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WO2001093455A1 - Procede permettant d'etablir un appel dans un systeme de communication, et methode de reglage de puissance dans un environnement de radiocommunication - Google Patents

Procede permettant d'etablir un appel dans un systeme de communication, et methode de reglage de puissance dans un environnement de radiocommunication Download PDF

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Publication number
WO2001093455A1
WO2001093455A1 PCT/EP2001/006148 EP0106148W WO0193455A1 WO 2001093455 A1 WO2001093455 A1 WO 2001093455A1 EP 0106148 W EP0106148 W EP 0106148W WO 0193455 A1 WO0193455 A1 WO 0193455A1
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WIPO (PCT)
Prior art keywords
call
communication system
averaged
user equipment
multiplicity
Prior art date
Legal status (The legal status 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 status listed.)
Ceased
Application number
PCT/EP2001/006148
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English (en)
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WO2001093455A8 (fr
Inventor
Rorie O'neil
Nicholas William Anderson
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Motorola Solutions Inc
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Motorola Inc
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Publication date
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Priority to AU2001272437A priority Critical patent/AU2001272437A1/en
Publication of WO2001093455A1 publication Critical patent/WO2001093455A1/fr
Publication of WO2001093455A8 publication Critical patent/WO2001093455A8/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
    • H04W52/04—Transmission power control [TPC]
    • H04W52/06—TPC algorithms
    • H04W52/12—Outer and inner loops
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
    • H04W52/04—Transmission power control [TPC]
    • H04W52/18—TPC being performed according to specific parameters
    • H04W52/22—TPC being performed according to specific parameters taking into account previous information or commands
    • H04W52/225—Calculation of statistics, e.g. average or variance
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
    • H04W52/04—Transmission power control [TPC]
    • H04W52/18—TPC being performed according to specific parameters
    • H04W52/22—TPC being performed according to specific parameters taking into account previous information or commands
    • H04W52/226—TPC being performed according to specific parameters taking into account previous information or commands using past references to control power, e.g. look-up-table
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
    • H04W52/04—Transmission power control [TPC]
    • H04W52/18—TPC being performed according to specific parameters
    • H04W52/24—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
    • H04W52/04—Transmission power control [TPC]
    • H04W52/18—TPC being performed according to specific parameters
    • H04W52/26—TPC being performed according to specific parameters using transmission rate or quality of service QoS [Quality of Service]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
    • H04W52/04—Transmission power control [TPC]
    • H04W52/18—TPC being performed according to specific parameters
    • H04W52/28—TPC being performed according to specific parameters using user profile, e.g. mobile speed, priority or network state, e.g. standby, idle or non-transmission
    • H04W52/283—Power depending on the position of the mobile
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
    • H04W52/04—Transmission power control [TPC]
    • H04W52/38—TPC being performed in particular situations
    • H04W52/50—TPC being performed in particular situations at the moment of starting communication in a multiple access environment

Definitions

  • This invention relates, in general, to communication systems, and is particularly, but not exclusively, applicable to a wideband or "spread spectrum" cellular communication system such as those employing code division multiple access (CDMA) and having a power control mechanism employed within a CDMA call set-up procedure to define a desired quality of service (QoS).
  • CDMA code division multiple access
  • QoS quality of service
  • a plurality of base stations provide radio telecommunication services to a plurality of subscriber units (interchangeably referred to as User Equipment, UE), principally mobile units moving at different velocities and in different radio propagation environments.
  • UE User Equipment
  • Each base station defines a particular geographical area or cell proximate to the base station, with these cells combining to produce an extensive coverage area.
  • the communications link from the base station to a mobile subscriber unit is referred to as the downlink.
  • the communications link from a mobile subscriber unit to the base station is referred to as the uplink.
  • Multiple access techniques permit simultaneous transmissions from several mobile subscriber units to a single base station over a plurality of communications channels. Some channels are used for carrying traffic while other channels (which may be logical or dedicated channels) are used for transferring control information, such as call paging, between the base station and the subscriber units. Some examples of multiple access techniques are frequency division multiple access (FDMA), time division multiplexing/multiple access (TDM, TDMA) and code division multiple access (CDMA).
  • FDMA frequency division multiple access
  • TDM time division multiplexing/multiple access
  • CDMA code division multiple access
  • a CDMA-type system employs spread spectrum signaling.
  • One of the communication protocols proposed for use in the Universal Mobile Telephone System (UMTS) is wideband code-division multiple access (W-CDMA).
  • a CDMA-based system has a universal frequency re-use that allows frequencies to be used across the entire network, i.e. there is a frequency re-use of one.
  • Such CDMA-based systems operate by virtue of the fact that a single carrier frequency supports a number of communication resources that are structured from discrete, coded sequences. More specifically, each channel is comprised from a unique coded sequence of "chips" that are selected from a relatively long pseudo-random spreading sequence (typically many millions of bits in length).
  • a communication device has access to an information-bearing channel by virtue of a communication device having particular and detailed knowledge of a specific code that identifies the specific bits used by the information-bearing channel.
  • each base station is assigned a single spreading code and each of the physical channels is then assigned a separate channelisation code; in UMTS the orthogonal variable spreading factor (OVSF) code set is used.
  • each mobile is assigned its own unique long spreading code.
  • Information (such as voice, data or video) is spread across many chips of the spreading sequence on a unique basis, with a processing gain of the system determined by the number of chips required to construct a single data bit. In this way, less than one bit of information is transmitted per chip.
  • the processing gain is a ratio defined by the number of chips required per symbol/bit (generally fixed for the network) against a rate at which the underlying information is transmitted. In general, it is therefore better that a receiver is subject to high processing gain in order that it is better able to distinguish each user signal against a background of other-user generated interference and system noise.
  • CDMA-based systems therefore inherently operate in an interference environment because many channels utilise the same carrier frequency, with individual channels merely differing from one another in terms of their uniquely defined coded sequences.
  • CDMA-based systems become statistically efficient for large populations of users, and therefore present an attractive and more efficient alternative to FDM-based systems.
  • the chip-rate is presently fixed at 3.84M chips per second, with the number of chips representing one information bit variable according to the rate and type/quality of service. As such, a decrease in the number of chips per information bit increases the rate of the service, but this decrease effectively requires increased levels of forward error correction or the like.
  • DSSS direct sequence spread spectrum
  • FHSS frequency hopping spread spectrum
  • One feature of the current GSM system which is envisaged for UMTS, allows the transceivers in the base station and subscriber unit to adjust their power output to take into account the distance between them. The closer the subscriber unit is to the base station's transceiver, the less power it and the base station's transceiver will be required to transmit. This feature saves battery power in the subscriber unit and also helps to reduce interference effects. Both up-link and down-link power settings can be controlled independently. Initial power settings for the subscriber unit, along with other control information, are set by the information provided on a broadcast control channel (BCCH) for a particular cell. The base station controls the transmit power of both the subscriber unit and the base station's transceiver.
  • BCCH broadcast control channel
  • the base station monitors the power in up-link transmissions received from the subscriber unit, and the power received in down-link transmissions from the base station is monitored by the subscriber unit and, generally, then reported to the base station. Using these measurements, the power of both the subscriber unit and the base station's transceiver can be adjusted accordingly to reflect optimum system performance and desired quality of service (QoS).
  • QoS quality of service
  • the broadcast control channel is transmitted by the base station's transceiver at all times and at constant power.
  • the BCCH also carries other information such as cell identity, a list of frequencies used in the cell, and a list of neighbouring cells to be monitored by the subscriber unit.
  • CDMA-based systems can benefit from the use of multiple carriers within specific cells and generally within the system as a whole, CDMA effectively provides a homogenous carrier frequency environment for an area served by a multiplicity of cells.
  • frequency based systems such as the global system for mobile communication (GSM), where carrier frequency re-use in adjacent or near- adjacent cells is restricted to avoid co-channel and adjacent channel interference.
  • GSM global system for mobile communication
  • FDD frequency division duplex
  • TDM time division multiplexing
  • UMTS and CDMA2000 an FDD-CDMA protocol has been adopted as an air interface standard.
  • CDMA-based systems (and the like) utilise power control functions to control the power transmitted by each user (whether this is controlled by the user or administered by the network) such that a serving cell-site should ideally receive an incident signal at an appropriate power level relative to all other interfering signals.
  • the serving cell will be the cell in which the user's subscriber unit (whether this is a mobile or a portable terminal) is located. Consequently, power control generally renders subscriber unit transmission at a relatively low power level. In fact, for a given capacity, the lower the allowed minimum user equipment (UE) transmit power the lower the noise rise (meaning greater system capacity, range and increased UE battery life).
  • UE allowed minimum user equipment
  • the actual transmit power of the mobile has a fixed dynamic range dictated by practical size and cost constraints. Consequently, the transmit power of, for example, a mobile is constrained to lie somewhere within this fixed dynamic range. If the mobile is situated close to a base station with which it is communicating, then the path loss between the mobile and the base should, in general, be low meaning that the transmission power of the mobile to achieve a given Signal to Interference Ratio (SIR) can also be low.
  • SIR Signal to Interference Ratio
  • Soft-handover relates to uplink communications from a subscriber unit within a specific cell, wherein such uplink communications are decoded by multiple base station sub-systems (BSSs) in adjacent (i.e. non-primary) cells.
  • BSSs base station sub-systems
  • Soft-handover is therefore designed to obviate some need for increasing up-link transmission power since it provides space diversity and consequently a better quality of service (QoS) for a nominally selected transmitted power level. Consequently, in systems that constantly seek to limit an interference environment, soft-handover can provide an improved QoS (e.g. reduced frame erasure rates (FERs) or reduced bit error rates (BERs)) for the same power.
  • FERs frame erasure rates
  • BERs bit error rates
  • QoS for a given connection is usually defined in terms of target bit error rate (BER), block error rate (BLER) or frame erasure rate (FER).
  • BER target bit error rate
  • BLER block error rate
  • FER frame erasure rate
  • the FDD interface is based on W-CDMA. As such, it is sensitive to power control mismatches in the uplink because of fast fading in the communication's channel. Fast fading is caused by the signal arriving at a receiver via a number of different paths). Therefore, in order to achieve maximum up-link capacity in a CDMA system, fast power control loops are required.
  • Node B i.e. a CDMA base station
  • subscriber unit has any idea of its radio environment, which environment supports scattering and multipath effects and which environment is nevertheless affected by mobile speed.
  • An outer power control loop essentially looks to a desired quality of service (QoS) metric for a connection and then maps the desired QoS to what appears to be a corresponding ratio of energy required per information bit to the noise power spectral density level, E b /No, for a connection.
  • QoS quality of service
  • the purpose of the outer loop is to set the required E /No target to achieve a given QoS, usually defined in terms of bit error rate (BER) or frame erasure rate (FER) targets that must be maintained.
  • BER bit error rate
  • FER frame erasure rate
  • Eb No essentially corresponds to a signal to noise (S/N) ratio, with N 0 representing a combined noise and interference measure.
  • Examples of factors which will impact the required E b /No to achieve a given QoS are the multipath power delay profile and the relative speed of motion of the mobile observed at the Node B. For example, for a basic 8kbps speech service, a change in speed from three kilometres per hour (3km/h) to 120 km/h degrades performance by around two decibels (2dB).
  • the inner power control loop therefore adjusts a subscriber unit's transmission power to counter the so- called near-far problem and to track the E /No requirement.
  • QoS Quality of Service
  • the inner power control loop controlled by the Node B therefore operates to instruct a subscriber unit to increase/decrease its transmission power in finite steps.
  • an assessment by the subscriber unit that the received/perceived QoS is "x" and a reply to the Node B that the desired QoS is "y” results in the inner power control loop altering the E b /N 0 to move towards/attain QoS "y".
  • this convergence time is typically between about 0.5 and one second (which is significant in radio management terms).
  • an outer loop threshold is required in both the user equipment (UE) and the Node B.
  • This threshold is set by the outer power control loop which is a function of a layer 3 radio network controller (RNC) for the Node B.
  • RNC radio network controller
  • E b /No targets are set at the same level (for a given service) in all BTS's; this apparently being representative of a reasonable starting point conditioned on observations of performance across a broad range of propagation conditions.
  • all BTS's are not placed in similar environments.
  • the outer power control loop then acts to converge to the actual required target (for each specific connection/service).
  • the responsibility of setting and controlling the outer and inner power control loops may reside with either or both of the infrastructure and the subscriber unit.
  • the inventors have recognised that it is clearly preferable that the E /N 0 parameter is determined by the base station subsystem since it is better placed to make a valued assessment of an overall interference environment.
  • a quality of service measurement at a subscriber unit may suggest the requirement for unnecessary high power transmissions (to satisfy a calculated Eb/No) from the subscriber unit which result in near-far problems.
  • CDMA-based systems must therefore necessarily impose and retain strict power controls on all transmissions, with this being particularly important in relation to transmissions from mobile communication devices.
  • CDMA systems are prone to operational instability, in the face of mobiles in close proximity to base station transceivers, and when such mobiles transmit at unnecessarily high power levels that directly interfere with reception at proximate cell sites. More particularly, as will now be appreciated, high-powered transmissions from the mobile will swamp the universal frequency carrier and therefore corrupt information-bearing communications.
  • unwarranted high power transmissions can ripple-through the CDMA environment and can potentially unbalance the whole CDMA system to an extent where system-wide failure can result; this is clearly catastrophic for a network operator and must be avoided at all costs.
  • a communication system supporting a call between a base station and user equipment, the communication system comprising: means for updating at least one initial outer power control loop threshold, for use by the base station and at least one user equipment when initiating a communication, wherein the updating of the initial threshold is performed dependent upon at least one communication service type.
  • the communication system is a CDMA-based system and the threshold is an E b /N 0 value
  • the CDMA-based communication system comprising: means for converging an estimated E b /N 0 value to a call-specific Eb No value representative of a desired quality of service between the base station and the user equipment.
  • a database stores a multiplicity of time-averaged Eb/No values obtained in relation to a plurality of geographic locations within the CDMA-based communication system and in relation to at least one service; and means for selecting one of the multiplicity of time-averaged Eb/No values, at call initiation between the base station and the user equipment, for use as the estimated E b /N 0 value within the outer power control loop, said one of the multiplicity of time-averaged E b /N 0 values selected from the database dependent upon at least an assessed geographic location of the user equipment.
  • said selected one of the multiplicity of time-averaged Eb/No values is selected by the means for selecting further based on a desired service for the call.
  • Converged call-specific E /N 0 values are preferably communicated to the database for updating the database on at least a periodic basis.
  • the database is associated with one of the base station and a radio network controller.
  • a method of setting- up a call between a base station and user equipment for setting up a call between a base station and user equipment of a communication system comprising the step of updating at least one initial outer power control loop threshold, for use by the base station and at least one user equipment when initiating communication, wherein the updating of the initial threshold is performed dependent upon at least one communication service type.
  • the communication system is a CDMA-based communication system, the call subject to power control from an outer power control loop that converges an estimated E /No value to a call-specific Eb/N 0 value representative of a desired quality of service between the base station and the user equipment; storing, in a database, a multiplicity of time-averaged E /No values obtained in relation to a plurality of geographic locations within the CDMA-based communication system and in relation to at least one service; and selecting one of the multiplicity of time-averaged E b /No values, at call initiation between the base station and the user equipment, for use as the estimated E b /No value within the outer power control loop, said one of the multiplicity of time-averaged E b /No values selected from the database dependent upon at least an assessed geographic location of the user equipment.
  • base site equipment for a communication system wherein the communication system is a CDMA communication system
  • the base site equipment further comprising means for controlling an outer power control loop for converging an estimated E b /N 0 value to a call-specific E b /No value representative of a desired quality of service between the transceiver and the user equipment.
  • the communication system is a CDMA-based communication system supporting a call between a transceiver and user equipment
  • the base site equipment comprising: means for controlling an outer power control loop for converging an estimated E b /N 0 value to a call-specific E b /No value representative of a desired quality of service between the transceiver and the user equipment; the base site equipment coupled, in use, to a database storing a multiplicity of time-averaged Eb/N 0 values obtained in relation to a plurality of geographic locations within the CDMA-based communication system and in relation to at least one service; and wherein the base site equipment further includes: means for selecting one of the multiplicity of time-averaged E b /N 0 values, at call initiation between the transceiver and the user equipment, for use as the estimated E b /No value within the outer power control loop, said one of the multiplicity of time-averaged E b /N 0 values selected from the database dependent upon at least an assessed geographic location of the user equipment.
  • a method of controlling, within base site equipment, set-up of a wideband call between a transceiver and user equipment of a CDMA-based communication system comprising the step of updating at least one initial outer power control loop threshold, for use by the base station and at least one user equipment when initiating a communication, wherein the updating of the initial threshold is performed dependent upon at least one communication service type.
  • the CDMA call is subject to power control from an outer power control loop that converges an estimated Eb/N 0 value to a call-specific Eb/No value representative of a desired quality of service between the transceiver and the user equipment; storing, in a database, a multiplicity of time-averaged Eb/N 0 values obtained in relation to a plurality of geographic locations within the CDMA-based communication system and in relation to at least one service; and selecting one of the multiplicity of time-averaged E b /N 0 values, at wideband call initiation between the transceiver and the user equipment, for use as the estimated Eb/No value within the outer power control loop, said one of the multiplicity of time-averaged E /No values selected from the database dependent upon at least an assessed geographic location of the user equipment.
  • a subscriber unit for a communication system the subscriber unit arranged, in use, to support a wideband call to a transceiver, the subscriber unit comprising: means for updating at least one initial outer power control loop threshold, for use by the base station and at least one user equipment when initiating a communication, wherein the updating of the initial threshold is performed dependent upon at least one communication service type.
  • the subscriber unit further comprises means for administering an outer power control loop that converges an estimated E b /N 0 value to a call- specific Eb/No value representative of a desired quality of service between the transceiver and the subscriber unit; a database storing a multiplicity of time- averaged E b /No values obtained in relation to a plurality of geographic locations within the CDMA-based communication system and in relation to at least one service; and means for selecting one of the multiplicity of time-averaged E b /No values, at wideband call initiation, for use as the estimated Eb/N 0 value within the outer power control loop, said one of the multiplicity of time-averaged E b /No values selected from the database dependent upon at least an assessed geographic location of the user equipment.
  • Said selected one of the multiplicity of time-averaged Eb/N 0 values may be selected by the means for selecting further based on a desired service for the call.
  • a communication system supporting a call between a base station and user equipment, the communication system comprising: means for controlling an operational parameter adversely influenced by a change in propagation environment;a database storing a multiplicity of time-averaged operational parameters obtained in relation to a plurality of geographic locations within the communication system; means for selecting one of the multiplicity of time- averaged operational parameters for use as an initial estimate of the operational parameter adversely influenced by a change in propagation environment, said one of the multiplicity of operational parameters selected from the database dependent upon at least an assessed geographic location of the user equipment; and means for converging the initial estimate of the operational parameter to a call-specific operational parameter optimised for the call.
  • the outer loop power control function and RNC are operable to maintain a continuously updated database that records converged outer loop targets (for a cell or geographic location) for a specific type of service.
  • the initial loop target is taken as the average from the database. In this way, any transient period between call establishment and convergence to the true required outer loop threshold is reduced, increasing overall network quality and capacity.
  • the initial default does not need to be chosen with particular care since it will soon be updated once the Node B goes live.
  • the present invention enhances capacity and improves quality of a CDMA environment, such as W-CDMA employed within UMTS.
  • FIG. 1 shows a block diagram of a cellular communications system which can be adapted to support the various inventive concepts of the preferred embodiments of the present invention
  • FIG. 2 is a representation of a database according to a preferred embodiment of the present invention, the database utilised within the cellular communication system of FIG. 1;
  • FIG. 3 is a flow diagram of a preferred operating methodology of the present invention.
  • FIG. 1 shows, in outline, a cellular communications system 10 supporting at least a CDMA-based communication protocol.
  • the cellular communication system may, in fact, support multiple air-interfaces (of which one offers a universal frequency re-use across a plurality of adjacent cells).
  • the communication system 10 may support a GSM communications protocol and a W-CDMA communications protocol.
  • the air-interface protocols are administered from (ostensibly) co-located base sites individually assigned to specific cells 11-16.
  • a plurality of subscriber units 17-20 such as a mixture of mobile units (MSs) and fixed terminals, communicate over a selected air-interface 21-25 with a plurality of Node Bs 26-31 (i.e. base transceiver stations in CDMA parlance).
  • the Node Bs 26-31 may be connected to a conventional public-switched telephone network (PSTN) 34 through radio network controllers (RNCs) 36-40 and mobile switching centres (MSCs) 42-44.
  • PSTN public-switched telephone network
  • RNCs radio network controllers
  • MSCs mobile switching centres
  • Each RNC 36-40 may control one or more Node Bs 26-31 , with specific RNCs 36-40 either directly connected or interconnected through MSCs 42-44.
  • the RNCs 36-40 are therefore able, if desired, to communicate with one another to pass system administration information therebetween, with RNCs responsible for establishing and maintaining control channel and traffic channels to serviceable subscriber units affiliated therewith.
  • the interconnection of RNCs therefore allows the cellular communication system to support soft-handover (as illustrated in relation to mobile subscriber unit 17).
  • Each MSC 42-44 provides a gateway to the PSTN 34, with MSCs interconnected through an operations and management centre (OMC) that administers general control of the cellular system 10, as will be understood.
  • OMC operations and management centre
  • the various systems elements, such as RNCs 36-38 and OMC 46, will include control logic 48-52, with the various system elements usually having an associated memory or database 54 (shown only in relation to RNC 38 for the sake of clarity).
  • the database 54 typically stores historically compiled operational data as well as in-call data and system information, such as neighbouring cell site lists (i.e. the BA list).
  • Databases associated with the RNCs further include measured Eb/N 0 values acquired (over time and preferably on a continuous basis) for different services offered in specific geographic locations.
  • this can be based on actual position (such as attained through global positioning systems), inferred displacement from Node B on the basis of timing advance and/or angle of arrival data obtained from a directional antenna) or merely on a cell specific basis.
  • the cellular communication system 10 may support underlay of a microcellular environment (or the like), with a plurality of micro-cells operationally controllable by a RNC.
  • the micro-cells may operate an identical air-interface to the macro- cell.
  • a subscriber unit (whether in-call or in idle mode) is in communication with its nearest Node B.
  • a subscriber unit such as mobile station 17
  • BSSs base station sub-system
  • deep fades prevent communication between a subscriber unit and its nearest neighbouring base stations. Consequently, a distant BSS may, by necessity, have to provide service to a remote subscriber unit.
  • the present invention proposes a mechanism that refines convergence time to a required Eb/N 0 position for a desired QoS within a particular service within a cell.
  • the RNC (of FIG. 1) operates on FER (or the like) to set Eb/No targets within the outer power control loop of CDMA-based environments.
  • the present invention contemplates that an initial (arbitrarily selected) default setting (for the outer control loop) is applied when the Node B is first deployed. Thereafter, for each service (such as voice, video or data), the RNC logs the converged Eb/N 0 value of the outer power control loop for at least some, if not all, calls (preferably on a refined geographic basis as opposed to merely a cell-wide basis).
  • a simple example can be used to illustrate the potential of the inventive technique of the present invention.
  • Node B's a first deployed adjacent to a motorway and a second deployed in a micro-cellular scenario in a pedestrian shopping area.
  • respective outer loop targets should be different (arising from relative subscriber unit speeds/velocities).
  • a speech user travelling along the motorway will (generally) require significantly more received power to achieve the same quality of service as a speech user in the pedestrian shopping area.
  • the preferred embodiment of the present invention is arranged to recognise the local physical environments of the subscriber units demanding service, which local physical environment can be inferred from one of, or a combination of: an averaged direction of arrival estimate (of up-link transmissions incident to a adaptive antenna); phase and space diversity; timing advance requirements; GPS location reports; signal strength reports from multiple sites; and measures of velocity (either reported or implied).
  • the Node B having regard to the type of service requested, e.g. voice, data or multimedia accesses its associated database of converged and averaged E b /N 0 values to acquire an E b /N 0 value as a start point for outer loop power control within the call.
  • the acquired E /No value should therefore approximate to the required QoS for the requested service.
  • the user equipment and/or the infrastructure-based equipment (such as the BTS, Node B or OMC) record converged and averaged E b /N 0 values in associated databases accessible at call-initiation.
  • the UE may communicate (during up-link control transmissions and on a regular, if not continuous, basis) converged Eb/N 0 values to the infrastructure to produce a more complete picture of the environment, especially in the case when the UE's outer power control loop is controlled from the infrastructure.
  • a multi-dimensional database (100 of FIG.
  • CDMA system performance is optimised by the present invention, with required QoS provided at lower power and with greater efficiency, thereby yielding improved system capacity through an effective reduction in interference during acquisition to convergence within the outer power control loop.
  • the underlying principle of the present invention can also be applied in user equipment (UE) per se, with the invention finding applicability in both up-link and down-link scenarios irrespective of whether outer loop power control is administered from the subscriber site or in response to network originating commands, such as those emanating from the RNC, Node B or OMC.
  • UE user equipment
  • the UE is arranged to store a database of its own mean outer loop target (for each service), preferably with respect to respective cells.
  • a database of its own mean outer loop target for each service
  • meaningful time-averaging of multiple converged values for each service may be difficult to acquire, with such time-averaged E b /No values adversely affected by any lack of accurate location information.
  • the UE can augment infrastructure-based control by feeding 'recommendations' (derived from previous stored convergence or inferred from an instantaneous interference environment) on its preferred and initial outer loop target as part of a call establishment routine.
  • Such recommendations may take the form of a UE's perceived E b /No requirement for the down-link, with the infrastructure ultimately making a determination of whether the recommendation is appropriate (having regard to the overall interference environment).
  • the operating methodology of the preferred embodiment of the present invention is also able to react to changes in environment, e.g. the building of a new road near to a Node B.
  • deployment of the present invention avoids the need to run extensive simulations or make further field measurements to derive the default outer loop threshold. Drive testing of a UE is not required since the present invention will produce a time- averaged converged E b /N 0 value that will generally improve with time.
  • FIG. 3 The operating methodology underlying a preferred embodiment of the present invention is shown in FIG. 3.
  • the process begins with either a page (from the Node B) or a RACH (i.e. an uplink call establishment request on a random access control channel [RACCH]) to initiate 150 call establishment from an idle mode.
  • Call set-up may subsequently follow conventional CDMA procedures, such as described in U.S. Patents 5,854,785 and 5,920,550.
  • a determination 152 is made as to the required type of service, although this can be set, in default, by the system subject to instantaneous loading/capacity.
  • the type of service is selected by the UE responsible for originating the call request, with the service requirement generally communicated between the UE and Node B (and hence the infrastructure equipment).
  • a QoS requirement for a specific baud rate/bandwidth, etc.
  • a determination or estimate 156 is then made as to UE location, with the system (generally the RNC or UE) selecting 158 a time- averaged E b /No value from the compiled database (100 of FIG. 2).
  • the call can then be commenced with the selected time-averaged E b /N 0 value.
  • the E b /N 0 value could actually be an arbitrarily selected default value set by an operator, although with time this value will change according to the underlying operational concept of the present invention.
  • the inner and outer power control loops continue to operate in a conventional manner, i.e. the system operates to converge 160 the outer control loop to an optimised Eb/No value for a desired QoS.
  • the database is up-dated 162 with the converged E b /No value with respect to UE location, with the E b /N 0 values within the database therefore time- averaged relative to location.
  • inventive concept can be provided as a software code update to existing equipment, with such software provided on a physical medium (such as a CD ROM) or by way of an air-interface transfer (or the like).
  • a computer program product 208 is shown in FIG. 1 to illustrate a commercial realisation of code.
  • the E b /No target could be set within a subscriber unit 18 based on subscriber unit position determined by a integrated GPS system 200 operationally responsive to a microcontroller 202 (or the like) within the subscriber unit.
  • E b /N 0 convergence data is therefore acquired with time and stored in a memory 204 of the subscriber unit 18 for future use during CDMA-type call set-up procedures.
  • time-averaged convergence E b /No values used within the outer power control loop of a CDMA-based system does not need to be limited to optimisation of the initial outer loop target.
  • time-averaged data collected by the system can be used to optimise any parameter of a Node B that is adversely influenced by a change in propagation environment, e.g. the bandwidth of the channel estimation filter.
  • the database may have a granularity for location on a cell-by-cell basis.

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

Abstract

Lors de demandes d'établissement de communication dans un système de communication de type CDMA (10), une fonction à boucle de réglage de puissance extérieure est initialement validée (158) avec une valeur Eb/No moyennée dans le temps, pour une qualité désirée de service (QoS) d'un type de service spécifique, par exemple, vocal, données ou vidéo, en un emplacement particulier. De manière plus explicite, différents emplacements (Xn, Yn) dans le système de communication (10) sont soumis à différents environnements de propagation, de sorte que les valeurs Eb/No moyennées dans le temps (110) varient suivant les services et les emplacements. De façon générale, comme spécifié à titre d'exemple à la figure 3, un RNC (36-40) est opérationnel pour maintenir une base de données actualisée en continu (100) par enregistrement de cibles à boucle extérieure convergente (pour un emplacement de cellule ou géographique), pour chaque type spécifique de service. Lorsqu'un nouvel appel est lancé (150), une cible à boucle de réglage de puissance extérieure initiale est prise (110) comme valeur Eb/No à partir de la base de données (100). On réduit de cette manière toute période transitoire (160) entre l'établissement d'une communication (150-158) et la convergence vers un seuil à boucle extérieure exactement requis, ce qui permet d'accroître la capacité et la qualité de l'ensemble du réseau. Le défaut initial dans la base de données (100) n'a pas besoin d'être sélectionné avec un soin particulier, du fait qu'il est déjà actualisé dès qu'un noeud B (26-31) est activé, évitant ainsi d'avoir recours à de nouveaux sites de noeuds B à test extensif du système, dans un environnement radio critique d'interférence. Le procédé d'actualisation de valeurs Eb/No convergentes spécifiques d'un emplacement peut être maintenu (168) lors de la communication.
PCT/EP2001/006148 2000-05-31 2001-05-30 Procede permettant d'etablir un appel dans un systeme de communication, et methode de reglage de puissance dans un environnement de radiocommunication Ceased WO2001093455A1 (fr)

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DE10228342A1 (de) * 2002-06-25 2003-09-04 Siemens Ag Verfahren, Funksystem und mobile Station zur Einstellung der Sendeleistung der mobilen Station
FR2852774A1 (fr) * 2003-03-21 2004-09-24 Evolium Sas Procede pour ameliorer les performances d'un systeme de radiocommunications mobiles
WO2005055463A1 (fr) * 2003-11-21 2005-06-16 Motorola Inc Reglage de puissance des communications
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GB2481254B (en) 2010-06-18 2017-07-12 Skype Determining network quality

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WO2003071710A1 (fr) * 2002-02-25 2003-08-28 Nokia Corporation Procede et element de reseau permettant de reguler la puissance et/ou la charge d'un reseau
CN100440751C (zh) * 2002-02-25 2008-12-03 诺基亚公司 用于控制网络中的功率和/或负载的方法和网络单元
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GB2363034B (en) 2004-04-28
AU2001272437A1 (en) 2001-12-11

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