Radio communication system, mobile station and method for system selection among systems with the same area coverage

A system Radio cell type having a power reception given in a common radio coverage area at least one other system of this type, these systems are said accessible by a mobile radio station in said common area when they received power is greater than a set value, said station comprising means for measuring the reception powers of these systems.

It also relates to a method for selecting manually implemented by a mobile station comprising communication means by radio link with at least one cellular-like wireless communication system having a receiving power level in a coverage area given a system of this type is available in said said area when its reception power is greater than a nominal value, to select a system from the systems available in the zone.

The invention further relates to a radio equipment mobile comprising:<ul><li>communication means by radio link with at under a system of radio transmissions of the type cell having a received power in an area of Data coverage, said system being accessed in said area when its reception power is greater than a setpoint,</li><li>means for measuring the reception powers of accessible systems.</li></ul>

The invention applies to all systems cellular radio telecommunications and in particular to systems operating according to GSM standards ( English Global System for Mobile communications), NMT (of English Nordic Mobile Telephone), DCS1800 (English Digital Communication System, operating at 1800 MHz), PCS1900 (Personal Communication System, operating at 1900 MHz), etc.

It is advantageous in the case of a system providing the ability for users with such subscribed adequate subscription to connect to another system to get more coverage or for a particular service.

This possibility is known, according to GSM nomenclature, known as "roaming". A subscriber performs a "roaming" when connecting to a system or network different from the one he has taken his subscription. This raises the question of choosing the network, given that there are usually several, managed by network providers, in which a subscriber "Roaming" is allowed to connect.

The US patent publication number US 5,586,338 discloses a system, method and a station mobile radio the kind mentioned in the preamble to automatically selecting a system based on predefined criteria. The selection criteria are preprogrammed in the mobile station at the time of configuration software by the network provider.

Thus, the selection is done transparently for the subscriber, that is to say that it is not involved in the system selection process, which may constitute a first disadvantage if its selection criteria are different from those used by its network provider.

In the case of a GSM type system operating according to the recommendation ETS 300 507 paragraph 3.2.2.2, an automatic network reselection can not be performed in two specific situations:<ul><li>Power-on of the mobile station and</li><li>in case of loss of the radio signal from the network said current, that is to say the network with which the station mobile is registered.</li></ul>

The standard does not expect reselection automatically as the system on which the mobile station connected to it provides coverage even lower; what can be a second disadvantage. Indeed, in some cases, a user may prefer to change the Network before losing completely the radio network signal power for better reception quality.

Moreover, this recommendation requires law display different "visible" networks by the station mobile or "available", that is to say comprising frequencies that the mobile station succeeds in synchronize. This display order ignores power radio signals.

The invention provides means to address in a large extent these drawbacks. In particular, it is expected to provide the user with information on the quality of radio links provided by the systems on which it is allowed to connect.

For this, a system of the type mentioned is remarkable in that the mobile station also comprises measurement results of controls to provide a user indication of said powers of Front accessible systems.

Similarly, a method of the type mentioned is remarkable in that it comprises:<ul><li>a step of measuring said received power levels by said radio station in the coverage area,</li><li>a step of displaying at said station radio, power codes corresponding to the levels measures.</li></ul>

According to one characteristic of the invention, such method may include more manual selection step to select, depending on codes displayed, a system among the systems available in the zone.

Finally, a mobile radio equipment such as mentioned is remarkable in that it comprises means for control of measurement results to provide a user Power indications associated with said systems.

According to an important characteristic of the invention, a mobile radio of its kind above is characterized in that it further comprises:<ul><li>manual selection means of a system from accessible systems</li><li>connection means to the system, to register with the selected system depending on its reception power in that area.</li></ul>

Thus, the selection is made on an order hand of the user and can be triggered at any time, in particular while the current system has a power sufficient reception to communicate with a station movable in the respective coverage area.

The invention provides the additional benefit of observe the display order imposed by recommendation cited, while providing the user with means for classifying the different networks available in an area of coverage, depending on their reception powers respectively.

The following description, given in light of accompanying drawings, all given by way of example not limiting will elucidate the invention can be performed.<sl><li>1 shows an exemplary system according to the invention.</li><li>2 shows a block diagram of a mobile station belonging to the system of Figure 1.</li><li>3 shows an exemplary method according to the invention to select a GSM system based on its reception power in a given coverage area.</li></sl>

Although the preferred embodiment of the invention is applied to a GSM system, it can advantageously be made for other systems with necessary modifications, obvious to those skilled art.

Figure 1 schematically represents a first GSM cellular system from which a user with a mobile station (or mobile) subscribed a contract, and a second system compatible with the standard GSM on which the mobile is allowed to connect through to agreements between suppliers of these systems.

In the example of the figure, the first system S1 is schematically represented by a single cell C1 covered by radio base station B1, while the second system S2 is represented by the indoor cell C2 by the station base B2. BS a mobile subscriber to the first system S1 is located S1 cover edge and thus receives a signal B1 radio mediocre. According to the invention, the BS is equipped control means for checking the reception quality radio signals from each system covering the area reception. These means comprise a display screen PLA and will be detailed in the following description.

The mobile appears on her monitor VISU both S1 and S2 systems accessible from the area where it is is accompanied by a code level representative receiving power. This code can be an integer, a graphic might illustrate different levels or a string, etc. According to the embodiment preferred of the invention, this code is an integer between 1 and 4.

In the example, S1 is assigned a code 1 to indicate that the signals from the station B1 are received with low power and S2 is assigned the figure 4 to indicate that the signals from the B2 station are received with much stronger power. The PLA mobile screen can display this information in the a table in which the systems are accessible arranged in the order determined in paragraph of 3.2.2.2.B recommendation ETS 300 507, corresponding to the selection mode manual. This order is:<sl><li>1) the HPLMN, English (Home Public Land Mobile Network), which is the system from which the user has purchased a subscription or service contract,</li><li>2) each PLMN contained in the "PLMN selector" of the SIM card, in order of priority,</li><li>3) other PLMN in random order.</li></sl>

A sample presentation is illustrated by Table 1.<tables><table><tgroup cols="2"><tbody><row><entry align="left">S1</entry><entry align="right">1</entry></row><row><entry align="left">S2</entry><entry align="right">4</entry></row></tbody></tgroup></table></tables>

In the example, the user wishes to transmit type of fax data using mobile. This kind of transmissions requiring a good quality radio link, the user will then select the S2 system with the better reception power to avoid errors transmissions.

The invention is also advantageous for test reception power levels of the different systems accessible from a certain geographical area. By example, before you subscribe to any of these systems, it is interesting to compare the level of reception power of each system in the region of coverage where we intend to use mobile. Gold, according to the state of the art, we only know the level receiving a system that when it is stored there, meaning that the user does not know the levels receiving systems where it is not allowed to to log in.

2 shows a general block diagram of the radiotelephone (BS) according to the invention.

It comprises transceiver circuits (Tx / Rx, 20/21) coupled to an antenna 22 for exchanging signaling messages with the systems present in the coverage area of ​​the BS and to connect to one of them selected by a method according to the invention.

According to the known GSM technology, the circuit Issue 20 receives voice signals from a microphone 22 via circuitry 24 comprising a analog-digital converter and conventional circuits of speech processing, then to transmit to the antenna 22. The receiving circuit 21 receives the antenna 22 signals to a loudspeaker 25 via a set circuits 26 whose role is to perform the treatment reverse to that achieved by the assembly 24. The circuit receipt 21 comprises a measuring device interacting with a COM radio control circuit for measuring the powers receptions of "visible" systems in the area of blanket.

The radiotelephone operations are controlled by member 27 which includes a microprocessor for .mu.P performing the processing of signals transmitted and received by the circuits 20, 21 through the COM interface circuitry as well as those from an MMI user interface performs the management of the screen 28 (PLA) and a keyboard 29.

The MMI especially allows the user to order the keyboard 29 to display the screen 28 a list of "visible" systems assigned a code power, this list is stored in volatile memory RAM type (standing for Random Access Memory) in the body 27. Manual selection of a system from the list of "Visible" to trigger a connection attempt on This system is also managed by MMI in cooperation with the organ 27. The data passes between the COM interfaces, MMI and the member 27 by a common bus 30.

The member 27 also includes a memory not volatile ROM (Read Only Memory English) for store the operating program of the executed phone by the microprocessor, the program including the necessary instructions for performing the method described in 3.

3 illustrates a method for selecting manual according to the invention. It is carried out by the mobile station at the request of the user and involves message exchanges (represented by arrows) between various software layers implemented in the station mobile.

MMI layer represents the user interface which manages the screen and keyboard. The MM layer handles information related to the mobility of the radiotelephone, the layer RR manages radio resources and the L1 layer performs the interface with the hardware.

The method starts by a manual control, in the operation menu of the device, to select a submenu titled eg "re-connect". This order triggers the execution of the method according to the invention for view the list of available PLMNs, in the order provided by the GSM standard, with a power information associated with each PLMN list.

MMI layer AVAIL_REQ address a request to the MM layer to request the list of PLMN "visible" or available. The MM layer address the query AVAIL_PLMN_REQ RR layer to know the visible PLMN. The RR layer POWER_REQ address the request to the L1 layer to ask the radio interface circuitry COM search channels visible frequencies by analyzing their reception level. For that, one tries to synchronize on each of these frequencies and measuring the received power level for each frequency.

Specifically, only said channels used, with a sufficient level are selected and entered in a table which is then raised to the RR layer. The frequency fi (where i is an index numbering) are rows in the table in order of powers decreasing (pi&gt; pi + 1).

For each of the n frequencies found fi (i = 1 to n), RR SYNC_REQ sends a request to ask for L1 the radio interface to synchronize to the frequency fi passed as a parameter, to listen to the information SYSINFO transiting on this frequency, and in particular the identifier of the PLMN to which the frequency belongs. L1 RR meets him going up the requested information or SYSINFO although a synchronization error message "SYNC_ERROR".

All fi frequencies and "decoded" to then be able to establish and memorize the list of PLMN visible with their power level. multiple frequencies may belong to the same PLMN, one remembers that once a PLMN with its power level. Indeed, as the frequencies are decoded in the order of powers decreasing, the first time a PLMN appears, its power associated necessarily correspond to that of its "Best cell", that is to say the cell that offers the frequency channel received with the highest power.

PLMN_AVAIL a list of PLMN, classified in decreasing order of power has returned to the layer MM. It then performs a cross between the list PLMN_AVAIL and two other lists stored in the mobile. This is a list of so-called forbidden PLMN with which Mobile does not have permission to connect and a said list of preferred PLMNs, on which the user benefit from cheaper rates. The latter list is possibly pre-recorded at the time of configuration software by the network provider or by the user itself.

A cross reference list is then displayed PLMN_SELECT the mobile screen; the PLMN are ranked by order there specified by the standard. The power levels associated with different PLMNs have optionally been coded to facilitate reading, for example using an integer between 1 and 4 to allow the user to estimate the power Relative receipt of each PLMN.

There remains then the user only manually select using the keyboard, the PLMN his choice based on the information displayed. A request Manual registration on the selected PLMN is then transmitted to the network using a conventional protocol.

A system, device and method are as described above using examples in accordance with the invention to enable a user to know the All systems receiving power operating in a coverage area provided in order to optionally Login to the most powerful system. Variants of realization apparent to those skilled in the art without departing from the scope of the invention.