MAC-PHY enhancement for 802.11b WLAN systems via cross-layering (original) (raw)

A performance analysis of MAC and PHY layers in IEEE 802.11ac wireless network

2016 18th International Conference on Advanced Communication Technology (ICACT), 2016

This paper gives an insight into IEEE 802.11ac by analysing its performance in terms of system throughput taking into consideration the key features of MAC and PHY layers. Throughput at MAC layer is calculated from transmission probability, contention window and transmission stage. Likewise, the new critical attributes of 802.11ac PHY (i.e. modulation and coding schemes, spatial streams, and channel bandwidth) are used to determine the throughput. To this end, a theoretical model is developed followed by simulation analysis. The results compare theoretical and simulation findings for different set of parameters. Furthermore, important trends and tradeoffs are identified between system throughput and (MAC + PHY) features as a function of number of contending stations and payload size.

WLAN throughput improvement via distributed queuing MAC

IEEE Communications Letters, 2005

This paper analyzes the performance of a MAC scheme for wireless local area networks (WLANs) that makes use of distributed queues to improve radio channel utilization. Analytical values for the maximum throughput performance are derived as a function of the system parameters. The obtained results show that the proposed scheme outperforms the legacy 802.11 MAC protocol in terms of maximum stable throughput. This benefit is obtained from eliminating back-off periods and collisions in data packet transmissions while minimizing the needed control overhead. The proposal also makes performance to be independent of the number of nodes transmitting in the system and provides stability for high load conditions. Index Terms-Distributed queuing, expected effective throughput, IEEE 802.11, MAC, WLAN.

Cross-Layer Design for the Physical, MAC, and Link Layer in Wireless Systems

EURASIP Journal on Advances in Signal Processing, 2009

During the past decade, the research community and wireless practitioners have provided overwhelming evidence that the strictly layered ISO/OSI architecture can lead to largely suboptimal operation of wireless networks. The reasons for such operation are rooted in the defining features of wireless communication: the variable link quality and the fact that the wireless medium should be shared by multiple users. In order to properly reflect these features in the protocol stack, the methodology of cross-layer design has been adopted. In short, the cross-layer methodology allows certain important information to influence decisions in a layer that is originally not defined to use that information (e.g., the SNR information at the link layer or the queue size at the baseband module).

Performance Analysis of the IEEE 802.11 MAC and Physical Layer Protocol

Sixth IEEE International Symposium on a World of Wireless Mobile and Multimedia Networks, 2005

We present in this paper an analytical model that accounts for the positions of stations with respect to the Access Point (AP) while evaluating the performance of 802.11 MAC layer. Our work is based on the Bianchi's model where the performance of 802.11 MAC layer is computed using a discrete time Markov chain, but where all stations are implicitly assumed to be located at the same distance to the AP. In our model, given the position of one station, we compute its saturation throughput while conditioning on the positions of the other concurrent stations. Further, our model provides the total saturation throughput of the medium. We solve the model numerically and we show that the saturation throughput per station is strongly dependent not only on the station's position but also on the positions of the other stations. Results confirm that a station achieves a higher throughput when it is closer to the AP but bring out that there is a distance threshold above which the throughput decrease is fast and significant. When a station is far from the AP compared to the other stations, it will end up by contending for the bandwidth not used by the other stations. We believe that our model is a good tool to dimension 802.11 wireless access networks and to study their capacities and their performances.

Performance analysis of the IEEE 802.11 MAC protocol for wireless LANs

Wireless local area networks (WLANs) are extremely popular being almost everywhere including business, office and home deployments. The IEEE 802.11 protocol is the dominating standard for WLANs. The essential medium access control (MAC) mechanism of 802.11 is called distributed co-ordination function (DCF). This paper provides a simple and accurate analysis using Markov chain modelling to compute IEEE 802.11 DCF performance, in the absence of hidden stations and transmission errors. This mathematical analysis calculates in addition to the throughput efficiency, the average packet delay, the packet drop probability and the average time to drop a packet for both basic access and RTS/CTS medium access schemes. The derived analysis, which takes into account packet retry limits, is validated by comparison with OPNET simulation results. We demonstrate that a Markov chain model presented in the literature, which also calculates throughput and packet delay by introducing an additional transition state to the Markov chain model, does not appear to model IEEE 802.11 correctly, leading to ambiguous conclusions for its performance. We also carry out an extensive and detailed study on the influence on performance of the initial contention window size (CW), maximum CW size and data rate. Performance results are presented to identify the dependence on the backoff procedure parameters and to give insights on the issues affecting IEEE 802.11 DCF performance. network connectivity, being a mouse-click away from key information and applications. Moreover, recent advances in wireless technology and mobile communications have equipped wireless capability portable devices including palmtop computers, laptops and personal digital assistants (PDAs) .

A cross-layer energy-saving mechanism for an enhancement of 802.11 WLAN systems

2004

Most multiple access collision avoidance-based (MAC) protocols for WLAN systems have been using fixed transmission power and have not considered energy-saving techniques targeted on channel estimation models. In order to prolong battery life and to improve the overall throughput performance of such systems, a novel PHY-MAC cross-layer energy-saving mechanism based on a distributed queuing MAC protocol and fuzzy logic theory is introduced for WLAN systems. Computer simulations have been performed and values for the throughput maximum performance and energy consumption have been obtained as a function of different scenario parameters. These values show that the throughput outperforms the one obtained with the IEEE 802.11 standard while reducing the energy consumption.

A Capacity Analysis for the IEEE 802.11 MAC Protocol

Wireless Networks, 2001

The IEEE 802.11 MAC protocol provides shared access to a wireless channel. This paper uses an analytic model to study the channel capacity -i.e., maximum throughput -when using the basic access (two-way handshaking) method in this protocol. It provides closed-form approximations for the probability of collision p, the maximum throughput S and the limit on the number of stations in a wireless cell.

PHY and MAC Performance Evaluation of IEEE 802.11a WLAN over Fading Channels

This paper presents an overview of physical (PHY) and medium access control (MAC) layers for IEEE 802.11a, which is a standard of a broadband high-speed wireless local area network (WLAN). IEEE 802.11a uses 5 GHz frequency band and its PHY is based on orthogonal frequency division multiplexing (OFDM). In this paper, we evaluate the OFDMbased PHY and MAC performance of IEEE 802.11a under various practical wideband channel models, which are abstracted from actual propagation measurements. The effects of different transmission modes defined in PHY on the IEEE 802.11 system performance are investigated. We also discuss the impact of link adaptation, which attempts to choose the best-suited transmission mode according to channel conditions, on the overall system performance.

Implementation and experimental evaluation of multi-channel MAC protocols for 802.11 networks

Ad Hoc Networks, 2010

ABSTRACT Multi-channel MAC protocols have recently obtained considerable attention in wireless networking research because they promise to increase capacity of wireless networks significantly by exploiting multiple frequency bands. However, most of these protocols remain as pure academic interest since they only exist on paper and in simulation code but have no practical implementation. In this paper, we report lessons learned from our endeavor in which we implement three representative multi-channel MAC protocols: Asynchronous Multi-channel Coordination Protocol (AMCP), Multi-channel MAC (MMAC), and Slotted Seeded Channel Hopping (SSCH) on off-the-shelf IEEE 802.11 hardware. We explore practical impacts of these multi-channel MAC protocols and present results of our experimental performance evaluation. The major findings of our performance evaluation are: (1) all multi-channel MAC protocols underperform the original 802.11 MAC at low load, (2) all multi-channel MAC protocols give better performance than the original 802.11 MAC at medium and high load, (3) AMCP performs worst among all multi-channel MACs in one-hop and multi-hop 802.11b scenario but delivers the best performance in multi-hop 802.11a scenario, and (4) SSCH attains the best results in one-hop scenarios or at low loads but loses its effectiveness at high loads in multi-hop scenarios.