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

• US 5,696,766 A
• Filed: 11/16/1995
• Issued: 12/09/1997
• Est. Priority Date: 06/02/1995
• Status: Expired due to Fees

• Current Assignee: Airspan Networks Inc.
• Original Assignee: DSC Communications Corp. (Nokia Corporation)
• Inventors: Cooper, Ian L., Yeung, Joemmane Chi Cheung
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Patel, Ajit
• Application Number:
  US08/558,445
• Time in Patent Office: 754 Days
• Field of Search: 370/18, 370/100.1, 370/101, 370/105.4, 370/105.5, 370/107, 370/208, 370/209, 370/320, 370/335, 370/504, 370/514, 370/515, 370/520, 455/51.1, 375/200, 375/205, 375/208, 375/209, 375/210, 375/354, 375/365, 375/367, 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
• 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:

establishing a downlink communication path from a central terminal to the subscriber terminal;

transmitting from a transmitter in the central terminal a downlink signal;

receiving at a receiver in the subscriber terminal the downlink signal;

identifying a code synchronization signal within the downlink signal;

comparing a code and phase of the code synchronization signal with a code and a phase of a slave code sequence in the subscriber terminal;

adjusting the phase of the slave code sequence to match the phase of the code synchronization signal;

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

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

3. The method of claim 2, wherein the code synchronization signal adjusts the phase of the transmitter in the subscriber terminal either forward or backward in one half increments.

12. The method of claim 1, wherein the code synchronization signal is decoded within an overhead channel of the downlink signal.

13. The method of claim 12, wherein the overhead channel is decoded in one bit of every ten bit positions of the downlink signal.

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

establishing a downlink communication path from a central terminal to the subscriber terminal;

transmitting from a transmitter in the central terminal a downlink signal;

receiving at a receiver in the subscriber terminal the downlink signal

identifying a code synchronization signal within the downlink signal;

adjusting a phase 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 transmitter in the subscriber terminal being equivalent to a phase of a receiver in the central terminal;

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

receiving the uplink signal at the receiver in the central terminal;

comparing a phase of the uplink signal to a phase of the receiver in the central terminal;

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

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

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

7. The method of claim 5, further comprising the steps of:

receiving the uplink signal at the receiver in the central terminal in phase with a phase of the receiver in the central terminal, receipt of the uplink signal matching the phase of the receiver in the central terminal indicating that a phase delay between the transmitter in the subscriber terminal and the receiver in the central terminal has been determined, determination of the phase delay indicating that an uplink communication path has been established from the subscriber terminal to the central terminal; and

transmitting the code synchronization signal having a value indicating that no further adjustments are needed to the phase of the transmitter in the subscriber terminal.

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

continuously comparing the phase of the uplink signal from the transmitter of the subscriber terminal to the phase of the receiver in the central terminal;

transmitting the code synchronization signal having a value indicating that a slight readjustment is to be made to the phase of the transmitter in the subscriber terminal in response to a change in the path delay between the transmitter in the subscriber terminal and the receiver in the central terminal.

9. The method of claim 8, wherein the code synchronization signal adjusts the phase of the transmitter in the subscriber terminal in a fine adjustment mode having one sixteenth increments of a chip period in response to changes in the path delay between the transmitter in the subscriber terminal and the receiver in the central terminal.

10. The method of claim 9, wherein the code synchronization signal adjusts the phase of the transmitter in the subscriber unit either forward or backward by one sixteenth increments.

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

establishing a downlink communication path from a central terminal to the subscriber terminal;

transmitting from a transmitter in the central terminal a downlink signal;

receiving at a receiver in the subscriber terminal the downlink signal

identifying a code synchronization signal within the downlink signal;

adjusting a phase 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 transmitter in the subscriber terminal being equivalent to a phase of a receiver in the central terminal;

monitoring the uplink communication path from the subscriber terminal to the central terminal;

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

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

a transmitter in a central terminal operable to transmit a downlink signal, the downlink signal including a code synchronization signal;

a receiver in a subscriber terminal operable to receive the downlink signal, the receiver in the subscriber terminal operable to extract the code synchronization signal from the downlink signal, the receiver operable to compare a code and phase of the code synchronization signal with a code and phase of a slave code sequence corresponding to the receiver, the receiver operable to adjust the phase of the slave code sequence such that the slave code sequence matches the phase of the code synchronization signal;

a transmitter in the subscriber terminal operable to transmit an uplink 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 a phase of the uplink signal;

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

15. The system of claim 14, wherein the code synchronization signal is decoded within an overhead channel of the downlink signal.

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

17. The system of claim 14, wherein the code synchronization signal incrementally adjusts the phase of the uplink signal either forward or backward in a coarse adjustment mode having one half increments of a chip period.

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

a transmitter in a central terminal operable to transmit a downlink signal, the downlink signal including a code synchronization signal;

a receiver in a subscriber terminal operable to receive the downlink signal, the receiver in the subscriber terminal operable to extract the code synchronization signal from the downlink signal;

a transmitter in the subscriber terminal operable to transmit an uplink 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 a phase of the uplink signal;

a receiver in the central terminal operable to receive the uplink signal, the receiver in the subscriber terminal operable to compare its receiver phase to the phase of the uplink signal to determine a match between the receiver phase and the phase of the uplink signal, the receiver in the subscriber terminal operable to set a value for the code synchronization signal in order to obtain a match of the phase of the uplink signal to the receiver phase, wherein the receiver in the central terminal continuously compares the phase of the uplink signal to the receiver phase, the receiver altering the code synchronization signal in response to the comparison to maintain the match between the phase of the uplink signal and the receiver phase.

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

20. A system for synchronizing communications in wireless communications system, comprising:

a transmitter in a central terminal operable to transmit a downlink signal, the downlink signal including a code synchronization signal;

a receiver in a subscriber terminal operable to receive the downlink signal, the receiver in the subscriber terminal operable to extract the code synchronization signal from the downlink signal;

a transmitter in the subscriber terminal operable to transmit an uplink 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 a phase of the uplink signal;

a receiver in the central terminal operable to receive the uplink signal, the receiver in the subscriber terminal operable to compare its receiver phase to the phase of the uplink signal to determine a match between the receiver phase and the phase of the uplink signal, the receiver in the subscriber terminal operable to set a value for the code synchronization signal in order to obtain a match of the phase of the uplink signal to the receiver phase, wherein the receiver in the central terminal measures a combined power of the phase of the uplink signal 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 uplink signal and the phase of the receiver in the central terminal.

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

a receiver operable to receive a downlink signal, the downlink signal including a code synchronization signal, the receiver operable to extract the code synchronization signal from the downlink signal, the receiver operable to compare a code and phase of the code synchronization signal with a code and phase of a slave code sequence corresponding to the receiver, the receiver operable to adjust the phase of the slave code sequence such that the slave code sequence matches the phase of the code synchronization signal;

a transmitter operable to transmit an uplink signal, the transmitter operable to receive the code synchronization signal, the code synchronization signal operable to adjust a phase of the uplink signal.

22. The subscriber terminal of claim 21, wherein the code synchronization signal is decoded within an overhead channel of the downlink signal.

23. The subscriber terminal of claim 22, wherein the overhead channel is decoded into one bit of every ten bit positions of the downlink signal.

24. The subscriber terminal of claim 21, wherein the code synchronization signal incrementally adjusts the phase of the uplink signal either forward or backward in a coarse adjustment mode having one half increments of a chip period.

25. The subscriber terminal of claim 21, wherein the code synchronization signal incrementally adjusts the phase of the uplink signal either forward or backward in a fine adjustment mode having one sixteenth increments of a chip period.