Patent Publication Number: US-2021185669-A1

Title: Increase diversity of slot aggregation using slot-specific cyclic delay diversity

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of and priority to U.S. Provisional Patent Application No. 62/947,884, filed Dec. 13, 2019, which is assigned to the assignee hereof and herein incorporated by reference in its entirety as if fully set forth below and for all applicable purposes. 
    
    
     BACKGROUND 
     Field of the Disclosure 
     Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for increasing diversity of transmissions with slot aggregation using slot-specific cyclic delay diversity (CDD). 
     Description of Related Art 
     Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasts, etc. These wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of such multiple-access systems include 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems, LTE Advanced (LTE-A) systems, code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems, to name a few. 
     These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. New radio (e.g., 5G NR) is an example of an emerging telecommunication standard. NR is a set of enhancements to the LTE mobile standard promulgated by 3GPP. NR is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL). To these ends, NR supports beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation. 
     However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in NR and LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies. 
     SUMMARY 
     The systems, methods, and devices of the disclosure each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this disclosure as expressed by the claims which follow, some features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description” one will understand how the features of this disclosure provide advantages that include improved coverage of physical downlink shared channel (PDSCH) and physical uplink shared channel (PUSCH) transmissions. 
     Certain aspects provide a method for wireless communication by a transmitting device. The method generally includes determining to transmit a signal using cyclic delay diversity (CDD) in a plurality of slots; and transmitting the signal using a different cyclic delay in each slot of the plurality of slots. 
     Certain aspects provide a method for wireless communication by a receiving device. The method generally includes determining that a signal from a transmitting device is transmitted using cyclic delay diversity (CDD) in a plurality of slots; and receiving the signal based on a different cyclic delay in each slot of the plurality of slots. 
     Certain aspects provide an apparatus for wireless communication. The apparatus generally includes a processor configured to: determine to transmit a signal using cyclic delay diversity (CDD) in a plurality of slots; and to transmit the signal using a different cyclic delay in each slot of the plurality of slots; and a memory coupled with the processor. 
     Certain aspects provide an apparatus for wireless communication. The apparatus generally includes a processor configured to: determine that a signal from a transmitting device is transmitted using cyclic delay diversity (CDD) in a plurality of slots; and to receive the signal based on a different cyclic delay in each slot of the plurality of slots; and a memory coupled with the processor. 
     Certain aspects provide an apparatus for wireless communication. The apparatus includes means for determining to transmit a signal using cyclic delay diversity (CDD) in a plurality of slots and means for transmitting the signal using a different cyclic delay in each slot of the plurality of slots. 
     Certain aspects provide an apparatus for wireless communication. The apparatus includes means for determining that a signal from a transmitting device is transmitted using cyclic delay diversity (CDD) in a plurality of slots; and means for receiving the signal based on a different cyclic delay in each slot of the plurality of slots. 
     Certain aspects provide a computer readable medium containing program instructions for causing a computer to perform operations including: determining to transmit a signal using cyclic delay diversity (CDD) in a plurality of slots; and transmitting the signal using a different cyclic delay in each slot of the plurality of slots. 
     Certain aspects provide a computer readable medium containing program instructions for causing a computer to perform operations including: determining that a signal from a transmitting device is transmitted using cyclic delay diversity (CDD) in a plurality of slots; and receiving the signal based on a different cyclic delay in each slot of the plurality of slots. 
     To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the appended drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects. 
         FIG. 1  is a block diagram conceptually illustrating an example telecommunications system, in accordance with certain aspects of the present disclosure. 
         FIG. 2  is a block diagram conceptually illustrating a design of an example a base station (BS) and user equipment (UE), in accordance with certain aspects of the present disclosure. 
         FIGS. 3A &amp; 3B  are schematic resource allocations  300  and  350  of signals sent using slot aggregation, according to previously known techniques. 
         FIG. 4  is a schematic diagram of an exemplary communications system in which CDD is used, according to previously known techniques. 
         FIG. 5  is a transmission sent with CDD, in accordance with certain aspects of the present disclosure. 
         FIGS. 6A &amp; 6B  are schematic representations of precoding for a spatially-multiplexed transmission, in accordance with certain aspects of the present disclosure. 
         FIG. 7  is a flow diagram illustrating example operations for wireless communication performed by a transmitting device, in accordance with aspects of the present disclosure. 
         FIG. 8  is a flow diagram illustrating example operations for wireless communication performed by a receiving device, in accordance with aspects of the present disclosure. 
         FIG. 9  illustrates a communications device that may include various components configured to perform the operations illustrated in  FIGS. 7 &amp; 8 , in accordance with aspects of the present disclosure. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one aspect may be beneficially utilized on other aspects without specific recitation. 
     DETAILED DESCRIPTION 
     Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for increasing diversity of transmissions with slot aggregation using slot-specific cyclic delay diversity (CDD). Slot aggregation is a technique in which a transmitter transmits the same data in the same frequency resources in each slot of a group of slots, and a receiver of the transmissions aggregates together the received signals to improve the probability that the receiver will successfully decode the data. Slot aggregation is supported in both Release 15 (Rel-15) and Release 16 (Rel-16) versions of 3GPP standards in order to improve coverage of physical downlink shared channel (PDSCH) and physical uplink shared channel (PUSCH) transmissions. In each aggregated slot, the resource element (RE) allocation for the transmission is the same, thus the transmission is repeated from slot to slot. There is no frequency diversity to be exploited in the current slot aggregation design, as the aggregated slots share the same frequency band, and the RE allocation in each slot is the same. CDD is a transmit diversity technique in which a transmitter adds a different phase delay for different orthogonal frequency division multiplexing (OFDM) tones on different transmission antenna ports. Considered in the frequency domain, each tone in each antenna port is multiplexed with a different phase rotation. Therefore, at a receiver, an equivalent channel on each tone, due to the different phase rotations, becomes different, even if the raw tone channel without CDD remains the same from tone to tone. Thus, frequency diversity can be exploited by a receiver after a transmitter applies CDD to a transmission. Considered in the time domain, equivalently, the payloads of different layers are cyclic shifted versions of each other. Thus, CDD can improve diversity of signals transmitted using slot aggregation, improving coverage for the transmitters transmitting those signals. 
     The following description provides examples of slot aggregation using slot-specific cyclic delay diversity (CDD) in communication systems, and is not limiting of the scope, applicability, or examples set forth in the claims. Changes may be made in the function and arrangement of elements discussed without departing from the scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as appropriate. For instance, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, features described with respect to some examples may be combined in some other examples. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to, or other than, the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects. 
     In general, any number of wireless networks may be deployed in a given geographic area. Each wireless network may support a particular radio access technology (RAT) and may operate on one or more frequencies. A RAT may also be referred to as a radio technology, an air interface, etc. A frequency may also be referred to as a carrier, a subcarrier, a frequency channel, a tone, a subband, etc. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs. In some cases, a 5G NR RAT network may be deployed. 
       FIG. 1  illustrates an example wireless communication network  100  in which aspects of the present disclosure may be performed. For example, the wireless communication network  100  may be an NR system (e.g., a 5G NR network). 
     As illustrated in  FIG. 1 , the wireless communication network  100  may include a number of base stations (BSs)  110   a - z  (each also individually referred to herein as BS  110  or collectively as BSs  110 ) and other network entities. A BS  110  may provide communication coverage for a particular geographic area, sometimes referred to as a “cell”, which may be stationary or may move according to the location of a mobile BS  110 . In some examples, the BSs  110  may be interconnected to one another and/or to one or more other BSs or network nodes (not shown) in wireless communication network  100  through various types of backhaul interfaces (e.g., a direct physical connection, a wireless connection, a virtual network, or the like) using any suitable transport network. In the example shown in  FIG. 1 , the BSs  110   a ,  110   b  and  110   c  may be macro BSs for the macro cells  102   a ,  102   b  and  102   c , respectively. The BS  110   x  may be a pico BS for a pico cell  102   x . The BSs  110   y  and  110   z  may be femto BSs for the femto cells  102   y  and  102   z , respectively. A BS may support one or multiple cells. The BSs  110  communicate with user equipment (UEs)  120   a - y  (each also individually referred to herein as UE  120  or collectively as UEs  120 ) in the wireless communication network  100 . The UEs  120  (e.g.,  120   x ,  120   y , etc.) may be dispersed throughout the wireless communication network  100 , and each UE  120  may be stationary or mobile. 
     According to certain aspects, the BSs  110  and UEs  120  may be configured for slot aggregation using slot-specific cyclic delay diversity (CDD). As shown in  FIG. 1 , the BS  110   a  includes a slot aggregation using CDD manager  112 . The slot aggregation using CDD manager  112  may be configured to determine to transmit a signal using cyclic delay diversity (CDD) in a plurality of slots; and to transmit the signal using a different cyclic delay in each slot of the plurality of slots, in accordance with aspects of the present disclosure. In some examples, the slot aggregation using CDD manager  112  may determine that a signal from a transmitting device is transmitted using cyclic delay diversity (CDD) in a plurality of slots; and receive the signal based on a different cyclic delay in each slot of the plurality of slots. As shown in  FIG. 1 , the UE  120   a  includes a slot aggregation using CDD manager  122 . The slot aggregation using CDD manager  122  may be configured to determine to transmit a signal using cyclic delay diversity (CDD) in a plurality of slots; and to transmit the signal using a different cyclic delay in each slot of the plurality of slots, in accordance with aspects of the present disclosure. In some examples, the slot aggregation using CDD manager  122  may determine that a signal from a transmitting device is transmitted using cyclic delay diversity (CDD) in a plurality of slots; and receive the signal based on a different cyclic delay in each slot of the plurality of slots. 
     Wireless communication network  100  may also include relay stations (e.g., relay station  110   r ), also referred to as relays or the like, that receive a transmission of data and/or other information from an upstream station (e.g., a BS  110   a  or a UE  120   r ) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE  120  or a BS  110 ), or that relays transmissions between UEs  120 , to facilitate communication between devices. 
     A network controller  130  may couple to a set of BSs  110  and provide coordination and control for these BSs  110 . The network controller  130  may communicate with the BSs  110  via a backhaul. The BSs  110  may also communicate with one another (e.g., directly or indirectly) via wireless or wireline backhaul. 
       FIG. 2  illustrates example components of BS  110   a  and UE  120   a  (e.g., in the wireless communication network  100  of  FIG. 1 ), which may be used to implement aspects of the present disclosure. 
     At the BS  110   a , a transmit processor  220  may receive data from a data source  212  and control information from a controller/processor  240 . The control information may be for the physical broadcast channel (PBCH), physical control format indicator channel (PCFICH), physical hybrid ARQ indicator channel (PHICH), physical downlink control channel (PDCCH), group common PDCCH (GC PDCCH), etc. The data may be for the physical downlink shared channel (PDSCH), etc. The processor  220  may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The transmit processor  220  may also generate reference symbols, such as for the primary synchronization signal (PSS), secondary synchronization signal (SSS), and cell-specific reference signal (CRS). A transmit (TX) multiple-input multiple-output (MIMO) processor  230  may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to the modulators (MODs)  232   a - 232   t . Each modulator  232  may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. Downlink signals from modulators  232   a - 232   t  may be transmitted via the antennas  234   a - 234   t , respectively. 
     At the UE  120   a , the antennas  252   a - 252   r  may receive the downlink signals from the BS  110   a  and may provide received signals to the demodulators (DEMODs) in transceivers  254   a - 254   r , respectively. Each demodulator  254  may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. A MIMO detector  256  may obtain received symbols from all the demodulators  254   a - 254   r , perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor  258  may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for the UE  120   a  to a data sink  260 , and provide decoded control information to a controller/processor  280 . 
     On the uplink, at UE  120   a , a transmit processor  264  may receive and process data (e.g., for the physical uplink shared channel (PUSCH)) from a data source  262  and control information (e.g., for the physical uplink control channel (PUCCH) from the controller/processor  280 . The transmit processor  264  may also generate reference symbols for a reference signal (e.g., for the sounding reference signal (SRS)). The symbols from the transmit processor  264  may be precoded by a TX MIMO processor  266  if applicable, further processed by the demodulators in transceivers  254   a - 254   r  (e.g., for SC-FDM, etc.), and transmitted to the BS  110   a . At the BS  110   a , the uplink signals from the UE  120   a  may be received by the antennas  234 , processed by the modulators  232 , detected by a MIMO detector  236  if applicable, and further processed by a receive processor  238  to obtain decoded data and control information sent by the UE  120   a . The receive processor  238  may provide the decoded data to a data sink  239  and the decoded control information to the controller/processor  240 . 
     The memories  242  and  282  may store data and program codes for BS  110   a  and UE  120   a , respectively. A scheduler  244  may schedule UEs for data transmission on the downlink and/or uplink. 
     The controller/processor  280  and/or other processors and modules at the UE  120   a  may perform or direct the execution of processes for the techniques described herein. For example, as shown in  FIG. 2 , the controller/processor  240  of the BS  110   a  has a slot aggregation using CDD manager  241  that may be configured for determining to transmit a signal using cyclic delay diversity (CDD) in a plurality of slots; and for transmitting the signal using a different cyclic delay in each slot of the plurality of slots, according to aspects described herein. The slot aggregation using CDD manager  241  may also be configured for determining that a signal from a transmitting device is transmitted using cyclic delay diversity (CDD) in a plurality of slots; and for receiving the signal based on a different cyclic delay in each slot of the plurality of slots. As shown in  FIG. 2 , the controller/processor  280  of the UE  120   a  has an slot aggregation using CDD manager  281  that may be configured for determining to transmit a signal using cyclic delay diversity (CDD) in a plurality of slots; and for transmitting the signal using a different cyclic delay in each slot of the plurality of slots, according to aspects described herein. The slot aggregation using CDD manager  281  may also be configured for determining that a signal from a transmitting device is transmitted using cyclic delay diversity (CDD) in a plurality of slots; and for receiving the signal based on a different cyclic delay in each slot of the plurality of slots. Although shown at the Controller/Processor, other components of the UE  120   a  and BS  110   a  may be used performing the operations described herein. 
       FIGS. 3A &amp; 3B  are schematic resource allocations  300  and  350  of signals sent using slot aggregation, according to previously known techniques. In the schematic resource allocation  300 , a signal  302   a  including a physical downlink control channel (PDCCH)  305   a , a demodulation reference signal (DMRS)  310   a , and a physical downlink shared channel (PDSCH)  315   a  is shown. Two repetitions  302   b  and  302   c  of the signal  302   a  are also shown in the same frequency resources and later slots. Each of the repetitions  302   b  and  302   c  includes a PDCCH  305   b  or  305   c , a DMRS  310   b  or  310   c , and a PDSCH  315   b  or  315   c . In the schematic resource allocation  350 , a signal  352   a  including a physical downlink control channel (PDCCH)  355   a , a demodulation reference signal (DMRS)  360   a , and a physical downlink shared channel (PDSCH)  365   a  is shown. Two repetitions  352   b  and  352   c  of the signal  352   a  are also shown in later slots and different frequency resources, thus the signals are transmitted with frequency diversity and slot aggregation. Each of the repetitions  352   b  and  352   c  includes a PDCCH  355   b  or  355   c , a DMRS  360   b  or  360   c , and a PDSCH  365   b  or  365   c.    
       FIG. 4  is a schematic diagram of an exemplary communications system  400  in which CDD is used, according to previously known techniques. In the exemplary communications system  400 , the data  405  is transmitted via a first antenna  410  and is cyclically shifted at  420  and transmitted via a second antenna  412 . Thus, a first version  430  of the data and a second version  432  of the data are received by the receiver  440 . The cyclic shift results in increased diversity between the 2 spatial paths, i.e., the first path from the first antenna  410  and the second path from the second antenna  412 . The increased diversity between the two paths improves the receiver&#39;s receiving of the data. 
       FIG. 5  is a transmission  500  sent with CDD represented in the time domain at  510  and in the frequency domain at  530 , according to aspects of the present disclosure. According to aspects of the present disclosure, a signal subject to a cyclic shift in time can be represented in the frequency domain as a phase shifted transmission. An original version  512  and a cyclically shifted version  514  of the data are shown. In the frequency domain, the unshifted version of the data is represented by a series of values S 0  to S N-1 , as shown at  532 , while the shifted version is represented by phase shifted values S 0  to S N-1 e j(N-1)θ , as shown at  534 . 
       FIGS. 6A &amp; 6B  are schematic representations  600  and  650  of precoding for a spatially-multiplexed transmission. In the representation  600 , a first data set  610  for layer 0 and a second data set  612  for layer 1 are acted on by a precoder  620  to generate symbols  630  for transmission via antenna port 0 and symbols  632  for transmission via antenna port 1. In the representation  600 , no CDD is used for the spatially-multiplexed transmission. In the representation  650 , a first data set  660  is acted on by a precoding matrix  662  to generate symbols  670  for transmission (see, e.g., 3GPP TS 36.211 sec. 6.3.4.2.1). If the signal is to be transmitted with CDD, then the data set is acted on by the precoding matrix and a delay matrix  680  to generate the shifted symbols  672  for transmission (see, e.g., 3GPP TS 36.211 sec. 6.3.4.2.2). 
     Example Increase Diversity of Slot Aggregation Using Slot-Specific Cyclic Delay Diversity 
     Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for increasing diversity of transmissions with slot aggregation using slot-specific cyclic delay diversity (CDD). CDD may be a transmit diversity mechanism implemented by applying a different phase delay for each OFDM subcarrier. CDD may be used in spatial multiplexing to increase diversity between the two spatial paths, with each path corresponding to an antenna. One antenna may transmit an original copy of data and the other antenna may transmit the cyclic delayed version of the original data, as shown in  FIG. 4 . The original version and the shifted version may be received together by a receiving entity (e.g., a UE). By adding delays to the copy from one antenna, in the frequency domain, different OFDM symbols in the copy have different phase shifts (that is, the cyclic delay or shift in time domain may be represented by a phase shift in frequency domain). At least some of those phase shifts may help the shifted version and the original version of the signals add up coherently in at least a subset of tones, which boosts the signal power received by the receiver, i.e., improves diversity in the frequency domain. 
     In aspects of the present disclosure, to increase frequency diversity for downlink (DL) transmissions, for different slots in the aggregation, a BS (e.g., a gNB) can use different delay values for different layers (e.g., slot specific CDD). For example, a BS may transmit a 1 st  slot with no CDD (0 delay difference), a 2 nd  slot with a certain value of delay difference between ports. In this way, the channel at each tone is different from slot to slot, due to adding different delay differences across ports. 
     According to aspects of the present disclosure, a delay for each slot may be determined by BS implementation (e.g., random small delays), based on one or more of rules in wireless communications standards (e.g., any of the 3GPP specifications, which are publicly available), signaling received from another device (e.g., a BS may use a delay for each slot requested by a receiving UE), or an indication (e.g., a measurement) of a channel to another device. 
     In aspects of the present disclosure, delay(s) chosen by a BS may be indicated to a receiving UE. 
     According to aspects of the present disclosure, a receiving UE may be notified (e.g., via an indication in a transmission from the BS) that CDD of different values of delay are applied to a transmission. 
     In aspects of the present disclosure, if a UE is not notified that CDD of different values of delay are applied to a transmission, a UE may assume a received channel is the same from slot to slot and try to soft-combine DMRS and/or data from the slots. 
     According to aspects of the present disclosure, slot-specific cyclic delay diversity may be triggered at a BS in response to a UE request. For example, a UE may determine, based on decoding previous slots, that the channel is very frequency flat, and the UE may then request more frequency diversity. 
     According to aspects of the present disclosure, to increase frequency diversity of uplink (UL) transmissions, for different slots in an aggregation, a UE can use different delay values of CDD. 
     In aspects of the present disclosure, a UE may start using different delay values of CDD after receiving an indication from a BS for the UE to start using the different delay values of CDD. The indication from the BS may contain the value of delay differences in each slot for each layer. 
     Additionally or alternatively, a UE may determine whether to start using different delay values of CDD and inform a BS (e.g., a gNB) that the UE is applying slot-specific CDD. 
     According to aspects of the present disclosure, the delay value for UL transmissions may be determined based on network communications standards (e.g., any of the 3GPP specifications, which are publicly available). 
     In aspects of the present disclosure, the delay value for UL transmissions may be specific to a UE implementation, and the UE may report the implementation to a BS. 
     According to aspects of the present disclosure, slot-specific CDD for UL signals may be triggered by the UE requesting to a BS for the UE to begin using slot-specific CDD for UL signals. In aspects of the present disclosure, a UE may request to begin using slot-specific CDD, and if a BS agrees that the UE should begin using slot-specific CDD, the BS sends an indication to the UE to start slot-specific CDD. 
       FIG. 7  is a flow diagram illustrating example operations  700  for wireless communication, in accordance with certain aspects of the present disclosure. The operations  700  may be performed, for example, by a transmitting device (e.g., such as the BS  110   a  in the wireless communication network  100 ). Operations  700  may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor  240  of  FIG. 2 ). Further, the transmission and reception of signals by the BS in operations  700  may be enabled, for example, by one or more antennas (e.g., antennas  234  of  FIG. 2 ). In certain aspects, the transmission and/or reception of signals by the BS may be implemented via a bus interface of one or more processors (e.g., controller/processor  240 ) obtaining and/or outputting signals. 
     The operations  700  may begin, at block  705 , by the transmitting device determining to transmit a signal using cyclic delay diversity (CDD) in a plurality of slots. For example, the transmitting device, such as the BS  110   a  of  FIG. 1 , determines to transmit a signal and one or more phase shifted copies, using CDD, of the signal in multiple slots to a receiving device, such as the UE  120   a  of  FIG. 1 . In some cases, the transmitting device may include a transmit processor such as the transmit processor  220  of  FIG. 2 . The transmit processor  220  may determine the CDD implementation and may operate with the controller processor  240 , which includes the slot aggregation using CDD manager  241 . 
     Operations  700  continue at block  710  with the transmitting device transmitting the signal using a different cyclic delay in each slot of the plurality of slots. For example, the transmitting device, such as the BS  110   a  of  FIG. 1 , transmits the signal to the receiving device, such as the UE  120   a  of  FIG. 1 , using a different cyclic delay in the transmitted signal in each of the plurality of slots. In some cases, the transmit processor  220  and/or the controller/processor  240  of  FIG. 2  may implement the different cyclic delay in the signal to be transmitted. For example, the transmit processor  220  may generate values for the different cyclic delay and implement the cyclic delay in CDD. 
     In some cases, the transmitting device, such as the BS  110   a  of  FIG. 1 , may implement the different delays according to various schemes, such as random small delays. Such delay schemes may be indicated to the UE. In some cases, the delay scheme may be based on certain rules in communication standards. In some cases, the UE may trigger certain delay schemes for an increase of frequency diversity by sending the gNB a request, such as when the UE determines, by decoding previous slots, that the channel has flat or monotonous frequency. 
     Operations  700  performed by the transmitting device, such as a base station (e.g., BS  110   a  of  FIG. 1 ), may apply to either or both downlink and uplink transmissions. For example, during a downlink transmission, the gNB may determine the delay scheme and indicates the chosen delay scheme to the UE. During an uplink transmission, the UE may implement the different delays after receiving the gNB indication. When the UE sends a request for increasing the frequency diversity, for an uplink or a downlink transmission, the UE may first send such request to the gNB, and operate according to the request after receiving acknowledgement from the gNB. 
     According to aspects of the present disclosure, a device performing operations  700  may decide the different cyclic delays based on at least one of a network communications specification (e.g., 3GPP specifications, which are publicly available), signaling received from another device, or a measurement of a channel to the other device. 
     In aspects of the present disclosure, transmitting the signal as in block  710  may include transmitting a same data portion in each slot for an intended recipient to receive using slot aggregation. 
     According to aspects of the present disclosure, a device performing operations  700  may receive a request from an intended recipient of the signal to transmit the signal using CDD, wherein the determining of block  705  is based on the request. In aspects of the present disclosure, the request may indicate the cyclic delays. 
     In aspects of the present disclosure, transmitting the signal as in block  710  may include transmitting the signal on a plurality of layers, and the cyclic delays of block  710  may include a cyclic delay for each of the layers in each of the slots. 
     According to aspects of the present disclosure, the determining of block  705  may be based on an indication of a channel condition (e.g., receiving a negative acknowledgment (NAK), receiving a request to increase transmit power, or a measurement of channel state) between the transmitting device and an intended recipient of the signal. 
     In aspects of the present disclosure, the determining of block  705  may be based on another signal from an intended recipient of the signal. 
     According to aspects of the present disclosure, a device performing operations  700  may transmit an indication of the determination of block  705  to transmit the signal using CDD. In aspects of the present disclosure, the indication may include an indication of the cyclic delays. 
     In aspects of the present disclosure, a device performing operations  700  may be a user equipment (UE) and the signal of blocks  705  and  710  may be an uplink (UL) signal. 
     According to aspects of the present disclosure, a device performing operations  700  may be a base station (BS) and the signal of blocks  705  and  710  may be a downlink (DL) signal. 
       FIG. 8  is a flow diagram illustrating example operations  800  for wireless communication, in accordance with certain aspects of the present disclosure. The operations  800  may be performed, for example, by a receiving device (e.g., such as a UE  120   a  in the wireless communication network  100 ). The operations  800  may be complimentary operations by the receiving device to the operations  800  performed by the transmitting device. Operations  800  may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor  280  of  FIG. 2 ). Further, the transmission and reception of signals by the UE in operations  800  may be enabled, for example, by one or more antennas (e.g., antennas  252  of  FIG. 2 ). In certain aspects, the transmission and/or reception of signals by the UE may be implemented via a bus interface of one or more processors (e.g., controller/processor  280 ) obtaining and/or outputting signals. 
     The operations  800  may begin, at block  805 , by the receiving device determining that a signal from a transmitting device is transmitted using cyclic delay diversity (CDD) in a plurality of slots. For example, the receiving device may be the UE  120   a  of  FIG. 1 . In the example, the UE  120   a  determines that a signal from a transmitting device (e.g., BS  110   a  in  FIG. 1 ) is transmitted using cyclic delay diversity (CDD) in a plurality of slots The UE  120   a  may include the receive processor  258  of  FIG. 2  that determines the signal being transmitted using CDD. In some cases, the receive processor  258  operates with the controller/processor  280 , which includes a slot aggregation using CDD manager  281 . 
     Operations  800  may continue, at block  810 , with the receiving device receiving the signal based on a different cyclic delay in each slot of the plurality of slots. For example, the UE  120   a  of  FIG. 1  receives the signal of block  805  based on a different cyclic delay in each slot of the plurality of slots. In some cases, the receive processor  258  and/or the controller/processor  280  of  FIG. 2  may use CDD to validate the signal on the different cyclic delay in each slot of the plurality of slots. For example, a first slot may not include any CDD, a second slot includes CDD with certain value of delay difference between ports, and a third slot includes CDD with another value of delay difference between ports, and so on. In this way, the channel at each tone is different from slot to slot due to adding difference delay differences across ports. The different cyclic delay then increases frequency diversity for the different slots in the aggregation. 
     Operations  800  performed by the receiving device, such as the UE  120   a , may apply to either or both downlink and uplink transmissions. For example, during a downlink transmission, the transmitting device (e.g., a base station such as gNB) may determine the delay scheme and indicate the chosen delay scheme to the receiving device. During an uplink transmission, the receiving device may implement the different delays after receiving the gNB indication. When the UE sends a request for increasing the frequency diversity, for an uplink or a downlink transmission, the UE may first send such request to the gNB, and operate according to the request after receiving acknowledgement from the gNB. 
     According to aspects of the present disclosure, receiving the signal as in block  810  may include receiving a same data portion in each slot using slot aggregation. 
     In aspects of the present disclosure, a device performing operations  800  may transmit a request to the transmitting device to transmit the signal using CDD, wherein the determining of block  805  may be based on the request. According to aspects of the present disclosure, the request may indicate the cyclic delays of block  810 . 
     According to aspects of the present disclosure, receiving the signal as in block  810  may include receiving the signal on a plurality of layers, and the cyclic delays may include a cyclic delay for each of the layers in each of the slots. 
     In aspects of the present disclosure, the determining of block  805  may be based on an indication of a channel condition (e.g., receiving a negative acknowledgment (NAK), receiving a request to increase transmit power, or a measurement of channel state) between the transmitting device and the receiving device. 
     According to aspects of the present disclosure, the determining of block  805  may be based on another signal from the transmitting device. 
     In aspects of the present disclosure, a device performing operations  800  may receive an indication from the transmitting device that the transmitting device will transmit the signal of blocks  805  and  810  using CDD. According to aspects of the present disclosure, the indication may include an indication of the plurality of cyclic delays. 
     According to aspects of the present disclosure, a device performing operations  800  may soft-combine two or more demodulation reference signals (DMRS), based on the cyclic delays of block  810 , each DMRS included in a different slot of the plurality of slots. 
     In aspects of the present disclosure, the receiving device may be a user equipment (UE) and the signal of blocks  805  and  810  may be a downlink (DL) signal. 
     According to aspects of the present disclosure, the receiving device may be a base station (BS) and the signal of blocks  805  and  810  may be an uplink (UL) signal. 
       FIG. 9  illustrates a communications device  900  that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein, such as the operations illustrated in  FIGS. 7 &amp; 8 . The communications device  900  includes a processing system  902  coupled to a transceiver  908 . The transceiver  908  is configured to transmit and receive signals for the communications device  900  via an antenna  910 , such as the various signals as described herein. The processing system  902  may be configured to perform processing functions for the communications device  900 , including processing signals received and/or to be transmitted by the communications device  900 . 
     The processing system  902  includes a processor  904  coupled to a computer-readable medium/memory  912  via a bus  906 . In certain aspects, the computer-readable medium/memory  912  is configured to store instructions (e.g., computer-executable code) that when executed by the processor  904 , cause the processor  904  to perform the operations illustrated in  FIGS. 7 &amp; 8 , or other operations for performing the various techniques discussed herein for increasing diversity of transmissions with slot aggregation using slot-specific cyclic delay diversity (CDD). In certain aspects, computer-readable medium/memory  912  stores code  914  for determining to transmit a signal using cyclic delay diversity (CDD) in a plurality of slots; code  915  for transmitting the signal using a different cyclic delay in each slot of the plurality of slots; code  916  for determining that a signal from a transmitting device is transmitted using cyclic delay diversity (CDD) in a plurality of slots; and cod  917  for receiving the signal based on a different cyclic delay in each slot of the plurality of slots. In certain aspects, the processor  904  has circuitry configured to implement the code stored in the computer-readable medium/memory  912 . The processor  904  includes circuitry  920  for determining to transmit a signal using cyclic delay diversity (CDD) in a plurality of slots; circuitry  922  for transmitting the signal using a different cyclic delay in each slot of the plurality of slots; circuitry  924  for determining that a signal from a transmitting device is transmitted using cyclic delay diversity (CDD) in a plurality of slots; and circuitry  926  for receiving the signal based on a different cyclic delay in each slot of the plurality of slots. 
     The techniques described herein may be used for various wireless communication technologies, such as NR (e.g., 5G NR), 3GPP Long Term Evolution (LTE), LTE-Advanced (LTE-A), code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), single-carrier frequency division multiple access (SC-FDMA), time division synchronous code division multiple access (TD-SCDMA), and other networks. The terms “network” and “system” are often used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA network may implement a radio technology such as NR (e.g. 5G RA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS). LTE and LTE-A are releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP). cdma2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). NR is an emerging wireless communications technology under development. 
     The techniques described herein may be used for the wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies. For clarity, while aspects may be described herein using terminology commonly associated with 3G, 4G, and/or 5G wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems. 
     In 3GPP, the term “cell” can refer to a coverage area of a Node B (NB) and/or a NB subsystem serving this coverage area, depending on the context in which the term is used. In NR systems, the term “cell” and BS, next generation NodeB (gNB or gNodeB), access point (AP), distributed unit (DU), carrier, or transmission reception point (TRP) may be used interchangeably. A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cells. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscription. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow 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, etc.). A BS for a macro cell may be referred to as a macro BS. A BS for a pico cell may be referred to as a pico BS. A BS for a femto cell may be referred to as a femto BS or a home BS. 
     A UE may also be referred to as a mobile station, a terminal, an access terminal, a subscriber unit, a station, a Customer Premises Equipment (CPE), a cellular phone, a smart phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet computer, a camera, a gaming device, a netbook, a smartbook, an ultrabook, an appliance, a medical device or medical equipment, a biometric sensor/device, a wearable device such as a smart watch, smart clothing, smart glasses, a smart wrist band, smart jewelry (e.g., a smart ring, a smart bracelet, etc.), an entertainment device (e.g., a music device, a video device, a satellite radio, etc.), a vehicular component or sensor, a smart meter/sensor, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium. Some UEs may be considered machine-type communication (MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., that may communicate with a BS, another device (e.g., remote device), or some other entity. A wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as Internet or a cellular network) via a wired or wireless communication link. Some UEs may be considered Internet-of-Things (IoT) devices, which may be narrowband IoT (NB-IoT) devices. 
     Certain wireless networks (e.g., LTE) utilize 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 (K) 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 (K) may be dependent on the system bandwidth. For example, the spacing of the subcarriers may be 15 kHz and the minimum resource allocation (called a “resource block” (RB)) may be 12 subcarriers (or 180 kHz). Consequently, the nominal Fast Fourier Transfer (FFT) size may be equal to 128, 256, 512, 1024 or 2048 for system bandwidth of 1.25, 2.5, 5, 10, or 20 megahertz (MHz), respectively. The system bandwidth may also be partitioned into subbands. For example, a subband may cover 1.08 MHz (e.g.,  6  RBs), and there may be 1, 2, 4, 8, or 16 subbands for system bandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively. In LTE, the basic transmission time interval (TTI) or packet duration is the 1 ms subframe. 
     NR may utilize OFDM with a CP on the uplink and downlink and include support for half-duplex operation using TDD. In NR, a subframe is still 1 ms, but the basic TTI is referred to as a slot. A subframe contains a variable number of slots (e.g., 1, 2, 4, 8, 16, . . . slots) depending on the subcarrier spacing. The NR RB is 12 consecutive frequency subcarriers. NR may support a base subcarrier spacing of 15 KHz and other subcarrier spacing may be defined with respect to the base subcarrier spacing, for example, 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc. The symbol and slot lengths scale with the subcarrier spacing. The CP length also depends on the subcarrier spacing. Beamforming may be supported and beam direction may be dynamically configured. MIMO transmissions with precoding may also be supported. In some examples, MIMO configurations in the DL may support up to 8 transmit antennas with multi-layer DL transmissions up to 8 streams and up to 2 streams per UE. In some examples, multi-layer transmissions with up to 2 streams per UE may be supported. Aggregation of multiple cells may be supported with up to 8 serving cells. 
     In some examples, access to the air interface may be scheduled. A scheduling entity (e.g., a BS) allocates resources for communication among some or all devices and equipment within its service area or cell. The scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more subordinate entities. That is, for scheduled communication, subordinate entities utilize resources allocated by the scheduling entity. Base stations are not the only entities that may function as a scheduling entity. In some examples, a UE may function as a scheduling entity and may schedule resources for one or more subordinate entities (e.g., one or more other UEs), and the other UEs may utilize the resources scheduled by the UE for wireless communication. In some examples, a UE may function as a scheduling entity in a peer-to-peer (P2P) network, and/or in a mesh network. In a mesh network example, UEs may communicate directly with one another in addition to communicating with a scheduling entity. 
     In some examples, two or more subordinate entities (e.g., UEs) may communicate with each other using sidelink signals. Real-world applications of such sidelink communications may include public safety, proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V) communications, Internet of Everything (IoE) communications, IoT communications, mission-critical mesh, and/or various other suitable applications. Generally, a sidelink signal may refer to a signal communicated from one subordinate entity (e.g., UE 1 ) to another subordinate entity (e.g., UE 2 ) without relaying that communication through the scheduling entity (e.g., UE or BS), even though the scheduling entity may be utilized for scheduling and/or control purposes. In some examples, the sidelink signals may be communicated using a licensed spectrum (unlike wireless local area networks, which typically use an unlicensed spectrum). 
     The methods disclosed herein comprise one or more steps or actions for achieving the methods. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims. 
     As used herein, a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c). 
     As used herein, the term “determining” encompasses a wide variety of actions. For example, “determining” may include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure), ascertaining and the like. Also, “determining” may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory) and the like. Also, “determining” may include resolving, selecting, choosing, establishing and the like. 
     The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Unless specifically stated otherwise, the term “some” refers to one or more. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. § 112(f) unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.” 
     The various operations of methods described above may be performed by any suitable means capable of performing the corresponding functions. The means may include various hardware and/or software component(s) and/or module(s), including, but not limited to a circuit, an application specific integrated circuit (ASIC), or processor. Generally, where there are operations illustrated in figures, those operations may have corresponding counterpart means-plus-function components with similar numbering. 
     The various illustrative logical blocks, modules and circuits described in connection with the present disclosure may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any commercially available processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
     If implemented in hardware, an example hardware configuration may comprise a processing system in a wireless node. The processing system may be implemented with a bus architecture. The bus may include any number of interconnecting buses and bridges depending on the specific application of the processing system and the overall design constraints. The bus may link together various circuits including a processor, machine-readable media, and a bus interface. The bus interface may be used to connect a network adapter, among other things, to the processing system via the bus. The network adapter may be used to implement the signal processing functions of the PHY layer. In the case of a user terminal  120  (see  FIG. 1 ), a user interface (e.g., keypad, display, mouse, joystick, etc.) may also be connected to the bus. The bus may also link various other circuits such as timing sources, peripherals, voltage regulators, power management circuits, and the like, which are well known in the art, and therefore, will not be described any further. The processor may be implemented with one or more general-purpose and/or special-purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuitry that can execute software. Those skilled in the art will recognize how best to implement the described functionality for the processing system depending on the particular application and the overall design constraints imposed on the overall system. 
     If implemented in software, the functions may be stored or transmitted over as one or more instructions or code on a computer readable medium. Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Computer-readable media include both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. The processor may be responsible for managing the bus and general processing, including the execution of software modules stored on the machine-readable storage media. A computer-readable storage medium may be coupled to a processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. By way of example, the machine-readable media may include a transmission line, a carrier wave modulated by data, and/or a computer readable storage medium with instructions stored thereon separate from the wireless node, all of which may be accessed by the processor through the bus interface. Alternatively, or in addition, the machine-readable media, or any portion thereof, may be integrated into the processor, such as the case may be with cache and/or general register files. Examples of machine-readable storage media may include, by way of example, RAM (Random Access Memory), flash memory, ROM (Read Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), registers, magnetic disks, optical disks, hard drives, or any other suitable storage medium, or any combination thereof. The machine-readable media may be embodied in a computer-program product. 
     A software module may comprise a single instruction, or many instructions, and may be distributed over several different code segments, among different programs, and across multiple storage media. The computer-readable media may comprise a number of software modules. The software modules include instructions that, when executed by an apparatus such as a processor, cause the processing system to perform various functions. The software modules may include a transmission module and a receiving module. Each software module may reside in a single storage device or be distributed across multiple storage devices. By way of example, a software module may be loaded into RAM from a hard drive when a triggering event occurs. During execution of the software module, the processor may load some of the instructions into cache to increase access speed. One or more cache lines may then be loaded into a general register file for execution by the processor. When referring to the functionality of a software module below, it will be understood that such functionality is implemented by the processor when executing instructions from that software module. 
     Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared (IR), radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Thus, in some aspects computer-readable media may comprise non-transitory computer-readable media (e.g., tangible media). In addition, for other aspects computer-readable media may comprise transitory computer-readable media (e.g., a signal). Combinations of the above should also be included within the scope of computer-readable media. 
     Thus, certain aspects may comprise a computer program product for performing the operations presented herein. For example, such a computer program product may comprise a computer-readable medium having instructions stored (and/or encoded) thereon, the instructions being executable by one or more processors to perform the operations described herein, for example, instructions for performing the operations described herein and illustrated in  FIG. 7  and/or  FIG. 8 . 
     Further, it should be appreciated that modules and/or other appropriate means for performing the methods and techniques described herein can be downloaded and/or otherwise obtained by a user terminal and/or base station as applicable. For example, such a device can be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, various methods described herein can be provided via storage means (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or floppy disk, etc.), such that a user terminal and/or base station can obtain the various methods upon coupling or providing the storage means to the device. Moreover, any other suitable technique for providing the methods and techniques described herein to a device can be utilized. 
     It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the methods and apparatus described above without departing from the scope of the claims.