US20150117372A1

US20150117372A1 - Assignment of radio resources to be used on downlink transmissions in a multiple input multiple output (mimo) communication system

Info

Publication number: US20150117372A1
Application number: US14/528,842
Authority: US
Inventors: Mårten Sundberg; Olof Liberg; Xun Qiu; Nicklas Johansson; John Walter Diachina
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2013-10-31
Filing date: 2014-10-30
Publication date: 2015-04-30
Also published as: US20150117371A1; WO2015063741A1; US9654191B2; WO2015063740A1

Abstract

An access point and method are described herein for receiving a report from the mobile station containing at least one of a channel quality and a signal strength for each of one or more streams associated with each of one or more transmission modes used during a period of time to send payload to the mobile station, and analyzing the received report to determine one or more downlink control parameters to be used for sending additional payload to the mobile station. In addition, a mobile station and method are described herein for detecting one or more modes of transmissions used by the access point during a period of time to send payload to the mobile station, generating a report containing at least one of a channel quality and a signal strength for each of one or more streams associated with each of the detected one or more transmission modes used by the access point to send the payload to the mobile station, and transmitting the report to the access point.

Description

CLAIM OF PRIORITY

This application claims the benefit of priority to U.S. Provisional Application No. 61/898,284, filed on Oct. 31, 2013, and further claims the benefit of priority to U.S. Provisional Application No. 61/898,296, filed on Oct. 31, 2013. The entire contents of each of these applications are hereby incorporated herein by reference for all purposes.

RELATED APPLICATION

This application is related to the co-assigned U.S. patent application Ser. No. ______ (Docket No. P42026-US2) entitled “Assignment of Radio Resources to be used on Uplink Transmissions in a Multi-User Multiple Input Multiple Output (MU-MIMO) Communication System”. The contents of this document are hereby incorporated herein by reference for all purposes.

TECHNICAL FIELD

The present disclosure relates in general to the wireless telecommunications field and, in particular, to at least the following: (1) an access point and method for receiving a report from the mobile station and analyzing the received report to determine one or more downlink control parameters to be used for sending additional payload to the mobile station, and (2) a mobile station and method for detecting one or more modes of transmissions used by the access point to send payload to the mobile station, generating a report containing at least one of a channel quality and a signal strength for each of one or more streams associated with each of the one or more transmission modes used by the access point to send the payload to the mobile station, and transmitting the report to the access point.

BACKGROUND

The following abbreviations are herewith defined, at least some of which are referred to within the following description of the prior art and the present invention.

BSS Base Station Subsystem

CRC Cyclic Redundancy Check

DL Downlink

EDGE Enhanced Data rates for GSM Evolution

EGPRS Enhanced General Packet Radio Service

GPRS General Packet Radio Service

GSM Global System for Mobile Communications

KBPS Kilo-Bits Per Second

MCS Modulation and Coding Scheme

MIMO Multiple Input Multiple Output

MS Mobile Station

MU Multi-User

PACCH Packet Associated Control Channel

PC Power Control

PDCH Packet Data Channel

PTCCH Packet Timing Advance Control Channel

RLC Radio Link Control

SU Single User

TBF Temporary Block Flow

TFI Temporary Flow Identity

TS Time Slot

TSC Training Sequence Code

UL Uplink

USF Uplink State Flag

In the wireless telecommunications field, the traditional communication MIMO system is typically addressing one user (mobile station), also referred to as a single-user MIMO system (SU-MIMO). In the case of SU-MIMO, the access point (base station) communicates with only one mobile station (the user) while both the access point and the mobile station are equipped with multiple antennas. Although the SU-MIMO technology works relatively well there are still problems that need to be addressed. For instance, if SU-MIMO were to be deployed on the downlink in a GSM/EDGE system then the access point may not receive appropriate feedback from the mobile station so as to be able to effectively determine downlink control parameters which are to be used to send payload to the mobile station. The present invention addresses this problem and other problems which are associated with the existing DL SU-MIMO technology.

SUMMARY

An access point, a mobile station, and various methods which address the aforementioned problem and other problems associated with the existing DL SU-MIMO technology are described in the independent claims. Advantageous embodiments of the access point, mobile station, and various methods are further described in the dependent claims.
In one aspect, the present invention provides an access point which is configured to interact with a mobile station. The access point comprises at least one processor, and at least one memory that stores processor-executable instructions, wherein the at least one processor interfaces with the at least one memory to execute the processor-executable instructions, whereby the access point is operable to perform a receive operation and an analyze operation. In the receive operation, the access point receives a report from the mobile station, where the report contains at least one of a channel quality and a signal strength for each of one or more streams associated with each of one or more transmission modes used during a period of time to send payload to the mobile station. In the analyze operation, the access point analyzes the received report to determine one or more downlink control parameters to be used for sending additional payload to the mobile station. The access point operating in this manner is able to dynamically and effectively decide what transmission mode (e.g., single stream transmission, dual stream transmission) and/or MCS(s) and/or power control level(s) and/or TSC(s) to be used for sending additional payload to the mobile station.
In another aspect, the present invention provides a method in an access point for interacting with a mobile station. The method comprises a receiving operation and an analyzing operation. In the receiving operation, the access point receives a report from the mobile station, where the report contains at least one of a channel quality and a signal strength for each of one or more streams associated with each of one or more transmission modes used during a period of time to send payload to the mobile station. In the analyzing operation, the access point analyzes the received report to determine one or more downlink control parameters to be used for sending additional payload to the mobile station. The assess point operating in this manner is able to dynamically and effectively decide what transmission mode (e.g., single stream transmission, dual stream transmission) and/or MCS(s) and/or power control level(s) and/or TSC(s) to be used for sending additional payload to the mobile station.
In still yet another aspect, the present invention provides a mobile station which is configured to interact with an access pint. The mobile station comprises at least one processor, and at least one memory that stores processor-executable instructions, wherein the at least one processor interfaces with the at least one memory to execute the processor-executable instructions, whereby the mobile station is operable to perform a detect operation, a generate operation, and a transmit operation. In the detect operation, the mobile station detects one or more transmission modes used by the access point during a period of time to send payload to the mobile station. In the generate operation, the mobile station generates a report containing at least one of a channel quality and a signal strength for each of one or more streams associated with each of the detected one or more transmission modes that was used by the access point to send the payload to the mobile station. In the transmit operation, the mobile station transmits the report to the access point. The mobile station operating in this manner is able to inform the access point about how it is performing in different downlink transmission modes so the access point can dynamically and effectively decide what transmission mode (e.g., single stream transmission, dual stream transmission) and/or MCS(s) and/or power control level(s) and/or TSC(s) should be used for sending additional payload to the mobile station.
In another aspect, the present invention provides a method in a mobile station for interacting with an access pint. The method comprises a detecting operation, a generating operation, and a transmitting operation. In the detecting operation, the mobile station detects one or more transmission modes used by the access point during a period of time to send payload to the mobile station. In the generating operation, the mobile station generates a report containing at least one of a channel quality and a signal strength for each of one or more streams associated with each of the detected one or more transmission modes that was used by the access point to send the payload to the mobile station. In the transmitting operation, the mobile station transmits the report to the access point. The mobile station operating in this manner is able to inform the access point about how it is performing in different downlink transmission modes so the access point can dynamically and effectively decide what transmission mode (e.g., single stream transmission, dual stream transmission) and/or MCS(s) and/or power control level(s) and/or TSC(s) should be used for sending additional payload to the mobile station.
Additional aspects of the invention will be set forth, in part, in the detailed description, figures and any claims which follow, and in part will be derived from the detailed description, or can be learned by practice of the invention. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be obtained by reference to the following detailed description when taken in conjunction with the accompanying drawings:

FIG. 1 is a diagram of an exemplary access point which is configured to interact with a mobile station and implement a method in accordance with an embodiment of the present invention; and

FIG. 2 is a diagram of an exemplary mobile station which is configured to interact with an access point and implement a method in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

To describe the technical features of the present invention, a detailed discussion is provided first to explain DL SU-MIMO technology and why an access point 100 needs appropriate feedback from a mobile station 102 to effectively determine downlink control parameters which are to be used to send payload to the mobile station. Thereafter, a detailed discussion with respect to FIGS. 1-2 is provided to explain in more detail the specially configured access point 100 and mobile station 102 and the associated methods 150 and 250 which are performed by these devices in accordance with different embodiments of the present invention.

DL SU-MIMO Technology

In DL SU-MIMO transmissions, transmissions are taking place from the access point 100 to the mobile station 102. The access point 100 need not command the mobile station 102 the chosen MCS as required for UL transmissions wherein the mobile station 102 needs to use the chosen MCS to send transmissions to the access point 100, but instead the access point 100 has complete control of the DL SU-MIMO transmission and chooses the MCS which is used to send DL transmissions to the mobile station 102, Typically, the mobile station 102 blindly detects the MCS used in the received DL transmissions. As for the power level used by the access point 100 (e.g., base station 100) to send DL transmissions to the mobile station 102, the access point 100 can to a large extent control the power imbalance between streams received from the mobile stations 102. However, in order for the access point 100 to make a proper choice of both MCS and power level for the DL transmissions to the mobile station 102, the access point 100 needs to understand how the mobile station 102 performs in different DL transmission modes (i.e. single stream or dual stream mode (in case of 2×2 MIMO)) that have been used by the access point 100 to send payload to the mobile station 102.
In this regard, the current behavior in the GSM/EDGE network is for the legacy access point (BSS) to request the legacy mobile station to provide feedback where the legacy mobile station reports both estimated channel quality and signal level based on per-burst measurements during the reporting period (from the previous time the legacy mobile station was requested to send feedback to the network, until the current request). However, the legacy mobile station makes no distinction between different DL transmission modes (single or dual stream transmission) in channel quality reporting, so the channel quality report received by the legacy access point will contain a single representative value over a time period irrespective of the actual transmission modes that have been used and this may prove problematic for the legacy access point in making the optimum MCS and power level decisions to be used for DL transmissions to the legacy mobile station.
Embodiments of the present invention described hereinafter introduce the access point 100 which is specially configured to dynamically and effectively decide what transmission mode (e.g., single stream transmission, dual stream transmission) and/or MCS(s) and/or power control level(s) and/or TSC(s) to use for DL transmissions to the mobile station 102. The access point 100 is able to accomplish this by understanding in a timely manner and with minimum impact on user plane throughput how the mobile station 102 performs in different DL transmission modes (i.e. single stream or dual stream mode) which have been used by the access point 100. In particular, the access point 100 is able to accomplish this by receiving a specially configured report 104 which contains desirable DL SU-MIMO feedback from the mobile station 102.
The desirable DL SU-MIMO feedback which enables the access point 100 to properly control the link adaptation, power level etc for DL transmissions to the mobile station 102 can be obtained by letting the mobile station 102 autonomously detect the mode of transmission (e.g., single stream or dual stream) and have it report the channel quality and/or signal strength separately for each stream associated with the detected transmission mode(s). For example, if the transmission mode in the network was a single transmission mode (i.e., MIMO is not used), then the report 104 from the mobile station 102 would contain information regarding the channel quality and/or signal strength for the received bursts in the single stream. And, if the transmission mode in the network was a dual transmission mode, then the report 104 from the mobile station 102 would contain two separate sets of information related to channel quality and/or signal strength for the received bursts within each of the two streams associated with the dual transmission mode. It should be noted that the access point 100 may use multiple transmission modes (e.g., signal stream and dual stream) during a period of time to send DL transmissions to the mobile station 102. For example, if the transmission modes in the network were a single transmission mode and a dual transmission mode, then the report 104 from the mobile station 102 would contain information regarding the channel quality and/or signal strength for the received bursts in the single stream associated with the signal transmission mode, and contain two separate sets of information related to channel quality and/or signal strength for the bursts in each of the two streams associated with the dual transmission mode. In this case, the mobile station 102 during a reporting period in which both dual and single stream transmissions are received will detect these transmission modes and provide feedback information for each stream in each transmission mode separately in the same reporting message 104.
To summarize, the mobile station 102 depending on the detected transmission mode(s) will send a report 104 containing the channel quality and/or signal level separated for:

- Single stream transmission mode; and/or
- Dual stream transmission mode,
  - One for first stream, and
  - One for second stream.
- etc. . . .

This reporting scheme is desirable because the mobile station 102 may experience different qualities in the different spatial streams. Hence, the mobile station 102 by reporting the quality of each stream to the access point 100 enables the best modulation scheme (for example) to be chosen respectively for each stream which is to be used when sending additional payload to the mobile station 102.
Given the volume of information expected in the channel quality report 104 when the mobile station 102 is using DL SU-MIMO means that an increase in the use of PACCH based reporting will be needed for the control plane signaling to transmit the report 104 to the access point 100. This is possible but it is desirable to minimize the control plane signaling and one alternative way for the mobile station 102 to transmit the report 104 to the access point 100 while minimizing PACCH based signaling is described next. Assuming the mobile station 102 is operating according to DL SU-MIMO and has an ongoing UL TBF, then a UL Mini-PACCH could be used to convey this feedback information (i.e., the report 104) to the access point 100 which enables the access point 100 to make fast decisions regarding what transmission mode and/or MCSs and/or TSCs to use on the DL. The UL Mini-PACCH is a piggy-backed Ack/Nack (PAN) field (or variation thereof) used in a dedicated message where the existing PAN space is treated as a Mini-PACCH in which the 20 payload bits of the current PAN are formatted in a new manner to contain the report 104 and support this new functionality. The Mini-PACCH can be sent in a RLC data block (i.e., user plane payload) rather than PACCH based signaling to minimize the impact of PDCH utilization.
Referring to FIG. 1, there is a diagram of an exemplary access point 100 which is configured to interact with a mobile station 102 and implement a method 150 in accordance with an embodiment of the present invention. As shown, the access point 100 includes an input interface 101, at least one processor 103, at least one memory 105, and an output interface 107. The access point 300 includes many other components which are well known in the art but for clarity the well known components are not described herein. The access point 300 functions wherein the at least one processor 403 interfaces with the at least one memory 405 to execute processor-executable instructions stored therein whereby the access point 300 is operable to implement the various steps of the method 400 as discussed next. Beginning at step 152, the access point 100 receives, from the mobile station 102, the report 104 containing at least one of a channel quality and a signal strength for each of one or more streams associated with each of one or more transmission modes used during a period of time to send payload to the mobile station 102. As discussed above, the access point 100 could receive the report 104 via UL control plane signaling or in a dedicated message which has a piggy-backed Ack/Nack (PAN) field (or variation thereof) in which the PAN space contains the report 104. In effect, the PAN space is treated as an UL Mini-PACCH which can be desirable because there is no need to allocate a full data block for the control signaling. Instead, the Ack/Nack is piggy-backed on the data block, effectively creating a data block and a control block in the same UL block transmission.
The following are some examples of what the report 104 could contain under several different circumstances. In one example, if the access point 100 used a single stream transmission mode to previously send payload during a period of time to the mobile station 102 then the received report 104 would contain at least one of the channel quality and the signal strength of one stream used in the single stream transmission mode. In another example, if the access point 100 used a dual stream transmission mode to previously send payload during a period of time to the mobile station 104 then the received report 104 would contain (a) at least one of the channel quality and the signal strength of a first stream used in the dual stream transmission mode, and (b) at least one of the channel quality and the signal strength of a second stream used in the dual stream transmission mode. In yet another example, if the access point 100 used a single stream transmission mode and a dual stream transmission mode to previously send payload during a period of time to the mobile station 102 then the received report 104 would contain: (a) at least one of the channel quality and the signal strength of one stream used in the single stream transmission mode; (b) at least one of the channel quality and the signal strength of a first stream used in the dual stream transmission mode, and (c) at least one of the channel quality and the signal strength of a second stream used in the dual stream transmission mode.
At step 154, the access point 100 analyzes the received report 104 to determine one or more DL control parameters which are to be used for sending additional payload to the mobile station 102. As described above, the DL control parameter(s) can comprise at least one of the following: one or more transmission modes, one or more MCSs, one or more power levels, one or more USFs, and one or more Training Sequence Codes (TSCs).
Referring to FIG. 2, there is a diagram of an exemplary mobile station 102 which is configured to interact with an access point 100 and implement a method 250 in accordance with an embodiment of the present invention. As shown, the mobile station 102 (e.g., mobile phone, tablet, laptop computer, machine-type-communication device etc. . . . ) includes an input interface 201, at least one processor 203, at least one memory 205, and an output interface 207. The mobile station 102 includes many other components which are well known in the art but for clarity the well known components are not described herein. The mobile station 102 functions wherein the at least one processor 203 interfaces with the at least one memory 205 to execute processor-executable instructions stored therein whereby the mobile station 102 is operable to implement the various steps of the method 250 as discussed next. Beginning at step 252, the mobile station 102 detects one or more transmission modes used by the access point 100 during a period of time to send payload to the mobile station 102. For instance, the mobile station 102 can detect the one or more transmission modes by detecting the training sequence used by the respective received stream(s). The training sequence is a pre-defined bit pattern and will be known to the mobile station 102 when the data carrier is set-up.
At step 254, the mobile station 102 generates the report 104 containing at least one of a channel quality and a signal strength for each of one or more streams associated with each of the detected one or more transmission modes used by the access point 100 to send the payload to the mobile station 102. To accomplish this, the mobile station 102 would have to measure at least one of the channel quality and the signal strength for each of one or more streams associated with each of the detected one or more transmission modes used by the access point 100 to send the payload to the mobile station 102. The following are some examples of what the report 104 could contain under several different circumstances. In one example, when the mobile station 102 detects a single stream transmission mode then the generated report 104 would contain at least one of the channel quality and the signal strength of one stream used in the single stream transmission mode. In another example, when the mobile station 102 detects a dual stream transmission mode then the generated report 104 would contain (a) at least one of the channel quality and the signal strength of a first stream used in the dual stream transmission mode, and (b) at least one of the channel quality and the signal strength of a second stream used in the dual stream transmission mode. In yet another example, when the mobile station 102 detects a single stream transmission mode and a dual stream transmission mode then the generated report 104 would contain: (a) at least one of the channel quality and the signal strength of one stream used in the single stream transmission mode; (b) at least one of the channel quality and the signal strength of a first stream used in the dual stream transmission mode, and (c) at least one of the channel quality and the signal strength of a second stream used in the dual stream transmission mode.
At step 256, the mobile station 102 transmits the report 104 via the output interface 207 to the access point 100. As discussed above, the mobile station 102 could transmit the report 104 using UL control plane signaling or in a dedicated message which has a piggy-backed Ack/Nack (PAN) field (or variation thereof) in which the PAN space contains the report 104. In effect, the PAN space is treated as an UL Mini-PACCH which can be desirable because there is no need to allocate a full data block for the control signaling. Instead, the Ack/Nack is piggy-backed on the data block, effectively creating a data block and a control block in the same UL block transmission.
Although multiple embodiments of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it should be understood that the invention is not limited to the disclosed embodiments, but instead is also capable of numerous rearrangements, modifications and substitutions without departing from the present invention that as has been set forth and defined within the following claims.

Claims

1. An access point configured to interact with a mobile station, the access point comprising:

at least one processor; and,

at least one memory that stores processor-executable instructions, wherein the at least one processor interfaces with the at least one memory to execute the processor-executable instructions, whereby said access point is operable to:

receive, from the mobile station, a report containing at least one of a channel quality and a signal strength for each of one or more streams associated with each of one or more transmission modes used during a period of time to send payload to the mobile station; and,

analyze the received report to determine one or more downlink control parameters to be used for sending additional payload to the mobile station.

2. The access point of claim 1, wherein the one or more downlink control parameters comprise at least one of the following: one or more transmission modes, one or more Modulation and Coding Schemes (MCSs), one or more power levels, one or more Uplink State Flags (USFs), and one or more Training Sequence Codes (TSCs).

3. The access point of claim 1, wherein when the access point used a single stream transmission mode to previously send the payload to the mobile station then the received report contains:

the at least one of the channel quality and the signal strength of one stream used in the single stream transmission mode.

4. The access point of claim 1, wherein when the access point used a dual stream transmission mode to previously send the payload to the mobile station then the received report contains:

the at least one of the channel quality and the signal strength of a first stream used in the dual stream transmission mode; and,

the at least one of the channel quality and the signal strength of a second stream used in the dual stream transmission mode.

5. The access point of claim 1, wherein when the access point used a single stream transmission mode and a dual stream transmission mode to previously send the payload to the mobile station then the received report contains:

the at least one of the channel quality and the signal strength of one stream used in the single stream transmission mode;

6. A method in an access point for interacting with a mobile station, the method comprising:

receiving, from the mobile station, a report containing at least one of a channel quality and a signal strength for each of one or more streams associated with each of one or more transmission modes used during a period of time to send payload to the mobile station; and,

analyzing the received report to determine one or more downlink control parameters to be used for sending additional payload to the mobile station.

7. The method of claim 6, wherein the one or more downlink control parameters comprise at least one of the following: one or more transmission modes, one or more Modulation and Coding Schemes (MCSs), one or more power levels, one or more Uplink State Flags (USFs), and one or more Training Sequence Codes (TSCs).

8. The method of claim 6, wherein when the access point used a single stream transmission mode to previously send the payload to the mobile station then the received report contains:

9. The method of claim 6, wherein when the access point used a dual stream transmission mode to previously send the payload to the mobile station then the received report contains:

10. The method of claim 6, wherein when the access point used a single stream transmission mode and a dual stream transmission mode to previously send the payload to the mobile station then the received report contains:

11. A mobile station configured to interact with an access point, the mobile station comprising:

at least one processor; and,

at least one memory that stores processor-executable instructions, wherein the at least one processor interfaces with the at least one memory to execute the processor-executable instructions, whereby said mobile station is operable to:

detect one or more transmission modes used by the access point during a period of time to send payload to the mobile station;

generate a report containing at least one of a channel quality and a signal strength for each of one or more streams associated with each of the detected one or more transmission modes that was used by the access point to send the payload to the mobile station; and,

transmit the report to the access point.

12. The mobile station of claim 11, wherein when the mobile station detects a single stream transmission mode then the generated report contains:

the at least one of the channel quality and the signal strength of one stream used in the detected single stream transmission mode.

13. The mobile station of claim 11, wherein when the mobile station detects a dual stream transmission mode then the generated report contains:

the at least one of the channel quality and the signal strength of a first stream used in the detected dual stream transmission mode; and,

the at least one of the channel quality and the signal strength of a second stream used in the detected dual stream transmission mode.

14. The mobile station of claim 11, wherein when the mobile station detects a single stream transmission mode and a dual stream transmission mode then the generated report contains:

the at least one of the channel quality and the signal strength of one stream used in the detected single stream transmission mode;

15. The mobile station of claim 11, wherein when the mobile station has an ongoing Uplink Link Temporary Block Flow (UL TBF) with the access point then the mobile station sends a dedicated message which has a piggy-backed Ack/Nack (PAN) field or variation thereof wherein space therein contains the report.

16. A method in a mobile station for interacting with an access point, the method comprising:

detecting one or more transmission modes used by the access point during a period of time to send payload to the mobile station;

generating a report containing at least one of a channel quality and a signal strength for each of one or more streams associated with each of the detected one or more transmission modes that was used by the access point to send the payload to the mobile station; and,

transmitting the report to the access point.

17. The method of claim 16, wherein when a single stream transmission mode is detected then the generated report contains:

18. The method of claim 16, wherein when a dual stream transmission mode is detected then the generated report contains:

19. The method of claim 16, wherein when a single stream transmission mode and a dual stream transmission mode are detected then the generated report contains:

20. The method of claim 16, wherein when the mobile station has an ongoing Uplink Link Temporary Block Flow (UL TBF) with the access point then the mobile station sends a dedicated message which has a piggy-backed Ack/Nack (PAN) field or variation thereof wherein space therein contains the report.