Abstract:
A system and method of operating a device in a wireless communication network including a plurality of user equipment UEs and a BS, including a first device generating a signaling message defining resource elements (REs) as an encoded time slot (TS) and subcarrier pairing. A subset of the REs is encoded, such as to create a discovery signal configured to enable discovery of the first UE by a second UE or the BS. The UE is configured to engage in device-to-device communications, including device centric UEs operable in 5G networks.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure is generally directed to network communications, and more particularly to signaling messages, such as to enable network discovery of neighboring devices and device-to-device (D2D) connectivity in wireless networks, such as 5G networks. 
       BACKGROUND 
       [0002]    A mobile device in mobile and non-mobile communication networks is commonly referred to as user equipment (UE). UE cooperation enabled by device-to-device (D2D) connectivity has been identified as an integral part of a fifth generation (5G) radio access virtualization framework. 
         [0003]    Direct mobile communication between two UEs requires that the UEs and/or the network (NW) “discover”, i.e. detect the presence of neighboring devices which can be identified as potential helpers in virtualized radio access networks. 
         [0004]    For 5G device-centric networks, UE discovery has many of the same functionalities as the cell search procedure in current 4G cell-centric networks. For instance, there is symbol and frequency synchronization in order to demodulate the control and data channels, there is acquisition of frame timing of the cell, and there is determining the physical-layer cell identity. 
         [0005]    Different levels of network involvement enable the UE discovery to be autonomous, network assisted, or network controlled. Virtualized radio access envisions an always-on connection state that relies on device-centric dedicated connection signatures (DCSs) that enable network-wide or region-based tracking of UEs. Due to mobility, network topology changes, therefore the UEs must update their neighbor&#39;s list periodically. Since many devices may simultaneously send their discovery signals, the discovery signals should not suffer from near-far effect, multiple discovery signals should be distinguishable, and energy consumption and UE battery drainage are important considerations as well. 
       SUMMARY 
       [0006]    This disclosure is directed to differential peak signaling in device-centric radio access networks. 
         [0007]    In one embodiment, a method of operating a device in a wireless communication network including a plurality of devices comprises generating a signaling message containing information representing a two-dimensional time-frequency grid consisting of a plurality of subcarriers in the frequency domain and a plurality of time slots (TSs) in the time domain together defining resource elements (REs). A subset of the REs is coded to create a signaling message. A first device sends the signaling message to a second device. 
         [0008]    In some embodiments, the first device and the second device may be a UE or a BS. In some embodiments, the signaling message is configured to enable discovery of a first UE by a second UE or a BS, or to send other signaling information intended for a second UE or the BS. 
         [0009]    In some embodiments, selected subcarriers in the signaling message are energized to have a radio frequency (RF) power greater than an RF power of other said subcarriers in the signaling message. The method establishes a relative distance between consecutively energized subcarriers in the signaling message to encode the signaling message, wherein the signaling message can be indicative of a signature of the first UE, such as a dedicated connection signature (DCS). A relative location of the energized REs in the signaling message is indicative of a value of the first UE DCS. In some embodiments, the REs are coded according to a maximum distance separable (MDS) code to distinguish the first UE DCS, wherein the MDS code may be a Reed-Solomon (RS) code. Only one RE is coded per orthogonal frequency-division multiplexing (OFDM) symbol and no data is modulated on a coded said RE, or some data is coded on the RE as long as the energized subcarrier can be detected. The first UE periodically generates the signaling message corresponding to its DCS. The first UE has a transmitter that uses a majority of its transmit power to generate the energized subcarriers. In some embodiments, the signaling message is mapped to an uplink time-frequency grid every P frames, wherein P is selectively configurable. A second said UE receives the signaling message and identifies the first UE as being proximate the second UE. 
         [0010]    In another embodiment, a user equipment (UE) is configured to operate in a wireless network including a base station (BS), the UE comprising a message generator configured to generate a signaling message containing information representing a two-dimensional time-frequency grid consisting of a plurality of subcarriers in the frequency domain and a plurality of time slots (TSs) in the time domain together defining resource elements (REs). A subset of the REs is coded to create a discovery signal configured to signaling message intended for a second UE or the BS. 
         [0011]    In some embodiments, the signaling message enables discovery of the UE by another UE or the BS. 
         [0012]    In some embodiments, the message generator is configured to select and energize subcarriers in the signaling message to have a radio frequency (RF) power greater than an RF power of other said subcarriers in the signaling message. The message generator is configured to establish a relative distance between consecutively energized said subcarriers in the signaling message to encode the discovery signal, wherein the discovery signal is indicative of a signature of the first UE, such as dedicated connection signature (DCS). A relative location of the energized REs in the signaling message is indicative of a value of the first UE DCS. In some embodiments, the message generator is configured to code the REs according to a maximum distance separable (MDS) code to distinguish the first UE DCS, wherein the MDS code may be a Reed-Solomon (RS) code. Only one RE is coded per orthogonal frequency-division multiplexing (OFDM) symbol and no data is modulated on a coded said RE. The message generator is configured to periodically generate the signaling message of the UE corresponding to its DCS. The UE has a transmitter that is configured to use a majority of its transmit power to generate the energized subcarriers. The signaling message is configured to be mapped to an uplink time-frequency grid every P frames, wherein P is selectively configurable. The DCS is configured to be managed by a base station (BS). 
         [0013]    In another embodiment, a base station (BS) is configured to operate in a wireless network including at least one user equipment (UE), and comprises a message generator configured to generate a signaling message. The signaling message contains information representing a two-dimensional time-frequency pattern consisting of a plurality of subcarriers in the frequency domain and a plurality of time slots (TSs) in the time domain together defining resource elements (REs), wherein a subset of the REs are coded to create a signaling message intended for at least one UE. 
         [0014]    In another embodiment, in a wireless communication network comprising a plurality of user equipment (UE) and a base station (BS), a method comprises a first UE or a BS generating a signaling message containing information representing a pattern consisting of either a plurality of subcarriers in the frequency domain or a plurality of time slots (TSs) in the time domain together defining resource elements (REs), wherein a subset of the REs are coded to create a signaling message intended for a second UE or a BS. 
         [0015]    In some embodiments, the signaling message pattern is encoded in a plurality of subcarriers in the frequency domain. In another embodiment, the signaling message pattern is encoded in a plurality of time slots (TSs) in the time domain. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, wherein like numbers designate like objects, and in which: 
           [0017]      FIG. 1  illustrates a wireless communications system including UEs and BSs operable according to this disclosure; 
           [0018]      FIGS. 2A and 2B  illustrate example devices including UEs that may implement the methods and teachings according to this disclosure; 
           [0019]      FIG. 3  illustrates dedicated time-frequency signaling resources referred to as a signaling zone according to this disclosure; 
           [0020]      FIG. 4  illustrates signaling resources configured in only the frequency domain; 
           [0021]      FIG. 5  illustrates the signaling resources configured in only the time domain. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]      FIG. 1  illustrates an example communication system  100  that uses differential peak signaling in device-centric virtual radio access networks according to this disclosure. In general, the system  100  enables multiple wireless users to transmit and receive data and other content. The system  100  may implement one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), or single-carrier FDMA (SC-FDMA). 
         [0023]    In this example, the communication system  100  includes user equipment (UE)  110   a - 110   c,  radio access networks (RANs)  120   a - 120   b,  a core network  130 , a public switched telephone network (PSTN)  140 , the Internet  150 , and other networks  160 . While certain numbers of these components or elements are shown in  FIG. 1 , any number of these components or elements maybe included in the system  100 . 
         [0024]    The UEs  110   a - 110   c  are configured to operate and/or communicate in the system  100 . For example, the UEs  110   a - 110   c  are configured to transmit and/or receive wireless signals or wired signals. Each UE  110   a - 110   c  represents any suitable end user device and may include such devices (or may be referred to) as a user equipment/device (UE), wireless transmit/receive unit (WTRU), mobile station, fixed or mobile subscriber unit, pager, cellular telephone, personal digital assistant (PDA), smartphone, laptop, computer, touchpad, wireless sensor, or consumer electronics device. 
         [0025]    The RANs  120   a - 120   b  here include base stations  170   a - 170   b,  respectively. Each base station  170   a - 170   b  is configured to wirelessly interface with one or more of the UEs  110   a - 110   c  to enable access to the core network  130 , the PSTN  140 , the Internet  150 , and/or the other networks  160 . For example, the base stations  170   a - 170   b  may include (or be) one or more of several well-known devices, such as a base transceiver station (BTS), a Node-B (NodeB), an evolved NodeB (eNodeB), a Home NodeB, a Home eNodeB, a site controller, an access point (AP), or a wireless router, or a server, router, switch, or other processing entity with a wired or wireless network. 
         [0026]    In the embodiment shown in  FIG. 1 , the base station  170   a  forms part of the RAN  120   a,  which may include other base stations, elements, and/or devices. Also, the base station  170   b  forms part of the RAN  120   b,  which may include other base stations, elements, and/or devices. Each base station  170   a - 170   b  operates to transmit and/or receive wireless signals within a particular geographic region or area, sometimes referred to as a “cell.” In some embodiments, multiple-input multiple-output (MIMO) technology may be employed having multiple transceivers for each cell. 
         [0027]    The base stations  170   a - 170   b  communicate with one or more of the UEs  110   a - 110   c  over one or more air interfaces  190  using wireless communication links. The air interfaces  190  may utilize any suitable radio access technology. 
         [0028]    It is contemplated that the system  100  may use multiple channel access functionality, including such schemes as described above. In particular embodiments, the base stations and UEs implement LTE, LTE-A, and/or LTE-B. Of course, other multiple access schemes and wireless protocols may be utilized. 
         [0029]    The RANs  120   a - 120   b  are in communication with the core network  130  to provide the UEs  110   a - 110   c  with voice, data, application, Voice over Internet Protocol (VoIP), or other services. Understandably, the RANs  120   a - 120   b  and/or the core network  130  may be in direct or indirect communication with one or more other RANs (not shown). The core network  130  may also serve as a gateway access for other networks (such as PSTN  140 , Internet  150 , and other networks  160 ). In addition, some or all of the UEs  110   a - 110   c  may include functionality for communicating with different wireless networks over different wireless links using different wireless technologies and/or protocols. 
         [0030]    Although  FIG. 1  illustrates one example of a communication system, various changes may be made to  FIG. 1 . For example, the communication system  100  could include any number of UEs, base stations, networks, or other components in any suitable configuration, and can further include the EPC illustrated in any of the figures herein. 
         [0031]      FIGS. 2A and 2B  illustrate example devices that may implement the methods and teachings according to this disclosure. In particular,  FIG. 2A  illustrates an example UE  110 , and  FIG. 2B  illustrates an example base station  170 . These components could be used in the system  100  or in any other suitable system. 
         [0032]    As shown in  FIG. 2A , the UE  110  includes at least one processing unit  200 . The processing unit  200  implements various processing operations of the UE  110 . For example, the processing unit  200  could perform signal coding, data processing, power control, input/output processing, or any other functionality enabling the UE  110  to operate in the system  100 . The processing unit  200  also supports the methods and teachings described in more detail above. Each processing unit  200  includes any suitable processing or computing device configured to perform one or more operations. Each processing unit  200  could, for example, include a microprocessor, microcontroller, digital signal processor, field programmable gate array, or application specific integrated circuit. 
         [0033]    The UE  110  also includes at least one transceiver  202 . The transceiver  202  is configured to modulate data or other content for transmission by at least one antenna  204 . The transceiver  202  is also configured to demodulate data or other content received by the at least one antenna  204 . Each transceiver  202  includes any suitable structure for generating signals for wireless transmission and/or processing signals received wirelessly. Each antenna  204  includes any suitable structure for transmitting and/or receiving wireless signals. One or multiple transceivers  202  could be used in the UE  110 , and one or multiple antennas  204  could be used in the UE  110 . Although shown as a single functional unit, a transceiver  202  could also be implemented using at least one transmitter and at least one separate receiver. Those skilled in the art will appreciate that transceiver  202  may be replaced with a transmitter and a receiver. In some embodiments it may be preferable to have individual components for specific design purposes. 
         [0034]    The UE  110  further includes one or more input/output devices  206 . The input/output devices  206  facilitate interaction with a user. Each input/output device  206  includes any suitable structure for providing information to or receiving information from a user, such as a speaker, microphone, keypad, keyboard, display, or touch screen. 
         [0035]    In addition, the UE  110  includes at least one memory  208 . The memory  208  stores instructions and data used, generated, or collected by the UE  110 . For example, the memory  208  could store software or firmware instructions executed by the processing unit (s)  200  and data used to reduce or eliminate interference in incoming signals. Each memory  208  includes any suitable volatile and/or non-volatile storage and retrieval device(s). Any suitable type of memory may be used, such as random access memory (RAM), read only memory (ROM), hard disk, optical disc, subscriber identity module (SIM) card, memory stick, secure digital (SD) memory card, and the like. 
         [0036]    As shown in  FIG. 2B , the base station  170  includes at least one processing unit  250 , at least one transmitter  252 , at least one receiver  254 , one or more antennas  256 , and at least one memory  258 . The processing unit  250  implements various processing operations of the base station  170 , such as signal coding, data processing, power control, input/output processing, or any other functionality. The processing unit  250  can also support the methods and teachings described in more detail above. Each processing unit  250  includes any suitable processing or computing device configured to perform one or more operations. Each processing unit  250  could, for example, include a microprocessor, microcontroller, digital signal processor, field programmable gate array, or application specific integrated circuit. 
         [0037]    Each transmitter  252  includes any suitable structure for generating signals for wireless transmission to one or more UEs or other devices. Each receiver  254  includes any suitable structure for processing signals received wirelessly from one or more UEs or other devices. Although shown as separate components, at least one transmitter  252  and at least one receiver  254  could be combined into a transceiver. Each antenna  256  includes any suitable structure for transmitting and/or receiving wireless signals. While a common antenna  256  is shown here as being coupled to both the transmitter  252  and the receiver  254 , one or more antennas  256  could be coupled to the transmitter(s)  252 , and one or more separate antennas  256  could be coupled to the receiver(s)  254 . Each memory  258  includes any suitable volatile and/or non-volatile storage and retrieval device(s). 
         [0038]    Additional details regarding UEs  110  and base stations  170  are known to those of skill in the art. As such, these details are omitted here for clarity. 
         [0039]    This disclosure consists of a system and method for differential signaling in wireless networks using relative distance between sequentially energized tones to encode signaling information and maximum distance separable (MDS) codes to distinguish between different signaling messages, such as Reed-Solomon (RS) codes. This disclosure benefits by energizing (boosting tone power) to help improve range and supports device-centric unified random access. The disclosure uses relative distance between energized subcarriers to achieve robustness to frequency offset errors. RF-based discovery is utilized, as opposed to location based discovery thereby providing accurate neighbor discovery. The disclosure can exploit the inherent link margin in transmission techniques such as those specified in long term evolution (LTE) to transmit the signaling messages concurrently with data transmissions, and can leverage the time-frequency abstraction of orthogonal frequency-division multiple access (OFDMA) to localize the interference caused by signaling messages to the data packets. It is not necessary for coding or modulation to be used, which can simplify receiver design since no channel estimation is needed. This disclosure avoids heavy beacon signals, such as preamble, pilots, or modulation/coding. Network assisted signaling provides tight interference and quality of signal (QoS) control and the ability to track UEs. There is no need for dedicated resources for signaling which saves on the scarce spectrum. 
         [0040]    This disclosure can advantageously use a differential signaling method for wireless networks. This includes determining the relative distance between consecutively energized tones to encode signaling information, and using MDSs codes to distinguish between different signaling messages. The NW manages assignments of DCSs which can be reused over different geographical regions. 
         [0041]    Signaling Zone 
         [0042]    Referring to  FIG. 3 , there is shown a signaling a signaling zone (SZ) which can be used to signal DCSs of a UE to other 
         [0043]    UEs and/or the BS. The SZ comprises a two-dimensional time-frequency grid. In an implementation where the underlying radio technology is based on LTE, and where LTE terminology is used, the SZ consists of Q subcarriers in the frequency domain, and N time slots in the time domain. The SZ contains (Q*N) resource elements (REs) where N≦Q. The SZ is periodically mapped to the uplink time-frequency grid every P LTE frames, where P is a configurable parameter that can be optimized to minimize the duty cycle for uplink signaling. For example, P=10, N=14 (1 subframe) thus the duty cycle ˜1/100=1%. If the number of subcarriers in the signaling zone Q is less than the total number of subcarriers, then the percentage of LTE resources used for signaling is actually less than the duty cycle i.e. &lt;=1%. One possibility is that NW can multicast discovery DCS sub-group information depending on UE relative position to further reduce the detection complexity and size of SZ. 
         [0044]    Signaling Method 
         [0045]    DCS is used to identify UEs within a geographical region either for UE discovery purposes or random access procedures. The signaling messages are transmitted over the SZ and each UE periodically broadcasts a signaling message corresponding to its DCS using the SZ resources by energizing a number of REs within the signaling zone. Only 1 subcarrier per orthogonal frequency-division multiplexing (OFDM) symbol is energized and no information is modulated onto that subcarrier. There is no need for channel estimation at the receiver as a simple energy detector is sufficient. The relative location of the energized REs in the SZ is used to indicate the value of the DCS. The relative subcarrier position of the energized tones is used to encode information. 
         [0046]    For example, if a UE sequentially energizes subcarriers  3  and  18 , then the difference 18−3=15, and subcarrier  15  is used to encode the DCS information. D2D transmissions are not necessarily synchronized, thus using the relative position of subcarriers in the SZ to encode DCS information is very suitable because it provides robustness against carrier frequency offset errors. Discovery/random access signals start by energizing a pre-designated subcarrier in the first TS of the SZ, then any deviation relative to the start-of-signal subcarrier is used as an estimate of the frequency offset between the transmitting and the receiving UEs. Because this disclosure uses the relative distance between subcarriers to encode the DCSs, such an estimate of the frequency offset can be accounted for during the decoding process. 
         [0047]    Peak Detection 
         [0048]    If the UE transmitter focuses all its power, or substantially all its power, on a single subcarrier, the energized tone has much more power relative to data transmission. Therefore, the energized tone&#39;s position in the time-frequency OFDM grid is easily detected using a simple peak detector at the receiver. 
         [0049]    One simple peak detector consists of computing a differential local average according to e.g.: 
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         [0000]    where N is a positive integer and y(i,j) is the received signal on coordinate (i,j). 
         [0050]    If D(i,j) is larger than some empirical threshold T, there it is likely to be an energized tone at coordinate (I,j). 
         [0051]    Separability with MDS Codes 
         [0052]    In order to be able to distinguish between different DCSs at the receiver, each signaling message is coded using a deterministic sequence according to a MDS code. For instance, Reed-Solomon (RS) codes are non-trivial MDS codes. The RS codes are deterministic non-binary linear block codes that can be constructed for any Galois Field (GF) of size Q, values of K, N such 1&lt;=K&lt;N&lt;=Q. 
         [0053]    The minimum distance for any two RS codewords is the maximum possible, i.e. dmin=N−K+1, thus matching the Singleton Bound for linear codes. There is a close relationship between decoding of RS codes and nonlinear recovery of sparse signals from narrowband data. 
         [0054]    Other interesting properties of RS codes include that: RS codes can correct up to 
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         [0000]    symbol errors (if
 
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         [0055]    RS codes can correct up to ρ=d min −1=N−K symbol erasures (location is known in advance) ; and 
         [0056]    RS codes can correct up to 2α+γ&lt;d min  simultaneous symbol errors and symbol erasures (α is the number of symbol error patterns and γ is the number of symbol erasure patterns). 
         [0057]    Encoding of Signal Messages 
         [0058]    Let the number of subcarriers in the SZ be Q=2 q  where q is a prime number and let the number of bits representing one discovery/random access signal, be Klog 2  (Q)=Kq bits where K≦N. Therefore, the number of signaling messages supported by the system is 2 Kq  =Q K    
         [0059]    GF(Q) is a finite field of size Q where Q is usually a prime power, i.e. p{circumflex over ( 0 )}n where p is a prime number and n is a positive integer. It is also called Galois Field, hence the abbreviation GF(Q). This is an algebraic concept designating a finite set for which the commutative operations of multiplication, addition, subtraction and division (by anything except zero) are defined. For example, the set of integers modulo 3 is a Galois field. 
         [0060]    In GF(Q), one signal c=[c 0 , c 1 , . . . , c K ] corresponding to the message symbols {c 0 , c 1 , . . . , c K } ⊂ GF(Q) can be represented by the polynomial 
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         [0061]    Let A={α 1 , α 2 , . . . , α N } ⊂ GF(Q)s.t.α i ≠α j ∀1≦i˜j≦N 
         [0062]    Then a RS code can be defined as: 
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         [0063]    The generator matrix for the RS code RS GF(Q),A [N,K] is the NxK Vandermonde matrix 
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         [0064]    Decoding of Signaling Messages 
         [0065]    Let S be the set of simultaneously transmitted discovery/random access messages, the number of possible combinations causing ambiguity at the receiver is |S| K  where |.| denotes the Cardinality operator. 
         [0066]    Dirichlet Principle: 
         [0067]    If N peaks are selected (one peak per OFDM symbol for each TS of a signaling period of size N), then at least 
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         [0000]    peaks belong
 
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         [0068]    Because RS codes are MDS codes then in case of perfect peak detection, the receiver will be able to uniquely map the signaling messages to the correct DCSs provided that 
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         [0069]    Superimposed Uplink Data Traffic 
         [0070]    An additional advantage of network-assisted UE discovery using peaked tones where UEs register their DCS with the network is that the SZ need not be exclusively dedicated for signaling. 
         [0071]    Other UEs not involved in the discovery/signaling process (some UE classes may not be discoverable) can still use the signaling zone resources to transmit uplink data traffic. 
         [0072]    The receiver of the uplink traffic data is the BS. The BS is aware of the DCSs currently being transmitted (active DCSs). Accordingly, the receiver can use this information to erase the data symbols that happen to coincide with the energized tones of the active DCSs. 
         [0073]    The decoder at the BS treats the demodulated bits for the energized tones as bit erasures which are easier to deal with than bit errors and usually require fewer redundancy bits to correct. 
         [0074]    Moreover, LTE-based systems often err on the conservative side and allow for some link margin to compensate for modulation and coding scheme (MCS) adaptation algorithms and imperfect channel state information (CSI). Therefore, such link margins should be enough to compensate for the erased symbols without sacrificing valuable data resources. 
         [0075]    In another embodiment, the BS can broadcast the SZ signaling messages on a downlink to a plurality of neighboring UEs or BSs. Similar in the uplink, the differential peak signaling method can also be used to signal traffic priority, and assist in downlink inter-cell interference coordination, interference avoidance and TP muting for energy saving purposes. 
         [0076]    Referring to  FIG. 4 , according to another embodiment of this disclosure, frequency domain signaling of the SZ can comprise of a plurality of REs coded in only the frequency domain. The different columns in  FIG. 4  use different contiguous chunks of Q subcarriers in the frequency domain. The differential encoding in this embodiment is between the relative positions of subcarriers in two consecutive chunks of Q subcarriers in the frequency domain. The REs are encoded in multiple subcarriers for a single time slot, shown in this example as time slot  0 . As described above, the deviation relative to the start-of-signal subcarrier can be used as an estimate of the frequency offset between the transmitting and receiving devices. The relative distance between subcarriers encodes the UE signature, such as the UE DCS. 
         [0077]    Referring to  FIG. 5 , according to another embodiment of this disclosure, time-domain signaling of the SZ can comprise of a plurality of REs coded in only the time domain. The different rows in  FIG. 5  use different contiguous chunks of time slots in the time domain. The REs are encoded in multiple timeslots for a single subcarrier, shown in this example as subcarrier  0 . The time-domain only signaling is perhaps a less interesting proposition as it has the downside of introducing more delay to the signaling scheme. 
         [0078]    While this disclosure has described certain embodiments and generally associated methods, alterations and permutations of these embodiments and methods will be apparent to those skilled in the art. Accordingly, the above description of example embodiments does not define or constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of this disclosure, as defined by the following claims.