Apparatus and method of synchronizing a transmitter in a subscriber terminal of a wireless communications system

• US 6,028,868 A
• Filed: 08/08/1997
• Issued: 02/22/2000
• Est. Priority Date: 06/02/1995
• Status: Expired due to Fees

• Current Assignee: Airspan Networks Inc.
• Original Assignee: Airspan Communications Corporation
• Inventors: Cooper, Ian L., Yeung, Joemmane Chi Cheung
• Primary Examiner(s): Patel, Ajit
• Application Number:
  US08/907,734
• Time in Patent Office: 928 Days
• Field of Search: 370/320, 370/335, 370/342, 370/441, 370/503, 370/514, 370/515, 370/208, 370/209, 370/504, 370/520, 375/200, 375/208-210, 375/354, 375/367, 375/365, 375/366
• US Class Current: 370/515
• CPC Class Codes: G06F 9/546 Message passing systems or structures, e.g. queues
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/70735 Code identification H04B1/7083 takes precedence
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 1/7077 Multi-step acquisition, e.g. multi-dwell, coarse-fine or validation
• CPC Class Codes: H04B 1/70775 Multi-dwell schemes, i.e. multiple accumulation times
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop
• CPC Class Codes: H04B 2001/70706 using a code tracking loop, e.g. a delay locked loop
• CPC Class Codes: H04B 2201/70702 Intercell-related aspects
• CPC Class Codes: H04B 2201/70706 with means for reducing the peak-to-average power ratio
• CPC Class Codes: H04B 2201/7071 with dynamic control of receiver resources
• CPC Class Codes: H04B 2201/70711 with modular structure
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04L 12/66 Arrangements for connecting between networks having differing types of switching systems, e.g. gateways
• CPC Class Codes: H04L 2209/80 Wireless network architectures or network communication protocols for wireless network security H04W12/00
• CPC Class Codes: H04L 41/0226 Mapping or translating multiple network management protocols
• CPC Class Codes: H04L 41/0233 Object-oriented techniques, for representation of network management data, e.g. common object request broker architecture [CORBA]
• CPC Class Codes: H04L 41/0816 the condition being an adaptation, e.g. in response to network events
• CPC Class Codes: H04L 41/22 : comprising specially adapted graphical user interfaces [GUI]
• CPC Class Codes: H04L 43/00 : Arrangements for monitoring or testing data switching networks
• CPC Class Codes: H04L 69/08 : Protocols for interworking; Protocol conversion
• CPC Class Codes: H04L 69/14 : Multichannel or multilink protocols
• CPC Class Codes: H04L 9/065 : Encryption by serially and continuously modifying data stream elements, e.g. stream cipher systems, RC4, SEAL or A5/3
• CPC Class Codes: H04L 9/12 : Transmitting and receiving encryption devices synchronised or initially set up in a particular manner
• CPC Class Codes: H04L 9/40 : Network security protocols
• CPC Class Codes: H04Q 11/04 : for time-division multiplexing H04Q11/0001 takes precedence
• CPC Class Codes: H04Q 2213/1305 : Software aspects
• CPC Class Codes: H04Q 2213/13093 : Personal computer, PC
• CPC Class Codes: H04Q 2213/13098 : Mobile subscriber
• CPC Class Codes: H04Q 2213/13109 : Initializing, personal profile
• CPC Class Codes: H04Q 2213/1319 : Amplifier, attenuation circuit, echo suppressor
• CPC Class Codes: H04Q 2213/13196 : Connection circuit/link/trunk/junction, bridge, router, gateway
• CPC Class Codes: H04Q 2213/13199 : Modem, modulation
• CPC Class Codes: H04Q 2213/13202 : Network termination [NT]
• CPC Class Codes: H04Q 2213/13204 : Protocols
• CPC Class Codes: H04Q 2213/13216 : Code signals, frame structure
• CPC Class Codes: H04Q 2213/13292 : Time division multiplexing, TDM
• CPC Class Codes: H04Q 2213/13296 : Packet switching, X.25, frame relay
• CPC Class Codes: H04Q 2213/13298 : Local loop systems, access network
• CPC Class Codes: H04Q 2213/13299 : Bus
• CPC Class Codes: H04Q 2213/13335 : Simulation, emulation
• CPC Class Codes: H04Q 2213/13376 : Information service, downloading of information, 0800/0900 services
• CPC Class Codes: H04W 52/04 : TPC
• CPC Class Codes: H04W 52/08 : Closed loop power control
• CPC Class Codes: H04W 52/24 : using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/52 : using AGC [Automatic Gain Control] circuits or amplifiers
• CPC Class Codes: H04W 56/00 : Synchronisation arrangements
• CPC Class Codes: H04W 84/14 : WLL [Wireless Local Loop]; RLL [Radio Local Loop]

Abstract

A wireless telecommunications system (1) includes a central terminal (10) for transmitting and receiving radio frequency signals to and from a subscriber terminal (20). A downlink communication path is established from a transmitter (200) of the central terminal (10) to a receiver (202) of the subscriber terminal (20). A downlink signal (212) is transmitted from the transmitter (200) to the receiver (202) during setup and operation of the wireless telecommunications system (1). The downlink signal (212) includes an overhead channel (224) having a code synchronization signal (234). The code synchronization signal (234) is capable of adjusting a phase of a transmitter (204) in the subscriber terminal (20). A receiver (206) in the central terminal (10) monitors an uplink signal (214) transmitted by the transmitter (204) in the subscriber terminal and provides changes to the code synchronization signal (234) such that the transmitter (204) is synchronized to the receiver (206). Synchronization of the transmitter (204) in the subscriber terminal (20) to the receiver (206) in the central terminal (10) facilitates establishment of an uplink communication path from the subscriber terminal (20) to the central terminal (10).

Claims

1. A method of synchronizing a transmitter in a subscriber terminal of a wireless telecommunications system, comprising the steps of:

transmitting an uplink signal;

receiving a downlink signal, the downlink signal including a code synchronization signal having a value in response to a phase of the uplink signal;

identifying the code synchronization signal within the downlink signal;

adjusting a phase of the uplink signal in response to the code synchronization signal;

inserting an overhead channel into the downlink signal, the overhead channel including the code synchronization signal, wherein the code synchronization signal is a multi-bit value specifying forward or backward incremental adjustments of the phase of the uplink signal, the multi-bit value enabling incremental adjustments of more than one size to be specified.

2. The method of claim 1, wherein the code synchronization signal adjusts the phase of the uplink signal in a coarse adjustment mode having one half increments of a chip period.

3. The method of claim 1, further comprising the steps of:

receiving the uplink signal at a receiver;

comparing a phase of the uplink signal to a phase of the receiver;

transmitting the code synchronization signal in response to the phase of the uplink signal not matching the phase of the receiver, the code synchronization signal having a value indicating that a further adjustment is to be made to the phase of the uplink signal.

4. The method of claim 3, wherein the comparing step includes measuring a combined power of the phase of the uplink signal and the phase of the receiver and determining a maximum combined power value that indicates a match between the phase of the uplink signal and the phase of the receiver.

5. A method according to claim 4, wherein the step of measuring the combined power comprises performing a correlation operation between PN codes of the uplink signal and a receiver reference signal.

6. The method of claim 4, further comprising the steps of:

receiving the uplink signal at a receiver in phase with a phase of the receiver, receipt of the uplink signal matching the phase of the receiver indicating that a phase delay has been determined, determination of the phase delay indicating that an uplink communication path has been established; and

transmitting the code synchronization signal having a values indicating that no further adjustments are needed to the phase of the uplink signal.

7. The method of claim 6, further comprising the steps of:

continuously comparing the phase of the uplink signal to the phase of the receiver;

transmitting the code synchronization signal having a value indicating that a slight readjustment is to be made to the phase of the uplink signal in response to a change in the path delay.

8. The method of claim 7, wherein the code synchronization signal adjusts the phase of the uplink signal in a fine adjustment mode having one sixteenth increments of a chip period in response to changes in the path delay.

9. The method of claim 8, wherein the code synchronization signal adjusts the phase of the uplink signal either forward or backward by one sixteenth increments.

10. The method of claim 6, further comprising the steps of:

monitoring the uplink communication path;

resetting the phase of the uplink signal to a previous value in response to an interruption in the uplink communication path in order to facilitate reestablishment of the uplink communication path.

11. The method of claim 6, wherein the overhead channel is decoded in one bit of every ten bit positions of the downlink signal.

12. A system for synchronizing communications in a wireless communication system, comprising:

a transmitter in a central terminal operable to transmit a downlink signal;

a receiver in a subscriber terminal operable to receive the downlink signal;

a transmitter in the subscriber terminal operable to transmit an uplink signal, the downlink signal including a code synchronization signal having a value determined in response to a phase of the transmitter in the subscriber terminal, the receiver in the subscriber terminal operable to extract the code synchronization signal from the downlink signal, the transmitter in the subscriber terminal operable to receive the code synchronization signal from the receiver in the subscriber terminal, the code synchronization signal operable to adjust the phase of the transmitter in the subscriber terminal;

a receiver in the central terminal operable to receive the uplink signal, the receiver in the central terminal operable to compare its phase to the phase of the transmitter in the subscriber terminal in response to the uplink signal to determine a match between the phase of the receiver in the central terminal and the phase of the transmitter in the subscriber terminal, the receiver in the central terminal operable to set a value for the code synchronization signal used to adjust the phase of the transmitter in the subscriber terminal in order to obtain a match of the phase of the receiver in the central terminal with the phase of the transmitter in the subscriber terminal.

13. The system of claim 12, further comprising;

means for inserting an overhead channel into the downlink signal, the overhead channel including the code synchronization signal.

14. The system of claim 13, wherein the code synchronization signal is a multi-bit value specifying forward or backward incremental adjustments of the phase of the transmitter in the subscriber terminal, the multi-bit value enabling incremental adjustments of more than one size to be specified.

15. The system of claim 13, wherein the overhead channel is decoded in one bit of every ten bit positions of the downlink signal.

16. The system of claim 12, wherein the code synchronization signal incrementally adjusts the phase of the transmitter in the subscriber terminal either forward or backward in a coarse adjustment mode having one half increments of a chip period.

17. The system of claim 12, wherein the receiver in the central terminal continuously compares the phase of the transmitter in the subscriber terminal to a phase of the receiver in the central terminal, the receiver in the central terminal altering the code synchronization signal in response to the comparison to maintain the match between the phase of the transmitter in the subscriber terminal and the phase of the receiver in the central terminal.

18. The system of claim 17, wherein the code synchronization signal incrementally adjusts the phase of the transmitter in the subscriber terminal either forward or backward in a fine adjustment mode having one sixteenth increments of a chip period.

19. The system of claim 12, wherein the receiver in the central terminal measures a combined power of the phase of the transmitter in the subscriber terminal and the phase of the receiver in the central terminal, the receiver in the central terminal determining a maximum combined power value that indicates a match between the phase of the transmitter in the subscriber terminal and the phase of the receiver in the central terminal.

20. A subscriber terminal in a wireless telecommunications system, comprising:

a transmitter for transmitting an uplink signal to a central terminal;

a receiver operable to receive a downlink signal, the downlink signal including a code synchronization signal having a value determined in response to a phase of the uplink signal, the receiver operable to extract the code synchronization signal from the downlink signal;

the transmitter operable to receive the code synchronization signal from the receiver and the transmitter operable to adjust a phase of the transmitter in response to the code synchronization signal;

means for inserting an overhead channel into the downlink signal, the overhead channel including the code synchronization signal, wherein the code synchronization signal is a multi-bit value specifying forward or backward incremental adjustments of the phase of the transmitter, the multi-bit value enabling incremental adjustments of more than one size to be specified.

21. The subscriber terminal of claim 20, wherein the overhead channel is decoded into one bit of every ten bit positions of the downlink signal.

22. The subscriber terminal of claim 20, wherein the code synchronization signal incrementally adjusts the phase of the transmitter either forward or backward in a coarcse adjustment mode having one half increments of a chip period.

23. The subscriber terminal of claim 20, wherein the code synchronization signal incrementally adjusts the phase of the transmitter either forward or backward in a fine adjustment mode having one sixteenth increments of a chip period.

24. A method of synchronizing a transmitter in a subscriber terminal of a wireless telecommunications system, comprising:

establishing a downlink communication path from a central terminal to the subscriber terminal by adjusting a phase of a slave code sequence of a receiver in the subscriber terminal to match a phase of a downlink signal from the central terminal;

transmitting an uplink signal from a transmitter in the subscriber terminal;

transmitting the downlink signal from a transmitter in the central terminal, the downlink signal including a code synchronization signal having a value determined as a result of comparing the phase of the uplink signal with phase of receiver in the central terminal;

receiving the downlink signal at the receiver in the subscriber terminal and identifying the code synchronization signal within the downlink signal;

adjusting a phase of a slave code sequence of the transmitter in the subscriber terminal in response to the code synchronization signal;

establishing an uplink communication path in response to the phase of the slave code sequence of the transmitter in the subscriber terminal being equivalent to the phase of the receiver in the central terminal.