Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
  • H04W52/04—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
  • H04W52/228—TPC being performed according to specific parameters taking into account previous information or commands using past power values or information
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
  • H04W52/04—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. TPC [Transmission Power Control], power saving or power classes
  • H04W52/04—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
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
  • H04W52/04—TPC
  • H04W52/06—TPC algorithms
  • H04W52/08—Closed loop power control
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
  • H04W52/04—TPC
  • H04W52/18—TPC being performed according to specific parameters
  • H04W52/20—TPC being performed according to specific parameters using error rate
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
  • H04W52/04—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. TPC [Transmission Power Control], power saving or power classes
  • H04W52/04—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
  • H04W52/286—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 during data packet transmission, e.g. high speed packet access [HSPA]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
  • H04W52/04—TPC
  • H04W52/30—TPC using constraints in the total amount of available transmission power
  • H04W52/34—TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
  • H04W52/04—TPC
  • H04W52/38—TPC being performed in particular situations
  • H04W52/40—TPC being performed in particular situations during macro-diversity or soft handoff

Definitions

• This invention relates to telecommunication systems and, more particularly, to a method of setting initial uplink and downlink power levels in a mobile station and a radio base station in a radio telecommunications network.
• Description of Related Art U.S. Patent No.4,696,027 to Bonta (Bonta) discloses a two-way radio system which employs power control of a mobile station to provide a predetermined received signal strength at a radio base station following a handoff. During the locating function, Bonta measures the uplink signal strength of signals transmitted by the mobile station to the target base station, and after accounting for path loss, etc., the post-handoff power level of the mobile station is determined.
• Bonta does not teach or suggest a method of setting an initial uplink (mobile station to base station) or downlink (base station to mobile station) power level at times such as system access when multiple signal strength measurements have not been made.
• a Base-Station Power Control (BSPC) function sets the initial downlink power level to its highest level when a mobile station first accesses the network and a call is being set up on a digital traffic channel. After uplink and downlink signal strength measurements have been reported, the BSPC function adjusts the downlink power level to a more optimum level. In most cases, this process ensures adequate downlink signal strength for call setup, but causes unnecessary peaks of energy in the downlink with a resultant increase in the interference level in the network. Therefore, some calls in co-channel cells may experience degraded radio quality performance, or may even be disconnected.
• TDMA Time Division Multiple Access
• the initial downlink power level is set at its lowest level, and is then incrementally increased until the mobile station can receive it. After the initial downlink signal is sent to the mobile station, the system must wait for an acknowledgment from the MS. If an acknowledgment is not received, the downlink power is increased, and the signal is sent again. This process may be repeated several times before an acknowledgment is received from the mobile station. Thus, this approach reduces interference levels in the network, but requires additional time for call setup.
• CDMA Code Division Multiple Access
• the present invention is a method of assigning an initial downlink power level from a base station to a mobile station.
• the method assigns the initial downlink power level based on historical data.
• the invention builds a historical database of signal strength measurements and path loss offsets in the system. These path loss offsets are then correlated with the downlink power used by the power control algorithm in the base station, and a statistical relationship between the two is determined.
• the uplink signal strength is measured, and then the downlink power corresponding to that measured signal strength is assigned.
• the method may be applied at initial system access or at intercell handoff, and is applicable to both circuit- switched calls and packet-switched data transactions.
• the method of the present invention maintains a historical database of signal strength measurements and downlink power level settings in the telecommunication system.
• the uplink signal strength of an initial signal sent from the mobile station to the base station is measured at the base station.
• the measured uplink signal strength is sent to the historical database where it is correlated with an associated downlink power level setting.
• the correlated downlink power level setting is sent to the base station where it is utilized as the initial downlink power level setting for a first transmission from the base station to the mobile station.
• a closed loop power control method may then be used to adjust the downlink power level to achieve an optimum received signal strength at the mobile station.
• the historical database is updated by sending the adjusted downlink power level to the historical database, and associating the adjusted downlink power level setting with the uplink signal strength of the initial signal sent from the mobile station to the base station.
• the present invention is a method of assigning an initial downlink power level at intercell handoff between a target base station and a mobile station in a radio telecommunication system. The method includes the steps of building a historical database which correlates measurements of radio quality parameters with downlink power level settings, measuring at the target base station a radio quality parameter from an initial signal sent from the mobile station to the target base station, and sending the measured radio quality parameter to the historical database.
• the method also includes correlating in the historical database the measured radio quality parameter with an associated downlink power level setting, sending the correlated downlink power level setting to the target base station, and utilizing the correlated downlink power level setting as the initial downlink power level setting for a first transmission from the target base station to the mobile station.
• the present invention is method of assigning an initial uplink power level from a mobile station to a base station in a radio telecommunication system.
• the method includes building a historical database which correlates measurements of radio quality parameters such as signal strength and interference measurements with uplink mobile station power level settings.
• the radio quality parameters are then measured at the base station.
• the method may measure a signal strength of an initial access signal sent from the mobile station to the base station, assign a packet data channel to the mobile station, and then measure an interference level on the assigned packet data channel.
• FIG. 1 is a signal flow diagram illustrating how the method of the present invention is utilized with the General Packet Radio Service (GPRS) and the Global System for Mobile Communications (GSM) to determine an initial downlink power level and to maintain the historical database
• FIG. 2 is a signal flow diagram illustrating how the method of the present invention is utilized with GPRS and GSM to determine an initial uplink power level and to maintain the historical database
• GPRS General Packet Radio Service
• GSM Global System for Mobile Communications
• FIG. 3 is an exemplary data structure for the historical database.
• the present invention is a method of assigning initial uplink and downlink power levels at times such as system access when multiple signal strength measurements between a mobile station and a base station have not been made.
• the invention assigns the initial power levels based on historical data. Rather than calculating a power level directly from signal strength measurements taken after the call has begun, the invention builds a historical database of signal strength measurements and path loss offsets in the system. These path loss offsets are then correlated, for example, with the downlink power used by the power control algorithm in the base station, and a statistical relationship between the two is determined.
• the uplink path loss is estimated, and then the downlink power corresponding to that path loss is assigned.
• a speech cell exists, and it is desired to begin the access at a near-optimum power level.
• the system may know only a single uplink signal strength measurement.
• the needed downlink power must be calculated from that single uplink measurement.
• a classical approach is to establish some fixed offset. To do so, however, the system must calculate path losses using a number of varying parameters which are not known.
• the uplink control signaling may be of very short duration, resulting in an unreliable measurement. Also, if interference is present, signal strength is not a good measure of radio quality.
• historical uplink and downlink path loss information can be stored as historical data.
• This historical data can then be associated with uplink signal strength measurements. Then, when a mobile station accesses the network, its uplink signal strength is measured, and the system can select a near-optimum initial uplink or downlink power level.
• a historical database may be built for each cell, transceiver, or mobile station type, depending on the level of accuracy desired. The database may also be built for each mobile individual or data transaction. This method can be applied to system access as well as handoff and data packet transfer.
• the present invention is useful for assigning initial power level in a variety of networks, and is particularly useful for packet data applications.
• the system may assign the initial downlink power based only on an uplink packet control acknowledgment. This saves additional signaling now utilized by the BSPC function.
• the system may assign an initial uplink power based on the signal strength of the packet channel request signal which the mobile station sends on the control channel, and an interference measurement on the assigned packet data channel. The historical database correlates these measurements with an optimum initial mobile station power level for the data transmission.
• the period of time utilized by existing BSPC functions to determine an optimum uplink or downlink power level may equate to a large percentage of the total transmission. For example, in a speech call, at least 20-30 seconds maybe spent in one cell, and the interference caused by the initial peak transmitter power lasts for only 1 or 2 seconds of that period.
• a packet transmission may only last a few seconds, and therefore using existing techniques, a larger percentage of the call may be utilized trying to find a good power level.
• a certain mobile station may have conducted a recent packet data transaction, and by retaining signal strength and power level information, the system can better estimate the initial power level required in a later transaction.
• the mobile station requests packets or acknowledges packets on the uplink signal channel. These requests or acknowledgments may be very short bursts. The signal strength of these requests or acknowledgments is measured, and a relationship is then built between the signal strength measurements and the power that is currently being used to eventually derive an optimum power level for packet transmission.
• radio quality parameters may be measured and stored in the historical database for later correlation. Then, at a later system access, pairs of parameters, or combinations of additional parameters maybe utilized to determine a most likely best initial power level. Examples of available radio quality measurements that can be utilized for the historical database are:
• Eb/No Energy-per-bit/Noise
• C/I Carrier-to-Interference
• Uplink measurements can be utilized to set initial downlink power.
• the historical database can be built for each cell, transceiver, mobile station type, mobile individual, or data transaction.
• the database may be built on a per-cell basis to adapt to each cell radio environment, to measurement devices inaccuracy, and to the uplink/downlink link budget difference.
• the database may be built on a per-transceiver basis to adapt to equipment differences and to channel reuse/interference differences between channels.
• the database may be built on the basis of mobile station type in order to adapt to different mobile station design characteristics.
• the database may be built on a per-mobile individual basis to adapt to each mobile station.
• the database may be built on a per-data transaction basis to retain and reuse data gathered about a particular radio environment during a packet data association.
• FIG. 1 is a signal flow diagram illustrating how the method of the present invention is utilized with the General Packet Radio Service (GPRS) and the Global GPRS
• GSM System for Mobile Communications
• a base station 11 Illustrated in the figure are a base station 11, a mobile station 12, and a historical database 13 which stores signal strength measurements, path loss offsets, and associated power level settings in the network.
• the signal flow illustrates a Temporary Block Flow (TBF) process in which one data packet is sent downlink using GPRS.
• the data packet has been split into a number of Radio Link Control (RLC) blocks, each of which is four GSM bursts. This equates to between 22 and 54 bytes payload depending on channel coding.
• RLC Radio Link Control
• the base station 11 When it is desired to transmit a packet to the mobile station 12, the base station 11 assigns a packet data channel and notifies the mobile station with a Packet
• Downlink Assignment signal 14 on the control channel Upon receipt of this signal, the mobile station sends a Packet Control Acknowledgment 15 as a response.
• the uplink signal strength of this acknowledgment is measured by the base station, and at 16, the measurement is passed to the historical database 13.
• the database utilizes the measured uplink signal strength and associated historical path loss offsets to select a near-optimum initial power level setting. At 17, the initial power level setting is returned to the base station. Meanwhile, the base station has sent a Packet Timing Advance/Power Control signal 18 to the mobile station on the control channel. The mobile station is then switched to the assigned packet data channel.
• the first RLC data block 19 is then sent from the base station 11 to the mobile station 12 with the initial power based on the selected initial power level setting from the historical database 13.
• the mobile station receives the first RLC data block and measures the downlink signal strength and C/I.
• the mobile station then sends a Packet Downlink Acknowledgment signal 21 to the base station and includes the downlink measurement results.
• the base station filters the received downlink measurements, and uses a closed loop power control process to adjust the power level of the second RLC data block based on the received downlink measurements.
• the adjusted power level is calculated to result in a more optimum received signal strength at the mobile station.
• the second RLC data block is then sent from the base station to the mobile station at the adjusted power level. Once again, the mobile station receives the RLC data block and measures the downlink signal strength and
• the mobile station then sends a second Packet Downlink Acknowledgment signal 24 to the base station and includes the downlink measurements from the second RLC data block.
• the base station again adjusts the power level of the transmitted RLC data blocks based on the received downlink measurements. This process continues until the closed loop power control has passed its initial phase, which is dependent on filter times. This is shown in FIG. 1 after "n" iterations where the mobile station 12 sends a Packet Downlink Acknowledgment signal 26 to the base station and includes the downlink measurement results from the n-lth RLC data block.
• the base station adjusts the power level of the nth RLC data block based on the received downlink measurements, and sends the data block to the mobile station at 28.
• the base station also passes the adjusted power level setting to the historical database 13 which stores this value along with the uplink measurement recorded at step 16. This can be done with filters, a look-up table, or any other suitable method. As noted above, the value may be associated with one parameter or with others on a per-cell, per-data transfer, etc. basis.
• the closed loop power control function may then continue until the last RLC data block is transmitted at 31 , and the last Packet Downlink Acknowledgment signal 32 is sent to the base station with downlink signal strength and C/I measurements.
• FIG. 2 is a signal flow diagram illustrating how the method of the present invention is utilized with GPRS and GSM to determine an initial uplink power level and to maintain the historical database.
• the mobile station sends a Packet Channel Request signal 41 on the control channel to the base station 11.
• the base station measures the uplink signal strength of the signal and sends a signal strength measurement 42 to the historical database 13.
• the base station also assigns a packet data channel to the mobile station and measures the idle signal strength on the assigned channel as an interference measurement 43 which is also sent to the historical database.
• the interference may be continuously measured on all packet data channels and recorded in the historical database so that the information is readily available and does not delay allocation when requested.
• the combination of signal strength of the Packet Channel Request signal 41 and interference on the assigned packet data channel 43 is then used in the historical database to look up an optimum initial mobile uplink power setting 44.
• the base station then sends a Packet Uplink Assignment signal 45 to the mobile station and includes the initial mobile uplink power setting.
• the mobile station 12 Upon receipt of the Packet Uplink Assignment signal 45, the mobile station 12 sends a first RLC data block 46 to the base station 11 utilizing the initial mobile uplink power setting 44 from the historical database 13.
• the base station receives the first RLC data block, analyzes the quality of the received block, and uses a closed loop power control process at 47 to compute an adjusted uplink power setting for the mobile station.
• the adjusted uplink power setting is sent to the mobile station in a
• Packet Uplink Acknowledgment signal 48 The mobile station then uses the adjusted uplink power setting to send the second RLC data block 49.
• the base station receives the RLC data block (in this case RLC data block 2), analyzes the quality of the received block, and uses a closed loop power control process at 51 to compute an adjusted uplink power setting for the mobile station.
• the adjusted uplink power setting is sent to the mobile station in a Packet
• the base station computes an adjusted uplink power setting for the mobile station, and sends a Packet Uplink Acknowledgment signal 55 to the mobile station with the adjusted power level setting.
• the base station also passes the adjusted power level setting to the historical database 13 which stores this value along with the uplink signal strength measurement 42 and the uplink interference measurement 43 previously recorded. This can be done with filters, a look-up table, or any other suitable method.
• FIG. 3 is an exemplary data structure for the historical database 13 in which the database is built for each cell 61.
• the historical database may be built for each cell, transceiver, or mobile station type, depending on the level of accuracy desired.
• the database may also be built for each mobile individual or data transaction. Essentially, a database can be built for each entity which has individual behavior for initial data, and for which enough data can be collected. In each database, a probability density function (PDF) is built for each combination of measurement values.
• PDF probability density function
• the combination of signal strength measurements 62 and interference measurements 63 results in a PDF 64 for each combination 65.
• the values can be rounded and truncated to limit the size of the database.
• the PDF may be programmed in several ways to identify a power level setting associated with the signal strength/interference combination. For example, the PDF may identify the most common resulting adjusted power level computed by the closed loop power control function and reported to the historical database. Alternatively, the PDF may identify a median value rather than the most common power level setting. It is thus believed that the operation and construction of the present invention will be apparent from the foregoing description. While the method shown and described has been characterized as being preferred, it will be readily apparent that various changes and modifications could be made therein without departing from the scope of the invention as defined in the following claims.

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

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• 2000
  • 2000-07-07 AU AU61936/00A patent/AU6193600A/en not_active Abandoned
  • 2000-07-07 CN CN 00813126 patent/CN1375137A/zh active Pending
  • 2000-07-07 EP EP00948455A patent/EP1205037A1/de not_active Withdrawn
  • 2000-07-07 WO PCT/SE2000/001460 patent/WO2001008322A1/en not_active Application Discontinuation

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