System and method applying transmission signaling techniques to enhance receiver interference mitigation performance, receiver apparatus and computer-readable medium

System and method using transmission communication technology to enhance receiver interference mitigation performance, receiver device and computer readable medium

Field of invention

The subject disclosed here is about technologies used to reduce the interference of the transmitted signal.

Background of the invention

Wireless communication systems are widely available. A receiver can be programmed to decode some desired received signals from one or more transmitters. However, because multiple transmitters generally transmit at the same time, the receiver may receive interference signals received from one or more transmitters. Interference may reduce the probability that the receiver can accurately reproduce the desired received signal. It is desirable to adjust the transmission to improve the possibility that a receiver can accurately reproduce the desired received signal.

According to an embodiment of the present invention, a system is specially proposed, which includes: at least two transmitters located in a network; a receiver located in the network for receiving signals from at least two transmitters and reducing The interference between the signals of the at least two transmitters; and a logic component used to coordinate the use of similar space-time coding schemes by the at least two transmitters and synchronize the actions of the receiver to receive codes from the at least two transmitters.

According to an embodiment of the present invention, a method is specially proposed, which includes the following steps: notifying at least two transmitters of a structured coding scheme used and a designated delay or advance; The coding scheme is applied to the transmission of the signal; and each of the at least two transmitters applies the specified delay or advance.

According to an embodiment of the present invention, a receiver device is specially proposed, which includes: at least two antennas for receiving signals from at least one transmitter; and a fast Fourier transform logic component for comparing signals received from the at least two antennas. Performing a fast Fourier transform operation; and a receiver for receiving signals from the fast Fourier transform logic component and applying an interference cancellation technique based on mean square error to reduce interference, wherein the at least two antennas use a similar coding scheme at least Two transmitters receive the symbols and simultaneously receive codes from at least two transmitters.

According to an embodiment of the present invention, a computer-readable medium storing instructions is specially proposed, which when executed by a computer causes the computer to perform the following steps: store a structured coding scheme; store a specified delay or Advance; apply the structured coding scheme to a signal to be sent to a receiver; and apply the specified delay or advance to a signal to be sent to a receiver.

Schematic description

The embodiments of the present invention are described by way of examples in the drawings but not limited, and similar reference signs indicate similar elements.

Figure 1 depicts an example of whether the received space-time encoded codeword groups from a desired transmitter and an interference transmitter are synchronized or asynchronous; Figure 2 depicts the desired signal and interference signal Figure 3 depicts an example of a suitable system for reducing interference in a receiver according to some embodiments of the present invention; Figure 4 depicts some examples of a system according to the present invention The embodiment is an example of a suitable procedure for reducing interference in a receiver.

Detailed description of the preferred embodiment

Reference to "an embodiment" in this specification means that a specific feature, structure, or characteristic described in conjunction with the embodiment is included in at least one embodiment of the present invention. Therefore, the appearances of the phrases "within an embodiment" or "an embodiment" in various places in this specification do not necessarily all refer to the same embodiment. In addition, specific features, structures, or characteristics may be incorporated into one or more embodiments.

The embodiments of the present invention can be used in various applications. Some embodiments of the present invention can be used in combination with various devices and systems, for example, a transmitter, a receiver, a transceiver, a transmitter-receiver, a wireless communication station, a wireless communication device, and a wireless connection. Access point (AP), a modem, a wireless modem, a personal computer (PC), a desktop computer, a mobile computer, a laptop computer, a notebook computer, a tablet computer, a server computer, A handheld computer, a handheld device, a PDA device, a handheld PDA device, a network, a wireless network, a local area network (LAN), a wireless LAN (WLAN), a metropolitan area network (MAN), a wireless MAN (WMAN), a wide area network (WAN), a wireless WAN (WWAN), according to the existing IEEE 802.11, 802.11a, 802.11b, 802.11e, 802.11g, 802.11h, 802.11i, 802.11n, 802.16, 802.16d, 802.16e, 802.16m or 3GPP standards and/or future versions and/or derivative versions of the above standards and / Or Long Term Evolution (LTE) version of the equipment and/or network, a personal area network (PAN), a wireless PAN (WPAN), units that are part of the above WLAN and/or PAN and/or WPAN network, and /Or equipment, one-way and/or two-way radio communication system, cellular radio-telephone communication system, a mobile phone, a wireless phone, a personal communication system (PCS) device, a PDA device including a wireless communication device, a multiple Input multiple output (MIMO) transceiver or device, a single input multiple output (SIMO) transceiver or device, a multiple input single output (MISO) transceiver or device, a multiple receiver chain (MRC) transceiver or device, A transceiver or device or the like with "small antenna" technology or multi-antenna technology. Some embodiments of the present invention can be used with one or more wireless communication signals and/or systems, such as radio frequency (RF), infrared (IR), frequency division multiplexing (FDM), orthogonal FDM (OFDM), and Time Multiplexing (TDM), Time Division Multiple Access (TDMA), Extended TDMA (E-TDMA), General Packet Radio Service (GPRS), Extended GPRS, Code Division Multiple Access (CDMA), Broadband CDMA (WCDMA), CDMA2000, Multi-Carrier Modulation (MDM), Discrete Multi-Tone (DMT), Bluetooth (RTM), ZigBee (TM) or similar. The embodiments of the present invention can be used in various other devices, equipment, systems, and/or networks.

Space-Time Coding (STC) is an efficient transmit diversity technology, which has been proposed in many emerging standards, such as but not limited to the following: Orthogonal Frequency Division Multiplexing (OFDM) and Orthogonal Frequency Division Multiplexing Multiple access (OFDMA). Examples of OFDM and/or OFDMA standards include but are not limited to the following: IEEE 802.16, IEEE 802.11, and 3GPP LTE and their variations. The block space-time code is particularly attractive for practical systems, because a simple linear receiver can obtain a spatial diversity order of some number of transmit antennas. In addition, these block space-time codes allow the use of simple interference suppression techniques.

If the receiver receives code asynchronous interference, the performance of linear receivers using such technologies as (but not limited to) interference cancellation technology based on minimum mean square error (MMSE-IC) may be severely reduced. For example, Figure 1 depicts an example in which the received space-time coded codeword groups from the desired transmitter and the interfering transmitter are code synchronized or code non-synchronized. In the synchronous situation, the codeword group symbols are aligned, but in the non-synchronous situation, the codeword group symbols are shifted by one or more symbol periods. Compared to asynchronous interference, synchronous interference is more desirable, at least because synchronous interference can lead to better receiver performance or can be more easily eliminated. In order to use technologies such as MMSE-IC (not limited to this) to improve the interference reduction of the receiver, the code synchronization interference in the receiver may be more expected than the code-asynchronous interference.

To aid understanding, the example provided here is described with respect to an interfering transmitter and a receiver, but the technique described here can be extended to any number of interfering transmitters and any number of receivers.

Figure 2 depicts an example of a system of transmitters with desired signals and interference signals. In this example, each transmitter sends a 2x2 space-time code. In Figure 2, a receiver receives a desired signal h(t) from a desired transmitter and an interference signal g(t) from an interfering transmitter. In the example of Figure 2, each of the transmitters and the receiver use two antennas, although other numbers of antennas can be used.

First consider the case of code synchronization interference. The effectively received signal can be expressed as:<maths><img file="TWI366359B_D0001.tif" /></maths>in<img file="TWI366359B_D0002.tif" />(If H has orthogonal characteristics),<img file="TWI366359B_D0003.tif" />，<i>h</i>_ijIs the channel gain between the i-th receiver and the j-th transmit antenna, and n is the covariance matrix<i>σ</i>²<b>I</b>Additive white Gaussian noise (AWGN).

Using MMSE technology, the desired signal can be estimated by:<maths><img file="TWI366359B_D0004.tif" /></maths>in,<img file="TWI366359B_D0005.tif" />and<img file="TWI366359B_D0006.tif" />If H has orthogonal characteristics, the expected signal can be estimated as:<maths><img file="TWI366359B_D0007.tif" /></maths>in<img file="TWI366359B_D0008.tif" />、<i>α</i>＝(∥<b>h</b>₁∥²＋∥<b>g</b>₁∥²+<i>σ</i>²)<b>I</b>and<i>β</i>＝(∥<b>h</b>₂∥²+∥<b>g</b>₂∥²＋<i>σ</i>²)<b>I</b>。

vector<b>h</b>_<i>i</i>and<b>g</b>_<i>i</i>Respectively<b>H</b>and<b>G</b>The i-th row. make<img file="TWI366359B_D0009.tif" />, And the vector can be calculated as:<b>y</b>₂＝(<b>M</b>^<i>H</i><b>M</b>－<i>αβ</i><b>I</b>)^－1(<b>M</b>^<i>H</i><b>r</b>₁－<i>α</i><b>r</b>₂) (4)<maths><img file="TWI366359B_D0010.tif" /></maths>Finally, the estimated expected signal given in (3) can be obtained by replacing equations (4) and (5).

One of the extensions of the code asynchronous situation can be obtained. For asynchronous situations, the effectively received signal can be given by:<maths><img file="TWI366359B_D0011.tif" /></maths>in<img file="TWI366359B_D0012.tif" />and<img file="TWI366359B_D0013.tif" />。

The estimated expected signal can be obtained by the same procedure as in the synchronization case.

When the codeword groups are synchronized, the receiver effectively experiences interference from a pair of interfering symbols. Therefore, a receiver with two receiving antennas has enough freedom to suppress interference. When the interference is code asynchronous, the receiver experiences interference from two interfering symbols and may not have enough freedom to suppress the interference. Therefore, when the interference is not symbol-synchronized, the interference suppression performance may be reduced. For example, an example of interference performance reduction is described by the following table, which describes errors in decoded symbols after interference suppression.

<tables><img file="TWI366359B_D0014.tif" /></tables>

By using the management code to transmit signals synchronously, some embodiments of the present invention can increase the interference suppression capability of the space-time coded OFDM(A) system. In some embodiments, in order to increase the possibility of synchronization interference, thereby increasing the interference cancellation capability of the receiver, one of the at least two transmitters in a cellular or other type of network can use a similar structure. Coding scheme and coordinated transmission so that the receiver synchronously receives co-channel signals. In some embodiments, users with a cell edge with a simple linear receiver can benefit from reduced interference.

For example, the OFDMA signal frame is designed so that the space-time or space-frequency codewords span the same resources of the cellular network. For example, in an OFDMA frame with 6 data symbols, all cells in a network use the same symbol pair for Alamouti space-time coding (for example, (1,2), (3,4) and (5,6)).

By providing at least two transmitters in a network that use similar structured coding schemes so that one or more interfering signals maintain the same structure as the time and frequency structure of the desired signal, some embodiments of the present invention can increase this The interference suppression capability of one or more receivers in the network. If at least two transmitters in a network use similar structured coding schemes to send to a receiver in the network, the receiver can more effectively reduce the interference from one or more interfering transmitters. Examples of structured coding schemes include but are not limited to the following: space-time block coding, Alamouti space-time coding and their variations.

In some embodiments, at least when the signal from the co-channel jammer arrives at a receiver within the cyclic prefix (CP) period of the desired signal, the receiver can receive the co-channel signal approximately in time synchronization. In some embodiments, when the signals from the co-channel jammer arrive at the receiver during the cyclic prefix (CP) of the desired signal, the frequency orthogonality of the desired signal and the sub-carriers within the interfering signal can be Keep. All transmitters can maintain a similar CP period. Cyclic prefix is a feature used by OFDM at least to resist inter-symbol interference (ISI) and inter-channel interference (ICI) caused by the multipath channel through which the signal propagates. The cyclic prefix can be realized by copying a part of the OFDM time domain waveform (from the back end of the waveform to the front end of the waveform) to generate a guard period. The period of the protection period can be longer than the worst delay spread of the target multipath environment and the propagation delay of the interference signal.

In some embodiments, coordination may occur between transmitters to achieve the use of a similar structured coding scheme and synchronize the receiver codes to receive co-channel signals. For example, a network element (e.g., a radio resource manager) can be designated to coordinate the transmitter to achieve the use of a similar structured coding scheme and synchronize the receiver code to receive co-channel signals. For example, each transmitter can communicate with at least another transmitter to achieve the use of a similar structured coding scheme. For example, a transmitter can instantly communicate with at least another transmitter to indicate the use of a structured coding scheme. For example, a central transmitter can be designated to transmit the coding scheme for use by transmitters in a network. Therefore, other transmitters can use similar schemes. The transmitters can communicate with each other using wired or wireless technology according to any standard.

In order for the receiver to receive co-channel signals in time synchronization, the transmitter may coordinate to start transmitting symbols with a certain delay value or an earlier (ie, negative delay) value. One or more transmitters or other network elements can communicate with the receiver to determine whether the receiver receives co-channel signals in time synchronization based on the used transmission delay scheme.

Figure 3 depicts an example of a system that can be used in some embodiments of the present invention. For example, the system may include the desired transmitter 300, interference transmitter 320, and receiver 350. The desired transmitter 300 may transmit the signal that the receiver 350 is planned to decode, while the interference transmitter 320 may transmit the interference signal. The system can use any wireless protocol.

The desired transmitter 300 may include encoding and modulation logic 302, code synchronization logic 304, transmit diversity encoder logic 306, inverse fast Fourier transform (IFFT) logic 308, cyclic prefix (CP) logic 309, and antenna 310. The encoding and modulation logic 302 can receive an input signal to be sent to the receiver 350. The encoding and modulation logic 302 may apply any of the following: forward error correction encoding, scrambled encoding, convolutional encoding, interleaving, mapping and steering, and zero insertion. Any mapping scheme can be used, such as the following but not limited to the following: Binary Phase Shift Keying (BPSK), Quadrature PSK (QPSK) and Quadrature Amplitude Modulation (QAM) and their variations. The encoding and modulation logic 302 can provide the generated signal to the transmit diversity encoder 306.

The code synchronization logic 304 can be used to coordinate the transmitters 300 and 320 to transmit similar structured coding schemes and the receiver 350 to receive co-channel signals from the transmitters 300 and 320 in a code synchronization manner.

The transmit diversity encoder logic 306 may apply the selected structured encoding scheme used by the multiple transmitters transmitted by the code synchronization logic 304 to the signal to be transmitted to a receiver. For example, the transmit diversity encoder logic 306 may use the following techniques for encoding, but is not limited to the following: space-time block encoding, Alamouti space-time encoding, and variations thereof. The transmit diversity encoder logic 306 can provide the generated signal to the IFFT logic 308.

The IFFT logic 308 may be logic capable of performing an inverse fast Fourier transform of the signal to be sent to the receiver 350. The IFFT logic 308 can operate in compliance with any applicable wireless standard. The CP logic 309 can insert a CP into the signal sent in the time domain signal. Based on the receiver's time-synchronization requirement, the CP logic 309 may delay or advance one or more transmitted signals to ensure that the receiver receives interference signals within one of the desired signals CP. For example, one or more transmitters or other network elements can communicate with the receiver to determine whether the receiver receives co-channel signals in time synchronization based on the transmission delay scheme used. The antenna 310 can transmit signals to one or more receivers. Two or more antennas can be used.

The interference transmitter 320 can be implemented in a manner similar to that of the transmitter 300. For example, the transmitter 320 may include the ability to adjust the coding scheme used to achieve code synchronization and/or delay or advance time based on communication with another transmitter, network element, and/or receiver. coding.

The receiver 350 may include an antenna 352, fast Fourier transform (FFT) logic 354, receiver logic 356, and demodulation and detection logic 358. The antenna 352 can receive transmitted signals from one or more transmitters, such as the transmitters 300 and 302, but is not limited thereto. Two or more antennas can be used. The antenna 352 may transmit the received signal to the FFT logic 354.

The FFT logic 354 can apply any fast Fourier transform technology specified by relevant standards. The FFT logic 354 may provide the generated signal to the receiver logic 356. The receiver logic 356 may perform any of the following: synchronization, channel estimation and equalization, demapping, de-interleaving, and/or de-stirring. The receiver logic 356 can use technologies such as (but not limited to) MMSE-IC technology to reduce the impact of interference from one or more interfering transmitters. Technologies other than MMSE-IC can be used, such as the following but not limited to the following: zero-forced IC, maximum likelihood-based IC, and non-linear IC. The receiver logic 356 can provide an output signal for any logic use, such as a host computer, but is not limited to this. The host computer may include, for example, one or more central processing units, a memory device, storage device, and user interface. The host computer can further access a transmitter similar to the transmitter 300 to send signals to one or more network components.

Figure 4 depicts an exemplary process that can be used in some embodiments of the present invention to reduce interference from received signals. In block 410, multiple transmitters may apply similar structured coding schemes. For example, the structured coding scheme can be any of the following: space-time block coding, Alamouti space-time coding, and variations thereof. For example, multiple transmitters can communicate with each other or with a central transmitter to determine the structured coding scheme to be applied. For example, the structured coding scheme can be set in real time or before a transmitter sends any data signals.

In block 420, multiple transmitters may coordinate so that a receiver receives codes in time synchronization. For example, when the receivers receive codes within a cyclic prefix of each other, the receivers can receive codes in time synchronization. For example, multiple transmitters can apply a delay or advance to the transmitted signal so that a receiver can receive codes synchronously. For example, multiple transmitters may determine the delay based on communication with each other, a central transmitter, and/or an interested receiver. In block 430, the receiver of interest may receive signals from one or more receivers.

In block 440, the interested receiver may reduce interference from one or more undesired transmitters. For example, the interested receiver can apply MMSE-IC technology to reduce interference. Technologies other than MMSE-IC can be used, such as the following but not limited to the following: zero-forced IC, maximum likelihood-based IC, and non-linear IC.

Embodiments of the present invention can be implemented as any or a combination of the following: one or more microchips or integrated circuits interconnected by a motherboard, hard-wired logic, stored by a memory device and stored by A microprocessor executed software, firmware, an application-specific integrated circuit (ASIC) and/or a field programmable gate array (FPGA). For example, the term "logic" can include software or hardware and/or a combination of software and hardware.

Embodiments of the present invention may be provided, for example, as a computer program product, which may include one or more machine-readable media having machine-executable instructions stored thereon, and the machine-executable instructions may be When executed by one or more machines (for example, a computer, a network of computers, or other electronic devices), the one or more machines can perform operations according to the embodiments of the present invention. A machine-readable medium may include but is not limited to the following: floppy disk, optical disk, CD-ROM (optical disk-read only memory) and magneto-optical disk, ROM (read only memory), RAM (random access memory) , EPROM (erasable and programmable read-only memory), EEPROM (electrically erasable and programmable read-only memory), magnetic or optical card, flash memory or other types of media suitable for storing machine executable instructions /Machine-readable media.

In addition, the embodiments of the present invention can also be downloaded as a computer program product, where the program can be implemented in a carrier or other media through a communication link (for example, a modem and/or network connection) Or the modulated one or more data signals are sent from a remote computer (for example, a server) to a requesting computer (for example, a client). Therefore, as used herein, a machine-readable medium may include this carrier wave, but this is not required.

The drawings and the above description give examples of the invention. Although described as some different functional items, those with ordinary knowledge in the field will understand that one or more of these elements can also be combined into a single functional element. Alternatively, some elements can be divided into multiple functional elements. Elements from one embodiment can be added to another embodiment. For example, the order of the processes described here can be changed and is not limited to the way described here. Moreover, the actions in the flowchart do not need to be implemented in the order shown, and not all actions need to be executed. Moreover, the actions that are dependent on other actions can be executed in parallel with the other actions. However, the scope of the present invention is by no means limited by these specific examples. Many changes (regardless of whether they are explicitly given in this specification) are possible, such as differences in structure, size, and use of materials. The scope of the present invention is at least as broad as the scope of the following patent applications.

<p>300. . . Desired sender</p><p>302. . . Coding and modulation logic</p><p>304. . . Code synchronization logic</p><p>306. . . Transmit diversity encoder logic</p><p>308. . . IFFT logic</p><p>309. . . CP logic</p><p>310. . . antenna</p><p>320. . . Interference transmitter</p><p>350. . . receiver</p><p>352. . . antenna</p><p>354. . . FFT logic</p><p>356. . . Receiver logic</p><p>410~440. . . step</p>

Figure 1 depicts an example of whether the received space-time encoded codeword groups from a desired transmitter and an interference transmitter are synchronized or asynchronous; Figure 2 depicts the desired signal and interference signal Figure 3 depicts an example of a suitable system for reducing interference in a receiver according to some embodiments of the present invention; Figure 4 depicts some examples of a system according to the present invention The embodiment is an example of a suitable procedure for reducing interference in a receiver.