Cellular cordless telecommunications system

• US 6,226,515 B1
• Filed: 11/19/1997
• Issued: 05/01/2001
• Est. Priority Date: 05/31/1995
• Status: Expired due to Fees

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Wewers, Otger, Neuhaus, Ralf, Pauli, Burkhard, Flake, Horst, Ide, Hans-Dieter
• Primary Examiner(s): Tsang, Fan
• Assistant Examiner(s): Ferguson, Keith
• Application Number:
  US08/952,608
• Time in Patent Office: 1,259 Days
• Field of Search: 455/426, 455/560, 455/554, 455/555, 455/445, 455/462, 455/502, 455/501, 455/517, 455/524, 455/550, 370/350, 370/328, 370/329, 370/524
• US Class Current: 455/426.1
• CPC Class Codes: H04B 7/269 Master/slave synchronisation
• CPC Class Codes: H04B 7/2693 Centralised synchronisation, i.e. using external universal time reference, e.g. by using a global positioning system [GPS] or by distributing time reference over the wireline network
• CPC Class Codes: H04J 3/0638 Clock or time synchronisation among nodes; Internode synchronisation synchronization for ring networks H04L12/422; data switching networks with synchronous transmission H04L12/43
• CPC Class Codes: H04M 1/733 with a plurality of base stations connected to a plurality of lines for selection in cordless PBX H04W84/16
• CPC Class Codes: H04M 2250/08 home cordless telephone systems using the DECT standard
• CPC Class Codes: H04Q 11/0457 Connection protocols
• CPC Class Codes: H04Q 11/0471 Terminal access circuits
• CPC Class Codes: H04Q 2213/098 Mobile subscriber
• CPC Class Codes: H04Q 2213/13098 Mobile subscriber
• CPC Class Codes: H04Q 2213/13106 Microprocessor, CPU
• CPC Class Codes: H04Q 2213/13202 Network termination [NT]
• CPC Class Codes: H04Q 2213/13209 ISDN
• CPC Class Codes: H04Q 2213/1322 PBX
• CPC Class Codes: H04Q 2213/1326 Consultation call, broker's call, call hold, toggling
• CPC Class Codes: H04Q 2213/1328 Call transfer, e.g. in PBX
• CPC Class Codes: H04Q 2213/13282 Call forward, follow-me, call diversion
• CPC Class Codes: H04Q 2213/13299 Bus
• CPC Class Codes: H04Q 2213/1332 Logic circuits
• CPC Class Codes: H04Q 2213/13322 Integrated circuits
• CPC Class Codes: H04Q 2213/1336 Synchronisation
• CPC Class Codes: H04Q 2213/298 : Loop or ring system
• CPC Class Codes: H04W 36/18 : for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 48/16 : Discovering, processing access restriction or access information

Abstract

In order to design a cellular cordless telecommunications system which makes it possible to implement a large number of performance features, for example synchronization, roaming, handover, internal links, hold, check-back, transfer etc. in the cellular cordless telecommunications system without any additional wire link between the cordless base stations in the cellular cordless telecommunications system, the cordless base stations are connected to an S₀ bus (i.e., a basic access line for a multi-device configured system).

Claims

1. A cellular cordless telecommunications system comprising:

(a) a large number of cordless base stations which are arranged in radio cells in the cellular cordless telecommunications system and are connected to a wire-based switching center for intercellular telecommunications or telecommunications between cells;

(a1) the switching center having at least one S₀ interface for a basic access multi-device line S₀; and

(a2) each of the cordless base stations having link means for producing an intercellular telecommunications link or a telecommunications link between cells with an S₀ transmitting stage constructed in accordance with a ISO/OSI layer model and with an S₀ receiving stage in accordance with the ISO/OSI (International Organization of Standardization/Open Standardization/Open System Interconnection) layer model, the transmitting and receiving stages being connected to the S₀ interface via an S₀ bus having two B channels and one D channel;

(b) at least one cordless mobile unit which telecommunicates with the cordless base stations;

(c) the cordless base stations, in a master-slave configuration having a master cordless base station and at least one slave cordless base station connected to the S₀ interface of the switching center;

(d) the master cordless base station and the at least one slave cordless base station being structured in terms of the link means such that, once a layer 1 of the S₀ transmitting stage and of the S₀ receiving stage has been set up in accordance with the ISO/OSI layer model, a synchronization message is transmitted between the cordless base stations connected to the S₀ interface, on the S₀ bus from the master cordless base station to the at least one slave cordless base station.

2. The cellular cordless telecommunications system as claimed in claim 1, wherein the link means of the slave cordless base stations are structured such that a received synchronization message is evaluated, and the slave cordless base station being one of abruptly synchronized or continuously synchronized to the master cordless base station, after this evaluation.

3. The cellular cordless telecommunications system as claimed in claim 1, wherein the master cordless base station of the cordless base stations connected to the S₀ interface is that for which further layers of the S₀ transmitting stage and of the S₀ receiving stage are set up first in accordance with the ISO/OSI layer model.

4. The cellular cordless telecommunications system as claimed in claims 1, wherein the master cordless base station is structured in terms of the link means such that the synchronization message transmitted by the master cordless base station is also received and evaluated by the master cordless base station.

5. The cellular cordless telecommunications system as claimed in claim 1, wherein the synchronization message is transmitted in the D channel of the S₀ bus and subsequently, in accordance with an echo function implemented in the S₀ interface, in an E channel.

6. The cellular cordless telecommunications system as claimed in claim 5, wherein the synchronization message is contained in the data field of a data frame in accordance with a LAP-D (Link Access Procedure D-Channel) protocol.

7. The cellular cordless telecommunications system as claimed in claim 1, wherein the synchronization message is transmitted in the B channel of the S₀ bus, which B channel is used for intercellular telecommunications or telecommunications between cells, in that wanted data transmitted in the B channel is replaced to a predetermined extent by the synchronization message.

8. The cellular cordless telecommunications system as claimed in claim 7, wherein the wanted data transmitted in the B channel is replaced by the synchronization message to an extent that transmission quality in the B channel is reduced only insignificantly by a reduction in a signal-to-noise ratio in the B channel.

9. The cellular cordless telecommunications system as claimed in claim 8, wherein each last bit of every fourth PCM octet of the wanted data transmitted in the B channel is replaced by the synchronization message.

10. The cellular cordless telecommunications system as claimed in claim 1, wherein the synchronization message is transmitted in the D channel of the S₀ bus in packet data form.

11. The cellular cordless telecommunications system as claimed in claim 10, wherein synchronization message is transmitted in the B channel in a data packet which, in terms of packet structure, is similar to an HDLC (High Data Link Control) data packet.

12. The cellular cordless telecommunications system as claimed in claim 7, wherein the means have a receiving device which is connected to the S₀ bus in parallel with an S₀ transmitting stage.

13. The cellular cordless telecommunications system as claimed in claim 1, wherein the link means for reception and for evaluation of the transmitted synchronization message are structured such that the synchronization message is identified and a trigger signal is derived from the synchronization message in substantially real time.

14. The cellular cordless telecommunications system as claimed in claim 1, wherein the link means are structured such that, for each cordless base station connected to the S₀ interface, once or continuously,

(a) a first data set is identified which initiates transmission of a data frame in accordance with a LAP-D (Link Access Procedure D-Channel) protocol;

(b) a bus-related data word is produced from a second data set in data frame, following the first data set, in accordance with a predetermined generation rule which is predetermined in a standard manner for all the cordless base stations;

(c) a base-station-specific time interval between a starting time of a radio time frame which occurs cyclically for channel related cordless transmission in a radio cell and a time of production of a bus-related data word is detected in a base-station-specific, radio-related data word form,

(d) a base-station-specific synchronization signature is formed from the bus-related data word and from the base-station-specific, radio-related data word, is stored and links S₀ bus timing to a base-station-specific radio timing.

15. The cellular cordless telecommunications system as claimed in claim 14, wherein the generation rule is based on polynomial division used to form CRC values.

16. The cellular cordless telecommunications system as claimed in claim 14, wherein the synchronization message is formed as a master synchronization signature, which corresponds to a synchronization signature of the master cordless base station.

17. The cellular cordless telecommunications system as claimed in claim 16, wherein the link means for producing the intercellular telecommunications link are structured such that

(a) a radio-related master data word which is transmitted with the received master synchronization signature is compared with the corresponding radio-related data word stored in the receiving slave cordless base station;

and

(b) if a difference is found between the data word to be compared, the starting time of the radio time frame indicated by the radio-related data word of the receiving slave cordless based station is corrected in a corresponding manner to the difference found.

18. The cellular cordless telecommunications system as claimed in claim 1, wherein the switching center is structured according to a Euro-ISDN (Euro-Integrated Services Digital Network) Standard.

19. The cellular cordless telecommunications system as claimed in claim 18, wherein

(a) the cordless base stations in a master-slave configuration having a master cordless base station and at least one slave cordless base station, are connected to the S₀ interface of the switching center, a first radio link being set up between the master cordless base station and a first cordless mobile unit during intercellular telecommunications or telecommunications between cells;

(b) the first cordless mobile unit is structured such that a second radio link to a second cordless base station is set up in the background and is useable as a telecommunications link during the intercellular telecommunications or telecommunications between cells;

(c) the switching center has a service feature “

terminal portability”

;

(d) the ink means for producing the intercellular telecommunications link or telecommunications link between cells as well as the switching center are structured such that, if radio quality of the second radio link is better than or equal to radio quality of the first radio link, the service feature “

terminal portability”

, which is available in the switching center, is utilized such that the second radio link serves as a new telecommunications link during the intercellular telecommunications or telecommunications between cells.

20. The cellular cordless telecommunications system as claimed in claim 1, wherein

(a) the cordless base stations in a master-slave configuration having a master cordless base station and at least one slave cordless base station, are connected to the S₀ interface of the switching center, a first radio link being set up between the master cordless station and the first cordless mobile unit during intercellular telecommunications or telecommunications between cells;

(b) the first cordless mobile unit is structured such that a second radio link to the second cordless base station is set up in the background and is useable as a telecommunications link during the intercellular telecommunications or telecommunications between cells;

(c) the master cordless base station and the at least one slave cordless base station are structured in terms of the link means such that a handover-relevant message is transmitted local intercommunication between the cordless base stations connected to the S₀ interface, on the S₀ bus from the master cordless base station to the at least one slave cordless base station.

21. The cellular cordless telecommunications system as claimed in claim 20, wherein the master cordless base station is structured in terms of the link means such that the message transmitted by the master cordless base station is also received and evaluated by the master cordless base station.

22. The cellular cordless telecommunications system as claimed in claim 1, wherein the link means have a receiving device which is connected to the S₀ bus in parallel with an S₀ transmitting stage.

23. The cellular cordless telecommunications system as claimed in claim 20, wherein the message is transmitted in the D channel of the S₀ bus and subsequently, in accordance with an echo function implemented in the S₀ interface, in an E channel.

24. The cellular cordless telecommunications system as claimed in claim 23, wherein the message is contained in a data field of a data frame in accordance with a LAP-D (Link Access Procedure D-Channel) protocol.

25. The cellular cordless telecommunications system as claimed in claim 20, wherein the message is transmitted in the B channel of the S₀ bus, which B channel is used for intercellular telecommunications or telecommunications between cells, in that wanted data transmitted in the B channel is replaced to a predetermined extent by the message.

26. The cellular cordless telecommunications system as claimed in claim 25, wherein the wanted data transmitted in the B channel is replaced by the message to an extent that transmission quality in the B channel is reduced only insignificantly by a reduction in signal-to-noise ratio in the B channel.

27. The cellular cordless telecommunications system as claimed in claim 26, wherein a last bit of every fourth PCM (Pulse Code Modulation) octet of the wanted data transmitted in the B channel is replaced by the message.

28. The cellular cordless telecommunications system as claimed in claim 25, wherein the message is transmitted in the B channel in a data packet which, in terms of the packet structure, is similar to an HDLC data packet.

29. The cellular cordless telecommunications system as claimed in claim 20, wherein the message is transmitted in the D channel of the S₀ bus in the packet data form.

30. The cellular cordless telecommunications system as claimed in claim 20, wherein the link means for reception and for evaluation of the transmitted message are structured such that handover-relevant information transmitted with the message is identified, and is used for virtually interruption-free handover, in substantially real time.

31. The cellular cordless telecommunications system as claimed in claim 30, wherein the handover relevant information contains telecommunications-specific identifiers.

32. The cellular cordless telecommunications system as claimed in claim 1, wherein the switching center is a digital local switching center with an upstream network termination.

33. The cellular cordless telecommunications system as claimed in claim 1, wherein the switching center is a private branch exchange.

34. The cellular cordless telecommunication system as claimed in claim 1, wherein the system further comprises a cordless base station having link means for producing an intercellular telecommunications link or a telecommunications link between cells, having an S₀ transmitting stage structured in accordance with the ISO/OSI layer model, and having an S₀ receiving stage in accordance with the ISO/OSI layer model, which stages are connectable to an S₀ interface of the switching center via an S₀ bus having two B channels and one D channel.

35. A cellular cordless telecommunications system, comprising:

(a) a large number of cordless base stations which are arranged in radio cells in the cellular cordless telecommunications system and are connected to a wire-based switching center for intercellular telecommunications or telecommunications between cells;

(a1) the switching center having at least one S₀ interface; and

(a2) each of the cordless base stations having link means for producing an intercellular telecommunications link or a telecommunications link between cells with an S₀ transmitting stage constructed in accordance with a ISO/OSI layer model and with an S₀ receiving stage in accordance with the ISO/OSI layer model, transmitting and receiving stages being connected to the S₀ interface via an S₀ bus having two B channels and one D channel;

(b) at least one cordless mobile unit which telecommunicates with the cordless base stations;

(c) the switching center structured according to a Euro-ISDN Standard;

(d) the cordless base stations in a master-slave configuration having a master cordless base station and at least one slave cordless base station, connected to the S₀ interface of the switching center, a first radio link being set up between the master cordless base station and a first cordless mobile unit as a telecommunications link during intercellular telecommunications or telecommunications between cells;

(e) the first cordless mobile unit structured such that a second radio link to a second cordless base station is set up in the background and is useable as a telecommunications link during the intercellular telecommunications or telecommunications between cells;

(f) the switching center having a service feature “

terminal portability”

;

(g) the link means for producing the intercellular telecommunications link or telecommunications link between cells as well as the switching center structured such that, if radio quality of the second radio link is better than or equal to radio quality of the first radio link, the service feature “

terminal portability”

, which is available in the switching center, is utilized such that the second radio link serves as a new telecommunications link during the intercellular telecommunications or telecommunications between cells.

36. The cellular cordless telecommunication system as claimed in claim 35, wherein the system further comprises a cordless base station having link means for producing an intercellular telecommunications link or a telecommunications link between cells, having an S₀ transmitting stage structured in accordance with the ISO/OSI layer model, and having an S₀ receiving stage in accordance with the ISO/OSI layer model, which stages are connectable to an S₀ interface of the switching center via an S₀ bus having two B channels and one D channel.

37. The cellular cordless telecommunications system as claimed in claim 35, wherein the switching center is a digital local switching center with an upstream network termination.

38. The cellular cordless telecommunications system as claimed in claim 35, wherein the switching center is a private branch exchange.

39. A cellular cordless telecommunications system comprising:

(a) a large number of cordless base stations which are arranged in radio cells in the cellular cordless telecommunications system and are connected to a wire-based switching center for intercellular telecommunications or telecommunications between cells;

(a1) the switching center having at least one S₀ interface for a basic access multi-device line S₀; and

(a2) each of the cordless base stations having link means for producing an intercellular telecommunications link or a telecommunications link between cells with an S₀ transmitting stage constructed in accordance with a ISO/OSI layer model and with an S₀ receiving stage in accordance with the ISO/OSI (International Organization of Standardization/Open Standardization/Open System Interconnection) layer model, the transmitting and receiving stages being connected to the S₀ interface via an S₀ bus having two B channels and one D channel;

(b) at least one cordless mobile unit which is capable of telecommunications with the cordless base stations;

(c) the cordless base stations in a master-slave configuration having a master cordless base station and at least one slave cordless base station connected to the S₀ interface of the switching center, a first radio link being set up between the master cordless base station and a first cordless mobile unit in the course of intercellular telecommunications or telecommunications between cells;

(d) the first cordless mobile unit structured such that a second radio link to a second cordless base station is set up in the background and is utilized as a telecommunications link during the intercellular telecommunications or telecommunications between cells;

(e) the master cordless base station and the at least one slave cordless base station being structured in terms of the link means such that a handover-relevant message is transmitted during local intercommunication between the cordless base stations connected to the S₀ interface, on the S₀ bus from the master cordless base station to the at least one slave cordless base station.

40. The cellular cordless telecommunication system as claimed in claim 39, wherein the system further comprises a cordless base station having link means for producing an intercellular telecommunications link or a telecommunications link between cells, having an S₀ transmitting stage structured in accordance with the ISO/OSI layer model, and having an S₀ receiving stage in accordance with the ISO/OSI layer model, which stages are connectable to an S₀ interface of the switching center via an S₀ bus having two B channels and one D channel.

41. The cellular cordless telecommunications system as claimed in claim 39, wherein the switching center is a digital local switching center with an upstream network termination.

42. The cellular cordless telecommunications system as claimed in claim 39, wherein the switching center is a private branch exchange.