HK1070228B - Method and apparatus for call setup latency reduction - Google Patents

Description

Method and apparatus for reducing call setup latency

Technical Field

The present invention relates generally to communications, and more specifically to a novel and improved method and apparatus for reducing call setup latency within a wireless communication system.

Background

Wireless communication systems are generally widely deployed to provide multiple users with multiple 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), Frequency Division Multiple Access (FDMA), or some other multiple access technique. A CDMA system may provide some advantages over other types of systems, such as 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-ModeWideband Spread Spectrum Cellular System" (IS-95 Standard), (2) the Standard provided by the "3 rd Generation Partnership Project" (3GPP) embodied within a set of documents including the Nos.3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS25.214(W-CDMA Standard), (3) the Standard provided by the alliance entitled "3 rd Generation Partnership Project 2" (3GPP2), embodied within a set of documents are "C.S0002-A Physical Layer Standard for cdma2000 Spread Spectrum Systems", "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) and (4) some other standards. These named standards are incorporated herein by reference.

Call setup is the process of establishing dedicated physical channels and negotiating service configuration parameters between the mobile station and the base station so that communication can take place. Call setup procedures fall into two categories. Mobile-originated call setup occurs when a mobile station user makes a call. Mobile terminated call setup occurs when a call is placed to a mobile station.

The call setup procedure involves signaling between a Mobile Switching Center (MSC) or Packet Data Serving Node (PDSN), one or more Base Stations (BS), and a Mobile Station (MS). As used herein, the term base station may be used interchangeably with the term access point. The term mobile station can be used interchangeably with the terms subscriber unit, subscriber station, access terminal, remote terminal or other corresponding terms used in the art. The term mobile station includes fixed wireless applications. The signal from the mobile station is referred to as the reverse link, reverse channel, or reverse traffic. The signal to the mobile station is referred to as the forward link, forward channel, or forward traffic.

Fig. 1 depicts a mobile-originated call setup procedure as defined in release a of the cdma2000 standard. In step 1, the mobile station sends an origination message 1 to the base station. The message indicates to the network that the mobile station user wants to make a call. It contains the dialed number and a service option number to indicate what type of call (i.e., voice, data, etc.). Also included in the message is a list of pilot signals from neighboring base stations that are received at the mobile station with sufficient strength so that the base station can determine which pilots to include in the active set.

In step 2, upon successful reception of the origination message 1, the base station transmits a base station acknowledgement order 2 to the mobile station. This message acknowledges receipt of the origination message 1.

In step 3, the base station sends a Connection Management (CM) service request message 3 to the MSC, which triggers the MSC to perform call setup. The message contains the relevant information in the origination message 1 received from the mobile station.

The MSC responds to the base station with an allocation request message 4 in step 4. The message instructs the base station to establish a radio channel. However, the base station may choose to set up the radio channel upon receiving the origination message 1.

It is noted that in this figure, as well as the figures described below, the order of transmission of the assignment request message 4 from the MSC to the base station is flexible with respect to the transmission of other messages. There are some rules that limit this flexibility. After the MSC receives the CM service request message 3 (for mobile-originated call setup) or the page response message 25 (for mobile-terminated call setup, described below), an assignment request message 4 is sent from the MSC to the base station. The allocation request message 4 arrives before the base station sends a service connect message 10 to the mobile station, as described below.

In step 5, the base station transmits a channel assignment message 5 to the mobile station. The standard also defines an extended channel assignment message. As defined herein, channel assignment message 5 represents any message. The message assigns a dedicated physical channel to the mobile station for carrying user traffic associated with the call. Which includes information about all pilots in the mobile station's active set. After this step, the mobile station enters the traffic state 450. A state diagram including this state and other states is described below in conjunction with fig. 4.

Upon receiving the channel assignment message 6, and after receiving two consecutive good frames on the forward link, the mobile station transmits a preamble to the base station to assist the base station in acquiring the reverse link signal from the mobile station, step 6. Once the reverse link is obtained, the base station transmits a base station acknowledgement order 7 to the mobile station in step 7. Upon receipt of the base station acknowledgement order 7, the mobile station sends a mobile station acknowledgement order 8 to the base station at step 8 to indicate that the mobile station has acquired the forward link of the base station transmission.

Dedicated physical channels have now been successfully established. In step 9, a service negotiation procedure between the mobile station and the base station is performed to determine the format of the information transmission. The negotiation items include frame rate, frame type, transmission rate, and traffic type (i.e., voice or data, if available, vocoder rate). Some of the entries are specified by the base station and therefore are not negotiable (e.g., mapping of logical channels to physical channels). The negotiation may involve multiple exchanges of service request messages and service response messages between the mobile station and the base station. The exchanged messages are included in the service configuration information record. The final negotiation message is a service connect message 10 sent from the base station to the mobile station at step 10. A service configuration information record and a non-negotiable service configuration information record are also sent. The standard also allows sending no service connect message but a general handover direction message or a general handover direction message in case a radio handover has to be done when service negotiation takes place.

In some instances, the service negotiation step 9 may be avoided. If the mobile station is to use a previously stored service configuration, the base station simply sends a service connect message 10 at step 10 indicating that the previously stored service configuration is to be used. In this standard, this corresponds to setting the USE _ OLD _ SERV _ CONFIG flag to '01'.

Upon receiving the service connect message 10, the mobile station sends a service connect complete message 11 to the base station indicating that it has received the proposed service configuration, step 11. Upon receiving the service connect complete message 11, the base station sends an assignment complete message 12 to the MSC to indicate that the base station has successfully established the call at step 12.

After step 10, the service connect message 10, i.e. the service configuration specified by the message, is validated. Call setup is now complete and there may be a flow of user traffic (i.e., voice or data) between the mobile station and the base station. After the assignment complete message 12 at step 12, traffic may flow between the base station and the MSC (for voice calls) or between the base station and the PDSN (for packet data calls).

Fig. 2 depicts a mobile terminated call setup procedure as in release a of the cdma2000 standard. First, the MSC sends a paging request message 21 to the base station to indicate that a call is incoming to the mobile station. Second, a general page message 22 is sent from the base station to the mobile station. The standard also identifies general page messages that function similarly to general page message 22, and the latter term is used throughout to refer to either of the two messages. The message may be sent in one or more sectors. The message indicates to the base station that it is receiving a call and that the service option number corresponds to the call.

Third, upon receiving the general page message 22, the mobile station sends a page response message 23 to the base station, which includes a pilot list, similar to that described above in the origination message 1, so that the base station can determine the appropriate active set. Fourth, upon successful receipt of the page response message 23, the BS sends a base station acknowledgement order 2 to the mobile station, as described above in relation to fig. 1, step 2. Which acknowledges receipt of the page response message 23.

Fifth, the base station sends a page response message 25 to the MSC, which triggers the MSC to set up the call. The successive steps shown in fig. 2 correspond to the same numbered steps and messages described above in relation to steps 4 to 12 of fig. 1.

Each step in the call setup process described above creates a call setup latency. Call setup latency, i.e., the time required for call setup, is an increasingly important factor in the design of wireless systems as data usage becomes more prevalent. Modern wireless data communication systems provide "always-on" connectivity. Those skilled in the art of packet-switched network design know that "always-on" connectivity does not mean that the physical channel is always dedicated to a particular user. This may be band inefficient and may not be cost effective for the subscriber. Conversely, when the mobile station is engaged in data communication, a call is established to enable one or more packets to be transmitted, and then the call is terminated to free up the channel for use by other users. In a typical data communication session, calls may be repeatedly established and terminated, with call setup latency for each call. Naturally, reducing call latency is not only important below voice communications, but also for the user experience of wireless data users.

Each of the steps described above introduces latency, partly due to the time required to transmit each message, and partly due to the processing time required to receive each message and determine the appropriate next step. In addition, much of the call setup signaling occurs on common channels that are shared by multiple mobile stations and base stations. Thus, a call setup latency component is introduced when the mobile station must make repeated attempts to acquire access to a common channel (referred to as an access channel). In addition, messages for a particular mobile station may be queued with other mobile station messages, which is another source of latency for implementing the steps described above. Thus, reducing the number of steps in the call setup process is an effective way to reduce latency while reducing the transmission and/or processing time associated with any remaining messages.

An example of a reduced latency call setup procedure is defined in the HDR specification, which is depicted in fig. 3. Such a SYSTEM is disclosed in U.S. patent application Ser. No. 09/707569, entitled "METHOD AND APPARATUS FOR ADAPTIVE TRANSMISSION CONTROL IN A HIGH DATA RATICOMMUNICATION SYSTEM", filed on 11/6/2000, assigned to the assignee of the present invention and incorporated herein by reference.

Fig. 3 depicts the mobile station aborting the call setup procedure, with reduced steps compared to that depicted in fig. 2. Steps 2 to 4, which correspond substantially to messages 22, 23 and 2, respectively, of figure 2, are removed. Instead of the base station sending a general page message 22 to the mobile station in response to the page request message 21 from the MSC, the base station now sends a modified channel assignment message 30. The channel assignment message 30 replaces the general paging message 22 (step 2 of fig. 2) and the channel assignment message 5 (step 7 of fig. 2). This eliminates the need for the page response message 23 (step 3 in fig. 2) and the base station acknowledgement order 2 (step 4 in fig. 2). The removal of these three steps significantly reduces call setup latency.

The steps of the process of fig. 3 are as follows. First, the MSC transmits a base station paging request message 21. In response, the base station sends a channel assignment message 30 to the mobile station identified in the page response message 21, as just described. The mobile station enters the traffic state 450 upon receiving the message. After two consecutive good frames are received on the forward link, the mobile station transmits a preamble 6 to the base station. The base station acknowledges the acquisition of the preamble 6 by sending a base station acknowledgement order 7 to the mobile station. In response, the mobile station sends a mobile station acknowledgement order 8 to the base station. The base station sends a page response message 25 to the MSC to trigger the MSC to set up the call. An assignment request message is communicated from the MSC to the base station. Allocation negotiation 9 then takes place unless there is an indication to USE the previously stored service configuration (i.e. set USE _ OLD _ SERV _ CONFIG to '01'). A service connect message 10 is sent from the base station to the mobile station to end any negotiation. The mobile station 11 receives the service connect message 10 with the service connect complete message. The base station lets the MSC know that the call is established with an assignment complete message 12.

After the service connect message 10, the service configuration specified by the message is validated. Call setup is now complete and user traffic (i.e., voice or data) between the mobile station and the base station may flow. As described above in relation to fig. 1, traffic also flows between the base station and the MSC (for voice calls) or between the base station and the PDSN (for packet data calls) following the assignment complete message 12 at step 12.

Fig. 4 depicts a mobile station state diagram. The states shown are general states useful for describing call setup and do not represent every state that a mobile station can enter. Additionally, not all possible state transitions are shown. But rather illustrate a useful subset for describing various aspects of the present invention. State 410 is a power on state that is entered when the mobile station is powered on. The mobile station then proceeds to an initial state 420 in which the mobile station attempts to acquire a system. Once the system timing for at least one base station is obtained, the mobile station enters an idle state 430 where it monitors the paging channel for any messages directed to it, such as general paging messages 22 or channel assignment messages 30 as described above.

From the idle state 430, the mobile station may enter the system access state 440 for a variety of reasons. When a mobile station wishes to communicate with a base station on an access channel (shared among multiple mobile stations), the system enters an access state. Another reason for entering the system access state and communicating on the access channel is that the mobile station has entered a new cell border or has just been powered on and needs to register its location with the base station. Another reason is to respond to the general page message 22 or the channel assignment message 30, as described above (for mobile terminated calls). The third reason is to send an origination message 1, as described above (for a mobile originated call). If a call setup procedure is initiated, the mobile station enters the traffic channel 450 after a successful call setup, as described above. This state is depicted in fig. 1-3.

When registration is complete (and call setup is not initiated), the mobile station leaves the system access state 440 to re-enter the idle state 430, the message is complete, it is not required that the mobile station remain in the access state, the mobile station cannot access the common access channel (for reasons including congestion due to access by other mobile stations) or when the base station cannot acknowledge the transmitted message. In addition, an access failure or a failure to receive an acknowledgement may cause the mobile station to revert to the initial state 420, depending on how the system is designed. It may be that after these failure events, it is better to attempt to acquire a different base station rather than make additional attempts at the unresponsive base station.

The idle state 430 transitions to the initial state 420 when: when the mobile station is unable to receive a page (meaning that a new base station may be acquired) or the mobile station is directed to perform an idle handoff (i.e., directed to cease monitoring the common channels of the current base station but instead to acquire the common channels of the neighboring base stations).

Useful within a wireless communication system is a Short Data Burst (SDB) feature. This enables small packets of information to be encapsulated within messages from the mobile station to the base station on the access channel. Thus, a full call setup is not required, as the traffic state is never entered. Such SDB features are specified in cdma 2000. The SDB process proceeds as follows. From the system access state, the mobile station sends a data burst message to the base station, the message including the SDB information packet. The base station sends an Application Data Delivery Service (ADDS) transfer message to the MSC that includes the SDB information packet and application layer information (i.e., identifying the packet type, such as SDB, Short Message Service (SMS), location fix, etc.). The base station acknowledges the data burst message by sending a base station acknowledgement order to the mobile station. The MSC (or PDSN) routes the packet data accordingly.

An example of the use of SDB is when Internet Protocol (IP) packets are encapsulated within SDB information. In this case, the MSC or PDSN may route the packet to some destination on the internet or intranet, possibly an application server. In some instances, SDB packets sent to an application server may be used to initiate data communication between the server and the mobile station, which may eventually require a traffic channel to be established to continue communication. In this case, the SDB message is followed by a complete call setup procedure, such as that described in fig. 1. And as noted above, continued communication between the application server and the mobile station may involve multiple call setups, which is a result of the nature of packet data communication. This example serves to further illustrate the need to minimize call setup latency.

As described above, call setup latency results from the transmission of multiple messages and corresponding acknowledgements, the length of each message, and the associated processing required for each message. Call setup latency is a cause of undesirable delays in many communication applications, such as voice communications and data communications. The delay introduced is typically exacerbated for the case of data, when multiple calls must be established during a communication session. There is therefore a need for a method of minimizing call setup latency in a communication system.

Disclosure of Invention

Embodiments disclosed herein address the need for a communication system that minimizes call setup latency. In an aspect, a channel assignment message is sent along with a flag to direct the use of previously negotiated service parameters. This aspect eliminates the need for service negotiation messages. In another aspect, a channel assignment message is sent along with an active set identifier instead of the active set and its parameters. This aspect reduces the transmission time of the channel assignment message. In another aspect, call setup without paging is simplified by the mobile station sending a pilot strength measurement message between active communication sessions so that the channel assignment message can be used for mobile station terminated call setup without the need for mobile station paging and related messages. In another aspect, the mobile station may send short data burst information and initiate call setup by sending an origination message containing the short data burst information. This aspect enables call setup to follow after a short data burst message without requiring additional messages. In another aspect, a reconnect message is sent to activate a dormant packet data call. This aspect reduces transmission time and message error rate, particularly when the reconnect message can be contained within a single frame. In the other aspect, the preamble is transmitted on the reverse link just after the channel assignment message. This aspect eliminates call latency introduced by waiting for forward link conditions before the preamble sequence is sent. Various other aspects of the invention are also shown. These aspects together have the following benefits: reducing message transmission time, reducing the number of messages sent, reducing associated processing requirements and increasing flexibility, the overall result is reduced call setup latency.

The present invention provides methods and system elements that implement various aspects, embodiments, and features of the present invention described in detail below.

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 depicts a mobile originated call setup procedure;

FIG. 2 depicts a mobile terminated call setup procedure;

FIG. 3 depicts a mobile terminated call setup procedure without paging;

FIG. 4 is a mobile station state diagram;

fig. 5 is a wireless communication system that supports multiple users and in which various aspects of the present invention may be implemented;

FIG. 6 depicts a method for updating pilot strength information between calls to enable call setup without paging;

FIG. 7 depicts another method for updating pilot strength information to enable call setup without paging;

FIG. 8 is a process for implementing mobility suspend or initiate call setup without using a service negotiation message;

fig. 9 depicts a method for simultaneously sending short data burst information and initiating a call;

FIG. 10 depicts a method for associating an active set identifier with an active set;

FIG. 11 depicts a method of reducing the length of a channel assignment message using an active set identifier;

fig. 12 depicts a method for a mobile station initiating a reconnection for an dormant packet data call;

fig. 13 depicts a mobile-terminated reconnection method for an dormant packet data call; and

fig. 14 depicts a method of immediately transmitting a preamble in response to a channel assignment message.

Detailed Description

Fig. 5 is an illustration of a wireless communication system 100 that supports multiple users and in which various aspects of the invention may be implemented. System 100 may be designed to support one or more standards and/or designs (e.g., IS-95 standard, cdma2000 standard, HDR specification). For simplicity, system 100 is shown to include three base stations 304 in communication with three mobile stations 106. The base station and its coverage area are often collectively referred to as a "cell". Each base station 104 communicates with an MSC or PDSN 102. The MSC or PDSN 102 may be in communication with a network, such as the Public Switched Telephone Network (PSTN), the Internet, or an intranet (not shown).

For mobile terminated calls, release a of the cdma2000 standard requires that the mobile must first be paged (either via a general page message or a general page message). However, when the mobile station transmits a page response message from the system access state, the base station may transmit a channel assignment (through a channel assignment message). The mobile station monitors the paging channel while waiting for channel allocation in the system access state.

As described above with reference to fig. 3, the enhancements allow the base station to bypass paging and instead send channel assignments directly to idle-state mobile stations. This has two benefits: it eliminates the need to send a general page message (general page message) to the mobile station and it also eliminates a time-consuming access attempt by the mobile station (to send a page response message). The net effect is to reduce call setup latency.

There are several reasons, however, to page a mobile station prior to channel assignment. One reason is to receive a pilot report within the page response message, which can be used to determine the active set. In some examples, however, it may be that the previously used active set is sufficient to maintain the call, such as when the elapsed time since the mobile station was last on the active channel is small. For these cases where an update is needed, an alternative paging approach may be used. The following are two ways of providing information for updating the active set in response to changes that occur between successive traffic channel operations.

One embodiment is depicted in fig. 6. The mobile station is in the idle state 430 when it determines that an update is needed. For example, the mobile station may determine that pilots need to be added to the active set. It proceeds to the system access state 440 and sends a Pilot Strength Measurement Message (PSMM)610 to the base station. After sending the message, the mobile station returns to the idle state 430. PSMM610 contains the information needed by the base station to update the active set (i.e., the strength of the pilots seen by the mobile station). Later, the base station is free to effect call setup as described in fig. 3, since the required base station will be in the updated active set. To reduce signaling on the access channel, PSMM610 need not be transmitted in order to remove a member from the active set, since a larger active set does not prevent successful communication. Once the mobile station is assigned to the traffic channel, the mobile station may send a signal on the traffic channel to the base station to remove members from the active set. Another way to control excessive access channel signaling is to have the PSMM610 update procedure only on a subset of mobile stations at a time.

Another embodiment avoids adding additional signaling to the access channel, thereby reducing the average access delay, but at the cost of increased maximum delay. In this embodiment, depicted by fig. 7, the active set is not updated between successive mobile station traffic channel operations. To initiate a new call, the base station sends a channel assignment message 30 to the mobile station, as described by the process of fig. 3. In decision block 710, the mobile station determines whether the current active set is correct. If so, the call setup process continues in block 750. When the likelihood that the active set remains the same across multiple calls is large as described above, then often the call setup process will proceed without added delay and avoid the additional channel signaling that the embodiment of fig. 6 may introduce.

In the event that the active set does not need to be updated, then the mobile station will proceed to transmit the PSMM720 to the base station on the access channel in decision block 710. PSMM720 may contain information similar to PSMM 610. In block 730, the base station reconfigures the active set and then sends an updated channel assignment message 740 to the mobile station, and call setup may continue in block 750. The additional signaling described in blocks 720 through 740 introduces additional delay compared to the setup process of fig. 3.

The system designer may use the embodiment of fig. 6, the embodiment of fig. 7, or a combination of both as desired to minimize the total call setup latency based on the likelihood of the active set change. As mentioned, the additional signaling over the access channel described in fig. 6 may be traded off against the possible increase in maximum call setup time (but decrease in average call setup time) of fig. 7. This approach may be used to reduce the average access time when the active set is more likely to be correct. However, the maximum average latency may increase (for the case where the active set has to be updated).

As an example, the base station may cause the mobile station to perform the process of fig. 6, roaming of these base stations introduces many variations in the received pilot strength of each neighboring base station, and may also disable the process of fig. 6, and the occasional increased maximum delay of fig. 7 may be selected when the subscriber unit is stationary or not moving often. Another option is that the base station may determine which call setup procedure to use based on the elapsed time since the previous mobile station access. If the elapsed time is small, it is likely that the mobile station is located in the same sector, a reduced latency procedure such as that described in fig. 3, 6 or 7 is used. If the elapsed time is greater than some threshold, the base station may decide to use a call setup procedure that includes paging, such as described in FIG. 2.

In release a of the cdma2000 standard, the page response message 23 is also used to send a verification value AUTH _ R. Authentication of the mobile station is achieved by implementing an authentication algorithm for generating AUTH _ R by a secret key and a random number shared between the base station and the mobile station. AUTH _ R is calculated in both the mobile station and the base station must receive the matching AUTH _ R from the mobile station to ensure the authenticity of the mobile station. Naturally, if the page response message 23 is omitted, other mechanisms must be introduced to send AUTH _ R for verification. One method is for the mobile station to send AUTH _ R on the traffic channel. Since the calculation of AUTH _ R may take some time, an additional benefit of this method is that the calculation can be made in parallel with the rest of the call setup process. The validation response is sent on the traffic channel once call setup is complete. It is worth noting that since user traffic cannot flow before the service connect message is sent, if the authentication on the traffic channel fails, the call is released immediately. This technique allows channel allocation without paging, thus reducing call setup latency.

In release a of the cdma2000 system, each time a dedicated channel is established for the purpose of establishing a call, the mobile station and the base station must agree on service configuration parameters (through service negotiations) that are used to exchange user and signaling information. As described above, releasing the dedicated channel and entering the idle state allows the mobile station and the base station to store agreed upon service configurations (i.e., service configuration information records and non-negotiated service configuration information records) together. These stored configurations can be restored upon re-establishment of the dedicated channel, thereby avoiding service negotiation. This reduces call setup latency. However, release a still requires that, upon establishing the dedicated traffic channel, the base station sends a service connect message instructing the mobile station to use the stored service configuration. The service connect message belongs to the class of service negotiation messages.

Fig. 8 depicts an embodiment of a call setup procedure that omits the service negotiation message, thereby reducing call setup latency. In this embodiment, the USE _ OLD _ SERV _ CONFIG flag (described above) is included in the channel assignment message 810. When the flag is set to '01', then the negotiation step (i.e., step 9 of fig. 1-3) is not required. In addition, since the flag is included in the channel assignment message 810, a service connect message and a service connect complete message (10 and 11, respectively, of fig. 1 to 3) are also omitted. In addition to the reduction in latency associated with eliminating the sending of these messages, the processing time associated therewith is also eliminated. Another benefit is that the mobile station and base station can immediately resume service configuration and begin exchanging user traffic once the dedicated traffic channel is established. The net effect is to reduce call setup latency.

The following is a more detailed description of the method of the embodiment described in FIG. 8. This embodiment is applicable to mobile-originated or mobile-terminated call setup procedures. In a first step, an origination message 1 or a page response message 23 is sent from the mobile station to the base station, depending on whether the call is mobile originated or mobile terminated, respectively. The base station responds by sending a base station acknowledge command 2 to the mobile station. The base station then sends either a connection management service request message 3 or a page response message 25 to the MSC depending on whether the call was mobile originated or mobile terminated, respectively. The base station then sends a channel assignment message 810 to the mobile station, which includes the USE _ OLD _ SERV _ CONFIG flag. The flag is set when the base station wishes to avoid the service negotiation step and has determined that the previously stored configuration may be sufficient. After this step, the mobile station enters the traffic state 450.

The remaining steps are similar to the call setup procedure described previously except for the removal of the service negotiation step as just described. Upon successive reception of two good frames on the forward link, the mobile station starts transmitting a preamble 6 to the base station. The MSC sends an allocation request message 4 to the base station. (the order in which the MSC sends the allocation request message 4 is not important because the previous configuration is being re-established.) the base station sends a base station acknowledgement order 7 to the mobile station. The mobile station responds to the base station with a mobile station acknowledge command 8 at which time traffic begins to flow between the base station and the mobile station. Finally, the base station reports an assignment complete message 12 to the MSC (at which time traffic begins to flow between the base station and the mobile station).

In the call setup procedure specified in release a, an assignment complete message 12 is sent from the base station to the MSC only upon receiving a service connection complete message 11 from the mobile station. In the embodiment of fig. 8, however, the assignment complete message 12 may be sent to the MSC when the dedicated channel or channels are established and an MS acknowledgment order is received from the mobile station. Thus, network-side connection establishment can occur somewhat in parallel with air interface connection establishment, thus reducing call setup latency.

In some cases, it may be desirable for the mobile station to discard a previously stored service configuration once it determines that service negotiation is required. For example, release a specifies an early channel allocation feature in which the base station responds to an origination message by randomly allocating channels to the mobile stations. If the channel assignment message 810 is used, the base station may not yet know whether the old service configuration can be used when the message is sent. In this case, the mobile station can retain the previous configuration information, since the service connect message 10 containing the USE _ OLD _ SERV _ CONFIG ═ 01' flag may arrive and service negotiation 9 may be avoided. One way to address this situation is for the mobile station to retain the stored previous configuration even when it receives the channel assignment message 810 and the flag is not set to use the previous configuration. The move discards previous data only when service negotiation begins.

Another approach is to add additional value to the USE _ OLD _ SERV _ CONFIG flag. For example, if the channel assignment message 810 is sent with a flag indicating that the previously stored configuration is valid, it is clear that the mobile station will not discard it. This situation does not occur when the mobile station does not know whether the previous configuration is valid. In this case, an additional flag value may be sent to indicate that it is not yet known whether the previous configuration is valid. At this point, the mobile station will retain the data and wait until service negotiation is needed to discard it. Finally, when this is not an early channel assignment, and the base station knows that the previous configuration is no longer valid, a flag value may be sent to indicate that the mobile station is free to drop data because service negotiation is required.

Another embodiment addresses call setup latency with a Short Data Burst (SDB) feature, as described above. There are applications where a mobile station needs to send a large amount of information over the air and therefore needs to establish a dedicated channel to carry data. This of course would require a call setup procedure. As described above, SDB provides a mechanism to send small amounts of data over a shared channel without effecting a full call setup.

To expedite the initiation of operation on the network side, the mobile station can first send a small amount of information on the common channel (to trigger network operation) using the SDB feature. Then, a dedicated channel or channels are established to transmit a large amount of data. Following the procedure defined in release a, the next step would require one common channel access and the subsequent transmission of a data burst message, followed by another access and the transmission of a subsequent origination message. I.e. two time-consuming access attempts may be required.

In the embodiment of fig. 9, the mobile station may simultaneously begin the call setup process and implement SDB by including SDB information in an origination message 910 that arrives at the base station to establish a dedicated channel. The base station then sends an Application Data Delivery Service (ADDS) delivery/CM service request message 920 that includes the SDB information and a data type indication identifying the data as SDB. In addition, the function of the CM service request message may be included in the message to omit an additional message on the network. Call setup then proceeds in block 930 according to one of the methods described above.

Thus, when the origination message access is successful, the network can forward the SDB content to the appropriate network entity while the remaining dedicated traffic channel setup is still in progress. This has several advantages. This removes the need for additional time consuming access attempts and removes ADDS transfer messages between the base station and the MSC. Network operation and establishment of the air interface dedicated channel occur in parallel. Processing within the mobile station is simplified. The net effect is to reduce call setup latency.

Another approach is to create an origination message that includes a request to recover a previous service configuration and deliver SDB information. It will be clear to those skilled in the art that these methods can be used with any of the call set-up procedures described above.

In a further embodiment depicted in fig. 12, a shorter version of the origination message is used, referred to herein as a reconnect message 1230, which carries the minimum fields needed to reconnect the dormant packet data call. The number of such fields is relatively small, as detailed below. This reconnect message 1230 can be used in place of the page response message 23 for the network initiated reconnection case for dormant calls. It is noted that current origination messages such as 1 or 910 or page response message 23 may still be used when a larger set of fields is needed.

A packet data call may be described using three states: empty, resting, and active. A packet data connection may last indefinitely, although it may change state frequently. When a packet data connection is first established, it is established from an empty state. Similar to establishing a voice call, all relevant parameters must be negotiated and agreed to. Once the call is established, it enters the active state, similar to the traffic state described above. In the active state, a physical channel is established and data flows between the mobile station and the base station. Packet data connections often need not be active because there is no data flow in both directions. At this point, the physical channel is released and the packet data call may go dormant.

When the packet data connection is dormant, service configuration information may be stored simultaneously in the mobile station and the base station. In addition, the protocol states are also stored in the mobile station and PDSN. For example, if point-to-point protocol (PPP) is used, its state, such as IP address, remains unchanged when the call goes from active to dormant. Only the physical channel itself needs to be released to free up resources for other users. Thus, when reconnecting a dormant call, only a small subset of the fields in the origination message are needed. As packet data calls increase, the percentage of call setup originations within the system are associated with bringing dormant packet data services back to an active state.

Version a originated messages are designed to initiate a variety of call types including voice, circuit switched data, packet switched data, and the like. Thus, it contains fields that are a superset of the fields required for each type of call setup. With respect to reconnecting dormant packet data calls, the fields within the origination message may be divided into three categories: not required, may be required or required. An example of fields that are not needed is specific to a voice call. In some cases, certain parameters have been negotiated in a previous call setup, so these are examples of fields that may not be needed. The SYNC _ ID field is an example of a field that is required because it indicates that a stored set of parameters is to be used. As can be seen, the reconnect message 1230 with these unwanted fields removed is much smaller than the version a originated message.

When using this embodiment, the reconnect message 1230 may be sent often within a single frame, resulting in multiple benefits. One benefit is to reduce transmission time. Another benefit is that the message error rate is reduced, i.e. now equal to the frame error rate. These benefits reduce call setup latency associated with reconnecting dormant packet calls.

Fig. 12 depicts an embodiment in which a mobile station initiates a dormant call reconnection. At step 1210, a previous packet data call is established, whether from a null state or from a dormant state reconnection. The call goes from active to dormant in step 1220. When the mobile station determines that the call should be reconnected, it sends a reconnect message 1230 to the base station that contains the minimum number of fields needed to reestablish the connection, as described above. This message replaces the original message (such as 1 or 910, as described above with respect to fig. 1 and 9, respectively). After sending the reconnect message 1230, call setup continues at step 1240 according to an embodiment disclosed herein.

Fig. 13 depicts an embodiment in which a mobile station suspends dormant call reconnection. Steps 1210 to 1240 are the same as the steps just described in fig. 12, except that the base station initiates the call, inserted between the inactivity 1220 and the reconnect message 1230 at step 1300. According to one procedure disclosed herein, the base station initiates reconnection of the call at step 1300, and the mobile station responds with a reconnection message 1230 instead of the page response message 23 described above.

Another embodiment addresses call latency introduced by the length of the channel assignment message, such as channel assignment message 5, 30, or 810 described above. In release a of the cdma2000 standard, each time a dedicated channel is established via a channel assignment message, the base station must indicate the complete active set in the message. The active set includes the number of pilots and the parameters required for each pilot, which includes the following: a pilot PN sequence offset index, a pilot record corresponding to the pilot type, a power control symbol combination indicator, a code channel index for the fundamental channel, a quasi-orthogonal function mask identifier for the fundamental channel, a code channel index for the dedicated control channel, and a quasi-orthogonal function mask identifier for the dedicated control channel. The pilot frequency recording comprises the following steps: transmit Diversity (TD) transmit power level, transmit diversity mode, Walsh code for the auxiliary/transmit diversity pilot, quasi-orthogonal function index for the auxiliary/transmit diversity pilot, and auxiliary transmit diversity pilot power level. These parameters will eventually have many bits. Each of these parameters may introduce latency caused by the time required to transmit them (if they result in the message extending to the next frame) and the processing time of the mobile station to process them.

The embodiments described in fig. 10 and 11 that include the method use the active set identifier to identify the active set and associated parameters. Instead of specifying a complete member list and active set parameters such as those described above, the base station may simply specify an active set identifier corresponding to a particular configuration. The technique can reduce the length of the channel allocation message and has the following advantages: the channel allocation message transmission time is reduced and the probability of erroneous reception of the channel allocation message is reduced. The net effect is to reduce the latency of call setup. Note that since some active set parameters may change, another approach is for the base station to send the active set identifier plus these changed parameters. This embodiment increases flexibility and may have a wider variety of applications.

The embodiments just described may include the methods described in fig. 10 or 11, or both. The method of FIG. 10 describes a method of assigning an active set identifier to a particular active set. In block 1000, a call setup procedure is performed. The base station then sends a channel assignment message 1010 including the full active set and parameters to the mobile station. In addition, the channel assignment message 1010 includes an active set identifier, which the mobile station can associate with the active set. In block 1020, the call setup process continues. Another method of assigning active set identifiers to the active set is for the base station to download such active set/active set identifier pairs to the mobile station before using them in the communication.

FIG. 11 depicts a method of utilizing active set identifiers once they have been assigned to an active set, using a method such as that described in FIG. 10. In block 1100, call setup is performed. The base station sends a channel assignment message 1110 including the active set identifier to the mobile station. Since the mobile station is aware of the members of the active set and the corresponding parameters for each member of the active set identifier, the active set identifier is sufficient to enable channel allocation. Alternatively, if the parameters associated with the active set identifier change, the message 1100 may contain the active set identifier along with the changed parameters. The call setup process continues in block 1120. The mobile station and base station can ensure that the active set configuration and its corresponding active set identifier are synchronized between the mobile station and base station using the mechanism specified in the cdma2000 standard for validating the SYNC _ ID, which is a method of recovering the stored service configuration.

Similar techniques may be used in conjunction with the methods described in fig. 6 and 7 to reduce the corresponding message lengths of PSMM610 and PSMM 720. A pilot identifier may be associated with each of a plurality of pilot configurations such that only the identifier is to be transmitted when the mobile station updates the base station with the currently identified pilot configuration. This is unlikely because the pilot strength can take many values and therefore can be difficult to associate with the identifier.

Another approach is to assign an identifier (and its associated parameters) to each member of the active set. Using this technique, multiple identifiers may be included within the channel assignment message 1110 to represent multiple members. This provides a more granular approach, which results in a slightly longer message, but with greater flexibility, since a large number of active sets can be identified using a relatively small combination of stored member configurations. The base station may use a combination of the techniques just described. These techniques may be used in combination to reduce the total transmission time associated with each transmitted channel assignment message 1110. It will be clear to those skilled in the art that these methods can be used with any of the call setup procedures described herein. It is noted that the method may be used within a message containing an active set. Another example includes a generic handoff direction message, with which the message size can be reduced, thereby reducing the message error rate.

In another embodiment depicted in fig. 14, call setup latency may be reduced by immediately transmitting a preamble 6 in response to a channel assignment message (such as 5, 30, 810, 1010, or 1110 described above). Release a requires the mobile station to receive two consecutive good frames on the forward link before activating the reverse link and transmitting a preamble. If the mobile station does not receive two consecutive good frames within one second, it must abort the call setup. The minimum time a mobile station must wait before transmitting a preamble is 40 to 60 milliseconds, since two frames correspond to 40ms and waiting at the frame boundary takes 0 to 20 ms.

In this embodiment, call setup is performed in step 1400. The base station then sends a channel assignment message, labeled 5 in fig. 15, but could be any channel assignment message such as 30, 810, 1010, or 1110, as described above. In response, the mobile station immediately establishes the reverse link and begins transmitting preamble 1410 without waiting for a good frame to be received on the forward link. Call setup then continues in step 1420 according to various call setup procedures, such as those described herein. The mobile station can continue to monitor the forward link for good frames and can terminate the call if a number of good frames are not received within a predetermined time frame. For example, the mobile station can wait within one second for two consecutive good frames, as described in release a. Or to reduce interference to other users, the mobile station can turn off the preamble if the requisite number of good frames have not been received within a predetermined time period. This time period may be shorter than the time period during which good frames are allowed to arrive. Thus, if the need for a good frame is not met for the first time period, the mobile station stops transmitting the preamble but continues to monitor for a good frame on the forward link for the second time period. If a final good frame arrives, the mobile station may send a preamble in response. This other technique may be used to reduce interference to other users when good frames are either arriving too slowly or never arriving. It is noted that in any of the embodiments disclosed herein, preamble 1410 may be replaced with the preamble of step 6.

In contrast to the method of release a, the mobile station may transmit on the reverse link for at least some time, even though the call may eventually be dropped. In these cases, the interference level to other users may increase slightly, along with its deteriorating effect with increasing other users interference. However, in many cases, the probability of receiving good frames on the forward link is still high, and using this embodiment reduces call latency and can obtain the attendant benefits beyond the degrading effects that sometimes can be caused by establishing a reverse link for an incomplete call.

It is noted that in all the embodiments described above, method steps may be interchanged without departing from the scope of the invention.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, circuits, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. The skilled person will recognize the interactivity of the hardware and software in these cases and how best to implement the described functionality for each particular application. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The implementation or execution of the various illustrative logical blocks, modules, and circuits may perform the functions described above with the following elements: a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or a combination of any of the above. A general purpose processor is preferably a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, or one or more microprocessors in conjunction with a DSP core or any other configuration.

The steps of a method or algorithm described herein in connection with the embodiments disclosed may be embodied directly in the steps of: hardware, a software module executed by a processor, or a combination of both. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. Or the storage medium may be integral to the processor. The processor and the storage medium may reside in an application specific integrated circuit, ASIC. The ASIC may reside in a user terminal. In addition, the processor and the storage medium may reside as discrete components in a user terminal.

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 (11)

1. A method for call setup in a wireless communication system, comprising:

a channel allocation message is transmitted from the first station to the second station to direct the use of the previously negotiated service parameters, the channel allocation message including a flag indicating whether the previously stored configuration is valid.

2. The method of claim 1, wherein the channel assignment message further includes an active set identifier associated with the active set and parameters of the active set.

3. The method of claim 2, wherein the channel assignment message is sent in response to an origination message from the mobile station.

4. The method of claim 3, wherein the origination message comprises short data burst information.

5. The method of claim 1, wherein the channel assignment message is transmitted in response to a paging sequence.

6. The method of claim 1 wherein said channel assignment message is sent to initiate a call without paging in response to a page request message from a Mobile Switching Center (MSC).

7. A wireless communication system, comprising:

a first station; and

a second station for transmitting a channel allocation message to the first station to direct use of the previously negotiated service parameters, the channel allocation message including a flag indicating whether the previously stored configuration is valid.

8. The apparatus of claim 7 wherein said channel assignment message includes a flag.

9. The method of claim 7, wherein the channel assignment message further includes an active set identifier associated with the active set and the parameters of the active set.

10. An apparatus for establishing a call in a wireless communication system, comprising:

a memory; and

a digital signal processor device communicatively coupled to the memory, the digital signal processor device capable of executing instructions to instruct the first station to transmit a channel assignment message to the second station to direct use of previously negotiated service parameters, the channel assignment message including a flag indicating whether a previously stored configuration is valid.

11. A wireless communication system, comprising:

first means for transmitting a signal; and

second means for transmitting a channel allocation message from the first station to the second station, said channel allocation message for directing use of previously negotiated service parameters, said channel allocation message comprising a flag indicating whether a previously stored configuration is valid.