Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via frequency channels
Reexamination Certificate
2000-01-06
2004-05-11
Patel, Ajit (Department: 2735)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via frequency channels
C370S486000, C370S208000, C370S210000, C370S443000, C375S260000, C375S346000, C708S403000, C708S404000
Reexamination Certificate
active
06735221
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a digital communication network system for multiple access system, in which a head-end controller (HC) sends data and medium-access control (MAC) information over a set of downstream channels to several stations, and these stations send information to the HC over a set of shared upstream channels.
The present application is related to the following applications even dated herewith: application Ser. No. 09/478,564, entitled “Filtered Multitone Transmission with Application to DSL Technologies” by inventors G. Cherubini, et al., application Ser. No. 09/478,565, entitled “Hybrid TDMA/CDMA System Based on Multitone Modulation” by inventors G. Cherubini, et al. which are incorporated herein by reference.
PRIOR ART
Digital communications network systems for multiple access in which a HC broadcasts data and MAC information over a set of downstream channels to several channels are believed to be the emerging two-way hybrid fiber/cable (HFC) systems (cf. E.g. MCNS Interim Specification “Data over Cable Interface Specifications-Radio Frequency Interface Specification” MCNS Holding, L. L. Mar. 26, 1997) as well as their wireless counterparts, i.e., multichannel multipoint distribution service (LMDS) (c.f.e.g. Honcharenko, W. et al., “Broadband Wireless Access” IEEE Comm. Mag., pp 128-135 (January 1997).
Specifically a hybrid fiber/coax (HFC) system is a point to multipoint, tree ans branch access network in the downstream direction, with downstream frequencies in the 50-860 MHz band, and a multipoint to point, bus access network in the upstream direction, with upstream frequencies in the 5-42 MHz band.
Prior-art systems include means for downstream transmission using an HC modem transmitter and station modem receiver; these systems have some technical challenges due to transmission rates in the order of 30 to 45 Mbit/s per downstream channel. However, owing to the continuous broadcast mode of downstream transmission over a channel with low distortion and high signal-to-noise ratio, (typically ≧42 dB in an HFC network by regulation) well known signal processing techniques can be applied. In the downstream direction, continuous broadcast operation is specified. The ITU J.83 recommendation defines two transmission schemes by which data rates in the range of 30-45 Mbit/s are achieved on 6 or 8 MHz channel bandwidths, with spectral efficiencies of 5-8 bits/s/Hz (cf. E.g., ITU Recommendations J.83).
In the upstream direction, implementation of physical (PHY) layer transmission and MAC layer functions pose considerable technical challenges. Firstly, because signals are transmitted in bursts, HC receivers with fast synchronization capabilities are essential. Secondly, individual station signals must be received at the HC at defined arrival times and power levels. Therefore, determination of the round-trip delay between the HC and each individual station and individual transmit power control for each station to compensate for widely varying attenuations in the upstream direction are important functions. Thirdly, the upstream channel is generally much more noisy and subject to distortion than the downstream channel. The required measurements and control actions to set upstream transmission parameters and round-trip delay compensation values are part of the registration process, which is performed when a station begins to participate in upstream transmission.
OBJECTS AND SUMMARY OF THE INVENTION
Now, the object of the present invention is a digital communication network system for multiple access with ranging and power adjustment of stations, where upstream transmission is based on multi-carrier modulation using orthogonal frequency division multiplexing (OFDM) such that transmission of a not yet registered station over a subchannel does not disturb the transmission of other stations over adjacent subchannels.
A further object of the invention is a digital communication network system specified above, which includes means at a station to send a ranging request message over a subchannel at a signal level such that said ranging request does not disturb enables a head-end controller means for detecting a ranging request message.
These objects and further advantages will be achieved according to the invention by a novel digital communication network system for multiple access with ranging and power adjustment of a station, at which a passband OFDM transmission technique yielding a high level of spectral containment of individual subchannels is employed for upstream transmission; during transmission of ranging request messages, the high level of spectral containment of individual subchannels is further increased by repetition coding, and/or by signal filtering.
According to a first general embodiment, the invention provides for a communications network system for multiple access having a head-end node and at least one station node, said system comprising a head-end controller (HC) means capable of transmitting data and medium-access control information to at least one station means, preferably a plurality of station means, over a set of downstream channels within a first frequency range, and receiving information from said plurality of station means over an upstream channel within a second frequency range, said upstream channel comprising a set of upstream subchannels, which system further comprises at least one first connection cable means for connecting said head-end controller means with at least one cable node means, and at least one second connection cable means for connecting said at least one cable node means with said plurality of stations means, wherein each of said station means including means for receiving data and medium-access control information from said head-end controller means, further including means for sending a data stream at a first signal level over at least one upstream subchannel, which station means further including means for sending at least one ranging request message to said head-end controller means over at least one upstream subchannel, said at least one ranging request message having a signal level that is lower than said first signal level of said data stream, and said at least one ranging request message being transmitted using repetition coding, so as to enable said head-end controller means for detecting said at least one ranging request message at a signal level such that said message does not disturb transmission over other upstream subchannels.
According to a second general embodiment, the invention provides for a communications network system for multiple access having a head-end node and at least one station node, said system comprising a head-end controller (HC) means capable of transmitting data and medium-access control information to at least one station means, preferably a plurality of station means, over a set of downstream channels within a first frequency range, and receiving information from said plurality of station means over an upstream channel within a second frequency range, said upstream channel comprising a set of upstream subchannels, which system further comprising at least one first connection cable means for connecting said head-end controller means with at least one cable node means, and at least one second connection cable means for connecting said at least one cable node means with said plurality of station means, wherein each of said station means including means for receiving data and medium-access control information from said head-end controller means, further including means for sending a data stream at a first signal level over at least one upstream subchannel, which station means further including means for sending at least one ranging request message to said head-end controller means over at least one upstream subchannel, said at least one ranging request message having a signal level that is lower than said first signal level of said data stream, and said at least one ranging request message being transmitted using signal filtering means, so as to enable said head-end cont
Beck Thomas A.
Herzberg Louis P.
Ho Chuong
Patel Ajit
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