WO2017194162A1

WO2017194162A1 - Transmission/reception sweeping subframe

Info

Publication number: WO2017194162A1
Application number: PCT/EP2016/060867
Authority: WO
Inventors: Esa Tapani Tiirola; Sami-Jukka Hakola; Kari Pekka Pajukoski; Eeva LAHETKANGAS
Original assignee: Nokia Solutions And Networks Oy
Priority date: 2016-05-13
Filing date: 2016-05-13
Publication date: 2017-11-16

Abstract

Various physical layer design considerations may benefit various communication systems. For example, fifth generation (5G) sidelink / self-backhaul may benefit from a suitable transmission (TX) / reception (RX) sweeping subframe. A method can include determining, by a network element, to conduct a communication process on a subframe. The method can also include conducting, by the network element, the communication process on the subframe. The subframe can include a plurality of communication opportunities. The communication opportunities can include a plurality of reception opportunities and a plurality of transmission opportunities. Each communication opportunity of the plurality of communication opportunities can include at least one symbol and a cyclic prefix. The subframe can include a plurality of guard periods adjacent to the communication opportunities. The network element can include a user equipment or access node.

Description

DESCRIPTION

TITLE

Transmission/Reception Sweeping Subframe

BACKGROUND: Field :

[0001 ] Various physical layer design considerations may benefit various communication systems. For example, fifth generation (5G) sidelink / self-backhaul / URLLC (Ultra Reliable Low Latency Communications) may benefit from a suitable transmission (TX) / reception (RX) sweeping subframe.

Description of the Related Art:

[0002] 5G New Radio physical layer includes a variety of considerations, such as physical layer design related to frame structure providing inbuilt support for certain features like a sidelink for device-to-device (D2D) communication, as well as and Ultra Reliable Low Latency Communication (URLLC). It may be desirable for such a physical layer frame structure to support at least the following: frequency division duplex (FDD) arrangement, time division duplex (TDD) arrangement, downlink transmission, uplink transmission, sidelink transmission, access link, backhau l/relay link, standalone operation in licensed band, non- standalone operation in licensed band, and licensed-assisted operation in unlicensed band.

[0003] Latency targets for such systems are described in document 3GPP TR38.913 "Study on Scenarios and Requirements for Next Generation Access Technologies." Within such a context, for URLLC the target for user plane latency should be 0.5ms for uplink (UL) and 0.5ms for downlink (DL). Furthermore, if possible, the latency should also be low enough to support the use of the next generation access technologies as a wireless transport technology that can be used within the next generation access architecture.

[0004] Various subframe formats may be considered for the access link. Figure 1 illustrates several subframe formats. TDD design in 5G is based on bi-directional subframe. It provides link direction switching between DL and UL, fully flexible traffic adaptation between UL and DL, and opportunity for low latency, provided that subframe length and/or transmission time interval (TTI) length is selected to be short enough.

[0005] In addition to bi-directional subframes, there are also DL subframes and UL subframes, as shown in Figure 1 . These may be needed at least in FDD mode, but also in certain TDD scenarios to allow longer transmission periods in the same direction. In order to support smooth coverage extension for an UE, it should be possible to extend the transmission of data and control channels over multiple subframes.

SUMMARY: [0006] According to certain embodiments, a method can include determining, by a network element, to conduct a communication process on a subframe. The method can also include conducting, by the network element, the communication process on the subframe. The subframe can include a plurality of communication opportunities. The communication opportunities can include a plurality of reception opportunities and a plurality of transmission opportunities. Each communication opportunity of the plurality of communication opportunities can include at least one symbol, e.g. OFDM symbol and associated cyclic prefix. The subframe can include a plurality of guard periods adjacent to the communication opportunities. The network element can include a user equipment or access node.

[0007] In certain embodiments, an apparatus can include at least one processor and at least one memory including computer program code. The at least one memory and the computer program code can be configured, to, with the at least one processor, cause the apparatus at least to determine, by a network element, to conduct a communication process on a subframe. The at least one memory and the computer program code can also be configured, to, with the at least one processor, cause the apparatus at least to conduct, by the network element, the communication process on the subframe. The subframe can include a plurality of communication opportunities. The communication opportunities can include a plurality of reception opportunities and a plurality of transmission opportunities. Each communication opportunity of the plurality of communication opportunities can include at least one symbol. The subframe can include a plurality of guard periods adjacent to the communication opportunities. The network element can include a user equipment or access node.

[0008] An apparatus, according to certain embodiments, can include means for determining, by a network element, to conduct a communication process on a subframe. The apparatus can also include means for conducting, by the network element, the communication process on the subframe. The subframe can include a plurality of communication opportunities. The communication opportunities can include a plurality of reception opportunities and a plurality of transmission opportunities. Each communication opportunity of the plurality of communication opportunities can include at least one symbol. The subframe can include a plurality of guard periods adjacent to the communication opportunities. The network element can include a user equipment or access node.

[0009] A computer program product, according to certain embodiments, can include instructions for performing a process. The process can include determining, by a network element, to conduct a communication process on a subframe. The process can also include conducting, by the network element, the communication process on the subframe. The subframe can include a plurality of communication opportunities. The communication opportunities can include a plurality of reception opportunities and a plurality of transmission opportunities. Each communication opportunity of the plurality of communication opportunities can include at least one symbol. The subframe can include a plurality of guard periods adjacent to the communication opportunities. The network element can include a user equipment or access node.

[0010] A non-transitory computer-readable medium can, in certain embodiments, be encoded with instructions that, when executed in hardware, perform a process. The process can include determining, by a network element, to conduct a communication process on a subframe. The process can also include conducting , by the network element, the communication process on the subframe. The subframe can include a plurality of communication opportunities. The communication opportunities can include a plurality of reception opportunities and a plurality of transmission opportunities. Each communication opportunity of the plurality of communication opportunities can include at least one symbol. The subframe can include a plurality of guard periods adjacent to the communication opportunities. The network element can include a user equipment or access node. BRIEF DESCRIPTION OF THE DRAWINGS:

[0011 ] For proper understanding of the invention, reference should be made to the accompanying drawings, wherein :

[0012] Figure 1 illustrates several subframe formats.

[0013] Figure 2 illustrates envisioned subframe types for 5G system.

[0014] Figure 3 illustrates a scenario with three user equipment employing sidelink.

[0015] Figure 4 illustrates a sweeping/discovery subframe according to certain embodiments.

[0016] Figure 5A illustrates configuration options according to certain embodiments.

[0017] Figure 5B illustrates a URRLC subframe format according to certain embodiments.

[0018] Figure 5C illustrates a subframe configuration according to certain embodiments. [0019] Figure 6 illustrates Tx/Rx patterns, according to certain embodiments.

[0020] Figure 7 illustrates a combination of RF sweeping and Tx/Rx sweeping, according to certain embodiments.

[0021 ] Figure 8 illustrates discovery between a node having multiple RF beams and UEs with an omni-antenna assumption, according to certain embodiments.

[0022] Figure 9 illustrates a method according to certain embodiments.

[0023] Figure 10 illustrates a system according to certain embodiments.

DETAILED DESCRIPTION: [0024] Figure 2 illustrates envisioned subframe types for 5G system. In Figure 2, Dc refers to DL control, Dd refers to Downlink Data, GP refers to Guard Period, Ud refers to Uplink data, and Uc refers to Uplink Control. Link direction switching with one Tx-Rx (DL-UL) cycle per subframe can be supported with subframe configurations including the guard period (GP).

[0025] Access link control signaling can be built (at least partially) around two control parts of the subframe (Dc, Uc). For example, sidelink could apply the same approach as data subframe configuration #1 or #7 of Figure 2. One issue related to current subframe types is that they cannot support bi-directional sidelink communication among more than two devices within a subframe. Figure 3 illustrates a scenario with three user equipment employing sidelink.

[0026] In Figure 3, half-duplex communications are assumed: UE cannot transmit on a certain carrier when the UE is receiving and vice versa. Half-duplex constraint applies typically when operating in unpaired band, whereas full-duplex communication is the baseline when operating in paired bands. However, half-duplex constraint may apply also at least for certain UE categories and/or band combinations in paired bands. Furthermore, half- duplex communication may be applied for sidelink communications when operating in a part (such as UL part) of the paired band. Two control portions of the subframe can be applied either in Tx or Rx phase. Four different Tx/Rx patterns can be assigned within a subframe: [Tx, Tx], which may not be relevant for bi-directional communication within a subframe; [Tx, Rx]; [Rx, Tx]; and [Rx, Rx], which may not be relevant for bi-directional communication within a subframe. Thus, only two patterns may provide bi-directional communications within a subframe. Hence, if the number of UEs involved is larger than two, it may not be possible to support bi-directional communication within a subframe in such a sidelink scenario. The same principle can also apply to any scenario with half-duplex nodes, such as communication between relay nodes (RNs) or eNBs. [0027] Taking multiple subframes together can address this issue of providing bi-directional communication for multiple user equipment. In such a case, there can be more than two Tx/Rx portions to use. These portions may not be consecutive but may be distributed in time over multiple subframes. Moreover, multiple Tx/Rx portions can support or enable increase of the pattern length. Increased pattern length can enable an increased number of UEs with bi-directional communication during the pattern length.

[0028] However, following this approach it may take a long time to support bidirectional control plane among all involved nodes, in order to support a sidelink/mesh network involving a high number of nodes. This may affect Key Performance Indicators (KPIs) defined for 5G. The effects may include the following: increased latency, increased battery consumption due to increased latency, and added complexity. Moreover, there may be considerable impact to access link operation. For example, a UE configured to participate in sidelink operation may not be able to transmit or receive control signaling to/from an evolved node B (eNB).

[0029] An additional issue may arise in use cases like discovery among nodes. In such cases nodes typically exchange small packets with each other. From a system complexity and UE complexity point of view, discovery occasions may beneficially be concentrated in time domain as much as possible. For example, it may be beneficial to avoid distributing a discovery process over multiple subframes on a per discovery period basis.

[0030] Furthermore, very frequent DLAIL data transmission opportunity may be needed in order to meet a user plane latency of, for example, 0.5ms for UL and 0.5ms for DL (even simultaneously). Thus, simply aggregating multiple subframes to provide more transmission opportunities may have an impact on latency.

[0031 ] Figure 4 illustrates a sweeping/discovery subframe according to certain embodiments. As illustrated in Figure 4, a sweeping/discovery subframe can be employed to facilitate low latency communication channel and/or for a control plane for sidelink/self- backhauling/multi-hop relaying.

[0032] The sweeping/discovery subframe can include the following aspects, as shown in Figure 4. The sweeping subframe can include multiple Tx/Rx opportunities, shown with dark shading. These Tx/Rx opportunities can also collectively be referred to as communication opportunities. Moreover, each Tx/Rx opportunity can contain one or more OFDMA symbols and can have an associated cyclic prefix (CP). Each Tx/Rx opportunity can contain one or more parallel resources. Each resource may contain a reference signal (RS) resource and/or a RS and data or control information resource.

[0033] Symbol timing can be arranged such that a guard period (GP) is included between different Tx/Rx opportunities within the sweeping/discovery subframe. The GP can provide an opportunity for link direction switching between Tx/Rx opportunities. The GP can also be included at the beginning and at the end of the sweeping portion, for example at the beginning and at the end of the sweeping subframe. GP duration may be predefined by the standard and it may vary according to configuration and/or scenario. At least some of the GPs, e.g. the one at the end of the sweeping portion, may be created using timing advance.

[0034] According to a first option, room for the plurality of GPs can be achieved by means of puncturing one or more OFDMA symbols from the subframe. The rest of the symbols can be used for building a number of Tx/Rx opportunities.

[0035] In the example of Figure 4, the subframe can include 14 OFDMA symbols. Of those, 9 OFDMA symbols can be used for providing 9 Tx/Rx opportunities within the sweeping/discovery subframe. The remaining resources, 5 OFDMA symbols, can be used for facilitating guard period within the sweeping/discovery subframe. The total GP time can be shared, for example as evenly as possible, around different Tx/Rx opportunities. The design shown in Figure 4 is just an example. Actual design may vary according to scenario. For example, the total number of symbols per subframe can be e.g. 7, 8, 14 or 16. Furthermore, the number of symbols reserved for Tx/Rx opportunities may be also larger (or smaller). For example, the share between Tx/Rx opportunities and GP in the 14 symbol case could be also 7/7, or 8/6, or (9/5), or 10/4, and so forth.

[0036] According to a second option, a specific scenario can be optimized for providing smooth coexistence between access link and sidelink/self-backhaul. In this option, symbol timing applied for an access link can also be maintained for the sweeping subframe. Switching gaps can be made by puncturing full symbols.

[0037] For example, Tx/Rx opportunities can be provided for symbols 1 , 3, 1 1 . Symbols 0, 2, 12 (and 13) can act as GP. Symbol 13 is an orphan symbol in the current example scenario (assuming that GP is required also in the end of sweeping subframe).

[0038] In one further implementation of this option, Tx/Rx opportunities can be provided for all symbols 1 , 2, 3, 1 1 . A pattern design can be made so that it allows the UE to lose one RX opportunity before and after its TX opportunity to be used for RX to TX and TX to RX switch, respectively, but still to detect all UEs within a certain discovery period.

[0039] This second option may allow fully synchronous operation between sidelink/self- backhaul and access link. Thus, this option may, for example, help to mitigate interference or the effects of interference. Latency target set for URLLC (Ultra-Reliable and Low Latency Communications) is relatively tough. This may be a challenging target especially when operating at relatively small sub-carrier spacing, such as 15 kHz sub- carrier spacing. [0040] Figure 5B illustrates a URRLC subframe format according to certain embodiments. One approach to support the latency target in this scenario is to define a specific URLLC subframe format, as illustrated in Figure 5B. An exemplary URLLC subframe as shown in Figure 5B can contain 7 OFDMA symbols, and extra GPs to support additional link direction switching within the subframe. The URLLC subframe can also support transmission and reception of up to two transport blocks/UE/spatial layer within a subframe. In this scenario, additional GP is not needed at the beginning of the URLLC subframe. GP at the end of subframe can be obtained using timing advance.

[0041 ] When considering UEs involved in Tx/Rx sweeping, there may be no room for data transmission or reception during the sweeping subframe. Control plane for access link may or may not be supported, as discussed below. However, other frequency resources in the related carrier may be used, for example, for UL communications for UEs not involved in Tx/Rx sweeping. In order to improve the coexistence especially when operating according to timing Option #1 , or for other reasons, the following principles can be applied. A guard band may be defined around the sidelink resources and/or filtering can be performed at BS receiving UL, which may be better for UEs that are performing sidelink, as it may have no direct impact on them.

[0042] Figure 5C illustrates a subframe configuration according to certain embodiments. In the embodiment illustrated in Figure 5C, the Tx/Rx opportunities are shown as arranged around fixed-size Mini slots. In the illustrated example, the subframe length is 7 symbols, with a subcarrier spacing of 15 kHz and symbol length of 66.6 microseconds (usee).

[0043] The Tx/Rx opportunities can be arranged around minislots of fixed size or approximately fixed size. For example, it may be approximately 0.125 ms. When the clock rate based on 30.72 MHz is applied, 16 extra (CP) samples may be included in the first CP corresponding to the 1 ^st symbol of the subframe. This will ensure symbol level alignment between LTE and 5G New Radio. At the same time, it may cause that those minislots are a bit longer, in terms of samples, compared to other minislots. Each minislot can contain a Tx/Rx opportunity, for example at least one symbol and corresponding CP. Size of GP in both sides of the Tx/RX opportunity may be predetermined. The minislot can also include related reference signals. There can also be GPs around the Tx/Rx opportunity.

[0044] The minislot can include a preamble. That kind of signal may be needed for example in sidelink to able to provide support for fast AGC and frequency/time synchronization.

[0045] In certain embodiments, the length of the sweeping subframe can be equal to the length of non-sweeping subframe. This may be an example of a sidelink being synchronized with the access link. Transmission and reception during a sweeping subframe can be controlled using predetermined patterns as briefly mentioned above and discussed in more detail below. The pattern length can be less than or equal to the number of Tx/Rx opportunities in the sweeping subframe.

[0046] In another embodiment, two or more sweeping Tx/Rx subframes can be combined together to build longer sequence of Tx/Rx opportunities. In this embodiment, pattern length can be greater than the number of Tx/Rx opportunities in the sweeping subframe. Increasing the pattern length can allow an increase in the number of nodes with bidirectional sounding capability.

[0047] Certain embodiments may combine radio frequency (RF) sweeping and Tx/Rx sweeping. Certain scenarios may utilize RF beamforming, which may involve sweeping also in the RF beam domain. This scenario may be relevant specifically in the self- backhauling scenarios where Access Points are operating at higher carrier frequency, such as cmWave or mmWave frequencies.

[0048] Nodes like relay or backhaul nodes may use hybrid architectures with one or multiple parallel RF beams. In discovery of such nodes, each RF beam can be considered as a discoverable node.

[0049] Parallel discovery resources can be allocated for the transceiver units (TXRU) of the node. An assumption may be that each transceiver unit would be able to form one RF beam at a time. In other words, a node (whether relay or backhaul) with N TXRUs, may be assigned N parallel TX RX resources.

[0050] In case of mixed discovery operation among different type of nodes, namely nodes with multiple more RF beams than TXRUs and nodes with equal number of RF beams and TXRUs such as a typical UE, the resource allocation can be made so that a first set of UEs, with more RF beams than TXRUs or which transmit discovery signal via multiple RF beams (for example, such UEs may advertise both node and beam), can be allocated consecutive TX resources without explicit GPs between each TX opportunity. By contrast, TX resources allocated to the second set of UEs may have GP between each of them. Thus, allocation of GPs can, in certain embodiments, be contingent on a determination of whether consecutive TX resources are under the control of a single device, such as a device having multiple TXRUs.

[0051 ] The sweeping/discovery subframe can be defined for low latency communication. Each Tx/Rx opportunity can contain one or more parallel data resources. Resources can be separated in frequency, space, or code domain. Moreover, the resources can be pre- allocated or contention based. The sweeping/discovery subframe can be triggered on an as-needed basis, rather than being triggered periodically. This need-based triggering may permit larger GP overhead for a sweeping/discovery subframe, as compared to a regular subframe applied for an access link.

[0052] Figure 5A illustrates configuration options according to certain embodiments. Configuration of the sweeping/discovery subframe may be built in different ways. As shown in Figure 5A, in option (a) a sweeping subframe can utilize the entire data portion of the bi-directional subframe. This option may allow opportunity for simultaneous DL and UL control plane for access link.

[0053] In option (b) , the sweeping subframe can contain DL control part of access link control (Dc) . In option (c), by contrast, the sweeping subframe can contain UL part of the access link control (Uc). In option (d), the sweeping subframe can occupy the entire subframe, similar to Figure 4.

[0054] There can be at least two options for sweeping/discovery subframe. According to a first option, sweeping/discovery subframes can be configured in a semi-static manner via higher layer signaling, such as RRC. The configuration may include subframe indices for the sweeping/discovery subframes, as well as the structure of the subframe. The configuration may also include information related to Tx/Rx pattern selection and radio resources to be applied.

[0055] According to a second option, sweeping subframes can be configured in dynamic manner, for example using common or group-specific Downlink Control Information (DCI). DCI may be transmitted, for example by eNB via DL part of the subframe. Triggering may involve a scheduling delay of /( subframes, where / may be an integer greater or equal to zero. Structure of the subframe, information related to Tx/Rx pattern selection as well as radio resources to be applied may be configured via higher layer signaling, such as RRC.

[0056] The sweeping subframe may have various uses. For example, the sweeping subframe can be used for sidelink discovery, bi-directional control plane for sidelink/self- backhaul, conveying a limited amount of data, and/or low latency communications, optionally include access link.

[0057] Figure 6 illustrates Tx/Rx patterns, according to certain embodiments. The Tx/Rx patterns shown in Figure 6 are just examples. Patterns can be designed in a way that bi- directional communication between all the patterns with the pattern length is guaranteed. Pattern length is 6 Tx/Rx phases in this example. The columns represent different Tx/Rx opportunities. Each row in this example corresponds to different Tx/Rx patterns having two transmitting phases and four receiving phases, respectively. When applying these patterns for D2D communications, each involved U E may apply a unique Tx/Rx pattern. The patterns can provide for bi-directional communications for 1 5 UEs, using a pattern length of 6, and two transmission phases. There are many parameters that can be varied such as pattern length and the number of Tx opportunities.

[0058] Figure 7 illustrates a combination of RF sweeping and Tx/Rx sweeping, according to certain embodiments. In this scenario, a discovery operation can take place among a relay node having hybrid architecture with one TXRU and 3 candidate RF beams, and two UEs. Thus, Figure 7 illustrates setup of one relay node and two UEs for discovery operation.

[0059] Figure 8 illustrates discovery between a node having multiple RF beams and UEs with an omni-antenna assumption, according to certain embodiments. As shown in Figure 8, two GP lengths can be defined inside a sweeping subframe. A first GP length can be for Tx/Rx sweeping. This GP can be within a cyclic prefix of an OFDM symbol as well. A second GP length can be for RF beam switching. Then, steps can include group communication from/to devices utilizing RF beam domain sweeping to certain subframes. The steps can also include group communication between devices with no beam switching need with normal GP for Tx/Rx switching to separate subframes.

[0060] Figure 9 illustrates a method according to certain embodiments. As shown in Figure 9, a method can include, at 910, determining, by a network element, to conduct a communication process on a subframe. This determination by the network element can involve any decision by the network element to conduct the communication process. Thus, communicating automatically is also included as an example of such determining. The determining step may be omitted in certain embodiments. The method can also include, at 920, conducting, by the network element, the communication process on the subframe.

[0061 ] The subframe can include a plurality of communication opportunities and the communication opportunities can include a plurality of reception opportunities and a plurality of transmission opportunities. Each communication opportunity of the plurality of communication opportunities can include at least one symbol and a cyclic prefix. The at least one symbol can be an orthogonal frequency division multiple access (OFDMA) symbol, orthogonal frequency division multiplexing (OFDM) symbol, or a single-carrier frequency division multiple access (SC-FDMA) symbol.

[0062] The subframe can also include a plurality of guard periods adjacent to the communication opportunities. The network element can be a user equipment or access node, broadly including, for example, relay nodes.

[0063] The subframe can be a sweeping subframe, for example a Tx/Rx sweeping subframe, as described above. The length of the sweeping subframe can equal the length of a corresponding non-sweeping subframe. For example, the sweeping subframe in sidelink can have the same length as a corresponding subframe in access. The non- sweeping subframe can be used for, for example, uni-directional communications with uni- directional control or uni-directional communications with bi-directional control.

[0064] Transmission and reception during the sweeping subframe can be controlled by using at least one predetermined pattern. The length of the predetermined pattern may be less than or equal to the number of communication opportunities in the sweeping subframe. Alternatively, two or more communication opportunities can be combined together to build a longer sequence of communication opportunities and a length of the predetermined pattern may be greater than the number of communication opportunities in the sweeping subframe.

[0065] Each of the plurality of transmission opportunities can include a plurality of parallel resources. Options for these parallel resources are described above. The parallel resources can include a reference signal resource, a reference signal and data or control information resource, or a both a reference signal resource and a reference signal and data or control information resource.

[0066] A plurality of guard periods can be provided by puncturing symbols from the subframe. For example, the entire subframe may be fourteen symbols. The subframe can include nine symbols used for the plurality of communication opportunities. The subframe can also include five symbols for facilitating guard periods.

[0067] In certain embodiments, symbol timing applied for an access link can also be maintained for the subframe. For example, the subframe can be a sidelink subframe that is synchronized with the access link.

[0068] The plurality of guard periods can include a guard period at a start of the subframe and a guard period at the end of the subframe. The guard period at the end of the subframe may be provided through timing advance instead of or in addition to being provided by puncturing.

[0069] The communication process can be a discovery process or any of the other communication processes described herein. For example, the communication process can include at least one of the following: sidelink/backhaul discovery, sidelink/backhaul scheduling, sidelink backhaul control signaling, sidelink/backhaul data communications, and low latency communications.

[0070] The network element performing the communication process can operate in unpaired spectrum under a half-duplex constraint. Unpaired spectrum can refer to spectrum in which an asymmetric uplink/downlink ratio is permitted, as distinct from paired spectrum.

[0071 ] Certain embodiments can address a combination of RF beamforming and sweeping subframe. For example, in certain embodiments the network element can be allocated parallel discovery resources for the transceiver units (TXRU) of the network element. For example, when each transceiver unit is able to form one RF beam at a time, the network element (for example, a relay node or backhaul node, with N TXRUs may be assigned N parallel TX/RX resources. The number of resources can correspond to the number transceiver units, either by being the same number or, for example in the case of each transceiver forming multiple RF beams, a multiple of the number of transceiver units.

[0072] In certain embodiments, a first type of user equipment and a second type of user equipment can be assigned transmission opportunities in the subframe. The first type of user equipment can be those UEs configured to advertise both node and beam and the second type of user equipment can be those UEs configured to advertise node only. The first type of user equipment and the second type of user equipment can be assigned corresponding guard period allocation.

[0073] Figure 10 illustrates a system according to certain embodiments of the invention. It should be understood that each block of the flowchart of Figure 9 may be implemented by various means or their combinations, such as hardware, software, firmware, one or more processors and/or circuitry. In one embodiment, a system may include several devices, such as, for example, network element 101 0 and user equipment (UE) or user device 1 020. The system may include more than one U E 1020 and more than one network element 101 0, although only one of each is shown for the purposes of illustration. A network element can be an access point, a base station, an eNode B (eNB) , or any other network element.

[0074] Each of these devices may include at least one processor or control unit or module, respectively indicated as 1014 and 1024. At least one memory may be provided in each device, and indicated as 1 015 and 1 025, respectively. The memory may include computer program instructions or computer code contained therein, for example for carrying out the embodiments described above. One or more transceiver 1016 and 1026 may be provided, and each device may also include an antenna, respectively illustrated as 1 017 and 1027. Although only one antenna each is shown, many antennas and multiple antenna elements may be provided to each of the devices. Other configurations of these devices, for example, may be provided. For example, network element 101 0 and UE 1 020 may be additionally configured for wired communication, in addition to wireless communication, and in such a case antennas 1017 and 1027 may illustrate any form of communication hardware, without being limited to merely an antenna.

[0075] Transceivers 101 6 and 1 026 may each, independently, be a transmitter, a receiver, or both a transmitter and a receiver, or a unit or device that may be configured both for transmission and reception. The transmitter and/or receiver (as far as radio parts are concerned) may also be implemented as a remote radio head which is not located in the device itself, but in a mast, for example. It should also be appreciated that according to the "liquid" or flexible radio concept, the operations and functionalities may be performed in different entities, such as nodes, hosts or servers, in a flexible manner. In other words, division of labor may vary case by case. One possible use is to make a network element to deliver local content. One or more functionalities may also be implemented as a virtual application that is provided as software that can run on a server.

[0076] A user device or user equipment 1020 may be a mobile station (MS) such as a mobile phone or smart phone or multimedia device, a computer, such as a tablet, provided with wireless communication capabilities, personal data or digital assistant (PDA) provided with wireless communication capabilities, vehicle, portable media player, digital camera, pocket video camera, navigation unit provided with wireless communication capabilities or any combinations thereof. The user device or user equipment 1 020 may be a sensor or smart meter, or other device that may usually be configured for a single location.

[0077] In an exemplifying embodiment, an apparatus, such as a node or user device, may include means for carrying out embodiments described above in relation to Figure 9.

[0078] Processors 1 014 and 1 024 may be embodied by any computational or data processing device, such as a central processing unit (CPU), digital signal processor (DSP), application specific integrated circuit (ASIC), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), digitally enhanced circuits, or comparable device or a combination thereof. The processors may be implemented as a single controller, or a plurality of controllers or processors. Additionally, the processors may be implemented as a pool of processors in a local configuration, in a cloud configuration, or in a combination thereof.

[0079] For firmware or software, the implementation may include modules or units of at least one chip set (e.g. , procedures, functions, and so on). Memories 1 01 5 and 1025 may independently be any suitable storage device, such as a non-transitory computer-readable medium. A hard disk drive (HDD), random access memory (RAM), flash memory, or other suitable memory may be used. The memories may be combined on a single integrated circuit as the processor, or may be separate therefrom. Furthermore, the computer program instructions may be stored in the memory and which may be processed by the processors can be any suitable form of computer program code, for example, a compiled or interpreted computer program written in any suitable programming language. The memory or data storage entity is typically internal but may also be external or a combination thereof, such as in the case when additional memory capacity is obtained from a service provider. The memory may be fixed or removable.

[0080] The memory and the computer program instructions may be configured, with the processor for the particular device, to cause a hardware apparatus such as network element 1 010 and/or UE 1 020, to perform any of the processes described above (see, for example, Figure 9). Therefore, in certain embodiments, a non-transitory computer- readable medium may be encoded with computer instructions or one or more computer program (such as added or updated software routine, applet or macro) that, when executed in hardware, may perform a process such as one of the processes described herein. Computer programs may be coded by a programming language, which may be a high-level programming language, such as objective-C, C, C++, C#, Java, etc. , or a low- level programming language, such as a machine language, or assembler. Alternatively, certain embodiments of the invention may be performed entirely in hardware.

[0081 ] Furthermore, although Figure 1 0 illustrates a system including a network element 1 010 and a UE 1020, embodiments of the invention may be applicable to other configurations, and configurations involving additional elements, as illustrated and discussed herein. For example, multiple user equipment devices and multiple network elements may be present, or other nodes providing similar functionality, such as nodes that combine the functionality of a user equipment and an access point, such as a relay node.

[0082] Certain embodiments may have various benefits and/or advantages. For example, certain embodiments may minimize latency from sidelink operations. In turn, such embodiments may also minimize UE battery consumption.

[0083] Certain embodiments may provide for low latency data communications. Although the GP overhead of a single sweeping/discovery subframe may be relatively high, total overhead including regular access link subframe may be reasonable

[0084] Certain embodiments may provide smooth integration into a 5G frame structure. Sidelink operation can be seen as an orthogonal subsystem with respect to access link operation. Moreover, certain embodiments may allow dynamic usage and smooth coexistence with access link operation. For example, it may be possible to maintain opportunities for access link control channels during the sweeping/discovery subframe. Additionally, certain embodiments may allow dynamic capacity allocation between sidelink/self-backhaul and access link.

[0085] One having ordinary skill in the art will readily understand that the invention as discussed above may be practiced with steps in a different order, and/or with hardware elements in configurations which are different than those which are disclosed. Therefore, although the invention has been described based upon these preferred embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of the invention.

[0086] List of Abbreviations

[0087] 5G The 5th Generation

[0088] BH Backhaul

[0089] cmWave Centimetre Wave

[0090] D2D De vice-to- Device

[0091 ] Dc Downlink Control

[0092] Dd Downlink Data

[0093] DL Downlink

[0094] eNB Enhanced Node B

[0095] GP Guard Period

[0096] IR Invention Report

[0097] LBT Listen Before Talk

[0098] mmWave Millimetre Wave

[0099] Rel Release

[0100] RF Radio Frequency

[0101 ] Rx Receiver

[0102] SIG Special Interest Group

[0103] SR Scheduling Request

[0104] TDD Time Division Duplexing

[0105] Tx Transmission

[0106] TXRU Transceiver Unit

[0107] Uc Uplink Control

[0108] Ud Uplink Data

[0109] UL Uplink

[01 10] ULRR Ultra-Reliable Low Laten

Claims

WE CLAIM:

1 . A method, comprising : determining, by a network element, to conduct a communication process on a subframe; and conducting, by the network element, the communication process on the subframe, wherein the subframe comprises a plurality of communication opportunities, wherein the communication opportunities comprise a plurality of reception opportunities and a plurality of transmission opportunities, wherein each communication opportunity of the plurality of communication opportunities comprises at least one symbol, wherein the subframe comprises a plurality of guard periods adjacent to the communication opportunities, and wherein the network element comprises a user equipment or access node.

2. The method of claim 1 , wherein the network element performing the communication process operates in unpaired spectrum under a half-duplex constraint.

3. The method of claim 1 or claim 2, wherein each communication opportunity of the plurality of communication opportunities comprises the at least one symbol and a cyclic prefix.

4. The method of any of claims 1 -3, wherein the subframe comprises a sweeping subframe defined for conducting the communication process on the subframe.

5. The method of claim 4, wherein a length of the sweeping subframe equals a length of a corresponding non-sweeping subframe, wherein non-sweeping subframe is used for at least one of: uni-directional communications with uni-directional control or unidirectional communications with bi-directional control.

6. The method of any of claims 1 -5, wherein transmission and reception during the sweeping subframe is controlled by using at least one predetermined pattern.

7. The method of claim 6, wherein a length of the predetermined pattern is less than or equal to a number of communication opportunities in the sweeping subframe.

8. The method of claim 6, wherein two or more communication opportunities are combined together to build a longer sequence of communication opportunities and a length of the predetermined pattern is greater than a number of communication opportunities in the sweeping subframe.

9. The method of any of claims 1 -8, wherein the at least one symbol comprises at least one of an orthogonal frequency division multiple access symbol, an orthogonal frequency division multiplexing symbol, or a single carrier frequency division multiple access symbol.

10. The method of any of claims 1 -9, wherein each of the plurality of transmission opportunities comprises a plurality of parallel resources.

1 1 . The method of claim 10, wherein the parallel resources comprise a reference signal resource, a reference signal and data or control information resource, or a both a reference signal resource and a reference signal and data or control information resource.

12. The method of any of claims 1 -1 1 , wherein a plurality of guard periods are provided by puncturing symbols from the subframe.

13. The method of any of claims 1 -12, wherein the subframe comprises M symbols, wherein K symbols are used for a plurality of communication opportunities and M-K symbols are used for facilitating guard periods.

14. The method of any of claims 1 -13, wherein symbol timing applied for an access link is also maintained for the subframe, wherein the subframe comprises a sidelink subframe.

15. The method of any of claims 1 -14, wherein the plurality of guard periods comprise a guard period at a start of the subframe and a guard period at the end of the subframe.

16. The method of any of claims 1 -1 5, wherein the communication process comprises at least one of the following: sidelink/backhaul discovery, sidelink/backhaul scheduling, sidelink backhaul control signaling, sidelink/backhaul data communications, and low latency communications.

17. The method of any of claims 1 -16, wherein parallel discovery resources are allocated for a plurality of transceiver units of the network element, wherein a number of parallel resources corresponds to a number of the plurality of transceiver units.

18. The method of any of claims 1 -17, wherein a first type of user equipment and a second type of user equipment are assigned transmission opportunities in the subframe.

19. The method claim 18, wherein the first type of user equipment is configured to advertise both node and beam and wherein the second type of user equipment is configured to advertise node only.

20. The method of claim 18 or claim 19, wherein the first type of user equipment and the second type of user equipment are assigned corresponding guard period allocation.

21 . The method of any of claims 1 -20, wherein the communication opportunities are provided in minislots, wherein each minislot comprises at least one of the communication opportunities surrounded by guard periods.

22. An apparatus, comprising: at least one processor; and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, to, with the at least one processor, cause the apparatus at least to perform the method according to any of claims 1 -21 .

23. An apparatus, comprising: means for performing the method according to any of claims 1 -21 .

24. A computer program product comprising instructions for performing a process, the process comprising the method according to any of claims 1 -21 .

25. A non-transitory computer-readable medium encoded with instructions that, when executed in hardware, perform a process, the process comprising the method according to any of claims 1 -21 .