Cellular communication system

• US 6,212,395 B1
• Filed: 09/11/1997
• Issued: 04/03/2001
• Est. Priority Date: 05/04/1995
• Status: Expired due to Fees

• Current Assignee: LGC Wireless Incorporated (TE Connectivity Limited)
• Original Assignee: Interwave Communications International SA (Alvarion Limited)
• Inventors: Lu, Priscilla Marilyn, White, Timothy Richard
• Primary Examiner(s): Tsang, Fan
• Assistant Examiner(s): SOBUTKA, PHILIP
• Application Number:
  US08/927,353
• Time in Patent Office: 1,300 Days
• Field of Search: 455/462, 455/463, 455/464, 455/465, 455/461, 455/403, 455/417, 455/422, 455/525, 455/550, 455/554, 455/555, 455/560, 455/561, 455/445
• US Class Current: 455/463
• CPC Class Codes: H04M 2215/2026 Wireless network, e.g. GSM, PCS, TACS
• CPC Class Codes: H04M 2215/32 Involving wireless systems
• CPC Class Codes: H04W 16/18 Network planning tools
• CPC Class Codes: H04W 4/24 Accounting or billing
• CPC Class Codes: H04W 88/085 Access point devices with remote components
• CPC Class Codes: H04W 88/10 adapted for operation in multiple networks, e.g. multi-mode access points
• CPC Class Codes: H04W 92/04 Interfaces between hierarchically different network devices
• CPC Class Codes: H04W 92/12 between access points and access point controllers
• CPC Class Codes: H04W 92/14 between access point controllers and backbone network device

Abstract

A cellular private branch exchange for facilitating cellular communication for a first plurality of mobile station units, which includes a first base station subsystem for communicating with a first and a second mobile station unit of the first plurality of mobile station units on respectively a first and a second cellular bearer data channel. The cellular private branch exchange further includes a cellular private branch exchange unit coupled to the first base station subsystem. In turn, the cellular private branch exchange unit includes a private mobile-services switching center for providing mobility management for the first plurality of mobile station units, the private mobile-services switching center representing a first cross-connect node capable of cross-connecting the first bearer data channel with the second bearer data channel for calls between the first and the second mobile station units. Further the cellular private branch exchange unit includes a private registry coupled to the private mobile-services switching center, the private registry storing subscriber information pertaining to the first plurality of mobile station units.

Claims

1. A cellular private branch exchange system for facilitating cellular communication for a first plurality of mobile station units, said cellular private branch exchange system also being configured for coupling with a public switching network, said cellular private branch exchange system comprising:

a first base station for communicating with first and second mobile station units of said first plurality of mobile station units on respectively a first and a second cellular bearer data channels wherein said first mobile station unit communicates with said second mobile station through said first base station; and

a cellular private branch exchange unit coupled to said first base station subsystem, said cellular private branch exchange unit being associated with at least one given public switching network telephone number known to said public switching network, said cellular private branch exchange unit comprising;

(a) a private mobile-services switching center for providing, in a cellular domain, mobility management for said first plurality of mobile station units, said private mobile-services switching center representing a first cross-connect node capable of cross-connecting said first cellular bearer data channel with said second cellular bearer data channel for calls between said first and said second mobile station units;

(b) a private registry coupled to said private mobile-services switching center, said private registry being decoupled from a registry associated with said public switching network, said private registry storing subscriber information pertaining to said first plurality of mobile station units, and

(c) a private exchange block for handling, in said cellular domain, call control for said first plurality of said mobile station units wherein said cellular private branch exchange system facilitates said cellular communication between said first mobile station unit and said second mobile station unit even if said first mobile station unit and said second mobile station unit are unknown to said public switching network.

2. The cellular private branch exchange system of claim 1 wherein a call path between said first and said second mobile station units, including said first cellular bearer data channel and said second cellular bearer data channel, for said calls between said first and said second mobile station units does not get transcoder rate adapted if said first and said second mobile station units communicate at the same rate.

3. The cellular private branch exchange system of claim 2 wherein a call path between said first and said second mobile station units, including said first cellular bearer data channel and said second cellular bearer data channel, for said calls between said first and said second mobile station units gets transcoder rate adapted only if said first and said second mobile station units communicate at different rates.

4. The cellular private branch exchange system of claim 3 wherein said cellular private branch exchange unit further comprises an external network interface for coupling said cellular private branch exchange to said public switching network and call paths for calls between said first mobile station unit and a telephone set in said public switching network are transcoder rate adapted.

5. The cellular private branch exchange system of claim 4 wherein a second plurality of mobile station units, which are not registered with said registry, are barred from using resources of said cellular private branch exchange for communicating with said public switching network.

6. The cellular private branch exchange system of claim 4 wherein a second plurality of mobile station units which are not registered with said private registry are barred from using resources of said cellular private branch exchange for communicating with any one of said first plurality of mobile station units.

7. The cellular private branch exchange system of claim 6 wherein said first and second plurality of mobile station units are standard GSM units.

8. The cellular private branch exchange system of claim 7 wherein said public switching network is a wired PSTN network.

9. The cellular private branch exchange system of claim 4 wherein said first plurality of mobile station units represent standard GSM units.

10. The cellular private branch exchange system of claim 1 wherein said private branch exchange block further contains circuits for performing private branch exchange functions.

11. The cellular private branch exchange system of claim 10 wherein said private branch exchange functions comprise call forwarding and call transfer among said first plurality of mobile station units.

12. The cellular private branch exchange system of claim 1 wherein said first plurality of mobile station units represent standard GSM units.

13. The cellular private branch exchange system of claim 1 wherein said first base station subsystem and said private mobile-services switching center co-locate on the same back plane of a physical chassis.

14. The cellular private branch exchange system of claim 1 wherein said first base station subsystem and said private mobile-services switching center are deployed at geographically dispersed locations from one another, said first base station subsystem and private mobile-services switching center are both implemented on physical chassis having identical back plane.

15. The cellular private branch exchange system of claim 1 wherein said first base station subsystem is a second cross-connect node capable of cross-connecting said first cellular bearer data channel with said second cellular bearer data channel for calls between said first and said second mobile station units.

16. The cellular private branch exchange system of claim 1, wherein:

said first base station provides at least a first and second cell wherein said first mobile station unit communicates from said first cell and said second mobile station unit communicates from said second cell such that said first mobile station unit communicates with said second mobile station through said first base station.

17. The cellular private branch exchange system of claim 1, further comprising:

said base station including at least one base station controller configured to provide at least a first and second cell wherein said first mobile station unit communicates from said first cell and said second mobile station unit communicates from said second cell such that said first mobile station unit communicates with said second mobile station through said at least one base station controller.

18. The cellular private branch exchange system of claim 1, further comprising:

said base station including at least one base station transceiver configured to provide at least a first and second cell wherein said first mobile station unit communicates from said first cell and said second mobile station unit communicates from said second cell such that said first mobile station unit communicates with said second mobile station through said at least one base station transceiver.

19. A cellular private branch exchange system for facilitating cellular communication for a first plurality of mobile station units, said cellular private branch exchange system also being configured for coupling with a public switching network, said cellular private branch exchange system comprising:

a first base station subsystem for communicating with first and second mobile station units of said first plurality of mobile station units on respectively a first and a second cellular bearer data channels; and

a cellular private branch exchange unit coupled to said first base station subsystem, said cellular private branch exchange unit being associated with a given public switching network telephone number known to said public switching network, wherein said cellular private branch exchange unit appears to said public switching network substantially like a wired private branch exchange (PBX), said cellular private branch exchange unit comprising;

(a) a private mobile-services switching center for providing, in a cellular domain, mobility management for said first plurality of mobile station units, said private mobile-services switching center representing a first cross-connect node capable of cross-connecting said first cellular bearer data channel with said second cellular bearer data channel for calls between said first and said second mobile station units;

(b) a private registry coupled to said private mobile-services switching center, said private registry being decoupled from a registry associated with said public switching network, said private registry storing subscriber information pertaining to said first plurality of mobile station units,

(c) a private exchange block for handling, in said cellular domain, call control for said first plurality of said mobile station units wherein said cellular private branch exchange system facilitates said cellular communication between said first mobile station unit and said second mobile station unit even if said first mobile station unit and said second mobile station unit are unknown to said public switching network; and

wherein said first base station subsystem and said private mobile-services switching center are deployed at geographically dispersed locations from one another, said first base station subsystem being implemented on a first physical chassis having a first back plane having a first number of slots and comprising a first TDM bus and a first control bus, said private mobile-services switching center being implemented on second physical chassis having a second back plane comprising a second TDM bus having the same features as said first TDM bus and a second control bus having the same features as said first control bus, wherein said second back plane having a second number of slots different from said first number of slots.

20. A cellular private branch exchange network for facilitating cellular communication among a first plurality of mobile station units implementing a first standard, said cellular private branch exchange network also being configured for coupling with a public switching network, said cellular private branch exchange network being associated with at least one given public switching network telephone number known to said public switching network, said cellular private branch exchange network comprising:

a private mobile services switching center for providing mobility management in a cellular domain for said first plurality of mobile station units wherein a first mobile station unit of said first plurality of mobile station units communicates through said private mobile services switching center with a second mobile station unit of said first plurality of mobile station units;

a private branch exchange block coupled to said private mobile services switching center for providing private branch exchange functions in said cellular domain for said first plurality of mobile station units; and

a registry coupled to at least one of said private mobile switching center and said private branch exchange block, said registry storing subscriber information pertaining to said first plurality of mobile station units, wherein said cellular private branch exchange network facilitates said cellular communication among said first plurality of mobile station units and between individual ones of said first plurality of said mobile station units with a telephone set outside of said cellular private branch exchange network but coupled to said public switching network even if mobile stations of said first plurality of mobile station units are unknown to said public switching network.

21. The cellular private branch exchange network of claim 20, further comprising a plurality of base station controllers coupled to said private mobile services switching center, said private mobile services switching center provides roaming and handoff capabilities for said first plurality of mobile station units when a first selected one of said first plurality of mobile station units roam among location areas controlled by said plurality of base station controllers.

22. The cellular private branch exchange network of claim 21 further comprising a plurality of base transceiver stations coupled to a first one of said plurality of base station controllers, a first one of said plurality of base transceiver stations couple using an air interface with said first plurality of mobile station units, said first one of said plurality of plurality of base station controllers handle roaming and handoff capabilities when a second selected one of said first plurality of mobile station units roam among location areas controlled by said plurality of base transceiver stations.

23. The cellular private branch exchange network of claim 22 wherein said first standard is a GSM standard.

24. The cellular private branch exchange network of claim 22 wherein said first one of said plurality of base station controllers includes a first transcoder rate adapter unit for performing rate conversion between a first mobile station unit and a second mobile station unit of said first plurality of mobile station units.

25. The cellular private branch exchange network of claim 24 wherein said first transcoder rate adapter unit does not perform rate conversion for calls between mobile station units of said first plurality of mobile station units that communicate at the same rate.

26. The cellular private branch exchange network of claim 24 wherein cellular bearer data channels from both said first mobile station unit and said second mobile station unit are cross connected at said first one of said plurality of base station controllers if both said first mobile station unit and said second mobile station unit are controlled by said first one of said plurality of base station controllers.

27. The cellular private branch exchange network of claim 22 wherein said first one of said plurality of base transceiver stations includes a first transcoder rate adapter unit for performing rate conversion between a first mobile station unit and a second mobile station unit of said first plurality of mobile station units.

28. The cellular private branch exchange network of claim 27 wherein said first transcoder rate adapter unit does not perform rate conversion for calls between mobile station units of said first plurality of mobile station units that communicate at the same rate.

29. The cellular private branch exchange network of claim 27 wherein cellular bearer data channels from both said first mobile station unit and said second mobile station units are cross connected at said first one of said plurality of base transceiver stations if both said first mobile station unit and said second mobile station unit are controlled by said first one of said plurality of base transceiver stations.

30. A cellular private branch exchange configured for coupling to at least one base station subsystem to form a cellular private branch exchange system for facilitating cellular communication for a first plurality of mobile station units, said cellular private branch further being configured for coupling to a public switching network, said cellular private branch exchange comprising:

a cellular private branch exchange unit configured for coupling to said at least one base station, said cellular private branch exchange being associated with at least one given public switching network telephone number known to said public switching network, said cellular private branch exchange unit comprising;

a private mobile service switching center for providing, in a cellular domain, mobility management for said first plurality of mobile station units through said at least one base station subsystem;

a private branch exchange block coupled to said private mobile service switching center, said private branch exchange block representing a first cross-connect node capable of cross-connecting a first cellular bearer data channel with a second cellular bearer data channel for calls between a first mobile station unit of said first plurality of mobile station units and a first phone set, said first phone set representing one of a second mobile station unit of said first plurality of mobile station units and a phone set outside said cellular private branch exchange system but coupled to said public switching network, said first mobile station unit being configured for communicating in a full duplex, cellular manner with said at least one base station subsystem on said first bearer data channel, and

a registry coupled to at least one of said private mobile switching center and said private branch exchange block, said registry storing subscriber information pertaining to said first plurality of mobile station units, wherein said cellular private branch exchange system facilitates said cellular communication between said first mobile station unit and said second mobile station unit without intervention by the public switching network, thereby allowing additional communication features to be added to said cellular private branch exchange system without any chances in said public switching network, said cellular private branch exchange system further facilitates said cellular communication between said first mobile station unit and said phone set outside said cellular private branch exchange system but coupled to said public switching network even if said first mobile station unit is unknown to said public switching network.

31. The cellular private branch exchange of claim 30 wherein said private registry is decoupled from a registry associated with said public switching network.

32. The cellular private branch exchange of claim 30 wherein said first plurality of mobile station units are standard GSM units.

33. The cellular private branch exchange of claim 30 wherein said public switching network is a PLMN network.

34. The cellular private branch exchange of claim 30 wherein said public switching network is a wired PSTN network.

35. The cellular private branch exchange of claim 30 wherein transcoder rate adaptation resource is provided in the base station subsystem and the cellular private branch exchange but a call path between said first and said second mobile station units, including said first cellular bearer data channel and said second cellular bearer data channel, for said calls between said first and said second mobile station units does not get transcoder rate adapted if said first and said second mobile station units communicate at the same rate.

36. The cellular private branch exchange of claim 30 wherein transcoder rate adaptation resource is provided in the base station subsystem and the cellular private branch exchange and a call path between said first and said second mobile station units, including said first cellular bearer data channel and said second cellular bearer data channel, for said calls between said first and said second mobile station units gets transcoder rate adapted only if said first and said second mobile station units communicate at different rates.

37. The cellular private branch exchange of claim 36 wherein said cellular private branch exchange unit further comprises an external network interface for coupling said cellular private branch exchange to said public switching network and call paths for calls between said first mobile station unit and a telephone set in said public switching network are transcoder rate adapted.

38. A cellular private branch exchange configured for coupling to at least one base station subsystem to form a cellular private branch exchange system for facilitating cellular communication for a first plurality of mobile station units, said cellular private branch further being configured for coupling to a public switching network, said cellular private branch exchange comprising:

a cellular private branch exchange unit configured for coupling to said at least one base station subsystem, said cellular private branch exchange being associated with a given public switching network telephone number known to said public switching network, wherein said cellular private branch exchange appears to said public switching network substantially like a wired private branch exchange (PBX), said cellular private branch exchange unit comprising;

private mobile service switching center for providing, in a cellular domain, mobility management for said first plurality of mobile station units through said at least one base station subsystem;

a private branch exchange block coupled to said private mobile service switching center, said private branch exchange block representing a first cross-connect node capable of cross-connecting a first cellular bearer data channel with a second cellular bearer data channel for calls between a first mobile station unit of said first plurality of mobile station units and a first phone set, said first phone set representing one of a second mobile station unit of said first plurality of mobile station units and a phone set outside said cellular private branch exchange system but coupled to said public switching network, said first mobile station unit being configured for communicating in a full duplex, cellular manner with said at least one base station subsystem on said first bearer data channel,

a register coupled to at least one of said private mobile switching center and said private branch exchange block, said registry storing subscriber information pertaining to said first plurality of mobile station units, wherein said cellular private branch exchange system facilitates said cellular communication between said first mobile station unit and said second mobile station unit without intervention by the public switching network, thereby allowing additional communication features to be added to said cellular private branch exchange system without any chances in said public switching network, said cellular private branch exchange system further facilitates said cellular communication between said first mobile station unit and said phone set outside said cellular private branch exchange system but coupled to said public switching network even if said first mobile station unit is unknown to said public switching network; and

the cellular private branch exchange further configured for coupling with another cellular private branch exchange via a direct link, said another cellular private branch exchange facilitates cellular communication for a second plurality of mobile station units, wherein calls between one of said second plurality of mobile station units and said first phone set are cross connected via said direct link, said direct link being external to said public switching network.

39. The cellular private branch exchange of claim 38 further configured for facilitating cellular communication to and from a given one of said second plurality of mobile station units when said given one of said second plurality of mobile station units roams within a domain of said cellular private branch exchange.

40. A cellular private branch exchange configured for coupling to at least one base station subsystem to form a cellular private branch exchange system for facilitating cellular communication for a first plurality of mobile station units, said cellular private branch further being configured for coupling to a public switching network, said cellular private branch exchange comprising:

a cellular private branch exchange unit configured for coupling to said at least one base station subsystem, said cellular private branch exchange being associated with a given public switching network telephone number known to said public switching network, wherein said cellular private branch exchange appears to said public switching network substantially like a wired private branch exchange (PBX), said cellular private branch exchange unit comprising;

a private mobile service switching center for providing, in a cellular domain, mobility management for said first plurality of mobile station units through said at least one base station subsystem;

a private branch exchange block coupled to said private mobile service switching center, said private branch exchange block representing a first cross-connect node capable of cross-connecting a first cellular bearer data channel with a second cellular bearer data channel for calls between a first mobile station unit of said first plurality of mobile station units and a first phone set, said first phone set representing one of a second mobile station unit of said first plurality of mobile station units and a phone set outside said cellular private branch exchange system but coupled to said public switching network, said first mobile station unit being configured for communicating in a full duplex, cellular manner with said at least one base station subsystem on said first bearer data channel,

a registry coupled to at least one of said private mobile switching center and said private branch exchange block, said registry storing subscriber information pertaining to said first plurality of mobile station units, wherein said cellular private branch exchange system facilitates said cellular communication between said first mobile station unit and said second mobile station unit without intervention by the public switching network, thereby allowing additional communication features to be added to said cellular private branch exchange system without any chances in said public switching network, said cellular private branch exchange system further facilitates said cellular communication between said first mobile station unit and said phone set outside said cellular private branch exchange system but coupled to said public switching network even if said first mobile station unit is unknown to said public switching network; and

the cellular private branch exchange further configured for coupling with a wired private branch exchange via a first direct link, said wired private branch exchange facilitates communication for a plurality of wired phones, wherein calls between one of said plurality of wired phones and one of said first plurality of mobile station units are cross connected via said first direct link without employing said public switching network.

41. The cellular private branch exchange of claim 40 further configured for coupling with another cellular private branch exchange via a second direct link, said another cellular private branch exchange facilitates cellular communication for a second plurality of mobile station units, wherein calls between one of said second plurality of mobile station units and one of said first plurality of mobile station units are cross connected via said second direct link without employing said public switching network.

42. The cellular private branch exchange of claim 40 further comprising circuits for performing at least one of a call forwarding function and a call transfer function between said one of said plurality of wired phones and said one of said first plurality of mobile station units.

43. A method for simplifying management of cellular communication for a first plurality of mobile station units, said simplifying including providing said cellular communication between a first mobile station unit of said first plurality of mobile station units and a phone set, said phone set representing one of a second mobile station unit of said first plurality of mobile station units and any telephone set coupled to a public switching network, said method including:

providing a cellular private branch exchange unit configured for coupling to at least one base station subsystem;

associating said cellular branch exchange unit with a given public switching network telephone number known to said public switching network, wherein said cellular branch exchange unit appears to said public switching network substantially like a wired private branch exchange (PBX), said cellular branch exchange unit representing a first cross-connect node capable of cross-connecting a first bearer data channel with a second bearer data channel for calls between said first mobile station unit and said second station unit, said cellular branch exchange unit also being configured for cross-connecting said first bearer data channel associated with said first mobile station unit with said public switching network for a call between said first mobile station unit and said any telephone set coupled to said public switching network; and

wherein a incoming call said any telephone set from said public switching network to any of said first plurality of said mobile station units is accomplished by coupling a call circuit associated with said incoming call, using said public switching network telephone number, with said cellular private branch exchange unit, said cellular branch exchange unit being configured to then couple said incoming call with a caller-indicated mobile station unit, thereby permitting said caller-indicated mobile station unit to communicate with said any telephone set in a cellular, full duplex manner even if said caller-indicated mobile station unit is unknown to said public switching network.

44. The method of claim 43 wherein an outgoing call from said first mobile station unit to said a desired telephone set coupled to said public switching network is accomplished by coupling a call circuit associated with said outgoing call with said cellular private branch exchange unit, said cellular private branch exchange unit being configured to then couple said outgoing call with said public switching network to complete a call circuit between said first mobile station unit and said any telephone set, thereby permitting said first mobile station unit to communicate with said desired telephone set in a cellular, full duplex manner even if said first mobile station unit is unknown to said public switching network.

45. The method of claim 43 further comprising providing a first transcoder rate adaptation unit (TRAU) in said cellular private branch exchange unit, wherein a call between said first mobile station unit and said second mobile station unit does not get transcoder rate adapted if said first mobile station unit and said second mobile station unit communicate at the same rate even if a call path between said first mobile station unit and said second mobile station unit traverses a node that has transcoder rate adaptation resource.

46. The method of claim 43 wherein a call between said first mobile station unit and said second mobile station unit is cross-connected at a first node, said first node representing said base station subsystem if sufficient resource exists within said base station subsystem to permit said cellular communication between said first mobile station unit and said second mobile station unit without cross-connecting through said cellular private branch exchange unit, said first node representing said cellular private branch exchange unit if there is insufficient resource in said base station subsystem to permit said cellular communication.

47. A method for simplifying management of cellular communication for a first plurality of mobile station units, said simplifying including providing said cellular communication between a first mobile station unit of said first plurality of mobile station units and a phone set, said phone set representing one of a second mobile station unit of said first plurality of mobile station units and any telephone set coupled to a public switching network, said method including:

providing a cellular private branch exchange unit configured for coupling to at least one base station subsystem;

associating said cellular branch exchange unit with a even public switching network telephone number known to said public switching network, wherein said cellular branch exchange unit appears to said public switching network substantially like a wired private branch exchange (PBX), said cellular branch exchange unit representing a first cross-connect node capable of cross-connecting a first bearer data channel with a second bearer data channel for calls between said first mobile station unit and said second station unit, said cellular branch exchange unit also being configured for cross-connecting said first bearer data channel associated with said first mobile station unit with said public switching network for a call between said first mobile station unit and said any telephone set coupled to said public switching network;

wherein a incoming call said any telephone set from said public switching network to any of said first plurality of said mobile station units is accomplished by coupling a call circuit associated with said incoming call, using said public switching network telephone number, with said cellular private branch exchange unit, said cellular branch exchange unit being configured to then couple said incoming call with a caller-indicated mobile station unit, thereby permitting said caller-indicated mobile station unit to communicate with said any telephone set in a cellular, full duplex manner even if said caller-indicated mobile station unit is unknown to said public switching network; and

coupling a wired PBX interface with said cellular private branch exchange unit, said wired PBX interface being configured for coupling with a wired PBX without employing said public switching network, wherein said cellular private branch exchange unit is configured to permit said first mobile station unit to communicate in a cellular, full duplex manner with a phone set associated with said wired PBX even if said first mobile station unit is unknown to both said public switching network and said wired PBX.

48. A cellular private branch exchange system for facilitating cellular communication for a first plurality of mobile station units, said cellular private branch exchange system also being configured for coupling with a public switching network, said cellular private branch exchange system comprising:

a first base station subsystem for communicating with first and second mobile station units of said first plurality of mobile station units on respectively a first and a second cellular bearer data channels; and

a cellular private branch exchange unit coupled to said first base station subsystem, said cellular private branch exchange unit being associated with a given public switching network telephone number known to said public switching network, wherein said cellular private branch exchange unit appears to said public switching network substantially like a wired private branch exchange (PBX), said cellular private branch exchange unit comprising;

(a) a private mobile-services switching center for providing, in a cellular domain, mobility management for said first plurality of mobile station units, said private mobile-services switching center representing a first cross-connect node capable of cross-connecting said first cellular bearer data channel with said second cellular bearer data channel for calls between said first and said second mobile station units;

(b) a private registry coupled to said private mobile-services switching center, said private registry being decoupled from a register associated with said public switching network, said private registry storing subscriber information pertaining to said first plurality of mobile station units,

(c) a private exchange block for handling, in said cellular domain, call control for said first plurality of said mobile station units wherein said cellular private branch exchange system facilitates said cellular communication between said first mobile station unit and said second mobile station unit even if said first mobile station unit and said second mobile station unit are unknown to said public switching network; and

a second base station subsystem for communicating with a third mobile station unit of said first plurality of mobile station units on a third cellular bearer data channel, said second base station subsystem unit being coupled to said first base station subsystem by a direct link, wherein calls between said third mobile station unit and said first mobile station unit are cross connected via said direct link.