Communications unit for seamless handover between networks and method of use therefor

• US 6,614,769 B1
• Filed: 06/01/1999
• Issued: 09/02/2003
• Est. Priority Date: 06/01/1999
• Status: Expired due to Term

• Current Assignee: CDC Propriete Intellectuelle
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Erlick, John Richard, Eteminan, Isaac, Hogberg, Shawn, Hanson, Duke Edward
• Primary Examiner(s): MARCELO, MELVIN C
• Application Number:
  US09/323,324
• Time in Patent Office: 1,554 Days
• Field of Search: 370/331-334, 455/436-444
• US Class Current: 370/331
• CPC Class Codes: H04W 36/30 by measured or perceived connection quality data

Abstract

A communications unit determines that a wireless link between itself and a first communications network has degraded beyond acceptable limits (FIG. 2, 200). The communications unit signals a second, unsynchronized, communications network during a pause in outgoing voice (230) in order to acquire a channel and continue the call using the second network. When the second communications network indicates that sufficient resources are available, the communications unit transmits a Handover Trigger to the second network (FIG. 4, 400). In response to the Handover Trigger, the first and second communications network establish a connection between each other (460, 470). When the connection has been established, the communications unit receives a channel assignment (500) and continues the call using the resources of the second communications network.

Claims

1. In a communications unit, a method of switching a call from a first communications network to a second communications network, comprising the steps of:

sensing a degradation in signal quality between said communications unit and said first communications network;

establishing a communications link with said second communications network by transmitting a signaling message to the second communications network during a pause in outgoing voice traffic to obtain a channel assignment from the second communications network;

using transmit frames to transmit said signaling message to said second communications network if the channel assignment has not been received before the end of said pause in outgoing voice traffic; and

switching said call from said first communications network to said second communications network in response to said channel assignment.

2. The method of claim 1, wherein said sensing step additionally comprises the step of measuring a bit error rate in a signal received from said first communications network.

3. The method of claim 1, wherein said sensing step additionally comprises the step of measuring a signal to noise ratio in a signal received from said first communications network.

4. The method of claim 1, wherein said establishing step additionally comprises the step of changing from a first operating frequency to a second operating frequency in order to receive a signal from said second communications network.

5. The method of claim 4, wherein said establishing step further comprises the step of returning to said first operating frequency if the channel assignment from said second communications network has not been received within a predetermined time period.

6. In a communications unit, a method for switching a call from a first communications network to a second communications network, comprising the steps of:

communicating with said first communications network;

determining that said second communications network delivers optimal service based on a predetermined criteria;

establishing a link with said second communications network during a pause in outgoing voice traffic;

using transmit frames to transmit a signaling message to said second communications network if a channel assignment has not been received before the end of said pause in outgoing voice traffic; and

switching said call to said second communications network based on said establishing step.

7. The method of claim 6, wherein said predetermined criteria comprises a requirement for minimum bandwidth.

8. The method of claim 6, wherein said predetermined criteria comprises maximum subscriber cost per billing increment.

9. A communications unit for switching a call from a first communications network to a second communications network, said communications unit comprising:

a link quality sensor for sensing a degradation in signal quality between said communications unit and said first communications network;

a band switching unit coupled to said link quality sensor for switching said call from said first communications network to said second communications network during a pause in outgoing voice traffic; and

a processor coupled to said band switching unit configured to determine whether said call should be switched to said second communications network, wherein said processor is operable to use transmit frames to transmit a signaling message to said second communications network if a channel assignment has not been received before the end of said pause in outgoing voice traffic.

10. The wireless communications unit of claim 9, wherein the switching unit comprises high isolation switches which reduce interference between said first and said second communications networks.