MXPA98010564A - Method and apparatus to reduce multiple pilots dominan - Google Patents

Method and apparatus to reduce multiple pilots dominan

Info

Publication number
MXPA98010564A
MXPA98010564A MXPA/A/1998/010564A MX9810564A MXPA98010564A MX PA98010564 A MXPA98010564 A MX PA98010564A MX 9810564 A MX9810564 A MX 9810564A MX PA98010564 A MXPA98010564 A MX PA98010564A
Authority
MX
Mexico
Prior art keywords
base station
transceiver
nearby
transceiver element
linking
Prior art date
Application number
MXPA/A/1998/010564A
Other languages
Spanish (es)
Inventor
Kuo Wenyi
Bi Qi
Francis Weaver Carl
Howard Meyers Martin
Albert Sanders Charles
Original Assignee
Lucent Technologies Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Lucent Technologies Inc filed Critical Lucent Technologies Inc
Publication of MXPA98010564A publication Critical patent/MXPA98010564A/en

Links

Abstract

A method for reducing multiple dominant pilots in a CDMA transmission system comprises linking a transceiver element with a nearby base station for transporting signals between the transceiver element and the nearby base station. Transmit from the transceiver element forward link signals from a nearby sector associated with the nearby base station. An apparatus is also described

Description

METHOD AND APPARATUS TO REDUCE MULTIPLE KEY DRIVERS WF9 4 »l mvraogjQn This invention relates to wireless communications and more particularly to multi-access wireless communications with code division (CDMA = Code Division Multiple Access). BACKGROUND OF THE INVENTION Wireless mobile communications provide the greatest convenience for users to access voice and data service, essentially anywhere and at any time. CDMA communication systems are one of the most promising digital wireless communications systems that can provide the desired mix of voice and data services. In addition, CDMA systems have features such as smooth transfer and frequency re-use that make CDMA a much more effective selection than other access technologies such as TDMA, GSM. Soft transfer is a transfer technique that allows a mobile user to communicate with two or more base stations at the same time. The REF. 28971 soft transfer can not only eliminate the potential ping-pong game of the transfer, but also allows a smooth transmission in the transfer without requiring quiet time. Unlike other access technologies, soft transfer can be increased in CDMA systems, because CDMA systems allow the same frequency to be reused between cells. In addition, allowing frequency reuse between cells in CDMA systems means that frequency planning is no longer necessary, it is one of the most difficult tasks in other access technology such as TDMA, GSM, LED, etc. However, CDMA systems have their own set of aspect and considerations. One aspect relating to successful soft transfer and allowing the use of frequency between cells anywhere is the interference pattern. In the practical field deployment, there are unavoidable situations in some areas, which result in the coexistence of several dominant pilots. That is, several base stations have approximately the same path loss to the same area. It should be noted that each base station has a unique pilot that serves as a beacon for that particular base station. The aspects associated with the situation of multiple dominant pilots are triple. First, since several base stations are approximately equal path loss, the signals thereof interfere with each other. In order to keep the call, all these base stations have to get involved in the smooth transfer with the mobile unit sooner or later. If the mobile unit moves at a relatively fast speed, then the fast transfer is critical to the survival of the call. This rapid transfer requirement presents a great challenge for both the mobile units and the infrastructure in the physical processing equipment. Second, when a high number of base stations are involved in a smooth transfer, that presents a high factor that reduces the performance on the transmission power needs and degrades the current capacity of the wireless system. Third, areas that have multiple dominant pilots are areas that have a higher probability of withdrawing calls or degrading voice quality. It would be beneficial to reduce areas that can have multiple dominant pilots on site or equivalently to reduce the number of pilots that are within several dBs of the strongest pilot. COMPENDIUM OF THE INVENTION The present invention relates to a method for reducing multiple dominant pilots in a CDMA transmission system. The method comprises linking a transceiver element with a nearby base station for transporting signals between the transceiver element and the nearby base station. Transmit from the transceiver element forward link signals from a nearby sector associated with the nearby base station. BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the present invention can be obtained by considering the following description in conjunction with the drawings in which: Figure 1 is a block diagram representative of a typical wireless network; Figure 2 is a practical representation of pilot signals that are within 6 dBs of the strongest pilot signal for a typical CDMA system. * Figure 3 is a diagrammatic representation of a CDMA cell showing three sectors, * Figure 4 is a graphical representation of pilot signals that are within 6 dBs of the strongest pilot signal for a CMDA system employing the present invention. DETAILED DESCRIPTION OF VARIOUS ILLUSTRATIVE MODALITIES Although the present invention is particularly well suited for a CDMA system and will thus be described, the present invention is equally well suited for use with other systems including broadband CDMA (W-CDMA). CDMA modulation techniques are used in communication systems, in order to allow a large number of users to communicate. In a typical CDMA communication system, all communication channels are multiplied into one or more common broadband frequencies. Each channel is differentiated by a unique dispersion code. Before transmission, information signal of each channel is modulated with a scatter code, in order to convert the information signal into a broadband signal. A receiver demodulates the broadband signal received, by combining the broadband signal, with the corresponding scatter code to recover the information signal. The dispersion code is typically a binary code. Since the same bandwidth is available to all users, information signals on other channels may appear as co-channel interference or noise, when the received signal is demodulated by the scatter code. Now with reference to Figure 1, a block diagram representative of a typical wireless network is illustrated. A mobile telephone switching office (MTSO) 10, also known as a mobile switching center (MSC = Mobile Switching Center), provides call switching between the wireless switching network and the switched wired network 12. The MTSO 10 controls the entire operation of a wireless communications system, configuration and verification of all wireless calls and tracking of the location of all wireless equipped vehicles, which travel in the system, arranging transfers and providing billing information. The MTSO 10 is connected to a plurality of base stations 14. The base station 14 is a multi-channel transceiver with fixed position in the wireless network, which is coupled through a radio port to an antenna 16. The geographic area for wherein the base station 14 acts as the communications gate, it is called a cell 18, the various cell nodes of the base station 14 are distributed at convenient locations. A mobile unit 20 communicates with the base station 14 within a particular cell 18 through a forward link or in the direction of the transmission and an inverted link. The field deployment of CDMA systems results in an unavoidable situation that from time to time results in several dominant pilots in one area. The signals of several base stations interfere with each other and with little movement or change with shadow fading, the relative signal strength can change significantly. The existence of several dominant pilots has a negative effect on the speed of success in access and the ability to have smooth uniform and smooth transfers. It would be beneficial to reduce the number of multiple dominant pilots, as well as the areas in which they occur. The characteristics of an area that has multiple dominant pilots are that the signal strength of several base stations 14 is within n close range to each other, such as within 3 to 6 dB. Because the signals are so close, they interfere with each other in such a way that with a small amount of movement by a mobile unit 20 or a change of shadow fading, the relative signal strength can change significantly. Two significant problems occur as a result of this characteristic. First, if a mobile unit 20 originates or responds to a page in the area having multiple dominant pilots, the mobile unit 20 can only latch on a pilot on a base station 14. The mobile unit 20 sends access probes to the station base 14 in which it has been nailed, requesting service. Conveniently, the mobile unit 20 in a couple of seconds of call processing will pass to soft transfer to secure the call. Before the call is secured and smooth transfer occurs, the mobile unit 20 operates in simplex, speaking with only one base station 14. The relative signal strength from a base station 14 can change rapidly and significantly, which will result in the call is canceled before making sure. Second, if the mobile unit 20 with a call in process enters an area that has multiple dominant pilots, there is a high potential need for carrying out transfer activities. If the mobile unit 20 is in a medium to high speed movement, then the transfer speed will need to be fast enough, otherwise the call quality will be degraded and it will even result in the call being removed. With reference to Figure 2, there is illustrated a graphical representation of pilot signals that are within 6 dBs of the strongest pilot signal for a typical CDMA system showing 10 base stations 14, representing 10 cells 18. With reference to the Figure 3, it can be seen that each cell 18 is typically composed of three sectors. A 92-degree antenna is used for the tuned antenna 30. The three sector 30 antennas are directed in directions of 60 °, 180 ° and 300 °. With reference again to Figure 2, an asterisk represents the placement of three-sector antennas for a cell 18. The number of multiple pilots within 6 dB of the strongest pilot is represented by a point for two, with a triangle for three. A square for four, for a plus sign for 5 and for a circle for 6. In order to reduce the number of dominant pilots in a high density area of multiple dominant pilots, the present invention uses a simultaneous broadcast element or a omnidirectional cell. The element of simultaneous diffusion or omnidirectional cell is inserted in a high density area of multiple dominant pilots. The increased local signal strength of the simulcast element or omnidirection cells reduces the number of dominant pilots in each geographic location. The simulcast element is essentially a repeater that transmits the forward link signal obtained from the base station 14 and receives the reverse link signal from the mobile unit 20. The communication link between the simultaneous broadcast element or omnidirectional cell and Base pressure 14 can be wired or wireless. With reference to Figure 4, a graphic representation of the pilot signals that are within 6 dBs of the strongest pilot signal for a CDMA system employing the present invention is illustrated, showing 10 base stations 14 representing 10 cells 18. A Asterisk represents the placement of the three sector antennas for a cell 18. A star (5-point) represents the placement of a simultaneous broadcast element 40. The number of multiple pilots within 6 dB of the strongest pilot is represented by a point for two, for a triangle for three, for a square for four, for a plus sign for five and for a circle for 6 or more. Three simultaneous broadcast elements 40 are illustrated. Each element of simultaneous diffusion has 10 dB less transmission power than a regular sector, and repeats the transmission and reception function of a nearby sector. Numerous modifications and alternate embodiments of the invention will be apparent to those skilled in the art., in view of the above description. Accordingly, this description should be considered as illustrative only and is for the purpose of illustrating to those skilled in the art, the best mode for carrying out the invention. Details of the structure can be varied substantially without departing from the spirit of the invention and the exclusive use of all modifications that fall within the scope of the appended claims, are reserved. It is noted that in relation to this date, the best method known to the applicant to carry. the practice of said invention is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims (27)

  1. CLAIMS 1.- A method for reducing multiple pilots-dominant, in a CDMA communications system, characterized in that it comprises the steps of: linking the transceiver element with a nearby base station to transport signals between the transceiver element and the nearby base station, * and transmitting from the transceiver element forward link signals from a nearby sector associated with the nearby base station.
  2. 2. - The method according to claim 1, characterized in that it further comprises the step of receiving inverted link signals of the transceiver element for the near sector associated with the nearby base station.
  3. 3. The method according to claim 1, characterized in that it further comprises locating the transceiver element in an area having high density of multiple dominant pilots.
  4. 4. - The method according to claim 1, wherein the step of linking comprises linking by wired connection.
  5. 5. - The method according to claim 1, characterized in that the step of linking further comprises linking by a wireless connection.
  6. 6. - The method according to claim 1, characterized in that the step of transmitting further comprises transmitting from the transceiver element with less power than transmitting from the near sector associated with the nearby base station.
  7. 7. - The method according to claim 6, characterized in that less power is approximately 10 dB of less power.
  8. 8. - The method according to claim 1, characterized in that the transceiver element can be selectively associated with a different nearby sector associated with the nearby base station.
  9. 9. - The method according to claim 1, characterized in that the transceiver element can be selectively associated with a different nearby base station.
  10. 10. The method according to claim 1, characterized in that the transceiver element is a simultaneous diffusion element.
  11. 11. The method according to claim 1, characterized in that the transceiver element is an omnidirectional base station.
  12. 12. - Method for reducing multiple dominant pilots in a CDMA communication system, characterized in that it comprises the steps of: selecting at least one area having a high density area of multiple dominant CDMA pilots, locating a transceiver element in the selected area as minimum, linking the transceiver element with a nearby base station to carry signals between the transceiver element and the nearby base station; and transmit forward link signals from the transceiver element.
  13. 13. - The method according to claim 12, characterized in that the step of transmitting further comprises transmitting forward link signals of a nearby sector associated, with the base station nearby.
  14. 14. - The method according to claim 12, characterized in that the transceiver element is a simultaneous broadcast element.
  15. 15. - The method according to claim 12, characterized in that the transceiver element is an onmidirectional base station.
  16. 16. The method according to claim 12, characterized in that it further comprises the step of receiving inverted link signals in the transceiver element for the near sector associated with the nearby base station.
  17. 17. - The method according to claim 12, characterized in that the linking step comprises linking by a wired connection.
  18. 18. The method according to claim 12, characterized in that the step of linking further comprises linking by a wireless connection.
  19. 19. The method according to claim 12, characterized in that the step of transmitting further comprises transmitting from the transceiver element with less power than transmitting from the near sector associated with the nearby base station.
  20. 20. The method according to claim 19, characterized in that less power is approximately 10 dB of less power.
  21. 21. The method according to claim 14, characterized in that the simulcasting element can be selectively associated with a different nearby sector associated with the nearby base station.
  22. 22. The method according to claim 14, characterized in that the simulcasting element can be selectively associated with a different nearby base station.
  23. 23. An apparatus for reducing multiple dominant pilots in a CDMA transmission system, characterized in that it comprises a transceiver located in an area of multiple dominant CDMA pilots where the transceiver transmits forward link signals, - a base station having a sector associated near the transceiver; linking means that couple the transceiver with the base station to allow transporting signals between the transceiver and the base station.
  24. 24. The apparatus according to claim 23, characterized in that the transceiver is a repeater.
  25. 25. The apparatus according to claim 23, characterized in that the transceiver is an omnidirectional base station.
  26. 26. The apparatus according to claim 23, characterized in that the transceiver transmits with less power than the base station.
  27. 27. The apparatus according to claim 24, characterized in that the repeater further comprises a receiver for reverse link signals.
MXPA/A/1998/010564A 1997-12-15 1998-12-11 Method and apparatus to reduce multiple pilots dominan MXPA98010564A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US990625 1997-12-15

Publications (1)

Publication Number Publication Date
MXPA98010564A true MXPA98010564A (en) 2000-07-01

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