WIRELESS INTERNET GATEWAYS (WINGS) J.J. Garcia-Luna-Aceves,

Abstract — Today’s internetwork technology has been extremely successful in linking huge numbers of computers and users. However, to date, this technology has been oriented to computer interconnection in relatively stable operational environments, and thus cannot adequately support many of the emerging civilian and military uses that require a more adaptive and more easily deployed technology. In particular, multihop packet radio networks are ideal for establishing “instant communication infrastructures ” in disaster areas resulting from flood, earthquake, hurricane, or fires, supporting U.S. military doctrine for reliable, secure infrastructures for communication among all tiers down to the soldiers “on-the-move, ” and extending the global communication infrastructure to the wireless, mobile environment

Floor Acquisition Multiple Access (FAMA) for Packet-Radio Networks

A family of medium access control protocols for single-channel packet radio networks is specified and analyzed. These protocols are based on a new channel access discipline called floor acquisition multiple access (FAMA), which consists of both carrier sensing and a collision-avoidance dialogue between a source and the intended receiver of a packet. Control of the channel (the floor) is assigned to at most one station in the network at any given time, and this station is guaranteed to be able to transmit one or more data packets to different destinations with no collision with transmissions from other stations. The minimum length needed in control packets to acquire the floor is specified as a function of the channel propagation time. The medium access collision avoidance (MACA) protocol proposed by Karn and variants of CSMA based on collision avoidance are shown to be variants of FAMA protocols when control packets last long enough compared to the channel propagation delay. The throug..

Complete Single-Channel Solutions to Hidden Terminal Problems in Wireless LANs

We specify and analyze two variants of floor acquisition multiple access protocols for single-channel wireless LANs (WLANs) with hidden terminals. One variant assumes that all stations have the same functionality, and the other assumes base-station control. These are the first protocols that solve the hidden-terminal problems of single-channel WLANS. Stations use carrier sensing and a three-way handshake, just as advocated in MACA, IEEE 802.11 and FAMA-NTR introduced in the past. However, the CTS from a receiver lasts long enough to be able to jam any hidden sender that did not hear the RTS being acknowledged and who started sending its RTS after the receiver started sending the CTS. We verify that this jamming of the "offending senders" by the receivers permits floor acquisition to be enforced correctly, i.e., that no data packet sent by a sender will ever collide at the intended receiver with any packet sent by any other station hidden or exposed from the sender. The performance of t..

Performance of Floor Acquisition Multiple Access in Ad-Hoc Networks

The performance of the FAMA-NCS protocol in ad-hoc networks is analyzed. FAMA-NCS (for floor acquisition multiple access with nonpersistent carrier sensing) guarantees that a single sender is able to send data packets free of collisions to a given receiver at any given time. FAMA-NCS is based on a three-way handshake between sender and receiver in which the sender uses non-persistent carrier sensing to transmit a request-to-send (RTS) and the receiver sends a clear-to-send (CTS) that lasts much longer than the RTS to serve as a "busy tone" that forces all hidden nodes to back off long enough to allow a collision-free data packet to arrive at the receiver. It is shown that that FAMA-NCS performs better than ALOHA, CSMA, and all prior proposals based on collision avoidance dialogues (e.g., MACA, MACAW, and IEEE 802.11 DFWMAC) in the presence of hidden terminals. Simulations experiments are used to confirm the analytical results. I. INTRODUCTION The medium access control (MAC) protocol wi..

Abstract Adding Adaptive Flow Control to Swift/RAID

We discuss an adaptive flow control mechanism for the Swift/RAID distributed file system. Our goal is to achieve nearoptimal performance on heterogeneous networks where available load capacity varies due to other network traffic. The original Swift/RAID prototype used synchronous communication, achieving throughput considerably less than available network capacity. We designed and implemented an adaptive flow control mechanism that provides greatly improved performance. Our design uses a simple automatic repeat request (ARQ) go back N protocol coupled with the congestion avoidance and control mechanism developed for the Transmission Control Protocol (TCP). The Swift/RAID implementation contains a transfer plan executor to isolate all of the communications code from the rest of Swift. The adaptive flow control design was implemented entirely in this module. Results from experimental data show the adaptive design achieving an increase in throughput for reads from 671 KB/s for the original synchronous implementation to 927 KB/s (a 38 % increase) for the adaptive prototype, and an increase from 375 KB/s to 559 KB/s (a 49 % increase) in write throughput.

Wireless Internet Gateways (Wings)

Today's internetwork technology has been extremely successful in linking huge numbers of computers and users. However, to date, this technology has been oriented to computer interconnection in relatively stable operational environments, and thus cannot adequately support many of the emerging civilian and military uses that require a more adaptive and more easily deployed technology. In particular, multihop packet radio networks are ideal for establishing "instant communication infrastructures" in disaster areas resulting from flood, earthquake, hurricane, or fires, supporting U.S. military doctrine for reliable, secure infrastructures for communication among all tiers down to the soldiers "on-the-move," and extending the global communication infrastructure to the wireless, mobile environment. The Defense Advanced Research Projects Agency (DARPA) is sponsoring the development of wireless internet gateways (WINGs) as part of the DARPA Global Mobile (GloMo) Information Systems program. WI..