LTE and Wimax

7/28/2019 LTE and Wimax

1/11

LTE & WiMAX- A Tale of Two Technologies

his paper aims to highlight the possible convergence path between LTE , WiMAX . LTE is the new kid on the

block, the talk of the town ever since its inception. It has been tipped as the future for data and voice

communication. LTE holds a lot of performance for the Telco operators worldwide in terms of catering for

the ever increasing consumer demands for high data rates on the move along with the native voice

communications. Therefore there is a great need to upgrade the current deployed networks to LTE. In an

increasingly interconnected world, consumers demand high-speed communication, ease of access and flexibility.

Digital convergence is revolutionizing the way data is delivered and consumed, however the challenges are to track

evolving consumer demands and meet the expectations for faster and more sophisticated digitization capabilities.

While WiMAX enjoys slight edge over relatively new LTE commercially, but the adoption of LTE will

surpass WiMAX sometime at the end of 2012. It is largely due to LTE is backward compatible with existing GSM

and HSPA networks, enabling mobile operators deploying LTE to continue to provide a seamless service across LTE

and existing deployed networks. Presently LTE and WiMAX exist independently; however, the union of these

technologies is expected to allow operators the flexibility to deploy multi-mode networks, enabling them to take

advantage of the relative strengths of each technology while downplaying its weakness. The technology used for

LTE is similar to that chosen for WiMAX even though they have both evolved from two different standards, i.e.

3GPP and IEEE802.16 respectively.The WiMAX/LTE network decision will be less complex if multimode devices are

available.The Broadband wireless market has been divided into the two main groups of wireless operators: the

established mobile operators with or without 3G spectrum and the new entrants, mainly greenfield operators and

other fixed line operators. The WiMAX Forum and 3GPP have been pursuing two separate avenues to reach the

same market mobile broadband.

WiMAX was for greenfield players or operators with TDD spectrum that did not need backward-

compatibility with legacy cellular technologies

supported by LTE. On the other hand, LTE was

developed by mobile operators along withtheir vendors with little likelihood they

would embrace a new disruptive standard. LTE

had never been appealing to WiMAX

operators as an FDD-only technology at least

not until TD-LTE appeared. There is plenty of

TDD spectrums available, and in most cases it

is cheaper and under-utilized. Even 3G licenses

frequently have TDD allocations and upcoming

2.5 GHz auctions in most cases contemplate

TDD bands. In response to these trends, the

WiMAX forum initiated the WiMAX 2.0upgrade that offers most of the same features

as LTE-Advanced while providing backward

compatibility to WiMAX 1.0. WiMAX 2.0.

T


2/11

Mobile Industry Technologies

As a technical point of view, mobile networks today are split into three main families with many different flavors,

and are usually based on where they originated from and from what industry there were emerging from

(Telecommunications versus PCs):

GSM (Global System for Mobile Communications) is the most popular standard for mobile telephony systems in

the world. GSM is used by over 3 billion people across 212 countries and territories, representing 80% of the global

mobile market uses (The GSM Association, 2009).

IS-95 (Interim Standard 95), which represents 15% of the global market, has been originally from the US and Asia

(outside Japan). The standard is more widely known under its latest release as CDMA and CDMA200 and has a

long-term plan to merge with the GSM technology at the LTE (Long Term Evolution) stage.

WiMAX (Worldwide Interoperability for Microwave Access) represents only 5% of the global market. The WiMAX

(IEEE 802.16 standard) comes

from IEEE family of protocols and

extendsthe wireless access fromthe Local Area Network (typically

based on the IEEE

802.11standard) to Metropolitan

Area Networks (MAN) and Wide

Area Networks (WAN). Ituses a

new physical layer radio access

technology called OFDMA

(OrthogonalFrequency Division

Multiple Access) for uplink and

downlink. While the initial

versions802.16-2004 focused onfixed and nomadic access, the

later version 802.16-2005, an

amendment to 802.16-2004

include many new features and

functionalities needed to support

enhanced QoS and high mobility

broadband services at speeds

greater than 120 Km/h. The

802.16-2004 is also called

802.16d and is referred to as fixed WiMAX while the 802.16-2005 is referred to as 802.16e or Mobile WiMAX. The

Mobile WiMAX uses an all IP backbone with uplink and downlink peak data rate capabilities of upto 75 Mbpsdepending on the antenna configuration and modulation, practicable to 10 Mbps within a 6 miles (10 Km) radius.

The earliest iterations of WiMAX was approved with the TDMA TDD and FDD with line of sight (LOS) propagation

across the 10 to 66 GHz frequency range which was later expanded to include operation in the 2 to 11 GHz range

with non line of sight (NLOS) capability using the robust OFDMA PHY layer with sub-channelization allowing

dynamic allocation of time and frequency resources to multiple users. The 802.16m (Mobile WiMAX Release 2)

Task-force is currently working on the next-generation systems with an aim for optimizations for improved

interworking and coexistence with other access technologies such as 3G cellular systems, WiFi and Bluetooth and


3/11

enhance the peak rates to 4G standards set by theITU under IMT-Advanced umbrella which calls for data rates of

100 Mbps for high mobility and 1 Gbps for fixed/nomadic wireless access.

LTE (Long Term Evolution) LTE, on the other hand evolves from the Third-generation technology which is based on

WCDMA and defines the long term evolution of the 3GPP UMTS/HSPA cellular technology. The specifications of

these efforts are formally known as the evolved UMTS terrestrial radio access (E-UTRA) and evolved UMTS

terrestrial radio access network (E-UTRAN), commonly referred to by the 3GPP project LTE. The first version of LTE

is documented in Release

8 of the 3GPP

specifications. It defines a

new physical layer radio

access technology based

on Orthogonal Frequency

Division Multiple Access

(OFDMA) for the downlink,

similar in concept to the

PHY layer of Mobile

WiMAX, and uses SC-

FDMA (single Carrier

Frequency Division

Multiple Access) for the

uplink. LTE supports high

performance mobile

access functional upto

350Km/h with 500Km/h

under consideration. Peak

data rates range from 100

to 326.4Mbps on the

downlink and 50 to 86.4

Mbps on the uplink

depending on the antenna

configuration and modulation depth. The LTE also targets to achieve the data rates set by the 4G IMT-Advanced

standard. The development of LTE interface is linked closely with the 3GPP system architecture evolution (SAE)

which defines the overall system architecture and Evolved Packet Core (EPC). The LTE aims to provide an all IP

backbone with reduction in cost per bit, better service provisioning, flexibility in use of new and existing frequency

bands, simple network architecture with open interfaces, and lower power consumption. The next step in this

development line was the introduction of HSPA, a 3Gtechnology capable of delivering theoretical data rates up to

14Mbps. The data rate was improved even further with the introduction of HSPA+ that increased the data rates

over the two link directions; the uplink and the downlink. This technology is considered the big step towards LTE. Itcan be considered as a revolutionary development along the line, since it departed from the split circuit packet

switch network by introducing, for the first time, an all-IP architecture as an option for the voice and data services.

In addition, HSPA+ integrated the MIMO technology as a major part of its PHY layer, paving the way for its

integration in LTE. A similar line of evolution was followed by the 3GPP2. It has progressively evolved IS-95 form a

mere voice services network into the Evolution Data Optimized (EVDO) Rev B, a network that efficiently supports

both data and voice services and at various mobility levels.


4/11

To enable possible deployment around the world, supporting as many regulatory requirements as possible, LTE is

developed for a number of

frequency bands, ranging from

800 MHz up to 3.5 GHz. The

available bandwidths are also

flexible starting with 1.4 MHz upto 20 MHz. LTE is developed to

support both the time division

duplex technology (TDD) as well

as frequency division duplex

(FDD). Since LTE provides high

spectral efficiency, supports high

data rates and implements

flexible access architecture, it is

proven to become a success

amongst operators as well as

customers.

Some Key Features of LTE Evolution

WCDMA HSPAHSPA+ LTE

(UMTS) HSDPA / HSUPA

Max downlink speed384 k 14 M 28 M 100M

bps

Max uplink speed128 k 5.7 M 11 M 50 M

bps

Latency

150 ms 100 ms 50ms (max) ~10 msround trip time

approx

3GPP releases Rel 99/4 Rel 5 / 6 Rel 7 Rel 8

Approx years of initial roll out2003 / 4

2005 / 6 HSDPA2008 / 9 2009 / 10

2007 / 8 HSUPA

Access methodology CDMA CDMA CDMA OFDMA / SC-FDMA


5/11

Are WiMAX and LTE really moving towards convergence?

WiMAX and LTE are expected to converge on

several levels as they have many common

characteristics and deliver similar performances. In

addition, several stakeholders are taking steps to

accelerate this union. Initially, these and otherwireless networks will converge in devices on a

service level through multi-mode device integration,

which are expected to be much simpler and more

effective in supporting seamless handoff of sessions.

It is believed that both WiMAX and LTE will co-exist

in certain regions, and that operators will use

WiMAX for one set of applications and LTE for

another. Some of the similarities can be seen below

These commonalities and developments make the merger of WiMAX and LTE a certainty in the near

future. As the rollout of LTE begins, base stations, handsets, and CPE equipment will be built using baseband and

RF devices that support WiMAX and LTE. LTE and WiMAX provide comparable performance,because they both use

an Internet Protocol (IP) core and an Orthogonal Frequency Division Multiple Access(OFDMA) air interface as theircore technologies. However, in commercial networks in most countries, WiMAX has reached a more mature state

that will take a few years for LTE to match.

Overlaying a LTE network to complement existing WiMAX networks will allow bundling of services and

dual-mode devices. This will help increase an operators subscriber base. Achieving this is not difficult because:

1. An LTE overlay on WiMAX would not require additional towers.2. The wired network infrastructure is mostly common between systems and network management, back-office

accounting, operations and billing.

3. Other functions will also be common (operator dependent).The 3 major factors that have made operators realize a possible convergence to LTE are Firstly, the growing

support for a TDD-version of LTE, known as time-division LTE (TD-LTE), has created a more direct competitor to

WiMAX. Interest in TD-LTE originated in China, but it has spread worldwide, with many mobile operators attracted

by the opportunities for international roaming and for using much less expensive TDD spectrum to boost capacity

in their domestic markets. Further demand for TD-LTE is driven by WiMAX operators who have started to take a

more active role in the TD-LTE standardization process. In the US, for instance, Clearwire has asked the Third

Generation Partnership Project (3GPP) to create a TD-LTE profile for the 2.5 GHz band it uses for its WiMAX rollout.


6/11

Second, vendors have introduced platforms that support multiple air interfaces through software upgrades, and

they plan to expand the selection of affordable multimode devices. The cost and complexity of migrating to a new

air interface has dropped, making it more attractive for WiMAX operators to switch to LTE or to support both

WiMAX and LTE.

Third, with a larger market size and commitment from most tier-one mobile operators, a powerful LTE ecosystem

is rapidly building, with a wider choice of subscriber devices and competitive equipment prices. The table belowshows a comparison of LTE and WiMAX

WIMAX LTE

IP-based technology with OFDMA modulation used in the

uplink and downlink.

IP-based technology with OFDMA modulation in the

downlink and Single Carrier Frequency Division Multiple

Access (SC-FDMA) in the uplink.

WiMAX networks operated by 559 operators covering more

than 620 million people in 147 countries and supporting a

rapidly growing subscriber base.

Few commercial networks for FDD LTE with a limited

number of subscribers, and none for TD-LTE to date

Commercial FDD LTE deployments are expected to

increase in early 2012.

Only TDD supported, in the 2.3 GHz, 2.5 GHz, and 3.5 GHz

bands. Additional bands might be added in the future.

Supports both TDD and FDD. TD-LTE frequencies range

from 1800 MHz to 2.6 GHz (with possible inclusion of the

3.5 GHz band in the future). LTE FDD bands range from700 MHz to 2.6 GHz.

Less complex solution for regional/rural operators who

dont need roaming with 3GPP networks.

Larger market share in the long term, with better

opportunities for international and domestic roaming

Standardization driven by vendors, operators, and

greenfield players at the Institute of Electrical and

Electronics Engineers (IEEE) and the WiMAX Forum.

3GPP standardization process led by mobile operators and top

vendors.

WiMAX Forum certification program supports

interoperability across vendors, but smaller market size

results in more limited choice of devices.

Powerful ecosystem with strong vendor and operator support

to ensure affordability and choice among devices.

The next version of WiMAXWiMAX 2, based on IEEE

802.16mis expected to be commercially available by end

2012.

Legacy support for Global System for Mobile

Communications (GSM), and High Speed Packet Access

(HSPA) gives LTE potential access to 4.6 billion mobile

subscribers. LTE Advanced is the next version of LTE; the

standard is still being developed.

Supports fixed, nomadic, and mobile usage scenarios. Developed with mobility in mind, but could support fixed

usage scenarios.


7/11

Hard realities of WiMAX-to-LTE conversion

Current subscriber base

Cost to convert a subscriber is high. Declaration of intent to convert may imply to customers that the current

network is obsolete.

Equipment

Will current RAN vendors solution support dual operation? (No = expensive) Some vendors RAN equipment

will support both WiMAX and LTE concurrently in the same base station, which can reduce the cost of running dual

networks but even these have restrictions about how this can be done. Motorola is one of the vendors claiming it

can support both WiMAX and LTE in the same base station with the LTE channel turned on as overlay to the

WiMAX channel. Of course a new card on the rack or a new rack can also be installed but everything that involves a

visit to the site will be expensive. Another challenge is whether the base station has enough processing power to

support two channels, as there may not be enough spectrum to run two parallel networks.

How long will it take to fully convert subscriber base to new devices? (Quick = expensive)

The core architecture of each standard is significantly different, requiring the concurrent operation of two core

networks until subscribers are completely migrated. There is a small percentage of the core network that is

suitable in both networks, such as the AAA and packet router, but mostly the carrier will buy separate core

equipment for WiMAX and for LTE. In the case of a migration, 80% of the core infrastructure would have to be

duplicated, the biggest expense being to replace the WiMAX ASN gateway with the LTE equivalent.

Spectrum

Concurrent networks require double the spectrum, albeit mitigated somewhat by variable channel sizes and

novel spectrum reuse techniques available in both standards

TDD and FDD are not compatible in adjacent spectrum, so most WiMAX carriers will be forced to deploy TD-LTE.


8/11

TOP WIMAX OPERATORS WORLDWIDE


9/11

IEEE 802.16 FAMILY

Standard Description Status

802.16-2001 Fixed Broadband Wireless Access (1066 GHz) Superseded

802.16.2-2001 Recommended practice for coexistence Superseded

802.16c-2002 System profiles for 1066 GHz Superseded

802.16a-2003 Physical layer and MAC definitions for 211 GHz Superseded

P802.16bLicense-exempt frequencies

(Project withdrawn)Withdrawn

P802.16dMaintenance and System profiles for 211 GHz

(Project merged into 802.16-2004)Merged

802.16-2004Air Interface for Fixed Broadband Wireless Access System

(rollup of 802.16-2001, 802.16a, 802.16c and P802.16d)Superseded

P802.16.2aCoexistence with 211 GHz and 23.543.5 GHz

(Project merged into 802.16.2-2004)Merged

802.16.2-2004Recommended practice for coexistence

(Maintenance and rollup of 802.16.2-2001 and P802.16.2a)Current

802.16f-2005 Management Information Base (MIB) for 802.16-2004 Superseded

802.16-2004/Cor 1-

2005

Corrections for fixed operations

(co-published with 802.16e-2005)Superseded

802.16e-2005 Mobile Broadband Wireless Access System Superseded

802.16k-2007Bridging of 802.16

(an amendment to IEEE 802.1D)Current

802.16g-2007 Management Plane Procedures and Services Superseded

P802.16iMobile Management Information Base

(Project merged into 802.16-2009)

Merged

802.16-2009

Air Interface for Fixed and Mobile Broadband Wireless Access System

(rollup of 802.16-2004, 802.16-2004/Cor 1, 802.16e, 802.16f, 802.16g and

P802.16i)

Current

802.16j-2009 Multihop relay Current

802.16h-2010 Improved Coexistence Mechanisms for License-Exempt Operation Current

802.16m-2011

Advanced Air Interface with data rates of 100 Mbit/s mobile and 1 Gbit/s

fixed.

Also known as Mobile WiMAX Release 2 or WirelessMAN-Advanced.

Aiming at fulfilling the ITU-R IMT-Advanced requirements on 4G systems.

Current

P802.16n Higher Reliability Networks In Progress

P802.16p Enhancements to Support Machine-to-Machine Applications In Progress


10/11

EVOLUTION PATH TO LTE FOR DIFFERENT OPERATORS AND TECHNOLOGIES

1) 3GPP operator examples

GSM(2G) GPRS(2.5g) EDGE(2.75g) WCDMA UMTS (3G) HSDPA (3.5g) HSUPA (3.75g) HSPA+

(3.95g) LTE (4G)

2) 3GPP2 operator examples

CDMA1x CDMA2000 EVDO Rev O EVDO Rev A EVDO Rev B(Wimax)(HSPA/HSPA+) LTE


11/11

3) TD-LTE specific operator examples

2G TD/SCDMA TD-LTE

LTE and Wimax

Documents