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Comparison of LTE and WiMAX

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This paper provides a high-level comparison …

This paper provides a high-level comparison
between LTE and WiMAX. The focus is on two primary areas: System Architecture and Physical Layer. The System Architecture describes the different functional elements in LTE and WiMAX and attempts to map similar functionality (such as mobility, security, access-gateway). We also compare and contrast the various aspects (such as transmission modes, duplexing types) of the physical layer.

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  • what the comparison LTE, Wi-Fi, and Wi-MAX?
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  • 哈哈哈,谢谢啦!
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  • Thank you for this...outlined the technical differences at a high level...very useful for a marketing person.
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  • Nice article :-) Was looking for something else. Found this.

    Swami.
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  • 1. Comparison of LTE and WiMAX by Rajesh S. Pazhyannur Abstract This article provides a high-level compari- son between LTE and WiMAX. The focus of paper is on two primary areas: System Architecture and Physical Layer. The Sys- tem Architecture describes the different functional elements in LTE and WiMAX and attempts to map similar functionality (such as mobility, security, access-gateway). We also compare and contrast the various aspects (such as transmission modes, duplexing types) of the physical layer. Introduction Figure 16 - Evolution of LTE LTE (Long Term Evolution) and WiMAX (Worldwide Interoperability for Microwave Access) are expected to be primary tech- nologies for mobile broadband wireless for the next 10 years. As with most emerg- ing and competing technologies, there is considerable effort by the correspond- Figure 17 - Evolution of Mobile WiMax ing technology advocates to frame the discussion as LTE versus WiMAX with the end result of declaring one technology as LTE Evolution support for EV-DO Rev C has waned and The first generation of cellular systems it has now become clear that the GPP2 the “winner”. We take a different approach were based on analog standards and radio interface evolution has effectively in this paper. We frame the discussion, introduced in the mid-80s. These quickly ceased, allowing a single cellular technol- rather, in terms of similarities and differ- led to a second generation of digital cel- ogy —LTE. ences across various technology/technical lular standards that made use of digital factors. This is motivated by the fact that 1) As shown in Figure 16, the GPP and modulation and signal processing. The technological factors only partially contrib- GPP2 cellular technology offerings have second generation also led to a technol- ute to determining winners, and in some evolved and GPP2 operators are now ogy fragmentation. At one point many cases play a small role and 2) technical dif- switching camps and backing a single competing standards existed, however ferences are not universally advantageous. specification based on LTE. what remains now are two main branches: The goal of the paper is to primarily focus referred to as GSM and CDMA branches WiMAX Evolution on technical/technology aspects as com- or alternately referred as the GPP and WiMAX evolved almost independently pared to business and strategic aspects. GPP2 branches. (GPP and GPP2 are (and in parallel) to the cellular standards The article is organized as follows.Firstly, the standardization bodies responsible for mentioned earlier. In the late 0s, IEEE we describe the evolution of LTE and technical specifications.) These branches started a working group to create an air- WiMAX as well as provide the primary remained separate as they migrated to G interface for point to multipoint broadband motivations. A system-level comparison of systems focusing on more efficient voice wireless standard. The working group lev- LTE and WIMAX focusing on system-archi- transport as well providing data-services. eraged DOCSIS (data over cable service tecture and protocol stacks for the control LTE originated in the GPP standards or- interface specification) standard heavily and user traffic is provided and the air ganization, and a competing specification especially in the definition of the MAC interfaces for LTE and WiMAX described. (EV-DO Rev C) started in the GPP2 body layers. The original standard was modified as the next evolutionary step. However, the into 802.16d in 2004 introducing OFDM as IP NGN ARCHITECTURE THOUGHT LEADERSHIP JOURNAL - Q1 FY2010
  • 2. Technology Highlights • Mobile Data Network: The primary UMTS (aka WCDMA) CDMA, Spread Spectrum, 5 MHz spectrum usage of both networks is to provide Circuit Voice and Packet Data (up to 84 Kbps) a data-centric network as compared Deployed since 200 to voice-centric network of 2G and G HSDPA (High Speed CDMA, Spread Spectrum, 5 MHz systems. This aspect is highlighted by Downlink Packet Downlink Only; Data Only the absence of any provisions to carry Access) Multiple Codes per Subscriber any circuit-type service. The networks Up to 16 QAM, Peak Rates of 14.4 Mbps do support voice, but in the form of Deployed since 2005 packetized VoIP service. HSUPA (High Speed CDMA, Spread Spectrum, 5 MHz • Improve Spectral Efficiency: Given the Uplink Packet Access) Uplink Only; Data Only scarcity of licensed spectrum, improv- Multiple Codes per Subscriber ing efficiency is a major impetus for Up to 16 QAM, Peak Rates of 4.5 Mbps both networks. The main technologies Deployed since 2007 to enable higher efficiency are to move towards higher modulation schemes HSPA+(Evolved High CDMA, Spread Spectrum, 5 MHz (like 64 QAM), smart antenna tech- Speed Packet Access) Up to 64 QAM, MIMO. Peak Rates (DL,UL): 42, 11 niques (MIMO, Beam Forming, etc) and Mbps OFDM. Likely to be deployed in 200-2010 LTE Scaleable OFDM on downlink, Single Carrier • Spectrum Flexibility: Unlike previous FDMA on uplink networks which operated on a fixed Variable Spectrum Width from  to 20 MHz width spectrum (5 MHz for WCDMA Up to 64 QAM, MIMO, Spatial Multiplexing(SM), and 1.25 MHz for CDMA-DO), both net- Beamforming works allow scaleability from 1.25 MHz Likely to be deployed between 2010-2012 up to 20 MHz. WiMAX Scaleable OFDM on downlink and uplink • Higher Peak Data Rates: Both networks Variable Spectrum Width from 1.25 to 10 MHz attempt to improve the peak data rate Up to 64 QAM, MIMO, Spatial Multiplexing, Beam- on the downlink and uplink so that high forming data rate services such as high-defi- Mobile WiMAX deployed since 2008 nition video can be transmitted over Table 1: Technology Summary broadband wireless links. Specifically, the goal is to increase the peak rates from range of (-10) Mbps to (50-100) the transmission scheme. This standard Looking forward, the 802.16e standard is Mbps. was targeted at fixed applications and is sometimes referred to as fixed WiMAX. evolving to 802.16m which focuses on en- hancements to air-interface specifications. • Lower Infrastructure Costs: Traditional cellular networks comprise a combina- This evolution is shown in Figure 17. In 2005, 802.16d was further enhanced tion of TDM and packet infrastructure to provide support for mobility as well as Technology Summary partly because of the need to carry provide a scalable OFDM transmission As seen from Table 1, the main differences circuit voice. LTE and WiMAX networks system. This standard is known as 802.16e between the G technologies and 4G simplify the network considerably, mi- and also as mobile WiMAX. (It should be technologies such as LTE/WiMAX are the grating towards an all-IP infrastructure noted that products based on 802.16d different transmission schemes (OFDM relying on IP network for transporting and 802.16e exist in the marketplace and compared to CDMA) and much higher data and control messages. Addition- both are classified as WiMAX products peak rates. ally, both networks embody a design leading to some ambiguity about which principle of “flattening” the architecture Motivation for LTE and WiMAX specific standard is supported—802.16d wherein the system eliminates a cen- The primary motivations for both LTE and or 802.16e.) tralized base station controller (or Radio WiMAX are similar and can be stated as:: Network Controller (RNC)) in favor of CISCO PUBLIC
  • 3. distributing the functionality to Base Stations and Access Gateways. System-Level Comparison Architecture Figure 18 provides a simplified view of the LTE and WiMAX architecture (not all nodes and interfaces are shown, only the main elements involved in user and control plane traffic). We first compare the main functional ele- ment below. • eNodeB and BS: Functionally speaking, the LTE and WiMAX BS are quite similar. Both handle the traffic to/from the subscriber device. This involves per- forming the function of Radio Resource Figure 18 - LTE and WiMAX System Architecture Management on the control plane, in terms of authentication, setting up connections, allocating resources and the packet network. Both systems use an IP tunnel to route user plane traffic to • MME/S-GW and ASN-GW: Function- ally speaking, the combined functions performing functions like packet trans- an access gateway. There are sig- of MME and S-GW match closely to missions, MAC, H-ARQ and link-adapta- nificant differences in the air interface those performed by the ASN-GW. This tion on the user-plane. In addition, the standards that are described next. element (in LTE and WiMAX) provides base stations provide an interface into mobility between BS, security func- tions, QoS functions, idle state (paging) management. LTE defines a functional element, the MME, for handling control plane traffic and another element for handling the user plane traffic called the Serving Gateway. WiMAX (at least in Profile C) does not separate the control and user plane handling into separate elements. The control and user plane traffic both are carried by the ASN- GW. The protocols used between the gateways and the BS’ differ between LTE and WiMAX as well. LTE uses GTP (GPRS Tunneling Protocol) for the S1u and S1-AP/SCTP for S1c interface, while WiMAX uses GRE/UDP as the tunnel- ing protocol and UDP for control plane transport. The specific control mes- sages transferred differ as well and are defined by corresponding specifica- tions: S1 for LTE and R6 for WiMAX. A function unique to MME and S-GW is to interface with legacy G networks IP NGN ARCHITECTURE THOUGHT LEADERSHIP JOURNAL - Q1 FY2010
  • 4. (omitted from Figure ). GPP has defined interfaces from the MME and S-GW to connect to WCDMA systems as well as CDMA-1X and EV-DO sys- tems. The WiMAX forum is expected to define corresponding interfaces between WiMAX and G systems in future releases. • PDN-GW and HA: Functionally speak- ing, the PDN-GW and HA are similar. Both provide mobility between the Access Gateways (S-GW for LTE and ASN-GW for WiMAX). In WiMAX R1.0, the defined protocol for the R inter- face is Mobile IPv4 (MIPv4), and in most instances, the ASN-GW performs Proxy MIP (PMIP). LTE defines two alterna- tives for the S5 interface: One is based Figure 19 - LTE and WiMAX User Plane Protocol Stacks on GTP (GPRS Tunneling Protocol) and the other is based on Proxy MIPv6 (PMIPv6). PMIPv6 is being defined as an option for WiMAX R1.5. Other Architectural Considerations All IP (Packet-only) Systems: As shown in Figure 18, LTE and WiMAX are packet- only systems. There are no defined inter- faces to circuit switched systems. More- over, all RAN and Core Network systems are IP based. Inter BS interface: LTE and WiMAX define interfaces to optionally route traffic related to handover between BS’ directly eliminat- Figure 20 - LTE and WiMAX Control Plane Protocol Stacks ing the need to go through a core network element. This is referred to as the R8 interface in WiMAX and X2 interface in LTE. Protocol Stacks control stacks for the subscriber. One stack This interface can improve the latency in The user and control plane stacks further is for RRM messages and is between the handovers between BS as well reduce the illustrate the similarities and differences UE and eNB. The other stack is for security, control and user plane traffic traversing the between LTE and WiMAX and are given in idle state management, QoS negotiation, access gateways. Figure 1 and Figure 20 respectively. As etc and is between the UE and the MME shown in Figure 1 the key difference is (and known as Non-Access Stratum (NAS) Multiple forms of Mobility: LTE and WiMAX that the interface between base-site and layer). In comparison, the subscriber sta- define multiple forms of mobility: across access-gateway uses GTP and S5 uses ei- tion (SS) never communicates directly with BS’ connected to the same Access Gate- ther PMIPv6 or GTP in LTE, while in WiMAX the ASN-GW. The 802.16e layer defines way (R8 or R6 relay in WiMAX), across BS’ the corresponding protocols are GRE and procedures between the SS and the connected to different Access Gateway PMIPv4. BS (shown as MAC in Figure 5) while the (R4 in WiMAX). WiMAX Forum defines the procedures As shown in Figure 20, the key difference between the BS and the ASN-GW (shown in the control plane is that LTE defines two as R6 in Figure 20). CISCO PUBLIC
  • 5. Remarks Remarks Scalable Band- LTE: 1.4,, 5, 10, 15, 20 MHz Duplexing Mode LTE is primarily for FDD (though TDD is defined). width WiMAX: 1.25, 5, 10 MHz WiMAX is primarily for TDD (though FDD is being considered) Downlink OFDMA Frequency Bands LTE: 700, 1700, 100, 2100, 2500, 2600 Transmission WiMAX: 200, 2500 and 500 MIMO 2x2 (STBC and SM) Uplink Transmission LTE: SC-FDMA Table 2: Air Interface Similarities WiMAX: Uplink Transmission is OFDMA Frame Duration and LTE: 1 msec frame; subcarrier frequency :15KHz SubCarrier Frequncy WiMAX: 5 msec frame; subcarrier frequency : 10KHz Table : Air Interface Differences Air Interface Similarities • Duplexing Mode: WiMAX is currently FDD is a natural choice for cellular Table 2 provides the key similarities be- defined as a TDD system (though there operators and partly explains the tween LTE and WiMAX air Interface. are plans to define a FDD system in a preference shown by existing cellular future release). LTE has a defined TDD • Scalable Bandwidth: G technolo- and FDD specifications, though most operators to migrate towards LTE. gies were designed to operate in a deployments are expected to be FDD. • Frequency Bands: The frequency fixed bandwidth. For example, WCDMA bands that LTE and WiMAX are ex- FDD uses “paired” spectrum (one for bandwidth is 5 MHz. Unlike G, LTE and pected to be deployed are quite differ- uplink and other for downlink). TDD WiMAX are defined over a wide range ent. This is also related to the fact that on the other hand requires contigu- of bandwidth ranging from 1.5 to 20 cellular operators are expecting to use ous spectrum. Cellular/G systems MHz. This allows the operators (service existing frequency bands for LTE usage are FDD and cellular operators have providers) deployment flexibility based in the future. See Figure 6 for more unused (or in-use) paired spectrum that on spectrum availability and capacity/ details. can be utilized for LTE. One of the key coverage needs. benefits of TDD is the reciprocal nature LTE is specified over a large number • Downlink Transmission: LTE and of the channel, facilitating the use of beamforming techniques to provide of spectrum bands owned by cellular WiMAX deploy OFDM for downlink provided throughout the world. improved edge of cell performance as transmission. The transmission is divided into time intervals (frames) and well as stabilizing multipath in wide area • Uplink Transmission: WiMAX deploys OFDMA in uplink and downlink direc- the spectrum is divided into a number MIMO deployments. Another techni- tions. LTE deploys OFDMA on the of subcarriers. Downlink Resources are cal aspect of TDD and FDD systems downlink but SC-FDMA (Single Carrier- managed by a scheduler at the Base is the synchronization requirement. Frequency Division Multiple Access) on Station that determines the number of TDD systems have to be synchronized the uplink. The choice of SC-FDMA is subcarriers and time intervals for each to ensure non-interference of uplink motivated by reducing the PAPR (Peak user on the downlink and uplink. and downlink burst across different to Average Power Ratio) on the uplink. BS’. FDD systems do not require this • MIMO: LTE and WiMAX allow for MIMO form of synchronization. A typical way PAPR ratio has a direct impact on the options comprising STBC (Space Time requirements of the power amplifier of implementation of achieving the Block Coding) or SM (Spatial Multiplex- and resulting battery life. (OFDM trans- synchronization is by using an accurate ing). WiMAX Release 1.0 defines 2 x missions consist of multiple subcarriers GPS receiver than can provide a pulse 2 MIMO (and higher MIMO are being leading to a relatively larger PAPR than at 1 PPS (Pulse per second). In low- developed for future release). The LTE those for a single-carrier.) end base stations such as Pico Base specification allows up to 4 x 4 MIMO. Stations and Femto Base Stations, the SC-FDMA provides a 1-2 dB PAPR Differences additional GPS receiver cost becomes advantage over OFDMA that in turn Table  provides the key similarities be- an important consideration while in improves battery life of subscriber tween LTE and WiMAX air Interface. A little indoor Femto Base stations, the non- devices (SC-FDMA would increase re- more detail is provided on these below availability of GPS signals becomes an ceiver complexity at the BS compared additional issue. to OFDMA receiver). This improve- IP NGN ARCHITECTURE THOUGHT LEADERSHIP JOURNAL - Q1 FY2010
  • 6. these elements are considerably different (motivated partly by the existing protocols in G systems and to facilitate backward compat- ibility with already deployed G systems). • Air Interface Efficiency: This is often a highly debated and con- tentious matter. The fact that both technologies use OFDMA and MIMO would lead to comparable spectral efficiency up to first order of approximation. However, design choices about protocol overheads, control channel overheads, would determine the resulting efficiency. Figure 21 - Frequency Bands for LTE and WiMAX Initial comparisons indicate that LTE efficiency is slightly better ment is available to users at the edge and Intel) plan to provide LTE and WiMAX than WiMAX Release 1.0, (see [] of the cell, e.g., in order to increase the equipment. Recently, some of the leading below) but author believes that this up-link coverage or throughput in such vendors announced that they are scaling improvement would disappear with scenarios. the investments in WiMaX. In most cases, modifications in WiMaX Release 1.5 and IEEE 802.16m. • Frame Duration: LTE uses a frame of the equipment vendors intend to leverage 1 msec while WiMAX uses a frame of the commonality in their product devel- opment. This may indicate that both may • Likely Deployments: LTE and 5 msec. The shorter duration leads to WiMAX have unique advantages successfully co-exist in a manner similar that will ultimately determine where more complex implementation in the to co-existence of GSM and CDMA for the they will be deployed. For example, form of larger processors, etc. However, last 10-15 years. LTE appears to be clear choice for this reduces end-end latency and can lead to improved H-ARQ (Hybrid ARQ) In closing, we suggest the following key operators with FDD spectrum as performance, faster channel quality takeaways: well as operators with existing G (GSM) deployments. WiMAX ap- feedback channel. • Similar Technology but different imple- pears to be the clear choice for op- Summary mentations: LTE and WiMAX have de- ployed similar air interface technology erators with TDD spectrum as well In this paper, we outlined the key similari- operators with frequency in the 2.5 (OFDMA, MIMO) but have considerably GHz and .5 GHz band and opera- ties and differences between the tech- different implementations (such as FDD tors with little or no legacy cellular nologies. The ultimate success of either versus TDD, 1 msec versus 5 msec deployments (mostly in emerging technology (as measured by number frames, etc). These design choices markets). of worldwide deployments, number of have been made for a variety reasons subscribers, total revenue, etc) will be and the relative merits of these are determined by a combination of tech- hotly contested by proponents of the nology and business factors. Given the LTE and WiMAX communities. From a relatively similar technology (for example, systems architecture standpoint they OFDM) and design choices, the business deploy similar functional decomposi- factors will play a bigger role in determin- tion (such as separating radio resource ing the success of LTE and WiMAX. Most management from IP management and of the major equipment vendors (such locating RRM in the BS and IP manage- as Cisco, Nokia-Siemens, etc) with a few ment in an access gateway). However, notable exceptions (such as Ericsson, the specific protocols used between CISCO PUBLIC
  • 7. Americas Headquarters Asia Pacific Headquarters Europe Headquarters Cisco Systems, Inc. Cisco Systems (USA) Pte. Ltd. Cisco Systems International BV San Jose, CA Singapore Amsterdam, The Netherlands Cisco has more than 200 offices worldwide. Addresses, phone numbers, and fax numbers are listed on the Cisco Website at www.cisco.com/go/offices. CCDE, CCENT, CCSI, Cisco Eos, Cisco HealthPresence, the Cisco logo, Cisco Lumin, Cisco Nexus, Cisco Nurse Connect, Cisco Stackpower, Cisco StadiumVision, Cisco TelePresence, Cisco WebEx, DCE, and Welcome to the Human Network are trademarks; Changing the Way We Work, Live, Play, and Learn and Cisco Store are service marks; and Access Registrar, Aironet, AsyncOS, Bringing the Meeting To You, Catalyst, CCDA, CCDP, CCIE, CCIP, CCNA, CCNP, CCSP, CCVP, Cisco, the Cisco Certified Internetwork Expert logo, Cisco IOS, Cisco Press, Cisco Systems, Cisco Systems Capital, the Cisco Systems logo, Cisco Unity, Collaboration Without Limitation, EtherFast, EtherSwitch, Event Center, Fast Step, Follow Me Browsing, FormShare, GigaDrive, HomeLink, Internet Quotient, IOS, iPhone, iQuick Study, IronPort, the IronPort logo, LightStream, Linksys, MediaTone, MeetingPlace, MeetingPlace Chime Sound, MGX, Networkers, Networking Academy, Network Registrar, PCNow, PIX, PowerPanels, ProConnect, ScriptShare, SenderBase, SMARTnet, Spectrum Expert, StackWise, The Fastest Way to Increase Your Internet Quotient, TransPath, WebEx, and the WebEx logo are registered trademarks of Cisco Systems, Inc. and/or its affiliates in the United States and certain other countries. All other trademarks mentioned in this document or website are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (0903R) Americas Headquarters Asia Pacific Headquarters Europe Headquarters Cisco Systems, Inc. Cisco Systems (USA) Pte. Ltd. Cisco Systems International BV San Jose, CA Singapore Amsterdam, The Netherlands Cisco has more than 200 offices worldwide. Addresses, phone numbers, and fax numbers are listed on the Cisco Website at www.cisco.com/go/offices. CCDE, CCENT, CCSI, Cisco Eos, Cisco HealthPresence, the Cisco logo, Cisco Lumin, Cisco Nexus, Cisco Nurse Connect, Cisco Stackpower, Cisco StadiumVision, Cisco TelePresence, Cisco WebEx, DCE, and Welcome to the Human Network are trademarks; Changing the Way We Work, Live, Play, and Learn and Cisco Store are service marks; and Access Registrar, Aironet, AsyncOS, Bringing the Meeting To You, Catalyst, CCDA, CCDP, CCIE, CCIP, CCNA, CCNP, CCSP, CCVP, Cisco, the Cisco Certified Internetwork Expert logo, Cisco IOS, Cisco Press, Cisco Systems, Cisco Systems Capital, the Cisco Systems logo, Cisco Unity, Collaboration Without Limitation, EtherFast, EtherSwitch, Event Center, Fast Step, Follow Me Browsing, FormShare, GigaDrive, HomeLink, Internet Quotient, IOS, iPhone, iQuick Study, IronPort, the IronPort logo, LightStream, Linksys, MediaTone, MeetingPlace, MeetingPlace Chime Sound, MGX, Networkers, Networking Academy, Network Registrar, PCNow, PIX, PowerPanels, ProConnect, ScriptShare, SenderBase, SMARTnet, Spectrum Expert, StackWise, The Fastest Way to Increase Your Internet Quotient, TransPath, WebEx, and the WebEx logo are registered trademarks of Cisco Systems, Inc. and/or its affiliates in the United States and certain other countries. All other trademarks mentioned in this document or website are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (0903R)