The present invention relates to mobile networks and more particularly, the present invention relates to a technique for informing a mobile network using an IP (Internet Protocol) transport mechanism of voice traffic.
In general, packet switched wireless networks provide communications for mobile terminals with no physical connection required for network access. The General Packet Radio Service (GPRS) in the Global System for Mobile communications (GSM) and the Universal Mobile Terrestrial System (UMTS) have both been developed to provide wireless communications networks with a packet switched side as well as a circuit switched side
As noted in their website, http://www.3gpp.org, the Third Generation Partnership Project, normally known by their acronym 3GPP, is an organization whose Partners have agreed to cooperate in the production of globally applicable Technical Specifications and Technical Reports for a 3rd Generation Mobile System based on GSM core networks and the radial access technologies that they support (i.e., Universal Terrestrial Radio Access (UTRA) both Frequency Division Duplex (FDD) and Time Division Duplex (TDD) modes).
The 3GPP Partners have further agreed to cooperate in the maintenance and development of Global System for Mobile communication (GSM) Technical Specifications and Technical Reports including evolved radial access technologies (e.g., General Packet Radio Service (GPRS) and Enhanced Data rates for GSM Evolution (EDGE)).
The 3GPP thus issues various Technical Specifications which are then utilized by the telecommunications industry to produce mobile terminals and associated systems which have been standardized such that a mobile terminal of one manufacturer can communicate with a system or mobile terminal of another manufacturer. These Technical Specifications are constantly revised in accordance with agreements by the 3GPP Partners to allow for changes and improvements in technology.
Technical Specification TS 23.060, Version V3.6.0, was issued in January, 2001 by the 3GPP and defines the stage-2 service description for the packet domain, which includes the GPRS in GSM and UMTS. This technical specification is incorporated by reference herein in its entirety. The description of various elements and their functions incorporated by reference herein merely constitute a non-limiting example of packet switched wireless communication networks and it is to be understood that the present invention is not limited to such networks.
A network subscriber can have one or more (PDP) addresses. Each PDP address is described by one or more PDP contexts in the Mobile Station (MS), the Service GPRS Support Node (SGSN), and the Gateway GPRS Support Node (GGSN). A GGSN is a gateway to an external network. Each PDP context may have routing and mapping information for directing the transfer of data to and from its associated PDP address and a Traffic Flow Template (TFT) for reviewing or filtering the transferred data.
Each PDP context can be selectively and independently activated, modified, and deactivated. The activation state of the PDP context indicates whether data transfer is enabled for a corresponding PDP address and TFT. If all PDP contexts associated with the same PDP address are inactive or deactivated, all data transfer for that PDP address is disabled. All PDP contexts of a subscriber are associated with the same Mobility Management (MM) context for the International Mobile Subscriber Identity (IMSI) of that subscriber. Setting up a PDP context means setting up a communication channel between the MS and the GGSN.
1) The MS sends an Activate PDP Context Request (NSAPI, TI, PDP Type, PDP Address, Access Point Name, QoS Requested, PDP Configuration Options) message to the SGSN. The MS shall use PDP Address to indicate whether it requires the use of a static PDP address or whether it requires the use of a dynamic PDP address. The MS shall leave PDP Address empty to request a dynamic PDP address. The MS may use Access Point Name to select a reference point to a certain external network and/or to select a service. Access Point Name is a logical name referring to the external packet data network and/or to a service that the subscriber wishes to connect to. QoS Requested indicates the desired QoS profile. PDP Configuration Options may be used to request optional PDP parameters from the GGSN (see GSM 09.60). PDP Configuration Options is sent transparently through the SGSN.
3) In UMTS, RAB setup is done by the RAB Assignment procedure, see subclause “RAB Assignment Procedure”.
5) The SGSN validates the Activate PDP Context Request using PDP Type (optional), PDP Address (optional), and Access Point Name (optional) provided by the MS and the PDP context subscription records. The validation criteria, the APN selection criteria, and the mapping from APN to a GGSN are described in annex A.
If no GGSN address can be derived or if the SGSN has determined that the Activate PDP Context Request is not valid according to the rules described in annex A, then the SGSN rejects the PDP context activation request.
If a GGSN address can be derived, the SGSN creates a TEID for the requested PDP context. If the MS requests a dynamic address, then the SGSN lets a GGSN allocate the dynamic address. The SGSN may restrict the requested QoS attributes given its capabilities, the current load, and the subscribed QoS profile.
The SGSN sends a Create PDP Context Request (PDP Type, PDP Address, Access Point Name, QoS Negotiated, TEID, NSAPI, MSISDN, Selection Mode, Charging Characteristics, Trace Reference, Trace Type, Trigger Id, OMC Identity, PDP Configuration Options) message to the affected GGSN. Access Point Name shall be the APN Network Identifier of the APN selected. PDP Address shall be empty if a dynamic address is requested. The GGSN may use Access Point Name to find an external network and optionally to activate a service for this APN. Selection Mode indicates whether a subscribed APN was selected, or whether a non-subscribed APN sent by MS or a non-subscribed APN chosen by SGSN was selected. Selection Mode is set. The GGSN may use Selection Mode when deciding whether to accept or reject the PDP context activation. For example, if an APN requires subscription, then the GGSN is configured to accept only the PDP context activation that requests a subscribed APN as indicated by the SGSN with Selection Mode. Charging Characteristics indicates which kind of charging the PDP context is liable for. The SGSN shall copy Charging Characteristics from Subscribed Charging Characteristics if received from the HLR. The SGSN shall include Trace Reference, Trace Type, Trigger Id, and OMC Identity if GGSN trace is activated. The SGSN shall copy Trace Reference, Trace Type, and OMC Identity from the trace information received from the HLR or OMC.
The GGSN creates a new entry in its PDP context table and generates a Charging Id. The new entry allows the GGSN to route PDP PDUs between the SGSN and the external PDP network, and to start charging. The GGSN may further restrict QoS Negotiated given its capabilities and the current load. The GGSN then returns a Create PDP Context Response (TEID, PDP Address, PDP Configuration Options, QoS Negotiated, Charging Id, Cause) message to the SGSN. PDP Address is included if the GGSN allocated a PDP address. If the GGSN has been configured by the operator to use External PDN Address Allocation for the requested APN, then PDP Address shall be set to 0.0.0.0, indicating that the PDP address shall be negotiated by the MS with the external PDN after completion of the PDP Context Activation procedure. The GGSN shall relay, modify, and monitor these negotiations as long as the PDP context is in ACTIVE state and use the GGSN-Initiated PDP Context Modification procedure to transfer the currently-used PDP address to the SGSN and the MS. PDP Configuration Options contain optional PDP parameters that the GGSN may transfer to the MS. These optional PDP parameters may be requested by the MS in the Activate PDP Context Request message, or may be sent unsolicited by the GGSN. PDP Configuration Options is sent transparently through the SGSN. The Create PDP Context messages are sent over the backbone network.
If QoS Negotiated received from the SGSN is incompatible with the PDP context being activated, then the GGSN rejects the Create PDP Context Request message. The compatible QoS profiles are configured by the GGSN operator.
7) The SGSN inserts the NSAPI along with the GGSN address in its PDP context. If the MS has requested a dynamic address, the PDP address received from the GGSN is inserted in the PDP context. The SGSN selects Radio Priority and Packet Flow Id based on QoS Negotiated, and returns an Activate PDP Context Accept (PDP Type, PDP Address, TI, QoS Negotiated, Radio Priority, Packet Flow Id, PDP Configuration Options) message to the MS. The SGSN is now able to route PDP PDUs between the GGSN and the MS, and to start charging.
Similarly,
The Secondary PDP Context Activation procedure may be used to activate a PDP context while reusing the PDP address and other PDP context information from an already active PDP context, but with a different QoS profile. Procedures for APN selection and PDP address negotiation are not executed. Each PDP context sharing the same PDP address and APN shall be identified by a unique TI and a unique NSAPI.
The Secondary PDP Context Activation procedure may be executed without providing a Traffic Flow Template (TFT) to the newly activated PDP context if all other active PDP contexts for this PDP address and APN already have an associated TFT, otherwise a TFT shall be provided. The TFT contains attributes that specify an IP header filter that is used to direct data packets received from the interconnected external packet data network to the newly activated PDP context.
1) The MS sends an Activate Secondary PDP Context Request (Linked TI, NSAPI, TI, QoS Requested, TFT) message to the SGSN. Linked TI indicates the TI value assigned to any one of the already activated PDP contexts for this PDP address and APN. QoS Requested indicates the desired QoS profile. TFT is sent transparently through the SGSN to the GGSN to enable packet classification for downlink data transfer. TI and NSAPI contain values not used by any other activated PDP context.
3) In UMTS, RAB setup is done by the RAB Assignment procedure.
4) The SGSN validates the Activate Secondary PDP Context Request using the TI indicated by Linked TI. The same GGSN address is used by the SGSN as for the already-activated PDP context(s) for that TI and PDP address.
The SGSN and GGSN may restrict and negotiate the requested QoS as specified in subclause “PDP Context Activation Procedure”. The SGSN sends a Create PDP Context Request (QoS Negotiated, TEID, NSAPI, Primary NSAPI, TFT) message to the affected GGSN. Primary NSAPI indicates the NSAPI value assigned to any one of the already activated PDP contexts for this PDP address and APN. TFT is included only if received in the Activate Secondary PDP Context Request message. The GGSN uses the same external network as used by the already-activated PDP context(s) for that PDP address, generates a new entry in its PDP context table, and stores the TFT. The new entry allows the GGSN to route PDP PDUs via different GTP tunnels between the SGSN and the external PDP network. The GGSN returns a Create PDP Context Response (TEID, QoS Negotiated, Cause) message to the SGSN.
6) The SGSN selects Radio Priority and Packet Flow Id based on QoS Negotiated, and returns an Activate Secondary PDP Context Accept (TI, QoS Negotiated, Radio Priority, Packet Flow Id) message to the MS. The SGSN is now able to route PDP PDUs between the GGSN and the MS via different GTP tunnels and possibly different LLC links.
An MS or GGSN can request, an SGSN can decide, possibly triggered by the HLR or triggered by a RAB Release procedure initiated by an RNC, or an MS and SGSN can decide after an RNC-initiated lu release, to modify parameters that were negotiated during an activation procedure for one or several PDP contexts. The following parameters can be modified:
QoS Negotiated;
Radio Priority;
Packet Flow Id;
PDP Address (in case of the GGSN-initiated modification procedure); and
TFT (in case of MS-initiated modification procedure).
The SGSN can request the modification of parameters by sending a Modify PDP Context Request message to the MS.
A GGSN can request the modification of parameters by sending an Update PDP Context Request message to the SGSN.
An MS can request the modification of parameters by sending a Modify PDP Context Request message to the SGSN.
An RNC can request an lu release by sending an lu Release Request message to the SGSN. After lu release the MS and SGSN shall modify the PDP contexts.
An RNC can request the release of a radio access bearer. After RAB release the MS and the SGSN shall locally modify the corresponding PDP context.
A trace may be activated while a PDP context is active. To enable trace activation in a GGSN, the SGSN shall send an Update PDP Context Request message to the GGSN. If PDP context modification is performed only to activate a trace, then the SGSN shall not send a Modify PDP Context Request message to the MS.
1) The SGSN may send an Update PDP Context Request (TEID, NSAPI, QoS Negotiated, Trace Reference, Trace Type, Trigger Id, OMC Identity) message to the GGSN. If QoS Negotiated received from the SGSN is incompatible with the PDP context being modified, then the GGSN rejects the Update PDP Context Request. The compatible QoS profiles are configured by the GGSN operator. The SGSN shall include Trace Reference, Trace Type, Trigger Id, and OMC Identity in the message if GGSN trace is activated while the PDP context is active. The SGSN shall copy Trace Reference, Trace Type, and OMC Identity from the trace information received from the HLR or OMC.
2) The GGSN may restrict QoS Negotiated given its capabilities and the current load. The GGSN stores QoS Negotiated and returns an Update PDP Context Response (TEID, QoS Negotiated, Cause) message.
4) The MS acknowledges by returning a Modify PDP Context Accept message. If the MS does not accept the new QoS Negotiated it shall instead de-activate the PDP context with the PDP Context Deactivation Initiated by MS procedure.
5) In UMTS, radio access bearer modification may be performed by the RAB Assignment procedure.
6) If BSS trace is activated while the PDP context is active, then the SGSN shall send an Invoke Trace (Trace Reference, Trace Type, Trigger Id, OMC Identity) message to the BSS or UTRAN. Trace Reference, and Trace Type are copied from the trace information received from the HLR or OMC.
1) The SGSN may send an Update PDP Context Request (TEID, NSAPI, QoS Negotiated, Trace Reference, Trace Type, Trigger Id, OMC Identity) message to the GGSN. If QoS Negotiated received from the SGSN is incompatible with the PDP context being modified, then the GGSN rejects the Update PDP Context Request. The compatible QoS profiles are configured by the GGSN operator. The SGSN shall include Trace Reference, Trace Type, Trigger Id, and OMC Identity in the message if GGSN trace is activated while the PDP context is active. The SGSN shall copy Trace Reference, Trace Type, and OMC Identity from the trace information received from the HLR or OMC.
2) The GGSN may restrict QoS Negotiated given its capabilities and the current load. The GGSN stores QoS Negotiated and returns an Update PDP Context Response (TEID, QoS Negotiated, Cause) message.
3) The SGSN selects Radio Priority and Packet Flow Id based on QoS Negotiated, and may send a Modify PDP Context Request (TI, QoS Negotiated, Radio Priority, Packet Flow Id) message to the MS.
4) The MS acknowledges by returning a Modify PDP Context Accept message. If the MS does not accept the new QoS Negotiated it shall instead de-activate the PDP context with the PDP Context Deactivation Initiated by MS procedure.
5) In UMTS, radio access bearer modification may be performed by the RAB Assignment procedure.
6) If BSS trace is activated while the PDP context is active, then the SGSN shall send an Invoke Trace (Trace Reference, Trace Type, Trigger Id, OMC Identity) message to the BSS or UTRAN. Trace Reference, and Trace Type are copied from the trace information received from the HLR or OMC.
1) The GGSN sends an Update PDP Context Request (TEID, NSAPI, PDP Address, QoS Requested) message to the SGSN. QoS Requested indicates the desired QoS profile. PDP Address is optional.
2) The SGSN may restrict the desired QoS profile given its capabilities, the current load, the current QoS profile, and the subscribed QoS profile. The SGSN selects Radio Priority and Packet Flow Id based on QoS Negotiated, and sends a Modify PDP Context Request (TI, PDP Address, QoS Negotiated, Radio Priority, Packet Flow Id) message to the MS. PDP Address is optional.
3) The MS acknowledges by returning a Modify PDP Context Accept message. If the MS does not accept the new QoS Negotiated it shall instead de-activate the PDP context with the PDP Context Deactivation Initiated by MS procedure.
4) In UMTS, radio access bearer modification may be performed by the RAB Assignment procedure.
5) Upon receipt of the Modify PDP Context Accept message, or upon completion of the RAB modification procedure, the SGSN returns an Update PDP Context Response (TEID, QoS Negotiated) message to the GGSN. If the SGSN receives a Deactivate PDP Context Request message, it shall instead follow the PDP Context Deactivation Initiated by MS procedure.
1) The MS sends a Modify PDP Context Request (TI, QoS Requested, TFT) message to the SGSN. Either QoS Requested or TFT or both may be included. QoS Requested indicates the desired QoS profile, while TFT indicates the TFT that is to be added or modified or deleted from the PDP context.
2) The SGSN may restrict the desired QoS profile given its capabilities, the current load, and the subscribed QoS profile. The SGSN sends an Update PDP Context Request (TEID, NSAPI, QoS Negotiated, TFT) message to the GGSN. If QoS Negotiated and/or TFT received from the SGSN is incompatible with the PDP context being modified (e.g., TFT contains inconsistent packet filters), then the GGSN rejects the Update PDP Context Request. The compatible QoS profiles are configured by the GGSN operator.
3) The GGSN may further restrict QoS Negotiated given its capabilities and the current load. The GGSN stores QoS Negotiated, stores, modifies, or deletes TFT of that PDP context as indicated in TFT, and returns an Update PDP Context Response (TEID, QoS Negotiated) message.
4) In UMTS, radio access bearer modification may be performed by the RAB Assignment procedure.
5) The SGSN selects Radio Priority and Packet Flow Id based on QoS Negotiated, and returns a Modify PDP Context Accept (TI, QoS Negotiated, Radio Priority, Packet Flow Id) message to the MS.
NOTE: If the SGSN does not accept QoS Requested, then steps 2 and 3 of this procedure are skipped, and the existing QoS Negotiated is returned to the MS in step 4.
In spite of the numerous details provided in the aforecited Technical Specification, many features associated with mobile networks have not been dealt with. Namely, techniques for informing the network that a call being setup is for voice traffic have yet to be incorporated in the aforecited technical specification and it is these details to which the present invention is directed.
In the present invention, the signaling exchanged by the application layers in the MS and in the network is arranged in accordance with the procedure/messages that need to be performed by the transport levels in the MS and in the network in order to set up IP multimedia calls.
When the application level in the MS sends a setup message to set up an IP multimedia call, before or after sending such a message over the radio interface, the MS performs the appropriate procedures, depending on the type of access adopted, to set up the appropriate bearers over the radio interface and in the network to satisfy the call requirements specified by the application level in the setup message
In setting up a call, one or more PDP contexts must be activated. In accordance with the present invention, when activating a PDP context, an indication is added to inform the network that voice traffic is to be transferred. The indication may consist of a specific parameter or even a new QoS (Quality of Service) traffic class.
The foregoing and a better understanding of the present invention will become apparent from the following detailed description of example embodiments and the claims when read in connection with the accompanying drawings, all forming a part of the disclosure of this invention. While the foregoing and following written and illustrated disclosure focuses on disclosing example embodiments of the invention, it should be clearly understood that the same is by way of illustration and example only and the invention is not limited thereto. The spirit and scope of the present invention are limited only by the terms of the appended claims.
The following is a brief description of the drawings, wherein:
Before beginning a detailed description of the subject invention, mention of the following is in order. When appropriate, like reference numerals and characters may be used to designate identical, corresponding, or similar components in differing drawing figures. Furthermore, and the detailed description to follow, example sizes/models/values/ranges may be given, although the present invention is not limited thereto. Lastly, well-known elements may not be shown within the drawing figures for simplicity of illustration and discussion and so as not to obscure the invention.
In addition to the aforecited Technical Specification, Technical Specification TS 23.228, Version V2.0.0, issued by the 3GPP in March, 2001, defines the stage-2 service description for the IP Multimedia (IM) Subsystem, which includes the elements necessary to support IP Multimedia (IM) services in UMTS. This technical specification is incorporated by reference herein in its entirety and, as in the case of the previously cited Technical Specification, the elements and their functions incorporated by reference herein are merely a non-limiting example of packet switched wireless communication networks and the present invention should not be construed as being limited thereto.
1. UE(A) starts a Session Initiation procedure to UE(B) that includes an SDP proposal.
2. The user at UE(B) is pre-alerted. (optional)
3. An indication of the pre-alerting may be sent towards UE(A). (optional)
4. User at UE(B) will then interact and express his/her wishes regarding the actual session. (optional)
5. UE(B) generates accepted SDP based on terminal settings, terminal preconfigured profiles and, optionally, the user's wishes.
6. The accepted SDP is forwarded to UE(A) in the payload of a reliable SIP response.
7. Initial bearer creation procedure is performed. During this bearer creation step, the resources in the UE(A)'s and UE(B)'s access network are reserved possibly with PDP context procedures. Bearer resources in eternal networks may also be reserved at this point.
8. Terminal at UE(B) starts ringing. (optional)
9. The alerting indication is sent towards UE(A). (optional)
10. User at UE(B) may interact and express his/her wishes regarding the actual session. (optional)
11. UE(A) and UE(B) may perform bearer modification procedure at this point if the initial bearers reserved in step 7 and the wishes of user at UE(B) are different. During this bearer modification step, the resources in the UE(A)'s and UE(B)'s access network may be modified by modifying the PDP context, and the resource reservation in the external network may also be modified.
12. Session initiation procedure is acknowledged.
It is well-known that voice traffic has very specific statistical characteristics. Normally, the bandwidth required for transferring voice traffic is less than that required for transferring data. Accordingly, when the GGSN, SGSN, or RNC make a determination as to whether a new PDP context can be admitted, is of course understood that they can admit more PDP contexts for use with voice traffic as compared with data. This allows for the more efficient use of available resources.
In addition to the aforementioned Technical Specifications, Technical Report TR 23.821, Version V1.0.0, issued by the 3GPP in June, 2000, includes an additional QoS parameter as a speech indication in Section 10.3 thereof. This Technical Report is incorporated herein in its entirety and, as with the previously cited Technical Specifications, the elements and their functions incorporated by reference herein are merely a non-limiting example of packet switched wireless communication networks and the present invention should not be construed as being limited thereto.
While the speech indication described in the Technical Report cited above provides an indication of voice traffic, for the SGSN, for example, to be informed of the transfer of voice traffic, it is necessary to also provide the voice traffic indication in the PDP context activation or modification, (that is, also in the UMTS Bearer Service attributes where it is currently not included).
Thus, in accordance with the present invention, the activate PDP Context Request message or Active Secondary PDP Context Request Message or Modify PDP context Request message, forwarded from the MS to the SGSN and then to the GGSN, for example, includes a voice traffic parameter which informs the SGSN and the GGSN that voice traffic is to be transferred.
In step 3, an Activate Secondary PDP Context Request message, for example, is forwarded to the SGSN to provide an indication that voice traffic is to be transferred. In step 4, a Radio Access Bearer Setup is arranged between the SGSN and the UE (that is, the MS). In step 5, a Create PDP Context Request message is forwarded from the SGSN to the GGSN to provide an indication that voice traffic is to be transferred. In steps 6 and 7, the GGSN forwards a Request message to the CSCF which in turn forwards a Decision message back to the GGSN. In step 8, in response to the Decision message from the CSCF, the GGSN forwards a Create PDP Context Response to the SGSN and in step 9, the SGSN forwards an Activate Secondary PDP Context Accept to the UE. Lastly, in step 10, the session initiation procedure is acknowledged.
Thus, in accordance with the present invention, a voice traffic indication is added when activating one or more PDP contexts. This indication may be added to the Activate PDP Context Request or the Activate Secondary PDP Context Request or the Modify PDP Context Request messages. The indication could be, for example, a new value for an existing parameter, a new parameter or even a new QoS traffic class.
By adding a voice traffic indication to one or more PDP contexts, the present invention solves a problem not previously addressed, namely, that the network elements in a GPRS network may need to know that a PDP context is used to transfer traffic related to a call.
For example, the GGSN already sends Charging Id at PDP Context Activation to the SGSN. When the PDP context is used for a call (that is, voice traffic), the GGSN may send Charging Id to the CSCF in order to enable charging coordination between the GPRS layer and the IP Telephony layer. The GGSN does not need to send the charging Id to the CSCF when a PDP context is activated for other purposes.
As another example, prepaid services for a call may be based on communication between the CSCF and the SCP only. The SGSN should not communicate with the SCP if a PDP context is used for a call. The SGSN may communicate with the SCP if a PDP context is activated for other purposes. The communication between the SGSN and the SCP on PDP context is already specified in CAMEL Rel 99, for example.
Still furthermore, coordination of the QoS between the GPRS layer and the IP Telephony layer has been discussed. This would mean that an accepted call may influence the QoS of the PDP context that is activated for the call. That is, if a normal call is accepted in the IP Telephony layer, it should not be possible to activate a PDP context capable of carrying a video call. For a PDP context used for other purposes, this kind of coordination is not needed.
In addition, by the addition of the voice traffic indication to one or more PDP contexts, the GGSN may use this voice traffic indication to determine whether or not a bearer authorization in PCF needs to be done.
A further exemplary embodiment in accordance with this invention is a program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform a method of providing a voice traffic indication in a communications network, the method comprising: setting up a communications session between a first network element and a first network; creating a request to set up a communication session in the first network element in order to establish a bearer on a second network for said session, including a voice traffic indication in said request; and forwarding the request to a second network element in the second network.
Another exemplary embodiment in accordance with this invention is a program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform a method of providing a voice traffic indication in a communications network, the method comprising: setting up a communications session between a first network element and a first network; creating a request to modify a communication session in the first network element in order to establish a bearer on a second network for said session, including a voice traffic indication in said request; and forwarding the request to a second network element in the second network.
This concludes the description of the example embodiments. Although the present invention has been described with reference to an illustrative embodiment thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this invention. More particularly, reasonable variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the foregoing disclosure, the drawings, and the appended claims without departing from the spirit of the invention. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will be apparent to those skilled in the art.
The present application is a continuation-in-part of U.S. application Ser. No. 09/546,209, filed in the U.S. Patent and Trademark Office on Apr. 10, 2000 now abandoned.
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Number | Date | Country | |
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Child | 09827980 | US |