Wimax & lte comparisons

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1. Introduction

Communication technology has been growing exponentially in the last decade and has influenced a part of everyday life. Each communication method has its own merits and demerits. Wireless and mobile network operators face the challenge continues to build networks that effectively manage the growth of traffic data rate.

Mobility and higher levels of multimedia content for end users require modifications to-end network support new services and a growing demand for broadband Internet access card. In addition, network operators consider the most cost-effective evolution to 4G networks.

Wireless mobile technology standards and requirements evolve to a higher bandwidth for both peaks rates and cellthroughput growth.

The rules relating to mobile and wireless technologies evolve to higher bandwidth requirements for both growth and maximum cellthroughput. The latest standards supporting this are HSPA+, WiMAX, and LTE.

This report provides a brief study on wireless generation's technologies. The next sections introduce the wireless model of WiMAX. In section 3, explore advantages & disadvantages and compressions. In section 4, introduces the wireless model of LTE. Section 5 presents different between WiMAX and LTE and section. Finally, section 7 concludes this report.

2. Mobile Network Generations

2.1 First Generation (1G) Wireless Technology

The first generation of wireless communications was on the analogue. Analogue system (AMPS), was implemented in North America. Analogue system was mainly based on circuit-switched technology and planned for voice only.

2.2 Second Generation (2G) Wireless Technology

It was mainly from low-band digital data signal. Global Systems for Mobile Communications (GSM) technology is a mixture of Time Division Multiple Access (TDMA) and Frequency division Multiple Access (FDMA). Every frequency is then divided via a TDMA scheme into eight timeslots.

GSM and TDMA-based systems, while others are the leading 2G wireless technologies, CDMA technology was known as offering clear voice quality with less noise, fewer dropped calls, enhanced security, increased reliability and greater network capacity. 2G wireless networks are mainly based on circuit switched technology. [2]

2.3 Second Generation (2G.5) Wireless Networks

The valuable data rate of 2G circuit-switched wireless systems is reasonably too slow for today's Internet. Therefore, GSM, TDMA, PDC system mobile and other providers and suppliers are based on a technology that is based 2G + and improves packet data communications at speeds as high as 384 kbps. [2]

These 2G+ systems technologies

ü High Speed Circuit-Switched Data (HSCSD) technology,

ü General Packet Radio Service (GPRS) technology

ü Enhanced Data Rates for Global Evolution (EDGE) technology.

HSCSD was one step headed for 3G wideband mobile data networks. This circuit-switching technology improves the data rates to 57.6 kbps with the introduced 14.4 kbps packet and by aggregating 4 radio channel 4 time intervals of 14.4 kbps.

GPRS is an intermediate step which is designed for the GSM world a full range of Internet services to continue without waiting for the full deployment of 3G wireless systems. GPRS is packet-based and designed to operate in parallel with the 2G GSM, PDC and TDMA systems used for voice and the look-up table to obtain GPRS user profiles based on Location Register data. GPRS uses a multiple of 1 to 8 slots of the radio station in the range of 200 kHz of frequency assigned to a frequency to transmit data rates up to 115 kbps. The data is packaged and transported to Public Land Mobile Networks (PLMN) using an IP backbone so that mobile users have access to Internet services such as SMTP / POP-based e-mail, FTP and HTTP-based Web services.

EDGE technology is a standard that was designed to improve performance per timeslot for both HSCSD and GPRS. The improvement of HSCSD is called ECSD, improvement of GPRS is called EGPRS. In ECSD, the maximum throughput does not exceed 64 kbps, due to restrictions on the interface A , but the data rate per timeslot will triple. In EGPRS, the data rate per time slot three-and excellence, will eight slots on the radio interface, more than 384 kbps.

Network of GPRS consists of an IP-based Public Land Mobile (PLMN), Base Station Services (BSS), phones (MS) and mobile switching centres (MSC) for circuit switched access to databases and data network. GPRS hold up nodes (SGSN) and Gateway GPRS hold up Nodes (GGSN), the PLMN. Homelessness is hosted by multiple PLMN. SGSN and GGSN interface to the interior location of the Registry (HLR) to retrieve the roaming user profiles to facilitate discussions. GGSN provides the connection to the external packet data (PDN) [2]

2.4 Fourth Generation (4G) Wireless Networks

"4G's goal is to replace the current proliferation of core cellular networks with a single worldwide cellular core network standard based on IP (Internet protocol) for control, video, packet data, and Voice over IP (VoIP). This would, states Kempf, provide uniform video, voice, and data services to the cellular handset or handheld Internet appliance, based entirely on IP".

Architecture

One of the most difficult problems of the deployment of 4G technology is how to access different networks of different mobile and wireless. The figures below are three possible architectures: the use of a multi-mode device, a super-network, or a common access protocol.[8]

I. Multimode devices

Configuration uses a single physical terminal with multiple interfaces to access services in wireless networks. The first examples of this architecture are the current Advanced Mobile Phone System / Code Division Multiple Access mobile phone dual role, dual function Iridium satellite phone, and the new Global System for Mobile telecommunications or Digital Enhanced Cordless Terminal dual-mode cordless phone. The architecture of the multi-mode device, the improvement of terminal and extend the effective coverage area. You must also provide reliable wireless coverage in the event of a network connection or no change. The user, device or network can cause the transition between networks. The device itself, incorporate most of the extra complexity, without the wireless network or the use of devices together. Each network may implement a database that keeps track of the location of the user, the device capabilities, network conditions and user preferences. Managing Quality of Service (QoS) issues in research remains an open question. [8]

II. Overlay network

In this architecture, a user a special network of different points of universal access. The PSU in turn, choose a wireless network based on availability, quality of service user-defined specifications and options. The PMU performs protocol and frequency translation, content adaptation and negotiation, renegotiation of QoS for the user. The specific network instead of the user or device performs the transfer of power to the user of one another. UAP stores a user, network and device information, skills and preferences. Because UAPs track of the various means of keeping the caller can use this architecture supports the unique billing and underwriting.

III. Common access protocol

This protocol is possible, if the wireless networks could support one or two standard access protocols. One possible solution, interaction between different wireless networks using Asynchronous Transfer Mode is required. Applications for wireless ATM, each wireless network should enable the transfer of ATM cells with additional headers in wireless networks. One or several types of satellite networks can use a protocol, while one or more terrestrial wireless networks use a different protocol. [9][8]

IV. QUALITY OF SERVICE

Supporting QoS in 4G networks will be a major challenge due to variations in flow, channel characteristics, levels of bandwidth allocation for fault tolerance and the transfer of support among heterogeneous wireless networks.QoS can be produced to support the compromise package, circuit, the user and the network level.

• Packet-level QoS applies to jitter, throughput, and error rate. Network resources such as buffer space and access protocol are likely influences.

• Transaction-level QoS describes both the time it takes to complete a transaction and the packet loss rate. Certain transactions may be time sensitive, while others cannot tolerate any packet loss.

• Circuit-level QoS includes call blocking for new as well as existing calls. It depends primarily on a network's ability to establish and maintain the end-to-end circuit. Call routing and location management are two important circuit-level attributes.

• User-level QoS depends on user mobility and application type. The new location may not support the minimum QoS needed, even with adaptive applications. In a complete wireless solution, the end-to-end communication between two users will likely involve multiple wireless networks. Because QoS will vary across different networks, the QoS for such users will likely be the minimum level these networks support.[8]

V. End-to-End QoS

Developers must work harder to meet the end -to end QoS. It may be that many of the regulations change the existing quality of service, including access control, dynamic resource reservation, and renegotiation of QoS for users of different QoS requirements to support 4G. The overhead for the implementation of these systems at different levels of quality of service requires a careful evaluation. A wireless network, your current quality of service information to other networks, a centralized or distributed so that they can effectively use the available network resources. Moreover, the deployment of an international quality of service to support the diverse needs of users with different mobility patterns. The effect of the introduction of a unique quality of service through networks rather than rely on the system of quality of service for each network requires a study.

VI. Handoff delay

Handoff delay poses another essential QoS-related matter in 4G wireless networks. Although they may be lower in the transfer intranet work, delays can be problematic in the internal network handoffs because of authentication procedures required for the exchange of messages, access to multiple databases and negotiation, renegotiation, since a significant difference between the quality of the services needed and available. During the transfer process the user a significant decrease in the quality of service which may affect the performance of the two upper layer protocols and applications. The implementation of an algorithm based on priority and use applications in locating the current slowdown, the relay and the variability of the quality of service. If there is potential for considerable variation between transmitters and receivers of the device capabilities, the use of receiver-specific filter within the closed network to the source effectively reducing the amount of traffic and processing Perhaps the needs of other QoS.[8]

VIII. Internet Speeds

2.5G is the intervening solution for 2G networks to 3G has the ability of 2.5G networks are designed to ensure a smooth transition (updated software) to 3G can be made. The 2.5G networks are an effective data rates up to 28kbps. In comparison, the hypothetically speed of 3G up to 2 Mbps, or about 200 times faster than the previous 2G networks. [10]. this increased speed and performance to run applications such as streaming video clips. It is expected that 4G speeds can reach 100 Mbps. Therefore 4G is another big leap in mobile Internet speed and image quality. Ericsson confirms that 4G could offer connection speeds up to 50 period quicker than 3G networks, and could provide three-dimensional visual experiences for the first time .[11]

3. Comparing 3G and 4G

Attribute

3G

4G

Major Characteristic

Predominantly voice- data as add-on

Converged data and VoIP

Network Architecture

Wide area Cell based

Hybrid - integration of Wireless Lan (WiFi), Blue Tooth, Wide Area

Frequency Band

1.6 - 2.5 GHz

2 - 8 GHz

Component Design

Optimized antenna; multi-band adapters

Smart antennas; SW multi-band; wideband radios

Bandwidth

5 - 20 MHz

100+ MHz

Data Rate

385 Kbps - 2 Mbps

20 - 100 Mbps

Access

WCDMA/CDMA2000

MC-CDMA or OFDM

Forward Error Correction

Convolution code 1/2, 1/3; turbo

Concatenated Coding

Switching

Circuit/Packet

Packet

Mobile top Speed

200 kmph

200 kmph

IP

Multiple versions

All IP (IPv6.0)

Operational

-2003

-2010

[ 1]

4. WiMAX

The concept of worldwide interoperability for microwave access in short WIMAX was established in 2001. It encompasses fixed, portable, nomadic and mobile flavours of broadband access technologies and term to stand on IEEE 802.16 standard. Intel has called 802.16 "the most important thing since the Internet itself"[2]. WiMAX is a future consideration, a thought for many broadband solutions and a standard considered to be the next step to DSL and cable solutions providing the capacity to deliver sufficient bandwidth covering long distances ranging up to 30 kilometres radius theoretically and in real world practice up to 3 to 10 kilometres with capacity of up to 40 Mbps for fixed and portable applications [13]. Broadband solutions providing standards like 3G, 4G, Wi-fi, Bluetooth, WiMAX, LTE and similar standards are said to be in constant battle in terms of speed, coverage and performance. It is the end to end reliable data transfer, under high speed, low cost and flexibility that makes the technology more attractive in the growing industry and thought to storm the next generation of wireless technology.

4.1 WiMAX Standards and Layers

IEEE 802.16 Standards Background

IEEE 802.16 organization established in 1998 is responsible for developing and structuring broadband wireless access standards. Under the umbrella of 802.16 standards a series of enhancements were defined that addresses specific range of frequencies for service parameters. Comparison of standards is tabulated below, that also illustrates the distinguishing features of one WiMAX operator network from other: [14][16]

IEEE 802.16 Reference Model

The basic idea was to develop integrated PHY layer specifications for broadband wireless services with necessary modifications to support and interact with MAC layer components[4]. Protocol model is shown below: [15]

Layered approach:

WiMAX is said to be a connection-oriented that operates on physical and data link layer (Mac) of the OSI model [14][15].

Data Link (MAC) Layer

Data link or MAC layer works in coordination with PHY layer, and is the point of interaction with user traffic. It communicates by sending SDU's over PHY layer and PHY layer in return communicates through 802.16 air link. Techniques involving packing, fragmentation, payload header suppression enhances the functionality to handle bursty traffic. Automatic Repeat Request(ARQ) and Link adaption functions maintains high data throughput. Data link in figure1 consists of sub layers that are [16]

Privacy Layer

: Data encryption, authentication and security issues are dealt at privacy sub layer.

MAC CPS:

MAC common part sub layer (MAC CPS) handles core functions including bandwidth utilization, uplink scheduling techniques, connection control and automatic repeat request .

CS:

Service specific convergence sub layer (CS) acts as bridge and access upper layers through CS service access point SAP.

Physical Layer

The bottom layer in OSI model has its significance in transmitting data digitally and in WIMAX it continues it task in collaboration with MAC layer. Modulation and duplexing techniques involve OFDM, TDD and FDD schemes .

Wireless MAN-SCa: Single carrier modulated air interface, Wireless MAN OFDM and Wireless MAN OFDMA. Mobile WiMAX includes Adaptive modulation and coding (AMC), Hybrid automatic repeat request (HARQ), and Fast Channel feedback (CQICH) for scalability and flexibility issues.[2] In downlink modulation techniques like quadrature phase shift keying (QPSK), 16 quadrature amplitude modulation (QAM) and 64 QAM are included though 64 QAM is optional in Uplink. Functional circuit diagram is shown below [16].

4.2 Access Technology

I. Line Of Sight Vs Non Line Of Sight

In wireless communications systems the radio channel could be whether LOS (Line Of Sight) or NLOS (Non LOS) .the main difference between these two is the capability of NLOS systems that can transmit signals even in environments with obstructions such as buildings and trees. In figure 5 a LOS system is shown.[17]

Also there is the multi path phenomenon which causes problems in LOS systems.

The advantage of NLOS systems is that they can handle these issues; also they reduce planning, installation and cell design costs. Figure 8 briefly represents the difference of LOS and NLOS radio transmission.[18]

II. NLOS Technology Solutions

There are several solutions that could be utilized to deploy a NLOS communication system.

OFDM technology

Basically there are several advantages using OFDM as the multiplexing method for transmission including distributing transmission on several orthogonal sub-carriers, eliminating frequency selective fading and reducing crosstalk and multi-path interference. On the other hand OFDM results in more efficient use of frequency spectrum. In figure 8 we can see the comparison between single carrier and OFDM transmission. [17]

Sub-Chanilization

This function is the power concentrated in firms with fewer OFDM transmission system increases the gain that can be used for the scope of the system to expand, overcoming the loss of penetration of the building and reducing energy consumption CPE. [19]

On the other hand usage of sub-channelization has advantages regarding power consumption and area coverage.

Error corrections and power control techniques

Error correction and power control techniques and algorithms are incorporated into WIMAX to reduce errors and power consumption of the system. [19]

Coverage Range

In general there are two kinds of base stations regarding coverage of the WIMAX systems. Standard and Full featured on standard version we have the simple implementation however on the full featured version we can have higher RF output power. The following figure 10 demonstrated the comparison.[8]

TDD VS FDD

Another issue in WIMAX is the Frequency Division vs. time Division .Implementing WIMAX whether based on FDD or TDD depends on the regulations and the manufacturers capabilities.[19]

Mobility

In order to implement mobility in WIMAX communication systems we must overcome some challenges including Handover, Adaptive Modulation and Power Efficiency. The solution to overcome these challenges is the use of SOFDMA instead of OFDM.[10]

Basically OFDMA is the multi-user version of OFDM and assigns subset of sub-carriers depending on bandwidth needed by stations.

Regarding available technologies in market and the techniques used in order to provide mobile wireless access the following figure 12 gives a comprehensive grasp of the stand point of different technologies that in some cases have overlapping properties.[19]

4.3 Strengths of WiMAX

Advantages of WiMAX

*

Flexibility -

WiMAX technology benefits wide coverage capabilities.

*

Standard -

WiMAX is becoming the worldwide technology-based standard for broadband wireless access, and is pushing competition among IT players in terms of servives.

·Low Cost -

Base stations will cost under $20,000 but will still provide customers with T1-class connections.

* Long Range - The most significant benefit of WiMAX compared to existing wireless technologies is the range as discussed in report.[20]

Benefits for Component Manufacturers, Operators and Service Providers

* Assured wide market acceptance of developed chips and component

· Lower production and network deployment costs Reduced interoperability risks

* Stable supply of low-cost components and chips

* Freedom to focus on development of network elements consistent with core competencies.

* Ability to tailor network to specific applications by use of hybrid technology [20]

Benefits for End Users

* Wide choice of terminals enable cost-performance analysis

* Portability when moving locations/networks

* Lower service rates [20]

Security Enhancement for WiMAX

Client/Server impersonation:

The session initiation protocol can enable registration of multiple contacts. By impersonation; hacker manipulates contact information, and intercepts server session.

·Firewall and NAT solution:

provides access to authorized devices and sets parameters to block unnecessary traffic.

·X.509 digital certificates:

Used to authenticate subscriber stations (SS).

Message and Session tampering:

Hackers may implement spoofed proxy servers and intercepts media session encryption methods including associated keys.

*

Signalling and media security

: Signalling security is based on MD-5 authentication and TLS/IPsec. Media security is based on secure RTP/IPsec.

*

Intrusion detection and prevention systems

: Detects signature-based attacks and intrusion. [20]

Future Enhancements

* WiMAX is considered to be the dominant technology within the next 5 years with its flexibility and interoparable nature.

* WiMAX a power intensive technology requires strong electrical support. Fujitsu and Intel already begin to make their Centrino laptop processors compatible to support power intensivity.

* Interference and noise issues can be dealt with innovative WiMAX technology.

* Security issues will be dealt by new methods for security evaluation, modelling end to end security and product adaptation to enable message injection.[20]

4. Long Term Evolution (LTE)

The 3GPP Long Term Evolution (LTE) is a major step in cell technology. LTE is designed to meet the needs of the service in transporting data at high speed, high capacity and voice services in the next decade. This includes high-speed data, multimedia unicast and broadcast. Although the technical specifications have not been completed, important details are emerging. This document focuses on the LTE physical layer (PHY). The LTE PHY is an effective means of providing data and control information between a solid base station (eNodeB) and mobile user equipment (UE). The LTE PHY uses some advanced technologies which are new to mobile applications. These include Orthogonal Frequency Division Multiplexing (OFDM) and Multiple Input Multiple Output (MIMO) data. Besides the LTE PHY uses orthogonal frequency division multiple access (OFDMA) downlink (DL) and frequency division multiple access single carrier (SC-FDMA) for uplink (UL).

Full version of OFDMA data should be directed to or from multiple users in the database a number of subcarrier subcarrier symbol times. Because of the novelty of these technologies in portable applications, they are described separately, before a description of the LTE PHY. Although the LTE specifications describe both Frequency Division (FDD) and Time Division (TDD) for UL and DL traffic separately, market preferences, requirements that most systems are deployed FDD. This document describes only so LTE FDD systems [21].

3GPP original LTE requirements summaries

* Greater than before peak data rates: 100Mbit/s downlink and 50Mbit/s uplink

* Decrease of Radio Access Network (RAN) latency to 10ms

* Better spectrum effectiveness (2 to 4 times compared with HSPA Release 6)

* Money-spinning migration from free 6 Universal Terrestrial Radio Access (UTRA)

Radio interface and architecture

* Better broadcasting

* IP-optimized (focus on services in the packet-switched domain)

* Scalable bandwidth of 20MHz, 15MHz, 10MHz, 5MHz and <5MHz

* maintain for both paired and unpaired spectrum

* Support for interworking with alive 3G systems and non-3GPP specified systems.

In parallel with the LTE radio access, packet core networks are also evolving to the flat SAE architecture. This new architecture is designed to optimize network performance, improve cost-efficiency and facilitate the uptake of mass-market IP- based services. There are only two nodes in the SAE architecture user plane: the LTE base station (eNodeB) and the SAE Gateway. The LTE base stations are connected to the Core Network using the Core Network-RAN interface, S1. This flat architecture reduces the number of involved nodes in the connections. Existing 3GPP (GSM and WCDMA/HSPA) and 3GPP2 (CDMA2000 1xRTT, EV-DO) systems are integrated to the evolved system through standardized interfaces providing optimized mobility with LTE. For 3GPP systems this means a signalling interface between the SGSN and the evolved core network and for 3GPP2 a signalling interface between CDMA RAN and evolved core network. Such integration will support both dual and single radio handover, allowing for flexible migration to LTE. Control signalling - for example, for mobility - is handled by the Mobility Management Entity (MME) node, separate from the Gateway. This facilitates optimized network deployments and enables fully flexible capacity scaling. The Home Subscriber Server (HSS) connects to the Packet Core through an interface based on Diameter, and not SS7 as used in previous GSM and WCDMA networks. Network signalling for policy control and charging is already based on Diameter. This means that all interfaces in the architecture are IP interfaces. Existing GSM and WCDMA/HSPA systems are integrated to the evolved system through standardized interfaces between the SGSN and the evolved core network. It is expected that the effort to integrate CDMA access also will lead to seamless mobility between CDMA and LTE. Such integration will support both dual and single radio handover, allowing for flexible migration from CDMA to LTE. LTE-SAE has adopted a Class-based QoS concept. This provides a simple, yet effective solution for operators to offer differentiation between packet services.

Advanced Antennas

Advanced antenna solutions that are introduced in evolved High Speed Packet Access (eHSPA) are also used by LTE. Solutions incorporating multiple antennas meet next-generation mobile broadband network requirements for high peak data rates, extended coverage and high capacity. Advanced multi-antenna solutions are key components to achieve these targets. There is not one antenna solution that addresses every scenario. Consequently, a family of antenna solutions is available for specific deployment scenarios. For instance, high peak data rates can be achieved with multi-layer antenna solution such as 2x2 or 4x4 Multiple Input Multiple Output (MIMO) whereas extended coverage can be achieved with beam-forming.

5. Comparing WiAX and LTE

WiMAX & LTE

» The two principal mobile broadband platforms for the next decade

» Extensive development communities for networks, devices & applications

» Field tested and market proven services

» Enable new revenue generating applications previously reserved to fixed line broadband

» Economies of scale leading to steep cost declines

» Built on IP foundations; integrating mobile broadband with IP networking

» Utilizing OFDM air interface, next generation base station design & advanced antennas

» Operating in licensed spectrum and addressing globally available bands

Leveraging the key technology enablers for next generation wireless broadband, the industry has demonstrated strong support for 802.16e-2005 and LTE to provide solutions applicable to a broad set of global operator segments with varying spectrum holdings.

WiMAX

LTE

Specification

IEEE 802.16e (2005)

3GPP Release 8 (due 12/2008)

Commercial availability

Today

Today

Peak throughput

70 Mbps download and 70 Mbps upload

Specifies up to 326 Mbps download and 84 Mbps upload

Downlink technology

OFDM

OFDM

Uplink technology

OFDM

SC-FDMA

Frequency

2.3, 2.5, and 3.5 GHz

Various: 700 MHz - 2.5 GHz

Quality of Service (QoS)

Yes

Yes

WiMAX market

While residents of the United States urban expect the first buds of wireless broadband, a number of countries are looking to WiMAX as a means to provide voice services to remote locations. India, Africa and Eastern Europe led to the adoption of WiMAX. And then there are consequences for outstanding initiatives in most developed markets for Clearwire U.S., Russian Yota, UQ in Japan. Yota is signing up 2,000 new subscribers per month in Saint Petersburg and Moscow, and has 200,000 since its launch last fall.

6. Conclusion

A thorough understanding of 3G, 4G, WiMAX and LTE standards, techniques, services, production architecture and transmission issues are dealt. We tried to cover every aspect of them and give a comprehensive knowledge on the subject. LTE is positioned to meet the needs of next generation mobile networks - both existing 3GPP/3GPP2 operators. This makes it possible to offer high performance, the mass market for mobile broadband through a combination of low interest rates and system performance - both uplink and downlink - with low latency. LTE infrastructure is designed to be as simple as possible to deploy and operate, thanks to a flexible technology that can be deployed in a wide range of frequency bands. LTE offers scalable bandwidth, less than 5MHz to 20MHz, with support for both paired FDD and unpaired TDD spectrum. The LTE SAE architecture reduces the number of nodes, supports flexible network configurations and provides a high level of service availability. Furthermore, LTE-SAE will interoperate with GSM, HSPA/WCDMA, CDMA and TD-SCDMA . LTE will be offered not only in 4G mobile phones but also in notebooks, ultra-portables, cameras, camcorders, fixed wireless terminals and other devices that use mobile broadband.

Reference

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