Multi-Round Transmission Contention Protocol for 802.11 MPR
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Solution Overview
Problem
The IEEE 802.11 standard for wireless local area networks (WLANs) faces inefficiencies in utilizing Multi-Packet Reception (MPR) capability, leading to suboptimal throughput due to the limited handling of control packets and contention periods in CSMA/CA protocols.
Innovation Solution
The proposed Multi-Round Transmission and Contention (MRTC) protocol modifies the CSMA/CA mechanism by increasing the number of Receiver Address fields in CTS and ACK packets, using optimal stopping rules to extend contention and transmission periods, and employing CTS packets as both acknowledgments and negative acknowledgments to manage multiple transmission rounds, thereby optimizing MPR capacity and reducing control packet usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the CSMA/CA protocol is used with standard CTS packet handling, then the protocol compatibility is maintained, but the MPR capability is not fully utilized leading to suboptimal throughput
Solution Approach 1:
The CTS packet is given multiple functions: it serves as both a Clear-To-Send acknowledgment for stations that transmitted DATA packets and as a Negative Acknowledgment for stations that did not transmit. This multi-functionality allows the protocol to fully exploit MPR capability without requiring separate control mechanisms, thereby improving throughput while limiting complexity growth.
Solution Approach 2:
The transmission period is divided into multiple transmission rounds, with each round handling a subset of stations. The CTS packet is sent after each transmission round to provide selective acknowledgments. This segmentation allows the system to manage multiple MPR-capable receivers efficiently, improving overall network productivity through structured multi-round transmissions.
2Productivity
If the number of RA fields in CTS and ACK packets is increased to match MPR capacity, then the MPR capability is fully utilized, but the control packet size and processing complexity increase
Solution Approach 1:
Instead of always including all MPR capacity RA fields in every CTS and ACK packet, the protocol uses partial action by including only the necessary number of RA fields for the current transmission round. The CTS packet includes RA fields for stations that should transmit in the next round, while ACK packets include RA fields only for stations that successfully transmitted DATA packets. This reduces control packet complexity while maintaining full MPR utilization.
3Productivity
If multiple transmission rounds are implemented to distinguish more active stations, then the MPR capacity utilization improves, but the contention period duration increases
Solution Approach 1:
The protocol implements periodic action through multiple transmission rounds separated by controlled contention periods. Each transmission round is followed by a CTS packet that prepares stations for the next round. This periodic structure allows the system to efficiently utilize MPR capacity across multiple rounds while keeping each contention period relatively short, thereby limiting total time loss compared to a single extended contention period.
Solution Approach 2:
The CTS packet is used to perform preliminary action by pre-assigning transmission slots to stations before the next transmission round begins. Stations receive advance notice through the CTS packet about when they should transmit their DATA packets, allowing them to prepare and reducing the need for extended contention periods. This preliminary assignment mechanism efficiency reduces overall contention time while maintaining high MPR utilization.
Data Source
AI summary
The present invention proposes a protocol based on multiple transmission and contention rounds that schedules several transmission rounds after the contention phase is completed. The multiple transmission rounds reduce the sending of control packets and substantially increase the cross traffic on the uplink to the AP. The supporting analytical expressions for determining the traffic carried of the proposed protocol demonstrate through simulation that about 94% of the ideal throughput of available throughput can be achieved by using as few as four transmission rounds during the transmission period.