| 60GHz wireless communication systems are able to supply data rates as much asmulti-Gigabits per second, which meets consumers’ desire for high speed wirelesscommunication systems. Many research institutions and industry groups have carriedout their research for60GHz wireless technology. However, most of the studies areconcentrated on the channel measurements, circuit design and so on, while detaileddiscussions of modulation, equalization, algorithm design at the physical layer,capacity and error rate analysis is deficient.On the other hand, existing60GHz wirelesscommunications systems are basically based on single carrier or Orthogonal frequencydivision multiplexing (OFDM) modulation schemes. These communication systemswith high carrier freguency present many disadvantages, such as complex hardwarestructures, high power consumption, sensitive to the channel’s multipath fading effectsand so on, so the complexity and cost of the entire system will be very high, whendeployed in the multipath environments. Pulse communication technology used byUltra-wideband communication systems is potential to overcome those shortcomingspresented by carrier communication sytems, and the corresponding theories aboutmodulation schemes, system design and performance studies have been very mature,so it is reasonable to propose a60GHz pulse wireless communication system based onthe principles of impulse radio. System capacity and BER performance was alsostudied in this paper.This paper provides four main contributions. First, a pulse communication schemein the60GHz band was proposed, and to establish a specific60GHz pulsecommunication system, this paper designed two60GHz pulses, adopted the basicPPM modulation scheme, and chose to use three different receivers: singlecorrelation receiver, RAKE receiver and energy detection receiver. Second, An indoorfrequency selective fading channel model is introduced for single user60GHzTH-PPM systems. The capacity and bit error rate (BER) with this channel model of a60GHz TH-PPM system based on the designed pulses is derived. Performance results are presented to illustrate the effects of the pulse waveforms and channel properties onthe channel capacity. Third, detailed analysis on both large-scale and small-scalefading characteristics of two channel models CM1and CM2was presented, and thecorresponding mathematical models used in the performance study were also derivated.Both the two models are recommended by IEEE TG3c group and based on the indoorresidentional environments. Fourth,Closed-form expressions for capacity and BER of60GHz single-user PPM systems with different receivers were derived and verified viasimulations. And the performance of the three receivers were also compared.Five conclusions were derived as follows. First,60GHz pulse waveformspresented deep effects on the performance of60GHz pulse communication systems, soit is important to design appropriate pulses. Closed-form of the capacity derived in thispaper can be used as a reference to test whether a pulse waveform is good or not.Second, the system designed in this paper is suitable for short-range high-speedwireless communications. For example, in the line of sight (LOS) channel CM1, the2PPM system can provide a high data transfer rate as much as5Gbps, with the BERbelow104, and the communication distance is less than70meters. Higher ary PPMsystems can suppot much higher data transfer rate while communication distance willbe reduced to less than20meters. In non-line-of-sight (NLOS) channel,communication distance of2PPM system with the same reliability and data transferrate, is only about5meters. Thirdly, since almost all the energy of the received signalis concentrated in the first arrival path and negligible in the other multipaths, CM1channel presents unobvious multipath effects and much better performance. WhileCM2channel is a typical frequency selective multipath fading channel, and energy ofthe received siganal is scattered over a large number of multipaths. So the multipathfading is severe in CM2channel and accordingly the system perfirmance in CM2isrelatively poor. However, RAKE receiver can provide diversity reception of multipathsand improve the system performance in CM2. Fourth, the optimal receiver in CM1channel is coherent receiver with a single set of correlators, while the MRC RAKEreceiver is the best choice for systems in CM2channel. With appropriate design of thebranch number and weighting factors, the MRC RAKE can provide excellent performance. Fifth, although performance of the energy detector receiver is relativelypoor, simple structure and low cost characteristics make it the sub-optimal receivingscheme for60GHz pulse communication system which is not very stringent inperformance. And with some improvement in the stucture and working flow, it ispossible for the energy detector receiver to achieve a better performance.The60GHz pulse communication scheme proposed in this paper is a supplementto physical layer transmission schemes for60GHz wireless communication systems.And all the work in this paper, mainly about analysis of the60GHz channels, designof the60GHz pulse waveforms, choices of receiver schemes, and study of bit error rateand capacity performance, have improved the theoretical basis of the60GHz pulsecommunication and provided guidance and theoretical support for the design anddevelopment of60GHz wireless communication systems, which is significant topromote applications of60GHz technology. |
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