WO2015178932A1

WO2015178932A1 - Blind technique for weight selection in simultaneous transmit and receive structure

Info

Publication number: WO2015178932A1
Application number: PCT/US2014/039404
Authority: WO
Inventors: Yang-Seok Choi; Shilpa Talwar
Original assignee: Intel Corporation
Priority date: 2014-05-23
Filing date: 2014-05-23
Publication date: 2015-11-26
Also published as: TW201545519A; CN106233638A; EP3146646A1; TWI556613B; EP3146646A4; CN106233638B

Abstract

Embodiments of a wireless communication system and methods for cancelling echo signals in the system are generally described herein. Some of these embodiments include phase shifters to generate output signals, each having a phase shift relative to a transmitted signal, a attenuator unit to attenuate the output signal of each of the phase shifters based on weights to generate attenuated signals, each corresponding to the output signal of one of the phase shifters, a weight calculator to perform an operation for selecting values for the weights without using components associated with the transmitted signal as inputs for calculating the values for the weights, and at least one summer to sum the attenuated signals and a received signal containing an echo signal to generate an echo-canceled signal.

Description

BLIND TECHNIQUE FOR WEIGHT SELECTION IN SIMULTANEOUS TRANSMIT AND RECEIVE STRUCTURE

TECHNICAL FIELD

[0001] Embodiments pertain to wireless communications. Some embodiments relate to transmission of signals in wireless networks including those networks that operate based on a 3GPP Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Long-Term-Evolution (LTE-A) advanced network standard.

BACKGROUND

[0002] In many wireless communication systems, weights are often used to control the value of an echo-cancelling signal generated by an echo-canceller of the system. The echo -canceller may use the echo-cancelling signal to cancel an unwanted echo signal in a receiving path of the system. The echo signal may be part of a signal from a transmitting path of the system that leaks into the receiving path. The values of the weights are often selected, such that the value of echo-cancelling signal may be as close to the value of the echo signal as possible in order to have an effective echo-cancelling operation. In some conventional systems, techniques for selecting such values for the weights may lead to complex echo-cancellation structure, slow cancellation operation, or both.

BRIEF DESCRIPTION OF THE DRAWINGS

[0003] FIG. 1 is a block diagram of a wireless communication system including an echo-canceller, according to some embodiments described herein.

[0004] FIG. 2 is a flowchart showing a method for operating a wireless communication system including an operation for selecting weighs to control attenuators of an echo-canceller, according to some embodiments described herein.

[0005] FIG. 3 shows a wireless communication network including a network station and wireless communication devices, according to some embodiments described herein. [0006] FIG. 4 shows a block diagram of a wireless communication device including echo-canceller, according to some embodiments described herein.

DETAILED DESCRIPTION

The following description and the drawings sufficiently illustrate specific embodiments to enable those skilled in the art to practice them. Other embodiments may incorporate structural, logical, electrical, process, and other changes. Portions and features of some embodiments may be included in, or substituted for, those of other embodiments. Embodiments set forth in the claims encompass all available equivalents of those claims.

[0008] FIG. 1 is a block diagram of a wireless communication system

100 including an echo -canceller 101 , according to some embodiments described herein. Wireless communication system 100 may have simultaneous transmit (Tx) and receive (Rx) (STR) capability (e.g., a full-duplex capability), such that it can simultaneously transmit and receive signals. As shown in FIG. 1 , wireless communication system 100 may include an antenna 102 to receive an incoming signal r(t), a receiver 110, and a transmitter 120. Receiver 110 may include a low noise amplifier (LNA) 111, a down converter 112, and an analog-to -digital (ADC) 113, all arranged to process signals from antenna 102. Transmitter 120 may include a digital-to-analog converter (DAC) 121, an up converter 122, and a power amplifier (PA) 123, all arranged to generate an analog signal x(t) based on a digital signal x(n) for transmission from wireless communication system 100 to other devices.

[0009] Transmission of signal x(t) (transmitted signal) from transmitter

120 may create an echo (e.g., echo signal) in the receiving chain of wireless communication system 100. The echo may be contained in signal y(t), which is also referred to as a received signal containing the echo. Thus, y(t) may include a combination of a desired signal sent to wireless communication system 100 from another device or system plus the echo.

[0010] In order to cancel (e.g., reduce or eliminate) the echo, echo- canceller 101 is arranged to perform an echo-cancellation operation to estimate the echo, generate an echo-cancelling signal, and then subtract the echo- cancelling signal from the received signal containing the echo y(t) to generate an echo-canceled signal z(t). In FIG. 1 , the echo-cancelling signal may include the combination (e.g., a sum) of signals Xi(t) and x₂(t), which are output signals at the output of echo-canceller 101. Echo-canceller 101 may subtract signals Xi(t) and x₂(t) from received signal containing the echo y(t) to generate echo-canceled signal z(t).

[0011] Signal Xi(t) and signal x₂(t) may be generated based on signals from selected taps on a signal path of transmitted signal x(t). FIG. 1 shows an example arrangement where two taps (e.g., a two-tap filter having taps T = 2) may be selected from transmitted signal x(t) for use in echo-canceller 101 to generate two corresponding signals xi(t) and signal x₂(t). The example two taps are associated with two delays tiand τ₂. Other arrangements may be used. For example, more than two taps (e.g., T > 2) may be used to generate an echo- cancelling signal (the combination of signals Xi(t) and x₂(t)) at the output of echo-canceller 101.

[0012] As shown in FIG. 1 , echo-canceller 101 may include a vector modulator 131 to generate signal xi(t) based on a selected tap (e.g., tap associated with T = 1 of the filter), and a vector modulator 132 to generate signal x₂(t) based on another selected tap (e.g., tap associated with T =2 of the filter). FIG. 1 shows two vector modulators 131 and 132 for generating two

corresponding signals (e.g., xi(t) and x₂(t)) as an example, the number of vector modulators may vary.

[0013] The values of signal xi(t) and signal x₂(t) may be controlled by the values of weights used in the corresponding vector modulator. For example, as shown in FIG. 1 , weights wi, w₂, and W3 may be used in vector modulator 131 to control the value of signal Xi(t). Weights w₄, w₅, and W6 may be used in vector modulator 132 to control the value of signal x₂(t). By appropriately selecting the values of these weights (e.g., wi through Wk, where k = 6 in this example) values of signals xi(t) and x₂(t) used to cancel the echo may be appropriately be obtained.

[0014] Echo-canceller 101 may include a weight calculator 160 arranged to calculate and select values for weights wi through Wk- Weight calculator 160 may use a signal Z(n) in the calculation for the values for weights wi through Wk. Signal Z(n) is a digital baseband signal generated based on echo-canceled signal z(t). As described in more detailed below, weight calculator 160 may use a signal Z(n) in an operation of calculating and selecting the values for weights wi through Wk without using components associated with transmitted signal x(t) (or x(n)) as inputs for calculating the values for these weights during the operation. This may allow the structure or operation (or both) of echo -canceller 101 to be less complex than the structure or operation of an echo -canceller 101 that uses components associated with transmitted signal x(t) (or x(n)) as inputs for calculating the values for the weights. Further, without using components associated with transmitted signal x(t) (or x(n)) as inputs for calculating the values for the weights, echo -canceller 101 may be relatively faster and less sensitive to RF impairments.

[0015] As shown in FIG. 1 , echo-canceller 101 may include a delay 103 coupled to the transmit path of transmitter 120. Delay 103 may provide a time delay to compensate for delays in other components (e.g., vector modulators 131 and 132 and summer 155) in the echo estimation path (e.g., path may be between delay τ_\ and summer 155) of echo-canceller 101 that are used in the generation echo-cancelling signals (e.g., xi(t) and x₂(t)). The value of delay 103 may be selected to make sure the delay of echo is between the values of delays of x(t) in xi(t) and x₂(t)).

[0016] Vector modulators 131 and 132 may include similar, or identical, components. Thus, for simplicity, detail of only vector modulator 131 is shown in FIG. 1. Vector modulator 131 may include fixed-phase phase shifters 141 , 142, and 143 arranged to receive an input signal x(t - τι), which is based on transmitted signal x(t) with a delay of τι. For example, input signal x(t - x_\) (a delayed version of transmitted signal x(t)) may be selected from tap T=l of transmitted signal x(t). Phase shifters 141 , 142, and 143 may be arranged for different fixed phase shifts (e.g., 0°, 60°, and 120°, respectively) with respect to transmitted signal x(t). Phase shifters 141 , 142, and 143 generate corresponding output signals at their outputs. The output signals may be attenuated by an attenuator unit, which may include a variable or stepped attenuator unit. The attenuator unit may include attenuators 151 , 152, and 153. Attenuators 151 , 152, and 153 may include variable or stepped attenuators. Attenuators 151 , 152, and 153 may be controlled by a group of weights wi, w₂, and W3, as shown in FIG. 1. Attenuators 151 , 152, and 153 generate attenuated signals at their outputs. Each of the attenuated signals corresponds to the output signal of one of the phase shifters 141, 142, and 143. The attenuated signals at the outputs of attenuator 151, 152, and 153 may be summed by a summer 154 to generate signal Xi(t), which is one of the output signals at the output of echo -canceller 101.

[0017] Vector modulator 132 may be arranged to receive an input signal x(t - T2), which is based on transmitted signal x(t) with a delay of Τ2- For example, input signal x(t - τ₂) (a delayed version of transmitted signal x(t)) may be selected from tap T=2 of transmitted signal x(t). Vector modulator 132 may include fixed -phase phase shifters, attenuators (e.g., variable or stepped attenuators), and a summer, similar to, or identical to, those of vector modulator 131 shown in FIG. 1. In vector modulator 132, the output signals at the outputs of the phase shifters may be attenuated by an attenuator unit (e.g., a variable or stepped attenuator unit). The attenuators (e.g., variable or stepped attenuators) in the attenuator unit may be controlled by a group of weights W4, w₅, and w_¾. The attenuated signals at the outputs of the attenuators of vector modulator 132 may be summed by the summer in vector modulator 132 to generate signal x₂(t), which is another output signal at the output of echo -canceller 101).

[0018] Summer 155 may be arranged to sum signals Xi(t) and x₂(t) and the received signal containing the echo y(t) to generate echo-canceled signal z(t).

[0019] As mentioned above, weight calculator 160 may use signal Z(n) in an operation of calculating and selecting values for weights wi through Wk. Weight calculator 160 may select the values for weights wi through Wk by performing an operation to search the values of the weights. The search may be based on a minimization of the cost function of signal Z(n). The cost function may be expressed as

where Z(t) is the output of echo-canceller 101, Y(t) is received signal containing the echo signals, X(t) is a vector signal of the transmitted signal with different delays and phase rotations and W = yv_\ .. . WK] ^T is the weight vector. As can be seen in Equation (1), the cost function is a quadratic function of the weight vector. Thus, the local minimum of the cost function is the global minimum of the cost function. Therefore, the values for weights wi through Wk may be selected by searching for a value of the weight that falls on the global minimum of the cost function, which is also the smallest value of the power of signal Z(n). Thus, a particular value of a weight can be selected by searching for the smallest value of the power of signal Z(n).

[0020] As shown in FIG. 1 , signal Z(n) may be generated from echo- canceled signal z(t) using a path that may include a band-pass filter 161, a variable gain amplifier (VGA) 162 to modify (e.g., amplify) echo-canceled signal z(t), a down converter 163 to down-convert echo-canceled signal z(t) after it modified by VGA 162 to generate a baseband signal, and an analog-to-digital converter (ADC) 164 to convert echo-canceled signal z(t) after it is modified by VGA 162 and down-converted by down converter 163 to generate signal Z(n). Weight calculator 160 of echo -canceller 101 may include a periodic

measurement unit 165 to measure the power (P) of signal Z(n) over a certain time interval based on Equation (2)

n

[0021] The operation of VGA 162 may change the power of signal Z(n). Thus, in order to maintain the value (e.g., true value) of signal Z(n) used in the calculation for searching for the values for the weights, the value of the power of signal Z(n) may be compensated by a compensated value (e.g., 1/g²) as shown in Equation (3)) by a unit 166. Therefore, the cost function of signal Z(n) with compensation for the gain of VGA 162 may be based on equation

where "g" is defined as the gain of VGA 162 in linear scale.

[0022] In an operation of calculating and selecting the values for the weight (as described in more detail with reference to FIG. 2), since ensemble averaging is not possible, a time average of signal Z(n) (which is a digital baseband signal) may be performed over a certain period. Wireless

communication system 100 may communicate with other systems or devices using orthogonal frequency division multiple (OFDM) access. In such an access, an OFDM signal can be averaged over an OFDM symbol or integer multiple of OFDM symbols. During the averaging of power, the weight may be fixed.

[0023] Weight calculator 160 may also include a weight selection unit

167 arranged to select the values for weights wi through Wk based on Equation (3), as described in detail below with reference to FIG. 2. After the values for weights wi through Wk are selected, they can be applied (at control inputs of attenuators of vector modulator 131 and 132) in echo-canceller 101 for controlling attenuators (e.g.., 151, 152, and 153 of vector modulators 131 and 132).

[0024] The selected values of the weight may remain unchanged after they are selected. Alternatively, echo-canceller 101 may adjust these values based on some predetermined condition. For example, echo-canceller 101 may include a power monitor 170 arranged to monitor the value of power of signal Z(n) measured by periodic measurement unit 165. Based on the monitored value of the power, power monitor 170 may cause echo-canceller 101 to adjust the values of the weights (e.g., by selecting new values for the weights). For example, during a weight recalibration of echo-canceller 101 , power monitor 170 may cause periodic measurement unit 165 to measure the power of signal Z(n) after some predetermined time intervals or when wireless communication system 100 is not receiving signals (e.g., downlink signals). If the value of the measured power during this measurement exceeds a threshold value (e.g., a predetermined value), power monitor 170 may cause echo-canceller 101 to adjust the values of the weights so that the value of the power may be reduced to an appropriate value. This may allow the values of the weights to maintain optimum values (e.g., selected values) in order to maintain proper echo- cancellation operation performed by echo-canceller 101.

[0025] FIG. 2 is a flowchart showing a method 200 for operating a wireless communication system including an operation for selecting weighs to control attenuators of an echo-canceller according to some embodiments described herein. Method 200 may be performed by wireless communication system 100 of FIG. 1. Thus, the echo-canceller used in method 200 may include echo-canceller 101 of FIG. 1.

[0026] In method 200, the goal is searching for the value for each of the weights (e.g., wi through W6 FIG. 1) that yields a minimum value (e.g., local minimum) of the cost function of signal Z(n) (shown in FIG. 1). As described above with reference to FIG. 1, since the cost function is a quadratic function of the weight vector, a minimum value of the cost function may be associated with weights where each of the weights may be a negative value or positive value (along the x-axis of the cost function C(W)). Thus, method 200 may start at activity 201 and perform activities 210 to 216 for searching for the sign

(negative or positive) of each of the weights. By searching for the sign, method 200 may arrive at a starting value for each of the weights that is relatively closer to the global minimum value. This may allow the final value (the value that falls on a global minimum) of each of the weights to be found faster. After the sign for each of the weights is determined, method 200 may use the starting values of the weights in searching for a final value for each of the weights, as described in activities 220 to 228. Method 200 may end at activity 299 after the final values are found.

[0027] To begin searching for the sign, activity 210 may include initializing all weights (e.g., wi through W6 FIG. 1) with a minimum value, such that Wk = Wmin, where "k" is an index of a particular weight. In method 200, attenuators (e.g., attenuators 151, 152, and 153) in the echo estimation path of the echo-canceller are assumed to have a dynamic range in linear scale of ^wmin - M - ^wmax where Wmm corresponds to the minimum value of the dynamic range and w_max corresponds to the maximum value of the dynamic range.

[0028] Activity 211 may include defining the difference between Wmm and w_max to be Δ = - .

[0029] Activities 212 to 216 may include performing an operation for determining the sign of each of the weights used to control the attenuators in the echo estimation path of the echo-canceller. The value of "K" in activity 212 may be equal to the number of the attenuators in the echo estimation path.

[0030] Activity 213 may include calculating two values Ci(W) and

C₂(W) based on different values of the weight Wk applied to the same attenuator at different time intervals. For example, as shown in activity 213, Ci(W) may be calculated with w¾ = Wmin + Δ/2 applied to a particular attenuator (e.g., attenuator 151 in FIG. 1) during a time interval. C₂(W) may be calculated with w¾ = -w _n - Δ/2 applied to that particular attenuator during another time interval. A unit

(e.g., 165 in FIG. 1) of the echo-canceller used in method 200 may measure the power of signal Z(n) at these two time intervals to calculate the values of Ci(W) and C₂(W). During these measurements for a particular weight (e.g., wi in FIG. 1) the values for the other weights (e.g., W2 through w ) may remain unchanged.

[0031] Activity 214 may include setting the value for a particular weight

(Wk) based on the value of w¾ (wmin + Δ/2 or -Wmin - Δ/2) that results in a smaller value between C_\{W) and C₂(W) calculated in activity 213. For example, activity 214 may set w¾ = w ,, + Δ/2 if C_\{W) < C₂(W) or set w¾ = -w^ - Δ/2 if

[0032] Method 200 may repeat the same operations (e.g., performing activities 213 through 216) for each of the weights (e.g., each of W2 through W6 in FIG. 1) until the sign (e.g., -w ,, - Δ/2 or Wmm + Δ/2) for each of the weights is determined (e.g., set).

[0033] After the signs of all of the K weights are set, method 200 may continue with activities 220 to 228 to perform M iterations to further refine the value for each of the weights to search for a final value of each of the weights. As shown in activity 223, in each iteration step m, the value of Wk used in a particular iteration to calculate the value of the cost function is lower than a previous value (e.g., w¾₀w) of w¾. Thus, the M iterations are performed with reduced step. For example, when m = 1, activity 223 may calculate the value of Ci(W) using w_k = w_k,oid + A/2^m+l = w_k,₀id + Δ/4, and C₂(W) using w_k = w_k,₀id - A/2^m+l = Wk,oU - Δ/4. In the next iteration m=2, activity 223 may calculate the value of

using w¾ = Wk,₀u + A/2^m+l = Wk,₀u + Δ/8, and C₂(W) using w¾ = w_kold - A/2^m+1 = w _old - A/8.

[0034] Activity 224 may including setting the value for a particular weight (wk) of a particular iteration based on the value of w¾ (w¾ = Wk,oU + A/2^m+l or Wk,oid - A/2^m+l) that results in a smaller value between Ci(W) and C₂(W) calculated in activity 223. For example, activity 224 may set w¾ = Wk,₀u + A/2^m+l if d(W) < C₂(W) or set w_k = w_k,_old - A/2^m+l if Ci( ) > C₂(W).

[0035] Thus, during a time interval associated with activities 221 through

228 of selecting a final value for each of the weights, method 200 may include applying a plurality of values of the weights (e.g., w¾ = Wk,₀u + Δ/2™⁺¹ or Wk,oid - A/2^m+l during M iterations) to control attenuators of the echo-canceller. The plurality of values are different from the values of the weight (e.g., Wmm + Δ/2 or Wmin - Δ/2) used for calculating and C₂(W) in activities 213. Activities 221 through 228 may also include calculating a plurality of values of the cost function (e.g., calculating C_\{W) and C₂(W) in activities 223) when the plurality of values of the weights are applied. For each of the weights, the value of the cost function of signal Z(n) during a time interval associated with activities 220 through 228 is a lowest value (e.g., global minimum) among the plurality of values of the cost function of the signal Z(n).

[0036] Method 200 may repeat the same operations (e.g., performing activities 221 through 228) for each of the weights (e.g., each of w₂ through W6 in FIG. 1) until the final value (value that falls on a global minimum of the cost function) for each of the weights is determined (e.g., set).

[0037] Method 200 may end at activity 299 after the final values of all of the weights are determined. Method 200 may select these values and apply them in the echo-canceller to control the attenuators of the echo-canceller.

[0038] As described above, method 200 searches for the weights that fall on the global minimum and selects those values for use in the echo-canceller.

Thus, by searching for the values of the weights, optimum values for the weights (e.g., that fall on the global minimum) can be selected. This may avoid an exhaustive search and avoid adaptively updating the weights. Avoiding such an exhaustive search and updating the weights may improve the speed for the search (e.g., faster search) for echo-canceller 101.

[0039] In method 200, the final values of the weight applied to the corresponding attenuators in the echo-canceller may be fixed. Alternatively, the final values of the weights may be adjusted (e.g., during a weight recalibration, as described above with reference to FIG. 1). For example, during a recalibration (after the final values are selected), method 200 may repeat activity 201 to 299 if a power monitor (e.g., power monitor 170 in FIG. 1) detects a change in the value of the power relative to a threshold value (e.g., a predetermined value). As an example, method 200 may repeat activity 201 to 299 if the value of the power (e.g., during a weight calibration) is greater than threshold value. Method 200 may repeat activity 201 to 299 in during a time interval where no incoming signal is expected to be received by the wireless communication system. This is to avoid the incoming signal being used in the power calculation that may result in an inaccurate selection for the values of the weights. [0040] Method 200 may include fewer or more activities than the activities shown in FIG. 2. For example, method 200 may also include or be included in operations of wireless communication system 100 described above with reference to FIG. 1 , a network station, or a wireless communication device described below with reference to FIG. 3 and FIG. 4.

[0041] As described above, method 200 may perform an operation for calculating and selecting the values for the weights based on the cost function of signal Z(n) without using components associated with the transmitted signal x(t) (or x(n)) as inputs for calculating the values for the weights. Therefore, method 200 may be referred to as a blind technique for calculating the weights. Method 200 may allow the echo-canceller used in method 200 to be less complex, relatively faster, and less sensitive to RF impairments.

[0042] FIG. 3 shows a wireless communication network 300 including a network station 302 and wireless communication devices 311 and 312, according to some embodiments described herein. Network station 302 may be arranged (e.g., configured) to wirelessly communicate with wireless communication device (WCD) 311 through a wireless connection 313 and with WCD 312 through a wireless connection 315. Each of network station 302 and WCDs 111 and 112 may include wireless communication system 100 described above with reference to FIG. 1. Thus, each of network station 302 and WCDs 111 and 112 may include components and operations similar to, or identical to, those described above with reference to FIG. 1 and FIG. 2. For example, each of network station 302 and WCDs 111 and 112 may include echo-canceller 101 of FIG. 1 and may be arranged to perform an echo-cancellation including an operation for calculating and selecting weights described above with reference to FIG. 1 and FIG. 2.

[0043] In FIG. 3, an example of wireless communication network 300 includes an evolved universal terrestrial radio access network (EUTRAN) using the 3rd Generation Partnership Project (3 GPP) long term evolution (LTE) standards. Additional examples of wireless communication network 300 include Worldwide Interoperability for Microwave Access (WiMax) networks, 3rd generation (3G) networks, Wi-Fi networks, and other wireless data

communication networks. [0044] An example of network station 302 includes a base station (BS), an enhanced node B (eNB), an access point (AP), or another type of network station or network equipment. Network station 302 may be arranged to operate based on the 3GPP-LTE standards or other wireless data communication standards.

[0045] Examples of WCDs 311 and 312 include user equipment (UE) and terminal equipment (e.g., data terminal equipment). Examples of user equipment and terminal equipment include cellular telephones (e.g., smartphones), tablet computers, e-readers (e.g., e-book readers), notebook computers, laptop computers, desktop computers, personal computers, servers, personal digital assistants (PDAs), digital cameras, medical devices (e.g., a heart rate monitor, a blood pressure monitor, etc.), televisions, web appliances, set-top boxes (STBs), network routers, network switches, network bridges, parking meters, sensors, and other types of devices and equipment.

[0046] WCDs 311 and 312 may be arranged (e.g., configured) to operate in different communication networks, such as a 3GPP-LTE network, a WiMax network, a wireless local area network (e.g., WiFi), and other communication networks. FIG. 3 shows wireless communication network 300 including only two WCDs (e.g., WCDs 311 and 312) to communicate with network station 302 as an example. Wireless communication network 300, however, may include more than two WCDs.

[0047] Network station 302 may have a simultaneous transmit (Tx) and receive (Rx) capability (STR capability), such that it may operate in STR mode to simultaneously (e.g., concurrently) transmit and receive signals (e.g., radio- frequency (RF) signals). Network station 302 may include an RF transceiver that has a full-duplex capability to simultaneously transmit and receive signals. For example, network station 302 may transmit a downlink (DL) signal to WCD 311 while network station 302 receives an uplink (UL) signal from WCD 312. In another example, network station 302 may transmit a DL signal to WCD 312 while network station 302 receives a UL signal from WCD 311.

[0048] FIG. 4 shows a block diagram of a WCD 400 including an echo- canceller 401, according to some embodiments described herein. WCD 400 may include components of wireless communication system 100 (FIG. 1). As shown in FIG. 4, WCD 400 may also include antennas 402 and 404, a transceiver 405 including a receiver 410 and transmitter 420, a controller 415, and a memory 430. Echo-canceller 401, receiver 410, and transmitter 420 may correspond to echo-canceller 101, receiver 110, and transmitter 120, respectively, of FIG. 1. Thus, echo-canceller 401, receiver 410, and transmitter 420 may be arranged to operate in ways similar to, or identical to, those of corresponding echo -canceller 101, receiver 110, and transmitter 120 of FIG. 1.

[0049] WCD 400 in FIG. 4 may also include one or more of a keyboard, a display (e.g., an LCD screen including a touch screen), a non- volatile memory port (e.g., a Universal Serial Bus (USB) port), speakers, and other mobile device elements.

[0050] Controller 415, echo-canceller 401, or both, may be arranged

(e.g., configured) to perform operations described above with reference to FIG. 1 through FIG. 3. For example, controller 415 and echo-canceller 401 may be arranged to perform an echo-cancellation operation including the operation for calculating and selecting weights as described above with reference to FIG. 1 and FIG. 2.

[0051] Controller 415 may be arranged (e.g., configured) to provide processing and control functionalities for WCD 400, including at least part of the echo-cancellation operation described above with reference to FIG. 1 through FIG. 3. Controller 415 may include one or more processors that may include one or more central processing units (CPUs), one or more graphics processing units (GPUs), or a combination of one or more CPUs and one or more GPUs.

[0052] Memory 430 may include volatile memory, non- volatile memory, or a combination of both. Memory 430 may store instructions (e.g., firmware programs, software programs, or a combination of both). Controller 415 may execute instructions in memory 430 to result in WCD 400 performing operations, such as echo-cancellation operation including the operation for selecting weights performed by wireless communication system 100 or method 200 described herein with reference to FIG. 1 through FIG. 2.

[0053] Antennas 402 and 404 may include one or more directional or omnidirectional antennas, including, for example, dipole antennas, monopole antennas, patch antennas, loop antennas, microstrip antennas or other types of antennas suitable for transmission of RF signals. In some embodiments, instead of two or more antennas, a single antenna with multiple apertures may be used. In these embodiments, each aperture may be considered a separate antenna. Antennas 402 and 404 may be arranged to support multiple-input and multiple- output (MIMO) communications. In some MIMO embodiments, antennas 402 and 404 may be effectively separated to benefit from spatial diversity and the different channel characteristics that may result between antennas 402 and 404 and the antennas of a transmitting station. In some MIMO embodiments, antennas 402 and 404 may be separated by up to 1/10 of a wavelength or more.

[0054] FIG. 4 shows WCD 400 including one transceiver 405 and two antennas 402 and 404 as an example. The number of transceivers 405 and antennas 402, 404 may vary. Controller 415 and transceiver 405 may be arranged to operate in different communication networks, such as a 3GPP-LTE network, a WiMax network, wireless local area network (e.g., WiFi), and other communication networks.

[0055] Although WCD 400 is shown as having several separate functional elements, one or more of the functional elements may be combined and may be implemented by combinations of software-configured elements, such as processing elements including digital signal processors (DSPs), and/or other hardware elements. For example, some elements may comprise one or more microprocessors, DSPs, application specific integrated circuits (ASICs), radio-frequency integrated circuits (RFICs) and combinations of various hardware and logic circuitry for performing at least the functions and operations described herein. In some embodiments, the functional elements may refer to one or more processes operating on one or more processing elements.

[0056] Embodiments may be implemented in one or a combination of hardware, firmware and software. Embodiments may also be implemented as instructions (e.g., firmware programs, software programs, or a combination of both) stored on a computer-readable storage medium, which may be read and executed by at least one processor to perform the operations described herein. A computer-readable storage medium may include any non-transitory mechanism (e.g., non-transitory computer-readable medium) for storing information (e.g., instructions) in a form readable by a machine (e.g., a computer). Examples of a computer-readable storage medium may include read-only memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash-memory devices, and other storage devices and media. In these embodiments, one or more processors of the WCD 400 may be configured with the instructions to perform the operations described herein.

Additional Notes and Examples

[0057] Example 1 includes subject matter (such as a device, apparatus, or machine) including an echo-canceller for a wireless communication system, the echo-canceller comprising phase shifters to generate output signals, each of the phase shifters generating one of the output signals, each of the output signals having a phase shift relative to a transmitted signal, a attenuator unit (e.g., a variable or stepped attenuator unit) to attenuate the output signal of each of the phase shifters based on weights to generate attenuated signals, each of the attenuated signals corresponding to the output signal of one of the phase shifters, a weight calculator to perform an operation for selecting values for the weights without using components associated with the transmitted signal as inputs for calculating the values for the weights, and at least one summer to sum the attenuated signals and a received signal containing an echo signal to generate an echo-canceled signal.

[0058] In Example 2, the subject matter of Example 1 may optionally include, wherein the weight calculator is arranged to perform the operation for selecting the weights based at least in part on a cost function of a digital signal generated based on the echo-canceled signal.

[0059] In Example 3, the subject matter of Example 1 may optionally include, wherein the weight calculator is arranged to perform the operation for selecting the weights based the equation

where Z(n) represents the digital signal, W represents a weight vector including the weights, and g represent a gain of a variable gain amplifier located on a path used to generate the digital signal.

[0060] In Example 4, the subject matter of Example 1 may optionally include, wherein the weight calculator is arranged to generate a signal based on the echo-canceled signal, calculate a first value of a cost function of the signal based on a first value of a weight applied to an attenuator (e.g., a variable or stepped attenuator) of the attenuator unit during a first time interval, calculate a second value of the cost function of the signal based on a second value of the weight applied to the attenuator unit during a second time interval, select a starting value of the weight to be equal to one of the first and second values of the weight, and perform an operation to search for a third value of the weight based on the starting value of the weight, such that when the third value of the weight is applied to the attenuator during a third time interval, a third value of the cost function of the signal during the third time interval is less than each of the first and second values of the cost function of the signal.

[0061] In Example 5, the subject matter of Example 1 may optionally include, wherein the echo-canceller is included in a user equipment (UE).

[0062] In Example 6, the subject matter of Example 1 may optionally include, wherein the echo-canceller is included in one of a base station and an enhanced node B (eNB).

[0063] Example 7 includes subject matter including a wireless communication system comprising a receiver to receive a signal containing an echo signal, a transmitter to transmit a transmitted signal, and an echo-canceller comprising a first vector modulator to generate a first output signal from a sum of a first plurality of signals, the first plurality of signals being attenuated based on a first group of weights, each signal in the first plurality of signals having a phase shift relative to a first delayed version of the transmitted signal, a second vector modulator to generate a second output signal from a sum of a second plurality of signals, the second plurality of signals being attenuated based on a second group of weights, each signal in the second plurality of signals having a phase shift relative to a second delayed version of the transmitted signal, a summer to sum the first and second output signals and the received signal containing the echo signal to generate an echo-canceled signal, and a weight calculator arranged to perform an operation for selecting values for the first and second groups of weights based on a value of a power of a digital signal associated with the echo-canceled signal.

[0064] In Example 8, the subject matter of Example 7 may optionally include, wherein the echo-canceller further includes a power measurement unit to measure the power of the digital signal over a period of time to obtain the value of the power of the digital signal.

[0065] In Example 9, the subject matter of Example 8 may optionally include, wherein the echo-canceller further includes a variable gain amplifier to modify the echo-canceled signal, and an analog-to-digital converter to convert the echo-canceled signal after the echo-canceled signal is modified by the variable gain amplifier to generate the digital signal.

[0066] In Example 10, the subject matter of Example 9 may optionally include, wherein the echo-canceller is arranged to compensate for the value of the power of the digital signal with a compensated value based on the gain of the variable gain amplifier.

[0067] In Example 11 , the subject matter of Example 7 may optionally include, further comprising a power monitor to monitor a value of a power of the digital signal after the values for the first and second groups of weights are selected, and to cause the echo-canceller to perform an additional operation for adjusting the values for the first and second group of weights if the value of the power of the digital signal exceeds a threshold value.

[0068] In Example 12, the subject matter of Example 7 may optionally include, wherein the receiver and transmitter are included in a full-duplex transceiver of the wireless communication system.

[0069] In Example 13, the subject matter of Example 7 may optionally include, wherein the receiver is arranged to receive a downlink signal.

[0070] In Example 14, the subject matter of Example 7 may optionally include, wherein the receiver is arranged to receive an uplink signal.

[0071] Example 15 includes subject matter including a method of operating a wireless communication system, the method comprising calculating a first value of a cost function of the signal based on a first value of a weight applied in the echo-canceller during a first time interval, calculating a second value of the cost function of the signal based on a second value of the weight applied in the echo-canceller during a second time interval, selecting a starting value of the weight to be equal to one of the first and second values of the weight, and performing an operation to search for a third value of the weight based on the starting value of the weight, such that when the third value of the weight is applied in the echo-canceller during a third time interval, a third value of the cost function of the signal during the third time interval is less than each of the first and second values of the cost function of the signal.

[0072] In Example 16, the subject matter of Example 15 may optionally include, wherein selecting the starting value of the weight includes selecting the starting value of the weight to be equal to the first value of the weight if the first value of the cost function of the signal is less than the second value of the cost function of the signal, and selecting the starting value of the weight to be equal to the second value of the weight if the first value of the cost function of the signal is greater than the second value of the cost function of the signal.

[0073] In Example 17, the subject matter of Example 15 may optionally include, wherein the cost function of the signal is

where Z(n) represents the signal based on the output signal, where W represents a weight vector including the weight, and g represents a gain of a variable gain amplifier located on a path used to generate the signal.

[0074] In Example 18, the subject matter of Example 15 may optionally include, wherein the first value of the weight is equal to w½in + Δ/2, and the second value of the weight is equal to - Δ/2, wherein Δ = w - Wmin, wherein w½in corresponds to a minimum value of a dynamic range of attenuators (e.g., variable or stepped attenuators) in an echo estimation path in the echo- canceller, and wherein w_max corresponds to a maximum value of the dynamic range.

[0075] In Example 19, the subject matter of Example 15 may optionally include, wherein the third value of the weight falls on a global minimum of the cost function of the signal.

[0076] In Example 20, the subject matter of Example 15 may optionally include, wherein performing the operation to search for the third value of weight includes applying a plurality of values of the weights to control attenuators (e.g., variable or stepped attenuators) of the echo-canceller, wherein the plurality of values are different from the first and second values of the weight, and calculating a plurality of values of the cost function when the plurality of values of the weight are applied, wherein the value of the cost function of the signal during the third time interval is a lowest value among the plurality of values of the cost function of the signal.

[0077] In Example 21 , the subject matter of Example 15 may optionally include, further comprising calculating a third value of the cost function of the signal based on a first value of an additional weight applied in the echo-canceller during a fourth time interval, wherein the fourth time interval occurs after the first and second time intervals and before the third time interval, calculating a fourth value of the cost function of the signal based on a second value of the additional weight applied in echo-canceller during a fifth time interval, wherein the fifth time interval occurs after the first and second time intervals and before the third time interval, selecting a starting value of the additional weight to be equal to first value of the additional weight if the third value of the cost function is less than the fourth value of the cost function, selecting the starting value of the additional weight to be equal to the second value of the additional weight if the third value of the cost function is greater than the fourth value of the cost function, and performing an operation to search for a third value of the additional weight, such that when the third value of the additional weight is applied in echo-canceller during a sixth time interval, a fifth value of the cost function of the signal during the sixth time interval is less than each of the third and fourth values of cost function of the signal.

[0078] In Example 22, the subject matter of Example 15 may optionally include, wherein selecting the starting value of the additional weight includes selecting the starting value of the additional weight to be equal to first value of the additional weight if the third value of the cost function is less than the fourth value of the cost function, and selecting the starting value of the additional weight to be equal to the second value of the additional weight if the third value of the cost function is greater than the fourth value of the cost function

[0079] Example 23 includes subject matter including a computer- readable storage medium for storing information, which when executed, causes a wireless communication device to generate a signal based on an output signal from an echo-canceller, calculate a first value of a cost function of the signal based on a first value of a weight applied in the echo-canceller during a first time interval, calculate a second value of the cost function of the signal based on a second value of the weight applied in the echo-canceller during a second time interval, select a starting value of the weight to be equal to one of the first and second values of the weight, and perform an operation to search for a third value of the weight based on the starting value of the weight, such that when the third value of the weight is applied in the echo-canceller during a third time interval, a third value of the cost function of the signal during the third time interval is less than each of the first and second values of the cost function of the signal

[0080] In Example 24, the subject matter of Example 23 may optionally include, wherein the starting value of the weight is selected to be equal to the first value of the weight if the first value of the cost function of the signal is less than the second value of the cost function of the signal, and the starting value of the weight is selected to be equal to the second value of the weight if the first value of the cost function of the signal is greater than the second value of the cost function of the signal.

[0081] In Example 25, the subject matter of Example 23 may optionally include, wherein the cost function of the signal is

where Z(n) represents the signal based on the output signal, where W represents a weight vector including the weight, and g represent a gain of a variable gain amplifier located on a path used to generate the signal.

[0082] The subject matter of Examples 1 through Example 25 may be combined in any combination.

[0083] The Abstract is provided to comply with 37 C.F.R. Section

1.72(b) requiring an abstract that will allow the reader to ascertain the nature and gist of the technical disclosure. It is submitted with the understanding that it will not be used to limit or interpret the scope or meaning of the claims. The following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separate embodiment.

Claims

CLAIMS What is claimed is:

1. An echo-canceller for a wireless communication system, the echo- canceller comprising:

phase shifters to generate output signals, each of the phase shifters generating one of the output signals, each of the output signals having a phase shift relative to a transmitted signal;

an attenuator unit to attenuate the output signal of each of the phase shifters based on weights to generate attenuated signals, each of the attenuated signals corresponding to the output signal of one of the phase shifters;

a weight calculator to perform an operation for selecting values for the weights without using components associated with the transmitted signal as inputs for calculating the values for the weights; and

at least one summer to sum the attenuated signals and a received signal containing an echo signal to generate an echo -canceled signal.

2. The echo-canceller of claim 1, wherein the weight calculator is arranged to perform the operation for selecting the weights based, at least in part, on a cost function of a digital signal generated based on the echo-canceled signal.

3. The echo-canceller of claim 2, wherein the weight calculator is arranged to perform the operation for selecting the weights based the equation

4. The echo-canceller of claim 1, wherein the weight calculator is arranged to:

generate a signal based on the echo-canceled signal;

calculate a first value of a cost function of the signal based on a first value of a weight applied to an attenuator of the actuator unit during a first time interval;

calculate a second value of the cost function of the signal based on a second value of the weight applied to the attenuator during a second time interval;

select a starting value of the weight to be equal to one of the first and second values of the weight; and

perform an operation to search for a third value of the weight based on the starting value of the weight, such that when the third value of the weight is applied to the attenuator during a third time interval, a third value of the cost function of the signal during the third time interval is less than each of the first and second values of the cost function of the signal.

5. The echo-canceller of claim 1, wherein the echo-canceller is included in a user equipment (UE).

6. The echo-canceller of claim 1, wherein the echo-canceller is included in one of a base station and an enhanced node B (eNB).

7. A wireless communication system comprising:

a receiver to receive a signal containing an echo signal;

a transmitter to transmit a transmitted signal, and

an echo-canceller comprising:

a first vector modulator to generate a first output signal from a sum of a first plurality of signals, the first plurality of signals being attenuated based on a first group of weights, each signal in the first plurality of signals having a phase shift relative to a first delayed version of the transmitted signal;

a second vector modulator to generate a second output signal from a sum of a second plurality of signals, the second plurality of signals being attenuated based on a second group of weights, each signal in the second plurality of signals having a phase shift relative to a second delayed version of the transmitted signal;

a summer to sum the first and second output signals and the received signal containing the echo signal to generate an echo-canceled signal; and a weight calculator arranged to perform an operation for selecting values for the first and second groups of weights based on a value of a power of a digital signal associated with the echo -canceled signal.

8. The wireless communication system of claim 7, wherein the echo- canceller further includes a power measurement unit to measure the power of the digital signal over a period of time to obtain the value of the power of the digital signal.

9. The wireless communication system of claim 8, wherein the echo- canceller further includes:

a variable gain amplifier to modify the echo-canceled signal; and an analog-to-digital converter to convert the echo-canceled signal after the echo-canceled signal is modified by the variable gain amplifier to generate the digital signal.

10. The wireless communication system of claim 9, wherein the echo- canceller is arranged to compensate for the value of the power of the digital signal with a compensated value based on the gain of the variable gain amplifier.

11. The wireless communication system of claim 7, further comprising a power monitor to monitor a value of a power of the digital signal after the values for the first and second groups of weights are selected, and to cause the echo- canceller to perform an additional operation for adjusting the values for the first and second group of weights if the value of the power of the digital signal exceeds a threshold value.

12. The wireless communication system of claim 7, wherein the receiver and transmitter are included in a full-duplex transceiver of the wireless

communication system.

13. The wireless communication system of claim 7, wherein the receiver is arranged to receive a downlink signal.

14. The wireless communication system of claim 7, wherein the receiver is arranged to receive an uplink signal.

15. A method of for echo cancellation a wireless communication system, the method comprising:

generating a signal based on an output signal from an echo -canceller; calculating a first value of a cost function of the signal based on a first value of a weight applied in the echo-canceller during a first time interval;

calculating a second value of the cost function of the signal based on a second value of the weight applied in the echo-canceller during a second time interval;

selecting a starting value of the weight to be equal to one of the first and second values of the weight; and

performing an operation to search for a third value of the weight based on the starting value of the weight, such that when the third value of the weight is applied in the echo-canceller during a third time interval, a third value of the cost function of the signal during the third time interval is less than each of the first and second values of the cost function of the signal.

16. The method of claim 15, wherein selecting the starting value of the weight includes:

selecting the starting value of the weight to be equal to the first value of the weight if the first value of the cost function of the signal is less than the second value of the cost function of the signal; and

selecting the starting value of the weight to be equal to the second value of the weight if the first value of the cost function of the signal is greater than the second value of the cost function of the signal.

17. The method of claim 15, wherein the cost function of the signal is

18. The method of claim 15, wherein the first value of the weight is equal to Wmin + Δ/2, and the second value of the weight is equal to Wmm - Δ/2, wherein Δ = Wmax - Wmin, wherein Wmm corresponds to a minimum value of a dynamic range of attenuators in an echo estimation path in the echo-canceller, and wherein w_max corresponds to a maximum value of the dynamic range.

19. The method of claim 15, wherein the third value of the weight falls on a global minimum of the cost function of the signal.

20. The method of claim 15, wherein performing the operation to search for the third value of weight includes:

applying a plurality of values of the weights to control attenuators of the echo-canceller, wherein the plurality of values are different from the first and second values of the weight; and

calculating a plurality of values of the cost function when the plurality of values of the weight are applied, wherein the value of the cost function of the signal during the third time interval is a lowest value among the plurality of values of the cost function of the signal.

21. The method of claim 15, further comprising:

calculating a third value of the cost function of the signal based on a first value of an additional weight applied in the echo-canceller during a fourth time interval, wherein the fourth time interval occurs after the first and second time intervals and before the third time interval;

calculating a fourth value of the cost function of the signal based on a second value of the additional weight applied in the echo -canceller during a fifth time interval, wherein the fifth time interval occurs after the first and second time intervals and before the third time interval;

selecting a starting value of the additional weight to be equal to the first value of the additional weight if the third value of the cost function is less than the fourth value of the cost function;

selecting the starting value of the additional weight to be equal to the second value of the additional weight if the third value of the cost function is greater than the fourth value of the cost function; and

performing an operation to search for a third value of the additional weight, such that when the third value of the additional weight is applied in the echo-canceller during a sixth time interval, a fifth value of the cost function of the signal during the sixth time interval is less than each of the third and fourth values of the cost function of the signal.

22. The method of claim 15, wherein selecting the starting value of the additional weight includes:

selecting the starting value of the additional weight to be equal to a first value of the additional weight if the third value of the cost function is less than the fourth value of the cost function; and

selecting the starting value of the additional weight to be equal to the second value of the additional weight if the third value of the cost function is greater than the fourth value of the cost function.

23. A computer-readable storage medium for storing information which, when executed, causes a wireless communication device to:

generate a signal based on an output signal from an echo-canceller; calculate a first value of a cost function of the signal based on a first value of a weight applied in the echo-canceller during a first time interval;

calculate a second value of the cost function of the signal based on a second value of the weight applied in the echo-canceller during a second time interval;

perform an operation to search for a third value of the weight based on the starting value of the weight, such that when the third value of the weight is applied in the echo-canceller during a third time interval, a third value of the cost function of the signal during the third time interval is less than each of the first and second values of the cost function of the signal.

24. The computer-readable storage medium of claim 23, wherein the starting value of the weight is selected to be equal to the first value of the weight if the first value of the cost function of the signal is less than the second value of the cost function of the signal, and the starting value of the weight is selected to be equal to the second value of the weight if the first value of the cost function of the signal is greater than the second value of the cost function of the signal.

25. The computer-readable storage medium of claim 23, wherein the cost function of the signal is