CN101908906B - User channel satellite capture method based on WCDMA (Wideband Code Diversion Multiple Access) system - Google Patents
User channel satellite capture method based on WCDMA (Wideband Code Diversion Multiple Access) system Download PDFInfo
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Abstract
The invention relates to a user channel satellite capture method based on a WCDMA (Wideband Code Diversion Multiple Access) system, comprising the following steps of: firstly screening access users out according to signing information of a PRACH (Physical Random Access Channel) access preamble on a wave beam access slot; then determining that a wave beam that each access user locates is a principle wave beam or a spanning wave beam; if the wave beam is the principle wave beam, determining the search starting time and a search interval of DPCH (Dedicated Physical Channel) channels corresponding to the access users by utilizing signing phases, searching the single-path retardation of the DPCH channels corresponding to the access users in the principle wave beam in the search interval, and then carrying out scrambling code tracking on the DPCH channels; and if the access users are the spanning wave beam access users, distributing the DPCH channels in the principle wave beam, determining the search starting time and a search interval of the DPCH channels corresponding to the spanning wave beam access users in the principle wave beam by taking the reference time of the principle wave beam as a reference, searching the single-path retardation of the DPCH channel corresponding to the spanning wave beam access users in the principle wave beam in the search interval, and then carrying out scrambling code tracking on the DPCH channels.
Description
Technical field
The invention belongs to satellite communication field, catching method on the user channel satellite when relating to a kind of spaceborne reception of 3G communication based on the WCDMA system.
Background technology
Consider the characteristics of GEO (Geosynchronous Earth Orbit geosynchronous earth orbit) satellite mobile communication system, and the restriction that receives aspect such as power consumption, volume on the satellite, the access processing mode on the star is different from ground system.
At present, the satellite communication system that does not still adopt the WCDMA system and on satellite, handle.And in the WCDMA mobile system of ground; Catching of subscriber channel comprises that PRACH (Physical random access channel Physical Random Access Channel) catches and DPCH (Dedicated Physical Channel downward special physical channel) catches, but two kinds catch between not directly contact.Because for ground, channel circumstance is complicated and changeable, and multipath effect is obvious, and the multidiameter delay ratio is bigger, and PRACH channel acquisition information is used for DPCH, and to catch difficulty bigger.Therefore, adopted the method for repeatedly catching separately in the WCDMA mobile system of ground, when promptly setting up communication link, need catch separately PRACH and DPCH.
Compare with the channel of land mobile communication system, it is main that the GEO satellite channel has its tangible characteristics: Yi Laisi (Rice) channel, and Rayleigh channel is few.Usually contain direct projection footpath (LOS) in the Rice channel again, and the energy in main footpath accounts for the overwhelming majority of signal energy.Therefore, multipath is handled and is become insignificant, if adopt the method for repeatedly catching separately the same with the land mobile communication system, can introduce the complicated arresting structure and the hardware resource of bulk redundancy.This shows that the method for repeatedly catching separately is not suitable for the satellite channel characteristics, receive the harsh constraint in aspect such as power consumption, volume on the star simultaneously and become infeasible.
Summary of the invention
Technology of the present invention is dealt with problems and is: overcome the deficiency of prior art, provide a kind of easy and simple to handle, acquisition speed fast based on catching method on the user channel satellite of WCDMA system.
Technical solution of the present invention is: a kind of based on catching method on the user channel satellite of WGDMA system, step is following:
(1) on the access slot of wave beam, obtain the signing messages of the PRACH access lead of subscriber equipment emission, and filter out the access user according to signing messages, described signing messages comprises subscriber channel signature energy, signature sequence and signature phase place;
(2) confirm that the access user belongs to wave beam; If belonging to wave beam, access user is this wave beam then change step (3); If access user belongs to wave beam for crossing over wave beam then change step (5); Described wave beam be satellite receive respectively import the wave beam that is being processed in the beam signal, all the other wave beams are for crossing over wave beam;
(3) utilize the signature phase place of access subscriber channel to confirm the search zero-time and the region of search of the DPCH channel corresponding with this access user; Search zero-time t
DPCH_start_time=t
Prach_delay+ T
FrameOffset+ T
ChipOffset+ Rx_Tx
Delay, t wherein
Prach_delayBe signature phase place, T
FrameOffsetBe vertical shift, T
ChipOffsetBe chip offset, Rx_Tx
DelayBe the constant time lag between uplink physical channel frame and the down physical channel frame; Search radius is to receive in this time period the user with respect to the variation distance L of satellite to DPCH behind the pilot capture
IntervalWith each chip radio range L
Signal/chipRatio, unit is chip;
(4) according to the result of step (3), single footpath retardation of the DPCH channel of access user correspondence in this wave beam of search utilizes corresponding scrambler and spreading code information that the DPCH channel is carried out the scrambler tracking then in the region of search, realizes despread-and-demodulation;
(5) in this wave beam, distributes the DPCH channel for crossing over wave beam access user, with fiducial time of this wave beam be reference, confirm search zero-time and the region of search of DPCH channel in this wave beam of this leap wave beam access user correspondence; Search zero-time t
DPCH_start_time=t
Pre_T_cell± Δ T
T_cell, t wherein
Pre_T_cellFor cross over wave beam access user under original wave beam with respect to the time-delay of fiducial time of original wave beam, Δ T
T_cellBe wave beam time migration T between current wave beam and the original wave beam
CellThe absolute value of difference, if the time migration of current wave beam is ahead of primary beam, then get "+", otherwise get "-"; Search radius N＞=2
*L
Interval/ L
Sihnal/chip, unit is chip;
(6) according to the result of step (5), in the region of search, search for single footpath retardation of the DPCH channel corresponding with said leap wave beam access user, utilize corresponding scrambler and spreading code information that the DPCH channel is carried out the scrambler tracking then, realize despread-and-demodulation.
The searching method of single footpath retardation is in said step (4) or the step (6): according to formula
Carry out matching operation, the correlation when obtaining different delay, wherein PDP (n) is the power time delay function, and S (k) is local scrambler, and R (k) receives signal for the base-band digital of wave beam input,
*The expression complex conjugate, K is a correlation intergal length, and for the search in the step (4), K chooses 8～16 times of hunting zone, and for the search in the step (6), K chooses 4～8 times of hunting zone.
Screening access user's method is in the said step (1): the signature energy to the PRACH access lead is correlated with or matching treatment; Then relevant or matching treatment result are carried out the Hadamard conversion, the energy of will signing at last satisfies the pairing user of PRACH access lead of channel signature energy threshold as the access user.
The present invention's advantage compared with prior art is: catching method of the present invention is considered the constraint of satellite channel characteristic and satellite platform; Abandoned the RAKE receiver pattern,, caught through the leading access of PRACH for the user in this wave beam; Realize slightly catching of user; The search zero-time and the region of search are provided for the narrow search of DPCH channel, have then realized carefully catching, follow the tracks of the precise synchronization that realizes scrambler through scrambler again through narrow search.For the user who crosses over wave beam, through wide search, realized striding into carefully catching of user DPCH channel in this wave beam from other wave beams, follow the tracks of the precise synchronization that realizes scrambler through scrambler again.In addition, adopt the mode of single path search during search, through search, simplified receiving handling process on the star with respect to many.Acquisition search process and hunting zone have been simplified in catching method operation of the present invention greatly, have accelerated acquisition speed.
Description of drawings
Fig. 1 is the flow chart of catching method of the present invention;
Fig. 2 is the time delay sketch map of PRACH search of the present invention;
Fig. 3 is the time delay sketch map of DPCH search of the present invention;
The schematic diagram of Fig. 4 for catching for PRACH access lead of the present invention.
Embodiment
As shown in Figure 1, be the flow chart of catching method of the present invention.When in a certain wave beam user's access being arranged; Satellite system will be informed corresponding spreading code, the scrambling code information of this user DPCH channel of capturing unit on the star; The signing messages of the PRACH access lead that capturing unit will be launched subscriber equipment (UE) on the access slot of this wave beam is correlated with or matching operation; Operation result is carried out Hadamard conversion and threshold judgement, and record signature energy is greater than signature sequence, signature phase place, the signature energy of thresholding; Whether judge the signature energy greater than the signature energy threshold, if continue signal is carried out matched filter processing less than then returning trapped state; If insert greater than then permitting; Further judge according to signing messages whether this user is this wave beam user again; If; Then calculate the search zero-time and the narrow region of search of corresponding DPCH channel according to formula, join the narrow search of carrying out DPCH channel list footpath retardation under scrambler, spreading code that satellite system is distributed and the search information of calculating, scrambler is followed the tracks of and despread-and-demodulation; If cross over the wave beam user; Then system distributes the DPCH channel for crossing over wave beam access user in this wave beam via satellite; Be reference the fiducial time with this wave beam; Calculate this according to formula and cross over corresponding search zero-time and the region of search of DPCH channel in this wave beam of wave beam access user, join the wide search of carrying out DPCH channel list footpath retardation under scrambler, spreading code that satellite system is distributed and the search information of calculating, scrambler is followed the tracks of and despread-and-demodulation.
Compare with the channel of land mobile communication system, it is main that the GEO satellite channel has its tangible characteristics: Yi Laisi (Rice) channel, and Rayleigh channel is few.Usually contain direct projection footpath (LOS) in the Rice channel again, and the energy in main footpath accounts for the overwhelming majority of signal energy.Therefore on satellite, from PRACH, directly extract the transmission delay of UE, adopt the search of close limit to compensate slightly, just can be used for the reception of Traffic Channel these time-delays to satellite (the Node B that is equivalent to ground); For distinguishing the user more between the wave beam, under the instruction of satellite, (delay value of original wave beam is provided), unaffected with the search Dan Jing of relative broad range to ensure user's communications.
For the GEO satellite channel, can the information that the PRACH channel leading is caught be used for catching of DPCH channel.As shown in Figure 2, for the PRACH channel, there is wave beam (sub-district) time migration (T the access slot downlink time with respect to the base station system time (BFN)
Cell), suppose that satellite (base station) emission radio-frequency channel processing delay is T
Txd, the skyborne propagation delay time of downstream signal is T late
PropDelay, after travelling carriage receives access slot, the targeting sequencing that emission is corresponding, the skyborne propagation delay time of upward signal is T late
PropDelay, satellite (base station) receiving RF channel processing delay is T
RXD, so the zero-time of satellite (base station) search should add T on the basis of BFN
Cell+ T
Txd+ T
RXD+ 2
*T
PropDelay, that is to say that with respect to base station system time (BFN), the zero-time of catching of PRACH channel leading is t
Prach_start=T
Cell+ T
Txd+ T
RXD+ 2
*T
PropDelay
As shown in Figure 3, for the DPCH channel, there is wave beam (sub-district) time migration (T the downlink time with respect to satellite (base station) system time (BFN)
Cell) add vertical shift (T
FrameOffset) and chip offset (T
ChipOffset), suppose that satellite (base station) emission radio-frequency channel processing delay is T
Txd, the skyborne propagation delay time of downstream signal is T late
PropDelay, after UE receives descending DPCCH/DPCH frame, can postpone a regular time Rx_Tx
DelayAfter, the up DPCCH/DPCH frame that emission is corresponding, the skyborne propagation delay time of upward signal is T late
PropDelay, satellite (base station) receiving RF channel processing delay is T
RXD, so the zero-time of satellite (base station) search should add T on the basis of BFN
Cell+ T
Txd+ T
RXD+ 2
*T
PropDelay+ T
FrameOffset+ T
ChipOffset+ Rx_Tx
Delay, that is to say that with respect to base station system time (BFN), the zero-time of catching of DPCH channel is t
DPCH_start=T
Cell+ T
Txd+ T
RXD+ 2
*T
PopDelay+ T
FrameOffset+ T
ChipOffset+ Rx_Tx
Delay
Comparison diagram 2 can find out that with Fig. 3 the region of search mainly comprises: and the two-way time delay of bringing because of propagated (Round Trip Delay, RDT), satellite (base station) emission radio-frequency channel processing delay T
TxdAnd satellite (base station) receiving RF channel processing delay T
RXDBecause vertical shift (T
FrameOffset), chip offset (T
ChipOffset) and wave beam (sub-district) time migration (T
Cell) to wait all be known, so through the PRACH acquisition search, the PRACH search value t that obtains
Prach_delay, the correction through a series of known conditions (vertical shift, chip offset and on/downlink constant time lag) can be used for catching of DPCH, shown in following formula: t
DPCH_start_time=t
Prach_delay+ T
FrameOffset+ T
ChipOffset+ Rx_Tx
Delay
In addition; After PRACH inserts and catches; The access of distance B PCH channel has the interval of one or several radio frames in time; This moment, UE maybe some variation for the space length of satellite (base station), introduced narrow search (choosing with respect to the characteristic that satellite distance changes with UE), and the search zero-time that estimates is searched for correction.
And for by adjacent beams more district and the DPCH channel that comes, owing to wave beam crossover region beam gain rises and falls and reason such as pattern is irregular, signal strength signal intensity has fluctuating; Desire accurately to estimate the original position and the region of search of its search window; Relatively more difficult, therefore, the present invention adopts the method for wide search; Can improve searching probability, soft handover is accomplished smoothly.
In sum; In satellite WCDMA GSM, because the channel circumstance variation slowly, and it is very limited to handle resource on the star; The inventive method is associated catching with catching of DPDH channel of PRACH channel; The scheme of catching employing " PRACH slightly catches, the narrow search of DPCH channel (wide search) is carefully caught and the DPCH scrambler is followed the tracks of " of scrambler realizes, is suitable for the satellite channel environment, can simplify implementation complexity on the star.
Schematic diagram as shown in Figure 4, as to catch for PRACH access lead of the present invention.Among the figure, relevant or matching operation is accomplished descrambling to targeting signal, is gone rotation and despreading, produces 16 input values of 16 Hadamard conversion; FHT is a quick Hadamard transformation; Scrambling generator produces local scrambler, and the scrambler real part is carried out I, Q two-way scrambler that pi/4 rotation produces is used for relevant or matching operation; The scrambler sequence number is by dispensing scrambling generator under the satellite system.Threshold judgement is accomplished the judgement to the signature energy; Record signature energy is greater than information such as the signature sequence of thresholding, the phase place of signing, signature energy; Threshold value is calculated by the acquisition probability and the false alarm probability of system requirements, and by dispensing threshold judgement device under the satellite system.
Narrow search mainly compensates behind the pilot capture when DPCH receives in this section period, UE (subscriber equipment) is with respect to the change in location of satellite (base station) and the variation between DPCH scrambler that causes and the local scrambling code phase that calculates, thus the precise synchronization between realization DPCH channel and the local scrambler.The hunting zone promptly changes distance/every chip radio range, and (WCDMA air interface wireless transmission rate is 3.84Mchips/s, and the radio velocity of wave propagation is 300000km/s, then every chip radio range=300000km/s
*(1chip/3.84Mchips/s)=78.125m).The scope of narrow search is relevant with the motion state of UE, and the high more region of search of UE speed is big more.For example; As UE during with the speeds of maximum 200km/h; The time difference to DPCH launch time its access lead launch time generally all is a second level, if calculate with 5s, UE is 277.8m (277.8=200000 ÷ 3600 * 5 to the maximum apart from the variable in distance of GEO satellite in the 5s time so; Be that the UE maximum rate multiply by 5s), be about the variable quantity of 3.6 chips (277.8m/78.125m).At this moment; On the basis of the search zero-time that obtains through the signature phase place; Carry out ± a N chip that (UE was apart from the corresponding chip numerical value of the ultimate range of satellite in this section period when N＞PRACH pilot capture received to DPCH, and calculating can be with reference to formula: the UE maximal phase is for the satellite maximal rate
*This section period/every chip radio range, carry out relevant or coupling through DPCH channel signal and the local scrambler that UE is sent, ask for relevant peaks, adjust local scrambling code phase, realize carefully catching.In other words, narrow search is the single footpath of the DPCH retardation of the corresponding channel of search access lead, carries out the despread-and-demodulation of DPCH channel in the wave beam then.
The user DPCH channel that comes being distinguished more by adjacent beams carries out wide search.The wide search here is on the basis of search zero-time, and its hunting zone is for narrow search is big.To the calculating of this hunting zone, the characteristic of the crossover region of main and wave beam is relevant, can be obtained by empirical data, is generally this user 2 times of the narrow region of search in wave beam originally, is informed by the system assignment indication information.But, there is fluctuating in wave beam crossover region signal strength signal intensity, if switching granary, upper strata is short, can increase the difficulty that wide search receives, execution switching indication in upper strata during suggestion signal intensity stabilization.
Cross over the user DPCH channel that wave beam is about to intrude this wave beam, in the time-delay down of original wave beam, calculate the search zero-time under new wave beam with respect to the time reference of physical channel according to the user, shown in following formula:
t
DPCH_start_time＝t
pre_T_cell±ΔT
T_cell
Wherein, t
Pre_T_cellBe the time-delay with respect to primary beam time reference of user under original wave beam, Δ T
T_cellBe wave beam time migration (T between current wave beam and the original wave beam
Cell) the difference absolute value.If the time migration of current wave beam is ahead of original wave beam, then gets "+", otherwise get "-".
It should be noted that; To any up DPCH channel; No matter experience that narrow search receives or wide search receives, its scrambler acquisition procedure is all: through to PRACH leading catch realization to slightly the catching of up DPCH channel, narrow (wide) search is carefully caught; The despread-and-demodulation unit is followed the tracks of, thereby realizes the precise synchronization of scrambler.
The basic principle of wide (narrow) search is the autocorrelation according to the PN sequence, and receiving terminal can obtain different correlations from the related operation of local sequence and receiving sequence.When receiver begins to receive the spread-spectrum signal that sends, the adjustment and the local frequency expansion sequence phase place of selective receiver, when the phase error of local sequence and receiving sequence was within very little scope, the correlation that obtains was more sharp-pointed.Through setting suitable correlation thresholding, can judge tentatively whether receiving terminal has reached Phase synchronization.In real system, all be to realize the synchronous of PN sign indicating number through similar method.
In the existing Multipath searching algorithm; With scrambler with receive the signal correlation intergal of sliding; Obtain the plural correlation function CRF (Complex Relation Function) of desired user; Get the quadratic sum of plural correlation function real part and imaginary part then, obtain power time delay function PDP (Power Delay Profile), the power time delay function is exactly a scrambler and the mould value of the coherent function that receives signal square in fact.From the power time delay function, find out functional value big (be correlation is big, power bigger) then or just think the position of multidiameter delay greater than the peak of certain thresholding.This method is shown in following document: Qi Yusheng, Shao Shixiang writes " Modern Mobile Communications Systems " (People's Telecon Publishing House), " CDMA:Principies of Spread Spectrum Communication " (the Addision_Wesley Publishing Company) of A.J.Viterbi etc.
As previously mentioned, because the GEO satellite channel, Yi Laisi (Rice) channel is main, and Rayleigh channel is few.Usually contain direct projection footpath (LOS) in the Rice channel again, and the energy in main footpath accounts for the overwhelming majority of signal energy, so, when search, just can give up the small and weak footpath of energy, the main footpath of direct search.
The main footpath of search i.e. to received signal single footpath retardation is searched for; Base-band digital through local scrambler S (k) and wave beam input receives signal R (k);
carries out matching operation according to formula; Correlation when obtaining different delay, i.e. power time delay function PDP (n).Wherein K is a correlation intergal length, i.e. sampled point number, "
*" expression complex conjugate.The K value is big more, and the signal to noise ratio of PDP is high more, but the calculating quantitative change is big, therefore needs compromise to select.In wide search, K can choose 8～16 times of hunting zone, and in narrow search, K can choose 4～8 times of hunting zone.
Utilize statistical property such as maximum, minimum value and the average of PDP value to obtain calculating filter threshold, be main footpath greater than thresholding, maximum functional value, its corresponding time-delay is time delays.Time-delay adjustment when this time-delay is used for the despreading tracking realizes local scrambler and the precise synchronization that receives signal.
The content of not doing to describe in detail in the specification of the present invention belongs to those skilled in the art's known technology.
Claims (3)
1. one kind based on catching method on the user channel satellite of WCDMA system, it is characterized in that step is following:
(1) on the access slot of wave beam, obtain the signing messages of the PRACH access lead of subscriber equipment emission, and filter out the access user according to signing messages, described signing messages comprises subscriber channel signature energy, signature sequence and signature phase place;
(2) confirm that the access user belongs to wave beam; If belonging to wave beam, access user is this wave beam then change step (3); If access user belongs to wave beam for crossing over wave beam then change step (5); Described wave beam be satellite receive respectively import the wave beam that is being processed in the beam signal, all the other wave beams are for crossing over wave beam;
(3) utilize the signature phase place of access subscriber channel to confirm the search zero-time and the region of search of the DPCH channel corresponding with this access user; Search zero-time t
DPCH_start_time=t
Prach_delay+ T
FrameOffset+ T
ChipOffset+ Rx_Tx
Delay, t wherein
Prach_delayBe signature phase place, T
FrameOffsetBe vertical shift, T
ChipOffsetBe chip offset, Rx_Tx
DelayBe the constant time lag between uplink physical channel frame and the down physical channel frame; Search radius is to receive in this time period the user with respect to the variation distance L of satellite to DPCH behind the pilot capture
IntervalWith each chip radio range L
Signal/chipRatio, unit is chip;
(4) according to the result of step (3), single footpath retardation of the DPCH channel of access user correspondence in this wave beam of search utilizes corresponding scrambler and spreading code information that the DPCH channel is carried out the scrambler tracking then in the region of search, realizes despread-and-demodulation, finishes;
(5) in this wave beam, distributes the DPCH channel for crossing over wave beam access user, with fiducial time of this wave beam be reference, confirm search zero-time and the region of search of DPCH channel in this wave beam of this leap wave beam access user correspondence; Search zero-time t
DPCH_start_time=t
Pre_T_cell± Δ T
T_cell, t wherein
Pre_T_cellFor cross over wave beam access user under original wave beam with respect to the time-delay of fiducial time of original wave beam, Δ T
T_cellBe wave beam time migration T between current wave beam and the original wave beam
CellThe absolute value of difference, if the time migration of current wave beam is ahead of primary beam, then get "+", otherwise get "-"; Search radius N＞=2*L
Interval/ L
Signal/chip, unit is chip;
(6) according to the result of step (5), in the region of search, search for single footpath retardation of the DPCH channel corresponding with said leap wave beam access user, utilize corresponding scrambler and spreading code information that the DPCH channel is carried out the scrambler tracking then, realize despread-and-demodulation.
2. according to claim 1 a kind of based on catching method on the user channel satellite of WCDMA system; It is characterized in that: the searching method of single footpath retardation is in said step (4) or the step (6):
carries out matching operation according to formula; Correlation when obtaining different delay; Wherein PDP (n) is the power time delay function, and s (k) is local scrambler, and R (k) receives signal for the base-band digital of wave beam input; * represent complex conjugate; K is a correlation intergal length, and for the search in the step (4), K chooses 8～16 times of hunting zone; For the search in the step (6), K chooses 4～8 times of hunting zone.
3. according to claim 1 a kind of based on catching method on the user channel satellite of WCDMA system; It is characterized in that: screening access user's method is in the said step (1): the signature energy to the PRACH access lead is correlated with or matching operation; Then relevant or matching operation result are carried out the Hadamard conversion, the energy of will signing at last satisfies the pairing user of PRACH access lead of channel signature energy threshold as the access user.
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| CN108627861B (en) * | 2017-03-24 | 2021-07-27 | 展讯通信（上海）有限公司 | Acquisition method, bit synchronization method and device for BDS non-GEO satellite B1 signal |
| CN111565448B (en) * | 2019-02-14 | 2021-05-11 | 电信科学技术研究院有限公司 | Method and equipment for random access |
| CN112116919B (en) * | 2019-06-19 | 2024-06-04 | 杭州海康威视数字技术股份有限公司 | Echo cancellation method and device and electronic equipment |
| CN114040474B (en) * | 2021-11-30 | 2023-09-26 | 新华三技术有限公司成都分公司 | Terminal access method, device and equipment |
| CN114884537B (en) * | 2022-07-13 | 2022-09-20 | 中国人民解放军国防科技大学 | Intelligent cognitive joint capturing method and system for multi-beam time division access signals |
| CN116015345B (en) * | 2022-12-27 | 2023-09-12 | 中国人民解放军军事科学院系统工程研究院 | Satellite communication spread spectrum signal blind analysis method based on independent component analysis |
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