WCDMA的优化常见的面试问题WCDMA Optimization Related Questions.docVIP

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WCDMA的优化常见的面试问题WCDMA Optimization Related Questions.doc

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WCDMA的优化常见的面试问题WCDMA Optimization Related Questions

WCDMA Optimization Related Questions 1. What is Significance of Eb/No? On what factors it is dependent? who provides Eb/No? What is typical Eb/No for AMR 12.2 for Node B and MS?Answer - Eb_No is related to QOS of a service which in terms related to bit error rate. Technically it is the minimum signal to noise needed by infrastructure equipment after despreading it signal. This is a value used to compare different infrastructure vendors. Eb_No changes with the service type. Typically Eb_No for AMR 12.2 is ~ 4 db for node B and 8 dB for MS. It is infrastructure vendor (NSN) provides the Eb_No for Node B.The Eb/N0 value is the value that needs to be reached for insuring the targeted service quality. This is the ratio between the energy per bit for the related service over the noise spectral efficiency over the whole spreading band.The spread signal is characterized by the ratio of the energy per chip over the spectral noise density Ec/N0.2. What effect is there on signal by spreading and dispreading?Answer - Spreading will increase the bandwidth of a as signal. A signal of 10 Kb/s will become 40 Kb/s after spreading and will become 10 Kb/s after despreading.The processing gain term expresses the gain achieved by spreading a narrow band signal over a wideband spectrum.This gain is the ratio between the spreading chip rate and the actual service bit rate measured at the RLC level 3. Define Processing Gain.Answer - Processing Gain is ratio between rate of spreaded signal and rate of non spreaded signal.PG= 10 log (Chip rate /Bit rate)4. What is a chip rate of WCDMA System? How much is the bandwidth required for WCDMA?Answer: - 3840 Kc/s. FDD 5 MHZ of paired band. TDD 5 MHz only.5. What is the processing gain for 384 Kb/s service?Answer:- =10*Log(3840/384)=10*log (10)=10*1=106. What is the relationship of SF and data rate?Answer; - They are inversely proportional. Lower the SF higher the data rate.7. What is the relationship between SF and powe