計(jì)算機(jī)第五代5g移動(dòng)通訊通信技術(shù)介紹簡(jiǎn)介概述外文文獻(xiàn)翻譯成品：5G的五個(gè)顛覆性技術(shù)方向中英文雙語(yǔ)對(duì)照

1、Five Disruptive Technology Directions for 5GABSTRACT: New research directions will lead to fundamental changes in the design of future 5th generation (5G) cellular networks. This paper describes five technologies that could lead to both architectural and component disruptive design changes: device-c

2、entric architectures, millimeter Wave, Massive -MIMO, smarter devices, and native support to machine-2-machine. The key ideas for each technology are described, along with their potential impact on 5G and the research challenges that remain.I.INTRODUCTION:5G is coming. What technologies will define

3、it? W川 5G be just an evolution of 4G, or will emerging technologies cause a disruption requiring a wholesale rethinking of entrenched cellular principles? This paper focuses on potential disruptive technologies and their implications for 5G. We classify the impact of new technologies, leveraging the

4、 Henderson-Clark model 1, as follows:.Minor changes at both the node and the architectural level, e.g., the introduction of codebooks and signaling support for a higher number of antennas. We refer to these as evolutions in the design.Disruptive changes in the design of a class of network nodes, e.g

5、., the introduction of a new waveform. We refer to these as component changes.Disruptive changes in the system architecture, e.g., the introduction of new types of nodes or new functions in existing ones. We refer to these as architectural changes. 4.Disruptive changes that have an impact at both th

6、e node and the architecture levels. We refer to these as radical changes.We focus on disruptive (component, architectural or radical) technologies, driven by our belief that the extremely higher aggregate data rates and the much lower latencies required by 5G cannot be achieved with a mere evolution

7、 of the status quo. We believe that the following five potentially disruptive technologies could lead to both architectural and component design changes, as classified in Figure 1.Device-centric architectures.The basestation-centric architecture of cellular systems may change in 5G. It may be time t

8、o reconsider the concepts of uplink and downlink, as well as control and data channels, to better route information flows with different priorities and purposes towards different sets of nodes within the network. We present device-centric architectures in Section II.Millimeter Wave (mmWave).While sp

9、ectrum has become scarce at microwave frequencies, it is plentiful in the mmWave realm. Such a spectrum eDorado has led to a mmWave goldush in which researchers with diverse backgrounds are studying different aspects ofmmWave transmission. Although far from fully understood, mmWave technologies have

10、 already been standardized for short-range services (IEEE 802.11ad) and deployed for niche applications such as sma-llcell backhaul. In Section III, we discuss the potential of mmWave for a broader application in 5G.Massive-MIMO.Massive-MIMO1 proposes utilizing a very high number of antennas to mult

11、iplex messages for several devices on each time-frequency resource, focusing the radiated energy towards the intended directions while minimizing intra- and inter-cell interference. Massive-MIMO may require major architectural changes, in particular in the design of macro base stations, and it may a

12、lso lead to new types of deployments. We discuss massiv-MIMO in Section IV .Smarter devices.2G-3G-4G cellular networks were built under the design premise of having complete control at the infrastructure side. We argue that 5G systems should drop this design assumption and exploit intelligence at th

13、e device side within different layers of the protocol stack, e.g., by allowing Device-to-Device (D2D) connectivity or by exploiting smart caching at the mobile side. While this design philosophy mainly requires a change at the node level (component change), it has also implications at the architectu

14、ral level. We argue for smarter devices in Section.V5.Native support for Machine-to-Machine (M2M) communicationA native2 inclusion of M2M communication in 5G involves satisfying three fundamentally different requirements associated to different classes of low-data-rate services: support of a massive

15、 number of low-rate devices, sustainment of a minimal data rate in virtually all circumstances, and very-low -latency data transfer. Addressing these requirements in 5G requires new methods and ideas at both the component and architectural level, and such is the focus of Section VI.COMPONENT (node)

16、disrupt.mm WaveNode-centncnetworksNative support ofM2M servicesFigure 1. flic llvedisruptivt: directions for 5G considered in this paper, chssiJied according to the Hetiderion-t lark modelII.DEVICE -CENTRIC ARCHITECTURESCellular designs have historically relied on the axiomatic role of cells as fund

17、amental units within the radio access network. Under such a design postulate, a device obtains service by establishing a downlink and an uplink connection, carrying both control and data traffic, with the base station commanding the cell where the device is located. Over the last few years, differen

18、t trends have been pointing to a disruption of this cell-centric structure:The basestation density is increasing rapidly, driven by the rise of heterogeneous networks. While heterogeneous networks were already standardized in 4G, the architecture was not natively designed to support them. Network de

19、nsification could require some major changes in 5G. The deployment of base stations with vastly different transmit powers and coverage areas, for instance, calls for a decoupling of downlink and uplink in a way that allows for the corresponding information to flow through different sets of nodes 5.T

20、he need for additional spectrum will inevitably lead to the coexistence of frequency bands with radically different propagation characteristics within the same system. In this context, 6 proposes the concept of a phantom cell where theand control planes are separated: the control information is sent

21、 by highpower nodes at microwave frequencies whereas the payload data is conveyed by lowpower nodes at mm-Wave frequencies. (cf. Section III.)A new concept termed centralized basebandrelated to the concept of cloud radio access networks is emerging (cf. 7), where virtualization leads to a decoupling

22、 between a node and the hardware allocated to handle the processing associated with this node. Hardware resources in a pool, for instance, could be dynamically allocated to different nodes depending on metrics defined by the network operator.Emerging service classes, described in Section VI, could r

23、equire a complete redefinition of the architecture. Current works are looking at architectural designs ranging from centralization or partial centralization (e.g., via aggregators) to full distribution (e.g., via compressed sensing and/or multihop).Cooperative communications paradigms such as CoMP o

24、r relaying, which despite falling short of their initial hype are nonetheless beneficial 8, could require a redefinition of the functions of the different nodes. In the context of relaying, for instance, recent developments in wireless network coding 9 suggest transmission principles that would allo

25、w recovering some of the losses associated with halfduplex relays. Moreover, recent research points to the plausibility of full - duplex nodes for short-range communication in a not-so-distant future.The use of smarter devices (cf. Section V) could impact the radio access network. In particular, bot

26、h D2D and smart caching call for an architectural redefinition where the center of gravity moves from the network core to the periphery (devices, local wireless proxies, relays). Based on these trends, our vision is that the cell-centric architecture should evolve into a device-centric one: a given

27、device (human or machine) should be able to communicate by exchanging multiple information flows through several possible sets of heterogeneousnodes. In other words, the set of network nodes providing connectivity to a given device and the functions of these nodes in a particular communication sessi

28、on should be tailored to that specific device and session. Under this vision, the concepts of uplink/downlink and control/data channel should be rethought (cf. Figure 2).While the need for a disruptive change in architectural design appears clear, major research efforts are still needed to transform

29、 the resulting vision into a coherent and realistic proposition. Since the history of innovations (cf. 1) indicates that architectural changes are often the drivers of major technological discontinuities, we believe that the trends above might have a major influence on the development of 5G.senrsocs

30、tow BSFigure 2, Example of dcx lee-centric archiiecture.III.MILLIMETER WA VE COMMUNICATIONMicrowave cellular systems have precious little spectrum: around 600 MHz are currently in use, divided among operators 10. There are two ways to gain access to more microwave spectrum:. To repurpose or refarm s

31、pectrum. This has occurred worldwide with the repurposing of terrestrial TV spectrum for applications such as rural broadband access. Unfortunately, repurposing has not freed up that much spectrum, only about 80 MHz, and at a high cost associated with moving the incumbents.To share spectrum utilizin

32、g, for instance, cognitive radio techniques. The high hopes initially placed on cognitive radio have been dampened by the fact that an incumbent not fully willing to cooperate is a major obstacle to spectrum efficiency for secondary users.Altogether, it appears that a doubling of the current cellula

33、r bandwidth is the best-case scenario at microwave frequencies. Alternatively, there is an enormous amount of spectrum at mmWave frequencies ranging from 3 to 300 GHz. Many bands therein seem promising, including most immediately the local multipoint distribution service at 28-30 GHz, the license-fr

34、ee band at 60 GHz, and the Eband at 71-76 GHz, 81-86 GHz and 92-95 GHz. Foreseeably, several tens of GHz could become available for 5G, offering well over an order-of-magnitude increase over what is available atpresent. Needless to say, work needs to be done on spectrum policy to render these bands

35、available for mobile cellular.3. Propagation is not an insurmountable challenge. Recent measurementsindicate similar general characteristics as at microwave frequencies, including distance-dependent pathloss and the possibility of nonine-of-sight communication. A main difference between microwave an

36、d mmWave frequencies is the sensitivity to blockages: the results in 11, for instance, indicate a pathloss exponent of 2 for line-of-sight propagation but 4 (plus an additional power loss) for non -line-of-sight. MmWave cellular research will need to incorporate sensitivity to blockages and more com

37、plex channel models into the analysis, and also study the effects of enablers such as higher density infrastructure and relays. Another enabler is the separation between control and data planes, already mentioned in Section II.Antenna arrays are a key feature in mmWave systems.Large arrays can be us

38、ed to keep the antenna aperture constant, eliminating the frequency dependence of pathloss relative to omnidirectional antennas (when utilized at one side of the link) and providing a net array gain to counter the larger thermal noise bandwidth (when utilized at both sides of the link). Adaptive arr

39、ays with narrow beams also reduce the impact of interference, meaning that mmWave systems could more often operate in noise-limited rather than interference-limited conditions. Since meaningful communication might only happen under sufficient array gain, new random access protocols are needed that w

40、ork when transmitters can only emit in certain directions and receivers can only receive from certain directions. Adaptive array processing algorithms are required that can adapt quickly when beams are blocked by people or when some device antennas become obscured by the user s own body.MmWave syste

41、ms also have distinct hardware constraints. A major one comes from the high power consumption of mixed signal components, chiefly the analog-to-digital (ADC) and digital-to-analog converters (DAC). Thus, the conventional microwave architecture where every antenna is connected to a hig-hrate ADC/DAC

42、is unlikely to be applicable to mmWave without a huge leap forward in semiconductor technology. One alternative is a hybrid architecture where beamforming is performed in analog at RF and multiple sets of beamformers are connected to a small number of ADCs or DACS; in this alternative, signal proces

43、sing algorithms are needed to steer the analog beamforming weights. Another alternative is to connect each RF chain to a 1-bit ADC/DAC, with very low power requirements; in this case, the beamforming would be performed digitally but on very noisy data. There are abundant research challenges in optim

44、izing different transceiver strategies, analyzing their capacity, incorporating multiuser capabilities, and leveraging channel features such as sparsity.A data rate comparison between technologies is provided in Fig. 3, for certain simulation settings, in terms of mean and 5% outage rates. MmWave op

45、eration is seen to provide very high rates compared to two different microwave systems. The gains exceed the 10 x spectrum increase because of the enhanced signal power and reduced interference thanks to directional beamforming at both transmitter and receiver.卜電 111r心 t ell daia rae cnnipuj is.uii.

46、 hchAcm microwsiveLniing 50 MH/ bandiJih iKingk-Lis盯sLnk-iinktiliL JilalM1MU h ml u Eh 譚 甲十 不式叫 Lth SOU diiirid 國(guó) bangleuser. Result are given m 依run* of gjm (%! w.r.(, che MIMO 4i4 baseline |cf loolncne L More details afauLt llie compuisin Mupiiw |Wm ided in (12.MASSIVE MIMOMassive MIMO (also refer

47、red to as Larg-Scale MIMO or Larg-Scale Antenna Systems ) is a form of multiuser MIMO in which the number of antennas at the base station is much larger than the number of devices per signaling resource 14. Having many more base station antennasthan devices renders the channels to the different devi

48、ces quas-orthogonal and very simple spatial multiplexing/de-multiplexing procedures quas-optimal. The favorable action of the law of large numbers smoothens out frequency dependencies in the channel and, altogether, huge gains in spectral efficiency can be attained (cf. Fig. 4).In the context of the

49、 Henderson-Clark framework, we argue that massive-MIMO has a disruptive potential for 5G:At a node level, it is a scalable technology. This is in contrast with 4G, which, in many respects, is not scalable: further sectorization therein is not feasible because of (i) the limited space for bulky azimu

50、thally -directive antennas, and (ii) the inevitable angle spread of the propagation; in turn, single-user MIMO is constrained by the limited number of antennas that can fit in certain mobile devices. In contrast, there is almost no limit on the number of base station antennas in massive- MIMO provid

51、ed that time-division duplexing is employed to enable channel estimation through uplink pilots.It enables new deployments and architectures. While one can envision direct replacement of macro base stations with arrays of low-gain resonant antennas, other deployments are possible, e.g., conformal arr

52、ays on the facades of skyscrapers or arrays on the faces of water tanks in rural locations. Moreover, the same massiveMIMO principles that govern the use of collocated arrays of antennas apply also to distributed deployments in which a college campus or an entire city could be covered with a multitu

53、de of distributed antennas that collectively serve many users (in this framework, the centralized baseband concept presented in Section II is an important architectural enabler).While very promising, massive-MIMO still presents a number of research challenges. Channel estimation is critical and curr

54、ently it represents the main source of limitations. User motion imposes a finite coherence interval during which channel knowledge must be acquired and utilized, and consequently there is a finite number of orthogonal pilot sequences that can be assigned to the devices. Reuse of pilot sequences caus

55、es pilot contamination and coherent interference, which grows with the number of antennasas fast as the desired signals. The mitigation of pilot contamination is an active research topic. Also, there is still much to be learned about massive-MIMO propagation, although experiments thus far support th

56、e hypothesis of channel quas-orthogonality. From an implementation perspective, massive-MIMO can potentially be realized with modular low -cost low-power hardware with each antenna functioning semi-autonomously, but a considerable development effort is still required to demonstrate the cost-effectiv

57、eness of this solution. Note that, at the microwave frequencies considered in this section, the cost and the energy consumption of ADCs/DACs are sensibly lower than at mmWave frequencies (cf. Section III).From the discussion above, we conclude that the adoption of massiveMIMO for 5G could represent

58、a major leap with respect to today ssate-of-the-art in system and component design. To justify these major changes, massivMIMO proponents should further work on solving the challenges emphasized above and on showing realistic performance improvements by means of theoretical studies, simulation campa

59、igns, and testbed experiments.percentteperoentile-204 8 antennas.事percentteperoentile-204 8 antennas.事antennas8192 antennasFigure 4. Cell dati rateisn for a fixed access plicaiioii of niaiSjve-MIMO. An a門3、0fm乩4叩6 utumuiiLi ulilizm 50 und u lolul ol 120 Wuib. 1000 um nindumlylocated m a cdl of radiu

60、m hkm Result* given ui lenm cf fiarn i1i) w r t ihc Ml叩 33 03n14 ：V.SMARTER DEVICESEarlier generations of cellular systems were built on the design premise of having complete control at the infrastructure side. In this section, we discuss some of the possibilities that can be unleashed by allowing t