WO2012023280A1

WO2012023280A1 - Apparatus and methods for data transmission synchronization for low power devices

Info

Publication number: WO2012023280A1
Application number: PCT/JP2011/004585
Authority: WO
Inventors: Chan Wah Ng; Hong Cheng; Chun Keong Benjamin Lim
Original assignee: Panasonic Corp
Current assignee: Panasonic Corp
Priority date: 2010-08-20
Filing date: 2011-08-15
Publication date: 2012-02-23
Anticipated expiration: 2013-02-20

Abstract

The present invention introduces apparatus and method that save power by minimizing the period of listening for paging signals. The apparatus comprises a radio interface (110), a paging reception unit (120), an access management unit (140), and a timing mapping table (130). The access management unit controls the radio interface to listen for paging signals in the first time period, and controls the radio interface to access the communications network in the second time period upon receiving the paging signal in the first time period.

Description

APPARATUS AND METHODS FOR DATA TRANSMISSION SYNCHRONIZATION FOR LOW POWER DEVICES

This invention relates to the field of telecommunications in a packet-switched data communications network. More particularly, it concerns a low power mobile terminal communicating with other devices using the reception of paging message as for synchronization of data transmission.

The cellular telecommunications has been under constant evolution, from the earlier days of GSM (Global System for Mobile communications) networks, to GPRS (General Packet Radio Service), to the modern system of UMTS (Universal Mobile Telecommunications System) which can be found in various big cities around the world. In the very near future, the next generation Long Term Evolution (LTE) networks are going to be deployed. Along with different access technologies, the experiences provided to end-user are also continuing to be enhanced. Many of these are optimized to reduce delay. For example, <US Patent No. 7092721B2> discloses a method to reduce delay of call setup by monitoring the wake-up time of user equipments, <US Patent No. 6810026B1> discloses a method of organizing paging and data slots to reduce the overall cumulative delay, and <US Patent Application No. 2008/0019373A1> teaches an approach to schedule data transmission based on the traffic condition.

However, today's cellular network is no longer only providing services for human oriented communications (such as voice, short text message transmission and access to the global Internet). Recently, new services have even been expanded to cover non-human communications, such as machine-to-machine (M2M) or machine-type communications. Machine-type communications can cover a very wide range of applications, from measurement collection from sensors, to remote control of devices. For such communications, delay need not be the foremost consideration, since they have a set of characteristics that is different from human oriented communications.

The Third Generation Partnership Project (3GPP) has started defining the requirements for a cellular network to support machine-type communications in <NPL 1>. Typically, machine-type communication in 3GPP consists of various communication devices that access the 3GPP cellular network to communicate with a server that is outside of the cellular network or to communicate with other communication devices in the cellular network. By having network improvement optimizations that take advantage of unique characteristics of machine-type communications, the cellular network will be even more suitable to support machine-type communications.

For instance, one such optimization known as Time Control is designed for use with M2M applications that needs only send data at operator defined access period. For example, a large variety of sensors and meters need only send their measurements in regular intervals under normal circumstances, and it usually not important for the interval to start at any particular time. For such applications, it will be advantages for the operator to schedule such access period to be in an off-peak period of human oriented communications (e.g. voice traffic). It will also be advantages to the devices since they can turn off their radio interface to conserve power until the pre-determined access period.

Another related optimization is the Low Mobility feature, where devices such as meters and sensors are either fixed installation or attached to slow moving objects (e.g. animals tags), are not expected to change their point of attachments frequently. In such cases, it will be desirable to reduce or even turn off the mobility signaling (i.e. sending what is known as Tracking Area Update, or TAU) procedure of the devices, thus reducing power consumption of the devices and signaling load of the network. Reducing power consumption for these devices is quite an important consideration, as many of them are battery-powered devices which are expected to remain in operation for years without replacing their battery.

There have been a few prior arts that optimize various procedures in the 3GPP networks in order to conserve the battery power of the devices. For example, <US Patent No. 6665307B1> discloses a method of scheduling less data slots for a device when the inactivity period of a device increases. <US Patent No. 6745056B2> teaches a method to separate paging slots from different services into different channels and uses a third channel to broadcast paging indications pointing to the respective paging channel. This allows the user equipment to listen only to the third channel, and jumping to the respective paging channel only when a paging indication is received. This is similar to <US Patent No. 7711377B2> and <European Patent No. 1806946B1> that teaches the use of a quick page channel to broadcast whether there is paging message for the mobile devices.

When the quick page channel indicates there is a paging message, the mobile device then tunes to the paging channel to receive the full paging message. A related method disclosed by <European Patent Application No. 1515575A1> wherein the paging message a device receives contains a service description part that indicates whether the device needs to listen to a second message. All these methods reduces the power consumption of devices by allowing them to listen to short paging message, and only listen for much longer messages when there is actually messages for the devices.

[PTL 1] US Patent No. 7092721B2 Harris et al., "Reducing delay in setting up calls", Aug 2006.
[PTL 2] US Patent No. 6810026B1 Huttunen, "Method of reducing radio channel access delay in GPRS system, and packet radio system", Oct 2004.
[PTL 3] US Patent Application No. 2008/0019373A1 Filipovich et al., "System and method for scheduling data transmissions", Jan 2008.
[PTL 4] US Patent No. 6665307B1 Rydnell et al., "Variable fast paging mode", Dec 2003.
[PTL 5] US Patent No. 6745056B2 Wang et al., "Method and system for improving battery performance in broadcast paging", Jun 2004.
[PTL 6] US Patent No. 7711377B2 Laroia et al., "Efficient paging in a wireless communication system", May 2010.
[PTL 7] European Patent No. 1806946B1 Butler et al., "Indirect paging for wireless terminal", Aug 2008.
[PTL 8] European Patent Application No. 1515575A1 Al-Bakri et al., "A 3rd generation cellular communication network, user equipment and method for the communication of paging indication messages", Mar 2005.

Non-Patent Literature

[NPL 1] 3GPP TS 22.368 V10.1.0, "Service requirements for Machine Type Communications", Jun 2010.

However, for all the above methods, the device still needs to keep its radio interface turned on permanently to listen for paging messages, even if the paging duration is reduced.

It is thus an object of the present invention to overcome or at least substantially ameliorate the afore-mentioned disadvantages and shortcomings of the prior art. Specifically, it is an object of the present invention to provide a mechanism so that it is possible for a communication device can achieve maximum power saving by minimizing the period of listening for paging signals.

Accordingly, the present invention provides for an apparatus of a communication device in a cellular communications system comprises of a radio interface configured to receive and transmit communications signal to and from the communications network; a paging reception unit configured to receive paging signal sent from the communications network via the radio interface; an access management unit configured to control the radio interface to access the communications network; and a timing mapping table indicating a first time period of receiving a paging signal by the paging reception unit and a second time period when the radio interface should access the communications network for data transmission; .wherein the access management unit controls the radio interface to listen for paging signals in the first time period, and controls the radio interface to access the communications network in the second time period upon receiving the paging signal in the first time period.

In one preferred embodiment of the present invention, the apparatus of communications device is provided wherein the access management unit controls the radio interface to send a transmission request in a third time period if the communication apparatus has uplink data to be transmitted.

In another preferred embodiment of the present invention, the apparatus of communications device is provided wherein the access management unit controls the radio interface to listen for broadcast message from the communications network in a fourth time period, the broadcast message comprising the first time period of receiving the paging signal and the second time period when the radio interface should access the communications network.

In yet another preferred embodiment of the present invention, the apparatus of communications device is provided wherein the access management unit controls the radio interface to listen for paging signals only during the first time period.

In a further preferred embodiment of the present invention, the apparatus of communications device is provided wherein the first time period is further divided into a plurality of divisions, and the second time period is further divided into a plurality of divisions, wherein the timing mapping table comprises a mapping between the plurality of divisions of the first time period and the plurality of divisions of the second time period, and wherein the access management unit determines, one of the plurality of divisions of the second time period when the radio interface should access the communications network for data transmission, based on the timing mapping table.

In a yet further preferred embodiment of the present invention, a method of communications is provided comprising the steps of : assigning an access period in which all communications involving the communication apparatus occur; assigning a first time period within the access time period, wherein the communications apparatus listens for paging signals in the first time period; and assigning a second time period within the access time period, wherein the communications apparatus accesses the communications network for data transmission in the second time period.

In another preferred embodiment of the present invention, the method of communications further comprises the step of assigning a third time period within the access time period, wherein the communications apparatus transmits a request for transmission in the third time period if the communications apparatus has uplink data to be transmitted.

In yet another preferred embodiment of the present invention, the method of communications further comprises the step of assigning a fourth time period within the access time period, wherein the communication apparatus listens for broadcast message from the communications network in the fourth time period, the broadcast message comprising the first time period of receiving the paging signal and the second time period when the radio interface should access the communications network for data transmission.

In a further preferred embodiment of the present invention, the method of communications further comprises the step of : dividing the first time period into a plurality of divisions, and the second time period into a plurality of divisions; mapping the plurality of divisions of the first time period to the plurality of divisions of the second time period; and determining by the a communication apparatus, one of the plurality of divisions of the second time period when the radio interface should access the communications network for data transmission, based on the mapping.

In a yet further preferred embodiment of the present invention, the method of communications is provided wherein the number of divisions in the first time period is the same as the number of divisions in the second time period.

In yet another preferred embodiment of the present invention, the method of communications is provided wherein the communication apparatus listening for paging signals by the communication apparatus only during the first time period within the access time period.

The invention has the advantage of saving power by minimizing the period of listening for paging signals.

Fig. 1 shows a preferred functional architecture of the communications device according to a preferred embodiment of the present invention. Fig. 2 shows a message sequence diagram according to a preferred embodiment of the present invention. Fig. 3 shows a message sequence diagram according to a preferred embodiment of the present invention. Fig. 4 shows a message sequence diagram according to a preferred embodiment of the present invention. Fig. 5 shows a message sequence diagram according to a preferred embodiment of the present invention. Fig. 6 shows a message sequence diagram according to a preferred embodiment of the present invention. Fig. 7 shows a deployment architecture according to a preferred embodiment of the present invention. Fig. 8 shows a flowchart for communication device according to a preferred embodiment of the present invention.

In the following description, for purposes of explanation, specific numbers, times, structures, protocol names, and other parameters are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to anyone skilled in the art that the present invention may be practiced without these specific details.

The present invention applies to the situation where a communication device receives a paging signal from the network, uses the time of receiving the paging signal to determine the time to wake up for accessing the network in order to perform data transfer. Essentially, this allows the communication device to only listen to paging signal within a first time period, and performs data transfer during a second time period. Outside of the said first time period, the communication device will not be paged, and hence may totally turn off its radio interface (unless, of course, it is performing data transfer in the second time period). When the communication device receives a paging signal within the said first time period, it uses the time of receiving this paging signal to determine the time to wake up in the second time period for accessing the network and performing data transfer. Typically, the first time period is short to reduce the amount of time the device needs to listen to paging signals, and the second time period may be as long as needed. This takes advantage of the fact that delay in data transmission is not important in certain types of machine-type communication applications to conserve power. In the following preferred embodiments, different variations and application of this mechanism will be detailed.

Fig. 1 depicts the preferred functional architecture of a communications device 100, comprising of a radio interface 110, a paging reception means 120, a timing mapping table 130 and an access management means 140.

Radio interface 110 is a functional block comprises of the hardware and firmware necessary to enable a communication device to communicate with the cellular base station. It may include the antenna, transmitting circuitry and receiving circuitry. It is obvious to anyone skilled in the art that this does not preclude the system to be used in a wired environment, i.e. the radio interface 110 function can be replaced with wired transmission means as long as

signal path

191 and 194 are kept intact. It is also possible that the radio interface 110 is in fact running on top of another layer of communications stack, e.g. the Unlicensed Mobile Access (UMA) or any variance of the Generic Access Network (GAN).

The paging reception means 120 is the functional block which receives a paging signal sent by the network through the radio interface 110. Based on the time of reception of the paging signal, the paging reception means 120 consults the timing mapping table to determine the appropriate time for the communication device to access the network for data transmission. This information is passed to the access management means 140 for the control of the radio interface 110 to access the network. The signal path 191 allows the paging reception means to be notified of a paging signal received by the radio interface 110. The signal path 192 allows the paging reception means 120 to consult the timing mapping table 130. The signal path 195 allows the paging reception means 120 to inform the access management means 140 the time to access the network for data transmission based on the time of receiving the paging signal and mapping information from the timing mapping table 130.

The timing mapping table 130 contains the mapping information between the time of receiving a paging signal to the time for the communication device to access the network for data transmission. The information on when the radio interface 110 should be listening for paging signal can also be stored in the timing mapping table 130. The information stored in the timing mapping table 130 can be configured by the network operator (through, for example, over-the-air OTA configuration updates, or Open Mobile Alliance Device Management OMA-DM protocol, or pre-configured at launch time) or configured by a machine-type communication server (through, for example, application specific means). The timing mapping table 130 may be stored in a Universal Subscriber Identity Module (USIM) in the communication device.

The access management means 140 controls the radio interface 110 for accessing the network. Based on information stored in the timing mapping table 130, the access management means 140 controls when the radio interface 110 should power up to listen for paging signal. Based on the time of receiving a paging signal informed by the paging reception means 120, the access management means 140 controls when the radio interface should power up to access the network for data transmission.

The signal path 194 allows the access management means 140 to control the radio interface 110. The signal path 193 allows the access management means 140 to obtain the time periods stored in the timing mapping table 130 for the communication device to listen for paging signal. The signal path 195 allows the access management means 140 to receive notification from the paging reception means 110 on the time to access the network for data transmission based on the time of receiving the paging signal and mapping information from the timing mapping table 130.

Fig. 2 illustrates the concept of the present invention in its simplest form. Two time periods, time period 250 and time period 270, are defined. In the first time period 250, the communication device 210 will listen for paging signal sent from the network/server 220. If a paging signal 240 is received, the communication device will wake up at some point in the second time period 270 to access the network for data transmission. Note that data transmission may refer to data being transmitted by the communication device 210, or data being received by the communication device 210, or both.

The time offset 272 into the second time period 270 when the communication device 210 performs the network access 260 is determined by the time offset 252 into the first time period 250 when the communication device 210 receives the paging signal 240. The relationship between the time offset 252 and time offset 272 may be, but not limited to, a linear proportion. For example, the value of time offset 272 may be given by the product of {the length of time period 270} and {the value of time offset 252} divided by {the length of time period 250}. Alternatively, the relationship between time offset 252 and time offset 272 may be given in a form of a mapping table, allowing more complex mapping.

The radio interface of the communication device 210 can be totally turned off to conserve power outside of time period 250, and only be turned on to listen for paging signals during time period 250. If there is no paging signal received, the communication device 210 can turn off the radio interface after time period 250 until the next scheduled time period 250. If a paging signal 240 is received, the time offset 252 is used to derive the time offset 272. The communication device 210 can then turn off its radio interface after time period 250 until the time offset 272 into time period 270 to access the network for data transmission.

Note that the communication device 210 may receive multiple paging signals during the time period 250. This means that there is multiple time instances within the time period 270 that the networks expects there to be data transmission for the communications device. Depending on the power capabilities and hardware limitations, the communication device may choose to keep the radio interface turned on throughout the period that encompasses all of the time instances, or turn the radio interface on and off as and when needed. Certain hardware may consume additional power during turn on and turn off, which makes it more economical to perform the former.

Note also that the time period 250 and time period 270 may be disjoint (as shown in Fig. 2), or adjacent (as in time period 270 begins immediately after time period 250), or even overlapping (where part or whole of time period 250 is within time period 270).

As described by this preferred embodiment, the communication device needs only listen to paging signals for a short time period 250 whereas data communications can occur in a larger time period 270. Hence, the objective of the present invention is achieved.

In another preferred embodiment, the mapping between the time offset of receiving a paging signal within the first time period and the time offset of accessing the network in the second time period is carried out by mapping time divisions within the first and the second time periods. This is shown in Fig 3. Here, the first time period 350 in divided into multiple

discrete time divisions

352, 354 to 358. Similarly, the second time period 370 is divided into multiple

discrete time divisions

372, 374 to 378. Each time division in time period 350 is mapped to one time division in time period 370. When the communication device 210 receives a paging signal 340 in one of the time divisions (say, time division 354) in time period 350, it knows that it needs to access the network in a corresponding time division (say, time division 374) within time period 370.

Note that there can be different number of time divisions in time period 350 and time period 370. In this case, one time division in time period 350 may be mapped to a plurality of time divisions in time period 370. The communication device may choose to access network in either of the mapped time divisions of time period 370. Note also the time divisions in time period 350 need not necessarily be of equal length. Similarly, the time divisions in time period 370 need not be of equal length. However, typical deployment would have the same number of divisions in time period 350 and time period 370, the time divisions in time period 350 all be of the same length, and the time divisions in time period 370 all be of the same length. This allows for an easy way of specifying the mapping. All that is needed is to define the time period 350 and time period 370, and the number of time divisions in each time period. The communication device can then calculate the length of each time division in the respective time period based on this information.

In the previous descriptions of the preferred embodiments, the data transmission is generalized to cover the cases of data being transmitted by the communication device 210, or data being received by the communication device 210, or both. In some machine communication applications, the communication device 210 may initiate the data communication session.

Coupled with the Time Controlled feature where communications may only occur within a defined access period, this means that many devices may be sending data to a server at roughly the same time, causing some congestion in the network, and lengthening the time needed to complete data transmission as compared to when there is no congestion. The longer the data transmission, the more power the devices would consume. Hence, it would desirable to schedule data transmission of each device within the access period so as to minimize the power consumed by the communication devices. Fig. 4 illustrates how this can be achieved.

The access period is divided into three defined time periods: a first time period 420 for communications device 210 to indicate whether it needs to perform transmission to the network/server 220, a second time period 450 for communication device 210 to listen to paging signal, and a third time period 470 for communication device 210 to access the network for data transfer. Assuming that the communication device 210 has determined that it needs to send data to the server, the communication device 210 will transmit a transmission request 410 in the time period 420. Upon receiving the transmission request, the server or network 220 will schedule a transmission slot for the communication device 210. This scheduling should be carried out in such a way to avoid congestion in consideration of transmission requests from other communication device (e.g. avoid having multiple devices transmitting at the same time).

To facilitate scheduling, the communication device may include in the transmission request 410 some parameters of the requested transmission, such as, the size of transmission, the bit-rate available, etc. The transmission slot scheduled will occur within time period 470. In order to avoid having the communication device to turn on its radio interface to listen for paging signal throughout time period 470 to know when its transmission slot begins, the present invention allows for the communication device to instead monitor the paging channel only in time period 450 (which should be much shorter than time period 470). By mapping the time offset of receiving a paging signal within time period 450 to a time offset within time period 470, the communication device can determine when its scheduled transmission slot begins.

For example, suppose after sending the transmission request 410 in time period 420, the communication device 210 receives a paging signal 440 in time period 450 at time offset 452. Based on the mapping information, communication device 210 can determine the time offset 472 from time offset 452. The communication device 210 can then access the network at its scheduled transmission slot, which begins at the time offset 472 in time period 470.

As described by this preferred embodiment, the communication device needs only to turn on its radio interface at three separate instances: firstly, to transmit the transmission request 410 within time period 420 (note that the radio interface needs not be powered on throughout time period 420, but only during the transmission of the transmission request 410); secondly, during time period 450 to listen to paging signals; and thirdly, at the scheduled transmission slot which begins at a time offset 472 in time period 470. Hence, the objective of the present invention is achieved.

The addition of a time period for sending transmission request allows the present invention to be applied to a case where communications devices need to be communicating with each other. In this situation, if transmission slot is not scheduled by the server or network, congestion may occur if there are too many devices communicating with one particular device at the same time. Fig. 5 illustrates how the present invention can be used.

Here, the defined access period for machine communication is divided into three time periods: a first time period 520 for communications devices to transmit data request to the network or server, said data request may be a request for data from other communication devices, or a request to send data to other communications devices; a second time period 550 for communication devices to listen to paging signal; and a third time period 570 for communication devices to access the network for data transfer.

The mapping between the time offset of receiving a paging signal within the time period 550 and the time offset of accessing the network in the time period 570 is carried out by mapping time divisions within the respective time periods. The time period 550 in divided into multiple

discrete time divisions

552, 554 to 558. Similarly, the time period 570 is divided into multiple

discrete time divisions

572, 574 to 578. Each time division in time period 550 is mapped to one time division in time period 570.

In Fig. 5, we consider that communication device 212 wishes to establish a data session with communication device 210. Hence, during time period 520, the communication device 212 sends a data request 510 to the network/server 220. This data request 510 indicates to the network/server 220 that a data session with communication device 210 is requested by communication device 212. By the end of the time period 520, the network/server 220 would have received all data requests from all the communication devices, and can schedule transmission slots in order to avoid congestion and minimize the power-on periods of communication devices.

To facilitate scheduling, the communication device may include in the data request 510 some parameters of the requested transmission, such as, the size of transmission, the bit-rate available, etc. Suppose that the data session between

communication devices

212 and 210 is scheduled in the time division 574 in time period 570. In this case, assuming that time division 554 is mapped to time division 574, the network/server 220 will send the paging signal 540 to communication device 210 and paging signal 542 to communication device 212 in the time division 554.

During time division 554, the

communication devices

210 and 212 will access network to establish data session. Suppose communication device 212 accesses the network first. It sends a query message 560 to the network/server 220. This query message 560 serves two purposes: firstly, communication device 212 informs network/server 220 that it has already woke up and ready to establish data session with other devices; and secondly, communication device 212 asks the network/server 220 with which other devices it is scheduled to establish data session in this time division.

The network/server 220 responds with response message 562, notifying communication device 212 that it is scheduled to establish communications with communication device 210, but communication device 210 is not-yet ready. Later, communication device 210 accesses the network and sends a query message 564 to the network/server 220. The network/server 220 responds with response message 566, notifying communication device 210 that it is scheduled to establish communications with communication device 212, and communication device 212 is ready. Communication device 210 then establishes the data session 568 with communication device 212.

As described by this preferred embodiment, the communication device needs only to turn on its radio interface at three separate instances: firstly, to transmit the data request 510 within time period 520 (note that the radio interface needs not be powered on throughout time period 520, but only during the transmission of the data request 510); secondly, during time period 550 to listen to paging signals; and thirdly, at the scheduled transmission slot within time division 574. Hence, the objective of the present invention is achieved.

In the previous descriptions of the preferred embodiments, the timing mapping is assumed to be known a priori. This can be achieved by storing the mapping information in the SIM card of the devices, configuring the device using over-the-air update or OMA-DM, or using Protocol Configuration Option (PCO) when the device first attaches to the network. These, however, assume that the timing mapping is relatively static. It is possible for the timing mapping information to be dynamically assigned at each access period. This has the advantage of the network or server being able to optimally assign the transmission slot based on the data needed to be sent, or the traffic condition. Fig. 6 illustrates a preferable way to do this.

In Fig. 6, the access period is divided into four time periods: a first time period 620 for communications devices to transmit data request to the network or server, said data request may be a request for data from other communication devices, or a request to send data to other communications devices; a second time period 630 for the network or server to broadcast the number of divisions in the third and fourth time periods and their respective length; a third time period 650 for communication devices to listen to paging signal; and a fourth time period 670 for communication devices to access the network for data transfer. The length of the first time period 620 and second time period 630 are known a priori.

During the second time period 630, the network or server will broadcast home long the

time periods

650 and 670 are, and how many divisions each timer period has. One way is for the

time periods

650 and 670 to have equal number of divisions. In this case, the mapping between the time offset of receiving a paging signal within the time period 650 and the time offset of accessing the network in the time period 670 is a one-to-one mapping. By knowing the number of divisions, the communication devices can work out that the time period 650 in divided into the specified number of

time divisions

652, 654 to 658, and the time period 670 is divided into equal number of

time divisions

672, 674 to 678.

In Fig. 6, we consider that communication device 212 wishes to establish a data session with communication device 210. Hence, during time period 620, the communication device 212 sends a data request 610 to the network/server 220. This data request 610 indicates to the network/server 220 that a data session with communication device 210 is requested by communication device 212. By the end of the time period 620, the network/server 220 would have received all data requests from all the communication devices.

The network/server 220 can determine the optimal number of divisions required in time period 670 and schedule transmission slots in order to avoid congestion and minimize the power-on periods of communication devices. To facilitate scheduling, the communication devices may include in the data requests some parameters of the requested transmission, such as, the size of transmission, the bit-rate available, etc. Once the number of divisions is determined, the network/server 220 can then broadcast this information to all the communications devices in time period 630. This is shown in Fig. 6 as division info 632. Communication devices must be listening to the broadcast channel in this time period 630 to receive the time period division information.

Once the information is received, the communication would know how long they need to listen for paging signals in time period 650, and the number of divisions in time period 650. Suppose that the data session between

communication devices

212 and 210 is scheduled in the time division 674 in time period 670. In this case, assuming that the time division 654 is mapped to the time division 674, the network 220 will send the paging signal 640 to communication device 210 and paging signal 642 to communication device 212 in the time division 654.

During time division 654, the

communication devices

210 and 212 will access network to establish data session. Suppose communication device 212 accesses the network first. It sends a query message 660 to the network/server 220. The query message 660 serves two purposes: firstly, communication device 212 informs network/server 220 that it has already woken up and ready to establish data session with other devices; and secondly, communication device 212 asks the network/server 220 with which other devices it is scheduled to establish data session in this time division.

The network/server 220 responds with response message 662, notifying communication device 212 that it is scheduled to establish communications with communication device 210, but communication device 210 is not-yet ready. Later, communication device 210 accesses the network and sends a query message 664 to the network/server 220. The network/server 220 responds with response message 666, notifying communication device 210 that it is scheduled to establish communications with communication device 212, and communication device 212 is ready. Communication device 210 then establish the data session 668 with communication device 212.

As described by this preferred embodiment, the communication device needs only to turn on its radio interface at three separate instances: firstly, to transmit the data request 610 within time period 620 (note that the radio interface needs not be powered on throughout time period 620, but only during the transmission of the data request 610); secondly, during

time periods

630 and 650 to listen to broadcast of division information and paging signals; and thirdly, at the scheduled transmission slot within time division 674. Hence, the objective of the present invention is achieved.

In the previous preferred embodiments, for purpose of illustrating the principle of the present invention, certain details are intentionally generalized. For example, the cellular network and the server for machine communications are lumped into one single entity. A person skilled in the art would appreciate that this is simply for the purpose of explanation and in no way restrict the present invention from being applied in different deployments. In the following preferred embodiments, various different deployments are given, with the aid of Fig 7 which shows the typical elements of a cellular network 220.

The core of a typical cellular network 220 will comprise of various cellular base stations eNB 750 and eNB 752, a mobility management entity MME 740, a serving gateway SGW 730, and a packet data network gateway PDNGW 720. The base stations eNB 750 and eNB 752 each provides cellular radio access to communications devices in their respective coverage areas. For example, communication device 210 gains access to the network 220 by attaching to eNB 750 via radio connection 780, and communication device 212 gains access to the network 220 by attaching to eNB 752 via radio connection 782.

The MME 740 manages the mobility of communication devices attached to the cellular network. SGW 730 is the anchor point for communication devices among a group of base stations. Under the instruction of MME 740, appropriate bearers between SGW 730 and the base stations will be established via the interface 788. The MME 740 has interface 786 with the SGW and interface 770 with the base stations. The PDNGW 720 is the gateway between the cellular network 220 and other packet-switched network (such as the global Internet).

When a data packet is received by PDNGW 720 for a communications device (say, for example, a data packet sent by the server 220a via the connection 790), the PDNGW 720 will route the packet to the serving gateway SGW 730 via the interface 784. SGW 730 then forwards the packet to the communications device via the bearer established with the base station (i.e. interface 788). If the bearer is not established, the SGW 730 will send a signal to MME 740. MME 740 will then page for the communication device via a group of base stations.

This involves instructing the base stations to transmit paging signal containing an identity of the communication device. When the communication device receives the paging signal, in the current art, it would normally access the network with a service request. This allows the MME 740 to know which base station the communication device is currently attached to, and can then instruct the SGW 730 and the base station to establish a bearer for data transmission.

There are various forms the present invention can be applied to the cellular network architecture as described above. In one preferred form, the present invention applies to a case of the base station scheduling for communication devices. Here, the communication device is configured with an access period comprising of a paging signal listening period and transmission period. The communication device is further configured with a mapping between divisions within the said paging listening period and transmission period. When the base station is instructed by the MME to page for the communication device, the base station will first schedule a transmission division within the said transmission period.

Then, based on the mapping between divisions of the paging signal listening period and transmission period configured on the communication device, the base station will send a paging signal containing an identity of the communication device within the division of paging signal listening period that is mapped to the scheduled transmission division within the transmission period. The communication device, upon receiving this paging signal, calculates the transmission division that is scheduled based on the time it receives the paging signal, and will contest for the transmission slot at the calculated transmission division to transmit the service request to the MME in response to the paging signal.

The configured access period (i.e. paging signal listening period and transmission period), and configured divisions within these periods may be different for different communications device based on their identities (e.g. IMSI). The access period may be a few minutes long. Each division in the paging signal listening period may be one or multiple paging cycles in length. The MME knows of the access period configured on the communication device and will assign an appropriate time-out length for paging the communication device before treating the communication device as unreachable.

The above is for the case of downlink data. For scheduling of up-link data, there is an additional transmission request period at the beginning of the access period. When a communication device has uplink data to transmit, it will send a signal to the base station during this transmission request period. At the end of the transmission request period, the base station will know all transmission requests made by communication devices in its coverage area, and can schedule the transmissions into divisions within the said transmission period.

Then, based on the mapping between divisions of the paging signal listening period and transmission period configured on the communication device, the base station will send a paging signal containing an identity of the communication device within the division of paging signal listening period that is mapped to the scheduled transmission division within the transmission period. The communication device, upon receiving this paging signal, calculates the transmission division that is scheduled based on the time it receives the paging signal, and will contest for the transmission slot at the calculated transmission division to transmit the service request to the MME to establish a bearer for uplink data transmission.

In another preferred form, the present invention applies to a case of the MME scheduling for communication devices. Here, the communication device is configured with an access period comprising of a paging signal listening period and transmission period. The communication device is further configured with a mapping between divisions within the said paging listening period and transmission period. When the MME receives a signal from SGW that there is downlink data for the communication device, the MME will first schedule a transmission division within the said transmission period.

Then, based on the mapping between divisions of the paging signal listening period and transmission period configured on the communication device, the MME instructs the base stations to send a paging signal containing an identity of the communication device within the division of paging signal listening period that is mapped to the scheduled transmission division within the transmission period. The communication device, upon receiving this paging signal, calculates the transmission division that is scheduled based on the time it receives the paging signal, and will contest for the transmission slot at the calculated transmission division to transmit the service request to the MME in response to the paging signal.

If the MME does not receive the service request within the access period, the MME may perform the scheduling and sending of paging signal in subsequent access periods. If there is still no service request received after multiple retries, the MME may then give up and inform the SGW that the communications device is unreachable.

The above is for the case of downlink data. For scheduling of up-link data, there is an additional transmission request period at the beginning of the access period. When a communication device has uplink data to transmit, it will send a non-access stratum message to the MME during this transmission request period. At the end of the transmission request period, the MME will know all transmission requests made by communication devices handled by the MME, and can schedule the transmissions into divisions within the said transmission period.

Then, based on the mapping between divisions of the paging signal listening period and transmission period configured on the communication device, the MME instructs the base station to send a paging signal containing an identity of the communication device within the division of paging signal listening period that is mapped to the scheduled transmission division within the transmission period. The communication device, upon receiving this paging signal, calculates the transmission division that is scheduled based on the time it receives the paging signal, and will contest for the transmission slot at the calculated transmission division to transmit the service request to the MME to establish a bearer for uplink data transmission.

In yet another preferred form, the present invention applies to a case of a server scheduling for communication devices. The server can be an external entity that the communication devices communicate with, or it can be an entity provided by the cellular network specifically for machine-type communications. In Fig. 7, it is shown as server 220a. Data communications between the server 220a and

communication devices

210 and 212 via the connection 790 and PDNGW 720. For signaling control, a special dedicated interface 792 between the server 220a and the MME 740 may be used. With this interface, the server 220a may inform the MME 740 to page for communication devices at a given division of the paging signal listening period.

Here, the communication device is configured with an access period comprising of a paging signal listening period and transmission period. The communication device is further configured with a mapping between divisions within the said paging listening period and transmission period. The access period may be a two-hour interval every day, typically configured by the network operator for machine-type communication to avoid peak hours of human oriented traffic. As explained earlier, such mapping may be pre-configured on the communications device, or dynamically configured using over-the-air methods.

At the beginning of the access period, the server will schedule communication devices for data transmission at different transmission division of the transmission period. The server then informs the MME to page for communications devices at the corresponding paging divisions in the paging signal listening period that maps to the scheduled transmission of the transmission division. Hence, at the informed paging divisions, the MME instructs the base stations to send paging signal containing an identity of the communication device. Since it is not expected for the communication device to respond immediately when receiving a paging signal but instead at a later time, the server may also inform the MME not to expect a response from communication device and not to re-attempt paging in the absence of a response.

The communication device, upon receiving this paging signal, calculates the transmission division that is scheduled based on the time it receives the paging signal, and will contest for the transmission slot at the calculated transmission division to transmit the service request to the MME in response to the paging signal. Once the service request is processed, data bearers will be established between the communication device and the PDNGW, and data transmission can occur between the server and the communication device.

The above is for the case of downlink data. For scheduling of up-link data, there is an additional transmission request period at the beginning of the access period. When a communication device has uplink data to transmit, it will send a non-transmission request message to the server during this transmission request period. At the end of the transmission request period, the server will know all transmission requests made by communication devices, and can schedule the transmissions into divisions within the said transmission period.

Then, based on the mapping between divisions of the paging signal listening period and transmission period configured on the communication devices, the server can then inform the MME of to page for the communication devices at the corresponding division of the paging signal listening period. At each specified paging division, the MME then instructs the base station to send a paging signal containing an identity of the communication device within the division of paging signal listening period that is mapped to the scheduled transmission division within the transmission period. The communication device, upon receiving this paging signal, calculates the transmission division that is scheduled based on the time it receives the paging signal, and will contest for the transmission slot at the calculated transmission division to transmit the service request to the MME to establish a bearer for uplink data transmission.

As the access period is scheduled at fix interval(s), the communication device can power its radio interface accordingly to only listen of paging signal during the paging signal listening period. Outside of the access period, the communication device can be detached from the network to conserve energy. The network may have the mechanism to page for a communication device that is detached; hence the communication device may even be detached during the paging signal listening period. It only needs to attach to the network at the scheduled transmission division if it has received a paging signal during the paging signal listening period.

Fig. 8 shows a flowchart that a communication device may employ. Initially at step 810, the communication device waits for the access period to begin. While waiting, the communication device may turn of fits radio interface. When the access period begins, the communication device then checks if it has any plink data to transmit in step 820. If there is, step 830 will be performed where the communication device transmit a transmission request signal during the transmission request period.

If there is no uplink data, the communication device waits unit the paging signal listening period begins and powers its radio interface to listen for paging signal in the paging signal listening period, as shown in step 840. If no paging signal is received during the paging signal listening period, the communication device may then power its radio interface down and return to step 810 to wait for the next access period. If a paging signal is received, step 850 is performed where the time of receiving the paging signal is used to obtain a time for accessing the network in the transmission period. The communication device then accesses the network for data transfer at the obtained time, as shown in step 860. After data transfer is completed, the communication device may then power its radio interface down and return to step 810 to wait for the next access period.

Although the present invention has been herein shown and described in what is conceived to be the most practical and preferred embodiment, it will be appreciated by those skilled in the art that various modifications may be made in details of design and parameters without departing from the scope and ambit of the present invention. For example, although the present invention describes the mapping of the time of receiving a paging signal to map to a time for accessing the network, a person skilled in art would appreciate that this mapping can be between the frequencies, or between frequency and time as well.

One way is for the time of receiving the paging signal to be mapped to a particular frequency channel for accessing the network. Another way is for the time of receiving the paging signal to be mapped to a particular frequency channel and a particular time slot of the said particular frequency channel. Yet another way is for the paging signal to be sent in different frequency channels, and the frequency at which the paging signal is received will be mapped to a particular frequency channel or a particular timeslot for accessing the network.

Further, each functional block used in the description of the embodiments of the present invention as given above can be realized as LSI (Large Scale Integration), typically represented by the integrated circuit. These may be produced as one chip individually or may be designed as one chip to include a part or all. Here, it is referred as LSI, while it may be called IC, system LSI, super LSI, or ultra LSI, depending on the degree of integration.

Also, the technique of integrated circuit is not limited only to LSI and it may be realized as a dedicated circuit or a general-purpose processor. FPGA (Field Programmable Gate Array), which can be programmed after the manufacture of LSI, or a reconfigurable processor, in which connection or setting of circuit cell inside LSI can be reconfigured, may be used.

Further, with the progress of semiconductor technique or other techniques derived from it, when the technique of circuit integration to replace LSI may emerge, the functional blocks may be integrated by using such technique. For example, the adaptation of biotechnology is one of such possibilities.

The invention has the advantage of saving power by minimizing the period of listening for paging signals. Therefore, the invention can be advantageously used as the field of telecommunications in a packet-switched data communications network.

Claims

A communications apparatus for communicating with a remote party across a communications network, the communications apparatus comprising:
- a radio interface configured to receive and transmit communications signal to and from the communications network;
- a paging reception unit configured to receive paging signal sent from the communications network via the radio interface;
- an access management unit configured to control the radio interface to access the communications network; and
- a timing mapping table indicating a first time period of receiving a paging signal by the paging reception unit and a second time period when the radio interface should access the communications network for data transmission;
- wherein the access management unit controls the radio interface to listen for paging signals in the first time period, and controls the radio interface to access the communications network in the second time period upon receiving the paging signal in the first time period.
The communications apparatus according to claim 1, wherein the access management unit controls the radio interface to send a transmission request in a third time period if the communication apparatus has uplink data to be transmitted.
The communications apparatus according to claim 1, wherein the access management unit controls the radio interface to listen for broadcast message from the communications network in a fourth time period, the broadcast message comprising the first time period of receiving the paging signal and the second time period when the radio interface should access the communications network.
The communications apparatus according to claim 1, wherein the access management unit controls the radio interface to listen for paging signals only during the first time period.
The communications apparatus according to claim 1, wherein the first time period is further divided into a plurality of divisions, and the second time period is further divided into a plurality of divisions,
- wherein the timing mapping table comprises a mapping between the plurality of divisions of the first time period and the plurality of divisions of the second time period, and
- wherein the access management unit determines, one of the plurality of divisions of the second time period when the radio interface should access the communications network for data transmission, based on the timing mapping table.
A method of communications for involving a communication apparatus communicating with a remote party across a communications network, the method comprising the steps of:
- assigning an access period in which all communications involving the communication apparatus occur;
- assigning a first time period within the access time period, wherein the communications apparatus listens for paging signals in the first time period; and
- assigning a second time period within the access time period, wherein the communications apparatus accesses the communications network for data transmission in the second time period.
The method according to claim 6, further comprising the step of assigning a third time period within the access time period, wherein the communications apparatus transmits a request for transmission in the third time period if the communications apparatus has uplink data to be transmitted.
The method according to claim 6, further comprising the step of assigning a fourth time period within the access time period, wherein the communication apparatus listens for broadcast message from the communications network in the fourth time period, the broadcast message comprising the first time period of receiving the paging signal and the second time period when the radio interface should access the communications network for data transmission.
The method according to claim 6, further comprising the steps of:
- dividing the first time period into a plurality of divisions, and the second time period into a plurality of divisions;
- mapping the plurality of divisions of the first time period to the plurality of divisions of the second time period; and
- determining by the a communication apparatus, one of the plurality of divisions of the second time period when the radio interface should access the communications network for data transmission, based on the mapping.
The method according to claim 9, wherein the number of divisions in the first time period is the same as the number of divisions in the second time period.
The method according to claim 6, further comprising the step of listening for paging signals by the communication apparatus only during the first time period within the access time period.