The present invention discloses a user terminal for use in a wireless communications system for voice calls and/or data sessions. The user terminal is equipped with means for receiving and transmitting encrypted voice and/or data traffic to and from a second terminal in the system via a first node in the system.
The invention also discloses a wireless communications system and a method which employs the same principles as the user terminal of the invention.
Secure communications in wireless communications systems such as, for example, mobile telephony systems, has attracted a great amount of interest lately.
The traditional method of achieving secure communications in wireless or other systems has been to encrypt the traffic. Due to recent advances in cryptology, a high degree of communications security can be achieved using this method. However, unbreakable or nearly unbreakable encryption still carries very high costs with it, if it can be achieved at all. Also, the demands for processor power in such systems is very high, both on the transmit and on the receive side.
As shown above, there is a need for a method and a system which could provide a high degree of communications security in a wireless communications system at a reasonable cost, and without excessive demands on processor power.
Such a method is provided by the present invention, in that it discloses a user terminal for use in a wireless communications system for voice calls and/or data sessions, the user terminal being equipped with means for receiving and transmitting encrypted voice and/or data traffic to and from a second terminal in the system via a first node in the system.
The user terminal is equipped with means for splitting encrypted traffic during one and the same voice conversation and/or one and the same data session, so that a first part of the encrypted traffic to said second terminal is sent via said first node, and a second part is sent via a second node in the system.
In one embodiment, the user terminal is additionally equipped with means for receiving split encrypted traffic from said second terminal in the system via at least two different nodes in the system, and for this purpose the user terminal is equipped with means for “de-splitting” the received traffic from said two nodes. Suitably, but not necessarily, said two nodes from which traffic is received are the same as those nodes to which traffic is sent from the user terminal.
Thus, a user terminal according to the invention can “spread” one and the same phone call or data session over a multitude of nodes, or in the case of cellular telephony, a multitude of base stations. Not only is the traffic encrypted, so that intercepted traffic will be difficult to understand, a possible eavesdropper will also have to intercept traffic to and from more than one base station (“node”), which is much more difficult than intercepting traffic to and from one base station.
The splitting or spreading of traffic to and from the user terminal can be done in a variety of ways, or in a combination of ways. Some such ways which can be mentioned are the use of different time slots, multiple transmit beams in an antenna of the user terminal, multiple polarizations in at least one antenna beam in an antenna of the user terminal, multiple frequency slots or multiple codes, or one or more steerable antenna beams
The invention also discloses a system and method which utilize the same fundamental principles as the user terminal of the invention.
The invention will be described in more detail below, with reference to the appended drawings, in which
All of the above components of the user terminal 100 and their functions will be described in more detail below.
The user terminal 100 can be used for voice calls and/or data sessions with other users (not shown) in the system 200. In order to enhance the communications security, the user terminal 100 is equipped with means for encrypting said voice and/or data traffic to and from other users (terminals) in the system, as well as means for decrypting received voice and/or data traffic from other users.
The encryption and corresponding decryption means can be of a wide variety of kinds, and can be either in hardware or software or a combination of those. Encryption algorithms or principles which are well known to those skilled in the art can be used with the invention, for which reason those principles will not be elaborated upon here.
In traditional cellular telephony, a user terminal communicates with other users in the system via a radio base station (RBS). There is a plurality of base stations in the system, and all traffic to and from one and the same terminal is routed via one RBS, usually the one with the best signal quality at the time. Thus, a user terminal will usually be listening to traffic not only from the base station through which its traffic is routed, it will also monitor signals from other base stations within range, in order to measure signal quality for use in deciding when the traffic should be routed through another base station than the one currently used, a so called “hand-over”. This situation is exemplified in
The user terminal 100 of the invention makes use of the principle mentioned above, i.e. that there is, at least in most environments, more than one RBS with signal strengths such that the terminal 100 could route its traffic via them. In the example of
According to the invention, the user terminal 100 is equipped with means 130 for splitting outgoing encrypted traffic during one and the same voice call or data session between two or more base stations, so that, in the case where two base stations are used, a first part of the encrypted traffic to another user is sent via a first base station, and a second part is sent via a second base station in the system.
In a corresponding manner, the user terminal 100 of the invention is also equipped with means 120 for “de-splitting” the received traffic from said first and second nodes
Some possible methods for use when splitting will be described below, but a possible scenario for use of the invention is as follows, with reference to the flow chart shown in
A user sets his terminal 100 to work in the “secure mode” of the invention, block 310 of the flow chart, or, alternatively, this is the only mode in which the terminal can operate, in which case the step of block 310 corresponds to activation of the terminal. As a third alternative, the terminal can be notified by the system, via at least one base station, that the system wants the terminal to use the secure mode.
Block 320 is used if the decision to use secure mode is taken at or by the user terminal: the user terminal notifies the system, via at least one base station of the decision to use the secure mode.
In blocks 330 and 340, decisions are made regarding which nodes or base stations that should be used in receiving traffic from (330) and sending traffic to (340) the user terminal. It should be pointed out that if there is a sufficient amount of base stations with a sufficient signal strength in the area, the same base stations need not be used for receiving traffic from the user terminal as are used for sending traffic to the user terminal.
Thus, outgoing traffic from the terminal can be split between a first and a second base station, and traffic can be received at the user terminal from two different base stations, where said first and second base stations are not the same as said two different base stations.
The decisions in blocks 330 and 340 are preferably made at “system level”, i.e. the system comprises a function which is able to coordinate the actions of the base stations and which takes the decisions regarding which base stations to use. These decisions can preferably be based on parameters such as the signal levels received at the user terminal from the base stations, and the signal levels received at the base stations from the terminal, as well as the load at each individual base station.
The signal levels measured at the user terminal from the base stations, and at the base stations from the user terminal are parameters which are already measured today, in order to decide and prepare for hand over of user terminals between different base stations.
As an alternative to having the decision on which base stations to use taken at system level, the decision can be taken at one of the base stations which would then have a special function for this, using the parameters mentioned above, which could be received via the system from other base stations and from the terminal, or from the terminal alone, in which case the terminal could pass on information from one base station to another.
It is also conceivable to have said decision taken at the user terminal, based on the criteria mentioned above. The decision would then be communicated by the user terminal to the base stations involved.
Also, if there is a large number of nodes detected in blocks 330 and 340 which meet the criteria for use, the decision can be to select only a sub-set of those nodes to be used for transmitting or receiving encrypted traffic to and from the user terminal respectively. Otherwise, what happens in the step of blocks 330 and 340 is that all of the available nodes are selected for use.
In block 350, a decision is made regarding the principle that is to be used for splitting the traffic from the user terminal to the base stations, and from the base stations to the terminal. Suitably, the same principle is used in both directions, although this need not be the case.
The user terminal is pre-programmed with the possibility of using a number of different principles for splitting outgoing traffic, and for de-splitting received or incoming traffic. The same principles can, if necessary, be programmed into the base stations of the system.
Although the same effect can conceivably be obtained with other principles, some examples of principles for split and “de-split” of the traffic to and from the user terminal, respectively, which are envisioned at present are:
It should be pointed out that the principle used for splitting traffic from the user terminal to the base station does not need to be the same as that used for splitting the traffic that is sent from the base stations to the user terminal, but in a preferred embodiment the same principle is used for traffic in both directions.
When the nodes to be used for communicating with the user terminal have been selected, blocks 330 and 340, and the principle/principles for use in splitting the traffic to/from the user terminal are chosen, block 350, the communication in “secure mode” can commence, block 360. As mentioned previously, the enhanced security in this mode is obtained by use of encryption as well as by means of the use of more than one node for receiving traffic from the user terminal and for sending traffic to the user terminal during one and the same voice call or data session, or conceivably a call that involves the transfer of both voice and data.
Thus, somebody wishing to eavesdrop on a user terminal according to the invention would need to intercept traffic between the user terminal and at least two base stations, and would then need to “de-split” the traffic according to the principle used by the system, in addition to breaking the encryption method used.
When the secure mode commences, block 360, this entails, as outlined above, splitting outgoing decrypted traffic at the user terminal, block 370, and “de-splitting” incoming decrypted traffic at the user terminal, block 380. Naturally, there are two alternatives here: either the traffic can first be split and the encrypted, or first encrypted and then split, and similarly for incoming traffic. However, in a preferred embodiment, outgoing traffic is first split and then encrypted, in order to enable the use of different encryption for different “traffic splits”, and incoming traffic is first decrypted and then “de-split”. However, the reverse order is of course also possible.
The invention is not limited to the examples of embodiments shown above, but may be varied freely within the scope of the appended claims. As an example of such a variation, it would be perfectly possible to switch split principle during an ongoing voice or data session, or to combine principles during one and the same session, provided that the standard of the system used permits this. For example, the GSM system would at present not permit a combination of time slot split and multiplex code split, but future systems such as, for example, systems beyond the 3G systems or WiMax might permit such combining.
Also, the number of RBS:s used by one and the same user terminal during one and the same session might be changed during an ongoing session.
In another embodiment of the invention, only one of the terminals involved in a communication use the principle of splitting and de-splitting traffic. In such an embodiment, the first terminal would send split traffic via a number of nodes, and the system as such would comprise means for de-splitting the traffic before it is sent to the second terminal. Thus, the enhanced security would be offered at one end of the communication, but not at the other end.
The principle of letting the system de-split the traffic can also be used even if both of the user terminals utilize the invention: in such a system, the traffic would be de-split by the system after being received form the first user terminal, and would then be split again before being sent to the second user terminal. Thus, four main cases can be discerned:
It should also be noted that in those cases where the traffic is de-split by the system, this can take place at a more or less arbitrarily chosen node in the system, in other words the traffic does not need to be de-split at “RBS level”.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/SE2006/000744 | 6/20/2006 | WO | 00 | 12/19/2008 |