- What is H-CRAN (Heterogeneous Cloud Radio Access Network)?
H-CRAN has elements of performing streamlining, cost adequacy, and enhanced energy effectiveness execution. H-CRAN can give productive resource sharing at the network, and framework levels. H-CRAN acquires the advantages of collective radio resources control and adaptability, cooperative processing, and systems administration methods. The idea of H-CRAN has been proposed as a cost-effective technology with various types of C-RANs and HetNets.
- What is H-field (Magnetic field)?
Magnetic field portrays the magnetic influence on moving electric charges, electric currents, and magnetic materials. Magnetic fields are created by moving electric charges and the intrinsic magnetic moments of elementary particles which is related to a fundamental quantum property. Magnetic fields are utilized all through present day innovation, like electrical engineering and electromechanics. The SI unit of magnetic field strength is ampere⋅turn/meter; a unit that depends on the magnetic field of a solenoid.
- What is HAPS (High Altitude Platform Stations)?
High-altitude platforms (HAPs) are aircraft, positioned above 20 km, in the stratosphere, to make a media communications arrangement or perform remote detecting. High-altitude platform station (HAPS) frameworks might conceivably be utilized to give both fixed broadband connectivity for end users and transmission association between the portable and core networks for backhauling traffic. The two sorts of HAPS applications would empower wireless broadband deployment in remote regions, including in mountainous, seaside and desert regions.
- What is HARQ (Hybrid automatic repeat and request)?
Hybrid automatic repeat request is a mixture of high-rate forward error correction (FEC) and automatic repeat request (ARQ) error-control. In Hybrid ARQ, the first information is encoded with an FEC code. Then the parity bits are either immediately transmitted along with the message or only possibly communicated upon demand when a receiver recognizes a mistaken message.
- What is HBRT (Hardware-Based Root of Trust)?
All secure operations of a computing framework depend on a hardware root of trust. It contains the keys utilized for cryptographic capacities and empowers a safe boot process. Compromised IoT devices can be effectively reinvented to stealthily violate consumer privacy, while associated apparatuses constrained by a remote attacker can potentially cause serious property damage. It gives a robust level of protection.
- What is HBT (Heterojunction Bipolar Transistor)?
The heterojunction bipolar transistor (HBT) is a sort of bipolar junction transistor (BJT). It utilizes contrasting semiconductor materials for the emitter and base. The emitter transition normally expects a heterojunction structure, for example a broadband gap material in the emitter region and a narrow band are utilized – gap materials are utilized for the base region. They form the basis for the utilization of various semiconductor materials for both the emission and collector basis.
- What is HCE (host card emulation)?
Host card emulation (HCE) is an innovation for protecting a mobile phone that tends to be utilized to make credit or debit transactions at a physical point-of-sale (POS) terminal. HCE empowers versatile applications to provide safe payment card and verification arrangements without the requirement for a payment card to be genuinely present. This innovation empowers the traders to provide payment cards solutions effectively through versatile closed-loop contactless payment arrangements.
- What is HCF (Hybrid Coordination Function)?
HCF characterizes the capacity for an 802.11 radio to send numerous frames when communicating on the RF medium. The Hybrid coordination function joined elements of Point Coordination Function (PCF) and Distributed Coordination Function (DCF). The HCF strategy was not significantly executed because of the trouble in the advancement of carrying out the HCCA system with the Access point keeping up all of the scheduling responsibilities.
- What is HCN (Heterogeneous Cellular Network)?
The HCNs are the key empowering agent for 5G cellular networks to guarantee better client availability in dense networks. The HCN is demonstrated as a multi-tier cellular network where every tier’s base stations (BSs) are located and have path loss exponent, spatial density, and bias towards admitting portable clients. The ultradense HCN performance in terms of the connection probability, average EE, is theoretically dissected by utilizing the stochastic geometry tool.
- What is HCS (Header Check Sequence)?
A header check sequence (HCS) is an error checking highlight for different header information structures. It might comprise a cyclic redundancy check (CRC) of the frame. The HCS has a 16-bit value for link modems. For example in the Media Access Control (MAC) header of Ethernet.
- What is HCS (Hierarchical Cell Structure)?
Hierarchical Cell Structure is a term normally utilized in GSM to depict the need of cells inside a mixed climate. Hierarchical cell structure utilized in versatile telecommunication. It permits the network to adequately utilize the geological region and serve an expanding population. In Hierarchical cellular structure (HCS), cells of various sizes are coordinated into various layers to give high coverage and capacity. At the point when Macro, Micro, and Pico cells may be seen as possibilities for cell reselection the priority depicted by the HCS will be utilized in the related computations.
- What is HD (Half duplex)?
Half-Duplex (HDX) is an activity wherein transmission among two terminals happens one or the other way but in only one direction at a time. An example of a half-duplex device is a walkie-talkie which has a press-to-talk button. At the point when the local user presses this button, they need to speak to the remote person, which turns on the transmitter and turns off the receiver, preventing them from hearing the remote person while talking. User releases the button to listen to the remote person, which turns on the receiver and turns off the transmitter.
- What is HDL (hardware description language)?
A hardware description language empowers formal depiction of an electronic circuit that takes into account the automated examination and simulation of an electronic circuit. It is a literary depiction comprising statements and control structures. HDLs structure an integral segment of electronic design automation (EDA) frameworks, particularly for complicated circuits, for example, application-specific integrated circuits, microprocessors, and programmable logic devices.
- What is HDMI (High-Definition Multimedia Interface)?
High-Definition Multimedia Interface (HDMI) is used for sending uncompressed video information and compressed or uncompressed digital information from an HDMI-compliant source device. It upholds high-quality, uncompressed, digital video and audio without the quality loss connection with analog associations. Rather than utilizing numerous links, a solitary link can be utilized for video and sound.
- What is HDSL (High-bit-rate Digital Subscriber Line)?
High-bit-rate Digital Subscriber Line innovation is a replacement for a T-1 repeatered line. It permits DS-1 signals to be transported over distances of up to 3700 meters at 1.544 Mbit/s and 2.048 Mbit/s, on unconditioned copper link, without a requirement for repeaters. It was the first digital subscriber line (DSL) innovation to utilize a higher recurrence range over copper, twisted pair cables. High-bit-rate digital subscriber line (HDSL) was normalized in 1994.
- What is HCI (Host Controller Interface)?
HCI empowers a host controller for IEEE 1394 equipment to communicate with a host controller driver in software. Host Controller is an interface that empowers a FireWire host controller to communicate with a driver. Host Controller Interface (Bluetooth) in Bluetooth protocols. HCI doesn’t get the register and the memory areas of a Bluetooth device straightforwardly. All things considered, it transmits command and information packets to the device and receives information packets and event-message packets from this device.
- What is HE (Horizontal Encoding)?
Horizontal Encoding is an instruction set where each field in an instruction word manages some functional unit or gate straightforwardly. Horizontal encoding permits all possible associations of control signals to be communicated as instructions. Horizontal micro-programmed control units make less use of ROM encoding than vertical micro-programmed control units.
- What is HEC (Header Error Check)?
Header Error Check is a test strategy utilized to decide if an Asynchronous Transfer Mode technology cell has been received correctly. The Header Error Control field is an 8bit Cyclic Redundancy Code inside the header of the Asynchronous Transfer Mode cell. It is utilized to examine the validity of the ATM cell control data. It is utilized in Asynchronous Transfer Mode (ATM), DQDB header, FHSS data frame, DSSS data frame and WLANs.
- What is HEMT (High Electron-Mobility Transistor)?
High Electron-Mobility Transistor is a type of field effect transistor. It uses an exceptionally narrow channel empowering it to work at extremely high frequencies. It includes a junction between two materials with various band gaps as the channel rather than a doped region. HEMTs are utilized in integrated circuits as digital on-off switches. HEMT transistors can work at higher frequencies than normal transistors, up to millimeter wave frequencies, and are utilized in high-recurrence products.
- What is HeNB (home eNB)?
HeNB is liable for all radio resource management, and allocation of user traffic to the downlink/uplink, security and relaying of higher layer Non Access Stratum signalling to the MME. It is intended to be conveyed in a home/office area as a component of a FemtoCell design. It is upgraded for sending for smaller coverage than macro eNodeB. The coverage of HeNB cells is commonly quite small in contrast to that of macro cells because of the low-power transmission capability.
- What is HeNB GW (home eNB gateway)?
HeNB GW is a network element (NE) introduced inside an operator’s network. It is located between the HeNB and the MME. The Home eNodeB Gateway is the HeNB network access concentrator utilized to control abilities important to oversee enormous groups of femtocells. The essential capacity of HeNB-GW is to empower straightforward, seamless, and exceptionally secure access to users as they roam between secure portable organizations and insecure public networks.
- What is HetNet (heterogeneous network)?
The heterogeneous network is a network associating computers where the operating frameworks and conventions have huge contrasts. Heterogeneous network likewise depicts wireless networks utilizing diverse access technologies. The concurrent activity of Macro-, micro-, pico- and femto-cells is named as heterogeneous networks. In heterogeneous networks the cells of various sizes are alluded to as macro-, micro-, pico- and femto-cells; listed in order of diminishing base station power.
- What is HEVC (High Efficiency Video Codec)?
HEVC provides from 25% to 50% better information compression at the similar degree of video quality. HEVC empowers 4K and High Dynamic Range. It significantly further developed video quality at the similar bit rate. It upholds resolutions up to 8192×4320, including 8K UHD, and dissimilar the primarily 8-bit AVC, HEVC’s higher fidelity Main10 profile has been included into essentially all supporting equipment.
- What is HF (High frequency)?
High frequency (HF) is the ITU designation for the range between 3 and 30 megahertz (MHz). High frequency wavelengthsS range from 100 to 10 m. High frequency spectrum is used in Military and governmental communication systems, Aviation air-to-ground communications, Amateur radio, and Over-the-horizon radar systems.
- What is HFC (Hybrid Fibre Coaxial)?
Hybrid fiber-coaxial (HFC) joins optical fiber and coaxial cable. The TV channels are transmitted from the cable framework’s distribution facility, to local networks through optical fiber subscriber lines in a hybrid fiber-coaxial cable framework. Hybrid Fiber Coaxial cable conveys voice, Internet, cable TV and other advanced interactive arrangements and administrations to individual users and associations. HFC cable is utilized by telecommunication, cable TV and Internet organizations.
- What is HFN (Hyper-Frame Number)?
HFN is utilized among the base station and the portable to restrict the quantity of bits that are utilized for sequencing over the radio interface. HFN is a timer at the next level to SFN. HFN ranges somewhere in the range of 0 and 1023. The value increments by 1 when SFN arrives at 1023 and reset to 0. The number may likewise be utilized as a feature of the security process.
- What are HIDs (Human interface devices)?
A human interface device is a kind of computer device. It is normally utilized by people that take input from people and provide output to them. The most widely recognized are the keyboards, PC speakers, webcams and headsets. All gadgets giving an interface between the client and PC machines are considered HIDs. HIDs regularly highlight controls that permit people to associate with the PC. The majority of modern Human Interface Devices utilize the Universal Serial Bus (USB) communication protocol.
- What is HIL (Hardware-In-the-Loop)?
Hardware-in-the-loop (HIL) simulation, is a strategy that is utilized in the development and test of complicated real-time embedded frameworks. HIL testing is a method where real signals from a controller are associated with a test framework that simulates reality, tricking the controller into thinking it is in the gathered product.
- What is HIP (Host Identity Protocol)?
The Host Identity Protocol (HIP) is a host identification technology for utilization on Internet Protocol (IP) networks. The Host Identity Protocol gives secure techniques for IP multihoming and portable computing. It was created at the IETF in 1999 and their first stable version in 2007. HIP upgrades the first Internet architecture by adding a name space utilized amongst the IP layer and the transport protocols.
- What is HIPAA (Health Insurance Portability and Accountability Act)?
The Health Insurance Portability and Accountability Act of 1996 (HIPAA) is a government law that needs the formation of public norms to shield sensitive patient health data from being disclosed without the patient’s assent. The US Department of Health and Human Services (HHS) gave the HIPAA Privacy Rule to execute the prerequisites of HIPAA. It was sanctioned by the 104th United States Congress and endorsed into law by President Bill Clinton on August 21, 1996.
- What is HLD (High Level Design)?
High Level Design (HLD) is a general framework plan and incorporates the depiction of the System engineering and plan. High level design should incorporate two key elements:
- Interactions and relations between different elements.
- Functionalities and characteristics of elements.
It portrays the UI carried out and depiction of equipment and programming interfaces. It portrays the execution necessities and flow of the client’s daily process. HLD incorporates configuration highlights and the design of the task.
- What is HLR (Home Location Register)?
Home Location Register (HLR) contains information in regards to approved subscribers utilizing a global system for mobile communication (GSM) core network. The home location register stores data going from telephone numbers to the current location of the user. HLRs do exclude data about endorsers that have a place with the Mobile Network Operator’s (MNO’s) roaming partners. Home Location Registers don’t follow endorsers’ locations continuously. The network intermittently transmit Tracking Area Updates (TAUs), which advise associated devices to share their location.
- What is HMAC (Hashed Message Authentication Code)?
Hash-based Message Authentication Code is a kind of a message authentication code (MAC). It is acquired by implementing a cryptographic hash function on the information to be confirmed and a secret shared key. HMACs can be utilized for Internet of things (IoT) because of less expense. HMACs give higher security. HMACs are ideal for high-performance frameworks.
- What is HO (Hand Over)?
Handovers are a center component in arranging and deploying cellular networks. A handover is used in telecommunications and versatile communications where an associated cell call or an information session is moved from one cell site to another without disconnecting the session. It permits clients to make information sessions or connect phone calls on the move.
- What is HPA (High Power Amplifier)?
The high-power amplifier (HPA) gives the RF power for a payload downlink. The HPA subsystem has capacities that Channel preamplification for the HPA, with the adaptability to make the downlink power autonomous of the uplink power over a wide range of uplink power. A high power amplifier is a non-linear device which amplifies a small signal to a significant level. The HPA composed of 12 HBTs AsGa/GaInP is indistinguishable to the transistor.
- What is HPBW (half-power beamwidth)?
Half Power Beam Width is an angular width. It is estimated on the major lobe of an antenna radiation pattern at half-power points at which the signal power is half that of its peak value. At the point when a line is drawn among the radiation pattern’s starting point and the half power points on the major lobe, on both the sides, the angle between those two vectors is named as HPBW, half power beam width.
- What is HPF (High Pass Filter)?
A high-pass filter (HPF) passes signals with a recurrence higher than a specific cutoff recurrence and attenuates signals with frequencies lower than the cutoff recurrence. A high-pass filter is generally displayed as a linear time-invariant system. The high-pass filter passes only longer frequencies. In optics a high pass filter is a translucent window of colored material that permits light longer than a specific frequency to go through and attenuates light of shorter frequencies.
- What is HPLMN (Home public land mobile network)?
Home Public Land Mobile Network distinguishes the Public Land Mobile Network in which the profile of the user is held. Users roaming to different networks will get subscription data from the HPLMN. Each SIM card has an HPLMN, where the endorser profile is arranged. HLR is the node in HPLMN, where a new subscriber has all subscription data and the sim card continues to update its location to the HLR during roaming. The home network has message and billing nodes.
- What is HPSK (Hybrid Phase Shift Keying)?
Hybrid Phase Shift Keying utilized in WCDMA because it has a low phase average ratio. This low ratio of peak to average power results in decreasing the quantity of zero crossing of transitions of the output transmitted signal. HPSK is an intricate spreading plan that is intended to limit the zero-crossing signal transition. There is a possibility that signal transitions of HPSK go through zero.
- What is HR (Half-rate)?
Half Rate is a speech coding framework for GSM, created in the mid 1990s. GSM HR utilizes the Vector-Sum Excited Linear Prediction algorithm. The VSELP algorithm is an analysis-by-synthesis coding procedure. GSM Half Rate is indicated in ETSI EN 300 969. Half-rate transmission needs only half the bandwidth for information transmission, which implies that twice as many channels can be transmitted over the similar bandwidth.
- What is HR/DSSS (High-rate/direct sequence spread spectrum)?
The HR/DSSS PHY is the upgraded physical layer defined by IEEE 802.11b which upholds data transfer at up to 11Mbps. HR/DSSS utilizes complementary code keying which divides the chip stream into a number of 8 bit code symbols. HR/DSSS utilizes the more limited 8 chip PN code, and this gives the higher rate of total codes per second. With the help of a higher rate of codes per second, the amount of resilience against interference is reduced. HRDSSS utilizes a mix of DQPSK and complementary code keying (CCK) for
- What is HRPD (high rate packet data)?
HELD is high speed wireless information technology dependent on CDMA, it is created by Qualcomm. It aims to raise the information transmission rate at the air interface. The HRPD gives high-speed information communications and has much lower data traffic cost. The high rate packet information transmission further develops use of the forward link and diminishes the transmission delay.
- What is HS (Hot spot)?
A hotspot is a physical location where individuals can access the Internet, typically utilizing Wi-Fi, through a wireless local area network (WLAN) with a router associated with an Internet service provider. A hotspot can be in a private location or a public one, for example, in a coffee shop, a hotel, an airport, or an airplane. Public hotspots are typically made from wireless access points configured to give Internet access, controlled to some degree by the venue. Utilizing an open public network is the most effortless approach to make a free hotspot. All that is required is a Wi-Fi router.
- What is HS (Harmonized Standard)?
The Harmonized Standard came into force in 1988 and has since been created and kept up with by the World Customs Organization. It contains in excess of 5,000 commodity groups. The HS contributes to the harmonization of Customs and exchange procedures, and the non-documentary trade information interchange in association with such procedures, hence diminishing the costs related to international trade. It is also extensively utilized by governments, international associations. The Harmonized System is administered by “The International Convention on the Harmonized Commodity Description and Coding System”.
- What is HS-DPCCH (High speed dedicated control channel)?
The HS-DPCCH conveys uplink feedback signalling related to downlink HS-DSCH transmission. This feedback signalling comprises Hybrid-ARQ Acknowledgement and Channel Quality Indication. The HS-DPCCH data is separated so that the HARQ acknowledgement is communicated in the first slot of the sub frame while the channel quality indication is transmitted in the rest slot.
- What is HS-PDSCH (High Speed Physical Downlink Shared Channel)?
The HS-PDSCH is utilized to convey the High Speed – Downlink Shared Channel transport channel. The HS-PDSCH might utilize QPSK or 16QAM modulation. High-Speed Physical Downlink Shared Channel is a channel added to UMTS to increment downlink information rates. This is characterized in Release 5 of the UMTS specifications. It conveys client information and layer 2 overhead bits mapped from the transport channel: HS-DSCH.
- What is HS-SCCH (High-Speed Shared Control Channel)?
High-Speed Shared Control Channel is an additional channel to UMTS to increment downlink information rates. This is characterized in Release 5 of the UMTS details. It is additionally essential for the HSDPA. It conveys the data of Modulation scheme(1 bit) QPSK or 16QAM, Channelization code set (7bits), Transport block size ( 6bits), HARQ number (3bits), Redundancy version (3bits), New Data Indicator (1 bit) and UE identity (16 bits).
- What is HS‐DPCCH (High Speed Dedicated Physical Control Channel)?
The HS-DPCCH conveys uplink feedback signalling identified with downlink HS-DSCH transmission. This feedback signalling comprises Hybrid-ARQ Acknowledgement and Channel Quality Indication. HSDPA empowers higher speed information transfer. HS-DPCCH is an HSDPA channel utilized to give feedback to the scheduler and it is situated in the uplink. It conveys Channel Quality data that is utilized to give instantaneous channel data to the schedule.
- What is HSC (Home Subscriber Server)?
The Home Subscriber Server (HSS) is a main component of LTE and IMS core networks. It is a user database that is stored in one single node. A Home Subscriber Server(HSS) serves as the essential database repository of endorser data inside a LTE/EPC or IMS network core. It permits Communications Service Providers (CSPs) to particular capacities like barring specific services and functions, enactment and deactivation of SIM cards.
- What is HSCSD (High Speed Circuit Switched Data)?
High Speed Circuit Switched Data is an upgrade in the information rate of circuit switched information in a GSM network. A transfer rate of up to 57.6 kbit/s can be reached, or 115 kbit/s if a network permits consolidating 8 slots rather than only 4. The principal advantage of HSCSD contrasted with different information upgrades presented later is that it is an inexpensive method to implement higher data rates in GSM networks.
- What is HSDPA (high speed downlink packet access)?
HSDPA permits networks to have higher information speeds and limits, which is dependent on the Universal Mobile Telecommunications System (UMTS). HSDPA additionally diminishes latency and the round trip time for applications. HSDPA is depends on shared channel transmission, and its main elements are shared channel and multi-code transmission, higher-order modulation, short transmission time interval (TTI), fast link adaptation and scheduling, and High Speed Downlink Shared Channels (HS-DSCH), quadrature phase-shift keying and 16-quadrature amplitude modulation.
- What is (Hardware security module)?
A hardware security module (HSM) protects and oversees digital keys, executes encryption and decryption capacities for digital signatures, confirmation and other cryptographic capacities. The highlights of an HSM are onboard secure cryptographic key generation and utilization of cryptographic and delicate information material, such as executing encryption functions. HSMs are additionally sent to oversee straightforward information encryption keys for databases and keys for storage devices such as disk or tape.
- What is HSN (Hopping Sequence Number)?
The HSN is utilized to characterize the hopping sequence from one recurrence list. It is a number that characterizes the recurrence hopping algorithm. It can fluctuate from 0 to 63, i.e. there are 64 hopping algorithms to be utilized in GSM. The hopping sequence decides the frequencies in the MA-list are to be utilized. The HSNs 1 – 63 are pseudo irregular successions utilized in the arbitrary hopping while the HSN 0 is held for a consecutive arrangement utilized in the cyclic hopping.
- What is HSPA (High-Speed Packet Access)?
High Speed Packet Access is a combination of two mobile protocols, High Speed Downlink Packet Access and High Speed Uplink Packet Access (HSUPA), that expands and enhances the execution of existing 3G versatile telecommunication networks utilizing the WCDMA protocols. It highlights peak data rates of up to 14 Mbps downlink and up to 5.7 Mbps uplink. It is reasonable for portable Web browsing, document downloads and VoIP. HSPA also gives mobile broadband capabilities to wireless carriers with its high data speeds.
- What is HSPA+ (Evolved High Speed Packet Access)?
Evolved High Speed Packet Access or HSPA+ is the second phase of HSPA. It is presented in release 7. HSPA+ can accomplish information rates of up to 42.2 Mbit/s. HSPA+ has further developed multiple input multiple output (MIMO) antenna and radio access network (RAN). HSPA+ is an advancement of HSPA that updates 3G networks and gives a strategy to telecom administrators to migrate towards 4G speeds that are more equivalent to the initially accessible speeds of newer LTE networks without conveying another radio interface.
- What is HSRP (Hot Standby Router Protocol)?
Hot Standby Router Protocol (HSRP) is a CISCO proprietary protocol. It gives redundancy for a local subnet. HSRP gateways conveys multicast hello messages to different gateways to inform them of their priorities for gateway and current status. HSRP permits to design at least two routers as standby routers and just a solitary router as an active router at a time.
- What is HSUPA (high speed uplink packet access)?
High-Speed Uplink Packet Access (HSUPA) is a 3G portable communication protocol in the HSPA. It was determined and normalized in 3GPP Release 6 to further develop the uplink data rate to 5.76 Mbit/s, expanding the limit, and diminishing latency. HSUPA has been supplanted by more up to date technologies further advancing transfer rates. LTE gives up to 300 Mbit/s for downlink and 75 Mbit/s for uplink.
- What is HTTP (HyperText Transfer Protocol)?
HyperText Transfer Protocol is the application layer protocol suite. It is utilized for dispersed, collaborative and hypermedia data frameworks. It was presented in 1991; 30 years ago. It was set up by Tim Berners-Lee at CERN in 1989. HTTP is the establishment of information communication for the World Wide Web, where hypertext reports incorporate hyperlinks to different resources that the client can undoubtedly get to.
- What is HTTPS (HTTP Secure)?
Hypertext Transfer Protocol Secure (HTTPS) is an augmentation of the Hypertext Transfer Protocol. HTTPS encodes and decodes client page demands just as the pages that are returned by the Web server. It is a protocol for protecting the communication between two frameworks for example the browser and the web server. It is utilized for secure communication over a computer network, and is generally utilized on the Internet. HTTPS makes a safe channel over an unreliable network.
- What is HWN (Heterogeneous wireless networks)?
Heterogeneous wireless networks give adaptable and differentiated wireless network access by incorporating cellular networks, wireless LANs, and ad hoc networks. A wireless network that offers assistance through a wireless LAN and can keep up with service when changing to a cellular network is known as wireless heterogeneous network. An HWN has a few advantages when contrasted with a traditional homogeneous wireless network, with expanded reliability, further developed range effectiveness, and expanded coverage.