WO2002069665A2

WO2002069665A2 - Cdma multi-carrier traffic management to provide capacity on demand

Info

Publication number: WO2002069665A2
Application number: PCT/US2001/050477
Authority: WO
Inventors: Chang-Gang Zhang
Original assignee: Nortel Networks Limited
Priority date: 2000-10-31
Filing date: 2001-10-24
Publication date: 2002-09-06
Also published as: WO2002069665A3; AU2002255464A1; EP1334635A2; WO2002069665B1

Abstract

Disclosed is an enhanced multi-carrier CDMA communications network. The network comprises a base station having a capacity-on-demand algorithm for providing additional capacity via a capacity-on-demand carrier when additional capacity is required. A base station performs carrier frequency allocation with a capacity-on-demand algorithm (CODA). The CODA receives as input a value for each of three network parameters that may be selected by a network manager. The parameters are frequency priority, capacity threshold, and carrier blocking threshold. During operation, whenever a frequency request is received at the base station, the CODA completes an analysis and provides additional capacity via the capacity-on-demand carrier when additional capacity is required.

Description

CDMA MULTI-CARRIER TRAFFIC MANAGEMENT TO PROVIDE CAPACITY ON DEMAND

This application claims priority from U.S. Patent Application No. 09/702,874 filed on October 31, 2000, and entitled "CDMA Multi-Carrier

Traffic Management to provide capacity on Demand " which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates in general to a wireless communications network, and in particular to frequency allocation on a wireless communications network. Still more particularly, the present invention relates to a method for managing frequency allocation on a CDMA cellular communications network to provide capacity on demand.

Description of the Prior Art

A typical code-division multiple access (CDMA) cellular communications network provides wireless communication service over a defined service area. At an initial stage, a CDMA network may utilize a single frequency carrier to provide service to the mobile units in the service area. Substantial increases in the utilization of cellular communication equipment, such as cellular telephones, results in a need for even higher bandwidth (i.e., more frequencies) within the service area, and a single frequency carrier is often unable to keep pace with increasing demands.

The need for higher bandwidth within CDMA networks led to the development of a multi-carrier network topology. Multi-carrier networks utilize several different frequency ranges in the available frequency spectrum for cellular communication. Thus, a first frequency range is utilized for a first carrier, a second frequency range is utilized for a second carrier, and so on.

Each carrier frequency has an associated capacity, which limits the total amount of traffic (i.e., the load) allowed on that carrier.

With the high increase of both voice and data traffic, multi-carrier deployments provide a practical way to handle increased traffic. However, traffic distribution among multi-carrier frequencies has proven to be a big hurdle for CDMA networks. For example, in many single-carrier and multi- carrier network environments, a need exists for an additional carrier frequency to carry additional loads, which are not continuous. The need may be either time-based, as during the high-volume (peak) call periods or due to geographical concentration of users.

Currently, there is no efficient way to distribute traffic within CDMA multi-carrier service areas that provides flexibility for service managers to define a carrier distribution. The CDMA standards (IS-95A or IS-95B) provide hashing and GSR (Global Service Redirection), which can only distribute idle traffic among carriers in a projected percentage.

One implementation of a multi-carrier network topology utilizes a multi-carrier traffic allocation (MCTA) algorithm to assign carrier frequencies to communication requests. The MCTA algorithm allocates traffic between all carriers available in a sector of a CDMA cell. MCTA provides the extra call processing needed for high traffic cell sites by allowing the base station transceiver subsystem (BSTS) operating with different carrier frequencies. At call setup, MCTA selects which carrier frequency will service the call.

With MCTA, traffic can be distributed across multi-carriers within areas having high service needs that are provided with two or more channel carrier frequencies to meet demand. Within a dual-carrier frequency service area, where a second carrier frequency is also covering the entire service area, a CDMA mobile unit is theoretically able to remain on one of the two carrier frequencies while the mobile unit is being moved within the service area. However, in practice because the second carrier frequency is intended for handling heavy traffic areas, the mobile unit has to switch its channel frequency while being moved across certain designated boundaries.

MCTA determines allocation of traffic based on the loading conditions of the multiple carrier frequencies. MCTA provides trunking efficiency by pooling carriers. But, MCTA does efficiently support capacity on demand.

The present invention recognizes that it would be desirable to provide capacity-on-demand within a CDMA cellular communications network to reduce network congestion. A multi-carrier CDMA network that provides flexibility to the service manager to define when to utilize the capacity-on- demand carrier would also be a welcomed improvement. These and other benefits are provided in the present invention.

SUMMARY OF THE INVENTION

Disclosed is an enhanced multi-carrier CDMA communications network. The network comprises a base station having a capacity-on-demand algorithm for providing additional capacity via a capacity-on-demand carrier when additional capacity is required. A base station performs carrier frequency allocation with a capacity-on-demand algorithm (CODA). The CODA receives as input a value for each of three network parameters that may be selected by a network manager. The parameters are frequency priority, capacity threshold, and carrier blocking threshold. During operation, whenever a frequency request is received at the base station, the CODA completes an analysis and provides additional capacity via the capacity-on- demand carrier when additional capacity is required.

All objects, features, and advantages of the present invention will become apparent in the following detailed written description.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention itself, as well as a preferred mode of use, further objects, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:

Figure 1 is an example CDMA communications network in which the invention may be implemented;

Figure 2 illustrates a multi-carrier frequency model of a CDMA communications network in which the invention may be implemented;

Figure 3 is a block diagram of a processing system utilized to carry out various functions of the invention in accordance with one embodiment of the present invention; and

Figure 4 illustrates a flow chart of the major processes involved in selecting a carrier frequency in accordance with one preferred embodiment of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

With reference now to the figures and in particular with reference to Figure 1, there is illustrated a CDMA network. CDMA network 30 includes a plurality of cells 12. A representative cell 58 of CDMA network represents a fan-out area for propagation of signals from base station antenna affiliated with base station 35. CDMA network 30 comprises a plurality of base stations 35 and affiliated base station antennae 38. Base station 35 in representative celi 58 also has an affiliated base station controller (BSC) 36, which manages the communication processes of base station 35. CDMA network 30 provides communication between one mobile unit (not shown) and another mobile unit or other communication unit via base station 35.

Figure 2 illustrates multiple carrier frequency distribution of a sectored cell representation of a CDMA network, such as CDMA network 30 of Figure

1. Two carrier frequencies, f_\ and f₂, are utilized in the illustrative example.

The first carrier frequency, f_ls is utilized throughout an entire coverage area 10, and the second carrier frequency, f , is utilized to cover only a small number of cells within a heavy traffic region 11 (illustrated as a shaded area in Figure 2) of coverage area 10. MCTA portion of CDMA network 30 covers a service area 12, which is a geographically defined area. Service area 12 comprises sectored cells, similar to the cells of Figure 1, but which include two carrier frequencies. The carrier frequencies at which communication messages propagate within service area 101 are typically set (i.e., enabled at base station controller 36) during an initial set-up of CDMA network 30.

Base station 35 (or typically base station controller 36) includes a data processing system or processor (e.g., router, switch and/or switching center) by which frequency allocation and other communication features (such as billing) of CDMA network 30 are controlled/managed. An exemplary configuration of a data processing system of base station controller 36, which may be advantageously utilized to complete the processes of the invention is illustrated in Figure 3. Data processing system 301 comprises a processor 303 that controls (i.e., executes) the operations provided in the present invention.

Coupled to processor 303 are memory 305, non-volatile storage 307, and input/output (I/O) devices 309.

During traffic routing, access to a carrier frequency for completing a communication is controlled by base station transceiver subsystem (BSTS)

311 connected to data processing system 301 of base station controller 36. In a prefened embodiment, software coded features of the present invention are stored in non- volatile storage 307 and executed on processor 303. Results generated from processor 308 during execution of the software code of the invention are then provided to carrier frequency controller (i.e., BSTS) 311, which operates to route a traffic request on a carrier supporting capacity-on- demand when particular criteria are met. Routing of traffic is completed via antenna 38 that is coupled to BSTS 311.

The present invention may be implemented as a software-based control mechanism to implement a capacity-on-demand (or standby) carrier overlay on top of existing in-service carriers of a CDMA multi-carrier network. The invention is capable of dynamically monitoring the traffic loading conditions on multiple carriers and direct traffic to a specific carrier as determined by user entered parameters. More importantly, the invention provides a capacity-on- demand algorithm by which traffic is allocated to the capacity-on-demand carrier only when the existing configured carriers are fully utilized. The traffic carried by the capacity-on-demand carrier may provide a revenue generator for the owner of the base station. The invention provides the capacity on demand functionality utilizing a Capacity-On-Demand Algorithm (CODA). CODA is preferably placed in non- volatile storage 307 of data processing system 301. CODA utilizes three (3) control parameters as inputs for carrier frequency selection processes. The three control parameters are (1) frequency priority, (2) capacity threshold, and (3) carrier blocking threshold. Each parameter is assigned a value, which is preferably selected by a BSS manager and inputted into CODA via I/O device 309 of data processing system 301.

The frequency priority parameter, which prioritizes the available frequencies, controls the order of in which the carrier frequencies are assigned by CODA. The capacity threshold parameter determines the loading condition at the particular frequency (i.e., maximum traffic supported by the carrier frequency). The carrier blocking threshold provides a predetermined blocking level at which a carrier is blocked from receiving additional traffic. With these control parameters, CODA offers BSS managers a way to configure the desired traffic loading allocation among the carriers. Particularly, in the preferred embodiment, CODA is configured to provide capacity on demand.

Turning now to Figure 4, there is illustrated a flow chart of the process by which the invention is implemented. Prior to the frequency allocation (typically during set-up of the base station CODA carrier) at a base station 35, the control parameters that serve as input for CODA are entered at the base station 35 (or base station controller 36) by a BSS manager. Once the control parameters are entered, the traffic allocations among the multiple carrier frequencies are completed following the sequence of steps below. The process begins at block 401 and thereafter proceeds to block 403 which illustrates monitoring carriers that are blossomed (i.e., carriers of a base station that is powered up and fully operational). The preferred frequency for allocation is determined at block 405 by checking frequency priority values previously entered by the BSS manager. A determination is then made at block 407 as to whether the capacity estimates of the frequency with highest priority (e.g., fl) is greater than the capacity threshold of fl. If the estimated capacity of fl is greater than the capacity threshold of fl, then fl is selected as the carrier frequency of the communication request at block 413. The process thereafter ends at block 419.

If, however, the capacity estimate of fl is not greater than the capacity threshold of fl, then a determination is made at block 409 whether the capacity estimate of fl is greater than the carrier blocking threshold of fl. If the capacity estimate off! is greater than the carrier blocking threshold of fl, then fl is selected as the carrier frequency for the communication request at block 413. Otherwise, a next determination is made at block 411 whether there are more frequencies available with the same priority. If there are more frequencies with the same priority, then the next frequency having the same priority is selected at block 415, and the evaluation process illustrated beginning at block 407 is performed. However, if there are no more carrier frequencies with the same priority that have not yet been evaluated, a frequency with the largest relative capacity or the frequency with the next highest priority (if available) is selected at block 417, and the process returns to block 407.

Tables I and II tabulate values for carrier frequency parameters in a standard MCTA network and a MCTA CODA network, respectively. Table I provides a first sequential loading model with two frequencies (fl, f2), a second sequential loading model with three frequencies (fl,f2,£3), and an even loading model with the same three frequencies. None of these three models support capacity on demand.

TABLE I CDMA MCTA

Conventional MCTA is designed to support two types of loading (1) even loading on all carriers and (2) sequential loading of carriers. With even loading, traffic is distributed across all carriers equally. Even loading offers trunking efficiency by pooling carriers and provides better coverage balance on overlaid multi-carriers. Sequential loading involves filling up the first carrier, then the second carrier, and so on. Sequential loading has the disadvantage of trunking inefficiency. Furthermore, MCTA sequential loading cannot be utilized to provide capacity on demand at desired levels because of the lack of good control of traffic distribution, for example, precise blocking statistics need to be used for configuration of the carriers.

Table II illustrates a frequency model in which a capacity-on-demand carrier frequency is provided.

TABLE π CDMA MCTA CODA

In Table π, an enhanced first sequential loading model provides two carriers, the second of which, f2, is a capacity on demand carrier (i.e., provides capacity on demand functionality with CODA). Both the enhanced second sequential loading model and enhanced even loading model include three carriers, the third of which, f3, is designated as a capacity on demand carrier. Each model of Table II also includes an additional parameter, the carrier blocking threshold, utilized in CODA's frequency allocation scheme. Note that the threshold of the capacity on demand carrier is set to 0 and that the priority values of that carrier is lower than the values of that other carriers.

In the preferred embodiment, the invention is dynamically implemented and is utilized to provide capacity on demand services only when the existing carriers are fully utilized. Also in the preferred embodiment, the capacity on demand carrier is designed to share the same base station controller 36 with the regular carriers. Additionally, the traffic carried by the capacity on demand carrier may provide a revenue generator based on established billing scheme. For example, in addition to the standard charge for utilization of the other carrier frequencies, the owner of the base station may charge a service fee for utilization of the capacity-on-demand carrier frequency. Thus, the invention offers a product edge over regular MTCA CDMA networks.

The utilization of CODA preferably includes unique deployment characteristics. In particular, in the preferred embodiment, no idle traffic is placed on the capacity-on-demand carrier, and the capacity-on-demand carrier preferably does not have continuous coverage due to economic factors.

Utilizing CODA, a BSS manager may determine when to support capacity on demand and thus implement a manager-desired way of traffic loading. The invention thus provides flexible control of traffic distribution among multiple carrier frequencies of a given BTS site. The invention supports even loading for regular carriers to distribute traffic across all regular carriers equally and to offer trunking efficiency by pooling regular carriers. Also the invention operates to give better coverage balance on overlaid regular multi-carriers. The invention further supports sequential loading between regular carrier(s) and a capacity on demand carrier. Thus, with the invention, regular carriers are filled up first then the capacity on demand carrier is utilized solely to provide capacity on demand.

As a final matter, it is important that while an illustrative embodiment of the present invention has been, and will continue to be, described in the context of a fully functional data processing system, those skilled in the art will appreciate that the software aspects of an illustrative embodiment of the present invention are capable of being distributed as a program product in a variety of forms, and that an illustrative embodiment of the present invention applies equally regardless of the particular type of signal bearing media used to actually carry out the distribution. Examples of signal bearing media include recordable type media such as floppy disks, hard disk drives, CD ROMs, and transmission type media such as digital and analogue communication links.

While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention. For, example, those skilled in the art understand that although the invention is described with particular reference to two or three carriers, the invention is applicable to larger numbers of carriers. Also, although the invention is described with reference to CDMA networks, other similarly configured networks may advantageously utilize the features of the invention.

Claims

CLAIMSWhat is claimed is:

1. A base station of a multiple carrier network comprising: a base station transceiver that routes a traffic request on one of a general carrier frequency or a capacity-on-demand carrier frequency; and a processor that controls selection of a particular one of said general carrier frequency or said capacity-on-demand carrier frequency to assign to said traffic request, wherein said processor selects said capacity-on-demand carrier frequency only when said traffic request cannot be assigned to said available carrier frequency based on pre-determined criteria.

2. The base station of Claim 1, further comprising a capacity-on-demand algorithm that executes on said processor and deterministically selects said particular one of said general carrier frequency or said capacity-on-demand carrier frequency utilizing a plurality of pre-selected parameter values.

3. The base station of Claim 2, further comprising an input mechanism for inputting said plurality of pre-selected parameter values to said capacity- on-demand algorithm.

4. The base station of Claim 3, wherein said plurality of pre-selected parameter values includes at least a value for a frequency priority, a capacity threshold, and a carrier blocking threshold for each of said general carrier frequency and said capacity on demand carrier frequency.

5. The base station of Claim 3, wherein said pre-determined criteria include: determining that said general carrier frequency has a higher frequency than said carrier-on-demand frequency and any other general carrier frequencies, which may be available for selection by said processor; evaluating whether a capacity estimate of said general carrier frequency is greater than said carrier blocking threshold of said general carrier frequency; and assigning said general carrier frequency when said capacity estimate is greater than said carrier blocking threshold.

6. The base station of Claim 5, wherein said predetermined criteria further comprises: eliminating said general carrier frequency from being assigned to said traffic request when said capacity estimate is not greater than said carrier blocking threshold of said carrier frequency; continuing a selection of a carrier frequency to assign to said traffic request with one of said other general carrier frequencies having a highest priority among said other general carrier frequencies until all of said other general carrier frequencies have been eliminated; and selecting said capacity-on-demand frequency when all of said other carrier frequencies have been eliminated.

7. A method for distributing traffic in a multi-carrier CDMA network comprising the steps of: overlaying a plurality of existing service carriers with a standby carrier; controlling distribution of traffic to said multi-carrier network utilizing a plurality of user-defined parameters to provide capacity on demand via said standby carrier.

8. The method of Claim 7, wherein said controlling step further includes the step of assigning a frequency priority to each carrier in said multi-carrier network, wherein said standby carrier is assigned a lowest relative frequency priority.

9. The method of Claim 8, further comprising the step of selecting a capacity threshold based on a loading condition for each carrier.

10. Method of Claim 9, further comprising the step of selecting a carrier blocking threshold for each carrier.

11. The method of Claim 10, wherein said controlling step includes the step of determining via a capacity on demand algorithm when to allocate a requesting traffic to said standby carrier such that capacity on demand is provided.

12. A computer program product for utilization in a CDMA multi-carrier network, said program product comprising: a computer readable medium; and program instructions on said computer readable medium for controlling distribution of traffic within said network utilizing a plurality of carrier parameters to provide capacity on demand via a standby carrier, which overlays a plurality of other service carriers.

13. The computer program product of Claim 12, further comprising program instructions for updating values of said plurality of carrier parameters with user-provided input.

14. The computer program product of Claim 12, wherein: said plurality of carrier parameters includes a frequency priority value, a capacity threshold, and a carrier blocking threshold for each carrier within said network; and said program product further comprising program instructions for: selecting a carrier that has a highest priority frequency from among said frequency priority values associated with said service carriers and said standby carrier; in response to said selecting step, determining whether a capacity estimate is greater than a capacity threshold of said highest priority frequency; and assigning said carrier to service a requesting traffic when a result of said determining step is affirmative.

15. The computer program product of Claim 14, further comprising program instructions for determining whether said capacity estimate is greater than a carrier blocking threshold of said highest priority frequency.

16. The computer program product of Claim 15, further comprising program instructions for selecting a carrier with a largest relative capacity to assign to said requesting traffic.

17. The computer program product of Claim 16, further comprising program instructions for selecting a carrier with a next highest priority frequency when a capacity estimate is greater than a capacity threshold of said next highest priority frequency.

18. A network comprising: a base station, which includes a base station controller that implements a capacity-on-demand algorithm to select a capacity-on-demand carrier frequency from among a plurality of carrier frequencies available to said base station when a traffic request is to be routed by said base station and more carrier capacity is required.