GB2472463A

GB2472463A - A femtocell access point is disabled when inactive for a time longer than the determined time between location or routing area update requests

Info

Publication number: GB2472463A
Application number: GB0913939A
Authority: GB
Inventors: Ajay Vachhani
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 2009-08-07
Filing date: 2009-08-07
Publication date: 2011-02-09
Also published as: GB0913939D0

Abstract

A method for disabling an access point base station, which may comprise a femtocell base station located within a macrocell, in a cellular communication network is disclosed. The method comprises the steps of determining (201,203) a period of time between User Equipment registration requests sent to the access point; starting a timer (211) to measure a period of inactivity of the access point and disabling (215) the access point in dependence upon the timer reaching a value corresponding to the determined period of time between registration requests. Determining the period of time between registration requests may comprise: extracting the periodic location registration time out value from a routing area update message or; reception, by the access point, of a location update time out value from the communication network.

Description

INTELLECTUAL

. .... PROPERTY OFFICE Application No. GBO9 13939.5 RTM Date:26 October 2009 The following terms are registered trademarks and should be read as such wherever they occur in this document:

UMTS

DECT

CDMA 2000 Intellectual Property Office is an operating name of the Patent Office www.ipo.gov.uk An Access point, a method for disabling an access point and computer program to implement the method This invention relates to mobile communications networks, in particular to a method for disabling an access point or femtocell.

Mobi!e communication systems operate on a cellular basis in which transmission and receiver base stations coupled to a network provide transmission and reception to user equipment (UE) such as mobile telephones in each cell in a network. There is usually a single base station in each cell. The base stations are usually referred to as macro base stations and the cells as macro cel Is.

Smaller cell sites called picocells have been proposed. These cover a smaller area such as a complex of buildings. Still smaller cell sites called femtocells are also proposed. This is a term used by mobile operators to refer to cell sites of the type which attempt to solve the often expensive problem of providing complete in-building coverage where macrocells are often unable to provide adequate coverage due to attenuation and scattering of the radio signal from the base station.

A femtocell is often referred to as an access point base station.

Femtocells are also known as Home NodeB or Home eNodeB cells. It is a small plug and play device which communicates with user equipment such as mobile handsets using second generation (2G) or third generation (3G) transmission reception using wireless cellular networks. It is connected to the cellular network via a broadband service using either Xdsl or WiMax technology. XdsI is a family of technologies in which a digital subscriber loop allows broadband communications over conventional copper telephone lines, and WiMax, is a wireless Technology defined by the IEEE 802.16 standard providing improved wireless broadband compared to conventional WiFiRTM systems. WiMaxTM is a pending trade mark application of the WiMax Forum, California, USA and Wi-FiRTM is a registered trade mark of the WiFiRTM Alliance, California, USA.

A femtocell can optionally incorporate the functionality of a broadband router so that a user has a completely integrated device. It is of course essential that the femtocell integrates seamlessly with the core network of the mobile communication system so that it can be remotely managed and updated. * 2

In Europe, one of the common 3G technologies, Universal Mobile Telecommunications System (UMTS), uses Wideband Code Division Multiple Access (W-CDMA) as the Radio Access Technology (RAT) to provide wireless communication. However, other RATs such as Code Division Multipte Access 2000 (CDMA 2000), Time Division Multiple Access (TD-CDMA), Universal Wireless Consortium (UWC), or Digital European Cordless Telecommunication (DECT) radio technologies may be used to implement 3-G networks.

In W-CDMA implemented 3G networks, there are two modes of data transmission; frequency division and time division. In the frequency division mode, communications between a mobile communication device and base station are provided in the frequency division mode by assigning one particular frequency for the uplink to the base station, and another frequency for the downlink from the base station to the mobile communication device. In this way, a mobile communication device is allocated part of the frequency spectrum for the entire duration of the communication. In the time division mode of operation, each user is allowed to transmit only for a length of time defined by an allocated slot, but is allowed to use the entire bandwidth of the channel for that transmission.

In this way, femtocells provide wireless networks which are deployed sharing the same or different carrier frequency as the macrocell. In cases where the femtocell shares the same frequency spectrum as the macrocell, managing the transmission radio power of the femtocell is critical to avoid interference between the macro cell and the neighbouring femtocell. In UMTS/3G, high interference causes the reduction of available capacity and coverage.

Interference between a femtocell sharing the same frequency spectrum as a macro cell destroys both the macro cell and the femtocell capacity and coverage.

Therefore the inventors have appreciated that whenever a femtocell is not in use, its transmitter should be disabled or the femtocell should be turned off in order to avoid interference between a femtocell and a macrocell. This maximises the capacity and coverage of the macrocell. However since femtocells are often deployed by private users, these users often forget to disable the femtocell when it is not in use. Furthermore, it is desirable to have an automatic mechanism to disable the femtocell if it has been determined that it is not in use. This avoids the need for the femtocell owner to manually check that the femtocell is not in use and disable the femtocell.

Summary of the Invention

The invention is defined in the appended claims to which reference should now be made.

Preferred embodiments of the invention determine the period of time between UE registration requests or the time out value of a periodic registration tinier. A timer measures a period of inactivity of the access point and if the measured period of inactivity corresponds to the determined period of time between registration requests or the time out value, then the access point is disabled. The time out value or period of time between registration requests is provided by the network or from a routing area update.

Embodiments of the invention provide improved communications for existing users using a macrocell neighbouring a femtocell because of the elimination of interference between the femtocell and the macrocell. This provides improved coverage and capacity of a macrocell. Embodiments of the invention also have the advantage of reduced femtocell power consumption because the radio transmitter within the femtocell is disabled or the femtocell itself as a whole is deactivated or shut down.

Brief Description of the Drawings

An embodiment of the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows schematically an access point such as a femtocell in communication with a number of pieces of user equipment; and Figure 2 shows a flow diagram of the main steps performed by an embodiment of the invention.

Detailed Description of the Preferred Embodiments of the Invention Although embodiments of the invention will be described with reference to W-CDMA, it is not in fact essential to use this technology, and other 3G or 2G technologies may be used instead. Furthermore, embodiments of the invention operate in both the Frequency Division (FDD) and Time Division (TDD) mode of operation.

Referring to Figure 1 of the drawings, this shows an access point or femtocell 2 which is coupled to a network. This access point comprises an antenna 4 coupled to, or integrated into a controller and a transmitlreceive unit. In the case of a femtocell, this covers a relatively small area such as a building or house or small office.

The area covered by the femtocell is usually co-located with the area covered by the macrocell. That is to say that the two cells neighbour each other or the two cells overlap with each other to some degree or the femtocell is contained within the macrocell. User Equipment (UE) such as a mobile telephone 6 or a portable computer (laptop) 8 with a data card may be within the building or house and therefore capable of communication with the access point 2. In a larger area such as an office environment there may be a number of different pieces of equipment capable of communicating with the access point 2.

When a piece of user equipment initially comes into range of the access point 2, it registers with the access point 2 as being a primary access point on the network for transmission and reception of data. Thus, when the user equipment next attempts to communicate by making a telephone call, it attempts to use this particular access point 2 to access the network. The access point 2 is connected to the network, typically using a conventional telephone line with a broadband connection using one of the technologies from the xdsl family, for example Asymmetric Digital Subscriber Line (ADSL).

The mobile network is divided into a number of location areas and routing areas. A location area is a set of base stations which are grouped together and each location area has a unique identifier assigned to it in order to identify a particular area. Each location area is further subdivided into a number of routing areas, each of which is also assigned a unique identifying code. The division of the network into location and routing areas allows for optimised transfer of communications between location areas and routing areas as mobile devices move between areas. As the UE moves between these location and routing areas, the UE receives the location area identifier or routing area identifier broadcast by the base station or femtocell and if this identifier is different from the identifier previously stored by the UE, it performs location or routing area updates to ensure the core network can determine the location of the UE. Periodic location registration is used by the core network to confirm the UE's location is still up to date and the UE is still connected (i.e. not turned off).

If the UE moves into an area where wireless communication may be provided by a different femtocell, and that particular LIE is allowed to use that particular femtocell, then the UE also performs location or routing area update/registration with that particular femtocell.

Additionally, both 2G and 3G mobile devices or UE's periodically perform location registration, in particular routing area update or location area update procedures, even if the LIE is not moving between location or routing areas.

In order to measure the period of time which elapses between one registration request and a subsequent registration request, mobile devices are provided with a UE timer. When the UE is stationary within a location or routing area, the UE does not need to signal its location to the core network until the location or routing area the timer has expired, i.e. when it has reached the time out value. If the core network has not received any location or routing area update requests from the femtocell when the timer, which may include a margin for error, has expired (i.e. the timer has reached the time out value), then the core network determines that there are no UE's attached to the network via that particular femtocell. The core network is also provided with a timer so that it can measure the period of time which has elapsed since a particular UE has made a registration request.

The default period between sequential updates, i.e. the default time out value, is 54 minutes. However, the time out value for the periodic location registration may be set anywhere within a range from 6 minutes (1 deci hour) to 25.5 hours (255 deci hours) with a granularity of 1 deci hour (i.e. 6 minutes).

The time out value is determined by the core network (i.e. Service General Packet Radio Service (GPRS) Support Node (SGSN) and Mobile Switch Centre (MSC) and is transmitted or conveyed to the mobile device during location registration procedure if the device or LIE is performing a routing area update procedure. If the device or LIE is performing a location update procedure, then the time out value is transmitted to the UE in the system broadcast information.

A flow diagram showing the main steps performed by an embodiment of the invention is shown in figure 2. This shows how a UE, such as a mobile communication device, an access point 2 and the core network communicate with * 6 each other. This assumes that the user equipment is already registered with the femtocell or access point and attempts to use this for its communications.

The femtocell detects whether a mobile communication device is using the access point for communications in the following way. At step 201, the UE (mobile device) sends a routing area or location update request to a femtocell, as previously described. This is performed after the UE's internal timer has reached the time out value -the predetermined value specifying the period of time which elapses between routing or location registration requests.

The femtocell then sends the routing area update request to the core network, although this step is not shown in figure 2.

The core network then sends a routing area update accept message to the femtocell, at step 203. The femtocell then receives the update accept message from core network and extracts the periodic location registration time out value from the routing area update accept message by extracting the value contained in the field "Periodic Routing Area update timer".

Alternatively, the core network may send a location area update accept message. In the case of the location area update accept message, this does not contain the location update time out value. Instead, the network sends to the femtocell the time out value or the femtocell picks up the time out value from the routing area update message. The femtocell only needs to extract the time out value once because operators use the same time out value for all mobile devices.

The femtocell then stores the periodic location registration time out value in a memory, at step 205. Alternatively, the routing area update accept message may not specify a periodic location registration time out value.

If the time out field is absent in the routing area update accept message, it means that the femtocell uses the core network's suggested default value of 54 minutes for the periodic location registration time out value, at step 205.

The femtocell may send the routing or location area update accept message to the mobile device, at step 207, although this step is not in fact essential for embodiments of the invention.

The femtocell then detects inactivity of a UE, at step 209, using any means for detecting inactivity. By inactivity, we mean a failure to receive a routing area update or a location area update request message from a mobile device or UE attached to, or registered with, a particular femtocell. If the femtocell determines that it is idle or inactive, as previously described, then the femtocell then starts an internal timer, a UE detection timer, at step 211. Once the timer has been started, the femtocell checks whether any UE's registered with that particular femtocell are active. The femtocell does this by checking if any routing area update or a location area update request messages have been received from a mobile device or UE attached to the femtocell since the timer has been started. The timer is stopped if any such activity is detected by the femtocell.

Furthermore, the femtocell stops the timer if it also detects activity such as a mobile device performing message or signalling handshaking with femtocell, at step 213. This may be a successful attach attempt from an incoming mobile device or UE if the periodic location or routing area timers have expired for a mobile device attached to the femtocell. Furthermore, the activity may be a new attach attempt either from a mobile device moving from macro to the femtocell coverage or from a mobile device being powered up under the femtocell coverage.

The femtocell or access point does not stop the timer for an unsuccessful attach attempt, i.e an attach attempt from a mobile device that was not authorised to use the femtocell.

When the message/signalling handshaking has finished the femtocell resets the timer to zero and then re-starts the timer at zero, at step 211. The process then continues as previously described.

If the timer reaches the predetermined time out value without detecting UE inactivity, the femtocell then disables itself at step 215 by either turning its radio transmitter off or by powering off the whole femtocell. Alternatively, the femtocell may enter a low power state such as standby. The fact that the timer has reached the predetermined time out value, is an indication that no active mobile devices are registered with the femtocell. This is because a mobile device does not attempt routing area update request if its internal timer is equal to or exceeds the time out value. In this case, all UE's which previously were registered with a particular femtocell have either moved off the femtocell and are now attached to or registered with a macrocell or different femtocell, or have been themselves disabled or powered down.

Femtocell access points according to embodiments of the invention may optionally display an appropriate visual indication to the end user that it has been disabled. The visual indication may be that one or more or all of any visual * 8 femtocell status indication means provided on the femtocells, such as light emitting diodes (LEDs) are turned red.

On the other hand, if at step 209 the femtocell determines that there are active mobile communication devices registered with the femtocell, so that no inactivity is detected at step 209, then the internal timer is not started, and the femtocell waits until the activity has finished, at step 210. The femtocell immediately or after a predetermined time period then attempts to determine whether the femtocell is inactive, at step 209. Embodiments of the invention then proceed with steps 211, 213, and 215 as previously described.

Furthermore, it is not in fact essential for the femtocell to detect inactivity, and so steps 209 and 210 are optional. Instead, the internal timer may be started at step 211 immediately after the femtocell has sent the last routing or location area update accept message to a particular mobile or UE. If however, the femtocell detects activity as previously described, it stops the timer, reset the timer to zero and wait until the femtocell determines that the activity has ended before restarting the timer after the last routing or location area update accept message has been sent to a particular mobile or UE. The process then continues as previously described.

Once a femtocell has been disabled, the femtocell owner can enable it by pressing a turn on radio button or turn on femtocell button or activating other femtocell enabling means to start femtocell operation.

Preferably, embodiments of the invention use the routing area update procedure, rather than a location area update because Universal Mobile Telecommunications System (UMTS) mobile devices support both circuit switched (CS) and packet switched (PS) services. The periodic location update allows the CS core network to track the UE's availability while the periodic routing area update allows the PS core network to track the UE's availability. Both should be used if the UE registered with CS and PS core network elements, for example a network operator's Mobile Switching Centre or a Serving GPRS Support Node.

Accordingly embodiments of the invention provide an automatic radio/power shut off functionality. In this mechanism femtocell device detects that no mobile device is present in femtocell radio coverage hence it can safely turn its radio off or alternatively turn the Power off (i.e. turn off the device). This * 9 reduces interference between a femtocell and a neighbouring macrocell and therefore improves the capacity of the macrocell due to reduced interference.

Although embodiments of the invention have been described with reference to W-CDMNUMTS, it will be appreciated by those skilled in the art that it is equally applicable to other 30 technologies.

Further embodiments of the invention may be implemented both in computer software as well as directly in chips and the like directly integrated into the access point or femtocell. The software may be provided on a carrier medium such as a CD ROM (Compact Disc Read-Only Memory) or may be transmitted overa network.

Claims

CLAIMS1. A method for disabling an access point base station in a cellular communication network, the method comprising the steps of: determining a period of time between User Equipment (UE) registration requests sent to the access point; starting a timer to measure a period of inactivity of the access point; wherein the access point is disabled in dependence upon the timer reaching a value corresponding to the determined period of time between registration requests.
2. A method according to claim 1 in which the UE registration request is a routing area update request.
3. A method according to claim 2 in which the step of determining the period of time between UE registration request is performed by extracting the periodic location registration time out value from the routing area update accept message.
4. A method according to claim 1 in which the UE registration request is a location area update request message.
5. A method according to claim 4 in which the step of determining the period of time between UE registration requests is performed by the access point base station receiving a location update time out value from the communication network.
6. A method according to claim 5 in which the time out value is sent when the location area update request message is received by the access point.
7. A method according to any preceding claim further comprising the step of storing the determined period of time between UE registration requests in a memory.
8. A method according to any preceding claim in which the timer only runs when the access point is inactive. * 11
9. A method according to claims 1 or 2 in which the access point is located within network coverage of a macro base station.
10. A method according to any preceding claim in which the access point has a shorter network range than the macro base station.
11. A method according to any preceding claim in which the access point is a fnitt-sII
12. A computer program for disabling an access point, said computer program comprising program code to perform the method of any one of claims 1 to 11 when the program is executed.
13. An access point for use in a cellular communication system comprising means for determining a period of time between User Equipment registration requests; means for measuring a period of inactivity of the access point; and means for disabling the access point wherein the access point is disabled in dependence upon the timer reaching a value corresponding to the determined period of time between registration requests.
14. A method for disabling an access point substantially as herein described with reference to the accompanying drawings.
15. An access point substantially as herein described with reference to the accompanying drawings.