[雙語(yǔ)翻譯]--外文翻譯--無(wú)線通信中l(wèi)te版本8與版本10的性能（原文）

1、Performance of LTE Release 8 and Release 10 in Wireless Communications M.F.L. Abdullah Faculty of Electrical and Electronic Engineering University Tun Hussein Onn Malaysia Johor, Malaysia faiz@uthm.e

2、du.my A.Z. Yonis Department of Communication Engineering College of Electronics Engineering, University of Mosul Mosul, Iraq aws_zuher@yahoo.com Abstract—LTE-Advanced (Release 10) is a preliminary mobile comm

3、unication standard formally submitted as a candidate 4G systems to the ITU-T. It is being standardized by the 3rd Generation Partnership Project (3GPP) as a major enhancement of the 3GPP Long Term Evolution (LTE-Relea

4、se 8) standard, which proved to be sufficient to satisfy market’s demand. The 3GPP group has been working on different aspects to improve LTE performance, where the purpose of the framework provided by LTE-Advanced,

5、includes higher order MIMO, carrier aggregation (carriers with multiple components), and heterogeneous networks (relays, picos). This paper presents a study on evolution LTE toward LTE-Advanced in terms of LTE e

6、nabling technologies (Orthogonal Frequency Division Multiplexing (OFDM) and Multiple-Input Multiple-Output (MIMO)). This paper also focuses on LTE-Advanced technologies MIMO enhancements for LTE-Advanced

7、, Coordinated Multi Point transmission (CoMP), repeaters and relays. Keywords-LTE; LTE-Advanced; MIMO; OFDMA; CoMP. I. INTRODUCTION Mobile communications has become an everyday commodity. In the last decades, it

8、 has evolved from being an expensive technology for a few selected individuals to today’s ubiquitous systems used by a majority of the world’s population. From the first experiments with radio communicati

9、on the road to truly mobile radio communication has been quite long. To understand the complex mobile- communication systems of today, it is important to understand where they came from and

10、how cellular systems have evolved. The task of developing mobile technologies has also changed, from being a national or regional concern, to becoming an increasingly complex task undertaken b

11、y global standards- developing organizations such as the Third Generation Partnership Project (3GPP) and involving thousands of people. Mobile communication technologies are often divided into generatio

12、ns, with 1G being the analog mobile radio systems of the 1980s, 2G the first digital mobile systems, and 3G the first mobile systems handling broadband data. The LTE is often called “4G”,

13、 but many also claim that LTE release 10, also referred to as LTE- Advanced, is the true 4G evolution step, with the first release of LTE (release 8). This continuing race of increasing seq

14、uence numbers of mobile system generations is in fact just a matter of labels. In this context, it must first be pointed out that LTE and LTE- Advanced is the same technology, with the “Advanced”

15、 label primarily being added to highlight the relation between LTE release 10 (LTE- Advanced) and ITU/IMT- Advanced. This does not make LTE- Advanced a different system than LTE and it is not in an

16、y way the final evolution step to be taken for LTE [1]. Section 2 of this paper discusses the current development processes from the first LTE release to LTE- Advanced and the limited resear

17、ch directions related to the development of communication systems, while section 3 describes the 3GPP LTE which is called release 8. The main specifications of LTE enabling technologies are describ

18、ed in section 4 with the important properties of OFDM and MIMO. In section 5, the major developments on LTE technology which called “LTE- Advanced” (Release 10) are reviewed appended by the charac

19、teristics of peak data rate, mobility and OFDMA. In section 6 the LTE- Advanced technologies are considered which include MIMO enhancements for LTE- Advanced with both types’ of uplink and downlink

20、 MIMO transmission, the coordinated multi- point transmission (CoMP) is also reviewed for relaying and repeater. Section 7 contains the summary and discussion of the main points for this paper

21、 which can be consider for reader to understand the current development for performance of release 8 and release 10 in wireless communications. Finally, section 8 concludes some general observations

22、and recommendations for this paper. II. FROM THE FIRST LTE RELEASE TO LTE- ADVANCED As a result of intense activity by a larger number of contributing companies than ever before in 3GPP, the specif

23、ications for the first LTE release (Release 8) had reached a sufficient level of completeness by December 2007 to enable LTE to be submitted to ITU- R as a member of the IMT family of ra

24、dio access technologies. It is therefore able to be deployed in IMT designated spectrum and the first commercial deployments were launched towards the end of 2009 in northern Europe. Meanwhile, 3GPP has

25、continued to improve the LTE system and to develop it to address new markets. Increasing LTE’s suitability for different markets and 978-1-4673-1677-4 236to the scheduler. Finally, it offers spectrum

26、 flexibility which facilitates a smooth evolution from already existing radio access technologies to LTE. In the FDD mode of LTE each OFDM symbol is transmitted over subcarriers of 15 or 7.5

27、 kHz. One subframe lasts 1ms, divided in two 0.5ms slots, and contains several consecutive OFDM symbols (14 and 12 for the 15 and 7.5 kHz modes, resp.). In the uplink, SC- FDMA is used r

28、ather than OFDM. SC- FDMA is also known as DFT- spread OFDM modulation. Basically, SC- FDMA is identical to OFDM unless an initial FFT is applied before the OFDM modulation. The objective of

29、 such modification is to reduce the peak to average power ratio, thus decreasing the power consumption in the user terminals [4]. B. Multiple-Input Multiple-Output (MIMO) The transmission diversity allows

30、 us to improve the link performance when the channel quality cannot be tracked at the transmitter which is the case for high mobility UEs. The transmission diversity is also useful for dela

31、y- sensitive services that cannot afford the delays introduced by channel- sensitive scheduling. The transmission diversity, however, does not help in improving the peak data rates as a single

32、data stream is always transmitted. The multiple transmission antennas at the eNB in combination with multiple receiver antennas at the UE can be used to achieve higher peak data rates by en

33、abling multiple data stream transmissions between the eNB and the UE by using MIMO (multiple input multiple output) spatial multiplexing. Therefore, in addition to larger bandwidths and high- o

34、rder modulations, MIMO spatial multiplexing is used in the LTE system to achieve the peak data rate targets. The MIMO spatial multiplexing also provides improvement in cell capacity and throu

35、ghput as UEs with good channel conditions can benefit from multiple streams transmissions. Similarly, the weak UEs in the system benefit from beam- forming gains provided by precoding signals tran

36、smitted from multiple transmission antennas [5]. MIMO is one of the most important means to achieve the high data rate objectives for LTE is multiple antenna transmission. In LTE downlink it

37、is supported one, two or four transmit antennas in the eNB and one, two or four receive antennas in the UE. Multiple antennas can be used in different ways: to obtain additional transmit/r

38、eceive diversity or to get spatial multiplexing increasing the data rate by creating several parallel channels if conditions allow to. Nevertheless, in LTE uplink although one, two or four receive

39、antennas are allowed in the eNB, only one transmitting antenna is allowed in the UE. Therefore, multiple antennas can be only used to obtain receive diversity. V. LONG TERM EVOLUTION- ADVANCED

40、 (RELEASE10) LTE- Advanced should be a real broadband wireless network that provides peak data rates equal to or greater than those for wired networks, i.e., fiber to the home (FTTH), while provid

41、ing better QoS. The major high- level requirements of LTE are reduced network cost (cost per bit), better service provisioning, and compatibility with 3GPP systems. LTE- Advanced being an evolutio

42、n from LTE is backward compatible. In addition to the advanced features used by LTE Release 8, LTE- Advanced enhanced these features that can be found in the following: The peak data rate: LTE- Adv

43、anced should support significantly increased instantaneous peak data rates. At a minimum, LTE- Advanced should support enhanced peak data rates to support advanced services and applications (100 M

44、bps for high and 1 Gbps for low mobility were established as targets for research) (Table 1). TABLE I. LTE AND LTE- ADVANCED CAPACITY COMPARISON Parameter LTE LTE-Advanced Scalable bandwidths 1.4-

45、20 MHz 20- 100 MHz Peak data rate downlink DL 300 Mbps 1 Gbps UL 75 Mbps 500 Mbps Transmission bandwidth DL 20 MHz 100 MHz UL 20 MHz 40 MHz Peak Spectrum Efficiency [bps/Hz] DL 15 30 UL 3.75

46、 15 Mobility: The system shall support mobility across the cellular network for various mobile speeds up to 350 km/h (or perhaps even up to 500 km/h depending on the frequency band). System

47、 performance shall be enhanced for 0–10 km/h and preferably enhanced but at least no worse than E- UTRA and E- UTRAN for higher speeds [6]. Orthogonal Frequency Division Multiple Access (OFDMA): I

48、n OFDM, all subcarriers are assigned to a single user. Hence, for multiple users to communicate with the BS, the set of subcarriers are assigned to each in a Time Division Multiple Access

49、(TDMA) fashion. Alternatively, an OFDM- based multiple access mechanism, namely the OFDMA, assigns sets of subcarriers to different users. In particular, the total available bandwidth is divided into M

50、 sets, each consisting of L subcarriers. Hence, a total of M users can simultaneously communicate with the BS. Subcarrier assignment can be either distributed or localized, as is shown in Figure

51、 2 [7]. While in localized assignment, chunks of contiguous subcarriers are allocated to each user, distributed assignment allocates equidistant subcarriers to different users. Despite the relatively

52、 straightforwardness of OFDMA, it has very attractive advantages. Probably the most important of these is its inherent exploitation of frequency and multiuser diversities. Frequency diversity is

53、 exploited through randomly distributing the subcarriers of a single user over the entire band, reducing the probability that all the subcarriers of a single user experience deep fades. Such

54、allocation is particularly the case when distributed subcarrier assignment is employed. On the other hand, multiuser diversity is exploited through assigning contiguous sets of subcarriers to us

55、ers experiencing good channel conditions [8]. Another important advantage of OFDMA is its inherent adaptive bandwidth assignment. Since the transmission bandwidth consists of a large number of orthog