A Survey of MAC Protocols Design Strategies and Techniques in Wireless Ad Hoc Networks
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paper_title: HYMAC: Hybrid TDMA/FDMA Medium Access Control Protocol for Wireless Sensor Networks

paper_content:

We describe HyMAC, a new hybrid MAC layer protocol for wireless sensor networks that is, to the best of our knowledge, the first effort to combine the strengths of both TDMA and FDMA schemes in these constrained networks. While allowing the network to operate in an energy-efficient collision-free manner, HyMAC takes advantage of the multiple frequencies provided in the radio component of recent sensor node hardware platforms such as MICAZ, TELOS and FireFly. We show how HyMAC outperforms protocols such as B-MAC, RT-Link and MMSN achieving high throughput and small bounded end- to-end delay suitable for newer types of sensor network applications such as real-time voice streaming.
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paper_title: Cross-layer design: a survey and the road ahead

paper_content:

Of late, there has been an avalanche of cross-layer design proposals for wireless networks. A number of researchers have looked at specific aspects of network performance and, approaching cross-layer design via their interpretation of what it implies, have presented several cross-layer design proposals. These proposals involve different layers of the protocol stack, and address both cellular and ad hoc networks. There has also been work relating to the implementation of cross-layer interactions. It is high time that these various individual efforts be put into perspective and a more holistic view be taken. In this article, we take a step in that direction by presenting a survey of the literature in the area of cross-layer design, and by taking stock of the ongoing work. We suggest a definition for cross-layer design, discuss the basic types of cross-layer design with examples drawn from the literature, and categorize the initial proposals on how cross-layer interactions may be implemented. We then highlight some open challenges and new opportunities for cross-layer design. Designers presenting cross-layer design proposals can start addressing these as they move ahead.
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paper_title: Smart antenna techniques and their application to wireless ad hoc networks

paper_content:

In this article the use of smart antennas in mobile ad hoc and mesh networks is discussed. We first give a brief overview of smart antenna techniques and describe the issues that arise when applying these techniques in ad hoc networks. We consider ad hoc/mesh networks with directional antennas, beamforming/adaptive antennas, and/or multiple-input-multiple-output (MIMO) techniques. We then show how the MAC/routing techniques can be modified to get the maximum benefit with smart antennas, while also showing examples of degradation in system performance, rather than improvement, when smart antenna techniques are added to networks with standard MAC/routing techniques
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paper_title: Smart antennas for wireless communications

paper_content:

Over the last decade, there has been a growing interest in improving system capacity and increasing coverage area in wireless communications using smart antennas. Smart antenna technology is being considered for mobile platforms such as automobiles, cellular telephones (mobile unit), and laptops. This paper presents the design of a smart antenna along with the associated signal processing algorithms for use in the next generation 20 GHz wireless communications systems. The results presented here are part of a broader project that considers this antenna system in the context of reconfigurable broadband (high-speed) networks. This paper concentrates only on the antenna design and on the development of efficient adaptive algorithms for beamforming and direction-of-arrival (DOA). The objective is to design an adaptive antenna that directs the maximum radiation of the antenna pattern toward the signal-of-interest (SOI), and places nulls toward the signal-not-of-interest (SNOI). The proposed antenna design and associated beamforming algorithms take into account mutual coupling for greater accuracy.
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paper_title: Range and throughput enhancement of wireless local area networks using smart sectorised antennas

paper_content:

At present, wireless local area networks (WLANs) such as HiperLAN2 and 802.11a are being developed and deployed around the world. In this letter, the use of sectorized antennas is considered as a means to improve the physical layer performance of WLANs. Results demonstrate that throughput and range can be enhanced and/or the transmit power can be reduced. However, these benefits are achieved with a small increase in multiple access protocol overhead. Simulations are performed using measured wideband channels in the 5-GHz band. In cases where the channel exhibits strong Rician characteristics, gains as high as 13 dB are demonstrated. These benefits substantially outweigh the associated medium access control overhead.
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paper_title: Applications Of Antenna Arrays To Mobile Communications, Part I: Performance Improvement, Feasibility, And System Considerations

paper_content:

The demand for wireless mobile communications services is growing at an explosive rate, with the anticipation that communication to a mobile device anywhere on the globe at all times will be available in the near future. An array of antennas mounted on vehicles, ships, aircraft, satellites, and base stations is expected to play an important role in fulfilling the increased demand of channel requirement for these services, as well as for the realization of the dream that a portable communications device the size of a wristwatch be available at an affordable cost for such services. This paper is the first of a two-part study. It provides a comprehensive treatment, at a level appropriate to nonspecialists, of the use of an antenna array to enhance the efficiency of mobile communications systems. It presents an overview of mobile communications as well as details of how an array may be used in various mobile communications systems, including land-mobile, indoor-radio, and satellite-based systems. It discusses advantages of an array of antennas in a mobile communications system, highlights improvements that are possible by using multiple antennas compared to a single antenna in a system, and provides details on the feasibility of antenna arrays for mobile communications applications.
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paper_title: A Survey On MAC Protocols for Wireless Adhoc Networks with Beamforming Antennas

paper_content:

The beamforming antenna technology is a promising solution to many challenges facing wireless ad hoc networks. Beamforming antennas have the ability to increase the spatial reuse, improve the transmission reliability, extend the transmission range and/or save the power consumption. If they are effectively used, they can significantly improve the network capacity, lifetime, connectivity and security. However, traditional Medium Access Control (MAC) protocols fail to exploit the potential benefits due to the unique characteristics of wireless ad hoc networks with beamforming antennas. To that end, numerous MAC protocols have been designed over the years to harness the offered potential. In this paper, we survey the literature on MAC protocols proposed for wireless ad hoc networks with beamforming antennas during the last decade. We discuss the main beamforming-related challenges facing the medium access control in ad hoc networks. We present taxonomy of the MAC protocols proposed in the literature based on their mode of operation and the mechanisms used to address the challenges. In addition, we provide a qualitative comparison of the protocols highlighting their features, benefits and requirements. Finally, we provide directions for possible future work.
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paper_title: Enhancements for IEEE 802.11 networks with directional antennas

paper_content:

Directional antennas have been introduced to improve the performance of 802.11 based wireless networks. Station equipped with directional antennas can beamform data in a specific direction. However, IEEE 802.11 is developed with omni-directional antennas in mind. Thus, deploying IEEE 802.11 in a directional antenna environment leads stations to be conservative in blocking their own transmissions in favor of the ongoing transmissions. In this paper we propose two opportunistic enhancements for the IEEE 802.11 networks using directional antennas. The first enhancement is to augment the 802.11 MAC protocol with additional information (i.e., location of the stations) that gives a node the flexibility to transmit data while there are ongoing transmissions in its vicinity. The second enhancement, using the augmented MAC protocol, alters the way the 802.11 accessing its MAC data queue.
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paper_title: On the performance of ad hoc networks with beamforming antennas

paper_content:

Beamforming antennas have the potential to provide a fundamental breakthrough in ad hoc network capacity. We present a broad-based examination of this potential, focusing on exploiting the longer ranges as well as the reduced interference that beamforming antennas can provide. We consider a number of enhancements to a convectional ad hoc network system, and evaluation the impact of each enhancement using simulation. Such enhancements include "aggressive" and "conservative" channel access models for beamforming antennas, link power control, and directional neighbor discovery. Our simulations are based on detailed modeling on detailed modeling of steered as well as swiched beams using antenna patterns of varying gains, and a realistic radio and propagation model. For the scenarios studied, our results show that beamforming can yield a 28% to 118% (depending upon the density) improvement in throughput, and up to a factor-of-28 reduction in delay. Our study also tells us which mechanisms are likely to be more effective and under what conditions, which in turn identifies areas where future research is neede
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paper_title: QoS parameters enhancement by using directional antennas in MANET

paper_content:

Mobile Ad hoc networks (MANET) typically consist of the nodes equipped with omni-directional antennas. The using of directional antennas may bring several benefits compared with omni-directional antennas, such as lower interference, better spatial reuse, longer transmission range and improvement of network capacity. This paper presents the application of directional antennas in wireless MANET network and its contribution to enhancement of quality of service (QoS) parameters. The model of wireless MANET network was created in NS-2 simulator with two types of antennas — omni-directional and directional. An apparent improvement of chosen QoS parameters was demonstrated by using directional antennas in MANET networks.
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paper_title: Multichannel CSMA with signal power-based channel selection for multihop wireless networks

paper_content:

We describe a new carrier-sense multiple access (CSMA) protocol for multihop wireless networks, using multiple channels and a distributed channel selection scheme. The proposed protocol divides the available bandwidth into N channels where the transmitting station selects an appropriate channel for packet transmission. The selection criterion is based on the interference power measurements on the channels. We show via simulations that this multichannel CSMA protocol provides a higher throughput compared to its single channel counterpart by reducing the packet loss due to collisions.
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paper_title: Distributed code assignments for CDMA packet radio networks

paper_content:

Code-division multi-access (CDMA) techniques allow many users to transmit simultaneously in the same band without substantial interference by using approximately orthogonal (low cross-correlation) spread-spectrum waveforms. Two-phase algorithms have been devised to assign and reassign spread-spectrum codes to transmitters, to receivers and to pairs of stations in a large dynamic packet radio network in polynomial times. The purpose of the code assignments is to spatially reuse spreading codes to reduce the possibility of packet collisions and to react dynamically to topological changes. These two-phase algorithms minimize the time complexity in the first phase and minimize the number of control packets needed to be exchanged in the second phase. Therefore, they can start the network operation in a short time, then switch to the second phase with the goal of adapting to topological changes. A pairwise code-assignment scheme is proposed to assign codes to edges. Simulations based on well-controlled topologies (sparse topologies) show that the scheme requires much fewer codes than transmitter-based code assignment, while maintaining similar throughput performance. >
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paper_title: Ad Hoc Networks Multi-Channel MAC Protocol Design and Channel Width Adaptation Technology

paper_content:

In wireless Ad hoc networks, using multi-channel technique on MAC layer to increase the network capacity is a promising technology. By extending the RTS/CTS mechanism of IEEE802.11 standard, we propose a busy tone-based multi-channel MAC protocol, which can significantly improve the network throughput by using busy tone to distribute the multiple channels and overcome the multi-channel hidden terminal problem. On the basis of the protocol, this paper further takes the advantage of channel width adaptation technique, with which one channel can be effectively divided into several sub-channels so that the collision probability can be decreased and the network throughput can be further improved. NS2 simulation results show that, firstly, the proposed MAC protocol can significantly improve the throughput via using multiple channels and the improvement on throughput is in direct ratio to the number of channels; Secondly, without increasing the total bandwidth, dividing a channel into several sub-channels via the technique of channel width adaptation can also improve the network performance.
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paper_title: Code assignment for hidden terminal interference avoidance in multihop packet radio networks

paper_content:

Hidden terminal interference is caused by the simultaneous transmission of two stations that cannot hear each other, but are both received by the same destination station. The authors investigate the problem of assigning orthogonal codes to stations to eliminate the hidden terminal interference and minimize the number of codes used. It is shown that this problem is computationally intractable, even for very restricted but very realistic network topologies. Optimal algorithms for code assignment in special networks, as well as both centralized and distributed suboptimal heuristic algorithms for general topologies, are presented. The results of extensive simulations to derive the average performance of the proposed heuristics on realistic network topologies are presented. >
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paper_title: Spreading code protocols for distributed spread-spectrum packet radio networks

paper_content:

Spreading code protocols for a distributed spread-spectrum packet radio network are presented. A distributed single-hop system (i.e. each terminal can hear all other terminals) with the users approximately synchronized and a set of prespecified spreading codes are presented. The spreading code protocol is a policy for choosing a spreading code to be used, given that a terminal has a packet to send, and a policy for monitoring spreading codes, given that a terminal is idle. A slotted system where a packet occupies a number of slots is considered, and two protocols that involve changing the spreading code of a transmission after an initial header is transmitted are presented. In one protocol, the header is transmitted on a common code, and in the other it is transmitted on a receiver-based code, the rest of the packet being transmitted on a transmitter-based code. In the receiving mode, a terminal monitors either a common code, in the first case, or a receiver-based code in the latter. Upon recognizing its own address and the source address, the receiver dynamically switches to a despreading code corresponding to the source. Throughput results are obtained for the case of geometrically distributed packet lengths. >
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paper_title: CDMA-based MAC protocol for wireless ad hoc networks

paper_content:

We propose a CDMA-based power controlled medium access protocol for mobile ad hoc networks (MANETs). Unlike previously proposed protocols, ours accounts for the multiple access interference (MAI), thereby addressing the notorious near-far problem that undermines the throughput performance in MANETs. Channel-gain information obtained from overheard RTS and CTS packets over an out-of-band control channel is used to dynamically bound the transmission power of mobile terminals in the vicinity of a receiver. By properly estimating the required transmission power for data packets, the proposed protocol allows for interference-limited simultaneous transmissions to take place in the neighborhood of a receiving terminal. Simulation results indicate that compared to the IEEE 802.11 approach, the proposed protocol achieves a significant increase in network throughput at no additional cost in energy consumption.
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paper_title: A multichannel CSMA MAC protocol with receiver-based channel selection for multihop wireless networks

paper_content:

We propose a CSMA-based medium access control protocol for multihop wireless networks that uses multiple channels and a dynamic channel selection method. The proposed protocol uses one control channel and N data channels, where N is independent of the number of nodes in the network. The source uses an exchange of control packets on the control channel to decide on the best channel to send the data packet on. Channel selection is based on maximizing the signal-to-interference plus noise ratio at the receiver. We present performance evaluations obtained from simulations that demonstrate the effectiveness of the proposed protocol.
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paper_title: New CDMA-Based MAC Protocol for Ad Hoc Networks

paper_content:

It is widely accepted that Ad Hoc networks are at the leading edge of the research in the domain of wireless networking. These networks are not supported by infrastructure to connect the mobile hosts, thereby they have to be self configured, self organized and the resources have to be allocated in a distributed manner. The medium access control (MAC) layer is seen as the bottleneck for the throughput in wireless Ad hoc networks. Hence, we propose in this work a new Multichannel MAC protocol. The proposed protocol can be based on Code Division Multiple Access (CDMA) or Frequency Division Multiple Access (FDMA). A channel can be represented by one spreading code in CDMA systems or by one frequency band in FDMA case. In our analysis and simulations, we assume that the protocol is based on CDMA technique. We consider one channel for control packets and multiple channels for transmitting data information. We propose that the reservation of a data cannel is done implicitly using the common channel. We show through computer simulations that our proposition of Multichannel MAC protocol improves significantly the communication performance in wireless Ad Hoc networks, even when the introduced overhead is considered.
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paper_title: A multi-radio unification protocol for IEEE 802.11 wireless networks

paper_content:

We present a link layer protocol called the multi-radio unification protocol or MUP. On a single node, MUP coordinates the operation of multiple wireless network cards tuned to non-overlapping frequency channels. The goal of MUP is to optimize local spectrum usage via intelligent channel selection in a multihop wireless network. MUP works with standard-compliant IEEE 802.11 hardware, does not require changes to applications or higher-level protocols, and can be deployed incrementally. The primary usage scenario for MUP is a multihop community wireless mesh network, where cost of the radios and battery consumption are not limiting factors. We describe the design and implementation of MUP, and analyze its performance using both simulations and measurements based on our implementation. Our results show that under dynamic traffic patterns with realistic topologies, MUP significantly improves both TCP throughput and user perceived latency for realistic workloads.
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paper_title: Distributed assignment of codes for multihop packet-radio networks

paper_content:

This paper describes and analyzes a distributed algorithm for assigning codes in a dynamic, multihop wireless radio network. The algorithm does not require any form of synchronization and is completely distributed. The algorithm can be used for both the transmitter oriented and receiver oriented code assignment. The algorithm is proven to be correct and its complexity is analyzed. The implementation of the code assignment algorithm as part of the medium access control (MAC) and routing protocols of a multihop packet-radio network is discussed.
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paper_title: A cooperative CDMA-based multi-channel MAC protocol for mobile ad hoc networks

paper_content:

In this paper, we present CCM-MAC, a cooperative CDMA-based multi-channel medium access control (MAC) protocol for mobile ad hoc networks (MANETs) in which each node has one half-duplex transceiver. The protocol mitigates the multi-channel hidden and exposed terminal problems by using information about channel usage gleaned from overhearing (cooperating) neighbours. By accounting for the multiple access interference, CCM-MAC also addresses the near-far problem of CDMA in MANETs enabling concurrent transmissions on each channel. We provide an analysis of the maximum throughput of CCM-MAC and validate it through simulation in Matlab. We also compare the throughput it achieves to IEEE 802.11, a multi-channel MAC protocol, and a CDMA-based MAC protocol.
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paper_title: A multichannel CSMA MAC protocol for multihop wireless networks

paper_content:

We describe a new carrier-sense multiple access (CSMA) protocol for multihop wireless networks, sometimes also called ad hoc networks. The CSMA protocol divides the available bandwidth into several channels and selects an idle channel randomly for packet transmission. It also employs a notion of "soft" channel reservation as it gives preference to the channel that was used for the last successful transmission. We show via simulations that this multichannel CSMA protocol provides a higher throughput compared to its single channel counterpart by reducing the packet loss due to collisions. We also show that the use of channel reservation provides better performance than multichannel CSMA with purely random idle channel selection.
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paper_title: Routing and interface assignment in multi-channel multi-interface wireless networks

paper_content:

Multiple channels are available for use in IEEE 802.11. Multiple channels can increase the available network capacity, but require new protocols to exploit the available capacity. This paper studies the problem of improving the capacity of multi-channel wireless networks by using multiple interfaces. We consider the scenario when multiple interfaces are available, but the number of available interfaces is lesser than the number of available channels. We provide a classification of interface assignment strategies, and propose a new strategy that does not require modifications to IEEE 802.11. We also identify routing heuristics that are suitable for use with the proposed interface assignment strategy.
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paper_title: Routing and interface assignment in multi-channel multi-interface wireless networks

paper_content:

Multiple channels are available for use in IEEE 802.11. Multiple channels can increase the available network capacity, but require new protocols to exploit the available capacity. This paper studies the problem of improving the capacity of multi-channel wireless networks by using multiple interfaces. We consider the scenario when multiple interfaces are available, but the number of available interfaces is lesser than the number of available channels. We provide a classification of interface assignment strategies, and propose a new strategy that does not require modifications to IEEE 802.11. We also identify routing heuristics that are suitable for use with the proposed interface assignment strategy.
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paper_title: Multi-channel mac for ad hoc networks: handling multi-channel hidden terminals using a single transceiver

paper_content:

This paper proposes a medium access control (MAC) protocol for ad hoc wireless networks that utilizes multiple channels dynamically to improve performance. The IEEE 802.11 standard allows for the use of multiple channels available at the physical layer, but its MAC protocol is designed only for a single channel. A single-channel MAC protocol does not work well in a multi-channel environment, because of the multi-channel hidden terminal problem . Our proposed protocol enables hosts to utilize multiple channels by switching hannels dynamically, thus increasing network throughput. The protocol requires only one transceiver per host, but solves the multi-channel hidden terminal problem using temporal synchronization. Our scheme improves network throughput signifiantly, especially when the network is highly congested. The simulation results show that our protocol successfully exploits multiple hannels to achieve higher throughput than IEEE 802.11. Also, the performance of our protocol is comparable to another multi-hannel MAC protocol that requires multiple transceivers per host. Since our protocol requires only one transceiver per host, it an be implemented with a hardware complexity comparable to IEEE 802.11.
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paper_title: TMMAC: An Energy Efficient Multi-Channel MAC Protocol for Ad Hoc Networks

paper_content:

This paper presents a TDMA based multi-channel MAC protocol called TMMAC for Ad Hoc Networks. TMMAC requires only a single half-duplex radio transceiver on each node. In addition to explicit frequency negotiation which is adopted by conventional multi-channel MAC protocols, TMMAC introduces lightweight explicit time negotiation. This two-dimensional negotiation enables TMMAC to exploit the advantage of both multiple channels and TDMA, and achieve aggressive power savings by allowing nodes that are not involved in communication to go into doze mode. Moreover, TMMAC dynamically adjusts its negotiation window size based on different traffic patterns, which further improves communication throughput and energy savings. In this paper, the performance of TMMAC is analyzed and evaluated. The evaluations show that TMMAC achieves up to 113% higher communication throughput while consuming 74% less per packet energy over the state-of-the-art multi-channel MAC protocols for single-transceiver wireless devices.
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paper_title: SSCH: slotted seeded channel hopping for capacity improvement in IEEE 802.11 ad-hoc wireless networks

paper_content:

Capacity improvement is one of the principal challenges in wireless networking. We present a link-layer protocol called Slotted Seeded Channel Hopping, or SSCH, that increases the capacity of an IEEE 802.11 network by utilizing frequency diversity. SSCH can be implemented in software over an IEEE 802.11-compliant wireless card. Each node using SSCH switches across channels in such a manner that nodes desiring to communicate overlap, while disjoint communications mostly do not overlap, and hence do not interfere with each other. To achieve this, SSCH uses a novel scheme for distributed rendezvous and synchronization. Simulation results show that SSCH significantly increases network capacity in several multi-hop and single-hop wireless networking scenarios.
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paper_title: HYMAC: Hybrid TDMA/FDMA Medium Access Control Protocol for Wireless Sensor Networks

paper_content:

We describe HyMAC, a new hybrid MAC layer protocol for wireless sensor networks that is, to the best of our knowledge, the first effort to combine the strengths of both TDMA and FDMA schemes in these constrained networks. While allowing the network to operate in an energy-efficient collision-free manner, HyMAC takes advantage of the multiple frequencies provided in the radio component of recent sensor node hardware platforms such as MICAZ, TELOS and FireFly. We show how HyMAC outperforms protocols such as B-MAC, RT-Link and MMSN achieving high throughput and small bounded end- to-end delay suitable for newer types of sensor network applications such as real-time voice streaming.
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paper_title: TMMAC: An Energy Efficient Multi-Channel MAC Protocol for Ad Hoc Networks

paper_content:

This paper presents a TDMA based multi-channel MAC protocol called TMMAC for Ad Hoc Networks. TMMAC requires only a single half-duplex radio transceiver on each node. In addition to explicit frequency negotiation which is adopted by conventional multi-channel MAC protocols, TMMAC introduces lightweight explicit time negotiation. This two-dimensional negotiation enables TMMAC to exploit the advantage of both multiple channels and TDMA, and achieve aggressive power savings by allowing nodes that are not involved in communication to go into doze mode. Moreover, TMMAC dynamically adjusts its negotiation window size based on different traffic patterns, which further improves communication throughput and energy savings. In this paper, the performance of TMMAC is analyzed and evaluated. The evaluations show that TMMAC achieves up to 113% higher communication throughput while consuming 74% less per packet energy over the state-of-the-art multi-channel MAC protocols for single-transceiver wireless devices.
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paper_title: CAM-MAC: A Cooperative Asynchronous Multi-Channel MAC Protocol for Ad Hoc Networks

paper_content:

Medium access control (MAC) protocols have been studied under different contexts for several years now. In all these MAC protocols, nodes make independent decisions on when to transmit a packet and when to back-off from transmission. In this paper, we introduce the notion of node cooperation into MAC protocols. Cooperation adds a new degree of freedom which has not been explored before. Specifically we study the design of cooperative MAC protocols in an environment where each node is equipped with a single transceiver and has multiple channels to choose from. Nodes cooperate by helping each other select a free channel to use. We show that this simple idea of cooperation has several qualitative and quantitative advantages. Our cooperative asynchronous multi-channel MAC protocol (CAM-MAC) is extremely simple to implement and, unlike other multi-channel MAC protocols, is naturally asynchronous. We conduct extensive simulation experiments. We first compare CAM-MAC with IEEE 802.11b and a version of CAM-MAC with the cooperation element removed. We use this to show the value of cooperation. Our results show significant improvement in terms of number of collisions and throughput for CAM-MAC. We also compare our protocol with MMAC and SSCH and show that CAM-MAC significantly outperforms both of them.
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paper_title: Cross-layer design: a survey and the road ahead

paper_content:

Of late, there has been an avalanche of cross-layer design proposals for wireless networks. A number of researchers have looked at specific aspects of network performance and, approaching cross-layer design via their interpretation of what it implies, have presented several cross-layer design proposals. These proposals involve different layers of the protocol stack, and address both cellular and ad hoc networks. There has also been work relating to the implementation of cross-layer interactions. It is high time that these various individual efforts be put into perspective and a more holistic view be taken. In this article, we take a step in that direction by presenting a survey of the literature in the area of cross-layer design, and by taking stock of the ongoing work. We suggest a definition for cross-layer design, discuss the basic types of cross-layer design with examples drawn from the literature, and categorize the initial proposals on how cross-layer interactions may be implemented. We then highlight some open challenges and new opportunities for cross-layer design. Designers presenting cross-layer design proposals can start addressing these as they move ahead.
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paper_title: Y-MAC: An Energy-Efficient Multi-channel MAC Protocol for Dense Wireless Sensor Networks

paper_content:

As the use of wireless sensor networks (WSNs) becomes widespread, node density tends to increase. This poses a new challenge for Medium Access Control (MAC) protocol design. Although traditional MAC protocols achieve low-power operation, they use only a single channel which limits their performance. Several multi-channel MAC protocols for WSNs have been recently proposed. One of the key observations is that these protocols are less energy efficient than single-channel MAC protocols under light traffic conditions. In this paper, we propose an energy efficient multi-channel MAC protocol, Y-MAC, for WSNs. Our goal is to achieve both high performance and energy efficiency under diverse traffic conditions. In contrast to most of previous multi-channel MAC protocols for WSNs, we implemented Y-MAC on a real sensor node platform and conducted extensive experiments to evaluate its performance. Experimental results show that Y-MAC is energy efficient and maintains high performance under high-traffic conditions.
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paper_title: Practical Multi-Channel MAC for Ad Hoc Networks

paper_content:

Multi-channel MACs have recently attracted significant attention in wireless networking research because they possess the ability to exploit multiple frequency bands in order to increase the capacity of wireless ad hoc networks. A number of multi-channel MACs have been proposed in the last few years. However, these protocols rely on two rather impractical assumptions: low channel switching latency and fine-grained clock synchronization. This paper presents Asynchronous Multi-channel Hopping Protocol (AMHP), a multi-channel MAC protocol that does not build on these two impractical assumptions. We conduct an extensive performance evaluation and compare AMHP with 802.11 MAC, Asynchronous Multi-channel Coordination Protocol (AMCP), Multi-Channel MAC (MMAC), and Slotted Seeded Channel Hopping (SSCH). The major findings of our performance evaluation are: (1) all multi-channel MACs underperform 802.11 MAC at low load but AMHP comes very close to 802.11 MAC's performance at this load, (2) all multi-channel MACs give better performance than 802.11 MAC at medium and high load, (3) SSCH attains good results in one-hop scenarios or at low loads but loses its effectiveness at high loads and in multi-hop scenarios, and (4) AMHP outperforms all other multi-channel MACs at all loads.
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paper_title: A Practical Multi-channel Media Access Control Protocol for Wireless Sensor Networks

paper_content:

Despite availability of multiple orthogonal communication channels on common sensor network platforms, such as MicaZ motes, and despite multiple simulation-supported designs of multi-channel MAC protocols, most existing sensor networks use only one channel for communication, which is a source of bandwidth inefficiency. In this work, we design, implement, and experimentally evaluate a practical MAC protocol which utilizes multiple channels efficiently for WSNs. A control theory approach is used to dynamically allocate channels for each mote in a distributed manner transparently to the application and routing layers. The protocol assumes that sensor nodes are equipped with one half-duplex radio interface which is most common in current hardware platforms. The protocol does not require time synchronization among nodes and takes the channel switching cost of current hardware into account. Evaluation results on a real testbed show that it achieves a non-trivial bandwidth improvement using 802.15.4 radios in topologies which are typical in WSNs. The MAC protocol was implemented in TinyOS-2.x and packaged as a software component to enable seamless use with existing applications.
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paper_title: Implementation and experimental evaluation of multi-channel MAC protocols for 802.11 networks

paper_content:

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.
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paper_title: Self-management in chaotic wireless deployments

paper_content:

Over the past few years, wireless networking technologies have made vast forays into our daily lives. Today, one can find 802.11 hardware and other personal wireless technology employed at homes, shopping malls, coffee shops and airports. Present-day wireless network deployments bear two important properties: they are unplanned, with most access points (APs) deployed by users in a spontaneous manner, resulting in highly variable AP densities; and they are unmanaged, since manually configuring and managing a wireless network is very complicated. We refer to such wireless deployments as being chaotic.In this paper, we present a study of the impact of interference in chaotic 802.11 deployments on end-client performance. First, using large-scale measurement data from several cities, we show that it is not uncommon to have tens of APs deployed in close proximity of each other. Moreover, most APs are not configured to minimize interference with their neighbors. We then perform trace-driven simulations to show that the performance of end-clients could suffer significantly in chaotic deployments. We argue that end-client experience could be significantly improved by making chaotic wireless networks self-managing. We design and evaluate automated power control and rate adaptation algorithms to minimize interference among neighboring APs, while ensuring robust end-client performance.
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paper_title: Cross-layer issues in MAC protocol design for MIMO ad hoc networks

paper_content:

In this article, we discuss research and design issues that arise in the development of networking protocols for an ad hoc network where nodes are equipped with multiple antenna elements and have the ability to perform signal processing operations as required by adaptive beamforming, interference cancellation, and space-time coding
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paper_title: Multi-channel mac for ad hoc networks: handling multi-channel hidden terminals using a single transceiver

paper_content:

This paper proposes a medium access control (MAC) protocol for ad hoc wireless networks that utilizes multiple channels dynamically to improve performance. The IEEE 802.11 standard allows for the use of multiple channels available at the physical layer, but its MAC protocol is designed only for a single channel. A single-channel MAC protocol does not work well in a multi-channel environment, because of the multi-channel hidden terminal problem . Our proposed protocol enables hosts to utilize multiple channels by switching hannels dynamically, thus increasing network throughput. The protocol requires only one transceiver per host, but solves the multi-channel hidden terminal problem using temporal synchronization. Our scheme improves network throughput signifiantly, especially when the network is highly congested. The simulation results show that our protocol successfully exploits multiple hannels to achieve higher throughput than IEEE 802.11. Also, the performance of our protocol is comparable to another multi-hannel MAC protocol that requires multiple transceivers per host. Since our protocol requires only one transceiver per host, it an be implemented with a hardware complexity comparable to IEEE 802.11.
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paper_title: SSCH: slotted seeded channel hopping for capacity improvement in IEEE 802.11 ad-hoc wireless networks

paper_content:

Capacity improvement is one of the principal challenges in wireless networking. We present a link-layer protocol called Slotted Seeded Channel Hopping, or SSCH, that increases the capacity of an IEEE 802.11 network by utilizing frequency diversity. SSCH can be implemented in software over an IEEE 802.11-compliant wireless card. Each node using SSCH switches across channels in such a manner that nodes desiring to communicate overlap, while disjoint communications mostly do not overlap, and hence do not interfere with each other. To achieve this, SSCH uses a novel scheme for distributed rendezvous and synchronization. Simulation results show that SSCH significantly increases network capacity in several multi-hop and single-hop wireless networking scenarios.
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paper_title: Layering as Optimization Decomposition: A Mathematical Theory of Network Architectures

paper_content:

Network protocols in layered architectures have historically been obtained on an ad hoc basis, and many of the recent cross-layer designs are also conducted through piecemeal approaches. Network protocol stacks may instead be holistically analyzed and systematically designed as distributed solutions to some global optimization problems. This paper presents a survey of the recent efforts towards a systematic understanding of layering as optimization decomposition, where the overall communication network is modeled by a generalized network utility maximization problem, each layer corresponds to a decomposed subproblem, and the interfaces among layers are quantified as functions of the optimization variables coordinating the subproblems. There can be many alternative decompositions, leading to a choice of different layering architectures. This paper surveys the current status of horizontal decomposition into distributed computation, and vertical decomposition into functional modules such as congestion control, routing, scheduling, random access, power control, and channel coding. Key messages and methods arising from many recent works are summarized, and open issues discussed. Through case studies, it is illustrated how layering as Optimization Decomposition provides a common language to think about modularization in the face of complex, networked interactions, a unifying, top-down approach to design protocol stacks, and a mathematical theory of network architectures
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paper_title: On the scalability of IEEE 802.11 ad hoc networks

paper_content:

The IEEE 802.11 standards support the peer-to-peer mode Independent Basic Service Set (IBSS), which is an ad hoc network with all its stations within each other's transmission range. In an IBSS, it is important that all stations are synchronized to a common clock. Synchronization is necessary for frequency hopping spread spectrum (FHSS) to ensure that all stations "hop" at the same time; it is also necessary for both FHSS and direct sequence spread spectrum (DSSS) to perform power management. This paper evaluates the synchronization mechanism, which is a distributed algorithm, specified in the IEEE 802.11 standards. By both analysis and simulation, it is shown that when the number of stations in an IBSS is not very small, there is a non-negligible probability that stations may get out of synchronization. The more stations, the higher probability of asynchronism. Thus, the current IEEE 802.11's synchronization mechanism does not scale; it cannot support a large-scale ad hoc network. To alleviate the asynchronism problem, this paper proposes a simple modification to the current synchronization algorithm. The modified algorithm is shown to work well for large ad hoc networks.
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paper_title: Cross-layer design: a survey and the road ahead

paper_content:

Of late, there has been an avalanche of cross-layer design proposals for wireless networks. A number of researchers have looked at specific aspects of network performance and, approaching cross-layer design via their interpretation of what it implies, have presented several cross-layer design proposals. These proposals involve different layers of the protocol stack, and address both cellular and ad hoc networks. There has also been work relating to the implementation of cross-layer interactions. It is high time that these various individual efforts be put into perspective and a more holistic view be taken. In this article, we take a step in that direction by presenting a survey of the literature in the area of cross-layer design, and by taking stock of the ongoing work. We suggest a definition for cross-layer design, discuss the basic types of cross-layer design with examples drawn from the literature, and categorize the initial proposals on how cross-layer interactions may be implemented. We then highlight some open challenges and new opportunities for cross-layer design. Designers presenting cross-layer design proposals can start addressing these as they move ahead.
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paper_title: Fine-grained network time synchronization using reference broadcasts

paper_content:

Recent advances in miniaturization and low-cost, low-power design have led to active research in large-scale networks of small, wireless, low-power sensors and actuators. Time synchronization is critical in sensor networks for diverse purposes including sensor data fusion, coordinated actuation, and power-efficient duty cycling. Though the clock accuracy and precision requirements are often stricter than in traditional distributed systems, strict energy constraints limit the resources available to meet these goals.We present Reference-Broadcast Synchronization, a scheme in which nodes send reference beacons to their neighbors using physical-layer broadcasts. A reference broadcast does not contain an explicit timestamp; instead, receivers use its arrival time as a point of reference for comparing their clocks. In this paper, we use measurements from two wireless implementations to show that removing the sender's nondeterminism from the critical path in this way produces high-precision clock agreement (1.85± 1.28μsec, using off-the-shelf 802.11 wireless Ethernet), while using minimal energy. We also describe a novel algorithm that uses this same broadcast property to federate clocks across broadcast domains with a slow decay in precision (3.68± 2.57μsec after 4 hops). RBS can be used without external references, forming a precise relative timescale, or can maintain microsecond-level synchronization to an external timescale such as UTC. We show a significant improvement over the Network Time Protocol (NTP) under similar conditions.
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paper_title: Reuse partitioning in cellular systems

paper_content:

The concept of reuse partitioning in cellular system design is introduced. It is shown that reuse partitioning has the potential for: • Increasing system capacity over that which can be achieved with a single reuse factor for a given performance objective. • Affording greater protection to those system users that need it most. • Being fully compatible with the concepts of overlaid cells and retained channel sets. • Having a minimal impact on cell-site RF architecture. • Providing a near continuum of equivalent reuse factors in cellular system design. The implications of reuse partitioning on cellular system performance, growth, channel assignment, RF hardware, supervisory-audio-tone (SAT) assignment, and channel selection and control are discussed.
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Title: A Survey of MAC Protocols Design Strategies and Techniques in Wireless Ad Hoc Networks

Section 1: INTRODUCTION
Description 1: Introduce the paper, categorize MAC protocols based on single-radio and multi-radio paradigms, discuss channel access methods, and outline the rest of the paper.

Section 2: SINGLE-RADIO SINGLE-CHANNEL MAC PROTOCOLS
Description 2: Explore the earliest MAC solutions for MANETs focusing on single-radio, single-channel protocols, notably IEEE 802.11DCF, and discuss enhancements with directional antennas.

Section 3: MULTI-RADIO MAC PROTOCOLS
Description 3: Discuss multi-radio MAC protocols aimed at enhancing throughput, covering protocols that use multiple radio interfaces and the associated challenges with energy consumption and device limitations.

Section 4: SINGLE-RADIO MULTI-CHANNEL MAC PROTOCOLS
Description 4: Describe protocols requiring one radio per node but operate on multiple channels, such as MMAC and SSCH, and discuss challenges like clock synchronization and channel switching delays.

Section 5: DISCUSSION AND CONCLUSION
Description 5: Summarize key aspects of MANET MAC protocols, highlight cross-layer design potential, and discuss practical challenges like energy consumption, synchronization, and frequency reuse for future MAC protocol developments.