PCF5083 datasheet(79/136 Pages) PHILIPS

79 / 136 page

1996 Oct 29

Philips Semiconductors

Objective speciﬁcation

GSM signal processing IC

PCF5083

FB_search_fcb

This procedure searches for a frequency correction burst (FB) by scanning

9 or more timeslots. FB_search_fcb can be used on 26 or 51-frames

multiframe structure. When serving a trafﬁc channel (TCH) the BCCH

carrier has to be scanned in the IDLE frames of the 26 multiframe structure

using search windows of 9 timeslots. After initialization with

FB_search_fcb_init (see below), FB_search_fcb has to be called in up to

11 consecutive IDLE frames. This time period is called an observation

interval, containing at least one FB.

The 51 multiframe structure is used in cell selection or IDLE mode and on

an SDDCH. If search windows of 9 timeslots are used to scan the BCCh

carrier, the search must be done by 15 successive calls to FB_search_fcb

within the following TDMA frames (N denotes the arbitrary TDMA frame

number of the ﬁrst call):

N, N+2, N+4, N+6, N+8,

N+11, N+13, N+15, N+17, N+19,

N+22, N+24, N+26, N+28, N+30.

If the search window is extended to 17 timeslots, the search can be done

by 7calls at the frames:

N, N+3, N+6, N+9, N+12, N+15, N+18.

Values of fb_found are deﬁned below:

fb_found =

−1; the search has been aborted and no FCB has been found.

fb_found = 0; no FB has been found up to now, FB_search_fcb should be

called again in the next Idle frame.

fb_found = > 0; the search has been successful. fb_found FBs have been

found within n_obser_int observation intervals.

The return value fb_toi is the start of the FB in bits (1 bit = 3.69

µs) relative

to ﬁrst complex sample of the observation window.

The fb_index indicates in which of the previous calls to FB_search_fcb the

FB has been actually found. If fb_index is zero, then the FB has been found

by fast detection during the current search. The fb_index =

−1 means that

no FB has been found within the current observation interval, if this is

combined with fb_found > 0 the call cannot be located and only fb_toi can

be used.

−

fb_found

fb_toi

fb_index

DESCRIPTION

PARAMETERS

RETURN

VALUES

PCF5083 데이터시트(PDF) 79 Page - NXP Semiconductors

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