CDMA蜂窝系统中的干扰及影响

分析ＣＤＭＡ蜂窝系统的基站发射机对ＥＴＡＣＳ蜂窝系统基站接收机的干扰，提出ＣＤＭＡ基站同ＥＴＡＣＳ基站间必须有保护措施，该保护措施至少提供１１４ｄＢ的损耗。本文结合北京等地区的电磁环境测试数据，应用将干扰的影响等效为基站噪声系数上升的方法，分析了外干扰对ＣＤＭＡ系统的影响，结果表明当外干扰达到－１０８ｄＢｍ时覆盖区将减少３０％。

Interference and Its Effect in CDMA Cellular System

CDMA is interference-limited, how to use the sPeCtrum effectively, how can CDMA and AMPS be existing at the same time, how is the result of external intefference, more attention must be Paid in designing the whole system. In CDMA system, there are three interference sourcesl one is the interference between mobile radio and base station which are at the same CDMA frequency catrier, the second comes from AMPS system which exists together with CDMA, the fast is due to other Systems, which is discussed in the Paper and the discussion focuses in the effect of the inteffer-ence. When teSting electronic-magnetic environment of 800MHz cellular fmpuency in Beijing and Xi-an, it is found that there are many intefference sources in this frequency band with the values are mor than - 107dBm. These will give CDMA a bad effect. The cost of external interference caq be a- by translating its impact into an equivalent rise in cell site noise figure. This increases result in decreawh cell coverage. This effect indicates that a-108dBm interference results in a 30% reduc-tion in coverage area at any loading.In China,870MHz-880MHz (for base-station transmitting ) belongs to CDMA system of and 880MHz-890MHz (for base-station receiving) ued for B system of ETACS. Becuse the fre-quency band of CDMA system and ETACS B system are adjacent, CDMA base-station interferes E-TACS base-station. Safeguard method must be applied to reject the interference between CDMA and ETACS, and the method must provide 114dB loss at least.