US 20070022441 A1
The invention relates to bandwidth signalling in a multicarrier wireless telecommunication system. The information is transferred in the band itself (bold carriers) and contains information of the size (f2-f1) and location (f1, f2) of the band (I). The information is repeated in a number of carriers (bold) through out the band.
14. A method in a multicarrier wireless telecommunication system for radio communication between base stations and mobile user stations, comprising the step of:
transmitting information signals, over an air interface, relating to operational bands of the radio spectrum used by the system;
wherein the signalling comprises information of the bandwidth and location in the spectrum of the operational bands as part of the information in one or more sub carriers of the bands.
15. The method of
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the mobile station searching the radio interface for an N-carrier band by looking for location and size information;
the communication system assigning a free band with N+ε carriers to the mobile upon the request where ε is zero or a small number compared to N; and,
the mobile station downloads the information.
23. A wireless multicarrier telecommunication system, comprising:
a traffic controlling centre; and,
transmitting units controlled by said traffic controlling centre, wherein the transmitting units transmit information signals relating to available resources of the system to mobile units, wherein the information signals comprise information about the size and location of available bandwidth in a number of operational bands allocated to the system.
24. A base station node in a multicarrier telecommunication system, comprising:
transmitting means for transmitting information relating to properties of available operational bands of the spectrum allocated to the system, wherein the transmitting means include means for transferring data related to size and location of the available operational bands.
25. A mobile station node in a multicarrier telecommunication system, comprising means for receiving information relating to available operational bands in terms of size and location in the radio spectrum.
26. The mobile station of
The present invention relates to signalling of available bandwidth especially in multicarrier wireless telecommunication systems.
A tendency of new wireless telecommunication systems is that they often require more bandwidth than existing systems, as new and more demanding services are likely to be introduced by the new systems. However, the available spectrum is limited and it is difficult to identify new spectrum for new communication systems, especially if the new spectrum shall be identical in all different regions of the world. This calls for a need of flexibility with respect to spectrum usage in the sense that pieces of radio spectrum of different size and in different frequency bands should be used with basically the same radio air interface.
For the sake of example, assume that the most demanding applications require that the system bandwidth needs to be 100 MHz. International standardisation and regulatory bodies will therefore have to make sure that there will be ample spectrum available so that a number of 100 MHz bands could be offered to the customers. However, it is also likely that certain regions will have smaller pieces of spectrum available here and there that are smaller than 100 MHz, say a 30 MHz band in one region and a 66 MHz band in another.
One possibility is to design many different air interfaces for a number of bandwidths—say 30, 66 and 100 MHz—and let the base stations and mobile users choose one or several of them depending on the situation, say a 25 MHz air interface for the 30 MHz band, a 50 MHz interface for the 66 MHz band and 100 MHz interface for the 100 MHz band. This however leaves some parts of the spectrum unused: 5 MHz in the 30 MHz band and 16 MHz in the 66 MHz band, while the 100 MHz band is fully used. Even if there is a high degree of commonality between different air interfaces, the complexity of equipment with several air interfaces will be significantly larger than if only one air interface can be used instead.
Another suggestion for better usage of available frequency spectrum is to let several operators share spectrum or rent or buy resources from each other.
The proposals and ideas referred to above suffers from a number of drawbacks. Already mentioned is that using different air interfaces in several parts of the spectrum causes greater complexity. Another is that available pieces of spectrum might be too big for certain applications, which leads to a waste of resources. Still another problem is how to inform the users of the existence and extent of free spectrum for a certain application at a certain moment in a certain location area. In other words there is a need for greater flexibility and fast allocation of resources whenever the users so request.
The solution is presented in the appended claims relating to a method and means for signalling the availability of spectrum in terms of bandwidth and location.
The invention is advantageously implemented in wireless multicarrier system where the total maximum bandwidth is made up of a large number of narrowband sub carriers like for example in Orthogonal Frequency Divisional Multiplexing, OFDM, Interleaved Frequency Divisional Multiplex, IFDM or similar. In OFDM and IFDM the sub carriers are ideally mutually orthogonal. Generally, very similar systems can be designed with pulse shapes that make the sub carriers slightly non-orthogonal but that have other good properties, for example better spectral properties. This difference does not have a bearing on the invention so when OFDM is mentioned in the examples below, also these other more general types of systems are applicable. The only thing that is important is that the system consists of a large number of sub carriers.
With a multicarrier system it is easy to adjust the used system bandwidth by simply switching off some blocks of sub carriers. However, a problem with this solution is how to inform the mobiles about the size and location of the spectrum that is currently used by the communication system. The invention described here solves this problem by including this size and location information within the sub carriers blocks themselves.
The information about which set of downlink carriers in a block that is available is sent downlink from the base station on an acquisition channel, a broadcasting channel or some other cell covering channel. At least one easily detected downlink channel must be transmitted which is within an operational band known to the mobile user and contains information about where this operational band starts and stops relative to the location of said downlink channel. It is enough if the user has a rough idea of where the operational band can be found. This kind of rough information could have been broadcasted to the user in an earlier cell search.
The format of the information about the size and location of the operational band could vary. Here are some examples:
The invention, together with further aspects and advantages is exemplified by reference to a number of embodiments and accompanying drawings wherein:
N is the number of sub carriers in each part. Lets assume that the 100 MHz band is divided into 4096 sub carriers of about 25 kHz each, (i.e. N=4096). In theory any number N could be activated making a large number of air interface bandwidths possible using just one air interface. This is a basic property of these types of systems.
An operator can, at different moments, have say 1000, 2000 or 4000 carriers to its disposal, varying with the demands and behaviours of the subscribers.
Assume that the mobile user knows or can guess the approximate location of all N carriers. First the mobile user must detect the presence of one or more acquisition channel(s) for cell search purposes. Such channels are designed so that there is a very small probability to mistake them for other types of signals, or for other types of signals to be mistaken for acquisition signals. In general the user must scan all possible locations to find this signal in order to unambiguously find one. Then the mobile knows that this channel lies within the operational bandwidth. After that, the information in this acquisition channel about the size and location of the actual carrier set is read.
As an example, the acquisition channel is represented by one or more of the bold marked carriers of block I in
Alternatively, based on acquisition channel information, the mobile finds another channel that broadcasts control of the system, and reads the bandwidth information there or part could be read from an acquisition channel and part from another channel that transmits broadcast control information.
The system information bold marked carriers are spread out among all possible sub bands of the operational band. Operator A's signalling is as follows: in the three bold sub carriers to the left in block I, information says that the bandwidth is 100 MHz and all sub bands are used i.e. the whole 100 MHz band, the next three defines a bandwidth of about 70 MHz in block II. Operator B's signalling is as follows: The single bold sub carrier defines a ca 30 MHz system bandwidth in block II, and the next three in block III define a full 100 MHz bandwidth.
If the operators, in some real time resource exchange or the like, decide that all bandwidth in the second block II should go to operator A, then operator B simply gracefully finalises or reallocates traffic from the allotted carriers in this block, signals that the resource in block II is closed for random access attempts, and stops transmitting in this band, while operator A starts to signal that the entire 100 MHz block is now available for its subscribers.
Since the terminals periodically read bandwidth information from the downlink control channels, this process could be made very quickly, in the order of milliseconds. Also, the terminals have or could have a full bandwidth detector running which makes it trivial to quickly start (de-) multiplexing data (from) to the newly available sub carriers.
A user, MS1 in
To conclude the invention has the following advantages: