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...ts transmission. This whole process is called Virtual Carrier Sensing, which allows the area around the sender and receiver to be reserved for communication, thus avoiding the hidden terminal problem =-=[10]-=-. Figure 1 illustrates the operation of IEEE 802.11 DCF. When node B is transmitting a packet to node C, node A overhears the RTS packet and sets its NAV until the end of ACK, and node D overhears the...

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...l and possible improvements. Finally, Section VIII concludes the paper. 2. RELATED WORK There are many related papers that study the benefit of using multiple channels. Dual Busy Tone Multiple Access =-=[3]-=- divides a common channel into two sub-channels, one data channel and one control channel. Busy tones are transmitted on a separate control channel to avoid hidden terminals, while data is transmitted...

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...annel at a time. So when listening to one channel, it cannot carrier sense on other channels. Unlike our scheme, many other multi-channel MAC protocols require each host to have multiple transceivers =-=[11, 9, 8]-=-. • The transceiver is capable of switching its channel dynamically. The time elapsed for switching the channel is 224µs [1]. • Nodes are synchronized, so that all nodes begin their beacon interval at...

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.... In [7] the protocol is extended to select the best channel based on signal power observed at the sender. These protocols require N transceivers for each host, which is very expensive. 223 Wu et al. =-=[8]-=- propose a protocol that assigns channels dynamically, in an on-demand style. In this protocol, called Dynamic Channel Assignment (DCA), they maintain one dedicated channel for control messages and ot...

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...le channels cannot be fully utilized, resulting in degraded throughput. If the ATIM window size is too large, 1 A similar observation about the impact of ATIM window on IEEE 802.11 PSM is reported in =-=[16, 17]-=-. 230 the throughput decreases because no benefit is obtained with increased overhead from having a longer ATIM window. The optimal ATIM window size depends mainly on the number of flows in the beacon...

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...e channel is 224µs [1]. • Nodes are synchronized, so that all nodes begin their beacon interval at the same time. Clock synchronization can be achieved using either out-of-band solutions such as GPS, =-=[12]-=-, or in-band solutions. If an out-ofband solution can be used, no additional overhead is imposed on the channels used by our protocol. However, if an in-band solution is used, we need to consider the ...

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...annels to improve throughput in wireless networks. The proposed scheme requires only one transceiver for each host, while other multi-channel MAC protocols require multiple transceivers for each host =-=[11, 9, 8]-=-. In order to avoid the multi-channel hidden terminal problem, we require nodes to be synchronized, so that every node starts each beacon interval at about the same time. At the start of each beacon i...

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... one transceiver for each host, but they only apply to frequency hopping networks, and cannot be used in systems using other mechanisms such as direct sequence spread spectrum (DSSS). Nasipuri et al. =-=[6]-=- propose a multi-channel CSMA protocol with “soft” channel reservation. If there are N channels, the protocol assumes that each host can listen to all N channels concurrently. A host wanting to transm...

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...le channels cannot be fully utilized, resulting in degraded throughput. If the ATIM window size is too large, 1 A similar observation about the impact of ATIM window on IEEE 802.11 PSM is reported in =-=[16, 17]-=-. 230 the throughput decreases because no benefit is obtained with increased overhead from having a longer ATIM window. The optimal ATIM window size depends mainly on the number of flows in the beacon...

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...terminals, while data is transmitted on the data channel. This scheme uses only one data channel and is not intended for increasing throughput using multiple channels. Hop Reservation Multiple Access =-=[4]-=- is a multi-channel protocol for networks using slow frequency hopping spread spectrum (FHSS). The hosts hop from one channel to another according to a predefined hopping pattern. When two hosts agree...

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...host wanting to transmit a packet searches for an idle channel and transmits on that idle channel. Among the idle channels, the one that was used for the last successful transmission is preferred. In =-=[7]-=- the protocol is extended to select the best channel based on signal power observed at the sender. These protocols require N transceivers for each host, which is very expensive. 223 Wu et al. [8] prop...

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...ay in a frequency hop for communication. Other hosts continue hopping, and more than one communication can take place on different frequency hops. Receiver Initiated Channel-Hopping with Dual Polling =-=[5]-=- takes a similar approach, but the receiver initiates the collision avoidance handshake instead of the sender. These schemes can be implemented using only one transceiver for each host, but they only ...

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...l [8] (DCA was explained in section II). Recall that the Time 227 DCA protocol uses a separate channel for exchanging control messages and uses other channels for data. This approach is also taken by =-=[9, 13]-=-. We used two metrics to evaluate the performance of our protocol. 1. Aggregate throughput over all flows in the network: Our protocol is expected to increase the total throughput of the network by ex...

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...ch may be to have each node transmits beacon with a probability p at each beacon interval. Developing a scheme for clock synchronization in multi-hop network is outside the scope of this paper. Also, =-=[18]-=- argues that even if we can achieve clock synchronization, two partitioned network might not be able to discover each other if their schedules are totally out of synchronization such that the ATIM win...

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...off, channel negotiation and transmission delay. The queue size at each node is 50 packets. We ignore lost packets in the average delay metric. 6.1 Simulation Model For simulations, we have used ns-2 =-=[14]-=- with CMU wireless extensions [15]. Simulations are performed in two network scenarios, wireless LAN and multi-hop networks. The bit rate for each channel is 2Mbps. The transmission range of each node...