WO2013171654A2

WO2013171654A2 - Method and apparatus for data transmissions

Info

Publication number: WO2013171654A2
Application number: PCT/IB2013/053873
Authority: WO
Inventors: Timo Koskela; Anna Pantelidou; Juho Pirskanen; Sami-Jukka Hakola; Samuli Turtinen
Original assignee: Renesas Mobile Corporation
Priority date: 2012-05-14
Filing date: 2013-05-13
Publication date: 2013-11-21
Also published as: WO2013171654A3

Abstract

(57) ABSTRACT A method, apparatus and computer program product are provided for enabling wireless data transmission. In this regard, a method is provided that comprises causing an uplink data transmission. The method of this embodiment may also include decoding an acknowledgement message received from an access point in response to the uplink transmission, the acknowledgement message configured to indicate that downlink data is buffered at the access point. The method of this embodiment may also include receiving downlink data, wherein the downlink data is transmitted by the access point following a predetermined time interval after the acknowledgement message.

Description

METHOD AND APPARATUS FOR DATA TRANSMISSIONS

TECHNOLOGICAL FIELD

[0001] Embodiments of the present invention relate generally to communications technology and, more particularly, to example wireless data transmissions.

BACKGROUND

[0002] Typical wireless networks, such as networks conforming to one of the Institute of Electrical and Electronics Engineers (IEEE) 802.1 1 standards, are arranged such that a plurality of communications devices each has a wireless connection to an access point. Typically, all of the communications devices communicate on the same channel (e.g. in the same range of frequency). This sharing of the communications medium may lead to collisions, which is where two or more communications devices attempt to use a channel simultaneously. Consequently, mechanisms are required to avoid collisions.

[0003] One known mechanism for dealing with collisions is known as a Distributed Coordination Function (DCF). A DCF works by requiring a communications device wishing to transmit to listen on the channel for a particular interval. If the channel is busy (e.g. another communications device is transmitting on the channel) the communications device defers attempting to access the channel for a "back-off period". The back-off period typically has a random element, so that communications devices do not synchronously defer access and then re-attempt access.

[0004] Under 802.1 lah, an access point, is configured to support a large number of communication devices or stations (STA) (e.g. 6000 or more) that operate on a strict energy budget. The communication devices that operate on a strict energy budget may include battery powered sensors which transmit and receive data very rarely and therefore stay in a low power operation mode for relatively long periods of time. In order to support such a large number of communication devices operating in the DCF mode, access points may utilize techniques to restrict the contention to the channel to avoid collisions of simultaneous transmissions in the collision domain. One such technique to reduce contention and collisions of transmission is a method that is configured to group communication devices into multiple groups and then to assign certain parameters for each group to indicate the specific group can access the channel (e.g. channel content). Such grouping information and parameters for the operation can be delivered to the communication devices in an association phase or, for example, in broadcast information such as in a beacon frame.

[0005] However, communication devices may operate in low power mode for prolonged periods of time and therefore grouping related parameters may not be valid anymore when the communication device wakes up and resumes a channel access operation. Also, broadcast messages, such as beacons, are transmitted relatively sparsely and if a communication device stays in low power mode for extended periods of time it may lose the synchronization (e.g. due to the internal clock drift in the access point and in the communication device) and may not able to estimate when the next beacon or other broadcast message would be transmitted by the access point. Such behavior, for example, may cause the communication device to stay awake for a relatively long duration trying to receive a beacon transmission.

BRIEF SUMMARY

[0006] In some example embodiments, a method is provided that comprises causing an uplink data transmission. The method of this embodiment may also include decoding an acknowledgement message received from an access point in response to the uplink transmission, the acknowledgement message configured to indicate that downlink data is buffered at the access point. The method of this embodiment may also include receiving downlink data. In some example embodiments, the downlink data is transmitted by the access point following a predetermined time interval after the acknowledgement message.

[0007] In further example embodiments, an apparatus is provided that includes at least one processor and at least one memory including computer program code with the at least one memory and the computer program code being configured, with the at least one processor, to cause the apparatus to at least cause an uplink data transmission. The at least one memory and computer program code may also be configured to, with the at least one processor, cause the apparatus to decode an acknowledgement message received from an access point in response to the uplink transmission, the acknowledgement message configured to indicate that downlink data is buffered at the access point. The at least one memory and computer program code may also be configured to, with the at least one processor, cause the apparatus to receive downlink data. In some example embodiments, the downlink data is transmitted by the access point following a predetermined time interval after the acknowledgement message.

[0008] In yet further example embodiments, a computer program product may be provided that includes at least one non-transitory computer-readable storage medium having computer-readable program instructions stored therein with the computer-readable program instructions including program instructions configured to cause an uplink data transmission. The computer-readable program instructions may also include program instructions configured to decode an acknowledgement message received from an access point in response to the uplink transmission, the acknowledgement message configured to indicate that downlink data is buffered at the access point. The computer-readable program instructions may also include program instructions configured to receive downlink data. In some example embodiments, the downlink data is transmitted by the access point following a predetermined time interval after the acknowledgement message.

[0009] In yet further example embodiments, an apparatus is provided that includes means for causing an uplink data transmission. The apparatus of this embodiment may also include means for decoding an acknowledgement message received from an access point in response to the uplink transmission, the acknowledgement message configured to indicate that downlink data is buffered at the access point. The apparatus of this embodiment may also include means for receiving downlink data. In some example embodiments, the downlink data is transmitted by the access point following a predetermined time interval after the acknowledgement message.

[0010] In some example embodiments, a method is provided that comprises receiving an uplink data transmission from a communication device. The method of this embodiment may also include causing an acknowledgement message to be transmitted to the communication device, the acknowledgement message configured to indicate that downlink data is buffered. The method of this embodiment may also include causing the downlink data to be transmitted to the communication device in a transmission following a predetermined time interval after the transmission of the acknowledgement message.

[0011] In further example embodiments, an apparatus is provided that includes at least one processor and at least one memory including computer program code with the at least one memory and the computer program code being configured, with the at least one processor, to cause the apparatus to at least receive an uplink data transmission from a communication device. The at least one memory and computer program code may also be configured to, with the at least one processor, cause the apparatus to cause an acknowledgement message to be transmitted to the communication device, the acknowledgement message configured to indicate that downlink data is buffered. The at least one memory and computer program code may also be configured to, with the at least one processor, cause the apparatus to cause the downlink data to be transmitted to the communication device in a transmission following a predetermined time interval after the transmission of the acknowledgement message.

[0012] In yet further example embodiments, a computer program product may be provided that includes at least one non-transitory computer-readable storage medium having computer-readable program instructions stored therein with the computer-readable program instructions including program instructions configured to receive an uplink data transmission from a communication device. The computer-readable program instructions may also include program instructions configured to cause an acknowledgement message to be transmitted to the communication device, the acknowledgement message configured to indicate that downlink data is buffered. The computer-readable program instructions may also include program instructions configured to cause the downlink data to be transmitted to the communication device in a transmission following a predetermined time interval after the transmission of the acknowledgement message.

[0013] In yet further example embodiments, an apparatus is provided that includes means for receiving an uplink data transmission from a communication device. The apparatus of this embodiment may also include means for causing an acknowledgement message to be transmitted to the communication device, the acknowledgement message configured to indicate that downlink data is buffered. The apparatus of this embodiment may also include means for causing the downlink data to be transmitted to the communication device in a transmission following a predetermined time interval after the transmission of the acknowledgement message.

[0014] In some example embodiments, a method is provided that comprises causing a request to operate in a pull only mode to be transmitted to an access point. In some example embodiments, in an instance in which pull only mode is activated the access point is configured to transmit downlink data within a predetermined duration of receiving a downlink data delivery request. The method of this embodiment may also include causing the downlink data delivery request from to be transmitted to the access point. The method of this embodiment may also include receiving downlink data in response to the downlink data delivery.

[0015] In further example embodiments, an apparatus is provided that includes at least one processor and at least one memory including computer program code with the at least one memory and the computer program code being configured, with the at least one processor, to cause the apparatus to at least cause a request to operate in a pull only mode to be transmitted to an access point. In some example embodiments, in an instance in which pull only mode is activated the access point is configured to transmit downlink data within a predetermined duration of receiving a downlink data delivery request. The at least one memory and computer program code may also be configured to, with the at least one processor, cause the apparatus to cause the downlink data delivery request from to be transmitted to the access point. The at least one memory and computer program code may also be configured to, with the at least one processor, cause the apparatus to receive downlink data in response to the downlink data delivery.

[0016] In yet further example embodiments, a computer program product may be provided that includes at least one non-transitory computer-readable storage medium having computer-readable program instructions stored therein with the computer-readable program instructions including program instructions configured to cause a request to operate in a pull only mode to be transmitted to an access point. In some example embodiments, in an instance in which pull only mode is activated the access point is configured to transmit downlink data within a predetermined duration of receiving a downlink data delivery request. The computer-readable program instructions may also include program instructions configured to cause the downlink data delivery request from to be transmitted to the access point. The computer-readable program instructions may also include program instructions configured to receive downlink data in response to the downlink data delivery.

[0017] In yet further example embodiments, an apparatus is provided that includes means for causing a request to operate in a pull only mode to be transmitted to an access point. In some example embodiments, in an instance in which pull only mode is activated the access point is configured to transmit downlink data within a predetermined duration of receiving a downlink data delivery request. The apparatus of this embodiment may also include means for causing the downlink data delivery request from to be transmitted to the access point. The apparatus of this embodiment may also include means for receiving downlink data in response to the downlink data delivery.

[0018] In some example embodiments, a method is provided that comprises receiving a request to operate in a pull only mode. The method of this embodiment may also include receiving a downlink data delivery request from a communication device. The method of this embodiment may also include causing downlink data to be transmitted. In some example embodiments, the downlink data is configured to be transmitted within a predetermined duration of receiving a downlink data delivery request.

[0019] In further example embodiments, an apparatus is provided that includes at least one processor and at least one memory including computer program code with the at least one memory and the computer program code being configured, with the at least one processor, to cause the apparatus to at least receive a request to operate in a pull only mode. The at least one memory and computer program code may also be configured to, with the at least one processor, cause the apparatus to receive a downlink data delivery request from a communication device. The at least one memory and computer program code may also be configured to, with the at least one processor, cause the apparatus to cause downlink data to be transmitted. In some example embodiments, the downlink data is configured to be transmitted within a predetermined duration of receiving a downlink data delivery request.

[0020] In yet further example embodiments, a computer program product may be provided that includes at least one non-transitory computer-readable storage medium having computer-readable program instructions stored therein with the computer-readable program instructions including program instructions configured to receive a request to operate in a pull only mode. The computer-readable program instructions may also include program instructions configured to receive a downlink data delivery request from a communication device. The computer-readable program instructions may also include program instructions configured to cause downlink data to be transmitted. In some example embodiments, the downlink data is configured to be transmitted within a predetermined duration of receiving a downlink data delivery request.

[0021] In yet further example embodiments, an apparatus is provided that includes means for receiving a request to operate in a pull only mode. The apparatus of this embodiment may also include means for receiving a downlink data delivery request from a communication device. The apparatus of this embodiment may also include means for causing downlink data to be transmitted. In some example embodiments, the downlink data is configured to be transmitted within a predetermined duration of receiving a downlink data delivery request.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Having thus described the example embodiments of the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

[0023] Figure 1 is a schematic representation of a system having a communication device that may enable wireless data transmission and that may benefit from example embodiments of the present invention;

[0024] Figure 2 is a block diagram of an apparatus that may be embodied by a communication device and/or an access point in accordance with some example embodiments of the present invention;

[0025] Figures 3 - 5 are example signaling flow diagrams illustrating wireless data transmissions in accordance with some example embodiments of the present invention;

[0026] Figure 6 is an example information element used in accordance with some example embodiments of the present invention;

[0027] Figure 7 is an example short form acknowledgement (ACK) format used in accordance with some example embodiments of the present invention; [0028] Figure 8 is a flow chart illustrating further operations performed by an example communication device in accordance with some example embodiments of the present invention;

[0029] Figure 9 is a flow chart illustrating further operations performed by an example access point in accordance with some example embodiments of the present invention;

[0030] Figure 10 is a flow chart illustrating further operations performed by an example communication device operating in pull only mode (POM) in accordance with some example embodiments of the present invention; and

[0031] Figure 11 is a flow chart illustrating further operations performed by an example access point operating in POM in accordance with some example embodiments of the present invention.

DETAILED DESCRIPTION

[0032] The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

[0033] As used in this application, the term "circuitry" refers to all of the following: (a)hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and (b) to combinations of circuits and software (and/or firmware), such as (as applicable): (i) to a combination of processor(s) or (ii) to portions of processor(s)/software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) to circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present. [0034] This definition of "circuitry" applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term "circuitry" would also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware. The term "circuitry" would also cover, for example and if applicable to the particular claim element, a baseband integrated circuit or application specific integrated circuit for a mobile phone or a similar integrated circuit in server, a cellular network device, or other network device.

[0035] In some wireless communication system examples, for example with respect to IEEE 802.1 1 , an access point may be configured to buffer data frames in an instance in which a communication device is in a low power state, is asleep, and/or the like. In such cases, the access point may be configured to notify a communication device about the buffered frames by indicating the presence of the buffered frames in a TIM (traffic indication map). In some examples, the TIM is transmitted in a beacon message. Once the communication device enters a powered state and/or awakes, the communication device then can retrieve the buffered frames, for example by transmitting uplink (UL) data. The transmission of data may indicate to the access point that the communication device is in a powered state or is awake. In some examples, the communication device may cause a power save poll (PS-poll) message to be transmitted. The PS-poll is configured to indicate to the access point that the communication device is awake and ready to receive data.

[0036] In some examples and as described herein, a communication device may operate in a low power state for a large portion of the time, for example under 802.1 1 ah, which is incorporated by reference herein. An example battery powered communication device may transmit UL data relatively rarely, but may receive DL data even less. As such, between data transfers, it is beneficial for the battery powered communication devices to utilize the awake periods efficiently and enter low power state as fast as possible.

[0037] The systems and methods as described herein, in some example embodiments, are configured to cause downlink (DL) data delivery in response to a communication devices UL data transmission. As such an access point may be configured to respond to a communication device UL transmission with an ACK and then immediately may transmit buffered DL data to the communication device. In some example embodiments, the ACK message may take the form of a Block Acknowledgement (BA), which is configured to acknowledge multiple packets. In some example embodiments, the ACK message may indicate to the communication device that DL data will be transmitted following the ACK. The communication device may, for example, delay and/or defer entering a low power or sleep state after determining that downlink data will be delivered. Alternatively or additionally, the access point and the communication device may operate in a pull only mode (POM), such that the access point may only deliver buffered downlink data when requested by the communication device.

[0038] Although the method, apparatus and computer program product as described herein may be implemented in a variety of different systems, one example of such a system is shown in Figure 1 , which includes a communication device (e.g., communication device 10) that is capable of communication via an access point 12, such as a base station, a macro cell, a Node B, an eNB, a coordination unit, a macro base station or other access point, with a network 14 (e.g., a core network). While the network may be configured in accordance with long term evolution (LTE™) or LTE-Advanced (LTE-A™), other networks may support the method, apparatus and computer program product of embodiments of the present invention including those configured in accordance with wideband code division multiple access (W-CDMA™), CDMA2000, global system for mobile communications (GSM™), general packet radio service (GPRS™), IEEE™ 802.1 1 standard for wireless fidelity (WiFi), wireless local access network (WLAN™) Worldwide Interoperability for Microwave Access (WiMAX™) protocols, and/or the like.

[0039] The network 14 may include a collection of various different nodes, devices or functions that may be in communication with each other via corresponding wired and/or wireless interfaces. For example, the network may include one or more cells, including access point 12 and which may serve a respective coverage area. The access point 12 could be, for example, part of one or more cellular or mobile networks or public land mobile networks (PLMNs). In turn, other devices such as processing devices (e.g., personal computers, server computers or the like) may be coupled to the communication device 10 and/or other communication devices via the network.

[0040] A communication device, such as the communication device 10 (also known as user equipment (UE), a mobile terminal or the like), may be in communication with other communication devices or other devices via the access point 12 and, in turn, the network 14. In some cases, the communication device 10 may include an antenna for transmitting signals to and for receiving signals from an access point 12.

[0041] In some example embodiments, the communication device 10 may be a mobile communication device such as, for example, a mobile telephone, portable digital assistant (PDA), pager, laptop computer, station (ST A), or any of numerous other hand held or portable communication devices, computation devices, content generation devices, content consumption devices, or combinations thereof. However, as is described herein, the communication device 10 may also take the form a communications enabled appliance, such as a thermostat configured to connect with an access point 12. Other such devices that are configured to connect to the network include, but are not limited to a refrigerator, a security system, a home lighting system, and/or the like. Communication devices may also take the form of low power, battery operated sensors. As such, the communication device 10 may include one or more processors that may define processing circuitry and a processing system, either alone or in combination with one or more memories. The processing circuitry may utilize instructions stored in the memory to cause the communication device 10 to operate in a particular way or execute specific functionality when the instructions are executed by the one or more processors. The communication device 10 may also include communication circuitry and corresponding hardware/software to enable communication with other devices and/or the network 14.

[0042] In one embodiment, for example, the communication device 10 and/or the access point 12 may be embodied as or otherwise include an apparatus 20 as generically represented by the block diagram of Figure 2. While the apparatus 20 may be employed, for example, by a communication device 10 or an access point 12, it should be noted that the components, devices or elements described below may not be mandatory and thus some may be omitted in certain embodiments. Additionally, some embodiments may include further or different components, devices or elements beyond those shown and described herein.

[0043] As shown in Figure 2, the apparatus 20 may include or otherwise be in communication with processing circuitry 22 that is configurable to perform actions in accordance with example embodiments described herein. The processing circuitry may be configured to perform data processing, application execution and/or other processing and management services according to an example embodiment of the present invention. In some embodiments, the apparatus or the processing circuitry may be embodied as a chip or chip set. In other words, the apparatus or the processing circuitry may comprise one or more physical packages (e.g., chips) including materials, components and/or wires on a structural assembly (e.g., a baseboard). The structural assembly may provide physical strength, conservation of size, and/or limitation of electrical interaction for component circuitry included thereon. The apparatus or the processing circuitry may therefore, in some cases, be configured to implement an embodiment of the present invention on a single chip or as a single "system on a chip." As such, in some cases, a chip or chipset may constitute means for performing one or more operations for providing the functionalities described herein.

[0044] In an example embodiment, the processing circuitry 22 may include a processor 24 and memory 28 that may be in communication with or otherwise control a communication interface 26 and, in some cases, a user interface 29. As such, the processing circuitry may be embodied as a circuit chip (e.g., an integrated circuit chip) configured (e.g., with hardware, software or a combination of hardware and software) to perform operations described herein. However, in some embodiments taken in the context of the communication device 10, the processing circuitry may be embodied as a portion of a mobile computing device or other mobile terminal.

[0045] The user interface 29 (if implemented) may be in communication with the processing circuitry 22 to receive an indication of a user input at the user interface and/or to provide an audible, visual, mechanical or other output to the user. As such, the user interface may include, for example, a keyboard, a mouse, a trackball, a display, a touch screen, a microphone, a speaker, and/or other input/output mechanisms. The apparatus 20 need not always include a user interface. For example, in instances in which the apparatus is embodied as an access point 12, the apparatus may not include a user interface. As such, the user interface is shown in dashed lines in Figure 2.

[0046] The communication interface 26 may include one or more interface mechanisms for enabling communication with other devices and/or networks. In some cases, the communication interface may be any means such as a device or circuitry embodied in either hardware, or a combination of hardware and software that is configured to receive and/or transmit data from to a network 14 and/or any other device or module in communication with the processing circuitry 22, such as between the communication device 10 and the access point 12. In this regard, the communication interface may include, for example, an antenna (or multiple antennas) and supporting hardware and/or software for enabling communications with a wireless communication network and/or a communication modem or other hardware/software for supporting communication via cable, digital subscriber line (DSL), universal serial bus (USB), Ethernet or other methods.

[0047] In an example embodiment, the memory 28 may include one or more non- transitory memory devices such as, for example, volatile and/or non-volatile memory that may be either fixed or removable. The memory may be configured to store information, data, applications, instructions or the like for enabling the apparatus 20 to carry out various functions in accordance with example embodiments of the present invention. For example, the memory could be configured to buffer input data for processing by the processor 24. Additionally or alternatively, the memory could be configured to store instructions for execution by the processor. As yet another alternative, the memory may include one of a plurality of databases that may store a variety of files, contents or data sets. Among the contents of the memory, applications may be stored for execution by the processor in order to carry out the functionality associated with each respective application. In some cases, the memory may be in communication with the processor via a bus for passing information among components of the apparatus.

[0048] The processor 24 may be embodied in a number of different ways. For example, the processor may be embodied as various processing means such as one or more of a microprocessor or other processing element, a coprocessor, a controller or various other computing or processing devices including integrated circuits such as, for example, an ASIC (application specific integrated circuit), an FPGA (field programmable gate array), or the like. In an example embodiment, the processor may be configured to execute instructions stored in the memory 28 or otherwise accessible to the processor. As such, whether configured by hardware or by a combination of hardware and software, the processor may represent an entity (e.g., physically embodied in circuitry - in the form of processing circuitry 22) capable of performing operations according to embodiments of the present invention while configured accordingly. Thus, for example, when the processor is embodied as an ASIC, FPGA or the like, the processor may be specifically configured hardware for conducting the operations described herein. Alternatively, as another example, when the processor is embodied as an executor of software instructions, the instructions may specifically configure the processor to perform the operations described herein.

[0049] In some example embodiments, DL data delivery is configured to occur as a response to a transmission of UL data from a communication device. A communication device 10, such as via the processing circuitry 22, the processor 24, the communications interface 26 or the like, may be configured to transmit UL data to an access point, such as access point 12. Such a transmission may occur in an instance in which the communication device enters a powered state or awake mode. Alternatively or additionally, the communications device 10, such as by the processing circuitry 22, the processor 24, the communication interface 26 or the like, may transmit a request for DL data delivery, for example, via a request in the frame control part of the medium access control (MAC) frame. In some embodiments, the communication device 10, such as via the communication interface 26, may indicate a "DL DATA Pull Request" in an UL data frame, for example, in the frame control field of the frame.

[0050] Upon receipt of the UL data the access point 12, such as by the processing circuitry 22, the processor 24, the communication interface 26 or the like, may be configured to generate an ACK and cause the ACK to be transmitted to the communication device 10. The communication device 10, such as via the communication interface 26, may receive an ACK from the access point 12. The ACK message may be configured such that it implicitly indicates to the communication device 10, that DL data is to be delivered within a predetermined period (e.g. within a certain number of beacons or after a certain amount of time units, such as seconds, milliseconds, micro seconds or the like) after the ACK. The ACK message may indicate that the DL data is to be transmitted based on an increased duration of the ACK field to include the duration of the data transmission. In instances in which the communication device 10 determines that DL data is incoming, such as when the ACK is decoded by the processing circuitry 22, the processor 24 or the like, the communication device may defer entering a low power or sleep state. Otherwise, once receiving an ACK, the communication device 10 may enter a sleep or low powered state. Alternatively or additionally, in some example embodiments, the access point 12 is configured to multiplex the DL data with the ACK.

[0051] The access point 12, such as by the processing circuitry 22, the processor 24, the communication interface 26, or the like may be configured to transmit an ACK message and DL data in response to received UL data. In some example embodiments, the access point 12 is configured to immediately deliver the DL data, such as within a predetermined period defined by a short interframe space (SIFS), a number of beacons or a time interval following an ACK message. DL data delivery may include the delivery of one or more data packets stored in a buffer at the access point 12.

[0052] In some example embodiments and in the case of segmentation, the communication device 10 may be configured to transmit UL data in fragments to the access point 12. Such transmissions may be accomplished in accordance with 802.1 Ire vMB, which is hereby incorporated by reference. In cases in which the UL data transmission segmented, the DL data may be transmitted by the access point after the final ACK of the transmission sequence is transmitted. Alternatively or additionally, the DL data transmitted by the access point 12 may also be segmented.

[0053] Alternatively or additionally, the communication device 10, such as by the processing circuitry 22, the processor 24, the communication interface 26 or the like, may buffer UL data for transmission to the access point. In such cases, the communications device may cause transmission of the UL data after receiving DL data from the access point and after the communication device has transmitted an ACK. The procedures for transmitting UL data may be similar to those procedures performed by the access point as described with respect to DL data delivery. For example, the access point 12 may be configured to determine that UL data is to be transferred based on an indication in an ACK received from the communication device 10.

[0054] Alternatively or additionally and in some example embodiments, DL data delivery may occur in a pull only mode (POM), such that an access point 12 buffers data for a communication device and then only delivers the buffered data when it receives a request for delivery by the communication device 10. The communication device 10, such as by the processing circuitry 22, the processor 24, the communication device 10 or the like, may cause a request to be transmitted to the access point 12 to have the access point 12 operate in a POM mode. For example, the request may be indicated in an association phase, in an association request management frame or in a new management frame e.g. POM mode activation request. In response, the access point, such as via a communication interface 26, may cause an acknowledgement or grant of POM operation to be transmitted in an association response or in the response to the POM mode activation request. The access point 12 or the communication device 10 may deactivate, in some example embodiments, the POM mode via unicast signaling, e.g. multiplexed in the DATA transmission, piggybacked or in a specific management frame.

[0055] Alternatively or additionally, in some example embodiments, the access point 12, such as via the communication interface 26, may cause a broadcast message to be transmitted, such as in a beacon frame, that a POM mode has been deactivated in the Basic Service Set (BSS). The POM mode may be deactivated for one communication device or multiple communications devices by a broadcast message. Alternatively or additionally, the access point 12 may enforce buffer size limitations and as such, the communication device 10 may be required to fetch and/or request the buffered data before the communication device is dropped by the access point. In further embodiments, the access point 12 may be configured to indicate a POM mode activation or deactivation duration.

[0056] In operation and according to some example embodiments, the communication device 10, such as by the communication interface 26, may cause a DL data delivery request frame or the like to be transmitted to an access point 12 in order to fetch DL data that has been buffered. In some examples, the POM mode of operation causes or obligates the access point 12 to respond with at least one buffered data frame. By way of further example, in an instance in which POM mode is active, the access point 12 may be restricted from delivering data to a communication device unless the data is requested.

[0057] Alternatively or additionally, in an instance in which the communication device causes a DL data delivery request to be transmitted, such as via the communication interface 26, and in response receives an ACK from the access point 12, the communication device 10 may enter a low power or sleep mode. For example, the access point 12 may not deliver data if a request is received before a next beacon is scheduled. In such cases the access point may not delay the beacon and thus does not deliver DL data to the communication device 10. Alternatively or additionally, in an instance in which the access point 12 does not immediately deliver DL data, the access point 12 may be configured to determine that the communication device 10 has entered a sleep or low power mode.

[0058] Figures 3 - 5 are example signaling flow diagrams illustrating wireless data transmissions in accordance with some example embodiments of the present invention. The operations performed in Figures 3-5 may be performed by means such as one or more of the processing circuitry 22, the processor 24, the communications interface 26, the memory 28 or the like. Figure 3 illustrates one example data transmission sequence in accordance with example embodiments described herein. As is shown with respect to Figure 3, the communications device 10 is configured to cause a data packet transmission (e.g. DATA STA l) 302 to the access point 12. In some example embodiments, the communication device 10 may indicate in data packet transmission 302 that it can receive a downlink data transmission and that it will not enter a low power or sleep state. In response and after a SIFS or other predetermined period, the access point 12 may transmit an ACK (e.g. ACK 1) 304 and after a SIFS the DL data (e.g. DATA AP 2) 306 may also be transmitted. In response, the communication device may transmit an ACK (e.g. ACK 2) 308. The ACK 308 may be followed by, in some examples, a Distributed Inter-Frame Space (DIFS).

[0059] Figure 4 illustrates one example data transmission sequence in accordance with example embodiments described herein. As is shown with respect to Figure 4, the communications device 10 is configured to cause a data packet transmission (e.g. DATA STA l) 402 to the access point 12. In some example embodiments, the communication device 10 may indicate in data packet transmission 402 that it can receive a downlink data transmission and that it will not enter a low power or sleep state. In response and after a SIFS or other predetermined period, the access point 12 may transmit an ACK (e.g. ACK 1 ) 404 and after a SIFS the DL data (e.g. DAT A AP 2) 406 may also be transmitted. In response, the communication device may transmit an ACK (e.g. ACK 2) 408. The ACK 308 may be followed by a SIFS and the communications device 10 may cause additional UL data to be transmitted in data packet transmission (e.g. DATA STA 3) 410 to the access point 12. Thus demonstrating by way of Figure 4, that the example methods and systems described herein may, for example, advantageously cause multiple DATA- ACK transactions per traffic direction.

[0060] Figure 5 illustrates one example segmented data transmission sequence in accordance with example embodiments described herein. As is shown with respect to Figure 5, the communications device 10 is configured to cause a segmented data packet transmission (e.g. Fragment 0) 502 to the access point 12. In response and after a SIFS, the access point 12 may transmit an ACK (e.g. ACK 0) 404. The communications device 10 may then be configured to cause an additional segmented data packet transmission (e.g. Fragment 1) 506 to the access point 12. After all of the data transmission fragments are received (e.g. at the conclusion of the transmission sequence), the access point 12 may cause a final ACK (e.g. ACK 1) 508 to be transmitted to the communication device 10 that indicates the conclusion of the transmission sequence. After a SIFS the DL data (e.g. DATA AP 2) 510 may be transmitted to the communication device 10. In response, the communication device 10 may transmit an ACK (e.g. ACK 2) 512. Alternatively or additionally, the DL data transmissions may be transmitted in a segmented manner.

[0061] Figure 6 is an example information element used in accordance with some example embodiments of the present invention. As is shown in with respect to Figure 6, the information element may comprise an Element ID 602 which is an identifier configured to identify an element. A Length field 604 may also be included in an information element; the length field 604 may indicate the length of an information part 606. The information part 606 may have a variable length. In some example embodiments, the POM mode activation request and/or DL data delivery request may be included as requests in the information part 606 of the information element frame. Additionally the POM mode de-activation can be transmitted in the information element shown in Figure 6.

[0062] In some example embodiments, the information elements may be conveyed, for example, in an association request, probe request or in a beacon frame. When operating in an infrastructure mode, the beacon frames are transmitted by the access point, however when operating in a mesh/ad hoc mode the communication device may also transmit beacons.

[0063] Figure 7 is an example short form ACK format used in accordance with some example embodiments of the present invention. In some example embodiments, a DL data delivery indication, as a response to the communication device transmission of UL DATA frame, may be indicated in a ACK frame/short ACK frame. The (short ) ACK message may include but is not limited to a short training field (STF) 702, a long training field (LTF1) 704 which may be configured for synchronization and a signal field (SIG) 706 which is configured to contain an information part of the ACK frame. Alternatively or additionally, the ACK/Short ACK may comprise a frame type indicator that is configured to indicate incoming DL data from the access point 12. The frame type indicator may include, but is not limited to a specific bit field in the frame control field when a specific frame subtype is used or in some cases a frame subtype value may also be used.

[0064] In one example embodiment, the ACK frame, which may be transmitted by an access point in response to the UL data frame, may further be configured to indicate the presence of at least one buffered DL data frame for the communications device that is unable to be immediately delivered. In such cases the ACK frame may take the form of a request for the communication device 10 to stay in a powered or awake state until the DL data is transmitted. Alternatively or additionally the ACK frame may take the form of a request that the communication device wakes up for the next contention free period scheduled by the access point 12.

[0065] Figures 8-11 illustrate example operations performed by a method, apparatus and computer program product, such as apparatus 20 of Figure 2 in accordance with one embodiment of the present invention. It will be understood that each block of the flowcharts, and combinations of blocks in the flowcharts, may be implemented by various means, such as hardware, firmware, processor, circuitry and/or other device associated with execution of software including one or more computer program instructions. For example, one or more of the procedures described above may be embodied by computer program instructions. In this regard, the computer program instructions which embody the procedures described above may be stored by a memory 28 of an apparatus employing an embodiment of the present invention and executed by a processor 24 in the apparatus. As will be appreciated, any such computer program instructions may be loaded onto a computer or other programmable apparatus (e.g., hardware) to produce a machine, such that the resulting computer or other programmable apparatus provides for implementation of the functions specified in the flowcharts' block(s). These computer program instructions may also be stored in a non-transitory computer-readable storage memory that may direct a computer or other programmable apparatus to function in a particular manner, such that the instructions stored in the computer-readable storage memory produce an article of manufacture, the execution of which implements the function specified in the flowcharts' block(s). The computer program instructions may also be loaded onto a computer or other programmable apparatus to cause a series of operations to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide operations for implementing the functions specified in the flowcharts' block(s). As such, the operations of Figures 8-1 1 , when executed, convert a computer or processing circuitry into a particular machine configured to perform an example embodiment of the present invention. Accordingly, the operations of Figures 8-1 1 define an algorithm for configuring a computer or processing circuitry 22, e.g., processor, to perform an example embodiment. In some cases, a general purpose computer may be provided with an instance of the processor which performs the algorithm of Figures 8-1 1 to transform the general purpose computer into a particular machine configured to perform an example embodiment.

[0066] Accordingly, blocks of the flowcharts support combinations of means for performing the specified functions and combinations of operations for performing the specified functions. It will also be understood that one or more blocks of the flowchart, and combinations of blocks in the flowcharts, can be implemented by special purpose hardware -based computer systems which perform the specified functions, or combinations of special purpose hardware and computer instructions.

[0067] In some embodiments, certain ones of the operations above may be modified or further amplified as described below. Moreover, in some embodiments additional optional operations may also be included. It should be appreciated that each of the modifications, optional additions or amplifications below may be included with the operations above either alone or in combination with any others among the features described herein.

[0068] Figure 8 is a flow chart illustrating operations performed by an example communication device in accordance with some example embodiments of the present invention. As is shown with respect to operation 802, the apparatus 20 embodied, for example, by a communications device 10, may include means, such as the processing circuitry 22, the processor 24, the communication interface 26 or the like, for causing an uplink data transmission. The communications device 10 may include means, such as the processing circuitry 22, the processor 24, the communication interface 26 or the like, for causing a request for downlink data to be transmitted to the access point. In some example embodiments, the request is a downlink data pull request in an uplink data frame. Alternatively or additionally, the request may be added to a frame control in a medium access control frame.

[0069] As is shown with respect to operation 804, the apparatus 20 embodied, for example, by a communications device 10, may include means, such as the processing circuitry 22, the processor 24, or the like, for decoding an acknowledgement message received from an access point in response to the uplink transmission, the acknowledgement message configured to indicate that downlink data is buffered at the access point. The communications device 10, such as by the processing circuitry 22, the processor 24, or the like, may determine that downlink data is to be transmitted by the access point after the acknowledgement message based on the duration value in the decoded acknowledgement message, wherein the duration value includes a duration of a data transmission. [0070] As is shown with respect to operation 806, the apparatus 20 embodied, for example, by a communications device 10, may include means, such as the processing circuitry 22, the processor 24, or the like, for causing a powered state to be maintained in an instance in which the acknowledgement message indicates that downlink data is buffered at the access point. As is shown with respect to operation 808, the apparatus 20 embodied, for example, by a communications device 10, may include means, such as the processing circuitry 22, the processor 24, or the like, for causing a transition to a low power state in an instance in which the acknowledgement message does not indicate that downlink data is buffered at the access point. As is shown with respect to operation 810, the apparatus 20 embodied, for example, by a communications device 10, may include means, such as the processing circuitry 22, the processor 24, the communication interface 26 or the like, for receiving downlink data, wherein the downlink data is transmitted by the access point following a predetermined time interval (e.g. within a certain number of beacons or after a certain amount of time units, such as seconds, milliseconds, micro seconds or the like) after the acknowledgement message.

[0071] Figure 9 is a flow chart illustrating operations performed by an example access point in accordance with some example embodiments of the present invention. As is shown with respect to operation 902, the apparatus 20 embodied, for example, by an access point 12, may include means, such as the processing circuitry 22, the processor 24, the communication interface 26 or the like, for receiving an uplink data transmission from a communication device. In some example embodiments, the request is a downlink data pull request in an uplink data frame. Alternatively or additionally, the request may be added to a frame control in a medium access control frame.

[0072] As is shown with respect to operation 904, the apparatus 20 embodied, for example, by an access point 12, may include means, such as the processing circuitry 22, the processor 24 or the like, for causing a duration value to be added to the acknowledgement message, wherein the duration value includes a duration of a data transmission that is configured to indicate to the communication device that downlink data is to be transmitted after the acknowledgement. The access point 12, may include means, such as the processing circuitry 22, the processor 24 or the like, for causing a duration value to be added to the acknowledgement message, wherein the duration value includes a duration of a data transmission that is configured to indicate to the communication device that downlink data is to be transmitted after the acknowledgement.

[0073] As is shown with respect to operation 906, the apparatus 20 embodied, for example, by an access point 12, may include means, such as the processing circuitry 22, the processor 24, the communication interface 26 or the like, for causing an acknowledgement message to be transmitted to the communication device, the acknowledgement message configured to indicate that downlink data is buffered. As is shown with respect to operation 908, the apparatus 20 embodied, for example, by an access point 12, may include means, such as the processing circuitry 22, the processor 24, the communication interface 26 or the like, for causing the downlink data to be transmitted to the communication device in a transmission following a predetermined time interval (e.g. within a certain number of beacons or after a certain amount of time units, such as seconds, milliseconds, micro seconds or the like) after the transmission of the acknowledgement message.

[0074] Figure 10 is a flow chart illustrating operations performed by an example communication device in accordance with some example embodiments of the present invention. As is shown with respect to operation 1002, the apparatus 20 embodied, for example, by a communications device 10, may include means, such as the processing circuitry 22, the processor 24, the communication interface 26 or the like, for causing a request to operate in a pull only mode to be transmitted to an access point, wherein in an instance in which pull only mode is activated the access point is configured to transmit downlink data within a predetermined duration of receiving a downlink data delivery request. As is shown with respect to operation 1004, the apparatus 20 embodied, for example, by a communications device 10, may include means, such as the processing circuitry 22, the processor 24, the communication interface 26 or the like, for causing the downlink data delivery request from to be transmitted to the access point. As is shown with respect to operation 1006, the apparatus 20 embodied, for example, by a communications device 10, may include means, such as the processing circuitry 22, the processor 24, the communication interface 26 or the like, for receiving downlink data in response to the downlink data delivery. [0075] The communications device 10, may include means, such as the processing circuitry 22, the processor 24, the communication interface 26 or the like, for receiving an acknowledgment request from the access point and causing a transition to a lower power mode in an instance in which downlink data is not received prior to a next scheduled beacon frame. The communications device 10 may further receive an indication that a POM mode has been deactivated.

[0076] Figure 11 is a flow chart illustrating operations performed by an example access point in accordance with some example embodiments of the present invention. As is shown with respect to operation 1102, the apparatus 20 embodied, for example, by an access point 12, may include means, such as the processing circuitry 22, the processor 24, the communication interface 26 or the like, for receiving a request to operate in a pull only mode. As is shown with respect to operation 1 104, the apparatus 20 embodied, for example, by an access point 12, may include means, such as the processing circuitry 22, the processor 24, the communication interface 26 or the like, for receiving a downlink data delivery request from a communication device.

[0077] As is shown with respect to operation 1 106, the apparatus 20 embodied, for example, by an access point 12, may include means, such as the processing circuitry 22, the processor 24, the communication interface 26 or the like, for causing downlink data to be transmitted, wherein the downlink data is configured to be transmitted within a predetermined duration of receiving a downlink data delivery request. The apparatus 20 embodied, for example, by an access point 12, may include means, such as the processing circuitry 22, the processor 24, the communication interface 26 or the like, for causing an acknowledgment request to be transmitted, wherein the communication device is configured to transition to a low power mode in an instance in which downlink data is not received prior to a next scheduled beacon frame. The access point 12 may further cause an indication that a pull only mode has been deactivated to be transmitted.

[0078] Alternatively or additionally and in one example embodiment, the systems and methods described herein may be configured for use in LTE device to device (D2D) communications, which may, for example, be configured to operate in a random access mode in addition to an infrastructure mode. Alternatively or additionally, the systems and methods described herein may also be configured for use in cellular machine to machine (M2M) communications in an instance in which transmission of DL data may occur within a predetermined period and in response to a UL data transmission. The systems and methods described herein may further be configured to operate in time division duplex (TDD) and frequency division duplex (FDD) systems where timing relations between downlink and uplink transmissions may be defined as "next available Uplink frame." For example, an access point may prioritize a DL transmission for a communications device which has just transmitted UL data. Advantageously and by way of further example, such an implementation enables a communication device to enter low power state or sleep state as fast as possible.

[0079] Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe example embodiments in the context of certain example combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

CLAIMS:

1. A method, c h a r a c t e r i z e d in comprising:

causing (802) an uplink data transmission;

decoding (804) an acknowledgement message received from an access point in response to the uplink data transmission, the acknowledgement message configured to indicate that downlink data is buffered at the access point; and

receiving (810) downlink data, wherein the downlink data is transmitted by the access point following a predetermined time interval after the acknowledgement message.

2. A method according to Claim 1, further comprising:

causing (806) a powered state to be maintained in an instance in which the acknowledgement message indicates that downlink data is buffered at the access point; and

causing (808) a transition to a low power state in an instance in which the acknowledgement message does not indicate that downlink data is buffered at the access point.

3. A method according to Claim 1 or 2, further comprising:

causing a request for downlink data to be transmitted to the access point.

4. A method according to Claim 3, wherein the request for downlink data is a downlink data pull request in an uplink data frame.

5. A method according to Claim 3, wherein the request for downlink data is added to a frame control in a medium access control frame.

6. A method according to any of Claims 1-5, further comprising: determining that downlink data is to be transmitted by the access point after the acknowledgement message based on a duration value in the decoded acknowledgement message, wherein the duration value includes a duration of a downlink data transmission.

7. A method according to any of Claims 1-6, wherein the downlink data is received within a duration indicated by a duration field in the decoded acknowledgement message.

8. A method according to any of Claims 1-7, wherein the acknowledgement message is a final acknowledgement message of a transmission sequence in an instance in which the uplink data transmission is segmented.

9. A method according to any of Claims 1-8, further comprising:

causing a transmission of buffered uplink data in response to receiving the downlink data.

10. An apparatus (10) comprising:

at least one processor; and

at least one memory including computer program code, c h a r a c t e r i z e d in that the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus (10) to at least:

cause an uplink data transmission;

decode an acknowledgement message received from an access point (12) in response to the uplink data transmission, the acknowledgement message configured to indicate that downlink data is buffered at the access point (12); and receive downlink data, wherein the downlink data is transmitted by the access point (12) following a predetermined time interval after the acknowledgement message.

11. An apparatus (10) according to Claim 10, wherein the at least one memory including the computer program code is further configured to, with the at least one processor, cause the apparatus (10) to:

cause a powered state to be maintained in an instance in which the acknowledgement message indicates that downlink data is buffered at the access point (12); and

cause a transition to a low power state in an instance in which the acknowledgement message does not indicate that downlink data is buffered at the access point (12).

12. An apparatus (10) according to Claim 10 or 11 , wherein the at least one memory including the computer program code is further configured to, with the at least one processor, cause the apparatus (10) to:

cause a request for downlink data to be transmitted to the access point (12).

13. An apparatus (10) according to Claim 12, wherein the request for downlink data is a downlink data pull request in an uplink data frame.

14. An apparatus (10) according to Claim 12, wherein the request for downlink data is added to a frame control in a medium access control frame.

15. An apparatus (10) according to any of Claims 10-14, wherein the at least one memory including the computer program code is further configured to, with the at least one processor, cause the apparatus (10) to: determine that downlink data is to be transmitted by the access point (12) after the acknowledgement message based on a duration value in the decoded acknowledgement message, wherein the duration value includes a duration of a downlink data transmission.

16. An apparatus (10) according to any of Claims 10-15, wherein the downlink data is received within a duration indicated by a duration field in the decoded acknowledgement message.

17. An apparatus (10) according to any of Claims 10-16, wherein the acknowledgement message is a final acknowledgement message of a transmission sequence in an instance in which the uplink data transmission is segmented.

18. An apparatus (10) according to any of Claims 10-17, wherein the at least one memory including the computer program code is further configured to, with the at least one processor, cause the apparatus (10) to:

cause a transmission of buffered uplink data in response to receive the downlink data.

19. A computer program product comprising:

at least one computer readable non-transitory memory medium having program code stored thereon, c h a r a c t e r i z e d in that the program code which when executed by an apparatus (10) cause the apparatus (10) at least to:

cause (802) an uplink data transmission;

decode (804) an acknowledgement message received from an access point (12) in response to the uplink data transmission, the acknowledgement message configured to indicate that downlink data is buffered at the access point (12); and receive (810) downlink data, wherein the downlink data is transmitted by the access point (12) following a predetermined time interval after the acknowledgement message.

20. A computer program product according to Claim 19, further comprising program code instructions configured to:

cause (806) a powered state to be maintained in an instance in which the acknowledgement message indicates that downlink data is buffered at the access point (12); and

cause (808) a transition to a low power state in an instance in which the acknowledgement message does not indicate that downlink data is buffered at the access point (12).

21 . A computer program product according to Claim 19 or 20, further comprising program code instructions configured to:

cause a request for downlink data to be transmitted to the access point (12).

22. A computer program product according to Claim 21 , wherein the request for downlink data is a downlink data pull request in an uplink data frame.

23. A computer program product according to Claim 21 , wherein the request for downlink data is added to a frame control in a medium access control frame.

24. A computer program product according to any of Claims 19-23, further comprising program code instructions configured to:

determine that downlink data is to be transmitted by the access point (12) after the acknowledgement message based on a duration value in the decoded acknowledgement message, wherein the duration value includes a duration of a downlink data transmission.

25. A computer program product according to any of Claims 19-24, wherein the downlink data is received within a duration indicated by a duration field in the decoded acknowledgement message.

26. A computer program product according to any of Claims 19-25, wherein the acknowledgement message is a final acknowledgement message of a transmission sequence in an instance in which the uplink data transmission is segmented.

27. A computer program product according to any of Claims 19-26, further comprising program code instructions configured to:

28. An apparatus (10), c h a r a c t e r i z e d in comprising:

means for causing an uplink data transmission;

means for decoding an acknowledgement message received from an access point (12) in response to the uplink data transmission, the acknowledgement message configured to indicate that downlink data is buffered at the access point (12); and

means for receiving downlink data, wherein the downlink data is transmitted by the access point (12) following a predetermined time interval after the acknowledgement message.

29. An apparatus (10) according to Claim 28, further comprising:

means for causing a powered state to be maintained in an instance in which the acknowledgement message indicates that downlink data is buffered at the access point (12); and means for causing a transition to a low power state in an instance in which the acknowledgement message does not indicate that downlink data is buffered at the access point (12).

30. An apparatus (10) according to Claim 28 or 29, further comprising:

means for causing a request for downlink data to be transmitted to the access point (12).

31. An apparatus (10) according to Claim 30, wherein the request for downlink data is a downlink data pull request in an uplink data frame.

32. An apparatus (10) according to Claim 30, wherein the request for downlink data is added to a frame control in a medium access control frame.

33. An apparatus (10) according to any of Claims 28-32, further comprising:

means for determining that downlink data is to be transmitted by the access point (12) after the acknowledgement message based on a duration value in the decoded acknowledgement message, wherein the duration value includes a duration of a downlink data transmission.

34. An apparatus (10) according to any of Claims 28-33, wherein the downlink data is received within a duration indicated by a duration field in the decoded acknowledgement message.

35. An apparatus (10) according to any of Claims 28-34, wherein the acknowledgement message is a final acknowledgement message of a transmission sequence in an instance in which the uplink data transmission is segmented.

36. An apparatus (10) according to any of Claims 28-35, further comprising: means for causing a transmission of buffered uplink data in response to means for receiving the downlink data.

37. A method, c h a r a c t e r i z e d in comprising:

receiving (902) an uplink data transmission from a communication device; causing (906) an acknowledgement message to be transmitted to the communication device, the acknowledgement message configured to indicate that downlink data is buffered; and

causing (908) the downlink data to be transmitted to the communication device in a transmission following a predetermined time interval after the transmission of the acknowledgement message.

38. A method according to Claim 37, wherein in an instance in which the acknowledgement message indicates that downlink data is buffered, a power state of the communication device is configured to be maintained such that the communication device receives the downlink data.

39. A method according to Claim 37 or 38, further comprising;

receiving a request for downlink data to be transmitted from the communication device.

40. A method according to Claim 39, wherein the request is a downlink data pull request in an uplink data frame.

41. A method according to Claim 39, wherein the request is added to a frame control in a medium access control frame.

42. A method according to any of Claims 37-41 , further comprising;

causing (904) a duration value to be added to the acknowledgement message, wherein the duration value includes a duration of a data transmission that is configured to indicate to the communication device that downlink data is to be transmitted after the acknowledgement message.

43. A method according to any of Claims 37-42, wherein the acknowledgement message is a final acknowledgement message of a transmission sequence in an instance in which the uplink data transmission is segmented.

44. A method according to any of Claims 37-43, wherein the downlink data is configured to be transmitted in segments.

45. A method according to any of Claims 37-44, further comprising:

receiving uplink data in response to the transmission of the downlink data, wherein the uplink data was buffered at the communication device.

46. An apparatus (12) comprising:

at least one processor; and

at least one memory including computer program code, c h a r a c t e r i z e d in that the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus (12) to at least:

receive an uplink data transmission from a communication device (10); cause an acknowledgement message to be transmitted to the communication device (10), the acknowledgement message configured to indicate that downlink data is buffered; and cause the downlink data to be transmitted to the communication device (10) in a transmission following a predetermined time interval after the transmission of the acknowledgement message.

47. An apparatus (12) according to Claim 46, wherein in an instance in which the acknowledgement message indicates that downlink data is buffered, a power state of the communication device (10) is configured to be maintained such that the communication device (10) receives the downlink data.

48. An apparatus (12) according to Claim 46 or 47, wherein the at least one memory including the computer program code is further configured to, with the at least one processor, cause the apparatus to;

receive a request for downlink data to be transmitted from the communication device (10).

49. An apparatus (12) according to Claim 48, wherein the request is a downlink data pull request in an uplink data frame.

50. An apparatus (12) according to Claim 48, wherein the request is added to a frame control in a medium access control frame.

51. An apparatus (12) according to any of Claims 46-50, wherein the at least one memory including the computer program code is further configured to, with the at least one processor, cause the apparatus (12) to;

cause a duration value to be added to the acknowledgement message, wherein the duration value includes a duration of a data transmission that is configured to indicate to the communication device (10) that downlink data is to be transmitted after the acknowledgement message.

52. An apparatus (12) according to any of Claims 46-51 , wherein the acknowledgement message is a final acknowledgement message of a transmission sequence in an instance in which the uplink data transmission is segmented.

53. An apparatus (12) according to any of Claims 46-52, wherein the downlink data is configured to be transmitted in segments.

54. An apparatus (12) according to any of Claims 46-53, wherein the at least one memory including the computer program code is further configured to, with the at least one processor, cause the apparatus (12) to:

receive uplink data in response to the transmission of the downlink data, wherein the uplink data was buffered at the communication device (10).

55. A computer program product comprising:

at least one computer readable non-transitory memory medium having program code stored thereon, c h a r a c t e r i z e d in that the program code which when executed by an apparatus (12) cause the apparatus (12) at least to:

receive (902) an uplink data transmission from a communication device (10);

cause (906) an acknowledgement message to be transmitted to the communication device (10), the acknowledgement message configured to indicate that downlink data is buffered; and cause (908) the downlink data to be transmitted to the communication device (10) in a transmission following a predetermined time interval after the transmission of the acknowledgement message.

56. A computer program product according to Claim 55, wherein in an instance in which the acknowledgement message indicates that downlink data is buffered, a power state of the communication device (10) is configured to be maintained such that the communication device (10) receives the downlink data.

57. A computer program product according to Claim 55 or 56, further comprising program code instructions configured to;

58. A computer program product according to Claim 57, wherein the request is a downlink data pull request in an uplink data frame.

59. A computer program product according to Claim 57, wherein the request is added to a frame control in a medium access control frame.

60. A computer program product according to any of Claims 55-59, further comprising program code instructions configured to;

cause (904) a duration value to be added to the acknowledgement message, wherein the duration value includes a duration of a data transmission that is configured to indicate to the communication device (10) that downlink data is to be transmitted after the acknowledgement message.

61. A computer program product according to any of Claims 55-60, wherein the acknowledgement message is a final acknowledgement message of a transmission sequence in an instance in which the uplink data transmission is segmented.

62. A computer program product according to any of Claims 55-61 , wherein the downlink data is configured to be transmitted in segments.

63. A computer program product according to any of Claims 55-62, further comprising program code instructions configured to:

64. An apparatus (12), c h a r a c t e r i z e d in comprising:

means for receiving an uplink data transmission from a communication device (10);

means for causing an acknowledgement message to be transmitted to the communication device (10), the acknowledgement message configured to indicate that downlink data is buffered; and

means for causing the downlink data to be transmitted to the communication device (10) in a transmission following a predetermined time interval after the transmission of the acknowledgement message.

65. An apparatus (12) according to Claim 64, wherein in an instance in which the acknowledgement message indicates that downlink data is buffered, a power state of the communication device (10) is configured to be maintained such that the communication device (10) receives the downlink data.

66. An apparatus (12) according to Claim 64 or 65, further comprising;

means for receiving a request for downlink data to be transmitted from the communication device (10).

67. An apparatus (12) according to Claim 66, wherein the request is a downlink data pull request in an uplink data frame.

68. An apparatus (12) according to Claim 66, wherein the request is added to a frame control in a medium access control frame.

69. An apparatus (12) according to any of Claims 64-68, further comprising;

means for causing a duration value to be added to the acknowledgement message, wherein the duration value includes a duration of a data transmission that is configured to indicate to the communication device (10) that downlink data is to be transmitted after the acknowledgement message.

70. An apparatus (12) according to any of Claims 64-69, wherein the acknowledgement message is a final acknowledgement message of a transmission sequence in an instance in which the uplink data transmission is segmented.

71 . An apparatus (12) according to any of Claims 64-70, wherein the downlink data is configured to be transmitted in segments.

72. An apparatus (12) according to any of Claims 64-71 , further comprising:

means for receiving uplink data in response to the transmission of the downlink data, wherein the uplink data was buffered at the communication device (10).

73. A method, c h a r a c t e r i z e d in comprising:

causing (1002) a request to operate in a pull only mode to be transmitted to an access point, wherein in an instance in which pull only mode is activated the access point is configured to transmit downlink data within a predetermined duration of receiving a downlink data delivery request; causing (1004) the downlink data delivery request from to be transmitted to the access point; and

receiving (1006) downlink data in response to the downlink data delivery request.

74. A method according to Claim 73, further comprising:

receiving an acknowledgment request from the access point; and

causing a transition to a lower power mode in an instance in which downlink data is not received prior to a next scheduled beacon frame.

75. A method according to Claim 73 or 74, further comprising:

receiving an indication that a pull only mode has been deactivated.

76. An apparatus (10) comprising:

at least one processor; and

cause a request to operate in a pull only mode to be transmitted to an access point (12), wherein in an instance in which pull only mode is activated the access point (12) is configured to transmit downlink data within a predetermined duration of receive a downlink data delivery request;

cause the downlink data delivery request from to be transmitted to the access point (12); and

receive downlink data in response to the downlink data delivery request.

77. An apparatus (10) according to Claim 76, wherein the at least one memory including the computer program code is further configured to, with the at least one processor, cause the apparatus (10) to:

receive an acknowledgment request from the access point (12); and cause a transition to a lower power mode in an instance in which downlink data is not received prior to a next scheduled beacon frame.

78. An apparatus (10) according to Claim 76 or 77, wherein the at least one memory including the computer program code is further configured to, with the at least one processor, cause the apparatus (10) to:

receive an indication that a pull only mode has been deactivated.

79. A computer program product comprising:

cause (1002) a request to operate in a pull only mode to be transmitted to an access point (12), wherein in an instance in which pull only mode is activated the access point (12) is configured to transmit downlink data within a predetermined duration of receive a downlink data delivery request;

cause (1004) the downlink data delivery request from to be transmitted to the access point (12); and

receive () 1006 downlink data in response to the downlink data delivery request.

80. A computer program product according to Claim 79, further comprising program code instructions configured to:

81 . A computer program product according to Claim 79 or 80, further comprising program code instructions configured to: receive an indication that a pull only mode has been deactivated.

82. An apparatus (10), c h a r a c t e r i z e d in further comprising:

means for causing a request to operate in a pull only mode to be transmitted to an access point (12), wherein in an instance in which pull only mode is activated the access point (12) is configured to transmit downlink data within a predetermined duration of receive a downlink data delivery request;

means for causing the downlink data delivery request from to be transmitted to the access point (12); and

means for receiving downlink data in response to the downlink data delivery request.

83. An apparatus (10) according to Claim 82, further comprising:

means for receiving an acknowledgment request from the access point (12); and

means for causing a transition to a lower power mode in an instance in which downlink data is not received prior to a next scheduled beacon frame.

84. An apparatus (10) according to Claim 82 or 83, further comprising:

means for receiving an indication that a pull only mode has been deactivated.

85. A method, c h a r a c t e r i z e d in comprising:

receiving (1102) a request to operate in a pull only mode;

receiving (1104) a downlink data delivery request from a communication device; and

causing (1106) downlink data to be transmitted, wherein the downlink data is configured to be transmitted within a predetermined duration of receiving a downlink data delivery request.

86. A method according to Claim 85, further comprising:

causing an acknowledgment request to be transmitted, wherein the communication device is configured to transition to a low power mode in an instance in which downlink data is not received prior to a next scheduled beacon frame.

87. A method according to Claim 85 or 86, further comprising:

causing an indication that a pull only mode has been deactivated to be transmitted.

88. An apparatus (12) comprising:

at least one processor; and

receive a request to operate in a pull only mode;

receive a downlink data delivery request from a communication device (10); and

cause downlink data to be transmitted, wherein the downlink data is configured to be transmitted within a predetermined duration of receive a downlink data delivery request.

89. An apparatus (12) according to Claim 88, wherein the at least one memory including the computer program code is further configured to, with the at least one processor, cause the apparatus (12) to:

cause an acknowledgment request to be transmitted, wherein the communication device (10) is configured to transition to a low power mode in an instance in which downlink data is not received prior to a next scheduled beacon frame.

90. An apparatus (12) according to Claim 88 or 89, wherein the at least one memory including the computer program code is further configured to, with the at least one processor, cause the apparatus (12) to:

cause an indication that a pull only mode has been deactivated to be transmitted.

91. A computer program product comprising:

receive (1102) a request to operate in a pull only mode;

receive (1104) a downlink data delivery request from a communication device (10); and

cause (1106) downlink data to be transmitted, wherein the downlink data is configured to be transmitted within a predetermined duration of receive a downlink data delivery request.

92. A computer program product according to Claim 91 , further comprising program code instructions configured to:

93. A computer program product according to Claim 91 or 92, further comprising program code instructions configured to:

94. An apparatus (12), c h a r a c t e r i z e d in comprising:

means for receiving a request to operate in a pull only mode;

means for receiving a downlink data delivery request from a communication device (10); and

means for causing downlink data to be transmitted, wherein the downlink data is configured to be transmitted within a predetermined duration of receiving a downlink data delivery request.

95. An apparatus (12) according to Claim 94, further comprising:

means for causing an acknowledgment request to be transmitted, wherein the communication device (10) is configured to transition to a low power mode in an instance in which downlink data is not received prior to a next scheduled beacon frame.

96. An apparatus (12) according to Claim 94 or 95, further comprising:

means for causing an indication that a pull only mode has been deactivated to be transmitted.