The Research And Analysis On Performance Of Millimeter Wave Communication System In 5G

The 5th Generation(5G)mobile communication system aims to provide services of large capacity,high data rate and diversification,by taking advantage of wider bandwidth and achieving more efficient resource utilization.On the one hand,millimeter wave(mmWave)communication with abundant spectrum is one of the essential technologies with broad application prospects in 5G.However,weak diffraction of mm Wave signal,which caused by the high-frequency characteristic,brings new difficulties and new methods to overcome but those problems are not necessary in scenarios of traditional microwave communication.On the other hand,5G is devoted to exploiting and applying the Time Division Duplex(TDD)scheme to support flexible and reliable dynamic duplex configuration for improvement of time-frequency resource utilization,but the usage of dynamic slot allocation scheme will easily lead to cross-slot interference and limit the system performance.Although both the application of mm Wave transmission and TDD scheme in low-frequency communication systems have been rapidly mastered,when trying to integrate the two parts to empower high-frequency communication systems,one still faces multiple challenges that cannot be ignored and urgently need to be tackled.The establishment of communication systems full of those technologies is still under research with great beginning.Based on all these facts,this subject research attempt to learn and analysis the mm Wave communication system with dynamic duplex mode.First,this thesis proposes then studies a mm Wave communication system with adjustable ratio of slot of Uplink(UL)/Downlink(DL).For any instant,at the system level,all communication devices are classified into two parts according to the transmission direction of associated link,in which the transmission of UL or DL signal is carried out respectively.The interference suffered by any receiving device not only comes from the same-direction link learned in most traditional researches,but also comes from the cross-slot reverse link which appears with dynamic TDD strategy.At the link level,the transmitting power is fixed for base stations(BSs)while it is dynamic adjustable based on pathloss for user equipment.Both effective signals or interfering signals are transmitted in the mmWave channel,in which communication links are affected by factors such as Line-of-sight attribute and directional beamforming technology.This article will focus on the coverage probability of the system.Secondly,considering the difference of average power of duplex signals and the existence of cross-slot interference,enlightened by the interference control mechanism named ABSF(Almost Blank SubFrame),this chesis designs a similar method named ABSL(Almost Blank SLot)and applies it to mmWave communication system.The basic art of ABSL mechanism is that part of DL BSs bringing severe interference may be determined to give up prepared DL data and transmit an almost blank but necessary signal with neglected power during current slot,so as to reduce the severe interference giving way to reception of UL signals,which may lead to improvement of coverage potentially.Finally,this chesis models communication devices as Poisson Point Processes(PPPs).Then for the communication scenarios before and after the application of ABSL mechanism,analytical expressions for both UL and DL coverage are respectively deduced and derived.Meanwhile,a simulation platform for the mmWave communication system is also designed and implemented to assist and verify the progress of theoretical analysis.Multiple configurations including parameters such as density of deployment and ratio of UL/DL are fed into the system thus numerical results indicating coverage probability are obtained.Those results suggest that the main factor degrading performance is interference and the UL coverage probability is benefited from high ratio of UL slots.In dense deployment,the DL interference is serious and heavy DL traffic will do harm to the reception of DL signals.while in relatively sparse deployment,interference from UL is higher and the increase of UL traffic will easily decrease the DL coverage unexpectedly.While the ABSL mechanism has a capability to significantly raise coverage probability especially for UL transmission by abandoning some DL traffic,a balanced trade-off between system throughput and coverage performance shall be hunt for in future consideration.