Abstract:
A battery sharing method to increase the service life of the batteries of PMR terminals having important uses, such as the terminal of the head of a group such as the police, firefighters, or the like, is disclosed. The technique is based on the detection of neighboring networks and/or neighboring nodes. The detection is facilitated by reiterating a selection (or reselection) of cells and a handover (HO)/vertical handover (VHO) procedure, while relaying and coordinating transmission and reception. The aim of the techniques is to improve communications as well as the duration thereof, in order to enable improved management of the battery of each terminal and to broaden coverage in areas that are not served by a network.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a method for establishing a strategy for saving the energy of mobile terminal batteries. The invention is particularly advantageously applicable to private mobile radio or professional mobile radio (PMR) digital mobile systems. The object of the invention has a further interest for what wireless terminals, known as mobile, intended to very high rates, such as wide band technologies based on LTE (Long Term Evolution), or 4G (4 th  generation of cellular network). 
       STATE OF THE ART AND TECHNICAL PROBLEMS ENCOUNTERED 
       [0002]    In the field of private mobile radio communication digital systems, called PMR hereinafter, there is a need to develop PMR networks based on narrowband technologies, and from the legacy generation, into PMR networks based on broadband technologies, or even very high speed broadband. By narrowband-based PMR network, it is meant a network of the TETRA, or TETRAPOL, or P25 technology. By broadband-based PMR network, it is meant a network of the IP-WAN technology. By IP-WAN networks, it is meant networks based on the WIFI (Wireless Fidelity), and/or WIMAX (Worldwide Interoperability for Microwave Access), and/or 2G (2 nd  generation of cellular network), and/or 3G (3 rd  generation of cellular network), and/or LTE (Long term Evolution), 4G (4 th  Generation) technologies and/or future technologies. 
         [0003]    This evolution is intended to enable new services based on IP (Internet Protocol) to be integrated, but also to continue to support services of PMR networks from prior generations, such as radio, as well as all the interfaces. 
         [0004]    However, within the scope of the evolution of such a PMR network into very high speed mobile broadband, such as LTE, or 4G, the most critical problem encountered is the low service life of the batteries of the terminals using the aforementioned technologies. 
         [0005]    There is thus a need to determine a technique or a set of techniques enabling the energy from each battery of the terminal to be saved. 
       DISCLOSURE OF THE INVENTION 
       [0006]    The present invention aims at solving all the drawbacks of the state of the art. For this, the invention provides a method for establishing a strategy for saving the energy of mobile terminal batteries, according to any of the characteristics of claim  1  and the following claims, allowing a better energy storage based on the battery level of each terminal, in order to reduce the energy consumption of the entire LTE- or 4G-type PMR telecommunication system. 
         [0007]    The object of the invention is based on the concept of battery sharing, which aims at increasing the service life of batteries for these PMR terminals which have important uses, such as for example the terminal of the head of a group such as the police, firefighters, or the like. This technique is based on the detection of neighbouring networks and/or neighbouring nodes. This detection is facilitated by reiterating a selection (or reselection) of cells and a Handover (HO)/Vertical Handover (VHO) procedure, while relaying and coordinating transmission and reception. The aim of these techniques according to the invention is to improve communications as well as their durations, in order on the one hand, to enable improved management of the battery of each terminal and, on the other hand, to broaden coverage in areas that are not served by a network (also called a “black” area in the trade jargon). 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0008]    The invention will be better understood upon reading the following description and upon examining the accompanying figures. These are given only by way of illustrating, but in no way limiting, purposes for the invention. The figures show: 
           [0009]      FIGS. 1-2 : schematic representations of a terminal battery, according to the state of the art; 
           [0010]      FIG. 3 : a schematic representation of the system, according to one embodiment of the invention, enabling the method according to  FIG. 4  to be implemented; 
           [0011]      FIG. 4 : a functional diagram of the operation of the method, according to one embodiment of the invention. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0012]    It is now noticed that the figures are not drawn to the scale. 
         [0013]    The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the characteristics only apply to a single embodiment. Simple characteristics of different embodiments can also be combined to provide other embodiments. 
         [0014]    The invention that will be hereinafter described has the purpose to enable a detection of networks as well as neighbouring nodes, while simultaneously enabling coordinating transmission and reception, depending on the battery level of a terminal. Thereby, the invention provides assistance in improving energy efficiency, as well as in improving the service life of batteries. More particularly, the improvements provided by the invention relate to batteries intended to 4G (4 th  generation of cellular network), or LTE (Long term Evolution) technology terminals, said terminals being provided, in a preferred embodiment, for a so-called PMR (Private/Professional Mobile Radio) use. 
         [0015]    The overall purpose of the invention is to allow a much more efficient management of the battery level of each terminal, for said battery not to be too quickly depleted, during an intervention of a user group (police gendarmerie, special unit, firefighters, or any other intervention unit entitled to use such a mobile terminal) on a geographic region, for example, and to come to be short of energy during said intervention or during next uses of said terminal. 
         [0016]    Consequently, the invention allows management of the battery  10  such that a terminal having a high level  11  of the battery  10  is in charge of the activities or tasks that are the most energy consuming, whereas a terminal having a low level  13  of the battery  10  is mainly in charge only of its operation and attempts to carry out some essential activities. 
         [0017]    The present invention relates to a method for detecting neighbouring networks located around a specific terminal. This embodiment according to the invention is based on IEEE 802.21 standard, and enables a terminal to be able either to reselect a new cell, or to carry out a Handover (HO), or to carry out a Vertical Handover (or VHO). By the term Handover, it is meant the fact that in mobile radio-communication cellular systems, it is possible to switch transmission means used by a communication without interrupting the same. This term Handover or HO will be used in the rest of the description referring to this definition. 
         [0018]    Likewise, by the term Vertical Handover, it is meant the possibility for a mobile radio-communication cellular system, to switch transmission means used by a communication, to an access to the support of another cellular network infrastructure, without interrupting the already established communication. The term Vertical Handover or VHO will be used in the rest of the description referring to this definition. 
         [0019]    IEEE 802.21 standard contemplates interconnections with IEEE 802 systems, and it also contemplates interconnections between IEEE 802 systems and non-IEEE 802 standardized systems. 
         [0020]    This IEEE 802.21 standard enables users and mobile operators to take fully advantage of heterogeneous networks. By heterogeneous networks, it is meant networks of any possible radio technologies as WLAN (WIFI), WPAN (Bluetooth), WMAN (WiMAX, 3GPP, and 3GPP2). This so-called IEEE 802 standard also provides a structure efficient for detecting networks and cleverly facilitates the VHO, based on the states of current network connections and the capacities thereof. IEEE 802.21 standard defines services allowing a Media Independent Handover or MIH, which interact with the highest layer of the stacked layers of the protocol, to facilitate a homogenized Handover between the different wireless networks located in a similar area. One of these services is the Media Independent Information Services (MIIS), which service provides a structure and a corresponding mechanism, to detect the existence of networks and obtain information about the potential candidate detected networks, around the network already in service, for the purpose of more easily obtaining a Vertical Handover. The MIIS server accommodates nearly all the static information about the candidate access networks. The dynamic change of the attributes and the state of the parameters have to be obtained by directly requiring an access to the respective networks. 
         [0021]    Within the scope of this invention, three types of terminals are distinguished. First, the terminals having a high level  11  of battery  10 , then the terminals having a medium level  12  of battery  10 , and finally the terminals having a low level  13  of battery  10 . This distinction is carried out by establishing two thresholds, including a high threshold  14  and a low threshold  15 . However, for a better understanding, the terminal will be referenced as  100  in the rest of the description. 
         [0022]    The operating method according to one embodiment of the invention will now be described and implemented by the controller (not represented) of each mobile terminal  100 . 
         [0023]    Such a controller is known to those skilled in the art and is not an object of our invention. A further description of this controller is thus useless. However, the actions undertaken by the controller of each terminal  100  are commanded by a microprocessor (not represented). This microprocessor produces, in response to the instruction codes recorded in a program memory (not represented), commands intended to implement the method of the invention, as well as the different members associated with said controller. To that end, the program memory includes several program areas, corresponding to a series of steps respectively. 
         [0024]    In a step  200 , the controller of the terminal  100  determines the state of its battery  100 . If the state of the battery  10  indicates that the same is charged at a high level, then the controller executes a step  210 . If the state of the battery  10  indicates that the same is charged at a medium level, then the controller executes a step  220 . If the state of the battery  10  indicates that the same is charged at a low level, then the controller executes a step  230 . The state of the battery can only be included in one of these three steps. 
         [0025]    In a step  210 , when the battery  10  is fully charged or at a high level  11 , in other words, when the terminal  100  has a battery  10  having a level higher than the high threshold  14 , then the controller determines the operational mode of the RRC layer (not represented) of the terminal  100 . If the operational mode of the RRC layer of the terminal  100  is in idle state or RRC_IDLE, then the controller executes a step  211 . If the operational mode of the RRC layer of the terminal  100  is connected or RRC_CONNECTED, then the controller executes a step  212 . 
         [0026]    In step  211 , the RRC layer of the terminal  100 , as those used for the LTE technology, has little time allocated for its controller to make a search for all the long-range networks available, such as 3GPP (3 rd  Generation Partnership Project) and WIMAX (Worldwide Interoperability for Microwave Access), or short-range networks available, such as WIFI (Wireless Fidelity) and Bluetooth. 
         [0027]    In a step  213 , the controller of the terminal  100  updates its local database  105  with all the networks detected in step  211 , with their position, the absolute time, and the technology of the network. The position can in particular be given by the terminal, if Global Navigation Satellite Systems (GNSS) are available or, more commonly, via a position calculating system with the RSS (Receiving Signal Strength). It is also possible to deduce the position of the terminal by using the Time Difference Observed of Arrival (TDOA). Indeed, the terminal measures the time differences between the broadcast channels of the WMAN system on which it is connected. A broadcast channel is present per each cell in order to distribute the synchro and system information. Reporting these measurements to the WMAN network enables the position of the terminal to be determined. 
         [0028]    As the RRC layer of the terminal  100  is in an RRC_IDLE mode, the controller of the terminal  100  has to update its local database  105  to be connected to the network. 
         [0029]    In a step  215 , the controller of the terminal  100  is able to autonomously carry out a reselection of a cell, if said terminal  100  finds a better network which, for example, requires less energy consumption, or if the terminal  100  is located close to a cell without leaving the RRC layer in an idle state. 
         [0030]    In a step  212 , the RRC layer of the terminal  100  is in a connected operational mode, RRC_CONNECTED, the controller of the terminal  100  sends data messages to the other terminals  100  belonging to a same user group. 
         [0031]    In a step  214 , the controller of the terminal  100  allocates a little time to carry out a search for potentially candidate networks. 
         [0032]    In a step  216 , the controller of the terminal  100  updates the MIIS server  110  via notifications of information relating to the availability of neighbouring networks that said controller has collected in the local database  105  of said terminal. 
         [0033]    In a step  218 , when a more suitable network has been detected because it guarantees, for example, a same quality of service for all the carriers and a lesser energy consumption, then the controller of the terminal  100  launches a Handover procedure initiated by the network, such as a switch from a 3GPP network to another 3GPP network, or directly initiated by the controller of the terminal  100 , because of the presence of heterogeneous technologies. 
         [0034]    In a step  220 , when the battery  10  is half-charged or at a medium level  12 , in other words, when the terminal  100  has a level higher than the low threshold  15 , but lower than the high threshold  14 , then the controller determines the operational mode of the RRC layer (not represented) of the terminal  100 . If the operational mode of the RRC layer of the terminal is in idle state, RRC_IDLE, then the controller executes a step  221 . If the operational mode of the RRC layer of the terminal is connected, RRC_CONNECTED, then the controller executes a step  222 . 
         [0035]    In a step  221 , the controller of the terminal  100  carries out a search for all the long-range networks available, such as the 3GPP, WIMAX, etc. networks. 
         [0036]    In a step  223 , the controller of the terminal  100  carries out an update of the MIIS server  110 , by sending notifications in its local database  105 , as previously seen in step  213 , but only by considering this reduced subset of detected networks. 
         [0037]    In an optional step  225 , the controller of the terminal  100  also carries out a cell reselection, if said terminal  100  deems it to be necessary. 
         [0038]    In a step  222 , the RRC layer of the terminal  100  is in a connected operational mode, RRC_CONNECTED, the controller of the terminal  100  sends data messages to all the terminals. 
         [0039]    In a step  224 , the controller of the terminal  100  determines all the long-range networks available, such as the 3GPP, WIMAX, etc. networks, in order to update the database server. 
         [0040]    In an optional step  226 , the controller of the terminal  100  also carries out a Handover procedure, if said terminal  100  deems it to be necessary. 
         [0041]    Irrespective of their operational mode, for a medium level  12  of the battery  10 , the controller of the terminal  100  is able to query the MIIS database  110  to obtain a state about whether short-range wireless networks located around said terminal  100  are present or not. 
         [0042]    In a step  230 , when the battery  10  is insufficiently charged or at a low level  13 , in other words, when the terminal  100  has a lower level than the low threshold  13 , the controller determines the operational mode of the RRC layer (not represented) of the terminal  100 . If the operational mode of the RRC layer of the terminal is in idle state, RRC_IDLE, then the controller executes a step  231 . If the operational mode of the RRC layer of the terminal is connected, RRC_CONNECTED, then the controller executes a step  232 . 
         [0043]    In a step  231 , the controller of the terminal  100  does not carry out any search for neighbouring networks any longer, and determines whether the controller has carried out a cell reselection. If the controller has carried out a cell reselection, then the controller requires the MIIS server  110  in a step  233 . 
         [0044]    Thus, in a step  235 , the controller sends the position of the terminal  100  to the base station to which it is connected, in order to determine which available networks are in the vicinity thereof. 
         [0045]    In a step  237 , the MIIS server  110  transmits a list of two or three most suitable networks to the controller of the terminal  100 . 
         [0046]    In a step  239 , the controller of the terminal  100  determines whether it is possible to carry out a cell reselection procedure for one of the networks listed in step  237 . If it is possible, then in a step  241 , the controller of the terminal  100  carries out a reselection procedure. If it is not possible, then in a step  243 , the controller of the terminal reiterates this reselection procedure with the remaining networks from the list. In a step  245 , the controller determines whether no attempt has been successful with one of the networks from the list. If no attempt has been successful, then in a step  247 , the controller of the terminal carries out itself a network scanning, in the same way as the one carried out if the battery were full. 
         [0047]    In a step  232 , the RRC layer of the terminal  100  is in a connected operational mode, RRC_CONNECTED, the controller  100  does not carry out any search for neighbouring networks any longer, and determines whether the controller has carried out a cell reselection. 
         [0048]    In a step  234 , if the controller of the terminal  100  has carried out a cell reselection, then the controller requires the MIIS server  110 . 
         [0049]    In a step  236 , the controller of the terminal  100  sends data messages to the other terminals. 
         [0050]    In a step  238 , the controller requires the MIIS server  110  from the available networks in proximity to its position. 
         [0051]    In a step  240 , the MIIS database  110  transmits a list of two or three most suitable networks for the terminal  100  to be able to be connected thereto. 
         [0052]    In a step  242 , the controller of the terminal  100  determines whether it is possible to carry out a Handover procedure for one of the networks listed in step  240 . If this is possible, then in a step  244 , the controller of the terminal  100  carries out a Handover procedure. If this is not possible, then in a step  246 , the controller of the terminal  100  reiterates this Handover procedure with the remaining networks from the list. In a step  248 , the controller of the terminal  100  determines whether no attempt has been successful with one of the networks from the list. If no attempt has been successful with one of the networks from the list, then in a step  250 , the controller of the terminal  100  directly carries out a network scanning, in the same way as that carried out if the battery were full. It is also possible for the Handover procedure to be launched before the transmission, for the terminal  100  to be able to be connected to the network with the most optimum energy efficiency possible, for the entire transmission, or during the transmission, if the environment has changed during the data transmission or data delivery in real time. 
         [0053]    In this embodiment of the invention, as previously described, when the battery  10  of a terminal  100  is at a low level  13 , the controller of said terminal  100  enables to carry out only essential activities, both for Handover/Vertical Handover requirements, or cell reselection, but still requiring the MIIS server  110 . This MIIS server  110  is periodically updated, by the controller of a terminal  100  having the greatest watt-hour capacity. By means of the method according to the invention, a trade-off is made between all the terminals  100  of the private communication group, such that “a shared battery” is obtained, where the terminals  100  which have a higher level of battery, carry out tasks for all the terminals  100 , whereas the terminals  100  having a battery  10  with a low level  13  take advantage of the tasks carried out by the terminals  100  having a battery  10  charged at a high level  11 . All the terminals  100  have a battery  10  which switches from a fully charged state to a lowly charged state and as a matter of fact, sooner or later, each terminal  100  takes advantage of the tasks carried out by the other terminals  100 .