Apparatus and method for improving handover in a global system for mobile communications

• US 10,397,839 B2
• Filed: 01/23/2014
• Issued: 08/27/2019
• Est. Priority Date: 08/09/2013
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Sundberg, Marten, Lowenmark, Stefan Eriksson, Lopez, Miguel, Schliwa-Bertling, Paul
• Primary Examiner(s): Tran, Phuc H
• Application Number:
  US14/911,165
• Publication Number:
  US 20160198375A1
• Time in Patent Office: 2,042 Days
• CPC Class Codes: H04L 5/1469 using time-sharing
• CPC Class Codes: H04W 36/00695 using split of the control plane or user plane
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 36/38 by fixed network equipment

Abstract

A method is provided for improving handover in a mobile station configured to operate a time division multiple access, TDMA, protocol in a global system for mobile communications, GSM, telecommunication network. The method comprises the steps of receiving a handover command requesting that the mobile station perform a handover operation from a serving cell to a target cell, and configuring the mobile station to transmit and receive user plane data with the serving cell and the target cell during a time period between receiving the handover command and the handover operation being completed.

Claims

1. A method for improving handover in a mobile station configured to operate a time division multiple access (TDMA) protocol in a global system for mobile communications (GSM) telecommunication network, the method comprising the steps of:

receiving a handover command requesting that the mobile station perform a handover operation from a serving cell to a target cell;

configuring the mobile station to transmit and receive user plane data with the serving cell and the target cell during a time period between receiving the handover command and the handover operation being completed; and

transmitting user plane data, during the time period, via an uplink connection switched between the serving cell and the target cell, wherein the transmitted user plane data includes;

a first speech frame transmitted via the serving cell; and

a second speech frame including a first portion transmitted via the serving cell and a second portion transmitted via the target cell.

2. The method of claim 1, further comprising the steps of adapting a TDMA transmission schedule such that a physical layer of the mobile station is configured to alternate between transmission and/or reception to/from the serving cell and target cell, while continuing to interchange signaling messages with the serving cell and target cell.

3. The method of claim 1, further comprising the steps of communicating speech data simultaneously with the serving cell and the target cell after receipt of a handover command, and prior to a handover operation being completed.

4. The method of claim 3, wherein the step of communicating simultaneously comprises the steps of alternately receiving from the serving cell, transmitting to the serving cell, receiving from the target cell, and transmitting to the target cell.

5. The method of claim 1, further comprising the steps of:

establishing a set of channel combinations, each channel combination relating to whether a traffic channel is operating in a full rate mode or half rate mode of communication;

establishing a set of simultaneous transmission modes, each simultaneous transmission mode relating to whether simultaneous communication is only provided in a downlink to the mobile station, only in an uplink from the mobile station, or in both downlink and uplink directions; and

scheduling the transmission and reception of TDMA timeslots based on which combination of channel combination mode and simultaneous transmission mode is selected.

6. The method of claim 1, further comprising the step of transmitting user data to a target cell after communicating set asynchronous balanced mode (SABM) information.

7. The method of claim 1, further comprising the step of temporarily shifting a frame structure of either the serving cell or target cell relative to one another by a selectable number of symbols.

8. The method of claim 1, wherein the first speech frame is transmitted after transmitting one or more access bursts in the target cell.

9. A mobile station configured to operate a time division multiple access (TDMA) protocol in a global system for mobile communications (GSM) telecommunication network, the mobile station comprising:

a processing circuit configured to control transmission and reception of user plane data with the serving cell and the target cell during a time period between receiving the handover command and the handover operation being completed; and

an interface circuit configured to;

receive a handover command requesting that the mobile station perform a handover operation from a serving cell to a target cell; and

transmit user plane data, during the time period, via an uplink connection switched between the serving cell and the target cell, wherein the transmitted user plane data includes;

a first speech frame transmitted via the serving cell; and

a second speech frame including a first portion transmitted via the serving cell and a second portion transmitted via the target cell.

10. The mobile station of claim 9, wherein the mobile station is configured to adapt a TDMA transmission schedule such that a physical layer of the mobile station is configured to alternate between transmission and/or reception to/from the serving cell and target cell, while continuing to interchange signaling messages with the serving cell and target cell.

11. The mobile station of claim 10, wherein the mobile station is configured to communicate speech data simultaneously with the serving cell and the target cell after receipt of a handover command, and prior to a handover operation being completed.

12. The mobile station of claim 11, wherein the mobile station is configured to communicate simultaneously by alternately receiving from the serving cell, transmitting to the serving cell, receiving from the target cell, and transmitting to the target cell.

13. The mobile station of claim 9, wherein the mobile station is configured to:

establish a set of channel combinations, each channel combination relating to whether a traffic channel is operating in a full rate mode or half rate mode of communication;

establish a set of simultaneous transmission modes, each simultaneous transmission mode relating to whether simultaneous communication is only provided in a downlink to the mobile station, only in an uplink from the mobile station, or in both downlink and uplink directions; and

schedule the transmission and reception of TDMA timeslots based on which combination of channel combination mode and simultaneous transmission mode is selected.

14. A method in a network node that is configured to operate a time division multiple access (TDMA) protocol in a global system for mobile communications (GSM) telecommunication network, the method comprising the steps of:

determining which channel combination (CC) and simultaneous transmission mode (STM) is being used to communicate with a mobile station;

determining which network resources are available for the combination of CC and STM; and

transmitting a handover signal to a mobile station, requesting that the mobile station perform a handover operation from a serving cell to a target cell, the handover signal containing information relating to the resources to be used during the handover for communicating user plane data, such that the mobile station is configurable to transmit and receive user plane data with the serving cell and the target cell during a time period between the handover signal transmitted from the network node being received by the mobile station and the handover operation being completed.

15. The method of claim 14, further comprising the step of determining a frame alignment between the serving cell and the target cell, and allocating resources in the target cell based on the determined frame alignment.

16. The method of claim 14, wherein for each combination of channel combination (CC) or simultaneous transmission mode (STM) the method further comprises the steps of establishing a plurality of switching classes, each switching class comprising a set of minimum acceptable switching times corresponding to one or more of:

a switching time between one transmission and another transmission;

a switching time between a transmission and a reception;

a switching time between a reception and a reception;

a switching time between a reception and a transmission.

17. The method of claim 16, wherein a switching time is defined as an integer value of a time slot, or a plurality of half-symbol periods, or a plurality of full-symbol periods.

18. The method of claim 14, further comprising the steps of determining the CC, the STM and the network resources to use in the target cell by analyzing a combination of one or more of:

the mode of the current connection in the serving cell,

the desired mode in the target cell,

the switching time capabilities of the mobile station,

the available resources in the target cell,

the relative timing of the two cells and the mobile station.

19. A network node configured to operate a time division multiple access (TDMA) protocol in a global system for mobile communications (GSM) telecommunication network, the network node comprising:

a processing circuit configured to;

determine which channel combination (CC) and simultaneous transmission mode (STM) is being used by a mobile station;

determine which network resources are available for the combination of CC and STM; and

an interface circuit configured to transmit a handover signal to a mobile station requesting that the mobile station perform a handover operation from a serving cell to a target cell, the handover signal containing information relating to the resources to be used during the handover for communicating user plane data, such that the mobile station is configurable to transmit and receive user plane data with the serving cell and the target cell during a time period between the handover signal transmitted from the network node being received by the mobile station and the handover operation being completed.