Enhanced Frame Structure Subframes Latency Compatibility
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The frame structure of IEEE standard 802.16e poses challenges for backward compatibility and fails to meet the latency requirements of IEEE standard 802.16m, which necessitates a shorter frame length to improve data throughput at high vehicular speeds while maintaining flexibility in allocation.
Innovation Solution
An enhanced frame structure is introduced, dividing the legacy 5 ms OFDMA frame into smaller subframes, allowing new mobiles to operate with a shorter frame length while ensuring legacy mobile stations can still operate transparently on the 5 ms frame size, enabling timely acknowledgments and improved channel quality feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the frame structure uses a 5 ms legacy frame size, then backward compatibility with IEEE 802.16e is maintained, but latency requirement of 10 ms for IEEE 802.16m cannot be met
Solution Approach 1:
The 5 ms legacy frame is segmented into multiple subframes (e.g., two 2.5 ms subframes). Each subframe contains downlink bursts, uplink bursts, and transition gaps. This segmentation allows the system to achieve 10 ms latency by enabling acknowledgments within the same frame while maintaining 5 ms frame structure for backward compatibility with legacy 802.16e devices.
2Loss of time
If the frame length is reduced to meet 10 ms latency requirement, then data throughput at high vehicular speeds is improved, but legacy mobile stations cannot operate transparently
Solution Approach 1:
The frame structure is designed to serve dual purposes: it maintains the 5 ms frame boundary required by legacy 802.16e devices while incorporating internal subframe structure that enables 10 ms latency performance for 802.16m devices. The frame handler transparently manages this duality, allowing both legacy and advanced devices to operate simultaneously on the same physical medium.
3Adaptability or versatility
If the frame structure is modified to support shorter frame length, then flexibility in allocation is improved, but device complexity increases due to dual format support
Solution Approach 1:
A frame handler acts as an intermediary layer between the physical medium and both legacy and advanced devices. It translates and manages the dual frame formats, handling the complexity of supporting both 5 ms legacy frames and shorter subframe structures. This intermediary absorbs the complexity, preventing it from propagating to the devices themselves.
4Ease of operation
If acknowledgments are delayed to match 5 ms frame boundaries, then legacy device operation is simplified, but data throughput decreases due to longer feedback loops
Solution Approach 1:
The frame structure includes preliminary downlink bursts followed by uplink bursts within the same frame, allowing acknowledgments to be sent before the 5 ms frame boundary. This preliminary action within the frame enables faster feedback loops for 802.16m devices while the overall 5 ms frame structure remains intact for legacy device synchronization.
Data Source
AI summary
A radio access network (RAN) (20) comprise a base station (28) and a wireless terminal (30). The base station 28 comprises a transceiver (38) and a frame handler (40), the wireless terminal (30) comprises a transceiver (48) and a wireless terminal frame handler (50). The frame handlers (40, 50) handle a enhanced frame F having enhanced frame structure. At least a downlink portion of the frame is formatted and handled in a manner whereby the frame can be perceived as a first format type of frame if the wireless terminal is a first type of wireless terminal and perceived as an enhanced or second format type of frame if the wireless terminal is a second type of wireless terminal. The frame handler configures the frame as plural subframes, each subframe having a downlink burst followed by an uplink burst. The frame is preferably configured to afford the second type of wireless terminal sufficient time to develop an acknowledgement for a message transmitted in a downlink burst, the acknowledgement being sent to the base station in an uplink burst which is within one frame length of the message.