HK1104744A - Method and system for optimizing system-access and soft-handoff parameters based on location information - Google Patents

Description

Method and system for optimizing system access and soft handoff parameters based on location information

The present application is a divisional application of the inventive patent application having an application date of 9/20/2002, an application number of 02823355.7, entitled "method and system for optimizing system access and soft handoff parameters based on location information".

Background

FIELD

The present invention relates generally to communication systems, and more particularly to a system and method for optimizing soft handoff and system access parameters in a telecommunications system.

Background

Cellular telecommunication systems feature a plurality of mobile units (e.g., cellular telephones) that communicate with one or more base stations. Signals transmitted by mobile units are received by a base station and are often relayed to a Mobile Switching Center (MSC). The MSC, in turn, routes the signal to a Public Switched Telephone Network (PSTN) or to another mobile unit. Also, signals may be transmitted from the PSTN to the mobile unit through the base stations and MSC.

Each base station covers a "cell" within which the mobile unit can communicate. The cells cover a limited geographic area in which calls from mobile units are routed to and from the telecommunications network through the MSC. Typically the coverage area of a cellular telecommunication system may be divided into several cells. Each cell may also be divided into several sectors. Different communication resources are typically allocated to each cell or sector to maximize communication system resources. When a mobile unit moves from a first cell to a second cell, or from a first sector to a second sector, a handoff must be performed to allocate new system resources associated with the second cell or sector.

The handoff includes performing negotiations between a group of mobile units and one or more managing base stations and/or MSCs. Handover improves system performance at the expense of more system resources. As smaller cells and/or sectors are used to meet the demands of increased communication system capacity, efficient and timely handoff procedures are becoming more important. Using smaller cells and/or sectors increases the number of cross-border and resource allocations, thereby increasing the need for an adaptive, efficient, fast, and cost-effective handover procedure.

The handover may be classified as a hard handover or a soft handover. Hard handoff procedures are used to transfer ongoing calls between neighboring cells or sectors having different frequency allocations, having different radio configurations, such as different frame offsets in the case of third generation wireless systems (3G), and even for handoffs between systems, such as between Code Division Multiple Access (CDMA) and Analog (AMPS). In hard handover, a first link of a first cell is disconnected and then a second link is established. In soft handover, the first link is maintained until the second link is established. Thus, there is a period of time during which the first link and the second link remain simultaneously. In either case, a large delay between dropping the first link and establishing the second link may result in an unacceptable quality of service for the communication.

Access handover is another characteristic of 3G systems. Due to the rapid dynamic changes in the Radio Frequency (RF) channel, the control (paging) channel may not be in soft handoff when the traffic channel is allocated and the mobile station may not be monitoring the best cell when receiving a page. Thus, the performance of a phone operating in a system access state is vulnerable. In order to improve system performance when a mobile station is in a system access state, some techniques are proposed. These techniques include access record handover, channel assignment into soft handover, access handover, and access probe handover.

In handling handover, the mobile unit uses various static handover parameters that may be wirelessly transmitted and stored by the mobile unit. One problem with using static handover parameters is that a mobile unit must use the same static handover parameters for all geographic areas regardless of the topography, traffic density, and other terrestrial characteristics of the cell location and/or sector. Thus, handoffs based on static handoff parameters are unacceptable for various geographic locations, may consume greater system resources and result in poor communication service performance.

Therefore, there is a need for an adaptive, fast, efficient and cost-effective method and system for facilitating reliable system access and soft handover in cellular telecommunication systems with optimized parameters based on location information.

Abstract

According to one aspect of the invention, a wireless communication system includes a first transceiver, a second transceiver, and a third transceiver that is capable of communicating with the first transceiver. The system may use a set of optimal system and soft handoff parameters determined based on the current location of the third transceiver to effect a soft handoff from the first transceiver to the second transceiver.

In accordance with another aspect of the present invention, a mobile unit may include hardware and software means for receiving a set of optimal system access parameters, which may be determined based on the current location of the mobile unit, for controlling the performance of the mobile unit. Controlling performance may include effecting a soft handoff from the first base station to the second base station using the set of optimal soft handoff parameters received as part of the optimal system access parameters.

In accordance with another aspect of the present invention, the base station may include hardware and software means for transmitting a set of optimal system access parameters that may be determined based on the current location of the mobile unit within the first coverage area for controlling the performance of the mobile unit. Control performance may include implementing initial open loop power, duration delay, power increment, randomization delay, backoff time, and acknowledgment timeout. These parameters may be used by the mobile station to access the system and may be sent as part of an access parameter message on a common or dedicated signaling channel. According to another aspect of the present invention, a method for updating a current set of system parameters in a communication system may comprise: the method includes determining a current location of the mobile unit in the first coverage area, determining a set of best parameters based on the current location of the mobile unit, and updating the set of current parameters using the set of best parameters. This approach may be used to optimize location related parameters that may be involved in system access and/or soft handover.

In accordance with another aspect of the present invention, a method and system for dynamically updating a current set of system parameters in a communication system based on the latest performance of a mobile station that has just traversed a given geographic area. For example, the intelligent system infers that a mobile station traveling the same path a period of time ago experienced unnecessary handoffs that could have been avoided without causing degradation in system performance. The intelligent system may also infer from open loop calculations that mobile stations in the same neighborhood have much higher unnecessary transmit power to access the system, so that the mobile unit under consideration may use less initial power for accessing the system.

In accordance with another aspect of the present invention, a method and system limits the mobility of a mobile unit in a telecommunications system. The method comprises the following steps: the method includes determining a current location of the mobile unit within the first coverage area, determining a set of parameters based on the current location of the mobile unit, and preventing the mobile unit from performing or establishing communication access based on the set of parameters if the current location is within the restricted area.

Brief description of the drawings

FIG. 1 is a block diagram of an exemplary CDMA cellular telephone system;

FIG. 2 is a simplified block diagram of a system for facilitating handover in accordance with an embodiment of the present invention;

fig. 3 is a simplified block diagram of an embodiment of a base station and a mobile station;

FIG. 4 is a diagram illustrating a service negotiation process for implementing a soft handoff;

FIG. 5 is a chart showing a set of soft handoff parameters;

FIG. 6 is a flow chart illustrating a soft handover parameter optimization procedure in accordance with the present invention;

fig. 7 is a flow chart illustrating an access parameter optimization procedure according to the present invention.

Description of The Preferred Embodiment

The phrase "exemplary" is used herein to mean "serving as an example, instance, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

A base station may send and receive data packets through one or more BSCs and may transfer data packets between multiple mobile units. The base stations may also be connected to additional networks outside the base stations, such as a corporate intranet or the internet, and may transport data packets between each mobile unit and such outside networks. A mobile unit that has established an active traffic channel connection with one or more base stations is referred to as an active mobile unit and is said to be in a traffic state. A mobile unit that is in the process of establishing an active traffic channel connection with one or more base stations is said to be in a connection setup state. A mobile unit may be any data device that communicates through a wireless channel or through a wired channel, such as fiber optic or coaxial cables. The mobile unit may also be any of several types of devices including, but not limited to, a PC card, compact flash, external or internal modem, or wireless or wireline phone. The communication link through which the mobile unit sends signals to the base stations is called a reverse link. The communication link through which a base station sends signals to a mobile unit is called a forward link.

The present invention is described herein in connection with exemplary embodiments for particular applications, but it should not be construed as being limited thereto. Those having ordinary skill in the art, with access to the teachings provided herein, will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility.

Fig. 1 is a block diagram of an exemplary CDMA cellular telephone system 10. The system 10 includes a Mobile Switching Center (MSC)12 having a Base Station Controller (BSC) 14. The Public Switched Telephone Network (PSTN)16 routes calls from telephone lines and other networks (not shown) to the MSC 12. The MSC12 routes calls from the PSTN16 between the source base station 18 and the target base station 20, the source base station 18 and the target base station 20 being associated with the first cell 22 and the second cell 20, respectively. The SBS18 directs the call to the mobile unit 26 within the first cell 22 via the first communication link 28. Communication link 28 may be a bi-directional link having a forward link 30 and a reverse link 32. When the base station 18 has established voice communication with the mobile unit 26, the link 28 has the characteristics of a traffic channel. Although each base station 18 and 20 is associated with only one cell, each base station may control or be associated with several cells or sectors.

As the mobile unit 26 moves from the first cell 22 to the second cell 24, the mobile unit may be handed off to the target base station 20. The handover may occur in an overlap region 36 where the first cell overlaps the second cell 24.

In soft handoff, the mobile unit 26 establishes a second communication link with the target base station 20 in addition to the first communication link with the source base station 18. After the mobile unit 26 has traversed into the second cell 24, it will drop the first communication link 28.

In hard handoff, when the mobile unit 26 moves from the first cell 22 to the second cell 24, the link 28 to the source base station 18 is dropped and a new link is formed with the target base station 20.

According to embodiments of the present invention, several types of handover procedures may be provided, including the following three handover procedures:

soft handoff, in which the mobile station begins communicating with the new base station without interrupting communication with the old base station. Soft handoff may only be used between CDMA channels having the same frequency assignment. Soft handoff may provide diversity of forward traffic channel and reverse traffic channel paths at the boundary between base stations. While the mobile station is in the access state, soft handoff may also be used during the access process to improve system performance.

CDMA to CDMA hard handoff, where the mobile station transitions between non-intersections of base stations, different band classes, different frequency allocations, or different frame offsets.

CDMA to analog handoff, in which the mobile station moves from a CDMA traffic channel to an analog traffic channel.

Fig. 2 is a block diagram of a system 40 for facilitating handover in accordance with an embodiment of the present invention. In this particular embodiment, system 40 may be configured for a CDMA telecommunications system that may include BSC14, base station 18, and mobile unit 26. The BSC14 may include a Selector Bank System (SBS)48 and a CDMA interconnect subsystem 54 in communication with a location database 50. The BSC14 may also include a BSC location detection system 46 in communication with the SBS 48. . The base station 18 may include a base station location detection system 56 in communication with a base station transceiver 58. The mobile unit 26 may include a mobile unit location detection system 60 in communication with a mobile unit transceiver 62.

In this particular embodiment, the base station position detection system 56, the mobile unit position detection system 60, and/or the BSC position detection system 46 may include Global Positioning System (GPS) equipment and associated computer software modules and interface devices for determining location information for the mobile unit 26

Those skilled in the art will recognize that other types of location detection techniques may be used in addition to or in place of GPS location techniques in order to implement the present invention without departing from the scope of the present invention.

In one embodiment, after the location of mobile unit 26 is determined by base station position detection system 56 and/or mobile unit position detection system 60, the location information is relayed to BSC14 via interface link 66. The location information may be received by the CDMA interconnect subsystem 54 and routed to the SBS 48. The SBS48 may run software routines for monitoring the location of the mobile unit 26.

The location database 50 may store location information for the coverage areas of the telecommunications system and may also store the best handover and system access parameters associated with each area. When the mobile unit 26 enters a new area, the SBS48 may send the relevant optimal system access and handover parameters to the mobile unit 26.

Moreover, a software routine, which may be readily developed and applied by those of ordinary skill in the art, is run on the SBS48 for comparing the current location information of the mobile unit 26 with the location information pre-stored in the location database 50.

A software routine running on the SBS48 may monitor the location of the mobile unit 26 and determine when new system access and handoff parameters are required, for example by comparing the received location information to location information pre-stored in the location database 50.

The BSC14 may also include call detail access 55, a home location register 53, and a base station manager 52 coupled to the CDMA interconnect subsystem 54. Call detail access 55 may facilitate maintaining billing records for each mobile unit user. The home location register 53 may hold information for each user and the services to which they subscribe. The base station manager 52 may monitor the overall operation of the BSC 14. It will be recognized by those skilled in the art that these elements may be omitted from system 40 or replaced with other equivalent circuits without departing from the scope of the present invention.

Once the base station location detection system 56, the mobile unit location detection system 60, or the BSC location detection system 46 determines the current location of the mobile unit 26, the relevant system access and handover parameters are sent to the mobile unit as part of the signaling process.

Fig. 3 shows a simplified block diagram of an embodiment of base station 18 and mobile unit 26 for implementing aspects of the present invention. For particular communications, voice data, packet data, and/or messages may be exchanged between base station 18 and mobile unit 26 over an air interface 64. Various types of messages may be sent, such as messages used to establish a communication session between a base station and a mobile unit and messages used to control data transmission, such as power control, data rate information, and acknowledgements.

For the reverse link, at mobile unit 26, voice and/or packet data, e.g., from a data source 210, and messages, e.g., from controller 130, may be provided to a Transmitter (TX) data processor 212, which may format the data and messages and encode the data and messages using one or more coding schemes. The coding mechanism may include any combination of Cyclic Redundancy Check (CRC), convolutional, turbo, block, or other coding techniques. Voice, data packets, and/or messages may be encoded using different mechanisms, and different types of messages may be encoded differently.

The coded data is then provided to a Modulator (MOD)214 and further processed, e.g., covered, spread with short PN sequences, and scrambled with a long PN sequence assigned to the mobile unit. The modulated data is then provided to a transmitter unit (TMTR)216 that conditions, e.g., converts to one or more analog signals, amplifies, filters, and quadrature modulates, to generate a reverse link signal. The reverse link signal may be routed through a duplexer (D)218 and transmitted via an antenna 220 to base station 18.

At base station 18, the reverse link signal is received by an antenna 250, routed through a duplexer (D)252, and provided to a receiver unit (RCVR) 254. RCVR unit 254 conditions, e.g., filters, amplifies, frequency downconverts, and digitizes the received signal for providing samples. A demodulator (DEMOD)256 receives and processes, e.g., despreads, decovers, and pilot demodulates the samples to provide recovered symbols. DEMOD256 may implement a rake receiver that processes multiple instances of a received signal to produce combined symbols. A Receiver (RX) data processor 258 then decodes the symbols to recover the data and messages transmitted on the reverse link. The recovered voice and/or packet data may be provided to a data sink 260 and the recovered messages may be provided to a controller 270. The processing by DEMOD256 and RX data processor 258 are complementary to that performed at mobile unit 26. The DEMOD256 and RX data processor 258 may further be operated to process multiple transmissions received via multiple channels, e.g., a reverse fundamental channel (R-FCH) and a reverse supplemental channel (R-SCH). Also, transmissions may be simultaneously from multiple mobile units, each of which may transmit on R-FCH, R-SCH, or both.

On the forward link, at base station 18, voice and/or packet data, e.g., from a data source 262, and messages, e.g., from controller 270, may be formatted and encoded by a Transmitter (TX) data processor 264, covered and spread by a Modulator (MOD)266, and then converted to analog signals, amplified, filtered, and quadrature modulated by a transmitter unit (TMTR)268 to generate a forward link signal. The forward link signal is routed through a duplexer (D)252 and transmitted via an antenna 250 to the mobile unit 26.

At the mobile unit 26, the forward link signal may be received by an antenna 220, routed through a duplexer 218, and provided to an RCVR 222. RCVR unit 222 conditions, e.g., down converts, filters, amplifies, quadrature modulates, and digitizes the received signal to provide samples. The samples are processed, e.g., despreaded, decovered, and pilot demodulated by a demodulator 224 to provide symbols, and the symbols are further processed, e.g., decoded and examined by a Receive (RX) data processor 226 to recover the data and messages transmitted on the forward link. The recovered data is provided to a data sink 228 and the recovered messages are provided to a controller 230.

The active set of pilots is the set of pilot signals that the mobile unit 26 is currently or may be preparing to demodulate. If the active pilot set used by the mobile unit 26 contains a pilot offset corresponding to the second cell 24 (fig. 1), the SBS48 may begin tracking the mobile unit 26 and initiate soft handoff when the mobile unit 26 enters the soft handoff region 36. The BSC14 may provide instructions for completing a handoff to a new MSC coverage area, which may be initiated by the SBS48 in response to the mobile unit 26 being within the soft handoff area 36.

Fig. 4 illustrates an exemplary call processing scheme for implementing a soft handoff from pilot channel a to pilot channel B in accordance with the present invention.

The mobile unit may measure the pilot channel strength in the neighboring cells. The pilot energy may be provided in decibels. The term pilot refers to a pilot channel identified by a pilot sequence offset, walsh function or quasi-orthogonal function, and frequency assignment. The pilot is associated with a forward traffic channel within the same forward CDMA channel. All pilots associated with the active set of pilots have the same CDMA frequency allocation. The mobile unit may search for pilots on the current CDMA frequency assignment to detect the presence of CDMA channels and to measure their energy strength. When the mobile unit detects a pilot of sufficient strength independent of any forward traffic channel assigned to it, a Pilot Strength Measurement Message (PSMM) or an Extended Pilot Strength Measurement Message (EPSMM) is sent to the base station. The base station then assigns a forward traffic channel associated with the pilot to the mobile unit and instructs the mobile unit to perform a handoff. The parameters for the pilot search procedure and the rules for PSMM or EPSMM transmission may be expressed in terms of the following set of pilots:

the active set includes a set of pilots associated with forward traffic channels assigned to a mobile unit.

The candidate set comprises a set of pilots that are not currently in the active set but have been received by the mobile unit with sufficient strength to indicate that their associated forward traffic channels can be successfully demodulated.

A neighbor set, comprising a set of pilots that are not currently in the active set or candidate set, but are likely candidates for handoff.

The remaining set, which includes all possible sets of pilots in the current system on the current CDMA frequency assignment, except for the neighbor set, the candidate set, and the active set.

The base station may provide the following parameters for searching the set of pilots:

the search window size of the active set and candidate set "SRCH _ WIN _ a". The base station may set this parameter field to a window size parameter corresponding to the number of PN chips for which the mobile station is to search for pilots in the active set and the candidate set.

The search window size of the neighbor set "SRCH _ WIN _ N". The base station may set this parameter field to a window size parameter corresponding to the number of PN chips for which the mobile station is to search for pilots in the neighbor set.

The search window size of the remaining set "SRCH _ WIN _ R". The base station may set this parameter field to a window size parameter corresponding to the number of PN chips that the mobile station will search for pilots in the remaining set.

The mobile unit 26 may transmit the PSMM or EPSMM to a base station in communication with the mobile unit 26. These messages may include all pilots with energies greater than T-ADD and all members of the current active pilot set whose measured pilot energy values have not fallen below T-DROP for more than a predetermined time period T-TDROP.

The base station may use pilot strength measurements in PSMM or EPSMM to determine the new active set. The base station may also use PN phase measurements in PSMM or EPSMM to estimate propagation delay to the mobile unit. This estimate may be used to reduce reverse link traffic channel acquisition time.

In an exemplary embodiment, the mobile unit may generate and transmit the PSMM and EPSMM upon detecting a change in pilot strength, according to the following three conditions:

1. the strength of the neighbor set or remaining set pilots is found to be above the threshold value T _ ADD.

2. The strength of the candidate set pilots exceeds the strength of the active set pilots by more than the threshold value T _ COMP.

3. The pilot loading of the active set has fallen below the threshold T DROP for more than a predetermined time period T _ TDROP.

The parameter T _ ADD, the pilot detection threshold, may be used by the mobile unit to trigger the transfer of pilots from the neighbor set or the remaining set to the candidate set, and to trigger the sending of PSMM or EPSMM for initiating the handoff procedure.

The parameter T _ DROP, the pilot-down threshold, may be used by the mobile unit to start the handoff-down timer in the active set and the candidate set.

Parameter T _ COMP, the comparison threshold of the active set to the candidate set, may be used by the mobile unit to send PSMM or EPSMM when the strength of the pilots in the candidate set exceeds the strength of the pilots in the active set by a certain limit.

The parameter T _ TDROP, the down timer value, is a timer value after which the mobile unit takes action on a pilot that is a member of the active set or candidate set and is not stronger than T _ DROP. If the pilot is a member of the active set, the PSMM or ESPMM is transmitted. If a pilot is a member of the candidate set, it may be moved to the neighbor set.

In an exemplary embodiment, the base stations identified in PSMM or EPSMM may be identified by their PN sequence offsets, their pilot energies corresponding to measurements, and/or an indication of whether the pilot should be held.

In another embodiment of the present invention, the mobile station may monitor the pilot signals, may compile the members of each of the above-mentioned sets, i.e., the active set, the candidate set, and the neighbor set, and may determine whether the current active set needs to be changed according to the following linear relationship:

Y1＝SOFT_SLOPE*COMBINED_PILOT+ADD_INTERCEPT(1)

Y2＝SOFT_SLOPE*COMBINED_PILOT+DROP_INTERCEPT(2)

fig. 5 shows a graphical representation of the relations (1) and (2). The dynamic thresholds Y1 and Y2 may be plotted as a function of the combined pilot energy (i.e., Ec/Io), which may be in dB. It can be seen that Y1 and Y2 are both linear functions of the SOFT _ SLOPE SLOPE and have the Y-INTERCEPT of ADD _ INTERCEPT and DROP _ INTERCEPT, respectively.

Y1 is a dynamic threshold above which the measured energy of the candidate set pilot should rise before the mobile unit requires it to be added to the revised active set, and Y2 is a dynamic threshold below which the pilot energy of the active set should fall before the mobile unit requires it to be moved from the active set to the candidate set.

The parameter SOFT SLOPE is the SLOPE within the inequality criterion for adding pilots to the active set. The parameters ADD _ interrupt and DROP _ interrupt are y-INTERCEPTs within the inequality criterion for adding or withdrawing pilots from the active set, respectively.

As can be seen from relations (1) and (2), if the measured energy of a certain active set pilot falls below Y2, the pilot can be moved to the candidate set. In order that the same pilot may be added back to the revised active set, the following two events may occur: the value of comblned _ PILOT is decreased by a certain amount Δ 1 or the measured energy of the PILOT itself is increased by a certain amount Δ 2. Thus, it can be seen that Δ 1 and Δ 2 are hysteresis values of combimed _ PILOT and individual PILOT energies, respectively, that are needed to prevent a given PILOT from being repeatedly moved in and out of the active set.

Thus, PILOTs may be added to the revised active set when the combied _ PILOT value is less than or equal to X1, and may be withdrawn from the active set when the combied _ PILOT value is greater than or equal to X2. From the relations (1) and (2), it can be shown that:

SOFT_SLOPE＝Δ2/Δ1；(3)

DROP inter-DROP-X2 Δ 2/Δ 1, and (4)

ADD_INTERCEPT＝DROP_INTERCEPT+Δ2(5)

The base station may send messages to the mobile units on the common control channel or the dedicated control channel for controlling access procedures, pilot searching, performance of the mobile units, and/or soft handoff procedures.

The base station communicating with the mobile unit may respond to the PSMM or EPSMM by accepting the PSMM or EPSMM from the mobile unit by sending an extended handover decision message, a normal handover direction message, or a generic handover direction message, as illustrated in fig. 4.

According to another embodiment, the base station may modify the values of the parameters SRCH _ WIN _ A, T _ ADD, T _ DROP, T _ COMP, and T _ TDROP by extending a handover direction message, a normal handover direction message, or a general handover direction message. Also, the base station may modify the values of the parameters SRCH _ WIN _ N, SRCH _ WIN _ R, SOFT _ SLOPE, ADD _ interrupt, and DROP _ interrupt through a general handover direction message or a general handover direction message.

According to one embodiment of the present invention, the soft handoff parameters may be optimized based on location information regarding the location of the mobile unit 26. When the mobile unit 26 moves into a new sector or cell, the location server or entity may determine the geographic characteristics of the mobile unit's location, including its latitude and longitude, and forward this location information to the BSC14 (fig. 2). The SBS48 (fig. 2) may use the location information of the mobile unit 26 to find a set of optimal system access and handover parameters in the location database 50. According to an embodiment of the invention, the location database 50 may contain a look-up table relating handover parameters to location information regarding the location of the mobile unit 50 within a cell or sector. The base station 18 may forward the optimal set of handoff parameters to the mobile unit 26 when the mobile unit is under control of the traffic channel, as will be described below.

Fig. 6 shows a flow diagram of an exemplary soft handover parameter optimization procedure, and fig. 6 shows a flow diagram of an exemplary access parameter optimization procedure according to an embodiment of the present invention.

When the mobile unit is on a traffic channel, i.e., in a two-way session, the location information of the mobile unit's current sector coverage area may be determined in step 604 as determined in step 602. The best set of handover parameters corresponding to the location information of the current sector coverage area may be obtained in step 606, for example from the location database 50. The optimal parameters may then be forwarded to the mobile unit in step 608. The base station may revise system access and handoff parameters in the mobile unit that operates on the traffic channel by sending parameters in the intra-traffic system parameters message. This parameter optimization technique can be applied at the sector level to update system access and soft handoff parameters within the mobile unit at the micro-level to make the handoff process more sensitive to the geographical characteristics of the mobile unit. Thus, handover is easier to implement according to optimal handover parameters, which advantageously prevents call loss and poor service performance in high traffic areas, crowded urban environments, and/or when moving around tall buildings or making sharp turns.

In one embodiment of the present invention, the mobility of the mobile unit is limited to a predetermined coverage area, which may include a cell or sector. When the location information of the mobile unit indicates that the mobile unit has entered a restricted area, the base station controller may send a set of parameters to the mobile unit that cause the mobile unit to release its access and be unable to implement or establish a communication link within the restricted area.

In one embodiment, the methods and systems disclosed herein dynamically update the current set of system access and/or soft handoff parameters based on the recent performance of mobile stations traversing a given geographic area. For example, the intelligent system may infer that a mobile station traversing the same route as the mobile station is going to traverse does not have to undergo a handoff, which may be omitted and cause no degradation in system performance. The intelligent system can also infer that mobile stations in the same geographic area are accessed to the system at much higher and unnecessary transmit power based on open loop calculations, so the mobile unit under consideration can use less initial power for accessing the system. Intelligent systems are well known in the art.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Those of skill would further appreciate that the various illustrative logical blocks, modules, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with: a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination of devices designed to perform the functions described herein. A general purpose processor is preferably a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or other such configuration.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without the use of the inventive faculty. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (4)

1. A method for optimizing system parameters in a telecommunications system including a mobile unit and an intelligent system, comprising:

tracking, by an intelligent system, performance of mobile units within a geographic area; and

if the mobile unit again spans the geographic area, system parameters are optimized based on the performance of the mobile unit.

2. A computer-readable medium embodying a method for optimizing system parameters in a telecommunications system, said telecommunications system including a mobile unit and an intelligent system, the method comprising:

tracking, by an intelligent system, performance of mobile units within a geographic area; and

if the mobile unit again spans the geographic area, system parameters are optimized based on the performance of the mobile unit.

3. An apparatus for optimizing system parameters in a telecommunications system, comprising:

means for tracking, by the intelligent system, performance of mobile units within a geographic area; and

and means for optimizing system parameters based on the performance of the mobile unit if the mobile unit again spans the geographic area.

4. An apparatus for optimizing system parameters in a telecommunications system, comprising:

a storage unit;

an intelligent system communicatively coupled to the storage unit, the intelligent system capable of tracking performance of the mobile unit within a geographic area; and

a Digital Signal Processing (DSP) unit communicatively coupled to the memory unit, the DSP capable of optimizing system parameters based on performance of the mobile unit if the mobile unit again spans the geographic area.