The table below shows how many subcarriers and resource blocks there are in each bandwidth for uplink and downlink. The bandwidths defined by the standard are 1.4, 3, 5, 10, 15, and 20 MHz. 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 underlying data carrier for an LTE frame is the resource element ( RE Resource Element, 1 subcarrier x 1 OFDM symbol the smallest data unit in LTE holding one complex IQ value per antenna port). OFDM is an alternative tranmission scheme to DSSS and FHSS.) or orthogonal frequency division multiple access (OFDMA) signal, the subcarrier whose frequency would be equal to the RF Radio Frequency: A generic term for radio-based technologies, operating between the Low Frequency range (30k Hz) and the Extra High Frequency range (300 GHz). downlink signal could be described as 25 resource blocks wide or 301 subcarriers wide ( DC subcarrier In an orthogonal frequency division multiplexing ( OFDM Orthogonal Frequency Division Multiplexing: OFDM employs multiple overlapping radio frequency carriers, each operating at a carefully chosen frequency that is Orthogonal to the others, to produce a transmission scheme that supports higher bit rates due to parallel channel operation. For instance, a 5 MHz Megahertz: A unit of frequency equal to one million hertz or cycles per second. The 89600 VSA LTE demodulator currently only supports resource blocks that are 12 subcarriers wide.įrequency units can be expressed in number of subcarriers or resource blocks. In frequency, resource blocks are either 12 x 15 kHz subcarriers or 24 x 7.5 kHz subcarriers wide The number of subcarriers used per resource block for most channels and signals is 12 subcarriers. wide in frequency and 1 slot long in time. The resource block is 180 kHz kiloHertz: A radio frequency measurement (one kilohertz = one thousand cycles per second). (0.5 ms) / 7 for normal CP 1) Contention period, orīelow is an illustration of an FDD frame.Ī resource block ( RB Resource Block) is the smallest unit of resources that can be allocated to a user. There are six time units: frame, half-frame, subframe, slot, symbol, and the basic time unit (T s), as shown in the following table. Terminologyįirst, an introduction to some of the terms used in describing an LTE Frame. Keysight has also released a book called LTE and the Evolution to 4G Wireless: Design and Measurement Challenges which contains detailed information on many of the aspects of LTE. This overview is not an exhaustive description of the physical layer, but is intended to provide you with a useful background when you configure the 89600 VSA LTE demodulator to make measurements.įor a more in depth explanation of LTE, see the 3GPP Long Term Evolution: System Overview, Product Development, and Test Challenges application note. Type 1 signals and LTE TDD Type 2 signals described in the standard documents listed in the About Opts BHD and BHE: LTE Modulation Analysis topic. This overview covers both LTE FDD Frequency Division Duplex: A duplex scheme in which uplink and downlink transmissions use different frequencies but are typically simultaneous. uses Time Division Duplexing (uplink and downlink separated in time). Type 1 uses Frequency Division Duplexing (uplink and downlink separated by frequency), and TDD Time Division Duplex: A duplexing technique dividing a radio channel in time to allow downlink operation during part of the frame period and uplink operation in the remainder of the frame period. There are two types of frame structure in the LTE Long Term Evolution standard, Type 1 and Type 2. LTE Physical Layer Overview LTE Physical Layer Overview