HK1079389A

HK1079389A - Handoff between base stations of different protocol revisions in a cdma system

Info

Publication number: HK1079389A
Application number: HK05111296.3A
Authority: HK
Inventors: L.赵; J.王
Original assignee: 高通股份有限公司
Priority date: 2002-04-11
Filing date: 2003-04-09
Publication date: 2006-03-31

Description

Handover between base stations with different protocol revisions in a CDMA system

Background

FIELD

The present invention relates generally to communications, and more specifically to techniques for supporting handoff of a terminal between base stations having different protocol revisions in a Code Division Multiple Access (CDMA) communication system.

Background

Wireless communication systems are widely deployed to provide various types of communication such as voice, data, and so on. These systems may be based on Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), or some other multiple access technique. CDMA systems offer certain advantages over other types of systems including increased system capacity.

A CDMA system is typically designed to conform to one or more CDMA standards. Examples of such CDMA standards include "TIA/EIA-95-B Mobile Station-Base Station Compatibility Standard for Dual-Mode Wireless Spread Spectrum Cellular System" (hereinafter referred to as IS-95 Standard), "TIA/EIA-98-D Recommended Minimum Standard for Dual-Mode Wireless Spread Spectrum Cellular Station" (hereinafter referred to as IS-98 Standard), and TIA/EIA/IS-2000 (hereinafter referred to as IS-2000 Standard). Each CDMA standard may also be associated with multiple releases, each of which may include updates and new features of some standards. For example, the IS-2000 standard includes version 0, version A, version B, and version C, among others. New CDMA standards and releases have been proposed and adopted.

The IS-95 standard covers the first generation CDMA, primarily for voice communications. Thus, it supports calls between the terminal and the base station at any time. The IS-95 standard covers the next generation of CDMA and supports both voice and data communications (albeit at lower data rates). The IS-2000 standard supports voice and high-speed data communications. For a family of standards including IS-95 and IS-2000, each newer CDMA standard and release within the family includes features and functions defined within previous CDMA standards and releases, and improvements and/or new features are added.

The CDMA standard/release may be assigned a specific signaling protocol revision layer (P REV), which may be used to clearly identify the standard/release. For example, on the base station side, IS-95B, IS-2000 version 0 and IS-2000 version A are associated with P _ REV of 5, 6 and 7, respectively. A new version of a given standard may be considered another standard. In general, newer CDMA standards are backward compatible with older CDMA standards. A terminal or base station designed to support a particular P _ REV (e.g., P _ REV ═ 7) can then also support lower P _ REVs (e.g., P _ REV ═ 5 and 6), and so on.

The wireless service provider may use different generations of base stations that are close or adjacent to each other because of the different configuration options available. This can lead to incompatibility problems if base stations with different P REVs are used to support communication for a given terminal. For such a hybrid configuration, the terminal may communicate with one base station of a particular P _ REV and thereafter hand over to another base station of a different P _ REV. A higher P REV is generally associated with more parameters because it supports more features and functions than a lower P REV. Thus, if a terminal switches between base stations of different P _ REVs, there is a challenge to handle parameters that are defined within one P _ REV but not defined within another P _ REV.

There is therefore a need for a technique to support handover of a terminal between base stations of different protocol revisions that may be associated with different parameters for communication.

SUMMARY

Techniques are provided herein to support handover of a terminal between base stations of different protocol revisions. Various schemes for supporting handover are described herein. The particular scheme for handover depends on the protocol revision of the terminal and the target base station and possibly other factors (e.g., whether there is a dormant call).

In one embodiment, a method is provided for supporting handoff of a terminal between base stations of different protocol revisions within a CDMA communication system. According to the method, a handover of the terminal from the first base station to the second base station is performed while the terminal is in an active call (data or voice call) with the first base station. The first base station supports a first protocol revision (e.g., P _ REV ≦ 5) and the second base station supports a second protocol revision (e.g., P _ REV ≧ 6) that is later than the first protocol revision. An active call between the terminal and the second base station may be maintained using a first service configuration previously established through the first base station for the active call.

The second service configuration may be established through the second base station of the active call. The second base station may query the terminal for the second service configuration or may simply assign the second service configuration. This query or assignment may be implemented after the second base station has been added to the terminal's active set or after a handover. Alternatively, the terminal may initiate the establishment of the second service configuration after being informed (e.g. by an active call release or a signaling message) that it can update its services. The second service configuration may also be used for dormant calls (if any) that were established prior to the handover. In any case, if an active call is available then it can be maintained using the second service configuration.

Each service configuration includes a specific service option instance for the associated call. The first service configuration may include a first service option instance for low speed packet data calls (e.g., SO 7) and the second service configuration may also include a second service option instance for high speed packet data calls (e.g., SO 33).

Various aspects and embodiments of the invention are described in more detail below. The invention also provides other methods, program codes, digital signal processors, terminals, base stations, systems, and other apparatuses and elements that implement various aspects, embodiments, and features of the invention, as described in more detail below.

Brief description of the drawings

The features, nature, and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify correspondingly throughout and wherein:

FIG. 1 is a diagram of a CDMA communications system in which various aspects and embodiments of the present invention may be implemented;

FIGS. 2A-2B are state machines for call processing at a terminal, as defined by IS-2000;

FIG. 3 IS a diagram illustrating a mapping between some of the sub-layers of layer 3 as defined by IS-2000;

fig. 4A-4H are terminal handoffs (with a particular MOB _ P _ REV) from base station 1(P _ REV ═ 5) to base station 2 (a particular P _ REV greater than 5) illustrating various operating scenarios; and

fig. 5 is a block diagram of a particular embodiment of various network elements within a system.

Detailed Description

Fig. 1 is a diagram of a CDMA communications system 100 in which various aspects and embodiments of the invention may be implemented. System 100 provides for communication for multiple cells, each of which may be served by a corresponding base station 104. Various terminals 106 are dispersed throughout the system (only one terminal is shown for clarity). Each terminal may communicate with one or more base stations 104 on the forward and reverse links at any given moment, depending on whether the terminal is active and in soft handoff. The forward link (i.e., downlink) refers to transmission from the base station to the terminal, and the reverse link (i.e., uplink) refers to transmission from the terminal to the base station.

System 100 may be designed to support one or more CDMA standards and releases, such as IS-95A, IS-95B, IS-2000 release 0, IS-2000 release a, and so on. For simplicity, each version of a given standard may also be considered a standard. Each of these standards is known in the art and may be included herein by reference. On the base station side, the various CDMA standards are associated with different signaling protocol revision layers (P _ REV). And at the terminal side, various CDMA standards are associated with different mobile signaling protocol revision layers (MOB _ P _ REV). In particular, IS-95B, IS-2000 Release 0 and IS-2000 Release A are associated with base station side P _ REV of 5, 6 and 7, respectively, and terminal side MOB _ P _ REV of 4/5, 6 and 7, respectively. The base station P _ REV and the terminal MOB _ P _ REV are not directly mapped for all CDMA standards.

Newer CDMA standards are generally backward compatible with older CDMA standards. Therefore, a terminal or base station designed to support a specific P _ REV (e.g., P _ REV ═ 7) can also support lower P _ REVs (e.g., P _ REV ═ 5 and 6).

Fig. 2A IS a state machine 200 for call processing at a terminal, as defined by IS-2000. At power on, the terminal transitions from the power on state 210 to the mobile station initialization state 212.

In state 212, the terminal selects a particular system for use. If an analog system is selected, the terminal transitions to state 214 and begins analog mode operation. Otherwise, if the CDMA system is selected, the terminal continues to acquire and synchronize to the selected CDMA system. After acquiring the timing for the selected CDMA system, the terminal enters the mobile station idle state 216.

In state 216, the terminal is "ON" but inactive. The terminal monitors the paging channel for messages from base stations in the active set. The active set is a list of one or more base stations with which the terminal is currently communicating. If the terminal is unable to receive the paging channel, or if a new base station is added to the terminal's active set, the terminal returns to state 212 and acquires the new base station. In state 216, the terminal may receive a message or enter a call, initiate a call, implement registration, send a message, or implement some other action. After initiating any of the above actions, the terminal transitions to system access state 218.

In state 218, the terminal sends messages to base stations in the active set on one or more access channels and receives messages from the base stations on a paging channel in an attempt to access the base stations. Depending on the outcome of the message exchange, the terminal may either return to idle state 216, if there is no active communication, or if there is a call to be processed, may proceed to mobile station control in traffic channel state 220. Before transitioning to state 220, the terminal is assigned a forward traffic channel for the call.

In state 220, the terminal communicates with the base station using the established forward and reverse traffic channels. After termination of the last call, the traffic channel is released and the terminal returns to state 212.

Each state shown in fig. 2A is defined by a respective state machine that includes a plurality of sub-states.

Fig. 2B IS a state machine controlled by the mobile station in the IS-2000 defined traffic channel state 220. From system access state 218, after receiving the assigned forward traffic channel, the terminal enters the traffic channel initialization substate 230 of state 220.

In substate 230, the terminal verifies that it can receive data on the forward traffic channel, starts transmitting data on the reverse traffic channel, and synchronizes the traffic channel between the terminal and the base station. The terminal then waits for an indication from layer 2 that the forward traffic channel has been acquired. Upon receiving the indication, the terminal transitions to the traffic channel substate 232.

In the substate 232, the terminal exchanges traffic channel frames with the base station according to the current service configuration. While in the substate 232, one or more Call Control (CC) instances (or calls) may be activated (as described below). The terminal remains in the substate 232 if any calls are active. After the last call is released by the end user or by a release order message or an extended release message from the base station), the terminal transitions to the release substate 234.

In the substate 234 the terminal interrupts the call and the physical channel. The terminal then returns to the traffic channel substate 232 if it receives an indication to enter the substate or transition back to the mobile station initialization state 212.

The state machine shown in FIGS. 2A and 2B IS further described below in the IS-2000 Standard document TIA/EIA/IS-2000-5, entitled "Upper Layer (Layer 3) Signaling Standard for CDMA 2000 Spread Spectrum Systems", month 3 of 2000, which IS incorporated herein by reference. Similar state machines are defined by other CDMA standards (e.g., IS-95B) for terminating call processing.

Fig. 3 IS a mapping between some of the sub-layers of layer 3 as defined by IS-2000. Layer 3 handles call processing and service configuration. As shown in fig. 3, layer 3 includes a Call Control (CC) sublayer 312 that resides above a Service Option Control (SOC) sublayer 314, the SOC sublayer 314 further residing above a Radio Resource Control (RRC) sublayer 316. The RRC sublayer 316 defines the physical traffic channels that may be used for data transmission. The SOC sublayer 314 defines a set of parameters for communication such as multiplexing options, power control, forward link traffic channel characteristics, and the like. The call control sublayer 312 identifies the set of pending calls being processed.

The following terms are used herein:

● Service Option (SO) -service capabilities of the system. The service selection may be an application such as voice, data, fax, etc.

● service option connection (SO Conn) -a particular instance or conversation in which the service defined by a particular service option is used. The service option connection is associated with (1) a reference (CON _ REF) for uniquely identifying the service option connection, (2) a service option specifying a particular profile of the service in use, (3) a forward traffic channel traffic type identifying which type of forward traffic channel traffic is used to support the service option connection, and (4) a reverse traffic channel traffic type specifying which type of reverse traffic channel traffic is used by the service option connection.

● service configuration-common attributes that the terminal and base station use for communication (i.e., to establish and interpret traffic channel frames exchanged between the terminal and base station). The set of attributes includes negotiable and non-negotiable parameters.

● Service Configuration Record (SCR) -a record of information used to send negotiable parameters, which includes (1) forward and reverse multiplexing options, (2) forward and reverse traffic channel configurations, (3) forward and reverse traffic channel transmission rates, and (4) service option connections. Each SCR may include one or more service option connection records, and each service option connection record is associated with a service reference identifier (srid).

● non-negotiable service configuration record (NNSCR) -records information used to send non-negotiable parameters.

● service reference identifier (SR _ ID). The SR ID identifies the associated service option instance.

A call is used to generally describe a certain type of communication session for a service (indicated by a service option number) between a terminal and a CDMA system. For IS-2000, there IS a one-to-one mapping between each call and the associated service option connection. Each call is therefore associated with a specific Service Option (SO), which formally defines the way in which data bits are handled by the terminals and base stations of the call. As an example, SO 7 is the service option for low speed packet data calls within P _ REV ≧ 5, and SO33 is the service option for high speed packet data calls within P _ REV ≧ 6.

For IS-2000 release a (i.e., P _ REV ═ 7), multiple calls can be concurrently processed. As each Call is connected, a new Call Control (CC) state machine is instantiated (with the Call)_xRepresentation). The type of CC state machine instantiated is selected based on the type of call being processed (e.g., voice, data, etc.). IS-2000 release a supports a number of different CC state machine types.

In the example shown in fig. 3, each Call (Call)_x) Processed within the CC sublayer 312 and mapped to a particular service option connection (SO Conn)_n). In the example shown in FIG. 3, a Call_AMapping to SO Conn₁And Call_BMapping to SO Conn₂. Subscripts a and B denote CALL identifiers (CALL _ ID) for identifying CALLs, and subscripts 1 and 2 denote references (CON _ REF) of established service option connections. In the example shown in FIG. 3, SO Conn₁Is mapped to (i.e., uses) a Dedicated Control Channel (DCCH) and a Supplemental Channel (SCH), and SO Conn₂Is mapped onto a Fundamental Channel (FCH) and a supplemental channel.

When a call mapped to a particular service option connection is released, the service option connection may also be released. Similarly, a particular physical channel may be released when the last service option connection mapped to that physical channel is released.

Each CDMA standard defines procedures for implementing service configuration and negotiation to set up various parameters for communication between a terminal and a base station. As described above, the service configuration includes negotiable and non-negotiable parameters. In the negotiating and/or acknowledging, information for negotiable parameters may be sent within a Service Configuration Record (SCR) included within an appropriate signaling message, and information for non-negotiable parameters may be sent within a non-negotiable service configuration record (NNSCR).

The service option connection may be negotiated between the terminal and the base station through a "service negotiation" procedure. If a service option connection is required to support the new call, the service option request and assignment may be completed using a service negotiation procedure. The service negotiation process IS described in detail by IS-2000.

Service options may also be negotiated between the terminal and the base station, or default service options may be selected. The service option negotiation procedure IS described by IS-2000 and IS-95.

Service negotiation and service option negotiation are implemented through the exchange of signaling messages between the terminal and the base station. For IS-2000, the following signaling messages are sent by the base station over the forward dedicated signaling logical channel (f-dsch):

● Service Connection Message (SCM): the base station may use the message to (1) accept the service configuration proposed by the terminal, (2) instruct the terminal to start using the service configuration included in the message, or (3) instruct the terminal to use a particular stored service configuration.

● Universal Handover Direction Message (UHDM): the base station may use the message to (1) indicate whether service negotiation or service option negotiation is to be implemented following a CDMA-to-CDMA hard handoff, (2) accept a service configuration proposed by the terminal, or (3) indicate to the terminal to begin using the service configuration included in the message.

● status request message (SRQM): the base station may use the message to request the current service configuration from the terminal.

● in-traffic system parameter message (ITSPM). The base station may send the message to inform the terminal that the packet zone has changed (described below).

● release the order message. The base station may use the message to release the active call.

● extend the system parameters message (ESPM). The base station may also transmit the message to inform the terminal that the packet zone has changed.

For IS-2000, the following signaling messages are sent by the terminal over either the reverse dedicated signaling logical channel (r-dsch) or the reverse common signaling logical channel (r-csch):

● origination message (ORM): the terminal can initiate a new call using the message.

● enhanced initiation message (EOM): the terminal can initiate a new call using the message.

● status response message (STRPM): the terminal may send the message to provide the current service configuration to the base station.

The above signaling messages are described in detail within the IS-2000 standard.

Table 1 lists some of the main features for calls supported by P _ REV ═ 5, 6, and 7.

Table 1

P_REV＝5

● support a data call and/or a voice call at any time.

P_REV＝6

● introduces the concept of service reference identifier (SR _ ID) to identify each service option instance.
	● introduces a call dormancy concept where the traffic channel can be released for a data call, but the SR _ ID and PPP session information is preserved during dormancy so that the data call can continue sooner later.
● support an active data call at any given time.

P_REV＝7

● introduces a burst service concept in which multiple calls can be supported concurrently, each call being uniquely identified by its associated SR _ ID.
	● Each dormant data call is also associated with an SR _ ID

The wireless service provider may use different generations of base stations with different P REVs that are adjacent to each other. This can lead to compatibility issues if base stations with different P REVs are designated to provide communication for a given terminal. For such a hybrid use, the terminal may communicate with one base station of a particular P _ REV and thereafter be handed off to another base station with a different P _ REV. Base stations with higher P REV support more call features and functions as shown in table 1 and are generally associated with more parameters for defining communications. Thus, if a terminal switches between base stations of different P _ REV, there are challenges associated with handling parameters (e.g., SR _ ID) that are defined within one P _ REV (P _ REV ≧ 6) and not defined within another P _ REV (P _ REV ≦ 5).

The various compatibility scenarios can be described simply with figure 1. In FIG. 1, base station 1 may be associated with P _ REV ≧ 5, and base station 2 may be associated with P _ REV ≧ 6. If the terminal is associated with a MOB _ P _ REV of 5 and is handed over from base station 1 to base station 2, base station 2 would need to operate at P _ REV _ IN _ USE 5 to communicate with the terminal and would not encounter an incompatibility. However, if the base station is associated with MOB _ P _ REV ≧ 6 and a handoff is made from base station 1(P _ REV ≦ 5) to base station 2(P _ REV ≦ 6), there may be ambiguity regarding the use of SR _ ID, which is defined within P _ REV ≧ 6 but not defined within P _ REV ≦ 5, for active and dormant calls. This is described in detail in the following figures.

For simplicity, P _ REV of 5, 6 and 7 are described in particular in the following figures. However, the techniques described herein to support handover may be extended to cover other P REVs and are within the scope of the present invention. In the following figures, base station 1 may be associated with P _ REV ≦ 5 in FIGS. 4A-4H, and base station 2 is associated with P _ REV ≦ 6 in FIGS. 4A-4B and 4G, and with P _ REV ≧ 7 in FIGS. 4C-4F and 4H.

For clarity of the following figures, specific service options SO 7 and SO33 (which are defined within IS-707) are described. Other service options may also apply and may be used for data calls. For example, SO 7 or some other low speed packet data service option may be used for data calls with base stations with P _ REV ≧ 5, and SO33 or some other high speed packet data service option may be used for data calls with base stations with P _ REV ≧ 6.

Fig. 4A is a diagram illustrating a terminal handover from base station 1(P _ REV ═ 5) to base station 2(P _ REV ═ 6) (MOB _ P _ REV ═ 6 or 7). For fig. 4A, there is no dormant data call (i.e., no data dormant) when a handover occurs, and P _ REV _ IN _ USE is 6 after the handover. Due to compatibility issues, P _ REV _ IN _ USE is determined by the lower of (1) the P _ REV of the target base station, and (2) the MOB _ P _ REV of the terminal (i.e., P _ REV _ IN _ USE ═ min { P _ REV, MOB _ P _ REV }. two cases, one with an active data call and the other with an active voice call, are shown IN fig. 4A.

In the first case, the terminal initiates a data call with the base station 1 at the beginning. Since base station 1 is associated with P _ REV ═ 5, the data call can be used for SO 7, which is a low speed packet data call service option. While the data call is still active, the terminal is handed over from base station 1 to base station 2. Since P _ REV _ IN _ USE is 6 after handover, the data call may be associated with SR _ ID. However, since only one call has been set up to this point, there is no ambiguity at the terminal and base station 2 as to which call is being handled. Thus, the SR _ ID may be omitted (i.e., unused) for the data call. If the SR _ ID is used for a data call, the base station 2 may transmit the SR _ ID of the call within a Service Configuration Record (SCR) included in a service connect message or a universal handover direction message (SCM/UHDM) transmitted to the terminal. The terminal and base station 2 will then use the SR _ ID for the data call.

In the second case, the terminal starts to initiate a voice call with the base station 1. The voice call may be used for multiplex option 1 and Radio Configuration (RC) 1, which are defined in IS-95 and IS-2000. While the voice call is still active, the terminal is handed over to the base station 2. Since P _ REV _ IN _ USE is 6 after handover, the voice call can be identified by SR _ ID. Also, since only one call has been set up so far, there is no ambiguity at the terminal and base station 2, and the srid can be omitted. However, if the SR _ ID is used for the voice call, the base station 2 may transmit the SR _ ID within an SCR included in the SCM/UHDM. The terminal and base station 2 thereafter use the SR _ ID for a voice call.

In an embodiment, for both cases described above, the target base station 2 sends the SCM/UHDM with the new service configuration record (e.g. new SCR and NNSCR, including SR _ ID) to the terminal after the base station is added to the active set. The message may be sent before or during the handover. For this embodiment, the terminal may store the service configuration record for later use.

In another embodiment, for both cases described above, the target base station 2 sends the SCM/UHDM with the new service configuration record to the terminal after the handover. For this embodiment, the SCM/UHDM may be sent only if service configuration records are needed (e.g., if SR _ ID is used for active calls).

Fig. 4B is a diagram illustrating a handover from base station 1(P _ REV ═ 5) to base station 2(P _ REV ═ 6) terminal (MOB _ P _ REV ═ 6 or 7), with data dormant and P _ REV _ IN _ USE ═ 6 after the handover. Also, two cases are shown in fig. 4B, one for active data call handover and the other for active voice call handover.

In the first case, the terminal initially sets up a data call (P _ REV ═ 6 or 7) with the base station, which may be base station 2 or another base station within the system. The data call may be for SO33, which is a service option for high speed packet data calls and may be assigned SR _ ID ═ x. Thereafter, the data call becomes dormant, and the terminal is handed over to the base station 1 during the dormant period.

For P _ REV ≧ 6, the terminal and the base station establish a PPP session at the beginning of the first data call. The PPP session may be maintained even though the data call is dormant, which allows data communication to continue faster if the dormant call is later reconnected or a new data call is established. The service configuration for dormant calls may or may not be retained by the terminal and network side, depending on the terminal and system implementation.

After which the terminal initiates a new data call with the base station 1. Since base station 1 has P _ REV ═ 5, the new data call may be for SO 7. While the data call is still active, the terminal is handed over from base station 1 to base station 2. Since P _ REV _ IN _ USE is 6 after handover, the active data call may be associated with SR _ ID.

In one embodiment, the SO 7 PPP session established for the active data call is cleared and the dormant SO33 instance is re-established for the active data call. The reconnected SO33 instance may be x for SR _ ID or z for new SR _ ID. The specific SR _ ID of the SO33 for reconnection may be determined based on various schemes. In the first scheme, the base station 2 brings the sleep session (SR _ ID ═ x) out of sleep. In a second scheme, the base station 2 simply assigns a new SR _ ID z to the reconnected SO33 instance. The SR _ ID of the reconnected SO33 (which may be the proposed SR _ ID or the assigned SR _ ID) may be transmitted to the terminal through the SCR within the SCM/UHDM. The SO33 PPP session may also be resynchronized if necessary (e.g., if SR _ ID z is the SO33 instance to be used for reconnection and not SR _ ID x).

In the second case, the terminal initially sets up a data call (with P _ REV ═ 6 or 7) with the base station and switches to base station 1 when the data call is dormant. The terminal then initiates a voice call with base station 1 while the voice call is still active and the terminal is handed over to base station 2. Since P _ REV _ IN _ USE is 6 after the handover, the voice call is associated with SR _ ID. However, since there is only one (active) voice call and one (dormant) data call (i.e. one call of each type), there is no ambiguity at the terminal and the base station 2 and the srid can be omitted for the voice call. If SR _ ID is used for the voice call, base station 2 may send the SR _ ID via an SCR in SCUHDM. The terminal and base station 2 will thereafter use the SR _ ID for the voice call.

Fig. 4C is a diagram illustrating a handover from base station 1(P _ REV ═ 5) to base station 2(P _ REV ═ 7) for one terminal (MOB _ P _ REV ═ 6), with no data dormant and P _ REV _ IN _ USE ═ 6 after the handover.

In the first case, the terminal initiates a data call with the SO 7 of base station 1 at the beginning and is handed over to base station 2 while the data call is still active. Even if the base station 2 has P _ REV equal to 7, it needs to drop to P _ REV equal to 6 because the terminal has MOB _ P _ REV equal to 6 and therefore P _ REV _ IN _ USE equal to 6. The active data call may then be processed in a similar manner, as described in fig. 4A. In particular, the srid may be omitted for this data call, since there is only one call and no ambiguity exists at the terminal and the base station 2. However, if the SR _ ID is to be used for a data call, base station 2 may transmit the SR _ ID through an SCR within the SCM/UHDM.

In a second scheme, the terminal initiates a voice call with base station 1, while the voice call is still active, the terminal is handed over to base station 2. Likewise, the base station 2 needs to drop to P _ REV _ IN _ USE _ 6 (i.e., P _ REV _ IN _ USE _ 6) and the voice call is processed IN a similar manner as described IN fig. 4A.

Fig. 4D is a diagram illustrating a handover from base station 1(P _ REV ═ 5) to base station 2(P _ REV ═ 7) for one terminal (MOB _ P _ REV ═ 6), with data dormant and P _ REV _ IN _ USE ═ 6 after the handover.

In the first case, the terminal initially sets up a data call with the base station (P _ REV ═ 6 or 7) for SO33, and may be assigned SR _ ID ═ x. Thereafter, the data call becomes dormant, and the terminal is handed over to the base station 1 during the dormant period. The terminal thereafter initiates a new data call with the base station 1 for SO 7. While the SO 7 data call is still active, the terminal is handed over to base station 2. Since P _ REV _ IN _ USE is 6 after handover, the active data call can be identified by SR _ ID. In one embodiment, the SO 7 PPP session is cleared and the dormant SO33 instance reconnects with SR _ ID x, and base station 2 assigns a new SR _ ID z. The SO33 PPP session may also be resynchronized, if necessary. In another embodiment, which is not shown in fig. 4D, the dormant SO33 session is cleared (e.g., after handoff to base station 1), and the SO 7 PPP session for the active data call is maintained by base station 2 after handoff. For this embodiment, the srid is omitted for active data calls (since there is only one type of data call and no ambiguity) or may be assigned by the base station 2 through the SCR in the SCM/UHDM.

In the second case, when the terminal is handed over to base station 1, the terminal has a dormant SO33 data call with SR _ ID ═ x. The terminal then initiates a voice call with base station 1 and is handed over to base station 2 while the voice call is still active. Since P _ REV _ IN _ USE is 6 after handover, the voice call may be associated with SR _ ID. However, since there is only one (active) voice call and one (dormant) data call, there is no ambiguity at the terminal and the base station 2, and the srid can be omitted. If SR _ ID is used for an active voice call, base station 2 may send SR _ ID via SCR within SCM/UHDM. The terminal and base station 2 thereafter use the SR _ ID for the voice call.

Fig. 4E is a diagram illustrating a handover from base station 1(P _ REV ═ 5) to base station 2(P _ REV ═ 7) for one terminal (MOB _ P _ REV ═ 7), after the handover, there is no data dormancy and P _ REV _ IN _ USE ═ 7.

In the first case, the terminal initiates a data call with base station 1 for SO 7 at the beginning and is handed over to base station 2 while the data call is still active. The srid may be omitted for the data call since there is no ambiguity as to only one pending data call. However, if the SR _ ID is used for the data call, base station 2 sends the SR _ ID through the SCR in the SCM/UHDM.

Since P _ REV ═ 7 supports multiple concurrent calls, another (data or voice) call can be initiated by the terminal with an enhanced initiation message (EOM) with the SR _ ID for the new call offer. In this case, two different srids would be needed for the current data call and the new call. The SR _ ID proposed by the terminal for the new call may be accepted by the base station 2 and used for the new call. The base station 2 may then assign another srid if one has not already been assigned for the current data call. The base station 2 then sends the SR _ ID proposed by the new call and the assigned SR _ ID of the current data call to the terminal through the SCR in the SCM/UHDM.

In the second case, the terminal initiates a voice call with base station 1, while the voice call is still active, and the terminal is handed over to base station 2. Also, the srid may be omitted for the voice call, since there is currently only one call. However, if SR _ ID is to be used, base station 2 may transmit SR _ ID through SCR in SCM/UHDM. Similar to the first case, if another call is initiated by the terminal with the proposed srid of the new call by means of the enhanced initiation message, the base station 2 may accept the proposed srid for the new call and assign another srid to the current voice call. In this way, both calls can be associated with a unique srid.

Fig. 4F is a diagram illustrating a handover from base station 1(P _ REV ═ 5) to base station 2(P _ REV ═ 7) for one terminal (MOB _ P _ REV ═ 7), with data dormant and P _ REV _ IN _ USE ═ 7 after the handover.

In the first case, the terminal initially sets up two data calls (P _ REV ═ 6 or 7) with the base station, which may or may not be base station 2. These data calls may be to SO33 and may be assigned SR _ ID ═ x and SR _ ID ═ y. In general, any number of data calls (from 2 to 7) may be established. Thereafter, the data call becomes dormant, and the terminal is handed over to the base station 1 during the dormancy. The terminal thereafter initiates a new data call with the base station 1 for SO 7. While the SO 7 data call is still active, the terminal is handed over to base station 2. Since P _ REV _ IN _ USE is 7 after handover, the current data call can be identified by SR _ ID.

In one embodiment, the SO 7 PPP session for the active data call is cleared and one of the two dormant SO33 instances is reconnected for the active data call. Since there are multiple dormant SO33 instances, the particular SO33 instance to reconnect may be determined based on several schemes. In one aspect, the terminal automatically selects which SR _ ID to use for the reconnected SO33 instance. The base station 2 queries the terminal for the current service configuration by means of a status request message. The terminal then responds to the query with a status response message that includes the SCR with the proposed SR _ ID for SO33 to be reconnected. If base station 2 accepts the proposed SR _ ID, it reconnects the corresponding SO33 instance. In a second scheme, the base station 2 simply allocates a new SR _ ID z to the reconnected SO33 instance without querying the terminal. For both schemes, the base station finally decides which SR _ ID to use, and the terminal accepts the decision. The reconnected SO33 instance may thus be x or y for SR _ ID or z for new SR _ ID. The SR _ ID to be used for the reconnect SO33 instance is then provided to the terminal through the SCR at the SCM/UHDM. The SO33 PPP session may also be a resynchronization if necessary (e.g., if SR _ ID z is to be used instead of SR _ ID x or y for the reconnected SO33 instance).

In another embodiment, the dormant SO33 instance is cleared (e.g., when the terminal is handed off to base station 1) and an SO 7 PPP session is maintained for the active data call when the terminal is handed off to base station 2. For this embodiment, the srjd may be omitted (since there is currently only one data call) or a new srjd may be assigned by the base station 2 via the SCR in the SCM/UHDM.

In the second scheme, the terminal initially establishes two data calls and is handed over to the base station 1 while the call is dormant. The terminal thereafter initiates a voice call with base station 1, and while the voice call is still active, the terminal is handed over to base station 2. Also, the srid may be omitted for the voice call, since there is no ambiguity in the case of only one voice call. However, if SR _ ID is used for the voice call, base station 2 may send SR _ ID through SCR in SCM/UHDM.

The terminal may also initiate a new data call by the enhanced origination message and may propose an SR _ ID for the data call. The proposed srjd may then be the srjd of one dormant data call (i.e. x or y) or another srjd (e.g. the smallest number not used and the current srjd available). The base station may accept the proposed SR _ ID for the new data call and may assign another SR _ ID for the current voice call. Thus, the new data call and the current voice call are associated with a unique srid.

Fig. 4G is a diagram illustrating a handover from base station 1(P _ REV ═ 5) to base station 2(P _ REV ═ 6) terminal (MOB _ P _ REV ═ 6 or 7), with data dormant and P _ REV _ IN _ USE ═ 6 after the handover. In this figure, the terminal initiates the use of a new SR _ ID to the base station with the higher P _ REV after handover.

Initially, the terminal sets up a data call (P _ REV ═ 6 or 7) with the base station for SO 33. Thereafter, the call becomes dormant, and the terminal is handed over to the base station 1 during the dormancy. The terminal thereafter initiates a data call with the base station 1 for SO 7. While the data call is still active, the terminal is handed over to base station 2. Since P _ REV _ IN _ USE is 6 after the handover, the active data can be identified by SR _ ID.

After handover to base station 2, the base station releases the active data call (this is a non-SO 33 call) by sending a release order message to the terminal. Upon receiving this message, the terminal enters an idle state to listen for an Extended System Parameters Message (ESPM) with the packet zone id (pzid) sent by the base station 2. By processing the ESPM from base station 2, the terminal can detect that the packet zone has changed and it may update its service options. Each P REV may be associated with a different packet zone, indicating the service options available for that zone. When the terminal is handed over from a base station with P _ REV ≧ 5 to a base station with P _ REV ≧ 6, the terminal can upgrade from SO 7 (low-speed packet data) to SO33 (high-speed packet data). The terminal may then initiate a new data call for SO33 via an origination message (ORM) with the proposed SR _ ID. A Data Ready (DRS) field within the ORM may be set to "1" to indicate that the terminal has data ready to transmit. The base station 2 may receive the request and a new SO33 instance with the proposed SR _ ID may be connected for a new data call.

Fig. 4G may also be applied to a handover diagram from base station 1(P _ REV ═ 5) to base station 2(P _ REV ═ 7) for one terminal (MOB _ P _ REV ═ 6). IN this example, P _ REV _ IN _ USE is 6 after the switch.

Fig. 4H is a diagram illustrating a handover from base station 1(P _ REV ═ 5) to base station 2(P _ REV ═ 7) terminal (MOB _ P _ REV ═ 7), with data dormant and P _ REV _ IN _ USE ═ 7 after the handover. In this figure, the terminal starts using the new SR _ ID after handover to the base station with the higher P _ REV. Initially, the terminal sets up two data calls for SO33 with a base station (P _ REV ═ 6 or 7), which may or may not be base station 2. In general, any number of data calls (from 2 to 7) may be established. The calls are then dormant and the terminal is handed off to base station 1 during the dormant period. The terminal thereafter initiates a new data call with the base station 1 for SO 7. While the SO 7 data call is still active, the terminal is handed over to base station 2. Since P _ REV _ IN _ USE is 7 after handover, the active data call can be identified by SR _ ID. The terminal may start using a new SR _ ID for the active data call after switching using several schemes.

In the first scheme, after handover to base station 2, the base station releases the active (non-SO 33) data call by sending a release order message to the terminal. Upon receiving the message, the terminal enters an idle state, listens for an Extended System Parameter Message (ESPM) with the packet zone ID transmitted from the base station 2, and detects that the packet zone has been changed. The terminal then initiates a new data call for the SO33 via an origination message (ORM) with the proposed SR _ ID. The base station 2 may accept the terminal request, in which case the SO33 with the proposed SR _ ID may be connected for a new data call.

In a second scheme, the terminal is handed over to the base station 2 which informs the terminal that the packet zone has changed by sending an in-traffic system parameters message (ITSPM) with a new Packet Zone Identifier (PZID) indicating that the terminal is in the new packet zone with SO 33. ITSPM may thus be used to trigger the terminal to re-initiate the active data call using SO 33. The terminal receives ITSPM and determines that it updates its service options. The terminal then initiates a new SO33 data call with an Enhanced Origination Message (EOM) requesting an SO33 instance with an SR _ ID (this may be SR _ ID x or y, or new SR _ ID z). The base station 2 may accept the terminal request, in which case the SO33 instance with the proposed SR _ ID may be connected for the new data call.

The first and second schemes represent two different mechanisms to inform the terminal that it can update its service options for the data call. IN the second case, ITSPM and EOM can be used if both the terminal and the base station are associated with P _ REV ≧ 7 (since EOM is not supported by P _ REV _ IN _ USE < 7).

Fig. 5 is a block diagram of a particular embodiment of various network elements within system 100. The system 100 includes a system controller 102, which may be a Mobile Switching Center (MSC) or a Base System Controller (BSC), in communication with a plurality of base stations 104 (only one base station is shown in fig. 5 for simplicity). The system controller 102 also interfaces with a Public Switched Telephone Network (PSTN)502 (e.g., for voice services) and a Packet Data Serving Node (PDSN)504 (e.g., for packet data services). The system controller 102 coordinates communication within the wireless communication system between the terminals and the base station 104, the PSTN 112, and the PSDN 114.

In the embodiment illustrated in fig. 5, the system controller 102 includes a call control processor 512, a plurality of selector elements 514 (only one selector element is shown in fig. 5 for simplicity), and a scheduler 516. The call control processor 512 controls call processing, processing negotiation, service option negotiation, and the like for each terminal. Call control processor 512 may implement the various handoff techniques described above. A selector element 514 is assigned to control communication between each terminal and one or more base stations (possibly different P REVs). A scheduler 516 is coupled to all selector elements 514 within system controller 102 and schedules data transmissions for packet data users. Memory unit 510 stores data and program codes used by call control processor 512 and possibly other units within system controller 102.

In the example shown in fig. 5, the base station 104 includes a plurality of channel elements 522a through 522 n. One channel element 522 is assigned to handle communications for each terminal and is coupled to an associated selector element 514 that is also assigned to the terminal. Each selector element 514 receives the scheduling (e.g., data rate, transmit power, and transmit time) for the assigned terminal from the scheduler 516 and forwards the scheduling to an associated channel element 522. Channel element 522 receives, encodes, and modulates (e.g., covers and spreads) data for the assigned terminal. The modulated data is then converted to one or more analog signals, quadrature modulated, filtered, and amplified by a transmitter (TMTR)524 to provide a forward modulated signal, which is then routed through a duplexer 526 and transmitted via an antenna 528.

At receiving terminal 106, the forward modulated signal is received by antenna 550 and routed to a front end unit 552. Front-end unit 552 filters, amplifies, frequency downconverts, and digitizes the received signal to provide samples. The samples are then demodulated by a demodulator (Demod)554, decoded by a decoder 556, and provided to a data sink 558. The demodulation and decoding implementations are complementary to the modulation and coding implemented at the base station.

Controller 560 directs the operation of various elements within terminal 106 and further controls call processing, service negotiation, service option negotiation, etc. for the terminal. The controller 560 may receive decoded data of a message to be transmitted by the base station from the decoder 556. A memory unit 562 stores data and program codes used by controller 560 and possibly other units within terminal 106.

Data transmission on the reverse link occurs in a similar manner. Data is provided from a data source 564, encoded by an encoder 566, and modulated by a modulator (Mod)568 to provide modulated data. The modulated data is then converted to an analog signal, upconverted and conditioned by a front end unit 552 to provide an inverse modulated signal, which is then transmitted via an antenna 550.

At base station 104, the reverse modulated signal is received by an antenna 528, routed through a duplexer 526, and provided to a receiver (RCVR) 530. Receiver 530 filters, amplifies, frequency downconverts, and digitizes the received signal and provides samples to channel elements 522, which are assigned to the terminal. The assigned channel element 522 demodulates and decodes the data samples in a manner complementary to the modulation and coding implemented at the terminal. The decoded data may be provided to a selector element 514 assigned to the terminal, which then forwards the data further to another base station 104, PSTN 502, or PDSN 504. As described above, the design supports both voice and packet data transmissions over the system. Other designs are also contemplated and are within the scope of the present invention.

Forward and reverse link processing (e.g., coding and modulation) are defined by a particular CDMA standard or implemented system (e.g., IS-95A, IS-95B and IS-2000).

The above-described techniques for supporting inter-base station terminal handoffs of different protocol revisions may be implemented in various ways. For example, these techniques may be implemented in hardware, software, or a combination thereof. For a hardware implementation, the elements used to support switching may also be implemented within one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof.

For software implementation, the techniques for supporting terminal handover between base stations of different protocol revisions may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described above. The terminal and base station (or network side) implement the appropriate activities to effect the handover. The software codes on the terminal and network sides may be stored in memory units (e.g., memories 562 and 510 in fig. 5) and implemented by processors (e.g., controller 560 and call control processor 512). Each memory unit may be implemented within or external to the controller/processor, in which case it can be communicatively coupled thereto in various ways as is known in the art.

The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without the use of the inventive faculty. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. In a CDMA communication system, a method for supporting handoff of a terminal between base stations having different protocol revisions, comprising:

enabling handover of the terminal from the first base station to the second base station, wherein the handover is enabled while the terminal is in an active call with the first base station, and wherein the first base station supports a first protocol revision and the second base station supports a second protocol revision that is later than the first protocol revision; and

the active call between the terminal and the second base station is maintained using a first service configuration previously established through the first base station for the active call.

2. The method of claim 1, further comprising:

establishing, by the second base station, a second service configuration, and wherein the active call is thereafter maintained using the second service configuration.

3. The method of claim 2, wherein the second service configuration is established after handover to the second base station.

4. The method of claim 2, wherein the second service configuration is established after the second base station is added to the active set of the terminal.

5. The method of claim 2, wherein each service configuration includes a specific service option instance for the associated call.

6. The method of claim 5, wherein the first service configuration comprises a first service option instance for a lower speed packet call.

7. The method of claim 5, wherein the second service configuration comprises a second service option instance for a high speed packet data call.

8. The method of claim 5, wherein the first service option instance IS SO 7 or other low-speed packet data service option instance defined in IS-707.

9. The method of claim 5, wherein the second service option instance IS an SO33 instance defined in IS-707.

10. The method of claim 2, further comprising:

establishing a third service configuration for the new call; and

the new call is maintained using the third service configuration.

11. The method of claim 1, further comprising:

reconnecting the dormant call with the second service configuration;

establishing, by the second base station, a third service configuration, wherein the third service configuration is established for the active call in response to the reconnection of the dormant call, and wherein the active call is thereafter maintained using the third service configuration.

12. The method of claim 2, further comprising:

a service reference identification number (SR _ ID) is assigned to the active call.

13. The method of claim 1, further comprising:

initiating a new call through the second base station; and

two service reference identification numbers are assigned for the active call and the new call.

14. The method of claim 1 wherein each protocol revision corresponds to a particular CDMA standard release.

15. The method of claim 1, wherein the first protocol revision corresponds to a standard version of IS-95B or earlier (P REV ≦ 5).

16. The method of claim 1, wherein the second protocol revision corresponds to IS-2000 version 0 or later (P _ REV ≧ 6).

17. In a CDMA communication system, a method for supporting handoff of a terminal between base stations having different protocol revisions, comprising:

enabling handover of the terminal from the first base station to the second base station, wherein the handover is enabled using the first service configuration while the terminal is in an active call with the first base station, and wherein the first base station supports the first protocol revision and the second base station supports 0 after the first protocol revision;

clearing the first service configuration for the active call prior to the handover; and

the active call between the terminal and the second base station is maintained after the handover using a second service configuration supported by a second protocol revision.

18. The method of claim 17, wherein the first service configuration comprises a service option instance for a low-speed packet data call and the second service configuration comprises a service option instance for a high-speed packet data call.

19. The method of claim 17, wherein the second service configuration is established for a previous data call prior to the handover.

20. The method of claim 17, wherein the second service configuration is proposed by a terminal.

21. The method of claim 17, wherein the second service configuration is selected by the second base station.

22. The method of claim 17, wherein a plurality of service configurations are established for a plurality of prior data calls prior to the handover, and wherein the second service configuration is selected from the plurality of previously established service configurations.

23. The method of claim 17, further comprising:

establishing a third service configuration for the new call; and

the new call is maintained using the third service configuration.

24. The method of claim 17, further comprising:

two service reference identifiers are assigned for the active call and the new call.

25. The method of claim 17 wherein each protocol revision corresponds to a particular CDMA standard release.

26. The method of claim 17, wherein the first protocol revision corresponds to the IS-95B or earlier standard version (P REV ≦ 5) and the second protocol revision corresponds to the IS-2000 version 0 or later standard version (P REV ≧ 6).

27. In a CDMA communication system, a method for supporting handoff of a terminal between base stations having different protocol revisions, comprising:

enabling handover of the terminal from the first base station to the second base station, wherein the handover is enabled while the terminal is engaged in an active call with the first base station using the first service configuration, and wherein the first base station supports a first protocol revision and the second base station supports a second protocol revision that is later than the first protocol revision;

releasing, by the second base station, the active call;

receiving a request to initiate a new call with a second service configuration; and

a new call between the terminal and the second base station is maintained using the second service configuration.

28. The method of claim 27, wherein the request is received via an origination message.

29. The method of claim 27, wherein the protocol revision corresponds to IS-95B or an earlier standard version (P REV ≦ 5) and the second protocol revision corresponds to IS-2000 version 0 or a later standard version (P REV ≧ 6).

30. In a CDMA communication system, a method for supporting handoff of a terminal between base stations having different protocol revisions, comprising:

enabling handover of the terminal from the first base station to the second base station, wherein the handover is enabled while the terminal is engaged in an active call with the first base station using a first service configuration, and wherein the first base station supports a first protocol revision and the second base station supports a second protocol revision subsequent to the first protocol revision;

transmitting a first message indicating a change in a packet zone;

a new call between the terminal and the second base station is maintained with the second service configuration.

31. The method of claim 30 wherein said first message is an in-traffic system parameters message.

32. The method of claim 30, wherein the request is received via an enhanced origination message.

33. The method of claim 30, wherein the first protocol revision corresponds to IS-95B or an earlier standard version (P REV ≦ 5) and the second protocol revision corresponds to IS-2000 version 0 or a later standard version (P REV ≧ 6).

34. A memory communicatively coupled to a Digital Signal Processing Device (DSPD) capable of interpreting digital information to:

enabling handover of the terminal from the first base station to the second base station, wherein the handover is enabled using the first service configuration while the terminal is in an active call with the first base station, and wherein the first base station supports a first protocol revision and the second base station supports a second protocol revision subsequent to the first protocol revision;

the active call between the terminal and the second base station is maintained using a second service configuration supported by a second protocol revision after the handover.

35. A computer program product for supporting handoff of a terminal between base stations having different protocol revisions, comprising:

code for effecting handover of a terminal from a first base station to a second base station, wherein the handover is effected using a first service configuration while the terminal is in an active call with the first base station, and wherein the first base station supports a first protocol revision and the second base station supports a second protocol revision subsequent to the first protocol revision;

code for clearing a first service configuration for the active call prior to the handover; and

code for maintaining an active call between the terminal and the second base station using a second service configuration supported by a second protocol revision after the handover; and

a computer usable medium for storing said code.

A terminal in a CDMA communication system, comprising:

means for effecting handover of a terminal from a first base station to a second base station within a CDMA system, wherein the handover is effected using a first service configuration while the terminal is in an active call with the first base station, and wherein the first base station supports a first protocol revision and the second base station supports a second protocol revision subsequent to the first protocol revision;

means for clearing the first service configuration for the active call prior to the handover; and

means for configuring, after the handover, the device to maintain the active call between the terminal and the second base station using a second service supported by a second protocol revision.

37. The terminal of claim 36, wherein the first protocol revision corresponds to IS-95B or an earlier standard version (P REV ≦ 5) and the second protocol revision corresponds to IS-2000 version 0 or a later standard version (P REV ≧ 6).

38. The terminal of claim 36, wherein the first service configuration includes a first service option instance for a low speed packet data call and the second service configuration includes a second service option instance for a high speed packet data call.

39. The terminal according to claim 36, characterized in that the second service configuration is proposed by the terminal.

40. The terminal of claim 36, wherein the second service configuration is selected by the second base station.

41. A CDMA communication system, comprising:

means for effecting handoff of the terminal from the first base station to the second base station in the CDMA system, wherein the handoff is effected using the first service configuration while the terminal is in an active call with the first base station, and wherein the first base station supports a first protocol revision and the second base station supports a second protocol revision subsequent to the first protocol revision;

means for maintaining the active call with the second base station using a second service configuration supported by a second protocol revision after the handover.

42. The terminal of claim 41, wherein the first protocol revision corresponds to the IS-95B standard version or earlier (P _ REV ≦ 5) and the second protocol revision corresponds to the IS-2000 version 0 or later (P _ REV ≧ 6).

43. The CDMA system of claim 41 wherein the first service configuration comprises a first service option instance for a low speed packet data call and the second service configuration comprises a second service option instance for a high speed packet data call.