Patent Application
20130029667
This application claims the benefit of People's Republic of China application Serial No. 201110209921.5, filed Jul. 26, 2011, the subject matter of which is incorporated herein by reference.
1. Field of the Invention
The invention relates in general to a method of a femtocell, and more particularly to an identification method and a switching method of a femtocell and a femtocell system.
2. Description of the Related Art
In a communication system, e.g., a 3G network, a femtocell connects to user equipments of users within home or small range via an air interface, and connects the user equipments to a network of an operator network via a broadband network to achieve mobile data off-loading. Thus, indoor communication quality is improved while audio and data services can be provided in reduced cost.
Femtocells can be categorized into home node-B (HNB) and home evolved node-B (HeNB). A femtocell is disposed in a home or a in a business to provide wireless coverage and access service for user equipments.
In the current 3G standard, methods adopted for a femtocell for identifying another femtocell or other types of base stations are not clearly defined. As a result, when switching between different types of cells, loading on a macrocell network cannot be reduced.
The invention is directed to an identification method and a switching method of a femtocell and a femtocell system.
According to an aspect of the present invention, an identification method of a femtocell for a femtocell to identify a type of another base station is provided. The method includes steps of: detecting an air message, and determining, according to signal strength, a base station corresponding to a broadcast message in the detected air message as a standby base station; determining whether a specific identification sequence in the broadcast message of the standby base station includes a predetermined femtocell identifier; and determining whether the specific identification sequence further includes a grouping code corresponding to the femtocell. When the specific identification sequence includes the predetermined femtocell identifier, the femtocell determines the standby base station is a femtocell.
According to another aspect of the present invention, a switching method of a femtocell applied to a femtocell is provided. The method includes steps of: a) detecting an air message, and determining, according to signal strength, a base station corresponding to a broadcast message in the detected air message as a standby base station; b) determining whether the standby base station is a femtocell according to a specific identification sequence and a pilot channel output power value in the broadcast message of the standby base station; according to step (b), determining a first standby base station corresponding to a first broadcast message as a base station of a first type; according to step (b), determining a second standby base station corresponding to a second broadcast message as a base station of a second type; and with respect to the first standby base station and the second standby base station, prioritizing the femtocell to switch to the first standby base station for service handover.
According to yet another aspect of the present invention, a femtocell system is provided. The femtocell system includes a mobile communication unit and a processing unit. The mobile communication unit detects an air message. The processing unit, coupled to the mobile communication unit to control the mobile communication unit, determines, according to signal strength, a base station corresponding to a broadcast message in the detected air message as a standby base station, and determines whether the standby base station is a femtocell according to a specific identification sequence and a pilot channel output power value in the broadcast message of the standby base station. The processing unit further determines a first standby base station corresponding to a first broadcast message as a base station of a first type according to a specific identification sequence and a pilot channel output power value in the first broadcast message, and determines a second standby base station corresponding to a second broadcast message as a base station of a second type according to a specific identification sequence and a pilot channel output power value in the second broadcast message. The processing unit further controls and prioritizes the femtocell system to switch to the first standby base station for service handover.
The above and other aspects of the invention will become better understood with regard to the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.
An identification method and a switching method of a femtocell and a femtocell system according to embodiments of the present invention shall be described below. In the identification method according to one embodiment, the femtocell identifies a type of another base station according to a specific identification sequence and a pilot channel output power value in a broadcast message from another base station. In the switching method according to another embodiment, after a femtocell identifies the type of another base station, switching for service handover is implemented in different priority sequences according to the type of the base station. A femtocell system capable of identifying the type of a base station and switching between other types of base stations is further provided according to yet another embodiment.
Referring to
Under practical situations, at indoors or within a home or an enterprise, the base station located near or other than the femtocell 100 may be a femtocell, or a non-femtocell such as an indoor distribution system (e.g., a picocell having a lower transmitting frequency than a macrocell) or a macrocell.
Another possible situation is that, multiple femtocells divided into different groups are installed in an enterprise or a business unit, or femtocells of different manufacturers or services providers are utilized. Alternatively, femtocells of a same manufacturer or service provider may be employed by two close-by organizations or enterprises, in a way that femtocells utilized by one organization ought to be distinguished from those of another organization.
In this regard, in one embodiment, a broadcast message generally transmitted from a base station is utilized to carry a predetermined femtocell identifier for identifying whether the base station is a femtocell. For example, under 3G Universal Mobile Telecommunication System (UMTS) specifications, a distinguishing code is defined in a specific identification sequence (e.g., one or multiple fields, bits or locations) in the broadcast message transmitted by the base station to record a predetermined femtocell identifier. For example, in the UMTS Radio Resource Control (RRC) protocol, an information element (IE) “Cell Identity” in SIB 3/4, i.e., system information block (SIB) type 3 or type 4, carried in system broadcasting information, can be utilized for defining a position for the above distinguishing code. For example, in the cell identity, the first 12 bits are for an RNC identifier and the last 16 bits are for “Cell ID”. Thus, for a same type of femtocells broadcasting in a small area, the femtocells may add a specific identification sequence to “Cell ID” and define certain bit(s) in the specific identification sequence as a distinguishing code. When the femtocell 100 performs searching, the femtocell 100 may identify whether a base station is a femtocell according to the distinguishing code. In this way, different femtocell manufacturers or service providers may also define respective predetermined femtocell identifiers carried in the specific identification sequence for distinguishing the femtocells from different manufacturers. Further, the femtocell identifier may also serve for other purposes rather than the example above.
In an alternative embodiment, a portion of the bits in the specific identification sequence may also be defined to represent a grouping code in addition to the distinguishing code. Taking the above “Cell ID” for example, a portion of the bits (e.g., 4 bits) in the specific identification sequence are defined as a distinguishing code while another portion (e.g., 10 bits) is defined as a grouping code. Further, other codes may also be defined in the specific identification sequence for other identification purposes in addition to the example above.
In one embodiment, it is determined whether a base station is a femtocell according to a pilot channel output power value obtained from a broadcast message transmitted from the base station. Regarding this, it is noted that total transmit power of a femtocell is smaller than that of other base stations such as a macrocell or an indoor distribution system. Further, transmit power of a pilot channel of a femtocell is substantially a fixed value. Thus, a base station is determined as a femtocell when the transmit power of the pilot channel is determined as not greater than a threshold. For example, in the UMTS RRC protocol, the common pilot channel (PICH) power offset of SIB type 5 or type 6 (i.e., SIB 5/6) carried in the system broadcast information can be employed to serve as a parameter for determining whether a base station is a femtocell. In WDCMA, the SIB 5/6 PICH power offset may be converted into the power value of a primary common pilot channel. In TD-SCDMA, the SIB 5/6 PICH power offset may be converted into the power value of a primary common control physical channel (PCCPCH). According to common definitions of a femtocell, a total transmit power Pmax is usually 20 dBm. In this way, a base station having a pilot channel transmit power not greater than a threshold Pmax−Poffset can be determined to be a femtocell. For example, the offset Poffset can be set to an empirical value of 10 dB for Wideband Code Division Multiple Access (WCDMA) and 5 dB for Time Division Synchronous Code Division Multiple Access (TD-SCDMA). It should be noted that, when implementing a femtocell, the above threshold is adjustable, and has a self-definable initial value, e.g., defined with reference to service provider's data.
As described above, the femtocell according to one embodiment is capable of distinguishing different base stations according to the specific identification sequence and the pilot channel output power value.
In step S10, an air message is detected, e.g., not from the femtocell or may be from other base station, and a base station corresponding to a broadcast message in the detected air message is determined, according to signal strength, as a standby base station. For example, the femtocell 100 detects an air message from base stations surrounding or near the femtocell 100. In step S10, for example, an approach for determining whether a base station is a standby base station is determining whether the signal strength of a broadcast message in the detected air message satisfies a condition. A base station corresponding to the broadcast message satisfying the condition is determined as the standby base station. For example, the above condition is whether the signal strength is less than a threshold, or other condition such as regarding one or multiple signal strength parameters as criteria. The determination of signal strength may be based on a received signal code power (RSCP) value. For example, it is determined whether the value of RSCP is greater than a threshold, e.g., −85 dBm. The following provides further determination with respect to the standby base station.
In continuation of the identification method of the femtocell, in step S20, it is determined whether the type of the standby base station is femtocell, based on the specific identification sequence and the pilot channel output value in the broadcast message (e.g., broadcast message BM1, BM2 or BM3 as illustrated in
In one embodiment, step S20 includes step S220. In step S220, it is determined whether a pilot channel output power value obtained from the broadcast message is not greater than a first threshold. For example, the threshold is the foregoing value of Pmax−Poffset corresponding to the femtocell. When the pilot channel output power value is not greater than the first threshold, it is determined that the standby base station corresponding to the pilot channel output power value is a femtocell. As shown in step S253, the standby base station is a femtocell having a third priority. When the pilot channel output power value is greater than the first threshold, the standby base station corresponding to the pilot channel output power value is not a femtocell.
In one embodiment, the femtocell 100 categorizes the identified standby base station to facilitate a prioritization process. For example, the femtocell 100 further introduces priority identification for service handover between base stations. Referring to
In one embodiment, step S220 is performed when it is determined in step S210 that the specific identification sequence does not include the predetermined femtocell identifier. In step 220, when it is determined that a pilot channel output power value obtained from a broadcast message is not greater than the above first threshold, a standby base station corresponding to the pilot channel output power value is a femtocell having a third priority. In one embodiment, with respect to a standby base station (e.g., a femtocell having a second priority or a third priority) corresponding to the broadcast message including the predetermined femtocell identifier and a femtocell having a third priority, the femtocell 100 is prioritized to switch to the femtocell corresponding to the broadcast message including the predetermined femtocell identifier for service handover.
As observed from the above embodiments, step S20 is capable of identifying whether a base station other than the femtocell 100 is a femtocell. Further, steps S210, S220 and S215 may be performed in a different order. For example, step S220 is performed before step S210 to identify the type of different femtocells or to prioritize the identified femtocells. Hence, step S20 may be implemented through several approaches rather being limited to the embodiments above.
In other embodiments, when it is determined that a standby base station is a non-femtocell in step S220, an approach similar to step S220 may be performed to categorize the non-femtocell as an indoor distribution system or a macrocell, for example. For example, in step S230, it is determined whether the pilot channel output power value of the non-femtocell is not greater than a second threshold, which is greater than the first threshold. For example, the second threshold is set to equal to Pmax−Poffset, wherein Pmax corresponds to total transmit power of an indoor distribution system or a picocell, such as 27, 28 or 30 dBm. When the pilot channel output power value is not greater than the second threshold, the femtocell 100 determines the standby base station corresponding to the pilot channel output power value is an indoor distribution system, and the standby base station is an indoor distribution system having a fourth priority, as shown in step S261. In one embodiment, with respect to a femtocell having a third priority (e.g., 110 or 120) and an indoor distribution system (e.g., 130), the femtocell 100 is prioritized to switch to the femtocell having the third priority for service handover. As shown in step S262, when the pilot channel output power value is greater than the second threshold, the femtocell 100 determines that the base station corresponding to the pilot channel output power value is a macrocell or another type of base station, and the standby base station is another base station. In one embodiment, with respect to an indoor distribution system and another base station, the femtocell 100 is prioritized to switch to the indoor distribution system for service handover.
Service handover is proceeded in compliance with of the requirements of communication standards (such as 3G) supported by the femtocell. That is, the handover can be performed according to the priority sequences in the embodiments, according to whether received signal code power (RSCP) is within a reasonable range for the communication standard.
In one embodiment, the first-type base station is a femtocell, and the first broadcast message includes a predetermined femtocell identifier, as exemplified above, and a grouping code corresponding to the femtocell 100. The second-type base station is a femtocell, and the second broadcast message includes the predetermined femtocell identifier but not the grouping code corresponding to the femtocell 100. Another possible situation is that, the second broadcast message of the second standby base station does not include the predetermined femtocell identifier. Yet another possible situation is that, the second-type base station is a femtocell, and the pilot channel output power value in the second broadcast message is not greater than the first threshold, e.g., Pmax−Poffset corresponding to the femtocell as exemplified above. Yet another possible situation is that, the second-type base station is a non-femtocell, and the pilot channel output power value in the second broadcast message is greater than the first threshold.
In another embodiment, the first-type base station is a femtocell, and the first broadcast message includes the predetermined femtocell identifier but not the grouping code corresponding to the femtocell 100. The second broadcast message of the second standby base station does not include the predetermined femtocell identifier. Regarding this embodiment, a possible situation is that, the second-type base station is a femtocell, and the pilot channel output power value in the second broadcast message is not greater than the first threshold. Another possible situation is that, the second-type base station is a non-femtocell, and the pilot channel output power value in the second broadcast message is greater than the first threshold.
In another embodiment, the first standby base station is a femtocell, and the first broadcast message does not include the predetermined femtocell identifier and the pilot channel output power value in the first broadcast message is not greater than the first threshold. In this case, a possible situation is that, the second-type base station is a non-femtocell, and the pilot channel output power value in the second broadcast message is greater than the first threshold.
In yet another embodiment, the first-type base station is a non-femtocell, and the pilot channel output power value in the first broadcast message is greater than the first threshold but smaller than the second threshold. The second-type base station is a non-femtocell, and the pilot channel output power value in the second broadcast message is greater than the first threshold and is also greater than the second threshold.
The mobile communication unit 410 may be regarded as an analog front end for wireless transceiving. The mobile communication unit 410 includes an antenna 411, a power amplification unit 413 and a transceiver unit 415. The antenna 411 is coupled to the power amplification unit 413, and the transceiver unit 415 is coupled to the power amplification unit 413. In other embodiments, the mobile communication unit 410 may be implemented in compliant with at least one or more communication modes (such as 2G, 3G or 4G) so as to modify the architecture or the number of components. Thus, the mobile communication unit 410 is not limited to the embodiment as shown in
The mobile communication unit 410 detects an air message (e.g., BM1 or BM2), which may be from a base station other than the femtocell system 400.
The processing unit 420, coupled to the mobile communication unit 410, controls the mobile communication unit 410 to operate in at least one mobile communication mode (e.g., 2G, 3G, or 4G mode).
The processing unit 420 determines whether signal strength of a broadcast message in the air message detected by the mobile communication unit 410 satisfies a standby condition. A base station corresponding to the broadcast message satisfying the condition is a standby base station. According to a specific identification sequence and a pilot channel output power value in the broadcast message of the standby base station, it is determined whether the standby base station is a femtocell.
According to a predetermined identification sequence and a pilot channel output power value in a first broadcast message (e.g., BM1), the processing unit 420 determines that a first standby base station (e.g., 110) corresponding to the first broadcast message is a first-type base station. According to a predetermined identification sequence and a pilot channel output power value in a second broadcast message (e.g., BM2), the processing unit 420 determines that a second standby base station (e.g., 120) corresponding to the second broadcast message is a second-type base station. For service handover, the processing unit 420 controls and prioritizes the femtocell system 400 to switch to the first standby base station.
The priority sequence for service handover may be implemented with reference to descriptions of the foregoing embodiments. Therefore, the femtocell system 400 is able to implement the identification method and the switching method according to the foregoing embodiments by ways of software, hardware or firmware.
For example, the processing unit 420 is implemented by a microcontroller (MCU), a digital signal processor (DSP), a field-programmable gate array (FPGA), an application specific integrated circuit (ASIC) or a system-on-chip (SoC).
Further, the processing unit 420 may implement a femtocell layer 1 (FL1) and a femtocell radio resource management (FRRM) as a femtocell entity that may be regarded as a femtocell system. In another embodiment, the FRRM can be implemented as an independent device, such as using a processing unit of a femtocell gateway, and the FL1 can be implemented by using a processing unit of the femtocell, such that the two (i.e., the femtocell gateway and femtocell) together can be regarded as a femtocell system. The FL1 unit represents a logic unit or a hardware unit for realizing operations for linking between a femtocell and a user equipment, by using such as a 3G mobile communication layer 1 Uu air interface. The FRRM unit represents a logic unit or a hardware unit for performing operations associated with radio resource management between the FL1 unit and a core network OAM (e.g., a network of a service provider (or operator)). In one embodiment, the FL1 and the FRRM can be combined to form a device of a femtocell entity. In another embodiment, the FRRM can be an independent device.
In another embodiment, to connect a user equipment to a service provider's network via a broadband network, the femtocell system 400 further includes a network unit 430 for providing an interface between the femtocell system 400 and the broadband network. In an alternative embodiment, the network unit 430 provides an interface between the femtocell system 400 and a femtocell gateway. Hence, the femtocell system 400 may be implemented to modify the architecture or the number of components or be implemented through other approaches, according to the design requirement, and is not limited to the examples above.
Further, in another embodiment, 3G protocols such as WCDMA or TD-SCDMA or even 4G may be implemented by the above embodiments according to actual requirements.
Therefore, with description of the above embodiments, the identification method and the switching method of a femtocell and the femtocell system disclosed are capable of identifying a femtocell from other femtocells or base stations. In certain embodiments, not only femtocells of a same type or different groups are further identified but also switching priority sequences between femtocells are implemented for service handover, so as to provide flexibility in the deployment and applications of the femtocells, thus embodying a self-optimizing network (SON). Thus, when switching between femtocells for service handover, the data offloading on a macrocell network can be achieved appropriately.
While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201110209921.5 | Jul 2011 | CN | national |
