WO2001089258A2

WO2001089258A2 - Dynamic hierarchical cell structure neighbor relations based on cell congestion

Info

Publication number: WO2001089258A2
Application number: PCT/US2001/015691
Authority: WO
Inventors: Hanna Maurer
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2000-05-17
Filing date: 2001-05-16
Publication date: 2001-11-22
Also published as: WO2001089258A3; AU2001264615A1

Abstract

A method of regulating network traffic in a wireless Hierarchical Cell Structure (HCS) networking system (11) having a first network (78) operating at a base band (850 MHz) and a second network (76) operating in a hyper band (1900 MHz) (76). A request is received for handoff in the MSC (30) from the serving BTS (26) and congestion levels of the first and second networks (78, 76) are determined in order to regulate network (11) traffic. First and second handoffs are attempted in the second network (76). Once a second handoff has been attempted, a neighboring cell (74) is evaluated as a candidate for handoff using the 'standard' (60) HCS neighbor relation algorithm instead of the 'non-preferred' (62) HCS neighbor relation algorithm.

Description

DYNAMIC HIERARCHICAL CELL STRUCTURE NEIGHBOR RELATIONS BASED ON CELL CONGESTION

TECHNICAL FIELD

This invention relates in general to wireless telecommunications networks and applications and, in particular, to a wireless Hierarchical Cell Structure (HCS) networking system having a first network operating at a base band and a second network operating in a hyper band. More particularly, the invention relates to a method of regulating network traffic in an HCS wireless network.

BACKGROUND OF THE INVENTION

Without limiting the scope of the invention, its background is described in connection with wireless Hierarchical Cell Structure (HCS) networking systems supporting a first network operating at a base band and a second network operating in a hyper band, as an example.

Present day mobile telephony has spurred rapid technological advances in both wireless and wire link communications. The wireless industry, in particular, is a rapidly growing industry, with advances, improvements, and technological breakthroughs occurring on an almost daily basis. Many mobile or wireless telecommunication systems have passed through several generations of advancement and development phases. System designers are now concentrating on further improvements to such systems to increase network capacity and provide optional subscriber services.

In particular, the wireless industry began to explore converting the existing analog network to digital as a means of improving capacity back in the late 1980's. In 1989, the Cellular Telecommunications Industry Association (CTIA) chose Time Division Multiple Access (TDMA) as the technology of choice for existing 850 MHz cellular markets and for emerging 1.9 GHz markets. The two major competing systems that split the Radio Frequency (RF) are TDMA and Code Division Multiple Access (CDMA) which is a spread-spectrum technology that allows multiple frequencies to be used simultaneously. CDMA codes every digital packet it sends with a unique key. A CDMA receiver responds only to that key and can pick out and demodulate the associated signal.

Because of its adoption by the European standard Global System for Mobile (GSM) Communications, the Japanese Digital Cellular (JDC), and North American Digital Cellular (NADC), TDMA and its variants are currently the technology of choice throughout the world. One of many improvements in wireless networking systems includes a new version of TDMA technology, also referred to as IS-136. IS-136 TDMA is a digital wireless standard that specifies an efficient and widely implemented wireless protocol. The IS-136 version of TDMA is specified as a Personal Communication Services (PCS) technology providing seamless service between the cellular (850 MHz) and PCS (1.9 GHz) spectrum in the United States.

In general, TDMA works by dividing each cellular channel into three time slots in order to increase the amount of data that can be carried. TDMA allows a number of users to access a single RF channel without interference by allocating unique time slots to each user within each channel. The TDMA digital transmission scheme multiplexes three signals over a single channel. The current TDMA standard for cellular divides a single channel into six time slots with each signal using two slots providing a three to one gaming capacity over Advanced Mobile Phone Service (AMPS). With TDMA, each caller is assigned a specific time slot for transmission, and by dividing each channel into three time slots with one voice conversation per slot, an increase of up to three times the capacity of analog systems is achieved. TDMA is the only technology that offers efficient utilization of Hierarchical Cell Structures (HCS) using pico, micro and macro cells. HCSs allow coverage for the system to be tailored to support specific traffic and service needs. By using this approach, system capacities of more than 40-times AMPS can be achieved in a cost efficient way. As such, the HCS further enhances network capacity, generating more revenues and reducing equipment costs. Multiple level HCS enables operators to boost capacity in "hot spots," or areas of high traffic density. With HCS, operators can also offer different services to different subscribers or areas within a network, for example, one set of services in the office and another set on the street.

IS-136 TDMA normally co-exists with interlocked channels on the same network. One advantage of this dual mode technology is that users can benefit from the broad coverage of established analog networks while IS-136 TDMA coverage grows within. At the same time, users take advantage of the more advanced technology of IS-136 TDMA where it exists. Furthermore, IS-136 TDMA introduces the Digital Control Channel (DCCH) for support of new applications and teleservices. DCCH enables operators to provide Personal Communications Services (PCS) such as Short Message Service and Sleep Mode capability, which dramatically increase both the functionality and the battery life of PCS phones. In addition, DCCH technology allows implementation of HCS, facilitating the introduction of private systems, differentiated service in charging areas, while increasing the overall capacity of the system. The DCCH forms the core of the IS-136 specification and is a primary enhancement to TDMA digital-wireless technology. In a PCS environment, a geographic area might be covered by a mix of macrocells and microcells as well as public and private systems. Macrocells are typically public cells, serving all wireless phone users. IS-136 DCCH TDMA technology enables the user of much smaller cells called microcells. Microcells provide customized service within the coverage of existing macrocells. Microcells typically provide WOS features to specific phones within a private building or campus environment. The combined coverage of both macrocells and microcells is called hierarchical cell coverage, with the microcells creating a second level of coverage under the existing level. Although macrocells are usually public and microcells are usually private, they can reverse roles.

Because of heavy traffic congestion, a PCS phone must assess the most suitable control channel in which to provide service, even if the signal strength of a neighboring cell is not the highest signal being received by the phone, but is of a sufficient level to provide quality service. PCS uses HCS to accomplish this by identifying neighboring cells as preferred, standard or non-preferred. A preferred cell has the highest preference. Typically, the PCS phone reselects a preferred cell even if its signal strength is lower than the serving cell. The main criterion here is that the preferred neighbor cell must have signal strength sufficient to provide quality service.

A standard cell relation has the second highest preference. A standard cell relation may also be referred to as a regular cell relation. The PCS phone reselects a standard neighbor cell if the cell's signal strength is greater than the serving cell (plus a hysteresis value) and there is no eligible preferred cell available. A non-preferred cell has the lowest preference. The PCS phone reselects a non-preferred cell only if the signal strength of the serving cell becomes insufficient to provide service and the signal strength of the non- preferred neighbor is greater than the serving cell (plus a hysteresis value). In one form of operation, HCS enables the DCCH to identify and designate neighboring cells as preferred, standard, or non-preferred. A PCS phone uses the hierarchical information to reselect a particular neighbor cell over another based on the type of relationship defined between the cell it is using (serving cell) and the adjacent neighbor cell. Each neighbor cell's designation dictates which type of algorithm the phone uses when it considers a cell as a reselection candidate. For example, when a low-power microcell is providing capacity in a dense traffic area that is also served by a high power macrocell, the HCS allows the phone to give preference to the weaker microcell. Without the multitier environment, the phones would have difficulty capturing microcells, and the cellular system would require highly specific parameter settings.

In another form of operation, HCS uses a Digital Traffic Channel (DCH) at handoff. As such, DCH is used to carry speech and traffic data. Traffic channels are defined using a 26-frame multi-frame, or group of 26 TDMA frames. The length of a 26-frame multi-frame is 120 ms, which is how the length of a burst period is defined (120 ms divided by 26 frames divided by 8 burst periods per frame). Out of the 26 frames, 24 are used for traffic, 1 is used for the Slow Associated Control Channel (SACCH) and 1 is currently unused. DCHs for the uplink and downlink are separated in time by 3 burst periods, so that the mobile station does not have to transmit and receive simultaneously, thus simplifying the electronics.

Today, when deploying a HCS network, there is no way of regulating handoff traffic based on congestion in the cells. When congestion occurs on the traffic channels in the hyper band level and handoffs fail due to voice channel congestion, there is no way of moving traffic to the underlying cells covering the same area (non-preferred HCS neighbors). As a result, revenue is lost due to blocking, dropped calls and quality also suffers due to dragged handoffs. Therefore, a need exists for a cost-effective method of regulating network traffic in a wireless Hierarchical Cell Structure (HCS) networking system having a plurality of neighboring cells with a first network operating at a base band and a second network operating in a hyper band. A means of determining congestion levels of the first and second networks and a means of adapting HCS network usage by forcing traffic from one network to a second network where congestion is less heavy would provide numerous advantages.

SUMMARY OF THE INVENTION The present invention provides a method and system for regulating network traffic in a wireless Hierarchical Cell Structure (HCS) networking system. With the present invention, the network operator can identify congestion in the HCS network and use the congestion information to increase capacity by improving performance dynamically and automatically without intervention from the operator.

Disclosed in one embodiment is a method of regulating network traffic in a wireless HCS networking system having a plurality of neighboring cells within a first network operating at a base band (i.e., 850 MHz) and a second network operating in a hyper band (i.e., 1900 MHz). The method comprises the step of determining congestion levels of the first and second networks. Once a neighbor cell has been evaluated as a candidate for handoff, the Received

Signal Strength (RSS) by the mobile station on a measurement channel of the candidate cell is compared with the RSS received from the current serving cell.

Based on the Mobile Switching Center (MSC), or Radio Base Station (RBS), the ongoing call is eligible for handoff according to the standard handoff criteria within the hyper band, and the target cell is requested to accept the "handed-in" call. If the target cell is congested, the handoff is rejected and a new evaluation is made. Therefore, if the target cell is still congested, the handoff cannot occur even though the received RSS by the mobile on the candidate, or target cells measurement channel is higher than the serving RSS on the current serving cell. The applied neighbor relation at handoff to the base band (850 MHz) network should therefore be adapted from a non-preferred to a standard cell relation when congestion occurs in the hyper band (1900 MHz) network. The method further comprises the step of adapting HCS network usage by forcing traffic from one network to a second network where congestion is less heavy. As such, the traffic flow is monitored in the first and second networks concurrently. Dynamically, a value is assigned to a traffic congestion parameter associated with the traffic flow in the first and second networks. This allows for the networks containing the greatest amount of traffic congestion to be identified prior to forcing traffic from one network to a second network where congestion is less heavy. Disclosed in another embodiment is a Hierarchical Cell Structure (HCS) networking system having a plurality of neighboring cells organized into a first network operating at a base band and a second network operating in a hyper band. The neighboring cells are identified as preferred (highest preference), standard (second highest preference), or non-preferred (lowest preference). Standard cells may also be referred to as regular cells. In one embodiment, the first network operates at a base band frequency of 850 MHz, while the second network operates at a hyper band frequency of 1900 MHz. The system comprises a plurality of macro cells creating a first level of coverage and a plurality of microcells creating a second level of coverage under the first level of coverage. The macrocells and microcells can be both private and public. The combined coverage of both macrocells and microcells is called hierarchical cell coverage.

The system further comprises a mobile switching center (MSC) adapted to control the combined coverage created by the macrocells and microcells. The system also comprises a base station subsystem (BSS) associated with the MSC. The BSS further includes a base transceiver station (BTS) and a base station controller (BSC). The system also comprises a means for determining congestion levels of the first and second networks, as well as a means for adapting HCS network usage by forcing traffic from one network to a second network where congestion is less heavy.

A technical advantage of the present invention includes a means for dynamically changing parameters of the network with regard to traffic congestion. Thus, the need for post processing of network congestion level data with subsequent remediation/alteration of the SS_SUFF parameter is eliminated.

Another technical advantage includes a less labor-intensive method of regulating network traffic in a HCS networking system that allows for an increase in the revenue of the network by allowing more users to access network resources via available channels.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, including its features and advantages, reference is made to the following detailed description of the invention, taken in conjunction with the accompanying drawings of which:

Figure 1 depicts a telecommunications network in which a preferred embodiment of the present invention may be implemented;

Figure 2 illustrates a network in which the invention may be practiced;

Figure 3 illustrates a macrocell/microcell configuration, in accordance with the preferred embodiment of the preferred invention;

Figure 4 illustrates reselection based on HCS cell type, in accordance with a preferred embodiment of the present invention;

Figure 5a shows deployment of a HCS network today with no method of regulating handoff traffic based on congestion in the cells; Figure 5b illustrates neighboring cells evaluated as candidates for handoff, in accordance with a preferred embodiment of the present invention; and Figure 6 is a high level logic flow diagram illustrating process steps for implementing the method and system of the present invention, in accordance with a preferred embodiment.

Corresponding numerals and symbols in the figures refer to corresponding parts in the detailed description unless otherwise indicated.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts which can be embodied in a wide variety of specific contexts. These specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention, and do not delimit the scope of the invention.

With reference to Figure 1 , therein is shown a diagram of a wireless communications network 10 in which the invention can be practiced. The network 10 is seen to include an originating mobile station (MS) 12, which can be a wireless communications device such as a Personal Communications Service (PCS) or cellular phone, but may also include a computer, a Personal Digital Assistant (PDA), or other wireless terminal, for example. A base station 19 provides cellular coverage via a Radio Frequency (RF) link to the MS 12 and other mobile stations within the cells 22 of network 10. The term "cell" or "cells" will be referred to interchangeably. Typically, several base stations 19 service a single mobile switching center (MSC) 30 through Base Station Controllers (BSCs) 28 to provide continuous geographical coverage. For illustrative purposes only, the coverage area of a particular cell 22 is shown as hexagonal. Hexagonal shaped cells are artificial and cannot be generated in the real world. However, this shape is chosen to simplify planning and design of a cellular system as hexagons fit together without any overlap or gap in between them. As the MS 12 moves between a first cell 22a to a second cell 22b, service (a call or data transmission) is handed off from a first base station 19a servicing the MS 12a in the first cell 22a to a second base station 19b in the second cell 22b. As the MS 12a crosses the regions serviced by the base station 19b in the second cell 22b, the MS 12a is arriving at the transfer point where the cell is handed off from the base station 19a to the second base station 19b (called a "handoff"). A handoff is typically managed by control systems contained in the MSC 30. The MSC 30 is typically in communication with multiple BSCs 28, as well as two fixed networks, such as the Public Switched Telephone Network (PSTN) 24 or an optical network, for example.

Figure 2 shows the typical layout of a wireless network 11 as the interface/signal flow between a MS 12, a Base Station Subsystem (BSS) 14, and a network subsystem 16 in the network 11. The network subsystem 16 includes the MSC 30, that performs the call switching functions between network users, as well as mobility management. The MS 12 and the BSS 14 communicate with one another across an interface 18, known as the air interface (or radio link, or Urn interface). Furthermore, the BSS 14 communicates with the MSC 30 of network subsystem 16 across an A-interface 20. Likewise, MSC 30 communicates with fixed networks 32 which may be the PSTN or other cellular networks, for example.

The mobile station 12 usually includes a mobile transceiver and a Subscriber Identity Module (SIM). The SIM may include an identity indicator (a "secret" key for authentication), and other relevant network/user information. The mobile transceiver itself is uniquely identified by the International Mobile Equipment Identity (IMEI — typically, a telephone number). The identification features of the MS 12 are independent, thereby allowing mobility of the user about the service area of the network 11. The BSS 14 typically comprises two parts: the Base Transceiver Station (BTS) 26 (commonly called a base station, or Radio Base Station (RBS)), and the Base Station Controller (BSC) 28. BTS 26 communicates across a standard Abis interface 30 with BSC 28, allowing operation between components. BTS 26 houses radio transceivers that communicate across a cell 22, and the BTS 26 handles the radio-link protocols that facilitate communication with the mobile station 12. BSC 28 manages the radio resources for one or more BTSs 26, and likewise, there may be several BSCs 28 within a single BSS 14. BSC 28 provides a communications platform between the mobile station 12 and the MSC 30 of network subsystem 16 which acts as an interface to one or more fixed networks 32. Among the other functions of the BSC 28 are radio-channel setup, frequency hopping, and handovers.

The central component of the network subsystem 16 is the MSC 30, which mirrors the performance of a normal switching node of the PSTN 24, and provides all the functionality needed to handle mobile subscriber communications, such as registration, authentication, location updating, handovers, and call routing to roaming subscribers. These functions are provided in conjunction with several other network entities. In the HCS networking system, the MSC 30 is responsible for servicing two networks, one operating at a hyper band (1900 MHz) and a second operating at a base band (850 MHz). It is the MSC 30 which contains the intelligence necessary to identify and control traffic flow.

As shown, the MSC 30 provides the connection mechanism to the fixed networks 32, which may include the PSTN 24 or an integrated service digital network (ISDN), for example. The Home Location Register (HLR) 34 and Visitor Location Register (VLR) 36, together with the MSC 30, provide call routing and roaming capabilities for the network 11. In particular, the HLR 34 contains administrative information of the subscriber registered in the corresponding network 11 , along with the current location of the mobile handset 12. Likewise, the VLR 36 contains selected administrative information from a MS's HLR 34 necessary for call control and provisioning of the subscriber services for each mobile currently located in the geographical area controlled by the VLR 36. Other registers are used for identification and security functions within the network subsystem 16.

In the wireless telecommunications industry, Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA) are two major competing systems which split the radio frequency. In general, TDMA works by dividing each cellular channel into three time slots in order to increase the amount of data that can be carried. Thus, TDMA allows a number of users to access a single Radio Frequency (RF) channel without interference by allocating unique time slots to each user within each channel. Furthermore, TDMA is the only technology that offers efficient utilization of HCS using pico, micro and macro cells.

The Telecommunications Industry Association (TIA) IS-136 specification is the basis of the TDMA PCS Air-Interface technology. IS-136 is designed to operate in both the 850 MHz and the 1900 MHz frequency bands, thus providing seamless operation on cellular and PCS systems. In a PCS environment, a geographic area might be covered by a mix of macrocells and microcells as well as public and private systems. With reference to Figure 3, therein is shown a macrocell/microcell configuration denoted generally as 50. Cell sites have traditionally existed as macrocells 52 on towers that cover areas up to several miles in diameter. Macrocells 52 are typically public celts serving all wireless phone users. IS-136 DCCH TDMA technology enables the use of much smaller cells called microcells 54. Microcells 54 provide customized service within the coverage of existing macrocells 52. For example, the Microcells 54 can provide WOS features to specific phones within a private building or campus environment.

The combined coverage of both macrocells 52 and microcells 54 is called hierarchical cell coverage, with the microcells 54 creating a second level of coverage under the existing level. Although macrocells 52 are usually public and microcells 54 are usually private, they can reverse roles. For example, a public macrocell 52 can also provide private WOS services to offices 56 within its coverage area. Conversely, a microcell 54 can provide public coverage to fill in geographic gaps due to topography or to enhance coverage in high density areas.

With reference to Figure 4, therein is shown the process and system for achieving reselection based on HCS cell type in accordance with the preferred embodiment of the present invention. In a PCS environment, a PCS phone must assess the most suitable control channel in which to provide service, even if the signal strength of a neighboring cell is not the highest signal being received by the phone, but is of a sufficient level to provide quality service. PCS uses Hierarchical Cell Structures (HCS) to accomplish this by identifying neighboring cells as preferred 64, standard 60, or non-preferred 62. A preferred cell 64 has the highest preference. The phone reselects it, even if its signal strength is lower than the serving cell. The main criterion here is that the preferred neighbor cell must have signal strength sufficient to provide quality service.

A standard cell 60 has the second highest preference. The phone reselects it if the cell's signal strength is greater than the serving cell (plus a hysteresis value) and there is no eligible preferred cell available. A non- preferred cell 62 has the lowest preference. The phone reselects it only if the signal strength of the serving cell becomes insufficient to provide service and the signal strength of the non-preferred neighbor is greater than the serving cell (plus a hysteresis value). As a result, the resources associated with the non- preferred cells 62 are not properly utilized. This increases the number of dropped calls and interference present.

Thus, HCSs enable the DCCH to identify and designate neighboring cells as preferred 64, standard 60, and non-preferred 62. A PCS phone uses the hierarchical information to reselect a particular neighbor cell over another base in the type of relationship defined between the cell it is using (serving cell) and the adjacent neighbor cell. Each neighbor cell's destination dictates which type of algorithm the phone uses when it considers the cell as a reselection candidate. For example, when a low power microcell 54 is providing capacity in a dense traffic area that is also served by a high power macrocell 52, the HCS allows the phone to give preference to the weaker microcell 54. Without the multi-tier environment, the phones would have difficulty capturing microcells 54, and the cellular system would require highly specific parameter settings.

In addition, HCS enables the DCH to carry speech and data traffic. As such, digital traffic channels are defined as using 26-frame multi-frame, or group of 26 TDMA frames. The length of a 26-frame multi-frame is 120 ms, which is how the length of a burst period is defined. Out of the 26 frames, 24 are used for traffic, 1 is used for the Slow Associated Control Channel (SACCH) and 1 is currently unused. To date, when deploying an HCS network as shown in Figure 5a, there is no way of regulating handoff traffic based on congestion in the cells. When congestion occurs on the hyper band 76 (preferred HCS neighbors 64) level and handoffs fail due to voice channel congestion, there is no way of moving traffic to the underlying cells covering the same area (non-preferred HCS neighbors 62) without letting the ongoing call's downlink RSS fall below the static SS_SUFF parameter. As a result, revenues are lost due to dropped calls and quality suffers due to dragged handoffs. As shown in Figure 5a, the system tries to handoff a call from "cell 1" 70 to "cell 2" 72 using a standard HCS neighbor relation. "Cell 2" 72 is congested, however, and the handoff fails. That is, in a network system 11 accommodating dual bands, a hyper band level (1900 MHz) 76 and base band level (850 MHz) 78 most traffic will occur in the hyper band level (1900 MHz) 76. Thus, the network system 11 can be thought of as comprised of two networks, with a first network 78 operating at a base band and a second network 76 operating at a hyper band. As such, it should be understood that the terms "first network" and "base band", as well as "second network" and "hyper band", can and are used interchangeably throughout. As a result, the resources of the base band level (850 MHz) 78 are not utilized to their fullest potential. Therefore, the handoff from "cell 1 " 70 to "cell 2" 72 would fail repeatedly if the target "cell 2" 72 continues to be congested. Eventually, after dragging and delaying the handoff, if the RSS received by the mobile 12 in "cell 1" 70 would fall below the static predetermined Signal Strength Sufficient Parameter (SS__SUFF), a handoff could occur to "cell A" 74, according to the non-preferred 62 HCS handoff criteria.

The present invention aims to solve the lack of utilization of the base band level (850 MHz) 78, as shown in Figure 5b, by removing the requirement for the RSS received by the mobile 12 in "cell 1" 70 to fall below the predetermined SS_SUFF as typically monitored by a network operator and manually accommodated for when congestion occurs. Instead, the present invention is adapted to dynamically alter the necessary parameters due to congestion on the hyper band level (1900 MHz) 76.

With reference to Figure 5b, a first handoff attempt is made and fails due to congestion in the target "cell 2" 72. A new handoff attempt is made at this stage. At this second handoff attempt, neighbor "cell A" 74, with this invention, is evaluated as a candidate for handoff using the "standard" 60 HCS neighbor relation algorithm instead of the "non-preferred" 62 HCS neighbor relation algorithm. If "cell 2" 72 is still congested, the call will be handed off to "cell A" 74 if the received RSS by the mobile 12 on cell A's measurement channel is higher than the serving RSS in "cell 1" 70. As a result, the handoff will not be delayed until the server's signal strength is below the SS_SUFF parameter, which means that the quality of the call is withheld and the possibility for dropping the call decreases. In addition, the resources available in the base band level (850 MHz) 78 are utilized resulting in increased revenues for wireless operators since calls are less likely to drop and a handoff is more likely to succeed. Also, co-channel interference is reduced, which is normally a result of dragging handoffs occurring today. The change in neighbor relations are only made on a per call basis when congestion occurs. The general HCS neighbor relation from "cell 1" 70 to "cell A" 74 remains set at "non-preferred" 62 for all handoff attempts, if no congestion occurs in target cells (e.g., "cell 2" 72) for handoff.

Figure 6 is a process flow diagram for the method of the present invention of regulating network traffic in a wireless HCS networking system. It can be appreciated by those skilled in the art that Figure 6, as illustrated and described herein, presents a self consistent sequence of steps leading to a desired result.

The steps are those requiring the physical manipulation of physical quantities.

Usually, although not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared and otherwise manipulated.

It has proven convenient at times by those skilled in the art, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like. It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities.

Further, the manipulations performed are often referred to in terms, such as "designating," "delivering" or "conveying", which are commonly associated with mental operations performed by a human operator. No such capability of a human operator is necessary or desirable in most cases of the operations described herein, which form part of the present invention. As indicated herein, these operations are primarily machine operations. Useful machines for performing operations of a preferred embodiment of the present invention include data-processing systems, such as a general-purpose digital computer or other similar devices. In all cases the distinction between the method of operations in operating a computer and the method of computation itself should be borne in mind. The present invention relates to method steps for regulating network traffic in a Hierarchical Cell Structure (HCS) networking system, and can be implemented via a computer or microcomputer. However, it is not necessary to maintain within a computer memory of a mobile station, or cellular telephone subscriber unit, instructions implementing these method steps. Such instructions can be maintained within a computer memory location of a MSC or at a central broadcasting center from which a MSC receives instructions. Implementation of the method described herein is left to the discretion of a particular wireless telephone system designer, whether cellular-based or otherwise. It can be appreciated by those skilled in the art that the methods described herein can be implemented as a program product (e.g., a control program residing in a computer memory). The program product contains instructions that when executed on a CPU, carry out the operations depicted in the logic flow diagram of Figure 6. While the present invention is described in the context of a fully functional telecommunications network, such as wireless network 11 , those skilled in the art will further appreciate that the present invention is capable of being distributed as a program product in a variety of forms. The present invention applies equally, regardless of the particular type of signal-bearing media utilized to actually carry out the distribution. Examples of signal-bearing media include recordable-type media, such as floppy disks, hard-disk drives and CD ROM's, and transmission-type media, such as digital and analog communication links. Preferred implementations of the invention can include implementations to execute the method or methods described herein as a program product residing in memory of a microcomputer within the MSC 30. Alternatively, a preferred embodiment of the present invention can include a program product residing in a microcomputer memory in communication with MSC 30. The MSC 30 controls system operations in cellular telephone networks and the program product thus includes sets of instructions for executing the method and system described herein. Until required by a microcomputer, the set of instructions may be stored as a computer-program product in another computer memory. For example, the set of instructions may be stored as a computer-program product in a disk drive attached to a microcomputer (which may include a removable memory such as an optical disk or floppy disk for eventual use in the disk drive).

The program product can also be stored at another computer and transmitted, when desired, to a user's workstation by an internal or external network. Those skilled in the art will appreciate that the physical storage of the sets of instructions physically changes the medium upon which it is stored so that the medium carries computer-readable information. The change may be electrical, magnetic, chemical, or some other physical change. While it is convenient to describe the invention in terms of instructions, symbols, characters, or the like, the reader should remember that all of these and similar terms should be associated with the appropriate physical elements.

Thus, Figure 6 is a process flow diagram, denoted generally as 100, illustrating a method of regulating network traffic, according to one embodiment of the invention. Initially, a request is received in the MSC from the serving BTS at step 110. At this point, the handoff criteria is fulfilled to cell 2 (preferred), but not to cell A (non-preferred). Next, a first handoff attempt is made at step 112 from cell 1 to cell 2 in the second network operating in a hyper band (1900 MHz) and having a target cell (e.g., "cell 2" 72). Congestion due to traffic is then determined at step 114, once the first handoff attempt has been made at step 112. This includes checking for the amount of congestion in the two network levels, hyper band (1900 MHz) and base band (850 MHz). Therefore, parameters present in the intelligence of the MSC which control traffic movement between the two networks can be adapted. That is, if an over abundance of users are present in one network (hyper band 1900 MHz), for example, the parameters can be changed in order to accommodate all users and decrease the number of dropped calls. Therefore, the change in parameters would allow for the excess traffic to be forced to another network (e.g., base band 850 MHz) where congestion my not be as heavy.

If cell 2 is not congested at step 114, the handoff to cell 2 is completed at step 116, and therefore successful. If, however, cell 2 is congested after the first handoff attempt made at step 112, a second handoff attempt from cell 1 to cell 2 at step 118 is made. Again, congestion in cell 2 is determined at step 120. If congestion does not exist at step 120 after making a second handoff attempt at step 118, handoff to cell 2 is complete and successful at step 122. However, if congestion exists in cell 2 at step 120, not allowing for handoff from cell 1 to cell 2 to be successful, then neighbor cell A is evaluated at step 124 as a candidate for handoff using the "standard" HCS neighbor relation algorithm instead of the "non-preferred" HCS neighbor relation algorithm.

If cell 2 remains congested, the call will be handed off to cell A at step 130 if cell A meets the standard neighbor handoff relation at step 126. That is, the handoff will occur if the received RSS by the mobile on cell As measurement channel is higher than the serving RSS in cell 1. This way, the handoff will not be delayed until the server's signal strength is below the SS_SUFF parameter, which means that the quality of the call is withheld and the possibility for dropping the call decreases. 1f, however, cell A does not meet the standard neighbor handoff relation at step 126, then a new handoff evaluation will occur at step 128. For example, neighbor cell B will be evaluated as a candidate for handoff, again using the "standard" HCS neighbor relation algorithm.

Since the sequence of steps shown in Figure 6 can be implemented within the architecture of known wireless networking systems, such as an HCS networking system using the macrocell/microcell configuration 50, the present invention provides a means for dynamically changing parameters within the network to control traffic congestion levels and regulate network traffic. In addition, by implementing the steps of Figure 6 within the cell control portion of a standard MSC, such as MSC 30, the present invention provides an automatic process for regulating network traffic in an HCS networking system that is less labor-intensive and eliminates post processing of network congestion level data.

While the invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense.

Various modifications in combinations of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description.

Claims

WHAT IS CLAIMED IS:

1. In a wireless Hierarchical Cell Structure (HCS) networking system having a plurality of neighboring cells with a first network operating at a base band and a second network operating in a hyper band, a method of regulating network traffic comprising the steps of: determining congestion levels of said first and second networks; and adapting HCS network usage by forcing traffic from one network to a second network where congestion is less heavy.

2. The method according to Claim 1 wherein said step of determining congestion levels of said first and second networks is preceded by the step of receiving a request for handoff.

3. The method according to Claim 2 wherein said step of receiving a request for handoff is followed by the step of attempting a first handoff in said second network operating in a hyper band, said network having a target cell.

4. The method according to Claim 3 wherein said step of attempting a first handoff is followed by the step of attempting a second handoff in said second network.

5. The method according to Claim 4 wherein said attempting step further includes the step of evaluating a neighbor cell as a candidate for handoff using the "standard" HCS neighbor relation algorithm instead of the "non-preferred" HCS neighbor relation algorithm, said neighbor cells having a measurement channel for measuring RSS.

6. The method according to Claim 5 wherein said evaluating step further includes the step of comparing the received RSS by said mobile station on a measurement channel of said candidate cell with the RSS from the current serving cell.

7. The method according to Claim 1 wherein said adapting step further comprises the step of monitoring the traffic flow in said first and second networks concurrently.

8. The method according to Claim 7 wherein said monitoring step further includes the step of dynamically assigning a value to a traffic congestion parameter associated with the traffic flow in said first and second networks.

9. The method according to Claim 1 wherein said adapting step is preceded by the step of identifying which of said networks contains the greatest amount of traffic congestion.

10. A Hierarchical Cell Structure (HCS) networking system having a plurality of neighboring cells with a first network operating at a base band and a second network operating in a hyper band, said system comprising: a plurality of macrocells creating a first level of coverage; a plurality of microcells creating a second level of coverage under said first level of coverage; a Mobile Station Center (MSC) adapted to control the combined coverage created by said macrocells and microcells; a Base Station Subsystem (BSS) associated with said MSC; a means for determining congestion levels of said first and second networks; and a means for adapting HCS network usage by forcing traffic from one network to a second network where congestion is less heavy.

11. The system according to Claim 10 wherein said neighboring cells are identified as preferred, standard, or non-preferred.

12. The system according to Claim 10 wherein said first network operates at a base band frequency of 850 MHz.

13. The system according to Claim 10 wherein said second network operates at a hyper band frequency of 1900 MHz.

14. The system according to Claim 10 wherein said macrocells and microcells are both private cells and public cells.

15. The system according to Claim 1 Q wherein said BSS further includes a Base Transceiver Station (BTS), or Radio Base Station (RBS), and a Base Station Controller (BSC).

16. The system according to Claim 10 wherein said means for determining congestion levels of said first and second networks further includes a means for receiving a request for handoff.

17. The system according to Claim 16 wherein said means for receiving a request for handoff further comprises a means for attempting a first and a second handoff in said second network.

18. The system according to Claim 17 wherein said means for attempting a first and a second handoff further includes a means for evaluating a neighbor cell as a candidate for handoff using the "standard" HCS neighbor relation algorithm instead of the "non-preferred" HCS neighbor relation algorithm.

19. The system according to Claim 18 wherein said means for evaluating a neighbor cell further includes a means for comparing the received RSS by said mobile station on a measurement channel of said candidate cell with the RSS from the current serving cell.

20. The system according to Claim 10 wherein said means for adapting HCS network usage further comprises a means for monitoring the traffic flow in said first and second networks concurrently.

21. The system according to Claim 20 wherein said means for monitoring the traffic flow further includes a means for dynamically assigning a value to a traffic congestion parameter associated with the traffic flow in said first and second networks.

22. The system according to Claim 10 wherein said means for adapting further includes a means for identifying which of said networks contains the greatest amount of traffic congestion.

23. A Hierarchical Cell Structure (HCS) networking system having a plurality of neighboring cells with a first network operating at a base band and a second network operating in a hyper band, a program product for regulating network traffic comprising: instruction means residing in a computer for determining congestion levels of said first and second networks; and instruction means residing in a computer for adapting HCS network usage by forcing traffic from one network to a second network where congestion is less heavy.

24. The program product according to Claim 23 wherein said instruction means residing in a computer for determining congestion levels of said first and second networks further comprising an instruction means residing in a computer for receiving a request for handoff.

25. The program product according to Claim 24 wherein said instruction means residing in a computer for receiving a request for handoff further comprising an instruction means residing in a computer for attempting a first and a second handoff in said second network.

26. The program product according to Claim 25 wherein said instruction means residing in a computer for attempting a first and a second handoff further comprising an instruction means residing in a computer for evaluating a neighbor cell as a candidate for handoff using the "standard" HCS neighbor relation algorithm instead of the "non-preferred" HCS neighbor relation algorithm, for identifying an acceptable threshold for said network for defining said regions.

27. The program product according to Claim 26 wherein said instruction means for evaluating a neighbor cell further comprising an instruction means residing in a computer for comparing the received RSS by said mobile station on a measurement channel of said candidate cell with the RSS from the current serving cell.

28. The program product according to Claim 23 wherein said instruction means residing in a computer for adapting HCS network usage further comprising an instruction means residing in a computer for monitoring the traffic flow in said first and second networks concurrently.

29. The program product according to Claim 28 wherein said instruction means residing in a computer for monitoring the traffic flow further comprising an instruction means residing in a computer for dynamically assigning a value to a traffic congestion parameter associated with the traffic flow in said first and second networks.

30. The program product according to Claim 23 wherein said instruction means residing in a computer for adapting HCS network usage further comprising an instruction means residing in a computer for identifying which of said networks contains the greatest amount of traffic congestion.