How To Increase 4G LTE Network Downlink

Capacity With a Simple Software Patch –

BOMA

2016

Global mobile data traffic will increase nearly eightfold [1] between 2015 and 2020.

To meet this exponential growth in data demand, Mobile Operators can take different approaches to boost network capacity as shown below.

2015 2020

Mobile Data

Traffic

8x growth [1]

Use new Spectrum Densification

Macro

Macro+

Pico

Increase Spectral Efficiency

Massive MIMO

Full Duplex Communication

[1] http://www.cisco.com/c/en/us/solutions/collateral/service-provider/visual-networking-index-vni/mobile-white-paper-c11-520862.pdf

Network Optimization

Site Acquisition +

Backhaul challenges

Chipset & Network

Hardware Development

Small Coverage

Capacity Low Frequency BandCoverage

High FrequencyBand

Limited deployment use cases such as indoor or point –to-point links

2016 2017 2018 2019 2020

Standardization & Channel

Models Study

Massive # of Sites Development due to small coverage

CommercialLaunch

Massive # of Sites Development due to small coverage

CommercialLaunch

Multi-year Standardization ActivityChipset & Network

Hardware Development

Network Testing

CommercialLaunch

• Current strategies require either massive CAPEX and/or at least several years of standardization and feature development.

• Mobile networks need a simple cost effective solution that can boost capacity TODAY!

25% DL Capacity Boost

PROS ~25% boost in downlink LTE Capacity.

CONS$18.2B CAPEX spending on spectrum. Network development will be additional.

3-5 years of lag-period between investment and actual network capacity boost.

In Jan 2015 AWS-3 spectrum auction, AT&T spent more than $18-billion to get ~20MHz of airwaves [1].

This will boost AT&T’s downlink spectrum for LTE deployment from an existing approx. 40MHz to 50MHz in most metro cities [2].

AT&T plans to start rolling out AWS-3 based network in 2017-2018 [1].

[1] http://www.fiercewireless.com/story/aws-3-auction-results-att-leads-182b-verizon-104b-dish-10b-and-t-mobile-18b/2015-01-30[2] https://s3.amazonaws.com/assets.fiercemarkets.net/public/007-Telecom/ATTSpectrum2.jpg

AWS-3

2015 2016 2017 2018

$18.2B spectrum purchase

CommercialLaunch

Device & Network Equipment

Development

Network Optimization

BOMA can provide Capacity Relief to Congested 4G LTE

Networks NOWand at a fraction of Cost.

BOMA [1-2] i.e. “Building Block Sparse Constellation based Orthogonal Multiple Access” is a groundbreaking air interface technique that can easily boost LTE network capacity by downloading simple software patches in the eNB and the mobile devices.

2016 2017 2018 2019 2020

BOMA

~ 6 months of Proprietary/Pre-Standard release Software Patch Development &

Testing

CommercialLaunch

New Spectrum/Densification/5G candidate

Features

CommercialLaunch

Site & Backhaul Acquisition, Standardization, Chipset & eNBHardware Development, Network optimization

[1]US Patent 8,077,790-”Tiled-building-lock trellis encoders,” Eric M. Dowling and John P. Fonseka[2] USPTO Application #14/999,006 – M. Ahsan Naim and John P. Fonseka -- pending

50-60% Downlink

Capacity boost

BOMA, through a simple software patch based upgrade in the LTE eNB and devices can boost network capacity by 50%-60% over traditional OFDMA currently used in 4G-LTE.

[1]US Patent 8,077,790-”Tiled-building-lock trellis encoders,” Eric M. Dowling and John P. Fonseka[2] USPTO Application #14/999,006 – M. Ahsan Naim and John P. Fonseka -- pending

Salient Features of BOMA

Software (Patch based) Change

• BOMA requires only minimal software changes in the LTE eNBand handsets to work.

• No hardware/network changes are required for BOMA; hence network capacity gain is achieved at a fraction of the cost.

Huge CAPEX savings.

Lag-period • Compared to other capacity augmentation strategies that require 3-5 years, a simple software patch for BOMA can be developed and deployed in 3-6 months time frame.

50%-60% capacity boost NOW.

Compatibility with 4G-LTE

• BOMA is fully compatible with 4G-LTE. It can be treated as an enhancement of 4G-LTE.

Minimal changes to existing

4G-LTE network.

FrequencyBands

• BOMA is implementable in all frequency bands i.e. Low, Medium & High frequency bands.

Capacity boost in all bands from 600MHz to mm-waves.

Average Capacity boost from BOMA in different propagation environments.

4G LTE uses QPSK, 16QAM and 64QAM (256QAM under very good signal conditions)as modulation schemes to carry 2, 4 and 6 (8) bits of user data with each symbolrespectively.

256QAM

8 bits/symbol

QPSK

16QAM

64 QAM

256QAM

QPSK (2bits/symbol) is used under weak channel conditions

such as cell edge

As the quality of channel improves (closer to base

station), the size of constellation is

increased.

….

A loaded LTE carrier (such as during busy hours) typically serves multiple mobile userswith different channel condition.

Air interface resources i.e. PRBs of the carrier are shared between mobile users withdifferent modulation schemes.

QPSK

16QAM

64 QAM

256QAM

LTE Carrier

Bit

s/Sy

mb

ol

QPSK Users

256QAM Users

16QAM Users

64QAM Users

[1] For simplicity, transmit diversity/rank 1/single stream transmission is assumed but Concept can also be generalized for other LTE transmission modes.

𝑨𝑽𝑮 𝑺𝑬 =𝟐 × 𝑷𝑹𝑩𝑸𝑷𝑺𝑲 + 𝟒 × 𝑷𝑹𝑩𝟏𝟔𝑸𝑨𝑴 + 𝟔 × 𝑷𝑹𝑩𝟔𝟒𝑸𝑨𝑴 + 𝟖 × 𝑷𝑹𝑩𝟐𝟓𝟔𝑸𝑨𝑴

𝑷𝑹𝑩𝑸𝑷𝑺𝑲 + 𝑷𝑹𝑩𝟏𝟔𝑸𝑨𝑴 + 𝑷𝑹𝑩𝟔𝟒𝑸𝑨𝑴 + 𝑷𝑹𝑩𝟐𝟓𝟔𝑸𝑨𝑴

𝑷𝑹𝑩𝑸𝑷𝑺𝑲 𝑷𝑹𝑩𝟏𝟔𝑸𝑨𝑴𝑷𝑹𝑩𝟔𝟒𝑸𝑨𝑴 𝑷𝑹𝑩𝟐𝟓𝟔𝑸𝑨𝑴

BOMA uses concept of sparse constellation to increase the average SE of the LTE carrier. A Sparse constellation has the same/similar minimum Euclidean distance separation

between constellation points as that of a standard constellation but contains only asubset of all constellation points as shown in few example figures below.

Standard 16QAM 4-bits per modulation Symbol

16QAM based Sparse Constellation3-bits per modulation Symbol

Standard 64QAM 6-bits per modulation Symbol

64QAM based Sparse Constellation4-bits per modulation Symbol

Standard 256QAM 8-bits per modulation Symbol

256QAM based Sparse Constellation4-bits per modulation Symbol

Both Standard and its corresponding Sparse constellation require similar channel quality (SINR) for similar performance (BLER) due to similar minimum Euclidean distance between constellation points.

However compared to standard constellation, a sparse constellation carries fewer data bits in each symbol.

No hardware change is needed to generate these sparse

constellations by existing LTE transmitters (eNB).

In order to understand BOMA, lets compare it with OFDMA in a two-user (U1, U2) scenario in an LTEcarrier, U1 with QPSK based transmission and U2 with 64 QAM based transmission.

OFDMA (LTE/LTE-A)

LTE/LTE-A system with OFDMA assigns: U1 with a PRB in which each RE(resource element) carries 2 bits of data using

QPSK constellation. U2 with second PRB in which each RE carries 6 bits of data using 64QAM

constellation.

Here 𝐴𝑉𝐺 𝑆𝐸 =2×1+6×1

2= 𝟒 𝒃𝒊𝒕𝒔/𝒔𝒚𝒎𝒃𝒐𝒍

QPSK

16QAM

64 QAM

256QAMU1

U2

BOMA

LTE/LTE-A system with BOMA assigns: U1 with a PRB in which each RE(resource element) carries a shared Tiled-Building Block

constellation(aka Sparse constellation) formed in two steps: Step A: Select a small QPSK building block (BB) constellation (based on 64QAM

spacing) from two bits of U2 Step B: Place four copies of the BB symmetrically in 4 quadrants as shown in figure

above. These four copies referred to as tiles are assigned the four combinations ofthe two bits from U1

U2 with second PRB in which each RE carries 6 bits of data using 64QAM constellation.

Here 𝐴𝑉𝐺 𝑆𝐸 =(2+2)×1+6×1

2= 𝟓 𝒃𝒊𝒕𝒔/𝒔𝒚𝒎𝒃𝒐𝒍

QPSK

16QAM

64 QAM

256QAMU1

U2

Extra Bits for U2

Compared to the standard OFDMA in a two-user (U1, U2) scenario in LTE where a carrier transmits atotal of 8 bits from U1 & U2 in 2 REs, BOMA using shared TBB transmits 10 bits in the same 2 REs forU1 & U2 as shown below.

Hence for this example, avg. bits per RE increases from 4 to 5 i.e. gain of 25% over LTE.

U1 Data Bit Stream (QPSK User) 0 0 1 0 1 1 1 0

U2 Data Bit Stream (64QAM User) 1 0 1 1 1 1 0 0

1st RE (Shared Tiled-Building Block Constellation)

A point is selected for transmission

based on 2 data bits in U1 Bits Stream

and 2 data bits in U2 Bits Stream on

shared TBB

2nd RE (Standard 64-QAM)

A point is selected for transmission

based on separate 6 data bits in U2 Bits Stream on standard

64-QAM

0 1 0 0 1 1 0 1

1 1 1 1 0 0 0 0

……

……

QPSK region

16QAM region

64QAM region

QPSK region user extracts its two bits by detecting the quadrant of the received signal. This corresponds to 2 MSBs (most significant bits) of the 4 bit TBB constellation point label. Note that bit labels of 2 MSBs in TBB remains unchanged within each quadrant.

64QAM region user extracts its own two bits by detecting one of the 4 points within a quadrant i.e. building block. This corresponds to 2 LSBs (least significant bits) of the 4 bit TBB constellation point label.

As shown in figure below, only a minor change in detection i.e. Bit Level Log-Likelihood Ratio Computation is needed. There is no change needed in the turbo decoder part of the receiver.

No hardware change is needed to update Bit Level Log-

Likelihood Ratio Computation by existing LTE receiver (UE).

A simple software update is sufficient!

3GPP parameter based simulation shows BOMA increase downlink average spectral efficiency by 50-60% in urban macro, urban micro and rural morphologies.

If you are interested in learning more about technical details on how BOMA pairs users with different modulation schemes (QPSK,16QAM, 64QAM, 256QAM), system capacity gain and performance of LTE Network with BOMA, please contact us and ask for BOMA whitepaper.

Contact Info:M. Ahsan Naim, Ph.D

Co-Founder, Trellis Linkahsan@trellislink.com

About US

Trellis Link, LLC is recently formed innovation and technology transfer company focusing on improving spectral efficiencies and energy efficiencies in 4G and 5G communications networks. Trellis Link’s improvements allow network operators to service more users and alleviate congestion in the networks they already have invested in or in the new networks they are fielding. Trellis Link LLC has patented technology, called BOMA, that is able to increase the OFDMA downlink efficiency by roughly 50-60% in current 4G LTE networks. This same technology can be applied to improve spectral efficiencies in next generation 5G networks as well. Trellis Link’s main focus is moving BOMA from the laboratory to the field.

Trellis link supplies consulting and technology transfer services to help its partners move BOMA into carrier networks infrastructure equipment and into mobile units.

Trellis link continues to perform research and development to develop related technologies to work with BOMA and to further help mobile networks increase the network coverage, capacity and number of users they can support with their existing and futurenetworks in a fixed amount of spectrum.