Embodiment
" exemplary " this speech is used to refer to " example or illustration as an example, " in this article.Be described as " exemplary " any embodiment herein and be not to be counted as being more preferably or superior than other embodiment.
Fig. 1 shows the exemplary WLAN 100 of the single access point (AP) 110 with a plurality of user terminals of service (UT) 120.Access point 110 is the many antennas stations that are equipped with a plurality of antennas that can be used for the data transmission and receive.Access point also can be known as base station, Node B or some other terms.Each user terminal 120 can be equipped with individual antenna or a plurality of antenna.User terminal also can be known as travelling carriage, subscriber equipment, wireless device or some other terms.
Access point 110 can send multiple-input and multiple-output (MIMO) transmission or send many single outputs of input (MISO) transmission to the single antenna user terminal to many antennas user terminal.Access point 110 can also receive from the MIMO transmission of many antennas user terminal or from single input of single antenna user terminal to export (SIMO) transmission more.A plurality of (N by the reflector place
T) a plurality of (N at transmitting antenna and receiver place
R) mimo channel that forms of reception antenna can be broken down into N
SIndividual space channel, wherein N
S≤ min{N
T, N
R.Can use N
SIndividual space channel sends data concurrently to obtain high-throughput more and/or redundant to send data to obtain bigger reliability.Form by single space channel by the MISO channel that a plurality of transmitting antennas and single receive antenna form.Can use a plurality of transmitting antennas to send data in the mode of improving reliability.Also form by the SIMO channel that single transmitting antenna and a plurality of reception antenna form by single space channel.Can use a plurality of reception antennas to receive data in the mode of improving reliability.
Access point 110 can be fixed station and can be arranged on any position in the WLAN deployment region, and wherein the WLAN deployment region can be one deck, dwelling house, office synthesis, shop of building, building etc.User terminal 120 can spread all over the WLAN deployment region and distribute.Some user terminals (for example, user terminal 120c and 120d) can be positioned at the position near access point 110, and some other user terminals (for example, user terminal 120a and 120b) can be positioned at the position away from access point 110.Each user terminal 120 can be static or move.Typically, in the WLAN deployment region, exist the barrier (for example, wall) that makes the RF Signal Degrade that between access point 110 and user terminal 120, sends.Also may exist other non-natural sign (for example, disturbing) that also can make the RF Signal Degrade.For the sake of simplicity, these barriers and non-natural sign are not shown in Fig. 1.
For to all perhaps multiple users 120 superperformance is provided, a plurality of antennas of access point 110 spread all over the WLAN deployment region and distribute.Access point 110 has L the local antenna 112a to 1121 that is installed on the access point or installs near access point.Usually, L can be zero, 1 or greater than 1, that is, and and L 〉=0.Access point 110 also has M the remote antenna 114a to 114m that is positioned at the diverse location that spreads all over the WLAN deployment region.Remote antenna 114 can be arranged on the different distance place apart from access point 110, with respect to the position, different angle of access point 110, or the like.Usually, M is 1 or bigger, that is, and and M 〉=1.But the sum of the local and remote antenna that access points 110 uses is N
Ap, N
Ap=L+M 〉=2.
Various types of antennas can be used as local antenna 112 and remote antenna 114, and they also are known as access point (AP) antenna.For example, each AP antenna can be cross-pole antenna, dipole antenna, chip aerial (patch antenna) (or chip) etc.Antenna also can be known as antenna element, radiant element etc.Each AP antenna is designed to the working band for WLAN 100 uses.Each AP antenna can also have any radiation diagram (radiationpattern).Can select the antenna type and the radiation diagram of this AP antenna based on the overlay area that each AP antenna is planned.For example, antenna with omnidirectional radiation pattern can be used as near the remote antenna 114d being arranged in the middle of Fig. 1 WLAN deployment region, and the antenna with directional radiation can be used as remote antenna 114a, 114c, 114e and the 114n that is positioned at WLAN deployment region corner.
For the embodiment shown in Fig. 1, each remote antenna 114 is connected to remote front-end (remote front-end RFE) 116 separately, and it carries out Signal Regulation (for example, amplification, filtering etc.) to the RF signal that transmits and receives via this remote antenna.Several embodiment of remote front-end 116 will be described below.The remote front-end 116 that is used for each remote antenna 114 is connected to access point 110 via cable 118.Cable 118 can be to be generally used for the coaxial cable of cable TV or can be the cable of certain other type of supporting to be used for the working band of WLAN 100.Can also come breakdown cable 118 with the communication link of other type (for example, RF, infrared etc.).Remote front-end 116 can reduce because therefore the loss of signal that cable 118 is caused also can improve performance.Usually, for each remote antenna 114, can or can not use remote front-end 116.
Can arrange and select to be used for the local and remote antenna of access point 110 in every way.The several exemplary configuration of local and remote antenna will be described below.Also use description to select antenna to carry out the several exemplary embodiment that data send below.
Fig. 2 A shows the access point 110a that does not have local antenna but have a plurality of (M>1) remote antenna 114a to 114m.Access point 110a is an embodiment of access point 110 among Fig. 1, and has the N that can be used for the data transmission and receive
Ap=M antenna.Each remote antenna 114 is connected to access point 110a via remote front-end 116 that is associated and cable 118.For the embodiment shown in Fig. 2 A, each remote antenna 114 is connected in the access point 110a power detector (Power Det) 290 separately.Each power detector 290 is measured the power of the RF signal that is received by associated antennas and is provided power measurement values to controller 220.Controller 220 uses from the power measurement values of all power detectors 290 and selects to be used for the antenna that data send and receive.
Fig. 2 B shows the access point 110b with single (L=1) local antenna 112 and a plurality of (M>1) remote antenna 114a to 114m.Access point 110b is another embodiment of access point 110 among Fig. 1, and has the N that can be used for the data transmission and receive
Ap=M+1 antenna.For the embodiment shown in Fig. 2 B, each in M+1 antenna is connected to the power detector separately 290 in the access point 110.Controller 220 receives from the power measurement values of all power detectors 290 and selects to be used for the antenna that data send and receive.
Fig. 2 C shows the access point 110c with a plurality of (L>1) local antenna 112a to 1121 and a plurality of (M>1) remote antenna 114a to 114m.Access point 110c is the another embodiment of access point 110 among Fig. 1, and has the N that can be used for the data transmission and receive
Ap=L+M antenna.Usually, L can maybe can be not equal to M.
For the embodiment shown in Fig. 2 A to 2C, at the available N in access point place
ApIn the individual antenna each can be selected for data individually and send and/or receive.Controller 220 can select the subclass of an antenna, available antenna or all available antenna to send and/or carry out Data Receiving from given user terminal to be used for carrying out data to given user terminal.Controller 220 can be selected antenna based on the power measurement values of available antenna, and is as described below.
Fig. 2 D shows the access point 110d with a plurality of (M>1) local antenna 112a to 112m and a plurality of (M) remote antenna 114a to 114m.Access point 110d is the another embodiment of access point 110 among Fig. 1, and has the N that can be used for the data transmission and receive
Ap=2M antenna.For the embodiment shown in Fig. 2 D, each local antenna 112 is associated with a remote antenna 114.Utilize M local antenna 112 and M remote antenna 114 to form M to antenna.In one embodiment, controller 220 selects one or more antennas to sending to be used for carrying out data to given user terminal, and for example further selects an antenna of this centering based on the power measurement values of two antennas of each selected centering.
WLAN 100 can apply such constraint: N antenna can be used for data and send at the most, and wherein N can equal two, four or certain other value.WLAN 100 can also support a plurality of transmission modes.Each transmission mode can require the antenna of the antenna of certain minimal amount or given number to be used to use the transfer of data of this transmission mode, and is as described below.For the sake of simplicity, following description supposition access point 110 can select nearly that N antenna carries out the data transmission to given user terminal.Access point 110 also selects to be used for the transmission mode of transfer of data based on the number of selected antenna.Access point 110 can select antenna to send to carry out data to user terminal in every way.
In one embodiment, N the antenna that access point 110 is selected to have the peak power measured value sends to be used for carrying out data to user terminal, wherein N<N
ApFor at the embodiment shown in Fig. 2 A to 2C, access point 110 receives N
ApThe power measurement values of individual available antenna sorts (for example, minimum from being up to) to power measurement values, and selects to have N antenna of N peak power measured value.For the embodiment shown in Fig. 2 D, access point 110 based on power measurement values select N optimal antenna to and select better person in two antennas of every centering.
In another embodiment, access point 110 selects to have nearly N the antenna above the power measurement values of predetermined power threshold Pth.Access point 110 can be compared the power measurement values of each antenna with power threshold, keep this antenna so if its power measurement values surpasses power threshold, otherwise abandon this antenna.If have power measurement values above power threshold more than N antenna, access point 110 is selected N optimal antenna so.Surpass power threshold if be less than the power measurement values of N antenna, access point 110 can only be selected these antenna so.If there is not antenna to have power measurement values above power threshold, access point 110 can be selected a best available antenna or a predetermined number optimal antenna so.
In another embodiment, access point 110 initial N optimal antennas of selecting to have the peak power measured value, the data that abandon the subtend user terminal then send all antennas that have only little contribution.Can prune by this antenna of realization as described below.Access point 110 comes they are sorted based on the power measurement values of N optimal antenna, for example from the peak power measured value P for N antenna
1To lowest power measured value P
NAccess point 110 calculates the antenna i of per two adjacent orderings and the power clearance delta P between the i+1 then
iAs their power measurement values poor, perhaps Δ P
i=P
i-P
I+1, i=1 ..., N-1.Next access point 110 determines the right power clearance delta P of any antenna
iWhether surpass predetermined amount delta P
Th, perhaps Δ P whether
i>Δ P
Th, i=1 ..., N-1.If the power clearance delta P of given antenna j
jSurpass scheduled volume, to abandon power measurement values be P to access point 110 so
I+1Or all lower antennas.This embodiment has removed the antenna that the transfer of data that is sent to user terminal is had only little contribution, and this has reduced crosstalking between antenna.
The foregoing description is used for based on carrying out a day line options in the available power measurement values in access point 110 places.Access point 110 can be based on other parameter that replaces received power, perhaps except based on also selecting antenna based on other parameter the received power.For example, access point 110 can be selected antenna based on following parameter: the signal noise ratio (SNR) that (1) receives, its be desired signal (for example, pilot tone) with the ratio of overall noise and interference, (2) signal strength signal intensity that receives, it is the ratio of desired signal and total received power, or certain other indication of (3) received signal quality.In the following description, the antenna measurement value can refer to be suitable for to be used for select the measured value (for example, power, SNR, signal strength signal intensity etc.) of any kind of antenna.
Access point 110 also can be selected antenna based on the out of Memory that can be the antenna acquisition.In one embodiment, access point 110 is selected antenna based on the positional information of local and remote antenna.Each antenna can be associated with near one group of one or more antenna.This positional information can be stored in the database.If obtained the high power measured value for given antenna, access point 110 can be selected near known one or more other antennas of this antenna that are positioned at so.For example, if obtained the high power measured value the remote antenna 114a in Fig. 1, access point 110 can select antenna 114b and/or antenna 114d to send to be used for carrying out data to user terminal so.
In another embodiment, access point 110 is selected antenna based on the positional information of local and remote antenna.If the position of the position of local and remote antenna and user terminal is known, access point 110 can select to be positioned near the one or more antennas of user terminal so.The position of AP antenna can be found out during disposing and provide.The position of user terminal can be similar to and/or otherwise find out via measured value.
In another embodiment, access point 110 is selected antenna based on the correlation information of local and remote antenna.Some antennas can have high correlation, and this causes too much crosstalking and poor apart between these antenna.Therefore, the antenna with high correlation should not selected together.The correlation information of available antenna can be found out based on arrangement, type and/or the measured value of antenna.For example, local antenna 112 is because their tight spacing and can have high correlation, and preferably only selects one or some local antennas to be used for transfer of data.
Access point 110 can also be selected antenna based on the information of the more high-rise acquisition that is positioned at the physical layer top from protocol stack.Access point 110 typically sends data to user terminal with grouping.This user terminal can send it back affirmation (ACK) at each grouping that is correctly decoded, and sends it back Negative Acknowledgement (NAK) at each grouping of decoded in error.Access point 110 can for example select one group of antenna to send to be used for carrying out data to user terminal based on power measurement values at first.If the grouping of big percentage is decoded mistakenly, access point 110 can select different antenna sets to be used for carrying out the data transmission to user terminal so.
Access point 110 can otherwise select antenna to be used for carrying out the data transmission to user terminal, and this within the scope of the invention.Access point 110 can be based on any standard or the incompatible selection antenna of any standard group.
Access point 110 can be selected different antenna sets to be used for carrying out data to different user terminals to send, for example based on the measured value of these user terminals.Access point 110 can carry out obtaining the measured value of each user terminal before the data transmission to user terminal, and can select to be used for one group of antenna of user terminal based on these measured values.This allows access point 110 that each transfer of data is all used best antenna sets.
Access point 110 can be being stored in the look-up table for the antenna sets of each user terminal selecting.This antenna sets can be enrolled index by the identifier of user terminal.Can to be access point 110 begin the medium access control identifier (MAC ID) of time-division provisioned user terminal or can be the identifier of certain other type at communication session this identifier.Table 1 shows the exemplary look-up table of the user terminal 120a to 120d that is used for example shown in Figure 1.
Table 1
User terminal |
Antenna sets |
User terminal 120a | Antenna | 114a |
User terminal 120b | Antenna | | | |
114a, 114d, 114e and 114f |
User terminal 120c | Antenna | |
112a, 1121 and 114m |
User terminal 120d |
Antenna |
1121 and 114c |
Access point 110 may also not have any measured value of given user terminal when user terminal carries out the data transmission in beginning.Access point 110 can utilize the MAC ID of user terminal to visit look-up table and fetch and before be the antenna sets of user terminal selecting then.Access point 110 can use this previous antenna sets of selecting to user terminal to transmit data till for example utilizing new measured value to upgrade this group.
Access point 110 selects first group of T antenna to be used for carrying out downlink transmission to user terminal, and selects second group of R antenna to be used for from user terminal receiving uplink transfer of data.Usually, N 〉=T 〉=1, N 〉=R 〉=1, and T can maybe can be not equal to R.R can if obtain the spatial manipulation support at access point 110 places, but not describe this possibility for simplicity greater than N yet.The number of transmitting antenna (T) depend on the good antenna that can be used for downlink transmission number, be used for the transmission mode of downlink transmission and possible other factors by access point 110.If antenna is by one or more choice criteria, if for example its power measurement values surpasses power threshold, this antenna can be considered to good so.The number of reception antenna (R) depends on the number that can be used for the good antenna that uplink data receives, is used for the transmission mode of uplink data transmission and possible other factors by user terminal.
Access point 110 can be selected first group of T transmitting antenna as mentioned above and can select second group of R reception antenna in a similar manner.First group of antenna can be identical or different with second group of antenna.Can also be used for the processing that Data Receiving is simplified access point 110 places by using single group antenna both to be used for the data transmission.In this case, each selected antenna both had been used to send the RF signal to user terminal and also had been used to the signal from user terminal reception RF.
Fig. 3 shows to be carried out by access point 110 and is used for to user terminal to transmit data and the processing 300 that receives data from user terminal., be that local and remote antenna obtains measured value (flow path block 310) for example at access point 110 places based on the pilot tone that sends by user terminal.Measured value can be at the power that is received and/or some other parameters.Based on measured value and/or out of Memory from the available N of access point 110
ApSelect first group of one or more (T) transmitting antenna, wherein N in the individual antenna
Ap>N 〉=T 〉=1 (flow path block 312).As mentioned above, can carry out a day line options in every way.If can use, so lastly be used for carrying out that group antenna that data send and fetch and to be used to current downlink transmission from look-up table to user terminal without any measured value.Number based on selected transmitting antenna selects transmission mode for the transfer of data of carrying out to user terminal.
Also based on measured value and/or out of Memory from the available N of access point 110
ApSelect second group of one or more (R) reception antenna, wherein N in the individual antenna
Ap〉=N 〉=R 〉=1 (flow path block 314).For example depend on the transmission mode that is used for down link and uplink data transmission, first and second groups of antennas that can have identical or different number.Even R=T, second group also can comprise with first group in the identical or different antenna of antenna.
Access point 110 comes deal with data (flow path block 316) according to the selected transmission mode that is used for down link, then handled data from first group of T antenna transmission to user terminal (flow path block 318).Access point 110 via second group of R antenna from user terminal receiving uplink transfer of data (flow path block 320).
Return and come, a plurality of user terminals 120 of access point 110 in can serving WLAN 100 with reference to Fig. 1.Each user terminal 120 can require specific one group of transmitting antenna to obtain good down-link performance and to require a specific group of received antenna to obtain good uplink performance.Access point 110 can dynamically switch between the different antennae group of different user terminals being used for, and makes that being utilized as each user terminal provides that group transmit/receive antenna of superperformance to serve this user terminal.The electronic equipment at access point 110 places can be designed to have the ability that (for example, based on every packet or based on every frame) promptly switches to the different antennae group that is used for different user terminals.
Fig. 4 shows the embodiment of access point 110.For this embodiment, access point 110 comprises digital section 210 that combine digital handles, is connected to the RF switch 280 of N antenna to N transceiver 230a to 230n of the RF of N antenna and baseband signal execution Signal Regulation and N transceiver 230, and wherein N antenna is from the available N of access point 110
ApSelect in the individual antenna.
Each transceiver 230 comprises transmitter unit (TMTR) 240 and acceptor unit (RCVR) 260.Reflector and acceptor unit can utilize superhet (super-heterodyne) framework or direct converting structure to realize.For super-heterodyne architecture, the frequency inverted between RF and the base band is carried out in a plurality of level, for example in a level from RF to the intermediate frequency (IF), and in another level from IF to the base band.For direct converting structure, frequency inverted is carried out in single level, for example directly from RF to the base band.For simplicity, Fig. 4 shows and utilizes the transmitter unit 240 that direct converting structure realizes and the embodiment of acceptor unit 260.
In transmitter unit 240, digital to analog converter (DAC) 242 receives the digital code laminar flow from digital section 210, is this chip transition what simulate, and analog baseband signal is provided.244 pairs of analog baseband signals of filter carry out filtering to remove the undesirable image that is produced by digital-to-analogue conversion and filtered baseband signal is provided then.Amplifier (Amp) 246 amplify and cushion filtered baseband signal and amplification be provided after baseband signal.Baseband signal after frequency mixer 248 utilizations are amplified is modulated from the TX_LO carrier signal of voltage controlled oscillator (VCO) (not shown among Fig. 4) and upconverted signal is provided.Power amplifier (PA) 250 amplifies upconverted signal and provides RF modulation signal to RF switch 280.
For transmit path, the transmitter unit 240 of RF switch 280 from N transceiver 230a to 230n receives nearly N RF modulation signal.RF switch 280 also receives the Ant_Sel control signal, and which transceiver is this Ant_Sel control signal indicate to be connected to which AP antenna.RF switch 280 is routed to selected local antenna 112 to the RF modulation signal of each reception or is used for the remote front-end 116 of selected remote antenna 114.For RX path, RF switch element 280 receives the RF input signal from each local antenna 112 and each remote antenna 114 that is selected for Data Receiving.RF switch element 280 is routed to the RF input signal of each reception the acceptor unit 260 in the transceiver 230 of appointment.RF switch element 280 can utilize emission/reception (T/R) switch, duplexer to wait and realize, and is such as known in the art.It is N that RF switch element 280 has been avoided at access point 110 places
ApIn the individual antenna each all provides the independently needs of transceiver 230.
In acceptor unit 260, low noise amplifier (LNA) 262 receives the RF input signal of selected AP antenna from RF switch 280.LNA 262 amplifies the RF signal after RF signal that is received and the adjusting that the signal level with expectation is provided.Frequency mixer 264 is used to come the RF signal after demodulation is regulated and switching signal is provided down from the RX_LO of VCO signal.266 pairs of following switching signals of filter carry out filtering so that desired signal component by and remove the noise and the undesirable signal that may produce by conversion process under the frequency.Amplifier 268 amplifies and cushions filtered signal and analog baseband signal is provided.Analog to digital converter (ADC) 270 makes the analog baseband signal digitlization and provides sample streams to digital section 210.
For the embodiment shown in Fig. 4, the RF signal that the power detector 290 in the acceptor unit 260 receives after regulating from LNA 262, the received power in the RF signal after the measuring and adjusting, and the master controller in digital section 210 220 provides power measurement values.Power detector 290 can also be measured received power based on baseband signal (for example, after filter 266 or amplifier 268).Can realize power detector 290 in every way, such as known in the art.
Fig. 4 shows the exemplary design that is used for reflector and acceptor unit.Usually, reflector and acceptor unit all can comprise one or more levels amplifier, filter, frequency mixer etc., and it can differently be arranged with the configuration shown in Fig. 4.Reflector can also comprise unshowned different and/or additional element among Fig. 4 with acceptor unit.
Fig. 4 also shows the embodiment of the digital section 210 that comprises the various processing units of carrying out the digital processing that is used for the data transmission and receives.In digital section 210, data processor 212 is carried out and is encoded, interweaves and sign map is separated mapping, deinterleaving and decoding to be used for Data Receiving to be used for data transmission and DO symbol.Spatial processor 214 (is for example carried out the reflector spatial manipulation, be used for wave beam formation, eigen steering (eigensteering) etc.) send to be used to carrying out data, and carry out receiver spatial manipulation (for example, spatial matched filtering) to be used to carrying out Data Receiving, as described below.Modulator 216 is carried out modulation (for example, being used for OFDM (OFDM)) and is sent to be used to carrying out data.Demodulator 218 is carried out demodulation (for example, being used for OFDM) to be used to carry out Data Receiving.Detection/acquisition unit 224 is carried out and is handled to detect and to obtain the signal from user terminal.The operation of various processing units and generation are to the control of transceiver 230 and remote front-end 116 in the master controller 220 control access points 110.For example, master controller 220 can produce the T that is used to enable and forbid each transmitter unit 230
iControl signal and the R that is used to enable and forbid each acceptor unit 260
iControl signal.The power management that power controller 226 is carried out access point 110.For example, power controller 226 can determine whether to send DC power to remote front-end 116.Data and program code that random-access memory (ram) and read-only memory (ROM) 222 storages are used by the various processing units in the digital section 210.For example, memory 222 can be stored as the antenna sets of each user terminal selecting.
Fig. 5 A shows the embodiment that can be used as the remote front-end 116x of each remote front-end 116 shown in Fig. 1.Remote front-end 116x can be used for being engraved in time division duplex (TDD) communication system that sends data on down link on the same frequency band and the up link when difference.For the embodiment shown in Fig. 5 A, remote front-end 116x comprises switch 510 and 540, power amplifier 520, low noise amplifier 530 and band pass filter 550.It is just to be access in a little 110 emissions or emission/reception (T/R) control signal that receives that switch 510 and 540 receives indication RF signal.Each switch is according to the indication of T/R control signal, its input is connected to " T " output during radiating portion, and its input is connected to " R " output during receiving unit.Master controller 220 can produce the T/R control signal and via the transceiver 230 that is associated (not shown among Fig. 4) this signal be offered each remote front-end 116.
For transmit path, RF modulation signal from the transmitter unit 240 that is associated is received via first port, be routed via switch 510, and amplify to obtain desired output signal level by power amplifier 520 with fixing or variable gain.Amplifying signal from power amplifier 520 is routed via switch 540, removing out-of-band noise and undesirable signal component, and is provided for the remote antenna 114 that is associated via second port by filter 550 filtering.For RX path, RF input signal from the remote antenna 114 that is associated is received via second port,, be routed to remove out-of-band noise and undesirable signal component by filter 550 filtering, and amplify by LNA 530 with fixing or variable gain via switch 540.Be routed and be provided for the acceptor unit 260 that is associated via switch 510 from the amplifying signal of LNA 530 via first port.
Power amplifier 520 and/or LNA 530 can any possible in by under electricity to reduce power consumption.For example, the T/R control signal can make 520 times electricity of power amplifier during receiving unit, and makes LNA 530 times during radiating portion.RF signal, T/R control signal and DC power can offer remote front-end 116x via cable 118 or by other means by access point 110.
Fig. 5 B shows the embodiment that also can be used as the remote front-end 116y of each remote front-end 116 shown in Fig. 1.Remote front-end 116y can be used in Frequency Division Duplexing (FDD) (FDD) communication system that sends data on the different frequency bands simultaneously on down link and up link.For the embodiment shown in Fig. 5 B, remote front-end 116y comprises duplexer 512 and 542, power amplifier 520 and LNA 530.
For transmit path, RF modulation signal from the transmitter unit 240 that is associated is received via first port, by duplexer 512 filtering, be routed to power amplifier 520, utilize gain to be exaggerated to obtain desired output signal level, by duplexer 542 filtering, and offer the remote antenna 114 that is associated via second port.For RX path, be received via second port from the RF input signal of associated antennas 114, by duplexer 542 filtering, be routed to LNA 530, utilize gain to be exaggerated,, and offer the acceptor unit 260 that is associated via first port by duplexer 512 filtering.For remote front-end 116y, do not need the T/R control signal.
Fig. 5 A and 5B show the specific embodiment of remote front-end 116x and 116y respectively.Usually, send and RX path all can comprise one or more levels amplifier, filter etc.Send and RX path can also comprise unshowned still less, the different and/or circuit chunk that adds among Fig. 5 A and the 5B.
For the sake of clarity, top description shows each remote antenna 114 and is connected to the remote front-end 116 that is associated, and each transceiver 230 is handled the RF signal that is used for an AP antenna.Usually, each remote front-end 116 and/or each transceiver 230 can be associated with one group of one or more antenna element.If remote front-end or transceiver are associated with a plurality of antenna elements, these antenna element can be regarded as being used for single (distributed) " antenna " of remote front-end or transceiver so.
In WLAN 100, " pseudo-(dummy) " stand and can spread all over the setting of WLAN deployment region and be used for various functions, such as the calibration of system configuration, reflector and receiver electronic equipment, sky line options etc.These pseudo-stations can be to have the cheap station of basic MAC/PHY function and can not need all required softwares of conventional station.
Can or divide into groups with regard to transmitting training/pilot tone/exploration (training/pilot/sounding) when being access in a little 110 indications in the moment of appointment in each pseudo-station.Access point 110 can use the training grouping to carry out various functions.For example, access point 110 can be based on training transmitter unit 240 and the frequency response of acceptor unit 260 and the frequency response of remote front-end 116a to 116m of dividing into groups to calibrate in the transceiver 230a to 230n.If pseudo-station is in known location, access point 110 can be found out the channel quality of being observed by remote antenna 114 and can use channel quality information to be used for a day line options so.
The exemplary cases that is used to use puppet to stand can be as described below.Pseudo-station can be arranged on key place and be positioned at the entrance and exit of overlay area, for example is positioned at the porch of the big office synthesis with many compartments and office.Each pseudo-station can be to the grouping of access point transmitting training, and described access point can be handled these training groupings and be configured to the eigenvector that transmits and receives at this puppet station.When new website has been in when entering this office synthesis under the ongoing state in active call (active call), new website can obtain simplifying to the switching of access point by using the precalculated eigenvector from immediate pseudo-station, and wherein immediate pseudo-station can be discerned based on signal strength measurement.This can make switching more level and smooth and quicker.Finally, transmission packets will make it possible to derive more excellent eigenvector into new website one by one, but pseudo-standing-meeting provides rational starting point.
WLAN 100 can support a plurality of transmission modes, such as not having (no steering), the beam steering (beamsteering) of manipulation, eigen steering (eigensteering), Space Time Transmit Diversity (STTD), space-frequency transmit diversity (SFTD) etc.Table 2 has been listed for each transmission mode and has been used for data number of antennas that sends and the number of antennas that is used for Data Receiving.N
ApBe the antenna sum available at the access point place, and N
UtBe to be scheduling to the available antenna sum that is used for down link and uplink data transmission at the user terminal place.Table 2 and below description in, for each transmission mode, T is used for carrying out to the user terminal that uses this transmission mode the number of antennas of downlink transmission by access point, N is the maximum number that is allowed to be used for the antenna of the transfer of data on down link and the up link by WLAN, and S
DnBe the number of the data flow that sends simultaneously to user terminal by access point, wherein S
Dn≤ min{N, N
UtAnd N
Ap>N.For each transmission mode, R is the number of antennas that is used for receiving the uplink data transmission that is sent by the user terminal that uses this transmission mode by access point, and S
UpIt is the number of the data flow that sends simultaneously to access point by user terminal.
Table 2
Identical or different transmission modes can be used for down link and the uplink data transmission between access point and the user terminal.Access point can use identical or different antenna sets to be used for the down link data transmission and uplink data receives.The spatial manipulation that access point 110 is carried out for the transmission mode of listing in the table 2 will be described below.
Access point 110 can be carried out beam steering and handle towards specific user terminal x and carry out downlink transmission.User terminal x can have individual antenna and can be user terminal 120a or 120c among Fig. 1.Access point 110 is from N
ApSelecting a plurality of (T) antenna to be used for carrying out data to user terminal x in the individual available antenna sends.Between the individual antenna at individual selected antenna of the T at access point 110 places and user terminal x place, formed the MISO channel.For each sub-band k, this MISO can be by the channel response row vector of 1 * T
h Dn, x(k)=[h
X, 1(k) h
X, 2(k) ... h
X, T(k)] characterize, wherein h
X, j(k) (j=1 ..., be for sub-band k T), the complex channel gain between AP antenna j and the single UT antenna.Access point 110 can execution as described below be used for the spatial manipulation that wave beam forms:
S wherein
Dn, x(k) be on sub-band k, to send to the data symbol of user terminal x,
x Dn, x(k) be that have at access point 110 places will be from T the vector of launching symbol of T selected antenna transmission, " H " represents conjugate transpose, and K is the sub-band number that is used for transfer of data.
Access point 110 can send S from reaching N day alignment user terminal y simultaneously
DnData flow.User terminal y has a plurality of (N
Ut) antenna and can be user terminal 120b or 120d among Fig. 1.Access point 110 is from N
ApSelect a plurality of (T) antenna to send in the individual available antenna, wherein T=S for not having manipulation to be used for carrying out down link data to user terminal y
DnAccess point 110 can execution as described below be used to not have the spatial manipulation of manipulation:
x dn,ns,y(k)=
s dn,y(k), for k∈{1,...,K},Eq(2)
Wherein for no manipulation situation,
s Dn, y(k) be to have on sub-band k, to send to the S of user terminal y
DnThe vector of data symbol, and
x Dn, ns, y(k) be to have with T vector that sends symbol on sub-band k from T selected antenna transmission to user terminal y.
Access point 110 can be carried out eigen steering and send a plurality of data flow to go up in orthogonal spatial channels (or eigenmodes (eigenmode)) to user terminal y.N at individual selected antenna of the T at access point 110 places and user terminal y place
UtFormed mimo channel between the individual antenna.For sub-band k, this MIMO can pass through N
UtThe channel response matrix of * T
H Dn, y(k) characterize, described channel response matrix can be expressed as:
H wherein
Y, i, j(k) (i=1 ..., N
UtAnd j=1 ..., T) be the complex channel gain between the antenna i at the antenna j at access point 110 places and user terminal y place for sub-band k.Channel response matrix
H Dn, y(k) can be as follows by diagonalization via eigen value decomposition:
Wherein
E Dn, y(k) be the unit matrix of eigenvector, and
Λ y(k) be the diagonal matrix of the eigenvalue for sub-band k.
Λ y(k) diagonal element is expression
H Dn, yThe eigenvalue of the power gain of the eigenmodes of S (k), S≤min{T wherein, N
Ut.Eigenmodes can be regarded as orthogonal spatial channels.Access point 110 can use
E Dn, y(k) eigenvector in (or row) is come
H Dn, y(k) send data on the eigenmodes.Access point 110 can
H Dn, y(k) send nearly S data flow, perhaps S on the S eigenmodes simultaneously
Dn≤ S.
Access point 110 can execution as described below be used for the spatial manipulation of eigen steering:
x dn,es,y(k)=
E dn,y(k)·
s dn,y(k),Eq (5)
Wherein for eigen steering,
x Dn, es, y(k) be to have with T vector that sends symbol on sub-band k from T selected antenna transmission to user terminal y.Access point 110 can also be by utilizing
H Dn, yThe eigenvector of best eigenmodes (k) is carried out the spatial manipulation that is used for beam steering and send data on this best eigenmodes, for example shown in equation (1).
Access point 110 can use STTD or SFDT to send individual traffic from two sky alignment user terminals.For STTD, access point 110 is every couple of data symbol s
1And s
2Produce two vectors
x Dn, td, 1=[s
1s
2]
TWith
Wherein " * " expression complex conjugate and " T " represent transposition.Access point 110 in first symbol period on a sub-frequency bands from two selected antenna transmission vectors
x Dn, td, 1In two coded identifications, then in second symbol period on identical sub-band from two identical antenna transmission vectors
x Dn, td, 2In two coded identifications.For SFDT, access point 110 on first sub-band from two selected antenna transmission vectors
x Dn, td, 1In two coded identifications and in identical symbol period, on second sub-band, send vector
x Dn, td, 2In two coded identifications.
Access point 110 can use a plurality of (R) antenna to come from user terminal receiving uplink transfer of data.Access point 110 is from N
ApSelect R antenna in the individual available antenna, wherein R depends on the transmission mode that is used for carrying out uplink data transmission by user terminal, and is as shown in table 2.If obtain the support of the spatial manipulation at access point place, R can also be greater than N so.For the TDD system, down link and up link can be assumed that reciprocal, make the channel response of up link equal the transposition of the channel response of down link, for example,
And
For the uplink data transmission from single antenna terminal x, the symbol that receives at access point 110 places can be expressed as:
r up,x(k)=
h up,x(k)·s
up,x(k)+
w up,x(k), Eq(6)
S wherein
Up, x(k) be the data symbol that on sub-band k, sends by user terminal x,
r Up, x(k) be vector with R receiving symbol of user terminal x, and w
Up, x(k) be the noise vector that access point 110 places receive.
Access point 110 can execution receiver as described below matched filtering:
Wherein
Be s
Up, x(k) estimation, and w
Up, x(k) be by s
Up, x(k) the reprocessing noise of Guan Chaing.
For the uplink data transmission from the multi-antenna terminal y that uses nothing manipulation or eigen steering, the symbol that receives at access point 110 places can be expressed as:
r up,y(k)=
H up,y(k)·
x up,y(k)+
w up,y(k)=
H eff,y(k)·
s up,y(k)+
w up,y(k),Eq(8)
Wherein
s Up, y(k) be the vector of the data symbol that sends by user terminal y,
x Up, y(k) be the N at user terminal y place
UtThe vector of the transmission symbol of individual antenna,
H Eff, y(k) be the efficient channel response matrix that is used for up link, and
r Up, y(k) be the vector of the symbol that for user terminal y, receives at access point 110 places.
H Eff, y(k) depend on the transmission mode that is used for uplink data transmission by user terminal y, for example, if user terminal y carries out eigen steering so
H Eff, y(k)=
H Up, y(k)
E Up, y(k), and if user terminal y carry out not have handle so
H Eff, y(k)=
H Up, y(k).
Access point 110 can execution receiver spatial manipulation as described below:
Wherein
M Up, y(k) be spatial filter matrices for sub-band k, and
It is the back detection noise.Access point 110 can use in the following equation any one to come the derived space electric-wave filter matrix
M Up, y(k):
Wherein,
D y(k)=[diag[
M'
Up, y3(k)
H Eff, y(k)]]
-1,
IBe unit matrix, and σ
n 2It is the variance of the noise at access point 110 places.Equation (10) is used for the matched filtering technique of eigen steering, and equation (11) is used for ZF (zero-forcing) technology, and equation (12) is used for least mean-square error (MMSE) technology.Chase after zero-sum MMSE technology and can be used for not having manipulation and eigen steering transmission mode.
For the uplink data transmission from the multi-antenna terminal y that uses STTD, the symbol that receives at access point 110 places can be expressed as:
r up,td,y1(k)=
h up,ya1(k)·s
y1(k)+
h up,ya2(k)·s
y2(k)+
w up,y1(k),and Eq(13)
S wherein
Y1(k) and s
Y2(k) be to use STTD at two data symbols that in two symbol periods, send on the sub-band k from two UT antenna y1 and y2,
h Up, yG1(k) and
h Up, ya2(k) be the vector of the channel gain between two UT antenna y1 and y2 respectively, and R is selected AP antenna,
r Up, td, y1(k) and
r Up, td, y2(k) be the vector of the receiving symbol for sub-band k in two symbol periods, and
w Up, y1(k) and
w Up, y2(k) be the noise vector of two symbol periods.For STTD and SFTD transmission mode, R 〉=1.
Access point 110 can two data symbols of derivation as described below s
Y1(k) and s
Y2(k) estimation:
And
Wherein
With
Be respectively s
Y1(k) and s
Y2(k) estimation, and
With
Be respectively by s
Y1(k) and s
Y2(k) the reprocessing noise of Guan Chaing.
Many antennas station described herein can be realized by various devices.For example, many antennas station and any function described herein can utilize the combination of hardware, firmware or software to realize.Be used for the AP antenna is measured, selection is used for that data send and the unit of the antenna that receives and deal with data and signal can be at one or more application-specific integrated circuit (ASIC)s (ASIC), digital signal processor (DSP), digital signal processor spare (DSPD), programmable logic device (PLD), field programmable gate array (EPGA), processor, controller, microcontroller, microprocessor, RF integrated circuit (RFIC), be designed for carrying out other electronic unit or the interior realization of its combination of the function of describing herein.
Can utilize hardware or software to carry out a day line options.For software implement scheme, can utilize the module (for example, program, function etc.) of the function that execution describes to carry out a day line options herein.Software code can be stored in the memory cell (for example, the memory cell among Fig. 4 222) and by processor (for example, controller 220) and carry out.Memory cell can be in processor inside or in the outside realization of processor, and under the outside situation about realizing of processor, memory cell can be connected to processor communicatedly via various devices quilts as known in the art.
To the above-mentioned explanation of the disclosed embodiments, be to realize or to use the present invention for any professional and technical personnel who makes this area.Multiple modification to these embodiment will be conspicuous concerning those skilled in the art, and defined herein General Principle can be applied to other embodiment under the situation that does not break away from the spirit or scope of the present invention.Therefore, the present invention should not be restricted to these embodiment shown in this article, but will meet and principle disclosed herein and novel feature the wideest consistent scope.