5G Random Access Uplink Selection via RSRP Thresholds

The patent segments the uplink transmission by introducing supplementary uplink (SUL) as a separate frequency band resource. When normal uplink coverage is insufficient, the system divides the uplink path into two segments: normal uplink for general traffic and SUL for coverage enhancement, allowing high data rates to be maintained while addressing coverage limitations through dedicated low-frequency resources.

The patent changes the frequency parameter of the uplink transmission by introducing SUL operating in lower frequency bands (e.g., 700 MHz) compared to normal uplink (e.g., 3.5 GHz). This parameter change exploits the inverse relationship between frequency and propagation loss, where lower frequencies experience less attenuation, thereby extending uplink coverage while maintaining the ability to achieve high data rates through beamforming and massive MIMO on the downlink.

The patent applies preliminary action by pre-configuring message 3 repetition parameters and selecting the repetition mode before the actual random access procedure begins. The UE determines whether to use repetition mode based on pre-established RSRP thresholds and pathloss conditions, and all repetition-related parameters are prepared in advance through system information blocks, eliminating the need for complex real-time decisions during the random access process.

The patent implements feedback mechanisms where the network provides RSRP thresholds and pathloss compensation factors through system information, and the UE uses this feedback to automatically determine whether to activate message 3 repetition. This feedback loop simplifies the UE's decision-making process by providing clear criteria (threshold comparisons) rather than requiring complex algorithms to assess coverage conditions.

The patent applies local quality by assigning different frequency band characteristics to different uplink purposes: normal uplink uses higher frequencies optimized for capacity and data rate, while supplementary uplink uses lower frequencies optimized for coverage and propagation. The system selectively activates the appropriate uplink type based on local conditions (pathloss and RSRP), giving each uplink option its specialized role rather than requiring both to perform all functions.

The patent introduces dynamic selection between normal uplink and supplementary uplink based on real-time RSRP measurements and pathloss conditions. The UE can switch between uplink types dynamically, and the network can reconfigure the active uplink based on changing channel conditions, making the system adaptive rather than static. This dynamic behavior reduces complexity by automatically selecting the appropriate uplink type without requiring manual configuration or complex optimization algorithms.