WO1999025143A1

WO1999025143A1 - Method and apparatus for increasing traffic channels within an amps/is-136 cellular system

Info

Publication number: WO1999025143A1
Application number: PCT/US1998/023853
Authority: WO
Inventors: Rajaram Ramesh; Kumar Balachandran
Original assignee: Ericsson Inc.
Priority date: 1997-11-12
Filing date: 1998-11-11
Publication date: 1999-05-20
Also published as: TW379494B; CA2309682A1; AU1391299A

Abstract

A base station providing communications with both AMPS and IS-136 mobile stations is disclosed. The base station includes a plurality of radio units providing a carrier signal. Each radio unit is selectively configurable to operate in at least one of a first idle state, a second state wherein the carrier signal operates according to the AMPS protocol, and a third state wherein the carrier signal operates according to the IS-136 protocol. A controller responsive to receipt of a call requests from a mobile unit switches the carrier signal between the first, second and third states.

Description

METHOD AND APPARATUS FOR INCREASING TRAFFIC CHANNELS WITHIN AN AMPS/IS-136 CELLULAR SYSTEM

BACKGROUND OF THE INVENTION Technical Field of the Invention

The present invention relates to AMPS/IS-136 cellular systems, and more particularly, to a method for increasing the flexibility with which an AMPSJS-136 cellular system may deal with short terms variations in traffic load levels. Description of Related Art Existing AMPSJS-136 cellular telephone systems provide the capability for both AMPS and IS-136 mobile stations to receive cellular communication services from a single base station. These types of systems provide carriers for mobile telecommunication services to .AMPS mobile station users and to triple data rate and normal rate IS-136 mobile station users. Existing AMPS/IS-136 cellular systems provide at the base station a fixed pool of AMPS radios and a fixed pool of IS-136 radios for providing the signal carriers for communicating with AMPS and IS-136 mobile stations.

This system is adequate as long as the number of AMPS or IS-136 calls being served by the base station is less than the total number of AMPS or IS-136 radios. However, once all of the .AMPS radios are serving a call and an additional AMPS call comes in, the additional call may not be served even though IS- 136 channels may be available. Likewise, if all IS-136 radios are being utilized, a subsequent IS-136 call may not be serviced. This provides the potential for a user to be blocked out of contacting a base station even though additional system resources exist for providing a carrier, although according to a differing protocol.

Thus, a manner for maximizing the number of available channels within an AMPS/IS- 136 cellular system is desired such that a user is not denied access to a base station unless no physical resources are available for providing the call connection. This improvement would enable a AMPSJS- 136 cellular system to have the flexibility to cope with short-term variations in traffic levels of the system. SUMMARY OF THE INVENTION

The present invention overcomes the foregoing and other problems with a system enabling commumcations between a base station and mobile stations utilizing a variety of types of communication protocols. The base station includes a plurality of reconfigurable radio units that each provide a carrier signal for communications with the mobile stations. The radio units are configurable to provide communications between the base station and the mobile stations according to at least first and second commumcations protocols. In a preferred embodiment, the communications protocols comprise the AMPS communications protocol and the IS- 136 communications protocol.

A control means located within either the base station or a mobile switching center associated with the base station automatically reconfigures a radio unit to provide a carrier signal according to the AMPS communications protocol in response to receipt of a call request at the base station by a mobile station using the AMPS communications protocol. Likewise, the control means automatically reconfigures the radio unit to provide a carrier signal according to the IS-136 communications protocol in response to receipt of a call request to the base station by a mobile station using the IS- 136 communications protocol. In this manner, mobile stations using either the AMPS or IS-136 communications protocols are not blocked from using the system unless the physical resources (i.e., a radio unit) are not available for providing a carrier signal.

BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawings wherein:

FIGURE 1 is a block diagram of the system of the present invention wherein a base station includes a plurality of reconfigurable radio units; FIGURE 2 is a flow diagram describing a call processing flow according to the system of the present invention; FIGURE 3a-3c are illustrations of how carriers are configured and assigned in accordance with the present invention; and

FIGURE 4 is an illustration of an intracell carrier hand-off.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the Drawings, and more particularly to FIGURE 1, there is illustrated the cellular system of the present invention, including a base station 10 capable of operating with both AMPS and IS-136 mobile stations 20. The system is comprised of a base station 10, mobile switching center 15 and mobile stations 20. The mobile stations 20 are of known design and configured to operate according to either the iAMPS or the IS-136 communications protocol. The mobile stations 20 generate a communications link 25 with the base station 10. The signals transmitted through the communications link 25 from the mobile stations 20 are received via an antenna 30 associated with the base station 10. The antenna 30 is interconnected with a plurality of reconfigurable radios 35.

The radios 35 provide a carrier signal (channel) for communications between the base station 10 and the mobile station 20 via transmission line 32 and antenna 30. The reconfigurable radios 35 have a first operating mode 40 wherein the radio operates according to the AMPS communications protocol. The reconfigurable radios 35 include a second operating mode 35 wherein the radios operate according to the IS-136 communications protocol. Finally, the radio 35 includes an idle mode 38 wherein the carrier is not being used for communications.

The reconfigurable radios 35 are responsive to instructions from a processing or reconfiguration means 50 located within the mobile switching center 15 associated with the base station 10. The reconfiguration means 50 configure the .AMPS or IS- 136 mode of the reconfigurable radios 35. Optionally, the reconfiguration means 50 may be located within the base station 10 rather than the mobile switching center 15. The reconfiguration means 50 sends control signals to the reconfigurable radios 35 via a control line 55. The reconfiguration means 50 preferably comprises some sort of software but may comprise any hardware, firmware or other means capable of reconfiguring the radios 35 to operate according to the plurality of protocols. Refeiring now to FIGURE 2, there is illustrated the procedure for granting a call connection request between the reconfigurable radios 35 and a mobile station 20 operating according to the AMPS or IS-136 communications protocol. A call connection request is initially received at step 60. A determination is made at inquiry step 65 as to whether the call connection request comes from a mobile station 20 operating according to either the AMPS or the IS-136 protocol. If an AMPS mobile station 20 is making the request, an idle radio unit 35 is configured to operate according to the aAMPS communications protocol at step 70. The requested call connection is then assigned at step 75 to the carrier signal (channel) provided by the reconfigured radio unit 35. The call will continue until the channel is freed by completion of the call. When the call is completed the radio unit 35 returns at step 85 to the idle state.

If inquiry step 65 determines the call connection request comes from an IS-136 mobile station 20, an initial determination is made at inquiry step 90 as to whether an idle timeslot presently exists within an already IS- 136 configured radio unit 35. If so, control will pass to step 100 and the call is assigned to the available timeslot. Otherwise, an idle radio unit 35 is configured at step 95 to provide an IS-136 carrier signal (channel) for the call connection. The call is assigned to an available timeslot within the newly configured carrier channel at step 100. The call remains assigned to the slot until completion. When the call is completed, inquiry step 105 determines if the carrier is completely available (i.e., all timeslots are available). If not, the carrier remains configured according to the IS- 136 communications protocol. If all timeslots within the carrier are idle, the carrier channel is returned to the idle state at step 85.

Referring now to FIGURES 3a-3c, there are illustrated the manner in which earner signal (channels) provided by the reconfigured radio units 35 are reconfigured according to the method of the present invention. Referring now more specifically to FIGURE 3a, there are illustrated carriers 1-4. Carrier no. 1 is configured to operate with an aAMPS system. Carrier no. 2 is configured to operate with an IS-136 system and includes three timeslots 130 which are each presently serving an IS-136 call. Carrier nos. 3 and 4 are in the idle state. An AMPS call connection request 135 alters the status of some of the carriers, such that carrier no. 3 is reconfigured and changes from the idle state to a carrier operating according to the .AMPS communications protocol. Carrier nos. 1, 2 and 4 remain unchanged.

Referring now to FIGURE 3b, there is illustrated a set of four carriers provided by the reconfigurable radio units 35 of the present invention. In this case, carrier no. 1 is again configured according to an AMPS system, and carrier no. 2 is configured to operate with an IS-136 system. However, each of the timeslots 130 of carrier no. 2 are not in use. The third timeslot 130c is in the idle state and not supporting a call. Carrier nos. 3 and 4 are also in the idle state. In response to an IS-136 call connection request 150, the idle timeslot 130c of carrier no. 2 is assigned to support the new IS- 136 call. Since the timeslot is available in a carrier already configured to support an

IS-136 call, neither carrier nos. 3 or no. 4 need be removed from the idle state.

Referring now to FIGURE 3 c, there is illustrated a set of four carriers initially configured as those illustrated in FIGU.RE 3a with earner no. 1 configured in the AMPS mode, carrier no. 2 configured in the IS-136 mode with each timeslot 130 currently supporting an IS-136 call and carrier nos. 3 and 4 being in the idle state. In response to an IS-136 call request 150, carrier no. 3 is reconfigured to support IS-136 calls. The call is assigned to the first timeslot 130a of the newly configured earner.

Using this system, when an AMPS user requests a call, an idle channel is configured to be an AMPS channel and the user is assigned to this channel. Thus, only if no idle carriers are available is an AMPS user blocked from accessing the base station 10. Likewise, an IS-136 user is only blocked when no idle timeslots exist on presently used carriers and no idle carriers are available.

Referring now back to FIGURE 1 , channel assignment circuitry 140 within the base station 10 may pack IS- 136 users into as few carriers as possible by performing intracell hand-offs. For example, as illustrated in FIGURE 4, if two carriers, 165 and

170, are both configured to support IS-136 calls but are only supporting three IS-136 calls with two timeslots 175 occupied in the first carrier 165 and one timeslot 175 occupied in the second carrier 170, intracell hand-offs may be utilized to move all users to a single carrier 165 while returning a second carrier 170 to an idle state. This frees up an additional carrier to allow for more AMPS traffic on the system and provides optimal use of system resources. The intracell hand-offs of FIGURE 4 may also be utilized in a system in which only IS-136 users are present and the number of available channels must be maximized for triple rate data users. This type of system would of course not utilize reconfigurable radios but would only have IS-136 radios. The method illustrated in FIGURE 4 would enable users to be packed into as few carriers as possible to create more empty carriers able to support triple data users.

Although a preferred embodiment of the method and apparatus of the present invention has been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it is understood that the invention is not limited to the embodiment disclosed, but is capable of numerous rearrangements, modifications, and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.

Claims

WHAT IS CLAIMED IS:

1. A system for communicating, comprising: a plurality of radio units for providing a carrier signal, the plurality of radio units being selectively configurable to operate according to at least a first and a second communications protocol; and control means for automatically reconfiguring a radio unit to provide a carrier signal according to the first communications protocol in response to receipt of a call request using the first communications protocol and for automatically reconfiguring a radio unit to provide a carrier signal according to the second communications protocol in response to receipt of a call request using the second communications protocol.

2. The system of claim 1, wherein the first communications protocol comprises an .AMPS protocol.

3. The system of claim 1, whereby the second communications protocol comprises an IS-136 protocol.

4. The system of claim 3 wherein the control means further includes means for assigning the call request using the IS-136 protocol to a carrier signal having an idle time slot.

5. The system of claim 1, wherein the control means further includes means for performing intracell hand-offs between radio unit carrier signals having idle time slots to return some radio unit carrier signals to the idle state.

6. The system of claim 1, wherein the control means further includes means for reconfiguring the plurality of radio units to support either the first or the second communications protocol.

The system of Claim 1, wherein the control means is located at a base station.

8. The system of claim 1 , wherein the control means is located in a mobile switching center associated with a base station.

9. The system of claim 1, wherein the call requests are received from mobile stations.

10. A base station, comprising: a plurality of radio units providing a carrier signal, each radio unit selectively configurable to operate in at least one of a first state wherein the carrier signal is idle, a second state wherein the carrier signal operates according to a first communications protocol and a third state wherein the carrier signal operates according to a second communications protocol; and a controller responsive to receipt of a call request for switching a carrier signal of a radio unit between the first, second and third states.

11. The base station of claim 10, wherein the first radio communications protocol comprises an AMPS protocol.

12. The system of claim 10, whereby the second communications protocol comprises an IS-136 protocol.

13. The base station of claim 12 wherein the control means further includes means for assigning the call request using the IS- 136 protocol to a radio unit earner signal having an idle time slot.

14. The base station of claim 10 wherein the control means further includes means for perfoiming intracell hand-offs between radio unit ca╧Çier signals having idle time slots to return some radio unit carrier signals to the idle state.

15. The base station of claim 10 wherein the control means further includes means for reconfiguring the plurality of radio units to support either the first or the second communications protocol.

16. A method for providing a communications link between a base station and mobile stations operating according to at least a first and a second communications protocol, comprising the steps of: receiving a call connection request from one of the mobile stations at the base station; determining whether the one mobile station uses the first or the second commumcations protocol; configuring a carrier signal to operate according to the one of the first and second communications protocols used by the mobile station; and establishing the communications link according to the one of the first and second communications protocols used by the mobile station.

17. The method of claim 16 wherein the first communications protocol comprises the AMPS communications protocol.

18. The system of claim 16, wherein the second communications protocol comprises an IS- 136 protocol.

19. The method of claim 16 further including the step of returning the ca╧Çier signal to an idle state upon completion of the call from the mobile station to the base station.

20. The method of claim 16, wherein the step of configuring further includes the step of configuring an existing carrier signal to utilize an additional timeslot.

21. The method of claim 16 further including the step of performing intracell hand-offs between radio unit carrier signals having idle time slots to return some radio unit carrier signals to the idle state.