Round trip delay adjustment in multipoint-to-point communication using orthogonal frequency division multiplexing

• US 7,426,177 B2
• Filed: 03/16/2007
• Issued: 09/16/2008
• Est. Priority Date: 02/06/1995
• Status: Expired due to Fees

• Current Assignee: HTC Corporation
• Original Assignee: ADC Telecommunications Incorporated (TE Connectivity Limited)
• Inventors: Geile, Michael J., Brede, Jeffrey
• Primary Examiner(s): Jain, Raj K.
• Application Number:
  US11/687,383
• Publication Number:
  US 20070162946A1
• Time in Patent Office: 550 Days
• Field of Search: None
• US Class Current: 370/206
• CPC Class Codes: G06F 17/14 Fourier, Walsh or analogous domain transformations , e.g. Laplace, Hilbert, Karhunen-Loeve, transforms for correlation function computation G06F17/156; spectrum analysers G01R23/16
• CPC Class Codes: G06F 17/142 Fast Fourier transforms, e.g. using a Cooley-Tukey type algorithm
• CPC Class Codes: H03M 13/1515 Reed-Solomon codes
• CPC Class Codes: H03M 13/356 Unequal error protection [UEP]
• CPC Class Codes: H04B 10/272 Star-type networks or tree-type networks
• CPC Class Codes: H04H 20/69 Optical systems
• CPC Class Codes: H04H 20/77 using carrier waves
• CPC Class Codes: H04H 20/78 CATV [Community Antenna Television] systems
• CPC Class Codes: H04H 20/79 using downlink of the CATV systems, e.g. audio broadcast via CATV network
• CPC Class Codes: H04H 20/80 having frequencies in two or more frequency bands, e.g. medium wave and VHF
• CPC Class Codes: H04H 60/11 Arrangements for counter-measures when a portion of broadcast information is unavailable
• CPC Class Codes: H04H 60/86 accessed over CATV networks
• CPC Class Codes: H04H 60/96 CATV systems for accessing the Internet H04H60/86
• CPC Class Codes: H04H 60/97 using uplink of the CATV systems
• CPC Class Codes: H04J 14/0298 with sub-carrier multiplexing [SCM]
• CPC Class Codes: H04J 3/14 Monitoring arrangements for SDH/SONET rings H04J3/085
• CPC Class Codes: H04K 1/00 Secret communication
• CPC Class Codes: H04K 3/226 Selection of non-jammed channel for communication spectrum sharing arrangements H04W16/14; selection of wireless resources by user or terminal H04W72/02
• CPC Class Codes: H04K 3/255 based on redundancy of transmitted data, transmission path or transmitting source
• CPC Class Codes: H04L 1/004 by using forward error control H04L1/0618 takes precedence; coding, decoding or code conversion, for error detection or correction H03M13/00
• CPC Class Codes: H04L 1/0045 : Arrangements at the receiver end
• CPC Class Codes: H04L 1/0057 : Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/0071 : Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/24 : Testing correct operation
• CPC Class Codes: H04L 12/10 : Current supply arrangements
• CPC Class Codes: H04L 12/12 : Arrangements for remote connection or disconnection of substations or of equipment thereof
• CPC Class Codes: H04L 12/2801 : Broadband local area networks
• CPC Class Codes: H04L 12/44 : Star or tree networks
• CPC Class Codes: H04L 2001/0093 : Point-to-multipoint
• CPC Class Codes: H04L 2027/0036 : using a recovered symbol clock
• CPC Class Codes: H04L 2027/0057 : quadrature phase
• CPC Class Codes: H04L 2027/0067 : Phase error detectors
• CPC Class Codes: H04L 25/03866 : using scrambling
• CPC Class Codes: H04L 27/2601 : Multicarrier modulation systems
• CPC Class Codes: H04L 27/2614 : Peak power aspects
• CPC Class Codes: H04L 27/2631 : with polyphase implementation
• CPC Class Codes: H04L 27/2634 : Inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators in combination with other circuits for modulation
• CPC Class Codes: H04L 27/2647 : Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 27/2652 : with polyphase implementation
• CPC Class Codes: H04L 27/26524 : Fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators in combination with other circuits for demodulation
• CPC Class Codes: H04L 27/2654 : Filtering per subcarrier, e.g. filterbank multicarrier [FBMC]
• CPC Class Codes: H04L 27/2655 : Synchronisation arrangements
• CPC Class Codes: H04L 27/2657 : Carrier synchronisation
• CPC Class Codes: H04L 27/2662 : Symbol synchronisation
• CPC Class Codes: H04L 27/34 : Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
• CPC Class Codes: H04L 41/0213 : Standardised network management protocols, e.g. simple network management protocol [SNMP]
• CPC Class Codes: H04L 41/064 : involving time analysis
• CPC Class Codes: H04L 41/0896 : Bandwidth or capacity management, i.e. automatically increasing or decreasing capacities flow or congestion control using dynamic resource allocation, e.g. in-call renegotiation, H04L47/76
• CPC Class Codes: H04L 43/00 : Arrangements for monitoring or testing data switching networks
• CPC Class Codes: H04L 43/022 : by sampling
• CPC Class Codes: H04L 43/067 : using time frame reporting
• CPC Class Codes: H04L 43/0811 : by checking connectivity
• CPC Class Codes: H04L 43/0817 : by checking functioning
• CPC Class Codes: H04L 43/0823 : Errors, e.g. transmission errors
• CPC Class Codes: H04L 43/0829 : Packet loss
• CPC Class Codes: H04L 43/0847 : Transmission error
• CPC Class Codes: H04L 43/0852 : Delays
• CPC Class Codes: H04L 43/0858 : One way delays
• CPC Class Codes: H04L 43/0864 : Round trip delays
• CPC Class Codes: H04L 43/0882 : Utilisation of link capacity
• CPC Class Codes: H04L 43/16 : Threshold monitoring
• CPC Class Codes: H04L 5/0007 : the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0037 : Inter-user or inter-terminal allocation
• CPC Class Codes: H04L 5/0044 : allocation of payload
• CPC Class Codes: H04L 5/023 : Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601
• CPC Class Codes: H04L 5/14 : Two-way operation using the same type of signal, i.e. duplex
• CPC Class Codes: H04L 5/143 : for modulated signals H04L5/1469 takes precedence
• CPC Class Codes: H04L 5/1484 : operating bytewise
• CPC Class Codes: H04M 7/006 : Networks other than PSTN/ISDN providing telephone service, e.g. Voice over Internet Protocol (VoIP) , including next generation networks with a packet-switched transport layer H04L65/00 takes precedence; aspects not specific to the type of network H04M3/00; special services in those networks H04M3/42
• CPC Class Codes: H04M 9/027 : Frequency division multiplex systems
• CPC Class Codes: H04N 21/2221 : being a cable television head-end CATV in broadcast systems H04H20/78
• CPC Class Codes: H04N 21/2383 : Channel coding or modulation of digital bit-stream, e.g. QPSK modulation arrangements for detecting or preventing errors in the information received by adapting the channel coding H04L1/0009; analogue front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 21/2385 : Channel allocation H04N21/266 takes precedence; Bandwidth allocation H04N21/24 takes precedence ; allocation of channels according to the instantaneous demands of the users in time-division multiplex systems H04J3/1682; admission control, resource allocation in open networks H04L12/5692; arrangements for maintenance or administration in data switching networks involving bandwidth and capacity management H04L41/0896; negotiating bandwidth in wireless networks H04W28/16
• CPC Class Codes: H04N 21/2402 : Monitoring of the downstream path of the transmission network, e.g. bandwidth available traffic monitoring in data switching networks H04L43/00; monitoring data switching networks utilization H04L43/0876
• CPC Class Codes: H04N 21/4382 : Demodulation or channel decoding, e.g. QPSK demodulation analog front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 21/6118 : involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 21/6137 : involving transmission via a telephone network, e.g. POTS
• CPC Class Codes: H04N 21/6168 : involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 7/17309 : Transmission or handling of upstream communications
• CPC Class Codes: H04N 7/22 : Adaptations for optical transmission
• CPC Class Codes: H04W 24/00 : Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 24/08 : Testing, supervising or monitoring using real traffic
• CPC Class Codes: Y02D 30/50 : in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

Systems and methods for bidirectional communication are provided. In one embodiment, a method for aligning communications from a plurality of remote units in a multipoint-to-point orthogonal frequency division multiplexed (OFDM) communications comprises sending a first signal from a host unit to a first remote unit; receiving a second signal transmitted from the first remote unit in response to the first signal; generating at least one timing adjustment signal based at least in part on a round trip delay between the sending of the first signal and the receiving of the second signal; transmitting the timing adjustment signal to the first remote unit; wherein the timing adjustment signal instructs the first remote unit to delay OFDM transmission of data to improve alignment of multiframes at the host unit when communications are received at the host unit from the plurality of remote units.

Claims

1. A multipoint-to-point, orthogonal frequency division multiplexed (OFDM) communication system comprising:

a plurality of remote units;

a host unit that includes a demodulator;

wherein each of the remote units transmits an upstream OFDM signal using a multiple access scheme to the host unit demodulator using at least one of a plurality of orthogonal tones within an OFDM waveform, wherein upstream OFDM signals from at least two of the plurality of remote units combine to a unified OFDM waveform at the host unit;

wherein the host unit receives the upstream OFDM signals from a plurality of the remote units, the tones of the upstream signals being substantially orthogonal when received at the host unit;

wherein portions of upstream OFDM signals from at least two of the remote units arrive at the host unit at the same time;

wherein the host unit demodulator demodulates said portions;

wherein the host unit detects a round trip delay between the host unit and each remote unit; and

wherein the host unit transmits at least one timing adjustment signal to at least one of the remote units based at least in part on at least one of the detected round trip delays to assist in aligning the upstream signals received by the host unit;

wherein the host unit detects a round trip delay between the host unit and each remote unit at least one of iteratively, repeatedly, and periodically to assist in maintaining alignment of signals at the host unit within the OFDM communication system.

2. The OFDM communication system of claim 1 wherein the system is used in a hybrid fiber coax network.

3. The OFDM communication system of claim 1 wherein the system is used in a wireless network.

4. The OFDM communication system of claim 1 wherein the host unit compares the round trip delay of a first remote unit to a reference value before transmitting the timing adjustment signal.

5. The OFDM communication system of claim 1 wherein the at least one timing adjustment signal instructs the at least one remote unit to delay transmission of its upstream signal to assist in aligning its upstream signal at the host unit with upstream signals from other remote units.

6. The OFDM communication system of claim 1 wherein the at least one remote unit makes a timing adjustment based at least in part on the timing adjustment signal from the host unit, and wherein the timing adjustment assists in achieving multiframe alignment at the host unit with upstream signals from other remote units in the OFDM communication system.

7. A system comprising:

a host unit;

a plurality of remote units using a multiple access scheme to communicate at the same time with the host unit using orthogonal frequency division multiplexing (OFDM), wherein upstream OFDM signals from at least two of the plurality of remote units combine to a unified OFDM waveform at the host unit;

wherein each of the at least two of the plurality of remote units transmits the upstream OFDM signals on at least one distinct tone of a plurality of orthogonal tones within the unified OFDM waveform;

wherein portions of the upstream OFDM signals from the at least two of the plurality of remote units arrive at the host unit at the same time;

wherein the host unit determines a round trip delay between the host unit and at least one remote unit; and

wherein the host unit uses the round trip delay to send a timing instruction to at least one of the remote units to improve alignment of multiframes received at the host unit from the plurality of remote units;

wherein the host unit determines a round trip delay between the host unit and the at least one remote unit at least one of iteratively, repeatedly, and periodically to assist in maintaining alignment of multiframes received at the host unit from the plurality of remote units.

8. The system of claim 7 further comprising a distribution network wherein the host unit communicates with the plurality of remote units using the distribution network, wherein the distribution network comprises at least one of a hybrid fiber coax network and a wireless system.

9. The system of claim 7 wherein the host unit determines the round trip delay by timing the interval between transmission of a first signal from the host unit to the remote unit and receipt of a response signal at the host unit from the remote unit.

10. The system of claim 7 wherein the host unit uses the round trip delay to send a timing instruction to at least one of the remote units so that multiframes received at the host unit from the plurality of remote units are aligned.

11. A method for aligning communications from a plurality of remote units in a multipoint-to-point orthogonal frequency division multiplexed (OFDM) communications system, the method comprising:

receiving a first signal from a host unit at a first remote unit;

sending a second signal from the first remote unit based on the first signal;

wherein a time in which the second signal is sent is based on the first signal;

receiving at least one timing adjustment signal at the first remote unit from the host unit, the timing adjustment signal based on the second signal;

wherein the timing adjustment signal instructs the first remote unit to delay OFDM transmission of data based on a time of arrival of the second signal at the host unit to improve alignment of multiframes at the host unit when communications are received at the host unit from the plurality of remote units; and

wherein the first remote unit is configured to share between a plurality of remote units an Orthogonal Frequency Division Multiplexing (OFDM) waveform for communicating with the host unit;

wherein an upstream OFDM signal from the first remote unit is configured to combine with an upstream OFDM signal from at least one other remote unit to a unified OFDM waveform at the host unit;

wherein the first remote unit receives a timing adjustment signal at least one of iteratively, repeatedly, and periodically to assist in maintaining alignment of multiframes at the host unit when communications are received at the host unit from the plurality of remote units.

12. The method of claim 11 wherein each of the first signal, the second signal, and the timing adjustment signal are transmitted over a distribution network that comprises at least one of a hybrid fiber coax network and a wireless system.

13. The method of claim 11 wherein the at least one timing adjustment signal comprises a path delay adjustment value that brings a round trip path delay for the first remote unit closer to that of other remote units in the system.