Medium access control schedulers for wireless communication

Patent metadata

Field	Value
Publication number	US-10075969-B2
Application number	US-201213455463-A
Country	US
Kind code	B2
Filing date	Apr 25, 2012
Priority date	Apr 25, 2011
Publication date	Sep 11, 2018
Grant date	Sep 11, 2018

Abstract

Wireless communication between a base station and at least one user equipment comprises the following. Each user equipment periodically measures channel quality of communication with the base station and transmits a channel quality indicator to the base station. The base station schedules communication with the at least one user equipment based upon the periodically transmitted channel quality indicators.

First claim

What is claimed is:

1. A method of wireless communication between a base station and at least one user equipment comprising the steps of:
each user equipment periodically transmitting a wide band Sounding Reference Signal (SRS) to the base station for uplink channel state estimation;
each user equipment transmitting along with each scheduled uplink transmission a DeModulation Reference Signal (DMRS) to the base station for uplink demodulation and interference estimation; and
the base station scheduling uplink communication with each user equipment based upon the SRS and DMRS signals transmitted by each user equipment, the scheduling including
estimating the user equipment's channel quality for each frequency chunk,
computing a corresponding user equipment's scheduling metric for each frequency chunk,
limiting the size of the user equipment's uplink allocation based upon reported headroom and buffer size, and
selecting for uplink transmission on a frequency chunk the user equipment with the highest scheduling metric with the constraint of scheduling a user equipment on contiguous frequency chunks; and

the base station signaling to the selected user equipment its scheduling grant.

2. The method of claim 1 , further comprising:
transmitting a schedule from the base station to a user equipment via a Physical Downlink Control Channel, wherein said step of scheduling communication for each allocation employs a Physical Downlink Control CHannel mapping function including computing a cost function for each Control Channel Element (CCE) by

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where: C i (n) is the CCE cost function to be calculated; S(n) is the set of active UEs at the n-th subframe; and A i,j (n) is the cost of user j associated with the i-th CCE at the n-th subframe; and
mapping a scheduled UE j to the available CCE combination within its user search space that minimizes C i (n); and
transmitting the PDCCH to the scheduled UEs.

3. A method of wireless communication between a base station and at least one user equipment comprising the steps of:
each user equipment periodically transmitting a wide band Sounding Reference Signal (SRS) to the base station for uplink channel state estimation;
each user equipment transmitting along with each scheduled uplink transmission a DeModulation Reference Signal (DMRS) to the base station for uplink demodulation and interference estimation; and
the base station scheduling uplink communication with the at least one user equipment based upon the SRS and DMRS signals transmitted by the at least one user equipment, said scheduling uplink communication includes a 2-step Signal to Interference plus Noise Ratio computation and link adaptation including:
in a first step referred to as pre-scheduling, computing the Signal to Interference plus Noise Ratio Y(b) for each frequency chunk b upon every new UE's Sounding Reference Signal instance;
in a second step referred to as post-scheduling, on every sub-frame, recomputing the Signal to Interference plus Noise Ratio Y(B k ) for each schedule user equipment k taking into account both the size of the final allocation B k and the freshest interference measurement; and
determining from Y(B k ) the modulation and coding scheme (MCS) to be used for each scheduled user equipment k; and

the base station signaling to each scheduled user equipment k its scheduling grant including said MCS.

4. The method of claim 3 , wherein:
said step of pre-scheduling further includes
calculating a per tone Signal to Interference plus Noise Ratio, and
calculating a per-frequency-chunk effective Signal to Interference plus Noise Ratio Y(b) by harmonic averaging across tones.

5. A method of wireless communication between a base station and at least one user equipment (UE) comprising the steps of:
each user equipment periodically transmitting a wide band Sounding Reference Signal (SRS) to the base station for uplink channel state estimation;
each user equipment transmitting along with each scheduled uplink transmission a DeModulation Reference Signal (DMRS) to the base station for uplink demodulation and interference estimation;
the base station scheduling uplink communication with the at least one user equipment based upon the SRS and DMRS signals transmitted by the at least one user equipment, said step of scheduling uplink communication includes a 2-step recursive maximum expansion calculation including
initial subband allocation and expansion, and
subband gap filling; and

the base station signaling to each scheduled user equipment its scheduling grant.

6. The method of claim 5 , wherein said step of initial subband allocation and expansion includes
sorting UEs with highest scheduling metric among competing UEs per subband to produce two UEs by subband tables, where the first table provides the indices of the sorted UEs and the second table provides the associated scheduling metric,
defining an allocation loop as a series of allocation iterations, each allocation iteration being an attempt to allocate one UE on one or multiple subbands including
an initial subband allocated to the remaining UE with the maximum scheduling metric,
performing a recursive maximum expansion (RME) on both sides of the initial allocated subband, the outcome of each allocation iteration disqualifying one UE as either not having a Physical Downlink Control Channel (PDCCH) resource or less than other remaining UEs with higher scheduling metrics on each side.

7. The method of claim 5 , wherein:
said step of subband gap filling is performed by maximum subband first including
finding the subband with a maximum metric for two edge target UEs,
checking if the subband with the maximum metric can be covered by power headroom (PHR) and buffered data of its target UE, and if so allocating that subband to the target UE, if not proceeding the next maximum subband, and
upon allocation of a subband allocating the subbands between that subband and the subband of the same UE to that UE for contiguous allocation.

8. The method of claim 5 , wherein:
said step of subband gap filling is performed by higher edge first including iteratively
comparing the metrics of two edge subbands of respective adjacent UEs,
allocating the subband having the higher metric to its edge UE, and
checking for power shortage.

9. The method of claim 5 , wherein:
said step of scheduling communication including 2-step recursive maximum expansion calculation wherein a special uplink communication is limited to a pre-determined transport block size that cannot be segmented including scheduling special uplink communication first allocating

Assignees

• Bertrand Pierre
• Jiang Jing
• Livshitz Michael
• Texas Instruments Inc

Inventors

• Bertrand Pierre
• Jiang Jing
• Livshitz Michael

Classifications

• H04W72/542 Primary

  using measured or perceived quality · CPC title

• H04W72/1231 Primary

  Electricity · mapped topic