This paper investigates the medium access control （MAC） stratifies for communication systems. Since the signals are naturally superposed in public medium, we introduce physical layer network coding into MAC system a...This paper investigates the medium access control （MAC） stratifies for communication systems. Since the signals are naturally superposed in public medium, we introduce physical layer network coding into MAC system and propose the physical layer network coded MAC （PNC-MAC） to utilize the collisions occurring in the MAC process. The implicit expressions of the throughput and average delay of the system operated with the new algorithm are derived in an iterative way. To show the performance of the algorithm, we compare the throughput and average delay induced by the new algorithm with current schemes via simulations. The results show that when operated with our proposed PNC-MAC, MAC system can achieve a larger throughput while the frames bear shorter average delay. Moreover, in many users case, the throughput increases slightly while the average delay ascends drastically.展开更多
This paper investigates the Medium Access Control(MAC)protocol performance in the IEEE 802.11g-over-fiber network for different payloads and fiber lengths using Direct Sequence Spread Spectrum-Orthogonal Frequency Div...This paper investigates the Medium Access Control(MAC)protocol performance in the IEEE 802.11g-over-fiber network for different payloads and fiber lengths using Direct Sequence Spread Spectrum-Orthogonal Frequency Division Multiplexing(DSSSOFDM)and Extended Rate PhysicalsOrthogonal Frequency Division Multiplexing(ERP-OFDM)physical layers using basic access mode,Request to Send/Clear to Send(RTS/CTS)and CTS-to-self mechanisms.The results show that IEEE 802.11g-over-fiber network employing the ERP-OFDM physical layer is much more efficient than that employing the DSSS-OFDM physical layer,with regards to both throughput and delay.For a given maximum throughput/minimum delay,the tradeoff among the access mechanism,the fiber length,and the payload size must be considered.Our quantified results give a selection basis for the operators to quickly select suitable IEEE 802.11g physical layers and the different access mechanisms,and accurately predict the data throughput and delay given the specific parameters.展开更多
In order to resolve the hidden and exposed terminal problems and improve the probability of concurrent packet transmissions for multihop Mobile Ad Hoc Networks （MANETs）, a novel slotted Asyrmaetric Dual-Channel Medi...In order to resolve the hidden and exposed terminal problems and improve the probability of concurrent packet transmissions for multihop Mobile Ad Hoc Networks （MANETs）, a novel slotted Asyrmaetric Dual-Channel Medium Access Control （ADC-MAC） protocol is proposed. It exploits sirmltaneous reservation with less collisions and conision-flee data packet transmissions, and achieves optimal transmission balance on the Control Channel （CCH） and Data Channel （DCH） by adjusting the relationship between Reservation Slot （RS） on the CCH and the data packet Transmission Slot （TS） on the DCH. Transmission interferences can be avoided by only observing CCH for the transmission time of a data packet. The proposed RS and contention micro-slot backoff mechanisms also greatly improve channel access efficiency. Simulation results show that compared to IFEE 802. 11 DCF and -Mc protocols, the proposed protocol can achieve a throughput gain of 88% in singlehop networks and 151% in nltihop networks at the same total data rate.展开更多
In a Wireless Mesh Network(WMN),the convenience of a routing strategy strongly depends on the mobility of the intermediate nodes that compose the paths.Taking this behaviour into account,this paper presents a routing ...In a Wireless Mesh Network(WMN),the convenience of a routing strategy strongly depends on the mobility of the intermediate nodes that compose the paths.Taking this behaviour into account,this paper presents a routing scheme that works differently accordingly to the node mobility.In this sense,a proactive routing scheme is restricted to the backbone to promote the use of stable routes.Conversely,the reactive protocol is used for searching routes to or from a mobile destination.Both approaches are simultaneously implemented in the mesh nodes so that the routing protocols share routing information that optimises the network performance.Aimed at guaranteeing the IP compatibility,the combination of the two protocols in the core routers is carried out in the Medium Access Control(MAC)layer.In contrast to the operation in the IP layer where two routing protocols cannot work concurrently,the transfer of the routing tasks to the MAC layer enables the use of multiple independent forwarding tables.Simulation results show the advantage of the proposal in terms of packet losses and data delay.展开更多
文摘This paper investigates the medium access control （MAC） stratifies for communication systems. Since the signals are naturally superposed in public medium, we introduce physical layer network coding into MAC system and propose the physical layer network coded MAC （PNC-MAC） to utilize the collisions occurring in the MAC process. The implicit expressions of the throughput and average delay of the system operated with the new algorithm are derived in an iterative way. To show the performance of the algorithm, we compare the throughput and average delay induced by the new algorithm with current schemes via simulations. The results show that when operated with our proposed PNC-MAC, MAC system can achieve a larger throughput while the frames bear shorter average delay. Moreover, in many users case, the throughput increases slightly while the average delay ascends drastically.
基金supported in part by the National Basic Research Program of China under Grant No. 2012CB315705 (973 program)National Natural Science Foundation of China under Grants No.61107058, No.61120106001, No.60932004, No.61001121, No.60837004+2 种基金National High-Tech Research and Development Program of China under Grant No.2011AA010306 (863 program)Beijing Excellent Doctoral Thesis Project under Grant No.YB20101001301Cooperation Project between Province and Ministries under Grant No.2011A090200025
文摘This paper investigates the Medium Access Control(MAC)protocol performance in the IEEE 802.11g-over-fiber network for different payloads and fiber lengths using Direct Sequence Spread Spectrum-Orthogonal Frequency Division Multiplexing(DSSSOFDM)and Extended Rate PhysicalsOrthogonal Frequency Division Multiplexing(ERP-OFDM)physical layers using basic access mode,Request to Send/Clear to Send(RTS/CTS)and CTS-to-self mechanisms.The results show that IEEE 802.11g-over-fiber network employing the ERP-OFDM physical layer is much more efficient than that employing the DSSS-OFDM physical layer,with regards to both throughput and delay.For a given maximum throughput/minimum delay,the tradeoff among the access mechanism,the fiber length,and the payload size must be considered.Our quantified results give a selection basis for the operators to quickly select suitable IEEE 802.11g physical layers and the different access mechanisms,and accurately predict the data throughput and delay given the specific parameters.
基金Acknowledgements This work was supported partially by the National Natural Science Foundation of China under Gants No. 60872011, No. 61171074 the National S＆T Major Project of China under Gant No. 2010ZX03003-003-03+1 种基金 the Program for New Century Excellent Talents in University the Fundamental Research Funds for the Central Universities.
文摘In order to resolve the hidden and exposed terminal problems and improve the probability of concurrent packet transmissions for multihop Mobile Ad Hoc Networks （MANETs）, a novel slotted Asyrmaetric Dual-Channel Medium Access Control （ADC-MAC） protocol is proposed. It exploits sirmltaneous reservation with less collisions and conision-flee data packet transmissions, and achieves optimal transmission balance on the Control Channel （CCH） and Data Channel （DCH） by adjusting the relationship between Reservation Slot （RS） on the CCH and the data packet Transmission Slot （TS） on the DCH. Transmission interferences can be avoided by only observing CCH for the transmission time of a data packet. The proposed RS and contention micro-slot backoff mechanisms also greatly improve channel access efficiency. Simulation results show that compared to IFEE 802. 11 DCF and -Mc protocols, the proposed protocol can achieve a throughput gain of 88% in singlehop networks and 151% in nltihop networks at the same total data rate.
文摘In a Wireless Mesh Network(WMN),the convenience of a routing strategy strongly depends on the mobility of the intermediate nodes that compose the paths.Taking this behaviour into account,this paper presents a routing scheme that works differently accordingly to the node mobility.In this sense,a proactive routing scheme is restricted to the backbone to promote the use of stable routes.Conversely,the reactive protocol is used for searching routes to or from a mobile destination.Both approaches are simultaneously implemented in the mesh nodes so that the routing protocols share routing information that optimises the network performance.Aimed at guaranteeing the IP compatibility,the combination of the two protocols in the core routers is carried out in the Medium Access Control(MAC)layer.In contrast to the operation in the IP layer where two routing protocols cannot work concurrently,the transfer of the routing tasks to the MAC layer enables the use of multiple independent forwarding tables.Simulation results show the advantage of the proposal in terms of packet losses and data delay.
