Wireless LAN Protocol Research Articles

Energy-efficient MAC protocol for wireless LANs with WiFi sensors

Abstract More and more mobile computing devices such as smartphones with limited battery power are being used in IEEE 802.11 wireless LANs, and WiFi sensors with very limited battery power are expected to get Internet access through wireless LANs in the near future. We propose an efficient MAC (Medium Access Control) protocol so that WiFi sensors and mobile devices are connected to APs (Access Points) in IEEE 802.11 wireless LANs in an energy-efficient manner.

Accurate indoor positioning using IEEE 802.11mc round trip time

WiFi time of flight (ToF) measurement has been supported recently by the wireless LAN protocols to improve WiFi localization. Specifically, the IEEE 802.11-2016 standard has a fine-time measurement (FTM) protocol that can be used to measure the WiFi signal round trip time (RTT). In this paper, we present the design and implementation of WiNar, a WiFi RTT-based indoor location determination system that combines the advantages of both fingerprint and ranging-based techniques to overcome the different challenges of indoor environments. Using commercial-off-the-shelf access points and mobile phones, WiNar leverages both the propagation time and received signal strength of the wireless signal with a fingerprinting model to address the multipath, non-line-of-sight, signal attenuation, and interference challenges of the indoor environments. Moreover, when leveraging the round trip time measurements, WiNar does not require clock synchronization between the transmitter and the receiver. We discuss the different components of the system and its implementation on the Android operating system. Our results show that WiNar has a sub-meter localization accuracy with an average localization error of less than 0.77 meters for two different testbeds. This accuracy outperforms the performance of the traditional signal strength (RSS) fingerprinting technique by at least 50% and ranging-based multi-lateration technique by at least 193%. Finally, our system is also robust to heterogeneous devices.

Extended RTS/CTS Control based on Transmission Request Distribution in Wireless Ad-Hoc Networks

In a wireless ad-hoc network where wireless nodes exchange data messages without help of stationary base stations, collisions of control and data messages are reduced and/or avoided by CSMA/CA and RTS/CTS control of wireless LAN protocols. Random backoff timers for avoidance of collisions among RTS control messages provides equally opportunities to transmit data messages to neighbor wireless nodes since the value of the backoff timer monotonically decreases. In usual wireless ad-hoc networks, wireless nodes are not equally distributed and frequency of transmission requests in wireless nodes is also not the same. Thus, especially in a region with high density of transmissions and receipts requests for data messages, it is not always possible to receive a response CTS control message even though a wireless node has an opportunity to transmit an RTS control message. Hence, the equal opportunities to transmit an RTS control message is not enough to realize the equal opportunities to transmit a data message. In order to solve this problem, this paper proposes a novel RTS/CTS control to equally provide opportunities to transmit data messages whose receiver node is hard to transmit a CTS control message on response to an RTS control message. Here, a transmission of a CTS control message precedes a transmission of an RTS control message in cases that transmissions of a CTS control message fail repeatedly.

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.

Resource Sharing in Dual-Stack Devices: Opportunistic Bluetooth Transmissions in WLAN Busy Periods

The coexistence problem of different wireless protocols that share a common frequency spectrum has attracted much attention owing to the proliferation of heterogeneous wireless networks in the research community. Recently, Bluetooth (BT) and Wireless LAN (WLAN) protocol stacks have been integrated as a single-chip communication module, and they now even share the antenna as well as the spectrum. In this paper, we show that this integration provides new opportunity for one protocol to better understand the other and to operate in harmony to avoid mutual interference. We develop an Opportunistic Bluetooth Transmission (OBT) scheme that enables a dual stack device having an integrated module to exploit previously-unused deferring times of the WLAN protocol. We evaluate its performance through not only model-based analysis but also practical implementation in a prototype testbed. The results show that the OBT scheme can significantly improve throughput of the dual-stack device.

Design and performance analysis of a MAC protocol for wireless LANs supporting multipacket reception

Recent advances in physical layer technologies, allows simultaneous reception of multiple packets by a node. This promising technology is called Multi-Packet Reception (MPR). In this paper, we analyze a modified IEEE 802.11 DCF based medium access control (MAC) protocol for Wireless Local Area Network (WLAN) with nodes having MPR capability. Our protocol modifies the backoff mechanism of the IEEE 802.11 DCF so that the backoff process quickly adapts to the prevailing traffic conditions while leveraging MPR. A Markov chain model for the backoff process of the nodes with MPR capability has been derived. Further a Markov chain model to capture the state of the MPR channel has been derived. Solving the Markov chains for stationary probabilities, we derive the saturated throughput and energy efficiency of our protocol. Effect of the number of nodes, MPR capability, contention window size, and sensing errors on the saturation throughput has been investigated. Proposed analytical model has been validated through extensive simulations. Our investigation has the potential to aid in the development of next generation WLAN MAC protocol.

タフ・ロボティクスのためのタフ・ワイヤレス技術の研究開発

Robots and unmanned aerial vehicles, or drones, are the hot research topics aiming at application to disaster response, infrastructure inspection, transportation, etc. 2.4GHz band wireless LAN is used for most of the control link of those robots because of cost and device availability. However, the wireless LAN protocol is not suitable for robot remote control because of fluctuation of transmission delay time and interference problem. Therefore, in this research, we have developed a multi-hop wireless network specialized for remote control link of robots and drones out of visual line-of-sight for future robot society. This paper presents the design and performance of prototype system obtained in field test.

Towards secure quantum key distribution protocol for wireless LANs: a hybrid approach

The primary goals of security such as authentication, confidentiality, integrity and non-repudiation in communication networks can be achieved with secure key distribution. Quantum mechanisms are highly secure means of distributing secret keys as they are unconditionally secure. Quantum key distribution protocols can effectively prevent various attacks in the quantum channel, while classical cryptography is efficient in authentication and verification of secret keys. By combining both quantum cryptography and classical cryptography, security of communications over networks can be leveraged. Hwang, Lee and Li exploited the merits of both cryptographic paradigms for provably secure communications to prevent replay, man-in-the-middle, and passive attacks. In this paper, we propose a new scheme with the combination of quantum cryptography and classical cryptography for 802.11i wireless LANs. Since quantum cryptography is premature in wireless networks, our work is a significant step forward toward securing communications in wireless networks. Our scheme is known as hybrid quantum key distribution protocol. Our analytical results revealed that the proposed scheme is provably secure for wireless networks.

Multi-channel cooperative MAC protocol for wireless LANs

Traditional IEEE 802.11-based wireless LANs use only a single channel in order to ensure the connectivity of networks, although multi-channel capability is available to provide higher network throughput by allowing simultaneous multiple transmissions that do not interfere with each other. However, using multiple channels results in several new challenges: finding the receiver, scheduling the next transmission, and balancing the load among channels. This paper proposes a novel and efficient control-channel-based, multi-channel mechanism that uses a single transceiver. Simulation results indicate that the proposed mechanism effectively exploits all available data channels with multiple packet transmissions, provides high network throughput, and requires a low overhead. For example, when we have 13 channels with a 54Mbps data rate, the proposed mechanism provides 349Mbps throughput, while the IEEE 802.11 MAC with a single channel achieves only 13Mbps throughput.

An adaptive MAC protocol for wireless LANs

This paper focuses on contention-based Medium Access Control (MAC) protocols used in Wireless Local Area Networks (WLANs). We propose a novel MAC protocol called Adaptive Backoff Tuning MAC (ABTMAC) based on IEEE 802.11 DCF. In our proposed MAC protocol, we utilize a fixed transmission attempt rate and each node dynamically adjusts its backoff window size considering the current network status. We determined the appropriate transmission attempt rate for both cases where the Request-To-Send/Clear-To-Send (RTS/CTS) mechanism was and was not employed. Robustness against performance degradation caused by the difference between desired and actual values of the attempt rate parameter is considered when setting it. The performance of the protocol is evaluated analytically and through simulations. These results indicate that a wireless network utilizing ABTMAC performs better than one using IEEE 802.11 DCF.

A link-adapted fragment and rate matching (FaRM) MAC protocol for wireless LANs

The paper proposes a fragment and rate matching (FaRM) MAC protocol for wireless LANs to resist the frequent change of channel quality so as to increase network throughput. In wireless transmissions, channel quality varies with time. The FaRM protocol estimates channel quality by detecting current signal-to-noise ratio (SNR) through frame exchanges. A finite state Markov chain (FSMC) is utilised to predict the variation in the channel conditions during the next frame transmission. According to the results obtained from the FSMC, the FaRM protocol enables the sender to dynamically select an appropriate transmission rate as well as an acceptable fragment length to transmit, such that the reliability and time of this transmission can be improved. As a result, the FaRM protocol can not only obtain better network throughput through the selection of the high transmission rate, but it can also increase the successful transmission rate by the determination of a suitable fragment length. Simulation results show that the FaRM protocol has better performance, higher transmission reliability, and lower transmission delay by FaRM in comparison to the related work.

A multichannel relay MAC protocol for IEEE 802.11 wireless LANs

SUMMARYOne of the challenging issues in wireless LANs (WLANs) is improving the network throughput. One of the possible solutions for the issue is maximizing the number of concurrent transmissions. Although some protocols have been proposed to exploit transmission concurrency in WLANs, their performance depends on the degree of the interference among links. Also, it is hard to obtain interference information because of their dynamics. In this paper, we propose an enhanced medium access control (MAC) protocol for WLANs, named multichannel relay MAC (MRMAC), which is able to transmit multiple frames simultaneously without considering interference. To enable concurrent transmissions, MRMAC adopts the concept of frame relaying. Furthermore, MRMAC utilizes several nonoverlapping channels to eliminate interferences. Through extensive simulations, we found that MRMAC shows better performance than existing well‐known MAC protocols. Copyright © 2013 John Wiley & Sons, Ltd.

Prevention of DoS and Memory Attacks: Enhanced 3-Way Handshake

In today’s world most organizations are moving from wireconnected LAN to wireless LAN. The phenomenal popularity of the 802.11 network standards stems from the fact that they provide for wireless connections with ease and convenience. Recently, security holes have been identified in the operation of 802.11 networks, and the 802.11i protocol has been announced to protect such networks. However, there are still security issues that prevent the 802.11 network from becoming the best choice protocol for wireless LANs. We reviewed 802.11i security with a focus on a denial of service attack. This attack exhausts the client’s memory using a vulnerability of the key derivation procedure in 802.11i. It is vulnerable to various Denial of Service attacks (DoS) which includes de-authentication and disassociation attacks including memory exhaustion attacks. For Dos and memory exhaustion attacks which are possible in 4-way handshake ,this paper provides an enhanced 3-way Handshake algorithm which is free from these attacks in comparison to original protocol and is more secure.

Order Matters: Transmission Reordering in Wireless Networks

Modern wireless interfaces support a physical-layer capability called Message in Message (MIM). Briefly, MIM allows a receiver to disengage from an ongoing reception and engage onto a stronger incoming signal. Links that otherwise conflict with each other can be made concurrent with MIM. However, the concurrency is not immediate and can be achieved only if conflicting links begin transmission in a specific order. The importance of link order is new in wireless research, motivating MIM-aware revisions to link-scheduling protocols. This paper identifies the opportunity in MIM-aware reordering, characterizes the optimal improvement in throughput, and designs a link-layer protocol for enterprise wireless LANs to achieve it. Testbed and simulation results confirm the performance gains of the proposed system.

A Service/Device Differentiation Scheme for Contention-Tone-Based Wireless LAN Protocol

A contention-tone-based wireless local area network (WLAN) protocol uses out-of-band signaling for contention resolution to achieve efficient medium access. It is shown that such a protocol can operate at near-optimal channel utilization in the medium access control (MAC) layer. This paper addresses the service differentiation design aspect of a contention-tone-based WLAN protocol. In particular, service and device differentiation schemes are proposed to fulfill a particular quality of service (QoS) for data packet transmissions for contention-tone-based WLANs. Our analysis shows that our design not only provides bandwidth differentiation that matches that specified in the IEEE 802.11e standard but operates at near-optimal channel utilization as well. Our design also incorporates device differentiation to eliminate the access-point bottleneck problem in WLANs. Analytical and simulation results confirm the performance advantages of our design.

Improving Spatial Reuse in Multihop Wireless Networks - A Survey

In multihop wireless ad-hoc networks, the medium access control (MAC) protocol plays a key role in coordinating the access to the shared medium among wireless nodes. Currently, the distributed coordination function (DCF) of the IEEE 802.11 is the dominant MAC protocol for both wireless LANs and wireless multihop ad hoc environment due to its simple implementation and distributed nature. The current access method of the IEEE 802.11 does not make efficient use of the shared channel due to its conservative approach in assessing the level of interference; this in turn affects the spatial reuse of the limited radio resources and highly affect the achieved throughput of a multihop wireless network. This paper surveys various methods that have been proposed in order to enhance the channel utilization by improving the spatial reuse.

A Self-Adaptive Routing Protocol in Wireless LANs Based on Attractor Selection

Wireless LANs, which consist of access points and wireless stations, have widely spread in recent years. Routing in wireless LANs suffers the problem that each wireless station selects an access point and a wired path to its destination station. It is desired to design an adaptive routing protocol for wireless LANs since throughputs of communications are dynamically affected by selections of other wireless stations and external environmental changes. In this paper, we propose a routing protocol for wireless LANs based on attractor selection. Attractor selection is a biologically inspired approach, and it has high adaptability to dynamic environmental changes. By applying attractor selection, each wireless station can adaptively select its access point and wired path with high throughput against environmental changes. In addition, we design the protocol with a new technique: combination of multiple attractor selections. The technique is useful because it enables us to divide a problem into several simpler problems. To the best of our knowledge, our protocol is the first one designed around a combination of multiple attractor selections. We show the effectiveness and adaptability of our protocol by simulations.

Energy-efficient protocols for wireless networks with adaptive MIMO capabilities

Transmission power control has been used in wireless networks to improve the channel reuse and/or reduce energy consumption. It has been mainly applied to single-input single-output (SISO) systems, where each node is equipped with a single antenna. In this paper, we propose a power-controlled channel access protocol for MIMO-capable wireless LANs with two antennas per node. Our protocol, called E-BASIC, extends the classic CSMA/CA access scheme by allowing for dynamic adjustment of the transmission mode and the transmission power on a per-packet basis so as to minimize the total energy consumption. By transmission mode we mean one of the four possible transmit/receive antenna configurations: 1 × 1 (SISO), 2 × 1 (MISO), 1 × 2 (SIMO), and 2 × 2 (MIMO). Depending on the transmitter-receiver distance, any of the four modes can be the optimal one in terms of minimizing the total energy consumption. We study the performance of E-BASIC in both ad hoc and access point topologies. We also incorporate E-BASIC in the design of a power-aware routing (PAR) scheme that selects minimum-energy end-to-end paths. Our adaptive designs are first conducted assuming fixed-rate transmission, but later extended to multi-rate systems. To account for the energy-throughput tradeoff in our designs, we impose a constraint on the average packet delivery time. Simulations indicate that the proposed adaptations achieve a significant reduction in the overall energy consumption relative to non-adaptive MIMO systems.

UWAN-MAC: An Energy-Efficient MAC Protocol for Underwater Acoustic Wireless Sensor Networks

In this paper, we propose a distributed, scalable, energy-efficient media access control (MAC) protocol that works despite long, unknown propagation delays of the underwater acoustic medium. This protocol can be used for delay-tolerant applications such as underwater ecological sensor networks between energy-limited nodes. Our protocol differs significantly from ALOHA, multiple access with collision avoidance (MACA), and the media access protocol for wireless LANs (MACAW) in that energy is the main performance metric in our case rather than bandwidth utilization. We show that under a realistic underwater sensor network scenario, our MAC protocol wastes only 4% of the transmit energy and only 1.5% of the receive energy due to collisions, when the average number of neighbors is four, and the duty cycle is 0.004. This distributed, scalable MAC protocol has the potential to serve as a primer for the development of energy-efficient MAC protocols for future underwater sensor networks.

A Power-Efficient Approach to Adaptive Polling Protocols for Wireless LANs

This paper proposes the low power adaptive polling (LPOAP) MAC protocol for infrastructure wireless LANs (WLANs). It operates efficiently under bursty traffic and can reduce mobile power consumption without performance penalties.