A survey on mac protocols for ad hoc networks with directional antennas
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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: The capacity of wireless networks

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When n identical randomly located nodes, each capable of transmitting at W bits per second and using a fixed range, form a wireless network, the throughput /spl lambda/(n) obtainable by each node for a randomly chosen destination is /spl Theta/(W//spl radic/(nlogn)) bits per second under a noninterference protocol. If the nodes are optimally placed in a disk of unit area, traffic patterns are optimally assigned, and each transmission's range is optimally chosen, the bit-distance product that can be transported by the network per second is /spl Theta/(W/spl radic/An) bit-meters per second. Thus even under optimal circumstances, the throughput is only /spl Theta/(W//spl radic/n) bits per second for each node for a destination nonvanishingly far away. Similar results also hold under an alternate physical model where a required signal-to-interference ratio is specified for successful receptions. Fundamentally, it is the need for every node all over the domain to share whatever portion of the channel it is utilizing with nodes in its local neighborhood that is the reason for the constriction in capacity. Splitting the channel into several subchannels does not change any of the results. Some implications may be worth considering by designers. Since the throughput furnished to each user diminishes to zero as the number of users is increased, perhaps networks connecting smaller numbers of users, or featuring connections mostly with nearby neighbors, may be more likely to be find acceptance.
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paper_title: Wireless medium access control protocols

paper_content:

Technological advances, coupled with the flexibility and mobility of wireless systems, are the driving force behind the Anyone, Anywhere, Anytime paradigm of networking. At the same time, we see a convergence of the telephone, cable and data networks into a unified network that supports multimedia and real-time applications like voice and video in addition to data. Medium access control protocols define rules for orderly access to the shared medium and play a crucial role in the efficient and fair sharing of scarce wireless bandwidth. The nature of the wireless channel brings new issues like location-dependent carrier sensing, time varying channel and burst errors. Low power requirements and half duplex operation of the wireless systems add to the challenge. Wireless MAC protocols have been heavily researched and a plethora of protocols have been proposed. Protocols have been devised for different types of architectures, different applications and different media. This survey discusses the challenges in the design of wireless MAC protocols, classifies them based on architecture and mode of operation, and describes their relative performance and application domains in which they are best deployed.
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paper_title: Application of Antenna Arrays to Mobile Communications, Part II: Beam-Forming and Direction-of-Arrival Considerations

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Array processing involves manipulation of signals induced on various antenna elements. Its capabilities of steering nulls to reduce cochannel interferences and pointing independent beams toward various mobiles, as well as its ability to provide estimates of directions of radiating sources, make it attractive to a mobile communications system designer. Array processing is expected to play an important role in fulfilling the increased demands of various mobile communications services. Part I of this paper showed how an array could be utilized in different configurations to improve the performance of mobile communications systems, with references to various studies where feasibility of apt array system for mobile communications is considered. This paper provides a comprehensive and detailed treatment of different beam-forming schemes, adaptive algorithms to adjust the required weighting on antennas, direction-of-arrival estimation methods-including their performance comparison-and effects of errors on the performance of an array system, as well as schemes to alleviate them. This paper brings together almost all aspects of array signal processing.
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paper_title: Using Directional Antennas for Medium Access Control in Ad Hoc Networks

paper_content:

A composition for use in the treatment for developing seedless fleshy berry of grapes. By treating the flower bunches of a grape tree with a composition containing gibberellin and cyclic 3',5'-adenylic acid in the form of an aqueous solution, it became possible to make seedless fleshy berry from grape trees belonging to varieties other than Delaware, namely belonging to Campbell-Arley, Berry A, Niagara, Kyoho, etc., from which seedless fleshy berry cannot be made by the conventional treatment with gibberellin.
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paper_title: Using Directional Antennas for Medium Access Control in Ad Hoc Networks

paper_content:

A composition for use in the treatment for developing seedless fleshy berry of grapes. By treating the flower bunches of a grape tree with a composition containing gibberellin and cyclic 3',5'-adenylic acid in the form of an aqueous solution, it became possible to make seedless fleshy berry from grape trees belonging to varieties other than Delaware, namely belonging to Campbell-Arley, Berry A, Niagara, Kyoho, etc., from which seedless fleshy berry cannot be made by the conventional treatment with gibberellin.
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paper_title: Deafness: a MAC problem in ad hoc networks when using directional antennas

paper_content:

This work addresses deafness - a problem that appears when MAC protocols are designed using directional antennas. Briefly, deafness is caused when a transmitter fails to communicate to its intended receiver, because the receiver is beamformed towards a direction away from the transmitter. Existing CSMA/CA protocols rely on the assumption that congestion is the predominant cause of communication failure, and adopt backoff schemes to handle congestion. While this may be appropriate for omnidirectional antennas, for directional antennas, both deafness and congestion can be the reason for communication failures. An appropriate directional MAC protocol needs to classify the actual cause of failure, and react accordingly. This paper quantifies the impact of deafness on directional medium access control, and proposes a tone-based mechanism as one way of addressing deafness. The tone-based mechanism, ToneDMAC, assumes congestion as the default reason for communication failures, and applies a corrective measure whenever the cause is deafness. Simulation results indicate that ToneDMAC can alleviate deafness, and perform better than existing directional MAC protocols.
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paper_title: Medium access control protocols using directional antennas in ad hoc networks

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Using directional antennas can be beneficial for wireless ad hoc networks consisting of a collection of wireless hosts. To best utilize directional antennas, a suitable medium access control (MAC) protocol must be designed. Current MAC protocols, such as the IEEE 802.11 standard, do not benefit when using directional antennas, because these protocols have been designed for omnidirectional antennas. In this paper, we attempt to design new MAC protocols suitable for ad hoc networks based on directional antennas.
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paper_title: Deafness: a MAC problem in ad hoc networks when using directional antennas

paper_content:

This work addresses deafness - a problem that appears when MAC protocols are designed using directional antennas. Briefly, deafness is caused when a transmitter fails to communicate to its intended receiver, because the receiver is beamformed towards a direction away from the transmitter. Existing CSMA/CA protocols rely on the assumption that congestion is the predominant cause of communication failure, and adopt backoff schemes to handle congestion. While this may be appropriate for omnidirectional antennas, for directional antennas, both deafness and congestion can be the reason for communication failures. An appropriate directional MAC protocol needs to classify the actual cause of failure, and react accordingly. This paper quantifies the impact of deafness on directional medium access control, and proposes a tone-based mechanism as one way of addressing deafness. The tone-based mechanism, ToneDMAC, assumes congestion as the default reason for communication failures, and applies a corrective measure whenever the cause is deafness. Simulation results indicate that ToneDMAC can alleviate deafness, and perform better than existing directional MAC protocols.
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paper_title: CSMA/CA with Beam Forming Antennas in Multi-hop Packet Radio

paper_content:

1 Visiting researcher from the Dept. of Electrical Engineering, National University of Engineering (UNI), P O Box 5595, Managua, Nicaragua. AbstractLow cost, reliable and easily deployed ad hoc rural-area wireless networks are needed for both civilian and military communications. In order to fulfill the requirement of easy deployment the network needs to be autonomous, self-organising and self-healing. Multi-hop Packet Radio Networks are a suitable solution to fulfill this requirement. In this type of network all nodes use the same frequency for transmission as well as using a store and forward procedure which enables communications between nodes that are out of direct radio range. There are a variety of multiple access protocols applicable to this type of system. Spatial Time Division Multiple Access (STDMA) has been studied and found to be efficient and fair, the draw-back is that it may not offer good peak rates for bursty data traffic. The Carrier Sense Multiple Access/ Collision Avoidance (CSMA/CA) protocol promises high efficiency and the ability to provide high peak data rates. Although CSMA/CA is not new there is very little work one considering the rural-area multi-hop environment. This paper presents the analysis of CSMA/CA in the rural-area multi-hop environment with and without adaptive antennas. An explanation of the system design with adaptive antennas is given as well as simulation results showing the expected performance gain.
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paper_title: A novel MAC layer protocol for space division multiple access in wireless ad hoc networks

paper_content:

Recently, MAC protocols using directional antennas for wireless ad hoc networks that are based on and similar to IEEE 802.11 type WLAN have been proposed. These protocols, however, are unable to attain substantial performance improvements because they do not enable the nodes to perform multiple simultaneous transmissions/receptions. In this paper, we propose a MAC layer protocol that exploits space division multiple access, thus using the property of directional reception to receive more than one packet from spatially separated transmitter nodes (equipped with smart antenna systems). Our simulation results show that drastic throughput improvements may be achieved through this scheme.
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paper_title: A busy-tone based directional MAC protocol for ad hoc networks

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In mobile wireless ad hoc networking environments, such as the future combat system (FCS), the shared wireless communication medium is an inherently limited resource and is collision prone. In this paper, we propose to adapt the dual busy tone multiple access (DBTMA) protocol for use with directional antennas, which further increases effective channel capacity. In contrast to other directional antenna based MAC protocols, our protocol, termed DBTMA/DA, is capable of reserving channel capacity in finer grain without relying on extra locationing support. A simulation study is performed to demonstrate the better network performance of DBTMA/DA over DBTMA and the IEEE 802.11a MAC protocols.
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paper_title: Using Directional Antennas for Medium Access Control in Ad Hoc Networks

paper_content:

A composition for use in the treatment for developing seedless fleshy berry of grapes. By treating the flower bunches of a grape tree with a composition containing gibberellin and cyclic 3',5'-adenylic acid in the form of an aqueous solution, it became possible to make seedless fleshy berry from grape trees belonging to varieties other than Delaware, namely belonging to Campbell-Arley, Berry A, Niagara, Kyoho, etc., from which seedless fleshy berry cannot be made by the conventional treatment with gibberellin.
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paper_title: A MAC protocol for full exploitation of directional antennas in ad-hoc wireless networks

paper_content:

Directional antennas in ad hoc networks offer many benefits compared with classical omnidirectional antennas. The most important include significant increase of spatial reuse, coverage range and subsequently network capacity as a whole. On the other hand, the use of directional antennas requires new approach in the design of a MAC protocol to fully exploit these benefits. Unfortunately, directional transmissions increase the hidden terminal problem, the problem of deafness and the problem of determination of neighbors' location. In this paper we propose a new MAC protocol that deals effectively with these problems while it exploits in an efficient way the advantages of the directional antennas. We evaluate our work through simulation study. Numerical results show that our protocol offers significant improvement compared to the performance of omni transmissions.
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paper_title: Directional virtual carrier sensing for directional antennas in mobile ad hoc networks

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This paper presents a new carrier sensing mechanism called DVCS (Directional Virtual Carrier Sensing) for wireless communication using directional antennas. DVCS does not require specific antenna configurations or external devices. Instead it only needs information on AOA (Angle of Arrival) and antenna gain for each signal from the underlying physical device, both of which are commonly used for the adaptation of antenna pattern. DVCS also supports interoperability of directional and omni-directional antennas. In this study, the performance of DVCS for mobile ad hoc networks is evaluated using simulation with a realistic directional antenna model and the full IP protocol stack. The experimental results showed that compared with omni-directional communication, DVCS improved network capacity by a factor of 3 to 4 for a 100 node ad hoc network.
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paper_title: A MAC protocol for mobile ad hoc networks using directional antennas

paper_content:

We propose a medium access control (MAC) protocol for an ad hoc network of mobile wireless terminals that are equipped with multiple directional antennas. Use of directional antennas in ad hoc networks can largely reduce the radio interference, thereby improving the packet throughput. However, the main problem of using directional antennas in such networks is due to the dynamic nature of the network caused by frequent node movements. This gives rise to problems such as locating and tracking during random channel access. The MAC protocol presented in this paper proposes a solution to these problems without the help of additional hardware. Results obtained from detailed computer simulations demonstrate the performance improvement obtained with the proposed scheme.
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paper_title: A network-aware MAC and routing protocol for effective load balancing in ad hoc wireless networks with directional antenna

paper_content:

Use of directional antenna in the context of ad hoc wireless networks can largely reduce radio interference, thereby improving the utilization of wireless medium. Our major contribution in this paper is to devise a routing strategy, along with a MAC protocol, that exploits the advantages of directional antenna in ad hoc networks for improved system performance. In this paper, we have illustrated a MAC and routing protocol for ad hoc networks using directional antenna with the objective of effective load balancing through the selection of maximally zone disjoint routes. Zone-disjoint routes would minimize the effect of route coupling by selecting routes in such a manner that data communication over one route will minimally interfere with data communication over the others. In our MAC protocol, each node keeps certain neighborhood status information dynamically in order that each node is aware of its neighborhood and communications going on in its neighborhood at that instant of time. This status information from each node is propagated periodically throughout the network. This would help each node to capture the approximate network status periodically that helps each node to become topology-aware and aware of communications going on in the network, although in an approximate manner. With this status information, each intermediate node adaptively computes routes towards destination. The performance of the proposed framework has been evaluated on QualNet Network Simulator with DSR (as in QualNet) as a benchmark. Our proposed mechanism shows four to five times performance improvement over DSR, thus demonstrating the effectiveness of this proposal.
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paper_title: Smart-802.11b MAC protocol for use with smart antennas

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Smart antennas enable a receiver to determine the direction of arrival (DOA) of multiple transmissions as well as to form nulls in some number of directions to maximize SINR (Signal to Interference and Noise Ratio) of the received signal. We utilize the benefits of these capabilities to develop a simple modified version of the popular 802.11b protocol. This protocol exhibits high throughput under a variety of network conditions and is fair. The performance of the protocol is examined exhaustively using joint simulation in OPNET and Matlab.
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paper_title: A MAC protocol based on adaptive beamforming for ad hoc networks

paper_content:

This paper presents a novel slotted MAC (medium access control) protocol for nodes equipped with adaptive antenna array in ad hoc network. The protocol relies on the ability of antenna to uses DOA (direction-of-arrival) information to beamform by placing nulls in the direction of interferers thus maximize SINR (signal to interference and noise ratio) at the receiver. We studied the performance of the protocol using joint simulation in OPNET and Matlab. We studied the impact of variable number of antenna elements, DOA algorithm, and nulling. The performance of our new protocol is compared against one of the recent directional MAC protocols [R.R.N.H.V. Romit Roy Choudhury, Xue Yang, 2002]. We observe that despite the simplicity of our protocol it achieves high throughput.
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paper_title: Transmission scheduling in ad hoc networks with directional antennas

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Directional antennas can adaptively select radio signals of interest in specific directions, while filtering out unwanted interference from other directions. Although a couple of medium access protocols based on random access schemes have been proposed for networks with directional antennas, they suffer from high probability of collisions because of their dependence on omnidirectional mode for the transmission or reception of control packets in order to establish directional links. We propose a distributed receiver-oriented multiple access (ROMA) channel access scheduling protocol for ad hoc networks with directional antennas, each of which can form multiple beams and commence several simultaneous communication sessions. Unlike random access schemes that use on-demand handshakes or signal scanning to resolve communication targets, ROMA determines a number of links for activation in every time slot using only two-hop topology information. It is shown that significant improvements on network throughput and delay can be achieved by exploiting the multi-beam forming capability of directional antennas in both transmission and reception. The performance of ROMA is studied by simulations, and compared with a well-know static scheduling scheme that is based on global topology information.
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paper_title: Smart-802.11b MAC protocol for use with smart antennas

paper_content:

Smart antennas enable a receiver to determine the direction of arrival (DOA) of multiple transmissions as well as to form nulls in some number of directions to maximize SINR (Signal to Interference and Noise Ratio) of the received signal. We utilize the benefits of these capabilities to develop a simple modified version of the popular 802.11b protocol. This protocol exhibits high throughput under a variety of network conditions and is fair. The performance of the protocol is examined exhaustively using joint simulation in OPNET and Matlab.
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Title: A survey on MAC protocols for ad hoc networks with directional antennas

Section 1: INTRODUCTION AND MOTIVATION
Description 1: Write a comprehensive introduction highlighting the importance of ad hoc networking, the role of directional antennas, challenges in MAC protocol design, and an overview of what the paper will cover.

Section 2: MEDIUM ACCESS PROBLEMS USING DIRECTIONAL ANTENNAS
Description 2: Summarize the key issues that arise when using directional antennas with conventional MAC protocols, including neighbor location, extended transmission range, side lobe pattern, directional carrier sensing, new hidden terminals, deafness, and antenna array rotation.

Section 3: MAC PROTOCOLS FOR DIRECTIONAL ANTENNAS
Description 3: Discuss various MAC protocols designed for directional antennas, focusing on how they extend or differ from the 802.11 DCF protocol. Include a detailed breakdown of both 802.11-type and non-802.11-type protocols.

Section 4: 802.11-type MAC protocols for directional antennas
Description 4: Provide a detailed survey of MAC protocols based on the IEEE 802.11 DCF protocol, their mechanisms, advantages, and performance impacts.

Section 5: "Non-802.11"-type MAC protocols for directional antennas
Description 5: Explore alternative MAC protocols that do not rely on the IEEE 802.11 RTS/CTS scheme, focusing on scheduled approaches and time-slotted protocols.

Section 6: COMPARISON OF MAC PROTOCOLS FOR DIRECTIONAL ANTENNAS
Description 6: Compare and contrast the different MAC protocols discussed, emphasizing how they manage spatial reuse, interference, and protocol overhead.

Section 7: CONCLUSIONS
Description 7: Summarize the key findings of the survey, discuss the potential benefits and challenges of implementing directional antennas in ad hoc networks, and suggest areas for future research.