Random Access Preamble Transmission Power Control for Wireless Systems
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Solution Overview
Problem
In wireless communication systems, particularly in LTE, the random access process is inefficient due to the use of a single initial transmission power for all events, leading to increased time delays and potential preamble failure at cell edges, where the base station may not receive the preamble.
Innovation Solution
A method and apparatus that dynamically allocate random access preamble transmission power based on specific events triggering the access, such as idle to connected mode transition, RRC connection re-establishment, handover, and DL/UL data resume, by setting distinct random access parameters including initial, ramping, and maximum transmission powers, as well as backoff windows and retrial numbers, to optimize preamble transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single initial transmission power is used for all random access events, then the device complexity is reduced and ease of operation is improved, but the time delay increases and reliability deteriorates at cell edges
Solution Approach 1:
The patent applies parameter changes by configuring different initial transmission power values (PreambleInitialPower) for different random access events. Specifically, it sets a first initial transmission power for idle-to-connected mode transition and a second initial transmission power for other events like handover or RRC re-establishment. This allows the system to adapt transmission power parameters according to the specific event type, reducing time delay while maintaining operational clarity through event-based parameter differentiation.
Solution Approach 2:
The patent implements local quality by applying different transmission power parameters to different local conditions or event types. Instead of using a uniform power level globally, it tailors the initial transmission power to the specific random access event (idle transition vs. handover vs. re-establishment), ensuring optimal performance for each local scenario without affecting other events.
2Ease of operation
If a single initial transmission power is used for all events, then the ease of operation is improved, but the reliability of preamble transmission at cell edges deteriorates
Solution Approach 1:
The patent changes the transmission power parameter based on the random access event type. By setting a higher second initial transmission power for events like handover or RRC re-establishment compared to the first initial transmission power for idle transitions, it ensures reliable preamble delivery at cell edges while maintaining simple event-based parameter management.
Solution Approach 2:
The patent applies different transmission power quality levels to different event types. For critical events like handover or re-establishment occurring at cell edges, it allocates higher transmission power locally to ensure reliability, while using lower power for less critical idle transitions, thus optimizing overall system reliability without complex global optimization.
3Reliability
If transmission power is increased for cell edge users, then the reliability of preamble reception is improved, but the loss of energy increases and time delay increases due to power ramping
Solution Approach 1:
The patent applies preliminary action by pre-configuring appropriate initial transmission power values for different event types before random access occurs. For events likely to occur at cell edges (handover, re-establishment), it sets a higher second initial transmission power in advance, eliminating the need for subsequent power ramping and associated time delays, thus ensuring reliable reception from the first transmission attempt.
Solution Approach 2:
The patent changes the initial transmission power parameter based on event type to prevent the need for power ramping. By setting appropriately high initial power for critical events, it achieves reliable preamble reception without requiring iterative power increases, thereby reducing both energy waste and time delay associated with re-transmissions.
4Reliability
If transmission power is increased for cell edge users, then the reliability is improved, but the use of energy increases
Solution Approach 1:
The patent applies local quality by allocating higher transmission power only to specific event types (handover, re-establishment) that are more likely to occur at cell edges and require higher reliability, while using lower power for idle transitions. This targeted approach improves reliability where needed without unnecessarily consuming energy in all transmissions.
Solution Approach 2:
The patent changes the transmission power parameter based on the specific random access event, setting a higher second initial transmission power for critical events and a lower first initial transmission power for routine idle transitions. This dynamic parameter adjustment ensures successful preamble transmission when required while minimizing energy consumption for routine accesses.
Data Source
AI summary
A method and an apparatus are provided that transmit and receive a random access preamble in a wireless communication system. A plurality of random access parameters having different values in accordance with a plurality of events for triggering random access are set. When one of the plurality of events for triggering random access has occurred, random access is performed according to at least one of the plurality of random access parameters corresponding to the event. Therefore, the time delay of random access can be reduced.