# US 7,466,684 B2 · Frame synchronization for a mobile communication system

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- Number: US 7,466,684 B2
- Document ID: US7466684B2
- Status: Granted
- Kind: B2
- Application number: 10/977,234
- Filed: 2004-10-28
- Published: 2005-07-14
- Granted: 2008-12-16
- Earliest claimed: 2003-10-28
- Assignees: LG Electronics Inc.
- Inventors: Seok-Il Chang
- Web page: https://patentgrep.com/patent/US7466684B2

## CPC

- H04B 7/2681: {Synchronisation of a mobile station with one base station}
- H04B 1/70735: {Code identification (H04B1/7083 takes precedence)}
- H04W 56/0085: {detecting a given structure in the signal}
- H04J 3/0605: {Special codes used as synchronising signal}
- H04L 7/042: {Detectors therefor, e.g. correlators, state machines (digital correlators in general G06F17/15)}
- H04B: TRANSMISSION
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

Methods and system for frame synchronization for a mobile communication system is disclosed. A downlink synchronization signal is detected. Multiple sub-frames on the basis of the detected synchronization signal are stored. An optimum position of a midamble sequence is detected using a correlation in accordance with sub-frames. A phase sequence of sub-frames is calculated by using a correlation value at the optimum position of the midamble sequence and a maximum correlation value of a synchronization signal. A frame synchronization is obtained on the basis of a phase position of a sub-frame. The frame synchronization is periodically updated.

## Claims

### Claim 1

A method to synchronize frames for establishing a connection in a mobile communication system, the method comprising:
providing a synchronization signal having a pre-determined number of sub-frames;
providing a midamble sequence for correlating communication in a connection;
calculating a first phase sequence using an optimum position for the midamble sequence based on the predetermined number of sub-frames and an optimum position for the synchronization signal based on the predetermined number of sub-frames;
providing a second phase sequence comprising a defined phase sequence;
calculating a maximum correlation value for a phase position of the pre-determined number of sub-frames using the first phase sequence and the second phase sequence; and
obtaining frame synchronization using the maximum correlation value of the phase position.

### Claim 2 (depends on 1)

The method of claim 1, wherein the midamble sequence includes a midamble of a first time slot of an arbitrary one of the predetermined number of sub-frames.

### Claim 3 (depends on 1)

The method of claim 1, further comprising inputting by a user of the mobile communication system the pre-determined number of sub-frames.

### Claim 4 (depends on 1)

The method of claim 1, wherein the pre-determined number of sub-frames is 4 and the pre-determined number of sub-frames are successive.

### Claim 5 (depends on 1)

The method of claim 1, wherein the optimum position for the midamble sequence and the optimum position for the synchronization signal are determined by:
storing the midamble sequence;
calculating a correlation value between a defined transmission training sequence and the stored midamble sequence; and
detecting a position of the stored midamble sequence having a maximum correlation value.

### Claim 6 (depends on 1)

The method of claim 1, wherein calculating the first phase sequence further comprises:
compensating for a phase shift of the synchronization signal from the optimum position by as much as a phase of the midamble sequence of the optimum position;
performing a compensation process for each of the pre-determined number of sub-frames; and
generating the first phase sequence by arranging phases compensated for every sub-frame.

### Claim 7 (depends on 1)

The method of claim 1, wherein the second phase sequence comprises information indicating a synchronization position of a frame.

### Claim 8

A frame synchronization method for establishing connection and for receiving signals from a first terminal to a second terminal of a mobile communication system, the method comprising:
detecting a synchronization signal having a plurality of sub-frames transmitted from the first terminal to the second terminal, each sub-frame having a midamble sequence;
storing successive sub-frames of the plurality of sub-frames at the second terminal, each of the stored sub-frames having a frame number;
detecting an optimum position of a midamble sequence based on a frame number from the stored sub-frames;
calculating a phase sequence using a correlation value of the optimum position of the midamble sequence based on the stored sub-frames and a correlation value of the synchronization signal based on the stored plurality of sub-frames;
obtaining frame synchronization on the basis of a phase position of a stored sub-frame having a maximum correlation value calculated by periodically correlating the calculated phase sequence and a defined phase sequence.

### Claim 9 (depends on 8)

The method of claim 8, wherein detecting the optimum position of the midamble sequence further comprises:
calculating a correlation value between an arbitrary receiving sequence having a predetermined length and a transmission midamble sequence according to the number of the stored sub-frame; and
detecting a position along the arbitrary receiving sequence having the maximum correlation value corresponding to the optimum position for the midamble sequence.

### Claim 10 (depends on 9)

The method of claim 9 wherein the mobile communication system includes a transmitter and a receiver and the transmission midamble sequence is a sequence recognized by the transmitter and the receiver.

### Claim 11 (depends on 10)

The method of claim 10 wherein the correlation value of the synchronization signal is a maximum correlation value between the synchronization signal detected by each sub-frame and a transmission synchronization signal.

### Claim 12 (depends on 11)

The method of claim 11 wherein the transmission synchronization signal is a signal recognized by the transmitter and the receiver.

### Claim 13 (depends on 10)

The method of claim 10 wherein the transmission sequence includes starting positional information for decoding of a P-CCPCH.

### Claim 14

A mobile communication device for managing messages received from and transmitted to another user by a user of the mobile communication device, the mobile communication device comprising:
an RF module comprising a transmitter to send the transmitted messages from a user and a receiver for receiving messages from another user;
means for storing a predetermined number of successive sub-frames;
means for detecting an optimum position of a midamble sequence by sub-frames;
means for detecting an optimum position of a synchronization signal by sub-frames;
means for calculating a phase sequence by using the optimum position of the midamble sequence and the optimum position of the synchronization signal by sub-frames;
means for calculating a maximum correlation value between the phase sequence and a defined phase sequence; and
means for obtaining a frame synchronization on the basis of a phase position of a sub-frame having the maximum correlation value.

### Claim 15 (depends on 14)

The device of claim 14, wherein the midamble sequence comprises a midamble of a first time slot of an arbitrary one of the predetermined number of sub-frames.

### Claim 16 (depends on 14)

The device of claim 14, wherein the pre-determined number of sub-frames are input by a user of the mobile communication device.

### Claim 17 (depends on 14)

The device of claim 14, wherein the predetermined number of sub-frames is 4.

### Claim 18 (depends on 14)

The device of claim 14, wherein detecting the optimum position of the midamble sequence further comprises:
calculating a correlation value between a defined transmission midamble sequence and a stored midamble sequence; and
detecting a position of the midamble sequence having a maximum correlation value.

### Claim 19

A network for radio communication in a mobile communication system, the network comprising:
a transmitter for transmitting a communication signal to a receiver;
means for detecting a synchronization signal having a plurality of sub-frames transmitted from a first terminal to a second terminal;
means for storing successive sub-frames of the plurality of sub-frames at the second terminal, each of the stored sub-frames having a frame number;
means for detecting an optimum position of a midamble sequence based on a frame number from the stored sub-frames;
means for calculating a phase sequence using a correlation value of the optimum position of the midamble sequence based on the stored sub-frames and a correlation value of the synchronization signal based on the stored sub-frames;
means for obtaining frame synchronization of the transmitted signal on the basis of a phase position of a stored sub-frame having a maximum correlation value calculated by periodically correlating the calculated phase sequence and a defined phase sequence.

### Claim 20 (depends on 19)

The network of claim 19, wherein the means for detecting the optimum position of the midamble sequence:
calculates a maximum correlation value between an arbitrary receiving sequence having a predetermined length and a transmission midamble sequence according to the number of the stored sub-frame; and
detects a position along the arbitrary receiving sequence corresponding to the maximum correlation value as the optimum position for the midamble sequence.

### Claim 21 (depends on 19)

The network of claim 19, wherein the transmission midamble sequence is a sequence recognized by the transmitter and the receiver.

### Claim 22 (depends on 19)

The network of claim 19, wherein the correlation value of the synchronization signal is a maximum correlation value between the synchronization signal detected by each sub-frame and a transmission synchronization signal.

### Claim 23 (depends on 22)

The network of claim 22, wherein the transmission synchronization signal is a signal recognized by the transmitter and the receiver.