Method of controlling transmit power in wireless communication system

(54) Title: METHOD OF CONTROLING TRANSMISSION POWER IN MOBILE STATION IN WIRELESS COMMUNICATION SYSTEM, AND DURING TRANSFER IN WIRELESS COMMUNICATION SYSTEM AND MOBILE STATION (30) Unionist Priority: 03/20/2007 kr 10 20070027159 (73 ) Holder (s): LG Electronics, INC.

(72) Inventor (s): Hyoun Hee Koo (74) Attorney (s): Bhering Advogados (57) Summary: method of controlling TRANSMISSION power in MOBILE STATION IN WIRELESS COMMUNICATION SYSTEM, AND DURING TRANSFER IN COMMUNICATION SYSTEM WIRELESS AND MOBILE STATION. One method of controlling a transmission power includes determining a power control parameter for a given time interval, where the value of the power control parameter is a default value if the given time interval is assigned without the power control parameter and the value of the power control parameter is 0 current value if the given time interval is already used by the mobile station and the determination of the transmission power in the uplink channel.

(86) International Order: pct KR2008001505 of 18/03/2008 (87) International Publication: wo 2008 / H4987de 25/09/2008

<td colspan="2">MS |</td><td colspan="2">NETWORK |</td>

<td></td><td>PACKAGE CHANNEL REQUEST</td><td>S110</td><td></td>

<td></td><td colspan="2">S120 PACKAGE UPLINK ASSIGNMENT f</td><td></td>

<td></td><td colspan="2"></td><td></td>

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ΡΙ0806738-4

METHOD OF CONTROLING TRANSMISSION POWER IN STATION

MOBILE IN WIRELESS COMMUNICATION SYSTEM, AND DURING TRANSFER IN WIRELESS COMMUNICATION SYSTEM AND MOBILE STATION

Technical Field

The present invention relates to wireless communication and, in particular, to a method of determining a transmission power in the uplink channel in a wireless communication system such as a general packet radio service (GPRS) system.

Background of the Invention

GSM (Global System for Mobile Communications) is a radio technology that has been developed as a system to standardize radio radio communication systems in Europe and that has been extensively developed worldwide. GPRS (Generalized Radio System based on Packets) is introduced to provide a packet switched data service in a switched data service provided from GSM. EDGE (Data Rate Optimization for GSM Evolution) employs 8PSK (Octagonal Phase Switching) instead of GMSK (Minimum Gaussian Switching) used in GSM. EGPRS (Generalized Radio System based on Optimized Packages) represents GPRS using EDGE.

The physical channel dedicated to GPRS / EGPRS traffic is called the Packet Data Channel (PDCH). Logical channels such as the common packet control channel (PCCCH), the Packet Mode Data Traffic Channel (PDTCH) and the Associated Packet Control Channel (PACCH) are mapped to the PDCH. The PCCCH is used for the control signaling necessary to initiate the packet transfer. PDTCH is used to transmit user data. PACCH is used for dedicated signaling.

The time division multiple access (TDMA) scheme is applied to GSM / GPRS / EDGE systems. In the TDMA scheme, each mobile station in a cell transmits and receives circuit-switched and / or packet-switched data over assigned time intervals. One to eight time slots can be allocated to a mobile station per TDMA frame. Time slots are shared by active users, and uplink and downlink time slots are allocated separately. Then, downlink means communication from a network to a mobile station, and uplink means communication from a mobile station to a network. In the system

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GPRS / EDGE, users can share a single time slot simultaneously with multiple users in a cell. A single user can transmit and receive data over multiple time slots simultaneously.

Power control is necessary to slow down co-channel interference in a wireless communication system. Maintaining low co-channel interference levels can result in a higher transfer rate over a cell, potentially increasing the cell's capacity. Effective power control ensures that the time slots used for the GSM / GPRS / EDGE system do not cause unacceptable levels of interference for the time slots used for voice calls in neighboring cocanal cells.

Inadequate power control can cause high error rates or, in the worst case, broken radio connections that are known as temporary block flows (TBFs). Power control errors can increase packet delays and decrease user transfer rates, thus causing service degradation.

The power control mechanisms of the uplink allow a network to adjust the uplink transmit power used by each mobile station by transmitting blocks of uplink data. Power control of the uplink provides an additional important benefit: the transmit power used by each mobile station can be reduced to adequate levels to achieve the appropriate link performance and the transmit power can be kept as low as possible without sacrificing the rate link transfer, giving users maximum link performance without unnecessarily draining the mobile station's battery.

Description of the Invention

Technical problem

The present invention provides a method of controlling a transmission power when a new time slot is allocated or a used time slot is updated.

Technical Solution

In one aspect, a method of controlling a transmission power at a mobile station in a wireless communication system is provided. The method includes determining a power control parameter for a given time interval, where the value of the power control parameter is a default value if the given time interval is assigned without

3/15 the power control parameter and the power control parameter value is the current value if the given time interval is already used by the mobile station; and determining the transmission power P_up on an uplink channel from the following equation:

P_CT⁼mm (C₀-Ç_Cjfy-r (Λ + 48), Pmax) where C_O is a power shift, Cch θ the power control parameter, r is a system parameter, L is a signal level received normalized at the mobile station and Pmax θ the maximum allowed power transmission in a cell.

In another aspect, a method of controlling a transmission power at a mobile station while transferring over a wireless communication system is provided. The method includes receiving a transfer command message from a network to command the mobile station to leave a current cell and move to a new cell, the transfer command message comprising the radio resources assigned to packet-switched services ( PS) in the new cell, the radio resources comprising the information in at least a certain time interval; determining a power control parameter for a given time interval as a default value if the given time interval is assigned without the power control parameter; and determining the transmission power P_up on the uplink channel from the following equation:

P_CZ7&gt;⁼min (C₀-Ç_{w / i}-r (Λ + 48), Pmax) where Co is a power shift, Cch θ the power control parameter, r is a system parameter, L is a normalized received signal level at the mobile station and Pmax θ the maximum allowed power transmission in a cell.

In yet another aspect, a mobile station includes an RF (radiofrequency) unit for transmitting radio signals using transmission power; a memory configured to store a default value for a power control parameter; and a processor coupled to the RF unit and memory, and configured to determine a power control parameter for a given time interval, where the value of the power control parameter is the default value if the given time interval is assigned without the power control parameter and the value of the power control parameter is the current value if the specified time interval is already

4/15 used by the mobile station; and determining the transmission power P_up from the following equation:

P _up- min. (C₀-Ç_ç//-r (Ζ, + 48), Pmax) where C_O is a power shift, Cch θ θ power control parameter, r is a system parameter, L is a signal level received normalized at the mobile station and Pmax θ the maximum allowed power transmission in a cell.

Advantageous Effects

When a mobile station is assigned a time interval or power updates and / or timing advance for the transmission of the uplink, the mobile station can stably control a transmission power of a time interval.

Brief Description of Drawings

FIG. 1 is a block diagram illustrating a wireless communication system.

FIG. 2 is a block diagram showing elements of a mobile station.

FIG. 3 is a flow chart illustrating a method of controlling a transmission power in accordance with an embodiment of the present invention.

FIG. 4 is a flow chart illustrating a method of controlling a transmission power in accordance with another embodiment of the present invention.

FIG. 5 is a flow chart illustrating a method of controlling a transmission power in accordance with yet another embodiment of the present invention.

FIG. 6 is a flow chart illustrating a method of controlling a transmission power in accordance with yet another embodiment of the present invention.

FIG. 7 is a flow chart illustrating a method of controlling a transmission power in accordance with yet another embodiment of the present invention.

FIG. 8 is a flow chart illustrating a method of controlling a transmission power in accordance with yet another embodiment of the present invention.

FIG. 9 is a flow chart illustrating a method of controlling a transmission power in accordance with yet another embodiment of the present invention.

Modalities of the Invention

FIG. 1 is a block diagram illustrating a wireless communication system. This shows a network based on GSM (Global System for Mobile Communications) / GPRS (General Packet Radio Service). The systems

5/15 wireless communications are widely used to provide a variety of voice communication services, packet data, and so on.

Referring to FIG. 1, a mobile station (MS) 10 refers to a communication instrument used by a user and can also be called by other terms such as UE (User Equipment), UT (User Terminal), SS (Station Subscriber), and a wireless device. A base station (BS) 20 includes a base transceiver station (BTS) 22 and a base station controller (BSC) 24. BTS 22 communicates with the MS 10 in a cellular area via a radio interface and a synchronization function with the MS 10. The BSC 24 interfaces with at least one BTS 22 with a mobile switching center (MSC) 30. BS 20 can be called as a base station subsystem, a Node-b, and an access point.

The MSC 30 connects BS 20 to a different type of network such as PSTN (Public Switched Telephone Network) 65 or PLMN (Public Terrestrial Mobile Network) with through GMSC (MSC gateway) 60. A VLR (Registry of Visitor Position) 40 stores temporary user data, which includes roaming information for all MSs 10 in an MSC 30 service area. An HLR (Home Position Record) 50 includes information about all subscribers on networks homemade. A SGSN (GPRS Server Support Node) 70 takes control of the mobility management of subscribers. A GGSN (Gateway Node for GPRS Support) 80 determines the route of a packet at the current position of the MS 10 to interface with the MS with an external packet data network such as PDN (public data network) 85.

A temporary block flow (TBF) is a logical connection offered by two Medium Access Control (MAC) entities to support the unidirectional transfer of the Radio Link Control Protocol (PDU) Unit on the physical subchannels basic. TBF is not provided in a package idle mode. In packet idle mode, no radio resource on a physical packet data channel is not assigned to the MS. At least one TBF is provided in a packet transfer mode. In packet transfer mode, radio resources on one or more physical packet data channels for packet data transfer are assigned to the MS. The MAC-inactive state means a state of the MAC-control entity where no basic physical subchannel is assigned. A Temporary Flow Identity (TFI) is assigned to each TBF over the network. MS assumes that the value of TFI is unique among TBFs competing in the same direction (uplink or downlink) in all

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Packet Data Channels (PDCHs) used for TBFs. The same TFI value can be used simultaneously for TBFs in other PDCHs in the same direction and for TBFs in the opposite direction.

FIG. 2 is a block diagram showing elements of a mobile station. A mobile station includes a processor 51, memory 52, an RF unit 53, a display unit 54, and a user interface unit 55. Memory 52 is attached to processor 51 and stores an operating system, applications and general files from MS. The display unit 54 shows various fragments of MS information and can employ known devices such as a liquid crystal display (LCD) or an organic light emitting diode (OLED). User interface unit 55 can consist of a combination of known user interfaces such as a keyboard and touch screen. RF unit 53 is coupled to processor 51 and transmits radio signals.

Processor 51 implements the functions of determining a transmission power. The memory stores a power control parameter and processor 51 determines the use of the transmit power based on the power control parameter. The RF unit transmits radio signals using the determined transmit power.

FIG. 3 is a flow chart illustrating a method of controlling a transmission power in accordance with an embodiment of the present invention. This can be a mobile station's uplink access to a network or it can also be called a random access procedure.

Referring to FIG. 3, a mobile station sends a packet channel request message to the network for radio access (S110). The packet channel request message can be a message to request radio access. The mobile station asks for the allocation of radio resources to the network for the transmission of the uplink. The packet channel request message can be transmitted in RACH (Random Access Channel) or PRACH (Packet Random Access Channel). If EGPRS is supported, the packet channel request message can be an EGPRS channel request message. The mobile station can relay the packet channel request message by a predetermined number when there is no response from the network after the predetermined time has passed. If the mobile station receives no response regarding the packet uplink assignment message from the network, random access fails.

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The network sends a packet uplink assignment message to the mobile station in response to the packet channel request message (S120). The packet uplink assignment message is a response from the network with respect to the radio station's request for radio access. The packet uplink assignment message can be transmitted in PCCCH (common packet control channel) or PACCH (associated packet control channel). The packet uplink assignment message may include information about the radio resources, which are required by the mobile station for the transmission of the uplink. In the GSM / GPRS system, radio resources can be an interval of time. Alternatively, the radio resources can be a radio block. In the GPRS system, a frame is comprised of eight time slots, and a radio block is comprised of four consecutive time slots that belong to different frames.

The mobile station determines a transmission power for each time slot determined for the transmission of the uplink in addition to the information on the time slot assignment. At the mobile station, a transmission power P_up on each PDCH (packet data channel) of the uplink can be obtained from the following equation:

Mathematical Figure 1

P _UP-min (C₀-Ç_CIfr (L ​​+ 48), Pmax) where Co is a power shift, Cch θ the power control parameter, r is a system parameter, L is a standardized received signal level at the mobile station and Pmax θ θ maximum allowed of power transmission in a cell. Cch θ is the channel-specific power control parameter. The power displacement C_O is a constant and can be adjusted to 39 dBm for GSM 900 and 36 dBm for DCS 1800 and PCS 1900. System parameter r is transmitted in a broadcast and control packet channel (PBCCH) or optionally sent to a mobile station in an RLC control message.

If the power control parameter Cch θ decided when the system parameter r and the power displacement Co are known, the mobile station can calculate the transmission power P_up with respect to the corresponding time interval.

The packet uplink assignment message can include a power control parameter for a time interval in addition to information about at least

8/15 minus a time interval, which is required by the mobile station for the transmission of the uplink. In this case, a transmission power can be found using the power control parameter included in the packet uplink assignment message. The problem is that the power control parameter with respect to each time interval cannot be set when the power control parameter is not included in the packet uplink assignment message. A method of setting the power control parameter is necessary in order to efficiently control a transmission power. A variety of methods can be used to define the power control parameter.

In one mode, if a time slot is assigned via the packet uplink assignment message, a mobile station! You can set a power control parameter for the given time interval to a default value. For example, the default value can be zero. By setting the power control parameter to the default value, when the packet uplink assignment message is received, the mobile station can calculate a transmit power with respect to the given time interval and perform the uplink transmission using the power calculated transmission rate.

In another embodiment, a mobile station can calculate a transmission power using a previous power control parameter. The previous power control parameter refers to a power control parameter that is already used in a packet transfer mode prior to the current packet transfer mode. That is, in the case where the mode changes from packet transfer mode to a packet idle mode and then becomes a current packet transfer mode again, a power control parameter that was used in a previous transfer mode packet is a previous power control parameter. If a corresponding time interval has a previous power control parameter, the mobile station calculates an output power based on the previous power control parameter. If the mobile station accesses the network for the first time after the power is turned on or is assigned to a time interval for the first time, a previous power control parameter does not exist. If a previous power control parameter does not exist, the mobile station can calculate a transmit power by setting a power control parameter as a default value.

If a power control parameter is not included in the

9/15 packet uplink assignment, the mobile station can find a transmit power using a previous power control parameter or a default value as the power control parameter. Hence, a user equipment can set a power control parameter automatically without the need to transmit the power control parameter to each user equipment whenever the network assigns a new time interval. Thus, programming is simplified and efficient power control in a cell is achieved.

FIG. 4 is a flow chart illustrating a method of controlling a transmission power in accordance with another embodiment of the present invention.

Referring to FIG. 4, a mobile station sends a packet channel request message to a network for radio access (S210). The network sends a multiple TBF uplink assignment message to the mobile station in response to the packet channel request message (S220). The multiple TBF uplink assignment message can be transmitted in PACCH. Unlike the packet uplink assignment message, the multiple TBF uplink assignment message assigns a multiple TBF to the mobile station. Multiple TBF uplink assignment messages include the time slot assignment information for the transmission of the uplink in each TBF.

If the power control parameter is not given directly with the multiple TBF uplink assignment message, a variety of methods can be used to find the transmit power.

In one embodiment, if a time slot is assigned via the multiple TBF uplink assignment message, the mobile station can set a power control parameter of the given time slot to a default value. For example, the default value can be zero. By setting the power control parameter to the default value, when the packet uplink assignment message is received, the mobile station can calculate a transmission power for a given time and perform the transmission of the uplink using the transmit power calculated.

In another embodiment, the mobile station can calculate a transmission power using a previous power control parameter. The previous power control parameter refers to a power control parameter that was used in a packet transfer mode prior to a current packet transfer mode. If there is a previous power control parameter with respect to a corresponding time interval, the

10/15 mobile station calculates an output power using the previous power control parameter. If there is no previous power control parameter, the mobile station can calculate a transmit power by setting the power control parameter to a default value.

FIG. 5 is a flow chart illustrating a method of controlling a transmission power in accordance with yet another embodiment of the present invention.

Referring to FIG. 5, in a packet transfer mode, a mobile station transmits packet data over a specified time interval (S310). During packet transfer mode, the network can update the power and / or TA (sync advance) of the mobile station by sending a packet / TA power control message to the mobile station (S320). The TA can be a value used to advance a transmission timing to the base station in order to compensate for the propagation delay at the mobile station. The packet / TA power control message can be transmitted on the PACCH.

Only the TA can be updated via the packet / TA power control message. That is, this corresponds to a case where the network sends only the TA. If the Ta is updated, the transmission power for each time interval can be found using a previous power control parameter. The previous power control parameter is a power control parameter that is used for a corresponding period of time in a current packet transfer mode. That is, since a current mode is a packet transfer mode, a transmit power parameter that has been used previously exists at each time interval in order to transmit old packet data. The transmission power of the time interval is found using the transmission power parameter that was used. If a previous transmit power parameter does not exist, the power control parameter can be set to a default value.

Only the power can be updated via the packet / TA power control message. This corresponds to a case where the network sends a power control parameter. Here, a transmission power is calculated using a received power control parameter.

The power with respect to only part of the time intervals can be updated via the packet / TA power control message. A transmit power with respect to some of the time intervals to which a transmit power parameter is given is

11/15 calculated using the given transmission power parameter. A transmit power with respect to the remaining time intervals for which a transmit power parameter is not given is calculated using a previous power control parameter.

Both power and TA can be updated via the packet / TA power control message. Even in this case, a transmission power of a time interval for which a power control parameter is not given is calculated using a previous power control parameter.

The mobile station transmits data in packets using the obtained transmission power and the updated power and / or TA (S330).

FIG. 6 is a flowchart illustrating a method of controlling a transmission power in accordance with yet another embodiment of the present invention.

Referring to FIG. 6, in a packet transfer mode, a mobile station transmits packet data over a specified time interval (S410). During packet transfer mode, a network can update the power and / or TA of the mobile station by sending a packet uplink ACK (acknowledgment) / NACK (non-acknowledgment) message to the mobile station (S420). The packet uplink ACK / NACK message is a message that is sent from the network to the mobile station in order to report the status of a received RLC (radio link control) data block and can be transmitted in PACCH. The packet uplink ACK / NACK message includes the power and / or TA and can update the power and / or TA.

Only the power can be updated via the packet uplink ACK / NACK message. In other words, this corresponds to a case where the network sends a power control parameter. Here, a transmission power is calculated using a received power control parameter.

The power for only a portion of the time slots can be updated via the packet uplink ACK / NACK message. A transmit power with respect to some of the time intervals at which a transmit power parameter is given is calculated using the received power control parameter. A transmit power with respect to the remaining time intervals for which a transmit power parameter is not given is calculated using a previous power control parameter.

Both power and TA can be updated via

12/15 packet uplink ACK / NACK message. Even in this case, a transmission power with respect to a time interval for which a power control parameter is not given is calculated using a previous power control parameter.

The mobile station transmits data in packets using the transfer power obtained and the updated power and / or TA (S430).

FIG. 7 is a flow chart illustrating a method of controlling a transmission power in accordance with yet another embodiment of the present invention.

Referring to FIG. 7, in a packet transfer mode, a mobile station transmits packet data with a specified time interval (S510). During packet transfer mode, the network can assign an uplink slot to the mobile station by sending a packet reset message to the mobile station (S520). The packet reset message can be transmitted in PACCH.

The packet time reset message may include a power control parameter with respect to a time slot in addition to information about at least one time slot, which is required by the mobile station for the transmission of the uplink. In this case, a transmission power can be found using the power control parameter included in the packet uplink assignment message. When the power control parameter is not included in the packet time interval reconfiguration message, a variety of methods can be used to define the power control parameter with respect to the time interval.

In one embodiment, if a time slot is assigned via the packet time slot reset message, the mobile station can set a power control parameter, with respect to the given time slot, to a previously set value . For example, the adjusted value can be zero. By adjusting the power control parameter to the previously set value, the mobile station can calculate a transmission power for the given time interval if the packet time interval reconfiguration message is received and perform the uplink transmission based on the power of the packet. calculated transmission.

In another embodiment, the mobile station can calculate a transmission power over a specified time using a

13/15 previous power control. The previous power control parameter can include two types. The first previous power control parameter is a power control parameter that has been used over a corresponding time interval in a current packet transfer mode. That is, if a given time interval was used once in a current packet transfer mode, a transmit power parameter that was used becomes a first previous power control parameter. The second previous power control parameter is a power control parameter that was used in a packet transfer mode prior to a current packet transfer mode. That is, in the case where the mode changes from a packet transfer mode to a packet idle mode and then becomes a packet transfer mode, it acts again, a power control parameter that was used in a previous packet transfer is a second previous power control parameter. The mobile station gives priority to the first previous power control parameter. If the first previous power control parameter exists, the mobile station can find transmission power using the first previous power control parameter. If the first previous power control parameter does not exist and the second previous power control parameter exists, the mobile station can find a transmit power using the second previous power control parameter. If the first previous power control parameter and the second previous power control parameter do not exist, the mobile station can find transmission power using a default value. As another example, the mobile station can find transmission power using only the first previous power control parameter or the second previous power control parameter.

The mobile station transmits data in packets using the obtained transmission power and the determined time interval (S530).

FIG. 8 is a flow chart illustrating a method of controlling a transmission power in accordance with yet another embodiment of the present invention.

Referring to FIG. 8, a mobile station transmits packet data to a network with a specified time interval (S610). During packet transfer mode, the network can assign an uplink time slot to the mobile station by sending a packet uplink assignment message to the mobile station (S620). That is, unlike the embodiment of FIG. 3, the

14/15 packet uplink assignment message can be sent from the network to the mobile station during packet data transmission not as a response to a packet channel request message in order to assign a new time slot. A default value can be used as a transmission power parameter with respect to a specified time interval.

The mobile station transmits the data in packets using the obtained transmission power and the determined time interval (S630).

FIG. 9 is a flow chart illustrating a method of controlling a transmission power in accordance with yet another embodiment of the present invention. This shows a method of controlling transmission power during transfer.

Referring to FIG. 9, the network transmits a transfer command message to the mobile station on the PACCH (S710). The transfer command message is a message to instruct that the mobile station must leave a current cell and arrive at a new cell. The transfer command message includes information about radio resources allocated to a packet-switched service in a new cell, and also includes at least time slot assignment information.

If a power control parameter with respect to a specified time interval is not given, the mobile station that received the transfer command message determines a power control parameter as an adjusted value. The mobile station finds a transmission power using the adjusted power control parameter.

The mobile station transmits a transfer access message to the network (S720). The transfer access message is to make the network aware that the mobile station has left the old cell and has reached the new cell. The transfer access message is sent on the PACCH associated with the uplink TBF allocated in the transfer command message.

If a cell is changed, a power control parameter has to be changed. The power control parameter is sensitive to loss of travel. Path loss is greatly influenced by the distance between a mobile station and a network. Thus, if only one time slot is assigned via a transfer command message during the transfer, but the power control parameter for the time slot is not given, a transmission power can be controlled stably by adjusting the

15/15 power control parameter at an adjusted value.

When a mobile station is assigned a time slot or updates the power and / or timing advance for the transmission of the uplink, the mobile station can stably control a transmission power of a time slot.

The functions described in relation to the modalities described here can be performed implemented by the hardware, software or a combination of them. The hardware can be implemented by a microprocessor, controller, application specific integrated circuit (ASIC) and processor. The design, development and execution of the software are known to those skilled in the art based on the detailed description.

As the present invention can be incorporated in various forms without departing from the spirit or essential characteristics of the same, it should also be understood that the modalities described above are not limited by any of the details of the previous description, unless otherwise specified , but should instead be interpreted widely within its spirit and scope as defined in the appended claims. Consequently, all changes and modifications that are within the limits of the claims, or are equivalent to those limits, are intended to be encompassed by the appended claims.

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