Utvärdering av en beslutsåterkopplad kanalestimator för tredje generationens mobiltelefonisystem
TelekommunikationTelecommunicationsM.sc.eeMasterThesisMagisterexamenMagister examenW-cdmaWcdmaCdmaUmtsImt-2000TelefonsystemMobiltelefoniChannel estimationKanalestimeringKanalEstimeringDecision directedBeslutsåterkopplad
This Masters thesis work describes a comparison between two different methods
for estimation of the down channel (base station to mobile subscriber) in
Wide-band Code Division Multiple Access (WCDMA).
The first estimation method, Optimal Feed-forward Channel Estimation (OFCE), is
a conventional method that bases the estimates on data that is known to both
sender and receiver, so called pilots. The second method, Decision Directed
Channel Estimation (DDCE), is an elaboration of OFCE. It also uses user data
for estimation.
Simulations show that DDCE, in comparison to OFCE, does not attain an
improvement in signal-to-noise-ratio (SNR) for high bit error rates (BER). An
improvement is only seen when the BER becomes much lower than what is common in
real situations.
In conclusion DDCE is complicated, involves many mathematical operations and
gives insignificant improvement of SNR when BER takes common values. It is
legitimate to question if it is possible to use the method in a real mobile
phone system.