Spread spectrum random access systems and methods for time division multiple access radiotelephone communication systems

• US 5,850,392 A
• Filed: 04/10/1996
• Issued: 12/15/1998
• Est. Priority Date: 04/10/1996
• Status: Expired due to Term

• Current Assignee: Unwired Planet LLC (JP Morgan Chase & Co)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Massingill, Larry W., Wang, Yi-Pin Eric, Hassan, Amer, Reinhold, Stanley L.
• Primary Examiner(s): Chan, Jason
• Assistant Examiner(s): VU, HUY DUY
• Application Number:
  US08/629,497
• Time in Patent Office: 979 Days
• Field of Search: 370/320, 370/321, 370/322, 370/323, 370/324, 370/335, 370/336, 370/337, 370/342, 370/347, 370/441, 370/442, 370/437, 370/514, 370/515, 375/200, 375/201, 375/202, 375/203, 375/204, 375/205, 375/206, 375/207, 375/208, 375/209, 375/210, 375/365, 375/366, 375/367, 375/368
• US Class Current: 370/335
• CPC Class Codes: H04B 7/212 Time-division multiple access [TDMA]
• CPC Class Codes: H04B 7/216 Code division or spread-spectrum multiple access [CDMA, SSMA]

Abstract

In a time division multiple access (TDMA) radiotelephone communications system, a spread spectrum random access channel signal representing a random access message is communicated from a radiotelephone to a central station according to a spreading sequence. In response, a TDMA radiotelephone communications channel is assigned to the radiotelephone. A time division multiplexed radiotelephone communications signal is communicated between the radiotelephone and the central station on the assigned TDMA radiotelephone communications channel over a time division multiplexed carrier frequency band. Preferably, in communicating the spread spectrum random access channel signal, a random access channel signal, representing the random access channel message, is direct sequence modulated according to the spreading sequence to produce a direct sequence modulated random access channel signal. According to a two-stage detection aspect, a synchronization sequence may be associated with a plurality of spreading sequences. The synchronization sequence may be first detected from the communicated spread spectrum random access channel signal, and in response to detection of the synchronization sequence, one of the plurality of spreading sequences associated with the detected synchronization sequence may be detected. A station identification may be assigned to the radiotelephone, with the station identification preferably represented by a digital station identification word. The synchronization sequence and the spreading sequence may be identified from the station identification word, thus associating the synchronization and spreading sequences. The spreading sequence may also be randomly generated from the station identification word.

Claims

1. A time division multiple access radiotelephone communications system for communicating between at least one central station and at least one radiotelephone over a carrier frequency spectrum, the system comprising:

code division multiple access (CDMA) random access channel communicating means for communicating a spread spectrum random access channel signal from a radiotelephone to a central station over the carrier frequency spectrum according to a spreading sequence, said spread spectrum random access channel signal representing a random access message; and

time division multiple access (TDMA) communicating means for communicating a time division multiplexed radiotelephone communications signal between said radiotelephone and said central station over a time division multiplexed carrier frequency band of the carrier frequency spectrum, said time division multiplexed radiotelephone communications signal representing a radiotelephone communications message;

wherein said CDMA random access channel communicating means comprises;

means for associating a synchronization sequence with a plurality of spreading sequences;

means for communicating a spread spectrum random access channel signal representing a random access channel symbol sequence representing a random access channel message and including a synchronization sequence, according to one of the plurality of spreading sequences associated with said synchronization sequence;

synchronization sequence detecting means, responsive to said means for communicating a spread spectrum random access channel signal representing a random access channel symbol sequence, for detecting a synchronization sequence from a communicated spread spectrum random access channel signal; and

spreading sequence detecting means, responsive to said synchronization sequence detecting means and to said means for communicating a spread spectrum random access channel signal representing a random access channel symbol sequence, for detecting one of the plurality of predetermined spreading sequences associated with a detected synchronization sequence, from the communicated spread spectrum random access channel signal;

said system further including means for assigning a station identification to said radiotelephone, and wherein said means for associating a synchronization sequence with a plurality of spreading sequences comprises;

synchronization sequence identifying means, responsive to said means for assigning a station identification, for identifying a synchronization sequence from the assigned station identification; and

spreading sequence identifying means, responsive to said means for assigning a station identification, for identifying a spreading sequence from the assigned station identification.

2. A system according to claim 1 wherein said station identification comprises a station identification word, and:

wherein said spreading sequence identifying means comprises means for identifying a spreading sequence from a group of bits of said station identification word; and

wherein said synchronization sequence identifying means comprises means for identifying a synchronization sequence from a subset of said group of bits of said station identification word.

3. A method of accessing a time division multiple access (TDMA) radiotelephone communications system, the method comprising the steps of:

communicating a spread spectrum random access channel signal from a radiotelephone to a central station over a carrier frequency spectrum according to a spreading sequence, the spread spectrum random access channel signal representing a random access message;

assigning a TDMA radiotelephone communications channel to the radiotelephone, in response to communication of the spread spectrum random access channel signal; and

communicating a time division multiplexed radiotelephone communications signal between the radiotelephone and the central station on the assigned TDMA radiotelephone communications channel, over a time division multiplexed carrier frequency band of the carrier frequency spectrum, the time division multiplexed radiotelephone communications signal representing a radiotelephone communications message;

wherein said step of communicating a random access channel message is preceded by the step of associating a synchronization sequence with a plurality of spreading sequences,

wherein said step of communicating a spread spectrum random access channel signal comprises the step of communicating a spread spectrum random access channel signal representing a random access channel symbol sequence including the synchronization sequence and an information sequence corresponding to the random access channel message, according to one of the plurality of spreading sequences associated with the synchronization sequence; and

wherein said step of communicating a spread spectrum random access channel signal is followed by the steps of;

detecting a synchronization sequence from the communicated spread spectrum random access channel signal; and

detecting one of the plurality of predetermined spreading sequences associated with the detected synchronization sequence from the communicated spread spectrum random access channel signal; and

wherein said step of communicating a random access channel message is preceded by the step of assigning a station identification to the radiotelephone, and wherein said step of associating a synchronization sequence with a plurality of spreading sequences comprises the steps of;

identifying a synchronization sequence from the assigned station identification; and

identifying a spreading sequence from the assigned station identification.

4. A method according to claim 3 wherein the station identification comprises a station identification word, and:

wherein said step of identifying a spreading sequence comprises the step of identifying a spreading sequence from a group of bits of the station identification word; and

wherein said step of identifying a synchronization sequence identifying comprises the step of identifying a synchronization sequence from a subset of the group of bits of the station identification word.