CN101299873A - Method for allocating random access channel - Google Patents

Abstract

The method of configuring the random access channel, the base station configures the length of the cyclic prefix of the random access burst signal, where the length of the cyclic prefix is determined by the length of the idle time, the length of the uplink subframe and the length of the random access preamble signal; the user equipment The random access burst signal is sent according to the configuration of the base station.

Description

The method of allocating random access channel

Technical field

The present invention relates to wireless communication system, relate to a kind of equipment and method of the allocating random access channel in wireless communication system in particular.

Background technology

Now, 3GPP standardization body has set about beginning its existing system standard is carried out long-term evolution (LTE).In the middle of numerous physical layer transmission technology, be the focus of research based on the downlink transfer technology of OFDM (OFDM) with based on the uplink technology that single-carrier frequency division multiple access inserts (SCFDMA).

Wireless communication system can be divided into Frequency Division Duplexing (FDD) (FDD) and time division duplex (TDD) according to its duplex mode.The FDD duplex mode is meant that the communication on the both direction in the wireless system finishes respectively on two frequencies separated by a distance, thereby communication entity can be finished the operation that receives and send simultaneously.The TDD duplex mode is meant that the communication on the both direction in the wireless system finishes on identical frequency, thus the operation that communication entity can not receive simultaneously and send, and the operation that promptly receives and send separates in time.Two kinds of frame structures are arranged: i.e. Class1 frame structure (Type 1 Frame Structure) and type 2 frame structures (Type 2 FrameStructure) in LTE.Two kinds of duplex modes of FDD and TDD are arranged in the Class1 frame structure, and have only TDD duplex mode in the Class1 frame structure.Hereinafter this two kinds of structures will be provided respectively.

According to the discussion result of current LTE, Fig. 1 is the downlink frame structure of LTE Class1, and radio frames (radio frame) time span (101-103) is 10ms; Each frame is divided into a plurality of time slots (slot) (104-107), and present hypothesis is that each radio frames comprises 20 time slots, and time slots length is 0.5ms; For the FDD duplex mode, each time slot comprises a plurality of OFDM symbols again, and for the TDD duplex mode, each descending time slot also comprises a plurality of OFDM symbols.According to present hypothesis, the time span of effective OFDM symbol is about 66.7 μ s in the LTE system.The time span of the CP of OFDM symbol can have two kinds, promptly the time span of short CP is approximately 4.69 μ s or 5.21 μ s, the time span of long CP is approximately 16.67 μ s, long CP time slot is used for many Cell Broadcast CB/multicasts and the very large situation of radius of society, short CP time slot (108) comprises 7 OFDM symbols, and long CP time slot (109) comprises 6 OFDM symbols.According to present discussion result, continuous two time slots constitute subframes (subframe), and Transmission Time Interval (TTI) is 1ms, equal the time span of a subframe.

According to the discussion result of current LTE, Fig. 2 is the frame structure of LTE type 2, and radio frames (radio frame) time span (201-203) is 10ms; Each frame is divided into the field (half-frame) (204,205) of two 5ms; Each field comprises 7 time slots (206～212) and three special territories, i.e. descending pilot frequency time slot (DwPTS) (213), protection be (GP) (214) and uplink pilot time slot (UpPTS) (215) at interval.And first time slot (206) and the DwPTS of each field are fixed for downlink transfer, and second time slot (207) of UpPTS and each field is fixed for uplink.With the sampling frequency is that 30.72MHz is an example, and each time slot (206～212) comprises 20736 sampling, and the time is 0.625ms; DwPTS comprises 2572 sampling, and the time is about 83.7 μ s; GP comprises 1536 sampling, and the time is 50 μ s; UpPTS comprises 4340 sampling, and the time is about 141.3 μ s.Identical with the FDD system, the time span of its effective OFDM symbol is about 66.7 μ s, and the time span of the CP of OFDM symbol can have two kinds, and the time span of short CP is approximately 7.29 μ s, and the time span of long CP is approximately 16.67 μ s.Short CP time slot (216) comprises 9 OFDM symbols and a slot time (TI) (218), and long CP time slot (217) comprises 8 OFDM symbols and a TI (219).The time span of noting two kinds of TI (218,219) is unequal.According to present discussion result, each time slot is a subframe.

In the system that adopts the TDD duplex mode, because base station and subscriber equipment all can not send and receive simultaneously, this position that just requires the downstream-to-upstream (DL-〉UL) at wireless frame structure and be up to descending (UL-〉DL) is provided with enough change-over time.According to current discussion result, Fig. 3 is the TDD system configuration DL-of LTE Class1〉method of UL change-over time.Here suppose that continuous 3 subframes (301 ~ 303) are used for downlink transfer; Continuous two subframes (304 and 305) are used for uplink, and the uplink random access channel distributes in subframe (304).At DL-〉UL dislocation, it is the position between descending sub frame (303) and the sub-frame of uplink (304), several OFDM symbols at the rear portion of base station by not sending descending sub frame (303) obtain free time section (IP, Idle period), and this IP is used for DL-〉the UL conversion.As shown in Figure 3, the base station not too big to coverage, 1 ~ 5 OFDM symbol by idle rear portion obtains IP.For example, 311 free time of frame structure an OFDM symbol, 312 free time of frame structure three OFDM symbols, 313 free time of frame structure five OFDM symbols.The base station very big to coverage, 12 OFDM symbols that at most can idle descending sub frame (303) rear portion obtain IP (314).

According to current discussion result, Fig. 4 is LTE type 2 configuration DL-〉method of UL change-over time.Example one (401) is used for the smaller situation of cell coverage area, and at this moment GP (404) is DL-in LTE type 2 frame structures〉UL change-over time, UpPTS (405) is used to transmit the uplink random access channel.Example two (402) is used for medium scale sub-district, and the GP and the UpPTS of LTE type frame structure have constituted DL-〉UL change-over time (406), a part of resource (407) of subframe 1 is used to transmit the uplink random access channel.Example three (403) is used for the king-sized sub-district of coverage, and at this moment, GP, UpPTS and the subframe #1 of LTE type frame structure have constituted DL-jointly〉UL change-over time (408), a part of resource (409) of subframe 2 is used to transmit the uplink random access channel.

According to the discussion result of current LTE, the structure of Fig. 5 uplink random access burst signal, it comprises that length is T _CPCyclic Prefix (501), length is T _PRETargeting signal (preamble) (502) and length be T _GTGuard time (503).In LTE Class1 system, T _PRETime be 24576 * T _s, i.e. 0.8ms; T _CPTime be 3152 * T _s, be about 0.1026ms; T _GTTime be 2992 * T _s, be about 0.0974ms.T _CPCompare T _GTLong approximately 5.2 μ s, this time difference is decided by the maximum delay of multipath channel.

Summary of the invention

The purpose of this invention is to provide a kind of in wireless communication system the equipment and the method for allocating random access channel.

According to an aspect of of the present present invention, a kind of method of allocating random access channel comprises the steps:

A) the base station configuration length of the Cyclic Prefix of access burst signal at random, the length of Cyclic Prefix is determined by the length of free time, the length of sub-frame of uplink and the length of arbitrary access front signal here;

B) subscriber equipment sends access burst signal at random according to the configuration of base station.

According to another aspect of the present invention, the method for a kind of allocating random access channel and transmission downlink information comprises the steps:

A) at DL-〉N at the rear portion of the descending sub frame at UL transfer point place _RIn the individual OFDM symbol, the base station does not send any information on the identical frequency of the frequency that takies with uplink random access burst signal, and is used to transmit access burst signal at random, remembers that its time is T _IP ^R

B) at DL-〉N at the rear portion of the descending sub frame at UL transfer point place _DIn the individual OFDM symbol, the base station does not send any information on the frequency beyond frequency that uplink random access burst signal takies, as the DL-of up-downgoing transfer of data〉UL change-over time, remember that its time is T _IP ^D

According to another aspect of the present invention, the method for a kind of allocating random access channel and transmission uplink information comprises the steps:

A) base station disposes the transmitting time of access burst signal and the length of Cyclic Prefix at random according to the length of the length of free time and sub-frame of uplink;

B) base station is at DL-〉front of the sub-frame of uplink at UL transfer point place distributes several special up symbols;

According to another aspect of the present invention, a kind of method that reduces the interference of Random Access Channel comprises the steps:

A) position of inserting the FFT detection window is at random calculated according to the longest IP in the base station;

B) during other length of base station configuration, adopt the FFT of the access at random detection window of same position.

According to another aspect of the present invention, a kind of in the FDD system method of allocating random access channel, comprise the steps:

A) base station stops to send several SCFDMA symbols in sending the adjacent sub-frame of uplink of the sub-frame of uplink of access burst signal at random, thereby increases the transmitting time of access burst signal and the length of Cyclic Prefix at random;

B) subscriber equipment sends access burst signal at random according to the configuration of base station.

According to another aspect of the present invention, a kind of method of constructing free time comprises the steps:

A) base station stops to send DL-〉the individual complete OFDM symbol of n (n is more than or equal to 0) at the rear portion of the descending sub frame at UL transfer point place;

B) thus the portion of time of idle this OFDM symbol is handled in the base station to n+1 OFDM symbol reciprocal;

Description of drawings

Below in conjunction with the detailed description of preferred embodiment of accompanying drawing to being adopted, above-mentioned purpose of the present invention, advantage and feature will become apparent by reference, wherein:

Fig. 1 shows the downlink frame structure of LTE Class1;

Fig. 2 shows the frame structure of LTE type 2;

Fig. 3 shows LTE Class1 configuration DL-〉method of UL change-over time;

Fig. 4 shows LTE type 2 configuration DL-〉method of UL change-over time;

Fig. 5 shows the structure of uplink random access burst signal;

Fig. 6 shows the signal of access burst at random of LTE Class1 TDD;

Fig. 7 shows the signal of access burst at random of LTE type 2TDD;

Fig. 8 shows the configuration method of two kinds of free times;

Fig. 9 shows the method for the interference that reduces Random Access Channel;

Figure 10 shows the method that the FDD system increases the Random Access Channel time span; And

Figure 11 shows the structure method of free time.

Embodiment

In LTE TDD system, at the DL-of its frame structure〉position of UL conversion need be provided with the free time section (IP) of certain-length, and the length of IP depends mainly on the cell coverage area that need reach.The uplink random access channel can be at DL-〉transmit in first subframe after the UL conversion, can utilize DL-like this〉IP of UL transfer point increases the cell coverage area that the uplink random access channel can be supported.The time span of note subframe is T _SF, DL-〉and the IP length of UL transfer point is T _IPAnd the total time of note uplink random access burst signal is T _RA, the length of its Cyclic Prefix is T _CP, the length of its targeting signal is T _PRE, the length of its guard time is T _GTIt should be noted that if system configuration n (n is greater than 1) sub-frame of uplink transmits access burst signal at random, T _SFThe total time length of n sub-frame of uplink of expression.DL-〉time of UL conversion determined the maximum coverage range that system supports, i.e. DL-〉time T of UL conversion _DUEqual the maximum round trip time delay (RTD) of sub-district, be designated as T _RTDIn LTE TDD system, except needing DL-〉time of UL conversion, also need UL-〉change-over time of DL, this time ratio is shorter, generally is the magnitude of several microseconds, remembers that its length is T _UDIn the description below the present invention, up or downlink transfer its front and the back is not produced with access burst signal at random that to disturb be criterion, if allow the existence of certain interference, requirement then of the present invention can be loosened.

The rear portion of sub-frame of uplink is not disposed the TDD system of TI, UL-〉T change-over time of DL _UDBe to obtain by IP.For example in LTE Class1 TDD system, obtaining the IP method is to stop to send DL-by the base station〉several OFDM symbols at the rear portion of the descending sub frame at UL transfer point place.Here, DL-〉UL T change-over time _RTDAnd UL-〉T change-over time of DL _UDAll be to obtain by this IP, i.e. T _IP〉=T _RTD+ T _UDIn LTE Class1 TDD system, this UL-〉T change-over time of DL _UDOnly in last sub-frame of uplink of uplink time period, just need configuration, but for the structure of the signal of access burst at random that guarantees to design does not rely on the number of the sub-frame of uplink in the uplink time period, need be according to having only a sub-frame of uplink to design the structure of access burst signal at random in the uplink time period.The access burst signal can not take UL-at random〉T change-over time of DL _UDWhen if subscriber equipment receives that at it moment of the end of last descending OFDM symbol that the base station sends sends at random the access burst signal, the formula below the structural parameters of access burst signal satisfy at random: T _CP+ T _PRE+ T ' _GT=T _IP+ T _SFHere T ' _GTBe the guard time of access burst signal back at random, be used to prevent to other that up or downstream signal produces disturb that it comprises UL-T change-over time of DL _UDWith guard time T _GTSo this formula also can be expressed as T _CP+ T _PRE+ T _GT=T _IP+ T _SF-T _UD=T _RA, i.e. T _CP==T _IP+ T _SF-T _UD-T _PRE-T _GTIn order to reduce or to avoid at random the access burst signal to the interference of previous descending sub frame, subscriber equipment postpones regular hour T in its moment of receiving the end of last descending OFDM symbol that the base station sends _DSend access burst signal at random, T _DMore than or equal to 0.Correspondingly, the formula below the structural parameters of access burst signal satisfy at random: T _CP+ T _PRE+ T _GT=(T _IP-T _D)+T _SF-T _UD=T _RA, i.e. T _CP=(T _IP-T _D)+T _SF-T _UD-T _PRE-T _GTEspecially, time of delay $T_D=\frac{(T_{\mathrm{IP}}-T_{\mathrm{UD}})}{2}.$

The rear portion of sub-frame of uplink has been disposed the TDD system of TI, UL-〉T change-over time of DL _UDIt is TI realization by the subframe back.For example in LTE type 2TDD system, following several acquisition IP method can be arranged.The GP of use pattern 2 frame structures is as IP; Perhaps the GP of use pattern 2 frame structures and UpPTS are jointly as IP; Perhaps GP, the UpPTS of use pattern 2 frame structures and subframe 1 are jointly as IP.The IP here is exclusively used in DL-〉change-over time of UL.The TI here, i.e. UL-〉T change-over time of DL _UD, can not be used for general transmitting uplink data, but this TI can be used for transmitting access burst signal at random.When if subscriber equipment receives that at it moment of the end of last descending OFDM symbol that the base station sends sends at random the access burst signal, the structural parameters of access burst signal are the formula below satisfying: T at random _CP+ T _PRE+ T _GT=T _IP+ T _SF=T _RA, i.e. T _CP=T _IP+ T _SF-T _PRE-T _GT, T here _SFBe the total time length of each subframe of LTE type 2 systems, comprise TI.In order to reduce or to avoid at random the access burst signal to the interference of previous descending sub frame, subscriber equipment postpones regular hour T in its moment of receiving the end of last descending OFDM symbol that the base station sends _DSend access burst signal at random, T _DMore than or equal to 0.Correspondingly, the formula below the structural parameters of access burst signal satisfy at random: T _CP+ T _PRE+ T _GT=(T _IP-T _D)+T _SF=T _RA, T _CP=(T _IP-T _D)+T _SF-T _PRE-T _GTEspecially, time of delay $T_D=\frac{T_{\mathrm{IP}}}{2}.$

The structure of the signal of access burst at random of two types the TDD system of LTE has been described above the present invention.T _CPLength can be 0, at this moment directly to send length when inserting at random be T to subscriber equipment _PREArbitrary access front signal.T _CPLength can be greater than 0, at this moment subscriber equipment sends when inserting at random that to have added length be T _CPThe length of Cyclic Prefix be T _PREArbitrary access front signal.T _CPCan be less than T _GTT _CPCan equal T _GTT _CPAlso can be greater than T _GT, especially, T _CPEqual T _GTTime span T with the CP of OFDM symbol in the system frame structure or SCFDMA symbol _CP ^SymbolAnd, promptly $T_{\mathrm{CP}}=T_{\mathrm{GT}}+T_{\mathrm{CP}}^{\mathrm{symbol}}.$ Like this, according to top formula T _CP+ T _PRE+ T _GT=T _RA, $T_{\mathrm{CP}}=\frac{T_{\mathrm{RA}}-T_{\mathrm{PRE}}+T_{\mathrm{CP}}^{\mathrm{symbol}}}{2},$ T _GT＝T _RA-T _PRE+T _CP。

A kind of T that is provided with _GTMode be to make T _GTMaximum round trip time delay T more than or equal to the sub-district _RTDThereby, guarantee that the access burst signal can not produce interference to follow-up up or downlink transfer at random.T perhaps is set _GTMaximum round trip time delay T less than the sub-district _RTD, at this moment at random the access burst signal with the up or downlink transfer of interfere with subsequent.

The coverage of TDD sub-district is mainly by the decision of two factors, on the one hand, and the time span T of IP _IPDetermined the maximum time lead T when the normal transmission upstream data _RTD, and then can determine the scope of sub-district; The T of access burst signal at random on the other hand _CPPerhaps T _GTDetermined the cell range that access burst signal at random can be supported.So best design should be that the largest cell radius of determining respectively according to these two factors is equated.At this moment, to LTE Class1 TDD system, according to T _IPAnd T _UDCan obtain the time span T of the maximum RTD that IP can support _RTD=T _IP-T _UDThe guard time T of access burst signal at random _GTEqual T _RTDThe Cyclic Prefix of access burst signal at random $T_{\mathrm{CP}}=T_{\mathrm{GT}}+T_{\mathrm{CP}}^{\mathrm{symbol}}=T_{\mathrm{IP}}-T_{\mathrm{UD}}+T_{\mathrm{CP}}^{\mathrm{symbol}};$ Perhaps when the access burst signal does not add Cyclic Prefix at random, T _CPEqual 0.To LTE type 2TDD system, obtain the time span T of the maximum RTD that can support according to IP _RTD=T _IPThe guard time T of access burst signal at random _GTEqual T _RTDThe Cyclic Prefix of access burst signal at random $T_{\mathrm{CP}}=T_{\mathrm{GT}}+T_{\mathrm{CP}}^{\mathrm{symbol}}=T_{\mathrm{IP}}+T_{\mathrm{CP}}^{\mathrm{symbol}};$ Perhaps when the access burst signal does not add Cyclic Prefix at random, T _CPEqual 0.

In the LTE of reality TDD system, after having considered other factor, the definite cell coverage area of these two kinds of factors of coupling that might be best.At this moment in that not up or downlink transfer produces under the prerequisite of disturbing to other, the minimum value of the radius of society of determining respectively according to these two kinds of factors is determined cell coverage area.When the cell coverage area of IP decision greater than according to the T of access burst signal at random _CPPerhaps T _GTDuring the coverage of decision, the actual covering by the T of access burst signal at random _CPPerhaps T _GTThe coverage of decision is determined; When the cell coverage area of IP decision less than according to the T of access burst signal at random _CPPerhaps T _GTDuring the coverage of decision, the actual covering by the cell coverage area of P decision determined;

When cell coverage area was subject to the coverage that access burst signal at random determines, promptly the radius of society of determining according to free time was greater than the radius of society of determining according to access burst signal at random.At this moment, in order to satisfy the coverage of access burst signal support at random, the free time of actual disposition is greater than the maximum round trip time delay T of sub-district _RTDThe free time that needs, thus cause resource waste.

First method is the free time of configuration different length on the frequency of the frequency that access burst signal at random takies and other remaining transmit ascending datas, for example is used for LTE Class1 TDD system.Specifically, on the one hand, at DL-〉N at the rear portion of the descending sub frame at UL transfer point place _RIn the individual OFDM symbol, the base station does not send any information on the identical frequency of the frequency that takies with uplink random access burst signal, remembers that the free time on the frequency that access burst signal at random takies is T _IP ^ROn the other hand, at DL-〉N at the rear portion of the descending sub frame at UL transfer point place _DIn the individual OFDM symbol, the base station is not sending any information on the frequency beyond frequency that uplink random access burst signal takies, remembers that the free time on the frequency beyond the frequency that access burst signal at random takies is T _IP ^DHere, N _R＞N _D, correspondingly $T_{\mathrm{IP}}^R>T_{\mathrm{IP}}^D.$ Here be T _IP ^RAnd T _IP ^DBe inter-related, promptly can calculate the another one amount according to one of them amount.For example, according to formula T _CP+ T _PRE+ T _GT=(T _IP-T _D)+T _SF-T _UD=T _RAFree time T on the frequency that takies of access burst signal at random _IP ^R, obtaining at random, the guard time of access burst signal is $T_{\mathrm{GT}}=\frac{(T_{\mathrm{IP}}-T_D+T_{\mathrm{SF}}-T_{\mathrm{UD}})-T_{\mathrm{PRE}}-T_{\mathrm{CP}}^{\mathrm{symbol}}}{2},$ Note T here _DBe greater than or equal to 0; According to T _GTCan obtain the maximum round trip time delay T that arbitrary access front signal is supported _TRD=T _GTFree time T on the frequency beyond the frequency that takies of access burst signal so at random _IP ^DNeed and T _RTD+ T _UDNumeric ratio more approaching, i.e. T _IP ^DCan equal T _RTD+ T _UD, T _IP ^DAlso can be a bit larger tham or be slightly smaller than T _RTD+ T _UDAdopt this method, the subscriber equipment that base station and execution insert at random may send signal simultaneously, but they can not interfere with each other, and this is that the access burst signal is what to separate on frequency because the frequency of base station transmission downstream signal sends at random with subscriber equipment.And do not exist the base station can not receive the problem of the signal of access burst at random of subscriber equipment here, though the base station subscriber equipment send access burst signal at random for the previous period in can not received signal because the structure of access burst signal is that at first to send length be T at random _CPCyclic Prefix, and then send targeting signal.As long as $T_{\mathrm{CP}}>T_{\mathrm{IP}}^R-T_{\mathrm{IP}}^D+T_{\mathrm{DU}}^{\mathrm{bs}},$ Be the base station can be transformed into up reception before access burst signal FFT detection window arrives effectively at random state, just can detect access burst signal, T here at random timely _DU ^BsIt is the base station is transformed into up accepting state from descending transmit status time.There is not uplink random access burst signal and the base station down interference between signals problem between the neighbor cell in this method, this is because in order to guarantee the their cross correlation of access burst signal at random, the Random Access Channel of neighbor cell is configured on the identical frequency and sends.

Second method is at DL-〉front of the sub-frame of uplink at UL transfer point place distributes several special up symbols, for example is used for LTE type 2TDD system, distributes one or more up SCFDMA symbol in the front of sub-frame of uplink.The up symbol of the increase here can be used to realize special function, and for example, the symbol of these increases can constitute a special sub-frame of uplink, and perhaps transmission is used to measure the reference signal (channel sounding RS) of up channel etc.The up SCFDMA symbol of these increases only distributes on the frequency frequency in addition that the access burst signal takies at random.Like this, similar with first method, at this moment there is the IP of two kinds of length, remember that the free time on the frequency that access burst signal at random takies is T _IP ^RFree time on the frequency beyond the frequency that takies of access burst signal is T at random _IP ^DFree time T according to LTE type 2 systems _IP ^RLength T with subframe _FS, and according to formula T _CP+ T _PRE+ T _GT=(T _IP-T _D)+T _SF=T _RAThe guard time that can calculate the random access guiding letter is $T_{\mathrm{GT}}=\frac{(T_{\mathrm{IP}}^R-T_D+T_{\mathrm{SF}})-T_{\mathrm{PRE}}-T_{\mathrm{CP}}^{\mathrm{symbol}}}{2},$ Note T here _DBe greater than or equal to 0; According to T _GTCan obtain the maximum round trip time delay T that arbitrary access front signal is supported _TRD=T _GTThe free time of actual needs is T on the frequency beyond the frequency that takies of access burst signal so at random _IP ^DNeed and T _RTDNumeric ratio more approaching, i.e. T _IP ^DCan equal T _RTD, T _IP ^DAlso can be a bit larger tham or be slightly smaller than T _RTDAccording to T _IP ^RAnd T _IP ^DCan calculate the number of the up SCFDMA symbol that increases newly, promptly

Here T ^SymbolIt is the time span of up SCFDMA symbol.

To LTE Class1 TDD system, the base station is by stopping to send DL-〉last OFDM symbol of the descending sub frame at UL transfer point place can support the sub-district of radius in 10 kilometer range, at this moment T _IPBe about 71.4 μ s; The base station is by stopping to send DL-〉latter two OFDM symbol of the descending sub frame at UL transfer point place can support the sub-district of radius in 20 kilometer range, T at this moment _IPBe about 142.8 μ s.The subframe lengths of LTE Class1 TDD system is 1ms; the length of arbitrary access front signal is 0.8ms, and the time of the remaining 0.2ms of the sub-frame of uplink at this uplink random access burst signal place can be used to transmit the Cyclic Prefix of access burst signal at random and/or as guard time.In both cases, the time span of IP is all less than 0.2ms, be the coverage that the cell coverage area of IP decision can be supported less than access burst signal at random, so system can be optimized the structure of the arbitrary access front signal under the both of these case.In general, the institute of the coverage that can support less than access burst signal at random the coverage of IP decision might IP configuration scene, a kind of criterion of optimization be make base station under these IP configuration scenes receive at random the FFT detection window of access burst signal aligns, thereby, can reduce the interference between signals of access burst at random of different districts when the base station of adopting these IP configuration scenes each other during neighbor cell.The IP length of remembering the scene that all these IPs of configuration in scenes are the longest is T _IP ^Max, and the length T of removing arbitrary access front signal in the note sub-frame of uplink _PRERemaining time be T _GAt this moment calculate the position of inserting the FFT detection window at random according to the longest scene of IP in these scenes.The scene the longest to this IP, among its IP except being used for UL-DL T change-over time _UDPart outside, be used to compensate the round-trip delay of sub-district fully, promptly $T_{\mathrm{RTD}}=T_{\mathrm{IP}}^{\max }-T_{\mathrm{UD}};$ Then, according to round-trip delay T _RTDDetermine the T of access burst signal at random _GTEqual T _RTD, $T_{\mathrm{CP}}=T_{\mathrm{RTD}}+T_{\mathrm{CP}}^{\mathrm{symbol}}=T_{\mathrm{IP}}^{\max }-T_{\mathrm{UD}}+T_{\mathrm{CP}}^{\mathrm{symbol}}.$ According to these parameters, subscriber equipment after receiving last OFDM symbol of base station downstream signal, time of delay T _D=T _G-T _CPAfter send access burst signal at random; The accurate FFT detection window that the base station receives access burst signal has at random postponed time T than the beginning border of sub-frame of uplink _G-T _IP ^Max

To LTE FDD system, according to the structure of as shown in Figure 5 the signal of access burst at random, when the access burst signal transmitted in a sub-frame of uplink at random, it can only support the coverage radius of cell within the certain limit.The uplink of other subscriber equipmenies is not being produced under the situation about disturbing, first kind of method that increases the coverage that Random Access Channel supports is in the previous sub-frame of uplink of Random Access Channel place sub-frame of uplink, the back N of this subframe of base station configuration _FIndividual SCFDMA symbol does not send any information on the identical frequency of the frequency that takies with Random Access Channel.Promptly pass through N _FIndividual SCFDMA symbol time corresponding is T _F, at this moment the time of Random Access Channel has increased T _F, i.e. T _RA=T _SF+ T _FThereby Random Access Channel can be supported bigger cell coverage area.Second kind of method that increases the coverage that Random Access Channel supports is in a back sub-frame of uplink of Random Access Channel place sub-frame of uplink, the preceding N of this subframe of base station configuration _BIndividual SCFDMA symbol does not send any information on the identical frequency of the frequency that takies with Random Access Channel.Promptly pass through N _BIndividual SCFDMA symbol time corresponding is T _B, at this moment the time of Random Access Channel has increased T _B, i.e. T _RA=T _SF+ T _BThereby Random Access Channel can be supported bigger cell coverage area.Second kind of method that increases the coverage that Random Access Channel supports is: in the previous sub-frame of uplink of Random Access Channel place sub-frame of uplink, base station configuration is N thereafter _FIndividual SCFDMA symbol does not send any information on the identical frequency of the frequency that takies with Random Access Channel, note N _FIndividual SCFDMA symbol time corresponding is T _FSimultaneously, in a back sub-frame of uplink of Random Access Channel place sub-frame of uplink, its preceding N of base station configuration _BIndividual SCFDMA symbol does not send any information on the identical frequency of the frequency that takies with Random Access Channel, note N _BIndividual SCFDMA symbol time corresponding is T _BLike this, the time T of Random Access Channel _RA=T _SF+ T _F+ T _BThereby Random Access Channel can be supported bigger cell coverage area.

In LTE Class1 TDD system, the method of structure free time is to stop to send DL-by the base station〉several OFDM symbols at the rear portion of the descending sub frame at UL transfer point place, here the time span of each OFDM symbol and CP thereof is greater than 70 μ s, be every idle descending OFDM symbol and CP thereof, can make the radius of society of support increase about 10 kilometers.So according to the method, the cell coverage area of LTE Class1 TDD system support is the change of granularity with 10 kilometers.In order to support to come the coverage of allocating cell with littler granularity, a kind of method of constructing free time is that the base station stops to send DL-〉the individual complete OFDM symbol of n (n is more than or equal to 0) at the rear portion of the descending sub frame at UL transfer point place, thus and n+1 OFDM symbol reciprocal handled the portion of time of idle this OFDM symbol.Here the method that n+1 OFDM symbol reciprocal handled is that size with smaller FFT generates the OFDM symbol.The size of FFT of writing down the general OFDM symbol of capable subframe is N ^FFT, the size of the FFT of this n+1 OFDM symbol reciprocal is

Here K=2 ^kBe 2 integral number powers, k is the integer more than or equal to 0.According to the FFT size

The time span of the OFDM symbol that generates is an original length Thereby this OFDM symbol be used as IP with part-time.In order to eliminate the influence of multipath channel, this is according to the FFT size

The OFDM symbol that generates adds the CP with n+1 OFDM symbol equal length reciprocal.

Embodiment

This part has provided six embodiment of this invention, and is too tediously long for fear of the description that makes this patent, in the following description, omitted the detailed description of function that the public is known or device etc.

First embodiment

The structural design of the signal of access burst at random of LTE Class1 TDD system is described in the present embodiment.Here suppose T time of delay in the moment of subscriber equipment in the end of receiving last descending OFDM symbol that the base station sends _DSend access burst signal at random afterwards.Here T _DLength more than or equal to 0.Work as T _DEqual at 0 o'clock, be equivalent to subscriber equipment and send access burst signal at random in the finish time of receiving last descending OFDM symbol that the base station sends.

As shown in Figure 6, the base station is by stopping to send DL-〉to have obtained length be T for several OFDM symbols at the rear portion of the descending sub frame at UL transfer point place _IPFree time.The access burst signal can not take UL-at random〉T change-over time of DL _UDSo the structural parameters of access burst signal satisfy formula at random: T _CP+ T _PRE+ T _GT=T _IP-T _D+ T _SF-T _UD=T _RALike this, to UE nearby, its targeting signal just in time is positioned at when arriving the base station and inserts the FFT detection window at random.To UE at a distance, the time of the finish time when its targeting signal arrives the base station apart from the border of sub-frame of uplink is T _UD, i.e. UL-〉and the length of change-over time of DL.Cyclic Prefix by access burst signal at random guarantees that the signal of accidental access signal in the FFT detection window of UE at a distance is the cyclic shift of targeting signal.

Second embodiment

The structural design of the signal of access burst at random of LTE type 2TDD system is described in the present embodiment.Here suppose T time of delay in the moment of subscriber equipment in the end of receiving the DwPTS that the base station sends _DSend access burst signal at random afterwards.Here T _DLength more than or equal to 0.Work as T _DEqual at 0 o'clock, be equivalent to subscriber equipment and send access burst signal at random in the finish time of receiving the DwPTS that the base station sends.

As shown in Figure 7, the access burst signal can take the TI of sub-frame of uplink at random, promptly takies UL-〉T change-over time of DL _UDSo the structural parameters of access burst signal satisfy formula at random: T _CP+ T _PRE+ T _GT=T _IP-T _D+ T _SF=T _RALike this, to UE nearby, its targeting signal just in time is positioned at when arriving the base station and inserts the FFT detection window at random.To UE at a distance, be the boundary of sub-frame of uplink the finish time when its targeting signal arrives the base station.Cyclic Prefix by access burst signal at random guarantees that the signal of accidental access signal in the FFT detection window of UE at a distance is the cyclic shift of targeting signal.

The 3rd embodiment

Be described in the method for the free time of configuration different length on the frequency of frequency that access burst signal at random takies and other remaining transmit ascending datas in the present embodiment.

As shown in Figure 8, on the one hand, at DL-〉in 5 OFDM symbols at the rear portion of the descending sub frame at UL transfer point place, the base station does not send any information on the identical frequency of the frequency that takies with uplink random access burst signal, and the time of these 5 OFDM symbols is about T _IP ^REqual 357 μ s; On the other hand, at DL-〉in 4 OFDM symbols at the rear portion of the descending sub frame at UL transfer point place, the base station is not sending any information on the frequency beyond the frequency that uplink random access burst signal takies, and the time of these 4 OFDM symbols is about T _IP ^DEqual 285.6 μ s.T _IP ^RBe used to transmit Random Access Channel with the time of sub-frame of uplink, so the time of Random Access Channel approximately is.1.357 μ s, so the T of access burst signal at random _CPPerhaps T _GTTime be approximately 278 μ s.This time and T _IP ^DTime equal substantially.Like this, system in the free time 5 OFDM symbols transmit Random Access Channel, idle 4 OFDM symbols come transmitting downlink data, thereby have reduced because obtain the overhead that free time brings.

The 4th embodiment

In the present embodiment in the LTE Class1 TDD system, the optimization method when coverage that the cell coverage area of IP decision can be supported less than access burst signal at random.Specifically, optimize the base station by stopping to send DL-〉structure of the signal of access burst at random when one or two OFDM symbols of the descending sub frame at UL transfer point place obtain IP.

As shown in Figure 9, obtain IP according to two OFDM symbols that stop to send descending sub frame and determine the position of the FFT detection window of access burst signal at random.In example one, the length that two OFDM symbols that note stops to send descending sub frame obtain IP is T _IP ², subscriber equipment after receiving last OFDM symbol of base station downstream signal, time of delay T _D=0.2ms-T _CPAfter send access burst signal at random, correspondingly, the accurate FFT detection window that the base station receives access burst signal has at random postponed time 0.2ms-T than the beginning border of sub-frame of uplink _IP ²In example two, to obtain the scene of IP according to an OFDM symbol that stops to send descending sub frame, note IP length is T _IP ¹, disposing its position of inserting the FFT detection window at random and two OFDM symbols that stop to send descending sub frame, to obtain the position of FFT detection window of scene of IP identical, its T _CPLength according to T _IP ¹Calculate.

The 5th embodiment

The method of the cell coverage area that the increase Random Access Channel is supported has been described in the present embodiment in LTE Class1 FDD system.When the Random Access Channel of LTE Class1 FDD system disposed in a sub-frame of uplink, its radius of society that can support approximately was 15 kilometers.

As shown in figure 10, in example one, in the previous sub-frame of uplink of Random Access Channel place sub-frame of uplink, back 4 SCFDMA symbols of this subframe of base station configuration do not send any information on the identical frequency of the frequency that takies with Random Access Channel.The time of 4 SCFDMA symbols approximately is 286 μ s, and the time of Random Access Channel is increased to about 1.286ms from 1ms like this, and its radius of society that can support is approximately 36 kilometers.In example two, in the previous sub-frame of uplink of Random Access Channel place sub-frame of uplink, base station configuration 2 SCFDMA symbols does not thereafter send any information on the identical frequency of the frequency that takies with Random Access Channel, the time of 4 SCFDMA symbols approximately is 143 μ s; Simultaneously, in a back sub-frame of uplink of Random Access Channel place sub-frame of uplink, its preceding 2 SCFDMA symbols of base station configuration do not send any information on the identical frequency of the frequency that takies with Random Access Channel, and its time is about 143 μ s equally.The time of Random Access Channel has increased about 286 μ s altogether like this, promptly is increased to about 1.286ms from 1ms, and its radius of society that can support is approximately 36 kilometers.

The 6th embodiment

Described in the present embodiment in LTE Class1 FDD system, disposed free time with littler granularity, thereby with the method for littler granularity allocating cell coverage.Here suppose that disposing the granularity of free time is the time span of half OFDM symbol, and the FFT size of the general OFDM symbol of note is N ^FFT, the FFT size of this OFDM symbol is

As shown in figure 11, at DL-〉rear portion of the descending sub frame (1101) at UL transfer point place, last complete OFDM symbol and CP (1102) thereof stop to send; Penult OFDM symbol (1104) with size is in addition

FFT generate, and add general CP (1105), obtain being equivalent to the free time (1103) of the length of half OFDM symbol like this, thereby total free time is 104.7 μ s, its radius of society that can support is approximately 15.6 kilometers, thereby has increased a kind of coverage radius of cell.

Although below show the present invention in conjunction with the preferred embodiments of the present invention, one skilled in the art will appreciate that under the situation that does not break away from the spirit and scope of the present invention, can carry out various modifications, replacement and change to the present invention.Therefore, the present invention should not limited by the foregoing description, and should be limited by claims and equivalent thereof.

Claims (19)

1. A method for configuring a random access channel, comprising the steps of: a) The base station configures the length of the cyclic prefix of the random access burst signal, where the length of the cyclic prefix is determined by the length of the idle time, the length of the uplink subframe and the length of the random access preamble signal; b) The user equipment sends a random access burst signal according to the configuration of the base station. 2. The method according to claim 1, wherein in step a), the cyclic prefix of the random access burst signal T _CP =T _IP +T _SF -T _UD -T _PRE -T _GT . 3. The method according to claim 1, characterized in that in step a), the cyclic prefix T _CP of the random access burst signal =(T _IP -T _D )+T _SF -T _UD -T _PRE -T _GT . 4. The method according to claim 1, characterized in that in step a), in the LTE type 2TDD system, the TI at the rear of the uplink subframe can be used to transmit a random access burst signal, and the random access burst signal The cyclic prefix of T _CP =T _IP +T _SF -T _PRE -T _GT . 5. The method according to claim 1, wherein in step a), in the LTE type 2TDD system, the TI at the rear of the uplink subframe can be used to transmit a random access burst signal, and the random access burst signal The cyclic prefix of T _CP =(T _IP -T _D )+T _SF -T _PRE -T _GT . 6. A method for configuring a random access channel and sending downlink information, comprising the steps of: a) In the _NR OFDM symbols at the back of the downlink subframe at the DL->UL transition point, the base station does not send any information on the same frequency as the frequency occupied by the uplink random access burst signal, and uses it for transmission Randomly access the burst signal, record its time as _TIP ^R ; b) In the N _D OFDM symbols at the back of the downlink subframe at the DL->UL transition point, the base station does not send any information on frequencies other than the frequency occupied by the uplink random access burst signal, as uplink and downlink data transmission The DL->UL transition time is recorded as T _IP ^D . 7. The method according to claim 6, characterized in that _NR > _ND , correspondingly $T_{\mathrm{IR}}^R>T_{\mathrm{IP}}^{\mathrm{D.}}.$ 8. The method according to claim 6, wherein the random access to the cyclic prefix of the burst signal $T_{\mathrm{CP}}>T_{\mathrm{IP}}^R-T_{\mathrm{IP}}^{\mathrm{D.}}+T_{\mathrm{DU}}^{\mathrm{bs}}.$ 9. A method for configuring a random access channel and sending uplink information, comprising the steps of: a) The base station configures the sending time of the random access burst signal and the length of the cyclic prefix according to the length of the idle time and the length of the uplink subframe; b) The base station allocates several special uplink symbols in front of the uplink subframe at the DL->UL transition point. 10. The method according to claim 9, wherein the added symbols can constitute a special uplink subframe, or transmit reference signals for measuring uplink channels. 11. The method according to claim 9, characterized in that the added uplink SCFDMA symbols are allocated only on frequencies other than those occupied by random access burst signals. 12. A method for reducing interference of a random access channel, comprising the steps of: a) The base station calculates the position of the random access FFT detection window according to the longest IP; b) When the base station configures other lengths, the random access FFT detection window at the same position is used. 13. A method for configuring a random access channel in an FDD system, comprising the steps of: a) The base station stops sending several SCFDMA symbols in the adjacent uplink subframe of the uplink subframe that sends the random access burst signal, thereby increasing the sending time of the random access burst signal and the length of the cyclic prefix; b) The user equipment sends a random access burst signal according to the configuration of the base station. 14. The method according to claim 13, wherein, the base station configures the following _NF SCFDMA symbols in the frequency occupied by the random access channel in the previous uplink subframe of the random access channel place uplink subframe No information is sent on the same frequency. 15. The method according to claim 13, wherein the base station configures its first N _B SCFDMA symbols at the frequency occupied by the random access channel in the subsequent uplink subframe of the random access channel uplink subframe No information is sent on the same frequency. 16. The method according to claim 13, wherein, the base station configures the following _NF SCFDMA symbols in the frequency occupied by the random access channel in the preceding uplink subframe of the random access channel place uplink subframe No information is sent on the same frequency; at the same time, in the uplink subframe after the uplink subframe where the random access channel is located, the first N _B SCFDMA symbols are configured on the same frequency as the frequency occupied by the random access channel. Send any information. 17. A method for constructing free time, comprising the steps of: a) The base station stops sending n (n is greater than or equal to 0) complete OFDM symbols at the back of the downlink subframe at the DL->UL transition point; b) The base station processes the penultimate (n+1) OFDM symbol and idles a part of the time of this OFDM symbol. 18. The method according to claim 17, characterized in that, the OFDM symbol processing method is to generate with a relatively small FFT size, and add a CP of general length. 19. The method according to claim 17, characterized in that, the size of the FFT of the general OFDM symbol of the down-row subframe is ^NFFT , and the size of the FFT of the penultimate n+1 OFDM symbol is Here K=2 ^k is an integer power of 2, and k is an integer greater than or equal to 0.

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