As an evolution after 3G-4G, do you know its technical characteristics? As one of the 4G standard record filing systems, wireless TD-LTE-Advanced adopts the multi-access method, frame structure similar to TD, and wireless MIMO technology. The following is a detailed introduction.
Features of wireless TD-LTE-Advanced Technology
1. Multiple Access Method
The wireless TD-LTE is based on OFDM technology, and OFDMA is used in the downlink. the uplink adopts the single carrier DFT-SOFDM as the multi-access method according to the link characteristics. According to the sub-carrier distribution feature of OFDM technology, the system uses 15 kHz sub-carrier bandwidth, according to the number of different sub-carriers, supports different system bandwidths of 1.4, 3, 5, 10, 15, and 20 MHz. In LTE-Advanced, you can also aggregate 5 20 MHz unit carriers by means of carrier aggregation to achieve a full system bandwidth of MHz.
2. Frame Structure
The wireless TD-LTE adopts the wireless frame structure, and the wireless frame length is 10 ms, which is divided into 10 sub-frames with a length of 1 ms as the unit of data scheduling and transmission (TTI ). Sub-frame #1 and #6 can be configured as special sub-frame, which contains three special time slots: DwPTS, GP and UpPTS, meaning and function is similar to the TD-SCDMA system.
Taking advantage of the flexible time allocation feature of TDD, wireless TD-LTE supports 7 different upstream/downstream time proportional allocation, from allocating most of the resources to the downstream "downstream: upstream = "until the upstream occupies a large proportion of resources" downstream: upstream = ". In actual use, the network can flexibly choose System Configurations Based on the business volume characteristics.
3. MIMO Solution
MIMO is a key technology of wireless TD-LTE system. According to the antenna deployment form and the actual application situation, three kinds of implementation solutions can be adopted: transmitting diversity, space multiplexing and beam shaping. For example, the spatial multiplexing scheme can be used to transmit multiple data streams at the same time for large-pitch non-correlated antenna arrays to achieve high data rates. For small-pitch related antenna arrays, the beam forming technology can be used, direct the antenna beam to the user to reduce interference between users.
The wireless TD-LTERelease8 version supports up to four downlink antennas for parallel transmission, which can reuse up to four data streams in space. In 20 MHz bandwidth, the peak rate of over Mbps can be achieved. In wireless TD-LTERelease10 and wireless TD-LTE-Advanced, the number of antennas supported by the downlink is extended to 8, and the maximum space can be reused for parallel transmission of 8 data streams, the peak rate is doubled, the peak spectrum efficiency reaches 30 bps/Hz. At the same time, the wireless TD-LTE-Advanced has introduced the MIMO function in the uplink. It supports up to four antennas for transmission and can reuse up to four data streams in space, the uplink peak spectrum efficiency reaches 16 bps/Hz.
Performance evaluation meets or exceeds 4G requirements
In preparing for the 4G candidate proposal, wireless TD-LTE-Advanced has fully evaluated the system performance, including spectrum efficiency, according to the 4G evaluation scenario specified by ITU, voIP capacity, service/switching latency, and other key indicators all meet or exceed the ITU4G technical requirements. Comparison between self-evaluation results of wireless TD-LTE-Advanced and ITU4G technical requirements, in four evaluated scenarios: "indoor", "micro-cell", "macro-cell", and "high-speed, both the "average spectrum efficiency" and "VoIP capacity" Network Operation indicators greatly exceed the ITU technical requirements.
For the recently completed technical submission, the ITU meeting has confirmed the integrity of the submitted information. The next step will be to assess whether the technical proposal meets the 4G technical performance requirements according to the ITU process, therefore, it determines whether to accept the 4G international standard. According to the current self-evaluation results, it is expected that the wireless TD-LTE-Advanced will pass the technical performance check and become the ITU4G international standard technical advice.
LTE-Advanced is currently the world's most popular 4G technology. As part of TDD, wireless TD-LTE-Advanced includes the unremitting efforts of relevant units in China, successfully realized the evolution and development of TD-SCDMA related technology.
The wireless TD-LTE uses OFDM and MIMO as the basic technology, and uses the most advanced technology and design concept of mobile communication at present: "adaptive scheduling of all groups", "simplified flat network architecture", "simplified system status", and "flexible and variable system bandwidth, it achieves Efficient wireless resource utilization, and its performance is much higher than that of the traditional 3G mobile communication system. More importantly, the simplified system design makes it possible to design the "low cost, high performance" design goals in the wireless TD-LTE phase.
The Release8 version of wireless TD-LTE has completed the standardization of the system design, and is currently in the testing stage of prototype equipment, actively preparing for the construction of the subsequent commercial network and industrial promotion. The wireless TD-LTERelease10 version (LTE-Advanced) has been further enhanced in the Release8 version, and all the system indicators have reached the technical requirements of ITU for 4G mobile communication systems, in addition, the evaluation results of key indicators such as "average throughput" and "VoIP capacity" greatly exceed the requirements of ITU.