CN105391664A - Method for counteracting analog interference in long term evolution (LTE) full duplex system based on multiple-input multiple-output (MIMO) - Google Patents
Method for counteracting analog interference in long term evolution (LTE) full duplex system based on multiple-input multiple-output (MIMO) Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
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- H04L25/03821—Inter-carrier interference cancellation [ICI]
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Abstract
The invention provides a new analog counteracting algorithm which is applied in analog counteracting in a long term evolution (LTE) full duplex system based on multiple-input multiple-output (MIMO). For settling a problem of bandwidth limitation, an antenna transmitting signal (RF signal) is divided into N signals; each signal is transmitted through a fixed delay and a programmable attenuator circuit; and furthermore analog counteraction of a self interference signal is realized in a manner of iterating an attenuator coefficient. For settling a technical problem of long interference cancellation circuit adjustment time in dynamic interference cancellation, a cascading-based MIMO full-duplex analog counteracting algorithm is utilized. The cascading-based MIMO full-duplex analog counteracting algorithm saves many resources (delay and attenuator) and furthermore reduces the interference cancellation circuit adjustment time over simply copying the algorithm of the SISO full-duplex analog counteracting system on each interference link.
Description
Technical field
The present invention relates to wireless communication technology field, particularly a kind of interference cancellation method of LTE full duplex system.
Background technology
Along with the development of wireless communication technology and application, personal terminal is radio interconnected rapidly to be popularized, and radio communication has become individual and the indispensable indispensable interactive means of society.But current radio spectrum resources is closely exhausted, and radio communication service but just rises at index to the demand of frequency spectrum resource.
Traditional viewpoint is thought: because wireless signal is with distance rapid decay, is hundreds thousand of times is better than the signal come from other node-node transmission from the signal of local transmitting antenna.Therefore, generally suppose, a node can not send signal while receiving signal on a same frequency always.Existing FDD (FrequencyDivisionDuplexing, Frequency Division Duplexing (FDD)) and TDD (TimeDivisionDuplexing, time division duplex) technology all avoid up-downgoing to disturb by the Radio Resource wasting half.CCFD (Co-frequencyCo-timeFullDuplex, with frequently simultaneously full duplex technology) Wireless Telecom Equipment uses identical time, identical frequency, transmit and receive wireless signal simultaneously, the spectrum efficiency of wireless communication link is doubled.CCFD has now become in the follow-up evolution technology of 4G the important directions excavating radio spectrum resources.
MIMO (Multiple-InputMultiple-Output, multiple-input and multiple-output) system is a technology considering for 802.11n.Throughput can be brought up to 100Mbps.MIMO is referred to as spatial diversity sometimes, because it uses multiple spatial channel transmission and receives data.The advantage of MIMO can increase wireless range and improve performance, improves the capacity of channel, also can improve the reliability of channel simultaneously, reduces the error rate.
If again in conjunction with MIMO technology in full duplex system, the space resources of channel just can be made full use of, improve the availability of frequency spectrum and the power efficiency of wireless communication system with this, the performance of effective improvement system.Therefore, can think in future mobile communication system, in order to improve the availability of frequency spectrum and the power efficiency of wireless communication system, the performance of effective improvement system, better structure wireless network, be necessary to carry out deep research to the full duplex under MIMO, improve the adaptation ability that the full duplex technology under MIMO is transmitted future mobile communications, thus improve the service efficiency of mobile communication system.
Realizing with the key of full duplex technology while of is frequently exactly eliminate local self-interference signal.Existing interference cancellation method is substantially all process local interference signal in three places: antenna offsets or adopt isolator, simulation Interference Cancellation, digital interference to offset.
In the method for existing realization with frequently simultaneously full duplex technology, the MayankJain of StanfordUniversity, the people such as JungllChoi propose a kind of Antenna Interference Cancellation, radio frequency interference is offset and the architectural framework of base band interference cancellation.Within 2011, they also been proposed a kind of method of visiing human relations and offsetting, and realize with full duplex while of frequently in conjunction with the method for digital Interference Cancellation.Bai Lun counteracting is mainly anti-phase with original signal by producing another road analog signal, follows the successive ignition of frequency shift (FS) to realize the maximization of offsetting by controlling amplitude fading.Digital cancellation be then by the method for channel estimating at numeric field to digital offset signal.
EhsanAryafar in 2012, Mohammad (Amir) Khojastepour and KarthikeyanSundaresan etc. have studied the system of MIDU (EnablingMIMOFullDuplex), and this is that in Wi-Fi first is by the design of full duplex together with MIMO combine with technique.Antenna technology for eliminating (the placement reception of this technology symmetry and transmitting antenna) in the RF technology of their design employing.
The DineshBharadia of StanfordUniversity in 2013, the people such as EmilyMcMilin, SachinKatti propose the scheme that a kind of New Ring-like Type antenna isolator, simulation Interference Cancellation and digital interference are offset.Circulator/isolator is offseted with the signal received by the signal adding a road wire transmission.Simulation Interference Cancellation and digital interference offset the pilot signal that all make use of local signal to rebuild interference signal and Received signal strength offsets.Within 2014, they also been proposed scheme new in offset same frequency interference signal in full duplex simultaneously based on MIMO.The program does not propose new interference cancellation techniques, but reuses in SISO full duplex existing from disturbing elimination system, and eliminates mutual interference by the mode (minimizing complexity) of the bucking-out system in cascade SISO full duplex.
Can reach good neutralization effect SISO full duplex self-interference cancellation system although there now have been, MIMO technology is combined with full duplex technology while of same frequency and is applied in LTE system also has a lot of technical barrier.
In the system of MIDU (EnablingMIMOFullDuplex), the program successfully can eliminate 45dB in 625KHz bandwidth signal, but they propose MIDU scheme and also there is many restrictions: 1. in order to realize M antenna MIMO under full duplex system, the program has but used 4M antenna; 2., in the LTE system of 20MHz bandwidth, this scheme of MIDU does not but reach demand to the elimination of the interference of self, and the method has very large restriction to bandwidth.
Also has a kind of simple realization based on the method for the same frequency full duplex system simultaneously of MIMO, exactly for each interfering link of the interference signal (self-interference+mutually disturb) of each reception antenna has the self-interference cancellation system of a SISO full duplex, although good neutralization effect can be reached like this, and bandwidth is unrestricted, but but need the quantity of SISO full duplex self-interference cancellation system be the quadratic power of antenna amount doubly.
For LTE system, due to the environment of movement, so environment changes along with time (interval) change, therefore need constantly to regulate disturbance elimination circuit.16 self-interference cancellation systems are needed altogether in the MIMO full duplex system of 4 antennas, due in former research, best adjustment algorithm needs 1 millisecond to regulate once, so this designs 16 milliseconds of times of minimum needs regulate disturbance elimination circuit, this speed is for too slow LTE system.
In sum, technical barrier main the LTE full duplex system based on MIMO is realized: 1. Bandwidth-Constrained.2. regulate the time of disturbance elimination circuit oversize in order to dynamic neutralization.
Summary of the invention
Based on above-mentioned analysis, the present invention proposes a kind of simulation cancellation algorithms newly, by this algorithm application in the simulation of the LTE full duplex system based on MIMO is offset.For the problem of Bandwidth-Constrained, antenna is sent signal (radiofrequency signal) and is divided into N road by the present invention's employing, the circuit of constant time lag device and programmable attenuator is all passed through on each road, and simulates counteracting self-interference signal by the mode of iterative attenuation device coefficient.For this technical barrier regulating the disturbance elimination circuit time long when dynamic counteracting is disturbed, adopt the simulation cancellation algorithms based on the MIMO full duplex of cascade, this algorithm is given on the algorithm of each interfering link than the simulation bucking-out system of simple copy SISO full duplex and is not only saved a lot of resource (delayer, attenuator), but also decreases the time regulating disturbance elimination circuit.
This invention takes following technical scheme:
Simulate an interference cancellation method based in the LTE full duplex system of MIMO, be applied to full duplex receive-transmit system while of frequently, described system has M transmit antennas.When eliminating the self-interference signal of reception antenna, adopting the simulation interference cancellation scheme based on SISO full duplex system, when eliminating mutual interference signal, adopting the simulation interference cancellation scheme of the MIMO full duplex of the mode based on cascade; Wherein, the described simulation interference cancellation scheme based on SISO full duplex system is: first via signal arrives receiver by transmitting antenna through near field channel, then produce the second road signal being similar to first via signal and realize simulation counteracting, finally balance out with first via signal subtraction on the receive path; Described second road signal passes through fixing time delay and the signal of variable decay by N road, then obtains this N road signal summation; The simulation interference cancellation scheme of the MIMO full duplex of the described mode based on cascade by reusing the at all levels system of disturbing that disappears in the elimination of self-interference signal, and passes through the mode of cascaded transmission function, realizes the Interference Cancellation of MIMO full duplex system; Particularly, the radiofrequency signal that the transmitting antenna i producing interference mutually launches is via C
itaps produces i-th grade of mutual interference-cancelled signals, again via C after the radiofrequency signal that the transmitting antenna i+1 that the described i-th mutual interference-cancelled signals in tunnel is disturbed mutually with generation launches is added
i+1taps produces the i-th+1 grade mutual interference-cancelled signals, and cascade like this, produces the mutual interference-cancelled signals of M-1 level, for offsetting the mutual interference of MIMO full duplex system; Wherein, C
itaps represents radiofrequency signal is divided into C
iroad leads to constant time lag device programmable attenuator, produces C
ifixing time delay and the signal of variable decay are passed through in road, then to this C
iroad signal summation.
Accompanying drawing explanation
Fig. 1 is self-interference signal in the MIMO full duplex system of 3 antennas and mutual interference signal schematic diagram;
Fig. 2 is the MIMO full duplex interference cancellation systems schematic diagram of 2 antennas of the prior art;
Fig. 3 is the MIMO full duplex interference cancellation systems schematic diagram of 2 antennas of the present invention;
Fig. 4 is the simulation interference cancellation algorithm block diagram based on SISO full duplex;
Fig. 5 is sinc sampling algorithm schematic diagram;
Based on the performance simulation figure of the simulation bucking-out system of SISO full duplex when Fig. 6 is N=6;
Based on the neutralization effect schematic diagram of the simulation cancellation algorithms of SISO full duplex when Fig. 7 is N difference;
Fig. 8 is the simulation bucking-out system schematic diagram of traditional MIMO full duplex based on 3 antennas;
Fig. 9 is the neutralization effect schematic diagram of the simulation cancellation algorithms of the MIMO full duplex of 2 traditional antennas;
The neutralization effect schematic diagram of the simulation cancellation algorithms of the MIMO full duplex of 2 antennas that Figure 10 is traditional when being N difference;
Figure 11 is the simulation bucking-out system schematic diagram of traditional MIMO full duplex based on 3 antennas;
Figure 12 is the neutralization effect schematic diagram of the simulation counteracting method of the MIMO full duplex based on cascade system of the present invention of 2 antennas;
Figure 13 is the N of more traditional simulation cancellation algorithms and simulation counteracting method of the present invention
alwaysthe schematic diagram of quantity.
Embodiment
Illustrate below in conjunction with accompanying drawing and embodiment the present invention is further described.
At the LTE based on MIMO with in full duplex system while of frequently, not only to eliminate self-interference signal (signal that the transmitting terminal of the antenna that receiving terminal have received belonging to local terminal sends) and also will eliminate mutual interference signal (receiving terminal have received the signal that the mimo antenna from the cooperation of adjacent this locality sends, and this signal does not comprise the signal that the antenna belonging to receiving terminal sends).Self-interference signal in the MIMO full duplex of 3 antennas and mutual interference signal are as shown in Figure 1.
In the interference cancellation techniques of existing SISO full duplex system (self-interference cancellation technology), main antenna counteracting, simulation Interference Cancellation (radio frequency interference counteracting), the digital interference of adopting offsets the architectural framework that multilevel combination interference such as (base band interference cancellations) is eliminated.
Antenna is offset and is divided into again three kinds of modes: mode one, utilizes many transmitting antennas by the position of putting, arrival reception antenna place to be cancelled out each other.Mode two, adopts the transceiver mode that consubstantiality does not form natural isolation between them to offset.Mode three, adopts transmitting and receiving machine be same antenna and utilize circulator/isolator technology, can be good at offsetting part interference.
The mode that the signal (radiofrequency signal) mainly sent by antenna reconstructs self-interference signal is offset in simulation.Two kinds of main modes that simulation is offset: mode one, adopting and antenna is sent signal by delayer and attenuator is all programmable circuit, simulates counteracting self-interference signal by the mode of the coefficient of iteration delayer and attenuator.Mode two, adopts and antenna is sent signal is divided into N road, and by the circuit of constant time lag device and programmable attenuator, and simulate counteracting self-interference signal by the mode of iterative attenuation device coefficient.
Digital cancellation mainly reconstructs the mode of self-interference signal by baseband signal.Two kinds of modes that digital cancellation is main: mode one, digital interference technology is offset based on linear signal.Mode two, digital interference technology is offset based on nonlinear properties.
In existing MIMO full duplex system, all mainly adopt the interference cancellation techniques based on SISO full duplex system when eliminating self-interference signal, when the mutual interference signal of elimination, by based on the system of disturbing that disappears at all levels simply copying in the perturbation technique of SISO full duplex system to the mode of mutual interfering link, realize the Interference Cancellation of MIMO full duplex system.The MIMO full duplex interference cancellation systems of 2 antennas as shown in Figure 2.Wherein TX1 and RX1 is respectively transmitting terminal and the receiving terminal of antenna 1, TX2 and RX2 is respectively transmitting terminal and the receiving terminal of antenna 2, ADC represents analog-to-digital conversion module, DAC represents D/A converter module, ACC represents that simulation disappears and disturbs control, and TXRFF represents that base band arrives the modular converter of radio frequency, and RXRFF represents that radio frequency is to baseband conversion module, DCC representative digit disappears and disturbs control, and Ntaps represents and radiofrequency signal to be divided into N road to lead to constant time lag device programmable attenuator.
The interference elimination method of MIMO full duplex system proposed by the invention, when elimination self-interference signal, also be all adopt the interference cancellation techniques based on SISO full duplex system, when the mutual interference signal of elimination, be not to the mode of mutual interfering link based on the system of disturbing that disappears at all levels simply copied in the perturbation technique of SISO full duplex system, but by reusing the at all levels system of disturbing that disappears in the technology for eliminating of self-interference signal, and pass through the mode of cascaded transmission function, realize the Interference Cancellation of MIMO full duplex system.The MIMO full duplex interference cancellation systems of 2 antennas of the present invention as shown in Figure 3.Wherein, Ctaps represents and radiofrequency signal to be divided into C road to lead to constant time lag device programmable attenuator.Here, the circulator based on isolation structure that the present invention adopts Stanford University to propose, transmitting and receiving adopt same antenna, adopt this technology that minimum antenna can be used to realize the full duplex of MIMO.But the present invention is equally also applicable to the mode adopting independent transmitting antenna and reception antenna.
Based on the simulation interference cancellation algorithm of SISO full duplex
Based on the simulation cancellation algorithms of SISO full duplex, the signal (radiofrequency signal) by antenna sends is adopted to be divided into N road, and pass through the circuit of constant time lag device and programmable attenuator, and simulate counteracting self-interference signal by the mode of iterative attenuation device coefficient.
As shown in Figure 4, a road signal arrives receiver by transmitting antenna through near field channel to this simulation cancellation algorithms specific implementation, and the task of Interference Cancellation produces another road signal approximation to complete counteracting in first via signal.Approximate signal is by N road signal by fixing time delay and variable decay, then to this N road signal summation, finally balances out with first via signal subtraction on the receive path.In fact, this N road signal is all the copy transmitted through different fixed delays and variable amplitude fading.The key that this method realizes how to select different fixed delays and correct selection variable attenuation to realize the maximum counteracting of self-interference signal.
The design of this algorithm is based on a kind of brand-new idea: can offsetting the problem regarding a sampling and difference as.Actual self-interference signal has a fixing time delay and amplitude fading, this is because signal is being fixing through near field channel and circuit substantially.The scope of the fixed delay once selected should be a bit larger tham the span that actual self-interference signal experiences various equipment.In practice, be difficult to the exact value knowing d, because it is the unknown function of signal through oversampling circuit, but the scope that it changes can be found.Suppose there is N number of fixed delay, the setting that N/2 postpones is postponed d lower than self-interference signal, N/2 other delay is then greater than self-interference signal and postpones d.
Can obtain now the leading different copies with lagging behind local self-interference signal, how could does that estimate local self-interference signal actual value at a time? change a kind of thinking, this is a difference problem substantially, and class dies from how this special digital sample of Gui.In how this special digital sample of Gui, the time interval of discrete signal samples is the inverse of sample frequency.How this special sampling thheorem of Gui to show that with how this special polydispersity index of Gui can not drop-out, in other words, can at any time reconstruction signal, reconstruction signal be at any one time before this moment with the weighted linear combination of sampling afterwards.The weight of these linear combinations can be obtained by standard sine difference theorem.The basic thought of sinusoidal difference theorem is: at a time reconstruction signal time, will be superimposed upon the sinc pulse of each sampling instant exactly and the value calculated at this moment sine pulse, this value is exactly the weight needing the linear combination of rebuilding.Repeat this algorithm to determine corresponding weight and to apply it to each sampling, signal calculates in the linear combination of the weight that the value of moment t just can be obtained by above-described sinc difference arithmetic.
This simulation cancellation algorithms is in fact also adopt similar method, and at a time can obtain the different copies of signal by equidistant time delay, this is just similar to digital sample.Be similar to digital sample above equally, need according to equidistant time delay d
1, d
2..., d
ndifferent copies estimate at time delay d signal.When the pad value a of signal by the different copies of equidistant time delay
1, a
2..., a
nwhen being set to the weight of sine pulse, just can perfectly reconstructing self-interference signal and complete counteracting at receiving terminal, figure 5 shows this calculation ratio juris.
Next, a is found out by calculating
1, a
2..., a
nlocal self-interference signal is reached minimize, is namely expressed as:
Wherein d
1, d
2..., d
nthe equally spaced different delay of N group,
the signal of baseband signal x (t) after frequency conversion, c (t-d
i) be the signal of the N road different delay of c (t), y (t)=A/A
ttc (t-d
0) be local self-interference signal, wherein A is amplitude, A
ttattenuation amplitude, d
0it is the time delay of self-interference signal.Calculate a
1, a
2..., a
nmethod, the present invention adopts the mode of Gradient Iteration, makes (1) formula reach minimum.
Below by the neutralization effect that matlab simulating, verifying is calculated based on the simulation Interference Cancellation of SISO full duplex.The design parameter of emulation is as shown in table 1.
The system parameter setting that table 1 emulates
Because no matter self-interference signal is offset by the mode adopting the different body of transceiver to form natural isolation, or adopt transmitting and receiving machine be same antenna and utilize circulator/isolator technology, part interference well can both be offset.This part disturbs about about 20dBm, therefore the power of self-interference signal also remaining about 0dBm.Self-interference signal passes through based on the performance simulation figure after the simulation bucking-out system of SISO full duplex as shown in Figure 6.As can be seen from accompanying drawing 6 we, the simulation cancellation algorithms for N=6 road can offset the interference of about 37dBm.In addition other parameter constant, also simulate the simulation cancellation algorithms on N=2 ~ 13 tunnel respectively, its neutralization effect as shown in Figure 7.As can be seen from accompanying drawing 7, along with the increase of N, the neutralization effect of simulation cancellation algorithms can be better, but can weaken gradually along with neutralization effect growth after N=11.This be due to along with the increase time delayed signal of N and the degree of correlation of self-interference signal more and more weak.
Traditional simulation interference cancellation algorithm based on MIMO full duplex
Traditional simulation cancellation algorithms based on MIMO full duplex, in fact namely based on simply copy SISO full duplex simulation bucking-out system give based on each interfering link in MIMO full duplex.Specifically as shown in Figure 8.
This system is the simulation bucking-out system that each interfering link replicates a Ntaps, N here representative be, in simulation bucking-out system based on SISO full duplex, the signal (radiofrequency signal) that antenna sends is divided into the N of N road signal.As for reception antenna RX1, it have received the self-interference signal that this antenna sends, and the mutual interference signal 1 that sends of RX2 and RX3 and mutual interference signal 2.Therefore to be respectively each mutual interference signal and copy a self-interference simulation bucking-out system.
As implied above, the simulation cancellation algorithms of the MIMO full duplex based on traditional approach of M root antenna is such as formula shown in (2):
Next, az is found out by calculating
1..., az
n, ah
1..., ah
n... the interference signal (self-interference+disturb mutually) that reception antenna is received reaches and minimizes.Calculate az
1..., az
n, ah
1..., ah
n... method, the present invention adopts the mode of Gradient Iteration, makes (2) formula reach minimum.
Below by the neutralization effect of the simulation interference cancellation algorithm of the traditional MIMO full duplex of matlab simulating, verifying.The design parameter of emulation is as shown in table 2.
The system parameter setting (traditional simulation cancellation algorithms) of the emulation of table 22 antenna
Because the mimo antenna of this locality cooperation is by separately certain distance, therefore can form natural isolation between antenna, mutual interference signal is smaller than self-interference signal power, and time delay is longer.By interference signal (self-interference signal that receiving terminal receives and mutual interference signal).Post-simulation figure is offset as shown in Figure 9 by traditional simulation based on MIMO full duplex.As can be seen from accompanying drawing 9, the simulation cancellation algorithms based on MIMO full duplex for the conventional method on N=6 (self-interference/interference cancellation systems quantity required respectively mutually) road can offset about 38dBm.In addition for other parameter constant, also simulate the simulation cancellation algorithms on N=2 ~ 13 tunnel respectively, its neutralization effect as shown in Figure 10.
Simulation interference cancellation method based on MIMO full duplex of the present invention
Simulation interference cancellation method based on MIMO full duplex of the present invention utilizes existing self-interference technology for eliminating in SISO to eliminate self-interference, by reusing the disturbance elimination circuit applied in these technology and reducing complexity by the mode of cascade filtering structure (eliminating the structure in self-interference circuit), thus effectively eliminate interference mutually.To be the transfer function of self-interference in the link of the transfer function of disturbing signal mutually and reception on reception antenna itself oneself obtained from the transmission link of adjacent antenna on reception antenna be its rationale (a similar environment shared by the antenna of the antenna and generation self-interference that is produce interference mutually, has similar reflection and decay) of very near relation.So the transfer function of interference mutually can be obtained by the transfer function of self-interference according to this relation.
Because the distance of the antenna placement of MIMO this locality cooperation is from obtaining very, therefore these antenna can be regarded as and share similar environment, namely under the environment that this is similar, have similar reflection, because antenna is from obtaining very, the distance therefore through reflection is also almost identical.But the mutual interference signal received at receiving terminal is compared to self-interference signal, just experienced by some to postpone more, therefore receive self-interference signal and mutual interference signal only dissimilates due to delay, but they can determine a fixing relation by the position of antenna of MIMO this locality cooperation and the environment of surrounding.Therefore the most important part of the design of MIMO full duplex be exactly by the transfer function of its self-interference signal of the transfer function of mutual interference signal and one in order to explain the separated distance of antenna modifying factor expressed by.
First, first analyze self-interference and mutual interference signal and form two principal elements.The first, come from the interference that components and parts amplify noise.The second, come from the decay of channel and the interference reflected to form of environment.Because the second factor distinguishes self-interference and the difference mutually between interference, therefore cascaded transmission function only needs the interference that elimination fading channel and Ambient are formed.
Set up the Mathematical Modeling of the transfer function of a cascade:
H
c(f)＝H
c(f)H
i(f)(3)
H in formula
ctf () is mutual interference signal transfer function, H
c(f) transfer function represented by modifying factor (also known as making cascaded transmission function), H
if transfer function that () is self-interference signal, typical H
cf () is exactly a simple time delay, this is that mutual jam-to-signal self-interference signal is through delay high a little because two antennas are separated.
In fact the mode should measured by experiment is to calculate concrete cascaded transmission function.Concrete steps are as follows:
(1) first from antenna transmission known signal, and the signal that the identical antenna of this root receives is measured.
(2) signal that transmission one is known in adjacent mimo antenna, and the signal transmitted is received with non-original antenna.
(3) channel response of Ambient measured in (1) and (2) is estimated respectively with classical channel estimation technique.
(4) transfer function of cascade is calculated with formula (3).
By the problem that analog-and digital-filter structure design cascade transfer function design cascade transfer function is individual optimum, target is exactly the design realizing cascaded transmission function with minimum filter structure, and the amount of disturbing that disappears of interference signal can reach demand mutually.
By the above analysis and designation simulation cancellation algorithms based on MIMO full duplex of the present invention as shown in Figure 11.This algorithm is when elimination self-interference signal, also be all adopt the simulation bucking-out system (Ntaps) based on SISO full duplex, when the mutual interference signal of elimination, be not based on simply copying the simulation bucking-out system of SISO full duplex to the mode of mutual interfering link, but by reusing the simulation bucking-out system of self-interference signal, and pass through the mode of cascaded transmission function (C/Dtaps), realize the simulation Interference Cancellation of MIMO full duplex system.
Below by the neutralization effect of the simulation interference cancellation algorithm (namely based on the mode of cascade filtering) of the MIMO full duplex proposed by the invention by matlab simulating, verifying 2 antennas.Here cascaded transmission function typical case namely uses N road signal (radiofrequency signal) to simulate a transfer function simple unknown time delay of the time delay of this unknown respectively by the mode of constant time lag device and programmable attenuator, then offset identical method by simulation, adopt N road signal (radiofrequency signal) to simulate the transfer function of the time delay of this unknown respectively by the mode of constant time lag device and programmable attenuator.The design parameter of emulation is as shown in table 3.
The system parameter setting (simulation cancellation algorithms of the present invention) of the emulation of table 32 antenna
By interference signal (self-interference signal that receiving terminal receives and mutual interference signal) by the simulation Interference Cancellation post-layout simulation results exhibit figure of the MIMO full duplex of the mode based on cascade of the present invention as shown in Figure 12, as can be seen from accompanying drawing 12, for N
z=6 (self-interference payment system requirements quantity), N
hthe simulation cancellation algorithms of the MIMO full duplex based on cascade system on=4 (quantity of the demand of cascaded transmission function) road can offset the interference of about 38dBm.N
alwaysbe expressed as the sum (signal is by time delay/decay total way) of taps required in the simulation cancellation algorithms of MIMO full duplex.
When two kinds of algorithms require to reach identical neutralization effect time, respectively to the N used in the simulation cancellation algorithms of traditional simulation cancellation algorithms based on MIMO full duplex of 2 antennas and the MIMO full duplex of the new algorithm based on cascade
alwaysquantity add up, and draw counteracting power-N
alwaysfigure as shown in Figure 13.Simulation result shows, in time reaching identical neutralization effect, the taps quantity that the simulation cancellation algorithms of the MIMO full duplex based on cascade of the present invention uses is fewer than traditional simulation cancellation algorithms based on MIMO full duplex.Therefore while can offsetting interference signal by the simulation cancellation algorithms of the MIMO full duplex based on cascade of the present invention, save a lot of resource (delayer, attenuator), the time regulating disturbance elimination circuit can also be reduced when dynamic neutralization.
In addition, if combined with existing antenna isolation technology and digital cancellation method by simulation counteracting method of the present invention, the same frequency full duplex technology simultaneously based on MIMO can better just be realized.
In sum, for the problem of Bandwidth-Constrained, antenna is sent signal (radiofrequency signal) and is divided into N road by the present invention's employing, the circuit of constant time lag device and programmable attenuator is all passed through on each road, and simulate counteracting self-interference signal by the mode of iterative attenuation device coefficient, unaffected to bandwidth.For this technical barrier regulating the disturbance elimination circuit time long when dynamic counteracting is disturbed, adopt the simulation cancellation algorithms based on the MIMO full duplex of cascade, this algorithm is given on the algorithm of each interfering link than the simulation bucking-out system of simple copy SISO full duplex and is not only saved a lot of resource (delayer, attenuator), but also decreases the time regulating disturbance elimination circuit.
Above content is in conjunction with concrete preferred implementation further description made for the present invention, can not assert that specific embodiment of the invention is confined to these explanations.For general technical staff of the technical field of the invention, without departing from the inventive concept of the premise, some simple deduction or replace can also be made, all should be considered as belonging to protection scope of the present invention.
Claims (4)
1. simulate interference cancellation method based in the LTE full duplex system of MIMO for one kind, be applied to full duplex receive-transmit system while of frequently, described system has M transmit antennas, it is characterized in that: when eliminating the self-interference signal of reception antenna, adopt the simulation interference cancellation scheme based on SISO full duplex system, when eliminating mutual interference signal, adopt the simulation interference cancellation scheme of the MIMO full duplex of the mode based on cascade;
Wherein, the described simulation interference cancellation scheme based on SISO full duplex system is: first via signal arrives receiver by transmitting antenna through near field channel, then produce the second road signal being similar to first via signal and realize simulation counteracting, finally balance out with first via signal subtraction on the receive path; Described second road signal passes through fixing time delay and the signal of variable decay by N road, then obtains this N road signal summation;
The simulation interference cancellation scheme of the MIMO full duplex of the described mode based on cascade by reusing the at all levels system of disturbing that disappears in the elimination of self-interference signal, and passes through the mode of cascaded transmission function, realizes the Interference Cancellation of MIMO full duplex system; Particularly, the radiofrequency signal that the transmitting antenna i producing interference mutually launches is via C
itaps produces i-th grade of mutual interference-cancelled signals, again via C after the radiofrequency signal that the transmitting antenna i+1 that the described i-th mutual interference-cancelled signals in tunnel is disturbed mutually with generation launches is added
i+1taps produces the i-th+1 grade mutual interference-cancelled signals, and cascade like this, produces the mutual interference-cancelled signals of M-1 level, for offsetting the mutual interference of MIMO full duplex system; Wherein, C
itaps represents radiofrequency signal is divided into C
iroad leads to constant time lag device programmable attenuator, produces C
ifixing time delay and the signal of variable decay are passed through in road, then to this C
iroad signal summation.
2. simulation interference cancellation method according to claim 1, is characterized in that: described second road signal is by N road signal through fixing time delay and variable decay, then obtains this N road signal summation, is specially: time delay d
1, d
2..., d
nbe equally spaced, wherein, the delay of N/2 signal postpones d lower than self-interference signal, and the delay of N/2 other signal is then greater than self-interference signal and postpones d; Pad value a
1, a
2..., a
nmeet:
Wherein, c (t) is through the signal of different delay, and y (t) is local self-interference signal.
3. simulation interference cancellation method according to claim 2, is characterized in that: adopt Gradient Iteration algorithm to estimate described pad value a
1, a
2..., a
n.
4. simulation interference cancellation method according to claim 1, it is characterized in that: described full duplex system additionally uses Antenna Interference Cancellation and digital interference cancellation technology, Antenna Interference Cancellation, simulation Interference Cancellation and digital interference are offset cascade and obtains higher co-channel interference reduction gain.
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