Abstract:
An apparatus and methods are disclosed for enabling quality-of-service and call admission control for wireless telecommunications terminals without first submitting a traffic specification. The illustrative embodiment of the present invention is particularly advantageous for IEEE 802.11e networks because the 802.11e standard, which in its currently-drafted form contains provisions for terminals to submit traffic specifications, might not require 802.11e terminals to submit traffic specifications in the finalized 802.11e standard. Proper call admission control and, consequently, quality-of-service for wireless applications therefore might not be universally available to future 802.11e-compliant terminals unless one or more embodiments of the present invention are deployed.

Description:
REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. provisional patent application Ser. No. 60/478,821 filed 17 Jun. 2003, entitled “Method For Coupling Call Admission Control And Shared Bandwidth Management,” (Attorney Docket: 503039-A-00-US), which is also incorporated by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to telecommunications in general, and, more particularly, to quality-of-service (QoS) and admission control.  
       BACKGROUND OF THE INVENTION  
       [0003]      FIG. 1  depicts a schematic diagram of telecommunications system  100  in the prior art. Telecommunications system  100  comprises telecommunications terminals  101 - 1  and  101 - 2 , network  110 , and server  120 , interconnected as shown. Network  110  is a communications network such as the Internet, the Public Switched Telephone Network (PSTN), etc., as is well-known in the art. Telecommunications terminals  101 - 1  and  101 - 2  are devices such as personal computers, telephones, etc. that communicate with other telecommunications terminals via network  110 . Each telecommunications terminal has an associated contact identifier (e.g., telephone number, email address, Internet Protocol address, etc.) that uniquely identifies that terminal in the address space of telecommunications system  100 . Server  120  (e.g., a Session Initiation Protocol [SIP] server, an SIP proxy server, etc.) maintains a list that maps user identifiers (e.g., user names, social security numbers, etc.) to contact identifiers.  
         [0004]     Server  120  enables the users of telecommunications terminals to communicate as illustrated by the following example: A first user, the user of telecommunications terminal  101 - 1 , enters a command into the terminal to place a call (e.g. voice call, email, text chat, video, etc.) to a second user. Telecommunications terminal  101 - 1  sends via an appropriate protocol (e.g., the Session Initiation Protocol [SIP], etc.) a message (e.g., an SIP INVITE message, etc.) server  120  that requests the contact identifier of the telecommunications terminal associated with the second user (i.e., the terminal that the second user is currently using). Server  120  then sends a response (e.g., an SIP acknowledgement [ACK], etc.) to telecommunications terminal  101 - 1  that indicates whether the second user can be reached, and if so, the associated contact identifier. Upon receiving the associated contact identifier, telecommunications terminal  101 - 1  sends one or more messages directly to telecommunications terminal  101 - 2  via network  110 , and telecommunications terminal  101 - 2 , which obtains the contact identifier of telecommunications terminal  101 - 1  via the received message(s), can respond directly to telecommunications terminal  101 - 2  via network  110 .  
         [0005]      FIG. 2  depicts a schematic diagram of wireless local-area network  200  in the prior art, which comprises access point  201  and wireless terminals  202 - 1  through  202 -N, wherein N is a positive integer, interconnected as shown. Each wireless terminal  202 -i, wherein i is member of the set of positive integers {1, . . . N}, is a device (e.g., a notebook computer, personal digital assistant [PDA], tablet PC, etc.) that communicates wirelessly with other terminals in network  200  via access point  201 .  
         [0006]     Access point  201  and wireless terminals  202 - 1  through  202 -N transmit messages over a shared-communications channel such that if two or more wireless terminals (or an access point and a wireless terminal) transmit messages simultaneously, then one or more of the messages can become corrupted (which results in a collision and the destruction of both messages). As a consequence, local-area networks typically employ protocols for ensuring that a wireless terminal or access point can gain exclusive access to the shared-communications channel for an interval of time in order to transmit messages without collisions.  
         [0007]     Such protocols can be classified into two types: contention-based protocols, and contention-free protocols. In a contention-based protocol, wireless terminals  202 - 1  through  202 -N and access point  201  compete to gain exclusive access to the shared-communications channel.  
         [0008]     In a contention-free protocol, in contrast, a coordinator (e.g., access point  201 , etc.) grants access to the shared-communications channel to one station at a time. One technique in which a coordinator can grant access to the shared-communications channel is polling. In protocols that employ polling, stations submit a polling request to the coordinator, and the coordinator grants stations exclusive access to the shared-communications channel sequentially in accordance with a polling schedule.  
         [0009]     The Institute of Electrical and Electronics Engineers (IEEE) 802.11e specification is an emerging set of protocols that provides quality-of-service (QoS) for wireless local-area networks, in addition to contention-based and contention-free shared-communications channel access. Quality-of-service is an important consideration for wireless local-area networks given the serialization of communications imposed by the shared-communications channel, as well as the growing bandwidth requirements of various applications. An IEEE 802.11e-compliant wireless terminal can transmit to the wireless access point a request to add a traffic stream (ADDTS), accompanied with the following information: 
        (i) a traffic specification (TSPEC) that specifies one or more parameters of future traffic that will be generated by the terminal (e.g., a temporal period for periodic traffic streams, a minimum service interval, a maximum service interval, etc.); and     (ii) a traffic class that indicates the priority of future traffic.        
 
         [0012]     The access point will either accept or decline the request, depending on the available bandwidth. If the request is declined the station may not transmit with the privileges of the traffic class indicated in the TSPEC. The ability of an access point to decline an ADDTS request enables bandwidth management, also known as “over-the-air admission control.” request enables bandwidth management, also known as “over-the-air admission control”.  
       SUMMARY OF THE INVENTION  
       [0013]     The present invention enables quality-of-service and over-the air call admission control for wireless terminals that engage in communications without first submitting a traffic specification (TSPEC). The illustrative embodiment of the present invention is particularly advantageous for IEEE 802.11e networks because the 802.11e standard, which in its currently-drafted form contains provisions for terminals to submit traffic specifications, might not require 802.11e terminals to submit traffic specifications in the finalized 802.11e standard. Proper call admission control and, consequently, quality-of-service for wireless applications therefore might not be universally available to future 802.11e-compliant terminals unless one or more embodiments of the present invention are deployed.  
         [0014]     The illustrative embodiment employs a gateway that connects to the wireless access points of one or more local-area networks (LANs) and sits between the LANs and a network (e.g., the Internet, the Public Switched Telephone Network (PSTN), etc.) that connects to a server (e.g., a Session Initiation Protocol [SIP] server, an SIP proxy server, etc.). In the illustrative embodiment, a first user&#39;s wireless terminal places a call to a second user by sending to its wireless access point a message that comprises: (i) a traffic stream description (e.g., an SIP Real-Time Protocol [RTP] payload type, etc.) that specifies the nature of a call (e.g., a voice telephone call, a video conference, a text-based instant message [IM], etc.), and (ii) a request for the contact identifier of the second user&#39;s telecommunications terminal. The message might also optionally include one or both of (iii) a traffic category, and (iv) a traffic specification. The wireless access point sends the message to the gateway for forwarding to the server. The gateway, before forwarding the message to the server, stores the traffic stream description (and if present, the traffic category and traffic specification) in a record associated with the call. In some embodiments, the gateway might include in the record a measure of communication resource usage of the shared-communications channel (e.g., channel capacity utilization, etc.) or might append this measure to the message before forwarding.  
         [0015]     The server  120  then sends a response (e.g., an SIP acknowledgement [ACK], etc.), to the first user&#39;s telecommunications terminal via the network, gateway, and wireless access point that indicates whether the second user can be reached, and if so, the associated contact identifier. The gateway, upon receiving the response, intercepts the response instead of forwarding the response to the appropriate wireless access point. When the response contains a positive acknowledgement, the gateway consults the appropriate record and checks whether a traffic specification was provided for the call. If no traffic specification was provided, the gateway determines, based on the traffic stream description and measure of communication resource usage, whether the amount of communication resource (e.g., bandwidth, channel idleness, etc.) currently available is sufficient to support the call (i.e., whether the call should be admitted). The gateway then sends a message to the server that indicates whether the call is admitted, and the server proceeds accordingly.  
         [0016]     A similar process occurs when a call is directed to a wireless terminal.  
         [0017]     Although the illustrative embodiment of the present invention is disclosed in the context of IEEE 802.11e local-area networks, it will be clear to those skilled in the art how to make and use embodiments of the present invention for other kinds of networks and network protocols. In addition, the term “call,” while normally used only in the context of telephone voice calls, will be used to encompass all manners of communication (e.g. email, text chat, video, etc.), and it will be clear to those skilled in the art how to make and use embodiments of the present invention for such alternative means of communication.  
         [0018]     The illustrative embodiment comprises: (a) a receiver for receiving a first message from a server, wherein the first message is based on a second message that (i) is sent from a first telecommunications terminal to the server, and (ii) specifies a traffic stream description for a call initiated by a second telecommunications terminal and directed to the first telecommunications terminal, and wherein the first message comprises an estimated communication resource requirement for the call that is based on the traffic stream description for the call; (b) a processor for determining whether to admit the call based on (i) the estimated communication resource requirement for the call, and (ii) a measure of communication resource usage of a shared-communications channel associated with the first telecommunications terminal; and (c) a transmitter for transmitting a third message to the server that indicates whether the call is admitted. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]      FIG. 1  depicts a schematic diagram of an exemplary telecommunications system in the prior art.  
         [0020]      FIG. 2  depicts a schematic diagram of an exemplary wireless local-area network in the prior art.  
         [0021]      FIG. 3  depicts a schematic diagram of a telecommunications system that involves at least one wireless terminal, in accordance with the illustrative embodiment of the present invention.  
         [0022]      FIG. 4  depicts a schematic diagram of wireless local-area network  301 -i, as shown in  FIG. 3 , in accordance with the illustrative embodiment of the present invention.  
         [0023]      FIG. 5  depicts a block diagram of the salient components of wireless access point  401 , as shown in  FIG. 4 , in accordance with the illustrative embodiment of the present invention.  
         [0024]      FIG. 6  depicts a block diagram of the salient components of gateway  306 , as shown in  FIG. 3 , in accordance with the illustrative embodiment of the present invention.  
         [0025]      FIG. 7  depicts a block diagram of the salient components of server  320 , as shown in  FIG. 3 , in accordance with the illustrative embodiment of the present invention.  
         [0026]      FIG. 8  depicts the message flows associated with a wireless terminal placing a call, in accordance with the illustrative embodiment of the present invention.  
         [0027]      FIG. 9  depicts the message flows associated with an admitted call placed by a wireless terminal, in accordance with the illustrative embodiment of the present invention.  
         [0028]      FIG. 10  depicts the message flows associated with a rejected call placed by a wireless terminal, in accordance with the illustrative embodiment of the present invention.  
         [0029]      FIG. 11  depicts the message flows associated with a wireless terminal receiving a call, in accordance with the illustrative embodiment of the present invention.  
         [0030]      FIG. 12  depicts the message flows associated with an admitted call to a wireless terminal, in accordance with the illustrative embodiment of the present invention.  
         [0031]      FIG. 13  depicts the message flows associated with a rejected call to a wireless terminal, in accordance with the illustrative embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0032]     For the purposes of the specification and claims, the term “traffic stream description” is defined as a datum that specifies (i) the nature of a traffic stream associated with a call (e.g., a voice traffic stream, a video stream, a text-based instant message [IM] traffic stream, etc.), and, optionally, (ii) one or more parameters associated with the traffic stream (e.g., periodicity, bandwidth requirements, latency tolerance, etc.)  
         [0033]     For the purposes of the specification and claims, the term “call” is defined as communication between two or more terminals (e.g. a voice telephone call, an email, a text-based instant message [IM] session, a video conference, etc.).  
         [0034]     For the purposes of the specification and claims, the term “communication resource usage” is defined as a datum that characterizes usage of a communication resource (e.g., bandwidth, channel idleness, etc.) associated with a communication medium.  
         [0035]      FIG. 3  depicts a schematic diagram of telecommunications system  300  that involves at least one wireless terminal, in accordance with the illustrative embodiment of the present invention. Telecommunications system  300  comprises one or more wireless local-area networks  301 -i through  301 -K, where K is a positive integer; gateway  306 ; server  320 ; and network  110 , as described above and with respect to  FIG. 1 ; interconnected as shown.  
         [0036]     Wireless local-area networks  301 -i through  301 -K, are similar to wireless local-area network  200  of  FIG. 2 , with the exception of different wireless terminals and wireless access points employed in lieu of terminals  202  and access point  201 , respectively. Wireless local-area networks  301 -i through  301 -K are described in detail below and with respect to  FIG. 4 .  
         [0037]     Gateway  306  connects wireless local-area networks  301 -i through  301 -K to network  110  in well-known fashion. In addition, gateway  306  performs logic, receives messages from wireless local-area networks  301 -i through  301 -K and from network  110 , and transmits messages to wireless local-area networks  301 -i through  301 -K and to network  110 , as described below and with respect to  FIG. 6  and  FIGS. 8 through 13 .  
         [0038]     Server  320  provides the functionality of server  110  in the prior art, and in addition, transmits special call-setup TSPEC (CS-TSPEC) messages as described below and with respect to  FIGS. 7 through 13 .  
         [0039]      FIG. 4  depicts a schematic diagram of wireless local-area network  301 -i, as shown in  FIG. 3 , in accordance with the illustrative embodiment of the present invention. Wireless local-area network  301 -i comprises wireless access point  401 , and wireless terminals  402 - 1  through  402 -N, interconnected as shown.  
         [0040]     Wireless access point  401  provides the functionality of access point  201  in the prior art, and in addition, appends information to call-setup messages sent from wireless terminals  202 , as described below and with respect to  FIGS. 8 through 13 .  
         [0041]     Wireless terminals  402 - 1  through  402 -N provide the functionality of wireless terminals  302  in the prior art, and in addition, provided additional quality-of-service services in accordance with a particular protocol (e.g., IEEE 802.11e, etc.). In the illustrative embodiment, wireless terminals  402 - 1  through  402 -N are IEEE 802.11e terminals, where each terminal  402 -i might or might not provide a traffic specification (TSPEC) for call requests.  
         [0042]      FIG. 5  depicts a block diagram of the salient components of wireless access point  401 , in accordance with the illustrative embodiment of the present invention. Wireless access point  401  comprises receiver  501 , processor  502 , memory  503 , and transmitter  504 , interconnected as shown.  
         [0043]     Receiver  501  is a circuit that is capable of receiving messages from wireless terminals  402 - 1  through  402 -N and from gateway  306 , in accordance with  FIGS. 8 through 13  below, and of forwarding the messages to processor  502 . It will be clear to those skilled in the art how to make and use receiver  501 .  
         [0044]     Processor  502  is a general-purpose processor that is capable of executing instructions stored in memory  503 , of reading data from and writing data into memory  503 , and of executing the tasks described below and with respect to  FIGS. 8 through 13 . In some alternative embodiments of the present invention, processor  502  is a special-purpose processor (e.g., a network processor, etc.). In either case, it will be clear to those skilled in the art, after reading this disclosure, how to make and use processor  502 .  
         [0045]     Memory  503  is capable of storing programs and data used by processor  502 , as is well-known in the art, and might be any combination of random-access memory (RAM), flash memory, disk drive, etc. It will be clear to those skilled in the art, after reading this specification, how to make and use memory  503 .  
         [0046]     Transmitter  504  is a circuit that is capable of receiving messages from processor  502 , in well-known fashion, and of transmitting the messages to wireless terminals  402 - 1  through  402 -N and to gateway  306  in accordance with  FIGS. 8 through 13  below. It will be clear to those skilled in the art how to make and use transmitter  504 .  
         [0047]      FIG. 6  depicts a block diagram of the salient components of gateway  306  in accordance with the illustrative embodiment of the present invention. Gateway  306  comprises receiver  601 , processor  602 , memory  603 , and transmitter  604 , interconnected as shown.  
         [0048]     Receiver  601  is a circuit that is capable of receiving messages from wireless local area networks  301  and from network  110  in accordance with  FIGS. 8 through 13  below, and of forwarding these messages to processor  602 . It will be clear to those skilled in the art how to make and use receiver  601 .  
         [0049]     Processor  602  is a general-purpose processor that is capable of executing instructions stored in memory  603 , of reading data from and writing data into memory  603 , and of executing the tasks described below and with respect to  FIGS. 8 through 13 . In some alternative embodiments of the present invention, processor  602  is a special-purpose processor (e.g., a network processor, etc.). In either case, it will be clear to those skilled in the art, after reading this disclosure, how to make and use processor  602 .  
         [0050]     Memory  603  is capable of storing programs and data used by processor  602 , as is well-known in the art, and might be any combination of random-access memory (RAM), flash memory, disk drive, etc. It will be clear to those skilled in the art, after reading this specification, how to make and use memory  603 .  
         [0051]     Transmitter  604  is a circuit that is capable of receiving messages from processor  602 , in well-known fashion, and of transmitting messages to local-area networks  200 -i through  200 -K and to network  110  in accordance with  FIGS. 8 through 13  below. It will be clear to those skilled in the art how to make and use transmitter  604 .  
         [0052]      FIG. 7  depicts a block diagram of the salient components of server  320 , in accordance with the illustrative embodiment of the present invention. Server  320  comprises receiver  701 , processor  702 , memory  703 , and transmitter  704 , interconnected as shown.  
         [0053]     Receiver  701  is a circuit that is capable of receiving messages from network  110  in accordance with  FIGS. 8 through 13  below, and of forwarding these messages to processor  702 . It will be clear to those skilled in the art how to make and use receiver  701 .  
         [0054]     Processor  702  is a general-purpose processor that is capable of executing instructions stored in memory  703 , of reading data from and writing data into memory  703 , and of executing the tasks described below and with respect to FIGS.  8  through  13 . In some alternative embodiments of the present invention, processor  702  is a special-purpose processor (e.g., a network processor, etc.). In either case, it will be clear to those skilled in the art, after reading this disclosure, how to make and use processor  702 .  
         [0055]     Memory  703  is capable of storing programs and data used by processor  702 , as is well-known in the art, and might be any combination of random-access memory (RAM), flash memory, disk drive, etc. It will be clear to those skilled in the art, after reading this specification, how to make and use memory  703 .  
         [0056]     Transmitter  704  is a circuit that is capable of receiving messages from processor  702 , in well-known fashion, and of transmitting messages to network  110  in accordance with  FIGS. 8 through 13  below. It will be clear to those skilled in the art how to make and use transmitter  704 .  
         [0057]      FIG. 8  depicts the message flows associated with the user of wireless terminal  402 -i placing a call, in accordance with the illustrative embodiment of the present invention.  
         [0058]     At time t 0 , wireless terminal  402 -i, the terminal of the user placing a call, sends a message via wireless access point  401  and gateway  306  to server  320  (e.g., an SIP INVITE message, etc.). The message comprises: (i) a traffic stream description (e.g., an SIP Real-Time Protocol [RTP] payload type, etc.) that specifies the nature of a call (e.g., a voice telephone call, a video conference, a text-based instant message [IM], etc.); and (ii) the user identifier of the person to be called. The message might also optionally include one or both of: (iii) a traffic category, and (iv) a traffic specification (TSPEC). Before transmitting the message to server  320 , gateway  306  stores the traffic stream description (and if present, the traffic category and traffic specification) in a newly-created record associated with this call.  
         [0059]     In some other embodiments of the present invention, wireless access point  401  might also append to the message (v) a measure of communication resource usage of the shared-communications channel (e.g., channel capacity utilization, etc.). In such embodiments, gateway  306 , before transmitting the message to server  320 , might also store the measure of communication resource usage in the newly-created record.  
         [0060]     At time t 1 , server  320  determines which terminal is currently associated with the user identifier of the called user (i.e., the “destination terminal”), and sends a message (e.g., an SIP OPTIONS message, etc.) to the destination terminal to determine the capabilities of the destination terminal (e.g., whether the destination terminal supports certain types of media, etc.).  
         [0061]     At time t 2 , server  320  sends a response to wireless terminal  402 -i indicating that the server is attempting to set up the call, in well-known fashion.  
         [0062]     At time t 3 , the destination terminal sends a response to server  320  (e.g., an SIP OK message, etc.) in well-known fashion.  
         [0063]     At time t 4 , server  320  sends a message addressed to wireless terminal  402 -i called a call-setup TSPEC (CS-TSPEC) request. In the illustrative embodiment, the CS-TSPEC is not a standard SIP message or an extension, as gateway  306  would not be able to interpret an SIP message addressed to wireless terminal  402 -i that is subject to security encapsulation. In the illustrative embodiment, the CS-TSPEC message is sent to a special reserved User Datagram Protocol (UDP) port that gateway  306  monitors, as is well-understood in the art. In some other embodiments, a Transmission Control Protocol (TCP) socket might be used instead of UDP; however, this might result in decreased efficiency. Like the SIP Resource Reservation Protocol (RSVP), the CS-TSPEC mechanism provides out-of-band signaling for bandwidth reservation.  
         [0064]     Gateway  306  intercepts the CS-TSPEC request and checks if wireless terminal  402 -i, the calling terminal, included a traffic specification (TSPEC) in the message sent at time t 0 . If not, gateway  306  determines, based on the traffic stream description and measure of communication resource usage stored at gateway  306 , whether the amount of communication resource (e.g., bandwidth, channel idleness, etc.) currently available is sufficient to support the call (i.e., whether the call should be admitted).  
         [0065]     At time t 5 , gateway  306  sends a message to server  320  that indicates whether the call is admitted, in well-known fashion. In the illustrative embodiment, the message is sent to a special reserved UDP port at server  320 , where it is awaited by a collocated daemon, synchronized with the pending invitation message, described below and with respect to  FIG. 9 .  
         [0066]     If the call was admitted, the message flows of the illustrative embodiment proceed as described below and with respect to  FIG. 9 ; otherwise, the message flows of the illustrative embodiment proceed as described below and with respect to  FIG. 10 .  
         [0067]      FIG. 9  depicts the message flows associated with an admitted call placed by a wireless terminal, in accordance with the illustrative embodiment of the present invention.  
         [0068]     At time t 6 , server  320  sends a message to the destination terminal that invites the user of the destination terminal to accept the call (e.g., an SIP INVITE message, etc.), in well-known fashion.  
         [0069]     At time t 7 , the destination terminal sends a response to server  320  indicating that the call is accepted (e.g., an SIP OK message, etc.), in well-known fashion.  
         [0070]     At time t 8 , server  320  sends a message to calling terminal  202 -i indicating that the call is admitted (e.g., an SIP OK message, etc.), in well-known fashion.  
         [0071]     At time t 9 , calling terminal  202 -i sends an acknowledgement to server  320 , in well-known fashion.  
         [0072]     At time t 10 , server  320  sends an acknowledgement to the destination terminal, in well-known fashion. When the destination terminal receives the acknowledgement, calling terminal  202 -i and the destination terminal can communicate as in the prior art.  
         [0073]      FIG. 10  depicts the message flows associated with a rejected call placed by a wireless terminal, in accordance with the illustrative embodiment of the present invention.  
         [0074]     At time t 6 , server  320  sends a message to calling terminal  202 -i that indicates that the call was rejected (e.g., an SIP “488 NOT ACCEPTABLE” message, etc.), in well-known fashion.  
         [0075]     At time t 7 , calling terminal  202 -i sends an acknowledgement to server  320 , in well-known fashion.  
         [0076]      FIG. 11  depicts the message flows associated with a wireless terminal receiving a call, in accordance with the illustrative embodiment of the present invention.  
         [0077]     At time t 0 , the terminal of the user placing a call, sends a message to server  320  (e.g., an SIP INVITE message, etc.). The message comprises: (i) a traffic stream description (e.g., an SIP Real-Time Protocol [RTP] payload type, etc.) that specifies the nature of a call (e.g., a voice telephone call, a video conference, a text-based instant message [IM], etc.); and (ii) the user identifier of the person to be called. If the calling terminal is a wireless terminal that is compliant with a quality-of-service protocol (e.g., IEEE 802.11e, etc.), the message might also optionally include one or both of: (iii) a traffic category, and (iv) a traffic specification (TSPEC).  
         [0078]     At time t 1 , server  320  determines which wireless terminal  402 -i is currently associated with the user identifier of the called user, and sends a message to the calling terminal that indicates that the server is attempting to set up the call, in well-known fashion.  
         [0079]     At time t 2 , server  320  sends a message to wireless terminal  402 -i (e.g., an SIP OPTIONS message, etc.) that indicates an incoming call, and comprises items (i) and (ii) above (and potentially one or both of items (iii) and (iv)) in well-known fashion.  
         [0080]     At time t 3 , wireless terminal  402 -i sends, via wireless access point  401  and gateway  306 , a response to server  320  (e.g., an SIP OK message, etc.) in well-known fashion. Gateway  306 , before transmitting the message to server  320 , stores the traffic stream description (and if present, the traffic category and traffic specification) in a newly-created record associated with this call.  
         [0081]     In some other embodiments, wireless access point  401  might also append to this message (v) a measure of communication resource usage of the shared-communications channel (e.g., channel capacity utilization, etc.). In such embodiments, gateway  306 , before transmitting the message to server  320 , might also store the measure of communication resource usage in the newly-created record.  
         [0082]     At time t 4 , server  320  sends a special message directed to wireless terminal  402 -i that requests a call-setup TSPEC (CS-TSPEC). In the illustrative embodiment, the CS-TSPEC message is sent to a special reserved User Datagram Protocol (UDP) port that gateway  306  monitors, as is well-understood in the art.  
         [0083]     Gateway  306  intercepts the CS-TSPEC request and checks if there is a traffic specification (TSPEC) for the call. If not, gateway  306  determines, based on the traffic stream description and measure of communication resource usage stored at gateway  306 , whether the amount of communication resource (e.g., bandwidth, channel idleness, etc.) currently available is sufficient to support the call (i.e., whether the call should be admitted).  
         [0084]     At time t 5 , gateway  306  sends a message to server  320  that indicates whether the call is admitted, in well-known fashion. In the illustrative embodiment, the message is sent to a special reserved UDP port at server  320 , where it is awaited by a collocated daemon, synchronized with the pending invitation message, described below and with respect to  FIG. 12 .  
         [0085]     If the call was admitted, the message flows of the illustrative embodiment proceed as described below and with respect to  FIG. 12 ; otherwise, the message flows of the illustrative embodiment proceed as described below and with respect to  FIG. 13 .  
         [0086]      FIG. 12  depicts the message flows associated with an admitted call to a wireless terminal, in accordance with the illustrative embodiment of the present invention.  
         [0087]     At time t 6 , server  320  sends a message to wireless terminal  402 -i that invites the user of the terminal to accept the call (e.g., an SIP INVITE message, etc.), in well-known fashion.  
         [0088]     At time t 7 , wireless terminal  402 -i sends a response to server  320  indicating that the call is accepted (e.g., an SIP OK message, etc.), in well-known fashion.  
         [0089]     At time t 8 , server  320  sends a message to the calling terminal indicating that the call is admitted (e.g., an SIP OK message, etc.), in well-known fashion.  
         [0090]     At time t 9 , the calling terminal sends an acknowledgement to server  320 , in well-known fashion.  
         [0091]     At time t 10 , server  320  sends an acknowledgement to wireless terminal  402 -i, in well-known fashion. When wireless terminal  402 -i receives the acknowledgement, the calling terminal and wireless terminal  402 -i can communicate as in the prior art.  
         [0092]      FIG. 13  depicts the message flows associated with a rejected call to a wireless terminal, in accordance with the illustrative embodiment of the present invention.  
         [0093]     At time t 6 , server  320  sends a message to the calling terminal that indicates that the call was rejected (e.g., an SIP “488 NOT ACCEPTABLE” message, etc.), in well-known fashion.  
         [0094]     At time t 7 , the calling terminal sends an acknowledgement to server  320 , in well-known fashion.  
         [0095]     As will be well-understood by those skilled in the art, when both the calling terminal and the called terminal are wireless terminals, the message flows associated with the call will be a composite of the message flows of  FIGS. 8 through 10  and  FIGS. 11 through 13 .  
         [0096]     It is to be understood that the above-described embodiments are merely illustrative of the present invention and that many variations of the above-described embodiments can be devised by those skilled in the art without departing from the scope of the invention. For example, in this Specification, numerous specific details are provided in order to provide a thorough description and understanding of the illustrative embodiments of the present invention. Those skilled in the art will recognize, however, that the invention can be practiced without one or more of those details, or with other methods, materials, components, etc.  
         [0097]     Furthermore, in some instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the illustrative embodiments. It is understood that the various embodiments shown in the Figures are illustrative, and are not necessarily drawn to scale. Reference throughout the specification to “one embodiment” or “an embodiment” or “some embodiments” means that a particular feature, structure, material, or characteristic described in connection with the embodiment(s) is included in at least one embodiment of the present invention, but not necessarily all embodiments. Consequently, the appearances of the phrase “in one embodiment,” “in an embodiment,” or “in some embodiments” in various places throughout the Specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments. It is therefore intended that such variations be included within the scope of the following claims and their equivalents.