Multiple channel communications system

• US 20030144018A1
• Filed: 09/06/2001
• Published: 07/31/2003
• Est. Priority Date: 01/29/1999
• Status: Active Grant

• Current Assignee: Trapeze Its USA LLC
• Original Assignee: Siemens Transportation Systems, Inc. (Siemens AG)
• Inventors: Krueger, David C., Bueter, Michael A., Coil, Jeffrey D., Minnick, James A.
• Granted Patent: US 6,950,658 B2
• Time in Patent Office: Days
• US Class Current: 455/519
• CPC Class Codes: H04W 36/22 for handling the traffic
• CPC Class Codes: H04W 4/18 Information format or content conversion, e.g. adaptation by the network of the transmitted or received information for the purpose of wireless delivery to users or terminals
• CPC Class Codes: H04W 40/02 Communication route or path selection, e.g. power-based or shortest path routing
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: H04W 74/00 Wireless channel access
• CPC Class Codes: H04W 8/26 Network addressing or numbering for mobility support
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A multi-channel communications system for communications between a mobile units and dispatch agencies through tower sites under control of a multi-channel communication controller. The method of communications used is time division multiple access with provisions for alternate methods. The mobile units and dispatch agencies have forms of identifications to route messages between the mobile units and dispatch agencies according to the forms of identification. The forms of identification are resolved from one form to another to operate with the alternate methods of communications. The mobile units are handed off from one communications channel to another by the multi-channel controller as channel loading conditions exceed a predetermined limit. Mobile units change tower sites as the geographic coverage of a tower site changes. Mobile units determine distance to a tower site by computing distance to a tower site by using GPS position information of the mobile unit and the known locations of the tower sites to compute signal strength.

Claims

1. A multi-channel communications system comprising:

a plurality of mobile units each having forms of identification and communications channels;

a tower site in a geographic area also having said communications channels for communications with the mobile units;

a plurality of dispatch agencies each having forms of identification to communicate with the mobile units in the plurality of mobile units having the same forms of identification;

a multi-channel controller connected to said tower site in a geographic area and to said dispatch agencies for directing messages between the dispatch agencies and the mobile units according to a first form of identification over a first communications channel, for selecting a communications method in use on said first communications channel, for mapping said forms of identification to a second form of identification when said first communications channel uses an alternate communications method requiring said second form of identification, for determining said first communications channel loading, for handing off the mobile units from said first communications channel to a second communications channel at said tower site when loading on said first communications channel becomes excessive, for routing messages to the second communications channel at said tower when communications fail on said first communications channel, and for granting tower site and channel change requests to mobile units to connect to a second tower site in a second geographic area when the geographic area covered by said tower site is inadequate;

a user interface for configuration of mobile unit and dispatch agency lookup tables, for viewing multi-channel communications system performance statistics, and for configuring multi-channel performance and redundancy parameters; and

a database for storing the mobile unit and dispatch agency lookup tables, the multi-channel communication system performance statistics, and the multi-channel controller performance and redundancy parameters.

2. The multi-channel communications system of claim 1 wherein the communications method is time division multiple access.

3. The multi-channel communications system of claim 1 wherein the alternate communications method is one of the group consisting of AMPS cellular, EDACS data, digital cellular data, and CDPD.

4. The multi-channel communications system of claim 1 wherein each of the plurality of mobile units comprises:

radio equipment for communicating data and control messages on the communications channels;

a GPS receiver for determining location of the mobile unit in relation to the tower site with a known location in a geographic area to determine if the tower site is within range of the mobile unit;

a display and keypad for reading and loading the data; and

a vehicle logic unit for controlling the operation of the radio equipment, the display and keyboard, and the GPS receiver;

generating the form of identification, interfacing the multi-channel controller, and switching the mobile unit from said tower site to the second tower site if said tower site is out of range.

5. The multi-channel communications system of claim 4 wherein the mobile unit vehicle logic unit interfaces the multi-channel controller by power up channel acquisition, by address mapping from the form of identification, by searching for a communications channel, by maintaining a list of alternate communications methods and tower site locations, by requesting channel changes, by requesting tower site changes and by handing off from one tower site to another tower to increase geographic coverage.

6. The multi-channel communications system of claim 1 wherein the tower site comprises:

radio equipment for transmitting to and receiving from the mobile units control and data messages on the communications channels;

a radio network controller connected to the radio equipment for controlling the radio equipment and passing the control and data messages; and

a connection between the radio network controller and the multi-channel controller for passing the control messages and data messages between the multi-channel controller and the radio network controller.

7. The multi-channel communications system of claim 6 wherein the radio network controller adds new mobile units during a logon and a handoff, notifies the multi-channel controller of the logon, computes and loads message statistics, processes requests from the multi-channel controller, removes mobile units during a handoff and a logoff, changes polling rates and replaces polling tables, dumps and loads message statistics, requests and synchronizes primary and secondary time division multiple access (TDMA) polling tables, and reconfigures the connection to the multi-channel controller during failures.

8. The multi-channel communications system of claim 6 wherein the connection is one of a group consisting of a telephone line and a microwave link.

9. The multi-channel communications system of claim 1 wherein the dispatch agency includes a computer terminal connected to the multi-channel controller for setting up and controlling the multi-channel controller, defining a form of identification for use by the dispatch agency to identify the mobile units for which it is responsible, defining and prioritizing the communications method and the alternate communications method allowed and supported by the communications channels, granting permission to other dispatch agencies to receive messages from the mobile units for which it is responsible and requesting permission to view messages from other dispatch agencies, requesting poll rate changes, and removing mobile units due to logoff or shutdown.

10. The multi-channel communications system of claim 1 wherein the multi-channel controller comprises:

gateways for interfacing the communications channels;

a multi-agency router for routing messages between the mobile units and the dispatch agencies through the gateways and the communications channels; and

a load service for performing load monitoring, balancing, and failure monitoring of the communications channels and for maintaining TDMA polling data for the communications channels.

11. The multi-channel communications system of claim 10 wherein the multi-agency router comprises:

a message routing function for routing messages between the mobile units and the dispatch agencies;

an identifier resolution function for determining the communications channel and method and message destination in accordance with an identifier attached to the messages;

a packet sniffing function for monitoring the messages from the mobile units, verifying the communications channel the mobile unit is operating on, examining the messages to determine if they are data messages or control messages, and examining the source and destination of the message and telling the message routing function to route accordingly;

a store and forward function for storing the data messages transmitted by a mobile unit when the mobile unit is changing communications channels; and

tables for storing static and dynamic data to accomplish the routing identifier resolution and the packet sniffing functions.

12. The multi-channel control system of claim 10 wherein the load service comprises:

a channel loading monitor for monitoring the loading on the communications channels for an overload condition;

a dynamic table with loading information on the communications channels the load service is responsible for and for making decisions based on the loading information; and

load balancing functions for actively and passively balancing the communications channel loads at a tower site.

13. A multi-channel communications system comprising:

a plurality of mobile units having communications channels and forms of identification;

a plurality of tower sites having communications channels for communications with the mobile units;

a plurality of dispatch agencies with forms of identification;

a multi-channel controller connected to said tower sites and said dispatch agencies said multi-channel controller further comprising;

a multi-agency router for routing messages between the mobile units and the dispatch agencies through the communications channels when the mobile units and the dispatch agencies have the same form of identification; and

a load service for performing communications channel load monitoring, balancing, and failure monitoring.

14. The multi-channel communications system of claim 13 further comprising a user interface for configuration of mobile unit and dispatch agency lookup tables, for viewing multi-channel communications system performance statistics, and for configuring multi-channel performance and redundancy parameters.

15. The multi-channel communications system of claim 14 further comprising a database for storing the mobile unit and dispatch agency lookup tables, the multi-channel communication system performance statistics, and the multi-channel controller performance and redundancy parameters.

16. The multi-channel communications system of claim 13 wherein the multi-agency router resolves the form of identification of the mobile units and the dispatch agencies to determine the communications channel and method and message source and destination;

monitors messages from the mobile units, verifies which of the communications channels the mobile unit is operating on, and examines the source and destination of the messages and routes the messages accordingly.

17. The multi-channel communications system of claim 13 wherein the load service determines a loading metric for a first communications channel and hands off mobile units exceeding the first communications channel loading metric from said first communications channel to a second communications channel at a first tower site in a first geographic area, selects and connects to a second tower site in a second geographic area when the first geographic area covered by said first tower site is inadequate, and routes messages to a second communications channel at said first tower site when communications fail on said first communications channel.

18. The multi-channel communications system of claim 17 wherein the loading metric is determined by how many mobile units are on the first communications channel and how fast the mobile units are polling.

19. A multi-channel communications system comprising:

at least one mobile unit having a first communications channel and at least one form of identification;

a first tower site in a geographic area having the first communications channel for communications with the mobile unit;

at least one dispatch agency having at least one form of identification for use by the dispatch agency to identify the mobile unit for which the agency is responsible; and

a multi-channel controller connected to the first tower site in a geographic area and to the dispatch agency for directing outgoing messages from the dispatch agency to the mobile unit and for routing incoming messages from the mobile unit to the dispatch agency according to the form of identification, for determining the first communications channel loading, for handing off the mobile unit from the first communications channel to a second communications channel at the tower site when loading on the first communications channel becomes excessive, for granting mobile unit requests to connect to another tower site in another geographic area when the geographic area covered by the first tower site is inadequate, and for routing outgoing and incoming messages to the second communications channel when communications fail on the first communications channel.

20. The multi-channel communications system of claim 19 wherein the first and second communications channels operate using time division multiple access.

21. The multi-channel communications system of claim 19 wherein the first channel operates using time division multiple access and the second channel operates using one of the group consisting of AMPS cellular, EDACS data, digital cellular data, and CDPD.

22. The multi-channel communications system of claim 19 wherein the mobile unit determines a pseudo signal strength for the first communications channel from the tower site by determining a mobile unit position using a GPS receiver and comparing the mobile unit position to a known position of the tower site and computing a distance from the mobile unit to the tower site, said distance being indicative of the pseudo signal strength.

23. The multi-channel communications system of claim 22 wherein the mobile unit uses the pseudo signal strength to select a tower site within communications range.

24. The multi-channel communications system of claim 19 wherein the mobile unit uses an external ID device for a static identifier.

25. The multi-channel communications system of claim 19 wherein the multi-channel controller resolves the mobile unit form of identification to an Internet Protocol address to route the incoming message to a dispatch agency to which the mobile belongs according to the Internet Protocol address.

26. The multi-channel communications system of claim 19 wherein the multi-channel controller operates redundantly on two computers each with multi-channel controller software.

27. A method of controlling a multi-channel communications system comprising the steps of:

analyzing messages from mobile units and dispatch agencies;

resolving an identifier on the messages;

routing the messages to the mobile units from a responsible dispatch agency and from the mobile units to the responsible agency according to the resolved identifier;

adding the mobile units to communications channels as the mobile units begin communicating through a communications channel and removing mobile units by either one of time out of a multi-channel controller message timer or by direction of the responsible dispatch agency; and

balancing loading on the communications channel said balancing performed by handing off the mobile unit to another communications channel as channel geographic coverage, loading conditions, and performance conditions change.

28. A method of routing a data message in a multi-channel communications system from a mobile unit to a dispatch agency comprising the steps of:

determining if the mobile unit is listed in a routing table;

routing the message to the dispatch agency destination if the mobile unit is listed in the routing table by performing the steps of;

verifying if the data message is on a current communications channel listed in the routing table;

determining if a communications channel change flag is set in the routing table;

looking up a dispatch agency destination the message is to be sent to in the routing table if the channel change flag is not set;

routing the message to the dispatch agency destination;

otherwise notifying a load service that a channel change is sensed if the channel change flag is set;

looking up a dispatch agency destination the message is to be sent to in the routing table; and

routing the message to the dispatch agency destination;

otherwise routing the message to the dispatch agency destination if the mobile unit is not listed in the routing table by performing the steps of;

adding the mobile unit address to the routing table by address resolution and determining the dispatch agency the mobile unit belongs to;

adding the mobile unit address to a multi-channel communications database and generating a log report;

looking up a dispatch agency destination the message is to be sent to in the routing table; and

routing the message to the dispatch agency destination.

29. A method of routing a message in a multi-channel communications system from a dispatch agency to a mobile unit comprising the steps of:

determining if the message is for a poll rate increase;

routing the message to the mobile unit if the message is not for a poll rate increase by performing the steps of;

determining if a channel change flag is set in a routing table;

providing a proper format for the message for a current channel if the channel change flag is not set;

incrementing a packet counter for use in evaluating communications channel usage;

routing the message to the mobile unit;

otherwise providing a proper format for the message for a the current channel and a new channel if the channel change flag is set;

routing the data packet to the current channel and a new channel;

incrementing the packet counter for the new channel for evaluating communications channel usage; and

routing the message to the mobile unit;

otherwise routing the message to the mobile unit if the message is for a poll rate increase by performing the steps of;

routing the message to a load service;

generating a log report;

generating a poll rate increase message;

sending the poll rate increase message to a radio network controller for processing; and

routing the poll rate increase message to the mobile unit.

30. A method of passive balancing mobile unit loading on communications channels of a multi-channel communications system employing time division multiple access where the mobile units operate at a predetermined polling rate comprising the steps of:

determining the communications channels in use at a tower site;

monitoring the loading on the communications channels;

calculating loading metrics for the communications channels from the number of mobile units and the mobile unit polling rates;

sending the loading metrics to the mobile units;

adding mobile units to a first communications channel as the mobile units come into the multi-channel communication system;

continuing the monitoring of the communications channels;

determining if a second communications channel at the tower site has a lower load metric than the first communications channel when said first communications channel reaches an overload condition;

commanding mobile units added to the first communications channel after the overload conditions has been reached to change channels to the second communications if the second communications channel is available; and

allowing the mobile units added to the first communications channel after the overload condition has been reached to stay on the first communications channel if the second communications channel is not available.

31. A method of active balancing mobile unit loading on communications channels of a multi-channel communications system employing time division multiple access where the mobile units operate at a predetermined polling rate comprising the steps of:

determining the communications channels in use at a tower site;

monitoring the loading on the communications channels;

calculating loading metrics for the communications channels from the number of mobile units and the mobile unit polling rates;

sending the loading metrics to the mobile units;

determining when the mobile unit polling rates are changed;

determining if a second communications channel at the tower site has a lower load metric than the first communications channel when said first communications channel reaches an overload condition;

commanding mobile units added to the first communications channel after the overload conditions has been reached to change channels to the second communications if the second communications channel is available; and

allowing the mobile units added to the first communications channel after the overload condition has been reached to stay on the first communications channel if the second communications channel is not available.

32. A method of mobile unit communications channel monitoring and changing in a multi-channel communications system comprising the steps of:

determining if there is a reason for a communications channel change from a current communications channel;

monitoring the current communications channel for messages if there is no reason for the communications channel change;

otherwise holding off sending queued messages until the communications channel change is complete if there is a reason for a channel change;

determining the reason for communications channel change;

switching to a commanded channel if the reason for change is a command from a multi-channel controller by performing the steps of;

determining if the commanded channel is acquired;

determining if a special acknowledgement signal has been received form the multi-channel controller in a predetermined time if the commanded channel has been acquired;

saving the commanded channel as a last used channel if the special acknowledgment signal has been received; and

monitoring the commanded channel for messages;

otherwise switching to a commanded channel if the reason for change is that all channels on a first tower site are overloaded by performing the steps of;

determining if there is a second tower site based on distance to said tower site;

requesting a least loaded channel at the second tower site;

sending a channel request message to a multi-channel controller;

starting a message timer in the multi-channel controller;

waiting for a response to the channel request message;

receiving a denied message from the multi-channel controller before the message timer has timed out;

returning to monitoring the current communications channel.

otherwise receiving no response to the channel request message from the multi-channel controller when the message timer has timed out;

incrementing a count in a retry counter in the multi-channel communications controller;

resending the channel request message if the count in the retry counter is less than a predetermined number;

returning to monitoring the current communications channel if the count in the retry counter is more than a predetermined number.

otherwise receiving a grant message containing a new commanded channel from the multi-channel controller before the message timer has timed out;

switching to the new commanded channel;

determining if the commanded channel is acquired;

determining if a special acknowledgment signal has been received form the multi-channel controller in a predetermined time if the commanded channel has been acquired;

saving the commanded channel as a last used channel if the special acknowledgment signal has been received; and

monitoring the commanded channel for messages.

otherwise switching to a commanded channel if the reason for change is that all channels on a first tower site distance are out of range by performing the steps of;

requesting a second tower site based on distance information;

requesting a least loaded channel at the second tower site;

sending a channel request message to a multi-channel controller;

starting a message timer in the multi-channel controller;

waiting for a grant message containing a new commanded channel;

switching to the new commanded channel;

determining if the commanded channel is acquired;

determining if a special acknowledgment signal has been received form the multi-channel controller in a predetermined time if the commanded channel has been acquired;

saving the commanded channel as a last used channel if the special acknowledgment signal has been received; and

monitoring the commanded channel for multi-channel controller messages.

33. A method of mobile unit communications channel monitoring in a multi-channel communications system comprising the steps of:

monitoring the commanded channel for multi-channel controller messages;

updating a table with communications channel status and loading when a multi-channel controller message is received;

checking the table for valid position and static data;

calculating a distance to a tower site if the position and static data is valid;

flagging the distance calculated as valid;

determining from the distance calculated if the tower site is in range;

marking the communications channels at the tower site as GO in a search table if the tower site is in range and NOGO in the search table if the tower site is out of range;

reordering the search table in a proper search order; and

determining if there is a reason for a communications channel change from a current communication channel.

34. A multi-channel communications system comprising:

a plurality of communications channels;

a plurality of mobile units for communicating over said communications channels said mobile units having forms of identification;

a plurality of dispatch agencies for communicating over said communications channels said dispatch agencies having a forms of identification; and

said mobile units communicating with said dispatch agencies over the communications channels according to the forms of identification.

35. The multi-channel communications system of claim 34 wherein any of said plurality of mobile units communicate with one of said dispatch agencies over one of said communications channels according to a form of identification common to the mobile units and the dispatch agency.

36. The multi-channel communications system of claim 34 further comprising a tower sites in geographic areas said tower sites having said plurality of communications channels for communicating with said mobile units.

37. The multi-channel communications system of claim 36 further comprising a multi-channel controller connected to said tower sites and said dispatch agencies said multi-channel controller routing messages between the mobile units and the dispatch agencies through the tower sites and the communications channels according to the forms of identification.

38. The multi-channel communications system of claim 37 wherein the multi-channel controller determines loading of the communications channels, hands off mobile units from a first communications channel to a second communications channel when loading on said first communications channel is excessive.