HK1078228A - Timing transitions between wireless communication systems - Google Patents

Description

Timing transfer between wireless communication systems

FIELD

Various embodiments relate to wireless communications, and more particularly to inter-system operations within a wireless communication system.

Background

Wireless communication systems are widely deployed to provide various types of communication such as voice and data communication. These systems may be based on a variety of modulation techniques, such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), or Frequency Division Multiple Access (FDMA). CDMA systems provide certain advantages over other types of systems, including increased system capacity.

The CDMA System may be designed to support one or more CDMA standards, such as (1) the "TIA/EIA-95-BMobject State-Base State Compatibility Standard for Dual-Mode Wireless Spread Spectrum Cellular System" (IS-95 Standard), (2) the standards proposed by the consortium named "third Generation partnership project" (3GPP) and included in a group of documents including documents No. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213 and 3G TS 25.214(W-CDMA Standard), (3) the standards proposed by the consortium named "third Generation partnership project 2" (3GPP2) and included in a group of documents including "C.S.0002-A Physical Layer Standard for CD 2000 Spread Spectrum Systems" C.S.S.S.S.S.P. Specification-Spray 2000 Standard "(Layer 2000) and" Layer Standard 2000 software code 2000) (Layer Standard "(Layer 3 Scdma 2000) and" Slayer code Standard "(Scdma 2000) for software code 2000), and (4) some other criteria.

A CDMA system supporting the CDMA2000 standard may include the IS856 specification (also known as the 1xEV specification) supporting several specifications, including, for example, High Data Rate (HDR) wireless communications, as well as the IS2000-1x specification for voice and data communications.

The IS856 standard provides high data rate services to data only Wireless Communication Devices (WCDs), or WCDs known as Hybrid Access Terminals (HATs), which support a number of standards, possibly including the IS-2000-1x standard. An IS 856-compliant system may be co-located or overlaid in some manner with an IS2000-1x network to provide enhanced high-rate data services. The separation between IS856 and IS2000-1x systems IS achieved in the frequency domain in the same manner as the separation between cdma2000 system channels. However, the IS856 and IS2000-1x standards do not provide compatibility between the two systems.

Abstract

In general, the disclosure is directed to various techniques that can be implemented within a wireless communication system. In one embodiment, a timer defined for use in the first wireless communication system is started. The duration of the transition from the first wireless communication system to the second wireless communication system is estimated as a function of the timer.

Other embodiments are directed to processor-readable media and devices incorporating these techniques. For example, one embodiment is directed to a wireless communication device comprising first wireless communication system hardware operating within a first wireless communication system and second wireless communication system hardware operating within a second wireless communication system. The interoperability module configures the wireless communication device in response to a transfer between the first and second wireless communication systems. The interoperation module is configured to be estimated for transition duration as a function of the watchdog timer.

Additional details of various embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

Brief description of the drawings

Fig. 1 is a block diagram illustrating a wireless communication system.

Fig. 2 is a block diagram depicting an example implementation of a WCD.

Fig. 3 is a timing diagram illustrating the interoperative timing relationships of a WCD in connected mode.

Fig. 4 is a flow chart illustrating the interoperation of a WCD in connected mode.

Fig. 5 is a timing diagram illustrating the interoperative timing relationships of a WCD in idle mode.

Fig. 6 is a flow chart illustrating the interoperation of a WCD in idle mode.

Description of The Preferred Embodiment

In general, the present invention facilitates interoperability between wireless communication systems by assisting a monitoring system with a watchdog timer. Various embodiments provide a WCD that can operate within at least two communication systems, such as IS2000-1x and IS856(HDR) systems. In some embodiments, one or more watchdog timers provided by the IS856 standard may be used to estimate the duration of a transfer from the IS856 system to another system, such as an IS2000-1x system. The WCD may then perform a series of tasks appropriate for the estimated duration of the transition. By using the watchdog timer to estimate the duration of a transfer to IS2000-1x or other system, task execution associated with the active transfer IS facilitated. Because the watchdog timer and the appropriate response to the watchdog timer condition are defined in the IS856 standard, this technique has little if any impact on any communication system.

Fig. 1 is a block diagram illustrating an exemplary spread spectrum wireless communication system 2 in which a base station 4 transmits signals 12-14 to a WCD6 over one or more paths. In particular, base station 4A transmits signal 12A to WCD6 via a first path and also transmits signal 12C to WCD6 via a second path, the second path being caused by reflections of signal 12B by obstacle 10. Obstacle 10 may be any structure similar to WCD 6A, such as a building, bridge, automobile, or even a person.

Base station 4A also transmits signal 13A to WCD6B over a first path from base station 4A, and transmits signal 13C over a second path resulting from the reflection of signal 13B by obstacle 10. In addition, base station 4A transmits signal 14A to WCD 6C. WCD6 may implement a structure known as a RAKE receiver to synchronously track different signals received from different base stations and/or from the same base station but over different paths. System 2 may include any number of WCDs and base stations. For example, as shown, another base station 4B receives signal 13D from WCD 6B. Also, base station 4B receives signal 14B from WCD 6C.

System 2 may be designed to support one or more CDMA standards including, for example, (1) "TIA/EIA-95-B Mobile Station-Base Station Compatibility Standard for Dual-Mode Wireless band Spread Spectrum Cellular System" (IS-95 Standard), (2) "TIA/EIA-98-C Recommended Minimum Standard for Dual-Mode Wireless band Spread Spectrum Cellular Mobile Station" (IS-98 Standard), (3) the Standard set forth by the consortium named "third Generation partnership project" (3GPP) including the documents 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214(W-CDMA Standard), (4) the Standard set forth by the consortium named "third Generation partnership project 2" (3GPP) including the document 5G TS 25.45, and the Standard set forth by the Specification "Splay 2000" "C.S0005-A Upper Layer (Layer 3) Signaling Standard for CDMA2000 Spread Spectrum Systems" and "C.S0024 CDMA2000 High Rate Packet Data Air Interface Specification" (CDMA2000 Standard), (5) HDR System document "CDMA 2000 High Rate Packet Data Air Interface Specification" in TIA/EIA-IS856, and (6) some other standards. Moreover, the system 2 may be designed to support other standards, such as the GSM standard or related standards, such as the DCS1800 and PCS1900 standards. The GSM system uses a combination of FDMA and TDMA modulation techniques. System 2 may also support other FDMA and TDMA standards.

WCD6 may be implemented as any of a variety of wireless communication devices, such as a cellular radiotelephone, a satellite radiotelephone, a PCMCIA card incorporated within a portable computer, a Personal Digital Assistant (PDA) equipped with wireless communication capabilities, and the like. The base stations 4 (sometimes referred to as base transceiver systems, or BTSs) are typically connected to a Base Station Controller (BSC)8 to provide an interface between the base stations 4 and a public switched telephone network 13.

In some embodiments, one or more WCDs 6 may be implemented as a Hybrid Access Terminal (HAT) supporting multiple systems. For example, WCD6 may support the 1x-CDMA2000 standard for voice communications and the IS856 standard for high-speed data communications. An IS 856-compliant system can be co-located or overlaid in some other manner with a 1x-CDMA2000 network to provide enhanced high-speed data services. The separation between systems can be performed in the frequency domain much like the system channels in a 1x-CDMA2000 system are separated. Neither system provides backward compatibility with each other, no specific messaging protocol exists in both systems to facilitate interoperability, and services can be provided on both systems. In this way, WCD6 can benefit from the advantages available on both networks.

To support both standards simultaneously, WCD6 must perform effective dual system monitoring. Moreover, some interoperability tasks require compliance with both standards. As described below in connection with fig. 2-6, WCD6 uses timers provided in the IS856 standard to facilitate efficient dual system monitoring and inter-system transfer.

Fig. 2 illustrates an example implementation of WCD6 that supports multiple systems. As depicted in FIG. 2, WCD6 supports the 1x-CDMA2000(IS2000-1x) and IS856 standards. Several modes of interoperation may be supported. For example, in data-only mode, WCD6 operates only in IS 856. In another mode, WCD6 supports IS2000-1x voice and IS856 data services without precedence over either network. Other patterns may be defined to meet different user needs.

In particular, WCD6 includes IS856 receiver hardware 20 and IS856 transmitter hardware 22 for receiving and transmitting data communications at high speeds. WCD6 also includes IS2000-1x receiver hardware 24 and IS2000-1x transmitter hardware 26 for receiving and transmitting voice communications. The wireless diplexer 28 performs multiplexing switching to allow the receiver hardware and the transmitter hardware to share a single antenna 30.

The controller 32 controls the operation of the IS856 receiver hardware 20, the IS856 transmitter hardware 22, the IS2000-1x receiver hardware 24, and the IS2000-1x transmitter hardware 26. The controller 32 also executes IS2000-1x control and processing software 36 to control the operation of the IS2000-1x receiver hardware and IS2000-1x transmitter hardware 26. In some embodiments, some software routines may be shared between the IS856 control and processing software 34 and the IS2000-1x control and processing software 36 for optimization purposes. Also, in some embodiments, some hardware components may be shared between the IS856 receiver hardware 20 and the IS2000-1x receiver hardware 24, or between the IS856 transmitter hardware 22 and the IS2000-1x transmitter hardware 26.

To support IS856 and IS2000-1x systems, WCD6 must perform an intersystem transfer, i.e., a transfer between the two systems, for hold and call support tasks. To facilitate inter-system transfer, the controller 32 executes interoperability control software 38, which performs several tasks related to transfer between the two systems. These tasks may include, for example, physically tuning to another frequency or CDMA channel, and switching hardware blocks and firmware to perform tasks associated with physical layer processing for a certain standard. The interoperability control software 38 also loads and executes the IS856 control and processing software 34 and the IS2000-1x control and processing software 36 as appropriate to control the receiver and transmitter hardware. The interoperability control software 38 may also load and execute software programs to perform higher level processing.

According to various embodiments, certain watchdog timers defined in the IS856 standard are used to coordinate these tasks. These timers prevent premature declarations of some monitoring failures or attempts to fail in order to allow WCD6 to continue operation. On the other hand, the expiration of the IS856 watchdog timer indicates that the monitoring or attempt failure occurrence condition may be non-transient, and that a new set of operations may be appropriate. Monitoring the timer at the IS856 also allows for the reallocation of active resources in certain circumstances. In some embodiments, the IS856 watchdog timer IS also used to indicate to WCD6 which actions that WCD6 requires after controller 32 performs an inter-system transfer.

Inter-system transfers may be characterized as "per command" transfers or static transfers. The controller 32 performs a transfer on command when certain tasks must be completed, such as updating the pilot strength information or acquiring the IS856 system after failure to acquire the IS2000-1x system within a predetermined time limit. Static transfers are periodic transfers of two systems for maintenance.

Static transfers may be further characterized according to whether WCD6 IS connected or idle in an IS856 system. This determination affects the manner in which the controller 32 performs the static transfer. WCD6 IS in connected mode when WCD6 IS assigned to both forward and reverse traffic channels and IS receiving and transmitting data in an IS856 system. Fig. 3-4 illustrate the interoperation of WCD6 in the connected mode. WCD6 IS in idle mode in an IS856 system when, on the other hand, WCD6 IS not receiving or transmitting any data in the IS856 system, but IS only monitoring control channel messages in the IS856 system. Fig. 5-6 illustrate the interoperation of WCD6 in idle mode.

Fig. 3 IS a timing diagram illustrating the interoperative timing relationships of WCD6 when connected in an IS856 system and idle in an IS2000-1x system. In this mode of operation, WCD6 operates in a slotted paging mode in IS2000-1x systems. In slotted paging mode, the base station transmits paging signals only during assigned paging slots, which are separated by a predetermined time interval. Slotted paging allows WCD6 to be in sleep mode during the time periods between consecutive paging slots without losing the paging signal. WCD6 IS interested in both timelines in the active HDR session of the IS856 system and in the slotted paging mode of the IS2000-1x system. In FIG. 3, the upper timeline illustrates the timing of events in an IS856 system, while the lower timeline illustrates the timing of events in an IS2000-1x system.

In the IS856 system timeline, point 50 represents the IS856 system time, which IS derived from the demodulation symbols of the earliest arriving WCD 6. WCD6 may incorporate a RAKE receiver with several demodulation fingers to track multipath signals. Likewise, point 52 in the IS2000-1x system timeline represents IS2000-1x system time. Thus, WCD6 derives IS2000-1x system time in a typical manner of a slotted paging mode. The time difference between points 50 and 52 represents a potential system time difference between the two timelines. At point 50, WCD6 receives the traffic channel data, and at point 54 WCD6 receives synchronization package (SC)56 of the control channel message. At point 58, a new data transmission IS initiated by the Access Network (AN), similar to the base station in the IS2000-1x system. During this data transmission, a set of operational timers on the IS856 system instruct WCD6 to prepare for a static transfer to the IS2000-1x system. WCD6 performs several actions in connection with this transition, including setting the Data Rate Control (DRC) cover and DRC value appropriately in advance to ensure that all multi-slot interleaved transmissions are received at the latest at point 60.

Point 60 represents the wakeup point of the IS2000-1x system. Also, point 60 represents the beginning of a period of "away" time slots 62 of the IS856 system. Leaving time slot 62 occurs when WCD6 wakes up in IS2000-1x mode and performs tasks related to the IS2000-1x system. WCD6 IS not available for IS856 related tasks during the departure slot 62. Therefore, WCD6 takes certain precautions to ensure predictable operation of WCD6 during these unavailable departure slots 62, as described below in connection with fig. 4.

The time interval between points 60 and 64 represents the time allocated to hardware and software overhead in preparation for receiving signals on the slotted paging channel. If no RF warm-up is required, point 60 may be moved closer to the actual beginning of the paging channel slot indicated by point 64. The paging channel slot ends at point 66. The time interval between points 66 and 68 represents the time allocated for hardware and software overhead after the end of the paging channel slot. At point 68, WCD6 returns to idle mode in an IS2000-1x system. Once WCD6 has transferred to the IS2000-1x system, WCD6 performs all tasks controlled by IS2000-1x control and processing software 36 of FIG. 2 up to point 68. The duration of the outgoing slot 62 is from point 60 to point 68, the entire length of the paging channel slot and hardware and software overhead before and after the paging channel slot. The duration of the departure time slot 62 can generally be estimated, but cannot be predicted to a high degree of accuracy.

Several events may affect the duration of the exit slot 62. For example, if the pilot search is successful, i.e., if a pilot is found and WCD6 has overhead information for the sector in which WCD6 is located, WCD6 does not need to update its overhead information. As a result, the duration of the exit slot 62 may be reduced. The duration of the departure time slot 62 may also be reduced when no messages on the paging channel are directed to WCD6 or when no action needs to be performed in conjunction with a paging message received on the paging channel.

On the other hand, if the pilot search was unsuccessful, i.e., if WCD6 failed to allocate a time period for searching for any signal path from an active or selected neighboring sector prior to the actual paging channel slot, the duration of the exit slot 62 may be increased. Thus, WCD6 must enter a non-slotted mode of operation. WCD6 may also enter non-slotted mode for other reasons, such as in response to a voice page. Thus, the duration of the outgoing slot 62 cannot be predicted, and IS856 operation IS suspended until WCD6 again enters slotted mode, i.e., a sleep state, in an IS2000-1x system.

When WCD6 IS operating in IS2000-1x mode, WCD6 does not attempt any action involving the IS856 system until WCD6 returns to sleep mode in the IS2000-1x system at point 66. Thus, again transitioning to IS856 at point 68. The action taken at point 68WCD6 may depend on the time elapsed between points 60 and 68, i.e., the duration of departure time slot 62. To determine the proper set of actions that the WCD should take when returning to the IS856 system, WCD6 can use the watchdog timer available in IS856 mode. Because the IS856 standard specifies actions to be taken in response to watchdog timers, the IS856 control and processing software 34 of fig. 2 includes routines required to perform these actions. Thus, there IS no need to know the state information of the IS2000-1x system.

Fig. 4 IS a flowchart illustrating an example sequence of actions performed by the interoperability control software 38 of fig. 2, the interoperability control software 38 incorporating monitoring of paging channels in IS2000-1x systems. Before transitioning to the IS2000-1x system to monitor the paging channel, the interoperability control software 38 sets the Data Rate Control (DRC) value to 0 and sets the DRC cover to 0 (100). Setting these values to 0 IS similar to the handling of transitions to IS2000-1x systems as short-term channel degradation in IS856 systems. That is, setting these values to 0 simulates reduced signal quality in the forward link, i.e., the link from the base station to WCD 6. When the DRC IS set to 0, the interoperability control software 38 starts a DRC watch timer (102) that runs for a duration of 240 milliseconds (ms), as required by the IS856 standard. The DRC watch timer may be set concurrently with the transition to the IS2000-1x system, although the actual DRC value calculated by WCD6 for the slot prior to the transition may not be 0.

The WCD6 then controls tasks associated with the processing software 36 to perform IS2000-1x in accordance with IS2000-1x (104) and returns to the IS856 system (106). The DRC watch timer allocates 240 milliseconds for WCD6 to transmit at least one non-zero DRC value while the DRC watch timer is still running. If a non-zero DRC value IS sent indicating an improved forward link condition before the DRC watch timer expires, the interoperability control software 38 resets the DRC watch timer as specified by the IS856 standard (108). Notably, if WCD6 returns from the IS2000-1x system before the DRC watch timer expires, WCD6 may attempt to transmit a non-zero DRC value and continue in the same state in which WCD6 transitions from the IS856 system in accordance with the standard IS856 task flow (110).

If, on the other hand, WCD6 returns from the IS2000-1x system after the DRC watch timer expires, i.e., if the IS2000-1x task requires longer than 240 milliseconds, the WXD6 may indicate a set of optional tasks using another IS856 timer. Another such timer that may be used in combination with the DRC watch timer IS the reverse channel traffic restart timer, also defined by the IS856 standard. The reverse channel traffic restart timer runs for 12 control channel cycles, or 5.12 seconds. In parallel with starting the DRC watchdog timer, the interoperability control software 38 also starts a combination timer (102), which runs the combined duration of the DRC watchdog timer and the reverse channel traffic restart timer (102). Thus, the combined timer extends the reverse channel traffic restart timer length by the length of the DRC watch-timer as specified by the IS856 standard. In most cases, the secondary combination timer should give WCD6 sufficient time to perform common tasks related to slotted paging channel monitoring during static or on-command transfers in IS2000-1x systems. Therefore, WCD6 can typically move back to the IS856 system before the expiration of the combination timer. Thus, WCD6 calculates successive DRC values for the most recent slot and a programmable number of subsequent slots (112). If the DRC value IS not 0, WCD6 may restart IS856 transmitter hardware 22(114) and reset the combining timer (116). The IS856 standard requires that sixteen consecutive non-zero DRC values be generated before the IS856 transmitter hardware 22 IS restarted. However, this requirement need not be met because the combining timer is not restarted in response to actual degradation in the forward link. Thus, the number of link DRC values calculated can be set to less than sixteen. In one embodiment, WCD6 only generates one non-zero DRC value before restarting IS856 transmitter hardware 22.

If the combination timer expires before the WCD returns from the IS2000-1x system, or if a specified number of consecutive non-zero DRC values were not generated, WCD6 transitions to an inactive state with a "monitor failed" indication (118). It is assumed that WCD6 does not assign a Forward Traffic Channel (FTC) in this state, and will likely have to go through a connection setup routine. In these cases, WCD6 may be required to return to the network acquisition state.

In this manner, the transfer between IS856 and IS2000-1x systems IS controlled by the watchdog timer specified by the IS856 standard. The interoperability software 38 uses these timers to determine the appropriate sequence of transfer tasks based on the duration of the away time slot 62 of fig. 3. As described above, the transfer task performed by WCD6 when returning to an IS856 system IS determined as follows: the transition of the IS856 system occurs before the DRC watchdog timer expires, after the DRC watchdog timer expires but before the combining timer expires, or after the combining timer expires.

WCD6 IS in an idle mode of the IS856 system when WCD6 IS not receiving and transmitting any data in the IS856 system and IS only monitoring control channel messages in the IS856 system. The interoperation in idle mode includes simpler requirements compared to the connected mode described above in connection with fig. 3-4. Fig. 5 is a timing diagram illustrating the interoperative timing relationships of WCD6 in idle mode. In fig. 5, the upper timeline illustrates the timing of events in an IS856 system, while the lower timeline represents the timing of events in an IS2000-1x system.

In the IS856 system timeline, point 150 represents the IS856 system time, which IS derived from the earliest arriving guide decoded by WCD 6. Likewise, point 152 in the IS2000-1x system timeline represents IS2000-1x system time. Thus, WCD6 derives IS2000-1x system time in a typical manner of a slotted paging mode. The time difference between points 150 and 152 represents a potential system time difference between the two timelines. At point 150, WCD6 receives the traffic channel data, and at point 154, WCD6 receives synchronization package (SC)156 of the control channel message. A sleep timer IS started after the traffic channel data IS received indicating when WCD6 has returned to the IS2000-1x system and stopped monitoring both systems for control or paging messages. If the sleep time expires at point 158, WCD6 will be idle in the IS856 system for sufficient time to ensure that no more data exchanges occur, and WCD6 saves power by operating only in the IS2000-1x system. If WCD6 subsequently needs to transmit data, then WCD6 can use a transfer on command to transfer back to the IS856 system.

Before the sleep timer expires, however, WCD6 continues to monitor IS856 and IS2000-1x systems while additional data may be exchanged. During this time, WCD6 may perform one or more transfers between IS856 and IS2000-1x systems to monitor the slotted paging channel. When the sleep timer expires at point 158, WCD6 either remains on the IS2000-1x system or moves to the IS2000-1x system and remains there.

Point 160 represents the wakeup point of an IS2000-1x system. In addition, point 160 represents the beginning of the "away" time slot 162 period of the IS856 system. Leaving slot 162 occurs when WCD6 wakes up in IS2000-1x mode and performs tasks related to the IS2000-1x system. During the departure time slot 162, WCD6 IS not available for IS856 related tasks.

The time interval between points 160 and 164 represents the time allocated to hardware and software overhead in preparation for receiving signals on the slotted paging channel. Because no RF warm-up is required, point 160 may be moved closer to the actual beginning of the paging channel slot indicated by point 164. The paging channel slot ends at point 166. The time interval between points 166 and 168 represents the time allocated for hardware and software overhead after the end of the paging channel slot. At point 168, WCD6 returns to the idle mode of the IS2000-1x system. Once WCD6 has transferred to the IS2000-1x system, WCD6 performs all tasks controlled by IS2000-1x control and processing software 36 of FIG. 2 up to point 168. The duration of the outgoing slot 162 is from point 160 to point 168, the entire length of the paging channel slot and hardware and software overhead before and after the paging channel slot. The duration of the departure time slot 162 can generally be estimated, but cannot be predicted to a high degree of accuracy.

Fig. 6 IS an exemplary sequence of actions performed by the interoperability control software 38 of fig. 2, the interoperability control software 38 incorporating monitoring of paging channels in IS2000-1x systems. In idle mode WCD6 monitors the synchronization Control Channel (CCH) envelope as specified by the IS856 standard. Thus, WCD6 utilizes the control channel monitor timer defined in the IS856 standard when operating in idle mode, rather than the DRC monitor timer or the reverse channel traffic restart timer. The control channel monitor timer IS started (180) when WCD6 enters a monitor state defined in the default idle state protocol of the IS856 standard. In this state, WCD6 monitors the CCH, listens for paging messages, and updates parameters received from the overhead message protocol as needed.

When operating in the idle mode, WCD6 may periodically transition between a monitor state and a sleep state in which some subsystems may be shut down to conserve power. In the monitor state, WCD6 attempts to demodulate the synchronized CCH encapsulation. While the sleep timer IS still active, when WCD6 monitors IS2000-1X and IS856 systems, interoperability control software 38 may start the control channel monitor timer immediately before transitioning to the IS2000-1X system (184). If WCD6 IS in a sleep state, as defined by the default idle state protocol of the IS856 standard, WCD6 may start a timer when WCD6 IS scheduled to transition to a monitoring state on the IS856 system, rather than immediately prior to transitioning to the IS2000-1x system. In both cases, the interoperability control software 38 may start the control channel monitor timer at the point of transfer to the IS2000-1x system, but the timer length may be adjusted accordingly. That IS, the timer length IS increased by an amount that the WCD6 remains in sleep state for as long as it does not have to transition to the IS2000-1x system.

WCD6 then performs IS2000-1 x-related tasks (186) under the control of IS2000-1x control and processing software 36, and returns to the IS856 system (188). When WCD6 returns to the IS856 system, the interoperability control software 38 checks the status of the control channel monitoring timer to determine that this action should be taken. If WCD6 returns to the IS856 system before the timer expires, WCD6 attempts to receive a synchronized CCH envelope (190) until the timer expires. If WCD6 is unable to receive the synchronous CCH envelope before the counter expires, WCD6 disables the control channel monitoring counter (192) and returns a "monitoring failed" indicator (194). If WCD6 does not receive a valid synchronous CCH envelope, then WCD6 continues to operate in idle mode. The time spent in IS2000-1x systems IS ultimately included in the total time allocated for WCD6 to receive a valid CCH package.

If the control channel monitoring timer expires before or slightly after WCD6 returns from the IS2000-1x system, WCD6 makes at least one additional attempt to modulate the next CCH synchronization package even after the timer expires. Depending on the outcome of this attempt, the WCD either continues in the idle state (196) or issues a "monitoring failure" indicator (194) and transitions to the network acquisition state as defined by the IS856 standard. From this point, WCD6 then complies with the rules specified by the IS856 standard.

Per-command transfers are handled similar to the static transfers described above in connection with fig. 3-6. Certain types of per-command transfers may be optimized for the tasks they are scheduled to perform. For example, a per-command transfer from an IS2000-1x system to an IS856 system in order to update pilot strength information may be optimized by performing pilot searching after the transfer back to the IS2000-1x system.

Instructions that cause a processor, such as controller 32, to be provided in WCD6 may be stored on a processor-readable medium. By way of example, and not limitation, processor-readable media may comprise storage media and/or communication media. Storage media includes volatile and nonvolatile, removable and fixed media implemented in any method or technology for storage of information such as processor readable instructions, data structures, program modules or other data. Storage media may include, but is not limited to, Random Access Memory (RAM), Read Only Memory (ROM), EEPROM, flash memory, fixed or removable disk media, including optical or magnetic media, or any other medium that may be used to store the desired information and that may be accessed by a processor within WCD 6.

Communication media typically embodies processor-readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term "modulated data signal" means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared and other wireless media. Computer readable media may also include a combination of any of the above.

Although a number of embodiments have been described, modifications can be made without departing from the spirit and scope of the invention. For example, several embodiments have been described in the context of interoperability between IS856 and IS2000-1x systems, other embodiments may provide interoperability between other systems. These and other embodiments are within the scope of the following claims.

Claims (18)

1. The wireless communication device includes:

first wireless communication system hardware for operating within a first wireless communication system;

second wireless communication system hardware for operating within a second wireless communication system;

an interoperability module for configuring the wireless communication device in response to a transition between the first and the dropped wireless communication systems, the interoperability module being configured to estimate a duration of the transition as a function of the watchdog timer.

2. The wireless communication device of claim 1, wherein the interoperation module is configured to estimate a duration of the transition as a function of a plurality of watchdog timers.

3. The wireless communication device of claim 1, wherein the first wireless communication system IS an IS856 system and the second wireless communication system IS an IS2000-1x system.

4. The wireless communication device of claim 3, wherein the watchdog timer is a control channel watchdog timer.

5. The wireless communication device of claim 4, wherein the interoperation module is configured to:

attempting to receive a synchronization control channel encapsulation; and

transitioning to a network acquisition state when attempting to receive synchronous control channel encapsulation is unsuccessful.

6. The wireless communication device of claim 3, wherein the watchdog timer is a Data Rate Control (DRC) watchdog timer, and wherein the interoperation module is configured to:

starting a combined timer; and

when returning to the IS856 system, the duration of the transition IS estimated as a function of the DRC watch timer and the combination timer.

7. The wireless communication device of claim 6, wherein the interoperation module is configured to:

restarting a transmitter in response to expiration of the DRC watchdog timer; and

transition to an inactive state in response to expiration of the combo timer.

8. An apparatus comprising:

for starting a timer defined for use in the first wireless communication system; and

a duration of the transition from the first wireless communication system to the second wireless communication system is estimated as a function of the timer.

9. The apparatus of claim 8, further comprising means for performing a predetermined operation associated with the timer.

10. The apparatus of claim 9, wherein the operation is predefined by the first communication system.

11. The apparatus of claim 8, wherein the timer comprises a watchdog timer.

12. The apparatus of claim 8, further comprising:

means for starting a plurality of timers defined for use within a first wireless communication system; and

means for estimating a duration of the transition as a function of a plurality of timers when returning to the first wireless communication system.

13. The apparatus of claim 8, further comprising:

means for attempting to receive a synchronized control channel envelope; and

means for transitioning to a network acquisition state when an attempt to receive synchronized control channel encapsulation is unsuccessful.

14. One method comprises the following steps:

starting a plurality of timers defined for use in a first wireless communication system; and

the duration of the transition from the 1 st wireless communication system to the second wireless communication system is estimated as a function of the timer.

15. The method of claim 14, further comprising performing a predetermined operation associated with the timer;

wherein this operation is predefined by the first wireless communication system.

16. The method of claim 14, wherein the timer comprises a watchdog timer.

17. The method of claim 14, further comprising:

starting a plurality of timers defined for use in a first wireless communication system; and

when returning to the first wireless communication system, the duration of the transition is estimated as a function of a plurality of timers.

18. The method of claim 14, further comprising:

a control channel encapsulation for attempting to receive synchronization; and

transitioning to a network acquisition state when an attempt to receive synchronized control channel encapsulation is unsuccessful.