CA2057068C - Method for handoff in a mobile radio communication system - Google Patents
Method for handoff in a mobile radio communication system Download PDFInfo
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- CA2057068C CA2057068C CA002057068A CA2057068A CA2057068C CA 2057068 C CA2057068 C CA 2057068C CA 002057068 A CA002057068 A CA 002057068A CA 2057068 A CA2057068 A CA 2057068A CA 2057068 C CA2057068 C CA 2057068C
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- 238000000034 method Methods 0.000 title claims abstract description 26
- 238000004891 communication Methods 0.000 title claims abstract description 9
- 239000013598 vector Substances 0.000 claims abstract description 54
- 230000001413 cellular effect Effects 0.000 claims description 5
- 239000006185 dispersion Substances 0.000 claims description 4
- 230000002452 interceptive effect Effects 0.000 claims description 4
- 230000002596 correlated effect Effects 0.000 abstract description 2
- 230000000875 corresponding effect Effects 0.000 description 2
- 101100311214 Xenopus laevis stat3.1 gene Proteins 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- FESBVLZDDCQLFY-UHFFFAOYSA-N sete Chemical compound [Te]=[Se] FESBVLZDDCQLFY-UHFFFAOYSA-N 0.000 description 1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/24—Reselection being triggered by specific parameters
- H04W36/32—Reselection being triggered by specific parameters by location or mobility data, e.g. speed data
- H04W36/322—Reselection being triggered by specific parameters by location or mobility data, e.g. speed data by location data
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/24—Reselection being triggered by specific parameters
- H04W36/32—Reselection being triggered by specific parameters by location or mobility data, e.g. speed data
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- Mobile Radio Communication Systems (AREA)
Abstract
The invention relates to a method in connection with handoff from a first base station (1) in a mobile radio communication system, in which method the signal strengths from a set of base stations (1) surrounding a mobile station are measured in the latter. When handoff is considered to be motivated, the signal strength vector formed by the measured signal strengths is correlated with stored characteristic signal strength vectors associated with the first base station (1). If the correlation between measured signal strength vector and one of said stored characteristic signal strength vectors exceeds a predetermined correlation level, handoff is commanded to a predetermined second base station (2-7) in the set having acceptable but not the highest signal strength in the measured signal strength vector, or is the handoff procedure interrupted and the connection between the mobile station and the first base station (1) maintained.
Description
A Method for Handoff in a Mobile Radio Communication System The present invention relates to a method in connection with handoff from a base station in a mobile radio communication system.
In mobile radio communication systems, for instance mobile telephony systems, a mobile station is in radio contact with a base station in a set of base stations located around the mobile station. When the signal strength from the current base station is weakened due to movement of the mobile station a so called handoff to another base station in the set is performed. Normally handoff is done to that base station in the set that has the highest signal strength at the mobile station at the moment in question.
This method, however, sometimes leads to a non-optimal choice of base station. Under certain circumstances it would be more advantages to chose another base station among the base stations in the set that have sufficiently high signal strength at the mobile station.
An object of the present invention is to provide a method in connection with handoff from the first base station in a mobile radio communication system, in which signal parameters that describes the signals between a mobile station and a set of base stations located around said mobile station are measured and used for handoff decisions.
Accordingly, the present invention relates to a method for handoff from a first base station in a cellular mobile radio communication system, in which signal parameters that describe, the reliability of signals between a mobile station and a set of base stations, including a second base station, surrounding the mobile station are measured and used by a mobile services switching center for handoff decisions, the method comprising the steps of: (a) calculating, when handoff is considered to be motivated, from the measured signal parameters a signal parameter vector which characterizes the geographical location of the mobile station within the cell that is associated with the first base station; (b) correlating the signal parameter vector with each of a set of stored characteristic signal parameter vectors associated with the first base station, each characteristic signal parameter vector characterizing a predetermined location in the cell; and (c) assigning the mobile station to a base station in the set of base stations other than the second base station, the second base station having the measured signal parameters corresponding to the most reliable signal, when the correlation between the measured signal parameter vector and one of the stored characteristic signal parameter vectors exceeds a predetermined correlation level.
The invention will be described more in detail below with reference to the accompanying drawings, in which:
Fig. 1 shows an embodiment of a cellular mobile telephony system;
Fig. 2 shows an example of a situation where handoff should not be made to that base station that-has the strongest signal;
Fig. 3 shows a number of cells in a cellular mobile telephony system, the base stations of which are 2a connected to a common mobile services switching centre;
Fig. 4 shows the structure of a record in a data base for storing signal strength patterns; and Fig. 5 illustrates a flow chart of one embodiment of the present invention.
Figure 1 shows the structure of one embodiment of a cellular mobile telephony system. Such a system comprises a number of cells, each cell in this embodiment comprising one base station BS. To simplify matters only a number of such base stations BS are shown in the figure. The base stations BS are in radio contact with a number of mobile stations MS, of which only one ~~ ir~~~~
~' ~ 91ii6~~z g P~CT/51:91/oali8 is shown in. the figure.' The mobile station MS generally communicates with the base station BS in that cell in which it is currently located. As the mobile station MS travels from cell to cell the communication from the base station BS in one cell is handed over to the base station BS in a neighbouring cell.
This procedure is called handoff. During handoff the old base station instructs the mobile stati~n MS to switch to another channel belonging to the new base,-station.
Figure 2 shows a situatian in, which handoff should not be made to the base station that has the strongest signal. In Figure 2 there are three base stations BS1~BS3. A mobile station is assumed to be on its way from~point A to point C over point B.
At point A the mobile station is in contact with base station BSl. At 'point B the signal strength from base station BS1 has -- ..weakened so that '= ariothe~ base ~ ~ station ~ has a ~~ ~-significantly stronger=signal, and therefore handoff is "ord~red~~ Since the mobile station continuously measures the signal -strength from surrounding base stations, it has been established in point B
-that base station HS2 hasvthe strongest signal strength, and therefore handoff~ in accordance with conventional methods is .ordered to this base station. As the mobile station then continuous to point C the signal from base station BS2 will be blocked by a building H so that the signal strength rapidly decreases and a new handoff has to be ordered. In this case handoff is made to base station BS3.
Thus, in the described situation a handof~ decision in point B
is very rapidly' followed 'by a~ new ~handoff decision in 'pint. C.
~:Iiowever;-..if base station' eS2 'already in point B has sufficient ".:a:.:
_ v signal ~ strength ~ to take -'over then communi~atioai~ -with ~~ the mobile ... station; wit ~ mould be" more'suitable 'to 'order handoff ~ already~~ at -.that point-to base station BS3 instead of to base station HS2.
Since the road in the described example always has the-same geographical form and the point C can be reached from point A
only over point B, it would therefore be desirable to 'somehow consider the fact that the building H soon will block signals 'f~5w~~~~~
' ~ 91/16772 ~ PCT/SE91/00118 from base station BS2~in connection with the handoff decision in point B.
The present invention is based on the insight that the geographical location of point B does not necessarily have to be characterized by the geographical coordinates of the point. And alternative way of characterizing the location of the point is by a signal strength vector formed by the signal strengths.from .
the surrounding base stations that are measured in the mobile station. Thus, point B can be identified by.a.characteristic signal strength vector associated with base station HS1. The reason for this association to base station BSl is that the specifically described situation arises, only if the mobile station travels~~in direction ABC. Thus,.only if handoff is to be made frombase station BSl to another-:base,:station is the 15measured signal strength vector of:,importance for identifying the geographical' location .and probable.later,~movement. of the mobile station. If, however, the mobile station.travels in the opposite direction, CBA, the mobile station at point B will still be in contact with base.station BS3.without requiring a handoff.
Handoff to base station BS1 is made only later somewhere..along the distance BA. Thus, .it.is essential,;"to associate the characteristic ,signal strength vector with a certain base station.
An embodiment'of the invention will be described more in detail below with reference to figures 3 and 4.
Figure 3 shows a set _of, base stations l~7 located around a mobile station. These",base stations are connected to a mobile.:. services _..,.., .. ..:. ; . .. .,._y, .~ .<..,; _,.. ,.. ..._. ._. .... ... _ . . . ..
.
switch~.ng ~ centre MSC, ; , in which handoff ;decisions _.. normally . are made. . In , Figure 3 ,all the base . . stations in . . the set _ that .~ is , surrounding the mobile station are connected to the same mobile services switching centre. However, this is not necessary instead certain base stations may be connected to one mobile services switching centre while other base stations .may be connected to other mobile service switching centres. In such a case the mobile services switching centres communicate with each other. However,.to simplify matters the case shown in Figure 3, ~~~w~~~J~
. ~~ 91/16772 5 fCI'/SE91/00118 where all the base stations in the set are connected to mobile services switching centre MSC will be described.
The mobile services switching centre MSC comprises a data file with characteristic signal strength vectors for "exception points", for instance point B in Figure 2. Figure 4 shows the structure of a record in such a data file. Each record comprises a field BS that identifies a base station to which the signal strength vector belongs. The remaining fields in the record contain signal strengths SSrl - SS 7 in the exception point.
Thus, on demand each base station that~is connected to the mobile services switching centre MSC can be associated with a number of exception points defined by signal strength vectors stored in the data file. These signal strength vectors or signal strength patterns axe measured and thereafter permanently stored in the ~ data file and can thereafter be considered~in connection with handoff decisions.
In the following it is assumed that the mobile station is in contact with base station 1 in Figure 3 when~a handoff is to be made to one of the stations 2-7. Furthermore, it is assumed that the mobile station continuously measures and reports signal strengths for surrounding base stations 1-°7 to base station 1, which directs these measurement values to the mobile services switching centre MSC. When the mobile services switching centre MSC determines that the signal strengths from base stations 1-7 measured at the mobile station have changed to such levels that the conditions for handoff are fulfilled, it is investigated whether thevdata base stored in the mobile services switching centre.'MSC contains any exception points'for this base station.
- If this is '~~the-~. case it isdetermined whether any ~-of these are sufficiently~carrelated~to, that 3a sufficieritly~-similar to the latest signal strength vector measured by the mobile station. If the correlation is-sufficient to consider the~mobile station to lie in exactly the point where the characteristic signal strength vector once has been measured, a handoff is performed to another base station among stations 2-7, but not to that base station that has the strongest signal. However, the chosen base station ~~~"l r~~
' 31/16772 ~' PCT/SE91/0011~
must still have acceptable signal strength at the mobile station, If it is determined that base station 1 is not associated with any exception paints or if the. last signal strength vector measured at the mobile station is not sufficiently correlated with any of the characteristic signal strength vectors for base station 1, a handoff is performed in.a conventional way to that base station 2-7 that has the strongest signal.
The correlation between a signal strength vector measured at the mobile station and a characteristic signal strength vector in the data file can easily be performed for instance by cale~alating the absolute value of the difference between respective vector components to form a deviation vector. This deviation vector can then be compared.to a stored deviation vector. If a sufficient number of components .in..th;e -calculated deviation vector are ~ smaller than the corresponding components in the stored deviation vector sufficient correlation is assumed to exist. The stored deviation vector can be common for all characteristic signal strength vectors or be unique for each characteristic, signal strength vector.
Tn certain situations, for instance when signals from base station 1 temporarily are blocked by a building, the most suitable procedure can be to completely ianterrupt the.handoff - procedure since according~to experience base station 1 shortly thereafter will~have an acceptable signal strength again. .., ~ ~In the above example the invention has been described in connection with signal strength.vectors that are reported by the .ui,~-:..-.. ' .~:-.. ;:.:. ..:;.:..,. , . :. -..~.. 3 ......- ._.'..... . ;~
. . ..
mobile station MS to the base station HS..However, the. mobile station ~ can also ~ measure , and , report other parameters that describe received signals. These parameters can also be of interest in connection with a handoff decision. Examples of such -parameters are:
- the bit error rate (HER) of signals transmitted from at least one of the base station 1-7;
' ~ 91/16772 PCT'/SE91/0011$
- the time dispersion, TD, of signals transmitted from at least one of the base stations 1-7; and - the ratio, C/I, between the signal strength of the carrier that has been transmitted from at least one of the base stations 1-7 and interfering signals.
A generalisation of the described embodiment of the invention is therefore to replace the signal strength vector with a signal parameter vector. The principals described above can then still be used if the mobile station instead measures the signal parameter vector and this vector is compared to stored characteristic signal parameter vectors. ~~-.
In an embodiment where also other parameters~than signal strength are considered it is possible that handoff in an exception poin~c is ordered to, that _ base station that has the strongest signal after all. It can for instance happen .that these further ,parameters do not have acceptalale values for.any other than the strongest base station. ~ ' In the described embodiment of the inventioi~ to simplify matters it has been assumed that signal parameters are measured in the mobile station and reported to a base station. However; this is not neces~ary.,.An equivalent way to obtain sign~l.paxameters is for-instance ao let the base station measure parameters that describe the: signal that is .transmitted by the mobile station and received.by the respective base stations. These.:parameters can then by each base stat3.on be reported to the unit that makes handoff decisions, for instance a mobile services switching centre. These signal parameters also form a signal parameter vector that characterizes the geographic location of the mobile station.
The signal parameters in such an embodiment can comprise at least one of the signal strengths measured at the base stations 1-7 in the set of a signal transmitted by the mobile station MS.
2d~"~~~)~
7 91/16772 PCI'/SE91/~0118 Further examples of signal parameters in this embodiment can comprise at least one of:
- the bit error rate, HSR, of a signal transmitted by the mobile station MS as measured at at least one base station 1-7 in the sett - the time dispersion, TD, of a signal transmitted by the mobile station MS as measured at at least one base station 1-7 in the set;
°: the ratio,' C/I, between the signal strength of the carrier transmitted 'by the mobiles station MS and interfering signals as measured at at least one base station Z-7 in the sete~ .. . . . .
.Thus,.with the present invention it i~ possible ~tci provide~more differentiated conditions for handoff, that is to deviate from , the condition that handoff is to~ be made to the base station that has the strongest signal in certain situations. Insteadi~handoff can be made, to some other predetermined base station or the connection -with the original base station can be maintained until the next handoff request.
The. man skilled ~in the art appreciates- that different changes and modificati~ns of the invention arm possible without deviation from. the scope of the invention; iahich is defined by theappended :, . Pa'~?.nt claims. . - _., . . . . . ~ . _...
In mobile radio communication systems, for instance mobile telephony systems, a mobile station is in radio contact with a base station in a set of base stations located around the mobile station. When the signal strength from the current base station is weakened due to movement of the mobile station a so called handoff to another base station in the set is performed. Normally handoff is done to that base station in the set that has the highest signal strength at the mobile station at the moment in question.
This method, however, sometimes leads to a non-optimal choice of base station. Under certain circumstances it would be more advantages to chose another base station among the base stations in the set that have sufficiently high signal strength at the mobile station.
An object of the present invention is to provide a method in connection with handoff from the first base station in a mobile radio communication system, in which signal parameters that describes the signals between a mobile station and a set of base stations located around said mobile station are measured and used for handoff decisions.
Accordingly, the present invention relates to a method for handoff from a first base station in a cellular mobile radio communication system, in which signal parameters that describe, the reliability of signals between a mobile station and a set of base stations, including a second base station, surrounding the mobile station are measured and used by a mobile services switching center for handoff decisions, the method comprising the steps of: (a) calculating, when handoff is considered to be motivated, from the measured signal parameters a signal parameter vector which characterizes the geographical location of the mobile station within the cell that is associated with the first base station; (b) correlating the signal parameter vector with each of a set of stored characteristic signal parameter vectors associated with the first base station, each characteristic signal parameter vector characterizing a predetermined location in the cell; and (c) assigning the mobile station to a base station in the set of base stations other than the second base station, the second base station having the measured signal parameters corresponding to the most reliable signal, when the correlation between the measured signal parameter vector and one of the stored characteristic signal parameter vectors exceeds a predetermined correlation level.
The invention will be described more in detail below with reference to the accompanying drawings, in which:
Fig. 1 shows an embodiment of a cellular mobile telephony system;
Fig. 2 shows an example of a situation where handoff should not be made to that base station that-has the strongest signal;
Fig. 3 shows a number of cells in a cellular mobile telephony system, the base stations of which are 2a connected to a common mobile services switching centre;
Fig. 4 shows the structure of a record in a data base for storing signal strength patterns; and Fig. 5 illustrates a flow chart of one embodiment of the present invention.
Figure 1 shows the structure of one embodiment of a cellular mobile telephony system. Such a system comprises a number of cells, each cell in this embodiment comprising one base station BS. To simplify matters only a number of such base stations BS are shown in the figure. The base stations BS are in radio contact with a number of mobile stations MS, of which only one ~~ ir~~~~
~' ~ 91ii6~~z g P~CT/51:91/oali8 is shown in. the figure.' The mobile station MS generally communicates with the base station BS in that cell in which it is currently located. As the mobile station MS travels from cell to cell the communication from the base station BS in one cell is handed over to the base station BS in a neighbouring cell.
This procedure is called handoff. During handoff the old base station instructs the mobile stati~n MS to switch to another channel belonging to the new base,-station.
Figure 2 shows a situatian in, which handoff should not be made to the base station that has the strongest signal. In Figure 2 there are three base stations BS1~BS3. A mobile station is assumed to be on its way from~point A to point C over point B.
At point A the mobile station is in contact with base station BSl. At 'point B the signal strength from base station BS1 has -- ..weakened so that '= ariothe~ base ~ ~ station ~ has a ~~ ~-significantly stronger=signal, and therefore handoff is "ord~red~~ Since the mobile station continuously measures the signal -strength from surrounding base stations, it has been established in point B
-that base station HS2 hasvthe strongest signal strength, and therefore handoff~ in accordance with conventional methods is .ordered to this base station. As the mobile station then continuous to point C the signal from base station BS2 will be blocked by a building H so that the signal strength rapidly decreases and a new handoff has to be ordered. In this case handoff is made to base station BS3.
Thus, in the described situation a handof~ decision in point B
is very rapidly' followed 'by a~ new ~handoff decision in 'pint. C.
~:Iiowever;-..if base station' eS2 'already in point B has sufficient ".:a:.:
_ v signal ~ strength ~ to take -'over then communi~atioai~ -with ~~ the mobile ... station; wit ~ mould be" more'suitable 'to 'order handoff ~ already~~ at -.that point-to base station BS3 instead of to base station HS2.
Since the road in the described example always has the-same geographical form and the point C can be reached from point A
only over point B, it would therefore be desirable to 'somehow consider the fact that the building H soon will block signals 'f~5w~~~~~
' ~ 91/16772 ~ PCT/SE91/00118 from base station BS2~in connection with the handoff decision in point B.
The present invention is based on the insight that the geographical location of point B does not necessarily have to be characterized by the geographical coordinates of the point. And alternative way of characterizing the location of the point is by a signal strength vector formed by the signal strengths.from .
the surrounding base stations that are measured in the mobile station. Thus, point B can be identified by.a.characteristic signal strength vector associated with base station HS1. The reason for this association to base station BSl is that the specifically described situation arises, only if the mobile station travels~~in direction ABC. Thus,.only if handoff is to be made frombase station BSl to another-:base,:station is the 15measured signal strength vector of:,importance for identifying the geographical' location .and probable.later,~movement. of the mobile station. If, however, the mobile station.travels in the opposite direction, CBA, the mobile station at point B will still be in contact with base.station BS3.without requiring a handoff.
Handoff to base station BS1 is made only later somewhere..along the distance BA. Thus, .it.is essential,;"to associate the characteristic ,signal strength vector with a certain base station.
An embodiment'of the invention will be described more in detail below with reference to figures 3 and 4.
Figure 3 shows a set _of, base stations l~7 located around a mobile station. These",base stations are connected to a mobile.:. services _..,.., .. ..:. ; . .. .,._y, .~ .<..,; _,.. ,.. ..._. ._. .... ... _ . . . ..
.
switch~.ng ~ centre MSC, ; , in which handoff ;decisions _.. normally . are made. . In , Figure 3 ,all the base . . stations in . . the set _ that .~ is , surrounding the mobile station are connected to the same mobile services switching centre. However, this is not necessary instead certain base stations may be connected to one mobile services switching centre while other base stations .may be connected to other mobile service switching centres. In such a case the mobile services switching centres communicate with each other. However,.to simplify matters the case shown in Figure 3, ~~~w~~~J~
. ~~ 91/16772 5 fCI'/SE91/00118 where all the base stations in the set are connected to mobile services switching centre MSC will be described.
The mobile services switching centre MSC comprises a data file with characteristic signal strength vectors for "exception points", for instance point B in Figure 2. Figure 4 shows the structure of a record in such a data file. Each record comprises a field BS that identifies a base station to which the signal strength vector belongs. The remaining fields in the record contain signal strengths SSrl - SS 7 in the exception point.
Thus, on demand each base station that~is connected to the mobile services switching centre MSC can be associated with a number of exception points defined by signal strength vectors stored in the data file. These signal strength vectors or signal strength patterns axe measured and thereafter permanently stored in the ~ data file and can thereafter be considered~in connection with handoff decisions.
In the following it is assumed that the mobile station is in contact with base station 1 in Figure 3 when~a handoff is to be made to one of the stations 2-7. Furthermore, it is assumed that the mobile station continuously measures and reports signal strengths for surrounding base stations 1-°7 to base station 1, which directs these measurement values to the mobile services switching centre MSC. When the mobile services switching centre MSC determines that the signal strengths from base stations 1-7 measured at the mobile station have changed to such levels that the conditions for handoff are fulfilled, it is investigated whether thevdata base stored in the mobile services switching centre.'MSC contains any exception points'for this base station.
- If this is '~~the-~. case it isdetermined whether any ~-of these are sufficiently~carrelated~to, that 3a sufficieritly~-similar to the latest signal strength vector measured by the mobile station. If the correlation is-sufficient to consider the~mobile station to lie in exactly the point where the characteristic signal strength vector once has been measured, a handoff is performed to another base station among stations 2-7, but not to that base station that has the strongest signal. However, the chosen base station ~~~"l r~~
' 31/16772 ~' PCT/SE91/0011~
must still have acceptable signal strength at the mobile station, If it is determined that base station 1 is not associated with any exception paints or if the. last signal strength vector measured at the mobile station is not sufficiently correlated with any of the characteristic signal strength vectors for base station 1, a handoff is performed in.a conventional way to that base station 2-7 that has the strongest signal.
The correlation between a signal strength vector measured at the mobile station and a characteristic signal strength vector in the data file can easily be performed for instance by cale~alating the absolute value of the difference between respective vector components to form a deviation vector. This deviation vector can then be compared.to a stored deviation vector. If a sufficient number of components .in..th;e -calculated deviation vector are ~ smaller than the corresponding components in the stored deviation vector sufficient correlation is assumed to exist. The stored deviation vector can be common for all characteristic signal strength vectors or be unique for each characteristic, signal strength vector.
Tn certain situations, for instance when signals from base station 1 temporarily are blocked by a building, the most suitable procedure can be to completely ianterrupt the.handoff - procedure since according~to experience base station 1 shortly thereafter will~have an acceptable signal strength again. .., ~ ~In the above example the invention has been described in connection with signal strength.vectors that are reported by the .ui,~-:..-.. ' .~:-.. ;:.:. ..:;.:..,. , . :. -..~.. 3 ......- ._.'..... . ;~
. . ..
mobile station MS to the base station HS..However, the. mobile station ~ can also ~ measure , and , report other parameters that describe received signals. These parameters can also be of interest in connection with a handoff decision. Examples of such -parameters are:
- the bit error rate (HER) of signals transmitted from at least one of the base station 1-7;
' ~ 91/16772 PCT'/SE91/0011$
- the time dispersion, TD, of signals transmitted from at least one of the base stations 1-7; and - the ratio, C/I, between the signal strength of the carrier that has been transmitted from at least one of the base stations 1-7 and interfering signals.
A generalisation of the described embodiment of the invention is therefore to replace the signal strength vector with a signal parameter vector. The principals described above can then still be used if the mobile station instead measures the signal parameter vector and this vector is compared to stored characteristic signal parameter vectors. ~~-.
In an embodiment where also other parameters~than signal strength are considered it is possible that handoff in an exception poin~c is ordered to, that _ base station that has the strongest signal after all. It can for instance happen .that these further ,parameters do not have acceptalale values for.any other than the strongest base station. ~ ' In the described embodiment of the inventioi~ to simplify matters it has been assumed that signal parameters are measured in the mobile station and reported to a base station. However; this is not neces~ary.,.An equivalent way to obtain sign~l.paxameters is for-instance ao let the base station measure parameters that describe the: signal that is .transmitted by the mobile station and received.by the respective base stations. These.:parameters can then by each base stat3.on be reported to the unit that makes handoff decisions, for instance a mobile services switching centre. These signal parameters also form a signal parameter vector that characterizes the geographic location of the mobile station.
The signal parameters in such an embodiment can comprise at least one of the signal strengths measured at the base stations 1-7 in the set of a signal transmitted by the mobile station MS.
2d~"~~~)~
7 91/16772 PCI'/SE91/~0118 Further examples of signal parameters in this embodiment can comprise at least one of:
- the bit error rate, HSR, of a signal transmitted by the mobile station MS as measured at at least one base station 1-7 in the sett - the time dispersion, TD, of a signal transmitted by the mobile station MS as measured at at least one base station 1-7 in the set;
°: the ratio,' C/I, between the signal strength of the carrier transmitted 'by the mobiles station MS and interfering signals as measured at at least one base station Z-7 in the sete~ .. . . . .
.Thus,.with the present invention it i~ possible ~tci provide~more differentiated conditions for handoff, that is to deviate from , the condition that handoff is to~ be made to the base station that has the strongest signal in certain situations. Insteadi~handoff can be made, to some other predetermined base station or the connection -with the original base station can be maintained until the next handoff request.
The. man skilled ~in the art appreciates- that different changes and modificati~ns of the invention arm possible without deviation from. the scope of the invention; iahich is defined by theappended :, . Pa'~?.nt claims. . - _., . . . . . ~ . _...
Claims (12)
1. A method for handoff from a first base station in a cellular mobile radio communication system, in which signal parameters that describe the reliability of signals between a mobile station and a set of base stations, including a second base station, surrounding said mobile station are measured and used by a mobile services switching center for handoff decisions, said method comprising the steps of:
(a) calculating, when handoff is considered to be motivated, from said measured signal parameters a signal parameter vector which characterizes the geographical location of said mobile station within the cell that is associated with said first base station;
(b) correlating said signal parameter vector with each of a set of stored characteristic signal parameter vectors associated with said first base station, each characteristic signal parameter vector characterizing a predetermined location in said cell; and (c) assigning said mobile station to a base station in said set of base stations other than said second base station, said second base station having the measured signal parameters corresponding to the most reliable signal, when said correlation between said measured signal parameter vector and one of said stored characteristic signal parameter vectors exceeds a predetermined correlation level.
(a) calculating, when handoff is considered to be motivated, from said measured signal parameters a signal parameter vector which characterizes the geographical location of said mobile station within the cell that is associated with said first base station;
(b) correlating said signal parameter vector with each of a set of stored characteristic signal parameter vectors associated with said first base station, each characteristic signal parameter vector characterizing a predetermined location in said cell; and (c) assigning said mobile station to a base station in said set of base stations other than said second base station, said second base station having the measured signal parameters corresponding to the most reliable signal, when said correlation between said measured signal parameter vector and one of said stored characteristic signal parameter vectors exceeds a predetermined correlation level.
2. The method of claim 1, wherein said signal parameters comprise at least one of the signal strengths of signals transmitted from said base stations in said set as measured at said mobile station.
3. The method of claim 1 or 2, wherein said signal parameters comprise at least one of:
the bit error rate of signals transmitted from at least one base station in said set;
the time dispersion of signals transmitted from at least one base station in said set; and the ratio between the signal strength of the carrier that has been transmitted from at least one base station in said set and interfering signals.
the bit error rate of signals transmitted from at least one base station in said set;
the time dispersion of signals transmitted from at least one base station in said set; and the ratio between the signal strength of the carrier that has been transmitted from at least one base station in said set and interfering signals.
4. The method of claim 1, wherein said signal parameters comprise at least one of the signal strengths measured at said base stations in said set of a signal transmitted by said mobile station.
5. The method of claim 4, wherein said signal parameters comprise at least one of:
the bit error rate of a signal transmitted by said mobile station as measured at at least one base station in said set;
the time dispersion of a signal transmitted by said mobile station as measured at at least one base station in said set; and the ratio between the signal strength of the carrier transmitted by said mobile station and interfering signals as measured at at least one base station in said set.
the bit error rate of a signal transmitted by said mobile station as measured at at least one base station in said set;
the time dispersion of a signal transmitted by said mobile station as measured at at least one base station in said set; and the ratio between the signal strength of the carrier transmitted by said mobile station and interfering signals as measured at at least one base station in said set.
6. The method of any one of claims 1 to 5, wherein handoff in step (c) is ordered to a base station having an acceptable but not the highest signal strength in said measured signal parameter vector.
7. The method of any one of claims 1 to 6, wherein said characteristic signal parameter vectors that are associated with said first base station are stored in a handoff decision means.
8. The method of claim 7, wherein said characteristic signal parameter vectors are stored as records in a data file, in which each record comprises a data field with an identification code for a base station and data fields for signal parameters of characteristic signal parameter vectors associated with this base station.
9. The method of claim 7, wherein said handoff decision means stores characteristic signal parameter vectors for all the base stations that are connected thereto.
10. The method of any one of claims 1 to 9, wherein said mobile station is assigned to a predetermined base station.
11. The method of any one of claims 1 to 10, wherein said handoff is interrupted and said mobile station remains assigned to said first base station when said signal parameter vector for said mobile station corresponds to a predetermined stored characteristic signal parameter vector.
12. The method of any one of claims 1 to 11, wherein said mobile station is assigned to said second base station when said correlation does not exceed a predetermined correlation level.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE9001497A SE466081B (en) | 1990-04-26 | 1990-04-26 | PROCEDURES FOR HANDOFFS IN A MOBILE RADIO SYSTEM |
| SE9001497-8 | 1990-04-26 | ||
| PCT/SE1991/000118 WO1991016772A1 (en) | 1990-04-26 | 1991-02-18 | A method for handoff in a mobile radio communication system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2057068A1 CA2057068A1 (en) | 1991-10-27 |
| CA2057068C true CA2057068C (en) | 2001-02-13 |
Family
ID=20379296
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002057068A Expired - Fee Related CA2057068C (en) | 1990-04-26 | 1991-02-18 | Method for handoff in a mobile radio communication system |
Country Status (12)
| Country | Link |
|---|---|
| US (1) | US5293643A (en) |
| EP (1) | EP0454638B1 (en) |
| JP (1) | JP3140772B2 (en) |
| CN (1) | CN1025102C (en) |
| AU (1) | AU636742B2 (en) |
| BR (1) | BR9105729A (en) |
| CA (1) | CA2057068C (en) |
| DE (1) | DE69102486T2 (en) |
| ES (1) | ES2055578T3 (en) |
| HK (1) | HK115294A (en) |
| SE (1) | SE466081B (en) |
| WO (1) | WO1991016772A1 (en) |
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| DE4307702A1 (en) * | 1993-03-11 | 1994-09-15 | Detecon Gmbh | A location-dependent handover method in mobile radio networks and device for carrying out the method |
| WO1995001068A1 (en) * | 1993-06-25 | 1995-01-05 | Roke Manor Research Limited | Apparatus for interference cancellation in a digital radio link between a fixed and a mobile radio unit |
| US5740208A (en) * | 1993-06-25 | 1998-04-14 | Roke Manor Research Limited | Interference cancellation apparatus for mitigating the effects of poor affiliation between a base station and a mobile unit |
| GB2280335B (en) * | 1993-07-22 | 1997-05-28 | Northern Telecom Ltd | Mobile communications |
| US5548808A (en) * | 1993-12-08 | 1996-08-20 | Motorola, Inc. | Method for performing a handoff in a communication system |
| US5448569A (en) * | 1994-04-12 | 1995-09-05 | International Business Machines Corporation | Handoff monitoring in cellular communication networks using slow frequency hopping |
| FI941779A (en) * | 1994-04-15 | 1995-10-16 | Nokia Telecommunications Oy | Handover procedure and arrangement |
| SE9401713D0 (en) * | 1994-05-16 | 1994-05-16 | Ericsson Telefon Ab L M | Method to improve measurement accuracy in handover decision |
| FI943609A (en) * | 1994-08-03 | 1996-02-04 | Nokia Telecommunications Oy | Method of allocating a channel in a cellular radio system |
| CA2196903C (en) * | 1994-08-09 | 2003-10-07 | Kumar Balachandran | Method and apparatus for efficient handoffs by mobile communication entities |
| US5669061A (en) | 1994-08-19 | 1997-09-16 | Trimble Navigation Limited | Automatic cellular phone tracking |
| JP3085154B2 (en) * | 1994-08-26 | 2000-09-04 | トヨタ自動車株式会社 | Mobile radio communication system |
| GB9510867D0 (en) * | 1995-05-30 | 1995-07-26 | Hong Kong Telecom Csl Limited | Digital cellular telephone networks |
| US5774809A (en) * | 1996-02-12 | 1998-06-30 | Nokia Mobile Phones Limited | Simplified mobile assisted handoff of signal between cells |
| US6449305B1 (en) * | 1996-05-10 | 2002-09-10 | Motorola, Inc. | Method and apparatus for performing handoff in a spread-spectrum communication system |
| US6014564A (en) * | 1996-09-19 | 2000-01-11 | Nortel Networks Corporation | Method and apparatus for determining virtual cell area |
| US5940761A (en) | 1997-01-15 | 1999-08-17 | Qaulcomm Incorporated | Method and apparatus for performing mobile assisted hard handoff between communication systems |
| FI104682B (en) | 1997-02-18 | 2000-04-14 | Nokia Networks Oy | Handover in a mobile communication system |
| FI104683B (en) | 1997-02-18 | 2000-04-14 | Nokia Networks Oy | Handover in a mobile communication system |
| US5970058A (en) * | 1997-04-12 | 1999-10-19 | Motorola, Inc. | Method and apparatus for freeing a frame to aid in handoff determination in a code division multiple access communication system |
| US6002933A (en) * | 1997-04-29 | 1999-12-14 | Qualcomm Incorporated | Inter-system soft handoff |
| US6141555A (en) * | 1997-06-09 | 2000-10-31 | Nec Corporation | Cellular communication system, and mobile and base stations used in the same |
| US5950134A (en) * | 1997-09-08 | 1999-09-07 | At&T Corp. | Method and apparatus for spatial redundancy in cellular networks |
| DE19742650C2 (en) * | 1997-09-26 | 2000-05-11 | Siemens Ag | Optimization of adjacent channel measurement reports |
| GB9810394D0 (en) * | 1998-05-14 | 1998-07-15 | Simoco Europ Limited | Radio communications system |
| SE519366C2 (en) * | 1998-11-17 | 2003-02-18 | Ericsson Telefon Ab L M | Method and devices for a radio communication system |
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| FI109639B (en) * | 1999-12-22 | 2002-09-13 | Nokia Corp | A method for transmitting an encryption number in a communication system and a communication system |
| JP3512090B2 (en) * | 2000-05-31 | 2004-03-29 | 日本電気株式会社 | System and method for switching reception base station of mobile terminal |
| US7865155B1 (en) | 2001-11-02 | 2011-01-04 | Cisco Technology, Inc. | Wireless communication system with signal selection and combination |
| US7068610B2 (en) | 2002-02-26 | 2006-06-27 | Unruh Lincoln J | System and method for reliable communications over multiple packet RF networks |
| KR100689508B1 (en) * | 2003-09-04 | 2007-03-02 | 삼성전자주식회사 | Method for performing handover in a communication system |
| KR101042763B1 (en) * | 2005-07-07 | 2011-06-20 | 삼성전자주식회사 | Hand-over method and apparatus between differential systems |
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| EP0292182B1 (en) * | 1987-05-15 | 1996-07-24 | Securicor Datatrak Limited | Mobile transmitter/receiver |
| GB2215932A (en) * | 1988-03-26 | 1989-09-27 | Gec Traffic Automation | Radio position finding system |
| JPH01321739A (en) * | 1988-06-24 | 1989-12-27 | Nec Corp | Channel switching system for cellular mobile communication |
-
1990
- 1990-04-26 SE SE9001497A patent/SE466081B/en not_active IP Right Cessation
-
1991
- 1991-02-18 AU AU75629/91A patent/AU636742B2/en not_active Ceased
- 1991-02-18 EP EP91850040A patent/EP0454638B1/en not_active Expired - Lifetime
- 1991-02-18 ES ES91850040T patent/ES2055578T3/en not_active Expired - Lifetime
- 1991-02-18 CA CA002057068A patent/CA2057068C/en not_active Expired - Fee Related
- 1991-02-18 BR BR919105729A patent/BR9105729A/en not_active IP Right Cessation
- 1991-02-18 WO PCT/SE1991/000118 patent/WO1991016772A1/en active Application Filing
- 1991-02-18 JP JP03506521A patent/JP3140772B2/en not_active Expired - Lifetime
- 1991-02-18 DE DE69102486T patent/DE69102486T2/en not_active Expired - Lifetime
- 1991-03-22 US US07/673,592 patent/US5293643A/en not_active Expired - Lifetime
- 1991-04-25 CN CN91102636A patent/CN1025102C/en not_active Expired - Lifetime
-
1994
- 1994-10-20 HK HK115294A patent/HK115294A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| WO1991016772A1 (en) | 1991-10-31 |
| SE9001497A (en) | 1991-10-27 |
| CN1025102C (en) | 1994-06-15 |
| CN1056213A (en) | 1991-11-13 |
| JP3140772B2 (en) | 2001-03-05 |
| JPH04507179A (en) | 1992-12-10 |
| BR9105729A (en) | 1992-05-19 |
| ES2055578T3 (en) | 1994-08-16 |
| SE9001497D0 (en) | 1990-04-26 |
| CA2057068A1 (en) | 1991-10-27 |
| AU7562991A (en) | 1991-11-11 |
| DE69102486D1 (en) | 1994-07-21 |
| EP0454638B1 (en) | 1994-06-15 |
| HK115294A (en) | 1994-10-27 |
| DE69102486T2 (en) | 1994-10-20 |
| AU636742B2 (en) | 1993-05-06 |
| EP0454638A1 (en) | 1991-10-30 |
| SE466081B (en) | 1991-12-09 |
| US5293643A (en) | 1994-03-08 |
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| Date | Code | Title | Description |
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| EEER | Examination request | ||
| MKLA | Lapsed | ||
| MKLA | Lapsed |
Effective date: 20040218 |