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ABSTRACT WIRELESS NETWORKS MULTIHOP WIRELESS NETWORKS ANTENNAS Infrastructure-based – Devices communicate with central Access Point (AP). Also, referred.

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Presentation on theme: "ABSTRACT WIRELESS NETWORKS MULTIHOP WIRELESS NETWORKS ANTENNAS Infrastructure-based – Devices communicate with central Access Point (AP). Also, referred."— Presentation transcript:

1 ABSTRACT WIRELESS NETWORKS MULTIHOP WIRELESS NETWORKS ANTENNAS Infrastructure-based – Devices communicate with central Access Point (AP). Also, referred to as Wireless Local Area Network (LAN). Peer-to-peer – Any two devices can communicate, when in range. Also, referred to as Personal Area Network (PAN) or an Ad hoc Network. AP Internet or Intranet Internet or Intranet Mobile Ad hoc Network (MANET)  Set of mobile station (MSs)  Lack of fixed infrastructure relay nodes  Dynamically changing topology  Applications – Military - Combat Systems, reconnaissance, surveillance – Disaster management – Medical emergency – Virtual navigation – Distance education Wireless Mesh Network (WMN)  A combination of infrastructure-based and peer-to-peer networks  Set of mobile and immobile stations  Dynamically changing topology  Applications – Intelligent transport systems – Public safety – Public internet access – Residential broadband access – Distance education Wireless Sensor Network (WSN)  Usually a set of small immobile nodes referred as motes  Generally static topology  Cheap alternative to monitor inaccessible or inhospitable terrains  Applications – Medical Applications – wireless bio-sensors – Nuclear and chemical plants – Environmental monitoring – Ocean monitoring – Battlefields Omnidirectional Antenna – Low throughput in Wireless Ad hoc networks due to poor spatial reuse. Directional Antenna – Better Spatial reuse. But a node still unable to fully utilize “spatial bandwidth”. AB C D E F G H X Nodes in Silent Zone AB C D E F G H MULTIPLE BEAM ANTENNA ARRAY (MBAA) MBAA TYPES AND APPLICATIONS MEDIUM ACCESS CONTROL (MAC) ANALYTICAL MODEL – ON-DEMAND MAC [Lal2004]  Exploits spatial bandwidth fully  A node can initiate more than one simultaneous transmissions (or receptions). This requires: – Synchronizing transmitting nodes to start their transmission for the common receiver at the same time  Concurrent Packet Reception (CPR) Condition – Synchronizing receiving nodes to start the reception from the common transmitter at the same time  Concurrent Packet Transmission (CPT) Condition DATA A B C D E F G A B C D E F G User 1 Interferer 1 top view (horizontal) User 3 User 2 Interferer 3 Interferer 2 top view (horizontal) Interferer 1 User User 3 9 User 2 Interferer 2 Interferer 3 1 Switched array Adaptive array Applications Military NetworksCellular Communication NetworksMultihop Wireless Networks On-Demand or Contention-based Scheduling or Contention-free Channel AllocationDynamicPre-defined Topological Change Adaptation GoodNew Schedules Required Time SynchronizationNoYes Energy UtilizationUncontrolledControlled Concurrent Receptions or Transmissions Local Synchronization Required Inherent Slotted Aloha  Synchronous on-demand protocol [Roberts1975]  Time is divided into slots of fixed size, each of one packet transmission time Carrier Sense Multiple Access  Asynchronous on-demand protocol [Kleinrock1975]  Data is transmitted if the channel is sensed free, otherwise, transmitting nodes defer channel access till the channel becomes free again Conclusions  Slotted Aloha gives better throughput than basic CSMA at lower loads  At heavier loads, CSMA gives better performance Asynchronous on-demand protocols like CSMA gives stable results for MBAA at higher loads MWN extends the coverage of single hop wireless network and is thus scalable, reliable, adaptable and easily deployable in rough terrains IEEE DCF BASED MAC FOR MBAA [Jain2005a] ESIF MECHANISM FOR MBAA [Jain2005b] CPR MODELING FOR IEEE DCF AND ESIF PERFORMANCE EVALUATION CONCLUSIONS  De-facto MAC for wireless LAN and ad hoc networks [IEEE]  Originally designed for omnidirectional communication, its virtual carrier sensing (VCS) mechanism is enhanced for directional communication to include direction of arrival also Random Backoff after DIFS wait Transmission Control Packets (RTS/CTS) MMAC-NB MDMAC-NBMDMAC-BB MMAC-BB DirectionalOmnidirectional Beam-based Node-based  ESIF, Explicit Synchronization via Intelligent Feedback, is the first attempt to achieve CPR in MBAA with on-demand MAC protocols  Is a hybrid of synchronous and asynchronous protocols  Embedded feedback is used to synchronize neighboring nodes  Cross layer information is used to guarantee long- term fairness Percentage of CPR for IEEE and ESIF over four and eight beam antennas A B C D E G F  ESIF is able to achieve CPR at common intermediate node D  Dynamic priority switch ensures data packets just received are transmitted (concurrently) in the next cycle, thus, maximizing throughput and minimizing delay  Concurrent packet reception in multiple beam antennas is highly improbable with IEEE DCF based protocols  ESIF removes the contention window based backoff in IEEE based protocols and uses embedded feedback to synchronize neighboring nodes  ESIF can thus support CPR and CPT in different beams  QoS over ESIF and its backward compatibility with IEEE DCF needs to be explored [IEEE1999] IEEE Standards Department, “ANSI//IEEE Standard ,” IEEE Press, [Jain2005a] Vivek Jain, Anurag Gupta, Dhananjay Lal, and Dharma P. Agrawal, “IEEE DCF Based MAC Protocols for Multiple Beam Antennas and Their Limitations,” in Proceedings of IEEE MASS, Nov [Jain2005b] Vivek Jain, Anurag Gupta, Dhananjay Lal, and Dharma P. Agrawal, “A Cross Layer MAC with Explicit Synchronization through Intelligent Feedback for Multiple Beam Antennas,” in Proceedings of IEEE GLOBECOM, Dec [Kleinrock1975] L. Kleinrock and F. Tobagi, “Packet Switching in Radio Channels: Part I--Carrier Sense Multiple-Access Modes and Their Throughput-Delay Characteristics,” in IEEE Transactions on Communications, Vol. 23, No. 12, pp – 1416, Dec [Lal2004] Dhananjay Lal, Vivek Jain, Qing-An Zeng, and Dharma P. Agrawal, “Performance Evaluation of Medium Access Control for Multiple Beam Antenna Nodes in a Wireless LAN,” in IEEE Transactions on Parallel and Distributed Systems, Vol.15, No. 12, pp , Dec [Roberts1975] L. G. Roberts, “ALOHA Packet Systems with and without Slots and Capture,” Computer Communications Review, Vol. 5, No. 2, pp , April REFERENCES FUTURE WORK  To develop MAC for MIMO antennas  To develop Unified MAC which can provide medium access with all types of antennas and can facilitate interoperability of different types of wireless networks Substantial research has been done in the past for medium access control (MAC) in multihop wireless networks (MWNs) with omnidirectional antennas and single beam directional antennas. However, system capacity can be considerably enhanced using smart antennas. Smart antenna refers to the “smartness” of transmitting (or receiving) signals either by beamforming techniques or using spatial signatures. While the former technique is used by multiple beam antenna array (MBAA) antennas, latter is used by multiple input multiple output (MIMO) antennas. Current MAC protocols cannot leverage the potential of concurrent data transmissions or receptions by smart antennas, thus requiring new protocols. In the present work, we concentrate on MBAA and the following questions motivate our research:  Can we develop an analytical framework for predicting throughput of on- demand medium access control protocols for MBAA?  Does the existing IEEE DCF based MAC protocols for single beamforming antennas yield optimal results for MBAA also?  Can we have a medium access control protocol that can support both omnidirectional and beamforming antennas including MBAA? Graduate Student (PhD, CSE) OBR Center for Distributed and Mobile Computing ECECS Department University of Cincinnati Cincinnati, OH – Url:


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