Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
  • H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
  • H01Q3/2605—Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays
  • H01Q3/2647—Retrodirective arrays
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B17/00—Monitoring; Testing
  • H04B17/10—Monitoring; Testing of transmitters
  • H04B17/11—Monitoring; Testing of transmitters for calibration
  • H04B17/12—Monitoring; Testing of transmitters for calibration of transmit antennas, e.g. of the amplitude or phase
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B17/00—Monitoring; Testing
  • H04B17/30—Monitoring; Testing of propagation channels
  • H04B17/309—Measuring or estimating channel quality parameters
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
  • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
  • H04B7/0682—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission using phase diversity (e.g. phase sweeping)
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
  • H04B7/0686—Hybrid systems, i.e. switching and simultaneous transmission
  • H04B7/0691—Hybrid systems, i.e. switching and simultaneous transmission using subgroups of transmit antennas

Definitions

• the described embodiments relate generally to wireless communications. More particularly, the described embodiments relate to methods and systems for beamforming a broadband signal through a multiport network.
• RF radio-frequency
• one station may be a mobile station (MS)
• another station may be a BS (BS).
• MS mobile station
• BS BS
• the path loss between the MS and the BS changes due to a number of factors including the change in distance between the stations as well as the presence of objects in the environment that serve to obstruct or attenuate the signals traveling from one station to the other.
• a critical component in a MS is the power amplifier that is used to transmit the signal to the BS.
• a power amplifier typically has a maximum output power rating.
• One method to attain reliable communication with a BS is to ensure that the power amplifier is equipped with sufficient power to overcome the fading and path loss present in a wireless medium.
• a system and/or method is provided for beamforming a broadband signal through a multiport network, substantially as illustrated by and/or described in connection with at least one of the figures, as set forth more completely in the claims.
• Figure 1 is a block diagram that shows an exemplary wireless communication system in connection with an embodiment of the invention.
• Figure 2 is a block diagram of illustrating portions of an examplary wireless subscriber transceiver, in accordance with an embodiment of the invention.
• Figure 3 is a block diagram that shows an example of achievable array gains for phase beamforming with constant power per transmit antenna, in connection with an embodiment of the invention.
• Figure 4 is a block diagram that shows an example of a multiport network known as a 90 degree quadrature hybrid, in connection with an embodiment of the invention.
• FIG. 5 is a block diagram illustrating portions of an exemplary wireless subscriber transceiver, in accordance with an embodiment of the invention.
• Figure 6 is a block diagram that shows an example of achievable array gains for phase beamforming using a multiport network, in accordance with an embodiment of the invention.
• Figure 7 is a block diagram that compares the achievable array gains for phase beamforming with and without a multiport network, in accordance with an embodiment of the invention.
• Figure 8 is a block diagram illustrating portions of an exemplary wireless subscriber transceiver, in accordance with an embodiment of the invention.
• Figure 9 is a block diagram illustrating portions of an exemplary wireless subscriber transceiver, in accordance with an embodiment of the invention.
• Figure 10 is a block diagram illustrating portions of an exemplary wireless subscriber transceiver, in accordance with an embodiment of the invention.
• FIG 11 is a block diagram that shows an exemplary multiple-input-multiple- output (MIMO) communication system, in accordance with an embodiment of the invention.
• MIMO multiple-input-multiple- output
• Figure 12 is a flow chart illustrating exemplary steps for operating a wireless subscriber transceiver, in accordance with an embodiment of the invention.
• the uplink and downlink wireless channels are reciprocal; this reciprocity can be exploited by transmitting from two or more antennas such that the transmitting signals coherently combine at the BS. Additionally, wireless channels often exhibit substantial imbalances at the MS receive antennas. In an effort to more effectively use the available transmit power of the both power amplifiers, a multiport network is used to provide gains even in the presence of a strong imbalance in the wireless channels.
• An embodiment includes a method of transmitting a transmission signal through a plurality of antennas.
• the method includes generating at least one dynamically adjustable phase shifted signal from the transmission signal.
• the transmission signal and the at least one dynamically adjustable phase shifted signal are separately amplified.
• the amplified transmission signal and the amplified at least one dynamically adjustable phase and/or amplitude shifted signal are combined with a multiport network.
• An output signal at one or more of the plurality of antennas is generated by the multiport network. Also include amplitude scaling. It can be beneficial to scale the amplitudes as well.
• Another embodiment includes a transmitter.
• the transmitter includes a means for generating at least one dynamically adjustable phase shifted signal from a transmission signal.
• a first amplifier amplifies the transmission signal and a second amplifier amplifies the at least one dynamically adjustable phase shifted signal.
• a multiport network combines the amplified transmission signal and the amplified at least one dynamically adjustable phase shifted signal, and generates an output signal for each of the plurality of antennas.
• Figure 1 shows an exemplary wireless communication system, in connection with an embodiment of the invention.
• the communication system may comprise a BS 110 and a subscriber station transceiver 120, wherein multiple propagation channels , , are formed between each BS antenna 112 and each subscriber station antenna 122, 124.
• the BS 110 may comprise multiple antennas
• the subscriber transceiver 120 may comprise more than two antennas.
• a wireless communication signal traveling from the BS 110 to the subscriber station 120 may be referred to as "downlink transmission”; a wireless communication signal traveling from the subscriber station 120 to the BS 110 is referred to as "uplink transmission”.
• the transmissions can be included within a frame that includes a downlink subframe and an uplink subframe.
• the BS transmits pilot signals which allow the subscriber station (SS) to estimate the wireless channels to each of its receive antennas.
• the pilots typically have support across frequency and time in the downlink subframe.
• Some wireless systems employ a preamble as part of the downlink transmission, e.g., the WiMAX 802.16e system.
• the preamble which occurs at the beginning of every downlink subframe, employs pilot tones occurring at every third tone across the frequency spectrum of a multi-carrier signal; additionally, the pilots in the preamble are transmitted at a higher power spectral density and contain modulation known to the receiver (subscriber station) as compared to data carrying subcarriers.
• the downlink signal contains pilots known as cell specific reference signals which can be similarly used to estimate the downlink wireless channel. Additionally, in the LTE system, the subscriber may estimate the Multi-Input Multi-Output (MIMO) wireless channel between the BS and the MS.
• MIMO Multi-Input Multi-Output
• FIG. 2 is a block diagram illustrating portions of an exemplary wireless transceiver, in accordance with an embodiment of the invention.
• the exemplary subscriber transceiver 200 comprises Tx signal processing block 202, power amplifiers 212 and 214, low noise amplifiers 242 and 244, switching elements 222 and 224, and antennas 232 and 234.
• Figure 2 depicts an exemplary case where there are two transmit antennas, and, correspondingly, two power amplifiers, low noise amplifiers, and signals Z[(t) and T 2 (t) the invention is not so limited. Aspects of the invention may scale to any number of antennas.
• the Tx signal processing block 202 may comprise suitable logic, circuitry, interfaces, and/or code that may be operable to generate a plurality of signals Txl(t) and Tx2(t) from a signal m(t), where the phase and/or amplitude of each of the signals Txl(t) and Tx2(t)may be dynamically adjustable during operation of the transceiver.
• the amount of phase and/or amplitude adjustment may be dynamically determined during operation based on, for example, real-time, or near-real-time, measurements of signal characteristics. Additionally or alternatively, the amount of phase and/or amplitude adjustments may be based on any other suitable information such as, for example, a predetermined table of values.
• the signal processing block 202 may operate in the digital domain, analog domain, or both.
• Power amplifiers 212 and 214 may comprise suitable logic, circuitry, interfaces, and/or code for amplifying the signals Txl(t) and Tx2(t), respectively.
• a gain of each of the power amplifiers 212 and 214 may be dynamically adjustable during operation of the wireless transceiver via, for example, one or more control signals from the Tx signal processing block 202.
• the low noise amplifiers 242 and 244 may comprise suitable logic, circuitry, interfaces, and/or code for amplifying signals received from antennas 232 and 234 to generate signals Rxl(t) and Rx2(t), respectively.
• a gain of each of the low noise amplifiers 242 and 244 may be dynamically adjustable during operation of the wireless transceiver via, for example, one or more control signals from the Tx signal processing block 202.
• a modulating signal m(t) may be input to the block 202.
• the block 202 may generate analog signals Txl(t) and Tx2(t) from m(t).
• the block 202 may dynamically adjust the phase and/or amplitude of each of the signals Txl(t) and Tx2(t).
• the signals Txl(t) and Tx2(t) may be amplified by power amplifiers 212 and 214 and applied to antennas 232 and 234, respectively, via switches 222 and 224.
• the adjustment of the signals is performed to achieve an array gain at the antenna of the receiver (e.g., antenna 1 12 of the BS 1 10 in Figure 1), as described in more detail the following paragraphs.
• ⁇ /> Rx 2 (f > t Bx ) ⁇ (3 ⁇ 4 denote the vector valued phases, indexed by frequency, at antennas 232 and 234, respectively, at time t ⁇ .
• ⁇ ( ⁇ ) : ⁇ N — [0, 2 ⁇ ) ⁇ denotes the angle operator, and corresponds to an interval in the downlink subframe during which the receiver makes phase measurements.
• the subscriber transceiver 200 may control the phase relationship of the transmitted signals, during the transmit interval t Tx to satisfy the relationship:
• the phase difference between ports 1 and 2 during time interval t Tx may be controlled to be the negative of the phase difference between ports 1 and 2 during time interval
• the phase difference during transmission may be controlled by multiplying the modulating signal, m(t) , by a weighting vector w (- ⁇ " ' ⁇ -*) to generate adjusted uplink signals ⁇ w ( ' ⁇ ) m ( _ j n an embodiment of the invention, w (- ⁇ " ' ⁇ -*) mav 3 ⁇ 4 e determined by the Tx signal processing block 202 utilizing eq. 2.
• the adjusted uplink signals Txl(t) and ⁇ 2( ⁇ ) ⁇ 2 ( ⁇ ) may then be input, respectively, to power amplifiers 212 and 214.
• the outputs of the power amplifiers may pass through the switches 222 and 224 to the antennas 232 and 234.
• the amplitude of the signal received at the BS is twice that of the value when transmitting from either of the antennas.
• the power received by the BS is increased by a factor of 4 with only a doubling of total transmit power.
• the doubling of power comes form the use of two amplifiers of the same power.
• the additional factor of two in received power at the BS is referred to as array gain. More generally, the array gain equals the 1 norm of the receive channel vector. The achievable gains are shown in Figure 3.
• Figure 3 shows an example of achievable array gains for phase beamforming with constant power per transmit antenna, in connection with an embodiment of the invention.
• FIG. 4 shows an example of an implementation of a multiport network commonly referred to as a 90 degree hybrid coupler, in connection with an embodiment of the invention.
• a 90 degree hybrid coupler may be realized using transmission lines with electrical lengths and characteristic impedances as shown.
• 0 denotes a ⁇
• characteristic impedance typically 50 ohms; ⁇ is a quarter wavelength line at the transmit center frequency.
• the S-parameter matrix for a 2-port network is commonly used to describe the relationship between the reflected, incident power waves according to: where 1 and 2 are the outputs and 1 and 2 are the inputs.
• the transfer function of the multiport network 410 may be represented by a matrix of S-parameters.
• the 90 degree hybrid coupler has nominal scattering parameters given by
• 90 degree hybrid couplers exhibit loss and the relationship deviates somewhat from (6).
• the 90 degree hybrid coupler 410 is a linear, time-invariant, passive, non-ferromagnetic circuit. Assume that the impedances seen by multiport by degree hybrid coupler 410 are nominal. Then, the following voltage relationship also holds:
• the 90 degree hybrid coupler is a bidirectional device and the transfer function from one port to another does not depend on which is the input or output.
• FIG. 5 is a block diagram illustrating portions of an exemplary wireless transceiver, in accordance with an embodiment of the invention.
• the exemplary subscriber transceiver 500 comprises a Tx signal processing block 202, Rx signal processing block 204, power amplifiers 212 and 214, low noise amplifiers 242 and 244, switching elements 222 and 224, a multiport network 910, and antennas 232 and 234.
• the a Tx signal processing block 202, power amplifiers 212 and 214, low noise amplifiers 242 and 244, switching elements 222 and 224, and antennas 232 and 234 may be as described with respect to Figure 2.
• the multi-port network 910 may, for example, be realized in and/or on a semiconductor substrate ("on-chip"), an IC package, and/or printed circuit board.
• the multiport network may be such that at least one port is responsive at least two other ports.
• the multi-port network 910 may be, for example, the hybrid 410 described in Figure 4.
• the outputs of the power amplifiers 212 and 214 and the inputs of the low noise amplifiers 242 and 244 are coupled to a plurality of first ports, ports 1 and 2, of the multi-port network 910.
• the antennas 232 and 234 are coupled to a plurality of second ports, ports 3 and 4, of the multi-port network 910.
• Operation of the transceiver 500 may be similar to operation of the transceiver 200 described with reference to Figure 2. However, introduction of the multiport network 910 impacts the array gain, as described in more detail in the following paragraphs.
• port 3 is connected to antenna
• multiport network 910 is a linear, time invariant, passive, non-ferromagnetic circuit and that the impedances seen by multiport network 910 are nominal, the following voltage relationships hold:
• h(f, t) A T h(f, t) , (10) where denotes the transpose.
• an( j ⁇ ⁇ , ⁇ D (3 ⁇ 4 d eno t e the vector valued phases, indexed by frequency, of ports 1 and 2, respectively, at time tRx .
• ⁇ ( ) ⁇ l ⁇ ) denotes the angle operator, and ⁇ corresponds to an interval in the downlink subframe during which the receiver makes phase measurements.
• ⁇ corresponds to an interval in the downlink subframe during which the receiver makes phase measurements.
• the subscriber transceiver 500 may control the phase relationship of the transmitted signals, during the transmit interval * ⁇ to satisfy the relationship: (bob fix)
• the phase difference between ports 1 and 2 during time interval t Tx may be controlled to be the negative of the phase difference between port 1 and 2 during time interval 1R x .
• the phase difference during transmission may be controlled by applying a weighting factor to the digital modulating signal, m(t) , to generate adjusted uplink signals ⁇ w (/' ⁇ &) m ( _ i n
• the weighting vector may be calculated as shown in eq. 12.
• a is a complex constant related to a common amplitude and phase of the transmit signals into the multiport network 910.
• the constant a may be chosen to compensate for differences in phase between the transmit and/or receive chains.
• the signals Txl(t) and Tx2(t) are input to power amplifiers 212 and 214 and pass through switches 222 and 224, respectively, resulting in amplified adjusted signals x(t) - w(f, t Ex )m(t) k e j n g a ii e( j to the plurality of first ports of the multiport network 910.
• the output of the multiport network 910 may be given by:
• the transmit weight vector is given by
• m( ) is the modulating signal.
• the signal received at the BS is given by
• a voltage gain of ' 21 ' ' 22 ' is realized as compared to transmitting the same power on each antenna without a multiport network.
• the gains of choosing the transmit phase relationship according to (11) are not limited to the case in which a strong imbalance exists between the amplitudes of the received signal. If the amplitudes are the same, array gain may still be realized.
• Figure 6 shows an example of achievable array gains for phase beamforming with constant power per transmit antenna, in connection with an embodiment of the invention.
• Figure 7 shows compares the achievable array gains for equal amplitude, phase beamforming with with and without a hybrid coupler as part of the channel. It is observed that equal amplitude, phase beamforming affords a gain of at 3dB as compared to transmitting from the first antenna, even if the channel to the second antenna is arbitrarily small in value. This is a desirable feature as wireless channels often exhibit strong imbalances.
• a common phase difference between the transmit signals is used for all frequencies, rather than generate a phase vector indexed by frequency; hence, the achievable array gains may be realized even in frequency selective channels.
• Figure 6 shows an example of achievable array gains for phase beamforming using a multiport network, in accordance with an embodiment of the invention.
• Figure 7 compares the achievable array gains for phase beamforming with and without a multiport network, in accordance with an embodiment of the invention.
• Figure 8 is a block diagram illustrating portions of an exemplary transceiver, in accordance with an embodiment of the invention.
• the exemplary subscriber transceiver 800 comprises a Tx signal processing block 202, Rx processing block 204, Tx phase detection block 802, calibration signal generator 804, power amplifiers 212 and 214, low noise amplifiers 242 and 244, switching elements 222 and 224, switching elements 822 and 824, directional couplers 812 and 814, and multi-port network 910.
• the Tx signal processing block 202, power amplifiers 212 and 214, low noise amplifiers 242 and 244, switching elements 222 and 224, antennas 232 and 234 may be as described with respect to Figure 2.
• the multi-port network 910 may be, for example, the hybrid 310 described in Figure 3.
• the multi-port network 910 may, for example, be realized in and/or on a semiconductor substrate ("on- chip"), an IC package, and/or printed circuit board.
• the directional couplers 812 and 814 may, for example, be realized in and/or on a semiconductor substrate ("on-chip"), an IC package, and/or printed circuit board.
• the Tx phase detection block 802 may comprise suitable logic, circuitry, interfaces, and/or code that may be operable to determine a phase difference between the signal at directional coupler 812 and the signal at directional coupler 814.
• amplitude and phase differences may exist in the transmit RF chains arising from one or more of the following factors: electrical delays, temperature, frequency, and calibration errors.
• the signals and are feedback signals which may be subsequently processed by the phase detection block 702 and used to control the amplitude and/or phase of the transmit signalsTxl(t) and Tx2(t).
• the outputs of low noise amplifiers 242 and 244 may be down-converted, digitized, and processed using digital signal processing techniques to yield phases of the received signals, ⁇ * ,i ( > ⁇ x ) an( j ⁇ , ⁇ ⁇ ⁇ R ⁇ ) _
• the feedback signals may be correlated with the transmit signal m ⁇ .
• the power present in the feedback signals may be measured.
• the feedback signals may have a power level that is approximately 18 dB below the power level of the input to the directional coupler
• calibration signals may be applied to Fb Fb
• These calibration signals may couple through directional couplers 812 and 814, and transmit receive switches 222 and 224 to the inputs of low noise amplifiers 242 and 244.
• These amplified calibration signals may be down-converted and subsequently processed to measure the phase delays of the receive chains from each of the directional couplers 812 and 814 to the respective outputs of the Tx signal processing block 202. These measured phase delays are used to compensate the measured phases of the received signals,
• FIG. 9 is a block diagram illustrating portions of an exemplary wireless subscriber transceiver, in accordance with an embodiment of the invention.
• the transceiver 900 may be substantially similar to the portion of the transceiver 800 described with respect to figure 8, but may additionally comprise coaxial switches 912 and 914.
• transmit input signals Txl(t) and Tx2(t) may be amplified by power amplifiers 212 and 214 and applied to a plurality of first ports of the multiport network 910.
• a plurality of transmit antennas, 232, 234 are connected to a plurality of second ports of multiport network 910.
• An embodiment of the multiport network is the 90 degree hybrid coupler 310.
• the transceiver 900 also comprises coaxial switches which allow the coupler to be bypassed. This may result in large savings in calibration time. Although the coaxial switches 912 and 914 are shown in the signal path between the directional couplers 812 and 814 and the multiport network 910, they could be located in other and/or additional points in the transmit and/or receive chain.
• FIG 10 is a block diagram illustrating portions of an exemplary wireless subscriber transceiver, in accordance with an embodiment of the invention.
• the exemplary subscriber transceiver 1000 comprises a plurality of power amplifiers 212 and 214, a multiport network 910, a plurality of antennas 232 and 234, switches 222 and 224, and directional couplers 812 and 814.
• multiport network 910 is part of the transmit path but not a part of the receive path.
• Directional couplers 812 and 814 are connected to the antennas 232 and 234.
• Portions of the transmit signals applied to antennas 232 and 234 are coupled, through directional couplers 812 and 814 to produce feedback signals Fb x and Fb 2 , which are subsequently processed to measure the phases of the signals transmitted via each of the antennas 232 and 234.
• the same ports of the directional couplers may be utilized to apply calibration signals to directional couplers 812 and 814 to enable measurement of the phase delays from directional couplers 812 and 814, through the receive chain.
• the wireless transceiver 1000 is operable to compensate for phase differences and/or other non-idealities in the transmit chains, phase differences and/or other non-idealities in the receive chains, and characteristics of the multi-port network 910.
• FIG 11 shows a block diagram block diagram of an exemplary multiple- input-multiple-output (MIMO) communication system.
• MIMO multiple- input-multiple-output
• the 3GPP Long Term Evolution LTE the Base Stations employ up to 4 transmit antennas.
• the pilots associated with these four transmit antennas are allocated in such that they do not overlap in both time and frequency.
• the pilots in accordance with an embodiment of the invention.
• the block diagram of a MIMO communication system 1100 is shown.
• receive (RX) chains are denoted BS ' TX and , respectively.
• RX receive
• M denotes the number of BS antennas.
• each of the transmit antennas transmits antenna specific reference signals that are modulated with cell-specific sequences; hence, the subscriber station to learn the full MIMO channel between the BS and SS.
• H ⁇ Mx2 i the UL propagation channel
• H e U 2xM the DL propagation channel.
• M the number of transmit antennas at the Base station.
• the received downlink signal is given by
• s is the signal transmitted by the BS
• ' is a vector of additive noises.
• the received uplink signal is given by
• phase shifting corresponds to weighting the transit signal by vector of "
• the power delivered to the BS antenna arra is given by:
• R H * H and ( ⁇ ) denotes conjugate transpose. It can be shown that an arbitrary phase rotation at the BS receive antenna does not affect the outcome as multiplication by a unitary matrix does not change the / 2 a vector.
• the Gram matrix R for the MIMO uplink channel is Hermetian and positive semi-definite; hence, it may be expressed as:
• the desired phase may be computed according to (24).
• the desired phase shift ⁇ may be profitably computed on a frequency selective basis, wherein for each frequency, the phase is chosen based upon entries of the Gram matrix formed by the channel estimates.
• the desired phase shift may be compensated for phase differences between the transmit and/or receive paths. Said phase differences may be determined using calibration techniques employing directional couplers.
• the multiport network may still be profitably employed.
• the multiport network appears as a change of coordinates in the received channel.
• the desired transmit phase may be calculated according to (24).
• a subscriber terminal may required to transmit an Alamouti code.
• phase term in (24) should be optimally chosen to maximize the power delivered to the base station array using knowledge of the UL .
• the first column in (25) identifies the transmitted signals from antennas 1 and 2 at the first unit of time
• the second column identifies the transmitted signals from the two antennas in the second unit of time.
• Wl and Wl two complex weight values that we may apply to the two antennas
• the BS processes these two received signals (representing two units of time) as follows: where n ' is and additive noise with the same distribution as n .
• the signal-to- noise ratio of the received signals is determined by the quantity:
• the signal-to-noise maximizing strategy for the subscriber is to use the transmit antenna that maximizes the total received power at the BS.
• FIG. 12 is a flow chart illustrating exemplary steps for operating a wireless subscriber transceiver, in accordance with an embodiment of the invention.
• the exemplary steps begin with step 1210 in which, during a reception time interval t Rx , the phase detection block 802 may determine a phase difference between the received signal at the coupler 812 and the received signal at the coupler 814. This determination may compensate for a phase difference introduced as a result of non-idealities in the two RF receive chains of the transceiver 800.
• the phase detection block 802 may output an indication of the determined phase difference to the Tx signal processing block 202.
• signals Txl(t) and Tx2(t) may be generated from modulating signal m(t) utilizing the phase determination generated in step 1210.
• Generation of the signals Txl(t) and Tx2(t) may comprise adjusting a phase and/or amplitude of one or both of the signals Txl(t) and Tx2(t) based on the phase determination made in step 1210.
• the signals Txl(t) and Tx2(t) may be separately amplified by PAs 212 and 214.
• the output of each of the amplifiers may be input to one of a plurality of first ports of the multi-port network 910.
• Each of the resulting signals at the plurality of second ports of the multi-port network may be conveyed to one of the plurality of antennas 232 and 234 for transmission.
• Embodiments include preprocessing transmit input signals to establish phase relationships between the amplified signals received by the multiport network 910. This phase relationship may be chosen to produce an improved Signal-to-Noise Ratio (SNR) at the base station (BS) that the transceiver (for example, a subscriber) is communicating with.
• SNR Signal-to-Noise Ratio
• BS base station
• TDD Time Division Duplex
• the SNR at the base station (BS) can be predicted from the received downlink signal; that is, from the signal received at the subscriber transceiver when receiving the transmitted signal from the BS.
• the phase relationships of the signals Txl(t) and Tx2(t) may be profitably selected on a frequency selective basis.
• the phase of the signals TXl(t) and Tx2(t) may be adjusted on a subcarrier-by- subcarrier basis.
• a common phase relationship of the signals Txl(t) and Tx2(t) may be used for all subcarriers. Additionally or alternatively, the phase relationships can be adjusted dynamically.
• the selection of the phase relationships in combination with the multiport network 910 essentially results in a selection of one of the transmit antennas (Ant. 1 through Ant. M) in which the majority of the transmission signal power is directed.
• the number of antennas is not limited, and the subset of antennas in which the signal power is directed is not limited to one.
• the antenna selection can be adaptively made over both subcarriers and time (symbols) of multicarrier signals.
• the number of antennas is not limited.
• the antenna selection can be adaptively made over both frequency (subcarriers) and time (symbols) of multicarrier signals.
• FIG. 1 A block diagram illustrating an exemplary computing environment in accordance with the present invention.
• FIG. 1 A block diagram illustrating an exemplary computing environment in accordance with the present invention.
• FIG. 1 A block diagram illustrating an exemplary computing environment in accordance with the present invention.
• FIG. 1 A block diagram illustrating an exemplary computing environment in accordance with the present invention.
• FIG. 1 A block diagram illustrating an exemplary computing environment in accordance with the present invention.
• a typical combination of hardware and software may be a general-purpose computer system with a computer program that, when being loaded and executed, controls the computer system such that it carries out the methods described herein.
• the present invention may also be embedded in a computer program product, which comprises all the features enabling the implementation of the methods described herein, and which when loaded in a computer system is able to carry out these methods.
• Computer program in the present context means any expression, in any language, code or notation, of a set of instructions intended to cause a system having an information processing capability to perform a particular function either directly or after either or both of the following: a) conversion to another language, code or notation; b) reproduction in a different material form.

Landscapes

• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Quality & Reliability (AREA)
• Mobile Radio Communication Systems (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=47143448

Family Applications (1)

Country Status (1)

Citations (3)

• 2011
  • 2011-02-08 EP EP11740548.0A patent/EP2534501A4/de not_active Withdrawn

Patent Citations (3)

Non-Patent Citations (2)

Also Published As

Similar Documents

Legal Events