Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W48/00—Access restriction; Network selection; Access point selection
  • H04W48/02—Access restriction performed under specific conditions
  • H04W48/06—Access restriction performed under specific conditions based on traffic conditions
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W76/00—Connection management
  • H04W76/10—Connection setup
  • H04W76/18—Management of setup rejection or failure
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
  • H04W16/24—Cell structures
  • H04W16/32—Hierarchical cell structures
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W48/00—Access restriction; Network selection; Access point selection
  • H04W48/20—Selecting an access point

Definitions

• This invention relates to controlling access to a mobile communications networks, in particular to a method for controlling access to a femtocell.
• Mobile communication systems operate on a cellular basis in which transmission and receiver base stations coupled to a network provide transmission and reception to user equipment (UE) such as mobile telephones in each cell in a network.
• UE user equipment
• the base stations are usually referred to as macro base stations and the cells as macrocells .
• picocells Smaller cell sites called picocells have been proposed. These cover a smaller area such as a complex of buildings. Still smaller cell sites called femtocells are also proposed. This is a term used by mobile operators to refer to cell sites of the type which attempt to solve the often expensive problem of providing complete in-building coverage where macrocells are often unable to provide adequate coverage due to attenuation and scattering of the radio signal from the base station.
• a femtocell is often referred to as an access point base station or home gateway. It is a small plug and play- device which communicates with user equipment such as mobile handsets using standard 2G or 3G transmission reception. It is connected to the cellular network via a broadband service using either Xdsl or WiMax technology.
• Xdsl is a family of technologies in which a digital subscriber loop allows broadband communications over conventional copper telephone lines, and WiMax, is a wireless Technology defined by the IEEE 802.16 standard providing improved wireless broadband compared to conventional Wi-Fi R TM systems .
• WiMaxTM is a pending trade mark application of the WiMax Forum, California, USA and Wi-Fi R TM is a registered trade mark of the Wi-Fi R TM Alliance, California, USA.
• a femtocell can optionally incorporate the functionality of a broadband router so that a user has a completely integrated device. It is of course essential that the femtocell integrates seamlessly with the core network of the mobile communication system so that it can be remotely managed and updated.
• Femtocells are typically implemented using second generation (2G) and third generation (3G) wireless cellular networks.
• 2G second generation
• 3G third generation
• UMTS Universal Mobile Telecommunications System
• W-CDMA Wideband Code Division Multiple Access
• RAT Radio Access Technology
• CDMA 2000 Code Division Multiple Access 2000
• TD-CDMA Time Division Multiple Access
• UWC Universal Wireless Consortium
• DECT Digital European Cordless Telecommunication
• the frequency division mode communications between a mobile communication device and base station are provided in the frequency division mode by assigning one particular frequency for the uplink to the base station, and another frequency for the downlink from the base station to the mobile communication device. In this way, a mobile communication device is allocated part of the frequency spectrum for the entire duration of the communication.
• each user is allowed to transmit only for a length of time defined by an allocated slot, but is allowed to use the entire bandwidth of the channel for that transmission.
• Femtocells generally provide wireless networks which typically cover small areas, such as residential environments, and as such they tend to offer limited bandwidth and therefore capacity in terms of the number of mobile communication devices that can simultaneously use the femtocell for wireless communication.
• the capacity of a femtocell to simultaneously handle voice calls may be as low as 4 voice calls at any one time. Consequently, as the number of mobile communication devices accessing or attempting to access the femtocell increases, there is a need to redirect devices from the femtocell to other neighbouring networks.
• 3GPP Known Third generation Partnership Project
• the redirection feature allows a femtocell to transfer mobile communication devices which are using the femtocell for wireless communications to another cell operating under another RAT or to another frequency in the same 3G RAT. Disclosure of Invention
• a further problem with known redirection techniques is that once the mobile communication device is redirected to another RAT or to another cell at the same or different frequency as the femtocell, then its return to the original cell, the femtocell, is not controlled.
• Embodiments of the invention have the advantage that for particular femtocells which have reached or are nearing full capacity, a UE such as a mobile telephone or mobile communication device (for example a laptop computer or other portable communication device) can be redirected from a 3G femtocell to another macrocell operating atthe same or different frequency as the femtocell (access point) .
• a UE such as a mobile telephone or mobile communication device (for example a laptop computer or other portable communication device) can be redirected from a 3G femtocell to another macrocell operating atthe same or different frequency as the femtocell (access point) .
• the device returns back to the original femtocell after completing its call or service with the macrocell which it was re-directed to, so that the macrocell can off load the UE ' s to the femtocell, thereby increasing the available bandwidth of the macrocell.
• Fig. 1 shows schematically a 3G access point such as a femtocell in communication with a number of pieces of user equipment;
• Fig. 2 shows a flow diagram of the main steps performed by an embodiment of the invention.
• Fig. 3 is a schematic diagram showing the location of the redirection information.
• embodiments of the invention will be described with reference to W-CDMA, it is not in fact essential to use this technology, and other 3G technologies may be used instead. Furthermore, embodiments of the invention operate in both the Frequency Division (FDD) and Time Division (TDD) mode of operation. [0020]
• FDD Frequency Division
• TDD Time Division
• FIG. 1 of the drawings shows an access point 2 which is coupled to a network.
• This access point comprises an antenna 4 coupled to, or integrated into a controller and a transmit/receive unit.
• antenna 4 coupled to, or integrated into a controller and a transmit/receive unit.
• this will cover a relatively small area such as a building or house or small office.
• the area covered by the femtocell is usually co-located with the area covered by the macrocell. That is to say that the two cells neighbour each other or the two cells overlap with each other to some degree or the femtocell is contained within the macrocell.
• the femtocell is deployed at the same frequency as a macrocell which is co-located with the femtocell.
• femtocell transmitter/receivers have a power of +10 decibel meters (dBm) . In this way the radio signal transmitted by the femtocell is substantially contained within the building in which it is deployed due to attenuation and scattering of the radio signal transmitted by the femtocell.
• the quality of the signal transmitted by the macrocell within the femtocell is not particularly good, due to scattering and attenuation of the signal by the building. However it is of sufficient quality to make a call or make data communications and for the femtocell to redirect the UEs to the macrocell.
• User Equipment such as a mobile phone 6 or a laptop 8 with a data card may be within the building or house and therefore capable of communication with the access point 2.
• a piece of user equipment When a piece of user equipment initially comes into range of the access point 2, it registers with the access point 2 as being a primary access point on the network for transmission and reception of data.
• the user equipment next tries to communicate such as by making a telephone call, it will attempt to use the access point 2 to access the network.
• the access point 2 is connected to the network, typically using a conventional telephone line with a broadband connection using one of the technologies from the xdsl family, for example Asymmetric Digital Subscriber Line (ADSL) .
• ADSL Asymmetric Digital Subscriber Line
• the access point 2 is designed for residential coverage, the total bandwidth, that is to say the capacity of the access point 2 to serve multiple simultaneous voice or/and data calls, that it is capable of supporting is considerably less than that of a base station in a macrocell in the network. This is because the access point is designed to take communications from a localised area within a macrocell and is not designed to handle the requirements of the whole macrocell. If the access point is a home gateway device, the maximum number of communications that it can handle simultaneously may be as little as 4.
• the access point is configured to redirect a piece of user equipment which has had its request rejected to use the macrocell within which the access point is positioned.
• FIG. 2 A flow diagram showing communications between a piece of user equipment and an access point 2 is shown in Fig. 2. This assumes that the user equipment is already registered with the access point and will attempt to use this for its communications . [0030]
• the user equipment When the user equipment wishes to make a communication such as a voice call via an access point, it first sends a radio resource control (RRC) connection request to the access point 2, step 210.
• RRC radio resource control
• the access point and the user equipment then perform an RRC connection set up which will initially establish this contact between the user equipment and the access point.
• a determination is then made at 220 as to whether or not the access point has reached maximum capacity. The access point does this by checking the available resources. If all the bandwidth has been used up then maximum capacity is reached. If maximum capacity has not been reached, then the normal call set up procedure between the user equipment and the access point is performed at step 230. This does not form the subject matter of the present invention and is therefore not described here, however it will be well known to those skilled in the art.
• Load balancing is achieved in a number of ways. Firstly, the femtocell can reject the new user request for service. However, this of course means that the UE cannot be provided with wireless communication. [0033]
• the femtocell can redirect or transfer the UE attempting to access the femtocell to a macrocell when the femtocell cannot accept any other UE ' s for communication since it has reached its maximum bandwidth.
• the Connection Reject message contains redirection information which allows a UE to be redirected to a macrocell operating at the same or different frequency as the femtocell when the maximum desired capacity has been reached, step 240, therefore balancing the load of the femtocell.
• the femtocell determines to which macrocell a UE should be redirected or transferred.
• the femtocell behaves like a mobile device (UE) and performs a cell search to determine the presence of surrounding neighbouring cells. If the femtocell determines that there is more than one macrocell available, then the femtocell (access point) selects the macrocell with the stronger signal as the macrocell to which it should redirect UE's. This also means that the femtocell can determine that the macrocell with a stronger signal is the closer macrocell, and hence the cell to which UE's should be redirected. If on the other hand, the femtocell determines that there is only one available macrocell, then it will redirect UE's to this macrocell.
• UE mobile device
• FIG. 3 A schematic diagram of the information contained in the redirection information is shown in Fig. 3.
• the UE When the UE receives a Connection Rejection Message, it locates the redirection information then finds the "UMTS target cell" information, which is a group of parameters that enable redirection to another macrocell operating at the same or different frequency as the femtocell. [0038]
• the UE first reads the Primary Common Pilot Channel (CPICH) information value within the UMTS target cell information. This is defined by an integer from 0 to 511. Once the UE has the CPICH information, this allows it to identify the scrambling code used by the UMTS target cell.
• the primary scrambling code, along with the target cell like frequency (UARFCN) are used to differentiate between base stations and define each particular cell.
• the UE reads UARFCN uplink and UARFCN downlink values in the UMTS target cell information and these parameters, each defined by an integer from 0 to 16383, define the frequencies of the uplink and downlink communications . [0040]
• redirection of the UE from the femtocell occurs soon after the UE receives the RRC Connection Reject message from the femtocell. It does not wait until the UE moves outside the femtocell.
• another new parameter is included in the redirection information, which is a "Return to Source Cell" parameter.
• the Return to Source Cell parameter is not part of UMTS Target Cell Information hence it is shown in Fig. 3 at a different indentation level to that of the UMTS target cell information.
• the mobile device remembers the Source Cell configuration and after releasing the call (in the procedure Cell selection after connect mode) it redirects the device to the source cell, after the user has finished communicating with the cell.
• This allows the UE to remember the source cell configuration, so that after the call or data transfer with the target cell has been completed, the UE is returned to the femtocell. In this way, the UE can rejoin the femtocell, so that they can take advantage of cheap calls via the femtocell, provided that the femtocell is not at maximum capacity, otherwise the UE will be redirected to another cell as previously described.
• This redirecting of the UE back to the femtocell also has the advantage of offloading users to the femtocell, which allows the macrocell to increase its available bandwidth because UE's are transferred to the femtocell, making more bandwidth available to the macrocell.
• the new parameter "Return to Source Cell” can be included in embodiments of the invention in which the femtocell (access point) is operating at the same frequency as the macrocell or in which the femtocell is operating at a different frequency as the macrocell.
• the communication request or communication reject signal or both comprise information identifying the access point from which the user equipment was redirected. Then the user equipment is redirected back to the access point (femtocell) when the user equipment has finished communicating with the macrocell, that is to say, when it has finished a call or service.
• Embodiments of the invention which redirect UE's from a femtocell to a macrocell operating at the same frequency provide an improved mechanism for redirecting to another cell over conventional known redirect mechanisms which redirect to a different frequency. This is because, in many cases, it is desirable to be able to provide 3G networks in which only one frequency is available for use in each cell. This allows the available bandwidth to be partitioned among more operators, therefore allowing more networks of different operators to be provided in one area. Furthermore, since each 3G-frequency license costs billions of pounds many small operators will only have one frequency available with which they can deploy the macrocells and femtocells.
• the present invention provides an improved redirection mechanism which provide load balancing of the femtocells when the femtocell is deployed in the same frequency as the macro cell, and when only one frequency is provided per cell, whilst still allowing the UE to communicate with the macrocell, [0046]
• Embodiments of the invention also have the advantage that they do not take as long to search and camp on to the macrocell as conventional redirection mechanisms, since the same frequency is used. Known redirection mechanisms must use a different frequency, which must first be searched for and then camped on to . [0047]
• Embodiments of the invention provide an improved redirection facility in which redirection to a femtocell co-located with a macrocell is possible in all cases even when the femtocell and macrocell operate at a different or the same frequency.
• the present invention provides a method for controlling access to a mobile communications networks.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Computer Security & Cryptography (AREA)
• Mobile Radio Communication Systems (AREA)
• Telephonic Communication Services (AREA)

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• 2008
  • 2008-01-16 GB GBGB0800767.6A patent/GB0800767D0/en not_active Ceased
  • 2008-12-18 CN CN2008801249476A patent/CN101911747A/zh active Pending
  • 2008-12-18 US US12/812,404 patent/US8594693B2/en active Active
  • 2008-12-18 WO PCT/JP2008/073679 patent/WO2009090848A1/en not_active Ceased
  • 2008-12-18 CN CN201410062224.5A patent/CN103906082A/zh active Pending
  • 2008-12-18 JP JP2010524690A patent/JP5263295B2/ja not_active Expired - Fee Related
  • 2008-12-18 EP EP08870800.3A patent/EP2235979B1/en not_active Not-in-force

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