Patent Application
20090046670
The invention relates to a method for data transmission in a radio communication system.
Radio communication systems are known in which identical carrier frequencies are used as radio transmission resources in adjacent radio cells. Considered over the radio cells, this results in a so-called “frequency reuse” of “one”.
This type of allocation is used, in particular, in the so-called “OFDM radio communication systems” in which adjacent radio cells use identical subcarriers for radio transmission. A plurality of subcarriers of a system can be combined to form a so-called “frequency chunk”.
In OFDM radio communication systems, subcarriers are also subdivided into time domains. Each time domain of a subcarrier then forms a radio transmission resource called “frames”.
A broadband development of the known UTRA radio transmission standard is called “evolved UTRA, E-UTRA”. In this context, both “time division duplex, TDD” transmission methods and “frequency division duplex, FDD” transmission methods or their combinations, respectively, are to be supported for radio transmissions. In the E-UTRA standard, OFDM radio transmission techniques are also used.
In the transmission technique called “FDD only”, different frequency bands are used simultaneously both for transmissions from a subscriber station to a base station and for transmissions from the base station to the subscriber station. For the direction from subscriber station to base station, called uplink UL, a frequency band fUL is used whereas a frequency band fDL is used for the direction from base station to subscriber station, called downlink DL. This transmission technique provides the advantage of very high data transmission rates.
In the transmission technique called “TDD only”, a common frequency band fDL=fUL is used for transmissions in the direction from subscriber station to base station, called uplink UL, and for the direction from base station to subscriber station, called downlink DL. Four time domains or time slots are shown for transmissions in the downlink DL direction and four time domains or time slots are shown for transmissions in the uplink UL direction, for example, which alternately follow one another.
In the transmission technique called “combined FDD/TDD” or also “half duplex FDD”, the “TDD only” and “FDD only” transmission methods are combined. Shown here are by way of example four time domains or time slots for transmissions in the uplink UL direction in the associated frequency band fUL and four time domains or time slots for transmissions in the downlink DL direction in the associated frequency band fDL. In “combined FDD/TDD”, it is possible to achieve simplified receiver structures at a subscriber station called “user equipment, UE”.
In this arrangement, so-called “subcarriers” are plotted along a horizontal frequency axis f whilst time sections or time domains are plotted along a vertical time axis t.
By way of example, twelve radio transmission resources FR are here allocated to a first subscriber A whilst a total of six radio transmission resources FR are allocated to a second subscriber B. Furthermore, a total of nine radio transmission resources FR are allocated to a third subscriber C and a total of five radio transmission resources FR are allocated to a fourth subscriber D.
A “subframe” frame has a time duration, called “subframe duration”, of 0.5 ms. Within the “subframe” frame, a total of four “data” time domains are provided which can be used for transmitting useful data of subscribers. In this arrangement, the “data” time domains of the “subframe” frame are allocated to one or more subscribers with the aid of a multiplexing method.
Furthermore, a “pilot” time domain is provided which can be used for transmitting a pilot signal. The pilot signal makes it possible to determine characteristics of radio transmission channels, by estimation if necessary.
To be able to distinguish the subscriber time domains “data” and the pilot signal time domain “pilot” mentioned, a so-called “cyclic prefix, CP” is transmitted in further five time domains CP.
The “subframe” frame has a time duration, called “subframe duration”, of 0.5 ms.
Within the “subframe” frame, a total of four “data” time domains are provided which can be used for a transmission of useful data by subscribers. In this arrangement, the “data” time domains of the “subframe” frame are allocated to one subscriber or to a plurality of subscribers with the aid of a multiplexing method.
Furthermore, two “pilot” time domains are provided as so-called “short blocks” which can be used for transmitting two pilot signals. The two pilot signals make it possible to determine characteristics of radio transmission channels, by estimation if necessary.
To be able to distinguish the “data” subscriber time domains and the two “pilot” pilot signal time domains mentioned, a so-called “cyclic prefix, CP” is again transmitted in further six time domains CP.
The “subframe” frame has a time duration, called “subframe duration”, of 0.5 ms.
Within the “subframe” frame, a total of four “data” time domains are provided which can be used for a transmission of useful data by subscribers. In this arrangement, the “data” time domains of the “subframe” frame are allocated to one subscriber or to a plurality of subscribers with the aid of a multiplexing method.
Furthermore, three “pilot” time domains are provided as so-called “short blocks” which can be used for transmitting pilot signals. The pilot signals make it possible to determine characteristics of radio transmission channels, by estimation if necessary.
To be able to distinguish the “data” subscriber time domains and the “pilot” pilot signal time domains mentioned, a so-called “cyclic prefix, CP” is again transmitted in further seven time domains CP.
The different frame structures, shown in figures
According to technical specification TR 25.913, Chapter 7.3, it is intended to support, in particular, three speed ranges in E-UTRA radio communication systems.
A first speed range for “low speeds” comprises the interval from 0 km/h to 15 km/h, a second speed range for “medium speeds” comprises the interval from 15 km/h to 120 km/h, and a third speed range for “high speeds” comprises the interval from 120 km/h to 350 km/h.
If a subscriber considered changes his individual speed, a continuously changing allocation of the frame structure of associated radio transmission resources is currently provided.
This continuously changing allocation of the frame structure leads to problems, in particular, if a plurality of subscribers must be combined in one frame structure by using a multiplexing method.
If a subscriber of a group combined by multiplexing changes his speed, the allocation of the group to a common frame structure is not optimal for all subscribes of the group.
Depending on the selected speed of progress of a subscriber considered, the associated frame structure or the pilot signal distribution determined thereby for this subscriber also influences the channel estimation. In turn, a transmission quality and/or transmission data rate is dependent on the accuracy of the channel estimation for each subscriber.
It is one possible object, therefore, to specify a method for assigning radio transmission resources in a radio communication system in which useful data can be transmitted by subscribers frame by frame and by using subcarriers, by which method an optimized subscriber useful-data transmission can be carried out.
The inventors propose a method in which, data of a plurality of subscribers are combined to form frames with the aid of a multiplexing method and are transmitted by subcarriers. At least two frame structures are provided for transmitting the frames, wherein the frame structures differ in a respective allocated number of pilot signals and/or in a respective distribution or grouping of allocated pilot signals, wherein the pilot signals can be used for determining radio transmission channel characteristics.
According to the proposed method, an individual speed of progress is determined by each subscriber and each subscriber is allocated to one of at least two speed ranges in dependence on his speed of progress.
For transmitting the data of subscribers who are allocated to an identical speed range due to their speed of progress, a frame structure individually allocated to the speed range, on the one hand, and an individually allocated number of subcarriers, on the other hand, is used.
If the frame structures have an identical number of pilot signals but which are differently distributed or grouped, this embodiment is advantageous particularly at high speeds.
In an advantageous development, a first frame structure is allocated to a first speed range, the first frame structure having two pilot signals in predetermined two time domains. This first frame structure is particularly suitable for the data transmission of subscribers who have a lower individual subscriber speed.
Correspondingly, a second frame structure is allocated to a second speed range, the second frame structure having three pilot signals in predetermined three time domains. This second frame structure is particularly suitable for the data transmission of subscribers who have a higher individual subscriber speed.
In an advantageous development, useful data of subscribers who, due to their individual subscriber speed, are allocated to an identical speed range are transmitted with little control complexity with the aid of a multiplexing method together in a common frame called “subframe”.
Due to the frame structure selected in dependence on the speed range, an accurate channel estimation, which can be adapted to the speed, is possible via the respective pilot signals of the frame structure.
Due to the proposed method, radio transmission resources or subcarriers or “chunks” are always assigned in optimized manner with little control complexity.
“Chunks” or radio transmission resources can be adaptively allocated to respective speed ranges in a particularly advantageous manner in dependence on a radio traffic volume and/or on predominant individual subscriber speeds.
In a further advantageous embodiment, the subcarriers or frequency domains allocated to the speed ranges are not coherently selected. This advantageously results in a subdivision of the frequency domain or of the subcarrier allocation from the total number of subcarriers or “chunks” which use the in each case one frame structure adapted to a particular speed.
The method provides for effective multiplexing particularly for car drivers who continuously change their respective speed in adaptation to the road traffic situation.
With continuous change in the individual speed of progress of a subscriber considered, it is not necessary to continuously change a frame structure within a subcarrier which would otherwise prevent effective multiplexing of the subscriber considered with other subscribers.
The inventors propose that one frame structure per subcarrier is retained. A subscriber is only placed onto another subcarrier if this has an optimum frame structure for the individual speed of progress of the subscriber.
Thus, only a subscriber changing with respect to speed is optimally adapted by displacement. Further subscribers combined in the same domain by multiplexing methods remain untouched by the change or altered allocation.
These and other objects and advantages of the present invention will become more apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which:
Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.
The subcarriers ST1 to ST4 are allocated to a first speed range GB1 and are used for radio transmissions of subscribers, the individual speed v1 of whom corresponds to an interval from 0 km/h to 15 km/h.
To the subcarriers ST1 to ST4, a first frame structure RS1 is allocated which, for example, corresponds to the frame structure according to
Due to its pilot signal, this frame structure is suitable for the comparatively low subscriber speeds.
The subcarriers ST5 to ST10 are allocated to a second speed range GB2 and are used for radio transmissions of subscribers, the individual speed v2 of whom corresponds to an interval from 15 km/h to 120 km/h.
A second frame structure RS2 which, for example, corresponds to the frame structure according to
Due to its two pilot signals, this frame structure is suitable for the comparatively medium subscriber speeds.
The subcarriers ST11 and ST12 are allocated to a third speed range GB3 and are used for radio transmissions of subscribers, the individual speed v3 of whom corresponds to an interval from 120 km/h to 350.
A third frame structure RS3 which, for example, corresponds to the frame structure according to
Due to its three pilot signals, this frame structure is suitable for the comparatively high subscriber speeds.
The individual speed of progress of a subscriber can be determined, for example, with the aid of a signal propagation measurement (determination of the time of arrival, TOA, between a transmitter and a receiver) or by successive determinations of position, if necessary by using GPS.
If a subscriber considered is, for example, a pedestrian, the first speed range GB1 is allocated to the subscriber. Useful data are then transmitted between the subscriber and a base station by using the first frame structure RS1 through one or through a plurality of the subcarriers ST1 to ST4.
If, however, the subscriber considered is a car driver on a freeway, he is allocated, for example, the third speed range GB3. Useful data are then transmitted between the subscriber and the base station by using the third frame structure RS3 through the subcarrier STI1 and/or through the subcarrier ST12.
The invention has been described in detail with particular reference to preferred embodiments thereof and examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention covered by the claims which may include the phrase “at least one of A, B and C” as an alternative expression that means one or more of A, B and C may be used, contrary to the holding in Superguide v. DIRECTV, 69 USPQ2d 1865 (Fed. Cir. 2004).
| Number | Date | Country | Kind |
|---|---|---|---|
| 05460029.1 | Oct 2005 | EP | regional |
This application is based on and hereby claims priority to application number PCT/EP2006/067295 filed on Oct. 11, 2006, and European Application No. 05460029, filed Oct. 20, 2005, the contents of which are hereby incorporated by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2006/067295 | 10/11/2006 | WO | 00 | 4/21/2008 |
