What modulation methods does LTE have, what are the characteristics of each, and what scenarios are

LTE modulation is available in the following ways:

1) QPSK: Orthogonal phase shift keying, QPSK is a kind of first-class phase modulation, with good anti-noise characteristics and frequency band utilization, and is widely used in satellite links, digital trunking and other communication services.

2) 16QAM: Quadrature amplitude modulation, which is a digital modulation method, which has the advantage of high information transmission rate.

3) 64QAM: i.e., phase orthogonal amplitude modulation, which has the characteristics of high bandwidth utilization and is suitable for cable TV cable transmission.

in the use of coaxial cables.

qpsk, 16qam, and 64qam modulation techniques are commonly used to send downlink data.

The data channel adopts QPSK, 16QAM, 64QAM, and the control channel adopts BPSK QPSK. The modulation of the control channel is fixed, and the modulation of the data channel is determined based on the quality of the feedback channel. It is related to the CQI of the UE side feedback.

Do you mean bpsk, qpsk, 16qam, 64qam or any of these things?

This is determined by the physical channel. Some physical channels need to be reliable or have a low amount of information and adopt a low modulation mode (e.g., phich, pdcch, pucch, pbch). Some channels are used to transmit data and are dynamically adjusted (PDSCH) according to the actual channel environment (Sinr) to ensure the balance between rate and quality.

Or ofdma, sc-ofdma?

Downlink: Because the base station does not consider the power problem and the cost of RF devices, OFDMA with a high peak-to-average ratio can be used

In the upside, considering the power consumption of the mobile phone and the cost of the device, SC-OFDMA is used

This is based on the specific physical channel, which is used in the standard and is now remembered.

The debugging mode of PDCCH is bpsk, qpsk, and PDSCH is qpsk, 16qam, 64qam

The remaining debugging methods for broadcast channels, etc., are low-order.

Commissioning of the antenna side.

Uplink sc-ofdma

Downlink OFDM

Only QPSK, 16QAM, and 64QAM are used by the service. The specific modulation mode used depends on the capabilities of the UE and the channel conditions.

There are two mainstream modes of LTE technology: TDD and FDD.

TD-LTE is a new generation of broadband mobile communication technology, which is the follow-up evolution technology of TD-SCDMA with independent intellectual property rights in China, which inherits the advantages of TDD and introduces multi-antenna MIMO and frequency division multiplexing OFDM technology. Compared with 3G, TD-LTE has improved system performance by leaps and bounds, providing users with more colorful mobile Internet services.

FDD-LTE is an FDD-LTE that applies FDD-type LTE. Due to the differences in wireless technology, the use of different frequency bands and the interests of various manufacturers, the standardization and industrial development of FDD-LTE are ahead of the mode is characterized by the separation (uplink and downlink frequency interval of 190MHz) on the two symmetrical frequency channels, the system receives and transmits, and separates the receiving and transmitting channels with the guaranteed frequency band.

Then the upstairs sister added: in addition to the uplink scrambling process, the downlink PDCCH also uses RNTI-based scrambling, and the scrambling sequences used also include si-rnti and p-rnti. You can go to the layer process protocol to see the specific rnti values, and I remember that it seems to be 4 hexadecimal numbers.

In addition, other scrambling sequences can refer to the scrambling process of each channel in He, and the scrambling sequences have actually been given, some are related to the cell ID, and some are related to the user RNTI.

There are six characteristics:

1.According to the different needs of terminals, terminals are divided into five categories, from focusing on supporting voice communication to supporting high-speed data connections that reach network peaks. All terminals will have the capacity to handle 20 MHz of bandwidth. Destruction of sheds.

2.Under the optimal conditions, small IP packets can have a latency of less than 5 milliseconds, and the phase dust has a shorter handover and connection preparation time than the original wireless connection technology.

3.Supports everything from femto-fem base stations covering tens of meters to macro cell base stations covering 100 kilometers. The lower frequency bands are used to provide suburban network coverage, with base station signals providing perfect service within 5 km coverage, high quality network service up to 30 km, and acceptable network service up to 100 km.

In urban areas, higher frequency bands can be used to provide high-speed mobile broadband services. In this band, the base station coverage area will likely be equal to or less than 1 km.

4.Packet-switched radio interfaces are supported.

5.The IP-based management network effectively prevents the handover of existing 3G technologies. Brother Lee.

6.Supports multicast and broadcast single-band networks. This feature can be used to provide services such as mobile TV using LTE networks and is a competitor to DVB broadcasting.

LTE does have two frame structures, called the first type of frame result and the second type of frame structure.

Both structures are 10ms a wireless frame.

1> The first type of frame structure, mainly used for FDD-LTE, frequency division multiplexing duplex. One of its wireless frames is 10ms and is divided into 10 subframes, each of which is divided into 2 time slots. Each time slot is divided into 6 or 7 OFDM symbol lengths depending on the length of the CP.

2> The second type of frame structure, mainly used for TDD-LTE, time division multiplexing duplex. One of its wireless frames is also 10ms, but it is divided into two half-frames of 5ms, each of which is 5ms. These 5ms can be divided into uplink subframes, downlink subframes, or special subframes, a total of 5 subframes.

Why do you have to use two different frame structures for LTE?

This is mainly due to the fact that LTE can employ different multiplexing techniques, i.e., TDD and FDD. Centralized FDD, since the uplink and downlink are separated in different frequency bands, from the time domain, each subframe can be uploaded and **. So a wireless frame is divided into 10 subframes, and each subframe has a number of symbols.

For TDD, it's not that simple. Since the uplink and downlink use the same frequency band, in order to avoid uplink and downlink conflicts, it is necessary to specify the time when the uplink is transmitted and the time when the downlink is transmitted. Therefore, TDD-LTE obviously cannot be the same as FDD, it must indicate that the current subframe is an uplink and downlink attribute.

In addition, it is important to note that there must be a guard interval in the middle of the subframe due to the uplink and downlink switching. So, inside TDD, there is also a special subframe. Among them, there are special subframes, which can be divided into DWPTS (for downlink), GP (protection interval) and UPPTS (for uplink).