Wireless communications system

• US 5,101,406 A
• Filed: 08/28/1989
• Issued: 03/31/1992
• Est. Priority Date: 08/24/1989
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Telesystems SLW, Inc. (Zebra Technologies Corporation)
• Inventors: Messenger, Steven
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Chin, Wellington
• Application Number:
  US07/398,928
• Time in Patent Office: 946 Days
• Field of Search: 370/94.1, 370/94.2, 370/94.3, 370/95.1, 370/95.3, 370/18, 375/1, 375/25, 375/26, 375/44, 375/45, 375/52, 455/1
• US Class Current: 370/349
• CPC Class Codes: H04B 1/69 Spread spectrum techniques
• CPC Class Codes: H04J 13/16 Code allocation
• CPC Class Codes: Y10S 370/913 Wireless or radio

Abstract

A wireless packet communication system is operable in a frequency band occupied by other transmission sources. The system includes a base station and several remote stations. Each remote station has a transceiver for transmitting and receiving data packets on electromagnetic carriers. The carrier frequency of the transceiver is selected in a pseudorandom manner from a predetermined set of carrier frequencies prior to transmission of each packet or in response to detection of transmission errors. Each carrier frequency may be associated with a unique pseudorandom noise code used to spread spectrum encode packets. The base station has a number of transceivers which operate simultaneously at the different carrier frequencies and which generate different noise codes for spread spectrum encoding and decoding. The base station records data for each remote station identifying the transceiver which last received a data packet and transmits packets addressed to each remote station with the identified transceiver.

Claims

1. A packet communication system comprising:

a base station;

a plurality of remote stations;

each of the remote stations comprising

(a) means for selecting a different encoding algorithm at intervals from among a plurality of predetermined encoding algorithms,

(b) means for transmitting data packets through air to the base station, the transmitting means comprising encoding means adapted to encode data packets according to any one of the predetermined encoding algorithms and controlled by the selecting means to encode each data packet transmitted to the base station according to the currently selected encoding algorithm,

(c) means for inserting into each data packet transmitted from the remote station an indicator identifying the remote station, and

(d) means for receiving data packets transmitted through air to the remote station, the receiving means comprising decoding means adapted to decode packets encoded according to any one of the predetermined encoding algorithms and controlled by the selecting means to decode any currently received data packet according to a decoding algorithm complementary to the currently selected encoding algorithm;

the base station comprising

(e) means defining a plurality of receiving channels operating simultaneously to receive any data packet transmitted through air to the base station, each receiving channel comprising means for decoding received data packets according to a predetermined decoding algorithm, the decoding algorithm associated with each receiving channel being complementary to a different one of the predetermined encoding algorithms,

(f) means cooperating with the receiving channels and responsive to indicators in data packets received by the receiving channels for recording with respect to each of the remote stations data identifying the encoding algorithm according to which a data packet last received from the remote station was encoded, and

(g) means for transmitting data packets through air to the remote stations, the transmitting means of the base station comprising encoding means adapted to encode any data packet transmitted to the remote stations according to any one of the predetermined encoding algorithms and responsive to the recording means to encode any data packet addressed to any particular one of the remote stations according to the encoding algorithm identified by the data recorded with respect to the particular remote station.

2. The packet communication system of claim 1 in which the selection means of each of the remote stations are adapted to select an encoding algorithm from among the predetermined encoding algorithms in a pseudorandom manner prior to transmission of each data packet transmitted from the remote station associated with the selection means.

3. The packet communication system of claim 1 in which:

each of the remote stations comprises means for detecting errors in transmission of data packets between the remote station and the base station;

the selection means of each of the remote stations are adapted to change the currently selected encoding algorithm to another of the predetermined encoding algorithms in response to detection of the transmission errors by the detecting means of the associated remote station.

4. The packet communication system of claim 1 in which the encoding means of the base station and of each of the remote stations are adapted to encode data packets onto electromagnetic carriers and in which each of the predetermined encoding algorithms is associated with a different predetermined carrier frequency.

5. The packet communication system of claim 4 in which the encoding means of the base station and of each of the remote stations are adapted to spread spectrum encode data packets by combining the packets with pseudorandom noise codes, and each of the predetermined encoding algorithms comprises spread spectrum encoding data packets with a different one of a plurality of predetermined pseudorandom noise codes prior to encoding onto an electromagnetic carrier.

6. The packet communication system of claim 5 in which:

the encoding means of each of the remote stations comprise means for generating any one of the plurality of predetermined pseudorandom noise codes, each of the pseudorandom noise codes corresponding to a different one of the predetermined carrier frequencies, and comprise means for direct sequence spread spectrum encoding each data packet transmitted by the remote station with the pseudorandom noise code corresponding to the carrier frequency of the currently selected encoding algorithm of the remote station;

the encoding means of the base station comprise means for generating any one of the plurality of predetermined pseudorandom noise codes and comprise means for direct sequence spread spectrum encoding each data packet transmitted by the base station with the pseudorandom noise code corresponding to the frequency of the electromagnetic carrier onto which the data packet is encoded by the encoding means of the base station;

the decoding means of each of the remote stations comprise means for direct sequence spread spectrum decoding data packets with the pseudorandom noise code corresponding to the carrier frequency of the currently selected encoding algorithm of the remote station;

each of the decoding means of the receiving channels of the base station decode received packets encoded onto a different one of the predetermined carrier frequencies and comprise means for direct sequence spread spectrum decoding data packets with the pseudorandom noise code corresponding to the different one of the carrier frequencies.

7. The packet communication system of claim 1 in which:

the encoding means of the base station and of each of the remote stations are adapted to spread spectrum encode data packets by combining the data packets with pseudorandom noise codes;

each of the predetermined encoding algorithms comprises direct sequence spread spectrum encoding data packets by combining the packets with a different predetermined pseudorandom noise code that is associated with the encoding algorithm, the predetermined pseudorandom noise codes associated with at least one of the predetermined encoding algorithms being shorter than the pseudorandom noise code associated with another of the predetermined encoding algorithms;

each of the remote stations comprises means for detecting errors in transmission of data packets between the remote station and the base station;

the selection means of each of the remote stations are adapted at intervals to select one of the predetermined encoding algorithms associated with a relatively short pseudorandom noise code and thereafter to select another of the predetermined algorithms associated with a relatively lone pseudorandom noise code in response to detection of transmission errors.