Transmitting Uplink Control Information
In accordance with some embodiments, uplink control information, including a channel quality index, may be transmitted using at least two layers. As a result, more information can be provided for use in situations, such as those involving carrier aggregation, where information for a large number of component carriers must all be provided on one primary component carrier.
This application claims priority to provisional application Ser. No. 61/504,054, filed on Jul. 1, 2011.
BACKGROUNDThis relates generally to cellular communications and, particularly, to techniques for signaling information about the nature of a channel between two wirelessly connected devices.
In order to initiate radio communications between two devices, one device needs to tell the other device about the channel conditions between the two devices. Then the transmitting device knows how to send the transmission because the transmitting device has information about the nature of the channel between the two devices.
One way such information may be exchanged is for a first device, called the base station or eNodeB, to trigger the transmission of channel information from another device, called the user equipment or a mobile station. In such case, the eNodeB sends a pilot (reference) signal to the user equipment and user equipment uses this signal to measure the channel. This channel information is sent to the eNodeB by user equipment through physical uplink shared channel (PUSCH) when the transmission is triggered by the eNodeB. The need for triggering is specific to aperiodic arrangements and is not typically used in periodic arrangements wherein the user equipment periodically advises the eNodeB of the channel conditions.
As system complexity increases, the amount of information that must be transmitted on the uplink channel in aperiodic triggering situations is increasing.
Uplink control information may include channel quality information (CQI) transmitted from a mobile station to a base station. In the case of some wireless technologies, such as the Long Term Evolution (LTE), the mobile station is generally known as the user equipment (UE) and the base station is generally known as the eNodeB (eNB).
When the transmission of information from the user equipment to the eNodeB is aperiodic, the transmission of the information may be triggered by a signal sent from the eNodeB to the user equipment. Uplink information is information that is sent from the user equipment to the eNodeB and downlink information is information sent from the eNodeB to the user equipment.
In some embodiments, once properly triggered, user equipment can send a substantial amount of information over the uplink channel. There are many reasons why the amount of information may become substantial. These will be discussed hereinafter. What will be discussed initially is to enumerate the ways in which more information may be provided on the uplink channel.
In some embodiments, the uplink channel may be segmented into one or more layers. Each layer may carry the same or different codewords. Thus, in one embodiment, two separate layers may provide one codeword (CW), as shown in
A problem may arise in that each of the layers may have different transmission conditions and, as a result, data in one layer may be more likely to be compromised than information on the other layers. Thus, a given codeword may be split up and shifted between layers so that a single codeword is broken up and pieces of the codeword may go on one layer and pieces of the same codeword may go on another layer. At the same time, the second codeword may be shifted in the same way. Thus, as shown in
One benefit of layer shifting is that, hopefully, enough information from each codeword gets through, even if it is only the portion that goes on the better quality stream, so that the necessary information is received by the eNodeB.
Still another option, shown in
The I_MCS provides indices 0 through 31, which are mapped to different modulation coding and signaling schemes. In some cases, a particular index, such as I_MCS=29 may be used for signaling in connection with uplink control information. Thus, by using two transport blocks, more information may be provided, including the provision of different MCSs for each stream. This allows for a combination of streams experiencing different transmission conditions.
Thus, referring to
The sequence begins by generating the codewords at block 12. Then the codewords are scrambled, as indicated in block 14. Next, each codeword is modulation mapped, as indicated in block 16. Each codeword is pre-coded at block 18. Then resource element mapping is done in block 20, followed by signal generation in block 22.
Generally, multiple-input/multiple-output (MIMO) transmission and receiving schemes are used. MIMO is a wireless technology that uses multiple transmitters and receivers to transfer more data at the same time. It takes advantage of a radio wave phenomenon called multipath, wherein transmitted information bounces off of walls, ceilings, and other objects, reaching the receiving antenna multiple times via different angles and at slightly different times. MIMO technology leverages multipath behavior by using multiple smart transmitters and receivers with an added spatial dimension to increase performance and range. Multiple antennas send and receive multiple spatial streams at the same time, allowing antennas to transmit and receive simultaneously. MIMO enables antennas to combine data streams arriving from different paths and at different times to effectively increase receiver signal-capturing power.
Aperiodic CQI-only transmission on PUSCH is generally signaled by the eNodeB using downlink control information (DCI) format 0 or 4 via a combination of I_MCS=29, which is a reserved modulation coding scheme, and a small number of allocated physical resource blocks (PRBs) for transmitting quality information. Generally, the number of physical resource blocks must be less than or equal to 4 for this purpose. The quality information may be the so-called channel quality index (CQI), which is a number indicating the quality of channel to the transmitter provided by a receiver. In general, the channel quality index is supplemented by a so-called pre-coding matrix indicator (PMI) to form what is called the channel state information (CSI). Of course, other ways of providing the channel quality information may also be contemplated.
More than one component carrier may be assigned in schemes that use carrier aggregation. Since service providers do not always have available a wide band for transmission, they sometimes aggregate narrower bands together to provide a given quality of wireless service. Each port may be one component carrier and, by combining the plurality of component carriers, carrier aggregation of two to five carriers may be accomplished to form a wider transmission band. However, generally, all the quality information is provided on only one of those component carriers, called the primary component carrier. This means that a large amount of quality feedback information must be provided on one component carrier due to the larger number of carriers and the larger maximum number of primary resource blocks supported by carrier aggregation. Specifically, up to 20 primary resource blocks may be used and all the quality information for all those resource blocks is provided on the primary component carrier.
Due to the limited number of primary resource blocks used for quality transmissions, it is desirable to increase the capacity for the CSI transmission, typically using physical uplink shared channel (PUSCH). (It should be noted that there is no particular reason why, in other embodiments, physical uplink control channel (PUCCH) could not be used, or some other comparable uplink physical channel.)
Thus, generally, when download control information is in format 0 or format 4, it causes the triggering of the transmission of the uplink control information described herein.
Currently, for a download control information format 0, the CQI-only transmission on PUSCH is triggered in one of two cases. In the first case, if the channel quality index request field is one bit and the channel quality index request field is one with the I_MSC=29 and the number of primary resource blocks being less than or equal to four, then the triggering will occur.
In the other situation for downlink control information format 0, if, instead, the channel quality index request field is two bits, then the transmission will be triggered in the following circumstances. If the channel quality index request field is 01, 10, or 11, and if a single downlink component carrier is reported with I_MCS=29 and the number of primary resource blocks is less than or equal to four, then the transmission will be triggered. However, if there are multiple downlink component carriers reported, then it is permissible if I_MCS=29 and the number of primary resource blocks is less than or equal to 20.
On the other hand, for the download control information format 4, the CQI-only transmission on PUSCH is triggered under the following circumstances. First the downlink control information format must indicate that only one transport block is enabled. Then, if the channel quality index request field is one bit, then the channel quality index request field must be one and for the enabled transport block, I_MCS must equal 29 and the number of programmable resource blocks must be equal to or less than four. However, if the channel quality index request field is two bits, then the channel quality request field must be 01, 10, or 11. Then, if a single downlink component carrier is reported for the enabled transport block I_MCS must be 29 and the number of programmable resource blocks must be less than or equal to four. However, if multiple downlink component carriers are reported, then, for the enabled transport block, I_MCS must be 29 and the number of programmable resource blocks must be less than or equal to 20.
In the situation shown in
In some embodiments, the modulation scheme for the uplink control information may be limited to QPSK. However, other modulations, such as 16 QAM, may also be used in some embodiments.
In the embodiments shown in
As another example of using two codewords and two layers with one MCS, two codewords supporting link adaption may be used, as indicated in
Transmitting the channel state information on PUSCH with rank higher than one may only be helpful when the uplink channel condition is good enough to support ranks higher than one for both data and the channel state information itself.
Of course, the examples of
For example, consider the case where the channel conditions for the first codeword are not good enough and can only support transmission with QPSK, while the second codeword sees good channel conditions which support 64 QAM transmission. In the embodiment of
Thus, in the embodiment of
Thus, as shown in
One benefit of layer shifting is to provide additional diversity between the two codewords. The benefit is clear when you consider the previous example. When the layer shifter is applied, some symbols of both codewords will experience the better channel and this will help the system to increase the probability of correct decoding. Therefore, this scheme may have better performance, in some embodiments.
Finally, as indicated in
The computer system 130, shown in
The chipset logic 110 may include a non-volatile memory port to couple the main memory 132. Also coupled to the logic 110 may be multiple antennas 121, 122 to implement multiple input multiple output (MIMO) in one embodiment. Speakers 124 may also be coupled through logic 110.
References throughout this specification to “one embodiment” or “an embodiment” mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation encompassed within the present invention. Thus, appearances of the phrase “one embodiment” or “in an embodiment” are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be instituted in other suitable forms other than the particular embodiment illustrated and all such forms may be encompassed within the claims of the present application.
While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.
Claims
1. A method comprising:
- aperiodically providing channel quality information; and
- using a physical uplink shared channel having at least two layers to provide said information.
2. The method of claim 1 including providing channel quality information using two layers with two modulation-coding-schemes.
3. The method of claim 1 including using at least two codewords.
4. The method of claim 3 including using link adaptation.
5. The method of claim 3 including using layer shifting.
6. The method of claim 3 including using at least two layers with two modulation-coding-schemes.
7. The method of claim 1 including sending the same codeword over two different layers.
8. A non-transitory computer readable medium storing instructions to enable a processor to:
- aperiodically provide channel quality information; and
- send said information over a physical uplink shared channel having at least two layers.
9. The medium of claim 8 further storing instructions to provide channel quality information using two layers with two modulation-coding-schemes.
10. The medium of claim 8 further storing instructions to use at least two codewords.
11. The medium of claim 10 further storing instructions to use link adaptation.
12. The medium of claim 10 further storing instructions to use layer shifting.
13. The medium of claim 10 further storing instructions to use at least two layers with two modulation-coding-schemes.
14. The medium of claim 8 further storing instructions to send the same codeword over two different layers.
15. A mobile station comprising:
- a processor to aperiodically provide channel quality information; and
- a wireless transceiver to send the information over a physical uplink shared channel having at least two layers.
16. The station of claim 15 said processor to provide channel quality information using two layers with two modulation coding schemes.
17. The station of claim 15 said processor to use at least two codewords.
18. The station of claim 17 said processor to use link adaptation.
19. The station of claim 17 said processor to use layer shifting.
20. The station of claim 17 said processor to use at least two layers with two modulation coding schemes.
21. The station of claim 15 said processor to send the same codeword over two different layers.
22. The station of claim 15 wherein said station is a user equipment.
Type: Application
Filed: Dec 30, 2011
Publication Date: Oct 10, 2013
Inventors: Hooman Shirani-Mehr (Portland, OR), Shafi Bashar (Santa Clara, CA), Jong-Kae Fwu (Sunnyvale, CA), Xiaogang Chen (Beijing), Apostolos Papathanassiou (San Jose, CA)
Application Number: 13/994,322
International Classification: H04W 72/04 (20060101);