METHOD AND SYSTEM FOR BALANCING LOAD ACROSS CARRIER

SEAMS IN A MULTI-BAND SYSTEM

RELATED APPLICATIONS

BACKGROUND OF THE INVENTION

[0001] Nowadays, cellular networks are rapidly changing with increased mobility of

communication devices. The communication devices themselves are multi-featured

and assist users in daily activities. Further, communication devices can now operate in

multi-band cellular networks. Examples of bands in a multi-band cellular network include the 800 MHz Code Division Multiple Access (CDMA) band in the United

States, the 800 MHz CDMA band in Japan, the 2.1 GHz CDMA band, and the 1900

MHz Personal Communications Service (PCS) band. Network load is increased due to the increased number of communication devices across the plurality of bands in the

multi-bands cellular networks. Load balancing is required to uniformly distribute the network load across all the bands in the plurality of regions in the multi-band cellular

networks.

[0002] In multi-band cellular networks, communication devices acquire carriers in

different frequency bands. A carrier in a particular band corresponds to a particular

frequency on which a communication device works. While a user of the

communication device travels across regions, the communication device may cross a carrier seam. This means that the communication device may lose contact with one

multi-band cellular network and have to connect to a second multi-band cellular

network. This may happen when, for example, the user travels to a different city, or

from a rural area to an urban area. By default, current communication devices connect

the same band in the second multi-band cellular network. For example, if a

communication device is connected to the 2.1 GHz CDMA band in the first multi-

band cellular network, it connects to the same band in the second multi-band cellular

network. This band can then get overloaded, while other bands in the second multi-

band cellular network remain under-utilized.

[0003] In a known method for load balancing, in case the band in the second multi-

band cellular network to which the communication device connects gets congested, a message is sent to the communication device to try connecting to another band.

However, the message is sent only when the band is already overloaded. The

overloading can lead to failures in connection of calls and disconnection of active calls. Further, in current multi-band cellular networks, load distribution is achieved

only at the infrastructure systems. Therefore, any changes in the methodology for load balancing require a change in the software at all infrastructure systems. Furthermore,

load balancing at the infrastructure level can impact large amounts of communication devices causing congestion on the target band.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The present invention is illustrated by way of example and not limitation in

the accompanying figures, in which like references indicate similar elements, and in

which:

[0005] FIG. 1 representatively illustrates a block diagram of a multi-band cellular

network, in accordance with an exemplary embodiment of the present invention.

[0006] FIG. 2 representatively illustrates a block diagram of a communication

device, in accordance with another exemplary embodiment of the present invention.

[0007] FIG. 3 representatively illustrates a block diagram of a communication

device sub-system performing hash operation for selecting a carrier, in accordance with yet another exemplary embodiment of the present invention.

[0008] FIG. 4 representatively illustrates a flowchart depicting a method for

balancing load across a carrier seam in a multi-band cellular network, in accordance with an exemplary embodiment of the present invention.

[0009] FIG. 5 representatively illustrates a flowchart depicting a method for balancing load across a carrier seam in a multi-band cellular network, in accordance with another exemplary embodiment of the present invention.

[0010] Skilled artisans will appreciate that elements in the figures are illustrated for

simplicity and clarity and have not necessarily been drawn to scale. For example, the

dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0011] Before describing in detail the particular method and system for balancing

load across carrier seams in a multi-band system in accordance with the present

invention, it should be observed that the present invention resides primarily in combinations of method steps and apparatus components related to method and

system for balancing load in a multi-band system. Accordingly, the apparatus components and method steps have been represented where appropriate by

conventional symbols in the drawings, showing only those specific details that are

pertinent to understanding the present invention so as not to obscure the disclosure

with details that will be readily apparent to those of ordinary skill in the art having the

benefit of the description herein.

[0012] hi this document, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without

necessarily requiring or implying any actual such relationship or order between such

entities or actions. The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method,

article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such

process, method, article, or apparatus. An element preceded by "comprises ... a" does not, without more constraints, preclude the existence of additional identical elements

in the process, method, article, or apparatus that comprises the element.

[0013] hi accordance with an embodiment of the present invention, a

communication device capable of operation in a multi-band system is disclosed. The

communication device includes a transceiver, a memory, a hashing module and a processor. The transceiver is used for detecting when the communication device

moves across a carrier seam. The memory stores a candidate carrier list. The candidate

carrier list includes carriers from at least two bands in the multi-band system. The hashing module performs at least one hash operation on a communication device

specific property over the candidate carrier list stored in the memory. The processor

then selects a carrier from the candidate carrier list based on the output of the at least

one hash operation.

[0014] hi accordance with another embodiment of the present invention, a method

for balancing load across carrier seams in a multi-band system is disclosed. To balance load, a candidate carrier list is generated at a communication device. The

candidate carrier list includes carriers from at least two bands in the multi-band system. After the candidate carrier list is generated, a band is selected through a

carrier selection from the candidate carrier list. Further, the communication device is

connected to a carrier from the band.

[0015] In accordance with yet another embodiment of the present invention, a

method for balancing load across carrier seams in a multi-band system is disclosed. The method includes generating a candidate carrier list at a communication device

wherein the candidate carrier list comprises carriers from at least two bands in the

multi-band system. A plurality of hash operations are performed on a communication

device specific property. A band is selected through a carrier selection from the candidate carrier list based on the plurality of hash operations. The communication

device is then connected to a carrier from the selected band.

[0016] FIG. 1 representatively illustrates a block diagram of an environment in

which various embodiments of the present invention can be practiced. FIG. 1 shows a

first multi-band system 102 and a second multi-band system 104. The multi-band

system 102 offers telecommunications services in a first region. Similarly, the multi-

band system 104 offers telecommunications services in a second region. For example,

the multi-band system 102 can offer services in a rural region, while the multi-band

system 104 can offer services in an urban region. A communication device 106 can

connect to and communicate through the bands in the multi-band systems 102 and 104

across the two regions. The communication device 106 can travel from the rural area

to the urban area and connect to a band in the multi-band system 104. The point at

which the communication device 106 disconnects from the multi-band system 102

and connects to the multi-band system 104 is referred to as a carrier seam 108.

Therefore, the carrier seam 108 provides an interface between the two regions. The

multi-band system 104 comprises two bands, namely band 1 and band 2. Each band includes a plurality of carriers. A carrier in a band corresponds to a frequency on

which a communication device receives and transmits data. As the concentration of

communication devices is likely to be higher in urban areas, the multi-band system

104 offers more channels as compared to the multi-band system 102. As shown in

FIG. 1, the multi-band system 104 has two bands with seven carriers, namely 1-1, 1-

2, 1-3, 1-4, 2-1, 2-2 and 2-3. Though various embodiments of the present invention are explained with respect to two multi-band systems, it should be appreciated that

these embodiments can be practiced when only one of the communication networks is

a multi-band system, and the communication device 106 travels into this multi-band

system.

[0017] FIG. 2 representatively illustrates a block diagram of a communication

device 106, in accordance with an exemplary embodiment of the present invention.

The communication device 106 can travel across the carrier seam 108 and connect to

the multi-band cellular network 104. The communication device 106 includes a

transceiver 202, a processor 204, a memory 206 and a hashing module 208. The

transceiver 202 detects when the communication device 106 moves across the carrier

seam 108 and needs to connect to the multi-band system 104. The communication

device 106 can request the multi-band system 104 to provide a list of carriers that are

available in each band. On obtaining lists of carriers from each of the bands of the

multi-band system 104, the communication device 106 creates a candidate carrier list

210. The candidate carrier list 210 comprises all carriers available in the bands in the

multi-band system 104 to which the communication device 106 can connect.

Therefore, the candidate carrier list 210 generated by the communication device 106

includes the carriers available with the two bands in the multi-band system 104. The

memory 206 stores the candidate carrier list 210. The hashing module 208 can perform a plurality of hash operations on a communication device specific property.

Based on the plurality of hash operations, a carrier is selected from the candidate

carrier list 210. Examples of the communication device specific property include, but

are not limited to, an Electronic Serial Number (ESN), an International Mobile

Subscriber Identity (IMSI), an International Mobile Equipment Identity (IMEI)

number and a Mobile Identification Number (MIN).

[0018] The processor 204 directs the communication device 106 to connect to the

carrier selected based on the result of the hashing module 208. The processor 204 can

be a microprocessor or an ASIC (Application Specific Integrated Circuit) embedded

in the communication device 106.

[0019] FIG. 3 representatively illustrates a block diagram showing the selection of a

final carrier 2-1, in accordance with an exemplary embodiment of the present

invention. The communication device 106 stores the candidate carrier list 210 in the

memory 206. The hashing module 208 performs a first hash operation over the

candidate carrier list 210, the result of which is a carrier 2-2 in the band 2. An

exemplary hash operation is described in a CDMA2000 standards documentation titled 'Upper Layer (Layer 3) Signaling Standard for cdma2000 Spread Spectrum

Systems', release D, published by the Third Generation Partnership Project 2

(3GPP2), on page 2-621. The hashing module 208 then performs a second hash

operation over the carriers list for the band 2 which results in the selection of the final

carrier 2-1. The communication device 106 then connects and starts communication through the final carrier 2-1.

[0020] FIG. 4 representatively illustrates a flowchart depicting a method for

balancing load across a carrier seam, in accordance with an exemplary embodiment of

the present invention. The carrier seam provides an interface between a first region

and a second region. The second region has a multi-band communication system.

Each band in the communication system has at least one carrier. A communication

device can connect to at least two bands in the multi-band communication system. At

step 402, a candidate carrier list is generated at the communication device. In an

embodiment of the invention, the list of carriers that form a part of the candidate

carrier list are obtained from the at least two bands of the multi-band communication

system. At step 404, a band is selected from the candidate carrier list through a carrier

selection. In accordance with an embodiment of the invention, the carrier selection

comprises performing a first hash operation on a communication device specific

property. Examples of the communication device specific property include, but are not limited to, an Electronic Serial Number (ESN), an International Mobile Subscriber

Identity (IMSI), an International Mobile Equipment Identity (IMEI) number and a

Mobile Identification Number (MIN). The first hash operation can be an existing carrier selection process described in a CDMA2000 standards documentation titled

'Upper Layer (Layer 3) Signaling Standard for cdma2000 Spread Spectrum Systems', release D, published by the Third Generation Partnership Project 2 (3GPP2), on page

2-621. At step 406, the communication device connects to a carrier selected from the

band selected at step 404. In an embodiment of the present invention, the carrier to

which the communication device connects is selected by performing a second hash operation on the communication device specific property to select the carrier from the

carriers obtained from the band that is selected at step 404. The second hash operation

can be similar to the first hash operation. However, the second hash operation selects

a carrier from the carriers obtained from the selected band, while the first hash

operation selects a band from all the carriers to which the communication device can

connect.

[0021] FIG. 5 representatively illustrates a flowchart depicting a method for

balancing load across a carrier seam, in accordance with another exemplary

embodiment of the present invention. The carrier seam provides an interface between

a first region and a second region. The second region has a multi-band communication

system. Each band in the communication system has at least one carrier. A communication device can connect to at least two bands in the multi-band

communication system. At step 502, a candidate carrier list is generated at a communication device. In an embodiment of the invention, the list of carriers that

form a part of the candidate carrier list are obtained from the at least two bands of the

region in the multi-band system. At step 504, at least one hash operation is performed on a communication device specific property. Examples of the communication device

specific property include, but are not limited to, an Electronic Serial Number (ESN),

an International Mobile Subscriber Identity (IMSI), an International Mobile Equipment Identity (IMEI) number and a Mobile Identification Number (MIN). The

first hash operation can be an existing carrier selection process described in a 3GPP2

document. Upper layer (Layer 3) Signaling Standard for CDMA2000 Spread Spectrum System 3GPPS C.S0005-D Version 1.0 dated February 2004 Section 2.6.7.1

page 2-621. At step 506, a band is selected through a carrier selection from the

candidate carrier list based on the results of a first hash operation. At step 508, the

communication device connects to a carrier selected from the band selected at step

506. In an embodiment of the invention, the carrier to which the communication

device connects is selected using a second hash operation. Both the hash operations

can be existing carrier selection processes.

[0022] Various embodiments of the present invention provide load balancing across

carrier seams in multi-band cellular networks offer many advantages. The communication device specific property is unique for every device. The result of the

hash operation of the communication device specific property randomly selects the

band, and subsequently the carrier, to which the communication device connects. Since this selection can be from any of the bands of the multi-band communication

system, and not just from a default band to which the communication device connects, the load across the carrier seams of the multi-band cellular network is more evenly

balanced. Further, various embodiments of the present invention can be implemented at the communication device. Therefore, no changes are required at the infrastructure

of the multi-band cellular network. The changes in the communication device are also

minimal, since existing carrier selection processes can be used while expanding the list of carriers from which the selection is made.

[0023] It will be appreciated that the communication device for balancing load

across carrier seams in a multi-band system described herein may be comprised of one

or more conventional processors and unique stored program instructions that control

the one or more processors to implement, in conjunction with certain non-processor

circuits, some, most, or all of the functions of the method and system described herein. The non-processor circuits may include, but are not limited to, a radio receiver,

a radio transmitter, signal drivers, clock circuits, power source circuits, and user input

devices. As such, these functions may be interpreted as steps of a method to balance loads in a multi-band system. Alternatively, some or all functions could be

implemented by a state machine that has no stored program instructions, or in one or more application specific integrated circuits (ASICs), in which each function or some

combinations of certain of the functions are implemented as custom logic. Of course,

a combination of the two approaches could be used. Thus, methods and means for

these functions have been described herein.

[0024] It is expected that one of ordinary skill, notwithstanding possibly significant

effort and many design choices motivated by, for example, available time, current

technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and

programs and ICs with minimal experimentation.

[0025] In the foregoing specification, the invention and its benefits and advantages

have been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be

made without departing from the scope of the present invention as set forth in the

claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be

included within the scope of present invention. The benefits, advantages, solutions to

problems, and any element(s) that may cause any benefit, advantage, or solution to

occur or become more pronounced are not to be construed as a critical, required, or

essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this

application and all equivalents of those claims as issued.