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

2019 ◽  
Vol 9 (19) ◽  
pp. 3951 ◽  
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.

scholarly journals Improving Spatial Reuse of Wireless LAN Uplink Using BSS Color and Proximity Information

2021 ◽  
Vol 11 (22) ◽  
pp. 11074
Author(s):  
Hyerin Kim ◽  
Jungmin So
Keyword(s):  
Wireless Lan ◽  
Multiple Access ◽  
Local Area Networks ◽  
Local Area ◽  
Wireless Local Area Networks ◽  
Spatial Reuse ◽  
Carrier Sense Multiple Access ◽  
Medium Access ◽  
Network Systems ◽  
Carrier Sensing

With the density of wireless networks increasing rapidly, one of the major goals in next-generation wireless LANs (Local Area Networks) is to support a very dense network with a large number of closely deployed APs (Access Points) and crowded users. However, the CSMA (Carrier-Sense Multiple Access)-based medium access control of current wireless network systems suffers from significantly degraded performance when the network becomes dense. Recent WLAN (Wireless Local Area Networks) standards include measures for increasing spatial reuse such as BSS (Basic Service Set) coloring, but the schemes based on BSS coloring such as OBSS/PD (Overlapping BSS/Preamble Detection) have limitations in improving spatial reuse. In this paper, we propose a spatial reuse method for uplink which can utilize BSS color and proximity information to improve the efficiency of carrier sensing and thus spatial reuse. Specifically, through the BSS color and the proximity information, a node receiving a preamble can figure out how far the receiver of the ongoing traffic is located. This information is used to determine whether the node should aggressively start transmitting or defer its transmission to protect the ongoing transmission. Simulation results show that the proposed method outperforms existing methods in terms of throughput and fairness.

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

2019 ◽  
Vol 2019 ◽  
pp. 1-16
Author(s):  
Ayinebyona Eliab ◽  
Yonghwi Kim ◽  
Joosang Lee ◽  
Jeong-Gun Lee ◽  
Jungmin So
Keyword(s):  
Spectral Efficiency ◽  
Mac Protocol ◽  
Wireless Lans ◽  
Performance Evaluations ◽  
System Throughput ◽  
Spatial Reuse ◽  
Fair Share ◽  
802.11 Dcf ◽  
Carrier Sense ◽  
Carrier Sensing

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.

ORCHESTRATING SPATIAL REUSE IN WIRELESS AD HOC NETWORKS USING SYNCHRONOUS COLLISION RESOLUTION (SCR)

2002 ◽  
Vol 03 (03n04) ◽  
pp. 167-195 ◽  
Author(s):  
JOHN A. STINE ◽  
GUSTAVO DE VECIANA ◽  
KEVIN H. GRACE ◽  
ROBERT C. DURST
Keyword(s):  
Access Control ◽  
Wireless Ad Hoc Networks ◽  
Ad Hoc ◽  
Mac Protocol ◽  
Medium Access Control Protocol ◽  
Control Mechanisms ◽  
Spatial Reuse ◽  
Medium Access ◽  
Signaling Mechanism ◽  
Key Factor

We propose a novel medium access control protocol for ad hoc wireless networks data to send can contend simultaneously for the channel. Nodes contend for access using a synchronous signaling mechanism that achieves two objectives: it arbitrates contentions locally and it selects a subset of nodes across the network that attempt to transmit simultaneously. The subset of nodes that survive the signaling mechanism can be viewed as an orchestrated set of transmissions that are spatially reusing the channel shared by the nodes. Thus the 'quality' of the subset of nodes selected by the signaling mechanism is a key factor in determining the spatial capacity of the system. In this paper, we propose a general model for such synchronous signaling mechanisms and recommend a preferred design. We then focus via both analysis and simulation on the spatial and capacity characteristics of these access control mechanisms. Our work is unique in that it specifically focuses on the spatial capacity aspects of a MAC protocol, as would be critical for ad hoc networking, and shows SCR is a promising solution. Specifically, it does not suffer from congestion collapse as the density of contending nodes grows, it does not suffer from hidden or exposed node effects, it achieves high capacities with a spatial usage exceeding 1 (i.e. more than one packet exchange in the area covered by a transmission), and it facilitates the integration of new physical layer capacity increasing technologies.

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

2019 ◽  
Vol 2019 ◽  
pp. 1-17 ◽  
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.

Packet-Loss Distinguishing Based Link Adaptation Enhancement for Wireless LANs

2011 ◽  
Vol 403-408 ◽  
pp. 1859-1864
Author(s):  
Yuan Cheng ◽  
Qiang Fan ◽  
Yun Shan Tang ◽  
Wei Wei Miao
Keyword(s):  
Local Area Networks ◽  
Link Adaptation ◽  
Local Area ◽  
Wireless Local Area Networks ◽  
System Throughput ◽  
Mac Layer ◽  
Medium Access ◽  
Adaptation Algorithm ◽  
Packet Losses ◽  
New Strategy

As we know, packet losses in wireless local area networks (WLANs) are due to collisions or link errors. In this paper, a new strategy that distinguishes the cause of packet losses in medium access control (MAC) layer is introduced. Based on the strategy, link adaptation algorithms, including the payload size adaptation algorithm and the data rate adaptation algorithm, are proposed and employed in WLANs. Simulation results show that both algorithms increase system throughput significantly.

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