WO1998008349A2 - Spatially-oriented subscriber configuration in a fixed wireless system - Google Patents
Spatially-oriented subscriber configuration in a fixed wireless system Download PDFInfo
- Publication number
- WO1998008349A2 WO1998008349A2 PCT/IB1997/001116 IB9701116W WO9808349A2 WO 1998008349 A2 WO1998008349 A2 WO 1998008349A2 IB 9701116 W IB9701116 W IB 9701116W WO 9808349 A2 WO9808349 A2 WO 9808349A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- mean value
- radiotelephone
- cell
- threshold
- range
- Prior art date
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/50—Allocation or scheduling criteria for wireless resources
- H04W72/54—Allocation or scheduling criteria for wireless resources based on quality criteria
- H04W72/542—Allocation or scheduling criteria for wireless resources based on quality criteria using measured or perceived quality
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W84/00—Network topologies
- H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
- H04W84/10—Small scale networks; Flat hierarchical networks
- H04W84/14—WLL [Wireless Local Loop]; RLL [Radio Local Loop]
Definitions
- the present invention relates to radio communications. More particularly, the present invention relates to spatially configuring a subscriber radiotelephone in a fixed wireless access system.
- a cellular radio communication system is typically comprised of a number of cells covering a geographic region. Each cell is allocated a number of radio channels. The cell may also be divided up into sectors with each sector having a number of different channels.
- a subscriber In a typical mobile system, a subscriber is not configured to a specific cell. In these systems, a radio voice channel is allocated to the mobile subscriber for call initiation based on the Received Signal Strength Indicator (RSSI) and the availability of the radio voice channel. As the mobile subscriber moves through a cellular system's different cells, radio voice channels are dynamically allocated to the mobile as the channel's signal strength changes.
- RSSI Received Signal Strength Indicator
- each subscriber is typically configured to a specific cell on a permanent basis.
- This type of system uses radiotelephones that are not mobile.
- a fixed wireless system is an attractive solution to implement communications in developing countries or in rural areas of developed countries where the telecommunications infrastructure is inadequate.
- FIG. 7 shows a subscriber (700) being configured to a home cell, Cell A.
- the home cell is providing normal coverage to the subscriber (700).
- the lower portion of FIG. 7 illustrates the shrinking of Cell A and the resulting loss of coverage experienced by the subscriber (700).
- the received signal level could drop below the minimum signal level required to keep the connection.
- This minimum signal level is the radio's minimum sensitivity - the signal level below which the radio cannot detect a signal
- the call is dropped or not set up, if it is a new call, since the subscriber is configured to only one home cell in wireless local loop systems. There is a resulting previously unknown need to provide improved coverage to subscribers located on the border of a cell in a wireless local loop system.
- the process of the present invention assigns cellular radio service to a radiotelephone unit in a wireless local loop system.
- the process first measures, at the radiotelephone unit, a mean value signal for each radio control channel signal received from each cell of a set of cells of the cellular system
- the set of cells is the cells that are within communication distance of the radiotelephone unit and includes the radiotelephone unit's home cell
- the process next identifies the cells with the largest and second largest mean values from the measured mean values. These mean values are compared with threshold level bands so as to categorize the cells based on into which threshold the particular mean value falls.
- the number of threshold levels is equal to the maximum number of serving cells allowed to be configured for a border cell radiotelephone unit
- the radiotelephone unit only needs to be assigned to the cell that generated the largest mean value, its home cell. If the largest mean value lies between the highest and lowest threshold levels, the radiotelephone unit is assigned to not only the home cell but also to the cells that generate sufficiently strong radio signals If the largest mean value goes below the lowest threshold level, the radiotelephone unit cannot be set up to initiate a call or an ongoing call is dropped
- FIG. 1 shows a block diagram of a typical fixed, wireless radiotelephone system of the present invention.
- FIG 2 shows a typical cell layout of the radiotelephone system of FIG. 1.
- FIG. 3 shows a flowchart of a preferred embodiment process of the present invention
- FIG 4 shows a flowchart of an alternate embodiment process of the present invention
- FIG 5 shows a distribution of a local mean in a two-neighboring cell situation
- FIG 6 shows a plot of probability density function versus signal level, as described from FIG. 5
- FIG 7 shows a typical cell layout experiencing the cell breathing phenomenon
- FIG 8 shows a table used to select threshold levels 111 a two serving cell embodiment.
- FIG 9 shows another alternate embodiment of the process of the present invention.
- FIG 10 shows a fixed wireless access system's RF coverage using the present invention.
- the wireless local loop radiotelephone system of the present invention enables a wireless radiotelephone user to access the public switched telephone network. By averaging, over the space domain, the mean value of the signals received by the radiotelephone, the system can optimally configure the radiotelephone to additional neighboring cells beyond the radiotelephone's home cell.
- FIG 1 shows a block diagram of the fixed wireless radiotelephone system of the present invention.
- This cellular system is comprised of multiple base stations (101-103) that communicate radiotelephone signals with the fixed subscriber radiotelephone (110)
- Each base station (101-103) is comprised of multiple receivers and transmitters that operate in any RF band
- the 800 and 900 MHz bands are typical for time division multiple access (TDMA) cellular service
- TDMA time division multiple access
- the radio base stations (101- 103) are connected to a fixed wireless controller (105)
- the controller (105) keeps track of which subscribers are configured to a particular base station (101, 102, or 103) and routes any calls from the public switched telephone network (PSTN) (120) to the appropriate base station (101, 102, or 103) for transmission to the subscriber radiotelephone (110)
- PSTN public switched telephone network
- FIG. 2 illustrates the cell layout of the present invention.
- the fixed subscriber radiotelephones (210, 220, and 230) each communicate with the appropriate base station (210, 220, and 230)
- the processes of the present invention determine to which base station (201-203) each subscriber radiotelephone (210, 220, and 230) is configured
- One subscriber radiotelephone (210) may be configured to a single base station (202).
- Another radiotelephone (220) may be configured to two base stations (201 and 202) while yet another radiotelephone may be configured to all three stations (201-203)
- the power received by a radiotelephone in the above wireless system is expressed as:
- P R (r) the received power at a distance r from the base station
- the close-in reference distance is greater than 1 39"G*H where G is the antenna gam and H is the antenna height
- the path-loss slope also referred to as the propagation constant, is well known in the art
- the path-loss slope is the rate of decay of signal strength as a function of distance and is typically in the range of 2-5 depending on the terrain and conditions For example, a path-loss slope of 2 is without any obstructions while a path-loss slope of 5 would be a dense urban environment.
- the component is the mean value of the received power, subsequently referred to as m
- the component M(r) is the local mean, also referred to m the art as the long-term fading component M(r) observes lognormal distribution around the mean value, m. M(r) varies due to the terrain contour between the base station and the radiotelephone
- the component R(r) is the multipath fading, or short-term fading, component.
- the variation of R(r) is due to the radio waves being reflected from man-made structures.
- the probability density function of M(r) can be expressed as:
- FIG. 5 shows the signal level contours and distribution of local mean values in the two-neighboring cell embodiment.
- This figure illustrates that in a home cell, Cell A, a subscriber (500) located in the interior of Cell A has a much higher mean signal level, m , received from its home cell, Cell A, than the mean signal level, m u , received from its neighboring cell.
- Cell B The two probability density functions of the signals from the two cells do not have much overlap In otherwords, the probability that the signal from Cell B is higher than that from Cell A due to signal fluctuation is low. In this case, the subscriber should be configured to Cell A only
- the probability that the signal received from a cell is higher than a particular value ⁇ can be calculated from the probability density function as-
- m . is greater than ⁇ n B by a large margin If the measured signal level from Cell A is ⁇ , then the probability that the received signal level from Cell B exceeding ⁇ is the shaded area in FIG G, which is the integral of the probability density function f f(x) over the range ( ⁇ , oo)
- FIG. 6 This figure shows a graph of the probability density functions versus the signal level in decibels.
- the lower graph of FIG. 6 shows that, near the Cell A borde ⁇ , the mean values, m and m , are very close and the probability density functions are heavily overlapped.
- the upper graph of FIG. 6 shows that, for a home cell subscriber, the probability is small that the signal from Cell B is higher that that from Cell A.
- the probability of a radiotelephone being covered by a cell is the integral of the probability density function f j ) over the range (S , oo) where S is the sensitivity of the radiotelephone.
- S is the sensitivity of the radiotelephone.
- the minimum sensitivity of a radiotelephone depends on the manufacturer but is typically -110 dBm.
- a probability density function for a mean value in - S + l.O ⁇ , the corresponding probability of coverage is:
- Cell A For a home cell subscriber located at the interior of the home cell, Cell A, the mean signal level received from Cell A, m , is strong enough to guarantee a high probability of RF coverage for the subscriber, such as 95% of the time in the preferred embodiment. Therefore, only Cell A should be configured to the subscriber.
- the main signal level of Cell A is not strong enough to guarantee a high probability of RF coverage for the subscriber, such as only 70% of the time in the preferred embodiment
- Cell B should be configured to the subscriber in addition to Cell A With two serving cells, the overall probability of receiving RF coverage is improved
- the process of the present invention illustrated in FIG. 3, ⁇ s,based on the mean values of the received signal levels from the neighboring cells withm communication distance of the subscriber radiotelephone.
- the mean values are averaged over the space domain This embodiment works for a maximum of two serving cells the subscriber's home cell and a second serving cell
- the preferred embodiment process begins with the mean value signals of the received signal levels from the neighboring cells being measured (301) at the radio subscriber's location when the fixed wireless radiotelephone svstem of the present invention is installed
- the mean values are then listed in descending order (305) For example, the mean values could be listed as follows
- the highest threshold level, Ti is defined to separate the home cell subscribers from the border cell subscribers This threshold level is associated with a high probability of coverage from a cell It is made up of two parameters, the minimum radiotelephone sensitivity, S ⁇ mn , and the standard deviation around the mean value, ⁇ These parameters are illustrated in FIG 8
- the lowest threshold level, S is the minimum radiotelephone sensitivity It identifies the subscribers located at the radio coverage holes, to whom no serving cells are to be assigned. This is because S is associated with a probability of coverage of only 50% on average. This is insufficient to guarantee satisfactory voice quality.
- m the mean value measured at the radiotelephone unit from Cell A, is greater than or equal to Ti, then the subscriber radiotelephone receives radio signal coverage from Cell A 90% of the time on average This is the case of a home cell subscriber located at the interior of a cell.
- Ti S + 1.7 ⁇ with a probability of coverage of 95.5%
- those who are located at the outer mid-po t of the home cell, Cell A are identified as the border cell subscribers. These subscribers will have additional cells configured that could result in unnecessary radio resource allocation.
- m A ⁇ Ti (310) the radiotelephone is identified as a home cell subscriber (315) and is configured to the home Cell A only. If m ⁇ S (350), the radiotelephone cannot receive a signal strong enough for communication. In this case, the subscriber cannot be configured to any of the cells (355).
- the radiotelephone is identified as a border cell subscriber (325).
- the second largest mean value signal, m is examined to determine if the subscriber should be assigned to another cell.
- the radiotelephone is configured to cells A and B (335). If m ⁇ S (340), then the signal from Cell B is too weak to be used by the radiotelephone. In this case, the radiotelephone is configured as a Cell A subscriber only (345).
- FIG. 4 A flowchart of an alternate embodiment process of the present invention is illustrated in FIG. 4. This embodiment determines if the radiotelephone subscriber should be assigned to three serving cells.
- the process of the alternate embodiment begins with measuring the mean value signals of the received signals from the neighboring cells (401). These mean values are listed in a descending order (402) to determine the largest mean value, the second largest mean value, and the third largest mean value. If the largest mean value, m A , is greater than or equal to the threshold,
- the radiotelephone is configured as a home cell subscriber (410). In this case, since the received signal is strong enough for adequate communications, a back-up service cell is not required. If the largest mean value is less than the minimum threshold, S min (415), then even the home cell cannot provide adequate coverage to enable the radiotelephone to communicate with the system (420).
- the radiotelephone is identified as a border cell subscriber (430).
- the alternate embodiment process then considers the second largest mean value m B combat (430). If Ti > t habiti > T2 (435), the mean values from the home Cell A and the second service Cell B are considered strong and the radiotelephone is configured to both cells (465). If m ⁇ ⁇ S (440), the signal from the second service cell is too weak for use and the radiotelephone is configured to the home Cell A only (480). If T2 > m B ⁇ S mm (445), the radiotelephone is again identified as a border cell subscriber (450). In this case, the signal from Cell B may not be strong enough to configure just to cells A and B and a third service cell is needed. Therefore, the third largest mean value, in (ros needs to be considered.
- T 2 > m C > S min (455) the mean values from cells B and C are in the same region.
- the subscriber radiotelephone is configured to cells A, B, and C (470) since the radiotelephone is receiving adequate signals from all three cells.
- FIG. 9 illustrates another alternate embodiment of the present invention.
- This embodiment is a generic embodiment in which a subscriber radiotelephone is assigned to N serving cells.
- the above described embodiments are only examples of the process of the present invention This process can be extended to configuring service cells beyond three if necessary due to terrain, buildings, or other factors Determining the number of serving cells is a choice of cost versus quality The more serving cells to which a radiotelephone is configured improves the quality of the communications but also increases the cost due to resource allocation, such as additional cell radios to handle the potential additional subscriber radiotelephones
- FIG 10. An example of one benefit of the present invention is illustrated in FIG 10.
- the upper portion of this figure shows a subscriber configured to both Cells A and B, with Cell A being the home cell. If the coverage of Cell A shrinks, as illustrated in the lower portion, coverage from Cell A is lost. However, since the subscriber is still withm Cell B's coverage area, communication ability is not lost It is obvious from the above description that the process and system of the present invention improves the quality of the communications for a subscriber on the border of a cell in a fixed wireless system. By configuring the radiotelephone to additional serving cells besides the home cell, when one of the cell's coverage areas changes the other serving cells enable the subscriber to continue the communication uninterrupted
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE69725991T DE69725991T2 (en) | 1996-08-16 | 1997-08-11 | Method for supplying a radio unit with cellular radio services in a fixed cellular radio system |
EP97937785A EP0919102B1 (en) | 1996-08-16 | 1997-08-11 | Method of assigning cellular radio service to a radio unit in a fixed cellular radio system |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US08/698,831 | 1996-08-16 | ||
US08/698,831 US5765103A (en) | 1996-08-16 | 1996-08-16 | Spatially-oriented subscriber configuration in a fixed wireless system |
Publications (2)
Publication Number | Publication Date |
---|---|
WO1998008349A2 true WO1998008349A2 (en) | 1998-02-26 |
WO1998008349A3 WO1998008349A3 (en) | 1998-04-23 |
Family
ID=24806838
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/IB1997/001116 WO1998008349A2 (en) | 1996-08-16 | 1997-08-11 | Spatially-oriented subscriber configuration in a fixed wireless system |
Country Status (5)
Country | Link |
---|---|
US (1) | US5765103A (en) |
EP (1) | EP0919102B1 (en) |
AR (1) | AR008302A1 (en) |
DE (1) | DE69725991T2 (en) |
WO (1) | WO1998008349A2 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2002023930A1 (en) * | 2000-09-14 | 2002-03-21 | Telefonaktiebolaget L M Ericsson (Publ) | Improvements in, or relating to, wireless broadband ip access system |
Families Citing this family (10)
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GB2327013B (en) * | 1997-06-30 | 2002-02-13 | Ericsson Telefon Ab L M | Mobile communications system |
FI106289B (en) | 1997-09-30 | 2000-12-29 | Nokia Mobile Phones Ltd | Procedure for selecting a cell and a mobile station |
US6349217B1 (en) * | 1998-04-24 | 2002-02-19 | Lucent Technologies Inc. | Multi-mode/multi-rate fixed wireless communication system |
WO2000019643A1 (en) * | 1998-09-28 | 2000-04-06 | Motorola Inc. | A terminal unit and a method for locating a terminal unit |
US6782262B1 (en) * | 1998-10-28 | 2004-08-24 | Telefonaktiebolaget Lm Ericsson | Self-tuning sufficient signal strength threshold |
US6434390B2 (en) * | 1999-06-03 | 2002-08-13 | Lucent Technologies Inc. | Macrodiversity control system having macrodiversity mode based on operating category of wireless unit |
US6701152B1 (en) | 1999-10-07 | 2004-03-02 | Utstarcom, Inc. | Method and system for assignment of fixed subscriber units in wireless local loop systems |
US6775552B2 (en) | 1999-12-30 | 2004-08-10 | Bellsouth Intellectual Property Corporation | Method and apparatus for fixing the location of a fixed wireless terminal in a wireless network |
US6775551B1 (en) | 1999-12-30 | 2004-08-10 | Bellsouth Intellectual Property Corporation | Method and apparatus for fixing the location of a fixed wireless terminal in a wireless network |
US20060274669A1 (en) * | 2003-04-01 | 2006-12-07 | Thomas Falck | Discovering proximate apparatus and services in a wireless network |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
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EP0505105A2 (en) * | 1991-03-22 | 1992-09-23 | Vodafone Limited | Communication request retry in cellular telecommunications networks and methods therefor |
EP0641135A2 (en) * | 1992-10-16 | 1995-03-01 | Nortel Networks Corporation | Low-power wireless system for telephone services |
WO1997022215A1 (en) * | 1995-12-14 | 1997-06-19 | Ionica International Limited | Enabling a subscriber unit in a radio network |
Family Cites Families (5)
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US4597105A (en) * | 1982-11-12 | 1986-06-24 | Motorola Inc. | Data communications system having overlapping receiver coverage zones |
JP2653000B2 (en) * | 1991-04-24 | 1997-09-10 | 日本電気株式会社 | Mobile wireless communication system |
US5275905A (en) * | 1991-05-28 | 1994-01-04 | Xerox Corporation | Magenta toner compositions |
GB2268854A (en) * | 1992-07-15 | 1994-01-19 | Orbitel Mobile Communications | Telecommunication system |
US5499386A (en) * | 1993-07-09 | 1996-03-12 | Telefonaktiebolaget L M Ericsson | Best server selection in layered cellular radio system |
-
1996
- 1996-08-16 US US08/698,831 patent/US5765103A/en not_active Expired - Lifetime
-
1997
- 1997-08-11 EP EP97937785A patent/EP0919102B1/en not_active Expired - Lifetime
- 1997-08-11 DE DE69725991T patent/DE69725991T2/en not_active Expired - Fee Related
- 1997-08-11 WO PCT/IB1997/001116 patent/WO1998008349A2/en active IP Right Grant
- 1997-08-19 AR ARP970103766A patent/AR008302A1/en active IP Right Grant
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0505105A2 (en) * | 1991-03-22 | 1992-09-23 | Vodafone Limited | Communication request retry in cellular telecommunications networks and methods therefor |
EP0641135A2 (en) * | 1992-10-16 | 1995-03-01 | Nortel Networks Corporation | Low-power wireless system for telephone services |
WO1997022215A1 (en) * | 1995-12-14 | 1997-06-19 | Ionica International Limited | Enabling a subscriber unit in a radio network |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2002023930A1 (en) * | 2000-09-14 | 2002-03-21 | Telefonaktiebolaget L M Ericsson (Publ) | Improvements in, or relating to, wireless broadband ip access system |
Also Published As
Publication number | Publication date |
---|---|
EP0919102B1 (en) | 2003-11-05 |
EP0919102A2 (en) | 1999-06-02 |
DE69725991D1 (en) | 2003-12-11 |
DE69725991T2 (en) | 2004-05-06 |
US5765103A (en) | 1998-06-09 |
WO1998008349A3 (en) | 1998-04-23 |
AR008302A1 (en) | 1999-12-29 |
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