Multicast Redundancy in Half-Duplex Wireless Networks
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Solution Overview
Problem
In wireless networks using half duplex frequency division duplex (HFDD), the inefficiency in uplink capacity utilization occurs due to multicast and broadcast service traffic, where mobile stations can only receive or transmit but not both simultaneously, leading to idle time on uplink channels.
Innovation Solution
The base station transmits multicast traffic in separate frames, allowing mobile stations to receive during one frame and transmit during another, thereby optimizing uplink bandwidth usage by scheduling mobile stations to alternate between receiving and transmitting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the base station transmits multicast traffic to all mobile stations simultaneously, then all mobile stations can receive the multicast traffic, but the uplink capacity is wasted because mobile stations cannot transmit during the reception period
Solution Approach 1:
The patent segments the mobile stations into multiple groups (first group and second group) and schedules them to receive multicast traffic in different time slots. The first group receives multicast traffic in the first frame while the second group transmits uplink traffic, and vice versa in the second frame. This segmentation resolves the contradiction by allowing multicast delivery to all stations while maintaining uplink capacity utilization through group-based time division.
2Productivity
If mobile stations receive multicast traffic in the same time slot, then they can all receive the traffic efficiently, but they cannot transmit uplink communications during that period
Solution Approach 1:
The patent implements periodic action by transmitting the same multicast traffic in multiple frames at different time slots. Mobile stations are scheduled to receive in one frame and transmit in another frame in a periodic manner. This allows efficient downlink multicast delivery in each frame while ensuring that mobile stations have periodic opportunities for uplink transmission in subsequent frames, thus resolving the time loss contradiction.
3Productivity
If the base station schedules mobile stations to transmit and receive at different times, then uplink capacity is optimized, but the same multicast traffic must be transmitted multiple times
Solution Approach 1:
The patent uses copying by transmitting duplicate copies of the same multicast traffic in different frames. Each mobile station group receives a copy of the multicast traffic in their designated reception frame. This copying approach resolves the contradiction by enabling time-diversity for uplink transmissions while ensuring reliable multicast delivery, as each group receives the traffic in at least one frame despite the redundant overall transmissions.
Data Source
AI summary
In a wireless network in which the base station has full duplex capability (can transmit on the downlink channel and simultaneously receive on the uplink channel), but the mobile stations have only half duplex capability (each can transmit on the uplink channel and receive on the downlink channel, but not simultaneously), the base station may transmit duplicate copies of multicast data in two or more frames. Some of the addressed mobile station may be scheduled to receive the first frame and transmit during the second frame, while the other addressed mobile stations may be scheduled to transmit during the first frame and receive the second frame.