A survey on control separation techniques in multi-radio multi-channel MAC protocols <s> C. Common Control Channel for Reservation <s> In this paper, we propose a new MAC protocol for ad-hoc networks that uses multiple channels and a dynamic channel selection scheme. The proposed protocol, DCC-MAC (dual control channel based MAC), deploys two control channels (CH/sub R/C/ and CH/sub ACK/ and N data channels, where N is independent of the number of nodes in the network. Through RTS/CTS dialogues on CH/sub R/C/ senders and receivers negotiate the most robust channel for data transmission with maximum-CIR selection criterion. ACK transmission on CH/sub ACK/ contributes to the unidirectional transmission on data channels and therefore the decrease of the co-channel reuse distance. Performance evaluation has been carried out and the simulation results demonstrate the effectiveness of the proposed protocol. <s> BIB001 </s> A survey on control separation techniques in multi-radio multi-channel MAC protocols <s> C. Common Control Channel for Reservation <s> The emergence of high speed WLANs, such as the IEEE 802.11a and IEEE 802.11g, has provided an alternative solution for mobile users to access a network in addition to the popular IEEE 802.11b solution. Although the channel data rate of those emerging high speed WLANs is five times higher than that of 802.11b, some recent studies have shown that the throughput of IEEE 802.11 drops as the channel data rate increases, and the throughput upper limit do exist when the channel data rate goes to infinite high. These findings indicate that the performance of a WLAN will not be efficiently improved by merely increasing the channel data rate. In this paper, we propose a new protocol scheme that makes use of an out-of-band signaling (OBS) technique. The proposed scheme provides better bandwidth usage compared to the in-band signaling technique in the existing scheme and is compatible with the existing IEEE 802.11 standard. <s> BIB002 </s> A survey on control separation techniques in multi-radio multi-channel MAC protocols <s> C. Common Control Channel for Reservation <s> Multiple channels are available for use in IEEE 802.11. Multiple channels can increase the available network capacity, but require new protocols to exploit the available capacity. This paper studies the problem of improving the capacity of multi-channel wireless networks by using multiple interfaces. We consider the scenario when multiple interfaces are available, but the number of available interfaces is lesser than the number of available channels. We provide a classification of interface assignment strategies, and propose a new strategy that does not require modifications to IEEE 802.11. We also identify routing heuristics that are suitable for use with the proposed interface assignment strategy. <s> BIB003 </s> A survey on control separation techniques in multi-radio multi-channel MAC protocols <s> C. Common Control Channel for Reservation <s> Radio spectrum allocated for use in unlicensed wireless networks is distributed across non-contiguous frequency bands. Existing MAC protocols, like IEEE 802.11, operate only in contiguous bands. Several small slices of frequency are available in lower frequency bands that are not utilized. We propose utilizing a sliver of unused spectrum in the lower frequency band as a low rate control channel to improve the capacity of infrastructure and multi-hop wireless networks. The proposed control channel-based MAC Protocol (C/sup 2/M) increases the throughput by moving the contention resolution overheads to the separate low rate channel. We allow simultaneous channel contention and data transmission by incorporating advance reservation on the control channel, and data aggregation on the data channel. Simulation results show that compared to IEEE 802.11, C/sup 2/M significantly improves network performance. <s> BIB004 </s> A survey on control separation techniques in multi-radio multi-channel MAC protocols <s> C. Common Control Channel for Reservation <s> To reduce medium access control (MAC) overhead and improve channel utilization, there has been extensive research on dynamically adjusting the channel access behavior of a contending station based on channel feedback information. This paper explores an alternative approach, named pipelined packet scheduling, to reduce the MAC overhead. MAC overheads can be divided into bandwidth-dependent and bandwidth-independent components and these overheads can both be reduced by using split-channel pipelining mechanisms, as demonstrated in this paper. In the past, pipelining mechanisms have not been well studied. This paper introduces two total pipelining schemes that attempt to fully pipeline contention resolution with data transmission. Further, the paper identifies shortcomings of total pipelining in the wireless environment and proposes a partial pipelining approach to overcome these shortcomings. Simulation results show that substantial performance improvement in channel utilization, average packet access delay, and access energy cost can be achieved with a properly designed scheme. <s> BIB005 </s> A survey on control separation techniques in multi-radio multi-channel MAC protocols <s> C. Common Control Channel for Reservation <s> In this paper, we propose a novel medium access control protocol with a separate control channel (MAC-SCC) to increase the channel efficiency and address the unfairness and instability problems of IEEE 802.11 MAC protocol. In MAC-SCC, the available bandwidth is partitioned into two channels: a data channel and a control channel, each associated with a network allocation vector (NAV). To reduce hardware complexity, the station transmits or receives on one channel only at any given time. In the network employing MAC-SCC, the next data frame can be pre-scheduled during the current data transmission via the separate control channel, and thus reducing the frame collision probability and the bandwidth wasted during backoff. Moreover the use of the separate control channel helps to achieve fair medium access and solve the instability problem resulted from frequent link failures. The optimal bandwidth partitioning between the two channels is analyzed via a statistical model, which shows 10% bandwidth for the control channel and 90% bandwidth for the data channel. The performance of MAC-SCC is quantified via extensive simulations in both a stand-alone simulator developed by using PARSEC and a comprehensive network simulator called QualNet with whole protocol stack. Our results show that MAC-SCC can effectively reduce the link failure probability, achieve fair medium access when running multiple TCP sessions, and yield a throughput gain up to 60% under high traffic load <s> BIB006
A few proposals have considered the use of separate control channels for contention resolution and channel reservation to improve the transmission over data channel BIB005 , BIB006 , BIB001 , BIB002 , BIB003 . In contrast to rendezvous-based approach, reservation-based protocols do not exploit parallel transmission of data. Instead, it explores the enhancement over standard IEEE 802.11 DCF handshake with separate control channels. The protocols in this class typically feature only one data channel and one or more control channels. The control channels are used for exchanging control messages and facilitating data transmission over data channel. As a result control traffic can be stripped away from data traffic, thereby reducing control packet collision and its associate overhead. The protocols also enable control packets to reserve data channel in advance while data channel is occupied, this would avoid backoff overhead caused by contention resolution at the start of data transmission. The operation of reservation based approach is shown in Figure 1b . The protocols in general follow standard RTS-CTS-DATA-ACK exchange, though RTS-CTS and DATA-ACK are operated in different band and can be working in parallel. That is to say, while current data is transmitting on data channel, at the same time, the contention resolution of subsequent data transmission can be arranged. Thus, as soon as the current data transmission is completed, the next data transmission can commence immediately. Yang et. al. BIB005 introduced a total pipelining strategy for IEEE 802.11 DCF using two channels called Dual Channel Pipelined Scheduling (DCPS). DCPS divides the channel into two sub-channels: a control channel and a data channel. The control channel is used for random backoff duration, collision detections, and RTS/CTS handshake; the data channel on the other hand is used for DATA/ACK exchange. The main feature of DCPS is that the overhead associated with contention resolution can be hidden (or partially hidden) by processing contention for next packet transmission in parallel with current packet transmission. However, the protocol has to ensure the RTS/CTS exchange for next data transmission must complete before current data transmission finishes, and subsequent RTS/CTS exchange can not begin until current data transmission terminates, otherwise, the efficiency of pipelining will be significantly reduced. Similarly, Li et. al. BIB006 proposed a MAC protocol using a separating control channel (MAC-SCC), in which both control and data channels manage their own Network Allocation Vector (NAV) respectively. The protocol assumes that the bandwidth of data channel is much greater than control channel, and the data transmission follows standard IEEE 802.11 RTS-CTS-DATA-ACK four-way handshake. During the data transmission, all frames can be transmitted through data channel, while the control channel can only be used to transmit RTS or CTS frame. MAC-SCC primarily uses data channel for transmission whenever the channel is free. If data channel is busy, control channel can be use to schedule subsequent transmission on data channel. In other word, the contention of next data transmission can be resolved during the transmission of the current data frame. The exchange of RTS and CTS frame on the control channel can be used to extend NAV of the data channel on the nearby nodes. Thus, as soon the data channel is released from current transmission, the next data transmission can proceed immediately. Zhang et. al. BIB001 indicated that the use of separate control channel for RTS/CTS will improve the performance of MAC protocol by keeping virtual carrier sensing while the node is in the transmitting state. This in effect would allow the nodes to be more aware of the channel state, thereby having more capability of initiating new transmission or responding to other nodes on the free data channel. Based on separating RTS/CTS control, Zhang et. al. proposed a new MAC protocol called Dual Control Channel based MAC (DCC-MAC) which further deploys a second control channel which is used exclusively for ACK transmission. Thus, two control channels are being used -one for RTS/CTS and the other for ACK respectively. The key advantage of using separate ACK reply contributes to the realization of unidirectional transmission on data channels. As a result, the frequent collision between data and ACK messages will be greatly reduced, and further improve the throughput. Tantra et. al. BIB002 explored the use of a separate low-rate control channel to improve the performance of a high ratedata channel in an infrastructure-based wireless network, and proposed a new MAC layer scheduling scheme called Out-ofBand Signalling (OBS). Unlike other existing multi-channel protocols that divide total available bandwidth into two separate control and data sub-channel, OBS uses a separate unused channel operating at lower rate to schedule the actual data transmission on the higher rate channel. During each data transmission, a RTS frame will be transmitted to Access Point (AP) using DCF. Upon the reception of RTS frame at AP, the AP will then schedule the data transmission to the next PCF period for exchanging data and acknowledgement. This mechanism exploits the advantage of less overhead imposed by PCF, and resolves PCF synchronization by employing of outof-band DCF control. As a result, it improves the performance by mitigating costly idle periods and transmission collision on higher rate data channel. Kyasanur et. al. have indicated that the use of OBS is restricted to infrastructure-based network, therefore proposing a novel Control Channel-based MAC protocol (C 2 M) BIB004 that features out of band control for multi-hop networks. C 2 M splits IEEE 802.11 DCF by operating the control portion of MAC protocol over a low-frequency, low-data rate, and long-range channel, while the data portion is operated over high-frequency, high data rate, and short-range channel. C 2 M highlights the use of small portion of spectrum at lower frequency to improve the performance of data transmission on the higher rate channel by allowing simultaneous channel contention resolution and data transmission. Further, it also exploits the advantage of longer transmission range at control channel in reducing the effect of hidden terminals on data channel.