Signal design for D2D subframe

Abstract

Embodiments of the present disclosure describe apparatus and methods for designing signals for device-to-device (D2D) subframes. Various embodiments include a UE having a wireless transceiver for communicating with other UEs via D2D communications. The UE also includes processing circuitry that generates a cyclic prefix (CP) for a first or second symbol of a D2D subframe on an orthogonal frequency division multiplexing (OFDM) resource block or a single-carrier frequency division multiple access (SC-FDMA) resource block. Other embodiments are described and / or claimed.

Description

[0001] This divisional application is a divisional application based on the Chinese patent application with application number 201480059034.6, application date November 6, 2014, and invention name “Signal design for D2D subframe”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. application Ser. No. 14 / 498,276, filed on Sep. 26, 2014, entitled “Signal Design for D2D Subframes,” which in turn claims priority to U.S. Provisional Patent Application Ser. No. 61 / 909,938, filed on Nov. 27, 2013, entitled “Advanced Wireless Communication Systems and Techniques,” which are incorporated herein by reference in their entirety. Technical Field

[0004] Embodiments of the present application generally relate to the field of wireless communications, and more particularly to an apparatus and method for signal design of a device-to-device (D2D) subframe. Background Art

[0005] The background description provided herein generally presents the context of the invention. Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art or admission of prior art by being summarized in this section.

[0006] D2D applications can provide a scalable, general architecture for connecting neighboring peers. There are different technical solutions for D2D applications, such as based on WiFi Direct or Near Field Communication (NFC) technology. Specific solutions involving the Third Generation Partnership Project (3GPP) are Proximity Services (ProSe), and Long Term Evolution (LTE) Direct.

[0007] The 3GPP Radio Access Network (RAN) working group (WG) is studying the support of D2D discovery and communication based on LTE. In this regard, the RAN1 WG believes that D2D discovery and communication under network coverage can be supported by the uplink (UL) spectrum in the frequency division duplex (FDD) system and the UL subframe or potential downlink (DL) subframe for the time division duplex (TDD) system. Summary of the invention

[0008] According to one aspect of the present disclosure, a user equipment UE is provided, comprising: a radio transceiver that communicates with another UE via Long Term Evolution LTE Proximity Service ProSe or LTE Direct; and a processing circuit that is coupled to the radio transceiver, the processing circuit transmitting a signal in the first symbol of a D2D subframe at an orthogonal frequency division multiplexing OFDM resource block or a single carrier frequency division multiple access SC-FDMA resource block for automatic gain control AGC setting at a receiving UE, wherein the processing circuit: uses an uplink demodulation reference signal UL-DMRS as the signal in the first symbol, and wherein a base sequence and a cyclic prefix of the UL-DMRS are the same as the base sequence and the cyclic prefix of the corresponding UL-DMRS on the fourth symbol and the eleventh symbol of the subframe.

[0009] According to another aspect of the present disclosure, a user equipment UE is provided, comprising: a radio transceiver that communicates with another UE via Long Term Evolution LTE Proximity Service ProSe or LTE Direct; and a processing circuit that is coupled to the radio transceiver, the processing circuit transmitting a signal in the first symbol of a D2D subframe at an orthogonal frequency division multiplexing OFDM resource block or a single carrier frequency division multiple access SC-FDMA resource block for automatic gain control AGC setting at a receiving UE, wherein the processing circuit uses an AGC reference signal as a signal, wherein the AGC reference signal is a sequence having a peak to average power ratio PAPR and is common to multiple transmitting UEs, and wherein the AGC reference signal is defined on a per resource block or per resource block set basis.

[0010] According to another aspect of the present disclosure, a method for a user equipment UE is provided, comprising: communicating with another UE via Long Term Evolution LTE Proximity Service ProSe or LTE Direct; and transmitting a signal in a first symbol of a D2D subframe at an orthogonal frequency division multiplexing OFDM resource block or a single carrier frequency division multiple access SC-FDMA resource block for automatic gain control AGC setting at a receiving UE, wherein an uplink demodulation reference signal UL-DMRS is used as the signal in the first symbol, and wherein a base sequence and a cyclic prefix of the UL-DMRS are the same as the base sequence and the cyclic prefix of the corresponding UL-DMRS on the fourth symbol and the eleventh symbol of the subframe.

[0011] According to another aspect of the present disclosure, a method for a user equipment UE is provided, comprising: communicating with another UE via Long Term Evolution LTE Proximity Service ProSe or LTE Direct; and transmitting a signal in the first symbol of a D2D subframe at an orthogonal frequency division multiplexing OFDM resource block or a single carrier frequency division multiple access SC-FDMA resource block for automatic gain control AGC setting at a receiving UE, wherein an AGC reference signal is used as a signal, wherein the AGC reference signal is a sequence having a peak to average power ratio PAPR and is common to multiple transmitting UEs, and wherein the AGC reference signal is defined on a per resource block or per resource block set basis.

[0012] According to another aspect of the present disclosure, a computer-readable medium is provided, on which instructions are stored, which, when executed by one or more processors, cause a user equipment UE to perform the following operations: communicate with another UE via Long Term Evolution LTE Proximity Service ProSe or LTE Direct; and transmit a signal in the first symbol of a D2D subframe at an orthogonal frequency division multiplexing OFDM resource block or a single carrier frequency division multiple access SC-FDMA resource block for automatic gain control AGC setting at a receiving UE, wherein an uplink demodulation reference signal UL-DMRS is used as the signal in the first symbol, and wherein a base sequence and a cyclic prefix of the UL-DMRS are the same as the base sequence and the cyclic prefix of the corresponding UL-DMRS on the fourth symbol and the eleventh symbol of the subframe.

[0013] According to another aspect of the present disclosure, a computer-readable medium is provided, on which instructions are stored, which, when executed by one or more processors, cause a user equipment UE to perform the following operations: communicate with another UE via Long Term Evolution LTE Proximity Service ProSe or LTE Direct; and transmit a signal in the first symbol of a D2D subframe at an orthogonal frequency division multiplexing OFDM resource block or a single carrier frequency division multiple access SC-FDMA resource block for automatic gain control AGC setting at a receiving UE, wherein an AGC reference signal is used as a signal, wherein the AGC reference signal is a sequence having a peak to average power ratio PAPR and is common to multiple transmitting UEs, and wherein the AGC reference signal is defined on a per resource block or per resource block set basis. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The embodiments are easily understood by the following detailed description in conjunction with the accompanying drawings. To facilitate this description, the same reference numerals are assigned to the same structural elements. The embodiments are shown in the form of examples and are not limited to the figures in the accompanying drawings.

[0015] Figure 1A wireless communication system according to various embodiments is schematically illustrated.

[0016] Figure 2 The figure is a principle block diagram showing two user equipments (UEs) in D2D communication according to different embodiments.

[0017] Figure 3 FIG. 1 is a flow chart showing a method of generating a D2D subframe according to different embodiments.

[0018] Figure 4 FIG. 4 is another flow chart showing generation of a D2D subframe according to different embodiments.

[0019] Figure 5-11 A principle block diagram illustrating subframe design according to various embodiments.

[0020] Fig.12 is a block diagram of an exemplary computing device for implementing various embodiments described herein.

[0021] Fig.13 Articles of manufacture having programming instructions incorporating aspects of the present invention according to various embodiments are shown. DETAILED DESCRIPTION

[0022] Embodiments of the present invention describe apparatus and methods for signal design of a device-to-device (D2D) subframe. Various embodiments include a UE having a radio transceiver for communicating with another UE via D2D communication. The UE also includes processing circuitry that generates a cyclic prefix (CP) having a length longer than 33.33 microseconds for a first or second symbol of a D2D subframe. These and other aspects of the present invention are described in more detail below. In the following detailed description,

[0023] In the description, reference is made to the accompanying drawings, which constitute a part of this document, in which like numerals designate like components, and are shown by way of exemplary embodiments that may be implemented. It should be understood that other embodiments may be used, and structural or logical changes do not depart from the scope of the present invention.

[0024] Different operations can be described as multiple independent actions or operations performed in turn, which are performed in a manner that is most conducive to understanding the subject matter claimed for protection. However, the order of the specification should not be interpreted as prompting the order that these operations must rely on. In particular, these operations should not be implemented in the order shown. The operations described herein can be implemented in an order different from the described embodiments. Different additional operations can be performed and / or described, and operations can also be omitted in additional embodiments.

[0025] For purposes of the present invention, the phrase "A and / or B" means (A), (B), or (A and B). For purposes of the present invention, the phrase "A, B, and / or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C). These descriptions may use the phrases "in an embodiment" or "in an embodiment," each of which refers to the same or different embodiments or embodiments. Furthermore, the terms "comprising," "including," "having," and the like, as used with reference to embodiments of the present invention, are synonymous.

[0026] As used herein, the term "circuitry" may relate to a portion of or include an application specific integrated circuit (ASIC) that executes one or more software or firmware programs, an electronic circuit, a processor (shared, dedicated, or group), and / or memory (shared, dedicated, or group), a combinational logic circuit, and / or other suitable hardware components that provide the described functionality.

[0027] Figure 1 The wireless communication system 100 in which different embodiments are installed is schematically shown. The wireless communication system 100 may include a backbone network 110, a core / access network 120 and a D2D network 130.

[0028] Backbone 110 may be part of a computer network architecture that interconnects different subnetworks and provides information exchange paths between these subnetworks. In various embodiments, backbone 110 may include Internet backbone 112, which may include the primary data routing between large strategically interconnected computer networks and core routing on the Internet.

[0029] The network 120 is connected to the backbone network 110. In various embodiments, the core / access network 120 includes one or more radio access networks, such as a Global System for Mobile Communications (GSM), a General Packet Radio Service (GPRS), a Universal Mobile Telecommunications System (UMTS), a High Speed ​​Packet Access (HSPA), an Evolved HSPA (E-HSPA), or a Long Term Evolution (LTE) network. In some embodiments, the radio access network includes GSM Enhanced Data Rates for GSM Evolved Radio Access Network (GERAN), a Universal Terrestrial Radio Access Network (UTRAN), or an Evolved UTRAN (E-UTRAN). The core / access network 120 operates in accordance with other network technologies in other embodiments.

[0030] Mobile communication technology relies on different standards and protocols to transmit data between base stations and wireless communication devices. Wireless communication system standards and protocols include standards such as 3GPP LTE; Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard, which is known to the industry group as Worldwide Interoperability for Microwave Access (WiMAX); and IEEE 802.11 standard, which is known as Wi-Fi. In the 3GPP Radio Access Network (RAN), according to LTE, the base station is an evolved Node B (commonly referred to as eNodeB, or eNB). It can communicate with a wireless communication device known as a user equipment (UE). Although the present invention uses terms and examples that are generally directed to 3GPP systems and standards, the teachings disclosed herein can be applied to any type of wireless network or communication standard.

[0031] In various embodiments, the core / access network 120 includes an eNB 124, a NB 126, a mobility management entity (MME), and a serving gateway (SGW) 122. The eNB 124 is more intelligent than the legacy NB 126, and can be used in a 3G network such as a UMTS network. For example, the functionality of a radio network controller (RNC) can be located in the eNB 124, rather than in a separate RNC entity. In LTE, the eNB 124 can be connected to another eNB via an X2 interface to transmit or share information. In some embodiments, the core / access network 120 is an Internet Protocol (IP)-based network, in which the interface between network entities (e.g., the eNB 124 and the MME / SGW 122) can be based on IP. In some embodiments, the MME / SGW 122 can communicate with the eNB 124, for example, based on an S1 interface. The S1 interface is similar to the S1 interface defined in 3GPP TS 36.410 V11.1.10 (2013-09) and supports a many-to-many relationship between MME / SGW 122 and eNB 124. For example, different operators may simultaneously operate the same eNB in ​​a network sharing setting. MME / SGW 122 is configured to manage signaling exchanges such as UE 132 authentication, or perform other actions related to the establishment of a communication link between UE 132 and core / access network 120. In some embodiments, MME / SGW 122 is responsible for tracking and calling user equipment, for example, when the UE is in idle mode.

[0032] For ease of understanding, different descriptions are provided herein to maintain consistency with 3GPP in communication system 100; however, the subject matter of the present invention is not limited in this respect, and the embodiments disclosed herein are beneficially applied to other wired or wireless communication protocols or networks. For example, in an embodiment where core / access network 120 includes UTRAN, NB 126 takes the form of an RNC, which can be configured to communicate with UE 132, 134, or 136. In an embodiment where core / access network 120 includes GERAN, eNB 124 represents a base station controller (BSC) configured to communicate with UE 132, 134, or 136 via a base transmission station (BTS).

[0033] In various embodiments, UE 132 may access core / access network 120 via a radio link with, for example, eNB 124. Downlink (DL) transmissions may be communications from eNB 124 to UE 132. Uplink (UL) transmissions may be communications from UE 132 to eNB 124. For ease of illustration, the core / access network 120 may be a radio link with, for example, eNB 124. Figure 1 Only a limited number of UEs and eNBs are shown. However, the communication system 100 includes any number of UEs, eNBs, or other servers to implement suitable embodiments of the present invention. As an example, in some embodiments, the core / access network 120 also includes other servers, such as a machine type communication (MTC) server (not shown) for MTC.

[0034] In some embodiments, UE 134 is configured to communicate with another machine using MTC technology.

[0035] As described above, the term MTC refers to data transmitted to or from a user device to another machine with little or no human intervention. For example, UE 134 can be electrically coupled to a wireless transceiver (e.g., see below). Figure 2 transceiver circuit 224) and can be configured to communicate with another MTC-capable machine with little or no intervention

[0036] In some embodiments, the wireless transceiver of the UE 134 is further configured to communicate with one of a wireless metropolitan area network, (WMAN), a wireless local area network (WLAN), or a wireless personal area network (WPAN).

[0037] In certain embodiments, UE 136 is a mobile communication device, subscriber station, or another device configured to communicate with core / access network 120 via, for example, eNB 124 in accordance with a suitable protocol (e.g., a multiple-input / multiple-output (MIMO) communication scheme).

[0038] In various embodiments, UE 132, UE 134, and UE 136 form a D2D network 130. In the D2D network 130, two adjacent UEs communicate directly with each other without the assistance of eNB 124 or other base stations and core networks. Direct communication between devices is known as device-to-device (D2D) communication or point-to-point (P2P) communication.

[0039] As discussed in further detail below, UE 132, 134, and / or 136 are configured to use specially designed subframes for D2D communication. Such subframes enable UE 132, 134, 136 to adapt to the switching time required for D2D communication transmission to reception or reception to transmission (hereinafter "Tx / Rx"). Further, such subframes enable UE 132, 134, or 136 to handle automatic gain control (AGC) setup time in D2D communication.

[0040] The D2D communication in the D2D network 130 is not visible to the core / access network 120 and occurs in the cellular spectrum (e.g., in-band) or the unlicensed spectrum (e.g., out-of-band). The D2D communication in the D2D network 130 can be implemented with different communication technologies. In some embodiments, short-range technologies such as Bluetooth or Wi-Fi can be used. In some embodiments, the D2D communication reuses the licensed LTE spectrum or the unlicensed LTE spectrum.

[0041] In various embodiments, D2D communication in the D2D network 130 first includes device discovery, and the UE will determine whether they are within range or available for D2D communication before establishing a D2D session. Proximity detection is facilitated by the core / access network 120 and is performed at least in part by the UE or mostly by the UE alone. In various embodiments, D2D discovery is restricted (known as closed D2D discovery), or open (known as promiscuous D2D discovery).

[0042] In various embodiments, D2D communications of D2D network 130 improve spectrum utilization, increase network throughput, reduce transmission delays, offload traffic from eNB 124, and mitigate conflicts in core / access network 120. In this regard, D2D communications have a variety of applications. For example, D2D network 130 is used for local social networking, content sharing, location-based transactions, service advertising, mobile-to-mobile applications, etc. Through the enhancements taught in the present invention, D2D network 130 becomes a public safety network that can operate even when core / access network 120 is unavailable or fails.

[0043] Reference now Figure 2 , which is a schematic block diagram showing a UE 210 and a UE 220 in a D2D communication mode according to different embodiments. Figure 1 132, 134, 136 are the same and are substantially interchangeable. In an embodiment, UE 210 includes one or more antennas 218 and a communication module 212. In various embodiments, the transceiver circuitry 214 and the processing circuitry 216 in the communication module 212 are coupled to each other as shown. Similarly, UE 220 includes one or more antennas 228 and a communication module 222. In various embodiments, the transceiver circuitry 224 and the processing circuitry 226 in the communication module 222 are coupled to each other as shown.

[0044] In D2D communication mode, UEs 210 and 220 that are either in network coverage or partially in or out of network coverage necessarily operate in TDD mode, because D2D devices must transmit and listen on the same carrier due to half-duplex limitations. Therefore, the challenge is to accommodate a Tx / Rx switching time of approximately 624Ts, where -Ts is 1 / (15000*2048) seconds, which is approximately 20.3 microseconds.

[0045] Further, UE 210 and 220 need to consider the AGC setup time in D2D communication mode. The AGC operating in D2D communication is different from the AGC operating in cellular operation, in which the UE only receives packets on the DL carrier (FDD) or subframe (TDD). In D2D communication, different UEs can be frequency-division multiplexed to different subframes. Further, the subframe setting also relies on the use of multiple transmission time interval (TTI) transmissions in different forms for D2D discovery and communication. Due to the randomness of the AGC operation in D2D communication, the UE 210 or 220 needs different AGC setup times for different subframes.

[0046] In various embodiments, the communication module 222 is coupled to the antenna 228 to facilitate air interface based signal transmission between the UE 220 and the UE 210 or another UE. For example, the transceiver circuit 224 is configured to provide different signal processing operations on the signal to the antenna 228 with appropriate characteristics. In various embodiments, the operations of the transceiver circuit 224 include but are not limited to filtering, amplification, storage, modulation, demodulation, deformation, etc.

[0047] The transceiver circuit 224 is configured to receive signals from the antenna 228 and transmit the signals to other components of the UE 220 and / or for internal processing by the processing circuit 226. In some embodiments, the processing circuit 226 at the receiving UE generates a guard interval at a subframe that provides a Tx / Rx switching time required for D2D communication. As an example, the processing circuit 226 generates a first or second cyclic prefix (CP) for a D2D subframe on an orthogonal frequency division multiplexing (OFDM) resource block or a single carrier frequency division multiple access (SC-FDMA) resource block. In the present invention, such a CP also refers to a CP for a first or second OFDM / SC-FDMA symbol, or simply a first or second symbol. In different embodiments, the CP is long enough (e.g., having more than 33.33 μs) to accommodate the Tx / Rx switching time required for D2D communication (e.g., approximately 20.3 μs). In different implementations

[0048] In the example, the processing circuit 226 generates a guard interval at the first symbol of the subframe for providing the AGC setup time at the receiving UE. In some embodiments, the processing circuit 226 transmits a reference signal (e.g., an uplink demodulation reference signal (UL-DMRS)) in the first OFDM / SC-FDMA symbol providing the AGC setup time. In some embodiments, the processing circuit 226 transmits one or more random quadrature phase shift keying (QPSK) symbols in the first OFDM / SC-FDMA symbol providing the AGC setup time. In different embodiments, such a guard interval has a duration of more than 33.33 microseconds. Therefore, the processing circuit 226 adjusts the AGC setup time and the Tx / Rx switching time for the D2D subframe. In some embodiments, the processing circuit 226 also uses similar techniques to adjust the AGC setup time and the Tx / Rx switching time at the edge of the D2D and WAN subframes, such as during the D2D communication and UE to eNB communication transition.

[0049] In some embodiments, UE 220 includes one or more antennas 228 to jointly use radio resources of multiple corresponding component carriers. For example, UE 220 is configured to use orthogonal frequency division multiple access (OFDMA) (such as in downlink communication) and / or single carrier frequency division multiple access (SC-FDMA) (such as in uplink communication). In some embodiments, UE 220 uses transceiver circuit 224 to communicate with another UE via LTE ProSe or LTE Direct. In some embodiments, UE 220 uses processing circuit 226 to generate subframes with appropriate guard intervals for D2D discovery and communication in LTE ProSe or LTE Direct.

[0050] In some embodiments, the communication module 222 is configured to provide communication services to one or more subscriber identity modules (SIMs) (not shown) coupled thereto. In some embodiments, the SIM is removably coupled to the communication module 222. In other embodiments, the SIM is hardware and / or firmware permanently coupled to the UE 220. In various embodiments, the SIM includes a full-size SIM, a mini SIM, a micro SIM, a tiny SIM, an embedded SIM, and / or a virtual SIM.

[0051] The SIM may be an integrated circuit that securely stores subscriber identity information, such as an International Mobile Subscriber Identity (IMSI) and associated keys used to identify and authenticate one or more subscribers using the UE 220. Each SIM may be associated with different subscriber identity information and may or may not be associated with a different carrier. In various embodiments, the IMSI and associated information are used to facilitate D2D discovery and D2D communication.

[0052] Part or all of the transceiver circuitry 224 and / or the processing circuitry 226 may be included in a radio frequency (RF) circuit or baseband circuit, as described below with reference to Fig.12 In various embodiments, the UE 220 or 210 may be or include, or be included in, a single sensor device, a cellular phone, a personal computer (PC), a notebook, an ultrabook, a netbook, a smart phone, an ultra-portable mobile PC (UMPC), a handheld mobile device, a universal integrated circuit card (UICC), a personal digital assistant (PDA), a customer premises equipment (Customer Premise Equipment, CPE), a handwritten computer device or other consumer electronic products, such as an MP3 player, a digital camera, etc. In some embodiments, the UE includes a mobile station as defined in IEEE 802.16 (e2005) or 802.16m (2009) or some other revision of the IEEE 802.16 standard, or a user equipment UE as defined in 3GPP LTE Release 8 (2008), Release 9 (2009), Release 10 (2011), Release 12 (2014), Release 13 (developed later) or some other revision or version of the 3GPP LTE standard.

[0053] Figure 3 3 is a flowchart for generating a D2D subframe according to different embodiments. The process 300 is performed by a UE, for example Figure 2 UE 210 or 220 or Figure 1 In various embodiments, process 300 enables the UE to adapt to the AGC setup time and the Tx / Rx switching time required for two D2D subframes or at the boundary of D2D and WAN subframes.

[0054] The process 300 includes, at 310, providing a first guard interval in a first symbol of a subframe to establish an AGC at a receiving UE. In some embodiments, the first guard interval may be provided by Figure 2 The processing circuit 216 or 226 is configured. In some embodiments, the subframe is located on an orthogonal frequency division multiplexing (OFDM) resource block or a single carrier frequency division multiple access (SC-FDMA) resource block.

[0055] The CP for a symbol may be repeated at the end of the symbol. The CP may serve as a guard interval to help the receiving UE mitigate inter-symbol interference from previous symbols. Further, the CP may facilitate simple frequency domain processing, such as channel estimation and equalization, because its repetitive nature enables frequency selective multipath channels to be modularized into circular convolutions. In various embodiments, the receiving UE discards the CP portion of the symbol. Thus, the CP may serve as a guard interval.

[0056] In some embodiments, the CP of the first symbol of the subframe is generated as the first guard interval. In some embodiments, the CP generated for the first symbol has a duration greater than 33.33 microseconds. In some embodiments, the PC for the second symbol of the subframe is generated as the first guard interval. The CP in this case has a duration greater than 66.67 microseconds.

[0057] Process 300 also includes, at 320, providing a second guard interval in the subframe to facilitate Tx / Rx switching at the receiving UE. Figure 2 The processing circuit 216 or 226 sets the second guard interval. In some embodiments, at least a portion of the last symbol of the subframe becomes the second guard interval to adjust the Tx / Rx switching time required at the receiving UE. In some embodiments, a portion of the first symbol of the subframe is punctured as a guard interval to adjust the Tx / Rx switching time required at the receiving UE. In some embodiments, at least a portion of the last symbol and at least a portion of the first symbol are punctured as the second guard interval to adjust the Tx / Rx switching time required at the receiving UE. In different embodiments, some or all of the punctured portions of the symbol may not be transmitted.

[0058] Figure 4 FIG. 4 is a flow chart showing another process for generating a D2D subframe according to various embodiments. The process 400 is performed by a UE, for example Figure 2 UE 210 or 220, or Figure 1 Any UE, such as UE 132, 134, or 136.

[0059] The process 400 includes, at 410, generating a CP having a length greater than 33.33 microseconds for a first or second symbol of a D2D subframe to facilitate establishing an AGC at a receiving UE. Due to the randomness of AGC operation in D2D communication, the receiving UE requires different AGC setup times for different subframes. Therefore, the AGC setup time in the subframe needs to be long enough to cover such variations. In various embodiments, such a CP has a duration greater than 33.33 microseconds to adjust the AGC setup time.

[0060] In some embodiments, a CP is generated for the first symbol to adjust the AGC setup time, for example, only the first half of the first symbol is used as the CP. In some embodiments, a CP is generated for the second symbol to adjust the AGC setup time, for example, only the second half of the first symbol is used as the CP or the entire first symbol is used as the CP. In the latter case, the CP for the second symbol has a duration of more than 66.67 microseconds. In different embodiments, different CP designs for the first or second symbol are used to meet the needs of different D2D applications.

[0061] Process 400 also includes, at 420, transmitting a signal in a first symbol of the D2D subframe to facilitate establishing AGC at a receiving UE. In some embodiments, the signal is a UL-DMRS or an AGC reference signal (RS). In some embodiments, a random quadrature phase shift keying (QPSK) symbol may be mapped to a resource element (RE) of the first symbol. In some embodiments, a normal (approximately 4.7 μs) or extended (approximately 16.7 μs) CP is typically provided for an LTE subframe, and thus, the available symbol length is less than the entire symbol length after a conventional CP is applied. In some embodiments, a CP at a first half of a useful symbol length of a first symbol is generated based on a second half of a useful symbol length of a second symbol. Further, the UL-DMRS remains at the second half of the useful symbol length of the first symbol.

[0062] In some embodiments, a new AGC reference signal is also defined for AGC setup purposes. The AGC RS uses a suitable reference signal sequence with a low peak-to-average power ratio (PAPR) that is common to many transmitting UEs. Further, the AGC RS is defined on a per-resource block or per-resource block setup basis. In some embodiments, during the first symbol for adjusting the AGC setup time, the transmission of random QPSK symbols is used to achieve the same performance.

[0063] Process 400 also includes, at 430, puncturing at least a portion of the last symbol or the first symbol of the subframe as a second guard interval. In some embodiments, at least a portion of the last symbol of the subframe is punctured as the second guard interval to adjust the Tx / Rx switching time required at the receiving UE. In some embodiments, at least a portion of the first symbol of the subframe is punctured as the second guard interval to adjust the Tx / Rx switching time required at the receiving UE. In some embodiments, if

[0064] When a subframe is transmitted before the downlink (DL) reference time of the serving or resident cell in a time division duplex (TDD) configuration, there is no need to puncture the last symbol or the first symbol. In some embodiments, a D2D subframe is transmitted at least 624 basic time units before the downlink reference time of the serving or resident cell in a TDD configuration, where one basic time unit is equal to 1 / 30720000 seconds. The offset of at least 624 basic time units is sufficient to cover the Tx / Rx switching time of approximately 20.3μs. In some cases, such a complete transmission of the last symbol can be applied to the TDD system.

[0065] In some embodiments, all D2D UEs with or without an activated timing advance (TA) value transmit according to a DL reference time (T1) with an offset (e.g., offset T2=624Ts). In other words, when there is no UL WAN after a D2D subframe, the UE transmits at time T=T1-T2. Therefore, overlap between D2D and UL WAN subframes can be avoided. Further, if there is no D2D subframe after a UL subframe, a D2D transmission scheme in a TDD system can have better coding gain by not puncturing the last symbol.

[0066] In some embodiments, the legacy UL subframe structure is used, the last symbol of the D2D subframe is used as a gap, and no special operation is required for the first symbol of the D2D subframe. In some embodiments, regardless of whether the last or first symbol of the D2D subframe is punctured, the increased gap for operating the Tx / Rx switching time is adjusted by transmitting the D2D subframe at least 624 basic time units (e.g., one basic time unit is equal to 1 / 30720000 seconds) before the corresponding reference time of the D2D subframe. As an example, UE 1 receives a D2D transmission from UE 2 on subframe n. Subframe n+1 is a cellular Ul subframe on which UE 1 is scheduled to transmit an UL PUSCH to the serving cell (e.g., when UE 1 is in connected mode of the serving cell). The PUSCH is transmitted after a transmission time given by T=(DL reference time-X), where X=(NTA+NTAoffset)TS, where NTA is a TA command from the eNB and NTAoffset is 624Ts. If subframe n is transmitted another 624Ts before UE 2, then now UE 1 will get an extra amount of this time slot (e.g., at the beginning of the last symbol slot in the D2D subframe) to switch from Rx to Tx mode. Thus, UE 1 transmits subframe n+1 with the appropriate advance time applied. This certainly helps in the case when the NTA value that UE 1 needs to apply in subframe n+1 is large, for example compared to one symbol duration.

[0067] In some embodiments, the UE is in RRC connected mode of the serving cell. In some embodiments, the UE resides in the resident cell in RRC idle mode, for example, to perform cell selection, receive information from the LTE network. Thus, the UE has a corresponding serving cell in RRC connected mode.

[0068] downlink reference time, and has a corresponding resident cell downlink reference time in RRC idle mode. In different embodiments, the D2D subframe is transmitted at least 624 basic time units between the serving or resident cell downlink reference time under time division multiplexing deployment. Therefore, as the last symbol of the D2D subframe is punctured, the receiving D2D UE obtains at least an additional 624Ts to switch to Tx mode and transmit the next subframe at an appropriate time in advance. In certain embodiments, the UE transmits D2D transmission according to the serving cell uplink reference time (SCURT) under the time division multiplexing configuration, where SCURT = SCDRT-TA, where SCDRT refers to the serving cell downlink reference time (Serving Cell Downlink Reference Time, SCDRT), and TA refers to the active timing advance value. In this case, the D2D subframe is transmitted at a transmission time given by T = SCURT-624Ts with an appropriate advance time.

[0069] Figure 5-11 FIG. 4 is a schematic block diagram showing a subframe design according to different embodiments. Figure 5-11 Different schematic diagrams for alternative D2D signal structures and their variations to adjust the AGC setup time and the Tx / Rx switching time required by the receiving UE are shown. In different embodiments, the data symbol is mapped to the first and / or last symbol. Further, the first and / or last symbol is punctured, for example, the transmitting UE transmits only a portion of the OFDM / SC-FDMA symbol to provide the guard interval required by the receiving UE. Various alternative designs incorporating this design principle will be described in detail below.

[0070] Figure 5 is a schematic diagram showing a subframe 500. The subframe 500 includes two time slots, each having a duration of about 0.5 milliseconds, and includes seven symbols. According to one embodiment, the first half of the first symbol 510 or the second half of the last symbol 520 is punctured and thus not transmitted. Therefore, the receiving UE can obtain at least 66.67 milliseconds of the guard interval as the Tx / Rx switching time.

[0071] Further, the second half of the first symbol is used for an effective longer CP 530 of the second data symbol 540. The CP is generated using the second half of the second data symbol 540. Note that the CP herein refers to a new effective CP, a normal or extended CP, in addition to the conventional CP application, which has been applied to the first or second symbol. Therefore, the subframe 500 provides better protection for the second data symbol 540 because the CP length is effectively increased. Therefore, the CP has a length of 33.33+4.7 microseconds in a conventional LTE CP application, or a length of 33.33+16.7 microseconds in an extended LTE CP application. At the same time, the subframe 500 provides at least 33.33 microseconds for the receiver to establish AGC.

[0072] In various embodiments, subframe 500 is modified to have the entire last symbol punctured or alternatively to have the entire last symbol retained for transmission. The previous modification provides for longer Tx / Rx switching time. The latter modification of complete transmission of the last symbol applies at least to TDD systems. In this case, when there is no UL WAN subframe after the D2D subframe, the UE transmits subframe 500 at time T=T1-T2, where T1 is the DL reference time and T2 is an offset, such as 624Ts.

[0073] Figure 6 6 is a schematic diagram showing a subframe 600. The subframe 600 includes two time slots, each having a duration of approximately 0.5 milliseconds, and includes seven symbols. Consistent with one embodiment, the second half of the last symbol 620 is protruded and thus cannot be transmitted. Therefore, the receiving UE can obtain at least 33.33 milliseconds of the guard interval as the Tx / Rx switching time. In other embodiments, according to the actual application in D2D communication, the guard time for adjusting the Tx / Rx switching time is obtained by partially, fully or completely puncturing the last symbol.

[0074] Subframe 600 and Figure 5 Compared with the subframe 500 of FIG. 5 , the first half of the first symbol 610 of the subframe 600 is not punctured. Instead, the entire first symbol is used as a longer CP for the second data symbol 640. The CP 630 is generated based on the second data symbol 640. In various embodiments, the extended CP 630 provides better protection for the second data symbol 640 to provide a longer time for the receiving UE to establish AGC.

[0075] Subframe 500 or 600 uses the first symbol to generate a substantially extended effective CP for the second symbol. Therefore, in various embodiments, the original CP for the second symbol (e.g., 4.7 μs for normal CP application) is omitted, provided that the AGC setup time of the receiving UE can be adjusted to 33.33 and 66.67 μs for subframes 500 and 600, respectively (without considering the original CP of 4.7 μs for the first symbol). Ultimately, the entire length of the second symbol is used to transmit data.

[0076] Figure 7 Schematic diagram of a subframe 700 is shown. The subframe 700 includes two time slots, each having a duration of about 0.5 milliseconds and including seven symbols. According to one embodiment, the second half of the last symbol 720 is punctured, so that the receiving UE can obtain at least 33.33 milliseconds of the guard interval as Tx / Rx switching time.

[0077] In other embodiments, the guard time for adjusting the Tx / Rx switching time is obtained by partially, completely or completely not puncturing the last symbol, depending on the specific D2D application. As an example, if the processing of the guard time is not operated within the D2D discovery or communication area, then the last symbol does not need to be punctured at all. Alternatively, the Tx / Rx switching time is handled by the scheduler restrictions for the D2D and WAN subframe boundaries.

[0078] Subframe 700 provides better coding gain that improves the likelihood of packet detection compared to subframes 500 or 600. In various embodiments, the first half of the first symbol 710 is not punctured. Alternatively, the first half of the first symbol 710 is used to generate an effective CP 730 for the second half 740 at the first symbol 710. Ultimately, in addition to the normal or extended CP for the D2D subframe, the CP 730 provides the receiving UE with at least 33.33 microseconds for establishing the AGC. As an example, the CP 730 uses a CP length of 38.03 microseconds (e.g., 33.33 μs for the first half of the first symbol, plus 4.7 μs for the normal CP for the first symbol) to adjust the AGC setup time. Compared to subframes 500 or 600, subframe 700 does not provide any additional protection for the second symbol, but provides better coding gain.

[0079] Figure 8 A schematic diagram of a subframe 800 is shown. The subframe 800 includes two time slots, each having a duration of approximately 0.5 milliseconds and including seven symbols. In accordance with one embodiment, the second half of the last symbol 820 is punctured to provide a guard interval of at least 33.33 milliseconds for the receiving UE as a Tx / Rx switching time.

[0080] In various embodiments, in addition to the UL-DMRS transmitted in the fourth symbol 830 and the eleventh symbol 840 of the subframe 800, the UL-DMRS is transmitted in the first symbol 810. In one embodiment, the base sequence and cyclic offset of the UL-DMRS used for the first symbol 810 are the same as those used for the UL-DMRS of the fourth symbol 830 or the eleventh symbol 840. In some embodiments, depending on

[0081] The time required to establish AGC is calculated by setting the conventional UL-DMRS

[0082] The first symbol 810 is mapped to the subcarriers to generate the first symbol 810. In this case, the subframe 800 provides approximately 71.37 microseconds (e.g., 66.67 μs for the first symbol, plus 4.7 μs for the normal CP for the second symbol) for the AGC setup time at the receiver. In some embodiments, the first half of the first symbol 810 can be punctured instead of or in addition to the punctured last symbol 820, thereby providing additional guard time to control the Tx / Rx switching time. In other embodiments, if the guard time is adjusted via partial or complete puncturing of the last symbol 820, then puncturing of the first symbol 810 is not necessary.

[0083] Fig. 9 Schematic diagram of subframe 900 is shown. In some embodiments, subframe 900 is similar to subframe 800, wherein the second half of the last symbol 920 is punctured to provide a guard interval of at least 33.33 microseconds as a Tx / Rx switching time for the receiving UE. Similarly, in various embodiments, in addition to the fourth symbol 930 and the eleventh symbol 940 of subframe 900, the UL-DMRS is transmitted in the first symbol 910.

[0084] In some embodiments, the required AGC setup time can be controlled at 33.33 microseconds. Therefore, after the UL-DMRS is mapped to the first symbol 910, a valid CP 950 is generated in the first half of the first symbol 910, for example, based on the second half of the first symbol 910, which still stores a portion of the reference signal 960. In this case, the CP has a length of at least 33.33 microseconds. Such a structure is conducive to better channel estimation and time tracking. For example, the portion of the reference signal 960 in the second half of the first symbol 910 is used to enhance channel estimation, time tracking (for example, by facilitating better time tracking to provide stronger robustness to the time offset between the Tx UE and the Rx UE), etc. However, the portion of the reference signal 960 in the first symbol 910 cannot be guaranteed to be used for channel estimation, time tracking, etc.

[0085] In various embodiments, all subcarriers used for the first symbol 910 are loaded as physical downlink shared channel (PUSCH) DMRS. In various embodiments, the first half of the first symbol 910 is also punctured to accommodate AGC setup time and Tx / Rx switching time.

[0086] Fig.10 Schematic diagram of subframe 1000 is shown. In some embodiments, subframe 1000 is similar to subframe 800, wherein the second half of the last symbol 1020 is punctured to provide a guard interval of at least 33.33 microseconds for the receiving UE as a Tx / Rx switching time. Similarly, UL-DMRS is transmitted at the fourth symbol 1030 and the eleventh symbol 1040 of subframe 1000.

[0087] However, subframe 1000 uses the first symbol 1010 to carry the AGC RS instead of the UL-DMRS transmission, which is the same as subframe 800. In some embodiments, the AGC RS has a lower PAPR. In some embodiments, the AGC RS is defined on a per-resource-block (RB) or per-resource-block-set basis. Any UE transmitting on the same RB transmits the same sequence as the AGC RS. The AGC RS is the same for all physical resources.

[0088] Similar to subframe 800, subframe 1000 also provides approximately 71.37 microseconds (e.g., 66.67 μs for the first symbol, plus 4.7 μs for the normal CP for the second symbol) for the receiver's AGC setup time. In some embodiments, the first half of the first symbol 1010 is punctured instead of or in addition to the last punctured symbol 1020 to provide additional guard time to control the Tx / Rx switching time.

[0089] Similar to subframe 900, subframe 1000 generates a valid CP in the first half of first symbol 1010, for example, in some embodiments, based on the second half of first symbol 1010. However, AGC RS is not used to improve channel estimation and time tracking for message packet demodulation because AGC RS is common to UEs.

[0090] Fig.11 1 is a schematic diagram showing a subframe 1100. In some embodiments, subframe 1100 is similar to subframe 1000, wherein the second half of the last symbol 1120 is punctured to provide a guard interval of at least 33.33 microseconds for the receiving UE as a Tx / Rx switching time. Similarly, UL-DMRS is transmitted in the fourth symbol 1130 and the eleventh symbol 1140 of subframe 1100.

[0091] However, subframe 1100 uses first symbol 1110 to carry random QPSK symbols instead of AGCRS in subframe 1000. Similarly, if guard time processing (e.g., for Tx / Rx switching time) needs to be applied to first symbol 1110, subframe 1100 can be modified by puncturing the first half of first symbol 1110 at the transmitter side.

[0092] Finally, as in Figure 8-11 As described above, the specific processing for the first and / or last symbol may not be applied to those subframes that occur in multi-TTI transmissions. For example, if a single discovery resource includes one or two physical resource blocks (PRBs) in the frequency domain and two TTIs in the time domain, then the last symbol of the first TTI and the first symbol of the second TTI need to be used as regular symbols to achieve higher coding gain.

[0093] like Figure 2 The UE 210 or 220 shown may be implemented in a system using any suitable hardware, firmware and / or software of a desired configuration. For one embodiment, Fig.12 An example system 1200 is shown that includes radio frequency (RF) circuitry 1210, baseband circuitry 1220, application circuitry 1230, memory / storage 1240, display 1250, camera 1260, sensor 1270, and input / output (I / O) interfaces, which are coupled to each other at least as shown.

[0094] Application circuit 1230 includes, but is not limited to, the following circuits: one or more single-core or multi-core processors. The processor includes any combination of general-purpose processors and special-purpose processors (e.g., graphics processors, application processors, etc.). The processor is coupled to memory / storage 1240 and is configured to execute instructions stored on memory / storage 1240 to enable different applications and / or operating systems running on system 1200.

[0095] The baseband circuit 1220 includes, but is not limited to, one or more single-core or multi-core processors. The processor includes a baseband processor. The baseband circuit 1220 operates to enable different radio control functions to communicate with one or more radio networks via the RF circuit 1210. The radio control functions include, but are not limited to, signal modulation, encoding, decoding, wireless frequency offset, etc. In some embodiments, the baseband circuit 1220 provides communications consistent with one or more radio technologies. For example, in some embodiments, the baseband circuit 1220 supports communications with E-UTRAN and / or other WMANs, WLANs, or WPANs. An embodiment in which the baseband circuit 1220 is configured to support radio communications of more than one wireless protocol refers to a multimode baseband circuit.

[0096] In various embodiments, baseband circuitry 1220 includes circuitry that operates on signals that are not strictly considered to be at baseband frequencies. For example, in some embodiments, baseband circuitry 1220 includes circuitry that operates on signals having intermediate frequencies, which are between baseband frequencies and wireless frequencies.

[0097] In certain embodiments, Figure 2 The processing circuit 216 or 226 is embedded in the application circuit 1230 and / or the baseband circuit 1220.

[0098] RF circuit 1210 enables communication with a wireless network using modulated electromagnetic radiation through a non-solid medium. In various embodiments, RF circuit 1210 includes switching, filtering, amplification, etc. to facilitate communication with a wireless network.

[0099] In various embodiments, RF circuitry 1210 includes circuitry that operates on signals that are not strictly considered to be radio frequencies. For example, in some embodiments, RF circuitry includes circuitry that operates on signals having intermediate frequencies, which are between baseband frequencies and radio frequencies.

[0100] In certain embodiments, Figure 2 The transceiver circuit 214 or 224 is embedded in the RF circuit 1210.

[0101] In certain embodiments, some or all of the constituent components of baseband circuitry 1220 , application circuitry 1230 , and / or memory / storage 1240 may be executed together on a system on a chip (SOC).

[0102] Memory / storage 1240 is used to load and store data and / or instructions, for example, for system 1200. Memory / storage 1240 for one embodiment includes a suitable combination of volatile (e.g., dynamic random access memory (DRAM)) or non-volatile memory (e.g., flash memory).

[0103] In various embodiments, the I / O interface 1280 includes one or more user interfaces that enable a user to interact with the system 1200, or peripheral component interfaces that enable peripheral components to interact with the system 1200. User interfaces include, but are not limited to, a physical keyboard or auxiliary keyboard, a touch pad, a speaker, a microphone, etc. Peripheral component interfaces include, but are not limited to, a non-volatile memory port, a universal serial bus (USB) port, an audio jack, and a power interface.

[0104] In various embodiments, sensor 1270 includes one or more sensing devices to determine environmental conditions and / or location information associated with system 1200. In various embodiments, sensors include, but are not limited to, gyroscopes, accelerometers, proximity sensors, ambient light sensors, and positioning units. Positioning units may also be part of or interact with baseband circuitry 1220 and / or RF circuitry 1210 to communicate with components of a positioning network, such as global positioning system (GPS) satellites.

[0105] In various embodiments, display 1250 includes a display such as a liquid crystal display, a touch screen display, etc. In some embodiments, camera 1260 includes a plurality of molded plastic aspheric lens elements manufactured using variable dispersion and refractive index. In some embodiments, camera 1260 includes two or more lenses to capture three-dimensional images for stereoscopic photographs.

[0106] In various embodiments, the system 1200 is a mobile computing device, such as but not limited to a laptop computing device, a tablet computing device, a notebook, an ultrabook, a smart phone, etc. In various embodiments, the system 1200 has more or less components, and / or a different architecture.

[0107] Fig.13 An article of manufacture 1310 with programmable instructions in combination with aspects of the present invention in accordance with various embodiments is shown. In various embodiments, the article of manufacture is used to implement various embodiments of the present invention. As shown, the article of manufacture 1310 includes a computer-readable non-transitory storage medium 1320, wherein instructions 1330 are configured to implement any embodiment or aspect of an embodiment of the present invention. Storage medium 1320 represents a wide range of persistent storage media consistent with the prior art, including but not limited to flash memory, dynamic random access memory, static random access memory, optical disk, magnetic disk, etc. In an embodiment, computer-readable storage medium 1320 includes one or more computer-readable non-transitory storage media. In other embodiments, computer-readable storage medium 1320 is temporary, such as a signal encoded using instruction 1330.

[0108] In various embodiments, in response to execution by the device, the instructions 1330 enable the device to perform various operations described herein. Consistent with embodiments of the present invention, as an example, the storage medium 1320 includes a device configured to enable Figure 2 The apparatus of the UE 210 shown is implemented in a Figure 3 Instructions 1330 for providing certain aspects of the guard interval in the subframe of the process 300. Consistent with an embodiment of the present invention, as another example, the storage medium 1320 includes a configuration to enable Figure 2 The apparatus of the UE 220 shown is implemented in a Figure 4Instructions 1330 of the process 400 of providing certain aspects of a guard interval within a subframe.

[0109] The following paragraphs describe examples of different embodiments.

[0110] Example 1 is a user equipment (UE) comprising a radio transceiver for communicating with another UE via device-to-device (D2D) communication. The UE also includes a processing circuit coupled to the radio transceiver for generating a cyclic prefix (CP) of a first or second symbol of a D2D subframe on an orthogonal frequency division multiplexing (OFDM) resource block or a single carrier frequency division multiple access (SC-FDMA) resource block, wherein the CP has a length greater than 33.33 microseconds.

[0111] Example 2 includes the subject matter of Example 1, wherein the processing circuit further punctures a first half of a useful symbol length of a first symbol and / or a second half of a useful symbol length of a last symbol of a D2D subframe.

[0112] Example 3 includes the subject matter of Example 1 or 2, wherein the processing circuit does not puncture the last symbol of the D2D subframe unless the D2D subframe follows an uplink subframe.

[0113] Example 4 includes the subject matter of Examples 1 to 3, wherein the processing circuit is to use a second half of the useful symbol length of the first symbol generated based on a second half of the useful symbol length of the second symbol as part of the CP of the second symbol.

[0114] Example 5 includes the subject matter of Example 4, wherein the processing circuit further punctures the entire last symbol of the D2D subframe, or punctures the first half of the useful symbol length of the first symbol and the second half of the useful symbol length of the last symbol.

[0115] Example 6 includes the subject matter of Examples 1 to 5, wherein the processing circuit is to use a first half of the useful symbol length of the first symbol generated based on a second half of the useful symbol length of the first symbol as part of the CP of the first symbol.

[0116] Example 7 includes the subject matter of Examples 1 to 6, wherein the processing circuit generates a CP for the second symbol having a length greater than 66.67 microseconds.

[0117] Example 8 is a user equipment (UE) comprising a radio transceiver for communicating with another UE via Long Term Evolution (LTE) Proximity Service (ProSe) or LTE Direct. The UE also includes a processing circuit coupled to the radio transceiver for transmitting a signal in a first symbol of a D2D subframe on an orthogonal frequency division multiplexing (OFDM) resource block or a single carrier frequency division multiple access (SC-FDMA) resource block for automatic gain control (AGC) setting at a receiving UE.

[0118] Example 9 includes the subject matter of Example 8, wherein the processing circuit further generates a cyclic prefix greater than 66.67 microseconds for a second symbol of the D2D subframe.

[0119] Example 10 includes the subject matter of Example 8 or 9, wherein the processing circuit uses an uplink demodulation reference signal (UL-DMRS) as the signal in the first symbol, wherein the base sequence and cyclic prefix of the UL-DMRS are the same as the base sequence and cyclic prefix used by the corresponding UL-DMRS in the fourth symbol and the eleventh symbol of the subframe.

[0120] Example 11 includes the subject matter of Example 10, wherein the processing circuit is used to: generate a portion of a cyclic prefix for the first symbol based on the second half of the useful symbol length of the first symbol, and use the first half of the useful symbol length of the first symbol as a part to maintain the UL-DMRS in the second half of the useful symbol length of the first symbol.

[0121] Example 12 includes the subject matter of Example 10, wherein the processing circuit maps the UL-DMRS to all of a non-cyclic prefix portion of the first symbol.

[0122] Example 13 includes the subject matter of Example 8 or 9, wherein the processing circuit uses an AGC reference signal as the signal, wherein the AGC reference signal is a sequence having a peak-to-average power ratio (PAPR) and is common to multiple transmitting UEs, and wherein the AGC reference signal is defined on a per-resource block or per-resource block set basis.

[0123] Example 14 includes the subject matter of Example 8 or 9, wherein the processing circuit transmits a random quadrature phase shift keying (QPSK) symbol as a signal at the first symbol.

[0124] Example 15 includes the subject matter of Examples 8 to 14, wherein the processing circuit punctures a first half of a useful symbol length of the first symbol.

[0125] Example 16 is a signal design method for a D2D subframe. The method includes providing a first guard interval at a first symbol of a subframe to facilitate establishing an AGC at a receiving UE; and providing a second guard interval at the subframe to facilitate switching from transmission to reception or reception to transmission at the receiving UE.

[0126] Example 17 includes the subject matter of Example 16, and further includes generating a CP for a first symbol of the subframe as the first guard interval, wherein the CP has a length greater than 33.33 microseconds.

[0127] Example 18 includes the subject matter of Example 16, and further includes generating a CP for a second symbol of the subframe as the first guard interval, wherein the CP has a length greater than 66.67 microseconds.

[0128] Example 19 includes the subject matter of Examples 16 to 18, and further includes mapping random quadrature phase shift keying (QPSK) symbols to resource elements (REs) of the first symbol.

[0129] Example 20 includes the subject matter of Examples 16 to 18, and further includes transmitting a signal in the first guard interval, and wherein the signal is a UL-DMRS or an AGC reference signal.

[0130] Example 21 includes the subject matter of Example 20, and also includes using a first half of the useful symbol length of the first symbol generated based on the second half of the useful symbol length of the first symbol as part of the cyclic prefix of the first symbol; and mapping the UL-DMRS to the second half of the useful symbol length of the first symbol.

[0131] Example 22 includes the subject matter of Example 20, and further includes defining an AGC reference signal on a per resource block or per resource block set basis; and configuring the AGC reference signal with a sequence having a low peak-to-average power ratio (PAPR) and being common to multiple transmitting UEs.

[0132] Example 23 includes the subject matter of Examples 16 to 22, and further includes puncturing at least a portion of a last symbol or a first symbol of the subframe as the second guard interval.

[0133] Example 24 is at least one storage medium having instructions configured to cause the apparatus to implement any of the subject matter of Examples 16-23 in response to execution of the instructions by an apparatus.

[0134] Example 25 is an apparatus for wireless communication, comprising components implementing any of the subject matter of Examples 16-23.

[0135] Example 26 is a user equipment (UE), comprising a radio transceiver for communicating with another UE via device-to-device (D2D) communication; and a processing circuit coupled to the radio transceiver for scheduling a D2D subframe so that the D2D subframe is transmitted at least 624 basic time units before a corresponding reference time of the D2D subframe, where one basic time unit is equal to 1 / 30720000 seconds.

[0136] Example 27 includes the subject matter of Example 26, wherein the corresponding reference time is a serving or resident cell downlink reference time under a time division multiplexing configuration.

[0137] Example 28 includes the subject matter of Example 26 or 27, wherein the processing circuit schedules the D2D subframe to transmit the D2D subframe 624 basic time units before a downlink reference time of a serving or camping cell in a time division multiplexing deployment.

[0138] Example 29 includes the subject matter of Example 26, wherein the corresponding reference time is the serving cell uplink reference time (SCURT) under time division multiplexing deployment, where SCURT = SCDRT-TA, where SCDRT is the serving cell downlink reference time and TA is the activation time advance value.

[0139] Example 30 includes the subject matter of Examples 26 to 29, wherein the processing circuit further punctures a last symbol of the D2D subframe.

[0140] The embodiments described in the present invention, including those described in the Abstract, are not intended to be exclusive or to limit the invention to the precise form disclosed. While the specific embodiments and examples described herein are for illustrative purposes, multiple equivalent embodiments or embodiments that can be substituted and / or achieve the same purpose are shown through the above description without departing from the scope of the present invention, as will be appreciated by those skilled in the art.

Claims

1. A user equipment UE, comprising: A radio transceiver for communicating with another UE via Long Term Evolution LTE Proximity Service (ProSe) or LTE Direct; and a processing circuit coupled to the radio transceiver, the processing circuit transmitting a signal in a first symbol of a D2D subframe at an orthogonal frequency division multiplexing OFDM resource block or a single carrier frequency division multiple access SC-FDMA resource block for automatic gain control AGC setting at a receiving UE, wherein the processing circuit uses an uplink demodulation reference signal UL-DMRS as the signal in the first symbol, and wherein a base sequence and a cyclic prefix of the UL-DMRS are the same as a base sequence and a cyclic prefix of a corresponding UL-DMRS on a fourth symbol and an eleventh symbol of the subframe, wherein the processing circuit uses the first half of the useful symbol length of the first symbol generated based on the second half of the useful symbol length of the first symbol as a part of the cyclic prefix of the first symbol, and The processing circuit punctures the entire last symbol of the D2D subframe, or punctures the first half of the useful symbol length of the first symbol and the second half of the useful symbol length of the last symbol.

2. The UE according to claim 1, wherein: The processing circuit may further generate a cyclic prefix greater than 66.67 microseconds for a second symbol of the D2D subframe.

3. The UE according to claim 1, wherein: The processing circuit maintains the UL-DMRS to a second half of a useful symbol length of the first symbol.

4. The UE according to claim 1, wherein: The processing circuit maps the UL-DMRS to all of a non-cyclic prefix portion of the first symbol.

5. A user equipment UE, comprising: A radio transceiver for communicating with another UE via Long Term Evolution LTE Proximity Service (ProSe) or LTE Direct; and a processing circuit coupled to the radio transceiver, the processing circuit transmitting a signal in a first symbol of a D2D subframe at an orthogonal frequency division multiplexing (OFDM) resource block or a single carrier frequency division multiple access (SC-FDMA) resource block for automatic gain control (AGC) setting at a receiving UE, wherein the processing circuit uses an AGC reference signal as the signal, wherein the AGC reference signal is a sequence having a peak-to-average power ratio (PAPR) and being common to a plurality of transmitting UEs, and wherein the AGC reference signal is defined on a per resource block or per resource block set basis, wherein the processing circuit uses the first half of the useful symbol length of the first symbol generated based on the second half of the useful symbol length of the first symbol as a part of the cyclic prefix of the first symbol, and The processing circuit punctures the entire last symbol of the D2D subframe, or punctures the first half of the useful symbol length of the first symbol and the second half of the useful symbol length of the last symbol.

6. A method for a user equipment UE, comprising: Communicate with another UE via LTE Proximity Service (ProSe) or LTE Direct; as well as transmitting a signal in a first symbol of a D2D subframe at an orthogonal frequency division multiplexing OFDM resource block or a single carrier frequency division multiple access SC-FDMA resource block for automatic gain control AGC setting at a receiving UE, wherein an uplink demodulation reference signal UL-DMRS is used as the signal in the first symbol, and wherein a base sequence and a cyclic prefix of the UL-DMRS are the same as a base sequence and a cyclic prefix of a corresponding UL-DMRS on a fourth symbol and an eleventh symbol of the subframe, Wherein, the method further comprises: using a first half of the useful symbol length of the first symbol generated based on the second half of the useful symbol length of the first symbol as a part of a cyclic prefix of the first symbol, and The entire last symbol of the D2D subframe is punctured, or the first half of the useful symbol length of the first symbol and the second half of the useful symbol length of the last symbol are punctured. 7 . The method of claim 6 , further comprising generating a cyclic prefix greater than 66.67 microseconds for a second symbol of the D2D subframe.

8. The method of claim 6, further comprising: The UL-DMRS is maintained until a second half of a useful symbol length of the first symbol.

9. The method of claim 6, further comprising mapping the UL-DMRS to all of a non-cyclic prefix portion of the first symbol.

10. A method for a user equipment UE, comprising: Communicate with another UE via LTE Proximity Service (ProSe) or LTE Direct; as well as transmitting a signal in a first symbol of a D2D subframe at an orthogonal frequency division multiplexing (OFDM) resource block or a single carrier frequency division multiple access (SC-FDMA) resource block for automatic gain control (AGC) setting at a receiving UE, wherein an AGC reference signal is used as the signal, wherein the AGC reference signal is a sequence having a peak-to-average power ratio (PAPR) and being common to a plurality of transmitting UEs, and wherein the AGC reference signal is defined on a per-resource block or per-resource block set basis, Wherein, the method further comprises: using a first half of the useful symbol length of the first symbol generated based on the second half of the useful symbol length of the first symbol as a part of a cyclic prefix of the first symbol, and The entire last symbol of the D2D subframe is punctured, or the first half of the useful symbol length of the first symbol and the second half of the useful symbol length of the last symbol are punctured.

11. A computer-readable medium having instructions stored thereon, which, when executed by one or more processors, cause a user equipment (UE) to perform the following operations: communicating with another UE via Long Term Evolution LTE Proximity Service (ProSe) or LTE Direct; and transmitting a signal in a first symbol of a D2D subframe at an orthogonal frequency division multiplexing OFDM resource block or a single carrier frequency division multiple access SC-FDMA resource block for automatic gain control AGC setting at a receiving UE, in, using an uplink demodulation reference signal UL-DMRS as the signal in the first symbol, and wherein a base sequence and a cyclic prefix of the UL-DMRS are the same as a base sequence and a cyclic prefix used for corresponding UL-DMRS on a fourth symbol and an eleventh symbol of the subframe, Wherein, when the instruction is executed by the one or more processors, the UE is further caused to: using a first half of the useful symbol length of the first symbol generated based on the second half of the useful symbol length of the first symbol as a part of a cyclic prefix of the first symbol, and The entire last symbol of the D2D subframe is punctured, or the first half of the useful symbol length of the first symbol and the second half of the useful symbol length of the last symbol are punctured.

12. The computer-readable medium of claim 11, wherein: The instructions, when executed via the one or more processors, further cause the UE to generate a cyclic prefix greater than 66.67 microseconds for a second symbol of the D2D subframe.

13. The computer-readable medium of claim 11, wherein: When the instructions are executed by the one or more processors, the UE further causes: The UL-DMRS is maintained until a second half of a useful symbol length of the first symbol.

14. The computer-readable medium of claim 11, wherein: The instructions, when executed via the one or more processors, further cause the UE to map the UL-DMRS to all of a non-cyclic prefix portion of the first symbol.

15. A computer-readable medium having instructions stored thereon, which, when executed by one or more processors, cause a user equipment (UE) to perform the following operations: communicating with another UE via Long Term Evolution LTE Proximity Service (ProSe) or LTE Direct; and A signal in a first symbol of a D2D subframe at an orthogonal frequency division multiplexing OFDM resource block or a single carrier frequency division multiple access SC-FDMA resource block is transmitted for automatic gain control AGC setting at a receiving UE, wherein, using an AGC reference signal as the signal, wherein the AGC reference signal is a sequence having a peak-to-average power ratio (PAPR) and being common to a plurality of transmitting UEs, and wherein the AGC reference signal is defined on a per-resource-block or per-resource-block-set basis, Wherein, when the instruction is executed by the one or more processors, the UE is further caused to: using a first half of the useful symbol length of the first symbol generated based on the second half of the useful symbol length of the first symbol as a part of a cyclic prefix of the first symbol, and The entire last symbol of the D2D subframe is punctured, or the first half of the useful symbol length of the first symbol and the second half of the useful symbol length of the last symbol are punctured.

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