Method and apparatus for autonomous selective routing during radio access in TDMA portable radio systems

• US 5,226,045 A
• Filed: 05/07/1992
• Issued: 07/06/1993
• Est. Priority Date: 05/07/1992
• Status: Expired due to Term

• Current Assignee: Intellectual Ventures II LLC (Intellectual Ventures LLC)
• Original Assignee: Bell Communications Research, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Chuang, Justin C.
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US07/880,054
• Time in Patent Office: 425 Days
• Field of Search: 455/33.1, 455/33.4, 455/34.2, 455/52.1, 455/53.1, 455/54.1, 455/54.2, 455/56.1, 455/62, 455/135, 379/58, 379/61, 379/63, 370/95.1, 370/95.3
• US Class Current: 370/332
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 40/02 Communication route or path selection, e.g. power-based or shortest path routing
• CPC Class Codes: H04W 48/20 Selecting an access point
• CPC Class Codes: H04W 74/00 Wireless channel access

Abstract

In a TDM/TDMA digital radio communications system, each portable unit in accessing the system must select the "best" port through which to route each call. The so called "best" port may not, however, have an idle time-slot to accommodate the call. Attempts to route a call through a busy "best" port, or busy "second best" port will decrease the throughput of the network and result in increased call setup time. An autonomous selective routing scheme is described which increases system throughput and decreases call setup time. When a user at a portable unit (301) desires to access the network, the portable unit scans (308, 309) the downlink frequencies associated with each of the ports in the system. For each port, the portable measures signal quality (310) and determines from the received bit patterns (313) whether the port has an idle time-slot. The highest signal quality measure for a port having an idle time-slot is determined (315) and the call is routed through that port if that highest signal quality measure exceeds (317) a predetermined quality measure threshold. Otherwise, the call is blocked.

Claims

1. In a frequency-reusing radio communications system having a plurality of fixed base units and a plurality of mobile transceivers, each fixed base unit transmitting signals at an associated downlink frequency to at least one mobile transceiver and receiving signals at an associated uplink frequency from at least one mobile transceiver, each mobile transceiver having a transmitter for transmitting signals at any one of a plurality of uplink frequencies to any one of said plurality of fixed base units and a receiver for receiving signals at any one of a plurality of associated downlink frequencies from any one of said plurality of fixed base units, a method of autonomously determining at a mobile transceiver the particular one of the plurality of fixed base units through which to access the system, comprising the steps of:

(a) measuring the quality of the signal received at a particular downlink frequency from a fixed base unit;

(b) determining from that downlink frequency signal whether that fixed base unit is available to accept a transmission from the mobile transceiver;

(c) repeating steps (a) and (b) for each of the downlink frequencies used in the system;

(d) determining from only the available fixed base units, the fixed base unit having the highest signal quality measure; and

(e) accessing the system by transmitting on the uplink frequency associated with the downlink frequency of the available fixed base unit having the highest signal quality measure.

2. In a frequency-reusing radio communications system having a plurality of fixed base units and a plurality of mobile transceivers, each fixed base unit transmitting signals at an associated downlink frequency to at least one mobile transceiver and receiving signals at an associated uplink frequency from at least one mobile transceiver, each mobile transceiver having a transmitter for transmitting signals at any of a plurality of uplink frequencies to any one of said plurality of fixed base units and a receiver for receiving signals at any one of a plurality of associated downlink frequencies from any one of said plurality of fixed base units, a method of autonomously determining at a mobile transceiver the particular one of the plurality of fixed base units through which to access the system, comprising the steps of:

(a) measuring the quality of the signal received at a particular downlink frequency from a fixed base unit;

(b) determining from that downlink frequency signal whether the fixed base unit is available to accept a transmission from the mobile transceiver;

(c) repeating steps (a) and (b) for each of the downlink frequencies used in the system;

(d) determining from only the available fixed base units, the fixed base unit having the highest signal quality measure;

(e) comparing that highest signal quality measure with a predetermined threshold signal quality measure; and

(f) accessing the system by transmitting on the uplink frequency associated with the downlink frequency of the available fixed base unit having the highest signal quality measure if that highest signal quality measure is greater than the predetermined threshold signal quality measure.

3. The method of claim 2 further comprising the step of blocking a transmission from the mobile transceiver if the highest signal quality measure is less than the predetermined threshold quality measure.

4. In a TDM/TDMA digital telephony system having a plurality of fixed ports and a plurality of mobile portable units, each port transmitting signals in a plurality of time-slots at an associated downlink frequency to at least one portable unit and receiving signals at an associated uplink frequency from at least one portable unit, each portable unit having a transmitter for transmitting signals at any one of a plurality of uplink frequencies to any one of said plurality of ports and a receiver for receiving signals at any one of a plurality of associated downlink frequencies from any one of said plurality of ports, a method at a portable unit of autonomously accessing the system, comprising the steps of:

(a) measuring the quality of the signal received at a particular downlink frequency from a port;

(b) determining from that downlink frequency signal whether that port has an idle time-slot;

(c) repeating steps (a) and (b) for each downlink frequency used in the system;

(d) determining from only the ports having an idle time-slot, the port having the highest signal quality measure; and

(e) accessing the system by transmitting on the uplink frequency associated with the downlink frequency of the port with an idle time-slot having the highest signal quality measure.

5. The method of claim 4 wherein the measure of quality of the signal received at each downlink frequency is that signal'"'"'s vector sum of the X and Y components of expanded and collapsed differential phase angles.

6. The method of claim 4 wherein the step of determining from the downlink signal whether a port has an idle time-slot comprises the step of examining each time-slot of the downlink signal for a predetermined idle bit pattern.

7. In a TDM/TDMA digital telephony system having a plurality of fixed ports and a plurality of mobile portable units, each port transmitting signals in a plurality of time-slots at an associated downlink frequency to at least one portable unit and receiving signals at an associated uplink frequency from at least one portable unit, each portable unit having a transmitter for transmitting signals at any one of a plurality of uplink frequencies to any one of said plurality of ports and a receiver for receiving signals at any one of a plurality of associated downlink frequencies from any one of said plurality of ports, a method at a portable unit of autonomously accessing the system, comprising the steps:

(a) measuring the quality of the signal received at a particular downlink frequency from a port;

(b) determining from that downlink frequency signal whether that port has an idle time-slot;

(c) repeating steps (a) and (b) for each downlink frequency used in the system;

(d) determining from only the ports having an idle time-slot, the port having the highest signal quality measure;

(e) comparing that highest signal quality measure with a predetermined threshold signal quality measure; and

(f) accessing the system by transmitting on the uplink frequency associated with the downlink frequency of the port with an idle time-slot having the highest signal quality measure if that highest signal quality measure is greater than the predetermined threshold signal quality measure.

8. The method of claim 7 further comprising the step of blocking a transmission from the portable unit if the highest signal quality measure is less than the predetermined threshold signal quality measure.

9. The method of claim 7 wherein the measure of quality of the signal received at each downlink frequency is that signal'"'"'s vector sum of the X and Y components of expanded and collapsed differential phase angles.

10. The method of claim 7 wherein the step of determining from the downlink signal whether a port has an idle time-slot comprises the step of examining each time-slot of the downlink signal for a predetermined idle bit pattern.

11. In a frequency-reusing radio communications system having a plurality of fixed base units and a plurality of mobile transceivers, each fixed base unit transmitting signals at an associated downlink frequency to at least one mobile transceiver and receiving signals at an associated unlink frequency from at least one mobile transceiver, each mobile transceiver comprising a transmitter for transmitting signals at any one of a plurality of uplink frequencies to any one of said plurality of fixed base units and a receiver for receiving signals at any one of a plurality of associated downlink frequencies from any one of the plurality of fixed based units, each mobile transceiver further comprising means for autonomously determining the particular fixed base unit through which to access the system comprising:

means for measuring the quality of a signal received from a fixed base unit at an input downlink frequency;

means for determining from the received downlink frequency signal whether the associated fixed base unit is available to accept a transmission;

means for scanning the downlink frequency input to said measuring means to each of the downlink frequencies used in the system;

means for determining from only the available fixed base units, the fixed base unit having the highest signal quality measure;

means for setting the uplink and downlink frequencies of the mobile transceiver'"'"'s transmitter and receiver, respectively, to the uplink and downlink frequencies associated with the available fixed base unit having the highest signal quality measure.

12. A mobile transceiver in a frequency-resuing radio communications system in accordance with claim 11 further comprising:

means for comparing the highest signal quality measure with a predetermined threshold signal quality measure; and

means for blocking a transmission by the mobile transceiver if the highest signal quality measure of available fixed base units is less than the predetermined threshold signal quality measure.

13. In a TDM/TDMA digital telephony system having a plurality of fixed ports and a plurality of mobile portable units, each port transmitting signals in a plurality of time-slots at a downlink frequency to at least one portable unit and receiving signals at an associated uplink frequency from at least one port, each portable unit comprising a transmitter for transmitting signals at any one of a plurality of uplink frequencies to any one of said plurality of ports and a receiver for receiving signals at any one of a plurality of associated downlink frequencies from any one of the plurality of ports, each portable unit further comprising means for autonomously determining the particular port through which to access the system comprising:

means for measuring the quality of a signal received from a port at an input downlink frequency;

means for determining from the received downlink frequency signal whether the associated port has an idle time-slot;

means for scanning the downlink frequency input to said measuring means to each of the downlink frequencies used in the system;

means for determining from only the ports having an idle time-slot, the port having the highest signal quality measure;

means for setting the uplink and downlink frequencies of the portable unit'"'"'s transmitter and receiver, respectively, to the uplink and downlink frequencies associated with the port having an idle time-slot and the highest signal quality measure.

14. A portable unit in a TDM/TDMA digital telephony system system in accordance with claim 13 further comprising:

means for comparing the highest signal quality measure of ports having an idle time-slot with a predetermined threshold signal quality measure; and

means for blocking a transmission by the portable unit if the highest signal quality measure of ports having an idle time-slot is less that the predetermined threshold signal quality measure.

15. A portable unit in accordance with claim 14 further comprising detecting means for determining whether a predetermined idle bit pattern is present in any of the time-slots of a signal received from any port.