Hi all,
In CDMA2000 network, how could the receiver got the frequency error
estimation after the local short PN sequence coarse synchronized with the
transmitted PN sequence in pilot channel,eg. spread rate1 1.23Mhz
bandwidth, short PN sequence spread.
Cause the pilot channel is all "1" before spread, could i use the
phi=sigma(zz*) under L symbols at 1.23M chip rate for frequency error
estimation? i worried about the additive noise would corrupt the estimation
result.
And further,could the pilot channel be used for fine timing
synchronization or be done aided by sync channel? how should deal with the
phase estimation?
A lot of questions and hope for your reply.
Thanks & Best Regards.
Laron
How to do frequency eror estimation in CDMA
Started by ●February 21, 2010
Reply by ●February 21, 20102010-02-21
On Feb 21, 4:04�am, "Laron" <jason.pi...@inbox.com> wrote:> Hi all, > > � � In CDMA2000 network, how could the receiver got the frequency error > estimation after the local short PN sequence coarse synchronized with the > transmitted PN sequence in pilot channel,eg. spread rate1 1.23Mhz > bandwidth, short PN sequence spread. > � � Cause the pilot channel is all "1" before spread, could i use the > phi=sigma(zz*) under L symbols at 1.23M chip rate for frequency error > estimation? i worried about the additive noise would corrupt the estimation > result. > � � And further,could the pilot channel be used for fine timing > synchronization or be done aided by sync channel? how should deal with the > phase estimation? > > A lot of questions and hope for your reply. > > Thanks & Best Regards. > > LaronThe pilot channel in the downlink can be used as a reference for coherent demodulation of the other traffic and control channels, and for symbol timing. John
Reply by ●February 21, 20102010-02-21
> >The pilot channel in the downlink can be used as a reference for >coherent demodulation of the other traffic and control channels, and >for symbol timing. > >John >Hi John, Your mean all synchronization except frame synch could be done aided by pilot channel, including frequency error, phase error? I'm stuck with this step,points listed below. 1.for frequency error,could i use the despread symbol "z" calculate the phase difference as phi=zz* at 1.23Mhz chip rate? any other better way? 2.Cause the pilot channel didn't have a fixed spread rate, the symbol timing should be done separately for different spread rate channel? and the same should be done for the phase estimation? Can you give any reference or detailed implementation info? Thanks. B.R. Laron
Reply by ●February 21, 20102010-02-21
On Feb 21, 7:56�pm, "Laron" <jason.pi...@inbox.com> wrote:> >The pilot channel in the downlink can be used as a reference for > >coherent demodulation of the other traffic and control channels, and > >for symbol timing. > > >John > > Hi John, > > � � Your mean all synchronization except frame synch could be done aided by > pilot channel, including frequency error, phase error? > � � I'm stuck with this step,points listed below. > 1.for frequency error,could i use the despread symbol "z" calculate the > phase difference as phi=zz* at 1.23Mhz chip rate? any other better way? > 2.Cause the pilot channel didn't have a fixed spread rate, the symbol > timing should be done separately for different spread rate channel? and the > same should be done for the phase estimation? > Can you give any reference or detailed implementation info? > > Thanks. > B.R. > > LaronFor phase and frequency sync, just multiply the traffic / control symbols by conjugate of pilot. The symbol timing for everything is established by despreading the pilot and locating the peak. This can be done in software by cross-correlating against the 32k chip short code. This is the only xcorr you need, the rest is just vector multiplication. John
Reply by ●February 22, 20102010-02-22
>On Feb 21, 7:56=A0pm, "Laron" <jason.pi...@inbox.com> wrote: >> >The pilot channel in the downlink can be used as a reference for >> >coherent demodulation of the other traffic and control channels, and >> >for symbol timing. >> >> >John >> >> Hi John, >> >> =A0 =A0 Your mean all synchronization except frame synch could be doneai=>ded by >> pilot channel, including frequency error, phase error? >> =A0 =A0 I'm stuck with this step,points listed below. >> 1.for frequency error,could i use the despread symbol "z" calculate the >> phase difference as phi=3Dzz* at 1.23Mhz chip rate? any other betterway?>> 2.Cause the pilot channel didn't have a fixed spread rate, the symbol >> timing should be done separately for different spread rate channel? andt=>he >> same should be done for the phase estimation? >> Can you give any reference or detailed implementation info? >> >> Thanks. >> B.R. >> >> Laron > >For phase and frequency sync, just multiply the traffic / control >symbols by conjugate of pilot. The symbol timing for everything is >established by despreading the pilot and locating the peak. This can >be done in software by cross-correlating against the 32k chip short >code. This is the only xcorr you need, the rest is just vector >multiplication. > >John >Hi John, Another question, cause traffic/control channel got lower data rate eg.19.2kbps,so after despreading, shall we just simply added these 64 despread symbols(corresponding to one data symbol) and compare with the threshold to make a decision +1 or -1, or using other method? Thanks B. R. Laron
Reply by ●February 22, 20102010-02-22
>On Feb 21, 7:56=A0pm, "Laron" <jason.pi...@inbox.com> wrote: >> >The pilot channel in the downlink can be used as a reference for >> >coherent demodulation of the other traffic and control channels, and >> >for symbol timing. >> >> >John >> >> Hi John, >> >> =A0 =A0 Your mean all synchronization except frame synch could be doneai=>ded by >> pilot channel, including frequency error, phase error? >> =A0 =A0 I'm stuck with this step,points listed below. >> 1.for frequency error,could i use the despread symbol "z" calculate the >> phase difference as phi=3Dzz* at 1.23Mhz chip rate? any other betterway?>> 2.Cause the pilot channel didn't have a fixed spread rate, the symbol >> timing should be done separately for different spread rate channel? andt=>he >> same should be done for the phase estimation? >> Can you give any reference or detailed implementation info? >> >> Thanks. >> B.R. >> >> Laron > >For phase and frequency sync, just multiply the traffic / control >symbols by conjugate of pilot. The symbol timing for everything is >established by despreading the pilot and locating the peak. This can >be done in software by cross-correlating against the 32k chip short >code. This is the only xcorr you need, the rest is just vector >multiplication. > >John >Hi John, Another question, cause traffic/control channel got lower data rate eg.19.2kbps,so after despreading, shall we just simply added these 64 despread symbols(corresponding to one data symbol) and compare with the threshold to make a decision +1 or -1, or using other method? Thanks B. R. Laron
Reply by ●February 22, 20102010-02-22
On Feb 22, 12:25�am, "Laron" <jason.pi...@inbox.com> wrote:> >On Feb 21, 7:56=A0pm, "Laron" <jason.pi...@inbox.com> wrote: > >> >The pilot channel in the downlink can be used as a reference for > >> >coherent demodulation of the other traffic and control channels, and > >> >for symbol timing. > > >> >John > > >> Hi John, > > >> =A0 =A0 Your mean all synchronization except frame synch could be done > ai= > >ded by > >> pilot channel, including frequency error, phase error? > >> =A0 =A0 I'm stuck with this step,points listed below. > >> 1.for frequency error,could i use the despread symbol "z" calculate the > >> phase difference as phi=3Dzz* at 1.23Mhz chip rate? any other better > way? > >> 2.Cause the pilot channel didn't have a fixed spread rate, the symbol > >> timing should be done separately for different spread rate channel? and > t= > >he > >> same should be done for the phase estimation? > >> Can you give any reference or detailed implementation info? > > >> Thanks. > >> B.R. > > >> Laron > > >For phase and frequency sync, just multiply the traffic / control > >symbols by conjugate of pilot. The symbol timing for everything is > >established by despreading the pilot and locating the peak. This can > >be done in software by cross-correlating against the 32k chip short > >code. This is the only xcorr you need, the rest is just vector > >multiplication. > > >John > > Hi John, > � � �Another question, cause traffic/control channel got lower data rate > eg.19.2kbps,so after despreading, shall we just simply added these 64 > despread symbols(corresponding to one data symbol) and compare with the > threshold to make a decision +1 or -1, or using other method? > > Thanks > > B. R. > LaronAll the channels except the pilot use symbol repetition to reduce the data rates. So you need to average adjacent symbols (number determined by symbol repetition) together first. The decision is not a simple threshold, it is a Viterbi Decoder. Don't forget to deinterleave also. There is plenty of info online for this. John
Reply by ●February 23, 20102010-02-23
>On Feb 22, 12:25=A0am, "Laron" <jason.pi...@inbox.com> wrote: >> >On Feb 21, 7:56=3DA0pm, "Laron" <jason.pi...@inbox.com> wrote: >> >> >The pilot channel in the downlink can be used as a reference for >> >> >coherent demodulation of the other traffic and control channels,and>> >> >for symbol timing. >> >> >> >John >> >> >> Hi John, >> >> >> =3DA0 =3DA0 Your mean all synchronization except frame synch could be=>done >> ai=3D >> >ded by >> >> pilot channel, including frequency error, phase error? >> >> =3DA0 =3DA0 I'm stuck with this step,points listed below. >> >> 1.for frequency error,could i use the despread symbol "z" calculateth=>e >> >> phase difference as phi=3D3Dzz* at 1.23Mhz chip rate? any otherbetter>> way? >> >> 2.Cause the pilot channel didn't have a fixed spread rate, thesymbol>> >> timing should be done separately for different spread rate channel?an=>d >> t=3D >> >he >> >> same should be done for the phase estimation? >> >> Can you give any reference or detailed implementation info? >> >> >> Thanks. >> >> B.R. >> >> >> Laron >> >> >For phase and frequency sync, just multiply the traffic / control >> >symbols by conjugate of pilot. The symbol timing for everything is >> >established by despreading the pilot and locating the peak. This can >> >be done in software by cross-correlating against the 32k chip short >> >code. This is the only xcorr you need, the rest is just vector >> >multiplication. >> >> >John >> >> Hi John, >> =A0 =A0 =A0Another question, cause traffic/control channel got lowerdata=> rate >> eg.19.2kbps,so after despreading, shall we just simply added these 64 >> despread symbols(corresponding to one data symbol) and compare with the >> threshold to make a decision +1 or -1, or using other method? >> >> Thanks >> >> B. R. >> Laron > >All the channels except the pilot use symbol repetition to reduce the >data rates. So you need to average adjacent symbols (number determined >by symbol repetition) together first. The decision is not a simple >threshold, it is a Viterbi Decoder. Don't forget to deinterleave also. >There is plenty of info online for this. > >John >A simple +-1 decision before the Viterbi decoder is a hard decision Viterbi decoder and suffers around 2-3 dB SNR loss compared to the soft Viterbi decoder. Typically 4 bits quantization is enough for the BPSK/QPSK modulation. If 16/64 QAM is used, 5-6 bits are needed, and soft-demapping is also needed for the high-order modulation.
Reply by ●February 24, 20102010-02-24
>>On Feb 22, 12:25=A0am, "Laron" <jason.pi...@inbox.com> wrote: >>> >On Feb 21, 7:56=3DA0pm, "Laron" <jason.pi...@inbox.com> wrote: >>> >> >The pilot channel in the downlink can be used as a reference for >>> >> >coherent demodulation of the other traffic and control channels, >and >>> >> >for symbol timing. >>> >>> >> >John >>> >>> >> Hi John, >>> >>> >> =3DA0 =3DA0 Your mean all synchronization except frame synch couldbe>= >>done >>> ai=3D >>> >ded by >>> >> pilot channel, including frequency error, phase error? >>> >> =3DA0 =3DA0 I'm stuck with this step,points listed below. >>> >> 1.for frequency error,could i use the despread symbol "z" calculate >th= >>e >>> >> phase difference as phi=3D3Dzz* at 1.23Mhz chip rate? any other >better >>> way? >>> >> 2.Cause the pilot channel didn't have a fixed spread rate, the >symbol >>> >> timing should be done separately for different spread rate channel? >an= >>d >>> t=3D >>> >he >>> >> same should be done for the phase estimation? >>> >> Can you give any reference or detailed implementation info? >>> >>> >> Thanks. >>> >> B.R. >>> >>> >> Laron >>> >>> >For phase and frequency sync, just multiply the traffic / control >>> >symbols by conjugate of pilot. The symbol timing for everything is >>> >established by despreading the pilot and locating the peak. This can >>> >be done in software by cross-correlating against the 32k chip short >>> >code. This is the only xcorr you need, the rest is just vector >>> >multiplication. >>> >>> >John >>> >>> Hi John, >>> =A0 =A0 =A0Another question, cause traffic/control channel got lower >data= >> rate >>> eg.19.2kbps,so after despreading, shall we just simply added these 64 >>> despread symbols(corresponding to one data symbol) and compare withthe>>> threshold to make a decision +1 or -1, or using other method? >>> >>> Thanks >>> >>> B. R. >>> Laron >> >>All the channels except the pilot use symbol repetition to reduce the >>data rates. So you need to average adjacent symbols (number determined >>by symbol repetition) together first. The decision is not a simple >>threshold, it is a Viterbi Decoder. Don't forget to deinterleave also. >>There is plenty of info online for this. >> >>John >> >A simple +-1 decision before the Viterbi decoder is a hard decisionViterbi>decoder and suffers around 2-3 dB SNR loss compared to the soft Viterbi >decoder. Typically 4 bits quantization is enough for the BPSK/QPSK >modulation. If 16/64 QAM is used, 5-6 bits are needed, and soft-demapping >is also needed for the high-order modulation. > >Thanks a lot, i'm doing with this now.
Reply by ●February 25, 20102010-02-25
On Feb 21, 2:04=A0pm, "Laron" <jason.pi...@inbox.com> wrote:> Hi all, > > =A0 =A0 In CDMA2000 network, how could the receiver got the frequency err=or> estimation after the local short PN sequence coarse synchronized with the > transmitted PN sequence in pilot channel,eg. spread rate1 1.23Mhz > bandwidth, short PN sequence spread. > =A0 =A0 Cause the pilot channel is all "1" before spread, could i use the > phi=3Dsigma(zz*) under L symbols at 1.23M chip rate for frequency error > estimation? i worried about the additive noise would corrupt the estimati=on> result. > =A0 =A0 And further,could the pilot channel be used for fine timing > synchronization or be done aided by sync channel? how should deal with th=e> phase estimation? > > A lot of questions and hope for your reply. > > Thanks & Best Regards. > > LaronHi all iam working on radiographic images , i need some assistance for the issues iam getting. can i post the questions in this group or any other group is related to image processing please help me, thank you
