Mobile terminal having improved digital control channel (DCCH) search procedure

• US 5,606,548 A
• Filed: 04/16/1996
• Issued: 02/25/1997
• Est. Priority Date: 04/16/1996
• Status: Expired due to Term

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Mobile Phones UK Limited (Nokia Corporation)
• Inventors: Vayrynen, Mika, Ylitervo, Matti
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): PHILLIPS, MATTHEW
• Application Number:
  US08/632,849
• Time in Patent Office: 315 Days
• Field of Search: 370/95.1, 370/95.3, 370/85.7, 370/29, 370/13, 370/110.1, 379/63, 340/825.04, 340/825 C
• US Class Current: 370/252
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information

Abstract

A method is disclosed for a user terminal (10) to obtain access to a DCCH transmitted on a TDM radio channel of a wireless communications system that also includes at least one TDM radio channel that transmits a DTC. The DCCH and DTC are each comprised of slots partitioned into fields. A first step (a) tunes a receiver (16) to a radio channel, receives a first slot, and decodes a predetermined first field from the first slot. The predetermined first field is a 12-bit CSFP field if the radio channel conveys a DCCH, or a 12-bit CDVCC if the radio channel conveys a DTC. A second step of the method calculates a CRC over the first field to determine if the first field is the CSFP field. If yes, the user terminal assumes that the radio channel conveys the DCCH and then uses information from the DCCH to access the wireless system. If the first field is determined not to be the CSFP field, the user terminal assumes that the radio channel conveys a DTC, and then calculates a CRC over the first field to determine if the CDVCC field was correctly received. If the CDVCC field is determined to be correctly received, the user terminal calculates a CRC over the CDL field to determine if the CDL field was correctly received. If the CDL field is determined to be correctly received, and after both the CDVCC and CDL fields are correctly received from n slots, the user terminal employs the CDL field to identify a radio channel that conveys a DCCH, thereby enabling the user terminal to access the system.

Claims

1. A method for operating a wireless user terminal of a type that receives a TDM signal from a wireless system, the TDM signal being comprised of slots partitioned into fields, one of the fields being a control-related field containing information that is used by the user terminal to locate a radio channel that transmits a control channel required to access the wireless system, comprising the steps of:

(a) receiving a slot and decoding a predetermined first field from the slot, the predetermined first field being a field other than the control-related field;

(b) determining if the decoded first field was correctly received;

(c) only if it is determined that the first field was correctly received, determining if the control-related field from the slot was also correctly received;

(d) if it is determined that the control-related field was also correctly received, determining if the steps (a)-(c) have been executed n times, where n is a positive integer that is equal to or greater than one; and

(e) if yes, using information from the control-related field to locate a radio channel that transmits a control channel required to access the wireless system.

2. A method for operating a wireless user terminal of a type that receives a TDM signal from a wireless system, the TDM signal being comprised of slots partitioned into fields, comprising the steps of:

(a) receiving a first slot and decoding a predetermined first field from the first slot;

(b) determining if the decoded first field indicates that the received slot is a first type of slot;

(c) if yes, using information coded in the received slot to access the wireless system;

(d) if no, assuming that the received slot is a second type of slot and determining if the decoded first field was correctly received;

(e) if yes, decoding a predetermined second field from the first slot and determining if the predetermined second field was correctly received; and

(f) if yes, using information coded in the predetermined second field to locate a radio channel on which is transmitted the predetermined first type of slot.

3. A method as set forth in claim 2, wherein the step (e) includes a further step of determining if at least the steps (a) through (e) have been executed a predetermined number of times and, if not, a step of executing steps (a) through (e) at least one more time to receive a further slot.

4. A wireless user terminal of a type that receives a TDM signal from a wireless system, the TDM signal being comprised of slots partitioned into fields, wherein some slots are traffic channel slots and some slots are control channel slots, said terminal comprising a receiver and a controller coupled to the receiver for decoding information contained in received slots, said controller operating with said receiver to receive a first slot and to decode a predetermined first field from the first slot;

said controller operating to determine if the decoded first field indicates that the received slot is a control channel slot;

if yes, said controller being operable to use information coded in the received control channel slot to access the wireless system and if no, said controller assuming that the received slot is a traffic channel slot and determining if the decoded first field was correctly received;

if yes, said controller being operable to decode a predetermined second field from the first slot and to determine if the predetermined second field was correctly received; and

if yes, said controller being further operable to use information coded in the predetermined second field to tune said receiver to an indicated radio channel on which is transmitted a control channel slot.

5. A method for operating a wireless user terminal to obtain access to a Digital Control Channel (DCCH) transmitted on a TDM radio channel of a wireless communications system that also includes at least one TDM radio channel that transmits a Digital Traffic Channel (DTC), the DCCH and DTC each being comprised of slots partitioned into fields, comprising the steps of:

(a) tuning a receiver to a radio channel, receiving a first slot, and decoding a predetermined first field from the first slot, the predetermined first field being a 12-bit Coded Superframe Phase (CSFP) field if the radio channel conveys a DCCH or a 12-bit Coded Digital Verification Color Code (CDVCC) if the radio channel conveys a DTC;

(b) calculating a CRC over the first field to determine if the first field is the CSFP field;

(c) if yes, assuming that the radio channel conveys the DCCH and using information from the DCCH to access the wireless system;

(d) if no, assuming that the radio channel conveys a DTC and calculating a CRC over the first field to determine if the CDVCC field was correctly received;

(e) if yes, calculating a CRC over the CDL field to determine if the CDL field was correctly received; and

(f) if yes, and after both the CDVCC and CDL fields are correctly received from n slots, where n is a positive integer that is equal to or greater than one, using the CDL field to identify a radio channel that conveys a DCCH.