Method and arrangement for reducing power consumption in a mobile communication network

TECHNICAL FIELD [0001] The present invention relates generally to a mobile communication network, and more particularly to a system allowing to reduce energy consumption in a mobile terminal, as well as a method for such a reduction. The invention further relates to a computer readable medium comprising a computer program for reducing energy consumption in a mobile terminal.

BACKGROUND OF THE INVENTION [0002] In packet transmission systems, data is packetized and transmitted along with control information such as the size (or beginning and end) of the data and the identity of the recipient (at least when communicating over a shared medium). In many systems, time is divided into time frames, each frame carrying zero or more packets with said control information.

[0003] A receiver in such a system monitors transmitted control information for the presence of packets that should be received by this receiver. In situations where the bit rate required by the application is significantly lower than the transmission bitrate, the receiver is essentially idle for most of the time, it only monitors the control information.

[0004] Examples of the above include all known cellular packet transmission techniques, i.e. GPRS / EDGE, WCDMA (R99, HSDPA and E-UL) and CDMA2000 (1x, EV-DO and EV-DV).

[0005] With many transmission technologies, active monitoring of control information can be very energy intensive, even if the control information itself contains little information and there is no data to be received. For example, a broadband radio transmission technique for high speed data transmission may require the receiver to demodulate and process the entire frequency band even though it is only interested in the control information. This is the case with, for example, WCDMA HSDPA and may be found in OFDM-based systems such as long-term evoiution (LTE) for UMTS.

[0006] This means that for a low bit rate service (such as a voice), power consumption can be significantly higher when using a broadband system compared to a narrowband system.

[0007] If the mobile terminal could sporadically enter "sleep mode", i.e. not monitor control information over a period of time, energy consumption could be reduced This type of sleep mode is currently used when the mobile terminal has entered the paging state. mobile occasionally listens to the "wake up" or "call" signal from the network. However, this method requires additional signaling between the network and the mobile terminal in order to "wake up" and not be suitable for use in short time intervals, for example between successive packets in the ongoing real-time data session.

[0008] US 6,236,850 B1 discloses a remote convenience system that, by means of a related method, causes remote control of the performance of a function. A portable, energizable transmitter in the system transmits signals that transmit function requests in the first portion of repeating request periods of predefined length, and is idle during the second set of request periods. The power control circuit keeps

- a power take off circuit 2 OFF for a first portion of recurring energy saving periods of a predefined length, and cycles ON power and power OFF in sequence for the second portion of the power save period so that the receive circuit is finally ON power during one from the first portions from one of the request periods and such that one of the transmitted signals is detected. The power control circuit thus maintains power ON when a signal is detected to receive the next next signal.

[0009] US 6,236,674 B1 discloses a transmitter-receiver that maintains circuits associated with a receiver in the power off state during periods when the Received Signal Power Indicator (RSSI) indicates that the received signal is below a predetermined threshold level. The transmitter is switched on as soon as it is determined that the received packet requires a response. The RSSI signal represents the power of any signal current that is received, and if the RSSI signal falls below a predetermined threshold, the digital circuit associated with the printed circuit of the receiver system is turned off. If the RSSI signal rises above the threshold level, the receiver's digital circuit is turned on. The control system in the transceiver processes the packet after it is received to determine if the packet requires a response. If it is determined that the answer is necessary,

[0010] EP 1 571 785 A2 discloses a method for controlling the modes of operation of a central access control layer by a mobile subscriber station in communication with wireless broadband access. The method comprises the following steps: changing the mode to idle mode when there is no data transmission between the serving base station and the mobile station during the predefined first time interval in the sleep mode; detecting the movement of a mobile subscriber station in an idle mode to a different paging zone including a target base station that is different from the paging area including the serving base station; and changing the mode to standby mode, performing the location update with the target base station after detecting the movement of the mobile subscriber's station.

[0011] EP 0 529 269 A2 discloses a method and an energy-saving device in a wireless computer interface of a computer operating on a battery, such as a portable laptop, as controlled by a protocol of planned multiple-access. A portable computer can act as a mobile unit in a multicellular wireless network. The planned multi-access protocol is implemented to effectively save battery power through appropriate control of the controller, transmitter and receiver units at the wireless link adapter by scheduling when the adapter is in normal operation or in standby mode, in which energy is saved.

SUMMARY OF THE INVENTION [0012] Accordingly, it is an object of the present invention to provide an improved method to enable reducing the power consumption of a user equipment in a mobile communication network including a radio base station transmitting data packets in a downlink channel to one or more user devices via an interface radio.

[0013] This object has been achieved by developing a method according to claim 1.

[0014] Another object of the present invention is to provide an improved system to enable reduction of energy consumption in a user equipment in a mobile communication network including a radio base station transmitting data packets in a downlink channel to one or more user devices via a radio interface.

[0015] This second object has been achieved by providing a user device according to the claim

12.

[0016] A further object of the present invention is to provide an improved computer-readable medium to enable reduction of energy consumption in a user equipment in a mobile communication network including a radio base station transmitting data packets in a downlink channel to one or more user devices via a radio interface.

[0017] This further objective has been achieved by developing a computer readable medium according to claim 23.

[0018] Further embodiments of the invention are set forth in the dependent claims.

[0019] By providing specific sleep rules, the power consumption of the user device, i.e. the mobile terminal, can be reduced, and thus, for example, the battery life can be increased.

[0020] The radio base stations, i.e. the wireless communications network and the user equipment, therefore agree on a rule that defines points at a time when the radio base station can not transmit anything to the user equipment, thus enabling the user equipment to turn off the reception processing. No additional signaling is needed when the user equipment should listen for control information, thus allowing the technique to be used for very short intervals, e.g. between packets in an ongoing session in real time. In addition, the proposed rules of rules, as well as the selection algorithms, are designed to work during ongoing sessions.

By running a low bit rate service in a broadband system, the radio base station and the user equipment can agree on a sleep rule that decides when the sender can send packets to the recipient, and when he can not. Such a rule will typically specify relatively long periods when no packets should be sent to the user equipment, so that the user equipment can stop monitoring the media for the control information.

[0022] Furthermore, consent to the rule prior to its use allows it to be flexibly ensured that only a rule that can be used by both the radio base station and the user equipment is used, which also allows more reliable transmission of packet data.

[0023] Still other objects and features of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings. It should be understood, however, that the drawings are intended solely for purposes of illustration and not for the definition of the limitations of the invention, to which reference should be made to the accompanying claims. It should further be understood that the drawings are not necessarily made to scale and that, unless otherwise indicated, they are only intended to schematically illustrate the structures and procedures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS [0024] In the drawings, similar references denote similar elements:

Fig. 1 shows an example communication block diagram;

Fig. 2 is a diagram of states of a user equipment in which the present invention is implemented. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 shows a communication system such as a WCDMA communication system, including a Radio Access Network (RAN), such as (UTRAN) UMTS Terrestrial Radio Access NetWork Architecture (UTRAN) containing at least one Base Radio Station (RBS) (Base Station (BS) or eNode B) 15

Connected to one or more Base Station Controllers (RNCs) 10. The RAN is connected to the core network (CN) 12. RAN and CN 12 provide communication and control for multiple user devices (UE) 18 {only one is shown in Fig. 1), so that each uses downlink (DL) channels (i.e. base-to-user or broadcast) and uplink channels (UL) (i.e., user-to-base or reverse). In the downlink channel 13, RBS 15 transmits to each user device 18 at an appropriate energy level. In the uplink channel 14, the UE 18 device transmits data to RBS 15 at an appropriate energy level. According to a preferred embodiment of the present invention, a communication system is described herein as a WCDMA communication system. The person who is proficient in the art is aware,

[0026] Sleep reguia should be set between the pair - the sender and the recipient. In the sender, the rule specifies when the sender has the right to water the packages to the recipient. These time moments will be referred to as active periods of wakefulness, while the remaining moments in time will be called active periods of sleep (inactive periods). During active sleep periods, the recipient can turn off their receiving, demodulation, and processing of hardware and software, thus saving energy.

[0027] The active sleep mode according to the invention differs from the inactive sleep state according to the prior art. In an inactive sleep mode according to the prior art, the terminal only listens on the paging channel and is usually assigned a long Radio NetWork Temporary identifier (RNTI). The terminal needs an awakening message in the recall channel to be able to receive any information. In order to achieve effective planning, the terminal requires a shorter RNTI that requires additional signaling.

[0028] In the active sleep mode according to the present invention, the terminal typically has a short RNTI, but it is not possible to transmit to the terminal if it is not in an active standby mode. However, the transition from active sleep to active waking does not require any signaling at all.

[0029] If the periods of active wakefulness of two or more terminals are configured to not overlap in time, it is possible to use the same short RNTI for all these terminals. The base station may then use a shared short RNTI in the transmission time interval corresponding to the period of active standby of the terminal with which it is to communicate. This can be used to increase the effectiveness of control signaling, since there are only a limited number of unique RNTI sequences of any given length, and to control signaling to consume little RNTI short resources, it should be as short as possible.

[0030] Fig. 2 is a diagram of states in which the active state UE is designated with 20. When the UE is active, it has a short Radio Radio Radio Network Identifier (RNTI) assigned and can send and receive data. According to the present invention, the active state has been divided into an active waking state 21 and an active sleep state 22.

[0031] In active standby 21:

• Actions initiated by the EU and by BS are allowed;

• the UE may receive DL control information, demodulate and decode the control channel;

• The UE can receive DL data.

[0032] In active sleep state 22: e Only actions initiated by the UE are allowed;

-5® Transmission in UL is possible;

® Measurements, channel estimation, cell search etc. are possible;

• Demodulation and decoding of the control channel can be turned off.

[0033] Switching 24 from active sleep 22 to active standby 21:

® is triggered by predefined rules (patterns);

«Is immediate, without the need for additional signaling;

«Can not be initiated by the transmitter.

[0034] Switching 24 from active standby 21 to active sleep 22:

• can be called by predefined rules (patterns);

• it may also be initiated by a transmitter, e.g. by a specific command or as a result of transmitting a data packet to the receiver;

• is immediate, without the need for additional signaling.

[0035] In contrast to active state 20, the UE also has an inactive sleep state designated 23. In an inactive sleep state 23:

® receiving EU radio is periodically turned off;

® UE listens only to BS paging messages;

• the EU is assigned a long RNTI;

® The transmitting EU radio can also be turned off.

[0036] The transition between active state 20 and inactive sleep state 23:

• BS can trigger transitions from inactive sleep 23 to active state only by giving an explicit awakening message.

• When entering active state 20, the UE will also enter into one of the sub-bases, i.e., active arming 21 or active sleep 22, executing pre-defined rules;

• Clock or overt signaling can cause transitions from active to inactive sleep 23.

[0037] There are two stages of the invention: rules for sleep rules, and algorithms for choosing sleep rules appropriate in specific scenarios.

[0038] Hereinafter, when discussing the "active" mode / period, it is understood as the active standby mode / period, active, and when discussing the "sleep" mode / period, it is understood as the active sleep mode / period.

[0039] One simple rule is to determine a permanent pattern of active periods and periods of dormancy. Such a pattern will usually be periodic. For example, in the case of voice (telephone) applications, it can be for a short active period (several frames) every 20 ms.

[0040] A disadvantage of a fixed pattern is the inevitable conflict between the flexibility of the dispatcher and energy consumption. If the active period is very short, the sender has little or no choice of recipients, to which he broadcasts at which time, which may reduce transmission performance. A longer active period gives the dispatcher more freedom, but requires the recipient to actively listen for a longer period of time, reducing profits on energy consumption.

[0041] A somewhat more advanced principle of rules is to specify that each active period begins at a specified time and ends when the packet has been received, after which the receiver can return to sleep mode. Such dynamic active periods can be specified to start periodically, e.g. once per

-620ms. If no packet is sent during the active period, it extends until the next active period that would start anyway. Alternatively, the active period can be determined to end after a certain time, e.g. 5 ms, if no packet is transmitted.

[0042] In order to shorten the active period for the receiver when there is nothing to receive, the sender may send a dummy / blank packet to the receiver to force the receiver to enter the sleep mode. This can be advantageous, especially in the case of low and medium loads, when unused transmission capacity is not available.

[0043] More generally, the sleep commands can be embedded in the transmission. For example, the network may send several packets, followed by a command that instructs the terminal to sleep for a certain period of time, or up to a point in time when it should wake up.

[0044] Sleep rules can also be combined with retransmission. If the packet has been received with an error and the recipient informs the sender with a negative acknowledgment, the new active period can be defined as the initiator as a result of this. The size of this active period should be related to the nature of the retransmission. For example, it should not start earlier than the earliest point at which a retransmission might possibly occur, e.g. due to delays in transmission and processing of acknowledgment. In addition, if the retransmission scheme states that retransmissions should take place at a certain point in time, the active period should be set to cover only this moment of time.

[0045] Another option is to reference active periods for reporting channel quality from the recipient. Such reporting is present, for example, in WCDMA HSDPA, in the form of CQI reports, which are transmitted with a period that is signaled from the network to the terminal. It may be desirable to maintain a long period of time to reduce the amount of radio resources devoted to reporting. The disadvantage is that the network has current channel quality information only directly after the CQI report. The accuracy of this information then decreases over time until the next report. In such cases, it may be beneficial to specify sleep rules so that each active period starts shortly after the CQI report, so that the network can use up-to-date channel quality information.

[0046] Naturally, in order for the sleep rules to be effective, they should be selected depending on the type of movement. This can be done on the basis of knowledge about the type of application (for example, whether it is a voice call or a video call), an agreed QoS for traffic, or based on the observed nature of the traffic.

[0047] If direct information about individual applications is available, for example from higher layers, pre-developed sleep rules can be compiled in the table for some applications. For example, a speech application may have a sleep rule in which the terminal immediately enters sleep mode upon receipt of the data packet and periodically returns to the active mode every 20 ms as discussed above.

[0048] Broadly speaking, the desired type of radio link may be known in parameterized form, for example in the form of RAB parameters [see 3GPP specification] or other type of QoS contract. This may, for example, include the maximum bit rate, guaranteed bit rate, maximum packet size and maximum delay. Then the sleep rule can be selected automatically using an algorithm. For example, the sleep rule can be designed to enter a period of active periodic period with a period that is determined by QoS parameters. This period can be calculated by comparing the maximum rate of incoming traffic with the estimated data rate w

-7 radio channel so that it is likely that in each active period, all buffered data can be transmitted in one transmission. With this algorithm, the sleep rule can be dynamically updated based on changes in the estimated bit rate.

[0049] An alternative may also be the use of an adaptive algorithm that determines the sleep rules based on the observed motion traits. An example of this is monitoring the time between packets arrival for each user and dynamically adjusting the sleep rule to that time. This can be done on the network or in the terminal (or even both), depending on the type of control signaling defined to configure the sleep rules.

[0050] The invention, if implemented correctly, can significantly reduce the power consumption of the terminal, thereby increasing battery life.

[0051] It should be noted that at least some of the procedures described above are repeated as necessary in response to time-varying channel properties between the transmitter and the receiver. To facilitate understanding, many aspects of the invention are described in the language of the sequence of actions to be carried out, for example, components of a programmable computer system. It will be appreciated that various operations can be performed by specialized circuits (e.g., discrete logic gates connected to each other to perform a specialized function or application-specific integrated circuits), by program instructions implemented by one or more processors, or a combination of both. [0052] Furthermore, the invention may further be considered to be implemented completely in any form of a computer-readable storage medium, having an appropriate instruction set stored therein, for use by or in combination with an instruction execution system, apparatus or device, such as a computer system, a processor-containing system or other system that can take instructions from the medium and execute instructions. As used herein, a "computer readable medium" can be any means that is able to contain, store, communicate, propagate or transport a program for use by or in combination with an instruction system, apparatus or device. The computer readable medium may be, e.g., but not limited to, an electronic, magnetic, optical, electromagnetic, infrared or semiconductor system, apparatus, device, or propagation medium.

[0053] Thus, a computer-readable medium comprising a computer program according to a preferred embodiment of the present invention for reducing energy consumption in a mobile terminal in a communication network including a sender transmitting packet data in a downlink channel to one or more recipients via a radio interface wherein the computer program performs the steps of: determining inactive moments of time and listening for moments of time during which said receiver listens for signaling from said transmitter, wherein less energy is consumed during said inactive moments of time.

[0054] Modifications of the embodiments of the invention described above are possible without departing from the scope of the invention as defined by the appended claims. Expressions such as "comprising", "including", "including", "consisting of", "has", "is", used to describe and claim the present invention, are intended to be constructed in a non-inclusive manner, i.e.

- presence of objects, subassemblies or elements that are not explicitly described. The reference to the singular shall also be understood as referring to the plural and vice versa.

[0055] The figures in brackets in the accompanying claims are intended to help understand the claims and should not be interpreted in any way as limiting to the subject claimed by these claims.