Research on Asymmetric Characteristics of Mobile Communications System Based on Electromagnetic Radiation

Abstract

It's well known that data tra-c brings asymmetry which is called Service Asym- metry (SA) to mobile communications system. This paper discusses asymmetry between uplink and downlink in mobile communications system in a new aspect | in view of the efiects of elec- tromagnetic radiation to human body, which is termed as Electromagnetic Asymmetry (EA). It's stated that both EA and SA should be taken into account, but EA has higher priority to SA. By calculating, it's concluded that under the restriction of electromagnetic radiation, the downlink data rate should be much higher than that of uplink. It is demonstrated that to adapt to EA and SA, the equivalent bandwidth of uplink should be narrower than that of downlink in view of duplex techniques including FDD and TDD. In the future, most mobile communications services will be asymmetric, such as high multime- dia (1,3). The downlink of service requirement is much greater than the uplink both in transmission total amount and transmission rate. So this asymmetric transmission characteristic is caused by tra-c demand (2{4). We call it as Service Asymmetry (SA) between uplink and downlink. Nowadays, only SA is considered as the efiect of asymmetric characteristic. In this paper, we also consider the asymmetric characteristic of uplink and downlink caused by electromagnetic radiation, which is termed as Electromagnetic Asymmetry (EA) between uplink and downlink. The in∞uence on surrounding environment caused by electromagnetic radiation is always a controversial problem. With the large-scale application of mobile communications, the total amount of electromagnetic radiation will increase and people will have to re-evaluate the social efiect of mobile communications (5). The in∞uence of electromagnetic radiation will be one of the most important elements which should be considered in research and design of mobile communications system. This paper analyzes the asymmetric characteristics of mobile communications system in∞uenced by electromagnetic radiation. The structure of this paper is as follows: Section 2 analyses the characteristics of asymmetric transmission caused by electromagnetic radiation in∞uence, Section 3 studies the methods to adapt to EA in view of duplex technique, and Section 4 is the conclusion. 2. THE ASYMMETRIC TRANSMISSION CHARACTERISTICS OF MOBILE COMMUNICATIONS CAUSED BY ELECTROMAGNETIC RADIATION It is notable that the mobile terminal is very close to human body, which is a small transceiver. The distance from mobile terminal to human body ranges from several centimeters to dozens of centimeters. In contrast to that, the distance from base station to human body is much longer, which ranges from dozens of meters to several kilometers. So the electromagnetic radiation impact on human body caused by mobile terminal is much more intense than that caused by base station. Then, we will respectively calculate the radiation power to human body caused by base station and mobile terminal. 1. Radiation power of base station absorbed by human body As there is a long distance from base station to human body, under the presupposition of ideal LOS propagation environment, we can use the Free Space Propagation Model. The power received by human body is Pr = AeGtPt 4…d 2 (1)