Chane L. Fullmer

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 throughput of FAMA protocols is analyzed and compared with the throughput of non-persistent CSMA. This analysis shows that using carrier sensing as an integral part of the floor acquisition strategy provides the benefits of MACA in the presence of hidden terminals, and can provide a throughput comparable to, or better than, that of non-persistent CSMA when no hidden terminals exist.

Solutions to hidden terminal problems in wireless networks

The floor acquisition multiple access (FAMA) discipline is analyzed in networks with hidden terminals. According to FAMA, 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 collisions. The FAMA protocols described consist of non-persistent carrier or packet sensing, plus a collision-avoidance dialogue between a source and the intended receiver of a packet. Sufficient conditions under which these protocols provide correct floor acquisition are presented and verified for networks with hidden terminals; it is shown that FAMA protocols must use carrier sensing to support correct floor acquisition. The throughput of FAMA protocols is analyzed for single-channel networks with hidden terminals; it is shown that carrier-sensing FAMA protocols perform better than ALOHA and CSMA protocols in the presence of hidden terminals.

Wireless internet gateways (WINGs)

Todays 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 US 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. WINGs are wireless IP routers that enable the seamless marriage of distributed, dynamic, self-organizing, multihop wireless networks with the emerging multimedia Internet. This paper describes the WING architecture and novel communication protocols for channel access and routing, as well as the hardware and software development environment used to prototype and demonstrate wireless mobile internetworking.

Floor acquisition multiple access (FAMA) in single-channel wireless networks

The FAMA‐NCS protocol is introduced for wireless LANs and ad‐hoc networks that are based on a single channel and asynchronous transmissions (i.e., no time slotting). FAMA‐NCS (for floor acquisition multiple access with non‐persistent 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 carrier sensing is needed to support collision‐free transmissions in the presence of hidden terminals when nodes transmit RTSs asynchronously. The throughput of FAMA‐NCS is analyzed for single‐channel networks with and without hidden terminals; the analysis shows 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. Simulation experiments are used to confirm the analytical results.

FAMA-PJ: a channel access protocol for wireless LANs

Abstract : We specify and analyze a new channel access protocol for wireless local area networks. The new protocol, FAMA-PJ, consists of both carrier sensing and a collision detection mechanism based on control packets and jamming that prevent collision of data packets with control or data packets from other stations. Control of the channel (which we call the floor) is assigned to at most one station in the network at a 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 control packet size required to enforce correct floor control is specified as a function of the channel propagation delay and transmit to receive turn around time. The throughput and delay of FAMA-PJ are analyzed and compared with the throughput and delay of non-persistent CSMA. This analysis shows that FAMA-PJ can provide similar or better throughput than non-persistent CSMA in a high-speed wireless local area network, and that is more stable and has better delay characteristics than non-persistent CSMA.

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 non-persistent 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 the 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.

Complete single-channel solutions to hidden terminal problems in wireless LANs

We specify and analyze two variants of floor acquisition multiple access protocols for CSMA 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 clear to send (CTS) from a receiver lasts long enough to be able to jam any hidden sender that did not hear the request to send (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 these protocols is compared by simulation with the performance of MACAW reported in the past.

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 near-optimal 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. 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.<<ETX>>