Mobile Phone Patent Abstract BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to mobile communications and, in particular, to a method for emergency service access using a mobile telephone.
2. Description of the Related Art
Providers of emergency services, such as fire, police and rescue departments have been greatly aided in their efforts to provide service to individuals in need by the introduction of the 911 emergency number which is now prevalent in the United States. Similarly, the widespread use of mobile telephones has decreased the emergency response time as more and more passing motorists are able to dial 911 shortly after an emergency situation arises. Occasionally, however, the caller's efforts to dial 911 are hampered because the mobile phone may be configured so as to require the entry of an access code to unlock the phone prior to making a telephone call. While the access code prevents the unauthorized use of the mobile telephone, its requirement delays or prevents the dialing of an emergency 911 call when it is the victim's phone which is used to make the call.
Clearly, there is a need in the art for a method of bypassing, in an emergency situation, the entry of an access code to unlock a phone prior to making a telephone call.
U.S. Pat. No. 5,479,482 to Grimes discloses a cellular terminal for providing public emergency call location information. The cellular terminal transmits information defining its location upon placing a 911 call using a global satellite positioning (GPS) device. In addition, the cellular terminal can be programmed to transmit personal characteristics the subscriber has programmed into the cellular terminal. In an emergency situation, the terminal transmits this information as digital information at the same time as the location information is transmitted to the public safety answering point (PSAP) system utilized by the emergency service provider. Unfortunately, the information that could be programmed into the cellular terminal would be limited and would be for a single individual. In an emergency situation information could be needed for an entire family. Therefore, there is a need in the art for a method of transmitting more extensive personal medical records and records for more than one individual to a PSAP system.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method for bypassing, in an emergency situation, the need for entering an access code to unlock the phone prior to sending a call from a mobile telephone that has been locked.
It is another object of the present invention to provide a method for sending emergency information from a mobile switching center (MSC) to a PSAP system in the form of an emergency contact record (ECR).
It is an additional object of the present invention to provide a method for transmitting a request to send emergency contact records to the PSAP in the event the mobile subscriber is not placing the call through their home system.
To achieve these objects, there is provided a method for emergency service access using a mobile telephone. The mobile telephone stores a list of emergency numbers to be used by mobile service providers. This list could include 911 and *911 for requesting a call to be placed to the nearest PSAP, *FIRE for the nearest fire department, *ER for the nearest emergency room, *HP for the nearest highway patrol office, and *POL for the nearest police station. The mobile service provider would estimate the mobile telephones location by what base station the mobile telephone is communicating with and would route the call to the nearest emergency service provider requested. When an emergency situation arises and the mobile telephone is locked and the caller enters a number followed by [send], the mobile telephone compares the entered value (*911) with a list of known emergency numbers stored in the memory of the mobile telephone. If the number entered is one of the known emergency numbers, the terminal will immediately place the emergency call even though the mobile phone is locked. All other key combinations will be compared to a user defined access code previously stored in memory. The previously entered access code is required to unlock the mobile telephone. This number prevents the unauthorized use of the mobile phone and deters theft. If the entered value matches the user access code stored in memory, the mobile phone will be unlocked and ready for normal use. If the values do not match, the mobile phone will remain locked.
In a preferred embodiment, when the 911 emergency sequence is keyed and transmitted to the MSC, the MSC will determine the proper PSAP to connect the subscriber to based on the base station through which they are connected. The MSC will also direct that base station and neighboring base stations to begin procedures for locating the subscriber's mobile telephone. Methods for locating a mobile caller are known in the art and disclosed in U.S. Pat. No. 5,388,147 to Grimes and U.S. Pat. No. 5,959,580 to Maloney et al.
The mobile service provider will provide for a set of emergency contact records (ECR) that may be maintained by the subscriber for themselves and their family. The subscriber may maintain these emergency contact records using a variety of methods including, but not limited to, talking with an administrator from the mobile provider, accessing a secure web page, or mailing in updates to the mobile provider. These emergency contact records may include information for each member in the family, including the individual's name, home address, phone number, physical description, emergency contact name and number, doctor's name and number, emergency medical information (such as drug allergies), temporary conditions (such as a pregnancy), a digital image, and any other information the subscriber deems relevant for the PSAP to know in an emergency.
At the time the emergency call is placed, if the MSC is part of the subscriber's home system, the MSC will have access to the subscriber's ECRs and will send them to the PSAP for use during the emergency. It should be noted that there are many possible methods for sending the ECRs to the PSAP. In a preferred embodiment, the ECRs are sent to the PSAP over the Internet. Other possible methods may include the sending of a facsimile transmission, the sending of an e-mail, or even directing an operator from the mobile service provider to call the PSAP and provide the information over the telephone. One skilled in the art will recognize that there are many possible and effective ways to communicate the ECRs to the PSAP system.
In the event the subscriber places a call while not in the subscriber's home system, the local MSC will send a request to the subscriber's home system asking the home system to send the subscriber's ECRs to the PSAP and will provide an ordered list of methods for transmitting the ECRs to the PSAP.
In an additional embodiment of the present invention, the ECRs are maintained by an independent organization and when a 911 emergency call is placed the MSCs will send a request to the independent organization which maintains ECRs and request the organization to send the information to the PSAP selected by the MSC.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings in which:
FIG. 1 is a schematic view of a reference model for a method for emergency service access using a mobile phone according to the present invention;
FIG. 2 is a diagram illustrating the data structure of an emergency contact record (ECR);
FIG. 3 is a schematic view of a model for a method for providing emergency service access using a mobile phone according to an additional embodiment of the present invention;
FIG. 4 is a schematic view of a model for a method for providing emergency service access using a mobile telephone according to an additional embodiment of the present invention; and
FIG. 5 is a schematic diagram of a mobile telephone and a method of bypassing, in an emergency situation, the need for entering an access code to unlock the mobile phone prior to sending an emergency call.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings, in which similar reference characters denote similar or identical elements throughout the several views, FIG. 1 shows a reference model for a method of providing emergency access service using a mobile telephone. A mobile telephone 100 comprises an antenna 109 for transmitting and receiving data, a display 110 for displaying information and a plurality of keys 105. The plurality of keys 105 contains the numerals zero through nine, a star (*) key 106 and a pound (#) key 107. In addition, a send key 115 and an end key 108 are similarly disposed on mobile telephone 100. A user may make an emergency 911 call by using the plurality of keys 105 and pushing the send button 115. A call is then transmitted via antenna 109 to at least one base station 120. A mobile switching center (MSC) 130 is connected to the at least one base station 120 and processes the call.
When the emergency sequence is keyed and transmitted to MSC 130, MSC 130 determines a proper public safety answering point PSAP 140 based on the base station 120 receiving the caller's signal and connects the subscriber thereto.
When the 911 emergency call is placed through the subscriber's home system using mobile telephone 100, the home MSC 130 provides emergency contact records (ECR) 200 (FIG. 2) to the PSAP 140.
Referring to FIG. 2, there is shown a block diagram of the data structure of an emergency contact record 200. Emergency contact record 200 comprises several fields including but not limited to a name field 210, an address field of the subscriber 220, a telephone number of the subscriber field 230, and a physical description 240 corresponding to the name field 210. In addition, emergency information such as an emergency contact number 250, a physician's name 260, a physician's telephone number 270, and a known allergies field 280. ECR 200 may also include a special condition field 290 which may include any information the subscriber deems important for PSAP 140 to be made aware of in an emergency situation. Some examples of special conditions are the presence of high blood pressure, the presence of current medications being taken, or the existence of a pregnancy. ECR 200 may also include a digital photo which could be used for identification purposes or medical diagnosis (recent X-rays).
The emergency contact records 200 may also be grouped together based on family relationships and comprise multiple ECRs, for example, ECR1, ECR2, to ECRn. In the event of an emergency situation, the entire ECR family record may be transmitted to the PSAP 140.
Referring now to FIG. 3, there is shown a schematic diagram of an additional embodiment of the present invention. One advantage of having a mobile telephone is that a subscriber may place a phone call in a wide geographic area and is limited only by the availability of the service in the area and the type of calling plan purchased. At times, a user may place a phone call outside of their home system serviced by their home MSC 130. The call would be picked up by base station 120 and transmitted to a local MSC 135. Local MSC 135 will not have access to the ECRs 200 of the subscriber, and therefore, MSC 135 will send a request to the subscriber's home MSC 130 asking the home MSC 130 to send the subscriber's ECRs 200 to the PSAP 140. In this manner, the PSAP 140 will have available vital information concerning the mobile subscriber placing the call. The availability of the ECRs 200 to PSAP 140 may help in the treatment and identification of a subscriber. The information included in ECR 200 is generally recorded in a non-emergency situation and would therefore be more complete and accurate than similar information obtained during an emergency situation. It should be noted that generally there is already a connection between MSCs to provide for call roaming and that requesting ECRs would be a new set of requests to be transmitted between MSCs.
Referring now to FIG. 4, there is shown a schematic diagram of an additional embodiment of the present invention. In this exemplary embodiment, a third-party emergency contact record providing organization 170 is contacted by MSC 130 via communication line 150 and requested to provide ECR 200 to PSAP 140. According to this exemplary embodiment, all 911 emergency calls will immediately generate a request to the ECR providing organization 170 to provide ECRs 200 directly to PSAP 140. This embodiment eliminates the need for MSC 130 to contact the subscriber's home MSC.
Referring to FIG. 5, there is shown a schematic diagram of the necessary components of a mobile telephone for implementing a method of bypassing, in an emergency situation, the need to input a user access code, when the mobile telephone is locked, prior to sending a call. The mobile telephone comprises a controller 300, a memory 310 and a keypad 105. Memory 310 may be any suitable type of permanent memory, such as a ROM or EEPROM. In addition, keypad 105 contains a * key 106 and a # key 107. When a mobile telephone is locked and the subscriber places an emergency call, the keypad input is compared to a list of known emergency numbers stored in the memory 310 of mobile telephone 100. If controller 300 determines that the input from keypad 105 is equal to an emergency number stored in memory 310, controller 300 directs the mobile telephone to send the emergency call even though the mobile telephone is locked. On the other hand, if the information input from keypad 105 is not an emergency call, but matches a user access code stored in memory 310, the controller 300 enables the mobile telephone for normal use. If the information entered by keypad 105 does not match an emergency number or the user access number stored in memory 310, the controller 300 leaves the mobile telephone locked. In this manner, if a mobile subscriber is unconscious and their mobile telephone is locked, any passerby may use the subscriber's mobile terminal to make an emergency call only. All other numbers entered, unless they match the user's access code, will leave the mobile telephone in a disabled state. Upon the setup of the emergency call, the subscriber's ECRs 200 are transmitted from MSC 130 to the proper PSAP 140.
While the present invention has been described in terms of a mobile communication system having a basic structure as disclosed in a code division multiple access (CDMA) system, it is understood that the present invention may be modified to work with other communication systems.
While several embodiments of the present invention have been shown and described, it is to be understood that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention as defined in the appended claims.
Mobile Phone Patent Claims What is claimed is:
1. Communication method between a base station comprising a network of N distinct antennae, N being a whole number greater than 1, and at least one mobile telephone, comprising the steps of: (a) estimating at the base station, the directions of arrival and the power values of radio-electrical path at the base station; (b) determining for this mobile telephone, a principal direction of arrival of said radio-electrical paths at the base station, by choosing a barycentre r of the directions of arrival of the different radio-electrical paths as being the principal direction of arrival, define as follows: ##EQU3## where i is a whole number, where J is the number of radio-electrical paths identified, where a.sub.i is the angle formed by the i.sup.th radio-electrical path in relation to the direction of the path which has the greatest radio-electrical power value, and where p.sub.i is the radio-electrical power value of the i.sup.th path; (c) selecting M antennae, M being a whole number strictly greater than 1 and less than N, of which the individual reception lobes have directions which are contained within an angular sector centered on the principal direction of arrival; (d) processing only the signals received by the selected M antennae from the mobile telephone.
2. The method of claim 1 further comprising the steps of: (a) selecting M antennae of which the individual transmission lobes have directions contained within an angular sector centered on the principal direction of arrival; (b) synthesizing only the signals to be transmitted by the selected M antennae.
3. A radio base station for communication with mobile telephones, comprising a network of N distinct antennae, N being a whole number greater than 1, and K reception or transmission chains, K being a whole number less than N.times.L, where L is the number of simultaneous communications, the radio base station comprising: means of estimating the directions of arrival and the radio electrical power values of the radio-electrical paths at the base station; means of determining, for a given mobile telephone, a principal direction of arrival of the radio-electrical paths at the base station, being the direction of arrival for which the radio-electrical power value received or transmitted and deriving from the mobile telephone is the greatest; means of selecting M antennae, M being a whole number strictly greater than 1 and less than N, of which the individual reception or transmission lobes have directions contained within an angular sector centered on the principal direction of arrival; means of switching, affecting, for each communications, M reception or transmission chains at the M antennae previously selected.
4. A radio base station for communication with mobile telephones, comprising a network of N distinct antennae, N being a whole number greater than 1, and K reception or transmission chains, K being a whole number less than N.times.L, where L is the number of simultaneous communications the radio base station comprising: means of estimating the directions of arrival and the radio electrical power values of the radio-electrical paths at the base station; means of determining, for a given mobile telephone, a principal direction of arrival of the radio-electrical paths at the base station, being the barycentre r of the directions of arrival of the different radio-electrical paths, defined as follows: ##EQU4## where i is a whole number, where J is the number of radio-electrical paths identified, where a.sub.i is the angle formed by the i.sup.th radio-electrical path in relation to the direction of the path which has the greatest radio-electrical power value, and where p.sup.i is the radio-electrical power value of the i.sup.th path; means of selecting M antennae, M being a whole number strictly greater than 1 and less than N, of which the individual reception or transmission lobes have directions contained within an angular sector centered on the principal direction of arrival; means of switching, affecting, for each communications, M reception or transmission chains at the M antennae previously selected.
Mobile Phone Patent Description The invention relates to a radio communication method at high frequency between a base station with N antennae and a mobile phone, and a base station for implementing same.
It can be applied to digital cell telephone systems in which one and the same station is provided with a network of antennae allowing it to serve a plurality of mobile phones in a cell.
In such a station, during transmission, the signals to be applied to each antenna are synthesised on the basis of the signal intended to reach the mobile phone.
To achieve this, in the transmission chain of each antenna a number of digital processes generally produce samples representing these signals. Then, by means of digital-analog conversion and modulation to the carrier frequency, each signal is synthesised then simplified and applied to the appropriate antenna of the network.
The complexity of the calculations necessary to synthesise these patterns, and the cost of the digital-analog conversion circuits and of modulation, increase with the number of antennae in the network.
Hereinafter, the term multi-sensor transmission device shall be used to refer to the whole of the circuits which produce the signals applied to each elementary antenna for transmission to the mobile phone.
At reception, in analog mode, the reception chain of each antenna feeds the signals received by this antenna into an intermediary frequency or the base band. The signals are then sampled and subjected to analog-digital conversion. The samples are then processed by digital processes to extract the information transmitted by the mobile phone.
The complexity and the cost of the circuits of the reception paths again increase with the number of antennae in the network.
Hereinafter, the term multi-sensor reception device shall be used to refer to the whole of the circuits which process the signals received from the mobile phone in order to extract the information transmitted.
The network of antennae may feature any geometry considered appropriate. In particular, the antennae may be disposed in line and regularly spaced. In this event, they are preferably directional, and their lobes point in the orthogonal direction to the right of which the antennae are aligned.
The antennae may equally be disposed in a circle and regularly spaced. In this event, the antennae are likewise preferably directional and their lobes point in a radial direction towards the outside of the circle on which they are disposed.
The invention applies likewise to a network of antennae presenting a regular polygon geometry such as an equilateral triangle, a square, a pentagon, a hexagon, etc., with antennae spaced regularly along its sides.
The objective of the invention is to reduce the complexity of the calculation and the cost of the processing procedures carried out by a base station provided with a network of antennae.
In order to achieve this objective, the invention proposes a method of communication between a base station consisting of a network of N distinctive antennae, N being a whole number greater than 1, and at least one mobile telephone, characterised in that: (a) The directions of arrival and the power values of the radio-electrical paths are estimated at the base station; (b) A principal direction of arrival is determined for said mobile telephone of said radio-electrical paths at the base station; (c) M antennae are selected, M being a whole number less than N, the individual reception lobes of which have directions contained in an angular sector centred on the principal direction of arrival; (d) Only the signals which are received by the M antennae selected and deriving from the mobile telephone are processed.
For the transmission according to this process, (e) M antennae are selected, of which the individual transmission lobes have directions contained within angular sector centred on the principal direction of arrival; (f) Only the signals to be transmitted by the M antennae selected are synthesised.
The invention likewise proposed a radio communications base station with mobile telephones, comprising a network of different N antennae, N being a whole number greater than 1, and K reception or transmission chains, K being a whole number less than N.times.L, where L is the number of simultaneous communications, characterised in that it comprises: Means of assessing the directions of arrival and the power values of the radio-electrical paths at the base station; Means of determining, for a given mobile telephone, a principal direction of arrival of the radio-electrical paths at the base station; Means of selection of M antennae, M being a whole number less than N, of which the individual reception or transmission lobes have directions contained within an angular sector centred on the principal direction of arrival; Means of switching, affecting, for each communication, M reception or transmission chains at the M antennae previously selected.
In a specific embodiment of the invention, the principal direction referred to heretofore is the direction of arrival for which the radio-electric power received or transmitted and reaching the mobile telephone (according to whether it is in reception or transmission mode) is the greatest.
In another specific embodiment of the invention, the principal direction referred to heretofore is the barycentre r of the directions of arrival of the different radio-electric paths, defined as follows: ##EQU1## where i is a whole number, where J is the number of radio-electrical paths identified, where a.sub.i is the angle formed by the i.sup.th radio-electrical path in relation to the direction of the path having the greatest radio-electrical power value, and where p.sub.i is the radio-electrical power of the i.sup.th path.
Other features and advantages of the invention are clearly indicated in the following detailed description of specified embodiments, given by way of non-limiting examples. The description refers to the accompanying drawings, in which:
FIG. 1 represents in schematic form traditional multi-sensor reception and transmission devices, wherein one single communication is being considered between the base station and a mobile telephone;
FIG. 2 represents in schematic form the reception and transmission devices comprised in a base station conforming to a particular embodiment of the invention, wherein a single communication is considered between the base station and a mobile telephone;
FIG. 3 is an organizational diagram of the process according to the invention, in a specific embodiment;
FIG. 4 illustrates a method of selection of M antennae among N, in a specific embodiment of the invention, wherein the network of antennae presents a circular geometry;
FIG. 5 represents in schematic form traditional multi-sensor reception and transmission devices, wherein the base station is processing L simultaneous communications; and
FIG. 6 represents in schematic form reception and transmission devices comprised in a base station in accordance with a specific embodiment of the invention, wherein the base station is processing L communications simultaneously.
The invention will first be described by considering one single communication between a base station and a given mobile telephone.
In the traditional situation represented in FIG. 1, whether in reception mode (left-hand part of the figure) or in transmission mode (right-hand part of the figure), the number N of antennae, each designated in the figure by the reference number 10, of the base station corresponds to the number of signals which are capable of being processed (in reception) or of being synthesised (in transmission) by a multi-sensor reception device 12 or a multi-sensor transmission device 14, comprised in the base station.
Typically, these devices comprise the same number of reception and transmission chains as there are elementary antennae in the network, this being N in the example illustrated.
It is recalled that each reception chain comprises essentially a pre-amplification module, a frequency conversion module for the transition to intermediary frequency or base band, and an analog-digital conversion module. Each transmission chain comprises essentially a numerical-digital conversion module, a frequency conversion module to pass to the transmission carrier frequency, and an amplification module.
The left-hand part of FIG. 2 represents a reception device included in a base station of N antennae in accordance with an embodiment of the present invention.
When a mobile telephone transmits a signal in the direction of the base station, the base station activates a module for estimating the directions of arrival and the power values of the radio-electrical paths at the base station (not represented in FIG. 2). A traditional process for locating the source is then put into effect, for example of the type of those described in the following documents: ANDERSON S., MILLNERT M., VIBERG M., WAHLBERG B. "An adaptive array for mobile communication systems", IEEE Transactions on Vehicular Technology, Vol. 40, No. 1, February 1991, pages 230-236; VIBERG M., OTTERSTEN B., "Sensor array processing based on subspace fitting", IEEE Transactions on Signal Processing, Vol. 39, No. 5, May 1991, pages 1110-1121; SCHMIDT R. O., "A signal subspace approach to multiple emitter location and spectral estimation", Ph.D. dissertation, Stanford Univ., Stanford, Calif., November 1981; ROY R. H., PAULRAJ A., KAILATH T., "ESPRIT--A subspace rotation approach to estimation of parameters of cisnoids in noise", IEEE Trans. Acoust., Speech Signal Processing, Vol. ASSP-34, No. 4, pages 1340-1342, October 1986.
The base station then determines, for this mobile telephone, a direction of arrival which is referred to as the principal direction of arrival. The signals emitted by the mobile telephone to the base station effectively undergo reflexions on various obstacles and give rise to multiple paths. The principal direction of arrival may be that for which the radio-electrical power received by the base station is the greatest.
As a variation, the principal direction of arrival may be the barycentre r of the directions of arrival of the different radio-electrical paths identified, weighted by a function of the radio-electrical power values of these paths.
The module for determining the principal direction of arrival is not shown in FIG. 2.
Let J be the number of radio-electrical paths identified. Let a.sub.i be the angle formed by the i.sup.th radio-electrical path, i being a whole number, in relation to the direction of the path for which the radio-electrical power is the greatest. Let p.sub.i be the radio-electrical power of the i.sup.th path. The barycentre r is defined by ##EQU2##
Once the principal direction of arrival has been determined, the base station activates a search or selection module (not shown) in order to determine, among the N antennae of the network, a more restricted set of antennae which will be exploited for the communication process under consideration. According to an advantageous embodiment of the invention, the set used for reception comprises M antennae, of which the individual reception lobes have directions contained within a predetermined amplitude angle sector, centred on the principal direction of arrival.
The number M may vary from one communication to another, and depends on the number of processing circuits available.
FIG. 4 shows a configuration in which an angular sector centred on a principal direction of arrival comprises m antennae, selected from among N, for a network of antennae of circular geometry; the N elementary antennae represented are disposed equally around the circle.
As FIG. 2 (left-hand part) shows, the base station comprises a reception switching matrix 16, which directs the signals received from the mobile telephone by the M antennae selected towards the multi-sensor reception device 18. The signals which are not processed by the multi-sensor reception device are orientated onto a load 20 which corresponds to the impedance of the N-M antennae not selected.
The right-hand section of FIG. 2 represents a transmission device integrated in a base station with N antennae, in accordance with a specific embodiment of the invention. In transmission mode, in a manner analogous to that just described for reception, the base station includes a search module (not shown) of M antennae, the individual transmission lobes of which have directions contained within an angular sector of a predetermined amplitude, centred on the principal direction of arrival.
The base station likewise comprises a multi-sensor transmission device 22, which synthesises only the M signals to be transmitted by the M antennae selected. A transmission switching matrix 24 directs the synthesised signals to apply them to these M antennae. The N-M antennae not selected are connected to a single load 26, corresponding to their impedance.
It is assumed in this situation that the same network of antennae serves for transmission and reception. Provision can be made for the reception and transmission switching matrices to be one and the same bi-directional matrix, the signals received and transmitted circulating in opposed directions on the same cables. As a variant, provision may be made for a duplex filter, which separates the signals received and transmitted at the level of each elementary antenna, and two distinct switching matrices operating in an independent manner.
It will be noted that the switching matrices for reception and transmission, depending on the means of realisation, may be either hardware devices, or software realisations.
In addition to this, in the specific case of the application of the invention to a system operating in time-division multiple access (TDMA) mode, the previous arrangement is effected for a given period of time. In effect, the group of M antennae selected is subject to being changed from one time sector to the one following, i.e. from one communication link to the other.
FIG. 3 provides a summarised version of the different stages of the process according to the invention, in a specific embodiment.
In the course of a first stage, the directions of arrival and the power values of the radio-electrical path values at the base station are estimated. A principal direction of arrival is then determined for this mobile telephone. Next a selection is made, from among the N antennae of the network, of M antennae of which the individual reception or transmission lobes have directions contained within an angular sector centred on the principal direction of arrival. In the final analysis, only the signals received or to be transmitted by the M antennae selected are processed (in reception) or synthesised (in transmission).
The description provided heretofore in relation to FIGS. 1 and 2 relate to a given communication link between the base station and a single mobile telephone. In practice, a base station serves a large number of simultaneous communications links with several mobile telephones. In the TDMA mode, the signals from the different communications links occupy different and identical time sectors within successive cycles. It is considered hereinafter that L communication links are effected simultaneously. The number L represents the number of communications links actually effected simultaneously, i.e., for example, sharing the same cycle of time sectors in TDMA mode.
In reception mode, in a traditional device such as that represented in the left-hand part of FIG. 5, the signals received by the N antennae are processed by N reception chains 28, which separate the signals corresponding to each of the L communications links for each antenna. The N.times.L signals which result are then received by a multi-sensor reception device 30, which processes the N signals received for each communications link.
In transmission mode (right-hand part of FIG. 5), in a traditional device, a multi-sensor transmission device 32 synthesises N signals to be transmitted by the N antennae of the network for each communication link. The N.times.L signals which result are transmitted to N transmission chains 34, which add together the contributions from each of the communications to be transmitted by each antenna. All the communications links then exploit all the antennae, both in reception and in transmission.
If the present invention is applied in reception mode (left-hand part of FIG. 6), for each of the L simultaneous communications links, the M antennae used are selected in the manner described heretofore in the case of a single communication link. M reception chains 36 then separate, for each of the M antennae selected, the communications signals which have selected this antenna. A multi-sensor reception device 38 then processes, for each communication link, M signals received.
If the present invention is applied in transmission mode (right-hand part of FIG. 6), for each of the simultaneous L communication links, the M antennae used by one of the L communication links are selected in the manner described heretofore in the case of a single communication link. A multi-sensor transmission device 40 synthesises, for each communication link, M signals to be transmitted by the M antennae selected. The resultant signals are transmitted to the transmission chains 42, which add up, for each antenna, the contributions from the communications which have selected this antenna. Each communication link accordingly only exploits a part of the antennae, which considerably reduces the complexity of the processing: In reception mode, these processing procedures exploit, for each communication link, M signals received instead of N, and, in transmission, for each communication link, M signals are synthesised instead of N.
If the base station comprises a total number K of transmission-reception chains, K being a whole number less than N.times.L, the maximum number of signals issued from the reception chains 36 or from the multi-sensor transmission device 40 is equal to K.
Depending on the situation, it may be of interest to choose: Either to fix M, and to make provision for a number K of chains equal to M.times.L, Or to allow M to vary, and to consider the whole of the transmission-reception chains as a group or pool, which is applied to each communication (as a function of the number of simultaneous communication links to be effected).
In the event that the principal directions of arrival associated with several mobile telephones correspond to groups of antennae comprised within angular sectors which overlap, i.e. which have one or more antennae in common, it is possible that a conflict of utilisation may arise between these communications links, involving the use of the same transmission-reception chains. It is appropriate to implement only a certain number of the communication links in conflict at these antennae, In accordance with a predetermined criterion. This criterion may consist, by way of a non-limiting example, of balancing the radio-electrical power values received, by assigning these antennae to the communication link for which the received power is the weakest.
Experience has shown that it is possible to attain performance values similar to those obtained with the complete network, making use only of half of the elementary antennae which constitute the network.
A further advantage of the invention is that it allows, at reduced cost and in a continuous manner, for the base station to carry out the whole of the spatial processing, by distinction from traditional base stations, consisting of sectoral antennae, which superimpose two spatial processing procedures, i.e. that of the antennae network and that of the sectorisation.
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