CN1298114C - A method for determining preact of time - Google Patents

Abstract

The present invention relates to a method for determining time preact, which relates to the determination of uplink synchronization time preact in the random access process of a TD-SCDMA system. The present invention has the technical scheme that period variable power emission is adopted on a downlink pilot time slot channel, and the emission power form of the downlink pilot time slot is broadcast on a PCCPCH channel of a broadcast channel. Terminal equipment calculates a power path loss factor. The distance d of the terminal equipment UE and a NodeB is determined through the value of the power path loss factor, and the time preact delta T<p> is determined according to the distance d of the terminal equipment and the NodeB. The present invention reduces the interference to adjacent subzones through the change of the emission power of DwPTS, the path loss measurement error of the UE and the Node B is eliminated, the path loss factor is accuracy determined, the time preact is further accurately estimated, and accordingly, the accuracy rate of uplink synchronization is enhanced.

Description

A kind of TD-SCDMA system determines the method for uplink synchronous Timing Advance

Technical field

The present invention relates to TD-SCDMA (Time Division-Code Division Multiple Access) system and determine the method for uplink synchronous Timing Advance in the random access procedure.

Background technology

TD-SCDMA is the synchronous communication system, and the terminal equipment (UE) that requires to insert must be within the receive window of connecting system Node B (NodeB) or base station transceiver system BTS (Base Transceiver Station) permission.In 3GPP (3rd Generation Partnership Project) standard, there are not computing formula and relevant criterion at Timing Advance, in initial access process, really be difficult to determine that apart from the actual range that inserts NodeB, there is the timing difference of NodeB and UE in UE.Suppose that NodeB is engraved in descending pilot frequency time slot DwPTS (Downlink Pilot Time Slot) emission pilot signal when T1, UE begins to receive the pilot signal of DwPTS, T2=T1+ Δ T constantly at T2 _d+ Δ T _p, Δ T _dBe the time measurement difference of UE and NodeB, Δ T _pBe propagation time difference.Because the detection window of NodeB is protection clearance G P (Guard Period)+UpPTS (Uplink Pilot Time Slot), so Δ T _d+ Δ T _p＜GP.How to obtain accurate Δ T _dWhen UE and NodeB have GPS (Global Position System) receiving system, think Δ T _d=0, T1 and T2 as can be known, obtain Δ T in same timing system _p=T2-T1.In the TD-SCDMA agreement, clearly do not adopt gps system, do not determine to adopt synchronous channel SCH (Synchronisation Channel) yet, UE may be another set of timekeeping system, T1 and T2 are without any getting in touch, only mention the method that adopts path loss to measure in the 3GPP agreement, do not make detailed description.

At first, Δ T _pThe measurement of determining to be based on path loss, consider the electromagnetic wave propagation time-delay, must be at T2+DwPTS+GP 2 Δ T in advance constantly _pConstantly launch the UpPTS detection zone that UpPTS could just in time drop on NodeB.Δ T _pMeasurement can only be based on power and the received signal code power RSCP (Received Signal Code Power) of UE on this channel of DwPTS in the broadcast, the power loss PL that tries to achieve (dB), try to achieve apart from d according to the electromagnetic wave propagation power loss factor, try to achieve the time that shift to an earlier date by distance D.The power path fissipation factor is relevant with the environment of UE, and measured is bigger apart from possible error.

In the TD-SCDMA system, each radio frames (10ms) comprises two identical subframes (5ms), and a descending pilot frequency time slot (DwPTS) is arranged in each subframe, is used for carrying out the down-going synchronous of UE.When establishing under the noiseless situation of DwPTS, radius is 11.25Km to radius of society by UpPTS, and at this moment the UpPTS signal by GP gap protection UE can drop in the detection window of NodeB.When radius of society during greater than 11.2Km, the correct time lead can improve the success rate that inserts at random.

Summary of the invention

The technical problem to be solved in the present invention is the method that proposes uplink synchronous Timing Advance in a kind of definite random access procedure newly, can improve accuracy.

Technical scheme of the present invention is:

1) adopt the variable period power emission on descending pilot frequency time slot (DwPTS) channel, the cycle size is decided according to the disturbed condition of sub-district, can be any integer multiple of 5ms;

2) the transmitting power form of broadcast downstream pilot time slot (DwPTS) on broadcast channel PCCPCH channel;

3) the terminal equipment UE rated output path loss factor (α);

4) by the power path loss factor values, determine terminal equipment UE and NodeB apart from d;

5) determine Timing Advance Δ T according to terminal equipment UE and NodeB apart from d _p

Described employing variable period power emission, be meant the descending pilot frequency time slot transmitting power is divided into a plurality of grades, be divided into 4 different grades in one embodiment of the present of invention, each power inserts the terminal equipment UE in the different districts radius, and be 4 subframes the launch time of each performance number.

The division methods of described 4 grades can be: the emitting power grade of largest cell radius correspondence number is 0, and transmitting power is P _Max, grade is that 1,2,3 transmitting power is respectively: 5P _Max/ 6,2P _Max/ 3, P _Max/ 2.

The described terminal equipment rated output path loss factor is to carry out double power measurement according to terminal equipment on descending pilot frequency time slot, and calculates according to measurement result.

With respect in the prior art being that Timing Advance is determined on the basis with the signal power strength, the present invention is by changing the transmitting power of DwPTS, minimizing is to the interference of adjacent cell, the path loss measure error of getting rid of UE and Node B, accurately determine the path loss factor, and then estimate Timing Advance more exactly, thereby improved the accuracy rate of uplink synchronous.

Description of drawings

Fig. 1 is the frame structure schematic diagram;

Fig. 2 is apart from schematic diagram between UE and the base station.

Fig. 3 is a flow chart of the present invention.

Embodiment

Describe the present invention below in conjunction with accompanying drawing.

As Fig. 1, in the TD-SCDMA system, the radio frames of each 10ms is divided into two identical 5ms subframes, and each subframe is fixed with a descending pilot frequency time slot.The effect of descending pilot frequency time slot is that indication cell carrier frequencies and guiding Your Majesty are total to channel PCCPCH, descending pilot frequency time slot length is 64chips, respectively there is a zero energy district at two ends, be easy to determine its position, determine just can determine the common channel PCCPCH of Your Majesty behind its position according to the phase relation of per 4 subframes.

1, the present invention adopts the variable period power emission on descending pilot frequency time slot (DwPTS) channel, as 301 among Fig. 3.The cycle size is decided according to the disturbed condition of sub-district, can be any integer multiple of 5ms.Described employing variable power emission, be meant the descending pilot frequency time slot transmitting power is divided into a plurality of grades, as 2,3 or 4 etc., one embodiment of the present of invention take to be divided into 4 grades, each power inserts the terminal equipment UE in the different districts radius, thereby reduces the interference of descending pilot frequency time slot to adjacent cell.In the present invention, the division of the grade of the transmitting power of 4 descending pilot frequency time slots is according to the subframe numbers  of system (SFN ÷ 4)  mod 4=N _PiWay.SFN is system's subframe numbers, and  (SFN ÷ 4)  represents that system's subframe numbers rounds N downwards after 4 _PiBe emitting power grade number, the rank that obtains is respectively 0,1,2,3.Be 4 subframes the launch time of each performance number.

The descending pilot frequency time slot DwPTS power of supposing largest cell radius correspondence is P _Max, P _MaxThe power emission rank of transmitting power correspondence be N _Pi=0, determine N _Pi=1 o'clock descending pilot frequency time slot DwPTS transmitting power is $\frac{N_{\mathrm{pi}}}{\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{N}_{\mathrm{pi}}}{P}_{\max }=\frac{5}{6}{P}_{\max };$ N _Pi=2 o'clock, descending pilot frequency time slot DwPTS transmitting power was $\frac{N_{\mathrm{pi}}}{\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{N}_{\mathrm{pi}}}{P}_{\max }=\frac{2}{3}{P}_{\max };$ N _Pi=3 o'clock, descending pilot frequency time slot DwPTS transmitting power was $\frac{N_{\mathrm{pi}}}{\underset{i=1}{\overset{3}{\mathrm{\&Sigma;}}}{N}_{\mathrm{pi}}}{P}_{\max }=\frac{1}{2}{P}_{\max }.$

2, determine Your Majesty channel PCCPCH altogether according to the position of descending pilot frequency time slot and the phase relation of per 4 subframes, as 302 among Fig. 3.

3, the transmitting power form of broadcast downstream pilot time slot (DwPTS) on broadcast channel PCCPCH channel; Terminal equipment is listened in broadcast channel.As among Fig. 3 303.

4, terminal equipment UE carries out double power measurement on descending pilot frequency time slot, and carry out the rated output path loss factor (α) according to measurement result, by the power path loss factor values, determine terminal equipment UE and NodeB apart from d, as 304 among Fig. 3.

Suppose the received power P that UE records for the first time _R1=P _R1a+ Δ P _e, the received power P that records for the second time _R2=P _R2a+ Δ P _e, P _R1aBe the actual power value of measuring for the first time, P _R2aBe the actual power value of measuring for the second time.Δ P _eBe the measure error that different UE brings into, think that here 2 measure errors of same UE are identical.For the first time with secondary difference power P _R1-P _R2=P _R1a-P _R2a, eliminated the measure error of different UEs.NodeB is transmitting power P for the first time _T1, transmitting power P for the second time _T2, transmitting power loss first time α ₁* P _T1, transmitting power loss second time α ₂* P _T2, eliminate the transmitting power sum of errors received power error of different NodeB and UE, draw equation:

P _t1-P _t2＝α ₁×P _t1+P _r1a-(α ₂×P _t2+P _r2a)

Under the situation that does not have to change in the position of UE, according to electromagnetic wave propagation theory, propagation loss is only relevant with the path, draws power path fissipation factor α=α ₁=α ₂, derive:

P _t1-P _t2＝α×(P _t1-P _t2)+P _r1a-P _r2a

Because P _R1a-P _R2a=P _R1-P _R2Known for the UE measurement, draw:

$\mathrm{\&alpha;}=\frac{(P_{t1}-P_{t2})-(P_{r1}-P_{r2})}{P_{t1}-P_{t2}}$

Path loss $\mathrm{PL}\left(\mathrm{dB}\right)=10\log \frac{P_t}{P_r}=10\log \frac{1}{\mathrm{\&alpha;}}=-10\log \mathrm{\&alpha;}$

Under the situation of antenna shown in Figure 2 far field, the free space propagation model:

$\mathrm{PL}\left(\mathrm{dB}\right)=10\log \frac{P_t}{P_r}=-10\log \left[\frac{G_t{G}_r{\mathrm{\&lambda;}}^2}{{\left(4\mathrm{\&pi;}\right)}^2{d}^2}\right],$ G wherein _tBe the gain of transmitting antenna, G _rBe the gain of reception antenna, λ is the wavelength of carrier frequency, all is the datum of sub-district.Draw: $\mathrm{\&alpha;}=\frac{G_t{G}_r{\mathrm{\&lambda;}}^2}{{\left(4\mathrm{\&pi;}\right)}^2{d}^2}$ Ideal situation.Need under the actual conditions to determine be radius of society greater than the T-R distance under the 11.25 axiom situations, be modified to bilinear model $d=\sqrt[4]{\frac{G_t{G}_r{h}_t^2{h}_r^2{\mathrm{\&lambda;}}^2}{{\left(4\mathrm{\&pi;}\right)}^2\mathrm{\&alpha;}}},$ h _tBe the height (30m-200m) of transmitting antenna, h _rReception height (1m-3m) for UE.

When in the city, should adopt the Okumura model, preferably in the broadcast of agreement, add the geographical feature information of some sub-districts.

5, determine Timing Advance Δ T according to terminal equipment UE and NodeB apart from d _p

The corresponding a kind of distance of each α value is determined Timing Advance Δ T according to distance d _pAs among Fig. 3 305.

$\mathrm{\&Delta;}{T}_P=\frac{d}{c},$ C is the light velocity.

The condition of above correspondence is that twice power measurement must carry out under identical receiving system, same position and identical transmitting carrier frequency, and at this moment the α value of Ce Lianging is the most accurate.At the path fading formula of UE that moves or the inapplicable free space of the possibility of the UE in the shadow region, but by the received power under the different transmission power being measured the small scale decline parameter that can obtain a plurality of UE, not within discussion scope of the present invention.

By above method, eliminate the measure error that different device is brought into, by the known result that will measure of broadcast UE.Fall at UE under the situation of shadow region or unconventional decline, should based on to 2 or three NodeB the Your Majesty altogether on the channel about the reception of the broadcast of power and the measurement of carrying out, get rid of unusual decline situation.

Claims (4)

1, a kind of TD-SCDMA system determines the method for uplink synchronous Timing Advance, comprising:

1) on the descending pilot frequency time slot channel, adopts the variable period power emission;

2) the transmitting power form of broadcast downstream pilot time slot on broadcast channel;

3) the terminal equipment UE rated output path loss factor;

4), determine the distance of terminal equipment and Node B by the power path loss factor values;

5) determine Timing Advance according to the distance of terminal equipment and Node B.

2, the described TD-SCDMA of claim 1 system determines the method for uplink synchronous Timing Advance, it is characterized in that, described employing variable period power emission, be meant the descending pilot frequency time slot transmitting power is divided into 4 different grades, the corresponding terminal equipment UE that inserts in the different districts radius of the performance number of each grade, be 4 subframes the launch time of each performance number.

3, the described TD-SCDMA of claim 2 system determines the method for uplink synchronous Timing Advance, it is characterized in that, the division methods of described 4 grades is: the emitting power grade of largest cell radius correspondence number is 0, and transmitting power is P _Max, grade is that 1,2,3 transmitting power is respectively: 5P _Max/ 6,2P _Max/ 3, P _Max/ 2.

4, the described TD-SCDMA of claim 1 system determines the method for uplink synchronous Timing Advance, it is characterized in that, the described terminal equipment UE rated output path loss factor, be on descending pilot frequency time slot, to carry out double different capacity according to described terminal equipment UE to measure, and calculate according to measurement result.

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