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WO2000019741A1 - Procede d'amelioration des performances d'un systeme de communication - Google Patents

Procede d'amelioration des performances d'un systeme de communication Download PDF

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Publication number
WO2000019741A1
WO2000019741A1 PCT/US1999/019215 US9919215W WO0019741A1 WO 2000019741 A1 WO2000019741 A1 WO 2000019741A1 US 9919215 W US9919215 W US 9919215W WO 0019741 A1 WO0019741 A1 WO 0019741A1
Authority
WO
WIPO (PCT)
Prior art keywords
channel
determining
base transceiver
transceiver station
communication system
Prior art date
Application number
PCT/US1999/019215
Other languages
English (en)
Inventor
Gary John Pregont
Jeffrey D. Bonta
Original Assignee
Motorola Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Motorola Inc. filed Critical Motorola Inc.
Publication of WO2000019741A1 publication Critical patent/WO2000019741A1/fr

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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
    • H04W16/04—Traffic adaptive resource partitioning
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/50—Allocation or scheduling criteria for wireless resources
    • H04W72/54—Allocation or scheduling criteria for wireless resources based on quality criteria
    • H04W72/541—Allocation or scheduling criteria for wireless resources based on quality criteria using the level of interference

Definitions

  • the present invention relates generally to communication systems, and more particularly to a method for improving performance in a communication system that has interference between base transceiver stations.
  • m performance enhancing algorithms This would include, inter alia, new handover algorithms and search routines. Many of these are based on the principle of detecting a problem, such as call quality degradation, and performing some corrective action for the proolem. The actions taken are typically a handover to a better cell. The problem with this solution is that some level of bad performance must occur before an action is taken. Many times, by the time the bad performance is detected, the call has dropped or the customer has become irritated by the reduced quality of the call . In addition, there is typically nothing in place to prevent this same condition from affecting a future call that experiences the same ⁇ ifflculties . Consequently, a need exists for a method for improved communication m a communication system, and more particularly for improved communication m communication systems that have interference between base transceiver stations.
  • FIG. 1 depicts a communication system in accordance with the preferred embodiment of the present invention
  • FIG. 2 depicts a flow diagram for improving performance m a communication system m accordance with the preferred embodiment of the present invention
  • FIG. 3 depicts a flow chart for determining if there is interference between a first channel and a second channel in accordance with the preferred embodiment of the present invention
  • FIG. 4 depicts a flow diagram for determining if there is a possible interfering channel pair m accordance with the preferred embodiment of the present invention
  • FIG. 5 depicts a coverage diagram for a first and second base transceiver station m accordance with an alternate embodiment of the present invention
  • FIG. 6 depicts a flow chart for determining if there are partially interfering channel pairs m accordance with the alternate embodiment of the present invention.
  • the present invention provides a method for improving performance in a communication system that includes a first base transceiver station having a first channel and a second base transceiver station having a second channel.
  • the method comprises determining that there is interference between the first channel and the second channel.
  • the first channel and the second channel are identified as an interfering channel pairing, and the assignment of the first or second channel when the other channel is m use is deprioritized, based at least in part upon the interfering channel pairing.
  • deprioritizmq the assignment of a channel that mignt interfere with a cnannel already in use, improved communication within a communication system is provided.
  • the present invention can be better understood with reference to FIGs. 1-6. Referring now to FIG.
  • GSM Global System for Mobile communications
  • Communication system 100 is preferably a GSM system, but could alternately be PDC, Advanced Mobile Phone Service (AMPS) , United States Time Division Multiple Access (US- TDMA) , Code Division Multiple Access (CDMA) , or any other suitable communication system.
  • AMPS Advanced Mobile Phone Service
  • US- TDMA United States Time Division Multiple Access
  • CDMA Code Division Multiple Access
  • FIG. 1 acronyms are used for convenience. The following is a list of the acronyms used m FIG. 1:
  • a first base transceiver station 101 is located m a first coverage area 104 and communicates witn a mobile station 105.
  • Mobile station 105 can be a mobile unit, a remote unit, a fixed wireless terminal, or any other unit capable of sending or receiving RF communications to or from first BTS 101.
  • Communication is via a first digital radio channel 112 that contains data information compatible with a GSM communication system.
  • Mobile station 106 communicates with second BTS 102 that is located m second coverage area 107.
  • Communication is via a second digital radio channel 113 that contains data information compatible with a GSM communication system.
  • Base transceiver stations 101 and 102 can include multiple channels.
  • FIG. 1 base transceiver station 102 located within coverage area 107.
  • BTSs 101 and 102 are each coupled to a base station controller (BSC) 114 which includes an XCDR 110.
  • BSC base station controller
  • XCDR 110 routes the speech information to and from the base transceiver stations 101 and 102.
  • the speech information is routed to an MSC 115 which provides switching functions for access to PSTN 120 or ISDN 122.
  • HLR 116 and VLR 117 provide location and billing services for the entire system as is well known m the art, while OMCS 124 and OMCR 112 provide diagnostics and maintenance services for the entire system, as is also well known m the art.
  • Mobile stations 105 and 106 each preferably include a receiver, a transmitter, a processor, and memory. The receiver receives information from BTSs 101 and 102, respectively, via first channel 112 and second channel
  • the transmitters transmit information to first base station 101 and second base station 102, respectively .
  • the processors update variables pertaining to mobile stations 105 and 106 based at least in part upon the information received from BTSs 101 and 102.
  • the memory stores information related to mobile stations 105 and 106.
  • Second channel 113 may determine, prior to being assigned, whether any other channel currently interferes with second channel 113.
  • BTS 102 determines whether second channel 113 interferes with any surrounding channels. This process is an improvement over prior art systems and leads to improved communication in communication systems by not only checking to see if any other channel interferes with the channel that is about to be assigned to a call, but also by checking to see if the channel that is about to be assigned to a call interferes with any channel currently in use.
  • second BTS 102 will not assign channel 113 if second BTS 102 determines that second channel 113 has previously interfered with first channel 112.
  • first channel 112 and second channel 113 are identified as an interfering channel pairing.
  • a channel that is associated with the assigned channel as an interfering channel pairing will be dep ⁇ oritized for call assignment purposes .
  • the channel will be lowered such that, if other channels are available for the call and do not have a history of interfering with the assigned channel, they will be assigned prior to the interfering channel.
  • the presence of an interfering channel pairing can alternately be used as one of many factors used during the assignment of a channel to a call. For example, other factors, such as signal strength, direction of movement of a mobile station, velocity of a mobile station, and capabilities of a channel, can also be used and weighted to determine the optimal channel to be assigned to the call.
  • FIG. 2 depicts a flow diagram for improving performance in a communication system.
  • a centralized controller such as a BSC determines (201) whether there is interference between a first channel and a second channel.
  • the first channel and the second channel are preferably channels within different base transceiver stations at different cellular sites that are transmitting at the same or similar frequencies.
  • the process of determining if there is interference between a first and a second channel is described in FIG. 3. If there is no interference between the first channel and the second channel, the process ends (299) . If there is interference between the first channel and the second channel, the first channel and the second channel are identified (203) as an interfering channel pair.
  • the interfering channel pairing is stored m a database that is accessible by the centralized controller.
  • the centralized controller then deprioritizes (205) the assignment of the first channel when the second channel is m use.
  • the assignment of one while the other is currently involved in a call is deprio ⁇ tized. This deprio ⁇ tization is preferably such that the channel is still m service, but will only be assigned as a last resort when all non-interfermg channels have been assigned.
  • the other channel can be taken out of service temporarily while the call on the first channel is continuing.
  • the second channel can then be assigned to a call.
  • FIG. 3 depicts a flow diagram for depicting the preferred process for determining if there is interference between the first channel and the second channel, as determined at box 201 in FIG. 2.
  • the centralized controller determines (301) the current quality of a signal. The determination can be made relating to a signal transmitted from a communication unit, such as a mobile station, or a base transceiver station. The centralized controller then determines (303) the average quality of the signal.
  • the centralized controller determines (305) the level of the signal, which is preferably determined by measuring the Radio Signal Strength Indicator (RSSI) .
  • RSSI Radio Signal Strength Indicator
  • the centralized controller determines (307) whether the current quality of the signal is significantly less than the average quality of the signal. If the current quality is significantly less than the average quality, this may indicate interference between two channels. As used herein, the current quality of the signal is significantly less than the average quality of the signal if the current quality falls below a predetermined threshold. In the preferred embodiment, the quality of a signal is measured on an eight point scale, with 0 being the best quality and 7 being tne lowest quality. In the preferred embodiment, a difference of three or more between the current quality and the average quality indicates that the current quality is significantly less than the average quality.
  • the base transceiver stations receive a series of quality metrics from the mobile stations.
  • these quality metrics have a value from 0 to 7, with 0 representing the best quality metric and 7 representing the worst metric, i.e. highest Bit Error Rate (BER) .
  • BER Bit Error Rate
  • the centralized controller determines (312) if there is a possible interfering channel pair. If the current quality is significantly less than the average quality, as determined at step 307, this is a strong indication that there is interference between channels. Step 312, which is depicted in further detail below in reference to FIG. 4, determines if there are channels that have the possibility of interfering with each other. If two interfering calls begin at approximately the same time, the current quality of the signal will not be significantly less than the average quality of the signal. Consequently, even though there is an interfering channel pair, box 307 will not indicate a Yes value. This case can be determined by the centralized controller by looking for a condition of poor quality in a strong signal condition.
  • the centralized controller determines (309) if the current quality is less than a first threshold. Poor quality is adjustable, but quality is typically considered poor when a quality rating of 5, 6, or 7 on the eight point scale is determined. Consequently, the first threshold is preferably set to 4. If the current quality is not less than the first threshold, the communication system indicates (313) that there is not interference between the two channels. The quality is typically a measure of the Bit Error Rate.
  • the centralized controller determines (311) if the current level of the signal is greater than a second threshold.
  • the second threshold is adjustable and will vary from cell to cell.
  • the second threshold is preferably set to a value that would typically provide a good quality call for the particular cell.
  • the level is typically measured via the RSSI. If the current quality is less than the first threshold and the current level of the signal is greater than a second threshold, this indicates that two calls are interfering with each other. Consequently, the centralized controller determines (312) if there is a possible interfering channel pair that might be accounting for this condition, as described in more detail in FIG. 4.
  • the centralized controller determines (401) the coverage area of the first oase station.
  • the centralized controller determines (403) the location of the second base station.
  • the locations are preferably determined as a set of coordinates that uniquely identify the physical location of the BTSs, and are preferably determined during system set up.
  • the centralized controller determines (407) if the location of the second base station is in the coverage area of the first base station. In the preferred embodiment of the present invention, to determine if the location of the second base station is m the coverage area of the first base station, the centralized controller determines if the second base station is in the beam width of the first base station antenna. The centralized controller then determines if the second base station is the closest base station to the first base station of all base stations in the beam width of the first base station antenna. The centralized controller also determines if the second base station uses the same or similar frequency as the first base station. The centralized controller also determines if the distance of the first oase station from the second base station exceeds a predetermined distance. In the preferred embodiment, the predetermined distance is about 2,500 meters. If all of these conditions are met, the centralized controller determines that the second base station is in the coverage area of the first base station .
  • the centralized controller determines (409) if the frequencies of the first channel and the second channel match. As used herein, the frequencies of the channels match if they are the same frequency, commonly referred to as co-channel interference, or if they are adjacent channels. If the frequencies of the first channel and the second channel match, the centralized controller indicates (411) that the first channel and the second channel are a possible interfering pair.
  • the centralized controller will indicate (413) that the first and second channels are not a possible interference channel pair. The process will then return a No value " D" in FIG. 3 after decision box 312.
  • the flowchart of FIG. 4 car represent the detection of possible interfering channel pairs for the uplink scenario and the downlink scenario.
  • downlink refers to signals generated from a piece of cellular infrastructure equipment, such as a base transceiver station, and transmitted for reception at a remote unit.
  • uplink refers to signals generated by a remote unit that are transmitted and intended for reception by cellular infrastructure equipment, such as base stations.
  • FIG. 4 depicts the preferred embodiment of the present invention and depicts the downlink scenario, it snould De understood that the uplink scenario is covered by the flowchart of FIG. 4 as well.
  • a second base station is located m the coverage area of a first base station that is transmitting a signal that interferes with a signal transmitted from the second base station.
  • an uplink signal sent from a second remote unit to the second base station interferes with a signal sent from a first remote unit to the first base station. Similar processing would occur to identify that first and second base transceiver stations as interfering channel pairs for the uplink case as m the downlink case described above.
  • FIG. 5 depicts a coverage diagram for a first and second base transceiver station m accordance with an alternate embodiment of the present invention.
  • a first base transceiver station 501 includes a unidirectional antenna that emits a signal m one direction. The signal covers a coverage area 511.
  • a second base transceiver station 502 also includes a unidirectional antenna that transmits a signal over a coverage area 512.
  • coverage areas overlap, which provides for increased possibility of call continuity due to the ability to transfer processing from a first base transceiver station to a second base transceiver station. However, this overlapping is not desirable when the two base stations are using the same channel.
  • First coverage area 511 and second coverage area 512 overlap in coverage area 513.
  • coverage area 513 is an overlap coverage area of coverage areas 511 and 512
  • a call associated w th a remote unit 507 that is m coverage area 513 might interfere with a call associated with a remote unit 505 or a call associated with a remote unit 506.
  • remote unit 507 is communicating with first BTS 501, and remote unit 506 attempts to make a call with second BTS 502
  • the two channels are approximately the same frequency, the call associated with remote unit 506 will interfere with the current call of remote unit 507.
  • remote unit 507 is communicating with second BTS 502
  • a call associated with remote unit 505 might interfere with a call associated with remote unit 507 if remote unit 505 is assigned a channel that has approximately the same frequency as that being used by second BTS 502.
  • a method is achieved that allows for communications in adjacent coverage areas that are identified as being partially interfering.
  • a centralized controller will allow two communications to continue if neither is currently m the overlapping coverage area.
  • the centralized controller would allow remote unit 506 to be assigned while m coverage area 512 while remote unit 505 is communicating with BTS 501 while in coverage area 511.
  • remote unit 507 is located m overlapping coverage area 513 and is communicating with first BTS 501, the centralized controller will not allow remote unit 506 to start a communication with second BTS 502, as tnis communication would interfere with the communication of remote unit 507.
  • the centralized controller will not allow remote unit 505 to start a communication with first BTS 501, since this communication would interfere with the communication of remote unit 507.
  • remote unit 505 is in communication with first BTS 501 or remote unit 506 is in communication with second BTS 502
  • the centralized controller would not allow remote unit 507 to begin a communication with the other BTS while it is located in the partially overlapping coverage area 513.
  • FIG. 6 depicts a flow chart for determining if there are partially interfering channel pairs m accordance with the alternate embodiment of the present invention.
  • a centralized controller determines (601) the coverage area of a first base transceiver station.
  • the centralized controller determines (603) the coverage area of a second base transceiver station.
  • the centralized controller determines (605) if there is an overlapping coverage area between the first coverage area and the second coverage area.
  • the determination of partially overlapping coverage areas is preferably performed at step 312 of FIG. 3 while determining if there is a possible interfering channel pair.
  • a partial overlapping coverage area may or may not be detectable using base station locations and antenna beam width information as described with regard to the preferred embodiment.
  • a possible partially interfering channel pair is considered when a call associated with a remote unit on a first base station is interfering with a call associated w tn a remote unit on a second base station, and the first base station and the second base station share the same channel frequency.
  • the location of the remote unit being interfered with is determined. For example, m FIG. 5, if remote unit 507 is being interfered with in the downlink, then the location of remote unit 507 is determined. If the interference is detected m the uplink, the location of a remote unit associated with a call at a second base station that shares the same channel frequency and timeslot is determined. For example, if remote unit 505 associated with a call on base station 501 is being interfered with on the uplink, the closest base stations that share the same channel frequency and timeslot are examined for the existence of an active call. In this case, second base station 502 shares the same channel frequency and timeslot as remote unit 505 and first base station 501. Remote unit 507 is an active call that is using this channel frequency and timeslot. In this manner the location of remote unit 507 is determined.
  • the location determination can be accomplished using techniques known in the art, such as by using GPS receivers, TDOA, TOA, AOA, or by using mobile reported signal strength vectors.
  • the location or signal strength vectors associated with each identified overlapping coverage area are stored with the interfering channel pairing information as a condition for channel deprio ⁇ tization .
  • the channel pair is now considered a partially interfering channel pair.
  • Channel assignment of a partially interfering channel in accordance with the alternate embodiment has tne additional requirement to compare the location of the remote unit with the stored location associated with the partially interfering channel pair.
  • the channel assignment at a first base station can not be made if the other channel m the partially interfering channel pair at the second base station is m use by another remote unit.
  • the threshold value is dependent upon the location method used.
  • the centralized controller determines (611) that the first and second channels are not a partially interfering channel pair. If there is an overlapping coverage area, the centralized controller determines (607) that the first and second channels are a partially interfering channel pair.
  • the alternate embodiment of the present invention works best m conjunction with the preferred embodiment of the present invention.
  • using the alternate embodiment with the preferred embodiment would allow the communication system to determine overlapping areas of interference and only deprioritizes calls when one of the remote units is within the overlapping coverage area. In this manner, not only is interference between adjacent channels decreased, but the coverage areas and overall coverage of the communication system is not greatly diminished.
  • the present invention provides a method for improving performance in a communication system. By identifying two channels as interfering channel pairings, the assignment of either cnannel wnen the other cnannel is currently m service is deprioritized. Consequently, a channel that is in service will have a reduced likelihood that interference will be introduced by a second channel coming into service.
  • the present invention provides for improved performance by looking at whether the channel to be assigned will potentially interfere with a channel in service, in addition to determining if any channel currently in service may interfere with the channel potentially coming into service. Consequently, since channels that are currently being used for communication will have a lower chance of being interfered with by a channel being assigned to a call, the performance of the communication system is improved.
  • a method is provided that allows for calls to be assigned m areas that are identified as interfering channels pairs if the location of the remote unit is outside of the overlapping coverage area of the two base transceiver stations. In this manner, calls are allowed to be processed, while deprioritizing the assignment of a call if it is in an area that might interfere with a call at an adjacent base transceiver station.

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

Abstract

La présente invention concerne un procédé d'amélioration des performances d'un système de communication (100) comprenant une première station émetteur-récepteur de base (101) ayant un premier canal (112) et une second station émetteur-récepteur (102) ayant un second canal (113). Le procédé consiste à déterminer qu'il existe des interférences entre le premier canal (112) et le second canal (113). Le premier canal (112) et le second canal (113) sont identifiés en tant qu'appariement de canaux parasites, et l'affectation du premier canal (112) ou du second canal (113) lorsque l'autre canal est utilisé et déclassé de l'ordre de priorité, sur la base au moins en partie de l'appariement des canaux parasites. Par déclassement d'ordre de priorité de l'affectation d'un canal pouvant perturber un canal déjà utilisé, on obtient une meilleure communication à l'intérieur du système de communication (100).
PCT/US1999/019215 1998-09-30 1999-08-24 Procede d'amelioration des performances d'un systeme de communication WO2000019741A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US16396998A 1998-09-30 1998-09-30
US09/163,969 1998-09-30

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WO2000019741A1 true WO2000019741A1 (fr) 2000-04-06

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5737691A (en) * 1995-07-14 1998-04-07 Motorola, Inc. System and method for allocating frequency channels in a two-way messaging network
US5901357A (en) * 1992-02-06 1999-05-04 Motorola, Inc. Frequency allocation for subscribers of multiple telephone systems having frequency sharing

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5901357A (en) * 1992-02-06 1999-05-04 Motorola, Inc. Frequency allocation for subscribers of multiple telephone systems having frequency sharing
US5737691A (en) * 1995-07-14 1998-04-07 Motorola, Inc. System and method for allocating frequency channels in a two-way messaging network

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