# Realization of Licensed/Unlicensed Spectrum Sharing Using eICIC in Indoor Small Cells for High Spectral and Energy Efficiencies of 5G Networks

## Abstract

**:**

## 1. Introduction

#### 1.1. Background

#### 1.2. Related Work

#### 1.3. Problem Statement and Contribution

- Dual-band enabled SBSs,
- A set of small cell deployed 3D buildings, and
- TD ABS based eICIC technique.

#### 1.4. Organization

#### 1.5. Declaration

## 2. System Architecture, Spectrum Sharing Technique, and Interference Management

#### 2.1. System Architecture

#### 2.2. Dedicated Access

#### 2.3. Co-primary Shared Access

#### 2.3.1. Dynamic Spectrum Sharing by Pooling

#### 2.3.2. Static Spectrum Sharing by Renting

- The strategy can help generate some revenues for MNO 2.
- No coordination between networks of MNOs 1 and 2 is needed.
- Unlike dynamic spectrum sharing, no CoRS is needed for real-time update and allocation of spectrum to the UEs of both MNOs.
- No spectrum is wasted because of the coordination control signaling exchanging over the backhaul between MNOs’ networks.
- Less complex and cost-effective solution in realization and maintenance as compared to the dynamic spectrum sharing since there is no cost associated with the CoRS implementation.
- No need for the interference management for static sharing since small cell UEs of MNO 1 and UEs of MNO 2 operate at the orthogonal spectrum of MNO 2.

**Remark**

**1.**

#### 2.4. Licensed Shared Access

- Multiband enabled SBSs serve small cell UEs at the satellite spectrum as follows. If a satellite UE is present inside a building, during non-ABSs ${t}_{\mathrm{non}-\mathrm{ABS}}^{\mathrm{SPS}}\in T|{T}_{\mathrm{ABS}}^{\mathrm{SPS}}$ of an APP, small cell UEs can be served and during ABSs ${t}_{\mathrm{non}-\mathrm{ABS}}^{\mathrm{SPS}}\in {T}_{\mathrm{ABS}}^{\mathrm{SPS}}$, satellite UEs can be served. However, if no satellite UE is present inside a building, in any TTI of an APP, small cell UEs can be served (Figure 5).
- Similarly, small cells UEs can be served by multiband enabled SBSs at the mobile spectrum as follows. At the presence of an indoor macro UE, during non-ABSs ${t}_{\mathrm{non}-\mathrm{ABS}}^{\mathrm{MNO},1}\in T|{T}_{\mathrm{ABS}}^{\mathrm{MNO},1}$ of an APP, small cell UEs can be served and during ABSs ${t}_{\mathrm{ABS}}^{\mathrm{MNO},1}\in {T}_{\mathrm{ABS}}^{\mathrm{MNO},1}$, indoor macro UEs can be served. In the absence of an indoor macro UE within a building, small cell UEs can be served at the mobile spectrum in any TTI of an APP (Figure 6).

#### 2.5. Licensed Assisted Access

- Availability of a huge amount of unused spectrum (57 to 66 GHz) can address high network capacity,
- High attenuation (specifically, additional free-space losses of 27.96 and 21.58 dB, respectively, on top of what at 2.4 GHz and 5 GHz for the same distance [22]) and large in-building material absorption results in low co-channel interference from neighboring cells,
- Small wavelength resulting in low aperture areas and hence enabling an array of antennas to deploy in small spaces to support high antenna directivity, and
- Low level of multipath effect and hence high possibility of the existence of line-of-sight (LOS) components at 60 GHz band than that at 2.4 GHz and 5 GHz band

#### 2.6. Algorithm

Algorithm 1. Realized spectrum sharing techniques |

01: Input: MNO 1 spectrum, MNO 2 spectrum, satellite spectrum, |

60 GHz unlicensed spectrum, T_{APP}, L |

02: For Transceiver 1 |

03: For Dedicated Spectrum Access |

04: If an indoor macro UE exists within a building |

05: TTI→ABS |

06: MNO 1 spectrum → indoor macro UEs |

07: Elseif an indoor macro UE does not exist within a building |

08: TTI→non-ABS |

09: MNO 1 spectrum → Transceiver 1 of in-building SBSs |

10: End |

11: End |

12: For CoPSA||LSA||LAA |

13: Run lines 04-11 once for each technique, i.e., CoPSA, LSA, and LAA |

14: End |

15: End // End of Transceiver 1 |

16: For Transceiver 2 |

17: If CoPSA |

18: Spectrum of MNO 2 → Transceiver 2 of small cells |

19: If Dynamic spectrum sharing by pooling (DySP) |

20: Allocate the outdoor UEs of MNO 1 to anywhere over the whole spectrum of MNO 1 |

21: Allocate the outdoor UEs of MNO 2 to anywhere over the whole spectrum of MNO 2 |

22: If TTI==ABS |

23: Allocate the spectrum of MNO 2 to UEs of MNO 2 within each 3D building |

24: Elseif TTI==non-ABS |

25: Allocate the spectrum of MNO 2 to small cell UEs of MNO 1 within each 3D building |

26: End |

27: Elseif Static spectrum sharing by renting (StSR) |

28: Allocate the outdoor UEs of MNO 1 to anywhere over the whole spectrum of MNO 1 |

29: If a UE of MNO 2 exists within a 3D building |

30: Allocate rented shared spectrum of MNO 2 to small cell UEs of MNO 1 |

within each 3D building |

31: Allocate the UE of MNO 2 to the rest of the spectrum of MNO 2 orthogonal |

to the rented shared spectrum for MNO 1 within each 3D Building |

32: Elseif a UE of MNO 2 exists outside of any 3D building |

33: Allocate the UE of MNO 2 to anywhere over the whole spectrum of MNO 2 |

34: End |

35: End |

36: Elseif LSA |

37: Spectrum of a Satellite System → Transceiver 2 of small cells |

38: If TTI==ABS |

39: Allocate the spectrum of a satellite system to satellite UEs within each 3D building |

40: Elseif TTI==non-ABS |

41: Allocate the spectrum of a satellite system to small cell UEs of MNO 1 |

within each 3D building |

42: End |

43: Elseif LAA |

44: 60 GHz Unlicensed Spectrum→ Transceiver 2 of small cells |

45: Allocate the 60 GHz Unlicensed Spectrum to small cell UEs of MNO 1 |

within each 3D building |

46: End |

47: End // End of Transceiver 2 |

48: Estimate and Output: Aggregate capacity, spectral efficiency, energy efficiency |

of UEs of MNO 1 for multiband enabled small cells |

## 3. Problem Formulation

#### 3.1. Preliminaries

_{MI}is considered inside a number of buildings over the coverage of a macrocell of MNO 1. The maximum number of buildings and the number of small cells, i.e., femtocells, per building are denoted respectively by L and S

_{F}. We assume that S

_{F}is the same for all buildings and each small cell serves exactly one UE in any TTI. Though in general, the number of small cell UEs in one building is independent of the other, for simplicity, we assume that in each of the L buildings, the same number of small cells is deployed.

**T**as the simulation run time such that

**T**= {1, 2, 3, …, Q} where Q represents the maximum time. Let

**T**denote the number of ABSs in every APP where an APP consists of eight subframes such that

_{ABS}**T**= {t: t = 8v + z; v = 0, 1, 2, …, Q/8; z = 1, …, T

_{ABS}_{ABS}}. Note that T

_{ABS}= 1, 2, …, 8 that corresponds to ABS patterns φ = 1/8, 2/8, …, 8/8, respectively. Let t

_{ABS}and t

_{non-ABS}denote respectively an ABS and a non-ABS such that ${t}_{non-ABS}\in {\mathit{T}}_{ABS}$ and ${t}_{\mathrm{non}-\mathrm{ABS}}\in \mathit{T}\backslash {\mathit{T}}_{ABS}^{SPS}$.

_{P}and S

_{M}denote respectively the number of picocell BSs (PBSs) per MBS and the number of MBSs in the system. Recall that there are S

_{F}SBSs per 3D building such that s ∈ {1, 2, …, S

_{F}}. Let P

_{SC,1}and P

_{SC,1}denote respectively the transmitting power of transceiver 1 and transceiver 2 of an SBS.

_{t,i}is the transmit power, ${N}_{t,i}^{\mathrm{s}}$ is the noise power, I

_{t,i}is the total interference signal power, and H

_{t,i}is the link loss for a link between a UE and a BS at RB = i in TTI = t.

_{t,i}can be expressed in dB as:

_{t}+ G

_{r}) and L

_{F}are respectively the total antenna gain and connector loss. LS

_{t,i}, SS

_{t,i}, and PL

_{t,i}, respectively, denote the large scale shadowing effect, small scale Rayleigh or Rician fading, and distance-dependent path loss between a BS and a UE at RB = i in TTI = t [23].

#### 3.2. Dedicated Access

_{MNO,}

_{1}RBs in t $\in $

**T**such that indoor macro UEs are scheduled only during ${t}_{\mathrm{ABS}}\in {\mathit{T}}_{ABS}^{MNO,1}$ and all other macro UEs are scheduled during ${t}_{\mathrm{non}-\mathrm{ABS}}\in {\mathit{T}}_{non-ABS}^{MNO,1}$.

#### 3.3. Co-primary Shared Access

#### 3.3.1. Dynamic Spectrum Pooling Technique

**Remark**

**2.**

#### 3.3.2. Static Spectrum Renting Technique

_{StSR}denote the number of RBs of MNO 2 that is rented to MNO 1 such that M

_{StSR}< M

_{MNO,1}. Then, the total spectrum of MNO 1 due to spectrum renting is given by:

_{StSR}RBs

_{,}in all TTIs t ∈

**T**, then the capacity served by an SBS is then given by,

**T**at the rented spectrum of M

_{StSR}RBs on transceiver 2, the aggregate capacity per 3D building for static spectrum renting technique is then given by,

#### 3.4. Licensed Shared Access

_{F}small cells, the aggregate capacity per 3D building is given by:

#### 3.5. Unlicensed Shared Access

_{F}SBSs, the aggregate capacity per 3D building is given by:

## 4. Optimal Number of ABSs and Default Parameters and Assumptions

#### 4.1. Optimal Number of ABSs Estimation

_{ABS}and T

_{non-ABS}of an APP T

_{APP,}respectively. Considering a fair allocation of time resources to each group of users, the allocation of T

_{ABS}and T

_{non-ABS}is defined in proportionate with ${\mathsf{\lambda}}_{1}$ and ${\mathsf{\lambda}}_{2}$ respectively. In such cases, an optimal value of T

_{non-ABS}can be found by solving the following optimization problem:

**Proof**

**1.**

_{ABS}and T

_{non-ABS}are strictly integers, by allowing a favor to ${\mathsf{\lambda}}_{2}$, the optimal value of T

_{non-ABS}is given by:

_{non-ABS}for dedicated, DySP, and LSA techniques can be found respectively as follows.

_{APP}for the dedicated, DySP and LSA techniques, respectively.

#### 4.2. Default System Parameters and Assumptions

## 5. Performance Evaluation and Comparison

#### 5.1. Performance Evaluation

#### 5.2. Optimal Value of L and Performance Comparison with 5G Mobile Network Requirements

**Proof**

**2.**

## 6. Conclusions

## Funding

## Acknowledgments

## Conflicts of Interest

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**Figure 1.**Scopes of the spectrum licensing policies realized using eICIC technique in multiband in-building small cells.

**Figure 2.**An example multiband enabled small cell configuration with major attributes for the realized spectrum access methods.

**Figure 3.**The system architecture of the concerned MNO1 and the use of the dedicated spectrum access technique to MNO 1.

**Figure 5.**Interference management for DySP. For static spectrum sharing, there is no need for interference management.

**Figure 6.**Intra-operator spectrum sharing technique and co-channel interference management using the ABS based eICIC technique for sharing mobile spectrums of MNO 1 with the transceiver 1 of its multiband enabled SBSs.

**Figure 9.**Performance responses of all the realized spectrum access techniques for small cells in a single building (i.e., L = 1): (

**a**) The spectral efficiency and (

**b**) energy efficiency.

**Figure 10.**Performance responses of all the realized spectrum access techniques for an ultra-dense deployment of small cells in multiple buildings (i.e., L > 1): (

**a**) The spectral efficiency and (

**b**) energy efficiency.

Abbreviation | Explanation |
---|---|

3D | 3-Dimensional |

3GPP | Third Generation Partnership Project |

5G | Fifth Generation |

ABS | Almost Blank Subframe |

APP | ABS Pattern Period |

ASA | Authorized Shared Access |

BS | Base Station |

CA | Carrier Aggregation |

CoPSA | Co-Primary Shared Access |

CoRS | Common Resource Scheduler |

CSI | Channel State Information |

DedA | Dedicated Access |

DySP | Dynamic Spectrum Sharing by Pooling |

EE | Energy Efficiency |

eICIC | Enhanced Inter-Cell Interference Coordination |

FCC | Federal Communications Commission |

FD | Frequency-Domain |

ICIC | Inter-Cell Interference Coordination |

ISD | Inter-Site Distance |

ISD | Inter-site distance |

ISM | Industrial, Scientific, and Medical |

J/b | Joules/Bit |

LAA | Licensed Assisted Access |

LBT | Listen-Before-Talk |

LOS | Line-of-Sight |

LSA | Licensed Shared Access |

LTE | Long-Term Evolution |

MBS | Macrocell Base station |

MNO | Mobile Network Operator |

NRA | National Regulatory Agency |

PBS | Picocell Base Station |

PF | Proportional Fair |

QoS | Quality-of-Service |

RB | Resource Block |

SBS | Small Cell Base Station |

SE | Spectral Efficiency |

SPS | Space Satellite System |

StSR | Static Spectrum Sharing by Renting |

TD | Time-Domain |

TTI | Transmission Time Interval |

UE | User Equipment |

ULS | Unlicensed Spectrum |

Notation | Definition |
---|---|

${\mathsf{\sigma}}_{\mathrm{MNO},1}^{\mathrm{MC},\mathrm{WIM}}$ | The aggregate capacity of all N macro UEs for ${M}_{\mathrm{MNO},1}$ RBs, Q TTIs, and L = 1 |

${\mathsf{\sigma}}_{\mathrm{MNO},1}^{\mathrm{SYS},\mathrm{DedA}}$ | The system-level capacity of MNO 1 for the dedicated access technique |

N | Number of macro UEs of MNO 1 |

$\mathsf{\varphi}$ | ABS pattern |

T | Simulation run time |

Q | Maximum number of TTIs in T each lasting 1 ms |

T_{ABS} | A set of ABSs in T |

t and i | Index of TTIs and RBs respectively |

${\rho}_{t,i}$ | Signal-to-interference-plus-noise ratio at RB = i in TTI = t |

${H}_{t,i}$ | Link loss at RB = i in TTI = t |

${\mathsf{\sigma}}_{t,i}$ | Link throughput at RB = i in TTI = t |

${M}_{\mathrm{MNO},1}$ | Number of RBs in the MNO 1 spectrum |

${M}_{\mathrm{MNO},2}$ | Number of RBs in the MNO 2 spectrum |

${M}_{\mathrm{MNO},\mathrm{T}}$ | Total spectrum due to the spectrum pooling at CoRS |

${M}_{\mathrm{StSR}}$ | Number of RBs of MNO 2 that is rented to MNO 1 |

${M}_{\mathrm{ULS}}$ | Number of RBs in the 60 GHz unlicensed spectrum |

${M}_{\mathrm{SPS}}$ | Number of RBs in SPS spectrum |

S_{F} | Number of small cells per building |

S_{P} | Number of picocells per macrocell |

S_{M} | Number of macrocells in the system |

P_{PC} | Transmit power of a picocell |

P_{MC} | Transmit power of a macrocell |

P_{SC,1} | Transmit power of transceiver 1 of an SBS |

P_{SC,2} | Transmit power of transceiver 2 of an SBS |

${\mathit{T}}_{ABS}^{SPS}$ | A set of ABSs in the satellite spectrum |

${\mathit{T}}_{ABS}^{MNO,1}$ | A set of ABSs in the MNO 1 spectrum |

${\mathit{T}}_{non-ABS}^{MNO,1}$ | A set of non-ABSs in the MNO 1 spectrum |

${\mathit{T}}_{ABS}^{MNO,2}$ | A set of ABSs in the MNO 2 spectrum |

${\mathit{T}}_{non-ABS}^{SPS}$ | A set of non-ABSs in the satellite spectrum |

${\mathit{T}}_{non-ABS}^{MNO,2}$ | A set of non-ABSs in the satellite spectrum |

L | Total number of buildings per macrocell |

${\mathsf{\lambda}}_{\mathrm{MNO},1,\mathrm{SU}}$ | The average rate of arrival of small cell UEs of MNO 1 into a building |

${\mathsf{\lambda}}_{\mathrm{MNO},2}$ | The average rate of arrival of UEs of MNO 2 into a building |

${\mathsf{\lambda}}_{\mathrm{SPS}}$ | The average rate of arrival of satellite UEs of SPS into a building |

${\mathsf{\lambda}}_{\mathrm{MNO},1,\mathrm{iMU}}$ | The average rate of arrival of indoor macro UEs of MNO 1 into a building |

${T}_{\mathrm{APP},\mathrm{DedA}}$ | The value of T_{APP} for the dedicated access technique |

${T}_{\mathrm{APP},\mathrm{DySP}}$ | The value of T_{APP} for the DySP technique |

$\text{}{T}_{\mathrm{APP},\mathrm{LSA}}$ | The value of T_{APP} for the LSA technique |

L_{ow} | External wall penetration loss |

${\mathsf{\sigma}}_{L}^{\mathrm{SE}}$ | Spectral efficiency for any value of $L\in {{\rm N}}_{>0}$ |

${\mathsf{\sigma}}_{L}^{\mathrm{EE}}$ | Energy efficiency for any value of $L\in {{\rm N}}_{>0}$ |

${\mathsf{\sigma}}_{5\mathrm{G}}^{\mathrm{SE}}$ | The minimum spectral efficiency requirement for 5G mobile systems |

${\mathsf{\sigma}}_{5\mathrm{G}}^{\mathrm{EE}}$ | The minimum energy efficiency requirement for 5G mobile systems |

${L}^{\ast}$ | An optimal value of L |

Parameters and Assumptions | Value | |||||||||
---|---|---|---|---|---|---|---|---|---|---|

E-UTRA simulation case1 | 3GPP case 3 | |||||||||

Cellular layout ^{2} and Inter-site distance (ISD) ^{1,2,5} | Hexagonal grid, dense urban, 3 sectors per macrocell site and 1732 m | |||||||||

Carrier frequency ^{2,3} and transmit direction | 2 GHz (microwave), 60 GHz (millimeter wave line-of-sight), and downlink | |||||||||

System bandwidth | 10 MHz downlink (for both 2 GHz and 60 GHz) | |||||||||

Number of cells | 1 macrocell, 2 picocells, 8 SBSs per building for MNO 1 | |||||||||

Total BS transmit power ^{1} (dBm) | 46 for microcell ^{1,4}, 37 for picocell^{1}, 20 (for 2 GHz) and 17.3 (for 60 GHz) for femtocell ^{1,3,4} | |||||||||

Co-channel fading model ^{1} | Frequency selective Rayleigh for the macrocell and picocells, and Rician for SBSs (for 2 GHz) | |||||||||

External wall penetration loss ^{1} (L_{ow}) | 20 dB | |||||||||

Path loss | MBS and a UE ^{1,5} | Indoor macro UE | PL(dB) = 15.3 + 37.6log_{10}R, R is in m | |||||||

Outdoor macro UE | PL(dB) = 15.3 + 37.6log_{10}R + L_{ow}, R is in m | |||||||||

PBS and a UE ^{1} | PL(dB) = 140.7 + 36.7log_{10}R, R is in km | |||||||||

SBS and a UE ^{1,2,3,6} | PL(dB) = 127 + 30log_{10}(R/1000), R in m (for 2 GHz),PL(dB) = 68 + 21.7log _{10}(R), R in m (for 60 GHz) | |||||||||

Lognormal shadowing standard deviation (dB) | 8 for MBS ^{2}, 10 for PBS ^{1}, and 10 (for 2 GHz) and 0.88 (for 60 GHz) for FCBS ^{2,3,6} | |||||||||

Antenna configuration | Single-input single-output for all terrestrial mobile BSs and UEs | |||||||||

Antenna pattern (horizontal) | Directional (120^{0}) for microcell ^{1}, omnidirectional for picocell ^{1} and SBS ^{1} | |||||||||

Antenna gain plus connector loss (dBi) | 14 for MCBS ^{2}, 5 for PCBS ^{1}, 5 (for 2 GHz) and 5 (for 60 GHz, Biconical horn) for FCBS ^{1,3,6} | |||||||||

UE antenna gain ^{2,3} | 0 dBi (for 2 GHz), 5 dBi (for 60 GHz, Biconical horn) | |||||||||

UE noise figure ^{2} and UE speed ^{1} | 9 dB, 3 km/hr | |||||||||

Total number of macro UEs for MNO 1 and Indoor macro UEs ^{1} | 30 and 35% | |||||||||

Picocell coverage and macro UEs offloaded to all picocells ^{1} | 40 m (radius), 2/15 | |||||||||

3D multi-storage building, and SBS models (regular square-grid) | Number of buildings | L | ||||||||

Number of floors per building | 2 | |||||||||

Number of apartments per floor | 4 | |||||||||

Number of SBSs per apartment | 1 | |||||||||

SBS activation ratio | 100% | |||||||||

SBS deployment ratio | 1 | |||||||||

Total number of SBSs per building | 8 | |||||||||

Area of an apartment | 10 × 10 m^{2} | |||||||||

Location of an SBS in an apartment | center | |||||||||

Scheduler and traffic model ^{2,5} | Proportional Fair (PF) and full buffer | |||||||||

Type of SBSs ^{5} | Closed Subscriber Group femtocell BSs | |||||||||

${\mathsf{\lambda}}_{\mathrm{MNO},1,\mathrm{SU}}$, ${\mathsf{\lambda}}_{\mathrm{MNO},1,\mathrm{iMU}}$, ${\mathsf{\lambda}}_{\mathrm{MNO},2}$, ${\mathsf{\lambda}}_{\mathrm{SPS}}$ | 8/8, 2/8, 4/8, 2/8 | |||||||||

${T}_{\mathrm{APP},\mathrm{DedA}},{T}_{\mathrm{APP},\mathrm{DySP}},\mathrm{and}{T}_{\mathrm{APP},\mathrm{LSA}}$ | 8 ms, 8 ms, and 8 ms | |||||||||

Channel State Information (CSI) | Ideal | |||||||||

TTI^{1,} and scheduler time constant (t_{c}) | 1 ms and 100 ms | |||||||||

Total simulation run time | 8 ms |

Spectrum Sharing Technique (SS) | L (To Meet the 5G Mobile System Requirements) | ||
---|---|---|---|

Spectral Efficiency (bps/Hz/cell) | Energy Efficiency (μJ/b) | Both Spectral and Energy Efficiencies (${L}^{\ast}$) | |

Dedicated access | 56 | 2 | 56 |

CoPSA (DySP) | 30 | 1 | 30 |

CoPSA (StSR) | 54 | 2 | 54 |

LSA | 28 | 1 | 28 |

LAA | 5 | 1 | 5 |

© 2019 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Saha, R.K.
Realization of Licensed/Unlicensed Spectrum Sharing Using eICIC in Indoor Small Cells for High Spectral and Energy Efficiencies of 5G Networks. *Energies* **2019**, *12*, 2828.
https://doi.org/10.3390/en12142828

**AMA Style**

Saha RK.
Realization of Licensed/Unlicensed Spectrum Sharing Using eICIC in Indoor Small Cells for High Spectral and Energy Efficiencies of 5G Networks. *Energies*. 2019; 12(14):2828.
https://doi.org/10.3390/en12142828

**Chicago/Turabian Style**

Saha, Rony Kumer.
2019. "Realization of Licensed/Unlicensed Spectrum Sharing Using eICIC in Indoor Small Cells for High Spectral and Energy Efficiencies of 5G Networks" *Energies* 12, no. 14: 2828.
https://doi.org/10.3390/en12142828