METHOD OF CONTROLLING A SMALL CELL BASE STATION

BACKGROUND

Field of the Invention

The present invention relates to telecommunications, in particular to
wireless telecommunications.

Description of the Related Art

Wireless telecommunications systems are well-known. Many such
systems are cellular, in that radio coverage is provided by a bundle of
radio coverage areas known as cells. A base station that provides
radio coverage is located in each cell. Traditional base stations provide
coverage in relatively large geographic areas and the corresponding
cells are often referred to as macrocells.
It is possible to establish smaller sized cells within a macrocell. Cells
that are smaller than macrocells are sometimes referred to as
microcells, picocells, or femtocells, but we use the terms femtocell or
small cell generically for cells that are smaller than macrocells. One
way to establish a femtocell is to provide a femtocell base station that
operates within a relatively limited range within the coverage area of a
macrocell. One example of use of a femtocell base station is to provide
wireless communication coverage within a building.
The femtocell base station is of a relatively low transmit power and
hence each femtocell is of a small coverage area compared to a
macrocell.
Femtocell base stations are intended primarily for users belonging to a
particular home or office. Femtocell base stations may be private
access or public access. In femtocell base stations that are private
access, access is restricted only to registered users, for example family
members or particular groups of employees. In femtocell base stations
that are public access, other users may also use the femtocell base
station, subject to certain restrictions to protect the Quality of Service
received by registered users.
One known type of Femtocell base station uses a broadband Internet
Protocol connection as "backhaul", namely for connecting to the core
network. One type of broadband Internet Protocol connection is a
Digital Subscriber Line (DSL). Others are coax cable or fiber to the
customer premises. The DSL connects a DSL transmitter-receiver
("transceiver") of the femtocell base station to the core network. The
DSL allows voice calls and other services provided via the femtocell
base station to be supported. The femtocell base station also includes
a radio frequency (RF) transceiver connected to an antenna for radio
communications.
Femtocell base stations are sometimes referred to as femtos.
Femtocell base stations are user-deployed base stations with a typical
coverage range of tens of meters. They have extensive auto
configuration and self-optimization capabilities so as to enable simple
plug-and-play deployment, and are designed to automatically
integrate themselves into an existing macrocellular network. In
addition, femtos may include some functionality traditionally provided
by a core network, namely a Serving GPRS Support Node (SGSN) and
a Gateway GPRS Support Node (GGSN). One example of a femto is a
UMTS Base Station Router (BSR), where UMTS denotes Universal
Mobile Telecommunications System (UMTS), which integrates some
functionality of a UMTS base station (NodeB), a Radio Network
Controller (RNC), SGSN and GGSN.
SUMMARY
The present invention relates to a method of controlling a small cell
base station.
In one embodiment, the method includes switching, at the base
station, from a sleep state to a receive active state to detect whether
service should be provided for an authorized mobile terminal. The
base station disables transmission and associated processing and
disables reception and associated processing in the sleep state. The
base station disables transmission and associated processing in the
receive active state, and the base station enables reception and
associated processing in the receive active state. The method further
includes switching, at the base station, from the receive active state to
a full active state if the base station detects that service should be
provided for an authorized mobile terminal. The base station enables
transmission and associated processing and enables reception and
associated processing in the full active state.
In one embodiment, the switching from a sleep state step is performed
based on at least one state control parameter. For example, the state
control parameter may be determined based on historical operation of
the base station. As such, the state control parameter may change
based on at least one of time of day, day of week, month of year, date
etc. and a combination thereof. The base station could learn the
optimal mix of states that it needs to be in based on how it is called
up on to serve mobiles.
In one embodiment, the state control parameters are received from a
macro base station or network controller in the network.
A further embodiment includes returning to the sleep state from the
receive active state after a length of time if an authorized mobile
terminal for which service should be provided is not detected.
Another embodiment includes switching from one of the sleep state
and the receive active state to the full active state in response to a
trigger from a macro base station or the network controller.
An additional embodiment involves switching from the full active state
to the sleep state after a period of inactivity at the base station.
The present invention also relates to a small cell base station.
In one embodiment the small cell base station includes signaling and
data circuitry and a mode controller. The signaling and data circuitry
includes circuitry for transmission and associated processing, and
circuitry for reception and associated processing. The mode controller
is configured to switch the signaling and data circuitry from a sleep
state to a receive active state to detect whether service should be
provided for an authorized mobile terminal. The signaling and data
circuitry disables transmission and associated processing and
disables reception and associated processing in the sleep state. The
signaling and data circuitry disables transmission and associated
processing in the receive active state, and the signaling and data
circuitry enables reception and associated processing in the receive
active state. The mode controller is further configured to switch the
signaling and data circuitry from the receive active state to a full
active state if the base station detects service should be provided for
an authorized mobile terminal. The signaling and data circuitry
enables transmission and associated processing and enables reception
and associated processing in the full active state.
In another embodiment, the small cell base station, includes signaling
and data circuitry. The signaling and data circuitry includes circuitry
for transmission and associated processing, and the signaling and
data circuitry includes circuitry for reception and associated
processing. The small cell base station further includes a mode
controller configured to switch the signaling and data circuitry from
one of a sleep state and a receive active state to a full active state in
response to a trigger from a macro base station or network controller.
The signaling and data circuitry disables transmission and associated
processing and disables reception and associated processing in the
sleep state. The signaling and data circuitry disables transmission and
associated processing in the receive active state, and the signaling and
data circuitry enables reception and associated processing in the
receive active state. The signaling and data circuitry enables
transmission and associated processing and enables reception and
associated processing in the full active state.
Some embodiments provide significant advantages over known
approaches. For example, known approaches involve frequent periodic
pilot transmissions when there is no active call connection involving
the femtocell base station. This involves a basically continuous
electromagnetic radiation exposure in the home, office, etc. Although,
the inventors know of no proof of any health risks, it is widely believed
that minimizing this exposure is desirable. The present invention in
several embodiments address this perceived problem by usually
disabling transmissions when the small cell base station is not in
active use, so significantly reducing user concerns and thereby
improving users' acceptance of deploying base stations in their homes,
offices, etc.
Furthermore, controlling energy consumption of small cell base
stations, in particular so as to help the environment, is increasingly
becoming an issue. This is particularly important as the numbers of
femtocells in use increases. The present invention in several
embodiments reduces the energy used, by disabling transmission,
reception and most processing for significant periods.
In femtocell deployments, it is possible that a pilot signal radiates
strongly out of a home or office in a busy area where user terminals
not registered with the femtocell base station they are passing by. In
consequence, those passing mobile terminals make handover
attempts or idle mode camping attempts to the femtocell base station
causing signaling to and from the core network. Some embodiments of
the present invention significantly reduce this signaling, because pilot
signals are not sent if a mobile terminal passes by while the femto is
in sleep state; and therefore, any camping attempts and associated
signaling are not triggered.
Furthermore, some embodiments of the present invention reduce
interference that transmissions from a femtocell base station provide
to its neighboring femtocell base stations, as the transmissions are
disabled most of the time.

BRIEF DESRCRIPTION OF THE DRAWINGS

Example embodiments of the present invention will become more fully
understood from the detailed description provided below and the
accompanying drawings, wherein like elements are represented by like
reference numerals, which are given by way of illustration only and
thus are not limiting of the present invention and wherein:
Figure 1 is a diagram illustrating a wireless communications network
according to a first embodiment of the present invention,
Figure 2 is a diagram illustrating an example femtocell base station
deployment within one macrocell shown in Figure 1,
Figure 3 is a diagram illustrating one of the femtocell base stations (or
femtos) shown in Figure 2,
Figures 4-6 illustrates example operations of femto in the sleep state.
Figure 7 illustrates a flowchart of the operation of a femto according
to an embodiment.
Figure 8 illustrates a flow chart of the operation of a femto according
another embodiment.
Figure 9 illustrates the mode controller of a femto according to
another embodiment.
DETAILED DESCRIPTION
Various example embodiments of the present invention will now be
described more fully with reference to the accompanying drawings in
which some example embodiments of the invention are shown.
Detailed illustrative embodiments of the present invention are
disclosed herein. However, specific structural and functional details
disclosed herein are merely representative for purposes of describing
example embodiments of the present invention. This invention,
however, may be embodied in many alternate forms and should not be
construed as limited to only the embodiments set forth herein.
Accordingly, while example embodiments of the invention are capable
of various modifications and alternative forms, embodiments thereof
are shown by way of example in the drawings and will herein be
described in detail. It should be understood, however, that there is no
intent to limit example embodiments of the invention to the particular
forms disclosed, but on the contrary, example embodiments of the
invention are to cover all modifications, equivalents, and alternatives
falling within the scope of the invention. Like numbers refer to like
elements throughout the description of the figures.
It will be understood that, although the terms first, second, etc. may
be used herein to describe various elements, these elements should
not be limited by these terms. These terms are only used to
distinguish one element from another. For example, a first element
could be termed a second element, and, similarly, a second element
could be termed a first element, without departing from the scope of
example embodiments of the present invention. As used herein, the
term "and/or" includes any and all combinations of one or more of the
associated listed items.
It will be understood that when an element is referred to as being
"connected" or "coupled" to another element, it can be directly
connected or coupled to the other element or intervening elements
may be present. In contrast, when an element is referred to as being
"directly connected" or "directly coupled" to another element, there are
no intervening elements present. Other words used to describe the
relationship between elements should be interpreted in a like fashion
(e.g., "between" versus "directly between", "adjacent" versus "directly
adjacent", etc.).
The terminology used herein is for the purpose of describing particular
embodiments only and is not intended to be limiting of example
embodiments of the invention. As used herein, the singular forms "a",
"an" and "the" are intended to include the plural forms as well, unless
the context clearly indicates otherwise. It will be further understood
that the terms "comprises", "comprising,", "includes" and/or
"including", when used herein, specify the presence of stated features,
integers, steps, operations, elements, and/ or components, but do not
preclude the presence or addition of one or more other features,
integers, steps, operations, elements, components, and/ or groups
thereof.
It should also be noted that in some alternative implementations, the
functions/ acts noted may occur out of the order noted in the figures.
For example, two figures shown in succession may in fact be executed
substantially concurrently or may sometimes be executed in the
reverse order, depending upon the functionality/ acts involved.
In the following description, illustrative embodiments will be described
with reference to acts and symbolic representations of operations (e.g.,
in the form of flowcharts) that may be implemented as program
modules or functional processes including routines, programs,
objects, components, data structures, etc., that perform particular
tasks or implement particular abstract data types and may be
implemented using existing hardware at existing network elements.
Such existing hardware may include one or more Central Processing
Units (CPUs), digital signal processors (DSPs), application-specificintegrated-
circuits, field programmable gate arrays (FPGAs) computers
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. Unless
specifically stated otherwise, or as is apparent from the discussion,
terms such as "processing," "computing," "calculating," "determining,"
"displaying," or the like, refer to the action and processes of a
computer system, or similar electronic computing device, that
manipulates and transforms data represented as physical, electronic
quantities within the computer system's registers and memories into
other data similarly represented as physical quantities within the
computer system memories or registers or other such information
storage, transmission or display devices.
Note also that the software implemented aspects of the example
embodiments are typically encoded on some form of tangible recording
(or storage) medium or implemented over some type of transmission
medium. The tangible storage medium may be magnetic (e.g.,, a
floppy disk or a hard drive), optical (e.g.,, a compact disk read only
memory, or "CD ROM"), solid state, etc; may be read only or random
access; and may be volatile or non-volatile. Similarly, the
transmission medium may be twisted wire pairs, coaxial cable, optical
fiber, or some other suitable transmission medium known to the art.
The example embodiments are not limited by these aspects of any
given implementation.
As used herein, the term "mobile terminal" may be considered
synonymous to, and may hereafter be occasionally referred to, as a
mobile, mobile unit, mobile station, mobile user, subscriber, user,
remote station, access terminal, receiver, user equipment, etc., and
may describe a remote user of wireless resources in a wireless
communication network. The term "base station" may be considered
synonymous to and/ or referred to as a base transceiver station (BTS),
NodeB, extended NodeB, evolved NodeB, femto cell, pico cell, access
point, etc. and may describe equipment that provides the radio
baseband functions for data and/ or voice connectivity between a
network and one or more users.
Also, as discussed above, cells that are smaller than macrocells are
sometimes referred to as microcells, picocells, or femtocells, but we
use the terms femtocell or small cell generically for cells that are
smaller than macrocells.
We now describe a network including femtocell base stations then
look in greater detail at a femtocell base station and its operation.
Network
As shown in Figures 1 and 2, a network 10 for wireless
communications, through which a user terminal 44 may roam,
includes two types of base stations, namely macrocell base stations
and femtocell base stations (the latter being sometimes called
"femtos"). One macrocell base station 22 is shown in Figures 1 and 2
for simplicity. Each macrocell base station has a radio coverage area
24 that is often referred to as a macrocell. The geographic extent of
the macrocell 24 depends on the capabilities of the macrocell base
station 22 and the surrounding geography.
Within the macrocell 24, each femtocell base station 30 provides
wireless communications within a corresponding femtocell 32. A
femtocell is a radio coverage area. The radio coverage area of the
femtocell 32 is much less than and may be at least partially included
within that of the macrocell 24. However, the femtocell 32 may
overlap more than one macrocell, or not be included in a macrocell.
Usually, the femtocell 32 corresponds in size to a user's office or
home.
As shown in Figure 1, the network 10 is managed by a radio network
controller, RNC, 170. The radio network controller, RNC, 170 controls
the operation, for example by communicating with macrocell base
stations 22 via a backhaul communications link 160. The radio
network controller 170 maintains a neighbor list which includes
information about the geographical relationship between cells
supported by base stations. In addition, the radio network controller
170 maintains location information which provides information on the
location of the user equipment within the wireless communications
system 10. The radio network controller 170 is operable to route
traffic via circuit-switched and packet- switched networks. For circuitswitched
traffic, a mobile switching center 250 is provided with which
the radio network controller 170 may communicate. The mobile
switching center 250 communicates with a circuit-switched network
such as a public switched telephone network (PSTN) 2 10. For packetswitched
traffic, the network controller 170 communicates with
service general packet radio service support nodes (SGSNs) 220 and a
gateway general packet radio support node (GGSN) 180. The GGSN
then communicates with a packet-switch core 190 such as, for
example, the Internet.
The MSC 250, SGSN 220, GGSN 180 and IP network constitute a socalled
core network 253. The SGSN 220 and GGSN 180 are connected
by an IP network 2 15 to a femtocell controller/ gateway 230.
The femtocell controller/ gateway 230 is connected via the Internet
190 to the femtocell base stations 30 of the femtocells 32. These
connections to the femtocell controller/ gateway 230 are broadband
Internet Protocol connections ("backhaul") connections.
In Figure 2, three femtocell base stations 30 and corresponding
femtocells 32 are shown for simplicity.
It is possible for a mobile terminal 44 within the macrocell 24 to
communicate with the macrocell base station 22 in any known
manner. When the mobile terminal 44 enters into a femtocell 32 for
which the mobile terminal is registered for communications within the
femtocell base station 30, it is desirable to handle initiation of
communication (e.g., calls) at the femtocell base station 30 and/or
handover an existing connection with the mobile terminal from the
macrocell to the femtocell. In the example shown in Figure 2, the user
of mobile terminal 44 is a registered user of the nearest of the
femtocells 32.
As will be appreciated, a public femtocell base station 30 will handle
communications for any mobile terminal. However, a private femtocell
base station 30 will handle communications only for authorized
mobile terminals.
As shown in Figure 2, the femtocell base stations 30 are connected via
the broadband Internet Protocol connections ("backhaul") 36 to the
core network and hence the rest of the telecommunications "world". In
an alternative embodiment, selected traffic may communicate directly
from the femto via the IP network with the world at large. The
"backhaul" connections 36 allow communications between the
femtocell base stations 30 through the core network. The macrocell
base station is also connected to the core network.
While it will be recognized that the above network architecture relates
to particular wireless standards, the present invention is not limited
to this architecture or those standards.
Femtocell Base Station
Figure 3 illustrates a femtocell base station or femto according to an
embodiment. As shown in Figure 3, each femto 30 includes an
antenna 52 for transmission and reception, and includes signaling
and data transmission/ reception circuitry 60 for control signaling and
for data. This circuitry 60 includes transmission circuitry 62 and
reception circuitry 64. The transmission circuitry 62 handles
transmission and associated processing, and the reception circuitry
64 handles reception and associated processing. It will be appreciated
that the transmission and reception circuitry may share circuits and
has been illustrated as separate elements only for the sake of
description.
A mode controller 58 controls the operational state of the signaling
and data transmission/ reception circuitry 60. In particular, the mode
controller 58 controls whether the circuitry 60 is in a sleep state,
receive active state, or a full active state. In the sleep state, the
circuitry 60 disables transmission and associated processing.
Accordingly, the femto 30 does not transmit any signal such as
beacons, pilots, broadcast, user data signals, etc. In the sleep state,
the femto 30 also disables reception and associated processing.
Accordingly, the femto 30 does not receive and process any signals
transmitted by nearby mobile terminals. In the sleep state, the femto
30 does not consume much energy, does not generate electromagnetic
radiation, and does not generate interference. However, in the sleep
state the femto 30 can receive signals including wakeup messages
from a network controller such as RNC 170 shown in Figure 1. When
the femto 30 receives such signals the femto 30 can wakeup to a full
active state or a receive active state based on the command received.
In the receive active state, the circuitry 60 disables transmission and
associated processing, but enables reception and associated
processing. Accordingly, in the receive active state energy
consumption is still reduced as compared to the full active state
described below, electromagnetic radiation is not produced, and
interference is not generated. In the receive active state the femto 30
can receive signals including wakeup messages from a network
controller such as RNC 170 shown in Figure 1. When the femto 30
receives such signals the femto 30 can wakeup to the full awake state
or revert to the sleep state based on the command received.
Furthermore, in the receive active state the femto 30 can continue to
communicate with the network controller such as RNC 170 and/ or
SGSN 180 and GGSN 220 shown in Figure 1. In the full active state,
the circuitry 60 enables reception and associated processing, and
enables transmission and associated processing. Namely, in the full
active state, the circuitry 60 operates in the conventional manner
including communicating with the macro and IP networks.
As shown in Figure 3, the mode controller 58 includes a controller 70
and state parameter memory 72. The state parameter memory 72
stores a plurality of state parameters, and may be any type of
memory. For example, the memory 72 may be a volatile or non-volatile
memory, may be a RAM or a ROM, etc. The controller 70 controls the
state of the circuitry 60 based on the state parameters stored by the
memory 72. The state parameters will be described in detail below
with respect to Figure 4.
Figure 4 illustrates an example operation of femto 30 in the sleep
state. As shown, the sleep state may be a periodic operation over an
interval of time I . During each interval I of duration T, the femto
switches from the sleep state to the receive active state W. The
duration T is a state parameter stored in the memory 72. The point in
time, t l in Figure 4, during the interval I that the femto switches to
the receive active state W is also a state parameter stored in the
memory 72. Still further, the length of time L that the femto 30
remains in the receive active state is a state parameter stored in the
memory 72. Accordingly, as shown in Figure 4, based on these state
parameters, the controller 70 may control transition from the sleep
state to the receive active state, and back to the sleep state again. As
will be described in more detail below, during the receive active state
the femto 30 monitors transmissions by nearby mobile terminals. If
the femto 30 detects a mobile terminal should be served (e.g., the
mobile terminal initiates communication) and the mobile terminal is
authorized to be served by the femto 30, the femto 30 will switch to
the full active state. Note that in order to determine that the mobile
terminal is authorized to be served by the femto 30, the femto 30 may
temporarily turn on the transmitter to communicate with the mobile
terminal.
As shown in Figure 4, the start time of the receive active state may be
periodic. Stated another way, the start time may be the same in each
interval I . Also, the length of time the femto 30 is in the receive active
state may be the same for each interval I . However, the present
invention is not limited to these operational constraints.
For example, as shown in Figure 5, the start time of the receive active
state may vary from interval I to interval I . In one embodiment, the
start time may be randomly generated by the controller 70. Still
further, as shown in Figure 6, the start time may progressively shift
from interval I to interval I . In Figure 6, the shift is a fixed offset tO,
but the invention is not limited to a fixed offset. Figure 6 also shows
that the length of time the femto 30 remains in the receive active state
may vary from interval I to interval I . Additionally, while the intervals
have been shown as having a fixed length of time T, this time may also
be varied. For instance, the memory 72 may store state parameters
setting forth the sleep and receive active states that vary based on
time of day, day of week, month of year, date, etc and these may be
based on learning algorithms adapting to legitimate user needs. As
will be appreciated any design is possible by programming the
memory 72 with desired state parameters.
In one embodiment, the state parameters may be set to default set. In
another embodiment, the state parameters may be user
programmable. In another embodiment, discussed in detail below with
respect to Figure 9, the state parameters may be autonomously and
adaptively determined. Still further, the memory 72 may store state
parameters sent by the macrocell. Again, it will be appreciated that
any method of determining and storing the state parameters may be
implemented.
Operation
Operation of the femto 30 will now be described in detail with respect
to Figure 7. Figure 7 illustrates a flowchart of the operation of femto
30 according to an embodiment. It is assumed, with respect to Figure
7, that the femto 30 has entered the sleep state. For example, after a
period of inactivity at the femto 30, the mode controller 58 may switch
the circuitry 60 from the full active to the sleep state and begin the
process illustrated in Figure 7.
As shown, in step S7 10 the controller 70 initializes a sleep clock to
zero and starts the sleep clock. In step S7 15, the controller 70 places
the circuitry 60 in the sleep state. Accordingly, the transmission,
reception and associated processing are disabled. However, based on
instructions from the network or the mode controller 58, the circuitry
60 may or may not continue to communicate with the network. Then,
the controller 70 determines if the sleep clock has reached the time to
place the circuitry 60 in the receive active state in step S720. Here,
the controller 70 obtains the point in time to start the receive active
state from the memory 72. As discussed above, this point in time is
one of the state parameters stored in the memory 72. As further
discussed, the point in time retrieved may depend on the time of day,
day of week, month, date, etc. or combination thereof. If the time
indicated by the sleep clock equals the point in time retrieved from the
memory 72, then in step S725, the controller 70 switches the circuitry
60 from the sleep state to the receive active state. Otherwise, step
S720 is continuously repeated until the sleep clock equals the time to
start the receive active state.
Having been placed in the receive active state, the femto 30 may
receive signals from nearby mobile terminals. In step S730, the
circuitry 60 will be able to retrieve and process any signal transmitted
by a mobile terminal that the femto 30 is designed to receive. The
circuitry 60 monitors received signals to detect whether service should
be provided for an authorized mobile terminal. For example, if the
femto 30 receives an access probe (AP) from a mobile terminal that
exceeds a threshold power level, the circuitry 60 determines whether
the mobile terminal is an authorized mobile terminal. If the femto 30
is a public femto, then the mobile terminal is assumed authorized
until further authentication is performed. However, if the femto 30 is a
private femto, then the femto 30 will provide service only for those
mobile terminals authorized to use the femto. This authorization
process is well-known, and will not be described in detail for the sake
of brevity. Furthermore, in this state the femto 30 may or may not
continue to communicate with the network
Assuming the mobile terminal detected is authorized, then the
circuitry 60 notifies the controller 70, and the controller 70 switches
the circuitry 60 to the full active state in step S735. Thus, the
circuitry 60 may react to the mobile terminal; provide the appropriate
response messages to the mobile terminal; and provide
communication services to the mobile terminal. The femto 30 may also
simultaneously signal the macrocell 22 and the RNC 170 over the
backhaul that it has woken up and will handle service to the mobile
terminal. If the circuitry 60 does not detect an authorized mobile
terminal, then in step S740, the controller 70 determines if the length
of time for the receive active state has expired. Namely, the controller
70 obtains the length of time for the receive active state from the
memory 72 as one of the state parameters. If the sleep clock equals
the start time of the receive active state plus the length of time for the
receive active state, then the controller 70 determines that that the
receive active state should end, and switches the circuitry 60 back to
the sleep state in step S745. Otherwise, processing returns to step
S730 and monitoring for mobile terminals continues.
Once back in the sleep state, the controller 70 determines whether the
sleep interval I has expired in step S750. Namely, the controller 70
obtains the period of the interval from the memory 72 as a state
parameter. And, if the sleep clock equals the time for the interval, the
controller 70 determines that the sleep interval has expired. As a
result, the sleep clock is initialized (or reset) in step S755, processing
proceeds to step S720, and the next sleep interval begins. If the sleep
clock has not reached the sleep interval period in step S750, then
processing remains at step S750 until the sleep clock does reach the
sleep interval period.
As will be appreciated, the femto 30 is kept at a low energy
consumption sleep state during periods of inactivity. The femto 30 is
wakened, but only in reception mode, to determine if the femto 30
should resume full activity. In this reception mode, no transmission
by the femto 30 takes place. Accordingly, energy consumption
remains reduced, electromagnetic radiation remains non-existent, and
interference from the femto 30 remains negligible.
As discussed above, once in the full active state, the mode controller
58 may switch the circuitry 60 to the sleep state after a period of
inactivity in the full active state. For example, if the femto 30 has not
handled communication from a mobile terminal for a threshold
amount of time, the mode controller 58 places the circuitry 60 in the
sleep state. The mode controller 58 may also signal the macrocell 22
and RNC 70 over the backhaul, that the femto 30 has been placed in
the sleep state. Still further, instead of directly placing the circuitry 60
in the sleep state, the mode controller 58 may first place the circuitry
60 in the receive active state for a period of time. If the circuitry 60
does not detect any authorized mobile terminals should be serviced
during this period of time, then the mode controller 58 places the
circuitry 60 in the sleep state. However, if the circuitry 60 does detect
an authorized mobile terminal should be serviced, then the mode
controller 58 returns the circuitry 60 to the full active state.
Figure 8 illustrates a flow chart of the operation of the femto 30
according another embodiment. This embodiment may be performed
concurrently with the embodiment of Figure 7, or may be performed
even if the embodiment of Figure 7 is not. This embodiment
contemplates that a mobile terminal has already established a
communication session via the macrocell base station, and the
macrocell determines to handoff serving the mobile terminal to the
femto 30 while the femto 30 is in the sleep or receive active state.
Here, the macrocell 22 and/or RNC 170 may determine that the
mobile terminal is authorized to receive services from the femto 30.
Namely, the macrocell 22 may store the same authorizing information
as the femtos. Having made the above determination, the macrocell 22
and/or RNC 170 sends a handoff request to the femto 30 over an
appropriate backhaul. This is just one example of a trigger that the
macrocell 22 and/or RNC 170 may send to the femto 30 to ensure the
femto 30 is in the full active state. Namely, the present invention is
not limited to this handover example as the trigger.
In step S8 10 of Figure 8, the controller 70 determines if a trigger to
bring the femto 30 out of the sleep state should the femto 30 currently
be in the sleep state is received from the macrocell. If no, the femto
remains in the sleep state in step S820, and processing returns to
step S8 10. If the determination in step S8 10 is positive, then in step
S815, the controller 70 switches the circuitry 60 to the full active
state.
As an alternative, the femto 30 may also determine whether the
mobile terminal is an authorized user of the femto 30. If authorized,
the femto 30 remains in the full active state. If not authorized, the
femto 30 re-directs the mobile station to the macro base station 22
and returns to the sleep state. Alternatively, this authorization
determination may be performed in the receive active state, and then
proceed to the full active state if the mobile terminal is determined as
an authorized user.
Other embodiments
Figure 9 illustrates the mode controller of a femto according to
another embodiment. As shown, the mode controller 58' includes a
controller 70 and state parameter memory 72 as discussed above.
However, the mode controller 58' also includes a database 74 and an
analyzer 76. The database 74 receives activity information from the
circuitry 60. Namely, the database 74 stores information on the state
of the circuitry 60. For example, the database 74 stores information
indicating the length and time the femto 60 was in at least the sleep
state and the full active. This information is cataloged over days,
weeks, months and by date.
The analyzer 76 analyzes the historical operation information in
database 74 for trends. For example, the femto 30 may be placed in a
shopping mall, and the information in database 74 indicates that the
femto 30 stays in the sleep mode from 10pm 12am and from 12am to
10am each weekday. Based on this historical operation information,
the analyzer 76 may set a much longer sleep interval for these periods
of time, than other periods of the day when the femto 30 becomes
more active. As will be appreciated, the analyzer 76 may be
programmed to identify patterns based on time of day, day of week,
month, date, etc. and combinations thereof.
The state parameters stored in the memory 72, whether determined as
described above or programmed therein, may be signaled to the
macrocell 22 over the backhaul.
It will be appreciated, that instead of being located at the femto 30,
the database 74 and analyzer 76 may be located at the macrocell 22
or RNC 170, and the macrocell 22 or RNC 170 may send the
determined state parameters to the femto 30 for storage in the
memory 72. For example, the state parameters may be communicated
in overhead messages from the macrocell 22.
As a further alternative to the previously described embodiments, the
femto 30 may include an indicator light that is externally visible. The
indicator light may be configured to indicate the state of the femto.
For example, the indicator light may display different colors depending
on whether the femto 30 is in the sleep state or full active state.
Additionally, or alternatively, the indicator light may provide a
different display depending on the state of the femto 30. For example,
the indicator light may blink in the sleep state, and may be steady in
the full active state. While different displays and colors were described
for only the sleep and full active states, a display and/ or color may
also be provided for indicating the receive active state.
The invention being thus described, it will be obvious that the same
may be varied in many ways. Such variations are not to be regarded
as a departure from the invention, and all such modifications are
intended to be included within the scope of the invention.

We claim:

1. Amethod of controlling a small cell base station, comprising:

switching (S275), at the base station (30), from a sleep state to a receive active state to detect whether service should be provided for an authorized mobile terminal, the base station disabling transmission and associated processing and disabling reception and associated processing in the sleep state, the base station disabling transmission and associated processing in the receive active state, and the base station enabling reception and associated processing in the receive
active state; and

switching (S730, S740, S735), at the base station, from the
receive active state to a full active state if the base station detects that
service should be provided for an authorized mobile terminal, the base
station enabling transmission and associated processing and enabling
reception and associated processing in the full active state.

2. The method of claim 1, wherein the switching from a sleep state
step is performed one of periodically during the sleep state, and
randomly during the sleep state.

3. The method of claim 1, wherein the switching from a sleep state
step is performed based on at least one state control parameter.

4. The method of claim 3, further comprising:
determining the state control parameter based on historical
operation of the base station.

5. The method of claim 3, wherein the state control parameter
changes based on at least one of time of day, day of week, month of
year, and date.

6. The method of claim 3, further comprising:
receiving the state control parameter from a macro base station
or network controller .

7. The method of claim 1, further comprising:
returning (S740, S745) to the sleep state from the receive active
state after a length of time if the base station does not detect that
service should be provided for an authorized mobile terminal.

8. The method of claim 1, further comprising:
switching (S8 10, S8 15) from one of the sleep state and the
receive active state to the full active state in response to a trigger from
at least one of a network controller and a macro base station.

9. The method of claim 1, further comprising:
switching from the full active state to the sleep state after a
period of inactivity at the base station.

10. Amethod of controlling a small cell base station, comprising:
switching (S8 10, S8 15), at the base station 30, from one of a
sleep state and a receive active state to a full active state in response
to a trigger from at least one of a network controller and a macro base
station, the base station disabling transmission and associated
processing and disabling reception and associated processing in the
sleep state, the base station disabling transmission and associated
processing in the receive active state, the base station enabling
reception and associated processing in the receive active state, and
the base station enabling transmission and associated processing and
enabling reception and associated processing in the full active state.