# Patent

## Title
Method and system for OFDM based MIMO system with enhanced diversity

## Abstract

Certain aspects of a method and system for orthogonal frequency division multiplexing (OFDM) based multi-input multi-output (MIMO) system having enhanced diversity are disclosed. Aspects of one method may include selecting a group of antennas from a plurality of antennas within a radio frequency (RF) system. Data may be communicated via the selected group of antennas. The selected group of antennas may comprise at least one polarized antenna that is orthogonally polarized with respect to adjacent polarized antennas. The plurality of coherently polarized antennas may be placed at a particular distance from each other.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE
This application makes reference to:
U.S. application Ser. No. 11/536,678, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,682, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,650, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,644, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,676, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,659, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,673, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,679, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,670, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,672, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,648, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,669, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,666, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,675, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,685, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,655, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,660, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,657, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,662, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,688, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,667, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,651, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,656, filed Sep. 29, 2006;
U.S. application Ser. No. 11/536,663, filed Sep. 29, 2006.
Each of the above referenced applications is hereby incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
Certain embodiments of the invention relate to wireless communication systems. More specifically, certain embodiments of the invention relate to a method and system for an orthogonal frequency division multiplexing (OFDM) based multi-input multi-output (MIMO) system having enhanced diversity.
BACKGROUND OF THE INVENTION
In most current wireless communication systems, nodes in a network may be configured to operate based on a single transmit and a single receive antenna. However, for many current wireless systems, the use of multiple transmit and/or receive antennas may result in an improved overall system performance. These multi-antenna configurations, also known as smart antenna techniques, may be utilized to reduce the negative effects of multipath and/or signal interference may have on signal reception. Existing systems and/or systems which are being currently deployed, for example, CDMA-based systems, TDMA-based systems, WLAN systems, and OFDM-based systems such as IEEE 802.11 a/g/n, may benefit from configurations based on multiple transmit and/or receive antennas. It is anticipated that smart antenna techniques may be increasingly utilized both in connection with the deployment of base station infrastructure and mobile subscriber units in cellular systems to address the increasing capacity demands being placed on those systems. These demands arise, in part, from a shift underway from current voice-based services to next-generation wireless multimedia services that provide voice, video, and data communication.
The utilization of multiple transmit and/or receive antennas is designed to introduce a diversity gain and array gain and to suppress interference generated within the signal reception process. Such diversity gains improve system performance by increasing received signal-to-noise ratio, by providing more robustness against signal interference, and/or by permitting greater frequency reuse for higher capacity. Systems that utilize multiple transmit and multiple receive antenna may be referred to as multiple-input multiple-output (MIMO) systems. One attractive aspect of multi-antenna systems, in particular MIMO systems, is the significant increase in system capacity that may be achieved by utilizing these transmission configurations. For a fixed overall transmitted power, the capacity offered by a MIMO configuration may scale with the increased signal-to-noise ratio (SNR).
In order to transfer maximum energy or power between a transmit and a receive antenna, both antennas should have the same spatial orientation, the same polarization sense and the same axial ratio. When the antennas are not aligned or do not have the same polarization, there may be a reduction in energy or power transfer between the two antennas. This reduction in power transfer may reduce the overall system efficiency and performance. When the transmit and receive antennas are both linearly polarized, physical antenna misalignment may result in a polarization mismatch loss.
Multipath signals may arrive at a mobile handset antenna via the reflection of the direct signal off of nearby objects. If the reflecting objects are oriented such that they are not aligned with the polarization of the incident wave, the reflected wave may experience a shift in polarization shift. The resultant or total signal available to the receiver at either end of the communications link may be a vector summation of the direct signal and all of the multipath signals. In many instances, there may be a number of signals arriving at the receive site that are not aligned with the polarization of the system antenna. As the receive antenna rotates from vertical to horizontal, it may intercept or receive energy from these multiple signals.
In polarization diversity systems, a dual linear polarized antenna may be utilized to receive samples and track the polarization output providing the strongest signal level. Each output may provide a total signal that may be a combination of all incident signals. This combined signal may be a function of the amplitude and phase of each signal as well as the polarization mismatch of each signal.
Transmit antenna diversity may be utilized to obtain diversity gain against Rayleigh fading in wireless systems where the mobile user has a limited number of antennas. Antenna hopping may utilize transmit antennas to obtain diversity gain. With antenna hopping, cyclic or pseudo-random hopping may be used to transform spatial diversity into time diversity, which may be exploited by, appropriate error correction codes and interleaving techniques, but the interleaving requirements and/or possible bandwidth expansion may incur latency due to the error correction code.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.
BRIEF SUMMARY OF THE INVENTION
A method and/or system for an orthogonal frequency division multiplexing (OFDM) based multi-input multi-output (MIMO) system, substantially as shown in and/or described in connection with at least one of the figures, as set forth more completely in the claims.
These and other advantages, aspects and novel features of the present invention, as well as details of an illustrated embodiment thereof, will be more fully understood from the following description and drawings.



BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
FIG. 1A is a block diagram illustrating a radio frequency (RF) system with a wireless communication host device and an associated radio, in accordance with an embodiment of the invention.
FIG. 1B is a diagram that illustrates antenna polarization in wireless communication systems, in accordance with an embodiment of the invention.
FIG. 1C is a block diagram of an exemplary OFDM based multi-input multi-output MIMO system, in accordance with an embodiment of the invention.
FIG. 2 is a block diagram of an exemplary radio frequency (RF) receiver, in accordance with an embodiment of the invention.
FIG. 3A is a diagram that illustrates an exemplary antenna architecture for multi-antenna orthogonal frequency division (OFD) based systems, in accordance with an embodiment of the invention.
FIG. 3B is a diagram that illustrates another exemplary antenna architecture for multi-antenna orthogonal frequency division (OFD) based systems, in accordance with an embodiment of the invention.
FIG. 4 is a block diagram of an exemplary switching mechanism in OFDM based multi-input multi-output MIMO system, in accordance with an embodiment of the invention.



DETAILED DESCRIPTION OF THE INVENTION
Certain embodiments of the invention may be found in a method and system for an orthogonal frequency division multiplexing (OFDM) based multi-input multi-output (MIMO) system having enhanced diversity. Certain aspects of the invention may include selecting a group of antennas from a plurality of antennas within a radio frequency (RF) system. Data may be communicated via the selected group of antennas. The selected group of antennas may comprise at least one polarized antenna that is orthogonally polarized with respect to adjacent polarized antennas. The plurality of polarized antennas may be placed at a particular distance from each other.
FIG. 1A is a block diagram illustrating a radio frequency (RF) system with a wireless communication host device and an associated radio, in accordance with an embodiment of the invention. Referring to FIG. 1A, there is shown a radio frequency (RF) system 100 that comprises a wireless communication host device 10 and an associated RF subsystem 60.
The wireless communication host device 10 may comprise a processing module 50, a memory 52, a radio interface 54, an input interface 58 and an output interface 56. The processing module 50 and the memory 52 may be enabled to execute a plurality of instructions. For example, for a cellular telephone host device, the processing module 50 may be enabled to perform the corresponding communication functions in accordance with a particular cellular telephone standard.
The radio interface 54 may be enabled to allow data to be received from and transmitted to the RF subsystem 60. The radio interface 54 may be enabled to provide the data received from the RF subsystem 60 to the processing module 50 for further processing and/or routing to the output interface 56. The output interface 56 may be enabled to provide connectivity to an output device such as a display, monitor, or speakers such that the received data may be displayed. The radio interface 54 may be enabled to provide data from the processing module 50 to the RF subsystem 60. The processing module 50 may be enabled to receive the outbound data from an input device such as a keyboard, keypad, or microphone via the input interface 58 or generate the data itself. The processing module 50 may be enabled to perform a corresponding host function on the data received via input interface 58 and/or route it to RF subsystem 60 via radio interface 54.
For cellular telephone hosts, RF subsystem 60 may be a built-in component. For personal digital assistants hosts, laptop hosts, and/or personal computer hosts, the RF subsystem 60 may be built-in or an externally coupled component. The RF subsystem 60 may comprise a host interface 62, a digital receiver processing module 64, an analog-to-digital converter 66, a filtering/gain module 68, a down-conversion module 70, a low noise amplifier 72, a receiver filter module 71, a transmitter/receiver (Tx/Rx) switch module 73, a local oscillation module 74, a memory 75, a digital transmitter processing module 76, a digital-to-analog converter 78, a filtering/gain module 80, an up-conversion module 82, a power amplifier 84, a transmitter filter module 85, and a plurality of antennas, antenna 1 86a, antenna 2 86b, and antenna 3 86c operatively coupled as shown. The antenna 2 86b may be shared by the transmit and receive paths as regulated by the Tx/Rx switch module 73.
Antenna 1 86a may be polarized with a zero degree polarization angle, for example. Antenna 2 86b may be orthogonally polarized with respect to antenna 1 86a, and may have a 90 degree polarization angle. Antenna 3 86c may be orthogonally polarized with respect to antenna 2 86b, and may be coherently polarized with respect to antenna 1 86a, and may have a zero degree or 180 degree polarization angle. The plurality of coherently polarized antennas, antenna 1 86a, and antenna 3 86c may be placed at a particular distance, d apart from each other. The plurality of antennas, antenna 1 86a, antenna 2 86b, and antenna 3 86c may be configured so as to provide isolation in space and/or time. The polarized antennas, antenna 1 86a, antenna 2 86b, and antenna 3 86c may enable reduction of space between the antennas and may provide isolation.
The digital receiver processing module 64 and the digital transmitter processing module 76, in combination with operational instructions stored in the memory 75, may be enabled to execute digital receiver functions and digital transmitter functions, respectively. The digital receiver functions may comprise, but are not limited to, demodulation, constellation demapping, decoding, and/or descrambling. The digital transmitter functions may comprise, but are not limited to, scrambling, encoding, constellation mapping, and modulation. The digital receiver and the transmitter processing modules 64 and 76, respectively, may be implemented using a shared processing device, individual processing devices, or a plurality of processing devices, for example, a microprocessor, micro-controller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that manipulates signals (analog and/or digital) based on operational instructions.
The memory 75 may be a single memory device or a plurality of memory devices. For example, the memory 75 may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, and/or any device that stores digital information. When the digital receiver processing module 64 and/or the digital transmitter processing module 76 implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory storing the corresponding operational instructions may be embedded with the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry. The memory 75 may be enabled to store, and digital receiver processing module 64 and/or digital transmitter processing module 76 may be enabled to execute, operational instructions corresponding to at least some of the functions illustrated herein.
In operation, the RF subsystem 60 may be enabled to receive outbound data from the wireless communication host device 10 via host interface 62. The host interface 62 may be enabled to route outbound data to the digital transmitter processing module 76. The digital transmitter processing module 76 may be enabled to process the outbound data in accordance with a particular wireless communication standard or protocol, for example, IEEE 802.11a, IEEE 802.11b, ZigBee, and Bluetooth to produce digital transmission formatted data. The digital transmission formatted data may be a digital baseband signal or a digital low IF signal, where the low IF may be in the frequency range of one hundred kilohertz to a few megahertz, for example.
The digital-to-analog converter 78 may be enabled to convert the digital transmission formatted data from the digital domain to the analog domain. The filtering/gain module 80 may be enabled to filter and/or adjusts the gain of the analog baseband signal prior to providing it to the up-conversion module 82. The up-conversion module 82 may be enabled to directly convert the analog baseband signal, or low IF signal, into an RF signal based on a transmitter local oscillation 83 provided by the local oscillation module 74. The power amplifier 84 may enable amplification of the RF signal to produce an outbound RF signal, which may be filtered by the transmitter filter module 85. The antenna 86b may be enabled to transmit the outbound RF signal to a targeted device such as a base station, an access point and/or another wireless communication device.
The RF subsystem 60 may be enabled to receive an inbound RF signal via antenna 86b, which was transmitted by a base station, an access point, or other wireless communication device. The antenna 86b may be enabled to communicate the inbound RF signal to the receiver filter module 71 via Tx/Rx switch module 73, where Rx filter module 71 bandpass filters inbound RF signal. The Rx filter module 71 may be enabled to communicate the filtered RF signal to the low noise amplifier 72, which may amplify the inbound RF signal to generate an amplified inbound RF signal. The low noise amplifier 72 may be enabled to communicate the amplified inbound RF signal to the down-conversion module 70, which may directly convert the amplified inbound RF signal into an inbound low IF signal or baseband signal based on a receiver local oscillation 81 provided by local oscillation module 74. The down-conversion module 70 may be enabled to communicate the inbound low IF signal or baseband signal to the filtering/gain module 68. The filtering/gain module 68 may be enabled to filter and/or attenuate the inbound low IF signal or the inbound baseband signal to produce a filtered inbound signal.
The analog-to-digital converter 66 may be enabled to convert the filtered inbound signal from the analog domain to the digital domain to generate digital reception formatted data. The digital receiver processing module 64 may be enabled to decode, descramble, demap, and/or demodulate digital reception formatted data to recapture inbound data. The host interface 62 may be enabled to communicate the recaptured inbound data to the wireless communication host device 10 via the radio interface 54.
The local oscillation module 74 may be enabled to adjust an output frequency of a received local oscillation signal. The local oscillation module 74 may be enabled to receive a frequency correction input to adjust an output local oscillation signal to generate a frequency corrected local oscillation signal output.
FIG. 1B is a diagram that illustrates antenna polarization in wireless communication systems, in accordance with an embodiment of the invention. Referring to FIG. 1B, there is shown a polarized antenna 150. The energy radiated by the polarized antenna 150 may be a transverse electromagnetic wave that comprises an electric field and a magnetic field. These fields are always orthogonal to one another and orthogonal to the direction of propagation. The electric field E of the electromagnetic wave may be utilized to describe its polarization. The total electric field of the electromagnetic wave may comprise two linear components, which are orthogonal to one another. Each of these components may have a different magnitude and phase. At any fixed point along the direction of propagation, the total electric field may trace an ellipse as a function of time. For example, at any instant in time, Ex is the component of the electric field in the x-direction and Ey is the component of the electric field in the y-direction. The total electric field E, is the vector sum of Ex and Ey.
The elliptical polarization may comprise two cases, for example, circular polarization and linear polarization. A circularly polarized electromagnetic wave may comprise two linearly polarized electric field components that are orthogonal, have equal amplitude and may be 90 degrees out of phase. In this case, the polarization ellipse traced by the wave is a circle. Depending upon the direction of rotation of the circularly polarized wave, the wave may be left hand circularly polarized or right hand circularly polarized. The phase relationship between the two orthogonal components, +90 degrees or −90 degrees, determines the direction of rotation. A linearly polarized electromagnetic wave may comprise a single electric field component and the polarization ellipse traced by the wave is a straight line.
FIG. 1C is a block diagram of an exemplary OFDM based multi-input multi-output MIMO system, in accordance with an embodiment of the invention. Referring to FIG. 1C, the RF system 170 may comprise a dedicated physical channel (DPCH) block 126, a plurality of mixers 128, 130 and 132, a plurality of combiners 134 and 136, a first antenna switch (SW1) 135, a second antenna switch (SW2) 137, a first group of transmit antennas 138 and 140, a second group of antenna 139 and 141, and an antenna controller 145 on the transmit side. On the receive side, the RF system 170 may comprise a plurality of receive antennas 1061 . . . M, a single weight generator (SWG) 110, a plurality of RF blocks 1141 . . . P, a plurality of chip matched filters (CMF) 1161 . . . P, and a baseband (BB) processor 126.
The DPCH 126 may be enabled to receive a plurality of input channels, for example, a dedicated physical control channel (DPCCH) and a dedicated physical data channel (DPDCH). The DPCH 126 may simultaneously control the power of DPCCH and DPDCH. The mixer 128 may be enabled to mix the output of DPCH 126 with a spread and/or scrambled signal to generate a spread complex valued signal that may be input to mixers 130 and 132. The mixers 130 and 132 may weight the complex valued input signals with weight factors W1 and W2, respectively, and may generate outputs to a plurality of combiners 134 and 136 respectively. The combiners 134 and 136 may combine the outputs generated by mixers 130 and 132 with common pilot channel 1 (CPICHL) and common pilot channel 2 (CPICH2) respectively. The common pilot channels 1 and 2 may have a fixed channelization code allocation that may be utilized to measure the phase amplitude signal strength of the channels.
The SW1 135 and the SW2 137 may comprise suitable logic, circuitry, and/or code that may be enabled to select from signals at two output ports, one of which may be coupled to an input port. The SW1 135 and SW2 137 may be implemented by utilizing, for example, single pull double throw (SPDT) switching devices or by utilizing a multiplexer (MUX), for example. The selection operation of the SW1 135 and SW2 137 may be controlled by a control signal such as a transmission control (TX_CTL) signal generated by the antenna controller 145. The SW1 135 may be enabled to switch between the plurality of antennas, 138 and 139 alternately in order to transmit communication signals from the plurality of antennas. The SW2 137 may be enabled to switch between the plurality of antennas, 140 and 141 alternately in order to transmit communication signals from the plurality of antennas.
The plurality of antennas, 138, 139, 140, and 141 may comprise suitable logic, circuitry, and/or code that may be enabled to provide transmission of communication signals. In this regard, the plurality of antennas, 138, 139, 140, and 141 may be utilized for transmission of a plurality of communication protocols. The plurality of antennas, 138, 139, 140, and 141 may be configured so as to provide isolation in space and/or time. The polarized antennas, 138, 139, 140, and 141 may enable reduction of space between the antennas and may provide isolation. The first group of antennas 138 and 140, or the second group of antennas, 139 and 141 may receive the generated outputs from the combiners 134 and 136 and may transmit wireless signals based on the position of the antenna switched SW1 135 and SW2 137.
The plurality of receive antennas 1061 . . . M may each receive at least a portion of the transmitted signal. The SWG 110 may comprise suitable logic, circuitry, and/or code that may be enabled to determine a plurality of weights to be applied to each of the input signals R1 . . . M. The SWG 110 may be enabled to modify the phase and amplitude of a portion of the transmitted signals received by the plurality of receive antennas 1061 . . . M and generate a plurality of output signals RF1 . . . P.
The plurality of RF blocks 1141 . . . P may comprise suitable logic, circuitry, and/or code that may be enabled to process an RF signal. The RF blocks 1141 . . . P may perform, for example, filtering, amplification, and analog-to-digital (A/D) conversion operations. The plurality of transmit antennas 138 and 140 may transmit the processed RF signals to a plurality of receive antennas 1061 . . . M. The single weight generator SWG 110 may comprise suitable logic, circuitry, and/or code that may be enabled to determine a plurality of weights, which may be applied to each of the input signals. The single weight generator SWG 110 may be enabled to modify the phase and amplitude of at least a portion of the signals received by the plurality of receive antennas 1061 . . . M and generate a plurality of output signals RF1 . . . P. The plurality of RF receive blocks 1141 . . . P may comprise suitable logic, circuitry and/or code that may be enabled to amplify and convert the received analog RF signals RF1 . . . P down to baseband. The plurality of RF receive blocks 1141 . . . P may each comprise an analog-to-digital (A/D) converter that may be utilized to digitize the received analog baseband signal.
The plurality of chip matched filters (CMF) 1161 . . . P may comprise suitable logic, circuitry and/or code that may be enabled to filter the output of the plurality of RF receive blocks 1141 . . . P so as to produce in-phase (I) and quadrature (Q) components (I, Q). In this regard, in an embodiment of the invention, the plurality of chip matched filters (CMF) 1161 . . . P may comprise a pair of digital filters that are enabled to filter the I and Q components. The outputs of the plurality of chip matched filters (CMF) 1161 . . . P may be transferred to the BB processor 126.
The BB processor 126 may be enabled to receive a plurality of in-phase and quadrature components (I, Q) from a plurality of chip matched filters (CMF) 1161 . . . P and generate a plurality of baseband combined channel estimates ĥ1 to ĥP. The BB processor 126 may be enabled to generate a plurality of estimates {circumflex over (X)}1 to {circumflex over (X)}P of the original input spatial multiplexing sub-stream signals or symbols X1 to XP. The BB processor 126 may be enabled to separate the different space-time channels utilizing a Bell Labs Layered Space-Time (BLAST) algorithm, for example, by performing sub-stream detection and sub-stream cancellation. The capacity of transmission may be increased almost linearly by utilizing the BLAST algorithm.
The plurality of cluster path processors CPP 1181 . . . P may generate a plurality of baseband combined channel estimates ĥ1 to ĥk that may correspond to the plurality of receive antennas 1061 . . . M. The channel estimator 122 may comprise suitable logic, circuitry, and/or code that may be enabled to process the received estimates ĥ1 to ĥP from the BB processor 126 and may generate a matrix Ĥ of processed estimated channels.
FIG. 2 is a block diagram of an exemplary radio frequency (RF) receiver antenna architecture for orthogonal frequency division (OFD) based systems, in accordance with an embodiment of the invention. Referring to FIG. 2, there is shown a RF receiver 200. The RF receiver 200 may comprise a plurality of polarized antennas 2101,2, . . . ,M, and 2111,2, . . . ,M, a plurality of switches 2091,2, . . . ,M, a plurality of amplifiers 2121,2, . . . ,M, an antenna controller 223, a weight generation block 214, a plurality of filters 2201,2, . . . ,N, a local oscillator 222, a plurality of mixers 2241,2, . . . ,N, a plurality of analog to digital (A/D) converters 2261,2, . . . ,N and a baseband processor 230.
The plurality of switches SW1,2, . . . ,M 2091,2, . . . ,M may comprise suitable logic, circuitry, and/or code that may be enabled to select from signals at two input ports, one that may be connected to an output port. The plurality of switches SW1,2, . . . ,M, 2091,2, . . . ,M may be implemented by utilizing, for example, single pull double throw (SPDT) switching devices, switching transistors, or by utilizing a multiplexer (MUX), for example. The selection operation of the plurality of switches SW1,2, . . . ,M, 2091,2, . . . ,M may be controlled by a control signal such as a receive control (RX_CTL) signal generated by the antenna controller 223. For example, switch 1 (SW1) 2091 may be enabled to switch between the plurality of antennas, 2101 and 2111 alternately in order to receive communication signals from the plurality of antennas. Similarly, switch M (SWM) may be enabled to switch between the plurality of antennas, 210M and 211M alternately in order to receive communication signals from the plurality of antennas.
The plurality of antennas, 2101,2, . . . ,M, and 2111,2, . . . ,M may comprise suitable logic, circuitry, and/or code that may be enabled to provide transmission and/or reception of communication signals. In this regard, the plurality of antennas, 2101,2, . . . ,M, and 2111,2, . . . ,M may be utilized for reception of a plurality of communication protocols. The plurality of antennas, 2101,2, . . . ,M, and 2111,2, . . . ,M may be configured so as to provide isolation in space and/or time. The antennas, 2101,2, . . . ,M, and 2111,2, . . . ,M may be polarized to enable reduction of space between the antennas and to provide isolation. The first group 207 of antennas, 2101,2, . . . ,M, or the second group 205 of antennas, 2111,2, . . . ,M may be selected to receive the communication signals based on selected group of antennas by the plurality of antenna switches 2091,2, . . . ,M.
In accordance with an embodiment of the invention, a plurality of antennas that are placed adjacently to at least one polarized antenna may be orthogonally polarized with respect to their adjacent placed polarized antennas. For example, antenna 1 2101 may be polarized with a zero degree polarization angle. Antenna 2 2102 may be orthogonally polarized with respect to antenna 1 2101, and may have a 90 degree polarization angle. Antenna 3 2103 may be orthogonally polarized with respect to antenna 2 2102, and may be coherently polarized with respect to antenna 1 2101, and may have a zero degree or 180 degree polarization angle. Similarly, antenna M-1 210M-1 may have a zero degree polarization angle, for example. Antenna M-2 210M-2 and antenna M 210M may be orthogonally polarized with respect to antenna M-1 210M-1, and may each have a 90 degree polarization angle.
The plurality of coherently polarized antennas, antenna 1 2101, antenna 3 2103, and antenna 5 2105 may be placed at a particular distance, d1, apart from each other. The plurality of coherently polarized antennas, antenna 2 2102, antenna 4 2104, and antenna 6 2106 may be placed at a particular distance, d2, apart from each other. In an embodiment of the invention, the particular distance, d1, may or may not be equal to the particular distance, d2.
The amplifiers 2121,2, . . . ,M may be enabled to amplify the M received input RF signals. The weight generation block 214 may comprise a plurality of amplitude and phase shifters to compensate for the phase difference between various received input RF signals. Weights may be applied to each of the input signals A1 . . . M to modify the phase and amplitude of a portion of the transmitted signals received by the plurality of receive antennas 2121 . . . M and generate a plurality of output signals RF . . . N. The plurality of filters 2201,2, . . . ,N may be enabled to filter frequency components of the RF substreams. The mixers 2241,2, . . . ,N may be enabled to downconvert the analog RF substreams to baseband. The local oscillator 222 may be enabled to provide a signal to the mixers 2241,2, . . . ,N, which may be utilized to downconvert the analog RF substreams to baseband. The analog to digital (A/D) converters 2261,2, . . . ,N may be enabled to convert the analog baseband substreams into their corresponding digital substreams. The baseband processor 230 may be enabled to process the digital baseband substreams and multiplex the plurality of digital signals to generate output signals.
In operation, the RF signals may be received by a plurality of M polarized antennas 2101,2, . . . ,M or 2111,2, . . . ,M at the receiver 200. Each of the M received signals may be amplified by a respective low noise amplifier 2121,2, . . . ,M. A plurality of weights may be applied to each of the input signals A1 . . . M to modify the phase and amplitude of a portion of the transmitted signals received by the plurality of receive antennas 2121 . . . M. A plurality of output signals RF1 . . . N may be generated, which may be filtered by a plurality of filters 2201,2, . . . ,N. The resulting N filtered signals may then be downconverted to baseband utilizing a plurality of N mixers 2241,2, . . . N, each of which may be provided with a carrier signal that may be generated by a local oscillator 222. The N baseband signals generated by the mixers 2241,2, . . . ,N may then be converted to digital signals by a plurality of analog to digital (A/D) converters 2261,2, . . . ,N. The N digital signals may further be processed by a baseband processor 230 to generate the output signals.
In one embodiment of the invention, the baseband processor 230 may be operating in accordance with one or more standards, including but not limited to, IEEE 802.11, Bluetooth, ZigBee, advanced mobile phone services (AMPS), global systems for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), Worldwide Interoperability for Microwave Access (WiMAX), fourth generation (4G), orthogonal frequency division multiplexing (OFDM) based systems, digital video broadcasting handheld (DVB-H), multi-channel-multi-point distribution systems (MMDS), global positioning system (GPS), frequency modulation (FM), enhanced data rates for GSM evolution (EDGE) and/or variations thereof.
FIG. 3A is a diagram that illustrates an exemplary antenna architecture for multi-antenna orthogonal frequency division (OFD) based systems, in accordance with an embodiment of the invention. Referring to FIG. 3A, there is shown a RF system 300 that comprises a plurality of antennas, antenna 1 302, antenna 2 304, antenna 3 306, antenna 4 308, antenna 5 310, and antenna 6 312.
The plurality of antennas, antenna 1 302, antenna 2 304, antenna 3 306, antenna 4 308, antenna 5 310, and antenna 6 312 may comprise suitable logic, circuitry, and/or code that may be enabled to provide transmission and reception of RF communication signals. In this regard, the plurality of antennas, antenna 1 302, antenna 2 304, antenna 3 306, antenna 4 308, antenna 5 310, and antenna 6 312 may be utilized for transmission and reception of a plurality of communication protocols including but not limited to, IEEE 802.11, Bluetooth, advanced mobile phone services (AMPS), global systems for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), Worldwide Interoperability for Microwave Access (WiMAX), fourth generation (4G), orthogonal frequency division multiplexing (OFDM) based systems, digital video broadcasting handheld (DVB-H), multi-channel-multi-point distribution systems (MMDS), global positioning system (GPS), frequency modulation (FM), enhanced data rates for GSM evolution (EDGE) and/or variations thereof.
Antenna 1 302 may be polarized with a zero degree polarization angle, for example. Antenna 2 304 may be orthogonally polarized with respect to antenna 1 302, and may have a 90 degree polarization angle. Antenna 3 306 may be orthogonally polarized with respect to antenna 2 304, and may be coherently polarized with respect to antenna 1 302, and may have a zero degree or 180 degree polarization angle. Similarly, antenna 4 308 may have a 90 degree polarization angle, antenna 5 310 may have either a zero degree or 180 degree polarization angle, and antenna 6 312 may have a 90 degree polarization angle. The plurality of coherently polarized antennas, antenna 1 302, antenna 3 306, and antenna 5 310 may be placed at a particular distance, d1, apart from each other. The plurality of coherently polarized antennas, antenna 2 304, antenna 4 308, and antenna 6 312 may be placed at a particular distance, d2, apart from each other. In an embodiment of the invention, the particular distance, d1, may or may not be equal to the particular distance, d2.
The plurality of antennas, antenna 1 302, antenna 2 304, antenna 3 306, antenna 4 308, antenna 5 310, and antenna 6 312 may be configured so as to provide isolation in space and/or time. The polarized antennas, antenna 1 302, antenna 2 304, antenna 3 306, antenna 4 308, antenna 5 310, and antenna 6 312 may enable reduction of space between the antennas and may provide isolation.
FIG. 3B is a diagram that illustrates another exemplary antenna architecture for multi-antenna orthogonal frequency division (OFD) based systems, in accordance with an embodiment of the invention. Referring to FIG. 3B, there is shown a RF system 300 that comprises a plurality of antennas that may be arranged in a matrix 350. Each cell within the matrix may comprise one polarized antenna.
Antenna 1 in the first cell 362 may be polarized with a zero degree polarization angle, for example. Antenna 2 in the adjacent cell 364 may be orthogonally polarized with respect to antenna 1 in the first cell 360, and may have a 90 degree polarization angle. Antenna 3 in the third cell 366 may be orthogonally polarized with respect to antenna 1 in cell 362, and may be coherently polarized with respect to antenna 2 in cell 364, and may have a 90 degree polarization angle. Similarly, antenna 4 in cell 368 may be coherently polarized with respect to antenna 1 in cell 362, and may be orthogonally polarized with respect to antenna 2 in cell 364, and antenna 3 in cell 366, and may have either a zero degree or 180 degree polarization angle. Antenna 5 in cell 370 may be coherently polarized with respect to antenna 4 in cell 368, and may be orthogonally polarized with respect to antenna 3 in cell 366, and may have either a zero degree or 180 degree polarization angle. Antenna 6 in cell 372 may be orthogonally polarized with respect to antenna 5 in cell 370, and may have a 90 degree polarization angle.
The plurality of coherently polarized antennas, antenna 1 in cell 362, antenna 4 in cell 368, and antenna 5 in cell 370 may be placed at a particular distance, d1, apart from each other. The plurality of coherently polarized antennas, antenna 2 in cell 364, antenna 3 in cell 366, may be placed at a particular distance, d2, apart from each other. The plurality of coherently polarized antennas, antenna 3 in cell 366 and antenna 6 in cell 372 may be placed at a particular distance, d2, apart from each other. In an embodiment of the invention, the particular distance, d1, may or may not be equal to the particular distance, d2.
FIG. 4 is a block diagram of an exemplary switching mechanism in OFDM based multi-input multi-output MIMO system, in accordance with an embodiment of the invention. Referring to FIG. 4, there is shown a portion of a RF system 400 that comprises a plurality of antenna switches, switch 1 410, switch 2 412, switch 3 414, and switch 4 416, a first group of antennas 420, and a second group of antennas 430. The first group of antennas 420 may comprise a plurality of antennas, antenna 1 422, antenna 2 424, antenna 3 426, and antenna 4 428. The second group of antennas 430 may comprise a plurality of antennas, antenna 5 432, antenna 6 434, antenna 7 436, and antenna 8 438.
The plurality of antenna switches, switch 1 410, switch 2 412, switch 3 414, and switch 4 416 may comprise suitable logic, circuitry, and/or code that may be enabled to select from signals at two input ports, one of which may be coupled to an output port. The plurality of switches switch 1 410, switch 2 412, switch 3 414, and switch 4 416 may be implemented by utilizing, for example, single pull double throw (SPDT) switching devices, switching transistors, or by utilizing a multiplexer (MUX), for example. The selection operation of the plurality of switches switch 1 410, switch 2 412, switch 3 414, and switch 4 416 may be controlled by a control signal such as a transmission control (TX_CTL) signal or receive control (RX_CTL) signal generated by the antenna controller 405.
For example, switch 1 410 may be enabled to switch between the plurality of antennas, antenna 1 422 and antenna 5 432 alternately in order to transmit and/or receive communication signals to/from the plurality of antennas. Switch 2 412 may be enabled to switch between the plurality of antennas, antenna 2 424 and antenna 6 434 alternately in order to transmit and/or receive communication signals to/from the plurality of antennas. Switch 3 414 may be enabled to switch between the plurality of antennas, antenna 3 426 and antenna 7 436 alternately in order to transmit and/or receive communication signals to/from the plurality of antennas. Switch 4 416 may be enabled to switch between the plurality of antennas, antenna 4 428 and antenna 8 438 alternately in order to transmit and/or receive communication signals to/from the plurality of antennas.
The plurality of antennas, antenna 1 422, antenna 2 424, antenna 3 426, antenna 4 428, antenna 5 432, antenna 6 434, antenna 7 436, and antenna 8 438 may comprise suitable logic, circuitry, and/or code that may be enabled to provide transmission and/or reception of communication signals. In this regard, the plurality of antennas, antenna 1 422, antenna 2 424, antenna 3 426, antenna 4 428, antenna 5 432, antenna 6 434, antenna 7 436, and antenna 8 438 may be utilized for transmission and/or reception of a plurality of communication protocols. The plurality of antennas, antenna 1 422, antenna 2 424, antenna 3 426, antenna 4 428, antenna 5 432, antenna 6 434, antenna 7 436, and antenna 8 438 may be configured so as to provide isolation in space and/or time. The plurality of antennas, antenna 1 422, antenna 2 424, antenna 3 426, antenna 4 428, antenna 5 432, antenna 6 434, antenna 7 436, and antenna 8 438 may be polarized to enable reduction of space between the antennas and to provide isolation. The first group of antennas 420, or the second group 430 may be selected to transmit and/or receive communication signals based on the selected group of antennas by the plurality of antenna switches, switch 1 410, switch 2 412, switch 3 414, and switch 4 416.
In accordance with an embodiment of the invention, a plurality of antennas that are placed adjacently to at least one polarized antenna may be orthogonally polarized with respect to their adjacent placed polarized antennas. For example, antenna 1 422 may be polarized with a zero degree polarization angle. Antenna 2 424 may be orthogonally polarized with respect to antenna 1 2101, and may have a 90 degree polarization angle. Antenna 3 426 may be orthogonally polarized with respect to antenna 2 424, and may be coherently polarized with respect to antenna 1 422, and may have a zero degree or 180 degree polarization angle. Antenna 4 428 may be orthogonally polarized with respect to antenna 3 426, and may have a 90 degree polarization angle. Similarly, antenna 5 432 may be polarized with a 90 degree polarization angle, for example. Antenna 6 434 may be orthogonally polarized with respect to antenna 5 432, and may have a zero degree polarization angle. Antenna 6 436 may be orthogonally polarized with respect to antenna 2 434, and may be coherently polarized with respect to antenna 1 432, and may have a 90 degree polarization angle. Antenna 4 438 may be orthogonally polarized with respect to antenna 3 436, and may be coherently polarized with respect to antenna 3 436 and may have a zero degree or 180 degree polarization angle.
The plurality of coherently polarized antennas, antenna 1 422, and antenna 3 426 may be placed at a particular distance, d1, apart from each other. The plurality of coherently polarized antennas, antenna 2 424, antenna 4 428 may be placed at a particular distance, d2, apart from each other. Similarly, the plurality of coherently polarized antennas, antenna 5 432, and antenna 7 436 may be placed at a particular distance, d1, apart from each other. The plurality of coherently polarized antennas, antenna 6 434, antenna 8 438 may be placed at a particular distance, d2, apart from each other. In an embodiment of the invention, the particular distance, d1, may or may not be equal to the particular distance, d2. Notwithstanding, the RF system 400 may comprise a plurality of groups of antennas, and each switch may be enabled to switch between a plurality of antennas.
In accordance with an embodiment of the invention, a method and system for orthogonal frequency division multiplexing (OFDM) based multi-input multi-output (MIMO) system having enhanced diversity may comprise a plurality of antenna switches, switch 1 410, switch 2 412, switch 3 414, and switch 4 416 within a radio frequency (RF) system 400 comprising a plurality of antennas, for example, antenna 1 422, antenna 2 424, antenna 3 426, antenna 4 428, antenna 5 432, antenna 6 434, antenna 7 436, and antenna 8 438 that may enable selection of at least one group of antennas, for example, a first group of antennas 420, or a second group of antennas 430.
The selected group of antennas, for example, the first group of antennas 420, may comprise at least one polarized antenna, for example, antenna 1 422, that may be orthogonally polarized with adjacent polarized antennas, for example, antenna 2 424. The polarized antenna, for example, antenna 1 422 may be placed at a particular distance, d1 from at least one other polarized antenna, for example, antenna 3 426 that is coherently polarized with respect to the polarized antenna, antenna 1 422. The adjacent polarized antenna, antenna 2 424 may be placed at a particular distance, d2 from at least one other polarized antenna, antenna 4 428, that is coherently polarized with respect to the adjacent polarized antenna, antenna 2 424.
At least one polarized antenna, antenna 3 426 that is orthogonally polarized with respect to adjacent polarized antennas, antenna 2 424 and antenna 4 428 may be enabled to transmit and/or receive data. The plurality of antenna switches, switch 1 410, switch 2 412, switch 3 414, and switch 4 416 may be enabled to switch between a plurality of selected groups of antennas, for example, a first group of antennas 420 or a second group of antennas 430. The plurality of antenna switches, switch 1 410, switch 2 412, switch 3 414, and switch 4 416 may be enabled to select at least one antenna from the selected group of antennas for communicating data. For example, switch 1 410 may be enabled to switch between the plurality of antennas, antenna 1 422 and antenna 5 432 alternately in order to transmit and/or receive communication signals to/from the plurality of antennas. Switch 2 412 may be enabled to switch between the plurality of antennas, antenna 2 424 and antenna 6 434 alternately in order to transmit and/or receive communication signals to/from the plurality of antennas.
Another embodiment of the invention may provide a machine-readable storage, having stored thereon, a computer program having at least one code section executable by a machine, thereby causing the machine to perform the steps as described above for orthogonal frequency division multiplexing (OFDM) based multi-input multi-output (MIMO) system having enhanced diversity. For example, any one or more of the components in the wireless communication host device 10 and/or the RF subsystem 60 may be controlled via code such as software and/or firmware. In this regard, in an exemplary embodiment of the invention, any one or more of the digital receiver processing module 64, ADC 66, filtering/gain module 68, down-conversion module 70, LNA 72 and Rx filter module 71 may be programmably controlled by code comprising software and/or firmware. In another exemplary embodiment of the invention, any one or more of the digital transmitter processing module 76, DAC 78, filtering/gain module 80, up-conversion module 82, PA 84, and Tx filter module 86, may be programmably controlled by code comprising software and/or firmware.
Accordingly, the present invention may be realized in hardware, software, or a combination of hardware and software. The present invention may be realized in a centralized fashion in at least one computer system, or in a distributed fashion where different elements are spread across several interconnected computer systems. Any kind of computer system or other apparatus adapted for carrying out the methods described herein is suited. 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.
While the present invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from its scope. Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed, but that the present invention will include all embodiments falling within the scope of the appended claims.

## Claims

1. A method for processing signals in a communication network, the method comprising:
in a radio frequency (RF) system comprising a plurality of polarized antennas, selecting at least one group of polarized antennas from said plurality of polarized antennas; and
communicating data via said selected at least one group of polarized antennas, wherein:
a first of said selected at least one group of polarized antennas is orthogonally polarized with respect to adjacent ones of said selected at least one group of polarized antennas; and
said first of said selected at least one group of polarized antennas is located at a substantially equal distance from corresponding non-adjacent ones of said selected at least one group of antennas.

2. The method according to claim 1, comprising placing said first of said selected at least one group of polarized antennas at said substantially equal distance from said corresponding non-adjacent ones of said selected at least one group of polarized antennas.

3. The method according to claim 1, comprising placing a first of said adjacent ones of said selected at least one group of polarized antennas at a substantially equal distance from at least one other of said adjacent ones of said selected at least one group of polarized antennas.

4. The method according to claim 1, comprising transmitting said data via said first of said selected at least one group of polarized antennas.

5. The method according to claim 1, comprising receiving said data via said first of said selected at least one group of polarized antennas.

6. The method according to claim 1, comprising switching between said first of said selected at least one group of polarized antennas and at least one of said adjacent ones of said selected at least one group of polarized antennas.

7. The method according to claim 1, wherein said first of said selected at least one group of polarized antennas is coherently polarized with respect to said corresponding non-adjacent ones of said selected at least one group of polarized antennas.

8. A non-transitory machine-readable storage having stored thereon, a computer program having at least one code section for processing signals in a communication network, the at least one code section being executable by a machine for causing the machine to perform steps comprising:
in a radio frequency (RF) system comprising a plurality of polarized antennas, selecting at least one group of polarized antennas from said plurality of polarized antennas; and
communicating data via said selected at least one group of polarized antennas, wherein:
a first of said selected at least one group of polarized antennas is orthogonally polarized with respect to adjacent ones of said selected at least one group of polarized antennas; and
said first of said selected at least one group of polarized antennas is located at a substantially equal distance from corresponding non-adjacent ones of said selected at least one group of polarized antennas.

9. The non-transitory machine-readable storage according to claim 8, wherein said at least one code section comprises code for placing said first of said selected at least one group of polarized antennas at said substantially equal distance from said corresponding non-adjacent ones of said selected at least one group of polarized antennas.

10. The non-transitory machine-readable storage according to claim 8, wherein said at least one code section comprises code for placing a first of said adjacent ones of said selected at least one group of polarized antennas at a substantially equal distance from at least one other of said adjacent ones of said selected at least one group of polarized antennas.

11. The non-transitory machine-readable storage according to claim 8, wherein said at least one code section comprises code for transmitting said data via said first of said selected at least one group of polarized antennas.

12. The non-transitory machine-readable storage according to claim 8, wherein said at least one code section comprises code for receiving said data via said first of said selected at least one group of polarized antennas.

13. The non-transitory machine-readable storage according to claim 8, wherein said at least one code section comprises code for switching between said first of said selected at least one group of polarized antennas and at least one of said adjacent ones of said selected at least one group of polarized antennas.

14. The non-transitory machine-readable storage according to claim 8, wherein said first of said selected at least one group of polarized antennas is coherently polarized with respect to said corresponding non-adjacent ones of said selected at least one group of polarized antennas.

15. A system for processing signals in a communication network, the system comprising:
one or more circuits within a radio frequency (RF) system comprising a plurality of polarized antennas, said one or more circuits being operable to select at least one group of polarized antennas from said plurality of polarized antennas; and
said one or more circuits are operable to communicate data via said selected at least one group of polarized antennas, wherein:
a first of said selected at least one group of polarized antennas is orthogonally polarized with respect to adjacent ones of said selected at least one group of polarized antennas; and
said first of said selected at least one group of polarized antennas is located at a substantially equal distance from corresponding non-adjacent ones of said selected at least one group of polarized antennas.

16. The system according to claim 15, wherein said first of said selected at least one group of polarized antennas is placed at said substantially equal distance from said corresponding non-adjacent ones of said selected at least one group of polarized antennas.

17. The system according to claim 15, wherein said first of said adjacent ones of said selected at least one group of polarized antennas is placed at a substantially equal distance from at least one other of said adjacent ones of said selected at least one group of polarized antennas.

18. The system according to claim 15, wherein said one or more circuits are operable to transmit said data via said first of said selected at least one group of polarized antennas.

19. The system according to claim 15, wherein said one or more circuits are operable to receive said data via said first of said selected at least one group of polarized antennas.

20. The system according to claim 15, wherein said one or more circuits are operable to switch between said first of said selected at least one group of polarized antennas and at least one of said adjacent ones of said selected at least one group of polarized antennas.

21. The system according to claim 15, wherein said first of said selected at least one group of polarized antennas is coherently polarized with respect to said corresponding non-adjacent ones of said selected at least one group of polarized antennas.