CN104954293B - Zero signal detection method and equipment - Google Patents
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Abstract
A user terminal for a wireless communication network and a method thereof are provided. The user terminal includes: a channel estimation unit which performs channel estimation for a target cell based on a training sequence for the target cell in a received signal; a channel window power calculation unit which calculates a signal power of a single channel window for a target cell according to a result of channel estimation; a power calculation unit of a training sequence for channel estimation which calculates a power of the training sequence for the target cell; and a null signal detection unit that compares a ratio of a signal power for the target cell to a power of the training sequence for the target cell of the channel window with a first predetermined threshold, determines that a part of the received signal in the channel window is a null signal if the ratio is smaller than the first predetermined threshold, and determines that the part of the received signal in the channel window is not a null signal if the ratio is not smaller than the first predetermined threshold.
Description
Technical Field
The present invention relates to the field of wireless communication technologies, and in particular, to a mobile terminal and a processing method thereof. .
Background
The apparatus described in this section can be practiced, but is not necessarily a method that has been previously conceived or pursued. Accordingly, unless otherwise indicated herein, the devices described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section. Moreover, all embodiments of the invention need not address all (or even any) of the issues presented in this section.
In wireless communication, many of the signal processing at the current receiving end is based on the detection of a signal. For example, the Control strategies include Automatic Gain Control (AGC), Automatic Frequency offset Control (AFC), Impulse Response Timing (IRT), and the like.
If the signal is continuously transmitted, the control strategy may also be continuously applied, however, in order to reduce the possible wireless Transmission interference and improve the effectiveness of the system, a Discontinuous Transmission (DTX) situation is introduced. In this case, the receiving end needs to quickly determine whether the signal is a signal or noise (i.e., determine whether the signal received by the receiving end is a zero signal) so as to adjust the processing of the signal in time. Otherwise, if various corresponding control strategies and subsequent signal processing are also performed on the noise, misoperation of the corresponding control strategies can be caused, so that the performance of the receiving end is reduced, the error rate is increased, and the energy consumption is increased.
In the prior art, the null detection is performed based on the comparison between the power of the received signal and the power of the interference signal. For example, in TD-SCDMA systems, it is determined whether it is a null signal based on the calculation of the window power of the Channel Impulse Response (CIR). However, under bad channel conditions, such as fading channels or channels with low signal-to-noise ratio, the signal and noise cannot be accurately determined, thereby affecting the result of null detection. For example, in a channel with a low signal-to-noise ratio, the noise power is so large that the system treats the power of the user code as noise, and such inversion necessarily results in erroneous detection results. Similarly, in the case where there is no signal but noise, the system may treat the noise as a signal and eventually detect it as a non-zero signal.
Disclosure of Invention
Therefore, there is a need for a new zero signal detection method and apparatus that addresses at least one of the problems noted above.
To this end, according to an aspect of the present invention, a user terminal for a wireless communication network is provided. The user terminal includes: a channel estimation unit configured to perform channel estimation for a target cell according to a training sequence for the target cell in a received signal; the channel window power calculation unit is configured to calculate the signal power of a single channel window aiming at the target cell according to the result of channel estimation; a power calculation unit of the training sequence for channel estimation, configured to calculate the power of the training sequence for the target cell; and a null signal detection unit configured to compare a ratio of a signal power of the channel window for a target cell to a power of the training sequence for the target cell with a first predetermined threshold, determine that a part of the received signal in the channel window is a null signal if the ratio is smaller than the first predetermined threshold, and determine that the part of the received signal in the channel window is not a null signal if the ratio is not smaller than the first predetermined threshold.
According to another aspect of the present invention, there is provided a method for a user terminal of a wireless communication network, the method comprising: performing channel estimation for a target cell according to a training sequence for the target cell in a received signal; calculating the signal power of a single channel window aiming at the target cell according to the result of the channel estimation; calculating the power of the training sequence for the target cell; and comparing a ratio of a signal power of the channel window for a target cell to a power of the training sequence for the target cell with a first predetermined threshold, determining that a portion of the received signal in the channel window is a null signal if the ratio is less than the first predetermined threshold, and determining that the portion of the received signal in the channel window is not a null signal if the ratio is not less than the first predetermined threshold.
According to another aspect of the present invention, there is provided an entity for a wireless communication network, the entity comprising: an acquisition unit configured to acquire a signal received by a user terminal and perform channel estimation for a target cell according to a training sequence for the target cell in the received signal; the channel window power calculation unit is configured to calculate the signal power of a single channel window aiming at the target cell according to the result of channel estimation; a power calculation unit of the training sequence for channel estimation, configured to calculate the power of the training sequence for the target cell; and a null signal detection unit configured to compare a ratio of a signal power of the channel window for a target cell to a power of the training sequence for the target cell with a first predetermined threshold, determine that a part of the received signal in the channel window is a null signal if the ratio is smaller than the first predetermined threshold, and determine that the part of the received signal in the channel window is not a null signal if the ratio is not smaller than the first predetermined threshold.
According to another aspect of the invention, there is provided a computer program product comprising instructions stored on a non-volatile storage medium, which when executed in a processor, perform the steps of a method according to an embodiment of the invention.
According to another aspect of the invention, there is provided a non-volatile storage medium having stored thereon instructions which, when executed in a processor, carry out the steps of a method according to an embodiment of the invention.
According to another aspect of the present invention, there is provided a wireless network entity for a wireless communication network, the network entity comprising: a memory configured to store instructions thereon; a processing system configured to execute the instructions; a network interface configured to transmit or receive data in a wireless communication network; the communication medium is configured for communication between the memory, the processing system, and the network interface; wherein: when executed in the processing system, performs the steps of a method according to an embodiment of the invention.
The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.
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For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:
FIG. 1 illustrates an environment in which embodiments of the invention may be practiced;
fig. 2 shows a flow diagram of a method performed in a user terminal according to an embodiment of the invention;
FIG. 3 shows a block diagram of a user terminal according to one embodiment of the invention;
FIG. 4 shows a block diagram of an entity, according to one embodiment of the invention;
fig. 5 shows a block diagram of a wireless network entity according to one embodiment of the invention.
Detailed Description
In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that the embodiments may be combined, or that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the scope of the various embodiments of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, but is intended to be illustrative. The scope of the invention is defined by the appended claims and equivalents thereof.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
The present invention is described below with reference to block diagrams and/or flowchart illustrations of methods, apparatus (systems) and/or computer program products according to embodiments of the invention. It will be understood that one block of the block diagrams and/or flowchart illustrations, and combinations of blocks, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computing device, special purpose computing device, and/or other programmable data processing apparatus, such that the instructions, which execute via the processor of the computing device and/or other programmable data processing apparatus, create means for implementing the functions/acts specified in the block diagrams and/or flowchart block or blocks.
Accordingly, the present invention may also be embodied in hardware and/or in software (including firmware, resident software, micro-code, etc.). Furthermore, the invention can take the form of a computer program product on a computer-usable or computer-readable storage medium having computer-usable or computer-readable program code embodied in the medium for use by or in connection with an instruction execution system. In the context of this document, a computer-usable or computer-readable medium may be any medium that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.
The present invention will be described below with reference to embodiments thereof in conjunction with the accompanying drawings.
Fig. 1 illustrates a wireless network environment in which the present invention is implemented. The wireless network 100 includes one or more Radio Base Stations (RBS) 101, and those skilled in the art understand that the Radio Base Station (RBS) 101 is sometimes referred to in the art as a Base Station, a macro Base Station (macro Base Station), a pico Base Station (femto Base Station), a node B (node B), a node B (B-node), an evolved node B (enode B), and so on, and may also refer to other receiving, originating, or wireless communication stations communicating with the UE.
In the illustrated environment, each RBS 101 is shown to serve one cell for simplicity. Each cell is represented by a circle around the respective RBS, however, it is understood by the skilled person that the RBS 101 may serve more than one cell. For example, two cells may utilize resources located at the same RBS.
User Equipment (UE), such as UE 102 shown in fig. 1, communicates with one or more RBSs 101 over a radio or air interface. For simplicity, the case of 1, 2, 3 and 4 UEs in 4 cells, respectively, is shown in fig. 1. It will be appreciated that the number of UEs served by each cell may also be other numbers, and that the number of UEs served by different cells may be the same or different. The term "user terminal" or "UE" as used herein may refer to any form of device capable of wireless communication, whether portable, pocket, hand-held, such as a mobile telephone, smartphone, personal digital assistant, device including computer apparatus (such as a desktop computer, laptop computer, vehicle, meter, appliance, medical device, multimedia device), etc., which may communicate voice and/or data via a wireless access network.
It should be understood that the RBS 101 is only described as one example of sending a signal to be detected to the UE 102, which signal to be detected may also be sent by other devices. And the transmission may be a direct transmission or an indirect transmission.
The following embodiments are described by taking TD-SCDMA standard as an example, and those skilled in the art will understand that the present invention is not limited to systems based on TD-SCDMA standard, but is applicable to all systems that can use the training sequence portion transmitted with data for channel estimation. For example, systems based on the Ultra-TDD standard may also be included, which also transmit with the data training sequences that can be used for channel estimation.
The physical channel of TD-SCDMA system adopts 4-layer structure of system frame, radio frame, sub-frame and time slot. A plurality of radio frames constitute a system frame, a radio frame of length 10ms is composed of two identical sub-frames of length 5ms, each sub-frame being assigned a different timeslot. The time slots are channels distinguished in the time domain, and the spreading codes are channels distinguished in the frequency domain, that is, different users can transmit data through different time slots or spreading codes. The TD-SCDMA system is divided into a special time slot and a conventional time slot, the length of the conventional time slot is 675 mu s, and the structure is as follows:
table 1: TD-SCDMA time slot structure.
It can be seen that a slot structure contains two data segments, a midamble and a guard interval. The intermediate code is located between two data domains, does not perform spread spectrum modulation, and is used for channel estimation. Because the duration of the time slot is extremely short, the impulse response of the channel in one time slot can be regarded as constant, and the impulse response of the channel estimated by the training sequence can be directly used for detecting data fields on two sides.
Fig. 2 shows a flow chart of a method performed in a user terminal according to an embodiment of the invention. Before entering the current flow, the required training sequence is obtained. This is typically achievable by existing UEs based on the TD-SCDMA standard. Further, the UE amplifies a Radio Frequency (RF) signal by a preamplifier, which is generally a Low Noise Amplifier (LNA), and then performs demodulation, amplification Low-pass filtering, analog-to-digital conversion, and finite impulse response filtering, and performs data separation on the signal obtained after the finite impulse response filtering to obtain a data signal and a training sequence. In the TD-SCDMA standard, the training sequence is a midamble (midamble). These are prior art and specific details will not be described herein.
Thereafter, in step 202, channel estimation is performed on the obtained training sequence. For example, channel estimation can be achieved by a Steiner estimator, namely:
wherein RM is the intermediate code part received by the receiving end, BM is the basic intermediate code,is the result of channel estimation. Specific schemes for performing Channel Estimation by using the Steiner estimator can be found in Steiner, Bernd, and PaulWalter Baier, "Low Cost Channel Estimation in the Uplink Receiver of CDMAMobile Radio Systems," FREQUENZE, 47(1993) 11-12, which will not be described in detail herein.
Those skilled in the art will understand that the signal received by the receiving end is distributed over a plurality of channel windows, and the number of the channel windows is defined by KcellDetermination of KcellInformed by the higher layer, the value can be 2, 4, 6, 8, 10, 12, 14, 16. The window length len of each channel window is 128/Kcell(see in particular the protocol "3 GPP TS 25.221 V10.0.0"). In this embodiment, K is usedcellIf = 8 is described as an example, then len = 16, the result of channel estimation
Comprising 8 windows of channel estimation results.
Preferably, one of the channel windows w is selected, and the channel estimation result of the channel window is extracted from formula (1), which is expressed as:
note here that h in equation (2)w(0) It does not necessarily mean h (0) in formula (1), and it is only when the channel window is the first channel window.
In step 204, the power for the cell in the one channel window is calculated. The power of each path in the extracted channel estimation result (see equation (2)) is first calculated:
those skilled in the art will appreciate that the power calculated from the channel estimation results may reflect the strength of the received signal.
Then, preferably, the path with the strongest power in the channel window is found out as the preferred path, and other paths around the preferred path are selected together as the effective path, which takes into account the possible drift in the presence of IRT and the multi-path factor. The selection mode is as follows: if the channel window is the first channel window and the preferred path is the first path of the first channel window, the effective path is the first four paths of the channel window; the sum WinPow of the powers of the calculated effective paths is expressed as follows:
（4）
in addition, the effective path is the preferred path, and the two paths on the left and right of the preferred path (those skilled in the art understand that the paths in the channel window are cyclically shifted, and therefore, the "left" and "right" are understood to be connected end to end in the channel window), and the effective path is four paths. Calculating the sum WinPow of the power of the effective paths:
those skilled in the art will appreciate that the choice of effective diameter is not so limited.
Next, at step 214, the power of the midamble for the own cell is calculated. The received midamble is recorded as:
in one example, in the case of no co-channel cell, i.e. single cell, the power of the midamble is calculated as follows:
thereafter, at step 304 WinPow and P are foundmidRatio of α:
and comparing α to a preset threshold epsilon, and if α < epsilon, determining that the received signal is a zero signal (step 218), otherwise determining that the received signal is not a zero signal (step 220).
In another example, in the presence of co-frequency cells, Interference Cancellation (IC) is introduced to more accurately calculate the midamble power. Recording the number of the cells with the same frequency (including the cell) as N, and eliminating the interference of the received intermediate code RM to obtain the intermediate code RM aiming at each celli：
Where i is the cell index and where i is the cell index,
is the interference of the reconstructed jth cell to the midamble of the ith cell:
whereinIs the channel impulse response of the jth cell,is the basic midamble of the jth cell.
Then the intermediate code after interference elimination processing is carried outCalculating midamble power for respective cells
:
Thereafter, at step 216 WinPow is foundiAnd PmidiRatio α ofi: (the calculation method of the power for the cell in this channel window is the same as the method in step 204 above, except that for the cell with index i, the power is recorded as WinPowi)
And will be
Comparing with a preset threshold value epsilon if
<E, the received signal is determined to be a zero signal (step 218), otherwise the received signal is determined not to be a zero signal (step 220). Those skilled in the art will appreciate that epsilon may be determined based on simulation and/or statistics.
In this example, interference cancellation may alternatively be performed in the frequency domain, which is shown in step 212. Firstly, the interference of the reconstructed jth cell on the midamble of the ith cell on the frequency domain is obtained
：
Wherein
Is the channel impulse response of the jth cell,is the basic midamble of the jth cell.
Then, interference cancellation in the frequency domain is performed:
(14)
wherein,
。
then the intermediate code represented in frequency domain for the ith cell after interference elimination
Calculating the power of the midamble of the ith cell:
the conversion to the frequency domain for calculation can reduce the complexity of the system and reduce the reaction time of the system, thereby improving the system performance.
Optionally, if the window power of the first channel window is zero, no interference cancellation operation is required for all channel windows. This example is based on a trade-off between complexity and accuracy. Generally, for most cases, when the window power of the first channel window is zero, the cell is a false cell, that is, the window power of all channel windows is zero, so that interference cancellation is not needed.
Optionally, for any one window, if the window power is less than another predetermined threshold(step 210), then interference cancellation is not necessary for the channel window. This example is based on a trade-off between complexity and accuracy. Generally, for most cases, if the window power is small enough, it also means that the cell is a false cell, i.e. the window power of all channel windows is zero, so that no interference cancellation is needed.
In this way, unnecessary interference cancellation calculations are reduced, thereby reducing system complexity, reducing system reaction time, and improving system performance.
It should be noted that, in the case of a single cell or a plurality of co-frequency cells, the detection of the null signal of any cell may be based on the detection of the null signal of any one or any plurality of channel windows, where the detection of the null signal of at least one channel window is based on the method of the foregoing embodiment; or may be the result of zero signal detection based on all channel windows, i.e.: in all channel windows of a cell, if a signal received in one channel window is detected as a non-zero signal, the received signal is determined to be a non-zero signal, and if the signals received in all channel windows are detected as zero signals, the received signal is determined to be a zero signal. This is determined for detection purposes.
Those skilled in the art will understand that, based on the TD-SCDMA standard, the methods described in the above embodiments may also be performed for the co-frequency cells, that is, based on the TD-SCDMA standard, the methods may perform channel estimation on the co-frequency cells based on the signals received by the cell, calculate the power of the midamble received by the co-frequency cells, and apply the interference cancellation method mentioned in the present invention.
The steps in the above embodiments should not be construed as limiting, and one skilled in the art can perform the above steps in various reasonable and possible orders under the teaching of the above embodiments.
The performance of the embodiments of the present invention is illustrated by the simulation results below. The first simulation conditions are set as: in gaussian channel condition, no fading, no co-channel cell, and Ior/Ioc-4 dB, multi-cell joint detection uses only a list of one cell and signals are transmitted. According to the method of the invention, the detection error rate is zero. According to a conventional method, the detection error rate is 10%. The second simulation conditions are set as: in Case3 channel condition, no co-channel cell, and 2dB Ior/Ioc, multi-cell joint detection uses a list of four cells and signals. According to the method of the present invention, the detection error rate is 1%. According to a conventional method, the detection error rate is 2%. The third simulation condition is set as: in Gaussian channel condition, co-frequency cell-free and multi-cell joint detection, only a list of cells is used, and only noise and no signal exist. According to the method of the present invention, the detection error rate is 0.1%. According to a conventional method, the detection error rate is 1.8%. The fourth simulation condition is set to: under the condition of a Gaussian channel, the number of co-channel cells is 2, Ior/Ioc is 4dB, a list of two cells is used for multi-cell joint detection, and the signal-to-noise ratio is 12. According to the method of the present invention, the detection error rate is 15%. Whereas according to one conventional method, the detection error rate is 15%.
Therefore, compared with the prior art, the embodiment of the invention obviously improves the detection accuracy, and particularly has a remarkable improvement effect under the condition of low signal-to-noise ratio.
Fig. 3 shows a block diagram of a user terminal according to an embodiment of the invention. In fig. 3, the user terminal 300 includes a channel estimation unit 301, a channel window power calculation unit 302, a midamble power calculation unit 303, and a zero signal detection unit 304. It should be understood that the user terminal 300 is not limited to the elements shown, but may include other conventional elements, as well as additional elements for other purposes.
The channel estimation unit 301 is configured to perform channel estimation for a target cell according to a training sequence for the target cell in a received signal. The specific channel estimation manner is given above in conjunction with the description of equations (1) and (2).
The channel window power calculation unit 302 is configured to calculate the signal power for a target cell for a single channel window according to the result of the channel estimation. The specific power calculation method is given above in conjunction with the descriptions of equations (3) - (5).
The power calculation unit 303 of the training sequence for channel estimation is configured to calculate the power of the training sequence for the target cell. The specific manner of power calculation is given above in connection with the description of equations (6) - (7), (11), and (15).
The null signal detection unit 304 is configured to compare a ratio of the signal power of the channel window for the target cell to the power of the training sequence for the target cell with a first predetermined threshold, determine that the portion of the received signal in the channel window is a null signal if the ratio is smaller than the first predetermined threshold, and determine that the portion of the received signal in the channel window is not a null signal if the ratio is not smaller than the first predetermined threshold. The specific calculation method is given above in conjunction with the descriptions of equations (8) and (12).
Additionally or alternatively, the user terminal 300 further includes an interference cancellation unit 305 configured to, in the presence of a plurality of intra-frequency cells of the target cell, perform interference cancellation on the training sequence for the target cell before calculating the power of the training sequence for the target cell, where the interference cancellation includes cancellation of interference of any one of the plurality of intra-frequency cells on the training sequence for the target cell in the channel window. The specific way of interference cancellation is given above in connection with the description of equations (9) and (10).
Alternatively, the interference cancellation may be performed in the frequency domain, in the manner given above in connection with the description of equations (13) - (14).
Additionally or alternatively, the user terminal 300 further includes an interference cancellation control unit 306, configured to instruct the interference cancellation unit not to cancel the interference of any one of the co-channel cells for the channel window when the signal power of the channel window for the any one of the co-channel cells is less than a second predetermined threshold.
Optionally, if the window power of the first channel window is zero, the interference cancellation control unit 306 indicates that no interference cancellation operation is required for all channel windows. This example is based on a trade-off between complexity and accuracy. Generally, for most cases, when the window power of the first channel window is zero, the cell is a false cell, that is, the window power of all channel windows is zero, so that interference cancellation is not needed.
Optionally, for any one window, if the window power is less than another predetermined threshold
The interference cancellation control unit 306 indicates that interference cancellation is not necessary for the channel window. This example is based on a trade-off between complexity and accuracy. Generally, for most cases, if the window power is small enough, it also means that the cell is a false cell, i.e. the window power of all channel windows is zero, so that no interference cancellation is needed.
In this way, unnecessary interference cancellation calculations are reduced, thereby reducing system complexity, reducing system reaction time, and improving system performance.
It should be noted that, in the case of a single cell or a plurality of co-frequency cells, the detection of the null signal of any cell may be based on the detection of the null signal of any one or any plurality of channel windows, where the detection of the null signal of at least one channel window is based on the method of the foregoing embodiment; or may be the result of zero signal detection based on all channel windows, i.e.: in all channel windows of a cell, if a signal received in one channel window is detected as a non-zero signal, the received signal is determined to be a non-zero signal, and if the signals received in all channel windows are detected as zero signals, the received signal is determined to be a zero signal. This is determined for detection purposes.
Compared with the prior art, the embodiment of the invention obviously improves the detection accuracy, and particularly has a remarkable improvement effect under the condition of low signal-to-noise ratio.
Fig. 4 shows a block diagram of an entity according to an embodiment of the invention. In fig. 4, an entity 400 includes an acquisition unit 401, a channel window power calculation unit 402, a midamble power calculation unit 403, and a zero signal detection unit 404. It should be understood that entity 400 is not limited to the elements shown, but may include other conventional elements, as well as additional elements for other purposes. The entity 400 may be built in the user terminal or may be externally connected to the user terminal, and is connected with the user terminal in a wired or wireless manner.
The acquisition unit 401 is configured to acquire a signal received by a user terminal and perform channel estimation for a target cell according to a training sequence for the target cell in the received signal. The specific channel estimation manner is given above in conjunction with the description of equations (1) and (2). The obtaining mode may be a wired mode, a wireless mode or any other suitable mode, depending on the position relationship and connection mode of the obtaining unit 401 and the user terminal.
The channel window power calculation unit 402 is configured to calculate the signal power for a target cell for a single channel window according to the result of the channel estimation. The specific power calculation method is given above in conjunction with the descriptions of equations (3) - (5).
The power calculation unit 403 of the training sequence for channel estimation is configured to calculate the power of the training sequence for the target cell. The specific manner of power calculation is given above in connection with the description of equations (6) - (7), (11), and (15).
The null signal detection unit 404 is configured to compare a ratio of the signal power of the channel window for the target cell to the power of the training sequence for the target cell with a first predetermined threshold, determine that the portion of the received signal in the channel window is a null signal if the ratio is smaller than the first predetermined threshold, and determine that the portion of the received signal in the channel window is not a null signal if the ratio is not smaller than the first predetermined threshold. The specific calculation method is given above in conjunction with the descriptions of equations (8) and (12).
Additionally or alternatively, the entity 400 further includes an interference cancellation unit 405 configured to, in the presence of a plurality of intra-frequency cells of the target cell, perform interference cancellation on the training sequence for the target cell before calculating the power of the training sequence for the target cell, where the interference cancellation includes cancelling interference of any one of the plurality of intra-frequency cells on the training sequence for the target cell in the channel window. The specific way of interference cancellation is given above in connection with the description of equations (9) and (10).
Alternatively, the interference cancellation may be performed in the frequency domain, in the manner given above in connection with the description of equations (13) - (14).
Additionally or alternatively, the entity 400 further includes an interference cancellation control unit 306 configured to instruct an interference cancellation unit not to cancel interference of any one of the plurality of intra-frequency cells for the channel window when the signal power of the channel window for the any one of the intra-frequency cells is less than a second predetermined threshold.
Optionally, if the window power of the first channel window is zero, the interference cancellation control unit 406 indicates that no interference cancellation operation is required for all channel windows. This example is based on a trade-off between complexity and accuracy. Generally, for most cases, when the window power of the first channel window is zero, the cell is a false cell, that is, the window power of all channel windows is zero, so that interference cancellation is not needed.
Optionally, for any one window, if the window power is less than another predetermined thresholdThe interference cancellation control unit 406 indicates that interference cancellation is not necessary for the channel window. This example is based on a trade-off between complexity and accuracy. Generally, for most cases, if the window power is small enough, it also means that the cell is a false cell, i.e. the window power of all channel windows is zero, so that no interference cancellation is needed.
In this way, unnecessary interference cancellation calculations are reduced, thereby reducing system complexity, reducing system reaction time, and improving system performance.
It should be noted that, in the case of a single cell or a plurality of co-frequency cells, the detection of the null signal of any cell may be based on the detection of the null signal of any one or any plurality of channel windows, where the detection of the null signal of at least one channel window is based on the method of the foregoing embodiment; or may be the result of zero signal detection based on all channel windows, i.e.: in all channel windows of a cell, if a signal received in one channel window is detected as a non-zero signal, the received signal is determined to be a non-zero signal, and if the signals received in all channel windows are detected as zero signals, the received signal is determined to be a zero signal. This is determined for detection purposes.
Compared with the prior art, the embodiment of the invention obviously improves the detection accuracy, and particularly has a remarkable improvement effect under the condition of low signal-to-noise ratio.
Fig. 5 shows a block diagram of a wireless network entity according to one embodiment of the invention. In fig. 5, a wireless network entity 500 includes memory 501, a processing system 502, a network interface 503, and communication media 504. It should be understood that the wireless network entity 500 is not limited to these illustrated elements, but may include other conventional elements, as well as additional elements for other purposes.
The network interface 503 is a device or article of manufacture that enables the wireless network entity 500 to send data to and receive data from a communication network. In different embodiments, the network interface 503 is implemented in different ways. For example, the network interface 503 may be implemented to support the TD-SCDMA standard.
The memory 501 stores various types of data and/or software instructions. For example, in the example of fig. 5, the steps of the method described above with reference to fig. 2 can be implemented when instructions stored in the memory 501 are executed in the processing system 502.
Compared with the prior art, the embodiment of the invention obviously improves the detection accuracy, and particularly has a remarkable improvement effect under the condition of low signal-to-noise ratio.
Claims (26)
1. A user terminal for a wireless communication network, comprising:
a channel estimation unit (301) configured to perform channel estimation for a target cell based on a training sequence for the target cell in a received signal;
a channel window power calculation unit (302) configured to calculate a signal power for a target cell for a single channel window according to a result of the channel estimation;
a power calculation unit (303) of the training sequence for channel estimation, configured to calculate the power of the training sequence for the target cell; and
a null signal detection unit (304) configured to compare a ratio of a signal power for the channel window for a target cell to a power of the training sequence for the target cell with a first predetermined threshold, determine that a portion of the received signal in the channel window is a null signal if the ratio is smaller than the first predetermined threshold, and determine that the portion of the received signal in the channel window is not a null signal if the ratio is not smaller than the first predetermined threshold.
2. The user terminal of claim 1, further comprising:
an interference cancellation unit (305) configured to, in the presence of a plurality of intra-frequency cells of the target cell, perform interference cancellation on the training sequence for the target cell before calculating power of the training sequence for the target cell, where the interference cancellation includes cancellation of interference of any one of the plurality of intra-frequency cells on the training sequence for the target cell in the channel window.
3. The user terminal of claim 2, wherein the interference cancellation is performed in the frequency domain.
4. The user terminal of claim 2, further comprising:
an interference cancellation control unit (306) configured to instruct an interference cancellation unit to cancel, for the channel window, interference for any one of the co-channel cells having a signal power in the channel window less than a second predetermined threshold.
5. The user terminal of claim 2, further comprising:
and the interference elimination control unit (306) is configured to instruct the interference elimination unit to eliminate the interference of any co-channel cell with zero signal power in the first channel window for all the channel windows.
6. The user terminal according to claim 1, wherein the target cell is any one of a cell served by the user terminal or an intra-frequency cell thereof.
7. The user terminal of claim 1, wherein the selection of the channel window is determined for the purpose of null detection.
8. The user terminal of claim 1, wherein the wireless communication network is a time division synchronous code division multiple access, TD-SCDMA, network.
9. A method for a user terminal of a wireless communication network, comprising:
performing channel estimation (202) for a target cell according to a training sequence for the target cell in the received signal;
calculating a signal power (203) of a single channel window for the target cell according to the result of the channel estimation;
calculating a power of the training sequence for the target cell (214); and
comparing (216) a ratio of a signal power for the channel window for a target cell to a power of the training sequence for the target cell to a first predetermined threshold, determining (218) that a portion of the received signal in the channel window is a null signal if the ratio is less than the first predetermined threshold, and determining (220) that the portion of the received signal in the channel window is not a null signal if the ratio is not less than the first predetermined threshold.
10. The method of claim 9, further comprising:
in the presence of a plurality of intra-frequency cells of the target cell, performing interference cancellation (212) on the training sequence for the target cell before calculating the power of the training sequence for the target cell, wherein the interference cancellation includes canceling interference of any one of the plurality of intra-frequency cells on the training sequence for the target cell in the channel window.
11. The method of claim 10, wherein the interference cancellation is performed in the frequency domain.
12. The method of claim 10, further comprising:
and instructing the interference elimination unit to eliminate the interference of any co-channel cell with the signal power smaller than a second preset threshold value in the channel window.
13. The method of claim 10, further comprising:
the interference elimination unit is indicated to eliminate the interference of any co-channel cell with zero signal power in the first channel window for all channel windows.
14. The method according to claim 9, wherein the target cell is any one of a cell served by the user terminal or an intra-frequency cell thereof.
15. The method of claim 9, wherein the selection of the channel window is determined for null detection purposes.
16. The method of claim 9, wherein the wireless communication network is a time division synchronous code division multiple access, TD-SCDMA, network.
17. An entity for a wireless communication network, comprising:
an acquisition unit (401) configured to acquire a signal received by a user terminal and perform channel estimation for a target cell according to a training sequence for the target cell in the received signal;
a channel window power calculation unit (402) configured to calculate a signal power for a target cell for a single channel window according to a result of the channel estimation;
a power calculation unit (403) of the training sequence for channel estimation, configured to calculate the power of the training sequence for the target cell; and
a null signal detection unit (404) configured to compare a ratio of a signal power for the channel window for a target cell to a power of the training sequence for the target cell with a first predetermined threshold, determine that a portion of the received signal in the channel window is a null signal if the ratio is less than the first predetermined threshold, and determine that the portion of the received signal in the channel window is not a null signal if the ratio is not less than the first predetermined threshold.
18. The entity of claim 17, further comprising:
an interference cancellation unit (405) configured to, in the presence of a plurality of intra-frequency cells of the target cell, perform interference cancellation on the training sequence for the target cell before calculating power of the training sequence for the target cell, where the interference cancellation includes cancellation of interference of any one of the plurality of intra-frequency cells on the training sequence for the target cell in the channel window.
19. The entity of claim 18, wherein the interference cancellation is performed in the frequency domain.
20. The entity of claim 18, further comprising:
an interference cancellation control unit (406) configured to instruct an interference cancellation unit to cancel, for the channel window, interference for any one of the co-channel cells having a signal power in the channel window less than a second predetermined threshold.
21. The entity of claim 18, further comprising:
and an interference elimination control unit (406) configured to instruct the interference elimination unit to eliminate the interference of any co-channel cell with zero signal power in the first channel window for all channel windows.
22. The entity of claim 17, wherein the target cell is any one of a cell served by the user terminal or an intra-frequency cell thereof.
23. The entity of claim 17, wherein the selection of the channel window is determined for the purpose of null detection.
24. The entity of claim 17, wherein the wireless communication network is a time division synchronous code division multiple access, TD-SCDMA, network.
25. A non-volatile storage medium having stored thereon instructions which, when executed in a processor, carry out the steps of the method according to any one of claims 9-16.
26. A wireless network entity for a wireless communication network, comprising:
a memory (501) configured to store instructions thereon;
a processing system (502) configured to execute the instructions;
a network interface (503) configured to transmit or receive data in a wireless communication network;
a communication medium (504) configured for communication between the memory, the processing system, and the network interface;
wherein:
when executed in the processing system, carry out the steps of the method according to any one of claims 9-16.
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| CN101686066A (en) * | 2008-07-18 | 2010-03-31 | 俊茂微电子（上海）有限公司 | Channel estimation method and device |
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