Study Of Preamble Signals In Next Generation Wireless Communication System

Compared with the design of data waveforms and radio access mode that is the hotspot research direction of modern wireless communications,the pilot signals for modern wireless communication system so far have received much less attention.Currently,the cellular system is extending from the Human-Type-Communication to Machine-Type-Communication applications and to the full frequency band,in which case the design of the new pilot signal is essential to satisfy the new requirement in the extended field.In massive Io T applications,synchronization is the first and arguably the most challenging step of MTC due to the largest time and frequency uncertainties present in transceivers.Direct use of the traditional cellular system design approach will cause serious power consumption and caculation complexity which is against the low power and low cost requiremnt of a mIoT devices.For the study of pilot signal for synchronization,the relevant research contents and achievements of this paper are as follows(1)To study the properties of direct correlation receiver and differential correlation receiver,and to point out that the reception performance of the above two traditional receivers will deteriorate under the condition of mIoT environment(i.e.,low symbol SNR and large initial frequency offset).The detection SNR of the above two receivers in different symbol SNR and frequency is mathematically deduced,which shows the destructive impact of low symbol SNR and high frequency offset on the detection performance.Based on the Cauchy-Schwartz inequality,a new type of waveform which can obtain the optimal SNR under the condition of frequency offset is found.The mathematical approach provides a useful analytical insight into the design of the synchronization signal waveform for the mIoT system.(2)To proposes a practical synchronization waveform that is resilient to frequency error for machinetype communications with applications in massive Internet of Things(IoT).Mathematical properties of the waveform are derived,which are keys to addressing the practical issues.In particular,it is shown that this type of waveform is asymptotically optimal in the presence of a frequency error,in the sense that its asymptotic performance is the same as the optimal matched-filter detector that is free of frequency error.This asymptotic property enables optimization of the waveform under the constraints imposed by an application.It is also shown that such optimized waveform comes in pairs,which facilitates the formation of a new waveform capable of frequency error estimation and timing refinement at the receiver.Detailed comparisons with the LTE narrowband Io T primary synchronization signal are provided.Currently,cellular networks are unexceptionally operating on the scarce licensed bands.Thus,the network capacity is ultimately upper-bounded by the availability of these licensed bands.More spectrums are apparently the ultimate solution,and are needed more than ever.Therefore,we need to look into spectrum bands beyond the limited licensed spectrum,such as the spectrum-rich 5 GHz license-exempt band for potential data rate boost.For the study of pilot signal for unlicensed cellular system,the relevant research contents and achievements of this paper are as follows(3)Analyze the realization options for a cellular system complying with the regulatory requirements on the unlicensed spectrum with focus on LBT,and its realization on the cellular transmission structure along with the techniques for co-existence with other systems while maximally preserving the cellular frame structure.The analytical results in terms of channel occupancy time of frame-based LBT when coexisting with the load-based LBT are derived.It is found that a load-based LBT mechanism is desirable in order to fairly coexist with load-based systems like WiFi.(4)A reservation signal is designed to be led by the Wi Fi CTS signal.Since the CTS-to-self is a Wi Fi message,it is understood and honored by all Wi Fi nodes that can receive it.As such,in the eyes of a Wi Fi system,a cellular system is no different than a regular Wi Fi system,and hence the medium access time as indicated in the CTS signal will be honored by a WiFi system,thereby providing better protection against WiFi transmissions.Since a cellular system in this design also honors the WiFi NAV mechanism during LBT,the protection naturally works both ways,ensuring smoother coexistence between cellular and WiFi systems.For the uplink multi-access device,the transmission of reservation signal will block channel access from other scheduled celluar devices.By injecting cellular feature information into the basic signal signal,celluar device is able to distinguish cellular reservation signal from WiFi systems'.In this way,the uplink reservation signal prevents other devices from taking away the right to use the channel,while not block the sibling devices.