CA2143930A1 - Frame synchronization method - Google Patents
Frame synchronization methodInfo
- Publication number
- CA2143930A1 CA2143930A1 CA002143930A CA2143930A CA2143930A1 CA 2143930 A1 CA2143930 A1 CA 2143930A1 CA 002143930 A CA002143930 A CA 002143930A CA 2143930 A CA2143930 A CA 2143930A CA 2143930 A1 CA2143930 A1 CA 2143930A1
- Authority
- CA
- Canada
- Prior art keywords
- dect
- multiframe
- frame
- cordless
- synchronization
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000000034 method Methods 0.000 title claims description 9
- 230000033764 rhythmic process Effects 0.000 claims abstract description 4
- 238000001514 detection method Methods 0.000 claims abstract 3
- 230000001360 synchronised effect Effects 0.000 claims description 9
- 230000005540 biological transmission Effects 0.000 claims description 6
- 238000009434 installation Methods 0.000 abstract description 5
- 239000000969 carrier Substances 0.000 abstract description 4
- 230000011664 signaling Effects 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
- H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
- H04B7/2662—Arrangements for Wireless System Synchronisation
- H04B7/2671—Arrangements for Wireless Time-Division Multiple Access [TDMA] System Synchronisation
- H04B7/2678—Time synchronisation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
- H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
- H04B7/2662—Arrangements for Wireless System Synchronisation
- H04B7/2671—Arrangements for Wireless Time-Division Multiple Access [TDMA] System Synchronisation
- H04B7/2678—Time synchronisation
- H04B7/2687—Inter base stations synchronisation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/0602—Systems characterised by the synchronising information used
- H04J3/0614—Systems characterised by the synchronising information used the synchronising signal being characterised by the amplitude, duration or polarity
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M1/00—Substation equipment, e.g. for use by subscribers
- H04M1/72—Mobile telephones; Cordless telephones, i.e. devices for establishing wireless links to base stations without route selection
- H04M1/725—Cordless telephones
- H04M1/733—Cordless telephones with a plurality of base stations connected to a plurality of lines
Landscapes
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Mobile Radio Communication Systems (AREA)
- Synchronisation In Digital Transmission Systems (AREA)
- Control Of Motors That Do Not Use Commutators (AREA)
Abstract
The problem of pulse frame synchronization occurs for example in a telecommunications system with cordless terminals operating according to the DECT standard. To establish a radio connection between base station and a cordless terminal, the base station scans its radio cell in sequence with the available ten high-frequency carriers in the DECT frame rhythm. In a multiple cell environment, the synchronization of all base stations belonging to a cordless telecommunications installation is necessary, to enable all base stations to scan the same frequency at the same time. This is achieved by blanking the DECT multi-frame synchronization pulses. The pulse gap is evaluated by error detection circuits which are present anyway, and used for the PSCN Primary receiver Scan Number-synchronization.
Description
~lq393~
-Field of the Invention The invention concerns a method for synchronizing pulse frames, particularly in a telecommunications system with cordless terminals, called a cordless 5 telecommunications system for short, whose basic functions and characteristics have been described by a European standardizationcommittee,theEuropeanTelecommunications Standards Institute ETSI, as the European standard for cordless telecommunication, DECT in short, the Digital 10 European Cordless Telecommunications - Standard.
Description of the Prior Art Synchronization processes are necessary to ensure an interruption-free channel change within a radio cell, or 15 to be able to undertake an interruption-free transition from a first cell bundle to a second cell bundle, the so-called handover, due to a change in the location of the cordless terminal in a multiple cell environment. Each radio cell is supplied by a base station, which can 20 operate a specified number of cordless terminals simultaneously. To that effect, the frequency band established by the DECT standard is divided into lo carrier frequencies. Each of these carriers is subdivided into 24 time slots, where the first twelve are used to 25 transmit from the base station to the cordless terminal, the remaining twelve for the inverse transmission direction. Thus, the DECT high frequency spectrum provides 120 full duplex channels. The 24 time slots are combined into a DECT frame. Each time slot is subdivided 30 into several fields, and in the present situation the A-field is used for the transmission of signalling information, and the B-field for the transmission of user data. A certain signalling capacity is made available in the A-field, which is assigned as necessary to a logic 35 channel such as an I-, C-, Q-, N-, M-, P-channel, defined by the DECT standard. Since 16 DECT frames are always ` 21l39~0 combined into a DECT multi-frame, the data of the logic channels are multiplexed through this DECT multi-frame.
In this way each logic channel of a DECT multi-frame is fully available, for example the synchronization 5 information for the DECT multi-frame, which is required by every cordless terminal of a cell bundle for its multi-frame synchronization, is transmitted in the eighth DECT
frame of the Q-channel.
The DECT standard describes a frequency scanning 10 algorithm for a cordless telecommunications system with several base stations, which can be implemented with a PSCN synchronization, PSCN is short for Primary receiver Scan carrier Number. Since every base station has the entire frequency spectrum assigned by the DECT standard 15 available, each above described base station has ten high-frequency carriers available, where each is subdivided into twelve full duplex transmission paths. Although the PSCN algorithm specifies that all base stations must scan the same frequency at the same point in time, in order to 20 be able to perform a cell change with a cordless terminal, also called a handover, no information is provided for the technical realization. The result is the task of presenting a method for the PSCN synchronization, which can be performed with a small expense for hardware.
Summary of the Invention According to the invention, this task is fulfilled by a method wherein the frames are synchronized by means of a frame alignment pulse and are combined into 30 multiframes and synchronized in the multiframe rhythm by means of a multiframe alignment pulse which follows after a given number of frames, characterized in that a multiframe sequence is synchronized by blanking a multiframe alignment pulse. The nature of the invention 35 includes evaluating missing pulse transmissions for information purposes, and using circuits in multivalent 21~39~
-form to detect errors in units which are used to manage the base stations.
Description of the Drawinqs In the following, the invention will be explained by means of a configuration example. The pertinent drawing illustrates:
Figure 1, a configurationofa cordlesstelecommunications system, and 10 Figure 2, the assembly in principle of a DECT frame, a DECT multi-frame and pulses for the synchronization of frames, multi-frames and PSCN.
15 Detailed Description of the Preferred Embodiment According to figure 1, a cordless telecommunications system, in this instance a cordless WPABX, Wireless Private Area Branch Exchange, essentially comprises a central unit CPU, which manages different interface 20 circuits via a system bus. Such an installation can be used as an autonomous installation for connecting wired and/or cordless terminals. However, it is also possible to connect the installation to existing networks. The connection to a Public Switched Telephone Network PSTN is 25 possible via the interface circuit for analog exchange lines, and the connection to an Integrated Services Digital Network ISDN can take place via the T0-interface circuit. The base stations BS1 ... BS5 are respectively connected by four-wire lines to the DECT interface 30 circuits 1, 2, 3. Each base station BS1 ... BS5 supplies one radio cell in which it establishes the radio connection with the cordless terminals. For example, in the condition illustrated in figure 1, the cordless terminals 11, 12 are located in the radio cell of base 35 station BS1, the cordless terminals 21, 22 are located in the radio cell of base station BS3, and the cordless 21~92~
-terminals 31, 32 in the radio cell of base station BS3.
Each DECT interface circuit 1, 2, 3 contains at least one application-specific circuit MAC-ASIC, to which a base station is connected in each instance. The base stations 5 are controlled, synchronized and remote-supplied via the four-wire line of the DECT interface.
To be able to establish a radio connection to the cordless terminals, each base station scans its radio cell with the ten available high-frequency carriers, in 10 sequence. Each frequency is scanned during the time of a DECT frame, thus for a time of 10 ms. In that way, 16 frequencies are scanned in a multi-frame, namely the frequencies fl to flO and fl to f6. If this scanning rhythm were to be maintained for each multi-frame, the 15 frequencies would be scanned at different times, and the frequencies f7 to flO would be at a disadvantage. It is therefore necessary to scan the frequencies continuously for the duration of five multi-frames, because then each of the ten frequencies is scanned eight times within a 20 time period of 80 DECT frames. Although each DECT
interface circuit 1, 2, 3 itself is synchronized to a multi-frame pulse and continuously scans the frequencies by itself, the synchronization to each other is missing.
This means that, during a cell bundle change, the cordless 25 terminal encounters two base stations that operate asynchronously with each other. Although it is basically possible for the cordless terminal to synchronize itself to the new base station, this however requires a relative long period of time and additional energy. The DECT
30 interface circuits 1, 2, 3 are also synchronized with each other in order to carry out a quick handover at a low expense of energy. This synchronization of the DECT
interface circuits is called a PSCN synchronization.
Figure 2 illustrates an overview of the connection between 35 DECT frames, English DECT frame, multi-frames, English multi-frame, and the pertinent synchronization pulses.
- 21439~
The PSCN synchronization is depicted in figure 2 at the 10th. multi-frame. A PSCN synchronization at a distance of five multi-frames and whole-number multiples thereof would be possible. The distance of ten multi-frames 5 advantageously produces a low load on the central CPU
unit.
According to the invention, the PSCN synchronization takes place by blanking a multi-frame synchronization pulse. Use is made of the fact that an interrupt-signal 10 is released by the DECT interface circuit, when an expected pulse is missing. This interrupt-signal usually serves to detect errors. But if an error is present, not only would a multi-frame synchronization pulse be missing, but also a DECT frame synchronization pulse. In this way, 15 the one-time missing of a multi-frame synchronization pulse can be used for the PSCN-synchronization of all DECT
interface circuits, so that all base stations belonging to a cordless telecommunications installation can scan the radio cells at the same time and at the same frequencies.
20 The PSCN- synchronization is then realized without any additional expense for hardware.
-Field of the Invention The invention concerns a method for synchronizing pulse frames, particularly in a telecommunications system with cordless terminals, called a cordless 5 telecommunications system for short, whose basic functions and characteristics have been described by a European standardizationcommittee,theEuropeanTelecommunications Standards Institute ETSI, as the European standard for cordless telecommunication, DECT in short, the Digital 10 European Cordless Telecommunications - Standard.
Description of the Prior Art Synchronization processes are necessary to ensure an interruption-free channel change within a radio cell, or 15 to be able to undertake an interruption-free transition from a first cell bundle to a second cell bundle, the so-called handover, due to a change in the location of the cordless terminal in a multiple cell environment. Each radio cell is supplied by a base station, which can 20 operate a specified number of cordless terminals simultaneously. To that effect, the frequency band established by the DECT standard is divided into lo carrier frequencies. Each of these carriers is subdivided into 24 time slots, where the first twelve are used to 25 transmit from the base station to the cordless terminal, the remaining twelve for the inverse transmission direction. Thus, the DECT high frequency spectrum provides 120 full duplex channels. The 24 time slots are combined into a DECT frame. Each time slot is subdivided 30 into several fields, and in the present situation the A-field is used for the transmission of signalling information, and the B-field for the transmission of user data. A certain signalling capacity is made available in the A-field, which is assigned as necessary to a logic 35 channel such as an I-, C-, Q-, N-, M-, P-channel, defined by the DECT standard. Since 16 DECT frames are always ` 21l39~0 combined into a DECT multi-frame, the data of the logic channels are multiplexed through this DECT multi-frame.
In this way each logic channel of a DECT multi-frame is fully available, for example the synchronization 5 information for the DECT multi-frame, which is required by every cordless terminal of a cell bundle for its multi-frame synchronization, is transmitted in the eighth DECT
frame of the Q-channel.
The DECT standard describes a frequency scanning 10 algorithm for a cordless telecommunications system with several base stations, which can be implemented with a PSCN synchronization, PSCN is short for Primary receiver Scan carrier Number. Since every base station has the entire frequency spectrum assigned by the DECT standard 15 available, each above described base station has ten high-frequency carriers available, where each is subdivided into twelve full duplex transmission paths. Although the PSCN algorithm specifies that all base stations must scan the same frequency at the same point in time, in order to 20 be able to perform a cell change with a cordless terminal, also called a handover, no information is provided for the technical realization. The result is the task of presenting a method for the PSCN synchronization, which can be performed with a small expense for hardware.
Summary of the Invention According to the invention, this task is fulfilled by a method wherein the frames are synchronized by means of a frame alignment pulse and are combined into 30 multiframes and synchronized in the multiframe rhythm by means of a multiframe alignment pulse which follows after a given number of frames, characterized in that a multiframe sequence is synchronized by blanking a multiframe alignment pulse. The nature of the invention 35 includes evaluating missing pulse transmissions for information purposes, and using circuits in multivalent 21~39~
-form to detect errors in units which are used to manage the base stations.
Description of the Drawinqs In the following, the invention will be explained by means of a configuration example. The pertinent drawing illustrates:
Figure 1, a configurationofa cordlesstelecommunications system, and 10 Figure 2, the assembly in principle of a DECT frame, a DECT multi-frame and pulses for the synchronization of frames, multi-frames and PSCN.
15 Detailed Description of the Preferred Embodiment According to figure 1, a cordless telecommunications system, in this instance a cordless WPABX, Wireless Private Area Branch Exchange, essentially comprises a central unit CPU, which manages different interface 20 circuits via a system bus. Such an installation can be used as an autonomous installation for connecting wired and/or cordless terminals. However, it is also possible to connect the installation to existing networks. The connection to a Public Switched Telephone Network PSTN is 25 possible via the interface circuit for analog exchange lines, and the connection to an Integrated Services Digital Network ISDN can take place via the T0-interface circuit. The base stations BS1 ... BS5 are respectively connected by four-wire lines to the DECT interface 30 circuits 1, 2, 3. Each base station BS1 ... BS5 supplies one radio cell in which it establishes the radio connection with the cordless terminals. For example, in the condition illustrated in figure 1, the cordless terminals 11, 12 are located in the radio cell of base 35 station BS1, the cordless terminals 21, 22 are located in the radio cell of base station BS3, and the cordless 21~92~
-terminals 31, 32 in the radio cell of base station BS3.
Each DECT interface circuit 1, 2, 3 contains at least one application-specific circuit MAC-ASIC, to which a base station is connected in each instance. The base stations 5 are controlled, synchronized and remote-supplied via the four-wire line of the DECT interface.
To be able to establish a radio connection to the cordless terminals, each base station scans its radio cell with the ten available high-frequency carriers, in 10 sequence. Each frequency is scanned during the time of a DECT frame, thus for a time of 10 ms. In that way, 16 frequencies are scanned in a multi-frame, namely the frequencies fl to flO and fl to f6. If this scanning rhythm were to be maintained for each multi-frame, the 15 frequencies would be scanned at different times, and the frequencies f7 to flO would be at a disadvantage. It is therefore necessary to scan the frequencies continuously for the duration of five multi-frames, because then each of the ten frequencies is scanned eight times within a 20 time period of 80 DECT frames. Although each DECT
interface circuit 1, 2, 3 itself is synchronized to a multi-frame pulse and continuously scans the frequencies by itself, the synchronization to each other is missing.
This means that, during a cell bundle change, the cordless 25 terminal encounters two base stations that operate asynchronously with each other. Although it is basically possible for the cordless terminal to synchronize itself to the new base station, this however requires a relative long period of time and additional energy. The DECT
30 interface circuits 1, 2, 3 are also synchronized with each other in order to carry out a quick handover at a low expense of energy. This synchronization of the DECT
interface circuits is called a PSCN synchronization.
Figure 2 illustrates an overview of the connection between 35 DECT frames, English DECT frame, multi-frames, English multi-frame, and the pertinent synchronization pulses.
- 21439~
The PSCN synchronization is depicted in figure 2 at the 10th. multi-frame. A PSCN synchronization at a distance of five multi-frames and whole-number multiples thereof would be possible. The distance of ten multi-frames 5 advantageously produces a low load on the central CPU
unit.
According to the invention, the PSCN synchronization takes place by blanking a multi-frame synchronization pulse. Use is made of the fact that an interrupt-signal 10 is released by the DECT interface circuit, when an expected pulse is missing. This interrupt-signal usually serves to detect errors. But if an error is present, not only would a multi-frame synchronization pulse be missing, but also a DECT frame synchronization pulse. In this way, 15 the one-time missing of a multi-frame synchronization pulse can be used for the PSCN-synchronization of all DECT
interface circuits, so that all base stations belonging to a cordless telecommunications installation can scan the radio cells at the same time and at the same frequencies.
20 The PSCN- synchronization is then realized without any additional expense for hardware.
Claims (4)
1. A frame synchronization method wherein the frames are synchronized by means of a frame alignment pulse and are combined into multiframes and synchronized in the multiframe rhythm by means of a multiframe alignment pulse which follows after a given number of frames, characterized in that a multiframe sequence is synchronized by blanking a multiframe alignment pulse.
2. A method as claimed in claim 1, characterized in that in a multicell environment within a telecommunications system based on the DECT standard, the PSCN algorithm described in said standard (PSCN = Primary receiver Scan Carrier Number) is implemented for all base stations by cyclically blanking the respective integral multiples of the fifth DECT multiframe pulses.
3. A method as claimed in claim 2, characterized in that an error detection circuit is used to detect the absence of the DECT multiframe alignment pulse.
4. A method as claimed in claim 3, characterized in that in the absence of a DECT multiframe alignment pulse, the error detection circuit generates a PSCN
synchronizing signal, and that in the absence of a DECT
multiframe alignment pulse and of further DECT frame alignment pulses, an interrupt signal is released which indicates a transmission error.
synchronizing signal, and that in the absence of a DECT
multiframe alignment pulse and of further DECT frame alignment pulses, an interrupt signal is released which indicates a transmission error.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE4407794A DE4407794A1 (en) | 1994-03-09 | 1994-03-09 | Synchronization of the pulse frame |
| DEP4407794.7 | 1994-03-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2143930A1 true CA2143930A1 (en) | 1995-09-10 |
Family
ID=6512223
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002143930A Abandoned CA2143930A1 (en) | 1994-03-09 | 1995-03-03 | Frame synchronization method |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0671825B1 (en) |
| AT (1) | ATE208105T1 (en) |
| CA (1) | CA2143930A1 (en) |
| DE (2) | DE4407794A1 (en) |
| ES (1) | ES2162873T3 (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19523489A1 (en) * | 1995-06-28 | 1997-01-02 | Sel Alcatel Ag | Method and circuit arrangement for the synchronization of pulse frames in multicellular telecommunications systems |
| DE19548153C2 (en) * | 1995-09-21 | 2001-10-31 | Deutsche Telephonwerk Kabel | Procedure for the synchronization of the exchange of characters between a private branch exchange and a base station |
| DE19543841C1 (en) * | 1995-11-23 | 1996-12-05 | Siemens Ag | Transmission system for DECT standard applications |
| NZ330678A (en) * | 1995-12-15 | 1999-11-29 | Ericsson Telefon Ab L M | Discrete phase locked loop |
| AU716935B2 (en) * | 1995-12-15 | 2000-03-09 | Telefonaktiebolaget Lm Ericsson (Publ) | Error correcting timing reference distribution |
| ATE306756T1 (en) * | 1995-12-22 | 2005-10-15 | Detewe Systems Gmbh | METHOD FOR SYNCHRONIZING CHARACTER EXCHANGE BETWEEN A PBX AND A BASE STATION |
| GB2315194B (en) * | 1996-07-11 | 2000-11-15 | Nokia Mobile Phones Ltd | Method and apparatus for resynchronizing two system clocks |
| DE19630048C1 (en) * | 1996-07-25 | 1997-04-17 | Siemens Ag | Operating method for TDMA radio communication system |
| KR100233710B1 (en) * | 1996-09-25 | 1999-12-01 | 윤종용 | Method for synchronizing synchronous information of each base station in cordtess telephone system |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3511430A1 (en) * | 1985-03-29 | 1986-10-02 | Philips Patentverwaltung Gmbh, 2000 Hamburg | METHOD FOR SYNCHRONIZING THE RECEIVING DEVICES IN A DIGITAL MULTIPLEX TRANSMISSION SYSTEM |
| JPH0824388B2 (en) * | 1987-01-16 | 1996-03-06 | 日本電信電話株式会社 | Connection control system for cordless telephone system |
| JPS63278436A (en) * | 1987-05-11 | 1988-11-16 | Nec Corp | Multi-frame synchronizing system |
| EP0419895B1 (en) * | 1989-09-27 | 1995-11-29 | Siemens Aktiengesellschaft | Clocksupply for multiplexsystems |
| EP0437835B1 (en) * | 1989-12-27 | 1995-04-26 | Nec Corporation | Frame synchronization system among multiple radio base stations for TDMA digital mobile communication system |
| US5177740A (en) * | 1991-09-03 | 1993-01-05 | General Electric Company | Frame/slot synchronization for U.S. digital cellular TDMA radio telephone system |
| US5274628A (en) * | 1992-04-24 | 1993-12-28 | Digital Equipment Corporation | Multisignal synchronizer with shared last stage |
-
1994
- 1994-03-09 DE DE4407794A patent/DE4407794A1/en not_active Withdrawn
-
1995
- 1995-03-03 CA CA002143930A patent/CA2143930A1/en not_active Abandoned
- 1995-03-07 DE DE59509767T patent/DE59509767D1/en not_active Expired - Fee Related
- 1995-03-07 EP EP95103233A patent/EP0671825B1/en not_active Expired - Lifetime
- 1995-03-07 ES ES95103233T patent/ES2162873T3/en not_active Expired - Lifetime
- 1995-03-07 AT AT95103233T patent/ATE208105T1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| DE4407794A1 (en) | 1995-09-14 |
| DE59509767D1 (en) | 2001-12-06 |
| EP0671825B1 (en) | 2001-10-31 |
| EP0671825A1 (en) | 1995-09-13 |
| ATE208105T1 (en) | 2001-11-15 |
| ES2162873T3 (en) | 2002-01-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |