Method for maintaining reliable communication in a wireless communication system

• US 6,330,447 B1
• Filed: 02/08/1999
• Issued: 12/11/2001
• Est. Priority Date: 07/30/1998
• Status: Expired due to Term

• Current Assignee: Eagle Technology, LLC (L3Harris Technologies, Inc.)
• Original Assignee: The Whitaker Corporation (Meggitt PLC)
• Inventors: Hengeveld, Thomas
• Primary Examiner(s): Bost, Dwayne
• Assistant Examiner(s): PERSINO, RAYMOND B
• Application Number:
  US09/245,751
• Time in Patent Office: 1,037 Days
• Field of Search: 455/432, 455/434, 455/435, 455/436, 455/437, 455/438, 455/439, 455/443, 455/444, 455/450, 455/451, 455/452, 455/453, 455/509, 455/512, 455/515, 370/350, 370/330
• US Class Current: 455/436
• CPC Class Codes: H04W 36/00835 Determination of neighbour cell lists
• CPC Class Codes: H04W 8/02 Processing of mobility data, e.g. registration information at HLR [Home Location Register] or VLR [Visitor Location Register]; Transfer of mobility data, e.g. between HLR, VLR or external networks

Abstract

A roaming decision is made and roaming channel selected in a wireless communications system based upon an evaluation of the operability of a data link layer interconnection, In a connection based protocol, the peer to peer data link layer interconnection is implemented through use of a unique connection identifier known in each peer functional layer of the data link interconnection. If the connection identifier has a value outside of a valid range, the interconnection is presumed nonoperational and the system makes a decision to roam.

Claims

1. A method of maintaining a wireless communications link between a mobile and a host comprising the steps of:

(a) identifying a list of possible channels over which communication can occur wherein each channel is associated with a roaming marker identifying mutually exclusive tried and untried channels,

(b) selecting one of said possible and untried channels to be a selected channel,

(c) requesting a connection identifier for the selected channel,

(d) determining whether there is an operational connection between the mobile and the host over the selected channel through a value assigned to the connection identifier,

(e) if the connection identifier is not received and valid, marking the selected channel as a tried channel and determining whether there is an untried channel among the possible channels, and if so, repeating the process beginning at the step of selecting the channel, and if not, selecting an alternate channel and ending, and

(f) if the connection identifier value is received, resetting all of the possible channels as untried channels;

(g) wherein the step of determining an ability of the mobile to communicate with the central office over an existing channel comprises the step of the mobile attempting to establish a session with the central office by receiving a temporary equipment identifier in response to a registration request.

2. A method of maintaining communications between a mobile and a central office as recited in claim 1 and wherein said set of possible channels is prioritized and defined the order in which the channel is selected for use in the step of requesting the connection identifier.

3. A method of maintaining communications between a mobile and a central office as recited in claim 2 wherein the mobile and the central office have a registered session over an established channel wherein the prioritized list of possible channels comprises a single preferred home channel and one or more in area channels that are defined as those channels that are in a same area as the established channel.

4. A method of maintaining a wireless communications link between a mobile and a host comprising the steps of:

a) identifying a list of possible channels over which communication can occur wherein each channel is associated with a roaming marker identifying mutually exclusive tried and untried channels,

b) selecting one of said possible and untried channels to be a selected channel,

c) requesting a connection identifier for the selected channel,

d) determining whether there is an operational connection between the mobile and the host over the selected channel through a value assigned to the connection identifier,

e) if the connection identifier is not received and valid, marking the selected channel as a tried channel and determining whether there is an untried channel among the possible channels, and if so, repeating the process beginning at the step of selecting the channel, and if not, selecting an alternate channel and ending, and

f) if the connection identifier value is received, resetting all of the possible channels as untried channels;

g) wherein said set of possible channels is prioritized and defines the order in which the channel is selected for use in the step of requesting the connection identifier; and

h) wherein the mobile and the central office have a registered session over an established channel wherein the prioritized list of possible channels comprises a single preferred home channel and one or more in area channels that are defined as those channels that are in a same area as the established channel.

5. A method of maintaining a wireless communications link between a mobile and a host comprising the steps of associating a first data link connection between the mobile and the host over a first channel with a connection identifier value characterized in the steps of:

determining whether the first data link connection is operational by comparing the connection identifier value against one or more thresholds,

selecting a second channel if the first data link connection is not operational, and establishing a second data link connection over the second channel;

wherein the step of selecting further comprises the steps of;

(a) choosing a potentially useful channel from a set of possible channels,

(b) evaluating whether the chosen channel is able to support the second data link connection,

(c) selecting the chosen channel if it is able to support the data link connection, and

(d) marking the chosen channel as a useless channel if it is not able to support the second data link connection, and repeating beginning at the step of choosing if the chosen channel not able to support the second data link connection;

wherein the possible channels include at least one moderate priority in area channel and wherein the in area channels are logically related to the first channel.

6. A method of maintaining a wireless communications link between a mobile and a host as recited in claim 5 wherein the mobile performs the recited steps.

7. A method of maintaining a wireless communications link between a mobile and a host as recited in claim 5 and further comprising the steps of marking the first channel as a tried channel if the first data link connection is not operational and repeating beginning at the step of determining wherein the second channel and respective connection identifier is redefined as the first channel and respective connection identifier.

8. A method of maintaining a wireless communications link between a mobile and a host as recited in claim 5 and further comprising the steps of;

associating a roaming marker with each channel in a set of possible channels to distinguish between tried and untried channels;

setting the roaming marker associated with the first channel identifying the first channel as a tried channel, and

selecting the second channel from the set of possible channels that are not tried channels.

9. A method of maintaining a wireless communications link between a mobile and a host as recited in claim 8 and further comprising the step of resetting each roaming marker if the first data link connection is operational.

10. A method of maintaining a wireless communications link between a mobile and a host as recited in claim 8 wherein the roaming marker is a roaming flag bit.

11. A method of maintaining a wireless communications link between a mobile and a host as recited in claim 5 wherein the step of determining whether the first data link connection is operational further comprises the steps of:

requesting a connection identifier value over the first channel,

waiting a predetermined amount of time for a response to the request, and

determining that the first data link is not operational in the absence of the response within the predetermined amount of time.

12. A method of maintaining a wireless communications link between a mobile and a host as recited in claim 11 wherein the step of determining repeats a predetermined number of times if the first data link is not operational.

13. A method of maintaining a wireless communications link between a mobile and a host as recited in claim 5 wherein the step of evaluating the chosen channel comprises determining whether or not the mobile is able to achieve synchronization with a base over the chosen channel.

14. A method of maintaining a wireless communications link between a mobile and a host as recited in claim 13 wherein there is a utility flag bit associated with each possible channel and marking the chosen channel as useless comprises setting the respective utility flag bit.

15. A method of maintaining a wireless communications link between a mobile and a host as recited in claim 14 and further comprising the step of resetting all possible channels as potentially useful channels if the chosen channel is able to support the data link connection.

16. A method of maintaining a wireless communications link between a mobile and a host as recited in claim 5 wherein the step of choosing a potentially useful channel further comprises choosing a highest priority home channel.

17. A method of maintaining a wireless communications link between a mobile and a host as recited in claim 16 wherein the home channel is predetermined.