A communication device for providing an efficient dormant mode for a group communication network

[Technical field]

【0001】

The present invention relates to a point-to-many point communication system, and more particularly to methods and devices for providing an efficient hibernate mode for PushTalk communication devices in a group communication network.

[Background technology]

【0002】

There have been various types of wireless service classes for many years, with quick and efficient one-to-one or one-to-many (group) communications in mind. In general, these services were half-duplex. In this service, the user presses the "Push Talk" (PTT) button on the phone or radio to initiate a call. Pressing a button indicates that the user has requested a "speak" in a suitable system that is being tuned for the radio or made through some type of server. If speaking is allowed, i.e. speaking, the user usually speaks for a few seconds. Then, when the PTT button is released, another speaker can request a statement. Communication is generally from one speaker to a group of listeners, but can be one-to-one. This service has traditionally been applied when a single "dispatcher" needs to communicate with a group, such as field service personnel or taxi drivers. Therefore, the name "dispatch" comes from services to field service personnel, taxi drivers, and so on.

【0003】

Recently, similar services have been offered on the Internet. It is commonly known as "voice chat". These services are typically implemented as Internet Protocol (IP) packets, a personal computer application that sends vocoder frames to a central group chat server via VoIP services. Alternatively, the client-to-client transmission may be performed by the peer-to-pier service.

【0004】

The main feature of these services is that they are fast, spontaneous, and usually started with the push of a PTT button, without going through a typical dial or call sequence. Communication in this type of service is generally very short, involving individual calls "sparts", typically on the order of a few seconds, and "conversations" that will probably last up to a minute or so.

【0005】

The time delay between when the user requests a statement and when the user receives confirmation from the server that the user is speaking and is allowed or denied to start speaking is half double. It is an important parameter for group communication systems. This time delay is known as PTT latency. As mentioned above, the dispatch system prioritizes short and quick conversations, which reduces service efficiency when the PTT waiting time is long.

【0006】

The existing group communication infrastructure (hereinafter, "infrastructure" is simply referred to as "infrastructure") has limited capacity when it comes to significantly reducing PTT latency. That is, the actual PTT latency must never be less than the time required to reestablish the traffic channel within the paused packet data session. Also, the only valid mechanism for initiating a hibernate group awakening is to wait for the reestablished speaker traffic channel to signal the server, so that the speaker-listener traffic channels are continuous. Will be generated. Currently, there is no mechanism for transmitting user signal data originating from mobile on a channel other than the traffic channel. This is a constraint that the traffic channel must be reestablished before any communication between the client and server can be made.

[Patent Document 1]

US Provisional Patent Application 60 / 291,454 (May 15, 2001) [Disclosure of Invention]

[Problems to be Solved by the Invention]

【0007】

Therefore, the PTT latency experienced by the speaker and the total time required to reestablish the traffic channel joining the mobile without negatively impacting system power, client battery life, or other resources. A mechanism to reduce both is desired.

[Means for solving problems]

【0008】

The embodiments disclosed herein are novel and improved methods and devices that provide efficient hibernation modes for PushTalk communication devices in group communication networks. In one aspect of the invention, a method of providing an efficient hibernate mode determines whether a communication device holding a dedicated traffic channel has been inactive for a predetermined first period of time. If so, put this communication device into control hold mode. This method also determines if the communication device that released the dedicated traffic channel was in control hold mode for a predetermined second period, and if so, this communication device. , Put into hibernation mode.

【0009】

Another aspect of the invention is a method of providing an efficient hibernate mode for a PushTalk communication device in a group communication network. This method determines if the communication device has been inactive for a predetermined period of time, and if so, puts the communication device in hibernation mode and enters hibernation mode. Before, this communication device is made to cache the service setting state.

【0010】

Another aspect is a communication device that provides a hibernate mode for a PushTalk communication device in a group communication network. The communication device includes a receiver, a storage unit, a transmitter, a receiver, a storage unit, and a processor connected so as to be able to communicate with the transmitter. This processor can execute each of the above processes. In some aspects, this communication device is a PushTalk device.

[Effect of the invention]

【0011】

According to the present invention, it is necessary to reestablish the PTT latency experienced by the speaker and the traffic channels participating in mobile without negatively impacting system power, client battery life, or other resources. It is possible to reduce both the total time.

[Best mode for carrying out the invention]

【0012】

This application claims the priority of Patent Document 1 above, the entire contents of which are incorporated herein by reference.

【0013】

Before describing the embodiments of the present invention in detail, it should be understood that the present invention is not limited to use for the details of the structure and arrangement of the configurations shown in the descriptions and drawings described below. The present invention can also be practiced in other embodiments and is practiced in a variety of ways. It should also be noted that the wording and terminology used herein are for explanatory purposes only and should not be restricted.

【0014】

FIG. 1 shows a typical functional block diagram of the group communication system 100. Group Communication 100 is also known as a PushTalk system, Net Broadcasting Services (NBS), dispatch system, or point-to-many point communication system. In the NBS100, a group of communication device users, known as net members, communicate with each other using the communication devices assigned to each net member. The term "net" means a group of communication device users who are allowed to communicate with each other.

【0015】

In one embodiment, the central database contains information that identifies the members of each particular net. Multiple nets can operate in the same communication system. For example, a first net with 10 members could be defined and a second net with 20 members could be defined. The 10 members of the first net can communicate with each other, but not with the members of the second net. In another embodiment, members of different nets can monitor communication between members of a plurality of nets, but can only send information to members within their own net.

【0016】

The net can operate through existing communication systems without substantial changes to existing infrastructure. Thus, controllers and users on the net may use, for example, code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, global (GSM) systems for mobile communications, Globalstar® or Iridium®. It can operate in any system that can send and receive packet information using the Internet Protocol (IP), such as satellite communication systems such as, or various other systems.

【0017】

Net members communicate with each other using their assigned communication devices, as shown as Communication Devices (CDs) 102, 104, 106, and 108. CD102,104,106, and 108 are audio devices such as terrestrial radiotelephones, radiotelephones with push talk capabilities, satellite phones with push talk capabilities, wireless video cameras, still cameras, music recorders or players. It can be a wired or wireless communication device, such as a laptop or desktop computer, a paging device, or a combination thereof. For example, the CD102 consists of a wireless ground telephone equipped with a video camera and a display. Further, each CD can send and receive information in either a secret mode or a non-secret (clear) mode. Through the discussion below, a wireless PushTalk phone is assumed as a reference for each CD. However, it should be understood that references to CDs are not intended to be limited to that and may include other communication devices capable of sending and receiving packet information according to the Internet Protocol (IP).

【0018】

In the NBS system 200 shown in FIG. 2, the transmission right generally means allowing a single user to transmit information to other net members at a given time. This transmission right is granted or denied to the requesting net member when the request is made, based on whether or not this transmission right is assigned to another net member. The process of permitting and disallowing submission requests is known as arbitrage. When deciding whether to grant the sending right to the requesting net member, the arbitrage scheme determines the priority level assigned to each CD, the number of failed attempts to obtain the sending right, and the net member sending. Evaluate the length of time you were entitled to, or each other factor.

【0019】

To participate in the NBS system 100, CD 102, 104, 106 and 108 can each have the ability to request transmission rights from the controller, ie Communication Manager (CM) 110. CM110 manages the net in real time and comprehensively. The CM can be any computer type device as long as it has at least one processor and memory. In one embodiment, Sun workstation Netra T1® is used as the CM.

【0020】

If permitted by the service provider, the CM110 may operate remotely through the communication system service provider and / or net members. The CM110 can acquire net definitions through an external management interface. A net member can be manipulated by its own service provider or member and request a management action through a management net function through a system defined as Security Manager (SM) 112 corresponding to the CM management interface. CM110 authenticates parties attempting to establish or modify the net.

【0021】

The SM112 performs tasks related to key management, user authentication, and secure net support. A single group communication system communicates with one or more SM112s. The SM112 is not included in the real-time control of the net, but is included in the net operation or PTT ruling. The SM112 has a management function compatible with the CM110 interface in order to automate the management function. The SM112 also acts as a data terminal intended to participate in the monitoring of the net, broadcast net keys, or simply net traffic.

【0022】

In one embodiment, the means of requesting transmission rights from the CM comprises a PushTalk (PTT) key or switch. When a user in NBS100 wants to send information to other net members, this user sends a speech control request by pressing the PushTalk switch located on his or her CD and obtains the transmission right from CM110. To do. If, at that time, no other member has been assigned a send right, the requesting user is granted the send right, and this user is given an audible, visual, or recognizable warning through the CD. You will be notified. After the sending right is granted to the requesting user, this user sends information to other net members.

【0023】

In one embodiment of the invention, each radio net member establishes forward and reverse links with one or more base stations 116 or satellite gateways 118, depending on the circumstances. Base station 116 is used to describe the communication channel from base station 116 or satellite gateway 118 to the CD. Satellite gateway 118 is used to describe the communication channel from the CD to base station 116 or satellite gateway 118. Voice and / or data is converted into data packets, for example using a CD. Data packets are suitable for a particular distributed network 120 where communication with other users can occur. In one embodiment, the distributed network 120 is the Internet.

【0024】

In one embodiment, dedicated forward channels are established in each communication system, i.e. terrestrial and satellite communication systems, to broadcast information from each net member to another net member. Each net member receives communications from other net members through this dedicated channel. In another embodiment, a dedicated reverse link is established in each communication system to transmit information to the CM110. In some examples, a combination of the schemes described above is used. For example, one scheme may include establishing a dedicated forward broadcast channel, but also requesting the wireless CD to send information to the CM110 through a dedicated reverse link assigned to each CD. sell.

【0025】

If the first net member wants to send information to other members of the net, this first net member presses the PushTalk key on his CD and formats it for transmission over the distributed network 120. Can generate the requested request and request the right to send. For CD 102 and 104, this request is transmitted through space to one or more base stations 116. The Mobile Switching Center (MSC) 122 for processing data packets is an interworking function (IWF), packet data serving node (PDSN), or packet control (PCF). It can have well-known functions such as function) and exists between BS116 and distributed network 120. For CD106, this request is sent via satellite gateway 118. For CD108, this request is sent to modem bank 126 through the Public Switched Telephone Network (PSTN) 124. Modem bank 126 receives this request and provides it to distributed network 120. The NBS terminal 128 monitors traffic from the NBS system through a connection to the distributed network 120. Since the NBS terminal 128 is connected to the distributed network 120, it does not need to be geographically close to the net participants.

【0026】

If none of the members have the transmission right at that time and the CM110 receives the transmission right request, the CM110 sends a message to the requesting net member to notify that the transmission right has been granted. Audio, visual, or other information from the first net member may be transmitted to the CM110 using just one of the described transmission paths and then to other net members. In one embodiment, CM110 then provides this information to other net members by copying this information and sending each copy to other net members. If a single broadcast channel is used, this information simply needs to be copied only once for the use of each broadcast channel.

【0027】

In an alternative embodiment, the CM110 is incorporated into the MSC122 so that data packets from supporting base stations are routed directly to the CM110 without being routed to the distributed network 120. In this embodiment, the CM110 is connected to a distributed network 120 so that other communication systems and devices can participate in group communication. In yet another embodiment, the CM is incorporated into a PDSN or MSC PCF module.

【0028】

In one embodiment, CM110 maintains one or more databases for managing information associated with each net member, as well as each defined net. This database contains, for example, for each net member the username, account number, telephone number or dial number corresponding to the member's CD, the mobile authentication number assigned to the CD, and whether or not the member is on the net. The current status of the member on the net, the priority code to determine whether the transmission right is assigned in the same way, the data telephone number corresponding to the CD, the IP address corresponding to the CD, the index of the net to which the member is allowed to communicate. It has information such as. Other relevant information is also stored in the database associated with each net member.

【0029】

In one embodiment, the CDs form connections with individual communication terminals, forming a single calling group or net. In addition, CM can have various functions in hardware and software. These features can be configured in different ways for application to different applications. In addition, the CM provides real-time, administrative, or authentication actions for the (NBS) net, pushtalk (PTT) request arbitrage, maintenance and distribution of net members and registration lists, and necessary communication call settings. It also has the ability to manage teardowns, systems such as CDMA, and network resources as well as overall control of net conditions.

【0030】

NBS Net can exist in standalone mobile systems or in large multi-site structures. When in a large structure, a large number of CMs are geometrically arranged to form a single integrated system. Here, each operates as a plug-in module built into the existing mobile infrastructure. As such, the new features introduced by NBS Net do not require any changes to the existing mobile infrastructure and are useful for mobile users.

【0031】

This CM maintains a defined list of NBS nets. In one embodiment, each net definition includes a net identifier, a member list containing a telephone number or other credentials, user priority information, and other general management information. A net is statistically defined as either clear or safe. Also, the transition between clear and safe is unacceptable. Secure NBS nets generally use media encryption technology to authenticate and guard against eavesdropping. Media encryption for a secure net is based on the end-to-end principle. This means that both encryption and decryption are done within the communication device. CM can work without knowledge of security algorithms, keys, or policies.

【0032】

FIG. 2 is a diagram showing a typical NBS net 200 to show the interaction between the communication device 202 and the CM204. A large number of commercials are arranged as required for large NBS nets. In Figure 2, CD202 has permission to send media to other members of the net. In this case, the CD202 is known as the speaker and transmits the media through the channel. If CD202 is designated as the speaker, the remaining net participants, CD206 and CD208, do not have permission to send media to the net.

【0033】

Therefore, CD206 and CD208 are designated as listeners.

【0034】

As mentioned above, CD202,206,208 are connected to CM204 using at least one channel. In one embodiment, this channel has a session initiation protocol (SIP). protocol) Divided into another channel consisting of channel 210, NBS media signal channel 212, and media traffic channel 214. SIP channel 210 and NBS media signal channel 212 may be used at any time by any of CD202,206,208, as bandwidth allows, whether designated by the speaker or listener. SIP is an application layer protocol defined by the Internet Engineering Task Force (IETF) that describes the control mechanism for establishing, modifying, and terminating multimedia sessions that operate through the Internet Protocol (IP). SIP determines user availability, call configuration, and call handling, as well as mechanisms for registering and locating users for call signal problems for Internet telephony applications, defining user capabilities and describing media parameters. It provides a general solution by supporting the mechanism.

【0035】

In one embodiment, SIP channel 210 is used for the start and end of CD participation within NBS Net 100. Session Description Protocol (SDP) protocol) can also be used within SIP channel 210. For example, if CD participation in the NBS net is configured by using SIP channel 210, for example, by using NBS media signal channel 212, real-time call control between the CD and CM Signaling causes. In one embodiment, NBS media signal channel 212 handles pushtalk requests and releases, mediates or speaks between requested requests, announces the start and end of information transmission, manages net outages, and tracks terminal connectivity. Used for requesting and exchanging net status, and for communicating any error messages. The NBS Media Signal Channel 212 protocol minimizes the most common message lengths and simplifies the task of interpreting responses and responding to requests while maintaining flexibility for future enhancements. The protocol of NBS media signal channel 212 also allows the request to be retransmitted without adversely affecting the protocol state.

【0036】

In one embodiment, the signal traffic on the NBS media signal channel 212 includes a signal that sets and controls the call and a media signal. The signal that sets up and controls the call can consist of a session solicitation request and confirmation. The media signal may include a real-time speech control request and associated asynchronous messages. Media traffic Media traffic on channel 214 includes real-time point-to-point audio and / or data broadcasting. Each message category has unique functional attributes. In addition, each CD issues a Domain Name Service (DNS) client request to facilitate a perfectly matched mapping to Internet network addresses.

【0037】

In one embodiment, NBS call configuration and call control signaling are performed according to the meaning of SIP. SIP can be carried using either the well-known User Datagram Protocol (UDP) or Transmission Control Protocol (TCP), but in one embodiment each CD has a UDP-based signaling function. Perform SIP based on. In addition, each CM is assumed to receive a SIP signalization request via UDP. Real-time signaling can occur via the dynamic UDP / IP interface on the CM and each CD. Other signaling can occur via a fixed TCP / IP interface between the CM and the CD, for example using SIP.

【0038】

(PTT Latency) In one embodiment, when packet data services are in operation, such as Base Station Transceiver Subsystem (BTS), Base Station Controller (BSC), Interaction Function (IWF), and Radio Link. Resources in the infrastructure are assigned to mobile stations (MS) in operation. In the IP-based VoIP dispatch service, each user's packet data connection remains active while there is active conversation between group participants. However, after a non-operating time such as "hang time" in group communication, the user traffic channel goes into hibernation.

【0039】

This hibernation transition preserves system power, reduces service costs and battery consumption, and allows the user to receive incoming traditional voice calls. For example, if a user is making a working packet data call, this user is generally considered to be "busy" for an incoming voice call. If this user's packet data call is in hibernation, this user will be able to receive the incoming voice call. For these reasons, it is desirable that this packet data call go into hibernation after a period of packet data inactivity.

【0040】

Radio frequency (RF) energy is at a low level to maintain synchronization with the base station and output control, even if packet data calls are in operation and no data packets are exchanged. Is sent by mobile phone. These transmissions result in significant output consumption for the phone. In hibernation, the phone does not perform RF transmissions. To preserve the phone output and extend battery life, the hang time is set to put the phone into hibernation mode after a period of no data transmission.

【0041】

While the packet data service is running for all users, PTT requests, which are IP datagrams sent between the MS and the dispatch server, have very short latency. However, if this user channel had previously transitioned to hibernation, the PTT wait time could be longer. The state information associated with the packet data session, including the mobile IP address, can be maintained while the packet data is dormant. However, the state information corresponding to the layer below PPP, such as the physical traffic layer, is either released or unallocated.

【0042】

In some infrastructures, traffic channels must be redistributed, resources must be redistributed, and the Radio Link Protocol (RLP) layer must be reinitialized to evoke hibernate data connections. The effect is that if a group of speakers has not spoken for a while and the user presses the PTT button to request a statement, the PTT wait time for the first conversation spurt is generally for the next conversation spurt. It is much longer than the PTT waiting time. Although relatively rare, this affects the usefulness of the service and should be minimized.

【0043】

In one embodiment, when the group communication device is dormant, the PTT latency is caused by:

【0044】

1. Delayed speaker channel allocation Delay in assigning and initializing traffic channels for the speaker's phone in response to the user pressing the PushTalk button and the dispatch application that initializes the IP-based request message.

【0045】

2. Delayed propagation of call request Time for the speech request message to propagate to the dispatch server.

【0046】

3. Delayed arbitrage Time for the dispatch server to process a large number of speech requests.

【0047】

4. Lagging message delay The time it takes for an IP message from a dispatch server to propagate to a mobile infrastructure that serves listeners, such as PDSN.

【0048】

5. Listener's paging delay Time delay due to the need to wait for the listener's phone to be awakened and receive the page for the appropriate paging channel slot.

【0049】

6. Listener channel allocation delay Delay in allocating and initializing the listener's telephone traffic channel.

【0050】

Some of these delays contribute significantly more to the overall PTT latency than others. For example, the speaker and listener channel allocation latency, and the listener's paging latency are more than an order of magnitude higher than other factors, so a combination of these ultimately determines PTT latency performance.

【0051】

To reduce PTT latency, in one embodiment, group call signals such as speech control requests, speech control responses, and wakeup messages from hibernation do not have to wait for a dedicated traffic channel to be reestablished. , Can be transmitted on a valid common channel. Such common channels are not always valid, regardless of mobile status. It also does not need to be requested or reassigned each time the user wants to initiate a group call. Thus, the group call signal may be exchanged even when the mobile is dormant and may provide a means of reestablishing a dedicated traffic channel for the speaker and listener mobiles in parallel.

【0052】

In one embodiment, the calling mobile sends a speech control request to the wireless infrastructure through a valid reverse common channel, such as a reverse access channel and a reverse fast access channel. The calling mobile may also receive a response to this speech control request through a valid forward common channel, such as a forward paging channel and a forward common control channel. In one embodiment, the dormant listener's mobile may receive a message to cause a pause on a valid forward common channel, such as a forward paging channel and a forward common control channel.

【0053】

(Short data burst ringing signal message) In one embodiment, the total actual pause time was significantly reduced and the PTT latency felt by the speaker was, for example, "TIA / EIA / IS-2000 Standards for". cdma2000 Spread Spectrum It can be improved by using the short data burst (SDB) messages given in "System" (hereinafter simply referred to as cdma2000). In one embodiment, the SDB message is a dedicated physical channel such as a forward basic channel (FCH) or a forward dedicated common control channel (F-DCCH), a reverse access channel (R-ACH), and a reverse enspeed. It can be transmitted through both an access channel (R-EACH), a forward common control channel (F-CCCH), or a common physical channel such as a paging channel (PCH). SDB messages can be carried by the Radio Burst Protocol (RBP). RBP maps the message to the appropriate and valid physical layer channel. SDB messages carry arbitrage IP traffic and can be sent through a common physical channel, so SDB messages exchange group call signals if the calling client's mobile does not have a dedicated traffic channel. Gives a mechanism to do.

【0054】

(Call signal message transmitted from mobile) In one embodiment, the media signal message carries an IP datagram through a reverse link or a link originating from the mobile. The client's mobile station promptly signals the CM if the user requests a statement but the dedicated reverse traffic channel is not immediately enabled. If the client's mobile station releases all dedicated traffic channels, the client's mobile station immediately forwards the speech control request through the reverse common channel of the wireless infrastructure. This relays this request to the CM. For example, if a dedicated reverse channel is not enabled, either the reverse access channel or the reverse fast access channel is used to send this message. In one embodiment, the client's mobile station sends a speech request message to the CM as an SDB message.

【0055】

FIG. 3 is a diagram showing a typical ringing signal for the speech control request process. The client mobile station (MS) receives a request from a user who wants to initiate a group call. In one embodiment, this client MS is a PTT device. In one embodiment, the client MS sends a PTT speech request 302 through a reverse common channel, such as an access channel or a fast access channel, before attempting to reestablish a dedicated traffic channel. In one embodiment, the client MS sends a PTT speech request 302 in an SDB message, regardless of which channel is being used.

【0056】

The client MS then initiates the re-establishment of dedicated traffic channel 304, for example, by executing "Service Option 33 Re-origination". This client MS also initiates Radio Link Protocol (RLP) Synchronization 306. In one embodiment, the client reestablishes a dedicated traffic channel and preferentially synchronizes the RLP in parallel with the transmission of the PTT speech request 302.

【0057】

Therefore, if the mobile station does not have a dedicated traffic channel in operation, to evoke participating mobiles by using the SDB feature, which is sending a speech control request to a valid reverse common channel and / or CM. Reduce the total time required. The speaker's client does not obtain a speech request permission confirmation until the speaker's forward traffic channel is reestablished, but due to its ability to quickly signal the CM to initiate awakening of participating listeners. Reduce overall waiting time.

【0058】

As shown in FIG. 3, the wireless infrastructure sends a PTT speech control request 308 to the packet data service node (PDSN) and then to the CM. In one embodiment, after receiving the speech control request 310, the CM arbitrates this request, sends a media signal evoking message (trigger) to the target participant's group (listener), and / or the participant (listener). Causes the reestablishment of the traffic channel of. If this CM allows the PTT speech request, the CM sends the PTT speech permission 312 to the infrastructure, and the infrastructure sends the PTT speech permission 314 to the client MS. In one embodiment, if the client's dedicated traffic channel is not reestablished, this infrastructure will provide PTT Speak Allowance 314, for example, a valid forward common, such as a forward paging channel or a forward common control channel. Send to client MS by channel. In one embodiment, the infrastructure sends PTT speak permission 314 to the client MS in SDB format, regardless of which channel is used.

【0059】

In one embodiment, the CM waits until the pause response timer expires before responding to the PTT speech control request. If the pause response timer of the group is set to zero, this CM immediately responds to this speech control request. In one embodiment, if the client MS completes the reestablishment of the traffic channel and the synchronization of the RLP, the client MS streams the buffered media 316 to the CM.

【0060】

(Call signal message originating from the network) In one embodiment, after receiving a speech control request, the CM sends a media signal awakening message to a group of target participants (listeners), and the traffic of the participants (listeners). Causes channel reestablishment. If the pause response timer for this group is set to zero, the CM immediately responds to the speech control request. In one embodiment, if the speaker immediately initiates the reestablishment of the traffic channel by sending a PTT request, the caller and listener traffic channels can be conveniently reestablished in parallel.

【0061】

FIG. 4 is a diagram showing a typical call signal in a hibernate wake-up process initiated by the network. After the CM receives the PTT speech control request 310 (FIG. 3), the CM sends a wake-up trigger 402 directly to the target listener. PSDN determines if a packet data session exists on the target mobile and forwards the trigger packet to the appropriate infrastructure element, such as a base station. This infrastructure may do page 406 for each target MS to initiate the reestablishment of dedicated traffic channels. At that time, the target MS initiates the reestablishment of the dedicated traffic channel 408, for example by executing "Service Option 33 Reorientation". This goal MS also initiates Radio Link Protocol (RLP) synchronization 410. In one embodiment, the target MS reestablishes a dedicated traffic channel and conveniently synchronizes the RLP in parallel with the same functionality as that done by the client MS.

【0062】

In one embodiment, after the target MS completes the reestablishment of the dedicated traffic channel and the synchronization of the RLP, the CM wakes up and retransmits the trigger 412 to the target MS. This target MS sends a wake-up response 414 to the CM to indicate that this target MS is ready to receive media. This CM sends a speaker announcement 416 to the client MS before streaming the buffered media 418 to the target MS.

【0063】

In one embodiment, the target listener's traffic channel has not been reestablished, while the infrastructure targets through several valid common forward channels, such as forward paging channels and forward common control channels. Awaken trigger 412 is sent to the listener. In one embodiment, the infrastructure sends a wake-up trigger 412 in SDB format to the target listener, regardless of which channel is used. If the PTT speech control request is sent as an SDB message through the speaker's reverse common channel and the pause response timer of the target group is set to zero in the CM, the actual PTT latency at the speaker client is in order. The SDB response message on the directional link is reduced to the time required to send the SDB request message on the subsequent reverse link.

【0064】

(Network interface to ring signal message) Determines which of the special traffic originating from the network, such as the SDB payload, was sent for an idle mobile station without a dedicated traffic channel. Therefore, some infrastructure policies or interfaces may be implemented to distinguish such traffic from other traffic.

【0065】

In the first embodiment, IP datagrams are filtered based on their size so that SDB messages can carry a restricted user payload. If an IP datagram smaller than the predetermined size limit is directed to a mobile that does not have a dedicated traffic channel, it will be sent as an SDB message. Since the application speech request response message is extremely small, for example, 34 bytes including the IP header, the group communication system can use such a filter.

【0066】

In the second embodiment, the infrastructure vendor can define an IP-based service for encapsulating IP traffic destined for mobile stations for distribution. IP servers with knowledge of this service may not have a dedicated traffic channel, such as UDP, with IP headers for services for delivery, as well as small, properly encapsulated IP datagrams. Send to. The group communication system can use this service to indicate to the infrastructure, for example, that this speak request response message has been delivered in SDB format to the requesting client MS. Coordinating SDB traffic with undetermined pages or service origination requests is also important to ensure fast and reliable delivery of user traffic.

【0067】

In a third embodiment, the IP server sends a special IP datagram, such as UDP, along with an IP header for delivery to a mobile that does not appear to have a dedicated traffic channel. The IP server may append an IP datagram instructing the infrastructure to deliver this IP datagram to the client MS, for example by specifying a special value in the IP header. This group communication system uses this service to indicate to the infrastructure that, for example, a speech request response message has been delivered to the requesting client MS in SDB format. In a third embodiment, UDP or TCP port ranges can be reserved for delivering special IP datagrams, such as SDB messages.

【0068】

(Mobile-initiated service origination request and paging) In one embodiment, the speaker's mobile station (MS) sends a speech control request 302 to a CM, for example in SDB format, as described with reference to FIG. To do. Immediately thereafter, a service origination request 304 is made to a wireless infrastructure such as CDMA in order to quickly reestablish the traffic channel. However, if the pause response timer is set to a small value, the CM responds quickly to this speech control request 310 and returns the response 312 to the speaker's MS. If this response reaches the infrastructure during the early stages of service origination process 304, the infrastructure will notice that this speaker MS has no active traffic channels and this speaker Attempt to page the response to MS. However, this paging behavior may disrupt the service origination process that is already in progress. In one embodiment, the speaker MS responds to this page, ensuring that this speech control response message has been delivered to the speaker. Then request service origination again. However, there is an unnecessary delay in reestablishing the speaker's traffic channel as a result of the interrupted original service origination attempt.

【0069】

In the first embodiment, in order to avoid a race condition between the service origination process and paging, the CM is configured not to respond quickly to the speech control request 310. Thus, for example, within a CM, the pause response timer is adjusted so that the CM can send a response 312 to the speaker MS after the service origination process 304 is complete.

【0070】

In the second embodiment, the PDSN that receives the CM-initiated response 312 and the mobile switching center (MSC) that responds to the speaker's service origination request are coordinated. That is, if the CM-initiated response 312 reaches the infrastructure, and if the PDSN determines that the packet data service origination process for the speaker MS is already in progress, the MSC will paging the speaker MS. Can be postponed. Once the service origination process is complete, the PDSN caches this response and sends it through the speaker's mobile forward traffic channel. Alternatively, if this service origination process is still in progress, the MSC sends this response as an SDB message to the speaker's MS.

【0071】

In the third embodiment, the speaker MS can avoid the race condition by not issuing the service origination request 304 until after the response to the speech control request 302 is received. In one embodiment, the speaker MS does not have a dedicated traffic channel in operation, so the CM responds to the speaker MS with a valid forward common channel, such as a forward paging channel or a forward common control channel. Send. In one embodiment, the CM sends a response to the speaker MS in SDB format. This speaker MS relies on the speech control message 312 generated by the CM to trigger the restart of the traffic channel. Similarly, the wake-up request sent by the CM triggers the reactivation of the traffic channel for the listener's mobile. The race condition is avoided by avoiding the potential for mobile-initiated service origination and network-initiated mobile paging to occur at the same time.

【0072】

(Cache of packet data triggers initiated by the network) IP datagrams that include awakening trigger 402, reach a wireless infrastructure such as CDMA, and are directed to the listener's mobile without a dedicated traffic channel are generally networks. , Or can be lost by either wireless infrastructure. In one embodiment, the wake-up trigger 402 sent to the listener mobile is actively retransmitted according to a defined schedule until the listener's response or group wake-up timer expires. For example, the wake-up trigger 402 is retransmitted every 500ms. However, retransmitting the wake-up trigger 402 at this rate can be up to 500 ms from the time the listener's traffic channel is reestablished to the time the next wake-up trigger directed at the listener reaches the infrastructure. Can result in a delay of up to 250 ms on average.

【0073】

In one embodiment, the infrastructure in the network, or perhaps another entity, caches the recall trigger 402 sent by the CM and delivers it to the target MS as soon as the target MS reestablishes its traffic channel. This eliminates the need to retransmit the recall request 412 made by the CM and reduces the total time required for pause recall. For example, by caching the recall trigger 402 as compared to retransmitting at a rate of 500 ms, a delay of up to 500 ms can be removed from the total time required for pause recall.

【0074】

(Media Buffering) In one embodiment, the user is allowed to start a conversation by buffering the media after requesting speech control and before the dedicated channel is reestablished between the client and the listener. .. By buffering the speaker's voice, the system allows the speaker to start a conversation before the listener's traffic channel is completely reestablished. This allows the speaker to start speaking faster and reduces the apparent PTT latency. The listener does not experience PTT latency and is not affected by this. That is, the PTT wait time is shifted from the speaker to the other part of the system. The speaker waits for a response from the listener before starting to speak. However, as mentioned above, the speaker already expects that the response to the beginning of the conversation will take longer than the response made in the actual conversation. The buffering at the beginning of the talk by the speaker is done on the CM side or the client MS side.

【0075】

(CM buffering) In one embodiment, the CM buffers the beginning of the speaker's speech. After the user presses his PTT button and the user's traffic channel is reestablished, the user is allowed to communicate with the CM. At this time, the listener's traffic channel has not yet been established, so the CM buffers the speaker's voice for future transmission to the target listener. CM buffering reduces the apparent PTT latency that the speaker considers to be the appropriate time to trigger the speaker's traffic channel. FIG. 5 is a diagram showing CM buffering according to an embodiment.

【0076】

(Client-side buffering) In one embodiment, if shorter apparent latency is desired, the speaker may be allowed to start speaking before his traffic is reestablished. Since the client MS has not yet communicated with the CM, the signal to the speaker to start the conversation is created by the client MS. If the speaker is allowed to speak before the speaker's traffic channel is reestablished, the client MS can buffer the voice. Permission to talk is given "optimistically" because communication with the CM has not been established. FIG. 6 is a diagram showing buffering by the client side according to an embodiment. In some embodiments, CM buffering and client-side buffering can work at the same time. Client-side buffering can reduce the apparent PTT latency.

【0077】

CM buffering may not change the total delay. The user may experience the same delay when receiving a response reply from the listener, but the speaker's apparent PTT delay is smaller.

【0078】

In one embodiment, the client MS buffers the media and controls the apparent PTT delay experienced by the user. The combination of mobile-originated SDBs and client-side media buffers reduces the delay associated with reestablishing active traffic channels.

【0079】

(Rapid paging channel) In one embodiment, the CM generates its own traffic channel until the group's wake-up time ends, or all listener clients respond to network-initiated triggers. Until, the response to the speaker's PTT request is delayed. The CM waits for all listeners to be paged before the speaker is allowed to stream the media in the group. The longer the group listener takes to respond to the page, the longer the PTT wait time felt by the speaker.

【0080】

In one embodiment, the CM individually sends a series of wake-up triggers to each listener client during the pause wake-up time. This causes one or more pages for each mobile by reaching infrastructure such as CDMA. After receiving the page, each mobile reestablishes the traffic channel, receives the next recall request sent, and responds to the CM with a response to the recall request. Most of the time the listener's handset is required to respond to this application-level "ping" is spent in the infrastructure waiting for the appropriate amount of time to page the mobile.

【0081】

To preserve battery life, the mobile does not need to constantly monitor each of the, for example, 2048 slots defined within the paging channel when idle. Rather, the mobile can monitor either the forward common control channel (F-CCCH) or the forward paging channel (F-PCH), depending on its capabilities. In addition, mobile can monitor paging slots according to the slot period index.

【0082】

In one embodiment, the mobile operates in "slot paging" mode to preserve battery life. In this mode, the mobile operates periodically for a short period of time, listening to pages sent by the base station (BS). This BS, which knows when the mobile listens, can send pages to this particular mobile during a particular paging slot.

【0083】

In one embodiment, the duration of mobile operation and listening to the paging channel is controlled by a parameter called the Slot Period Index (SCI). The higher the SCI, the more mobile will work and the longer the inter-slot time to listen to the paging channel. Since the phone is dormant most of the time, a large slot cycle value increases the phone's standby time, but increases the amount of time the BS has to wait before pausing this phone.

【0084】

The total BS time that a page needs to be delayed for a phone varies between zero and full slot cycles. Zero if the phone slot is started when the BS needs to page. It is a full slot cycle when the phone slot is finished until the BS needs to page the phone. On average, the delay due to having a phone slot coming in is half the slot period time. The shorter the slot cycle used by mobile, the faster the listener will be paged by the infrastructure. However, the shorter the slot cycle, the higher the rate of battery consumption.

【0085】

In one embodiment, when there are undecided pages without the mobile needing to monitor the paging channel, the forward rapid paging channel (F-QPCH) is that this mobile is in efficient output. It is used to enable the determination of things. Mobile, which can monitor F-QPCH, operates for each predetermined number of slots and extracts the value of a 1-bit indicator within 80 ms, for example, on the paging channel. If the extracted bits are not set, there are no undecided pages in the paging channel and the mobile pauses in another slot cycle. If the extracted bits are set, the page for this mobile is undecided, the mobile will start working and will self to monitor the paging channel at the next appropriate paging channel slot. Schedule.

【0086】

The modulation applied by the F-QPCH allows the mobile to monitor the F-QPCH much more efficiently than it can monitor the paging channel. This allows the mobile to operate efficiently with efficient output and very short slot cycles. One advantage of using F-QPCH is that mobile detects common page messages from the infrastructure, ie wake-up request messages from CM, with faster slot cycles than allowed at the same battery consumption rate. And have the means to respond to this. This translates into the ability to minimize one component of delay. That is, it directly contributes to the PTT waiting time and the total time required to wake up the pause, that is, the time required to reestablish the listener's traffic channel.

【0087】

(Slot Timer) In one embodiment, the mobile may operate in a non-slot paging mode coupled with a "slot timer". When operational, this slot timer requires the mobile to monitor the paging channel in non-slot mode by releasing a dedicated traffic channel and entering idle mode for the time period defined by the slot timer. .. The value of this timer can be set at the base station. This feature allows the infrastructure to instruct the mobile to monitor each slot in the paging channel, for example 80ms, when in idle mode. This feature also provides the infrastructure with a way to page mobile within any slot. When using the rapid paging channel feature alone, one advantage of using non-slot mode is that it provides a means for mobile to detect and respond to pages more quickly, even at the same battery consumption rate. This reduces the time required to reestablish the listener's traffic channel during the pause awakening period.

【0088】

Without the rapid paging channel capability, long-term use of non-slot monitors can be expensive in terms of battery life. However, the combined use of this rapid paging channel with non-slot mode provides a means to page mobile very quickly, for example within one or two slot periods, 80ms to 160ms.

【0089】

Non-slot mode can be considered as one of two intermediate pauses in effect for mobile stations. When operating in non-slot mode, mobile is considered technically dormant as it does not have a dedicated physical channel. However, in this mode, the mobile is paged essentially immediately in the slot, thus avoiding the paging delay associated with network-initiated restarts.

【0090】

(Control Hold Mode) In one embodiment, the mobile may operate under the packet data standard. The standard provides additional hibernation that allows mobile and infrastructure to maintain a mobile-related PPP tier state, while allowing terminals to release dedicated traffic channels and resources associated with mobile packet data service option calls. / Provide an idle state. Either mobile or infrastructure reestablishes the traffic channel and renegotiates with RLP to shift the state of packet data invocation from hibernation / idle to operational. The time required to reestablish a traffic channel depends on whether the mobile or infrastructure has initiated a reestablishment. However, in any case, this delay is comparable to the delay required to generate a new call in the system, as essentially all system resources are required and need to be allocated to mobile. is there.

【0091】

In one embodiment, the mobile may operate in a "control hold" mode, which acts as an intermediate position between the operating mode and the idle mode. In control hold mode, the dedicated traffic channel associated with the mobile is released, allowing the mobile reverse pilot to operate in "gate" mode. In some embodiments, a dedicated common control channel and / or RLP state is also managed. In essence, control hold mode gives a semi-hibernation state. In this state, most system resources are allocated, but the average reverse link transmission output is reduced to the gate pilot to reduce the impact on system capabilities. FIG. 7 is a diagram showing a typical configuration for a wireless mode.

【0092】

In one embodiment, the mobile may transition from operation mode to control hold mode by sending either a resource release request message or a resource release request mini-message. The mobile can transition from control hold mode to operation mode by sending either a resource request message or a resource request mini message. These messages can be carried via a dedicated control channel. The mini-message can then be sent by using shorter frames, eg 5ms. This allows for a quick transition to and from control hold mode. The advantage of the control hold mode is that, as mentioned above, a relatively quick transition from the control hold mode to the operating mode is possible compared to the traditional idle mode or hibernate / idle mode.

【0093】

In one embodiment, upon receiving an indication from the CM that the registered group has transitioned to group hibernation, the client mobile first initiates the transition to control hold mode, after a period of duration of operation, and then further. Shift to idle mode. Therefore, once the user presses the PTT or a recall request trigger is received in the infrastructure, control hold mode provides a mechanism to significantly reduce the time required to reestablish a dedicated traffic channel. To do.

【0094】

(Stored Service Settings) In one embodiment, the infrastructure provides the ability to cache or store service settings state on mobile and infrastructure when transitioning to idle mode. When returning to operational mode and reestablishing the traffic channel, the mobile indicates whether the service settings for the call have been cached or stored, either by an origination message or a page response message. Mobile may also include a Cyclic Redundancy Check (CRC) in its origination or page response message. This can be calculated through the total length of the service configuration. If the base station also caches the service settings, the base station uses the received CRC to verify that the service settings match the service settings stored on the mobile. And if there is a match, the BS indicates in the "service connection message" that this mobile is using the previously stored service settings.

【0095】

In one embodiment, transitioning from idle mode does not require changing service settings by using the packet data service option. Therefore, by using the stored service settings, the time required to reestablish a dedicated traffic channel resource is significantly reduced. Therefore, the stored service configuration feature is idle by reducing the time required to reestablish the traffic channel carrying both the PTT signal and associated media and providing a mechanism to significantly reduce PTT latency. Brings significant improvements to the mode.

【0096】

In one embodiment, the transition from the operating mode of the client MS to the idle mode can be achieved as follows. 1. The group is up and mobile has its own traffic channel. 2. After a downtime that exceeds the group hang time timer, the application layer group pause announcement is received through the mobile forward traffic channel. 3. Mobile shifts to control hold mode and caches the state of service settings. Moreover, the client base station also caches the state of the service settings. 4. After the downtime, the mobile releases the dedicated channel and goes into idle mode. Mobile begins rapid paging channel monitoring and enters non-slot mode when directed by the infrastructure. The mobile is put into operation mode if it has a relatively short downtime, either due to a PTT press by a local user or packet data traffic from other group participants originating from the network. Before returning, it will not reach idle mode. In this case, the mobile has a dedicated channel, so it quickly returns to operating mode. In one embodiment, the hibernate wake-up event is executed as follows: 1. The group is dormant and all mobiles are idle without a dedicated physical channel. Mobile monitors quick paging channels. 2. In response to the user's PushTalk, the speaker's mobile signals the CM through several valid reverse common channels, along with a request message from the application layer. This message can be in short data burst format. The speaker's mobile can start buffering the previous user media from this point. 3. The speaker's mobile sends an "origination message" to the infrastructure to reestablish the traffic channel. This caches the service configuration and indicates in the request that it contains a CRC through the configuration data. This initiates the process of reestablishing the speaker's mobile traffic channel. 4. The CM receives the request for speech, decides whether or not to accept the request through the arbitrage process, and sends a request for speech response message to the speaker. The CM will also begin sending a series of recall requests to all participants. 5. By getting each wake-up request, the infrastructure pages each listener's mobile with the first decision to determine the next appropriate slot. This first decision is to page the listener's mobile and signal via F-QPCH prior to the slot where the page is undecided about paging the channel to the listener's mobile. 6. Each listener mobile monitors the paging channel for the page by getting the display in F-QPCH where the page is undecided. 7. By retrieving pages on the paging channel, each listener mobile responds to a page indicating that the service settings are cached and contain CRC via the settings data. This initiates the process of reestablishing the listener's mobile traffic channel. 8. After establishing the speaker's traffic channel, the next speech request response from the CM is received by the speaker. The speaker starts streaming the media to the commercial. 9. After establishing each listener's traffic channel, the next wake-up request sent by the CM is received by the listener. The listener responds with a wake-up response message. 10. Once all listeners have responded or the group wake-up timer has expired, the CM will begin streaming media to the group. The CM receives the request for speech, decides whether or not to accept the request through the arbitrage process, and sends a request for speech response message to the speaker. The CM will also begin sending a series of recall requests to all participants. 5. By getting each wake-up request, the infrastructure pages each listener's mobile with the first decision to determine the next appropriate slot. This first decision is to page the listener's mobile and signal via F-QPCH prior to the slot where the page is undecided about paging the channel to the listener's mobile. 6. Each listener mobile monitors the paging channel for the page by getting the display in F-QPCH where the page is undecided. 7. By retrieving pages on the paging channel, each listener mobile responds to a page indicating that the service settings are cached and contain CRC via the settings data. This initiates the process of reestablishing the listener's mobile traffic channel. 8. After the speaker's traffic channel is established, the next speech request response from the CM is received by the speaker. The speaker starts streaming the media to the commercial. 9. After establishing each listener's traffic channel, the next wake-up request sent by the CM is received by the listener. The listener responds with a wake-up response message. 10. Once all listeners have responded or the group wake-up timer has expired, the CM will begin streaming media to the group. The CM receives the request for speech, decides whether or not to accept the request through the arbitrage process, and sends a request for speech response message to the speaker. The CM will also begin sending a series of recall requests to all participants. 5. By getting each wake-up request, the infrastructure pages each listener's mobile with the first decision to determine the next appropriate slot. This first decision is to page the listener's mobile and signal via F-QPCH prior to the slot where the page is undecided about paging the channel to the listener's mobile. 6. Each listener mobile monitors the paging channel for the page by getting the display in F-QPCH where the page is undecided. 7. By retrieving pages on the paging channel, each listener mobile responds to a page indicating that the service settings are cached and contain CRC via the settings data. This initiates the process of reestablishing the listener's mobile traffic channel. 8. After the speaker's traffic channel is established, the next speech request response from the CM is received by the speaker. The speaker starts streaming the media to the commercial. 9. After establishing each listener's traffic channel, the next wake-up request sent by the CM is received by the listener. The listener responds with a wake-up response message. 10. Once all listeners have responded or the group wake-up timer has expired, the CM will begin streaming media to the group. By getting each wake-up request, the infrastructure pages each listener's mobile with a first decision to determine the next appropriate slot. This first decision is to page the listener's mobile and signal via F-QPCH prior to the slot where the page is undecided about paging the channel to the listener's mobile. 6. Each listener mobile monitors the paging channel for the page by getting the display in F-QPCH where the page is undecided. 7. By retrieving pages on the paging channel, each listener mobile responds to a page indicating that the service settings are cached and contain CRC via the settings data. This initiates the process of reestablishing the listener's mobile traffic channel. 8. After the speaker's traffic channel is established, the next speech request response from the CM is received by the speaker. The speaker starts streaming the media to the commercial. 9. After establishing each listener's traffic channel, the next wake-up request sent by the CM is received by the listener. The listener responds with a wake-up response message. 10. Once all listeners have responded or the group wake-up timer has expired, the CM will begin streaming media to the group. By getting each wake-up request, the infrastructure pages each listener's mobile with a first decision to determine the next appropriate slot. This first decision is to page the listener's mobile and signal via F-QPCH prior to the slot where the page is undecided about paging the channel to the listener's mobile. 6. Each listener mobile monitors the paging channel for the page by getting the display in F-QPCH where the page is undecided. 7. By retrieving pages on the paging channel, each listener mobile responds to a page indicating that the service settings are cached and contain CRC via the settings data. This initiates the process of reestablishing the listener's mobile traffic channel. 8. After establishing the speaker's traffic channel, the next speech request response from the CM is received by the speaker. The speaker starts streaming the media to the commercial. 9. After establishing each listener's traffic channel, the next wake-up request sent by the CM is received by the listener. The listener responds with a wake-up response message. 10. Once all listeners have responded or the group wake-up timer has expired, the CM will begin streaming media to the group. After the speaker's traffic channel is established, the next speech request response from the CM is received by the speaker. The speaker starts streaming the media to the commercial. 9. After establishing each listener's traffic channel, the next wake-up request sent by the CM is received by the listener. The listener responds with a wake-up response message. 10. Once all listeners have responded or the group wake-up timer has expired, the CM will begin streaming media to the group. After the speaker's traffic channel is established, the next speech request response from the CM is received by the speaker. The speaker starts streaming the media to the commercial. 9. After establishing each listener's traffic channel, the next wake-up request sent by the CM is received by the listener. The listener responds with a wake-up response message. 10. Once all listeners have responded or the group wake-up timer has expired, the CM will begin streaming media to the group.

【0097】

Therefore, an embodiment for a method and device for reducing latency in a group communication network described above is to exchange group call signals even when the mobile is in hibernation and the traffic channel is not in operation. Significantly reduces the actual total time required for pause wake-up time and PTT waiting time. This method and device exchange group call signals by using short data burst (SDB) message signals. This method and device conveniently reestablishes a dedicated traffic channel for the speaker's mobile and the dormant listener's mobile in parallel.

【0098】

In another embodiment, the hibernate-wake wait time in a group communication network caches the wake trigger from the network directed to the target listener and targets the wake trigger as soon as the target mobile station reestablishes the traffic channel. It is reduced by delivering to the station.

【0099】

In another embodiment, simultaneous service origination and paging on mobile operating in a group communication network is avoided by sending a response to a speech control request after the service origination process is complete. In one embodiment, if the service origination process is not completed, the response to the speech control request will be of SDB type. In another embodiment, the service origination process for this source communication device is started after this response has been sent to the source communication device.

[Simple explanation of drawings]

【0100】

FIG. 1 is a diagram showing a group communication system.

FIG. 2 is a diagram showing an interaction between a communication device and a communication manager.

FIG. 3 is a diagram showing details of a call signal for a speech control request process according to an embodiment.

FIG. 4 shows details of a call signal for a network-initialized wake-up process according to an embodiment.

FIG. 5 is a diagram showing media buffering on the communication manager side according to an embodiment.

FIG. 6 is a diagram showing media buffering on the client side according to an embodiment.

FIG. 7 is a diagram showing a typical wireless link mode according to an embodiment.

[Explanation of symbols]

【0101】

100 ... Group communication system, 102,104,106,108,202,206,208 ... Communication device (CD), 110,204 ... Communication manager (CM), 112 ... Security manager (SM), 116 ... Base station (BS), 118. .. Satellite gateway, 120 ... distributed network, 122 ... mobile switching center (MSC), 124 ... public communication exchange network, 126 ... modem bank, 128 ... NBS terminal, 200 .. .NBS System, 210 ... Session Start Protocol Channel (SIP), 212 ... NBS Media Signal Channel, 214 ... Media Traffic Channel, 302 ... PTT Speak Request, 304,408 ... Dedicated Traffic Channel, 306,410 ... wireless link protocol synchronization, 308,310 ... PTT speech control request, 312,314 ... PTT speech permission, 316,418 ... media, 402,412 ... trigger, 406 ... page, 414 ... recall response , 416 ... Speaker announcement