Method for setting side reference frequency source of base station in time division communication system

Abstract

This invention discloses a method for designing a reference frequency source beside a base station in time dividing system chacterizing that a base band at the side of the base station applies a local reference source strictly synchronous to the system clock, the RF part applies an independent high precision reference frequency source and designing method in this invention either ensures synchronous data treatment of the time dividing system or satisfies the needs of RF part to send / receive signal frequency stability. The added frequency source generator and its additive circuit are greatly lower than clock stability circuits added in conventional methods in complexity and cost.

Description

technical field [0001] The invention relates to a base station of a time division multiplexing (TDMA) digital mobile communication system, in particular to a method for setting a base station side reference frequency source. Background technique [0002] As we all know, communication systems that work in time division multiplexing (TDMA), especially personal wireless communication systems (PCS), because their channels and uplink and downlink data operations are distinguished according to time, it is required that communication networks that work in this way Whether it is between the base stations or between the base stations and the network, the clock synchronization relationship must be maintained, so that data can be received and sent correctly and mutual interference between the base stations can be avoided. For this reason, each base station in the communication network must share the same system clock, and the clock is transmitted from the network side to the base stati...

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Problems solved by technology

[0003] In practical applications, the system clock provided by the network side is usually sent to each base station with cables through several relays. The transmission distance of the cables is generally relatively long. In this way, the clock jitter is inevitable during the transmission process. The resulting clock frequency deviation will directly affect the frequency stability and accuracy of the reference frequency source on the base station side

This will bring the following problems to the use of the system: 1. The reference frequency source used in the baseband part needs to keep frequency synchronization with the system clock, so as to ensure that the data sending and receiving and processing beats are strictly consistent with the network side

Therefore, when the frequency deviation of the network clock is large and the local reference frequency source on the base station side also has a large deviation, although it has no effect on the data processing of the baseband part, it cannot meet the frequency stability requirements of the reference frequency source used by the radio frequency part of the base station.

The direct result is that in this case, the receiving and transmitting frequency deviation of the base station is large, which may cause the base station to be unable to use normally

2. Even if the deviation of the system clock on the network side is within the frequency deviation range required by the radio frequency, there are still problems: because the local reference frequency source on the base station side will always be phase-locked according to the change of the system clock after the base station is powered on, even if the base station is running normally Afterwards, the local reference frequency source is still fine-tuned through phase-locking, and the slight jitter of the system clock will cause the adjustment of the local reference frequency source on the base station side.

This method can indeed ensure the high precision and high frequency stability of the system clock at the base station, but the disadvantage of this method is that it increases the complexity of the system at the base station and increases the cost.

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