CN100388861C - Signal processing method in mobile terminal random access process - Google Patents
Signal processing method in mobile terminal random access process Download PDFInfo
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- CN100388861C CN100388861C CNB200410086049XA CN200410086049A CN100388861C CN 100388861 C CN100388861 C CN 100388861C CN B200410086049X A CNB200410086049X A CN B200410086049XA CN 200410086049 A CN200410086049 A CN 200410086049A CN 100388861 C CN100388861 C CN 100388861C
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Abstract
The present invention discloses a signal processing method in the random access process of mobile terminals. When the method is used, first, according to prefix feature codes configured in cells, the arrival time of different access signals is captured; then, according to the maximum extent value of multipath distribution, the access signals are merged. When the method of the present invention is used for processing signals in the process of the random access of mobile terminals, base stations determine a possible maximum extent value of the multipath distribution of the received signals from a mobile terminal and merge the received signals according to the maximum extent value of the multipath distribution so that the received signals from different mobile terminals are distinguished, which avoids access failure caused by error mergence and improves the call completing rate of the system.
Description
Technical field
The present invention relates to the random access procedure of wireless communication field portable terminal, be specifically related to the signal processing method in a kind of mobile terminal random access process, relate in particular to carry out in the random access procedure multipath before merging to inserting the Signal Processing method.
Background technology
The accidental access method of portable terminal is based on time slot A LOHA (random access collision method) mode of catching indication fast that has in the WCDMA system.Portable terminal can begin transmission at a predefined access slot.The structure of portable terminal emission information comprises that one or more length are prefix condition code and long message part for 10ms or 20ms of 4096 chips as shown in Figure 1 in the random access procedure.Portable terminal at first initiates to carry the access request of prefix condition code, the base station captures access request and the feedback access confirmation message that portable terminal is initiated, after portable terminal receives the confirmation message, change the transmission of message part again over to, next, base station receiver is handled the access signal of receiving from portable terminal, to finish random access procedure.
In the prior art, receiver to the Signal Processing method is in the mobile terminal random access process: at first catch the different times of advent of inserting signal according to the prefix condition code of cell configuration; Next, because the spread-spectrum signal that portable terminal sends, in transmission course, be subjected to the reflection and the refraction of various barriers such as different buildings, hummock, each wave beam has different delays when arriving receiver, form multipath signal, so the WCDMA mobile communication system need be passed through Direct Sequence Spread Spectrum Communication to the message part that receives, employing correlation reception, multipath signal is carried out multipath merge, with the antagonism multipath effect; Indication is confirmed to inserting successful portable terminal in last base station, finishes whole access random access procedure.
But, because in the WCDMA system, when inserting at random, portable terminal takes the mode selected at random for the prefix condition code, when the portable terminal in the sub-district initiates to insert request, a plurality of portable terminals may adopt identical prefix condition code to initiate to insert request at an access slot, to exist between a plurality of portable terminals this moment and insert collision, if therefore a plurality of portable terminals adopt identical prefix condition code to insert at random, it is because the access collision phenomenon that a plurality of portable terminals are initiated that receiver can't be distinguished when carrying out signal processing to the received signal, and still single mobile terminal is initiated inserts the multipath effect that the process multipath propagation environment causes at random.Multi-path environment as shown in Figure 2, two portable terminals initiate to insert at random request simultaneously in the sub-district, and the signal that portable terminal 1 sends arrives base station receiver through 3 paths, and their multipath transmisstion postpones to be respectively t1, t2, t3; The signal that portable terminal 2 sends also arrives base station receiver through 3 paths, and their multipath transmisstion postpones to be respectively T1, T2, T3; If the Access Preamble sign of two portable terminal employings is identical, because two portable terminals adopt identical access slot in same sub-district, the base station is when receiving the request of access at random of two portable terminals initiations, RAKE receiver captures Access Preamble, whether can't distinguish is the multipath signal that two portable terminals are initiated, can only merge its multipath signal of being used as a portable terminal initiation, just the multipath transmisstion of portable terminal 2 is postponed T1, T2, T3 is as the 4th of portable terminal 1 the, 5,6 footpath signals, the multipath signal t1 that like this signal of two portable terminals is used as a portable terminal, t2, t3, t4, t5, t6 handles, and the result will influence two portable terminals and all can't successfully insert.
In sum, in the prior art in the mobile terminal random access process shortcoming of method for processing signals be: when a plurality of portable terminals initiate to insert at random, if their Access Preamble is identical, system docking is gone into the multipath signal that can't correctly merge when signal carries out signal processing from different mobile terminal, causes portable terminal because access is collided and access failure.
Summary of the invention
The technical problem to be solved in the present invention is: the signal processing method in a kind of mobile terminal random access process is provided, when different mobile terminal inserts at random with identical Access Preamble, the multipath signal from different mobile terminal can be distinguished by system, avoid owing to the signal mistake with different mobile terminal merges the access failure problem that causes, thereby improve the call completing rate of system.
For solving the problems of the technologies described above, the invention provides the signal processing method in a kind of mobile terminal random access process, comprise step:
1) catches the different times of advent of inserting signal according to the prefix condition code of cell configuration;
2) the maximum magnitude value that distributes according to multipath is distinguished the access signal from different mobile terminal;
3) will merge respectively from the access signal of different mobile terminal.
Wherein, determine the maximum magnitude value that multipath distributes according to different communication environments.
Wherein, the maximum magnitude value that chip period of the longest multidiameter time lengthening in the described communication environments is distributed as described multipath.
And, according to following step described access signal is merged:
The access signal and the time of advent that will be less than or equal to first maximum magnitude value sum that inserts time of arrival (toa) and the distribution of described multipath the time of advent merge respectively greater than the access signal that first inserts the maximum magnitude value sum of time of arrival (toa) and the distribution of described multipath.
In addition, last footpath time of arrival (toa) in the described communication environments can also be prolonged the maximum magnitude value that a chip period distributes as described multipath.
And following step merges described access signal:
The access signal that will be less than or equal to the maximum magnitude value that distributes greater than described multipath the access signal of the maximum magnitude value that described multipath distributes and the time of advent time of advent merges respectively.
Wherein, obtain the different times of advent of multipath signal according to following step:
A) baseband signal that receives is carried out channel estimating, catch the prefix condition code of described cell configuration;
B) according to the prefix condition code of described cell configuration signal strength signal intensity is adjudicated the access multipath, catch the different times of advent of inserting multipath signal respectively.
Compared with prior art, the invention has the beneficial effects as follows: when using method of the present invention to carry out signal processing in the mobile terminal random access process, the maximum magnitude value that distributes and may exist from the received signal multipath of a portable terminal has been determined in the base station, and the maximum magnitude value that distributes according to described multipath merges to received signal, thereby distinguished received signal from different mobile terminal, and then avoided mistake to merge the access failure that causes, improved the call completing rate of system.
Further, because three or three above users adopt the probability of same Access Preamble less relatively in actual applications, therefore, this programme will be not access signal in the maximum magnitude that multipath the distributes multipath signal that directly is considered as another portable terminal merge, improve the processing speed of system, thereby shortened the turn-on time of portable terminal.
In addition, the present invention has determined different multipath distribution maximum magnitude values according to different communication environments, thereby makes judgement more accurate rationally.
Description of drawings
Fig. 1 is the structure chart that inserts emission at random;
Fig. 2 is a radio communication multipath transmisstion model schematic diagram;
Fig. 3 is the procedure chart of signal processing in the mobile terminal random access process of the present invention.
Embodiment
Method for processing signals is in the prior art in the mobile terminal random access process of the present invention, when a plurality of portable terminals initiate to insert at random, if their prefix condition code is identical, it is the access collision phenomenon of initiating owing to a plurality of portable terminals that system can't distinguish, or the problem proposition that inserts the multipath effect that causes through multipath propagation environment at random of single mobile terminal initiation.
When the access signal that uses the method for the invention that portable terminal is inserted is at random handled, at first obtain the different times of advent of multipath signal respectively according to the pre-configured prefix condition code in sub-district; The maximum magnitude value that distributes according to multipath merges the access signal of portable terminal then.
Core of the present invention is the different characteristics that multipath that the different characteristics according to mobile communication environment causes distributes, and chooses the maximum magnitude value that different multipaths distributes, and determines that multipath is distributed in the distribution of different communication environments.When RAKE receiver is inserting when catching multipath signal at random, if when detecting the multipath signal distribution and surpassing the scope that to exist, decision signal comes from different portable terminals, owing to considering that the possibility that two above portable terminals adopt same prefix condition code to insert simultaneously is very little, the multipath signal that therefore will exceed the maximum magnitude value of multipath distribution is considered as the multipath signal of another portable terminal, to merge respectively from the signal of different mobile terminal then, thereby merge phenomenon owing to insert the mistake that collision phenomenon causes when avoiding portable terminal to insert.
Below the related concrete principle of this programme is described in detail.
The present invention realizes that in the Base-Band Processing functional module of base station equipment Fig. 3 is the process block diagram of signal processing in the mobile terminal random access process provided by the invention.
In the WCDMA system, mobile terminal UE can begin transmission in a predefined access slot.The structure that terminal inserts emission information at random comprises that one or more length are prefix and long message part for 10ms or 20ms of 4096 chips.Portable terminal and base station be not contact at ordinary times, when portable terminal will be communicated by letter, at first needs to get in touch with the base station foundation of network side, and described prefix condition code is exactly that being used for that system adopts on common signal channel initiates to set up the special symbol of getting in touch with the base station.The prefix condition code always has 16, at same time slot, a plurality of Access Preambles can be arranged, each portable terminal all be independently, Access Preamble of the selection at random of probability equalization initiates request.The base station captures prefix access request and the feedback access confirmation message that UE initiates, and after terminal receives the confirmation message, changes the transmission of message part again over to.
The base station baseband processing module receives all baseband signals from each user, then the baseband signal that receives is carried out channel estimating, capture the Access Preamble condition code that comes from different user when channel estimating, the prefix condition code of sending according to UE receives the access signal of this condition code correspondence subsequently.Owing to have mulitpath in the radio propagation process, make the signal that arrives receiving terminal produce the phenomenon of decline and broadening.The spread-spectrum signal that portable terminal sends, in transmission course, be subjected to the reflection and the refraction of various barriers such as different buildings, hummock, each wave beam has different delays when arriving receiver, form multipath signal, so the WCDMA receiver merges the signal to noise ratio that multipath signal improves received signal by RAKE.The specific implementation of RAKE receiver is by each the road signal in a plurality of correlation detector receiving multipath signals, and they are combined.When propagation delay surpassed a chip period, in fact multipath signal can be counted as incoherent mutually, and the RKAE receiver can come different wave beam differences.These different beams are passed through different delay lines respectively, align and combine, being originally that interference signals becomes useful signal and combines.
As shown in Figure 3, receiver to the process that the access signal that receives carries out signal processing is: baseband processing module carries out channel estimating to the baseband signal that receives, and catches prefix condition code (step 1); According to the prefix condition code signal strength signal intensity judgement is inserted multipath then, obtain signal that portable terminal sends arrives receivers via different paths time (step 2) respectively; As previously mentioned, because a plurality of portable terminals are independently to select at random to the Access Preamble condition code, therefore probably choose identical Access Preamble condition code, therefore before carrying out the multipath merging, the present invention carries out collision detection judgement (step 3) to each the road multipath signal that obtains, to distinguish the multipath signal that different mobile terminal sends, the collision checking method for concrete will be explained in greater detail below; Then according to court verdict, the multipath signal in the different paths that same portable terminal is sent carries out multipath and merges (step 4) respectively; Confirm indication (step 5) to inserting successful different mobile terminal respectively at last, finish at random and insert.
Below introduce two kinds of above methods of the judgement of the collision detection in the random access procedure in the step 3.
RAKE receiver is when whether judgement has multi-mobile-terminal to adopt identical Access Preamble to insert, determine the scope that its multipath distributes according to the residing communication environments of portable terminal, system has determined different multipath distribution maximum magnitude values according to the characteristics of different communication environments when practical application, judges the scope whether signal belongs to the multipath signal existence of certain portable terminal that inserts according to described maximum magnitude value T.For definite method of maximum magnitude value T, can realize according to following two kinds of methods:
Method one: owing to consider that the propagation multidiameter delay in the mobile communication is different because of the restriction of propagation conditions, terrain and its features, when determining that multipath distributes the maximum magnitude value T that may exist, determine the multipath quantity that under various environment, may exist in the difference under the varying environment according to signal strength signal intensity earlier; Determine the multipath delay time and the average power of each footpath signal then; Delay time that last basis is the longest and average power are comprehensively determined the value of maximum magnitude value T.T is than bigger value of the longest multipath delay time in general, when determining the occurrence of T, consider because the merging principle of receiver is if propagation delay surpasses a chip period, then multipath signal is regarded as incoherent mutually, therefore, with the longest multidiameter time postpones a chip period backward as concrete maximum magnitude value T.
When judging whether to have the access collision, from receiving the first footpath t1 time of advent of first portable terminal, the maximum magnitude value T that distributes and to exist according to this environment multipath, if in the t1+T scope, the multipath signal that captures merges processing as the multipath signal of same portable terminal in time period t 1; If capture signal later at moment t1+T, just think the access that other portable terminal is initiated, and with its merging.
Method two, because the time of advent of last footpath signal that the first footpath time of arrival (toa) and the longest multidiameter time sum may exist under portable terminal environment of living in fact exactly in the said method one, therefore, also the value of maximum magnitude value T directly can be defined as postponing the value of a chip period than last footpath time of arrival (toa) under the described communication environments.When judging whether to have the access collision, from receiving the first footpath t1 time of advent of first portable terminal, the maximum magnitude value T that distributes and to exist at this environment multipath, if in the T scope, the multipath signal that captures merges processing as the multipath signal of same portable terminal in time period t 1; If capture signal later at moment T, just think the access that other portable terminal is initiated, and with its merging.
For can be the more directly perceived complete the present invention that understands, below in conjunction with specific embodiments the present invention is further introduced at the method for definite maximum magnitude value T mentioned above.
Consider that the propagation multidiameter delay in the mobile communication is different with the restriction of propagation conditions, terrain and its features.Different ambient signals is propagated the quantity difference of back multipath, and the signal strength signal intensity in every footpath is also different, and four kinds of scenes shown in following table are typical representatives.
Multipath fading communication environments table
In the last table, the delay 976ns of environment one, multipath are distributed in 4 chip range; The delay 20000ns of environment two, multipath are distributed in 77 chip range; The delay 781ns of environment three, multipath are distributed in 3 chip range; The delay 781ns of environment three, multipath are distributed in 3 chip range.The present invention is directed to different covering scene, the multipath distribution is carried out value, thereby judge random access collision.The concrete physical significance of environment one is under this environment, and the rate travel of portable terminal is 3 kilometers walkings hourly, and signal is by two paths, and the time difference between the two was 976 nanoseconds, and the difference of intensity is 9db.
T is the maximum of multipath distribution, and its occurrence is determined as the case may be.
At environment one, T is the value than a big chip of 976 nanoseconds in the method one; As at environment two, T should be the value than a big chip of 20000 nanoseconds; For environment one, T is the value that inserts the big chip of value of time of arrival (toa)+976ns than first in the method two.
At the described concrete environment of last table, introduce the detailed step of the embodiment of signal processing in the mobile terminal random access process in conjunction with the method for determining the maximum magnitude value T that multipath distributes:
Portable terminal obtains the prefix condition code of access at random by selecting at random, and connects according to obtaining prefix condition code and base station;
RAKE receiver is carried out channel estimating to the baseband signal that receives, and captures the Access Preamble condition code;
Judgement inserts multipath to the prefix condition code that estimation is caught according to signal to signal strength signal intensity, obtains the multipath information of different time t1, t2, t3, t4, t5, t6 respectively;
Definite method for a pair of maximum magnitude value of said method T, from receive first the footpath time t1, there is value range T in the maximum possible that distributes in conjunction with this environment multipath, judges whether t2, t3, t4, t5, t6 arrive in the t1+T scope in time period t 1, and then judges whether to exist collision;
If all multipath t2, t3, t4, t5, t6 arrive in the t1+T scope in time period t 1, then judgement is not collision;
All multipath signals at t1, t2, t3, t4, t5, t6 place are merged;
Confirm indication to inserting successful portable terminal;
If have only multipath t2, t3 to arrive in the t1+T scope in time period t 1, multipath t4, t5, t6 then are the access request that another portable terminal is initiated, and then judgement is for there being collision;
All multipath signals at t1, t2, t3 place are merged;
Confirm indication to inserting successful portable terminal 1;
All multipath signals at t4, t5, t6 place are merged (here, adopt the probability of the access that same prefix condition code initiates less relatively owing to consider three users, therefore only consider two users' situation, can do similar processing for a plurality of users, not overslaugh protection scope of the present invention);
Confirm indication to inserting successful portable terminal 2, finish and insert acquisition procedure at random.
Definite method for two pairs of maximum magnitude values of said method T, from receive first the footpath time t1, there is value range T in the maximum possible that distributes in conjunction with this environment multipath, judges whether t2, t3, t4, t5, t6 arrive in the T scope in time period t 1, and then judges whether to exist collision;
If all multipath t2, t3, t4, t5, t6 arrive in the T scope in time period t 1, then judgement is not collision;
All multipath signals at t1, t2, t3, t4, t5, t6 place are merged;
Confirm indication to inserting successful portable terminal;
If have only multipath t2, t3 to arrive in the T scope in time period t 1, multipath t4, t5, t6 then are the access request that another portable terminal is initiated, and then judgement is for there being collision;
All multipath signals at t1, t2, t3 place are merged;
Confirm indication to inserting successful portable terminal 1;
All multipath signals at t4, t5, t6 place are merged;
Confirm indication to inserting successful portable terminal 2, finish and insert acquisition procedure at random.
In order to understand the present invention more intuitively, listed data in the table in the reference are enumerated the embodiment of an actual application environment for definite method of a pair of T of method.
With environment one is example, different ambient signals is propagated the quantity difference of back multipath, the signal strength signal intensity on every road is also different, the concrete physical significance of environment one is under this environment shown in the last table, the rate travel of terminal is 3 kilometers walkings hourly, signal is by two paths, and the time difference between the two was 976 nanoseconds, and the difference of intensity is 9db.Because it is 260ns that each chip of signal of WCDMA system occupies certain width in time, therefore, maximum magnitude value T is decided to be long delay time and chip period sum, i.e. a 1236ns here.
Portable terminal obtains the prefix condition code of access at random by selecting at random, and connects according to obtaining prefix condition code and base station;
RAKE receiver is carried out channel estimating to the baseband signal that receives, and captures the Access Preamble condition code;
Judgement inserts multipath to the prefix condition code that estimation is caught according to signal to signal strength signal intensity, obtains the multipath information of different time t1, t2, t3, t4 respectively;
From the time t1 in first footpath that receives, there is value range T=1236ns in the maximum possible that distributes in conjunction with this environment multipath, judge t2, t3, t4 whether in time period t 1 in the t1+1236ns scope, and then judge whether to exist and collide;
If all multipath t2, t3, t4 arrive in the t1+1236ns scope in time period t 1, then judgement is not collision;
All multipath signals at t1, t2, t3, t4 place are merged;
Confirm indication to inserting successful portable terminal;
If have only multipath t2 to arrive in the t1+1236ns scope in time period t 1, multipath t3, t4 then are the access request that another portable terminal is initiated, and then judgement is for there being collision;
All multipath signals at t1, t2 place are merged;
Confirm indication to inserting successful portable terminal 1;
All multipath signals at t3, t4 place are merged;
Confirm indication to inserting successful portable terminal 2, finish and insert acquisition procedure at random.
The above only is a preferred implementation of the present invention; should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the principle of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.
Claims (7)
1. the signal processing method in the mobile terminal random access process is characterized in that, comprises step:
1) catches the different times of advent of inserting signal according to the prefix condition code of cell configuration;
2) the maximum magnitude value that distributes according to multipath is distinguished the access signal from different mobile terminal;
3) will merge respectively from the access signal of different mobile terminal.
2. the signal processing method in the mobile terminal random access process according to claim 1 is characterized in that: determine the maximum magnitude value that multipath distributes according to different communication environments.
3. the signal processing method in the mobile terminal random access process according to claim 2 is characterized in that: with the maximum magnitude value of chip period of the longest multidiameter time lengthening in the described communication environments as described multipath distribution.
4. the signal processing method in the mobile terminal random access process according to claim 2 is characterized in that: last footpath time of arrival (toa) in the described communication environments is prolonged the maximum magnitude value that a chip period distributes as described multipath.
5. the signal processing method in the mobile terminal random access process according to claim 3 is characterized in that, according to following step described access signal is merged:
The access signal and the time of advent that will be less than or equal to first maximum magnitude value sum that inserts time of arrival (toa) and the distribution of described multipath the time of advent merge respectively greater than the access signal that first inserts the maximum magnitude value sum of time of arrival (toa) and the distribution of described multipath.
6. the signal processing method in the mobile terminal random access process according to claim 4 is characterized in that, according to following step described access signal is merged:
The access signal that will be less than or equal to the maximum magnitude value that distributes greater than described multipath the access signal of the maximum magnitude value that described multipath distributes and the time of advent time of advent merges respectively.
7. according to the signal processing method in any one described mobile terminal random access process in the claim 1 to 6, it is characterized in that, obtain the different times of advent of multipath signal according to following step:
A) baseband signal that receives is carried out channel estimating, catch the prefix condition code of described cell configuration;
B) according to the prefix condition code of described cell configuration signal strength signal intensity is adjudicated the access multipath, catch the different times of advent of inserting multipath signal respectively.
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| CN1273469A (en) * | 1999-05-10 | 2000-11-15 | 日本电气株式会社 | Code division multiple access receiver with controllable hunting zone and control method |
| CN1140075C (en) * | 2000-12-18 | 2004-02-25 | ***电信传输研究所 | Initial sync and small area search device of CDMA system based on multipath energy window |
| JP2004064560A (en) * | 2002-07-30 | 2004-02-26 | Nec Corp | Cdma random access system and method therefor |
| CN1141816C (en) * | 2001-10-22 | 2004-03-10 | ***电信传输研究所 | Multipath signal processing method with slow path search and multi-window fast channel estimation |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1273469A (en) * | 1999-05-10 | 2000-11-15 | 日本电气株式会社 | Code division multiple access receiver with controllable hunting zone and control method |
| CN1140075C (en) * | 2000-12-18 | 2004-02-25 | ***电信传输研究所 | Initial sync and small area search device of CDMA system based on multipath energy window |
| CN1141816C (en) * | 2001-10-22 | 2004-03-10 | ***电信传输研究所 | Multipath signal processing method with slow path search and multi-window fast channel estimation |
| JP2004064560A (en) * | 2002-07-30 | 2004-02-26 | Nec Corp | Cdma random access system and method therefor |
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