LTE Introduction and Technical Features

LTE is the abbreviation of Long Term Evolution. LTE is also commonly known as 3.9G. It has a data download capacity of 100Mbps and is regarded as the mainstream technology for the evolution from 3G to 4G.

LTE research includes some generally considered important aspects, such as reduced waiting time, higher user data rates, improved system capacity and coverage, and reduced operating costs.

The 3GPP Long Term Evolution (LTE) project is the largest new technology research and development project launched by 3GPP in the past two years. This technology with OFDM/FDMA as the core can be regarded as a "quasi-4G" technology. The main performance goals of the 3GPP LTE project include: providing a peak rate of 100Mbps downlink and 50Mbps uplink in a 20MHz spectrum bandwidth; improving the performance of users at the cell edge; increasing cell capacity; reducing system latency, with the one-way transmission delay within the user plane less than 5ms, the control plane migration time from sleep state to active state less than 50ms, and the migration time from resident state to active state less than 100ms; supporting cell coverage with a radius of 100Km; being able to provide access services of >100kbps for 350Km/h high-speed mobile users; supporting paired or unpaired spectrum, and flexible configuration of multiple bandwidths from 1.25 MHz to 20MHz.

Main technical features of LTE

3GPP has described LTE in detail from aspects such as "system performance requirements", "network deployment scenarios", "network architecture", and "service support capabilities". Compared with 3G, LTE has the following technical features:

(1) The communication rate has been improved, with the peak rate of downlink reaching 100 Mbps and that of uplink reaching 50 Mbps.

(2) Improved spectrum efficiency: 5 (bit/s)/Hz for the downlink, 3-4 times that of the R6 version of HSDPA; 2.5 (bit/s)/Hz for the uplink, 2-3 times that of the R6 version of HSU-PA.

(3) With packet domain services as the main goal, the system will be based on packet switching in its overall architecture.

(4) QoS guarantee: through system design and strict QoS mechanism, the service quality of real-time services (such as VoIP) is guaranteed.

(5) The system is flexible in deployment and can support a variety of system bandwidths between 1.25MHz and 20MHz, as well as "paired" and "unpaired" spectrum allocation, ensuring flexibility in future system deployment.

(6) Reduce wireless network latency: Subframe lengths of 0.5 ms and 0.675 ms solve the problem of backward compatibility and reduce network latency. The latency can reach U-plan < 5 ms and C-plan < 100 ms.

(7) Increased cell boundary bit rate, while keeping the current base station location unchanged. For example, MBMS (Multimedia Broadcast and Multicast Service) can provide a data rate of 1 bit/s/Hz at the cell boundary.

(8) Emphasis on backward compatibility, supporting the coordinated operation of existing 3G systems and non-3GPP standard systems.

Compared with 3G, LTE has more technical advantages, which are embodied in: high data rate, packet transmission, reduced latency, wide area coverage and backward compatibility.

LTE application development

At present, there are three main evolution paths for mobile wireless technology: the first is WCDMA and TD-SCDMA, both of which evolved from HSDPA to HSDPA+ and then to LTE; the second is CDMA2000 along EV-DO Rev.0/Rev.A/Rev.B, and finally to UMB (Motorola's recent new plan is that CDMA2000 will also evolve to LTE in a certain way, and 3GPP2 has basically abandoned the UMB plan); the third is the 802.16m WiMAX route. Among them, LTE has the most supporters, followed by WiMAX.

LTE is a technology developed by major telecom equipment manufacturers such as Ericsson, Nokia Siemens, and Huawei. CDMA-based Alcatel-Lucent and Nortel Networks have also invested in it. CDMA has been losing ground in recent years. Alcatel-Lucent wrote off $3.7 billion in assets related to CDMA technology standards last week and will establish a joint venture with Japan's NEC to develop LTE.

Since Qualcomm, an American company, held the core patents of the technology in the 3G era, the LTE camp deliberately used OFDM to bypass Qualcomm's main technology. It is certain that Qualcomm's position will be weakened compared to the 3G era. At the same time, although Qualcomm's UMB technology has not been popular, the company also announced in Barcelona that it will launch a multi-mode LTE chipset in 2009, and Qualcomm will still maintain profits in this field.