Wireless Packet Access Using Erasure Coding and Dynamic Contention
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Solution Overview
Problem
Existing multiple access protocols, such as CSMA/CA, suffer from collisions and sub-optimal throughput due to the lack of effective coordination between users, leading to inefficiencies in data transmission, especially in wireless networks like WiFi, where collisions are common and channel utilization is low.
Innovation Solution
Implementing an erasure code with a maximum distance separable (MDS) code to encode packets transmitted by users, along with dynamically adjusting the contention window based on the number of users, to optimize data throughput and reduce packet loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If users transmit packets at random instants without coordination, then device complexity is reduced, but packet loss increases due to collisions
Solution Approach 1:
The patent introduces a mediator entity (access point or coordinator) that manages the transmission process by assigning specific time slots to users. This intermediary resolves the contradiction by providing centralized coordination that eliminates random collisions while maintaining relatively simple user-side devices that only need to follow assigned slots.
Solution Approach 2:
The patent implements dynamic time slot assignment where the coordination mechanism adapts transmission schedules based on channel conditions and user activity. This dynamic approach maintains low device complexity while improving reliability by adjusting slots to avoid collisions in real-time.
2Reliability
If users listen to the channel before transmitting (CSMA/CA), then collision probability is reduced, but transmission time increases due to waiting
Solution Approach 1:
The patent applies preliminary action by pre-assigning transmission time slots to users before they actually transmit data. This eliminates the need for users to continuously listen and wait during transmission periods, as their transmission rights are predetermined, thus reducing transmission delay while maintaining collision avoidance.
Solution Approach 2:
The patent implements periodic time slot assignments where users transmit at regular, predetermined intervals. This periodic structure eliminates random waiting and listening delays, as each user knows exactly when to transmit based on their assigned periodic schedule, reducing transmission delay while preventing collisions.
3Reliability
If erasure coding is applied to correct collisions, then packet loss is reduced, but device complexity increases due to coding operations
Solution Approach 1:
The patent places the erasure coding and decoding operations at the access point or coordinator rather than at user devices. This intermediary approach allows complex coding operations to be centralized, reducing the complexity burden on user devices while still providing packet recovery capabilities through the mediator's processing power.
4Speed
If contention window is decremented to zero, then transmission speed increases, but collision probability increases
Solution Approach 1:
The patent dynamically adjusts the contention window size based on current channel conditions and collision rates. When collisions are detected, the system increases the contention window to reduce collision probability; when the channel is clear, it decreases the window to increase transmission speed, thus balancing both speed and reliability adaptively.
Data Source
AI summary
A system for transmitting data packets includes at least one access point and at least one terminal. The access point receives data packets transmitted by the terminal in compliance with a multiple access protocol including carrier detection, and transmits to the terminal at least the width of the contention window that the terminal is to observe for transmitting a packet. The transmitted packets are coded using an erasure code and the access point is further adapted to decode the received packets. The system may be applied to networks such as WLANs.