Frame structure Type 1 is illustrated in the upper portion of Figure 9-66. A TDD frame structure is shown in below figure. I am happy to share the top articles of ShareTechNote in 2022 for 5G NR, 4G LTE and Engineering Math. The air interface described in this book covers the concepts of LTE frame structure, downlink and uplink scheduling, and detailed illustrations of the data flow across the protocol layers. Alternative frame structures are defined for use with TDD. LTE frame structure is enhanced in 5G New Radio (NR) to support users with highly diverse service requirements for enhanced Mobile Broad Band (EMBB), Massive Machine Type Communications (MTC) and. This generic frame structure is used with FDD. A typical LTE frame is 10 ms (milliseconds) long. In TDD mode, the SF is either of type DL, UL or special (Spc). Three different types of physical channels are defined for theIn LTE, a subframe is used as a minimum scheduling unit in time-domain while in NR, a slot is used as a dynamic scheduling unit. On-Demand Demo. The figure depicts LTE-M frame structure similar to LTE technology. In TDD, one single frequency will be used at. As shown in the figure below, an LTE TDD frame is made of total 20 slots, each of 0. A. Here, the idea is to compress the whole transmission chain of waiting for a transmit opportunity and preparing for a transmission, transmitting the data, and finally processing the received data. Differently to LTE, the 5G frame structures is more flexible. 1. The mobile equipment has the following core modules: All communication functions are handled by Mobile Termination (MT). The resulting location of the process is as shown in Reference Signal section of Downlink Frame Structurepage. The Frame Controller controls the subframe and frame indices. Figure 1 shows frame structure type 1, which can be used in either full-duplex or half-duplex FDD mode. Two consecutive time slots will form one subframe. This generic frame structure is used with FDD. Selection of normal or extended prefix e. One slot is defined as 14 OFDM symbols, which corresponds to once a frame or one millisecond in LTE. These two frames, which are incompatible with each other, will require new functionalities to avoid interference at borders. Just take a look at the overall uplink slot structure. There are two types of frame structures in LTE; type 1 used for FDD and type 2 for TDD, as shown in the diagrams above. Each radio frame of length Tf = 307200*Ts = 10 ms consists of two half-frames of length Tf = 153600*Ts = 5 ms each. Further each radio frame is divided into two sub frames each of 5ms. of slots=20. Subframes #0 and #5 are always assigned to DL, and subframe #2 is always assigned to UL. Leveraging its extensive experience in 3G markets, Anritsu has developed the MD8430A as a powerful LTE protocol R&D test platform enabling developers bring LTE terminals to market as fast as possible. As shown 5 ms periodicity frame have two “S” subframe and 10 mili sec frames. However, unlike LTE-U, LAA use a special physical layer frame structure called Frame Structure Type 3 which didn't exisit before. 8 supports scalable RF channel bandwidths from 1. . The Evolved UMTS Terrestrial Radio Access Network (E-UTRAN). Demodulating an LTE Signal in MATLAB with LTE System Toolbox. For more information, see LTE Toolbox™. The downlink subframe structure in LTE-M only uses a part of the downlink subframe REs in LTE. Total 17 frames are used for carrying information data and 1 frame (i. 3 Downlink frame structure 190 9. There are two types of LTE frame structure: Type 1: used for the LTE FDD mode systems. In this tutorial, TDD frame structure below will be used, which is a DDDSU slot pattern with 2. Yang Chamsol. 211 frame structure type 2 (DL / UL / SSF) Correct choice of Configuration value is essential when setting the UL/DL ratio for CableFree LTE networks using TDD bands. D = downlink sub-frame; U = uplink sub-frame; S = special sub-frame. Network Structure . 1), where the downlink and uplink transmissions are per-formed in different carrier frequencies. 27/06/2023 0. C. LTE system basic parameters and LTE Frame structure: Frame Size=10ms. Alternative frame structures are defined for use with TDD. 9. The Fig 1: Shows the position of RACH in the Uplink LTE channel Structure. 25 MHz to 20 MHz. LTE Parameters and Downlink Modulation. No. Rrc Parameters. It does not show any structure in frequency domain. Learn the basics behind 5G NR waveforms, frame structure, and numerology. . Downlink ※ Reference - 3GPP TS 36. Introduction The communication scenario in the world is growing at a large pace and the industry is gearing up for a thousand times more faster and reliable data rates. 2. 7. There are seven different Type 2 frame structures as shown in the figure, which can be changed flexibly. CellAdvisor LTE frame analysis — unicast (PDSCH) and broadcast (MBMS) allocations Performance MBMS-SFN services are static and do not vary over time. Type 1 radio frame has a duration 10 ms and consists of equally sized 20 slots each of 0. (normal cyclic prefix) or six (extended cyclic prefix). 72 (=0. Resource Elements and Resource Blocks. LTE Frame Structure 5. For FDD, whether downlink and uplink In this chapter, we introduce the OFDM‐based LTE signal and frame structure to explain how the user‐plane and control‐plane data from the higher layers, such as the Radio Link Control (RLC) layer and Media Access Control (MAC) layer are multiplexed with physical layer control and Reference Signals (RSs) for data transmission. The PSS & SSS generation generates PSS,. Number of Subframes in a Radio Frame = 10. The frame structure below ( Figure 1) is applicable to TDD. 0056532 Tzu-chin Liu 15 th March 2012. To address these challenges, we propose a novel frame structure design that incorporates several key changes relative to current LTE systems: Flexible TTI duration: The current LTE system uses a fixed transmission time interval (TTI) of one subframe (1 ms). 2. But in new subframe, the reference signal is distributed across frequency domain only. Each LTE frame has a duration of 10 ms, and is subdivided into 10 equal-size subframes of 1 ms; each subframe comprises two slot periods of 0. 2 Initiation over S1 14 6. However, in addition to the other modulation schemes used in 4G, radio conditions allowing, it can use 256-state quadrature amplitude modulation (256QAM). The number of symbols per slot depends on the size of the cyclic prefix. 16e standards WiMAX MAC layer Frame Structure as per OFDM 802. The 10 ms frame comprises two half frames, each 5 ms long. The data streams are terminated in Terminal Equipment (TE). Hybrid ARQ Transmission Short Frame Sizes of 10ms and 1ms faster feedback and better efficiency at high speed. LTE FDD. Download scientific diagram | LTE Frame Structure for FDD Systems. The LTE frame structure for the FDD and TDD schemes was discussed in Chapter 9. For LTE TDD only, SRSs can be transmitted in an ordinary sub-frame or in UpPTS sub-frame to improve spectral efficiency. Some parameters do not apply to the Basic LTE PRACH and Basic LTE-A PRACH. This application note describes the Long Term Evolution (LTE) of the universal mobile telecommunication system (UMTS) standard by the 3rd Generation Partnership Project (3GPP). There are two types of LTE frame structure: Type 1: used for the LTE FDD mode systems. – Frame structure type 1 (FS1): FDD. 04/02/2023 10 Types of Frame Structure in LTE: • Types of Frame structure in LTE: 3GPP defines two types of frames based on the duplexing scheme used. 11. LAA stands for Licence Assisted Access. Bandwidth vs RBs • LTE physical layer supports any bandwidthTime Domain transmission pattern of SS Block in NR is more complicated than LTE SS Block (Actually LTE has only one pattern of SSB Transmission in Time Domain as shown in LTE Frame Structure. OFDMA and Downlink Frame Structure Details. 5 msec. Increasing frame configuration; Configuration: 3GPP release: Downlink to uplink switch point. We show that this fixed TTI duration is extremely inefficient whenThe radio frame is a key structure defining transmission time slots. A typical LTE frame is 10 ms (milliseconds) long. LTE Introduction. In the special slot, symbols allocated for downlink, gap and uplink are 10:2:2 respectively. 211 V16. Then why we need to care of this kind of thing in LTE-Unlicensed technology ? Basically LTE Unlicensed technology (e. Each radio frame will have a total of ten subframes, each with two time slots. The Evolved Packet Core (EPC). 5 ms. Slideshow 2210075 by allieIn LTE physical layer, the LTE frame structure is of two types: 1. Some parameters do not apply to the Basic LTE PRACH and Basic LTE-A PRACH. For example, TDD networks share the same radio spectrum for the downlink (DL) and uplink (UL) transmissions which means scaling needs to be applied to the expected throughputs. K. Figure 1. The LTE specifications define both FDD and TDD modes of operation. The access frame is access of 15 access slots and lasts 20 ms (2 radio frames). Page 2 - 2 - INHA UNIVERSITY. when μ = 0. Design verification. It only shows the structure of one frame in time domain. In LTE, the subframe number and OFDM symbol number within the subframe is always same in any cases). Frame-Structure in LTE. The first three columns of SONET frame is referred as transport overhead. There are total 10 subframes in a frame. The maximum number of subframes in one. 1. (I created following subframe structure using LTE Resource Grid and edited to fit the topics of this page)A frame has a duration of 10 ms and consists of 10 subframes. Type 1, applicable to FDD- Here there are. 5 ms repetition period. LTE Frame Structure Made Simple. Type-1 LTE Frequency Division Duplex (FDD) mode systems: Type-1 frame structure works on both half duplex and full duplex FDD modes. Traditionally, the system models were made using the 3GPP spatial channel model for LTE and a number of parameters have to be varied at the backend. Access Procedure & Signaling. This frame system is used where there are possibilities of heavy rain and snow. Please share this video with your friends. in 1 slot, the number of symbols are fixed that is 14-with normal cyclic prefix (CP) and 12-with extended CP. V. 8. LTE: Key Features (Cont) 8. As shown in Figure 1, LTE frame trans-The detailed radio frame structure for both frame structure types is shown in Figure 2. cyclic prefix). 19/06/2016 0. LTE frame is 10 ms in duration and consists of 10 subframes. Figure 1 LTE Frame structure . A phone must typically perform the following tasks (Figure 5): Acquire a signal on a given LTE carrier frequency. • The PSS is constructed from a frequency-domain ZC sequence of length 63. 5G NR Supports two frequency ranges FR1 (Sub 6GHz) and FR2 (millimeter wave range, 24. (Please refer to diagram for better understanding) 1) In time domain, 1 Radio frame (RF) is of 10 ms. But in NR, the number of slots varies according to the numerology. · Time slot size= 0. One resource block is 0. The following are the two types of radio frame structures: (i) Type 1: supports FDD mode. Because of variable subcarrier spacing, the. There are total 10 subframes in a frame. Slot duration=0. 2) There are 10 Sub-frames in each Radio frame. IP packets are reformed in the PDCP SDUs and flow through the RLC, MAC, and PHY layers. As described above, in 5G/NR multiple numerologies (waveform configuration like subframe spacing) are supported and the radio frame structure gets a little bit different. crostrip line with a 0. 212 5. Type 2: Used in LTE TDD. Protocols RACH SIB PAGING MAC RLC PDCP Full Stack Basic Call Idle Mode Multi Cell UE. Evolved Packet Core (EPC) 4. Radio Resource Scheduling: The most important objective of LTE scheduling is to satisfy Quality of Service (QoS) requirements of all users by trying to reach, at the same time, an optimal. LTE-A Frame Structure. The LTE frame is formed of 10 subframes (SF) of duration 1 ms each and sub-divided into 14 OFDM symbols. 5. The duration of each subframe is 1 ms. The LTE physical layer supports two types of frame structures as types 1 and 2. 10 subframes (= 20 slots) are fit into 10 ms in LTE while various number of slots depending on Numerology are fit into 10 ms in 5G NR. Following equation is based on 36. 3. The minimum unit being frame (or TDMA frame) is made of 8 time slots. 5 ms each). of slots=20. 2. structure Basic unit of resource is the Physical Resource Block (PRB). If you are interested in some historical aspects of the 5G Frame structure, it would be good to read through this. It uses a 20 MHz channel with 2048 subcarriers. To configure the downlink signal in this slot pattern, two separate DL-SCHs will be needed to represent two different channel. • Three PSS sequences are used in LTE, corresponding to the three physical layer identities within each group of cells. 6 Mobility. 12. The physical frame structure of LTE is a combination of time domain OFDM symbols and frequency domain subcarrier indices. e. In the LTE standard (E-UTRA Citation 2019), OFDM signals are specified by three parameters, namely, the number of subcarriers or the Fast Fourier. LTE Frame structure in muted MBSFN subframe based DSS. - In LTE there is only one subcarrier. In this video we discuss three focus areas; Downlink Frame Structure, Uplink Frame Structure, and TDD Options. In 5G/NR, we don't have any predefined pattern. (As you know, one sample (Ts) is 1/30. When an LTE system in one country is within the footprint of a satellite service owned by another country, to prevent the interference from the satellite services, the LTE system will avoid using the overlapped frequency bands. 211: Physical Channels and Modulation - 3GPP TS 36. Myung 17 Frame Structure • Two radio frame structures defined. • LTE interoperates with CDMA2000, W-CDMA and GSM systems. As seen in the figure, in each frame some subframes are allocated for uplink transmissions and some subframes are allocated for downlink transmission,. There are two cell search procedures in LTE: one for initial synchronization and another for detecting. There are two types of LTE frame structure: 1. LTE tutorial videos, articles, and code examples introduce key LTE concepts and effective techniques and workflows for LTE physical layer development including: Waveform generation. LTE will bring many. Type 1 lasts 10 ms equivalent to 10 subframes. Overview Network architecture Protocol stack Resource element Frame structure TDD frame configuration TDD special subframe MIMO Random access procedure. The Fading parameters are available for Advanced LTE and Advanced LTE-A TDD carriers only. 104: Evolved Universal Terrestrial. < SIB 2 and 36. The LTE half-frames are further split into. The REs are. 211 V16. Frame Structure 2. 5 ms 1 subframe = 1 ms #0 #1 #19 Special subframes containing: DwPTS: downlink pilot time slot UpPTS: uplink pilot time slot GP: guard period for TDD operation Possible uplink-downlink configurations (D=Downlink,There are two types of LTE frame structures. 5 99 198 396 397. LTE-V2X PHY-layer Structure 10 LTE frames divided into 1 subframes Channel divided into resource blocks (RBs) 180 kHz RB contains:. Secondly, 5G supports a single carrier of upto 275 RBs while LTE only supported a single carrier of 100 RBs. 5 ms. It describes NB-IoT Frame Structure with 15 KHz Subcarrier spacing and 3. In recent time, much data is needed inFrame structure with Numerologies. LTE tutorial videos, articles, and code examples introduce key LTE concepts and effective techniques and workflows for LTE physical layer development including: Waveform generation. · Radio frame size= 10 ms. Alternative PDSCH DM-RS pattern when LTE CRS rate matching is configured; 7. 5 ms each). 75 KHz Subcarrier Spacing. How many Time-Slot are present in Sub-Frame? Q04. The 51-frame Control Channel Multiframe in GSM. Design verification. 5 Paging over S1 15 6. The resulting location of the process is as shown in Reference Signal section of Downlink Frame Structurepage. The evolved packet core communicates with packet data networks in the outside world such as the internet, private corporate networks or. 19/06/2016 0. 55ns. Source publication. e. Three different types of physical channels are defined for theRadio Frame Structure for LTE. What is Cyclic Prefix (CP) in Frame-Structure? Q05. RACH stands for R andom A ccess Ch annel. Although a slot is a typical unit for transmission upon which scheduling operates, NR enables transmission toThere are two types of frame structure in the LTE standard, Type 1 and Type 2. · It consists in a category of Frame 2. LTE FDD Radio Frame structure :-. Modulation: OFDM with QPSK, 16 QAM, 64 QAM 10. The channels in LTE system are mainly categorized into logical, transport and physical channels based on their functions. The cyclic shifts are generated based on cell-identity group number, which. A standard LTE system architecture consists of an Evolved UMTS Terrestrial Radio Access Network, more commonly known as E-UTRAN, and the System Architecture Evolution, also known as SAE. Switching Points . Figure 2 shows frame structure type 2 for the SC-FDMA uplink. One slot is defined as 14 OFDM symbols, which corresponds to once a. In telecommunications, long-term evolution ( LTE) is a standard for wireless broadband communication for mobile devices and data terminals, based on the GSM / EDGE and UMTS / HSPA standards. Now consider the details of a symbol. Long Term Evolution (LTE) is the latest buzzword on everyone’s lips, but are you as conversant with the LTE architecture as you would like to be, or — more importantly —. One frame is divided into 10 subframes of 1ms each and each subframe is distributed into 2 slots of 0. 211 - Figure 9: Frame structure for downlink DPCH > HS-SCCH(HS Shared Control Channel) HS-SCCH is to carry the control information for HS-PDSCH and it has fixed rate of 60 kbps and spreading factor of 128. Uplink physical channels and uplink physical signals are as follows. 5 ms each. Low Layer Procedures DCI HARQ PHY Processing MIMO MIMO/CA(Big Pict. 0 (2007-06): Physical Channels and Modulation. Type 2 LTE frame structure. It describes the details of the optimization process including performance measurements and troubleshooting mechanisms in addition to demonstrating common. 4 Frame structure type 2 177 8. The Fading parameters are available for Advanced LTE and Advanced LTE-A TDD carriers only. Type 1: FDD : Frequency Division Duplex. The fre-quency index of an RE maps to an LTE subcarrier, and its time index maps to an LTE symbol. In recent time, much data is needed inLong Term Evolution (LTE) is the next step forward in cellular 3G services. ) Precoding Fading Power Control PUCCH. 4G - LTE FRAME STRUCTURE |FRAME , SUBFRAME, SLOT, RE | MJTECHSTAR#MJTECHSTARIf the spatial domain is also considered the resource allocation structure actually becomes a 3-dimensional arrangment. LTE DL Frame Structure in a Nutshell. A common frame structure as defined by 3GPP TS 38. Each subframe consists of two slots. TDD have a special sub frame (1,6) when downlink-to. OFDMA2. In TDD there are about 7 frame configurations, based on different DL/UL. The highest level view from 36. In the LTE standard (E-UTRA Citation 2019), OFDM signals are specified by three parameters, namely, the number of subcarriers or the Fast Fourier. from publication: Robust Doubly-Differential Primary Synchronization Approach for 3GPP LTE Systems. A phone must typically perform the following tasks (Figure 5): Acquire a signal on a given LTE carrier frequency. The 5G NR frame structure depicts subframes,slot and symbol configurations. 5G, and 5G are covered in subsequent modules. 2. A standard LTE system architecture consists of an Evolved UMTS Terrestrial Radio Access Network, more commonly known as E-UTRAN, and the System Architecture Evolution, also known as SAE. 12 6. The air interface described in this book covers the concepts of LTE frame structure, downlink and uplink scheduling, and detailed illustrations of the data flow across the protocol layers. 10. 2. Frame Structure; LTE-NB : Physical Layer : Uplink : SC-FDMA Baseband Signal Generation; LTE-NB : Channel Structure; LTE-NB : HARQ; LTE-NB : Multi Carrier Operation (Anchor. In order to make use of the overlapped LTE bands, a Downlink Only Frame Structure (DOFS) approach is proposed in this. ② SR（Scheduling Request）. Frame Structure Downlink Uplink Reference Signal. Depending on the cyclic prefix (CP) duration, each slot carries a number of orthog-LTE TDD Frame Structure ? FDD|| TDD क्या है I अगर प्रोटोकॉल टेस्टिंग की है तैयारी तो जरूर देखो. design, LTE frame structure dedicated some channels for data and they are called data channels while others for control information, known as control channels. Frame Structure2. Hierarchy of Frame Structure : Frame (Radio Frame) --> SubFrame --> Slot (Same as in 5G/NR) Number of slots within 1 subframe : 2 only, but the concept of slot is not used often in LTE. Since the modulation format is OFDM (regular OFDM for the downlink, and DFT- precoded OFDM in the uplink. A slot consists of 7 ofdm symbols (if normal cyclic prefix is used) separated by. It has characterstics as listed below. Slot duration=0. FDD (Frequency division duplex), which uses type 1 frame structure. LTE DL Frame Structure in a Nutshell. iv) Transmit every 40 ms , repeat every 10 ms . OFDMA System Model LTE (Long Term Evolution) uses OFDMA and SC-FDMA atThe first one is defined for FDD mode and it is called frame structure type 1. A non-exhaustive list of. If you can interpret these tables into a correct graphical format, you already understand all the details of Uplink frame structure. Determine frame synchronization and cell identification (cell search procedure) based. Each frame is composed of 10 subframes of 1 msec duration. The first choice has the advantage of compatibility with the LTE frame structure used by French networks and The second choice is not compatible with LTE. 1-1: Mapping between cell-identity group and the indices m0 and. Downlink modulation types: QPSK, 16-QAM, and 64-QAMthe LTE communication protocol. The high-level network architecture of LTE is comprised of following three main components: The User Equipment (UE). This page introduces several candiates for 5G Frame Structure before 3GPP finalize the specification. 2. LTE has radio frame of duration 10ms consisting of 10 subframes. 5ms duration. LTE standard has been published by 3GPP as an extension of UMTS (based on 3GPP standard) and 1xEV-DO (base on 3GPP2 standard. LTE frame structures used for TDD 36. This is then divided into a total of 20 individual slots. Type 1 LTE Frame Structure The basic type 1. Moreover, if Carrier Aggregation is done with a couple of such carriers, it will provide a huge throughput gain. To fulfill these requirements, orthogonal frequency division multiplex (OFDM) was selected as the basis for the PHY layer. This video looks at OFDM waveforms, and the different subcarrier spacings supported in 5G NR. The subframes may be divided into standard sub frames of special sub frames. A Radio frame/System frame is of 10 msec. In LTE the physical layer is driven by OFDMA in the downlink and SC-FDMA in the uplink. It describes 5G frame as per NR (New Radio) 3GPP standard. 1. Suresh Sahni. 1 primary and 4 secondary). 6 8. Transmit Diversity & Receive Diversity . LTE Frame Structure; LTE channels and mappings; RLC, RRC / NAS, PDSCH, PDCCH, HO; 5G core reference architecture; Towards the end of the 4G LTE course, you will learn in-depth about the LTE MAC Scheduler, LTE EPC nodes and interfaces. Frame Structure Type 1. Type 1 uses Frequency Division Duplexing (uplink and downlink separated by frequency), and TDD uses Time Division Duplexing (uplink and downlink separated in time). Full size image. As shown in Fig. The second component enables shorter transmission durations (Figure 2), which is a more radical change of the LTE frame structure. But in NR, the number of slots varies according to the numerology. Each radio frame of length Tf = 307200*Ts = 10 ms consists of two half-frames of length Tf = 153600*Ts = 5 ms each. Yes it brought multiple options in sub-carrier. Type 2: used for the LTE TDD systems. No of Slots per Sub frame =2. 4) is applied to Time Division Duplex (TDD) mode maintaining only full duplex operation. The resource element, which is 1 subcarrier x 1 symbol, is the smallest discrete part of the frame and contains a single complex value representing data from a physical channel or signal. The UE and eNB communicate with each other based on the radio frame structure, as shown in Figure 22. 5G Frame Structure in Detail . 2 μs. Increasing frame configuration; Configuration: 3GPP release: Downlink to uplink switch point periodicity (ms). frame structure type, number of antennas, number of symbols in PDCCH and the scaling factor Ng. 3 16. lets take few example to understand frame structure in more details . The frame structure for the type 2 frames used on LTE TDD is somewhat different. 7 μs. Learn the details of LTE-NB frame structure for downlink operation mode, including the subframe mapping, the reference signal, the NPBCH, NPSS and NSSS. Base stations need to. Please share this video with your friends. This provides several benefits, including:“10ms” version, and gives greater opportunity for uplink/downlink flexibility. It introduces several changes in terms of frame structure and slot formats compared to previous generations like 4G LTE. LTE Frame Structure Types. 211 V1. In TDD there are about 7 frame configurations, based on different DL/UL. Ok now on to our Downlink LTE frame structure. Type 2 LTE Frame Structure. However, unlike LTE-U, LAA use a special physical layer frame structure called Frame Structure Type 3 which didn't exisit before. It only shows the structure of one frame in time domain. LTE tutorial- This tutorial on LTE covers LTE system overview, LTE air interface,LTE SAE and provide link for LTE Frame structure, LTE physical layer,LTE protocol stack,LTE terminologies,LTE advanced,LTE vendors etc. Now (as of Sep 2017) 3GPP official specification (38. The air interface described in the chapter covers the concepts of LTE frame structure, downlink and uplink scheduling, and detailed illustrations of the data flow across the. Physical layer. Figure 2. Uplink Frame Structure of LTE-NB can be summarized in the following three tables. In this example we will be simulating what happens when a mobile phone is turned on. 211) defines the Frame Structure. · Radio frame size=. But in new subframe, the reference signal is distributed across frequency domain only. Each GSM superframe composed of multiframes (either 26 or 51 as described below). System Requirement. • Transmitted on 6th symbol of slot 0 and slot10 of each radio frame on 72 subcarriers centered. Contents. . , Frame Structure Type 3) was introduced to facilitate unlicensed spectrum operation consisting of 10 subframes of length 1 ms as illustrated in Fig. LTE: Key Features 2. Frame Structure Type 1.