Receiver initiated fast sequential collision resolution in 802.11 WLAN (original) (raw)
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IEEE 802.11 distributed coordination function, (DCF), provides contention-based distributed channel access for stations to share the wireless medium. However, Performance of IEEE 802.11 DCF protocol, in terms of delay and throughput, degrades dramatically as the number of active stations increases, especially when each station transmits in its saturated state. Therefore, development of an efficient Medium Access Control (MAC) protocol providing both high throughput for data traffic and quality of service (QoS) for real-time applications has become a major focus in WLAN research. In this paper, we propose an adaptive collision-free MAC adaptation. Proposed scheme prevents collisions and allows stations to enter an uninterrupted collision-free state, regardless of the traffic types (saturated or unsaturated) and the number of stations on the medium. Simulation results indicate that proposed scheme dramatically enhances the overall throughput and supports QoS maintaining real-time services at high level over 802.11-based WLANs.
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A new collision resolution mechanism to enhance the performance of IEEE 802.11 DCF
IEEE Transactions on Vehicular Technology, 2004
The medium-access control (MAC) protocol is one of the key components in wireless local area networks (WLANs). The main features of a MAC protocol are high throughput, good fairness, energy efficiency, and support priority guarantees, especially under distributed contention-based environment. Based on the current standardized IEEE 802.11 distributed coordination function (DCF) protocol, this paper proposes a new efficient collision resolution mechanism, called GDCF. Our main motivation is based on the observation that 802.11 DCF decreases the contention window to the initial value after each success transmission, which essentially assumes that each successful transmission is an indication that the system is under low traffic loading. GDCF takes a more conservative measure by halving the contention window size after consecutive successful transmissions. This "gentle" decrease can reduce the collision probability, especially when the number of competing nodes is large. We compute the optimal value for and the numerical results from both analysis and simulation demonstrate that GDCF significantly improve the performance of 802.11 DCF, including throughput, fairness, and energy efficiency. In addition, GDCF is flexible for supporting priority access by selecting different values of for different traffic types and is very easy to implement it, as it does not requires any changes in control message structure and access procedures in DCF.
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Wireless technologies are a good choice for work in industrial environments, where it is necessary to interconnect mobile systems or it wants to avoid sensors and controllers wiring in plant. However, these technologies present reliability and timing problems inherent in the radio channels, mechanisms for medium access, etc. The standard 802.11e provides two alternatives for medium access (EDCA and HCCA) by differentiating traffic into four Access Categories (ACs). This paper proposes a mechanism for controlling the medium access, so-called WRTMAC, developed from the EDCA scheme of standard 802.11e. The handling of the arbitration inter frame spaces (AIFS) has been modified in order to make deterministic the medium access, even in terms of high traffic next to the saturation of the system.
A Mechanism to Mitigate Collision Rate in Wireless Local Networks
Presently, IEEE 802.11 DCF is MAC protocol applied in wireless local networks. DCF would be inefficient, since there are two types of overload: Collision time and channel's idle time. Present paper, evaluated the performance and proposed an efficient MAC protocol for these networks called D-CW. D-CW will decrease both the channel's idle time and the collision time. D-CW, by dividing the value of contention window (CW) by two, reduces the time required for a successful node forwarding, and by selecting variable contention window for packet forwarding from each node with a random uniform function, what if a successful forwarding or an unsuccessful one, decreases the collision time. Stations, after selecting a value from the window contention own, follow the Backoff mechanism, and after counting the number of their own idle slots, do the forwarding. Simulation results indicate D-CW can improve the throughput of the system, delay reduction and collision rate on 802.11 DCF significantly.
International Journal of Communication Systems, 2021
The IEEE 802 standards rely on the distributed coordination function (DCF) as the fundamental medium access control method. DCF uses the binary exponential backoff (BEB) algorithm to regulate channel access. The backoff time determined by BEB depends on a contention window (CW) whose size is doubled if a station suffers a collision and reset to its minimum value after a successful transmission. Doubling the size of CW reduces channel access time, which decreases the throughput. Resetting it to its minimum value harms fairness since the station will have a better chance of accessing the channel compared to stations that suffered a collision. We propose an algorithm that addresses collisions without instantly increasing the CW size. Our algorithm aims to reduce the collision probability without affecting the channel access time and delay. We present extensive simulations for fixed and mobile scenarios. The results show that, on average, our algorithm outperforms BEB in terms of throughput and fairness. Compared to exponential increase exponential decrease (EIED), our algorithm improves, on average, throughput and delay performance. We also propose analytical models for BEB, EIED, and our algorithm. Our models extend Bianchi's popular Markov chain-based model by using a collision probability that is dependent on the station transmission history. Our models provide a better estimation of the probability that a station transmits in a random slot time, which allows a more accurate throughput analysis. Using our models, we show that both the saturation throughput and maximum throughput of our algorithm are higher than those of BEB and EIED.
A Fast-and-Fair Collision Resolution Protocol Tailored for Ad Hoc Wireless Networks
Journal of Computer Science, 2016
Wireless technologies have permeated a significant number of devices over the years. On the other hand, Medium Access Control (MAC) protocols strive to deal with an increasing number of contending nodes on crowded frequency bands. This work presents an efficient medium access control resolution protocol. The proposed protocol, termed Collision Resolution Protocol (CRP), uses pulse/tone signaling that works in both Collision Detection (CD) and Non-Collision Detection (NCD) environments. Given n>1 contending nodes, CRP selects a single transmitting node in 16n and 40n time slots, respectively, for the CD and the NCD scenarios, with probability of at least 1-2-1.5n. Furthermore, CRP does not require an exact number, or estimation, of the contending nodes. Extensive simulations on the OMNeT++ shows that, for n = 256 and considering CD-capability, CRP successfully grants channel access in 0.03% of the time required by the IEEE 802.11 standard while improving the number of transmissions per second in 100%. In addition, CRP provides fair resource allocation and reduced channel access latency.
COLLISION RECOVERY IN IEEE 802.11 WLANS
We dene a procedure to exploit collision resolution algorithms based on signal processing. The procedure is aimed at the 802.11 Wireless Local Area Networks, and it is dened as an enhancement of the current standard, targeted to infrastruc- tured Basic Service Sets; coexistence with legacy 802.11 devices is possible. We also develop an extremely accurate analytical model of the procedure, and validate it through simulations. We then carry out an extensive set of numerical evaluations, and nd that signican t gains in performance can be attained by introducing the collision recovery capability.