Cell assignment method during group calls

• US 6,725,052 B1
• Filed: 12/20/1999
• Issued: 04/20/2004
• Est. Priority Date: 12/20/1999
• Status: Expired due to Term

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Raith, Alex Krister
• Primary Examiner(s): Tran, CongVan
• Application Number:
  US09/467,711
• Time in Patent Office: 1,583 Days
• Field of Search: 455/509, 455/512, 455/517, 455/518-519, 455/520, 455/527, 455/449, 455/450-454, 455/422, 455/436, 455/437, 455/439, 455/440, 455/442, 455/525, 455/514, 370/331, 370/332
• US Class Current: 455/518
• CPC Class Codes: H04W 36/0009 for a plurality of users or terminals, e.g. group communication or moving wireless networks user group management H04W4/08; processing of subscriber group data H04W8/186
• CPC Class Codes: H04W 36/04 Reselecting a cell layer in multi-layered cells
• CPC Class Codes: H04W 4/06 Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services
• CPC Class Codes: H04W 48/20 Selecting an access point
• CPC Class Codes: H04W 8/186 Processing of subscriber group data

Abstract

A cell assignment process strives to minimize the number of cells assigned to mobile terminals involved in any given group call session in both circuit-switched and packet-data environments. In one embodiment, when a cell assignment trigger event is encountered during a group call, the decision whether to change cells or not is based at least in part upon whether the relevant cell is already participating in that group call session with another mobile terminal or not. If so, the cell assignment process preferentially selects such a cell for switching to or avoids changing cell assignment if already assigned there. In another embodiment other cells involved in the group call session are actively sought out and the cell assignments of the mobile terminals involved in the group call session are changed to those cells, even when the signal quality may be acceptable in the current cell. The mobile terminals involved in group call sessions may optionally be given preferential priority when switching cells so as to help minimize disruption to the group call session. Thus, the mobile terminals involved in the group call session are gradually urged toward congregating in the fewest possible cells under the circumstances. Accordingly, the present invention helps provide better service with less of a system capacity penalty for group call sessions.

Claims

1. A method of controlling cell assignment of a wireless communications mobile terminal during a group call session, comprising:

storing a list of candidate cells;

determining whether at least one of said candidate cells is participating in said group call session;

selecting a new cell from said list of candidate cells based on whether said candidate cells, including said at least one of said candidate cells, are participating in said group call session in response to a cell selection trigger event during said group call session;

wherein said mobile terminal communicates with at least one wireless communications system during said group call session;

wherein selecting a new cell from said list of candidate cells based on whether said candidate cells are participating in said group call session in response to the cell selection trigger event during said group call session is performed by said wireless communications system; and

sending said mobile terminal an indication of which of said candidate cells are participating in said group call session by said wireless communications system via a broadcast message.

2. The method of claim 1 wherein said determining whether said at least one of said candidate cells is participating in said group call includes determining which, if any, of said candidate cells is participating in said group call.

3. The method of claim 1 wherein said selecting a new cell from said list of candidate cells based on whether said candidate cells are participating in said group call session in response to a the cell selection trigger event during said group call session is performed by said mobile terminal.

4. The method of claim 1 wherein selecting a new cell from said list of candidate cells based on whether said candidate cells are participating in said group call session in response to a cell selection trigger event during said group call session is performed by a wireless communications system in communication with said mobile terminal and further including said mobile terminal changing cell selection based on instructions received from said wireless communications system.

5. The method of claim 1 wherein said sending said mobile terminal an indication of which of said candidate cells are participating in said group call session by said wireless communications system is performed via a broadcast message via an addressed message.

6. The method of claim 5 wherein said sending said mobile terminal an indication of which of said candidate cells are participating in said group call session by said wireless communications system is performed via a broadcast message to all mobile terminals active in said group call.

7. A method of controlling cell assignment of a wireless communications mobile terminal during an active packet data group call session, comprising:

storing a list of candidate cells including a current cell;

receiving, at the mobile terminal, said list of candidate cells from a corresponding wireless communications system;

determining whether at least one of said candidate cells is participating in said group call session;

said mobile terminal determining whether to stay with said current cell or to select a new cell in response to a cell selection trigger event during said group call session, said mobile terminal determining to remain with the current cell if;

i) said current cell provides at least minimally acceptable signal quality; and

ii) said current cell is participating in said group call session with another mobile terminal assigned to said current cell; and

iii) no acceptable candidate cells, not including said current cell, are participating in said group call session.

8. The method of claim 7 wherein said receiving, at the mobile terminal, said list of candidate cells from the corresponding wireless communications system includes said mobile terminal receiving a message addressed to all active group members in said group call session.

9. The method of claim 8 further including said wireless communications system broadcasting a neighbor list of candidate cells and wherein said message addressed to all active group members in said group call session includes a bit map indicating which of said candidate cells on said neighbor list are active in said group call session.

10. The method of claim 7 further including said wireless communications system broadcasting a neighbor list of candidate cells on a broadcast control channel and wherein said broadcast control channel further includes information indicating which of said candidate cells on said neighbor list are active in said group call session.

11. The method of claim 7 wherein said mobile terminal determining whether to stay with said current cell or to select a new cell in response to a cell selection trigger event during said group call session is based on an algorithm that includes a bias weighting factor parameter and further including said wireless communications system transmitting a message revising said bias weighting factor parameter so as to deter changes in cell selection.

12. The method of claim 11 wherein said wireless communications system transmitting a message revising said bias weighting factor parameter so as to deter changes in cell selection is performed by transmitting a broadcast message.

13. The method of claim 11 wherein said wireless communications system transmitting a message revising said bias weighting factor parameter so as to deter changes in cell selection is performed by transmitting a message addressed to all active group members in said group call session.

14. The method of claim 7 wherein said mobile terminal determining whether to stay with said current cell or to select a new cell in response to a cell selection trigger event during said group call session is based on an algorithm that includes a bias weighting factor parameter and further including preprogramming said bias weighting factor parameter into said mobile terminal so as to deter changes in cell selection into cells not actively supporting said group call session.

15. A method of controlling cell assignment of a wireless communications mobile terminal by a wireless communications system during an active packet data group call session, comprising:

storing a list of candidate cells including a current cell;

determining whether at least one of said candidate cells other than said current cell is participating in said group call session;

receiving notification at the corresponding wireless communications system that the mobile terminal has encountered a cell selection trigger event during said group call session;

thereafter, said wireless communications system determining whether said mobile terminal should stay with the current cell or change in response to said cell selection trigger event, said wireless communications system determining that said mobile terminal should change cells unless;

i) the current cell provides at least minimally acceptable signal quality to said mobile terminal;

ii) the current cell is participating in said group call session with another mobile terminal assigned to said current cell; and

iii) no acceptable candidate cells, not including the current cell, are participating in said group call session;

said wireless communications system instructing said mobile terminal to change cells if said wireless communications system determines that said mobile terminal should change cells.

16. A method of controlling cell assignment of a wireless communications mobile terminal operating in conjunction with a wireless communications system during an active circuit switched group call, comprising:

storing a list of candidate cells including a current cell at said wireless communications system;

said wireless communications system determining which, if any, of said candidate cells is participating in said group call;

said wireless communications system determining whether said mobile terminal should stay with the current cell or be handed off to another cell in response to a handoff trigger event, said wireless communications system determining that said mobile terminal should be handed off to another cell unless;

i) said current cell provides at least minimally acceptable signal quality to said mobile terminal;

ii) said current cell is participating in said group call with another mobile terminal assigned to said current cell; and

iii) no acceptable candidate cells, not including said current cell, are participating in said group call;

said wireless communications system instructing said mobile terminal to change cells if said wireless communications system determines that said mobile terminal should be handed off to another cell.

17. A method of controlling cell assignment of a wireless communications mobile terminal operating in conjunction with a wireless communications system during an active circuit switched group call, comprising:

communicating with said mobile terminal via a first cell during said group call;

assigning a greater than normal priority to said mobile terminal and handing off said mobile terminal to a second cell with said greater than normal priority in response to a handoff trigger event during said group call.

18. A method of controlling cell assignment of a wireless communications mobile terminal operating in conjunction with a wireless communications system during an active circuit switched group call, comprising:

communicating with said mobile terminal via a first cell during said group call;

assigning a greater than normal priority to said mobile terminal and handing off said mobile terminal to a second cell with said greater than normal priority in response to a handoff trigger event during said group call, said second cell maintaining a queue of channel assignment requests; and

assigning a preferential position in said queue to said handed-off group call.

19. The method of claim 18 further including said second cell maintaining a queue of channel assignment requests and further including assigning the most preferential position in said queue to said handed-off group call.

20. A method of controlling cell assignment of a wireless communications mobile terminal operating in conjunction with a wireless communications system during an active circuit switched group call, comprising:

communicating with said mobile terminal via a first cell during said group call;

assigning a greater than normal priority to said mobile terminal and handing off said mobile terminal to a second cell with said greater than normal priority in response to a handoff trigger event during said group call, said second cell maintaining a queue of channel assignment requests; and

allowing said handed-off group call to bypass said queue.

21. A method of controlling cell assignment of a wireless communications mobile terminal operating in conjunction with a wireless communications system during an active circuit switched group call, comprising:

communicating with said mobile terminal via a first cell during said group call;

assigning a greater than normal priority to said mobile terminal and handing off said mobile terminal to a second cell with said greater than normal priority in response to a handoff trigger event during said group call; and

wherein said second cell includes normal and reserve channels and further including allocating said handed-off group call one of said reserve channels.

22. A method of controlling cell assignment of a wireless communications mobile terminal participating in a group call session, comprising:

assigning said mobile terminal to a first cell;

storing a list of candidate cells including a second cell;

determining if said second cell is participating in said group call session;

selectively changing the cell assignment of said mobile terminal from said first cell to said second cell based on participation of said first and second cells in said group call session;

wherein said selectively changing the cell assignment of said mobile terminal includes changing the cell assignment of said mobile terminal from said first cell to said second cell if;

said first cell is not participating in said group call session with another mobile terminal assigned to said first cell;

said second cell is participating in said group call session; and

said second cell provides at least minimally acceptable signal quality to said mobile terminal.

23. A method of controlling cell assignment of a wireless communications mobile terminal participating in a group call session, comprising:

assigning said mobile terminal to a first cell;

storing a list of candidate cells including a second cell;

determining if said second cell is participating in said group call session;

selectively changing the cell assignment of said mobile terminal from said first cell to said second cell based on participation of said first and second cells in said group call session;

wherein said selectively changing the cell assignment of said mobile terminal includes changing the cell assignment of said mobile terminal from said first cell to said second cell if;

said first cell is not participating in said group call session with another mobile terminal assigned to said first cell;

said second cell is participating in said group call session; and

said second cell provides signal quality of better than a predetermined level to said mobile terminal.

24. A method of controlling cell assignment of a wireless communications mobile terminal participating in a group call session, comprising:

assigning said mobile terminal to a first cell;

storing a list of candidate cells including a second cell;

determining if said second cell is participating in said group call session;

selectively changing the cell assignment of said mobile terminal from said first cell to said second cell based on participation of said first and second cells in said group call session;

wherein said mobile terminal is a first mobile terminal and further including assigning a second mobile terminal to said second cell prior to said determining if said second cell is participating in said group call session and wherein said selectively changing the cell assignment of said mobile terminal includes changing the cell assignment of said mobile terminal from said first cell to said second cell because said second mobile terminal is participating in said group call session in said second cell.

25. A method of controlling cell assignment of a wireless communications mobile terminal participating in a group call session, comprising:

assigning said mobile terminal to a first cell;

storing a list of candidate cells including a second cell;

determining if said second cell is participating in said group call session;

selectively changing the cell assignment of said mobile terminal from said first cell to said second cell based on participation of said first and second cells in said group call session;

wherein selectively changing the cell assignment of said mobile terminal from said first cell to said second cell based on participation of said first and second cells in said group call session includes said mobile terminal controlling said selectively changing the cell assignment of said mobile terminal from said first cell to said second cell based on participation of said first and second cells in said group call session.