CN1391737A - Improvement of mobile telecommunication system - Google Patents

Abstract

Described herein is a method of determining when propagation delays measured in both directions between two base stations i and j relate to the earliest path and not to a later path. Once synchronisation has been achieved, the measurement of the propagation delay is compared with predetermined limits and if falling within those limits is stored. Subsequent measurements of propagation delay are also compared with the predetermined limits and are only stored if they fall within those limits and are better than the currently stored measurement.

Description

The improvement of mobile communication system

The present invention relates to the improvement of mobile communication system.

It is basic with being combined as of code division multiple access (CDMA) and hybrid TDMA (TDMA) that the UMTS terrestrial wireless inserts time division duplex (UTRA TDD) pattern.Those skilled in the art understands that all UMTS is the initialism of Universal Mobile Telecommunications System.

In the UTRA tdd mode that comprises combination TD-CDMA multiple access scheme, reliable operation require to comply with in the telecommunication system between each base station synchronously.And this pattern also requires to provide positional information to the travelling carriage that is under the jurisdiction of each base station.For maximized system capacity also expect between the base station synchronously.Thereby, the level that must reach time slot, frame and multiframe synchronously between the base station, wherein multiframe is the circulation repeatedly of several frames.

Common unsettled UK Patent Application 0007143.1 and 0007144.9 has been described a kind of synchronous method that realizes between a plurality of base stations of telecommunication system, it is included in each sub-district Random Access Channel is provided.Travelling carriage receives Resource Unit by Random Access Channel, and the Random Access Channel in sub-district of use, base station is to be sent to synchronizing signal at other stations in the system.

These base stations by the transmission between the base station realize common synchronously.This relates to timing difference or the side-play amount of measuring between the base station on two-way, to eliminate the influence of propagation delay.Regularly difference or side-play amount are reported back center radio network controller (RNC), and radio network controller calculates necessary timing renewal and sends it back the base station.

If measurement is accurate and clock all moves with same speed, this method can reach perfectly synchronously in theory.

The common unsettled UK Patent Application GB9927919.2 and 0010363.0 of the filing same period (our reference: 1999P04886) described the regularly method of measurement that realizes.Yet this method is subjected to by noise that shows as the strongest measurement or the influence that can not stablize the latent fault that is identified and causes by path the earliest.

Thereby, the object of the present invention is to provide a kind of method that can significantly reduce wrong measurement.

According to an aspect of the present invention, provide a kind of method that makes the measurement synchronization of two propagation delays between the base station, this method may further comprise the steps:

A) between two base stations, reach synchronous;

B) calculate initial propagation delay;

C) storing initial propagation delay;

D) calculated for subsequent propagation delay;

E) determine whether that follow-up propagation delay is in preset range;

F) if in preset range then use follow-up propagation delay;

G) if in preset range and, when then storing follow-up propagation less than initial propagation delay

Prolong;

H) repeating step d) to g).

Preferably step c) comprises determining whether initial propagation delay reaches following requirement: ${\mathrm{\&tau;}}_{i,j}^{\min }<\frac{d_{i,j}+d_{j,i}}{2}<{\mathrm{\&tau;}}_{i,j}^{\max }$ τ wherein ^Min _{I, j}And τ ^Max _{I, j}Be respectively the minimum value and the maximum of acceptable propagation delay preset range; And d _{I, j}And d _{J, i}It is respectively in the opposite direction time difference between base station i and the j.

According to the present invention, RNC can filter measured value with the acquisition consistency, thereby significantly reduces wrong use of measuring.

Among the present invention, carry out two-way measurement between two base stations, the result comprises composition that relates to propagation delay and the composition that relates to the time difference.Ideally, such bidirectional measurement should be offset the composition of propagation delay, but because unique method that makes it unanimity is to measure on the path the earliest, thereby have only when all measuring same path in both cases just possible.

Yet, at first can be in orientation measurement path and in another orientation measurement path that lags the earliest, but owing to reached synchronously, the path will be measured on both direction the earliest.

And, might lose path the earliest owing to decline, and in path the earliest with lag and switch between the path.Thereby expectation knows that measurement is when based on lagging path and ignore them.

When carrying out bidirectional measurement, they are grouped into by two one-tenth.Consider to have two base stations of subscript i and j.When base station j was sent to base station i, it measured time difference d _{I, j}:

d _{I, j}=δ _{I, j}+ τ _{I, j}(1) δ wherein _{I, j}Be time of clock of the leading base station j of clock of base station i, and τ _{I, j}=τ _{J, i}Be two propagation delays between the base station.

And, in reciprocal measurement:

d _j，i＝δ _j，i+τ _j，i

Now, δ _{J, i}=-δ _{I, j}Make

d _j，i＝-δ _i，j+τ _i，j (2)

Equation (1) (2) addition is drawn ${\mathrm{\&tau;}}_{i,j}=\frac{d_{i,j}+d_{j,i}}{2}$

To the expansion that provides, τ _{I, j}Limit.Simply, τ _{I, j}＞0 and τ _{I, j}＜d _Max/ c, wherein d _MaxBe the maximum magnitude between the base station, c is the light velocity.Be necessary artificially to increase d _MaxTo contain the invalid situation of opticpath.

In addition, if know the position of base station i and j, in the time may needing positioning service is provided, τ _{I, j}Can carry out stricter qualification.

The method according to this invention utilizes following boundary to test, that is: at this moment ${\mathrm{\&tau;}}_{i,j}^{\min }<\frac{d_{i,j}+d_{j,i}}{2}<{\mathrm{\&tau;}}_{i,j}^{\max }$

Timing difference d between any a pair of base station that can not pass through to test _{I, j}And d _{J, i}Be considered to unreliable and be not used.Should be pointed out that owing to measure and to carry out in sizable time in difference to have that necessity is expanded boundary a little so that measure d occurring in _{I, j}And d _{J, i}Between clock jitter take into account.

The home window of supposing Measuring Time is 10 ⁶Chip, and supposition τ ^Min _{I, j}=0 and τ ^Max _{I, j}=50.In this case, the mistake possibility that occurs in the measurement in the test window significantly reduces.And even mistake occurs in the test window, because mistake itself is considerably little, its influence is also little.

Along with proceeding of Synchronous Processing, can retrofit testing by older measured value and new measured value.For example, make d ⁿ _{I, j}Be d _{I, j}Measure for the n time.So, ${\mathrm{\&tau;}}_{i,j}^n=\frac{d_{i,j}^n+d_{j,i}^n}{2}$ Can estimate then ${\mathrm{\&tau;}}_{i,j}^n-\mathrm{\&Delta;}<\frac{d_{i,j}^{n+1}+d_{j,i}^{n+1}}{2}<{\mathrm{\&tau;}}_{i,j}^n+\mathrm{\&Delta;}$ Wherein Δ is a little surplus.Certainly, in this case, can not guarantee d ⁿ _{I, j}And d ⁿ _{J, i}Be to compare d ^N+1 _{I, j}And d ^N+1 _{J, i}Good measured value.

But this method can be used for detecting when regularly measuring and detect than slow path, path the earliest.This is by storage τ ⁿ _{I, j}Previous value realizes, and test becomes when new measurement is carried out ${\mathrm{\&tau;}}_{i,j}^{\min }<{\mathrm{\&tau;}}_{i,j}^m<{\mathrm{\&tau;}}_{i,j}^n+\mathrm{\&Delta;}$ Common corresponding 0.25 chip of Δ wherein.

If test is true, then Cun Chu τ ⁿ _{I, j}By τ ^m _{I, j}Replacement is also adopted this measured value.If test is not true, then Cun Chu τ ⁿ _{I, j}Not by τ ^m _{I, j}Replace and do not adopt this measured value.

Like this, the value of storage trends towards based on path the earliest, only makes just to be used based on the measured value in path the earliest.

Because the drift between the clock, this method may be too strict and can't carry out in the synchronous last stage.In this case, can use wideer boundary (if suitably also can not having boundary) at the very start.When detecting a resonable degree synchronous, can apply stricter test again.Can being detected synchronously of this resonable degree, for example, the amplitude of upgrading by the timing of estimating to be calculated.

Understand the present invention easily and only be applicable to that when reaching synchronous situation significantly increase otherwise propagation delay will have one, it does not relate to measures the path that lags.

Be to be understood that method of the present invention allows minimizing rather than increase in order to determine the measured propagation delay in path the earliest.

Claims (3)

1. A method of synchronizing measurements of propagation delay between two base stations, the method comprising the steps of: a) achieving synchronization between said two base stations; b) Calculate the initial propagation delay; c) storing the initial propagation delay; d) Calculate the subsequent propagation delay; e) determining whether the subsequent propagation delay is within a predetermined range; f) using said subsequent propagation delay if within said predetermined range; g) if within the predetermined range and less than the initial propagation delay, store the Subsequent propagation delay; h) Repeat steps d) to g). 2. The method of claim 1, wherein step c) comprises determining whether the initial propagation delay meets the following requirements: ${\mathrm{\&tau;}}_{i,j}^{\min }<\frac{d_{i,j}+d_{j,i}}{2}<{\mathrm{\&tau;}}_{i,j}^{\max }$ where τ ^min _{i,j and} τ ^max _{i,j are} the minimum and maximum values of the predetermined range of acceptable propagation delay, respectively; time difference. 3. A method of synchronizing measurements of propagation delay between two base stations, substantially as hereinbefore described.