Patent Publication Number: US-10320693-B2

Title: Method for packet data convergence protocol count synchronization

Description:
PRIORITY CLAIM 
     This application claims priority to and the benefit of Provisional Patent Application No. 62/359,135 filed in the U.S. Patent and Trademark Office on Jul. 6, 2016, the entire content of which is incorporated herein by reference as if fully set forth below in its entirety and for all applicable purposes. 
    
    
     TECHNICAL FIELD 
     The technology discussed below relates generally to wireless communication systems, and more particularly, to Packet Data Convergence Protocol (PDCP) COUNT synchronization. Embodiments can provide techniques for initiating COUNT synchronization in-band or out-of-band. 
     INTRODUCTION 
     In 3rd Generation Partnership Project (3GPP) standards, the Packet Data Convergence Protocol (PDCP) sublayer is located in the radio protocol stack in both the Universal Mobile Telecommunications System (UMTS) and Long Term Evolution (LTE) air interface on top of the Radio Link Control (RLC) sublayer. The PDCP sublayer provides various services, such as transfer of user and control plane data, header compression, ciphering, and integrity protection. The ciphering and deciphering of packets are based on the packet COUNT value in the PDCP header. For example, a packet may be ciphered using a COUNT value generated by the transmitting side PDCP and deciphered using a COUNT value expected by a receiving side. 
     Thus, in order to correctly decipher the packet at the receiver side, the transmitter and receiver must maintain an accurate record of the COUNT value associated with each packet. In principle, the COUNT value is not reused during a session, and therefore the COUNT space is long, e.g., 32 bits in LTE. However, in LTE, for example, the transmitter and the receiver communicate the COUNT value of a packet by including only part of the COUNT value corresponding to the sequence number of a packet in the PDCP header in order to reduce overhead. The sequence number (SN) has a smaller space, e.g. 7 bits or 12 bits. The transmitter and receiver also locally maintain a hyper frame number (HFN), which is incremented by 1 each time the SN wraps around. The COUNT value of a packet may thus be inferred by concatenating the locally maintained HFN with the SN received in the packet. 
     HFNs at both the transmitter and receiver are normally in sync for high data rate applications due to the protection provided by the RLC Acknowledged Mode (AM), requiring an Acknowledged/Not Acknowledged (ACK/NACK) from the receiver for every transmission. However, in next generation (e.g., 5G) networks, the RLC Unacknowledged Mode (UM) may be utilized with high data rate applications on dual connectivity devices for better performance and lower device cost. Therefore, there is a potential risk of losing HFN synchronization between the transmitter and the receiver. For example, when an undetected SN error occurs at the receiver side or the number of lost RLC UM packet data units (PDUs) exceeds the UM SN space, the transmitter and receiver HFNs may become out-of-sync. When HFN de-synchronization occurs, the receiver may incorrectly decipher the packet, resulting in data loss. 
     BRIEF SUMMARY OF SOME EXAMPLES 
     The following presents a simplified summary of one or more aspects of the present disclosure, in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated features of the disclosure, and is intended neither to identify key or critical elements of all aspects of the disclosure nor to delineate the scope of any or all aspects of the disclosure. Its sole purpose is to present some concepts of one or more aspects of the disclosure in a simplified form as a prelude to the more detailed description that is presented later. 
     Various aspects of the present disclosure provide for count synchronization in a wireless communication network. A respective count value may be maintained for each packet transmitted over a wireless connection, where each count value includes a respective hyper frame number and a respective sequence number. To synchronize a current count value associated with a current packet, a count synchronization process may be initiated to transmit at least a current hyper frame number of the current count value over the wireless connection. 
     In one aspect of the disclosure, a method of count synchronization in a wireless communication network is provided. The method includes maintaining a respective count value for each packet transmitted over a wireless connection, where each count value includes a respective hyper frame number and a respective sequence number. The method further includes initiating a count synchronization of a current count value, where the current count value corresponds to the respective count value of a current packet, and transmitting at least a current hyper frame number of the current count value over the wireless connection to synchronize the current count value. 
     Another aspect of the disclosure provides an apparatus configured for count synchronization in a wireless communication network. The apparatus includes a processor, a memory communicatively coupled to the processor, and a transceiver communicatively coupled to the processor. The processor is configured to maintain a respective count value for each packet transmitted over a wireless connection, where each count value includes a respective hyper frame number and a respective sequence number. The processor is further configured to initiate a count synchronization of a current count value, where the current count value corresponds to the respective count value of a current packet, and transmit at least a current hyper frame number of the current count value over the wireless connection to synchronize the current count value. 
     Another aspect of the disclosure provides an apparatus configured for count synchronization in a wireless communication network. The apparatus includes means for maintaining a respective count value for each packet transmitted over a wireless connection, where each count value includes a respective hyper frame number and a respective sequence number. The apparatus further includes means for initiating a count synchronization of a current count value, where the current count value corresponds to the respective count value of a current packet, and means for transmitting at least a current hyper frame number of the current count value over the wireless connection to synchronize the current count value. 
     Examples of additional aspects of the disclosure follow. In some aspects of the present disclosure, the current packet is received for transmission over the wireless connection. In some examples, a full count value is included in a header of the current packet in response to initiating the count synchronization, where the full count value includes the current hyper frame number and a current sequence number. The current packet including the full count value in the header may then be transmitted over the wireless connection. An indication that the current packet includes the full count value may also be included in the current packet. In some examples, the header may include a Packet Data Convergence Protocol (PDCP) header, a Radio Link Control (RLC) header, or a Media Access Control (MAC) header. 
     In some aspects of the present disclosure, the current packet may include a short count value in a header thereof, where the short count value includes only a current sequence number. In some aspects of the present disclosure, the current hyper frame number and a current sequence number of the current count value may be transmitted over the wireless connection to synchronize the current count value. 
     In some aspects of the present disclosure, an out-of-sync flag may be received over the wireless connection in response to transmitting at least the current hyper frame number of the current count value. In response to receiving the out-of-sync flag, data transmission and reception may be suspended over the wireless connection, a new hyper frame number may be transmitted over the wireless connection to synchronize the current count value, and data transmission and reception may then be resumed over the wireless connection. In some examples, the new hyper frame number exceeds the current hyper frame number. In some examples, a hyper frame number synchronization complete indication may be received over the wireless connection prior to resuming data transmission and reception. 
     In some aspects of the present disclosure, at least the current hyper frame number of the current count value may be transmitted within a control message. In some examples, the control message includes a Radio Resource Control (RRC) message, a Packet Data Convergence Protocol (PDCP) HFN packet data unit (PDU), a Radio Link Control (RLC) HFN PDU, or a Media Access Control (MAC) Control Element (CE). In some examples, an integrity protection signature may also be included within the PDCP HFN PDU, the RLC HFN PDU or the MAC CE including the current hyper frame number. In some examples, a control PDU sequence number may also be included within the PDCP HFN PDU, the RLC HFN PDU or the MAC CE including the current hyper frame number to enable retransmission and ciphering of the control message. 
     In some aspects of the present disclosure, the count synchronization may be initiated based on a number of packets transmitted after a previous count synchronization, upon expiration of a timer, in response to a fade event, or in response to a packet loss event. In some examples, a counter may be initialized in response to the previous count synchronization to count transmitted packets, and the count synchronization may be initiated when the counter reaches a predetermined number of the transmitted packets. In some examples, the timer may be initialized in response to the previous count synchronization. In some examples, the count synchronization may be triggered in response to determining a signal-to-noise ratio has dropped below a threshold. In some examples, the count synchronization may be triggered in response to determining a number of lost packets exceeds a threshold. 
     These and other aspects of the invention will become more fully understood upon a review of the detailed description, which follows. Other aspects, features, and embodiments of the present invention will become apparent to those of ordinary skill in the art, upon reviewing the following description of specific, exemplary embodiments of the present invention in conjunction with the accompanying figures. While features of the present invention may be discussed relative to certain embodiments and figures below, all embodiments of the present invention can include one or more of the advantageous features discussed herein. In other words, while one or more embodiments may be discussed as having certain advantageous features, one or more of such features may also be used in accordance with the various embodiments of the invention discussed herein. In similar fashion, while exemplary embodiments may be discussed below as device, system, or method embodiments it should be understood that such exemplary embodiments can be implemented in various devices, systems, and methods. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a conceptual diagram illustrating an example of a radio access network. 
         FIG. 2  is a diagram illustrating an example of a radio protocol architecture for the user and control plane. 
         FIG. 3  is a diagram illustrating an example of a format of a Packet Data Convergence Protocol (PDCP) Packet Data Unit (PDU) in accordance with aspects of the disclosure. 
         FIG. 4  is a diagram illustrating an example of a COUNT value in accordance with aspects of the disclosure. 
         FIG. 5  is a block diagram illustrating an example of a hardware implementation for a wireless communication device employing a processing system, according to aspects of the disclosure. 
         FIG. 6  is a diagram illustrating an example of a format of a packet including a full COUNT value in accordance with aspects of the disclosure. 
         FIG. 7  is a diagram illustrating an example of a format of a control message including at least the hyper frame number (HFN) in accordance with aspects of the disclosure. 
         FIG. 8  is a flow chart of a method of count synchronization according to some aspects of the disclosure. 
         FIG. 9  is a flow chart of a method of in-band count synchronization according to some aspects of the disclosure. 
         FIG. 10  is a flow chart of a method of out-of-band count synchronization according to some aspects of the disclosure. 
         FIG. 11  is a packet flow diagram illustrating an example of in-band count synchronization according to some aspects of the disclosure. 
         FIG. 12  is a packet flow diagram illustrating an example of out-of-band count synchronization according to some aspects of the disclosure. 
         FIG. 13  is a flow chart of a method of initiating count synchronization according to some aspects of the disclosure. 
         FIG. 14  is a flow chart of another method of initiating count synchronization according to some aspects of the disclosure. 
         FIG. 15  is a flow chart of another method of initiating count synchronization according to some aspects of the disclosure. 
         FIG. 16  is a flow chart of another method of initiating count synchronization according to some aspects of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts. 
     The various concepts presented throughout this disclosure may be implemented across a broad variety of telecommunication systems, network architectures, and communication standards. Referring now to  FIG. 1 , as an illustrative example without limitation, a simplified schematic illustration of a radio access network  100  is provided. The radio access network  100  may be a legacy access network or a next generation access network. In addition, one or more nodes in the radio access network  100  may be next generation nodes or legacy nodes. 
     As used herein, the term legacy access network refers to an access network employing a third generation (3G) wireless communication technology based on a set of standards that complies with the International Mobile Telecommunications-2000 (IMT-2000) specifications or a fourth generation (4G) wireless communication technology based on a set of standards that comply with the International Mobile Telecommunications Advanced (ITU-Advanced) specification. For example, some the standards promulgated by the 3rd Generation Partnership Project (3GPP) and the 3rd Generation Partnership Project 2 (3GPP2) may comply with IMT-2000 and/or ITU-Advanced. Examples of such legacy standards defined by the 3rd Generation Partnership Project (3GPP) include, but are not limited to, Long-Term Evolution (LTE), LTE-Advanced, Evolved Packet System (EPS), and Universal Mobile Telecommunication System (UMTS). Additional examples of various radio access technologies based on one or more of the above-listed 3GPP standards include, but are not limited to, Universal Terrestrial Radio Access (UTRA), Evolved Universal Terrestrial Radio Access (eUTRA), General Packet Radio Service (GPRS) and Enhanced Data Rates for GSM Evolution (EDGE). Examples of such legacy standards defined by the 3rd Generation Partnership Project 2 (3GPP2) include, but are not limited to, CDMA2000 and Ultra Mobile Broadband (UMB). Other examples of standards employing 3G/4G wireless communication technology include the IEEE 802.16 (WiMAX) standard and other suitable standards. 
     As further used herein, the term next generation access network refers to an access network employing a fifth generation (5G) wireless communication technology based on a set of standards that complies with the guidelines set forth in the 5G White Paper published by the Next Generation Mobile Networks (NGMN) Alliance on Feb. 17, 2015. For example, standards that may be defined by the 3GPP following LTE-Advanced or by the 3GPP2 following CDMA2000 may comply with the NGMN Alliance 5G White Paper. One example of a next generation access network is the New Radio (NR) access network. 
     The geographic region covered by the radio access network  100  may be divided into a number of cellular regions (cells) that can be uniquely identified by a user equipment (UE) based on an identification broadcasted over a geographical from one access point or base station.  FIG. 1  illustrates macrocells  102 ,  104 , and  106 , and a small cell  108 , each of which may include one or more sectors. A sector is a sub-area of a cell. All sectors within one cell are served by the same base station. A radio link within a sector can be identified by a single logical identification belonging to that sector. In a cell that is divided into sectors, the multiple sectors within a cell can be formed by groups of antennas with each antenna responsible for communication with UEs in a portion of the cell. 
     In general, a base station (BS) serves each cell. Broadly, a base station is a network element in a radio access network responsible for radio transmission and reception in one or more cells to or from a UE. A BS may also be referred to by those skilled in the art as a base transceiver station (BTS), a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), an access point (AP), a Node B (NB), an eNode B (eNB), a gNodeB (gNB) or some other suitable terminology. 
     In  FIG. 1 , two high-power base stations  110  and  112  are shown in cells  102  and  104 ; and a third high-power base station  114  is shown controlling a remote radio head (RRH)  116  in cell  106 . That is, a base station can have an integrated antenna or can be connected to an antenna or RRH by feeder cables. In the illustrated example, the cells  102 ,  104 , and  106  may be referred to as macrocells, as the high-power base stations  110 ,  112 , and  114  support cells having a large size. Further, a low-power base station  118  is shown in the small cell  108  (e.g., a microcell, picocell, femtocell, home base station, home Node B, home eNode B, etc.) which may overlap with one or more macrocells. In this example, the cell  108  may be referred to as a small cell, as the low-power base station  118  supports a cell having a relatively small size. Cell sizing can be done according to system design as well as component constraints. It is to be understood that the radio access network  100  may include any number of wireless base stations and cells. Further, a relay node may be deployed to extend the size or coverage area of a given cell. The base stations  110 ,  112 ,  114 ,  118  provide wireless access points to a core network for any number of mobile apparatuses. 
       FIG. 1  further includes a quadcopter or drone  120 , which may be configured to function as a base station. That is, in some examples, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile base station such as the quadcopter  120 . 
     In general, base stations may include a backhaul interface for communication with a backhaul portion of the network. The backhaul may provide a link between a base station and a core network, and in some examples, the backhaul may provide interconnection between the respective base stations. The core network is a part of a wireless communication system that is generally independent of the radio access technology used in the radio access network. Various types of backhaul interfaces may be employed, such as a direct physical connection, a virtual network, or the like using any suitable transport network. Some base stations may be configured as integrated access and backhaul (IAB) nodes, where the wireless spectrum may be used both for access links (i.e., wireless links with UEs), and for backhaul links. This scheme is sometimes referred to as wireless self-backhauling. By using wireless self-backhauling, rather than requiring each new base station deployment to be outfitted with its own hard-wired backhaul connection, the wireless spectrum utilized for communication between the base station and UE may be leveraged for backhaul communication, enabling fast and easy deployment of highly dense small cell networks. 
     The radio access network  100  is illustrated supporting wireless communication for multiple mobile apparatuses. A mobile apparatus is commonly referred to as user equipment (UE) in standards and specifications promulgated by the 3rd Generation Partnership Project (3GPP), but may also be referred to by those skilled in the art as a mobile station (MS), a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal (AT), a mobile terminal, a wireless terminal, a remote terminal, a handset, a terminal, a user agent, a mobile client, a client, or some other suitable terminology. A UE may be an apparatus that provides a user with access to network services. 
     Within the present document, a “mobile” apparatus need not necessarily have a capability to move, and may be stationary. The term mobile apparatus or mobile device broadly refers to a diverse array of devices and technologies. For example, some non-limiting examples of a mobile apparatus include a mobile, a cellular (cell) phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal computer (PC), a notebook, a netbook, a smartbook, a tablet, a personal digital assistant (PDA), and a broad array of embedded systems, e.g., corresponding to an “Internet of things” (IoT). A mobile apparatus may additionally be an automotive or other transportation vehicle, a remote sensor or actuator, a robot or robotics device, a satellite radio, a global positioning system (GPS) device, an object tracking device, a drone, a multi-copter, a quad-copter, a remote control device, a consumer and/or wearable device, such as eyewear, a wearable camera, a virtual reality device, a smart watch, a health or fitness tracker, a digital audio player (e.g., MP3 player), a camera, a game console, etc. A mobile apparatus may additionally be a digital home or smart home device such as a home audio, video, and/or multimedia device, an appliance, a vending machine, intelligent lighting, a home security system, a smart meter, etc. A mobile apparatus may additionally be a smart energy device, a security device, a solar panel or solar array, a municipal infrastructure device controlling electric power (e.g., a smart grid), lighting, water, etc.; an industrial automation and enterprise device; a logistics controller; agricultural equipment; military defense equipment, vehicles, aircraft, ships, and weaponry, etc. Still further, a mobile apparatus may provide for connected medicine or telemedicine support, i.e., health care at a distance. Telehealth devices may include telehealth monitoring devices and telehealth administration devices, whose communication may be given preferential treatment or prioritized access over other types of information, e.g., in terms of prioritized access for transport of critical service user data traffic, and/or relevant QoS for transport of critical service user data traffic. 
     Within the radio access network  100 , the cells may include UEs that may be in communication with one or more sectors of each cell. For example, UEs  122  and  124  may be in communication with base station  110 ; UEs  126  and  128  may be in communication with base station  112 ; UEs  130  and  132  may be in communication with base station  114  by way of RRH  116 ; UE  134  may be in communication with low-power base station  118 ; and UE  136  may be in communication with mobile base station  120 . Here, each base station  110 ,  112 ,  114 ,  118 , and  120  may be configured to provide an access point to a core network (not shown) for all the UEs in the respective cells. 
     In another example, a mobile network node (e.g., quadcopter  120 ) may be configured to function as a UE. For example, the quadcopter  120  may operate within cell  102  by communicating with base station  110 . In some aspects of the disclosure, two or more UE (e.g., UEs  126  and  128 ) may communicate with each other using peer to peer (P2P) or sidelink signals  127  without relaying that communication through a base station (e.g., base station  112 ). 
     Unicast or broadcast transmissions of control information and/or traffic information (e.g., user data traffic) from a base station (e.g., base station  110 ) to one or more UEs (e.g., UEs  122  and  124 ) may be referred to as downlink (DL) transmission, while transmissions of control information and/or traffic information originating at a UE (e.g., UE  122 ) may be referred to as uplink (UL) transmissions. In addition, the uplink and/or downlink control information and/or traffic information may be time-divided into frames, subframes, slots, mini-slots and/or symbols. As used herein, a symbol may refer to a unit of time that, in an orthogonal frequency division multiplexed (OFDM) waveform, carries one resource element (RE) per sub-carrier. A slot may carry 7 or 14 OFDM symbols. A mini-slot may carry less than 7 OFDM symbols or less than 14 OFDM symbols. A subframe may refer to a duration of 1 ms. Multiple subframes or slots may be grouped together to form a single frame or radio frame. Of course, these definitions are not required, and any suitable scheme for organizing waveforms may be utilized, and various time divisions of the waveform may have any suitable duration. 
     The air interface in the radio access network  100  may utilize one or more multiplexing and multiple access algorithms to enable simultaneous communication of the various devices. For example, multiple access for uplink (UL) or reverse link transmissions from UEs  122  and  124  to base station  110  may be provided utilizing time division multiple access (TDMA), code division multiple access (CDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), discrete Fourier transform (DFT)-spread OFDMA or single-carrier FDMA (DFT-s-OFDMA or SC-FDMA), sparse code multiple access (SCMA), resource spread multiple access (RSMA), or other suitable multiple access schemes. Further, multiplexing downlink (DL) or forward link transmissions from the base station  110  to UEs  122  and  124  may be provided utilizing time division multiplexing (TDM), code division multiplexing (CDM), frequency division multiplexing (FDM), orthogonal frequency division multiplexing (OFDM), sparse code multiplexing (SCM), or other suitable multiplexing schemes. 
     Further, the air interface in the radio access network  100  may utilize one or more duplexing algorithms Duplex refers to a point-to-point communication link where both endpoints can communicate with one another in both directions. Full duplex means both endpoints can simultaneously communicate with one another. Half duplex means only one endpoint can send information to the other at a time. In a wireless link, a full duplex channel generally relies on physical isolation of a transmitter and receiver, and suitable interference cancellation technologies. Full duplex emulation is frequently implemented for wireless links by utilizing frequency division duplex (FDD) or time division duplex (TDD). In FDD, transmissions in different directions operate at different carrier frequencies. In TDD, transmissions in different directions on a given channel are separated from one another using time division multiplexing. That is, at some times the channel is dedicated for transmissions in one direction, while at other times the channel is dedicated for transmissions in the other direction, where the direction may change very rapidly, e.g., several times per subframe. 
     In the radio access network  100 , the ability for a UE to communicate while moving, independent of their location, is referred to as mobility. The various physical channels between the UE and the radio access network are generally set up, maintained, and released under the control of a mobility management entity (MME). In various aspects of the disclosure, a radio access network  100  may utilize DL-based mobility or UL-based mobility to enable mobility and handovers (i.e., the transfer of a UE&#39;s connection from one radio channel to another). In a network configured for DL-based mobility, during a call with a scheduling entity, or at any other time, a UE may monitor various parameters of the signal from its serving cell as well as various parameters of neighboring cells. Depending on the quality of these parameters, the UE may maintain communication with one or more of the neighboring cells. During this time, if the UE moves from one cell to another, or if signal quality from a neighboring cell exceeds that from the serving cell for a given amount of time, the UE may undertake a handoff or handover from the serving cell to the neighboring (target) cell. For example, UE  124  may move from the geographic area corresponding to its serving cell  102  to the geographic area corresponding to a neighbor cell  106 . When the signal strength or quality from the neighbor cell  106  exceeds that of its serving cell  102  for a given amount of time, the UE  124  may transmit a reporting message to its serving base station  110  indicating this condition. In response, the UE  124  may receive a handover command, and the UE may undergo a handover to the cell  106 . 
     In a network configured for UL-based mobility, UL reference signals from each UE may be utilized by the network to select a serving cell for each UE. In some examples, the base stations  110 ,  112 , and  114 / 116  may broadcast unified synchronization signals (e.g., unified Primary Synchronization Signals (PSSs), unified Secondary Synchronization Signals (SSSs) and unified Physical Broadcast Channels (PBCH)). The UEs  122 ,  124 ,  126 ,  128 ,  130 , and  132  may receive the unified synchronization signals, derive the carrier frequency and subframe/slot timing from the synchronization signals, and in response to deriving timing, transmit an uplink pilot or reference signal. The uplink pilot signal transmitted by a UE (e.g., UE  124 ) may be concurrently received by two or more cells (e.g., base stations  110  and  114 / 116 ) within the radio access network  100 . Each of the cells may measure a strength of the pilot signal, and the access network (e.g., one or more of the base stations  110  and  114 / 116  and/or a central node within the core network) may determine a serving cell for the UE  124 . As the UE  124  moves through the radio access network  100 , the network may continue to monitor the uplink pilot signal transmitted by the UE  124 . When the signal strength or quality of the pilot signal measured by a neighboring cell exceeds that of the signal strength or quality measured by the serving cell, the network  100  may handover the UE  124  from the serving cell to the neighboring cell, with or without informing the UE  124 . 
     Although the synchronization signal transmitted by the base stations  110 ,  112 , and  114 / 116  may be unified, the synchronization signal may not identify a particular cell, but rather may identify a zone of multiple cells operating on the same frequency and/or with the same timing. The use of zones in 5G networks or other next generation communication networks enables the uplink-based mobility framework and improves the efficiency of both the UE and the network, since the number of mobility messages that need to be exchanged between the UE and the network may be reduced. 
     In various implementations, the air interface in the radio access network  100  may utilize licensed spectrum, unlicensed spectrum, or shared spectrum. Licensed spectrum provides for exclusive use of a portion of the spectrum, generally by virtue of a mobile network operator purchasing a license from a government regulatory body. Unlicensed spectrum provides for shared use of a portion of the spectrum without need for a government-granted license. While compliance with some technical rules is generally still required to access unlicensed spectrum, generally, any operator or device may gain access. Shared spectrum may fall between licensed and unlicensed spectrum, wherein technical rules or limitations may be required to access the spectrum, but the spectrum may still be shared by multiple operators and/or multiple RATs. For example, the holder of a license for a portion of licensed spectrum may provide licensed shared access (LSA) to share that spectrum with other parties, e.g., with suitable licensee-determined conditions to gain access. 
     In some examples, access to the air interface may be scheduled, wherein a scheduling entity (e.g., a base station) allocates resources (e.g., time—frequency resources) for communication among some or all devices and equipment within its service area or cell. Within the present disclosure, as discussed further below, the scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more scheduled entities. That is, for scheduled communication, UEs or scheduled entities utilize resources allocated by the scheduling entity. 
     Base stations are not the only entities that may function as a scheduling entity. That is, in some examples, a UE may function as a scheduling entity, scheduling resources for one or more scheduled entities (e.g., one or more other UEs). In other examples, sidelink signals may be used between UEs without necessarily relying on scheduling or control information from a base station. For example, UE  138  is illustrated communicating with UEs  140  and  142 . In some examples, the UE  138  is functioning as a scheduling entity or a primary sidelink device, and UEs  140  and  142  may function as a scheduled entity or a non-primary (e.g., secondary) sidelink device. In still another example, a UE may function as a scheduling entity in a device-to-device (D2D), peer-to-peer (P2P), or vehicle-to-vehicle (V2V) network, and/or in a mesh network. In a mesh network example, UEs  140  and  142  may optionally communicate directly with one another in addition to communicating with the scheduling entity  138 . 
     The radio protocol architecture for a radio access network, such as the radio access network  100  shown in  FIG. 1 , may take on various forms depending on the particular application. An example for an LTE radio access network will now be presented with reference to  FIG. 2 .  FIG. 2  is a conceptual diagram illustrating an example of the radio protocol architecture for the user and control planes. 
     As illustrated in  FIG. 2 , the radio protocol architecture for the UE and the eNB includes three layers: Layer 1, Layer 2, and Layer 3. Layer 1 is the lowest layer and implements various physical layer signal processing functions. Layer 1 will be referred to herein as the physical layer  206 . Layer 2 (L2 layer)  208  is above the physical layer  206  and is responsible for the link between the UE and eNB over the physical layer  206 . 
     In the user plane, the L2 layer  208  includes a media access control (MAC) sublayer  210 , a radio link control (RLC) sublayer  212 , and a packet data convergence protocol (PDCP)  214  sublayer, which are terminated at the eNB on the network side. Although not shown, the UE may have several upper layers above the L2 layer  208  including a network layer (e.g., IP layer) that is terminated at the Packet Data Network (PDN) gateway on the network side, and an application layer that is terminated at the other end of the connection (e.g., far end UE, server, etc.). 
     The PDCP sublayer  214  provides multiplexing between different radio bearers and logical channels. The PDCP sublayer  214  also provides header compression for upper layer data packets to reduce radio transmission overhead, security by ciphering the data packets, and handover support for UEs between eNBs. The RLC sublayer  212  provides segmentation and reassembly of upper layer data packets, retransmission of lost data packets, and reordering of data packets to compensate for out-of-order reception due to hybrid automatic repeat request (HARQ). The MAC sublayer  210  provides multiplexing between logical and transport channels. The MAC sublayer  210  is also responsible for allocating the various radio resources (e.g., resource blocks) in one cell among the UEs. The MAC sublayer  210  is also responsible for HARQ operations. The physical layer  206  is responsible for transmitting and receiving data on physical channels (e.g., within slots). 
     In the control plane, the radio protocol architecture for the UE and eNB is substantially the same for the physical layer  206  and the L2 layer  208  with the exception that there is no header compression function for the control plane. The control plane also includes a radio resource control (RRC) sublayer  216  in Layer 3. The RRC sublayer  216  is responsible for obtaining radio resources (i.e., radio bearers) and for configuring the lower layers using RRC signaling between the eNB and the UE. 
     In general, packets received by a sublayer from another sublayer may be referred to as Service Data Units (SDUs), while packets output from a sublayer to another sublayer may be referred to as Protocol Data Units (PDUs). For example, packets received by the PDCP sublayer  214  from an upper layer may be referred to as PDCP SDUs, and packets output from the PDCP sublayer  214  to the RLC sublayer may be referred to as PDCP PDUs or RLC SDUs. 
     An example of a PDCP packet data unit (PDU) format is illustrated in  FIG. 3 . The PDCP PDU format  300  includes a header  302  and body  304 . The header  302  includes a D/C field  306  and SN field  308 . The D/C field  306  is located within a first octet  312   a  and may include, for example, a single bit for indicating whether the PCDP PDU contains user plane data or control plane data. In the example shown in  FIG. 3 , the SN field  308  occupies the remainder of the first octet  312   a , along with a second octet  312   b . The SN field  308  contains the sequence number (SN) of the PDCP PDU. In some examples, the SN may contain 7 bits or 12 bits. The body  304  contains uncompressed or compressed user or control plane data  310  and may include one or more octets (only one of which octet  312   c  is shown for simplicity). 
     In order to accurately cipher and decipher the PDCP PDU  300 , both the transmitter and receiver involved in a session over a wireless connection must have knowledge of the full COUNT value. Referring now to  FIG. 4 , the COUNT value  400  includes a Hyper Frame Number (HFN)  402  and a Sequence Number (SN)  404 . Since the COUNT value is not reused during a session, the COUNT space is long, e.g., 32 bits in LTE. However, as shown in  FIG. 3 , only the SN of the PDCP PDU is included in the PDCP header  302  in order to reduce overhead. The transmitter and receiver each locally maintain the HFN  402  and increment the HFN  402  by one each time the SN  404  wraps around. The COUNT value  400  of a PDCP PDU may thus be inferred or generated by concatenating the locally maintained HFN  402  with the SN  404  received in the SN field  308  of the PDCP header  302 . 
     In various aspects of the disclosure, to ensure the HFNs  402  at both the transmitter and receiver are in sync, the transmitter may initiate or trigger a COUNT synchronization process. During count synchronization, the transmitter transmits the current HFN indicated or maintained locally on the transmitter to the receiver to enable the receiver to reset and/or synchronize the HFN locally on the receiver. In some examples, the HFN is transmitted together with the current SN. In some examples, the transmitter and receiver may each be embodied within a respective wireless communication device, such as a user equipment (UE), base station (eNB or gNB) or other device capable of communicating wirelessly with other devices. 
       FIG. 5  is a conceptual diagram illustrating an example of a hardware implementation for an exemplary wireless communication device  500  employing a processing system  514 . For example, the wireless communication device  500  may be a user equipment (UE), a base station, or any other suitable apparatus or means for wireless communication. 
     The wireless communication device  500  may be implemented with a processing system  514  that includes one or more processors  504 . Examples of processors  504  include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. In various examples, the wireless communication device  500  may be configured to perform any one or more of the functions described herein. That is, the processor  504 , as utilized in a wireless communication device  500 , may be used to implement any one or more of the processes described below and illustrated in  FIGS. 6-10 . 
     In this example, the processing system  514  may be implemented with a bus architecture, represented generally by the bus  502 . The bus  502  may include any number of interconnecting buses and bridges depending on the specific application of the processing system  514  and the overall design constraints. The bus  502  communicatively couples together various circuits including one or more processors (represented generally by the processor  504 ), a memory  505 , and computer-readable media (represented generally by the computer-readable medium  506 ). The bus  502  may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further. A bus interface  508  provides an interface between the bus  502  and a transceiver  510 . The transceiver  510  provides a means for communicating with various other apparatus over a transmission medium (e.g., air). For example, the transceiver  510  may include a transmitter  520  configured to transmit a signal (e.g., control and/or user data traffic) over a wireless connection to another wireless communication device and a receiver  530  configured to receive a signal (e.g., control and/or user data traffic) over the wireless connection from the other wireless communication device. Depending upon the nature of the apparatus, a user interface  512  (e.g., keypad, display, speaker, microphone, joystick) may also be provided. 
     The processor  504  is responsible for managing the bus  502  and general processing, including the execution of software stored on the computer-readable medium  506 . The software, when executed by the processor  504 , causes the processing system  514  to perform the various functions described below for any particular apparatus. The computer-readable medium  506  and the memory  505  may also be used for storing data that is manipulated by the processor  504  when executing software. 
     One or more processors  504  in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The software may reside on a computer-readable medium  506 . The computer-readable medium  506  may be a non-transitory computer-readable medium. A non-transitory computer-readable medium includes, by way of example, a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., a compact disc (CD) or a digital versatile disc (DVD)), a smart card, a flash memory device (e.g., a card, a stick, or a key drive), a random access memory (RAM), a read only memory (ROM), a programmable ROM (PROM), an erasable PROM (EPROM), an electrically erasable PROM (EEPROM), a register, a removable disk, and any other suitable medium for storing software and/or instructions that may be accessed and read by a computer. The computer-readable medium may also include, by way of example, a carrier wave, a transmission line, and any other suitable medium for transmitting software and/or instructions that may be accessed and read by a computer. The computer-readable medium  506  may reside in the processing system  514 , external to the processing system  514 , or distributed across multiple entities including the processing system  514 . The computer-readable medium  506  may be embodied in a computer program product. By way of example, a computer program product may include a computer-readable medium in packaging materials. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system. 
     In some aspects of the disclosure, the processor  504  may include circuitry configured for various functions. For example, the processor  504  may include communication circuitry  542 . The communication circuitry  542  may include one or more hardware components that provide the physical structure that performs various processes related to wireless communication (e.g., signal reception and/or signal transmission) as described herein. The communication circuitry  542  may operate in coordination with communication software  552 . The processor  504  may also include signal processing circuitry  544 . The signal processing circuitry  544  may include one or more hardware components that provide the physical structure that performs various processes related to signal processing (e.g., processing a received signal and/or processing a signal for transmission) as described herein. The signal processing circuitry  544  may operate in coordination with signal processing software  554 . 
     In various aspects of the disclosure, the processor  504  may further include PDCP processing circuitry  546  configured to process Service Data Units (SDUs) received from adjacent layers in the radio protocol stack. In some examples, upon reception of a PDCP SDU from an upper sublayer, the PDCP processing circuitry  546  may associate a Sequence Number (SN) corresponding to the next SN in a session to the PDCP SDU. The PDCP processing circuitry  546  may further perform header compression, integrity protection and ciphering of the PDCP SDU using a COUNT value for the PDCP SDU. The COUNT value may correspond to the concatenation of a current Hyper Frame Number (HFN) maintained locally (e.g., in memory  505 ) and the SN associated with the PDCP SDU. The PDCP processing circuitry  546  may further increment the next SN by one upon assigning the current SN to the PDCP PDU. However, if the next SN exceeds the maximum SN, the processing circuitry  546  may reset the next SN to 0 and increment the HFN by one. The PDCP processing circuitry  546  may then output the resulting PDCP Packet Data Unit (PDU) to a lower sublayer (e.g., the RLC sublayer  212  shown in  FIG. 2 ). 
     In some examples, upon reception of a PDCP SDU containing an SN field from a lower sublayer, the PDCP processing circuitry  546  may decipher the PDCP SDU and verify the integrity of the PDCP SDU (if applicable) using the COUNT value (e.g., the concatenation of the current HFN maintained locally and the SN included within the PDCP SDU). The PDCP processing circuitry  546  may further increment the next SN by one. However, if the next SN exceeds the maximum SN, the processing circuitry  546  may reset the next SN to 0 and increment the HFN by one. The PDCP processing circuitry  546  may then output the resulting PDCP Packet Data Unit (PDU) to an upper sublayer (e.g., the RRC sublayer  216  shown in  FIG. 2 ). The PDCP processing circuitry  546  may operate in coordination with PDCP processing software  556 . 
     The processor  504  may further include count synchronization circuitry  548  configured to initiate or trigger a COUNT synchronization with another wireless communication device in wireless communication with the wireless communication device  500 . For example, the wireless communication device  500  may be engaged in a session with the other wireless communication device over a wireless connection (e.g., over an air interface). During the session, each packet transmitted between the wireless communication device  500  and the other wireless communication device may have a COUNT value (e.g., a combination of an HFN and SN) assigned thereto that uniquely identifies the packet in the sequence of packets transmitted between the wireless communication devices. In some examples, the COUNT value is not reused during a session, and therefore, the number of bits for the COUNT value may be large, e.g., 32 bits. However, to reduce overhead, only the SN of the COUNT value, which may be 7 or 12 bits, may be transmitted in the header of the packet. The HFN is retained locally (e.g., in memory  505 ) on both of the wireless communication devices. 
     When operating in an Unacknowledged Mode (UM) (e.g., HARQ UM), there may be a potential risk of losing HFN synchronization between the wireless communication devices. To ensure the HFN remains synchronized on both the wireless communication device  500  and the other wireless communication device during the session, the count synchronization circuitry  548  may be configured to periodically or in response to a trigger, initiate a COUNT synchronization with the other wireless communication device. For example, the count synchronization circuitry  548  may initiate a COUNT synchronization based on the number of packets transmitted after a previous COUNT synchronization, upon expiration of a timer, in response to a fade event, or in response to a packet loss event. 
     In some examples, the count synchronization circuitry  548  may initialize a counter  515  in response to completion of a previous COUNT synchronization in order to count the packets transmitted after completion of the previous COUNT synchronization. The counter  515  may be maintained, for example, in memory  505 . The count synchronization circuitry  548  may then initiate the COUNT synchronization when the counter  515  reaches a predetermined number of transmitted packets. The number of transmitted packets may correspond to the number of packets transmitted by the wireless communication device  500  during the session, the number of packets received by the wireless communication device  500  (e.g., packets transmitted by the other wireless communication device) during the session or the total number of packets transmitted and received by the wireless communication device  500  (e.g., packets transmitted by both the wireless communication device  500  and the other wireless communication device) during the session. 
     In some examples, the count synchronization circuitry  548  may initialize a timer  516  in response to completion of a previous COUNT synchronization. The timer  516  may be maintained, for example, in memory  505 . The count synchronization circuitry  548  may then initiate a new COUNT synchronization upon expiration of the timer  516 . 
     In some examples, the count synchronization circuitry  548  may trigger the COUNT synchronization in response to a fade event. For example, the count synchronization circuitry  548  may determine that a signal-to-noise ratio of the wireless connection has dropped below a threshold (T)  517 , and thus, may initiate a COUNT synchronization. In some examples, the count synchronization circuitry  548  may trigger the COUNT synchronization in response to a packet loss event. For example, the count synchronization circuitry  548  may trigger a COUNT synchronization in response to determining that the number of lost packets within a predefined time period exceeds a threshold (T)  517 . Thus, the threshold (T)  517  may include more than one threshold, depending on the COUNT synchronization trigger. The determination of the number of lost packets may be based on, for example, ACK/NACK messages received from the other wireless communication device. 
     Upon initiating a COUNT synchronization, the count synchronization circuitry  548  may transmit at least a current hyper frame number (HFN) of the current COUNT value, as determined locally on the wireless communication device  500 , over the wireless connection to synchronize the current COUNT value. The COUNT synchronization may be performed in-band or out-of-band. In some examples, in-band COUNT synchronization may be initiated by either the UE or base station (eNB), whereas out-of-band COUNT synchronization may be initiated by only the base station (eNB or gNB). 
     For in-band COUNT synchronization, the count synchronization circuitry  548  may be configured to receive a packet to be transmitted to the other wireless communication device during the session and include the full COUNT value (e.g., both the HFN and SN) in the header of the packet. The count synchronization circuitry  548  may thus operate in coordination with the PDCP processing circuitry  546  to modify the header of the PDCP PDU to include the full COUNT value and provide the PDCP PDU with the modified header to the lower sublayers for transmission of the packet with the modified PDCP header to the other wireless communication device via the transmitter  520 . In some examples, the full COUNT value may be included in a Radio Link Control (RLC) header or a Media Access Control (MAC) header, instead of a PDCP header. 
     The count synchronization circuitry  548  may further be configured to operate in coordination with the PDCP processing circuitry  546  to include an indication of the format of the COUNT value (e.g., full COUNT value) in the PDCP PDU. In some examples, the PDCP processing circuitry  546  may include the format indication (e.g., full COUNT value or short COUNT value) in each PDCP PDU. If the short COUNT value format is indicated, the packet may contain only the SN, and not the HFN. 
     For out-of-band COUNT synchronization, the count synchronization circuitry  548  may be configured to transmit the current HFN of the current COUNT value within an out-of-band control message (e.g., separate from a packet containing a SN). For example, the out-of-band message may include a Radio Resource Control (RRC) message or a user plane control message (e.g., PDCP/RLC/MAC). In some examples, when transmitting the HFN within a RRC message, the PDCP-config Information Element (IE) may be modified to include a parameter (hfn) when operating in the Unacknowledged Mode (UM) as follows: 
     
       
         
           
               
             
               
                   
               
             
            
               
                 -- ASN1START 
               
            
           
           
               
               
            
               
                 PDCP-Config ::= 
                 SEQUENCE { 
               
               
                  discardTimer 
                  ENUMERATED { 
               
               
                   
                   ms50, ms100, ms150, ms300, 
               
               
                 ms500, 
                   
               
               
                   
                   ms750, ms1500, infinity 
               
            
           
           
               
               
               
            
               
                  } 
                   
                 OPTIONAL,     -- 
               
            
           
           
               
               
            
               
                 Cond Setup 
                   
               
            
           
           
               
               
               
            
               
                  rlc-AM 
                   
                  SEQUENCE { 
               
               
                   
                 statusReportRequired 
                   BOOLEAN 
               
            
           
           
               
               
               
            
               
                  } 
                   
                 OPTIONAL,     -- 
               
            
           
           
               
               
            
               
                 Cond Rlc-AM 
                   
               
               
                  rlc-UM 
                  SEQUENCE { 
               
            
           
           
               
               
               
            
               
                   
                 pdcp-SN-Size 
                   ENUMERATED {len7bits, 
               
            
           
           
               
               
            
               
                 len12bits} 
                   
               
            
           
           
               
               
               
            
               
                  } 
                   
                 OPTIONAL,     -- 
               
            
           
           
               
               
            
               
                 Cond Rlc-UM 
                   
               
            
           
           
               
               
               
               
            
               
                  hfn 
                  INTEGER 
                 OPTIONAL 
                   
               
            
           
           
               
               
               
            
               
                  headerCompression 
                  CHOICE { 
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 notUsed 
                   
                   NULL, 
                   
               
            
           
           
               
               
               
               
            
               
                   
                 rohc 
                   SEQUENCE { 
                   
               
            
           
           
               
               
               
               
            
               
                   
                   
                 maxCID 
                    INTEGER (1..16383) 
               
            
           
           
               
               
               
            
               
                  DEFAULT 15, 
                   
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                   
                 profiles 
                   
                    SEQUENCE { 
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                   
                 profile0x0001 
                   
                 BOOLEAN, 
                   
               
               
                   
                   
                   
                 pr0file0x0002 
                   
                 BOOLEAN, 
                   
               
               
                   
                   
                   
                 pr0file0x0003 
                   
                 BOOLEAN, 
                   
               
               
                   
                   
                   
                 pr0file0x0004 
                   
                 BOOLEAN, 
                   
               
               
                   
                   
                   
                 pr0file0x0006 
                   
                 BOOLEAN, 
                   
               
               
                   
                   
                   
                 profile0x0101 
                   
                 BOOLEAN, 
                   
               
               
                   
                   
                   
                 pr0file0x0102 
                   
                 BOOLEAN, 
                   
               
               
                   
                   
                   
                 pr0file0x0103 
                   
                 BOOLEAN, 
                   
               
               
                   
                   
                   
                 pr0file0x0104 
                   
                 BOOLEAN 
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 }, 
                   
                   
               
               
                   
                   
                 ... 
                   
                   
               
               
                   
                 } 
                   
                   
                   
               
            
           
           
               
               
               
            
               
                  }, 
                   
                   
               
               
                  ..., 
                   
                   
               
            
           
           
               
               
               
               
            
               
                  [ [  
                 rn-IntegrityProtection-r10 
                  ENUMERATED {enabled} 
                 OPTIONAL   -- 
               
            
           
           
               
               
               
            
               
                 Cond RN 
                   
                   
               
               
                  ] ], 
                   
                   
               
            
           
           
               
               
               
               
            
               
                  [ [  
                 pdcp-SN-Size-v1130 
                  ENUMERATED {len15bits} 
                 OPTIONAL   -- 
               
            
           
           
               
               
               
            
               
                 Cond Rlc-AM2 
                   
                   
               
               
                  ] ], 
                   
                   
               
            
           
           
               
               
               
               
            
               
                  [ [  
                 ul-DataSplitDRB-ViaSCG-r12 
                  BOOLEAN 
                 OPTIONAL,     -- 
               
            
           
           
               
               
               
            
               
                 Need ON 
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 t-Reordering-r12 
                  ENUMERATED { 
                   
               
            
           
           
               
               
            
               
                   
                  ms0, ms20, ms40, ms60, ms80, ms100, 
               
               
                 ms120, 
                   
               
               
                   
                  ms140, ms160, ms180, ms200, ms220, 
               
               
                   
                 ms240, 
               
               
                   
                  ms260, ms280, ms300,ms500, ms750, 
               
               
                   
                 spare14, 
               
               
                   
                  spare13, spare12, spare11, 
               
               
                   
                 spare10,spare9, 
               
               
                   
                  spare8, spare7, spare6, spare5, 
               
               
                   
                 spare 4, 
               
               
                   
                  spare3, spare2, spare1} 
               
            
           
           
               
               
               
            
               
                   
                   
                 OPTIONAL 
               
               
                   
                  -- Cond SetupS 
                   
               
               
                  ] ] 
                   
                   
               
               
                 } 
                   
                   
               
               
                 -- ASN1STOP 
               
               
                   
               
            
           
         
       
     
     In some examples, when transmitting the HFN within a user plane control message, the count synchronization circuitry  548  may utilize modified PDCP/RLC control packets (e.g., PDCP HFN PDU or RLC HFN PDU) or modified MAC control elements (CE) (e.g., MAC CE). In addition, the modified user plane control packets may be integrity protected and/or ciphered for security (e.g., the control PDU may include a SN and/or signature). For example, an integrity protection signature may be included within the PDCP HFN PDU, the RLC HFN PDU or the MAC CE carrying the current hyper frame number. In addition, a control PDU sequence number may be included within the PDCP HFN PDU, the RLC HFN PDU or the MAC CE carrying the current hyper frame number to enable retransmission and ciphering of the out-of-band control message. 
     The count synchronization circuitry  548  may further be configured to include the current SN of the current COUNT value in the out-of-band control message to indicate to the other wireless communication device that the HFN maintained locally on the other wireless communication should be synchronized to the received HFN value for the current SN onward, taking into consideration SN wrap-around. Thus, by including the SN with the HFN in the out-of-band control message, HFN synchronization may be achieved online (e.g., without interruption of data transmission and reception during the session). 
     However, if the current SN is not included within the out-of-band control message, and the HFN is out-of-sync on the other wireless communication device, the other wireless communication device may transmit an out-of-sync flag to the wireless communication device  500  to cause the count synchronization circuitry  548  to trigger an offline resync procedure. The other wireless communication device may further include the current HFN value locally maintained on the other wireless communication device with the out-of-sync flag. When the offline resync procedure is triggered, the count synchronization circuitry  548  may suspend data transmission and reception of user plane data and control plane data on both sides (e.g., on both the wireless communication device  500  and the other wireless communication device). For example, the count synchronization circuitry  548  may transmit a message to the other wireless communication device to suspend data transmission and reception. 
     The count synchronization circuitry  548  may then select a new HFN that is equal to or larger than the largest current HFN maintained locally on both the wireless communication device  500  or the other wireless communication device, reset the current HFN to the new HFN locally (e.g., within memory  505 ) and transmit the new HFN to the other wireless communication device to synchronize the HFN. For example, the new HFN may be transmitted to the other wireless communication device via an RRC message or a user plane control message. In addition, upon selecting and transmitting the new HFN, the wireless communication device  500  and the other wireless communication device may update the HFN of all packets in their receive, retransmission and transmission buffers  518  to the new HFN. The buffers  518  may be separate from memory  505 , as shown in  FIG. 5 , or included within memory  505 . The count synchronization circuitry  548  may then resume data transmission and reception on both the wireless communication device  500  and the other wireless communication device. In some examples, upon receiving an HFN synchronization complete indication over the wireless connection from the other wireless communication device indicating that the other wireless communication device has reset its locally stored HFN to the new HFN, the count synchronization circuitry  548  may resume data transmission and reception. 
     The COUNT synchronization may also be initiated by the other wireless communication device. For example, the count synchronization circuitry  548  may receive an in-band COUNT synchronization packet from the other wireless communication device. The count synchronization circuitry  548  may then determine whether a full COUNT value is included in the header (e.g., PDCP, RLC or MAC header) of the packet, and if so, decipher the packet payload using the full COUNT value. The count synchronization circuitry  548  may further synchronize the locally maintained HFN based on the HFN included in the full COUNT value. 
     When receiving an out-of-band COUNT synchronization control message, the count synchronization circuitry  548  may receive the current HFN in the out-of-band control message. If the out-of-band control message further includes the current SN, the count synchronization circuitry  548  may set the locally maintained HFN to the received HFN value for the received SN and all SNs after the received SN (e.g., greater than the received SN), taking into consideration HFN wrap-around. The count synchronization circuitry  548  may then transmit an HFN synchronization complete message to the other wireless communication device. 
     If the out-of-band control message does not include the current SN, the count synchronization circuitry  548  may compare the received HFN with the locally stored HFN. If the HFN&#39;s match, the count synchronization circuitry  548  may transmit an HFN synchronization complete message to the other wireless communication device. However, if the HFN&#39;s do not match (e.g., the HFN&#39;s are out-of-sync), the count synchronization circuitry  548  may transmit an out-of-sync flag, together with the current locally stored HFN value, to the other wireless communication device to trigger a resync procedure. During the resync procedure, the count synchronization circuitry  548  may suspend data transmission and reception with the other wireless communication device and receive a new HFN from the other wireless communication device. The count synchronization circuitry  548  may then set the locally stored HFN to the new HFN, transmit the HFN synchronization complete indication to the other wireless communication device, and resume data transmission and reception with the other wireless communication device. The count synchronization circuitry  548  may operate in coordination with count synchronization software  558 . The circuitry included in the processor  504  is provided as non-limiting examples. Other means for carrying out the described functions exists and is included within various aspects of the present disclosure. 
       FIG. 6  illustrates an example of a format of a packet  600  including a full COUNT value in accordance with aspects of the present disclosure. The packet may correspond to, for example, a PDCP PDU. The packet format  600  includes a header  602  and a body  604 . The header  602  includes a format indication field  606  and a COUNT value field  608 . The format indication (FI) field  606  may include a single bit for indicating whether the full COUNT value or the short COUNT value is included in the packet  600 . If the format indication field  606  indicates that the full COUNT value is included in the packet, the COUNT value field  608  includes both the hyper frame number (HFN)  610  and the sequence number (SN)  612 . However, if the format indication field  606  indicates that the short COUNT value is included in the packet, the COUNT value field includes only the SN  612 , as shown and described above in reference to  FIG. 3 . The body  604  contains uncompressed or compressed user or control plane data  614 , as shown and described above in reference to  FIG. 3 . 
       FIG. 7  illustrates an example of a format of a control message  700  including at least a hyper frame number (HFN)  702  in accordance with aspects of the present disclosure. For example, the out-of-band message may include a Radio Resource Control (RRC) message or a user plane control message (e.g., PDCP/RLC/MAC). In some examples, when the control message  700  is a user plane control message, the user plane control message  700  may also include an integrity protection signature (IPS)  704  and a control PDU sequence number (Control SN)  706  to enable retransmission and ciphering of the control message. In some examples, the control message  700  may include the full COUNT value  708 , including both the HFN  702  and the current SN  710 , to indicate to the other wireless communication device that the HFN maintained locally on the other wireless communication should be synchronized to the received HFN value for the current SN onward, taking into consideration SN wrap-around. 
       FIG. 8  is a flow chart illustrating an exemplary process  800  for performing COUNT synchronization in accordance with some aspects of the present disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In some examples, the process  800  may be carried out by the wireless communication device  500  illustrated in  FIG. 5 . In some examples, the process  800  may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below. 
     At block  802 , the wireless communication device may maintain a COUNT value for each packet transmitted over a wireless connection with another wireless communication device. For example, the PDCP processing circuitry  546  shown and described above in reference to  FIG. 5  may maintain the COUNT value. 
     At block  804 , the wireless communication device may determine whether a COUNT synchronization has been triggered. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may determine whether a COUNT synchronization has been triggered. In some examples, the COUNT synchronization may be triggered based on a number of packets transmitted after a previous COUNT synchronization, upon expiration of a timer, in response to a fade event or in response to a packet loss event. 
     If a COUNT synchronization has been triggered (Y branch of block  804 ), at block  806 , the wireless communication device may transmit the current Hyper Frame Number (HFN) maintained locally on the wireless communication device to the other wireless communication device over the wireless connection therebetween to synchronize the current COUNT value on the wireless communication devices. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may transmit the current HFN. In some examples, the current Sequence Number (SN) may also be transmitted with the HFN. In addition, the HFN (with or without the SN) may be transmitted in-band or out-of-band. 
       FIG. 9  is a flow chart illustrating an exemplary process  900  for performing in-band count synchronization according to some aspects of the present disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In some examples, the process  900  may be carried out by the wireless communication device  500  illustrated in  FIG. 5 . In some examples, the process  900  may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below. 
     At block  902 , the wireless communication device may receive a packet to be transmitted to another wireless communication device over a wireless connection. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may receive the packet in coordination with the PDCP processing circuitry  546  shown and described above in reference to  FIG. 5 . 
     At block  904 , the wireless communication device may determine whether a COUNT synchronization has been triggered. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may determine whether a COUNT synchronization has been triggered. In some examples, the COUNT synchronization may be triggered based on a number of packets transmitted after a previous COUNT synchronization, upon expiration of a timer, in response to a fade event or in response to a packet loss event. 
     If a COUNT synchronization has been triggered (Y branch of block  904 ), at block  906 , the wireless communication device may transmit the packet with a full COUNT value (e.g., both the current Hyper Frame Number (HFN) maintained locally on the wireless communication device and the Sequence Number (SN)) to the other wireless communication device over the wireless connection therebetween to synchronize the current COUNT value on the wireless communication devices. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may transmit the full COUNT value within the header of the packet. In some examples, the full COUNT value may be included within a PDCP, RLC or MAC header of the packet. 
     If a COUNT synchronization has not been triggered (N branch of block  904 ), at block  908 , the wireless communication device may transmit the packet with the short COUNT value (e.g., only the SN). For example, the PDCP processing circuitry  546  shown and described above in reference to  FIG. 5  may include only the SN in the header of the packet. 
       FIG. 10  is a flow chart illustrating an exemplary process  1000  for performing out-of-band count synchronization according to some aspects of the present disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In some examples, the process  1000  may be carried out by the wireless communication device  500  illustrated in  FIG. 5 . In some examples, the process  1000  may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below. 
     At block  1002 , the wireless communication device may maintain a COUNT value for each packet transmitted over a wireless connection with another wireless communication device. For example, the PDCP processing circuitry  546  shown and described above in reference to  FIG. 5  may maintain the COUNT value. 
     At block  1004 , the wireless communication device may determine whether a COUNT synchronization has been triggered. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may determine whether a COUNT synchronization has been triggered. In some examples, the COUNT synchronization may be triggered based on a number of packets transmitted after a previous COUNT synchronization, upon expiration of a timer, in response to a fade event or in response to a packet loss event. 
     If a COUNT synchronization has been triggered (Y branch of block  1004 ), at block  1006 , the wireless communication device may determine whether to include the current SN with the current HFN to synchronize the COUNT values. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may determine whether to include the SN with the HFN. If the SN is to be included (Y branch of block  1006 ), at block  1008 , the wireless communication device may transmit both the current SN and the current HFN to the other wireless communication device over the wireless connection to reset the COUNT value on the other wireless communication device and synchronize the COUNT values on both wireless communication devices. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may transmit the SN and HFN over the wireless connection. In some examples, the SN and HFN may be transmitted within an out-of-band control message, such as a Radio Resource Control (RRC) message or a user plane control message (e.g., PDCP/RLC/MAC). 
     If the SN is not to be included with the HFN (N branch of block  1006 ), at block  1010 , the wireless communication device may transmit the current HFN to the other wireless communication device over the wireless connection to synchronize the COUNT values. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may transmit the current HFN over the wireless connection. In some examples, the current HFN may be transmitted within an out-of-band control message, such as a Radio Resource Control (RRC) message or a user plane control message (e.g., PDCP/RLC/MAC). 
     At block  1012 , the wireless communication device determines whether an out-of-sync flag has been received from the other wireless communication device, indicating that the current HFN transmitted to other wireless communication device does not match the locally stored HFN on the other wireless communication device. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may determine whether the out-of-sync flag is received. 
     If the out-of-sync flag is received (Y branch of block  1012 ), at block  1014 , the wireless communication device may suspend data transmission and reception over the wireless connection. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may suspend the data transmission and reception. At block  1016 , the wireless communication device may select and transmit a new HFN value over the wireless connection to reset the COUNT value on the other wireless communication device. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may transmit the new HFN over the wireless connection. In some examples, the new HFN is greater than or equal to the largest current HFN maintained locally on either wireless communication device. 
     At block  1018 , the wireless communication device may resume data transmission and reception over the wireless connection. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may resume data transmission and reception. In some examples, the wireless communication device may resume data transmission and reception after receiving an HFN synchronization complete indication from the other wireless communication device. 
       FIG. 11  is a packet flow diagram illustrating an example of in-band count synchronization  1100  according to some aspects of the present disclosure. In the example shown in  FIG. 11 , a transmitter  1102  (e.g., a transmitter within a wireless communication device) is engaged in a session with a receiver  1104  (e.g., a receiver within a wireless communication device) over a wireless connection. At  1106 - 1110 , the transmitter  1102  may transmit a plurality of data packets, each including a short COUNT value (e.g., only the SN), to the receiver  1104 . The transmitter  1102  may then trigger a COUNT synchronization at  1112 . Upon triggering the COUNT synchronization, at  1114 , the transmitter may transmit a data packet with the full or long COUNT value (e.g., both the HFN and SN) to the receiver  1104  to synchronize the COUNT values on the transmitter  1102  and receiver  1104 . After COUNT synchronization, at  1116 , the transmitter  1102  may again transmit data packets to the receiver  1104  using the short COUNT value. 
       FIG. 12  is a packet flow diagram illustrating an example of out-of-band count synchronization according to some aspects of the present disclosure. In the example shown in  FIG. 12 , a UE  1202  or other wireless communication device is engaged in a session with an access network (AN)  1204  (e.g., a base station or eNB) over a wireless connection. At  1206 , the wireless connection between the UE  1202  and AN  1204  may be established. At  1208 , the AN  1204  may initiate a COUNT synchronization by transmitting a Radio Resource Connection (RRC) connection reconfiguration message including the current HFN (and optionally the current SN) to the UE  1202  to synchronize the COUNT values on the UE  1202  and AN  1204 . At  1210 , the UE  1202  may transmit an RRC connection reconfiguration complete message to the AN  1204  to indicate that the HFN maintained locally on the UE  1202  has been synchronized with the HFN maintained locally at the AN  1204 . At  1212 , the UE  1202  determines that user data traffic is available to be transmitted to the AN  1204  and requests a grant of uplink resources to transmit the user data traffic. At  1214 , the UE  1202  transmits the user data traffic on the uplink to the AN  1204  based on the grant with the current COUNT value determined using the synchronized HFN. 
       FIG. 13  is a flow chart illustrating an exemplary process  1300  for initiating count synchronization according to some aspects of the present disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In some examples, the process  1300  may be carried out by the wireless communication device  500  illustrated in  FIG. 5 . In some examples, the process  1300  may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below. 
     At block  1302 , the wireless communication device may initialize a counter. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may initialize the counter. At block  1304 , the wireless communication device may transmit a packet over a wireless air interface to a receiving wireless communication device. For example, the transceiver  510  together with the communication circuitry  542  and signal processing circuitry  544  shown and described above in reference to  FIG. 5  may generate and transmit the packet to the receiving wireless communication device. 
     At block  1306 , after transmitting the packet, the wireless communication device may increment the counter by one. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may increment the counter. At block  1308 , the wireless communication device may determine whether the counter has reached a predetermined value (PDV) corresponding to a predetermined number of transmitted packets. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may determine whether the counter value is equal to the PDV. 
     If the counter value is not equal to the PDV (N branch of block  1308 ), at block  1310 , the wireless communication device may determine whether another packet has been transmitted, and if so (Y branch of block  1310 ), return to block  1306  to increment the counter by one. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may determine whether another packet has been transmitted, and if so, increment the counter again by one. 
     If the counter value is equal to the PDV (Y branch of block  1308 ), at block  1312 , the wireless communication device may initiate count synchronization, and then return to block  1302  to re-initialize the counter to zero. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may initiate count synchronization upon the counter reaching the PDV, and then re-initialize the counter to zero. 
       FIG. 14  is a flow chart illustrating another exemplary process  1400  for initiating count synchronization according to some aspects of the present disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In some examples, the process  1400  may be carried out by the wireless communication device  500  illustrated in  FIG. 5 . In some examples, the process  1400  may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below. 
     At block  1402 , the wireless communication device may initialize a timer. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may initialize the timer. At block  1404 , the wireless communication device may determine whether the timer has expired. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may determine whether the timer has expired. 
     If the timer has not expired (N branch of block  1404 ), the wireless communication device may transmit a packet over the wireless air interface to a receiving wireless communication device. For example, the transceiver  510  together with the communication circuitry  542  and signal processing circuitry  544  shown and described above in reference to  FIG. 5  may generate and transmit the packet to the receiving wireless communication device. 
     If the timer has expired (Y branch of block  1404 ), at block  1408 , the wireless communication device may initiate count synchronization, and then return to block  1402  to re-initialize the timer. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may initiate count synchronization upon expiration of the timer and then re-initialize the timer. 
       FIG. 15  is a flow chart illustrating another exemplary process  1500  for initiating count synchronization according to some aspects of the present disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In some examples, the process  1500  may be carried out by the wireless communication device  500  illustrated in  FIG. 5 . In some examples, the process  1500  may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below. 
     At block  1502 , the wireless communication device may measure a signal-to-noise ratio (SNR) of a channel between the wireless communication device and another wireless communication device. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may measure the SNR. At block  1504 , the wireless communication device may determine whether the SNR has dropped below a threshold. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may determine whether the SNR is less than the threshold. 
     If the SNR is less than the threshold (Y branch of block  1504 ), at block  1506 , the wireless communication device may initiate count synchronization, and then return to block  1502  to measure the SNR. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may initiate count synchronization upon expiration of the timer and then measure the SNR again. 
       FIG. 16  is a flow chart illustrating another exemplary process  1600  for initiating count synchronization according to some aspects of the present disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In some examples, the process  1600  may be carried out by the wireless communication device  500  illustrated in  FIG. 5 . In some examples, the process  1600  may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below. 
     At block  1602 , the wireless communication device may initialize a number of lost packets to zero. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may initialize the number of lost packets. At block  1604 , the wireless communication device may transmit a packet over a wireless air interface to a receiving wireless communication device. For example, the transceiver  510  together with the communication circuitry  542  and signal processing circuitry  544  shown and described above in reference to  FIG. 5  may generate and transmit the packet to the receiving wireless communication device. 
     At block  1606 , after transmitting the packet, the wireless communication device may determine whether the packet was lost. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may determine whether the packet was lost. If the packet was not lost (N branch of block  1606 ), the process may return to block  1604 , where another packet may be transmitted. If the packet was lost (Y branch of block  1606 ), at block  1608 , the wireless communication device may increment the number of packets lost by one. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may increment the number of lost packets. 
     At block  1610 , the wireless communication device may determine whether the number of lost packets is greater than a threshold. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may determine whether the number of lost packets is greater than the threshold. If the number of lost packets is not greater than the threshold (N branch of block  1610 ), the process may return to block  1604 , where another packet may be transmitted. 
     If the number of lost packets is greater than the threshold (Y branch of block  1610 ), at block  1612 , the wireless communication device may initiate count synchronization, and then return to block  1602  to re-initialize the number of lost packets to zero. For example, the count synchronization circuitry  548  shown and described above in reference to  FIG. 5  may initiate count synchronization upon the number of lost packets exceeding the threshold, and then re-initialize the number of lost packets to zero. 
     Several aspects of a wireless communication network have been presented with reference to an exemplary implementation. As those skilled in the art will readily appreciate, various aspects described throughout this disclosure may be extended to other telecommunication systems, network architectures and communication standards. 
     By way of example, various aspects may be implemented within other systems defined by 3GPP, such as Long-Term Evolution (LTE), the Evolved Packet System (EPS), the Universal Mobile Telecommunication System (UMTS), and/or the Global System for Mobile (GSM). Various aspects may also be extended to systems defined by the 3rd Generation Partnership Project 2 (3GPP2), such as CDMA2000 and/or Evolution-Data Optimized (EV-DO). Other examples may be implemented within systems employing IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Ultra-Wideband (UWB), Bluetooth, and/or other suitable systems. The actual telecommunication standard, network architecture, and/or communication standard employed will depend on the specific application and the overall design constraints imposed on the system. 
     Within the present disclosure, the word “exemplary” is used to mean “serving as an example, instance, or illustration.” Any implementation or aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects of the disclosure. Likewise, the term “aspects” does not require that all aspects of the disclosure include the discussed feature, advantage or mode of operation. The term “coupled” is used herein to refer to the direct or indirect coupling between two objects. For example, if object A physically touches object B, and object B touches object C, then objects A and C may still be considered coupled to one another—even if they do not directly physically touch each other. For instance, a first object may be coupled to a second object even though the first object is never directly physically in contact with the second object. The terms “circuit” and “circuitry” are used broadly, and intended to include both hardware implementations of electrical devices and conductors that, when connected and configured, enable the performance of the functions described in the present disclosure, without limitation as to the type of electronic circuits, as well as software implementations of information and instructions that, when executed by a processor, enable the performance of the functions described in the present disclosure. 
     One or more of the components, steps, features and/or functions illustrated in  FIGS. 1-16  may be rearranged and/or combined into a single component, step, feature or function or embodied in several components, steps, or functions. Additional elements, components, steps, and/or functions may also be added without departing from novel features disclosed herein. The apparatus, devices, and/or components illustrated in  FIGS. 1 and 5  may be configured to perform one or more of the methods, features, or steps described herein. The novel algorithms described herein may also be efficiently implemented in software and/or embedded in hardware. 
     It is to be understood that the specific order or hierarchy of steps in the methods disclosed is an illustration of exemplary processes. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the methods may be rearranged. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented unless specifically recited therein. 
     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 are 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. 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 and b; a and c; b and c; and a, b and c. 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.”