Patent Publication Number: US-2020305233-A1

Title: System and method for pipelining lte signaling

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 15/918,864, filed Mar. 12, 2018, which application claims priority to U.S. Provisional Application Ser. No. 62/469,905 (hereinafter “&#39;905 provisional”), filed 10 Mar. 2017. Both applications are incorporated herein by reference in their entirety. 
    
    
     THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
     The presently claimed invention was made by or on behalf of the below listed parties to a joint research agreement. The joint research agreement was in effect on or before the date the claimed invention was made and the claimed invention was made as a result of activities undertaken within the scope of the joint research agreement. The parties to the joint research agreement are CABLE TELEVISION LABORATORIES, INC. and CISCO SYSTEMS, INC. 
     TECHNICAL FIELD 
     This disclosure relates in general to the field of communications and, more particularly, techniques for integration of wireless access and wireline networks. 
     BACKGROUND 
     Today&#39;s communication systems may include separate wireless and wireline portions, each of which may be owned and controlled by different operators. Even though some cable operators, also known as Multiple System Operators (“MSOs”) use Data Over Cable Service Interface Specification (“DOCSIS”) networks for backhauling Internet traffic, separate networks, such as mobile core, DOCSIS, and radio, have limited to no visibility into parts of the other network types. Typically, each network type, such as DOCSIS and LTE, have separate traffic scheduling algorithms. As a result, currently when these types of networks are networks are combined, the resulting architecture may be inefficient and may result in longer latency 
     SUMMARY OF THE INVENTION 
     In an embodiment, the present pipelining system and method utilized in a wireless-wired backhaul environment is formed at least partially within and utilized by the backhaul system, which includes a modem and a Modem Termination System (MTS) in communication with a wireless system, which includes a remote radio head and a wireless core. The wireless system herein is discussed as, but not limited to, an LTE wireless system. In these non-limiting embodiments, the remote radio head is represented and discussed as an eNodeB and the wireless core is represented and discussed as an Mobility Management Entity (MME). The wired backhauls system is sometimes discussed herein as a DOCSIS backhaul system, although it will be understood that this is a non-limiting example and merely to ease understanding. It will be understood by the skilled artisan that backhaul system may be any backhaul system and does not even need to be a wired backhaul system. Furthermore, it will be understood that the MTS may be anyone one of a CMTS, an ONT, an OLT, a Network Termination Units, a Satellite Termination Units, and other termination systems, collectively herein called a “Modem Termination System” or “MTS.” The MTS in the present embodiment includes a modem termination system (MTS) device in a backhaul system for backhauling a Stream Control Transmission Protocol (SCTP) initialization message to a MME and/or a centralized Small Cell (cSC). To expedite the backhaul process, the MTS periodically provides unsolicited grants/MAPs to a modem communicatively coupled with the MTS in the backhaul system. The remote radio head (e.g., an eNodeB) also provides a bandwidth report (BWR) to notify the backhaul system that a SCTP initialization message/NAS signaling is forthcoming. The backhaul system advantageously employees the unsolicited grant and BWR with notification to expedite or pipeline the SCTP initialization message/NAS signaling. That is, the at least one unsolicited backhaul grant (e.g., an unsolicited MAP in a DOCSIS embodiment) is put into place within the backhaul system for the purpose of preparing the backhaul communication system to immediately forward the BWR with notification, which acts as a SCTP initialization/NAS notification sent from the eNodeB to the backhaul system. 
     Other embodiments contemplated utilize an optical network. An optical network may be formed with, by way of example, an Optical Network Terminal (ONT) or an Optical Line Termination (OLT), and an Optical Network Unit (ONU), and may utilize optical protocols such as EPON, RFOG, or GPON. Embodiments also contemplated exist in other communication systems capable of x-hauling traffic, examples include without limitation satellite operator&#39;s communication systems, Wi-Fi networks, optical networks, DOCSIS networks, MIMO communication systems, microwave communication systems, short and long haul coherent optic systems, etc. X-hauling is defined here as any one of or a combination of front-hauling, backhauling, and mid-hauling. To simplify description, a termination unit such as a CMTS, an ONT, an OLT, a Network Termination Units, a Satellite Termination Units, and other termination systems are collectively called a Modem Termination System or MTS. To simplify description a modem unit such as a satellite modem, a modem, an Optical Network Units (ONU), a DSL unit, etc. collectively called a “modem.” Further, to simplify description a protocol such as DOCSIS, EPON, RFOG, GPON, Satellite Internet Protocol, is called a “protocol.” 
    
    
     
       BRIEF DESCRIPTION OF THE INVENTION 
         FIG. 1  shows one simplified block diagram and timing diagram for a prior art Remote Radio Head-BackHaul (RRH-BH) communication system in a wireless-wired Backhaul environment, in an embodiment. 
         FIGS. 2A-2C  are simplified block diagrams illustrating various arrangements of RRH-BHs, shown as Small Cell-BackHaul (“SC-BH”) systems, which include a standalone small cell (SC) for connecting user equipment (“UE”) to a mobile core in accordance with embodiments described herein. 
         FIGS. 2D-2F  are simplified block diagrams illustrating various arrangements of RRH-BHs, shown as rSC-BH system including a split small cell for connecting UE to a mobile core in communicatively coupled with a centralized small cell in accordance with embodiments described herein. 
         FIG. 3  shows one exemplary simplified block diagram and timing diagram for a RRH-BH communication system configured for Pipelining Non-Access Stratum (NAS) messages, in an embodiment. 
         FIG. 4  shows one exemplary simplified block diagram and timing diagram for a RRH-BH communication system configured for Enhanced Pipelining Non-Access Stratum (NAS) messages, in an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE FIGURES 
     The present system and method pipelines or otherwise expedites wireless signaling, such as LTE signaling in one embodiment, via a backhaul network. The present disclosure utilizes a DOCSIS type backhaul network in the bulk of its explanations, embodiments, and examples. This is merely to ease understanding and is not meant to be limiting in any way. The present system and method may be incorporated or implemented in any network capable of backhauling this type wireless data. For example, other possible backhaul networks would be apparent to the skilled artisan. 
     Furthermore, the present system and method are discussed as they relate to LTE signaling, but it will be understood by the skilled artisan that other types of wireless data and signaling may be backhauled. For example, other types of data and signaling that may be backhauled include, but not limited to, 2G, 3G, 4G, 5G, IEEE 802 standards such as but not limited to Wi-Fi, Wi-Fi SON, WiMax, etc., and other wireless protocols known to the skilled artisan. It is also contemplated that the present system and method may be advantageously utilized to backhaul wired data. 
       FIG. 1  shows one prior art simplified block diagram and timing diagram for a RRH-BH communication system  100  shown as an LTE-Backhaul system, in one non-limiting embodiment. System  100  employs an eNodeB  110  (also called herein an eNB) located between and in wireless communication with a User Equipment (UE)  102  and wired communication with a modem  122 . Modem  122  is also in wired communication with a modem termination unit (MTS)  125 . MTS  125  is in communication with an Mobility Management Entity (MME)  127 . A backhaul system  130  is shown here to include modem  122  and MTS  125 . 
     LTE signaling messages are sent on the air interface with a Signaling Radio Bearer (SRB). An SRB is a radio bearer that carries DCCH signalling data. An SRB is used during connection establishment to establish the Radio Access Bearers (RABs) and then also to deliver signalling while on the connection, for example, to perform a handover, reconfiguration, or release. 
     In the embodiment shown in  FIG. 1  signaling includes Radio Resource Control (RRC) messages between the UE and the eNB sent on wireless link therebetween. In one example, messages are sent by Signalling radio bearer 0 (SRB0) on Common Control Channel (CCCH) or Signalling radio bearers 1 (SRB1) on Dedicated Control Channel (DCCH). 
     In addition, NAS messages are sent between the UE and the MME, encapsulated in an RRC which is transmitted from the UE to the MME via the backhaul system, described further below. NAS messages may be sent on SRB2 on DCCH. 
     For NAS messages sent from the UE to the MME, at UE startup the eNB maps Logical Channel 2 (LC2)/SRB2 to a Logical Channel Group (LCG). When the UE becomes operational after start-up, the eNB provides a grant to the UE for SRB2 in a subframe. After eNB receives the NAS message it establishes an SCTP stream with the MME. eNB then sends the NAS message to the MME via the backhaul system. The following is one simplified version of the above described serial process as known in the prior art. 
     UE  102  transmits a Status Report (SR) data to eNodeB  110 . Upon receipt of the SR eNodeB  110  generates an Uplink (UL) grant and transmits it back to UE  102 . As shown, the transmission of the SR and receipt of the of the UL grant occurs within the standard 4 ms window. UE  102  processes the UL grant and generates a Logical Channel Group 0 (LCG0) Buffer Status Report (BSR) (called herein after BSR (LCG0)) within the next 4 ms time segment. UE  102  then transmits the BSR (LCG0) to eNodeB  110 . Upon receipt of the BSR (LCG0) eNodeB  110  generates a second UL grant, which is sent back to UE  102 , again a process taking place in the standard 4 ms window. Upon receipt of the second UL grant at UE  102  an RRC encapsulated NAS signaling is generated and prepared for transmission, again, taking place within the standard 4 ms window. 
     The RRC encapsulated NAS signaling/message(s) is then transmitted from UE  102  to eNodeB  110 . Upon receipt of the RRC encapsulated NAS signaling, eNodeB  110  preparers and transmits a Stream Control Transmission Protocol (SCTP) initialization to MME  127  via backhaul system  130 . Upon receipt of the SCTP initialization message modem  122  waits for a contention region. In a non-limiting DOCSIS embodiment described here, the total time scheduled in a single bandwidth allocation map (MAP) message is referred to as the MAP length and the time interval assigned to the contention channel is called the contention region, whereas the remaining part of the MAP length is termed the reservation region. Waiting for the contention region may take as little as 2 ms but will depend on traffic and vender implementation. Modem  122  then sends a request for resources (REQ) to MTS  125 . MTS  125  processes the received REQ and schedules and generates a MAP for modem  122  to transmit the SCTP initialization. MTS  125  transmits the MAP back to modem  122  which, upon receipt, transmits the SCTP initialization at the MTS determined time slot. Upon receipt of the SCTP initialization from modem  122 , MTS  125  forwards the SCTP initialization to MME  127 , finalizing the process described in  FIG. 1 . 
       FIG. 2A  illustrates a simplified block diagram of one embodiment of a small cell-backhaul (SC-BH) system communications environment  200 A in which a communication network, such as but not limited to a DOCSIS network, is used to provide a backhaul for small cell data, such as but not limited to an LTE eNB, 4G, 5G, WiMAX, Wi-Fi, etc. data. The communication environment  200 A supports connection of at least one UE (not shown, but similar to that shown in communication system  100 ), via a radio frequency (“RF”) interface to a standalone small cell (SC)  204 A. Small cells are available for a wide range of air interfaces including GSM, CDMA2000, TD-SCDMA, W-CDMA, LTE and WiMAX. In 3GPP terminology, a Home Node B (HNB) is a 3G femtocell. A Home eNodeB (HeNB) is an LTE femtocell. Wi-Fi is a small cell but does not operate in licensed spectrum. As used herein, UE can be associated with clients, customers, or end users wishing to initiate a communication in a communication system via some network. The term “user equipment” is inclusive of devices used to initiate a communication, such as a computer, a personal digital assistant (PDA), a laptop or electronic notebook, a cellular telephone, an smartphone, an IP phone, or any other device, component, element, or object capable of initiating voice, audio, video, media, or data exchanges within a communication system. UE may also be inclusive of a suitable interface to the human user, such as a microphone, a display, or a keyboard or other terminal equipment. UE may also be any device that seeks to initiate a communication on behalf of another entity or element, such as a program, a database, or any other component, device, element, or object capable of initiating an exchange within a communication system. The detail and best practice associated with the deployment of small cells varies according to use case and radio technology employed Data, as used herein in this document, refers to any type of numeric, voice, video, media, or script data, or any type of source or object code, or any other suitable information in any appropriate format that may be communicated from one point to another. On power up, UE can be configured to initiate a request for a connection with a service provider. A user agreement can be authenticated by the service provider based on various service provider credentials (e.g., subscriber identity module (“SIM”), Universal SIM (“USIM”), certifications, etc.). More specifically, a device can be authenticated by the service provider using some predetermined financial relationship. 
     Referring again to  FIG. 2A , the SC  204 A is connected to a modem  206 A. The modem  206 A may be connected to one or multiple SC  204 A. The modem  206 A is connected to a modem termination system (“MTS”)  208 A via a communication link, such as but not limited to a hybrid fiber coax (“HFC”), for example. In the embodiment illustrated in  FIG. 2A , the MTS  208 A is implemented as an integrated MTS (“I-MTS”). The MTS  208 A connects SC  204 A/modem  206 A to a wireless core, which in the illustrated embodiment comprises a mobile core  210 A. It will be recognized that wireless core may also comprise a Wi-Fi core, LTE packet core, a 5G core, WiMAX core or any other wireless network core. It will be understood that modem  206 A may be collocated with SC  204 A or may be located separate and independent from SC  204 A. Additionally, a collocated combination of SC  204 A/modem  206 A may be referred to herein as a SC-BH network element. 
       FIG. 2B  illustrates a simplified block diagram of another embodiment of a SC-BH system communications environment  200 B in which a communication network, such as but not limited to a DOCSIS network, is used to provide a backhaul for SC  204 B, an example of which is an LTE eNB. Similar to the communications environment  200 A, the communications environment  200 B supports connection of at least one UE via an RF interface to a standalone SC  204 B. One or multiple SC  204 B may be connected to a modem  206 B. In the embodiment shown in  FIG. 2B , MTS functionality is split between a MTS core  208 B and a Remote PHY Device (RPD)  209 B. The RPD  209 B/MTS core  208 B connects the SC  204 B and modem  206 B to a mobile core  210 B, which may be implemented as an LTE packet core. It will be understood that modem  206 B may be collocated with SC  204 B or may be located separate and independent from the SC. Additionally, a collocated combination of the SC  204 B/modem  206 B may be referred to herein as a SC-BH network element. 
       FIG. 2C  illustrates a simplified block diagram of yet another embodiment of a SC-BH system communications environment  200 C in which a communication network, such as but not limited to a DOCSIS network, is used to provide a backhaul for an LTE eNB. Similar to the communications environment  200 A, the communications environment  200 C supports connection of at least one UE via an RF interface to a standalone SC  204 C. One or multiple SC  204 C is connected to a modem  206 C. In the embodiment shown in  FIG. 2C , MTS functionality is split between a remote MAC/PHY  207 C and a router  209 C. The remote MAC/PHY  207 C/router  209 C connects the SC  204 C/modem  206 C to a mobile core  210 C, which may be implemented as an LTE packet core. It will be understood that modem  206 C may be collocated with SC  204 C or may be located separate and independent from the SC. Additionally, a collocated combination of the SC  204 C/modem  206 C may be referred to herein as a SC-BH network element. 
       FIG. 2D  illustrates a simplified block diagram of one embodiment of a SC-BH system communications environment  200 D in which a communication network, such as but not limited to a DOCSIS network, is used to provide a backhaul for an LTE eNB. The communications environment  200 D supports connection of at least one UE via an RF interface to a remote Small Cell (rSC)  204 D portion of a split small cell, which also includes a centralized Small Cell (cSC) portion  205 D. One or more rSC  204 D is connected to a modem  206 D (also sometimes called just “modem” herein. The modem  206 D is connected to a modem termination system (“MTS”)  208 D via hybrid fiber coax (“HFC”), for example. In the embodiment illustrated in  FIG. 2D , the MTS  208 D is implemented as an I-MTS. The MTS  208 D/cSC  205 D connects the rSC  204 D/modem  206 D to a mobile core  210 D, which may be implemented as an LTE packet core. It will be understood that modem  206 D may be collocated with rSC  204 D or may be located separate and independent from the rSC. Additionally, a collocated combination of the rSC  204 D/modem  206 D may be referred to herein as a SC-BH network element. In certain embodiments, I-MTS, cSC, and/or mobile core may also be collocated. 
       FIG. 2E  illustrates a simplified block diagram of another embodiment of a SC-BH system communications environment  200 E in which a communication network, such as but not limited to a DOCSIS network, is used to provide a backhaul for an LTE eNB. Similar to the communications environment  200 A, the communications environment  200 E supports connection of at least one UE via an RF interface to an rSC  204 E portion of a split SC, which also includes a cSC portion  205 E. One or more rSC  204 E is connected to a modem  206 E. In the embodiment shown in  FIG. 2E , MTS functionality is split between a MTS core  208 E and an RPD  209 E. The RPD  209 E/MTS core  208 E/cSC  205 E connects the rSC  204 E/modem  206 E to a mobile core  210 E, which may be implemented as an LTE packet core. It will be understood that modem  206 E may be collocated with rSC  204 E or may be disposed in a location separate and independent from the rSC. Additionally, a collocated combination of the rSC  204 E/modem  206 E may be referred to herein as a SC-BH network element. 
       FIG. 2F  illustrates a simplified block diagram of yet another embodiment of a SC-BH system communications environment  200 F in which a communication network, such as but not limited to a DOCSIS network, is used to provide a backhaul for an LTE eNB. Similar to the communications environment  200 A, the communications environment  200 F supports connection of at least one UE via an RF interface to an rSC  204 F portion of a split SC, which also includes a cSC portion  205 F. One or more rSC  204 F is connected to a modem  206 F. In the embodiment shown in  FIG. 2F , MTS functionality is split between a remote MAC/PHY  207 F and a router  209 F. The remote MAC/PHY  207 F/router  209 F/cSC  205 F connects the rSC  204 F/modem  206 C to a mobile core  210 F, which may be implemented as an LTE packet core. It will be understood that modem  206 F may be collocated with rSC  204 F or may be disposed in a location separate and independent from the rSC. Additionally, a collocated combination of the rSC  204 F/modem  206 F may be referred to herein as a SC-BH network element. 
     It will be noted that  FIGS. 2A-2C  illustrate embodiments comprising a standalone SC, while  FIG. 2D-2F  illustrate embodiments comprising a split SC. It will be recognized that techniques described herein are equally applicable to any of the embodiments shown in  FIGS. 2A-2F . It will be further recognized that the embodiments illustrated in  FIGS. 2A-2F  are provided for purposes of example only and are not meant to be an exhaustive list of embodiments in which the techniques described herein may be advantageously implemented. Moreover, although not illustrated in  FIGS. 2A-2F , a network interface device (“NID”) may optionally be provided between the SC/rSC and modem. 
       FIG. 3  shows one exemplary system and timing diagram  300  for backhauling wireless signaling, LTE signaling in the present embodiment, in an expedited or pipelined manner. 
     System and timing diagram  300  contains the same components and connections as that shown environment  100 , namely a UE  102 , a remote radio head or eNodeB  110 , an MTS  125 , and an MMP  127 . To highlight the differences between system and timing diagram  300  of  FIG. 3  and environment  100  of  FIG. 1 , new processes and timing flows are shown in dashed lines. As can be seen a significant latency reduction is achieved over the prior art process discussed in  FIG. 1 . 
     UE  102  sends a Status Report (SR) to eNodeB (eNB)  110 . eNB  110  process the SR and provides a first UL grant back to UE  102  in a subframe. UE  102  then generates the Logical Channel Group 0 (LCG0) Buffer Status Report (hereinafter BSR (LCG0)) associated with the previously transmitted SR. Note, the same process may be applied to a different Logical Channel Group, such as LCG1 to generate a BSR (LCG1). The generated BSR (LCG0) is sent back to eNB  110 . eNB  110  then generates a second UL grant for UE  102  to send its RRC encapsulated NAS signaling data. Since eNodeB  110  has data which identifies which logical channel group it is providing this grant for, eNodeB  110  also knows when to expect the associated NAS message. Thus, when eNodeB  110  generates and sends a second UL grant back for the NAS message to UE  102  it also sends a BWR containing a notification for SCTP initialization to the backhaul system, which enables MTS  125  to generate a pre-grant for the transfer of the SCTP initialization message to MME  127 . This allows the SCTP stream to be established earlier than has been done in the prior art, discussed in  FIG. 1 , above. 
     After eNodeB  110  receives the RRC encapsulated NAS message from UE  102 , eNodeB  110  sends a SCTP initialization message to modem  122 . Since SCTP initialization message uses MME  127 &#39;s IP destination, the SCTP initialization message can be classified by modem  122  to use the pre-granted MAP for SCTP initialization sent from MTS  125 . One nonlimiting system and processes is described in more detail, below. 
     UE  102  sends a Status Report (SR) to eNodeB (eNB)  110 . eNB  110  process the SR and provides a first UL grant back to UE  102  in a subframe. UE  102  then generates a BSR (LCG0) associated with the previously transmitted SR. Prior to and during the transmission of the SR, UL grant, and the BSR (LCG0) between UE  102  and eNB  110  the MTS  125  periodically generates and transmits a grant (called a MAP in a DOCSIS environment) in preparation for the arrival of a bandwidth report (BWR) at modem  122 . Upon the arrival BSR (LCG0) at eNB  110  the eNodeB generates a BWR and sends it to modem  122 . This BWR represents a notification for SCTP initialization. As the MAP for BWR has been pre-sent by MTS  125  to modem  122  in anticipation of the arrival of the BWR notification for SCTP initialization, the BWR is transmitted from modem  122  to MTS  125  without any additional communication required or undue delay. 
     Upon receipt of the BWR at MTS  125 , MTS  125  prepares a MAP for the SCTP initialization in anticipation of its arrival at modem  122 . At the same time the receipt of the BWR and the preparation of the MAP occurs at MTS  125  the eNB  110  prepares and transmits an UL grant to UE  102 . In response UE  102  prepares and transmits the RRC encapsulated NAS signaling/message back to eNodeB  110 . Upon receipt of the RRC encapsulated NAS signaling the eNodeB  110  prepares and transmits the SCTP initialization to modem  122 , where the previously discussed MAP for SCTP awaits it for immediate transmission to MTS  125  which then forwards it to MME  127 . MME  127  then prepares and sets up a SCTP stream for the transmission of the NAS message held at eNodeB  110  (the process not shown as it is known in the art). 
     By configuring eNodeB  110  to generate and transmit a BWR (notification for SCTP initialization) to the backhaul system and configuring MTS  125  to periodically generate and transmit a MAP for the BWR such that modem  122  can then immediately forward the BWR to MTS  125  for preparation of the MAP for SCTP, a significant latency reduction is realized. 
       FIG. 4  shows one exemplary simplified block diagram and timing diagram for a RRH-BH communication system configured for Enhanced Pipelining Non-Access Stratum (NAS) messages, in an embodiment. 
     UE  102  sends a Status Report (SR) to eNodeB (eNB)  110 . eNB  110  process the SR and provides a first UL grant back to UE  102  in a subframe. UE  102  then generates a BSR (LCG0) associated with the previously transmitted SR and received grant. Prior to and during the transmission of the SR, UL grant, and the BSR (LCG0) between UE  102  and eNB  110  the MTS  125  periodically generates and transmits unsolicited grant (called a MAP in a DOCSIS environment) in preparation for the arrival of a bandwidth report (BWR) at modem  122 . Upon the arrival BSR (LCG0) at eNB  110  the eNodeB generates a BWR and sends it to modem  122 . This BWR represents a notification for SCTP initialization. As the MAP for BWR has been pre-sent by MTS  125  to modem  122  in anticipation of the arrival of the BWR notification for SCTP initialization, the BWR is transmitted from modem  122  to MTS  125  without any additional communication required or undue delay. 
     Upon receipt of the BWR at MTS  125 , MTS  125  prepares a MAP for the SCTP initialization in anticipation of its arrival at modem  122 . At the same time the receipt of the BWR and the preparation of the MAP occurs at MTS  125  the eNB  110  prepares and transmits an UL grant to UE  102 . Before or after eNodeB  110  sends the UL grant to UE  102 , eNodeB  110  initializes the process to pre-setup the SCTP stream and sends a pre-generated SCTP initialization to MME  127  via modem  122  and MTS  125 . MME  127  then prepares and transmits a SCTP Initialization ACK back to eNodeB  110  via MTS  125  and modem  122 . All of this occurs prior to (or at least proximate in time to) the arrival of the RRC encapsulated NAS signaling at eNodeB  110  such that the NAS message is expedited to MME  127 . 
     In response to the UL grant arriving at UE  102 , the UE generates the NAS signaling and packages it in an RRC encapsulation. UE  102  then transmits the RRC encapsulated NAS signaling/message back to eNodeB  110 . Upon receipt of the RRC encapsulated NAS signaling the eNodeB  110  prepares and transmits the NAS message via the previously set-up SCTP stream to MME  127  via modem  122  and MTS  125 . 
     Changes may be made in the above methods and systems without departing from the scope hereof. It should thus be noted that the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all generic and specific features described herein, as well as all statements of the scope of the present method and system, which, as a matter of language, might be said to fall there between.