Patent Publication Number: US-8995418-B2

Title: Admission control of emergency connections

Description:
PRIORITY APPLICATIONS 
     This application is a continuation application claiming priority from U.S. application Ser. No. 12/674,978, filed Feb. 24, 2010, which is the U.S. national phase of International Application No. PCT/EP2007/058801 filed 24 Aug. 2007, which designated the U.S., the entire contents of each of which are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The technology relates to emergency or prioritized communication in a telecommunications network and in particular to setting up a communication link for emergency or prioritized communication. 
     BACKGROUND 
     The setup of traffic connections for the air interface in a telecom system is traditionally handled by a specific node BSC for GSM, RNC for UMTS, and ASN-GW for an IEEE802.16/WiMAX network. The setup of a service is typically requested by a mobile station (MS) and signaled to an application server in the core network. 
     However in a loaded network, it may be difficult for the MS to get access to air interface resources even to request the setup of a service. In case the service is needed for emergency purposes, i.e. 911 there is a strong wish to be able to prioritize this request and minimize the latency for setup of such services. 
     The IEEE802.16 has support for different QoS, which can have different priority settings. However before a setup of a service is possible to make the MS must be authenticated and admitted to the network. 
     Also as IEEE 802.16 is an OFDMA based system where all air interface resources are shared between users a mobile station (MS) may encounter problems to be granted bandwidth to request the setup of a service if the air interface is fully utilized and as there today exist no possibility to differentiate different users during initial ranging or bandwidth request. 
     SUMMARY 
     It is therefore an object to remedy at least some of the problems relating to known solutions. This is provided in a number of aspects in which a first is a method of handling emergency communication between a mobile station, MS, and a base station, BS, comprising the steps of:
         initiating an emergency communication link;   obtaining specific emergency communication establishment sequences;   using the specific emergency communication establishment sequences during negotiation of access to the BS;   wherein the sequences are also used as communication division codes.       

     Specific CDMA codes may be used to indicate emergency access. 
     The MS may send a second indication of emergency access in an identification message. 
     Specific random access preamble sequences may be used to indicate emergency access. 
     The method may further comprise a step of receiving emergency sequences from the BS. 
     The method may further comprise a step of reading stored pre set emergency sequences in the MS. 
     The step of obtaining emergency sequences may comprise a step of choosing the sequence randomly from a set of available emergency sequences. 
     The step of using the sequences during negotiation may be performed during initial access establishment and/or during negotiation during bandwidth establishment. 
     In another aspect, a mobile station for a wireless communication network is provided, comprising:
         an transceiver for wireless communication with a base station, i.e. BS;   a processor arranged to execute functions for:
           initiating an emergency communication link;   obtaining specific emergency communication establishment sequences;   using the specific emergency communication establishment sequences during negotiation of access to the BS;   
           wherein the sequences are also used as communication division codes.       

     In yet another aspect of the present invention, a base station is provided for wireless communication with a mobile Station, i.e. MS, comprising means for detecting communication establishment sequences, means for identifying specific emergency sequences from the establishment sequences, and means for handling emergency communication, wherein the sequences are also used as communication division codes. 
     Still another aspect of the present invention, a computer program is provided for a mobile station, i.e. MS, comprising instruction sets for:
         controlling wireless communication with a base station, i.e. BS;   initiating an emergency communication link;   obtaining specific emergency communication establishment sequences;   using the specific emergency communication establishment sequences during negotiation of access to the BS;   wherein the sequences are also used as communication division codes.       

     Usage of standardized/specific multiple-access sequences only allowed for emergency purposes are proposed to ensure priority of emergency setups. 
     A specific parameter is suggested to be included for a number of call management messages for fast detection of emergency calls and thus give the base station (system) the possibility for prioritization of the requested traffic during admission control to the system. 
     Handling of emergency calls are enhanced as the probability of successful setup is increased, which is very much desired in a telecommunication system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates schematically a network; 
         FIG. 2  illustrates schematically in a block diagram a flowchart of a method; 
         FIG. 3  illustrates schematically a situation for two mobile stations connecting simultaneously to a base station; 
         FIG. 4  illustrates schematically in a block diagram a mobile device; and 
         FIG. 5  illustrates schematically in a block diagram an infrastructure device. 
     
    
    
     DETAILED DESCRIPTION OF NONLIMITING EXAMPLE EMBODIMENTS 
     In  FIG. 1  reference numeral  1  generally indicate a network configuration according to the present invention, comprising a base station BS)  5  or similar network access gateway for accessing from a mobile station (MS) (which can be any type of wireless terminal, including but not limited to, e.g. a mobile phone, laptop, PDA (Personal Digital Assistant), security appliance, and so on)  2 ,  3  to a communication network  6 . The MS communicates wirelessly  4  with the BS  5  using any suitable protocol and radio link. The technology described in this application addresses the problem when an MS tries to connect to a communication network under certain circumstances where there is a need to increase the probability to actually get a connection: for instance when there is an emergency situation and there is a need to communicate with an emergency organization  7  (e.g. police, fire brigade, and medical help), connection of alarm equipment, and/or surveillance equipment to a central receiving facility  7 . These circumstances will be discussed further in this document. 
     The wireless link between the MS and the BS may be of any suitable type involving some means for registration of the MS, including but not limited to any version of IEEE 802.11, 802.15, 802.16, 802.20, and 802.22 series of communication standards and variations thereof (e.g. WiFi, WiMAX, and Wibro), LTE (Long term evolution) in 3GPP, or similar communication systems. WiMAX has means for registering the MS using a ranging function at early stages of connection establishment and in that process using CDMA codes for random access and in LTE there is a Random Access (RA) preamble/response function used in establishment of the MS. In WiMAX specific ranging CDMA codes may be used for alerting the network about the emergency and/or prioritized link and in LTE specific RA preamble sequences may have corresponding function. CDMA codes in WiMAX and preamble sequences in LTE are two examples of multiple-access sequences. These multiple-access sequences may be orthogonal or non-orthogonal as understood by the skilled person. 
     Multiple-access sequences are used to distinguish communication links from each other when all users within a communication cell communicate on the same frequency range and encode information to be transmitted with a pseudo-random digital sequence unique for each user in the cell (or unique for each thread set up; a user may have several threads open at the same time depending on communication configuration) 
     It should be noted that the communication link between the BS and the network may be of any suitable kind including either a wired or wireless link. The link may use any suitable protocol depending on type and level of layer (e.g. as indicated by the OSI model) as understood by the person skilled in the art. 
     The BS may be alerted about the level of emergency or level of priority desired using different ways depending on type of connection, type of communication protocol, and level of connection already established: 
     1. If the MS has not been connected yet, establishment sequences specifically agreed upon as emergency sequences may be used. 
     2. If the MS is connected but has not been granted bandwidth it may also use emergency sequences. 
     3. If connection and bandwidth has been negotiated about, information elements in call management messages may be used to alert the BS about the emergency connection. 
     An overall flowchart for handling of emergency calls is shown in  FIG. 2 : 
       201 . A decision to connect to a service is taken in first step. 
       202 . It is checked if the MS is registered in the network. 
       203 . If it is registered it is checked if the MS has been granted bandwidth. 
       204 . If it has been granted bandwidth call management messages with emergency information elements are used. 
       205 . If the MS is not registered emergency random access operation is used. 
       206 . If the MS is registered but has not yet been granted bandwidth, emergency bandwidth request is used. 
     Each of the involved processes is described in the sections below. 
     MS Requests Setup of Emergency Call 
     When a user or a machine determines that there is a need for establishing a contact with a receiving service, the MS is initiated to connect to the network  6 . Typically this is done by a user dialing 112, 911, or some other emergency call number (depending on type of emergency and/or country); however, the MS may be arranged to be informed about the emergency number to be used where the connection is to be established). However, this could also be a connection from a machine in a system which is capable of automatically determining that a connection is to be started, e.g. a by authorities and operators approved surveillance camera automatically requesting to start sending data or video upon an alarm or triggering event. The receiving service can be an emergency center  7  directing the call to suitable service needed (police, ambulance services and so on) or it may be a security center receiving for instance a distress alarm or burglar alarm signal. Similarly the receiving service may be part of a surveillance system for elderly or handicapped people, e.g. in relation to home care services, where the person under care can contact the home care system for general help or help in a distress situation. There are today many solutions where an elderly or handicapped person has a personal alarm in the form of an arm wrist device with a distress call button. This arm wrist device may be arranged to communicate with a distress call center using a communication protocol compatible with the technology described in this application. Similarly, surveillance cameras and similar devices may be arranged to use a communication protocol compatible with the technology described in this application and arranged to transmit images to a central storage or handling center if a triggering event has occurred, for instance a motion detection event (internally in the camera as a software detector using the images or an external dedicated motion detector). 
     When pushing the call setup button or initiating the connection in any other suitable manner, the MS will start to request the setup of a transport connection or activate a pre-setup connection to carry the requested service. 
     The MS can be in different states and will perform different operations depending on its current state in the system:
         Normal/active registered in the system with active services.   Normal/active registered in the system with no active services   Idle and not registered or even belonging to the system. Idle in this context is interpreted as not connected to the current BS. The MS may be registered in a core network (or ASN-GW in the WiMAX case).
 
MS is Registered in the System and has Granted UL Bandwidth.
       

     This is a typical case if the terminal or device already is active performing other tasks, such as transferring data files etc. It may then use the already granted UL bandwidth for the request of an additional service for the emergency purpose. 
     In the IEEE802.16 this is typically done by sending a dynamic service flow addition request message (DSA-REQ). In this message a number of parameters are set among these are QoS parameter set type, scheduling service type and traffic priority. Depending on the previous authentication of the user the operator may allow/set these parameters differently. 
     A generic parameter (e.g. a TLV-coded information element in the IEEE802.16 standard), may be added to control communication, which may be optionally included to call management messages indicating that these are emergency related. 
     Examples of IEEE802.16 messages where an emergency parameter have benefit are: 
     1. DSA-REQ/RSP 
     2. DSC-REQ/RSP 
     The BS (system) may also use this information for prioritizing of this connection for further data transfer, i.e. enhancing the probability for the specific communication data to be delivered to the final destination and granting access to the network. 
     MS is Registered in the System but Need UL Bandwidth. 
     In this case the MS needs to perform random access in order to request bandwidth (BW). To improve both the probability of a successful request of BW as well as minimize the latency for grant of BW for UL transmission it is proposed to have separate multiple-access sequences allocated for BW-request for emergency purposes. 
     It may be relevant to add emergency parameters in any subsequent management messages (e.g. DSA-REQ/RSP and DSC-REQ/RSP for IEEE802.16). 
     MS is not Registered in the System. 
     In this case the MS is not registered in a system. This can be due to lack of roaming agreement with a system (visited NW) where it has coverage or due to admission control rejection from its own NW (full network). Specified multiple-access sequences also for initial random access will then improve the setup of emergency connections as admission control functionality may be adjusted for this purpose. 
     The emergency parameter described earlier may be added to additional IEEE802.16 messages used for network entry below: 
     1. RNG-REQ/RSP 
     2. SBC-REQ/RSP 
     3. PKM-REQ/RSP 
     4. REG-REQ/RSP 
     5. DSA-REQ/RSP 
     In this case authentication processes may be simplified or omitted and the MS is allowed to enter the system. 
     Static or Dynamic Information Transfer of Emergency Sequences. 
     Two methods for determining specific multiple-access sequences for use are proposed. 
     1. Static specification by reserving a limited number of multiple-access sequences in the standard. This method is very simple and ensures simple interoperability between different manufacturers and system vendors. The multiple-access sequences are then known to the MS and stored in a memory of the MS. 
     2. Dynamic specification by broadcast information. Two new groups of multiple-access sequences for emergency initial random access and emergency BW request are added to the specification and broadcasted in a similar way as CDMA codes for initial ranging, BW request, periodic ranging, and handover are signaled today for IEEE802.16. By this method it is possible for the system to increase the number of multiple-access sequences for emergency purposes dynamically so that the case when many MSs (wireless terminals, cameras, etc) need access to the system simultaneously may be taken care of without the collision probability being higher for emergency calls than for normal calls. 
     The system may by this method even be solely dedicated for authority devices for public safety purposes as no multiple-access sequences for normal operation are sent. 
     The probability of successful reception is increased as the collision risk is decreased.  FIG. 3  illustrates this situation; two mobile stations  2 ,  3  simultaneously try to connect to a common base station  5 . Collision risk of UL BW request ranging can be reduced if dedicated multiple-access sequences are used solely for emergency purposes. For instance, if a first MS (A)  2  need to make an emergency BW request it may use a sequence  4  different from a second MS (B)  3  sequence  4 ′ used for regular connection purposes. The probability for both MS A and MS B is in need of an emergency connection is low. However, in order to reduce the problem of two MS doing emergency connection at the same time, each MS may choose randomly an emergency sequence from a fixed set of available emergency sequences. This would reduce the risk of two MS at the same cell using the same emergency sequence and thus reduce the risk of collision. This may be used in any of the situations as described in this document. 
     The technology described in this application may be used in connecting mobile stations  2 ,  3  during emergency or other prioritized events. Such a mobile station  400  is shown in  FIG. 4 . The solution may be implemented in software run in a processing unit  401  and stored in a memory  402 . Furthermore, the mobile station may comprise an interface  403  for connecting the processing unit  401  with other components of the mobile station as understood by the person skilled in the art. Furthermore, the mobile station comprises a communication interface  404  for wireless communication with the BS  5 . The processing unit  401  may comprise any suitable computational unit such as but mot limited to a microprocessor, FPGA (Field Programmable Gate Array), ASIC (Application Specific Integrated Circuit), or similar units. The mobile station comprises at least one memory  402  of volatile and/or non-volatile type. The memory may be for instance a RAM, DRAM, ROM, EEPROM, Flash memory, hard disk, and so on as understood by the skilled person. The communication interface may be any suitable as discussed earlier using a code division protocol. 
     In the solution, the BS device  5  has functionality for detecting and understanding these emergency or priority multiple-access sequences. Such a device  500  is shown in  FIG. 5 . The device  500  comprises also a processing unit  501 , at least one memory  502 , and an interconnection interface  503  for connecting to other components (not shown) of the BS  5 . Furthermore, the device  500  may comprise a downlink communication interface  504  and an uplink communication interface  505 . The downlink communication interface is arranged to communicate with the mobile stations (directly or indirectly using further downstream infrastructure devices (not shown)) and the uplink interface  505  is arranged to communicate with the communication network. The downlink and uplink communication interfaces may be built into the same physical interface in some application configurations. 
     It should be noted that with the term base station is meant an entity that receives or transmits wireless communication between wireless terminals and a communication network. This may include for instance a base station in cellular mobile phone networks, an access point or gateway in a Wireless Local Area Network (WLAN), or similar network access gateway devices. 
     It should be noted that the word “comprising” does not exclude the presence of other elements or steps than those listed and the words “a” or “an” preceding an element do not exclude the presence of a plurality of such elements. It should further be noted that any reference signs do not limit the scope of the claims, and that several “means”, “units” or “devices” may be represented by the same item of hardware, and that at least part of the technology described in this application may be implemented in either hardware and/or software controlled hardware. 
     The above mentioned and described embodiments are only given as examples and should not be limiting. Other solutions, uses, objectives, and functions within the scope of the claims should be apparent for the person skilled in the art. 
     DEFINITIONS AND ABBREVIATIONS 
     ASN-GW Access service network gateway 
     BS Base Station 
     BSC Base station controller 
     BW Bandwidth 
     CDMA Code division multiple access 
     DSA Dynamic Service flow Addition 
     DSC Dynamic Service flow Change 
     IEEE Institute of Electrical and Electronics Engineers 
     NW Network 
     OFDMA Orthogonal frequency division multiple access 
     PKM Privacy Key Management 
     QoS Quality of service 
     REG Registration 
     REQ Request 
     RNC Radio network controller 
     RNG Ranging 
     RSP Response 
     SBC SS Basic Capabilities 
     SS Subscriber Station 
     TLV Type, Length, Value 
     UL Uplink