Full Duplex Technique Based Efficient Concurrent MAC Protocol Design In Wireless Network

Wireless network is a promising technique in both civil and military areas,such as intelligent house,mobile payment,eHealthy system,military communication/detection/-monitoring and so on.With the development of the internet of thing,the density and amount of wireless device have dramatically increased in the wireless network.Due to the increasing number of wireless applications,the requirement for communication quality and data rate is infinite.Current wireless techniques are becoming limitation factors for future development.Therefore,it is meaningful to discuss more efficient wireless scheduling mechanism.Due to the broadcasting nature of wireless communication,surrounding nodes could overhear the broadcasting message.When two or more concurrent transmissions are overheard by a receiver node,signals in receiver are mixed and can not be decoded.To eliminate the interference,MAC protocol allows nodes to cooperate mutually.However,when advanced physical techniques(such as OFDM,MIMO,Full duplex communication)are deployed in network,the physical data rate has increased from 802.11 b at 11 Mbps to802.11 ac at 1Gbps.Since the coordination overhead can not be declined as the same magnitude,the improvement by new techniques is overlapped by those coordination overhead.Thus,coordination overhead is the key factor for network performance enhancement.Based on electromagnetic wave communication,nodes in wireless network could transmit at different time/frequency/antennas concurrently.In conventional network,interference avoidance in temporal domain can not meet the requirement for efficient communication.Basically,to achieve a higher network performance,multiple dimensions(temporal domain,frequency domain,spacial domain)information should be wisely utilized to promote MAC scheduling scheme.Full duplex(FD)communication mechanism is an alternative technology for 5G realization,which breakthroughs the half duplex communication in wireless network.FD enables node the capability of transmitting and receiving simultaneously.Technically,if FD is equipped to enhance the data transmission performance,the throughput and channel utilization can be enhanced.However,the coordination overhead does not reduce in the same magnitude,resulting in the network performance improvement by employing FD is covered.As a result,the performance can be enhanced as we adopt the high physical data rate transmission and efficient scheduling mechanism cooperatively.Significant process has been made in FD technique,which allows nodes to mimic the function of collision detection employed in wired network.Naturally,FD collision detection can be adopted in wireless channel contention.In such mechanism,potential interference can be avoided effectively.Combined with interference cancellation with known signals,nodes inject the interference information actively during the data transmission.Basically,the design of wireless network aims not to avoid interference,but to inject interference to coordinate among network nodes.It is a breakthrough to reuse the data transmitting channel for simultaneous coordination.Due to the great potential to reduce the coordination overhead,FD is expected to use widely in the coming future.Through FD communication has been equipped in the network,little attention has been paid to use the interference for coordination.In comparison,we strive to utilize FD in the areas of channel contention and side-channel interference coordination.As FD could reuse transmission channel for coordination.However,the interference is still harmed for the decoding of concurrent transmission.Further,when two or more injected interference messages are transmitted,not only the coordination information but the concurrent transmission decoding process will be interfered.To operate reused interference wisely and efficiently,we divide the content and novel results of this thesis into four parts:Firstly,the study of virtual frame aggregation based channel contention in the singlehop Adhoc network.we present two kinds of VFA(virtual frame aggregation)model to achieve high coordination efficiency by amortizing the overhead over multiple transmitters.Firstly,ideal VFA model provides a novel way to construct a winner cluster and allows multiple winners to transmit successively and sequently.Specifically,in multi-subcarrier network,each node chooses a random subcarrier for contention.Simultaneously,those nodes are ordered by the index of chosen subcarrier.In such mechanism,when two or more contenders choose the same subcarrier for contention,an additional slot is provided to reorder the conflicted nodes.Finally,all the ordered nodes are formed the winner cluster and the sequenced subframes are organized into the virtual frame.When energy leakage and channel fading problems are considered in VFA,we further develop practical VFA model to mimic the actual wireless environment.Simulation results show that usually two slots are enough to construct a sufficiently large winner cluster.Moreover,VFA achieves a notable throughput gain over IEEE 802.11 as high as 165% with better fairness under various scenarios.Secondly,the study of asymmetric full duplex based channel access in single-hop Adhoc network.In order to resolve the coordination problem among multiple nodes,we present a novel asymmetric full duplex(AFD)based channel access technique by allowing data transmission and channel contention to operate concurrently,where the coordination overhead is respected to ‘0' in analyse.AFD organizes a 3D pipeline channel contention scheme and the process of contention is divided into several stages in temporal,frequency,spacial domain.To eliminate the interference cased by collision,AFD adopts a singleton PN sequence as contention Pilot signal.Moreover,we expand full duplex communication into a network scale.Simulation and experiment results show that,compared with IEEE802.11,AFD outperforms dramatically in terms of throughput and Jain's fairness index,like Jain's fairness index is above 0.95 with a throughput gain up to 120%.Thirdly,the study of receiver assisted contention based channel access in multiplehops Adhoc network.we propose two approaches RAC(receiver assisted contention)and ?RAC,to achieve high throughput by allowing receivers to assist in the channel contention and further enhance the network fairness.Specifically,based on full duplex technique,RAC organizes a transmitter and its corresponding receiver to sense and contend for the channel cooperatively.Through such cooperation,the hidden terminal problem is overcomed and the exposed terminals are allowed to transmit simultaneously.In order to assist in the channel contention,a receiver should be informed before the data transmission period.Basically,an information of next transmission(INT)coding scheme is proposed to inform the receiver about the coming transmission.Then,RAC encodes INT message into multiple pilot signals,where detail messages are contained in those positions of each pilot.Furthermore,in order to balance the fairness metric of the network,we introduce degree of connection based ?RAC to adjust the channel access probability of each node.Analysis and simulation results show that RAC achieves a notable throughput gain over Back2 f as high as 145% in theory and 143% in simulation.Compared with RAC,?RAC obtains a better fairness performance with only small throughput reduction.Fourthly,the study of full duplex based concurrent communications scheme in WLANThis paper presents,Pillow Talks MAC(PT-MAC),a novel spectrum sharing mechanism to create an extra channel(pt-channel)for client-to-client transmission in WLAN.Obviously,The basic challenge in our proposal is how pt-channel works concurrently and transparently with AP transmissions.To address the issue,in PT-MAC,selected clients are allowed to contend for pt-channel during uplink transmissions and talk freely under the ongoing downlink transmissions.Based on advanced physical techniques,pt-channel transmitter receives and forwards the AP signals simultaneously within OFDM cyclic prefix,resulting in mixed signals are overheard by receiver in pt-channel.However,the mixed message can be recovered by pt-decoding system.Simulations and analytical results show that,PT-MAC reuses the spectrum in WLAN and achieves a throughput gain as large as 92% with similar fairness,when the ratio of downlink traffic is about 80%.In summary,based on full duplex communication technique,we discuss the wireless concurrent transmission issues in single hop,multiple hops Adhoc network and WLAN,design full duplex based MAC protocols and reveal the characteristics of network operation.Further,we develop four high efficient protocols,that are amortized coordination overhead MAC protocol,hidden coordination overhead MAC protocol,cooperation channel contention MAC protocol and channel resource reused MAC protocol.Those researches achieve meaningful value in practical wireless system and provide a new solution for improving wireless network performance.Then,the system model and analysis discussion can be reused in other MAC protocols design.