Narrowband/wideband packet data communication system

• US 5,022,046 A
• Filed: 04/14/1989
• Issued: 06/04/1991
• Est. Priority Date: 04/14/1989
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Morrow, Robert K. Jr.
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US07/338,908
• Time in Patent Office: 781 Days
• Field of Search: 370/60, 370/94.1, 370/18, 375/1, 380/46, 380/49, 380/50
• US Class Current: 375/130
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 4/18 Information format or content conversion, e.g. adaptation by the network of the transmitted or received information for the purpose of wireless delivery to users or terminals
• CPC Class Codes: H04W 88/02 Terminal devices
• CPC Class Codes: H04W 88/06 adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals

Abstract

The best features of narrowband and wideband signaling are merged to provide a simple and reliable multiple-access network. This is done by transmitting the header of the packet using narrowband signaling coupled with an associated channel access protocol such as carrier-sense multiple-access. The data portion of the packet is then sent as a spread-spectrum signal with a spreading sequence that is common to all nodes in the network. The narrowband headers allow easy monitoring of channel loading and busy nodes while acting as a synchronization aid to the wideband signal. The multiple-access capability of spread-spectrum signaling increases channel throughput dramatically over a conventional narrowband-only system, and the anti-multipath feature allows increased data transmission rates on a multipath-prone channel. Common spreading sequences simplify transceiver design and allow packet broadcasting on the network.

Claims

1. A packet data communication network with a plurality of nodes, employing features of unspread and spread signaling, wherein each node comprises a processor, a data link coupled to the processor for incoming and outgoing data signals, a transmitter comprising a modulator and an RF amplifier, with the modulator coupled to receive signals from the processor and the RF amplifier coupled to receive signals from the modulator and amplify them, means for coupling the RF amplifier to antenna means for propagation, a receiver comprising an RF/IF amplifier unit and a detector, with the RF/IF amplifier unit coupled to the antenna means for receiving signals and the detector coupled between the RF/IF amplifier unit and the processor, and a sequence generator coupled to the processor, to the modulator and to the detector, to provide control signals to and from the processor, control signals to the modulator, control signals to the RF/IF amplifier unit, status signals from the detector, and status signals from the modulator, a transmit power control line from the processor to the RF amplifier;

wherein the sequence generator includes means for outputting a given non-spreading waveform on a given unspread channel for an unspread mode, and means for outputting a given long spreading sequence which is common to all nodes in the network for a spread mode;

wherein the processor includes means for placing data signals from the data link in packet form by providing a data portion for each packet and attaching thereto a preamble, header, error control encoding, and any other information required by higher system protocols;

means for checking the unspread channel for activity by the processor sensing signals from the detector for presence or absence of an unspread signal;

wherein the modulator includes means for modulating the signals from the processor under the control of the sequence generator, beginning with transmission of the header of the packet using unspread signaling coupled with a given channel access protocol with said given non-spreading waveform on the given unspread channel, followed by transmission of the data portion of the packet as a spread-spectrum signal with said given long spreading sequence, the time between the end of the unspread signal and the start of spread transmission being identical for all transmitters on the network;

means effective when a node is idle, not receiving a packet, for causing the receiver to monitor a communication channel for unspread signals, with the sequence generator producing said given non-spreading waveform, each unspread signal being checked by the processor to determine if it contains a valid packet header, which means that the signal originated within the network and that no collision of headers occurred, and if the header shows that this particular receiver is not the recipient of the packet, the receiver continues to monitor the unspread channel;

otherwise, the receiver switches to the spread mode and attempts to synchronize on the remainder of the packet;

whereby since the time between the end of the unspread header and the beginning of the spread signal is known and independent of propagation delay, the receiver can synchronize rapidly on the spread signal;

means in the processor for then converting the packet into a data format and sending it via the data link.

2. A packet data communication network according to claim 1, wherein each node further includes an unspread spectrum receiver interposed between the antenna means and the processor in order to provide a means of monitoring activity of a channel during spread signal reception periods.

3. A method of packet data communication in a network, employing features of unspread and spread signaling, comprising the following steps at a node of the network:

placing data to be transmitted in proper packet form by attaching a preamble, header, error control encoding, and any other information required by higher system protocols;

checking an unspread channel for activity by sensing the output of a receiver detector, and beginning transmission in accordance with a given unspread channel-access technique, first transmitting the packet preamble and header unspread, followed by the remainder of the packet with a sequence generator in a spread mode, the time between the end of the unspread signal and the start of spread transmission being identical for all transmitters on the network.

4. A method of packet data communication according to claim 3, which further includes decoding received signals in two steps, first when the node is idle, not receiving a packet, producing a given non-spreading waveform with the sequence generator, to monitor a communication channel for unspread signals, checking each unspread signal to determine if it contains a valid packet header, which means that the signal originated within the network and that no collision of headers occurred, if the header shows that this particular receiver is not the recipient of the packet, continuing to monitor the unspread channel, and second otherwise switching reception to the spread mode and attempting to synchronize on the remainder of the packet, then converting the packet into a data format for use.