JP2003506935A - Base station tracking system in wireless communication network - Google Patents

Abstract

SUMMARY A wireless communication network having a plurality of base stations (4) for servicing one or more mobile stations (6) is disclosed. When each mobile station (6) moves from the cell of the first base station (4) to the cell of the second adjacent base station (4), each base station (4) Maintain records of other neighbor base stations (4) to support "handoff" during The mobile station (6) transmits to the base station (4) a report indicating the acquisition of a pilot signal from another base station (4). The base station (4) maintains and updates records of other neighboring base stations (4) based on the report from the mobile station (6).

Description

Detailed Description of the Invention

Background 1. FIELD OF THE INVENTION The description herein relates to wireless communication systems. In particular, this description relates to systems including base stations that provide communication services to mobile stations.

2. RELATED TECHNOLOGY Wireless communication networks typically include a plurality of base stations that are spread over a geographical area and provide communication services to subscriber mobile stations, such as in a mobile cellular telephone network. A base station is typically capable of serving one or more mobile stations located within the geographical area surrounding the base station known as a "cell". As a mobile station moves geographically in the network, it may be served by different base stations along the path of travel. Such movement of the mobile station through the network places the mobile station in and out of the cell associated with a particular base station. When a mobile station transitions from one cell to another cell, it may no longer be able to receive service from the base station of the previous cell and may request service from the base station of the new cell. I don't know. This transition uses a "handoff" technique that is well known to those familiar with the technology of mobile communications.
) ”Facilitated by the procedure.

As part of the handoff procedure, a mobile station typically has its “neighbors”.
hboring "base station identifying information is used. The mobile base station's neighbor base stations are typically in the current radio frequency (RF) environment.
It is defined as a base station that can serve a mobile station at the current location of the mobile station.
Thus, the mobile station may transition to receive service from a neighboring base station by transitioning from the cell of the first base station to the cell of the second base station.
The second base station then resumes serving the mobile station according to the handoff procedure.

Mobile stations typically identify neighboring base stations by detecting a "pilot" signal transmitted by the base station that can provide service to the mobile station. Thus, the mobile station searches for pilot signals transmitted by potential neighbor base stations. The pilot signal from the base station is typically spread according to the code associated with the base station. A mobile station may detect a pilot signal of a neighboring base station by despreading the pilot signal of the neighboring base station with a code associated with the base station. Searching for pilot signals from potential neighbor base stations at mobile stations from a large number of base stations in the network is computationally intensive.

Intelligent allocation of computing resources to mobile stations in order to rank the search for neighboring base stations and thus to search for pilot signals from among a large number of potential neighboring base stations in the network. For this reason, base stations are typically referred to as "neighbors".
et) "or" neighbor list "to transmit information to the mobile station indicating the members. The neighbor group is to include base stations that may be able to support the handoff. , Typically includes a memory that maintains data indicating the identification of adjacent base stations in the neighbor group, which is typically the individual base stations when the wireless network was established. These memories in a base station are typically used to indicate the addition or removal of base stations from a neighbor population, as base stations are added to and removed from the network. Manually reprogrammed, a less cumbersome and more convenient method and system for establishing and maintaining neighbor groups in base station memory. Stem is needed.

Overview An object of embodiments of the present invention is to improve the flexibility of establishing a base station in a wireless communication network.

Another object of the embodiments of the present invention is to provide a method for dynamically notifying a base station of a wireless communication network about the presence of a neighboring base station.

Another object of embodiments of the present invention is to simplify the integration of a new base station into a wireless communication network that includes one or more existing base stations.

Another object of the embodiment of the present invention is to simplify removal of a base station of a wireless communication network.

It is another object of embodiments of the present invention to further provide an efficient system and method for dynamically maintaining information to base stations of a wireless communication network regarding the presence of neighboring base stations. .

Briefly, embodiments of the present invention identify base station identities in a population of neighbors.
Aiming at a wireless communication network including a first base station having a memory for accumulating data for displaying the (ity). The second base station transmits a pilot signal including information indicating the identity of the second base station. The mobile station acquires the pilot signal and extracts the information indicating the identity of the second base station. If the identity of the second base station extracted by the mobile station is not included in the neighbor group, the data indicating the identity of the base station in the neighbor group may include the identity of the second base station. Will be updated.

Detecting neighboring base stations at the mobile station eliminates the need for complex pre-programming of the neighbor population at the base stations of the wireless network when new base stations are added.
When a new base station is added, the subscriber's mobile station acquires the pilot signal of the new base station. If the newly acquired base station is not in the neighbor list, the neighbor list is defective.
The subscriber mobile station preferably notifies the defective surrounding base station by transmitting a code associated with the pilot signal of the newly acquired base station to the surrounding base station. And, again, the system causes the base station to remove a particular base station from its neighbor population if no mobile station has, for some time, identified the particular base station as a neighbor.

DETAILED DESCRIPTION According to an embodiment of the present invention, a base station in a wireless communication network updates and maintains a record identifying "neighboring" base stations in response to a message received from a mobile station in the network. To do. Each mobile station acquires a pilot signal transmitted by the base station to ascertain which base station is included as a neighbor base station in the record of the particular base station currently serving the mobile station. The mobile station transmits a message having information identifying a base station adjacent to the base station currently serving the mobile station. Upon receiving these messages, the base station currently serving the mobile station updates the record identifying its neighbor base station.

According to an embodiment, the mobile station receives a transmission from the base station currently serving the mobile station, including the neighbor list. The mobile station keeps a copy of the neighbor list received,
And search for pilot signals associated with base stations in the neighbor list and pilot signals for base stations not in the neighbor list. If the mobile station obtains a pilot signal for a base station that is not in the neighbor list, the mobile station sends an indication to the base station currently serving the mobile station that the neighbor list is defective. This indication may be in the form of a data packet that alerts the base station about a defect in the neighbor roster and confirms the sign of the pilot associated with the base station not in the neighbor roster. Upon receiving the data packet, the base station currently serving the mobile station adds the newly acquired base station to its neighbor list.

FIG. 1 shows a topographical map of a wireless communication network including a plurality of base stations 4 and a plurality of mobile stations 6.
As shown in FIG. 1, the wireless communication network includes a plurality of cells 2. Mobile stations 6 in cell 2 are served by the corresponding base station 4. FIG. 1 shows that cells 2 are adjacent but non-overlapping. However, such adjacent cells that may be served by either the base stations 6 respectively corresponding to the cell 2 in which the mobile station in the overlapping area overlaps, or both base stations may overlap. It is understood that there is no.

Mobile stations in one cell 2 served by the corresponding base station 4 may move to different cells 2 to be served by different base stations 4. As an example, mobile station 6H is shown to be in cell 2 and served by base station 4C, as indicated by the solid arrow connecting base station 4C to mobile station 6H. Since the mobile station 6H is moving in the direction toward the base station 4D,
Mobile station 6H will eventually move out of cell 2C and into cell 2D. At some point, base stations 4C and 4D will coordinate a "handoff" with mobile station 6H such that the responsibility for servicing mobile station 6H transitions from base station 4C to base station 4D. Therefore, the base stations 4C and 4D are neighboring base stations.

According to an embodiment, each of the base stations 4 maintains data in a memory displaying a “neighbor population” containing information indicating the identity of one or more neighboring base stations. Referring to FIG. 1, the base station 4D has its neighbor base stations 4A, 4B, 4C, 4E, 4F and 4G as cells 2D corresponding to the base station 4D, and the cell 2D is a cell of each of these neighbor base stations. Adjacent to 2X. The neighbor population stored in memory at base station 4D may potentially include the identities of each of these six adjacent base stations 4X.
Similarly, the base station 4B has base stations 4A, 4D and 4E as its adjacent base stations. The neighbor population stored in memory at base station 4B may potentially have information identifying base stations 4A, 4D and 4E at that time.

Each base station 4 serves the mobile station 6 in its cell 2C by transmitting to the mobile station 6 on the forward transmission link and from the mobile station 6 on the reverse transmission link. . Such a communication system is referred to as "IS-95 Standard (IS-95 Sta
"TIA / EIA / IS-95 Mobile Station-Base Station Compatibility Standard (TIA / EIA / IS-95 Mobile Station-for Dual-Mode Wideband Spread Spectrum Cellular Systems)
Base Station Compatibility Standard
for Dual-Mode Wideband Spread Spectr
um Cellular System) -based code division multiple access (CDMA)
) System based. Of course, embodiments of the present invention also include other mobile radios in which the base station provides communication services to the mobile station on the forward transmission link and the mobile station transmits control information to the base station on the reverse transmission link. It is also applicable to communication systems. Such an alternative embodiment is "Method and Apparatus for High Ra".
te Packet Data Transmission ", which is described in US patent application Ser. No. 08 / 963,386, which is entitled Qualcomm.
Comm, Inc. ), And incorporated herein by reference.

FIG. 2 illustrates a processing configuration of the base station in the wireless communication network according to the embodiment. Base station configuration 100 includes a plurality of base station controllers (BSCs) 104 that provide the processing resources of base station 4 shown in FIG. Each of the BSCs 104 communicates with a public switched telephone network (PSTN) for facilitating voice communication, or a master system controller (MSC) 102 that communicates with a network 106 such as an internet gateway for data communication.
Be combined with. The MSC 102 controls the communication between the BSCs 104 and the individual Bs
It manages communication traffic between the SC 104 and the network 106. MSC102 is M
It communicates with network 106 over the telephone interface in that SC 102 is essentially a node in network 106.

FIG. 2 illustrates the processing configuration of BSC 104A including central bus 124 coupling the processing resources of BSC 104 to MSC 102. BSC 104A also includes a general purpose processor 122, memory 118, RF front end 114 and antenna 116.
The RF front end 114 and antenna 116 provide a bidirectional transmission interface between the BSC 104A and individual mobile stations. Thus, the RF front end 1
All forward and reverse traffic is facilitated by 14 and antenna 116.

FIG. 3 shows a processing configuration 200 of the mobile station 6. RF front end 214 and antenna 216 receive transmissions from base station 4 on the forward transmission link and transmit to select base station 4 on the reverse transmission link. A central bus (not shown) enables communication between a user interface (not shown), general purpose processor 222 and memory 218.

The forward link of the base station transmits a "pilot signal" which is included with the transmission data and which contains information identifying the transmitting base station. The pilot signal transmitted on the forward link is initially acquired by the base station 6 (in
initial acquisition, phase recovery (phase recovery)
ry), timing recovery, and ratio combining (r
audio combining). The mobile station 6 also has a signal-to-noise and interference ratio (signal-to-noise-and-interf).
The pilot signal is used to measure the erence ratio (C / I). The transmission of pilot channels in such a forward transmission link is described in the aforementioned US patent application Ser. No. 08 / 963,386, with respect to FIG. 3A thereof, which is incorporated herein by reference. The pilot signal transmitted by a particular base station is spread with a code associated with the transmitting base station. According to an embodiment, each base station 4 has an associated code for spreading its respective pilot channel, which pilot channel is all other for spreading the signals of other base stations 6 in the network. Orthogonal to the pilot code of. According to an embodiment, the pilot signal is the same as in the above-mentioned US patent application Ser. No. 08 / 963,386.
It was transmitted in the manner described with respect to FIG. 4B and is hereby incorporated by reference.

Each base station 4 broadcasts the pilot signal to all mobile stations 6 within the range in which the pilot signal is acquired. A particular mobile station 6H may acquire pilot signals for more than one base station 4. For example, FIG. 1 shows mobile station 6 spanning cells 2C and 2D. The mobile station 6 is therefore able to acquire the pilot signals transmitted by each of the base stations 4C and 4D. Similarly, mobile station 6E is located within the triangle formed by base stations 4B, 4D and 4E. The mobile station 6E is able to acquire the pilot signals transmitted by each of the base stations 4B, 4D and 4E.

Upon obtaining the pilot signal from the base station 4, the mobile station 6 despreads the pilot signal using the pilot spreading code assigned to the base station 4,
The base station 4 transmitting the pilot signal can be confirmed. Therefore, when the mobile station 6 acquires a pilot signal of a particular base station 4, the mobile station 6 determines that the base station 4 can serve the mobile station 6 in the current RF environment. . For example, the mobile station 6E acquires the pilot signals transmitted by the base stations 4B, 4D and 4E. Mobile station 6E therefore determines that it can receive data services from any of these three base stations 4. In addition, mobile station 6E determines that base stations 4B and 4D should be neighbors of base station 4E.

The mobile station 6 preferably reports the detection of a neighbor base station to the base station currently serving the mobile station with a message transmitted on the reverse communication link. IS-
In an embodiment of the invention implemented in a system according to the H.95 standard, such a message is preferably a pilot strength measure transmitted by a mobile station in such a system.
Included in the "replace message" (PSMM). Here, the PSSM preferably includes at least the identity of the base station 4 corresponding to the acquired pilot signal. The base station 4 receiving the PSMM can then update the neighbor population in its memory.

Of course, this message reporting the acquisition of the pilot signal may be transmitted on any other control channel of the reverse transmission link. For example, in an embodiment of the invention embodied in a system such as that described in the aforementioned US patent application Ser. No. 08 / 963,386, this message is currently providing data services to mobile station 6. Traffic channel request (traf) transmitted by the mobile station 6 to the base station 4.
Fic channel request (TCR). In this embodiment, (1) whether the mobile station 6 is not ringing and requests the base station to be ringing, or (2) whether the mobile station 6 detects a reliable change in the RF environment. At any time, mobile station 6 will transmit the TCR to base station 4 on the reverse link data channel.

Regardless of the type of reverse link message used, each mobile 6 preferably confirms which base stations should be included in the neighbor population of the base stations currently serving mobile station 6. Data is included in the reverse link message while the call is in progress (eg, as part of PSMM or TCR). Alternatively, each mobile station 6 may transmit equivalent data when not ringing (eg, on a connection channel). That is, mobile station 6 receives and acquires one or more base station pilot signals during the previous time slot. Having determined the identities of those base stations 4 that are transmitting the acquired pilot signals, the mobile station 6 determines that those base stations that are to be included in the neighbor population of the base stations currently serving the mobile station 6. Information may be included in the message on the reverse link that displays the identity of the person.

The base station 4 receives the reverse link message and from it (as determined by the mobile station 6 transmitting the reverse link message) other neighbors to be included in the neighbor population receiving the reverse link message. The information displaying the base station 4 is extracted.
The general purpose processor 122 of the associated BSC 104 (FIG. 2) that receives the reverse link message accesses the data representative of the base stations known to be in the neighbourhood and stored in memory 118. General purpose processor 122 then associates the data extracted from the reverse link message received (indicating the identification of the base stations that should be in the neighbor population) with the neighbor population data stored in memory 118. If the identification of any base station extracted from the reverse link message does not match the corresponding base station in the neighbor population data in memory, general purpose processor 122 determines the neighbor population in memory 118 that contains the unmatched neighbor base station 4. Update the data.

By determining its neighbor base station from the signal provided by the mobile station 6, the base station 4 dynamically determines its neighbors without the need to specially program the memory that stores the data representing the neighbor population. Can be determined. When the new base station 4 is added to the wireless communication network, the mobile station will receive its pilot signal and inform the existing base station 4 of its new neighbor base station. The neighbor population maintained at these existing base stations is then updated to include information identifying the newly added base station 4.

In another embodiment of the invention, the members of the neighbourhood, maintained at the base stations 4, are aged out of time, and if these base stations should no longer be considered as neighbors. If is determined, it is removed from the neighbor group. This is useful, for example, in updating neighbor populations to reflect that a base station has been removed or is unavailable from the network. And, again, this embodiment is useful for accommodating changes in the RF environment that result in changes in the size of cell 2 affecting whether or not the base stations are adjacent.

Here, for each base station member of the neighbor group maintained in the memory of the base station 4,
The base station 4 may send a message to the base station 4A that the particular base station in the neighbor group received on the reverse link (eg, a base station identified as a neighbor through acquisition of a pilot signal at the mobile station and the base station 4A). Or the next confirmation in the PSMM message) to keep a record of the last confirmation as a neighbor. According to an embodiment, upon receiving a reverse link message indicating the acquisition of a pilot signal for a particular base station in the neighbor population, the base station 4 receiving the reverse link message starts or resets a timer. When the set number of time slots have elapsed and the value of the timer has been increased to the threshold value, the base station 4 determines that the member base stations in the neighbourhood should be removed. The removed member base station re-adds to its neighbors group at some time in the future upon receiving a reverse link message indicating acquisition of its pilot at the mobile station transmitting the reverse link message, as previously discussed. May be done. Removing the ineffectiveness of base stations from the network by obsolete the members of the neighbourhood maintained in base station memories eliminates the need to reprogram these memories.

While what has now been considered to be the preferred embodiments of the invention have been illustrated and described, various other variations may be made without departing from the true scope of the invention, and Those skilled in the art will appreciate that equivalents may be used instead. In addition, many modifications may be made to adapt a particular situation to the teachings of the invention without departing from the central inventive concept described herein. Therefore, the present invention is not limited to the particular embodiments disclosed, but it is intended that the present invention include all embodiments falling within the scope of the appended claims.

[Brief description of drawings]

FIG. 1 is a topology of a wireless communication including a base station and a mobile station according to an embodiment of the present invention (to
is shown.

2 shows a schematic diagram illustrating a configuration of processing hardware in a base station according to the embodiment of FIG.

3 shows a schematic diagram illustrating a configuration of processing hardware in a mobile station according to the embodiment of FIG.

[Explanation of symbols]

2 ... cell 4 ... base station 6 ... mobile station BSC 104 ... base station controller 122,
222 ... General-purpose processor 114, 214 ... RF front end 116, 21
6 ... Antenna 118, 218 ... Memory

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Claims (10)

[Claims] 1. A first base station includes a memory for accumulating data indicating the identities of neighbor group base stations, and a second base station indicates the identities of second base stations. In a wireless communication network transmitting a pilot signal containing information, a mobile subscriber station obtains a pilot signal transmitted by a second base station to extract information indicating the identity of the second base station. Then, in order to determine whether the neighbor group includes the identity of the second base station, the extracted information displaying the identity of the second base station is used to display the identity of the base station of the neighbor group. And if the identity of the second base station is not included in the neighbor group, update the data indicating the identity of the base station of the neighbor group to include the second base station. Update the data showing the identity of the base station Methods for. 2. A first from a mobile subscriber station on a control channel of a reverse transmission link.
The method of claim 1, further comprising sending the message to a th base station. 3. A base in which the wireless communication network further includes a base station transmitter and one or more mobile stations associated with a base station of the neighbor population, the base including information indicating the identity of the base station associated with the base station transmitter. Sending a pilot signal from each of the transmitters, detecting that no mobile station has acquired the pilot signal transmitted from a particular base station transmitter by any mobile station for a set time, and detecting that there is no acquisition The method of claim 1, further comprising: disconnecting the identity of the base station associated with the particular base station transmitter from the neighbor population in the memory of the first base station. 4. Transmitting the extracted information indicating the identity of the second base station from the mobile station to the first base station and displaying the identity of the second base station to determine the match. The method of claim 1, further comprising: comparing the extracted information with the data indicative of the identity of the base stations of the neighbor population. 5. The mobile station transmits data indicating the identities of the base stations of the neighbor group, and the mobile station extracts the extracted information indicating the identities of the second base station to determine the match with the neighbors. Includes the identity of the second base station of the neighbor group if the identity of the second base station does not match the identity of any base station of the neighbor group in association with the data indicating the identity of the base station of the group. The method of claim 1, further comprising: transmitting a signal from the mobile station to the first base station to initiate 6. A pilot signal including information indicating the identities of a first base station and a second base station, which includes a memory for accumulating data indicating the identities of base stations of a neighbor group. Second
The second base station, the mobile station acquiring the pilot signal of the second base station to extract information indicating the identity of the second base station, the identity of the second base station included in the neighbor group A logic unit for comparing the extracted information indicating the identity of the second base station with the data indicating the identity of the base station of the neighbor group to determine whether it is included in the neighbor group. A wireless communication network including a logic unit for updating data indicating the identity of the base stations of the neighbor group to include the identity of the second base station if not present. 7. The wireless communication network of claim 6, wherein the mobile station includes circuitry for transmitting a message to the first base station on the control channel of the reverse transmission link. 8. A plurality of base stations each of which transmits a pilot signal including information indicating the identity of the base station associated with the base station transmitter, the plurality of mobile stations being at least one base station. A plurality of mobile subscriber stations acquiring pilot signals, detecting the absence of acquisition of a particular one pilot signal of the plurality of base stations at each of the mobile stations for a set time and first 7. The wireless communication network of claim 6, further comprising: a logic unit for disconnecting from a neighbor group in the memory of the th base station. 9. A logic unit for the mobile station to transmit and compare the extracted information indicating the identity of the second base station to the first base station and a logic unit for updating and a logic unit for updating. 7. The wireless communication network of claim 6, implemented by circuitry at the first base station. 10. The first base station transmits to the mobile station a signal containing data indicative of the identity of the neighbor group base stations, and the mobile station further comprises a second base station to determine a match. A logic unit for associating the extracted information indicating the identity of the station with the data indicating the identity of the base station of the neighbor group, and the identity of the second base station to match the identity of any base station of the neighbor group. 7. The wireless communication network of claim 6, further comprising circuitry for transmitting a signal to the first base station to initiate inclusion of the identity of the second base station of the neighbor population.