What are reference signals in LTE?

LTE Advanced – Downlink Reference Signal | ShareTechnote. Most of the channels (e.g, DPSCH, DPCCH, PBCH etc) is for carrying a special information (a sequence of bits) and they have some higher layer channel connected to them, but Reference Signal is a special signal that exists only at PHY layer.

What is reference signal?

One reference signal is transmitted from each downlink antenna port. The downlink reference signal can be used for the following purposes: Cell search and initial acquisition. Downlink channel quality measurements. Downlink channel estimation for coherent demodulation/detection at the UE.

Why are there 12 subcarriers in LTE?

In the downlink, the subcarriers are split into resource blocks. This enables the system to be able to compartmentalise the data across standard numbers of subcarriers. Resource blocks comprise 12 subcarriers, regardless of the overall LTE signal bandwidth. They also cover one slot in the time frame.

What is a symbol in LTE?

The smallest modulation structure in LTE is the Resource Element. A Resource Element is one 15 kHz subcarrier by one symbol. … Twelve consecutive subcarriers in the frequency domain and six or seven symbols in the time domain form each Resource Block. The number of symbols depends on the Cyclic Prefix (CP) in use.

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What is demodulation reference signal?

2 Demodulation Reference Signals. In contrast to CRS, a demodulation reference signal (DM-RS) is intended to be used for channel estimation by a specific device and is then only transmitted within the resource blocks assigned for transmission to that device.

What is PCI in LTE?

A Physical Cell Id (PCI) is the identifier of a cell in the physical layer of the LTE net- work, which is used for separation of different transmitters. Due to the construction of PCIs, the number of PCIs are limited to 504.

What is the LTE DL reference signals used for?

The purpose of this Reference Signal is to deliver the reference point for the downlink power. These reference signal are carried by multiples of specific Resource Elements in each slots and the location of the resource elements are specifically determined by antenna configuration.

What modulation does LTE use?

LTE uses the popular orthogonal frequency division multiplex (OFDM) modulation scheme. It provides the essential spectral efficiency to achieve high data rates but also permits multiple users to share a common channel. OFDM divides a given channel into many narrower subcarriers.

What is a subframe in LTE?

A subframe comprises two slots, thus one radio frame has 10 sub‐frames. … In FDD mode, half of the subframes are available for downlink, and the other half are available for uplink transmission in each 10 ms interval, where downlink and uplink transmission are separated in the frequency domain.

What is DC carrier in LTE?

DC stands for Direct Current and it is a subcarrier that has no information sent on it. This is an important subcarrier in OFDM based systems. It is used by the mobile device to locate the center of the OFDM frequency band. So, if LTE does not have a DC subcarrier, it would be a big deal.

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Why scrambling is used in LTE?

Scrambling the bits make them less prone to interference as the process make the value of bits to be transmitted to be psuedo random. The scrambling code used is a length 31 gold sequence which yields 2^31 puseddo random sequences.

What is LTE frame structure?

In LTE, DL and UL transmissions are organized into radio frames of 10 ms each. Each frame is divided into ten equally sized subframes. The duration of each subframe is 1 ms. Moreover, each subframe is further divided into two equally sized time slots, that is, each slot is 0.5 ms.

What is LTE TTI?

TTI, Transmission Time Interval, is a parameter in UMTS (and other digital telecommunication networks) related to encapsulation of data from higher layers into frames for transmission on the radio link layer. TTI refers to the duration of a transmission on the radio link.

What is reference signal in control system?

the reference or set point is the temperature that you set your thermostat to be. the feedback signal is the actual temperature that is measured with some kinda thermometer. … the difference between those two signals is what drives your “controller”.

What is the use of UE specific reference signal?

UE-RSUEUser Equipment (e.g. cell phone)-specific Reference Signal is the UE-specific Reference Signal and is used to enhance communication reliability by using beamforming which is accomplished by changing the phase and magnitude of a PDSCHPhysical Downlink Shared Channel allocation (including UE-RS) sent to each …

What is Dmrs?

DMRS refers to demodulation reference signal. It is used by a receiver for radio channel estimation for demodulation of associated physical channel.

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