WO2013068369A1 - Distribution d'informations systèmes dans un système de télécommunications à accès sans fil - Google Patents

Distribution d'informations systèmes dans un système de télécommunications à accès sans fil Download PDF

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Publication number
WO2013068369A1
WO2013068369A1 PCT/EP2012/071967 EP2012071967W WO2013068369A1 WO 2013068369 A1 WO2013068369 A1 WO 2013068369A1 EP 2012071967 W EP2012071967 W EP 2012071967W WO 2013068369 A1 WO2013068369 A1 WO 2013068369A1
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WO
WIPO (PCT)
Prior art keywords
cell
system information
terminal
cells
radio interface
Prior art date
Application number
PCT/EP2012/071967
Other languages
English (en)
Inventor
Haibin Zhang
Ljupco Jorguseski
Job Cornelis Oostveen
Jacob Cornelis Van Der Wal
Original Assignee
Koninklijke Kpn N.V.
Nederlandse Organisatie Voor Toegepast-Natuurwetenschappelijk Onderzoek Tno
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Koninklijke Kpn N.V., Nederlandse Organisatie Voor Toegepast-Natuurwetenschappelijk Onderzoek Tno filed Critical Koninklijke Kpn N.V.
Priority to EP12781323.6A priority Critical patent/EP2777330A1/fr
Priority to JP2014540425A priority patent/JP5856689B2/ja
Publication of WO2013068369A1 publication Critical patent/WO2013068369A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W48/00—Access restriction; Network selection; Access point selection
    • H04W48/08—Access restriction or access information delivery, e.g. discovery data delivery
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0055—Transmission or use of information for re-establishing the radio link
    • H04W36/0061—Transmission or use of information for re-establishing the radio link of neighbour cell information
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W48/00—Access restriction; Network selection; Access point selection
    • H04W48/08—Access restriction or access information delivery, e.g. discovery data delivery
    • H04W48/14—Access restriction or access information delivery, e.g. discovery data delivery using user query or user detection
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/04—Large scale networks; Deep hierarchical networks
    • H04W84/042—Public Land Mobile systems, e.g. cellular systems
    • H04W84/045—Public Land Mobile systems, e.g. cellular systems using private Base Stations, e.g. femto Base Stations, home Node B
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

  • the invention relates to the field of wireless telecommunications. More specifically, the invention relates to the field of distributing system information from a cell to a terminal.
  • a cellular wireless access telecommunications network typically includes multiple base stations, also known as, for example, base transceiver station in GSM, NodeB in WCDMA (UMTS), and evolved NodeB or eNB in LTE.
  • a base station includes at least transmitting and receiving equipment to support wireless communication with a (possibly mobile) terminal, in standardization more formally known as UE (User Equipment).
  • UE User Equipment
  • the range that can be covered with the transmitter/receiver in a base station is limited.
  • the area that can be served by the transmitter/receiver of a base station is referred to as its "coverage area" or as the "cell.”
  • the term "cell" refers to both the base station itself and to its associated coverage area.
  • a cell relates to a particular sector (e.g. 120 degrees) radiating out from the base station position, where multiple sectors (cells) may cover the entire area around the base station position or may cover an particular area of interest (e.g. a narrow sector to cover a highway section).
  • a sector e.g. 120 degrees
  • multiple sectors may cover the entire area around the base station position or may cover an particular area of interest (e.g. a narrow sector to cover a highway section).
  • a cell (base station) in a cellular network is typically connected to the remainder of the network via one or more backhaul links, for example, via optical fibre, via copper wire or wirelessly.
  • a base station further includes processing capabilities, for example for the wireless transmission and recep- tion and for handling the protocols specified between the base station and the terminal and between the base station and the network, including other base stations (cells).
  • different cells may have different sizes, indicated e.g. as macrocells, microcells, picocells or femtocells in decreasing order of cell size.
  • Cells may show a partial overlap with nearby cells or a smaller cell (e.g. picocell) may be entirely overlapped by a larger cell (e.g. macrocell).
  • Multiple cells may thus form a cellular network providing near contiguous coverage in a very large area.
  • a terminal In a cellular wireless network it is common to distinguish a terminal to be in an 'idle mode' or in an 'active mode'.
  • the terminal In the active mode, the terminal is able to exchange data (e.g. sending/receiving an e-mail or making a phone call) via a cell in which the terminal is located.
  • This requires resources in the network (e.g. frequencies and/or codes and/or time slots) and also requires the terminal and the network to provide power for the purpose.
  • the terminal In the idle mode the terminal is not able to exchange data and, therefore, does not require the above resources and consumes less power.
  • a terminal in the idle mode only regularly listens to signals broadcast by the cells and selects a 'best cell', for example the cell with the signal that the terminal receives as strongest.
  • a terminal in the idle mode also monitors the paging channel transmitted by the selected cell for a paging message addressing the terminal.
  • Such an (idle mode) terminal is said to 'camp on' the selected cell.
  • the terminal may re-select the different cell as 'best cell' and camp on the newly selected cell.
  • a terminal in the idle mode normally does not inform the cell and/or the network about which cell the terminal is camping on, also not when re-selecting a different cell as best cell.
  • LA or RA - routing area which the terminal may determine from the cell's system information
  • LA or RA update procedure which comprises an exchange of signalling or network control messages between the terminal and the cell
  • LA or RA update procedure which comprises an exchange of signalling or network control messages between the terminal and the cell
  • each cell aka base transceiver station, NodeB, or eNB
  • NodeB nodeB
  • eNB when in operation, broadcasts so-called "system information" for reception by the terminals in the coverage area of the cell.
  • FIG. 1 shows that a cell 1 is broadcasting system information 9 in the cell's coverage area (in FIG. 1 illustrated as a lightly shaded sector), which system information may be received by terminals 2 in the cell.
  • FIG. 1 also illustrates that the cells 1 are connected to a network 3.
  • System information transmitted by a cell may relate to a wide variety of information associated with the cell and/or the network it operates in. Below are provided some examples of system information and possible uses of that information by the terminals. A person skilled in the art will recognize that system information may include one or more of these examples as well as other kinds of system information according to which a terminal receiving the information can configure itself.
  • the system information may include an indication of the network, such as e.g. Public Land-based Mobile Network (PLMN), the cell belongs to, enabling the terminal receiving this information to determine whether the terminal may possibly use that cell at all.
  • the system information may include an indication of the cell's status, e.g. whether the cell is in operation and/or whether or not any restrictions, such as e.g. access class, apply. Such information enables the terminal to determine whether the terminal may use that cell at the moment.
  • the system information may include an indication of the identity of the cell (Cell ID), enabling the terminal to determine the cell's identity within that network.
  • the system information may include an indication of the cell's configuration, e.g.
  • the system information may include neighbour cell information, such as e.g. a neighbour cell list comprising identity and/or transmit frequency and/or codes and/or time slots for neighbour cells.
  • RATs Radio Access Technologies
  • neighbour cell info may be provided separately, e.g. per RAT. This enables or facilitates the terminal to (quickly) find a neighbour cell e.g. for assessing the neighbour cell for the purpose of a potential cell re-selection or handover.
  • the system information may include indications about the criteria for e.g. cell re-selection and/or threshold for performing and/or reporting measurements on neighbour cells and/or on other frequencies and/or RATs, allowing the network to inform terminals about the criteria that should be applied in the network and/or in the cell.
  • a cell broadcasts the system information, e.g. on a broadcast channel, such that all terminals in the cell's coverage area are able to receive the cell's system information.
  • the cell transmits the system information cyclically, in a sequential order, and in a substantially continuous way, e.g. cyclically repeating transmission of system information in a carousel-like structure, as is schematically illustrated in FIG. 2.
  • a cycle 4 includes system information orga- nized in different categories shown as blocks M, S1 , S2, S3, and S4.
  • Block M is intended to illustrate an example of a Master Information Block (MIB) containing system information which is essential for most or all terminals in the network, while blocks S1-S4 are intended to illustrate additional System Information Blocks (SIB) with additional information that may be needed only for some terminals.
  • MIB Master Information Block
  • SIB System Information Blocks
  • the cycle 4 may then be continuously repeated as shown with a sequence 5 of transmitted system information.
  • Some- times, some blocks of system information may be replaced with other blocks, as shown with a sequence 6 illustrating that the last occurrence of blocks S3 and S4 shown in the sequence 6 is replaced with new blocks of system information S5 and S6. Nevertheless, as shown in FIG. 2, with both sequences 5 and 6, the system information is transmitted continuously.
  • a large part of a cell's resources e.g. a high bit rate and/or wide frequency bandwidth
  • a smaller part the cell's resources for broadcasting the system information e.g. a large part of the resources allows realizing a short cycle time and enables a terminal to receive all of the system information with only a small latency, but demands significant resources of the cell.
  • using a smaller part of the resources results in a longer cycle time where a terminal has to accept a higher latency in receiving all or a particular piece of system information.
  • High bit rate data connections can be much more efficiently provided with a larger number of (at least partially overlapping) small cells (e.g. microcells, picocells, femtocells) than with a fewer number of larger cells (e.g. macrocells).
  • a further as- pect in the new architecture is that the power consumption of a cell is envisioned to scale, as much as possible, with the service actually provided (e.g. with the number of active terminals served, with the bit rate provided to a terminal, with the distance covered by the connection to a terminal, etc.).
  • One approach for realizing this vision includes putting those cells that do not actually serve an active terminal into a power-save mode, e.g. switching those cells almost completely off.
  • Another, complementary, approach includes significantly reducing or refraining from transmitting broadcast signals that are common in conventional networks. The transmission of these broadcast signals causes a substantial overhead, in particular for cells operating at less than full load.
  • the new architecture envisions distinguishing between different types of cells.
  • a first type of cells in this text referred to as 'SA-cell' and illustrated in FIG. 3 as a cell 7, is primarily optimized to support the wireless exchange of data with active terminals 2. The energy-efficiency improvements as outlined above are focused on the SA-cells.
  • a second type of cells in this text referred to as 'LA-cell' and illustrated in FIG. 3 as a cell 8, is primarily optimized for other functions in a cellular network, including those also found in conventional networks. Thus, it is envisioned to reduce the overhead in the system to that attributed to the LA-cells.
  • An LA-cell typically covers a larger area, for example comparable to that of a conventional macrocell.
  • the LA-cells together provide near contiguous coverage in the area desired to be covered, much like in a conventional network.
  • An LA-cell may broadcast system information, much like a conventional cell; an idle terminal may camp on an LA-cell and may also initiate a signalling connection with the LA-cell, e.g. to perform an LA RA update or to detach from the network.
  • An SA-cell typically covers a smaller area, for example comparable to that of a conventional microcell, picocell or femtocell.
  • the SA-cells together may support a certain bit rate in the near- contiguous area desired to be covered.
  • An SA-cell only transmits signals when and in so far it is needed; it may be regarded to be normally 'off or in a power-save or stand-by mode.
  • An idle terminal also does not camp on an SA-cell.
  • BCG2 Beyond Cellular Green Gen- eration
  • a terminal may have to deal with two types of cells, one or more LA-cells and one or more SA-cells, the terminal may need relevant system information for one or more relevant LA-cells and for one or more relevant SA-cells.
  • Two problems may then arise.
  • One problem arises from the fact that when an idle terminal becomes active, i.e. when an idle terminal is establishing a data session, a process referred to as a "session set-up," an appropriate SA-cell needs to be selected to support the session.
  • the terminal may need to acquire relevant system information for one or more candidate SA-cells, for example, cell ID, frame timing, cell bandwidth, etc.
  • a terminal may need additional system information for that SA-cell. If the selected SA-cell is currently switched off or in an energy-conserving mode, which is part of the BCG2 concept, the SA-cell needs to be activated. Selection and activation of an appropriate SA-cell may require some time. As a result, it may also take some time before that SA-cell is sufficiently activated to provide the necessary system infor- mation to the terminal. Further, since the concept of an energy-efficient cellular wireless network envisages a highly dynamic configuration of SA-cells, using previously acquired and stored SA-cell system information for a particular SA-cell (e.g.
  • LA-cell configuration might be less dynamic then the SA-cell configuration, using previously acquired LA-cell system information (e.g. the LA-cell system information acquired before establishing a data session) also bears a risk that the previously acquired and stored LA-cell system information is no longer valid. This could be the case e.g.
  • the terminal could again perform the cell search procedure, similar to the cell search procedure at power-on. Thus, it may take some time before the terminal has found an appropriate LA-cell to camp on and before the terminal is able to again monitor the paging channel of that LA-cell.
  • a method for the terminal to obtain at least LA-cell system information and SA-cell system infor- mation includes, when the terminal is in the active mode and an SA-cell radio interface of the terminal is enabled, the terminal receiving at least a first part of the SA-cell system information and at least a first part of the LA-cell system information from the SA-cell via the SA-cell radio interface.
  • Embodiments of this solution are based on the idea that an SA-cell may be used to transmit SA-cell system information as well as LA-cell system information regarding at least some of the LA-cells possibly relevant for the terminal in the coverage area of the SA-cell.
  • the SA-cell may be configured to use a broadcast/common channel to transmit all of the system information for the terminals, while in an alternative embodiment the SA-cell may be configured to use one or more dedicated channels with active terminals for transmitting at least some of the system information to individual terminals.
  • the method may further include the terminal configuring one or more of its settings based, at least partially, on the received SA-cell system information and/or the received LA- cell system information. Additionally or alternatively, the terminal may store at least part of the received SA-cell system information and/or LA-cell system information for future use. In a further embodiment, an idle terminal, as long as it remains in idle mode, is likely to apply only the received and, possibly, stored
  • LA-cell system information to configure its settings
  • the received SA-cell system information is likely to be just stored for possible later use. Only when the terminal is about to enter into active mode, the terminal is likely to also apply the received and, possibly, stored SA-cell system information to further configure its settings for the particular SA-cell with which the terminal is about to be connected and/or is connected.
  • expressions "information transmitted by a cell for a terminal,” “information for a terminal” and variations thereof describe system information which is intended for the terminal, e.g. for a possible benefit of the terminal.
  • some system information may be intended primarily for a terminal in idle mode, some other system information may be intended primarily for a terminal in active mode and some system information may be intended for a terminal regardless its mode.
  • LA-cell and "SA-cell” are used to differentiate between two different types of cells.
  • the first type of cell refers to a cell that is able to cover a larger area with a smaller bit rate, as compared with the second type of cell.
  • the LA-cell is primarily intended for carrying signaling messages from/to a terminal, e.g. the LA-cell is intended to at least be able to page a terminal.
  • a terminal in idle mode may further be assumed to 'camp' on at least one of these LA- cells.
  • the LA-cell is not primarily intended to be used to carry wireless user data from/to a terminal, it is not precluded that other signaling than paging or that also some user data is carried via an LA-cell.
  • the intended coverage area of the wireless access network it may be assumed that at least one LA-cell is fully operational or, in other words, an LA-cell is 'normally on.'
  • the second type of cell refers to a cell that is able to cover a smaller area with a higher bit rate, as compared with the LA-cell.
  • the SA-cell is primarily intended to carry user data from/to a terminal over the established data connection (i.e., the SA-cell is primarily intended to handle connections with active terminals). Yet, it is not precluded that also some other information and/or some signalling is carried via an SA-cell.
  • the intended coverage area of the wireless access network it may be assumed that at least one SA-cell is able to provide coverage.
  • An SA-cell is only fully operational when and to the extent that it is needed or, in other words, an SA-cell is 'normally off.'
  • the SA-cells may occur in any mix of frequency bands and/or radio access technologies (RATs). It is also not precluded that there are differently sized SA-cells (e.g. macro, micro, pico and femto SA-cells, with or without a hierarchical organisation), where larger SA-cells may e.g. more efficiently serve highly mobile terminals.
  • RATs radio access technologies
  • the expression "data connection between a terminal and an SA-cell” refers to a communication path for a wireless exchange of user data between the terminal and the SA-cell.
  • the communication path for user data is usually set up according to a set of parameters, for example, depending on what type of user data needs to be exchanged (e.g. for sending/receiving e-mail, for making a voice or video call, etc.).
  • the set of pa- rameters commonly referred to in the art as "QoS parameters" or "QoS profile,” may include parameters such as e.g. maximum bitrate, guaranteed (minimum) bitrate, bit error ratio and delay/latency.
  • signalling messages exchanged between the terminal and the LA-cell do not contain user data and are exchanged between e.g. the terminal and various entities in the telecommunication system.
  • Signalling messages may be exchanged without establishing a connection or via a "signalling connection" with a modest bit rate and with a quality sufficient for most signalling information to arrive uncorrupted.
  • a signalling connection when used, is to a large extent also independent of the parameters of the "data connection" it may be associated with.
  • user data and “user terminal” do not necessarily imply a presence of a human user and the embodiments of the present invention may also be applicable to e.g. a smartphone checking e-mail without human intervention and to machine-to-machine (M2M) communications and/or Machine-Type Communications (MTC).
  • M2M machine-to-machine
  • MTC Machine-Type Communications
  • a terminal may be either in an "active mode” or an “idle mode.”
  • the expression “a terminal in an idle mode” refers to a terminal that is neither exchanging user data nor able to exchange user data but is camping on a LA-cell and is monitoring possible paging messages for the terminal from the LA-cell.
  • the expression “a terminal in an idle mode” is used to describe a terminal which does not have support for the wireless exchange of user data between the terminal and an SA-cell.
  • the expression “a terminal in an active mode” refers to a terminal that is either exchanging user data or able to exchange user data via at least one SA-cell.
  • an active terminal supports or is able to support the wireless exchange of user data between the terminal and the SA-cell(s).
  • the method further includes, when the terminal is in the active mode and the SA-cell radio interface of the terminal is enabled, the terminal receiving, via the SA-cell radio interface, at least a second part of SA-cell system information regarding the SA-cell and/or at least a part of SA-cell system information regarding at least one of one or more other SA-cells in the wireless access network.
  • the terminal advantageously provides the terminal with system information regarding neighbouring SA-cells.
  • the system information regarding the SA-cells other than the SA-cell with which the terminal has established the data connection with can be provided to the terminal from the SA-cell with which the terminal has the data connection.
  • This embodiment is particularly advan- tageous for energy-efficient networks because it allows the terminal to obtain system information regarding other SA-cells without the terminal having a data connection with those cells and even when one or more of those SA-cells are inactive.
  • each of the other SA-cells can provide their own system information to the terminal, the terminal receiving the system information from the different SA-cells via its SA-cell radio interface.
  • the method further includes, when the terminal is in the idle mode and an LA-cell radio interface of the terminal is enabled, the terminal receiving at least a second part of the LA-cell system information.
  • an SA-cell may be used to transmit SA-cell system information as well as LA-cell system information regarding at least some of the LA-cells possibly relevant for the terminal in the coverage area of the SA-cell, in order to support idle terminals, at least some part of the LA-cell system information may still need to be transmitted by the LA-cell.
  • the method further includes, when the terminal is in the idle mode and the LA-cell radio interface of the terminal is enabled, the terminal receiving at least a second part of the SA-cell system information from the LA-cell via the LA-cell radio interface.
  • the method further includes, when the terminal is in the active mode and the SA-cell radio interface of the terminal is enabled, the terminal receiving at least a part of LA-cell system information regarding at least one of one or more other LA-cells in the wireless access network from the SA-cell via the SA-cell radio interface.
  • the terminal may obtain not only system information regarding the LA-cell on which the terminal was camping before, but also regarding other relevant LA-cells.
  • the method further includes disabling the SA-cell radio interface when the LA-cell radio interface is enabled and disabling the LA-cell radio interface when the SA-cell radio interface is enabled.
  • an SA-cell for use in the methods described herein.
  • the SA-cell is configured at least for obtaining the at least the first part of the LA-cell system information from the LA-cell or from a network management entity in the wireless ac- cess network and transmitting the at least the first part of the LA-cell system information and the at least the first part of the SA-cell system information.
  • the SA-cell may also be configured for obtaining and transmitting system information regarding other SA-cells and/or other LA-cells, which information could also be obtained from the other cells directly and/or from a network management entity of the wireless access telecommunications network.
  • At least a part of the at least the first part of the LA-cell system information and/or the at least the first part of the SA-cell system information may be transmitted repeatedly during a first time period adjacent to a second time period during which no part of the LA-cell system information and no part of the SA-cell system information is transmitted.
  • the second time period may be at least as long as the first time period.
  • At least one portion of the at least the first part of the LA-cell system information and/or the at least the first part of the SA-cell system information may be transmitted upon the SA-cell receiving a trigger from the terminal, from the LA-cell, from a further node in the wireless access network, and/or from a network management entity of the wireless access network.
  • the at least one portion of the at least the first part of the LA-cell system information and/or the at least the first part of the SA-cell system information may be transmitted after expiration of a predetermined delay period following receipt of the trigger.
  • an SA-cell transmits system information regarding at least one LA-cell and possibly regarding more LA-cells as well as transmits system information regarding at least the SA-cell itself. It is also possible that the SA-cell transmits system information regarding several other SA-cells, e.g. for all its neighbour SA-cells. In such a case, it may be ex- expected that much of the system information is the same for the SA-cells or at least for a fraction or group of the SA-cells. This situation lends itself for a very efficient way of transmission where the SA-cell may be configured to transmit system information for the terminal in such a manner that the parts of the system information which are the same for different cells are not duplicated. Of course the information still needs to be transmitted in such a manner that the terminal can identify which system information regards which cell, but a person skilled in the art can easily think of various manners to ensure this, all of which manners are supposed to be within the scope of the present invention.
  • an LA-cell for use in the methods described herein is disclosed.
  • the LA-cell is configured at least for providing the at least the first part of the LA-cell system information to at least one of the SA-cells in the wireless access network for transmission for the terminal.
  • a terminal a computer program with portions (possibly distributed) for performing the various functions described herein, a data carrier for such software portions, and a telecommunications system are disclosed.
  • the telecommunications system may include two or more of the terminal, the LA-cell, and the SA-cell as described herein.
  • FIG. 1 is a schematic illustration of system information distribution in a conventional network
  • FIG. 2 is a schematic illustration of continuous transmission of system information according to prior art
  • FIG. 3 is a schematic illustration of SA- and LA-cells in an energy-efficient cellular wireless access telecommunications network
  • FIG. 4 is a schematic illustration of intermittent periodic transmission of system information, according to an embodiment of the present invention.
  • FIG. 5 is a schematic illustration of triggered transmission of system information, accord- ing to various embodiments of the present invention.
  • FIG. 6 is a schematic illustration of an energy-efficient telecommunications system, according to an embodiment of the present invention
  • FIG. 7 is a schematic illustration of coverage areas of the LA-cell and a plurality of SA- cells in a telecommunications network, according to one embodiment of the present invention
  • FIG. 8 is a schematic illustration of an SA-cell radio interface and an LA-cell radio interface of a terminal being enabled alternatively in a time-multiplexing mode, according to one embodiment of the present invention
  • FIG. 9 is a schematic illustration of an SA-cell providing SA-cell system information and an LA-cell providing LA-cell system information to a terminal, according to one embodiment of the present invention.
  • FIG. 10 sets forth a flow diagram of method steps for obtaining system information for one or more SA-cells and system information for one or more LA-cells, according to one embodiment of the present invention
  • FIG. 1 1 is a schematic illustration of an LA-cell providing both LA-cell system information and SA-cell system information to a terminal, according to one embodiment of the present invention
  • FIG. 12 is a schematic illustration of an LA-cell providing both LA-cell system information and SA-cell system information to a terminal, according to another embodiment of the present invention.
  • FIG. 13 is a schematic illustration of an SA-cell providing both SA-cell system information and LA-cell system information to a terminal, according to one embodiment of the present invention.
  • FIG. 14 is a schematic illustration of an SA-cell providing both SA-cell system information and LA-cell system information to a terminal, according to another embodiment of the present invention.
  • Solutions # 1-4 below provide various methods and systems for distributing system information.
  • Solution # 1 is described with references to a conventional network, such as the one shown in FIG. 1 , while solutions # 2-4 are described as being specifically adapted for distributing system infor- mation in energy efficient networks.
  • solutions # 2-4 are described as being specifically adapted for distributing system infor- mation in energy efficient networks.
  • a person skilled in the art will realize that the teachings regarding distribution of system information by a cell in a conventional network, as provided in solution # 1 , are applicable for distribution of system information by SA-cells and LA-cells in energy efficient networks.
  • Solution # 1 Distribution of system information according to various embodiments of the present invention
  • Solution # 1 is intended to primarily focus on the possibilities to improve the efficiency (including energy-efficiency) of distributing system information by a cell. As described above, solution # 1 is described with a reference to a conventional network such as the one illustrated in FIG. 1 , but the embod- iments of solution # 1 can be applied to any cell distributing system information, not only to conventional cells such as base transceiver stations, NodeBs or eNBs, but also to SA-cells and/or LA-cells in energy efficient networks. Solution # 1 provides five different ways to improve energy efficiency of distributing system information by a cell.
  • a first way is based on broadcasting system information for only a fraction of the time and not transmitting any system information (or transmitting significantly less system information) for the remaining fraction of the time, rather than the usual substantially continuous transmission as is done in prior art.
  • a second way is based on broadcasting system information when triggered to do so by a particular event.
  • a third way is based on, rather than broadcasting with the usual full power to reliably reach the furthest, in terms of path loss, edge of a cell's coverage area, transmitting system information with a substantially reduced power.
  • a fourth way is based on, rather than using the usual cyclic transmission system information parts, transmitting only a reduced fraction of system information.
  • a fifth way is based on, rather than using the usual broadcast channel and transmitting system information to all terminals that possibly might be present in the cell's coverage area, transmitting system information to only a particular terminal via a dedicated channel.
  • a first way to achieve a more energy efficient distribution of system information is for a cell, such as e.g. the cell 1 illustrated in FIG. 1 , to only transmit system information intermittently, i.e. for a fraction of the time.
  • a cell may be configured to transmit a system information signal for 100 milliseconds (ms), followed by 900 ms of not transmitting any system information, corresponding to a fraction 1/10 th .
  • the cell may include at least a transmitter and a controller for preparing a signal for transmission.
  • the cell may further include a memory for storing computer program instructions according to which the controller and/or the transmitter may be configured to operate as well as a processing unit for processing data and running the computer programs on.
  • the duration of transmitting a system information signal may correspond to a full cycle of a cell's system information or to a particular system information part. This is schematically illustrated in FIG. 4 with a signal 10, where the full cycle of the cell's system information 10a comprising blocks M, S1 , S2, S3, and S4 is transmitted during a time period of duration t1 adjacent to a time period of duration t2 where no system information 10b is transmitted.
  • a cell can then repeatedly transmit the signal 10, thus repeatedly transmitting system information blocks M and S1-S4 corresponding to 10a during the time period t1 adjacent to transmitting no system information corresponding to 10b during the time period t2, as shown with a signal 1 1.
  • some of the system information portions may be replaced by other portions, as shown with a signal 12 where, in some case, system information blocks S5 and S6 are present instead of the blocks S3 and S4.
  • the duration of transmitting a system information signal may also be shorter, e.g. correspond to only a fraction of a system information (or system information part) cycle. Then, a full cycle of system information or system information part transmission may be distributed over multiple periods of transmitting and not transmitting the system information signal, as shown in FIG. 4 with a signal 13, thus increasing the time a terminal may need to acquire the entire system information (or system information part) compared to a case with substantially continuous transmission of system information.
  • the duration of transmitting a system information signal may also be longer than a full cycle of system information or system information part. For example, this could be the case for a duration that corresponds to a multiple of cycles of system information or system information part.
  • a terminal failed to receive a system information element or the terminal detected or suspects that it received a system information element erroneously transmitting system information in this manner enables the terminal an additional opportunity to acquire or to double-check the repeated system information element, within the same period of system information transmission.
  • Varying the duty cycle i.e. the ratio between the "on” and “on”+”off' times for transmitting the system information or system information part signal
  • Varying the duty cycle allows reducing the power of the emitted presence signal to roughly the same fraction, as opposed to a conventional approach where a system information transmission would be substantially 100% of the time.
  • the maximum duty cycle for an intermittent system information or system information part signal emitted by a cell could be e.g. 1/2 or 1/8 th , which could result in an 2-fold or 8-fold, respectively, power saving in comparison with the same signal emitted continuously.
  • Different duty cycles may be applied to the transmission of different system information parts, e.g. according to the (estimated or expected) urgency with which a terminal may need the information.
  • the terminal when a terminal is powered on, the terminal initiates a cell search procedure to find a suitable cell to camp on. As a part of such a procedure, the terminal needs to identify one or more candidate cells and then, for a particular candidate cell, may need to determine, for example, the network (Public Land Mobile Network) the cell relates to, an indication of the cell identity and/or the operational status of the cell (e.g. whether or not it is currently barred for the terminal's access class and/or possibly overloaded).
  • the network Public Land Mobile Network
  • a substantially continuous or very frequent broadcast of system information may very well suit such a terminal's needs.
  • Such broadcast is not energy efficient if there is, in a particular period of time, no terminal being powered on and/or no terminal performing a cell search procedure on that par- ticular cell.
  • energy efficiency is improved by transmitting the system information part intended for terminals performing a cell search procedure only for a fraction of the time, e.g. once every second.
  • a terminal, attempting to receive the particular system information part may have to wait for some time before being able to actually receive it. In this example, in worst case, the waiting time would be a second, but, on average, the waiting time would be half a second.
  • a transmission upper bound may be selected differently for different system information parts, e.g. when terminals tolerate more latency for a particular system information part than for another system information part.
  • the transmission upper bound for the system information part that comprises the cell's handover parameters may be selected considerably higher than the one for the system infor- mation part that comprises the cell's RACH (Random Access CHannel) parameters, e.g. with the motivation that a terminal initiating contact with the selected cell via its RACH requires the RACH parameters before being able to do so, while a terminal which made a handover to a new cell is unlikely to immediately need information regarding that cell's handover parameters.
  • RACH Random Access CHannel
  • the period of time between successive transmissions of a system in- formation part or the upper bound to that period may be modified over time. For example, during peak hours, such as e.g. in the morning when people tend to switch on their cell phone, a low value, such as e.g. 0.25 seconds (s), may be selected for the transmission upper bound of a system information part typically used by terminals that perform a power-on procedure. Later in the day, when most terminals can be expected to be already powered-on, a higher value, such as e.g. 1 second, may be selected. During the night, still a higher value, such as e.g. 5 seconds, may be selected. At this time, even a value so high that it is beyond what a terminal would normally tolerate, could be regarded as acceptable in view of the energy saving achieved.
  • peak hours such as e.g. in the morning when people tend to switch on their cell phone
  • a low value such as e.g. 0.25 seconds (s)
  • a higher value such as e.
  • nearby cells may transmit its system information at times 1.0, 2.0, 3.0, etc. second, nearby cell B - at times 1 .1 , 2.1 , 3.1 , etc. second, and nearby cell C - at times 1 .4, 2.4, 3.4, etc. second.
  • the system information part of up to 10 cells could be received in a time frame of about 1 second whereas without such 'staggered' transmission times of that system information part, it could take up to 10 seconds in the worst case scenario (i.e., 10 times the worst case delay of 1 second), or, on average, 5 seconds (i.e., 10 times the average delay of 0.5 second).
  • the worst case scenario i.e., 10 times the worst case delay of 1 second
  • 5 seconds i.e., 10 times the average delay of 0.5 second
  • cells within a same PLMN or in a set of co-operating PLMNs can be expected to benefit from the approach.
  • a trigger for transmission of a system information part may comprise an implicit or an explicit trigger.
  • the network when a terminal establishes a data session via a cell (usually the cell the terminal was camping on), the network, and in particular the cell involved in the data session, may expect that the terminal may need additional system information parts.
  • the terminal may need parameters specifying the criteria for making measurements on other cells and criteria for reporting (e.g. so- called 'events' in the context of handover, an event being e.g. the signal level of the serving cell drops below a predetermined threshold and/or the signal level of a neighbour cell exceeds the signal level of the serving cell by some predetermined margin, the margin being either positive or negative).
  • the cell may transmit this system information part e.g. shortly after a session set-up via the cell. Doing so will result in a considerable energy saving compared to the usual case of substantially always repeating transmission of this system information part.
  • the cell may apply a delay, e.g. 10 seconds, between the mo- ment a first trigger has been received (e.g. a session set-up via the cell has been completed) and the transmission of the related system information part (i.e. the system information part possibly needed by the terminal).
  • a delay e.g. 10 seconds
  • Other terminals having established a session via the same cell (each of which may be interpreted as a trigger) within the delay period, may also receive the same system information part, thus relieving the cell from transmitting the same information multiple times.
  • the delay value should not exceed a predetermined value corresponding to e.g. a maximum latency generally considered as acceptable to a terminal, such as e.g. 15 seconds.
  • a predetermined value corresponding to e.g. a maximum latency generally considered as acceptable to a terminal, such as e.g. 15 seconds.
  • a person skilled in the art will recognize that applying a delayed transmission is beneficial only when other triggers related to some system information part (e.g. one or more additional session set-ups) can be expected within the delay time, such as e.g. during peak hours.
  • the rate of triggers e.g. session set-ups
  • the delay is preferably set to a smaller value or to zero.
  • the delayed transmission of a triggered system information part may be combined with the option of a reduced power transmission described in greater detail below. Then, the reduced power setting should be in correspondence with the most distant, in terms of path loss, terminal in the group of terminals that completed a session set-up within the particular delay time period.
  • the cell is configured for multiple RACH channels, one generic RACH channel (i.e. a predetermined RACH channel configured for all cells in a network or at least for multiple cells in an area) and one or more RACH channels configured per-cell.
  • a terminal not (yet) having received the RACH channel configuration for a particular cell may direct its first request via the generic RACH channel of that cell. That request may be handled by the cell or may be discarded, de- pending on system configuration and depending on the load of the cell.
  • a cell, having received a RACH request on its generic RACH channel may consider such an event as a trigger to transmit the system information part related to its RACH channel configuration, such that subsequent requests from the terminal that transmitted the request may be directed to any of the per-cell configured RACH channels.
  • a terminal which finds itself in need for some particular system information part may issue a system information part request towards the cell.
  • a request is not found in conventional networks and may be a request specially designed for the purpose.
  • Such a request may be implemented e.g. similar to a RACH request.
  • the system information part request would advantageously allow the terminal to specify which system information part or, possibly, multiple system information parts the terminal requests.
  • the cell may be configured to transmit the requested system information part, which is then received by the requesting terminal and possibly also by other, additional terminals monitoring that cell's system information channel.
  • a cell may interpret an explicit request also as an implicit additional request and transmit additional system information parts that were not specified in the explicit request. This could be the case for example if the cell expects, e.g. based on experience, that such additional system information parts are typically also and/or subsequently requested. Such an embodiment could be particularly advantageous if an explicit system information part request does not allow multiple system information parts to be requested.
  • FIG. 5 provides an exemplary illustration of the concept of transmitting system information in response to a trigger, either implicit or explicit.
  • a cell may be configured to repeatedly transmit a signal, e.g. a signal 20 shown in FIG.
  • FIG. 5 comprising system information blocks M, S1 , and S2, similar to these blocks illustrated in FIG. 4, followed by a time period t2 where no system information is transmitted.
  • the repeated transmission of a signal 20 is shown in FIG. 5 with a signal 21.
  • the cell may receive a trigger, as either an implicit or explicit trigger described above to transmit a system information block S3 and, in response to the trigger, transmit the requested block S3 for receipt by (at least) the requesting terminal.
  • a signal 22 schematically illustrating occurrence of two different triggers for system information S3, the first trigger illustrated as "tr(S3)-1 " and the second trigger illustrated as "tr(S3)-2".
  • the cell may be configured to apply a predetermined delay period Td after receipt of a trigger, before transmitting the requested information.
  • a predetermined delay period Td is applied after occurrence of the first trigger, illustrated as "tr(S3)-1 ".
  • FIG. 5 illustrates that S3 is transmitted when the delay period Td expires.
  • another trigger for the system information block S3 may be received, as shown with a fifth trigger, "tr(S3)-5".
  • the cell may then be configured to again apply the predetermined delay period Td before transmitting the requested block S3 (which second transmission of the requested block S3 is not shown in FIG. 5).
  • the transmit power for a broadcast signal transmitted from a cell is typically selected such that also a terminal at the most distant, in terms of path loss, cell edge will most likely be able to reliably receive the broadcasted information.
  • a cell may choose to transmit some system information or system information part(s) with reduced power, for example when the cell estimates the terminal(s) for which the system information part is intended are less distant, in terms of path loss, than at the most distant cell edge.
  • the power to be used for transmitting a system information part from a cell to a particular terminal may be estimated e.g.
  • the cell may choose to apply a higher power setting than for transmission to the terminal via a dedicated channel, thus increasing the probability that the system information transmitted on the common channel can be received and acquired in one transmission, i.e. in most cases not requiring a retransmission of the system information or part(s) thereof.
  • the cell may estimate a suitable transmit power for transmission of system information via a common channel from a RACH request received from the terminal.
  • a RACH request may contain an indication of the power with which the terminal transmitted the RACH request.
  • the cell measuring the power with which it received the RACH request, is then able to determine the path loss the RACH request experienced from the difference between the terminal's transmit power and the cell's receive power.
  • the cell may then be configured to use this information and the fact that path loss in the uplink and downlink directions is typi- cally the same to estimate a suitable transmit power for transmitting system information to the terminal via a common channel.
  • Yet another way to estimate a suitable transmit power for transmitting system information from a cell to a terminal may be based on the power with which the terminal received some signal from the cell.
  • Such measurements may e.g. be made by the terminal in the context of cell re-selection and/or handover.
  • handover such information is typically provided to the network, and the network, possibly via a different cell, may provide relevant parts of such information to the cell expected to transmit system information to the terminal. Otherwise, the terminal may provide measurement information directly to the cell.
  • the reduced power to be applied may be determined by the most distant, in terms of path loss, terminal among these multiple terminals.
  • the terminal when a terminal is performing a handover from one cell to a new cell, the terminal needs to be informed about the neighbour list of the new cell.
  • each cell transmits its neighbour cell list.
  • the old cell and the new cell may share some neighbours, such that transmitting the full neighbour cell list to the terminal making a handover contains duplicate information.
  • the cell instead of transmitting a full neighbour cell list, the cell (either the new cell or the old cell) may suffice to transmit only the difference or delta between the two lists.
  • Such a delta transmitted by the new cell could e.g. contain information indicating that old cell ID1 1 , ID12, ... etc. should be deleted and that new cell ID21 , ID22, ... etc. should be added.
  • the delta lists for multiple terminals may be combined in a single transmission. This may also be done if terminals handed over to the new cell originate from different old cells, e.g. by the terminals ignoring a delete instruction referring to a cell ID not contained in the terminal's neighbour cell list and by ignoring an add instruction referring to a cell ID already present in the terminal's neighbour cell list.
  • the new cell may be configured to monitor the rate of handovers directed to the cell, to monitor also the old cells from which these handovers were made and to choose a system information transmission strategy which the cell considers or estimates to be most resource-efficient.
  • This approach could also be applied to many other parameters distributed via system in- formation, such as handover parameter settings, which quite often have a same value in many cells in a network. For example, if a handover is made from an old cell to a new cell, and if at least some particular parameters have the same value in both cells (e.g. handover settings), the new cell may refrain from transmitting in its system information these particular parameters. In other words, the difference (delta) between these particular parameters (parameter values) in the old cell and the new cell is zero. In other cases, e.g. if a handover is made from another old cell to the new cell and if some particular parameters (e.g.
  • the new cell may transmit in its system information at least these parameters such that the terminal may obtain and apply the parameters associated with the new cell (e.g. replace an old parameter value by the new parameter value or add a new parameter).
  • a fifth way to improve the energy efficiency of distributing system information includes, ra- ther than using the usual broadcast channel and transmitting the system information to all terminals that possibly might be present in the cell's coverage area, transmitting the system information or part thereof to only a particular terminal via a dedicated channel.
  • This solution may not apply or may not be practical for all system information parts or all system information elements. For example, it would not apply to particular system information part that is required to request or set up a dedicated channel. Also, it may be not practical for system information parts or system information elements typically used in cell search. Then, the additional (energy) overhead (both for the terminal and the network) for setting up a dedicated channel only for the purpose to receive some system information part, may be a larger burden than the gain achieved by using a dedicated channel instead of a broadcast or common channel.
  • distribution of system information via a broadcast or common channel may be efficient if multiple terminals are receiving system information or a system information part and when this system information was unavailable to the terminals before the system information transmission.
  • informing ten terminals simultaneously with a single system information transmission is more efficient than informing only a single terminal.
  • typically a high transmit power is used in order to be certain to be able to also reach the most distant, in terms of path loss, of the intended terminals. If only a few terminals are receiving and acquiring the transmitted information, the energy efficiency of such a transmission is doubtful. If only a single terminal is receiving and acquiring the transmitted information, the information is provided in an energy-inefficient way. If no terminal is receiving and obtaining the thus transmitted information, the energy is just wasted.
  • the cell may be configured to transmit at least some system information parts via a dedicated channel from the cell to a particular terminal.
  • a dedicated channel is typically power-controlled, transmission of a given amount of data to a single terminal via a dedicated channel is likely to be more energy efficient.
  • dedicated channels typically operate in both directions, in the downlink direction from the cell to the terminal and in the uplink direction from the terminal to the cell, such that an erroneous reception of some system information part or system information element may be quickly and efficiently corrected by a retransmission requested by the terminal.
  • the use of a dedicated channel very well suits the terminal to trigger a cell, e.g. with an explicit trigger, to transmit system information or part thereof and also to only transmit the system information part(s) or system information element(s) as actually needed by and requested by the terminal, including using the 'difference-only' or 'delta' option as described above.
  • not all combinations of the above-described five power saving options may be equally suitable and/or applicable, while others may be more easily combined.
  • using a dedicated channel for the transmission of system information to a terminal may very well be combined with only transmitting a delta (option #4 described above) and/or with an implicit and/or explicit triggering (option #2 described above).
  • Also using an implicit and/or explicit triggering may very well be used in combination with intermittent transmission (option #1 described above), in particular with a very low repetition rate (i.e. t2 much larger than t1 ) for selected parts of the system information.
  • intermittent transmission may be less applicable for combining it with using a dedicated channel for the transmission of system information to a terminal (option #5 described above) and reduced power (option #3 described above) may already be implied in the use of a dedicated channel.
  • a special case of distribution of system information includes a cell updating (i.e. modifying) a particular system information part.
  • the modified system information part should be distributed over at least those terminals that earlier received the 'outdated' system information and are still in the cell's coverage area. This may be most efficiently performed by broadcasting at least once the modified system information part.
  • System information modification may be performed most efficiently as in conventional systems via a broadcast channel or common channel, preferably with a power setting for the most distant terminal.
  • System information notification may be provided via paging channel, as in UMTS, or via the MIB which then should be monitored near-continuously.
  • the same mechanism of a system information modification may also be applied instead of the currently usual mechanism of a system information validity timer in each terminal.
  • the cell instead of the terminal-driven validity timer, the cell may be configured to maintain a refresh timer. When the cell's refresh timer expires, the cell may be configured to announce a refresh, e.g. similar to a system information modification, and broadcasts the full set of system information at least once, such that all terminals currently in its coverage area may refresh and/or check existing system information parts and additionally complement and store currently still missing system information parts.
  • the telecommunication system 30 which is preferably a cellular wireless access telecommunication system, includes at least an LA-cell 32, and SA-cells 33 and 34.
  • FIG. 6 also illustrates a user terminal 35.
  • Other elements not shown in FIG. 6, may also be present and are within the scope of the present invention.
  • Such "other elements” may include e.g. additional SA-cells, additional LA-cells, additional terminals, further network nodes such as e.g. management entities, as well as further elements to the telecommunication system and the backhaul links connecting each cell with the telecommunication system and/or with each other.
  • the LA-cell 32 is an LA-cell cell configured to at least be able to enable terminal 35 to camp on LA-cell 32 and to page the terminal 35 in a conventional manner known in the art. According to some embodiments of the present invention, the LA-cell 32 is also configured to receive service request messages from the terminal 35 indicating that a data connection needs to be established between the terminal 35 and one of the SA-cells for supporting wireless traffic (i.e. wireless exchange of user data), not shown in FIG 6.
  • wireless traffic i.e. wireless exchange of user data
  • LA-cell 32 is not primarily intended to be used to carry wireless user data from/to the terminal 35, it is not precluded that other signalling than paging or that also some user data traffic is carried via the LA-cell 32, for example low bit rate traffic (such as a voice call) for the full duration or for a part of the duration of the data session (call).
  • low bit rate traffic such as a voice call
  • the LA-cell 32 is typically configured to cover a larger geographical area with a smaller bit rate.
  • the geographical area where an idle terminal selects the LA cell to camp on is referred to as the coverage area of the LA-cell.
  • a terminal within that area is usually also capable of successfully receiving the system information and signalling messages from the LA-cell (for example a paging message). This is assumed to also apply in the reverse direction, i.e. when a terminal, camping on an LA-cell, transmits a signalling message (for example a service request message) to the LA cell it is camping on, the LA cell is usually capable of successfully receiving the message.
  • a signalling message for example a service request message
  • At least one LA-cell in FIG. 6, the LA-cell 32
  • the LA-cell 32 is fully operational or 'normally on' and is capable of supporting exchange of signalling messages with the terminals.
  • this may mean that the LA cell 32 is always fully functional ( ⁇ ').
  • power-saving options suitable for LA-cells may be applied to the LA-cell 32, meaning that the LA-cell 32 would not necessarily always be On'.
  • the terminal 35 may be a terminal operated by an actual human user, such as e.g. a mobile phone with which the user can make a voice call or browse the Internet, but may also be a smart phone or a data-centric terminal (e.g. laptop or tablet computer) operating without human intervention (e.g. sending/receiving e-mail), and may also be an MTC (Machine-Type Communications) device, such as e.g. a smart electricity meter, a car navigation device or a camera surveillance device.
  • MTC Machine-Type Communications
  • the terminal 35 may be in an active mode or in an idle mode. As used herein, the terminal 35 is said to be in an idle mode while there is no support for a wireless exchange of user data or traffic between the terminal 35 and the SA-cells 33 or 34. As used herein, the terminal 35 is said to be in an active mode when it is able to exchange data with at least one of the SA-cells 33, 34. Note that while these notions of idle mode and active mode may be comparable with the meaning of like terms in standardized conventional networks, as used herein, they do not necessarily coincide exactly with such standardized definitions.
  • the terminal 35 may support some form of power-saving options (i.e., be in a power-save mode or in an operational mode, where the terminal consumes less power in the power-save mode than in the operational mode). Since the differentiation between power-save and operational modes is based on the amount of power consumed by the terminal, while the differentiation between idle and active modes is based on the presence of the support for wireless exchange of user data with the SA- cells, a terminal may e.g. be in the operational mode but still be an idle terminal (or the terminal in the operational mode may be in active mode). Similarly, a terminal in a power-save mode can be either active or idle, depending on whether the terminal supports wireless exchange of user data with at least one of the SA-cells.
  • some form of power-saving options i.e., be in a power-save mode or in an operational mode, where the terminal consumes less power in the power-save mode than in the operational mode. Since the differentiation between power-save and operational modes is based
  • the terminal 35 in an idle mode may be assumed to 'camp' on at least the LA-cell 32, which may also be realized in a conventional manner.
  • the LA-cells may broadcast a pilot signal or a beacon signal which can be received by the terminal 35 which then uses the information contained in the received signal to select or re-select the LA-cell to camp on.
  • the signals transmitted by LA-cell 32 and received by the terminal 35 are illustrated as a solid arrow from the LA-cell 32 to the terminal 35.
  • the terminal 35 may be capable of informing the network about the change of location/routing area in order to facilitate the paging function of the LA-cell 32, not shown in
  • the SA-cells 33 and 34 are primarily intended to carry user data traffic from/to the terminal 35 over the data connections established for that purpose, e.g. via a dedicated channel. However, it is not precluded that also some other information and/or some signalling is carried via one or more of the SA-cells.
  • Each of the SA-cells 33 and 34 is typically configured for covering a smaller area with a higher bit rate, as opposed to the LA-cell 32. In a typical deployment scenario, the areas that can possibly be covered by nearby SA-cells may show a considerable overlap. In the intended coverage area of the wireless access network it may be assumed that at least one of the SA-cells 33, 34 is able to provide coverage.
  • An SA-cell is only fully operational when and to the extent that it is needed or, in other words, is 'normally off'.
  • An SA-cell is assumed to support at least one form of power-saving, e.g. a power-save mode or stand-by mode. To that end, an exemplary embodiment of FIG.
  • FIG. 6 illustrates that the SA-cell 33 is an SA-cell in a power-save mode (indicated in FIG. 6 as a white triangle), while the SA-cell 34 is an SA- cell in an active mode (indicated in FIG. 6 as a dark triangle).
  • the signals transmitted by active SA-cell 34 and received by the terminal 35 are illustrated as a solid arrow, while a possible signal transmitted by SA-cell 33, which is in power-save mode, and received by the terminal 35 is illustrated as a dashed arrow.
  • Each of the terminal 35, the LA-cell 32, and the SA-cells 33, 34 may include at least one or more of a communications interface for transmitting and receiving information, a memory unit for storing data (possibly received over the communications interfaces), and a processor for processing data and possibly running computer programs on, the communications interfaces, processors, and memory units appropriately configured for carrying out functionalities of these units described herein.
  • a communications interface for transmitting and receiving information
  • a memory unit for storing data (possibly received over the communications interfaces)
  • a processor for processing data and possibly running computer programs on, the communications interfaces, processors, and memory units appropriately configured for carrying out functionalities of these units described herein.
  • a terminal may have to communicate with both LA-cells and SA-cells, according to various embodiments of the present invention, at least three different configurations are envisioned for the terminal 35 to receive signals from and, where applicable, transmit signals to a cell of either such cell type.
  • a first configuration for the terminal 35 envisages an active terminal to simultaneously support two radio interfaces - an LA-cell radio interface for communicating with the LA-cell 32 (and possibly other LA-cells not shown in FIG. 6) and an SA-cell radio interface for communicating with the SA-cells 33, 34 (and possibly other SA-cells not shown in FIG. 6).
  • this configuration involves some more complexity than a terminal with only a single radio interface.
  • such a terminal needs only an LA-cell radio receiver so that the terminal can receive information from the LA-cell via the LA-cell radio interface but the terminal does not need to have capabilities to also transmit information to the LA-cell.
  • other solutions e.g.
  • Such a terminal also needs an LA-cell radio transmitter so that the terminal can transmit information to the LA-cell. Because the exchange of signalling information with an LA-cell only requires low bit rate, the additional complexity, cost and energy consumption in maintaining the LA-cell radio interface may be kept low.
  • the terminal 35 in configuration (i) may, also in active mode, receive signals from and/or exchange data with the LA-cell 32 at any time.
  • a second configuration for the terminal 35 envisages a terminal in the active mode to support two radio interfaces, an LA-cell radio interface for the LA-cell(s) and an SA-cell radio interface for the SA-cell(s), in quickly alternating mode of operation, i.e. operating in time division mode.
  • such a terminal would have, at one moment, the LA-cell radio interface enabled and, at another moment, the SA-cell radio interface enabled.
  • the terminal 35 in configuration (ii) is in the active mode and actually exchanges data with the SA-cell 34 it is envisaged that the SA-cell radio interface is enabled for the larger part of the time.
  • the exchange of data with the SA-cell 34 is interrupted for only a brief period of time such that the interruption is not aggravating to the terminal user, e.g. less than a fraction of a second, such as 100 ms.
  • a terminal according to configuration (ii) may, also in active mode, reconfigure its radio interface from the SA-cell radio interface to the LA-cell radio interface and then receive signals from and/or exchange data with LA-cells at any time but only for a relatively brief period (e.g. 100 ms) before restoring its radio interface configuration to the SA-cell radio interface. In this manner, a quasi- simultaneous mode of operation may be achieved.
  • the operations of a terminal having reconfigured its radio interface to LA-cell and the SA-cell transmitting user data to the terminal (and/or transmitting system information to the terminal and possibly also to other terminals) may be synchronized to one other to the extent that an SA-cell does not transmit user data to a particular terminal (and/or transmit system information to this particular terminal and possibly to other terminals) in the period that the terminal has configured its radio interface for receiving data from the LA-cell.
  • Such an embodiment allows avoiding the SA-cell transmitting user data to the terminal in vain, and therewith wasting SA-cell resources.
  • occurrences of a terminal configuring its LA-cell radio interface need not be very frequent and the total time that the terminal has its LA-cell radio interface enabled may only comprise a relatively very small fraction of the time.
  • a third possible configuration for the terminal 35 envisages an active terminal supporting two radio interfaces (one for the LA-cell and one for the SA-cell) alternately, yet without the quickly alternating (succession of) operation modes as described for configuration (ii).
  • a quasi-simultaneous mode of operation as described for configuration (ii) is not used, e.g. because it is considered not necessary and/or because the implementation does not support a quick configuration, for example if reconfiguring the radio interface requires more time than to qualify as 'quickly', e.g. more than a second.
  • a terminal according to configuration (iii) is assumed to have its radio interface configured for the SA-cell for the duration of exchanging user data with an SA-cell.
  • the exchange of user data can be performed at the maximum rate possible, without requiring short interruptions as for configuration (ii).
  • an active terminal according to configuration (iii) may be unable to check whether it still is in the coverage area of the same LA-cell when the data session was established.
  • a system information modification of the LA-cell may be not noticed. Consequently, a terminal having concluded its data exchange via an SA-cell and after having reconfigured its radio interface to LA-cell, a cell search procedure may have to be performed and the LA-cell system information may need to be obtained.
  • the LA-cell radio interface and the SA-cell radio interface may be two separate physical radio interfaces, with separate RF front ends, or share the same physical radio interface (e.g. in the case that the LA-cell and the SA-cell operate in the same frequency band but on different carriers).
  • the "SA-cell radio interface” and "LA-cell radio interface” only differ in "soft" configurations of a physical radio interface.
  • a single physical radio interface may be sufficient which is either enabled as an LA-cell radio interface (while the SA-cell radio interface is disabled) or enabled as an SA-cell radio interface (while the LA-cell radio interface is disabled).
  • the term "enabled” for a cell type in the context of SA- cell or LA-cell radio interfaces being enabled or disabled is used to describe that the interface is able to receive signals from the cell type and to support an exchange of data (which may comprise any type of data such as user data, signalling data, network control messages, etc.) with the cell type, while the term “disabled” is used to describe that the interface is not able to receive signals from and not able to support such an exchange with the cell type.
  • the disabled radio interface could be a radio interface turned completely off, with no power supply being provided to the relevant part of the electronic components of the interface.
  • the radio interface may be considered to be “disabled” when it is simply not being used even though the interface itself is physically completely up and running. The latter embodiment could be advantageous because the time needed to enable the interface again would be minimum since there would be no or minimum delay in getting the disabled interface ready for operation when it needs to be enabled again.
  • Various other embodiments of how a radio interface could be considered to be disabled that are between these extreme embodiments would be known to a person skilled in the art and are intended to be within the coverage of the present invention.
  • FIG. 7 is a schematic illustration of coverage areas of an LA-cell and a plurality of SA- cells in a telecommunications network, according to one embodiment of the present invention.
  • an LA-cell 42 which could be the LA-cell 32 illustrated in FIG. 6, may have a relatively large coverage area, shown with a dashed circle 43.
  • the SA-cells 44 may have different, relatively smaller coverage areas, shown with solid circles, such as circles 45.
  • FIG. 7 further illustrates idle mode terminals 46 and active mode terminals 47 (the active mode terminals indicated as bold outlined terminals).
  • Each of the terminals 46 and 47 could be the terminal 35 illustrated in FIG. 6 and could be within one or more of the coverage areas 45.
  • the idle mode terminals 46 within the coverage area 43 of the LA-cell 42 are said to be camping on the LA-cell 42.
  • the SA-cells 44 having coverage areas 45 shown in white are intended to illustrate the SA-cells in the power-save mode, while the SA-cells 44 hav- ing coverage areas 45 shown in dark grey are intended to illustrate the SA-cells in the active mode and may have ongoing data sessions with one or more active terminals 47.
  • the coverage areas 43 and 45 do not have to be circular and do not have to cover an omnidirectional sector around the location of the base station (cell).
  • a typical example of the behaviour of the terminal 35 in an energy- efficient network may be as follows.
  • the terminal 35 When the terminal 35 has no need to exchange user data with the network (i.e. an idle terminal), it will camp on the LA-cell 32, much in the same way as in conventional networks an idle terminal camps on a cell.
  • the terminal 35 When the terminal 35 has a need to exchange user data with the network (i.e. needs to enter into an active mode) it establishes a data session with an appropriate SA-cell in the network, in FIG. 6 shown as the SA-cell 34.
  • the appropriate SA-cell may have previously been deactivated (i.e.
  • the terminal 35 may exchange user data (and possibly also signalling), e.g. via a dedicated channel, via/with the SA-cell 34.
  • the SA-cell 34 may then be deactivated (i.e. may be switched off or may enter into an energy-conserving state) if the SA-cell has no or only little remaining traffic (in the latter case after transferring remaining sessions to another SA-cell).
  • the terminal 35 will resume to idle mode, camping on an LA-cell, which may be the same LA-cell it was camping on before establishing the data session (i.e., the LA-cell 32) or it may be a different LA-cell if the terminal moved into another LA-cell's coverage area.
  • an LA-cell which may be the same LA-cell it was camping on before establishing the data session (i.e., the LA-cell 32) or it may be a different LA-cell if the terminal moved into another LA-cell's coverage area.
  • Solution # 2 LA-cell distributes LA-cell system information, SA-cell distributes SA- cell system information in an energy-efficient network
  • the terminal 35 is first assumed to be an active terminal configured to exchange user data with the SA-cell 34 via a data connection established between the terminal 35 and the SA-cell 34 for that purpose, e.g. via a dedicated channel.
  • Embodiments of solution # 2 address the problem of the terminal 35 obtaining SA-cell system information comprising system information regarding at least the SA-cell 34 and LA-cell system information regarding the LA-cell 32, as well as, possibly, system information regarding other SA-cells and other LA-cells in the network 30 which may be relevant for the terminal 35.
  • the LA-cell 32 transmits its LA-cell system information and the SA-cell 34 transmits its SA-cell system information and that the SA-cell radio interface and the LA-cell radio interface of the terminal 35 in the configuration (ii) are enabled alternately in a time-divided multiplexing mode, as is schematically illustrated in FIG. 8.
  • the LA-cells and the SA-cells may transmit their respective system information, as is schematically illustrated in FIG. 9 with the SA-cell 34 transmitting its system information via broadcast channel 51 , illustrated as a grey triangle, and/or via dedicated channels 52, 53, illustrated as double- pointed arrows, to the individual active terminals 35 and with the LA-cell 32 transmitting its system information via broadcast channel 54, illustrated as a dotted triangle.
  • the terminal 35 When the terminal 35 is in the idle mode, the terminal 35 is configured to receive transmission of the LA-cell system information by the LA-cell 32 that the terminal is camping on, via the LA-cell radio interface enabled for such an idle terminal.
  • the SA- cell radio interface may then be disabled.
  • the terminal 35 When the terminal 35 is in the active mode and actually exchanges data with the SA-cell 34 via its established data connection, for the larger part of the time, the SA-cell radio interface of the terminal 35 is enabled and the LA-cell radio interface is disabled. In that time, the terminal 35 may exchange user data with the SA-cell 34 as well as receive other signals, includ- ing system information, from the SA-cell 34 and the terminal 35 may also receive signals, including system information, from other SA-cells in the network 30.
  • the LA-cell radio interface of the active terminal 35 is enabled and the SA-cell radio interface is disabled.
  • the terminal 35 may receive signals, including system information, from the LA-cell 32 as well as, possibly, support a signalling connection via the LA-cell 32 and the terminal 35 may also receive sig- nals, including system information, from other LA-cells in the network 30.
  • a terminal in an active mode and exchanging data with an SA-cell via an SA-cell radio interface may be configured to temporarily interrupt or pause its exchange of user data with the SA-cell and to enable its LA-cell radio interface at one or more of particular times when the LA-cell or LA-cells are expected by the terminal to transmit their system information so that the terminal may receive LA-cell system information transmitted by one or more LA-cells.
  • Such a terminal is configured to receive the SA-cell system information from one or more SA-cells when the SA-cell radio interface is enabled.
  • solution # 1 can be applied to the distribu- tion of system information by each of the LA-cells and the SA-cells to be received by the terminal 35 via the corresponding radio interface, independent of the other radio interface.
  • FIG. 10 sets forth a flow diagram of method steps for obtaining system information regarding one or more SA-cells and system information regarding one or more LA-cells, according to one embodiment of the present invention. While the method steps are described in conjunction with FIG. 6, persons skilled in the art will recognize that any system configured to perform the method steps, in any order, is within the scope of the present invention.
  • the method begins in step 61 , where the terminal 35 is in the active mode and the SA- cell radio interface of the terminal 35 is enabled.
  • the terminal 35 then receives at least a part of the SA- cell system information regarding the SA-cell 34 from the SA-cell 34 via the SA-cell radio interface of the terminal (of course, the terminal 35 may also exchange data with the SA-cell 34).
  • the terminal 35 may then also receive SA-cell system information from other SA-cells relevant for the terminal 35.
  • the terminal 35 enables its LA-cell radio interface during one or more of a plurality of LA time periods to receive, in step 63, LA-cell system information for the LA-cell 32 via the enabled LA-cell radio interface.
  • the LA-cell 32 transmits its system information for only a fraction of the time, e.g. during 100 ms (or less). It is also preferred that the LA-cell transmits its system information in predetermined periods of time or at least starts transmitting its system information at predetermined moments in time, e.g. a cyclic repetition of 100 ms LA-cell system information transmission each second.
  • the pattern for transmitting the LA-cell system information may either be set by the LA-cell 32 itself or by some other network entity such as e.g. a network management or OAM (Operation, Administration and Maintenance) entity and/or a synchronization entity.
  • the active terminal When an indication of when the transmission of the LA-cell system information takes place is provided to the terminal 35, the active terminal is able to reconfigure its radio interface to LA-cell, e.g. just before the LA-cell system information transmission is expected to start, to receive the LA-cell system information and, optionally, also perform other LA-cell-related operations such as measuring its signal strength in order to assess whether the terminal 35 is still in the coverage area of the LA-cell 32. When that is finished, the terminal 35 may reconfigure its radio interface back to the SA-cell (and also may continue exchanging e.g. user data via the SA-cell 34).
  • the terminal 35 may configure one or more of its settings based, at least partially, on the received SA-cell system information and/or the received LA-cell system information.
  • the terminal 35 may be configured to store at least a part of the received system in- formation, both for the SA-cell(s) and the LA-cell(s), for future use.
  • the SA-cell system information transmitted by SA-cell 34 is not restricted to regard exclusively SA-cell 34, it may also regard one or more other, active or inactive, SA-cells in the network, e.g. neighbouring SA-cells, such as SA-cell 33 as shown in FIG. 6.
  • a terminal 35 receiving and storing also SA-cell system information regarding another SA-cell than just the serving SA-cell 34 is considered an advantage, e.g. in case of a handover to a different, e.g. neighbouring, SA-cell. Then, the system information or the most relevant part thereof regarding the new SA-cell can already be obtained by the terminal before performing the handover, instead of after the handover.
  • Such 'advanced' obtaining of system information regarding another cell than the serving cell facilitates the handover to be completed more quickly compared to the usual approach where most of the system information is only obtained after having performed the hando- ver.
  • the SA-cell may not yet be fully capable of transmitting its SA-cell system information such that a terminal 35 may advantageously use the stored system information for that particular SA-cell to configure itself for the handover.
  • the system information transmitted by LA-cell 32 is not restricted to regard exclusively LA-cell 32, but may also regard one or more other LA-cells in the network (not shown in FIG. 9), e.g. neighbouring LA-cells, though the above-mentioned advantages apply to the LA-cells to a lesser extent.
  • a similar advantage of storing system information applies to an active terminal, having kept up to data the LA-cell system infor- mation, and reverting back to idle mode when exchange of user data has been completed.
  • the terminal 35 when the terminal 35 becomes idle again, the terminal is likely to apply the stored LA-cell system information to configure its settings. In all cases it is preferred that the terminal is enabled to quickly check whether the stored system information for a particular cell (SA-cell or LA-cell) is still valid. This may be realised in a conventional manner, e.g. by a system information version numbering. For broadcasted sys- tern information, such version number is preferably frequently broadcasted; for system information provided via a dedicated channel it is suggested that the terminal transmits an indication of the stored system information version number to the cell and that the cell responds either with a confirmation that this version is still valid or with the most recent version number and provides the most recent (i.e.
  • the network 30 may be configured so that the terminal may obtain the SA-cell and the LA-cell system information, referred to herein as a "very simple configuration,” “more flexible configuration,” and “most flexible configuration,” which are described in greater detail below.
  • an SA-cell e.g. the SA-cell 34
  • an LA-cell e.g. the LA-cell 32
  • the LA-cell 34 transmits user data for the other 900 ms each second.
  • the predetermined peri- ods of time for the LA-cell system information transmission are reserved for allowing a terminal to receive and obtain the LA-cell system information and not for receiving user data via the SA-cell, thereby reducing the SA-cell's achievable throughput for user data, in this example to 90% compared to a situation where the SA-cell could transmit user data for 100% of the time.
  • the periods when the SA-cell may transmit user data will now be referred to in this example as "first periods" while the predetermined peri- ods when the LA-cell is configured to transmit its LA-cell system information may be referred to as
  • first and second periods While the first and second periods are configured to not overlap each other, they don't have to be adjacent periods (i.e., there may be gaps between these periods) as some additional margin may be applied, e.g. to allow the reconfiguration of a terminal's radio interface to be completed and to allow for some inaccuracies between the timing of both cell types.
  • an SA-cell may have more than a single LA-cell partially overlapping the SA-cell coverage area, the SA-cell for its first periods would be required to take into account the second periods of each of the relevant LA-cells.
  • the LA-cells synchronise their second periods to each other such that these occur as much as possible overlapping, e.g. substantially simultaneously.
  • the second periods of 100 ms each second would be used substantially simultaneously by all LA-cells relevant for the SA-cell. .
  • the SA-cell may transmit its system information.
  • the SA-cell may be configured to transmit SA-cell system information during the second period (i.e. the period when no user data is transmitted), possibly also in the gaps between the first and second periods but not during the first period.
  • the SA-cell system information may be transmitted at a relatively high data rate because, in these periods, the SA-cell does not need any transmit resources for user data and, thus, a large amount of SA-cell system information may be transmitted in a relatively short time.
  • the SA-cell may be configured to transmit SA-cell system information any time, including transmission of the SA-cell system information during the first periods, during the second periods, and/or during the gaps.
  • the SA-cell system information transmission rate may be set to a relatively high rate, e.g. to the rate comparable to that of the first alternative.
  • the SA-cell is not restricted in the periods in which it may receive user data from the terminal; the SA-cell may be configured for receiving any time, where the terminal may choose whether or not to transmit user data to the SA-cell.
  • TDD Time Division Duplex
  • the LA-cell may be configured to transmit LA-cell system information for an active terminal only during the second period (i.e. not during the first period and also not in the gaps).
  • the LA-cell may be configured to also transmit some LA-cell system information outside the second period, e.g. system information not intended for an idle terminal and/or (partially) the same system information transmitted in a different format (e.g. at a lower bit rate, simpler coding, etc.) to better suit an idle terminal.
  • the exchange of data via an LA-cell e.g. for supporting a dedicated signalling connection and/or the exchange of some user data via the LA-cell, may be performed any time (in case of TDD, of course, taking into acount the assigned time slots as mentioned above).
  • the different LA-cells may be configured to synchronize transmission of their system information to occur substantially simultaneously, e.g. some time within the time period of 100 ms.
  • An advantage of such implementation is that the SA-cell needs not differentiate between terminals and/or between the LA-cells to which the terminals may be associated and that the SA-cell needs only schedule a single user data transmission-free period of 100 ms.
  • a disadvantage of such implementation may be that the terminal may possibly receive and acquire system information from only a single LA-cell in any one 100 ms time period.
  • the different LA-cells may be configured to synchronize transmission of their system information to occur substantially in consecutive periods of e.g.
  • the terminal has the advantage of being able to receive and acquire system information from several (e.g. two) LA-cells in the corresponding consecutive 100 ms time slots.
  • the disadvantage of such an implementation is a further reduction of the achievable SA-cell throughput of user data and, possibly, the need of a per-terminal (or at least per pair of LA-cells) scheduling of SA-cell transmission-free periods.
  • An active terminal not in need for any LA-cell system information may be configured to keep its radio interface configured to the SA-cell, may transmit user data any time, may receive user data during the first periods and may receive SA-cell system information during the second periods (and possibly also during the gaps).
  • An active terminal that wants to receive LA-cell system information may be configured to continue transmitting and/or receiving user data during the first period. Then, towards the end of a first period, the terminal would reconfigure its radio interface to the LA-cell (a time gap may facilitate this), receive the LA-cell system information, and, not later than towards the end of the second period, reconfigure its radio interface to the SA-cell (a time gap, again, may facilitate this). After that, the terminal may resume transmitting and/or receiving user data via the SA-cell during the next first period.
  • the transmissions of system information by the SA-cell and the LA-cell are coordinated to occur substantially simultaneously during the second periods, where the SA-cell system information transmission may additionally take place in gaps between the first and second periods.
  • An SA-cell may transmit user data to a particular terminal either continuously or an
  • SA-cell may transmit user data with interruptions or pauses in downlink user data transmission, where the pauses in the SA-cell user data transmission are predetermined and specified, indicated, and/or commanded to the SA-cell beforehand by the particular terminal.
  • the terminal is enabled full control over if and when the terminal would need an SA-cell user data transmission-free period, e.g. for the pur- pose of receiving system information from one or more LA-cells, making signal level measurements on one or more LA-cells, and/or for contacting (e.g. exchanging signalling information with) one or more LA- cells.
  • This also allows a terminal-specific and occasion-specific sizing of the SA-cell's user data transmission-free period.
  • a terminal which implements a slow reconfiguration of its radio interface may command a longer SA-cell transmission-free period than another terminal implementing a quick re- configuration of its radio interface or a terminal requiring only a particular system information part may command a shorter SA-cell transmission-free period than the exemplified 100 ms, positioned around the expected transmission time of the particular system information part, than another terminal aiming to receive and obtain the full system information in an e.g. 100 ms period.
  • the SA-cell when an SA-cell interrupts its downlink user data transmission to a particular terminal, the SA-cell may continue transmitting user data to other terminals for which no interruption is specified.
  • the SA-cell may be configured to transmit its SA-cell system information in the conventional, near-continuous, manner at a modest bit rate.
  • the SA-cell may be configured to transmit its SA-cell system information in short bursts at a higher bit rate.
  • the SA-cell may be configured to receive user data at any time; the terminal may choose whether or not to transmit user data to the SA-cell (in case of TDD, of course, taking into acount the assigned time slots as mentioned above).
  • the LA-cell may be configured to transmit its LA-cell system information preferably in short bursts and preferably according to a predetermined schedule (e.g. periodically), predetermined by the LA-cell or other network node, such as e.g. some network management entity or a synchronization entity, and known to or detectable by a terminal monitoring the LA-cell.
  • a predetermined schedule e.g. periodically
  • the LA-cell or other network node such as e.g. some network management entity or a synchronization entity, and known to or detectable by a terminal monitoring the LA-cell.
  • an LA-cell also transmits some LA-cell system information outside the second period.
  • the exchange of data via an LA-cell may be performed any time (in case of TDD, of course, taking into acount the assigned time slots as mentioned above).
  • An active terminal not in need for any LA-cell system information may keep its radio interface configured to the SA-cell, may transmit user data any time, may receive user data any time and may receive SA-cell system information any time (at least when the SA-cell system information is transmitted).
  • An active terminal that needs LA-cell system information may be configured to first provide an indication to the SA-cell with which the terminal has a data connection as to when the SA-cell should pause (interrupt) its downlink transmission of user data to that particular terminal.
  • the terminal may provide an indication of e.g. a single interruption with specified start time and end time, a single interrup- tion with specified start time and duration of the interruption, or multiple interruptions, e.g. according to a periodic schedule.
  • a period of time when the SA-cell downlink user data transmission is paused (interrupted) may be compared to the second time period described in the "very simple configuration," with the difference that, in this more flexible configuration, such a period is terminal-defined and terminal-specific and may occur not at all, may occur once or may occur repeatedly (possibly with different durations).
  • the terminal after having provided an indication to the SA-cell, may then continue transmitting and/or receiving user data until the interruption start time. At or after the start time, the terminal may reconfigure its radio interface to the LA-cell. The time to do so is assumed to be known to the terminal and is assumed to be taken into account when specifying the downlink user data interruption start time to the SA-cell.
  • the terminal with enabled LA-cell radio interface may then receive LA-cell system information or at least the relevant part of that information, and, not later than towards the interruption end time, reconfigure its radio interface back to the SA-cell. Similar to the time for reconfiguring the terminal radio interface to the LA- cell, the time to reconfigure the terminal radio interface to the SA-cell is assumed to be known to the terminal and is assumed to be taken into account when specifying the downlink user data interruption end time to the SA-cell. The terminal may then resume transmitting and/or receiving user data from the interruption end time onwards.
  • this configuration does not require a coordination of the transmission of system information by an SA-cell and an LA-cell.
  • a terminal that needs to monitor LA-cell system information, and during those times ('second time periods') is unable to monitor the SA-cell system information would repeatedly and consistently miss all SA-cell system information. This could happen if SA-cell system information is transmitted in short bursts coinciding with the LA-cell system information transmissions.
  • the terminal could also repeatedly and consistently miss a particular part of SA-cell system information even if the SA-cell system information is transmitted substantially continuously.
  • the SA-cell and the LA-cell would synchronize transmission of their respective system information so that the repetition rate of SA-cell system information transmission differs from the repetition rate of LA-cell system information.
  • the part of the SA-cell system information that the terminal may miss would not be re- peatedly and consistently the same part of the SA-cell system information but would shift along the
  • SA-cell system information This cold be realised, for example, by selecting an SA-cell system information repetition time that is either shorter or longer than the LA-cell system information repetition time by a time that corresponds to the (presumably short) duration of the LA-cell system information transmission for an active terminal (i.e. the duration of a second period).
  • Alternative solutions are also possible, such as a terminal skipping a second period and keeping its radio interface configured to SA-cell in order to receive and obtain the SA-cell system information or a terminal explicitly requesting, e.g. via the dedicated channel used for the exchange of user data, the SA-cell to provide some specified SA-cell system information to the terminal, e.g. again via the dedicated channel used for the exchange of user data, in which case applying options # 2 and # 5 of solution # 1 may be particularly advantageous.
  • an SA-cell may have a coverage area that is, at least partially, overlapped by the coverage area of multiple LA-cells, in this configuration, it is not required that LA-cells nearby each other synchronize their LA-cell system information transmission to occur substantially simultaneously.
  • a terminal may indicate and/or command an interruption of the SA-cell downlink user data transmission corresponding to the period in which the LA-cell (i.e., the particular LA-cell the terminal desires to monitor) transmits its LA-cell system information.
  • synchronized LA-cell system information transmission may still be implemented. Such an implementation may be advantageous for the terminal because no different interruption periods need to be specified for different LA-cells.
  • Most flexible configuration may be advantageous for the terminal because no different interruption periods need to be specified for different LA-cells.
  • This configuration largely corresponds to the "more flexible" configuration described above, where the start and the end of an SA-cell downlink user data interruption (i.e., pause and resume downlink user data transmission) is specified by the active terminal moment-by-moment.
  • the terminal may send a command to pause the SA-cell downlink user data transmission without specifying a time instant or with specification of a particular time instant in the future to which the command applies.
  • the SA-cell receiving the command may be configured to interpret a command without time specification as to relate to the current moment, i.e. to be applied immediately or as soon as reasonably possible. For example, after receiving such a command for an immediate pause, the SA-cell may be configured to complete e.g. the current transmission block or frame of user data, and then cease any further transmission to that terminal. After receiving a command for an immediate resume, the SA-cell may be configured to immediately resume transmission to that terminal.
  • the terminal may send a command to pause the SA-cell downlink user data transmission at some specified time.
  • An SA-cell receiving a time-specified pause command may be configured to interpret the command as that SA-cell transmission to that terminal must be ceased at the specified time at the latest.
  • a time-specified resume command indicates that the SA-cell may resume transmission to that terminal from the specified time at the earliest.
  • Solution # 3 LA-cell distributes LA-cell system information and SA-cell system information in an energy-efficient network
  • the terminal 35 is first assumed to be an idle terminal which does not exchange user data via the SA-cells 33, 34, and is camping on the LA-cell 32.
  • the terminal 35 may also become active where it would exchange user data with the SA-cell 34 via a data connection established between the terminal 35 and the SA-cell 34 for that purpose, e.g. by using a dedicated channel.
  • Embodiments of solution # 3 address the problem of the terminal 35 obtaining SA-cell system information comprising system information regarding at least the SA-cell 34 and LA-cell system information regarding the LA-cell 32, as well as, possibly, system information regarding other SA-cells and other LA-cells in the network 30 which may be relevant for the terminal 35.
  • Embodiments of this solution are based on the idea that an LA-cell, e.g. the LA-cell 32, may be used to transmit LA-cell system information as well as SA-cell system information for at least some of the SA-cells possibly relevant for the terminal in the coverage area of the LA-cell.
  • Solution # 3 may be separated into two main embodiments, illustrated in FIGs. 1 1 and 12, respectively.
  • the LA-cell 32 uses a broadcast/common channel to transmit all of the system information for the terminals.
  • the LA-cell 32 uses one or more dedicated signalling channels for transmitting at least some of the system information to individual terminals.
  • FIG. 1 1 is a schematic illustration of an LA-cell providing both LA-cell system information and SA-cell system information to a terminal, according to one embodiment of the present invention.
  • the embodiment shown in FIG. 1 1 illustrates that the LA-cell 32 transmit its system information as well as the system information for one or more SA-cells relevant for the terminal 35 via broadcast channel 71.
  • An idle terminal then needs only to enable its LA-cell radio interface, at least for the duration the LA-cell system information broadcast channel is monitored. This enables an idle terminal to acquire all system information for the LA-cell and for all SA-cells possibly relevant in the LA-cell's coverage area.
  • An idle terminal may store the acquired system information and also keep it up to date.
  • An idle terminal may, further, use the stored system information for a particular SA-cell when establishing a data session with the particular SA-cell.
  • Such operation of the terminal is supported by any one of the terminal configurations (i), (ii), and (iii), described above.
  • Each of the active terminals exchanging user data with the SA-cell 34 via dedicated data channels 72, 73, and 74, shown in FIG. 1 1 may further be configured to monitor the system information broadcasted by the LA-cell 32.
  • the terminal 35 may be configured to monitor the LA-cell and SA-cell system information broadcasted by the LA-cell 32 either periodically or upon receiving a trigger to do so.
  • an active terminal is configured to use its SA-cell radio interface to exchange user data via the SA-cell 34, possibly continuously and/or to the extent needed for the user data exchange.
  • the terminal is configured to occasionally enable its LA-cell radio interface for a relatively short period of time, e.g. periodically or upon receiving a trigger to do so, in order to monitor the LA-cell system information broadcast by the LA-cell 32, the broadcast channel 71 comprising LA-cell and SA-cell system information.
  • One advantage of such configuration is that the exchange of user data via the SA-cell may continue uninterrupted.
  • the terminal however, needs to support two radio interfaces simultaneously, at least for a short period of time, which results in higher hardware complexity.
  • an active terminal may be configured to alternate between the two radio interfaces.
  • the terminal has the SA-cell radio interface enabled to support the exchange of user data via the SA-cell 34.
  • the LA-cell radio interface is then disabled.
  • the terminal has only the LA-cell radio interface enabled in order to monitor the LA-cell system information broadcast channel 71 comprising LA-cell and SA-cell system information.
  • the SA-cell radio interface is then disabled.
  • the SA-cell system information may be grouped per SA-cell or group of SA-cells.
  • the LA-cell 32 may be configured to transmit the SA-cell system information only when and to the extent needed, e.g. only for those SA-cells that are active or are shortly to be activated.
  • the LA-cell 32 may be configured to transmit the system information of all SA-cells, e.g. including an indication about the
  • both a terminal in idle mode and a terminal in active mode are able to acquire, store and keep up-to-date the system information for their respective LA-cell and SA-cells by only monitoring the LA-cell's broadcast channel. Since the system information can be made available to the terminal even before the terminal may need this information, this approach allows speeding up the procedure of establishing a data session via an active SA-cell, the procedure of establishing a data session via a to-be-activated SA-cell, and the procedure of making a handover from one SA-cell to another SA-cell.
  • the set of cells for which the LA-cell 32 distributes system information may be extended further, e.g. to system information regarding neighbouring LA-cells and/or to system information regarding SA-cells that are outside but near the coverage area of the LA-cell 32.
  • a further refinement to the embodiment illustrated in FIG. 1 1 is to provide a trigger signal or trigger message to an active terminal in case a relevant part of the system information is modi- fied.
  • a trigger signal or signal message may e.g. be transmitted by the network via a dedicated connection to the terminal or may be broadcasted by one or more SA-cells in the network.
  • the trigger may optionally also indicate to which cell or cells the modification is relevant. A terminal receiving such a trigger signal or message is thus notified about a modification to some of the system information and that it may be relevant to the terminal to obtain the modified system information.
  • an active terminal may interpret some event as a trigger, for example when the terminal performs, e.g. due to mobility, a handover from an old SA-cell to a new SA-cell and needs to obtain, update, or verify the system information of the new SA-cell.
  • Providing a trigger to active terminals relieves the active terminals from performing regular, e.g. periodic, monitoring of the LA-cell broadcast channel for possible modifications, which could be an advantage in particular with the terminal configuration (ii).
  • the embodiment illustrated in FIG. 1 1 provides an advantage that a terminal is enabled to acquire the system information of all SA-cells in the LA-cell's coverage area and to store this information for later use.
  • the terminal is enabled to more quickly apply the settings relevant for the SA-cell compared to a situation where the terminal typically only acquires most of the system information for the SA-cell when session establishment or handover to the SA-cell has been completed.
  • This embodiment also enables distribution of SA-cell system information to idle terminals beforehand, i.e. before a terminal sets up a data session, even if there is no SA-cell active in the neighbourhood of the idle terminal.
  • a dedicated signalling approach can be used. This is illustrated in FIG. 12, schematically illustrating that the LA-cell 32 transmits its system information as well as the system information regarding one or more SA-cells relevant for the idle terminals 35a via a broadcast channel 81 , while providing SA-cell system information and/or LA-cell system information and modifications thereof to an active terminal 35b via a dedicated signalling channel 82.
  • the LA-cell 32 may be configured to provide, via dedicated signalling connection 82, all the relevant system information regarding the SA-cell that is selected to support the session.
  • the dedicated signalling channel 82 via the LA-cell 32 may be used to transmit the modified system information to the active terminal 35b.
  • an active terminal may use its SA-cell radio interface to exchange user data via the SA-cell 34, possibly continuously and/or to the extent needed for the user data exchange.
  • the terminal 35b is configured to occasionally enable its LA-cell radio interface for a relatively short period of time, e.g. periodically or on receiving a trigger to do so, in order to support the dedicated signalling connection 82 via the LA-cell in order to receive any modifications (updates) there may be to the LA-cell system information regarding LA-cell 32 or to the SA-cell system information regarding any of the SA-cells 34.
  • the advantage of such implementation is that the exchange of user data via the SA-cell 34 may continue uninterrupted.
  • the terminal 35b needs to support two radio interfaces simultaneously, at least for a short period of time, which results in higher hardware complexity.
  • an active terminal may be configured to alternate between the two radio interfaces.
  • the terminal has only the SA-cell radio interface enabled to support the exchange of user data via the SA-cell 34, while for the smaller part of the time the terminal has only its LA-cell radio interface enabled in order to receive any modifications (updates) there may be to the LA-cell system information regarding LA-cell 32 or to the SA-cell system information regarding any of the SA-cells 34.
  • FIG. 12 is expected to be more energy-efficient than that of FIG. 1 1.
  • this embodiment may have advantages other than those related to energy efficiency of system information distribution. For example, consider that a mobile terminal may have to frequently handover to a different SA-cell and that in each handover procedure there is a possibility of failure, possibly losing all contact between the network and the terminal. In such a scenario of frequent and error-prone handovers, it may be very attractive to have a stable and consistent signalling connection via the LA-cell 32, via which signalling connection a failed handover may be quickly repaired. Then, it may make sense to provide the terminal with the required SA-cell system information parts via the LA-cell's signalling connection, as described above.
  • the terminal 35 is first assumed to be an idle terminal which does not exchange user data via the SA-cells 33, 34, and is camping on the LA-cell 32.
  • the terminal 35 may also become active where it would exchange user data with the SA-cell 34 via a data connection established between the terminal 35 and the SA-cell 34 for that purpose, e.g. using a dedicated channel.
  • Embodiments of solution # 4 address the problem of the terminal 35 obtaining SA-cell system information comprising system information regarding at least the SA-cell 34 and LA-cell system information regarding the LA-cell 32, as well as, possibly, system information regarding other SA-cells and other LA-cells in the network 30 which may be relevant for the terminal 35.
  • Embodiments of this solution are based on the idea that an SA-cell, e.g. the SA-cell 34, may be used to transmit SA-cell system information as well as LA-cell system information for at least some of the LA-cells possibly relevant for the terminal in the coverage area of the SA-cell.
  • Solution # 4 may be separated into two main embodiments, illustrated in FIGs. 13 and 14, respectively.
  • the SA-cell 34 uses a broadcast/common channel to transmit all of the system information for the terminals.
  • the SA-cell 34 uses its dedicated channels with the active terminals for transmitting at least some of the system information to individual terminals.
  • FIG. 13 is a schematic illustration of an SA-cell providing both SA-cell system information and LA-cell system information to a terminal, according to one embodiment of the present invention.
  • the embodiment shown in FIG. 13 illustrates that the SA-cell 34 transmit its system information as well as the system information for one or more LA-cells relevant for the active terminals 35b via a broadcast channel 91 (in FIG. 13 illustrated as a grey triangle).
  • the SA-cell 34 may also include system information regarding neighbouring SA-cells into the broadcast channel 91.
  • the SA- cell 34 also has established data connections 92, 93, and 94 (e.g via a dedicated channel), with each of the active terminals 35b.
  • the LA-cell is configured to notify the modification to all SA-cells which may be relevant to the LA-cell's coverage area, as shown with an arrow 95 in FIG. 13.
  • a notification may be provided e.g. via the access net- work interface analogous to e.g. the X2 interface in LTE.
  • the SA-cell 34 receiving such a notification will then broadcast a notification of modified system information and the modified LA-cell system information via the broadcast channel 91 .
  • the SA-cell 34 also broadcasts system information of another (e.g. neighbouring) SA-cell, the same applies to the modified system information of a neighbouring SA-cell, i.e.
  • the other SA-cell is configured to notify the relevant (e.g. neighbour) SA-cells (not shown in FIG. 13) and the SA-cell 34 will then broadcast a notification of modified system information and the modified SA-cell system information regarding the another SA-cell via the broadcast channel 91.
  • An active terminal 35b receiving a notification of modified system information obtains the modified system information regarding the LA-cell and/or regarding the another SA-cell via the broadcast channel 91 of the serving SA-cell 34.
  • the embodiment illustrated in FIG. 13 is very attractive from the view point of energy efficiency.
  • the LA-cell system information e.g. the LA-cell network, the LA-cell identity, various parameters related to the LA-cell broadcast channel, the LA-cell neighbour cell list, etc.
  • this gain in energy- efficiency applies mostly to the part of the LA-cell system information that is relevant only for active terminals, such as e.g. handover parameters.
  • the LA-cell system information part relevant for idle terminals may also be transmitted by the SA-cell 34, which provides an advantage of this information being available to the active terminal 35b for a very quick cell search and/or cell re-selection after concluding the data session.
  • this embodiment may result in duplicate transmission of this LA-cell system information, somewhat reducing the energy efficiency gain.
  • An SA-cell broadcasting at least some LA-cell system information of one or more LA-cells with which it shares some coverage area may have an additional advantage of providing an active terminal with information regarding the relevant LA-cell(s) without requiring the terminal to use its LA-cell radio interface. For example, when the SA-cell 34 would broadcast some system information for a single LA-cell, an active terminal receiving this system information may conclude that, when it would conclude the data session, it would almost certainly find itself re-camping on that particular LA-cell.
  • the terminal may conclude that, when it would conclude the data session, it would almost certainly find itself to make a selection between those sole two prime candidates for re-camping.
  • transmission of the LA-cell system information for the two LA-cells may trigger the terminal to perform
  • the terminal While providing all system information for those (possibly multiple) LA-cells may not be the most energy efficient from the narrow point of view of distributing the LA-cell's system information, it may nevertheless be beneficial for a terminal with terminal configuration (ii) because doing so may significantly reduce the time period for which the, typically low data rate, LA-cell radio interface needs to be enabled.
  • terminal configuration (iii) described above, the terminal only needs to acquire the LA-cell system information distributed by the SA-cell in which it concludes its data session.
  • the number of LA-cells for which system information is distributed by a given SA-cell is likely to be more limited, e.g. one, two, or three LA-cells, thus speeding up the cell search and/or cell re-selection procedure for the terminal, because it already obtained the relevant system information for these LA-cells.
  • a dedicated signalling approach can be used. This is illustrated in FIG. 14, schematically illustrating that the SA-cell 34 transmits LA-cell system information or a modification regarding that information and, optionally, also SA-cell system information regarding other (e.g. neighbouring) SA-cells and modifications thereof, to the active terminals 35b via the dedicated signalling channels 102-104 established with these terminals, shown in FIG. 14 as solid arrows for transmission of user data via the dedicated channels, similar to channels 92-94 of FIG. 13, and additional dashed arrows for transmission of the system information and/or modification thereof via the dedicated signalling channels 102-104.
  • a broadcast channel 101 (in FIG. 14 illustrated as a grey triangle) is used by the SA-cell 34 to broadcast its SA-cell system information for the active terminals 35b, similar to the broadcast channel 91 described above.
  • the LA-cell is configured to notify the modification to all SA-cells which may be relevant to the LA-cell's coverage area, as shown with an arrow 105 in FIG. 14, similar to the notification 95 described above.
  • the broadcast channel 106 for the LA-cell 32 to transmit at least some of the LA-cell system information, e.g. the LA-cell network, the LA-cell identity, various parameters related to the LA-cell broadcast channel, the LA-cell neighbour cell list, etc., in order to sup- port idle terminals 35a is similar to the broadcast channel 96 described above.
  • an active terminal does not need the LA-cell system information before conclusion of the session and resuming to idle mode, e.g. if for an active terminal no LA-cell handover is foreseen, it is even more efficient for the SA-cell to refrain from transmitting LA-cell system information modifications and/or refrain from providing indications of moving into another LA-cell coverage area until at conclusion of the session. Then, for example as part of the data connection release procedure, it suffices that only that SA-cell provides the terminal with the most recent LA-cell system information via the corresponding dedicated signalling channel 102-104. In this manner, it may be avoided to transmit possibly numerous LA-cell system information modifications and/or indications of modified LA-cell coverage area while the terminal is still active and not actually needs such LA-cell system information. Because the dedicated signalling channels 102-104 are assumed to support a high bit rate, the transfer of this LA-cell system information can be completed without significant delay compared to the situation that each modification is transmitted immediately to the terminals 35b.
  • the embodiment illustrated in FIG. 14 is expected to be the most energy-efficient, considering that using a dedicated channel is more energy-efficient than a broadcast channel and considering that an SA-cell has only small size and that, therefore, it is less likely that more than a single terminal receiving a broadcast or common channel will benefit from the transmitted system information.
  • the additional advantages as described above for the use of broadcast/common channel embodiment as shown in FIG. 13 also apply to this embodiment.
  • Embodiments of the solutions # 3 and # 4 described above may also be combined.
  • embodiments of the solution # 3 could be used for distributing appropriate SA-cell and LA-cell system information for idle terminals
  • embodiments of the solution # 4 could be used for distributing appropriate SA-cell and LA-cell system information for active terminals.
  • an LA-cell may be configured to transmit appropriate SA-cell and LA-cell system information for terminals in the idle mode
  • an SA-cell may be configured to transmit appropriate SA-cell and LA-cell system information for terminals in the active mode.
  • solution # 1 may be advantageously applied to the SA-cells and LA-cells distributing SA-cell and/or LA-cell system information in accordance with solutions # 2-4.
  • Various embodiments of the invention may be implemented as program products for use with a computer system.
  • the program(s) of the program product define functions of the embodiments
  • Non-writable storage media e.g., read-only memory devices within a computer such as CD- ROM disks readable by a CD-ROM drive, ROM chips or any type of solid-state non-volatile semiconductor memory
  • writable storage media e.g., floppy disks within a diskette drive or hard-disk drive or any type of solid-state random-access semiconductor memory, flash memory
  • the computer program may be run on the processors described herein.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Computer Security & Cryptography (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

L'invention concerne un système de réseau de télécommunications à accès sans fil comprenant au moins une cellule SA avec laquelle un terminal en mode actif est configuré pour avoir une connexion de données établie et une cellule LA sur laquelle le terminal en mode veille est configuré pour être mis en garde. Un procédé permettant au terminal d'obtenir au moins des informations systèmes de cellule LA et des informations systèmes de cellule SA consiste, quand le terminal est en mode actif et une interface radio de cellule SA du terminal est activée, à recevoir, par le terminal, au moins une première partie des informations systèmes de cellule SA et au moins une première partie des informations systèmes de cellule LA en provenance de la cellule SA par l'interface radio de cellule SA.
PCT/EP2012/071967 2011-11-08 2012-11-07 Distribution d'informations systèmes dans un système de télécommunications à accès sans fil WO2013068369A1 (fr)

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US10856223B2 (en) 2014-07-09 2020-12-01 Nederlandse Organisatie Voor Toegepast-Natuurwetenschappelijk Onderzoek Tno Method of, and transceiver station and mobile terminal for, distributing system information in a cellular telecommunications network
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CN113115406A (zh) * 2015-06-11 2021-07-13 苹果公司 用于无线通信的低开销系统信息获取
US10588064B2 (en) 2015-10-29 2020-03-10 Huawei Technologies Co., Ltd. Method for transmitting system information, base station, terminal, and system
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EP2777330A1 (fr) 2014-09-17
JP2017216733A (ja) 2017-12-07
JP5856689B2 (ja) 2016-02-10
JP2016106452A (ja) 2016-06-16
JP2015502062A (ja) 2015-01-19
JP2019062559A (ja) 2019-04-18

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