Method and apparatus for call setup latency reduction

IS 2 390 000 T3

DESCRIPTION

Procedure and device to reduce the call set-up call

Countryside

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

Background

Wireless communication systems are widely used to provide various types of communications such as voice, data, and so on. These systems can be based on code division multiple access (CDMA), time division multiple access (TDMA), or some other modulation techniques. A CDMA system provides certain advantages over other types of systems, including an increase in system capacity.

A CDMA system may be designed to support one or more CDMA standards, such as (1) the mobile phone standard with spread spectrum “TIA / EIA-95-B Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System ”(the IS-95 standard), (2) the standard offered by a consortium called the“ 3rd Generation Partnership Project ”(3GPP) and embodied in a set of documents that includes Documents No. 3G TS 25.211, 3G TS 25.212 , 3G TS 25.213, and 3G TS 25.214 (the W-CDMA standard), (3) the standard offered by a consortium called “3rd Generation Partnership Project 2” (3GPP2) and embodied in a set of documents that include “C. S0002-A Physical Layer Standard for cdma2000 Spread Spectrum Systems ”,“ C. S0005-A Upper Layer (Layer3) Signaling Standard for cdma2000 Spread Spectrum Systems ”and“ C. S0024 cdma2000 High Rate Packet Data Air Interface Specification ”(the cdma2000 standard), and (4) some other standards.

Call setup is the process of establishing dedicated physical channels and negotiating service configuration parameters between a mobile station and a base station so that communication can take place. Call setup procedures are divided into two classes. Call setup initiated at the mobile station occurs when a user of a mobile station makes a call. Call setup completed by a mobile station occurs when a call is made to the mobile station.

Call setup procedures involve sending signals between a mobile switching center (MSC) or a packet data serving node (PDSN), one or more base stations (BS), and a mobile station (MS). As used herein, the term "base station" can be used interchangeably with the term "access point". The term "mobile station" may be used interchangeably with the terms "subscriber unit", "subscriber station", "access terminal", "remote terminal", or other corresponding terms known in the art.

The term "mobile station" encompasses fixed wireless applications. The signals from the mobile station are known as "reverse link", "reverse channel", or "reverse traffic". The signals that are directed to the mobile station are known as "direct link", "direct channel" or "direct traffic".

FIG. 1 represents a call setup procedure initiated at the mobile station as defined in Publication A of the cdma2000 standard. In step 1, the mobile station sends a Start Message 1 to the base station. This message indicates to the network that the user of a mobile station wants to make a call. Contains the dialed number and a service option number to indicate the type of call (ie voice, data, etc.). Also included in this message is a list of pilot signals from nearby base stations that have been received at the mobile station with sufficient power, so that the base station can determine which pilots to include in the active set.

In step 2, after successfully receiving Start Message 1, the base station sends a Base Station Acknowledgment Order 2 to the mobile station. This message confirms receipt of Start Message 1.

In step 3, the base station sends a Connection Management Service Request (CM) Message 3 to the MSC, which causes the MSC to set up the call. This message contains relevant information received from the mobile station in Start Message 1.

The MSC responds with an Assignment Request Message 4 to the base station in step 4. This message instructs the base station to establish the radio channel. However, the base station has the option to set the radio channel as soon as Start Message 1 is received.

IS 2 390 000 T3

Note that in this figure, as well as in the figures described below, the order in which the Assignment Request Message 4 is sent from the MSC to the base station in relation to other message submissions is somewhat flexible. There are rules that limit this flexibility. Assignment Request Message 4 will be sent from the MSC to the base station after the MSC receives CM Service Request Message 3 (for a call setup initiated at the mobile station) or Radio Message Response Message 25 (for a call setup completed at the mobile station, described below). Assignment Request Message 4 arrives before the base station sends Service Connect Message 10 to the mobile station, described below.

In step 5, the base station sends a Channel Assignment Message 5 to the mobile station. The standard also defines an Extended Channel Assignment Message. As defined herein, Extended Channel Assignment Message 5 represents either of the two messages. This message allocates a dedicated physical channel to the mobile station for the purpose of carrying user traffic associated with the call. It includes the relevant information for all pilots in the active set of the mobile station. After this step, the mobile station enters traffic state 450. A state diagram is detailed below with reference to FIG. 4 that includes that and other states.

In step 6, after receiving Channel Assignment Message 6, and after receiving two consecutive good frames on the forward link, the mobile station sends a preamble to the base station to help the station acquire reverse link signals. from the mobile station. Once the reverse link has been acquired, the base station sends the Base Station Acknowledgment Order 7 to the mobile station in step 7. Upon receiving the Base Station Acknowledgment Order 7, the mobile station sends the Mobile Station Acknowledgment Order 8 to the base station in step 8 to indicate that the mobile station has acquired the direct link that is being transmitted by the base station.

At that time the dedicated physical channels have been successfully established. In step 9, a service negotiation procedure takes place between the mobile station and the base station to determine the information transfer format. Examples of negotiated properties include frame rate, frame type, transmission rates, and traffic type (ie, voice or data, vocoder or speech coder rate, if applicable). Some properties are specified by the base station and therefore are not negotiable (eg 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 information exchanged is contained in a Service Configuration information record. The final negotiation message sent, in step 10, is a Service Connect Message 10 from the base station to the mobile station. Both the Service Configuration information record and a Non-Negotiable Service Configuration information record are sent. The standard also allows the Address Message of "Handoff" or General Transfer or the Address Message of "Handoff" or Universal Transfer to be sent instead of the Service Connection Message in situations where a radio transfer or " radio handoff ”while service negotiation is in progress.

Sometimes the negotiation of the service, step 9, can be avoided. If the mobile station is going to use a previously stored service configuration, the base station simply sends a Service Connection Message 10, step 10, with an indication to use the configuration. previously stored service. In the standard, this corresponds to setting the USE OLD SERV CONFIG flag to "01".

In step 11, after receiving the Service Connection Message 10, the mobile station sends a Service Connection Completion Message 11 to the base station to indicate that it has accepted the proposed service configuration. After receiving Service Connection Completion Message 11, in step 12, the base station sends an Assignment Completed Message 12 to the MSC to indicate that the base station has successfully established the call.

After step 10, Service Connection Message 10, the service configuration specified by the message becomes effective. At that time the call setup is completed and user traffic (ie, voice or data) can flow between the mobile station and the base station. Traffic will circulate between the base station and the MSC (for voice calls) or between the base station and the PDSN (for packet data calls) after step 12, Assignment Complete Message 12.

FIG. 2 depicts a call setup procedure completed at the mobile station as defined in Publication A of the cdma2000 standard. First, the MSC sends a Radio Message Request Message 21 to the base station to indicate that a call is coming in to the mobile station. Second, a General Radio Message 22 is sent from the base station to the mobile station. The standard also identifies a Universal Radio Message, whose function is similar to that of General Radio Message 22, and the last expression will be used throughout the document to indicate either message. This message can be sent by one or more sectors. This message indicates to the mobile station that it is receiving a call, and the Service Option number corresponding to the call.

IS 2 390 000 T3

Third, after receiving the General Radio Message 22, the mobile station sends a Response Radio Message 23 to the base station, which includes the list of pilots, similar to the one described in Start Message 1 above, so that the station basis can determine the appropriate active set. Fourth, after successfully receiving the Answer Radio Message 23, the base station or BS sends a Base Station Acknowledgment Order 2 to the mobile station, as described in step 2 with respect to FIG. 1 above. This message confirms the reception of the Reply Radio Message 23.

Fifth, the base station sends a Radio Message Response Message 25 to the MSC, which causes the MSC to set up the call. The subsequent steps shown in FIG. 2 correspond to the stages of the same numbering and to the messages described in stages 4 to 12 previously indicated with respect to FIG. 1.

Each stage in the call setup procedures just described contributes to the call setup latency. Call setup latency, or the time required to set up a call, is an increasingly important parameter in wireless system design as data usage is becoming more prevalent. Wireless modem data communication systems offer “always-on” connectivity. As is known to experts in packet-switched network design, "always-on" connectivity does not mean that a physical channel is permanently dedicated to a specific user. This would result in inefficient bandwidth and probably not profitable for subscribers. Instead, when a mobile station establishes a data communication, a call is established to allow the transmission of one or more packets, then the call is canceled to release the channel for another user. In a typical data communication session, calls will be established and dropped repeatedly, with a call setup latency on each call. Naturally, reducing call latency, in addition to being important in voice communications, is very important in providing a stimulating user experience to the wireless data user.

Each stage, described above, introduces a latency due in part to the time required to transmit each message, and in part due to the processing time required to receive each message and determine the next appropriate stage. Furthermore, much of the sending of call setup signals occurs on common channels that are shared by a number of mobile stations and a base station. As such, a call setup latency component is introduced when a mobile station must make repeated attempts to access the common channel (known as an access channel). Furthermore, it may be that a message for a particular mobile station has to wait in a message queue along with messages for other mobile stations, which represents yet another source of latency when carrying out the steps described above. Accordingly, reducing the number of stages in the call setup procedure is an effective means of reducing call latency, as is reducing the transmission and / or processing time associated with any pending messages.

An example of a reduced latency call setup procedure is defined in the HDR specification and is depicted in FIG. 3. Such a system is described in US patent application number 09 / 707,569 (PCT publication number WO 2002/037890, entitled "METHOD AND APPARATUS FOR ADAPTIVE TRANSMISSION CONTROL IN A HIGH DATA RATE COMMUNICATION SYSTEM", filed on November 6, 2,000, assigned to the owner of the present invention.

FIG. 3 depicts a call setup procedure completed at the mobile station with a reduced number of steps compared to the procedure described with respect to FIG. 2. Fundamentally, steps 2 through 4, corresponding to messages 22, 23, and 2 in FIG. 2, respectively. Instead of the base station sending the General Radio Message 22 to the mobile station in response to the Radio Message Request Message 21 from the MSC, the base station sends a modified Channel Assignment Message 30. Channel Assignment Message 30 replaces General Radio Message 22 (stage 2 in FIG. 2) and Channel Assignment Message 5 (stage 7 in FIG. 2). This eliminates the need for Response Radio Message 23 (step 3 in FIG. 2) and Base Station Acknowledgment Order 2 (stage 4 in FIG. 2). Eliminating these three stages significantly reduces call setup latency.

The steps of the method of FIG. 3 are as follows. First, the MSC sends the Radio Message Request Message 21 from the base station. In response, the base station sends to the mobile station identified in the Radio Message Request Message 21 a Channel Assignment Message 30, as just described. The mobile station enters traffic state 450 after receiving this message. After receiving two consecutive good frames on the forward link, the mobile station sends a preamble 6 to the base station. The base station confirms the acquisition of the preamble 6 by sending a Base Station Acknowledgment Order 7 to the mobile station. In response, the mobile station sends a Mobile Station Acknowledgment Order 8 to the base station. The base station sends the MSC a Radio Message Reply Message 25 to cause the MSC to set up the call. The Assignment Request message 4 is sent from the MSC to the base station. Negotiation service 9 takes place next, unless it is mitigated by an indication to use a previously stored service configuration (ie, by setting the USE OLD SERV CONFIG flag to "01"). The Service Connection Message 10 is sent from the base station to the mobile station to finish

IS 2 390 000 T3 all negotiation. The mobile station accepts the Service Connection Message 10 with a Service Connection Termination Message 11. The base station lets the MSC know that the call has been established with an Assignment Complete Message 12.

After Service Connection Message 10, the service configuration specified by the message becomes effective. At that point the call setup is terminated and user traffic (ie, voice or data) can flow between the mobile station and the base station. As described above with respect to FIG. 1, traffic will also circulate between the base station and the MSC (for voice calls) or between the base station and the PDSN (for packet data calls) after step 12, Assignment Complete Message 12.

FIG. 4 represents a state diagram of the mobile station. The states shown are general states useful for describing call setup, and do not represent all states that a mobile station may enter. Also, not all possible state transitions are shown. Rather, the subset useful for discussing the various aspects of the present invention is shown. State 410 is a startup state, which state a mobile station enters when it is turned on. The mobile station then goes to initialization state 420, in which the mobile station attempts to acquire a system. Once synchronization with the system is acquired for at least one base station, the mobile station enters the idle state 430, in which it monitors the paging channel for any messages addressed to it, such as the General Radio Message 22 or Channel Assignment Message 30, described above.

From the idle state 430, the mobile station may enter the system access state 440 for a number of reasons. The system access state is entered when the mobile station wishes to communicate over the access channel (shared among a plurality of mobile stations) to a base station. One reason for entering the system access state and communicating on the access channel is that a mobile station has entered a new cell boundary or has recently started up and needs to register its location with a base station. Another reason is to respond to a General Radio Message 22 or a Channel Assignment Message 30, previously described (for calls terminated by the mobile station). A third reason is to send a Start Message 1, described above (for calls initiated at the mobile station). If a call setup procedure is initiated, such as those described above, the mobile station enters traffic state 450 upon successful call setup. This state is referenced in FIGS. 1-3 above.

The mobile station allows re-entering the idle state 430 from the system access state 440 when a registration has been completed (and no call setup has been initiated), a message is completed that does not require the mobile station remains in the access state, the mobile station is unable to access the common access channel (for reasons including congestion due to access by other mobile stations), or when the base station fails to confirm receipt of a transmitted message. In addition, failure to access or failure to receive the acknowledgment may return the mobile station to the initialization state 420, depending on how the system is designed. It may be that after these failures, it is convenient to try to acquire a different base station instead of making additional attempts with a base station that is not responding.

It goes from idle state 430 to initialization state 420 when the mobile station is unable to receive paging (meaning it may be necessary to acquire a new base station), or the mobile station is directed to carry out a handover procedure. in idle mode called 'idle handoft' (ie directed to stop monitoring the common channel of the current base station and instead acquire the common channel of a nearby base station).

A useful feature in a wireless communication system are short messages of the SBD type (“Short Data Burst” or Short Data Burst). This allows a small information packet to be encapsulated in a message from a mobile station to a base station on the access channel. Therefore, a complete call setup is not required, since the traffic state is never entered. Such an SBD feature is specified in the cdma2000 standard. The SDB procedure is carried out as follows. From the system access state, a mobile station sends a Data Burst Message to the base station that includes the SDB information packet. The base station sends an Application Data Sending Service (ADDS) Transfer Message to the MSC, which includes the SDB information packet as well as the application layer information (i.e., packet type identification, such as example SDB, short message service (SMS), position location, and the like). The base station confirms the receipt of the Data Burst Message by sending an Acknowledgment Order from the Base Station to the mobile station. The MSC (or PDSN) routes the data packet accordingly.

An example of the use of SBD is when an Internet Protocol (IP) packet is encapsulated in the SBD information. In this case, the MSC or PDSN can route the packet to a destination on the Internet or an intranet, perhaps an application server. On some occasions, an SDB packet sent to an application server can serve to initiate data communication between the server and the mobile station which may ultimately require the establishment of a traffic channel for continuous communication. In these circumstances, the SDB message will be followed by a full call setup procedure as described in reference to

ES 2 390 000 T3 FIG. 1 and, as mentioned above, ongoing communication between the application server and the mobile station can involve numerous call set-ups, a consequence of the nature of packet data communication. This example serves to further highlight the need to minimize call setup latency.

As described above, the call setup latency is formed by the multiple message transmissions and corresponding acknowledgments, the length of each message, and the associated processing required on each message. Call setup latency is an undesirable cause of delay in many communications applications: voice communications as well as data communications. As multiple calls must be established during a communication session, a typical scenario with data, the delay introduced increases.

A method and procedure for re-establishing an interrupted packet data call in a telecommunications system is described in the state of the art document EP 0 872 982 A1. According to this procedure, if communication is interrupted or delayed, a release message is sent indicating that the call can be re-established from a part of a pair of transceiver devices. Either device can then initiate call reestablishment. Call reestablishment is accomplished using a call reestablishment message, where reestablishment is based on using a set of call setup data stored in the other part of the pair of transceiver devices.

International patent application WO 00/44133 A2 refers to instant activation of a point-to-point protocol (PPP) connection using a PPP state. A PPP state of a PPP session between a communication device and a network access server is not removed from the network access server after the session becomes idle and the PPP state is changed from the idle session to a new session when a new call establishment message arrives from the communications device.

Accordingly, there is a need in the art for communication systems that minimize call setup latency.

SUMMARY

The embodiments described herein address the need for communication systems that minimize call setup latency. According to one aspect, a channel assignment message is sent with an indicator to direct the use of previously negotiated service parameters. This aspect eliminates the need for service negotiation messages. According to another aspect, a channel assignment message is sent with an active set identifier corresponding to and instead of an active set and its parameters. This aspect reduces the transmission time of the channel assignment message with an overall result of a reduction in call setup latency.

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

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristics, nature, and advantages of the present invention will become apparent from the detailed description presented below when considered in conjunction with the drawings in which similar reference characters are correspondingly identified throughout the document and in which:

FIG. 1 represents a call setup procedure initiated at the mobile station;

FIG. 2 represents a call setup procedure completed at the mobile station;

FIG. 3 represents a call setup procedure completed at the mobile station without sending paging;

FIG. 4 is a state diagram of a mobile station;

FIG. 5 is a wireless communication system that supports a number of users, and that can implement various aspects of the invention;

FIG. 6 depicts a procedure for updating pilot power information between calls to allow call setup without sending paging;

FIG. 7 depicts an alternative procedure for updating pilot power information to allow call setup without sending paging;

IS 2 390 000 T3

FIG. 8 is a procedure for carrying out the completed or initiated call setup at the mobile station without using service negotiation messages;

FIG. 9 depicts a method for sending information in the form of a short data burst and initiating a call simultaneously;

FIG. 10 depicts a method for associating active set identifiers with active sets;

FIG. 11 depicts a procedure for reducing the length of the Channel Assignment Message using active set identifiers.

FIG. 12 depicts a procedure for mobile station initiated reconnection of a dormant packet data call;

FIG. 13 depicts a procedure for completed reconnection at the mobile station of a dormant packet data call; and

FIG. 14 depicts a procedure for the immediate transmission of a Preamble in response to a Channel Assignment Message.

DETAILED DESCRIPTION

FIG. 5 is a diagram of a wireless communication system 100 that supports a number of users, and that can implement various aspects of the invention. System 100 may be designed to support one or more standards and / or designs (eg, IS-95 standard, cdma2000 standard, HDR specification). For the sake of simplicity, a system 100 is shown that includes three base stations 104 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 the MSC or PDSN 102. The MSC or PDSN 102 can communicate with a network, such as the Public Switched Telephone Network (PSTN), the Internet, or an intranet (not shown).

For calls terminated at the mobile station, Publication A of the cdma2000 standard requires a page to be sent to the mobile station (via General Radio Message or Universal Radio Message). Then, when the mobile station sends the Answer Radio Message from the system access state, the base station can send the channel assignment (via the Channel Assignment Message). While waiting for the channel assignment in the system access state, the mobile station monitors the paging channel.

As described above with reference to FIG. 3, an enhancement allows the base station to skip the sending of paging by sending the channel assignment directly to the mobile station in the idle state. This has two advantages: it eliminates the need to send the General Radio Message (or the Universal Radio Message) to the mobile station, and it eliminates the need for a time-consuming mobile station access attempt (to send the Answer Radio Message). The overall effect is that the latency of the call setup is reduced.

However, there are several reasons for sending a page to the mobile station prior to channel assignment. One is to receive the pilot report in the Radio Response Message, which can be used to determine the active set. But on some occasions, such as when the time elapsed since the mobile station was last on the traffic channel is short, the previously used active set is likely to be sufficient to maintain the call. For those cases where an update is required, an alternative to paging can be used. The following are two procedures for providing the information to update the active set in response to changes that occur between successive traffic channel operations.

In FIG. 6 an embodiment is shown. The mobile station is in the idle state 430 when it determines that an update is required. For example, the mobile station may determine that a pilot needs to be added to the active set. It enters system access state 440 and sends a Pilot Power Measurement Message 610 (PSMM) to the base station. After this message transmission the mobile station returns to the idle state 430. The PSMM message 610 contains the information the base station needs to update the active set (ie, the pilot powers seen by the mobile station). Subsequently, the base station is free to carry out a call setup as described in FIG. 3, since the required base stations will be in the updated active set. To reduce signaling on the access channel, it is not necessary to send the PSMM 610 message to discard a member of the active set, because a larger active set will not prevent successful communication. The mobile station can send a signal to the base station on a traffic channel to remove a member from the active set once the mobile station has been assigned to that traffic channel. Another means of controlling excessive signaling to the access channel is to enable the PSMM 610 message update procedure only on a subset of mobile stations at a time.

An alternative embodiment avoids adding an additional signaling to the access channel, reducing the average access delay but with the disadvantage of increasing the maximum delay. In this embodiment,

ES 2 390 000 T3 shown in FIG. 7, the active set is not updated between successive traffic channel operations at the mobile station. To initiate a new call, the base station sends a Channel Assignment Message 30 to the mobile station, as described in the procedure of FIG. 3. In decision block 710, the mobile station determines whether or not the current active set is correct. If correct, then the call setup procedure is continued at block 750. When, as described above, the circumstances are such that the probability that the active set remains stable over a number of calls is high, then very often the call setup procedure will continue without an increase in delay. , and the extra signaling to the access channel that would have been introduced by the embodiment of FIG. 6.

In case the active set does not need to be updated, then in decision block 710 the mobile station will proceed to send the PSMM 720 message to the base station on an access channel. The PSMM 720 message may contain information similar to that of the PSMM 610 message. At block 730, the base station reconfigures the active set, then sends the updated Channel Assignment Message 740 to the mobile station, and then call setup can continue at block 750. This additional signaling, described in blocks 720 to 740, introduces an additional delay compared to the call setup procedure of FIG. 3.

System designers can use the embodiment of FIG. 6, the embodiment of FIG. 7, or a combination of both as desired to minimize the overall call setup latency based on the likelihood of changes to the active sets. As described above, sending additional signals on the access channel, described in FIG. 6, may have the disadvantage of increasing the maximum call setup time (but with a reduced average call setup time) with the method of FIG. 7. When the active set is more likely to be successful, this procedure can be used to decrease the average access time. However, the maximum delay can be increased (in those situations where the active set needs to be updated).

By way of example, a base station can enable the procedure of FIG. 6 for mobile stations whose roaming is introducing many changes to the pilot powers received from the various nearby base stations, and may disable the procedure of FIG. 6, opting for the occasional increased maximum delay of FIG. 7, for subscriber units that are fixed or do not travel often. Another option is that a base station can determine which call setup procedure to use based on the time interval that has elapsed since the previous access of a mobile station. If the time interval is short, it could be that the mobile station is in the same sector, and a reduced latency procedure is necessary as described in FIGS. 3, 6 or 7. If the time interval is greater than a threshold, the base station may decide to use a call setup procedure that includes the sending of paging, as described in FIG. 2.

In Publication A of the cdma2000 standard, Radio Message Reply 23 is also used to send an authentication value, AUTH_R. Mobile station authentication is achieved by executing a shared secret authentication algorithm between the base station and the mobile station and a random number to produce the AUTH_R value. The AUTH_R value is calculated at both the mobile station and the base station, and the base station must receive a matching AUTH_R value from the mobile station to ensure that the mobile station is authentic. Naturally, if the Reply Radio Message 23 is removed, an alternative mechanism must be introduced to send the AUTH_R value for authentication. Another alternative is for the mobile station to send an AUTH_R value on the traffic channel. Since the calculation of the AUTH_R value may take some time, this alternative has the added benefit of allowing the calculation to take place in parallel with the remaining part of the call setup procedure. The authentication response is sent over the traffic channel after the call setup is complete. Note that since user traffic cannot circulate before the Service Connection Message is sent, if authentication on the traffic channel fails, the call can be released immediately. This technique enables channel assignment without paging and therefore reduces call setup latency.

In CDMA2000 Publication A systems, each time dedicated channels are established for the purpose of establishing a call, the mobile station and base station must agree (by negotiating the service) on the configuration parameters. of the service that will be used to exchange user information and send signals. As described above, there is the ability to allow mobile station and base station to store mutually agreed service configuration (i.e., Service Configuration information register and Non-Negotiable Service Configuration information register) after the release of the dedicated traffic channels and when entering the idle state. This stored configuration can be restored after the reestablishment of the dedicated channels, thus avoiding carrying out the service negotiation. This reduces the latency of the call setup. However, Publication A still requires that, after the establishment of the dedicated traffic channels, the base station send the Service Connect Message instructing the mobile station to use the stored service configuration. The Service Connection Message belongs to the class of service negotiation messages.

IS 2 390 000 T3

FIG. 8 depicts one embodiment of a call setup procedure that eliminates service negotiation messages, 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 this flag is set to "01", then the negotiation stage is not required (ie, stage 9 of FIGS. 1-3). In addition, since the indicator is included in the Channel Assignment Message 810, the Service Connection Message and Service Connection Completion Message are also removed (10 and 11, respectively, of FIGS. 1-3 ). In addition to reducing latency by eliminating the transmission of these messages, the processing time associated with them is also eliminated. Another benefit is that the mobile station and base station can immediately restore the stored service configuration and begin exchanging user traffic as soon as the dedicated traffic channels have been established. The overall effect is that the latency of the call setup is reduced.

The following is a more detailed description of the procedure of the embodiment depicted in FIG. 8. This embodiment is applicable to both mobile station initiated call setup procedures and mobile station terminated call procedures. In the first stage, an Initiation Message 1 or a Response Radio Message 23 is transmitted from the mobile station to the base station, depending on whether the call was initiated at the mobile station or ended at the mobile station, respectively. The base station responds by sending a Base Station Acknowledgment Order 2 to the mobile station. The base station then communicates to the MSC either a Connection Management Service Request Message 3 or a Radio Message Response Message 25, depending on whether the call has been initiated or ended at the mobile station, respectively. The base station then sends the mobile station a Channel Assignment Message 810 that includes a USE_OLD_SERV_CONFIG flag. This flag is set whenever the base station wishes to avoid the service negotiation stage and has determined that the previously stored configuration may be adequate. After this stage, the mobile station enters traffic state 450.

The remaining stages are similar to the call setup procedures described above, except for the elimination of the service negotiation stages as just described. After receiving two consecutive good frames on the forward link, the mobile station begins transmitting preamble 6 to the base station. The MSC sends an Assignment Request Message 4 to the base station. (The order in which the MSC sends the Assignment Request Message 4 is not important since a previous configuration is being restored). The base station sends a Base Station Acknowledgment Order 7 to the mobile station. The mobile station responds to the base station with a Mobile Station Acknowledgment Command 8, at which point traffic can begin to flow between the base station and the mobile station. Lastly, the base station sends an Assignment Complete Message 12 to the MSC (at which point the traffic circulates between the base station and the MSC).

In the call setup procedure as specified in Publication A, the Assignment Completed Message 12 is sent from the base station to the MSC only upon receipt of the Service Connection Completion Message 11 from the mobile station. But in the embodiment of FIG. 8, the Assignment Completed Message 12 can be sent to the MSC just after the establishment of the dedicated channel or dedicated channels and the receipt of the Acknowledgment command from the mobile station MS from the mobile station. In this way, the network-side connection establishment can, to some extent, happen in parallel with the air interface connection establishment, further reducing the call setup latency.

In some circumstances, it may be desirable for a mobile station to discard a previously stored service configuration once it determines that a service negotiation is to be required. For example, Publication A specifies a channel pre-assignment feature, in which the base station responds to an initiation message by blindly assigning a channel to the mobile station. If a Channel Assignment Message 810 is used, it may turn out that the base station does not yet know if the old service configuration can be used at the time the message is transmitted. In these circumstances, the mobile station should retain the previous configuration information, since a Service Connect Message 10 may still arrive containing a USE oLd SERV CONFIG = "01" flag and a Service 9 Negotiation may still be avoided. Another method to address this issue is for the mobile station to retain the previously stored configuration even if a Channel Assignment Message 810 is received without the flag set to use the previous configuration. The mobile station should discard the above data only when beginning the service negotiation.

An alternative is to add additional values ​​to the USE_OLD_SERV_CONFIG flag. For example, if Channel Assignment Message 810 is sent with an indicator indicating that the previous stored configuration is valid, clearly the mobile station will not discard it. This would not happen in the case where the base station did not know if the previous configuration is valid or not. In that case, an additional flag value could be sent to indicate that it is not yet known whether or not the above configuration is valid. At this point the mobile station would retain the data, and wait to discard it until service negotiation is required. Finally, when it is not a previous channel assignment, and the base station knows that the previous configuration is no longer suitable, it can

ES 2 390 000 T3 send an indicator value indicating that the mobile station is free to discard the data, as a service negotiation will be required.

Another embodiment addresses call setup latency with respect to short data burst (SBD) characteristics, described above. There are applications where the mobile station needs to send a large amount of information over the air, therefore it needs to establish dedicated channels to transport the data. This, of course, would require a call setup procedure. As previously noted, SBD provides a mechanism for transmitting a small amount of data on the common channel, without performing a full call setup.

To facilitate the start of operations on the network side, the mobile station may first send a small amount of information over the common channels (to trigger operations on the network) using the SDB feature. Subsequently, a dedicated channel or dedicated channels can be established to transmit the large amount of data. Following the procedures defined in Publication A, the foregoing would require access to a common channel and subsequent transmission of the Message in the form of a Data Burst, followed by another access and subsequent transmission of an Initiate Message. That is, it would take two time-consuming access attempts.

In the embodiment of FIG. 9, the mobile station can simultaneously start the call setup procedure and carry out an SBD by including the information in the form of an SBD in an Initiate Message 910 addressed to the base station to establish the dedicated channels. The base station then transmits an Application Data Sending Service (ADDS) Transfer Service Request / CM Message 920 that includes the information in the form of an SDB and a data type indicator that identifies the data as SDB. In addition, the functionality of the Cm Service Request Message can be included in this message to eliminate an extra message on the network. Then, at block 930, call setup may proceed according to one of several procedures described above.

In this way, when the Start Message access is successful, the network can send the SDB content to the appropriate network entity, while the rest of the dedicated traffic channel establishment is still on the way. This has several advantages. It eliminates the need for an additional time-consuming access attempt and eliminates the ADDS Transfer Message between the base station and the MSC. The operations in the network and the establishment of the dedicated air interface channel happen in parallel. Processing at the mobile station is simplified. The overall effect is that the latency of the call setup is reduced.

Yet another alternative is to create a startup message that includes a request to restore the previous service configuration as well as send the information in the form of an SDB. It will be clear to those skilled in the art that these procedures can be used with any of the call setup procedures described above.

In an alternative embodiment, depicted in FIG. 12, a shorter version of the Initiate Message is employed, referred to herein as Reconnect Message 1230, which carries the minimally required fields to reconnect a dormant packet data call. The number of such fields is relatively small, as detailed below. For the case of reconnection initiated on the dormant calling network, this Reconnect Message 1230 may be used in place of the Answer Radio Message 23. Note that when a larger set of fields is required, the current Start Message, such as Message 1 or 910, or Answer Radio Message 23, can still be used.

Packet data calls can be described using three states: null, sleeping, and active. A packet data connection can last indefinitely, although it can change state frequently. When a packet data connection is established for the first time, it is created from a null state. Similar to the establishment of a voice call, all relevant parameters must be negotiated and agreed. Once the call is created it enters the active state, similar to the traffic state described above. In the active state, a physical channel is established and data circulates between the mobile station and the base station. From time to time, the packet data connection may no longer need to be active, since there is no data flowing in either direction. At this point, the physical channel is disconnected, and the packet data call enters the dormant state.

While the packet data connection is in the dormant state, the service configuration information can be stored in both the mobile station and the base station. Furthermore, the status of the protocol is also stored in the mobile station and in the PDSN. For example, if Point-to-Point Protocol (PPP) is used, its status, such as IP address, etc., is maintained while the call switches from active to dormant. Only the physical channel itself needs to be released to release the resource for other users. In this way, when a dormant call is reconnected, only a small subset of fields is required in the Initiate Message. With the increasing use of packet data calls, the percentage of call setup starts in a system is associated with returning a dormant packet data service to the active state.

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The Publication A Initiation Message was designed to isolate a variety of call types including voice, circuit switched data, packet switched data, etc. As such, it contains fields that are a superset of fields required for each type of call setup. With respect to reconnecting a dormant packet data call, the fields in the Initiate Message can be classified into three classes: not necessary, possibly necessary, or necessary. Examples of unnecessary fields are those specific to voice calls. In some cases, certain parameters have been negotiated in a previous call setup, so these are examples of fields that may not be required. The SYNC_ID field is an example of a required field, as it indicates that the set of stored parameters is to be used. As can be easily understood, a Reconnect 1230 Message that removes those fields not required will be significantly smaller than the Start Message from Post A.

When using this embodiment, the Reconnect Message 1230 can often be transmitted in a single frame, resulting in a number of benefits. One benefit is that transmission time is reduced. Another benefit is that the message error rate, at this time equal to the frame error rate, is reduced. Both benefits result in reduced call setup latency associated with reconnecting an idle packet call.

FIG. 12 depicts one embodiment of a dormant call reconnection initiated at the mobile station. In step 1210, a previous packet data call is established, either from the null state or a reconnection from the dormant state. The call switches 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, which message contains the minimum fields required to re-establish the connection, as described above. This message replaces the Start Message, such as Message 1 or 910, as described above with respect to FIGS. 1 and 9, respectively. After the Reconnect Message 1230 is sent, the call setup continues to step 1240, according to one of the procedures described herein.

FIG. 13 depicts one embodiment of a completed dormant call reconnection at the mobile station. Steps 1210 to 1240 are identical to the steps just described in relation to FIG. 12, with the exception that step 1300, where the base station initiates the call, is inserted between the sleep state 1220 and the Reconnect Message 1230. The base station, in step 1300, initiates the reconnection of the call, according to one of the procedures described herein, and the mobile station responds with the Reconnect Message 1230, instead of the Response Radio Message 23, described above.

Another embodiment addresses the call latency introduced by the length of the channel assignment message, such as Channel Assignment Message 5, 30 or 810, described above. In Publication A of the cdma2000 standard, each time dedicated channels are established using the Channel Assignment Message, the base station must specify the entire active set in this message. The active set consists of a number of pilots and the parameters required for each pilot, including the following: pilot PN sequence offset index, pilot register corresponding to pilot type, power control symbol combination indicator, code channel index for fundamental channel, quasi-orthogonal function mask identifier for fundamental channel, code channel index for the dedicated control channel and quasi-orthogonal function mask identifier for the fundamental channel for the dedicated control channel. Pilot register contains: transmit diversity (TD) transmit power level, transmit diversity mode, Walsh code for transmit / auxiliary diversity pilot, quasi-orthogonal function index for transmit diversity pilot / auxiliary, and the transmit / auxiliary diversity pilot power level. These parameters can end up being a significant number of bytes. Each of these parameters can introduce latency due to the time required to transmit them (if they cause the message to extend to the next frame), and the processing time for the mobile station to process them.

The embodiment consisting of the procedures depicted in FIG. 10 and in FIG. 11 uses an active set identifier to identify an active set and associated parameters. Instead of specifying the full list of active set members and parameters, as described above, the base station simply specifies the active set identifier corresponding to the particular configuration. This technique can reduce the length of the Channel Assignment Message, and has the following advantages: reducing the transmission time of the Channel Assignment Message and reducing the probability that the Channel Assignment Message will be received incorrectly. The overall effect is that the latency of the call setup is reduced. Note that since some of the active set parameters are likely to have changed, an alternative is for the base station to send the active set identifier plus those parameters that have changed. This alternative embodiment adds flexibility, which can lead to use in a greater variety of applications.

The embodiment just described may consist of any of the methods depicted in FIG. 10, in FIG. 11, or both. The procedure of FIG. 10 depicts a procedure for assigning an active set identifier to a specific active set. In block 1000, the call setup procedure is in progress. The base station then sends a Message to the mobile station

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1010 Channel Assignment that Includes the active set and the complete parameters. In addition, Channel Assignment Message 1010 includes an active set identifier that the mobile station can associate with that active set. At block 1020, the call setup process continues. An alternative method of assigning active set identifiers to active sets is for the base station to download said active set / active set identifier pairs to the mobile station prior to the communication in which they will be used.

FIG. 11 depicts a procedure for using the active set identifier once it has been assigned to an active set, using a procedure such as that described in FIG. 10. At block 1100, the call setup procedure is in progress. The base station sends the mobile station a Channel Assignment Message 1110 that includes the active set identifier. Since the mobile station knows the members of the active set and the corresponding parameters for each of the members corresponding to the active set identifier, the active set identifier is sufficient to carry out the channel assignment. Alternatively, if the parameters associated with the active set identifier have changed, message 1110 may include the active set identifier, along with the changed parameters. The call setup procedure continues at block 1120. The mobile station and the base station can ensure that the active set configurations and their corresponding active set identifiers are in synchronization between the mobile station and the base station using the mechanism specified in the cdma2000 standard for SYNC_ID validation, that is, the procedure for restoring stored service configurations.

A similar technique can be employed in conjunction with the procedures described in FIG. 6 and in FIG. 7 to reduce the message length of the PSMM 610 and PSMM 720 messages, respectively. A pilot identifier may be associated with each of a series of pilot patterns, so that only one identifier needs to be transmitted as the mobile station updates the base station with one of the currently identified pilot patterns. But this may be less likely since the pilot power can take many values ​​and therefore can be difficult to associate with an identifier.

Another alternative procedure is to assign identifiers to each member of an active set (and their associated parameters). With this technique, a plurality of identifiers would be included in the Channel Assignment Message 1110 to represent a plurality of members. This provides a more granular method, resulting in a slightly longer message, but allows greater flexibility in that a large number of active sets can be identified using combinations of a relatively smaller set of stored member configurations. A base station could use a combination of the techniques just described. These techniques can be used in combination to reduce the overall transmission time associated with each Channel Assignment Message 1110 transmitted. It will be clear to those skilled in the art that these procedures can be used with any of the call setup procedures described herein. Note that this procedure can be used in all messages in which the active set is included. Another example includes the Universal Handoff Addressing Message, where by employing this procedure the size of the message can be reduced and consequently also the error rate of the message can be reduced.

In another embodiment, depicted in FIG. 14, the call setup latency can be reduced by immediately transmitting Preamble 6 in response to a Channel Assignment Message such as Message 5, 30, 810, 1010 or 1110, described above. As mentioned above, Publication A requires a mobile station to wait to receive two consecutive good frames on the forward link before enabling the reverse link and transmitting the preamble. If the mobile station does not receive two consecutive good frames within one second, it must abandon the call setup. The minimum time a mobile station must wait before transmitting the preamble is 40 to 60 milliseconds, since two frames correspond to 40 milliseconds and waiting for a frame boundary takes another 0 to 20 milliseconds.

In this embodiment, call setup is in progress in step 1400. The base station then sends a Channel Assignment Message, called Message 5 in FIG. 14, but it could be any Channel Assignment Message, such as Message 30, 810, 1010, or 1110, described above. In response, the mobile station immediately establishes the reverse link and begins transmitting Preamble 1410, without waiting to receive good frames on the forward link. Next, in step 1420, call setup continues according to a variety of call setup procedures, such as those described herein. The mobile station can continue to monitor the forward link for good frames, and can end the call if a series of bu frames is not received. within the prescribed time window. For example, the mobile station may search for two consecutive good frames within one second, as described in Publication A. Alternatively, to reduce interference with other users, the mobile station can remove the preamble if the required number of good frames is not received in the prescribed period of time. This time period may be less than the time period allowed for good frames to arrive. In this way, if the requirement for good frames is not met during the first time period, the mobile station can stop transmitting the preamble, but continue to monitor the good frames on the forward link within the second time period. If the good plots come

ES 2 390 000 T3 finally, the mobile station can start transmitting the preamble in response. This alternative technique can be used to reduce interference with other users in situations where good frames are either slow to materialize or never arrive. Note that Preamble step 1410 may be substituted for Preamble step 6 in any of the embodiments described herein.

Unlike the Post A procedure, the mobile station will be transmitting on the reverse link, at least for a certain period of time, even when the call is ultimately aborted. In these situations, the level of interference with other users will increase slightly, with all the harmful effects that accompany increased interference with another user. However, in many cases, the probability of receiving good frames on the forward link will be high, and using this embodiment will reduce the latency of the call, with all the accompanying benefits, outweighing the detrimental effects of occasionally establishing a reverse link for a call that cannot be completed.

It should be noted that in all the embodiments described above, the process steps can be interchanged without departing from the scope of the invention.

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

Those skilled in the art will further understand that the various illustrative logic blocks, modules, circuits, and algorithm steps described in connection with the embodiments described herein may be implemented as electronic hardware, computer software, or combinations thereof. To clearly illustrate this interchangeability of hardware and software, 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 on the specific application and the design constraints imposed on the overall system. Those skilled in the art can implement the described functionality in various ways for each specific application, but it should be understood that such implementation decisions are not outside the scope of the present invention.

The various illustrative logic blocks, modules, and circuits described in connection with the embodiments described herein may be implemented or carried out with a general purpose processor, a digital signal processor or DSP, an integrated circuit for specific applications. or ASIC circuit, an array of field programmable gates or FPGAs or other programmable logic devices, discrete gates, or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor can be a microprocessor, but alternatively, the processor can be any conventional processor, controller, microcontroller, or state machine. A processor can also be implemented as a combination of computational devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of a procedure or algorithm described in connection with the embodiments described herein can be performed directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module can reside in RAM memory, in flash memory, in ROM memory, in EPROM memory, in EEPROM memory, in registers, on a hard disk, on a removable disk, on a CD-ROM, or in any other way. of storage medium known in the art. An example storage medium is coupled to the processor so that the processor can read information from the storage medium and write information to it. Alternatively, the storage medium can be integrated into the processor. The processor and storage medium can reside in an ASIC circuit. The ASIC circuit may reside in a user terminal. Alternatively, the processor and storage medium can reside as discrete components in a user terminal.

The foregoing description of the described 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 general principles defined herein may be applied to other embodiments without departing from the scope of the invention. Therefore, the present invention is not intended to be limited to the embodiments shown herein but should be given the broadest scope consistent with the principles and novel features disclosed herein.