WO2017109571A1

WO2017109571A1 - Methods and apparatuses for contention-based communication and associated communication system

Info

Publication number: WO2017109571A1
Application number: PCT/IB2016/001900
Authority: WO
Inventors: Li Yang; He Wang
Original assignee: Alcatel Lucent
Priority date: 2015-12-24
Filing date: 2016-12-13
Publication date: 2017-06-29
Also published as: TW201724892A; CN106922001B; CN106922001A; TWI621367B

Abstract

Embodiments of the present disclosure provide methods and apparatuses for contention-based communication and an associated communication System. In a method of contention-based communication, a message is transmitted to a network node in a first contention frame at a first contention layer. The method further includes receiving first feedback information for the first contention frame from the network node indicating the number of frames which indicates an accumulative number of frames determined by the network node at the first contention frame as to be allocated to a second contention layer following the first contention layer; in response to a failure of the transmission of the message, determining, at least based on the first feedback information, positions of a second contention frame and an end frame at the second contention layer; and switching, based on the positions of the second contention frame and the end frame, to a sleep mode in a duration of frames at the second contention layer other than the second contention frame and the end frame.

Description

METHODS AND APPARATUSES FOR CONTENTION-BASED

COMMUNICATION AND ASSOCIATED COMMUNICATION SYSTEM

FIELD

[0001] Embodiments of the present disclosure generally relate to the field of communication, and more specifically, to methods and apparatuses for contention-based communication and an associated communication system.

BACKGROUND

[0002] In recent development of communication, focus is made on deployment of machine-to-machine (M2M) network. The M2M network is aimed to internetwork massive terminal devices which can operate autonomously for a long time (for example, years or decades) to perform tasks such as information collecting, information processing, information reporting, and the like. Therefore, these devices are required to have less power consumption. A characteristic of the M2M network is that the massive terminal devices may send data to the upper layer network nodes at the same time but the size of the data sent by each device is generally small. Because of this, the devices in the M2M network would cost large amount of power due to collision of data transmission and signaling overheads.

[0003] In communication systems, there are generally two approaches to enable a terminal device to obtain resources for data transmission. For current communication systems such as Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) networks, a reservation-based scheme is utilized, which requires the network nodes such as the base stations being aware of the network topology in advance so as to establish a scheduling mechanism to allow each serving device to transmit data without collisions. However, due to limit of available scheduling resources, the reservation-based scheme cannot be applied in the M2M network which has high-density deployment of devices. Meanwhile, in the M2M network, small data transmission occurs in high frequency within a short time. If resources are scheduled in the reservation-based scheme, a large amount of signaling overheads would be produced.

[0004] Another approach is a contention-based scheme which requires no prior knowledge of the network topology. In this scheme, the terminal devices are allowed to send data directly instead of wasting time and power on extra scheduling signaling. Specifically, various devices transmit data directly in each of the contention periods. Data transmission succeeds when there is no contention in this contention period (that is, only one device contends for this period). Otherwise, the devices, which have not transmitted data successfully, will continue to contend for a next contention period.

[0005] However, the collisions due to contentions of the massive devices would cause the terminal device to take a longer time to transmit data successfully, which thus significantly reduces the power efficiency of the devices and the system performance, especially for those networks that serve low-power-consumption devices with small data transmission.

[0006] It is to be noted that the above problems are not limited to any specific communication environments and devices but may occur in any possible systems. SUMMARY

[0007] Embodiments of the present disclosure provide a solution for contention-based communication.

[0008] In a first aspect of the present disclosure, there is provided a method of contention-based communication which can be implemented at a terminal device. The method includes transmitting a message to a network node in a first contention frame at a first contention layer. The method also includes receiving first feedback information for the first contention frame from the network node. The feedback information indicates the number of frames which indicates an accumulative number of frames determined by the network node at the first contention frame to be allocated to a second contention layer following the first contention layer. The method also includes: in response to a failure of the transmission of the message, determining, at least based on the first feedback information, positions of a second contention frame and an end frame at the second contention layer. The method further includes switching, based on the positions of the second contention frame and the end frame, to a sleep mode in a duration of frames at the second contention layer other than the second contention frame and the end frame.

[0009] In a second aspect of the present disclosure, there is provided a method of contention-based communication which can be implemented at a network node. The method includes determining a contention state for a first contention frame at a first contention layer, at least one terminal device transmitting a message in the first contention frame. The method also includes determining, based on the contention state, the number of frames for the first contention frame which indicates an accumulative number of frames determined at the first contention frame to be allocated to a second contention layer following the first contention layer. The method further includes transmitting feedback information for the first contention frame including the determined number of frames.

[0010] In a third aspect of the present disclosure, there is provided an apparatus for contention-based communication. The apparatus includes a message transmitter configured to transmit a message to a network node in a first contention frame at a first contention layer. The apparatus further includes a feedback receiver configured to receive first feedback information for the first contention frame from the network node, the first feedback information indicating the number of frames which indicates an accumulative number of frames determined by the network node at the first contention frame to be allocated to a second contention layer following the first contention layer. The apparatus further includes a contention determining device configured to, in response to a failure of the transmission of the message, determine, at least based on the first feedback information, positions of a second contention frame and an end frame at the second contention layer. The apparatus further includes a mode switcher configured to switch, based on the positions of the second contention frame and the end frame, to a sleep mode in a duration of frames at the second contention layer other than the second contention frame and the end frame.

[0011] In a fourth aspect of the present disclosure, there is provided an apparatus for contention-based communication. The apparatus includes a contention state determining device configured to determine a contention state for a first contention frame at a first contention layer, at least one terminal device transmitting a message in the first contention frame. The apparatus further includes a frame number determining device configured to determine, based on the contention state, the number of frames for the first contention frame which indicates an accumulative number of frames determined at the first contention frame to be allocated to a second contention layer following the first contention layer. The apparatus further includes a feedback transmitter configured to transmit feedback information for the first contention frame including the determined number of frames.

[0012] In a fifth aspect of the present disclosure, there is provided a communication system. The communication system includes at least one terminal device each including the apparatus according to the above third aspect. The communication system further includes a network node which includes the apparatus according to the above fourth aspect.

[0013] It would be appreciated through the following description that, according to example embodiments of the present disclosure, when determining feedback information for a contention frame at a contention layer, a network node not only determines a contention state of the frame but also determines an accumulative number of frames to be allocated to a next contention layer at the current frame. Due to the increase of the accumulative number, the network device can determine a position of a contention frame at the next layer by only monitoring feedback information for a small number of frames. The terminal device can switch to a sleep mode in frames at the next layer other than the contention frame (as well as the end frame to be monitored for determining a position of the contention frame). According to the embodiments of the present disclosure, the terminal device is only required to consume power in a fewer frames for transmitting data and monitoring feedback information and can switch to an energy-effective sleep mode in other frames. As such, the power efficiency of the terminal device is significantly improved and the overall performance of the system is enhanced. Other advantages of the example embodiments of the present disclosure will be apparent by the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The above and other objectives, features, and advantages of example embodiments of the present disclosure will become apparent through the following detailed description with reference to the accompanying drawings. Various example embodiments of the present disclosure will be illustrated by way of example but not limitation in the drawings in which:

[0015] Fig. 1 illustrates a diagram of an example environment in which apparatuses and/or methods described herein may be implemented;

[0016] Fig. 2 illustrates a schematic diagram of example contention transmission in a conventional scheme based on a contention tree;

[0017] Fig. 3 illustrates a schematic diagram of comparison of contention frames and monitor frames in the conventional scheme based on the contention tree;

[0018] Fig. 4 illustrates a flowchart of a method of contention-based communication at a terminal device in accordance with an embodiment of the present disclosure;

[0019] Fig. 5 illustrates a schematic diagram of example contention communication of a contention-based process in accordance with an embodiment of the present disclosure;

[0020] Fig. 6 illustrates a schematic diagram of a structure of feedback information in accordance with an embodiment of the present disclosure; [0021] Fig. 7 illustrates a schematic diagram of comparison between a conventional scheme based on a contention tree and a scheme of contention-based communication in accordance with an embodiment of the present disclosure;

[0022] Fig. 8 illustrates a schematic diagram of example contention communication of a contention-based contention process in accordance with another embodiment of the present disclosure;

[0023] Fig. 9 illustrates a schematic diagram of comparison between contentions using data and using a request message in accordance with an embodiment of the present disclosure;

[0024] Fig. 10 illustrates a flowchart of a method of contention-based communication at a network node in accordance with an embodiment of the present disclosure;

[0025] Fig. 11 illustrates a block diagram of a communication apparatus at a terminal device in accordance with an embodiment of the present disclosure;

[0026] Fig. 12 illustrates a block diagram of a communication apparatus at a network node in accordance with an embodiment of the present disclosure; and

[0027] Fig. 13 illustrates a block diagram of an example computer system/server suitable for implementing embodiments of the present disclosure.

DETAILED DESCRIPTION

[0028] Principles of example embodiments disclosed herein will now be described with reference to various example embodiments illustrated in the drawings. It would be appreciated that description of those embodiments is merely to enable those skilled in the art to better understand and thus implement example embodiments of the present disclosure and is not intended for limiting the scope disclosed herein in any manner.

[0029] As used herein, the term "includes" and its variants are to be read as open-ended terms that mean "includes, but is not limited to." The term "or" is to be read as "and/or" unless the context clearly indicates otherwise. The term "based on" is to be read as "based at least in part on." The term "one example embodiment" and "an example embodiment" are to be read as "at least one example embodiment." The terms "first," "second," and the like may refer to different or identical objects. Other explicit or implicit definitions may be included hereinafter.

[0030] In description of embodiments of the present disclosure, a terminal device may refer to a mobile terminal (MT), a subscriber station (SS), a portable subscriber station (PSS), a mobile station (MS), or an access terminal (AT), and some or all functions included thereof. The terminal device may be any type of mobile terminal, fixed terminal, or portable terminal, such as a mobile telephone, station, unit, device, multimedia computer, multimedia tablet, Internet node, communicator, desktop computer, laptop computer, notebook computer, netbook computer, tablet computer, personal communication system (PCS) device, personal navigation device, personal digital assistant (PDA), audio/video player, digital camera/video camera, positioning device, television receiver, radio broadcast receiver, E-book device, gaming device, intelligent meter, meter or other intelligent electronics connected in a machine-to-machine (M2M) network, or any combinations thereof, including accessories and peripherals of these devices or any combinations thereof.

[0031] In description of embodiments of the present disclosure, the term "network node" is sometimes called as "base station (BS)", "BS/node", "wireless access node", or "transport point" to be consistent with 3GPP terms. It is to be noted that the term "BS/node," "node," "transmission node" and "BS" have the same meaning in the present disclosure, and each of them may indicate a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a radio header (RH), a remote radio head (RRH), a relay, a low power node such as a femto station and a pico station, and the like. The coverage of a base station, that is, a geographical range where the base station serves is referred to as a cell. [0032] In dense networks such as machine-to-machine (M2M) networks, usually a large number of devices are deployed within a geographical range. A plurality of devices may always transmit data to a serving network node located within that range at the same time or almost at the same time. Fig. 1 depicts such a network environment 100 where terminal devices 121-124 are all served by a network node 110. The terminal devices 121-124 may transmit data to the network node 110 at the same time. As discussed above, to save power of the devices, a contention-based scheme of data transmission can be employed. The terminal devices 121-124 can transmit data directly to the network node 110. Dependent on the contention condition on certain resource(s), the network node 100 can determine if the data are successfully transmitted. [0033] It would be appreciated that although four terminal devices are illustrated in Fig. 1, the network node 110 can serve more or less terminal devices. The types of the served terminal devices can be the same or different. [0034] A simple contention-based scheme is the contention scheme based on frame-timeslot. The network node allocates a series of frames for a plurality of terminal devices to content. Each of the frames is divided into a plurality of timeslots. In each frame, each terminal device randomly selects a timeslot from the plurality of timeslots of the frame and attempts to transmit data in that selected timeslot. The network node determines feedback information for this frame based on the contention condition, which feedback information indicates the contention state of each of the timeslots. A contention state can be categorized to three types: (1) a non-transmission state, that is, no device contending for the timeslot; (2) a success state, that is, only one terminal device attempting to transmit data in the timeslot and thus the data is successfully received by the network node; and (3) a collision state, namely, two or more terminal devices attempting to transmit data in the timeslot, resulting in collision.

[0035] The network node feeds back the contention states of all the timeslots in each frame. Each of the terminal devices receives the contention states of each frame and determines if its data transmission succeeds based on the contention states. If the contention state for a timeslot for which a terminal device contends is the success state, then the terminal device determines that its data has been transmitted successfully and the contention process can be stopped. If it is determined that the corresponding contention state is a collision state, then the terminal device continues the contention process in the next frame until its data is transmitted successfully. In other words, as long as the terminal device has not successfully transmits the data, the following frame will still be regarded as a contention frame for the terminal device.

[0036] With the above contention-based scheme, data transmission of a terminal device may not succeed until multiple rounds of contention. The duration of contention may also keep increasing as the number of devices contending at the same time increases. Therefore, each device has to waste a large amount of time and power on failed transmissions.

[0037] Another contention-based scheme is the scheme based on a contention tree. In this scheme, each frame is also divided into a plurality of timeslots. Devices expecting to transmit data may firstly contend for a plurality of timeslots in a frame that is allocated by the network node. If there is collision in a certain timeslot, that is, if a plurality of devices contend for that timeslot at the same time, then the network node generates a next contention frame for that timeslot for further contention by these devices. This contention scheme is schematically illustrated in Fig. 2. [0038] In the example shown in Fig. 2, each frame for data transmission is divided into three timeslots. It is supposed that there are 14 terminal devices at a certain time that are expecting to transmit data to a network node at the same time. In the first frame 1 210 at the start of the contention process, all the 14 terminal devices randomly select the timeslots of the frame 1 210 to attempt to transmit their data. The number of devices contending for each timeslot is represented with a number in that timeslot, as shown. The network node determines that the three timeslots in the frame 1 210 all have collisions. Thus, feedback information 211 indicates that each of the three timeslots is in a collision state. Meanwhile, based on such contention state, the network node allocates a new frame for each of the three timeslots of the frame 1 210, that is, a frame 2 220, a frame 3 222, and a frame 4 224, so that the devices contending for the respective timeslots can continue to contend for data transformation in the new frames. The frame 1 210 may be referred to the first contention layer, that is, the layer 1. The new frames 2 220, 3 222 and 4 224 form the second contention layer, that is, the layer 2. [0039] The feedback information 211 of the frame 1210 is broadcasted and received by all the 14 terminal devices. These terminal devices determine if their data transmission succeeds based on the feedback information 211 and determines, if the data transmission fails, in which frame the contention should be continued. It is supposed that a device A among the 14 terminal devices contends for the second timeslot of the frame 210. Due to the collision, the device A detects from the received feedback information 211 a contention state for the second timeslot and then determines that contention for data transmission should continue. The device A also learns from the feedback information 211 that the three timeslots of the frame 210 all correspond to the collision state and thus determines that its contention should continue in the frame 3 222 among the three frames on the layer 2. In other words, the frame 3 222 is a contention frame for the device A at the layer 2.

[0040] Then, the device A randomly selects the third timeslot in its contention frame 3 222 to attempt to transmit data and listens for the feedback information 223 of the frame 3 so as to determine a new frame(s) allocated for the frame 3. For frames that are not the contention frames for the device A, the device A will not attempt to transmit data in those frames. However, to prepare for continued contention at a layer following the layer 2 (that is, layer 3) due to failed data transmission at the layer 2, the device A should continue monitoring the feedback information of all these frames at the layer 2 to determine how many new frames will be further allocated by the network node for each of these frames. The monitored feedback information is used to determine the position of a next contention frame for the device A. The device A will not stop the contention process until it is determined that data transmission succeeds from the feedback information of a contention frame, such as feedback information 241 corresponding to the frame 10 240 as shown in Fig. 2. [0041] It can be known from the above process that though the contention-tree-based scheme can reduce contention time compared to the contention scheme based frame-timeslot, a terminal device is required to stay active in each frame during the contention process to monitor the feedback information for the frame in order to determine the position of a next contention frame. It can be known from the example shown in Fig. 2 that for each device, the frames allocated during the contention process can be grouped into a contention frame set and a monitor frame set. A contention frame refers to the frame for which a device actually contends for data transmission used; a monitor frame set refers to the frame in which the device monitors the feedback information which is used for determining the position of its next contention frame. [0042] For example, for the device A in the above example, the frames 1, 3, 7, and 10 in Fig. 2 are its contention frames and the remaining frames 2, 4, 5-6, and 8-9 are its monitor frames. If there are more terminal devices contending for resources at the same time, the number of monitor frames may be much larger than that of contention frames. In other words, a terminal device needs to spend more power to monitor the feedback information for the monitor frames. For instance, Fig. 3 illustrates the average accumulative numbers of contention frames and of monitor frames for each device when different numbers of devices are transmitting data at the same time, in which case each frame is divided into m=20 timeslots. In this example, it is supposed that all the devices cannot transmit data successfully until to the last contention layer. It can be seen that as the number of devices transmitting data at the same time increases, the curve 320 shows that the accumulative number of monitor frames for each device increases significantly and the curve 310 shows that the accumulative number of contention frames for each device does not. This is because there is only one contention frame for each device at a contention layer and the number of contention frames is only related to the number of contention layers. Therefore, with the increase of the number of contending devices, the power efficiency of each device is decreased and the overall performance of the system is affected.

[0043] Embodiments of the present disclosure are described in detail below. In accordance with the embodiments of the present disclosure, there is provided a contention-based communication scheme. In this scheme, when determining feedback information for a contention frame of a terminal device at a contention layer, a network node will not only determine the contention state for the frame but also determine an accumulative number of frames that are planned to be allocated to a next contention layer at the time of current frame. Due to increase of this accumulative number, the terminal device can determine a position of a contention frame at the next layer only by monitoring feedback information of a small number of frames. In frames other than the contention frame (and the end frame that should be monitored to determine the position of a contention frame) at the next layer, the terminal device can switch to a sleep mode. In accordance with the embodiments of the present disclosure, the terminal device only needs to consume power in fewer frames for transmitting data and monitoring feedback information while switches to an energy-conserving sleep mode in other frames. As such, the power efficiency of the terminal device is significantly improved and the overall performance of the system is enhanced.

[0044] Fig. 4 illustrates a flowchart of a method of contention-based communication 400 in a terminal device. Although example blocks of the method 400 are illustrated in Fig. 4, in some other embodiments, the method 400 may include other blocks, less blocks, different blocks, or blocks arranged differently from these depicted in Fig. 4. Alternatively, or in addition, two or more blocks of the method 400 can be performed in parallel. In some embodiments, the method 400 can be performed at any of the terminal devices 121-124 as shown in Fig. 1.

[0045] At block 410, the terminal device transmits a message to a network node in a first contention frame at a first contention layer. Generally, the network node allocates frame(s) for transmission of a plurality of terminal devices. A frame in which a terminal device attempts to contend for message transmission can be referred to as a contention frame for the device. Each frame may be divided into a predefined number of timeslots, which may be 3, 10, 20, or any other number. Each of the divided timeslots may be the same or different in length. In some embodiments, the terminal device may randomly select one timeslot from the timeslots in its contention frame for transmission attempt. In other embodiments, the terminal device may select a fixed time slot. For instance, each time the terminal device may select the first timeslot in the contention frame for transmission attempt. Alternatively, the terminal device may also select two or more timeslots to transmit different messages. The scope of the present disclosure is not limited in this regard.

[0046] It is possible that a plurality of devices are attempting to transmit data at the same time. In accordance with the embodiments of the present disclosure, the network node employs the contention-tree-based scheme to allocate frame(s) to the plurality of terminal devices that are transmitting messages at the same time. In the contention-tree-based scheme, when the network node detects that there is contention in a timeslot of a frame at a contention layer, a new frame is allocated for the devices that are contending for the timeslot. All the new allocated frames constitute a next contention layer. The devices may continue to contend at the next contention layer until they have transmitted the messages successfully or give up the transmission.

[0047] Fig. 5 shows a diagram illustrating an example contention-tree-based contention process in accordance with an embodiment of the present disclosure. In the example shown in Fig. 5, each frame is divided into three timeslots. It is supposed that at a frame 1 510, there are 14 terminal devices that are attempting to transmit data at the same time. At the layer 1, the frame 510 is a contention frame for each of the devices. In the example shown in Fig. 5, the number of devices contending for each timeslot in a frame is represented with a number in that timeslot.

[0048] Generally, at the start of the contention process, a device set including the terminal devices is allocated with a frame for contention. In this case, the first contention layer includes only one frame, as shown by the layer 1 and its frame 510 in Fig. 5. If two different sets of devices contend in two frames, the network node may combine the two sets of devices into one contention process. In other words, for the two sets of devices, the first contention layer may include two frames. The same scheme applies for more sets of devices.

[0049] After attempting to transmit data, at block 420, the terminal device receives from the network node feedback information for the first contention frame. It would be appreciated that the transmission in the contention frame of the terminal device is uplink transmission which is from the terminal device to the network node; transmission of feedback information is downlink transmission which is from the network node to the terminal device. After each contention frame, the network node determines feedback information based on the contention state in the frame and broadcasts the feedback information to the terminal devices.

[0050] In some embodiments, the feedback information indicates a contention state for each timeslot in the first contention frame. In an example, the contention state may include: (1) a no-transmission state, that is, no device contending for the timeslot; (2) a success state, that is, only one terminal device attempting to transmit data in the timeslot and thus the data is successfully received by the network node; and (3) a collision state, namely, two or more terminal devices attempting to transmit data in the timeslot, resulting in collision. In an embodiment, two bits are used to represent a contention state for a timeslot. For example, the non-transmission state is represented by "00," the success state is represented by "01," and the collision state is represented by "11." In other embodiments, other contention states can be determined and thus more bits may be used to distinguish these contention states.

[0051] In accordance with the embodiments of the present disclosure, to reduce the time for monitoring feedback information by the terminal device and to enable the terminal device to determine the position of a next contention frame, in addition to the contention state, the network node further determines a number of numbers and includes this number into the feedback information. The number of frames indicates an accumulative number of frames determined by the network node at the first contention frame to be allocated to a second contention layer following the first contention layer. The number of frames can be determined based on the contention states for the first contention frame. [0052] Still referring to the example of Fig. 5, after the frame 510, the network node determines and broadcasts feedback information 511. The feedback information 511 may include the contention states for the respective timeslots of the frame 510 and the corresponding number of frames. Because all the timeslot of the frame 510 have collisions, the contention states of feedback information 511 may be, for example, "11," "11," and "11." Moreover, due to the collisions, the network node may allocate a new frame to each of the timeslots at a next contention layer 2 for contention transmission. Thus, based on the contention states, the network node determines the number of frames in the feedback information 511 as three.

[0053] Fig. 6 shows a schematic diagram illustrating a structure of feedback information in accordance with an embodiment of the present disclosure. As shown, the feedback information indicates a contention state for each timeslot. If a frame is divided into m timeslots and the contention state for each timeslot is represented with two bits, then the contention states in the feedback information occupy mx2 bits. The feedback information further includes an additional field for transmitting the number of frames. In an embodiment, the length of the field representing the number of frames may depend on the number of devices contending for transmission in the network at the same time. Thus, depending on different systems, a field of a different length may be added in the feedback information to carry the number of frames. The scope of the present disclosure is not limited in this regard. It is to be understood that only an example of the structure of feedback information is illustrated in Fig. 6. In other examples, the relative position of fields of the number of frames and the contention states may be varied. For example, the field of the number of frames can be placed before the fields of the contention states or inserted between fields of the contention states.

[0054] After obtaining the feedback information of the first contention frame, at block 430 of the method 400, in response to a failure of the transmission of the message, the terminal device determines, at least based on feedback information, a position of a second contention frame for retransmitting the message at the second contention layer and a position of an end frame of the second contention layer. In some embodiments, the contention states in the feedback information can be used to determine if data transmission is successful. Specifically, reference can be made to a contention state corresponding to the timeslot in which the terminal device attempts to transmit the message. For example, in the example as shown in Fig. 5, the device A attempts to transmit a message in the second timeslot of the frame 510. Since the contention state corresponding to the second timeslot in feedback information 511 is represented as a collision state of "11," the device A determines that the previous message transmission is failed.

[0055] If the message is not successfully transmitted, the terminal device may determine a position of a next contention frame to continue transmitting the message in that determined contention frame. In accordance with the embodiments of the present disclosure, the position of the contention frame at a next contention layer can be determined at least based on the feedback information. Depending on different conditions of the first contention frame, the method for determining the position of the next contention frame may be different. Moreover, in the embodiments of the present disclosure, to enable the terminal device to continue to determine the contention frame in the following contention process, the end frame at the next contention layer may also be determined based on the feedback information. The determination of the contention frame and end frame will be discussed below.

[0056] At block 440, based on the determined positions of the second contention frame and the end frame, the terminal device switches to a sleep mode in a duration of frames at the second contention layer other than the second contention frame and the end frame.

[0057] After the first contention layer, for example, after the end frame of the first contention layer, the contention process of the terminal device enters the second contention layer. At the second contention layer, the terminal device does not need to monitor the feedback information of each frame. Therefore, the terminal device switches to the sleep mode in other frames than the second contention frame and the end frame. During the sleep mode, the terminal device usually operates with a low power so as to save energy. In the second contention frame, the terminal device switches to a wakeup mode to select a certain timeslot in that frame for retransmitting the message that was not transmitted successfully previously and to monitor the corresponding feedback information. In the end frame, the terminal device can also switch to the wakeup mode to monitor the feedback information for this frame. The feedback information for the second contention frame and the end frame at the second contention layer can be used to further determine a contention position at a next layer in case that the terminal device has not yet transmitted the message successfully.

[0058] Accordingly, in the embodiments of the present disclosure, due to addition of the number of frames in the feedback information, the terminal device can remain active only in a small number of frames at each contention layer and switch to an energy-conserving sleep mode in other frames. For example, the terminal device may at most remain active in its contention frame and the end frame at each contention layer while sleep in other frames. Particularly, if the determined contention frame is also the end frame of a contention layer, a terminal device can remain in the active mode only in one frame, which is especially beneficial for terminal devices that have limited electric power and thus are required to operate in a power-effective way, such as terminal devices in a M2M network. Further, since the contention position at a next contention layer can be determined based on feedback information for the contention frame and end frame of the current contention layer, the storage space of the terminal device can be saved.

[0059] In the following, it will discuss how the positions of the second contention frame and end frame at the second contention layer can be determined based on the feedback information for the first contention frame.

[0060] In some embodiments, depending on the position of the first contention frame at the first contention layer, different information can be considered in the determination of the second contention frame and the end frame at the second contention layer. In an embodiment, if the first contention frame is an end frame (the determination of the end frame will be discussed later) of the first contention layer, the second contention frame at the following second contention layer may be determined based on a position of the first contention frame (for example, the Frame Number of the first contention frame) and the feedback information. The number of frames in the feedback information may indicate how many frames are to be allocated to the second contention layer by the network node at the time of the first contention frame (that is, at the end of the first contention layer). Therefore, the position of the end frame at the second contention layer can be determined based on the Frame Number of the first contention frame and the accumulative number of frames at the second contention layer.

[0061] Further, an adjustment can be determined based on the contention states in the feedback information for adjusting from the position of the end frame. For example, based on the contention states for the respective timeslots, it can be determined how many new frames will be generated for the first contention frame at the second contention layer. As discussed above, when a contention state for a timeslot is a collision state, the network node may allocate a new frame for the devices which contend for this timeslot. If the contention state is a success state or non-transmission state, no new frames is needed to be allocated. Thus, it can be determined from the contention states which of the allocated frames is the frame generated for the timeslot in which the message of the terminal device is transmitted, that is, which is the second contention frame. Specifically, based on a contention state for a timeslot after the timeslot in which the message is transmitted, the adjustment from the position of the current end frame can be determined.

[0062] For example, it is assumed that in the example shown in Fig. 5, the device A contends the transmission of the message in the second timeslot of the frame 510. As the frame 510 is the end frame of the layer 1, the device A can determine a position of an end frame of the layer 2 based on the Frame Number of the frame 510 and the number of frames in feedback information 511. Particularly, based on the Frame Number of the frame 510 being 1 and the number of frames of the feedback information 511 being 3, the device A can determine that the Frame Number of the end frame at the layer 2 is 1+3=4, that is, the frame 4 524. Based on the contention states in the feedback information 511, the device A can determine that three new frames will be generated for the frame 510. Moreover, since the contention state for the third timeslot after the second timeslot in which the device A transmits the message is a collision state, the device A determines that the frame generated for the timeslot 2 for which it contends, that is, its next contention frame, is located in one frame prior to the end frame 4 at the layer 2 (that is, the amount of adjustment is 1). Therefore, the device A can determine that the Frame Number of the contention frame at the layer 2 is the Frame Number of the end frame at the layer 2 (that is, 4) subtracted by the amount of adjustment (that is, 1) determined based on contention state, which is, the Frame Number of the frame 3 522.

[0063] It has been discussed above how to determine the second contention frame and end frame at the second contention layer for the terminal device when the first contention frame is the end frame of the first contention layer. It would be appreciated that in this case, the terminal device only needs to stay in the active state during the first contention frame at the first contention layer to contend for the message transmission and to monitor the following feedback information. In other frames of the first contention layer, the terminal device may switch to the sleep mode.

[0064] In some embodiments, if the first contention frame is not the end frame of the first contention layer, the terminal device may receive the feedback information of the end frame at the first contention layer and determine the second contention frame and end frame at the second contention layer based on the feedback information for the first contention frame and the end frame. As stated above, when the first contention layer is the first layer of the contention process, the end frame of the terminal device is also its contention frame. In this case, embodiments can be implemented as discussed above. If the first contention layer is another layer in the contention process, the position of the end frame at the first contention layer has generally been determined at a contention layer prior to the first contention layer. Thus, the terminal device can monitor the feedback information for the end frame based on the position of the end frame that has been determined in advance. The feedback information for the end frame includes the number of frames which indicates the accumulative number of frames allocated by the network node to the second contention layer at the time of the end frame. Similar to the contention frame, the feedback information for the end frame also includes contention states indicating the contention conditions in the respective timeslots in the end frame. [0065] In some embodiments, similar as discussed above, the terminal device can determine a position of an end frame at the second contention layer based on the position of the end frame at the first contention layer and the number of frames included in the feedback information of the end frame. In some embodiments, the terminal device can determine the position of the second contention frame based on the position of the end frame at the first contention layer, the number of frames and the contention states in the feedback information for the first contention frame. Specifically, based on the number of frames in the feedback information for the first contention frame, the terminal device can determine how many frames have been allocated for the second contention layer by the network node accumulatively up to the first contention frame. As discussed above, depending on the contention states, the terminal device can determine the amount of adjustment based on the current accumulative number of frames, so as to distinguish which of the allocated frames are the frames that are generated in the timeslot in which the terminal device contends for transmission. Based on such information, the terminal device can determine the position of the second contention frame.

[0066] In the example shown in Fig. 5, it is supposed that the first contention layer is the layer 2 and the first contention frame of the device A is the frame 3. The device A selects the first timeslot in the frame 3 for transmitting a message. The device A expects to determine a position of a contention frame at the following layer 3 and the end frame of the layer 3. Since the frame 3 is not the end frame of the layer 2, the device A continues to monitor the feedback information 525 for the end frame 4 at the layer 2. It is to be understood here that the position of the end frame 4 at the layer 2 is determined by the device A based on feedback information 511 after the end frame 1 at the layer 1. Based on the Frame Number of the end frame 4 at the layer 2 and the number of frames in feedback information 525 for the end frame 4 (which is 5), the device A can determine that the Frame Number of the end frame at the layer 3 is 4+5=9, that is, the frame 9 538. Based on the number of frames (that is, 4) in feedback information 523 for the frame 3, the device A determines that four new frames will be allocated to the layer 3 till the frame 3. On the basis of the Frame Number 4 of the end frame at the layer 2 and the number of frames 4 in the feedback information, the device A determines that till the frame 3, the maximum Frame Number of a frame allocated to the layer 3 is 4+4=8. Further, the device A determines that the corresponding contention state for the third timeslot of frame 3 after the second timeslot is a collision state by referring to the contention states in feedback information 523 and thus determines that the last frame among the 8 frames at the layer 3 is generated for the third timeslot. Hence, the device A can determine that the frame 7 before the frame 8 is its contention frame.

[0067] In some embodiments, after determining the contention frame and end frame of the next contention layer, as discussed above, the terminal device switches to the sleep mode in frames other than the contention frame and end frame of the next contention layer. Furthermore, the terminal device can switch to an active mode in the contention frame to select one of the timeslots and attempt to transmit the message in this timeslot, and monitor the feedback information for the contention frame. The terminal device also switches to the active mode in the end frame and monitors feedback information for the end frame. The feedback information can be used to determine positions of a contention frame and end frame at the following layer.

[0068] The contention process described above can repeat until the terminal device determines that the message has been transmitted successfully based on the corresponding contention state in feedback information for a contention frame. For example, if the terminal device determines that the contention state for the timeslot in which the message is attempted to be transmitted is a success state, it determines that this message has been successfully transmitted to the network node. Then, the terminal device stops the contention process.

[0069] In the example shown in Fig. 5, the device A can continue to attempt to transmit the message in the second timeslot of the contention frame 7 at the layer 3 and monitor feedback information 535 for the frame 7 and feedback information 539 for the end frame 9 at the layer 3. The device A determines that a contention frame in the following contention layer 4 is the frame 10 and the end frame is also the frame 10. Then, the device A continues to select a timeslot of the frame 10, for example, the second timeslot, to contend for message transmission. Based on the feedback information 541 received, the device A determines that the contention state for the second timeslot of the frame 10 is succeeded and thus identify that the message has been successfully transmitted.

[0070] In some embodiments, the message that terminal device attempts to transmit in a timeslot of each contention frame may carry data to be transmitted by the terminal device. If the message is transmitted successfully, it means that the terminal device completes the data transmission in this round. In the example shown in Fig. 5, all of the terminal devices contend for data transmission directly.

[0071] Compared with the conventional contention-tree-based contention scheme, the contention scheme in accordance with the embodiments of the present disclosure can save more power for the terminal device as the terminal device can stay in the power-conserving sleep mode in most of the frames. Fig. 7 is a diagram illustrating comparison between the current contention-tree-based scheme and the contention-based communication scheme in accordance with the embodiments of the present disclosure. As shown, the curve 710 illustrates the average power consumption for each device in accordance with the conventional contention-tree-based scheme while the curve 720 illustrates the average power consumption for each device of the scheme in accordance with the embodiments of the present disclosure. It can be seen that as the increase and decrease of the number of devices, the curve 710 illustrates that the average power consumption for each device keeps increasing. As discussed above, this is because of the fact that the user device may consume more power to receive more feedback information for the monitor frame (as shown in Fig. 3). However, the curve 720 illustrates that as the increase and decrease of the number of devices, the average power consumption for each device stays at a low level and barely changes because the devices need to stay in the active mode in only a few frames (the contention frames and end frames) at each contention layer and can switch to the sleep mode in other frames according to the embodiments of the present disclosure.

[0072] Data transmission usually consumes more power because the effective load of data is relatively large. Therefore, in some other embodiments of the present disclosure, the terminal device does not need to attempt to transmit data directly in the contention frame but may try to transmit a request message during the contention process. The request message is used to request the network node to allocate one or more frames for data transmission. Therefore, the effective load of the request message can be smaller than that of the data to be transmitted. For instance, in some embodiments, the load of data to be transmitted by terminal device each time may be 200 bits while the request message may occupy only 10 bits. Since only the request message with a small and effective load is to be transmitted for each round of contention, the power consumption of the terminal device can be further reduced. In these embodiments, the contention process described in Fig. 4 can be employed for the transmission of the request message.

[0073] In some embodiments, if the request message of the terminal device is transmitted successfully, for example, if the contention state corresponding to the timeslot for transmitting the request message is a success state, then the network node may allocate a data frame to the terminal device at the next contention layer to transmit data. For example, if the terminal device attempts to transmit the request message in the first contention frame at the first contention layer and this transmission succeeds, then the data can be transmitted in a data frame allocated for this request message at the second contention layer. The data frame may or may not be divided into timeslots. The terminal device may place the information to be transmitted in the data frame to transmit to the network node. As the data frame is dedicated to be used for transmission of the device, the terminal device does not need to contend with other devices in the data frame.

[0074] In some embodiments, the terminal device may also determine the position of the data frame at least based on feedback information for the contention frame and then transmit the data in the data frame based on the position of the data frame. Determination of the position of the data frame at the next contention layer is similar to the determination of the position of the contention frame at the next contention layer as discussed above because the allocation of the data frame is similar to that of the contention frame, which is also performed with respect to a contention state for a certain timeslot. For the sake of simplicity, the process of determining the position of the data frame is omitted here. It would be appreciated that since the data frame is allocated for the timeslot with a success state for contention during the contention process based on the request message, this may be taken into account when determining the position of the data frame based on the contention states.

[0075] In the embodiments of contention based on the request message, it would be appreciated that the network node only allocates, for the terminal devices that have not yet transmitted the request message successfully, contention frames at the next contention layer for retransmission of the request message based on contention states, but also allocates data frames at the next layer for data transmission by the terminal devices that have transmitted the request message successfully. Regardless of allocating the contention frames or the data frames, for the feedback information discussed above, the frames allocated to the next layer by the network node are taken into account in accumulating the number of allocated frames.

[0076] In some embodiments, when accumulating the number of allocated frames, if the contention state for a timeslot is a success state, the network node may also increase the value of the number because a new frame(s) is to be generated for data transmission at the next layer due to the states. It would be appreciated that the network node can allocate more than one data frame to the terminal device each time. This case can also be taken into account when the determining number of allocated frames.

[0077] In some other embodiments, since the frames for data transmission and the frames for the request message are both placed at the next contention layer, the data frames may be located as the end frames of the contention layer. In this case, the network node also determines feedback information for the data frame. The feedback information may include the number of frames determined to be allocated to the next contention layer at the time of this data frame. The terminal device can detect the feedback information for the end frame at the contention layer and thus determine the positions of its contention frame and end frame at the following contention layer. In some embodiments, the feedback information for the data frame and for the contention frame may have the same size, that is, the feedback information for the data frame does not carry the contention states. In this way, the synchronization between the network node and the terminal device can be achieved so that the terminal device can receive and transmit data at the right time.

[0078] Fig. 8 shows a schematic diagram illustrating example contention communication in a contention process based on a request message in accordance with another embodiment of the present disclosure. Different from the example shown in Fig. 5, the 14 terminal devices transmit their request messages in the respective contention frames. Each time when a request message is transmitted successfully, the terminal device can transmit data in the corresponding position for the next time.

[0079] It is supposed that the terminal device A, after the required operations, attempts to transmit a request message in the first timeslot of the contention frame 3 522 at the contention layer 2 and then receives feedback information 523. As for the first and second timeslots in frame 2520, the network node decides to generate two new frames to the next layer 3 respectively for the devices contending for the two timeslots. Due to the success state for the third timeslot, the network node allocates a new data frame to the layer 3 for data transmission of the device in the timeslot. Further, since the contention states for both of the two timeslots in the frame 3 522 are the collision states, the network node generates two new frames at the layer 3 respectively for devices contending for the two timeslots. Therefore, at the time of the frame 3 at the layer 2, the network node can determine that there are five new frames to be generated at the following layer 3, including four contention frames and one data frame. Similarly, the device A monitors feedback information 525 for the end frame 4 524 at the layer 2 which indicates that the network node allocates eight frames to the layer 3 at the time of the frame 4.

[0080] Based on the feedback information 523 for the contention frame at the layer 2, the device A can determine the position of its contention frame at the layer 3. The position is determined as the Frame Number 4 of the end frame at the layer 2 plus the number of frames (that is, 5) in the feedback information 523. Based on the amount of adjustment (that is, 1) determined from the contention states (since the contention states corresponding to the second and third timeslots other than the first timeslot in which the transmission is contended for are the collision and non-transmission states, the adjustment may be determined as only one), the position of the contention frame of the layer 3 can be obtained as the frame 8. On the basis of feedback information 525 for the end frame at the layer 2, the device A can determine the position of the end frame at layer 3. The position is determined as the Frame Number 4 of the end frame at the layer 2 plus the number of frames (that is, 8) in the feedback information 525, which is in the position of the end frame at the layer 3, that is, the frame 12 834.

[0081] It can be seen that at the layer 3, in addition to transmitting the request message in the contention frame 8 and monitoring the respective feedback information 535, the device A monitors feedback information at end frame 12 834 of the layer 3. It can be known that the frame 12 834 is a data frame allocated to the device that has successful contention in the third timeslot at the previous layer 2. However, the network node also broadcasts feedback information 835 after the data frame, in which the number of frames that the network node has decided at the time of the frame 12 to allocate to the next layer 4 is 10. Based on the feedback information 835 and 535 and the Frame Number of the end frame at the layer 3, the device A can determine its position of the contention frame at the layer 4 (the frame 18 540) and the position of the end frame at the layer 4 (the frame 22 856).

[0082] At the layer 4, the device A selects the second timeslot in the contention frame 18 540 and attempts to transmit the request message again and then monitors feedback information 541 for the frame 18 and feedback information 857 for the end frame 22. Based on the contention states in feedback information 541, the device A can determine that the request message is transmitted successfully and thus it determines a position of the data frame to transmit data at the next layer. The device A can determine the position of the data frame at the next layer 5 based on the feedback information 541 and the position of the end frame of the layer 4 that has been determined in advance. Specifically, based on the Frame Number 22 of the end frame of the layer 4 and the number of frames (that is, 2) in the feedback information 541 and based on the adjustment amount of 0 from the contention states, the position of the data frame can be determined as in the frame 24. The device A can transmit data in the frame 24 and ends the contention process.

[0083] Although in the example of Fig. 8 the network node broadcasts feedback information after each data frame (e.g. data frame 830-832, 840-856 and 860-862), in some cases, the network node may not broadcast the feedback information for all the data frames. In embodiments of the present disclosure, the terminal device monitors the feedback information of the data frame only when the data frame is an end frame of the contention layer. Therefore, the network node can determine if an allocated data frame is located at the end of a certain contention layer based on the overall contention condition and if not, the feedback information for the data is not needed to be determined and broadcasted. Only when it determines that the data frame is at the end of the contention layer, its feedback information (that is, the number of frames) is to be monitored by the terminal device. [0084] Fig. 9 illustrates the average power consumed by each terminal device using the data-based direct contention and the request-message-based contention as described above (indicated by curves 910 and 920 respectively). It can be seen that if resources are contended with a request message having a small load and data is transmitted in a specific data frame(s) after the contention succeeds (as shown by the curve 920), the power consumption of the terminal device can be further reduced.

[0085] Fig. 10 shows a diagram illustrating a method of contention-based communication 1000 in a network node in accordance with an embodiment of the present disclosure. The method 1000 provides some example operations of the network node in the process of the communication method 400 shown in Fig. 4. Although example blocks of the method 1000 are illustrated in Fig. 10, in some other embodiments, the method 1000 may include other blocks, less blocks, different blocks, or blocks arranged differently from these depicted in Fig. 10. Alternatively, or in addition, two or more blocks of the method 1000 can be performed in parallel. In some embodiments, the method 1000 can be implemented, for example, at network node 110 in Fig. 1.

[0086] At block 1010, the network node determines a contention state for a first contention frame at a first contention layer, at least one terminal device transmitting a message in the first contention frame. At block 1020, the network node determines, based on the contention state, the number of frames for the first contention frame which indicates an accumulative number of frames determined at the first contention frame to be allocated to a second contention layer following the first contention layer. Then, at block 1030, the network node transmits feedback information for the first contention frame including the determined number of frames. The terminal device that is interested in the feedback information (for example, the terminal device transmitting the message in the first contention frame) can receive the feedback information.

[0087] In some embodiments, in response to a failure of the transmission of the message by the terminal device in the first contention frame, the network node allocates at least one contention frame to the second contention layer for retransmission of the message .

[0088] In some embodiments, the transmitted information may be a request message. Thus, in response to a success of the transmission of the request message by the terminal device in the first contention frame, the network node allocates at least one data frame to the second contention layer for transmission of data to be transmitted by the terminal device. [0089] In some embodiments, the network device receives the data from the terminal device in the allocated data frame and then determines feedback information for the data frame, the feedback information for the data frame including the number of frames. Here, the number of frames indicates the accumulative number of frames determined at the data frame to be allocated to the second contention layer. The feedback information may be transmitted to the terminal device.

[0090] Fig. 11 is a block diagram illustrating a communication apparatus 1100 in a terminal device in accordance with an embodiment of the present disclosure. The apparatus 1100 may be for example any of the terminal devices 121-124 as shown in Fig. 1 or may be included therein.

[0091] As shown in Fig. 11, the apparatus 1100 comprises a message transmitter 1110 configured to transmit a message to a network node in a first contention frame at a first contention layer. The apparatus 1100 further includes a feedback receiver 1120 configured to receive first feedback information for the first contention frame from the network node. The first feedback information indicates the number of frames which indicates an accumulative number of frames determined by the network node at the first contention frame to be allocated to a second contention layer following the first contention layer. The apparatus 1100 further includes a contention determining device 1130 configured to, in response to a failure of the transmission of the message, determine, at least based on the first feedback information, positions of a second contention frame and an end frame at the second contention layer. The apparatus 1100 further includes a mode switcher 1140 configured to switch, based on the positions of the second contention frame and the end frame, to a sleep mode in a duration of frames at the second contention layer other than the second contention frame and the end frame. [0092] In some embodiments, the contention determining device 1130 is configured to, in response to the first contention frame being the end frame on the first contention layer, determine the position of the end frame at the second contention layer based on a position of the first contention frame and the number of frames in the first feedback information; and determine the position of the second contention frame at the second contention layer based on the position of the end frame at the first contention layer and the contention state in the first feedback information.

[0093] In some embodiments, the feedback receiver 1120 is further configured to: in response to the first contention frame being other than an end frame at the first contention layer, receive second feedback information for the end frame at the first contention layer, the second feedback information indicating the number of frames which indicates an accumulative number of frames determined by the network node at the end frame of the first contention layer to be allocated to the second contention layer . In these embodiments, the contention determining device 1130 is configured to determine the positions of the second contention frame and the end frame at the second contention layer based on the first and second feedback information.

[0094] In some embodiments, the contention determining device 1130 is configured to: determine the position of the second contention frame at the second contention layer based on a position of an end frame at the first contention layer, and the number of frames and the contention state in the feedback information; and determine the position of the end frame at the second contention layer based on the position of the end frame at the first contention layer and the second feedback information. [0095] In some embodiments, the message transmitter 1110 is further configured to retransmit the message to the network node in the second contention frame. In these embodiments, the feedback receiver 1120 is further configured to receive, from the network node, feedback information for the second contention frame and feedback information for the end frame. [0096] In some embodiments, the first contention frame includes a plurality of timeslots. In these embodiments, the message transmitter 1110 is configured to select at least one timeslot from the plurality of timeslots in the first contention frame for transmitting the message.

[0097] In some embodiments, the first feedback information further indicates a contention state, the contention state including a success state, a collision state, or a non-transmission state for each of the timeslots. The apparatus 1100 may further include a transmission determining device configured to determine whether the message is transmitted successfully based on the contention state of the timeslot in which the message is transmitted.

[0098] In some embodiments, the message includes a request message. In these embodiments, the apparatus 1100 further includes: a data frame determining device configured to, in response to a success of the transmission of the request message, determine, at least based on the first feedback information, a position of a data frame allocated for the request message at the second contention layer; and a data transmitter configured to transmit data to be transmitted in the data frame based on the determined position of the data frame..

[0099] In some embodiments, the feedback receiver 1120 is further configured to, in response to the data frame being an end frame at the second contention layer, receive feedback information for the data frame, the feedback information for the data frame including an accumulative number of frames determined by the network node at the data frame to be allocated to the second contention layer.

[00100] Fig. 12 is a block diagram illustrating a communication apparatus 1200 in a network node according to an embodiment of the present disclosure. The apparatus 1200 may be for example the network node 110 shown in Fig. 1, or may be included therein.

[00101] As shown in Fig. 12, the apparatus 1200 includes a contention state determining device 1210 configured to determine a contention state for a first contention frame at a first contention layer, at least one terminal device transmitting a message in the first contention frame. The apparatus 1200 further includes a frame number determining device 1220 configured to determine, based on the contention state, the number of frames for the first contention frame which indicates an accumulative number of frames determined at the first contention frame to be allocated to a second contention layer following the first contention layer. The apparatus 1200 further includes a feedback transmitter 1230 configured to transmit feedback information for the first contention frame including the determined number of frames.

[00102] In some embodiments, the apparatus 1200 further includes a frame allocator configured to in response to a failure of the transmission of the message by the terminal device in the first contention frame, allocate at least one contention frame to the second contention layer for retransmission of the message by the terminal device. [00103] In some embodiments, the message includes a request message. The apparatus 1200 further includes a frame allocator configured to, in response to a success of the transmission of the request message by the terminal device in the first contention frame, allocate at least one data frame to the second contention layer for transmission of data to be transmitted by the terminal device. [00104] In some embodiments, the apparatus 1200 further includes: a data receiver configured to receive the data from the terminal device in the allocated data frame; a data feedback determining device configured to determine feedback information for the data frame, the feedback information for the data frame including an accumulative number of frames determined at the data frame to be allocated to the second contention layer; and a data feedback transmitter configured to transmit the feedback information for the data frame.

[00105] It can be seen that the apparatus 1100 of Fig. 11 can perform the operations of the terminal device in the process described with reference to any of Figs. 4-9 and the apparatus 1200 of Fig. 12 can perform the operations of the network node in the process described with reference to any of Figs. 4-10. Although not shown, the apparatus 1100 or 1200 may include more functional units to perform various embodiments depicted with reference to Figs. 4-10.

[00106] Embodiments of the present disclosure further provide a communication system which may include at least one terminal device. Each of the terminal devices includes the apparatus 1100 as shown in Fig. 11. The communication system further includes a network node which includes the apparatus 1200 as shown in Fig. 12.

[00107] Fig. 13 is a block diagram illustrating an example computer system/server 12 suitable for implementing embodiments of the present disclosure. In some embodiments, any of terminal devices 121-124 or network node 110 may include one or more computer systems/servers 12 and/or one or more components of computer systems/server 12. The computer system/server 12 shown in Fig. 13 is merely an example and is not be regarded as any limitation to the function and usage scope of the embodiments of the present disclosure.

[00108] As shown in Fig. 13, the computer systems/server 12 can be implemented in the form of general-purpose computing device. The components of the computer system/server 12 may include, but are not limited to, one or more processors or processing units 16, a system memory 28, and a bus 18 connecting various system components (including the system memory 28 and the processing units 16).

[00109] The bus 18 represents one or more of bus architectures, including a memory bus or a memory controller, a peripheral bus, an accelerated graphics port, and a processor or a local bus utilizing any of various bus architectures. By way of example but not limiting, such architectures include an Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, Video Electronics Standards Association (VESA) local bus, and Peripheral Component Interconnect (PCI) bus. [00110] The computer system/server 12 typically includes various computer system readable media. The media can be any available media accessible by the computer system/server 12, including volatile and non-volatile media, removable and non-removable media. [00111] The system memory 28 may include a computer system readable media in the form of volatile memory, such as a memory 30 and/or a buffer 32. The computer system/server 12 may further include other removable or non-removable and volatile or non- volatile computer system memory media. Although not shown in Fig. 2, a disc drive is provided for reading from and writing to a removable and non-volatile disc (for example, floppy disc) and an optical drive is provided for reading from and writing to a removable non-volatile optical disc (for example, CD-ROM, DVD-ROM or other optical media). In such case, each drive is connected to the bus 18 via one or more data media interfaces. The memory 28 includes at least one program product having a group of (for example, at least one) program modules configured to implement functions of embodiments of the present application.

[00112] A program/utility tool 40 having a set of (or at least one) program module(s) 42 may be stored in the memory 28 for instance. Such program module 42 include, but is not limited to, an operation system, one or more applications, other program modules, and program data; each or a certain any combination of these examples may include an implementation of the network environment. The program module 42 generally performs the functions and/or methods described in the embodiments of the present disclosure.

[00113] As required, the computer system/server 12 may also communicate with one or more external devices (for example, a display device 24, a memory device 14 or the like.), or may also communicate with one or more devices enabling the user to interact with the computer system/server 12, and/or communicate with any devices (for example, a network card, a modem and the like.) that enable the computer system/server 12 to communicate with one or more other computing devices. The communication is performed through an input/output (I/O) interface 22. Moreover, the computer system/server 12 may also communicate with one or more networks (for example, a local area network (LAN), a wide area network (WAN) and/or a public network such as Internet) through a network adapter 20. The network adapter 20 communicates with other modules of the computer system/server 12 through the bus 18 as shown. It should be understood that although not being illustrated, other hardware and/or software modules may be utilized in combination with the computer system/server 12, which include, but are not limited to, a microcode, a device driver, a redundancy processing unit, an external disc drive array, a RAID system, a disc drive, a data back-up storage system and the like.

[00114] It would be appreciated that the embodiments of the present disclosure can be implemented in software, hardware, or a combination thereof. The hardware part can be implemented by a special logic; the software part can be stored in a memory and executed by a suitable instruction execution system such as a microprocessor or special purpose hardware. Ordinary skilled in the art may understand that the above method and system may be implemented with computer executable instructions and/or in processor-controlled code, for example, such code is provided on a carrier medium such as a magnetic disk, CD, or DVD-ROM, or a programmable memory such as a read-only memory (firmware), or a data bearer such as an optical or electronic signal bearer. The apparatuses and their units in the present disclosure may be implemented by hardware circuitry of a programmable hardware device such as a hyper-scale integrated circuit or gate array, a semiconductor such as a logical chip or transistor, or hardware circuitry of a programmable hardware device such as a field-programmable gate array or a programmable logical device, or implemented by software executed by various processors, or implemented by any combination of the above hardware circuitry and software.

[00115] It is to be noted that although various units or sub-units of the apparatus have been mentioned in the above detailed description, such partitioning is not for limitation. In practice, according to the embodiments of the present invention, the features and functions of two or more units described above may be embodied in one unit. In turn, the features and functions of one unit described above may be further embodied in more units.

[00116] Further, although operations of the present methods are described in a particular order in the drawings, it does not require or imply that these operations are necessarily performed according to this particular sequence, or a desired outcome can only be achieved by performing all shown operations. On the contrary, the execution order for the blocks as depicted in the flowcharts may be varied. Alternatively, or in addition, some blocks may be omitted, a plurality of blocks may be merged into one block, or a block may be divided into a plurality of blocks for execution.

[00117] Although the present disclosure has been described with reference to various embodiments, it should be understood that the present disclosure is not limited to the disclosed embodiments. The present disclosure is intended to cover various modifications and equivalent arrangements included in the spirit and scope of the appended claims. The scope of the appended claims meets the broadest explanations and covers all such modifications and equivalent structures and functions.

Claims

I/We Claim:

1. A method of contention-based communication, comprising:

transmitting a message to a network node in a first contention frame at a first contention layer;

receiving first feedback information for the first contention frame from the network node, the first feedback information indicating the number of frames which indicates an accumulative number of frames determined, by the network node at the first contention frame, to be allocated to a second contention layer following the first contention layer;

in response to a failure of the transmission of the message, determining, at least based on the first feedback information, positions of a second contention frame and an end frame at the second contention layer; and

switching, based on the positions of the second contention frame and the end frame, to a sleep mode in a duration of frames at the second contention layer other than the second contention frame and the end frame.

2. The method according to Claim 1, wherein the first feedback information further indicates a contention state, and wherein determining positions of a second contention frame and an end frame at the second contention layer comprises:

in response to the first contention frame being an end frame at the first contention layer,

determining the position of the end frame at the second contention layer based on a position of the first contention frame and the number of frames in the first feedback information; and

determining the position of the second contention frame at the second contention layer based on the position of the end frame at the first contention layer and the contention state in the first feedback information.

3. The method according to Claim 1, further comprising:

in response to the first contention frame being other than an end frame at the first contention layer, receiving second feedback information for the end frame at the first contention layer, the second feedback information indicating the number of frames which indicates an accumulative number of frames determined by the network node at the end frame of the first contention layer to be allocated to the second contention layer; and wherein determining positions of a second contention frame and an end frame at the second contention layer comprises determining the positions of the second contention frame and the end frame at the second contention layer based on the first and second feedback information.

4. The method according to Claim 3, wherein the first feedback information further indicates a contention state and wherein determining the positions of the second contention frame and the end frame at the second contention layer based on the first and second feedback information comprises:

determining the position of the second contention frame at the second contention layer based on a position of an end frame at the first contention layer, and the number of frames and the contention state in the feedback information; and

determining the position of the end frame at the second contention layer based on the position of the end frame at the first contention layer and the second feedback information.

5. The method according to Claim 1, further comprising:

retransmitting the message to the network node in the second contention frame; and receiving, from the network node, feedback information for the second contention frame and feedback information for the end frame.

6. The method according to Claim 1, wherein the first contention frame includes a plurality of timeslots, and transmitting a message to the network node in a first contention frame comprises:

selecting at least one timeslot from the plurality of timeslots in the first contention frame for transmitting the message.

7. The method according to Claim 6, wherein the first feedback information further indicates a contention state, the contention state including a success state, a collision state, or a non-transmission state for each of the timeslots, the method further comprising:

determining whether the message is transmitted successfully based on the contention state of the timeslot in which the message is transmitted.

8. The method according to any of Claims 1-7, wherein the message includes a request message, the method further comprising: in response to a success of the transmission of the request message, determining, at least based on the first feedback information, a position of a data frame allocated for the request message at the second contention layer; and

transmitting data to be transmitted in the data frame based on the determined position of the data frame.

9. The method according to Claim 8, further comprising:

in response to the data frame being an end frame at the second contention layer, receiving feedback information for the data frame, the feedback information for the data frame including an accumulative number of frames determined by the network node at the data frame to be allocated to the second contention layer.

10. A method of contention-based communication, comprising:

determining a contention state for a first contention frame at a first contention layer, at least one terminal device transmitting a message in the first contention frame;

determining, based on the contention state, the number of frames for the first contention frame which indicates an accumulative number of frames determined at the first contention frame to be allocated to a second contention layer following the first contention layer; and

transmitting feedback information for the first contention frame including the determined number of frames.

11. The method according to Claim 10, further comprising:

in response to a failure of the transmission of the message by the terminal device in the first contention frame, allocating at least one contention frame to the second contention layer for retransmission of the message by the terminal device.

12. The method according to Claim 10, wherein the message includes a request message, the method further comprising:

in response to a success of the transmission of the request message by the terminal device in the first contention frame, allocating at least one data frame to the second contention layer for transmission of data to be transmitted by the terminal device.

The method according to Claim 12, further comprising: receiving the data from the terminal device in the allocated data frame; determining feedback information for the data frame, the feedback information for the data frame including an accumulative number of frames determined at the data frame to be allocated to the second contention layer; and

transmitting the feedback information for the data frame.

14. An apparatus for contention-based communication, comprising:

a message transmitter configured to transmit a message to a network node in a first contention frame at a first contention layer;

a feedback receiver configured to receive first feedback information for the first contention frame from the network node, the first feedback information indicating the number of frames which indicates an accumulative number of frames determined by the network node at the first contention frame to be allocated to a second contention layer following the first contention layer;

a contention determining device configured to, in response to a failure of the transmission of the message, determine, at least based on the first feedback information, positions of a second contention frame and an end frame at the second contention layer; and a mode switcher configured to switch, based on the positions of the second contention frame and the end frame, to a sleep mode in a duration of frames at the second contention layer other than the second contention frame and the end frame.

15. The apparatus according to Claim 14, wherein the contention determining device is configured to, in response to the first contention frame being the end frame on the first contention layer,

determine the position of the end frame at the second contention layer based on a position of the first contention frame and the number of frames in the first feedback information; and

determine the position of the second contention frame at the second contention layer based on the position of the end frame at the first contention layer and the contention state in the first feedback information.

16. The apparatus according to Claim 14, wherein the feedback receiver is further configured to:

in response to the first contention frame being other than an end frame at the first contention layer, receive second feedback information for the end frame at the first contention layer, the second feedback information indicating the number of frames which indicates an accumulative number of frames determined by the network node at the end frame of the first contention layer to be allocated to the second contention layer; and

wherein the contention determining device is configured to determine the positions of the second contention frame and the end frame at the second contention layer based on the first and second feedback information.

17. The apparatus according to Claim 16, wherein the first feedback information further indicates a contention state, and wherein the contention determining device is configured to:

determine the position of the second contention frame at the second contention layer based on a position of an end frame at the first contention layer, and the number of frames and the contention state in the feedback information; and

determine the position of the end frame at the second contention layer based on the position of the end frame at the first contention layer and the second feedback information.

18. The apparatus according to Claim 14, wherein the message transmitter is further configured to retransmit the message to the network node in the second contention frame; and wherein the feedback receiver is further configured to receive, from the network node, feedback information for the second contention frame and feedback information for the end frame.

19. The apparatus according to Claim 14, wherein the first contention frame includes a plurality of timeslots, wherein the message transmitter is configured to select at least one timeslot from the plurality of timeslots in the first contention frame for transmitting the message.

20. The apparatus according to Claim 19, wherein the first feedback information further indicates a contention state, the contention state including a success state, a collision state, or a non-transmission state for each of the timeslots, the apparatus further comprising: a transmission determining device configured to determine whether the message is transmitted successfully based on the contention state of the timeslot in which the message is transmitted.

21. The apparatus according to any of Claims 14-20, wherein the message includes a request message, the apparatus further comprising:

a data frame determining device configured to, in response to a success of the transmission of the request message, determine, at least based on the first feedback information, a position of a data frame allocated for the request message at the second contention layer; and

a data transmitter configured to transmit data to be transmitted in the data frame based on the determined position of the data frame.

22. The apparatus according to Claim 21, wherein the feedback receiver is further configured to:

in response to the data frame being an end frame at the second contention layer, receive feedback information for the data frame, the feedback information for the data frame including an accumulative number of frames determined by the network node at the data frame to be allocated to the second contention layer.

23. An apparatus for contention-based communication, comprising:

a contention state determining device configured to determine a contention state for a first contention frame at a first contention layer, at least one terminal device transmitting a message in the first contention frame;

a frame number determining device configured to determine, based on the contention state, the number of frames for the first contention frame which indicates an accumulative number of frames determined at the first contention frame to be allocated to a second contention layer following the first contention layer; and

a feedback transmitter configured to transmit feedback information for the first contention frame including the determined number of frames.

24. The apparatus according to Claim 23, further comprising:

a frame allocator configured to in response to a failure of the transmission of the message by the terminal device in the first contention frame, allocate at least one contention frame to the second contention layer for retransmission of the message by the terminal device.

25. The apparatus according to Claim 23, wherein the message includes a request message, the apparatus further comprising:

a frame allocator configured to in response to a success of the transmission of the request message by the terminal device in the first contention frame, allocate at least one data frame to the second contention layer for transmission of data to be transmitted by the terminal device.

26. The apparatus according to Claim 25, further comprising:

a data receiver configured to receive the data from the terminal device in the allocated data frame;

a data feedback determining device configured to determine feedback information for the data frame, the feedback information for the data frame including an accumulative number of frames determined at the data frame to be allocated to the second contention layer; and a data feedback transmitter configured to transmit the feedback information for the data frame.

27. A communication system, comprising:

at least one terminal device each comprising the apparatus according to any of Claims 14-22; and

a network node comprising the apparatus according to any of Claims 23-26.