Patent Publication Number: US-2007097924-A1

Title: Method and system for inter-technology active handoff of a hybrid communication device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      The present application is a continuation-in-part of U.S. patent application Ser. No. 11/272,934, attorney docket no. CE13376R, entitled “METHOD AND SYSTEM FOR INTER-TECHNOLOGY ACTIVE HANDOFF OF A HYBRID COMMUNICATION DEVICE,” filed Nov. 22, 2005, and further claims priority from provisional U.S. patent application No. 60/629,929, attorney docket no. CE13376R, entitled “METHOD AND SYSTEM FOR INTER-TECHNOLOGY ACTIVE HANDOFF OF A HYBRID COMMUNICATION DEVICE,” filed Nov. 23, 2004, and provisional patent application No. 60/742,584, attorney docket no. CE15795R, entitled “METHOD AND SYSTEM FOR INTER-TECHNOLOGY ACTIVE HANDOFF OF A HYBRID COMMUNICATION DEVICE,” filed Dec. 5, 2005, which patent applications are commonly owned and incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates generally to wireless communication systems, and more specifically to handoff of a hybrid communication device between cellular communication networks implementing different air interface technologies.  
     BACKGROUND OF THE INVENTION  
      The evolution of cellular communications has resulted in a proliferation of networks of different technologies and corresponding different air interfaces. As a result, during the course of a single call, a wireless mobile station may roam among multiple networks, wherein each such network implements a different technology than the other networks of the multiple networks. Among the different network technologies are high rate packet data (HRPD) Code Division Multiple Access (CDMA) technologies, such as CDMA 2000 1XEV-DO (1X Evolution Data Optimized) or packet switched CDMA 1XRTT (1X Radio Transmission Technology), that are capable of providing high rate packet data communication services, and legacy CDMA 2000 1X networks.  
      As the mobile station roams among a legacy CDMA communication network such as a CDMA 2000 1X network and an HRPD CDMA communication network such as a CDMA 2000 1XEV-DO network, it may be beneficial to system performance to handoff the mobile station from the former network to the latter network. For example, the channel conditions associated the latter network may be more favorable than the channel conditions associated with the former network due to such factors as fading, adjacent and co-channel interference, and available power at a serving base station (BS) or radio access network (RAN). By way of another example, an operator of both a legacy CDMA 2000 1X network and an HRPD CDMA 2000 1XEV-DO network may desire to move the mobile station from one such network and to the other such network for purposes of system loading.  
      Currently, the only defined method for executing a handoff between a legacy CDMA 2000 1X network and an HRPD CDMA 2000 1XEV-DO network is an execution of a dormant hard handoff, wherein a mobile station must go dormant and drop a radio resource of a network of a first CDMA technology and then acquire a radio resource of a network of a second CDMA technology. A result is a brief period of time during which the mobile station is not actively engaged in a communication session with either network. Further, when executing a dormant hard handoff there is no linkage between the two networks as the mobile station must drop the first network and acquire the second network without any assistance from the BS or RAN of either network. As a result, voice/data traffic may be lost during the handoff, resulting in poor system performance and efficiency and disgruntled end users.  
      Therefore, a need exists for a method and apparatus for implementing an active hard handoff of a communication session between a legacy CDMA 2000 1X network and a HRPD CDMA 2000 1XEV-DO network that minimizes an amount of time that a mobile station is not actively engaged in a communication session with either network during a handoff. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a block diagram of a wireless communication system in accordance with an embodiment of the present invention.  
       FIG. 2  is a block diagram of a base station controller in accordance with an embodiment of the present invention.  
       FIG. 3  is a block diagram of a mobile station in accordance with an embodiment of the present invention.  
       FIG. 4  is a block diagram of a mobile station in accordance with another embodiment of the present invention.  
       FIG. 5  is a logic flow diagram of a method executed by the communication system of  FIG. 1  in handing off of a communication session from a first network of  FIG. 1  to a second network of  FIG. 1  in accordance with an embodiment of the present invention.  
       FIG. 6  is a bit map of an exemplary High Rate Packet Data (HRPD) Information message in accordance with an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      To address the need that exists for a method and apparatus that implements an active hard handoff of a communication session between a first CDMA 2000 network and a high rate packet data CDMA 2000 network, a communication system is provided that provides for reporting a pilot channel of a second network when a mobile station is operating in a first network, wherein the second network implements a different air interface communication technology than the first network. While the mobile station is operating in the first network via radio frequency (RF) resources associated with the first network, the mobile station monitors a pilot channel associated with the second network and determines whether to report the monitored pilot channel based on one or more of an inter-system hard handoff add threshold and an inter-system hard handoff drop threshold. The inter-system hard handoff add and drop thresholds may be pre-programmed into the mobile station or may be provisioned to the mobile station by the first network.  
      Generally, an embodiment of the present invention encompasses a method for reporting a pilot channel of a second network when a mobile station is operating in a first network, wherein the second network implements a different air interface communication technology than the first network. The method includes conveying forward link bearer traffic to, and receiving reverse link bearer traffic from, the mobile station via radio frequency (RF) resources associated with the first network, while operating in the first network, monitoring a pilot channel associated with the second network, and determining whether to report the monitored pilot channel based on one or more of an inter-system hard handoff add threshold and an inter-system hard handoff drop threshold.  
      Another embodiment of the present invention encompasses a method for facilitating a reporting of a pilot channel of a second network associated with a different air interface communication technology when a mobile station is operating in a first network, wherein the second network implements a different air interface communication technology than the first network. The method includes conveying, by the first network, the inter-system hard handoff add threshold and the inter-system hard handoff drop threshold and receiving, by the first network from the mobile station, a pilot channel quality associated with the pilot channel of the second network.  
      Still another embodiment of the present invention encompasses a mobile station capable of operating in each network of a plurality of networks, wherein each network of the plurality of networks is associated with a different air interface communication technology than the other networks of the plurality of networks. The mobile station includes an at least one memory device that maintains one or more of an inter-system hard handoff add threshold and an inter-system hard handoff drop threshold and a processor coupled to the at least one memory device that is configured to, when operating in a first network of the plurality of networks, convey forward link bearer traffic and receive reverse link bearer traffic via radio frequency (RF) resources associated with the first network, monitoring a pilot channel associated with a second network of the plurality of networks, and determine whether to report the monitored pilot channel based on one or more of the inter-system hard handoff add threshold and the inter-system hard handoff drop threshold.  
      Yet another embodiment of the present invention encompasses a base station controller of a first network that facilitates a reporting of a pilot channel associated with a second network, wherein the second network implements a different air interface communication technology than the first network, wherein the base station controller comprises a processor that is configured to convey an inter-system hard handoff add threshold and the inter-system hard handoff drop threshold and to receive a pilot channel quality associated with the pilot channel of the second network.  
      Turning now to the drawings, the present invention may be more fully described with reference to  FIGS. 1-6 .  FIG. 1  is a block diagram of a wireless communication system  100  in accordance with an embodiment of the present invention. Communication system  100  includes a first network  110  such that implements a first air interface technology and a second, network  130  that implements an second, different air interface technology. Each of network  110  and network  130  includes a respective Base Station  114 ,  134  that comprises a respective Base Transceiver Station (BTS)  116 ,  136  coupled to a respective Base Station Controller (BSC)  118 ,  138 . Network  110  further includes a Mobile Switching Center (MSC)  120  that is coupled to BS  114 , and in particular to BSC  118 . MSC  120  may be further coupled to BS  134 , and in particular to BSC  138 . Networks  110  and  130 , and more particularly BSs  114  and  134 , are each further coupled to a Packet Data Serving Node (PDSN)  124  and via the PDSN to an external network (not shown) for an exchange of communications with distant parties external to communication system  100 .  
      MSC  120  is coupled to a Home Location Register (HLR) (not shown) and a Visited Location Register (VLR) (not shown). As is known in the art, the HLR and VLR includes mobility and provisioning information associated with each mobile station subscribed to and/or registered for the services of the MSC&#39;s associated network  110 , such as a profile of the mobile station, including the capabilities of the mobile station, and a BS currently serving the mobile station. BSs  114  and  134  each provides wireless communication services to the mobile stations located in a coverage area of the BS via a respective air interface  112 ,  132 . Each air interface  112 ,  132  includes a forward link that includes multiple forward link traffic channels and multiple forward link signaling channels, such as common and dedicated signaling channels. Each air interface  112 ,  132  further includes a reverse link that includes multiple reverse link traffic channels, multiple reverse link signaling channels, such as common and dedicated signaling channels, and an access channel. Each of the forward link and reverse link of air interface  132  further comprises a channel that is dedicated to first network-type messaging, that is, to an exchange of 3G1X (Third generation 1X) messages when the first network is a CDMA 2000 1X system, in the second network, such as a CDMA 2000 1XEV-DO network. For ease of reference, this channel is referred to herein as a 3G1X channel.  
      Each of network  110  and network  130 , and more particularly BSs  114  and  134 , communicate with each other, and with Packet Data Serving Node (PDSN)  124 , via an Internet Protocol (IP)-based network  122 . In various embodiments of the present invention, BSs  114  and  134  may communicate via a proprietary interface, a new ‘A’ interface, or via a well-known intersystem protocol, such as the protocol described in the 3GPP2 (Third Generation Partnership Project 2) TIA-41 (Telecommunications Industry Association-41) standard, that is, 3GPP2 N.S0005. The TIA-41 standard provides standardized intersystem procedures for mobility management in cellular systems and prescribes messaging among Mobile Switching Centers, Home Location Registers (HLRs), Visited Location Registers (VLRs), Authentication, Authorization, and Accounting functionality (AAAs), and other core network elements of cellular systems in order to provide services to mobile stations when interaction is required between different cellular systems. In another embodiment of the present invention, BSs  114  and  134  may communicate via an extension of an A1 interface by providing a connection between the BSs via MSC  120 .  
      Communication system  100  further includes a wireless mobile station (MS)  102 , for example but not limited to a cellular telephone, a radiotelephone, or a Personal Digital Assistant (PDA), personal computer (PC), or laptop computer equipped for wireless voice communications. In various communications systems, mobile station  102  may also be referred to as an access terminal (AT). Mobile station  102  comprises a hybrid terminal that is capable of engaging in a voice or data call with both first network  110  and second network  130 . For example, in one embodiment of the present invention, mobile station  102  may include a separate transceiver for operation in each of first network  110  and second network  130 , thereby allowing the mobile station to concurrently transmit or receive in each of the two networks.  
       FIG. 2  is a block diagram of a BSC  200 , such as BSCs  118  and  138 , in accordance with an embodiment of the present invention. BSC  200  includes a processor  202 , such as one or more microprocessors, microcontrollers, digital signal processors (DSPs), combinations thereof or such other devices known to those having ordinary skill in the art. The particular operations/functions of processor  202 , and thus of BSC  200 , is determined by an execution of software instructions and routines that are stored in a respective at least one memory device  204  associated with the processor, such as random access memory (RAM), dynamic random access memory (DRAM), and/or read only memory (ROM) or equivalents thereof, that store data and programs that may be executed by the corresponding processor.  
      Referring now to  FIG. 3 , in one embodiment of the present invention, a hybrid MS  300 , such as MS  102 , capable of operating in communication system  100  may include multiple transceivers, that is, a first transceiver  302  for operation in first network  110  and a second transceiver  304  for operation in second network  130 , thereby allowing the MS to concurrently transmit or receive in each of the two networks. Each transceiver is coupled to a vocoder  306  and a processor  308 , which processor is further coupled to an at least one memory device  310 .  
      In another embodiment of the present invention, and referring now to  FIG. 4 , a hybrid MS  400 , such as MS  102 , capable of operating in communication system  100  may include a single transceiver  402  that emulates the operation of dual transceivers, such as transceivers  302  and  304 . Transceiver  402  is coupled to a processor  404 , which processor is further coupled to an at least one memory device  406 . Processor  404  may cause transceiver  402  to rapidly switch between networks  110  and  130  to give the appearance of concurrent operation. Further, MS  400  may maintain apriori information in at least one memory device  406  that facilitates the switching between networks at optimum times.  
      Each of processors  308  and  404  may comprise one or more microprocessors, microcontrollers, digital signal processors (DSPs), combinations thereof or such other devices known to those having ordinary skill in the art, which processor is configured to execute the functions described herein as being executed by mobile station  102 . Each of at least one memory devices  310  and  406  may comprise random access memory (RAM), dynamic random access memory (DRAM), and/or read only memory (ROM) or equivalents thereof, that store data and programs that may be executed by the associated processor and that allow mobile station  102  to perform all functions necessary to operate in communication system  100 .  
      The embodiments of the present invention preferably are implemented within BSC  118  and MS  102 , and more particularly with or in software programs and instructions stored in the respective at least one memory device  204 ,  310 ,  406  and respectively executed by processors  202 ,  308 ,  404  of the BSC and MS. However, one of ordinary skill in the art realizes that the embodiments of the present invention alternatively may be implemented in hardware, for example, integrated circuits (ICs), application specific integrated circuits (ASICs), and the like, such as ASICs implemented in one or more of BSC  118  and MS  102 . Based on the present disclosure, one skilled in the art will be readily capable of producing and implementing such software and/or hardware without undo experimentation.  
      In order for MS  102  to engage in a voice call with a distant party via one or more of network  110  and network  130 , each of MS  102  and networks  110  and  130  operates in accordance with well-known wireless telecommunications protocols. Preferably, first network  110  is a CDMA 2000 1X system that operates in accordance with the CDMA 2000 1X standards. Further, second network  130  preferably is a CDMA 2000 1XEV-DO (1X Evolution Data Optimized) system that operates in accordance with the 3GPP2 and TIA/EIA (Telecommunications Industry Association/Electronic Industries Association) IS-856 and 3GPP2 C.S0024 standards, which provide compatibility standards for CDMA 2000 1XEV-DO systems. While each of network  110  and network  130  may implement a high rate packet data (HRPD) communication technology, references herein to an HRPD BS, pilot channel, pilot channel measurement, pilot channel threshold, and so on may be deemed to refer to a BS, pilot channel, pilot channel measurement, pilot channel threshold, etc. associated with network  130 .  
      Further, each of air interfaces  112  and  132 , and correspondingly each of network  110 , network  130 , and mobile station  102 , preferably operates in accordance with the TIA/EIA (Telecommunications Industry Association/Electronic Industries Association) IS-2001 (3GPP2 A.S0011 to A.S0017 Inter Operability Specification, or IOS) standards, which provide a compatibility standard for cellular mobile telecommunications systems that operate as a CDMA 2000 system, such as 1X, 1XEV-DO, 1XEV-DV, and 1XRTT, or any other technology supported by a TIA-2001 based Access Network. In addition, MS  102 , air interface  132 , and BS  134  preferably further operates in accordance with the 3GPP2 A.S0008-0 v3.0 and 3GPP2 A.S0007-A v1.0 Inter Operability Specifications (IOS) for a High Rate Packet Data (HRPD) access network. To ensure compatibility, radio system parameters and call processing procedures are specified by the standards, including call processing steps that are executed by an MS and a base station serving the MS and between the BS and associated infrastructure in order to establish a call or execute a handoff.  
      In communication system  100 , MS  102  may roam through the system when the MS is engaged in a voice or data communication session. As a result of the roaming, situations may arise where it is desirable to hand off MS  102  from first network  110  to second network  130 . In order to facilitate a handoff of MS  102 , communication system  100  provides a method and apparatus for an active handoff of the MS from first network  110  to second network  130  when the MS is actively engaged in a communication session. Referring now to  FIG. 5 , a logic flow diagram  500  is provided that depicts a handoff executed by communication system  100  in handing off a communication session from first network  110  to second network  130  in accordance with an embodiment of the present invention.  
      Logic flow diagram  500  begins when MS  102  is actively engaged ( 502 ) in a communication session with a distant party via a current network in use, that is, first network  110 . In order to participate in the communication session via first network  110 , MS  102  must already be registered with the first network. Registration procedures are well-known in the art and will not be described in detail herein except to note that when an MS registers with a network, the network stores in an associated HLR or VLR, or an associated Foreign Agent (FA) or Home Agent (HA), whichever is appropriate, an identification of a BS associated with the network and serving the MS.  
      MS  102  maintains ( 506 ), in an at least one memory device of the MS, such as at least one memory device  310  or  406 , first (1X) intra-system soft handoff add and drop thresholds that are associated with first network  110 , which intra-system add and drop thresholds are utilized by the MS to add a BS and/or BTS to, and to drop a BS and/or BTS from, an active set of the MS. MS  102  further maintains ( 508 ), in the an at least one memory device of the MS, inter-system hard handoff add and drop thresholds associated with second network  130 , which inter-system add and drop thresholds are utilized by the MS to determine whether to request an inter-system handoff from first network  110  to second network  130 . When a quality of a pilot channel (hereinafter referred to as a “pilot”) of second network  130 , and more particularly of air interface  132 , is measured by MS  102  while the MS is operating in first network  110 , and when the measured quality compares favorably to the inter-system hard handoff add threshold (exceeds the threshold in the event of a signal strength measurement), the MS reports the pilot back to BS  114 , and more particularly BSC  118 . When a previously reported pilot of second network  130 , and more particularly of air interface  132 , is measured by MS  102  when operating in first network  110  and compares unfavorably with the inter-system hard handoff drop threshold (falls below the inter-system hard handoff drop threshold in the event of a signal strength measurement), the MS reports the pilot back to BS  114 , and more particularly BSC  118 .  
      In one embodiment of the present invention, an operator of communication system  100  may program into MS  102  the inter-system hard handoff add and drop thresholds associated with second network  130 . In another embodiment of the present invention, BS  114 , and more particularly BSC  118  of the BS, may provision ( 504 ) the inter-system hard handoff add and drop thresholds to MS  102  via an overhead message, which inter-system hard handoff add and drop thresholds may be maintained by the BS in an at least one memory device  204  of BSC  118 . In one such embodiment, the overhead message may comprise an HRPD Information message instructing MS  102  to report HRPD signal strengths. Referring now to  FIG. 6 , a bit map is provided of an exemplary HRPD Information Message  600  in accordance with an embodiment of the present invention. HRPD Information Message  600  includes a HRPD_ADD data field  604  that informs of an inter-system hard handoff add threshold and a HRPD_DROP data field  606  that informs of an inter-system hard handoff drop threshold. Preferably, HRPD Information Message  600  further includes a message type data field identifying the message as an HRPD Information message (for example, MSG_TAG: HRPDIM) and an HRPD_TRSH_INCL data field  602  that informs whether HRPD pilot strength thresholds are included in the message.  
      BS  114  may set a value of HRPD_TRSH_INCL data field to ‘1’ if HRPD capable MSs, such as MS  102 , are required to report HRPD pilot strength measurements in accordance with the HRPD_ADD and HRPD_DROP threshold values; otherwise, this field may be set to ‘0’. HRPD_ADD corresponds to an HRPD pilot detection threshold. When HRPD_TRSH_INCL is set to ‘1,’ BS  114  may include HRPD_ADD data field  604  in HRPD Information message  600  and include a value in the field corresponding to a signal strength value sufficient to facilitate a hard handoff from first network  110  to second network  130 ; otherwise, data field  604  may be omitted. BS  114  may set HRPD_ADD data field  604  to a pilot detection threshold, expressed as an unsigned binary number equal to ‘−2×10×log 10  E c /I 0 .’ HRPD_DROP data field  606  corresponds to an HRPD pilot drop threshold. When HRPD_TRSH_INCL  602  is set to ‘1’, BS  114  may include the HRPD_DROP data field  606  in HRPD Information message  600  and include a value in the field corresponding to a signal strength value that triggers an MS, such as MS  102 , to report a drop in signal strength of previously reported HRPD pilots; otherwise, data field  606  may be omitted. BS  114  may set HRPD_DROP data field  606  to a pilot drop threshold, expressed as an unsigned binary number equal to └−2×10×log 10  E c /I 0 ┘.  
      As part of the communication session, mobile station  102  conveys  202  reverse link frames comprising bearer traffic to PDSN  124  via a reverse link traffic channel of air interface  112 , BS  114 , and IP network  122  for routing to the distant party via an external network (not shown). Further, when PDSN  124  receives bearer traffic from the distant party and intended for mobile station  102 , the PDSN routes  203  the voice information to BS  114  via IP network  122  and the BS conveys forward link frames comprising the bearer traffic to mobile station  102  via a forward link traffic channel of air interface  112 .  
      While MS  102  is engaged in the communication session with BS  114 , the MS monitors ( 510 ) qualities, in particular a signal strength or alternatively any of a variety of other signal qualities such as a signal-to-noise ratio (SNR), a carrier-to-interference ratio (C/I), pilot power-to-total power (Ec/Io) ratio, a bit error rate (BER), or a frame error rate (FER), of pilots associated with each of BS  114  of network  110  and BS  134  of network  130 . MS  102  may monitor the pilots of each network  110 ,  130  concurrently or may switch between networks in monitoring the pilots. MS  102  may self-determine when or whether to monitor the pilots associated with BS  134  of second network  130  or may monitor the pilots in response to receiving an instruction to do so from first network  110 , and in particular one of BSC  118  and MSC  120 .  
      MS  102  reports ( 512 ) the monitored pilot(s) of first BS  114  and air interface  112  in accordance with well known reporting procedures. For example, when a monitored pilot exceeds a 1X intra-system soft handoff add threshold, the MS reports this pilot, and the measured pilot channel strength, to BS  114 , and in particular to BSC  118 , in a Pilot Strength Measurement Message (PSMM) conveyed to the BS via the reverse link of air interface  112 . Similarly, when a monitored pilot falls below a 1X intra-system soft handoff drop threshold, the MS reports this pilot, and the measured pilot signal strength, to BS  114 , and in particular to BSC  118 , in a PSMM conveyed to the BS via the reverse link of air interface  112 . BSC  118  then stores the reported first network pilot measurements in the at least one memory device  204  of the BSC. In the prior art, a report of a pilot that exceeds a 1X intra-system soft handoff add threshold is an indicator to add a first BS/BTS associated with that pilot to soft handoff with the MS and a report of a pilot that falls below a 1X intra-system soft handoff drop threshold is an indicator to drop a BS/BTS associated with that pilot from soft handoff with the MS.  
      When a quality of a pilot of second network  130 , and more particularly of air interface  132 , is measured by MS  102  when operating in first network  110  and exceeds the inter-system hard handoff add threshold, or a quality of a previously reported pilot of second network  130 , and more particularly of air interface  132 , is measured by MS  102  when operating in first network  110  and falls below the inter-system hard handoff drop threshold, the MS reports ( 514 ) the monitored HRPD pilot(s) back to first BS  114 , and more particularly BSC  118 . BSC  118  then stores the reported HRPD pilot measurements in the at least one memory device  204  of the BSC.  
      MS  102  may report HRPD pilot strengths by sending a modified version of a first network  110  message delivery mechanism, such as a Data Burst Message (DBM), to BS  114  on a reverse link dedicated signaling channel (r-dsch) of air interface  112 . In response to receiving the DBM, first BS  114  parses the message and recognizes the message as comprising an HRPD pilot signal strength measurement. The DBM includes a BURST_TYPE data field that is set to ‘001001’ or another identifier that identifies the message as reporting HRPD pilot signal strengths. Various data field of the DBM may be set as follows: a MSG_NUMBER data field may be set to ‘00000001,’ a NUM_MSGS data field may be set to ‘00000001,’ a NUM_FIELDS data field may be set to a number of octets in the HRPD Pilot Strength Report Record, and CHARi data fields may be set to the corresponding octets of the HRPD Pilot Strength Report Record as in the following table:  
                              HRPD Pilot Strength Report Record                             Data Field   Length (bits)                                         REF_PN   9           PILOT_STRENGTH   6           NUM_HRPD_PILOTS   4                         NUM_HRPD_PILOTS occurrences of the following record:           {NUM_HRPD_PILOTS                             HRPD_PILOT_PN_PHASE   15           HRPD_PILOT_STRENGTH   6           }NUM_HRPD_PILOTS           RESERVED   0-7 (as needed)                      
 
 REF_PN corresponds to a time reference pseudorandom number (PN) sequence offset associated with first network  110 . MS  102  may set this field to the PN sequence offset of the CDMA 2000 1X pilot used by the MS to derive its time reference, relative to the zero offset pilot PN sequence, in units of 64 PN chips. PILOT_STRENGTH corresponds to a measured strength of a pilot of first network  110 , in dB. MS  102  may set this field to 
 
└−2×10 log 10  PS┘, 
 
 where ‘PS’ is the strength of a first pilot, such as a CDMA 2000 1X pilot, used by MS  102  to derive its time reference. If this value (−2×10 log 10  PS) is less than 0, then MS  102  may set this field to ‘000000’. If this value is greater than ‘111111’, then MS  102  may set this field to ‘111111’. NUM_HRPD_PILOTS corresponds to a number of HRPD pilots reported by MS  102 . MS  102  may set this field to the number of HRPD pilots being reported. 
 
      For each HRPD handoff candidate, MS  102  may include in the DBM a two field record for each measured occurrence of a pilot associated with that candidate, that is, a first, HRPD_PILOT_PN_PHASE data field and a second, HRPD_PILOT_STRENGTH data field. HRPD_PILOT_PN_PHASE corresponds to a phase of the pilot measured by MS  102 . MS  102  may set this field to the phase of the HRPD pilot PN sequence relative to the zero offset pilot PN sequence of the pilot, in units of one PN chip. HRPD_PILOT_STRENGTH corresponds to a pilot strength of the measured pilot, in dB. MS  102  may set HRPD_PILOT_STRENGTH to 
 
└−2×10 log 10  PS┘, 
 
 where ‘PS’ is the strength of the HRPD pilot. If this value (−2×10 log 10  PS) is less than 0, MS  102  may set this field to ‘000000’. If this value is greater than ‘111111’, MS  102  may set this field to ‘111111’. 
 
      MS  102  report HRPD pilot strengths in accordance with the HRPD_ADD and HRPD_DROP threshold settings if these fields are included in the HRPD Information Message. When a measured pilot(s) first exceeds the HRPD_ADD threshold, MS  102  may report the pilot strength(s) by sending the above described DBM, with BURST_TYPE data field set to ‘001001’. Similarly when the strength of these same pilot(s) fall below the HRPD_DROP threshold, MS  102  may report this to BS  114  via the DBM, again with BURST_TYPE data field set to ‘001001’.  
      In another embodiment of the present invention, instead of sending the measured HRPD pilot strengths to BS  114  via a DBM, MS  102  may convey the measured HRPD pilot strengths in a modified version of a CDMA1X Pilot Strength Measurement Message (PSMM), which message is modified to include data fields informing of the measured HRPD pilot strengths. Use of a modified version of a CDMA1X PSMM would minimize extra messaging required by a DBM.  
      Based on the first pilot measurements associated with BS  114  and the HRPD pilot measurements associated with BS  134  and reported by MS  102 , first network  110 , and in particular BS  114  or MSC  120  may then determine ( 516 ) to handoff MS  102  to second network  130  and BS  134 . For example, when a pilot of BS  114  compares unfavorably to (is below, in the case of a signal strength threshold) the 1X intra-system soft handoff drop threshold and/or a pilot of BS  134  compares favorably to (exceeds, in the case of a signal strength threshold) the HRPD inter-system hard handoff add threshold, this may indicate a desirability of a handoff. By way of another example, costs associated with operating MS  102  on network  110  may be different from the costs associated with operating MS  102  on network  130 . In turn, an operator (or operators) of networks  110  and  130  may charge a different fee for use of each network. If second network  130  is the lower cost network, a user of MS  102  may program into the MS a directive to operate on the second network  130  whenever a measurement of a pilot associated with the second network compares favorably to the HRPD inter-system hard handoff add threshold. By way of still another example, for load leveling purposes, for network cost consideration purposes, or due to a need to clear traffic channels in a coverage area in order to facilitate emergency communications, an operator of a communication system such as communication system  100  may find it desirable to move an MS, such as mobile station  102 , that is actively engaged in a voice call in first network  110  to second network  130  whenever a measurement of a pilot associated with the second network compares favorably to the HRPD inter-system hard handoff add threshold.  
      On the other hand, the processing of an inter-system hard handoff may be time consuming or, even when desirable, may nevertheless get deferred. As a result, communication system  100  provides for a continuing monitoring of the pilot(s) associated with second network  130  (that is, BS  134 ) and when a pilot that compared favorably to the inter-system hard handoff add threshold later, in a subsequent monitoring of the pilot and prior to consummation of the handoff, compares unfavorably to the inter-system hard handoff drop threshold, the handoff may be terminated ( 518 ) by MS  102  or BS  114 , in particular BSC  118 , or the pilot may be dropped by the MS, BS, and/or BSC as a potential handoff target.  
      In response to determining to handoff MS  102  from first network  110  and BS  114  to second network  130  and BS  134 , first network  110  instructs ( 520 ) MS  102  to move to second network  130  and BS  134 . MS  102  may then be handed off from first network  110  and BS  114  to second network  130  and BS  134  in accordance with one of the various inter-technology handoff techniques described in detail in U.S. patent application Ser. No. 11/272,934, entitled “METHOD AND SYSTEM FOR INTER-TECHNOLOGY ACTIVE HANDOFF OF A HYBRID COMMUNICATION DEVICE,” filed Nov. 22, 2005, and U.S. patent application Ser. No. 11/282,918, entitled “METHOD AND APPARATUS FOR INTER-SYSTEM ACTIVE HANDOFF OF A HYBRID MOBILE STATION,” filed Nov. 22, 2005, which patent applications are commonly owned and incorporated herein by reference in its entirety. Logic flow  500  then ends.  
      In one embodiment of the invention, first network  110  may instruct MS  102  to move to second network BS  134  without assigning a traffic channel to the MS. For example, BS  114  may convey to MS  102 , and the MS may receive from the BS, a Data Burst Message (DBM) on a forward link dedicated signaling channel (f-dsch) of air interface  112  instructing the MS to monitor a pilot associated with second network  130 , and more particularly with BS  134 . The DBM may then comprise a ‘BURST_TYPE’ data field set to ‘001000’ and a ‘TCH_ASSIGN_INCL’ data field set to ‘0.’ In response to receiving the DBM, MS  102  may set HRPD_HO_TARGET_BAND s  to HRPD_HO_TARGET_BAND r , set HRPD_HO_TARGET_FREQ s  to HRPD_HO_TARGET_FREQ r , and set HRPD_HO_TARGET_PN s  to HRPD_HO_TARGET_PN r , wherein ‘s’ represents ‘stored’ values and ‘r’ represents ‘received’ values and wherein the ‘received’ values are copied to the ‘stored’ variable. MS  102  may the proceed to open a connection on target second network  130  in accordance with the system information received in the BDM message.  
      In another embodiment of the invention, first network  110  may instruct MS  102  to move to second network BS  134  while assigning a traffic channel to the MS. For example, BS  114  may convey to MS  102 , and the MS may receive from the BS, a DBM on an f-dsch of air interface  112  instructing the MS to monitor a pilot associated with second network  130 , and more particularly with BS  134 , which DBM comprises a ‘BURST_TYPE’ field set to ‘001000’ and a ‘TCH_ASSIGN_INCL’ data field set to ‘1.’ In response to receiving such a DBM, MS  102  may then set HRPD_HO_TARGET_BAND s  to HRPD_HO_TARGET_BAND r , set traffic channel assignment internal variables received in a TCH_ASSIGN_BLOB, as is known in the art, in accordance with the Connection Layer TrafficChannelAssignment message format, and proceed to acquire the target HRPD traffic channel specified in the DBM in accordance with known Traffic Channel Assignment message processing procedures.  
      Further, when BS  114  directs MS  102  to handoff to second network  130 , the BS sends a DBM on a forward link dedicated signaling channel (f-dsch) of air interface  112  with the BURST_TYPE field set to 001000. BS  114  may include an HRPD Handoff Record in the DBM wherein the BS may set a MSG_NUMBER value to ‘00000001,’ may set a NUM_MSGS value to ‘00000001,’ may set a ‘NUM_FIELDS’ value to a number of octets in the HRPD Handoff Record, and may set CHARi data fields to corresponding octets of the HRPD Handoff Record as noted in the following table:  
                              HRPD Handoff Record                             Field   Length (bits)                       HRPD_HO_TARGET_BAND   5           TCH_ASSIGN_INCL   1           HRPD_HO_TARGET_FREQ   0 or 11           HRPD_HO_TARGET_PN   0 or 9           TCH_ASSIGN_BLOB   Refer to [1]           RESERVED   0-7 (as needed)                      
 
      The HRPD_HO_TARGET_BAND data field corresponds to a band class of the target second network  130 . BS  114  may set this field to the band class of the target second network that the MS is expected to acquire. The TCH_ASSIGN_INCL data field informs whether a traffic channel assignment is included in the DBM. BS  114  may set this field to ‘1’ when including an HRPD traffic channel assignment in the message and may otherwise set this field is set to ‘0’. The HRPD_HO_TARGET_FREQ data field corresponds to a frequency of target second network  130 . When TCH_ASSIGN_INCL is set to ‘0’, BS  114  may include this field and set it to the frequency of target second network  103  that MS  102  is expected to acquire; otherwise, this field may be omitted. The HRPD_HO_TARGET_PN data field corresponds to a pseudorandom number (PN) offset of the target second network. When TCH_ASSIGN_INCL is set to ‘0’, BS  114  may set this field to the PN sequence offset of second network  130  that the MS is expected to acquire; otherwise, this field may be omitted. The TCH_ASSIGN_BLOB data field provides traffic channel information when a traffic channel assignment is included in the DBM. When TCH_ASSIGN_INCL is set to ‘1’, BS  114  may include HPRD traffic channel assignment information here, which includes data fields that may conform to the Connection Layer message format defined for a TrafficChannelAssignment message; otherwise, this field is not included.  
      While the present invention has been particularly shown and described with reference to particular embodiments thereof, it will be understood by those skilled in the art that various changes may be made and equivalents substituted for elements thereof without departing from the scope of the invention as set forth in the claims below. Furthermore, one of ordinary skill in the art realizes that the components and operations of the transmitting communication device and receiving communication device detailed herein are not intended to be exhaustive but are merely provided to enhance an understanding and appreciation for the inventive principles and advantages of the present invention, rather than to limit in any manner the invention. Accordingly, the specification and figures are to be regarded in an illustrative rather then a restrictive sense, and all such changes and substitutions are intended to be included within the scope of the present invention.  
      Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or element of any or all the claims. As used herein, the terms “comprises,” “comprising,” or any variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Furthermore, unless otherwise indicated herein, the use of relational terms, if any, such as first and second, top and bottom, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions.