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1 Fourth Generation Cellular Systems: Spectrum Requirements Joseph M. Nowack Member of the Technical Staff Communication Systems and Technologies Labs.

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Presentation on theme: "1 Fourth Generation Cellular Systems: Spectrum Requirements Joseph M. Nowack Member of the Technical Staff Communication Systems and Technologies Labs."— Presentation transcript:

1 1 Fourth Generation Cellular Systems: Spectrum Requirements Joseph M. Nowack Member of the Technical Staff Communication Systems and Technologies Labs December 6, 2000

2 2 What is 4G? The simple answer: 4G is the next major generation of mobile cellular systems, to be deployed around the year 2010 The multiple choice answer: The twelve views of 4G * Is that your final answer? Service provider s Cost reductio n User services Wireless wireline Technolog y trends New network New air interface Wireless Internet 4G will not exist Higher bit rates White space Strict generatio n * source: CSTL 4G white paper Wireless wireline New network New air interface Technolog y trends Cost reduction Higher bit rates User services White space Service provider s Wireless Internet

3 3 A View of 4G Domain of 4G extends beyond 1G, 2G, and 3G > 2 Mbps in a wide-area mobile system (> 20 Mbps peak) Could coexist with 2G and 3G 4G is not necessarily defined by the bit rate, but by a significant advance in system capability beyond what can be achieved with 3G Data Rate Coverage Area, Mobility Macrocell, High Mobility Microcell, Limited Mobility Fixed Access 64kbps 2Mbps 200Mbps P-MP (LMDS) Milli-wave LAN 2G WLA N 4G 3G

4 4 Some Key Challenges Coverage –Transmit power limitations and higher frequencies limit the achievable cell size Capacity –Current air interfaces have limited peak data rate, capacity, and packet data capability Spectrum –Location and availability are key issues –Lower carrier frequencies (< 5 GHz) are best for wide-area coverage and mobility

5 5 The Coverage Problem - Carrier Frequency and Data Rate

6 6 SpectrumSpectrum Carrier frequency has a larger impact on cell size than data rate In order to enable wide-area coverage, 4G needs mobile friendly spectrum (ideally less than 5 GHz) –Mobile devices have low transmit power, limited antenna gain, and predominately non-line-of-sight propagation Fixed wireless systems are more easily able to take advantage of higher carrier frequencies –No movement -> low Doppler –Higher transmit power –Power consumption/heat dissipation less critical –Line-of-sight more likely –High-gain, high-elevation antenna

7 7 Broadband Wireless Content Successful wireless services are preceded by growth of wired demand POTS Mobile Telephony Dial-up Internet WAP, Cellular Data DSL, Cable Data 4G Broadband Wireless Content is rapidly expanding to serve the Cable/DSL connected consumer –Many sites focused on video delivery of Broadband video (typically 300 kbps and faster) MovieFlix, VideoSeeker, QTV, Quokka Sports Combinations of existing content may be valuable to mobile information consumers –Expressway Travel Information – real time web cameras, traffic status and advisories –Entertainment Selections – movie trailers, ticket reservation, TV guide, video-on-demand –Business Guide – Stock market information, real-time video briefings, breaking news

8 8 User Session Traffic Characterization Web browsing session (TCP)Video Download (UDP) Internet Telephony Audio – from ClientInternet Telephony Audio – to Client

9 9 Typical Observations 200-second sections of sessions using three applications Packet data traffic rates are provided in bytes per second Browsing the World Wide Web ( TCP & HTTP ) 8.0 Peak-to-Average Bit Rate Ratio – 8.0 Ratio of Download Byte Volume 8.8 To Upstream – 8.8 164720 average = 2059 Bursty data traffic Acquisition of various sources for a single site Long pauses by user TCP upstream packet traffic volume moderate Interactive Internet Telephony ( UDP & Internet Phone ) 1.85 Peak-to-Average Bit Rate Ratio – 1.85 Ratio of Download Byte Volume 1.27 To Upstream – 1.27 24740 average = 1362 Packet data rates reflect telephone speech patterns Remote participant responsible for more speech and packet traffic than client in this trace Byte volumes generally comparable Video + Audio Download ( UDP & VXtreme ) 1.37 Peak-to-Average Bit Rate Ratio – 1.37 Ratio of Download Byte Volume 394.8 To Upstream – 394.8 71662853 average = 5232 UDP data uses fewer upstream packets than TCP Peak-to-Average data rate ratio low in this trace Mainly due to embedded constant bit rate (CBR) audio stream of the downloaded sample Variable bit rates (VBR) are more common for most video applications

10 10 4G Concept System A demonstration of broadband mobile systems in Schaumburg, Illinois –A one-directional broadband downlink carrier on DVB-T (WA9XHI) –A narrowband uplink via a cellular data connection (Sprint CDMA data) Proving ground for asymmetric mobile broadband Develop application understanding to apply to broadband air interface designs Platform to demonstrate custom applications Increasing levels of integration –Phase 1 – Vehicular mobility with a larger off-the-air receiver – May 2000 –Phase 2 – Personal mobility with an integrated laptop receiver – Progressing Sprint PCS Intranet/ Internet Server Proxy & Router

11 11 4G System Research Areas Adaptive Antennas for Broadband Air Interface Research Broadband Implementations 4G System Design

12 12 Potential Coverage and Capacity Solutions

13 13 4G Air Interface Characteristics Higher bit rates than 3G (20 Mbps < peak < 200 Mbps) Higher spectral efficiency and lower cost per bit than 3G Air interface and MAC optimized for IP traffic (IPv6, QoS) –Adaptive modulation/coding with power control, hybrid ARQ Smaller cells, on average, than 3G –However, cell size will be made as large as possible via: Asymmetry - used to boost uplink range when necessary Adaptive antennas (4 to 8 elements at base station, 2 elements at terminal) Higher frequency band than 3G (below 5 GHz preferred) RF channel bandwidths of 20-100 MHz OFDM is promising (especially for downlink), but also investigating other methods

14 14 ClosingClosing 4G still in a formative stage (commercial 2010) Frequency bands less than 5 GHz preferred for wide-area, mobile services 4G system bandwidth between 20 and 100 MHz (paired or unpaired) ITU Working Group 8F beginning to consider the requirements and spectrum needs International 4G spectrum harmonization

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