Wireless system using different bands in the transmit and receive direction and applying frequency shifts for bandwidth expansion

A wireless access point is configured to communicate in millimeter wave frequency bands in the downlink direction and in sub-6 GHz frequency bands in the uplink direction. The wireless access point includes a signal processing circuit configured to generate different spatial streams signals and a frequency shift circuit configured to apply different frequency shifts to the different spatial streams signals. The wireless access point includes a mixer driven by a local oscillator, which up-converts the frequency shifted signals to millimeter wave frequency band signals, wherein the millimeter wave frequency band signals are transmitted by a MIMO transmit antenna array. A wireless communication device applies different frequency shifts to the different spatial streams signals after down-converting the signals received at a higher millimeter wave frequency to a lower frequency below 6 GHz. The wireless communication device applies no frequency-shifts to different spatial streams signals transmitted at lower frequency below 6 GHz.

BACKGROUND

The invention generally relates to wireless communications and more specifically to wireless communications using different spectrum bands in the transmit and receive direction.

DESCRIPTION OF THE RELATED ART

Currently, wireless access methods are based on two popular standards: a wide area network (WAN) standard referred to as The Fourth Generation Long Term Evolution (4G LTE) system; and a local area network (LAN) standard called Wi-Fi. Wi-Fi is generally used indoors as a short-range wireless extension of wired broadband systems. The 4G LTE systems on the other hand provide wide area long-range connectivity both outdoors and indoors using dedicated infrastructure such as cell towers and backhaul to connect to the Internet.

As more people connect to the Internet, increasingly chat with friends and family, watch videos, listen to streamed music, and indulge in virtual or augmented reality, data traffic continues to grow at unprecedented rates. In order to address the continuously growing wireless capacity challenge, the next generation of LAN and WAN systems are expected to rely on higher frequencies referred to as millimeter waves in addition to currently used frequency bands below 6 GHz.

SUMMARY OF THE INVENTION

According to disclosed embodiments, a wireless access point (or radio base station) is configured to communicate in millimeter wave frequency bands in the downlink direction and in sub-6 GHz frequency bands in the uplink direction. The wireless access point (or radio base station) comprises a multiple input multiple output (MIMO) transmit antenna array configured to operate in the millimeter wave frequency bands and a multiple input multiple output (MIMO) receive antenna array configured to operate in the sub-6 GHz frequency bands. The wireless access point comprises a signal processing circuit configured to generate different spatial streams signals and a frequency shift circuit configured to apply different frequency shifts to the different spatial streams signals. The wireless access point comprises a mixer driven by a local oscillator, which up-converts the frequency shifted signals to millimeter wave frequency band signals, wherein the millimeter wave frequency band signals are transmitted by the MIMO transmit antenna array.

According to disclosed embodiments, a wireless communication device applies different frequency shifts to the different spatial streams signals after down-converting the signals received at a higher millimeter wave frequency to a lower frequency below 6 GHz. The wireless communication device applies no frequency-shifts to different spatial streams signals transmitted at lower frequency below 6 GHz.

The wireless access point comprises a mixer driven by a local oscillator configured to down-convert the millimeter wave frequency band signals of different spatial streams. The wireless access point comprises a frequency shift circuit configured to apply different frequency shifts to the different spatial streams signals and a signal processing circuit configured to process the down converted signals.

In another embodiment, the wireless access point comprises a signal processing circuit configured to generate a different spatial streams signals and a frequency shift circuit configured to apply frequency shifts to a first group of the different spatial streams signals, wherein no frequency shifts are applied to a second group of the different spatial streams signals.

In yet another embodiment, the wireless access point comprises a frequency shift circuit configured to apply different inverse frequency shifts to the down-converted different spatial streams signals. The different inverse frequency shifts negate the frequency shifts applied to the millimeter wave frequency band signals prior to reception by the MIMO receive antenna array.

DETAILED DESCRIPTION

According to disclosed embodiments, a wireless system uses different spectrum in the transmit and receive directions. In one direction, the wireless system uses conventional radio spectrum below 6 GHz used by 4G LTE and Wi-Fi systems while in the other direction, the system uses higher millimeter wave spectrum. Table 1 lists millimeter wave bands.

FIG. 1illustrates an exemplary wireless network100according to disclosed embodiments. The wireless network100relies on different spectrum in the transmit and receive directions to/from anchor access points (or radio base stations) A0and A1which provide service to communication devices C0-C5and to non-anchor access points A1and A3in its coverage area. The anchor access points A0and A1are connected to the Internet104(or any other telecommunications network) using Gigabit/s high-speed wired links104such as optical fiber communications. The non-anchor access points A2and A3do not rely on wired high-speed links but rather connect to the Internet108(or any other telecommunications network) via wireless links to the access points A0and A1.

The anchor access point A0provides services to communication devices C0, C1and C2using frequency f2on the downlink and frequency f1on the uplink. Similarly, anchor access point A1provides services to communication devices C3, C4and C5using frequency f2on the downlink and frequency f1on the uplink. First non-anchor access point A2communicates with the anchor access point A1using frequency f2in the direction from A1to A2and on frequency f1in the direction from A2to A1.

Second non-anchor access point A3communicates with the anchor access point A1using frequency f2in the direction from A1to A3and frequency f1in the direction from A3to A1. The non-anchor access points A2provides services to communication device C6on frequency f1. The non-anchor access points A3provides service to communication device C7on a third frequency f3. Alternatively, the third frequency f3can be the same as the first frequency f1or second frequency f2.

FIGS. 2 and 3illustrate a wireless communications chain in accordance with disclosed embodiments. The wireless communications chain transmits and receives at two different frequencies. The wireless communications chain may be implemented in the access points A0-A3and the communication devices C0-C8.

Referring toFIG. 2, the wireless communications chain includes Medium Access Control (MAC)204and Physical (PHY) layer208functions. In some embodiments, same MAC204protocol or Physical layer208may be used in the two directions at frequency f1and frequency f2allowing components re-use thereby reducing system cost and form factor. The Physical (PHY) layer208functions include channel encoding and decoding212schemes such as low-density parity check (LDPC) codes, modulation and demodulation216schemes such as BPSK, QPSK, 16-QAM, 64-QAM and 256-QAM, MIMO precoding and detection220schemes, and multiple access schemes such as orthogonal frequency division multiplexing (OFDM)224.

Referring now toFIG. 3, in the transmit direction at a frequency f2, the physical layer208provides digital baseband In-Phase (I) and Quadrature (Q) signals that are converted into analog baseband In-Phase (I) and Quadrature (Q) signals using a set of data converters (DAC/ADCs)308. The analog baseband In-Phase (I) and Quadrature (Q) signals are modulated using a set of quadrature modulators or quadrature mixers312driven by a first Local Oscillator (LO1) generating a set of signals at frequency f1. These signals at frequency f1can optionally be amplified using a RF front-end320. The RF front end320includes power amplifiers324and low noise amplifiers328. A control function332sends a signal to switches336to enable connection to the power amplifiers324operating at frequency f1. Mixers340driven by a second local oscillator (LO2) convert the signals to a frequency f2. These signals are amplified by power amplifiers344operating at frequency f2and transmitted by an antenna array348operating at frequency f2. According to some disclosed embodiments, the antenna array348is configured to transmit millimeter wave band signals.

To receive signals in the receive direction at frequency f1, the control function332sends a signal to the switches336to enable connections to the low-noise amplifiers (LNA)328. The signals received at an antenna array352operating at frequency f1are amplified by the low-noise amplifiers (LNAs)328and demodulated using a set of quadrature modulators or quadrature mixers312driven by the first Local Oscillator (LO1) generating a set of analog baseband In-Phase (I) and Quadrature (Q) signals. The analog baseband In-Phase (I) and Quadrature (Q) signals are converted to digital baseband In-Phase (I) and Quadrature (Q) signals using a set of analog-to-digital converters (ADCs)308. These digital baseband In-Phase (I) and Quadrature (Q) signals are fed into the physical (PHY) layer208where they undergo digital signal processing.

According to disclosed embodiments, the MAC204and PHY208layers are implemented on application-specific integrated circuit (ASIC) system-on-a-chip (SoC). In some implementations, the SoC includes the digital-to-analog (DAC) and analog-to-digital converter (ADC) functions. In other implementations, a radio frequency integrated circuit (RFIC) incorporating quadrature mixers, amplification and filtering functions are implemented on the system-on-a-chip (SoC).

FIG. 4illustrates a system400configured for multiple input multiple output (MIMO) and beamforming for transmission and reception at two different frequencies according to the principles of the current invention. The system400includes a system-on-chip (SoC)404that implements MAC, Physical (PHY) layers as well as a radio frequency integrated circuit (RFIC) including quadrature mixers illustrated inFIGS. 2 and 3.

The SoC404outputs signals centered at frequency f1. The SoC404can support transmission of M multiple input multiple output (MIMO) spatial streams (SS). In the exemplary embodiment illustrated inFIG. 4, the SoC404supports eight spatial streams. However, in other embodiments, the number of spatial streams supported by the SoC404can be any integer number (e.g., 2, 4, 8, 12, 16, 18, 24, 32, 64).

The SoC404applies Tx/Rx control signal420to switches408and412to switch between transmit and receive modes. The signals at frequency f1out of the SoC404can optionally be amplified by using a RF front-end. The transmit/receive control signal420is provided to the switches408to enable connection to power amplifiers424operating at frequency f1. Mixers428driven by a second local oscillator (LO2) convert the signals to a frequency f2. These signals are amplified by power amplifiers432operating at frequency f2and transmitted by antenna array436operating at frequency f2.

To receive signals in the receive direction at frequency f1, Tx/Rx control signal420is applied to the switches408and412to enable connections to the low-noise amplifiers (LNA)440. The signals received at the antenna array444operating at frequency f1are amplified by the low-noise amplifiers (LNAs)440and fed into the SoC404.

FIG. 5illustrates a system500that features transmit bandwidth expansion when multiple input multiple output (MIMO) technique is used. The bandwidth expansion enables transmission of signals at wider bandwidths compared to the bandwidth of a single transmit chain. The bandwidth expansion is achieved by applying frequency sifts to signals from different antennas. When these frequency-shifted signals are transmitted over the air, they occupy larger bandwidth compared to the bandwidth of signals from a single antenna. The system500transmits at frequency f2and receives signals at frequency f1. In the system500, a frequency shift is applied to the spatial streams generated by the SoC504to implement bandwidth expansion.

Referring toFIG. 5, the SoC504sends a Tx/Rx control signal520to the switches508and512to enable connection to the power amplifiers524operating at frequency f1. In the exemplary embodiment ofFIG. 5, eight spatial streams are divided into two groups of four spatial streams each, first group for transmission on the horizontally polarized antennas530and the second group for transmission on the vertically polarized antennas530.

A frequency shift of f0is applied to the first spatial stream in each group, a frequency shift of f0+Δ is applied to the second spatial stream in each group, a frequency shift of f0+2Δ is applied to the third spatial stream in each group and finally a frequency shift of f0+3Δ is applied to the fourth spatial stream in each group. Optionally, f0can be set to zero. For example, when the carrier frequency f2of the transmit signals is f2=28 GHz, f0=0 and Δ=160 MHz=0.16 GHz, a frequency shift of 0 is applied to the first spatial stream in each group, a frequency shift of 0.16 GHz is applied to the second spatial stream in each group, a frequency shift of 0.32 GHz is applied to the third spatial stream in each group and finally a frequency shift of 0.48 GHz is applied to the fourth spatial stream in each group. Thus the carrier frequency for the first, second, third and fourth spatial stream are 28 GHz, 28.16 GHz, 28.32 GHz and 28.48 GHz respectively. Alternatively, frequency shifts are applied to signals from different antennas which may be precoded spatial stream signals.

The frequency shifted signals are combined separately for horizontal and vertical polarization signal paths. According to some disclosed embodiments, Δ=−Ω where any frequency shift comprises Δ, however other values may be selected for Δ. Mixers512and516driven by local oscillators (LO2) convert the signals to a frequency f2. These up-converted signals can optionally be split into multiple paths and appropriate phased shifting can be applied to achieve analog beamforming. The phase-shifted signals on the horizontal and vertical polarization paths are amplified by power amplifiers524operating at frequency f2and transmitted by the antenna array528operating at frequency f2.

By applying different frequency shifts to the spatial streams, the spatial streams can be made to occupy different channels in the electromagnetic spectrum, thus decreasing statistical correlation between spatial streams or signals from different antennas. Also, as the spatial streams occupy different channels in the electromagnetic spectrum, data is transmitted over a wider bandwidth, which increases data throughput. Also, high dimension MIMO processing is achieved in the transceiver by adapting the frequency shifts even if the wireless propagation conditions do not support high dimension MIMO processing.

In the embodiment illustrated inFIG. 5, the frequency shifts are applied to the signals at frequency f1after amplification by the power amplifiers operating at frequency f1. In other embodiments, the frequency shifts may be applied to the signals at frequency f1before amplification. In yet other embodiments, the frequency shifts are applied to the signals before the RFIC in the baseband.

FIG. 6illustrates reception of bandwidth expanded signals in a MIMO wireless communication system600employing transmission and reception at two different frequencies. The higher millimeter wave signals received on the vertically and horizontally polarized antennas604are amplified by low noise amplifiers (LNA)608and612operating at frequency f2. Phase shifting can be applied by phase shifters616and620to the amplified signals and the resulting signals are combined coherently on each of the horizontal and vertical polarization paths to provide the analog beamforming gain. The resulting signals on the horizontal and vertical polarization paths are down-converted to lower frequency f1by mixers616driven by local oscillators (LO2). The down-converted signals are optionally filtered and split into two sets of four signal streams.

The first received signal stream is frequency shifted down by f0in each group, the second signal stream is frequency shifted down by f0−Δ in each group, the third signal stream is frequency shifted down by f0−2Δ in each group and finally the fourth signal stream is frequency shifted by f0−3Δ in each group. Optionally, f0can be set to zero. For example, when the frequencies of the receive signals for the first, second, third and fourth spatial stream are 28 GHz, 28.16 GHz, 28.32 GHz and 28.48 GHz respectively and f0=0 and Δ=160 MHz=0.16 GHz, the first spatial stream signal is down-shifted by 0, the second spatial stream signal is down-shifted by 0.16 GHz, the third spatial stream signal is down-shifted by 0.32 GHz, and finally the fourth spatial stream signal is down-shifted by 0.48 GHz. This makes all spatial stream signals to be centered at 28 GHz. Alternatively, frequency shifts are applied to signals from different antennas signals.

As described before, Δ=−Ω or any other suitable value. The resulting signals from frequency translation that are now centered at the same frequency are amplified by the low-noise-amplifiers (LNAs)630and634operating at frequency f1and fed into the eight spatial streams inputs of the SoC640. The frequency translation can be performed either using real or quadrature mixers. In case of real mixers, signal spectrum at image frequency is created which is suppressed using bandpass filters. In the receive path, the image signal may not be eliminated as the filtering in the receiver can accommodate for this undesired signal and reject it.

In the embodiment illustrated inFIG. 6, the eight signal streams are each frequency shifted to remove the frequency shifts added by the transmitter (as illustrated inFIG. 5). The value of the frequency shifts in the receiver are the negative value of the frequency shifts in the transmitter. In general, the purpose of frequency shifts illustrated inFIG. 6is to invert the frequency shifts illustrated inFIG. 5.

The frequency shifts can also be applied during up-conversion by using frequency shifted values for the Local Oscillator (LO2). For example, if f1=5 GHz and f2=28 GHz, a Local Oscillator (LO2) value of 23 GHz can be used to up-convert 5 GHz to 28 GHz (23+5=28 GHz). A Local Oscillator (LO2) value of 23.16 GHz can be used to up-convert 5 GHz to 28.16 GHz (23.16+5=28.16 GHz). A Local Oscillator (LO2) value of 23.32 GHz can be used to up-convert 5 GHz to 28.32 GHz (23.32+5=28.32 GHz). A Local Oscillator (LO2) value of 23.48 GHz can be used to up-convert 5 GHz to 28.48 GHz (23.48+5=28.48 GHz).

The frequency shifts can also be applied during down-conversion by using frequency shifted values for the Local Oscillator (LO2). For example, if f1=5 GHz and f2=28 GHz, a Local Oscillator (LO2) value of 23 GHz can be used to down-convert 28 GHz to 5 GHz (28−23=5 GHz). A Local Oscillator (LO2) value of 23.16 GHz can be used to down-convert 28.16 GHz to 5 GHz (28.16−23.16=5 GHz). A Local Oscillator (LO2) value of 23.32 GHz can be used to down-convert 28.32 GHz to 5 GHz (28.32−23.32=5 GHz). A Local Oscillator (LO2) value of 23.48 GHz can be used to down-convert 28.48 GHz to 5 GHz (28.48-23.48=5 GHz).

To transmit signals at frequency f1, Tx/Rx control signal is applied to the switches660and664to enable connections to the power amplifiers644and648operating at frequency f1. The amplified signals at frequency f1are transmitted from the antenna array652operating at frequency f1.

FIG. 7illustrates a system700comprising multiple SoCs704A-704N that feature transmit bandwidth expansion when multiple input multiple output (MIMO) technique is used. The system700transmits signals at frequency f2and receives signals at frequency f1. The signals at frequency f1out of the SoCs can optionally be amplified by using a RF front-end.

According to disclosed embodiments, eight transmit spatial streams from each SoC are divided into two groups of four spatial streams each, first group for transmission on the horizontally polarized antennas and the second group for transmission on the vertically polarized antennas.

For the SoC704A, no frequency shift is applied to the first spatial stream in each group, a frequency shift of Δ is applied to the second spatial stream in each group, a frequency shift of 2Δ is applied to the third spatial stream in each group and finally a frequency shift of 3Δ is applied to the fourth spatial stream in each group. The four signals on each of the horizontal and vertical polarization paths are combined and the resulting signals are input respectively to the horizontal and vertical polarization combiners that combine the signals across the multiple SoCs.

For the SoC704B, a frequency shift of 4Δ−fd2is applied to the first spatial stream in each group, a frequency shift of 5Δ−fd2is applied to the second spatial stream in each group, a frequency shift of 6Δ−fd2is applied to the third spatial stream in each group and finally a frequency shift of 7Δ−fd2is applied to the fourth spatial stream in each group. Here, fd2represents the frequency offset of the center frequency of the SoC704B relative to the SoC704A. For example, when the signals out of the SoC704A are centered at frequency fcand the signals out of the SoC704B are centered at frequency fc+fd2. Similarly, fd3represents the frequency offset of the center frequency of the third SoC (not shown inFIG. 7) relative to the SoC704A. In other embodiments, fd2, fd3and fd4etc. can be set to zero.

For example, when the carrier frequency f2of the transmit signals is f2=28 GHz, f0=0 and Δ=160 MHz=0.16 GHz, the carrier frequencies for the first, second, third and fourth spatial stream from the first SoC are 28 GHz, 28.16 GHz, 28.32 GHz and 28.48 GHz respectively. Assuming, fd2=0, the carrier frequencies for the first, second, third and fourth spatial stream from the second SoC are 28.64 GHz, 28.80 GHz, 28.96 GHz and 29.12 GHz respectively. Alternatively, frequency shifts are applied to signals from different antennas which may be precoded spatial stream signals.

Different values for fd2, fd3and fd4etc. allows to accommodate different f1frequencies from different SoCs. For example, f1frequencies can be centered at 5.0 and 5.2 GHz for the first and the second SoC respectively. In this case fd2=5.2−5.0=0.2 GHz, a frequency shift of 4Δ−fd2is applied to the first spatial stream in each group, a frequency shift of 5Δ−fd2is applied to the second spatial stream in each group, a frequency shift of 6Δ−fd2is applied to the third spatial stream in each group and finally a frequency shift of 7Δ−fd2is applied to the fourth spatial stream in each group in the second SoC which makes the carrier frequencies for the first, second, third and fourth spatial stream from the second SoC at 28.64 GHz, 28.80 GHz, 28.96 GHz and 29.12 GHz respectively. Thus the signals from the first SoC and the second SoC centered at 28 GHz, 28.16 GHz, 28.32 GHz, 28.48 GHz, 28.64 GHz, 28.80 GHz, 28.96 GHz and 29.12 GHz will occupy contiguous frequency spectrum of 27.92-29.2 GHz with channel size Δ=160 MHz which is 8 times 160 MHz or 1.28 GHz (27.92-29.2 GHz). For example, for Δ=0.16 GHz, for the fourth spatial stream total frequency shift applied would be 7Δ−fd2=1.12−0.2=0.920 GHz making the center frequency f2=5.2+0.920 GHz=6.12 GHz which will be up-converted to 29.12 GHz (23+6.12=29.12 GHz). Alternatively, shifts can be applied during the up-conversion process by frequency-shifting the Local Oscillator (LO2) as discussed earlier.

The four signals on each of the horizontal and vertical polarization paths are combined and the resulting signals are input respectively to the horizontal and vertical polarization combiners708and712that combine the signals across the multiple SoCs. The foregoing pattern of frequency-shifts continues for the remaining SoCs in the system700. Thus, a unique frequency shift is applied to each pair of horizontal and vertical spatial streams (SS). A phase shifting by phase shifters716and720can be applied for the analog beamforming on the combined frequency shifted signals of multiple spatial streams (SS) and multiple SoCs. The resulting signals are up-converted by the mixers724and728driven by local oscillators (LO2). In alternative embodiments, the phased shifting for the analog beamforming is applied after up-conversion to frequency f2. The up-converted signals on the horizontal and vertical polarization paths are amplified by the power amplifiers732and736and transmitted on the horizontally and vertically polarized antennas740respectively at frequency f2.

The receive signals at frequency f1from receive antennas764are amplified by low-noise-amplifiers (LNAs)768and772and are split by splitter776and optionally filtered before feeding into the SoCs704A-704N. In other embodiments, horizontally and vertically polarized antennas can also be used for the receiving signals at frequency f1.

FIG. 8illustrates bandwidth expansion for the case of multiple SoCs employing different center frequencies. InFIG. 8, a system800comprising SoCs804A-804N each employ different center frequencies.

The system800transmits signals at frequency f1and receives signals at frequency f2. The signals at frequency f1out of the SoCs can optionally be amplified by using a RF front-end.

The transmit signals at frequency f1from SoCs804A-804N are combined by combiner808for transmission by the antennas812operating at frequency f1. The combined transmit signals can optionally be amplified by a set of power amplifiers (PA)816and820before transmission by the antennas812over the air. In other embodiments, horizontally and vertically polarized antennas can also be used for transmitting signals at frequency f1.

The received signals on the horizontally and vertically polarized antennas824at frequency f2are amplified by a set of LNAs828and832and down-converted frequency f1by the mixers836and840driven by local oscillators (LO2).

A phase-shifting to achieve receive beamforming gain is applied to the down-converted signals by using a set of phase shifters844and848. In alternative embodiments, the phased shifting for the analog beamforming is applied before down-conversion to frequency f1. The down-converted signals on the horizontal and vertical polarization paths are split by splitters852and856for feeding into the multiple SoCs804A-804N.

For the signals destined for the SoC804A, no frequency shift is applied to the first spatial stream in each group, a frequency shift of −Δ is applied to the second spatial stream in each group, a frequency shift of −2Δ is applied to the third spatial stream in each group and finally a frequency shift of −3Δ is applied to the fourth spatial stream in each group. The four signals on each of the horizontal and vertical polarization paths are then fed into the SoC804A.

For the SoC804B, a frequency shift of −(4Δ−fd2) is applied to the first spatial stream in each group, a frequency shift of −(5Δ−fd2) is applied to the second spatial stream in each group, a frequency shift of −(6Δ−fd2) is applied to the third spatial stream in each group and finally a frequency shift of −(7Δ−fd2) is applied to the fourth spatial stream in each group. The four signals on each of the horizontal and vertical polarization paths are then fed into the SoC804B.

This pattern of frequency-shifts continues for the remaining SoCs in the system. Thus, a unique frequency shift is applied to each pair of horizontal and vertical spatial streams (SS).

FIG. 9illustrates partial transmit bandwidth expansion by a system900featuring multiple SoCs. The system900transmits signals at frequency f2and receives signals at frequency f1. The signals at frequency f1out of the SoC can optionally be amplified by using a RF front-end.

Referring toFIG. 9, eight transmit spatial streams are divided into two groups of four spatial streams each, first group for transmission on the horizontally polarized antennas and the second group for transmission on the vertically polarized antennas.

For the SoC904A, no frequency shift is applied to the first and second spatial streams in each group, a frequency shift of Δ is applied to the third and fourth spatial streams in each group.

For the SoC904B, a frequency shift of 2Δ−fd2is applied to the first and second spatial streams in each group, a frequency shift of 3Δ−fd2is applied to the third and fourth spatial streams in each group. The signals on each of the horizontal and vertical polarization paths are combined and the resulting signals are input respectively to the horizontal and vertical polarization combiners that combine the signals across the multiple SoCs.

This pattern of frequency-shifts continues for the remaining SoCs in the system. A phased shifting can be applied for the analog beamforming on the combined frequency shifted signals of multiple spatial streams (SS) and multiple SoCs. The resulting signals are up-converted by the mixers driven by a local oscillator (LO2). In alternative embodiments, the phased shifting for the analog beamforming is applied after up-conversion to frequency f2. The up-converted signals on the horizontal and vertical polarization paths are amplified by the power amplifiers and transmitted on the horizontally and vertically polarized antennas respectively at frequency f2.

The receive signals at frequency f1for each of the receive antennas are amplified by low-noise-amplifiers (LNAs) and are split and optionally filtered before feeding into the multiple SoCs.

FIG. 10illustrates transmit bandwidth expansion across multiple SoCs when multiple input multiple output (MIMO) technique is used in a wireless communication system1000employing transmission and reception at two different frequencies. The system1000transmits signals at frequency f2and receives signals at frequency f1. The signals at frequency f1out of the SoC can optionally be amplified by using a RF front-end.

Referring toFIG. 10, eight transmit spatial streams into two groups of four spatial streams each, first group for transmission on the horizontally polarized antennas and the second group for transmission on the vertically polarized antennas.

For the SoC1004A, no frequency shift is applied to any of the spatial streams. For the SoC1004B, a frequency shift of Δ−fd2is applied to all spatial streams. The signals on each of the horizontal and vertical polarization paths are input respectively to the horizontal and vertical polarization combiners1044and1048that combine the signals across the multiple SoCs. This pattern of frequency-shifts continues for the remaining SoCs in the system. A phased shifting can be applied by phase shifters1012and1016for the analog beamforming on the combined frequency shifted signals of multiple SoCs. The resulting signals are up-converted by mixers1020and1024driven by a local oscillator (LO2). In alternative embodiments, the phased shifting for the analog beamforming is applied after up-conversion to frequency f2. The up-converted signals on the horizontal and vertical polarization paths are amplified by the power amplifiers1028and1032and transmitted on the horizontally and vertically polarized antennas1036respectively at frequency f2.

The receive signals at frequency f1for each of the receive antennas1050are amplified by low-noise-amplifiers (LNAs)1054and1058and are split and optionally filtered before feeding into the multiple SoCs.

FIG. 11illustrates 5 GHz unlicensed band channels used in the uplink according to disclosed embodiments.FIG. 12illustrates an example where unlicensed 5 GHz spectrum and 37/38 GHz bands are used in the receive and transmit directions, respectively, in the wireless communications system in accordance with disclosed embodiments. In the example illustrated inFIG. 11, a maximum bandwidth used at 5 GHz spectrum is 40 MHz. If a maximum bandwidth expansion factor is 4, the maximum bandwidth transmitted at 37/38 GHz band is 160 MHz. By using 12 channels, each of 40 MHz at 5 GHz spectrum, the bandwidth is expanded to 1.92 GHz which is equivalent to 12 channels, each of 160 MHz at 37/38 GHz band.

FIG. 13depicts an example where unlicensed 5 GHz spectrum and 37-40 GHz bands are used in the receive and transmit directions, respectively, in the wireless communications system in accordance with disclosed embodiments. In the example illustrated inFIG. 13, a maximum bandwidth used at 5 GHz spectrum is 20 MHz. If a maximum bandwidth expansion factor is 8, the maximum bandwidth transmitted at 37-40 GHz bands can be 160 MHz. By using 24 channels, each of 20 MHz at 5 GHz spectrum, the bandwidth is expanded to 3.0 GHz which is equivalent to 14 channels of 160 MHz each, 9 channels of 80 MHz and a single channel of 40 MHz at 37-40 GHz bands.

FIG. 14depicts an example where unlicensed 5 GHz spectrum and 28 GHz bands are used in the receive and transmit directions, respectively. In the example illustrated in FIG. 14, a maximum bandwidth used at 5 GHz spectrum is 80 MHz and different bandwidth expansion factors can be used for different channels.

The channel42using 80 MHz bandwidth at 5 GHz is expanded by a factor of 2 to a total bandwidth of 160 MHz at 28 GHz band. The channel54using 40 MHz bandwidth at 5 GHz is expanded by a factor of 4 to a total bandwidth of 160 MHz at 28 GHz band. The channel102using 40 MHz bandwidth at 5 GHz is expanded by a factor of 2 to a total bandwidth of 80 MHz at 28 GHz band. The channel122using 80 MHz bandwidth at 5 GHz is expanded by a factor of 4 to a total bandwidth of 160 MHz at 28 GHz band. The channel132using 20 MHz bandwidth at 5 GHz is expanded by a factor of 2 to a total bandwidth of 40 MHz at 28 GHz band. The channel142using 40 MHz bandwidth at 5 GHz is expanded by a factor of 4 to a total bandwidth of 160 MHz at 28 GHz band. The channel151using 40 MHz bandwidth at 5 GHz is expanded by a factor of 2 to a total bandwidth of 80 MHz at 28 GHz band.

FIG. 15illustrates an example of channel selection and bandwidth expansion in a wireless communications system in accordance with disclosed embodiments. In particular,FIG. 15illustrates the case when anchor access point A1communicates with devices C3, C4and C5and non-anchor access points A2and A3on a first frequency f1on the uplink and a second frequency f2on the downlink. In the example illustrated inFIG. 15, the first frequency in the uplink is 5 GHz unlicensed band and the second frequency in the downlink is 28 GHz band.

Access point A1allocates primary 20 MHz channel numbers36,60,102,116and136to communication devices C3, C4and C5and non-anchor access points A2and A3respectively. Access point A1also sets the maximum Wi-Fi channel bandwidth to 80 MHz with a bandwidth expansion factor of 2. With a bandwidth expansion factor of 2, the maximum bandwidth allocated to communication devices C3, C4and C5and non-anchor access points A2and A3is limited to 160 MHz for transmission over the second frequency f2of 28 GHz. This results in maximum bandwidth utilization of 800 MHz which is equivalent to five 160 MHz channels at the second frequency f2of 28 GHz.

Access point A1and the communication device C3with their primary 20 MHz channel number36determines that 80 MHz wide channel number42can be used for communication. Using bandwidth expansion principles disclosed in this invention, access point A1performs a bandwidth expansion by a factor of 2 resulting in total 160 MHZ bandwidth use on the second frequency f2of 28 GHz.

Access point A1and the communication device C4with their primary 20 MHz channel number60determines that 40 MHz wide channel number62can be used for communication. Using bandwidth expansion principles disclosed herein, access point A1performs a bandwidth expansion by a factor of 2 resulting in total 80 MHZ bandwidth use on the second frequency f2of 28 GHz.

Access point A1and the communication device C3with their primary 20 MHz channel number102determines that 40 MHz wide channel number106can be used for communication. Using bandwidth expansion principles disclosed herein, access point A1performs a bandwidth expansion by a factor of 2 resulting in total 80 MHZ bandwidth use on the second frequency f2of 28 GHz.

Access point A1and the non-anchor access point A2with their primary 20 MHz channel number116determines that 80 MHz wide channel number122can be used for communication. Access point A1performs a bandwidth expansion by a factor of 2 resulting in total 160 MHZ bandwidth use on the second frequency f2of 28 GHz.

Access point A1and the non-anchor access point A3with their primary 20 MHz channel number136determines that the larger 40 or 80 MHz bandwidth channels are not available. Therefore, primary 20 MHz channel number136is used for communication with a bandwidth expansion factor of 2 resulting in total 40 MHz bandwidth use on the second frequency f2of 28 GHz.

According to disclosed embodiments, the primary 20 MHz channels are selected to minimize the channel overlap between the neighboring access points.FIG. 15adds channel use in access point A0in addition to the access point A1. The wireless access point A0selects primary 20 MHz channel numbers52,108and140when it communicates with communication devices C3, C4and C5respectively.

Access point A0and the communication device C0with their primary 20 MHz channel number52determines that 40 MHz wide channel number54can be used for communication. Access point A0performs a bandwidth expansion by a factor of 2 resulting in total 80 MHZ bandwidth use on the second frequency f2of 28 GHz. Different primary 20 MHz channel selection in the two access points makes the 40 MHz transmissions on channels54and62non-overlapping reducing interference between these two access points.

Access point A0and the communication device C1with their primary 20 MHz channel number108determines that 40 MHz wide channel number110can be used for communication. Access point A0performs a bandwidth expansion by a factor of 2 resulting in total 80 MHZ bandwidth use on the second frequency f2of 28 GHz. Different primary 20 MHz channel selection in the two access points makes the 40 MHz transmissions on channels102and110non-overlapping reducing interference between these two access points.

Access point A0and the communication device C2with their primary 20 MHz channel number140determine that the larger 40 or 80 MHz bandwidth channels are not available. Therefore, primary 20 MHz channel number140is used for communication with a bandwidth expansion factor of 2 resulting in total 40 MHz bandwidth use on the second frequency f2of 28 GHz. Different primary 20 MHz channel selection in the two access points makes the 20 MHz transmissions on channels136and140non-overlapping reducing interference between these two access points.

According to disclosed embodiments, not only the transmissions at 5 GHz are non-overlapping, the expanded transmissions at frequency f2of 28 GHz are also non-overlapping therefore preserving benefits of non-overlapping primary channel selections after bandwidth expansion.

FIG. 16illustrates an example where unlicensed 5 GHz spectrum and 37/38 GHz bands are used in the uplink and downlink directions, respectively, in the wireless communications system in accordance with disclosed embodiments. In the example illustrated inFIG. 16, a maximum bandwidth used at 5 GHz spectrum is 160 MHz. With a bandwidth expansion factor is 2, the maximum bandwidth transmitted at 37/38 GHz band is 320 MHz. By using 2 channels, channel number50and channel number114, each of 160 MHz at 5 GHz spectrum, the bandwidth is expanded to 640 MHz which is equivalent to 2 channels, each of 320 MHz at 37/38 GHz band.

According to disclosed embodiments, the MAC may facilitate dynamic selection of the bandwidth allocation through system metrics, including the contention condition within different segments of the allocated spectrum.FIG. 17shows an example of dynamic bandwidth selection through request-to-send (RTS) and clear-to-send (CTS) messages for the downlink between access point A0and communication device C0. a transmitter intends to transmit over a contiguous section of spectrum around frequency f1, split into four even subsections of width Δ. A0initially sends RTS messages over each Δ-wide spectrum section. If C0successfully receives an RTS message and determines that the corresponding spectrum section is free from interference, it may respond with a CTS message on the associated uplink spectrum section. In this example, interference was observed on spectrum sections f1and f1+Δ, and either the RTS message was not received or future message integrity on these sections could not be guaranteed. C0responds with CTS messages on uplink spectrum sections f2+2Δ and f−2+3Δ, which are associated with the downlink spectrum sections f1+2Δ and f1+2Δ, respectively, for which favorable interference conditions were detected.

When CTS messages are successfully received over these two spectrum sections, A0responds by transmitting data messages (DATA) over a single 2Δ-wide spectrum section to include individual spectrum sections f1+2Δ and f1+3Δ. If the DATA messages are successfully received by C0, C0will transmit acknowledgement (ACK) messages over a single 2Δ-wide spectrum section to include individual spectrum sections f2+2Δ and f2+3Δ.

Of course, those of skill in the art will recognize that, unless specifically indicated or required by the sequence of operations, certain steps in the processes described above may be omitted, performed concurrently or sequentially, or performed in a different order. Further, no component, element, or process should be considered essential to any specific claimed embodiment, and each of the components, elements, or processes can be combined in still other embodiments.