Demodulation method and apparatus in high-speed time division multiplexed packet data transmission

• US 6,515,976 B1
• Filed: 04/06/1998
• Issued: 02/04/2003
• Est. Priority Date: 04/06/1998
• Status: Expired due to Term

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Dutta, Santanu, Dent, Paul W.
• Primary Examiner(s): NGUYEN, STEVEN H D
• Application Number:
  US09/055,491
• Time in Patent Office: 1,765 Days
• Field of Search: 370/312, 370/313, 370/314, 370/315, 370/316, 370/321, 370/324, 370/326, 370/336, 370/337, 370/345, 370/442, 370/311, 375/136, 375/137, 375/133, 375/134, 375/143, 375/147, 375/149, 375/150, 375/151, 375/152, 375/153, 375/324, 375/338, 375/340, 375/202, 375/344, 455/32.1, 455/67.1, 455/38.3, 455/132, 455/134, 455/135, 455/343, 455/574, 455/182.3, 342/357.16, 342/385, 329/311, 329/312, 329/334, 329/336, 340/7.32, 340/7.33, 340/7-4-, 340/7-2-
• US Class Current: 370/336
• CPC Class Codes: H04B 7/2125 Synchronisation
• CPC Class Codes: H04J 3/0605 Special codes used as synchronising signal
• CPC Class Codes: H04L 2007/047 using a sine signal or unmodulated carrier
• CPC Class Codes: H04L 7/0004 Initialisation of the receiver H04L7/0075 and H04L7/10 take precedence

Abstract

A method and apparatus for demodulating a communication signal transmitted at a first rate is provided, wherein the communication signal includes a plurality of addresses and corresponding data packets. The demodulating method includes the steps of receiving the communication signal at a user terminal, identifying which of the plurality of data packets are destined to the receiving user terminal, and demodulating, at a second rate less than the first rate, only the data packets identified as being destined to the receiving user terminal.

Claims

1. A method of demodulating a communication signal transmitted at a first rate, the communication signal including a plurality of addresses, corresponding data packets, a preamble having a first continuous wave segment followed by a synchronization word, and a second continuous wave segment following the plurality of addresses and corresponding data packets, said demodulating method comprising:

receiving the communication signal at a user terminal;

detecting a presence of energy in the first continuous wave segment of the preamble, said detection of energy indicating receipt of the communication signal at the user terminal;

filtering the synchronization word with a matched filter at the receiving user terminal to confirm the detection of energy in the first continuous wave segment;

writing the received communication signal to a memory in the receiving user terminal;

terminating the step of writing the received communication signal to a memory in the receiving user terminal is terminated upon detecting a presence of energy in the second continuous wave segment;

identifying which of the plurality of data packets are destined to the receiving user terminal;

reading from the memory only the data packets identified as being destined to the receiving user terminal; and

demodulating, at a second rate less than the first rate, the data packets identified as being destined to the receiving user terminal.

2. The method of claim 1, wherein the first and second continuous wave segments have different center frequencies.

3. An apparatus for demodulating a communication signal received at a user terminal at a first rate, the communication signal including a plurality of addresses, corresponding data packets, a preamble having a first continuous wave segment followed by a synchronization word, and a second continuous wave segment following the plurality of addresses and corresponding data packets, said apparatus comprising:

a memory receiving and storing the communication signal at the first rate;

a preamble detect circuit detecting the presence of energy in the first continuous wave segment of the preamble, said detection of energy indicating receipt of the communication signal at the user terminal, and confirming the detection of energy in the first continuous wave segment via the synchronization word;

an address list preprocessor receiving only the plurality of addresses from the memory, said address list preprocessor demodulating the plurality of addresses and detecting which of the plurality of addresses matches the receiving user terminal address;

a demodulator receiving only data packets from the memory whose corresponding addresses match the receiving user terminal address, and demodulating said received data packets at a second rate less than the first rate; and

an end detection circuit detecting the presence of energy in the second continuous wave segment, wherein the detection of energy in the first continuous wave segment initiates storage of the communication signal in the memory, and wherein the detection of energy in the second continuous wave segment terminates storage of the communication signal in the memory.

4. The apparatus of claim 3, wherein the first and second continuous wave segments have different center frequencies.

5. A method of demodulating a communication signal transmitted at a first rate, the communication signal including a preamble having a first continuous wave segment followed by a synchronization word, a plurality of addresses and corresponding data packets, and a second continuous wave segment following the plurality of addresses and corresponding data packets, said demodulating method comprising:

detecting a presence of energy in the first continuous wave segment of the preamble, said detection of energy indicating receipt of the communication signal at the user terminal;

writing the received communication signal to a memory in the receiving user terminal upon detecting energy in said first continuous wave segment;

filtering the synchronization word with a matched filter at the receiving user terminal to confirm the detection of energy in the continuous wave segment;

identifying which of the plurality of data packets are destined to the receiving user terminal;

reading from the memory only the data packets identified as being destined to the receiving user terminal;

demodulating, at a second rate less than the first rate, the data packets identified as being destined to the receiving user terminal; and

terminating writing the received signal to memory upon detecting a presence of energy in the second continuous wave segment.

6. The method of claim 5, wherein the first and second continuous wave segments have different center frequencies.

7. In a digital wireless communication system having a transmitter using data packet switching to transmit a communications signal having data packets intended for a plurality of user terminals, the communications signal including user terminal addresses and corresponding data packets and transmitted at a first rate, a demodulating method, comprising:

receiving the communications signal at a user terminal;

stoning the communications signal in a memory;

transferring the terminal addresses from the memory to an address detector;

detecting the packet addresses intended for the receiving user terminal;

transferring data packets intended for the receiving user terminal from the memory to a data demodulator;

demodulating the data packets intended for the receiving user terminal at a second rate less than the first rate; and

wherein the user terminal addresses comprise a series of bits and the addresses are error-correction coded before transmission, and the received addresses are detected and then decoded, and the decoding is terminated when it is evident that the address does not agree with the address of the receiving user terminal.

8. In a digital wireless communication system having a transmitter using data packet switching to transmit a communications signal in successive bursts at a first rate, each burst having a preamble with continuous wave and sync fields and data packets, a demodulating method, comprising:

receiving the communications signal at a user terminal, the terminal being in an idle mode with an inactive data packet demodulator;

detecting the continuous wave field;

detecting the sync field to verify receipt of the continuous wave field;

activating the data packet demodulator; and

demodulating the data packets at a second rate less than said first rate.

9. The method of claim 8 including deactivating the data packet demodulator when all data packets intended for the receiving user terminal have been demodulated.

10. The method of claim 8 wherein the CW field is detected with a narrow band filter.

11. The method of claim 8 wherein the sync field is detected with a matching filter.

12. The method of claim 11 wherein the sync field is detected in analog form with an analog filter.

13. The method of claim 12 wherein the analog sync signal is filtered with a surface acoustic wave filter.

14. The method of claim 11 in which the sync signal is detected in digital form with a digital filter.