Queue Prediction for Virtual Handoff Latency Reduction
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Solution Overview
Problem
In high-rate packet data wireless communication systems, soft virtual handoff leads to delays and resource wastage due to queue synchronization issues between source and target cells during the handoff process, causing interruptions and inefficiencies in data transmission.
Innovation Solution
The target cell predicts the amount of data to be transmitted by the source cell before the handoff and begins transmitting data from an offset in its queue corresponding to this prediction, allowing immediate data delivery upon selection, with adjustments made based on actual queue pointers received later.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the target cell waits for queue pointers from the source cell before transmitting data, then queue synchronization is achieved, but handoff latency increases
Solution Approach 1:
The target cell performs preliminary actions by obtaining a prediction of the amount of data transmitted by the source cell before the handoff occurs. This allows the target cell to pre-position its transmit buffer offset, so that when the handoff occurs, data transmission can begin immediately without waiting for actual queue pointers, thus reducing handoff latency while maintaining queue synchronization
Solution Approach 2:
The system uses feedback mechanisms where the target cell receives actual queue pointers from the source cell after handoff and compares them with the predicted values. Based on this feedback, the target cell can adjust its transmission offset to correct any prediction errors, ensuring accurate queue synchronization while having already reduced the initial handoff latency
2Loss of time
If the target cell transmits data immediately upon selection, then handoff latency is reduced, but data redundancy occurs when source cell packets are retransmitted
Solution Approach 1:
The target cell performs preliminary calculation of the transmit buffer offset by obtaining a prediction of the data amount transmitted by the source cell during the handoff period. This preliminary action enables the target cell to start transmission at the correct offset immediately upon selection, avoiding both latency delays and redundant retransmissions of already-sent packets
Solution Approach 2:
The prediction mechanism acts as an intermediary between the source cell's actual transmission and the target cell's transmission start. By using this intermediate prediction value to set the offset, the system bridges the timing gap between handoff occurrence and queue pointer receipt, enabling immediate transmission without redundancy
Data Source
AI summary
In a high-rate packet data (HRPD) wireless communication network, an Access Terminal (AT) selects its serving cell, and additionally provides an advance indication of a pending cell selection. Upon receipt of the advance indication, the network directs data packets destined for the AT to the indicated target cell, which queues the data. The target cell obtains a prediction of an amount of data that the currently serving, or source, cell may transmit to the AT between the advance indication and the cell selection. Following the cell selection, the target cell transmits data packets to the AT beginning at an offset into the transmission queue that corresponds to the predicted data amount. When the target cell receives the actual transmitted data amount from the source cell, it may make adjustments in data packet transmission to the AT to ameliorate the effects of any miss-prediction.