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
  • H04W16/02—Resource partitioning among network components, e.g. reuse partitioning
  • H04W16/12—Fixed resource partitioning
• • 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
  • H04W16/02—Resource partitioning among network components, e.g. reuse partitioning
• • 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

Definitions

• the present invention relates to an arrangement for different frequency planning in a mobile telecommunication system in which narrow lobes have been introduced by means of directional antenna arrays.
• the narrow lobes result in increased capacity and less interference.
• wide lobes must still be used for the call set-up procedure.
• two sets of base stations are located at each base station site.
• One set of base stations has wide lobes for broadcast system channels and one set of base stations has narrow lobes for the traffic channels. This means that a tighter frequency reuse can be used in the base stations having narrow lobes than in the base stations having wide lobes.
• a tighter frequency reuse results in an increased relative capacity in the system.
• a technology related to the present invention is known from US-A-4 , 723, 266.
• This document discloses a cellular communication system in which control channels are shared between original omni-directional cells and subdivisions of the original cells to reduce the number of control channels.
• the subdivisiones may be obtained by cell sectoring using directional antennas .
• the invention also solves the problem of introducing base stations with narrow lobes without changing the existing mobile telephone exchanges m that a base station with wide lobes sends an artificial message to a mobile 10 telephone exchange which is caused to effect a handover to a base station with narrow lobes.
• a telecommunication system comprising a mobile telephone exchange, a number of base station sites with base stations controlled by the mobile telephone exchange and mobile stations.
• the arrangement includes means for effecting a handover of the mobile station from the first base station to the second base station as soon as the call is set up.
• Broadcast or system channels have to be transmitted as a wide lobe over the whole cell area.
• these channels are called CC (Calling Channel) and TC-free (Traffic Channel free) .
• CC Calling Channel
• TC-free Traffic Channel free
• the site reuse of the broadcast channels must be less tight than for the narrow lobes because of the greater interference of wide lobes .
• FIG. 1 a schematic representation is shown of a possible frequency planning of the two sets of base stations (BS) .
• base stations at the same site can be integrated with each other.
• the term base station in this context also refers to logical definition of the channels in the telephone exchange.
• a site 1 is located in the centre of each hexagon.
• the coverage area of a site is represented by a hexagonal ring as is conventional, even though it is well known that the coverage area in reality has an irregular shape.
• Each site is divided in sectors.
• Each sector of a site has two sets of base stations defined under the mobile telephone exchange MTX. The two sets of base stations does not necessarly have to have the same coverage area.
• the first type of a base station is a CC base station with wide lobe calling channels, wide lobe free traffic channels and narrow lobe traffic channels .
• the CC base stations forms a first set 2 of base stations as is shown in Figure 1. This type of base station has longer reuse distances, m this example each frequency group 4 comprises seven sites.
• the second type of base station is a TC base station with narrow lobe traffic channels and free traffic channels.
• the TC base stations form a second set 3 having shorter reuse distances to give high capacity. As is shown in the figure for this example, each frequency group 5 of this set of base stations has three sites .
• a wide lobe calling channel In the call set-up procedure, m the downlink case, that is a call set-up initiated by the mobile telephone exchange, a wide lobe calling channel has to be transmitted over the whole cell area, since the location of the mobile station (MS) is not known.
• the calling channel is transmitted over one sector in a wide lobe.
• the wide lobe In this case, the wide lobe is 120° and may be regarded as a cell.
• the call set-up is done and the narrow lobe traffic channel of the CC base station is allocated to the mobile and established for the call.
• the procedure is as follows.
• the mobile telephone exchange checks the quality of the traffic channel by ordering a signal strength measurement SSM, so that the mobile telephone exchange can order a handover if the signal strength falls below a threshold.
• the telephone exchange orders a signal strength measurement immediately after the call set up. Since, m this case, a handover is desired, a unit m the CC base station reports "bad quality" m a message to the mobile telephone exchange, as is shown m Figure 4.
• the CC base station can report bad quality to the MTX without prior measurement order.
• the mobile telephone exchange thereafter checks the quality of the surrounding base stations.
• the TC base station is defined as a "surrounding" base station of the CC base station in the mobile telephone exchange.
• the actual quality of the TC base station is reported to the mobile telephone exchange.
• the mobile telephone exchange is caused to effect a handover to a narrow lobe in the TC base station, under which the call continues, as is shown in Figure 5.
• the mobile station may lock to a wide lobe free traffic channel transmitted by the CC base station or the mobile may lock to a narrow free traffic channel transmitted by the TC base station.
• Free traffic channels of the TC base station may be transmitted in narrow lobes in frequently used directions as determined by the base station control unit.
• the mobile station when the mobile locks to the CC base station, the mobile station locks to the wide lobe traffic channel and starts an ordinary call set-up.
• the SSM order is received from the MTX and the CC base station responds by transmitting a message indicating bad quality, thereby causing handover to the TC base station.
• the mobile station when the mobile locks to the TC base station, the mobile station is already locked to a narrow lobe traffic channel of the TC base station. Thus, no handover is required, and the TC base station responds to SSM order by returning a message indicating the actual quality of the channel. Of course, if the actual quality is bad a handover will be effected to another cell in a conventional manner.
• TC base stations may be introduced without requiring any modifications of the mobile telephone exchange software by responding to an SSM order with an artificial message indicating bad quality. This also makes the modernised system independent of the MTX manufacturer.
• the mobile telephone exchange is also modernised, for instance by modification of the software.
• the MTX is aware of the dual base station systems and the MTX orders handover to the TC base station as soon as the call is set-up. Thus, no signal strength measurement order is sent to the CC base station but the handover is ordered straight away.
• the signal strength of the TC base station is monitored in the conventional manner as is mentioned above.
• the NMT system is standard with three sectors per site and a base station site reuse of seven, that is 21 base stations in a frequency group.
• the capacity per site is 12.6 erlang.
• the relative capacity is set to 1.
• the capacity per site is 31.9 erlang and, thus, the relative capacity is increased by a factor of 2.5.
• the present invention provides an arrangement enabling introduction of phased array antennas with tight frequency reuse resulting in an increased relative capacity.
• the introduction of narrow lobes is made without modifications of the existing mobile telephone exchanges.
• the mobile telephone exchanges are also adapted to the combination of wide lobe base stations and narrow lobe base stations.
• the invention may be implemented in various ways through hardware and/or software, as is readily appreciated by a person skilled in the art. The scope of the invention is only limited by the claims below.

Landscapes

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

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20408778

Family Applications (1)

Country Status (3)

Citations (4)

• 1997
  • 1997-10-29 SE SE9703939A patent/SE515893C2/sv not_active IP Right Cessation
• 1998
  • 1998-10-27 AU AU97708/98A patent/AU9770898A/en not_active Abandoned
  • 1998-10-27 WO PCT/SE1998/001928 patent/WO1999022543A1/en active Application Filing

Patent Citations (4)

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