Subframes in a cellular communications system

Abstract

The invention discloses a method for a cellular communications system, in which traffic is sent in frames, each frame comprising a first number of subframes, with a second number of said subframes being available for at least either uplink or downlink traffic. At least one of said second number of subframes is made to comprise at least three parts, as follows:

• • One part which is utilized for uplink traffic,
  • One part which is utilized for downlink traffic,
  • One part which is utilized as a guard period,
    with said guard period part being scheduled between the uplink and the downlink parts. The duration of at least two of said three parts may be varied to fit the current system need.

Description

for downlink traffic as a guard period, step 525,

One part which is utilized as a guard period for downlink traffic, step 530.

The guard period part of step 525 is scheduled between the uplink and the downlink parts, and as shown in step 532, the duration of at least two of the three parts of steps 520, 525 and 530 may be varied to fit the current system need.

As indicated in step 540, the method of the invention may suitably be applied to a TDD-system, Time Division Duplex, i.e. a system with an unpaired spectrum, so that uplink and down link traffic in at least a first plurality of cells in the system occur during different subframes, but on the same frequency.

However, as indicated in step 535, the method of the invention may also be applied to a half duplex FDD-system, Frequency Division Duplex, so that uplink and down link traffic in at least a first plurality of cells in the system occur during different subframes, and on different frequencies.

As shown in step 550, in one embodiment of inventive method, the guard period is one of said at least two of three parts, and the guard period is varied in duration with respect to at least one of the following parameters:

• • Interference from or with other cells in the same system, or other cells in other adjoining or co-located systems,
  • The size of the cell, which determines the maximum propagation round trip time, RTT, in the cell,
  • The modulation scheme used for traffic in the cell.

As shown in step 545, the guard period may also be varied with respect to the interference from or with other cells in the system, so that the duration of the guard period is adapted to be at least equal to the propagation time of signals from at least one controlling node in another cell in the system.

In one embodiment, as shown in step 560, the inventive method may be applied in a system in which an OFDM modulation method, Orthogonal Frequency Division Modulation is used in at least one of the uplink and downlink directions, and at least one of the uplink traffic and downlink parts in said second number of subframes is given a duration which corresponds to an integer number of OFDM symbols in the modulation method.

Also, in a further embodiment of the method of the invention, the subframe which is made to comprise at least three parts is interposed after a subframe used for downlink traffic and is followed by a subframe which is used for uplink traffic, with the downlink part being first in said subframe.

However, in an alternative embodiment, the inventive subframe which is made to comprise at least three parts is interposed after a subframe used for uplink traffic and is followed by a subframe which is used for downlink traffic, with the uplink part being first in said subframe.

As shown in step 570, the method of the invention can be applied to an LTE system, Long Term Evolution.

FIG. 6 shows a block diagram of some parts of a first transceiver 600 which is intended for use as a controlling node in a system of the invention. With retained use of the exemplary LTE terminology, the transceiver 600 will be referred to as an eNodeB. Since the eNodeB of the invention works basically according to the method which has been described above, all of the details of the operation of the eNodeB will not be repeated again here.

The decision or decisions regarding the details of the inventive subframe 420, such as, for example, the duration of the three parts, the DwPTS, the GP and the UpPTS, can be decided in a number of different ways in a system of the invention. For example, the decision can be taken by the operator of the system, and simply forwarded to the eNodeB 600. In order to open for this possibility, the eNodeB will comprise input means 610 for receiving such decisions. The input means 610 are suitably an interface towards another, “higher” node in the system, via which the eNodeB communicates with the system.

The decision from the operator of the system can also be to let the eNodeB decide the particulars of the inventive subframe in a more or less autonomous manner. For example, the eNodeB can be instructed to decide the particulars of the inventive subframe in a completely autonomous manner, based on, for example, interference measurements which the eNodeB carries out. To open up for such a possibility, the eNodeB comprises measurement means 620, which can measure the interference in the cell.

A third possibility is that the operator instructs the eNodeB to decide the particulars of the inventive subframe in a semi-autonomous manner, e.g. based on interference measurements, but with certain conditions which are laid down by the operator, such as, for example, that the duration of one of the three parts, the DwPTS, the GP and the UpPTS, may not exceed or be shorter than a certain specified period of time.

Regardless of how the particulars of the inventive subframe are arrived at by the eNodeB 600, the eNodeB 600 will comprise means 630 for taking a decision to arrive at these particulars. As shown in FIG. 6, this decision making means 630 can receive information both from the input means 610 and the measurement means 620. The decision means 630 will also suitably carry out the actual setting of the particulars of the inventive subframe in the eNodeB 600. Suitably, the decision and setting means will comprise a microcomputer or some similar computing component.

In addition, the eNodeB 600 will also need to communicate the details of the inventive subframe to the UEs in the cell, as well as to UEs which are on their way in to the cell, i.e. UEs in a so called “hand over procedure”, and also to UEs which are turned on in the cell, i.e. UEs which have entered the cell with their power turned off, and which are switched on in the cell. For this reason, the eNodeB 600 is shown as comprising communication means 640, which will suitably comprise a transmitter and an antenna, which are normally comprised in an eNodeB for communication with the UEs in a cell.

Thus, the information regarding the inventive subframe which the eNodeB communicates to the UEs in the cell will comprise the duration of the different parts of the subframe of the invention, i.e. the DwPTS, GP and UpPTS. One preferred method of signaling this information to the UEs in a cell is to use the channel known as BCH, the “Broadcast Channel”, although the information may in principle be communicated to the UEs via other control channels in the system.

FIG. 7 shows a block diagram of some parts of a second transceiver 700 of the invention, which is intended for use as a user terminal (telephone/portable computer etc) in a system of the invention. With retained use of the exemplary LTE terminology, the transceiver 700 will be referred to as a UE, “User Equipment”. Since the UE of the invention works basically according to the method which has been described above, all of the details of the operation of the UE will not be repeated again here.

The UE 700 of the invention is, as is indicated in FIG. 7, equipped with means for receiving instructions from the eNodeB of the cell regarding the duration of the three parts of the inventive subframe, i.e. the DwPTS, the GP and the UpPTS. Suitably, these instructions are received via the same means as other communication from the eNodeB, i.e. via a receiver and an antenna of the UE.

The instructions which are received from the eNodeB are then processed by the UE, i.e. the UE is set to those values of the DwPTS, GP and UpPTS. This is done by means 720 for setting or reconfiguring the DwPTS, GP and UpPTS in the UE. The setting and/or reconfiguration means will suitably comprise microcomputer or some similar computing component.

In conclusion, the invention facilitates harmonization of the two frame structures in LTE for TDD into a single frame structure which can be given a subframe duration of 1 ms. In addition, the invention also solves a number of drawbacks of present solutions, for example:

• • Allows for increased flexibility in creating of UL and DL period lengths, which is beneficial from co-existences perspective with TD-CDMA as well as TD-SCDMA and WiMAX.
  • Allows fine granularity when it comes to allocating resources to UL and DL, as well as increased flexibility when creating guard periods.

Another principle which may be used is so called half duplex FDD, Frequency Division Duplex, in which uplink and downlink transmissions from one and the same terminal in the system occur on different frequencies and during different intervals in time, such as the previously mentioned subframes. The invention can also be applied in such a system, i.e. a half duplex FDD system.

The invention is not limited to the examples of embodiments described above and shown in the drawings, but may be freely varied within the scope of the appended claims.

Claims

1. A radio transceiver comprising:

a transmitter and a receiver, said transmitter and said receiver being configured to send and receive radio frames, respectively, at least some of said radio frames including at least one downlink subframe which contains downlink traffic but no uplink traffic, at least one uplink subframe which contains uplink traffic, but no downlink traffic and, disposed between said at least one downlink subframe and said at least one uplink subframe, a special subframe, said special subframe consisting of:

a first part which is utilized for downlink traffic;

a second part which is utilized as a guard period; and

a third part which is utilized for uplink traffic;

wherein said guard period of said second part is entirely disposed between the first part and the third part;

such that a sum of a duration of the first part, the second part and the third part constitute an entire subframe length;

wherein a duration of at least two of said first part, said second part and said third part may be varied.

2. The transceiver of claim 1, additionally being equipped with means for receiving information from an external source in the system regarding the varying of said three parts.

3. The transceiver of claim 1, being equipped with means for transmitting to users in a cell of the system information regarding the duration of said three parts.

4. The transceiver of claim 1, adapted to be used in a TDD-system, Time Division Duplex, i.e., a system which uses an unpaired spectrum, so that uplink and downlink traffic occur during different subframes.

5. The transceiver of claim 4, adapted to be used on the same frequency for both uplink and downlink traffic.

6. The transceiver of claim 1, adapted to be used in a half duplex FDD-system, Frequency Division Duplex, so that uplink and downlink traffic for one and the same user occur during different subframes, and on different frequencies.

7. The transceiver of claim 1, in which the guard period is one of said at least two of three parts, and the transceiver is equipped with means configured for varying the guard period in duration with respect to at least one of the following parameters:

Interference from or with other cells in the same system, or other cells in other adjoining or co-located systems,

The size of the cell, which determines the maximum propagation round trip time, RTT, in the cell,

The modulation scheme used for traffic in the cell.

8. The transceiver of claim 7, adapted to vary the guard period with respect to the interference from or with other cells in the system, so that the duration of the guard period is adapted to be at least equal to the propagation time of signals from at least one controlling node in another cell in the system.

9. The transceiver of claim 1, being adapted for use in a system in which an OFDM modulation method, Orthogonal Frequency Division Modulation, is used in at least one of the uplink and downlink directions, being equipped with means the transceiver being configured for giving at least one of the uplink traffic and downlink parts in said special subframe a duration which corresponds to an integer number of OFDM symbols in the modulation method.

10. The transceiver of claim 1, which comprises means is configured for interposing said special subframe which consists of at least three parts after said at least one downlink subframe is used for downlink traffic and before said at least one uplink subframe which is used for uplink traffic, with the downlink part being first in said special subframe.

11. The transceiver of claim 1, which comprises means is configured for interposing said special subframe which consists of at least three parts after said at least one uplink subframe is used for uplink traffic and before said at least one downlink subframe which is used for downlink traffic, with the uplink part being first in said special subframe.

12. The transceiver of claim 1, applied to an LTE system, Long Term Evolution.

13. A method for transmitting traffic in frames in a cellular communication system, the method comprising:

dividing said frames into a plurality of subframes, said plurality of subframes including at least one downlink subframe which contains downlink traffic but no uplink traffic, and at least one uplink subframe which contains uplink traffic but no downlink traffic;

transmitting said at least one downlink subframe and said at least one uplink subframe; and

transmitting, between said at least one downlink subframe and said at least one uplink subframe, a special subframe consisting of:

a first part which is utilized for downlink traffic;

a second part which is utilized as a guard period; and

a third part which is utilized for uplink traffic;

wherein said guard period of said second part is entirely disposed between the first part and the third part;

such that a sum of a duration of the first part, the second part and the third part constitute an entire subframe length, and wherein a duration of at least two of said first part, said second part and said third part may be varied.

14. The method of claim 13, applied to a TDD-system, Time Division Duplex, i.e. a system which uses an unpaired frequency spectrum, so that uplink and downlink traffic in at least a first plurality of cells in the system occur during different subframes.

15. The method of claim 14, in which the uplink and the downlink traffic occur on the same frequency.

16. The method of claim 13, applied to a half duplex FDD-system, Frequency Division Duplex, so that uplink and downlink traffic for one and the same user in at least a first number of cells in the system occur during different subframes, and on different frequencies.

17. The method of claim 13, according to which the guard period is one of said at least two of three parts, and according to which method the guard period is varied in duration with respect to at least one of the following parameters:

Interference from or with other cells in the same system, or other cells in other adjoining or co-located systems,

The size of the cell, which determines the maximum propagation round trip time, RTT, in the cell,

The modulation scheme used for traffic in the cell.

18. The method of claim 17, according to which the guard period is varied with respect to the interference from or with other cells in the system so that the duration of the guard period is made at least equal to the propagation time of signals from at least one controlling node in another cell in the system.

19. The method of claim 13, according to which the system is one in which an OFDM modulation method, Orthogonal Frequency Division Modulation is used in at least one of the uplink and downlink directions, and in which at least one of the uplink traffic and downlink parts in said special subframe is given a duration which corresponds to an integer number of OFDM symbols in the modulation method.

20. The method of claim 13, according to which said special subframe which is made to consist of three parts is interposed after said at least one downlink subframe is used for downlink traffic and is followed by said at least one uplink subframe which is used for uplink traffic, with the downlink part being first in said special subframe.

21. The method of claim 13, according to which said special subframe which is made to consist of three parts is interposed after said at least one uplink subframe is used for uplink traffic and is followed by said at least one downlink subframe which is used for downlink traffic, with the uplink part being first in said special subframe.

22. The method of claim 13, applied to an LTE system, Long Term Evolution.