Method for determining cell boundary during base station deployment

• US 6,148,194 A
• Filed: 12/10/1997
• Issued: 11/14/2000
• Est. Priority Date: 12/10/1997
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Nortel Networks Corporation
• Inventors: Smith, Roland A., Bird, William, Kao, Joel
• Primary Examiner(s): Vo, Nguyen
• Assistant Examiner(s): NGUYEN, DUC M
• Application Number:
  US08/988,086
• Time in Patent Office: 1,070 Days
• Field of Search: 455/423, 455/446, 455/449, 455/67.1, 455/67.4, 455/561, 455/67.7, 455/421, 455/67.3
• US Class Current: 455/421
• CPC Class Codes: H04B 17/0085 using test signal generators
• CPC Class Codes: H04B 17/23 Indication means, e.g. displays, alarms, audible means
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04W 16/18 Network planning tools

Abstract

An improved radio deployment tool (RDT) for determining cell boundaries is disclosed. An RDT used to carry-out active deployment procedures consists of an RDT wireless handset (RDTWH) that a deployment engineer uses to generate test signals, and an RDT base station (RDTBS) that is used to measure the RSSI of the test signals sent by the RDTWH. The RDTBS factors in the impact of short-term fades and dispersion, as well as long-term fading, by measuring and processing bit error rate (BER) and received signal strength intensity (RSSI) levels. BER levels can be measured for signals whose RSSI-levels have been driven into a testing range at which signals are susceptible to short-term fades and dispersion. A sufficient resolution of BER measurements is achieved by filling the payload fields of test packets exchanged by the RDTWH and RDTBS, with BER test data. The payload fields of the test packets can be filled by pressing down the mute button of the RDTWH.

Claims

1. A method of obtaining, for base station deployment purposes, a determination of whether a wireless handset at a location is inside or outside a cell boundary of a base station, said method comprising the steps of:

(a) the wireless handset transmitting a test signal from the location, said signal carrying a transmitted test sequence of bits;

(b) the base station receiving from the wireless handset a received signal carrying a received sequence of bits;

(c) the base station measuring a received signal strength intensity (RSSI) level for the received signal;

(d) the base station measuring a high resolution bit error rate (BER) level for the received sequence, with reference to the transmitted test sequence;

(e) the base station making the determination that the handset is outside the cell boundary if the measured RSSI-level is less than an RSSI threshold;

(f) the base station making the determination that the handset is outside the cell boundary if the BER-level exceeds a BER threshold; and

(g) the base station indicating the determination.

2. The method of claim 1 wherein the step of indicating the determination comprises the step of indicating the determination only as the determination is undergoing a transition from indicating the location is inside to indicating the location is outside, such that the method can be used to define whether or not the location is at a cell boundary point of the base station.

3. The method of claim 2, wherein steps (a) through (f) are repeated as a user of the RDT holding the wireless handset repeatedly walks radially away from the base station in a plurality of fixed directions, so as to determine a plurality of cell boundary points that can be collectively used to define a cell boundary for the base station.

4. The method of claim 1 wherein the step of the wireless handset transmitting each test signal further comprises the step of inserting the test sequence into a payload field of a test packet, and wherein the step of the base station measuring a high resolution bit error rate (BER) further comprises the steps of extracting a received packet from the received signal, and extracting from the payload field of the received packet the received sequence.

5. The method of claim 1 wherein the BER threshold is equal to 0.1%.

6. The method of claim 1 wherein the step of indicating the determination comprises the step of the base station directly communicating the determination to a user.

7. The method of claim 1 wherein the step of indicating the determination comprises the steps of the base station communicating the determination to the wireless handset, and the wireless handset communicating the determination to a user.

8. The method of claim 7 wherein the step of the wireless handset communicating the determination to a user includes the step of using a plurality of types of ringing sounds, each type of ringing sound being designated to represent a different message.

9. The method of claim 7 wherein the step of the wireless handset communicating the determination to a user includes the step of placing the determination on the display of the wireless handset.

10. The method of claim 9 wherein the step of placing the determination on the display of the wireless handset includes the step of continuously displaying measured RSSI and BER levels.

11. The method of claim 1 wherein all the steps are completed within a period of time that is not substantially greater than one second.

12. A method according to claim 1 wherein the BER is determined by making bit-by-bit comparison of the received sequence with the transmitted test sequence.

13. A method according to claim 1 further comprising attenuating the received signal to simulate a fade before making the BER measurement.

14. A method of obtaining, for base station deployment purposes, a determination of whether a wireless handset at a location is inside or outside a cell boundary of a base station, said method comprising the steps of:

(a) the wireless handset transmitting a test signal from the location, said signal carrying a transmitted test sequence of bits;

(b) the base station receiving from the wireless handset a received signal carrying a received sequence of bits;

(c) the base station measuring a received signal strength intensity (RSSI) level for the received signal;

(d) the base station measuring a high resolution bit error rate (BER) level for the received sequence, with reference to the transmitted test sequence;

(e) the base station making the determination that the handset is outside the cell boundary if the measured RSSI-level is less than an RSSI threshold;

(f) the base station making the determination that the handset is outside the cell boundary if the BER-level exceeds a BER threshold; and

(g) the base station indicating the determination;

wherein the step of the wireless handset transmitting the test signal further comprises the step of scrambling a known test sequence of bits to produce the transmitted test sequence, and wherein the step of the base station measuring a high resolution bit error rate (BER) further comprises the step of extracting a scrambled received sequence of bits from the received signal, and descrambling the scrambled received sequence to produce the received sequence.

15. A method of obtaining, for base station deployment purposes, a determination of whether a wireless handset at a location is inside or outside a cell boundary of a base station, said method comprising the steps of:

(a) the wireless handset transmitting a test signal from the location, said signal carrying a transmitted test sequence of bits;

(b) the base station receiving from the wireless handset a received signal carrying a received sequence of bits;

(c) the base station measuring a received signal strength intensity (RSSI) level for the received signal;

(d) the base station measuring a high resolution bit error rate (BER) level for the received sequence, with reference to the transmitted test sequence;

(e) the base station making the determination that the handset is outside the cell boundary if the measured RSSI-level is less than an RSSI threshold;

(f) the base station making the determination that the handset is outside the cell boundary if the BER-level exceeds a BER threshold; and

(g) the base station indicating the determination;

wherein the step of the wireless handset transmitting a test signal includes the step of a user activating the mute feature of the wireless handset thereby resulting in the transmitted test sequence being entirely comprised of zero-bits, and wherein the step of the base station measuring a high resolution BER-level includes the step of counting the number of non-zero bits in the received sequence.

16. A method of obtaining, for base station deployment purposes, a determination of whether a wireless handset at a location is inside or outside a cell boundary of a base station, said method comprising the steps of:

the wireless handset transmitting a plurality of test signals from the location, each signal containing a respective transmitted sequence;

the base station receiving through a receive path a plurality of received signals, each containing a respective received sequence;

the base station inserting a selectable, known and varying attenuation in the receive path, to generate RDT-attenuated signals;

the base station estimating an average RSSI-level of the received signals not including the attenuation;

the base station calculating a high resolution bit error rate (BER) level of each RDT-attenuated signal, with reference to its respective transmitted sequence;

the base station making the determination on the basis of the average RSSI-level and the calculated BER-levels; and

the base station indicating the determination.

17. The method of claim 16 wherein the step of making the determination comprises the step of determining that the location is outside the cell boundary if the measured RSSI exceeds an RSSI threshold or if one or more of a selected set of the calculated BER-levels exceed a BER threshold.

18. The method of claim 17 wherein a fading range is defined to extend from the average RSSI-level down a predetermined number of decibels, and wherein the selected set of calculated BER levels are derived from the RDT-attenuated signals whose RSSI-levels fall within the fading range.

19. The method of claim 16 wherein the step of inserting an attenuation comprises the step of setting the RSSI-levels of the RDT-attenuated signals so that they fall within a predetermined testing range of values.

20. The method of claim 19 wherein the testing range extends from the RSSI threshold to 16 dB below the RSSI threshold.

21. The method of claim 20 wherein the step of setting the RSSI-levels of the RDT-attenuated signals comprises the step of setting the signals to 16 different RSSI-levels that are evenly spaced across the testing range.

22. The method of claim 19 wherein the testing range extends from the RSSI threshold to 32 dB below the RSSI threshold.

23. The method of claim 22 wherein the step of setting the RSSI-levels of the RDT-attenuated signals comprises the step of setting the signals to 32 different RSSI-levels that are evenly spaced across the testing range.

24. The method of claim 16 wherein the step of estimating an average RSSI-level comprises the step of combining RSSI measurements of the RDT-attenuated signals using a weighted averaging method.

25. The method of claim 16 wherein the step of calculating a bit error rate (BER) level for each RDT-attenuated signal, comprises the step of combining, for each calculation, BER measurements of the RDT-attenuated signal with an average of BER measurements calculated using previously received RDT- attenuated signals at a like RSSI-level, said combining being done using a weighted averaging method.

26. A radio deployment tool (RDT) comprising:

a wireless handset comprising means for transmitting a test signal containing a transmitted test sequence to the base station; and

a base station comprising means for receiving a received signal from the wireless handset, an RSSI detector for measuring the received signal strength intensity (RSSI) level of the received signal, a processor for calculating a bit error rate (BER) of a received sequence carried by the received signal and for comparing the RSSI and the BER-levels to RSSI and BER thresholds, respectively, in making a determination that the handset is outside a cell boundary of the base station if the RSSI is less than the RSSI threshold and making a determination that the handset is outside a cell boundary of the base station if the BER is greater than the BER threshold, and an indicating device for communicating the determination to a user.

27. The RDT of claim 26 wherein the base station additionally has a means for varying the RSSI-level of the received signal to a level lying inside a testing range.

29. The RDT of claim 26 wherein the indicating device comprises a transmitter for communicating a message containing the determination to the wireless handset, and wherein the wireless handset further comprises a receiver for receiving the message from the base station, and a man-machine interface device (MMI) for communicating the determination to the user.

28. The RDT of claim 28 wherein the means for varying the RSSI-level includes adjustable attenuation pads, adjustable antennas, and means for controlling the receive-sensitivity.

30. A radio deployment tool (RDT) comprising:

a wireless handset comprising means for transmitting a test signal containing a transmitted test sequence to the base station; and

a base station comprising means for receiving a received signal from the wireless handset, an RSSI detector for measuring the received signal strength intensity (RSSI) level of the received signal, a processor for calculating a bit error rate (BER) of a received sequence carried by the received signal and for comparing the RSSI and the BER-levels to RSSI and BER thresholds, respectively, in making a determination that the handset is outside a cell boundary of the base station if the RSSI is less than the RSSI threshold and making a determination that the handset is outside a cell boundary of the base station if the BER is greater than the BER threshold, and an indicating device for communicating the determination to a user;

wherein the wireless handset further comprises a mute button for producing a known test sequence of zero-bits, and a scrambler for scrambling the known test sequence thereby producing the transmitted test sequence, and wherein the base station further comprises a descrambler for descrambling the contents of a scrambled received sequence thereby creating the received sequence, and a processor for counting the number of non-zero bits in the received sequence.

31. The RDT of claim 30 wherein the wireless handset is a standard personal communications systems (PCS) mobile unit.

32. The RDT of claim 30 wherein the means for transmitting a test signal and the means for receiving a received signal both operate in accordance with the Digital European Cordless Telecommunications (DECT) protocol.

33. The RDT of claim 30 wherein the means for transmitting a test signal and the means for receiving a received signal both operate in accordance with the Group Special Mobile (GSM) protocol.

34. A base station for obtaining, for base station deployment purposes, a determination of whether or not a location falls outside or inside its cell boundary, the apparatus comprising, an RSSI detector for measuring the received signal strength intensity (RSSI) level of a received signal originating from the location, a processor for measuring the bit error rate (BER) level of a received sequence carried by the received signal and for considering both levels in making the determination such that if the BER fails a respective threshold test the determination is made that the location falls outside the cell boundary, and if the RSSI fails a respective threshold test the determination is made that the location falls outside the cell boundary, and an indicating device for communicating the determination.