Abstract:
In a multi-network environment, a request signal is sent from a user terminal to each of a number of communications networks. In response, the network returns a response signal. Based on the response signals received from all networks, the user selects one of the networks. The response signal contains information on communication services of the requested network such as tariff data and current congestion level. The user terminal then establishes a connection to the selected communications network. In a modified embodiment, request signals may be sent during a handover to base stations of different wireless networks to request for congestion information for selecting a network having the lowest congestion level as a handover destination. In a further modification, when a congestion is encountered in a first network in response to a user&#39;s request, a second network of low congestion level is selected and indicated to the user.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to communications networks and more specifically to a multi-network communication system in which the user can select one of a plurality of communications networks owned and operated by different service providers. 
   2. Description of the Related Art 
   There are a number of communications networks owned and operated by different service providers. Users compare the service features of the networks to select one that meets their desired feature and purchase a mobile terminal of the selected network. In a service area where networks of different service providers co-exist one network may be carrying heavy traffic while another is carrying light traffic with a sufficient remaining capacity to handle new calls. In such instances, it is desirable for users to access the light-traffic network. To meet this objective, a multi-network user terminal has been developed to allow the user to use a desired one of the networks the terminal can access. However, none of these networks sends back a response signal that indicates the current level of network traffic. Therefore, the user has to arbitrarily choose one network and makes a call attempt. If congestion is encountered, the user abandons the call and switches over to another network and repeats the same process. The process may be repeated until the user encounters a network that can complete the call. 
   Therefore, a need does exist to provide a multi-network environment that allows users to receive services from a number of communications networks without the need for making a manual switchover from one network to another. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to provide a multi-network communications system in which the user can access a desired network. 
   According to a first aspect, the present invention provides a method of establishing a connection to a desired communications network, comprising the steps of sending a request signal to each of a plurality of communications networks, receiving response signals from the networks, indicating the received response signals, allowing a user to select one of the networks based on the indicated response signals, and establishing a connection to the selected communications network. 
   According to a second aspect, the present invention provides a communication terminal comprising a network interface for sending a request signal to each of a plurality of communications networks and for receiving response signals from the networks, and a user interface for indicating the received response signals to allow a user to enter a command signal based on the indicated response signals and selecting one of the networks according to the entered command signal. The network interface establishes a connection to one of the networks which is selected by the user interface. 
   According to a third aspect, the present invention provides a communication system comprising a plurality of wireless networks and a user communication terminal. Each of the wireless networks produces a response signal upon receipt of a request signal. The user communication terminal comprises a wireless interface for sending request signals to the wireless networks and for receiving response signals from the networks. A user interface indicates the received response signals to allow the user to enter a command signal and selects one of the wireless networks according to the entered command signal. The wireless interface establishes a connection to one of the communications networks which is selected by the user interface. 
   According to a fourth aspect, the present invention provides a method of performing a handover operation, comprising the steps of sending a handover request signal to each of a plurality of wireless networks, receiving response signals from the wireless networks, the response signals indicating respective traffic congestion levels of the wireless networks, selecting one of the wireless networks based on the response signals received from the networks, and establishing a connection to the selected wireless network. 
   According to a fifth aspect, the present invention provides a mobile terminal comprising a wireless interface for sending a handover request signal to each of a plurality of wireless networks and receiving response signals from the wireless networks, the response signals indicating respective traffic congestion levels of the networks, and control circuitry for selecting one of the wireless networks based on the received response signals. The wireless interface establishes a connection to the wireless network selected by the control circuitry. 
   According to a sixth aspect, the present invention provides a communication system comprising a plurality of wireless networks, each of said networks producing a response signal upon receipt of a handover request signal which indicates traffic congestion level of the network, and a wireless terminal. The wireless terminal comprises a wireless interface for sending the handover request signal to the wireless networks and receiving the response signals from the wireless networks. Control circuitry selects one of the wireless networks based on the received response signals. The wireless interface establishes a connection to one of the wireless networks which is selected y the control circuitry. 
   According to a seventh aspect, the present invention provides a method of establishing a connection to a selected network. The method comprises the steps of receiving, at a first communications network, a connection request from a user terminal, sending a request signal from the first communications network to a traffic management center if the connection request encounters a traffic congestion, sending a rerouting message from the center to the user terminal via the first communications network for identifying a second communications network whose congestion level is lower than a predefined threshold level to thereby allow a user to send a connection request to the second communications network. 
   According to an eighth aspect, the present invention provides a communication system including a traffic management center, and a plurality of communications networks. A first one of the communications networks receives a connection request from a user terminal and sends a request signal to the traffic management center when a traffic congestion is encountered in the first communications network. The traffic management center responds to the request signal by sending a message to the requesting network identifying a second one of the networks whose congestion level is lower than a predetermined threshold level. The message sent from the center is retransmitted to the user terminal to allow the user to switch to the second communications network. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be described in detail further with reference to the following drawings, in which: 
       FIG. 1  is a block diagram of a multi-network communication system according to the present invention; 
       FIG. 2  is a flowchart of the operation of a user terminal according to a first embodiment of the present invention; 
       FIG. 3  is a flowchart of the operation of a communications network according to the first embodiment of this invention; 
       FIG. 4  is a flowchart of the operation of a user terminal according to a second embodiment of the present invention; 
       FIG. 5  is a flowchart of the operation of a wireless network according to the second embodiment of this invention; 
       FIG. 6  is a block diagram of a second embodiment of the multi-network communication system of the present invention; 
       FIG. 7  is a flowchart of the operation of a communication network according to the second embodiment of the present invention; and 
       FIG. 8  is a flowchart of the operation of a traffic management center according to the second embodiment. 
   

   DETAILED DESCRIPTION 
   In  FIG. 1 , there is shown a user terminal  10  which can selectively access to a plurality of wireless communication networks  11 ,  12  and  13 , which are respectively owned and operated by different service providers. User terminal  10  is either a mobile terminal of cellular phone network or a fixed terminal of a wireless network connected by a fixed wireless access (FWA) system, for example. 
   As will be described, the user at the terminal  10  selects a desired network according to response signals received from the wireless networks  11 ,  12  and  13 . For this purpose, the user terminal  10  is essentially comprised of a wireless interface  21 , a controller  22  and a user interface  23 . Controller  22  directs the wireless interface  21  to send a request signal to and receive a response signal from each wireless network. User interface  23  includes a display and an annunciator for indicating the received response signal to permit the user to select a desired network and enter a command signal. Controller  22  directs the wireless interface  21  to establish a connection to the network which is selected by the user interface  23 . 
   Each of the wireless networks is essentially comprised of a wireless interface  31 , a controller  32 , a memory or database  33  and a traffic monitor  34 . Database  33  stores network service information such as tariff of the network. Traffic monitor  34  constantly monitors the network for detecting the traffic congestion level of the network. In response to a request signal from the user terminal  10 , the controller  32  of an accessed wireless network reads tariff data from the database  33  and formulates a response signal with the tariff data and the congestion level detected by the traffic monitor  34  and transmits the response signal to the requesting user terminal  10 . 
   These wireless networks have different tariffs and traffic handling capacities. For example, the wireless network  11  has lowest phone rate and lowest traffic handling capacity (i.e., highest congestion level), the wireless network  12  has medium phone rate and medium traffic handling capacity (i.e., medium congestion level), and the wireless network  13  has highest phone rate and highest traffic handling capacity (i.e., lowest congestion level). 
   According to a flowchart shown in  FIG. 2 , the operation of the controller  22  proceeds by initially setting a network identifying variable “i” to 1 at step  101 . Controller  22  selects a network (i) at step  102  and sends a request signal to the selected network for requesting it to send a phone rate schedule of the network and the current traffic level (step  103 ). 
   In  FIG. 3 , the network identified by the variable “i” responds to the request signal (step  201 ) and reads the tariff data from the database  33  and causes the traffic monitor  34  to detect the current traffic level of the network (step  202 ) and formulates and sends a response signal to the requesting user to communicate the tariff and congestion data. 
   In  FIG. 2 , the user terminal receives the response signal at step  104 . The response signal is converted by the controller  22  into a vocal announcement which is supplied to an annunciator or converted to textual data which is supplied to display unit (step  105 ). If all networks are not tested (step  106 ), the variable “i” is incremented by one at step  107 . Steps  102  to  105  are repeated on the next wireless network until requested information are obtained from all networks. 
   If all networks have been tested, flow proceeds from step  106  to step  108  to prompt the user to enter a command signal for selecting one of the communications networks. When a select command is entered from the user interface  23  at step  109 , the controller  22  directs the wireless interface  21  to establish a connection to the selected network (step  110 ). 
   The present invention can be advantageously used to perform a handover when communication signals transmitted from the user terminal  10  fall below a critical level during a call. 
     FIG. 4  is a flowchart of the operation of the user terminal  10  when the communicating wireless network is performing a handover. When the mobile terminal detects that a handover operation is in progress (step  301 ), a variable “j” is incremented by 1 at step  302 . Variable “j” identifies a wireless network other than the network with which the mobile terminal is currently in communication. Mobile terminal  10  selects a base station of the wireless network (j) at step  303  and sends a handover request signal to the selected network (step  304 ). 
   In  FIG. 5 , the network identified by the variable “j” responds to the handover request signal (step  401 ) and detects the current traffic level of the network with its traffic monitor (step  402 ) and sends a response signal to the requesting user to inform the detected congestion level (step  403 ). 
   In  FIG. 4 , the requesting user terminal receives the congestion level indicating signal from the selected network (step  305 ). Steps  303  to  305  are repeated on surrounding base stations of other wireless networks by incrementing the variable “j” by one at step  307  until all surrounding base stations have been tested (step  306 ). 
   At step  308 , the user terminal selects one of the wireless networks whose congestion level is of the lowest value and establishes a handover connection to the base station of the selected wireless network (step  309 ). 
   The present invention can also be implemented in a different configuration as shown in  FIG. 6  in which a user terminal  20  can operate in multiple modes. In a mobile mode, the user terminal is served by a wireless network  21  and in a fixed mode it is served by an optical network  22  or a metallic wireline (copper or coaxial) network  23 . User terminal  20  is essentially comprised of a wireless interface  41 , an optical line interface  42  and a wireline interface  43  for establishing a connection to the wireless network  21 , the optical network  22  and the wireline network  23 , respectively. A controller  44  is provided between the interfaces  41 ,  42 ,  43  and a user interface  45 . 
   A traffic management center  50  is provided, which includes a user-information database  52 , a routing database  53  and a controller  51  connected to both databases. Networks  21 ,  22  and  23  are also connected to the controller  51 . The information stored in the database  52  identifies networks to which registered users are accessible. Routing database  53  maintains cost data indicating the cost of a call routed through each of the networks  21 ,  22 ,  23  to a particular destination. Controller  51  monitors networks  21 ,  22  and  23  to detect their congestion levels. If a request signal is received from a user terminal via one of the networks the controller  51  reads the information of the requesting user from the database  52  and determines whether the user is accessible to other networks. If this is the case, the controller  51  returns a response signal to the user terminal to indicate another network as an alternate route if the congestion level of the current network exceeds some threshold level. 
   In operation, the user initially selects one of the communications networks  21 ,  22  and  23 . If the selected network is the wireless network  21 , the user establishes a wireless link via wireless interface  41  to a base station by manipulating the operating keys of the user terminal. If the initially selected network is one of networks  22  and  23 , the user attaches the user terminal  20  to the line terminal of the selected network through the corresponding line interface  42  or  43  and establishes a connection to the selected network. Such line terminals may be provided in a public telephone booth or an office environment in which users can access a number of different networks via a private branch exchange. 
   The operation of each of the networks  21 ,  22  and  23  proceeds according to the flowchart of  FIG. 7  and the operation of the traffic management center  50  proceeds according to the flowchart of  FIG. 8 . 
   If a user encounters a congestion in the initially selected network (step  501 ), the selected network sends a request signal to the traffic management center  50  (step  502 ). When the controller  51  of management center receives the request signal from one of the networks  21 ,  22 ,  23  (step  601 ), it reads user information from the database  52  (step  602 ) to determine whether the user is entitled to access other networks (step  603 ). If the user is not entitled to access other networks, flow proceeds from step  603  to step  610  to send a busy message to the requesting network, and returns to the starting point of the routine. If the decision at step  603  is affirmative, flow proceeds to step  604  to compare the congestion levels of other networks with a predefined threshold level and determines if the congestion level of a network is lower than the threshold level (step  605 ), If this is the case, flow proceeds from step  605  to step  606  to check to see if all other networks have been tested. If not, flow returns to step  604  to repeat the comparison step on the next network. If all other networks have been tested, flow proceeds to step  607  to determine the network having a least routing cost, and the controller  51  sends a rerouting message to the requesting network (step  608 ). If the congestion levels of all other networks are higher than the threshold, flow proceeds through steps  605  and  609  to step  610  to send a busy message to the requesting network, 
   When the requesting network receives a rerouting message or a busy message from the traffic management center  50  (step  503 ), it retransmits the receive message to the requesting user as a response signal (step  504 ) and returns to the starting point of the routine. 
   When the user receives a response signal from the initially selected network, the user terminal  20  may be switched to another interface for re-establishing a connection.