# US 9,521,560 B2 · Multicell beamforming system and methods for OFDMA small-cell networks

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- Number: US 9,521,560 B2
- Document ID: US9521560B2
- Status: Granted
- Kind: B2
- Application number: 14/231,290
- Filed: 2014-03-31
- Published: 2015-10-01
- Granted: 2016-12-13
- Earliest claimed: 2014-03-31
- Assignees: NEC Corporation
- Applicants: NEC Laboratories America, Inc.
- Inventors: Karthikeyan Sundaresan; Mohammad Ali Khojastepour; Sampath Rangarajan; Jongwon Yoon
- Web page: https://patentgrep.com/patent/US9521560B2

## CPC

- H04W 16/28: using beam steering
- H01Q 3/00: Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system {(means for positioning H01Q1/125)}
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)
- H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72)

## Abstract

Disclosed are systems, methods and structures that provide improved spatial reuse of spectral resources in small-cell wireless networks including WiMAX, LTE, LTE-Advanced, etc. Advantageously, the systems and method disclosed while leveraging beamforming for spatial reuse across small cells also decouple it from per-frame scheduling at a small cell base station thereby allowing for beam selections to be computed with a granularity measured in seconds. In realizing these advantages, systems, methods and structures disclosed integrate beam selection with client association.

## Claims

### Claim 1

A computer implemented method for providing beamforming and spatial reuse in a small-cell wireless network comprising:
providing a central controller (CC) to perform resource and interface management for small cells jointly with a high speed backhaul which interconnects the small cells with the CC thereby providing for information exchange between the small cells;
receiving signals from the small-cell wireless network with wireless transceivers;
estimating a signal-to-interference-plus-noise ratio (SINR) of clients in the small cells to determine any interference dependencies between small cells in the wireless network in the presence of beamforming, wherein said SINR is determined from signal-to-noise (SNR) measurement according to the following relationship
SINR
ij
=
SNR
ij
∑
k
≠
i
⁢
INR
kj
+
1
such that only a linear number of measurements is made, where SINR at client j from a base station i is related to its SNR and net interference-to-noise ratio (INR) from other base stations by
INR
kj
=
∑
k
≠
i
⁢
INR
kj
+
1
and INR+1≈INR; and
associating one or more of the clients with the particular beamforming;
selecting particular beam patterns for each small cell such that spatial reuse is increased; and
providing beamforming and spatial reuse for transmission using the transceivers in a small-cell wireless network.

### Claim 2 (depends on 1)

The method of claim 1 wherein beamforming is independent of client scheduling.

### Claim 3 (depends on 1)

The method of claim 1, comprising providing spatial reuse.

### Claim 4 (depends on 1)

The method of claim 1, comprising performing in each epoch of time: (i) interference estimation for beamforming where clients measure an average signal to noise ratio (SNR) on each beam from each base station (BS) and forward it to the CC, which then infers corresponding SNR for beam combinations at the BS.

### Claim 5 (depends on 4)

The method of claim 4, comprising joint beam selection and client association based on interference information collected, wherein the CC runs a spatial reuse technique to determine a beam choice for each of the small cells as well as clients associated with the small cell for a particular epoch.

### Claim 6 (depends on 4)

The method of claim 4, wherein each small cell BS receives a beam choice and client set, comprising scheduling clients locally using a scheduler for each frame in an epoch while applying the beam selected to frame transmissions.

### Claim 7

A computer implemented method for providing beamforming and spatial reuse in a small-cell wireless network comprising:
providing a central controller (CC) to perform resource and interface management for small cells jointly with a high speed backhaul which interconnects the small cells with the CC thereby providing for information exchange between the small cells;
receiving signals from the small-cell wireless network with wireless transceivers;
estimating a signal-to-interference-plus-noise ratio (SINR) of clients in the small cells to determine any interference dependencies between small cells in the wireless network in the presence of beamforming, wherein said SINR is estimated from signal-to-noise (SNR) measurement for a given beam configuration π={π(i)}, ∀i, beam choices for small cells according to the following relationship
SINR
ij
⁢
⁢
π
⁡
(
dB
)
=
SNR
ij
⁢
⁢
π
⁡
(
i
)
⁡
(
dB
)
⁢
-
10
⁢
⁢
log
10
(
∑
k
≠
i
⁢
SNR
kj
⁢
⁢
π
⁡
(
k
)
)
+
β
⁡
(
dB
)
where SINRijπ is the SINR for client j from a base station i at beam configuration π and β is an offset; and
associating one or more of the clients with the particular beamforming;
selecting particular beam patterns for each small cell such that spatial reuse is increased; and
providing beamforming and spatial reuse for transmission using the transceivers in a small-cell wireless network.