Abstract:
A system and method for coordinating network operation modes of a GPRS network is disclosed. The system includes a database storing a preferred list of network operation modes of the GPRS network. A SGSN detects the status of an interface for GPRS packet data services and reports the status to a BSC. BSC decides which network operation mode to use based on the preferred list. The GPRS network is then switched to the preferred network operation mode.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to communications methods and systems, and more particularly, to providing selections of operation modes of such communications systems. 
     2. Description of Related Art 
     A General Packet Radio System (“GPRS”) is a service that provides data packet communications for mobile Global system for Mobile Communications (GSM) and time-division multiple access (TDMA) users. In addition to GSM, GPRS also provides services to other digital cellular networks, such as DCS and PCS. As is known, GPRS uses this packet-mode technique to transfer high-speed and low-speed data and signaling in an efficient manner over GSM radio networks. 
     GPRS provides a variety of new and unique services to mobile wireless subscribers. For example, GPRS can maintain constant voice and data communications while mobile subscribers are in transit. Subscribers also are enabled to obtain connectivity whenever needed, regardless of location and without a lengthy login session. Via a GPRS mobile telephone, a subscriber can maintain an online connection while initiating a communication, without an overhead of setting up a data call. Finally, localization enables subscribers to obtain information that is relevant to their respective current locations. For example, GPRS enables location-based services that provide information about weather, traffic, restaurants, or retail stores, based on a subscriber&#39;s location at a particular moment in time. 
       FIG. 1  illustrates a basic architecture of a GPRS network  100  and a data transfer route in the GPRS network. The GPRS network attempts to reuse the existing GSM network element as much as possible. In order to effectively build a packet-based mobile cellular network, some new network elements, interfaces and protocols that handle packet traffic are also required. For example, the existing Mobile Station Switch Centers (“MSC&#39;s”) are based upon circuit-switched central-office technology and cannot handle packet traffic. Therefore, enabling GPRS on a GSM network requires the addition of two core modules, a Serving GPRS Service Node (“SGSN”)  110  and a Gateway GPRS Service Node (“GGSN”)  112 , as shown in  FIG. 1 . GGSN  112  acts as a gateway between GPRS network  100  and an external IP network  114  such as an Internet or an x.25 Network, or another GPRS network (to facilitate GPRS roaming), and is connected with SGSN  110  via an IP-based GPRS backbone network  124 . SGSN  110  is at the same level as MSC  118 , and can be viewed as a “packet-switched MSC” (mobile station switch center). SGSN  110  provides packet routings to and from its service area for all MS&#39;s in that service area. SGSN  110  also detects new GPRS MS&#39;s in a given service area, processes registration of new MSs, and keeps a record of their respective locations inside the given area. 
     MS  102  is physical equipment used by the mobile subscribers, such as a mobile telephone or a laptop computer, which is GPRS-attached and can handle an enhanced air interface in GPRS network  100  and can packetize traffic directly. The GPRS-attached MSs may include a high-speed version of current telephones to support high-speed data access, a PDA (Personal Digital Assistant) device with an embedded GSM telephone, and PC cards for laptop computers. All MS&#39;s profiles are preserved in home location registers (“HLR”)  120  that are accessible by SGSN  110  and GSM MSC  118 . A physical link (e.g., interface Gs) can be established and maintained between an MSC and a specific SGSN in each mobile network. The Gs interface allows the MSC to be aware of the status of a subscriber in the SGSN. The presence of the Gs interface facilitates combined signaling procedures from the MS. 
     SGSN  110  is also coupled to a BSC (Base Station Controller)  106  via a Frame Relay connection. BSC  106  manages radio resources including Base Transceiver Station (“BTS”)  104 . BTS  104 , is physical equipment, such as a radio tower, that is used to transmit radio frequencies over an air interface. The BSC  106  may be connected to several BTS&#39;s. Each BTS may serve more than one MS. The BSC and BTS, as a whole, are generally referred to as a BSS (Base Station System). To be utilized in the GPRS network, BSC  106  is linked to a Packet Control Unit (“PCU”)  108  that provides a physical and logical data interface out of the BSS for packet data traffic. PCU  108  converts packet data to/from SGSN  110  into a format that can be transferred to server  116 /MS  102  and implements quality of service (QoS) measurements. For example, when either voice or data traffic is originated at the mobile subscriber, it is transported over the air interface to BTS  104 , and from BTS  104  to BSC  106  in the same way as in a standard GSM call. However, at the output of BSC  106 , the traffic is separated. Circuit-switched voice is sent to MSC  118  via circuit-switched channels (through interface A) per standard GSM, and data is sent to SGSN  110  via PCU  108  over the Frame Relay Interface (through interface Gb) and packet-switched signaling channels (through interface Gs). 
     Currently, the GPRS network can be designed to operate in three network operation modes (NOM 1 , NOM 2 , and NOM 3 ), which are shown in  FIGS. 2 and 3 . The network operation mode of the GPRS network is indicated by a parameter transmitted in system information messages within a cell that dictates to a GPRS MS where to listen for paging messages and how to signal towards the core network. The network operation mode represents the capabilities of the GPRS network. In a NOM 1  network, a MS can receive pages from the circuit switched domain (voice call) when engaged in a data call. The MS can suspend the data call or take both simultaneously, depending on the ability of the MS. In a NOM 2  network, when engaged in a data call, pages may not be received from the circuit switched domain, since the MS is receiving data and not listening to the paging channel. In a NOM 3  network, the MS can monitor pages from a CS network while receiving data and vice versa. However, it is very difficult to achieve in reality due to the processing power required. 
     There are also three classes of GPRS MS&#39;s, Class A, B, or C. These various GPRS MS&#39;s support various services. For example, a class A MS supports GPRS and other GSM services (such as SMS and voice) simultaneously, such that a class A MS can use circuit-switched voice and GPRS data services at the same time. A class B MS can monitor GSM and GPRS channels simultaneously, but can only support one of these service at one time. That is, the class B MS can simultaneously register circuit-switched voice and packet-switch data services but may only use one kind of service at a time. A class C MS supports either voice only or data only and thus cannot be simultaneously attached. The subscriber must select which service to connect to. Therefore, a class C MS can make or receive calls from only the manually (or default) selective service. The service that is not selected is not reachable. All classes of the MS&#39;s can operate in all network operation modes (NOM 1 , NOM 2 , and NOM 3 ). 
     A GPRS MS, in either class, has three states: idle, standby, and active. Data is transmitted between a MS and the GPRS network only when the MS is in the active state because in the active state, the GPRS network knows the location of the MS and has an active connection. However, in the idle and standby state, the location of the MS is known only as to which cell (idle) or routing area (standby) it is in. (Each routing area may include more than one cell within a GSM location area.) Therefore, when the network wants to send a packet to a MS that is in the standby state, the MS must be paged. When the MS responds to the page from the BSS/SGSN, the SGSN now has an established connection and packets can be sent to the MS. When packets are sent/received (connection established), the MS is allocated in a Temporary Block Flow (TBF). When a TBF is allocated, this is the situation where paging coordination is required between the MSC and SGSN for circuit switched pages to be received. 
       FIG. 2  is a diagram showing the first network operation mode NOM 1  of the GPRS network, in which GRPS MS  201  is attached to, through BSC  202 , both SGSN  203  via interfaces Gb and Gs and to other GSM services through MSC  204  via interface A, and MS  201  supports simultaneous operation of GPRS and other GSM services. As shown, in NOM 1 , the network sends all paging messages for GRPS MS  201  either on a Common Control Channel (CCCH) or the GPRS paging channel or on a GRPS traffic channel (if a data transfer is in progress), such as interfaces Gs and Gb. MS  201  only needs to monitor one paging channel thus allowing it to “sleep” longer. Further, the paging load could be reduced since paging is performed on the routing area level. 
       FIG. 3  is a diagram illustrating the second and third network operation modes NOM 2  and NOM 3  of the GPRS network, in which GPRS MS  301  is attached to, through BSC  302 , both SGSN  303  via interface Gb and other GSM services through MSC  304  via interface A and can only operate one set of services at a time. In NOM 2 , the network sends all paging messages for GPRS MS  301  out on the CCCH. The MS must monitor this channel even when allocated a GPRS data channel. In NOM 3 , the network sends out the CS paging for GPRS MS  301  on the CCCH, and GPRS paging out on a Packet Paging channel (PPCH). If PPCH are present in the cell, then MS  301  must monitor both the CCCH and the PPCH channels. The CS paging occurs at the Location Area level and the PS paging occurs at the cell or Routing Area level. 
     The primary difference between NOM 1 , NOM 2  and NOM 3  is that paging and signaling coordinate in NOM 1  to occur between MSC  203  and SGSN  204 . The primary difference between NOM 2  and NOM 3  is that in NOM  3 , the GRPS MS  301  can be required to monitor different paging channels. NOM 1  has two flavors, one with different paging channels for CS only and CS/PS combined pages (PPCH), and one with a single, common paging channel for use by both CS and PS pages. 
     Currently, the MS receives the network operation mode from system information transmitted within the cells. However, there is no coordination between each node (BSC, SGSN and MSC) that determines what operation mode the network can support. Since the network operation mode indicates how the MS signals and receives signals from the network, it is possible for the MS to perform or behave in a manner indicated by the received mode of operation, and for other nodes in the network to expect a different behavior. This can result in prolonged loss of service for the MS. 
     Accordingly, a communications system and method that provides more flexible communications service to MS subscribers is thus desirable. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a method and system for coordinating operation modes of a GPRS network. The present invention can automatically switch the operation mode of the GPRS network based on the status of an interface between a MSC and a SGSN so that the GPRS network can provide more flexible and effective communications services. 
     In accordance with an embodiment of the present invention, a method for coordinating network operation modes of a GPRS network is disclosed, in which a preferred list of operation modes is stored. Based on the preferred list of operation modes, the method determines what second operation mode is supported and route the paging messages through the second operation mode if a current operation mode can not be supported due to a failure within the network. 
     In accordance with an embodiment of the present invention, a method for coordinating operation modes of a GPRS network comprises transmitting a paging message to a mobile subscriber through a primary network operation mode that the mobile subscriber is registered for the GPRS network. If the primary network operation mode fails, the method automatically switches the transmission of the paging message through a secondary network operation mode that the mobile subscriber is registered for. The method switches back the transmission of further paging messages through the primary network operation mode when the primary network operation mode is recovered. 
     In accordance with another embodiment of the present invention, a method for coordinating operation modes of a GPRS network comprises transmitting a paging message to a mobile subscriber via one of a first routing and a second routing based on a preferred list of the mobile subscriber. In the first routing, the paging message is sent via a first interface and a second interface. In the second routing, the paging message is sent via a third interface. In the case that the first routing is selected as a primary operating mode and the second routing is selected as a secondary operating mode, if the first routing is unavailable for transmitting the paging message, the method transmits the paging message to the mobile subscriber via the second routing. The method then transmits the paging messages via the first routing after the first routing is recovered. 
     The present invention further provides a system for coordinating operation modes of a GPRS network. The system comprises a MSC for transmitting/receiving calls to/from the mobile subscriber, a BSC for managing the calls transmitted/received to/from the mobile subscriber, a SGSN between the mobile subscribers and the MSC, and a database for storing a preferred list of network operation modes of the GPRS network that the mobile subscriber registers. According to the system, the network operation modes of the GPRS network can be automatically switched according to the registered preferred list of network operation modes based on the interface status between the MSC and the SGSN. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an exemplary GPRS network. 
         FIG. 2  is a schematic diagram showing a first network operation mode (NOM 1 ) of a GPRS network. 
         FIG. 3  is a schematic diagram showing a second and third network operation modes (NOM 2 , NOM 3 ) of a GPRS network. 
         FIG. 4  is a schematic diagram of a system for coordinating operation modes of a GPRS network in accordance with an embodiment of the present invention. 
         FIG. 5  is a timing diagram for coordinating operating modes of a GPRS network according to a first embodiment of the present invention. 
         FIG. 6  is timing diagram for coordinating operating modes of a GPRS network according to a second embodiment of the present invention. 
         FIG. 7  is timing diagram for coordinating operating modes of a GPRS network according to a third embodiment of the present invention. 
         FIG. 8  is a timing diagram for coordinating operating modes of a GPRS network according to a fourth embodiment of the present invention. 
         FIG. 9  is a timing diagram for coordinating operating modes of a GPRS network according to a fifth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       FIG. 4  is a schematic diagram of a system for coordinating operation modes of a GPRS network in accordance with an embodiment of the present invention. The system may include one or more MS&#39;s  401  (only one MS is represented), a BSC  402 , a MSC  404 , a SGSN  403 , a GGSN  405 , and a HLR  406 . BSC  402  manages calls received/transmitted from/to MS  401 . MSC  404  is coupled to a GSM network (not shown). SGSN  403  provides packet-switched channels and circuit-switched channels for delivering packet data and voice signals, respectively, between MSC  404  and BSC  402 . GGSN  405  serves as a gateway between the GPRS network and other packet data networks (e.g., the internet). HLR  406  stores information regarding MS subscribers. 
     The system of the present invention can automatically switch operation modes of the network based on a preferred list of operation modes. The preferred list is stored in database  407  of BSC  402 . In operation, BSC  402  instructs MS  401  to use an appropriate operation mode based on the stored preferred list. The preferred list may be, for example, (1) NOM 1  without PPCH (2) NOM 3  (3) NOM 2 , or (1) NOM 1  (2) NOM 2 , or (1) NOM 1  with PPCH, (2) NOM 2 . In operation, BSC  402  may query SGSN  403  or MSC  404  on the status of interface Gs (that is between SGSN  403  and MSC  404 ) to ascertain what operation mode to transmit. SGSN  403  or MSC  404  can also signal BSC  402  when a change in status of interface Gs occurs, so that SGSN  403  or MSC  404  can adjust its transmitted operation mode. With the list concept, BSC  402  can also adjust the transmitted operation mode if interface Gb (that is between SGSN  403  and BSC  402 ) failure occurs. 
     For example, if a primary operation mode of MS  401  is NOM 1 , the network transmits, in NOM 1 , voice signals and packet data from MSC  403  to SGSN  403  and to BSC  402  via interface Gs and Gb, as shown in arrows  411  and  412 , and MS  401  listens to packet signaling channels. When interface Gs is unavailable to transmit the signals, SGSN  404  sends a notice message to BSC  402  indicating the failure, as shown in arrow  413 . Upon receiving this message, BSC  402  sends an acknowledge message to SGSN  403  that indicates to use NOM 2  for transmission, as shown in arrow  414  and changes the NOM transmitted in system information, as indicted by the preferred list. MS  401  in turn listens to circuit-switched channels as there is no packet signaling channels in NOM 2 , and the signals can be transmitted directly from MSC  404  to BSC  402  through interface A. As MS  401  now listens to the right channels, a loss of the paging signals can be avoided. 
       FIG. 5  illustrates a first embodiment of a method employed by the system of  FIG. 4  for coordinating operation modes of the GPRS network. Assuming that the network is operated in NOM 1  as a primary operation mode, when an incoming call to MS  402  is received by the network, a paging process will be executed from MSC  404  to BSC  402  through SGSN  403 . That is, MSC  404  sends a first paging message  501  to SGSN  403 , and SGSN  403  in turn sends a second paging message  502  to BSC  402 . The second paging message is then downloaded from BSC  402  to MS  401  (shown in  FIG. 4 ) for notifying MS  402  of a new incoming call. 
     In the case that interface Gs fails, SGSN  403  sends a failure indicated message  503  to BSC  402 . Upon receiving this failure indicated message, BSC  402  responds to the failure indicated message by sending an acknowledge message  504  to SGSN  403 . After receiving this instruction, MSC  404  sends paging message  505  to BSC  402  directly via the interface A, as in NOM 2 , until interface Gs recovers. 
     Once interface Gs recovers, SGSN  403  sends a recovery indicated message  506  to BSC  402 , indicating that the operation mode can be returned to NOM 1 . BSC  402  responds to this recovery message by sending an acknowledge message  507  to SGSN  403  to accept this recovery. SGSN  403  in turn sends an accept recovery message  508  to MSC  404 , indicating that the operation mode of the network has switched back to NOM 1 . Afterward, MSC  404  again transmits paging messages to BSC  402  through SGSN  403 , as shown in arrows  509  and  510 . 
     The above embodiment shows that SGSN  403  reports a change of the status of interface Gs to BSC  402  so that BSC  402  can indicate MS  401  to switch the network operation mode to a next preferred operation mode according to the preferred list stored in database  407 . Although not shown in this figure, when BSC  402  wishes to send a signal to the GPRS network, BSC  402  can also send a query to either SGSN  403  or MSC  404  to ask for the status of interface Gs so that BSC  402  can send the call in an appropriate network operation mode. 
       FIG. 6  shows a second embodiment of a method employed by the system of  FIG. 4  for coordinating operation modes of a GPRS network. In this embodiment, BSC  402  prefers to use NOM 2  for signal transmission. Therefore, as shown in arrow  601 , the paging message is sent from MSC  404  to BSC  402 . 
     As SGSN  403  is responsible for reporting a change of the status of interface Gs to BSC  402 , when interface Gs exists, SGSN  403  sends a Gs indication message  602  to BSC  402 . If MS  402  does not have data set up for being transmitted by using the NOM 1 , BSC  402  can send an acknowledge signal to SGSN  403  in arrow  603 , and can instruct SGSN  403  to block interface Gs, as shown in arrow  604 . In this manner, the method can assure that the paging message is sent from MSC  404  to BSC  402  under NOM 2 , as shown in arrow  605 . 
     The embodiment of  FIG. 6  is applicable when MS  401  registers and the network is indicating to use NOM 2  as its operation mode. As shown in arrow  606 , in this case, BSC  402  sends a NOM 1 -request message to SGSN  403 . Upon receiving this message  606 , SGSN  403  sends a Gs-unblocked message  607  to MSC  404  indicating that the operation mode has been changed to NOM 1 , and sends an acknowledge message  608  to BSC  402  indicating interface Gs is now unblocked and a change to NOM 1  is completed. Afterward, MSC  404  transmits the paging message in the manner of NOM 1 ; that is, the paging message is sent from MSC  404  to SGSN  403 , in arrow  609 , and then to BSC  402 , in arrow  610 . 
     Accordingly, the method and system in accordance with the present invention provide a flexible management of network operation modes based on the registered preferred list of the MS and the status of interface Gs. As SGSN  403  is capable of reporting any change of the status of interface Gs to BSC  402 , BSC  402  has controls on what operation mode to use to route the signals. 
     In an alternative embodiment, the registered preferred list of operation modes can also be stored in a database of MSC  404  (not shown). In this case, the operation mode of the network is sent from MSC  404  to MS  401  through BSC  402 . 
     The methods as described with reference to  FIGS. 5 and 6  provide a solution for coordinating operation modes of the GPRS network. In some cases, network data being set incorrectly in a network so that the network could indicate NOM 1  when in fact it cannot perform coordinated signaling. When this happens, MS  402  will not monitor the correct channels and so will fail to get service. To prevent this from happening, the network needs to ensure that NOM 1  is only transmitted when coordination is possible. In doing so, another embodiment of the present invention reserves a BTS Virtual Connection Identifier (BVCI) between BSC  402  and SGSN  403  for coordinating the network operation mode. The BVCI is unblocked if the network is able to support NOM 1  and would be blocked or left blocked if the network cannot support NOM 1  (i.e., NOM 1  is failed). 
     Therefore, by applying the BVCI, the methods of  FIGS. 5 and 6  employed by the system of the present invention can be revised to be the embodiments as shown in  FIGS. 7 and 8 . 
       FIG. 7  illustrates a third embodiment revised from the method of  FIG. 5  after embodying the BVCI concept. Similar to the embodiment of  FIG. 5 , NOM 1  is the primary operation mode and NOM 2  is the secondary operation mode. Therefore, as shown in arrows  701  and  702 , in NOM 1 , paging messages are sent from MSC  404  to SGSN  403  and from SGSN  403  to BSC  402 . 
     When interface Gs fails, instead of sending the failure indication message, SGSN  403  sends a BVCI-blocked message  703  to BSC  402  indicating that interface Gs fails and NOM 1  is no longer available. In response to the BVCI-block message  703 , BSC  402  sends a BVC-blocked acknowledge message  704  to SGSN  403  indicating that NOM 2  should be used. Afterward, MSC  404  sends the paging messages to BSC via interface A, as is in NOM 2 . 
     Similarly, when interface Gs recovers, SGSN  403  sends a BVCI-unblocked message  706  to BSC  402  indicating that NOM 1  is now available. BSC  402  in turn responds to this message by sending a BVCI-unblocked acknowledge message  707  indicating that the recovery is accepted. Afterward, MSC  404  sends the paging messages to BSC  402  through SGSN  403 , i.e., through interface Gs and Gb, as shown in arrows  708  and  709 . 
       FIG. 8  shows a fourth embodiment revised from the method of  FIG. 6  after embodying the BVCI concept. Similar to the embodiment of  FIG. 6 , NOM 2  is the primary operation mode (this is given that all MSs support NOM 1 .) Therefore, as shown in arrows  801 , in NOM 2 , paging messages are sent from MSC  404  to BSC  402  via interface A. 
     As described above, SGSN  403  reports a change of the status of interface Gs to BSC  402  whenever the change occurs, as shown in arrow  802 . However, BSC  402  is not in the position to support NOM 1  and it indicates this by automatically blocking the BVCI, as shown in arrow  803 . The SGSN responds with a BVC-block acknowledgement in arrow  805  and blocks the Gs interface in arrow  806 . When the BSC is prepared for NOM 1 , it unblocks the BVCI, as shown in arrow  807 . The SGSN responds by unblocking the Gs interface in arrow  808  and acknowledges the BVC unblock to the BSC in arrow  809 . The BSC now receives and transmits signals as per NOM 1 , that signals are sent from MSC  404  to SGSN  403  and then to BSC  402 , as shown in arrows  810  and  811 . 
       FIG. 9  illustrates a timing diagram showing a signal routing when a MS sends signals to the network in accordance with the present invention. As shown in the figure, MS  401  sends a signal to the network through BSC  402  via an operation mode that BSC  402  supports. When BSC  402  supports NOM 1 , BSC  402  sends combined LAU (Location Area Update)/RAU (Routing Area Update) signals to SGSN  403  in arrow  901  and SGSN  403  in turn sends a LAU signal to MSC  404  in arrow  902 . When Gs exits, MSC  404  accepts the LAU signal and sends a LAU accept signal back to SGSN  403  so that SGSN  403  sends a combined LAU/RAU accept signal to BSC  402 , as shown in arrows  904  and  904 . Accordingly, BSC-transmits signals to MSC  404  through SGSM  403  via NOM 1 . 
     When Gs fails, i.e., NOM  1  is no longer available, SGSN  403  sends a BVC-block signal to BSC  402  in arrow  905 . BSC  402  acknowledges the signal by sending a BVC-block ACK signal in arrow  905  and transmits the signals to MSC  404  directly through NOM 2 . That is, BSC  402  sends LAU signals to MSC  404  and MSC  404  responds a LAU accept signal, as shown in arrows  907  and  908 . When Gs is recovered, BSC  402  again sends a RAU signal to SGSN  403  in arrow  909 . SGSN  403  responds the RAU signal by sending a RAU accept signals and a BVC-unblock signal to BSC indicating that NOM 1  is now available, as shown in arrows  910  and  911 . After BSC  402  returns a BVC-unblock ACK signal to SGSN  403  in arrow  912 , BSC  402  again transmits network signals to MSC via NOM 1 . 
     In accordance with the present invention, the use of the BVCI ensures that the network can be used in NOM 1  when NOM 1  is indicated available. As the present invention reserves a singular BVCI value of the existing BVC to indicate the availability of NOM 1 , the use of BVCI does not change the protocol of the existing GPRS network. 
     The foregoing disclosure of the preferred embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many variations and modifications of the embodiments described herein will be apparent to one of ordinary skill in the art in light of the above disclosure. The scope of the invention is to be defined only by the claims appended hereto, and by their equivalents. 
     Further, in describing representative embodiments of the present invention, the specification may have presented the method and/or process of the present invention as a particular sequence of steps. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the specification should not be construed as limitations on the claims. In addition, the claims directed to the method and/or process of the present invention should not be limited to the performance of their steps in the order written, and one skilled in the art can readily appreciate that the sequences may be varied and still remain within the spirit and scope of the present invention.