1. Introduction to Super Uplink Technology
The current state of 5G networks
Currently, 5G uplink speeds are limited by terminals, frame structures, and frequency bands, resulting in a significantly inferior experience compared to downlink speeds.
Issues include weak uplink coverage and low uplink capacity in the 3.5GHz band.
Traditional uplink enhancement technology
3GPP has proposed two uplink enhancement technologies: SUL and UL CA.
The essence of SUL and uplink CA technology is to enhance the driving force of super uplink by using TDD/FDD and high-frequency/low-frequency synergy and complementarity.
Traditional SUL and UL CA technologies have certain shortcomings and cannot fully leverage the advantages of FDD+TDD dual-carrier collaboration:
SUL:
• Uplink data transmission can only occur on one carrier at a time.
• Primarily used to improve the speed at the cell edge, but cannot improve the capacity of the uplink near point.
UL CA
• Uplink two-carrier concurrency
• For 2T terminals, the improvement in uplink capacity at the nearest point is limited, and may even reduce uplink capacity.
Super Uplink technology can effectively address the shortcomings of traditional SUL and uplink CA technologies.
Definition and principle of super uptrend
China Telecom leads the development of the R16 "Super Uplink" standard:
June 2019: China Telecom unveils its "Super Uplink" technology solution at the Shanghai Exhibition.
September 2019: Super Uplink was successfully approved in R16, covering three scenarios: CA, SUL, and EN-DC.
2020H2: R16 Super Uplink Standard Frozen
The telecom's definition of Super Uplink:
Super Uplink is an uplink enhancement technology that combines TDD/FDD and high/low frequency complementarity. It achieves selective transmission between TDD/FDD frequency bands based on channel conditions through the uplink selective transmission function of the terminal, thereby enhancing uplink coverage and speed.
Super Uplink technology is achieved through Uplink Tx Switching uplink selective transmission.
The 2Tx terminal has two working modes: case1 and case2. Case1 is further divided into case1, option1, and case1 option2 depending on whether concurrency is supported.
The principle of super uptrend
Uplink Tx Switching enables switching between two working modes of the terminal, case 1 and case 2:
» Generally, the switching between case 1 option 1 and case 2 is called uplink Tx Switching option 1, and the switching between case 1 option 2 and case 2 is called uplink Tx Switching option 2. » For SUL and UL CA, 3GPP defines three levels of switching latency {35µs, 140µs, 210µs}.
» The switching period is configurable and is typically located on the FDD carrier.
» Achieving TDM transmission on uplink dual carriers for the terminal
2. Super Upward (SUL) Route Analysis
The main methods for implementing Super Uplink based on SUL are as follows:
1. SUL parameter configuration
• The frequency band information of the SUL carrier in a cell is provided by the cell's system message SIB1.
• The configuration parameters of the SUL carrier, such as subcarrier spacing, PUCCH resources, and SRS resources, are provided by the cell's RRC reconfiguration message.
2. Terminal access method
• Access can be initiated on a non-SUL carrier.
• When the SSB threshold is configured in the SIB1 message of the cell, the terminal can initiate access on the SUL carrier when the SSB-RSRP measured by the terminal is less than the threshold value.
3. Activation Method
• When the Super Uplink switch is enabled, Super Uplink will be activated when the UE initiates access on a non-SUL carrier, regardless of the traffic volume.
• If the UE initiates access on the SUL carrier, it will generally default to single-carrier transmission on the SUL carrier.
