BR112016017079B1 - OPERATION MODE SWITCHING IN D2D COMMUNICATIONS - Google Patents

Abstract

SWITCHING OPERATION MODE IN D2D COMMUNICATIONS. Methods, systems, and devices are described for switching a mode of operations in device-to-device (D2D) communications. A UE in the coverage area of a base station can communicate directly with other UEs using a centralized transmission feature program. Before experiencing radio link failure (RLF), the UE can determine which switching parameters have been met and transition to an intermediate mode based on a distributed transmission program using a pool of resources established by the base station. In one example, switching parameters may be received from the base station in a connection response message. In another example, the UE may send a switching request to the base station before initiating the transition to intermediate mode. In some cases, after transitioning to intermediate mode, the UE may experience a radio link failure and transition to a distributed mode using a predetermined pool of resources.

Description

REFERENCES

[0001] The present patent application claims priority to US patent application no. 14/599,254 by Patil et al., entitled “Switching mode of operation in D2D communications,” filed on January 16, 2015; and US provisional patent application no. 61/9332,729 by Patil et al., entitled “Switching mode of operation in D2D communications,” filed January 28, 2015; each of which is assigned to the assignee hereof.

BACKGROUND FIELD OF REVELATION

[0002] The following relates generally to wireless communication, and more specifically to switching a mode of operations in device-to-device (D2D) communications.

DESCRIPTION OF RELATED TECHNIQUE

[0003] Wireless communication systems are widely used to provide various types of communication content such as voice, video, packet data, message sending, broadcast, and so on. These systems may be multiple access systems capable of supporting communication with multiple users by sharing available system resources (e.g., time, frequency, and power). Examples of such multiple access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and frequency division multiple access (FDMA) systems. by orthogonal frequency division (OFDMA).

[0004] In general, a wireless multiple access communication system may include a number of base stations, each simultaneously supporting communication to multiple mobile devices or other user equipment (UE) devices. Base stations can communicate with UEs on both downstream and upstream links. Each base station has a coverage range, which can be referred to as the cell's coverage area. D2D communications involve direct wireless communications between UEs in or beyond the coverage area of a base station. D2D communications can be facilitated by scheduling transmissions from a base station if the devices are within a coverage area.

[0005] In some cases, D2D communications are used by public safety officials such as police, firefighters and rescue teams. Public safety teams using D2D communications can move in and out of wireless network coverage. When a UE leaves a coverage area it may transition from a mode in which communications are facilitated by a base station to a mode that is independent of a base station. In some cases, this transition may temporarily disrupt D2D communications. A temporary disruption in a public safety team's communications can negatively impact their ability to carry out their mission in a timely manner.

SUMMARY

[0006] The described aspects relate generally to one or more improved systems, methods or apparatus for switching a mode of operations in device-to-device (D2D) communications. A UE in the coverage area of a base station can communicate directly with other UEs using a centralized transmission resource program from the base station. Before experiencing a radio link failure (RLF) with the base station, the UE may determine that one or more switching parameters have been met and initiate a transition to an intermediate mode that does not rely on a centralized program. The intermediate mode may be based on a broadcast program distributed using a pool of resources established by the base station. In one example, switching parameters may be received from the base station in a connection response message. In another example, the UE may send a switching request to the base station before initiating the transition to intermediate mode. In some cases, after transitioning to intermediate mode, the UE may experience a radio link failure and transition to a distributed transmission mode using a predetermined resource pool.

[0007] In another example, a UE communicates directly with other UEs using D2D communications based on a distributed transmission program using preconfigured resources before entering the coverage area of a base station. Before entering the coverage area, the UE may receive system information with a pool of resources for use in D2D communications. The UE can switch to an intermediate mode based on distributed transmission program using the pool of resources indicated by the base station. In some cases, after switching to intermediate mode, the UE may establish a connected state with the base station. After establishing the connected state, the UE can switch to a D2D communications mode based on a centralized transmission resource program.

[0008] A method of wireless device-to-device (D2D) communication in a user equipment (UE) is described, comprising establishing communications with one or more other UEs in accordance with a first D2D mode, the first D2D mode based at least in part in a centralized broadcast resource program received from a base station; determining that one or more mode switching parameters have been met; and switching to a second D2D mode, the second D2D mode based at least in part on a distributed transmission schedule using a pool of resources allocated by the base station.

[0009] An apparatus for wireless device-to-device (D2D) communication in a user equipment (UE) is also described, comprising: means for establishing communications with one or more other UEs in accordance with a first D2D mode, the first D2D mode based at least in part on a centralized transmission resource program received from a base station; means for determining that one or more mode switching parameters have been met; and means for switching to a second D2D mode, the second D2D mode based at least in part on a distributed transmission schedule using a pool of resources allocated by the base station.

[0010] An apparatus for wireless device-to-device (D2D) communication in a user equipment (UE) is also described, comprising: a processor; memory in electronic communication with the processor; and instructions stored in memory, the instructions being executable by the processor to: establish communications with one or more other UEs in accordance with a first D2D mode, the first D2D mode based at least in part on a centralized transmission resource program received from a base station; determining that one or more mode switching parameters have been met; and switching to a second D2D mode, the second D2D mode based at least in part on a distributed transmission schedule using a pool of resources allocated by the base station.

[0011] A computer program product for wireless device-to-device (D2D) communication in a user equipment (UE) is also described, the computer program product comprising a non-transitory computer-readable medium that stores executable instructions by a processor to: establish communications with one or more other UEs in accordance with a first D2D mode, the first D2D mode based at least in part on a centralized transmission resource program received from a base station; determining that one or more mode switching parameters have been met; and switching to a second D2D mode, the second D2D mode based at least in part on a distributed transmission schedule using a pool of resources allocated by the base station.

[0012] Some examples of the method, apparatus or computer program product described above may further comprise monitoring communications from the base station for an indication of the resource pool; determining that a message from the base station indicating the resource pool is not receivable; and switching to a third D2D mode, the third D2D mode based at least in part on distributed transmission using a preconfigured resource pool.

[0013] Some examples of the method, apparatus, or computer program product described above may further comprise sending a connection configuration request to the base station, the connection configuration request comprising a D2D mode indication; and receiving a connection response message from the base station comprising one or more mode switching parameters. Some examples of the method, apparatus, or computer program product described above may further comprise receiving one or more mode switching parameters via a broadcast system information block (SIB) message.

[0014] In some examples of the method, apparatus, or computer program product described above one or more mode switching parameters comprise at least one of an out-of-sync indication. Related to a number of bad frames, a sync indication. Related to a number of good frames, a period of time, a path loss threshold, and signal-to-noise ratio (SINR) threshold.

[0015] In some examples of the method, apparatus, or computer program product described above one or more mode switching parameters comprise at least one of a threshold number of random access channel (RACH) requests, a period of time after an unsuccessful RACH attempt, a period of time after a status report (SR), a buffer status report (BSR) or a resource request, or an indication of a handover failure or an incomplete handover. In some examples of the method, apparatus, or computer program product described above one or more mode switching parameters are received from a system information broadcast.

[0016] In some examples of the method, apparatus or computer program product described above one or more mode switching parameters comprise a period of time and at least one additional mode switching parameter; and determining that one or more mode switching parameters have been met comprises determining that at least one additional mode switching parameter has been met and waiting until the period of time has elapsed before switching to a second D2D mode.

[0017] Some examples of the method, apparatus or computer program product described above may further comprise sending a mode switching request to the base station. In some examples of the method, apparatus, or computer program product described above one or more mode switching parameters comprise an indication from a user application and the mode switching request comprises a user initiated mode switching indication.

[0018] Some examples of the method, apparatus or computer program product described above may further comprise receiving a response from the base station indicating that a mode switch is permitted. In some examples of the method, apparatus or computer program product described above the switching to a second D2D mode is performed autonomously before receiving a response from the base station.

[0019] In some examples of the method, apparatus or computer program product described above one or more mode switching parameters comprises a modified radio link failure threshold (RLF). In some examples of the method, apparatus or computer program product described above the modified RLF threshold is configured to be met before reaching an unmodified RLF threshold.

[0020] Some examples of the method, apparatus or computer program product described above may further comprise storing a record of mode switching information comprising one or more of a timestamp, a UE location, a radio interface condition , a UE speed, a cell ID and a carrier frequency. Some examples of the method, apparatus or computer program product described above may further comprise maintaining a media access control (MAC) or radio link control (RLC) configuration after switching to the second D2D mode.

[0021] Some examples of the method, apparatus or computer program product described above may further comprise reconfiguring a media access control (MAC) or radio link control (RLC) configuration according to a predetermined state after switching to the second D2D mode. Some examples of the method, apparatus or computer program product described above may further comprise continuing communications based on distributed transmission programming until one or more hysteresis parameters are met.

[0022] In some examples of the method, apparatus or computer program product described above one or more hysteresis parameters include at least one of a time period, a path loss parameter, a number of good frames, and a ratio signal to noise ratio (SINR).

[0023] Some examples of the method, apparatus or computer program product described above may further comprise resetting a protocol layer configuration based at least in part on switching.

[0024] Some examples of the method, apparatus or computer program product described above may further comprise utilizing the pool of resources associated with the second D2D mode until a connection is established with the base station; and establish the connection with the base station. Some examples of the method, apparatus or computer program product described above may further comprise switching to the first D2D mode, the first D2D mode based at least in part on the centralized transmission resource program received from the base station.

[0025] A device-to-device (D2D) wireless communication method is also described, comprising: establishing communications with one or more other UEs in accordance with a first D2D mode, the first D2D mode based at least in part on a pre-configured pool of transmission resources; receiving system information from a base station by allocating a pool of resources for transmission; and switching to a second D2D mode, the second D2D mode being based on distributed transmission scheduling using the pool of resources allocated by the base station.

[0026] An apparatus for device-to-device (D2D) wireless communication is also described, comprising: means for establishing communications with one or more other UEs in accordance with a first D2D mode, the first D2D mode based at least in part in a pre-configured pool of transmission resources; means for receiving system information from a base station by allocating a pool of resources for transmission; and means for switching to a second D2D mode, the second D2D mode being based on distributed transmission scheduling using the pool of resources allocated by the base station.

[0027] An apparatus for wireless device-to-device (D2D) communication is also described, comprising: a processor; memory in electronic communication with the processor; and instructions stored in memory, the instructions being executable by the processor to: establish communications with one or more other UEs in accordance with a first D2D mode, the first D2D mode based at least in part on a pre-configured pool of transmission resources ; receiving system information from a base station by allocating a pool of resources for transmission; and switching to a second D2D mode, the second D2D mode being based on distributed transmission scheduling using the pool of resources allocated by the base station.

[0028] A computer program product for wireless device-to-device (D2D) communication is also described, the computer program product comprising a non-transitory computer readable medium storing instructions executable by a processor for: establishing communications with a or more other UEs in accordance with a first D2D mode, the first D2D mode based at least in part on a preconfigured pool of transmission resources; receiving system information from a base station by allocating a pool of resources for transmission; and switching to a second D2D mode, the second D2D mode being based on distributed transmission scheduling using the pool of resources allocated by the base station.

[0029] Some examples of the method, apparatus or computer program product described above may further comprise establishing a connected state with the base station; and switching to a third D2D mode, the third D2D mode being based on a centralized transmission resource program received from the base station subsequent to establishing the connected state.

[0030] Further scope of applicability of the described methods and apparatus will become apparent from the following detailed description, claims and drawings. The detailed description and specific examples are given by way of illustration only, as various changes and modifications understood in the spirit and scope of the description will become apparent to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] A further understanding of the nature and advantages of the present invention can be achieved by reference to the following drawings. In the accompanying figures, similar components or aspects may have the same reference label. Additionally, multiple components of the same type can be distinguished by following the reference label by a dash and a second label that distinguishes between similar components. If only the first reference label is used in the specification, the description is applicable to any of the similar components having the same first reference label independent of the second reference label.

[0032] Figure 1 illustrates an example of a wireless communication system according to various embodiments;

[0033] Figure 2 illustrates an example of a wireless communication system in which UEs involved in D2D communications are leaving a network coverage area according to various embodiments;

[0034] Figure 3 illustrates an example of a wireless communication system in which UEs involved in D2D communications are entering a network coverage area according to various embodiments;

[0035] Figure 4 shows a block diagram of a device for switching a mode of operations in D2D communications according to various embodiments;

[0036] Figure 5 shows a block diagram of a device for switching a mode of operations in D2D communications according to various embodiments;

[0037] Figure 6 shows a block diagram of a D2D communications module according to various embodiments;

[0038] Figure 7 is a block diagram of a system for switching a mode of operations in D2D communications according to various embodiments;

[0039] Figure 8 shows a flowchart illustrating a method for switching a mode of operations in D2D communications when a UE is leaving a base station coverage area;

[0040] Figure 9 shows a flowchart illustrating a method for switching a mode of operations in D2D communications according to various modalities;

[0041] Figure 10 shows a flowchart illustrating a method for switching a mode of operations in D2D communications according to various modalities;

[0042] Figure 11 shows a flowchart illustrating a method for switching a mode of operations in D2D communications according to various modalities;

[0043] Figure 12 shows a flowchart illustrating a method for switching a mode of operations in D2D communications when a UE is entering a base station coverage area; It is

[0044] Figure 13 shows a flowchart illustrating a method for switching a mode of operations in D2D communications according to various modalities.

DETAILED DESCRIPTION

[0045] The described aspects relate generally to one or more improved systems, methods or apparatus for switching a mode of operations in device-to-device (D2D) communications. a UE in the coverage area of a base station can communicate directly with other UEs using a centralized transmission resource program from the base station. Before experiencing radio link failure (RLF) with the base station, the UE may determine that one or more switching parameters have been met and indicate a transition to an intermediate mode that does not rely on a centralized program. The intermediate mode may be based on a distributed transmission program using a pool of resources established by the base station. In one example, switching parameters may be received from the base station in a connection response message. In another example, the UE may send a switching request to the base station before initiating the transition to intermediate mode. In some cases, after transitioning to intermediate mode, the UE may experience a radio link failure and transition to a distributed transition mode utilizing a predetermined pool of resources.

[0046] In another example, a UE communicates directly with other UEs using D2D communication based on a distributed transmission program using preconfigured resources before entering the coverage area of a base station. After entering the coverage area, the UE can receive system information with a pool of resources for use in D2D communications. The UE can switch to an intermediate mode based on distributed transmission program using the pool of resources indicated by the base station. In some cases, after switching to intermediate mode, the UE may establish a connected state with the base station. After establishing the connected state, the UE can switch to a D2D communication mode based on a centralized transmission resource program.

[0047] Thus, the techniques described here can allow efficient switching from a D2D mode that relies on a base station for centralized programming to a mode that uses distributed programming using preconfigured resources by using an intermediate mode. This can allow users to transition in and out of a base station coverage area without experiencing significant disruption in D2D communications. This can be particularly important for public safety teams employing direct D2D communication.

[0048] The following description provides examples, and is not limiting the scope, applicability, or configuration set out in the claims. Changes can be made to the function and arrangement of elements discussed without departing from the spirit and scope of the revelation. Various embodiments may omit, replace, or add various procedures or components as appropriate. For example, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, aspects described with respect to certain embodiments may be combined in other embodiments.

[0049] Figure 1 illustrates an example of a wireless communication system 100, according to various embodiments. The system 100 may include a base station 105, communication devices, also known as a user equipment (UE) 115, and a core network 130. The base stations 105 may communicate with the UEs 115 under the control of a network controller. base station (not shown), which may be part of the core network 130 or base stations 105 in various embodiments. The base stations 105 may communicate control information and/or user data with the core network 130 via backhaul links 132. In embodiments, the base stations 105 may communicate, directly or indirectly, with each other via return transport channel links 134, which may be wired or wireless communication links. The system 100 can support operation on multiple carriers (waveform signals of different frequencies). Wireless communication links 125 may be modulated according to various radio technologies. Each modulated signal can carry control information (e.g. reference signals, control channels, etc.), overhead information, data, etc. Wireless communication links 125 may also be established between UEs 115 in a configuration known as device-to-device (D2D) communication.

[0050] The base stations 105 may communicate wirelessly with the UEs 115 via one or more base station antennas. Each of the base stations 105 may provide communications coverage for a respective geographic area 110. In some embodiments, the base stations 105 may be referred to as a base transceiver station, a radio base station, an access point, a radio transceiver, radio, a basic service set (BSS), an extended service set (ESS), a NodeB, eNodeB (eNB), native NodeB, a native eNodeB, or some other suitable terminology. The coverage area 110 for a base station 105 may be divided into sectors comprising only a portion of the coverage area (not shown). The system 100 may include base stations 105 of different types (e.g., macro, micro, and/or peak base stations). There may be areas of overlapping coverage for different technologies.

[0051] System 100 may be a heterogeneous LTE/LTE-A network in which different types of base stations provide coverage for various geographic regions. For example, each base station 105 may provide communications coverage for a macro cell, a pico cell, a femto cell, or other cell types. A macro cell typically covers a relatively large geographic area (e.g., several kilometers in radius) and can allow unrestricted access by UEs with service subscriptions with the network provider. A pico cell would generally cover a relatively smaller geographic area and may allow unrestricted access by UEs with service subscriptions with the network provider. A femto cell would also generally cover a relatively small geographic area (e.g., a house) and, in addition to unrestricted access, may also provide restricted access by UEs having an association with the femto cell.

[0052] The core network 130 may communicate with the base stations 105 via a backhaul channel 132 (e.g., S1, etc.). The base stations 105 may also communicate with each other, directly or indirectly via backhaul links 134 (e.g., X2, etc.) and/or via backhaul links 132 (e.g., via core network 130). The wireless communication system 100 may support synchronous or asynchronous operation. For synchronous operation, base stations can have similar frame timing, and transmissions from base stations can be approximately aligned in time. For asynchronous operation, base stations may have different frame timing, and transmissions from different base stations may not be time aligned. The techniques described here can be used for synchronous or asynchronous operations.

[0053] The UEs 115 are dispersed throughout the wireless communication system 100, and each UE is stationary or mobile. A UE 115 may communicate with other UEs 115 using D2D communications. One or more of a group of UEs 115 using D2D communications may be comprised within the coverage area 110 of a cell. Other UEs 115 in such a group may be outside the coverage area 110 of a cell, or otherwise unable to receive transmissions from a base station 105. Groups of UEs 115 communicating via D2D communications may utilize a one-to-many system. (1:M) where each UE 115 transmits to every UE 115 in the group. In some cases, a base station 105 facilitates programming of resources for D2D communications. in other cases, D2D communications are performed independent of a base station 105.

[0054] A UE 115 may also be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device wire, a wireless communication device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a client, or some other suitable terminology. A UE 115 may be a cellular telephone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a tablet computer, a laptop computer, a cordless telephone, a loop station wireless location (WLL), or similar. A UE may be able to communicate with macro eNBs, pico eNBs, femto eNBs, relays and the like.

[0055] Communication links 125 shown in system 100 may include uplink (UL) transmissions from a UE 115 to a base station 105, or downlink transmissions (DL), from a base station 105 to a UE 115 via DL carriers. They can also represent D2D communication links. Downlink transmissions can also be called forward link transmissions while uplink transmissions can also be called reverse link transmissions.

[0056] Figure 2 illustrates an example of a wireless communication system 200 in which UEs 115 a-c are engaged in D2D communication and are leaving a network coverage area 110-a according to various embodiments. One or more UEs 115 may establish D2D communications in the coverage area 110-a of a base station 105-a. The UEs 115 may communicate directly using mode 1 D2D communications. Mode 1 may be based on a centralized transmission resource program received from the base station 105-a. That is, the base station can direct the UEs 115 to use specific resources for transmission. The UEs 115 and base station 105-a may be examples of the UEs 115 and base stations 105 illustrated in Figure 1.

[0057] If one or more UEs 115 are about to leave the cell's coverage area 1100-a, they may transition to a Mode 2 of D2D communication. Mode 2 may be based on distributed transmission scheduling using a pool of resources allocated by base station 105-a. That is, the UEs 115 can determine which resources to use from a set of resources indicated by the serving base station 105-a. In some cases, the transition to Mode 2 may be initiated by the user through an application on the UE 115. In other cases, the transition is initiated based on the determination that certain switching parameters have been met.

[0058] Switching parameters may be received from a base station 105-a or may be configured prior to connection to a base station. The switching parameters may refer to an indication that a radio link failure (RLF) with the base station 105-a is imminent. In some cases, switching parameters may include an out-of-sync indication. (OOS), a number of incorrectly received (bad) frames, a period of time, a number of correctly received (good) frames, a path loss measurement, an indication of channel quality, or a signal-to-noise ratio ( SINR). Other examples of criteria that can be used to determine when a UE should switch modes include a threshold number of random access channel (RACH) requests, a period of time after an unsuccessful RACH attempt, a period of time after a report of status (SR), a buffer status report (BSR) or resource request, or an indication of a handover failure or an incomplete handover. The determination that a complete handover message was not sent may be an indication of an incomplete handover. The above switching parameters may apply both when the UE 115 is in a radio resource control (RRC) idle state and when it is in an RRC connected state. Parameters based on an imminent RLF may be more aggressive than another set of RLF parameters. That is, they can be configured to indicate an imminent RLF before the RLF actually occurs. Thus, in some cases a wireless link to a base station can be maintained after the D2D-related RLF threshold is met.

[0059] After transitioning to Mode 2, a UE 115 may continue to monitor for, and receive indications from, the base station 105-a that carries a pool of resources to use for distributed broadcast scheduling. In some cases, a UE 115 may be in a radio resource control (RRC) idle state while operating in D2D communication Mode 2. a UE can reset a protocol layer setting (such as an RRC status setting or a Media Access Control (MAC)) when switching modes. In other examples, the layer configuration may be maintained after switching modes.

[0060] After a UE 115 has exited the coverage area or experienced RLF with the in-service base station 105-a, the UE may determine that it may no longer be able to receive such resource grants. Then, the UE 115 may switch to a Mode 3 of D2D communication. Mode 3 can be based on distributed transmission using a pre-configured resource pool. As a result, in Mode 3 the UEs may not receive any messages from a base station 105-a and may transmit according to a coordinated schedule among the UEs 115 using a predetermined pool of resources. In some cases, a protocol layer configuration may be changed after a switch to Mode 3 although it would not be changed subsequent to a switch to Mode 2.

[0061] In some cases preconfigured switching parameters or transmission resource program may be determined as part of a connection process with base station 105-a. for example, a UE 115-a may send a connection request that includes an indication that it may operate in a D2D mode. Base station 105-a may receive the request and transmit a connection response that includes one or more D2D parameters. The UE 115-a may receive the response and configure the Mode 3 switching parameters or transmission program accordingly.

[0062] In one example, a UE 115-a may send a mode switching request to base station 105-a prior to switching to Mode 2. Base station 105-a may then send a response granting or denying the request. For example, the base station 105-a may deny the request if the UE 115-a has a low priority, or if the base station has a queue of data to transmit to the UE 115-a and the transition would interfere with the communication link. After receiving permission to switch modes, the UE 115-a may begin the transition. In some cases, a UE 115-a may also send a request to switch to Mode 3. However, the UE 115-a may experience RLF and in some cases may switch modes autonomously without waiting for a response.

[0063] In one example, a UE 115 may modify switching parameters after switching modes according to a hysteresis method to avoid rapid switching between D2D modes (i.e., ping pong). Hysteresis can be based on a time period, a path loss issue, a number of good or bad frames, a SINR, or another measurement of channel quality. The UE 115 may wait until hysteresis parameters are met before reconnecting with a base station 105-a or switching D2D modes.

[0064] In some cases, a UE may maintain a record of information related to D2D mode switches. For example, it may record a timestamp, a location, a radio link condition, a speed, a cell ID, a frequency or frequency range. The UE 115 may provide information related to previous D2D mode switches to a base station 105-a upon request or at preconfigured intervals.

[0065] Figure 3 illustrates an example of a wireless communication system 300 in which UEs 115 d-f are engaged in D2D communications and are entering a network coverage area 110-b according to various embodiments. The UEs 115 and base station 105-b may be examples of the UEs 115 and base stations 105 illustrated in Figures 1 or 2. One or more UEs 115 may establish D2D communications outside the coverage area 110-b of a base station 105-b . The UEs 115 can communicate directly using Mode 3 D2D communication. Mode 3 can be based on distributed transmission using a pre-configured resource pool. If one or more UEs 115 enter the coverage area 110-b of the cell, they may transition to a Mode 2 of D2D communication. Mode 2 may be based on distributed transmission scheduling using a pool of resources allocated by base station 105-a. The transition can be initiated based on the determination that certain switching parameters have been met. Switching parameters can be pre-configured. In some cases, the parameters may be related to receiving system information from the base station 105-b indicating a pool of resources that may be used for D2D communications.

[0066] In one example, after a UE 115 has transitioned to Mode 2, it may establish a connected state with the base station 105-b. Before being in a connected state, the UE 115 may continue D2D communication in Mode 2. Subsequently, the UE 115 may switch to D2D communication Mode 1. Mode 1 may be based on a centralized transmission resource program received from base station 105-b.

[0067] Figure 4 shows a block diagram 400 of a 115-g device for switching a mode of operations in D2D communication according to various embodiments. Device 115-g may include a UE that may be an example of one or more aspects of a UE 115 described with reference to Figures 1-3. Device 115-g may include a receiver 405, a D2D communication module 410, or a transmitter 415. Device 115-g may also be a processor. Each of these components can be in communication with each other.

[0068] The components of device 115-g may, individually or collectively, be implemented with one or more application-specific integrated circuits (ASICs) adapted to perform some or all of the applicable hardware functions. Alternatively, the functions may be performed by one or more other processing units (or cores) on one or more integrated circuits. In other embodiments, other types of integrated circuits may be used (e.g., platform/structured ASICs, Field Programmable Gate Arrays (FPGAs), and other semi-custom ICs), which may be programmed in any mode known in the art. . The functions of each unit can also be implemented, in whole or in part, with instructions embedded in a memory, formatted to be executed by one or more application-specific or general processors.

[0069] Receiver 405 may receive information such as packets, user data, or control information associated with the various information channels (e.g., control channels, data channels, etc.). Information may be passed to the D2D communication module 410, and to other components of the device 115-g. In some examples, the receiver 405 may be configured to receive a connection response message from the base station comprising one or more mode switching parameters. It can also be configured to receive a response from the base station indicating that a mode switch is permitted. In some cases, receiver 405 may also be configured to receive system information from a station allocating a pool of resources for transmission.

[0070] The D2D communication module 410 may be configured to establish communication with one or more other UEs in accordance with a first D2D mode. In some cases, the first D2D mode may be based on a centralized transmission resource program received from a base station. For example, the first mode may be Mode 1 as described with reference to figures 2-3. It can also be configured to determine that one or more mode switching parameters have been met and switch to a second D2D mode before a radio link failure (RLF) occurs, the second D2D mode being based on distributed transmission scheduling using a pool of resources allocated by the base station. In an example, the second mode may be Mode 2 as described above. In some cases, the D2D communication module 410 may be configured to establish communications with one or more other UEs in accordance with a D2D mode based on a preconfigured pool of transmission resources. For example, the first established mode may be Mode 3 as described above.

[0071] Transmitter 415 may transmit to one or more signals received from other components of device 115-g. In some embodiments, the transmitter 415 may be co-located with the receiver 405 in a transceiver module. Transmitter 415 may include a single antenna, or may include a plurality of antennas. In some cases, the transmitter 415 may be configured to send a connection configuration request to a base station comprising a D2D mode indication. Transmitter 415 may also be configured to send a mode switching request to the base station.

[0072] Figure 5 shows a block diagram 500 of a device 115-h for switching a mode of operations in D2D communications according to various embodiments. Device 115-h may include a UE that may be an example of one or more aspects of a UE 115 described with reference to Figures 1-4. Device 115-h may include a receiver 405-a, a D2D communication module 410-a, or a transmitter 415-a, which may be examples of corresponding components of device 115-g. Device 115-h may be a processor. Each of these components can be in communication with each other. The D2D communications module 410-a may include a communications establishment module 505, a mode selection module 510, and a switching parameter module 515. The receiver 405-a and the transmitter 415-a may perform the functions of the receiver. 405 and transmitter 415, in figure 4, respectively.

[0073] The components of device 115-h may, individually or collectively, be implemented with one or more application-specific integrated circuits (ASICs) adapted to perform some or all of the applicable hardware functions. Alternatively, the functions may be performed by one or more other processing units (or cores) on one or more integrated circuits. In other embodiments, other types of integrated circuits may be used (e.g., platform/structured ASICs, Field Programmable Gate Arrays (FPGAs), and other semi-custom ICs), which may be programmed in any mode known in the art. . The functions of each unit can also be implemented, in whole or in part, with instructions embedded in a memory, formatted to be executed by one or more application-specific or general processors.

[0074] The communication establishment module 505 may be configured to establish communication with one or more other UEs in accordance with a first D2D mode. In some cases the first D2D mode may be based on a centralized transmission resource program received from a base station. In some cases, the first D2D mode may be based on a pre-configured pool of transmission resources.

[0075] The mode selection module 510 can be configured to select a D2D communications mode. For example, it can be configured to select between Mode 1, Mode 2 and Mode 3 as described with reference to figures 2-3. In some cases, the mode selection module 510 may be configured to switch from a first D2D mode to a second D2D mode, the second D2D mode based on a distributed transmission schedule using the pool of resources allocated by the base station.

[0076] The switching parameter module 515 may be configured to store a set of switching parameters and determine whether conditions based on the parameters have been met. In some cases, the switching parameters may be modified radio link failure criteria (RLF). These criteria can be configured so that the device 115-h can switch D2D modes before an effective RLF. In this way, the mode switching parameters can be configured so that the D2D mode switching criteria are met before the non-modifying RLF criteria are met. Examples of switching parameters include an out-of-sync indication. Related to a number of bad frames, a sync indication. Related to a number of good frames, a period of time, a path loss threshold, and a signal-to-noise ratio (SINR) threshold. Other examples include a threshold number of Random Access Channel (RACH) requests, a period of time after a status report (SR) or a resource request, or an indication of a handover failure or an incomplete handover. In some cases, the switching parameter module 515 may determine that one or more mode switching parameters have been met and wait until a period of time has elapsed before switching to a different D2D mode. In one embodiment, the mode switching parameter may be an indication of a user application.

[0077] The switching parameter module 515 may monitor one or more of the above parameters and coordinate with the mode selection module 510 to determine when the device 115-h should switch from one D2D mode to another. The switching parameters may be preconfigured before communicating with a base station 105, received from a base station 105 during a connection procedure, or received from a base station 105 via a system information broadcast (e.g., a system information block (SIB) broadcast).

[0078] Figure 6 shows a block diagram 600 of a D2D communication module 410-b that may be an example of one or more aspects of a D2D communication module 410 described with reference to Figures 4-5.

[0079] The D2D communications module 410-b may include a communications establishment module 505-a, a mode selection module 510-a, and a switching parameter module 515-a which may be examples of corresponding components of device 115-h with reference to FIG. 5. The D2D communications module 410-b may also include a switching information recording module 605. The mode selection module 510-a may include a mode selection submodule 510-a. centralized transmission 610, a distributed transmission scheduling sub-module 615, a resource allocation sub-module 620, and a protocol layer configuration sub-module 615. The switching parameter sub-module 515-a may include a radio link failure (RLF) submodule 630, a timing submodule 635, and a hysteresis submodule 640.

[0080] The switching information register module 605 may be configured to store a mode switching information register comprising one or more of a timestamp, a UE location, a radio interface condition, a speed of UE, a cell ID, and a carrier frequency. Switch registration information may be provided to a base station 105 upon request or at predetermined intervals. In some cases, the switching information can subsequently be used to evaluate network coverage or refine the mode switching process.

[0081] The centralized broadcast scheduling sub-module 610 may configure a UE 115 to a D2D mode based on a broadcast program received from a base station 105. For example, the centralized broadcast scheduling sub-module 610 may be used to configure a UE for Mode 1 D2D communications. Mode 1 operations may be conducted while a UE is in coverage area 110 of a base station 105, and has not determined that RLF is imminent.

[0082] The distributed transmission programming sub-module 615 may configure a UE 115 for a D2D mode based on a distributed transmission program. That is, a UE 115 can schedule transmissions in coordination with other UEs 115 rather than relying on a base station 105 for centralized scheduling. Mode 2 and Mode 3 of D2D communication can be examples of distributed broadcast scheduling. Mode 2 and mode 3 operations may be appropriate when a UE 115 has experienced RLF, an unsuccessful handover, is outside a base station 105 coverage area, or is transitioning between connection states. A UE 115 may also utilize distributed broadcast scheduling when directed by a user.

[0083] The resource allocation sub-module 620 may be configured to determine a set of resources that the UE may use for transmission during D2D communications. in some cases the resource allocation sub-module 620 may determine that the UE may use specific resources as directed by a base station 105 while the UE is operating in a centralized D2D transmission scheduling mode such as Mode 1 described above. In other cases, the resource allocation submodule 620 may determine that the UE may use resources from a pool of resources indicated by a base station 105 in a UE-specific message or information block broadcast transmission. (SIB). This may be an example of D2D mode 2 communications. In other cases, the resource allocation submodule 620 may determine that the UE should use a pre-configured pool of resources, such as in D2D mode 3 operations. - resource configuration may be used when a UE is not in the coverage area of a base station 105 or otherwise cannot receive system information broadcasts.

[0084] The protocol layer configuration sub-module 625 can configure radio protocol settings during a mode switch. For example, you can reconfigure a media access control (MAC) or radio link control (RLC) configuration after switching to D2D Mode 2. In some cases, the protocol layer configuration submodule 625 may maintain the same configuration after a mode switch. In some cases, the protocol layer configuration submodule 625 may set a media access control (MAC) configuration or a radio link control (RLC) configuration according to a predetermined state after switching to the second mode. D2D.

[0085] The radio link failure (RLF) submodule 630 may be configured to store a set of RLF-related switching parameters and determine whether conditions based on the parameters have been met. The switching parameters can be modified radio link failure criteria (RLF). These criteria can be configured so that the UE 115 can switch D2D modes before an effective RLF. In this way, the mode switching parameters can be configured so that the D2D mode switching criteria are met before the unmodified RLF criteria are met. Examples of switching parameters include an out-of-sync indication. Related to a number of bad frames, a sync indication. Related to a number of good frames, a time period, a path loss threshold, and a signal-to-noise ratio (SINR) threshold.

[0086] The timing sub-module 635 can determine whether timing parameters have been met. For example, a UE 115 may autonomously switch modes a certain period of time after one or more parameters related to channel quality have been met, or after sending a message to a base station 105 and waiting for a response. The timing sub-module 635 may also coordinate with the hysteresis module to prevent a UE from quickly switching between D2D modes.

[0087] The hysteresis sub-module 640 can be configured to maintain a set of hysteresis parameters and determine whether the parameters have been met. Hysteresis parameters can be configured to prevent a UE 115 from rapidly switching D2D modes or connection status (i.e., ping pong). The hysteresis parameters may include at least one of a time period, a path loss parameter, a number of good frames, and a signal to noise ratio (SINR). A UE 115 may be configured such that even if another set of switching parameters indicates that a switching threshold has been met, the UE 115 may continue communication based on distributed transmission scheduling until hysteresis parameters are met.

[0088] Figure 7 shows a diagram of a system 700 for switching a mode of operations in D2D communications according to various embodiments. System 700 may include a UE 115-i, which may be an example of the UEs 115 of Figures 1-5. The UE 115-i may generally include components for two-way voice and data communications including components for transmitting communications and components for receiving communications.

[0089] The UE 115-i may include antenna(s) 740, a transceiver module 735, a processor module 705, and memory 715 (including software (SW) 720) that each may communicate, directly or indirectly, with each other (e.g., through one or more buses 845). Transceiver module 735 may be configured to communicate bidirectionally, via antenna(s) 740 or one or more wired or wireless links, with one or more networks, as described above. For example, transceiver module 735 may be configured to communicate bidirectionally with a base station 105-c or another UE 115-j. The transceiver module 735 may include a modem configured to modulate packets and provide the modulated packets to the antenna(s) 740 for transmission and demodulate packets received from the antenna(s) 740. Although the UE 115-i may include a single antenna 740, the UE 115-i may also have multiple antennas 740 capable of simultaneously transmitting or receiving multiple wireless transmissions. The transceiver module 735 may be capable of simultaneously communicating with one or more base stations 105 via multiple component carriers.

[0090] The UE 115-i may include a D2D communication module 710, which may perform the functions described by the D2D communication modules 410 of Figures 4-6. The UE 115-i may also include a channel quality module 730 and a base station communications module 725. The channel quality module 730 may perform channel measurements and interference measurements for communications links 125. For example, can measure channel quality indicators that can be used as switching parameters such as a path loss parameter or a SINR.

[0091] Base station communication module 725 may be configured to manage communications with a base station 105. In some cases, coordination with a base station 105 may be part of D2D communication mode or mode switching. For example, the base station communication module 725 may be configured to monitor communications from the base station for a resource pool indication and determine that a message from the base station indicating the resource pool is not receivable. In another example, the base station communication module 725, in coordination with the transceiver 735, may send a connection configuration request to the base station 105. The connection configuration request may include a D2D mode indication. may also receive a connection response message from the base station with one or more mode switching parameters. In another example, the base station communication module 725, in coordination with the transceiver 735, may send a mode switching request to a base station 105, and receive a mode switching response. The mode switching request may indicate whether the request is user-initiated. The response may grant the request or, in some cases, deny the switching request. The base station communication module 725 may also receive information from a base station by scheduling D2D transmissions or allocating a pool of resources for D2D communications.

[0092] Memory 715 may include random access memory (RAM) and read-only memory (ROM). Memory 715 may store computer-executable, computer-readable firmware/software code 720 containing instructions that are configured to, when executed, cause processor module 705 to perform various functions described herein (e.g., call processing, management database, carrier mode indicator processing, CSI report, etc.). Alternatively, firmware/software code 720 may not be directly executable by processor module 705, but be configured to cause a computer (e.g., when compiled and executed) to perform functions described herein. The processor module 705 may include an intelligent hardware device (e.g., a central processing unit (CPU), a microcontroller, an application-specific integrated circuit (ASIC), etc.).

[0093] Figure 8 shows a flowchart illustrating a method for switching a mode of operations in D2D communications according to various modalities. Flowchart functions 800 may be implemented by a UE 115 or components thereof as described with reference to Figures 1-7. In certain examples, flowchart blocks 800 may be executed by a D2D communication module 410 of Figures 4-6.

[0094] In block 805, the UE 115 may establish communications with one or more other UEs in accordance with a first D2D mode, the first D2D mode based on a centralized transmission resource program received from a base station. For example, the first D2D mode may be D2D Mode 1 as described above with reference to Figure 2. In certain examples, the functions of block 805 may be performed by communications establishment module 505.

[0095] In block 810, the UE 115 may determine that one or more mode switching parameters have been satisfied. In some cases, the switching parameters may be modified Radio Link Failure Criteria (RLF). These criteria can be configured so that the UE 115 can switch D2D modes before an effective RLF. In this way, the mode switching parameters can be configured such that the D2D mode switching criteria are met before the unmodified RLF criteria are met. Examples of switching parameters include an out-of-sync indication. Related to a number of bad frames, a sync indication. Related to a number of good frames, a period of time, a path loss threshold, and signal-to-noise ratio (SINR) threshold. Other examples include a threshold number of random access channel (RACH) requests, a period of time after a status report (SR) or a resource request, or an indication of a handover failure or an incomplete handover. In certain examples, the functions of block 810 may be performed by switching parameter module 515.

[0096] In block 815, the UE 115 may switch to a second D2D mode before a radio link failure (RLF) occurs, the second D2D mode based on distributed transmission scheduling using a pool of resources, allocated by the station base. The second D2D mode may be D2D Mode 2 as described above with reference to Figure 2. In certain examples, the functions of block 815 may be performed by the mode selection module 50.

[0097] It should be noted that method 800 is only one implementation and that the operations of method 800 may be rearranged or otherwise modified so that other implementations are possible.

[0098] Figure 9 shows a flowchart 900 illustrating a method for switching a mode of operations in D2D communications according to various modalities. The functions of flowchart 900 may be implemented by a UE 115 or components thereof as described with reference to Figures 1-7. In certain examples, the functions of flowchart 900 may be performed by a D2D communications module 410 of Figures 4-6. Flowchart 900 may also incorporate aspects of flowchart 800 of Figure 8.

[0099] In block 905, the UE 115 may establish communications with one or more other UEs in accordance with a first D2D mode, the first D2D mode based on a centralized transmission resource program received from a base station. In certain examples, the functions of block 905 may be performed by communications establishment module 505. In block 910, UE 115 may determine that one or more mode switching parameters have been met. In certain examples, the functions of block 910 may be performed by switching parameter module 515. In block 915, the UE 115 may switch to a second D2D mode before a radio link failure (RLF) occurs, the second mode D2D being based on distributed broadcast scheduling using a pool of resources allocated by the base station. In certain examples, the functions of block 915 may be performed by mode selection module 510.

[0100] In block 920, the UE 115 may monitor communications from the base station for an indication of the pool of resources it may use for transmission. In some cases, this may be received in a system information block (SIB) broadcast. In certain examples, the functions of block 920 may be performed by base station communications module 725.

[0101] In block 925, the UE 115 may determine that a message from the base station 105 indicating the resource pool is not receivable. For example, the UE 115 may have left the coverage area of the base station 105, may have experienced RLF, or may have undergone a failed handover. In certain examples, the functions of block 925 may be performed by base station communications module 725.

[0102] In block 930, the UE 115 may switch to a third D2D mode, the third D2D mode being based on distributed transmission using a pool of pre-configured resources. For example, the third D2D mode may be D2D Mode 3 described above with reference to Figure 2. In certain examples, the functions of block 930 may be performed by the mode selection module 510.

[0103] It should be noted that method 900 is only one implementation and that the operations of method 900 may be rearranged or otherwise modified so that other implementations are possible.

[0104] Figure 10 shows a flowchart 1000 illustrating a method for switching a mode of operations in D2D communications according to various embodiments. The functions of flowchart 1000 may be implemented by a UE 115 or components thereof as described with reference to Figures 1-7. In certain examples, the functions of flowchart 1000 may be performed by a D2D communications module 410 of Figures 4-6. Flowchart 1000 may also incorporate aspects of flowcharts 800 and 900 of Figures 8-9.

[0105] In block 1005, the UE 115 may send a connection configuration request to a base station comprising a D2D mode indication. That is, the UE 115 can indicate to the base station 105 that it will be communicating directly with other UEs 115. In this way, the base station can allocate resources for D2D communications. In certain examples, the functions of block 1005 may be performed by base station communications module 725 or transmitter 415.

[0106] In block 1010, the UE 115 may receive a connection response message from the base station comprising one or more mode switching parameters. Thus, in some cases the base station 105 may determine the parameters based on which the UE 105 may switch from one D2D mode to another. In certain examples, the functions of block 1015 may be performed by base station communications module 725 or receiver 405.

[0107] In block 1015, the UE 115 may establish communications with one or more other UEs in accordance with a first D2D mode, the first D2D mode based on a centralized transmission resource program received from a base station. In certain examples, the functions of block 1015 may be performed by the communications establishment module 505. In block 1020, the UE 115 may determine that one or more mode switching parameters have been met. In certain examples, the functions of block 1020 may be performed by the switching parameter module 515. In block 1025, the UE 115 may switch to a second D2D mode before a radio link failure (RLF) occurs, the second mode D2D based distributed broadcast scheduling using a pool of resources allocated by the base station. In certain examples, the functions of block 1025 may be performed by mode selection module 510.

[0108] It should be noted that method 100 is only one implementation and that the operations of method 1000 may be rearranged or otherwise modified so that other implementations are possible.

[0109] Figure 11 shows a flowchart 1100 illustrating a method for switching a mode of operations in D2D communications according to various embodiments. The functions of flowchart 1100 may be implemented by a UE 115 or components thereof as described with reference to Figures 1-7. In certain examples, the functions of flowchart 1100 may be performed by a D2D communications module 410 of Figures 4-6. Flowchart 1100 may also incorporate aspects of flowcharts 800, 900 and 1000 of Figures 8-10.

[0110] In block 1105, the UE 115 may establish communications with one or more other UEs in accordance with a first D2D mode, the first D2D mode being based on a centralized transmission resource program received from a base station. In certain examples, the functions of block 1105 may be performed by the communications establishment module 505. In block 1110, the UE 115 may determine that one or more mode switching parameters have been met. In certain examples, the functions of block 1110 may be performed by switching parameter module 515.

[0111] In block 1115, the UE 115 may send a mode switching request to the base station. In some examples, the mode switching request may include an indication of whether the switching was initiated based on meeting mode switching parameters and whether it is a user-initiated switching request. In certain examples, the functions of block 1115 may be performed by base station communications module 725 or transmitter 415.

[0112] In block 1120, the UE 115 may receive a response from the base station indicating that a mode switch is permitted. In some cases, the UE 115 may receive a response that a mode switch is not permitted. In this case, the UE may not proceed to block 1125. In some cases, the UE 115 may initiate a mode switch autonomously after waiting for a certain period of time and not receiving a response from a base station 105. In certain examples , the functions of block 1120 may be performed by base station communications module 725 or receiver 405.

[0113] In block 1125, the UE may switch to a second D2D mode before a radio link failure (RLF) occurs, the second D2D mode being based on distributed transmission scheduling using a pool of resources allocated by the base station. In certain examples, the functions of block 1125 may be performed by mode selection module 510.

[0114] It should be noted that method 1100 is only one implementation and that the operations of method 1100 may be rearranged or otherwise modified so that other implementations are possible.

[0115] Figure 12 shows a flowchart 1200 illustrating a method for switching a mode of operations in D2D communications according to various embodiments. The functions of flowchart 1200 may be implemented by a UE 115 or components thereof as described with reference to Figures 1-7. In certain examples, the functions of flowchart 1200 may be performed by a D2D communications module 410 of Figures 4-6.

[0116] In block 1205, the UE 115 may establish communications with one or more other UEs in accordance with a first D2D mode, the first D2D mode based on a pre-configured pool of transmission resources. For example, the UE 115 may be outside the coverage area of a base station 105, and may initiate communications with other UEs 115 in accordance with D2D Mode 3 as described above with reference to Figure 3. In certain examples, the functions of the block 1205 may be performed by communications establishment module 505.

[0117] In block 1210, the UE 115 may receive system information from a base station by allocating a pool of resources for transmission. In some cases, the UE may receive system information after entering the coverage area of the base station 105. In certain examples, the functions of the block 1310 may be performed by the base station communications module 725 or receiver 405.

[0118] In block 1215, the UE 115 may switch to a second D2D mode, the second D2D mode based on a distributed transmission schedule using the pool of resources allocated by the base station. For example, the second mode may be D2D Mode 2 as described above with reference to Figure 3. Thus, the UE 115 may not immediately attempt to communicate using D2D Mode 1 when it enters a base station coverage area. Instead, it may first transition to Intermediate Mode 2. In certain examples, the functions of block 1215 may be performed by mode selection module 510.

[0119] It should be noted that method 1200 is only one implementation and that the operations of method 1200 may be rearranged or otherwise modified so that other implementations are possible.

[0120] Figure 13 shows a flowchart 1300 illustrating a method for switching a mode of operations in D2D communications according to various embodiments. The functions of flowchart 1300 may be implemented by a UE 115 or components thereof as described with reference to Figures 1-7. In certain examples, the functions of flowchart 1300 may be performed by a D2D communications module 410 of Figures 4-6. Flowchart 1300 may also incorporate aspects of flowchart 1200 of Figure 12.

[0121] In block 1305, the UE 115 may establish communications with one or more other UEs in accordance with a first D2D mode, the first D2D mode based on a pre-configured pool of transmission resources. In certain examples, the functions of block 1305 may be performed by communications establishment module 505. In block 1310, UE 115 may receive system information from a base station by allocating a pool of resources for transmission. In certain examples, the functions of block 1310 may be performed by the base station communications module 725 or receiver 405. In block 1315, the UE 115 may switch to a second D2D mode, the second D2D mode based on a distributed transmission schedule. using the pool of resources allocated by the base station. In certain examples, the functions of block 1315 may be performed by mode selection module 510.

[0122] In block 1320, the UE 115 may establish a connected state with the base station. In block 1325, the UE 115 may switch to a third D2D mode, the third D2D mode being based on a centralized transmission resource program received from a base station subsequent to the establishment of the connected state. For example, the third D2D mode may be D2D Mode 1 as described above with reference to Figure 3. In this way, the UE 115 may wait until it has obtained connected status before attempting to use a centralized scheduling mode for D2D communications. In certain examples, the functions of block 1325 may be performed by mode selection module 510.

[0123] It should be noted that method 1300 is only one implementation and that the operations of method 1300 may be rearranged or otherwise modified so that other implementations are possible.

[0124] The detailed description set forth above in relation to the attached drawings describes exemplary embodiments and does not represent the only embodiments that can be implemented or that are within the scope of the claims. The term “exemplary” used throughout this description means “serving as an example, instance, or illustration” and not “preferred” or “advantageous over other embodiments.” The detailed description includes specific details for the purpose of providing an understanding of the techniques described. These techniques, however, can be put into practice without these specific details. In some instances, well-known structures and devices are shown in block diagram form to avoid obscuring the concepts of the described embodiments.

[0125] Information and signals can be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic particles or fields, optical particles or fields or any combination of the same.

[0126] The various illustrative blocks and modules described in connection with the disclosure of the present invention can be implemented or executed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), an array field programmable gate (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described here. A general-purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in combination with a DSP core, or any other such configuration.

[0127] The functions described here can be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored in or transmitted as instructions or code on a computer-readable medium. Other examples and implementations are within the scope and spirit of the disclosure and appended claims. For example, due to the nature of software, functions described above may be implemented using software executed by a processor, hardware, firmware, wiring, or combinations of any of these. Features implementing functions may also be physically located in various positions, including being distributed so that such portions of functions are implemented in different physical locations. Also, as used herein, including in the claims, “or” as used in a list of items (e.g., a list of items prefaced by the phrase “at least one of” or “one or more of”) indicates a disjunctive list so that, for example, a list of “at least one of A, B, or C” means A or B or C or AB or AC or BC or ABC (that is, A and B and C).

[0128] Computer-readable media includes both computer-readable media and communication media including any media that facilitates transfer of a computer program from one place to another. A storage medium can be any available medium that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, computer readable media may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other media that can be used to load or storing desired program code media in the form of instructions or data structures and that can be accessed by a general purpose or special purpose computer, or a general purpose or special purpose processor. Also any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio and microwave, then coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the media definition. Disk and disc, as used here, include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disc, and blu-ray disc where disks typically reproduce data magnetically, while discs reproduce data optically with lasers . Combinations of the above shall also be included in the scope of computer-readable media.

[0129] The foregoing description of the disclosure is provided to enable a person skilled in the art to use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Throughout this disclosure the term “example” or “exemplary” indicates an example or instance and does not imply or require any preference for the example mentioned. Accordingly, the disclosure should not be limited to the examples and designs described here, but the broadest scope compatible with the novel principles and features disclosed here should be agreed upon.

[0130] Techniques described here can be used for various wireless communication systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other systems. The terms “system” and “network” are often used interchangeably. A CDMA system can implement a radio technology such as CDM2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000, IS-95 and IS-856 standards. IS-2000 releases 0 and A are commonly referred to as CDMA2000 1X, 1X, etc. IS-856 (TIA-856) is commonly referred to as CDMA2000 1xEV-DO, High Rate Packet Data (HRPD), etc. UTRA includes wideband CDMA (WCDMA) and other CDMA variants. A TDMA system can implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA system can implement radio technology such as Ultra Mobile Broadband (UMB), Developed UTRA (E-UTRA), IEEE 802.11 (WiFi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of the universal Mobile Telecommunications System (UMTS). Long-Term Evolution 3GPP (LTE) and LTE-Advanced (LTE-A) are new releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in documents from an organization called the “3rd Generation Society Project” (3GPP). CDMA2000 and UMB are described in documents from an organization called “3rd Generation Society Project 2” (3GPP2). The techniques described here can be used for the radio systems and technologies mentioned above as well as other radio systems and technologies. The above description, however, describes an LTE system for example purposes, and LTE terminology is used throughout much of the above description, although the techniques are applicable beyond LTE applications.

Claims (13)

1. Device-to-device (D2D) wireless communication method in a user equipment (UE) comprising: receiving (1005) a connection response message from a base station comprising one or more mode switching parameters, wherein the one or more mode switching parameters relates to an indication of an imminent radio link failure (RLF) with the base station; establishing (1015) communications with one or more other UEs in accordance with a first D2D mode, the first D2D mode being based at least in part on a centralized transmission resource program received from the base station; determining (1020) that the one or more mode switching parameters have been met; and switching (1025) to a second D2D mode before the RLF occurs, the second D2D mode being based at least in part on a distributed transmission schedule using a pool of resources allocated by the base station; monitor base station communications for an indication of the resource pool; determining that a message from the base station indicating the resource pool is not receivable; and switching to a third D2D mode, the third D2D mode being based at least in part on distributed transmission using a pool of pre-configured resources. 2. Method according to claim 1, characterized by the fact that it further comprises: sending a connection configuration request to the base station, wherein the connection configuration request comprises a D2D mode indication. 3. Method according to claim 1, characterized by the fact that the one or more mode switching parameters comprise at least one of an out-of-sync indication related to a number of bad frames, an in-sync indication related to a number of good frames, a period of time, a path loss threshold and signal to noise ratio (SINR) threshold. 4. Method according to claim 1, characterized by the fact that the one or more mode switching parameters comprise at least one of a threshold number of random access channel (RACH) requests, a period of time after a unsuccessful RACH attempt, a period of time after a Status Report (SR), a Staging Status Report (BSR), or a feature request, or an indication of an autochange failure or an incomplete autochange. 5. Method according to claim 1, characterized by the fact that the one or more mode switching parameters comprises a period of time and at least one additional mode switching parameter; and wherein determining that the one or more mode switching parameters have been met comprises determining that the at least one additional mode switching parameter has been met and waiting until the period of time has elapsed before switching to a second mode D2D. 6. The method of claim 1, further comprising: sending a mode switching request to the base station. 7. The method of claim 6, wherein the one or more mode switching parameters comprise an indication from a user application and the mode switching request comprises a user initiated mode switching indication. . 8. The method of claim 1, further comprising: storing a record of switching information comprising one or more of a timestamp, a UE location, a radio interface condition , a UE speed, a cell ID, and a carrier frequency. 9. The method of claim 1, further comprising: continuing communication based on distributed transmission programming until one or more hysteresis parameters are met. 10. The method of claim 1, further comprising: utilizing the pool of resources associated with the second D2D mode until a connection is established with the base station; and establish the connection with the base station. 11. Computer-readable memory, characterized by the fact that it has instructions stored therein that, when executed, cause a computer to perform the method as defined in any one of claims 1 to 10. 12. Apparatus for wireless device-to-device (D2D) communication in a user equipment (UE), characterized in that it comprises: means for receiving (405-a) a connection response message from a station- base comprising one or more mode switching parameters, the one or more mode switching parameters relating to an indication of an imminent radio link failure (RLF) with the base station; means for establishing (505) communications with one or more other UEs in accordance with a first D2D mode, the first D2D mode being based at least in part on a centralized transmission resource program received from the base station; means for determining (515) that the one or more mode switching parameters have been met; and means for switching (510) to a second D2D mode before the RLF occurs, the second D2D mode being based at least in part on a distributed transmission schedule using a pool of resources allocated by the base station; means for monitoring base station communications for an indication of the resource pool; means for determining that a message from the base station indicating the resource pool is unreceivable; and means for switching to a third D2D mode, the third D2D mode being based on distributed transmission using a pool of pre-configured resources. 13. The apparatus of claim 12, further comprising: means for sending a connection configuration request to the base station, wherein the connection configuration request comprises a D2D mode indication.