Contention-Free Scheduling Request Channel for Wireless Networks
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Solution Overview
Problem
In wireless cellular communication systems, particularly in OFDMA and SC-FDMA systems, the existing scheduling request mechanisms face inefficiencies due to high overhead costs and contention-based channels, which hinder fast and robust scheduling requests from synchronized user equipment (UEs) without scheduling grants.
Innovation Solution
A physical channel definition is introduced that allows synchronized UEs to send scheduling requests with low overhead, using an extended preamble format and cyclic shift dimensioning, enabling contention-free scheduling requests by assigning unique identifiers and utilizing orthogonal reference signals for channel sounding and synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If contention-based random access channels are used for scheduling requests, then any UE can access the channel, but overhead costs increase and access efficiency decreases
Solution Approach 1:
The patent segments the scheduling request channel into two distinct types: contention-based random access channels for initial access and contention-free dedicated channels for synchronized UEs. This segmentation allows the system to apply different channel access mechanisms appropriate to each UE state, reducing overall overhead while maintaining accessibility where needed.
Solution Approach 2:
The patent introduces an intermediary mechanism where the eNodeB assigns dedicated physical uplink shared channel (PUSCH) resources and unique identifiers to synchronized UEs. This intermediary allocation creates a dedicated pathway that eliminates contention and reduces overhead for UEs that have achieved synchronization, while preserving the contention-based mechanism for initial access scenarios.
2Adaptability or versatility
If contention-based channels are used for scheduling requests, then channel access is available to all UEs, but scheduling speed and robustness decrease
Solution Approach 1:
The patent implements a dynamic channel access mechanism where the available channel type depends on the UE's synchronization state. Synchronized UEs dynamically access dedicated contention-free channels for fast scheduling requests, while non-synchronized UEs use contention-based channels. This dynamic adaptation optimizes scheduling speed for synchronized UEs while maintaining universal channel availability.
Solution Approach 2:
The patent applies preliminary action by requiring UEs to achieve synchronization and receive resource allocation beforehand before accessing the fast dedicated scheduling request channel. This preliminary setup phase enables subsequent rapid scheduling requests without contention, improving speed for synchronized UEs while preserving channel availability through the initial synchronization process.
3Quantity of substance
If dedicated resources are allocated for scheduling requests, then overhead is reduced for synchronized UEs, but system complexity increases
Solution Approach 1:
The patent applies universality by using the physical uplink shared channel (PUSCH) for multiple purposes: data transmission, scheduling requests, and channel quality indicators. This multi-functionality reduces the need for separate dedicated signaling channels, thereby reducing overhead for synchronized UEs while avoiding excessive system complexity through resource consolidation.
Solution Approach 2:
The patent implements self-service by enabling synchronized UEs to autonomously use their allocated dedicated PUSCH resources for scheduling requests without requiring complex centralized channel assignment procedures. The UEs self-manage their dedicated resources, reducing system complexity while achieving low overhead for scheduled requests.
4Productivity
If multiple UEs use the same physical channel for scheduling requests, then resource utilization is efficient, but interference and collision increase
Solution Approach 1:
The patent segments the scheduling request transmission into separate contention-based and contention-free channels. Synchronized UEs use dedicated contention-free PUSCH resources with unique identifiers, eliminating interference and collision among these UEs. Meanwhile, resource utilization efficiency is maintained by allowing multiple UEs to share the system resources through time-division and frequency-division multiplexing of the dedicated channels.
Solution Approach 2:
The patent applies local quality by assigning unique local identifiers and dedicated resources to each synchronized UE within the contention-free channel group. This localized differentiation eliminates interference among synchronized UEs using the same physical channel, while the overall system maintains high resource utilization through efficient allocation of these localized resources across multiple UEs.
Data Source
AI summary
In a method for transmitting a contention free scheduling request in a cellular network, a set of N frequency opportunities is defined within a scheduling request slot. A set of R CAZAC root sequences is then defined per frequency opportunity. A set of C cyclic shifts is then defined per CAZAC root sequence. Within a given cell, a unique identification number is assigned to each user equipment (UE) that is in an uplink (UL) synchronized state. Each UL synchronized UE is mapped to a unique combination of one of the N frequency opportunities, one of the R CAZAC root sequences and one of the C cyclic shifts. A cyclic shifted preamble sequence for a given UE is transmitted as a scheduling request on the mapped frequency, CAZAC root sequence and cyclic shift opportunity, wherein the unique identification number of the given UE is encoded by the combination of the frequency opportunity, CAZAC root sequence opportunity, and amount of cyclic shift, such that up to all of the plurality of UE can transmit a schedule request (SR) in a non-contentious manner in one schedule request slot.