WO2018143854A1 - A wireless device and a method therein for performing sidelink communication - Google Patents

A wireless device and a method therein for performing sidelink communication Download PDF

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Publication number
WO2018143854A1
WO2018143854A1 PCT/SE2017/051347 SE2017051347W WO2018143854A1 WO 2018143854 A1 WO2018143854 A1 WO 2018143854A1 SE 2017051347 W SE2017051347 W SE 2017051347W WO 2018143854 A1 WO2018143854 A1 WO 2018143854A1
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WIPO (PCT)
Prior art keywords
wireless device
utc
value
time
synchronization
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PCT/SE2017/051347
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French (fr)
Inventor
Yunxi LI
Qianxi Lu
Tomas Hedberg
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Telefonaktiebolaget Lm Ericsson (Publ)
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Publication of WO2018143854A1 publication Critical patent/WO2018143854A1/en

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Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W56/00Synchronisation arrangements
    • H04W56/001Synchronization between nodes
    • H04W56/002Mutual synchronization
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W76/00Connection management
    • H04W76/10Connection setup
    • H04W76/14Direct-mode setup
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W92/00Interfaces specially adapted for wireless communication networks
    • H04W92/16Interfaces between hierarchically similar devices
    • H04W92/18Interfaces between hierarchically similar devices between terminal devices

Definitions

  • Embodiments herein relate to a wireless device, and to a method therein.
  • embodiments herein relate to performing sidelink communication by a first wireless device operating in a first coverage area of a wireless communications network and capable of using synchronization to a Global Navigation Satellite System (GNSS).
  • GNSS Global Navigation Satellite System
  • Communication devices such as terminals or wireless devices are also known as e.g. User Equipments (UEs), mobile terminals, wireless terminals and/or mobile stations.
  • UEs User Equipments
  • Such terminals are enabled to communicate wirelessly in a wireless communication system or a cellular communications network, sometimes also referred to as a cellular radio system or cellular networks.
  • the communication may be performed e.g. between two wireless devices, between a wireless device and a regular telephone and/or between a wireless device and a server via a Radio Access Network (RAN) and possibly one or more core networks, comprised within the wireless communications network.
  • RAN Radio Access Network
  • the above terminals or wireless devices may further be referred to as mobile telephones, cellular telephones, laptops, or tablets with wireless capability, just to mention some further examples.
  • the terminals or wireless devices in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle- mounted mobile devices, enabled to communicate voice and/or data, via the RAN, with another entity, such as another terminal or a server.
  • the cellular communications network covers a geographical area which is divided into cell areas, wherein each cell area being served by an access node such as a base station, e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. "eNB”, “eNodeB”, “NodeB”, “B node”, or Base Transceiver Station (BTS), depending on the technology and terminology used.
  • a base station e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. "eNB”, “eNodeB”, “NodeB”, “B node”, or Base Transceiver Station (BTS), depending on the technology and terminology used.
  • the base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size.
  • a cell is the geographical area where radio coverage is provided by the base station at a base station site.
  • each base station may support one or several communication technologies.
  • the base stations communicate over the air interface operating on radio frequencies with the terminals or wireless devices within range of the base stations.
  • the expression Downlink (DL) is used for the transmission path from the base station to the mobile station.
  • the expression Uplink (UL) is used for the transmission path in the opposite direction i.e. from the mobile station to the base station.
  • a Universal Mobile Telecommunications System is a third generation (3G) telecommunication network, which evolved from the second generation (2G) Global System for Mobile Communications (GSM).
  • the UMTS terrestrial radio access network (UTRAN) is essentially a RAN using wideband code division multiple access (WCDMA) and/or High Speed Packet Access (HSPA) for user equipment.
  • WCDMA wideband code division multiple access
  • HSPA High Speed Packet Access
  • 3GPP Third Generation Partnership Project
  • telecommunications suppliers propose and agree upon standards for third generation networks, and investigate enhanced data rate and radio capacity.
  • 3GPP Third Generation Partnership Project
  • radio network nodes may be connected, e.g., by landlines or microwave, to a controller node, such as a radio network controller (RNC) or a base station controller (BSC), which supervises and coordinates various activities of the plural radio network nodes connected thereto.
  • RNC radio network controller
  • BSC base station controller
  • This type of connection is sometimes referred to as a backhaul connection.
  • the RNCs and BSCs are typically connected to one or more core networks.
  • EPS Evolved Packet System
  • the EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long Term Evolution (LTE) radio access network, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network.
  • E-UTRAN/LTE is a variant of a 3GPP radio access network wherein the radio network nodes are directly connected to the EPC core network rather than to RNCs.
  • SAE System Architecture Evolution
  • the RAN of an EPS has an essentially "flat" architecture comprising radio network nodes connected directly to one or more core networks, i.e. they are not connected to RNCs.
  • the E- UTRAN specification defines a direct interface between the radio network nodes, this interface being denoted the X2 interface.
  • base stations which may be referred to as eNodeBs or even eNBs, may be directly connected to one or more core networks.
  • the 3GPP LTE radio access standard has been written in order to support high bitrates and low latency both for uplink and downlink traffic. All data transmission is in LTE controlled by the radio base station.
  • Multi-antenna techniques may significantly increase the data rates and reliability of a wireless communication system. The performance is in particular improved if both the transmitter and the receiver are equipped with multiple antennas, which results in a Multiple-Input Multiple-Output (MIMO) communication channel.
  • MIMO Multiple-Input Multiple-Output
  • Such systems and/or related techniques are commonly referred to as MIMO systems.
  • the LTE standard has been extended with support of Device to
  • D2D Device
  • sidelink features targeting both commercial and Public Safety applications.
  • Some applications enabled by Rel-12 LTE are device discovery, where devices are able to sense the proximity of another device and associated application by broadcasting and detecting discovery messages that carry device and application identities.
  • Another application includes direct communication based on physical channels terminated directly between devices.
  • V2x communication includes any combination of direct communication between vehicles, pedestrians and infrastructure.
  • V2x communication may take advantage of a network (NW) infrastructure, when available, but at least basic V2x connectivity should be possible even in case of lack of coverage.
  • NW network
  • Providing an LTE-based V2x interface may be economically advantageous because of the LTE economies of scale and it may enable tighter integration between communications with the NW infrastructure (V2I) and a pedestrian (V2P) and a vehicle (V2V), as compared to using a dedicated V2x technology.
  • Figure 1 is a schematic diagram illustrating V2x scenarios for an LTE-based Radio
  • a Radio Network Node (RNN) 102 such as an eNB operates in the communications network 100.
  • the RNN 102 provides coverage within a coverage area 102a, sometimes referred to as a cell.
  • Vehicle-to-lnfrastructure (V2I) communications may be provided between a vehicle, e.g. a vehicle 104-2, 104-4, and the radio access network (RAN), e.g. the RNN 102.
  • Vehicle-to-Vehicle (V2V) communications may be provided directly between wireless devices of different vehicles, e.g. between the vehicle 104-2 and a vehicle 104-5 and/or between the vehicle 104-4 and the vehicle 104-5, without communicating through the radio access network.
  • Vehicle-to-Pedestrian (V2P) communications may be provided directly between a wireless device of a vehicle, e.g. the vehicle 104-2, and a device, e.g., a smartphone, a tablet computer, etc., held/carried by the pedestrian.
  • Vehicle-to-anything (V2X) communications are meant to include any/all of V2I, V2P, and V2V communications.
  • V2x communications may carry both non-safety and safety information, where each of the applications and services may be associated with specific requirements sets, e.g., in terms of latency, reliability, capacity, etc.
  • SL sidelink
  • MCPTT Mission-Critical Push To Talk
  • V2x the sidelink should be able to cope with higher load scenario (e.g., hundreds of cars could potentially contend for physical resources), to carry time/event triggered V2x messages, e.g. Cooperative Awareness Message (CAM), a Decentralized Environmental Notification Message (DENM), and high mobility.
  • CAM Cooperative Awareness Message
  • DENM Decentralized Environmental Notification Message
  • 3GPP has discussed possible enhancements to the sidelink physical layer.
  • mode-3 which comprises SL Semi Persistent Scheduling (SPS) and dynamic SL grant a-la mode- 1
  • mode-4 which corresponds to UE autonomous resource selection a-la mode-2 with some enhancements.
  • SPS Semi Persistent Scheduling
  • mode-4 which corresponds to UE autonomous resource selection a-la mode-2 with some enhancements.
  • enhancements comprise the so-called sensing procedure in which the wireless device is required to sense the channel for at least a certain time-frame before selecting the proper resources.
  • the wireless device may select as a synchronization source not only the eNB timing (i.e., acquired via the eNB timing).
  • PSS/SSS PSS/SSS
  • the timing of UEs in the surroundings i.e., acquired via the Sidelink
  • Synchronization Signals SLSS Synchronization Signals SLSS
  • Which synchronization source the wireless device should prioritize may be indicated by the eNB or it may be pre- configured.
  • a Coordinated Universal Time (UTC) time obtained from the GNSS may be used for synchronization of V2X sidelink communication between wireless devices on a V2X dedicated carrier.
  • UTC Coordinated Universal Time
  • the GNSS-based D2D Frame Number (DFN) may be derived from the UTC time by the following formulae:
  • SubframeNumber Floor (Tcurrent - Tref) mod 10
  • Tcurrent is the current UTC time and Tref is the reference UTC time 00:00:00 on Gregorian calendar date 1 January, 1900 (midnight between
  • the wireless device When the wireless device is performing V2X transmission on a carrier other than its LTE carrier, the wireless device may use the GNSS synchronization. However, it may happen that the GNSS synchronization is lost due to some reason, such as the wireless device being moving in a tunnel or moving in an underground parking, or due to a GNSS module malfunction, etc. This may further lead to the failure of the wireless device to obtain the GNSS synchronization, and to the failure in the V2X transmission.
  • the RNN e.g. the eNB
  • the wireless device should provide the wireless device with an offset between the eNB synchronization and the GNSS synchronization, and when the GNSS synchronization is lost, the wireless device is able to calculate the DFN from a System Frame Number (SFN) and the offset.
  • SFN System Frame Number
  • a drawback with such a solution is that the RNN, e.g. the eNB, needs to support V2X communication in order to be able to provide the wireless device with the offset between the eNB synchronization and the GNSS synchronization.
  • the RNN e.g. the eNB
  • the RNN needs to comprise a GNSS receiver in order to be able receive a GNSS synchronization to obtain the offset between the eNB synchronization and the GNSS synchronization.
  • an aim of some embodiments disclosed herein is to overcome or mitigate at least some of the drawbacks with the prior art.
  • the object is achieved by a method performed by a first wireless device for performing sidelink communication when operating in a first coverage area of a wireless communications network.
  • the first wireless device is capable of using information obtained from a navigation system for synchronization of the sidelink communication.
  • the first wireless device determines a second UTC value.
  • UTC Coordinated Universal Time
  • the first wireless device determines a Device-to-device Frame Number (DNF) based on the determined second UTC time value and performs the sidelink communication with a second wireless device using the determined DFN.
  • DNF Device-to-device Frame Number
  • the object is achieved by a first wireless device for performing sidelink communication when operating in a first coverage area of a wireless communications network.
  • the first wireless device is capable of using information obtained from a navigation system for synchronization of the sidelink communication.
  • the first wireless device is configured to determine a second UTC value in the absence of receipt of a UTC value from the navigation system.
  • the first wireless device is configured to determine a Device-to-device Frame Number ( DNF) based on the determined second UTC time value and to perform the sidelink communication with a second wireless device using the determined DFN.
  • DNF Device-to-device Frame Number
  • the object is achieved by a computer program, comprising instructions which, when executed on at least one processor, causes the at least one processor to carry out the method performed by the first wireless device.
  • the object is achieved by a carrier comprising the computer program, wherein the carrier is one of an electronic signal, an optical signal, a radio signal or a computer readable storage medium.
  • the first wireless device determines a second UTC value in the absence of receipt of a UTC value from the navigation system, the first wireless device is able to continue performing sidelink communication with a second wireless device without having to put the ongoing sidelink communication on hold until the first wireless device has selected another synchronization successfully. This results in an improved performance in the wireless communications network.
  • V2X communication e.g. V2X communication
  • GNSS GNSS
  • RNN e.g. the eNB
  • the RNN e.g. the eNB
  • a further advantage with some embodiments disclosed herein is that they will work regardless of whether or not the RNN, e.g. the eNB, is able to receive a GNSS
  • a further advantage with some embodiments disclosed herein is that they will work in any kind of wireless communications network, such as in a GSM communications network, a WCDM communications network, a TD-SCDMA communications network, an LTE communications network, a 5G communications network or other non-cellular wireless network, e.g. WIFI communications network.
  • an advantage with some embodiments disclosed herein is that no signaling between the RNN, e.g. the eNB, and the first wireless device, e.g. the UE, is needed whereby radio resources may be saved.
  • Figure 1 schematically illustrates a wireless communications network according to prior art:
  • Figure 2 schematically illustrates embodiments of a wireless communications network
  • Figure 3 is a flowchart depicting embodiments of a method performed by a first wireless device
  • Figure 4 is a schematic block diagram illustrating embodiments of a first wireless device;
  • Figure 5 schematically illustrates UTC calculation;
  • Figure 6 schematically illustrates updating of the correlation information when the first wireless device is moving into a new coverage area.
  • An object addressed by embodiments herein is how to improve performance in a wireless communications network.
  • a first wireless device may store a correlation between synchronizations to two different systems.
  • the first wireless device may store a wireless communication network synchronization, e.g. an eNB synchronization, and a navigation system synchronization, e.g. a UTC value from the GNSS.
  • a wireless communication network synchronization e.g. an eNB synchronization
  • a navigation system synchronization e.g. a UTC value from the GNSS.
  • the first wireless device calculates the UTC, and then calculates a DFN based on the calculated UTC value. All procedures may be UE implementations without requiring eNB support, i.e. without requiring support from the wireless communications network.
  • Network Node e.g. core network node or Radio network Node (RNN):
  • Examples of a RNN is gNB, NodeB, eNB, MeNB, SeNB, a network node belonging to a Master Cell Group (MCG) or a Secondary Cell Group (SCG), Base Station (BS), multi- Standard Radio (MSR) radio node such as MSR BS, eNodeB, network controller, radio Network Controller (RNC), Base Station Controller (BSC), relay, donor node controlling relay, Base Transceiver Station (BTS), Access Point (AP), transmission points, transmission nodes, Remote Radio Unit (RRU), Remote Radio Head (RRH), nodes in Distributed Antenna System (DAS).
  • MSR Multi- Standard Radio
  • BTS Base Transceiver Station
  • AP Access Point
  • RRU Remote Radio Unit
  • RRH Remote Radio Head
  • DAS Distributed Antenna System
  • Examples of a core network node is e.g.
  • MSC Mobile Switching Center
  • MME Mobility Management Entity
  • O&M Operations and Maintenance
  • OSS Operations Support System
  • SON Self-organizing Network
  • positioning node e.g. Enhanced Serving Mobile Location Center (E-SMLC)
  • E-SMLC Enhanced Serving Mobile Location Center
  • MDT Mobile Data Terminal
  • wireless device In some embodiments the non-limiting terms wireless device, Mobile Station (MS) and User Equipment (UE) are used and they refer to any type of wireless device communicating with a network node and/or with another UE in a cellular or mobile communication system.
  • UE/wireless device are Device- to-Device (D2D) UE, machine type UE or UE capable of machine to machine (M2M) communication, Personal Digital Assistant (PDA), Tablet, mobile terminals, smart phone, Laptop Embedded Equipped (LEE), Laptop Mounted Equipment (LME), Universal Serial Bus (USB) dongles, Customer premises Equipment (CPE) etc.
  • D2D Device- to-Device
  • M2M machine to machine
  • PDA Personal Digital Assistant
  • Tablet Tablet
  • smart phone Laptop Embedded Equipped
  • LME Laptop Mounted Equipment
  • USB Universal Serial Bus
  • CPE Customer premises Equipment
  • LTE Long Term Evolution
  • 5G Fifth Generation
  • WCDMA Wideband Code Division Multiple Access
  • GSM Global System for Mobile Communications
  • WMAX Worldwide Interoperability for Microwave Access
  • WLAN Wireless Local Area Network
  • LR-WPAN Low Rate Wreless Personal Access Network
  • IEEE 802.15.4 a Bluetooth network, a SIGFOX network, a Zigbee network, a Bluetooth Low Energy (BLE) network such as a Bluetooth Smart network, or a Cellular Internet of Things (CloT) network such as an Enhanced Coverage GSM-loT (EC-GSM- loT) network, a Narrow Band loT (NB-loT) network or a network comprising one or more wireless devices configured for Machine Type Communication (MTC) sometimes herein referred to as an eMTC network, may also benefit from exploiting the ideas covered within this disclosure.
  • BLE Bluetooth Low Energy
  • CloT Cellular Internet of Things
  • E-GSM- loT Enhanced Coverage GSM-loT
  • NB-loT Narrow Band loT
  • eMTC network a network comprising one or more wireless devices configured for Machine Type Communication (MTC) sometimes herein referred to as an eMTC network
  • gNB gigaNodeB
  • eNodeB eNodeB
  • UE eNodeB
  • terminology such as gNB, eNodeB and UE should be considering non-limiting and does in particular not imply a certain hierarchical relation between the two; in general “eNodeB” could be considered as device 1 and “UE” device 2, and these two devices communicate with each other over some radio channel.
  • Figure 2 depicts an example of a combined communication and navigation system 200 wherein embodiments herein may be implemented.
  • a navigation system 201 may be comprised in the combined communication and navigation system 200.
  • the navigation system 201 may be a Global Navigation Satellite System (GNSS) such as a Global Position System (GPS), GLONASS, Galileo or BeiDou, etc., just to mention some examples.
  • GNSS Global Navigation Satellite System
  • GPS Global Position System
  • GLONASS Global Position System
  • Galileo Galileo
  • BeiDou BeiDou
  • a wireless communications network 202 may be comprised in the combined communication and navigation system 200.
  • the wireless communications network 202 may be a cellular communications network such as a NR network, a 5G network, an LTE network, a WCDMA network, a GSM network, any 3GPP cellular network, or a short range communications network, such as a WLAN, an LR-WPAN, a Bluetooth network, WiMAX network, a SIGFOX network, a Zigbee network, a BLE network such as a Bluetooth Smart network, or a CloT network such as an EC-GSM-loT network, a NB-loT network or an eMTC network, or a combination of one or more of the aforementioned communications networks just to mention some examples.
  • a cellular communications network such as a NR network, a 5G network, an LTE network, a WCDMA network, a GSM network, any 3GPP cellular network, or a short range communications network, such as a
  • a Radio Network Node (RNN) 203 is arranged and configured to operate in the communication network 202.
  • the RNN 203 is configured for wireless communication with one or more wireless devices, such as a first wireless device 204, when they are located within a coverage area 203a, e.g. a geographical area served by the RNN 203.
  • the RNN 203 may serve or manage a plurality of coverage areas 203a, e.g. a first coverage area 203a-1 and a second coverage area 203a-2, even though only two are illustrated in Figure 2 for clarity reasons.
  • the one more coverage areas 203a are sometimes in this disclosure referred to as one or more cells 203a.
  • the RNN 203 may be a transmission point such as a radio base station, for example an eNB, an eNodeB, or an Home Node B, an Home eNode B or any other network node capable to serve a user equipment or a machine type communication device in a communications network, such as the communications network 203.
  • the RNN 203 may further be configured to communicate with a core network node.
  • a first wireless device 204 is operating in the wireless communications network 202.
  • the first wireless device 204 is configured to perform sidelink communication to a second wireless device 205. That is the first and second wireless devices 204,205 are configured to communicate with each other via sidelink communication.
  • the first and second wireless devices 204,205 also sometimes referred to as wireless communications devices, user equipment, UEs, mobile stations or MSs, may be located in the wireless communications network 202.
  • the first and second wireless devices 204,205 may e.g. be loT devices, user equipment, mobile terminals or wireless terminals, mobile phones, computers such as e.g. laptops, Personal Digital Assistants (PDAs) or tablet computers, with wireless capability, or any other radio network units capable to communicate over a radio link in a wireless communications network.
  • PDAs Personal Digital Assistants
  • tablet computers with wireless capability, or any other radio network units capable to communicate over a radio link in a wireless communications network.
  • the term user equipment used in this document also covers other wireless devices such as Machine to Machine
  • first wireless device 204 and the second wireless device 205 are configured to perform any kind of V2X communication.
  • one of the first and second wireless devices 204,205 may be mounted at or carried by a vehicle while the other one of the first and second wireless devices 204,205 may be mounted at or carried by a vehicle, a pedestrian, or a network infrastructure device, e.g. a network node such as a radio network node, just to mention some examples.
  • Figure 1 it is schematically illustrated that the first wireless device 204 is moving with a velocity v in a direction from the first coverage area 203a-1 into the second coverage area 203a-2.
  • the first wireless device 204 may perform the sidelink communication when operating in the first coverage area 203a-1 of the wireless communications network 202. Further, the first wireless device 204 is capable of using information obtained from the navigation system 201 for synchronization of the sidelink communication.
  • the methods comprise one or more of the following actions. It should be understood that these actions may be taken in any suitable order and that some actions may be combined.
  • the first wireless device 204 may store correlation information specific for a first point of time and for the first coverage area 203a-1.
  • the correlation information may comprises a first synchronization information received from the RNN 203 operating in the wireless communications network 202 and a first UTC value received from the navigation system 201.
  • the correlation information may be used for synchronizing the sidelink communication.
  • the first synchronization information may comprise a first system frame number and a first subframe number.
  • the first synchronization information may comprise a first super frame number, a first multi frame number, a first frame number and a first slot number.
  • the first wireless device 204 may store correlation information updated to be specific for an update point of time and for the second coverage area 203a-2.
  • the correlation information may comprise new synchronization information received from the RNN 203 and a new UTC value.
  • the new UTC value may be obtained from the navigation system 201 , e.g. the GNSS, if possible, or be determined, e.g. calculated, based on the first synchronization information and the first UTC value.
  • the new synchronization information comprises a new system frame number received from the RNN 203 and a new subframe number received from the RNN 203.
  • the new UTC value is obtained from the navigation system 201 , e.g. the GNSS, or determined based on the first system frame number, the first subframe number and the first UTC value.
  • the first wireless device 204 determines a second UTC value.
  • the first wireless device 204 determines, e.g. calculates, the second UTC value. For example, this may be the case in the absence of receipt of one or more navigation signals S, e.g. one or more GNSS signals, from the navigation system 201 or when the navigation signal received is too weak.
  • the one or more navigation signals may provide one or more UTC values.
  • the first wireless device 204 determines the second UTC value at a second point of time x based on second synchronization information received from the RNN 203 for the second point of time x and based on the stored correlation information.
  • the first wireless device 204 may determine the second UTC value by determining the second UTC value at a second point of time x based on a system frame number and a subframe number for the second point of time x and received from the RNN 203, and based on the stored correlation information.
  • the first wireless device 204 may determine the second UTC value as
  • the first wireless device 204 determines a Device-to-device Frame Number (DNF) based on the determined second UTC time value.
  • DNF Device-to-device Frame Number
  • the first wireless device 204 determines the DFN as:
  • SubframeNumber Floor (Tcurrent -Tref) mod 10
  • Tcurrent is the set to the UTC time calculated. This value is expressed in milliseconds; Tref is the reference UTC time 00:00:00 on Gregorian calendar date 1 January, 1900 (midnight between Thursday, December 31 , 1899 and Friday, January 1 , 1900). This value is expressed in milliseconds.
  • SubframeNumber Floor ((Tcurrent -Tref+dfnOffset)/1000) mod 10
  • Tcurrent is set to UTC time calculated; This value is expressed in milliseconds; Tref is the reference UTC time 00:00:00 on Gregorian calendar date 1 January, 1900 (midnight between Thursday, December 31 , 1899 and Friday, January 1 , 1900). This value is expressed in microseconds; and dfnOffset is the value configured by RRC in parameter dfnOffset to shift the DFN with respect to the reference time derived from GNSS. This value is expressed in microseconds. Action 305
  • the first wireless device 204 provides or performs the sidelink communication with the second wireless device 205 using the determined DFN.
  • the first wireless device 204 may be configured according to an arrangement depicted in Figure 4. As mentioned above, the first wireless device 204 is configured to operate in the first coverage area 203a-1 of the wireless communications network 202 and to use synchronization to the navigation system 201 , e.g. the GNSS. Thus, the first wireless device is capable of using information obtained from the navigation system 201 for synchronization of the sidelink communication.
  • the first wireless device 204 comprises an input and/or output interface 400 configured to communicate with one or more wireless devices, e.g. the second wireless device 205 and/or one or more network nodes, e.g. the RNN 203.
  • the input and/or output interface 400 may comprise a wireless receiver (not shown) and a wireless transmitter (not shown).
  • the first wireless device 204 is configured to receive, by means of a receiving module 401 configured to receive, a transmission, e.g. a data packet, a signal or information, from one or more network nodes, e.g. the RNN 203 and/or from one or more other wireless devices, e.g. the second wireless device 205.
  • the receiving module 401 may be implemented by or arranged in communication with a processor 407 of the first wireless device 204.
  • the processor 407 will be described in more detail below.
  • the first wireless device 204 is configured to transmit, by means of a
  • transmitting module 402 configured to transmit, a transmission, e.g. a data packet, a signal or information, to one or more network nodes, e.g. the RNN 203 and/or to one or more other wireless devices, e.g. the second wireless device 205.
  • the transmitting module 402 may be implemented by or arranged in communication with the processor 407 of the first wireless device 204.
  • the first wireless device 204 is configured to store, by means of a storing module 403 configured to store, information such as correlation information.
  • the storing module 403 may be implemented by or arranged in communication with the processor 407 of the first wireless device 204.
  • the first wireless device 204 is configured to determine, by means of a determining module 404 configured to determine, a UTC and/or a DFN.
  • the determining module 404 may be implemented by or arranged in communication with the processor 406 of the first wireless device 204.
  • the first wireless device 204 is configured to provide/perform, by means of a providing/performing module 405 configured to provide/perform, a sidelink
  • the second wireless device 205 communicates with another device, e.g. the second wireless device 205.
  • the second wireless device 205 e.g. the second wireless device 205.
  • providing/performing module 405 may be implemented by or arranged in communication with the processor 407 of the first wireless device 204.
  • the first wireless device 204 is configured to perform, by means of one or more other modules configured to perform one or more further actions described herein.
  • the one or more other modules may be implemented by or arranged in communication with the processor 407 of the first wireless device 204.
  • the first wireless device 204 may also comprise means for storing data.
  • the first wireless device 204 comprises a memory 406 configured to store the data.
  • the data may be processed or non-processed data and/or information relating thereto.
  • the memory 406 may comprise one or more memory units.
  • the memory 406 may be a computer data storage or a semiconductor memory such as a computer memory, a read-only memory, a volatile memory or a non-volatile memory.
  • the memory is arranged to be used to store obtained information, data, configurations, and
  • Embodiments herein for providing sidelink communication may be implemented through one or more processors, such as the processor 406 in the arrangement depicted in Fig. 4, together with computer program code for performing the functions and/or method actions of embodiments herein.
  • the program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the first wireless device 204.
  • One such carrier may be in the form of an electronic signal, an optical signal, a radio signal or a computer readable storage medium.
  • the computer readable storage medium may be a CD ROM disc or a memory stick.
  • the computer program code may furthermore be provided as program code stored on a server and downloaded to the first wireless device 204.
  • the input/output interface 400, the receiving module 401 , the transmitting module 402, the storing module 403, the determining module 404, the providing/performing module 405, and the one or more other modules above may refer to a combination of analogue and digital circuits, and/or one or more processors configured with software and/or firmware, e.g. stored in the memory 406, that when executed by the one or more processors such as the processors in the first wireless device 204 perform as described above.
  • processors may be included in a single Application-Specific Integrated Circuitry (ASIC), or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a System-on-a-Chip (SoC).
  • ASIC Application-Specific Integrated Circuitry
  • SoC System-on-a-Chip
  • the navigation system 201 is a GNSS and the communications network 202 is an LTE communications network.
  • the first wireless device 204 may store correlation information.
  • the correlation information comprises information correlating a GNSS synchronization with a RNN synchronization.
  • the correlation information is sometimes, e.g. when the RNN 203 is an LTE eNB, in this disclosure referred to as a correlation triple as it may comprises three elements; a system frame number SYSTEM_FRAME, a subframe number SUB_FRAME and a UTC time UTC_TIME.
  • the correlation triple is valid within a coverage area 203a, e.g. within the first coverage area 203a-1.
  • the correlation information needs to be updated.
  • the correlation triple may be valid for a period of time, e.g. a defined time of period, i.e. 10 seconds. When the period of time elapses, the correlation information needs to be updated. Updating of the correlation information will be described in more detail in Action 302 above.
  • the first wireless device 204 sets correlation information
  • This relates e.g. to Action 301 previously described.
  • the first wireless device 204 sets, e.g. initiates, the correlation information.
  • X At a certain point of time X:
  • the point of time X should be the beginning of a subframe, say sub_frame_X, which belongs to a system frame system_frame_X;
  • the first wireless device 204 sets, e.g. initiates, the correlation information as below:
  • the first wireless device 204 calculates the UTC time
  • This relates e.g. to Action 302 and Action 303 previously described.
  • the first wireless device 204 calculates the UTC time when the first wireless device 204 is performing a sidelink communication, e.g. a V2X communication, using a GNSS synchronization and when the first wireless device 204 is not able to obtain an UTC from the GNSS.
  • a sidelink communication e.g. a V2X communication
  • the first wireless device 204 calculates the UTC time when the first wireless device 204 is updating correlation information as described in Action 302 and when the first wireless device 204 is not able to obtain the UTC from the GNSS.
  • the first wireless device 204 calculates the corresponding UTC time UTC_Y as:
  • the first wireless device 204 is storing correlation triple (SYSTEM_FRAME, SUB_FRAME, UTC_TIME) The first wireless device 204 calculates an offset and the UTC value UTC_Y as below:
  • UTC_Y [ (system_frame_Y *10 + sub_frame_Y) - (SYSTEM_FRAME *10 + SUB_FRAME) ] mod 10240 + UTC_TIME (the unit of result is millisecond)
  • UTC_Y [ (system_frame_Y *10 + sub_frame_Y) - (SYSTEM_FRAME *10 + SUB_FRAME) ] mod 10240 *1000 + UTC_TIME (the unit of result is microsecond)
  • Figure 5 schematically illustrates embodiments of a method performed by the wireless device 204 for performing sidelink communication.
  • the first wireless device 204 is able to receive synchronization from both the communications network 202 and the navigation network 201.
  • the first wireless device 204 has lost the GNSS synchronization.
  • the first wireless device 204 will calculate the UTC time at the second point of time T2 as below:
  • the first wireless device 204 initiates correlation triple:
  • the first wireless device 204 has following information:
  • system_frame_x 8
  • sub frame x is 1 the first wireless device 204 calculates UTC time UTC_x at the second point of time T2 as below:
  • the first wireless device 204 calculates DFN
  • This relates e.g. to Action 304 previously described.
  • the first wireless device 204 When the first wireless device 204 is configured to perform sidelink communication using navigation synchronization, e.g. V2X communication using GNSS synchronization, and the first wireless device 204 may calculate the DFN as
  • SubframeNumber Floor (Tcurrent -Tref) mod 10
  • Tcurrent is the set to UTC time calculated. This value is expressed in
  • Tref is the reference UTC time 00:00:00 on Gregorian calendar date 1 January, 1900 (midnight between Thursday, December 31 , 1899 and Friday, January 1 , 15 1900). This value is expressed in milliseconds.
  • DFN may be calculated in other ways, e.g. as
  • SubframeNumber Floor ((Tcurrent -Tref+dfnOffset)/1000) mod 10
  • Tcurrent is set to UTC time calculated; This value is expressed in milliseconds;
  • Tref is the reference UTC time 00:00:00 on Gregorian calendar date 1 January, 1900 (midnight between Thursday, December 31 , 1899 and Friday, January 1 , 1900). This value is expressed in microseconds; and dfnOffset is the value configured by the RRC in parameter dfnOffset to shift the DFN with respect to the reference time derived from the 25 GNSS. This value is expressed in microseconds.
  • the first wireless device 204 updates correlation information
  • This relates e.g. to Action 302 previously described.
  • the first wireless device 204 updates correlation information between GNSS synchronization and eNB synchronization according to Action 301 described above or according the description under section "The first wireless device 204 sets correlation information" above.
  • the first wireless device 204 may update the correlation information periodically. This may for example be the case when a period of time for period updates has elapsed and when the first wireless device 204 has not moved to another coverage cell. In such cases, first wireless device 204 may update the correlation information between the GNSS synchronization and the eNB synchronization when the period of time for period updates has elapsed and when the first wireless device 204 is in receipt of an UTC from the navigation system 201.
  • the correlation information may be updated according to Action 301 described above or according the description under section "The first wireless device 204 sets correlation information" above.
  • the first wireless device 204 moves to a new cell, e.g. from the first coverage area 203a-1 to the second coverage area 203a-2, via cell reselection or handover, and the first wireless device 203 is not able to obtain the UTC from the navigation system 201 , e.g. the GNSS , and there is correlation between GNSS synchronization and eNB synchronization available, the first wireless device 204 updates the correlation information between the GNSS synchronization and the eNB
  • the first wireless device 204 stores correlation triple (SYSTEM_FRAME,
  • the first wireless device 204 stores following information upon moving to a new cell, as shown in Figure 6:
  • a first point of time T1 is the beginning of subframe succeeding the last subframe when the first wireless device 204 is connected/camped to the "old cell"; the system frame number and subframenumber of this subframe is system_frame_old and sub_frame_old.
  • a second point of time T2 is the beginning of the first subframe when the first wireless device 204 is synchronized the "new cell"; the system frame number and subframenumber of this first subframe is
  • the duration between the first and second points of time T1 and T2 is SyncDelay.
  • the first wireless device 204 calculates a first UTC time for the first point of time T1 according Action 303 and gets the result UTC_old.
  • the first wireless device 204 calculates a second UTC time for the second point of time T2 as below:
  • the first wireless device 204 updates the correlation information as below:
  • first wireless device may be moving from operation within the first coverage area 203a-1 to operation within the second coverage area 203a-2 and the first and second coverage areas area may be served by two different radio network nodes operating in two different wireless communications networks.
  • the first wireless device 204 may move between different types of wireless communications networks, such as GSM, WCDM, TD-SCDMA, LTE, 5G, WIFI and etc.
  • the procedure of calculating UTC time when the GNSS synchronization is lost may be provided with following modification:
  • the correlation information which comprises SYSTEM_FRAME,
  • UTC_TIME for LTE may comprise the corresponding synchronization factors and UTC_TIME in the concerned wireless communications network
  • V2x Vehicle-to-anything-you-can-imagine

Abstract

A first wireless device and a method therein for performing sidelink communication when operating in a first coverage area of a wireless communications network. The first wireless device is capable of using information obtained from a navigation system for synchronization of the sidelink communication. In the absence of receipt of a Coordinated Universal Time, UTC, value from the navigation system, the first wireless device determines (303) a second UTC value. The first wireless device determines (304) a Device-to-device Frame Number, DFN, based on the determined second UTC time value and performs (305) the sidelink communication with a second wireless device using the determined DFN.

Description

A WIRELESS DEVICE AND A METHOD THEREIN FOR PERFORMING
SIDELINK COMMUNICATION
TECHNICAL FIELD
Embodiments herein relate to a wireless device, and to a method therein.
Especially, embodiments herein relate to performing sidelink communication by a first wireless device operating in a first coverage area of a wireless communications network and capable of using synchronization to a Global Navigation Satellite System (GNSS). BACKGROUND
Communication devices such as terminals or wireless devices are also known as e.g. User Equipments (UEs), mobile terminals, wireless terminals and/or mobile stations. Such terminals are enabled to communicate wirelessly in a wireless communication system or a cellular communications network, sometimes also referred to as a cellular radio system or cellular networks. The communication may be performed e.g. between two wireless devices, between a wireless device and a regular telephone and/or between a wireless device and a server via a Radio Access Network (RAN) and possibly one or more core networks, comprised within the wireless communications network.
The above terminals or wireless devices may further be referred to as mobile telephones, cellular telephones, laptops, or tablets with wireless capability, just to mention some further examples. The terminals or wireless devices in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle- mounted mobile devices, enabled to communicate voice and/or data, via the RAN, with another entity, such as another terminal or a server.
The cellular communications network covers a geographical area which is divided into cell areas, wherein each cell area being served by an access node such as a base station, e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. "eNB", "eNodeB", "NodeB", "B node", or Base Transceiver Station (BTS), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A cell is the geographical area where radio coverage is provided by the base station at a base station site. One base station, situated at the base station site, may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the terminals or wireless devices within range of the base stations. In the context of this disclosure, the expression Downlink (DL) is used for the transmission path from the base station to the mobile station. The expression Uplink (UL) is used for the transmission path in the opposite direction i.e. from the mobile station to the base station.
A Universal Mobile Telecommunications System (UMTS) is a third generation (3G) telecommunication network, which evolved from the second generation (2G) Global System for Mobile Communications (GSM). The UMTS terrestrial radio access network (UTRAN) is essentially a RAN using wideband code division multiple access (WCDMA) and/or High Speed Packet Access (HSPA) for user equipment. In a forum known as the Third Generation Partnership Project (3GPP), telecommunications suppliers propose and agree upon standards for third generation networks, and investigate enhanced data rate and radio capacity. In some RANs, e.g. as in UMTS, several radio network nodes may be connected, e.g., by landlines or microwave, to a controller node, such as a radio network controller (RNC) or a base station controller (BSC), which supervises and coordinates various activities of the plural radio network nodes connected thereto. This type of connection is sometimes referred to as a backhaul connection. The RNCs and BSCs are typically connected to one or more core networks.
Specifications for the Evolved Packet System (EPS), also called a Fourth
Generation (4G) network, have been completed within the 3GPP and this work continues in the coming 3GPP releases, for example to specify a Fifth Generation (5G) network. The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long Term Evolution (LTE) radio access network, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E- UTRAN/LTE is a variant of a 3GPP radio access network wherein the radio network nodes are directly connected to the EPC core network rather than to RNCs. In general, in E-UTRAN/LTE the functions of an RNC are distributed between the radio network nodes, e.g. eNodeBs in LTE, and the core network. As such, the RAN of an EPS has an essentially "flat" architecture comprising radio network nodes connected directly to one or more core networks, i.e. they are not connected to RNCs. To compensate for that, the E- UTRAN specification defines a direct interface between the radio network nodes, this interface being denoted the X2 interface.
In the 3GPP LTE, base stations, which may be referred to as eNodeBs or even eNBs, may be directly connected to one or more core networks. The 3GPP LTE radio access standard has been written in order to support high bitrates and low latency both for uplink and downlink traffic. All data transmission is in LTE controlled by the radio base station.
Multi-antenna techniques may significantly increase the data rates and reliability of a wireless communication system. The performance is in particular improved if both the transmitter and the receiver are equipped with multiple antennas, which results in a Multiple-Input Multiple-Output (MIMO) communication channel. Such systems and/or related techniques are commonly referred to as MIMO systems. During Release 12, the LTE standard has been extended with support of Device to
Device (D2D) (specified as "sidelink") features targeting both commercial and Public Safety applications. Some applications enabled by Rel-12 LTE are device discovery, where devices are able to sense the proximity of another device and associated application by broadcasting and detecting discovery messages that carry device and application identities. Another application includes direct communication based on physical channels terminated directly between devices.
In Rel-14, the extensions for the device to device work includes support of V2x communication, which includes any combination of direct communication between vehicles, pedestrians and infrastructure. V2x communication may take advantage of a network (NW) infrastructure, when available, but at least basic V2x connectivity should be possible even in case of lack of coverage. Providing an LTE-based V2x interface may be economically advantageous because of the LTE economies of scale and it may enable tighter integration between communications with the NW infrastructure (V2I) and a pedestrian (V2P) and a vehicle (V2V), as compared to using a dedicated V2x technology.
Figure 1 is a schematic diagram illustrating V2x scenarios for an LTE-based Radio
Access Network 100. A Radio Network Node (RNN) 102 such as an eNB operates in the communications network 100. The RNN 102 provides coverage within a coverage area 102a, sometimes referred to as a cell. As shown in Figure 1 , Vehicle-to-lnfrastructure (V2I) communications may be provided between a vehicle, e.g. a vehicle 104-2, 104-4, and the radio access network (RAN), e.g. the RNN 102. Vehicle-to-Vehicle (V2V) communications may be provided directly between wireless devices of different vehicles, e.g. between the vehicle 104-2 and a vehicle 104-5 and/or between the vehicle 104-4 and the vehicle 104-5, without communicating through the radio access network. Further, Vehicle-to-Pedestrian (V2P) communications may be provided directly between a wireless device of a vehicle, e.g. the vehicle 104-2, and a device, e.g., a smartphone, a tablet computer, etc., held/carried by the pedestrian. Vehicle-to-anything (V2X) communications are meant to include any/all of V2I, V2P, and V2V communications.
V2x communications may carry both non-safety and safety information, where each of the applications and services may be associated with specific requirements sets, e.g., in terms of latency, reliability, capacity, etc.
Sidelink transmissions, also known as D2D transmissions or Proximity Service (ProSe) transmissions, over the so-called PC5 interface in cellular spectrum have been standardized in 3GPP since Rel-12. In 3GPP Rel-12 two different operative modes have been specified in 3GPP. In one mode (mode-1), a UE in RRC_CONNECTED mode requests D2D resources and the eNB grants them via Physical Downlink Control Channel PDCCH (DCI5) or via dedicated signaling. In another mode (mode-2), a UE autonomously selects resources for transmission from a pool of available resources that the eNB provides in broadcast via SIB signaling for transmissions on carriers other than the PCell or via dedicated signaling for transmission on the PCell. Therefore, unlike the first operation mode, the second operation mode may be performed also by wireless devices in RRCJDLE.
In Rel.14, the usage of sidelink (SL) is extended to the V2x domain. The design of the sidelink physical layer in Rel.12 has been dictated by the assumptions of relatively few UEs competing for the same physical resources in the spectrum, to carry voice packet for Mission-Critical Push To Talk (MCPTT) traffic, and low-mobility. On the other hand, in V2x the sidelink should be able to cope with higher load scenario (e.g., hundreds of cars could potentially contend for physical resources), to carry time/event triggered V2x messages, e.g. Cooperative Awareness Message (CAM), a Decentralized Environmental Notification Message (DENM), and high mobility. For such reasons, 3GPP has discussed possible enhancements to the sidelink physical layer.
In particular, in Rel.14 two new operations modes have been introduced: mode-3 which comprises SL Semi Persistent Scheduling (SPS) and dynamic SL grant a-la mode- 1 , and mode-4 which corresponds to UE autonomous resource selection a-la mode-2 with some enhancements. Such enhancements comprise the so-called sensing procedure in which the wireless device is required to sense the channel for at least a certain time-frame before selecting the proper resources.
Among the enhancements to sidelink a new synchronization framework has been introduced. In particular, unlike the Rel.12 sidelink synchronization, the wireless device may select as a synchronization source not only the eNB timing (i.e., acquired via the
PSS/SSS) or the timing of UEs in the surroundings (i.e., acquired via the Sidelink
Synchronization Signals SLSS), but also from the GNSS. Which synchronization source the wireless device should prioritize may be indicated by the eNB or it may be pre- configured.
A Coordinated Universal Time (UTC) time obtained from the GNSS may be used for synchronization of V2X sidelink communication between wireless devices on a V2X dedicated carrier. Specifically, in the current specification (3GPP TS 36.331 V14.0.0, Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Medium Access Control (MAC) protocol specification (Release 14)), the GNSS-based D2D Frame Number (DFN) may be derived from the UTC time by the following formulae:
DFN= Floor (0.r(Tcurrent -Tref)) mod 1024
SubframeNumber= Floor (Tcurrent - Tref) mod 10
Where, Tcurrent is the current UTC time and Tref is the reference UTC time 00:00:00 on Gregorian calendar date 1 January, 1900 (midnight between
Thursday, December 31, 1899 and Friday, January 1, 1900).
When the wireless device is performing V2X transmission on a carrier other than its LTE carrier, the wireless device may use the GNSS synchronization. However, it may happen that the GNSS synchronization is lost due to some reason, such as the wireless device being moving in a tunnel or moving in an underground parking, or due to a GNSS module malfunction, etc. This may further lead to the failure of the wireless device to obtain the GNSS synchronization, and to the failure in the V2X transmission.
It has been proposed in R2-167925, "Discussion on DFN offset", Huawei
HiSilicon, 3GPP TSG RAN WG2 Meeting #96 Reno, USA, 14-18 November, 2016, that the RNN, e.g. the eNB, should provide the wireless device with an offset between the eNB synchronization and the GNSS synchronization, and when the GNSS synchronization is lost, the wireless device is able to calculate the DFN from a System Frame Number (SFN) and the offset.
A drawback with such a solution is that the RNN, e.g. the eNB, needs to support V2X communication in order to be able to provide the wireless device with the offset between the eNB synchronization and the GNSS synchronization. Another drawback is that the RNN, e.g. the eNB, needs to comprise a GNSS receiver in order to be able receive a GNSS synchronization to obtain the offset between the eNB synchronization and the GNSS synchronization.
Yet another drawback is that some additional signaling is needed for the RNN, e.g. the eNB, to provide the offset to the wireless device(-s), which signaling may be completely useless if there is no wireless device transmitting V2X data using the GNSS synchronization.
Approaches described in the Background section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in the Background section are not prior art to the inventive embodiments disclosed in this application and are not admitted to be prior art by inclusion in the Background section. Therefore, any description contained in the Background section may be moved to the Detailed Description section.
SUMMARY
An aim of some embodiments disclosed herein is to overcome or mitigate at least some of the drawbacks with the prior art. According to an aspect of embodiments herein, the object is achieved by a method performed by a first wireless device for performing sidelink communication when operating in a first coverage area of a wireless communications network.
The first wireless device is capable of using information obtained from a navigation system for synchronization of the sidelink communication.
In the absence of receipt of a Coordinated Universal Time (UTC) value from the navigation system, the first wireless device determines a second UTC value.
Further, the first wireless device determines a Device-to-device Frame Number (DNF) based on the determined second UTC time value and performs the sidelink communication with a second wireless device using the determined DFN.
According to another aspect of embodiments herein, the object is achieved by a first wireless device for performing sidelink communication when operating in a first coverage area of a wireless communications network. The first wireless device is capable of using information obtained from a navigation system for synchronization of the sidelink communication. The first wireless device is configured to determine a second UTC value in the absence of receipt of a UTC value from the navigation system.
Further, the first wireless device is configured to determine a Device-to-device Frame Number ( DNF) based on the determined second UTC time value and to perform the sidelink communication with a second wireless device using the determined DFN.
According to another aspect of embodiments herein, the object is achieved by a computer program, comprising instructions which, when executed on at least one processor, causes the at least one processor to carry out the method performed by the first wireless device.
According to another aspect of embodiments herein, the object is achieved by a carrier comprising the computer program, wherein the carrier is one of an electronic signal, an optical signal, a radio signal or a computer readable storage medium.
Since the first wireless device determines a second UTC value in the absence of receipt of a UTC value from the navigation system, the first wireless device is able to continue performing sidelink communication with a second wireless device without having to put the ongoing sidelink communication on hold until the first wireless device has selected another synchronization successfully. This results in an improved performance in the wireless communications network.
An advantage with some embodiments disclosed herein is that sidelink
communication, e.g. V2X communication, is supported regardless the GNSS
synchronization availability as long as there is wireless communications network available, which wireless communications network may or may not support sidelink communication.
Another advantage with some embodiments disclosed herein is that the RNN, e.g. the eNB, will not be impacted, which simplifies the eNB implementation and reduces the eNB cost.
Yet another advantage with some embodiments disclosed herein is that the RNN, e.g. the eNB, may or may not support sidelink communication, e.g. V2X communication.
A further advantage with some embodiments disclosed herein is that they will work regardless of whether or not the RNN, e.g. the eNB, is able to receive a GNSS
synchronization. Yet a further advantage with some embodiments disclosed herein is that they will work in any kind of wireless communications network, such as in a GSM communications network, a WCDM communications network, a TD-SCDMA communications network, an LTE communications network, a 5G communications network or other non-cellular wireless network, e.g. WIFI communications network.
Furthermore, an advantage with some embodiments disclosed herein is that no signaling between the RNN, e.g. the eNB, and the first wireless device, e.g. the UE, is needed whereby radio resources may be saved.
BRIEF DESCRIPTION OF DRAWINGS
Examples of embodiments herein will be described in more detail with reference to attached drawings in which:
Figure 1 schematically illustrates a wireless communications network according to prior art:
Figure 2 schematically illustrates embodiments of a wireless communications network; Figure 3 is a flowchart depicting embodiments of a method performed by a first wireless device;
Figure 4 is a schematic block diagram illustrating embodiments of a first wireless device; Figure 5 schematically illustrates UTC calculation; and
Figure 6 schematically illustrates updating of the correlation information when the first wireless device is moving into a new coverage area.
DETAILED DESCRIPTION
An object addressed by embodiments herein is how to improve performance in a wireless communications network.
Therefore, as mentioned above, according to embodiments herein, a way of improving the performance in the wireless communications network is provided.
According to some embodiments disclosed herein a first wireless device may store a correlation between synchronizations to two different systems. For example, the first wireless device may store a wireless communication network synchronization, e.g. an eNB synchronization, and a navigation system synchronization, e.g. a UTC value from the GNSS. When the first wireless device is not able to obtain the UTC from the GNSS, for example when the first wireless device has lost the synchronization to the navigation system, the first wireless device calculates the UTC, and then calculates a DFN based on the calculated UTC value. All procedures may be UE implementations without requiring eNB support, i.e. without requiring support from the wireless communications network.
Terminology
The following terminology is used in embodiments described herein and is elaborated below:
Network Node (NN) e.g. core network node or Radio network Node (RNN):
Examples of a RNN is gNB, NodeB, eNB, MeNB, SeNB, a network node belonging to a Master Cell Group (MCG) or a Secondary Cell Group (SCG), Base Station (BS), multi- Standard Radio (MSR) radio node such as MSR BS, eNodeB, network controller, radio Network Controller (RNC), Base Station Controller (BSC), relay, donor node controlling relay, Base Transceiver Station (BTS), Access Point (AP), transmission points, transmission nodes, Remote Radio Unit (RRU), Remote Radio Head (RRH), nodes in Distributed Antenna System (DAS). Examples of a core network node is e.g. a Mobile Switching Center (MSC), a Mobility Management Entity (MME), an Operations and Maintenance (O&M), an Operations Support System (OSS), a Self-organizing Network (SON), a positioning node, e.g. Enhanced Serving Mobile Location Center (E-SMLC)), Mobile Data Terminal (MDT) etc. In some embodiments the more general term "network node" is used and it may correspond to any type of radio network node or any network node, which communicates with a wireless device and/or with another network node.
User equipment/wireless device: In some embodiments the non-limiting terms wireless device, Mobile Station (MS) and User Equipment (UE) are used and they refer to any type of wireless device communicating with a network node and/or with another UE in a cellular or mobile communication system. Examples of UE/wireless device are Device- to-Device (D2D) UE, machine type UE or UE capable of machine to machine (M2M) communication, Personal Digital Assistant (PDA), Tablet, mobile terminals, smart phone, Laptop Embedded Equipped (LEE), Laptop Mounted Equipment (LME), Universal Serial Bus (USB) dongles, Customer premises Equipment (CPE) etc. In this disclosure the terms wireless device and UE are used interchangeably.
Note that although terminology from LTE is used in this disclosure to exemplify the embodiments herein, this should not be seen as limiting the scope of the embodiments herein to only the aforementioned system. Other wireless systems, such as for example a NR network, 5G network, a Wideband Code Division Multiple Access (WCDMA) network, a Global System for Mobile Communications (GSM) network, any 3GPP cellular network, a Worldwide Interoperability for Microwave Access (WMAX) network, a Wreless Local Area Network (WLAN), a Low Rate Wreless Personal Access Network (LR-WPAN) as defined in e.g. IEEE 802.15.4, a Bluetooth network, a SIGFOX network, a Zigbee network, a Bluetooth Low Energy (BLE) network such as a Bluetooth Smart network, or a Cellular Internet of Things (CloT) network such as an Enhanced Coverage GSM-loT (EC-GSM- loT) network, a Narrow Band loT (NB-loT) network or a network comprising one or more wireless devices configured for Machine Type Communication (MTC) sometimes herein referred to as an eMTC network, may also benefit from exploiting the ideas covered within this disclosure.
In this section, the embodiments herein will be illustrated in more detail by a number of exemplary embodiments. It should be noted that these embodiments are not mutually exclusive. Components from one embodiment may be assumed to be present in another embodiment and it will be obvious to a person skilled in the art how those components may be used in the other exemplary embodiments.
Also note that terminology such as gNB, eNodeB and UE should be considering non-limiting and does in particular not imply a certain hierarchical relation between the two; in general "eNodeB" could be considered as device 1 and "UE" device 2, and these two devices communicate with each other over some radio channel.
In the following section, embodiments herein will be illustrated in more detail by a number of exemplary embodiments. It should be noted that these embodiments are not mutually exclusive. Components from one embodiment may be assumed to be present in another embodiment and it will be obvious to a person skilled in the art how those components may be used in the other exemplary embodiments.
Some exemplifying embodiments will now be described in more detail. Figure 2 depicts an example of a combined communication and navigation system 200 wherein embodiments herein may be implemented.
A navigation system 201 may be comprised in the combined communication and navigation system 200. The navigation system 201 may be a Global Navigation Satellite System (GNSS) such as a Global Position System (GPS), GLONASS, Galileo or BeiDou, etc., just to mention some examples. Further, even if reference sometimes in this disclosure is made to the GNSS and to the GNSS signal it should be understood that some embodiments herein are equally applicable to other navigation systems and navigation signals, and thus the terms GNSS and GNSS signal should not be interpreted limiting but to also cover other suitable navigation systems and navigations signals.
A wireless communications network 202 may be comprised in the combined communication and navigation system 200. The wireless communications network 202 may be a cellular communications network such as a NR network, a 5G network, an LTE network, a WCDMA network, a GSM network, any 3GPP cellular network, or a short range communications network, such as a WLAN, an LR-WPAN, a Bluetooth network, WiMAX network, a SIGFOX network, a Zigbee network, a BLE network such as a Bluetooth Smart network, or a CloT network such as an EC-GSM-loT network, a NB-loT network or an eMTC network, or a combination of one or more of the aforementioned communications networks just to mention some examples.
A Radio Network Node (RNN) 203 is arranged and configured to operate in the communication network 202. The RNN 203 is configured for wireless communication with one or more wireless devices, such as a first wireless device 204, when they are located within a coverage area 203a, e.g. a geographical area served by the RNN 203. It should be understood that the RNN 203 may serve or manage a plurality of coverage areas 203a, e.g. a first coverage area 203a-1 and a second coverage area 203a-2, even though only two are illustrated in Figure 2 for clarity reasons. The one more coverage areas 203a are sometimes in this disclosure referred to as one or more cells 203a.
The RNN 203 may be a transmission point such as a radio base station, for example an eNB, an eNodeB, or an Home Node B, an Home eNode B or any other network node capable to serve a user equipment or a machine type communication device in a communications network, such as the communications network 203. The RNN 203may further be configured to communicate with a core network node.
A first wireless device 204 is operating in the wireless communications network 202. The first wireless device 204 is configured to perform sidelink communication to a second wireless device 205. That is the first and second wireless devices 204,205 are configured to communicate with each other via sidelink communication. The first and second wireless devices 204,205, also sometimes referred to as wireless communications devices, user equipment, UEs, mobile stations or MSs, may be located in the wireless communications network 202. The first and second wireless devices 204,205 may e.g. be loT devices, user equipment, mobile terminals or wireless terminals, mobile phones, computers such as e.g. laptops, Personal Digital Assistants (PDAs) or tablet computers, with wireless capability, or any other radio network units capable to communicate over a radio link in a wireless communications network. It should be noted that the term user equipment used in this document also covers other wireless devices such as Machine to Machine (M2M) devices, even though they are not handled by any user.
Further it should be understood that the first wireless device 204 and the second wireless device 205 are configured to perform any kind of V2X communication. Thus, one of the first and second wireless devices 204,205 may be mounted at or carried by a vehicle while the other one of the first and second wireless devices 204,205 may be mounted at or carried by a vehicle, a pedestrian, or a network infrastructure device, e.g. a network node such as a radio network node, just to mention some examples.
In Figure 1 it is schematically illustrated that the first wireless device 204 is moving with a velocity v in a direction from the first coverage area 203a-1 into the second coverage area 203a-2.
An example of a method performed by the first wireless device 204 for performing sidelink communication will now be described with reference to a flowchart depicted in Figure 3. As mentioned above, the first wireless device 204 may perform the sidelink communication when operating in the first coverage area 203a-1 of the wireless communications network 202. Further, the first wireless device 204 is capable of using information obtained from the navigation system 201 for synchronization of the sidelink communication.
The methods comprise one or more of the following actions. It should be understood that these actions may be taken in any suitable order and that some actions may be combined.
Action 301
The first wireless device 204 may store correlation information specific for a first point of time and for the first coverage area 203a-1. The correlation information may comprises a first synchronization information received from the RNN 203 operating in the wireless communications network 202 and a first UTC value received from the navigation system 201. The correlation information may be used for synchronizing the sidelink communication.
In some embodiments, e.g. when the communications network 202 is an LTE communications network, the first synchronization information may comprise a first system frame number and a first subframe number. However, in other communications networks, e.g. in a GSM communications network, the first synchronization information may comprise a first super frame number, a first multi frame number, a first frame number and a first slot number.
Action 302
When the first wireless device 204 is moved to operate in a second coverage area 203a-2, or when a period of time, e.g. a defined period of time, elapses, the first wireless device 204 may store correlation information updated to be specific for an update point of time and for the second coverage area 203a-2. The correlation information may comprise new synchronization information received from the RNN 203 and a new UTC value. The new UTC value may be obtained from the navigation system 201 , e.g. the GNSS, if possible, or be determined, e.g. calculated, based on the first synchronization information and the first UTC value.
In some embodiments, e.g. when the communications network 202 is a LTE communications network, the new synchronization information comprises a new system frame number received from the RNN 203 and a new subframe number received from the RNN 203. In such embodiments the new UTC value is obtained from the navigation system 201 , e.g. the GNSS, or determined based on the first system frame number, the first subframe number and the first UTC value.
Action 303
In the absence of receipt of a UTC value from the navigation system 201 , the first wireless device 204 determines a second UTC value.
Thus, when the first wireless device 204 cannot obtain a UTC value from the navigation system 201 , e.g. the GNSS, the first wireless device 204 determines, e.g. calculates, the second UTC value. For example, this may be the case in the absence of receipt of one or more navigation signals S, e.g. one or more GNSS signals, from the navigation system 201 or when the navigation signal received is too weak. The one or more navigation signals may provide one or more UTC values.
In some embodiments, the first wireless device 204 determines the second UTC value at a second point of time x based on second synchronization information received from the RNN 203 for the second point of time x and based on the stored correlation information.
The first wireless device 204 may determine the second UTC value by determining the second UTC value at a second point of time x based on a system frame number and a subframe number for the second point of time x and received from the RNN 203, and based on the stored correlation information.
The first wireless device 204 may determine the second UTC value as
second UTC value = first UTC value + offset between the first synchronization information and the second synchronization information. Action 304
The first wireless device 204 determines a Device-to-device Frame Number (DNF) based on the determined second UTC time value.
In some embodiments, the first wireless device 204 determines the DFN as:
DFN= Floor (0.1*(Tcurrent -Tref)) mod 1024
SubframeNumber= Floor (Tcurrent -Tref) mod 10
Wherein Tcurrent is the set to the UTC time calculated. This value is expressed in milliseconds; Tref is the reference UTC time 00:00:00 on Gregorian calendar date 1 January, 1900 (midnight between Thursday, December 31 , 1899 and Friday, January 1 , 1900). This value is expressed in milliseconds.
However, the equations above are only given as examples and it should be understood that the DFN may be calculated in other ways, e.g. as
DFN= Floor (0.1*(Tcurrent -Tref+dfnOffset) /1000) mod 1024
SubframeNumber= Floor ((Tcurrent -Tref+dfnOffset)/1000) mod 10
Wherein Tcurrent is set to UTC time calculated; This value is expressed in milliseconds; Tref is the reference UTC time 00:00:00 on Gregorian calendar date 1 January, 1900 (midnight between Thursday, December 31 , 1899 and Friday, January 1 , 1900). This value is expressed in microseconds; and dfnOffset is the value configured by RRC in parameter dfnOffset to shift the DFN with respect to the reference time derived from GNSS. This value is expressed in microseconds. Action 305
The first wireless device 204 provides or performs the sidelink communication with the second wireless device 205 using the determined DFN.
To perform the method for performing sidelink communication, the first wireless device 204 may be configured according to an arrangement depicted in Figure 4. As mentioned above, the first wireless device 204 is configured to operate in the first coverage area 203a-1 of the wireless communications network 202 and to use synchronization to the navigation system 201 , e.g. the GNSS. Thus, the first wireless device is capable of using information obtained from the navigation system 201 for synchronization of the sidelink communication.
In some embodiments, the first wireless device 204 comprises an input and/or output interface 400 configured to communicate with one or more wireless devices, e.g. the second wireless device 205 and/or one or more network nodes, e.g. the RNN 203. The input and/or output interface 400 may comprise a wireless receiver (not shown) and a wireless transmitter (not shown). The first wireless device 204 is configured to receive, by means of a receiving module 401 configured to receive, a transmission, e.g. a data packet, a signal or information, from one or more network nodes, e.g. the RNN 203 and/or from one or more other wireless devices, e.g. the second wireless device 205. The receiving module 401 may be implemented by or arranged in communication with a processor 407 of the first wireless device 204. The processor 407 will be described in more detail below.
The first wireless device 204 is configured to transmit, by means of a
transmitting module 402 configured to transmit, a transmission, e.g. a data packet, a signal or information, to one or more network nodes, e.g. the RNN 203 and/or to one or more other wireless devices, e.g. the second wireless device 205. The transmitting module 402 may be implemented by or arranged in communication with the processor 407 of the first wireless device 204.
The first wireless device 204 is configured to store, by means of a storing module 403 configured to store, information such as correlation information. The storing module 403 may be implemented by or arranged in communication with the processor 407 of the first wireless device 204.
The first wireless device 204 is configured to determine, by means of a determining module 404 configured to determine, a UTC and/or a DFN. The determining module 404 may be implemented by or arranged in communication with the processor 406 of the first wireless device 204.
The first wireless device 204 is configured to provide/perform, by means of a providing/performing module 405 configured to provide/perform, a sidelink
communication with another device, e.g. the second wireless device 205. The
providing/performing module 405 may be implemented by or arranged in communication with the processor 407 of the first wireless device 204. In some embodiments, the first wireless device 204 is configured to perform, by means of one or more other modules configured to perform one or more further actions described herein. The one or more other modules may be implemented by or arranged in communication with the processor 407 of the first wireless device 204. The first wireless device 204 may also comprise means for storing data. In some embodiments, the first wireless device 204 comprises a memory 406 configured to store the data. The data may be processed or non-processed data and/or information relating thereto. The memory 406 may comprise one or more memory units. Further, the memory 406 may be a computer data storage or a semiconductor memory such as a computer memory, a read-only memory, a volatile memory or a non-volatile memory. The memory is arranged to be used to store obtained information, data, configurations, and
applications etc. to perform the methods herein when being executed in the first wireless device 204. Embodiments herein for providing sidelink communication may be implemented through one or more processors, such as the processor 406 in the arrangement depicted in Fig. 4, together with computer program code for performing the functions and/or method actions of embodiments herein. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the first wireless device 204. One such carrier may be in the form of an electronic signal, an optical signal, a radio signal or a computer readable storage medium. The computer readable storage medium may be a CD ROM disc or a memory stick.
The computer program code may furthermore be provided as program code stored on a server and downloaded to the first wireless device 204.
Those skilled in the art will also appreciate that the input/output interface 400, the receiving module 401 , the transmitting module 402, the storing module 403, the determining module 404, the providing/performing module 405, and the one or more other modules above may refer to a combination of analogue and digital circuits, and/or one or more processors configured with software and/or firmware, e.g. stored in the memory 406, that when executed by the one or more processors such as the processors in the first wireless device 204 perform as described above. One or more of these processors, as well as the other digital hardware, may be included in a single Application-Specific Integrated Circuitry (ASIC), or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a System-on-a-Chip (SoC).
Examples relating to some embodiments wherein the navigation system 201 is a GNSS and the communications network 202 is an LTE communications network.
Correlation information
As previously described, e.g. in Action 301 above, the first wireless device 204 may store correlation information. For example, the correlation information comprises information correlating a GNSS synchronization with a RNN synchronization. The correlation information is sometimes, e.g. when the RNN 203 is an LTE eNB, in this disclosure referred to as a correlation triple as it may comprises three elements; a system frame number SYSTEM_FRAME, a subframe number SUB_FRAME and a UTC time UTC_TIME.
The correlation triple is valid within a coverage area 203a, e.g. within the first coverage area 203a-1. When the first wireless device 204 moves to a new coverage area, e.g. to the second coverage area 203a-2, the correlation information needs to be updated. The correlation triple may be valid for a period of time, e.g. a defined time of period, i.e. 10 seconds. When the period of time elapses, the correlation information needs to be updated. Updating of the correlation information will be described in more detail in Action 302 above.
The first wireless device 204 sets correlation information
This relates e.g. to Action 301 previously described.
If correlation information is not available for the first wireless device 204 and when the first wireless device 204 is within coverage of the wireless communications network 202 and when the first wireless deice 204 is in receipt of an UTC from the navigation system 201 , the first wireless device 204 sets, e.g. initiates, the correlation information. At a certain point of time X:
The point of time X should be the beginning of a subframe, say sub_frame_X, which belongs to a system frame system_frame_X;
The corresponding UCT which is obtained from the GNSS at the point of time X is UTC_X
The first wireless device 204 sets, e.g. initiates, the correlation information as below:
- SYSTEM_FRAME = system_frame_X
- SUB_FRAME = sub_frame_X
- UTC_TIME = UTC_X
The first wireless device 204 calculates the UTC time
This relates e.g. to Action 302 and Action 303 previously described.
The first wireless device 204 calculates the UTC time when the first wireless device 204 is performing a sidelink communication, e.g. a V2X communication, using a GNSS synchronization and when the first wireless device 204 is not able to obtain an UTC from the GNSS.
Alternatively or additionally, the first wireless device 204 calculates the UTC time when the first wireless device 204 is updating correlation information as described in Action 302 and when the first wireless device 204 is not able to obtain the UTC from the GNSS.
For a certain point of time Y, which should be the beginning of a subframe, say sub_frame_Y, which belongs to a system frame system_frame_Y, the first wireless device 204 calculates the corresponding UTC time UTC_Y as:
The first wireless device 204 is storing correlation triple (SYSTEM_FRAME, SUB_FRAME, UTC_TIME) The first wireless device 204 calculates an offset and the UTC value UTC_Y as below:
offset = [ (system_frame_Y *10 + sub_frame_Y) - (SYSTEM_FRAME *10 + SUB_FRAME) ] mod 10240 (unit is millisecond)
UTC_Y = offset + UTC_Time
It should be understood that the UTC time may be given in a different unit than millisecond, and thus the formula needs to be transformed accordingly.
For example, if the UTC time is given in millisecond, the formula is:
UTC_Y = [ (system_frame_Y *10 + sub_frame_Y) - (SYSTEM_FRAME *10 + SUB_FRAME) ] mod 10240 + UTC_TIME (the unit of result is millisecond)
As another example, if the UTC time is given in microsecond, the formula is:
UTC_Y = [ (system_frame_Y *10 + sub_frame_Y) - (SYSTEM_FRAME *10 + SUB_FRAME) ] mod 10240 *1000 + UTC_TIME (the unit of result is microsecond)
Figure 5 schematically illustrates embodiments of a method performed by the wireless device 204 for performing sidelink communication. At a first point of time T1 , the first wireless device 204 is able to receive synchronization from both the communications network 202 and the navigation network 201. However, at a second point of time T2, the first wireless device 204 has lost the GNSS synchronization. According to embodiments described herein the first wireless device 204 will calculate the UTC time at the second point of time T2 as below:
At the first point of time T1 , the first wireless device 204 initiates correlation triple:
- SYSTEM_FRAME is 100
- SUB_FRAME is 6
- UTC_TIME is 1000 (unit is ms)
At the second point of time T2, the first wireless device 204 has following information:
system_frame_x is 8
sub frame x is 1 the first wireless device 204 calculates UTC time UTC_x at the second point of time T2 as below:
- UTC_x = [(8*10+1) - (100*10+6)] mod 10240 + 1000 = 10315 (unit is ms)
5 The first wireless device 204 calculates DFN
This relates e.g. to Action 304 previously described.
When the first wireless device 204 is configured to perform sidelink communication using navigation synchronization, e.g. V2X communication using GNSS synchronization, and the first wireless device 204 may calculate the DFN as
10 DFN= Floor (0.1*(Tcurrent -Tref)) mod 1024
SubframeNumber= Floor (Tcurrent -Tref) mod 10
wherein Tcurrent is the set to UTC time calculated. This value is expressed in
milliseconds; Tref is the reference UTC time 00:00:00 on Gregorian calendar date 1 January, 1900 (midnight between Thursday, December 31 , 1899 and Friday, January 1 , 15 1900). This value is expressed in milliseconds.
However, this is only given as an example and it should be understood that the DFN may be calculated in other ways, e.g. as
DFN= Floor (0.1*(Tcurrent -Tref+dfnOffset) /1000) mod 1024
SubframeNumber= Floor ((Tcurrent -Tref+dfnOffset)/1000) mod 10
20 Wherein Tcurrent is set to UTC time calculated; This value is expressed in milliseconds;
Tref is the reference UTC time 00:00:00 on Gregorian calendar date 1 January, 1900 (midnight between Thursday, December 31 , 1899 and Friday, January 1 , 1900). This value is expressed in microseconds; and dfnOffset is the value configured by the RRC in parameter dfnOffset to shift the DFN with respect to the reference time derived from the 25 GNSS. This value is expressed in microseconds.
The first wireless device 204 updates correlation information
This relates e.g. to Action 302 previously described.
30 When the first wireless device 204 moves to a new cell, e.g. from the first
coverage area 203a-1 to the second coverage area 203a-2, via cell reselection or handover, and if the first wireless device 204 is not able to obtain the UTC from the navigation system 201 , e.g. the GNSS, it updates correlation information between GNSS synchronization and eNB synchronization according to Action 301 described above or according the description under section "The first wireless device 204 sets correlation information" above.
The first wireless device 204 may update the correlation information periodically. This may for example be the case when a period of time for period updates has elapsed and when the first wireless device 204 has not moved to another coverage cell. In such cases, first wireless device 204 may update the correlation information between the GNSS synchronization and the eNB synchronization when the period of time for period updates has elapsed and when the first wireless device 204 is in receipt of an UTC from the navigation system 201. The correlation information may be updated according to Action 301 described above or according the description under section "The first wireless device 204 sets correlation information" above.
When the first wireless device 204 moves to a new cell, e.g. from the first coverage area 203a-1 to the second coverage area 203a-2, via cell reselection or handover, and the first wireless device 203 is not able to obtain the UTC from the navigation system 201 , e.g. the GNSS , and there is correlation between GNSS synchronization and eNB synchronization available, the first wireless device 204 updates the correlation information between the GNSS synchronization and the eNB
synchronization, as following:
The first wireless device 204 stores correlation triple (SYSTEM_FRAME,
SUB_FRAME, UTC_TIME)
Further, the first wireless device 204 stores following information upon moving to a new cell, as shown in Figure 6:
o A first point of time T1 is the beginning of subframe succeeding the last subframe when the first wireless device 204 is connected/camped to the "old cell"; the system frame number and subframenumber of this subframe is system_frame_old and sub_frame_old.
o A second point of time T2 is the beginning of the first subframe when the first wireless device 204 is synchronized the "new cell"; the system frame number and subframenumber of this first subframe is
system_frame_new and sub_frame_new.
o The duration between the first and second points of time T1 and T2 is SyncDelay.
Furthermore, the first wireless device 204 calculates a first UTC time for the first point of time T1 according Action 303 and gets the result UTC_old. The first wireless device 204 calculates a second UTC time for the second point of time T2 as below:
UTC_new = UTC_old + syncDelay
Yet further, the first wireless device 204 updates the correlation information as below:
o SYSTEM_FRAME = system_frame_new
o SUB_FRAME = sub_frame_new
o UTC_TIME = UTC_new
Even if embodiments have been described with reference to the first wireless device operating in an LTE communications network, it should be understood that embodiments herein are equally applicable to the first wireless device operating in another type of wireless communications networks, such as a GSM communications network, a WCDM communications network, a TD-SCDMA communications network, a 5G communications network, a WIFI communications network, etc.
Further, even if embodiments have been described with reference to a first wireless device operating in a single wireless communications network, it should be understood that embodiments herein are equally applicable to a first wireless device operating in a plurality of wireless communications networks. Thus, the first wireless device may be moving from operation within the first coverage area 203a-1 to operation within the second coverage area 203a-2 and the first and second coverage areas area may be served by two different radio network nodes operating in two different wireless communications networks.
For example, the first wireless device 204 may move between different types of wireless communications networks, such as GSM, WCDM, TD-SCDMA, LTE, 5G, WIFI and etc.
Further, the procedure of calculating UTC time when the GNSS synchronization is lost may be provided with following modification:
- The correlation information, which comprises SYSTEM_FRAME,
SUB_FRAME, UTC_TIME for LTE; may comprise the corresponding synchronization factors and UTC_TIME in the concerned wireless communications network
- All procedures may be updated according to the conversion between the
corresponding synchronization factors and the UTC time. ABBREVIATION EXPLANATION
3G Third Generation of Mobile Telecommunications Technology BSM Basic Safety Message
BW Bandwidth
BSR Buffer Status Report
CAM Cooperative Awareness Message
CBR Channel Busy Ratio
DPTF Data Packet Transmission Format
D2D Device-to-Device Communication
DENM Decentralized Environmental Notification Message
DSRC Dedicated Short-Range Communications
eNB eNodeB
ETSI European Telecommunications Standards Institute
LTE Long-Term Evolution
NW Network
RS Reference Signals
TF Transport Format
SAE System Architecture Evolution
UE User Equipment
V2I Vehicle-to-lnfrastructure
V2P Vehicle-to-Pedestrian
V2V Vehicle-to-vehicle communication
V2x Vehicle-to-anything-you-can-imagine
SPS Semi Persistent Scheduling
DMRS Demodulation reference signals
OCC Orthogonal cover code
PDCCH Physical Downlink Control Channel
DBS Delay-Based Scheduler
MAC Medium Access Control
MAC CE MAC Control Element
PUSCH Physical Uplink Shared Channel
PUCCH Physical Uplink Control Channel
PDU Packet Data Unit 3GPP Third Generation Partnership Project
LCID Logical Channel Identity
RRC Radio Resource Control
IP Internet Protocol
PPPP ProSe Per Packet Priority
ProSe Proximity Services
PRB Physical Resource Block
SL Sidelink
UL Uplink
DL Downlink
LCG Logical Channel Group
SFN System Frame Number
TTI Transmission Time Interval
SCI Sidelink Control Information
When the word "comprise" or "comprising" is used in this disclosure it shall be interpreted as non-limiting, i.e. meaning "consist at least of".
Modifications and other variants of the described embodiment(s) will come to mind to one skilled in the art having the benefit of teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the embodiment(s) herein is/are not be limited to the specific examples disclosed and that modifications and other variants are intended to be included within the scope of this disclosure. Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

WHAT IS CLAIMED IS:
1. A method performed by a first wireless device (204) for performing sidelink communication when operating in a first coverage area (203a-1) of a wireless
communications network (202), wherein the first wireless device (204) is capable of using information obtained from a navigation system (201) for synchronization of the sidelink communication, and wherein the method comprises:
- in the absence of receipt of a Coordinated Universal Time, UTC, value from the navigation system (201), determining (303) a second Coordinated Universal Time, UTC, value;
- determining (304) a Device-to-device Frame Number, DNF, based on the determined second UTC time value; and
- performing (305) the sidelink communication with a second wireless device (205) using the determined DFN.
2. The method of claim 1 , further comprising:
- storing (301) correlation information specific for a first point of time and for the first coverage area (203a-1), wherein the correlation information comprises a first synchronization information received from a Radio Network Node, RNN, (203) operating in the wireless communications network (202) and a first UTC value received from the navigation system (201).
3. The method of claim 2, further comprising:
- when the first wireless device (204) is moved to operate in a second coverage area (203a-2) of the wireless communications network (202), storing (302) correlation information updated to be specific for an update point of time and for the second coverage area (203a-2), wherein the correlation information comprises a new synchronization information received from the RNN (203) and a new UTC value determined based on the first synchronization information and the first UTC value.
4. The method of claim 2, further comprising:
- when a period of time has elapsed, storing (302) correlation information updated to be specific for an update point of time, wherein the correlation information comprises a new synchronization information received from the RNN (203) and a new UTC value which is received from the navigation system (201) if possible or determined based on the first synchronization information and the first UTC value.
5. The method of any one of claims 2-4, wherein the determining (303) of the second UTC value comprises:
- determining the second UTC value at a second point of time x based on second synchronization information received from the RNN (203) for the second point of time x and based on the stored correlation information.
6. The method of claim 5, wherein the determining (303) of the second UTC value comprises:
- determining the second UTC value as
second UTC value = first UTC value + offset between the first synchronization information and the second synchronization information.
7. The method of any one of claims 1-6, wherein the navigation system is a
Global Navigation Satellite System, GNSS.
8. A first wireless device (204) capable of performing sidelink communication when operating in a first coverage area (203a-1) of a wireless communications network (202), wherein the first wireless device (20) is capable of using information obtained from a navigation system (201) for synchronization of the sidelink communication, and wherein the first wireless device (204) is configured to:
- determine a second Coordinated Universal Time, UTC, value in the absence of receipt of a Coordinated Universal Time, UTC, value from the navigation system (201);
- determine a Device-to-device Frame Number, DNF, based on the determined second UTC time value; and
- perform the sidelink communication with a second wireless device (205) using the determined DFN.
9. The first wireless device (204) of claim 8, further being configured to:
- store correlation information specific for a first point of time and for the first coverage area (203a-1), wherein the correlation information comprises a first
synchronization information received from a Radio Network Node, RNN, (203) operating in the wireless communications network (202) and a first UTC value received from the navigation system (201).
10. The first wireless device (204) of claim 9, further being configured to:
- store correlation information updated to be specific for an update point of time and for a second coverage area (203a-2) of the wireless communications network (202) when the first wireless device (204) is moved to operate in a second coverage area (203a-2), wherein the correlation information comprises a new synchronization information received from the RNN (203) and a new UTC value determined based on the first synchronization information and the first UTC value.
1 1. The first wireless device (204) of claim 9, further being configured to:
- store correlation information updated to be specific for an update point of time when a period of time has elapsed, wherein the correlation information comprises a new synchronization information received from the RNN (203) and a new UTC value which is received from the navigation system (201) if possible or determined based on the first synchronization information and the first UTC value.
12. The first wireless device (204) of any one of claims 9-11 , wherein the first wireless device (204) is configured to determine the second UTC value by being configured to:
- determine the second UTC value at a second point of time x based on second synchronization information received from the RNN (203) for the second point of time x and based on the stored correlation information.
13. The first wireless device (204) of claim 12, wherein the first wireless device (204) is configured to determine the second UTC value by being configured to:
- determine the second UTC value as
second UTC value = first UTC value + offset between the first synchronization information and the second synchronization information.
14. The first wireless device (204) of any one of claims 8-13, wherein the navigation system is a Global Navigation Satellite System, GNSS.
15. A computer program, comprising instructions which, when executed on at least one processor, causes the at least one processor to carry out the method according to any one of claims 1-7.
16. A carrier comprising the computer program of claim 15 wherein the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium.
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