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... longer needed that a communicating pair of nodes negotiate a channel beforehand. A. Multichannel Hidden Terminal Problem The above scheme presents a new form of the wellknown hidden terminal problem =-=[24]-=-. Similar problems were also observed in [22] in a slightly different context. When a transmitter A, for data transmission, switches its interface from its quiescent channel p to the receiver B’s quie...

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...s of interference or protocol behavior, and assumptions on average traffic. The papers in literature using this approach pose the problem as essentially an optimization problem [18], [19], [3], [12], =-=[4]-=-, [11]. The other approach is more dynamic. It relies on the capability of the radio interface to switch channels on the fly with negligible delay. Here, multiple channels can be utilized even with a ...

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...gle packet interface only. We show, via extensive ns-2 simulations, that these two protocols significantly outperform similar protocols that appeared in literature recently, such as DCA [20] and MMAC =-=[22]-=-. The rest of the paper is organized as follows. In the following section similar multichannel approaches in literature are reviewed to provide a context for our work. In Section III the simple receiv...

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...iple channels, and on developing techniques to use the legacy 802.11 MAC with multiple channels efficiently. We review them in this section to provide a context for our work. A. Dynamic Approaches In =-=[5]-=- the authors proposed Slotted Seeded Channel Hopping (SSCH), a link-layer protocol that uses unmodisified 802.11 MAC layer. Each node in SSCH switches channels at slot-boundaries in a pseudo-random se...

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...c and is based on models of interference or protocol behavior, and assumptions on average traffic. The papers in literature using this approach pose the problem as essentially an optimization problem =-=[18]-=-, [19], [3], [12], [4], [11]. The other approach is more dynamic. It relies on the capability of the radio interface to switch channels on the fly with negligible delay. Here, multiple channels can be...

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...is to implement a “channel memory” that helps propagate the channel state to a potential transmitter at all times. An easy and well-known way to implement “channel memory” is by using busy tones [24] =-=[7]-=- [27]. Busy tones are single frequency tones used for signaling. The advantage of using busy tones relative to using a separate control channel (as in DCA [20]) is that the issue of determining the ri...

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...adios such that some of them have static channel assignment and the rest do dynamic channel switching. They also propose a new routing strategy based on channel switching and route diversity cost. In =-=[16]-=-, the authors develop asymptotic capacity models for multichannel networks with multiple interfaces per node. III. RECEIVER DIRECTED TRANSMISSION AND PERFORMANCE ISSUES In this section, we will develo...

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...tter would defer its transmission on the data channel. This deferment is designed exactly similar to the collision avoidance mechanism in 802.11 [8] that uses a variation of the p-persistent protocol =-=[10]-=-. For brevity, this mechanism is not discussed here. Note that use of the busy tone prevents any collision of data packets. B. Addressing Deafness There are simple solutions to deafness; but they all ...

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...is based on models of interference or protocol behavior, and assumptions on average traffic. The papers in literature using this approach pose the problem as essentially an optimization problem [18], =-=[19]-=-, [3], [12], [4], [11]. The other approach is more dynamic. It relies on the capability of the radio interface to switch channels on the fly with negligible delay. Here, multiple channels can be utili...

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...between a packet interface and a tone interface to contrast our approach with similar approaches that use a separate control channel and thus two packet interfaces (see, for example, the DCA protocol =-=[20]-=-). Tone interfaces are much simpler to implement than packet interfaces. The second protocol, called local coordination-based multichannel (LCM) MAC, uses a single packet interface only. We show, via ...

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... 2 graph, where G is the original communication graph and G 2 has edges between node pairs (i, j) such that distance between i and j in G is at most 2. We can use the existing approximation algorithm =-=[9]-=- for the Max k-cut problem to do channel assignment in this case. In the more realistic case where traffic is varies dynamically, we propose a periodic quiescent channel selection mechanism using chan...

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...e Hop Reservation Multiple Access (HRMA) [23] and Receiver-initiated Channel-hopping with Dual Polling [25] have been proposed for use with frequency hopping spread spectrum (FHSS) wireless cards. In =-=[17]-=- the authors propose use of multiple radios such that some of them have static channel assignment and the rest do dynamic channel switching. They also propose a new routing strategy based on channel s...

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...ed on models of interference or protocol behavior, and assumptions on average traffic. The papers in literature using this approach pose the problem as essentially an optimization problem [18], [19], =-=[3]-=-, [12], [4], [11]. The other approach is more dynamic. It relies on the capability of the radio interface to switch channels on the fly with negligible delay. Here, multiple channels can be utilized e...

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...xt of directional antennas [6]. Similar situation happens in the basic 802.11 protocol as well, but one additional hop away. This situation has been referred to as information asymmetry in literature =-=[26]-=- and is one cause of fairness problems in 802.11. Our simulations (not described here due to lack of space) indicate that both these problems occur frequently enough at a high load causing throughput ...

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...he latter indeed attempts the next retry, the receiver could have switched to another channel for transmission. Similar deafness problems have been noted before in the context of directional antennas =-=[6]-=-. Similar situation happens in the basic 802.11 protocol as well, but one additional hop away. This situation has been referred to as information asymmetry in literature [26] and is one cause of fairn...

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...o implement a “channel memory” that helps propagate the channel state to a potential transmitter at all times. An easy and well-known way to implement “channel memory” is by using busy tones [24] [7] =-=[27]-=-. Busy tones are single frequency tones used for signaling. The advantage of using busy tones relative to using a separate control channel (as in DCA [20]) is that the issue of determining the right b...

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...interference or protocol behavior, and assumptions on average traffic. The papers in literature using this approach pose the problem as essentially an optimization problem [18], [19], [3], [12], [4], =-=[11]-=-. The other approach is more dynamic. It relies on the capability of the radio interface to switch channels on the fly with negligible delay. Here, multiple channels can be utilized even with a single...

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...back to the default channel for another round of negotiations. The time line showed in Figure 1 illustrates a simple working scenario of LCM MAC. The protocol is similar in some details to the MACA-P =-=[2]-=- protocol and the POWMAC [14] protocol for transmit power control. LCM also has some similarities with the MMAC [22] protocol in channel negotiations. However, MMAC follows a rigid schedule and the ne...

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...DUCTION Use of multiple frequency channels offers tremendous potential to improve the capacity of a wireless network. This potential has been recognized in existing standards, such as the IEEE 802.11 =-=[8]-=-, that can operate on multiple orthogonal channels. Using multiple frequency channels enables conflict-free transmissions in a physical neighborhood so long as pairs of transmitters and receivers can ...

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...election of fixed parameters such as slot size in SSCH and beacon periods in MMAC. One of the earliest works to utilize dynamic channel switching was the Receiver Directed Transmission (RDT) protocol =-=[21]-=-. In RDT, each node has a quiescent channel on which it always listens to when idle. Any transmitter must switch to the receiver’s quiescent channel to transmit. We describe RDT in detail in the next ...

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...eir effectiveness. C. Other Related Works Several other works are also worthy of mention here. The Hop Reservation Multiple Access (HRMA) [23] and Receiver-initiated Channel-hopping with Dual Polling =-=[25]-=- have been proposed for use with frequency hopping spread spectrum (FHSS) wireless cards. In [17] the authors propose use of multiple radios such that some of them have static channel assignment and t...

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... VI. SIMULATION-BASED PERFORMANCE EVALUATION We evaluate xRDT and LCM MAC and compare them against two known multichannel protocols, DCA and MMAC, using the ns2 simulator with CMU wireless extensions =-=[13]-=-. The simulations were performed for two scenarios with different density of nodes. The following common parameters were used in each experiment, all the radio parameters being ns2 defaults. The radio...

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...e of data channel bandwidth. We also note here that similar protocols were developed in the past, that splits one single channel into multiple subchannels and uses only a subchannel for communication =-=[15]-=-. However, the issue, there, was to reduce the overhead of contention. B. Static, Multi-radio Approaches There has been a body of work recently that look at the multi-channel protocols from a differen...

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... models of interference or protocol behavior, and assumptions on average traffic. The papers in literature using this approach pose the problem as essentially an optimization problem [18], [19], [3], =-=[12]-=-, [4], [11]. The other approach is more dynamic. It relies on the capability of the radio interface to switch channels on the fly with negligible delay. Here, multiple channels can be utilized even wi...

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...lly, when k channels are available, the problem of assigning quiescent channels for maximum concurrency in the network can be shown to be equivalent to the problem of finding a maximum weighted k-cut =-=[1]-=- in the G 2 graph, where G is the original communication graph and G 2 has edges between node pairs (i, j) such that distance between i and j in G is at most 2. We can use the existing approximation a...