JP3818668B2 - Method and apparatus for assigning communication channels in a communication system - Google Patents

Description

TECHNICAL FIELD The present invention relates generally to communication systems, and more particularly to a method and apparatus for providing priority access services in a wireless telephone communication system.
Background of the Invention Wireless communication systems are well known and can be of many types including terrestrial mobile radio, cellular radiotelephone, personal communication system (PCS) and other communication systems. For example, in a cellular radiotelephone communication system, a plurality of communication cells serviced by a base transceiver station (BTS) form a base station controller (BSC) that forms a base station system (BSS). base station controller). Furthermore, the BSC is linked to a mobile switching center (MSC) that connects the BSS and the public switched telephone network (PSTN) and interconnects the BSSs. A mobile communication unit (or mobile station (MS)) operating in a communication cell transmits and receives signals to and from a BSS that provides a service using wireless communication. The signal is processed by the BTS, BSC and MSC to complete a communication transaction with another MS or a PSTN with a landline telephone user.
In certain radiotelephone communication systems, such as the Global System for Mobile Communication (GSM) radiotelephone communication system, the BSS is via a broadcast control channel (BCCH). Continuously transmit signals to all MSs in the signal range. This signal includes information necessary for the MS to access the system. Within this signal, information about the access class that allows the BSS to access the system is particularly important.
GSM Recommendation 4.08 defines three access classes: normal class, emergency class, and special service access class. There are 10 normal access classes (0-9 optional), 1 emergency class (10) and 5 special service access classes (11-15). Hereinafter, the emergency access class and the special service access class are collectively referred to as “priority access class” to distinguish from the normal access class.
In a normal MS call procedure, the MS enters the communication cell, receives the BCCH, and determines whether the BSS has an appropriate access class to support in that cell. In some cases, the MS sends to the BSS via a 1-byte message signal commonly referred to as a random access burst (RAB) that is sent to the BSS over a random access channel (RACH). Request service. If the MS does not receive a response to the RAB from the BSS within a certain time interval, the MS times out and issues a second RAB. For security reasons, the RAB contains little information and has no information about the specific identifier of the MS requesting the service. Therefore, there is no way for the BSS to recognize that the second RAB is from the same MS as the first RAB, and in fact it is only necessary to serve one request, trying to accommodate both these requests. To do. As a result, communication resource allocation in such a system becomes inefficient.
This phenomenon is particularly problematic in situations where priority access is required by the MS user, for example in an emergency situation where the user needs immediate access to the system. The 1-byte RAB does not include information regarding a specific identifier of the MS, but includes 1 bit called an emergency word (EW). When this EW is enabled, the request is distinguished as an emergency access request. There are three cases where EW is enabled. (1) That is, when the MS has an emergency access class (10). (2) The MS has a normal access class but wants to make an emergency call (ie 911). (3) Or when the MS has a special service access class and tries an emergency call such as 911. The service request is identified as urgent via the EW, but the specific identifier of the MS remains unknown. Accordingly, there remains a situation in which multiple RABs cause an inefficient load on the BSS. As a result, the BSS performs inefficient operation when the user needs the BSS quick service most.
Thus, there is a need for a method and apparatus for quickly accessing a radiotelephone communication system to accommodate priority access calls without overloading the system and without sacrificing the confidentiality of current RAB structures. is there.
[Brief description of the drawings]
FIG. 1 is a block diagram of a cellular radiotelephone communication system suitable for implementing a priority access service according to the present invention.
FIG. 2 is an example of a flow diagram illustrating an embodiment of a call processing procedure according to the prior art for normal access service requests.
FIG. 3 is a block diagram of a radiotelephone communication system for realizing the priority access service function according to the present invention.
FIG. 4 is an example of a flow diagram illustrating an embodiment of a priority access service according to the present invention.
FIG. 5 generally shows the RAB structure defined in GSM Recommendation 4.08.
FIG. 6 shows the relationship between the index and the ratio of the number of received emergency service requests to the number of communication channels available in the communication system.
Detailed Description of the Preferred Embodiment The communications system 115 receives a paging signal 103 from a mobile station 100 requesting service, and if the paging signal 103 includes information identifying the service request as an emergency 502, the base transceiver station Communication channels in 105, 107, and 109 are directly assigned to provide services to the mobile station 100. If the communication channel is not immediately available, the communication system 115 attempts to make the communication channel available. A distinguishing feature of the communication system 115 is that it monitors an indicator 600 representing emergency call traffic on the communication system 115. Based on the status of the indicator 600, the communication system 115 takes appropriate measures to provide a priority service to the mobile station 100 having a priority access class. By providing priority services in this way, the communication system 115 efficiently allocates communication resources to the mobile station 100 having a priority access class that urgently requires resources.
The present invention comprises a communication system 115 that assigns communication channels in the system to users requesting emergency services 502. The communication system 115 first performs this by receiving from the user 100 a signal 103 containing emergency service information 502. Based on the status of the emergency service information 502 included in the signal 103, the communication system 115 directly assigns a communication channel and does not waste time by using the standard call processing procedure of FIG. Respond to requests. If the communication channel is not immediately available, the communication system 115 assigns a control channel to temporarily incorporate emergency service requests and at the same time release the voice channel, thereby creating a newly available communication channel. . Thereafter, the newly available communication channel is assigned to the emergency service request.
Another feature of the communication system 115 is pre-restricting access to users with a preferred access class in an emergency. The communication system 115 receives a plurality of corresponding signals 103 from a plurality of users 100 having a priority access class, monitors an indicator 600 representing emergency call traffic on the communication system 115, and the indicator 600 reaches a specific threshold. Once reached, this is done by denying access to the communication system 115 to non-users with priority access classification. Thus, according to the claimed invention, another improvement over the prior art is that the communication system 115 tracks an index 600 representing the emergency access load on the communication system 115 and, when a threshold is reached, requests other than priority access requests. Reject everything and provide the best service to these users.
The present invention is described in an embodiment relating to a Global System for Mobile Communication (GSM), time division multiple access (TDMA) radiotelephone communication system. It will be apparent to those skilled in the art that the present invention can be applied to any radiotelephone communication system such as analog, code division multiple access (CDMA) or other TDMA. Referring to FIG. 1, there is shown a block diagram of an example of a cellular radiotelephone communication system suitable for implementing the priority access service according to the present invention. FIG. 1 illustrates a radiotelephone communication system comprising a plurality of base transceiver stations (BTS) 105-109 serviced by a base station controller (BSC) 111 that builds a base station system (BSS) 115. . The BSC 111 is coupled to a mobile switching center (MSC) 120, which is further coupled to a public switched telephone network (PTSN) 130. A mobile station (one shown as MS 100) operates in a communication cell serviced by BTSs 105-109, and in a well-known manner via radio frequency (RF) signal 103, BTSs 105-109 Communicate with one. Calls originating at or terminating at the MS 100 can be routed through the MSC 120 to wired telephone customers linked to the PSTN 130, or other wireless telephone communication systems serviced by the MSC 120 or other MSC (not shown). Processed to the user.
In the preferred embodiment, a mobile station (MS) 100 served by the BSS 115 is assigned an access class that manages access to the BSS. To request a service of the BSS 115, the MS 100 sends a signal 103, usually called a page, to all BTSs 105-109. In the preferred embodiment, this page is called a Random Access Burst (RAB) and is an 8-bit (1 byte) message sent by the MS 100 to all BTSs 105-109 in the BSS 115 requesting service. It is. Of particular importance within the RAB is the emergency word (EW), which, when enabled, identifies a service request as an emergency call.
Referring to FIG. 5, an example representation of the structure of an 8-bit RAB 500 that identifies a 3-bit EW 502 within the RAB 500 is illustrated. The EW 502 is enabled in one of three ways: (1) That is, the MS 100 has an emergency access class. (2) The MS 100 has a normal access class but issues an emergency call (ie 911). (3) The MS 100 has a special service access class and tries an emergency call such as 911. Therefore, even if the BSS 115 does not know the specific identifier of the MS 100, when the EW 502 included in the RAB 500 is enabled, it recognizes that the service request is urgent. In the preferred embodiment, when EW 502 is enabled as described above, it is set to a logic state "1", and conversely, it is set to a logic state "0".
Referring to FIG. 2, a flow diagram illustrating an example of a prior art call processing procedure for a normal access service request is shown. Under normal call conditions, when the MS 100 requests access on the BSS 115, it sends a signal 103 requesting normal service as shown in step 200 (ie, EW is not enabled). In step 202, in response to this random request for service, the BSS 115 allocates an available control channel to the MS 100 and informs the MS 100 that the BSS 115 has accepted the request for service (step 206). However, the control channel cannot handle voice calls and will only be used for notification. Thus, at step 208, while the MS 100 is temporarily resident in the control channel, the BSS 115 informs the MSC 120 that the BSS 115 has an incoming call from the MS 100, and at step 210 the MSC 120 requires voice service. It is determined whether or not there is. Unlike the control channel, the communication channel can handle not only information but also voice calls. If MSC 120 determines at step 212 that a communication channel is not required, the control channel processes the call (step 220). Alternatively, if it is determined in step 212 that a communication channel is required, the MSC 120 notifies the BSS 115 in step 214 that a communication channel is required. In step 216, the BSS 115 determines which communication channel to assign and informs the MS 100 to tune to a specific frequency and access the communication channel (step 218) via the control channel, thereby Release the control channel.
In connection with the preferred embodiment of the GSM communication system, the control channel is referred to as a stand-alone dedicated control channel (SDCCH) and the communication channel is referred to as a traffic channel (TCH).
Referring to FIG. 3, a representative example of a block diagram of a radiotelephone communication system for realizing the priority access service function according to the present invention is shown. In this embodiment, the signal 103 including the RAB 500 is sent from the MS 100 to the antenna 302 of the BTS 105 to 109. Received signal 103 is delivered via amplifier 304 to channel equalizer / detector 306, which detects the presence of RAB 500 in signal 103. The communication channel determination / allocation apparatus 310 then determines whether or not the RAB 500 in the incoming signal 103 has an enabled EW 502, and if so, allocates an available TCH to the MS 100. When the BTSs 105 to 109 do not have an available TCH, the communication channel determination / allocation apparatus 310 determines whether or not the SDCCH is available, and if it is available, assigns it to the MS 100 and simultaneously assigns the TCH to the MS 100. Disassemble to use. If the communication channel determination / allocation device 310 determines that the SDCCH is not available, it adjusts the index 600 to respond to the emergency call request in preparation for a future call request. When a TCH becomes available, it functions in the well-known manner 308, 312, 330, 320, 318, 316, 314. The communication channel determination / allocation device 310 is used only to determine whether the TCH is available, and if so, assigns it to the MS and sets the number of emergency service requests received by the BSS. Always track in the form of an index 600.
FIG. 4 is an example of a flow diagram illustrating an embodiment of a priority access service according to the present invention. In step 400, BSS 115 receives signal 103 that includes RAB 500. In the emergency call origination procedure, at step 402, the BSS 115 determines that the EW 502 of the RAB 500 sent by the MS 100 is enabled, and after adjusting the indicator (step 404), the request is processed immediately by one of the available TCHs. (Steps 408 to 412), the MS 100 is informed that the BSS 115 has accepted the request, thereby making optimum access to the emergency request. Thus, one improvement of the present invention over the prior art is that when the BSS 115 receives a RAB 500 with an EW 502 enabled to notify an emergency service request, the request is immediately processed by the available TCH and not the SDCCH, thereby Minimize the time required to complete a call.
In step 408, if the BSS 115 does not have an available TCH, an available SDCCH is allocated (steps 414 to 418), and the MS 100 is notified that the request has been accepted (normal random request for service). As such, it initiates “disassembly” of the TCH carrying the non-emergency call (step 420). This “disassembly” procedure closes the communication path between the MS 100 and the BSS 115, thereby releasing the communication channel. In the preferred embodiment, the newly available TCH is made available to the MS 100 that is temporarily resident on the SDCCH (steps 422-424). Therefore, another improvement over the prior art is that when the TCH is not available but the SDCCH is available, the BSS 115 temporarily places the MS 100 on the SDCCH (this notifies the MS 100 that the request has been accepted). To prevent time-out / re-RAB problems) and to initiate “disassembly” of lower priority calls to minimize the time it takes to provide the MS 100 with the necessary services.
If the BSS 115 does not assign an SDCCH or TCH to the emergency call in step 416, the MS 100 will not receive a response to its initial RAB 500. MS 100 times out waiting for BSS 115 to respond and issues RAB 500 again at step 416. Accordingly, the BSS 115 may receive a plurality of RABs 500 from the same MS 100. Thus, if one cell is overutilized, some non-emergency calls may be terminated and one TCH may be attempted to be released for repeated emergency RAB 500.
Since several MSs may attempt the same emergency call, the BSS 115 tracks an indicator representing an indication of the degree of emergency call traffic at step 426. When the indicator reaches the threshold (stage 426), the BSS 115 pre-limits the normal access class in favor of the priority access class (stage 432). Accordingly, another improvement over the prior art is that the present invention allows the BSS 115 to respond to emergencies by predicting the enhanced need for a communication channel and reserving the channel for the MS 100 with a preferred access class. Be able to.
Finally, referring to the indicators referenced in step 426, FIG. 6 shows an example of an indicator measure 600 that the BSS employs in tracking the emergency call load imposed on the system. In particular, FIG. 6 represents an indicator 600 defined as related to the ratio of the number of emergency service requests 602 within a certain time to the number of communication channels 604 available within a BSS.
In summary, the presently claimed invention provides two significant improvements over the prior art. First, when the communication system receives a page containing emergency service information, any available communication channel will immediately process the request directly. In contrast, in the prior art, a normal BSS-MSC communication cycle is performed. Secondly, the communication system tracks an indicator representing emergency call traffic imposed on the system, and in the event of an emergency, pre-denies access to the communication system except for users with a priority access service class. Together, these two improvements enable a much more responsive and efficient communication system in an emergency.

Claims (5)

A method for assigning communication channels within a communication system, comprising:
Receiving a signal including emergency service information from a first user;
Determining whether there is an available communication channel;
Allocating the available communication channel to the first user based on the status of the emergency service information;
Determining whether there is a control channel available only to notify the first user whether a service request has been accepted if the communication channel is unavailable;
Assigning the same control channel available to the first user if it is determined that the control channel is available;
Receiving a signal including emergency service information from the first user when the control channel is unavailable . The method of claim 1, further comprising excluding a second user not having an emergency access class from the communication channel to generate an available communication channel. An apparatus for allocating a communication channel in a communication system,
Means for receiving a signal including emergency service information from a first user;
Means for determining whether there is an available communication channel;
Means for allocating the available communication channel to the first user based on the status of the emergency service information;
Means for determining whether there is a control channel available only to notify the first user whether a service request has been accepted if the communication channel is unavailable;
Means for allocating the available control channel to the first user when it is determined that the control channel is available;
Means for receiving a signal including emergency service information from the first user when the available control channel is unavailable. 4. The apparatus of claim 3, further comprising excluding a second user not having an emergency access class from the communication channel to generate an available communication channel. An apparatus for allocating a traffic channel in a base station system to a mobile station,
Means for receiving from the mobile station an access signal with an emergency word enabled;
A means of determining whether there is an available traffic channel;
Means for assigning a pre-SL available traffic channel to the mobile station,
Means for determining if there is a control channel available only to notify the first user whether a service request has been accepted if the traffic channel is unavailable;
Means for allocating the control channel to the mobile station when it is determined that the control channel is available;
Means for receiving an access signal from the mobile station with an emergency word enabled when the available control channel is unavailable.

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