CN1443416A - Method of applying quadature amplitude modulation to radio mobile communication system - Google Patents
Method of applying quadature amplitude modulation to radio mobile communication system Download PDFInfo
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- H—ELECTRICITY
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Abstract
The present invention relates to a method of applying quadature amplitude modulation to a radio communication system, especially to a radio high-speed mobile communication system. The method comprises the steps of: (a) selecting a appropriate method of fading-reducing according the requirement of the radio mobile communication system, simultaneously selecting a Star QAM constellation and optimizing it; (b) according the interference degree of the system, improving the front end signal-to-interference ratio to reduce the interference of the system; (c) transmitter side using the QAM constellation selected and optimized in step (a) to modulate the signal to be transmitted with QAM; (d) receiver side using the QAM constellation selected, and optimized in step (a) and corresponding with transmitter side, to demodulate the received signal with QAM and judge receiving.
Description
A kind of method and technology field that quadrature amplitude modulation is applied to mobile radio system
The present invention relates to wireless mobile telecommunication technology, particularly relate to one kind and quadrature amplitude modulation is used in mobile radio system, especially wireless high-speed GSM（QAM, Quadrature Amplitude Modulation) carry out Digital Transmission method.Background of invention
With the arrival in informationized society and personal communication epoch, people become more and more urgent to improving the spectrum efficiency in wireless communication system, because frequency resource is extremely limited.So-called spectrum efficiency refers to when given user passes letter rate with system bandwidth, in a cell（) or sector cell（Sector) the open ended maximum number of user of interior system, its linear module is every cell (or sector）Total biography letter rate that per unit bandwidth system is supported.Obviously, the higher power system capacity of spectrum efficiency is bigger.
Quadrature amplitude modulation（QAM it is) a kind of amplitude modulation(PAM), is the efficient narrowband modulation mode of technology maturation.With the development of mobile communication, it is desirable to high-speed, the Digital Transmission of spectral efficient, attention of the QAM because causing people the characteristics of it has spectral efficient, 16QAM and 64QAM modulator approaches particularly therein.
Typically, the expression formula of M members QAM modulation is：
y(t) = Am cos ωαί + Bm sin oj 0≤t < TbIn formula, 7；For symbol width, and it is discrete amplitude, m=l, 2 ..,.
As can be seen from the above equation, modulated signal is formed by stacking by the mutually orthogonal carrier wave of two-way, and two road-load ripples are divided to Do to be modulated by two groups of discrete amplitudes { } and {, }, thus referred to as orthogonal is shaken
Width is modulated.Its amplitude 4, and ^ can be expressed as：
K - emA
A is fixed amplitude in formula, relevant with the mean power of signal.（^,e) represent that qam signal vector end-points, in the coordinate of signal space, are determined by input information data.The process for determining vector end-points coordinate by input information data is called constellation mapping, and planisphere can be referred to as by mapping formed coordinate diagram by these phasor coordinates, and a typical rectangle QAM modulation constellation is as shown in Figure 1.
Vector in planisphere is mapped as by input information bits stream 0100 it can be seen from Fig. 1（3a, a), input information bits stream 1011 are mapped as the vector in planisphere（- a, -3a) etc..Wherein, a is determined by the mean power of signal.
It can be seen that by QAM modulation expression formula, the bandwidth of QAM modulated signals is equal with the bandwidth of multi-system Modulation and Amplitude Modulation, and in the case where taking same band, QAM modulation has the symbol transmission rate doubled compared with multi-system Modulation and Amplitude Modulation, it can be seen that, QAM is a kind of narrowband modulation with spectral efficient.
The principle of QAM modulation inputs binary bits flow data in the modulator as shown in Fig. 2, is divided into two-way through serial to parallel conversion conversion, then respectively through the conversion of two level to L level, forms ^ and ^.Every A Bm ( m=l525..., V) correspond to log2Individual binary bits.In order to suppress the out-of-band radiation of modulated signal, and ^ will by premodulated low pass filter, then respectively with two-way carrier multiplication, form two-way amplitude shift keying（ASK) signal.Finally, two paths of signals is added and just obtains modulated QAM output signals.
The principle of QAM demodulation is as shown in Fig. 3, and input signal is divided into two-way, is multiplied respectively with two quadrature carriers of local recovery, by LPF, the judgement of many level and L level to two
Level conversion, two paths of signals progress parallel serial conversion finally just obtained receiving data.More general QAM demodulation principles are as shown in figure 4, receive after signal is multiplied with the quadrature carrier of local recovery, then integrated sampling, it is possible to obtain modulated signal（, Bm) valuation（D, e), then by calculating（D, e) be possible to transmission signaling point（ Am, ）The distance between, with（D, e) signaling point with minimum range is obtained optimum output signals point after judgement.Such a decision method is referred to as minimum Eustachian distance judgement.
Weigh a kind of the good with can badly be carried out by its planisphere of modulation system performance.
If signal phasor x in planisphere (m=0, l, 2 ... M) sent, it is Y that channel transmission, which is followed by receiving signal phasor, definition judgement domain 1 and！：It is as follows：
If Ye im, then judge send signal asX, it is correct judgement.
Signal is x, (' ≠ m), as mistaken verdict.
Understand according to theoretical proof and engineering are actual, error performance and | Υ-χ2It is relevant.Therefore, if the distance in signal constellation (in digital modulation) figure between each signal phasor end points is bigger, noise robustness is then better, and bit error performance is better；Distance between each signal phasor is smaller, and noise robustness is then poorer, and bit error performance is poorer.Minimum range of the upper limit of error performance between signal phasor end points in planisphere is determined.A kind of good signal constellation (in digital modulation) distribution should ensure that between each signal constellation point there is maximum distance.
It is well known that the randomness change of wireless mobile communications especially wireless high-speed mobile communication is more stronger than wire communication, so that anti fading performance when it transmit to signal and higher to the adaptivity requirement of translational speed, described in detail below：
1) mobile telecommunication channel is typical random time-varying channel, wherein existing by Doppler
The random resistant frequency diffusion that effect is produced, and spread by the randomness time that multipath transmisstion effect is produced.Random resistant frequency diffusion will make reception signal generation time Selective intensity, i.e. received signal level to have different random fluctuations to become with the time；The diffusion of randomness time will make reception signal produce frequency selective fading, that is, receive signal different spectral component and have different random fluctuation changes.Decline will also significantly reduce the capacity of system in addition to the performance of severe exacerbation system.The signal transmitted in fading channel is not only influenceed by noise, also suffers from the multiplier interferences such as flat fading or frequency selective fading, the amplitude of reception signal is decayed, and phase produces additional phase shift.Frequency selective fading can also cause intersymbol interference.Also Chan gives birth to the few bit error rates of Bu Ke Minus to doppler spread because of caused by motion（irreducible BER ) .At this moment, construction signal constellation (in digital modulation) figure will not only consider the minimum range between signal phasor, while also to take into account signal phasor has as few as possible amplitude and phase kind number, to ensure that planisphere has preferable anti fading performance.
Existing GSM is for speech business all using binary phase conversion modulation (BPSK), quaternary PSK/differential coding QPSK（QPSK/ DQPSK), GMSK Gaussian-filtered minimum shift keying（GMSK) modulate, and with the development of mobile communication, it is desirable to high-speed, the Digital Transmission of spectral efficient, user require that these requirements BPSK, QPSK/DQPSK, GMSK is difficult to reach for the data service of high-speed.Existing QAM technologies are mainly used in wire message way communication and radio communication slow channel variation Slow, and for the faster mobile communication of channel variation particularly high-speed mobile communications Rayleigh（Rayleigh) fading channel, to make the bit error rate meet data service requirement less than 1.0e-6, the needed blunt height of thresholding signal to noise ratio of QAM（Thresholding signal to noise ratio as needed for John G. Proakis obtain 4QAM under the Rayleigh fading channel conditions of two-set diversity in its digital communication (Digital Communications) P788 is 32dB), but due to intersymbol interference present in existing GSM
(ISI), the interference of neighbor cell and adjacent channel（), ACI the multi-access inference in CDMA systems（MAI), this causes carrier/interface ratio（C/I) it is difficult to reach the needed thresholding letter Qiao ratios of higher-dimension QAM.
2) wireless mobile communications environmental range is very big, for same mobile terminal, it may transfixion indoors, outdoor communication, it may also be communicated with several kilometers of walking translational speed, it is also possible to be communicated using speed as tens kilometers to hundreds of kilometer/hour, this requires there is translational speed stronger adaptivity.The content of the invention
It can be seen that by above-mentioned analysis, it is a primary object of the present invention to provide a kind of method that quadrature amplitude modulation is applied to wireless communication system, making it, especially high-speed mobile communication system has preferable anti fading performance in mobile telecommunication channel, there is good adaptivity simultaneously for the translational speed of mobile terminal.
To reach above-mentioned purpose, the technical proposal of the invention is realized in this way：
A kind of method that quadrature amplitude modulation is applied to wireless communication system, it is important that this method at least comprises the following steps：
A. appropriate anti-attenuation method is selected according to the requirement of mobile radio system first, while choosing star QAM modulation constellation, and the planisphere is optimized；
B. according to the annoyance level of system, using appropriate raising judgement front end wanted to interfering signal ratio technology reduction system interference；
C originating parties carry out QAM modulation using the star QAM planisphere selected by step a and after optimization to the signal to be transmitted；
D. after debit uses step a selected and optimized, and the star QAM consistent with originating party
Planisphere, QAM demodulations judgement is carried out to received signal and is received.
Wherein, the optimization of described planisphere is by the proportionality coefficient optimization of each signal amplitude in planisphere.
The requirement of the mobile radio system refers to the capacity and spectral efficiency requirements of mobile radio system, or refers to the fading environment and Doppler frequency shift scope of high speed data transfer business need and the system.
Described anti-attenuation method is Maximal ratio combiner, or channel interleaving, or multipath（Rake) receive anti-fading.
Described system interference is by multi-access inference（MAI), intersymbol interference（) or adjacent channel, neighbor cell interference ISI（ACI size) is determined.
Described raising judgement front end wanted to interfering signal ratio technology is balancing technique or channel coding technology or diversity technique or spread spectrum.
Signal modulation described in above-mentioned steps c further comprises following Bu Sudden：
1) the binary bits flow data of input modulator is divided into two-way through serial to parallel conversion first；
2) again by conversion of the two-way level through two level to many level, generation discrete amplitude value AmAnd Bra;
3) discrete amplitude value1And BmOutput valve by low pass filter premodulated respectively with two-way carrier multiplication, generate two-way amplitude shift keying（ASK) signal；
4) two paths of signals sum output is required qam signal.
Described each discrete amplitude value correspondence log2Individual binary bits.
Demodulation judgement described in above-mentioned step Sudden d further comprises following step：
1) after reception signal is multiplied with the quadrature carrier of local recovery, then integrated sampling, obtain
To modulated signal (Am , Bm) valuation (d, e)；
2) valuation of the modulated signal is exported again after channel compensation and channel estimation remove the multiplier interference of fading channel；
3) calculate the output valve and be possible to the signaling point of transmission（ Am , BmThe distance between), the signaling point for obtaining having minimum range with the output valve is exported as the optimum signal point after judgement.
Described channel estimation is decision directed channel estimation, or linear EV model, or Gauss interpolation channel estimation, or CP continuous pilot channel estimation.
Described channel compensation is phase compensation, or Amplitude Compensation, or multipath（Rake channel compensation) is received.
Described star QAM modulation constellation is the star-like modulation constellations of 16QAM, the star-like modulation constellations of 32QAM or the star-like modulation constellations of 64QAM.
The 16QAM is star-like to be modulated to 28 mutually star-like modulation constellations, or 44 mutually star-like modulation constellations, or other equivalent star QAM modulation constellations.
The 32QAM is star-like to be modulated to 2 16 mutually star-like modulation constellations, or 48 mutually star-like modulation constellations, or 84 mutually star-like modulation constellations, or other equivalent star QAM modulation constellations.
The 64QAM is star-like to be modulated to 2 32 mutually star-like modulation constellations, or 4 16 mutually star-like modulation constellations, or 88 mutually star-like modulation constellations, or other equivalent star QAM modulation constellations.Brief Description Of Drawings
Fig. 1 is a typical rectangle QAM modulation constellation schematic diagram；
Fig. 2 is the theory diagram of QAM modulation；
Fig. 3 is the theory diagram that QAM is demodulated；
Fig. 4 is the theory diagram that another QAM is demodulated；
Fig. 5 is the QAM demodulation principle block diagrams by fading channel；
Fig. 6 (a) is a kind of 28 mutually star-like 16QAM constellations schematic diagrames of the present invention；
Fig. 6 (b) is general rectangle 16QAM constellation schematic diagrames；
Fig. 7 is 28 mutually star-like 16QAM and rectangle 16QAM performance comparision figures；Fig. 8 is 44 mutually star-like 16QAM constellations schematic diagrames of the present invention；Fig. 9 is 28 mutually star-like 16QAM and rectangle 16QAM Gray code figures；Figure 10 is 28 mutually star-like 16QAM and performance comparision figures of the rectangle 16QAM under awgn channel；
Figure 11 is Homogeneous Random time varying channel model schematic；
The uniform time delay power spectrum schematic diagram in the footpaths of Figure 12 tri-；
Figure 13 is the system frame structure figure that uses in embodiment；
Figure 14 is RAKE receiver schematic diagram；
Figure 15 is judgement domain schematic diagram；
Figure 16 is general rectangle 64QAM constellation schematic diagrames；
Figure 17 is 4 16 mutually star-like 64QAM (64qam4al6p) constellation schematic diagrames；Figure 18 is performance comparision figures of 4 16 mutually star-like 64QAM from rectangle 64QAM under different speeds；
Figure 19 is that 4 16 mutually star-like 64QAM are combined with Turbo Coding technologies
The error performance schematic diagram arrived.Implement the mode of the present invention
In the method for the invention, the signal constellation (in digital modulation) figure of selection optimization, that is, it is that QAM modulation is applied to wireless mobile communications, especially wireless high-speed mobile communication a key to refer to the star QAM modulation pattern for selecting performance good.The maximum phase tolerance of traditional rectangle QAM modulation is simultaneously bad, result in its anti fading performance in high-speed mobile communications channel undesirable, it can prove this improved star QAM modulator approach applying to its performance of wireless communication system better than traditional rectangular QAM modulation method, especially high-speed mobile communication system has preferable anti fading performance in mobile telecommunication channel for it, has good adaptivity to the translational speed of mobile terminal.Below just so that 16QAM is modulated as an example, compare and improve superior part of the QAM modulation relative to traditional QAM modulation.
Improved 16QAM modulator approaches are using shown in a kind of 28 phase star planisphere such as Fig. 6 (a), and Fig. 6 (b) is the 16QAM square constellations with identical minimum range.
This star-like 16QAM may be considered the combination of amplitude modulation(PAM) and phase-modulation.It is with rectangle 16QAM Qu Do：It has two kinds of amplitudes, eight kinds of phases.During modulation, input information is divided into two parts：A part carries out baseband amplitude modulation, and another part carries out phase ^ modulation.28 mutually star-like 16QAM signals, each code element is made up of four bits, divides it into first bit and rear three bit two parts.The former is used to determine signal amplitude size, and when input bit is " 0 ", signal amplitude is 2.6131a, and when input bit is " 1 ", signal amplitude is 4.6131a, and a is determined by average power signal.Three bits are used to select a kind of signal phase afterwards：One of [0, π/4, pi/2,3 π/4, π, 5/4,3 pi/2s, 7 π/4].
28 mutually star-like 16QAM and rectangle 16QAM minimum signal distances are 2a, then
Their antimierophonic performances are identicals.When each signaling point equiprobability occurs, average signal transmission power is：
Rectangle 16QAM:
： 4(α2 + 2 ) + s[a2 + (3α)2 ]+ 4[(3a)2 + (3α)2 ] _ 2
αν =16 star-like 16QAM:
= 8 « (2.6131α)2 + 8 . (4.6131α)2 =
16 i.e. average signal power difference 1.47dB, it can be seen that in additive white Gaussian noise（AWGN) in channel, under conditions of the same bit error rate is reached, 28 mutually star-like 16QAM required signal-to-noise ratios 1.47dBs higher than rectangle 16QAM.However, planisphere optimal under awgn channel but differ under fading channel be set to it is optimal.Star-like 16QAM improves the arrangement of rectangle 16QAM constellations, reduces the kind number of amplitude and phase, increases the phase error of largest tolerable.
And traditional rectangle 16QAM planispheres are three kinds of range values, 12 kinds of phase values, its maximum tolerance phase error is only 13.3., as shown in Table 1.
The largest tolerable phase error of table one compares
Thus, 28 mutually star-like 16QAM anti fading performance should be better than rectangle 16QAM, and simulation result is as shown in Figure 7.
Improved 16QAM modulation can also be using 44 mutually star-like 16QAM planispheres as shown in Fig. 8.Above-mentioned 28 phase planispheres and 44 phase constellations can also be used
Figure corresponding planisphere after mathematic(al) manipulation, for example, rotate each signaling point in 28 mutually star-like 16QAM planispheres the planisphere obtained behind π/8.
It similar can also obtain being correspondingly improved QAM modulation method for other QAM modulations, such as, can be using 2 32 mutually star-like 64QAM, 4 16 mutually star-like 64QAM for 64QAM, 88 mutually star-like 64QAM etc..
The description modulated according to described technical scheme and to star QAM, the basic step that the present invention is implemented is such：
The first step, according to fading environment, the Doppler frequency shift scope of the capacity and spectral efficiency requirements of mobile radio system either high speed data transfer business need and the system, using effective anti-fading method, such as Maximal ratio combiner, Rake receptions, channel interleaving, and choose the good star QAM modulation constellation of performance and optimize, the radius of each circle such as inside and outside it（The amplitude of namely each signal）The optimization of proportionality coefficient, makes system have preferable anti fading performance, and have good adaptivity to different Doppler frequency shifts.
Second step, according to the interference of system, such as MAI, ACI, ISI size, the wanted to interfering signal ratio for adjudicating front end is improved using technologies such as equilibrium, channel coding, diversity, spread spectrums, the threshold SJR needed for the requirement of corresponding service can be reached.
3rd step, the planisphere that originating party is chosen according to the first step is modulated, as shown in Figure 2 to the signal for needing to transmit.
4th step, debit chooses the star QAM planisphere consistent with originating party according to the first step, the signal received is demodulated and adjudicated reception, as shown in figure 5, Fig. 5 is the theory diagram demodulated by the QAM of fading channel.
Due in wireless mobile communications, when signal is transmitted in fading channel being multiplied property do
Disturb, so as to occur amplitude fading and produce additive phase movement.Therefore, in absolute amplitude modulation or absolute phase modulation scheme, amplitude reference or phase reference are needed during demodulation judgement.QAM is modulated to quadrature amplitude modulation, then increase channel estimation circuit and channel compensation circuit is needed in QAM demodulator circuits, to ensure that QAM signals can be adjudicated correctly after fading channel.
Wherein channel estimation can be using channel estimation methods such as decision-feedback, linear interpolation, Gauss interpolation, CP continuous pilots, and channel compensation can use the channel compensating methods such as phase compensation, Amplitude Compensation, RAKE receptions.
The present invention is further elaborated on by three embodiments and accompanying drawing again below.
Embodiment one and two is carried out on the COSSAP emulation platforms of SY OPSYS companies of the U.S..All simulation works are based on uplink downlink and have realized chip synchronization, the hypothesis of carrier synchronization.
Embodiment one：
The simulation work of the embodiment point awgn channel and Rayleigh fading channels two parts are completed.
Compare error performance of two kinds of planispheres in awgn channel first.System is spread using LAS codes, and rectangle and star-like 16QAM modulation is respectively adopted, and channel model is additive white Gaussian channel, and the adverse effect that additive white Gaussian noise is only existed in channel estimation and compensation loop, channel is not needed now.Demodulation, judgement are using the minimum Eustachian distance arbitration schemes shown in Fig. 5, and information source information uses Gray code, as shown in Figure 9.
Two kinds of planisphere error code curves are as shown in Figure 10 in emulation gained awgn channel.
Compare error code result curve can be seen that：In awgn channel, under conditions of star-like 16QAM modulation reaches the same bit error rate with rectangle 16QAM modulation, needed for star-like 16QAM
Signal to noise ratio is higher than rectangle 16QAM about 1.4dB, and this is consistent with the result that hereinbefore theory analysis is obtained.
In the emulation under carrying out fading channel, the analog simulation of fading channel utilizes three footpath channel models in the IS95 storehouses provided in COSSAP to produce.The delay spread parameter and power distribution of three footpath channels are as shown in figure 11.
(0, (0 be three footpath independences flat Rayleigh fading, its power spectrum be Doppler frequency shift power spectrum, average is 0, and variance is respectivelyσ。、 σ2, and set： '
Three footpath Rayleigh fadings employ the uniform time delay power spectrum as shown in Figure 12 with time delay at equal intervals with equal power, i.e. emulation.Such a channel model is called Homogeneous Random time varying channel (HRTVC Homogeneous Random Time Variable Channel) model.LAS-CDMA system emulations are in order to find out worst situation during chip synchronization, to test the performance of synchronization loop using the purpose of such a channel model.The emulation of its selection on modulation system, fading channel estimation and compensation be do not have it is influential.
The frame structure that system is used in the present embodiment is as shown in Figure 13, wherein broadcast channel
(Broadcast Channel), continue channel（Access Channel) complete uplink downlink first dielectric, broadcast channel also have automatic growth control（AGC), automated power control
(APC) and automatic frequency correction（AFC) field, completes gain control, the coarse adjustment of Power Control and carrier synchronization function.
Traffic Channel is made up of nine service subframes, and each service subframe includes pilot tone and business datum two parts.Traffic Channel is modulated using 16QAM（Rectangle is star-like）, frequency pilot sign sends known signal bit stream " 1000 ", i.e., with maximum power transmission, for providing 16QAM
Start amplitude and phase reference needed for demodulation.
Receive and use five footpath RAKE receivers, as shown in figure 14.Middle three rakes（The footpath of k==0, k=l, k=2 three）Demodulation output be used for carrying out symbol judgement, the energy output of five rakes is used for forming automatic energy control（APC, automatic power control), automatic growth control（AGC, automatic gain control) and automatic time delay control（ADC, automatic delay control) control signal.
I, Q correlator and channel estimation loop (IQC＆CAE) on each rake of RAKE receivers, when comparing first using decision directed channel estimation road, the performance of rectangle 16QAM and star-like 16QAM under fading channel.
Using channel model described above, system frame structure, RAKE receiver, decision directed channel estimation loop and Maximal ratio combiner, under three footpath Rayleigh fading channels, during different speeds, error code curve when rectangle 16QAM and star-like 16QAM is modulated is respectively adopted as shown in 7.
As can be seen from Figure：The performance that star-like 16QAM is modulated under fading channel has greatly improvement than rectangle 16QAM, moreover, with the raising of speed, the increase of Doppler frequency shift, the gap of both performances is bigger.When speed reaches 180km/h, rectangle 16QAM modulation can not normal work（See error code curve in figure）, and star-like 16QAM modulation still has preferable performance, this is consistent with the result above analyzed.This example demonstrates 28 mutually star-like 16QAM modulator approaches in mobile telecommunication channel, there is good anti fading performance especially in high-speed mobile communication system, there is the adaptive life of ' 1 well for the translational speed of mobile terminal.
Embodiment one is mainly based upon large area synchronous CDMA (LAS-CDMA) system,
The system is spread using LAS spreading codes.
Embodiment two：
Referring to shown in Figure 16, Figure 17, in the emulation under carrying out fading channel, the analog simulation of fading channel utilizes three footpath channel models in the IS95 storehouses provided in COSSAP to produce, and the parameter such as delay spread parameter and power distribution of channel uses the parameter of Vehicle environment A defineds in Rec.ITU-RM.1225.Channel estimation uses CP continuous pilot method of estimation.RAKE receiver, Maximal ratio combiner etc. and embodiment 1 are same.Obtain under three footpath Rayleigh fading channels, during different speeds, error code curve when rectangle 64QAM and star-like 64QAM modulation is respectively adopted is as shown in figure 18.
As can be seen from Figure：The performance that star-like 64QAM is modulated under fading channel has greatly improvement than rectangle 64QAM, moreover, with the raising of speed, the increase of Doppler frequency shift, the gap of both performances is bigger.When speed reaches 180km/h, rectangle 64QAM modulation has been unable to reach the bit error rate required for data service（See error code curve in figure）, and star-like 64QAM modulation still has preferable performance.The embodiment is by taking 4 16 mutually star-like 64QAM modulation as an example, reconfirm that star QAM modulator approach is applied in mobile telecommunication channel, there is good anti fading performance especially in high-speed mobile communication system, there is good adaptivity simultaneously for the translational speed of mobile terminal.
Above-mentioned two embodiment can fully prove star QAM modulator approach applying to wireless communication system, not only with good anti fading performance, and have good adaptivity to the translational speed of mobile terminal.
QAM modulation is applied in channel of wireless mobile communication, especially wireless high-speed Mobile Fading Channels, it should meet two conditions：
(1) the judgement front end wanted to interfering signal ratio of system have to be larger than the required bit error rate of the corresponding corresponding service of QAM modulation（Such as speech business 1.0e-3, data service 1.0e-6) thresholding signal to noise ratio.
(2) system has preferable anti fading performance, for different channel circumstances, different vehicle-mounted mobile speed（It is substantially corresponding to different Doppler frequency shifts）, system can provide high-quality service.
And above-mentioned two embodiment only meets second condition, in Practical Project realization, if it is desired to meeting first condition, following two methods can be used：1) reduction interference.Reduce intersymbol interference present in GSM（), ISI the interference (ACI) of neighbor cell and adjacent channel, multi-access inference（MAI) etc..As CDMA systems use the less spreading code of MAI, ACI, such as LAS-CDMA systems；Such as use the small intersymbol interference of equilibrium Ji Shu Minus（ISI) etc..2) signal to noise ratio of judgement front end is improved using technologies such as channel coding, Rake receivers, diversity, spread spectrums.
Below just by taking the technology using channel coding as an example, the change for adding system determination front end signal to noise ratio after channel coding is further illustrated, the embodiment uses Turbo Coding coding techniques.Embodiment three：
Turbo Coding technologies are combined to improve the signal to noise ratio (C/I) of judgement front end by the embodiment with this improved QAM modulation technology.Turbo Coding are Claude Berrou, and Alain Glavieux, Punya Thitimajshima etc. 1993 is in " Near Shannon Limit Error Correcting Coding and Decoding:A kind of high performance channel coding method proposed in Turbo Codes ".The present embodiment is completed with a recursive coder with feedback, and the multinomial that it is used is as follows：
Wherein i/ ()=l+i)2 + £»3 , n(D) = \ + D + D3, D is a timer.
The code efficiency of the encoder is 1/2, Turbo Coding interleavers using pseudo- interleaver（Pseudo-random interleaver), weaving length is 4096 bits, and input decoder sentences information to be hard, and decoding iteration number of times is 8 times.Using 4 shown in Figure 17 16 phase QAM planispheres, other are identical with embodiment two, available simulation result such as Figure 19.From Figure 19 it can be seen that when speed is 300km/h, 180km/h, during 120km/h, as Eb/N0=18dB, the bit error rate is 0;It is 60km/h for speed, during 30km/h, as Eb/N0=21dB, the bit error rate is 0.The Eb/ Ν Ο are the power of each bit, and wherein N0 is noise power spectral density, and the value is lower, and channel performance is more superior.Compared with Figure 18, Turbo Coding coding gain is more than 15dB, and channel coding is effectively improved the signal to noise ratio of judgement front end.
Above-described embodiment illustrates the method for the present invention using the QAM modulation improved and optimized, its phase ambiguity tolerance and amplitude can be made to obscure tolerance to improve, and there is good adaptivity to different Doppler frequency shifts, make system that there is preferable anti fading performance, for different channel circumstances, different translational speeds, system can provide high-quality service.Especially after channel coding technology is added, it can be obviously improved the signal to noise ratio of wireless communication transmissions, and then make the quality of radio communication higher.
Claims (1)
- Claims1st, a kind of method that quadrature amplitude modulation is applied to wireless communication system, especially wireless high-speed GSM, it is characterised in that this method at least comprises the following steps：A. appropriate anti-attenuation method is selected according to the requirement of mobile radio system first, while choosing star QAM modulation constellation, and the planisphere is optimized；B. according to the annoyance level of system, using appropriate raising judgement front end wanted to interfering signal ratio technology reduction system interference；C originating parties carry out QAM modulation using the QAM constellation selected by Bu Sudden a and after optimization to the signal to be transmitted；D. after debit uses step a selected and optimized, and the QAM constellation consistent with originating party, QAM demodulations judgement reception is carried out to received signal.2nd, according to the method described in claim 1, it is characterised in that：Described star QAM modulation constellation is the star-like modulation constellations of 16QAM, the star-like modulation constellations of 32QAM or the star-like modulation constellations of 64QAM.3rd, the method according to claim 2, it is characterised in that：Described 16QAM is star-like to be modulated to 28 mutually star-like modulation constellations, or 44 mutually star-like modulation constellations, or other equivalent star QAM modulation constellations.4th, the method according to claim 2, it is characterised in that：Described 32QAM is star-like to be modulated to 2 16 mutually star-like modulation constellations, or 48 mutually star-like modulation constellations, or 84 mutually star-like modulation constellations, or other equivalent star QAM modulation constellations.5th, the method according to claim 2, it is characterised in that：Described 64QAM is star-like to be modulated to 2 32 mutually star-like modulation constellations, or 4 16 mutually star-like modulation constellation, Or 88 mutually star-like modulation constellations, or other equivalent star QAM modulation constellations.6th, the method according to claim 1, it is characterised in that：Described planisphere optimization is by the proportionality coefficient optimization of each signal amplitude in planisphere.7th, the method according to claim 1, it is characterised in that the signal modulation described in step Sudden c further comprises following step：A. the binary bits flow data of input modulator is divided into two-way through serial to parallel conversion first；B. again by conversion of the two-way level through two level to many level, generation discrete amplitude value A Bm;C. discrete amplitude value eight1And BmOutput valve by low pass filter premodulated respectively with two-way carrier multiplication, generate two-way amplitude shift keying（ASK) signal；D. two paths of signals sum output is required qam signal.8th, the method according to claim 7, it is characterised in that：Described each discrete amplitude value correspondence Iog2Individual binary bits.9th, the method according to claim 1, it is characterised in that the demodulation judgement described in step d further comprises following step：After a. receptions signal is multiplied with the quadrature carrier of local recovery, then integrated sampling, obtain modulated signal（ Am , Bm) valuation（D, e)；B. the valuation of the modulated signal is exported again after channel compensation and channel estimation remove the multiplier interference of fading channel；C. calculate the output valve and be possible to the signaling point of transmission（ Am , BmThe distance between), the signaling point that there is minimum range with the output valve is obtained as the optimum signal point after judgement Output.10th, method according to claim 9, it is characterised in that：Described channel estimation is decision directed channel estimation, or linear EV model, or Gauss interpolation channel estimation, or CP continuous pilot channel estimation.11st, method according to claim 9, it is characterised in that：Described channel compensation is phase compensation, or Amplitude Compensation, or multipath（Rake channel compensation) is received.12nd, according to the method described in claim 1, it is characterised in that：The requirement of the mobile radio system refers to the capacity and spectral efficiency requirements of mobile radio system, or refers to the fading environment and Doppler frequency shift scope of high speed data transfer business need and the system.13rd, according to the method described in claim 1, it is characterised in that：Described anti-attenuation method is Maximal ratio combiner, or channel interleaving, or multipath（Rake) receive anti-fading.14th, according to the method described in claim 1, it is characterised in that：Described system interference is by multi-access inference（MAI), intersymbol interference（) or adjacent channel and neighbor cell interference ISI（ACI size) is determined.15th, according to the method described in claim 1, it is characterised in that：Described raising judgement front end signal to noise ratio technology is balancing technique or channel coding technology or diversity technique or spread spectrum.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/CN2001/000804 WO2002093861A1 (en) | 2001-05-17 | 2001-05-17 | A method of applying quadature amplitude modulation to a radio mobile communication system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN1443416A true CN1443416A (en) | 2003-09-17 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN01812972.2A Pending CN1443416A (en) | 2001-05-17 | 2001-05-17 | Method of applying quadature amplitude modulation to radio mobile communication system |
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| Country | Link |
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| CN (1) | CN1443416A (en) |
| WO (1) | WO2002093861A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100558096C (en) * | 2007-07-25 | 2009-11-04 | 北京天碁科技有限公司 | A kind of quadrature amplitude modulation demodulation method and device that is applied to communication system |
| CN101558570B (en) * | 2006-10-05 | 2015-06-17 | 科达无线私人有限公司 | Improving receiver performance in a communication network |
| CN106850499A (en) * | 2017-04-13 | 2017-06-13 | 桂林电子科技大学 | A kind of angular difference QAM demodulation methods and demodulator |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ATE162035T1 (en) * | 1991-06-03 | 1998-01-15 | British Telecomm | RADIO SYSTEM |
| US5659578A (en) * | 1994-11-23 | 1997-08-19 | At&T Wireless Services, Inc. | High rate Reed-Solomon concatenated trellis coded 16 star QAM system for transmission of data over cellular mobile radio |
-
2001
- 2001-05-17 CN CN01812972.2A patent/CN1443416A/en active Pending
- 2001-05-17 WO PCT/CN2001/000804 patent/WO2002093861A1/en active Application Filing
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101558570B (en) * | 2006-10-05 | 2015-06-17 | 科达无线私人有限公司 | Improving receiver performance in a communication network |
| CN100558096C (en) * | 2007-07-25 | 2009-11-04 | 北京天碁科技有限公司 | A kind of quadrature amplitude modulation demodulation method and device that is applied to communication system |
| CN106850499A (en) * | 2017-04-13 | 2017-06-13 | 桂林电子科技大学 | A kind of angular difference QAM demodulation methods and demodulator |
| CN106850499B (en) * | 2017-04-13 | 2023-03-24 | 桂林电子科技大学 | Angle differential QAM demodulation method and demodulator |
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| Publication number | Publication date |
|---|---|
| WO2002093861A1 (en) | 2002-11-21 |
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