Method of synchronizing a radio receiver with an incoming radio signal

• US 5,329,558 A
• Filed: 04/10/1992
• Issued: 07/12/1994
• Est. Priority Date: 04/12/1991
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Ugland, Jon K., Larsson, Lars G., Raith, Alex K.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): GHEBRETINSAE, TEMESGHEN
• Application Number:
  US07/866,853
• Time in Patent Office: 823 Days
• Field of Search: 375/114, 375/106, 370/105.1, 370/105.4
• US Class Current: 375/365
• CPC Class Codes: H04L 7/042 Detectors therefor, e.g. correlators, state machines digital correlators in general G06F17/15
• CPC Class Codes: H04W 56/00 Synchronisation arrangements

Abstract

A method of synchronizing a baseband demodulator in a radio receiver, which may be stationary or mobile. The demodulator is a phase-shift demodulator and detects a baseband signal incoming from a sampling A/D-converter in the receiver. The baseband signal is transmitted from a radio transmitter in the form of bursts, in time slots in accordance with the TDMA-principle. One time slot, in addition to the data word, also includes in a known manner a synchronization part which has a given, fixed bit pattern. Prior to demodulation in the baseband demodulator, differential correlation of the received baseband signal is effected with the known synchronization pattern, wherein a time-dependent correlation function is obtained. The absolute magnitude of the maximum value is calculated and the corresponding time position for this maximum value is detected, which denotes the time position of the synchronization part of the received baseband signal.

Claims

1. A method of synchronizing a baseband demodulator in a radio receiver with a synchronization part (s(i)) of a sampled baseband signal (y(n)) arriving at the demodulator, said sample baseband signal being transmitted from a radio transmitter over a radio medium in the form of bursts, each of which occupies a given time slot included in a number of time slots within a frame, wherein the radio medium exhibits time dispersion with limited spread of delayed signals to received radio signal and wherein each of the tim slots includes a data apart and a synchronization part which includes a known bit patterns (s_o (i)), comprising the steps of forming a time-dependent correlation signal (r(n)) by carrying out in the radio receiver differential correlation of the received baseband signal (y(n)) with the know synchronization pattern (s_o (i)), and determining a time position (n_o) of an extreme value of the time-dependent correlation signal (r(n)), a time position of said synchronization part of the received signal (y(n)) being the time position (n_o ) of the extreme value.

2. A method according to claim 1, further including the steps of deriving said extreme value of the time-dependent correlation signal by calculating the absolute value of the time-dependent correlation signal and determining the maximum of the calculate absolute value.

3. A method according to claim 1, wherein the step of forming the time-dependent correlation signal further includes the steps of:

a) forming from the know synchronization patters (s_o (i)) the differential magnitude

_s (i) =S_o (i+i)·

S_o^* (i), where S_o^I (i) denotes the complex conjugate of S_o (i);

b) forming from the received signal y(n) a corresponding differential magnitude

Δ

_y (i)=(i)·

y^* (i-u), where y^* is the complex conjugate of y(i) and u is an up-sampling factor; and

c) correlating the two differential magnitudes Δ

_s (i) and Δ

_y (i) by forming the time-dependent correlation function according to ##EQU4##

4. A method of calculating a frequency error in a sampled baseband signal arriving at a radio receiver, said baseband signal being transmitted from a radio transmitter over a radio medium in the form of bursts, each of which occupies a given time slot in a number of time slots within a frame, wherein the radio medium exhibits time dispersion with limited spread of delayed signals to the received radio signal, and wherein each of the time slots includes a data part and a synchronization part which includes a known, fixed bit pattern, comprising the steps of forming a time-dependent correlation signal (r(n)) by carrying out differential correlation of the received baseband signal with the know synchronization pattern in the radio receiver, determining a time position of an extreme value of the time-dependent correlation signal, calculating a complex argument of the time-dependent correlation signal for the time position of the extreme value, and estimating the frequency error with respect to a sampling rate of the baseband signal received in the radio receiver from the complex argument.

5. A method for synchronizing a radio reciver with a radio signal transmitted form a radio transmitter, said method comprising the steps of:

receiving a baseband signal in a plurality of time slots in a frame, each of said time slots including a synchronization portion with a known bit pattern and a data portion;

correlating said baseband signal with a known synchronization pattern to form a differential signal; and

detecting a time position of said synchronization portion of the baseband signal form a magnitude of said differential signal.