LTE & LTE-A PROSPECTIVE OF MOBILE BROADBAND

International Journal of Recent Innovation in Engineering and Research Scientific Journal Impact Factor - 3.605 by SJIF e- ISSN: 2456 2084 LTE & LTE-A PROSPECTIVE OF MOBILE BROADBAND G.Madhusudhan 1 and Ajay P Betur 2 1 Research Scholar Department of PG Studies & Research in Electronics Shankaraghatta-577451 2 Assistant Professor, Department of E &CE, JNNCE, Navule,Shivamogga-577201 Abstract- This paper provides an in-depth view on the technologies being considered for Long Term Evolution (LTE) and Long term Evolution -Advanced (LTE-Advanced). First, the evolution from third generation (3G) to fourth generation (4G) is described in terms of main characteristics and performance requirements, the new network architecture developed by the Third Generation Partnership Project (3GPP), which supports the integration of current and future radio access technologies which is highlighted. Then, the main technologies for LTE-Advanced are explained, together with possible improvements, their associated challenges, and theoretical approaches that have been considered to tackle those challenges. Through this paper a clear view regarding the Comparison between two giant outgrowth in modern era of mobile communication i.e. LTE and LTE-A can be drawn as per each key features concerned in both the standards. Keywords-LTE,Downlink,Uplink,lteadvanced,4G,Carrieaggregation,comp,Relay,MIMO,PDCCH, PUCCH. I. INTRODUCTION A. Evolution of wireless standards Wireless communications have evolved from the so-called second generation (2G) systems of the early 1990s, which first introduced digital cellular technology through the deployment of third generation (3G) systems with their higher speed data networks to the much-anticipated fourth generation technology being developed today. This evolution is illustrated in Figure 1, which shows that fewer standards are being proposed for 4G than in previous generations, with only two 4G candidates being actively developed today: 3GPP LTE-Advanced and IEEE 802.16m, which is the evolution of the WiMAX standard known as M obile WiMAX. Figure 1: Wireless evolution 1990 2011 and beyond LTE (both radio and core network evolution) is now in the market. Release 8 was frozen in December 2008 and this has been the basis for the first wave of LTE equipment. LTE specifications are very stable, with the added benefit of enhancements having been introduced in all subsequent 3GPP Releases. B. The motivation for LTE Need to ensure the continuity of competitiveness of the 3G system for the future. User demand for higher data rates and quality of service Packet Switch optimized system. Continued demand for cost reduction (CAPEX and OPEX) @IJRIER-All rights Reserved -2017 Page 35

Low complexity; avoid unnecessary fragmentation of technologies for paired and unpaired band operation. Figure 2: LTE system II. SUMMARY OF LTE FEATURES The Long Term Evolution project was initiated in 2004. The motivation for LTE included the desire for a reduction in the cost per bit, the addition of lower cost services with better user experience, the flexible use of new and existing frequency bands, a simplified and lower cost network with open interfaces and a reduction in terminal complexity with an allowance for reasonable power consumption. These high level goals led to further expectations for LTE, including reduced latency for packets, and spectral efficiency improvements above Release 6 high speed packet access (HSPA) of three to four times in the downlink and two to three times in the uplink. Flexible channel bandwidths a key feature of LTE are specified at 1.4, 3, 5, 10, 15, and 20 MHz in both the uplink and the downlink. This allows LTE to be flexibly deployed where other systems exist today, including narrowband systems such as GSM and some systems in the U.S. based on 1.25 MHz. Speed is probably the feature most associated with LTE. Examples of downlink and uplink peak data rates for a 20 MHz channel bandwidth are shown in Table 1. Downlink figures are shown for single input single output (SISO) and multiple input multiple output (MIMO) antenna configurations at a fixed 64QAM modulation depth, whereas the uplink figures are for SISO but at different modulation depths. These figures represent the physical limitation of the LTE frequency division duplex (FDD) radio access mode in ideal radio conditions with allowance for signaling overheads. Lower rates are specified for specific UE categories and performance requirements under non-ideal radio conditions have also been developed. Table [1] for LTE s time division duplex (TDD) radio access mode are comparable, scaled by the variable uplink and downlink ratios. Table 1: Uplink and Downlink data rates. Unlike previous systems, LTE is designed from the beginning to use MIMO technology, which results in a more integrated approach to this advanced antenna technology than does the addition of MIMO to legacy system such as HSPA. Finally, in terms of mobility, LTE is aimed primarily at low mobility applications in the 0 to 15 km/h range, where the highest performance will be seen. The system is capable of working at higher speeds and will be supported with high performance from 15 to 120 km/h and functional support from 120 to 350 km/h. Support for speeds of 350 to 500 km/h is under consideration. A. Radio Interface Concepts Of LTE The ability to provide a high bit rate is a key measure for LTE. LTE is designed to meet the requirements of peak data rate up to 150 Mbps in down-link, 75 Mbps at up-link. The characteristics of LTE will be cellular coverage, Mobility, scalable bandwidth of 1.3, 3, 5, 10, 15, 20 MHz, FDD (Frequency Division Duplexing) and TDD (Time Division Duplexing). Thedown-link by OFDMA Available Online at : www.ijrier.com Page 36

(Orthogonal Frequency Division Multiplexing Access), up-link by SCFDMA (Single Carrier Frequency Division Multiplexing Access), MIMO (Multiple Input Multiple Output), and modulations by 16 QAM, 64 QAM technologies are used by LTE for meeting the data rate requirements mentioned above. B. Down-link OFDMA OFDMA is a multi-user version of a digital modulation scheme called Orthogonal Frequency-Division Multiplexing (OFDM). In OFDM the signal is first split into independent subcarriers and these closely-spaced orthogonal subcarriers are used to carry the data. The data is divided into several parallel data streams or channels, one for each subcarrier. Each sub-carrier is modulated with a conventional modulation scheme (such as quadrature amplitude modulation or phase shift keying) at a low symbol rate, maintaining total data rates similar to conventional single carrier modulation schemes of the same bandwidth[3]. A general analogy for OFDM can be of many small lamps in a hall rather than a single big lamp. The advantage is that light will be distributed across the hall equally as compared to a single lamp and increase redundancy a defect in one lamp will not affect the light in the hall. The primary advantage of OFDM over single-carrier scheme is its ability to cope with severe channel conditions without complex equalization filters. For example, attenuation of high frequencies in a long copper wire, narrowband interference and frequencyselective fading due to multipath. Figure 3: Multi Path Fading With the help of OFDM, channel equalization is simplified as OFDM may be viewed as using many slowly-modulated narrowband signals rather than one rapidly-modulated wideband signal. With the duration of each symbol being long, it is feasible to insert a guard interval between the OFDM, making it possible to handle time-spreading and eliminate inter-symbol interference (ISI). This mechanism also facilitates the design of single-frequency networks, where several adjacent transmitters send the same signal simultaneously at the same frequency. As the signals from multiple distant transmitters may be combined constructively, rather than interfering as would typically occur in a traditional single-carrier system. C. Uplink Single-Carrier FDMA with Dynamic Bandwidth To improve the RF transmission power efficiency in the UE, Single Carrier Frequency Division Multiple Access (SCFDMA) is used. SC-FDMA has similar performance and essentially the same overall structure as those of an OFDM. A system one prominent advantage of SC-FDMA over OFDMA is that the SC-FDMA signal has lower peak-to-average power ratio (PAPR). In the uplink communications low PAPR greatly benefits the User Equipment (UE) in terms of transmit power efficiency. Guard intervals with cyclic repetition are introduced between blocks of symbols as in OFDM explained earlier. In OFDM, FFT is applied on the receiver side on each block of symbols, and IFFT on the transmitter side. In SC-FDMA, both FFT and IFFT are applied on the transmitter side, and also on the receiver side. However SC-FDMA requires transmissions in consecutive bands, and thus introduces restrictions on the frequency domain packet scheduling for individual users compared to OFDMA. Available Online at : www.ijrier.com Page 37

D. Multi-Antenna Solutions Multiple Input Multiple Output (MIMO) is the major feature used to improve the performance of the LTE system, it allows in improving the spectral efficiency and data throughput[4]. MIMO consists of multiple antennas on the receiver and transmitter to utilize the multipath effects. This reduces the interference and leads to high throughputs. Multipath occurs when the different signals arrive at the receiver at various times intervals. MIMO divides a data stream into multiple unique streams, transmits data streams in the same radio channel at the same time. The receiving end uses an algorithm or employs special signal processing to generate one signal that was originally transmitted from the multiple signals. Figure 4: MIMO Block In LTE, the MIMO concepts vary from down-link to up-link to keep the terminal (UE) cost low. The base station either consists of two or four transmitting antennas and two receiving antennas on the terminal (UE) side for the down-link, and UE employs MU-MIMO (Multi User MIMO) for the up-link. With this scheme UE only have one transmit antenna which reduces the cost of the equipment. Interference due to transmission of data in the same channel by multiple mobile terminals is reduced by using mutually orthogonal pilot patterns. III. EVOLUTION OF LTE-ADVANCED LTE-A should be real broadband wireless network that provides peak data rates equal to or greater than those for wired networks, i.e., FTTH (Fiber To The Home), while providing better QoS. The major high-level requirements of LTEA are reduced network cost (cost per bit), better service provisioning and compatibility with 3GPP systems. LTE-A being an evolution from LTE is backward compatible. Some of the major technology proposals of LTE-A are : A. Asymmetric transmission bandwidth Access such as Frequency Division Duplex (FDD) and Time Division Duplex (TDD) are the two most prevalent duplexing schemes used in fixed broadband wireless networks. FDD uses two distinct radio channels and supports two-way radio communication and TDD uses a single frequency to transmit signals in both the downstream and upstream directions. Symmetric transmission results when the data in down-link and in the up-link are transmitted at the same data rate. This is one of the cases in voice transmission which transmits the same amount of data in both directions[5]. However, for internet connections or broadcast data (for example, streaming video), it is likely that more data will be sent from the server to the UE (the down-ink).based on the current and future traffic demands in cellular networks the required bandwidth in up-link will be narrower than that in down-link.so asymmetric transmission bandwidth will be a better solution for efficient utilization of the bandwidth. Figure 5: Support of Asymmetric Bandwidths for LTE Advanced Available Online at : www.ijrier.com Page 38

B. Layered OFDMA In layered structure, the entire system bandwidth comprises multiple basic frequency blocks. The bandwidth of basic frequency block is, 15 20 MHz. Layered OFDMA radio access scheme in LTE-A will have layered transmission bandwidth, support of layered environments and control signal formats. The support of layered environments helps in achieving high data rate (user throughput), QoS, or widest coverage according to respective radio environments such as macro, micro, indoor, and hotspot cells. The control signal formats are a straightforward extensions of L1/L2 control signal formats of LTE to LTE-A. Independent control channel structure is used for each component carrier. Control channel supports only shared belonging to the same component carrier. C. Advanced Multi-cell Transmission/Reception Techniques In a multi-user multi-cell environment employing multi-transmission/reception antenna devices for each cell have multiple first units and a second units in wireless communication. The first units consists of a predetermined antenna and the second unit consists of the following sub units: a. Estimation unit: Estimates channel information on signals from the individual first units and estimates information of noise and interference signals from adjacent cells. b. Calculation unit: Calculates the sum of transfer rates for each user group having at least one first unit using the information estimated by the estimation unit. c. Determination unit: Determines one user group by comparing the sum of the transfer rates of each user group calculated by the calculation unit. d. Feedback unit: Information on the user group determined by the determination unit is fed back to the first units of the corresponding cell. In LTE-A, the advanced multi-cell transmission/reception processes (also called as coordinated multipoint transmission/reception) helps in increasing frequency efficiency and cell edge user throughput. Faster handovers among different inter-cell sites are achieved by employing Inter- Cell Interference (ICI) management (that is, inter-cell interference coordination (ICIC) aiming at inter-cell orthogonalization). D. Enhanced Multi-antenna Transmission Techniques Mobile traffic in wireless communications has been increasing multi folds over the years, which amplifier the requirement of higher-order MIMO channel transmissions and higher peak frequency efficiency than LTE. In LTE-A, the MIMO scheme has to be further improved in the area of spectrum efficiency, average cell throughput and cell edge performances. With multipoint transmission/reception, where antennas of multiple cell sites are utilized in such a way that the transmitting/receiving antennas of the serving cell and the neighboring cells can improve quality of the received signal at the UE/eNodeB and reduces the co-channel interferences from neighboring cells. Peak spectrum efficiency is directly proportional to the number of antennas used[6]. In LTE-A the antenna configurations of 8x8 in DL and 4x4 in UL are planned. Figure 6: MIMO Tx & Rx Schemes LTE-A (8 X 4 MIMO) Available Online at : www.ijrier.com Page 39

E. Enhanced Techniques to Extend Coverage Area Remote Radio Requirements (RREs) using optical fiber should be used in LTE-A as effective technique to extend cell coverage. Layer 1 relays with non-regenerative transmission, that is, repeaters can also be used for improving coverage in existing cell areas[7]. Layer 2 and Layer 3 relays can achieve wide coverage extension through an increase in Signal to Noise Ratio (SNR) Figure 7: RRE using optical fibers F. Support of Larger Bandwidth in LTE-Advanced Peak data rates up to 1Gbps are expected from bandwidths of 100MHz. OFDM adds additional sub-carrier to increase bandwidth. The available bandwidth may not be continuous as a result of fragmented spectrum[8]. To ensure backward compatibility to the current LTE, the control channels such as synchronization, broadcast, or PDCCH/PUCCH might be needed for every 20 MHz. Figure 8: Support of larger Bandwidths PDCCH stands for Physical Downlink Shared Channel whereas PUCCH stands for Physical Uplink Shared Channel used in synchronization broadcasting. The above described technology proposals of LTE-A[8] will help us to: Lower the total cost of network ownership. Easily deploy the network. Increase user throughput for fully multi-media feature services. Achieve spectrum flexibility support scalable bandwidth and spectrum aggregation. Achieve backward compatibility and inter-working with LTE with 3GPP legacy systems. Enable extended multi-antenna deployments and denser infrastructure in a cost-efficient way. IV. ADVANTAGES Some advantages that are applicable to the 4th Generation mobile communications are also applicable to LTE-A.With average download speeds of 400 Kbps to 700 Kbps, the network offers enough bandwidth to enable cell phone users to surf and download data from the Internet. LTE-A should significantly lower the bit-cost for the end-users and the total cost of ownership for the operators. At the same time, LTE-A should meet new emerging challenges such as energy-efficient Radio Access Network (RAN) design, increase the flexibilities of network deployments, and off load networks from localized user communications. Regardless of the actual technology, the forthcoming technology will also be able to allow the complete interoperability among heterogeneous networks and associated technologies, thus providing clear advantages in terms of: Coverage: The user gets best QoS and widespread network coverage as there is network availability at any given time. Available Online at : www.ijrier.com Page 40

Bandwidth: Sharing the resources among the various networks will reduce the problems of spectrum limitations of the third generation. V. KEY FEATURES Friendliness and Personalization: User friendliness exemplifies and minimizes the interaction between applications and the user. Thanks to a well designed transparency that allows the person and the machine to interact naturally (for example, the integration of new speech interface is a great step to achieve this goal). Heterogeneous Services: Services that are heterogeneous in nature (for example, different types of services such as audio, video etc.) such as quality and accessibility may not be the same due to the heterogeneity of the network. For instance, a user in proximity of the shopping mall but out of the coverage of a WLAN can still receive pop-up advertisements using the multi-hop ad hoc network setup in his surrounding. VI. COMPARISION BETWEEN LTE AND LTE-ADVANCED Comparison of performance requirements of LTE with Advanced and IMT-Advanced (4G) Table [2] are: some of the current agreements of LTE Table 2: Difference between LTE and LTE-A Available Online at : www.ijrier.com Page 41

VII. LTE-ADVANCED FREQUENCY BANDS Operating bands of LTE and LTE-A are identified by ITU-R. E-UTRA (LTE) are shown in Table[ 3]. g bands for Table 3: Operating bands for LTE / LTE-Advanced VIII. CONCLUSION LTE system has brought the wings for newer technologies in the world of communication standards. Whereas LTE-A helps in integrating the existing networks with new networks, services and terminals to suit the escalating user demands. The technical features of LTE-A may be summarized with the word integration. LTE-Advanced will be standardized in the 3GPP specification Release 10 (Release 10 LTE-A) and will be designed to meet the 4G requirements as defined by ITU. LTE-A as a system needs to take many features into considerations due to optimization at each level which involves lots of complexity and challenging implementation. Numerous changes on the physical layer can be expected to support larger bandwidths with more flexible allocations and to make use of further enhanced antenna technologies. Coordinated base stations, scheduling, MIMO, interference management and suppression will also require changes on the network architecture. REFERENCES [1] Rohde & Schwarz: Application Note 1MA111.UMTS Long Term Evolution (LTE)Technology Introduction. [2] Rohde & Schwarz: Application Note 1MA166.LTE-Advanced Signals Generation and. Analysis. [3] 3GPP TR 36.912 V 10.0.0, March 2011; Technical Specification Group Radio Access Network; Feasibility study for further advancements for E-UTRA (LTE Advanced), Release 10 [4] 3GPP TR 36.913 V 10.0.0, March 2011; Technical Specification Group Radio Access Network; Requirements for further advancements for Evolved Universal Terrestrial Radio Access (E-UTRA) LTE-Advanced, Release 10 [5] 3GPP TS 36.101 V10.6.0, March 2012; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE) radio transmission and reception, Release 10 [6] 3GPP, TR 36.201, Evolved Universal Terrestrial Radio Access (E-UTRA); Long Term Evolution (LTE) physical layer; General description [7] H. Ekström et al., Technical Solutions for the 3G Long-term Evolution, IEEE Communications Magazine. Available Online at : www.ijrier.com Page 42

[8] 3GPP TSG RAN Tdoc RP-070466 [9] 3GPP TR 36.913 V9.0.0 (2009-12), Requirements for Further Advancements of E-UTRA (LTE-Advanced). [10] ITU-R M.[IMT-TECH] Requirements related to technical performance for IMT-Advanced radio interface(s), [11] Madhusudhan G., S.V.Mahapurush, Dr.Priyatam Kumar, CELLULAR NETWORK TO THE LTE SYSTEM, International Conference on Electrical Electronics and Data Communication (ICEEDC) in Association with institute of research and journals, 5th July 2014. Vol.08, pp: 85-89. ISBN: 978-93-84209-33-9. Bangalore, India. Available Online at : www.ijrier.com Page 43