WO2017083025A1

WO2017083025A1 - Enhanced device-to-device discovery gap

Info

Publication number: WO2017083025A1
Application number: PCT/US2016/054229
Authority: WO
Inventors: Rui Huang; Yang Tang
Original assignee: Intel IP Corporation
Priority date: 2015-11-09
Filing date: 2016-09-28
Publication date: 2017-05-18

Abstract

Embodiments of enhanced sidelink discovery gap are generally described herein. A user equipment (UE) receives, from a higher layer, an indication of a synchronization source and an indication of a synchronization window, for sidelink communication. The UE determines a sidelink inter-frequency discovery gap based on the synchronization source and the synchronization window. The UE encodes sidelink signals for transmission to a second UE within the sidelink inter-frequency discovery gap, the sidelink signals for transmission on component carriers of a non-serving cell, the second UE operating in the non-serving cell.

Description

ENHANCED DEVICE-TO-DEVICE DISCOVERY GAP PRIORITY CLAIM

[0001] This application claims priority under 35 U.S.C. § 119 to United

States Provisional Patent Application Serial No. 62/252,968, filed November 9, 2015, and titled, "ED2D DISCOVERY GAP," which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] Embodiments pertain to wireless communications. Some embodiments relate device-to-device communication, sidelink communication, and radio access network (RAN). Some embodiments relate to enhanced device- to-device (eD2D) discovery gap.

BACKGROUND

[0003] In recent years, device-to-device (D2D) communication has become more and more ubiquitous in cellular networks. There are general needs for improvements in D2D communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] FIG. 1 is a functional diagram of a wireless network, in accordance with some embodiments.

[0005] FIG. 2 illustrates an example signal including a gap when a WAN signal serves as a synchronization source and discSyn Window is W2, in accordance with some embodiments. [0006] FIG. 3 illustrates an example signal including a gap when a wireless area network (WAN) signal serves as a synchronization source and discSynWindow is Wl, in accordance with some embodiments.

[0007] FIG. 4 illustrates an example signal including a gap when sidelink synchronization signal (SLSS) serves as a synchronization source and discSynWindow is Wl, in accordance with some embodiments.

[0008] FIG. 5 illustrates an example signal including a gap when a WAN signal serves as a synchronization source, discSynWindow is W2, and a dedicated receive chain is used for device-to-device (D2D), in accordance with some embodiments.

[0009] FIG. 6 is a flow chart illustrating an example method 600 for data transmission within a D2D inter-frequency discovery gap, in accordance with some embodiments.

[0010] FIG. 7 illustrates components of a communication device, in accordance with some embodiments.

[0011] FIG. 8 illustrates a block diagram of a communication device, in accordance with some embodiments.

[0012] FIG. 9 illustrates another block diagram of a communication device, in accordance with some embodiments.

DETAILED DESCRIPTION

[0013] The following description and the drawings sufficiently illustrate specific embodiments to enable those skilled in the art to practice them. Other embodiments may incorporate structural, logical, electrical, process, and other changes. Portions and features of some embodiments may be included in, or substituted for, those of other embodiments. Embodiments set forth in the claims encompass all available equivalents of those claims.

[0014] FIG. 1 shows an example of a portion of an end-to-end network architecture of a Long Term Evolution (LTE) network 100 with various components of the network in accordance with some embodiments. As used herein, an LTE network refers to both LTE and LTE Advanced (LTE- A) networks as well as other versions of LTE networks to be developed. The network 100 may comprise a radio access network (RAN) (e.g., as depicted, the E-UTRAN or evolved universal terrestrial radio access network) 101 and core network 120 (e.g., shown as an evolved packet core (EPC)) coupled together through an SI interface 1 15. For convenience and brevity, only a portion of the core network 120, as well as the RAN 101, is shown in the example.

[0015] The core network 120 may include a mobility management entity

(MME) 122, serving gateway (serving GW) 124, and packet data network gateway (PDN GW) 126. The RAN 101 may include evolved node Bs (eNBs) 104 (which may operate as base stations) for communicating with user equipment (UE) 102. The eNBs 104 may include macro eNBs 104a and low power (LP) eNBs 104b. In some cases, the connection between a UE 102 and an eNB 104 is a LTE-Uu connection. In some cases, one or more of the UEs 102 includes a proximity service (ProSe) application for device-to-device (D2D) or enhanced D2D (eD2D) communication via a PC5 connection. The UEs may have a PC3 connection to a ProSe Function 130.

[0016] As used herein, D2D communication may refer to sidelink (SL) communication, and a D2D channel may be a sidelink channel. D2D and sidelink each encompass their plain and ordinary meaning and may be used interchangeably.

[0017] The MME 122 may be similar in function to the control plane of legacy Serving GPRS Support Nodes (SGSN). The MME 122 may manage mobility aspects in access such as gateway selection and tracking area list management. The serving GW 124 may terminate the interface toward the RAN 101, and route data packets between the RAN 101 and the core network 120. In addition, the serving GW 124 may be a local mobility anchor point for inter-eNB handovers and also may provide an anchor for inter-3GPP mobility. Other responsibilities may include lawful intercept, charging, and some policy enforcement. The serving GW 124 and the MME 122 may be implemented in one physical node or separate physical nodes.

[0018] The PDN GW 126 may terminate a SGi interface toward the packet data network (PDN). The PDN GW 126 may route data packets between the EPC 120 and the external PDN, and may perform policy enforcement and charging data collection. The PDN GW 126 may also provide an anchor point for mobility devices with non-LTE access. The external PDN can be any kind of IP network, as well as an IP Multimedia Subsystem (IMS) domain. The PDN GW 126 and the serving GW 124 may be implemented in a single physical node or separate physical nodes.

[0019] The eNBs 104 (macro and micro) may terminate the air interface protocol and may be the first point of contact for a UE 102. In some

embodiments, an eNB 104 may fulfill various logical functions for the RAN 101 including, but not limited to, RNC (radio network controller functions) such as radio bearer management, uplink and downlink dynamic radio resource management and data packet scheduling, and mobility management. In accordance with embodiments, UEs 102 may be configured to communicate orthogonal frequency division multiplexed (OFDM) communication signals with an eNB 104 over a multicarrier communication channel in accordance with an OFDMA communication technique. The OFDM signals may comprise a plurality of orthogonal subcarriers.

[0020] The SI interface 115 may be the interface that separates the RAN

101 and the EPC 120. It may be split into two parts: the Sl-U, which may carry traffic data between the eNBs 104 and the serving GW 124, and the Sl-MME, which may be a signaling interface between the eNBs 104 and the MME 122. The X2 interface may be the interface between eNBs 104. The X2 interface may comprise two parts, the X2-C and X2-U. The X2-C may be the control plane interface between the eNBs 104, while the X2-U may be the user plane interface between the eNBs 104.

[0021] With cellular networks, LP cells 104b may be typically used to extend coverage to indoor areas where outdoor signals do not reach well, or to add network capacity in areas with dense usage. In particular, it may be desirable to enhance the coverage of a wireless communication system using cells of different sizes, macrocells, microcells, picocells, and femtocells, to boost system performance. The cells of different sizes may operate on the same frequency band, or may operate on different frequency bands with each cell operating in a different frequency band or only cells of different sizes operating on different frequency bands. As used herein, the term LP eNB refers to any suitable relatively LP eNB for implementing a smaller cell (smaller than a macro cell) such as a femtocell, a picocell, or a microcell. Femtocell eNBs may be typically provided by a mobile network operator to its residential or enterprise customers. A femtocell may be typically the size of a residential gateway or smaller and generally connect to a broadband line. The femtocell may connect to the mobile operator's mobile network and provide extra coverage in a range of typically 30 to 50 meters. Thus, a LP eNB 104b might be a femtocell eNB since it is coupled through the PDN GW 126. Similarly, a picocell may be a wireless

communication system typically covering a small area, such as in-building (offices, shopping malls, train stations, etc.), or more recently in-aircraft. A picocell eNB may generally connect through the X2 link to another eNB such as a macro eNB through its base station controller (BSC) functionality. Thus, LP eNB may be implemented with a picocell eNB since it may be coupled to a macro eNB 104a via an X2 interface. Picocell eNBs or other LP eNBs LP eNB 104b may incorporate some or all functionality of a macro eNB LP eNB 104a. In some cases, this may be referred to as an access point base station or enterprise femtocell.

[0022] In some embodiments, the UE 102 may communicate with an access point (AP) 104c. The AP 104c may use only the unlicensed spectrum (e.g., WiFi bands) to communicate with the UE 102. The AP 104c may communicate with the macro eNB 104 A (or LP eNB 104B) through an Xw interface. In some embodiments, the AP 104c may communicate with the UE 102 independent of communication between the UE 102 and the macro eNB 104 A. In other embodiments, the AP 104c may be controlled by the macro eNB 104A and use LWA, as described in more detail below.

[0023] Communication over an LTE network may be split up into 10ms frames, each of which may contain ten 1ms subframes. Each subframe of the frame, in turn, may contain two slots of 0.5ms. Each subframe may be used for uplink (UL) communications from the UE to the eNB or downlink (DL) communications from the eNB to the UE. In one embodiment, the eNB may allocate a greater number of DL communications than UL communications in a particular frame. The eNB may schedule transmissions over a variety of frequency bands (fi and f₂). The allocation of resources in subframes used in one frequency band and may differ from those in another frequency band. Each slot of the subframe may contain 6-7 OFDM symbols, depending on the system used. In one embodiment, the subframe may contain 12 subcamers. A downlink resource grid may be used for downlink transmissions from an eNB to a UE, while an uplink resource grid may be used for uplink transmissions from a UE to an eNB or from a UE to another UE. The resource grid may be a time-frequency grid, which is the physical resource in the downlink in each slot. The smallest time-frequency unit in a resource grid may be denoted as a resource element (RE). Each column and each row of the resource grid may correspond to one OFDM symbol and one OFDM subcarrier, respectively. The resource grid may contain resource blocks (RBs) that describe the mapping of physical channels to resource elements and physical RBs (PRBs). A PRB may be the smallest unit of resources that can be allocated to a UE. A resource block may be 180 kHz wide in frequency and 1 slot long in time. In frequency, resource blocks may be either 12 x 15 kHz subcarriers or 24 x 7.5 kHz subcarriers wide. For most channels and signals, 12 subcarriers may be used per resource block, dependent on the system bandwidth. In Frequency Division Duplexed (FDD) mode, both the uplink and downlink frames may be 10ms and frequency (full-duplex) or time (half-duplex) separated. In Time Division Duplexed (TDD), the uplink and downlink subframes may be transmitted on the same frequency and are multiplexed in the time domain. The duration of the resource grid 400 in the time domain corresponds to one subframe or two resource blocks. Each resource grid may comprise 12 (subcarriers) * 14 (symbols) =168 resource elements.

[0024] Each OFDM symbol may contain a cyclic prefix (CP) which may be used to effectively eliminate Inter Symbol Interference (ISI), and a Fast Fourier Transform (FFT) period. The duration of the CP may be determined by the highest anticipated degree of delay spread. Although distortion from the preceding OFDM symbol may exist within the CP, with a CP of sufficient duration, preceding OFDM symbols do not enter the FFT period. Once the FFT period signal is received and digitized, the receiver may ignore the signal in the CP.

[0025] There may be several different physical downlink channels that are conveyed using such resource blocks, including the physical downlink control channel (PDCCH) and the physical downlink shared channel (PDSCH). Each subframe may be partitioned into the PDCCH and the PDSCH. The PDCCH may normally occupy the first two symbols of each subframe and carries, among other things, information about the transport format and resource allocations related to the PDSCH channel, as well as H-ARQ information related to the uplink shared channel. The PDSCH may carry user data and higher layer signaling to a UE and occupy the remainder of the subframe. Typically, downlink scheduling (assigning control and shared channel resource blocks to UEs within a cell) may be performed at the e B based on channel quality information provided from the UEs to the eNB, and then the downlink resource assignment information may be sent to each UE on the PDCCH used for

(assigned to) the UE. The PDCCH may contain downlink control information (DCI) in one of a number of formats that indicate to the UE how to find and decode data, transmitted on PDSCH in the same subframe, from the resource grid. The DCI format may provide details such as number of resource blocks, resource allocation type, modulation scheme, transport block, redundancy version, coding rate etc. Each DCI format may have a cyclic redundancy code (CRC) and be scrambled with a Radio Network Temporary Identifier (RNTI) that identifies the target UE for which the PDSCH is intended. Use of the UE- specific RNTI may limit decoding of the DCI format (and hence the

corresponding PDSCH) to only the intended UE.

[0026] In some implementations of LTE networks, gaps may be introduced into Uu. Gaps introduced for discovery transmission and reception may apply to both inter-frequency and intra-frequency cases for connected UEs. The eNB may control the gap configuration on a per-UE basis. The gap created for discovery may take into account additional overhead (e.g., for

synchronization and subframe offset) and interruption time for retuning. The UE may request gaps for discovery reception or transmission. In the request, the UE may inform the eNB of the subframes (corresponding to the timing of the serving cell) on which the UE needs gaps for transmission or reception.

[0027] Additional overheads may be included in the sidelink gaps. The additional overheads may include the delay due to synchronization, subframe offset between serving carrier and ProSe discovery carrier, and interruption because of frequency retuning. [0028] In some cases of the subject technology, both intra-frequency discovery gap (discovery on PCell and serving SCell) and inter-frequency discovery gap (discovery on a non-serving cell) may be supported in multiple- carrier D2D discovery.

[0029] Aspects of the subject technology are directed to intra-frequency

D2D discovery gap. For intra-frequency D2D discovery, the D2D discovery may be transmitted or received in the same carriers as the serving cell (e.g., PCell or serving SCell). The D2D discovery transmission/ reception timing may be based on the serving cell's timing. Thus, no overhead of synchronization time is needed for the D2D discovery gap. Some example policies for the intra- frequency D2D discovery gap are set forth in Table 1.

Table 1. Example policies for the intra-frequency D2D discovery gap

[0030] Aspects of the subject technology are directed to inter-frequency

D2D discovery gap when a single RX chain is shared by wireless area network (WAN) and D2D. For inter-frequency D2D discovery, the D2D discovery may be transmitted or received in the carriers of the non-serving cell. The D2D discovery transmission/ reception timing might not be based on the serving cell's timing. However a retuning time of the additional overhead of the D2D discovery gap (in terms of subframe offset and synchronization time) may be implemented. Synchronization may be performed with the reference source in the backend. D2D discovery may be transmitted or received until the

synchronization with the reference source is obtained.

[0031] In some cases, more than one D2D discovery gap cycle is needed to obtain the D2D synchronization and the D2D discovery TX/RX sequentially. A D2D discovery resource pool may include a subframe that is shorter than the overhead of synchronization time. The gap for the D2D discovery data transmission and reception may, in some cases, be the same as that for D2D synchronization.

[0032] In some cases, a unified D2D gap configuration may be applied to D2D synchronization and D2D discovery TX/RX sequentially. In particular, as shown in Table 2, in some implementations, both the primary synchronization signal (PSS)/ secondary synchronization signal (SSS) of WAN and sidelink synchronization signal (SLSS) of D2D may potentially be used to derive the timing synchronization. According to the different radio resource control (RRC) signalling (e.g., SL-syncConfigIndex-rl2 and discSyncWindow) the

synchronization source, synchronization window, and the resource pool for D2D discovery may be different.

Table 2. D2D discovery reference synchronization source

[0033] Regarding the different synchronization sources for D2D discovery under the specific scenarios, the D2D discovery gap overhead in terms of synchronization time may be distinguished between the following two cases: (1) WAN (e.g., PSS/SSS) serving as the synchronization source, and (2) SLSS (e.g., primary sidelink synchronization signal (PSSS)/ secondary sidelink synchronization signal (SSSS) serving as the synchronization source.

[0034] According to one embodiment, shown in FIG. 2, a WAN signal is the synchronization source and discSyncWindow is W2. The WAN signal serves as the synchronization reference source for inter-frequency D2D discovery in the non-serving cell carriers.

[0035] FIG. 2 illustrates an example signal 200 including a gap 260 when a WAN signal serves as a synchronization source and discSynWindow is W2, in accordance with some embodiments. As shown, the signal 200 includes serving cell carrier F0 210, which includes the gap 260. The signal 200 includes UE RX chain for D2D @F1 (DL) 220, WAN TX @F1 (DL) 230, UE RX chain for D2D @F2 (UL) 240, and D2D TX @F2 (UL) 250. Fl and F2 are different frequencies.

[0036] FIG. 2 shows the gap 260 when WAN serves as the

synchronization source and discSyncWindow is W2. When WAN is the D2D discovery synchronization source, the synchronization window indicated by the network may be less than W2, which denotes the length corresponding to the normal cyclic prefix divided by two. Accordingly, in some cases, the subframe offset overhead may be ignored. The synchronization signal in WAN (e.g., PSS/SSS) maybe founded every 5 ms. Accordingly, a gap length of 6 ms may provide at least one pair of PSS/SSS received within a single D2D discovery gap- [0037] If the WAN synchronization source is used for D2D discovery, and the synchronization window is W2, the inter-frequency discovery gap may be similar to the measurement gap. Thus, the inter-frequency D2D discovery gap, when WAN serves as the synchronization source and W2 is indicated as the D2D synchronization window, may re-use the existing gap configuration for inter-measurement gap.

[0038] In one embodiment, WAN is the synchronization source, and discSyncWindow is Wl . In comparison with the above scenario, the

synchronization window indicated by the serving eNB can be as large as +/- Wl, which is +/- 5 ms. As a result, the subframe offset impacts on D2D discovery gap may be considered. An example of the D2D discovery gap is provided with FIG. 3.

[0039] FIG. 3 illustrates an example signal 300 including a gap 360 when a wireless area network (WAN) signal serves as a synchronization source and discSynWindow is Wl, in accordance with some embodiments. As shown, the signal 300 includes a UE RX chain 310, a WAN TX chain 320, and multiple UE RX chains 330, each having a different offset for synchronization windows 340. The UE RX chain 310 includes the gap 360.

[0040] According to some aspects of the subject technology, if no interruption is allowed (e.g., interruption due to radio frequency (RF) tuning), the D2D discovery gap in the implementation of FIG. 3 may be up to 17 ms.

[0041] According to one embodiment, SLSS is the synchronization source, and discSyncWindow is Wl . When SLSS is used as the synchronization source for D2D discovery, in comparison with the embodiment of FIG. 2, the synchronization window indicated by the serving eNB may be as large as +/1 Wl, which is +/1 5 ms. As a result, the subframe offset impacts on the D2D discovery gap may be considered. At the same time, there is one PSSS/SSSS synchronization signal over 40 ms. An example of the D2D discovery gap in this scenario is illustrated in FIG. 4.

[0042] FIG. 4 illustrates an example signal 400 including a gap 460 when sidelink synchronization signal (SLSS) serves as a synchronization source and discSynWindow is Wl, in accordance with some embodiments. As shown, the signal 400 includes a UE RX chain at serving cell 410, a D2D TX chain 420, and multiple UE RX chains for D2D 430. Each of the UE RX chains for D2D 430 has a different offset for the synchronization window 440. The gap 460 is shown in the UE RX chain at serving cell 410. The length of the D2D discovery gap may be as large as 23 ms if the D2D synchronization window (Wl) indicated by the network is 5 ms.

[0043] One embodiment relates to inter-frequency D2D discovery gap when a dedicated RX chain is used for D2D. If there is a single RX chain shared by WAN and D2D TX/RX, the D2D discovery gap may be used for D2D synchronization and D2D discovery. In some cases, the gap overhead is higher. For example, when SLSS serves as the synchronization source, the overhead D2D discovery gap may be greater than 50% or as high as 23/40, given that the periodicity of this gap is 40 ms.

[0044] The overhead of D2D inter-frequency discovery may be larger than 50%, which may not be acceptable in terms of network efficiency. On the other hand, if the dedicated TX/RX chain is used for D2D discovery, the simultaneous WAN and D2D synchronization or discovery RX may be possible. Therefore, the UE might not turn off WAN data TX/RX when performing D2D synchronization and discovery. This can improve the network efficiency significantly. However, as shown in FIG. 5, potential interruption due to D2D RX chain retuning may occur. For example, if the minimum gap periodicity is 40ms, the maximum interruption rate may be 2/40=5%). In order to reduce the interruption rate, the network may configure a higher D2D gap periodicity.

[0045] FIG. 5 illustrates an example signal 500 including a gap 560 when a WAN signal serves as a synchronization source, discSyn Window is W2, and a dedicated receive chain is used for device-to-device (D2D), in accordance with some embodiments. As shown, the signal includes a UE RX chain at serving cell 510, a D2D TX chain 520, and multiple UE RX chains for D2D 530. Each UE RX chain for D2D 530 includes a synchronization window 540 having a different offset. The gap 560 is shown in the UE RX chain at the serving cell 510.

[0046] According to some implementations, if a dedicated RX chain is used for D2D discovery, the interruption due to D2D RX chain retuning may be permitted if the overhead of the D2D inter-frequency discovery gap exceeds a threshold (e.g., 50%>). For the inter-frequency discovery gap, the overhead that may be taken is summarized in Table 3.

Table 3. Inter-frequency D2D discovery gap overhead

WAN synchronization 10ms 17ms No source, 2ms 5 ms

disc SyncWindow=w 1

SLSS synchronization 10ms 23ms No source, 2ms 11ms

disc SyncWindow=w 1

Dedicated - - Yes

- - TX/RX

[0047] FIG. 6 is a flow chart illustrating an example method 600 for data transmission within a D2D inter-frequency discovery gap. The method 600 is implemented at a UE. At operation 610, the UE decodes a device-to-device (D2D) synchronization source indicated by a higher layer and a D2D

synchronization window indicated by the higher layer. At operation 620, the UE encodes for data transmission within a D2D inter-frequency discovery gap based on the indicated D2D synchronization source and the indicated D2D

synchronization window, the D2D inter-frequency discovery gap being accessible by a second UE operating at a second operating frequency different from a first operating frequency of the first UE, and the D2D inter-frequency discovery gap including information for use, by the second UE, in D2D synchronization or D2D discovery.

[0048] Embodiments described herein may be implemented into a system using any suitably configured hardware and/or software. FIG. 7 illustrates components of a UE in accordance with some embodiments. At least some of the components shown may be used in an e B or MME, for example, such as the UE 102 or eNB 104 shown in FIG. 1. The UE 700 and other components may be configured to use the synchronization signals as described herein. The UE 700 may be a stationary, non-mobile device or may be a mobile device. In some embodiments, the UE 700 may include application circuitry 702, baseband circuitry 704, Radio Frequency (RF) circuitry 706, front-end module (FEM) circuitry 708 and one or more antennas 710, coupled together at least as shown. At least some of the baseband circuitry 704, RF circuitry 706, and FEM circuitry 708 may form a transceiver. In some embodiments, other network elements, such as the eNB may contain some or all of the components shown in FIG. 7. Other of the network elements, such as the MME, may contain an interface, such as the SI interface, to communicate with the e B over a wired connection regarding the UE.

[0049] The application or processing circuitry 702 may include one or more application processors. For example, the application circuitry 702 may include circuitry such as, but not limited to, one or more single-core or multi- core processors. The processor(s) may include any combination of general- purpose processors and dedicated processors (e.g., graphics processors, application processors, etc.). The processors may be coupled with and/or may include memory/storage and may be configured to execute instructions stored in the memory/storage to enable various applications and/or operating systems to run on the system.

[0050] The baseband circuitry 704 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The baseband circuitry 704 may include one or more baseband processors and/or control logic to process baseband signals received from a receive signal path of the RF circuitry 706 and to generate baseband signals for a transmit signal path of the RF circuitry 706. Baseband processing circuity 704 may interface with the application circuitry 702 for generation and processing of the baseband signals and for controlling operations of the RF circuitry 706. For example, in some embodiments, the baseband circuitry 704 may include a second generation (2G) baseband processor 704a, third generation (3G) baseband processor 704b, fourth generation (4G) baseband processor 704c, and/or other baseband processor(s) 704d for other existing generations, generations in development or to be developed in the future (e.g., fifth generation (5G), 6G, etc.). The baseband circuitry 704 (e.g., one or more of baseband processors 704a-d) may handle various radio control functions that enable communication with one or more radio networks via the RF circuitry 706. The radio control functions may include, but are not limited to, signal modulation/demodulation,

encoding/decoding, radio frequency shifting, etc. In some embodiments, modulation/demodulation circuitry of the baseband circuitry 704 may include FFT, precoding, and/or constellation mapping/demapping functionality. In some embodiments, encoding/decoding circuitry of the baseband circuitry 704 may include convolution, tail-biting convolution, turbo, Viterbi, and/or Low Density Parity Check (LDPC) encoder/decoder functionality. Embodiments of modulation/demodulation and encoder/decoder functionality are not limited to these examples and may include other suitable functionality in other

embodiments.

[0051] In some embodiments, the baseband circuitry 704 may include elements of a protocol stack such as, for example, elements of an evolved universal terrestrial radio access network (E-UTRAN) protocol including, for example, physical (PHY), media access control (MAC), radio link control (RLC), packet data convergence protocol (PDCP), and/or radio resource control (RRC) elements. A central processing unit (CPU) 704e of the baseband circuitry 704 may be configured to run elements of the protocol stack for signaling of the PHY, MAC, RLC, PDCP and/or RRC layers. In some embodiments, the baseband circuitry may include one or more audio digital signal processor(s) (DSP) 704f. The audio DSP(s) 704f may be include elements for

compression/decompression and echo cancellation and may include other suitable processing elements in other embodiments. Components of the baseband circuitry may be suitably combined in a single chip, a single chipset, or disposed on a same circuit board in some embodiments. In some embodiments, some or all of the constituent components of the baseband circuitry 704 and the application circuitry 702 may be implemented together such as, for example, on a system on a chip (SOC).

[0052] In some embodiments, the baseband circuitry 704 may provide for communication compatible with one or more radio technologies. For example, in some embodiments, the baseband circuitry 704 may support communication with an evolved universal terrestrial radio access network (EUTRAN) and/or other wireless metropolitan area networks (WMAN), a wireless local area network (WLAN), a wireless personal area network (WPAN). Embodiments in which the baseband circuitry 704 is configured to support radio communications of more than one wireless protocol may be referred to as multi-mode baseband circuitry. In some embodiments, the device can be configured to operate in accordance with communication standards or other protocols or standards, including Institute of Electrical and Electronic Engineers (IEEE) 802.16 wireless technology (WiMax), IEEE 802.11 wireless technology (WiFi) including IEEE 802.11 ad, which operates in the 60 GHz millimeter wave spectrum, various other wireless technologies such as global system for mobile communications (GSM), enhanced data rates for GSM evolution (EDGE), GSM EDGE radio access network (GERAN), universal mobile telecommunications system (UMTS), UMTS terrestrial radio access network (UTRAN), or other 2G, 3G, 4G, 5G, etc. technologies either already developed or to be developed.

[0053] RF circuitry 706 may enable communication with wireless networks using modulated electromagnetic radiation through a non-solid medium. In various embodiments, the RF circuitry 706 may include switches, filters, amplifiers, etc. to facilitate the communication with the wireless network. RF circuitry 706 may include a receive signal path which may include circuitry to down-convert RF signals received from the FEM circuitry 708 and provide baseband signals to the baseband circuitry 704. RF circuitry 706 may also include a transmit signal path which may include circuitry to up-convert baseband signals provided by the baseband circuitry 704 and provide RF output signals to the FEM circuitry 708 for transmission.

[0054] In some embodiments, the RF circuitry 706 may include a receive signal path and a transmit signal path. The receive signal path of the RF circuitry 706 may include mixer circuitry 706a, amplifier circuitry 706b and filter circuitry 706c. The transmit signal path of the RF circuitry 706 may include filter circuitry 706c and mixer circuitry 706a. RF circuitry 706 may also include synthesizer circuitry 706d for synthesizing a frequency for use by the mixer circuitry 706a of the receive signal path and the transmit signal path. In some embodiments, the mixer circuitry 706a of the receive signal path may be configured to down-convert RF signals received from the FEM circuitry 708 based on the synthesized frequency provided by synthesizer circuitry 706d. The amplifier circuitry 706b may be configured to amplify the down-converted signals and the filter circuitry 706c may be a low-pass filter (LPF) or band-pass filter (BPF) configured to remove unwanted signals from the down-converted signals to generate output baseband signals. Output baseband signals may be provided to the baseband circuitry 704 for further processing. In some embodiments, the output baseband signals may be zero-frequency baseband signals, although this is not a requirement. In some embodiments, mixer circuitry 706a of the receive signal path may comprise passive mixers, although the scope of the embodiments is not limited in this respect.

[0055] In some embodiments, the mixer circuitry 706a of the transmit signal path may be configured to up-convert input baseband signals based on the synthesized frequency provided by the synthesizer circuitry 706d to generate RF output signals for the FEM circuitry 708. The baseband signals may be provided by the baseband circuitry 704 and may be filtered by filter circuitry 706c. The filter circuitry 706c may include a low-pass filter (LPF), although the scope of the embodiments is not limited in this respect.

[0056] In some embodiments, the mixer circuitry 706a of the receive signal path and the mixer circuitry 706a of the transmit signal path may include two or more mixers and may be arranged for quadrature downconversion and/or upconversion respectively. In some embodiments, the mixer circuitry 706a of the receive signal path and the mixer circuitry 706a of the transmit signal path may include two or more mixers and may be arranged for image rejection (e.g., Hartley image rejection). In some embodiments, the mixer circuitry 706a of the receive signal path and the mixer circuitry 706a may be arranged for direct downconversion and/or direct upconversion, respectively. In some embodiments, the mixer circuitry 706a of the receive signal path and the mixer circuitry 706a of the transmit signal path may be configured for super-heterodyne operation.

[0057] In some embodiments, the output baseband signals and the input baseband signals may be analog baseband signals, although the scope of the embodiments is not limited in this respect. In some alternate embodiments, the output baseband signals and the input baseband signals may be digital baseband signals. In these alternate embodiments, the RF circuitry 706 may include analog-to-digital converter (ADC) and digital-to-analog converter (DAC) circuitry and the baseband circuitry 704 may include a digital baseband interface to communicate with the RF circuitry 706.

[0058] In some dual-mode embodiments, a separate radio IC circuitry may be provided for processing signals for each spectrum, although the scope of the embodiments is not limited in this respect. [0059] In some embodiments, the synthesizer circuitry 706d may be a fractional -N synthesizer or a fractional N/N+1 synthesizer, although the scope of the embodiments is not limited in this respect as other types of frequency synthesizers may be suitable. For example, synthesizer circuitry 706d may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer comprising a phase-locked loop with a frequency divider.

[0060] The synthesizer circuitry 706d may be configured to synthesize an output frequency for use by the mixer circuitry 706a of the RF circuitry 706 based on a frequency input and a divider control input. In some embodiments, the synthesizer circuitry 706d may be a fractional N/N+1 synthesizer.

[0061] In some embodiments, frequency input may be provided by a voltage controlled oscillator (VCO), although that is not a requirement. Divider control input may be provided by either the baseband circuitry 704 or the applications processor 702 depending on the desired output frequency. In some embodiments, a divider control input (e.g., N) may be determined from a lookup table based on a channel indicated by the applications processor 702.

[0062] Synthesizer circuitry 706d of the RF circuitry 706 may include a divider, a delay-locked loop (DLL), a multiplexer and a phase accumulator. In some embodiments, the divider may be a dual modulus divider (DMD) and the phase accumulator may be a digital phase accumulator (DP A). In some embodiments, the DMD may be configured to divide the input signal by either N or N+l (e.g., based on a carry out) to provide a fractional division ratio. In some example embodiments, the DLL may include a set of cascaded, tunable, delay elements, a phase detector, a charge pump and a D-type flip-flop. In these embodiments, the delay elements may be configured to break a VCO period up into Nd equal packets of phase, where Nd is the number of delay elements in the delay line. In this way, the DLL provides negative feedback to help ensure that the total delay through the delay line is one VCO cycle.

[0063] In some embodiments, synthesizer circuitry 706d may be configured to generate a carrier frequency as the output frequency, while in other embodiments, the output frequency may be a multiple of the carrier frequency (e.g., twice the carrier frequency, four times the carrier frequency) and used in conjunction with quadrature generator and divider circuitry to generate multiple signals at the carrier frequency with multiple different phases with respect to each other. In some embodiments, the output frequency may be a LO frequency (fix)). In some embodiments, the RF circuitry 706 may include an IQ/polar converter.

[0064] FEM circuitry 708 may include a receive signal path which may include circuitry configured to operate on RF signals received from one or more antennas 710, amplify the received signals and provide the amplified versions of the received signals to the RF circuitry 706 for further processing. FEM circuitry 708 may also include a transmit signal path which may include circuitry configured to amplify signals for transmission provided by the RF circuitry 706 for transmission by one or more of the one or more antennas 710.

[0065] In some embodiments, the FEM circuitry 708 may include a

TX/RX switch to switch between transmit mode and receive mode operation. The FEM circuitry may include a receive signal path and a transmit signal path. The receive signal path of the FEM circuitry may include a low-noise amplifier (LNA) to amplify received RF signals and provide the amplified received RF signals as an output (e.g., to the RF circuitry 706). The transmit signal path of the FEM circuitry 708 may include a power amplifier (PA) to amplify input RF signals (e.g., provided by RF circuitry 706), and one or more filters to generate RF signals for subsequent transmission (e.g., by one or more of the one or more antennas 710.

[0066] In some embodiments, the UE 700 may include additional elements such as, for example, memory/storage, display, camera, sensor, and/or input/output (I/O) interface as described in more detail below. In some embodiments, the UE 700 described herein may be part of a portable wireless communication device, such as a personal digital assistant (PDA), a laptop or portable computer with wireless communication capability, a web tablet, a wireless telephone, a smartphone, a wireless headset, a pager, an instant messaging device, a digital camera, an access point, a television, a medical device (e.g., a heart rate monitor, a blood pressure monitor, etc.), or other device that may receive and/or transmit information wirelessly. In some embodiments, the UE 700 may include one or more user interfaces designed to enable user interaction with the system and/or peripheral component interfaces designed to enable peripheral component interaction with the system. For example, the UE 700 may include one or more of a keyboard, a keypad, a touchpad, a display, a sensor, a non-volatile memory port, a universal serial bus (USB) port, an audio jack, a power supply interface, one or more antennas, a graphics processor, an application processor, a speaker, a microphone, and other I/O components. The display may be an LCD or LED screen including a touch screen. The sensor may include a gyro sensor, an accelerometer, a proximity sensor, an ambient light sensor, and a positioning unit. The positioning unit may communicate with components of a positioning network, e.g., a global positioning system (GPS) satellite.

[0067] The antennas 710 may comprise one or more directional or omnidirectional antennas, including, for example, dipole antennas, monopole antennas, patch antennas, loop antennas, microstrip antennas or other types of antennas suitable for transmission of RF signals. In some multiple-input multiple-output (MTMO) embodiments, the antennas 710 may be effectively separated to take advantage of spatial diversity and the different channel characteristics that may result.

[0068] Although the UE 700 is illustrated as having several separate functional elements, one or more of the functional elements may be combined and may be implemented by combinations of software-configured elements, such as processing elements including digital signal processors (DSPs), and/or other hardware elements. For example, some elements may comprise one or more microprocessors, DSPs, field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), radio-frequency integrated circuits (RFICs) and combinations of various hardware and logic circuitry for performing at least the functions described herein. In some embodiments, the functional elements may refer to one or more processes operating on one or more processing elements.

[0069] Embodiments may be implemented in one or a combination of hardware, firmware and software. Embodiments may also be implemented as instructions stored on a computer-readable storage device, which may be read and executed by at least one processor to perform the operations described herein. A computer-readable storage device may include any non-transitory mechanism for storing information in a form readable by a machine (e.g., a computer). For example, a computer-readable storage device may include readonly memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash-memory devices, and other storage devices and media. Some embodiments may include one or more processors and may be configured with instructions stored on a computer-readable storage device.

[0070] FIG. 8 is a block diagram of a communication device 800 in accordance with some embodiments. The communication device 800 may be a UE or eNB, for example, such as the UE 102 or e B 104 shown in FIG. 1. The physical layer circuitry 802 may perform various encoding and decoding functions that may include formation of baseband signals for transmission and decoding of received signals. The communication device 800 may also include medium access control layer (MAC) circuitry 804 for controlling access to the wireless medium. The communication device 800 may also include processing circuitry 806, such as one or more single-core or multi-core processors, and memory 808 arranged to perform the operations described herein. The physical layer circuitry 802, MAC circuitry 804 and processing circuitry 806 may handle various radio control functions that enable communication with one or more radio networks compatible with one or more radio technologies. The radio control functions may include signal modulation, encoding, decoding, radio frequency shifting, etc. For example, similar to the device shown in FIG. 2, in some embodiments, communication may be enabled with one or more of a WMAN, a WLAN, and a WPAN. In some embodiments, the communication device 800 can be configured to operate in accordance with 3 GPP standards or other protocols or standards, including WiMax, WiFi, WiGig, GSM, EDGE, GERAN, UMTS, UTRAN, or other 3G, 3G, 4G, 5G, etc. technologies either already developed or to be developed. The communication device 800 may include transceiver circuitry 812 to enable communication with other external devices wirelessly and interfaces 814 to enable wired communication with other external devices. As another example, the transceiver circuitry 812 may perform various transmission and reception functions such as conversion of signals between a baseband range and a Radio Frequency (RF) range. [0071] The antennas 801 may comprise one or more directional or omnidirectional antennas, including, for example, dipole antennas, monopole antennas, patch antennas, loop antennas, microstrip antennas or other types of antennas suitable for transmission of RF signals. In some MTMO embodiments, the antennas 801 may be effectively separated to take advantage of spatial diversity and the different channel characteristics that may result.

[0072] Although the communication device 800 is illustrated as having several separate functional elements, one or more of the functional elements may be combined and may be implemented by combinations of software-configured elements, such as processing elements including DSPs, and/or other hardware elements. For example, some elements may comprise one or more

microprocessors, DSPs, FPGAs, ASICs, RFICs and combinations of various hardware and logic circuitry for performing at least the functions described herein. In some embodiments, the functional elements may refer to one or more processes operating on one or more processing elements. Embodiments may be implemented in one or a combination of hardware, firmware and software. Embodiments may also be implemented as instructions stored on a computer- readable storage device, which may be read and executed by at least one processor to perform the operations described herein.

[0073] FIG. 9 illustrates another block diagram of a communication device 900 in accordance with some embodiments. The communication device 100 may correspond to the UE 102 or the eNB 104. In alternative embodiments, the communication device 900 may operate as a standalone device or may be connected (e.g., networked) to other communication devices. In a networked deployment, the communication device 900 may operate in the capacity of a server communication device, a client communication device, or both in server- client network environments. In an example, the communication device 900 may act as a peer communication device in peer-to-peer (P2P) (or other distributed) network environment. The communication device 900 may be a UE, eNB, PC, a tablet PC, a STB, a PDA, a mobile telephone, a smart phone, a web appliance, a network router, switch or bridge, or any communication device capable of executing instructions (sequential or otherwise) that specify actions to be taken by that communication device. Further, while only a single communication device is illustrated, the term "communication device" shall also be taken to include any collection of communication devices that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein, such as cloud computing, software as a service (SaaS), other computer cluster configurations.

[0074] Examples, as described herein, may include, or may operate on, logic or a number of components, modules, or mechanisms. Modules are tangible entities (e.g., hardware) capable of performing specified operations and may be configured or arranged in a certain manner. In an example, circuits may be arranged (e.g., internally or with respect to external entities such as other circuits) in a specified manner as a module. In an example, the whole or part of one or more computer systems (e.g., a standalone, client or server computer system) or one or more hardware processors may be configured by firmware or software (e.g., instructions, an application portion, or an application) as a module that operates to perform specified operations. In an example, the software may reside on a communication device readable medium. In an example, the software, when executed by the underlying hardware of the module, causes the hardware to perform the specified operations.

[0075] Accordingly, the term "module" is understood to encompass a tangible entity, be that an entity that is physically constructed, specifically configured (e.g., hardwired), or temporarily (e.g., transitorily) configured (e.g., programmed) to operate in a specified manner or to perform part or all of any operation described herein. Considering examples in which modules are temporarily configured, each of the modules need not be instantiated at any one moment in time. For example, where the modules comprise a general-purpose hardware processor configured using software, the general-purpose hardware processor may be configured as respective different modules at different times. Software may accordingly configure a hardware processor, for example, to constitute a particular module at one instance of time and to constitute a different module at a different instance of time.

[0076] Communication device (e.g., computer system) 900 may include a hardware processor 902 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof), a main memory 904 and a static memory 906, some or all of which may communicate with each other via an interlink (e.g., bus) 908. The

communication device 900 may further include a display unit 910, an alphanumeric input device 912 (e.g., a keyboard), and a user interface (UI) navigation device 914 (e.g., a mouse). In an example, the display unit 910, input device 912 and UI navigation device 914 may be a touch screen display. The communication device 900 may additionally include a storage device (e.g., drive unit) 916, a signal generation device 918 (e.g., a speaker), a network interface device 920, and one or more sensors 921, such as a global positioning system (GPS) sensor, compass, accelerometer, or other sensor. The communication device 900 may include an output controller 928, such as a serial (e.g., universal serial bus (USB), parallel, or other wired or wireless (e.g., infrared (IR), near field communication (NFC), etc.) connection to communicate or control one or more peripheral devices (e.g., a printer, card reader, etc.).

[0077] The storage device 916 may include a communication device readable medium 922 on which is stored one or more sets of data structures or instructions 924 (e.g., software) embodying or utilized by any one or more of the techniques or functions described herein. The instructions 924 may also reside, completely or at least partially, within the main memory 904, within static memory 906, or within the hardware processor 902 during execution thereof by the communication device 900. In an example, one or any combination of the hardware processor 902, the main memory 904, the static memory 906, or the storage device 916 may constitute communication device readable media.

[0078] While the communication device readable medium 922 is illustrated as a single medium, the term "communication device readable medium" may include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) configured to store the one or more instructions 924.

[0079] The term "communication device readable medium" may include any medium that is capable of storing, encoding, or carrying instructions for execution by the communication device 900 and that cause the communication device 900 to perform any one or more of the techniques of the present disclosure, or that is capable of storing, encoding or carrying data structures used by or associated with such instructions. Non-limiting communication device readable medium examples may include solid-state memories, and optical and magnetic media. Specific examples of communication device readable media may include: non-volatile memory, such as semiconductor memory devices (e.g., Electrically Programmable Read-Only Memory (EPROM), Electrically Erasable Programmable Read-Only Memory (EEPROM)) and flash memory devices; magnetic disks, such as internal hard disks and removable disks;

magneto-optical disks; Random Access Memory (RAM); and CD-ROM and DVD-ROM disks. In some examples, communication device readable media may include non-transitory communication device readable media. In some examples, communication device readable media may include communication device readable media that is not a transitory propagating signal.

[0080] The instructions 924 may further be transmitted or received over a communications network 926 using a transmission medium via the network interface device 920 utilizing any one of a number of transfer protocols (e.g., frame relay, internet protocol (IP), transmission control protocol (TCP), user datagram protocol (UDP), hypertext transfer protocol (HTTP), etc.). Example communication networks may include a local area network (LAN), a wide area network (WAN), a packet data network (e.g., the Internet), mobile telephone networks (e.g., cellular networks), Plain Old Telephone (POTS) networks, and wireless data networks (e.g., Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards known as Wi-Fi®, IEEE 802.16 family of standards known as WiMax®), IEEE 802.15.4 family of standards, a Long Term Evolution (LTE) family of standards, a Universal Mobile Telecommunications System (UMTS) family of standards, peer-to-peer (P2P) networks, among others. In an example, the network interface device 920 may include one or more physical jacks (e.g., Ethernet, coaxial, or phone jacks) or one or more antennas to connect to the communications network 926. In an example, the network interface device 920 may include a plurality of antennas to wirelessly communicate using at least one of single-input multiple-output (SFMO), MIMO, or multiple-input single-output (MISO) techniques. In some examples, the network interface device 920 may wirelessly communicate using Multiple User MFMO techniques. The term "transmission medium" shall be taken to include any intangible medium that is capable of storing, encoding or carrying instructions for execution by the communication device 900, and includes digital or analog communications signals or other intangible medium to facilitate communication of such software.

[0081] The subject technology is described below in conjunction with various examples.

1. An apparatus of a first user equipment (UE), the apparatus comprising: processing circuitry and memory; the processing circuitry to:

receive, from a higher layer, an indication of a synchronization source and an indication of a synchronization window, for sidelink communication; determine a sidelink inter-frequency discovery gap based on the synchronization source and the synchronization window;

encode sidelink signals for transmission to a second UE within the sidelink inter-frequency discovery gap, the sidelink signals for transmission on component carriers of a non-serving cell, the second UE operating in the non- serving cell.

2. The apparatus of Example 1, wherein the processing circuitry compri a baseband processor.

3. The apparatus of any of Examples 1-2, wherein:

the synchronization source comprises a signal from a wireless area network (WAN); and

a configuration of the sidelink inter-frequency discovery gap comprises an inter-measurement gap configuration.

4. The apparatus of any of Examples 1-2, wherein:

the sidelink inter-frequency discovery gap is less than or equal to 17 ms.

5. The apparatus of any of Examples 1-2, wherein: the synchronization source comprises sidelink synchronization signal (SLSS); and

the sidelink inter-frequency discovery gap is less than or equal to 23 ms.

6. The apparatus of any of Examples 1-2, wherein the synchronization source comprises a signal from a wireless area network (WAN), and wherein the processing circuitry is further to:

forego interruption to WAN data transmission at the first UE.

7. The apparatus of Example 6, wherein the processing circuitry is further to:

dedicate a transmit (TX)/ receive (RX) chain, including the sidelink inter- frequency discovery gap, for use in sidelink communication; and

forego using the sidelink inter-frequency discovery gap to improve WAN efficiency.

8. The apparatus of Example 7, wherein the processing circuitry is further to:

interrupt the sidelink inter-frequency discovery gap due to re-tunneling of the TX/RX chain.

9. The apparatus of any of Examples 1-2, wherein the sidelink signals for transmission to the second UE comprise signals or data from a physical sidelink channel.

10. The apparatus of Example 9, wherein the physical sidelink channel comprises one of a Physical Sidelink Control Channel (PSCCH), a Physical Sidelink Shared Channel (PSSCH), a Physical Sidelink Discovery Channel (PSDCH), and a Physical Sidelink Broadcast Channel (PSBCH).

11. The apparatus of any of Examples 1-2, further comprising transceiver circuitry to:

transmit a signal within the sidelink inter-frequency discovery gap. 12. The apparatus of Example 11, further comprising an antenna coupled to the transceiver circuitry.

13. An apparatus of a first user equipment (UE), the apparatus comprising: processing circuitry and memory; the processing circuitry to:

decode a sidelink synchronization source indicated by a higher layer and a sidelink synchronization window indicated by the higher layer; and

encode for data transmission within a sidelink inter-frequency discovery gap based on the indicated sidelink synchronization source and the indicated sidelink synchronization window, the sidelink inter-frequency discovery gap being accessible by a second UE operating at a second operating frequency different from a first operating frequency of the first UE.

14. The apparatus of Example 13, wherein the sidelink inter-frequency discovery gap includes information for use, by the second UE, in sidelink synchronization or sidelink discovery.

15. The apparatus of Example 13, wherein:

16. The apparatus of Example 13, wherein:

the sidelink inter-frequency discovery gap is less than or equal to 17 ms.

17. The apparatus of Example 13, wherein:

the synchronization source comprises sidelink synchronization signal (SLSS); and

the sidelink inter-frequency discovery gap is less than or equal to 23 ms. 18. The apparatus of Example 13, wherein the synchronization source comprises a signal from a wireless area network (WAN), and wherein the processing circuitry is further to:

forego interruption to WAN data transmission at the first UE.

19. A machine-readable medium storing instructions for execution by processing circuitry of a first user equipment (UE) to configure a sidelink inter- frequency discovery gap, the instructions causing the processing circuitry to: receive, from a higher layer, an indication of a synchronization source and an indication of a synchronization window, for sidelink communication; determine a sidelink inter-frequency discovery gap based on the synchronization source and the synchronization window;

20. The machine-readable medium of Example 19, wherein the sidelink inter-frequency discovery gap includes information for use, by the second UE, in sidelink synchronization or sidelink discovery.

21. An apparatus of a first user equipment (UE), the apparatus comprising: means for receiving, from a higher layer, an indication of a

synchronization source and an indication of a synchronization window, for sidelink communication;

means for determining a sidelink inter-frequency discovery gap based on the synchronization source and the synchronization window;

means for encoding sidelink signals for transmission to a second UE within the sidelink inter-frequency discovery gap, the sidelink signals for transmission on component carriers of a non-serving cell, the second UE operating in the non-serving cell. 22. The apparatus of Example 21, wherein the sidelink inter-frequency discovery gap includes information for use, by the second UE, in sidelink synchronization or sidelink discovery. [0082] Although an embodiment has been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. The accompanying drawings that form a part hereof show, by way of illustration, and not of limitation, specific embodiments in which the subject matter may be practiced. The embodiments illustrated are described in sufficient detail to enable those skilled in the art to practice the teachings disclosed herein. Other embodiments may be utilized and derived therefrom, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. This Detailed Description, therefore, is not to be taken in a limiting sense, and the scope of various embodiments is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled.

[0083] Although specific embodiments have been illustrated and described herein, it should be appreciated that any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the above description.

[0084] In this document, the terms "a" or "an" are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of "at least one" or "one or more." In this document, the term "or" is used to refer to a nonexclusive or, such that "A or B" includes "A but not B," "B but not A," and "A and B," unless otherwise indicated. In this document, the terms "including" and "in which" are used as the plain-English equivalents of the respective terms "comprising" and "wherein." Also, in the following claims, the terms "including" and "comprising" are open-ended, that is, a system, UE, article, composition, formulation, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms "first," "second," and "third," etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.

[0085] The following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separate embodiment.

Claims

CLAIMS What is claimed is:

2. The apparatus of claim 1, wherein the processing circuitry comprises a baseband processor.

3. The apparatus of any of claims 1-2, wherein:

4. The apparatus of any of claims 1-2, wherein:

the sidelink inter-frequency discovery gap is less than or equal to 17 ms.

5. The apparatus of any of claims 1-2, wherein:

the sidelink inter-frequency discovery gap is less than or equal to 23 ms.

6. The apparatus of any of claims 1-2, wherein the synchronization source comprises a signal from a wireless area network (WAN), and wherein the processing circuitry is further to:

forego interruption to WAN data transmission at the first UE.

7. The apparatus of claim 6, wherein the processing circuitry is further to: dedicate a transmit (TX)/ receive (RX) chain, including the sidelink inter- frequency discovery gap, for use in sidelink communication; and

8. The apparatus of claim 7, wherein the processing circuitry is further to: interrupt the sidelink inter-frequency discovery gap due to re-tunneling of the TX/RX chain.

9. The apparatus of any of claims 1-2, wherein the sidelink signals for transmission to the second UE comprise signals or data from a physical sidelink channel.

10. The apparatus of claim 9, wherein the physical sidelink channel comprises one of a Physical Sidelink Control Channel (PSCCH), a Physical Sidelink Shared Channel (PSSCH), a Physical Sidelink Discovery Channel (PSDCH), and a Physical Sidelink Broadcast Channel (PSBCH).

11. The apparatus of any of claims 1-2, further comprising transceiver circuitry to:

transmit a signal within the sidelink inter-frequency discovery gap.

12. The apparatus of claim 11, further comprising an antenna coupled to the transceiver circuitry.

14. The apparatus of claim 13, wherein the sidelink inter-frequency discovery gap includes information for use, by the second UE, in sidelink synchronization or sidelink discovery.

15. The apparatus of claim 13, wherein:

16. The apparatus of claim 13, wherein:

the sidelink inter-frequency discovery gap is less than or equal to 17 ms.

17. The apparatus of claim 13, wherein:

the sidelink inter-frequency discovery gap is less than or equal to 23 ms.

18. The apparatus of claim 13, wherein the synchronization source comprises a signal from a wireless area network (WAN), and wherein the processing circuitry is further to:

forego interruption to WAN data transmission at the first UE.

20. The machine-readable medium of claim 19, wherein the sidelink inter- frequency discovery gap includes information for use, by the second UE, in sidelink synchronization or sidelink discovery.

means for encoding sidelink signals for transmission to a second UE within the sidelink inter-frequency discovery gap, the sidelink signals for transmission on component carriers of a non-serving cell, the second UE operating in the non-serving cell.

22. The apparatus of claim 21, wherein the sidelink inter-frequency discovery gap includes information for use, by the second UE, in sidelink synchronization or sidelink discovery.