Type 1 and type 2 hopping for device-to-device communications

Methods, systems, and devices are described for coordinating a device to device (D2D) hopping scheme with a wide area network (WAN) hopping scheme. In one aspect, a method may include identifying, by a base station, a WAN frequency hopping scheme. The base station may coordinate a D2D frequency hopping scheme a D2D enabled user equipment (UE) with the identified WAN frequency hopping scheme, and communicate the D2D frequency hopping scheme to the D2D enabled UE. In one aspect, the D2D frequency hopping pattern may apply to retransmissions between two D2D enabled UEs. Another method may include receiving, by a D2D enabled UE, a D2D frequency hopping scheme from a base station, where the D2D frequency hopping scheme is coordinated with a WAN frequency hopping scheme. The D2D enabled UE may transmit at least one message to a second D2D enabled UE according to the D2D frequency hopping scheme.

FIELD OF THE DISCLOSURE

The following relates generally to wireless communication, and more specifically to coordinating re-transmission schemes for device to device (D2D) communications in a wide area network (WAN).

DESCRIPTION OF RELATED ART

Generally, a wireless multiple-access communications system may include a number of base stations, each simultaneously supporting communication for multiple mobile devices or user equipments (UEs). Base stations may communicate with UEs on downstream or forward links and on upstream or uplinks. Each base station has a coverage range, which may be referred to as the coverage area of the cell.

Multiple UEs connected to a WAN or other networks may transmit data or control information on the uplink to a serving base station at the same time, which may cause inter-cell or intra-cell interference. WANs may utilize different types of frequency hopping techniques or schemes to reduce the inter-cell and intra-cell interference for data transmission or retransmission.

Some UEs may also be configured to communicate with other UEs via D2D communication protocols. The transmission or retransmission techniques utilized for D2D communications may conflict, and thus cause interference with the inter-cell or intra-cell frequency hopping implemented in the WAN.

SUMMARY

The described features generally relate to one or more improved systems, methods, or apparatuses for coordinating D2D frequency hopping schemes with WAN frequency hopping schemes. More particularly, some examples are directed to coordinating D2D retransmissions with WAN HARQ transmissions.

In one aspect, a method of wireless communication may include identifying, by a base station, a wide area network (WAN) frequency hopping scheme. The method may further include coordinating a device to device (D2D) frequency hopping scheme for at least one D2D enabled user equipment (UE) with the identified WAN frequency hopping scheme, and communicating the D2D frequency hopping scheme to the at least one D2D enabled UE. In some cases, coordinating the D2D frequency hopping scheme with the WAN frequency hopping scheme may include configuring the D2D frequency hopping scheme to reduce interference with the WAN frequency hopping scheme. In some aspects, the WAN frequency hopping scheme may include a fixed offset signaled via a Physical Downlink Control Channel (PDCCH) for every other transmission of a Hybrid Automatic Repeat Request (HARQ) process.

In some examples, coordinating the D2D frequency hopping scheme with the WAN frequency hopping scheme may include utilizing a first offset for even transmissions, wherein each even transmission is transmitted an even number of subframes after a first transmission, and utilizing a second offset for odd transmissions. In some implementations, the second offset may be set to zero. Communicating the D2D frequency hopping scheme to the at least one D2D enabled UE may include transmitting at least one of the first offset, or the second offset, or both, via the PDCCH. At least one of the fixed offset, or the first offset, or the second offset, or a combination thereof may include a number of resource blocks. In certain aspects, the method may include identifying a set of resources specific to D2D communications, wherein the D2D frequency hopping scheme is based at least in part on the identified set of resources.

In some cases, the WAN frequency hopping scheme may include a cell specific hopping and mirroring scheme. In this scenario, coordinating the D2D frequency scheme with the WAN frequency hopping scheme may include associating a cell identification (ID) of the base station with the D2D frequency hopping scheme. Communicating the D2D frequency hopping scheme to the at least one D2D enabled UE may include transmitting a D2D scheduling grant via the PDCCH to the at least one D2D enabled UE. In some cases, the D2D scheduling grant may include instructions instructing the D2D enabled UE to transmit the cell ID to a second D2D enabled UE not associated with the cell ID.

In some aspects, communicating the D2D frequency hopping scheme to the at least one D2D enabled UE may include transmitting a D2D scheduling grant to the at least one D2D enabled UE specifying a first resource to transmit the scheduling assignment. The D2D scheduling grant may include instructions instructing the D2D enabled UE to transmit the cell ID to a second D2D enabled UE not associated with the cell ID. In this scenario, the first resource may implicitly indicate the cell ID.

In some examples, the WAN frequency hopping scheme may include a cell specific hopping and mirroring scheme, such that coordinating the D2D frequency hopping scheme with the WAN frequency hopping scheme includes determining a subset of resources for the D2D frequency hopping scheme based on resources for the WAN frequency hopping scheme. In some cases, communicating the D2D frequency hopping scheme to the at least one D2D enabled UE may include transmitting an indication of the subset of resources for the D2D frequency hopping scheme to the at least one D2D enabled UE. The indication of the subset of resources may include a low resource block threshold or a high resource block threshold, or both. In some cases, the WAN frequency hopping scheme may apply to uplink transmissions. Additionally or alternatively, the WAN frequency hopping scheme may utilize HARQ.

In another aspect, a method of wireless communication may include receiving, by a D2D enabled UE, a D2D frequency hopping scheme from a base station associated with a WAN. The D2D frequency hopping scheme may be coordinated with a WAN frequency hopping scheme. The method may further include transmitting at least one message to a second D2D enabled UE according to the D2D frequency hopping scheme. In some cases, the at least one message may include a scheduling assignment.

In some examples, the D2D frequency hopping scheme may include a first offset to be applied for even transmissions, wherein each even transmission is transmitted an even number of subframes after a first transmission. In some cases, the D2D frequency hopping scheme may additional include a second offset to be applied for odd transmissions.

In some cases, the WAN frequency hopping scheme may include a cell specific hopping and mirroring scheme. In this scenario, the D2D frequency hopping scheme may be associated with a cell ID, which is further associated with the WAN frequency hopping scheme. The method may further include determining resources for transmitting the at least one D2D message based on the WAN frequency hopping scheme. Additionally, the at least one D2D message may be transmitted on a first resource, with the first resource implicitly indicating the cell ID.

In other cases, where WAN frequency hopping scheme may include a cell specific hopping and mirroring scheme and the D2D frequency hopping scheme may include a low resource block threshold or a high resource block threshold. In this scenario, the method may additionally include determining resources for transmitting the at least one D2D message based on the low resource block threshold or the high resource block threshold.

In another aspect, a base station may include means for identifying a WAN frequency hopping scheme, and means for coordinating a D2D frequency hopping scheme for at least one D2D enabled UE with the identified WAN frequency hopping scheme. The base station may additionally include means for communicating the D2D frequency hopping scheme to the at least one D2D enabled UE.

In another aspect, a UE may include means for receiving a D2D frequency hopping scheme from a base station associated with a WAN. The D2D frequency hopping scheme may be coordinated with a WAN frequency hopping scheme. The UE may further include means for transmitting at least one message to a second D2D enabled UE according to the D2D frequency hopping scheme.

In yet another aspect, a base station may include a WAN frequency hopping module to identify a WAN frequency hopping scheme. The base station may additionally include a D2D frequency hopping module to coordinate a D2D frequency hopping scheme for at least one D2D enabled UE with the identified WAN frequency hopping scheme. The base station may further include a transmitter to communicate the D2D frequency hopping scheme to the at least one D2D enabled UE.

In one aspect, a UE may include a D2D frequency hopping determination module to receive a D2D frequency hopping scheme from a base station associated with a WAN, where the D2D frequency hopping scheme is coordinated with a WAN frequency hopping scheme. The UE may additionally include a transmitter to transmit at least one message to a second D2D enabled UE according to the D2D frequency hopping scheme.

In some examples, a non-transitory computer-readable medium may store computer-executable code for wireless communication. The code may be executable by a processor of a base station to identify a WAN frequency hopping scheme and to coordinate a D2D frequency hopping scheme for at least one D2D enabled UE with the identified WAN frequency hopping scheme. The code may further be executable by the processor to communicate the D2D frequency hopping scheme to the at least one D2D enabled UE.

In some examples, a non-transitory computer-readable medium may store computer-executable code for wireless communication. The code may be executable by a processor of a D2D enabled UE to receive a D2D frequency hopping scheme from a base station associated with a WAN, where the D2D frequency hopping scheme is coordinated with a WAN frequency hopping scheme. The code may further be executable by the processor to transmit at least one message to a second D2D enabled UE according to the D2D frequency hopping scheme.

DETAILED DESCRIPTION

The described features generally relate to one or more improved systems, methods, or apparatuses for coordinating device to device (D2D) frequency hopping schemes with wide area network (WAN) frequency hopping schemes. In one aspect, a base station, which may be associated with a WAN, may identify a WAN frequency hopping scheme. The base station may coordinate a D2D frequency hopping scheme for at least one D2D enabled user equipment (UE) with the identified WAN frequency hopping scheme. The base station may then communicate the D2D frequency hopping scheme to the D2D enabled UE. The WAN may coordinate or configure the D2D frequency hopping scheme to reduce interference with the WAN frequency hopping scheme. In some examples, the described techniques may be applied to coordinating uplink D2D retransmissions with uplink WAN Hybrid Automatic Repeat Request (HARQ) transmissions/retransmissions.

In one aspect, the WAN frequency hopping scheme may include using a fixed frequency offset for every other retransmission in a HARQ process (type 1 frequency hopping). In FDD systems, HARQ transmissions/retransmissions may occur every 8th subframe. The D2D UE, on the other hand, may use a randomized transmission/retransmission scheme that may potentially interfere or conflict (overlap) with the resources used by the WAN frequency hopping scheme. In this scenario, coordinating the D2D frequency hopping scheme may include setting a first frequency offset for retransmissions of a control block over even numbered subframes after the first transmission of the same control block. Similarly, a second frequency offset may be set for odd numbered retransmissions. In some cases, the second offset may be set to zero. In this way, interference due to overlapping resources used for WAN HARQ transmissions and D2D transmissions may be reduced.

In one aspect, the WAN frequency hopping scheme may include using cell-specific frequency hopping and mirroring (type 2 frequency hopping). As in the type 1 case, D2D transmissions/retransmissions may interfere with type 2 WAN frequency hopping schemes. To avoid/reduce this interference, the WAN base station may associate a cell identification (ID) with a D2D frequency hopping scheme. The D2D frequency hopping scheme may be generated by the same random or pseudo random number generator seed as the WAN frequency hopping scheme. The base station may communicate the cell ID/D2D frequency hopping scheme to the D2D UE, for example in a scheduling grant over the Physical Downlink Control Channel (PDCCH). The D2D UE may then communicate the cell ID (which is associated with the D2D frequency hopping scheme) to another D2D UE, for instance, that is not associated with the same cell, in a scheduling assignment (either explicitly or implicitly). In this way, communications of the D2D UE with an inter-cell D2D UE may be coordinated with the WAN frequency hopping scheme to reduce interference.

In yet one aspect, coordinating a D2D frequency hopping scheme with a type 2 WAN frequency hopping scheme may include determining a subset of available resources and reserving those resources for D2D transmissions/retransmissions. That is, resources (e.g., time and frequency) may be specifically allocated for, or assigned to, D2D communications (i.e., some resources may be D2D-specific resources). The subset of resources may be defined by a low resource block threshold, a high resource block threshold, or both. The subset of resources may be communicated to the D2D UE(s) and other devices associated with the WAN to enable coordination and thus reduce interference between D2D and WAN communications. In some examples, a base station may associate a D2D frequency hopping scheme with D2D-specific resources. That is, the D2D frequency hopping scheme may be specific to the resources allocated or reserved for D2D use.

The WAN base station may communicate a D2D frequency hopping scheme to a D2D UE in the form of one or more instructions. The D2D UE may then transmit one or more messages (e.g., a scheduling assignment) to another D2D UE according to the D2D frequency hopping scheme. In some examples, the base station may communicate the resources that are specifically allocated for D2D communications to the D2D UE. In certain aspects, the base station may communicate the D2D-specific resources and the associated D2D frequency hopping scheme to the D2D UE.

Referring first toFIG. 1, a block diagram illustrates an example of a wireless communications system100. The wireless communications system100includes base stations (or cells)105, user equipments (UEs)115, and a core network130. The base stations105may communicate with the UEs115under the control of a base station controller, which may be part of the core network130or the base stations105in various examples. Base stations105may communicate control information or user data with the core network130through backhaul132. In some examples, the base stations105may communicate, either directly or indirectly, with each other over backhaul links134, which may be wired or wireless communication links. The wireless communications system100may support operation on multiple carriers (waveform signals of different frequencies). Multi-carrier transmitters may transmit modulated signals simultaneously on the multiple carriers. For example, each communication link125, between a base station105and UE115, or communication link126, between two UEs115, may be a multi-carrier signal modulated according to the various radio technologies described above. Each modulated signal may be sent on a different carrier and may carry control information (e.g., reference signals, control channels, etc.), overhead information, data, etc.

The base stations105may wirelessly communicate with the UEs115via one or more base station antennas. Each of the base station105sites may provide communication coverage for a respective coverage area110. In some examples, a base station105may be referred to as a base transceiver station, a radio base station, an access point, a radio transceiver, a basic service set (BSS), an extended service set (ESS), a NodeB, an evolved NodeB (eNodeB or eNB), a Home NodeB, a Home eNodeB, or some other suitable terminology. The coverage area110for a base station may be divided into sectors making up only a portion of the coverage area. The wireless communications system100may include base stations105of different types (e.g., macro, micro, or pico base stations). There may be overlapping coverage areas for different technologies.

In some examples, the wireless communications system100may be an LTE/LTE-A network, wide area network (WAN), etc. In LTE/LTE-A networks, the terms evolved Node B (eNB) may be generally used to describe the base stations105. The wireless communications system100may be a Heterogeneous LTE/LTE-A network in which different types of eNBs provide coverage for various geographical regions. For example, each eNB105may provide communication coverage for a macro cell, a pico cell, a femto cell, or other types of cell. A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscriptions with the network provider. A pico cell may generally cover a relatively smaller geographic area and may allow unrestricted access by UEs with service subscriptions with the network provider. A femto cell may also generally cover a relatively small geographic area (e.g., a home) and, in addition to unrestricted access, may also provide restricted access by UEs having an association with the femto cell (e.g., UEs in a closed subscriber group (CSG), UEs for users in the home, and the like). An eNB for a macro cell may be referred to as a macro eNB. An eNB for a pico cell may be referred to as a pico eNB. And, an eNB for a femto cell may be referred to as a femto eNB or a home eNB. An eNB may support one or multiple (e.g., two, three, four, and the like) cells.

The core network130may communicate with the eNBs105via a backhaul132(e.g., S1, etc.). The eNBs105may also communicate with one another (e.g., directly or indirectly) via backhaul links134(e.g., X2, etc.) or via backhaul132(e.g., through core network130). The wireless communications system100may support synchronous or asynchronous operation. For synchronous operation, the eNBs may have similar frame timing, and transmissions from different eNBs may be approximately aligned in time. For asynchronous operation, the eNBs may have different frame timing, and transmissions from different eNBs may not be aligned in time. The techniques described herein may be used for either synchronous or asynchronous operations.

The UEs115may be dispersed throughout the wireless communications system100, and each UE may be stationary or mobile. A UE115may also be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology. A UE115may be a cellular phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a tablet computer, a laptop computer, a cordless phone, a wireless local loop (WLL) station, or the like. A UE may be able to communicate with macro eNBs, pico eNBs, femto eNBs, relays, and the like.

In some cases, a UE115may operate within the coverage areas110of more than one base station105. A UE115may also operate within the coverage area110of a single base station105. In either case, various UEs115may be within close enough proximity to communicate directly via D2D communications.

The communication links125shown in wireless communications system100may include uplink (UL) transmissions from a UE115to a base station105, or downlink (DL) transmissions, from a base station105to a UE115. The downlink transmissions may also be called forward link transmissions while the uplink transmissions may also be called reverse link transmissions. In some cases, communication links126may support device to device (D2D) communications between UEs115.

In some instances, interference may occur between D2D communications over link(s)126and uplink communications over link(s)125. For example, wireless communications system100, which may also be called a WAN, or base station105of WAN100may implement a WAN frequency hopping scheme for communications over links125, particularly for retransmissions according to a HARQ process. The WAN frequency hopping scheme may conflict with D2D communications between two UEs115over links126, thus causing interference and degrading communication performance (e.g., throughput, error correction, etc.).

Referring toFIG. 2, a block diagram illustrates an example of a wireless communications system200. The wireless communications system200, which may be an example of wireless communications system100described in reference toFIG. 1, includes two D2D enabled UEs115-aand115-band a base station105-a. D2D UE105-amay communicate with base station105-aover link125-aand with UE115-bover link126-a. UEs115-aand115-bor base station105-amay be examples of UEs115or base stations105described in reference toFIG. 1.

In some examples, base station105-amay implement a frequency hopping scheme or sequence for communications across link125-awith UE115-a. The frequency hopping scheme may be a type 1 hopping scheme (fixed frequency offset for transmissions) or a type 2 hopping scheme (cell specific hopping and mirroring), or other types of hopping schemes. In some cases, type 1 WAN frequency hopping may provide for hopping with limited resource options, whereas type 2 WAN frequency hopping may provide for better diversity due to sub-band hopping and mirroring operations. Type 2 hopping may provide for better inter-cell interference management. In yet some cases, both type 1 and type 2 are limited by resource allocation constraints, as both are limited by the size of resource allocation field in DCI format 0. Additionally, the maximum number of RBs for a single user for type 2 hopping is further limited by the size of a sub-band.

In order to reduce signaling overhead for the retransmissions of UE115-a, the retransmissions of UE115-amay assume synchronous operation (e.g., fixed timing across a cell served by base station105) with automatic scheduling of retransmissions every fixed number of subframes (e.g., 8 subframes).

In some examples, the frequency hopping scheme may be applied to uplink communications from the UE115-aover links125-a, such as for HARQ retransmissions when a first transmission over link125-afails (e.g., when an acknowledgment (ACK) message is not received by the UE115-a). HARQ retransmissions by the UE115-amay occur at set intervals after the first (original) transmission is sent. For example, in FDD systems, the interval may be every 8th subframe.

In some cases, the UE115-amay concurrently communicate with base station105-aover link125-aand UE115-bover link126-a. The UE115-amay communicate with UE115-bover link126-avia D2D communication protocols, which may be different than WAN communication protocols used by the UE115-ato communicate with base station105-aover link125-a. In particular, D2D frequency hopping schemes for retransmissions may be random or pseudo random. This may result in interference between WAN HARQ retransmissions over link125-aand D2D retransmissions over link126-a.

In order to mitigate this interference, the base station105-amay coordinate a D2D frequency hopping scheme with a WAN frequency hopping scheme. The base station105-amay communicate the D2D frequency hopping scheme to the UE115-avia control signaling over link125-a(e.g., using the PDCCH). In this way, the UE115-amay communicate with UE115-bover link126-awithout causing unavoidable interference with WAN communications, and particularly uplink HARQ transmissions from UE115-aand other UEs115(not shown) communicating with base station105-a.

Referring toFIGS. 3A and 3B, block diagrams illustrates communication resources300-aand300-bincluding one subframe305divided into resource blocks that may be used by a UE115for communicating with one or more UEs115or base stations105on the uplink, as described in reference toFIG. 1 or 2. Each subframe305may be approximately 1 millisecond (ms) in duration, and 10 subframes may make up a radio frame. Each subframe305may include two slots,310,315. Each radio frame may thus include 20 slots.

LIE utilizes orthogonal frequency division multiplexing (OFDM) on the downlink and single-carrier frequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDM partition the system bandwidth into multiple orthogonal subcarriers, which are also commonly referred to as tones, bins, etc. Each subcarrier may be modulated with data. In general, modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDM. The spacing between adjacent subcarriers may be fixed, and the total number of subcarriers may be dependent on the system bandwidth. For example, the number of subcarriers may be equal to 128, 256, 512, 1024 or 2048 for system bandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively.

Resource blocks320-a,320-bmay be defined in each slot310,315. Each resource block may cover multiple subcarriers (e.g., 12 subcarriers) in one slot310,315. The number of resource blocks in each slot may be dependent on the system bandwidth and may range from 6 to 110. The resource blocks may also be referred to as physical resource blocks (PRBs). Multiple subbands (not shown) including one or more PRBs may also be defined, where the number of subbands may be dependent on the system bandwidth.

Referring in particular to resources300-aofFIG. 3A, multiple resource blocks320numbered nPRB=0 to nPRB=nRBUL−1 of subframe305are shown. Each resource block320may be partitioned by slot, such as m=0 through m=3. The physical resource mapping for each slot310,315of resource block300-amay be represented by:

wherenPRBPhysical resource block numbernsSlot number within a radio frame

Referring now to resources300-bofFIG. 3B, a frequency hopping pattern may be repeated across subframes in a radio frame for the same resource index. The hopping pattern may be carried out over the Physical Uplink Control Channel (PUCCH), and may include multiple PUCCH formats, such as 1/1a/1b, 2/2a/2b, 3, etc. For example, generally each resource block per slot may be represented by:

NRB(2)
(in resource blocks (RBs)) is specified by higher layers, and the PUCCH resource index

nPUCCH(2,p~)
is given by higher layers for periodic CSI reporting.

For PUCCH formats 2/2a/2b, each resource block may be mapped on band-edge RBs (m=0,1), where m may be represented by:

For PUCCH formats 1/1a/1b mixed with formats 2/2a/2b (m=2), m may be represented by:

m={NRB(2)⁢⁢if⁢⁢nPUCCH(1,p~)<c·Ncs(1)/ΔshiftPUCCH
In some cases, multiplexing may be performed by applying different cyclic time shifts to formats 1/1a/1b and 2/2a/2b. For example, with 12 shifts,

Ncs(1)∈{0,1,…⁢,7}
are assigned to format 1/1a/1b, resulting in

ΔshiftPUCCH∈{1,2,3}.
In some cases, both parameters may be provided by higher layers. A non-mixed region may be allocated if

Ncs(1)=0.
In addition, for each time shift, a parameter c representing a number of time domain orthogonal spreading codes for multiplexing (also corresponding to the number of reference symbols per slot) may be chosen resulting in a total of

cNcs(1)⁢/⁢ΔshiftPUCCH
possible resource indices for format 1/1a/1b.

For PUCCH formats 1/1a/1b (e.g., not mixed with formats 2/2a/2b) (m=3, 4, or 5), m may be represented by:

m={⌊nPUCCH(1,p~)-c·Ncs(1)⁢/⁢ΔshiftPUCCHc·NscRB/ΔshiftPUCCH⌋+NRB(2)+⌈Ncs(1)8⌉
In some cases, the calculation of the number of indices may be the same as the mixed case described above, with all 12 shifts applied.

nPUCCH(1,p~)
may be determined for semi-persistent scheduled downlink data transmissions over the Physical Downlink Shared Channel (PDSCH) by a higher layer. For dynamic downlink data transmissions (including HARQ retransmissions for semi-persistent data),

nPUCCH(1,p~)
may be determined implicitly based on the index of the first CCE of the PDCCH message.

For PUCCH format 3, such as for multiple acknowledgement/negative acknowledgements (ACK/NACKs) for carrier aggregation, m may be represented by:

NSF,0PUCCH
represents a number of non-reference symbols in the first slot of a subframe (which may also correspond to the number of orthogonal spreading codes).

Referring toFIG. 4, a block diagram illustrates uplink communication resources400divided into 0 through 49 resource blocks (RBs)405and multiple subframes represented by index i410. Resources400may be examples of one or more aspects of resources300-aor300-bdescribed in reference toFIG. 3A or 3B. Resources400may be used for uplink communications, such as over links125,126by a UE115(e.g., UE115-aofFIG. 2), with base station(s)105(e.g., base station105-aofFIG. 2), or communications with UE(s)115(e.g., UE115-bofFIG. 2), as described above in reference toFIG. 1 or 2.

As illustrated, resources415and420(corresponding to RBs0-2and47-49) may be reserved for communication over the PUCCH, such as for control information, etc.; however, it should appreciated that other RBs405may be reserved or utilized for the PUCCH. Additionally, RBs0-49may represent one subband, with RBs3-46representing PUSCH resources. However, it should be appreciated that any other number of RBs405are contemplated herein, and the RBs405may be divided into any number of subbands. In the example illustrated, resources400are utilized by three UEs115and a D2D UE. For example, UE1may assigned to transmit on the uplink at resources425, UE2at430, and UE3at435. D2D UE transmissions may be scheduled on resources440.

A serving base station105may assign particular resources to each of UE1through UE3and may define a WAN frequency hopping pattern for such transmissions (e.g. for uplink transmissions to the base station105). In some cases, a transmission from any of UEs1-3may fail such that the same information (e.g., packet, code block, etc.) may need to be retransmitted. In some cases, retransmission may be scheduled according to a HARQ process, such that retransmissions occur at a given interval of subframes after the first failed transmission (e.g., when no ACK is received). For example, in FDD systems, the interval may be set at 8 subframes.

Base station105may instruct UEs1-3to utilize a fixed frequency offset for every other retransmission for HARQ, to improve transmission diversity and reduce interference. This may correspond to type 1 hopping. The first time slot (which may represent a subframe410as shown inFIG. 4or a slot, such as310,315ofFIGS. 3A and 3B) may be represented by:

NPRBS⁢⁢1⁡(i)=n~PRBS⁢⁢1⁡(i)+N~RBHO⁢/⁢2⁢⁢where⁢⁢N~RBHO=NRBHO+(NRBHO⁢⁢mod⁢⁢2)andnPRBs⁢⁢1⁡(i)=RBSTART⁢(obtained⁢⁢from⁢⁢uplink⁢⁢scheduling⁢⁢grant)
where NRBHOis equal to the PUSCH hopping offset determined by the higher layers.
The second time slot may be determined by applying the fixed offset:

nPRB⁡(i)=n~PRB⁡(i)+N~RBHO⁢/⁢2
and may be according to the following relationship:

For example, UE1may transmit on RBs5-7in subframe0at425-a. After determining that transmission425-awas not properly received, UE1may then be instructed to retransmit at RBs26-29in subframe8at425-b. This retransmission may be according to a fixed offset of 22 RBs; however, it should be appreciated that other frequency offsets may be utilized. If the retransmission fails again, UE1may be instructed to retransmit over RBs4-7in subframe16at425-c, and so forth. UEs2and3may be instructed to follow the same retransmission hopping pattern (e.g., 22 RB offset for every other transmission), but starting at different RBs (e.g., UE2at RBs11-20in subframe0at430-aand UE3at RBs35-41in subframe1at435-a).

To coordinate a D2D frequency hopping pattern for retransmissions with the type 1 WAN frequency hopping described above, the base station105may instruct the D2D UE to apply a first offset on even numbered subframes after the first transmission440-aand apply a second offset on odd numbered subframes after the first transmissions440-a. In some cases, the second offset may be set to zero RBs. Because D2D retransmission schemes are generally not synchronized as HARQ retransmission schemes, D2D retransmissions may occur on a more random basis such that retransmissions may occur at any number of subframes after a first transmission440-a. A base station105may determine the D2D frequency hopping scheme and communicate the scheme to the D2D UE. In this way, interference/conflicts on RBs may be reduced between WAN HARQ retransmissions425,430, or435, and D2D retransmissions440.

As illustrated, the D2D UE may first transmit to another D2D UE at440-aincluding RBs22-25at subframe0. The D2D UE may be instructed to retransmit440-bin subframe1at the zero offset (e.g., at RBs22-25). The D2D UE may then be instructed, according to the D2D frequency hopping pattern, to retransmit at440-cin subframe4(even subframe) at RBs38-41(e.g., a 16 RB offset), at440-dat RBs22-25in subframe9(e.g., a 0 RB offset), and at440-eat RBs38-41in subframe16(e.g., a 16 RB offset). In this way, a D2D retransmission frequency hopping scheme may be coordinated by the base station105to avoid or minimize collisions with other uplink transmissions of UEs115communicating via the WAN.

It should be appreciated that other offsets are contemplated for D2D retransmissions, and may vary for each retransmission. Furthermore, other numbers of subframe intervals may be implemented between D2D retransmissions, according to different schemes, patterns, etc. The D2D frequency hopping scheme may be determined based on congestion in the served network, number of UEs115communicating on the uplink, previously collected or determined interference metrics, etc.

Inter-subframe hopping is shown inFIG. 4. However, it should be appreciated that intra-subframe hopping may be implemented in a similar manner, with every subframe split into two slots310,315.

Referring toFIG. 5, a block diagram illustrates uplink communication resources500divided into 0 through 49 resource blocks (RBs)405-aand multiple subframes represented by index i410-a. Resources500may be examples of one or more aspects of resources300-a,300-b, or400described in reference toFIG. 3A, 3B, or4. Resources500may be used by a UE115(e.g., UE115-aofFIG. 2) for uplink communications over links125with base station(s)105, and D2D communications over link126with other D2D UE(s)115, as described above in reference toFIG. 1 or 2.

As illustrated, resources415-aand420-a(corresponding to RBs0-2and47-49) may be reserved for communication over the PUCCH, such as for control information, etc. RBs3-46(e.g., PUSCH resources) may be partitioned into 4 subbands505,510,515, and520, with each subband including 11 RBs. In the example illustrated, resources500are utilized by four UEs115and a D2D UE. For example, UE1may assigned to transmit on the uplink at resources525, UE2at530, UE3at535, and UE4at545. D2D UE transmissions may be scheduled on resources540.

A serving base station105may assign particular resources to each of UE1through UE4and may define a WAN frequency hopping pattern for such transmissions (e.g., for uplink transmissions to the base station105). In some cases, a transmission from any of UEs1-4may fail, such that the same information (e.g., packet, code block, etc.) may need to be retransmitted. In some cases, retransmission may be scheduled according to a HARQ process, such that retransmissions occur at a given interval of subframes after the first failed transmission (e.g., 8 subframes).

Base station105may instruct UEs1-4to utilize a type 2 frequency hopping scheme for HARQ retransmissions, for example to improve transmission diversity and reduce interference. Type 2 hopping may include cell-specific hopping and mirroring. Type 2 hopping may be represented by:

nPRB⁡(ns)={n~PRB⁡(ns)Nsb=1n~PRB⁡(ns)+⌈NRBHO⁢/⁢2⌉Nsb>1⁢⁢where⁢⁢Nsb⁢:⁢⁢number⁢⁢of⁢⁢sub⁢-⁢bands⁢⁢given⁢⁢by⁢⁢higher⁢⁢layers⁢⁢NRBHO⁢:⁢⁢pusch⁢-⁢HoppingOffset,given⁢⁢by⁢⁢higher⁢⁢layers
Type 2 hopping may also be represented by:

NRBsb={NRBULNsb=1⌊(NRBUL-NRBHO-NRBHO⁢mod⁢⁢2)⁢/⁢Nsb⌋Nsb>1
The subband hopping function may be represented by:

In one example, UE1may transmit on resources525-a(RBs9-13) in subframe0in subband505. After determining that transmission525-awas not properly received, UE1may then retransmit, according to a WAN frequency hopping scheme, at525-b(RBs42-46) in subframe8in subband520. This retransmission may represent a subband hop of 3 subbands and no mirroring (transmissions525-bis at the end of subband520as transmission525-awas also at the end of subband505). Similarly, UE3may be instructed to transmit on resources535-a(RBs30-35) in subframe0in subband515. After a failed transmission, UE3may, according to a WAN frequency hopping pattern, retransmit at resources535-b(RBs20-24) in subframe8in subband510. This retransmission may represent a subband hop of 1 subband and no mirroring. UE2may first transmit at530-a(RBs36-40) in subframe1in subband520. After a failed transmission, UE2may retransmit at530-b(RBs30-35) in subframe9in subband515. UE4may first transmit at545-a(RBs14-19) in subframe1in subband510, and after a failed transmission, may retransmit at545-b(RBs8-13) in subframe9in subband505. The retransmissions of one or more of UEs1-4may continue according to any of a variety of hopping schemes. Thus, because the resources utilized according to type 2 hopping are less consistent than type 1 hopping, a simple offset based on the number of subframes may be less effective (e.g., the example described in reference toFIG. 4).

To coordinate a D2D frequency hopping pattern for retransmissions with the type 2 WAN frequency hopping described above, the base station105may associate a cell identification (ID) of the base station105with a D2D frequency hopping scheme. The D2D frequency hopping scheme may be coordinated with the type 2 WAN frequency hopping scheme. In some cases, coordinating may include seeding the D2D frequency hopping pattern with the same seed used for the type 2 WAN frequency hopping scheme (e.g., based on the equations as described above, with the same seed in a random number generator, etc.). In other cases, coordinating may include predictively avoiding resources utilized by the WAN frequency hopping scheme. In some aspects, the base station105may associate D2D-specific resources with a D2D frequency hopping scheme. For instance, the D2D frequency hopping scheme may be specific to the resources reserved for D2D communications.

In some cases, the WAN frequency hopping scheme and the D2D frequency hopping scheme may have the same logical RB to physical RB mapping sequence. In this scenario, the base station105may know which logical RBs are occupied by the WAN UEs1-4due to the nature of synchronous HARQ implemented on the uplink. In this case, the base station105may easily allocate D2D resources to avoid collisions.

In some examples, the base station105may determine the D2D frequency hopping scheme. In other examples, the D2D UE115may receive information of the WAN frequency hopping scheme, and determine at least part of the D2D frequency hopping scheme/determine when to transmit one or more messages to another D2D UE115based on the WAN frequency hopping information.

As illustrated, the D2D UE may first transmit to another D2D UE at540-a(RBs14-19) in subframe0in subband510. The D2D UE may be instructed to retransmit at540-b(RBs30-35) in subframe1in subband515. The D2D UE may then be instructed, according to the D2D frequency hopping pattern, to retransmit at540-c(RBs20-24in subframe4in subband510), and at540-d(RBs25-30in subframe9in subband515), and so on. In this way, a D2D retransmission frequency hopping scheme may be coordinated by the base station105to avoid or minimize collisions with other uplink transmissions of UEs115communicating via the WAN.

In some examples, the base station105may transmit a D2D scheduling grant according to the D2D frequency hopping scheme via the PDCCH to the D2D enabled UE115. The scheduling grant may include instructions instructing the D2D enabled UE to transmit the cell ID to a second D2D enabled UE, wherein the second D2D enabled UE is not associated with the cell ID (i.e., is associated with another cell). In this way, inter-cell interference may be mitigated by coordinating inter-cell D2D retransmissions.

In other examples, the scheduling grant may specify a first resource for the D2D UE115to transmit a scheduling assignment to an inter-cell D2D UE115. In this scenario, the first resource used to transmit the scheduling assignment may implicitly indicate the cell ID. In this instance, the base station105may establish rules for determining/indicating which resources are associated with different neighboring cell IDs, and thus what D2D frequency hopping scheme is applicable. When the D2D UE115transmits a scheduling assignment to an inter-cell D2D UE115, the inter-cell D2D UE115may determine which cell ID (and hence what D2D frequency scheme) is to be utilized for communications with the sending D2D UE115. In some examples, the base station105may determine a D2D frequency scheme based on the resources specifically reserved for D2D communications. In such an instance, the base station105may send an indication of the D2D-specific resources and the associated frequency hopping scheme to the D2D UE115.

Inter-subframe hopping is shown inFIG. 5. However, it should be appreciated that intra-subframe hopping may be implemented in a similar manner, with every subframe split into two slots310,315.

Referring toFIG. 6, a block diagram illustrates uplink communication resources600divided into 0 through 49 resource blocks (RBs)405-band multiple subframes represented by index i410-b. Resources600may be examples of one or more aspects of resources300-a,300-b,400, or500described in reference toFIG. 3A, 3B, 4, or5. Resources600may be used by a UE115(e.g., UE115-aofFIG. 2) for uplink communications over links125with base station(s)105, and D2D communications over link126with other D2D UE(s)115, as described above in reference toFIG. 1 or 2.

As illustrated, resources415-band420-b(corresponding to RBs0-2and47-49) may be reserved for communication over the PUCCH, such as for control information, etc. RBs3-46(e.g., PUSCH resources) are partitioned into 4 subbands505-a,510-a,515-a, and520-a, with each subband including 11 RBs. In the example illustrated, resources600are utilized by four UEs115and a D2D UE. For example, UE1may assigned to transmit on the uplink at resources525, UE2at530, UE3at535, and UE4at545. D2D UE transmissions may be scheduled on resources540. The frequency hopping for uplink transmissions for UEs1-4may follow a type 2 hopping pattern as described above in reference toFIG. 5. Accordingly, the frequency hopping of UEs1-4will not be repeated here for the sake of brevity.

As illustrated inFIG. 6, coordination of a D2D frequency hopping scheme with a type 2 WAN frequency hopping scheme may include partitioning off a portion or subset of PUSCH resources (e.g., RBs3-7and42-46as illustrated) for D2D communications only. The base station105may set one or more thresholds to indicate to the D2D UE115and UEs1-4which resources are to be utilized by the D2D UE115. In some cases the threshold may include one or more high resource block thresholds, such as605,610, or one or more low resource block thresholds615,620. In this example, the D2D UE may transmit/retransmit between thresholds605and610in subframe0, and between thresholds610and620in subframes1,4, and9. In this implementation, intra-cell and inter-cell interference may be reduced or eliminated with minimum overhead (e.g., only the four thresholds may be needed to implement this D2D frequency hopping scheme). It should be appreciated that other hops of varying subframes, RBs, etc., may be utilized with similar effect. In this scenario, a default cell ID may be used at least in part to indicate the D2D frequency hopping scheme (e.g., a value of 510).

In any of the examples described above in reference toFIG. 4, 5, or6, the D2D frequency hopping scheme may be communicated by the base station105to the D2D UE115via a scheduling grant. The scheduling grant may be in the form of a system information block (SIB) and may include one or more of the following parameters:1. A PUSCH upper hopping offset (N_HO_RB), which may indicate how many RBS are utilized on each edge of the available resources for the PUCCH;2. A number of subbands (N_sb), which may indicate the number of sub-bands for Type 2 hopping;3. A PUSCH lower hopping offset (N_LO_RB), which may be used to avoid conflict with PUSCH for D2D only communications; or4. A D2D cell ID, which may be used for D2D hopping pattern determination.

FIG. 7shows a block diagram700of a base station105-bconfigured for coordinating a D2D frequency hopping scheme with a WAN frequency hopping scheme, in accordance with various examples described herein. The base station105-bmay be an example of at least one aspect of base stations105described above with reference toFIG. 1 or 2. The base station105-bmay communicate with at least one UE115via communication link125, as described above in reference toFIG. 1 or 2or via the coordination techniques described in reference toFIG. 4, 5, or6. The base station105-bmay include a receiver module705, a WAN frequency hopping module710, a D2D frequency hopping coordination module715, and a transmitter module735. In various examples, the D2D frequency hopping coordination module715may include one or more of a D2D offset module720, an inter-cell scheduling grant module725, or a D2D resource determination module730. Each of these components may be in communication with each other.

The components of the base stations105may, individually or collectively, be implemented using at least one application-specific integrated circuit (ASICs) adapted to perform some or all of the applicable functions in hardware. Alternatively, the functions may be performed by at least one other processing unit (or core), on at least one integrated circuit. In other examples, other types of integrated circuits may be used (e.g., Structured/Platform ASICs, Field Programmable Gate Arrays (FPGAs), and other Semi-Custom ICs), which may be programmed in any manner known in the art. The functions of each unit may also be implemented, in whole or in part, with instructions embodied in a memory, formatted to be executed by at least one general or application-specific processor.

The receiver module705may receive information such as packet, data, or signaling information regarding what the base station105-bhas received or transmitted. The received information may be utilized by the base station105-bfor a variety of purposes. In some cases, the receiver module705may be configured to receive data or transmissions, for example from at least one UE115, to further enable the various techniques described above for coordinating a D2D retransmission frequency hopping scheme with a WAN frequency hopping scheme for D2D enabled UEs115.

The transmitter module735may transmit information such as packet, data, or signaling information from the base stations105-b. In some cases, the transmitter module735may be configured to transmit data to one or more UEs115, such as to coordinate D2D communications or retransmissions.

The WAN frequency hopping module710, and in some cases with the receiver module705, may identify a WAN frequency hopping scheme utilized in the WAN served by the base station105-b. In some cases, the WAN frequency hopping module710may configure the WAN frequency hopping scheme, and in other cases the hopping scheme may be accessed from another network device via a request transmitted by the transmitter module735. The WAN frequency hopping module710may communicate the WAN hopping scheme to the D2D frequency hopping coordination module715.

The D2D frequency hopping coordination module715may utilize the WAN frequency hopping scheme to coordinate a D2D frequency hopping scheme, to be utilized for D2D retransmissions, that may interfere with uplink communications in the WAN. The D2D frequency hopping scheme may be coordinated to minimize interference with the WAN frequency hopping scheme. The D2D frequency hopping coordination module715may then communicate the D2D frequency hopping scheme to the transmitter module735to be transmitted to a D2D enabled UE115, to implement the frequency hopping scheme.

In some examples, the D2D frequency hopping coordination module715may include a D2D offset module720. If the WAN frequency hopping module710determines that the WAN frequency hopping scheme is type 1, the D2D offset module720may then be instructed to determine a first or second offset for D2D retransmissions. The D2D offset module720may determine a first offset for transmissions transmitted an even number of subframes after a first transmission or a second offset for transmissions transmitted an odd number of subframes after a first transmission. In some instances, the first or second offsets may be set to zero. The D2D offset module720may then communicate the first or second offsets to the transmitter module735to be transmitted to a D2D enabled UE115, for example over the PDCCH.

In some examples, the D2D frequency hopping coordination module715may include an inter-cell scheduling grant module725and a D2D resource determination module730. If the WAN frequency hopping module710determines that the WAN frequency hopping scheme is type 2, the inter-cell scheduling grant module725may then be instructed to configure a scheduling grant to be communicated via transmitter module735to a D2D enabled UE115. The scheduling grant may include an indication of resources reserved for D2D communications. Accordingly, the scheduling grant may include a D2D frequency hopping scheme associated with the D2D-specific resources. In some cases, the scheduling grant may include an indication of the D2D frequency hopping scheme associated with a cell ID of the base station105-b. The scheduling grant may further include instructions instructing the D2D enabled UE115to transmit the cell ID to a second D2D enabled UE115, where the second D2D enabled UE115is not associated with the cell ID (e.g., an inter-cell UE115). In this way, D2D inter-cell communications may be coordinated with the WAN frequency hopping scheme.

In some examples, the D2D resource determination module730may determine a subset of available PUSCH resources to be reserved for D2D communications (e.g., retransmissions). This may include determining a low resource block threshold, a high resource block threshold, or both. The D2D resource determination module may then communicate the one or more thresholds to the transmitter module735to be transmitted to the D2D enabled UE115to similarly reduce interference between WAN uplink retransmissions and D2D retransmissions.

FIG. 8shows a block diagram800of a UE115-cconfigured for retransmitting one or more messages to a D2D enabled UE115according to a D2D frequency hopping scheme communicated by a base station105, in accordance with various examples described herein. The UE115-cmay be an example of at least one aspect of UEs115described above with reference toFIG. 1, or2. The UE115-cmay communicate with at least one base station105via communication link125or at least one UE115via link126as described above in reference toFIG. 1 or 2or via the coordination techniques described in reference toFIG. 4, 5, or6. The UE115-cmay include a receiver module805, a D2D frequency hopping determination module810, which may further include an offset determination module815, and a transmitter module820. Each of these components may be in communication with each other.

The components of the UE115-cmay, individually or collectively, be implemented using at least one application-specific integrated circuit (ASICs) adapted to perform some or all of the applicable functions in hardware. Alternatively, the functions may be performed by at least one other processing unit (or core), on at least one integrated circuit. In other examples, other types of integrated circuits may be used (e.g., Structured/Platform ASICs, Field Programmable Gate Arrays (FPGAs), and other Semi-Custom ICs), which may be programmed in any manner known in the art. The functions of each unit may also be implemented, in whole or in part, with instructions embodied in a memory, formatted to be executed by at least one general or application-specific processor.

The receiver module805may receive information such as packet, data, or signaling information regarding what the UE115-chas received or transmitted. The received information may be utilized by the UE115-cfor a variety of purposes. In some cases, the receiver module805may be configured to receive data or transmissions, for example from a base station105, to further enable the various techniques described above for communicating with a D2D enabled UE115according to a base station determined D2D frequency hopping scheme.

The transmitter module820may transmit information such as packet, data, or signaling information from the UE115-c. In some cases, the transmitter module820may be configured to transmit data on the uplink to a one or more base stations105via links125or transmit one or more D2D messages to a D2D enabled UE115via links126described in reference toFIG. 1 or 2.

The receiver module805may receive a D2D frequency hopping scheme from a base station105associated with a WAN with a coverage are corresponding to a location of the UE115-c. The D2D frequency hopping scheme may be coordinated with a WAN frequency hopping scheme, for example by the base station105. The receiver module805may communicate this information to the D2D frequency hopping determination module810, which may identify the communicated D2D frequency hopping scheme.

In some instances, the offset determination module815of the D2D frequency hopping determination module810may identify/determine one or more offsets (e.g., in the WAN type 1 hopping scheme example), for retransmitting one or more messages to another D2D enabled UE115. In some cases, a first offset may correspond to transmissions transmitted on even subframes after a first transmission, whereas a second offset may correspond to transmissions transmitted on odd subframes after the first transmission. Once the offsets have been identified/determined from the information communicated in the message from the base station105, the offset determination module815may instruct the transmitter module830to transmit a scheduling assignment/retransmit a D2D message according to the first or second offsets to the another D2D enabled UE115.

In other instances, the D2D frequency hopping determination module810may determine resources reserved for D2D communications. In such a case, the D2D frequency hopping determination module810may determine a D2D frequency hopping scheme based on the D2D-specific resources. In this or other instances, the D2D frequency hopping determination module810may determine resources for transmissions/retransmissions to another D2D enabled UE115based on information received from the base station105. In some cases, this may include identifying one or more thresholds for D2D allocated resources. The D2D frequency hopping determination module810may then instruct the transmitter module820to transmit/retransmit to the D2D UE115on the allocated resources.

In some cases, the D2D frequency hopping determination module810may determine a cell ID associated with the base station105or the WAN frequency hopping scheme implemented by the base station105. The UE115-cmay then instruct the transmitter module820to communicate the cell ID to the inter-cell D2D enabled UE115to instruct the inter-cell D2D enabled UE115to avoid retransmitting on resources utilized by the WAN hopping scheme, etc., as described above.

FIG. 9shows a block diagram900of a base station105-cconfigured for coordinating a D2D frequency hopping scheme with a WAN frequency hopping scheme for a D2D enabled UE115, in accordance with various examples described herein. The base station105-bmay be an example of at least one aspect of base stations105described above with reference toFIG. 1, 2 or 7or may implement at least one aspect of the WAN frequency hopping module710or the D2D frequency hopping coordination module715described above with reference toFIG. 7. The base stations105-cmay communicate with at least one UE115via communication link125, as described above in reference toFIG. 1 or 2or via the coordination techniques described in reference toFIG. 4, 5, or6.

The components of the base station105-cmay, individually or collectively, be implemented using at least one application-specific integrated circuit (ASIC) adapted to perform some or all of the applicable functions in hardware. Alternatively, the functions may be performed by at least one other processing unit (or core), on at least one integrated circuit. In other examples, other types of integrated circuits may be used (e.g., Structured/Platform ASICs, Field Programmable Gate Arrays (FPGAs), and other Semi-Custom ICs), which may be programmed in any manner known in the art. The functions of each unit may also be implemented, in whole or in part, with instructions embodied in a memory, formatted to be executed by at least one general or application-specific processor.

The base station105-cincludes antenna(s)915, transceiver(s)920, memory935, a processor930, and I/O devices925, which each may be in communication, directly or indirectly, with each other, for example, via at least one bus945. The transceiver(s)920may be configured to communicate bi-directionally, via the antennas915with at least one wired or wireless link, such as any of communication links125or126described above in reference toFIG. 1, or2. The transceiver(s)920may include a modem configured to modulate the packets and provide the modulated packets to the antennas915for transmission, and to demodulate packets received from the antennas915. The transceiver(s)920may, in conjunction with the antennas915, transmit and receive packets. The transceiver(s)920may be configured to maintain multiple concurrent communication links using the same or different radio interfaces (e.g., Wi-Fi, cellular, etc.). The base station105-cmay include a single antenna915, or the base station105-cmay include multiple antennas915. The base station105-cmay be capable of employing multiple antennas915for transmitting and receiving communications in a multiple-input multiple-output (MIMO) communication system.

The memory935may include random access memory (RAM) and read-only memory (ROM). The memory935may store computer-readable, computer-executable software940containing instructions that are configured to, when executed, cause the processor930to perform various functions described herein. Alternatively, the software940may not be directly executable by the processor930but may be configured to cause the computer (e.g., when compiled and executed) to perform functions described herein. The processor930may include an intelligent hardware device (e.g., a central processing unit (CPU), a microcontroller, an application specific integrated circuit (ASIC), etc.).

According to the architecture ofFIG. 9, the base station105-cmay further include a WAN frequency hopping module710-aand a D2D frequency hopping coordination module715-a. By way of example, these components of base station105-cmay be in communication with some or all of the other components of the base station105-cvia bus945. Additionally or alternatively, functionality of these modules may be implemented via the transceiver920, as a computer program product stored in software940, or as at least one controller element of the processor930. In some examples, the WAN frequency hopping module710-aand the D2D frequency hopping coordination module715-a, including one or more of the D2D offset module720, the inter-cell scheduling grant module725, or the D2D resource determination module730, may be implemented as subroutines in memory935/software940executed by the processor930. In other cases, these modules may be implemented as sub-modules in the processor930itself.

The WAN frequency hopping module710-aand the D2D frequency hopping coordination module715-aof base station105-cmay further implement the procedures described above for coordinating a D2D frequency hopping pattern with a WAN frequency hopping pattern for D2D retransmissions of a UE115, and for the sake of brevity, will not be repeated here.

FIG. 10is a block diagram1000of a UE115-dconfigured for retransmitting one or messages to a D2D enabled UE115according to a D2D frequency hopping scheme communicated by a base station105, in accordance with various examples described herein. The UE115-dmay be an example of at least one aspect of UEs115described above with reference toFIG. 1, 2, or8or may implement at least one aspect of the D2D frequency hopping determination module810or the offset determination module815described above with reference toFIG. 8. The UE115-dmay communicate with at least one base station105via communication link125or at least one UE115via link126as described above in reference toFIG. 1 or 2or via the coordination techniques described in reference toFIG. 4, 5, or6. The UE115-dmay have any of various configurations, such as personal computers (e.g., laptop computers, netbook computers, tablet computers, etc.), smartphones, cellular telephones, PDAs, wearable computing devices, digital video recorders (DVRs), internet appliances, routers, gaming consoles, e-readers, display devices, printers, etc. The UE115-dmay have an internal power supply (not shown), such as a small battery, to facilitate mobile operation.

The components of the UE115-dmay, individually or collectively, be implemented using at least one application-specific integrated circuit (ASIC) adapted to perform some or all of the applicable functions in hardware. Alternatively, the functions may be performed by at least one other processing unit (or core), on at least one integrated circuit. In other examples, other types of integrated circuits may be used (e.g., Structured/Platform ASICs, Field Programmable Gate Arrays (FPGAs), and other Semi-Custom ICs), which may be programmed in any manner known in the art. The functions of each unit may also be implemented, in whole or in part, with instructions embodied in a memory, formatted to be executed by at least one general or application-specific processor.

The UE115-dincludes antenna(s)1015, transceiver(s)1020, memory1035, a processor1030, and I/O devices1025, which each may be in communication, directly or indirectly, with each other, for example, via at least one bus1045. The transceiver(s)1020may be configured to communicate bi-directionally, via the antennas1015with at least one wired or wireless link, such as any of communication links125or126described above in reference toFIG. 1, or2. The transceiver(s)1020may include a modem configured to modulate the packets and provide the modulated packets to the antennas1015for transmission, and to demodulate packets received from the antennas1015. The transceiver(s)1020may, in conjunction with the antennas1015, transmit and receive packets. The transceiver(s)1020may be configured to maintain multiple concurrent communication links using the same or different radio interfaces (e.g., Wi-Fi, cellular, etc.). The UE115-dmay include a single antenna1015, or the UE115-dmay include multiple antennas1015. The UE115-dmay be capable of employing multiple antennas1015for transmitting and receiving communications in a multiple-input multiple-output (MIMO) communication system.

The memory1035may include random access memory (RAM) and read-only memory (ROM). The memory1035may store computer-readable, computer-executable software1040containing instructions that are configured to, when executed, cause the processor1030to perform various functions described herein. Alternatively, the software1040may not be directly executable by the processor1030but may be configured to cause the computer (e.g., when compiled and executed) to perform functions described herein. The processor1030may include an intelligent hardware device (e.g., a central processing unit (CPU), a microcontroller, an application specific integrated circuit (ASIC), etc.).

According to the architecture ofFIG. 10, the UE115-dmay further include a D2D frequency hopping determination module810-a. By way of example, this and other components of UE115-dmay be in communication with some or all of the other components of the UE115-dvia bus1045. Additionally or alternatively, functionality of these modules may be implemented via the transceiver1020, as a computer program product stored in software1040, or as at least one controller element of the processor1030. In some examples, the D2D frequency hopping module810-a, including the offset determination module815, may be implemented as subroutines in memory1035/software1040executed by the processor1030. In other cases, these module may be implemented as sub-modules in the processor1030itself.

The D2D frequency hopping determination module810-amay further implement the procedures described above for communicating (e.g., via retransmissions) with a D2D enabled UE115according to a D2D frequency hopping scheme communicated from a serving base station105, and for the sake of brevity, will not be repeated here.

FIG. 11is a flow chart illustrating one example of a method1100for coordinating a D2D frequency hopping scheme for D2D retransmissions with a WAN frequency hopping scheme used for HARQ retransmissions, in accordance with various examples described herein. For clarity, the method1100is described below with reference to at least one aspect of one of the base stations105described with reference toFIG. 1, 2, 7, or9. In some examples, a device, such as one of the base stations105, may execute at least one set of codes to control the functional elements of the device to perform the functions described below.

At block1105, a base station105may identify a WAN frequency hopping scheme used in the WAN served by the base station105. The operation(s) at block1105may in some cases be performed using the WAN frequency hopping module710described with reference toFIG. 7 or 9.

At block1110, the base station105may coordinate a D2D frequency hopping scheme for at least one D2D enabled UE with the identified WAN frequency hopping scheme. The operation(s) at block1110may in some cases be performed using the D2D frequency hopping module715described with reference toFIG. 7 or 9.

At block1115, the base station105may communicate the D2D frequency hopping scheme to the at least one D2D enabled UE. The operation(s) at block1115may in some cases be performed using the transmitter module735described with reference toFIG. 7 or 9.

Thus, the method1100may provide for coordinating a D2D frequency hopping scheme with a WAN frequency hopping scheme. It should be noted that the method1100is just one implementation and that the operations of the method1100may be rearranged or otherwise modified such that other implementations are possible.

FIG. 12is a flow chart illustrating one example of a method1200for communicating with a D2D enabled UE115according to a D2D frequency hopping scheme coordinated with a WAN frequency hopping scheme, in accordance with various examples described herein. For clarity, the method1100is described below with reference to at least one aspect of one of UEs115described with reference toFIG. 1, 2, 8, or10. In some examples, a device, such as one of the UEs115, may execute at least one set of codes to control the functional elements of the device to perform the functions described below.

At block1205, a UE115may receive a D2D frequency hopping scheme, which is coordinated with a WAN frequency hopping scheme, from a base station105associated with the WAN. The operation(s) at block1205may in some cases be performed using the WAN frequency hopping determination module810or the receiver module805described with reference toFIG. 8 or 10.

At block1210, UE115may transmit at least one message to a second D2D enabled UE115according to the D2D frequency hopping scheme. The operation(s) at block1210may in some cases be performed using the WAN frequency hopping determination module810or the transmitter module820described with reference toFIG. 8 or 10.

Thus, the method1200may provide for communicating with a D2D enabled UE115according to a D2D frequency hopping scheme. It should be noted that the method1200is just one implementation and that the operations of the method1200may be rearranged or otherwise modified such that other implementations are possible.