G-DCF: Improving System Spectral Efficiency through Concurrent Transmissions in Wireless LANs

This paper presents G-DCF, a MAC protocol for wireless LANs that can improve system spectral efficiency of wireless LANs by allowing more concurrent transmissions. The 802.11 DCF creates exposed terminals which are nodes that can transmit successfully but are blocked by carrier sensing. More potential exposed terminals are created when APs are densely placed, limiting spatial reuse of channels and thus system throughput. In order to allow concurrent transmissions from exposed terminals, G-DCF establishes groups in the network. Members of a group are nodes located within the carrier sense range of each other but can transmit packets concurrently. Whenever one member of a group wins the channel and transmits its packet, other nodes in the group also start transmission, triggered by the group ID included in the preamble. Contention window is adjusted according to the group size for fair share of the channel. Performance evaluations show that G-DCF can significantly improve system throughput and fairness over 802.11 DCF, especially when the APs are densely deployed.

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Dynamic Carrier-Sense Threshold Selection for Improving Spatial Reuse in Dense Wireless LANs

Applied Sciences ◽

10.3390/app9193951 ◽

2019 ◽

Vol 9 (19) ◽

pp. 3951 ◽

Cited By ~ 1

Author(s):

Jungmin So ◽

Joosang Lee

Keyword(s):

Wireless Lan ◽

Medium Access Control Protocol ◽

System Throughput ◽

Spatial Reuse ◽

Medium Access ◽

Packet Losses ◽

Single Carrier ◽

Carrier Sense ◽

Carrier Sensing ◽

Key Techniques

As density of a wireless LAN grows, per-user throughput degrades severely, deteriorating user experience. To improve service quality, it is important to increase system spectral efficiency. Controlling carrier-sense threshold is one of the key techniques to achieve the goal, because frequently transmissions are unnecessarily blocked by carrier sensing, even though these transmissions can take place without causing packet losses. Using high carrier-sense threshold and allowing nodes to transmit aggressively may increase the system throughput, but this approach can lead to unfair channel share and cause starvation for the edge nodes. In this paper, we propose a medium access control protocol where transmitters include the carrier-sense threshold required to protect its packet in the preamble. Nodes receiving the preamble only transmit concurrently, when they are confident that their own transmission as well as the on-going transmission will both be successfully received at the respective receivers. The simulation results show that this dual-threshold approach can achieve higher system throughput compared to using a single carrier-sense threshold, without penalizing edge nodes.

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A Distributed Spatial Reuse (DSR) MAC Protocol for IEEE 802.11 Ad Hoc Wireless LANs

10th IEEE Symposium on Computers and Communications (ISCC'05) ◽

10.1109/iscc.2005.9 ◽

2005 ◽

Cited By ~ 1

Author(s):

Kuei-Ping Shih ◽

Chien-Min Chou ◽

Mu-Ying Lu ◽

Szu-Min Chen

Keyword(s):

Ieee 802.11 ◽

Ad Hoc ◽

Mac Protocol ◽

Wireless Lans ◽

Spatial Reuse

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Fair MAC protocol for IEEE 802.11 wireless LANs with hidden node problem

Journal of Electrical Engineering ◽

10.2478/jee-2020-0050 ◽

2020 ◽

Vol 71 (5) ◽

pp. 365-367

Author(s):

Woo-Yong Choi

Keyword(s):

Ieee 802.11 ◽

Mac Protocol ◽

Wireless Lans ◽

Sensing Range ◽

Backoff Algorithm ◽

Hidden Node ◽

Carrier Sensing ◽

802.11 Wireless Lans ◽

Node Problem ◽

Hidden Nodes

Abstract In IEEE 80211 wireless LANs, hidden nodes can disrupt the backoff algorithm of other nodes that are located outside the physical carrier sensing range of hidden nodes. The fairness problem between the nodes that are vulnerable and not vulnerable to the hidden node problem is dealt with in this paper. We propose an efficient fair MAC protocol to resolve the fairness problem.

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A Simple and Practical Scheme Using Multiple Channels for Improving System Spectral Efficiency of Highly Dense Wireless LANs

Wireless Communications and Mobile Computing ◽

10.1155/2019/2149606 ◽

2019 ◽

Vol 2019 ◽

pp. 1-17 ◽

Cited By ~ 1

Author(s):

Jungmin So ◽

Joosang Lee

Keyword(s):

Single Channel ◽

Wireless Lans ◽

Multiple Channels ◽

Medium Access ◽

Simple Scheme ◽

Carrier Sense ◽

Hidden Terminals ◽

Carrier Sensing ◽

Simulation Results ◽

Practical Scheme

As the density of wireless LANs increases, performance degradation caused by hidden terminals and exposed terminals becomes significant. These problems come from carrier sensing based medium access control used in current wireless LANs. Hidden terminals are created if carrier sense threshold is too high, whereas exposed terminals are created if carrier sense threshold is too low. A good threshold depends on how far nodes are placed from their destinations, but that cannot be controlled by the system. In this paper, we propose a simple scheme that makes use of multiple channels. Multiple channels could be utilized by equipping multiple radios or using advanced hardware such as SDR to divide a single channel into multiple channels. Nodes are assigned channels based on their estimated distance from the AP. Once the assignment is done, carrier sense threshold for the channel is selected so that as many concurrent transmissions take place as possible, while preventing hidden terminals. Simulation results show that the proposed mechanism achieves significantly higher throughput without causing starvation at the edge nodes.

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