Classifications

• • 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
  • H04W16/18—Network planning tools
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W24/00—Supervisory, monitoring or testing arrangements
  • H04W24/08—Testing, supervising or monitoring using real traffic

Definitions

• the invention relates to a method for estimating the interference level in a cellular radio system comprising in each cell at least one base sta- tion, and a number of subscriber terminals communicating with one or several base stations, in which method the terminals measure power levels from those frequencies which are on a list that is maintained by the terminals and comprise those base stations and frequencies which allow a handover to be performed by the terminal.
• Frequency planning In which the resources available to a system are distributed to the different parts of the system. Frequency planning should be carried out with care, since it has a great influence on the capacity and the quality of the connections in the system.
• co-channel interference is one of the most significant factors restricting the system capacity.
• Co-channel interference means the interference of the signals transmitted at the same frequency in neighboring cells in a desired signal. Consequently, cellular radio systems have conventionally been designed to use the same frequency in cells which are at a sufficiently long distance from each other, whereby the interfering signals do not exceed the permissible limits due to the path attenuation of the signals. This results in a so-called frequency recurrence pattern in the cellular structure.
• the estimation or measurement of interference levels is thus an essential part of frequency planning at each frequency. The frequency planning is performed in two steps: with the aid of computer simulation while the system is being set up and, on the other hand, with the aid of actual measurements when the system is already in use.
• AFP Automatic Frequency Planning
• the object of the present invention is to implement a method for gaining information required in frequency planning without separate measuring arrangements. This is achieved by the method described in the introduction, the method being characterized in that the list further comprises frequencies whose power level information is used for the frequency planning of the system.
• the method of the invention has several advantages. It is easy to implement since it does not necessitate separate investments in equipment.
• the desired frequency channels easily provide sufficient information for the needs of the frequency planning. The gathering and transmission of information occurs smoothly without disturbing the normal telephone traffic.
• Figure 1 shows a cellular radio system to which the method of the invention can be applied
• Figures 2a and 2b illustrate a measuring list maintained by a termi- nal.
• the method of the invention can be applied to any radio system in which frequency planning is needed and in which terminals monitor nearby base stations as part of their normal operation.
• a radio system of this type is the digital GSM system.
• FIG. 1 illustrating a cellular radio system to which the method of the invention can be applied.
• the drawing shows a number of radio cells 100 to 104, each of which is served by one base station 106 to 110.
• the base stations thus communicate with the sub- scriber terminals in their area.
• terminals 1 12 to 116 are placed in cell 100 by way of example.
• the terminals and the base station communicate on a traffic channel, and the terminals simultaneously measure other channels and their power levels for handover.
• terminal 114 is near the border between cells 100 and 104, and if it moves in the direction of cell 104 a handover to a frequency used in cell 104 has to be performed.
• it thus already in advance measures the power level of the broadcast channel used in the cell to ensure that a potential handover can be performed at a proper time.
• Each base station thus transmits a particular broadcast channel, which is used as an aid in the handover.
• Each terminal maintains a list comprising the broadcast channel frequencies of those base stations to which the terminal can perform the handover and which frequencies the terminal thus measures.
• the list of the terminal is updated from time to time by the base station, depending on the meas- urement results and the location of the terminal.
• the list maintained by the terminal also comprises frequencies whose power level information is used for the frequency planning of the system.
• the list may comprise frequencies monitored for the frequency planning of the system, the frequencies thus being also measured by the terminal. Information can thus be obtained from every frequency needed.
• the system updates the measuring list of terminal 112 by means of base station 106 to correspond to Figure 2b, whereby the list comprises not only the previous frequencies ,, f 2 , f 3 , but also new frequencies f 4 and f 5> which are potential frequencies for the new cell.
• the list maintained by the terminal can be dynamically updated in connection with telephone calls for the frequencies measured for power level information. Altematively, for the frequencies to be measured for power level information, the list can be updated at regular intervals, for instance once a day.
• the updating of the measuring list for the frequencies measured for power level information is carried out in the same manner as for the frequencies measured for handover. It is obvious that when the terminal is on the move the measuring list is dynamically updated for these frequencies. Similarly, the transferring of the measurement results to the base station is carried out in a known manner, as is done for the frequencies measured for handover.
• the location of each terminal is taken into account. Since the terminals are randomly located with respect to the base station, it is advantageous to measure different frequencies in different parts of the cell to obtain an applicable frequency spectrum. Interference levels may deviate from each other in different parts of the cell on account of the different frequencies of the neighboring cells on different sides of the cell. In frequency planning it is advantageous to know the actual interference situation of the terminals and the audibility of the terminals in the neighboring cells. With reference to Figure 1 , for example, terminals 114 and 116 in cell 100 can measure different frequencies. Thus the frequencies measured for the power level information vary in different terminals within the same cell.
• the list maintained by each terminal can comprise frequencies used by the terminal in the neighboring cell.
• the location of the terminal can be defined in several manners. In a preferred embodiment the coverage areas of the neighboring base stations in the cell concerned are defined in advance.
• the base station can conclude, on the basis of audibility information, the direction in which the terminal is. Alternatively, the location can be estimated with no advance information.
• the base station knows the direction in which each neighboring base station is.
• the base station can conclude from the audibility information which base stations the terminal can receive, and thereby estimate the location of the terminal. The latter method is more inaccurate than the former one.
• the desired frequencies are measured both before and after a new base station using fre- quencies chosen on the basis of the measurements is put to use. Measurements are performed both in the area of the new base station and in the area of the neighboring cells of the new base station. By comparing the results thus obtained it is possible to determine how successful the decisions made in frequency planning are in respect of the network quality.
• a control measurement can be performed controlled by the base station controller, either manually or automatically. The base station controller knows the neighboring cells of the new base station and it can automatically perform measurements in every nearby cell of the new base station.
• a new base sta- tion is mounted and its operation is commenced at a test frequency reserved for this purpose. It is thus possible to perform measurements in the target cell and the neighboring cells and subsequently choose the final frequencies on the basis the measurements. Thus the interference information is obtained as reliably as possible in the actual coverage area of the new base station, even before the new base station is put to use.
• Measurements can also be performed in other than the actual neighboring cells, such as in those nearby cells in which the frequency to be introduced in the new cell is already in use.

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• 1997
  • 1997-02-21 FI FI970754A patent/FI970754A/fi unknown
• 1998
  • 1998-02-20 CN CN98802741A patent/CN1248359A/zh active Pending
  • 1998-02-20 EP EP98904201A patent/EP0962066B1/en not_active Expired - Lifetime
  • 1998-02-20 DE DE69831481T patent/DE69831481T2/de not_active Expired - Fee Related
  • 1998-02-20 US US09/367,568 patent/US6442387B1/en not_active Expired - Lifetime
  • 1998-02-20 ES ES98904201T patent/ES2247675T3/es not_active Expired - Lifetime
  • 1998-02-20 AU AU62172/98A patent/AU734836B2/en not_active Ceased
  • 1998-02-20 JP JP53630298A patent/JP2001511990A/ja active Pending
  • 1998-02-20 AT AT98904201T patent/ATE304249T1/de not_active IP Right Cessation
  • 1998-02-20 WO PCT/FI1998/000156 patent/WO1998037646A2/en active IP Right Grant
• 1999
  • 1999-08-20 NO NO994028A patent/NO994028D0/no not_active Application Discontinuation

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