CN1689347A - Method and system for providing a hard handoff in communications in a CDMA system - Google Patents

Method and system for providing a hard handoff in communications in a CDMA system Download PDF

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Publication number
CN1689347A
CN1689347A CN02829795.4A CN02829795A CN1689347A CN 1689347 A CN1689347 A CN 1689347A CN 02829795 A CN02829795 A CN 02829795A CN 1689347 A CN1689347 A CN 1689347A
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China
Prior art keywords
sign indicating
indicating number
power
sub
district
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CN02829795.4A
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Chinese (zh)
Inventor
李建业
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Linkair Communications Inc
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Linkair Communications Inc
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Publication of CN1689347A publication Critical patent/CN1689347A/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/16—Performing reselection for specific purposes
    • H04W36/20—Performing reselection for specific purposes for optimising the interference level
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/38—TPC being performed in particular situations
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/38—TPC being performed in particular situations
    • H04W52/40—TPC being performed in particular situations during macro-diversity or soft handoff

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

A method and system for providing a hard handoff in communications in a CDMA system, comprising the steps of: increasing the signal power of home cell before the handoff;increasing the power of the code channel in the target cell and dropping the code channel in the home cell during the handoff; readjusting the power of the new code channel according to E b I o; shifting the new code for n*T c if the E b/I o; is poor for the new code channel after handoff. The present invention provides a substantial improvement over conventional cellular telephone systems by providing additional system reliability and quality in communications.

Description

A kind of method and system that direct-cut operation is provided in cdma communication system
Technical field
The present invention relates to mobile telephone system.It relates in code division multiple access (CDMA) system, the handover control system of a kind of new mobile unit in the communication of mobile radio station.More particularly, the present invention is a kind of method and system that direct-cut operation is provided in cdma communication system.
Background technology
Up to the present, all cdma systems all adopt soft handover.This is because Walsh (Walsh) sign indicating number that existing cdma system adopts can not overcome interference among adjacent cells (ACI), particularly on the border of sub-district, is disturbing under the very high situation between neighbor cell.Soft handover is the means of a kind of employing diversity planning (diversity scheme), so that strengthen and protect the signal that is in the soft handoff range by obtaining signal from cell-of-origin and these two sub-districts, purpose sub-district.These two signals from two sub-districts are known as two pointers.Usually, because many peripheral cells comprise plural pointer, so in the soft switching process of 3G system, the situation that seven pointers meet can take place.Therefore, soft switching process is very complicated.In addition, because in the switching scope, two signalling channels provide service for a user, so power system capacity is lowered.Sometimes, owing to adopt soft switching system, 1/3rd capacity is lost.
Summary of the invention
The present invention relates to a kind of method and system that direct-cut operation is provided in cdma communication system.When all transmission signals (passage) were quadrature, direct-cut operation can take place in a system, for example frequency division or time-division system.In the FDMA system (for example AMPS), except the suitable interior same frequency of distance multiplexing, all transmission signals are different frequencies.Therefore, there is not the ACI problem in principle, so can realize direct-cut operation.Gsm system is a tdma system.Therefore, it can adopt direct-cut operation.If in cdma system, can find satisfy following characteristic one group sign indicating number { C cleverly i}
Auto-correlation Rc i(τ)=o wherein: τ ≠ o ,-t 1τ≤t 1
Cross-correlation Rc ic j(τ)=and o is for all τ, has :-t 2τ≤t 2
The window features-t here 1τ≤t 1With-t 2τ≤t 2Must eliminate ACI, so direct-cut operation can be realized.
Now, several sign indicating numbers cleverly find.But it only has window-3t by 32 cτ≤3t cSign indicating number constitute t here cIt is the interval of chip.For in 32 identical code characters of different districts identification, the different device that is used to discern the sub-district is added into.Majority among them will cause the white noise effect, promptly destroy the zero correlation window of two code characters distributing to two neighbor cells.So because ACI direct-cut operation in vogue can not be realized.Now, one group of new sign indicating number cleverly that is called characteristic orthogonal code (DOC) is arranged, this code character has the characteristic of sign indicating number cleverly above-mentioned.In addition, distribute to the sign indicating number c of cell x iAnd distribute to sub-district y the sign indicating number c jHave following characteristic:
Rx Ciy Cj(τ)=o τ ≠ o wherein, and-t 2τ≤t 2
At window-t 2τ≤t 2Scope in, except τ ≠ o, do not have ACI at cell boarder in principle.
Although always in fact ACI exists, but it can be reduced by the present invention and control.The present invention is by providing spare system, thereby provides a kind of reliability of traditional mobile telephone system communication and quality of making to be able to practical improved method.Technical scheme of the present invention is:
A kind of method that direct-cut operation is provided in the communication of cdma system, it may further comprise the steps:
Before switching, promote the signal power of cell-of-origin;
In handoff procedure, promote the power of sign indicating number passage in the Target cell, and reduce the power of the sign indicating number passage in the cell-of-origin;
According to E b/ I oReadjust the power of new sign indicating number passage;
After switching, if E b/ I oFor described new sign indicating number passage is poor, then passes through nT cNew sign indicating number is changed.
Described soft handover or the direct-cut operation of switching to.
The phasing not of uniform size of described cell-of-origin and purpose sub-district etc.
Described switching can be applied to the switching of a sector in the sub-district to the sector.
Described sign indicating number can be converted into arbitrary value, comprise on the occasion of or negative value.
The lifting of described power can be independent be raised, perhaps promote along with the conversion of sign indicating number.
The conversion of sign indicating number can be changed separately, perhaps changes along with the lifting of power.
The present invention also provides a kind of system that direct-cut operation is provided in cdma communication system, in mobile telephone system (cellular telephone system), the information signal of communicating by letter between mobile subscriber and another mobile subscriber at least need be through a sub-district in a plurality of geographical zones, each sub-district all is defined as geographic service area separately, when a mobile subscriber changed the sub-district of its coverage, directly the system that communicates by letter with described mobile subscriber at least need be through in the described sub-district; Described system comprises: switching device shifter; Power improves device; The code conversion device.
The present invention is by providing described spare system, from having changed the reliability and the communication quality of traditional mobile telephone system communication in fact.
Description of drawings
Characteristic of the present invention and advantage will be clearer and more definite after the specific descriptions in conjunction with following four accompanying drawings.
Figure 1A is the direct-cut operation schematic diagram when not having ACI in FDMA/TDMA;
Figure 1B is the soft handover schematic diagram when having ACI in FDMA/TDMA;
Fig. 2 A is the direct-cut operation schematic diagram in the cdma system with one group of special sign indicating number cleverly and energy gain (before switching);
Fig. 2 B is the direct-cut operation schematic diagram in the cdma system with one group of special sign indicating number cleverly and energy gain (switching the back);
Fig. 3 A is the DOC (characteristic orthogonal code) that does not have energy gain;
Fig. 3 B is the DOC with energy gain (before direct-cut operation);
Fig. 3 C is the DOC with energy gain (direct-cut operation is latter half of);
Fig. 4 is the schematic diagram according to code conversion method of the present invention.
Embodiment
The invention provides a kind of method of the direct-cut operation in cdma communication system, this method may further comprise the steps:
Before switching, increase the signal power of cell-of-origin;
In handoff procedure, in Target cell, increase the energy of sign indicating number passage, and in the cell-of-origin, reduce the energy of sign indicating number passage;
According to condition E b/ I oReadjust the energy of new sign indicating number passage;
If after switching, for the passage of new sign indicating number, E b/ I oBe poor, then new sign indicating number be converted to nT c
In the face of real environment;
Rx Ciy Cj(τ)=δ τ ≠ o wherein, and-t 2τ≤t 2
Here δ is that ACI wishes a little value reaching.The ACI of a cell-of-origin can come from the directapath and the mulitpath of all neighbor cells.What ACI had the greatest impact is cell boarder, can adopt the characteristic of ingenious sign indicating number to reduce ACI there, except the point of τ=o.
At first, in Figure 1A, Figure 1B and Fig. 2 A, Fig. 2 B, demonstrated the method that solves the ACI problem in the prior art.Because there is not ACI, direct-cut operation is used in FDMA or the tdma system.And owing to non-zero correlation zone characteristic has ACI, soft handover is used in the cdma system.What demonstrate among Fig. 2 A, Fig. 2 B, Fig. 2 C is, the special code character that is made of sign indicating number DOC cleverly.High cross-correlation is ACI when τ=o, and this is inevitable.
Improved the power of signal in the time of the weak point of the present invention before direct-cut operation.Its result satisfies following formula:
C I = R x ( o ) R xy ( o ) = X 2 ‾ X · Y ρ xy ( o ) ≈ X Y ρ xy ( o )
Here, ρ Xy(o) be cross-correlation coefficient (1≤ρ≤1).
When the power of C increased, C/I also correspondingly increased.We are needed just for this.
Second step of the present invention is: during direct-cut operation, at the power of Target cell increase sign indicating number passage, reduce the power of sign indicating number passage in the cell-of-origin.After direct-cut operation is finished, according to E b/ I oReduce the power of sign indicating number passage.
When two cell size equated, ACI was a critical condition.If sub-district is greater than its neighbor cell, then when τ=o (it is half a distance between two base stations), ACI is positioned at bigger sub-district, near its base station.In this case, mobile unit is covered by stronger signal.
After direct-cut operation is finished, reduce the power of new sign indicating number passage, if E b/ I oFor new sign indicating number passage is poor, can pass through nT cNew sign indicating number is changed, and as shown in Figure 4, the span of n can be 1 to 3 or-3 to-1; Suppose C 1Be the sign indicating number of cell x, and C 2It is the sign indicating number of sub-district y.With C 2Sign indicating number is transformed into the device on the right, and ACI zero moment peak value is converted into the base station near sub-district y like this.With C 2Sign indicating number is transformed into the device on the left side, and ACI zero moment peak value is converted into the base station near cell x like this.This step page or leaf provides more assurance, so that ACI can be transferred from the position of received power, that is to say that autocorrelative position equals zero, and direct-cut operation can carry out successfully.
Should be noted in the discussion above that when using the solution of the present invention that the size of two sub-districts does not need to equate completely.Here can be any yardage and the size of correlation window arbitrarily.In the process of switching, code conversion can be transformed to any value, on the occasion of or negative value, and the raising of power can be by independent raising, or is accompanied by code conversion and improves.Equally, code conversion can be by independent conversion, also can be accompanied by the raising of power and conversion.In addition, in order to reduce various interference, code conversion provided by the invention can be applied to any environment.
A kind of system that direct-cut operation is provided in cdma communication system of the present invention, in a mobile telephone system, the information signal of communicating by letter between mobile subscriber and another mobile subscriber at least need be through a sub-district in a plurality of geographical zones, and each sub-district all is defined as a geographic service area separately.When a mobile subscriber changed the sub-district of its coverage, directly the system that communicates by letter with described mobile subscriber at least need be through in the described sub-district.Described system comprises: switching device shifter; Power improves device; The code conversion device.
The present invention is by providing a kind of spare system, makes traditional mobile communication system at communication reliability with improvement in essence arranged qualitatively.
The description of above-mentioned embodiment provides a kind of and can make and use technical scheme of the present invention.Exist multiple disposable technical scheme when enforcement is of the present invention, the scheme of these conversion is easy to be derived, and therefore, above-mentioned embodiment only is used to illustrate the present invention, but not is used to limit the present invention.

Claims (8)

1. method that direct-cut operation is provided in cdma communication system is characterized in that may further comprise the steps:
Before switching, promote the signal power of cell-of-origin;
In handoff procedure, promote the power of sign indicating number passage in the Target cell, and reduce the power of the sign indicating number passage in the cell-of-origin;
According to E b/ I oReadjust the power of new sign indicating number passage;
After switching, if E b/ I oFor described new sign indicating number passage is poor, then passes through nT cNew sign indicating number is changed.
2. method according to claim 1 is characterized in that, described soft handover or the direct-cut operation of switching to.
3. method according to claim 1 is characterized in that, the phasing not of uniform size of described cell-of-origin and purpose sub-district etc.
4. method according to claim 1 is characterized in that, described switching can be applied to the switching of a sector in the sub-district to the sector.
5. method according to claim 1 is characterized in that, described sign indicating number can be converted into arbitrary value, comprise on the occasion of or negative value.
6. method according to claim 1 is characterized in that, what the lifting of described power can be independent is raised, and perhaps promotes along with the conversion of sign indicating number.
7. method according to claim 2 is characterized in that, the conversion of sign indicating number can be changed separately, perhaps changes along with the lifting of power.
8. system that direct-cut operation is provided in cdma communication system, in mobile telephone system, the information signal of communicating by letter between mobile subscriber and another mobile subscriber at least need be through a sub-district in a plurality of geographical zones, each sub-district all is defined as geographic service area separately, when a mobile subscriber changed the sub-district of its coverage, directly the system that communicates by letter with described mobile subscriber at least need be through in the described sub-district; It is characterized in that described system comprises: switching device shifter; Power improves device; The code conversion device.
CN02829795.4A 2002-11-11 2002-11-11 Method and system for providing a hard handoff in communications in a CDMA system Pending CN1689347A (en)

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PCT/CN2002/000800 WO2004045227A1 (en) 2002-11-11 2002-11-11 Method and system for providing a hard handoff in communications in a cdma system

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CN1689347A true CN1689347A (en) 2005-10-26

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101123817B (en) * 2006-08-07 2010-12-29 株式会社Ntt都科摩 Radio communication control device, radio communication control system, and radio communication control method

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1740000A1 (en) * 2005-06-27 2007-01-03 Siemens Aktiengesellschaft Method for handover of a radio transmission by transmission power control of the base stations

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* Cited by examiner, † Cited by third party
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US5982760A (en) * 1997-06-20 1999-11-09 Qualcomm Inc. Method and apparatus for power adaptation control in closed-loop communications
US6438116B1 (en) * 1998-07-16 2002-08-20 Telefonaktiebolaget L M Ericsson (Publ) Adaptive power margin for hard handoffs in code division multiple access based systems
GB2358109B (en) * 2000-01-10 2004-03-24 Fujitsu Ltd Soft hand-off in cellular mobile communications networks
US8099122B1 (en) * 2000-06-05 2012-01-17 Qualcomm Incorporated Method and apparatus for improved forward link power control while in soft handoff

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101123817B (en) * 2006-08-07 2010-12-29 株式会社Ntt都科摩 Radio communication control device, radio communication control system, and radio communication control method

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