/receptions and Pilot Interference offset processing can realization in the module that realizes function described here (for example process, function etc.).Software code can be stored in memory cell interior (the for example memory cell 732 and 772 in Fig. 7) and carry out (for example controller 730 and 770) by processor.Memory cell can be implemented in the processor or processor outside, externally under the situation, it can arrive processor through variety of way communicative couplings known in the art.

Title is comprised at this and is used for reference and is used for helping some chapters and sections of location.These titles are not to be used to limit the notion of describing under the title, and these notions can be applied to other chapters and sections of whole explanation.

Those skilled in the art is further appreciated that the described various illustrative logical blocks of combination the embodiments described herein, module and the algorithm steps of announcement can use electronic hardware, computer software or both combinations to realize here.As various illustrative assemblies, square frame, module, circuit and the step 1 according to its functional elaboration.These are functional realizes certain applications program and the design of depending on that whole system adopts as hardware or software actually.The technical staff can recognize the interactivity of hardware and software under these situation, and the said function that how to realize each application-specific best.

The description of above-mentioned preferred embodiment makes those skilled in the art can make or use the present invention.The various modifications of these embodiment are conspicuous for a person skilled in the art, and the General Principle of definition can be applied among other embodiment and do not exceed scope of the present invention here.Therefore, the embodiment that the present invention is not limited to illustrate here, and will meet and the principle and the novel feature the most wide in range consistent scope that disclose here.

Claims (10)

1. the receiver place in wireless multi-carrier communication system offsets the method for Pilot Interference, it is characterized in that comprising:

Be that a plurality of subbands obtain the code element that receives, the wherein said code element that receives comprises expected symbol that receives from first transmitting entity and the pilot frequency code element that receives from second transmitting entity;

Based on receiving symbol is that said second transmitting entity is derived pilot frequency code element and estimated, wherein said pilot frequency code element estimates it is the estimation of the pilot frequency code element that on a plurality of subbands, receives from said second transmitting entity; And

The pilot frequency code element that from the said code element that receives, deducts said second transmitting entity is estimated to obtain the code element after pilot tone offsets.

2. the method for claim 1 is characterized in that, said derivation and deduct step and separately carry out for each of a plurality of subbands.

3. the method for claim 1 is characterized in that, said derivation comprises:

Obtain the channel estimating of said second transmitting entity, wherein said pilot frequency code element estimated service life channel estimating derives.

4. the method for claim 1 is characterized in that, the expected symbol of said first transmitting entity is a pilot frequency code element.

5. the method for claim 1 is characterized in that, the expected symbol of said first transmitting entity is a data symbols.

6. the method for claim 1 is characterized in that, said derivation comprises:

Each pilot frequency code element and an orthogonal code of a plurality of subbands multiply by pilot frequency code element after the covering that obtains subband mutually, and wherein said orthogonal code is used for pilot transmission by said second transmitting entity; And

The channel estimating of pilot frequency code element and subband after each the covering of a plurality of subbands multiply by the pilot frequency code element that obtains said subband mutually to be estimated.

7. method as claimed in claim 6 is characterized in that, said derivation also comprises:

With each pilot frequency code element and pilot frequency code element after chip from scrambler multiply by the scrambler that obtains said subband mutually of a plurality of subbands, and wherein behind the scrambler pilot frequency code element and orthogonal code multiply by the pilot frequency code element that obtains after the covering mutually.

8. the method for claim 1 is characterized in that, the said code element that receives also comprises the pilot frequency code element that receives from the 3rd transmitting entity, and said method also comprises:

Derive the pilot frequency code element of the 3rd transmitting entity estimates based on the said code element that receives; And

The pilot frequency code element that from the code element that receives, deducts said the 3rd transmitting entity is estimated to obtain the code element after pilot tone offsets.

9. the device in the wireless multi-carrier communication system is characterized in that comprising:

Obtain the device of the code element that receives of a plurality of subbands, the wherein said code element that receives comprises expected symbol that receives from first transmitting entity and the pilot frequency code element that receives from second transmitting entity;

Derive the device that the pilot frequency code element of said second transmitting entity is estimated based on the code element that receives, wherein said pilot frequency code element estimates it is the estimation of the pilot frequency code element that on a plurality of subbands, receives from said second transmitting entity; And

The pilot frequency code element that from the code element that receives, deducts said second transmitting entity is estimated to obtain the device of the code element after pilot tone offsets.

10. the terminal in the wireless multi-carrier communication system is characterized in that comprising:

At least one Pilot Interference estimator; The code element that receives that is used to handle a plurality of subbands is to obtain the pilot frequency code element estimation of said a plurality of subbands; The wherein said code element that receives comprises expected symbol that receives from first transmitting entity and the pilot frequency code element that receives from second transmitting entity, and wherein said pilot frequency code element estimates it is the estimation of the pilot frequency code element that on a plurality of subbands, receives from said second transmitting entity; And

Adder is used for deducting said pilot frequency code element from the code element that receives and estimates to obtain the code element after pilot tone offsets.

Images