infocom 2014. what is mmac? ▣ multi-channel mac channel negotiation and assignment (sender –...
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What is MMAC? (cont.) ▣ Multi-Channel Exposed Terminal Problem What If switching to a busy channel in the middle of data transmission? (Suppose B is transimitting data to A and C is transmitting to D)TRANSCRIPT
INFOCOM 2014
What is MMAC?▣ Multi-Channel MAC
Channel negotiation and assignment (sender – destination pair) Destination discovery (same channel) and load balancing (exploit all channels)
▣ Multi-Channel Hidden Terminal Problem If node C is a neighbor of A and B, C defers from transmission for MTU + ACK.
What is MMAC? (cont.)▣ Multi-Channel Exposed Terminal Problem
What If switching to a busy channel in the middle of data transmission?
(Suppose B is transimitting data to A and C is transmitting to D)
Previous MMAC protocols▣ Split-phase MMAC ( SP-MMAC )
Time is devided to alternating control and data phases. During the control phase, all nodes converge to a default channel to negotiate
the channel assignment using RTS/CTS. During the data phase, nodes exchange data on the assigned channels. Hidden Terminal and extra message overhead avoided. However, low spectural
efficiency with high contention conditions due to control phase.
▣ Dedicated Control Channel MMAC ( DCC-MMAC ) Nodes are equipped with 2 radios. One radio is always tuned to a control channel
and the other radio switches between the remaining channels for transmissions. Hidden Terminal avoided. However, higher device cost and low spectural effi-
ciency due to dedicated control channel. (DCC can also be a bottle neck in high-contention scenarios.)
▣ Randezvous MMAC ( MMAC ) Nodes hop between channels using predefined hopping sequences. Initial discovery is incurred until sender’s and dest’s hop sequences overlap. No solution for Hidden Terminal Problem.
FD-MMAC
▣ Full-Duplex MMAC
First to exploit FD communication(single radio). Nodes independently switch to idle channels by tracking the
state of each channel. (w/o exchange of control messages) Common synchronized time-slotted system. (GPS) Physical Layer Technique (SIS, EVM, RSS, Signal correlation)
Full-Duplex in a channel▣ Cross correlation technique (SIGCOMM’08)
Nodes can apply signal correlation techniques for detecting transmission of known bit patterns. Common in frame de-tection even in the presence of collisions.
Review
▣ Multi-channel Transmission The delay and throughput performance of wireless networks
can be significantly improved by accommodating parallel transmissions over orthogonal frequency channels.
A BHT ET
F E
Review (cont.)▣ Problems - MMAC
Channel negotiation & destination discovery Load balancing Multi-channel HT, ET.
Full-Duplex in a channel▣ Cross correlation technique (SIGCOMM’08)
Nodes can apply signal correlation techniques for detecting transmission of known bit patterns. Common in frame de-tection even in the presence of collisions.
A BF E
State Classification
RSS – Received Signal Strength
Hidden & Exposed
A B C
Destination & Sender State machine
Sample Scenarios
Experimental Result
▣ Elimination of channel negotiation and VCS + single-channel ET.