Wireless Future. OUTLINE My thought on Wireless Future Before March 11 After March 11

Transcription

1 VTC-Spring Panel:Wireless Future, 8:30~10:00am, 17 May, 2011, Budapest, Hungary Wireless Future Tohoku U. Aobayama-campus Fumiyuki Adachi Wireless Signal Processing & Networking (WSP&N) Lab. Dept. of Electrical and Communications Engineering, Tohoku University, Japan OUTLINE My thought on Wireless Future Before March 11 After March /5/17 FA/Tohoku University 1

2 Wireless Future There was a big technical leap from 2G to 3G systems. Voice+data Voice+Data 1G Analog (FDMA) ~2.4kbps 2G Digital (TDMA) ~64kbps Big leap 3G/3.5G Digital (CDMA) ~2Mbps ~14Mbps 4G/5G Digital Improved frequency utilization Narrowband Increased no. of channels Broadband Increased peak rate Increased throughput 2011/5/17 FA/Tohoku University 2

3 Wireless Future Service Cloud Computing Network A variety of data services through Internet Wireless Access Network Big wireless pipe (>1Gbps) User terminals 2011/5/17 FA/Tohoku University 3

4 Technical Goal Of Wireless The available bandwidth and power are limited The ultimate goal of wireless technology is to provide extremely high rate data services uniformly over an area with as much low energy and narrow bandwidth as possible Ultimate goal 1G Analog (FDMA) ~2.4kbps 2G Digital (TDMA) ~64kbps Big leap 3G/3.5G Digital (CDMA) ~2Mbps ~14Mbps 4G/5G Digital Extremely high data rate with as much low energy narrow bandwidth as possible 2011/5/17 FA/Tohoku University 4

5 LTE-Advanced 1Gbps/BS is not enough in densely populated area Total bit rate per one BS There may be many users simultaneously accessing the same BS The average data rate per user is much less than 1Gbps Example Active user density: one user/(50x50)m 2 1km cell 1,256 users/bs 0.8Mbps/user Ultimate goal >1 Gbps/BS wireless access (>10Mbps/user) As low energy and narrow bandwidth as possible Uniform quality over a service area 2011/5/17 FA/Tohoku University 5

6 Frequency Reuse Frequency reuse is indispensible to efficient utilization of limited spectrum It seems that the cluster size of 4 may maximize the spectrum efficiency (bps/hz/bs) irrespective of the path loss exponent Effective bandwidth/bs is 25% of total. 2011/5/17 FA/Tohoku University 6

7 Reduced Communication Range Is A Problem For broadband communications, communication range shrinks significantly because of the transmit power limitation. Fundamental change is necessary in wireless access network. Core Network Radio control station Core Network Base station Base station 2011/5/17 FA/Tohoku University 7

8 Uniform Quality Uniform quality over an BS area Uniform quality over an BS area Throughput Present Cellular Distance from BS 2011/5/17 FA/Tohoku University 8

9 Coordinated Multi-point Transmission (CoMP) To improve the communication quality for a user near the cell edge, the coordinated multi-point transmission (CoMP) was introduced. Improved SINR (increased capacity) with limited transmit power This is the first step towards the realization of distributed antenna network (DAN). Core Network Base station 2011/5/17 FA/Tohoku University 9

10 Possible Solution Short-range communication is a promising way to improve the spectrum efficiency while reducing the transmit power. Reducing the communication distance by half is equivalent to 10dB decrease in the transmit power for an increase of 3.5bps/Hz C (bps/hz) Normalized distance r/r /5/17 FA/Tohoku University 10

11 High bit rate services with lowest transmit power/uniform quality over a service area Distributed antenna network (DAN) Huge transmit power Low spectrum efficiency Non-uniform quality High bit rate with limited bandwidth Very low transmit power High spectrum efficiency Uniform quality distributed MIMO multiplexing/diversity/relay/beamforming 2011/5/17 FA/Tohoku University 11

12 Distributed Antenna Network (DAN) Many antennas are spatially distributed around a center, which is a gateway to the network With a high probability, some antennas close to an MT can always be visible Antennas are connected with a SPC by a means of optical fiber or wireless links Many antennas co-operate and act as distributed MIMO multiplexing, diversity, or relay The problems can be mitigated which result from distance-dependent path loss and shadowing loss as well as the instantaneous signal power variations due to the multi-path fading *Distributed MIMO relay *Distributed wireless network coding DAN Processing Center Distributed MIMO multiplexing/ diversity Optical fiber cable Distributed wireless port Distributed network antenna 2011/5/17 FA/Tohoku University 12

13 Personal Cell Formulation Center of personal cell is a user Personal cell moves according to user movement BS is the center of cell Each user is the center of cell Huge transmit power Very low transmit power Low spectrum efficiency High spectrum efficiency No-nuniform quality Uniform quality 2011/5/17 FA/Tohoku University 13

14 Advanced equalization The channel transfer function H(f, t) varies both in frequency and time according to user movement, resulting in a doubly selective fading channel. Severe frequency-selective channel Advanced equalization for distributed MIMO L=16-path exponential profile, delay factor of 1.0 db, time delay separation of 150ns, carrier frequency of 5 GHz, moving speed of 4km/h 2011/5/17 FA/Tohoku University 14

15 Concluding Remarks Before March 11 Future wireless networks will require Giga-bit wireless technology of >1Gbps (>80bps/Hz/BS) with least transmit power under severe MAI and co-channel interference. Energy and spectrum efficient network Distributed antenna network (DAN) with multiplexing, diversity or relay can solve the transmit power problem while increasing the spectrum efficiency CCI management antenna selection Self organizing function Frequency-domain signal processing MIMO frequency-domain equalization may be indispensible techniques. Other promising solutions? 2011/5/17 FA/Tohoku University 15

16 March 11 s Earthquake of M9.0 Earthquake and Tsunami of March 11 Hit Very Wide Area Tsunami: size of once in 1,000years 2011/5/17 FA/Tohoku University 16

17 What Happened? Power cut down Strict call control: call success probability of about 10% Running out of terminal battery Power cut down Fixed & mobile users Overload Huge no. of call requests (50~60times) Core network BS Call restriction to protect the network (10%) Huge no. of call requests (50~60times) Mobile users 2011/5/17 FA/Tohoku University 17

18 What Changes in System Design Are Necessary? Facing disaster, the most important requirement is to provide Realtime voice communication channel: quality is not a serious problem With as many users as possible Total amount of bit volume may be smaller than the broadband service Broadband network 10Mbps/user x 10users=100Mbps/BS Real time very lowrate voice eg 0.5kbps/user x 20,000users=100Mbps/BS (only 10% of BS capacity). 2011/5/17 FA/Tohoku University 18

19 There was a big technical leap from 2G to 3G systems. Voice+data Voice+Data Mixture of broadband data and low rate voice 1G Analog (FDMA) ~2.4kbps Narrowband Increased no. of channels 2G Digital (TDMA) ~64kbps Big leap 3G/3.5G Digital (CDMA) ~2Mbps ~14Mbps 4G/5G Digital Broadband/narrowband Very lowrate voice *Increased peak rate/increased throughput *Increased no. of lowrate voice channels 2011/5/17 FA/Tohoku University 19

20 Robust Wireless Network against Disaster People want to talk to confirm their safety. Realtime both-way voice communication is important How to accommodate huge no. of users? Two order increase in the link capacity in terms of no. of users is necessary Wireless access with high order of multiplexing, very low rate voice codec, efficient resource allocation How about core network? Obviously circuit switched networks can t work since a huge number of call should be handled. IP packet network can work. 2011/5/17 FA/Tohoku University 20

21 How to cope with cutdown of power supply? Stable communications power supply: Large capacity battery, robust power supply network, energy harvesting, etc Heterogeneous network Terrestrial (mobile and fixed) network Satellite Adhoc network Visible light commun. network, etc Terminal battery life needs to be longer solar battery or dry battery-operated, etc 2011/5/17 FA/Tohoku University 21

22 Concluding Remarks After March 11 Future wireless network should include realtime voice communication function 2-layer network may work Broadband layer: DAN architecture Real time lowrate voice layer: conventional cellular Terminal transmit power can be very low because of very lowrate voice longer battery life Broadband service 4/5G band Lowrate voice f DAN-SPC & BS Realtime very lowrate voice service 2011/5/17 FA/Tohoku University 22