A survey on control separation techniques in multi-radio multi-channel MAC protocols <s> B. Common Control Channel for Rendezvous <s> The wireless mobile ad hoc network (MANET) architecture has received a lot of attention recently. This paper considers the access of multiple channels in a MANET with multi-hop communication behavior. We point out several interesting issues when using multiple channels. We then propose a new multi-channel MAC protocol, which is characterized by the following features: (i) it follows an "on-demand" style to assign channels to mobile hosts, (ii) the number of channels required is independent of the network topology and degree, (iii) it flexibly adapts to host mobility and only exchanges few control messages to achieve channel assignment and medium access, and (iv) no clock synchronization is required. Compared to existing protocols, some assign channels to hosts statically (thus a host will occupy a channel even when it has no intention to transmit) some require a number of channels which is a function of the maximum connectivity, and some necessitate a clock synchronization among all hosts in the MANET. Extensive simulations are conducted to evaluate the proposed protocol. <s> BIB001 </s> A survey on control separation techniques in multi-radio multi-channel MAC protocols <s> B. Common Control Channel for Rendezvous <s> In a mobile ad-hoc networks (MANET), one essential issue is medium access control (MAC) which addresses how to utilize the radio spectrum efficiently and to resolve potential contention and collision among mobile hosts on using the medium. Existing work is dedicated to using multiple channels and power control to improve the performance of MANET. We investigate the possibility of bringing the concepts of power control and multi-channel medium access together in the MAC design problem in a MANET. Existing protocols only address one of these issues independently. The proposed protocol is characterized by the following features: it follows an "on-demand" style to assign channels to mobile hosts; the number of channels required is independent of the network topology and degree; it flexibly adapts to host mobility; no form of clock synchronization is required; and power control is used to exploit frequency reuse. Power control may also extend battery life and reduce signal interference, both of which are important in wireless communication. Through simulations, we demonstrate the advantage of our new protocol. <s> BIB002 </s> A survey on control separation techniques in multi-radio multi-channel MAC protocols <s> B. Common Control Channel for Rendezvous <s> We propose a CSMA-based medium access control protocol for multihop wireless networks that uses multiple channels and a dynamic channel selection method. The proposed protocol uses one control channel and N data channels, where N is independent of the number of nodes in the network. The source uses an exchange of control packets on the control channel to decide on the best channel to send the data packet on. Channel selection is based on maximizing the signal-to-interference plus noise ratio at the receiver. We present performance evaluations obtained from simulations that demonstrate the effectiveness of the proposed protocol. <s> BIB003 </s> A survey on control separation techniques in multi-radio multi-channel MAC protocols <s> B. Common Control Channel for Rendezvous <s> A flexible and effective adaptive acquisition collision avoidance (AACA) multiple access protocol is proposed. It integrates the concept of multichannel and random reservation with piggyback to effectively solve hidden terminal and exposed terminal problems caused by the multihop architecture. In the protocol, every node adaptively reserves an idle traffic channel by request-to-send and clear-to-send (RTS/CTS) dialogue on the common channel. After successful reservation, the packet transmission of related other nodes do not interrupt other nodes. The protocol can use any number of channels. It performs better than the single channel RTS/CTS protocol under the assumption of the same total bandwidth if the number of the channels is not too large experiments. <s> BIB004 </s> A survey on control separation techniques in multi-radio multi-channel MAC protocols <s> B. Common Control Channel for Rendezvous <s> The MAC protocol of a cognitive radio (CR) device should allow it to access unused or under-utilized spectrum without (or with minimal) interference to primary users dynamically. To fulfill such a goal, we propose a cognitive MAC protocol using statistical channel allocation and call it SCA-MAC in this work. SCA-MAC is a CSMA/CA-based protocol, which exploits statistics of spectrum usage for decision making on channel access. For each transmission, the sender negotiates with the receiver on transmission parameters through the control channel. A model is developed for CR devices to evaluate the successful rate of transmission. A CR device should pass the threshold of the successful transmission rate via negotiation before it can begin a valid transmission on data channels. The operating range and channel aggregation are two control parameters introduced to maintain the MAC performance. To validate our ideas, we conducted theoretical analysis and simulations to show that SCA-MAC does improve the throughput performance and guarantee the interference to incumbents to be bounded by a predetermined acceptable rate. The proposed MAC protocol does not need a centralized controller, as the negotiation between the sender and the receiver is performed using the CSMA/CA-based algorithm. <s> BIB005
Many multi-channel MAC protocols BIB001 , BIB002 , BIB003 ,  , BIB004 , BIB005 assign one dedicated control channel to enable the other interfaces to switch and transmit on pre-arranged channel from control channel. These protocols typically consist of a least two or more radio interfaces: one interface has to be tuned to a fixed common channel for control purposes, while the other interfaces can be dynamically switched between the remaining channels for data exchange. Figure 1a illustrates the operation of rendezvous-based protocol. The dedicated control channel used in these protocols enables a node to arrange a rendezvousing data channel with its communicating counterpart. During every communication, the nodes must use control interface to exchange control messages in order to acquire the common data channel for exchanging data. The arrangement made by two communicating counterparts can also be heard by other nodes as the reference for the future data channel arrangement decision. Based on the information obtained from control interface, the data interface will be dynamically assigned as the common data channel and commence actual data transfer on the agreed channel. Dynamic Channel Assignment (DCA) BIB001 is one of such rendezvousing method. In DCA protocol, each node manages two lists, namely: Channel Usage List (CUL) and Free Channel List (FCL) for the lists of busy and idle channels respectively. The main idea of DCA is that for every communication, a sender must initiate an RTS which piggybacks its CUL to the receiver. The receiver compares its FCL with the CUL from sender to select a data channel (if any) for the subsequent communication and reply a CTS with additional channel selection information. Upon receiving CTS from receiver, the sender will send a reservation (RES) packet to inform nearby nodes about reservation of the selected channel. Finally, both sender and receiver will switch their data interface to the selected channel, and commence data transmission. In the subsequent work of DCA, Wu et. al. integrate the concept of power control into DCA protocol. This new protocol is known as Dynamic Channel Assignment with Power Control (DCA-PC) BIB002 . In DCA-PC, the protocol maintains an additional list called POWER which specifies the power level that should be used to transmit the data. The value of POWER can be dynamically adjusted as the node continuously monitoring the communication around itself on the control channel. Similar to DCA, DCA-PC goes through the same RTS/CTS/RES dialog to acquire a common data channel. When a data transmission is commenced on data interface, the sender will transmit the data with the power level that is specified on POWER list, thereby reducing energy consumption and signal interference. Jain et. al. BIB003 identified the deficiency of DCA in which the data channel is randomly selected from a pool of free channels, and there is no clear indication on whether the best channel has been selected. Thus, they proposed a Receiver-Based Channel Selection (RBCS) scheme to support the functionality of DCA. Upon each successful reception of RTS along with a list of available channels, RBCS selects the best channel with least received power according to its own sensing if there is any. Once both sender and receiver have reached the consensus, data transmission will begin on agreed data channel. Similarly, Hung et. al. also proposed Dynamic Private Channel (DPC)  that consists of one multicast control channel (CCH) and multiple unicast data channels (DCHs). DPC is a connection-oriented protocol, if two nodes intend to communication, the sender will initiate the setup process by specifying a selected DCH in an RTS frame and sending to the receiver through CCH. Once the RTS is received by receiver, the receiver will reply a Reply to RTS (RRTS) to accept the selected DCH or suggest alternative DCH. This process will continue until both sides reach an agreement on common DCH. Once channel negotiation comes to the end, the data exchange will commence with receiver sending out CTS to sender on selected DHC, and DATA-ACK exchange thereafter. Liu et. al. BIB004 proposed an Adaptive Acquisition Collision Avoidance (AACA) protocol for ad hoc network. AACA resembles a typical rendezvousing scheme with one control channel and several data channels. Within AACA, there are three variations of AACA, they are -AACA with Single Designated Transmission Channel (AACA-SDT), AACA with Multiple Designated Transmission Channels (AACA-MDT) and AACA with Receiver Designated Transmission Channel (AACA-RDT) respectively, and these variations can be differentiated by the way of their data channel selection. In AACA-SDT, the sender makes the initiative on channel selection, and attaches the selected channel information to the RTS packet. The decision on whether the receiver agrees on the selected channel can be determined through reception of receiver's CTS packets. The AACA-MDT on the other hand is yet another version of DCA BIB001 -the list of free channels at the sender is piggybacked on an RTS packet, the receiver randomly selects a channel from the list, and encapsulates the channel information in CTS. If sender agrees with the channel selection, a sending acknowledgement (SACK) will be broadcast to inform nearby neighbors about the decision. Conversely, the channel selection decision in AACA-RTS is triggered by the receiver. The receiver selects a data channel from its viewpoint and relevant information is enclosed in a CTS packet. The channel agreement from sender is done through a sending acknowledgement (SACK). Hsu et. al. explored the cognitive radio context and proposed a CSMA/CA based cognitive MAC protocol which is known as Statistical Channel Allocation MAC (SCA-MAC) BIB005 . Similar to other common channel rendezvousing schemes, SCA-MAC utilizes a common channel for initiating hand-shaking, while DATA/ACK messages are transmitted over data channel. The control channel SCA-MAC employs CSMA/CA scheme in which the node is permitted to transmit when the contention window expires and the channel remains idle. Thus, when the node is ready to transmit, the transmitting node sends a Control-channel-Request-To-Send (CRTS) message. Upon receiving CRTS, the receiving node exploits its own statistics of spectrum usage and the current status to allocate the channel for data transmission, and then replies with a Control-channelClear-To-Send (CCTS) message which contains the information of the best communication opportunity. Renegotiation is required if CRTS/CCTS can not be successfully exchanged or both sender and receiver do not have sufficient choice to make mutual agreement. Once CRTS/CCTS have been successfully exchanged, both sender and receiver will tune to agreed data channel, and then commence data transmission on data channel.