CN1977493B - Method and system for providing channel access for voice transmission - Google Patents

Abstract

In a TDMA system, a plurality of subscriber units (SU; 12, 14, 22) and a plurality of base stations (BR; 5, 7, 13) provide channel access for voice transmissions. The SU requests a voice transmission by pressing "talk-back" on the mobile unit (202). The SU then determines whether the voice transmission is scheduled for "polite" channel access (216). If the "polite" channel access specifies that the SU is for all "polites" (216), the SU sends negative feedback to the SU user (220). Alternatively, if the "polite" channel access specifies that the SU is not for all "polites" (218), but for its own color code "polites" (218), then the SU performs slot synchronization with the BR.

Description

Method and system for providing channel access for voice transmission

technical field

The present invention relates generally to wireless communication systems, and more particularly to speech transmission in Time Division Multiple Access (TDMA) systems.

Background technique

A wireless communication system may generally include a set of "subscriber units," which are typically the terminus of a communication path, and a set of "base stations," which are generally stationary and serve as an intermediary through which base stations may establish or maintain access to Subscriber Unit (SU) communication path. One such type of system is a time division multiple access (TDMA) communication system in which the wireless medium is divided into time slots to carry the communications of the system. Since the wireless medium is a shared medium, access to the wireless medium needs to be managed and SUs need to be allowed to use the wireless medium for voice communication.

Specifically, for a SU to transmit, the SU must first activate the Base Radio (BR) and get synchronized. Once synchronization is obtained, the SU calls to set up the call and then transmits over the wireless medium. Since BR activation and synchronization are necessary, additional time is required to establish the call. Thus, it is desirable to avoid these procedures, thereby reducing the time required to set up a call. Furthermore, there are situations where during the context of an active call, a particular SU requires preferential access to the wireless medium and needs to be given access to the wireless medium for that SU to transmit.

Thus, there is a need to provide access to channels for voice communications.

Contents of the invention

According to one aspect of the present invention, there is provided in a wireless communication system comprising a plurality of subscriber units and a plurality of base stations, a method of allowing a first subscriber unit to access a channel for voice transmissions, the The method comprises the steps of: determining that a first subscriber unit is provided for polite access to a channel, wherein said first subscriber unit considers the type of communication currently taking place on the channel before accessing the channel for its own communications, wherein The first subscriber unit is characterized by a first color code and a first conversation group ID; the channel is detected for voice transmission from a second subscriber unit having a second color code and a second a conversation group ID; and if the first conversation group ID matches the second conversation group ID, allowing the first subscriber unit to access the channel for voice transmission even if the channel is being used by the second subscriber unit for voice transmission.

According to another aspect of the present invention, there is provided in a wireless communication system comprising a plurality of subscriber units and a plurality of base stations, a method of allowing a first subscriber unit to access a channel for voice transmissions, The method comprises the steps of:

determining that the first subscriber unit is provisioned for polite access to a channel, wherein the first subscriber unit considers the type of communication currently taking place on the channel before accessing the channel for its own communications, wherein the first the subscriber unit is characterized by a first color code;

detecting a channel for voice transmissions from a second subscriber unit having a second color code; and

If the first color code and the second color code do not match, the first subscriber unit is permitted to access the channel for voice transmission even if the channel is being used by the second subscriber unit for voice transmission. channel.

Description of drawings

Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 shows a block diagram of an example wireless communication system according to an embodiment of the present invention.

2 shows a flowchart of an example method of providing channel access for voice transmissions.

FIG. 3 shows a continuation of the example shown in FIG. 2 .

FIG. 4 shows a further continuation of the example shown in FIGS. 2 and 3 .

It will be understood that, for simplicity and clarity of the drawings, the various components shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the features are exaggerated relative to each other. Further, where considered appropriate, repeated reference numerals have been used in the drawings to refer to like parts.

Detailed ways

Referring now to FIG. 1 , an example of the method and apparatus of the present invention is shown as it is used and integrated into a commonly used wireless communication system 100 . The illustrated example includes a plurality of cells, each having a base radio (BR) 3, 5, 7, 9, 11, 13 located generally at the center of the cell, and a plurality of subscriber units 12, 14, 16, 18, 20, 22. Subscriber units 12, 14, 16, 18, 20, 22 utilize base stations 3, 5, 7, 9, 11, 13 to send and receive communications.

A Subscriber Unit (SU) preferably comprises a mobile or portable device (such as a vehicular or hand-held radio or a wireless telephone) capable of communicating with the BR using the Time Division Multiple Access (TDMA) or Time Division Duplex (TDD) techniques described above. A communication in which a specific period of time is divided into time slots allocated for each communication. In the exemplary embodiment of the present invention, the wireless communication system 100 adopts a TDMA communication system of two time slots, however, other time slot ratios may be used in a TDMA communication system, and this still belongs to the spirit of the present invention and falls within the scope of the present invention. within the protection scope of the present invention. In an exemplary embodiment, the SU initiates voice communication with a push to PTT (push to talk), which sends a request for the wireless medium to the BR.

The BR preferably includes fixed equipment for communicating data/control and voice information to and from SUs to facilitate communication between SUs in the wireless communication system 100 . An illustrative embodiment of the invention includes a BR that (dekeys) 5 seconds after the BR determines that there is no valid SU activity on the wireless medium. In an exemplary embodiment, such a timer is referred to as a Subscriber Off Timer (SIT). In the above embodiment, the SIT is turned off for 5 seconds after it is determined that there is no valid SU activity on either of the two time slots of the TDMA communication system. The SIT is started when there is no valid SU activity on the wireless medium, and is stopped whenever the BR determines that there is valid SU activity on the wireless medium. In another illustrative embodiment, wireless communication system 100 includes a BR that also shuts down after 180 seconds. The above time period is specified in the BR and is called a time-out timer (TOT). The TOT is reset when a new SU transmission is detected on the wireless medium. The TOT is stopped when the BR is closed due to a SIT timeout, and the BR is closed when the TOT expires, which will end any communications in progress.

Communications initiated or repeated by a BR and sent to a Subscriber Unit (SU) are defined as downlink, while communications initiated by a SU and sent to a BR are defined as uplink. In the exemplary embodiment, each BR 3, 5, 7, 9, 11, 13 does not transmit downlink continuously, but each BR maintains synchronous communication such that multiple The slots are kept synchronized based on the BR downlink.

In an illustrative embodiment, synchronization is provided by a message identifying the center of a TDMA burst. In SU or BR, the receiver performs symbol recovery and identification of TDMA burst centers using matched filters and correlators. Once the receiver is synchronized to the channel, the receiver uses pattern matching to detect the presence of messages indicating that the channel exists and is synchronized. The message indicates the type of synchronization that exists on the channel. In an illustrative embodiment, the messages are used to distinguish: a) voice bursts from data/control bursts, and from voice bursts to reverse channel bursts; b) inbound channels from outbound channels ; c) the type of modulation on the channel, such as Motorola P25Phase 1 FDMA vs. Motorola P25Phase 2 TDMA; and d) the type of wireless communication system, such as Motorola P25system vs. Motorola Low Tier Digital system.

As used herein, the terms "communication" and "transmission" are used interchangeably and refer to a continuous TDMA burst sent from one station in one time slot. Thus, transmission generally refers to: voice, data or control information associated with the wireless communication system 100 . The term "call" refers to an associated voice transmission between SUs in the wireless communication system 100 . In an exemplary embodiment, voice transmissions in a call are separated by idle times announced by messages informing the user that the wireless medium is in an idle state. Furthermore, the message informing the user that the wireless medium is idle is sent on the downlink due to an idle time occurring on the uplink.

As known in the art, the term "burst" refers to the smallest independent unit of a TDMA transmission. In the illustrative embodiment, for bursts occurring in the Motorola Low Tier Digital system, the defined transmission is 216 bits of payload and 48 bits of synchronization or embedded signaling. The defined transfer takes 27.5 milliseconds to send, and there is a guard time of 1.25 milliseconds on both sides of the actual transfer. Thus, the "burst" in the aforementioned Motorola Low TierDigital system is 30 milliseconds.

Before accessing the wireless medium (also called "channel" in the prior art) for voice communication, the SU considers the mode required for the requested voice communication. For example, a SU may send voice communications in a repeater mode or in a talk (talk) mode. If the requested voice communication requires relay mode, the SU asks the BR to complete the voice communication. In an illustrative embodiment, repeater mode is defined as a SU voice transmission in which the SU transmits at an uplink frequency and radiates RR energy to the BR. The BR then converts the voice transmission to a downlink frequency and radiates RF energy to the target SU. If the requested voice communication requires intercom mode, the SU does not ask the BR to complete the voice communication. In an illustrative embodiment, talkback mode is defined as a SU voice transmission in which the SU transmits at a downlink frequency and radiates RF energy to the target SU. As known in the prior art, intercom mode is also known as direct mode and is characterized in that the SU voice transmission is that the SU transmits at the downlink frequency without the assistance of the BR.

In an illustrative embodiment, either the SU or the BR may radiate RF energy, where radiating means transmitting on a channel. Additionally, the communication between SU and BR can be voice or data/control. Thus, there are four types of communication on the channel: SU source speech, SU source data (/control), BR source speech and BR source data (/control). In order for the receiver in the SU or BR to know what type of communication was sent, and for the receiver to process the communication appropriately, the communication contains a 48-bit (24-symbol) frame synchronization word that identifies the type of communication.

Before accessing the channel for voice communication, the SU takes into account the defined characteristics of the SU. A defined property of a SU is a programmed attribute or characteristic that instructs the SU how to operate. In the illustrative embodiment, Customer Specified Software (CPS), also known as Radio Service Software (RSS), developed by Motorola Corporation, is used to assign defined characteristics to the SU. For example, a SU may access a channel according to a "polite" prescribed characteristic, where "polite" means considering what type of communication currently exists on the channel before accessing the channel for the SU's own communication. In an exemplary embodiment, "polite" is subdivided into being "polite" to all voice communications on the channel, and "polite" only to other voice communications on the channel from other SUs with the same color code. SU "polite" to all means that the SU is "polite" to any detected channel activity.

If the SU is not "polite", it has the specified property of "disrespectful", where "disrespectful" means that the SU starts transmitting without first verifying that the channel is valid and clear. In an exemplary embodiment, an "urgent" communication is an "offensive" communication.

As known in the art, a "color code" is a common identifier used by a set of SU groups utilizing the same BR. For example, as shown in Figure 1, since SU 12, 14, and 22 use the same BR, namely BR9, they have the same color code. In addition, color code fields can be present in embedded signaling messages and generally in data bursts to provide a means of addressing wireless networks or specific repeaters so that co-channel interference can be excluded. Also known in the prior art, a "session group" is a group of SUs sharing an RF frequency and time slot and having the same color code. In an illustrative embodiment, a conversation group is identified by a 16-bit session group identifier (TGID) and individual subscriber units are identified by a 24-bit subscriber unit identifier (SUID). Thus, in an illustrative embodiment, SUs that share a color code are further divided into talkgroups such that SUs in one talkgroup cannot hear SUs in another talkgroup.

In an exemplary embodiment, a SU with a prescribed characteristic of "disrespect" and in direct mode has access to the channel to send voice communications regardless of whether the channel is busy or any other factor of the channel.

In an exemplary embodiment, a SU that has a "polite" specified characteristic to all other SUs regardless of the color code and is in direct mode will be allowed access to the channel unless RF energy is present on the channel. The term "RF energy on the channel" means that the RF energy on the channel exceeds the threshold specified in the SU. Thus, in an exemplary embodiment, a SU is prohibited from accessing a channel when the measured RF energy level on the channel is above the CPS characteristic for channel access. In addition, if the SU is a party to the call, the SU is allowed to transmit "insolently", where "insolently" means that the SU starts transmitting immediately after the voice transmission.

In an exemplary embodiment, unless RF energy is present on the channel or unless voice transmissions on the channel match the SU's color code, a SU with the prescribed characteristic of "polite" to the same color code and in direct mode will be allowed to access the channel. Therefore, before allowing or disabling a requested voice transmission, the SU considers the presence or absence of RF energy on the channel and determines the color code for the voice transmission. The above transmissions require time slot synchronization to determine the color coding of voice transmissions on the channel. In addition, if the SU is a party to the call, the SU is allowed to transmit "insolently", where "insolently" means that the SU starts transmitting immediately after the voice transmission.

In an exemplary embodiment, when a SU is in repeater mode and has the prescribed characteristic of being "disrespectful" to voice communications on the channel, the SU requires the SU to be downlink-synchronized with the BR before allowing voice communications, for the correct The color code is checked and identifies the TDMA channel. In an exemplary embodiment, synchronization with the BR may require performing a BR wake-up procedure if the BR is not awake, specifically if the downlink of the BR is not active. A SU in repeater mode with the specified characteristic of "disrespect" provides no protection for calls or transmissions on the channel. Thus, regardless of whether the voice transmission is analog or digital, has the same color code, or is the same call, the "disrespectful" SU will access the channel for its own communication.

In an exemplary embodiment, if the SU has a prescribed characteristic of "polite" for all voice communications on the channel and is in repeater mode, the SU is allowed access to the channel only after taking into account the channel state. If the SU is in repeater mode and is "polite" for all voice communications, protect co-channel users regardless of whether those transmissions are analog or digital, have the same color code, or are the same call transmission. Furthermore, if the SU is a party to an ongoing call, the SU is allowed to transmit "indecently," where "indecently" means immediately following a valid transmission in progress. If the SU is not a party to an ongoing call, the SU is not allowed to access the channel. In operation, the above combination requires the SU to consider the presence or absence of RF energy on the channel before accessing the channel for voice communication; requires the BR to downlink synchronize, check for correct color codes, and identify the TDMA channel. Further, synchronization with the BR may require performing a BR wake-up procedure if the BR is not awake, specifically if the downlink of the BR is not active.

In an exemplary embodiment, a SU that is in repeater mode and has a defined characteristic of "politeness" for the same color code allows the SU to access the wireless channel only after taking into account the channel state. The above combination provides protection for digital co-channel users using the same color code. In addition, a SU is allowed to send rudely if it is a party to any ongoing call or transmission. Similar to the above scenario, when the SU is in repeater mode and has the specified characteristics of "disrespect", the SU is required to consider RF energy detection, synchronization with BR downlink, correct color code before voice transmission is allowed Test and identify TDMA channels. Further, synchronization with the BR may require performing a BR wake-up procedure if the BR is not awake, specifically if the downlink of the BR is not active.

Referring to Figures 2-4, in operation, the subscriber unit must wake up and request access for voice transmissions. As shown in FIG. 2, the subscriber unit requests voice transmission by pressing the PTT (block 202). If PTT is pressed, the SU checks to see if it is a party to an ongoing call (block 203). If the SU is a party to an ongoing call (block 203), the SU may be allowed access to the channel for voice transmission (block 416). If the SU is not, and if the SU has not been woken up (block 204), the SU must be woken up (block 208). If the SU is awake, it is determined whether the SU is scanning RF channels (block 206). If the SU is scanning, the SU stops scanning and tunes to a specific frequency to request voice transmission (block 210). If the SU is not scanning, the process continues.

Next, the SU requests voice transmission. If the SU requests voice transmission (block 212) in the direct mode in which no repeaters are required in the communication, the SU monitors the RF energy of the channel (block 214). Direct mode is also known as talkback mode. If the SU requests voice transmission in indirect mode (also known as relay mode) (block 212), the SU monitors the RF energy of the channel (block 222). In an illustrative embodiment, in direct mode, the SU transmits at a downlink frequency using SU source synchronization, and in relay mode, the SU transmits at an uplink frequency using SU source synchronization.

In direct mode, if the RF energy threshold is exceeded (block 214), the SU looks for synchronization and color code information. For further clarification, see the discussion of synchronization and color coding above. Based on the synchronization and color code information, the SU determines whether the voice transmission is a non-emergency call and is defined as a "polite" channel access (block 216). Additionally, if the "polite" channel access specifies that the SU is "polite" to all (block 218), the SU sends negative feedback to the SU user (block 220). Therefore, no voice transmission is performed over the wireless channel. Optionally, if the channel access of "polite" stipulates that SU is not all "polite" (block 218), but has "polite" (block 218) to its own color code, then As shown in 3, the SU judges whether the time slot is synchronized.

Further, if in direct mode and RF energy is not exceeded (block 214), the SU is ready to transmit as shown in FIG. 4 (block 418). Additionally, if in direct mode and the RF energy threshold is exceeded (block 214) and the voice transmission is an emergency call or the voice transmission is "disrespectful" (block 216), then as shown in FIG. Use wireless channels for voice communication.

In repeater mode, if the RF energy threshold is not exceeded (block 222), then the base station repeater (BR) needs to be woken up (block 224), if not woken up. The wake-up process (block 224) begins with the SU sending a slot wake-up message to the BR (block 228). The wake-up message is an idle message carrying synchronization information and color code information. BR checks whether the color code is correct and activates the downlink. Thus, as shown in Figure 2, if the BR is not activated or if the wake-up procedure fails in waking the BR, the request for voice transmission is not allowed. If the attempt to wake up the BR is unsuccessful after two attempts (block 226), negative feedback is given to the SU user (block 230).

Further, in repeater mode, if the RF energy threshold is exceeded, as shown in Figure 3, the SU determines whether the time slot is in sync (block 302). Also, as mentioned above, if the RF energy threshold is exceeded, the SU will look for sync and color code information.

Referring now to FIG. 3, the SU first checks to see if the communication between the SU and BR is in sync (block 302). If not, the SU attempts to synchronize (block 304). After attempting to synchronize (block 304), the SU checks the mode (block 308), communication type (block 310), and "polite" type (blocks 310, 312), where the communication type is, for example, emergency or non-urgent, and the "polite" type is, for example, "polite" to all, "polite" to one's own color code, or "disrespectful". If the SU cannot synchronize the communication between the BR and the SU or cannot check the above parameters, a negative feedback is given to the user (block 314).

In an exemplary embodiment, synchronizing between the BR and SU (block 304) includes waiting for a predetermined period of time in order to detect a slot synchronization signal. The slot sync signal is a 48-bit (also called 24-symbol) frame sync word. For a time slot, the slot synchronization signal is available every 360 milliseconds during a voice call and every 60 milliseconds during other conditions including: call hang time, channel hang time, and data transmission. The step of synchronizing (block 304) is completed when a slot synchronization signal is detected within a predetermined period of time (block 306).

If the communication between the SU and BR is in sync (block 302) or the SU successfully completes synchronization between the BR and SU (block 304), the SU recovers the color code from the TDMA channel (block 316). In an exemplary embodiment, the recovered color code is available in every burst except the burst containing the voice sync. Further, in an exemplary embodiment, the SU matches the recovered color code to the SU specified color code twice before a match is deemed to have occurred (block 318). If the recovered color code in the SU matches the SU specified color code (block 318) and the SU is in direct mode, the SU is not allowed to transmit and negative feedback is issued to the SU user (block 324). If in direct mode (block 320) and the recovered color code does not match the color code specified by the SU (block 318), then as shown in Figure 4, the SU is allowed to use the wireless channel for voice communications (block 418) .

Referring now to FIG. 4, there are various situations in which negative feedback is issued to the SU user (blocks 408, 420). One of these situations is that the SU is in repeater mode, has detected RF energy, is in sync with the BR, and the recovered color code matches the specified color code, but the SU cannot identify which time slot is one and which for a predetermined period of time Which slot is two (block 404). The SU determines the slot number by decoding the TDMA channel field in the Common Announcement Channel (CACH) message. In an exemplary embodiment, the SU matches the TDMA channel field in the CACH message twice (block 404) before determining the slot number. If the SU cannot determine the slot number within a predetermined period of time (block 406), negative feedback is sent to the SU user (block 408).

Additionally, if the SU determines that the voice transmission is a non-emergency call and is provisioned for "polite" channel access (block 410), and the time slot is being used by system-wide communications (block 416) or the time slot is being used by another If a SU is occupied (block 414), negative feedback is issued to the SU user (block 420). In all other cases, the SU is allowed to use the wireless channel for voice communications (block 418). For example, if the emergency feature of a "polite" SU is activated, the SU behaves "politely" and can access the channel.

In order for the SU to allow voice transmission (block 418), the SU may determine whether the target time slot is free (block 412). If the channel status field in the CACH message indicates an idle channel, the target time slot is considered to be idle. Further, in order for the SU to determine whether a time slot is being used by system-wide communications (block 416), the SU first determines whether the time slot is free or occupied. This may be accomplished by decoding the access type field in the CACH message (block 412). If the access type field indicates that the slot is free, the SU confirms the free judgment by decoding another CACH message and checking the access type field. If the access type field indicates that the slot is not free, the SU determines whether the SU is an active participant on the slot (block 414). The SU determines whether it is an active participant by observing the link control information on the channel. If the link control information indicates that the SU is not a participant in the activity, the SU determines whether the activity on that time slot is being used by a system-wide activity. If the activity on the time slot is not system-wide activity (block 416), then the SU is allowed to access the channel for voice transmission (block 418).

Once the SU has completed the voice transmission, the BR sends a dead time message, where the dead time is defined as the period of time from the end of the SU's voice transmission without activity on the uplink. The SU is given the opportunity to make channel access requests during dead time and to take advantage of uplink slack. Exemplary embodiments of the present invention divide conventional hang time periods into call hang time periods and channel hang time periods. As used here, a call ends when the BR transitions to channel deadtime, when the BR is turned off, or when the channel is over-occupied by "offensive" transmissions.

During the call hang time, the BR sets the channel status bit to busy even if the uplink is not busy. Further, the BR sends link control information, thereby informing each SU that is a party to the call that the channel status bit can be ignored and the channel can be accessed for voice transmission. Further, since the BR has already been activated, there is no need for the SU to wake up the BR. Specifically, without performing a BR wake-up procedure, a SU that is a party to a call can access the channel for a new voice transmission that is not related to the previous call. The call hang time starts when the SU voice transmission ends and ends when the channel hang time starts. In an exemplary embodiment, the call hang time lasts a few seconds after the call, for example for 3 seconds.

During the channel dead time, the BR sets the channel status bit to idle, which allows any SU to gain access to the channel without first sending a BR wakeup sequence. Since the BR has already been activated (key), there is no need for the SU to wake up the BR. Thus, a SU wishing to access the channel saves time since there is no need to wake up the BR. During channel dead time, the BR sends idle TDMA bursts to confirm that the channel is not being used and is not reserved for use. Channel hangtime is defined as the period of time that starts when the call hangtime ends and ends when the SIT expires and the BR turns off. Further, the SIT covers the time of call hang time plus channel hang time. In an exemplary embodiment, the channel hangtime begins at the end of the call hangtime and lasts for a few seconds, for example two seconds.

In an exemplary embodiment of the invention, the SU considers dead time and "politeness" before accessing the channel. Specifically, during call hang time, a SU that is a party to a call can access the channel regardless of whether the SU is specified for "polite" or "disrespectful" channel access. Thus, if a SU as a call participant receives an indication that the channel is in call hang time, the SU can request access to the channel. On the other hand, if the SU is specified for "polite" channel access, then during the call hang time, SUs that are not part of the call may not transmit. Thus, the SU that is part of the call is first given the opportunity to continue the call before another call is allowed to start on the channel.

In the case of "disrespectful" channel access, a SU designated as "disrespectful" channel access may initiate voice transmission at any time, including a) during another SU's active transmission, b) during call hang time During, c) during channel dead time, and d) even if the BR is not awake. Thus, a SU defined as "disrespectful" channel access ignores the channel state field in the CACH message and makes no attempt to distinguish between call hang time and channel hang time.

Thus, the present invention allows the SU to take into account the actual situation on the channel before making a voice transmission. By doing so, the time to access the channel is reduced in most cases. Furthermore, the present invention reduces the likelihood that a call will be interrupted by an SU that is not a party to the call but has the same color code, thereby preserving the continuity of the ongoing call.

Although the invention has been described in conjunction with specific embodiments thereof, additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the details, the representative arrangement, and illustrative examples shown and described. From the above description, those skilled in the art can easily make various substitutions, modifications and changes. Therefore, it should be understood that the present invention is not limited to the above description, but encompasses all such substitutions, modifications and changes according to the spirit and scope of the appended claims.

Claims (11)

1. in a kind of wireless communication system, said wireless communication system comprises a plurality of subscriber units and radio station, a plurality of base station, and a kind of permission first subscriber unit is voice transfer and the method for access channel, and said method comprises the steps:

Confirm that first subscriber unit is defined as the visit to the courtesy of channel; Wherein said first subscriber unit is considered the type of the current communication of on channel, carrying out before for its oneself communication access channel, and wherein said first subscriber unit is characterised in that first colour coding and first ID of conversation group;

To the voice transfer of Channel Detection from second subscriber unit, wherein said second subscriber unit has the secondary color code and second ID of conversation group; And

If first ID of conversation group and second ID of conversation group are complementary, even then channel is used for voice transfer by second subscriber unit, also allow first subscriber unit for voice transfer access channel.

2. the method for claim 1 further comprises the steps:

If first colour coding and secondary color code are complementary and first ID of conversation group and second ID of conversation group are complementary; If then first subscriber unit be in dead time that channel is not used to voice transfer during the section in, be voice transfer and access channel with regard to allowing first subscriber unit.

3. method as claimed in claim 2 is defined as the time period that begins after the end of calling wherein said dead time.

4. the method for claim 1 further comprises the steps:

If first colour coding and secondary color code are not complementary,, be voice transfer and access channel with regard to not allowing first subscriber unit if in then first subscriber unit is in during calling section dead time that channel is being used to voice transfer.

5. the method for claim 1, wherein first subscriber unit is characterised in that Direct Model, first subscriber unit sends voice transfer to the 3rd subscriber unit of a plurality of subscriber units thus, and need not radio station, base station auxiliary in radio station, a plurality of base station.

6. the method for claim 1, wherein first subscriber unit is characterised in that repeater mode, first subscriber unit sends voice transfer through the radio station, base station of using radio station, a plurality of base station to the 3rd subscriber unit of a plurality of subscriber units thus.

7. the method for claim 1, the message of expression channel idle is sent at least one radio station, base station in the radio station, wherein said a plurality of base station.

8. method as claimed in claim 7, wherein said message are to call out message dead time.

9. method as claimed in claim 8, if wherein first ID of conversation group is complementary with the ID of conversation group that calls out message dead time, then allowing first subscriber unit is voice transfer and access channel.

10. the method for claim 1, wherein said wireless communication system is a tdma system.

11. in a kind of wireless communication system, said wireless communication system comprises a plurality of subscriber units and radio station, a plurality of base station, a kind of permission first subscriber unit is voice transfer and the method for access channel, and said method comprises the steps:

Confirm that said first subscriber unit is defined as the visit to the courtesy of channel; Wherein said first subscriber unit is considered the type of the current communication of on channel, carrying out before for its oneself communication access channel, and wherein said first subscriber unit is characterised in that first colour coding;

To the voice transfer of Channel Detection from second subscriber unit, wherein said second subscriber unit has secondary color code; And

If said first colour coding and said secondary color code do not match; Then be in Direct Model and when on said channel, having the predetermined characteristic of " courtesy " when said first subscriber unit from the voice transfer that is other subscriber units of characteristic with said first colour coding; Even said channel is used for voice transfer by said second subscriber unit, also allow said first subscriber unit to visit said channel for voice transfer.

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