4G

LTE: In telecommunication, Long-Term Evolution is a standard for wireless broadband communication for mobile devices and data terminals, based on the GSM/EDGE and UMTS/HSPA technologies. It increases the capacity and speed using a different radio interface together with core network improvements.

LTE的目标是什么?

提高移动数据业务的速率，适应多媒体应用的需要。

简要描述LTE采用的上下行通信技术。

上行(移动台到基站): SC-FDMA: Single-carrier FDMA (SC-FDMA) is a frequency-division multiple access scheme. It is also called linearly precoded OFDMA (LP-OFDMA). Like other multiple access schemes (TDMA, FDMA, CDMA, OFDMA), it deals with the assignment of multiple users to a shared communication resource.

下行(基站到移动台): OFDMA: Orthogonal frequency-division multiple access (OFDMA) is a multi-user version of the popular orthogonal frequency-division multiplexing (OFDM) digital modulation scheme. Multiple access is achieved in OFDMA by assigning subsets of subcarriers to individual users.

4G移动通信的关键技术有哪些?

  1. LTE的多址传输技术: SC-FDMA, OFDMA

  2. LTE的多天线技术: MIMO(multiple-input and multiple-output)，基站两个发射天线，用户设备两根天线

  3. LTE的调制技术: 3G基础上(BPSK、QPSK、8PSK) + 16QAM、64QAM

  4. LTE的信道编码: Turbo、LDPC(low-density parity-check)

4G移动通信技术的特点是什么?

  1. 高传输速率

  2. 终端兼容性更好、真正全球漫游(一卡全球通用)

  3. 基于IP的网络

  4. 通信应用更丰富

  5. 通信费用更低

当前有哪些4G移动通信标准?

  • LTE-Advanced

  • WirelessMAN-Advanced / IEEE802.16m

中国的: TD-LTE-Advanced，FDD-LTE-Advanced

第四代移动通信系统与第一、第二和第三代移动通信系统有什么不同?

比以前的系统更好，抗干扰能力更强、传输速率更大、容量更大、成本更低、更智能化、IP网络化。

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