Research On Link-layer Based QoS Of Cognitive Communication In Wireless Networks

Cognitive communication is regarded as the basis to support the heavy capacity in wireless network with spectrum shortage and ever increasing of capacity demands.Based on the analyses on the cognitive communication,it is of great significance to do research on the cognitive communication in improving the transmission performances.The link layer drives physical layer downward,which results in controlling the spectrum resource and channel states.That has a great impression in the communication performances.To improve the radio resource efficiency,the primary user emulator,channel sensing strategies,link-layer data transmission and multi-mode transmission transition are investigated based on the existing research results.The main works are as follows:(1)A channel states sensing strategy and link-layer based evaluation method for transmission performances are proposed to characterize the transmission process in non-relay cognitive wireless networks with primary user emulators existing.1)A joint decision strategy is proposed to sense the channel states.Energy detection is adopted to implement the channel sensing by individual sensors.The sensing results are processed in fusion center and final result is decided under different decision strategies.2)The detection probability,miss detection probability and false alarm probability are derived to describe the channel states with primary user emulators existing under different decision strategies.3)Under the individual sensing results,for the secondary users,the transmission states transit as a result of transmission outage.The transmission transition probability is derived with the channel state sensing results changing.4)Based on the sensing results and state transition matrix,a link-layer based evaluation method is proposed to evaluate the transmission performances with primary user emulators existing in cognitive wireless networks.(2)A cognitive wireless communication system is investigated with relay nodes existing.In the system,there is primary user,primary user emulator,secondary user and relay nodes.The main research on the system includes:1)With the analyses on the individual transmission performances,a transmission model is proposed with primary user emulator being absent or not.2)We do analyses on the 9 individual states which are from the actual states and sensing states of the channels.Based on the Shannon theorem,the individual instantaneous capcacity expressions are derived under the 9 individual states.3)With the transmission performance analyses,the success and failure states of the transmission performances are futherly analyzed.Then a transmission model is proposed under the different transmission states.4)Based on the transmission performances of the users,the transmission transition models of secondary users and relay nodes are proposed.5)Based on the transmission transition matrix of the secondary users and relay nodes,the effective capacity of the secondary user,relay nodes and overall effective capacity are derived respectively to evaluate the transmission performances based on link-layer level.(3)The multi-mode transmission in wireless network is taken into consideration and link-layer QoS is analyzed.In multi-mode wireless network,according to the actual situation of wireless communication in V2P,V2V and V2I/N modes,the transmission mode of the users is modeled and transmission performances are investigated:1)According to the transmission performances of V2P and V2I/N,a model is proposed to investigate the transmission performances.Based on the transmission model,the direct transmission and indirect transmission are evaluated respectively.2)In the vehicular network,the transmission transition model is proposed based on whether the transmission is successful or not.The transition matrix is derived after the analyses on the transmission mechanism.3)Effective capacity is adopted to evaluate the transmission performances based on the data transmission and transmission mode transition in the network under ideal environment and non-ideal environment respectively.Based on the research of the 3 topics,the 3 novel research methods and models are proposed correspondingly.Besides,the models are analyzed and simulated respectively.Simulation results show that the expected results are obtained.Finally,some potential research fields are discussed for the future research.In the thesis,the transmission modes are investigated and link-layer QoS is proposed which is implemented in non-relay wireless network,relay wireless network and multi-mode wireless network.And some new research results are obtained.