Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-10-06
2003-09-30
Vo, Nguyen T. (Department: 2685)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S458000
Reexamination Certificate
active
06628942
ABSTRACT:
FIELD OF THE INVENTION
The present invention finds application to cellular communications and relates to mobile terminal responses to pages in a mobile communications system.
BACKGROUND OF THE INVENTION
A cellular telephone is one example of what is generally characterized as a “mobile station” (MS), a “mobile terminal” (MT), or even more generally as “user equipment” (UE). The term mobile terminal is employed hereafter for purposes of description. Telecommunications services are provided between a cellular telecommunications network and a mobile terminal over an air interface, e.g., over radio frequencies. An active mobile terminal communicates over the air interface with one or more base stations. The base stations are managed by base station controllers (BSCs), which in some systems, are known as radio network controllers (RNCs). The term RNC is employed hereafter for purposes of description. Radio network controllers are coupled to one or more telecommunications networks by way of one or more control nodes such as a mobile switching center (MSC) node for connecting to connection-oriented, circuit-switched networks such as PSTN and/or ISDN, and a general packet radio service.(e.g., GPRS) node for connecting to connectionless, packet-switched networks such as the Internet.
A simplified cellular communications system is shown in function block format in FIG.
1
. An example core network is connected to several radio network controllers (RNC) including RNC
1
, RNC
2
, and RNC
3
. Each RNC controls the allocation of radio resources and radio connectivity operations for a set of cells: RNC
1
controls cells
1
:
1
-
1
:
5
, RNC
2
controls cells
2
:
1
-
2
:
5
, and RNC
3
controls cells
3
:
1
-
3
:
5
. The RNCs communicate by way of a signaling network, e.g., signaling system number
7
(SS
7
), and a transport network. Each cell is a geographical area where radio coverage is provided by radio base station equipment at the base station site. A base station may serve one or more cells. A “handover” occurs as a mobile terminal travels from an old cell to a new cell which permits mobile terminals to “roam” considerable distances. Each cell is identified using a unique identity broadcast in that cell over a common broadcast channel.
As indicated in
FIG. 1
, the RNCs, the interconnecting signaling and transport network, and the radio base station equipment in each of the cells together comprise a radio access network (RAN). Mobile terminals (MTs) permit a subscriber access to telecommunications services offered by the core network via the RAN. The radio access network controls radio connections and transmissions between the core network and the mobile terminals.
Different roles may be assigned to RNCs in the RAN depending on circumstances, configurations, etc. One RNC role is that of a “controlling” RNC (CRNC) which controls the radio resources in its set of cells. In the example shown in
FIG. 1
, the RNC
1
is the controlling RNC for cells
1
:
1
to
1
:
5
, the RNC
2
is the controlling RNC for cells
2
:
1
to
2
:
5
, and the RNC
3
is the controlling RNC for cells
3
:
1
to
3
:
5
.
FIG. 2
shows adjacent cells in a cellular communications network. An active cell denotes the cell currently supporting a radio connection with a mobile terminal. Adjacent neighboring cells may be selected by the mobile terminal via forward handover to support the connection. Forward handover or cell reselection is a process where a mobile terminal itself continues an established connection between a core network and the mobile terminal as the mobile terminal moves between different cells in the radio access network. Contrasted with traditional handover, the mobile terminal in forward handover independently re-establishes the radio connection with a new cell. This re-establishment of the connection is performed without prior notification via the old cell. Nor is there advance preparation in the network to continue the communication via the new cell. It is the mobile terminal that initiates and orchestrates forward handover rather than the core network, the core network node (e.g., an MSC), or the radio access network (RAN).
FIG. 3
illustrates an example where cells controlled by RNC
1
-RNC
3
are grouped into registration areas, RA
1
-RA
6
, each consisting of one or several cells. Information transmitted on the broadcast channel in each cell may contain cell and registration area identifiers for purposes of registration control. As long as such cell and registration area identifiers broadcast by a specific cell contain the same cell and registration area identifiers assigned to the mobile terminal during the most recent cell or RA update procedure, the mobile terminal need not register. However, when the terminal mobile terminal does not recognize the broadcast cell and registration area identifiers in the cell, it initiates an RA update procedure.
To reach a mobile terminal, the radio network initiates a paging procedure. More specifically, a paging message containing the mobile terminal identity is transmit on a paging channel. In order for the paging message to be directed to an area where the mobile terminal is located, the radio network stores in memory, determines the current location of the mobile station either on a cell level, on a registration area level, or on some other level. The page is then transmitted in a paging area which may, for example (although not necessarily), be identical to the registration cell or a registration area. Another example paging area may correspond to cells
1
:
1
-
1
:
5
associated with RNC
1
as shown in FIG.
1
.
When the mobile terminal listens to the paging channel in its current cell, it may be decide to change to another cell using a cell reselection process as a result of changed radio conditions. More specifically, another cell may have better, current radio conditions for communication for that mobile terminal. The cell reselection may be decided based on one or more cell selection evaluation criteria. For example in a CDMA based system, the mobile terminal listening for pages need only be concerned about the quality of the downlink transmission from the base station in the current cell. On the other hand, if the mobile terminal must respond to the page, it must consider the uplink radio conditions over which it must transmit in that cell. The uplink conditions may not be optimal, meaning that the mobile would have to transmit at a higher power than it would from a more optimal cell. In this example, the mobile may select the more optimum cell before it transmits a response to the page. If the mobile terminal changes its current cell, the new cell may belong to a new registration area. Normally, this would trigger a registration procedure.
Balancing the desire to select the most optimal cell, e.g., to find and select the cell with the best uplink and downlink radio conditions, is the need to conserve battery power of the mobile terminal. Therefore, the mobile terminal may limit cell selection evaluation to certain time periods such as only when the mobile terminal is listening to the paging channel. Otherwise, the mobile terminal must use precious battery power to perform the cell reselection evaluation process at another time separate from the time it is powered up to listen to the paging channel.
The mobile terminal responds to a page by sending a paging response message to the radio network. Traditionally, the mobile terminal responds to the paging message in the same cell where it received that paging message. However, because the mobile terminal is listening to the paging channel, it may also be evaluating whether the current cell is the optimum cell, e.g., for uplink transmission in response to the page in a CDMA-based system, before responding to the page. If the mobile terminal happens to select another, more optimum cell and send a paging response message to that new cell, that message may not be routed to the paging originator. For example, if the newly selected cell belongs to a different RNC than the RNC that originated the page, t
Beming Per
Müller Walter
Nordstrand Ingrid
Palm Håkan
Wallentin Pontus
Nixon & Vanderhye P.C.
Telefonaktiebolaget LM Ericsson (publ)
Vo Nguyen T.
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