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Exploration and Comparison of Different 4G Technologies Implementations: A

Survey Parul Datta Sakshi Kaushal

Computer Science and Engineering Department Computer Science and Engineering Department UIET, Panjab University UIET, Panjab University

Chandigarh, India Chandigarh, India paruldatta14@gmail.com sakshi@pu.ac.in

Abstract-Wireless networks avoid the installation costs incumbent in wired networks. Nowadays, users of mobile Internet have grown significantly and require instant accessibility of various high speed Internet applications. This paper presents a review of Fourth Generation (4G) networks and its evolution. A Long Term Evolution (LTE) network provides mobile Internet users with all-IP solutions and seamless connectivity. A detailed analysis of different 4G technologies e.g. WiMAX and LTE network is presented in this paper. In addition, this paper presents a discussion about the architecture of LTE network and various issues faced in LTE technology.

Keywords- LTE; WiMAX; GSM; GPRS; EDGE; UMTS; HSPA

I. INTRODUCTION Recently, mobile Internet access has grown significantly. Wireless telecommunications networks are generally implemented for this purpose [1]. Costly installation connections between various locations are avoided in wireless networks. Millions of mobile applications and high speed Internet access on mobile devices has led to the development of new technologies such as LTE networks [2]. Predecessors of fourth generation are not in use due to their limitations. Zero generation systems like Push to Talk were half duplex communication systems which made use of procedure words like “over” and “out”. First generation systems made use of analog wave and these became obsolete due to no encryption. Second generation systems made use of digitally encrypted, digital voice data along with newly introduced services such as Short Message Service (SMS).

Third generation systems offers greater security and better quality for services like Mobile TV, and GPS, etc. Fourth generation systems provide All-IP solution where voice, data and streamed multimedia can be given to users on “anytime, anywhere” basis.

Fourth generation systems have two candidate systems: Mobile WiMAX and Long Term Evolution (LTE). To accommodate day-by-day increasing usage of mobile and multimedia applications, 3GPP developed LTE network [3]. Organizations in order to increase their effectiveness in exchanging images and live video streams from the incident areas require wireless data transmission capabilities. But, these requirements cannot be fulfilled by narrowband technologies. This led to the development of technologies like LTE which provide transmission of high definition video streams [4].

The organization of the paper is as follows. The next section provides an insight into evolution of LTE, technical comparison of LTE network and WiMAX followed by characteristics of LTE. Then, Section III gives a detailed view of LTE architecture. In Section IV some of the issues in LTE are highlighted. Finally, Section V concludes the study.

II. RELATED WORK

A. LTE Evolution A highly flexible radio interface was deployed in 2009 known as 3rd Generation Partnership Project (3GPP) Long Tem Evolution (LTE) [7]. LTE has many legacy technologies which led to its development. These technologies are discussed below.

1) GSM (Global System for Mobile Communications)

In the early years of this decade, a pan-European Mobile communication system in 900 MHz band was introduced known as GSM [8]. For wireless communication, GSM is the most widely deployed second generation cellular systems in the world.

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Proceedings of 2014 RAECS UIET Panjab University Chandigarh, 06-08 March, 2014

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Using the cell concept, GSM telephone systems were developed in the `80s [9]. Base stations corresponding to each cell were placed on towers or buildings. GSM provides low cost implementation of Short Message Service (SMS).

2) GPRS (General Packet Radio Service)

GPRS is a best-effort service. This implies that throughput and latency depend on the number of users sharing the service concurrently. GPRS usage is charged based on the volume of data transferred. A higher handover dropping rate to GSM voice may be caused by GPRS [10]. Due to difference in transmission protocols, capacity performance in the downlink differs from that of uplink.

3) EDGE (Enhanced Data Rates for GSM Evolution)

Improved data transmission rates and higher bit-rates per radio channel are provided by EDGE. As compared to GSM, EDGE provides higher spectral efficiency [11]. EDGE can carry a bandwidth up to 236 Kbit/s. EDGE can handle four times as much traffic as GPRS. Evolved EDGE provides reduced latency and doubled performance.

4) UMTS (Universal Mobile Telecommunications System)

6) WiMAX

The first major WiMAX standard for fixed access was developed by IEEE in 2004 known as IEEE 802.16 standard. Later in 2005, IEEE developed IEEE 802.16e known as Mobile WiMAX [1]. Interoperability of WiMAX products from various vendors is certified by the WiMAX Forum which comprises of more than 300 companies. Around the world, a number of WiMAX networks have been commercially deployed.

7) LTE

Advancements in High Speed Packet Access led to the development of 3GPP LTE [1]. First commercial deployment of LTE was done by Swedish telecom operator TeliaSonera in December 2009 in Stockholm, Sweden and Oslo, Norway. Ericsson supplied Stockholm’s network and Huawei supplied Oslo’s network. Samsung supplied the modems.

B. Technical Specifications

Table I shows the main technical specifications for 3GPP LTE and Mobile WiMAX IEEE 802.16e [5] [6].

A common service platform and transport for 3G networks based on IP is the major motivation behind building UMTS systems based on IP [12]. UMTS is a mobile cellular system for networks based on GSM standard. Wideband Code Division Multiple Access (W-CDMA) radio access technology is used in UMTS to provide greater spectral efficiency and bandwidth to mobile network operators. New base stations and new frequency allocations are needed by UMTS.

5) HSPA (High Speed Packet Access)

High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA) were amalgamated in order to extend and improve the performance of existing 3rd generation networks which resulted in HSPA. HSPA allows bit-rates of 168 Mbit/s in the downlink and 22 Mbit/s in the uplink. The limitations of these technologies and the need for high speed Internet access on mobile devices has led to the development of LTE network.

C. Characteristics of LTE There are many characteristics possessed by LTE networks. On the basis of these characteristics a comparison of LTE network is shown with WiMAX in Table I. Some of these are discussed below:

1) High throughput: High data rates can be achieved in both downlink as well as uplink. This causes high throughput.

2) Low latency: Time required to connect to the network is in range of a few hundred milliseconds and power saving states can now be entered and exited very quickly.

3) Seamless Connection: LTE network will also support seamless connection to existing networks such as GSM, CDMA and WCDMA.

4) High Quality of Service (QoS) 5) Smooth handover across heterogeneous

networks 6) High network capacity 7) Simple architecture

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TABLE I. LTE AND WiMAX TECHNICAL SPECIFICATIONS

Aspect

3GPP LTE

Mobile WiMAX (IEEE 802.16e)

Legacy

GSM/GPRS/EDGE/UMTS/HSPA

IEEE 802.16 a through d

Core Network

UTRAN moving towards All-IP E-UTRA core network with IMS and SAE architecture

WiMAX Forum All-IP network

Peak data Rate: Downlink (DL) Uplink (UL)

100 to 326.4 Mbps 50 to 86.4 Mbps

75 Mbps 25 Mbps

Cell capacity

>200 users at 5 MHz >400 users for larger bandwidth

100-200 users

Cell Radius

5 Km

~20.7 Km for 3.5 or 7 MHz bandwidth ~8.4 Km for 5or 10 MHz bandwidth

Radio Access Modes

TDD and FDD

TDD and FDD

Antenna Scheme

MIMO

MIMO

Mobility: Speed Handover

Up to 350 Km/hr Inter-cell soft handovers supported

Up to 120 Km/hr Optimized hard handovers supported

Roaming

New

Auto through existing GSM/UMTS

III. ARCHITECTURE OF LTE Architecture of LTE comprises of two networks: the E-UTRAN (as shown in Fig. 1) and the Evolved Packet Core (as shown in Fig. 2) [3].

Evolved Universal Terrestrial Radio Access Network (E-UTRAN) handles the communications between the mobile and the Evolved Packet Core (EPC) and has just one component, the evolved base stations, called eNodeB or eNB [3]. Each eNB is a base station that controls the mobiles. The base station that is communicating with a mobile is known as its serving eNB.

Two main functions supported by eNB are:

1. The eNB sends and receives transmissions to all the mobiles.

2. The eNB controls the low-level operation of all its mobiles, by sending them signaling messages such as handover commands.

Each eNB connects with the EPC by means of the S1 interface and it can also be connected to nearby base stations by the X2 interface, which is mainly used for signaling and packet forwarding during handover.

Interfaces connecting each of the network elements are standardized in order to provide multi-vendor interoperability. Thus, it is possible for network operators to source different network elements from different vendors.

This overall network architecture comprising of E-UTRAN, i.e., the access network and EPC, i.e., the core network should provide users with security and privacy, and network protection against fraudulent use.

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Fig.1. E-UTRAN [3]

Fig.2. EPC Network [3]

The Evolved Packet Core (EPC) network has the following components [3]:

The Home Subscriber Server (HSS) is a central database that contains information about all the network operator's subscribers. The Packet Data Network (PDN) Gateway (P-GW) acts as a default router for the User Equipment (UE) and communicates with the outside world, using SGi interface.

The Serving Gateway (S-GW) acts as a router, and forwards data between E-UTRAN and P-GW.

There are many interfaces used as reference point in LTE network architecture [3]:

SGi is the interface between P-GW and PDN, S1-U is the reference point between E-UTRAN and S-GW, S5/S8 is the reference point between S-GW and P-GW, S6a is the reference point between MME and HSS, S11 is the reference point between MME and S-GW, S1-MME is the reference point between E-UTRAN and MME, and S10 is the reference point between MME and MME.

The Mobility Management Entity (MME) controls the high-level operation of managing mobiles and their sessions.

MME

MME

S-GW P-GW

HSS

E-UTRAN

Servers PDNs

S6a

S11

SGi S5/S8

S10

S1-U

S1-MME

Signals

Data

X2

X2

X2

UE EPC

eNB

eNB eNB

S1

E-UTRAN

Signals

Data

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IV. RESEARCH ISSUES IN LTE There are many issues in LTE networks which need to be addressed. Some of the important issues are discussed below:

A. Mobile Internet Application issue

There are two radio states in LTE networks e.g., RRC_Connected and RRC_Idle. In traditional applications, traffic was only generated in Active (Connected) state. At the end of user session, traffic generation also ended and the radio is allowed to move to the Inactive (Idle) state [2]. There is a constant stream of user generated traffic at all times in newer applications like Facebook, Twitter, etc. Therefore, the clear boundary between Connected and Idle state has diminished. Many mobile devices move between Connected and Idle states frequently, thus causing excessive signaling overhead. An optimal solution is required to decrease the signaling overheads.

B. Handover issues

Fast and seamless access of voice and multimedia services and guaranteed QoS increased the frequency of handovers in LTE networks. This leads to degradation in system performance in terms of delay and packet loss [13]. Reduced latency requirements and increased capacity, coverage and throughput can be ensured by using proper handover algorithms [14].

C. Quality of Service issues

There are different QoS requirements for E-UTRAN, Backhaul network and EPC network [15]. So, these differences will cause problems when domains intersect. Flexibility in QoS is highly desirable for the emerging mobile Internet applications [16]. Mechanisms are required to ensure that the QoS is met at the different levels, i.e., application level and connection level. For management of network resources and satisfactory end user service delivery, QoS is a fundamental requirement for Internet applications.

D. Interoperability issues

Acceptability and reach of LTE network is based on seamless interoperability in 2G/3G networks. Users should be able to roam seamlessly for voice, data and SMS and actuate mobility and location management. So, synchronization in legacy technologies and LTE networks is the main requirement [17].

E. Scheduling issues

Distribution of radio resources among different stations with fine time and frequency resolutions is important in high speed networks. Packet scheduling mechanisms play a fundamental role in choosing these. Resource allocation algorithms must be correctly implemented [18].

V. CONCLUSION Wireless networks avoid the installation

costs incumbent in wired networks. Nowadays, users of mobile Internet have grown significantly and require instant accessibility of various high speed Internet applications. LTE is currently one of the most widely used 4G technologies. In this paper, the performance of existing mobile technologies e.g. WiMAX and LTE networks is analyzed and their aspects are tabulated along with their characteristics. It is shown that LTE is advantageous over WiMAX in every aspect. LTE architecture consists of two networks- the access network, i.e., E-UTRAN network and the core network, i.e., EPC network. Some challenging issues for research in LTE networks are also discussed. These issues need to be addressed to further improve the performance of LTE networks.

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